MMWR Recomm Rep, 1993 Nov 12, 42(RR-15), 1 - 28 Tuberculosis control laws--United States, 1993 . Recommendations of the Advisory Council for the Elimination of Tuberculosis (ACET) Activity of P-glycoprotein in B-cell chronic lymphocytic leukemia determined by a flow cytometric assay. Department of Internal Medicine, University of Innsbruck, AustriaBACKGROUND: Chemoresistance in some hematologic malignancies has been associated with overexpression of P-glycoprotein, which is encoded by the MDR1 gene (also known as PGY1) . However, inconsistencies in data on frequency and clinical relevance of multidrug resistance in B-cell chronic lymphocytic leukemia (B-CLL) may reflect a need for improved techniques to detect this overexpression . PURPOSE: Our purpose was to measure P-glycoprotein activity in peripheral blood cells of B-CLL patients and to analyze possible clinical correlations (disease duration, prior treatment, Rai disease stage, lymphocyte counts, and disease progression) . METHODS: P-glycoprotein activity was assayed in peripheral blood cells of 42 consecutive B-CLL patients (22 treated and 20 untreated) . We used dual fluorescence in a flow cytometric assay that detects efflux of the fluorescent dye rhodamine 123, which is transported from the cell by the P-glyprotein pump . Leukemia cells were costained with monoclonal antibody Leu12/CD19, and rhodamine 123 efflux was measured . Expression of MDR1 and MDR3 (also known as PGY3) messenger RNA (mRNA) was quantitatively evaluated by polymerase chain reaction (PCR) in 26 cases . RESULTS: Marked rhodamine 123 efflux was observed in 34 (81%) of the 42 cases and was abolished in the presence of multidrug resistance inhibitors . Rhodamine 123 efflux was not associated with Rai stage, lymphocyte counts, duration of disease, or disease progression . Although rhodamine 123-negative cases were about equally distributed among untreated and previously treated patients, the percentage of cells with rhodamine 123 efflux was significantly lower for untreated patients than for those treated with chemotherapy regimens including at least one multidrug resistance-associated drug . MDR1 mRNA was detected in 25 of 26 cases and MDR3 mRNA in all 26 . MDR1 mRNA expression was significantly correlated with rhodamine 123 efflux, whereas MDR3 mRNA expression was not significantly correlated; MDR1 and MDR3 mRNA expression was not significantly associated with Rai stage, prior treatment, or disease progresssion . CONCLUSIONS: These findings suggest that P-glycoprotein overexpression in B-CLL is intrinsic rather than acquired and that P-glycoprotein activity is enhanced after exposure to multidrug resistance-associated drugs . This enhanced activity does not seem to be associated with more aggressive disease . Our results also indicate that an assay of P-glycoprotein function combined with PCR is suitable for clinical multidrug resistance screening . IMPLICATIONS: Additional studies are needed to determine whether functional activity of P-glycoprotein, measured by rhodamine 123 efflux, is directly related to clinical drug resistance. Biochem Pharmacol, 1993 Nov 2, 46(9), 1613 - 9 Rapid stimulation of rhodamine 123 efflux from multidrug-resistant KB cells by progesterone; Jancis EM et al.; Rhodamine 123 is a mitochondrial dye that is retained for prolonged periods by carcinoma cells . While investigating causes of retention of this dye, we found that 10 microM progesterone caused a rapid stimulation of efflux of rhodamine 123 within 15 min from KB V20C cells, which overexpress the multidrug resistance pump . Progesterone did not stimulate efflux from KB cells that do not overexpress the pump, and verapamil blocked rhodamine 123 efflux in the presence or absence of progesterone, indicating that rhodamine 123 is removed from KB V20C cells by the multidrug resistance pump . Progesterone, however, is unlikely to stimulate rhodamine 123 efflux by simply increasing pump activity for two reasons: (1) progesterone inhibited the efflux of daunomycin from KB V20C cells, so it did not stimulate efflux of all drugs, and (2) progesterone inhibited efflux of rhodamine 123 from L1210/VMDRC cells and had little effect on Adr MCF7 cells; both overexpress the multidrug resistance pump . In the experiments with KB V20C cells, progesterone was the most active steroid tested . At 10 microM, progesterone caused a 70-fold stimulation, desoxycorticosterone, testosterone, promegestone and estradiol about 20-fold, and others had little or no effect . Progesterone may act by a non-genomic mechanism to decrease intracellular binding of rhodamine 123, making the dye accessible to the multidrug resistance pump. Antimicrob Agents Chemother, 1993 Nov, 37(11), 2344 - 7 Therapy of multidrug-resistant tuberculosis: lessons from studies with mice; Klemens SP et al.; The activities of antituberculosis agents were evaluated in a murine tuberculosis model using a drug-resistant isolate . A multidrug-resistant clinical isolate from a recent outbreak of tuberculosis in the New York State correctional system was used for infection . Approximately 10(7) viable Mycobacterium tuberculosis ATCC 49967 (strain CNL) organisms were given intravenously to 4-week-old female outbred mice . Treatment was started 1 day after infection and given for 4 weeks . Spleens and lungs were homogenized, and viable cell counts were determined . Statistical analysis indicated that ethionamide, sparfloxacin, ofloxacin, capreomycin, clarithromycin, and clofazimine are active in the murine test system with this multidrug-resistant tuberculosis isolate . Sparfloxacin is the most active quinolone . Despite in vitro resistance, isoniazid has moderate activity . In vitro susceptibility data coupled with evaluation of agents against drug-resistant isolates in the murine system should provide information necessary to design clinical trials for treatment of infections with these organisms. Ann Oncol, 1993 Nov, 4(9), 723 - 33 Protracted drug infusions in cancer treatment: an appraisal of 5-fluorouracil, doxorubicin, and platinums; DelaFlor-Weiss E et al.; The feasibility to deliver chemotherapeutic agents by protracted i.v . infusion has greatly increased in the recent past . Indwelling ports, longer lasting central venous catheters requiring less than daily maintenance 'flushing', surgical expertise in placement, use in analgesia and nutrition, and 'smart' pump technology have all contributed to their increasing popularity . Justification for use of infusions in cancer chemotherapy has been slow in appearing with few studies proceeding to the comparative stage . This review will focus on three drugs in common use in cancer treatment, with the purpose of appraising the role of such infusions in cancer therapeutics and of deriving some lessons that might be applicable to other drugs or to drug development in general . For fluorouracil and doxorubicin the rationale and clinical findings favoring further development of infusion regimens is particularly strong . In the case of platinum compounds, some toxicologic advantages have emerged, but other measures designed to protect against the toxicities of cisplatin compete with infusion regimens in this regard . The therapeutic potential for this form of drug delivery, therefore, appears still confined to a subset of patients . Stronger rationales for the use of protracted infusions may be forthcoming from pharmacodynamic findings as in the case of etoposide, combined modality therapy with radiation for FU and cisplatin, biochemical modulation for FU, and reversal of multidrug resistance and its modulation for doxorubicin . While awaiting research into these areas of clinical and pre-clinical investigations, the role of infusion appears most evident in the cardiotoxicity protection of anthracyclines, and in further efficacy exploration (through dose or modulation) of FU . Both mechanistic and pharmacologic considerations could also provide additional stimulus for development of new formulations such as long circulating liposomes, and drugs more suitable for oral administration. AIDS, 1993 Nov, 7(11), 1453 - 60 A nosocomial outbreak of multidrug-resistant Mycobacterium bovis among HIV-infected patients . A case-control study; Bouvet E et al.; OBJECTIVE: To identify risk factors in a nosocomial outbreak of multidrug-resistant Mycobacterium bovis (MDRMB) tuberculosis (TB) among HIV-infected patients . DESIGN: We evaluated the study period (from the first to the last MDRMB smear-positive patients hospitalized in the unit) using a case-control study with three control groups . Since MDRMB is extremely rare, we assumed that a single strain was responsible for all six cases . SETTING: A 19-bed infectious diseases unit in Paris, France . PATIENTS: The index case was an AIDS patient who was hospitalized in September 1989 because of MDRMB TB . The cases were five HIV-infected patients who developed MDRMB TB between January 1990 and October 1991 . Controls were randomly selected from HIV-infected patients in our unit during the study period (case-control study 1, 15 patients), during the contact period (at least one MDRMB smear-positive patient hospitalized in the unit; case-control study 2,20 patients), and patients matched according to the length of contact (case-control study 3, 24 patients) . INTERVENTIONS: After detecting the nosocomial outbreak, we took respiratory isolation precautions for all patients suspected of having active TB . MAIN OUTCOME MEASURES: Risk factors for MDRMB nosocomial transmission, and the occurrence of new cases of MDRMB infection in HIV-infected patients and health-care workers after the introduction of isolation precautions . RESULTS: The most important predictor of nosocomial transmission of MDRMB to HIV-infected patients was the (mean +/- s.d.) length of contact in days {cases, 22 +/- 15.8; study 1 controls, 11.2 +/- 18.9 (P = 0.07); study 2 controls, 14.6 +/- 8.5 (P = 0.043)} . Only one case of MDRMB TB resulted from exposure to MDRMB-smear-positive patient after the introduction of respiratory isolation measures . The incubation period in the single health-care worker who developed MDRMB TB was longer than in the cases . CONCLUSION: In a nosocomial outbreak of MDRMB TB, the contact time was the main risk factor of transmission to HIV-infected patients . Respiratory isolation measures appear to be effective. Clin Infect Dis, 1993 Nov, 17 Suppl 2, S442 - 6 Drug-resistant tuberculosis; Riley LW; Multidrug-resistant tuberculosis (MDRTB) is an iatrogenic disease that is emerging as a major infectious disease problem throughout the world . The AIDS pandemic, increased incidence of tuberculosis in populations with easy access to antituberculosis medications, the deterioration of the public health infrastructure, and inadequate training of health care providers in the epidemiology of tuberculosis are some of the factors contributing to the increased incidence of MDRTB . Mortality from MDRTB exceeds 80% in persons infected with human immunodeficiency virus (HIV) but is also high in patients free of HIV . The management of MDRTB is complicated by the lack of methods for rapid detection of resistant strains of Mycobacterium tuberculosis . The risk of infection among close contacts of patients with MDRTB, the probability of the development of active MDRTB after infection, and the likelihood of cure of MDRTB need to be determined quantitatively . Attributable risk estimates for factors associated with MDRTB should be calculated for each community as part of the strategies to prevent MDRTB . Issues regarding chemoprophylaxis in newly infected contacts of MDRTB cases remain unanswered . Basic research on the mechanisms of action of existing antituberculosis drugs may contribute to an understanding of the mechanism of resistance in M . tuberculosis . There is an urgent need to expand the scope of epidemiological, clinical, and laboratory research to address these problems. Ann Hematol, 1993 Nov, 67(5), 227 - 30 Idarubicin is active on MDR cells: evaluation of DNA synthesis inhibition on P388 cell lines; Petrini M et al.; Multidrug resistance is frequently found in patients affected by hematological malignancies and has been related to a poor prognosis of acute leukemia . In the present paper we report results concerning the activity of idarubicin, an anthracycline derivative, on the leukemic P388 and P388 doxorubicin-resistant cell lines . The results clearly show that idarubicin inhibits DNA synthesis in the resistant cell line more actively than doxorubicin. Proc Natl Acad Sci U S A, 1993 Nov 1, 90(21), 10226 - 9 Cationic drug analysis using matrix-assisted laser desorption/ionization mass spectrometry: application to influx kinetics, multidrug resistance, and intracellular chemical change; Rideout D et al.; Highly sensitive and convenient analysis of intracellular cationic drugs has been achieved by applying matrix-assisted laser desorption/ionization mass spectrometry (MALD-MS) . Tetraphenylphosphonium cation was readily identified and quantified (using methyltriphenylphosphonium cation as an internal standard) at subpicomole levels in crude lysate from < 4 x 10(3) FaDu human hypopharyngeal carcinoma cells . A quantitative MALD-MS time course for tetraphenylphosphonium cation accumulation into FaDu cells was comparable to a time course using scintillation counting with tritiated tetraphenylphosphonium . MALD-MS was also capable of demonstrating the reduced accumulation of the cationic drug rhodamine-123 by DoxR MCF7, a multiply drug-resistant human breast adenocarcinoma cell line, relative to the nonresistant parent line MCF7 . In addition, MALD-MS was used to follow a chemical reaction inside intact FaDu cells: the formation of a hydrazone (II-51) from benzaldehyde and an acylhydrazide, 5-{tris(4-dimethylaminophenyl)phosphonio}pentanoyl hydrazide (II-25) . These results suggest that MALD-MS may provide a rapid and practical alternative to existing methods for the analysis of cationic drugs, toxins, and their metabolites in cells and tissues. Med Clin North Am, 1993 Nov, 77(6), 1391 - 409 The epidemiology of multidrug-resistant tuberculosis in the United States; Kent JH; There has been a significant increase in the number of cases of MDR-TB in the