Cancer Res, 1994 Nov 1, 54(21), 5607 - 13 Overexpression of the multidrug resistance-associated protein (MRP) gene in vincristine but not doxorubicin-selected multidrug-resistant murine erythroleukemia cells; Slapak CA et al.; Multidrug-resistant sublines of the murine erythroleukemia cell line PC4 were sequentially selected in increasing vincristine concentrations (5-160 ng/ml) . The low- and intermediate-level resistant cell lines, selected in < or = 40 ng/ml of vincristine, demonstrated resistance to Vinca alkaloids and to an epipodophyllotoxin but little or none to an anthracycline . The expression of murine mdr genes, as analyzed by Northern blotting, revealed a baseline expression of murine mdr2 in parental cells that was unchanged in the drug-resistant cell lines . Overexpression of mdr3 was observed only in the highest-level resistant cell line, PC-V160, whereas mdr1 mRNA was not detected in any of the cell lines . The polymerase chain reaction, using mdr3-specific primers, excluded the possibility that low levels of P-glycoprotein expression contributed to the resistance phenotype in the low and intermediate-level resistant cell lines . Northern blot analysis using a human complementary DNA probe for the multidrug resistance-associated protein (MRP) demonstrated overexpression of murine mrp in each of the vincristine-selected sublines . Genomic amplification of the mrp gene was coincident with mrp overexpression . The expression of mrp was also examined in two series of previously characterized doxorubicin-selected cell lines derived from parental PC4 and C7D murine erythroleukemia cells . In contrast to the vincristine-selected cell lines, overexpression of mrp was not detected . These studies demonstrate that, in murine erythroleukemia cells selected for vincristine resistance, overexpression of murine mrp occurred prior to that for murine mdr . In contrast to human MRP, selection for vincristine, but not doxorubicin resistance, resulted in the overexpression of murine mrp. Haematologica, 1994 Nov-Dec, 79(6), 500 - 7 Restoring uptake and retention of daunorubicin and idarubicin in P170-related multidrug resistance cells by low concentration D-verapamil, cyclosporin-A and SDZ PSC 833; Michieli M et al.; BACKGROUND . Overexpression of the mdr-1 gene that codes for a 170 Kd transmembrane glycoprotein (P170) is a factor responsible for decreased cell sensitivity to anthracyclines and other drugs, and is related to treatment failure in acute leukemia and other tumors . Several agents, including verapamil and cyclosporine derivatives, can modify P170-related resistance in vitro and can be proposed as adjuvant treatment for leukemia and cancer . MATERIALS AND METHODS . To investigate the optimal conditions for adjuvant treatment, D-verapamil (D-VRP), cyclosporin-A (CyA) and the cyclosporine derivative SDZ PSC 833 (PSC) were used alone and in combination at drug concentrations that can be achieved and maintained in vivo . The drugs were tested for their capacity to restore intracellular daunorubicin (DNR) and idarubicin (IDA) accumulation in high-resistance (CEM VLB 300) and intermediate-resistance (CEM VLB 100) cells to levels found in the non-resistant parental cell line (CCRF CEM) . RESULTS . In intermediate-resistance cells, IDA alone was more easily restored than DNR plus modifiers, and intracellular IDA concentration was returned to the level of non-resistant cells with low-dose D-VRP (1 microM), CyA (0.8 microM) and PSC (0.4 microM) . In high-resistance cells no modifier or modifier combination was able to restore intracellular DNR concentration to the value of non-resistant cells . Intracellular IDA concentration was almost completely restored only with D-VRP (2-3 microM) and CyA (0.8-1.6 microM) in combination or with PSC alone (0.4 microM) . CONCLUSIONS . These data suggest that as far as P170-related resistance is concerned, IDA alone is as efficient as or even more efficient than DNR plus modifiers, and that residual resistance to IDA can be overcome with a combination of D-VRP and Cy-A at a clinically achievable concentration, or with a more powerful modifier like SDZ PSC 833. Clin Infect Dis, 1994 Nov, 19(5), 916 - 21 Cellular transport of drugs; Steinberg TH; The ability of drugs to enter cells and to reach an adequate concentration within the appropriate intracellular compartment may be an important determinant of the efficacy of therapy for infections due to intracellular pathogens . Antibiotics vary considerably in their ability to accumulate within cells . All solutes can be taken up by endocytosis, and some compounds reach high intracellular concentrations after crossing the plasma membrane by diffusion or by specific transport processes . Cellular organelles have properties that affect the intracellular distribution of drugs and that may account for the net accumulation of drugs within cells . An important example is the ability of acidic organelles to trap lysosomotropic weak bases . Cells also express transport proteins that may limit the intracellular accumulation of drugs by secreting them across the plasma membrane into the extracellular medium . Thus, cellular organic anion transporters can decrease the intracellular accumulation of certain antibiotics, and the multidrug-resistance transporter, or p-glycoprotein, confers resistance to antineoplastic agents . Inhibition of organic anion transport may have therapeutic value . A better appreciation of the mechanisms by which drugs accumulate within cells and within specific intracellular compartments may lead to the design of agents that reach higher concentrations at clinically relevant intracellular sites. Somat Cell Mol Genet, 1994 Nov, 20(6), 463 - 80 Subclonal heterogeneity of the multidrug resistance phenotype in a cell line expressing antisense MDR1 RNA; Hanchett LA et al.; A multidrug resistant (MDR) cell line was transfected with an antisense MDR1 expression vector and transfectant clones were analyzed for reversion of the MDR phenotype . Only one of 10 antisense-expressing transfectants showed a reduction in drug resistance, MDR1 mRNA and P-glycoprotein . Observations made using rhodamine-123, a fluorescent substrate for P-glycoprotein, revealed that dye retention in individual cells was highly variable within this antisense-expressing clone . Subpopulations were established from the original clone based on differences in rhodamine-123 retention . Rhodamine-123 retention varied inversely with levels of P-glycoprotein and MDR1 mRNA . All subpopulations expressed similar levels of antisense MDR1 RNA yet had dramatic differences in MDR1 mRNA levels . Analysis of vector integration site restriction fragment length polymorphisms confirmed that all populations originated from the same transfectant clone . Nuclear run-on analysis indicated that the mdr1 gene is transcribed at the same rate in all populations, suggesting that the reduction in MDR1 mRNA is mediated posttranscriptionally . Cells with the greatest reduction in MDR1 mRNA accumulate distinct antisense RNA transcripts in the nuclear RNA fraction, suggesting that antisense effectiveness in this system is associated with a nuclear event or process . These results reveal that antisense RNA activity is not necessarily distributed equally within a clonal population. Mol Biochem Parasitol, 1994 Nov, 68(1), 81 - 91 The P-glycoprotein-related gene family in Leishmania; Legare D et al.; P-glycoprotein gene amplification has been described in several drug-resistant parasitic protozoa . The first P-glycoprotein related gene described in Leishmania was ltpgpA, a gene frequently amplified in arsenite resistant Leishmania . Hybridization experiments indicated that ltpgpA was part of a gene family . In addition to ltpgpA, four novel genes were cloned that are present in two loci: ltpgpB and ltpgpC tandemly linked to ltpgpA on a 800-kb chromosome; and ltpgpD and ltpgpE closely linked on a chromosome ranging from 950 kb to 1400 kb, depending on the Leishmania species . Another P-glycoprotein gene, homologous to the more recently described ldmdr1, was linked to ltpgpD and ltpgpE . Nucleotide sequencing of ltpgpB and ltpgpE revealed that the Leishmania P-glycoprotein-related genes have diverged considerably from the main branch of P-glycoproteins and are more homologous to the recently described multidrug resistance-associated protein found in multidrug-resistant human lung cancer cell lines . Cross-resistance studies and gene transfection experiments indicated that under the conditions tested only ltpgpA and ldmdr1 are involved in resistance to arsenite and antimonials or hydrophobic drugs such as vinblastine respectively. J Hepatol, 1994 Nov, 21(5), 754 - 63 Effect of colchicine and heat shock on multidrug resistance gene and P-glycoprotein expression in rat liver; Vollrath V et al.; The multidrug resistance genes encode plasma membrane glycoproteins named P-glycoproteins, that act as an ATP-dependent drug efflux pump and decrease the cytosolic concentration of chemotherapeutic agents . It has been hypothesized that in rat liver, this protein may have a physiological role as a biliary transporter of xenobiotics and endobiotics . Some human tumor cell lines turn on the human multidrug resistance gene in response to high temperature and after exposure to toxic chemicals . Accordingly, it has been proposed that the human multidrug resistance gene is a heat shock gene . We have assessed whether two environmental stresses, heat shock or acute exposure to cytotoxic drugs (colchicine, vincristine, vinblastine and daunomycin), induce changes in the expression of multidrug resistance genes in the rat . Total cellular RNA extracted from rat liver was hybridized to a labeled human multidrug resistance gene cDNA probe . Temperature upshift did not increase the steady-state of mdr mRNA levels in the tissues studied, suggesting that the mdr genes are not activated as part of a heat shock response . The mdr mRNA levels increased in rat liver as early as 3 h after a single injection of colchicine, reached a peak (500%; p < 0.05) after around 24 h and returned to constitutive levels after 48 h . Changes in the relative content of mdr mRNA were not detected in kidney, adrenal gland and small bowel, suggesting that the in vivo induction of the mdr gene in the liver is a tissue-specific response . The other cytotoxic drugs that were tested did not increase the steady-state of mdr mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS) AIDS Res Hum Retroviruses, 1994 Nov, 10(11), 1471 - 8 Zidovudine induces the expression of cellular resistance affecting its antiviral activity; Dianzani F et al.; We have previously shown that multidrug-resistant cells expressing the multidrug transporter P-glycoprotein are less sensitive to the antiviral activity of AZT . Subsequently, we addressed the question whether AZT itself is able to induce cellular resistance to the drug . Indeed, CEM cells propagated in the presence of increasing concentrations of AZT become resistant to the antigrowth and antiviral activity of AZT but do not express detectable level of P-glycoprotein . Sensitivity of these cells to other compounds, such as vinblastine, vincristine, ddI, and ddC remained unchanged, indicating that, in contrast to P-glycoprotein-positive cells, AZT-induced resistance is specific for AZT . Interestingly, in AZT-induced resistant cells the intracellular accumulation of AZT and exogenous deoxythymidine, as well as thymidine kinase activity, are significantly reduced when compared with the parental cell line . Our findings show that AZT itself may directly induce the expression of cellular mechanisms leading to the acquisition of specific cellular resistance that can affect its antiviral activity. Res Commun Mol Pathol Pharmacol, 1994 Nov, 86(2), 195 - 203 Reduced drug resistance in a multidrug resistant cell line by 5,8,11,14-eicosatetraynoic acid; Anderson KM et al.; We examined whether the arachidonic acid competitive antagonist, ETYA (5,8,11,14-eicosatetraynoic acid), modulated drug sensitivity in a cell line that over-expresses the multiple drug resistance protein, MDR1 . ETYA was nontoxic to drug-sensitive parental KB3-1 cells or drug-resistant MDR KB8-5-11 cells, with an IC50 of 190 microM for both lines . ETYA (20 microM) increased rhodamine 123 accumulation in KB8-5-11 MDR cells but not in KB3-1 sensitive cells . Arachidonic acid at 20 microM did not alter rhodamine accumulation in either cell line . Increasing the concentration of ETYA from 40 to 160 microM or incubation beyond 30 min did not increase KB8-5-11 dye retention . Forty microM or more ETYA increased KB3-11 dye retention . In a 6 day proliferation assay of KB8-5-11 cells, a nontoxic (40 microM) concentration of ETYA reduced the IC50 for doxorubicin 4-fold, the IC50 for colchicine 2-fold, but had no effect on the IC50 for vinblastine . ETYA at 40 microM did not alter the IC50 for any drug tested with KB3-1 cells . Therefore: (a) ETYA (20 or 40 microM) modulated resistance of KB8-5-11 cells to several drugs to a limited extent, without potentiating toxicity in the parental line, while arachidonic acid did not . (b) Since cationic rhodamine 123 is concentrated in mitochondria, the extent is dependent upon the transmembrane potential, and increased dye retention due to ETYA may in part be related to altered ETYA-induced cell membrane potential. Leuk Lymphoma, 1994 Nov, 15(5-6), 453 - 68 Evaluation of the clinical relevance of the anionic glutathione-s-transferase (GST pi) and multidrug resistance (mdr-1) gene coexpression in leukemias and lymphomas; Russo D et al.; By using RNA slot-blot technique, the frequency and the degree of GST pi and mdr-1 gene coexpression were investigated in 23 AML patients, 9 ALL, 9 CLL and 11 cases of NHL in an attempt to study their clinical and prognostic relevance . GST pi and mdr-1 levels were expressed as arbitrary units (U) with respect to the negative controls (U = 0), MCF7 and HL60 sensitive cell lines, and the positive controls (U = 10), MCF7/DOXO and HL60/DNR resistant cell lines . The concomitant GST pi/mdr-1 gene overexpression showed a negative prognostic value