Cancer Res, 1991 Oct 1, 51(19), 5417 - 24 Chemotherapy and chemosensitization of transgenic mice which express the human multidrug resistance gene in bone marrow: efficacy, potency, and toxicity; Mickisch GH et al.; A common form of multidrug resistance in human cancer results from expression of the MDR1 gene which encodes a plasma membrane energy-dependent multidrug efflux pump . We have engineered transgenic mice which express this multidrug transporter in their bone marrow cells and demonstrated that peripheral WBC of these animals provide a rapid and reliable system for assessing the bioactivity of agents that reverse multidrug resistance . Immunocytochemical analysis of bone marrow smears suggests that the activation of the MDR1 transgene has probably occurred at a very early stage of bone marrow differentiation since most bone marrow cells express the transporter . Expression of this transgene in bone marrow produces about 10-fold resistance to leukopenia induced by taxol compared to normal bone marrow . Chemosensitization of MDR1 mice to daunomycin and taxol, measured by a fall in WBC, is detectable at a dose as low as 0.01 mg/kg R-verapamil . A dose of 0.5 mg/kg R-verapamil reduces the WBC by nearly 50% . Chemosensitization of MDR-transgenic mice with 5 mg/kg R-verapamil, which is highly effective in reversing MDR and readily tolerated by mice, necessitates a reduction of the maximum tolerated dose of most chemotherapeutic agents by only 20% . In addition, detailed histopathological examination shows that treatment of mice with chemotherapeutic drugs and R-verapamil does not change the organ-related toxicity pattern but only moderately accentuates inherent toxic side effects of the chemotherapeutic agents . We conclude that MDR1-transgenic mice represent a valid model for evaluating efficacy, potency, and toxicity associated with chemotherapy and chemosensitization of multidrug-resistant cells in animals. Br J Cancer, 1991 Oct, 64(4), 705 - 9 Modulation of vinblastine sensitivity by dipyridamole in multidrug resistant fibrosarcoma cells lacking mdr1 expression; Shalinsky DR et al.; We examined the ability of dipyridamole (DPM) to act synergistically with vinblastine (VBL) in HT1080 fibrosarcoma cells and a drug-resistant variant, HT1080/DR4, which lacks mdr1 expression, in order to determine whether DPM requires P-glycoprotein to modulate drug sensitivity . Median effect analysis of clonogenic assay was used to produce the combination index (CI50, values less than 1 indicate synergy) . DPM was mildly synergistic with VBL producing a CI50 of 0.83 +/- 0.13 for HT1080 cells and 0.80 +/- 0.16 for HT1080/DR4 cells . HT1080 and HT1080/DR4 cells accumulated 6.7 +/- 0.7 and 5.6 +/- 0.9 pmol 3H-VBL mg cells-1 at steady state (Css) and 20 microM DPM elevated the Css by 1.8 and 2.9-fold, respectively . In comparison, the CI50 was 1.1 +/- 0.2 in parental KB-3-1 cells and 0.1 +/- 0.1 in mdr1-expressing KB-GRC1 cells . The KB-3-1 and KB-GRC1 cells had a Css of 3.8 +/- 0.8 and 0.7 +/- 0.2 pmol 3H-VBL mg cells-1, respectively, and DPM elevated the Css by 9.2-fold in KB-GRC1 cells . These studies demonstrate that DPM can produce synergy independently of mdr1 expression but that much greater levels of synergy are achievable in mdr1-expressing tumour cells. J Urol, 1991 Oct, 146(4), 982 - 6; discussion 986-7 Flow cytometric determination of the multidrug resistant phenotype in transitional cell cancer of the bladder: implications and applications; Benson MC et al.; We detail our experience with a monoclonal antibody to detect the cell surface P-glycoprotein product of the multidrug resistance gene (MDR-1) in the human bladder . A total of 32 patients had 44 different specimens analyzed . The samples consisted of 8 normal bladders, 21 transitional cell carcinomas, 1 mucinous adenocarcinoma, 3 P-0 bladder wall specimens and 10 nonmalignant urothelial samples from cystectomies . P-glycoprotein was not detected in the normal adult or pediatric bladder . Bladder specimens from 3 children with a neurogenic bladder revealed enhanced expression (21%, 14% and 4% positivity) . Transitional cell carcinoma usually demonstrates low expression at diagnosis (less than 6%), although 3 patients had enhanced initial expression (11%, 12% and 31%) . Three patients treated with chemotherapy demonstrated 56%, 76% and 50% expression of MDR-1 . Nonmalignant tissue from cystectomy specimens had low expression of MDR-1 . The specificity of this system was confirmed with human bladder cell lines . The ability of flow cytometry to detect and quantify the expression of MDR-1 may allow for the early detection of chemotherapy resistance in patients with transitional cell carcinoma treated with systemic and intravesical therapy. Exp Cell Res, 1991 Oct, 196(2), 323 - 9 Laser scanning and confocal microscopy of daunorubicin, doxorubicin, and rhodamine 123 in multidrug-resistant cells; Weaver JL et al.; The multidrug-resistant gene (MDR1) encodes an energy-dependent drug efflux pump (P-glycoprotein) for many anti-cancer drugs . We have studied the intracellular distribution of rhodamine 123 (R123), daunorubicin (DN), and doxorubicin (DOX) in cells expressing a human MDR1 gene . The distribution of these fluorescent drugs was measured by laser scanning microscopy and confocal microscopy . We devised a new method for analysis of fluorescence line scan data to determine the intracellular distribution of fluorescent probes . This method and confocal microscopy showed that R123, DN, and DOX are localized to both plasma membrane and intracellular compartments in multidrug-resistant cells . When the cells are treated with verapamil, an inhibitor of the multidrug transporter, the amount of DOX, DN, and R123 associated with the cell rises . After inhibition, the relative distribution of DOX and DN between the cell surface and intracellular structures does not change dramatically . However, R123 tends to relocalize to intracellular sites from predominantly plasma membrane sites, indicating that this dye behaves differently than the anti-cancer drugs . These results show the subcellular distributions of R123, DN, and DOX in plasma membrane, cytoplasm, and intracellular membrane systems, but do not allow definitive distinctions among existing models of how P-glycoprotein affects the distribution of drugs. Cancer Res, 1991 Oct 1, 51(19), 5093 - 9 Antagonistic effect of aclarubicin on daunorubicin-induced cytotoxicity in human small cell lung cancer cells: relationship to DNA integrity and topoisomerase II; Jensen PB et al.; The effect of combinations of the anthracyclines aclarubicin and daunorubicin was investigated in a clonogenic assay using the human small cell lung cancer cell line OC-NYH and a multidrug-resistant (MDR) murine subline of Ehrlich ascites tumor (EHR2/DNR+) . It was found that the cytotoxicity of daunorubicin in OC-NYH cells was antagonized by simultaneous exposure to nontoxic concentrations of aclarubicin . Coordinately, aclarubicin inhibited the formation of daunorubicin-induced protein-concealed DNA single-strand breaks and DNA-protein cross-links in OC-NYH cells when assayed by the alkaline elution technique . Aclarubicin had no influence on the accumulation of daunorubicin in these cells . In contrast, the accumulation of daunorubicin in EHR2/DNR+ cells was enhanced by more than 300% when the cells were simultaneously incubated with the MDR modulator verapamil, aclarubicin, or the two agents combined . Yet the cytotoxicity of daunorubicin was potentiated significantly only by verapamil . The increased cytotoxicity of daunorubicin in the presence of verapamil was completely antagonized when aclarubicin was used together with the MDR modulator . Finally, the effect of daunorubicin on the DNA cleavage activity of purified topoisomerase II in the presence and absence of aclarubicin was examined . It was found that daunorubicin stimulated DNA cleavage by topoisomerase II at specific DNA sites . The addition of aclarubicin completely inhibited the daunorubicin-induced stimulation of DNA cleavage . Taken together, these data indicate that aclarubicin-mediated inhibition of daunorubicin-induced cytotoxicity is due mainly to a drug interaction with the nuclear enzyme topoisomerase II . This antagonism at the nuclear level explains why aclarubicin is a poor modulator of daunorubicin resistance even though aclarubicin is able to increase the intracellular accumulation of daunorubicin in a MDR cell line. Cancer Res, 1991 Sep 15, 51(18), 4955 - 63 Subcellular distribution of daunorubicin in P-glycoprotein-positive and -negative drug-resistant cell lines using laser-assisted confocal microscopy; Gervasoni JE Jr et al.; Four well defined multidrug-resistant cell lines and their drug-sensitive counterparts were examined for intracellular distribution of daunorubicin (DNR) by laser-assisted confocal fluorescence microscopy: P-glycoprotein-negative HL-60/AR cells, and P-glycoprotein-positive P388/ADR, KBV-1, and MCF-7/ADR cells . Both drug sensitive cell lines (HL-60/S, P388/S, KB3-1, and MCF-7/S) and drug-resistant cell lines (HL-60/AR, P388/ADR, KBV-1, and MCF-7/ADR) exposed to DNR showed a similar rapid distribution of drug from the plasma membrane to the perinuclear region within the first 2 min . From 2-10 min, the drug sensitive HL-60/S, P388/S, and MCF-7/S cells redistributed drug to the nucleus and to the cytoplasm in a diffuse pattern . In contrast, drug-resistant HL-60/AR, P388/ADR, and MCF-7/ADR redistributed DNR from the perinuclear region into vesicles distinct from nuclear structures, thereby assuming a "punctate" pattern . This latter redistribution could be inhibited by glucose deprivation (indicating energy dependence), or by lowering the temperature of the medium below 18 degrees C . The differences in distribution between sensitive and resistant cells did not appear to be a function of intracellular DNR content, nor the result of drug cytotoxicity . Drug-sensitive KB3-1 and -resistant KBV-1 cells did not fully follow this pattern in that they demonstrated an intracellular DNR distribution intermediate between HL-60/S and HL-60/AR cells with both "punctate" and nuclear/cytoplasmic uptake sometimes in the same cell . These data indicate that the intracellular distribution of DNR is an important determinant of drug resistance regardless of the overexpression of P-glycoprotein . The intracellular movement of drug requires the presence of glucose and a temperature above 18 degrees C, implicating energy-dependent processes and vesicle fusion in the distribution process . This intracellular transport of DNR away from the nucleus in multidrug-resistant cells may protect putative cell targets such as DNA against drug toxicity. J Biol Chem, 1991 Sep 25, 266(27), 18224 - 32 Study of membrane orientation and glycosylated extracellular loops of mouse P-glycoprotein by in vitro translation; Zhang JT et al.; Increased expression of P-glycoprotein (Pgp) has been demonstrated to cause multidrug resistance (MDR) in vitro, and it may be responsible for chemotherapy failure in a number of human cancers . Pgp is a plasma membrane protein thought to function as an energy-dependent drug transporter . From its deduced protein sequence the topology of Pgp was proposed to contain 12 transmembrane domains with six extracellular loops and two cytoplasmic ATP-binding sites . To investigate further the membrane orientation of Pgp, we have expressed a full length cDNA of mouse mdr1, as well as its truncated forms, in a cell-free system supplemented with dog pancreatic microsomal membranes (RM) . We determined which domains of the in vitro-synthesized Pgp had transversed the RM membranes by analyzing their resistance to protease digestion and their glycosylation state . To our surprise, this system revealed that a significant portion of in vitro-synthesized Pgp molecules has an additional glycosylated domain in the C-terminal half . Previously, only the first predicted extracellular loop near the N terminus had been thought to be glycosylated . Furthermore, we discovered that Pgp has at least two functional signal recognition particle/docking protein dependent signal sequences, one at the N-terminal half and the other at the C-terminal half . These findings suggest a new topological model for in vitro synthesized P-glycoprotein which may be relevant to its in vivo topology. Biochim Biophys Acta, 1991 Sep 23, 1097(2), 111 - 6 Etoposide-induced DNA damage in human tumor cells: requirement for cellular activating factors; Sinha BK et al.; Previous studies with the multidrug-resistant human HL60 cell line have shown a 3-4-fold decrease in VP-16 accumulation compared to the sensitive cell line, while the degree of resistance to VP-16 was 300-fold, indicating that other mechanisms of resistance are also operative . Since VP-16 has been shown to interfere with topoisomerase II activity, we have evaluated VP-16-dependent DNA strand break formation in the drug-sensitive and -resistant HL60 cells . Studies reported here show that the drug-resistant HL60 cells are extremely resistant to VP-16-dependent DNA cleavage compared to the sensitive cells . This decrease in DNA cleavage activity in the presence of VP-16 was, in part, related to a 2-3-fold decrease in both the amount and activity of topoisomerase II in the resistant cell line compared to the sensitive cells . Nuclei from the resistant cell line were markedly more resistant to VP-16-dependent DNA cleavage than the WT cell nuclei . Interestingly, WT nuclei were found to be relatively more resistant to VP-16-induced DNA cleavage than the intact WT cells . Addition of WT cytosolic proteins to WT nuclei, however, significantly stimulated VP-16-dependent DNA cleavage and slightly increased DNA cleavage in resistant cell nuclei . In contrast, cytosolic proteins from the resistant cells had no effect on DNA cleavage in nuclei isolated from either cell line . These observations indicate that a decrease in the amount and activity of topoisomerase II in resistant HL60 cells translates into a decrease in VP-16-dependent DNA breakage and contributes to the resistance