United States . Although cases of MDR-TB have been reported from many areas of the country, the majority of the cases are concentrated in large urban areas . MDR-TB is difficult and expensive to treat . CDC has developed a National Action Plan to Combat Multidrug-Resistant Tuberculosis . The main elements of this plan include (1) greater surveillance and epidemiologic studies of drug-resistant TB; (2) initiatives to make the laboratory diagnosis of MDR-TB more rapid, sensitive, and reliable; (3) education of health care professionals about MDR-TB, its prevention, control, and treatment; and (4) measures to facilitate the development of new antituberculous drugs . CDC has published guidelines for the prevention of nosocomial spread of MDR-TB . to prevent the development and spread of MDR-TB, medical practitioners must suspect TB and make the diagnosis as rapidly as possible . Once a patient is diagnosed with TB, the most important step to prevent the development of drug-resistant disease is to ensure that patients take all of their medication . Directly observed therapy is the best way of ensuring this . In addition, more specific interventions, such as the use of incentives to improve compliance in certain situations, may need to be applied to groups in which high rates of drug resistance have been found, such as HIV-positive persons, IDUs, homeless persons, and persons who have been exposed to persons with MDR-TB . Quick and effective public health interventions targeted at these defined groups should help to control the spread of both drug-susceptible and drug-resistant TB. Med Clin North Am, 1993 Nov, 77(6), 1335 - 51 Tuberculosis in children; Jacobs RF et al.; The dramatic resurgence and increase in the total number of cases of tuberculous infection and disease in children is alarming in the United States . With poverty, poor access to health care, overcrowding (predominantly in inner-city areas), and an increase in immigration from areas with high endemic rates of TB, the problem in children will continue to increase . If the impact of coinfection with HIV and M . tuberculosis becomes significant in children, as it has in adults in the United States, the increase in the total number of cases of tuberculous disease in children could be staggering . The impact of multidrug-resistant strains of M . tuberculosis and the current crises in availability of effective anti-TB drugs will need a similar resurgence. Med Clin North Am, 1993 Nov, 77(6), 1277 - 88 The treatment of tuberculosis; Brausch LM et al.; Short-course chemotherapy has made the treatment of TB easier and better than ever, but it works only when patients take the drugs regularly . Compliance is a must for therapy to be successful . Physicians treating patients with tuberculosis should be acutely aware of noncompliance, and every effort to ensure adequate treatment must be put forth . Directly supervised therapy is an excellent option when enough resources are available . Intermittent regimens markedly reduce the manpower required for observed therapy . New agents are being tested for in vitro activity against M . tuberculosis, and clinical studies of those found to be potentially effective are needed to formulate new regimens against the ever-increasing threat of multidrug-resistant TB. In Vivo, 1993 Nov-Dec, 7(6A), 519 - 23 Modulation of doxorubicin efficacy in P388 leukemia following co-administration of verapamil in mini-osmotic pumps; Slate DL et al.; Co-administration of doxorubicin and verapamil in Alzet mini-osmotic pumps increased the survival of B6D2F1 mice bearing the multidrug-resistant P388/ADR leukemia . A range of doxorubicin and verapamil combinations was studied to define dose-dependent efficacy and toxicity . High doses of doxorubicin (10 mg/kg/day) and verapamil (150 mg/kg/day) could be administered alone without any effect on survival . However, combining high doses of these two agents resulted in host toxicity . Doxorubicin doses of 1 to 10 mg/kg/day in combination with verapamil at 25-100 mg/kg/day were found to improve survival compared with either agent alone . Combination therapy also improved the survival of mice bearing the drug-sensitive P388/0 leukemia when compared to anthracycline treatment alone . The efficacy of the mini-osmotic pump delivery protocol was compared with other regimens delivering the same total cumulative dose of doxorubicin via repeated i.p . injections. Anal Biochem, 1993 Nov 1, 214(2), 506 - 10 Method for determination of intracellular sodium in perfused cancer cells by 23Na nuclear magnetic resonance spectroscopy; Hansen LL et al.; Changes of intracellular sodium concentrations are often an indication of disease or malfunction . In this work, shift reagent-aided 23Na NMR spectroscopic determination of intracellular sodium was adapted to measurements with perfused cells embedded in agarose gel threads . Ehrlich ascites tumor cells (EHR2) and their multidrug-resistant counterparts (EHR2/DNR+) were immobilized and perfused until the metabolic steady state had been reached as shown by 31P NMR spectroscopy . Subsequent addition of 5 mM dysprosium(III) bis(tripolyphosphate) to the perfusion medium caused a separation of extracellular and intracellular 23Na NMR signals, making quantification of the intracellular sodium possible . The dysprosium shift reagent was apparently nontoxic to the cells, as shown by the unchanged level of ATP and other intracellular phosphates . NMR visibility of the intracellular sodium was determined in suspensions of EHR2 and EHR2/DNR+ cells by treatment with digitonin; the increase of intensity of the extracellular sodium resonance observed after the digitonin treatment corresponded well (97 +/- 3%) to the sum of intracellular and extracellular sodium observed with intact cells prior to the digitonin treatment . The resistant EHR2/DNR+ cells contained a moderately higher intracellular sodium level than the wild-type EHR2 cells, 1.02 +/- 0.10 and 0.77 +/- 0.07 mumol Na/mg protein, respectively . Closely similar levels of intracellular sodium were found by flame photometry . Thus, 23Na NMR offers a reliable method for noninvasive quantification of intracellular sodium in perfused cancer cells. Cancer Res, 1993 Nov 1, 53(21), 5225 - 32 Cross-resistance to diverse drugs is associated with primary cisplatin resistance in ovarian cancer cell lines; Hamaguchi K et al.; We have previously obtained, by exposure to near continuous increasing concentrations of cisplatin, a panel of human ovarian cancer cell lines that exhibit a wide range of primary resistance to the drug (9- to > 400-fold) . These cells had strikingly increased (4- to 50-fold) levels of glutathione (GSH) as compared with the drug-sensitive cells of origin (A . K . Godwin et al., Proc . Natl . Acad . Sci . USA, 89: 3070-3074, 1992) . Utilizing this panel of resistant cell lines, we evaluated cross-resistance to classical alkylating agents, natural product drugs, and irradiation . We observed that cross-resistance to carboplatin paralleled that of cisplatin, culminating in approximately 250-fold resistance . Similarly, melphalan cross-resistance continued to increase to > 400-fold and again paralleled the primary cisplatin resistance . Cell lines with low to very high levels of resistance to cisplatin are 8- to 850-fold resistant to the epipodophyllotoxin derivative etoposide . Cross-resistance is also observed for other natural product drugs, including Adriamycin (approximately 80-fold), mitoxantrone (approximately 440-fold), and taxol (approximately 40-fold) . Cross-resistance to irradiation is, however, modest (< 2-fold) . The cells with the greatest primary resistance to cisplatin most commonly had the highest cross-resistance to the other drugs examined . The cross-resistance to the natural product category drugs was found not to be mediated by the products of either the multidrug resistance 1 (MDR1) or multidrug resistance-associated protein (MRP) genes based on lack of coordinate increased expression or amplification of these genes as assessed by Northern and Southern blot analyses . Furthermore, verapamil failed to markedly increase drug sensitivity . Although there was no indication that these natural product drug efflux pumps were operative, we observed decreased doxorubicin accumulation in these cell lines cross-resistant to natural products . In addition, alternations in DNA topoisomerase II mRNA levels, which have been observed in a variety of human tumor cell lines selected in vitro for resistance to etoposide or teniposide, were not detected . Only intracellular levels of GSH correlated with cross-resistance to these diverse anticancer agents and partial loss of resistance was associated with a marked decrease in glutathione levels . In the absence of alternative mechanisms, we speculate that the very broad clinically relevant cross-resistance seen in this model system may, at least in part, be the direct result of GSH-mediated drug inactivation or may be due to a combination of GSH conjugation to drug and conjugate efflux mediated by the putative ATP-dependent glutathione S-conjugate export pump. Br J Cancer, 1993 Nov, 68(5), 939 - 46 Genistein modulates the decreased drug accumulation in non-P-glycoprotein mediated multidrug resistant tumour cells; Versantvoort CH et al.; In tumour cells the pharmacological basis for multidrug resistance (MDR) often appears to be a reduced cellular cytostatic drug accumulation caused by the drug efflux protein, P-glycoprotein (Pgp MDR), or by other drug transporters (non-Pgp MDR) . Here we report the reversal of the decreased daunorubicin (DNR) accumulation in five non-Pgp MDR cell lines (GLC4/ADR, SW-1573/2R120, HT1080/DR4, MCF7/Mitox and HL60/ADR) by genistein . Genistein inhibited the enhanced DNR efflux in the GLC4/ADR cells . In these cells the decreased VP-16 accumulation was also reversed by genistein . Three other (iso)flavonoids biochanin A, apigenin and quercetin also increased the DNR accumulation in the GLC4/ADR cells . In contrast to the effects on non-Pgp MDR cells, 200 microM genistein did not increase the reduced DNR accumulation in three Pgp MDR cell lines (SW-1573/2R160, MCF7/DOX40 and KB8-5) or in the parental cell lines . In conclusion the use of genistein provides a means to probe non-Pgp related drug accumulation defects. Br J Cancer, 1993 Nov, 68(5), 898 - 908 Changes in subcellular doxorubicin distribution and cellular accumulation alone can largely account for doxorubicin resistance in SW-1573 lung cancer and MCF-7 breast cancer multidrug resistant tumour cells; Schuurhuis GJ et al.; Doxorubicin accumulation defects in multidrug resistant tumour cells are generally small in comparison to the resistance factors . Therefore additional mechanisms must be operative . In this paper we show by a quantitative approach that doxorubicin resistance in several P-glycoprotein-positive non-small cell lung cancer and breast cancer multidrug resistant cell lines can be explained by a summation of accumulation defect and alterations in the efficacy of the drug once present in the cell . This alteration of efficacy was partly due to changes in intracellular drug localisation, characterised by decreased nuclear/cytoplasmic doxorubicin fluorescence ratios (N/C-ratios) . N/C-ratios were 2.8-3.6 in sensitive cells, 0.1-0.4 in cells with high (> 70-fold) levels of doxorubicin resistance and 1.2 and 1.9 in cells with low or intermediate (7.5 and 24-fold, respectively) levels of doxorubicin resistance . The change of drug efficacy was reflected by an increase in the total amount of doxorubicin present in the cell at equitoxic (IC50) concentrations . N/C ratios in highly resistant P-glycoprotein-containing cells could be increased with the resistance modifier verapamil to values of 1.3-2.7, a process that was paralleled by a decrease of the cellular doxorubicin amounts present at IC50 . At the low to moderate residual levels of resistance, obtained with different concentrations of verapamil, a linear relationship between IC50 and cellular doxorubicin amounts determined at IC50 was found . This shows that at this stage of residual resistance, extra reversal by verapamil should be explained by further increase of drug efficacy rather than by increase of cellular drug accumulation . A similar relationship was found for P-glycoprotein-negative MDR cells with low levels of resistance . Since in these cells N/C ratios could not be altered, verapamil-induced decrease of IC50 must be due to increased drug efficacy by action on as yet unidentified targets . Although the IC50 of sensitive human cells cannot be reached with resistance modifiers, when using these relationships it can be shown by extrapolation that cellular and nuclear doxorubicin amounts at IC50 at complete reversal of resistance were the same as in sensitive cells . It is concluded that doxorubicin resistance factors for multidrug resistant cells can for a large part, and in the case of P-glycoprotein-containing cells probably fully, be accounted for by decreased amounts of drug at nuclear targets, which in turn is characterised by two processes only: decreased cellular accumulation and a shift in the ratio nuclear drug/cytoplasmic drug. J Urol, 1993 Nov, 150(5 Pt 1), 1544 - 7 Role of the MDR-1-encoded multiple drug resistance phenotype in prostate cancer cell lines; Theyer G et al.; The treatment of advanced metastatic prostate cancer by hormone manipulation or orchiectomy is frequently followed by the appearance of hormone-insensitive and highly chemoresistant tumor cells . In this study we have investigated the contribution of the P-glycoprotein-mediated drug efflux (multidrug-resistance; MDR) to the cellular resistance of prostate carcinoma-derived cell lines to diverse cytotoxic drugs by detection of P-glycoprotein (P-gp) measurement of P-gp-mediated drug transport and reversal of MDR by chemosensitizers . The in vitro chemosensitivity of three prostate cancer cell lines (PC-3, DU-145 and LNCaP) to doxorubicin was measured in a thymidine incorporation proliferation assay . Growth of the partially hormone-sensitive cell line LNCaP is inhibited by low doses of doxorubicin (IC50:27 ng./ml.), but PC-3 and DU-145 are highly resistant to the drug, with IC50 