Cell Biol Int, 1997 Dec, 21(12), 793 - 9 Alpha-fetoprotein-mediated targeting--a new strategy to overcome multidrug resistance of tumour cells in vitro; Moskaleva EYu et al.; The possibility of overcoming the multidrug resistance of human malignant cells by using doxorubicin conjugated to alpha-fetoprotein (AFP) was studied . It was shown that this type of antitumour drugs, penetrating the cell by receptor-mediated endocytosis with AFP as a vehicle, raises the sensitivity of the tumour cells that are resistant due to the expression of the multidrug resistance gene mdr1 . The sensitivity of antibiotic-resistant cell lines SKVLB (a human ovarian carcinoma) and MCF-7 AdrR (a human breast carcinoma) increased by 10- and 4-fold, respectively, when AFP-conjugated doxorubicin was used . The rationale of using human AFP-antitumour drug conjugates for the development of new chemotherapeutic approaches to cancer treatment is discussed. Zentralbl Bakteriol, 1995 Nov, 283(1), 5 - 13 On the development of mycobacterial infections . I . A review concerning the common situation; Schutt-Gerowitt H; In this review concerning the common situation of mycobacterial infections the following problems are discussed: (1) The worldwide epidemiological situation of tuberculosis reveals an increase in the developing countries but even in some industrialized countries like the United States . The reasons for this development are mainly socioeconomic factors . (2) The association between tuberculosis and HIV infection has caused in general a marked increase in the incidence of tuberculosis in some countries . Because of its ability to destroy the immune system, HIV is a significant risk factor for the progression of tuberculosis infection as a clinical disease . Taking into account that 5 million persons worldwide are infected with tuberculosis as well as with HIV (most of them living in the Sub-Saharan Africa), enormous future problems can be anticipated . (3) The new fear of tuberculosis has resulted mainly from reports about outbreaks with multidrug resistant strains of Mycobacterium tuberculosis in the United States . These strains are at least resistant to the most important antituberculotic drugs isoniacid and rifampicin . The frequency of multidrug-resistant tuberculosis in the USA is reported to be overall 3-7%, however for New York 19% is estimated . The main reason for this development is inadequate chemotherapy mostly due to poor compliance . Therefore in the United States the directly observed therapy has been established . Complete and reliable reports of the resistance situation in other countries are not available because most of these have no resistance surveillance programs . (4) As immunocompromised patients become more numerous, the importance of nontuberculous mycobacteria has significantly increased . Mainly organisms of the Mycobacterium avium-intracellulare complex play a special role as opportunistic pathogens for AIDS patients in later stages of their disease . Therapy for these infections is problematic due to the high resistance of most ubiquitous mycobacteria to antituberculotic drugs . (5) New laboratory techniques have shortened the detection time (radiometric culture systems) and the time needed for the identification of the most important mycobacteria species (DNA probes) . A further improvement of the laboratory diagnosis of tuberculosis is expected in the near future by nucleic acid amplification techniques (polymerase chain reaction and others). Cancer Res, 1998 Nov 1, 58(21), 4790 - 3 Increased sensitivity of adriamycin-selected tumor lines to CTL-mediated lysis results in enhanced drug sensitivity; Fisk B et al.; The emergence of drug resistance to chemotherapeutic agents is a major cause of treatment failure in cancer therapy . Therefore, much effort has been aimed at circumventing or reversing this undesired effect . Recently, we found that tumor cell lines selected for their multidrug-resistant phenotype can also exhibit increased levels of TAP mRNA and MHC class I proteins . This raised the question of whether drug-resistant tumors are more readily recognized by MHC-restricted CTLs . In this report, we show that five of five MHC class I+ tumor cell lines grown in medium containing Adriamycin developed into variants that expressed higher levels of MHC class I than did their corresponding parental cell lines . This was not observed with a MHC class I- cell line . No similar association was noted for changes in the expression of either HER-2 or intercellular adhesion molecule 1 protein . We also found that MHC class I+ drug-selected variants were more readily lysed by MHC-restricted, tumor-associated CTLs than were the drug-sensitive parental cell lines . When the drug-selected variants were cocultured with the same CTLs to eliminate tumor cells expressing higher levels of MHC-I (MHC-Ihi), the CTL-resistant tumor cells exhibited a drug sensitivity profile similar to that of the parental cell lines that were not exposed to Adriamycin . These findings suggest that certain chemotherapeutic drugs may increase the immunogenicity of some tumors, and that CTL immunotherapy may help reverse drug resistance. Gen Pharmacol, 1998 Nov, 31(5), 721 - 8 Analogs of staurosporine: potential anticancer drugs? Gescher A. 1 . Protein kinase C (PKC) is a family of serine/threonine-directed protein kinases that are pivotal regulators of cellular growth, transformation and death . PKC has therefore been considered to be a suitable target for novel antineoplastic drugs . 2 . Twenty years ago, staurosporine was isolated from bacteria and identified as a potent inhibitor of PKC activity . Its analogs UCN-01 and CGP 41251 effectively arrest the growth of several human-derived tumor cell lines in vitro . They also possess antineoplastic activity in vivo in human tumors grown as xenografts in nude mice . CGP 41251 reverses the multidrug-resistance phenotype of cancer cells . Both agents are currently under clinical evaluation as potential antitumor drugs . 3 . Staurosporine analogs inhibit "conventional" PKC isoenzymes more potently than "novel" and "atypical" ones . They are also potent modulators of the cyclin-dependent kinase system, which determines the progression of cells through the cell cycle . The nature of this interaction is complex . UCN-01 blocks cells in G1 phase by promoting accumulation of dephosphorylated retinoblastoma protein as a consequence of inhibition of the activity of certain cyclin-dependent kinases, downregulation of their partner cyclins and an increase in the expression of cyclin-dependent kinase inhibitor proteins . 4 . Preliminary results of early clinical trials suggest that UCN-01 and CGP41251 are without remarkable toxicity but display high binding to human plasma protein. Exp Hematol, 1998 Nov, 26(12), 1111 - 7 In acute myeloid leukemia, coexpression of at least two proteins, including P-glycoprotein, the multidrug resistance-related protein, bcl-2, mutant p53, and heat-shock protein 27, is predictive of the response to induction chemotherapy; Kasimir-Bauer S et al.; To identify prognostic factors alternative or additional to P-glycoprotein (Pgp), we studied the impact of the multidrug resistance-related protein (MRP), bcl-2 (flow cytometry), mutant p53 (single-strand conformation polymorphism), and heat-shock protein 27 (HSP27, Western blotting) in myeloid blasts obtained at the time of diagnosis in patients with de novo acute myeloid leukemia (AML) . We collected bone marrow samples from untreated AML patients, prepared the cells as well as the cellular protein, and froze all the material . We then analyzed 20 patients who responded with complete remission (CR) and 20 patients who had blast persistence (BP) . The purpose of the study was to determine whether leukemic blasts from patients with BP were more resistant to chemotherapy than those from patients with CR . There was no significant correlation between the expression of any of these proteins alone and treatment outcome in both groups studied . In contrast, there was a significant correlation between the coexpression of at least two of these proteins and response (p = 0.0298), which turned out to be a significant independent prognostic factor for treatment failure (p = 0.0329, relative risk = 1.5) according to multivariate analysis . We conclude that drug resistance in AML is multifactorial . Thus, coexpression of different resistance mechanisms may be responsible for the primary drug resistance in de novo AML. Br J Urol, 1998 Oct, 82(4), 544 - 7 The expression of mdr-1-related gp-170 and its correlation with anthracycline resistance in renal cell carcinoma cell lines and multidrug-resistant sublines; Yu DS et al.; OBJECTIVES: To clarify the role of the membranous glycoprotein gp-170 in renal cell carcinoma (RCC) cell lines and their multidrug resistant (MDR) sublines . and to correlate gp-170 with the natural and acquired drug resistance of these cell lines to anthracyclines . MATERIALS AND METHODS: The expression of gp-170 in five cultured RCC cell lines and serial RCC8701 MDR sublines was analysed by immunofluorescent flow cytometry . The chemosensitivity of these tumour cells to the anthracycline anticancer drugs adriamycin and epirubicin was measured using the microplate tetrazolium (MTT) cytotoxicity assay, and the results correlated with gp-170 expression . RESULTS: All six natural RCC cell lines showed a variably increased expression of gp-170, with the A704 and Caki-1 cell lines the highest . In contrast, gp-170 expression increased and then was suppressed in acquired MDR sublines of RCC8701 cultured in increasing concentrations of adriamycin . The A704 and Caki-1 cells were much more resistant to adriamycin and epirubicin than the A498, ACHN and RCC8701 cell lines, in parallel with the expression of gp-170 . The resistant cell line cultured long-term in 800 ng/mL adriamycin, RCC8701/ADR800, was 122 times more resistant to adriamycin and 238 times more resistant to epirubicin than the parent cell line: the pattern differed from that in native RCC cell lines and was unrelated to the expression of gp-170 . CONCLUSION: Membranous gp-170 plays an important role in MDR of native RCC cell lines, while acquired MDR cells have different mechanisms of obtaining drug resistance in addition to gp-170 . This phenomenon may be applicable to the clinical treatment of patients newly diagnosed with RCC or those with disease refractory to chemotherapy. Mol Pharmacol, 1998 Nov, 54(5), 907 - 17 Enhanced 9-(2-phosphonylmethoxyethyl)adenine secretion by a specific, indomethacin-sensitive efflux pump in a mutant 9-(2-phosphonylmethoxyethyl)adenine-resistant human erythroleukemia K562 cell line; Hatse S et al.; We have investigated the molecular basis of the 100-fold resistance of mutant human erythroleukemia K562/PMEA-1 cells to the antiproliferative potential of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) . Upon exposure to high PMEA concentrations, comparable intracellular PMEA levels were initially observed in mutant K562/PMEA-1 and wild-type K562/0 cells, indicating that PMEA influx was unaltered . However, after 4 hr of exposure to 0.2 microM {3H}bis(pivaloyloxymethyl)-PMEA {bis(POM)-PMEA}, the total intracellular level of unphosphorylated and mono- and diphosphorylated PMEA was 2.8-fold lower in K562/PMEA-1 than in K562/0 cells . Increased PMEA secretion from K562/PMEA-1 cells (compared with K562/0 cells) became more pronounced upon prolonged exposure to bis(POM)-PMEA; after 24 hr, K562/PMEA-1 cells showed 65-fold lower total intracellular PMEA levels than K562/0 cells and at 48 hr, >400-fold less total PMEA was detected in K562/PMEA-1 cells . In