to VP-16 . Furthermore, the cytosolic fraction from WT cells contains some factor, not present in the resistant cells, which is necessary for the maximal drug-induced DNA cleavage. J Natl Cancer Inst, 1991 Sep 18, 83(18), 1307 - 15 Effect of recombinant fibroblast interferon and recombinant immune interferon on growth and the antigenic phenotype of multidrug-resistant human glioblastoma multiforme cells; Reddy PG et al.; To study the effect of drug resistance on the response of stage IV astrocytomas to interferon, a human glioblastoma multiforme cell line, GBM-18, was transfected with an expression-vector plasmid containing a human multidrug resistance (MDR) gene (pHaMDR1/A), and clones surviving in colchicine were isolated . GBM-18 multidrug-resistant subclones displayed cross-resistance to other chemotherapeutic agents, including vincristine, doxorubicin, and dactinomycin . The multidrug-resistant phenotype was reversible when GBM-18 multidrug-resistant cells were cultured in colchicine and the calcium-channel blocker verapamil . The level of the MDR1 gene (also known as PGY1) message was increased in GBM-18 multidrug-resistant cells selected for increased resistance to colchicine, and this effect was not correlated with an amplification of the MDR1 gene . In both parental GBM-18 and GBM-18 multidrug-resistant cells, growth was suppressed to a greater degree when cultures were treated with the combination of fibroblast interferon (IFN-beta) and immune interferon (IFN-gamma) . Parental cells and multidrug-resistant subclones varied in their de novo and/or interferon-modulated expression of HLA class I and class II antigens, a high-molecular-weight melanoma-associated antigen, and intercellular adhesion molecule 1 (ICAM-1) . Of the antigens tested, ICAM-1 and HLA class I antigens were the most sensitive to enhanced expression induced by IFN-beta and IFN-gamma when used alone or in combination . The results of the present study indicate that multidrug-resistant human glioblastoma multiforme cells retain their increased sensitivity to the antiproliferative activity of the combination of IFN-beta plus IFN-gamma, and differences in antigenic phenotype are apparent in independent multidrug-resistant glioblastoma multiforme clones. Cancer Res, 1991 Sep 15, 51(18), 4898 - 902 Reversal of adriamycin resistance by recombinant alpha-interferon in multidrug-resistant human colon carcinoma LoVo-doxorubicin cells; Scala S et al.; Reversal of the drug resistance phenotype by the use of agents which induce cell differentiation offers an experimental approach to the study of chemoresistance . In numerous in vitro models, alpha-interferon (alpha-IFN) has been shown to induce phenotypical changes and to modulate the growth of cancer cells . The aim of the present study was to define the effect of alpha-IFN on the Adriamycin sensitivity of the human colon adenocarcinoma cell line, LoVo, and its Adriamycin-resistant variant, LoVo/DX . Pretreatment of LoVo/DX cells with 500 units/ml of alpha-IFN increased sensitivity to low doses of Adriamycin . Similar treatment conditions did not change the sensitivity of the parental cell line . Following treatment of the LoVo/DX cells with alpha-IFN plus 100 ng/ml Adriamycin for 1 h, 30% of the cells survived compared to 100% of untreated cells . This effect was not related to changes in cell cycle kinetics induced by alpha-IFN treatment and did not result from variations in the expression of P-glycoprotein at the cell surface, as assessed by flow cytometric analysis using monoclonal antibody MRK16 . Adriamycin accumulation was increased by alpha-IFN as assessed by spectrofluorometric analysis . Thus, the data suggest that in LoVo/DX cells, alpha-IFN increased Adriamycin cytotoxicity through modulation of the multidrug resistance phenotype. Biochem Pharmacol, 1991 Sep 12, 42(7), 1427 - 32 The role of protein kinase C and the phosphatidylinositol cycle in multidrug resistance in human ovarian cancer cells; Anderson L et al.; The present study aimed to investigate the role of protein kinase C (PKC), the phosphatidylinositol pathway (PI) and cytosolic calcium in multidrug resistance (MDR) in human ovarian carcinoma cells . Binding of the phorbol ester 13,14-dibutyrate (PDBu) was 3-fold higher in resistant A2780AD versus sensitive A2780 cells indicating increased PKC activity . However, when inositol phosphate production (IP) was measured in quiescent cells similar total IP release was seen in both lines suggesting no difference in the basal turnover of PI . Non-specific stimulation of the PI pathway was achieved with the calcium ionophore A23187 which increased IP production in a time- and dose-dependent fashion in both cell lines but was significantly less effective in A2780AD . The PI pathway was investigated further using the agonists aluminium fluoride, serum and bombesin but these agents failed to elicit a response . The effect of a wide range of Adriamycin concentrations on the PI cycle and cell growth was also studied . Intracellular calcium was measured with the fluorescent dye fura-2-pentaacetoxymethylester (Fura-2) . A23187 produced a rise in cytosolic calcium in A2780 and A2780AD but from a level 3-fold lower in the unstimulated resistant cell line . The dose responsiveness of this effect was greater but irreversible in A2780AD cells . Collectively these results imply that alterations in PI turnover appear not to be responsible for the differences in PDBu binding and calcium handling observed between A2780 and A2780AD and suggests only a minor role for the PI cycle in the maintenance of MDR in human ovarian cancer cell lines. J Biol Chem, 1991 Sep 5, 266(25), 16796 - 800 Azidopine noncompetitively interacts with vinblastine and cyclosporin A binding to P-glycoprotein in multidrug resistant cells; Tamai I et al.; It is believed that P-glycoprotein (P-gp) is an energy-dependent drug efflux pump responsible for decreased drug accumulation in multidrug resistant (MDR) cells . In this study, we investigated whether azidopine, a photoactive dihydropyridine calcium channel blocker, is transported by P-gp in MDR Chinese hamster lung cells, DC-3F/VCRd-5L, and whether its binding site(s) on P-gp are distinct from those of Vinca alkaloids and cyclosporins . The efflux of azidopine from MDR cells was energy-dependent and inhibited by the cytotoxic agent vinblastine (VBL) . Cyclosporin A (CsA), a modulator of MDR, also increased azidopine accumulation in MDR cells by decreasing the energy-dependent efflux of azidopine . P-gp in these cells was the only protein specifically bound to {3H}azidopine in photoaffinity experiments . The specific photoaffinity labeling of P-gp by {3H}azidopine was inhibited by CsA, SDZ 33-243, nonradioactive azidopine, and VBL with median concentrations (IC50) of 0.5, 0.62, 1.7, and 25 microM, respectively . The equilibrium binding of azidopine to plasma membranes of MDR variant DC-3F/VCRd-5L cells showed a single class of specific binding sites having a dissociation constant of 1.20 microM and a maximum binding capacity of 4.47 nmol/mg of protein . Kinetic analysis indicated that the inhibitory effect of VBL and CsA on azidopine binding to plasma membranes of MDR cells was noncompetitive, indicating that azidopine binds to P-gp at a binding site(s) different from the binding site(s) of these drugs. Br J Haematol, 1991 Sep, 79(1), 50 - 6 Analysis of multidrug resistance (MDR-1) gene expression in chronic lymphocytic leukaemia (CLL); Shustik C et al.; Multidrug resistance (MDR) in cultured human cells is caused by the overexpression of the MDR-1 gene . This gene codes for P-glycoprotein, a proposed ATP-dependent drug efflux pump, which reduces the net intracellular accumulation of a large group of chemotherapeutic agents in resistant cells . We have measured the level of expression of the human MDR-1 gene in a series of patients with chronic lymphocytic leukaemia (CLL) . Forty-eight patients included in the study were at different stages of disease and were either untreated or had been treated with alkylating agents or alkylating agents in combination with drugs of the MDR spectrum, and were tested over a period of 3 years . The level of MDR-1 expression was monitored by Northern blotting analysis using a specific cDNA hybridization probe and also after polymerase chain reaction (PCR) amplification of MDR-1 complementary DNA (cDNA) . Four of 28 previously untreated patients showed intrinsically high levels of MDR-1 mRNA while 5/19 treated patients had elevated MDR-1 expression . Elevated MDR-1 expression in treated patients was unrelated to the type of chemotherapy and was independent of previous exposure to drugs of the MDR spectrum . Intrinsic MDR-1 gene expression in positive patients did not appear to influence their response to chemotherapy with non-MDR drugs such as alkylating agents. Exp Cell Res, 1991 Sep, 196(1), 26 - 32 Restoration of daunomycin retention in multidrug-resistant P388 cells by submicromolar concentrations of SDZ PSC 833, a nonimmunosuppressive cyclosporin derivative; Boesch D et al.; Overexpression of P-glycoprotein may cause increased efflux of a variety of anticancer drugs (ACD) leading to multidrug resistance (MDR) of tumor cells . Two sublines of murine monocytic leukemia P388 cells were used, one parental (Par-P388) and one multidrug resistant (MDR-P388) . In cell growth inhibition assays in vitro, the Par-P388 cells showed a normal sensitivity to daunomycin (DAU) while the MDR-P388 cells were 200-fold resistant . In cellular fluorescence assays, DAU retention in MDR-P388 cells reached only 5% of the level achieved in Par-P388 cells . This cell line pair was used to compare the nonimmunosuppressive cyclosporin analog PSC 833 with several resistance-modifying agents (RMAs) for their in vitro chemosensitizing activity and for their restoration of DAU retention . PSC 833 sensitized the MDR-P388 cells 60- and 140-fold when used at 0.1 and 0.3 micrograms/ml (0.08 and 0.25 microM), respectively, a complete restoration of sensitivity being obtained at 1.0 micrograms/ml PSC 833 . Similarly as little as 0.1 micrograms/ml (0.08 microM) PSC 833 was sufficient to restore intracellular DAU retention to 60% of the level found in Par-P388 cells, a 3-fold higher concentration restoring virtually the whole DAU retention . For both these activities, PSC 833 was at least one order of magnitude more active than CsA, which was itself an order of magnitude stronger than verapamil, another RMA already used in clinic . Since PSC 833 had no effect on the PAR-P388 cells, neither on chemosensitization nor on drug retention, it is assumed that it acts on the P-glycoprotein, which is highly expressed on the membrane of the MDR-P388 cells, by inhibiting the function of the P-glycoprotein pump and thus restoring a normal ACD-sensitivity of the MDR-P388 cells. Cancer Res, 1991 Sep 1, 51(17), 4665 - 70 Characterization of multidrug resistance by fluorescent dyes; Kessel D et al.; Fluorimetric techniques were used to examine accumulation of fluorescent probes by the P388 murine leukemia and an anthracycline-resistant subline, P388/Adriamycin(ADR), which expresses the multidrug-resistant phenotype . P388 could be differentiated from P388/ADR on the basis of fluorescence intensity measurements using 3 classes of cationic dyes that are sensitive to membrane potential differences: rhodamine esters, cyanines, and styrylpyridinium dyes . But fluorescence intensity differences were also observed with potential-insensitive dyes: zwitterionic rhodamines and an acridine orange derivative . In all cases, fluorescence intensity differences were caused by impaired dye accumulation, and could be eliminated by treatment of P388/ADR cells with verapamil . Moreover, fluorescence signals from 2 anionic potential-sensitive dyes, merocyanine 540 and a bis-oxonol, were identical in P388 and P388/ADR . None of these dyes could be used to delineate CCRF-CEM, a lymphoblastic leukemia of human origin from the CEM/VM-1 subline that exhibits a markedly atypical drug resistance pattern not based on an enhanced outward transport . But accumulation of both neutral and cationic dyes was impaired in CEM/VLB100, a subline of CCRF-CEM expressing mdr . These studies show that many cationic and neutral fluorescent probes are substrates for the enhanced outward drug transport system associated with P388/ADR cells, and cannot be used to probe membrane-potential differences in cells expressing the mdr phenotype . With several dyes, differences in fluorescence intensity were sufficient so that flow cytometry could be used to delineate P388 from P388/ADR and CCRF-CEM from CEM-VLB100 . The latter technique may be useful for identifying malignant cell populations expressing multidrug resistance in patients with neoplastic disease. Southeast Asian J Trop Med Public Health, 1991 Sep, 22(3), 380 - 5 Clinical trial of artesunate and artemether on multidrug resistant falciparum malaria in Thailand . A preliminary report; Bunnag D et al.; A 5-day course of oral artesunate at total doses of 1200, 600, 650 mg and intramuscular artemether 480 mg proved effective (90-100% cured) in the treatment of multidrug resistant falciparum malaria in Thailand . Shorter courses yielded high recrudescence rates . The fever clearance and parasite clearance times were short . The side effects were mild and transient including occasional abnormal electrocardiograms and pain at the injection site . Slight reduction of neutrophil leucocytes and reticulocytes was observed . Further studies of artesunate and artemether should be carried out to find the optimum dosage regimen and to clarify the hematological effects. Trans R Soc Trop Med Hyg, 1991 Sep-Oct, 85(5), 578 - 83 Genetic diversity of Plasmodium falciparum in a village in eastern Sudan . 