Leuk Res, 1995 Apr, 19(4), 275 - 82 Drug resistance mechanisms and MRP expression in response to epirubicin treatment in a human leukaemia cell line; Davey RA et al.; A drug resistant series of sublines were developed by treating the human leukaemia CCRF-CEM cell line with 16-1000 ng/ml of the anthracycline, epirubicin . The sublines developed resistance in two stages, neither involving detectable levels of P-glycoprotein . Treatment with up to 50 ng/ml epirubicin produced sublines with cross resistance limited to the anthracyclines and etoposide . Treatment with 100-1000 ng/ml epirubicin produced sublines with increased expression of the mrp gene, increased resistance to the anthracyclines and etoposide, additional cross resistance to vincristine and colchicine, decreased drug accumulation and reversal of resistance by verapamil and by buthionine sulphoximine (BSO; an inhibitor of glutathione synthesis) . Our results indicate an interaction between MRP and glutathione metabolism as a mechanism for multidrug resistance. Leuk Res, 1995 Apr, 19(4), 257 - 61 Evaluation of resistance index of several anticancer agents on parental and resistant P-388 cell lines; Testi R et al.; Multidrug resistance is frequently detected in haematological malignancies and in acute leukaemias with a poor prognosis . In the last few years, several reports seem to suggest that the new anthracycline derivative idarubicin and the anthraquinone mitoxantrone have some advantages in the management of untreated or relapsed acute leukaemias compared with older anthracyclines . This could be due to a different interaction of these drugs with multidrug resistance . To evaluate this possibility, we compared the activity of doxorubicin (DOXO), epirubicin (EPI), idarubicin (IDA) and mitoxantrone (MITO) on a murine, multidrug resistant, leukaemic cell line (P-388/Dx) cultured in vitro . ID50 of IDA and MITO was in the ng range whereas that of DOXO and EPI was in the microgram(s) range . Moreover, IDA has a resistance index of 50 whereas DOXO has one of 250 . Verapamil is able to almost completely abolish the resistance to IDA . Efflux experiments confirm that verapamil increases IDA intracellular concentration . IDA and MITO appear to be less involved in multidrug resistance than older anthracyclines. Br J Dermatol, 1995 Apr, 132(4), 551 - 5 P-glycoprotein expression in primary and metastatic malignant melanoma; Schadendorf D et al.; Metastatic malignant melanoma is notoriously resistant to chemotherapeutic agents, but the exact mechanisms involved in this drug resistance are unknown . One recently defined major mechanism of multidrug resistance involves the overexpression of P-glycoprotein on cell membranes . In order to evaluate the significance of this putative drug efflux pump for chemoresistance of malignant melanoma, five different antibodies were employed to examine P-glycoprotein expression on tissue from 33 primary malignant melanomas and 35 metastases, before and after chemotherapy, using immunohistological techniques . The expression of P-glycoprotein was low on primary cutaneous melanomas (three of 33), and on metastases (one of 35) . Normal tissue in and around the melanoma showed reactivity of endothelial cells, stromal cells and eccrine sweat glands with several antibodies tested . Chemotherapy with drugs commonly used in metastatic melanoma, including agents known to induce P-glycoprotein expression in other tumours (vindesine, cisplatin) had no effect on P-glycoprotein expression in human melanoma metastases . The high chemoresistance of human melanoma cells in vitro and in vivo is probably not mediated via P-glycoprotein, and other possible mechanisms involved will have to be explored in future studies. Photochem Photobiol, 1995 Apr, 61(4), 390 - 6 Inhibition of the ATPase activity of P-glycoprotein by porphyrin photosensitization of multidrug-resistant cells in vitro; Gibson SL et al.; The effectiveness of photodynamic therapy against P-glycoprotein ATPase activity in multidrug-resistant cells was studied . Chinese hamster ovary AUXB1 (drug-sensitive) and CR1R12 (multidrug-resistant) cell lines were compared with respect to uptake of 14C-polyhematoporphyrin and porphyrin photosensitization . Phototoxicity of Photofrin was similar in both cell lines, and no major differences in uptake or efflux of 14C-polyhematoporphyrin were observed . Porphyrin photosensitization in vitro of CR1R12 cells or isolated plasma membranes from these cells caused inhibition of P-glycoprotein ATPase activity . Application of porphyrin photosensitization at a sublethal level to CR1R12 cells resulted in a small but significant increase in adriamycin-induced cytotoxicity . The hydrophobic "picket-fence" porphyrin, meso-tetrakis-(o-propionamidophenyl)porphyrin, alpha,alpha,alpha,beta-isomer, was more inhibitory toward P-glycoprotein ATPase activity than the two less hydrophobic porphyrins tetraphenylporphine tetrasulfonate and Photofrin. Am J Clin Pathol, 1995 Apr, 103(4), 443 - 8 CD31 quantitative immunocytochemical assays in breast carcinomas . Correlation with current prognostic factors; Charpin C et al.; The distribution of PECAM-1/CD31 molecule was investigated in 133 breast carcinomas using monoclonal antibody and frozen sections . Anti-CD31 labels endothelial cells and reflects stromal angiogenesis . The CD31 immunoreactivity was evaluated by computer-assisted analysis of digitized microscopic images . The automatic screening of the whole preparation and the measurements of the mean CD31 immunostained surface was performed in each case . A similar procedure was achieved for p53, cathepsin D, P-gp, pHER-2/neu, Ki67, pS2 estrogen and progesterone antigenic sites immunodetection . The image analysis of positive CD31 surface was variable, ranging from 4% to 33% (mean 14.7%, SD = 5.43) . The CD31 positive surface correlated (P < .01) with the Nottingham prognostic index, but not with the tumor size, the node status, the tumor grade, nor with the patient age . Also the CD31 immunoreactivity was independent of the pHER-2/neu, Ki67 antigen, p53, ER, PR and pS2 immunodetectable expression in tumors, but correlates with that of cathepsin D (P = .024) and P-gp (P = .028), which reflects the multi-drug resistance capacity of tumor cells . In conclusion, CD31 positive vessels assessed on frozen sections by image analysis constitute an excellent method of evaluating tumor stromal angiogenesis, and can be further used for clinical purposes . The results also suggest that the CD31/PECAM molecule may be involved in the spread of tumor by interacting with extracellular matrix lysis that results from the tumor cell proteasic activity and with multidrug resistance. Mutat Res, 1995 Apr, 342(3-4), 113 - 23 Increased genotoxicity of acetylaminofluorene by modulators of multixenobiotic resistance mechanism: studies with the fresh water clam Corbicula fluminea; Waldmann P et al.; The presence of a 'multixenobiotic resistance' {MXR} mechanism in gills of the freshwater clam Corbicula fluminea was investigated . Western blot analyses of membrane vesicles from gills, applying antibodies to vertebrate P170 multidrug resistance (MDR) protein, revealed a 135 kDa immunoreactive protein . Verapamil caused a reduction of 3H-vincristine (3H-VCR) binding onto vesicles from clam . Exposure of clams to 3H-VCR in the presence of verapamil or staurosporine (STP) enhanced the accumulation of 3H-VCR over control values . Furthermore, clams were exposed instead to VCR, to a model carcinogen, 2-acetylaminofluorene (AAF), to determine the verapamil- and STP-dependent increase of single-strand breaks (SSBs) in DNA from gills of this organism . Verapamil caused no or little increase of SSBs induced by exposure to 0.01 or 0.10 microM AAF, respectively, as measured by the alkaline elution technique . In contrast, in the presence of STP a highly significant and dose-dependent enhancement of AAF-mediated SSBs was measured already at exposure to 0.01 microM AAF . These data indicate (i) that the clam C . fluminea is provided with a P-glycoprotein-like element of the MDR-mechanism, (ii) that this system can be poisoned by chemosensitizers such as verapamil and STP, (iii) the role of protein kinase C in the regulation of MXR function and (iv) the importance of the MXR modulators for the assessment of ecotoxicological effects of pollutants. Br J Cancer, 1995 Apr, 71(4), 877 - 81 Continuous-infusion verapamil with etoposide in relapsed or resistant paediatric cancers; Cowie FJ et al.; This study evaluates the use of a multidrug resistance (MDR) modulator (verapamil) in combination with a standard dose of single-agent etoposide in relapsed or refractory paediatric malignancy . A total of 20 patients (median age 6.5 years) were treated with an infusion of verapamil (loading dose 0.1 mg kg-1, followed by continuous infusion 0.15 mg kg-1 h-1) for 72 h . Etoposide was given daily (150 mg m-2 day-1) for three doses (each over 1 h); the first dose was given 12 h into the verapamil infusion . Cardiovascular toxicity was monitored by ECG and 2 hourly blood pressure and pulse recordings . Verapamil and norverapamil plasma concentrations were measured daily . Disease response was assessed after two courses . A total of 29/35 treatment courses were given at the desired verapamil dose; five courses required a dose reduction owing to cardiovascular toxicity . No patient required intensive monitoring . All patients who developed cardiovascular toxicity were over 14 years old . There was no correlation between plasma verapamil or norverapamil concentrations and toxicity . There were six partial responses (three rhabdomyosarcoma, three neuroblastoma) after two courses, but because of variation in the dose and schedule of etoposide these cannot be unequivocally contributed to MDR reversal . In conclusion, a regimen using a continuous infusion of verapamil combined with divided-dose etoposide is tolerable in children, and this strategy may be effective in refractory neuroblastoma and rhabdomyosarcoma. Br J Cancer, 1995 Apr, 71(4), 738 - 43 Buthionine sulphoximine-mediated sensitisation of etoposide-resistant human breast cancer MCF7 cells overexpressing the multidrug resistance-associated protein involves increased drug accumulation; Schneider E et al.; Preincubation of etoposide-resistant human MCF7 breast cancer cells (MCF7/VP) with buthionine sulphoximine (BSO) resulted in their sensitisation to etoposide and vincristine . Chemosensitisation was accompanied by elevated intracellular drug levels . In contrast, simultaneous exposure to BSO did not result in increased drug accumulation . Similar, but quantitatively smaller, effects were also observed when sensitive wild-type MCF7/WT cells were treated with BSO . In agreement with its effect on drug accumulation, BSO pretreatment also increased VP-16-stimulated cleavable complex formation between DNA topoisomerase II and cellular DNA . BSO treatment also led to a significant increase in acid-precipitable VP-16 levels in MCF7/VP, but not MCF7/WT cells . In contrast, no clear effects of BSO on drug efflux were observed and drug retention was only minimally increased after BSO treatment of both MCF7/WT and MCF7/VP cells and no difference between the two cell lines was detected . Thus, chemosensitisation by BSO appeared to be mediated through increased intracellular drug concentrations and/or protein binding. Br J Cancer, 1995 Apr, 71(4), 670 - 5 Inhibition of N-linked glycosylation of P-glycoprotein by tunicamycin results in a reduced multidrug resistance phenotype; Kramer R et al.; Characterisation of altered glycosylation of P-glycoprotein (P-gp) found associated with the absence of a multidrug resistance (MDR) phenotype in cell lines prompted an investigation to assess the role of post-translational processing in establishing P-gp efflux pump functionally . The clone A cell line used in this study displays a strong MDR phenotype mediated by high constitutive levels of expression of P-gp . Incubation of clone A cells with tunicamycin for different periods resulted in a time-dependent increase in daunorubicin accumulation, reflecting a reduction in P-gp function . Parallel experiments conducted with verapamil resulted in no loss of P-gp functionality in clone A cells . Reduction in surface-associated P-gp following exposure to tunicamycin was established by FACS analysis, Western blot analysis and immunoprecipitation of surface-iodinated P-gp . In addition, immunoprecipitation of P-gp from 32P-orthophosphate-labelled cells demonstrated reduced phosphorylation of P-gp associated with tunicamycin exposure . From these studies we conclude that glycosylation of P-gp is required to establish the cellular MDR phenotype. Med Pediatr Oncol, 1995 Apr, 24(4), 235 - 40 Vincristine disposition in children with acute lymphoblastic leukemia; de Graaf SS et al.; Vincristine (VCR) has been widely used to treat childhood malignancies for over thirty years, but its plasma disposition has not yet been well-defined . Therefore, we conducted a pharmacokinetic study of VCR in 17 children with acute lymphoblastic leukemia (ALL) receiving the first dose of VCR . A new high-performance liquid chromatographic assay was used for the measurement of VCR in plasma . A two-compartment pharmacokinetic model was fit to the data by nonlinear least-squares regression . Estimated pharmacokinetic parameters were highly variable; mean (S.D.) volume of distribution at steady-state was 360 (176) L.m-2; total body clearance was 431 (238) ml.min-1.m-2, and elimination half-life was 823 (390) min . These results were compared to data from eight adults with lung cancer . Mean volume of distribution in adults and children were similar, but VCR clearance was significantly larger in children (P = 0.01), resulting in a significantly longer elimination half-life in the adults (P < 0.01) . We conclude that administration of a standard dosage of VCR to children with ALL results in a highly variable systemic drug exposure, which may have implications for the oncolytic effect and/or toxicity in individual patients . Comparison