addition, PMEA phosphorylation was 25- to 50-fold less efficient in K562/PMEA-1 than in K562/0 cells, pointing to an additional defect at the level of the metabolism of PMEA . The PMEA efflux mechanism was shown to be temperature- and azide-dependent, was markedly inhibited by indomethacin, and did not recognize adenine nucleotides or the phosphorylated metabolites of 3'-azido-3'-deoxythymidine . Also, over a 28-hr period, PMEA efflux was not affected by an inhibitor of RNA synthesis (actinomycin D) or protein synthesis (cycloheximide) . Our studies revealed that resistance of K562/PMEA-1 cells to PMEA is the combined result of a severely impaired PMEA phosphorylation on the one hand, and an enhanced PMEA secretion by a highly specific, indomethacin-sensitive efflux pump, different from the classical P-glycoprotein- and multidrug resistance protein-mediated resistance mechanisms, on the other hand. Mol Pharmacol, 1998 Nov, 54(5), 802 - 14 Using the national cancer institute anticancer drug screen to assess the effect of MRP expression on drug sensitivity profiles; Alvarez M et al.; The MRP gene contributes to one form of multidrug resistance . To identify drugs interacting with MRP, we measured MRP mRNA expression by quantitative PCR in 60 cell lines of the National Cancer Institute Anticancer Drug Screen . Expression was detected in all cell lines (highest in lung carcinomas and central nervous system tumors) with a range of 14-fold . A mean graph of MRP mRNA levels was constructed to determine Pearson correlation coefficients (PCCs) with mean graphs of >40,000 compounds using the COMPARE analysis . Only 20 compounds had PCCs of >/=0.500 . The PCCs for VP-16, doxorubicin, and vincristine were 0.008, 0.13, and 0.257, respectively . Initially, 36 compounds with PCCs of >/=0.428 were analyzed using two MRP-overexpressing cell lines; low levels of cross-resistance was demonstrated for 23 compounds (1.3-9.4-fold) . Twenty-four compounds also were available for further studies . Using a fluorescence activated cell sorter assay to measure competition of calcein efflux from MRP-overexpressing cells, 10 compounds were found to increase calcein retention by >/=2-fold . Ten compounds also were able to reduce ATP-dependent {3H}LTC4 transport into vesicles from MRP-overexpressing cells . These results contrast with previous studies with MDR-1 in which high correlations were found and confirmed for a large number of compounds . Although other assays may be more revealing, in these unselected cell lines, MRP mRNA expression was a poor predictor of drug sensitivity . This raises the possibility that other factors, including conjugating enzymes, glutathione levels, or other transporters, confound the MRP effect. Mol Biochem Parasitol, 1998 Sep 15, 95(2), 193 - 201 Selection at a P-glycoprotein gene in ivermectin- and moxidectin-selected strains of Haemonchus contortus; Blackhall WJ et al.; Resistance to anthelmintics that are used to control parasite populations in domestic animals has become a serious problem worldwide . The development of resistance is an evolutionary process that leads to genetic changes in parasite populations in response to drug exposure . The anthelmintic ivermectin is known to bind to the human membrane transport protein, P-glycoprotein, and P-glycoprotein-deficient mice treated with ivermectin have shown signs of neurotoxicity . P-glycoprotein is believed to be involved in the multidrug resistance phenotype seen in some human cancers and for drug resistance in some protists . We have examined the genetic variation of a P-glycoprotein homologue from the nematode Haemonchus contortus to see if an association exists between specific alleles of this gene and survival to exposure to ivermectin or moxidectin . Two parasite strains passaged without drug treatment and three strains, subjected to anthelmintic selection and derived from the unselected strains, were examined . Allelic variation in the unselected strains showed this locus to be highly polymorphic . chi 2 analyses of allele frequencies showed significant differences between the unselected and the drug-selected derived strains . In all three drug-selected strains, an apparent selection for the same allele was observed . These findings suggest that P-glycoprotein may be involved in resistance to both ivermectin and moxidectin in H . contortus. Biochem Pharmacol, 1998 Nov 1, 56(9), 1219 - 28 In vitro and in vivo reversal of cancer cell multidrug resistance by the semi-synthetic antibiotic tiamulin; Baggetto LG et al.; A large number of multidrug resistance (MDR) modulators, termed chemosensitizers, have been identified from a variety of chemicals, but most have been proven to be clinically toxic . Low concentrations of the pleuromutilin-derived semi-synthetic antibiotic tiamulin (0.1 to 10 microM) sensitized the three highly resistant P-glycoprotein (Pgp)-overexpressing tumor cell lines P388 (murine lymphoid leukemia), AS30-D (rat hepatoma), CEM (human lymphoblastic leukemia), and the barely resistant AS30-D/S cell lines to several MDR-related anticancer drugs . Flow cytometric analysis showed that tiamulin significantly increased the intracellular accumulation of daunomycin . When compared to reference modulating agents such as verapamil and cyclosporin A, tiamulin proved to be 1.1 to 8.3 times more efficient in sensitizing the resistant cell lines . Moreover, when given i.p . (1.6 microg/mg body weight), tiamulin increased the survival rate of adriamycin-treated mice bearing the P388/ADR25 tumor line by 29% . In the presence of an anticancer drug, tiamulin inhibited both ATPase and drug transport activities of Pgp in plasma membranes from tumor cells . Tiamulin is thus a potent chemosensitizer that antagonizes the Pgp-mediated chemoresistance in many tumor cell lines expressing the MDR phenotype at different levels and displays no toxic effects on contractile tissues at active doses, therefore providing the promise for potential clinical applications. Biochem Pharmacol, 1998 Nov 1, 56(9), 1209 - 17 Kinetics of anthracycline accumulation in multidrug-resistant tumor cells: relationship to drug lipophilicity and serum albumin binding; Demant EJ et al.; A multidrug-resistant Ehrlich ascites tumor cell line (EHR2/DNR+) was used to examine the membrane transport kinetics of lipophilic anthracycline derivatives in the presence of serum albumin . We present a model for theoretical data analysis with consideration of drug-albumin complex formation . For a set of five derivatives (doxorubicin, daunorubicin, 4-demethoxydaunorubicin, 4'-deoxy-4'-iododoxorubicin, and 13-dihydro-4'-deoxy-4'-iododoxorubicin), data were given on the rates of diffusional drug uptake, and membrane permeability coefficients of the noncharged molecules were estimated . Both the initial rates and the steady-state levels of drug uptake were found to decrease by addition of BSA at concentrations ranging from 5 to 75 mg/mL . For each drug, this effect of serum albumin could be accounted for by the altered distribution between free and protein-bound drug molecules in the bulk aqueous medium . A good fit of theoretical accumulation curves to the experimental data was obtained . It was concluded that a mathematical simulation method makes it possible to predict the uptake characteristics of lipophilic anthracycline compounds into tumor cells under serum conditions. Biochem Pharmacol, 1998 Nov 1, 56(9), 1157 - 66 Selective cytotoxicity of topoisomerase-directed protoberberines against glioblastoma cells; Sanders MM et al.; Protoberberines are a new class of organic cations that are dual poisons of topoisomerases I and II . Certain protoberberines exhibit greater in vitro cytotoxicity against cell lines derived from solid tumors than from leukemias . Using a group of seventeen different protoberberine analogs, the structural basis for selective cytotoxicity toward sensitive SF-268 glioblastoma cells as compared with resistant RPMI 8402 lymphoblast cells was explored . The selective cytotoxicity is associated with the presence of an imminium ion and other structural features of protoberberines, and is not shared by drugs such as camptothecin, doxorubicin, vinblastine, and etoposide, which are either equally or more cytotoxic against RPMI 8402 cells than SF-268 cells . The selective cytotoxicity of protoberberines against SF-268 over RPMI 8402 cells is not due to differences in topoisomerase levels or known drug efflux systems such as multidrug resistance (MDR1) and multidrug-resistance protein (MRP) . Comparative in vitro studies of the accumulation of coralyne, a fluorescent protoberberine, into sensitive and resistant cells demonstrated a correlation between drug accumulation and selective cytotoxicity . Inhibitors of coralyne uptake included several protoberberine-related compounds . Of these, palmatine, a minimally cytotoxic protoberberine, both inhibited coralyne accumulation and reduced cytotoxicity against SF-268 cells, but not against RPMI 8402 cells . Despite the structural resemblance of protoberberines to catecholamines, our experiments using inhibitors and cells expressing biogenic amine uptake systems have ruled out the involvement of biogenic amine uptake1, uptake2, and vesicular monoamine transport systems . Uptake systems remaining as candidates, supported by preliminary data, include transport via vesicles derived from specialized membrane invaginations and selected carrier-mediated organic amine transport systems. Curr Opin Oncol, 1998 Aug, 10 Suppl 1, S15 - 9 Multidrug resistance: clinical relevance in solid tumours and strategies for circumvention; Kaye SB; Strictly speaking, multidrug resistance (MDR) describes the experimental observation of cross resistance to various structurally unrelated cytotoxic agents in laboratory models of cancer . These drugs have in common their origin as natural products, and in 1985 the basis of this MDR was established as the over-expression of a membrane glycoprotein, called P-glycoprotein (Pgp), which acts as a drug efflux pump actively depleting intracellular drug concentrations in resistant tumour cells . Since then, MDR has arguably taken on a second meaning, i.e . 