2 . Drug resistance, molecular karyotypes and the mdr1 genotype of recent isolates; Babiker HA et al.; Isolates of Plasmodium falciparum from a Sudanese village have been collected as part of a study of parasite genetic diversity during seasonal malaria epidemics . The sensitivity in vitro to chloroquine, pyrimethamine and mefloquine of these isolates has been determined . To assess the utility of pulse field gel chromosome separations in isolate characterization, 18 samples from individual patients in a single village were studied using this technique . Extensive variation in chromosome size was detected, no 2 isolates having identical molecular karyotypes . No multidrug resistance (mdr) gene amplification polymorphisms were detected in either chloroquine-resistant or chloroquine-sensitive isolates in this sample. Pathol Res Pract, 1991 Sep, 187(7), 892 - 905 What's new in cytostatic drug resistance and pathology; Dietel M; A major problem in cytostatic treatment of malignant tumors is the development of chemoresistant cell clones . An increased understanding of chemoresistance related mechanisms, improved methods for the detection and localization of resistant cell populations including predictive conclusions on the effectiveness of cytostatic drugs would contribute to the advancement of anti-tumor strategies . This paper reviews current concepts suggested for the development of cellular resistance to natural product drugs (anthracyclines, Vinca alkaloids, epipodophyllotoxines, antibiotics; so-called multidrug resistance substances), alkylating agents (nitrosureas, busulfan and mitomycin C), heavy metal compounds (cisplatin) and antifolates (5-fluorouracil, methotrexate) and describes the role of drug transporting and binding proteins (P-170-glycoprotein), detoxifying enzymes (glutathion-S-transferase, dihydrofolate reductase), DNA repair enzymes (topoisomerase I and II, polymerase alpha and beta), and genomic alterations (amplification, double minutes and homogeneous staining regions) due to resistance . It is focussed on the employment of morphological methods (light microscopy, immunocytochemistry, electron microscopy, fluorescence analysis, in situ hybridization, computer aided morphometric analysis) which will help to detect resistant cell clones in tumor biopsies . First correlations between histological data and clinical course will be reported . In the future, the morphological determination of chemoresistance may play an important role in applied functional tumor pathology. J Pediatr Surg, 1991 Sep, 26(9), 1107 - 12 Multidrug resistance in human neuroblastoma cells; LaQuaglia MP et al.; Neuroblastoma remains a significant problem in pediatric oncology . Recently a "multidrug-resistance" gene that may cause cells to become resistant to various chemotherapeutic agents has been cloned . The gene encodes the high-molecular-weight plasma membrane protein known as P-glycoprotein . To study the expression of this gene in cells exhibiting the multidrug-resistant phenotype, a panel of sublines selected with several different natural product drugs was established . The drug-sensitive parental BE(2)-C cells were clonally isolated from the human neuroblastoma SK-N-BE(2) line and exhibit a 150-fold increase in the copy number of the N-myc protooncogene . Sublines were selected by stepwise increases in the concentration of actinomycin-D, doxorubicin, vincristine, or colchicine . Gene amplification was assessed using Southern analysis, and RNA levels were determined by Northern and dot-blot analysis . Western blotting was used to determine protein levels . N-myc amplification and expression were simultaneously determined to assess possible alterations associated with development of multidrug resistance . Amplified P-glycoprotein-encoding genes were not seen in control lines but were clearly present in those that had undergone exposure to each of the chemical agents . Similarly, steady-state messenger RNA and protein levels were greatly increased in the drug-resistant sublines . We conclude that human neuroblastoma cells can acquire the multidrug-resistant phenotype after exposure to various chemotherapeutic agents. Ophthalmology, 1991 Sep, 98(9), 1425 - 31 Multidrug-resistant phenotype in retinoblastoma correlates with P-glycoprotein expression; Chan HS et al.; Chemotherapy plays an important role in therapy for patients with extraocular and metastatic retinoblastoma . The authors used chemotherapy for management of selected patients with uncontrolled intraocular tumors or tumors larger and more posteriorly located than those conventionally treated with local cryotherapy or photocoagulation . Rapid regrowth of some tumors after an initial excellent chemotherapy response led us to investigate the hypothesis that failure of treatment is caused by P-glycoprotein-related multidrug resistance . By using a sensitive immunoperoxidase method, increased P-glycoprotein was detected in five multidrug-resistant and two selectively plant alkaloid-resistant retinoblastoma cell lines and in the intraocular and metastatic tumors from which they were derived . In four chemotherapy-treated cases, increased P-glycoprotein in the tumor samples correlated with clinically relevant drug resistance . None of the four chemosensitive tumor cell lines had increased P-glycoprotein expression . Continuous surveillance of P-glycoprotein levels in metastatic retinoblastoma may be a useful guide to drug therapy. J Cell Physiol, 1991 Sep, 148(3), 479 - 84 Modulation of ATP and drug binding by monoclonal antibodies against P-glycoprotein; Georges E et al.; The role of P-glycoprotein in mediating the drug-resistance phenotype in multidrug resistant cells is now well documented . It is thought to function as an energy-dependent drug-efflux pump of broad specificity . Structurally, P-glycoprotein is an internally duplicated molecule containing two large multi-spanning transmembrane domains and two cytoplasmic ATP binding domains . In this report we demonstrate that monoclonal antibodies C219, C494, and C32 directed against short linear regions of the P-glycoprotein molecule inhibit ATP binding to P-glycoprotein in vitro . We also provide direct evidence that both predicted ATP-binding domains bind ATP and that there is co-operativity between the two sites . In addition, the capacity of P-glycoprotein to bind the calcium channel blocker, azidopine, is inhibited differentially by the antibodies . These observations are the first evidence linking specific perturbations of the P-glycoprotein molecule with ATP and drug binding. Schweiz Med Wochenschr, 1991 Aug 31, 121(35), 1249 - 53 {Interactions of cytostatic agents with other drugs}; Sauter C; With the degree of polypharmacy currently practiced in the field of oncology, there are undoubtedly many drug interactions . In the present study the influence of "non-cytotoxic" drugs on anticancer drugs is discussed, but not the reverse . Not only is the augmentation (reversal of multidrug resistance) or the reduction of antitumor properties of cytotoxic drugs observed, but also cytostatic activities of "non-cytotoxic" drugs themselves . Examples are calmodulin inhibitors such as phenothiazines and tricyclic antidepressants . Interactions may also increase side effects of cytostatic drugs or even neutralize the antitumoral activity . To ensure that interactions are not overlooked, all medicaments being administered should be listed . It is, however, not feasible yet to determine serum concentrations of all the drugs given to the patient . The antitumor activity of supportive care could be evaluated in randomized studies (e.g . cytostatic drugs +/- antidepressants). MMWR Morb Mortal Wkly Rep, 1991 Aug 30, 40(34), 585 - 91 Nosocomial transmission of multidrug-resistant tuberculosis among HIV-infected persons--Florida and New York, 1988-1991; Interaction of forskolin with the P-glycoprotein multidrug transporter; Molecular Pharmacology Laboratory, Food and Drug Administration, Bethesda, Maryland 20892Forskolin and 1,9-dideoxyforskolin, an analogue that does not activate adenylyl cyclase, were tested for their ability to enhance the cytotoxic effects of adriamycin in human ovarian carcinoma cells, SKOV3, which are sensitive to adriamycin and express low levels of P-glycoprotein, and a variant cell line, SKVLB, which overexpresses the P-glycoprotein and has the multidrug resistance (MDR) phenotype . Forskolin and 1,9-dideoxyforskolin both increased the cytotoxic effects of adriamycin in SKVLB cells, yet had no effect on SKOV3 cells . Two photoactive derivatives of forskolin have been synthesized, 7-O-{{2-{3-(4-azido-3- {125I}iodophenyl)propionamido}ethyl} carbamyl}-7-deacetylforskolin, 125I-7-AIPP-Fsk, and 6-O-{{2-{3-(4-azido-3- {125I}iodophenyl)propionamido}ethyl}carbamyl}forskolin, 125I-6-AIPP-Fsk, which exhibit specificity for labeling the glucose transporter and adenylyl cyclase, respectively (Morris et al., 1991) . Both photolabels identified a 140-kDa protein in membranes from SKVLB cells whose labeling was inhibited by forskolin and 1,9-dideoxyforskolin . There was no specific labeling of proteins in membranes from the SKOV3 cells . The overexpressed 140-kDa protein in SKVLB membranes was identified as the P-glycoprotein by immunoblot analysis and immunoprecipitation using anti-P-glycoprotein antiserum . Total inhibition of photolabeling of the P-glycoprotein was observed with verapamil, nifedipine, diltiazem, and vinbalastine, and partial inhibition was observed with colchicine and cytochalasin B . Forskolin was less effective at inhibiting the photolabeling of the P-glycoprotein than 1,9-dideoxyforskolin or a lipophilic derivative of forskolin . The data are consistent with forskolin binding to the P-glycoprotein analogous to that of other chemosensitizing drugs that have been shown to partially reverse MDR.(ABSTRACT TRUNCATED AT 250 WORDS) Tidsskr Nor Laegeforen, 1991 Aug 20, 111(19), 2423 - 7 {Resistance to chemotherapeutic agents in the treatment of cancer . Emphasizing the multiresistant phenotype}; Holte H; Despite considerable efforts, rather limited progress has been achieved in the treatment of disseminated cancer with chemotherapeutic agents during the last decade . Most tumours, especially those of epithelial origin, are more or less resistant to cytostatics right from initiation of therapy . Other tumours, on the other hand, like leukemias and lymphomas, are highly responsive initially but may become resistant during the course of therapy (secondary resistance) . This type of resistance is due to random mutations in the malignant cells . Several mechanisms of cellular resistance have been described, the most important being characterized by simultaneous resistance to several unrelated chemotherapeutic agents (pleiotropic drug resistance or multidrug resistance) . This mechanism is due to a membrane-associated efflux pump which transports the cytostatic agents out of the cells . The clinical importance of multidrug resistance and the possibility of inhibiting the function of the pump by pharmacological agents are currently being examined. Cancer Res, 1991 Aug 15, 51(16), 4243 - 9 Isolation and initial characterization of mouse tumor cells resistant to porphyrin-mediated photodynamic therapy; Luna MC et al.; Photodynamic therapy (PDT)-resistant variants of the RIF-1 mouse tumor cell line have been isolated following a protocol of repeated porphyrin incubation and light treatments . Two porphyrin incubation procedures, employing either an extended (16 h) or a short (1 h) incubation, were used in order to obtain cell strains exposed to conditions with differing intracellular photosensitizer localization . Two clones from each PDT porphyrin incubation protocol were selected for in vitro and in vivo analyses based on degree of resistance and plating efficiency . Resistant variants had increased protein content and were larger than the parental RIF-1 cells . In vitro growth rates were similar for all cell strains . Both 16-h PDT-resistant variants exhibited modest resistance to ionizing radiation and one of the 16-h PDT-resistant variants demonstrated increased sensitivity to hyperthermia . The PDT-resistant variants did not exhibit a multidrug resistance phenotype nor did they have altered porphyrin uptake properties . The parental and resistant RIF cells had comparable basal levels of antioxidant enzymes, reduced glutathione and stress proteins, but the number of cells required to produce in vivo tumor growth in 50% of inoculated animals was increased for all PDT-resistant variants . The resistant cells exhibit a stable phenotype and should be useful in studies designed to define PDT mechanisms of action. Proc Natl Acad Sci U S A, 1991 Aug 15, 88(16), 7386 - 90 Multidrug resistance after retroviral transfer of the human MDR1 gene correlates with P-glycoprotein density in the plasma membrane and is not affected by cytotoxic selection; Choi K et al.; Multidrug resistance (MDR) in mammalian cells is associated with the expression of the MDR1 gene encoding P-glycoprotein (P-gp), an and active efflux pump for various lipophilic compounds . MDR transfectants can be isolated after MDR1 gene transfer and selection with cytotoxic drugs; low levels of drug resistance have also been observed in unselected NIH 3T3 mouse cells after retrovirus-mediated transfer of mouse mdr1 cDNA . MDR cell lines possess multiple phenotypic changes, suggesting that P-gp function could be complemented by some additional mechanisms associated with cytotoxic selection . To determine whether cytotoxic selection contributes to the MDR phenotype of MDR1-expressing cells, NIH 3T3 cells infected with a recombinant retrovirus carrying the human MDR1 gene were selected by two different procedures: (i) noncytotoxic selection for increased P-gp expression on the cell surface by multiple rounds of immunofluorescence labeling and flow sorting or (ii) one or more steps of selection with a cytotoxic drug . The levels of MDR in both types of infectants showed an excellent correlation with the P-gp density in the plasma membrane, expressed as immunoreactivity with a P-gp-specific antibody normalized by reactivity with an antibody against an unrelated antigen . Cytotoxic selection conferred no additional increase in resistance relative to P-gp density . These results indicate that P-gp density in the plasma membrane may be sufficient to determine the level of MDR. Cancer Res, 1991 Aug 15, 51(16), 4226 - 33 In vivo circumvention of P-glycoprotein-mediated multidrug resistance of tumor cells with SDZ PSC 833; Boesch D et al.; The new nonimmunosuppressive cyclosporin analogue, SDZ PSC 833, is a very potent multidrug-resistance modifier . In vitro, it was shown to be at least 10-fold more active than cyclosporin A (Sandimmune), itself more active than verapamil, on most P-glycoprotein-expressing multidrug-resistant (MDR) tumor cell lines . In vivo, SDZ PSC 833 was tested in a few protocols of combined therapy with either Vinca alkaloids or doxorubicin as anticancer drugs, using the homologous tumor-host system (P388 cells of DBA/2 origin grafted into DBA/2 or B6D2F1 mice) . Although these MDR-P388 tumor cells belong to a highly resistant variant that in vitro required about 150-fold more anticancer drug for 50% cell growth inhibition than the parental P388 cells, significant prolongation of survival times of the MDR-P388 tumor-bearing mice was obtained when treated with a combination of SDZ PSC 833 p.o . were otherwise ineffective doses of anticancer drugs given i.p . This chemosensitizing effect of SDZ PSC 833 was dose-dependent and was most effective in a protocol combining administration of SDZ PSC 833 p.o . 