Bull Cancer, 1994 May, 81(5), 409 - 13 {Value of rhodamine 123 in the detection of minor amounts of multidrug resistant cells}; Maynadie M et al.; The neoplasias resistance to chemotherapy is mainly due to multidrug resistance phenomenon (MDR) mediated by an ATP-dependent efflux pump called P-glycoprotein . This function can be reversed by many multidrug reversing agents so numerous chemotherapy regimens have been initiated in malignancies . To make sure the success of these protocols it is necessary to detect as soon and as certain as possible the presence of resistant cells among malignant population . We have chosen to evaluate functional test using rhodamine 123 in this aim in view . We have made various mixtures of resistant ans sensitive cells of three cell lines . Rhodamine 123 allows to detect 1% of resistant cells among sensitive cells . Influence of dead cells on the interpretation is discussed. Bull Cancer, 1994 May, 81(5), 400 - 8 {Structure and function of P-glycoprotein}; Robert J; P-glycoprotein is a membrane ATPase transporter responsible for multidrug resistance . Its primary structure is known from cDNA sequencing, but its tri-dimension structure remains hypothetical . Its physiological role in detoxification, as well as its involvement in anticancer drug transport, are no longer questioned, but its molecular mechanism of action remains unknown . It appears likely that it extrudes the drugs laterally, in the plane of the membrane, that several distinct drug or modulator binding sites exist, that its activity is regulated by phosphorylation . Purification and reconstitution of P-glycoprotein will probably allow to better understand its mechanism of action. Bull Cancer, 1994 May, 81(5), 392 - 9 {The multidrug resistance phenotype: some morphological and biological characteristics except efflux pump}; Jardillier JC et al.; Recent data from the literature together with personal results strongly suggest that multidrug resistance phenotype is overwhelming the sole expression of P170 glycoprotein efflux pump . Morphological alterations have been put in evidence in MDR cells after transmission and scanning electron microscopy . They include presence of osmiophilic vesicles and modifications of nuclear and nucleolar chromatin . Biological characteristics include the hypersecretory pattern of lysosomal enzymes from MDR cells . Such a fact could be more or less related to the increased occurrence of mdr1 RNA in metastasis, especially in breast cancers, compared to primary tumors . If the P170-mediated efflux is one of the key mechanism of MDR, a decreased influx of anticancer drugs cannot be excluded . Liposomes, for instance made of cardiolipin, are thus able to increase the intracellular drug uptake of vinblastine without any action upon efflux mechanism. Bull Cancer, 1994 May, 81(5), 386 - 91 {Pharmacological control of P-glycoprotein expression}; Muller C et al.; Calcium channel inhibitors, such as verapamil, have been identified as having the ability to modulate the multidrug-resistant (MDR) phenotype due to overexpression of P-glycoprotein (Pgp) . We have studied the effect of verapamil on Pgp expression levels in a cell line originating from acute myeloblastic leukemia and resistant to adriamycin, K562/ADR . In this line, the addition of 15 microM verapamil in the culture medium gives a 3-fold decrease of Pgp expression after 72 hours of treatment . Similar results have been obtained for two other MDR cell lines, which suggest that this phenomenon is not specific of a single model . The level of mdr1 mRNAs is decreased in the presence of verapamil (with a maximum effect obtained at the 24th hour), which suggests that the mechanism of action of verapamil is transcriptional and/or post-transcriptional . We have also studied the effect of verapamil on the level of expression of mdr1 mRNAs in non-drug selected cells such as the HEL line (human acute myeloblastic leukemia) and the parental K562 line, which present a very low level of expression of Pgp, detectable only by PCR . In these lines, verapamil treatment has no effect on the level of expression of mdr1 mRNAs . The effect of verapamil is therefore restricted to drug-selected lines presenting high levels of Pgp expression . The impact of the negative regulation of Pgp expression on the MDR phenotype has been studied in the K562/ADR line . When the cells are treated for 72 h by verapamil, there is a decrease of resistance and an increase of intracellular accumulation of anticancer agents such as daunorubicin or vinblastine . Negative regulation of Pgp expression appears therefore as a possible strategy for MDR phenotype reversal . The effect of verapamil, whose molecular mechanism of action is being studied, could constitute a basis for this strategy. Bull Cancer, 1994 May, 81(5), 381 - 5 {Cellular resistance to DNA-topoisomerase II inhibitors}; Jacquemin-Sablon A et al.; Chinese hamster lung cells resistant to 9-OH-ellipticine (DC-3F/9-OH-E) present a complex phenotype . These cells, which are about 150-fold resistant to 9-OH-E, display a cross-resistance to other topo-II inhibitors, such as m-AMSA or VP-16, which stabilize the cleavable complex . In addition, these cells display also a cross-resistance to suramin, which is also a topo-II inhibitor, but does not stabilize the cleavable complex . Finally, DC-3F/9-OH-E present a multidrug-resistant phenotype (MDR) which confers a cross-resistance to natural products such as actinomycin D, taxol or vincristine, due to a decrease of cellular accumulation of these drugs . Analysis of expression of the genes encoding topo-II alpha and beta, and the evaluation of both enzyme forms by immunoblotting, revealed that DC-3F cells contained about 20-fold less of the beta form than of the alpha form . The alpha form was decreased by about 4-5-fold in DC-3F/9-OH-E, whereas the beta form became undetectable . Purification and characterization of topo-II activities in sensitive and resistant cells is presently in progress . Analysis of the expression of pgp1, 2, 3 genes, involved in the MDR phenotype in hamster, by Northern blotting or by immunoblotting, has shown that the MDR phenotype in DC-3F/9-OH-E cells is due to the overexpression of pgp1 gene . In these cells, pgp3 expression is positively regulated by myc oncogene expression . Overexpression of the myc gene is followed by an overexpression of the pgp3 gene and is associated to a reversal of the MDR phenotype. Biochem Pharmacol, 1994 Apr 29, 47(9), 1601 - 6 Analysis of MRP mRNA in mitoxantrone-selected, multidrug-resistant human tumor cells; Futscher BW et al.; MRP, a gene recently isolated from a non-P-glycoprotein-mediated multidrug-resistant small cell lung cancer cell line, is a candidate multidrug-resistance gene . Mitoxantrone, an anthracenedione antitumor agent, frequently selects for non-P-glycoprotein-mediated multidrug resistance in in vitro models . To determine whether mitoxantrone-selected multidrug resistance was due to overexpression of MRP, we examined the expression of MRP in four mitoxantrone-selected, multidrug-resistant human tumor cell lines, using a reverse transcriptase/polymerase chain reaction assay . Results from these experiments suggest that overexpression of MRP does not appear to play a primary role in mitoxantrone-selected multidrug resistance in these cell lines, and that other novel drug-resistance mechanisms are likely. J Biol Chem, 1994 Apr 29, 269(17), 12797 - 803 Solubilization and characterization of the overexpressed PDR5 multidrug resistance nucleotide triphosphatase of yeast; Decottignies A et al.; A 160-kDa plasma membrane protein of the yeast Saccharomyces cerevisiae was overexpressed by mutating the PDR1 or the PDR3 transcription factor gene . The protein is the membrane-bound ATP binding cassette transporter PDR5 (Balzi, E., Wang, M., Leterme, S., Van Dyck, L., and Goffeau, A . (1994) J . Biol . Chem . 269, 2206-2214) . PDR5 was solubilized with n-dodecyl-beta-D-malto-side and separated from the PMA1 plasma membrane H(+)-ATPase by glycerol gradient centrifugation . The PDR5 protein hydrolyzes nucleoside diphosphates and triphosphates . This activity is sensitive to low concentrations of vanadate, of oligomycin, and of a variety of hydrophobic compounds . Many of these properties liken PDR5 to the purified mammalian P-glycoprotein responsible for multidrug resistance. N Engl J Med, 1994 Apr 28, 330(17), 1179 - 84 The effect of directly observed therapy on the rates of drug resistance and relapse in tuberculosis; Weis SE et al.; BACKGROUND . Tuberculosis has reemerged as an important public health problem, and the frequency of drug resistance is increasing . A major reason for the development of resistant infections and relapse is poor compliance with medical regimens . In Tarrant County, Texas, we initiated a program of universal directly observed treatment for tuberculosis . We report the effect of the program on the rates of primary and acquired drug resistance and relapse among patients with tuberculosis . METHODS . We collected information on all patients with positive cultures for Mycobacterium tuberculosis in Tarrant County from January 1, 1980, through December 31, 1992 . Through October 1986, patients received a traditional, unsupervised drug regimen . Beginning in November 1986, nearly all patients received therapy under direct observation by health care personnel . RESULTS . A total of 407 episodes in which patients received traditional treatment for tuberculosis (January 1980 through October 1986) were compared with 581 episodes in which therapy was directly observed (November 1986 through December 1992) . Despite higher rates of intravenous drug use and homelessness and an increasing rate of tuberculosis during this 13-year period, the frequency of primary drug resistance decreased from 13.0 percent to 6.7 percent (P < 0.001) after the institution of direct observation of therapy, and the frequency of acquired resistance declined from 14.0 percent to 2.1 percent (P < 0.001) . The relapse rate decreased from 20.9 percent to 5.5 percent (P < 0.001), and the number of relapses with multidrug-resistant organisms decreased from 25 to 5 (P < 0.001) . CONCLUSIONS . The administration of therapy for M . tuberculosis infection under direct observation leads to significant reductions in the frequency of primary drug resistance, acquired drug resistance, and relapse. Proc Natl Acad Sci U S A, 1994 Apr 26, 91(9), 3497 - 504 Cell biological mechanisms of multidrug resistance in tumors; Simon SM et al.; Multidrug resistance (MDR) is a generic term for the variety of strategies tumor cells use to evade the cytotoxic effects of anticancer drugs . MDR is characterized by a decreased sensitivity of tumor cells not only to the drug employed for chemotherapy but also to a broad spectrum of drugs with neither obvious structural homology nor common targets . This pleiotropic resistance is one of the major obstacles to the successful treatment of tumors . MDR may result from structural or functional changes at the plasma membrane or within the cytoplasm, cellular compartments, or nucleus . Molecular mechanisms of MDR are discussed in terms of modifications in detoxification and DNA repair pathways, changes in cellular sites of drug sequestration, decreases in drug-target affinity, synthesis of specific drug inhibitors within cells, altered or inappropriate targeting of proteins, and accelerated removal or secretion of drugs. Presse Med, 1994 Apr 23, 23(16), 731 - 3 {Association of tuberculosis and HIV infection}; Perronne C; Eight million people contract tuberculosis every year, 95% of them in developing countries, and one-third of the world's population is infected with Mycobacterium tuberculosis . Annually, tuberculosis causes three million deaths (in Africa 26% of the avoidable deaths) . The main cause of dissemination is the absence of early diagnosis and insufficient treatment . Today, 3% of the new cases of tuberculosis are related to infection with the human immunodeficiency virus (HIV), a proportion which is rising rapidly . HIV infection does not change the classic rules of treatment; rifampicin, isoniazid, ethambutol and pyrazinamide for 2 months followed by at least 4 more months with a two-drug regimen (rifampicin and isoniazid) . No-compliance is the major cause of recurrence, together with the risk of infection with another strain of M . tuberculosis . Certain authors suggest that in Africa, due to poor compliance and the lack of a sufficient provision of major antituberculous agents, treatment should be continued for life in HIV positive patients . Others propose chemotherapy for an HIV infected patients who are healthy carriers of M . tuberculosis . The risk of selecting mutant strains could be avoided by limiting prophylaxis to non-febrile patients . Nevertheless, the long-term effect of generalized chemoprophylaxis on the epidemiology of resistant strains is unknown . The only method of screening for healthy carriers is the tuberculin skin test but interpretation is complicated by prior BCG vaccination and now by HIV infection . There are two crucial steps required to control tuberculosis in this era of the tuberculosis-HIV partnership . First, patients should have easy and cost-free access to antituberculous drugs and second, compliance must be improved . Certain barriers have been lifted, including the requirement of patient identification to obtain free drugs . Hospital staffs must renew their efforts and attempt to follow-up their patients to assure compliance after discharge . All these measures will be difficult to implement but are the price we must pay to eradicate a new rise in the incidence of tuberculosis and the risk of multidrug-resistant strains . The only alternative may well be a return to pre-antibiotic days. J Biol Chem, 1994 Apr 22, 269(16), 11751 - 9 Benzo{a}pyrene-resistant MCF-7 human breast cancer cells . A unique aryl hydrocarbon-nonresponsive clone; Moore M et al.; Wild-type MCF-7 human breast cancer cells were cultured for 3 months in 1 microM benzo{a}pyrene (BaP), and resistant clones were screened for inducibility of CYP1A1 