in the set of newly diagnosed AML pts (10 cases), furthermore higher GST pi and mdr-1 mRNA levels were averagely detected in the relapsed/resistant ALL pts (4 cases), and in CLL (7 cases) and NHL (8 cases) heavily pretreated patients who were unresponsive to chemotherapy and with a disease progression . These preliminary data show that two different mechanisms of drug resistance can be coexpressed at the same time in those leukemias and lymphomas with a clinically unfavourable course. Anticancer Res, 1994 Nov-Dec, 14(6B), 2685 - 9 Lacidipine and josamycin: two new multidrug resistance modulators; Crosta L et al.; In this paper we report the results obtained treating a multidrug resistant (MDR) murine erythroleukemia cell line with daunomycin (DNM) in association with two new modulators characterized by a favourable therapeutic index, lacidipine (LCD), a dihydropyridine calcium antagonist, and josamycin (JSM), a macrolide antibiotic . LCD and JSM exhibited a greater MDR reversal activity than verapamil (VRP) and erythromycin (ERY) respectively . The accumulation of DNM in the DRTL cells exposed to modulators was similar to that of the parental cell line FLC . In the case of LCD, it was possible to ascertain that at a very low concentration this molecule can circumvent MDR without modifying DNM accumulation, suggesting that multiple different determinants may be responsible for MDR other than P-170 in this cell line. Anticancer Res, 1994 Nov-Dec, 14(6B), 2643 - 8 Combined activity of interleukin-1 alpha or TNF-alpha and doxorubicin on multidrug resistant cell lines: evidence that TNF and DXR have synergistic antitumor and differentiation-inducing effects; Borsellino N et al.; We report on the antiproliferative effects that interleukin-1 alpha (IL-1) or TNF-alpha (TNF) in combination with doxorubicin (DXR) exert on DXR-sensitive (B16 melanoma, Friend, K562 and CCRF/CEM leukemias) and -resistant (B16-DXR, FLC-DXR, K562-DXR) cell lines in vitro . Multidrug resistance (MDR) of the latter lines entails cross-resistance to vincristine and overexpression of P-glycoprotein . Il-1 showed only a very marginal growth inhibitory activity and the effects of its combination with DXR were essentially additive in all the cell lines, except in chemosensitive B16, where a slight synergism occurred . TNF demonstrated greater antiproliferative activity in the MDR B16 and Friend tumors than in their parent variants . The combination of TNF and DXR produced synergistic growth inhibition in B16, K562 and, particularly, also in the MDR sublines of these two tumors . In addition, TNF and DXR induced synergistically erythroid differentiation in K562 and multidirectional differentiation in K562-DXR . The synergism was critically schedule-dependent in that it was achieved only when DXR application preceded or was simultaneous with that of TNF . Finally, TNF did not modify drug accumulation and retention in the cells . Our present findings stress especially the fact that DXR and TNF may exert useful antitumor synergism even in MDR lines; however, it is not likely that their interaction will occur at the specific MDR process level. Anticancer Res, 1994 Nov-Dec, 14(6B), 2605 - 9 Multidrug resistance phenotype evaluation by immunofluorescence and functional tests: comparison of two monoclonal antibodies and three fluorescent dyes in three cells lines; Maynadie M et al.; Various agents have been shown to enhance drug sensitivity of multidrug resistant (MDR) cells and are thus of interest when the MDR phenotype is identified . Detection of MDR cells is of importance and can be carried out either by immunofluorescence with monoclonal antibodies or by functional tests using fluorescent dyes uptake . MDR has been analysed by flow cytometry on three sensitive and resistant cell lines, with MRK16 and C219 monoclonal antibodies directed against P-glycoprotein (P-gp) and with rhodamine 123, Hoechst 33342 and daunorubicin . Resistant cells were revealed by MRK16 and C219 but the results obtained with MRK16 gave higher both percentages of fluorescent cells and mean fluorescence . Fluorescence intensity observed with daunorubicin was lower than with rhodamine 123 . With Hoechst 33342, mean fluorescence was quite identical on sensitive and on resistant cells . It was concluded that MRK16 and rhodamine 123 were well adapted to detect P-gp and evaluate its functional ability. Anticancer Res, 1994 Nov-Dec, 14(6B), 2589 - 95 Effects of vinblastine, colchicine, and verapamil on rhodamine 123 accumulation in human P-glycoprotein-positive leukemia cells; Lautier D et al.; Multidrug-resistant (MDR) cells have been characterized by reduced accumulation of rhodamine 123 (R123) . We addressed the question of whether R123 could compete with substrates or inhibitors (vinblastine, colchicine, verapamil) of P-glycoprotein (Pgp) overexpressed in MDR cells, using fluorescence image cytometry . Verapamil caused a dose-dependent increase in R123 accumulation . R123 accumulation was increased by vinblastine only at high levels and colchicine had no effect on R123 accumulation . Treatments with two drugs altered R123 accumulation depending on drug concentration ratio . The results indicate that vinblastine, R123 and verapamil can compete for outward transport by Pgp . A dual effect of vinblastine suggests that vinblastine can activate Pgp at low concentrations and inhibit R123 transport at higher concentrations. J Nat Prod, 1994 Nov, 57(11), 1517 - 22 Indole alkaloids from Peschiera laeta that enhance vinblastine-mediated cytotoxicity with multidrug-resistant cells; You M et al.; Coronaridine {1}, conoduramine {2}, and voacamine {3}, three indole alkaloids isolated from Peschiera laeta, have been found to enhance the cytotoxic response mediated by vinblastine {4} with multidrug-resistant KB cells . Inhibition of vinblastine binding with membrane vesicles isolated from this cell line was also assessed, and the bisindole alkaloids conoduramine {2} and voacamine {3} were found to be more potent inhibitory agents than the monomeric alkaloid, coronaridine {1} . Thus, these compounds appear to function by binding with P-glycoprotein. Cell Mol Biol (Noisy-le-grand), 1994 Nov, 40(7), 957 - 64 Ornithine decarboxylase--a predictor for tumor chemosensitivity; Bachrach U et al.; The activity of ornithine decarboxylase (ODC) was determined in P388 murine leukemia cells treated with adriamycin (ADR) and methotrexate (MTX) . Some of the cell lines were resistant to ADR, MTX or their combinations . A similar pattern was found between the cytotoxicity and the suppression of ODC activity in these cell lines in terms of drug concentrations . In a cell line resistant to one drug, a relatively high concentration of that drug was required to inhibit ODC activity . This effect was independent of the sensitivity of the cells to the other drug . A similar correlation between arrest of growth and the inhibition in the induction of ODC was also observed in human epithelial carcinoma cells . In this case too, the growth of multidrug resistant cells was not affected by vinblastine, neither was the induction of ODC . On the other hand, both the growth and the induction of ODC were inhibited by vinblastine in drug-sensitive cells . These findings suggest that ODC measurements might be used for predicting the chemosensitivity of tumor cells. Pediatr Infect Dis J, 1994 Nov, 13(11), 990 - 4 Therapy of multidrug-resistant typhoid fever with oral cefixime vs . intravenous ceftriaxone; Bhutta ZA et al.; We randomly allocated 80 children with suspected multidrug-resistant tyhpoid fever to therapy with either cefixime or ceftriaxone . Of these, an alternative diagnosis was subsequently made in 10 children and another 10 were excluded because cultures were negative . In 9 cases the typhoidal organisms isolated were susceptible to first-line drugs . In all, 50 children were randomly allocated to receive therapy with either intravenous ceftriaxone (65 mg/kg/day once daily, Group A, n = 25) or oral cefixime (10 mg/kg/day divided every 12 hours, Group B, n = 25) for 14 days . The two groups were comparable in their clinical characteristics, duration and severity of illness at the time of admission . The time to defervescence was comparable in both groups (8.3 +/- 3.7 vs . 8.0 +/- 4.1 days, P = not significant) . An equal number (3 in each group) failed to respond and underwent a change in therapy . Three children in Group A and one in Group B relapsed . No adverse effects were seen in either group during the course of therapy . Our data suggest that oral cefixime can be used as effectively as parenterally administered ceftriaxone for management of typhoid fever in children. Kekkaku, 1994 Nov, 69(11), 711 - 7 {New drugs against tuberculosis and nontuberculous mycobacterial infections: a review}; Amitani R et al.; The number of cases with tuberculosis is again increasing in many countries, and recently several nosocomial outbreaks of multidrug-resistant tuberculosis have occurred in the United States . The number of patients with disseminated Mycobacterium avium complex (MAC) infections in AIDS population, and patients with MAC pulmonary disease unassociated with HIV seem to be also increasing . It takes at least 6 to 9 months for an initial treatment of active tuberculosis due to drug-sensitive strains with the standard regimen which includes isoniazid (INH) and rifampicin (RFP) . Treatment for the diseases caused by drug-resistant M . tuberculosis and MAC is much more time-consuming and more toxic than for the diseases caused by drug-sensitive strains, and often unsuccessful . For the reasons described above, the developments of new agents with potent antimycobacterial activities are highly desired . The new agents should also be useful for treating patients who have acquired resistance to many of the currently available drugs . In this review the new antimycobacterial drugs are summarized . Some of them have already been used clinically, but many are still in experimental evaluations . 1) Rifamycin derivatives: rifabutin (RBT), KRM-1648 (KRM), rifapentin (RPT), FCE-22250, FCE-22807, CGP-7040, SPA-S-565 and other rifamycin derivatives . New rifamycin derivatives including RBT, KRM have increased in vitro antimycobacterial activities . RBT and KRM are much more active in vitro and in vivo than RFP against both M . tuberculosis and MAC . KRM seems to be more potent than RBT against MAC in experimental studies.(ABSTRACT TRUNCATED AT 250 WORDS) Anticancer Res, 1994 Nov-Dec, 14(6A), 2389 - 93 Effect of S9788, cyclosporin A and verapamil on intracellular distribution of THP-doxorubicin in multidrug-resistant K562 tumor cells, as studied by laser confocal microspectrofluorometry; Sebille S et al.; S9788 modulating resistance effect has been investigated on the activity of THP-DOX against multidrug-resistant K562R cells and compared to that of cyclosporin A and verapamil . Intracellular THP-DOX distribution and particulary its intranuclear concentration, with or without modulators, has been measured using confocal laser microspectrofluorometry . The kinetics of intranuclear accumulation of THP-DOX (1 microM in the medium), as a function of time, were rapid in K562S and K562R cells . Maximum accumulation of THP-DOX is reached in a few minutes (K562S, 400 microM; K562R, 40 microM) . The addition of S9788, cyclosporin A and verapamil (5 microM) after one hour THP-DOX incubation, led to respectively 290, 250 and 114 microM . Uptake of THP-DOX was increased in K562R cells by a factor of 7 when S9788 was added . Results obtained on THP-DOX efflux from nuclei of K562S and K562R cells, after 3 hours of incubation without drug, showed a very short T1/2 (time corresponding to 50% decrease of intranuclear concentration of THP-DOX) in K562R cells (12 min) compared to that in K562S cells (150 min) . The addition of S9788, cyclosporin A and verapamil (5 microM) led to a T1/2 of 90, 30 and 20 min respectively . The T1/2 of THP-DOX was increased in K562R cells by a factor of 7.5 when S9788 was added . We tried to correlate these results with those obtained in growth inhibition study . The IC50 (concentration which induces 50% growth inhibition) of THP-DOX, corresponding to one hour THP-DOX treatment and 3 days culture of K562S and K562R cells were respectively 230 and 7000 nM, and the RI (resistance index) value is 30 . The addition of S9788, cyclosporin A and verapamil (5 microM), during the one hour treatment, led to an IC50 value of 350, 2000 and 5000 nM respectively . S9788 induced an IC50 value 20 times lower than without the modulator . Our study suggests that the higher activity of THP-DOX against K562R cells in the presence of S9788, compared to cyclosporin A and verapamil, is due to a higher intranuclear THP-DOX accumulation and to a strong decrease of drug efflux from K562R nuclei . This could be explained by a higher affinity of S9788 for membrane P-glycoprotein of K562R cells and/or an additional mechanism of action. Anticancer Res, 1994 Nov-Dec, 14(6A), 2383 - 7 Study of sodium orthovanadate as a reverser of multidrug resistance on lymphoblastic leukemic CEM/VLB100 cells; Colin M et al.; The occurrence of multidrug resistance (MDR) is the major cause of failure of cancer chemotherapy . Finding a way to circumvent this problem is now a major challenge in oncology . Multidrug resistant CEM/VLB100 cells accumulate 10 times less vinblastine (VLB) after 30 min than their sensitive counterparts (CEM cells) . At a non-cytotoxic concentration (1 mM) of sodium orthovanadate (OVN), uptake by CEM/VLB100 cells was increased 4 times while no effect was observed on CEM cells . The action on VLB uptake of OVN and verapamil (VPL), an usual MDR modulator, was additive . In CEM/VLB100 cells, OVN did not alter efflux . Its cellular mechanism of action could involve a transitory stimulation of VLB influx (x3) . OVN uptake in CEM and CEM/VLB100 cells was not significantly different and reached saturation after 30 s (180 pmol/10(6) CEM cells and 150 pmol/10(6) CEM/VLB100 cells) . This OVN uptake was concentration dependent . IC50 of VLB and doxorubicin were decreased by approximately 43 and 62% after 1 