4 h before a doxorubicin i.p . injection: in comparison with the survival of MDR-P388 tumor-bearing mice treated with the anticancer drug alone, the pretreatment with SDZ PSC 833 at 25 and 50 mg/kg gave 2- to 3-fold increases of survival times . Since the MDR-P388 tumor cells used in our studies belong to a highly resistant variant, with a much higher degree of drug resistance than the one known to occur in cancer patients, SDZ PSC 833 appears to be a very promising chemosensitizer. Cancer Res, 1991 Aug 15, 51(16), 4213 - 8 Decreased DNA topoisomerase II in daunorubicin-resistant Ehrlich ascites tumor cells; Friche E et al.; We have previously shown that the multidrug-resistant EHR2/DNR+ cells, which overexpress P-glycoprotein, accumulate only about 20-30% of daunorubicin at steady state compared to the sensitive cells . These cells have been thought to be a "pure" P-glycoprotein cell line . We now report that the EHR2/DNR+ cells exhibit decreased DNA topoisomerase II catalytic activity . We also found that the amount of immunoreactive DNA topoisomerase II from these cells is about one-third that seen in the drug-sensitive cell line . In agreement with the decreased activity and amount of topoisomerase II, the number of DNA-protein complexes stabilized by teniposide (VM-26) was reduced by about 50% in nuclear extracts from EHR2/DNR+ cells . Furthermore, using an intact cell assay for DNA protein complexes, we found that the VM-26-stimulated complexes formed in the drug-resistant cells never reached the level seen in the drug-sensitive cells . Verapamil and Cremophor EL block P-glycoprotein-mediated efflux of "natural product" drugs and increase their accumulation in resistant cells . Coincubation of the EHR2/DNR+ cells with VM-26 and either of these modulators increased the number of complexes formed in the resistant cells . However, neither modulator increased the number of topoisomerase II-DNA complexes in the drug-resistant cells to the level seen in the EHR2 cells . We conclude that the resistance of EHR2/DNR+ cells is due in part to reduced amounts of DNA topoisomerase II . Furthermore, we note that a single cell line can express features of both P-glycoprotein-associated multidrug resistance and altered topoisomerase II-associated multidrug resistance. J Natl Cancer Inst, 1991 Aug 7, 83(15), 1098 - 102 Involvement of vacuolar H(+)-adenosine triphosphatase activity in multidrug resistance in HL60 cells; Marquardt D et al.; HL60 cells isolated for resistance to vincristine (HL60/Vinc cells) or doxorubicin (HL60/Adr cells) contain enhanced levels of an energy-dependent drug efflux pump . HL60/Vinc cells contain the drug transporter P-glycoprotein, whereas the HL60/Adr isolate does not . In the present study, we examined the possible involvement of vacuolar H(+)-adenosine triphosphatase (H(+)-ATPase) activity in drug resistance in HL60 cells . We utilized bafilomycin A1, an agent which selectively inhibits vacuolar H(+)-ATPase activity at low concentrations . The results showed that bafilomycin A1 induced a major increase in drug accumulation and inhibited drug efflux in both HL60/Adr cells and HL60/Vinc cells . Similar results were obtained with 7-chloro-4-nitrobenz-2-oxa 1,3 diazole, an agent which is also capable of inhibiting vacuolar H(+)-ATPase . Azide, an inhibitor of F1F0 mitochondrial ATPase, and vanadate and ouabain, which are inhibitors of E1E2-type ATPase, did not affect drug levels in resistant cells . We also observed that bafilomycin A1 did not compete with {3H}azidopine binding to P-glycoprotein . Thus, bafilomycin A1 does not appear to function as a substrate for P-glycoprotein . These results suggest an involvement of vacuolar H(+)-ATPase activity in the pathway of drug efflux from HL60/Adr cells and HL60/Vinc cells . The mechanism of this action remains to be determined. Mol Cell Biol, 1991 Aug, 11(8), 3940 - 8 Isolation and characterization of Drosophila multidrug resistance gene homologs; Wu CT et al.; Mammalian multidrug-resistant cell lines, selected for resistance to a single cytotoxic agent, display cross-resistance to a broad spectrum of structurally and functionally unrelated compounds . These cell lines overproduce a membrane protein, the P-glycoprotein, which is encoded by a member(s) of a multigene family, termed mdr or pgp . The amino acid sequence of the P-glycoprotein predicts an energy-dependent transport protein with homology to a large superfamily of proteins which transport a wide variety of substances . This report describes the isolation and characterization of two Drosophila homologs of the mammalian mdr gene . These homologs, located in chromosomal sections 49EF and 65A, encode proteins that share over 40% amino acid identity to the human and murine mdr P-glycoproteins . Fly strains bearing disruptions in the homolog in section 49EF have been constructed and implicate this gene in conferring colchicine resistance to the organism . This work sets the foundation for the molecular and genetic analysis of mdr homologs in Drosophila melanogaster. J Neurosurg, 1991 Aug, 75(2), 277 - 83 Cross-resistance patterns in ACNU-resistant glioma sublines in culture; Saito Y et al.; Three ACNU-resistant clones (R1, R3, and R12) were isolated from 9L rat glioma cells under selection pressure of ACNU in vitro . The authors have investigated the mechanisms of resistance and characteristics of these clones at the cellular level by studying cross-resistance patterns to chemical and physical agents . Although these resistant sublines showed complete cross-resistance to methyl-chloroethylnitrosourea (MCNU), no cross-resistance was observed for other alkylating agents, while each of the resistant sublines showed partial cross-resistance to structurally dissimilar toxic agents (vinblastine, Adriamycin, and VP-16) . No difference in ACNU uptake was observed between 9L and R3 cells, and resistance patterns among alkylating agents suggested that the mechanism of ACNU resistance was specific to bifunctional nitrosoureas . Based on a transport study, this multidrug resistance could be explained by reduced intracellular uptake of these drugs, but there seemed little possibility that membrane P-glycoprotein, which usually is observed in typical multidrug-resistant cells, was expressed in these ACNU-resistant cells because enhanced drug efflux was not found in ACNU-resistant sublines . Significant collateral sensitivity to L-asparaginase indicated that ACNU might disturb the asparagine synthetic pathways by its mutagenic action . The increased level of total glutathione in the resistant sublines may be one mechanism of radiation or ACNU resistance. Curr Opin Oncol, 1991 Aug, 3(4), 677 - 83 Rhabdomyosarcoma and other soft tissue sarcomas of childhood; Goren MP; Often treated as a single clinical entity, the pediatric soft tissue sarcomas include neoplasms of diverse histology that can originate from any anatomic site and exhibit varied patterns of local spread and metastasis . Recent developments with potential clinical impact include new diagnostic and prognostic markers stemming from advances in molecular biology, and increasing concern for the late effects of therapy in a growing population of long-term survivors . Initial clinical data indicate the value of MyoD1 protein expression in classifying previously indeterminate primitive undifferentiated tumors . The reported sensitivity and specificity of P-glycoprotein expression for the identification of chemoresistant disease in pediatric sarcomas should spawn studies to clarify its prognostic value and potential therapeutic strategies to circumvent the multidrug-resistance phenotype . Tumor cell DNA ploidy may also have prognostic and diagnostic value . An abundant interest in alleviating the late effects of adjuvant therapy and surgery is reflected in many clinical reports by oncologists, surgeons, radiotherapists, ophthalmologists, and other specialists. Br J Cancer, 1991 Aug, 64(2), 361 - 4 A phase II study of epidoxorubicin in colorectal cancer and the use of cyclosporin-A in an attempt to reverse multidrug resistance; Verweij J et al.; We determined the ability of the multidrug resistance (MDR) reversal agent cyclosporin-A to increase anthracycline drug accumulation in colorectal tumour cells in vitro, using the technique of on-line flow cytometry . Data of four previously untreated patients showed that cyclosporin-A can increase intracellular net-uptake of daunorubicin . A phase II study was initiated in 24 colorectal cancer patients . They received cyclosporin-A at a dose of 3 mg kg-1 over 1 h as i.v . infusion, at 7 h and at 1 h preceding cytotoxic drug administration . At the end of the second cyclosporin-A administration epidoxorubicin 90 mg m-2 was administered as i.v . bolus . Cycles were repeated every 3 weeks . Median cyclosporin-A peak blood levels and levels at 18 h after cytotoxic drug administration appeared to be 6248 ng ml-1 and 1012 ng ml-1 respectively . Only one partial response was observed, despite these high cyclosporin-A levels . Cyclosporin-A did not cause major toxicity, only a 29% incidence of hot flushes was observed . Epidoxorubicin toxicities were as expected but the frequency of severe leucocytopenia was striking . This treatment schedule can not be considered active in colorectal cancer. Br J Cancer, 1991 Aug, 64(2), 267 - 73 Resistance to the antimitotic drug estramustine is distinct from the multidrug resistant phenotype; Speicher LA et al.; Following EMS mutagenesis, three estramustine (EM) resistant DU 145 human prostatic carcinoma cell lines were clonally selected by exposure to incrementally increasing concentrations of the drug . Although only low levels of resistance (approximately 3-fold) were attainable, this resistance was stable in the absence of continuous drug exposure . These EM-resistant clones (EMR 4,9,12) did not exhibit cross resistance to vinblastine, taxol, or adriamycin, and had collateral sensitivity to cytochalasin B . None of the lines had elevated expression of P-glycoprotein mRNA or glutathione S-transferase activity, suggesting a phenotype distinct from the classic multi-drug resistance phenotype . This conclusion was supported further by the observation that two MDR cell lines (FLC mouse erythroleukaemic and SKOV3 human ovarian carcinoma cells) showed sensitivity to EM . Fluorescent activated cell sorting analysis of the effects of EM on cell cycle traverse revealed that at EM concentrations up to 20 microM an increasing percentage of wild type cells were blocked in G2/M; no such effect occurred in EMR lines . Differential interference contrast microscopy was employed to study EM's effect on mitosis . EMR lines were able to form functional, albeit smaller, spindles at EM concentrations that resulted in chromosomal disorganisation and inhibition of mitotic progression in wild type cells . EMR lines were able to progress through mitosis and cytokinesis at the same rate as untreated cells . Tritiated EM was used to evaluate potential drug uptake/efflux mutations in ERM clones . EMR 4 and 9 incorporate less EM than wild type cells; however, they have significantly decreased cellular volumes . The initial efflux rate constants for EMR clones were greater than for wild type cells . Within 5 min greater than 70% of the drug was lost from resistant cells compared to a 50% loss by the wild type . Although the specific mechanisms of resistance have yet to be defined, the lack of collateral resistance to other MDR/anti-microtubule agents could serve as the basis for the clinical use of EM in combination chemotherapy. FASEB J, 1991 Aug, 5(11), 2523 - 8 Molecular manipulations of the multidrug transporter: a new role for transgenic mice; Pastan I et al.; Multidrug resistance in human cancer is associated with overexpression of the MDR1 gene which encodes a 170,000 molecular weight membrane glycoprotein that transports cytotoxic drugs out of cancer cells . The MDR1 gene is normally expressed in intestine, kidney, liver, and adrenal glands, and in tumors derived from these tissues, but it is not expressed in normal bone marrow . Transgenic mice that express the MDR1 gene in their bone marrow have been developed, and because of this expression these mice are resistant to the bone marrow-suppressive effects of daunomycin, doxorubicin, taxol, and several other anticancer drugs . These mice can be used in several different ways to develop new types of drugs to treat human cancer.