'misunderstood drug resistance', through the understandable, but mistaken assumption by many scientists and some clinicians that the clinical observation in cancer patients treated with chemotherapy of resistance to a wide range of cytotoxic drugs (either as a primary or acquired property) inevitably involves the same mechanism . At present, the evidence from clinical studies to support such a notion is clearly lacking, particularly in solid tumours . However, increased Pgp expression has been observed in a number of clinical situations, and its relevance requires further elucidation . Current data indicate that increased Pgp expression represents an adverse prognostic factor, for reasons which may be quite unrelated to developing drug resistance . Experimentally, MDR can be reversed by simultaneous treatment with a number of non-cytotoxic agents which competitively inhibit Pgp function . Despite the reservations outlined, numerous clinical trials of this approach have been conducted . The results have generally been negative in solid tumours, although some have been more promising in haematological cancers . The most recent studies have used more potent modulating agents, such as the cyclosporin analogue, PSC833 . Interpretation of data from these trials is complicated by pharmacokinetic interactions between the target cytotoxic drug and the modulating agent . Randomized trials are now underway in a number of tumour types; thus a clearer picture of the clinical relevance of MDR should emerge over the next few years. Anal Biochem, 1998 Oct 15, 263(2), 198 - 207 Interaction of doxorubicin with ATP: quantification of complexes and effect on its diffusion into DNA-loaded liposomes--implication for ATP-driven transport studies; Chambon MH et al.; Doxorubicin, a drug largely used in chemotherapy, is transported by P-glycoprotein, a protein involved in the multidrug-resistance phenotype . Taking advantage of the doxorubicin fluorescence quenching upon interaction with DNA, a sensitive assay of this active transport can be carried out: quantitative in vitro studies could be achieved with DNA-loaded proteoliposomes, after correction for the doxorubicin passive diffusion through phospholipids . In this paper, we describe experimental conditions that will be relevant to P-glycoprotein studies . Efficient DNA entrapment in preformed liposomes was obtained using the freeze/thawing procedure, and the doxorubicin passive diffusion was quantified in the presence of ATP/Mg2+, the second substrate of P-glycoprotein . The doxorubicin diffusion rate decreases in the presence of ATP, indicating an interaction between doxorubicin and ATP that will hinder any measurement of ATP-driven transport . The interaction between doxorubicin and ATP was studied by fluorescence quenching, octanol/buffer partition coefficient, and diffusion rate into DNA-loaded liposomes . The results give evidence for complex interactions . However, under our experimental conditions, these interactions are only slightly modified in the presence of Mg2+ . Since this cation is essential for P-glycoprotein activity, it can be concluded that in these conditions the accurate evaluation of P-glycoprotein-catalyzed doxorubicin transport will be obtained from the Mg2+-sensitive transport into DNA-loaded proteoliposomes . Thorax, 1998 Jul, 53(7), 536 - 48 Chemotherapy and management of tuberculosis in the United Kingdom: recommendations 1998 . Joint Tuberculosis Committee of the British Thoracic Society; In vitro and in vivo activities of trybizine hydrochloride against various pathogenic trypanosome species; Swiss Tropical Institute, Basel, SwitzerlandTrybizine hydrochloride {O,O'-bis(4,6-diamino-1,2-dihydro-2, 2-tetramethylene-s-triazine-1-yl)-1,6-hexanediol dihydrochloride} was active in vitro against the sleeping sickness-causing agents Trypanosoma brucei subsp . rhodesiense and T . brucei subsp . gambiense; against a multidrug-resistant organism, T . brucei subsp . brucei; and against animal-pathogenic organisms Trypanosoma evansi, Trypanosoma equiperdum, and Trypanosoma congolense; but not against the intracellular parasites Trypanosoma cruzi and Leishmania donovani . Cytotoxic effects against mammalian cells were observed at approximately 10(6)-fold higher concentrations than those necessary to inhibit T . brucei subsp . rhodesiense . Trybizine hydrochloride was able to eliminate T . brucei subsp . rhodesiense and T . brucei subsp . gambiense in an acute rodent model with four intraperitoneal doses of 0.25 mg kg of body weight-1 or four doses of 1 mg kg-1, respectively, or with four oral doses of 20 mg kg-1 . The compound expressed activity against suramin-resistant T . evansi strains in mice . However, these concentrations were not sufficient to cure mice infected with multidrug-resistant T . brucei subsp . brucei . A late-stage rodent model with central nervous system involvement could not be cured, indicating that trybizine may not pass the blood-brain barrier in sufficient quantities. Clin Cancer Res, 1998 Oct, 4(10), 2321 - 9 Phase I trial of cremophor EL with bolus doxorubicin; Millward MJ et al.; Cremophor EL (cremophor), a component of the paclitaxel formulation, can potentially reverse P-glycoprotein-associated multidrug resistance . A Phase I trial of cremophor as a 6-h infusion every 3 weeks was performed with bolus doxorubicin (50 mg/m2) . The cremophor dose was escalated from 1 to 60 ml/m2 . A standard paclitaxel premedication was given before cremophor . Using a bioassay, potentially active cremophor levels (> or = 1 microl/ml) were measured in plasma from patients receiving cremophor doses of 30, 45, and 60 ml/m2 . A cross-over design was used to assess the influence of cremophor 30 ml/m2 on the pharmacokinetics of doxorubicin and doxorubicinol . The plasma area under the concentration versus time curve (AUC) of doxorubicin increased from 1448 +/- 350 to 1786 +/- 264 ng/ml x h (P = 0.02) in the presence of cremophor, whereas the AUC of doxorubicinol increased from 252 +/- 104 to 486 +/- 107 ng/ml x h (P = 0.02) . This pharmacokinetic interaction was associated with significantly increased neutropenia . With reduction of the doxorubicin dose to 35 mg/m2, the cremophor dose was increased to 60 ml/m2 . Dose-limiting toxicities occurred in two of six patients after 45 ml/m2 and two of four patients after 60 ml/m2, which included febrile neutropenia and grade III cremophor-related toxicities of rash, pruritus, headache, and hypotension . All patients who received 45 ml/m2 cremophor reached plasma levels > or = 1.5 microl/ml, but at 60 ml/m2, only two of four reached this level, and the calculated plasma clearance of cremophor was significantly faster at this dose . One patient with hepatoma resistant to epirubicin achieved a near-complete response . Cremophor 45 ml/m2 over 6 h with 35 mg/m2 doxorubicin is recommended for further studies . The pharmacokinetic interaction between cremophor and doxorubicin is quantitatively similar to that described in trials of paclitaxel with doxorubicin and suggests that the cremophor in the paclitaxel formulation is responsible. Hepatology, 1998 Nov, 28(5), 1371 - 7 Adenosine triphosphate-dependent transport of estradiol-17beta(beta-D-glucuronide) in membrane vesicles by MDR1 expressed in insect cells; Huang L et al.; MDR1, an ABC transporter that confers multidrug resistance in tumor cells, is constitutively expressed in normal liver canalicular membrane . Human MDR1-expressing multidrug-resistant cells display increased resistance to estradiol-17beta(beta-D-glucuronide) (E217G) . MDR1 substrates/modulators inhibit adenosine triphosphate (ATP)-dependent transport of E217G in the rat canalicular membrane and protect against E217G-mediated cholestasis in isolated perfused rat liver . The present studies were designed to determine if E217G is a substrate for MDR1 using a baculovirus expression system and if other estrogen glucuronides interact with MDR1 . ATP-dependent transport of E217G (10 micromol/L) was linear for up to 2 minutes and yielded a rate of 45.6 pmol/min/mg protein in membrane vesicles from Sf9 cells infected with MDR1-baculovirus . This transport was saturable (Km = 62 micromol/L) and occurred into an osmotically sensitive space . ATP-dependent transport of E217G (10 micromol/L) was inhibited 63% by 10 micromol/L daunomycin, but not by 100 micromol/L S-(2,4-dinitrophenyl)glutathione (GS-DNP) (a substrate for canalicular multispecific organic anion transporter {cMOAT}) . Glucuronide conjugates of the estrogen D-ring (100 micromol/L), estriol-17beta(beta-D-glucuronide) (E317G) and estriol-16(beta-D-glucuronide) (E316G), inhibited MDR1-mediated E217G transport by 58% and 35%, respectively . In contrast, noncholestatic glucuronides, estradiol-3-(beta-D-glucuronide) (E23G) or estradiol-3-sulfate-17beta(beta-D-glucuronide) (E23SO417G), had no effect . E217G neither stimulated MDR1 ATPase activity nor inhibited verapamil-stimulated ATPase activity . Infusion of 1.5 micromol/L doxorubicin or 1 micromol/L taxol protected against cholestasis induced by E316G and E317G in isolated perfused rat liver . These studies identify E217G, and probably E316G and E317G, as endogenous substrates for MDR1. Hepatology, 1998 Nov, 28(5), 1332 - 40 Expression of the apical conjugate export pump, Mrp2, in the polarized hepatoma cell line, WIF-B; Nies AT et al.; The polarized rat hepatoma/human fibroblast hybrid cell line, WIF-B, forms apical vacuoles into which cholephilic substances are secreted . We studied expression, localization, and function of the apical conjugate export pump, Mrp2, in WIF-B cells . Mrp2, the apical isoform of the multidrug resistance protein, alternatively termed canalicular Mrp (cMrp) or canalicular multispecific organic anion transporter (cMoat), is a 190-kd membrane glycoprotein mediating adenosine triphosphate (ATP)-dependent transport of glucuronides, glutathione S-conjugates, and other amphiphilic anions across the hepatocyte canalicular membrane into bile . Expression of the rat mrp2 gene in WIF-B cells was shown by reverse-transcription polymerase chain reaction (PCR), followed by sequencing of the amplified 789-bp fragment . Immunoblotting, using antibodies reacting with the amino-terminal or with the carboxyl-terminal sequence of rat Mrp2, detected the 190-kd glycoprotein in WIF-B cell homogenates . Immunofluorescence microscopy localized Mrp2 to the apical membrane domain . Preloading of WIF-B cells with a membrane-permeable ester of the calcium-dependent fluorescent indicator, Fluo-3, was followed by Mrp2-mediated secretion of the amphiphilic anion, Fluo-3, into the apical vacuoles . This transport was potently inhibited by cyclosporin A added to the culture medium . Direct measurements of ATP-dependent transport into Mrp2-containing plasma membrane vesicles in comparison with Mrp2-deficient vesicles established that Fluo-3 is transported by Mrp2 with a Km value of 3.7 micromol/L . Our results indicate that the polarized WIF-B cells express the rat ortholog of the apical conjugate-transporting ATPase, Mrp2 . The function of Mrp2 as well as the action of inhibitors can thus be analyzed by use of the fluorescent amphiphilic anion, Fluo-3. Cell Physiol Biochem, 1998, 8(5), 246 - 60 Swelling-activated chloride currents in a drug-sensitive cell line and a P glycoprotein-expressing derivative are underlied by channels with the same pharmacological properties; Horton JK et al.; It has been proposed that P glycoprotein (Pgp) expression is associated with swelling-activated Cl- currents in multidrug-resistant cells . The Pgp substrate vinblastine and the modulator verapamil produced a reversible concentration-dependent block of swelling-activated Cl- currents in both a drug-sensitive cell line (MCF-7) and a Pgp-expressing derivative (BC19/3) . The similarity of the results obtained in both cell lines suggests that the mechanism of block is not related to Pgp expression and supports the hypothesis that Pgp expression is not necessary for the swelling activation of Cl- currents . In contrast to the results obtained with vinblastine, two other cytoskeleton-disrupting agents, colchicine and cytochalasin D, were not able to affect the swelling-activated Cl- currents in either cell line . The data provided no evidence for the involvement of the cytoskeleton in the swelling activation of Cl- channels in these cell lines . The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino)benzoic acid and 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid, each produced a similar reversible concentration-dependent block in the swelling-activated currents in both the Pgp-expressing and nonexpressing cells . This strongly suggests that the Cl- channel(s) responsible for the swelling-dependent current in both cell lines are the same and, since MCF-7 cells do not express Pgp, that Pgp is not the channel responsible for the volume-activated Cl- currents in these cells. Tsitologiia, 1998, 40(7), 652 - 60 Resistance to adriamycin in human chronic promyeloleukemia line K562 correlates with directed genome destabilization--amplification of MDR1 gene and nonrandom changes in karyotype structure}; Grinchuk TM et al.; Three independent