of data from children and adults suggests that VCR elimination rate is a function of age; this could account for more severe neurotoxicity in older patients . However, it cannot be excluded that differences between the children and adults may be due to other variables than age . Future studies should focus on the possible influence of multidrug resistance modulating agents on VCR pharmacokinetics and on pharmacokinetic-pharmacodynamic relationships in individual patients. Singapore Med J, 1995 Apr, 36(2), 209 - 11 Tuberculosis--fighting a losing battle? Tan KK. Tuberculosis has resurfaced as a "global emergency" in recent years not only in terms of increase in number of cases world-wide but also the emergence of the deadly multidrug-resistant tuberculosis . World Health Organisation (WHO) has issued a call for the global community to step up its vigilance against the disease . Chemotherapy is the most powerful tool in the fight against tuberculosis and should be used with utmost care and under stringent conditions . It is not enough just to prescribe the correct medication, but more importantly, the patient must be closely monitored for compliance and progress . Any facility which provides for the treatment of tuberculosis must have a good working mechanism to detect treatment defaulter and take immediate remedial action . Only then can we maintain a high standard of control of the disease and prevent the emergence of drug-resistant organisms. J Chemother, 1995 Apr, 7(2), 157 - 9 Role of protein kinase beta isozyme in multidrug resistance in murine leukemia P388/ADR cells; Gollapudi S et al.; To define a role of protein kinase C (PKC) in multidrug resistance (MDR), we examined the influence of PKC isozyme specific antibodies delivered intracellularly, on drug sensitivity and drug accumulation in P388/ADR cells . Drug sensitive (P388) and drug resistant (P388/ADR) cells were permeabilized at 4 degrees C with L-lysolecithin and were incubated with rabbit anti-PKC, alpha, beta antibodies, or normal rabbit serum for 10 minutes at 37 degrees C . Daunorubicin (DNR) accumulation and drug sensitivity were studied by flow cytometry and MTT assay, respectively . Anti-PKC beta antibody partially corrected drug accumulation defect and completely reversed resistance to DNR . Anti-PKC alpha antibody had no effect on either parameter of MDR . These results suggest that PKC beta plays an important role in MDR in P388/ADR cells . Furthermore, the technique of intracellular delivery of antibodies provides a new approach to discern the role of PKC isoforms in multidrug resistance in various tumor cells. Minerva Pediatr, 1995 Apr, 47(4), 147 - 51 {Treatment of metastatic osteosarcoma with verapamil, cyclosporine and chemotherapy . A case report}; Brach Del Prever A et al.; Studies on the use of revertants to overcome MDR have aroused a great interest even if they failed to prove their actual usefulness . A case of 10 years and 6 months old boy is described . He suffered from osteoblastic osteosarcoma and underwent chemotherapy following CNR-NEO3 protocol, wide surgical resection and postoperative chemotherapy . Nineteen months after diagnosis he underwent the removal of a little subpleural nodule in the right lung . Forty-five days later, in the same site, a large local metastasis was observed together with many others secondaries localizations spred in both lungs . Because of the rapid evolution they were considered not suitable for surgical treatment . A cyclosporine and verapamil treatment in association with adryamicin and etoposide was begun with the aim overcoming multidrug resistance . Five treatments were provided . ECG monitoring during verapamil infusion did not show any trouble; mielotoxicity was mild, with no need of transfusions . A lung CT scan at the end of the therapy demonstrated an important decrease of the subpleural metastasis and the vanishing of lung nodules . Another surgical intervention was provided together with 2 postoperative chemotherapy treatments . Twenty-six months later no sign of the disease was observed . Association of verapamil and cyclosporine with chemotherapy allowed to get a good clinical response with a very low toxicity, in a critical situation in which chemotherapy alone did not seem to offer any real possibility. Hematol Oncol Clin North Am, 1995 Apr, 9(2), 363 - 82 Clinical studies with modulators of multidrug resistance; Fisher GA et al.; Improved understanding of the mechanisms underlying chemotherapeutic failure has led to new strategies to circumvent drug resistance . Expression of the multidrug transporter, P-glycoprotein (P-gp), is likely to be a significant mechanism contributing to the clinical resistance of some cancers to chemotherapy . Phase I trials of currently available MDR modulators have yielded important pharmacologic principles pertaining to normal tissue P-gp function and its influence on the disposition of MDR-related anticancer drugs . Currently available P-glycoprotein inhibitors lack the potency to completely reverse the MDR phenotype at clinically achievable concentrations . Despite this, encouraging clinical results have been obtained in the hematolymphoid malignancies . As these more potent modulators become available, careful characterization of pharmacologic interactions with MDR-related cytotoxins will be critical to the rational design of Phase II and III studies that will ultimately test the efficacy of MDR modulation. Hematol Oncol Clin North Am, 1995 Apr, 9(2), 337 - 61 Modulators of multidrug resistance . Preclinical studies; Ford JM; The study of the cellular, biochemical, and molecular biology and pharmacology of MDR has provided one of the most active and exciting areas within cancer research for translation into potential clinical benefit . Although convincing evidence for the functional role of P-gp in mediating clinical drug resistance in humans remains scant, studies of the clinical expression of P-gp and trials of chemosensitizers with cancer chemotherapy suggest "resistance modification" strategies may be effective in some tumors with intrinsic or acquired drug resistance . However, even if P-gp-associated MDR proves to be a relevant and reversible cause of clinical drug resistance, numerous problems remain to be solved before effective clinical chemosensitization may be achieved . Such factors as absorption, distribution, and metabolism, the effect of chemosensitizers on chemotherapeutic drug clearance, toxicity to normal tissues expressing P-gp, and the most efficacious modulator regimens all remain to be defined in vivo . Clearly, the identification of more specific, more potent, and less clinically toxic chemosensitizers for clinical use remains critical to the possible success of this approach . However, the finding that a number of pharmacologic agents can antagonize a well-characterized form of experimental drug resistance provides promise for potential clinical applications . Further study of chemosensitizers in humans and the rational design of novel chemosensitizers with improved activity should define the importance of MDR to clinically resistant cancer. Hematol Oncol Clin North Am, 1995 Apr, 9(2), 275 - 318 Multidrug resistance in pediatric malignancies; Chan HS et al.; PURPOSE: Increased expression of P-glycoprotein is an important cause of multidrug resistance in tumor cell lines in vitro . Whether this mechanism is equally relevant as a cause of clinical chemoresistance has not been established and is currently being investigated . This review has examined the immunohistochemical and molecular biologic tools suitable for assessing P-glycoprotein expression in patient samples and methodologic issues important for evaluating the results of clinical studies . Current evidence that supports a role for P-glycoprotein in limiting the efficacy of cancer chemotherapy has been reviewed . DESIGN: Malignancies that have been successfully treated by chemotherapeutic substrates of P-glycoprotein, in which a proportion of patients still fail therapy, may be the most useful models for determining whether this drug efflux transporter is a clinically relevant cause of chemoresistance . RESULTS: Studies of acute myelogenous leukemia, lymphoma, and myeloma in adults have so far provided the best evidence for a relevant role for P-glycoprotein as a cause of clinical multidrug resistance . A similar strong association has been observed between the expression of P-glycoprotein and outcome of treatment in certain malignancies in children, such as neuroblastoma, rhabdomyosarcoma, and acute lymphoblastic leukemia . Some apparent controversies related to this issue of clinical relevance may be explained by the differences in P-glycoprotein detection techniques, methodology, and experimental designs used in different studies . Because several clinical trials have already been initiated to determine whether pharmacologic chemosensitization improves the outcome of chemotherapy in certain malignancies, the successful verification of multidrug resistance limiting the cure rates of these tumors becomes a more critical issue, and identification of those patients with lower levels of P-glycoprotein expression early in the course of their disease, when they are most likely to benefit from multidrug resistance reversal, has assumed an even greater relevance . CONCLUSION: The clinical relevance of the multidrug resistance P-glycoprotein may ultimately be confirmed by the successful prevention of chemotherapy failure by chemosensitizers that specifically reverse this drug efflux mechanism. Hematol Oncol Clin North Am, 1995 Apr, 9(2), 251 - 73 P-glycoprotein in adult solid tumors . Expression and prognostic significance; Leighton JC Jr et al.; Several potential mechanisms of chemotherapy resistance have been identified in adult solid tumors . The multidrug resistance (MDR) phenotype is one mechanism by which tumors may simultaneously develop resistance to multiple chemotherapeutic agents and is associated with P-glycoprotein expression . In this article, the authors examine the literature and summarize the various techniques used to measure MDR1 gene expression, patterns of expression in adult solid tumors. J Nat Prod, 1995 Apr, 58(4), 598 - 604 (-)-Roemerine, an aporphine alkaloid from Annona senegalensis that reverses the multidrug-resistance phenotype with cultured cells; You M et al.; A known aporphine alkaloid, (-)-roemerine {1}, isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells . In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive . As indicated by its ability to inhibit ATP-dependent {3H}vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein . In addition to alkaloid 1, three inactive compounds {the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin {2} (a new natural product), and (+)-syringaresinol} were also isolated. Clin Microbiol Rev, 1995 Apr, 8(2), 180 - 99 Tuberculosis in the AIDS era; Sepkowitz KA et al.; A resurgence of tuberculosis has occurred in recent years in the United States and abroad . Deteriorating public health services, increasing numbers of immigrants from countries of endemicity, and coinfection with the human immunodeficiency virus (HIV) have contributed to the rise in the number of cases diagnosed in the United States . Outbreaks of resistant tuberculosis, which responds poorly to therapy, have occurred in hospitals and other settings, affecting patients and health care workers . This review covers the pathogenesis, epidemiology, clinical presentation, laboratory diagnosis, and treatment of Mycobacterium tuberculosis infection and disease . In addition, public health and hospital infection control strategies are detailed . Newer approaches to epidemiologic investigation, including use of restriction fragment length polymorphism analysis, are discussed . Detailed consideration of the interaction between HIV infection and tuberculosis is given . We also review the latest techniques in laboratory evaluation, including the radiometric culture system, DNA probes, and PCR . Current recommendations for therapy of tuberculosis, including multidrug-resistant tuberculosis, are given . Finally, the special problem of prophylaxis of persons exposed to multidrug-resistant tuberculosis is considered. Int J Cancer, 1995 Mar 29, 61(1), 142 - 7 P-glycoprotein epitope mapping . II . The murine monoclonal antibody MM6.15 to human multidrug-resistant cells binds with three distinct loops in the MDR1-P-glycoprotein extracellular domain; Cianfriglia M et al.; A new murine monoclonal antibody (MAb), MM6.15, to human MDR1 P-glycoprotein was found to be reactive in ELISA with synthetic peptides selected from the predicted sequences of the first, fourth and sixth extracellular loop of MDR1-P-glycoprotein . In order to precisely define the MM6.15-binding site, a peptide library of overlapping 5- to 9-mer residues covering the entire sixth extracellular loop of both human and rodent class-1 P-glycoproteins was synthesized on polyethylene pins and tested for MAb binding . The results of this ELISA demonstrated that the MAb MM6.15 reacts only with human synthetic peptides and that the critical component of the MAb recognition is made up of the amino-acid sequence LVAHKL (residues 963-968 of the MDR1-P-glycoprotein) with histidine (H), lysine (K) and possibly leucine (L), key residues of this immunogenic domain. Biochemistry, 1995 Mar 21, 34(11), 3858 - 72 Kinetics of transport of dialkyloxacarbocyanines in multidrug-resistant cell lines overexpressing P-glycoprotein: interrelationship of dye alkyl chain length, cellular flux, and drug resistance; Wadkins RM et al.; The membrane transport properties of a series of dialkyloxacarbocyanine {DiOCn(3)} dyes in multidrug-resistant KB cell lines were investigated to determine the influence of alkyl chain length on the ability of p-glycoprotein (i) to protect cells from the toxicity of the dyes and (ii) to affect the plasma membrane flux of the dyes . Cytotoxicity assays revealed that increased levels of p-glycoprotein led to increased resistance to the toxicity of the DiOCn(3) relative to the