--Pastan, I.; Willingham, M . C.; Gottesman, M . Molecular manipulations of the multidrug transporter: a new role for transgenic mice. Proc Natl Acad Sci U S A, 1991 Aug 1, 88(15), 6585 - 9 Reversed siderophores act as antimalarial agents; Shanzer A et al.; We describe here a family of biomimetic iron carriers that display high binding efficiency for ferric ions and favorable permeation properties across erythrocytic membranes . These carriers inhibit in vitro growth of Plasmodium falciparum by scavenging intracellular iron . The chemical features were realized by reproducing the iron-binding cavities of natural iron carriers (siderophores) and by systematic substitutions of their hydrophilic envelopes for more hydrophobic ones . In contrast to natural carriers, which participate in receptor-mediated iron uptake in cells and act as growth promoters, our synthetic carriers were designed to penetrate cellular membranes by diffusion, scavenge intracellular iron, and thereby act as growth inhibitors . Based on these properties we designate the compounds reversed siderophores and refer to the specific analogs of the natural ferrichrome as synthetic ferrichromes . The antimalarial activity of the synthetic ferrichromes correlated with their lipophilicity, and this antimalarial activity was averted when the chelators were applied as iron (III) complexes . The sites of synthetic ferrichrome action reside in the intraerythrocytic parasite and not in serum or on normal erythrocyte components . The agents were effective against all stages of parasite growth and against a variety of multidrug-resistant strains of P . falciparum . The most potent agent of this synthetic ferrichrome series, SF1-ileu, was not toxic to mammalian cells in culture and was 15-fold more potent and 20-fold faster acting than desferrioxamine . Taken in toto, these agents constitute a series of promising candidates for future use in malaria chemotherapy. Blood, 1991 Aug 1, 78(3), 586 - 92 Multidrug resistance (mdr1) gene expression in adult acute leukemias: correlations with treatment outcome and in vitro drug sensitivity; Marie JP et al.; Resistance to multiple chemotherapeutic agents has been related to the production of P-glycoprotein, a trans-membrane drug efflux pump that is encoded by the multidrug resistance (MDR) gene mdr1 . To investigate whether mdr1 could be involved in clinical resistance to chemotherapy in acute leukemias, we have analyzed retrospectively the RNA from adult acute leukemia cells by slot-blot hybridization with a human mdr1 probe . Units of mdr1 expression were defined by reference to drug-sensitive human sarcoma and K562 leukemia cell lines (1 U) and the highly resistant doxorubicin selected leukemia cells K562/R7 (50 U) . We studied 41 adult patients with acute leukemias: 5 acute lymphoblastic leukemias, 23 acute myeloid leukemias, and 13 secondary leukemias or blast crisis of chronic myelogenous leukemia . Expression of 10 U or more of mdr1 was found in 6 of 31 (19%) leukemias at diagnosis, versus 5 of 10 (50%) after relapse from therapy, P = .06 . The complete remission rate and in vitro sensitivity to daunorubicin were both correlated with low expression (1 U, v 2 U or more) of mdr1 . Among 36 evaluable attempts to induce remission, the complete remission rate was 67% (8 of 12) for patients with undetectable or minimal mdr1 expression (1 U), versus 29% (7 of 24) in patients with 2 U or more of expression, P = .03 . In vitro resistance to daunorubicin or other MDR-related drugs was associated with expression of 2 U or more of mdr1 in 11 of 11 cases, while specimens that were sensitive to these agents were negative for mdr1 expression in 5 of 11 cases, P = .03 . These data suggest that mdr1 expression contributes to chemoresistance in acute leukemia . Determination of mdr1 gene expression may be useful in designing therapy for patients with leukemia. Invest New Drugs, 1991 Aug, 9(3), 219 - 25 Differences in N-acetylation of the experimental antitumor agent batracylin in the mouse and the rat; Ames MM et al.; Batracylin (NSC-320846) is a quinalzolineone recently evaluated as a potential antitumor agent by the National Cancer Institute . The analog was active against a number of murine tumors, including colon adenocarcinoma 38 and multidrug resistant sublines of P-388 leukemia . Preclinical toxicity studies revealed that batracylin was much more toxic when administered orally to rats than to mice . The combined sex LD10 in mice was 5,655 mg/m2 while 576 mg/m2 was lethal to all rats treated at that dose . We determined that following oral administration of batracylin, systemic exposure of parent drug to the rat was only 14.9% of that to the mouse . It was subsequently noted that systemic exposure of a relatively non-polar metabolite was approximately 9 times greater in the rat than in the mouse . The metabolite was identified as N-acetylbatracylin by TLC, HPLC and mass spectral analyses . Observations by the National Cancer Institute that N-acetylbatracylin was not toxic following oral administration to mice or rats prompted evaluation of systemic exposure following oral administration to rats . Following oral administration of N-acetylbatracylin to rats, systemic exposure was almost nil . Indeed, exposure of rats to N-acetylbatracylin was several orders of magnitude greater following oral administration of six-fold lower doses of the parent drug, batracylin . Thus, N-acetylation may play a role in the toxicity of batracylin despite the lack of toxicity observed following oral administration of N-acetylbatracylin . In addition, further metabolism of the N-acetyl conjugate, analogous to that of other aromatic amines, may be involved in the pharmacology of batracylin and similar analogs. Arzneimittelforschung, 1991 Aug, 41(8), 855 - 8 {Reversal of multidrug resistance with (R)-verapamil in vitro and in vivo}; Pommerenke EW et al.; The clinical use of racemic (R/S)-verapamil (CAS 52-53-9) as resistance modifier is limited because of the cardiovascular activity of the substance . The stereoisomer (R)-verapamil shows significant less cardiovascular activity . Therefore we tested the resistance modifying abilities of (R)-verapamil and (R/S)-verapamil in murine multidrug-resistant L 1210 ascites-tumor-cells in vitro and in vivo . The present results demonstrate, that the (R)-isomer has the same resistance modifying effects as racemic verapamil . Both modifying substances have no effects in the parental (sensitive) and cytosine-arabinoside resistant L 1210 ascites-tumor-cells . Thus, (R/S)-verapamil and (R)-verapamil show their resistance modifying abilities only in multidrug-resistant tumor-cells. Planta Med, 1991 Aug, 57(4), 341 - 3 Antimalarial activity of Tanzanian plants and their active constituents: the genus Uvaria; Nkunya MH et al.; Petroleum ether, dichloromethane, and methanol extracts of leaves, stem, and root bark of nine Uvaria species: U . dependens, U . faulknerae, U . kirkii, U . leptocladon, U . lucida ssp . lucida, Uvaria sp . (Pande)k U scheffleri, and U . tanzaniae were tested for their in vitro activity against the multidrug resistant K1 strain of Plasmodium falciparum . The IC50 values of the extracts varied between 5 and 500 micrograms/ml . The most active extracts were obtained from the stem and root bark of U . lucida ssp . lucida and Uvaria sp . (Pande) and the root bark of U . scheffleri, all of which had IC50 values between 5 and 9 micrograms/ml . Among the compounds isolated, uvaretin, diuvaretin, and (8',9'-dihydroxy)-3-farnesylindole were the most active (IC50 = 3.49, 4.20, and 2.86 micrograms/ml, respectively). Protein Expr Purif, 1991 Aug, 2(4), 256 - 65 Strategies for the purification of P-glycoprotein from multidrug-resistant Chinese hamster ovary cells; Doige CA et al.; P-glycoprotein, a hydrophobic 170-kDa integral protein overexpressed in the plasma membrane of multidrug-resistant cells, is proposed to function as an ATP-dependent drug efflux pump . Plasma membrane preparations highly enriched in P-glycoprotein were isolated from multidrug-resistant cells by discontinuous sucrose gradient and Ca2+ precipitation methods . Several strategies were used for P-glycoprotein purification, with the goal being to achieve both good yields and purity, while keeping experimental manipulation to a minimum . P-glycoprotein was solubilized from the plasma membrane using 3-{(3-cholamidopropyl)dimethylammonio}-1-propanesulfonate . Immunoaffinity chromatography using C219 monoclonal antibody produced low yields of moderately pure protein . Sequential lectin affinity chromatography on RCA-120 followed by lentil lectin resulted in a P-glycoprotein preparation that showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis . A fraction of P-glycoprotein did not bind to RCA-120, most likely as a result of heterogeneous glycosylation . A combination of chromatography on RCA-120 followed by immunoaffinity chromatography on C219 resulted in low yields of very pure P-glycoprotein. Acta Trop, 1991 Aug, 49(3), 215 - 25 The effect of verapamil alone and in combination with trypanocides on multidrug-resistant Trypanosoma brucei brucei; Kaminsky R et al.; Following previous studies of verapamil reversal of multidrug resistance in cancer cells and chloroquine resistance in malaria, the effect of the calcium channel blocker verapamil was investigated on multidrug-resistant and susceptible Trypanosoma brucei brucei . Resistance of cloned parasites to diminazene aceturate (Berenil) and isometamidium chloride (Samorin) was expressed in a cell-free in vitro culture system . Verapamil showed antitrypanosomal activity against both, multidrug-resistant and susceptible trypanosomes at concentrations above 1 micrograms/ml . Verapamil did not reverse multidrug resistance when used at concentrations of 0.1 or 1.0 micrograms/ml in combination with diminazene aceturate or isometamidium chloride . Results obtained in vitro correlate with observations in mice . It is suggested that multidrug resistance in African trypanosomes is due to mechanisms other than those occurring in cancer cells, malaria or South-American trypanosomiasis. Histopathology, 1991 Aug, 19(2), 131 - 40 Immunohistochemical detection of the multidrug transport protein P170 in human normal tissues and malignant lymphomas; Pileri SA et al.; Two monoclonal antibodies, MRK16 and C219, both directed at the 170 kDa P-glycoprotein multidrug resistance agent, were applied to frozen sections or cytospin preparations from normal human tissues and 60 non-Hodgkin's malignant lymphomas . Adrenal gland, kidney, liver and pancreas were always stained by the reagents, albeit with slightly different patterns . Brain capillaries as well as macrophages and some elements of the bone marrow, peripheral blood, ovarian stroma and colonic, gastric and jejunal mucosa were positive in all examined preparations . There were differences in the staining patterns with the two antibodies . Among the 60 non-Hodgkin's lymphomas, 25 contained a number of positive cells, which ranged from 2% to 100% . No correlation was seen between the expression of P170 and histological type, stage, clinical symptoms or growth fraction . A close relationship was shown between the presence of P170 positive elements and the clinical course of the disease (P less than 0.001). Bioessays, 1991 Aug, 13(8), 381 - 7 Multidrug resistant transgenic mice as a novel pharmacologic tool; Mickisch GH et al.; Multidrug resistance resulting from expression of an energy-dependent drug efflux pump encoded by the human MDR1 gene is a major impediment to effective cancer therapy . Pharmacologic intervention aimed at inhibiting this multidrug transporter should improve existing chemotherapy of human cancer, but drug development has been delayed by the difficulty and expense of developing valid animal models . Using recombinant DNA technology, a transgenic mouse has been engineered whose bone marrow is protected from the toxic effects of chemotherapy by expression of the MDR1 gene . This animal system allows the rapid screening of drugs which inhibit the multidrug transporter and heralds a new era of using transgenic animals for pharmacologic screening. Semin Cancer Biol, 1991 Aug, 2(4), 227 - 33 On the origins of clinical drug resistance; O'Brien JP et al.; Recent progress in understanding the clinical importance of certain laboratory models of drug resistance is cause for clinical oncologists to rethink some of the current concepts used in developing chemotherapy programs . The following discussion will reexamine a popular model of resistance development and highlight certain insights gained from clinical and laboratory studies of multidrug resistance . Such insights both challenge traditional concepts of cancer treatment and suggest new therapeutic approaches that would otherwise not have been apparent. Semin Cancer Biol, 1991 Aug, 2(4), 213 - 26 Multidrug resistance mediated by P-glycoproteins; Schinkel AH et al.; Overexpression of P-glycoprotein genes is a well-established cause of one form of multidrug resistance . P-glycoproteins are plasma membrane proteins containing two ATP-binding sites and twelve putative transmembrane segments . P-glycoproteins are thought to act as ATP-dependent drug efflux pumps, actively extruding a range of structurally different, hydrophobic drugs from the cell . This simple model can account for the properties of multidrug resistant cells, even those that seem to require more complex explanations . The structure and function of P-glycoprotein genes has been studied in mammals and in several lower eukaryotes . These studies are helping to delineate the range of drugs that can be transported by P-glycoproteins; the genetic mechanisms that can lead to elevated cellular P-glycoproteins levels; and the evolution of the versatile and prolific P-glycoprotein gene family . The physiological function of the human P-glycoproteins encoded by the MDR1 and MDR3 (or MDR2) genes remains a matter of speculation. Eur J Haematol, 1991 Aug, 47(2), 146 - 51 Absence of correlation between cytotoxicity and drug transport by P-glycoprotein in clinical leukemic cells; Kato S et al.; Development of resistance to cytotoxic agents is a common problem in the treatment of acute leukemia . In cell lines having multidrug resistance (MDR) phenotype, a decrease in the intracellular accumulation of drugs has been closely related to the overexpression of P-glycoprotein/mdr1 genes . We analyzed the relationship between the cytotoxicity of adriamycin (ADR) in vitro, intracellular accumulation of ADR, and the