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) . One of the BaP-resistant (BaPR) clones exhibited unique genotypic expression which distinguished it from both wild-type and drug-resistant (AdrR) variant MCF-7 cells . Glutathione levels, glutathione S-transferase activities, estrogen receptor levels, estrogen responsiveness, and expression of the multidrug-resistant MDR1 and MRP mRNA levels were similar in the wild-type and BaPR cells, whereas these parameters were reported to be altered in AdrR cells . In contrast, TCDD induced CYP1A1 gene expression and inhibited selected estrogen-induced responses in wild-type but not BaPR MCF-7 cells . Treatment of wild-type and BaPR cells with {3H}TCDD resulted in formation of the radiolabeled aryl hydrocarbon (Ah) 6 S nuclear receptor complex in both cell lines . The loss of Ah responsiveness in the BaPR variant cells correlated with the failure of the nuclear or transformed cytosolic Ah receptor complex to bind genomic dioxin-responsive elements as determined in gel retardation assays. J Biol Chem, 1994 Apr 22, 269(16), 12332 - 8 Human leukemia K562 cell mutant (K562/OA200) selected for resistance to okadaic acid (protein phosphatase inhibitor) lacks protein kinase C-epsilon, exhibits multidrug resistance phenotype, and expresses drug pump P-glycoprotein; Zheng B et al.; A human leukemia K562 cell mutant (K562/OA200) selected for resistance to okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A (PP1/PP2A), has been established . In wild type cells, the cytotoxicity of OA was associated with mitotic arrest and concentration- and time-dependent DNA fragmentation, a hallmark of apoptosis . The mutant was 100-fold more resistant to OA in terms of effects on these parameters . Although the synthesis of several proteins was altered, enzyme assay and immunoblot analysis indicated that the levels of PP1 and PP2A were unchanged in the mutant . Protein kinase C (PKC) assays and immunoblot analysis of calcium-dependent (cPKC) and calcium-independent (nPKC) isoforms revealed that nPKC-epsilon was strikingly absent in the mutant, which otherwise expressed in comparable amounts all other isotypes (cPKC-alpha, cPKC-beta, and nPKC-zeta) also present in the wild type . Northern blot analysis confirmed an absence of PKC-epsilon mRNA in the mutant cells . The OA200 cells were cross-resistant not only to another PP1/PP2A inhibitor, calyculin A, but also to structurally unrelated anticancer drugs (such as vinblastine and taxol) and furthermore, overexpressed the verapamil-sensitive drug pump P-glycoprotein at both the protein and mRNA levels . The mutant, however, was not cross-resistant to several PKC inhibitors tested including cardiotoxin, mastoparan, staurosporine, and an alkylphospholipid . Cardiotoxin, at a subtoxic concentration, enhanced by 6-fold vinblastine cytotoxicity in OA200 cells . These findings indicate that the multidrug resistance phenotype can be induced by cytotoxic agents other than conventional anticancer drugs, show that the development of multidrug resistance is not necessarily associated with increased cPKC activity, and identify certain PKC inhibitors that have potential as resistance modulators. Science, 1994 Apr 15, 264(5157), 375 - 82 Inactivation of antibiotics and the dissemination of resistance genes; Davies J; The emergence of multidrug-resistant bacteria is a phenomenon of concern to the clinician and the pharmaceutical industry, as it is the major cause of failure in the treatment of infectious diseases . The most common mechanism of resistance in pathogenic bacteria to antibiotics of the aminoglycoside, beta-lactam (penicillins and cephalosporins), and chloramphenicol types involves the enzymic inactivation of the antibiotic by hydrolysis or by formation of inactive derivatives . Such resistance determinants most probably were acquired by pathogenic bacteria from a pool of resistance genes in other microbial genera, including antibiotic-producing organisms . The resistance gene sequences were subsequently integrated by site-specific recombination into several classes of naturally occurring gene expression cassettes (typically "integrons") and disseminated within the microbial population by a variety of gene transfer mechanisms . Although bacterial conjugation once was believed to be restricted in host range, it now appears that this mechanism of transfer permits genetic exchange between many different bacterial genera in nature. Int J Cancer, 1994 Apr 15, 57(2), 229 - 39 Reversal of multidrug resistance by tyrosine-kinase inhibitors in a non-P-glycoprotein-mediated multidrug-resistant cell line; Takeda Y et al.; We have already established a human leukemia sub-line resistant to the growth-inhibitory effect of TPA (12-O-tetradecanoylphorbol 13-acetate) (K562/TPA) derived from K562 . K562/TPA was found to be a non-P-glycoprotein-mediated multidrug-resistant cell line, in which intracellular drug accumulation was not reduced . In K562/TPA, adriamycin (ADM) was distributed mainly in the cytoplasm and was scarcely observed in the nucleus . We determined the relative levels of multidrug-resistance-associated protein (MRP), which was recently identified as the novel transporter . The relative levels of MRP in K562/TPA were the same as in K562 . Although the catalytic activity of K562/TPA topoisomerase II was about half that of the parental cells, resistance to other drugs could not be explained by topoisomerase-II activity . To elucidate the mechanism of drug resistance in K562/TPA, we tried to find chemicals that would reverse the drug resistance . Tyrosine-kinase inhibitors enhanced the cytotoxicity of anti-neoplastic drugs against K562/TPA . Therefore we examined the modification of nuclear ADM accumulation in K562/TPA by one of these tyrosine-kinase inhibitors, genistein . Although the amount of ADM was decreased in the nuclei of K562/TPA cells, it was significantly increased after incubation in the presence of genistein . The formation of DNA single-strand breaks by ADM, etoposide, and ACNU was significantly lower in K562/TPA than in K562, but was significantly increased in the presence of genistein . These results suggest that genistein could overcome drug resistance by enhancing the accumulation of drug into the nuclear fraction of K562/TPA. Proc Natl Acad Sci U S A, 1994 Apr 12, 91(8), 3176 - 80 Drug-selected coexpression of human glucocerebrosidase and P-glycoprotein using a bicistronic vector; Aran JM et al.; Bicistronic cassettes under control of a single promoter have recently been suggested as useful tools for coordinate expression of two different foreign proteins in mammalian cells . Using the long 5' untranslated region of encephalomyocarditis virus as translational enhancer of the second gene, a bicistronic unit composed of cDNA for human P-glycoprotein {the product of the multidrug resistance gene, MDR1 (also called PGY1)} as selectable marker and cDNA for human glucocerebrosidase (GC; EC 3.2.1.45) (a membrane-associated lysosomal hydrolase) was constructed . NIH 3T3 cells transfected with a Harvey murine sarcoma virus retroviral vector carrying this bicistronic cassette (pHaMCG) express active P-glycoprotein and GC and expression of both proteins augments coordinately with selection for increased colchicine resistance . Percoll gradient analysis of homogenates showed that GC was targeted to the lysosomal fraction . The ability to select for expression of GC with natural product drugs after introduction of the pHaMCG retroviral vector may be useful in gene therapy strategies for Gaucher disease. Biochemistry, 1994 Apr 12, 33(14), 4163 - 74 Detection of oligomeric and monomeric forms of P-glycoprotein in multidrug resistant cells; Poruchynsky MS et al.; P-glycoprotein (P-gp) is thought to function as a drug efflux pump in multidrug resistant (MDR) cells . The functional form of P-gp in its native state is not known . Previous results from radiation target size analysis have suggested that P-gp occurs as dimers in MDR cell plasma membranes {Boscoboinik et al . (1990) Biochim . Biophys . Acta 1027, 225-228} . In this study, we used sucrose gradient velocity sedimentation to determine if P-gp oligomers could be retrieved from detergent extracts of hamster and human MDR cell lines . The proportion of P-gp recovered as higher order oligomers was dependent on the detergents used for solubilization of the cells . When a detergent such as CHAPS was used, 50% or more of the P-gp sedimented as higher order oligomers . In contrast, in the presence of SDS, only monomers were retrieved, but naturally occurring oligomers could be preserved if the cells were treated with a cross-linker prior to detergent solubilization . The oligomers and monomers were both able to bind the photoactive analog of ATP (8-azido{alpha-32P}ATP) or the drug {3H}azidopine in membrane preparations . P-gp is a phosphoprotein, and its phosphorylated state is thought to be important for function . When MDR cells were labeled with {32P}orthophosphate in vivo, we observed that the monomer and dimer were more highly phosphorylated than the larger oligomers, suggesting that these different forms of P-gp may be functionally distinct . The assembly of oligomers appears to occur in an early bisynthetic compartment, and asparagine-linked glycosylation is not required for their formation . Our findings indicate that oligomers of P-gp exist in MDR cells and raise the possibility that the dynamics of oligomer formation and dissociation may be important in the mechanism of action of P-gp. J Biol Chem, 1994 Apr 8, 269(14), 10739 - 46 Reversible transcriptional activation of mdr1 by sodium butyrate treatment of human colon cancer cells; Morrow CS et al.; We investigated the mechanism of sodium butyrate (NaB)-mediated induction of mdr1 mRNA in parental (wild type) and multidrug-resistant (Ad1000) SW620 colon cancer cell lines . NaB treatment resulted in reversible, time-dependent increases in nuclear run-on transcription of endogenous mdr1 in these cell lines that paralleled the reversible increases of mdr1 mRNA in both timing and magnitude . In contrast, NaB treatment had no effect on mdr1 mRNA stability . Thus, the effects of NaB on mdr1 mRNA levels are fully attributable to altered mdr1 transcription . Furthermore, NaB induces the expression of transiently transfected chloramphenicol acetyltransferase reporter plasmids that are under the transcriptional control of the mdr1 promoter (mdrCAT vectors) . Transfections using mdrCAT vectors modified by deletion and site-directed mutagenesis of the mdr1 promoter indicate that NaB-mediated induction of these vectors is at least partially dependent upon sequences present in the basal mdr1 promoter between -89 and +11 relative to the start site of transcription . The Y-box motif located between -82 and -73 contributes to NaB inducibility of mdrCAT vector expression in Ad1000 SW620 cells. Anticancer Drug Des, 1994 Apr, 9(2), 129 - 37 Synthesis and biological activity of 3'-deamino-3'-haloanthracyclines; Demetzos C et al.; 4'-O-Acetyl-3'-deamino-3'-chloro and 4'-O-acetyl-3'-deamino-3'-bromoepidaunorubicin analogs have been synthesized by condensation of daunomycinone with the corresponding hexopyranosyl chlorides . The glycosides obtained were less potent than adriamycin (ADR) in inhibiting the proliferation of tumor cells in vitro, but they have shown promising activity against a variety of multidrug resistant (MDR) cell lines. Am J Trop Med Hyg, 1994 Apr, 50(4), 522 - 6 New, antimalarial, tricyclic 1,2,4-trioxanes: evaluations in mice and monkeys; Posner GH et al.; We have concluded initial preclinical studies with synthetic trioxanes numbered 3-9 and have compared them with artemisinin (numbered 1) using CD-1 mice infected with Plasmodium berghei . Based on their antimalarial effectiveness in mice, two of these synthetic trioxanes were selected for evaluation in Aotus monkeys infected with multidrug-resistant (MDR) P . falciparum . Trioxane numbered 8 (12 and 48 mg/kg), trioxane numbered 9 (12 and 48 mg/kg) and arteether (numbered 2, 48 mg/kg) were administered intramuscularly in three 12-hr doses to A . lemurinus lemurinus (Panamanian owl monkeys) infected with the Vietnam Smith/RE strain of P . falciparum and monitored for parasitemia . Trioxane numbered 8 at 12 mg/kg cleared parasitemia in two monkeys, but recrudescence occurred in one animal . Treatment of the recrudescent infection with 48 mg/kg was curative . Infections in two monkeys treated initially with 48 mg/kg were cured (six-month follow-up) . Trioxane numbered 9 produced a similar outcome: 12 mg/kg suppressed parasitemia in two monkeys but was not curative; however, 48 mg/kg cured infections in all four monkeys treated . These preliminary observations show synthetic trioxanes numbered 8 and 9 to be as effective as arteether (numbered 2) against MDR in P . falciparum in the Aotus monkey. J Clin Oncol, 1994 Apr, 12(4), 835 - 42 Phase I trial of doxorubicin with cyclosporine as a modulator of multidrug resistance; Bartlett NL et al.; PURPOSE: To study the effects of cyclosporine (CsA), a modulator of multidrug resistance (MDR), on the pharmacokinetics and toxicities of doxorubicin . PATIENTS AND METHODS: Nineteen patients with incurable malignancies entered this phase I trial . Initially patients received doxorubicin alone (60 or 75 mg/m2) as a 48-hour continuous intravenous (i.v.) infusion . Patients whose tumors did not respond received CsA as a 2-hour loading dose of 6 mg/kg and a 48-hour continuous infusion of 18 mg/kg/d with doxorubicin . Target CsA levels were 3,000 to 4,800 ng/mL (2.5 to 4.0 mumol/L) . Doxorubicin doses were reduced to 40% of the prior dose without CsA, and then escalated until myelosuppression equivalent to that resulting from doxorubicin alone was observed . Doxorubicin pharmacokinetics were analyzed with and without CsA . RESULTS: Thirteen patients received both doxorubicin alone and the combination of doxorubicin and CsA . Mean CsA levels were more than 2,000 ng/mL for all cycles and more than 3,000 ng/mL for 68% of cycles . Dose escalation of doxorubicin with CsA was stopped at 60% of the doxorubicin alone dose, as four of five