subclones (B2, B3 and C9) of human myelogenous leukemia cell line K562 selected with adriamycin (ADM) were analysed . Cross-resistance of these ADM-resistant cells was examined for a resistance to the number of drugs including colchicine, actinomycin D and ethidium bromide . MDR 1 gene amplification in B3 and C9 subclones was detected using Southern-hybridization with specific probe . Additional genetical material was found in genomes of resistant cells by analysis of G-banded metaphase chromosomes . An extraordinarily long marker chromosome was observed in every C9 metaphase plate . The character of this chromosome G-banding suggests that it may be a derivative of chromosome 5 containing a large homogeneously staining region (HSR) in locus 5q15 . Both B2 and B3 subclones expressed double minute chromosomes (DMs) in 5% of cells . In the course of a prolonged cultivation (about 2 years) of C9 cells in the presence of ADM a progressive karyotype destabilization was observed: the frequency of new markers formation in C9 cells increased, cells having additional copies of marker chromosome with HSR appeared, the length of HSR varied, coexistence of HSR and DMs being found in several C9 cells . These karyotypical changes may be regarded as patterns of genome destabilization due to the multidrug resistance of K562/ADM cells. Biol Chem, 1998 Aug-Sep, 379(8-9), 1121 - 6 Human mast cells secreting leukotriene C4 express the MRP1 gene-encoded conjugate export pump; Bartosz G et al.; Mast cells are known to secrete endogenously synthesized leukotriene C4 (LTC4), but the identity of the responsible export pump in human mast cells was unknown . The multidrug resistance proteins MRP1 and MRP2 have been identified as primary-active ATP-dependent export pumps for various amphiphilic anions including the glutathione conjugate LTC4 . We therefore studied the expression at the RNAand protein levels of both MRP1 and MRP2 as well as the ATP-dependent LTC4 transport in the human mast cell line HMC-1 . Upon stimulation by 1 microM ionomycin, intact HMC-1 cells generated 26 pmol LTC4/10(8) cells within 20 min . Transport experiments using inside-out HMC-1 membrane vesicles demonstrated an ATP-dependent LTC4 transport amounting to 1.4 pmol x (mg protein)(-1) x min(-1) . Reverse transcription PCR indicated that HMC-1 cells express mRNA of MRP1, but not of MRP2 or MRP3 . Cloning and sequencing of the amplified PCR fragment confirmed its identity with the human MRP1 sequence . Immunoblots using antibodies against MRP1 and MRP2 demonstrated that HMC-1 cells contain the MRP1 but not the MRP2 protein . Our results indicate that the 190 kDa integral membrane glycoprotein MRP1 mediates the ATP-dependent export of LTC4 from human mast cells to the extracellular space. Biochem Biophys Res Commun, 1998 Oct 9, 251(1), 307 - 12 A leukotriene receptor antagonist, ONO-1078, modulates drug sensitivity and leukotriene C4 efflux in lung cancer cells expressing multidrug resistance protein; Nakano R et al.; ONO-1078 is a new class of peptide leukotriene receptor antagonist, and multidrug resistance protein (MRP) is a membrane tranporter of multiple anticancer drugs and endogenous leukotriene C4 (LTC4) . We investigated the effects of ONO-1078 on drug sensitivity and LTC4-efflux in MRP-expressing lung cancer cells . Drug sensitivity, intracellular vincristine accumulation, and intracellular and extracellular LTC4 concentrations were measured with or without ONO-1078 . The effect of ONO-1078 on MRP-mediated calcein-efflux was determined by flow cytometry . ONO-1078 (1 to 10 microM) dose-dependently enhanced the sensitivity of NCI-H520 cells to vincristine with the reduced accumulation, and also enhanced the sensitivity to doxorubicin and etoposide . ONO-1078 inhibited both LTC4- and calcein-efflux from the cells with increased intracellular accumulations . Our findings indicate that ONO-1078 modulates multidrug resistance and inhibits LTC4-efflux in lung cancer cells, by inhibition of MRP function . Gynecol Oncol, 1998 Sep, 70(3), 378 - 85 Immunophenotype of ovarian cancer as predictor of clinical outcome: evaluation at primary surgery and second-look procedure; Goff BA et al.; OBJECTIVE: This study was undertaken to evaluate whether immunophenotyping of advanced epithelial ovarian cancer could predict response to initial chemotherapy and whether tumor immunophenotype changed after chemotherapy . STUDY DESIGN: Fifty-four patients with stage III and IV ovarian cancer, treated at the University of Washington Medical Center, had pathology specimens evaluated . A subset of 23 patients also had specimens from a secondary surgery evaluated . Using immunocytochemistry, tumors were immunostained for overexpression of c-erb-B-2, epidermal growth factor receptor (EGFR), p53, and expression of the Ki67-defined antigen (a marker of cellular proliferation), tumor necrosis factor alpha (TNFalpha), estrogen receptor (ER), progesterone receptor (PR), and P-glycoprotein (P170, a marker of multidrug resistance) . Twenty-four patients had a good response to chemotherapy (defined as a negative, or microscopically positive second look), and 30 had a poor response (defined as grossly positive second look or progressive disease) . RESULTS: Comparison of tumor markers from the initial and the secondary surgeries revealed that the only significant change was in the Ki67-defined cell proliferation rate, which showed a marked reduction in those with a good response to chemotherapy (P = 0.002) . Comparison of tumor markers at initial surgery between good and poor responders revealed a correlation with p53 expression . Good responders were less likely to have p53 overexpression compared to poor responders, and this result approached significance (P = 0.058) . Comparison of tumor markers at secondary surgery revealed a significant reduction in Ki67-defined cell proliferation rate in good responders compared to poor responders (P = 0.01) . No significant differences were found between good and poor responders for the other tumor markers evaluated . CONCLUSIONS: The only tumor markers to predict for response to chemotherapy were p53 at initial surgery (P = 0.058) and Ki67 indices at secondary surgery (P = 0.001) . Expression of steroid hormone receptors, TNFalpha, and P-glycoprotein and overexpression of c-erb-B-2 or EGFR are not associated with chemoresistance . Am J Trop Med Hyg, 1998 Oct, 59(4), 577 - 81 Molecular epidemiology of malaria in Yaoundé, Cameroon . III . Analysis of chloroquine resistance and point mutations in the multidrug resistance 1 (pfmdr 1) gene of Plasmodium falciparum; Basco LK et al.; It has been postulated that chloroquine resistance may be associated with a single point mutation at codon 86 of the Plasmodium falciparum multidrug resistance 1 (pfmdr 1) gene . Using a simple and rapid molecular technique involving polymerase chain reaction and restriction fragment length polymorphism, the frequency of the Asn-to-Tyr mutation associated with chloroquine resistance was established among 129 clinical isolates obtained from indigenous patients in Yaounde, Cameroon . The results showed that 110 of 129 isolates display a mutant codon . The other clinical isolates had either a pure wild-type Asn-86 codon (n = 12) or mixed Asn/Tyr alleles (n = 7) . In vitro drug assays were performed to compare the genotype and phenotype in 102 clinical isolates . Of these isolates, 86 displayed pure Tyr-86 mutant codon; 48 (56%) mutant isolates were chloroquine-resistant (50% inhibitory concentration {IC50} > 100 nM), as expected, but 38 (44%) mutant isolates were chloroquine-sensitive (IC50 < 100 nM) . Three chloroquine-resistant isolates and seven chloroquine-sensitive parasites carried a wild-type Asn-86 codon . Mixed alleles were found in six isolates (four chloroquine-sensitive and two chloroquine-resistant isolates) . Our results did not confirm previous observations on the possible association between chloroquine resistance phenotype and genotype based on the pfmdr 1 gene. Acta Physiol Scand Suppl, 1998 Aug, 643, 213 - 8 Catalytic mechanism of P-glycoprotein; Senior AE; We generated Chinese hamster ovary cells which are highly multidrug-resistant by selection in colchicine . Purified plasma membranes from these cells are enriched in P-glycoprotein (Pgp), up to 32% w/w of membrane protein . From plasma membranes we purified Pgp to homogeneity and reconstituted it in proteoliposomes . Both plasma membranes and purified reconstituted Pgp show drug-stimulated ATPase activity (approximately 20 s-1), comparable to other transport ATPases . These materials enable investigation and characterization of the catalytic sites and mechanism . Various approaches have been used, notably enzyme kinetics, photoaffinity and other covalent labelling, use of vanadate as transition-state analog, and inhibition by beryllium and aluminum fluoride . Both Pgp nucleotide sites hydrolyse MgATP and are of relatively low specificity and affinity for nucleotides . Trapping of nucleotide by vanadate in either site blocks catalysis at both sites; covalent inactivation of either site completely blocks turnover . Therefore the catalytic sites interact strongly, and it appears that when one site enters the transition-state conformation the other site is prohibited from doing so . A minimal reaction scheme for ATP hydrolysis has been determined . We have proposed an alternating catalytic sites scheme, in which drug-transport is coupled to relaxation of a high chemical potential conformation of the catalytic site (Pgp.MgADP.Pi) which is generated by the hydrolysis step itself . Photoaffinity labelling of Pgp catalytic sites has revealed equivalent Tyr residues which lie close to the adenine ring of bound MgATP in both sites. Biophys J, 1998 Nov, 75(5), 2255 - 61 Continuous in situ electrochemical monitoring of doxorubicin efflux from sensitive and drug-resistant cancer cells; Yi C et al.; One of the least well understood problems in cancer chemotherapy is the cross-resistance of certain tumor cells to a series of chemically unrelated drugs . Multidrug resistance (MDR) can be attributed to several different biophysical processes, among them increased drug efflux . This has been found to correlate with overexpression of the cell surface 170-kDa P-glycoprotein that actively excludes cytotoxic drugs against their concentration gradient . To better understand MDR, experimental methods are needed to study drug efflux from cancer cells . Continuous measurement of efflux of nonfluorescent drugs on the same cell culture in situ, or assessing efflux from a few cells or even a single cell, is beyond the capabilities of existing technologies . In this work, a carbon fiber (CF) microelectrode is used to monitor efflux of doxorubicin from a monolayer of two cell lines: an auxotrophic mutant of Chinese hamster ovary cells, AUXB1, and its MDR subline, CHRC5 . Because doxorubicin is both fluorescent and electroactive, the results could be validated against existing data obtained optically and with other techniques on the same cell lines, with good agreement found . The electrochemical detection, however, is capable of in situ monitoring with high temporal resolution and is suitable for single-cell studies. Cancer Chemother Pharmacol, 1998, 42(6), 483 - 90 Circumvention of multidrug resistance by a quinoline derivative, MS-209, in multidrug-resistant human small-cell lung cancer cells and its synergistic interaction with cyclosporin A or verapamil; Shrivastava P et al.; PURPOSE AND METHODS: To develop a clinically useful approach to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) in MDR human small-cell lung cancer (SCLC), we examined the ability