sensitive KB-3-1 parent line . This resistance could be fully or partially reversed by 10 microM verapamil . Monitoring of DiOCn(3) fluorescence changes allowed the measurement of accumulation and efflux rates for the dyes in the parent and two resistant cell lines at 1.5-s resolution . The flux of DiOCn(3) into and out of the KB85 and KBV1 cell lines was shown to be dramatically different from the parental KB-3-1 line when n < 5, while the transport properties of n = 7 were identical in the three cell lines examined . The membrane transport properties were shown not to be correlated with the 7-day toxicity of DiOCn(3) . Verapamil affected the kinetic processes of DiOC2-5(3) involving redistribution of the dyes within the cells once they had initially passed the plasma membrane . Fluorescence microscopy was used to show no alteration in the subcellular distribution of the DiOCn(3), in response to neither chain length nor cell line . Our results indicate that an alkyl chain length of 5 carbons is the critical length necessary for p-glycoprotein to affect membrane transport of DiOCn(3) but not to protect the cells from the cytotoxicity of the dyes. Eur J Biochem, 1995 Mar 15, 228(3), 1020 - 9 Potentiation of anticancer-drug cytotoxicity by multidrug-resistance chemosensitizers involves alterations in membrane fluidity leading to increased membrane permeability; Drori S et al.; We are studying the mechanism underlying chemosensitization of anticancer-drug cytotoxicity in wild-type and multidrug-resistant (MDR) mammalian cells . We show here that the chemosensitizers, reserpine and verapamil, display a dramatic potentiation of taxol, anthracycline and Vinca alkaloids cytotoxicity in P-glycoprotein-(P-gp)-deficient hamster and human nasopharyngeal carcinoma cells . We have therefore utilized this phenomenon to probe for the putative P-gp-independent component of cytotoxicity chemosensitization . These chemosensitizers yielded a marked increase in the accumulation of taxol in parental hamster and human carcinoma cells that are devoid of P-gp . These chemosensitizers and non-ionic detergents brought about a pronounced increase in the accumulation of structurally and mechanistically diverse lipophilic chromophores in parental and MDR hamster cells . Furthermore, non-toxic concentrations of these non-ionic detergents yielded a marked potentiation of taxol cytotoxicity in parental cells . These findings were consistent with a chemosensitizer-mediated, P-gp-independent increase in membrane permeability . Thus, several aspects of chemosensitizers' interaction with lipid bilayers and biomembranes were studied . In this respect, like various mild detergents, chemosensitizers induced a dose-dependent leakage of carboxyfluorescein encapsulated in liposomes . Like specialized membrane fluidizers, various chemosensitizers induced a dose-dependent membrane fluidization (and sometimes rigidification) in both liposomes and various wild-type and MDR animal and human cells, as revealed by diphenylhexatriene fluorescence polarization . Furthermore, a favorable correlation was observed between the ability of chemosensitizers to permeabilize lipid bilayers and their capacity to potentiate anticancer-drug cytotoxicity . Thus, we propose that chemosensitizer-mediated changes in the physical properties of biomembranes, including altered fluidity and increased permeability, may be important factors in achieving potentiation of anticancer-drug cytotoxicity in wild-type and MDR mammalian cells . This study offers a basis for the chemosensitizer-mediated potentiation of drug toxicity to healthy tissues, thus emphasizing the importance of a prior evaluation of the potential untoward toxicity when simultaneously using MDR chemosensitizers and cytotoxic agents in the clinic. Biochem Pharmacol, 1995 Mar 15, 49(6), 755 - 62 Characterization of an anthracycline-resistant human promyelocyte leukemia (HL-60) cell line with an elevated MDR-1 gene expression; Jonsson K et al.; Multidrug resistance to a variety of cytotoxic drugs is due to decreased drug accumulation at the intracellular site of drug action . When due to increased energy-dependent drug efflux, this transport change is often associated with increased expression of an efflux pump for various lipophilic compounds, for example the P-glycoprotein which is the product of the MDR-1 gene . However, previously described HL-60 human promyelocytic leukemia cell lines resistant to the cytotoxic effect of anthracyclines have been reported not to express P-glycoprotein . We have isolated, by drug selection, an anthracycline-resistant HL-60 cell line that, in comparison to parental drug sensitive cells, exhibits a multidrug resistant phenotype including diminished intracellular drug retention, cross-resistance to multiple cytotoxic drugs, increased expression of a monoclonal antibody C219-reactive 180 kDa P-glycoprotein detected by Western blot analysis as well as increased expression of MDR-1 mRNA as determined by Northern blot and solution hybridization/RNAse protection analyses . Evidence is presented that the anthracycline-resistant HL-60 cells have amplified the MDR-1 gene. Biochemistry, 1995 Mar 14, 34(10), 3338 - 43 Phosphorylation of the multidrug resistance associated protein gene encoded protein P190; Ma L et al.; Recent studies suggest that multidrug resistance of HL60/ADR cells is related to an overexpression of the MRP (multidrug resistance associated protein) gene which encodes a 190-kDa ATP-binding membrane glycoprotein . In the present study we have further characterized P190 and have examined phosphorylation properties of the protein . The results demonstrate that P190 is highly phosphorylated and that the phosphate groups are metabolically active and undergo cycles of phosphorylation and dephosphorylation in the cell . Serine is the single amino acid phosphorylated in P190 and the phosphate groups are contained in nine tryptic peptides . Experiments have also been conducted to analyze the effect of various protein kinase inhibitors on phosphorylation levels of P190 . The results show that H-7, staurosporine, and chelerythrine can reduce the phosphorylation of this protein . In the presence of both H-7 (200 microM) and staurosporine (200 nM) the phosphorylation of P190 is completely blocked . It has also been found that in the presence of these agents there is a major increase in drug accumulation and concomitant inhibition in drug efflux of resistant cells . These results therefore suggest the possibility that certain phosphate groups of protein P190 play an important role in modulating drug accumulation in resistant cells. Biochem Biophys Res Commun, 1995 Mar 8, 208(1), 345 - 52 The leukotriene LTD4 receptor antagonist MK571 specifically modulates MRP associated multidrug resistance; Gekeler V et al.; The multidrug resistant cell lines HL60/AR and GLC4/ADR show high overexpression of the gene encoding the multidrug resistance associated protein MRP compared to their drug sensitive parental counterparts . This and the virtual absence of mdr1/P-glycoprotein gene expression was proven by a complementary DNA polymerase chain reaction (cDNA-PCR) approach . Applying a 72-hour tetrazolium based colorimetric MTT-assay we demonstrate on both MDR sublines a dose-dependent modulation of drug resistances by the leukotriene LTD4 receptor antagonist MK571 . A complete reversal of vincristine resistances was achieved at final MK571 concentrations of 30 microM (HL60/AR) or 50 microM (GLC4/ADR) which by itself did not disturb cellular proliferation . The drug resistance of a mdr1/P-gp overexpressing multidrug-resistant HL60 subline, in contrast, was not significantly affected by MK571 . Similar effects were seen using the glutathione (GSH) synthesis inhibitor buthionine sulfoximine (BSO) . Our results point to a relationship between MRP and a conjugate transporter and identify MK571 as a new tool structure for developing modulators specific for a MRP associated multidrug resistance. Int J Cancer, 1995 Mar 3, 60(5), 676 - 84 Mechanisms of MRP over-expression in four human lung-cancer cell lines and analysis of the MRP amplicon; Eijdems EW et al.; Some multidrug resistant cell lines over-express the gene encoding the multidrug-resistance-associated protein (MRP) . In all cell lines reported thus far, over-expression is associated with gene amplification . We have studied the predominant mechanisms of MRP over-expression in 4 human lung-cancer cell lines that cover a range of drug-resistance levels, and we have analyzed the MRP amplicon . In the SW-1573-derived, weakly resistant cell line 30.3M, MRP mRNA is elevated 3-fold in the absence of gene amplification . Run-on analysis shows that the increased MRP gene expression in this cell line is due to transcriptional activation . In the highly resistant GLC4/ADR and COR-L23/R cells, MRP gene amplification predominates, whereas in the moderately resistant MOR/R cells, gene amplification is combined with a mechanism resulting in an additional increase in the level of MRP mRNA . Fluorescence in situ hybridization shows that, in the GLC4/ADR cells, amplified MRP sequences are present both in double minute chromosomes (DM) and in homogeneously staining regions (HSR) . By pulsed-field gel electrophoresis we show that the MRP-containing DM are 1 Mb in length . Chromosome-16-specific repetitive sequences adjacent to the MRP gene are also present in the DM and HSR, compatible with the involvement of these sequences in recombination events underlying MRP gene amplification . Our results show that low levels of drug resistance may arise by transcriptional activation of the MRP gene, whereas at high levels of drug resistance amplification of the MRP gene predominates, possibly facilitated by the presence of recombination-prone sequences. Spec Care Dentist, 1995 Mar-Apr, 15(2), 50 - 5 Tuberculosis risk in the hospital dental practice; Harlow RF et al.; Tuberculosis has re-emerged as a serious public health concern . Multidrug-resistant strains and an increase in the number of high-risk groups are posing a difficult problem for health care providers . The risk of TB transmission in hospital dental practices is potentially increasing . A 20-question survey was mailed to the membership of the American Association of Hospital Dentists, addressing various issues relating to tuberculosis . One hundred thirty-two surveys were analyzed . Twelve per cent of respondents reported at least one TB skin test conversion by a dental provider within the past year at their institution . Five respondents reported one dental provider contracting TB through patient contact . Oral TB was reported in 21 cases . Over 34% reported that active TB patients are not isolated to negative-pressure isolation rooms, 45% reported that patients are allowed to frequent public areas, and only 59% believed that drug compliance monitoring was adequate . Over 86% support TB screening in the Hospital Dental Practice . It was concluded that Hospital Dental Practice personnel may be at increased risk for exposure to TB . Dental providers must exercise strict TB prevention and employ meticulous referral and follow-up procedures for high-risk patients. Southeast Asian J Trop Med Public Health, 1995 Mar, 26(1), 154 - 63 Integration of control measures for malaria vectors in endemic areas of Thailand; Kanda T et al.; Various vector control measures were applied in different endemic areas in two provinces, Saraburi and Chanthaburi, with comparison among different control measures . Application of IGR (insect growth regurator, pyriproxyfen) was introduced at Wat Tam Pra Pothisat, Tab-Kwang District, Saraburi Province . Some integration measures were performed at villages 6 and 8, Patavee, Makham District, Chanthaburi Province . In Tab-Kwang District with low malaria endemicity at the study site predators were not able to be released due to rapid velocity of running water . IGR could effectively control malaria compared to the basin released predators . Another endemic areas villagers 6 and 8, Patavee, Makham, Chanthaburi Province was chosen . Highly endemic multidrug resistant malaria has been prevalent for many years in this area . Integration of Kanda's trapping system, application of IGR, use of both residual spraying and impregnated bed-net methods with etofenprox successfully interrupted malaria infection . The application of these methods as an integrated control system could be adjusted to environmental conditions . The results of this study suggest rapid effective vector control. Biochem Pharmacol, 1995 Mar 1, 49(5), 603 - 9 Mechanism of action of dexniguldipine-HCl (B8509-035), a new potent modulator of multidrug resistance; Hofmann J et al.; It has previously been shown that dexniguldipine-HCl (B8509-035) is a potent chemosensitizer in multidrug resistant cells {Hofmann et al., J Cancer Res Clin Oncol 118: 361-366, 1992} . It is shown here that dexniguldipine-HCl causes a dose-dependent reduction of the labeling of the P-glycoprotein by azidopine, indicating a competition of dexniguldipine-HCl with the photoaffinity label for the multidrug resistance gene 1 (MDR-1) product . Exposure to dexniguldipine-HCl results in a dose-dependent accumulation of rhodamine 123 in MDR-1 overexpressing cells . In the presence of 1 microM dexniguldipine-HCl, rhodamine 123 accumulated in multidrug resistant cells to similar levels as in the sensitive parental cell lines . At this concentration, dexniguldipine-HCl enhances the cytotoxicities of Adriamycin and vincristine . The resistance modulating factors (RMF), i.e . IC50 drug/IC50 drug + modulator, were found to be proportional to the expression of MDR-1, ranging from 8 to 42 for Adriamycin and from 16 to 63 for vincristine . Transfection with the MDR-1 gene was found to be sufficient to sensitize cells to the modulation by dexniguldipine-HCl . The compound does not affect the expression of the MDR-1 gene . Dexniguldipine-HCl has no effect on a multidrug resistant phenotype caused by a mutation of topoisomerase II . It is concluded that dexniguldipine-HCl modulates multidrug