patients at this dose level had WBC nadirs equivalent to those seen with doxorubicin alone . Nonhematologic toxicities were mild . Reversible hyperbilirubinemia occurred in 68% of doxorubicin/CsA courses . The addition of CsA to doxorubicin increased grade 1 and 2 nausea (87% v 47%) and vomiting (50% v 10%) compared with doxorubicin alone . There was no significant nephrotoxicity . Paired pharmacokinetics were studied in 12 patients . The addition of CsA increased the dose-adjusted area under the curve (AUC) of doxorubicin by 55%, and of its metabolite doxorubicinol by 350% . CONCLUSION: CsA inhibits the clearance of both doxorubicin and doxorubicinol . Equivalent myelosuppression was observed when the dose of doxorubicin with CsA was 60% of the dose of doxorubicin without CsA . Understanding these pharmacokinetic interactions is essential for the design and interpretation of clinical trials of MDR modulation, and should be studied with more potent MDR modulators. Blood, 1994 Apr 1, 83(7), 1731 - 7 Interleukin-4 induces programmed cell death (apoptosis) in cases of high-risk acute lymphoblastic leukemia; Manabe A et al.; We investigated the effects of interleukin-4 (IL-4) on the survival of leukemic and normal B-cell progenitors cultured on bone marrow stroma . IL-4 (at 100 U/mL) was cytotoxic in 16 of 21 cases of B-lineage acute lymphoblastic leukemia, causing reductions in CD19+ cell numbers that ranged from 50% to greater than 99% (median 83.5%) of those in parallel cultures not exposed to the cytokine . All nine cases with the t(9;22)(q34;q11) or the t(4;11)(q21;q23), chromosomal features that are often associated with multidrug resistance and a fatal outcome, were susceptible to IL-4 toxicity . IL-4 cytotoxicity resulted from induction of programmed cell death (apoptosis); there was no evidence of cell killing mediated by T, natural killer, or stromal cells . IL-4 cytotoxicity extended to a proportion of normal B-cell progenitors . After 7 days of culture with IL-4 at 100 U/mL, fewer CD19+, CD34+ normal lymphoblasts (the most immature subset) survived: in five experiments the mean (+/- SEM) reduction in cell recoveries caused by IL-4 was 60.0% +/- 6.0% . By contrast, reductions in recovery of more differentiated bone marrow B cells (CD19+, CD34-, surface Ig+) were low (6.6% +/- 2.2%; P < .001 by t-test) . Our findings indicate that IL-4 is cytotoxic for human B-cell precursors and support clinical testing of IL-4 in cases of high-risk lymphoblastic leukemia resistant to conventional therapy. Cancer Res, 1994 Apr 1, 54(7), 1649 - 52 Expression complementary DNA library transfer establishes mrp as a multidrug resistance gene; Kruh GD et al.; The emergence of drug-resistant cancer cells is a major obstacle to cancer treatment . Resistant cells often display a multidrug-resistant phenotype that reduces the promise of combination chemotherapy, the classic approach to the prevention of drug resistance . mdr1, a member of the ABC cassette superfamily of transporters which encodes an energy-dependent drug efflux pump, is the only gene known to confer the multidrug-resistant phenotype . Other multidrug resistance mechanisms must exist, since cell lines which have this phenotype in the absence of mdr1 overexpression have been described . We report here the application of a novel approach involving expression complementary DNA library transfer to the identification of drug-resistant genes . Using this approach we establish that mrp, a member of the ABC cassette superfamily of transporters, is capable of conferring a multidrug-resistant phenotype . This approach should be useful in the identification of other novel resistance genes. J Infect Dis, 1994 Apr, 169(4), 722 - 9 Combination therapy with zidovudine and didanosine selects for drug-resistant human immunodeficiency virus type 1 strains with unique patterns of pol gene mutations; Shafer RW et al.; Drug resistance conferred by specific human immunodeficiency virus type 1 (HIV-1) pol gene mutations has been associated with clinical progression in HIV-infected patients receiving anti-retroviral therapy . This study examined drug susceptibilities and pol mutations of HIV-1 strains from patients treated for 1 year with zidovudine, didanosine (ddI), or zidovudine and ddI . Ten (42%) of 24 patients receiving combination therapy versus 8/26 (31%) receiving only zidovudine had HIV-1 strains with phenotypic zidovudine resistance or a zidovudine resistance pol mutation at codon 215 (P = .6) . In contrast, a ddI resistance mutation at codon 74 was less common among patients receiving combination therapy (2/24) than among those receiving ddI only (17/26; P < .001) . Two patients receiving combination therapy developed resistance to zidovudine and ddI; they had HIV strains with amino acid mutations at codons 62, 75, 77, 116, and 151 . Combination therapy with zidovudine and ddI selects for zidovudine-resistant HIV-1 strains lacking a ddI resistance mutation and for multidrug-resistant strains containing novel pol mutations. Ann Trop Med Parasitol, 1994 Apr, 88(2), 137 - 44 In vitro susceptibility of Cambodian isolates of Plasmodium falciparum to halofantrine, pyronaridine and artemisinin derivatives; Basco LK et al.; Multidrug-resistant Plasmodium falciparum is widespread in Cambodia . The in vitro susceptibilities of 14 Cambodian isolates to chloroquine, quinine, mefloquine, halofantrine, pyrimethamine, cycloguanil, pyronaridine, artemisinin, arteether, artemether and artelinate were studied using a semi-microtest on day 0 and after 15-30 days of culture . The culture-adapted isolates were all resistant to chloroquine, pyrimethamine and cycloguanil . The susceptibility to quinine was generally low . Three isolates were resistant to mefloquine . A comparison of susceptibility to cycloguanil, quinine, and mefloquine prior to and after culture adaptation showed a trend toward a higher resistance level in some isolates . Halofantrine, pyronaridine and artemisinin derivatives were highly active against the multidrug-resistant Cambodian isolates, with very similar 50% inhibitory concentrations (IC50) . These results confirm the presence of multidrug-resistant P . falciparum isolates in Cambodia and indicate that quinine- and mefloquine-resistant populations of the parasite may already exist in the field . The high in vitro activities of halofantrine, pyronaridine and artemisinin derivatives indicate their potential usefulness for the treatment of multidrug-resistant malaria. Lymphokine Cytokine Res, 1994 Apr, 13(2), 125 - 31 Enhanced expression of HLA-A,B,C and inducibility of TAP-1, TAP-2, and HLA-A,B,C by interferon-gamma in a multidrug-resistant small cell lung cancer line; Fisk B et al.; Recent evidence suggests that deficient HLA Class I expression in SCLC lines may be due, in part, to down-regulation of TAP-1 and TAP-2 expression, and, thus, deficient antigen processing . Given the capability of the multidrug transporter mediating MDR, P-gp, to transport peptides, we hypothesized that P-gp may substitute for TAP-1/TAP-2 and enhance antigen processing in SCLC . To investigate this, we studied the H69 line (parent SCLC) and VPR-2 (MDR subline selected in etoposide, P-gp +) . HLA-A,B,C expression was significantly increased in VPR-2 cells relative to H69, and was much more inducible with IFN-gamma . TAP-1 and TAP-2 were expressed at low levels in both lines . Differential induction of TAP-1 expression with IFN-gamma exposure was observed, with a dramatic increase in VPR-2 cells, and no change in H69 . TAP-2 expression was enhanced in both lines with IFN-gamma, but to a greater degree in VPR-2 . VPR-2 cells were resistant to LAK killing relative to H69, and were minimally sensitized with IFN-gamma . In contrast, IFN-gamma enhanced susceptibility of H69 to LAK killing 3-fold . The direct correlation between enhancement of HLA-A,B,C expression by IFN-gamma and the differential inducibility of TAP-1 and TAP-2 expression in P-gp-SCLC lines is novel . Relative LAK sensitivity of H69 and its increase by IFN-gamma may have clinical implications. Am J Infect Control, 1994 Apr, 22(2), 65 - 74 Evaluation of single-use masks and respirators for protection of health care workers against mycobacterial aerosols; Chen SK et al.; BACKGROUND: The recent increase in multidrug-resistant tuberculosis has spawned a major controversy concerning the degree of respiratory protection needed by health care workers, particularly during sputum-inducing procedures . The objective of this study was to measure the filtration efficiencies of a single-use submicron surgical mask, two disposable dust/mist respirators, a dust/mist/fume respirator, and a high-efficiency particulate air respirator against aerosolized mycobacteria . Facial fit was not addressed . METHODS: In a specially designed enclosed test apparatus, an aerosol was generated with a Collison nebulizer from a known concentration of Mycobacteria chelonae, used as a surrogate for Mycobacterium tuberculosis . Aerosol concentrations were measured with Anderson samplers upstream and downstream of the test masks and respirators, which were heat sealed to a metal plate . RESULTS: Mean efficiencies ranged from approximately 97% for the surgical mask and a dust/mist respirator to more than 99.99% for the high-efficiency particulate air respirator . Measurements of filter efficiency with an Aerodynamic Particle Sizer for the M . chelonae aerosol and independent challenge tests with latex spheres correlated closely with measurements of M . Chelonae collection efficiency determined with Andersen samplers . CONCLUSIONS: Analysis of variance and Tukey's method for multiple comparisons indicated that the dust/mist/fume respirator and the HEPA respirator collected M . chelonae with significantly greater efficiency than did either the surgical mask or the dust/mist respirator . Even the least efficient mask tested, however, had a filter efficiency of more than 97% against particles averaging less than 1 micron in aerodynamic diameter. Br J Haematol, 1994 Apr, 86(4), 792 - 7 Gene amplification in non-Hodgkin's lymphoma; Ben-Yehuda D et al.; Among 426 consecutively ascertained and karyotypically abnormal non-Hodgkin's lymphoma (NHL) tumours, cytological evidence for gene amplification in the form of homogeneously staining regions (HSRs) was encountered in nine cases of large cell diffuse lymphoma (LC-DL) . The mean age of patients with HSRs was 62.9 years and four died within a year of diagnosis . To identify candidate gene(s) amplified in these tumours, we performed a Southern blot analysis of tumour DNA using probes for 23 known protooncogenes and the multidrug resistance gene, PGY1 . Besides a two-fold amplification of the BCL2 gene in two cases, no evidence for overt amplification of any of the genes assayed was found . To confirm DNA amplification in these specimens we performed the DNA in-gel renaturation assay . Evidence for presence of amplified DNA fragments was obtained in four of seven specimens . These results suggest amplification of a novel gene(s) . To our knowledge, this is the first formal study of gene amplification in a large consecutively ascertained series of fresh lymphoma biopsies. Neuropathol Appl Neurobiol, 1994 Apr, 20(2), 118 - 21 Detection of multidrug resistance gene product (P-glycoprotein) expression in ependymomas; Geddes JF et al.; A neurosurgical series of 33 ependymal tumours was examined for expression of the membrane transport molecule P-glycoprotein, which is linked with the development of multidrug resistance in many human tumours . We employed the monoclonal antibodies JSB1 and C219, raised to two different epitopes of the P-glycoprotein molecule, and found P-glycoprotein expression both in normal ependyma and in 29 of the tumours . This is the first time that ependymal tumours have been demonstrated to express the protein, and we conclude that its expression may contribute to the reported failure of adjuvant chemotherapy to improve outcome in ependymomas. Proc Natl Sci Counc Repub China B, 1994 Apr, 18(2), 64 - 70 The induction of multidrug resistance in human cervical carcinoma cell lines by estrogenic hormones; Biing JT et al.; The role of estrogenic hormones on the induction of drug resistance was studied in cervical cancer cell lines, SiHa and Caski . After the cells were inoculated with estradiol (E2) or diethylstilbestrol (DES) in various dosages, the cell survival rates with adriamycin treatment were examined by MTT (3-{4,5-dimethyl-thiazole-2-yl}-2,5-diphenyl-tetrazolium-bromide) test and the intracellular accumulation of adriamycin was evaluated by flow cytometry . In the same condition, the expression of multidrug resistance gene-1 (mdr-1 gene) was detected either by Northern blot hybridization for mdr-1 mRNA or by immunoblot for P-glycoprotein 170 . The data in this study indicated that estrogenic hormones had the capacity to induce drug resistance in cervical carcinoma cell lines . When cells were treated with estrogenic hormones and adriamycin simultaneously, the intracellular accumulation of adriamycin declined and corresponded with the drug resistance . Since the expression of the mdr-1 gene induced by E2 or DES results in drug resistance, it is suggested that the mdr-1 gene in SiHa cells may contain the estrogenic responsive element (ERE) in its regulatory region . However, the mechanism of drug resistance induced by estrogenic hormones in Caski cells is different from SiHa cells due to the absence of mdr-1 gene expression . Despite that, this experiment may provide a model to investigate the relationships between estrogenic hormones and drug resistance in other female genital cancers. Anticancer Drugs, 1994 Apr, 5(2), 229 - 38 Extent and persistence of P-glycoprotein inhibition in multidrug-resistant P388 cells after exposure to resistance-modifying agents; Boesch D et al.; The low daunomycin (DAU) retention in P388 cells displaying P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) can be increased by the presence of various resistance-modifying agents (RMAs) . Taking the DAU retention restoration as an indicator of Pgp function inhibition and using a few RMAs, including