values of 10 micrograms./ml . and 7.5 micrograms./ml., respectively . The chemosensitivity of the PC-3 and DU-145 cells is increased in response to 1 microM . verapamil, 1 micrograms./ml . cyclosporine A and 2 microM . tamoxifen, which are known to partially reverse the MDR phenotype in other resistant tumors . A verapamil-sensitive drug efflux has been demonstrated for the PC-3 and Du-145, but not for the LNCaP, cell lines, using flow cytometric measurements of the P-gp substrate rhodamine 123 efflux from preloaded cells . In agreement with the functional measurements, the expression of the P-glycoprotein was detected in the PC-3 and Du-145 cell lines in Western blots using the monoclonal C 219 antibody . In conclusion, the chemoresistant and hormone-insensitive PC-3 and Du-145 cell lines express P-gp and exhibit verapamil-sensitive drug efflux, indicative of MDR . However, the low MDR-reversal rates observed in these cell lines in response to chemosensitizers in clinically achievable concentrations (approximately 2- to 3-fold reversal), point to non-MDR-associated cellular mechanisms as dominant factors of chemoresistance in prostate cancer. Pharmacol Ther, 1993 Nov, 60(2), 215 - 34 Design and tumor targeting of anthracyclines able to overcome multidrug resistance: a double-advantage approach; Priebe W et al.; A novel, 'double-advantage approach' to developing more effective chemotherapies will be reviewed . This approach is based on a presumption that analogs designed on a sound hypothesis, and combined with a rationally selected drug delivery system, will optimize antitumor activity by creating drugs that are more active and that can be more specifically targeted to tumors . In the design of drugs superior to doxorubicin, we have focused on typical multidrug resistance and new anthracycline analogs, whose uptake is not affected by P-glycoprotein . Analysis of structural elements of anthracyclines affecting activity against multidrug resistant tumors and affinity for liposomes will be discussed . Annamycin, a lipophilic anthracycline analog, was selected for further preclinical development as a liposomal formulation and demonstrated, in the initial biological evaluation, high activity against tumors resistant to doxorubicin. Pharmacol Ther, 1993 Nov, 60(2), 289 - 99 Classical and novel forms of multidrug resistance and the physiological functions of P-glycoproteins in mammals; Borst P et al.; In this paper, we review recent work on multidrug resistance (MDR) in Amsterdam . We have generated mice homozygous for a disruption of one of their P-glycoprotein (Pgp) genes . The mutations do not interfere with viability or fertility, showing that these Pgps have no indispensable role in early development or metabolism . Mice homozygous for a disruption of their mdr2 gene, however, develop liver disease and this appears to be due to their complete inability to secrete phospholipids into bile . This suggests that the mdr2 Pgp (and, by inference, its human MDR3 homologue) is essential for translocating phospholipids through the hepatocyte canalicular membrane in which this Pgp is located . These and other results show the importance of the genetic approach for studying drug metabolism . MDR is not only caused by increased activity of Pgps . When the human non-small cell lung carcinoma cell line SW-1573 is selected in vitro for low level doxorubicin resistance, the resistant variants are nearly always multidrug resistant, but this is not due to increased Pgp activity . Only when resistance is pushed to higher levels does activation of the MDR1 Pgp gene occur . This suggests that clinically relevant levels of drug resistance in some cells may be caused predominantly by non-Pgp-mediated drug resistance mechanisms . The protein responsible for MDR in the SW-1573 cells has not yet been identified and experiments are in progress to find the gene encoding it. Curr Opin Oncol, 1993 Nov, 5(6), 1029 - 34 Doxorubicin and multidrug resistance; Kruh GD et al.; The circumvention of P-glycoprotein function by pharmacologic agents is a major focus of clinical trials aimed at increasing the cytotoxicity of multidrug resistance-associated drugs, including doxorubicin . The success of this approach will likely depend on the clinical significance of P-glycoprotein expression, which has not yet been elucidated for the common solid tumors, and the ability to achieve effective levels of circumventing agents without dose-limiting toxicities . Initial clinical studies suggested that biologically relevant concentrations of multidrug resistance modulators, eg, cyclosporine, can be achieved . Because pharmacologic agents that inhibit drug efflux by P-glycoprotein are themselves pumped out of cells by the transporter, this approach may have an inherent barrier to success . Laboratory studies have suggested alternative strategies for circumventing P-glycoprotein action, eg, the use of monoclonal antibodies directed against P-glycoprotein and liposome-encapsulated drugs. Anticancer Res, 1993 Nov-Dec, 13(6A), 2059 - 63 The multidrug-resistance modifiers verapamil, cyclosporine A and tamoxifen induce an intracellular acidification in colon carcinoma cell lines in vitro; Hamilton G et al.; In this study we have investigated the effects of the multidrug-resistance (MDR) modifiers verapamil (VPM), cyclosporin A (CsA) and tamoxifen (TMX) on the intracellular pH(pHi) of four colon carcinoma-derived cell lines with low P-glycoprotein expression (CaCo-2, HT-29, SW 620 and SW 480) . Addition of VPM (1 mu M), CsA (1 microgram/ml) or TMX (2 microM) in HEPES- or bicarbonate/CO2-buffered Ringer's solution was followed by dose-dependent and reversible decreases of the pHi (0.1-0.3 units) of all cell lines, as measured ratiometrically by the changes in the pH-dependent fluorescence of bis(carboxyethyl)carboxyfluorescein (BCECF) . Testing the effects of the resistance modifiers on the Na+/H+ antiporter and bicarbonate trans-porters under appropriate buffer conditions and addition of inhibitors (amiloride, DIDS) revealed that the chemomodulator-induced acidification does not interfere with the function of these major pHi-regulating acid-base transporters . The induction of changes in pHi shows no correlation with MDR-reversing activity of the drugs and our data do not support the P-gp-inhibition-mediated accumulation of acidic substrates as underlying mechanism . In addition to the P-gp-directed MDR-reversal, chemomodulator-induced intracellular acidification may enhance the chemosensitivity of the cells especially under alkaline extracellular conditions, and contribute to the decreased efficacy of MDR-modifiers in acidic extracellular environments and to the chemosensitising effect of VPM in P-gp-negative cell lines. Jpn J Cancer Res, 1993 Nov, 84(11), 1201 - 8 Multidrug resistance in rat colon carcinoma cell lines CC531, CC531mdr+ and CC531rev; Gheuens E et al.; A rat colon carcinoma cell line, CC531, was exposed to stepwise increasing concentrations of colchicine . A cell line, CC531mdr+, which grows in the presence of 0.2 microM of colchicine was obtained . A revertant cell line, CC531rev was isolated upon colchicine withdrawal . The CC531mdr+ displayed a multidrug-resistant phenotype . Marked resistance to the selecting agent colchicine, was found (RF = 37.5) as well as to vinblastine (RF = 11.3) and actinomycin D (RF = 2.6) . Cross resistance to doxorubicin (RF = 8) and daunorubicin (RF = 13.3) was demonstrated . Verapamil was able to reverse drug resistance to colchicine and daunorubicin . The revertant cell line, CC531rev, showed increased sensitivity to colchicine (RF = 0.43), vinblastine (RF = 0.13), doxorubicin (RF = 0.28) and daunorubicin (RF = 0.56) . Marked cross resistance to cis-platinum (RF = 6.9) was also induced in CC531mdr+ and was maintained in CC531rev . We conclude that CC531 displays an intrinsic low-level multidrug-resistant phenotype, which was amplified in the CC531mdr+ variant . This correlates with a higher level of expression of P-glycoprotein . CC531rev lacks the multidrug-resistant phenotype and can be used as the drug-sensitive counterpart of the latter two cell lines . Furthermore, it has been shown that in these cell lines cis-platinum resistance is mediated through a mechanism independent of the multidrug-resistant phenotype, since the revertant cell line CC531rev has lost the multidrug-resistant phenotype while retaining the concomitantly induced cis-platinum resistance of the multidrug-resistant variant CC531mdr+. Leukemia, 1993 Nov, 7(11), 1888 - 90 Relationship between p53 gene mutations and multidrug resistance (mdr1) gene expression in myelodysplastic syndromes; Preudhomme C et al.; P glycoprotein, the product of multidrug resistance (mdr1) gene, is frequently expressed in advanced myelodysplastic syndromes (MDS) with an excess of bone marrow blasts and could explain their frequent resistance to chemotherapy . P53 gene mutations are also found in 10 to 15% of advanced MDS . Because it has recently been suggested that normal p53 suppressed, but that mutated p53 activated, the mdr1 gene promoter, we tried to correlate p53 mutations and P glycoprotein expression in 34 patients with MDS and an excess of bone marrow blasts (> 5%) . P glycoprotein expression was assessed by immunocytochemistry using JSB1 monoclonal antibody and was found positive in 13 out of the 34 patients . p53 mutations were detected both by immunocytochemistry using three different monoclonal antibodies and by single stranded conformation polymorphism (SSCP) analysis of exons 5 to 8 of the P53 gene . Both methods detected a point mutation in 5 out of the 34 patients . Only one out of the 5 patients with a p53 mutation expressed P glycoprotein, as compared to 12 out of the 29 patients without p53 mutations . This suggested the mutant and normal p53 are not major determinants of the regulation of mdr1 expression in vivo, at least in MDS. Leuk Res, 1993 Nov, 17(11), 941 - 7 Common expression of the multidrug resistance marker P-glycoprotein in B-cell chronic lymphocytic leukaemia and correlation with in vitro drug resistance; Sparrow RL et al.; The expression of P-glycoprotein (Pgp), which is associated with multidrug resistance (MDR), was investigated in 20 B-cell chronic lymphocytic leukaemia (B-CLL) patients by flow cytometry using two Pgp-specific monoclonal antibodies (mAb), MRK-16 which recognizes an extracellular epitope, and JSB-1 which recognizes an intracellular epitope . Sixteen (80%) patients were positive with MRK-16 whereas all patients were positive with JSB-1 . The proportion of Pgp-positive lymphocytes from each patient sample varied from 2-94% for MRK-16 and 20-93% for JSB-1 . There was no correlation between the level of positivity and disease stage or treatment history . In vitro drug resistance to vincristine (VCR) and doxorubicin (DOX) was determined by the colorimetric MTT assay . All patients were resistant to one or both drugs being consistent with the expression of Pgp . There was no correlation between the level of resistance and disease stage or drug treatment . We investigated the expression of Pgp in the normal counterpart of the B-CLL cells, CD5+CD19+ B-lymphocytes . A minor subpopulation (3%) of CD5+CD19+ lymphocytes isolated from normal controls expressed Pgp suggesting that these cells may be the potential precursors to the B-CLL cell . We conclude that Pgp expression and drug resistance are inherent characteristics of the B-CLL lymphocyte. J Cell Physiol, 1993 Nov, 157(2), 392 - 402 Differential expression of P-glycoprotein genes in primary rat hepatocyte culture; Lee CH et al.; The multidrug resistance (MDR)-associated protein, P-glycoprotein (Pgp), is expressed on the bile canalicular surface of hepatocytes, where it is thought to function in the detoxification of xenobiotics or in the transport of specific metabolites . Several studies have shown that Pgp expression in rat liver can be perturbed in vivo and in vitro; however, it is not known which of the 3 Pgp genes (class I, II, or III) are involved . In rodents, the class I and II Pgp genes have been shown to mediate MDR while the class III gene apparently does not . In this report, we have used gene-specific probes generated from the 3'-untranslated regions of the three rat Pgp genes (Deuchars et al.: Biochim . Biophys . Acta, 1130:157-165, 1992) to investigate Pgp gene expression in primary rat hepatocytes . We observed that the class II Pgp mRNA, the least abundant in the intact liver, is dramatically increased in culture over a 48 h period, while the class I Pgp showed only a modest increase in mRNA level . In contrast, the class III Pgp mRNA, which is the most abundant in the intact liver, exhibited a gradual decline . In rat liver hepatocytes, different culture conditions, as well as drugs such as cytochalasin D and colchicine, appear to affect the level of the class II Pgp gene expression . Moreover, under all these conditions, there is a strong correlation between the level of the class II Pgp and cytoskeletal (actin and tubulin) mRNAs . Thus, there may be a common mechanism regulating the expression of cytoskeletal protein genes and the class II Pgp gene . These findings have implications for our understanding of the regulation of Pgp gene expression in normal and malignant tissues. Hepatology, 1993 Nov, 18(5), 1202 - 7 Expression of multidrug resistance genes in rat liver during regeneration and after carbon tetrachloride intoxication; Nakatsukasa H et al.; We analyzed expression of multidrug resistance (mdr) genes in rat liver during regeneration after partial hepatectomy or carbon tetrachloride-induced necrosis . In situ hybridization revealed that in the normal liver the cellular distribution of mdr transcripts and protein is restricted to hepatocytes and that a gradient, highest in zone 1 and lowest in zone 3, exists in the level of the mdr transcripts in the liver acinus . Increased levels of mdr1a and mdr1b transcripts were observed 3 hr after administration of carbon tetrachloride and remained increased for the next 5 days . In contrast, increased expression of mdr1a and mdr1b was first observed 24 hr after partial hepatectomy . Use of gene-specific probes to compare the time courses of mdr1b and mdr2 