resistance by direct interaction with the P-glycoprotein. Leukemia, 1995 Mar, 9(3), 513 - 6 MDR-related P170-glycoprotein modulates cytotoxic activity of homoharringtonine; Russo D et al.; Homoharringtonine (HHT) is a new drug with antileukemic activity which is currently tested for treatment of acute and chronic leukemias, either alone or in combination with other agents . Since HHT showed a low efficacy in refractory and relapsed acute leukemia and in the blastic phase of chronic myeloid leukemia (CML) which are frequently characterized by an overexpresion of the multidrug resistance (MDR)-related P170-glycoprotein, we postulated a relationship between the poor antileukemic effect of HHT in these leukemias and the expression of P170-glycoprotein . For this reason, sensitive (LOVO109 and CEM) and MDR (LOVO DX and CEM VLB) cell lines were exposed to HHT with or without some MDR modifiers, namely, Cyclosporine A (CyA), the Cyclosporine derivative SDZ PSC 833 (PSC), and the D-isomer of Verapamil (DVRP) . It was found that MDR cells were about 15 times more resistant to HHT than non-MDR cells, and that resistance to HHT was significantly decreased by all the MDR modifiers that were tested . This in vitro study showed that HHT belongs to the category of MDR-related drugs, like anthracyclines, vinca alkaloids, epipodophylline derivatives, and taxol. Br J Cancer, 1995 Mar, 71(3), 556 - 61 Constitutive expression of the c-H-ras oncogene inhibits doxorubicin-induced apoptosis and promotes cell survival in a rhabdomyosarcoma cell line; Nooter K et al.; Drugs used in anti-cancer chemotherapy are thought to exert their cytotoxic action by induction of apoptosis . Genes have been identified which can mediate or modulate this drug-induced apoptosis, among which are c-myc, p53 and bcl-2 . Since expression of oncogenic ras genes is a frequent observation in human cancer, we investigated the effects of the c-H-ras oncogene on anti-cancer drug-induced apoptosis . Apoptosis induced by a 2 h doxorubicin exposure was measured by in situ nick translation and flow cytometry in a rat cell line (R2T24) stably transfected with the c-H-ras oncogene and in a control cell line (R2NEO) transfected only with the antibiotic resistance gene neo . Both cell lines (R2T24 and R2NEO) had nearly identical growth characteristics, including cell doubling time, distribution over the cell cycle phases and plating efficiency in soft agar . Doxorubicin exposure of the R2NEO cells led to massive induction of apoptosis . In contrast, R2T24 cells, expressing the c-H-ras oncogene, showed significantly less apoptosis after doxorubicin incubation . Doxorubicin induced approximately 3- to 5-fold less cytotoxicity in the R2T24 cells than in the R2NEO cells, as determined by clonogenic assay in soft agar . No difference was observed in intracellular doxorubicin accumulation between the two cell lines, indicating that the classical, P-glycoprotein-mediated multidrug resistance phenotype is not involved in the observed differences in drug sensitivity . In conclusion, our data show that constitutive expression of the c-H-ras oncogene suppresses doxorubicin-induced apoptosis and promotes cell survival, suggesting that human tumours with ras oncogene expression might be less susceptible to doxorubicin treatment. Br J Cancer, 1995 Mar, 71(3), 505 - 11 Different vimentin expression in two clones derived from a human colocarcinoma cell line (LoVo) showing different sensitivity to doxorubicin; Conforti G et al.; We selected two clones, isolated from the human colocarcinoma cell line LoVo, showing a sensitivity to doxorubicin similar to (LoVo clone 5) or three times lower than (LoVo clone 7) the parental cell line . Since vimentin was atypically expressed in a human breast carcinoma cell line made resistant to doxorubicin, we looked at vimentin expression in these two clones with spontaneously different sensitivity to the drug . For comparison we used the parental cell line LoVo WT and LoVo/DX made resistant pharmacologically . mRNA for vimentin was undetectable by Northern blot analysis in LoVo WT and in LoVo clone 5, while expression of this gene was high in LoVo clone 7 and in LoVo/DX . This increase in mRNA levels was not related to an amplification of DNA, as suggested by Southern blot analysis . Immunofluorescence and immunocytochemistry findings confirmed, at protein level, the mRNA data . In LoVo clones 5 and 7, there were respectively 8.6% and 71% vimentin-positive cells, although the two clones showed similar expression of multidrug resistance gene 1 (mdr-1) and accumulated intracellular doxorubicin at similar levels . Similarly, drug efflux was the same for both clones . Our results show for the first time that cells resistant to doxorubicin express vimentin independently of the mdr glycoprotein . However when cells from clone 5 were transfected with human vimentin cDNA, they did not become resistant, indicating that vimentin can be considered as a marker of resistance in these cells but does not give rise to a resistant phenotype by itself. Br J Cancer, 1995 Mar, 71(3), 489 - 97 Mechanisms of resistance to combinations of vincristine, etoposide and doxorubicin in Chinese hamster ovary cells; Soues S et al.; We have isolated from Chinese hamster ovary cells, 30 sublines resistant to vincristine, doxorubicin or etoposide and 43 sublines evading treatment with a pair of these drugs . Isolated in one step and under low selective pressure, sublines were 3- to 25-fold more resistant to their selecting drug(s) than the parental cells . Possible P-glycoprotein-associated multidrug resistance was investigated through pgp gene copy number and mRNA expression level . DNA topoisomerase II alteration was evaluated from the ability of nuclear extracts to form cleavable complexes . Vincristine (all sublines) and doxorubicin (6/7 sublines) preferentially selected for pgp gene amplification and mRNA overexpression, whereas selection with etoposide resulted in a decrease of cleavable complex formation in 11 out of 13 sublines . A common pgp gene-mediated resistance was found in the 13 doxorubicin plus vincristine-selected sublines, whereas all but one of the 12 etoposide plus vincristine-resistant sublines displayed both pgp mRNA overexpression and decreased ability to form cleavable complexes . Among the 18 doxorubicin plus etoposide selected sublines, five exhibited a decreased ability to form cleavable complexes only, six exhibited pgp mRNA overexpression only and six exhibited both alterations . Overall, drug resistance could not be attributed to either mechanism in three of the 73 sublines . We conclude that under low selective pressure it is possible to find a combination of drugs which require simultaneous selection of more than one resistance mechanism; such cells emerge with very low frequency. J Cell Biol, 1995 Mar, 128(5), 793 - 804 A Chinese hamster ovary cell mutant defective in the non-endocytic uptake of fluorescent analogs of phosphatidylserine: isolation using a cytosol acidification protocol; Hanada K et al.; Transmembrane movement of phosphatidylserine (PS) and various PS analogs at the plasma membrane is thought to occur by an ATP-dependent, protein-mediated process . To isolate mutant CHO cells defective in this activity, we first obtained conditions which inhibited the endocytic, but not the non-endocytic pathway of lipid internalization since PS may enter cells by a combination of these two pathways . We found that acidic treatment of cells, which blocks clathrin-dependent endocytosis, enhanced the energy-dependent uptake of 1-palmitoyl-2-(6-{(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino}caproyl -sn- glycero-3-phosphoserine (C6-NBD-PS) in CHO cells from donor vesicles (liposomes) by about twofold . Control experiments demonstrated that the enhanced uptake of C6-NBD-PS at acidic pH was not due to: (a) an increase in the capacity of the plasma membrane to incorporate C6-NBD-PS from the donor vesicles; (b) a decrease in the rate of loss of C6-NBD-PS from the cells; or (c) fusion or engulfment of the donor vesicles . When cytosolic acidification (to pH 6.3) was imposed without acidification of the extracellular medium, C6-NBD-PS uptake by intact cells was increased by about 50% compared to control values determined in the absence of acidification . These results suggested that a protein and energy dependent system(s) for transbilayer movement of the fluorescent PS was stimulated by cytosolic acidification . A screening method for mutant cells defective in the non-endocytic uptake of fluorescent PS analogs with replica cell colonies at acidic pH was then devised . After selection of mutagenized CHO-K1 cells by in situ screening, we obtained a mutant cell line in which uptake of fluorescent PS analogs was reduced to about 25% of the wild type level at either pH 6.0 or 7.4 . Control experiments demonstrated that the reduced uptake of fluorescent PS analogs in the mutant cells was unrelated to multidrug resistance, and that endocytosis of another plasma membrane lipid marker occurred normally in the mutant cells . These results suggested that a non-endocytic pathway responsible for uptake of fluorescent PS analogs was specifically affected in the mutant cells. Cancer Res, 1995 Mar 1, 55(5), 1086 - 91 Differential effects of P-glycoprotein inhibitors on NIH3T3 cells transfected with wild-type (G185) or mutant (V185) multidrug transporters; Cardarelli CO et al.; Multidrug resistance (MDR) may be associated with the expression of the MDR1 gene which encodes the 170-kDa cell surface P-glycoprotein (PGP) acting as an energy-dependent multidrug efflux pump . This pump can be inhibited by a variety of drugs including cyclosporin A, quinidine, and verapamil . Substrate specificity of the MDR1 gene product can be altered by a point mutation at amino acid residue 185 in which valine is substituted for glycine, but the effect of this mutation on inhibition of PGP is unknown . Multidrug-resistant NIH3T3 cells transfected with the MDR1 retroviral vector pHaMDR-1/A (G185) or pHaMDR1/A (V185) expressing comparable levels of PGP were compared for patterns of drug resistance and inhibition of drug resistance by MDR reversing agents . The NIH-MDR-G185 transfectants were somewhat preferentially resistant to daunorubicin, taxol, and vinblastine . The mutant (V185) conferred increased resistance to colchicine . This MDR phenotype in both NIH-MDR-G185- and NIH-MDR-V185-transfected NIH3T3 cells was overcome by the addition of cyclosporin A, quinidine, or verapamil . Verapamil was the most potent of the three agents affecting wild-type PGP . However, specific inhibitors showed different potency with wild-type or mutant transporters, depending on the cytotoxic drug whose resistance was being reversed . For example, cyclosporin A at a concentration of 1 microgram/ml, was a powerful reverser of taxol and colchicine resistance for the mutant drug transporter, but was much less effective for the wild-type transporter . In contrast, verapamil reversed resistance to vinblastine more efficiently for the wild-type transporter than for the mutant transporter . These results suggest that the sensitivity of a multidrug transporter to a reversing agent will depend on the reversing agent, the cytotoxic drug, and the presence or absence of mutations which alter substrate specificity. J Neurosurg, 1995 Mar, 82(3), 469 - 74 Combination therapy with cisplatin and nifedipine inducing apoptosis in multidrug-resistant human glioblastoma cells; Kondo S et al.; The authors found that multidrug-resistant human glioblastoma GB-1 cells demonstrated significantly more resistance to cisplatin than did nondrug-resistant human glioblastoma U87-MG cells (p < 0.1) . They therefore attempted to determine whether calcium channel blockers enhance the antitumor activity of cisplatin against GB-1 cells . Nifedipine, a dihydropyridine calcium channel blocker, significantly enhanced the antitumor effect of cisplatin on GB-1 cells (p < 0.05) . In the absence of normal extracellular Ca++, nifedipine enhanced the cytotoxicity of cisplatin . In addition, the antitumor activity of combined cisplatin and nifedipine was inhibited both by actinomycin D and cycloheximide, suggesting that such activity is dependent upon new RNA and protein synthesis . Surprisingly, DNA fragmentation assay demonstrated that synergism between cisplatin and nifedipine resulted in apoptosis (programmed cell death) at a relatively low concentration of cisplatin, which when tested alone did not induce apoptosis . In addition, it was demonstrated that nuclei from GB-1 cells lacked a Ca(++)-dependent endonuclease that degrades chromatin into nucleosomes and that calcium ionophore A 23187 did not decrease the viability of GB-1 cells . The above findings suggest the hypothesis that the noncytotoxic agent nifedipine synergistically enhances the antitumor effect of cisplatin on multidrug-resistant GB-1 cells lacking Ca(++)-dependent endonuclease, and subsequently induces apoptosis via its interaction with an as yet uncharacterized functional site other than the calcium channel on GB-1 cells. Cell Growth Differ, 1995 Mar, 6(3), 347 - 54 Overexpression of the class II P-glycoprotein gene in primary rat hepatocyte culture: evidence for increased mRNA stability; Lee CH et al.; The overexpression of P-glycoprotein (Pgp) appears to be responsible for multidrug resistance in some human cancers . The molecular basis of this overexpression is not understood . We have used primary monolayer cultures of adult rat hepatocytes as a model system to study the regulation of Pgp gene expression (Lee et al., J . Cell . Physiol., 157: 392-402, 1993) . We observed a dramatic and specific overexpression of class II Pgp as a function of the time in culture . This isoform of Pgp, which is expressed at a very low level in normal liver, has also been shown to be predominantly overexpressed in several models of rat liver carcinogenesis . In the present study, we have used nuclear run-on assays and mRNA decay studies to investigate the mechanism for the overexpression of class II Pgp in cultured hepatocytes . We conclude that an increased mRNA stability is the major factor involved in the increased expression of class II Pgp . Studies using various drugs indicate that the integrity of the cytoskeleton is important for the maintenance of high expression of class II Pgp . Disruption of the cytoskeleton in cultured hepatocytes with cytochalasin D did not affect the transcriptional activity of the class II Pgp gene but rapidly destabilized its mRNA . This raises the possibility that an association between class II Pgp mRNA and cytoskeletal elements may underlie the mechanism that regulates class II Pgp mRNA stability . These findings have important implications for our understanding of the overexpression of class II Pgp during liver carcinogenesis. Trans R Soc Trop Med Hyg, 1995 Mar-Apr, 89(2), 213 - 5 Artemether-mefloquine combination in multidrug resistant falciparum malaria; Bunnag D et al.; Plasmodium falciparum in Thailand is highly resistant to chloroquine and sulfadoxine/pyrimethamine and there is increasing resistance to the alternative antimalarials, quinine and mefloquine . In eastern Thailand, the cure rates of mefloquine at 750 and 1250 mg were 30% and 55%, respectively . The use of drug combinations may be necessary in areas where drug-resistant parasites exist . 