hour's exposure to OVN and 48 hours of culture . Under these conditions, OVN was more efficient than OVN. Anticancer Res, 1994 Nov-Dec, 14(6A), 2371 - 3 Proposals for concomitant use of several modulators of multidrug resistance in clinics; Robert J; Numerous modulators of multidrug resistance present a good in vitro activity which has not always been reproduced in vivo or in clinics . One reason is the fact that the plasma concentration required might exceed the maximum tolerated dose of modulator, due to its own toxicity . In addition, it has been suggested that the different modulators thus far identified might act on different sites of P-glycoprotein and eventually on different targets . It has been shown that the combination of verapamil and quinine, and of verapamil and cyclosporine A, behave synergistically in the circumvention of multidrug resistance . There is therefore a good rationale for the evaluation of protocols combining two different modulators to cytotoxic chemotherapy. Br J Haematol, 1994 Nov, 88(3), 566 - 74 Development of extended multidrug resistance in HL60 promyelocytic leukaemia cells; Su GM et al.; In an attempt to mimic clinical conditions for the treatment of leukaemia, the HL60 promyelocytic cell line was treated for 18 h with low, clinically relevant, levels of the anthracycline epirubicin and the Vinca alkaloid vinblastine . The resulting drug-resistant sublines not only expressed P-glycoprotein and the MDR phenotype but were also cross-resistant to chlorambucil, methotrexate and cisplatinum, and had increased resistance to radiation . Development of resistance was associated with an aberrant differentiation phenotype with decreased expression of myeloid antigens and expression of glycophorin A, an antigen normally associated with erythroid differentiation . The ability of HL60 cells to terminally differentiate in response to all-trans-retinoic acid (vitamin A acid) was lost in the sublines . These results suggest that either a single novel mechanism is responsible for multiple drug resistance or the initial response to drug treatment is the co-induction of multiple mechanisms . These cells and the method by which they were generated therefore provide a clinically relevant model for the study of the initial events in the development of not only multidrug resistance but also the extended multiple drug resistance usually encountered in the treatment of leukaemia. In Vivo, 1994 Nov-Dec, 8(5), 835 - 41 Regulation of the multidrug resistance (MDR1) gene expression; Chin KV et al.; The emergence of drug resistance poses a major obstacle to the success of chemotherapy for a large number of human cancers . Development of the multidrug resistance phenotype in human malignancies is an especially pressing problem because the tumors become cross-resistant to multiple chemotherapeutic agents that are both chemically and physically unrelated . The increased resistance to multiple cytotoxic natural product chemotherapeutic drugs is due to overexpression of the mdr gene, which encodes a plasma membrane ATP-dependent efflux pump . Expression of P-glycoprotein is tissue specific and found in a number of normal tissues, including colon, small intestine, kidney, liver and adrenal gland, as well as in the capillaries of brain and testis . The precise physiological functions in these tissue localizations is unclear at present . Intense efforts in many laboratories currently are invested on elucidating the functions of P-glycoprotein and investigating mechanisms that regulate the mdr gene expression. In Vivo, 1994 Nov-Dec, 8(5), 829 - 34 Modes of resistance to antitumor agents; Kessel D; Drug resistance has complicated chemotherapy of neoplastic disease since the early beginnings of the field . Successful use of drug therapy requires that tumor cells be more drug-responsive than the tissue of origin . This can occur with rapidly-dividing tumors which will be highly-responsive to drugs toxic in the S-phase of the cell cycle . Another drug sensitive population will consist of neoplastic cells unable to repair drug-induced damage which can be repaired by normal host cells . Even if one of these conditions is initially found, mutational events leading to drug resistance often occur . The most thoroughly explored mode of drug resistance involves MDR (multidrug resistance), an outward transport system which limits penetration of a variety of cytotoxic agents into the cytoplasm and nucleus . MDR is expressed by many normal cell types, and attempts at MDR circumvention appear to lead to new modes of host toxicity . It appears that new directions in cancer therapy will be needed to yield responses in the common slow-growing tumors which tend to be inherently drug-resistant. Eur J Clin Microbiol Infect Dis, 1994 Nov, 13(11), 902 - 7 Tuberculosis at the end of the twentieth century; Sepkowitz KA et al.; Tuberculosis has once again emerged as a significant public health problem in Western countries . Much of the rise has been fueled by the growing numbers of persons infected with HIV . Co-infection with Mycobacterium tuberculosis and HIV has been shown to result in high rates of active tuberculosis, and possibly in acceleration of progression to AIDS . Primary tuberculosis occurs at high rates among dually infected persons, further emphasizing the need for effective isolation of infectious cases . Recent preliminary studies have demonstrated that the survival of persons with multidrug-resistant tuberculosis can be six months and longer, far in excess of the 4 to 12 weeks reported previously . At least seven health care workers have died of occupationally-acquired multidrug-resistant tuberculosis, making control of the spread of tuberculosis in health care settings an urgent public health priority. Am J Physiol, 1994 Nov, 267(5 Pt 1), C1351 - 8 Expression and function of P-glycoprotein in human mesangial cells; Bello-Reuss E et al.; P-glycoprotein (PGP), responsible for multidrug resistance (MDR) in cancer cells, is normally expressed in kidney proximal tubules and mesangium . PGP expression and function were studied in human mesangial cell cultures . MDR1 gene expression was demonstrated by reverse transcription-polymerase chain reaction . PGP expression was determined using MRK16 monoclonal antibody and its function was assessed by the efflux of rhodamine-123 (R123) . R123 efflux had a half time of 25 +/- 5 s . Efflux was inhibited by cyclosporin A (10 microM), verapamil (10 microM), and vinblastine (100 microM) with half times of 380, 535, and 312 s, respectively . Incubation with MDR1-antisense oligonucleotide decreased R123 efflux (half time = 304 s) . Verapamil, cyclosporin A, and PSC-833 augmented the cytotoxicity of Adriamycin by reducing the 50% maximal growth-inhibitory dose from 730 nM to 130, 110, and 90 nM, respectively . We conclude that human mesangial cells express MDR1 and demonstrate xenobiotic transport inhibitable by several known PGP substrates . Concomitant exposure of mesangial cells to PGP-transported drugs causes intracellular accumulation of toxic PGP substrates and ultimately damages the mesangial cells. Cancer Lett, 1994 Oct 28, 86(1), 135 - 42 High mdr1- and mrp-, but low topoisomerase II alpha-gene expression in B-cell chronic lymphocytic leukaemias; Beck J et al.; Fifteen samples from 11 patients suffering from chronic lymphocytic leukaemia (CLL; 5 untreated, 6 chemotherapeutically treated) were analysed for their individual gene expression of the multidrug resistance (MDR) associated genes encoding mdr1/P-glycoprotein, mrp, and topoisomerase II alpha/beta-isoenzymes by a complementary DNA polymerase chain reaction (cDNA-PCR) approach . The expression of glyceraldehyde-3-phosphate dehydrogenase (gapdh) served as standard . Thereby, we generally found high mdr1- and mrp-, but low topoisomerase II alpha-mRNA levels . While mdr1 levels of the CLL samples were mostly found to be in the range of values measured in the T-lymphoblastoid, P-glycoprotein MDR cell line CCRF VCR 100, mrp levels were usually found to be 2-4-fold higher compared therewith . This might represent a multifactorial MDR in CLL . In contrast to the low or even absent topoisomerase II alpha gene expression, however, the expression of the topoisomerase II beta gene was generally high in the CLL lymphocytes exceeding the value observed in the cell line CCRF VCR 100 up to 5-fold . mdr1 gene expression correlated significantly with mrp gene expression in samples from patients having received chemotherapy (rs = 0.5833, P < 0.05, n = 10) . In two patients the follow-up analysis revealed combined increases in mdr1- and mrp-gene expression levels in the course of the disease. Biochemistry, 1994 Oct 25, 33(42), 12665 - 75 Analysis of drug transport kinetics in multidrug-resistant cells using a novel coumarin-vinblastine compound; Bornmann WG et al.; We have synthesized an analogue of vinblastine wherein a coumarin molecule is attached to the C17 of the vindoline moiety via a succinimide bridge (cou-VBL) . cou-VBL exhibits fluorescence similar to that exhibited by coumarin . Chinese hamster ovary fibroblasts (LR73 cells) that exhibit an IC50 for vinblastine (VBL) of about 100 nM in growth inhibition assays are similarly sensitive to the cou-VBL compound . LR73 cells transfected with the mu MDR 3 gene that were subsequently selected on vinblastine (MDR35 cells) exhibit resistance to cou-VBL that is similar to their VBL resistance . A large change in the quantum efficiency of cou-VBL fluorescence accompanies efflux from intact cells, and comparison between cou-VBL and {3H}VBL efflux from the MDR35 cells reveals that the transport kinetics of the fluorescent analogue is very similar (if not identical) to that exhibited by {3H}VBL . Thus, similar to continuous monitoring of fluorescence (CMF) studies performed with the naturally fluorescent chemotherapeutic doxorubicin (Roepe, 1992), cou-VBL may be used in CMF studies aimed at rigorously defining the kinetics of VBL efflux from multidrug-resistant (MDR) cells . Initial data suggest the following: (1) A single exponential term approximates efflux from sensitive cells, whereas two exponentials are required to fit efflux from MDR35 cells . (2) The faster MDR35 term is virtually identical to the single term for the sensitive cells, whereas the other defines a process that is 5-20 times slower than passive diffusion, depending on the drug concentration . (3) The slower component has a much steeper and nearly linear dependence on drug concentration, whereas the fast passive diffusion component becomes asymptotic near 0.3 pM exchangeable drug/microgram of cell protein. J Biol Chem, 1994 Oct 21, 269(42), 26058 - 65 Transport of polypeptide ionophores into proteoliposomes reconstituted with rat liver P-glycoprotein; Eytan GD et al.; The aim of this study was to examine the peptide transport activity of a naturally occurring P-glycoprotein such as that present in rat liver canalicular membrane vesicles . The peptide ionophores valinomycin and gramicidin D, which are known substrates of P-glycoprotein, served to monitor the P-glycoprotein activity indirectly as the ATP-dependent uptake of 86Rb+ mediated by these ionophores . Canalicular membrane vesicles proved inherently permeable to K+ ions, which prevented assay of transport ionophore activity . Therefore, P-glycoprotein was extracted from canalicular membrane vesicles and reconstituted into proteoliposomes that are relatively impermeable to cations . P-glycoprotein activity in the proteoliposomes was dependent on ATP hydrolysis since it was not observed with non-hydrolyzable analogs of ATP . Maximal ATP-dependent 86Rb+ uptake occurred at 50 nM gramicidin D and at 500 nM valinomycin thus possibly reflecting higher affinity of P-glycoprotein for gramicidin D . Nigericin, which does not participate in the multidrug resistance phenomenon, did not support an ATP-dependent uptake of 86Rb+ . ATP hydrolysis increased the amount of 86RB+ transported into the proteoliposomes . Furthermore, preincubation of the proteoliposomes in the presence of gramicidin D and 86Rb+, allowing for maximal ATP-independent 86Rb+ uptake to occur, did not interfere with subsequent ATP-dependent uptake, indicating the latter to constitute an active transport mechanism . The ATP-dependent component of 86Rb+ uptake occurred neither with liposomes nor with proteoliposomes reconstituted with proteins extracted from sinusoidal vesicles that lack P-glycoprotein . The ATP-dependent uptake was blocked by the known inhibitors of the ATPase activity associated with P-glycoprotein, oligomycin and vanadate, as well as by its established substrates, daunorubicin, doxorubicin, vinblastine, and the tripeptide N-acetyl-leucyl-leucyl-norleucinal . Thus, the reconstituted P-glycoprotein catalyzes the ATP-dependent 86Rb+ uptake that appears to occur by an energy-dependent translocation of the 86Rb(+)-ionophore complex . In this case, the actual substrate of P-glycoprotein is the ionophore-cation complex, which is both hydrophobic and positively charged as are most of the substrates of P-glycoprotein . This is the first demonstration of transport of a naturally occurring polypeptide by proteoliposomes reconstituted with physiologically expressed P-glycoprotein. J Natl Cancer Inst, 1994 Oct 19, 86(20), 1539 - 45 Quantitative immunocytochemical assays of P-glycoprotein in breast carcinomas: correlation to messenger RNA expression and to immunohistochemical prognostic indicators; Charpin C et al.; BACKGROUND: Chemotherapy failure that is due to cellular drug resistance remains a major problem in most cancer patients . One type of drug resistance that has been characterized is the multidrug resistance phenomenon, which demonstrates a reduced ability of cancer cells to accumulate drugs as a result of the effects of an energy-dependent unidirectional drug efflux pump with a broad substrate specificity . This drug pump is composed of a 170-kd transmembrane glycoprotein referred to as the P-glycoprotein (P-gp) that uses energy in the form of adenosine triphosphate to transport drugs through a channel formed by transmembrane segments . PURPOSE: Our