expression after carbon tetrachloride administration showed distinctly different patterns of expression; mdr1b reached a maximum level of expression at 12 hr, whereas increased mdr2 expression was first observed 48 hr after administration . Nuclear run-on analysis at 12 and 24 hr after carbon tetrachloride administration demonstrated 10-fold and eightfold increases in mdr transcription, respectively . However, 72 hr after carbon tetrachloride treatment the rate of mdr transcription was back to the control level . The cellular patterns of mdr expression after partial hepatectomy and carbon tetrachloride administration were similar; the increase was first observed in zone 1 and gradually extended into zone 3 . These data strongly suggest that the physiological roles of mdr1b and mdr2 are different and that liver regeneration is an appropriate model for elucidating these differences. Blood, 1993 Nov 1, 82(9), 2829 - 36 p53 and N-ras mutations in two new leukemia cell lines established from a patient with multilineage CD7-positive acute leukemia; Abo J et al.; Two new myeloid cell lines (K051 and K052) were established from a patient with multilineage CD7-positive acute leukemia . The K051 and K052 were established from the patient's bone marrow cells at diagnosis and at relapse, respectively . The K051 cell expressed myeloid-associated antigens (CD13 and CD33), a platelet-associated antigen (CD41), and an erythroid antigen (glycophorin A) . The K052 cell expressed myeloid-associated antigens (CD13, CD14, and CD33), lymphoid markers (CD2, CD5, and CD7), and HLA-DR . Chromosome analysis of both cell lines showed a 17p- chromosome . Both cell lines were investigated for aberrations of the p53 gene and the N-ras gene . A p53 mutation detected in both cell lines consisted of a C-->T substitution in codon 248 . An N-ras mutation detected only in the K052 cell consisted of a G-->C substitution in codon 13 . Expression of the multidrug resistance gene (MDR1) was also investigated by the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) . MDR1-mRNA was more highly expressed by the K052 cell than the K051 cell, being equivalent to that in HEL cells . The functional MDR1-protein against vincristine was also observed, and its function was inhibited by verapamile and Cyclosporin A . The K052 cells were capable of phenotypic or morphologic differentiation after being incubated with granulocyte colony-stimulating factor, interleukin-2, phorbol 12-myristate 13-acetate, or 1,25-dihydroxy-vitamin D3 . In contrast, the K051 cells responded phenotypically to retinoic acid . Thus, the K051 and K052 cell lines will be useful for investigating the cellular and molecular events in leukemogenesis and differentiation, and the mechanism of expression of the MDR1 gene. Biochim Biophys Acta, 1993 Oct 29, 1154(2), 173 - 81 Inhibition of the multidrug resistance efflux pump; Wigler PW et al.; An ATP-dependent efflux pump is found in the plasma membrane of certain multidrug resistant (MDR) cancer cells . Drug resistance is due to decreased intracellular drug levels that have been reduced to subcytotoxic concentrations . Inhibition of the MDR efflux pump with a reversal agent may 'trap' the cytotoxic drug inside the cell; thus, cellular drug resistance is reversed . Although many different lipophilic substances exhibit reversal activity, inhibition of the pump is stereospecific with respect to the chiral agent cinchonine . In this article, several methods for the estimation of reversal potency are reviewed . Furthermore, information on the transport characteristics of reversal agents is presented . The rate equations for ATP-dependent drug efflux, competitive inhibition of the MDR pump, and noncompetitive inhibition of the pump are derived . A method is presented that discriminates between competitive or noncompetitive inhibition of the pump . These studies show the potential contribution of fundamental inhibition studies to the design of clinical reversal protocols. Int J Cancer, 1993 Oct 21, 55(4), 667 - 71 Role of cell cholesterol in modulating vincristine uptake and resistance; Pallares-Trujillo J et al.; The relationship between cell-membrane permeability to vincristine and cholesterol/phospholipid levels was studied in L5178Y murine leukemic lymphoblasts and in 2 multidrug-resistant cell sublines, VCR/P60 and VCR/P200, which expressed increasing levels of vincristine resistance . The uptake of 3H-vincristine was measured in all cell lines and in cholesterol-depleted and -reloaded L5178Y and VCR/P200 cells . The initial rate of drug entry in resistant cells was lower than that measured in the parental cell line and it decreased as the relative resistance increased . An increment of cholesterol content, characterized in resistant cells, was directly proportional to the relative resistance to vincristine . Cholesterol depletion in both sensitive and resistant cells resulted in an increase in the rate of vincristine uptake, which reverted to the respective basal levels when each cell line was cholesterol-reloaded . The rate of drug uptake was inversely correlated with the molar ratio of cholesterol to phospholipids . Although both VCR/P cell sublines, but not the sensitive parental cells, expressed the P-glycoprotein in their plasma membrane, there were no differences in drug efflux and retention between resistant and parental cells . These results indicate that cholesterol modulates the permeation of vincristine through the plasma membrane and strongly suggest that increased levels of cholesterol/phospholipid account for the lower drug accumulation and greater resistance in these multidrug-resistant cells. Int J Cancer, 1993 Oct 21, 55(4), 636 - 9 Flunarizine as a modulator of doxorubicin resistance in human colon-adenocarcinoma cells; Silvestrini R et al.; The potential of the calcium-entry blocker flunarizine in modulating the cytotoxicity of doxorubicin was investigated in human colon-adenocarcinoma cell lines sensitive to (LoVo) or with experimentally induced resistance (LoVo/DX) to doxorubicin . Exposure to 1 to 2 micrograms/ml flunarizine for intervals of up to 24 hr did not affect cell survival in either line . Simultaneous exposure to flunarizine and doxorubicin for 1 hr selectively enhanced doxorubicin activity in the resistant cell line and not in the sensitive cell line . In particular, the doxorubicin concentration able to reduce cell survival by 50% dropped to one third . Moreover, simultaneous exposure to flunarizine significantly increased intracellular doxorubicin accumulation, as evaluated by fluorescence spectrophotometry . Again, flow-cytometric analysis showed hyperpolarization of the membrane in resistant cells, starting from 15 min of exposure to 2 micrograms/ml flunarizine . Finally, in LoVo/DX cells, which normally express gp170, a 24-hr treatment with flunarizine markedly reduced the immunoreactivity of cells with 2 monoclonal antibodies (MAb57 and MRK16) directed against different external epitopes of the glycoprotein . The results from our study indicate the ability of flunarizine to positively modulate doxorubicin-resistance in human colon-adenocarcinoma cells expressing the multidrug-resistance phenotype. J Natl Cancer Inst, 1993 Oct 20, 85(20), 1685 - 90 Measurement of cremophor EL following taxol: plasma levels sufficient to reverse drug exclusion mediated by the multidrug-resistant phenotype; Webster L et al.; BACKGROUND: Paclitaxel (Taxol) is the first of a new class of cytotoxic agents with activity against tumors resistant to other drugs . For clinical use, paclitaxel is currently formulated in a vehicle of 50% ethanol and 50% polyethoxylated surfactant Cremophor EL (Cremophor) . We have previously shown that Cremophor will block the P-glycoprotein drug efflux pump responsible for the multidrug-resistant phenotype . Overexpression of P-glycoprotein is one mechanism of in vitro resistance to a number of currently used cytotoxic agents including paclitaxel . PURPOSE: Our aim was to develop a bioassay to measure plasma levels of Cremophor and to determine whether or not plasma levels of Cremophor achieved during paclitaxel therapy are sufficient to inhibit the activity of the P-glycoprotein . METHODS: All patients studied had histologically proven, advanced ovarian carcinoma with measurable or evaluable disease and had received at least one prior platinum-containing regimen . The bioassay used flow cytometry to measure the increase in equilibrium intracellular daunorubicin levels in multidrug-resistant human T-cell leukemia cells (CEM/VLB100) in the presence of a series of concentrations of Cremophor . Levels of Cremophor were measured in plasma from 21 patients after a 3-hour infusion of 135 or 175 mg/m2 paclitaxel . Both dose levels were given following premedication with oral dexamethasone, intravenous promethazine hydrochloride, and intravenous cimetidine . The Cremophor bioassay involved incubation of CEM/VLB100 cells (5 x 10(5)) for 1 hour with 2 micrograms/mL daunorubicin in 0.5 mL HL-1 medium plus 0.5 mL plasma prior to flow cytometric analysis . Pretreatment plasma was used to derive a standard curve for the effect of Cremophor on equilibrium daunorubicin levels . All measurements were done in triplicate . RESULTS: In vitro experiments indicated that, for maximal inhibition of P-glycoprotein activity, concentrations of Cremophor of 0.1% (vol/vol) were required . At the end of a 3-hour infusion of paclitaxel, plasma levels of Cremophor in 19 of 21 patients were 0.1% or higher and 0.09% in the remaining two . Concentrations of 5-20 microM paclitaxel dissolved in ethanol without Cremophor did not inhibit P-glycoprotein in this assay . CONCLUSION: The concentrations of Cremophor measured in plasma drawn from patients after a 3-hour infusion of paclitaxel at 135 or 175 mg/m2 were found to be sufficient to inhibit P-glycoprotein activity in vitro . IMPLICATIONS: The efficacy of paclitaxel against some tumors may be aided by its administration in a vehicle solution containing Cremophor in quantities that reach concentrations in the plasma sufficient to reverse multidrug resistance of neoplastic cells. Biochem Pharmacol, 1993 Oct 19, 46(8), 1421 - 4 Chloroquine resistance in Plasmodium falciparum is not reversed by BIBW-22, a compound reversing the multidrug resistance phenotype in mammalian cancer cells; Dieckmann-Schuppert A et al.; The pteridine derivative BIBW-22 (4-{N-(2-hydroxy-2-methyl-propyl)-ethanolamino}-2,7-bis(cis-2,6-di methyl-morpholino)-6-phenylpteridine), which had been developed for the treatment of multidrug-resistant cancer and binds to P-glycoprotein, was tested against chloroquine resistant Plasmodium falciparum strains in culture . Based on the result that BIBW-22 enhanced rather than lowered chloroquine resistance in vitro, it is concluded that chloroquine resistance in malaria parasites may not be mechanistically linked to the multidrug-resistant phenotype of chloroquine resistant P . falciparum. Biochemistry, 1993 Oct 19, 32(41), 11042 - 56 Lower electrical membrane potential and altered pHi homeostasis in multidrug-resistant (MDR) cells: further characterization of a series of MDR cell lines expressing different levels of P-glycoprotein; Roepe PD et al.; Recently {Roepe, P.D . (1992) Biochemistry 31, 12555-12564}, increased steady-state levels of chemotherapeutic drug efflux from multidrug-resistant (MDR) myeloma cells were correlated with intracellular alkalinization . To better understand elevated pHi in MDR cells, Na(+)- and Cl-dependent recovery of pHi upon intracellular acid or alkaline shock has been examined for this same series of MDR cell lines . In agreement with another recent report {Boscoboinik, D., Gupta, R.S., & Epand, R.M . (1990) Br . J . Cancer 61, 568-572}, we find that the rate of Na(+)-induced alkalinization after an intracellular acid shock is increased in the MDR cells, relative to the drug-sensitive parent . Interestingly, we also now find that mRNA encoding the human Na+/H+ exchanger (NHE) is overexpressed in these MDR cells, but the level of overexpression does not correlate with the relative drug resistance or steady-state pHi . It is also found that the efficiency of Cl(-)dependent reacidification of pHi, after an intracellular alkaline shock is reduced in the MDR cells . This effect appears to correlate with the relative expression of MDR protein, but not the relative expression of Cl-/HCO3- exchanger (AE), which we now find is also altered in the series of cells . Since elevated pHi will increase delta pH across the plasma membrane, we have also measured the electrical potential for these cells using three different methods . Most interestingly, the magnitude of the plasma membrane electrical potential (delta psi) decreases concomitant with increased expression of the MDR protein . Energy provided by increased delta pH compensates for the lowered delta psi, such that the total electrochemical membrane potential (delta mu H+) remains similar among the cells in this series (delta mu H+ = delta psi - Z delta pH) . These data, along with other recent experiments that associated an increased Cl- conductance with the expression of MDR protein {Valverde, M., Diaz, M., Sepulveda, F.V., Gill, D.R., Hyde, S.C., & Higgins, C.F . (1992) Nature 355, 830-833}, are consistent with a model for MDR protein-mediated multidrug resistance that does not entail direct active transport of lipophilic drugs by the MDR protein. Biochem Pharmacol, 1993 Oct 19, 46(8), 1317 - 26 The efflux of anthracyclines in multidrug-resistant cell lines; Coley HM et al.; In order to address the association of enhanced drug efflux with the multidrug-resistant (MDR) phenotype, we have studied the cellular pharmacokinetics of anthracyclines in the P-glycoprotein (Pgp)-positive MDR cell lines H69/LX4 (human small cell lung cancer) and EMT6/AR1.0 (mouse mammary tumour) . Both doxorubicin (DOX) and daunorubicin (DNR) were accumulated to a lesser extent and effluxed at a higher rate by MDR cells than by their drug-sensitive counterparts . In contrast, the 9-alkyl substituted compound, aclacinomycin A (ACL), was accumulated and effluxed from parent and MDR cells at an identical rate . In experiments designed to examine energy-dependent efflux, DOX and DNR were shown to be efficiently effluxed against the concentration gradient in the presence of glucose . However, in the same experiments the analogues ACL and Ro 31-3294 (9-alkyl and morpholinyl substituted), which have previously been shown to retain activity against MDR cell lines, were accumulated and effluxed at identical rates in parent and MDR EMT6 cells . Hence, 9-alkyl and morpholinyl substituted compounds appear to behave less favourably as substrates for energy-driven drug efflux by Pgp-positive MDR cells than do DOX or DNR . Resistance modifiers verapamil and cyclosporin A appeared to abolish energy-dependent efflux for DOX and DNR in both the EMT6 and H69 MDR lines whereas they had no effect on the cellular efflux of ACL . The altered cellular pharmacology in MDR cell lines may provide a rational basis for the use of modified anthracycline analogues (e.g . 