159 male Thai patients in Chantaburi, eastern Thailand, were allocated at random to receive either oral artemether at a single dose of 300 mg on the first day followed by mefloquine 750 mg at 24 h and 500 mg at 30 h (group A), or oral artemether at a single dose of 300 mg on the first day, mefloquine 750 mg at 24 h and placebo at 30 h (group B) . The follow-up was on days 1, 2, 7, 14, 21, 28, 35 and 42 . Most patients in both groups had a rapid initial response to treatment, parasitaemia being cleared within 24 h and fever cleared within 48 h in both groups . The cure rates were 97% and 90%, respectively, for groups A and B . No serious adverse effect was seen in either group; mild and transient nausea, vomiting and loss of appetite were noted . The adverse effects did not differ between the 2 groups . The results suggested that a single oral dose of artemether (300 mg) can markedly improve the cure rate of mefloquine at a dose of 750 or 1250 mg in multiple drug-resistant falciparum malaria. Hum Immunol, 1995 Mar, 42(3), 245 - 53 Cell surface expression of major histocompatibility class I antigens is modulated by P-glycoprotein transporter; Masci AM et al.; P-glycoprotein (Mdr1), a member of the ABC superfamily, is a pump able to transport several compounds across plasma membranes . It displays a high level of similarity with the MHC-linked transporters TAP1 and TAP2 which are involved in the delivery of immunogenic peptides across the endoplasmic reticulum . In the present study we analyze the P-glycoprotein's ability to interfere with the biosynthetic pathway of the MHC class I molecules . Our results show that P-glycoprotein is involved in the modulation of the MHC class I expression in multidrug-resistant tumor cell lines, COS1 cells transfected with mdr1 gene, and human T lymphocytes . Epitope screening evokes the possibility that P-glycoprotein induces a modulation of the different MHC class I forms expressed on the cell surface . We propose that P-glycoprotein is involved in the transport of antigenic protein fragments from the cytosol into the endoplasmic reticulum . The suggested mechanism could be physiologically relevant in tissues displaying a high Mdr1 activity, where this transporter could contribute to the regulation of locoregional immune responses. Diagn Mol Pathol, 1995 Mar, 4(1), 59 - 65 Correlation of p-glycoprotein detection by immunohistochemistry with mdr-1 mRNA levels in osteosarcomas . Pilot study; Kandel RA et al.; All the factors that influence prognosis in patients with osteosarcomas have not been fully determined . One reported predictor of poor outcome is increased multi-drug resistant gene (mdr-1) expression, as measured by reverse transcription and polymerase chain reaction (RT-PCR) . We examined whether immunostaining for p-glycoprotein, the protein product of mdr-1, could be used instead of RT-PCR to indicate the presence of the multidrug-resistant phenotype . The sensitivity of the immunostaining was determined using KB cell sublines . For 13 cases of osteosarcoma, samples were immunostained for p-glycoprotein and the levels of mdr-1 expression quantitated with use of RT-PCR . Three osteosarcomas with undetectable levels of mdr-1 expression by RT-PCR were negative immunohistochemically . Ten cases showed mdr-1 expression ranging from approximately 1 to 32 copies of mdr-1 mRNA/cell . Of these cases, five cases contained occasional tumour cells with positive immunostaining . There was no correlation between levels of expression and the presence or number of immunoreactive cells . These results indicate that the presence of p-glycoprotein immunostaining does not reliably correlate with the level of mdr-1 expression . However it may be useful in conjunction with RT-PCR to further define different subgroups of osteosarcomas that may have different prognoses, and this is currently under investigation. Anticancer Drug Des, 1995 Mar, 10(2), 103 - 18 Cinchonine per os: efficient circumvention of P-glycoprotein-mediated multidrug resistance; Genne P et al.; We have previously suggested that quinine and cinchonine could be good candidates for the clinical circumvention of multidrug resistance (MDR) in haematological malignancies because of their tolerance and their retained efficacy in serum . We have also shown that cinchonine was more efficient than quinine as an anti-MDR agent in vitro, ex vivo and in vivo after parenteral administration . Here, we report that cinchonine administered per os (po) is much more active than quinine po in circumventing MDR in rats bearing resistant colon tumours . The pharmacokinetics of cinchonine and quinine administered po in rat are shown to be very different . Cinchonine demonstrates a greater absolute bioavailability than quinine (44% versus 30%, respectively) . Its serum concentration correlates with the anti-MDR activity measured ex vivo and in vivo . Cinchonine administered po does not significantly modify the pharmacokinetics of intravenous doxorubicin (DXR) . However, cinchonine induces a significant increase of DXR uptake in organs which express the mdr1 gene (liver, kidney, lung) . When associated with VAD (vincristine, adriamycin, dexamethasone) combined therapy in rats, cinchonine does not significantly increase the toxicity of the cytotoxic drugs . Based on these experimental data, a phase I clinical trial is currently in progress to test the tolerance of this potent MDR-reversing agent administered po. Carcinogenesis, 1995 Mar, 16(3), 637 - 41 Gene amplification and multidrug resistance induced by the phosphatase-inhibitory tumor promoter, okadaic acid; Wang SJ et al.; The mechanism by which tumor promoters contribute to cellular transformation and tumorigenesis is not completely understood . To investigate further the molecular events involved in these processes, we used okadaic acid, a non-phorbol ester type tumor promoter that specifically inhibits certain protein phosphatases . We describe here that the continuous treatment of murine NIH 3T3 fibroblast cell cultures with okadaci acid resulted in a 50-fold amplification of two genes, mdr-1a and mdr-1b, that conferred multidrug resistance . As a consequence, the cells became cross-resistant to the cytotoxic effects of adriamycin, an antineoplastic drug used in the treatment of human tumors . Since genetic changes have been correlated with cell transformation and tumorigenesis, our results suggest that these processes may constitute an additional factor contributing to tumor promotion by okadaic acid. Cancer Genet Cytogenet, 1995 Mar, 80(1), 47 - 54 Evolution of chromosomal alterations and biologic features in two small cell lung carcinoma cell lines established from one patient during the course of the disease; Goguel AF et al.; Two small cell lung cancer (SCLC) cell lines were established from metastases of a patient during the course of the disease . SCLC 74A was derived from biopsy material obtained at the time of diagnosis and SCLC 74B was from a biopsy specimen of a relapsed tumor obtained after treatment . A transition occurred from SCLC 74A, an intermediate form with 5% large cells to SCLC 74B, a standard mixed form with 20% of large cells, with a decrease in neuroendocrine markers and a substantial increase in P-glycoprotein, a multidrug resistance marker . For both cell lines, R-banding and FISH indicated a del(1)(p35pter) also found in other neural-crest-derived tumors, the loss of regions with suspected tumor suppressor genes at 3p, 5q, and 17p, and a recurrent translocation of the 6q24-6qter region to 10p14 . Further genetic modifications in SCLC 74B affected chromosomes 2, 3, 5, 10, 11, 14, and 15 . The main observations were a der(2)t(2;5)(p16;q?); a der(3;11)(q10;p10) in SCLC 74A which became der(3;14)(q10;p10) and der(11;14)(p10;q10) in SCLC 74B; and the insertion of the 5q13-5q31 region in the der(10)t(6;10) . The finding of the same structural abnormalities in both cell lines suggests a monoclonal origin for both metastases . Hypotetraploid cells were in the same proportion as large cells whose number was a characteristic feature of each cell line . They possessed twice the same chromosomal alterations observed in the hypodiploid cells . This suggests a permanent process of tetraploidization. Bull Cancer, 1995 Mar, 82(3), 211 - 7 Evaluation of multidrug resistant phenotype by flow cytometry with monoclonal antibodies and functional tests; Lizard G et al.; Multidrug resistant (MDR) phenotype is characterized by a defect in drug accumulation caused by overexpression of a transmembrane glycoprotein, the P-glycoprotein (P-gp) . MDR phenotype can be characterized either with monoclonal antibodies raised against P-gp or with functional tests, most often based on the incorporation of fluorescent compounds . In the present study, data obtained with the monoclonal antibodies C219, JSB1 and MRK16 are compared to those of functional tests performed by flow cytometry including uptake of daunorubicin (DNR), Rhodamine 123 (Rh 123) or Hoechst 33342 . Sensitive and resistant cell lines K562S, K562R, KBA1 and KB31, derived either from a human chronic myeloid leukemia or from a human epithelial carcinoma, were used . In resistant cells, P-gp expression was revealed with either the monoclonal antibodies C219, JSB1 or MRK-16 . The most specific results were obtained with MRK-16 . With functional tests, no matter which dyes were used, the fluorescence was always stronger in sensitive than in resistant cells . However, with DNR and Hoechst 33342, an incorporation of these dyes was exhibited in resistant cells . This phenomenon was not observed with Rh 123, which makes it possible to distinguish clearly between sensitive and resistant cells and to detect as few as 1% of resistant cells . Because of its high sensitivity, the functional test involving incorporation of Rh 123 was successfully used in acute myeloid leukemia to detect multichemoresistant cells. Infect Control Hosp Epidemiol, 1995 Mar, 16(3), 160 - 5 Transmission of multidrug-resistant Mycobacterium tuberculosis among persons exposed in a medical examiner's office, New York; Ussery XT et al.; OBJECTIVE: To determine the prevalence of and risk factors for having a positive tuberculin skin test (TST) result among employees at a medical examiner's office (MEO) . DESIGN: Cohort study, environmental investigation . SETTING: Several employees at a medical examiner's office were found to have positive TST results after autopsies were performed on persons with multidrug-resistant tuberculosis (MDR-TB) . PARTICIPANTS: Employees of the MEO . RESULTS: Of 18 MEO employees, 5 (28%) had a positive TST result; 2 of these 5 had TST conversions . We observed a trend between TST conversion and participation in autopsies on persons with MDR-TB (2 of 2 converters versus 3 of 13 employees with negative TST; relative risk = 4.3; 95% confidence interval 1.61 to 11.69; P = 0.10) . The environmental investigation revealed that the autopsy room was at positive pressure relative to the rest of the MEO and that air from the autopsy room mixed throughout the facility . CONCLUSIONS: A systematic approach to preventing transmission of Mycobacterium tuberculosis in autopsy suites should include effective environmental controls and routine tuberculin skin testing of employees. Infect Control Hosp Epidemiol, 1995 Mar, 16(3), 152 - 9 Nosocomial tuberculosis: an outbreak of a strain resistant to seven drugs; Ikeda RM et al.; OBJECTIVE: To evaluate nosocomial transmission of multidrug-resistant (MDR) tuberculosis (TB) . DESIGN: Outbreak investigation: review of infection control practices and skin test results of healthcare workers (HCWs); medical records of hospitalized TB patients and mycobacteriology reports; submission of specimens for restriction fragment length polymorphism (RFLP) typing; and an assessment of the air-handling system . SETTING: A teaching hospital in upstate New York . RESULTS: Skin-test conversions occurred among 46 (6.6%) of 696 HCWs tested from August through October 1991 . Rates were highest on two units (29% and 20%); HCWs primarily assigned to these units had a higher risk for conversion compared with HCWs tested following previous incidents of exposure to TB (relative risk {RR} = 53.4, 95% confidence interval {CI95} = 6.9 to 411.1; and RR = 37.4, CI95 = 5.0 to 277.3, respectively) . The likely source patient was the only TB patient hospitalized on both units during the probable exposure period . This patient appeared clinically infectious, was associated with a higher risk of conversion among HCWs providing direct care (RR = 2.37; CI95 = 1.05 to 5.34), and was a prison inmate with TB resistant to seven antituberculosis agents . The MDR-TB strain isolated from this patient also was isolated from other inmate and noninmate patients, and a