purpose was to detect the levels of P-gp expression in frozen untreated breast carcinomas by immunocytochemical assays and to correlate these levels to current prognostic indicators and, in a few cases, to MDR1 (also known as PGY1) mRNA expression by polymerase chain reaction (PCR) . METHODS: The immunocytochemical expression of the multidrug resistance gene, P-gp, was investigated using a specific monoclonal antibody (JSB1) against P-gp in 5-microns frozen sequential sections of breast carcinomas obtained from 213 patients . Microscopic images of immunostained preparations were evaluated by image analysis and were compared with MDR1 transcription (mRNA) assessed by PCR in 16 patients . Quantitative P-gp immunocytochemical assays were correlated to histoprognostic factors and immunocytochemical indicators . RESULTS: Among the 213 breast carcinomas tested, 113 (53%) were P-gp positive, but in 28% of the tumors, the immunostained surface accounted for less than 5% of the total area stained . Quantitative immunocytochemistry reflecting the amount of intracellular P-gp antigen strongly correlated (r = 0.865; two-sided, P < .0001; Pearson's test) with the quantitative evaluation of the scanner analysis of mRNA transcripts . The P-gp expression was significantly (two-sided, P < .001) correlated with p53 expression in tumors, to cathepsin D and Ki67 (two-sided, P < .01) immunoreactivity, and to a lesser extent, the detection of estrogen receptor antigenic sites (two-sided, P = .019) . P-gp expression was found to be independent of expression of progesterone receptor and pS2, pHER-2/neu, and CD31 in tumors and from patient age, tumor size, histologic types, grades and Nottingham prognostic index, and nodal status . CONCLUSIONS: The quantitative immunocytochemical assays of P-gp are correlated to PCR analysis of MDR1 expression, and such correlations can be useful in evaluating potential multidrug resistance in breast cancer . However, the clinical significance of P-gp immunodetections remains to be further determined. Biochem Pharmacol, 1994 Oct 18, 48(8), 1641 - 6 Expression and function of multidrug resistance P-glycoprotein in a cultured natural killer cell-rich population revealed by MRK16 monoclonal antibody and AHC-52; Kobayashi Y et al.; Natural killer (NK) cells have been reported recently to be the highest in expressing multidrug resistance (MDR) P-glycoprotein among normal mature lymphoid cells . Using a cultured NK cell-rich population, we have examined the expression and function of P-glycoprotein, in particular its role in NK cell-mediated cytotoxicity, by employing two MDR-reversing agents (nicardipine and AHC-52, a nicardipine analog almost devoid of calcium channel blocking activity) and monoclonal antibody against P-glycoprotein (MRK-16) . The expression of P-glycoprotein was detected by flow cytometry and polymerase chain reaction of reverse transcribed mRNA . P-glycoprotein was functional in terms of rhodamine dye excretion and its susceptibility to the MDR-reversing agents . Since the concentration of nicardipine required for 50% inhibition (IC50) of rhodamine dye excretion (2 microM) was close to that of AHC-52 (5 microM), it was suggested that their inhibitory effects were not due to calcium channel blocking activity, and that ACH-52 is a selective inhibitor for P-glycoprotein . The IC50 of nicardipine for NK cell-mediated cytotoxicity (33 microM) was also close to that of AHC-52 (26 microM), indicating that P-glycoprotein is involved in NK cell-mediated cytotoxicity . In support of this, MRK16 inhibited NK cell-mediated cytotoxicity in a concentration-dependent manner . Both binding of target cells to NK cells and post-binding events were affected by AHC-52, suggesting that P-glycoprotein is involved in several steps in NK cell-mediated cytotoxicity. Int J Cancer, 1994 Oct 15, 59(2), 282 - 6 Resistance to verapamil sensitization of multidrug-resistant cells grown as multicellular spheroids; Sakata K et al.; The ability of verapamil to overcome resistance to adriamycin in a multidrug-resistant derivative of the V79 cell line (LZ), grown as multicellular spheroids or as monolayers, was examined . Verapamil was much less effective in overcoming resistance to adriamycin in spheroids than in monolayers . Verapamil increased the adriamycin content of cells grown as monolayers, but had no significant effect on the drug content of spheroids . This occurred in spite of the same mdr-I mRNA and protein levels in monolayers and spheroids . When the surviving fraction of cells was normalized to the cellular adriamycin content, cells both in monolayers and spheroids treated with verapamil were still more sensitive to adriamycin than their counterparts not treated with verapamil . The observed resistance of spheroids to adriamycin and verapamil sensitization may be caused by a drug-resistance mechanism that is functional only in spheroids, in addition to the activity of P-glycoprotein . Multicellular tissue architecture and cell-cell contact may play significant roles in this type of multidrug-resistance mechanism. Int J Cancer, 1994 Oct 15, 59(2), 275 - 81 Daunorubicin efflux against a concentration gradient in non-P-glycoprotein multidrug-resistant lung-cancer cells; Mulder HS et al.; Multidrug-resistant, human non-small-cell lung carcinoma SW-1573/2R120 (2R120) cells, not containing the drug efflux pump P-glycoprotein (Pgp), have reduced initial daunorubicin (DN) accumulation rates and decreased cellular steady-state drug concentrations . Previously we found indications of the presence of a plasma membrane "vacuum cleaner", pumping DN directly from the membrane, and reported evidence of active DN pumping using digitonin . Further evidence of active DN pumping is now provided via a different methodology and the active drug pump flux is estimated . Cells were exposed to a flowing medium containing the cytotoxic agent DN . After reaching a steady state, in which net DN uptake equals net DN efflux, high concentration pulses of vincristine (VCR) were injected into the flowing medium . A rapid increase in cellular DN content was observed, while only a minimal effect was seen in SW-1573 wild-type cells . After passage of the VCR pulse, the extra accumulated DN was effluxed against a concentration gradient . Upon increasing the VCR concentration, a maximum pump inhibition was reached which was similar to the effect of cellular energy depletion . Similar effects were observed for Pgp-containing SW-1573/2R160 (2R160) cells as well as non-Pgp MDR human small-cell lung carcinoma GLC4/ADR cells . With increasing extracellular DN concentrations, saturation of the VCR-induced DN influx was observed (DN medium concentration 2.5 microM at 1/2 Vmax) . At an extracellular DN concentration of 5 microM, higher concentrations of VCR were needed to reach the maximum effect in 2R120 cells than at 0.5 microM DN . This is an indication of competitive interaction between DN and VCR for the putative DN efflux system . In summary, we found indications of inhibition of active DN efflux by VCR and DN efflux against a concentration gradient in non-Pgp MDR 2R120 and GLC4/ADR cells . These features are consistent with the presence of a multidrug transporter, different from Pgp, in the plasma membrane of these cells. Int J Cancer, 1994 Oct 15, 59(2), 208 - 11 Induction of multidrug resistance (MDR) by transfection of MCF-10A cell line with c-Ha-ras and c-erbB-2 oncogenes; Sabbatini AR et al.; To investigate the relationship between oncogene activation and appearance of multidrug resistance (MDR) we transfected the human breast epithelial cell line MCF-10A, negative for the expression of the P-glycoprotein, with c-Ha-ras and/or c-erbB-2 oncogenes . The appearance of the MDR phenotype was then studied by evaluating mdr-1 mRNA expression, the presence of P-glycoprotein on the cell membrane and the onset of doxorubicin resistance, together with the effect of the reversing agent verapamil . We found that only MCF-10A transfected with both c-Ha-ras and c-erbB-2 oncogenes acquired the MDR phenotype. Cancer Res, 1994 Oct 15, 54(20), 5368 - 73 Effects of amiodarone, cyclosporin A, and PSC 833 on the cytotoxicity of mitoxantrone, doxorubicin, and vincristine in non-P-glycoprotein human small cell lung cancer cell lines; van der Graaf WT et al.; The multidrug resistance (MDR) modulators amiodarone (AM), cyclosporin A (CsA), and PSC 833 were tested for their potential to modulate cytotoxicity of doxorubicin (DOX), vincristine (VCR), and mitoxantrone (MX) in a sensitive human small cell lung carcinoma cell line GLC4, in its DOX-resistant non-P-glycoprotein subline GLC4-Adr, and in its cisplatin-resistant subline GLC4-CDDP . GLC4-Adr, in which overexpression of the so-called multidrug resistance-associated protein has been demonstrated, is 91-fold resistant for DOX, 22-fold for VCR, and 7.5-fold for MX, compared with its sensitive cell line . AM previously modulated DOX and VCR resistance in the P-glycoprotein-positive human colon cancer cell line COLO 320 . Cytotoxicity was studied in the microtiter well tetrazolium assay . In the small cell lung carcinoma cell lines described above, AM did not increase cytotoxicity of DOX, but increased VCR cytotoxicity; moreover, AM was shown to be a potent modulator of MX cytotoxicity . CsA did not potentiate DOX cytotoxicity, but, at a concentration of 4 microM, it modestly increased VCR cytotoxicity in GLC4 . However, 0.8 and 4.0 microM CsA protected against MX cytotoxicity in GLC4 and GLC4-CDDP, but no effect was observed in GLC4-Adr . At the much higher ID10 concentration CsA modulated MX cytotoxicity 1.6-fold in GLC4-Adr and slightly in GLC4 and GLC4-CDDP . PSC 833, a nonimmunosuppressive CsA analogue, did not alter the cytotoxicity of DOX or MX in these cell lines, but potentiated VCR cytotoxicity in GLC4-Adr at a concentration of 0.4 microM . The modulation of MX cytotoxicity by AM and the protection by CsA was confirmed in a clonogenic assay . In the colony-forming unit granulocyte-monocyte assay, no additional MX toxicity on normal bone marrow by AM was observed . Flow cytometry of cellular MX fluorescence was performed in order to elucidate the mechanism behind the AM-induced increased MX cytotoxicity . This revealed an increase in cellular MX after 1-h incubation of MX combined with AM and an inhibition of efflux from GLC4 and GLC4-Adr; CsA and PSC 833 had no effect on MX efflux . An increase in MX-induced cleavable complexes by AM in GLC4 was observed using the K+/sodium dodecyl sulfate coprecipitation assay, but no effect of CsA was found . In conclusion, AM enhances MX and VCR cytotoxicity in these sensitive, non-P-glycoprotein DOX and cisplatin-resistant small cell lung carcinoma cell lines . It also inhibits efflux of MX and causes more MX-induced cleavable complexes. Arch Intern Med, 1994 Oct 10, 154(19), 2161 - 7 Tuberculosis susceptibility patterns, predictors of multidrug resistance, and implications for initial therapeutic regimens at a New York City hospital; Weltman AC et al.; BACKGROUND: Multidrug resistance has complicated tuberculosis therapy . We studied antibiotic susceptibilities of Mycobacterium tuberculosis and predictors of multidrug resistance to assist in determining initial drug regimens . METHODS: We conducted a case-control study based on chart review of patients with and without multidrug-resistant tuberculosis, including outpatients and inpatients with culture-proved tuberculosis seen at a large New York, NY, hospital during 1991 and 1992 . Patient characteristics studied included serologic findings for human immunodeficiency virus and the presence of the acquired immunodeficiency syndrome . Descriptive analysis considered potential initial drug regimens . A theoretically effective regimen was assumed to contain at least two drugs to which an isolate was susceptible . RESULTS: For 172 patients, 28.5% of isolates were resistant to isoniazid, at least 20.9% to rifampin, 15.7% to ethambutol, 8.1% to pyrazinamide, 18.6% to streptomycin, 9.9% to ethionamide, 8.1% to kanamycin, and none to capreomycin, cycloserine, and ciprofloxacin; 18.6% were resistant to both isoniazid and rifampin . Chart review of 159 patients showed that acquired immunodeficiency syndrome, human immunodeficiency virus seropositivity, female gender, residence in the Bronx, and race were associated with multidrug resistance . The four-drug regimen of isoniazid, rifampin, ethambutol, and pyrazinamide was theoretically effective for 81% to 85% of patients . No subset of patients would have a markedly better theoretical benefit from that regimen . Only five- or six-drug regimens that used the combinations of capreomycin plus ciprofloxacin, capreomycin plus cycloserine, ciprofloxacin plus cycloserine, or all three drugs together theoretically offered significantly higher effectiveness . CONCLUSIONS: Tuberculosis isolates at our hospital have a high frequency of multidrug resistance . Only five- or six-drug regimens are theoretically adequate as initial therapy for our patients. Biochem Pharmacol, 1994 Oct 7, 48(7), 1437 - 45 Modulation of adriamycin accumulation and efflux by flavonoids in HCT-15 colon cells . Activation of P-glycoprotein as a putative mechanism; Critchfield JW et al.; Since P-glycoprotein (P-gp) in normal tissues may serve as a cellular defense mechanism against naturally occurring xenobiotics, we considered whether physiologically active components of commonly ingested plant foods could influence P-gp function . To examine this possibility, a series of flavonoids commonly found in plant foods was tested for their ability to modulate {14C}Adriamycin ({14C}ADR) accumulation and efflux in P-gp-expressing HCT-15 colon cells . Many flavonoids, in the micromolar range, inhibited the accumulation of {14C}ADR . Detailed experiments utilizing flavonoids with the greatest activity in reducing {14C}ADR accumulation, i.e . galangin, kaempferol, and quercetin, revealed that the efflux of {14C}ADR is increased markedly in the presence of these compounds . Flavonoid-induced stimulation of efflux was rapid and was blocked by the multidrug-resistant (MDR) reversal agents