9-alkyl and morpholinyl (substituted) and resistance of modifying agent in the treatment of tumours expressing a Pgp-mediated phenotype. Cancer Lett, 1993 Oct 15, 74(1-2), 37 - 41 Inhibition of MDR1 gene expression by H-87, a selective inhibitor of cAMP-dependent protein kinase; Kim SH et al.; N-{2-(p-bromocinnamylmethylamino) ethyl}-5-isoquinolinesulfonamide (H-87), a newly synthesized inhibitor of protein kinase A, significantly decreased the drug resistance of multidrug resistant human U937/M cells, mouse FM3A/M and P388/M cells . Northern blot analysis showed MDR1 gene expression was decreased in H-87-treated P388 M cells . H-87 inhibited the activity of MDR1 (multidrug resistance-1) promoter in a dose-dependent manner in transient expression assay . In contrast, the expression of c-raf-1 gene significantly enhanced the activity of MDR1 promoter . We therefore examined the effect of H-87 on MDR1 gene expression in c-raf-1 transfected CV-1 cells (CV-1/raf) . A significant decrease in the level of MDR1 mRNA was observed after H-87 treatment of the CV-1/raf cells . These results suggest that inhibition of MDR1 gene expression by H-87 is associated with circumvention of drug resistance in MDR cells. Proc Natl Acad Sci U S A, 1993 Oct 15, 90(20), 9735 - 8 Changes in intra- or extracellular pH do not mediate P-glycoprotein-dependent multidrug resistance; Altenberg GA et al.; P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) is thought to result from active extrusion of lipid-soluble, titratable chemotherapeutic agents . Given the lack of demonstration of coupling between ATP hydrolysis and drug transport, the resistance to chemically unrelated compounds, and findings of elevated intracellular pH (pHi), it has been proposed that reduced intracellular accumulation of drugs in MDR is due to changes in the pH difference across the plasma membrane . Elevation of pHi or decrease in local extracellular pH (pHo) could reduce the intracellular accumulation of the protonated chemotherapeutic drugs and account for Pgp-mediated MDR . Alternatively, changes in pHi or pHo could increase drug efflux by other mechanisms, such as coupled transport involving H+ or OH-, or allosteric effects on Pgp or other proteins . Both mechanisms could operate independently of the charge of the substrate . The possibility of a role of pHi in drug efflux is important to test because of the clinical significance of the phenomenon of MDR of tumors . We tested this hypothesis and found that MDR can occur in cells with low, normal, or high pHi . Further, resistant cells exhibited reduced steady-state drug accumulation and increased efflux without changes in local pHo . Finally, acute changes in pHi had no appreciable effect on Pgp-mediated drug efflux . We conclude that Pgp-mediated MDR is not a consequence of changes in pHi or pHo. J Biol Chem, 1993 Oct 15, 268(29), 21493 - 6 Fluorescent cellular indicators are extruded by the multidrug resistance protein; Homolya L et al.; In this report we show that NIH-3T3 mouse fibroblasts stably expressing the human multidrug transporter (MDR1 or P-glycoprotein), in contrast to the control NIH-3T3 cells, actively extrude the hydrophobic acetoxymethyl ester (AM) derivatives used for cellular loading of various fluorescent calcium and pH indicators . This dye extrusion is blocked by competing substrates and inhibitors of the multidrug transporters, e.g . by verapamil, vincristine, sodium orthovanadate, oligomycin, and a monoclonal anti-MDR1 antibody . The hydrophilic free acid forms of the indicators are not exported by MDR1 . We also demonstrate that in isolated cell membranes the MDR1-ATPase, similar to that by known substrates of the transporter, is stimulated by the AM derivatives of fluorescent dyes whereas the free acid forms of the dyes are without effect . Since (i) the AM derivatives of the fluorescent indicators rapidly permeate the cell membrane and are readily cleaved by high activity and large capacity cytoplasmic esterases and (ii) the free acid forms are not substrates for export by MDR1, the observations above suggest that dye extrusion by MDR1 may occur without a cytoplasmic appearance of the AM compounds . These data also call attention to the possible interaction of widely used hydrophobic fluorescent indicators with MDR1 and offer an efficient detection of MDR1-expressing tumor cells as well as a screening method for examining drug interactions with the multidrug transporter. Schweiz Rundsch Med Prax, 1993 Oct 5, 82(40), 1108 - 11 {Disseminated tuberculosis with a multiresistant strain of Mycobacterium tuberculosis in an HIV-infected Swiss male}; Gunthard H et al.; Multidrug-resistant M . tuberculosis in HIV-infected people has not yet been reported in Switzerland, and there have been no nosocomial epidemics as they have recently occurred in the USA . We present the case of a 38-ear-old HIV-infected man who developed disseminated tuberculosis as AIDS-defining disease . Initially he was treated with isoniazid, pyrazinamide and rifampin . Due to the emergence of resistance to isoniazid and streptomycin, ethambutol was added for one month . Later the therapy was changed back to the initial three drugs . The patient responded well to this therapy, but five months later developed a relapse . In addition to the originally diagnosed double-drug resistance, a reduced susceptibility to rifampin appeared . Ethambutol, ciprofloxacin and amikacin were added to the original three-drug regimen . This resulted in rapid clinical improvement, although sputum cultures remained positive for M . tuberculosis two months later . This isolate was resistant to pyrazinamide . For that reason pyrazinamide was replaced by clofazimine . 14 months after diagnosis the patient died of hepatic failure . Because there was a delay in isolation of one week, 37 potentially exposed health care workers were tested by the Mantoux skin test . No conversions were observed . This case report demonstrates that tuberculosis in HIV-infected patients in Switzerland may be caused by multidrug-resistant M . tuberculosis . We propose that until the results of a susceptibility assay are known, a four-drug combination should be used initially in this patient group. Schweiz Rundsch Med Prax, 1993 Oct 5, 82(40), 1105 - 7 {Multiresistant tuberculosis in New York}; Salfinger M; New Yorkers have to deal with a tuberculosis situation which is of greater extent and a health-care system which is less prepared than in the sixties . Poverty and the HIV epidemic have had a negative impact on the control of tuberculosis . The emergence of nosocomial multidrug-resistant tuberculosis has created an explosive situation . In 1991, rifampin resistance was 33% in patients who had received antituberculosis therapy and 10% among the patients who had never been treated. Schweiz Rundsch Med Prax, 1993 Oct 5, 82(40), 1096 - 100 {Multiresistant tuberculosis in the Zurich Höhenklinik Wald from 1984 to 1992}; Linnenberg HS et al.; Out of a total of 386 patients with culture-proven tuberculosis, ten cases of multidrug-resistant tuberculosis were treated in a high altitude chest clinic in Switzerland between 1984 and 1992 . Two patients, Swiss, were alcoholics, the other eight foreigners . None of the patients were HIV-positive . Both Swiss had primary INH resistance, then developed secondary INH/RMP resistance due to poor compliance . All patients were treated with at least two additional in-vitro-sensitive drugs as well as with INH . Five patients underwent resection of lung parenchyma . One of these patients has had three operations and remains the sole therapy failure . One patient died before an operation could be performed . All others are well . Possible reasons for multidrug-resistance and the management of the ten cases are discussed in accordance with the literature. Lancet, 1993 Oct 2, 342(8875), 841 - 4 Molecular approach to identifying route of transmission of tuberculosis in the community; Genewein A et al.; There is growing concern that tuberculosis is spread in Europe in the way that it is in the USA . We have used DNA "fingerprinting" in a systematic evaluation of tuberculosis cases notified in our community to uncover foci of transmission . An IS6110 probe was used to test all isolates from culture-confirmed tuberculosis cases (163 patients) notified in 1991-92 in the Canton of Berne . In total, 45 patients (27.6%), potentially linked on the basis of restriction fragment length polymorphism, were investigated epidemiologically . The largest group (n = 22) included members of a defined social group (drug addicts, homeless persons, alcoholics), from whom tuberculosis spread to the general population . A key patient developed multidrug-resistant tuberculosis during the surveillance period . This population study showed that (i) extensive transmission of Mycobacterium tuberculosis is now taking place in Europe in the same social setting as in the USA; (ii) there is definite "spillover" to the general population; (iii) the dimensions of the problem cannot be recognised easily by routine public health service activities because of the complexity of the transmission network; and (iv) multidrug-resistant tuberculosis develops in this setting. J Cell Physiol, 1993 Oct, 157(1), 110 - 8 Increased epidermal growth factor receptor in an estrogen-responsive, adriamycin-resistant MCF-7 cell line; Dickstein B et al.; We examined the expression of the estrogen and epidermal growth factor (EGF) receptors in a drug-resistant subline of MCF-7 cells in order to study potential alterations in hormone dependence or in the growth factor pathway that could be related to the development of drug resistance in human breast cancer . The drug-resistant subline was derived from MCF-7 cells by selection with Adriamycin in the presence of the P-glycoprotein antagonist, verapamil, to prevent acquisition of the classical multidrug resistance phenotype . The Adriamycin-resistant cells retain estrogen-binding, estrogen-responsive monolayer growth, and estrogen-dependent tumorigenesis . Estrogen-binding studies demonstrate 1.4 x 10(6) sites per cell with unaltered affinity when compared to parental MCF-7 cells, which have 2.7 x 10(5) sites per cell . An increase in expression of EGF receptor, eight to 12-fold, occurred early in the selection for drug resistance, and appears to be unrelated to verapamil exposure, since cells maintained in Adriamycin without verapamil also have increased EGF receptor expression . Partially drug-sensitive revertants carried a verapamil, but out of Adriamycin, demonstrate a decline in EGF receptor expression . We postulate that activation of growth factor pathways in drug-resistant cells may enhance mechanisms of drug resistance, or provide mitogenic stimuli for cells to recover after damage by drug exposure. Cancer Immunol Immunother, 1993 Oct, 37(5), 337 - 42 Drug resistance in rat colon cancer cell lines is associated with minor changes in susceptibility to cytotoxic cells; Van de Vrie W et al.; The development of resistance to anticancer drugs urges the search for different treatment modalities . Several investigators have reported the concomitant development of drug resistance and resistance to natural killer (NK), lymphokine-activated killer (LAK) or monocyte/macrophage cell lysis, while others described unchanged or even increased susceptibility . We investigated this subject in the rat colon carcinoma cell line, CC531-PAR, which is intrinsically multidrug-resistant (MDR), and in three sublines derived from this parental cell line: a cell line with an increased MDR phenotype (CC531-COL), a revertant line from CC531-COL (CC531-REV), which demonstrates enhanced sensitivity to anticancer drugs of the MDR phenotype, and an independently developed cisplatin-resistant line (CC531-CIS) . In a 4-h 51Cr-release assay we found no difference in susceptibility to NK cell lysis . No significant differences in lysability by adherent LAK (aLAK) cells were observed in a 4-h assay . In a prolonged 20-h 51Cr-release assay an enhanced sensitivity to aLAK-cell-mediated lysis was observed in the revertant, P-glycoprotein-negative cell line and in the cisplatin-resistant cell line (CC531-CIS) . None of the cell lines was completely resistant to lysis by aLAK cells . Therefore, a role for immunotherapy in the treatment of drug-resistant tumors remains a realistic option. Cancer Res, 1993 Oct 1, 53(19), 4658 - 64 Effect of verapamil on doxorubicin cardiotoxicity: altered muscle gene expression in cultured neonatal rat cardiomyocytes; Akimoto H et al.; Verapamil reverses multidrug resistance acquired by cancer cells during treatment with chemotherapeutic agents such as doxorubicin by inhibiting the function of P-glycoprotein . Verapamil has also been suggested to potentiate the cardiotoxicity of doxorubicin . We have recently demonstrated that selective inhibition of cardiac muscle gene expression is among the earliest events in doxorubicin cardiotoxicity . To explore the influence of verapamil on doxorubicin cardiotoxicity, we evaluated {14C}-doxorubicin accumulation, cardiac muscle gene expression by Northern blot analysis, and ultrastructural changes in cultured cardiomyocytes in the presence and absence of verapamil . Treatment with a combination of doxorubicin and verapamil for 24 h did not augment doxorubicin accumulation in