SDZ PSC 833, SDZ 280-446, cyclosporin A (CsA) and verapamil, we compared different conditions of MDR cell exposure to the RMA . The 'co + post-RMA' treatments (RMA present during both DAU uptake and efflux phases) generally led to higher DAU retention levels than the 'co-RMA' treatments (RMA present during the DAU uptake phase only) . The magnitude and persistence of Pgp function inhibition induced by the RMA was further examined by only pulsing the cells with the RMA and growing them in RMA-free medium before the DAU retention assay ('pre-RMA' treatment) . While recovery of Pgp function was nearly complete within minutes after a pulse exposure to verapamil, this took increasing times with CsA, SDZ 280-446 and SDZ PSC 833, the latter RMA leaving traces of inhibition of Pgp function even 2 days after the pulse exposure of the MDR-P388 cells . The persistence of Pgp inhibition conferred by some RMAs being much longer than by others, this feature should be taken into account when designing chemotherapy protocols in the clinic. Hematol Oncol Clin North Am, 1994 Apr, 8(2), 383 - 410 Multidrug resistance . Clinical opportunities in diagnosis and circumvention; Chan HS et al.; Increased P-glycoprotein expression has been shown to be the molecular cause of multidrug resistance in tumor cell lines . Sensitive immunohistochemical and molecular biologic techniques have been developed to detect P-glycoprotein/mdr1 mRNA expression in clinical samples of tumors . We have reviewed the tools now available for assessment of P-glycoprotein expression in the clinic, the current evidence for a relevant role of the protein in mediation of resistance to chemotherapy, and one strategy used to overcome therapeutic failures due to multidrug resistance . It is now recognized that low levels of increased P-glycoprotein/mdr1 mRNA can occur at diagnosis and during the course of treatment in some cases of acute myelogenous leukemia, non-Hodgkin's lymphoma, multiple myeloma, breast carcinoma, rhabdomyosarcoma and undifferentiated sarcoma of children, neuroblastoma, and retinoblastoma, and these relatively low levels of mdr1 overexpression appear to be associated with poor prognosis . In contrast, it has not been established whether a multidrug resistance mechanism is the rate-limiting factor in response to chemotherapy in carcinomas that arise from tissues normally expressing increased P-glycoprotein . Clinical trials have been initiated to determine whether pharmacologic chemosensitization improves the outcome of chemotherapy-treated malignancies . Preliminary results suggest that chemosensitizers can modulate the effects of increased P-glycoprotein in low-expressing tumors for which effective multiagent chemotherapy is available . Further research is needed for more potent chemosensitizers or combinations of agents that can be used more effectively . The successful circumvention of chemotherapy failure by chemosensitizers will ultimately establish the clinical relevance of the P-glycoprotein efflux mechanism. Leuk Res, 1994 Apr, 18(4), 283 - 91 Transport and metabolism of polyamines in wild and multidrug resistant human leukemia (K 562) cells; Khan NA et al.; Multidrug resistance (MDR) can be defined as the resistance of cancer cells not just to chemotherapeutic agents to which they have been exposed but also to other apparently unrelated compounds . This MDR phenotype is commonly associated with the high expression of levels of 170 kDa P-glycoprotein, encoded by MDR genes . In the present study, the uptake kinetics of polyamines and their biosynthesis were studied in wild and multidrug resistant (MDR) K 562 cells in culture . The rate (Vmax) of polyamine uptake was significantly lower in MDR cells than that in wild type cells, whereas the Km for the uptake was not significantly different in these cells, suggesting that polyamine transporter is not modified in MDR cells, though their different physiological state influences the uptake process . In a 32 h chase, the transported radioactive polyamines were gradually interconverted . {14C}putrescine was converted into {14C}spermidine following between 15 min and 32 h of culture, and into {14C}-spermine after 16 h of culture, in both the cell types; however, the levels of interconverted radioactive polyamines were always lower in MDR cells as compared with wild type cells . Similarly, internalized {14C}spermidine was converted into {14C}spermine, but not into {14C}putrescine in both the cells types . {14C}spermidine is metabolized into {14C}spermine after 4 h of culture in wild type cells, whereas in MDR cells the interconversion of {14C}spermidine into {14C}spermine is seen only after 16 h of culture . Blocking of the transmembrane drug efflux pump, expressed in the MDR cells, by preincubation in the presence of verapamil, did not influence the uptake of either of the two polyamines (putrescine and spermidine) by MDR cells . On the contrary, this kind of preincubation of wild type cells in the presence of verapamil significantly increased the uptake of these two polyamines . The levels of intracellular polyamine contents in MDR cells were always lower than those in the parental cell line . These results demonstrate that MDR cells are defective in both the uptake of polyamines and their biosynthesis as compared with wild type cells. Leuk Res, 1994 Apr, 18(4), 233 - 43 Clinical relevance of P-glycoprotein expression in haematological malignancies; Nooter K et al.; Although, generally speaking, haematological malignancies are chemotherapy-responsive tumours and high remission induction rates are obtained, disease-related death is the rule rather than the exception . The appearance of cell populations, resistant to multidrug-based chemotherapy, constitutes the major problem to achieve cures in these patients . Advances in cell biology have partly contributed to the elucidation of different multidrug resistance (MDR) mechanisms, which enable cells to survive the cytotoxic effects of multiple chemotherapeutic agents . Of these resistance mechanisms, the one that is referred to as classical MDR is the most extensively studied, both in the laboratory as well as in patients, and here we will focus on its clinical relevance in haematological malignancies . The classical MDR phenotype is caused by enhanced cellular drug efflux due to increased activity of a membrane-bound glycoprotein (P-glycoprotein) drug pump, that can pump out anthracyclines, anthracenediones, vinca alkaloids and epipodophyllotoxins, thereby actively lowering the intracellular drug concentrations to sublethal levels . As soon as molecular probes for the detection of MDR cells became available, clinical studies were initiated to answer three main questions . Do human tumor cells express P-glycoprotein? If so, is the expression indicative of a bad prognosis, c.q . resistant disease? And last but not least, can we interfere with the P-glycoprotein drug pump in the patient? Clinical data indicate that classical MDR may be involved in the development of drug resistance, especially in some haematological malignancies, such as acute myelocytic leukaemia (AML), non-Hodgkin's lymphomas (NHL), and multiple myelomas (MM) . In almost all types of haematological malignancies, either untreated or treated, elevated P-glycoprotein levels have been reported, ranging from low to high . However, the acquisition of clinical MDR associated with P-glycoprotein expression occurs only in those diseases (for example, AML and MM) that are heavily treated with MDR-related drugs, probably by selection of pre-existing P-glycoprotein-expressing malignant cells . Since P-glycoprotein is found to be expressed on the membrane of normal haemopoietic progenitor cells as well, it seems likely that P-glycoprotein-positive haematological tumours develop by malignant transformation of P-glycoprotein-expressing normal haemopoietic counterparts . Especially for AML, convincing data have been reported in the literature to show that P-glycoprotein expression at diagnosis is a bad prognostic factor that predicts refractoriness . Using in vitro model systems for classical MDR, a large number of agents have been identified that can circumvent P-glycoprotein-mediated drug resistance, the so-called resistance modifying agents (RMA).(ABSTRACT TRUNCATED AT 400 WORDS) Eur J Biochem, 1994 Apr 1, 221(1), 363 - 73 The multidrug-resistance-reverser verapamil interferes with cellular P-glycoprotein-mediated pumping of daunorubicin as a non-competing substrate; Spoelstra EC et al.; We examined P-glycoprotein-mediated verapamil transport, using two drug-sensitive and multi-drug resistant cell-line couples, i.e . A2780, 2780AD and SW-1573, SW-1573/1R500 . The interaction of 3H-labeled verapamil with cells was measured using a flow-through system . The verapamil-containing medium was pumped over the cells and monitored on-line for radioactivity . In the P-glycoprotein-expressing cells, verapamil accumulation was increased by vinblastine and some known multidrug resistant (MDR) modifiers . Subsequent removal of these modifiers caused release of verapamil into the medium against a verapamil concentration gradient . In this manner, we obtained evidence that verapamil is actively transported by the MDR-related P-glycoprotein . Using the flow-through system, we also exposed the cells to flowing culture medium containing daunorubicin, and measured the inhibition of daunorubicin efflux by verapamil . We found that, although the active efflux of daunorubicin was maximally blocked by verapamil short-term, longer-term active efflux of daunorubicin resumed . At a daunorubicin concentration in the flowing medium of 5 microM, increasing the verapamil concentration resulted in the same short-term effects, but in a significantly longer period of a maximal inhibition of daunorubicin efflux from the cells . At a daunorubicin concentration of 20 microM, increasing the verapamil concentration affected neither the short-term nor the long-term effects . These and other observations are in agreement with a model in which daunorubicin and verapamil are non-competing substrates for P-glycoprotein . In conclusion, we obtained evidence that verapamil is actively transported by the MDR-related P-glycoprotein and that verapamil and daunorubicin are non-competing substrates for P-glycoprotein . Consequently, the effectiveness of verapamil as an MDR antagonist may be compromised because it is extruded by P-glycoprotein. Biochem J, 1994 Apr 1, 299 ( Pt 1), 309 - 15 Phosphorylation by protein kinase C and cyclic AMP-dependent protein kinase of synthetic peptides derived from the linker region of human P-glycoprotein; Chambers TC et al.; Specific sites in the linker region of human P-glycoprotein phosphorylated by protein kinase C (PKC) were identified by means of a synthetic peptide substrate, PG-2, corresponding to residues 656-689 from this region of the molecule . As PG-2 has several sequences of the type recognized by the cyclic AMP-dependent protein kinase (PKA), PG-2 was also tested as a substrate for PKA . PG-2 was phosphorylated by purified PKC in a Ca2+/phospholipid-dependent manner, with a Km of 1.3 microM, and to a maximum stoichiometry of 2.9 +/- 0.1 mol of phosphate/mol of peptide . Sequence analysis of tryptic fragments of PG-2 phosphorylated by PKC identified Ser-661, Ser-667 and Ser-671 as the three sites of phosphorylation . PG-2 was also found to be phosphorylated by purified PKA in a cyclic AMP-dependent manner, with a Km of 21 microM, and to a maximum stoichiometry of 2.6 +/- 0.2 mol of phosphate/mol of peptide . Ser-667, Ser-671 and Ser-683 were phosphorylated by PKA . Truncated peptides of PG-2 were utilized to confirm that Ser-661 was PKC-specific and Ser-683 was PKA-specific . Further studies showed that PG-2 acted as a competitive substrate for the P-glycoprotein kinase present in membranes from multidrug-resistant human KB cells . The membrane kinase phosphorylated PG-2 mainly on Ser-661, Ser-667 and Ser-671 . These results show that human P-glycoprotein can be phosphorylated by at least two protein kinases, stimulated by different second-messenger systems, which exhibit both overlapping and unique specificities for phosphorylation of multiple sites in the linker region of the molecule. Gan To Kagaku Ryoho, 1994 Apr, 21(5), 665 - 70 {Study for modifying activity of solvents on antitumor activity of paclitaxel}; Fujimoto S; Paclitaxel, a novel diterpenoid compound, has been used by dissolving in Cremophor EL (polyoxyethylene castor oil) due to its poor aqueous solubility . Cremophor EL was shown to reverse multidrug resistant phenotypes of various cell lines as well as to reverse cross-resistance to paclitaxel of a multidrug resistant cell line in vitro . Thus, a study was carried out to determine the modifying activity of Cremophor EL on the antitumor activity of paclitaxel against P388 leukemia, adriamycin-resistant subline (P388/ADM) and vincristine-resistant subline (P388/VCR) in vivo . Dimethyl sulfoxide (DMSO) was used as a counterpart solvent . The results showed that, although no significant antitumor activity was observed by paclitaxel in both solvents against P388/ADM, a significantly higher antitumor activity was induced by paclitaxel dissolved in Cremophor EL-based solvent compared with DMSO-based solvent against P388/VCR . However, more significant difference in the antitumor activity of paclitaxel against P388 parental line was observed between two solvents and both resistant sublines showed an obvious cross-resistance to paclitaxel . Therefore, it appeared that cross-resistance reversing activity of Cremophor EL is not so high as to be detectable at in vivo level. Gan To Kagaku Ryoho, 1994 Apr, 21(5), 583 - 90 {Microtubules and antineoplastic drugs}; Arioka H et al.; Microtubules, which are composed of polymerized tubulin dimers, play an important role in various cell functions . For example, they maintain cell shape, form mitotic spindles in M phase of cell cycle, and carry an axonal transport in nerve cells . Microtubules have also been an important target of cancer chemotherapy . Vinca alkaloids depolymerize microtubules, the mechanisms