verapamil, vinblastine, and quinidine . The magnitude of flavonoid-stimulated efflux in sodium butyrate-treated cells with a 4-fold induction of P-gp protein was similar to that in uninduced cells . {3H}Azidopine photoaffinity labeling of P-gp in crude membrane preparations revealed mild to no competition for binding by flavonoids possessing either activity or inactivity in reducing ADR accumulation . Although flavonoid hydrophobicity was found to be unrelated to flavonoid activity in altering {14C}ADR accumulation, certain structural features were associated with enhancement or diminution of activity . Finally, the significance of flavonoid-related reduction of {14C}ADR accumulation was underscored in cell growth studies, showing partial protection by quercetin against ADR-induced growth inhibition . It is concluded that certain naturally occurring plant flavonoids may acutely upregulate the apparent activity of P-gp. FEBS Lett, 1994 Oct 3, 352(3), 380 - 4 Effect of unmodified triple helix-forming oligodeoxyribonucleotide targeted to human multidrug-resistance gene mdr1 in MDR cancer cells; Scaggiante B et al.; The human mdr1 gene encodes a transmembrane glycoprotein the over-expression of which is associated with development of multidrug resistance in human tumor cells . A negative modulation of human mdr1 has been attempted via a 27-mer unmodified triple helix-forming oligonucleotide, named 1D, targeted to a homopurine sequence in the coding region of the gene . By administering 10 microM of 1D we could find a significant reduction in MDR1 mRNA levels in the human drug-resistant cell line CEM-VLB100 . This effect appears to be specific and due to a transient block of RNA polymerase mediated by triple helix formation. Hautarzt, 1994 Oct, 45(10), 678 - 84 {Drug resistance of malignant melanoma . Mechanisms and possible modulation}; Schadendorf D et al.; Response rates of metastatic malignant melanoma to cytostatic treatment are disappointingly low . Although immunomodulators such as interferons are more commonly being used in combination with cytostatics, no major breakthrough has been achieved . The mechanisms underlying the high chemoresistance of melanoma cells are so far ill-defined, and investigations are only just being initiated . Several mechanisms of chemoresistance have, however, been studied with other tumours and might be relevant for human melanoma: (1) "Classical" multidrug resistance, determined by the expression of the p-glycoprotein which resembles a membrane pump that eliminates natural and synthetic agents from the cell interior . Different drugs, including calcium antagonists, interfere with its function and can thus modulate chemoresistance . Preliminary data from investigations of these mechanisms indicate that p-glycoprotein is not, however, involved in the multidrug resistance of malignant melanoma . (2) Detoxification, involving glutathione-S-transferases (GST) . GST are a multigene family of enzymes which inactivate alkylating agents by conjugation to glutathione . Their relevance for chemoresistance in melanoma has not yet been clarified . (3) Topoisomerase II, which is involved in DNA recombination and DNA transcription events and represents the target of several inhibitory cytotoxic agents . Low levels of the enzyme render cells resistant to the action of specific drugs . Again nothing is yet known regarding the relevance of this mechanism in human melanoma . Further studies of these potentially important resistance mechanisms are thus urgently needed in order to develop more effective therapies for advanced malignant melanoma. Mol Pharmacol, 1994 Oct, 46(4), 677 - 84 Mechanisms of resistance to ansamycin antibiotics in human breast cancer cell lines; Benchekroun MN et al.; We recently reported that multidrug-resistant, P-170 glycoprotein-positive, Adriamycin-selected, human breast tumor (MCF7/ADRR) cells were resistant to the benzoquinonoid ansamycin antibiotics geldanamycin (GL) and herbimycin A (HA) and that significantly fewer hydroxyl radicals were formed in resistant cells . We have carried out additional studies to define the mechanisms of cytotoxicity of and resistance to GL and HA, by directly examining the interactions of these drugs with P-170 glycoprotein using photoaffinity labeling . We found that both GL and HA inhibited binding of azidopine to P-170 glycoprotein in a dose-dependent manner . We have developed a 10-fold GL-resistant cell line (MCF7/GLR) by continuous drug exposure . Our studies indicated no significant differences in free radical formation between wild-type MCF7 cells and MCF7/GLR cells . Uptake and efflux studies indicated a small decrease in the GL accumulation but no difference in the efflux of GL in these cells . Verapamil had no effect on cellular accumulation of GL in wild-type MCF7 cells or MCF7/GLR cells . Verapamil significantly increased the accumulation of GL in MCF7/ADRR cells and enhanced GL cytotoxicity 12-fold, suggesting that GL interacted with the P-170 glycoprotein . Using reverse transcription-polymerase chain reaction, we found no expression of the mdr1 gene; however, expression of the multidrug resistance-associated protein was about 2-fold higher in MCF7/GLR cells . Taken together, these studies indicate that the mechanisms of GL resistance are multifactorial . Although decreased free radical formation may not play a significant role in low levels of GL resistance, e.g., in MCF7/GLR cells, both overexpression of mdr1 and decreased free radical formation contribute to GL resistance in highly resistant cells such as MCF7/ADRR cells. Mol Pharmacol, 1994 Oct, 46(4), 627 - 38 Rhodamine efflux patterns predict P-glycoprotein substrates in the National Cancer Institute drug screen; Lee JS et al.; Fifty-eight cell lines in the National Cancer Institute drug screen were analyzed for their ability to efflux the fluorescent dye rhodamine 123 as a functional assay for P-glycoprotein (Pgp) . Using flow cytometry, the rhodamine fluorescence was measured for each cell line under four incubation conditions, i.e., after accumulation in the presence or absence of the Pgp antagonist cyclosporin A and after efflux in rhodamine-free medium in the presence or absence of cyclosporin A . The results in some cell lines were compatible with Pgp-mediated efflux . There was a significant correlation between mdr-1 expression and rhodamine efflux in the 58 cell lines (r = 0.788, p = 0.0001) . Using the rhodamine efflux data as a seed for COMPARE analysis with the cytotoxicity data on > 30,000 compounds in the National Cancer Institute drug screen database, hundreds of compounds with high correlation coefficients were identified . Selected compounds were tested for reversal of cross-resistance in a multidrug-resistant cell line . A high degree of reversibility, up to 10,000-fold, for some of the compounds was noted in the presence of the Pgp antagonist PSC 833 . This finding suggested that compounds with predominately Pgp-mediated resistance were being identified . Using these compounds as seeds for COMPARE analysis against a more restricted database of 187 standard agents, a series of standard compounds were repeatedly identified as having high correlation coefficients with the newly identified Pgp substrates . These standard agents, including phyllanthoside, bisantrene, and homoharringtonine, constitute an mdr-1 profile . New agents identified as being highly correlated with these compounds may benefit from clinical trials with Pgp antagonists. Lab Invest, 1994 Oct, 71(4), 595 - 603 A sensitive multilayer immunoalkaline phosphatase method for detection of P-glycoprotein in leukemic and tumor cells in the bone marrow; Haddad G et al.; BACKGROUND: Relatively low levels of the multidrug resistance P-glycoprotein have correlated with poor prognosis in rhabdomyosarcoma, neuroblastoma, acute myelogenous leukemia, lymphoma, myeloma and breast carcinoma . A sensitive, nonradioactive method, less costly and time-consuming than the present molecular biologic techniques, is desirable for direct measurement of P-glycoprotein in tumor cells versus normal cells . EXPERIMENTAL DESIGN: We have devised an immunoalkaline phosphatase method using four antibody layers to amplify the primary signal considerably and refined staining conditions to optimize the 'signal-to-noise' ratio . Immunoalkaline phosphatase is preferred to immunoperoxidase for testing leukemic and tumor cells in bone marrow, because it avoids myeloperoxidase staining in myeloblasts and myeloid progenitors that interferes with P-glycoprotein interpretation . RESULTS: Multilayer immunoalkaline phosphatase detected low levels of P-glycoprotein overexpression, that could not be identified by conventional immunoperoxidase or immunoblot, in a low-resistance (8-fold) cell line with a barely detectable transcript . Our technique also detected increased P-glycoprotein in malignant cells in bone marrow of relapsed acute lymphoblastic leukemia (10/11), acute myelogenous leukemia (2/2), lymphoma (1/1), neuroblastoma (7/7), and rhabdomyosarcoma (2/2) . Increased P-glycoprotein was not identified at diagnosis in 6 patients with acute lymphoblastic leukemia, and two with stage IV and three with stage IVS neuroblastoma that remained relapse-free in the long-term, but was detected in 4 patients with stage IV neuroblastoma and three with rhabdomyosarcoma who ultimately relapsed . CONCLUSIONS: Our new technique is more sensitive than conventional immunoperoxidase and immunoblot for assaying P-glycoprotein in low-resistance cell lines . It may be potentially applicable for detecting low levels of P-glycoprotein overexpression in leukemic and tumor cells in bone marrow . Early identification of low levels of multidrug resistance may be clinically relevant by allowing poor-prognostic patients to receive alternative therapy. Ann Hematol, 1994 Oct, 69(4), 159 - 71 P-glycoprotein-mediated multidrug resistance in normal and neoplastic hematopoietic cells; Licht T et al.; The multidrug transporter, P-glycoprotein (P-gp), is expressed by CD34-positive bone marrow cells, which include hematopoietic stem cells, and in other cells in the bone marrow and peripheral blood, including some lymphoid cells . Multidrug resistance mediated by P-gp appears to be a major impediment to successful treatment of acute myeloid leukemias and multiple myelomas . However, the impact of P-gp expression on prognosis has to be confirmed in several other hematopoietic neoplasms . The role of P-gp in normal and malignant hematopoiesis and clinical attempts to circumvent multidrug resistance in hematopoietic malignancies are reviewed . The recent transduction of the MDR1 gene into murine hematopoietic cells, which protects them from toxic effects of chemotherapy, suggests that MDR1 gene therapy may help prevent myelosuppression following chemotherapy. Am J Physiol, 1994 Oct, 267(4 Pt 1), C1095 - 102 ATP-activated chloride channel inhibited by an antibody to P glycoprotein; Zhang JJ et al.; In this report, we present the characteristics of a Cl- channel found in lens fiber cells . The single channel has a conductance of 17 pS, a linear current-voltage curve, is activated by ATP or strong depolarization and is blocked by verapamil, quinidine, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, 5-nitro-2-(3- phenylpropylamino)benzoate, dideoxyforskolin, and tamoxifen . These properties are similar to those reported for a volume-activated Cl- channel associated with the multidrug resistance (MDR) gene product, P glycoprotein (24) . Confirming this connection, we demonstrate that our lens Cl- channel is inhibited by an antibody to P glycoprotein . The data we present here may, therefore, be the first characterization of the single channel activity of the Cl- channel associated with P glycoprotein. J Neurosurg, 1994 Oct, 81(4), 587 - 94 Reversal of chemoresistance in malignant gliomas by calcium antagonists: correlation with the expression of multidrug-resistant p-glycoprotein; Kiwit JC et al.; Resistance to multiple drugs is often observed in malignant gliomas . The authors used a microtiter tetrazolium test to analyze primary in vitro chemoresistance and chemosensitivity of 15 early cultures of human malignant glioma exposed to 50 micrograms/ml (1,4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a (ACNU), 50 micrograms/ml cisplatin, 1 microgram/ml vincristine, or combinations of these chemotherapeutic agents . Primary chemoresistance was observed in 87% of tumors for ACNU, in 87% for cisplatin, and in 83% for vincristine . All tumors were examined for expression of multidrug-resistant p-glycoprotein, a transport protein of 170,000 D, by means of immunohistochemical staining with the JSB-1 antibody on paraffinized tumor sections . Eight of 15 specimens (53%) showed positive staining for the monoclonal antibody . Primary chemoresistance was overcome by addition of the calcium antagonists verapamil or nimodipine to the cultures if the original tumor expressed p-glycoprotein (p < 0.01 for verapamil, p < 0.05 for nimodipine) . In tumors not expressing p-glycoprotein, addition of calcium antagonists to the cell cultures did not influence primary chemoresistance . It is concluded from these data that addition of calcium antagonists to the adjuvant chemotherapy of malignant gliomas might overcome primary chemoresistance in tumors expressing the multidrug-resistant phenotype. J Infect Dis, 1994 Oct, 170(4), 971 - 7 Treatment of multidrug-resistant Plasmodium falciparum malaria with 3-day artesunate-mefloquine combination; Nosten F et al.; Studies of 652 adults and children with acute uncomplicated falciparum malaria were done to determine the optimum treatment of multidrug-resistant Plasmodium falciparum malaria on the Thai-Burmese border . Single-dose artesunate (4 mg/kg) plus mefloquine (25 mg of base/kg) gave more rapid symptomatic and parasitologic responses than high-dose mefloquine alone but did not improve cure rates . Three days of artesunate (total dose, 10 mg/kg) plus mefloquine was 98% effective compared with a 28-day failure rate of 31% with high-dose mefloquine alone (relative risk {RR}, 0.06; 95% confidence