prison correctional officer exposed in the hospital . Mycobacterium tuberculosis isolates from all of these patients had matching RFLP patterns . Infection control practices closely followed established guidelines; however, several rooms housing TB patients had marginal negative pressure with variable numbers of air changes per hour, and directional airflow was disrupted easily . CONCLUSIONS: These data strongly suggest nosocomial transmission of MDR-TB to HCWs, patients, and a prison correctional officer working in the hospital . Factors contributing to transmission apparently included prolonged infectiousness of the likely source patient and inadequate environmental controls . Continued urgent attention to TB infection control is needed. Infect Control Hosp Epidemiol, 1995 Mar, 16(3), 141 - 7 Evaluation of infection control measures in preventing the nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis in a New York City hospital; Stroud LA et al.; OBJECTIVE: To evaluate the efficacy of Centers for Disease Control and Prevention (CDC)-recommended infection control measures implemented in response to an outbreak of multidrug-resistant (MDR) tuberculosis (TB) . DESIGN: Retrospective cohort studies of acquired immunodeficiency syndrome (AIDS) patients and healthcare workers . The study period (January 1989 through September 1992) was divided into period I, before changes in infection control; period II, after aggressive use of administrative controls (eg, rapid placement of TB patients or suspected TB patients in single-patient rooms); and period III, while engineering changes were made (eg, improving ventilation in TB isolation rooms) . SETTING: A New York City hospital that was the site of one of the first reported outbreaks of MDR-TB among AIDS patients in the United States . PARTICIPANTS: All AIDS patients admitted during periods I and II . Healthcare workers on nine inpatient units with TB patients and six without TB patients . RESULTS: The epidemic (38 patients) waned during period II and only one MDR-TB patient presented during period III . The MDR-TB attack rate among AIDS patients hospitalized on the same ward on the same days as an infectious MDR-TB patient was 8.8% (19 of 216) during period I, decreasing to 2.6% (5 of 193; P = 0.01) during period II . In a small group of healthcare workers with tuberculin skin test data, conversions during periods II through III were higher on wards with than without TB patients (5 of 29 versus 0 of 15; P = 0.15), although the difference was not statistically significant . CONCLUSIONS: Transmission of MDR-TB among AIDS patients decreased markedly after enforcement of readily implementable administrative measures, ending the outbreak . However, tuberculin skin-test conversions among healthcare workers may not have been prevented by these measures . CDC guidelines for prevention of nosocomial transmission of TB should be implemented fully at all US hospitals. Curr Probl Cancer, 1995 Mar-Apr, 19(2), 65 - 124 Clinical reversal of drug resistance; Goldstein LJ; Although combination chemotherapy has had a significant impact on survival for malignancies such as Hodgkin's disease, testicular cancer, and childhood acute leukemias, the majority of cancers are either initially resistant to chemotherapy (renal, colon, etc.) or are initially chemosensitive but acquire resistance during treatment, such as lymphoma and breast cancer . Resistance to chemotherapy remains an obstacle to the successful treatment of human cancer and has been the subject of numerous investigations aimed at identifying the molecular mechanisms of resistance in cancer cells . An improved understanding of the mechanisms by which tumor cells develop resistance to chemotherapy may not only enhance the activity of cytotoxic therapy in advanced malignancies but may ultimately improve the impact of adjuvant therapy, potentially resulting in prolonging disease-free intervals and survival . In this review, therefore, we discuss our current understanding of the MDR1 gene, encoding P-glycoprotein, which is responsible for one mechanism of multidrug resistance (MDR) . We also review the evidence supporting the clinical relevance of the MDR1 gene and clinical trials aimed at reversing MDR-mediated resistance . Although MDR-mediated drug resistance has been well characterized in preclinical models, its role in clinical drug resistance is not as well characterized and requires further investigation . Prospective studies are necessary to establish the role of MDR1 gene expression in the clinical resistance . The ability to identify tumors with increased MDR1 gene expression has several potential applications (for example, the prediction of response to chemotherapy and the design of studies aimed at reversal of resistance with agents that inhibit MDR-mediated drug efflux) . The initial goal of such trials is to demonstrate the ability to reverse MDR1-mediated drug resistance in the appropriate advanced refractory malignancies . Ultimately, it will be important to incorporate these reversal strategies in the treatment of early-stage disease, at which time the tumor burden is smaller and fewer mechanisms of resistance may be present . Prospective phase I, II, and III clinical trials using reversing agents in conjunction with chemotherapy in malignancies that express the MDR1 gene, such as the hematologic malignancies and breast cancer, are necessary before routine use of agents such as verapamil, quinidine, and cyclosporine, which carry innate toxicities . MDR is a mechanism of drug resistance that provides the potential for an alteration in drug efflux, which may have a significant impact on response and possibly result in improved survival for some cancer patients. In Vivo, 1995 Mar-Apr, 9(2), 133 - 8 P-170 glycoprotein expression in gastric and colorectal carcinomas and normal mucosa . An immunocytochemical study; Caruso ML et al.; During the past few years it has become apparent that simultaneous resistance of tumour cells to a number of heterocyclic drugs (multidrug resistance) is often correlated with overexpression of a P-glycoprotein (P-gp or P-170) . P-gp expression can be studied by molecular biology and immunohistochemical techniques . The latter provide a rapid, sensitive and specific screening method suitable for testing even a relatively small number of tumour cells like those obtained at biopsy . The aim of this study was to detect and localize the immunohistochemical expression of P-gp in normal and neoplastic gastrointestinal tissue using the Mab JSB-1 in formalin-fixed paraffin-embedded specimens . A particularly striking finding of our study was the consistent, prevalent higher expression of P-gp in the stomach than in the colon, with a higher percentage of immunostaining in normal than in neoplastic tissue . This is in agreement with the fact that not only is the prognosis known to be worse for stomach cancer, but also the response to treatment is lower . Further studies should be carried out to verify the possibility of making routine tests of this kind for the evaluation of multidrug resistance, to guide the selection of patients for treatment of cancer with chemotherapeutic drugs. Minerva Endocrinol, 1995 Mar, 20(1), 105 - 9 Cytotoxic chemotherapy for adrenocortical carcinoma; Dogliotti L et al.; The efficacy of mitotane in providing objective tumour responses in patients with adrenocortical carcinoma (ACC), has been recently questioned . Experience with non specific chemotherapy is limited . Tumour responses have been reported with cisplatin administered as a single agent or in combination . Other reports however failed to show benefit from cytotoxic chemotherapy . The very low number of patients included in each study, mostly of them previously treated with mitotane, may account for these controversial results . The finding that multidrug resistance mediated by MDR-1/P-glycoprotein can be reverted by mitotane provides a rational basis for exploring the use of mitotane in combination with chemotherapeutic agents . In a multicenter cooperative (SWOG) phase II study, a combination of mitotane+cisplatin appeared active in advanced ACC, with 30% response rate in 37 eligible patients . These results prompted us to evaluate the activity of a combination chemotherapy of Eto-poside, Adriamycin and Cisplatin (EAP) in association with mitotane (4 g daily per os) . Up to now we treated 6 patients, obtaining 3 partial responses . Recently, new drugs as suramin and gossypol have been show to have some activity in patients with surgically unresectable ACC, suggesting the need for further investigation . In conclusion, cytotoxic drugs+mitotane and new adrenocorticolytic/cytotoxic agents, should be explored as first line treatments in patients with advanced ACC . However, due to the extreme rarity of the disease, coordinated multicenter investigations should be highly encouraged. Haematologica, 1995 Mar-Apr, 80(2), 103 - 7 Glutathione-S-transferase activity and multidrug resistance phenotype in chronic lymphocytic leukemia: do they have any clinical relevance? Di Simone D, Testi R, Caracciolo F, Capochiani E, Ambrogi F, Grassi B, Petrini M. BACKGROUND . Lymphocytes from patients affected by B-cell chronic lymphocytic leukemia (B-CLL) have frequently been shown to be positive for the multidrug resistance (MDR) phenotype . However, this phenotype does not seem to be responsible for the resistance to alkylating agents usually employed in the management of CLL . METHODS . Lymphocytes from 42 patients were evaluated by flow cytometry for P-170 expression and by spectrophotometry for glutathione-S-transferase (GST) activity . RESULTS . Our findings show that GST is not related to any clinical parameter but is increased in treated patients . Conversely, 85% of patients were positive for P-170 and this was related to the percentage of CD5/CD19-positive lymphocytes . CD5/CD19-negative patients were also negative for P-170 . MDR was not related to any clinical parameter evaluated nor to GST activity in lymphocytes . CONCLUSIONS . MDR is constitutively expressed in B-cell chronic lymphocytic leukemia and seems to be related to a CD5/CD19 B-CLL phenotype . The increase of GST activity in treated patients is statistically significant (p < 0.005). Blood Rev, 1995 Mar, 9(1), 47 - 52 Modulation of multidrug resistance in de novo adult acute myeloid leukemia: variable efficacy of reverting agents in vitro . Eastern Cooperative Oncology Group; Paietta E et al.; The efficacy of verapamil and cyclosporine A as modulators of P-glycoprotein, the multidrug resistance (MDR1) gene product, was studied in leukemic blast cells from 56 patients with de novo acute myeloid leukemia (AML) in vitro . Rhodamine123 dye-efflux was measured flow cytometrically as a cellular parameter reflecting P-glycoprotein activity . While dye-efflux was measurable in 3/4 of the cases, the capacity of the P-glycoprotein inhibitors varied substantially among patients . In 23 patients, P-glycoprotein function was completely inhibited by the resistance modulators, whereas in 17 patients neither verapamil nor cyclosporine had any reverting effect on dye-efflux at concentrations even 10-times higher than achievable in vivo . Cells with a drug-sensitive rhodamine123-pump effluxed more efficiently (p = 0.0016) and contained significantly higher levels of MDR1 specific RNA transcripts (p = 0.0002), as determined by quantitative PCR, than cells exhibiting an efflux process that could not be inhibited . However, flow cytometric evaluation of the staining of gated blast cells with the anti-P-glycoprotein antibody, 4E3.16, revealed no difference in P-glycoprotein expression between modulator-sensitive and -insensitive cases (p = 0.86), indicating disproportionate translation of MDR1 mRNA . In leukemic cell populations with increased P-glycoprotein function that could be inhibited, significantly more blasts expressed the progenitor cell antigen, CD34 (median 83%), than was the case in leukemias with P-glycoprotein activity that could not be inhibited (median 7%) (p = 0.0001) . The present study demonstrates that a substantial fraction of AML patients constitutively display a drug-efflux mechanism suggestive of P-glycoprotein activity.