of which action have extensively been investigated recently . Clinical trials of vinorelbine (navelbine), a new semisynthetic vinca alkaloid, are ongoing in Japan . One of advantages of the drug is reduced risk of neurotoxicity . Estramustine may act on microtubule-associated proteins (MAPs) as well as tubulin . It shows additive or synergistic cytotoxicity preclinically when used in combination with vinblastine . This combination was active against hormone-refractory prostate cancer . Another novel drug rhizoxin, which has a similar mechanism of action to that of vinca alkaloids, is also a promising cytotoxic agent and is examined clinically in Europe . Taxanes, which include paclitaxel (Taxol) and taxotere, are interesting drugs because they promote polymerization of tubulin and stabilize microtubules . They show promising antitumor activity against breast, ovarian and lung cancers . Phase I and II trials are ongoing in Japan . Paclitaxel may also potentiate cytotoxicity of radiation . There are several mechanisms of resistance to microtubule-acting drugs . One is multidrug resistance mediated by P-glycoprotein . Other mechanisms include mutation of tubulin. J Clin Oncol, 1994 Apr, 12(4), 812 - 9 Clinical and pharmacologic study of multidrug resistance reversal with vinblastine and bepridil; Linn SC et al.; PURPOSE: To achieve an adequate plasma concentration of bepridil, a calcium channel blocker, which reverts multidrug resistance (MDR) in vitro, when administered in combination with vinblastine in patients with advanced colorectal cancer, a tumor characterized by high MDR1 gene expression . To study the pharmacokinetics of both drugs, tolerability and antitumor activity in relation to the MDR1 expression in tumor tissue . PATIENTS AND METHODS: Sixteen colorectal cancer patients entered the study . Bepridil was administered by central venous catheter as 5-mg/kg bolus over 30 minutes, followed by 12 mg/kg for 12 hours and 5 mg/kg for 24 hours . Vinblastine 5 mg/m2 was administered as an intravenous (i.v.) bolus 24.5 hours after the start of bepridil . MDR1/P-glycoprotein (Pgp) expression was assessed in 14 tumor samples by immunohistochemistry and RNase protection assay . RESULTS: The bepridil plasma level was greater than 2 mumol/L at the time of vinblastine administration in all patients investigated . At the dose used in the study, bepridil produced a QTc-prolongation more than 50 ms, which prevented further dose escalation . However, cardiac toxicity was asymptomatic in all treated patients, and other side effects were mild . MDR1/Pgp expression was positive in nine of 14 cases . Of fifteen patients assessable for response, one complete remission of 8 months' duration and 14 progressions were observed . The responding patient attained complete remission again when re-treated on progression with vinblastine alone . CONCLUSION: Bepridil plasma concentrations needed in vitro to modulate MDR could be achieved in this study with tolerable toxicity; however, despite most tumors being MDR1/Pgp-positive, no response was obtained that could be attributed to the drug combination . Mechanisms of drug resistance other than MDR are probably implicated in drug resistance of colorectal cancer. Int J Cancer, 1994 Apr 1, 57(1), 104 - 10 The protein kinase C inhibitor CGP 41251, a staurosporine derivative with antitumor activity, reverses multidrug resistance; Utz I et al.; Multidrug resistance (MDR) is frequently associated with overexpression of a 170-kDa P-glycoprotein (Pgp) . Data suggest altered protein kinase C (PKC) activity in cells expressing the multidrug-resistant phenotype . The staurosporine derivative CGP 41251, an experimental anticancer drug, has been shown to exert selectivity for inhibition of protein kinase C activity and to exhibit antitumor activity in vitro and in vivo . Here we show that CGP 41251 is also able to reverse MDR . After treatment of the multidrug-resistant human lymphoblastoid cell line CCRF-VCR1000 with 500 nM Adriamycin, cell proliferation was reduced to 81% of untreated controls . A combination of 500 nM Adriamycin with a non-toxic concentration of 150 nM CGP 41251 (IC50 for inhibition of cell proliferation 420 nM CGP 41251) inhibits cell proliferation of CCRF-VCR1000 cells to 29% of untreated controls . In sensitive CCRF-CEM cells no enhancement of Adriamycin-induced cytotoxicity was observed upon addition of 150 nM CGP 41251 . Strong synergism of the inhibition of cell proliferation was also observed after concomitant treatment of KB-8511 cells with CGP 41251 and Vinblastine or Adriamycin . Drug-sensitive KB-31 cells could not be further sensitized to Adriamycin or Vinblastine with CGP 41251 doses above 100 nM . Pretreatment with 50-1000 nM CGP 41251 for 30 min led to a dose-dependent increase in the intracellular accumulation of rhodamine 123, a substrate of P-glycoprotein . Treatment of multidrug-resistant CCRF-VCR1000 cells with CGP 41251 for 10 min was sufficient to inhibit the efflux of rhodamine 123 . Preincubation with CGP 41251 for 12 or 24 hr did not alter multidrug resistance gene (mdrI)-mRNA levels . CGP 41251, a drug with antitumor efficacy in experimental systems, might offer an attractive combination partner for the treatment of tumors expressing the MDR phenotype. Br J Cancer, 1994 Apr, 69(4), 680 - 6 Increased mdr1 gene transcript levels in high-grade carcinoma of the bladder determined by quantitative PCR-based assay; Clifford SC et al.; Overexpression of the multidrug resistance (mdr1) gene has been implicated in resistance to a number of the chemotherapeutic agents currently used in the treatment of bladder cancer (doxorubicin, vincristine and epirubicin) . We report the development and validation of a quantitative assay for the determination of mdr1 gene transcript levels based on reverse transcription and the polymerase chain reaction (PCR), sensitive to less than 2-fold variations in transcript levels . Using these techniques, mdr1 mRNA levels were investigated in 32 primary untreated transitional cell carcinomas of the bladder . mdr1 mRNA was detected in all samples, with levels varying between individual tumours over a 63-fold range . These variations were not associated with the proliferative status of the tumour . mdr1 mRNA levels were significantly higher in poorly differentiated high-grade (G3) tumours than in well- and moderately differentiated low-grade (G1 and G2) tumours (P = 0.0057) . The results suggest that this relationship may extend to mdr1 mRNA levels being an indicator of poor prognosis, as anticipated on the basis of the observed relationship to tumour stage and grade . No evidence was found to implicate mdr1 mRNA levels as a predictor of tumour recurrence or progression . Given that mdr1 mRNA levels are increased in a proportion of high-grade bladder tumours that are routinely subjected to chemotherapy, we discuss the possibility that mdr1 mRNA levels may be clinically significant as determinants of chemotherapeutic response and outcome in bladder cancer. Pathol Biol (Paris), 1994 Apr, 42(4), 328 - 37 Cross resistance relevance of the chemical structure of different anthracyclines in multidrug resistant cells; Tapiero H et al.; Positively charged doxorubicin (DOX) and non-positively charged anthracyclines, aclarubicin (ACR) and morpholino-carminomycin (KRN 8602), have been investigated with respect to pharmacological parameters, cytotoxicity, DNA damage and repair in DOX-sensitive and -resistant murine and human cells . Friend leukemia cells (FLC) resistant to high concentrations of doxorubicin (DOX-RFLC3) or daunorubicin (DNR-RFLC3) (1771 and 1543 fold resistance respectively) express less than 10 fold resistance to aclarubicin (ACR) . In these cells, the intracellular accumulation of ACR is similar in sensitive and resistant cells . Resistance to ACR was not observed in either DOX-RFLC1 or DNR1 with a lower level of resistance (27 fold) . Increased expression of a 170,000-dalton surface antigen (gp-170) was found to be correlated with the level of resistance . However, when the selective agent in ACR, despite the low level of resistance (2.8 fold) both high expression of gp 170 and resistance to DOX (77 fold) or DNR (62 fold) are observed . It is assumed therefore that induction of multidrug resistance phenotype can be achieved by compounds which do not display cross resistance with DOX or DNR . Reduced levels or absence of cross-resistance can be related to the electrical charge of the compound . This assumption is supported by further studies on DOX-sensitive or -resistant human K562 cells exposed to another non-positively charged anthracycline, KRN 8602 . In the continuous presence of drug, K562/DOX were less resistant to KRN 8602 (2.9 fold) than to DOX (31 fold) . After short time exposure followed by growth in drug-free medium, absence of cross-resistance to KRN 8602 has been observed in K562/DOX . Furthermore, accumulation experiments showed that high intracellular drug concentrations were rapidly achieved (within 15 min) in both DOX-sensitive and -resistant cells . In cells exposed to DOX, DNA single-strand break (DNA-SSBs) frequencies were related to time and drug concentration while those produced by KRN 8602 or ACR were maximal after short time incubation . DNA-SSBs produced by these anthracyclines are not repaired when cells are incubated in drug free medium . In DOX resistant cells, DNA-SSBs produced by DOX were repaired whereas those produced by ACR or KRN 8602 were not . It is suggested, therefore, that absence of cross resistance to various anthracyclines is related to differences in the chemical electrical charge, which may influence drug accumulation and DNA repair in resistant cells. Mol Pharmacol, 1994 Apr, 45(4), 773 - 6 Direct demonstration of high affinity interactions of immunosuppressant drugs with the drug binding site of the human P-glycoprotein; Rao US et al.; The interactions between the human P-glycoprotein (Pgp) and two different types of immunosuppressant drugs known to modulate multidrug resistance in tumor cells have been directly investigated using our newly developed drug-stimulated ATPase assay for Pgp function . The macrolides FK506 and FK520 stimulate the Pgp-ATPase activity with affinities in the 100 nM range, nearly 10 times higher than that of verapamil, a well known Pgp substrate . On the other hand, the cyclic peptides cyclosporin A and dihydrocyclosporin C do not stimulate the Pgp-ATPase activity at all . They do, however, act as potent competitive inhibitors of verapamil-stimulated Pgp-ATPase activity, with affinity constants in the 20-25 nM range . Thus, although these two classes of immunosuppressant drugs affect the Pgp in different ways, they both probably interact with high affinity at the transported drug binding site(s) of the Pgp, which would explain their ability to resensitize multidrug-resistant cells to the killing action of certain antitumor drugs . Possible implications of these findings for Pgp function, cancer chemotherapy, and immunosuppression are discussed. Mol Cell Biol, 1994 Apr, 14(4), 2419 - 28 Expression of the plasmodial pfmdr1 gene in mammalian cells is associated with increased susceptibility to chloroquine; van Es HH et al.; Chloroquine (CQ)-resistant (CQR) Plasmodium falciparum malaria parasites show a strong decrease in CQ accumulation in comparison with chloroquine-sensitive parasites . Controversy exists over the role of the plasmodial pfmdr1 gene in the CQR phenotype . pfmdr1 is a member of the superfamily of ATP-binding cassette transporters . Other members of this family are the mammalian multidrug resistance genes and the CFTR gene . We have expressed the pfmdr1-encoded protein, Pgh1, in CHO cells and Xenopus oocytes . CHO cells expressing the Pgh1 protein demonstrated an increased, verapamil-insensitive susceptibility to CQ . Conversely, no increase in drug susceptibility to primaquine, quinine, adriamycin, or colchicine was observed in Pgh1-expressing cells . CQ uptake experiments revealed an increased, ATP-dependent accumulation of CQ in Pgh1-expressing cells over the level in nonexpressing control cells . The increased CQ accumulation in Pgh1-expressing cells coincided with an enhanced in vivo inhibition of lysosomal alpha-galactosidase by CQ . CHO cells expressing Pgh1 carrying two of the CQR-associated Pgh1 amino acid changes (S1034C and N1042D) did not display an increased CQ sensitivity . Immunofluorescence experiments revealed an intracellular localization of both mutant and wild-type forms of Pgh1 . We conclude from our results that wild-type Pgh1 protein can mediate an increased intracellular accumulation of CQ and that this function is impaired in CQR-associated mutant forms of the protein . We speculate that the Pgh1 protein plays an important role in CQ import in CQ-sensitive malaria parasites. Biochem Biophys Res Commun, 1994 Mar 30, 199(3), 1428 - 35 Involvement of a DNA binding protein, MDR-NF1/YB-1, in human MDR1 gene expression by actinomycin D; Asakuno K et al.; The human multidrug resistance 1 (MDR1) gene is an SOS gene that responds to environmental stress including various anticancer agents . The chloramphenicol acetyltransferase (CAT) gene was linked to various lengths of MDR1 promoter, and these constructs were integrated into the genome of human cancer KB cells . Using these cell lines, we previously demonstrated that various environmental stimuli lead to an increased abundance of both CAT enzymatic activity and CAT mRNA in a sequence dependent manner . We examined the molecular mechanism of this stress response using actinomycin D, a potent RNA synthesis inhibitor . We found that CAT activity was significantly increased more than 10 fold by actinomycin D itself without comparable elevation of CAT mRNA . CAT induction was, however, lost in the presence of a deletion from position -136 to -76 . Gel mobility shift assays showed that the specific DNA binding activity of the transacting protein, MDR-NF1/YB-1, which binds to the inverted CCAAT box, was augmented in nuclear extracts from the cells treated with actinomycin D . We also found that actinomycin D increased the steady state levels of