interval {CI}, 0.02-0.2; P < .0001) . By day 63, the reinfection adjusted failure rates were 2% and 44%, respectively (P < .0001) . Artesunate also prevented high-grade failures . Both drugs were well tolerated . No adverse effects were attributable to artesunate . Vomiting was reduced significantly by giving mefloquine on day 2 of treatment (RR, 0.40; 95% CI, 0.20-0.79; P = .009 . Artesunate (10 mg/kg over 3 days) plus mefloquine (25 mg/kg) is currently the most effective treatment for falciparum malaria in this area of increasing mefloquine resistance. Int J Cancer, 1994 Oct 1, 59(1), 83 - 93 Ecto-5'-nucleotidase (CD73) in multidrug-resistant cell lines generated by doxorubicin; Ujhazy P et al.; Cytochemical screening for a panel of enzymes revealed increased 5' nucleotidase (5'NT) expression in 3 of 3 P-glycoprotein 170 (Pgp170)-positive multidrug-resistant (MDR) variants of the murine EL4 T-lymphoma cell line (EL4/ADM, ER2 and ER13) . Electron microscopic localization established the presence of the membrane-bound ecto-form of the enzyme . Nine other murine, human and Chinese hamster cell lines and their MDR variants were tested for ecto-5'NT . Of these, 4 MDR variants (human cell lines MCF7A6, MCF7A2, HeLaJ2C and the murine cell line L1210A) showed increased expression of ecto-5'NT, when compared with their parental cell lines . The findings with cells of human origin were confirmed by immunofluorescent localization with a specific monoclonal antibody (MAb) (27.2) against the human ecto-5'NT . All MDR cell lines with elevated ecto-5'NT expression were generated by doxorubicin treatment . These cells were more sensitive than their parental cell lines to AMP at concentrations of 1.5-3.0 mM, confirming that the expressed ecto-5'NT was biologically active . The parental and MDR cells did not differ, in general, in their sensitivity to adenosine . An inhibitor of ecto-5'NT, alpha,beta-methyleneadenosine 5'-diphosphate, completely reversed the resistance of the EL4/ADM cell line to doxorubicin . The possibility exists of a functional relationship between the ecto-5'NT molecule and the members of the ATP-binding cassette transporter superfamily, important components of MDR, in some cell types. Int J Cancer, 1994 Oct 1, 59(1), 133 - 40 Myeloid and lymphoid cell alterations in normal mice exposed to chemotherapy with doxorubicin and/or the multidrug-resistance reversing agent SDZ PSC 833; Froidevaux S et al.; The cyclosporin SDZ PSC 833 (PSC) is a potent in vivo chemosensitizer for tumor cells with P-glycoprotein(Pgp)-dependent multidrug resistance (MDR) . However, Pgp expression also occurs in CD8+ T cells, NK cells, macrophages and stem cells . In order to find whether PSC might display specific myelotoxicity or potentiate the toxicity of anti-cancer drugs, healthy mice were exposed to single doxorubicin (DOX) and combined (DOX + PSC) chemotherapy protocols known to be near or above the borderline of toxicity for tumor-bearing mice . Mice treated with DOX alone or with (DOX + PSC) showed transient spleen hypoplasia, with a general decrease of all leucocyte lineages and a persistent fall in the numbers of B cells in the bone marrow . In (DOX + PSC)-treated mice, PSC only potentiated the DOX effects without inducing specific depletions of the Pgp-expressing leukocytes (CD8+ and Mac-I+ cells) . Hematopoietic cell grafts from normal mice to (DOX +/- PSC)-treated mice did not correct their B-cell lineage deficiency . When lethally irradiated mice were rehabilitated with hematopoietic cells from (DOX +/- PSC)-treated mice (including those with very reduced survival), all chimeras survived for at least 8 months after the cell graft, at which time their leucocyte population profiles were similar to those of control chimeras. Cancer Res, 1994 Oct 1, 54(19), 5036 - 40 Expression of the multidrug resistance-associated protein (MRP) gene correlates with amplification and overexpression of the N-myc oncogene in childhood neuroblastoma; Bordow SB et al.; The MRP gene (Cole et al., Science (Washington DC), 258: 1650-1654, 1992) encodes a membrane-bound glycoprotein the expression of which correlates with non-P-glycoprotein-mediated multidrug resistance in a variety of cultured human cell lines . Using an RNA-polymerase chain reaction assay, expression of this gene was examined in the highly chemoresistant pediatric malignancy, neuroblastoma . MRP expression was observed in 5 human neuroblastoma cell lines and in all 25 primary neuroblastoma tumors of stage I through IVS . Tumors with amplification of the N-myc oncogene were found to have significantly higher MRP expression that those with no amplification (P = 0.0016) . Expression of the MRP gene in the tumor specimens was highly correlated with expression of the N-myc gene (P = 0.0009), while expression of the MDR1 gene, encoding P-glycoprotein, was not related to expression of either the N-myc or MRP genes . Decreased expression of the N-myc oncogene in neuroblastoma cell lines SH-SY5Y and BE(2)-C, following treatment with retinoic acid, was paralleled by down-regulation of MRP gene expression, contrasting with increased expression of the MDR1 gene . Expression of the MRP gene is thus common in both primary neuroblastoma tumors and cultured cell lines, and correlates with amplification and overexpression of the N-myc oncogene, which is central to the malignant phenotype of this disease. Cancer Res, 1994 Oct 1, 54(19), 5029 - 32 Volume-activated chloride current is not related to P-glycoprotein overexpression; Dong Y et al.; It has been suggested that P-glycoprotein (P-gp), an ATP-dependent transporter responsible for classical multidrug resistance, is also a volume-regulated chloride channel . We reexamined this hypothesis by use of whole-cell patch clamp recordings of three matched pairs of cell lines, which were either drug-sensitive or drug-resistant due to P-gp overexpression . We demonstrate here that volume-regulated chloride-selective currents can be induced in cells with or without P-gp expression . Overexpression of either P-gp or cystic fibrosis transmembrane conductance regulator, the protein product of the CF gene and another member of the ATP-dependent transporters, is associated with a hypotonicity-induced, rapid onset, transient current prior to onset of the volume-sensitive chloride-selective current, an apparent nonspecific effect related to the overexpression of an integral membrane protein . These results suggest that there is no relationship between P-gp and the chloride channel activated by cell swelling. Curr Genet, 1994 Oct, 26(4), 285 - 94 Saccharomyces cerevisiae YDR1, which encodes a member of the ATP-binding cassette (ABC) superfamily, is required for multidrug resistance; Hirata D et al.; A multidrug resistance gene, YDR1, of Saccharomyces cerevisiae, which encodes a 170-kDa protein of a member of the ABC superfamily, was identified . Disruption of YDR1 resulted in hypersensitivity to cycloheximide, cerulenin, compactin, staurosporine and fluphenazine, indicating that YDR1 is an important determinant of cross resistance to apparently-unrelated drugs . The Ydr1 protein bears the highest similarity to the S . cerevisiae Snq2 protein required for resistance to the mutagen 4-NQO . The drug-specificity analysis of YDR1 and SNQ2 by gene disruption, and its phenotypic suppression by the overexpressed genes, revealed overlapping, yet distinct, specificities . YDR1 was responsible for cycloheximide, cerulenin and compactin resistance, whereas, SNQ2 was responsible for 4-NQO resistance . The two genes had overlapping specificities toward staurosporine and fluphenazine . The transcription of YDR1 and SNQ2 was induced by various drugs, both relevant and irrelevant to the resistance caused by the gene, suggesting that drug specificity can be mainly attributed to the functional difference of the putative transporters . The transcription of these genes was also increased by heat shock . The yeast drug-resistance system provides a novel model for mammalian multidrug resistance. Occup Med, 1994 Oct-Dec, 9(4), 695 - 721 Medical surveillance for workers exposed to tuberculosis; Moline JM et al.; This detailed discussion of medical surveillance techniques addresses such issues as the administration and interpretation of the tuberculin skin test, the importance of BCG vaccine, preventive therapy with isoniazid, the identification of groups at high risk for TB, multidrug-resistant tuberculosis, and regulatory requirements for PPD testing, including CDC guidelines. Biochem Mol Biol Int, 1994 Oct, 34(4), 773 - 80 Etoposide-resistance in the multidrug-resistant LZ-8 cells; Liengswangwong V et al.; The multidrug-resistant LZ-8 cells were found to exhibit marked resistance to etoposide compared to wild-type, parental V79 cells . The multidrug resistant phenotype did not significantly contribute to this etoposide-resistance . Following exposure of LZ-8 cells and V79 cells to equivalent concentrations of etoposide, there was a dramatic reduction in the number of etoposide-induced stabilized DNA-topoisomerase II complexes in the LZ-8 cells compared to V79 cells, however, this reduction was not found when nuclei isolated from LZ-8 and V79 cells were exposed to equivalent concentrations of etoposide . These results suggest that cytoplasmic factors are involved in the etoposide-resistance of LZ-8 cells. Acta Med Okayama, 1994 Oct, 48(5), 249 - 55 Immunohistochemical analysis of P-glycoprotein expression in diverse histological types of epithelial ovarian tumors; Kodama J et al.; P-glycoprotein is a transmembrane protein which acts as an energy-dependent drug efflux pump for a variety of anti-cancer drugs . The mdr-1 gene which encodes P-glycoprotein was successfully cloned in 1986 . To investigate P-glycoprotein expression in diverse ovarian tumors, including benign, low malignant potential and malignant, immunohistochemical study was done using a monoclonal antibody (C 219) . Overall, 8 out of the 59 epithelial ovarian tumors (13.6%) expressed P-glycoprotein . It was noted that 5 of the 12 mucinous tumors were found to express P-glycoprotein, while none of the 31 serous tumors were immunohistochemically positive . In 10 malignant ovarian tumors, P-glycoprotein immunostaining was examined both prior to and after chemotherapy . Nine of them did not express any P-glycoprotein before or after chemotherapy . However, one tumor expressed P-glycoprotein after six courses of multidrug resistance-related drug administration . These findings indicate that P-glycoprotein expression is not so common in ovarian tumors, regardless of their malignant potential . Nevertheless, the results suggest a strong association between P-glycoprotein expression and certain histological cell types in epithelial ovarian tumors . It is also possible that P-glycoprotein appears as a result of chemotherapy, but such a phenomenon can not occur unless chemotherapy is administered at high doses for a long period of time. J Chemother, 1994 Oct, 6(5), 343 - 8 Effect of buthionine sulfoximine on the sensitivity to doxorubicin of parent and MDR tumor cell lines; Crescimanno M et al.; We have studied the interaction of glutathione-depleting concentrations of buthionine sulfoximine (BSO) with the anti-proliferative activity of doxorubicin (DXR) in three tumor lines, the mouse B16 melanoma . Friend erythroleukemia and the human K562 leukemia, both as DXR-sensitive and-resistant (with typical multidrug resistance) variants . BSO significantly enhanced the DXR effects in the wild-type Friend and K562 leukemias, and especially in the drug-resistant subline of Friend leukemia . BSO did not modify DXR accumulation and retention in the latter clone . Moreover, neither BSO nor verapamil used alone completely reversed the resistance to DXR of this cell line; their combination was more efficient and increased its drug sensitivity to a level closer to that of the parental counterpart . These results seem to indicate that the status of glutathione and of the enzymes related to it contributes to the resistance of Friend leukemia to DXR . An interesting additional finding was that BSO significantly synergizes with the antiproliferative effects of vincristine in the drug-sensitive variants of Friend and K562 leukemias. Anticancer Drugs, 1994 Oct, 5(5), 598 - 600 Effects of lovastatin on a human myeloma cell line: increased sensitivity of a multidrug-resistant subline that expresses the 170 kDa P-glycoprotein; Holmberg M et al.; Using a fluorometric microculture cytotoxicity assay for measuring cell viability and proliferation we examine the cytotoxic effect of lovastatin on a drug sensitive myeloma cell line (RPMI 8226) and a multidrug resistant (MDR) clone (8226/Dox40), that was approximately 100-fold less sensitive to doxorubicin . The RPMI 8226 cells were sensitive to lovastatin with an IC50 of 15.8 micrograms/ml . However, the MDR subline exhibited a collateral sensitivity to lovastatin, with an IC50 of 1.7 microM, thus having a 9.3-fold greater sensitivity to lovastatin than the parental cell line . The combination of doxorubicin and lovastatin did not show any synergistic or antagonistic effects on any of the cell lines . The increased sensitivity to lovastatin of the P-gp 170-expressing MDR cells 8226/Dox40 might be part of a more general phenomenon that merits further investigation. Trends Microbiol, 1994 Oct, 2(10), 407 - 11 Microbial multidrug-resistance ABC transporters; Ouellette M et al.; Multidrug resistance in tumor cells is often caused by the increased efflux of a wide variety of drugs, mediated by P glycoprotein, a member of the superfamily of ATP-binding cassette (ABC) transporters . The genes encoding members of this superfamily have also been isolated from drug-resistant microorganisms, and the role of microbial ABC transporters in drug resistance is being investigated. Cell Growth Differ, 1994 Oct, 5(10), 1145 - 52 Enhanced expression by the brain matrix of P-glycoprotein in brain capillary endothelial cells; Tatsuta T et al.; P-glycoprotein (PGP), an active efflux pump of antitumor agents in multidrug-resistant tumor cells, exists in brain capillary endothelium