cardiomyocytes, although substantial augmentation of doxorubicin accumulation by verapamil in cardiac fibroblasts was observed . Further, treatment with verapamil for 24 h did not augment the decrease in expression of muscle genes induced by doxorubicin (myosin light chain 2 slow, troponin I, M isoform creatine kinase) . However, we found that verapamil reduced alpha-actin gene expression in a direct, doxorubicin-independent manner . Furthermore, the effect of doxorubicin plus verapamil on alpha-actin gene expression was additive over a wide range of doxorubicin and verapamil concentrations, resulting in a selective augmentation of doxorubicin-induced inhibition of gene expression for this single muscle protein gene . This was reflected in a substantial increase in cardiac myocyte damage when treatment with verapamil and doxorubicin was compared to treatment with doxorubicin alone by thin section electron microscopy . This suggests a possible mechanism by which verapamil may potentiate doxorubicin cardiotoxicity. Cancer Res, 1993 Oct 1, 53(19), 4595 - 602 In vitro and in vivo reversal of multidrug resistance by GF120918, an acridonecarboxamide derivative; Hyafil F et al.; N-(4-{2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl}- phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918) has been selected from a chemical program aimed at identifying an optimized inhibitor of multidrug resistance (MDR) . The potency of GF120918 is assessed by dose-dependent sensitization of CHRC5, OV1/DXR and MCF7/ADR cells to the cytotoxicity of doxorubicin and vincristine respectively: GF120918 fully reverses multidrug resistance at 0.05 to 0.1 microM and is half maximally active at 0.02 microM . The spectrum of drugs sensitized by GF120918 coincides with those having the classical MDR phenotype . In CHRC5 cells, 0.01-0.1 microM GF120918 enhances the uptake of {3H}daunorubicin and blocks the efflux from preloaded cells . It is also shown that GF120918 is still active several hours after being taken away from the culture medium showing that it is not, like verapamil, effluxed rapidly by P-glycoprotein . GF120918 effectively competes with {3H}azidopine for binding P-glycoprotein, pointing to this transport membrane protein as its likely site of action . After i.v . administration to mice, GF120918 penetrates thoroughly various organs that have a tissue level/blood level ratio above 10 . It is eliminated from organs and blood with a half-time of approximately 2.7 h . It is well absorbed after p.o . administration . In mice implanted i.p . with the MDR P388/Dox tumor, a single i.v . or p.o . dose of GF120918 restores sensitivity of the tumor to a single i.p . dose (5 mg/kg) of doxorubicin administered 1 h later . A statistically significant effect is observed at 1 mg/kg GF120918 i.v . and maximal effect is reached at 5 mg/kg . Similarly, whereas neither drug alone is effective, GF120918 (10 mg/kg i.p.) associated with doxorubicin (5 mg/kg i.p.) inhibits the growth of the moderately MDR C26 tumor implanted s.c . as assessed by tumor size at day 19 . GF120918 does not modify significantly the distribution or the elimination of doxorubicin in mice ruling out the possibility that the antitumor effects seen might be explained by pharmacokinetic interactions. Br J Cancer, 1993 Oct, 68(4), 691 - 4 MDR1 gene expression in primary colorectal carcinomas; Pirker R et al.; The expression of the MDR1 gene, a multidrug resistance gene, was prospectively determined in 113 primary colorectal carcinoma specimens and correlated with clinical data including survival durations of the patients . MDR1 RNA was detected in 65% of the carcinomas . No expression of the MDR2 gene was seen, MDR1 gene expression was independent of age and sex of the patients, size and histologic grading of the tumour, lymph node involvement and distant metastasis . Kaplan-Meier analysis revealed that the durations of both relapse-free survival and overall survival were not different between patients with MDR1 RNA positive tumours and those with MDR1 RNA negative tumours. Ann Trop Med Parasitol, 1993 Oct, 87(5), 443 - 9 Resistance of Plasmodium falciparum to antimalarial drugs in Equatorial Guinea; Roche J et al.; One hundred and sixty-six children from Equatorial Guinea, all under 10 years of age and with acute uncomplicated falciparum malaria, were randomly allocated to four groups and treated with one of the following regimens: chloroquine or amodiaquine (25 mg base/kg body weight over 3 days), quinine (8 mg/kg every 8 h for 3 or 5 days), and sulphadoxine-pyrimethamine (25-1.25 mg/kg, in one dose) . The parasite clearance rates up to day 14 were 28% with chloroquine, 74% with amodiaquine, and 95% with quinine or sulphadoxine-pyrimethamine . The times required to clear asexual blood forms of Plasmodium falciparum in sensitive cases were 64, 70, 73 and 65 h, respectively . Although quinine and sulphadoxine-pyrimethamine are equally effective, quinine is recommended for treatment of multidrug-resistant malaria in paediatric patients, essentially because of the risk of serious reactions to sulpha drugs . Health providers are, however, encouraged to keep supplies of sulphadoxine-pyrimethamine as an option and to refer patients quickly, if required. Cell Biol Int, 1993 Oct, 17(10), 907 - 17 Multidrug resistance and behavioural phenotype of cancer cells; Bashir I et al.; Resistance to cytotoxic chemotherapy is a major obstacle preventing successful treatment of cancer, allowing dissemination of tumour metastases, and may be viewed as the ultimate cause of death in the majority of patients with a malignant disease . Although cytotoxic chemotherapy is classically employed to produce maximal killing of malignant cells, the therapeutic doses of individual drugs required to achieve this objective are, in general, highly toxic to non-neoplastic host tissues . However, there are several different aspects of cancer cell biology, distinct from their susceptibility to cytotoxicity, that might be exploited in order to alter the behavioral phenotypes of malignant neoplasms . Such features include regulation of cell proliferation, tumorigenicity and metastatic potential . Non-cytotoxic modulation of malignant cells may provide an alternative, and more effective, method of controlling the aggressive behaviour of cancer cells while exhibiting less iatrogenic morbidity and mortality than the therapeutic regimens presently employed. Arzneimittelforschung, 1993 Oct, 43(10), 1118 - 21 Increase of alkaline phosphatase in multidrug-resistant tumor cells and their cross-resistance to 6-thioguanine; Efferth T et al.; The expression of alkaline phosphatase (AP) was analyzed in multidrug-resistant (MDR) tumor cells (sarcoma 180, lung carcinoma, and renal cell carcinoma cell lines) by means of immunocytochemistry . MDR cell cultures showed an overexpression of AP and a cross-resistance to 6-thioguanine (6-TG, CAS 154-42-7) . Significant correlations between AP expression and doxorubicin or vincristine resistance and P-glycoprotein (P-170) expression were found in these cell cultures . A specific AP inhibitor, levamisole, reversed resistance to 6-TG, but not to doxorubicin . This indicates that 6-TG resistance is certainly associated to P-170 but a causal function of AP for the development of MDR does not exist. Md Med J, 1993 Oct, 42(10), 981 - 7 Tuberculosis: optimism, pessimism, frustration; Matuszak DL et al.; The re-emergence of tuberculosis as a serious public health threat has captured the nation's attention . Tuberculosis more frequently affects the ethnic minorities and the socially and economically disadvantaged residents of Maryland . Effective regimens are available to treat and prevent tuberculosis . Consistent application of proven infection control measures and of treatment and prevention regimens will prevent the development and spread of multidrug-resistant tuberculosis. Antimicrob Agents Chemother, 1993 Oct, 37(10), 2054 - 8 Direct, automated detection of rifampin-resistant Mycobacterium tuberculosis by polymerase chain reaction and single-strand conformation polymorphism analysis; Telenti A et al.; A rapid screening test was recently established for the detection of mutations in the rpoB gene of Mycobacterium tuberculosis, a region identified as the locus for rifampin resistance (Rifr) . The detection method involved the amplification by polymerase chain reaction (PCR) of the Rifr region and the identification of mutations by single-strand DNA conformation polymorphism analysis (SSCP) of the amplification products . Experience using two different PCR-SSCP formats for the evaluation of BACTEC cultures and sputum is presented here; the previously described manual procedure for the detection for the detection of radiolabelled amplification products and an automated SSCP by which fluorescein-labelled products were detected on a Pharmacia DNA sequencer apparatus . All 17 different Rifr mutations known to date were consistently detected . PCR-SSCP could be used for the evaluation of minimally grown cultures (BACTEC 12B medium with a growth index of < or = 100) and for direct screening of microscopically positive sputa with greater than 10 organisms per field (magnification, x250) . Implementation of this technique could result in rapid detection of rifampin resistance in M . tuberculosis, a marker of multidrug-resistant tuberculosis. Photochem Photobiol, 1993 Oct, 58(4), 623 - 6 Sites of photodamage by the iminium salt of a copper octaethylbenzochlorin; Kessel D; Because the benzochlorin derivative copper (II) alpha-meso-N,N'-dimethyloctaethylbenzochlorin iminium chloride (CDS1) is not fluorescent, sites of drug localization in L1210 cells were detected by indirect methods involving using a series of fluorescent probes . The CDS1-mediated cytotoxicity was associated with mitochondrial damage, a decreased membrane potential and an increase in the heterogeneity of membrane sites of binding of a polar analog of diphenylhexatriene . Although CDS1 is a cationic compound, its accumulation was not impaired in a cell line exhibiting the multidrug resistance phenotype. Br J Surg, 1993 Oct, 80(10), 1259 - 61 Multidrug-resistant colonic cancer cell line LoVoDx is efficiently killed by lymphokine-activated killer cells from patients with carcinoma of the colon; Mooney EF et al.; Multidrug-resistant (MDR+) cancer cells have the ability to grow in the presence of cytotoxic concentrations of antineoplastic drugs as a result of possessing the transmembrane drug efflux pump p-glycoprotein . The MDR+ colonic cancer cell line LoVoDx (derived from the drug-sensitive line LoVo) was tested for sensitivity to lymphokine-activated killer (LAK) cell-mediated toxicity . LAK cells were cultured from patients with colonic cancer and from matched controls with benign disorders . LAK cells from patients with cancer were as effective as those from controls in mediating cytotoxicity . The MDR+ cell line was significantly more sensitive to LAK cell-mediated cell killing than its parental drug-sensitive line LoVo (P < 0.05) . These results indicate a possible role for adoptive immunotherapy in MDR+ tumours expressing p-glycoprotein. Mol Pharmacol, 1993 Oct, 44(4), 767 - 74 Dual topoisomerase I and II inhibition by intoplicine (RP-60475), a new antitumor agent in early clinical trials; Poddevin B et al.; The mechanisms of action of intoplicine (RP-60475), a 7H-benzo{e}pyrido{4,3-b}indole derivative that is presently in early clinical trials, have been investigated . Intoplicine induced both topoisomerase I- and II-mediated DNA strand breaks, using purified topoisomerases . The topoisomerase cleavage site patterns induced by intoplicine were unique, relative to those of camptothecin, 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), and other known topoisomerase inhibitors . Both topoisomerase I- and II-induced DNA breaks decreased at drug concentrations higher than 1 microM, which is consistent with the DNA-intercalating activity of intoplicine . DNA damage was investigated in KB cells in culture by using alkaline elution . Intoplicine induced single-strand breaks (SSB) in a bell-shaped manner with respect to drug concentration (maximum frequency at 1 microM approximately 220 rad-equivalents) . SSB formation was fast, whereas reversal after drug removal was slow . Similar bell-shaped curves were obtained for DNA double-strand breaks (DSB) and DNA-protein cross-links . SSB and DNA-protein cross-link frequencies were approximately equal, and no protein-free breaks were detectable, indicating the protein concealment of the breaks, as expected for topoisomerase inhibition . Comparison of SSB and DSB frequencies indicated that intoplicine produced a significant amount of SSB not related to DSB, which is consistent with concomitant inhibition of both DNA topoisomerases I and II in cells . Data derived from resistant cell lines indicated that multidrug-resistant cells were cross-resistant to intoplicine but that m-AMSA- and camptothecin-resistant cells were sensitive to intoplicine . Hence, intoplicine might circumvent topoisomerase I-mediated and topoisomerase II-mediated resistance by poisoning both enzymes simultaneously. Clin Pharmacol Ther, 1993 Oct, 54(4), 421 - 9 Modulation of vinblastine resistance with cyclosporine: a phase I study; Samuels BL et al.; OBJECTIVE: Tumor cell resistance is a major cause of failure to cure advanced malignancies . Multidrug resistance is thought to be an important mechanism of such resistance . Our aims were to identify doses of cyclosporine that would achieve blood levels effective in modulating multidrug resistance to vinblastine and to evaluate the toxicities and maximum tolerated dose of cyclosporine when administered in conjunction with vinblastine . METHODS: We conducted a phase I trial of vinblastine and escalating doses of cyclosporine . Cyclosporine was given by continuous intravenous infusion over 120 hours and vinblastine was administered by continuous infusion from hour 12 to hour 108 . Sixty-two patients entered the trial, of whom 60 were evaluable . RESULTS: Cyclosporine was escalated from 1 to 15.6 mg/kg/day . Vinblastine doses were reduced to 1.6 and then 1.2 mg/m2/day because of increasing vinblastine toxicity at