(ABSTRACT TRUNCATED AT 250 WORDS) Neurosurgery, 1995 Mar, 36(3), 565 - 71; discussion 572 Effects of protein kinase C modulators on multidrug resistance in human glioma cells; Matsumoto T et al.; To identify the role of protein kinase C (PKC) in multidrug resistance, the effects of phorbol-12-myristate-13-acetate (PMA), a PKC activator, or calphostin C, a PKC inhibitor, on intracellular vincristine accumulation and expression of P-glycoprotein phosphorylation were studied in one multidrug-resistant and three multidrug-sensitive human glioma cell lines . Basal PKC activities and immunoreactivities of PKC-alpha and -zeta were higher in multidrug-resistant cells than in multidrug-sensitive cells . There was no significant difference in the immunoreactivity of PKC-delta between multidrug-resistant and -sensitive cells, and immunoreactive PKC-beta, -gamma, and -epsilon were not detected in either multidrug-resistant or -sensitive cells . The treatment of multidrug-resistant cells with 100 nM PMA for 2 hours resulted in the activation not of PKC-zeta but of PKC-alpha, with concomitant decrease in vincristine accumulation and increase in P-glycoprotein phosphorylation . The exposure of multidrug-resistant cells to 100 nM PMA for 24 hours induced down-regulation not of PKC-zeta but of PKC-alpha, with concurrent decrease in vincristine accumulation, and reduced but still increased P-glycoprotein phosphorylation . The treatment of multidrug-resistant cells with 100 nM calphostin C for 2 hours decreased immunoreactive PKC-zeta and not immunoreactive PKC-alpha, inducing increase in vincristine accumulation, with concomitant decrease in P-glycoprotein phosphorylation . There was no evidence of significant change in vincristine accumulation in multidrug-sensitive cells treated with PMA or calphostin C . This may suggest that at least two isozymes of PKC, PKC-alpha and -zeta, are involved in P-glycoprotein phosphorylation and that vincristine efflux function in multidrug-resistant human glioma cells is closely associated with P-glycoprotein phosphorylation and is decreased by PKC inhibitor. FEBS Lett, 1995 Feb 27, 360(2), 165 - 8 Tamoxifen inhibits uptake and metabolism of ethanolamine and choline in multidrug-resistant, but not in drug-sensitive, MCF-7 human breast carcinoma cells; Kiss Z et al.; Tamoxifen (TAM), a widely used agent in the hormonal therapy of breast cancer, is also an antagonist of P-glycoprotein (P-gp), a cell surface protein which confers drug resistance to cells . Here we report that in an estrogen receptor-deficient multidrug-resistant subline of MCF-7 human breast carcinoma cells (MCF-7/MDR), but not in the parent drug-sensitive cells (MCF-7/WT), clinically relevant concentrations (1-5 microM) of TAM inhibited the uptake and phosphorylation of ethanolamine and choline . These inhibitory effects resulted in decreased synthesis of the corresponding phospholipids . In view of the known dependence of P-gp function on phosphatidylethanolamine (PtdEtn), inhibition of PtdEtn synthesis may represent an additional mechanism by which TAM inhibits P-gp-mediated drug efflux. Biochem Biophys Res Commun, 1995 Feb 27, 207(3), 1003 - 8 Two distinct K(+)-ATPase activities in rabbit distal colon; Abrahamse SI et al.; The distribution of K(+)-ATPase activity in surface and crypt cells from rabbit distal colon was studied . Separation of surface and crypt cells was validated using the multidrug resistance gene (mdr 1) product, P-glycoprotein, as marker for differentiated surface epithelial cells . Western blot analysis revealed a 6-fold higher expression level of P-glycoprotein in colonic surface cells . K(+)-stimulated ouabain-insensitive ATPase activity was present in surface and in crypt cells . In surface cells, this K(+)-ATPase activity was only partly inhibitable by 10 microM SCH 28080, while in crypt cells K(+)-ATPase activity equalled SCH 28080-sensitive ATPase activity . These results strongly suggest the presence of two distinct K(+)-ATPases in colonic epithelial cells. Biochim Biophys Acta, 1995 Feb 21, 1260(3), 285 - 93 Isolation and molecular cloning of human sorcin a calcium-binding protein in vincristine-resistant HOB1 lymphoma cells; Wang SL et al.; A vincristine-resistant lymphoma cell line (HOB1/VCR1.0) that is resistant to 1.0 microM of vincristine has been established from a human immunoblastic B lymphoma cell line, HOB1 . HOB1/VCR1.0 cells demonstrated the typical multidrug resistant phenotypes . Using two-dimensional gel electrophoresis, we discovered one protein with a molecular mass of 22 kDa and pI 5.7 that was overexpressed in HOB1/VCR1.0 cells . This protein was purified to the degree of apparent homogeneity by preparative isoelectric focusing and sodium dodecylsulfate-polyacrylamide gel electrophoresis . The identification of this protein with sorcin was revealed by comparing the internal amino acid sequence of three Lys-C digested peptides from the purified protein with the sequence previously determined for hamster sorcin . The complete primary structure of the human sorcin was deduced from nucleotide sequence analysis of its cDNA clones . It is composed of 198 amino acid residues with a calculated molecular weight of 21,676, and its sequence is highly similar to that of hamster sorcin (95%) . Direct-binding assay with calcium showed that human sorcin is a calcium-binding protein with four 'E-F hand' structures typical of calcium-binding sites . Like the sorcin of hamster, two of the calcium-binding sites of human sorcin contain putative recognition sites for cAMP-dependent protein kinase . Southern and Northern blot analyses showed that the human sorcin gene was greatly amplified and overexpressed in resistant HOB1/VCR1.0 cells but not detected in the parental HOB1 cells . The overproduction of this protein in resistant cells implies that sorcin plays a role in expression of the resistant phenotype. Experientia, 1995 Feb 15, 51(2), 137 - 40 Expression of multidrug resistance (mdr) gene(s) in primary lymphoid organs of chicken immune system during embryonic development; Petrini M et al.; The presence of a multidrug resistance (MDR) related protein, P-170, in normal and pathological lymphoid cells has been described . The present report evaluates the expression of the mdr 1 gene by using the reverse Polymerase Chain Reaction (PCR) on cells obtained from the thymus and bursa of chicken embryos starting from day 12 until hatching . Results show that the thymic cells are positive from day 12 to the end of the observation period . In contrast, mdr mRNA was detected in the bursa from day 14 to day 17 of embryonic life . Possible relationships between the expression of mdr and the development of T and B lymphocytes are discussed. Gene, 1995 Feb 14, 153(2), 299 - 300 The human mdr1 (multidrug-resistance) gene harbours a long homopyrimidine.homopurine sequence next to a cluster of Alu repeated sequences in intron 14; Pauly M et al.; In order to identify specific DNA sequences useful as 'genetic landmarks' in the construction of a complete map of the human mdr1 (multidrug-resistance) gene, we investigated the introns in the central region . In intron 14, we identified a long stretch of a homopyrimidine.homopurine sequence most probably adopting an unconventional DNA conformation, followed by a cluster of three Alu repeated sequences in an inverted orientation . Here, we describe the structure, formation and nucleotide sequence of these DNA elements. Gan To Kagaku Ryoho, 1995 Feb, 22(3), 365 - 70 {Development of drugs to overcome drug resistance--basic approaches}; Tsuruo T; P-glycoprotein plays a key role in the mechanisms of multidrug resistance in experimental tumors as well as in clinical tumors both in acquired and intrinsic-type resistance . Thus the therapeutic approaches targeting P-glycoprotein would provide benefits in eradication of drug-resistant tumor cells, although some potential problems concerning side effects still remain to be studied . Practical approaches to overcoming multidrug resistance by targeting the P-glycoprotein would be (1) to use antibodies against P-glycoprotein; and (2) to use agents, including calcium channel blocker-related agents and membrane-modifying agents, that interact with P-glycoprotein . These therapeutic approaches will be discussed in the symposium. Leukemia, 1995 Feb, 9(2), 350 - 6 Low frequency of activity of P-glycoprotein (P-170) in acute lymphoblastic leukemia compared to acute myeloid leukemia; Ludescher C et al.; The purpose of our investigations was to measure P-glycoprotein (P-170) activity in blast cells of 35 adults with acute myeloid leukemia (AML), and 24 children and adults with acute lymphoblastic leukemia (ALL) at time of diagnosis . Studies were based on a flow cytometric assay that detects efflux of the fluorescent dye rhodamine 123 (Rh123), which is transported from the cell by the P-170 pump . Dual-fluorescence staining with Rh123 and phycoerythrin-labeled monoclonal antibodies allowed selective measurement of Rh123 efflux in blast cells . Samples were scored positive when the fraction of blast cells showing Rh123 efflux exceeded 10% after a 120-min incubation . Activity of P-170 was observed in 19 (54%) of the 35 AML cases and was completely blocked in the presence of multidrug resistance inhibitors . Efflux activity was significantly higher in CD34-positive AML samples (p < 0.02) . All AML patients with the FAB-subtype M5 (n = 5) lacked Rh123 pumping activity (p < 0.03) . The complete remission rate in response to induction chemotherapy was significantly higher for Rh123-negative (11/13, 85%) than for Rh 123-positive AML patients (4/15, 27%) (p < 0.007) . At a median follow-up of 9 months overall survival was significantly shorter for Rh123-positive than for Rh123-negative patients (p < 0.05) . In contrast to AML, we could detect Rh123 efflux in only two (8%) out of 24 ALL cases . The immunological subtypes of these two positive cases was of B-ALL and pre-T-ALL . Bone marrow cryostat sections from 13 AML and five ALL patients were further analyzed for staining with monoclonal antibodies MM4.17 and JSB1 . Ten of 13 AML and two of five ALL cases expressed the MDR protein . Our results indicate that there is a rather low frequency of P-170 pumping activity in ALL compared with AML . Further, functional activity of P-170 contributes to chemoresistance in de novo AML. Am J Pathol, 1995 Feb, 146(2), 398 - 408 Relationship between P-glycoprotein expression and cyclosporin A in kidney . An immunohistological and cell culture study; Garcia del Moral R et al.; P-glycoprotein (P-gp), encoded in humans by the mdr-1 gene, acts physiologically as an efflux pump to expel hydrophobic substances from cells . This glycoprotein is closely related to multidrug resistance in tumor cells and can be modulated by cyclosporin A (CsA) . We investigated the relationship between CsA and P-gp in 52 renal allograft biopsies and in cultures of Madin-Darby canine kidney (MDCK) renal tubule cells to determine whether the intrarenal accumulation of CsA or chronic stimulation with the drug modified the expression of P-gp . Expression of P-gp and CsA was analyzed by immunohistochemistry . Immunostaining was evaluated semiquantitatively . Modulation of P-gp in MDCK cells after chronic stimulation with CsA for 7, 30, and 60 days was analyzed by flow cytometry . P-gp and CsA immunostaining in renal post-transplant biopsies showed considerable overlap in all cases (Spearman's test, r = 0.577, P < 0.001) . After 7 days in vitro, the number of cells expressing P-gp increased progressively; a further increase in mean fluorescence was found after 60 days (P < 0.001, Student's t-test) . Our findings suggest that in non-neoplastic cells, CsA may stimulate P-gp as a mechanism of detoxification . Individual differences in the adaptive responses to glycoprotein may be responsible for the appearance of nephrotoxicity or a CsA-resistant rejection reaction in cases of overexpression on lymphocytes and macrophages. Emerg Med Clin North Am, 1995 Feb, 13(1), 179 - 98 Tuberculosis in the HIV-infected patient; Waxman S et al.; After decades of decline, tuberculosis has emerged as a global health challenge . In the setting of HIV immunocompromise, TB occurs frequently, early, and often atypically . New infections can take an accelerated course . The usual tests for diagnosing Mycobacterium tuberculosis infection are less sensitive when CD4+ counts are low . Increased prevalence of treatment failure, drug-resistant strains, and nosocomial transmission of multidrug-resistant TB are discussed as are new diagnostic tests that will accelerate the time to diagnosis and allow better epidemiologic tracking . Early recognition, isolation, appropriate therapy, and environmental controls that will protect staff and patients from the risk of exposure are also described. Br J Cancer, 1995 Feb, 71(2), 306 - 10 Selective photodynamic inactivation of a multidrug transporter by a cationic photosensitising agent; Kessel D et al.; We have characterised sites of photodamage catalysed by the cationic photosensitiser tetrabromorhodamine 123, using P388 murine leukaemia cells and a subline (P388/ADR) which has a multidrug resistance phenotype and hyperexpresses mdr1 mRNA for P-glycoprotein . Fluorescence emission spectra were consistent with sensitiser localisation in hydrophobic regions of the P388 cell, and in more aqueous loci in P388/ADR . Subsequent irradiation resulted in photodamage to the P388 cells, resulting in loss of viability . In contrast, P388/ADR cells were unaffected except for an irreversible inhibition of P-glycoprotein, leading to enhanced accumulation of daunorubicin and rhodamine 123 and a corresponding increase in daunorubicin cytotoxicity . These results are consistent with the premise that substrates for P-glycoprotein are confined to membrane loci associated with the transporter, and indicate a very limited migration of cytotoxic photo-products in a cellular environment. Br J Cancer, 1995 Feb, 71(2), 294 - 9 Interaction of tamoxifen with the multidrug resistance P-glycoprotein; Callaghan R et al.; Tamoxifen is an anti-oestrogen which is currently being assessed as a prophylactic for women at high risk of breast cancer . Taxoxifen has also been shown to reverse multidrug resistance in P-glycoprotein (P-gp)-expressing cells, although the mechanism of action is unknown . In this study we demonstrate that tamoxifen interacts directly with P-gp . Plasma membranes from P-gp-expressing cells bound {3H}tamoxifen in a specific and saturable fashion . A 180 kDa membrane protein in these membranes, labelled by the affinity analogue tamoxifen aziridine and azidopine, was shown to be P-gp . Tamoxifen reduced the binding of vinblastine and azidopine to P-gp, and tamoxifen increased {3H}vinblastine accumulation in P-gp-expressing cells to levels approaching those in non-P-gp-expressing cells . However, the cellular accumulation of {3H}tamoxifen itself was not influenced by the presence of P-gp . Thus, tamoxifen appears to reverse multidrug resistance by binding to P-gp and inhibiting the transport of cytotoxic drugs, but does not itself appear to be transported by the protein. Cancer Res, 1995 Feb 1, 55(3), 603 - 9 In vivo antitumor activity of two new seven-substituted water-soluble camptothecin analogues; Emerson DL et al.; The development of camptothecin-like compounds as inhibitors of topoisomerase I for the treatment of resistant tumors has generated clinical excitement in this new class of drugs . We have developed two novel water-soluble camptothecin analogues which are specific inhibitors of topoisomerase I and are potent cytotoxins with significant antitumor activity . We added water-solubilizing groups off position 7 in the B ring of either 10,11-ethylenedioxy- or 10,11-methylenedioxy-20(S)-camptothecin . These water-soluble camptothecin analogues were demonstrated to be nanamolar inhibitors of the topoisomerase I enzyme in the