MDR-NF1/YB-1 mRNA, which encodes the inverted CCAAT box binding protein . These results indicate that MDR-NF1/YB-1 mediates the response of the MDR1 gene to environmental stress. Biochem Biophys Res Commun, 1994 Mar 30, 199(3), 1181 - 7 Mycobacterium tuberculosis induces expression of P-glycoprotein in promonocytic U1 cells chronically infected with HIV type 1; Gollapudi S et al.; A productive infection with HIV-1 is associated with an increased expression of a 170 kd plasma membrane P-glycoprotein (P-gp), that functions as a metabolically active drug efflux pump, in human T and macrophage cell lines . In this investigation we show that phagocytosis of M . tuberculosis by U1 cells, that are chronically infected with HIV-1 but produce minimal or no virus, resulted in an expression of P-gp that was associated with increased production of HIV-1 p24 antigen . In addition, U1 cells that had phagocytosed M . tuberculosis accumulated significantly less intracellular isoniazid (INH) as compared to U1 cells . Furthermore, verapamil, that binds to P-gp, increased the intracellular accumulation of INH and the sensitivity of M . tuberculosis to INH . These data suggest induction of P-gp expression may be one of the host mechanisms for the development of multidrug resistant M . tuberculosis in HIV 1 infection. J Biol Chem, 1994 Mar 25, 269(12), 8667 - 74 Pyridine nucleotide redox potential modulates cystic fibrosis transmembrane conductance regulator Cl- conductance; Stutts MJ et al.; Cl- conductance of the apical membrane of airway epithelial cells has properties of a passive diffusion mechanism but is decreased by inhibition of oxidative metabolism . Recent reports that cAMP-dependent Cl- conductance also requires ATP at the intracellular domains of the cystic fibrosis transmembrane conductance regulator (CFTR) suggests that ATP concentration could mediate metabolic regulation of Cl- conductance . However, metabolic inhibitors affect processes other than ATP free energy levels, including notably the metabolic pathways that set the redox potential of pyridine nucleotides within the cell . We have investigated the possibility that CFTR-mediated Cl- conductance is affected by the ratio of oxidized to reduced intracellular pyridine nucleotides . CFTR was expressed in airway and heterologous cells and studied under whole cell voltage clamp conditions, which permitted the intracellular NAD(P)+/NAD(P)H ratio to be varied independently of ATP concentration . In three cell types expressing CFTR, whole cell dialysis with reduced pyridine nucleotides inhibited activation of Cl- currents by forskolin and 8-(4-chlorophenylthio)-cAMP (CPT-cAMP), whereas dialysis with oxidized pyridines increased both basal and stimulated CFTR-mediated Cl- conductance . In cell-attached membrane patches, the open probability of 5-6-picosiemens Cl- channels that had been activated by forskolin and CPT-cAMP was further and reversibly increased by permeant oxidants . Neither swelling-induced whole cell K+ currents in CFTR-expressing cells nor swelling-induced whole cell Cl- currents in multidrug resistance protein-expressing cells were affected by NADPH . Pyridine nucleotide redox potential had little effect on phosphorylation of histone by protein kinase A . We conclude that CFTR Cl- conductance function can be modulated by pyridine nucleotide redox potential . This effect points to the existence of a mechanism or mechanisms by which cytosolic nucleotides other than ATP can affect plasma membrane Cl- conductance and may help explain how a passive ion conductance is linked to cellular energy metabolism. N Z Med J, 1994 Mar 23, 107(974), 99 - 101 Drug resistant tuberculosis in Auckland 1988-92; Bradley A et al.; AIM . To report the prevalence of drug-resistant Mycobacterium tuberculosis in Auckland . METHOD . Review of all M tuberculosis culture positive cases from January 1988 to December 1992 . Ethnicity was recorded from the national Paxus medical information data base and drug sensitivity results from the Green Lane Hospital tuberculosis reference laboratory . The clinical details of all patients with drug resistant tuberculosis were extracted from hospital case records . RESULTS . Of the 417 patients with positive cultures, 43 (10%) had isolates resistant to one or more antituberculous drugs . Only 4 patients had multidrug-resistant organisms (defined as resistance to at least isoniazid and rifampicin) and there is no evidence that this is an increasing problem . Resistance rates were highest in those previously treated for M tuberculosis, and those born in, or likely to have acquired their organism from, Samoa, all other Pacific Islands, or South East Asia . CONCLUSIONS . Drug resistant M tuberculosis is a problem in Auckland but rates and patterns are little different from 1980-1982 . Multidrug-resistance is not yet a problem in Auckland, as it is in the United States of America . Ways of maintaining this situation are discussed. FEBS Lett, 1994 Mar 21, 341(2-3), 295 - 8 Partial restoration of the actin cytoskeleton in transformed Syrian hamster fibroblasts selected for low levels of 'typical' multidrug resistance; Erokhina MV et al.; Two independent colchicine (CLC)-resistant sublines of Rous sarcoma virus-transformed Syrian hamster fibroblasts were isolated . Each subline represented variants with 11- and 12.4-fold resistance, respectively, their 23- and 23.7-fold resistant descendants, as well as variants cultured in CLC-free medium for 10 months without loss of resistance . All variants demonstrated 'typical' multidrug resistance . The parental cells contained actin in dispersed form, as determined by rhodamine-phalloidin staining . In contrast, already in 11- and 12.4-fold resistant sublines up to 30% of cells demonstrated restored stress fibers . Cultivation in CLC-free medium leads to the accumulation of cells with a partially restored actin cytoskeleton . Putative mechanisms of up-regulation of stress fiber assembly in cells with P-glycoprotein-mediated multidrug resistance are discussed. J Biol Chem, 1994 Mar 18, 269(11), 7976 - 81 Alterations in Ca2+ transport ATPase and P-glycoprotein expression can mediate resistance to thapsigargin; Gutheil JC et al.; Resistance to the intracellular Ca2+ pump inhibitor thapsigargin (TG) is associated with overexpression of both Ca2+ transport ATPase and the multidrug resistance (mdr) transporter P-glycoprotein (pgp) . This is supported by increased resistance to TG following transfection of a functional pgp1 cDNA, and reversal of TG resistance with known inhibitors of pgp function . However, pgp is unlikely to represent the only mechanism of resistance to TG . Cell lines selected for high levels of resistance to TG (250-fold) show only a 3.7-fold increase in pgp expression and a 2-fold increase in cross-resistance to other drugs of the mdr class . Overexpression of endogenous Ca2+ transport ATPase may represent a second mechanism of resistance to TG . Increased Ca2+ ATPase expression (3-fold) is seen in cells made resistant to TG, and TG resistance increases with the transfection of a specific Ca2+ ATPase cDNA into DC-3F cells . If these transfectants are then made resistant to TG, both the endogenous Ca2+ ATPase and the exogenously transfected Ca2+ ATPase become overexpressed . These studies suggest that while TG may be a substrate for pgp, acquired resistance to TG can involve alterations in both pgp and Ca2+ ATPase expression . Additional, as yet unidentified, mechanisms of resistance may be involved in resistance to TG. Cancer Res, 1994 Mar 15, 54(6), 1479 - 84 Antitumor activity of free and liposome-entrapped annamycin, a lipophilic anthracycline antibiotic with non-cross-resistance properties; Zou Y et al.; The lipophilic anthracycline antibiotic annamycin (Ann) was entrapped in liposomes of different size {median diameter: 1.64 microns, multilamellar liposomal Ann (L-Ann); 0.030 micron, small unilamellar Ann (S-Ann)} with > 90% entrapment efficiency and tested in vitro against four pairs of sensitive and multidrug-resistant (MDR) tumor cell lines and in vivo by the i.v . route in five tumor models: advanced s.c . B16 melanoma; s.c . M5076 reticulosarcoma; lung metastases of Lewis lung carcinoma; and s.c . KB and KB-V1 xenografts in nude mice . Predetermined optimal doses of the different formulations were used and the results were compared with doxorubicin (Dox) . In vitro, Ann, either in suspension in 10% dimethyl sulfoxide (F-Ann) (1 mg/ml) or entrapped in liposomes, was able to partially overcome resistance in all four pairs of sensitive and MDR KB, 8226, P388, and CEM cell lines (resistance indexes 63, 269, 333, and 356 for Dox versus 4, 5, 19, and 8.7 for L-Ann, respectively) . In vivo, both F-Ann and liposome-entrapped Ann were slightly more effective than Dox in inhibiting the growth of advanced s.c . B16 melanoma tumors . L-Ann was markedly more effective than Dox and moderately more effective than F-Ann in prolonging the life span of animals bearing s.c . M5076 and lung metastases of Lewis lung carcinoma tumors . All drugs were equally effective at optimal doses in delaying the growth of s.c . KB xenografts, whereas all Ann formulations were markedly more effective than Dox in delaying the growth of s.c . KB-V1 (MDR) xenografts . In all in vivo experiments, S-Ann was consistently more effective than L-Ann and L-Ann was more effective than F-Ann . These results indicate that (a) Ann is more effective than Dox by the i.v . route against several tumor models and that MDR tumors are partially not cross-resistant to Ann both in vitro and in vivo, (b) liposomes enhance the in vivo antitumor properties of Ann, and (c) small liposomes are more effective than large liposomes in enhancing Ann antitumor activity. Blood, 1994 Mar 15, 83(6), 1619 - 25 Analysis of treatment failure in patients with minimally differentiated acute myeloid leukemia (AML-M0); Stasi R et al.; Reports of treatment of patients with minimally differentiated acute myeloid leukemia (AML-M0) are limited, heterogeneous, and controversial . We verified the prognosis of this subtype by analyzing the results of 189 consecutive patients with de novo AML . Fifteen cases fitting the criteria of AML-M0 were identified . No clinical features distinguished them from other patients with AML . The median age was 61 years (range 27 to 70), with a leukocyte count ranging from 0.6 to 185 x 10(9)/L . In all cases the leukemic cells expressed CD34 and reacted with at least one of the antibodies to early myeloid antigens, ie, CD13, CD33, or myeloperoxidase . Immunophenotypic analysis also showed positivity for CD7 in seven samples and the multidrug-resistance P-glycoprotein (P-170) in six . Cytogenetic analysis was abnormal in 12 of the 13 patients in whom an adequate number of mitoses could be evaluated . No single abnormality prevailed, the most common findings being trisomy 8 (three cases) and aberrations of chromosome 7 (two cases) . Antileukemic treatment differed according to age, but for remission induction, all patients received a combination of cytosine arabinoside and an anthracycline or mitoxantrone . The prognosis of patients with AML-M0 was remarkably poor as compared with the other French-American-British subtypes . Whereas the overall rate of complete remission (CR) was 58% with a median survival of 63 weeks, only 6 of the 15 patients with AML-M0 achieved a CR, and the median survival of this group was 16 weeks (range 3 to 39) . The major determinant of treatment failure was unresponsiveness to chemotherapy, as only one patient died of infection during the hypoplastic phase . The CR duration of responders was short, ranging from 3 to 22 weeks, and no second remissions were observed . We conclude that conventional combination chemotherapy yields disappointing results in AML-M0 . The reason for this may be the convergence of various unfavorable prognostic factors, such as (1) the high incidence of cytogenetic abnormalities; (2) the lack of differentiation features and the expression of immaturity markers such as CD34 and CD7; and (3) the frequent expression of P-170 . Nonconventional therapeutic approaches should be developed to alter the prognosis of this form of leukemia. Biochem Biophys Res Commun, 1994 Mar 15, 199(2), 855 - 61 Increased P-type ATPase activity in Leishmania tropica resistant to methotrexate; Sanchez A et al.; In the present report, we show evidence that the membrane from the protozoan parasite Leishmania tropica (LRC-L39), in vitro resistant to 1 mM of methotrexate (MTX), has a significative increased ATPase activity with respect to wild-type line . This ATPase activity is vanadate sensitive, a characteristic of the P-type ATPases included in the ATP-binding casette (ABC) superfamily of transporters, such as P-glycoprotein involved in the multidrug resistance in mammalian cells . Also, this ATPase activity is not modified by MTX, ammonium molybdate and other detergents such as Triton X-100, Brij 58 and lysophosphatidylcholine . However, unlike the P-glycoprotein, we have observed that the ATPase activity is not stimulated by the drugs verapamil and puromycin . This significative ATPase activity could be related to the overexpressed putative P-glycoprotein, with unknown function in these MTX-resistant parasites. Cancer Res, 1994 Mar 15, 54(6), 1536 - 41 MDR1 gene-specific monoclonal antibody C494 cross-reacts with pyruvate carboxylase; Rao VV et al.; Overexpression of P-glycoprotein, the plasma membrane protein product of the MDR1 gene, is a major determinant in the development of resistance to a large number of cancer chemotherapeutic agents . A battery of antibodies, including the MDR1 gene-specific monoclonal antibody (mAb) C494, is used to evaluate human tissues in clinical multidrug resistance surveillance and modulation trials . In rat liver fractions, we report that mAb C494 strongly cross-reacted with a nonmembranous M(r) approximately 130,000 protein, comigrating with core-glycosylated human MDR1 on 7% sodium dodecyl sulfate-polyacrylamide gel electrophoresis . By immunoblotting and microsequence analysis, this protein was identified as pyruvate carboxylase (PC), an