of a novel quinoline compound, MS-209, to reverse MDR by inhibition of P-gp function in combination with other MDR-reversing drugs using a cytotoxicity assay . RESULTS: We established MDR human SCLC cells by culture in medium with gradually increasing concentrations of adriamycin (ADM) . Compared with the parental human SCLC cells, SBC-3, the MDR variant SBC-3 cells obtained (SBC-3/ADM) were highly resistant to various chemotherapeutic agents due to P-gp expression . MS-209 reversed the resistance to ADM and vincristine (VCR) of SBC-3/ADM and H69/VP cells in a dose-dependent manner . Moreover, MS-209 in combination with cyclosporin A (CsA) or verapamil (VER) synergistically enhanced the antitumor effects of ADM and VCR on SBC-3/ADM cells . MS-209 restored ADM incorporation and this effect was enhanced by CsA and VER, suggesting that these synergistic effects were due to competitive inhibition of P-gp function . CONCLUSION: MS-209 in combination with CsA or VER might increase the efficacy of these chemotherapeutic agents against MDR human SCLC cells. Cancer Chemother Pharmacol, 1998, 42(6), 454 - 60 Circumvention of P-glycoprotein-mediated multidrug resistance by S16020-2: kinetics of uptake and efflux in sensitive and resistant cell lines; Pierre A et al.; PURPOSE: In contrast to Adriamycin (ADR), the novel olivacine derivative S16020-2 has demonstrated potent antitumor activity in vitro and in vivo against cell lines displaying the P-glycoprotein (Pgp)-mediated multidrug-resistance phenotype (MDR), suggesting that this compound is not transported by Pgp . The purpose of this work was to study the accumulation of S16020-2 in Pgp-overexpressing cells . METHODS: The kinetics of accumulation and retention of radiolabeled S16020-2 and ADR in sensitive KB-3-1, P388, and S1 cells and their resistant counterparts KB-A1, P388/VCR-20, and S1/tMDR cells were investigated . RESULTS: The rates of efflux of S16020-2 and ADR were similar and were higher in KB-A1 cells than in KB-3-1 cells . A modulator of MDR, S9788, inhibited the efflux of both compounds only in KB-A1 cells . These results demonstrate that S16020-2 is effectively transported by Pgp overexpressed by KB-A1 cells with an efficiency close to that of ADR . A similar conclusion was obtained with the P388/VCR-20 cell line . In addition, the initial rate of uptake and the accumulation of S16020-2 were markedly higher than those of ADR in the cell lines tested . CONCLUSIONS: The cytotoxic potency of S16020-2 toward tumor cells overexpressing Pgp is thus likely to be due to its rapid rate of uptake, which bypasses Pgp and thus leads to a high cellular accumulation. Cancer Chemother Pharmacol, 1998, 42(6), 441 - 6 Lack of correlation of MRP and gamma-glutamylcysteine synthetase overexpression with doxorubicin resistance due to increased apoptosis in SV40 large T-antigen-transformed human mesothelial cells; Ogretmen B et al.; PURPOSE: Evidence suggests that viral proteins such as simian virus large T-antigen (SV40 TAg) play a role in the response of cancer cells to chemotherapeutic agents . In this study, we investigated whether SV40 TAg-immortalized human mesothelial cells express drug resistance-related proteins and display resistance to chemotherapy, and whether SV40 TAg transformation affects apoptosis . METHODS: We determined the mRNA and protein levels of the multidrug resistance-associated protein (MRP), gamma-glutamylcysteine synthetase heavy subunit (gamma-GCSh), and P-glycoprotein (product of the MDR1 gene) by RT-PCR and Western blotting, respectively, in normal human mesothelial (NHM) cell and SV40 TAg-transformed human mesothelial (Met-5A) cells . The effect of increasing concentrations of doxorubicin (DOX) on these cells was investigated using an MTT cytotoxicity assay, and the glutathione (GSH) content was measured spectrophotometrically . DOX accumulation in these cells was measured by treating the cells with {14C}DOX followed by scintillation counting . Cytoplasmic bNA fragmentation due to apoptosis following DOX treatment of the cells was quantitated by ELISA . RESULTS: We showed that the MRP and gamma-GCSh genes, but not MDR1, are coordinately overexpressed in Met-5A cells compared with NHM cells . Expression of MRP protein as detected by an anti-MRP antibody correlated with increased GSH levels and decreased accumulation of {14C}DOX in Met-5A cells compared with NHM cells . However, Met-5A cells were twofold more sensitive to DOX than NHM cells . In addition, quantitative measurement of apoptosis when cells were treated with 0.05 and 0.5 microM DOX revealed that drug-induced apoptotic cell death was increased about 1.4- and 3.0-fold, respectively, in Met-5A cells compared with NHM cells . CONCLUSIONS: These results suggest that increased levels of apoptosis might help overcome the DOX resistance effects of MRP/gamma-GCSh overexpression in SV40 TAg-transformed Met-5A cells. Respiration, 1998, 65(5), 335 - 42 Tuberculosis and HIV infection: a global perspective; Murray JF; The incidence of HIV-associated tuberculosis has been increasing worldwide since the beginning of the AIDS epidemic, and is expected to increase even further during the foreseeable future, especially in developing countries . There is no doubt now that, in the presence of HIV infection, new-onset tuberculous infection progresses rapidly to clinically significant disease and the likelihood that latent tuberculous infection progresses rapidly to clinically significant disease and the likelihood that latent tuberculous infection will reactivate is enormously increased . The accelerating and amplifying influence of HIV infection is contributing to the increasing incidence of disease caused by multidrug-resistant strains of Mycobacterium tuberculosis . Neither clinical features nor radiographic abnormalities reliably distinguish the majority of patients with HIV-associated tuberculosis from those without HIV infection . Some persons with HIV infection, however, present with atypical manifestations of tuberculosis and these patients may be difficult to diagnose . Six months of daily or thrice weekly chemotherapy with the usual regimen of 4 then 2 antituberculosis drugs cures most patients, but many die during or after treatment of other AIDS-related complications. Leuk Res, 1998 Nov, 22(11), 1049 - 56 Characterization of cytotoxicity induced by sphingolipids in multidrug-resistant leukemia cells; Klostergaard J et al.; Certain sphingolipids (SLs) exert fundamental roles in differentiative, growth-inhibitory and apoptotic pathways induced by a number of agents in leukemia cells . Multidrug-resistance (MDR) is a major cause of therapeutic failure in leukemia . SLs are among the diverse substrates for the MDR p-170 glycoprotein drug-efflux pump . We tested the hypothesis that expression of MDR would thereby block the cytotoxicity induced by the SLs sphingosine, sphinganine and N-hexanoyl-sphingosine . An MDR-expressing subline of murine P388 leukemia cells demonstrated an ED50 value > or = 2 log10 higher than the parental line in response to doxorubicin . In contrast, the ED50 values for each of the SLs were only approximately 1.5 to two-fold higher in the MDR line than in the parental; induction of DNA damage by SLs was comparable or actually greater in MDR compared to parental cells . Therefore, expression of MDR does not significantly affect the cytotoxic function of these SLs, nor do these SLs likely contribute to MDR. Ther Drug Monit, 1998 Oct, 20(5), 581 - 7 Resistance to anticancer drugs: are we ready to use biologic information for the treatment of patients with cancer? Robert J. Multidrug resistance (MDR) to anticancer drugs can be diagnosed in tumors by molecular biology techniques (expression of the MDR1 gene), by immunologic techniques (expression of P-glycoprotein), and by functional approaches (dye exclusion) . Numerous studies have tried to correlate the MDR status of tumors to the clinical response to the treatment, but wide discrepancies prevented definitive conclusions . As a consequence, the routine use of these techniques is still not possible, and continuous efforts are needed for their standardization . The development of MDR modulators in the clinical setting is a promising approach that requires rigorous clinical trials, especially with sequential design of phase 2 protocols . Definitive results are still lacking concerning the interest of combining an MDR modulator to standard chemotherapy for resistant cancers. Ther Drug Monit, 1998 Oct, 20(5), 577 - 80 Therapeutic approach to drug resistant tumors; Naito M et al.; Drug resistance is a major problem in cancer chemotherapy . P-glycoprotein plays a major role in multidrug resistance in cancer cells . P-glycoprotein is expressed in some normal tissues and has physiological functions . These include protecting the brain against toxic substances at the blood-brain barrier site, excreting toxic substances from the liver, kidney, and gastrointestinal tracts, and transporting steroidal hormones in the adrenal grand . Once expressed in cancer cells . P-glycoprotein effluxes a variety of anticancer drugs, such as doxorubicin, vinca alkaloids, etoposide and taxol, and thereby allows cancer cells to show resistance to these drugs. Oncol Res, 1998, 10(4), 185 - 92 Activation of the LRP (lung resistance-related protein) gene by short-term exposure of human leukemia cells to phorbol ester and cytarabine; Komarov PG et al.; Treatment-induced secondary drug resistance of tumor cells is a major cause of relapsed disease and therapeutic failure in cancer patients . It has been shown that the expression of the multidrug resistance MDR1/P-glycoprotein gene could be induced by short-term in vitro exposure of cells to protein kinase C (PKC) agonists or different chemotherapeutic drugs . We studied whether other genes involved in drug resistance are regulated by similar signaling pathways . Transient (up to 24 h) treatment of HL-60 or K562 leukemia cells with phorbol 12-myristate 13-acetate (TPA) resulted in increased steady-state level of LRP (lung resistance-related protein) mRNA and protein . Among conventional chemotherapeutic drugs tested, only cytarabine (Ara C) induced the LRP mRNA expression though no increase in LRP protein was detected . LRP gene activation was not detectable in either H9 T-cell leukemia or in solid carcinoma cell lines (BT-20, ZR-75-1, and SW 1573) . None of the agents influenced the levels of MRP (multidrug resistance-associated protein) mRNA in any cell line tested . In HL-60 cells, the LRP activation by TPA or Ara C was sustained for at least 23 days after withdrawal of inducing agents . bis-Indolylmaleimide I, a potent PKC inhibitor, attenuated TPA-induced LRP activation . In contrast, the inhibitor had no effect on the LRP induction by Ara C . These data indicate that the LRP gene can be activated by different mechanisms, some of which involve PKC. Biochemistry, 1998 Oct 20, 37(42), 14833 - 7 Transbilayer movement of NBD-labeled phospholipids in red blood cell membranes: outward-directed transport by the multidrug resistance protein 1 (MRP1); Dekkers DW et al.; The outward movement (flop) of fluorescently labeled analogues of phosphatidylserine (PS) and phosphatidylcholine (PC) in human and murine red blood cells (RBC) was examined . 1-Oleoyl-2-{6(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino}caproyl (C6-NBD) analogues of PS and PC were incorporated in the inner leaflet of the plasma membrane through the action of aminophospholipid translocase or through equilibration upon prolonged incubation, respectively . After removal of noninternalized probe, externalization of C6-NBD-PS or C6-NBD-PC from the inner to outer leaflet was monitored by continuous incubation of the cells in the presence of bovine serum albumin . Flop rates for both probes in intact human RBC were virtually identical (t1/2 approximately 1.5 h), confirming earlier findings by Bitbol et al . {Bitbol, M., et al . (1988) Proc . Natl . Acad . Sci . U.S.A . 