expression of P-glycoprotein on fresh leukemic cells from 19 patients at their initial presentation and from 9 relapsed patients . Pretreatment patients showed significantly higher ratio of complete remission than relapsed patients, and mean value of IC50 for adriamycin in initial presentation was higher than at relapse . But we found no significant relationship between in vitro cytotoxicity and drug transport . In addition, only 2 of the 5 relapsed patients examined by monoclonal antibody C219 expressed the P-glycoprotein . These results suggest that the acquisition of clinical drug resistance may involve various mechanisms other than the reduction of drug accumulation with P-glycoprotein expression. J Urol, 1991 Aug, 146(2), 447 - 53 New potent verapamil derivatives that reverse multidrug resistance in human renal carcinoma cells and in transgenic mice expressing the human MDR1 gene; Mickisch GH et al.; Multidrug resistance in human renal cell carcinoma is mainly caused by expression of the MDR1 gene and is characterized by a broad spectrum cross resistance to many natural product chemotherapeutic agents . This resistance can be overcome by applying chemosensitizers which inhibit the function of the MDR1 gene product P-glycoprotein . The development of new reversing agents with fewer side effects and a higher potency in modifying resistance is a high priority of research on drug resistance . We have evaluated four new verapamil derivatives on 21 primary human renal cell carcinomas in vitro, and also tested them in an MDR-transgenic mice model . These mice express the human MDR1 gene in their bone marrow cells and measurement of their white blood counts provides a simple, rapid and reliable system to screen for the potency of MDR-reversing agents in vivo . We demonstrate here that all four drugs are effective in reversing multidrug resistance in primary cultures of human renal cell carcinomas when used in combination with vinblastine chemotherapy, and to a lesser extent with doxorubicin or daunomycin chemotherapy . Our in vivo data indicate that two of these reversing agents display low toxicity at high concentrations and are more effective at low, clinically achievable concentrations, than the other two drugs and R-verapamil . These results make the two new drugs attractive candidates to be taken into clinical trials. Cancer Commun, 1991 Aug, 3(8), 265 - 70 Selenium-dependent glutathione peroxidase expression is inversely related to estrogen receptor content of human breast cancer cells; Townsend AJ et al.; The absence of estrogen receptors (ER) in human breast tumors has been associated with a poorer prognosis compared to patients with ER positive breast cancer . Previous studies from our laboratory have shown that a multidrug resistant human breast cancer cell line selected for resistance to Adriamycin (ADR) exhibited markedly increased expression of both the pi class glutathione S-transferase (GST-pi) and the selenium-dependent glutathione peroxidase . These studies also revealed that the ER status was inversely related to the expression of GST-pi in six human breast cancer cell lines and primary tumor specimens . In the present study, we have examined the relationship between ER status and several biological properties of these cells, including their levels of glutathione peroxidase (GSH-Px) and catalase expression, their capacity to generate toxic hydroxyl radicals (degrees OH) by redox cycling of ADR, and their sensitivities to the cytotoxic effects of ADR and the oxidant, H2O2 . Our results show that expression of GSH-Px, but not catalase, is inversely related to the ER status in these cell lines . Formation of the degree OH induced by treatment of cells with ADR was inversely proportional to the GSH-Px activity in these cell lines, and thus directly related to the ER status . Sensitivity of these cells to ADR or to H2O2, however, was not consistently related to ER status, GSH-Px, or catalase activity, or to ADR induced degree OH radical formation . These results indicate that these parameters are not predictive of cellular susceptibility to oxidative damage in these cell lines under the conditions studied. Cell, 1991 Jul 12, 66(1), 85 - 94 Expression and activity of P-glycoprotein, a multidrug efflux pump, in human hematopoietic stem cells; Chaudhary PM et al.; Hematopoietic stem cells show reduced staining with a mitochondrial fluorescent dye, rhodamine 123 (Rh-123), which was supposed to indicate decreased mitochondrial activity in these cells . Rh123 and several other fluorescent dyes are substrates for transport mediated by P-glycoprotein (P-gp), an efflux pump responsible for multidrug resistance in tumor cells . We have found that staining of human bone marrow cells with fluorescent dyes is potentiated by P-gp inhibitors and inversely correlated with P-gp expression . P-gp is expressed in practically all hematopoietic progenitor cells, including long-term culture-initiating cells . The highest levels of P-gp among the progenitors are associated with cells displaying characteristics of pluripotent stem cells . These results have implications for stem cell purification and bone marrow resistance to cancer chemotherapy. Biochim Biophys Acta, 1991 Jul 10, 1093(2-3), 147 - 52 Cellular daunomycin fluorescence in multidrug resistant 2780AD cells and its relation to cellular drug localisation; Lankelma J et al.; Multidrug resistant (MDR) 2780AD human ovarian carcinoma cells were loaded with the fluorescent anticancer agent daunomycin (DN) . Fluorescence anisotropy was lower than for corresponding A2780 wild-type cells, indicating that DN was less rigidly bound than in the wild-type cells . Average fluorescence quenching of DN was lower for 2780AD cells . Data were fitted into a model with a highly quenched fraction (fraction A), corresponding to DN intercalated in DNA, and an unquenched fraction (fraction B) . The ratio A/B was one order of magnitude lower for the MDR cells than for the wild-type cells . Two other MDR cell lines were investigated and low A/B ratios were found in both cases . Thus, evidence has been provided that in MDR cells the DNA-bound fraction is relatively low and that more free DN is present, for example in acidic vesicles. Biochem Pharmacol, 1991 Jul 5, 42(2), 391 - 402 Biochemical and pharmacological characterization of MCF-7 drug-sensitive and AdrR multidrug-resistant human breast tumor xenografts in athymic nude mice; Mimnaugh EG et al.; The phenotypic expression of multidrug resistance by the doxorubicin-selected AdrR human breast tumor cell line is associated with overexpression of plasma membrane P-170 glycoprotein and increased cytosolic selenium-dependent GSH-peroxidase activity relative to the parental MCF-7 wild-type line (WT) . To determine whether doxorubicin resistance by AdrR cells persists in vivo, and to further investigate the possibility of biochemical differences between WT and AdrR solid tumors, both tumor cell lines were grown as subcutaneous xenografts in athymic nude mice . Tumorigenicity depended upon cell inoculation burden, and tumor incidence was similar for both cell lines (greater than 80% tumor takes at 10(7) cells/mouse) at 14 days, provided 17 beta-estradiol was supplied to the animals bearing the WT tumors . However, the growth rate for the AdrR xenografts was only about half that of WT xenografts . Doxorubicin (2-8 mg/kg, i.p., injected weekly) significantly diminished the growth of the WT tumors, but AdrR solid tumors failed to respond to doxorubicin . The accumulation of 14C-labeled doxorubicin was 2-fold greater in WT xenografts that in AdrR, although there were no differences in host organ drug levels in mice bearing either type of tumors . Membrane P-170 glycoprotein mRNA was detected by slot-blot analysis in the AdrR tumors, but not in WT . Electron spin resonance 5,5-dimethylpyrroline-N-oxide-spin-trapping experiments with microsomes and mitochondria from WT and AdrR xenographs demonstrated a 2-fold greater oxygen radical (superoxide and hydroxyl) formation from activated doxorubicin with WT xenographs compared to AdrR . Selenium-dependent glutathione (GSH)-peroxidase, superoxide dismutase and GSH-S-aryltransferase activities in AdrR xenografts were elevated relative to WT . Although the activities of the latter two enzymes were similar to those measured in both tumor cell lines, GSH-peroxidase activities were elevated 70-fold (WT) and 10-fold (AdrR) in xenografts compared to tumor cells . In contrast, in both WT and AdrR solid tumors in vivo, catalase, NAD(P)H-oxidoreductases, and glutathione disulfide (GSSG)-reductase activities, and GSH and GSSG levels were not markedly different, and were essentially the same as in cells in vitro . Like the MDR cells in culture, AdrR tumor xenografts were extremely resistant to doxorubicin and retained most of the characteristics of the altered phenotype . These results suggest that WT and AdrR breast tumor xenografts provide a useful model for the study of biochemical and pharmacological mechanisms of drug resistance by solid tumors in vivo. Cancer Lett, 1991 Jul 4, 58(3), 189 - 93 Distinct patterns of phorbol ester-induced downregulation of protein kinase C activity in adriamycin-selected multidrug resistant and parental murine fibrosarcoma cells; Ward NE et al.; Specific activators of protein kinase C (PKC), including the phorbol-ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), can reduce the chemosensitivities of a variety of mammalian tumor cell lines and their cytotoxic drug-selected multidrug resistant (MDR) variants to MDR-linked drugs, thus implicating PKC in the MDR phenotype . Previously, we reported that the adriamycin-selected MDR murine fibrosarcoma cell line UV-2237M-ADRR has approximately twice as much PKC activity as the parental UV-2237M line . In this report, we show that the level of {3H}phorbol-12,13-dibutyrate specific binding activity was elevated 3.5-fold in the MDR cells, thus establishing that phorbol-ester responsive PKC is overexpressed in the MDR line . Phorbol esters mediate downregulation of PKC by stimulating proteolysis of the enzyme, without altering the rate of PKC synthesis . We report that the kinetics of TPA-induced downregulation of PKC activity differ markedly in parental and MDR UV-2237M cells, providing evidence that the overexpression of phorbol-ester responsive PKC in adriamycin-selected MDR UV-2237M-ADRR cells results, at least in part, from a reduced rate of PKC degradation in the cells. DNA Cell Biol, 1991 Jul-Aug, 10(6), 433 - 41 Murine mdr-1, mdr-2, and mdr-3 gene expression: no coinduction with the Cyp1a-1 and Nmo-1 genes in liver by 2,3,7,8-tetrachlorodibenzo-p-dioxin; Teeter LD et al.; Multidrug-resistance (MDR) genes are induced in the liver of rodents treated with a variety of foreign chemicals and hepatocarcinogens . It has been reported that 2,3,6,7-tetrachlorodibenzo-p-dioxin (TCDD) might increase hepatic MDR transcripts in the Fischer rat and the C57BL/6 (B6) inbred mouse strain having the high-affinity aromatic hydrocarbon (Ah) receptor, but not in the DBA/2 (D2) strain having the low-affinity Ah receptor . These intriguing results suggest that TCDD might activate MDR gene expression by way of an Ah receptor-mediated signal transduction pathway . We have attempted to confirm these data in four inbred mouse strains: two (B6 and BALB/c) having the high-affinity Ah receptor, and two (D2 and AKR) having the low-affinity Ah receptor . The RNase protection assay was used to distinguish between the MDR1, MDR2, and MDR3 mRNAs . TCDD treatment at high (100 micrograms/kg) and low (1 mu/kg) doses, a time course from 6 to 96 hr of TCDD treatment, progeny from the B6D2F1 x D2 backcross, and transcriptional run-on experiments were performed . The Cyp1a-1 (cytochrome P1450) and Nmo-1 {NAD(P)H:menadione oxidoreductase} genes, two members of the TCDD-inducible {Ah} battery, were used as positive controls . We were unable to detect significant coinduction of MDR1, MDR2, or MDR3 mRNA with CYP1A1 mRNA or with Cyp1a-1 or Nmo-1 transcription under any conditions . Therefore, we conclude that any effects that TCDD might have on MDR expression must be substantially different from TCDD effects on genes known to be induced via the Ah receptor. J Med Chem, 1991 Jul, 34(7), 1947 - 51 Additional nucleotide derivatives of mitosenes . Synthesis and activity against parental and multidrug resistant L1210 leukemia; Iyengar BS et al.; Cytidine 5'-monophosphate and 5'-ara-CMP conjugates of 2,7-diaminomitosene, with the phosphate groups linked to C-1, were prepared by treating mitomycin C with the appropriate nucleotides . 5'-UMP conjugates were prepared from mitomycin A, 7 (M-83), and 8 (BMY-25282) by similar procedures . A conjugate could not be prepared from mitomycin C and 6-MPRP, but a sulfur-linked derivative was made with 6-MP ribonucleoside . The corresponding 1-hydroxy-2-aminomitosenes were prepared from the parent mitomycin analogues for structure-activity comparisons . All compounds were tested against L1210 murine leukemia in the MTT tetrazolium dye assay . In general, the conjugates were less potent than the parent mitomycins; however 5'-ara-CMP conjugate 14 derived from mitomycin C was more potent than the parent compound or any mitomycin tested except mitomycin A . It also was more potent than ara-C . This result establishes the value of this approach to prodrugs, at least in cell culture . Against a multi-drug-resistant L1210 cell line, all of the conjugates derived from mitomycin C were more potent than the parent compound . 