abundant mitochondrial enzyme . A search of the National Center for Biotechnology Information data base, using the epitope-specific sequence of mAb C494, revealed that PC (mouse) contains four of the five most reactive amino acids (TLEG), located near the COOH-terminal end of PC at positions 1167-1170 . mAb C494 specifically reacted with PC purified from bovine liver; immunoreactivity was completely abolished by preincubating mAb C494 in the presence of excess synthetic C494 epitope-specific peptide . Furthermore, in cryosections of human skeletal muscle, a tissue known not to express P-glycoprotein, peptide-displaceable immunohistochemical staining with mAb C494 showed a distinct mitochondrial pattern specific to type 1 fibers . Variable immunostaining results were obtained with formaldehyde-fixed, paraffin-embedded muscle and isolated liver mitochondrial preparations . In summary, mAb C494 cross-reacted strongly with rat, bovine, and human PC . Caution is warranted in interpretation of immunoblots and immunohistochemical sections with this putative MDR1 gene-specific mAb. J Biol Chem, 1994 Mar 11, 269(10), 7145 - 9 Relationships between rhodamine 123 transport, cell volume, and ion-channel function of P-glycoprotein; Altenberg GA et al.; The P-glycoprotein (Pgp), a plasma membrane protein overexpressed in multidrug-resistant tumor cells, is thought to be both an ATPase that actively exports cytotoxic drugs and a Cl- channel activated by cell swelling . The partial reversal of multidrug resistance by Cl- transport blockers suggests a possible role for Cl- in Pgp-mediated drug transport . We used multidrug-resistant Chinese hamster fibroblasts and human breast cancer cells expressing Pgp to study the roles of Cl- (and also Na+ and HCO3-/CO2) on Pgp-mediated efflux of the fluorescent dye rhodamine 123 (R123) . In Pgp-expressing Chinese hamster fibroblasts, exposed to isosmotic solutions, the unidirectional efflux of R123 was not measurably changed by a approximately 60-min removal of Cl- (or by exposure to Na(+)-free, or nominally HCO3-/CO2-free medium); short term (2-3 min) ion substitutions were also ineffective . In human breast cancer cells transfected with human mdr1 cDNA, hyposmotic solutions activated a Cl- current but had no effect on the Pgp-mediated unidirectional efflux of R123 . Additionally, in human breast cancer cells, the intracellular presence of R123 did not prevent activation of the Cl- current by hyposmotic solution . The lack of detectable effect of removal of Cl-, Na+, or HCO3- on Pgp-mediated R123 transport rules out direct coupling between substrate transport and transport of either of these ions by Pgp . The persistence of Pgp-mediated R123 efflux in osmotically swollen cells indicates that activation of the Pgp-associated Cl- current does not hinder the Pgp pump function . The lack of effect of R123 on swelling-activated Cl- current denotes that Pgp-mediated transport of organic substrates and Pgp-associated Cl- currents can occur at the same time in a single cell . These results underscore the dissociation between Pgp-mediated active drug transport and electrodiffusive Cl- transport. JAMA, 1994 Mar 2, 271(9), 665 - 71 Nationwide survey of drug-resistant tuberculosis in the United States; Bloch AB et al.; OBJECTIVE--To determine antituberculosis drug resistance patterns, geographic distribution, demographic characteristics, and risk factors of reported tuberculosis (TB) patients in the United States . DESIGN--Survey of reported TB cases in the United States . For culture-positive cases reported to the Centers for Disease Control and Prevention, we asked health departments to provide drug susceptibility test results from initial Mycobacterium tuberculosis isolates . STUDY POPULATION--Culture-positive TB cases in the United States reported during the first quarter of 1991 . MAIN OUTCOME MEASURES--Individual TB case reports submitted to the Centers for Disease Control and Prevention and drug susceptibility test results . RESULTS--Resistance to one or more antituberculosis drugs was found in 14.2% of cases . Resistance to isoniazid and/or rifampin was found in 9.5% of cases whose isolates were tested against one or both drugs; such cases were found in 107 counties in 33 states . Resistance to both isoniazid and rifampin (multidrug-resistant {MDR} TB) was found in 3.5% of cases whose isolates were tested against both drugs; such cases were found in 35 counties in 13 states . New York City accounted for 61.4% of the nation's MDR TB cases . The 3-month population-based incidence rate of MDR TB in New York City was 52.4 times (95% confidence interval {CI}, 35.5 to 78.3) that of the rest of the nation (9.559 vs 0.182 cases per million population) . Compared with the rate in non-Hispanic whites in the rest of the nation (0.032 cases per million), the relative risk of MDR TB in New York City non-Hispanic whites was 39.0 (95% CI, 8.1 to 164.5), 299.3 (95% CI, 112.5 to 927.1) in Hispanics, 420.9 (95% CI, 121.0 to 1515.8) in Asian/Pacific Islanders, and 701.0 (95% CI, 296.4 to 2018.1) in non-Hispanic blacks . CONCLUSIONS--With nearly 10% of TB patients resistant to isoniazid and/or rifampin, greater use of four-drug regimens and directly observed therapy is indicated . Aggressive intervention to prevent the further spread of MDR TB is needed to find every TB patient and to provide optimal patient management to ensure completion of chemotherapy. Trends Biochem Sci, 1994 Mar, 19(3), 119 - 23 Multidrug resistance pumps in bacteria: variations on a theme; Lewis K; Multidrug resistance pumps (MDRs) arise from three different gene families and are widespread in bacteria . For example, in Escherichia coli alone, there seem to be seven distinct MDRs . The most common belong to the major facilitator family of membrane translocases; this type of MDR is closely related to specific antibiotic extrusion pumps such as the tetracycline/H+ antiporter . This similarity in design, and the high incidence of apparently independent evolution of MDRs, suggests that the property of multidrug resistance might have resulted from a loss of specificity in a specific hydrophobic-drug efflux pump. Trends Pharmacol Sci, 1994 Mar, 15(3), 83 - 9 Tamoxifen: new membrane-mediated mechanisms of action and therapeutic advances; Wiseman H; Tamoxifen protects membranes and lipoprotein particles against oxidative damage . This antioxidant action is likely to contribute to the observed cardioprotective action of tamoxifen and supports the use of this compound in treating and even preventing breast cancer . Membrane-mediated mechanisms of tamoxifen action, through a putative modulation of membrane fluidity, are likely to play an important role in its anticancer action and its ability to reverse multidrug resistance, and could also lead to clinical uses as an anti-Candida and anti-viral agent . In this review, Helen Wiseman discusses the interaction of tamoxifen with membranes and lipoprotein particles, and considers the possible clinical implications. J Infect Dis, 1994 Mar, 169(3), 595 - 603 Mefloquine prophylaxis prevents malaria during pregnancy: a double-blind, placebo-controlled study; Nosten F et al.; A double-blind, placebo-controlled study of mefloquine antimalarial prophylaxis in pregnancy (> 20 weeks of gestation) was conducted in 339 Karen women living in an area of multidrug-resistant malaria transmission on the Thai-Burmese border . Mefloquine gave > or = 86% (95% confidence interval {CI}, 59%-94%) protection against Plasmodium falciparum and complete protection against Plasmodium vivax infections . Mefloquine prophylaxis was well tolerated; use of an initial loading dose (10 mg/kg) was associated with transient dizziness, but there were no other significant adverse effects on the mother, the pregnancy, or infant survival or development (followed for 2 years) . Falciparum malaria was associated with maternal anemia and a mean reduction in birth weight in gravidae I, II, and III of 225 g (95% CI, 26-423) . Maternal anemia at delivery (hematocrit < 30%) was associated with increased infant mortality: 26% versus 15% (relative risk, 1.9; 95% CI, 1.1-3.2) . Mefloquine is safe and effective for antimalarial prophylaxis in the second half of pregnancy. Br J Cancer, 1994 Mar, 69(3), 609 - 12 Immunohistochemical detection of mutant p53 protein in epithelial ovarian cancer using polyclonal antibody CMI: correlation with histopathology and clinical features; Renninson J et al.; Approximately 30-50% of cases of ovarian adenocarcinoma harbour mutations in the p53 tumour-suppressor gene associated with elevated levels of the protein detected by immunohistochemical staining . To investigate any relation between the presence of mutant p53 and clinicopathological features of disease, we examined a series of 50 cases of epithelial ovarian adenocarcinoma for expression of p53 by immunohistological staining on fixed, paraffin-embedded tissue sections using the polyclonal antibody CM1, and by direct nucleotide sequencing of polymerase chain reaction-amplified DNA from selected cases . Of the 50 cases examined, 28 (56%) were p53 positive and there was no significant correlation between p53 status and differentiation stage, clinical (FIGO) stage, multidrug resistance (mdr-1 P-glycoprotein) expression or response to treatment . However, we observed a statistically significant difference between the high prevalence of p53-positive serous tumours (18 out of 23) and the lower prevalence of p53-positive cases in mucinous tumours (3 of 12) suggesting that factors related to disease aetiology, associated with these histological subtypes, may determine the prevalence of functional inactivation of the p53 tumour-suppressor gene in ovarian adenocarcinoma. Cancer Res, 1994 Mar 1, 54(5), 1271 - 5 Reversal of drug sensitivity in multidrug-resistant tumor cells by an MDR1 (PGY1) ribozyme; Kobayashi H et al.; In order to reverse P-glycoprotein-mediated drug resistance in a specific manner, we designed two hammerhead ribozymes which can cleave the GUC sequence in codon 179 and 196 of MDR1 (PGY1) mRNA . The ribozymes were directly synthesized using a set of primers, one containing a bacteriophage T7 RNA polymerase promoter . A target MDR1 RNA was created by a reverse transcription polymerase chain reaction using a MOLT-3 human acute leukemia cell line resistant to trimetrexate (TMQ) (MOLT-3/TMQ800), which displayed MDR1 overexpression . In a cell-free system, both ribozymes cleaved a target piece of MDR1 RNA into 2 fragments at the specific sites at a physiological pH and temperature . The cleavage reaction was dependent on time, ribozyme:substrate ratio, and magnesium concentration . The 196 MDR1 ribozyme was more active than the 179 MDR1 ribozyme . The 196 MDR1 ribozyme was then cloned into a human expression vector, and MOLT-3/TMQ800 cells were transfected . The original MOLT-3/TMQ800 cells were nearly 700-fold resistant to vincristine, whereas the transfectant cells selected in G418 became only 20- to 30-fold resistant . The level of resistance and the amount of MDR1 RNA expressed appeared to correlate inversely with the amount of ribozyme expression . A disabled 196 MDR1 ribozyme was capable of neither specific cleavage in vitro nor decreasing MDR1 expression in transfectant cells . These results indicate that it was the ribozyme activity and not antisense activity which was responsible for decreased MDR1 RNA . This approach may be applicable to cancer patients as a specific means to reverse tumors with P-glycoprotein-mediated MDR phenotype back to a drug-sensitive one. Blood, 1994 Mar 1, 83(5), 1337 - 47 Synergistic reversal of multidrug-resistance phenotype in acute myeloid leukemia cells by cyclosporin A and cremophor EL; Ross DD et al.; Cremophor (Crem) EL, the vehicle for intravenous delivery of cyclosporin A (CsA), has been reported to counteract multidrug resistance (MDR) in P-glycoprotein (Pgp)-over-expressing cell lines . Because of this, we sought to determine whether Crem functions independently as a modulator of MDR in blast cells obtained from acute myelogenous leukemia (AML) patients, and the nature of its interaction in combination with CsA in reversing an MDR phenotype . In the phenotypically classical MDR AML cell lines HL-60/Vinc (overexpresses Pgp) or HL-60/AR (does not overexpress Pgp), the dose causing half-maximum enhancement (D50) of daunorubicin (DNR, 1 micrograms/mL, 3 hours) accumulation was achieved by the combination of CsA and Crem (CsA/Crem) at 1.2 mumol/L CsA . In contrast, the D50 for Crem alone was approached at an amount that would be needed to suspend 6.2 mumol/L CsA for HL-60/Vinc, and 81 mumol/L CsA for HL-60/AR . The D50 concentrations for CsA alone (dissolved in ethanol, which does not alter DNR accumulation) were also higher than those for CsA/Crem, being 6.5 mumol/L for HL-60/Vinc, and 3.1 mumol/L for HL-60/AR . The maximum absolute level of enhancement of DNR accumulation (Emax) in each cell line was approximately equivalent for CsA/Crem or CsA alone, and was equal to the 3 hr intracellular DNR accumulation observed in parental, drug sensitive HL-60/W cells . For Crem alone, HL-60/AR and HL-60/Vinc cells showed markedly different responses: HL-60/Vinc cells attained intracellular DNR content comparable to HL-60/W, whereas HL-60/AR cells achieved only approximately 35% of this level . Multiple-drug effects were analyzed by calculation of the Combination Index (Chou and Talalay, Adv Enzyme Regul 22:27, 1984), which indicated that CsA and Crem are synergistic in causing enhancement of DNR accumulation in these MDR HL-60 cell lines . In blasts from AML patients, 5 mumol/L CsA/Crem or an equivalent amount of Crem alone each caused significant (P < .001) enhancement of DNR accumulation (60 AML-patient marrow samples) or DNR retention (51 AML-patient marrows) . Similarly, CsA/Crem or Crem alone caused significant (P < .01) enhancement of the cytotoxicity of DNR in 36 AML blast cell specimens . The degree of enhancement of accumulation/retention or cytotoxicity by CsA/Crem was approximately equivalent to that obtained with Crem alone . These studies indicate that Crem can reverse an MDR phenotype in patient AML blast cells.