85, 6783-6787} and Connor et al . {Connor, J., et al . (1992) J . Biol . Chem . 267, 19412-19417} . Flop activity in resealed RBC ghosts could only be found upon coinclusion of both ATP and oxidized glutathione (GSSG) . Furthermore, flop in intact cells was sensitive to verapamil (IC50 = 5-7 microM), vincristine (IC50 = 20 microM), and indomethacin (IC50 = 50 microM), suggesting the involvement of proteins conferring multidrug resistance (MDR) . Experiments with RBC from knock-out mice for multidrug resistance P-glycoproteins (Mdr1a/1b-/- and Mdr2-/-) and multidrug resistance protein 1 (Mrp1-/-) revealed that Mrp1 is responsible for the observed flop of the fluorescent lipid analogues . We found no indications for outward transport of endogenous PS by any of these drug-transporting proteins as measured by a sensitive prothrombinase assay . Neither aminophospholipid translocase nor Ca2+-induced lipid scramblase activities were affected in RBC of these knock-out mice . We conclude that lipid floppase activity, as detected with lipid probes, reflects the activity of MRP1 recognizing the modified lipid analogues as xenobiotics to be expelled from the cell. Infect Control Hosp Epidemiol, 1998 Sep, 19(9), 635 - 9 Nosocomial transmission of a drug-sensitive W-variant Mycobacterium tuberculosis strain among patients with acquired immunodeficiency syndrome in Tennessee; Haas DW et al.; OBJECTIVE: To use DNA fingerprinting to characterize nosocomial spread of Mycobacterium tuberculosis following hospitalization of a patient with acquired immunodeficiency syndrome and active pulmonary tuberculosis, for whom respiratory isolation was not initiated promptly . DESIGN: Epidemiological investigation . SETTING: A tertiary-care medical center in Tennessee . PARTICIPANTS: Patients and healthcare workers potentially exposed to the infectious patient in 1992 . RESULTS: Of 172 healthcare workers exposed, 35 (20%) were judged to have acquired tuberculous infection . Risk of acquisition was greatest for nurses and medical receptionists . Active tuberculosis later developed in one healthcare worker and one hospitalized patient . Nosocomial transmission was supported by epidemiological evidence and DNA fingerprinting . The outbreak strain of Mycobacterium tuberculosis differed from other isolates at this hospital, but its DNA hybridization pattern was highly similar to that of the multidrug-resistant outbreak strain W that has been prevalent in New York City, suggesting a common strain ancestry . However, the Tennessee isolates were susceptible to all first-line antituberculous agents . CONCLUSIONS: This report suggests the possibility that a molecular characteristic(s) shared by these successful outbreak strains is associated with increased transmissibility or pathogenicity and emphasizes the need for continued vigilance for tuberculosis in the nosocomial setting. Infect Control Hosp Epidemiol, 1998 Sep, 19(9), 629 - 34 The costs of healthcare worker respiratory protection and fit-testing programs; Kellerman SE et al.; OBJECTIVE: We studied hospital costs associated with healthcare worker (HCW) respiratory protection and respirator fit-testing programs recommended by the Centers for Disease Control and Prevention (CDC) and mandated by the Occupational Safety and Health Administration to decrease nosocomial or occupational Mycobacterium tuberculosis (TB) . DESIGN: The number and cost of high-efficiency particulate air (HEPA)-filter and dust-mist (DM) respirators for 1989 to 1994 were obtained from study hospital purchasing departments, and the costs of HCW fit-testing and education programs for 1994 were estimated from information provided by infection control practitioners . Costs of N-class respirator programs were estimated for study hospitals using retrospective cost analysis and an observational study . SETtING: Four urban hospitals with, and one rural community hospital without, documented nosocomial or occupational transmission of multidrug-resistant TB . RESULTS: During the study period, four of five hospitals introduced HEPA and DM respirators and respirator education and fit-testing programs . Median costs in 1994 were $83,900 (range, $2,000-$223,000) for respirators and $17,187 (range, $8,736-$26,175) for respiratory fit-testing programs . The projected median annual cost of N95 respirators was $62,023 (range, $270-$422,526) . CONCLUSIONS: Compliance with CDC TB guidelines may require a substantial investment . However, outlays for respirators and education and fit-testing programs are more reasonable than would be suggested by analyses that estimated the costs of preventing one case of nosocomial TB. Leukemia, 1998 Sep, 12 Suppl 1, S2 - 6 Molecular genetic features of myelodysplastic syndromes (MDS) Willman CL. Recent developments in molecular genetics have provided insights on the molecular mechanisms that lead to myelodysplasias (MDS), secondary acute myelogenous leukemia (AML), therapy-induced AML, and elderly AML . These disorders are characterized by dysregulation of growth and differentiation of multilineage stem cells, a genetic profile characterized by unbalanced abnormalities that result in "unfavorable cytogenetics," and an increased frequency of intrinsic multidrug resistance . The unfavorable cytogenetics associated with this group of disorders include chromosome 5 and 7 monosomy, deletions of the long arm of chromosomes 5 and 7, inversions of chromosome 3, translocations, deletions and trisomies involving several other chromosomes . Presumably, these unbalanced chromosomal aberrations result in hemizygosity and unmasking of oncogenes or inactivation of tumor suppressor genes . In addition, polymorphisms in genes encoding metabolic detoxification enzymes, defective DNA repair mechanisms, and intrinsic chromosomal instability have been implicated in the etiology of the myelodysplastic syndromes . It is evident that the cytogenetics associated with MDS are highly complex and heterogeneous . This review summarizes the most recent developments in the understanding of the molecular changes associated with the development of myelodysplasias and related leukemic disorders. Somat Cell Mol Genet, 1998 Jan, 24(1), 53 - 69 Construction and characterization of single-transcript tricistronic retroviral vectors using two internal ribosome entry sites; Metz MZ et al.; We describe a series of retroviral vectors containing two internal ribosome entry sites (IRES) for the co-transcription of three genes . Transcription of the single-transcript tricistronic mRNA is under the control of a Harvey murine sarcoma virus long terminal repeat . The 5'-most open reading frame is under either cap-dependent or cap-independent translational control, while the two downstream open reading frames are translated in a cap-independent fashion using the initiation codons of their respective IRES elements . Both IRES elements are taken from the encephalomyocarditis virus . To characterize these vectors, we used the human multidrug resistance gene (MDR1) in the 5' position, the gene for green fluorescent protein (GFP) in the middle position, and neo in the 3' position . The vectors were either transfected directly into NIH3T3 mouse fibroblasts or packaged into retrovirus and then transduced into NIH3T3 cells . Gene transfer was followed by selection with colchicine, which selects for expression of the MDR1 gene, or with G418, which selects for expression of the neo gene . Thus, we could determine the function of the tricistronic vectors under conditions of selection for either the 5'-most or the 3'-most gene . In DNA-mediated transfections, we were able to achieve expression of all three open reading frames under either selection condition . We obtained higher expression of all three genes when colchicine was used to select for MDR1 expression than when G418 was used to select for neo expression . Expression of the non-selected GFP gene (the middle cistron) was unstable, most likely due to loss of integrated GFP DNA sequences during long-term culturing . We were able to achieve retrovirus-mediated transduction of all three genes, but this was an inefficient process. Biochem Pharmacol, 1998 Oct 15, 56(8), 1013 - 21 Combined expression of multidrug resistance protein (MRP) and glutathione S-transferase P1-1 (GSTP1-1) in MCF7 cells and high level resistance to the cytotoxicities of ethacrynic acid but not oxazaphosphorines or cisplatin; Morrow CS et al.; We tested the hypothesis that combined increased expression of human glutathione S-transferase P1-1 (GSTP1-1), an enzyme that catalyzes the conjugation with glutathione of several toxic electrophiles, and the glutathione-conjugate efflux pump, multidrug resistance protein (MRP), confers high level resistance to the cytotoxicities of anticancer and other drugs . To accomplish this, we developed MCF7 breast carcinoma cell derivatives that express high levels of GSTP1-1 and MRP, alone and in combination . Parental MCF7 cells, which express no GSTP1-1 and negligible MRP, served as control cells . We found that either MRP or GSTP1-1 alone conferred significant resistance to ethacrynic acid cytotoxicity . Moreover, combined expression of GSTP1-1 and MRP conferred a high level of resistance to ethacrynic acid that was greater than resistance conferred by either protein alone . Increased MRP was also associated with modest resistance to the oxazaphosphorine compounds mafosfamide, 4-hydroxycyclophosphamide, and 4-hydroperoxycyclophosphamide . However, coordinated expression of GSTP1-1 with MRP failed to augment this modest resistance . Similarly, GSTP1-1 had no effect on the sensitivities to cisplatin of MCF7 cells regardless of MRP expression . These results establish that coordinated expression of MRP and GSTP1-1 can confer high level resistance to the cytotoxicities of some drugs, including ethacrynic acid, but that such resistance is variable and does not apply to all toxic drugs that can potentially form glutathione conjugates in either spontaneous or GSTP1-1-catalyzed reactions. Biochem Pharmacol, 1998 Oct 1, 56(7), 861 - 9 PKC-independent modulation of multidrug resistance in cells with mutant (V185) but not wild-type (G185) P-glycoprotein by bryostatin 1; Spitaler M et al.; Bryostatin 1 is a new antitumor agent which modulates the enzyme activity of protein kinase C (PKC, phospholipid-Ca2+-dependent ATP:protein transferase, EC 2.7.1.37) . Several reports have suggested that the pumping activity of the multidrug resistance gene 1 (MDR1)-encoded multidrug transporter P-glycoprotein (PGP) is enhanced by a PKC-mediated phosphorylation . It was shown here that bryostatin 1 was a potent modulator of multidrug resistance in two cell lines over-expressing a mutant MDR1-encoded PGP, namely KB-C1 cells and HeLa cells transfected with an MDR1-V185 construct (HeLa-MDR1-V185) in which glycine at position 185 (G185) was substituted for valine (V185) . Bryostatin 1 is not able to reverse the resistance of cells over-expressing the wild-type form (G185) of PGP, namely CCRF-ADR5000 cells and HeLa cells transfected with a MDR1-G185 construct (HeLa-MDR1-G185) . Treatment of HeLa-MDR1-V185 cells with bryostatin 1 was accompanied by an increase in the intracellular accumulation of rhodamine 123, whereas no such effect could be observed in HeLa-MDR1-G185 cells . HeLa-MDR1-V185 cells expressed the PKC isoforms alpha, delta and zeta . Down-modulation of PKC alpha and delta by 12-O-tetradecanoylphorbol-13-acetate (TPA) did not affect the drug accumulation by bryostatin 1 . Bryostatin 1 depleted PKC alpha completely and PKC delta partially . In HeLa-MDR1-V185 cells, short-term exposure to bryostatin 1, which led to a PKC activation, was as efficient in modulating the pumping activity of PGP as long-term exposure leading to PKC depletion . Bryostatin 1 competed with azidopine for binding to PGP in cells expressing the MDR1-V185 and MDR1-G185 forms of PGP . It is concluded that bryostatin 1: i) interacts with both the mutated MDR1-V185 and the wild-type MDR1-G185; ii) reverses multidrug resistance and inhibits drug efflux only in PGP-V185 mutants; and iii) that this effect is not due to an interference of PKC with PGP . For gene therapy, it is important to reverse the specific resistance of a mutant in the presence of a wild-type transporter and vice versa . Our results show that it is possible to reverse a specific mutant PGP. Biochem Pharmacol, 1998 Oct 1, 56(7), 841 - 9 Enhancement of doxorubicin content by the antitumor drug lonidamine in resistant Ehrlich ascites tumor cells through modulation of energy metabolism; Floridi A et al.; The effect of the antitumor drug lonidamine (LND) on respiration, aerobic glycolysis, adenylate pool, doxorubicin (DOX) uptake, and efflux in DOX-resistant and DOX-sensitive Ehrlich tumor cells was investigated . The results may be summarized as follows: 1) In both types of cells, LND inhibited both respiration and glycolysis in a dose-dependent manner and lowered the ATP concentration . The effect was more marked in cells incubated in glucose-free medium; 2) LND raised, to a remarkable extent, the intracellular content of DOX in resistant and sensitive cells respiring on endogenous substrates because of reduced ATP availability, whereas in glucose-supplemented medium, where both respiration and glycolysis contributed to ATP synthesis, the increase was lower; and 3) when LND was added to DOX-loaded cells, it failed to significantly inhibit DOX efflux because of time-dependent phenomena . These findings indicated that LND, a drug currently employed in tumor therapy, might also be useful in reducing or overcoming multidrug resistance (MDR) of those cells with a reduced ability to accumulate and retain antitumor drugs. Biochem Pharmacol, 1998 Oct 1, 56(7), 807 - 16 Chemical synthesis and biological properties of novel fluorescent antifolates in Pgp- and MRP-overexpressing tumour cell lines; Robson C et al.; We have synthesised a series of fluorescent analogues of methylbenzoprim, a diaminopyrimidine antifolate which we have previously shown to exhibit in vivo antitumour activity in a methotrexate (MTX) "transport-resistant" tumour cell line . The analogues bear the dansyl, nitrobenzoxodiazole or methoxycoumarin fluorophores . The cytotoxicity of the compounds was evaluated using the 3-{4,5-dimethylthiazol-2-yl}-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay against two human lung cancer cell lines, together with their multidrug resistant (MDR) sublines . H69/P is a small cell line and its multidrug resistant subline H69/LX4 overexpresses P-glycoprotein (Pgp) . COR-L23/P is a large cell line and its multidrug resistant subline COR-L23/R overexpresses the multidrug resistance associated protein (MRP) . IC50 values for the compounds (i.e . concentration to reduce cell growth by 50%) in the 3-{4,5-dimethylthiazol-2-yl}-2,5-diphenyltetrazolium bromide assay ranged from 0.20 to 0.81 microM in the H69 parental line and from 0.83 to 5.10 microM in the COR-L23 parent line . The MDR sublines both showed clear cross-resistance to each of the compounds, with resistance factors (ratio of IC50 value in resistant vs parental cell line) ranging from 16 to 137 in H69/LX4 and from 5 to 16 in COR-L23/R . For compounds (10) and (11) where drug accumulation was studied using flow cytometry, resistance was associated with an approximately 10-fold reduction in cellular drug accumulation over a period of 30 min . The drug resistance modifiers verapamil (used at 6.6 microM) and cyclosporin A (used at 4.2 microM) were tested for their ability to sensitise the resistant lines . Whereas verapamil showed little activity, cyclosporin A partially restored the activity of compound (10), and fully restored the activity of compound (11) in H69/LX4 cells . This sensitisation of H69/LX4 by cyclosporin A was associated with a partial restoration of the drug accumulation deficit in this line . Hence, these novel lipophilic antifolates appear to be substrates for both the P-glycoprotein and MRP resistance mechanisms . Therefore, although they have been designed to overcome one mechanism of methotrexate resistance, namely impaired drug transport, this has been achieved only at the cost of rendering them susceptible to alternative mechanisms. Zhongguo Yao Li Xue Bao, 1996 Mar, 17(2), 179 - 81 Reduction of doxorubicin resistance by tetrandrine and dauricine in harringtonine-resistant human leukemia (HL60) cells; He QY et al.; AIM: To study whether tetrandrine (Tet) and dauricine (Dau) can reduce doxorubicin (Dox) resistance in the harringtonine (Har)-resistant human leukemia cells . METHODS: The drug cytotoxities were determined by counting cell numbers and colony formation . Cell cycle phases were assayed by flow cytometry, Dox contents were quantified by Dox fluorescence . RESULTS: The non-cytotoxic concentrations of Tet and Dau potentiated the growth-inhibitory actions of Dox in the Har-resistant HL60 cells . The colony formation effiencies were reduced from 60% by Dox to 0.2% by Tet + Dox and 9.2% by Dau + Dox . Retardation of the G2M phase cells was increased . But Tet and Dau did not potentiate Dox cytotoxities in the sensitive HL60 cells . Dox accumulation in the Har-resistant HL60 cells treated by Tet was increased . CONCLUSION: Dox resistance in the Har-resistant HL60 cells treated by Tet or Dau was reduced, due to the increase of Dox accumulation in the cells . One of the mechanisms of multidrug resistance in tumor cells is overexpression of cell membrane glycoproteins, termed P-glycoprotein (PGP) . PGP pumps antitumor drugs out of tumor cells, causing drug resistance . Calcium antagonists and some calmodulin inhibitors such as verapamil, nifedepine, trifluorapine have effect on reversion of drug resistance, binding directly to PGP, but side effect of them is intolerable in clinical use . So searching for other potentiators to overcome drug resistance may be another avenue . Tetrandrine (Tet) effectively circumvented the resistance of Chinese hamster ovary cells to doxorubicin (Dox) . Dauricine (Dau) is a bisbenzylisoquinoline alkaloid from Stephaia tetrandra . In this paper we studied whether Tet and Dau could reduce Dox resistance in the harringtonine (Har)-resistant human leukemia 60 (HL60) cells. Zhonghua Yi Xue Za Zhi, 1997 Jul, 77(7), 494 - 6 {The reversion of multidrug resistance in tumour cell line MCF-7/Adr by ribozyme}; Yuan Y et al.; OBJECTIVE: To construct a specific hammerhead ribozyme possessing catalytic activity that cleaves the mdr1 mRNA for reversing the resistant phenotype in tumour cell line . METHODS: A DNA sequence encoding the ribozyme gene was incorporated into a eukaryotic expression vector (pH beta Apr-1 neu) and transfected into the human breast carcinoma cell line MCF-7/Adr, which is resistant to adriamycin and expresses the MDR phenotype . RESULTS: The ribozyme was stably expressed in the cell line, and decreased the level of mdr1 mRNA expression by 83.5% . The ribozyme inhibited the formation of P-glycoprotein and reduced the cell's resistance to adriamycin . CONCLUSION: The resistant cells were 1,000-fold more resistant than the parental cell line (MCF-7), whereas those cell clones that showed ribozyme expression were only 6-fold more resistant than the parental cell line. Zhonghua Yi Xue Za Zhi, 1997 Jul, 77(7), 488 - 90 {Clinical significance of expression of multidrug resistance gene in breast cancer tissue}; Liu X et al.; OBJECTIVES: To investigate the role of expression of multidrug resistance gene (mdr-1 gene) in chemotherapeutic resistance of breast cancer and to determine if expression of mdr-1 gene may act as an index for predicting chemotherapy response and prognosis . METHODS: Using reverse transcription-polymerase chain reaction (RT-PCR) technique, we determined the levels of mdr-1 mRNA in 82 breast cancer samples . RESULTS: Positive expressions of mdr-1 gene were 34.3% in 35 cases of untreated primary breast cancer and 59.0% in 47 cases of relapsed metastatic breast cancer, separately, and the difference was statistically significant (P < 0.05) . In 28 cases of relapsed metastatic breast cancer of mdr-1 gene positive expression, 22(78.6%) were ever treated with MDR related drugs . Levels of mdr-1 gene expression of all 7 cases were higher after chemotherapy than before chemotherapy . Positive expressions were 16.7% and high grade positive expressions were 5.6% in 18 sensitive cases . Positive expressions were 71.4% and high grade positive expressions were 50.0% in 14 resistant cases . The difference was statistically significant (P < 0.01) . There were no relations between expression of mdr-1 gene and ages, menopause status, lymphnode involvements, clinical stages, and estrogen receptor levels . CONCLUSION: The results indicated that retreated metastatic breast cancer is more extensively resistant than untreated primary breast cancer and acquired drug resistance is an important reason . Expression of mdr-1 gene seems to be a reference index for predicting response of chemotherapy. Bull Cancer . 1998 Sep;85(9):785. Multicellular resistance: another mechanism for multidrug resistance? Desoize B, Gimonet D, Jardillier JC. Cells cultured as spheroids present an heterogeneity similar to that of tumours in vivo . In the spheroid peripheral layers, cells are proliferating, deeper cells are non-cycling, when in the aggregate centre, cells form often a necrotic core . A multicellular resistance appears in spheroids, it is a result of the cell contact to other cells (homogeneous or heterogeneous cells) and/or to the extracellular matrix . The mechanism of this resistance is not known, nevertheless, it can be hypothesised to be linked to the spheroid centre hypoxia, to the quiescence of a large fraction of the cell population and to the apoptose inhibition due to the cell contact . The classical or unicellular mechanisms of resistance, as mdr1, MRP, can coexist with the multicellular resistance, but are not responsible for this resistance . The spheroid model of culture is a good opportunity to study a resistance type which looks close to the tumour resistance found in vivo in mice and in patients . A new class of therapeutic molecules appears that can reverse this multicellular resistance, inhibit tumours growth and preclude metastases . The principal mechanism of action of this new pharmacological class appears to be the disruption of the intercellular adhesion forces . Preliminary results obtained with these compounds in patients are promising. Cancer Chemother Pharmacol, 1998, 42(5), 367 - 72 Prophylactic intravesical instillation chemotherapy against recurrence after a transurethral resection of superficial bladder cancer: a randomized controlled trial of doxorubicin plus verapamil versus doxorubicin alone . The Kyushu University Urological Oncology Group; Naito S et al.; PURPOSE: We investigated whether verapamil (VR), a known chemosensitizing agent of P-glycoprotein-mediated multidrug resistance, could enhance the preventative effect of doxorubicin (Adriamycin, ADM) on both intravesical recurrence and disease progression