higher cyclosporine doses . The maximum tolerated dose of cyclosporine at 1.2 mg/m2/day vinblastine was 12.5 mg/kg/day; at this dose level, mean blood cyclosporine level was 1.25 +/- 0.41 mumol/L . Significant nephrotoxicity was observed at higher cyclosporine doses in two of four patients . Nephrotoxicity was not significant at doses at or lower than this maximum tolerated dose and was not cyclosporine dose dependent . Myelosuppression, neurotoxicity, and transient hyperbilirubinemia were observed and were cyclosporine dose dependent . CONCLUSIONS . Cyclosporine by continuous infusion may be safely given in high doses concurrently with continuous-infusion vinblastine . Plasma levels of cyclosporine > or = 1 mumol/L can be sustained during vinblastine administration . No sustained effect on T-cell subsets was observed . Vinblastine toxicity is enhanced by cyclosporine in a dose-dependent fashion and correlates with cyclosporine-induced hyperbilirubinemia. J Environ Pathol Toxicol Oncol, 1993 Oct-Dec, 12(4), 193 - 7 Biological effects of PEMF (pulsing electromagnetic field): an attempt to modify cell resistance to anticancer agents; Pasquinelli P et al.; Pulsing Electromagnetic Field (PEMF) effects lead to a modification of the multidrug resistance (MDR) of cells in vitro and in vivo . The murine leukemic doxorubicin-resistant cell line, P388/Dx, subjected to PEMF irradiation in vitro, showed a significant difference in thymidine incorporation when the concentration of doxorubicin reached a level of 1 microgram/mL, which corresponds to the inhibition dose 50 (ID50) . The human lymphoblastic leukemia vinblastine-resistant cell line, CEM/VLB100, also showed a significant modification under the same experimental conditions at the in vitro ID50 corresponding to a vinblastine concentration of 100 ng/mL . BDF1 mice transplanted with P388/Dx cells also had an increase in their life span when doxorubicin was injected intraperitoneally in fractionated doses, while being subjected to PEMF irradiation. Proc Natl Acad Sci U S A, 1993 Oct 1, 90(19), 9209 - 13 Functional expression of mouse mdr1 in Escherichia coli; Bibi E et al.; We describe functional expression of the mouse multidrug-resistance protein (P-glycoprotein; P-gp) in an Escherichia coli mutant defective in the outer membrane protease ompT . Heterologously expressed mdr1 appears as an unglycosylated species with an apparent molecular mass of 140 kDa in the membrane of the mutant . Unglycosylated mdr1 retains the ability to bind the photoactivatable drug analog {125I}iodoarylazidoprazosin and confers resistance to tetraphenylphosphonium (TPP+) and tetraphenylarsonium (TPA+), known mdr1 substrates . In vivo resistance is linked to reduced cellular accumulation and energy-dependent efflux of the lipophilic cations . Surprisingly, discrete mutations in the predicted nucleotide binding folds of mdr1 that abolish drug resistance in mammalian cells have no apparent effect on TPA+ efflux via mdr1 in E . coli. J Infect Dis, 1993 Oct, 168(4), 1052 - 5 Transmission of multidrug-resistant Mycobacterium tuberculosis among persons with human immunodeficiency virus infection in an urban hospital: epidemiologic and restriction fragment length polymorphism analysis; Coronado VG et al.; From January 1990 to December 1991, 16 patients with multidrug-resistant tuberculosis (MDR-TB) caused by Mycobacterium tuberculosis resistant to isoniazid, rifampin, and streptomycin were diagnosed at Elmhurst Hospital . Compared with other TB patients, MDR-TB patients were more likely to have human immunodeficiency virus (HIV) infection (14/16 vs . 21/204, P < .001) and a prior admission (10/16 vs . 3/204, P < .001) . HIV-infected patients hospitalized for > 10 days within three rooms of an infectious MDR-TB patient had higher risk of acquiring MDR-TB than did HIV-infected patients with shorter hospitalizations or locations further from the MDR-TB patient(s) (6/28 vs . 2/90, P < .001) . Isolates of 6 of 8 MDR-TB patients in a chain of transmission were identical by restriction fragment length polymorphism DNA typing . Ambulation on the wards of inadequately masked TB patients and lack of negative pressure in isolation rooms probably facilitated transmission . This report documents nosocomial transmission of MDR-TB and underscores the need for effective isolation practices and facilities in health care institutions. Lung Cancer, 1993 Oct, 10(1-2), 1 - 12 Immunohistochemical study of P-glycoprotein distribution in lung cancer; Pujol JL et al.; Indirect immunoperoxidase was used to determine the reactivity of C219 (P-glycoCHEK C219, Centocor Diagnostics, Malvern, PA), a monoclonal antibody (Mab) with high affinity for an internal epitope of the P-glycoprotein encoded by the multidrug resistance (MDR1) gene, in 40 surgically resected primary lung tumours . C219 reactivity was qualitatively classified in seven small cell lung cancers (SCLC), 29 non small cell lung cancers (NSCLC), and four carcinoid tumours . Ploidy was analysed by means of static cytometry using a computer-assisted image processor following Feulgen staining of cytologic prints of 32/40 lung tumours . Indirect immunoperoxidase reactivities of Mabs S-L 11.14 and MOC-1 were also studied to characterize the expression of cluster 1 lung cancer antigens and hence to determine among the NSCLC those which expressed the neural cell adhesion molecule (NCAM) . Eighteen (45%) lung tumours strongly expressed P-glycoprotein as an immunostaining of many islets of malignant cells or almost all malignant cells . In addition, 8/40 tumours (20%) showed a weak reactivity (few immunostained cells) and 14/40 (35%) no reactivity . There was no difference of reactivity when NSCLC were compared with SCLC . The expression of P-glycoprotein in NSCLC did not vary significantly when the stage of disease was considered . Among the 29 NSCLC, 10 (36%) expressed S-L 11.14 and MOC-1 . The NCAM positive NSCLC did not show any difference of P-glycoprotein expression in comparison with NCAM negative ones . Finally, C219 immunoperoxidase reactivity did not significantly differ according to the ploidy status . In conclusion, the internal epitope of the P-glycoprotein encoded by the MDR1 gene is frequently expressed by lung tumours of any histological type . This expression is not higher in Stage III and IV lung cancers in comparison with Stage I and II ones, or in NSCLC in comparison with SCLC either . Thus, the C219 related epitope seems to have a weak implication in the lower chemosensitivity of both advanced stages and NSCLC. Leuk Lymphoma, 1993 Oct, 11(3-4), 239 - 48 Flow cytometric assessment of multidrug resistance (MDR) phenotype in acute myeloid leukaemia; Hart SM et al.; Forty one patients with acute myeloid leukemia (AML), including 27 at presentation and 14 relapsed or resistant cases, were assessed for laboratory evidence of the MDR phenotype . Leukaemic cells from all 41 cases were studied by immunocytochemistry using the JSB-1 monoclonal antibody and simultaneously by reverse transcription polymerase chain reaction (RT-PCR) to evaluate expression of the mdr 1 gene . Cells from 32/41 cases were also assessed for daunorubicin (DNR) accumulation and retention by flow cytometry (FC) . Nineteen of the 41 (46%) patients were positive for MDR by JSB-1 immunocytochemistry (11/27 {41%} at presentation and 8/14 {57%} relapsed or resistant cases) . Nine of the 19 (47%) P-gp positive, de novo patients achieved complete remission . 22 patients were negative by JSB-1 immunocytochemistry (16/27 {59%} at presentation and 6/14 {43%} of the relapsed or resistant cases) and 11/22 (50%) P-gp negative patients achieved a complete remission . Of the 32 patients assessed by FC, 7 (22%) were positive for the MDR phenotype with increased DNR accumulation and retention in the presence of the MDR reversing agent verapamil (VPM) . 6/7 of the FC positive cases were also JSB-1 positive, and 6 had additional poor risk features . Of the twenty five FC negative patients, 6 had received previous chemotherapy and 15 (60%) achieved complete remission . Mdr 1 mRNA levels were increased in all seven FC positive cases whereas only 7/19 JSB-1 positive cases had raised mdr 1 mRNA levels . These results suggest that the assessment of MDR status by immunocytochemistry using JSB-1 is not predictive of response to chemotherapy . Flow cytometric analysis of blast cells appears to correlate well with mdr 1 mRNA levels and may be a better predictor of treatment outcome. Oncology (Huntingt), 1993 Oct, 7(10), 23 - 8, 32; discussion 32, 35-8 Multidrug resistance: clinical relevance in acute leukemia; List AF; The multidrug resistance (MDR) phenotype represents an important major mechanism of resistance to anthracyclines and related natural products that lends itself to clinical exploitation . Overexpression of the mdr1 gene or its glycoprotein product has been linked to a number of poor prognostic factors in acute myeloid leukemia and adversely affects treatment outcome . Clinical trials are now under way testing pharmacologic modulators of MDR in acute leukemia . Although preliminary results are encouraging, MDR modulators may alter the clearance of some antineoplastics and thereby confound interpretation of randomized trials . This review examines diagnostic methods of MDR detection, its prevalence and impact in acute leukemia, and strategies for MDR reversal. J Histochem Cytochem, 1993 Oct, 41(10), 1573 - 7 Ultrastructural localization of daunomycin in multidrug-resistant cultured cells with modulation of the multidrug transporter; Rutherford AV et al.; We localized the chemotherapeutic drug daunomycin inside cultured cells by taking advantage of its inherent fluorescence . Multidrug-resistant cultured cells, in which the accumulation of daunomycin can be reversibly controlled with verapamil to block the multidrug transporter, were incubated in daunomycin and verapamil and the accumulated daunomycin was visualized with epifluorescence optics . After fixation under a variety of different conditions to make cells permeable to diaminobenzidine (DAB), the internal daunomycin was illuminated under the fluorescence microscope in the presence of DAB . Photooxidation of DAB in sites of fluorescing daunomycin (photoconversion) resulted in intracellular deposition of oxidized DAB product . These sites were then visualized by transmission electron microscopy . In cells in which the multidrug transporter was inhibited by verapamil, daunomycin was localized in the nucleus of cells by mild fixation conditions such as formaldehyde . Increasing amounts of glutaraldehyde in the fixative caused apparent quenching of the nuclear fluorescence but still allowed fluorescence to occur in other cell organelles, which were then well preserved . Daunomycin was found in the nuclear envelope, the endoplasmic reticulum, and in lysosomes in cells in which the multidrug transporter was inhibited . Lysosomal accumulation has been previously described and was expected because of the known accumulation of positively charged molecules in organelles with low pH . However, the accumulation of daunomycin in the nuclear envelope and endoplasmic reticulum has not been previously observed . These results clearly demonstrate the utility of fluorescence photoconversion methodology for the high-resolution ultrastructural localization of fluorescent materials. Cytometry, 1993 Oct, 14(7), 736 - 46 Evaluation of flow cytometry for multidrug resistance detection in low resistance K562 cells using daunorubicin and monoclonal antibodies; Van Acker KL et al.; We compared the effectiveness of two flow cytometric methods for the detection of the multidrug resistance (MDR) phenotype . The sensitivity of both methods depended on the ability to discriminate low resistance cells from sensitive ones . Therefore, K562 cells with decreasing vinblastine (VLB) resistance levels were examined, the lowest resistance level being nonmeasurable with a colorimetric MTT assay . The fluorescent drug daunorubicin (DNR) was measured in combination with two modulators of MDR, cyclosporin-A (CsA) and verapamil (Vp) in a functional flow cytometric assay . When compared to sensitive cells, DNR uptake levels at steady state were reduced in all resistant cell lines, except for the lowest resistant cell line . The effect of modulator, CsA, on DNR uptake was seen in all resistant sublines, compared to sensitive cells, except for the lowest resistant cells . In another assay, the P-glycoprotein (Pgp) expression was analysed with monoclonal antibodies, MRK16 and C219 . MRK16 was found to be the most sensitive antibody to screen for MDR+ cells, since we could show Pgp hyperexpression in all resistant cells . C219 reactivity became evident in cells possessing resistance factors higher than 5 . These results indicate that both the functional assay and the Pgp assay are sensitive to be used for screening of MDR+ cells. Int J Cancer, 1993 Sep 30, 55(3), 478 - 84 Binding properties of monoclonal antibodies recognizing external epitopes of the human MDR1 P-glycoprotein; Schinkel AH et al.; Monoclonal antibodies (MAbs) recognizing external epitopes of the human MDR1 P-glycoprotein have been used both for the detection of multidrug-resistant cells and as specific inhibitors of P-glycoprotein-mediated multidrug resistance . Using a panel of recently developed transfected or transgenic cell lines containing variants of the human MDR1 and MDR3 P-glycoproteins, we have compared the specificity and binding properties of the previously isolated MAbs MRK16, HYB-241, UIC2 and 4E3, and of the newly isolated MAb 7G4 . The removal of 1, 2 or all 3 of the N-glycosylation sites present in the first extracellular loop of MDR1 P-glycoprotein did not significantly affect the binding of these MAbs . In contrast, 20 amino acid deletion in the first extracellular loop of MDR1 P-glycoprotein completely abolished binding of UIC2, whereas the binding of all other MAbs was hardly affected . None of the MAbs tested bound detectably to cell lines containing a high level of the human MDR3 P-glycoprotein . The differences in the binding specificity between UIC2 and the other tested antibodies parallel the reported functional differences in the ability of these