(ABSTRACT TRUNCATED AT 400 WORDS) Trop Med Parasitol, 1994 Mar, 45(1), 45 - 6 In vitro activity of the enantiomers of N-desbutyl derivative of halofantrine; Basco LK et al.; The in vitro activity of the enantiomers of N-desbutylhalofantrine, the major human metabolite of halofantrine, was compared using the semi-microtest against the multidrug-resistant Plasmodium falciparum FCM 29/Cameroon clone . The mean 50% inhibitory concentration (IC50) values (+/- standard deviation) of the enantiomers were equivalent (2.07 +/- 0.41 and 1.70 +/- 0.33 nmol/L) . The enantiomers of the metabolite of halofantrine, as well as those of the parent compound, have the same antimalarial activity . Since (+)-halofantrine and enantiomer-1 of the metabolite attain higher plasma concentrations in man, our study suggests that these enantiomers may be more active in vivo. Br J Haematol, 1994 Mar, 86(3), 547 - 54 Characterization and modulation of drug transport kinetics in K562 c1.6 daunorubicin-resistant cell line; Jiang XR et al.; The effects of cyclosporin A (CSA) and cellular energy depletion on daunorubicin (DAU) transport kinetics were investigated in a human erythroid leukaemia cell line K562 c1.6 selected for resistance to daunorubicin . K562 c1.6/DAU resistant cells displayed high levels of P-glycoprotein and a high level of multidrug resistance against several antitumour drugs . The resistance factors of K562 c1.6/DAU cells to DAU, doxorubicin, vinblastine and etoposide were 106, 114, 85 and 13 respectively . A 1.6-fold decrease (P < 0.01, n = 8) in DAU accumulation and a 4-fold increase (P < 0.001, n = 8) in DAU efflux were shown in the resistant cells when compared to K562 c1.6 drug-sensitive parental cells . K562 c1.6/DAU cells were also shown to reach a DAU saturation level (SL) 8-fold faster (P < 0.001, n = 8) than the parental cells . Addition of CSA to the resistant cells led to a dose-dependent increase in cellular DAU retention, while no such effect was observed in the sensitive cells by the introduction of CSA . Resistance to the antitumour drugs could be reduced to various extents by CSA . The patterns of changes and modulations of DAU transport kinetics, as well as chemosensitivity in K562 c1.6/DAU cells were found to be similar to a vinblastine-resistant leukaemia cell line CEM/VLB100 . However, K562 c1.6/DAU cells were more resistant to DAU, doxorubicin and etoposide than the CEM/VLB100 cells . An increase in DAU accumulation, intracellular SL and the time to reach 90% saturation level (SL90), and a decrease in DAU efflux in the resistant but not the sensitive cells were found in response to ATP depletion by sodium azide . These effects could be completely reversed by addition of glucose . Our results suggest that the presence of an energy-dependent effluxing mechanism responsible for the decreased drug accumulation and enhanced drug efflux may make a major contribution to the mechanism of resistance in K562 c1.6/DAU resistant cells. Anticancer Res, 1994 Mar-Apr, 14(2A), 433 - 5 Molecular interrelationships in multidrug resistance (review); Kellen JA; A brief review of the "state of the art" (1993) knowledge concerning the interrelationships of oncogenes and tumour suppressor gene p53 in multidrug resistance is presented . Gene products which induce malignant transformation and uncontrolled proliferation may play a role in activating gene(s) involved in multidrug resistance . In view of the fact that drug resistance remains the major reason for chemotherapy failure in cancer therapy, a better understanding of the genetic connections which influence the final outcome of cancer could help rationalizing treatment. Anticancer Res, 1994 Mar-Apr, 14(2A), 397 - 403 Sensitivity of multidrug-resistant MCF-7 cells to a transferrin-doxorubicin conjugate; Lemieux P et al.; Two multidrug-resistant breast cancer cell lines (MCF-7/AdrVp and MCF-7/D.40) each expressing a different membrane protein, involved in the drug resistance, have been treated with a transferrin-doxorubicin conjugate . Conjugates have shown an increase of activity over free doxorubicin on these resistant cell lines . Growth inhibition of doxorubicin-resistant cells, as evaluated by the MTT-assay, was higher for conjugates than for free doxorubicin especially for a 4-day contact period . I D 50 were twice and 10-fold lower for the conjugate than for free doxorubicin on resistant cells . MCF-7/AdrVp seemed to be particularly affected by the conjugate even if its intracellular content of doxorubicin was similar . With the Trf-Dox conjugate, an inverted correlation does exist between the drug-DNA content and the cytotoxicity of the conjugate . Verapamil influenced the uptake of free doxorubicin but not the uptake of Trf-Dox conjugate, thus showing a different mechanism of entry. Lung Cancer, 1994 Mar, 10 Suppl 1, S67 - 72 Fundamental bases of combined therapy in lung cancer: cell resistance to chemotherapy and radiotherapy; Duchesne GM; This overview briefly examines the mechanisms of drug resistance in lung cancer, including multidrug resistance and its atypical phenotypes, the role of cytoplasmic protectors such as glutathione, and resistance at the level of the DNA through topoisomerases, gene amplification or mutation, and DNA repair . Understanding of radioresistance is less advanced, but resistance may arise through limitation of the amount of DNA damage inflicted or by its subsequent modification by intracellular protectors or DNA repair . The mechanisms of radioresistance are generally distinct from those of chemoresistance providing a rationale for the use of combined modality therapy. Haematologica, 1994 Mar-Apr, 79(2), 119 - 26 p170-dependent multidrug resistance . Restoring full sensitivity to idarubicin with verapamil and cyclosporin A derivatives; Michieli M et al.; BACKGROUND . Cell sensitivity to anthracyclines and other drugs depends on several factors, including overexpression of a 170Kd transmembrane glycoprotein (P170) that enhances drug efflux from the cells . Since the result of treatment is negatively related to the expression of P170 in leukemia, malignant lymphoma and other tumors, it is important to investigate drugs and methods that can modify multidrug resistance (MDR) . MATERIALS AND METHODS . Using an MTT-microcultured tetrazolium colorimetric method, we assayed sensitivity to daunorubicin (DNR) and to its 4-demethoxy derivative idarubicin (IDA) in two MDR cell lines (CEM VLB and LOVO DX) and in their respective non-MDR parental lines (CEM and LOVO 109), with and without three MDR modifiers, namely the D-isomer of verapamil (DVRP), cyclosporin A (CyA) and the new CyA derivative SDZ PSC 833 . RESULTS . We showed that down-modulation of resistance with MDR modifiers was greater for DNR than for IDA in MDR cells . However, we also demonstrated that restoration of full sensitivity could only be achieved for IDA, not for DNR . DVRP and CyA in combination were more effective than either compound alone and could abolish P170-related resistance to IDA at concentrations of 1-2 microM and 1.6 microM, respectively . SDZ PSC 833 alone was even more effective and set MDR to zero at a concentration ranging between 0.8 and 1.6 microM . CONCLUSIONS . These data suggest that combinations of IDA and MDR modifiers may improve the results of cancer and leukemia treatment and that they are worth investigating in vivo, with attention to possible effects on drug pharmacokinetics and on normal tissue damage. Br J Haematol, 1994 Mar, 86(3), 540 - 6 Quantitation of multidrug resistant MDR1 transcript in acute myeloid leukaemia by non-isotopic quantitative cDNA-polymerase chain reaction; Lyttelton MP et al.; Drug resistance in acute myeloid leukaemia (AML) may be caused by overexpression of the P glycoprotein (PGP), an efflux pump encoded by the multidrug resistance mdr 1 gene . Previous studies have suggested that increased PGP expression in the leukaemic blasts is of prognostic significance, and that use of PGP antagonists may be beneficial in treatment . We describe preliminary results with a non-isotopic quantitative MDR 1 cDNA-PCR assay, using an artificial RNA construct sharing primer recognition sites with the target MDR 1 mRNA (MDR 1 nucleic acids 483-504 and 624-644) as an internal control . KB 3.1 parent and KB 8.5 MDR positive cell lines expressed 0.004 and 1.96 molecules MDR 1 mRNA/pg total RNA . Semiquantitative screening of 60 RNA samples from 53 AML cases detected MDR 1 transcript ranging from 0 to 1.81 molecules per pg RNA . The median value at presentation (33 patients) was 0.055 and was higher in 14 patients at relapse (0.13) and in seven patients with refractory disease (0.14) . Quantitation of MDR 1 transcript in serial samples in seven treated patients between presentation and relapse showed the decrease in three patients (0.18-0.02 x) to be as marked as the increase in three other patients (3-16 x) . The method described is well suited for the study of clinical samples because it is sensitive, specific, rapid and requires small amounts of clinical material. Anticancer Res, 1994 Mar-Apr, 14(2A), 581 - 5 Inhibition of rhodamine 123 secretion by cyclosporin A as a model of P-glycoprotein mediated transport in liver; Stapf V et al.; The interaction between P-glycoprotein modulators and P-glycoprotein mediated transport was investigated using rhodamine 123 in the isolated perfused rat liver of a mutant (TR-) rat strain . TR- rats, deficient in the canalicular multispecific anion transport system, are unable to extrude organic anions (glucuronides) and therefore excrete solely unconjugated rhodamine 123 via P-glycoprotein . Cyclosporin A, a modulator of multidrug resistance in tumor cells, inhibited the biliary secretion of rhodamine 123 dose dependently in a non-competitive manner . Both cyclosporin A and rhodamine inhibited photoaffinity labeling of immunoprecipitated P-glycoprotein with azidopine, indicating binding to hepatic P-glycoprotein . Our results indicate that monitoring the biliary rhodamine 123 secretion in the isolated perfused liver of TR- rats offers a new system for testing modulators of P-glycoprotein like cyclosporin A. Anticancer Res, 1994 Mar-Apr, 14(2A), 571 - 6 Multidrug resistance of murine leukemia cells characterization and correlation with cytochrome P-450 dependent activities, cytosolic calcium and cell cycle state; Pfeil D et al.; This paper reports studies on P388 leukemic cells sensitive and resistant to ADR and VCR . The P450 dependent enzyme system and the cytosolic calcium were estimated and are discussed in relation to MDR . It could be shown, in comparison to sensitive P388 cells, that the plasma membrane permeability for fluorescent dyes like rhodamine 123 and fura-2 and the biotransformation of xenobiotics are changed in resistant cells . Whereas the transport behaviour for the dyes is similarly induced in resistant cells independent of the drug which made the MDR, the P450 dependent enzyme activities are strongly increased in P388/ADR in comparison to the P388 and P388/VCR . The cell cycle analysis shows the same effect . Many more cells of P388/ADR are in the S-phase in comparison to P388 or P388/VCR . The LI is also increased in this direction . Therefore, it can be concluded that, depending on the kind of drug which made the MDR, different biochemical mechanisms are activated. Yeast, 1994 Mar, 10(3), 377 - 83 Mapping and sequencing of two yeast genes belonging to the ATP-binding cassette superfamily; Dean M et al.; ATP-binding cassette (ABC) transporters share significant sequence identity within their ATP-binding domains . Degenerate oligonucleotides based on highly conserved portions of the ATP-binding domain genes were used to clone portions of two members of the ABC gene superfamily from Saccharomyces cerevisiae DNA . These genes were designated MDL1 and MDL2 (for multidrug resistance-like) . Each MDL gene is predicted to encode a single set of transmembrane domains and a single ATP-binding domain, thus the MDL gene products are 'half-molecule' ABC proteins . The two genes were mapped to precise regions on chromosomes XII and XVI and show a considerable similarity to the mammalian P-glycoprotein/multidrug resistance (MDR) and peptide transporter (TAP) genes . Preliminary analysis of null mutants constructed by gene replacement has indicated that the MDL genes are not essential for viability of yeast . The sequences have been deposited in the GenBank data library under Accession Numbers L16958 (Locus YSCBCSA) and L16959 (Locus YSCBCSB). Cell Mol Biol (Noisy-le-grand), 1994 Mar, 40(2), 137 - 45 Actinomycin D causes multidrug resistance and differentiation in a human rhabdomyosarcoma cell line; Melguizo C et al.; The emergence of drug-resistant tumor cells remains a major problem in cancer chemotherapy . Resistance to multiple unrelated antineoplastic drugs may be related, in part, to expression of the P-glycoprotein . The cell line RD, derived from an embryonic rhabdomyosarcoma tumor, was used as an in vitro model to examine the development of drug resistance . A cell line resistant to actinomycin D (RD-DAC) was developed by growing RD in increasing concentrations of the drug . The ID50 (concentration of drug needed to induce a 50% reduction in cell growth) of the resultant line to actinomycin D was more than 15 times that of the parental line . The resistant line was cross-resistant to vincristine and doxorubicin . Resistance to actinomycin D resulted in increased P-glycoprotein expression, which was associated with a change in desmin and vimentin expression . These results suggest that exposure to chemotherapeutic drugs can induce not only classical multidrug resistance, but also a process of cellular differentiation in rhabdomyosarcoma cells. Bull Math Biol, 1994 Mar, 56(2), 207 - 23 A mathematical model for the inhibition of the multidrug resistance-associated P-glycoprotein pump; Michelson S et al.; An extension of an earlier model of the p170 glycoprotein pump is presented . In an earlier work (Michelson and Slate, Bull . math . Biol . 54, 1023-1038, 1992), the pump was modeled using an energy-dependent model of facilitat