cleavable complex assay . The compounds, GI147211 {7-(4-methylpiperazinomethylene)-10,11-ethylenedioxy-20(S)-camp tot hecin}, and GI149893 {7-(4-methylpiperazinomethylene)-10,11-methylenedioxy-20(S)-cam pto thecin}, were compared to topotecan, a known water-soluble inhibitor of topoisomerase I . Both GI compounds were found to be slightly more potent than topotecan as inhibitors of topoisomerase I in the cleavable complex assay and were 1.5-2 times more soluble . Tumor cell cytotoxicity assays using 5 separate cell lines demonstrated that both GI compounds were 5-10 times more potent than topotecan, although by comparison all three topoisomerase I inhibitors were unaffected by the multidrug resistance P-glycoprotein . The antitumor activity of all three topoisomerase I inhibitors was compared concomitantly in two human colon xenograft models . In both models, GI147211 and GI149893 were able to induce regression of established HT-29 and SW-48 colon tumors by as much as 60% . The antitumor activity of both compounds were also demonstrated in the MX-1 and PC-3 xenografts . Microscopic examination of selected tissues indicated that drug-induced toxicity was primarily limited to the gastrointestinal tract and was comparable among the three compounds . Further clinical development of this class of compounds is ongoing. Cancer Res, 1995 Feb 1, 55(3), 590 - 6 Sensitization of human renal cell carcinoma cells to cis-diamminedichloroplatinum(II) by anti-interleukin 6 monoclonal antibody or anti-interleukin 6 receptor monoclonal antibody; Mizutani Y et al.; Cytotoxic chemotherapy has shown little antitumor activity against renal cell carcinoma (RCC) . It has been demonstrated that RCC cells secrete interleukin 6 (IL-6) and express IL-6 receptors (IL-6Rs) . IL-6 inhibits apoptosis and enhances manganese superoxide dismutase expression . Several anticancer chemotherapeutic agents exert their cytotoxic activity in part through the induction of apoptosis and the production of free radicals . Thus, the resistance of RCC cells to the anticancer agents might correlate with IL-6 expression . The present study tested this hypothesis by examining the effect of anti-IL-6 mAb and anti-IL-6R mAb on the sensitivity of human RCC cells to anticancer chemotherapeutic agents . Treatment of Caki-1 cells with anti-IL-6 mAb or anti-IL-6R mAb in combination with cis-diamminedichloroplatinum(II) (CDDP) or mitomycin C overcame their resistance to CDDP or mitomycin C . However, treatment of Caki-1 cells with anti-IL-6 mAb or anti-IL-6R mAb in combination with Adriamycin, vinblastine or 5-fluorouracil did not overcome their resistance to these anticancer agents . Treatment of CDDP-resistant Caki-1 cells (Caki-1/DDP), two other RCC cell lines (ACHN and A704), and three freshly derived RCC cells with CDDP in combination with anti-IL-6 mAb or anti-IL-6R mAb reversed the resistance to CDDP in all these tumors . We then studied the effectiveness of other platinum derivatives . Treatment of Caki-1 cells with anti-IL-6 mAb or anti-IL-6R mAb enhanced their sensitivity to carboplatin, but not to trans-diamminedichloroplatinum(II) . Several experiments investigated the mechanism of the antibody-mediated sensitization of RCC cells to CDDP . Incubation of Caki-1 cells with anti-IL-6 mAb or anti-IL-6R mAb did not change the intracellular accumulation of CDDP . The expressions of the multidrug resistant phenotype (gp170) and c-myc oncogene were not affected by the antibody-mediated sensitization . Treatment of Caki-1 cells with the anti-IL-6 mAb or anti-IL-6R mAb down-regulated the expression of glutathione S-transferase pi mRNA . This study demonstrates that treatment of RCC cells with CDDP in combination with anti-IL-6 mAb or anti-IL-6R mAb can overcome their CDDP-resistance and that the down-regulation of glutathione S-transferase pi expression by anti-IL-6 mAb or anti-IL-6R mAb might play a role in the enhanced cytotoxicity obtained.(ABSTRACT TRUNCATED AT 400 WORDS) Cancer Res, 1995 Feb 1, 55(3), 459 - 62 Sequential coexpression of the multidrug resistance genes MRP and mdr1 and their products in VP-16 (etoposide)-selected H69 small cell lung cancer cells; Brock I et al.; Resistance to drugs included in the multidrug-resistance phenotype has been attributed to overexpression of either mdr1 or MRP genes and their products in numerous cell lines, while coexpression, to our knowledge, has not previously been reported in the same cells . Human small cell lung cancer H69/VP cells were developed by continuous incubation in increasing doses of VP-16 . In reverse transcription-PCR assays we found over-expression of both mdr1 and multidrug-resistance protein (MRP) genes, and immunoblots showed both elevated P-glycoprotein and MRP in H69/VP cells . Double immunocytochemical staining demonstrated the expression of both MRP and P-glycoprotein in the same cells, indicating that the observations do not result from the selection of two independent clones . Examination of early passages of H69/VP cells showed that overexpression of MRP mRNA occurred prior to mdr1 . Thus, cell lines and clinical samples in the future should be tested for both mdr1/P-glycoprotein and MRP since a positive result for one of the phenotypes does not preclude the existence of the other. Cancer, 1995 Feb 1, 75(3), 815 - 20 A phase III randomized study of oral verapamil as a chemosensitizer to reverse drug resistance in patients with refractory myeloma . A Southwest Oncology Group study; Dalton WS et al.; BACKGROUND . Multiple myeloma is considered to be a drug responsive disease; however, there is no cure for this disease and virtually all patients will develop drug resistance . One form of drug resistance that has been documented is the multidrug resistance phenotype or MDR . METHODS . A randomized trial of the combination of vincristine, doxorubicin, and dexamethasone (VAD) and VAD plus oral verapamil (VAD/v) in drug refractory multiple myeloma patients was performed by the Southwestern Oncology Group . Verapamil was used as a chemosensitizing agent to attempt to overcome or prevent MDR and improve the therapeutic outcome . RESULTS . Response rates between the two treatment arms were similar with an overall response rate of 41% for the VAD alone arm and 36% for the VAD/v arm . Overall survival of patients was also similar with a median survival of 10 months for the VAD arm and 13 months for the VAD/v arm . The toxicity profile was also similar for both treatments, with myelosuppression being the dose-limiting toxicity . No significant correlation was observed between expression of P-glycoprotein, serum verapamil levels, and response to therapy . CONCLUSIONS . No beneficial effect was observed from the addition of oral verapamil to the VAD chemotherapy regimen for the treatment of drug-resistant myeloma patients . More effective and less toxic chemosensitizers are needed to study the role of chemosensitizers in reversing MDR in the clinic. Eur Respir J, 1995 Feb, 8(2), 278 - 84 Drug-resistant pulmonary tuberculosis in Berlin, Germany, 1987-1993; Schaberg T et al.; Resistance of Mycobacterium tuberculosis (M.tb) strains is an increasing problem worldwide . Since no public health data are available for urban populations in Germany, we investigated resistance in our hospitalized patients (n = 1,011) over the last 7 yrs . We therefore evaluated clinical data and results of susceptibility tests (breakpoint technique/proportion method) for isoniazid, streptomycin, rifampin, pyrazinamide, protionamide and ethambutol . Since 1987, there has been a relatively constant rate of 5.9% (3.9%-7.8%) for single-drug resistance (SDR), but an increasing rate of multidrug-resistant (MDR) strains (> or = 2 first-line drugs) from 1.7% in 1987 to 5.8% in 1993 . Sixty nine percent of patients with MDR strains showed resistance to two drugs, and 31% to three or more drugs . Risk factors for SDR and MDR tuberculosis revealed previous therapy (odds ratio (OR) (95% confidence interval (95% CI)); SDR 2.2 (1.7-4.0); MDR 4.5 (2.3-8.8)); and foreign-born status (SDR 2.2 (1.3-3.6); MDR 3.5 (1.8-6.8)) to be the most important factors associated with resistance . Both primary and acquired resistance were higher in foreign-born than in German-born patients . We conclude that there was a considerable increase in multidrug-resistant tuberculosis in our hospital from 1987 to 1993 . Since previously treated patients and patients born in countries with a high level of primary resistance had an increased risk of drug-resistant tuberculosis, we would advise a four drug regimen as initial therapy in those patients. Eur J Nucl Med, 1995 Feb, 22(2), 177 - 80 Sequential functional imaging with technetium-99m hexakis-2-methoxyisobutylisonitrile and indium-111 octreotide: can we predict the response to chemotherapy in small cell lung cancer? Moretti JL, Caglar M, Boaziz C, Caillat-Vigneron N, Morere JF. A case of small cell lung carcinoma (SCLC) demonstrating uptake on functional indium-111 octreotide scintigraphy is presented . Technetium-99m hexakis-2-methoxyisobutylisonitrile (MIBI) scintigraphy clearly delineated an absence of radionuclide uptake at the tumour site . This suggested the presence of multidrug resistance-mediated P glycoprotein (Pgp) on tumour cells, which recognizes certain chemotherapeutic agents as well as MIBI as a substrate and avoids radionuclide concentration . Following three courses of chemotherapy, the patient failed to improve and eventually died . This case demonstrates the importance of functional images, which have the potential to predict the outcome in response to chemotherapy. Anticancer Drugs, 1995 Feb, 6(1), 135 - 46 Cyclosporin A, verapamil and S9788 reverse doxorubicin resistance in a human medullary thyroid carcinoma cell line; Massart C et al.; Multidrug resistance was investigated in TT cells, a human medullary thyroid carcinoma (MTC) cell line and in normal thyrocytes . MDR1 mRNA was revealed by polymerase chain reaction (PCR) analysis both in normal and neoplastic cells despite the absence of glycoprotein P (Pgp) by immunohistochemistry using JSB-1 monoclonal antibody . Glutathione-S-transferase mRNA was undetectable by Northern blotting in TT cells . Doxorubicin-induced cytotoxicity was evaluated in TT cells with MTT, lacticodehydrogenase (LDH), glutathione (GSH) assays and neutral red uptake . IC50 values obtained for MTT assays were higher than those obtained with the three other tests . Cyclosporin A (CSA) (3 microM), verapamil (10 microM) and S9788 (5 microM) partially reversed the resistance to doxorubicin after a 48 h co-incubation (followed by a 24 h post-incubation for the S9788) . Under these conditions, GSH levels were altered by verapamil and S9788, whereas CSA decreased LDH activity . CSA and verapamil had no effect on MTT assay . In conclusion this MTC cell line exhibited over-expression of the MDR1 gene and its resistance to doxorubicin can be partially reversed by CSA, verapamil and S9788. Cytometry, 1995 Feb 1, 19(2), 126 - 33 Is reduced accumulation of Hoechst 33342 in multidrug resistant cells related to P-glycoprotein activity? Lahmy S, Viallet P, Salmon JM. Although bisbenzimidazole-DNA interactions have been studied in solution, little information has been available in living cells . The reduced accumulation of the nuclear dye Hoechst 33342 (H342) in cells with multidrug resistant (MDR) phenotype suggested its possible use in a functional test for detection of these cells . We performed experiments to elucidate the mechanisms involved in the H342-exclusion from resistant cells . As contradictory results have been reported in literature, we compared the entire fluorescence spectra of H342 in solution and in intact living cells under different experimental conditions . The study was performed by fluorescence image cytometry . This technique allow accurate quantification of the amount of H342 bound to DNA in living cells . The dye uptake was followed in sensitive and resistant cells, a lymphoblastoid cell line, CCRF-CEM, and its resistant variant selected with vinblastine CEM/VLB100 under conditions that could modulate H342-cell binding . Competition experiments with sodium azide, verapamil, and vinblastine indicated that resistant cells did not differ in the number of possible binding sites for H342 . The obtained results ruled out the possibility of discriminating cells on the basis of a spectral shift . Two modes of binding, differing in their affinity for the dye, seem to co-exist in intact cells . Although it clearly appeared that the P-glycoprotein expressed in MDR cells was mainly responsible for the H342-exclusion, other mechanisms might also be involved. Cell Biol Int, 1995 Feb, 19(2), 113 - 9 Colchicine-resistance and enhancement of P-glycoprotein activity after co-cultivation of drug-sensitive cells with multidrug resistant variants; Eliseenkova AV et al.; The role of cellular interactions in the resistance of Djungurian hamster cells to colchicine (CH) and in the efficiency of P-glycoprotein function was studied . Mixtures of CH-resistant and CH-sensitive cells as well as control unmixed cells were propagated for 3 days and the sensitivity of the cells to CH was measured by colony forming assay . Identification of individual subpopulations was possible due to genetic marker (6TG-resistance) . The data show that the survival of CH-sensitive cells in CH-supplemented medium increased after co-cultivation with CH-resistant counterparts . To measure Pgp activity the fluorescent dye RH123 and FACScan analysis were used . Pgp-mediated RH123 efflux increased after co-cultivation of CH-sensitive and CH-resistant cells. Calcif Tissue Int, 1995 Feb, 56(2), 170 - 4 P-glycoprotein is expressed in parathyroid epithelium and is regulated by calcium; Axiotis CA et al.; P-glycoprotein (Pgp), the multidrug resistance (mdr) gene product, has been described in normal tissues with diverse physiologic functions . A broad role as a transporter protein for toxins, hormones, and physiologic metabolites has been provisionally deduced, based on structural analysis and immunoanatomic localization .