antibodies to inhibit P-glycoprotein-mediated drug efflux. Nature, 1993 Sep 30, 365(6445), 451 - 3 Convergent combination therapy can select viable multidrug-resistant HIV-1 in vitro; Larder BA et al.; The reverse transcriptase enzyme of human immunodeficiency virus type 1 (HIV-1) is the target for many inhibitors . Amino-acid substitutions in functional regions of the enzyme that abolish reverse transcriptase activity also prevent HIV-1 replication . But selection pressure by drugs such as AZT (3'-azido-3'deoxythymidine, zidovudine), ddI (2',3'-dideoxyinosine) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) causes outgrowth of resistant variants due to non-lethal mutations in the enzyme . Reports of synergy and lack of cross-resistance between reverse transcriptase inhibitors (refs 7, 9, 10, 12-14, 17, 18, 20, 21), plus the reversal of AZT resistance by mutations induced by ddI and NNRTIs, have indicated that specific drug combinations directed at reverse transcriptase might curtail resistance . Chow et al . extended this concept in a report that specific multiple combinations of resistance mutations in the reverse transcriptase can significantly impair HIV-1 replication . They concluded that evolutionary limitations may exist to prevent the emergence of multidrug resistance to inhibitors of reverse transcriptase . We report here that HIV-1 co-resistant to AZT, ddI and the NNRTI nevirapine can be readily selected in cell culture starting with dual AZT- and ddI-resistant virus . We found no evidence for 'replication incompatible' combinations of resistance mutations, although a mutation (M184-->V) conferring oxathiolane-cytosine nucleoside resistance in reverse transcriptase completely suppressed AZT resistance in a triple-resistant background . These in vitro observations suggest that triple drug combination therapy might ultimately result in co-resistant HIV-1, although they do not preclude assessment of such combinations for treatment of HIV-1 disease. Lancet, 1993 Sep 25, 342(8874), 756 - 7 Tuberculosis recurrence in Africa: true relapse or re-infection? Daley CL. PIP: HIV-seropositive patients respond to rifampicin-containing anti tuberculosis (TB) regimens as well as HIV-seronegative patients . In Nairobi, Kenya, 90% of HIV-positive patients who suffered a recurrence of TB first received a non-rifampicin-containing regimen . The overall unadjusted recurrence rate for HIV-positive patients was 16.7% while it was .5% for HIV-seronegative patients . An earlier, similar study in Zaire also showed a higher recurrence rate in HIV positive patients . A study in the US found a low recurrence rate among HIV-positive patients on rifampicin-containing regimens . A possible explanation for the higher recurrence rates may be that the thiacetazone-containing regimen is not as potent as the rifampicin containing regimen . Another possible explanation may be that no one knows the optimum duration of therapy for HIV-infected patients . 70% of HIV-positive patients in nairobi who suffered a recurrence of TB experienced a cutaneous-hypersensitivity reaction, resulting in a change in therapy and maybe affecting compliance . The researchers of the Nairobi study used DNA fingerprinting to determine whether the patients truly relapsed or were reinfected (cultures were available from only 3 HIV-positive patients) . 1 patient was reinfected by a different strain of Mycobacterium tuberculosis . 4 of 17 AIDS patients in New York City were reinfected with a different multidrug resistant strain of M . tuberculosis . Reinfection is more likely to happen in sub-Saharan Africa where TB an HIV are very prevalent . Physicians cannot accurately determine a treatment regimen in HIV-infected patients in an area of high prevalence of TB . Thus, we need to determine reinfection rates in HIV infected patients to plan a response . Cancer Res, 1993 Sep 15, 53(18), 4156 - 60 Inwardly rectifying K+ channels and volume-regulated anion channels in multidrug-resistant small cell lung cancer cells; Jirsch J et al.; Studies of multidrug-resistant H69AR cells which overexpress the multidrug resistance-associated protein, compared with drug-sensitive parental H69 cells and revertant H69PR cells, revealed an inwardly rectifying K+ channel current (conductance, 231 pS/pF) and increased volume-regulated anion current (limiting conductance, 2 nS/pF) . The anion current was selective for Cl- ions and sensitive to 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (0.1-1 mM) but ATP was not required for initial current activation even in excised patch experiments . K+ current reversal potential varied 52 mV/10-fold change in the external K+ concentration and current was blocked by BaCl2 (0.1-1 mM) . The results indicate that overexpression of multidrug resistance-associated protein is accompanied by increases in both K+ channel and volume-regulated Cl- channel current in the multidrug-resistant cell line H69AR. Cancer Res, 1993 Sep 15, 53(18), 4238 - 42 Bovine serum albumin-doxorubicin conjugate overcomes multidrug resistance in a rat hepatoma; Ohkawa K et al.; A bovine serum albumin-conjugated doxorubicin via the glutaraldehyde bridge (BSA-DXR conjugate) showed potent dose-dependent inhibition of cell growth against daunorubicin-resistant AH66 (AH66DR) cells as well as parental AH66 (AH66P) cells in vitro as compared to treatment with DXR or BSA-glutaraldehyde conjugate without DXR (BSA-GA) . In the culture of AH66DR with BSA-DXR conjugate, drug accumulation in the AH66DR cells increased as a function of time up to 24 h reaching approximately the same drug level as AH66P cells treated with DXR . The intracellular accumulation of the BSA-DXR conjugate was inhibited by the addition of ammonium chloride, while that of DXR alone was not inhibited . Intracellular DXR was effluxed rapidly from AH66DR cells, but BSA-DXR conjugate or pharmacologically active DXR adduct remained in the cells at a relatively high concentration over a 36-h time period . The life-prolonging effect of the conjugate was assessed using rats inoculated i.p . with AH66P or AH66DR . The rats were treated with the BSA-DXR conjugate, DXR, a mixture of DXR with BSA, or BSA-GA by either the i.p . or i.v . route . Treatment with DXR had no significant surviving effect as compared to that with saline in AH66P-bearing rats . By contrast, BSA-DXR conjugate showed a significant life-prolonging effect as compared with DXR alone in the same degree both in AH66P- and AH66DR-bearing rats . BSA-GA did not show any toxicity in vivo as well as in vitro . These results indicate that the BSA-DXR conjugate allows DXR to escape from the multidrug resistance mechanism. J Biol Chem, 1993 Sep 15, 268(26), 19505 - 11 SP1 activates the MDR1 promoter through one of two distinct G-rich regions that modulate promoter activity; Cornwell MM et al.; To define sequences in the human multidrug resistance (MDR1) promoter that influence transcription, we measured the activity of MDR1 promoter constructs using luciferase as a reporter gene . Deletion of promoter sequences to -121 (relative to the transcription initiation site) had very little effect on promoter activity in transiently transfected cells . Further deletion to -88 increased activity about 4-fold, while deletion to -51 decreased activity about 10-fold . The data indicated that between -121 and -88 and between -73 and -51 were sequences that modulated promoter activity . Because these two regions contain G-rich sequences, which are important for function in other promoters, the effect of mutation of the G-rich regions (-110 to -103 and -61 to -43) on MDR1 promoter activity was measured . Mutation of the -110 G-box (-110 to -103) resulted in a 6-fold increase in promoter activity and inhibited the formation of a specific nuclear protein complex, suggesting that this region functions as a transcriptional "repressor" binding site in cycling cells . In contrast, mutation of the -50 G-box (-61 to -43) reduced promoter activity 5-fold . DNase-I footprinting and electrophoretic mobility shift analysis indicated that specific but distinct protein-DNA complexes formed at each of these two G-rich regions . The -50 G-box contains overlapping sites to which both SP1 and EGR-1 bind specifically . Co-transfection of MDR1 promoter constructs with SP1 into cells that lack SP1 (Drosophila Schneider 2 cells) activated equivalently both the wild type MDR1 promoter and a synthetic promoter containing the MDR1 -50 GC box and MDR1 initiator element. Biochem Pharmacol, 1993 Sep 14, 46(6), 1096 - 9 Restricted transport of cyclosporin A across the blood-brain barrier by a multidrug transporter, P-glycoprotein; Tsuji A et al.; The blood-brain barrier permeability of cyclosporin A (CsA), an immunosuppressive cyclic peptide, is restricted despite its highly lipophilic nature . In this study, the uptake of CsA by primary cultured bovine brain capillary endothelial cells (BCEC) was investigated in order to clarify whether P-glycoprotein (P-gp), an ATP-dependent drug efflux pump expressed in the luminal surface of BCEC, causes the decreased transport of CsA into the brain . P-gp, having a molecular mass of 130-140 kDa, was detected with anti-P-gp monoclonal antibody, C219, using western blot analysis of the membrane fraction isolated from the bovine brain capillary . The uptake of CsA by primary cultured bovine BCEC was time-dependent, and the steady-state uptake of CsA was increased in the presence of several multidrug resistance reversing agents including verapamil and steroid hormones and the substrate of P-gp in BCEC, vincristine . The steady-stage uptake was increased significantly to approximately 4-fold when cellular ATP was depleted by treating with 2,4-dinitrophenol, suggesting that the efflux process is ATP dependent . Furthermore, in the presence of an anti-P-gp monoclonal antibody, MRK16, at a 10 micrograms/mL concentration, the uptake of CsA was increased approximately 3-fold . These results suggest that the low permeability of CsA into the brain is caused by the active efflux from BCEC by P-gp present in the luminal surface of cells. N Engl J Med, 1993 Sep 9, 329(11), 784 - 91 Treatment of multidrug-resistant tuberculosis; Iseman MD; The frequency of infections with M . tuberculosis resistant to antituberculous drugs is increasing in the United States and globally . This increase is a major threat to tuberculosis treatment and control programs . To prevent this situation from worsening, initial treatment programs that entail directly observed therapy supported by effective inducements or enforcements must be used . Retreatment of patients who have multidrug-resistant tuberculosis should be carried out in programs with comprehensive microbiologic, pharmacokinetic, psychosocial, and nutritional support systems . Regimens of multiple drugs, which generally are poorly tolerated and more toxic than traditional regimens, must be administered for 18 to 36 months . Resectional surgery may be required for substantial numbers of patients . For patients with AIDS who acquire tuberculosis caused by multiply-resistant strains, the disease may prove lethal before effective therapy can be implemented . Ultraviolet irradiation systems should be used to protect health care personnel and other patients in high-risk environments . Enhanced federal, state, and local programs for prevention and control are urgently needed, and research to identify new medications and systems for their delivery is essential. Biochemistry, 1993 Sep 7, 32(35), 9156 - 64 Differential modulation of P-glycoprotein transport by protein kinase inhibition; Bates SE et al.; Previous studies of P-glycoprotein have demonstrated that its function can be modulated by phosphorylation . In the present study, inhibition of protein kinase C with calphostin C or stauroporine or prolonged treatment with the phorbol ester TPA decreased phosphorylation of P-glycoprotein, and impaired transport of vinblastine . Calphostin C also inhibited transport of actinomycin D, vincristine, rhodamine, and azidopine in SW620 Ad300 multidrug-resistant human colon carcinoma cells . Photoaffinity labeling of P-glycoprotein with azidopine was decreased by calphostin C, suggesting that dephosphorylation alters the affinity of P-glycoprotein for its substrates . Impaired transport of rhodamine in normal T lymphocytes treated with staurosporine demonstrates that modulation of P-glycoprotein function is not limited to cells selected for drug resistance in vitro . Transport of P-glycoprotein antagonists in SW620 Ad300 cells was also affected by calphostin C . Cyclosporin A transport decreased, while verapamil transport increased . Cyclosporin A in calphostin C-treated cells resulted in additive P-glycoprotein antagonism, while no additive effect could be demonstrated with verapamil, suggesting that the increase in verapamil transport makes it a poorer P-glycoprotein antagonist . These studies suggest that transport by P-glycoprotein is a dynamic process which can be modulated by phosphorylation, and that antagonists may block P-glycoprotein differently in different phosphorylation states. Nippon Rinsho, 1993 Sep, 51(9), 2343 - 52 {PMP70, the 70-kDa peroxisomal membrane protein: a member of the ATP-binding cassette transporters}; Kamijo K et al.; We have isolated the cDNA of the 70-kDa peroxisomal membrane protein (PMP70) from rat and human liver cDNA libraries . The nucleotide sequence of the cDNA of PMP70 contains an open reading frame of 1977 bp which encodes an amino acid sequence of 659 residues . Possible two domains were identified by hydropathy analysis . One is a hydrophobic region, which presumably contains six transmembrane segments . The other is a hydrophilic domain, which shows striking similarity to the sequences of the ATP-binding cassette (ABC) transporter proteins, including bacterial periplasmic transport proteins, the human multidrug resistance P-glycoprotein (MDR1), cystic fibrosis transmembrane conductance regulator (CFTR), and the putative adrenoleukodystrophy gene product (ALDP) . Based on its transmembrane structure and the homology to ABC proteins, PMP70 may be involved in ATP-dependent transport through peroxisomal membrane. Ann Hematol, 1993 Sep, 67(3), 107 - 9 Itraconazole and