6-Mercaptopurine ribonucleoside conjugate 15 was more active against the resistant cells than it was against the parental cell line. Trans R Soc Trop Med Hyg, 1991 Jul-Aug, 85(4), 424 - 9 Malaria during pregnancy in an area of unstable endemicity; Nosten F et al.; A prospective study of malaria during pregnancy was conducted between September 1986 and December 1989 in an area of unstable (mesoendemic) malaria transmission on the Thai-Burmese border . Antenatal clinics were set up in camps for displaced persons of the Karen ethnic minority and 1358 pregnant women were enrolled at a mean estimated gestational age of 23 weeks (standard deviation 5.7 weeks) and were followed weekly until delivery . Malaria developed in 505 women (37.2%); 80.2% of infections were Plasmodium falciparum, 17.1% were P . vivax, and 2.7% were mixed . Primigravidae were infected more commonly than multigravidae: 153/322 (47.5%) compared with 318/953 (33.3%) (P less than 0.001) . The incidence of malaria declined from the 20th week of gestation (12%) towards term (4.4%) . Most infections were detected before symptoms developed, and there were no deaths associated with malaria . Despite this, malaria was associated with an overall 123 g reduction in birthweight (95% confidence interval {CI} 34-212 g) . This reduction was largely accounted for by lower birthweights of babies born to infected primigravidae (mean reduction 151 g, 95% CI 21-282 g) and women in their 2nd and 3rd pregnancies (mean reduction 185 g, 95% CI 84-286 g) . The incidence of anaemia requiring treatment was higher in women who developed malaria, 149/420 (35.4%) compared with 191/670 (28.5%), and was proportional to the number of parasitaemic episodes . Thus, despite regular antenatal clinic attendance with prompt detection and treatment of malaria (the currently employed antimalarial strategy in areas with multidrug-resistant P . falciparum), malaria still had a significant adverse effect on pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS) Anticancer Res, 1991 Jul-Aug, 11(4), 1379 - 82 Distribution, DNA damage and cytotoxic effects of etoposide in human tumor xenografts in vivo; Ullmann CA et al.; Mechanisms of resistance to VP-16 in vivo were studied using sensitive and multidrug resistant human breast tumor (MCF-7) cells, implanted bilaterally in nude mice . Administration of VP-16 (40 mg/kg, i.p.) indicated that there were no significant differences in either accumulation and retention of VP-16 or in the drug-induced bulk DNA damage in sensitive or resistant solid xenografts . Furthermore, under these conditions, no differential cytotoxic response to VP-16 was observed in solid tumors. Anal Biochem, 1991 Jul, 196(1), 161 - 9 Quantitation of mRNA by the kinetic polymerase chain reaction assay: a tool for monitoring P-glycoprotein gene expression; Hoof T et al.; The overexpression of P-glycoprotein (mdr1) induces the phenotype of multidrug resistance to many chemically unrelated drugs . Absolute mdr1 mRNA levels in tissues, neoplasms and cell lines from various rodents and man were estimated by primer-directed reverse transcription (RT) and subsequent polymerase chain reaction (PCR) with 32P-labeled nucleotide . Aliquots taken during PCR were analyzed for product formation by two-dimensional densitometry of autoradiograms of separated cDNA on dried agarose gels . The kinetic RT/PCR assay was calibrated for the range of 10(-3) to 10(3) amol of specific mRNA by utilizing mdr1 RNA transcribed from a full-length cDNA as the external standard and aldolase mRNA as the internal standard in order to assess RNA degradation of the specimen . For various cDNA fragments differing between 200 and 600 bp in size, the yield of cDNA during logarithmic growth increased by 1.78 +/- 0.02 per cycle . Hence, the sensitive and reproducible quantitation of transcript is feasible by monitoring RT/PCR kinetics without the need for any competing cRNA or cDNA fragment provided that a high-performance thermal cycler is employed for PCR. Anticancer Drug Des, 1991 Jul, 6(3), 189 - 93 The new potent immunosuppressant FK-506 reverses multidrug resistance in Chinese hamster ovary cells; Epand RF et al.; The macrolide FK-506, produced by Streptomyces tsukubaensis, is effective in sensitizing a multidrug resistant strain of Chinese hamster ovary cells to the cytotoxic action of vinblastine . FK-506 also promotes Adriamycin accumulation into both wild type and resistant cell lines . FK-506 may be a useful drug to enhance the effectiveness of anti-tumour cytotoxic drugs. Anticancer Drug Des, 1991 Jul, 6(3), 179 - 88 Enhancement of activities of anti-tumor drugs by dipyridamole against multidrug-resistant human hepatoma PLC/PRF/5 cells; Tatsuta T et al.; Dipyridamole (DPM) at 10 microM enhanced the cytotoxicity of anti-tumor drugs, which were associated with multidrug resistance, more in multidrug-resistant human hepatoma PLC/PRF/5 cells (PLC/COL) than in its parental cells (PLC/S) . DPM increased, dose-dependently, the intracellular accumulation of {3H}vinblastine in PLC/COL . However, the effect was immediately diminished by its removal from the medium, indicating that DPM needed to be present together with the anti-tumor drugs to enhance the intracellular accumulation of the drugs . DPM inhibited the efflux of {3H}vinblastine from the PLC/COL cells, the binding of {3H}vinblastine to membrane vesicles of PLC/COL, and the binding of {3H}azidopine to P-glycoprotein in the plasma membrane of PLC/COL . Apparently DPM binds to P-glycoprotein and inhibits active efflux . {14C}labeled DPM was quickly incorporated into the cells and the cellular level of {14C}DPM reached a plateau after 5 min . It was slightly higher in PLC/S than in PLC/COL . The cellular {14C}DPM quickly disappeared after its removal from the medium . These results indicate that DPM binds quickly but reversibly to various kinds of cellular proteins including P-glycoprotein and inhibits active efflux of some anti-tumor drugs in multi-drug-resistant tumor cells, resulting in the enhancement of the activities of these drugs. Am J Trop Med Hyg, 1991 Jul, 45(1), 98 - 111 Characteristics of multidrug resistance in Plasmodium and Leishmania: detection of P-glycoprotein-like components; Grogl M et al.; Multidrug-resistance (MDR) in neoplastic cells is frequently characterized by the overexpression of P-glycoprotein (PGP), a 170 kDa transmembrane glycoprotein that binds multiple cytotoxic drugs as well as calcium channel antagonists . Chloroquine resistance in Plasmodium falciparum appears to be analogous to MDR in neoplastic cells, where the induction of resistance with one drug confers resistance to other structurally and functionally unrelated drugs . To test the hypothesis that chloroquine resistance in P . falciparum and antimony resistance in Leishmania is mediated by a similar mechanism of MDR in mammalian neoplastic cells, a PGP-specific monoclonal antibody (C219) was used to determine the presence of PGP genes in resistant and sensitive Plasmodium and Leishmania parasites by indirect immunofluorescence assays and Western blotting procedures . These PGP-like components were detected in both drug-sensitive and -resistant Plasmodium and Leishmania cells . A 40-42 kDa component was observed to be greater in a chloroquine-resistant P . berghei (C line) than in a chloroquine-susceptible P line . Differences observed between Pentostam-resistant and -sensitive Leishmania promastigote clones and isolates included the increased expression of 96-106 and 23-25 kDa peptides in drug-resistant L . enrietti, and increased amounts of two different peptides in two drug-resistant L . panamensis clones (i.e., 96-106 and 43-45 kDa in WR-746-CL4, and 53 and 23-25 kDa in kDa) in amastigotes as in MDR KB carcinoma cells (KB-V1) . Comparative indirect immunofluorescent studies suggested that a correlation existed between the degree of antimony susceptibility and the concentration of the moiety recognized by C219 in two L . panamensis clones . Binding of the C219 monoclonal antibody to the PGP-like component of Leishmania was blocked by Pentostam, while the binding of C219 to multiple-drug resistant KB-V1 PGP was not inhibited by Pentostam, regardless of the PGP concentration . This suggests some degree of specificity in the binding of Pentostam to the Leishmania PGP-like components . In addition, these studies have demonstrated that drug-sensitive Leishmania accumulate two to five times more 125Sb-Pentostam than resistant clones. Br J Cancer, 1991 Jul, 64(1), 15 - 22 Multidrug resistance-associated antigens on drug-sensitive and -resistant human tumour cell lines; Mirski SE et al.; In this paper the biochemical properties of the antigens detected by six murine monoclonal antibodies (MAbs) are described . These MAbs react selectively with the multidrug-resistant small cell lung cancer (SCLC) cell line, H69AR, compared to its sensitive parent cell line, H69 (Mirski & Cole, 1989) . Because H69AR cells do not overexpress P-glycoprotein, the antigens detected by these MAbs may be markers for non-P-glycoprotein-mediated mechanisms of resistance . We found that the 36 kDa protein precipitated by MAb 3.186 is phosphorylated and has a pI of approximately 6.7 . The 55 kDa protein precipitated by MAb 3.50 is also phosphorylated and has a pI of approximately 5.7 . Several observations suggest that MAbs 3.80, 3.177 and 3.187 recognise the same 47 kDa molecule and hence only MAb 3.187 was characterised further . This MAb precipitates an acidic protein which runs as a streak on isoelectric focusing gels . The 25 and 22.5 kDa cell surface proteins precipitated by MAb 2.54 both have a pI of approximately 7.6 . Treatment of immunoprecipitates with glycosidase F indicated that none of the proteins detected by MAbs 2.54, 3.187, 3.50 and 3.186 have large N-linked carbohydrates . The peptide nature of the epitopes detected by MAbs 2.54 and 3.186 was unequivocally demonstrated by precipitation from in vitro translation products of H69AR RNA . The antigens detected by MAbs 3.50 and 3.187 were not detectable in immunoprecipitates of translation products but the epitopes are probably peptides because they were destroyed by boiling in sodium dodecyl sulphate . When the reaction of the MAbs with a panel of 15 paired drug-sensitive and -resistant cell lines was examined in a cell enzyme-linked immunosorbent assay, only a few resistance associated reactions were observed . Most of the reactions were either negative or not resistance-associated . When tested with three SCLC cell lines, MAb 3.187 reacted in a manner consistent with the relative resistance of the cell lines . Antigens that had similar electrophoretic mobility to those from H69AR cells were precipitated from extracts of five human cell lines of various tumour types . These data indicate that the cross-reactivities of the MAbs are due to antigens shared among the cell lines and not just the expression of common epitopes on different proteins . Resistance-associated proteins with the biochemical properties of the antigens described in this paper have not been reported previously and they remain potential markers for the as yet to be determined mechanisms of drug resistance in SCLC and other human malignancies. Leukemia, 1991 Jul, 5(7), 592 - 7 P-glycoprotein expression and in vitro reversion of doxorubicin resistance by verapamil in clinical specimens from acute leukaemia and myeloma; Solary E et al.; The expression of the P-glycoprotein which is associated with the development of multidrug resistance in various cell lines was investigated in 87 fresh acute leukaemia and multiple myeloma samples using the specific mouse monoclonal antibody MRK16 in an indirect immunofluorescence assay . Considering a 10% positive cell cut-off value, a heterogeneous expression of P-glycoprotein was observed in 5/22 (22.7%) de novo acute leukaemias, 7/22 (31.8%) relapse or secondary acute leukaemias, 14/27 (51.8%) acute transformation of myeloproliferative or myelodysplastic syndromes and 5/16 (31.2%) multiple myelomas . This expression was not associated with specific cytogenetic abnormalities, especially alterations of chromosome 7q . Verapamil, a calcium channel blocker, has been demonstrated to circumvent the multidrug resistance in cell lines, possibly by interfering with P-glycoprotein function . Using the microculture tetrazolium assay, verapamil was demonstrated to increase the sensitivity of fresh leukaemic or myeloma cells to doxorubicin in 19/43 (43.1%) samples . The doxorubicin IC50 level and the capacity of verapamil to increase the sensitivity of blast cells to doxorubicin in vitro did not correlate with the expression of P-glycoprotein . We conclude that high non-cytotoxic concentrations of verapamil were able to increase the in vitro doxorubicin sensitivity of fresh acute leukaemia and myeloma cells without detectable expression of the P-glycoprotein. Blood, 1991 Jul 1, 78(1), 44 - 50 Multidrug-resistant myeloma: laboratory and clinical effects of verapamil as a chemosensitizer; Salmon SE et al.; Verapamil was evaluated as a chemosensitizer for reversing multidrug resistance in multiple myeloma both in vitro and in clinical trials . Bone marrows from 59 myeloma patients in relapse were evaluated for several resistance parameters: expression of p-glycoprotein (MDR1), doxorubicin (Adriamycin) and vincristine sensitivity, and the ability of added verapamil to reduce resistance to the cytotoxic agents . We found that verapamil was capable of sensitizing myeloma cells that exhibited resistance to doxorubicin and vincristine in vitro, but did not enhance sensitivity of cells that were drug sensitive (P less than .001) . Myeloma cells expressing MDR1 immunohistochemically tended to be more doxorubicin resistant in vitro than MDR1-negative cells . In the clinical trials, 22 patients with myeloma refractory to vincristine-Adriamycin-dexamethasone (VAD) were treated with VAD plus high-dose intravenous verapamil (Ve) . Among the 22 patients treated with VAD/Ve, five achieved a partial remission (23%) . The median relapse-free survival for the VAD/Ve responders was 5.4 months and their overall survival from the start of VAD/Ve was better than that of the nonresponders . Among the subset of 10 patients whose myeloma cells were MDR1 positive, four responded clinically (40%), whereas none of five patients with MDR1-negative myeloma cells achieved remission with VAD/Ve . We also observed that myeloma cells from three of four VAD/Ve clinical responders exhibited in vitro chemosensitization with verapamil, whereas in vitro verapamil chemosensitization was seen in only one of six clinical nonresponders . Our observations demonstrate that