and could be functionally involved in the blood-brain barrier . To study the regulatory mechanism of PGP expression in brain capillary endothelium, various mouse tissue matrices were tested for their abilities to enhance the expression of PGP in mouse brain capillary endothelial cells (MBEC), which express relatively small amounts of PGP . Of the four tissue matrices we examined, PGP expression in MBEC cultured on the brain matrix increased 2.0-fold . The PGP-inducing activity was similarly detected in bovine brain matrix, and the activity was enriched in the fraction of pl 9.0 by isoelectric focusing . The fraction, named PIC-fraction (PGP-inducing component), increased the PGP expression in MBEC 3.5-fold . By Northern blot analysis, a 3.3-fold enhancement of mdr gene expression was observed in MBEC cultured on the PIC-fraction . The PGP-inducing activity of the PIC-fraction was reduced by the treatment with trypsin but not with collagenase, suggesting that a proteinaceous factor distinct from type I collagen might be responsible for the PGP-inducing activity of PIC-fraction . Although the PIC-fraction increased the PGP expression in other mouse brain capillary endothelial cells, the PIC-fraction did not increase PGP expression in mouse aortic endothelial cells and KB carcinoma cell lines expressing various amounts of PGP . These observations suggest that PGP expression in brain capillary endothelium is specifically regulated by a tissue-specific factor in the brain matrix. Antimicrob Agents Chemother, 1994 Oct, 38(10), 2492 - 4 Loss of function mutation in the yeast multiple drug resistance gene PDR5 causes a reduction in chloramphenicol efflux; Leonard PJ et al.; The yeast (Saccharomyces cerevisiae) PDR5 gene product encodes a 160-kDa protein related to the large ABC family of transporters, including the human MDR1 multidrug resistance p-glycoprotein . Loss of function mutations in PDR5 result in chloramphenicol hypersensitivity . A pdr5::Tn5 loss of function mutant exhibits a markedly impaired efflux of chloramphenicol compared with that of an isogenic PDR5 (wild-type) control. Antimicrob Agents Chemother, 1994 Oct, 38(10), 2380 - 6 Characterization of rifampin-resistance in pathogenic mycobacteria; Williams DL et al.; The emergence of rifampin-resistant strains of pathogenic mycobacteria has threatened the usefulness of this drug in treating mycobacterial diseases . Critical to the treatment of individuals infected with resistant strains is the rapid identification of these strains directly from clinical specimens . It has been shown that resistance to rifampin in Mycobacterium tuberculosis and Mycobacterium leprae apparently involves mutations in the rpoB gene encoding the beta-subunit of the RNA polymerases of these species . DNA sequences were obtained from a 305-bp fragment of the rpoB gene from 110 rifampin-resistant and 10 rifampin-susceptible strains of M . tuberculosis from diverse geographical regions throughout the world . In 102 of 110 rifampin-resistant strains 16 mutations affecting 13 amino acids were observed . No mutations were observed in rifampin-susceptible strains . No association was found between particular mutations in the rpoB gene and drug susceptibility patterns of multidrug-resistant M . tuberculosis strains . Drug-resistant M . tuberculosis strains from the same outbreak and exhibiting the same IS6110 DNA fingerprint and drug susceptibility pattern contained the same mutation in the rpoB gene . However, mutations are not correlated with IS6110 profiling outside of epidemics . The evolution of rifampin resistance as a consequence of mutations in the rpoB gene was documented in a patient who developed rifampin resistance during the course of treatment . Rifampin-resistant strains of M . leprae, Mycobacterium avium, and Mycobacterium africanum contained mutations in the rpoB gene similar to that documented for M . tuberculosis . This information served as the basis for developing a rapid DNA diagnostic assay (PCR-heteroduplex formation) for the detection of rifampin susceptibility of M . tuberculosis. Ann Oncol, 1994 Oct, 5(8), 733 - 9 Biochemical modulation of 'classical' multidrug resistance by BIBW22BS, a potent derivative of dipyridamole; Jansen WJ et al.; BACKGROUND: Modulators of the 'classical' multidrug resistance (mdr) phenotype have low efficacy in patients with solid tumors . We analyzed BIBW22BS, 4-{N-(2-hydroxy-2-met- hyl-propyl)-ethanolamino}-2,7-bis(cis-2,6-dimethyl-morpho- lino)-6-phenylpteridine, a derivative of dipyridamole, for its higher potential to modulate mdr . MATERIALS AND METHODS: Four human malignant cell lines: BRO, A2780, GLC4, SW1573, the Pgp-positive sublines: BRO/mdr1.1, 2780AD and the non-Pgp sublines: GLC4/ADR, SW1573/2R120 were used in vitro to investigate BIBW22BS as a modulator of the antiproliferative effects of vincristine and doxorubicin and to compare the potency of BIBW22BS with that of dipyridamole, verapamil, bepridil and flunarizine . BRO/mdr1.1 s.c . well-established xenografts in nude mice were used to study the modulating properties of BIBW22BS 50 mg/kg i.v . followed after one h by vincristine 1 mg/kg i.p . or doxorubicin 8 mg/kg i.p . weekly x 2 . RESULTS: BIBW22BS was 20- to 100-fold more potent than dipyridamole in the reversal of resistance in the Pgp-positive sublines . Reversal of resistance was obtained in a dose-dependent manner and was complete at concentrations of 0.5-2.5 microM . At non-toxic, equimolar concentrations of 1.0 microM BIBW22BS showed higher modulating potency than the calcium-channel blockers . BIBW22BS did not affect resistance in the non-Pgp sublines . BRO/mdr1.1 s.c . xenografts have stable multidrug-resistance characteristics upon serial transplantation . BIBW22BS, vincristine, or doxorubicin as single agents were not effective in vivo, while the addition of BIBW22BS could significantly reduce the tumor growth expressed as the T/C% of vincristine from 109% to 48% and that of doxorubicin from 55% to 32% . However, reversal of vincristine resistance in BRO/mdr1.1 xenografts was not complete when compared to the efficacy of vincristine in BRO xenografts . CONCLUSION: The results encourage the further preclinical development of BIBW22BS as a modulator of 'classical' multidrug resistance in cancer patients. Minerva Pediatr, 1994 Oct, 46(10), 463 - 70 {Use of cyclosporin and verapamil in association with chemotherapy in the treatment of pediatric patients with advanced-stage neoplasms . A pilot study}; Miniero R et al.; Multidrug resistance represents one of the most important factors that may lead to a therapeutic failure in some patients affected by malignancies . One of the best known mechanisms is linked to the genic amplification or the overproduction of a membrane glycoprotein, GP170, that is the product of the gene MDR1 . The existence of drugs (calcium blockers, cyclosporine, tamoxifen, reserpine, quinidine) able to bind themselves to gp170 and to paralyze its activity in vitro is well known . We studied 20 pediatric patients (median age 9 years) affected by acute lymphoblastic leukemia (ALL), osteosarcoma, neuroblastoma and medulloblastoma, in advanced stage of disease . We employed in all cases the association of cytostatics with verapamil (50-70 mg/m2 i.v.) and cyclosporine (5-8 mg/kg i.v.) with different infusion schedules . In leukemias we administered vincristine (1.5 mg/m2), and daunomycin (40 mg/m2), in solid tumors VP16 (150 mg/m2) and adriamycin (60 mg/m2) . Seventy-two therapeutic courses were performed: 39 in ALL, 16 in osteosarcoma, 16 in neuroblastoma and 1 in medulloblastoma . On the whole 5 complete remissions were achieved in ALL patients and 1 in an osteosarcoma patient . We did not observe a significant myelosuppression during treatment, therefore few infectious complications occurred; furthermore electrocardiographic changes have been mild and promptly resolved after temporary discontinuation of verapamil infusion . Our data suggest a synergy of verapamil and cyclosporine in the inhibition of multidrug resistance induced by gp170, without the occurrence of heavy toxicity . The results obtained in ALL patients are encouraging., especially in view of a possible subsequent bone marrow transplantation, while in solid tumors they are not as satisfying. Br J Haematol, 1994 Oct, 88(2), 348 - 56 High expression of the multidrug resistance-associated protein (MRP) in chronic and prolymphocytic leukaemia; Burger H et al.; The expression of the multidrug resistance-associated protein (MRP), a new glycoprotein involved in drug resistance, was investigated in tumour samples from 80 patients with chronic B-cell malignancies by a quantitative RNase protection assay . In B-cell chronic lymphocytic leukaemia (B-CLL) (n = 32), either treated (n = 18) or untreated (n = 14), a high percentage of patients (20/32: 63%) had relatively high expression levels of the MRP gene (25U or more) . In addition, hyperexpression of the MRP gene was demonstrated in 4/10 (40%) untreated patients with B-cell prolymphocytic leukaemia (B-PLL) . In contrast, low MRP mRNA expression levels were detected in hairy cell leukaemia (n = 7), non-Hodgkin's lymphoma (n = 13) and multiple myeloma (n = 18) . Statistical analysis of MRP expression in untreated CLL (mean +/- SD 29.2 +/- 18.5 U) versus treated CLL (mean +/- SD 26.7 +/- 13.7 U) did not show significant differences in MRP expression between the two groups . Southern blot analysis did not reveal amplification of the MRP gene in the leukaemia samples with elevated MRP mRNA levels . We conclude that B-PLL and B-CLL frequently display high MRP expression and that this hyperexpression is probably due to transcriptional activation and/or increased mRNA stability. Br J Haematol, 1994 Oct, 88(2), 318 - 24 Retrovirus-mediated transfer of the multidrug resistance gene into human haemopoietic progenitor cells; Bertolini F et al.; We report the utilization of cord blood (CB) or bone marrow (BM) derived low density or purified CD34+ cells as a target for human multidrug resistance (MDR1) gene transfer . Cells were cocultivated for 48 h with an irradiated MDR1 retroviral producer line . Since some degree of MDR1 gene expression has been reported to occur in haemopoietic progenitor cells and in peripheral blood cells, efficiency of MDR1 gene transfer was assessed by: (1) Drug selection and culture in presence of 50 ng/ml doxorubicin, 10 ng/ml colchicine and 0.85 micrograms/ml taxol . In uninfected control, 1-2% of CFU-GM and CFU-GEMM were found to be drug-resistant, while 14-31% of original clonogenic activity was found after 2 weeks of culture of transduced cells . Efficiency of MDR1 transfer was significantly enhanced by prestimulation with cytokines, and found to be significantly superior in CB-derived compared to BM-derived progenitors . (2) Analysis of MDR1 gene expression by evaluating MDR1 mRNA through polymerase chain reaction . MDR1 expression was very low in cultures of uninfected controls, whereas, after drug selection, MDR1 mRNA levels in transduced cells was as high as in the MDR1 retroviral producer line (positive controls) . (3) Flow cytometric analysis of the expression of CD34 and P-glycoprotein, the product of the MDR1 gene . After MDR1 transduction and 2 weeks of culture, membrane expression of P-glycoprotein was found on 17-25% of viable CD34+ cells . (4) Cytochemical localization by APAAP staining of P-glycoprotein . No specific localization was found in untransduced controls, whereas transduced and cultured CB-cells expressed P-glycoprotein on plasma and nuclei membrane . In conclusion, MDR1 gene transfer into CB- and BM-derived progenitor cells seems a feasible and attractive approach to generate a drug-resistant haemopoiesis. Bull Cancer, 1994 Oct, 81(10), 894 - 6 {Modulation of adriamycin cytotoxicity on K 562 and K562adri cells by interferon alpha and/or all-trans-retinoic acid}; Dufour P et al.; Multidrug Resistant (MDR) plays a major role in chemoresistance . Alpha Interferon (IFN) and all trans retinoic acid (ATRA) have antiproliferative effect and IFN regulates several genes, some of them implicated in the regulation of MDR gene expression . We have studied the modulations of adriamycin cytotoxicity by IFN and/or ATRA on K 562 (MDR-) and resistant to adriamycin K 562 adri (MDR+) cell lines . We observed an important increase of adriamycin cytotoxicity on both K 562 and K 562 adri by low dose of IFN and ATRA . Studies of MDR gene expression shows an increase in K 562 adri after exposure to IFN or ATRA . So the observed effect is not due to a down regulation of MDR gene expression but probably to the own antiproliferative effect of IFN and ATRA in combination with the cytotoxicity of adriamycin. Bull Cancer, 1994 Oct, 81(10), 891 - 3 {Characterization of the mechanism of cross-resistance to vinca alkaloids and taxoids in the human J82 bladder tumor cell line}; Debal V et al.; A phenotype of resistance to the new vinca alkaloid Navelbine was induced in the J82 human bladder carcinoma cells . The resistance factor of the resistant cell line (J82-NVB) to Navelbine was 17 . The resistance phenotype of these cells is not a multidrug-resistance (MDR) phenotype . J82-NVB cells lack overexpression of P-glycoprotein and cross-resistance to MDR drugs like doxorubicin, epipodophyllotoxins or colchicine . Navelbine efflux was similar in sensitive and resistant cells, and resistance could not be explained by a difference of drug accumulation in these two cell lines . The cells were cross-resistant to vinca alkaloids and taxoids whose targets are microtubules . Immunofluorescence study of microtubules showed that depolymerization occured for the same Navelbine concentration in sensitive and resistant cells . This concentration induced growth inhibition in sensitive but not in resistant cells . Moreover, depolymerization induced by Navelbine treatment was reversible, after drug removal, in resistant cells only . This study suggests that J82-NVB cell resistance mechanism involves alterations of microtubule dynamics, allowing recovery of microtubules functions after treatment. Immunobiology, 1994 Oct, 191(4-5), 337 - 43 Epidemiology of tuberculosis: the impact of HIV and multidrug-resistant strains; Crawford JT; The recent reemergence of tuberculosis in the United States and other developed countries has been attributed to a number of factors including a decreased emphasis on tuberculosis control and immigration . Perhaps the most significant factor is the association of tuberculosis and HIV/AIDS . Infection with HIV greatly increases susceptibility to infection and increases the risk of developing active disease . In addition, progression of tuberculosis can be very rapid in patients with greatly reduced immune function . The increasing incidence of drug resistance is also contributing to the difficulty in controlling tuberculosis . Multidrug-resistance not only adversely affects the patient but contributes to prolonged infectiousness. Zhonghua Nei Ke Za Zhi, 1994 Oct, 33(10), 666 - 8 {Detection of P-glycoprotein expression in patients with acute leukaemia and clinical significance}; Feng K et al.; Anti-P-glycoprotein monoclonal antibody JSB-1 and alkaline phosphatase-anti-alkaline phosphatase (APAAP) immunocytochemical staining technique were used to study the relation between P-glycoprotein expression and clinical multidrug resistance (MDR) in 42 patients with acute leukaemia (23 ALL and 19 ANLL) . 