clinical reversal of multidrug resistance can be achieved in some patients with VAD-refractory myeloma with the use of verapamil . In addition to their value in drug development, in vitro tests of MDR1 expression and of chemosensitizers plus cytotoxic drugs on the patients' bone marrow myeloma cells may identify patients who will respond clinically to chemosensitizer-containing regimens . We anticipate that chemosensitizer regimens capable of inhibiting multidrug resistance will play an increasing role in the treatment of hematologic malignancies, including B-cell neoplasms such as multiple myeloma and the non-Hodgkin's lymphomas. Cancer Res, 1991 Jul 1, 51(13), 3345 - 52 Non-P-glycoprotein-mediated multidrug resistance in a small cell lung cancer cell line: evidence for decreased susceptibility to drug-induced DNA damage and reduced levels of topoisomerase II; Cole SP et al.; Data obtained from clinical samples suggest that non-P-glycoprotein mechanisms of multidrug resistance are likely to be important in small cell lung cancer . The H69AR cell line was derived from the H69 small cell lung cancer cell line by selection in doxorubicin (adriamycin) and does not overexpress P-glycoprotein as detected by monoclonal antibody C219 (S.E.L . Mirski et al., Cancer Res., 47:2594, 1987) . In the present study, we have used the polymerase chain reaction to verify that H69AR cells do not overexpress P-glycoprotein . Further, transport studies with radiolabeled daunomycin, VP-16, and vinblastine demonstrate that differences in net drug accumulation or efflux are not part of the resistance phenotype of H69AR cells . To determine if H69 and H69AR cells differ in their susceptibility to drug-induced DNA damage, DNA single-strand breaks (SSB) generated by VP-16 and Adriamycin were measured using the alkaline filter elution assay . Readily detectable SSB were produced in intact H69 cells by 5 microM VP-16, but 100 microM drug was required to cause similar damage in H69AR cells . H69AR cells were also resistant to SSB induction by Adriamycin . The formation of SSB by VP-16 was similarly reduced in isolated H69AR nuclei, indicating that resistance to this drug resides, at least in part, in the nucleus . No significant differences were observed in the rate or extent of repair of VP-16-induced DNA SSB in H69 and H69AR cells . The reduced susceptibility to drug-induced SSB may result from alterations in topoisomerase II, since less immunoreactive topoisomerase II was found in H69AR cells compared to H69 cells . However, changes in topoisomerase II cannot explain the resistance of H69AR cells to such drugs as the Vinca alkaloids and gramicidin D, indicating that multiple mechanisms contribute to drug resistance in this small cell lung cancer cell line. Mol Cell Biol, 1991 Jul, 11(7), 3407 - 18 A possible role for a mammalian facilitative hexose transporter in the development of resistance to drugs; Vera JC et al.; We show that D- but not L-hexoses modulate the accumulation of radioactive vinblastine in injected Xenopus laevis oocytes expressing the murine Mdr1b P-glycoprotein . We also show that X . laevis oocytes injected with RNA encoding the rat erythroid/brain glucose transport protein (GLUT1) and expressing the corresponding functional transporter exhibit a lower accumulation of {3H}vinblastine and show a greater capacity to extrude the drug than do control oocytes not expressing the rat GLUT1 protein . Cytochalasin B and phloretin, two inhibitors of the mammalian facilitative glucose transporters, can overcome the reduced drug accumulation conferred by expression of the rat GLUT1 protein in Xenopus oocytes but have no significant effect on the accumulation of drug by Xenopus oocytes expressing the mouse Mdr1b P-glycoprotein . These drugs also increase the accumulation of {3H}vinblastine in multidrug-resistant Chinese hamster ovary cells . Cytochalasin E, an analog of cytochalasin B that does not affect the activity of the facilitative glucose transporter, has no effect on the accumulation of vinblastine by multidrug-resistant Chinese hamster cells or by oocytes expressing either the mouse Mdr1b P-glycoprotein or the GLUT1 protein . In all three cases, the drug verapamil produces a profound effect on the cellular accumulation of vinblastine . Interestingly, although immunological analysis indicated the presence of massive amounts of P-glycoprotein in the multidrug-resistant cells, immunological and functional studies revealed only a minor increase in the expression of a hexose transporter-like protein in resistant versus drug-sensitive cells . Taken together, these results suggest the participation of the mammalian facilitative glucose transporter in the development of drug resistance. J Clin Endocrinol Metab, 1991 Jul, 73(1), 18 - 29 Mitotane enhances cytotoxicity of chemotherapy in cell lines expressing a multidrug resistance gene (mdr-1/P-glycoprotein) which is also expressed by adrenocortical carcinomas; Bates SE et al.; P-Glycoprotein (Pgp), product of the mdr-1 gene, is a 130- to 180-kDa plasma membrane phosphoglycoprotein which mediates multidrug resistance in cell culture by increasing efflux of the natural product chemotherapeutic agents . High levels of expression of mdr-1/Pgp are found in both the normal adrenal and adrenocortical cancers . By RNA in situ hybridization the expression in adrenocortical cancer is shown to be widely distributed . The present study demonstrates that decreased drug accumulation mediated by mdr-1/Pgp can be overcome by clinically achievable concentrations of mitotane (o,p'-DDD) . The increase in drug accumulation with the addition of mitotane is due at least in part to a decrease in drug efflux and results in an increase in cytotoxicity when agents of the natural product class are used . This effect is observed in cells with a broad range of mdr-1/Pgp expression, including levels comparable to those found in most adrenocortical cancers . Similar increases in drug accumulation can be demonstrated in an unselected adrenocortical cancer cell line that expresses mdr-1/Pgp . The finding that multidrug resistance mediated by mdr-1/Pgp can be reversed by mitotane provides a rational basis for exploring the use of mitotane in combination with natural product chemotherapeutic agents in adrenocortical cancer. Res Microbiol, 1991 Jul-Aug, 142(6), 701 - 4 Site-specific recombination and shuffling of resistance genes in transposon Tn21; Avila P et al.; Many multidrug-resistant transposons found in natural isolates of Gram-negative bacteria are close relatives of Tn21 . Thus, the Tn21 subgroup of the Tn3 family of transposable elements is the most successful homogeneous group in acquiring resistance to newly introduced antibiotics . This paper summarizes the mode of acquisition of resistance genes by these elements. Biochem Pharmacol, 1991 Jun 15, 41(12), R21 - 6 Effect of the calmodulin inhibitor trifluoperazine on phosphorylation of P-glycoprotein and topoisomerase II: relationship to modulation of subcellular distribution, DNA damage and cytotoxicity of doxorubicin in multidrug resistant L1210 mouse leukemia cells; Ganapathi R et al.; The results from the present study using the sensitive and progressively DOX resistant L1210 model system demonstrated that the effects of TFP are not due to redistribution of DOX to the nucleus, and modulation of cytotoxicity is related to effects on DOX-induced DNA strand breaks . Although TFP affects phosphorylation of PGP and TOPO II (R2 greater than R1), the comparable DNA strand breaks at lower DOX levels with TFP in the resistant sublines suggest that modulation of TOPO II function related to drug-induced DNA damage by calmodulin-mediated events may be an important mode of action. Biochem Pharmacol, 1991 Jun 15, 41(12), 1967 - 79 Study of molecular markers of resistance to m-AMSA in a human breast cancer cell line . Decrease of topoisomerase II and increase of both topoisomerase I and acidic glutathione S transferase; Lefevre D et al.; Resistance to 0.8 microM 4'-(9-acridinylamino)methanesulphon-m-anisidide (m-AMSA) was induced by stepwise increases of drug concentration in the human tumor cell line CALc18 originating from a breast adenocarcinoma . The resistant cell line CALc18/AMSA exhibited a resistance index of 10 and a cross-resistance to other topoisomerase II inhibitors . A 3-fold decrease in the levels of topoisomerase II decatenating activity was found in CALc18/AMSA cells . By contrast, topoisomerase I activity was increased by about 3-fold in resistant cells . Interestingly this line was hypersensitive to camptothecin, a specific inhibitor of topoisomerase I . Restriction endonuclease patterns of the topoisomerase I and topoisomerase II loci were found to be identical in CALc18/AMSA and CALc18 with no evidence of gene amplification and rearrangements . Alkaline elution of m-AMSA-treated cells showed that DNA single strand breaks and DNA-protein crosslinks were decreased in CALc18/AMSA . The DNA lesions also obtained in m-AMSA-treated nuclei indicated that no drug uptake modification occurred in both cells . Moreover, the in vitro m-AMSA-induced DNA cleavage per unit of decatenating activity and the inhibitory effects of antitumoral drugs on decatenation were not found to be different with topoisomerase II from sensitive or resistant cells . However the specific cleavage induced by m-AMSA/per mg of crude protein from resistant cells was 2 to 3 times decreased . Multidrug resistance gene transcripts were not detected while levels of acidic glutathione S transferase mRNA were found to be 8 to 10-fold greater in resistant than in sensitive cell line with no amplification of the gene . In conclusion, the diminution of topoisomerase II activity and the increase of both topoisomerase I and acidic glutathione S transferase transcripts could contribute to the resistant phenotype of these breast cancer cells. Nurs Clin North Am, 1991 Jun, 26(2), 331 - 9 Chemotherapy update; Miaskowski C; The administration of chemotherapy is one of the major forms of cancer treatment . Recent progress in the use of chemotherapeutic agents has evolved from an understanding of the basic mechanisms of tumor cell kinetics and the molecular and biochemical basis for individual and multidrug resistance patterns . These advances have led to the development of novel approaches to the administration of cancer chemotherapeutic agents . Nurses must remain knowledgeable about these concepts to understand the mechanisms underlying the administration of various combinations of cancer chemotherapy. Southeast Asian J Trop Med Public Health, 1991 Jun, 22(2), 183 - 9 Comparison of mefloquine, chloroquine plus pyrimethamine-sulfadoxine (Fansidar), and chloroquine as malarial prophylaxis in eastern Thailand; Boudreau EF et al.; From July 1983 to March 1984 a randomized double blind prophylactic trial in Thai gem miners working across the border in Cambodia was conducted to determine the prophylactic efficacy of 3 drug regimens against P . falciparum and P . vivax malaria along the Thai-Cambodian border . Gem miners have a high incidence of malaria . Maximum duration of individual participation was 14 weeks . Of 334 participants in this study who were seen every 2 weeks, 145 received mefloquine 500 mg fortnightly, 112 received chloroquine 300 mg base weekly plus Fansidar (1000 mg sulfadoxine and 50 mg pyrimethamine) fortnightly and 77 received chloroquine as 300 mg base weekly . The significant reduction of vivax malaria in study subjects (compared to background incidence) implied good compliance with self administration of chloroquine in the intervening weeks between scheduled appointments . The attack rate in each prophylactic regimen was 2188 cases/1000/year with mefloquine, 8338 cases/1000/year with chloroquine-Fansidar and 10,207 cases/1000/year receiving chloroquine alone . There was a 79% prophylactic efficacy for mefloquine and 18% efficacy for the chloroquine plus Fansidar regimen compared to chloroquine . Using life table analysis, 56% of the mefloquine group, 6% of the chloroquine-Fansidar group and 4% of the chloroquine group were malaria free at the end of the 14 weeks study . The chloroquine plus sulfadoxine-pyrimethamine regimen prescribed for prophylaxis is no longer effective for multidrug resistant strains of P . falciparum in the study area . This study also seriously questions the efficacy of mefloquine prophylaxis. Anticancer Drugs, 1991 Jun, 2(3), 279 - 83 FK-506 (fujimycin) reverses the multidrug resistance of tumor cells in vitro; Pourtier-Manzanedo A et al.; Cyclosporin A (CsA) and FK-506 have similar immunosuppressive activity profiles and cyclophilin-like intracellular targets . Since CsA can reverse the multidrug resistance of tumor cells showing P-glycoprotein-mediated drug efflux, the possible resistance-modulating activity of FK-506 was evaluated in vitro with multidrug-resistant P388 cells and their sensitive parental controls . Higher concentrations of FK-506 than CsA were needed to achieve a similar degree of chemosensitization, suggesting that FK-506 might interact less efficiently than CsA with the P-glycoprotein expressed in multidrug-resistant tumor cells . However, FK-506 was active on a broader range of concentrations than CsA, particularly because of direct cytostatic effects of CsA which appeared at concentrations only slightly higher than those required to show a significant resistance-modulating activity. Curr Opin Oncol, 1991 Jun, 3(3), 537 - 44 Renal cell carcinoma; Reese JH; Renal cell carcinoma represents a significant challenge to surgeons and oncologists treating urologic malignancies . Diagnostically, it is critically important to identify the precise extent of the tumor prior to therapeutic intervention . Therapeutically, a number of controversies continue to be debated, including the role of renal-conserving surgery and the role of surgery in patients with metastatic disease . New research is beginning to identify factors involved in the multidrug-resistant properties of these tumors that may allow us, in the future, to treat these tumors more effectively with systemic c