10 of 17 patients who were diagnosed as refractory or relapsed acute leukaemia were positive with P-glycoprotein expression, while only 3 of 14 newly diagnosed and 1 of 11 who were in complete remission were positive . The preliminary results indicated that there was a close association between the P-glycoprotein expression and the clinical resistance to chemotherapy in some patients. Cancer Lett, 1994 Sep 30, 85(1), 59 - 63 The riminophenazine agents clofazimine and B669 reverse acquired multidrug resistance in a human lung cancer cell line; Van Rensburg CE et al.; The potential of the riminophenazine agents clofazimine and B669, at therapeutically relevant concentrations, to reverse P-glycoprotein-mediated multidrug-resistance (MDR) in a human lung cancer cell line (H69/LX4) has been investigated in vitro . Cyclosporin A, a well-documented MDR-modifying agent, was included for comparison . Clofazimine, B669 and cyclosporin A at minimally cytotoxic concentrations of 1, 0.5 and 5 micrograms/ml, respectively, were equally effective in restoring sensitivity to vinblastine, doxorubicin, daunorubicin and mitomycin C in the H69/LX4 cell line . All three chemosensitizing agents also increased the accumulation of {14C}vinblastine by H69/LX4 cells . Riminophenazines, which are relatively non-toxic, non-carcinogenic and non-myelosuppressive agents, are promising contenders for evaluation in experimental and clinical oncology as modulators of acquired MDR. J Biol Chem, 1994 Sep 16, 269(37), 22983 - 9 Overexpression and purification of the carboxyl-terminal nucleotide-binding domain from mouse P-glycoprotein . Strategic location of a tryptophan residue; Baubichon-Cortay H et al.; The cDNA encoding the C-terminal nucleotide-binding domain (NBD2) from mouse P-glycoprotein involved in multidrug resistance was obtained from adrenal cell mRNA and amplified by reverse transcriptase polymerase chain reaction . NBD2 was highly overexpressed in Escherichia coli in fusion with glutathione S-transferase and could be purified after efficient thrombin cleavage . Both fused and purified NBD2 bound TNP (2',3'-O-(2,4,6-trinitrophenyl))- derivatives of nucleotides with high affinity . TNP-ATP or TNP-ADP binding at micromolar concentrations produced a characteristic blue-shifted enhancement of extrinsic fluorescence and was specifically prevented or chased by ATP or ADP at millimolar concentrations . A similar affinity binding was monitored by quenching of intrinsic fluorescence . The spectrum of fusion protein, containing 5 tryptophan residues, was maximally quenched at 328 nm upon interaction with TNP-nucleotides . TNP-GTP exhibited a lower affinity than TNP-ATP but produced a higher maximal quenching (44% instead of 28%) . The intrinsic fluorescence of purified NBD2, containing a single tryptophan residue, exhibited a narrow spectrum with a maximum at 328 nm characteristic of a hydrophobic tryptophan environment . A high quenching was observed upon nucleotide interaction with similar affinity . The results put forward a functional role for the tryptophan-containing sequence of P-glycoprotein NBD2 that was not detected up to now. Cancer Res, 1994 Sep 15, 54(18), 4958 - 66 Differences between drug-sensitive and -resistant human leukemic CEM cells in c-jun expression, AP-1 DNA-binding activity, and formation of Jun/Fos family dimers, and their association with internucleosomal DNA ladders after treatment with VM-26; Kim R et al.; Although the DNA topoisomerases are critical intracellular targets of a number of clinically important anticancer drugs, the mechanism(s) by which inhibition of these enzymes causes cell death are poorly understood . We found that treatment of human leukemic lymphoblasts (CCRF-CEM) with teniposide (VM-26), under conditions that stabilize DNA-topoisomerase II complexes, caused the formation of internucleosomal DNA ladders . However, it appeared unlikely that the VM-26-stabilized DNA-topoisomerase II-cleavable complexes directly produce these internucleosomal DNA ladders, since similar nucleosomal DNA ladders were observed following either continuous or a short (1 h) exposure of cells to VM-26 . Under continuous exposure to VM-26, the internucleosomal DNA ladders were associated with the transient induction of c-jun mRNA in a dose-dependent fashion, reaching maximum expression at 6 h after treatment with VM-26 and being down-regulated to basal levels by 12 h . The induction of c-jun mRNA by VM-26 apparently preceded DNA ladder formation . However, in CEM sublines selected for resistance to VM-26 (CEM/VM-1 and CEM/VM-1-5; approximately 50- and 140-fold resistant, respectively) and which display the phenotype of multidrug resistance associated with altered DNA topoisomerase II (at-MDR), we found that the induction of c-jun mRNA by VM-26 and subsequent DNA ladder formation were progressively attenuated in proportion to the resistance of the cells, apparently due in part to decreased stabilization of DNA-topoisomerase II-cleavable complexes . Further, the attenuated induction of c-jun in the at-MDR cells was found to be associated with a decreased rate of c-jun transcription and an increase in the instability of its mRNA following VM-26 treatment . The attenuation of c-jun mRNA induction was also reflected in decreased production of c-Jun protein in the at-MDR cells . Of interest was the fact that no significant induction of c-fos mRNA by VM-26 was observed in either CEM or at-MDR cells . Furthermore, the induction of c-jun was related to the activation of AP-1 DNA-binding activity in a time- and dose-dependent manner in CEM cells, whereas the activation of AP-1 binding was attenuated in at-MDR cells in proportion to their resistance to VM-26 . Using Jun and Fos family member antibody inhibition experiments in gel-mobility shift assays, we found that AP-1-binding activity appeared to be preferentially mediated by c-Jun/Fra-1 heterodimers in both CEM and at-MDR cells.(ABSTRACT TRUNCATED AT 400 WORDS) Biochem Pharmacol, 1994 Sep 15, 48(6), 1129 - 36 Competitive inhibition by genistein and ATP dependence of daunorubicin transport in intact MRP overexpressing human small cell lung cancer cells; Versantvoort CH et al.; In several multidrug resistant tumor cell lines without overexpression of P-glycoprotein (non-Pgp MDR), a decreased accumulation of drugs has been shown to contribute to resistance . We have recently reported that daunorubicin (DNR) accumulation was decreased in the multidrug resistance-associated protein overexpressing GLC4/ADR non-Pgp MDR small cell lung cancer cell line due to an enhanced energy-dependent efflux which could be inhibited by the isoflavonoid genistein . The purpose of this work was 2-fold: (i) to investigate the mechanism by which genistein inhibits the DNR efflux in the GLC4/ADR cells; and (ii) to characterize the dependence of DNR transport on ATP concentration in intact GLC4/ADR cells . The active transport of DNR in GLC4/ADR cells appeared to be a saturable process with an apparent Km of DNR of 1.4 +/- 0.4 microM . Genistein increased the apparent Km value of DNR, suggesting that this agent is a competitive inhibitor of DNR transport . These data provide additional evidence that energy-dependent DNR transport in GLC4/ADR cells is a protein-mediated process . In addition, genistein decreased cellular ATP concentration in a dose-dependent manner in sensitive as well as in resistant cells . Marked inhibition of DNR transport activity in intact GLC4/ADR cells was found when cellular ATP concentration was decreased below 2 mM by sodium azide or 2-deoxy-D-glucose . Thus, since DNR transport in intact GLC4/ADR is already inhibited at modest cellular ATP depletion, a limitation in ATP supply might open ways to make MDR cells more susceptible to drug toxicity. Biochem J, 1994 Sep 15, 302 ( Pt 3), 649 - 54 Phorbol ester selectively stimulates the phospholipase D-mediated hydrolysis of phosphatidylethanolamine in multidrug-resistant MCF-7 human breast carcinoma cells; Kiss Z et al.; The phospholipase D (PLD)-mediated synthesis of phosphatidylethanol (PtdEtOH) and the hydrolysis of phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho) were examined in drug-sensitive and multidrug-resistant lines of MCF-7 human breast carcinoma cells . In drug-sensitive (MCF-7/WT) cells, the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) failed to enhance either the synthesis of PtdEtOH or the hydrolysis of either phospholipid . In the drug-resistant (MCF-7/MDR) cells, 100 nM PMA greatly enhanced both the synthesis of PtdEtOH (approximately 21-fold) and the hydrolysis of PtdEtn (approximately 29-fold), but had no effect on the hydrolysis of PtdCho . The PLD activators sphingosine and H2O2 were found to elicit only a slight (1.28-1.4-fold) stimulatory effect on PtdCho hydrolysis in both the MCF-7/WT and MCF-7/MDR cell types, and had only a small effect on PtdEtn hydrolysis in the MCF-7/WT cells as well . However, these agents significantly (approximately 2.6-3.5-fold) stimulated PtdEtn hydrolysis in the MCF-7/MDR cells . These data indicate that MCF-7/MDR cells contain a PtdEtn-specific PLD activity which can be selectively stimulated by PMA, sphingosine and H2O2. Int J Cancer, 1994 Sep 15, 58(6), 860 - 4 Possible involvement of multidrug-resistance-associated protein (MRP) gene expression in spontaneous drug resistance to vincristine, etoposide and adriamycin in human glioma cells; Abe T et al.; The multidrug-resistance phenotype in human tumors is partly associated with over-expression of the 170 kDa-P-glycoprotein encoded by the multidrug-resistance-1 (MDR1) gene . Another related, but non-P-glycoprotein, multidrug-resistance-associated protein (MRP) gene encodes a 190 kDa-membrane ATP-binding protein . Glioblastoma multiforme is a highly malignant primary neoplasm of the central nervous system which is refractory to anti-cancer chemotherapy, but the mechanism underlying this drug resistance is unknown . Out of glioma cell lines, 2, namely IN500 and T98G, which had elevated MRP mRNA levels, showed the highest resistance to multiple anti-cancer agents such as etoposide, vincristine and adriamycin, and decreased intracellular accumulation of etoposide . In the remaining 5 cell lines, various degrees of sensitivity to adriamycin and etoposide appeared to correlate with their respective MRP mRNA levels . Our study proposes that MRP may be involved in spontaneous multidrug resistance in human gliomas. Biochem Biophys Res Commun, 1994 Sep 15, 203(2), 1210 - 6 Chinese hamster ovary cells resistant to okadaic acid express a multidrug resistant phenotype; Tohda H et al.; Two Chinese hamster ovary cell clones resistant to okadaic acid (OA) were isolated . The OA-resistance was associated with resistance to colchicine, Vinca alkaloids and inhibitors of DNA topoisomerase (topo) II . Drug accumulation assays showed that the intracellular levels of OA, vinblastine and vincristine, but not the topo II inhibitor etoposide, were significantly lowered in the OA-resistant mutants than in the parental cells . These results, together with the finding of an increased level of P-glycoprotein (P-gp) in the mutant cells, indicate that the resistances to OA, Vinca alkaloids and colchicine are due to a P-gp-mediated mechanism . Resistance to topo II inhibitors, however, was associated with reduced activity of topo II . Thus, at least two events, overexpression of P-gp and reduction of topo II activity, occurred in a single OA-resistant cell line, contributing to expression of the MDR phenotype. Cancer Lett, 1994 Sep 15, 84(2), 163 - 72 Glutathione S-transferases and P-glycoprotein in normal rat hepatocytes and hepatoma cells: analysis using flow cytometry; Mehta R et al.; Using indirect immunofluorescence with fluorescein isothiocyanate-conjugated antibodies, in combination with flow cytometry (FCM), we have developed a technique to detect the alpha, mu and pi isozymes of GST in cell suspensions from normal rat liver, and in H4IIE cells, a rat hepatoma cell line . Cell suspensions fixed in 1% paraformaldehyde were observed to require cell membrane permeation with lysolecithin to allow access and binding of antibodies to immunoreactive proteins within the cytoplasm . FCM analysis indicated normal rat hepatocytes to be positive for GST alpha and mu, but not GST pi, and the H4IIE cells to be positive for all three GST isozymes . Further analysis by FCM for the expression of P-glycoprotein (mdr), a membrane-associated protein product of the multidrug resistance gene, showed an association between the presence of GST pi and mdr in the two cell types . Thus, mdr was detected in significant amounts in H4IIE cells, but not in rat hepatocytes . The method described here has potential applications in screening, sorting and further characterisation for GST pi-positive hepatocytes for mechanistic studies during s