after transurethral resection (TUR) of superficial bladder cancer . METHODS: The patients were randomized into two groups: one group received an intravesical instillation of ADM (30 mg) plus VR (15 mg) after TUR of superficial bladder cancer (19 times over 1 year), and the other group received ADM alone on the same treatment schedule . The nonrecurrence rate, the incidence of disease progression at the first recurrence and the side effects were compared over a median follow-up of 38.5 months . RESULTS: Of the 226 patients registered, 157 were evaluable . No significant differences were observed in the patients' characteristics between the two groups . Although the incidence of disease progression at the first recurrence was not significantly different between the two groups, the ADM plus VR instillation group did show a significantly higher nonrecurrence rate than the ADM-only instillation group, and such significance persisted even when any possible bias was allowed for in a multivariate analysis . In terms of side effects, the incidence and severity of bladder irritation symptoms were not significantly different between the two groups . CONCLUSIONS: Intravesical instillation chemotherapy with ADM plus VR was found to have a significantly greater beneficial effect than with ADM alone for preventing recurrence after TUR of superficial bladder cancer. Cancer Chemother Pharmacol, 1998, 42(5), 363 - 6 Pharmacokinetic analysis of high-dose toremifene in combination with doxorubicin; Wurz GT et al.; PURPOSE: Toremifene (Fareston) is an orally administered triphenylethylene derivative with chemosensitizing activity in vitro in estrogen receptor-negative multidrug-resistant human breast cancer cells . The purpose of this study was to evaluate the effects of high-dose toremifene (600 mg/day for 5 days) on the plasma pharmacokinetics of doxorubicin in humans . The 600-mg dose had been previously established as the maximum tolerated dose in a phase I study of 35 patients . METHODS: Doxorubicin was administered as an intravenous (i.v.) bolus over 15 min at a dose of 60 mg/m2 to 11 patients in the absence of toremifene pretreatment to establish baseline doxorubicin pharmacokinetics . Six of these patients received 600 mg/day toremifene for 5 days 4 weeks later, followed by an i.v . bolus dose of doxorubicin (60 mg/m2) on day 5 . During toremifene pre-treatment, blood specimens (5 ml) were drawn at 0, 2, 4, and 24 h after dosing to assess peak levels . Following doxorubicin administration in each cycle, blood specimens were collected over a 72-h period for determination of the terminal half-life of elimination . Plasma concentrations of doxorubicin and toremifene were assessed by high-performance liquid chromatography (HPLC) . Cumulative linear areas under the time-concentration curve (AUC) for doxorubicin were calculated using a noncompartmental model . RESULTS: Prior to toremifene dosing, baseline doxorubicin pharmacokinetic studies showed an average terminal half-life of elimination of 40.04+/-7.86 h in 4 patients, and an average AUC of 135 600+/-67 600 microg/ml.h in 11 patients . In 4 of the patients receiving 600 mg/day toremifene for 5 days, the average terminal half-life of elimination was 38.12+/-7.81 h, and the average AUC was 141 900+/-62 900 microg/ml.h in 6 patients, i.e . a slight increase of 4.6% . No statistically significant change in the doxorubicin elimination kinetics with or without toremifene therapy was observed . CONCLUSIONS: Toremifene does not appear to interfere with the elimination kinetics of doxorubicin. Cancer Metastasis Rev, 1998 Jun, 17(2), 163 - 8 PSC-833, a frontier in modulation of P-glycoprotein mediated multidrug resistance; Atadja P et al.; The expression of drug efflux mechanisms by cancer cells during chemotherapy leads to multidrug resistance (MDR) and constitutes a major obstacle in the effective treatment of cancer . The most widely characterized drug effluxes pump is P-glycoprotein (P-gp) and efforts are being directed towards identifying agents that reverse P-gp mediated drug resistance . PSC-833 is a non-immunosuppressive cyclosporin derivative that potently and specifically inhibits P-gp . The current review focuses on the elucidation of the mechanism of action of PSC-833 as a potential MDR reversing agent, using syngeneic multidrug resistant sublines of MDA435 human breast adenocarcinoma cell line that express increasing levels of P-gp . In vitro experiments indicate that PSC-833 interacts directly with P-gp with high affinity and probably interferes with the ATPase activity of P-gp . Studies in multidrug resistant tumor models confirm P-gp as the in vivo target of PSC-833 and demonstrate the ability of PSC-833 to reverse MDR leukemias and solid tumors in mice . Presently, PSC-833 is being evaluated in the clinic. J Med Chem, 1998 Oct 8, 41(21), 4161 - 4 Halogenated chalcones with high-affinity binding to P-glycoprotein: potential modulators of multidrug resistance; Bois F et al.; Previous studies have shown that flavonoids are modulators of the transmembrane P-glycoprotein (P-gp) which mediates cell multidrug resistance . Some structural elements have been identified which seem to contribute to these compounds' activity . In the present study, a series of halogenated chalcones was prepared to further explore the structural requirements for the P-gp modulation . Four halogenated chalcones have been synthesized and evaluated as potential modulators of P-gp-mediated multidrug resistance of cancer cells by in vitro assays using a purified recombinant domain of the transporter containing the modulator binding site . Halogenated chalcones exhibited high-affinity binding, the 2',4', 6'-trihydroxy-4-iodochalcone behaving as the most potent compound with a KD value in the nanomolar range. J Med Chem, 1998 Oct 8, 41(21), 4001 - 11 Substituted 4-acylpyrazoles and 4-acylpyrazolones: synthesis and multidrug resistance-modulating activity; Chiba P et al.; A series of 4-acyl-3-pyrazolone derivatives with a 3-substituted 2-hydroxy-3-aminopropyl chain attached to pyrazole N-1 (7-20) as well as isomeric 4-acyl-5-(3-substituted 3-amino-2-hydroxypropoxy)pyrazole derivatives (5, 6) were synthesized, and their multidrug resistance (MDR)-modulating activity was measured using the daunomycin efflux assay . Reaction of N1-substituted 4-acyl-3-pyrazolones (tautomer to 4-acyl-5-hydroxypyrazoles) with excessive epichlorohydrin and successive treatment with an appropriate amine resulted in N-alkylation and thus afforded the target pyrazolone derivatives 7-20 . In contrast, O-alkylation occurred upon reaction with 1 equiv of epichlorohydrin and subsequent treatment with amine leading to the corresponding 4-acyl-5-pyrazolyl ethers 5 and 6 . QSAR studies showed a good correlation of MDR-modulating activity with lipophilicity of the compounds . Inclusion of hydrogen bond acceptor strength and steric parameters as descriptors led to a QSAR equation with remarkably increased predictive power (r2cv = 0.92) . Additionally, ortho substitution of the propanolamine side chain and the acyl moiety is favorable . Detailed NMR spectroscopic investigations were carried out with the title compounds. Mol Microbiol, 1998 Sep, 29(5), 1307 - 15 Yeast gene YRR1, which is required for resistance to 4-nitroquinoline N-oxide, mediates transcriptional activation of the multidrug resistance transporter gene SNQ2; Cui Z et al.; We have cloned and characterized a Saccharomyces cerevisiae gene YRR1 that is important for resistance to the mutagen 4-nitroquinoline N-oxide (4-NQO) . The wild-type YRR1 gene encodes a protein that contains a Zn(II)2Cys6-type zinc-finger motif . Disruption of the YRR1 gene leads to hypersensitivity to 4-NQO . A dominant mutation (YRR1-1) that confers strong resistance to 4-NQO has been identified . Epistasis analysis demonstrated that 4-NQO resistances mediated by the YRR1 and YRR1-1 alleles require the presence of the SNQ2 gene that encodes a multidrug resistance ATP binding cassette superfamily protein responsible for 4-NQO export . Northern blot analysis of SNQ2 mRNA levels indicated that Yrr1p is involved in basal and drug-induced transcriptional activation of SNQ2, whereas Pdr1p/Pdr3p transcription factors are mainly involved in basal SNQ2 expression . In the YRR1-1 mutant, the level of SNQ2 mRNA is constitutively elevated . These results establish that Yrr1p is important for 4-NQO resistance by mediating transcriptional activation of the SNQ2 gene in response to the stress imposed by 4-NQO . The gain-of-function mutation of Yrr1-1p was attributable to the duplication of a 12-amino-acid sequence generated near the carboxy terminus. Kidney Int, 1998 Oct, 54(4), 1139 - 49 Therapeutic concentrations of cyclosporine A, but not FK506, increase P-glycoprotein expression in endothelial and renal tubule cells; Hauser IA et al.; BACKGROUND: The immunosuppressive drugs cyclosporine A (CsA) and tacrolimus (FK506) are extruded from cells by the multidrug resistance P-glycoprotein (P-gp), an efflux pump for drugs and xenobiotics, which may limit their therapeutic effectiveness and/or incidence of toxic side effects . In the present study, we investigated the effect of therapeutic concentrations of CsA and FK506 on the expression of P-gp in cultured endothelial and proximal tubule cells . METHODS: P-gp expression in human arterial endothelial (HAEC) and rat proximal tubule cells (RPTC) was determined by immunoblotting and immunocytochemistry, and correlated with P-gp-mediated transport by measuring the intracellular accumulation of the fluorescent probe calcein . RESULTS: Following incubation of HAEC with therapeutic concentrations of 0.1 to 1.6 microM CsA up to seven days, P-gp expression increased in a time- and concentration-dependent manner, maximally to 291 +/- 42% of controls with 0.8 microM CsA for seven days . Similar effects of CsA were observed in RPTC . In contrast, therapeutic concentrations of FK506 (0.01 to 0.2 microM up to 7 days) did not change P-gp expression in either cell type, though at higher, supratherapeutic concentrations of FK506 (0.6 to 1.2 microM) P-gp expression was also increased . Immunocytochemistry revealed increased P-gp expression in the plasma membrane of HAEC and RPTC treated with 0.8 microM CsA, which was reflected by a decrease of P-gp-mediated accumulation of calcein in both cell types . CONCLUSIONS: The data suggest that the induction of P-gp expression in HAEC and RPTC at concentrations of CsA or FK506 above 0.5 microM is part of the protective answer of cells to toxic concentrations of the drugs and could therefore interfere with the therapeutic effectiveness of CsA in vivo. Leukemia, 1998 Oct, 12(10), 1539 - 44 Characterization of H+-ATPase-dependent activity of multidrug resistance-associated protein in homoharringtonine-resistant human leukemic K562 cells; Benderra Z et al.; Multidrug resistance (MDR), caused by overexpression of either P-glycoprotein or the multidrug resistance-associated protein (MRP), is characterized by a decreased cellular drug accumulation due to an enhanced drug efflux . Many studies on cells overexpressing MRP and/or Pgp, have shown a concentration of the drug inside cytoplasmic acidic vesicles followed by an exocytotic process . In this study, we examined the effects of 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole or NBD (a H+-ATPase pump inhibitor), buthionine sulphoximine or BSO (an inhibitor of glutathione (GSH) biosynthesis) and verapamil or VPL (a calcium channel blocker) on the subcellular distribution of daunorubicin or DNR in K562 cells overexpressing MRP (K-H30) and Pgp (K-H300) and A549 cells overexpressing spontaneously MRP . Nucleo-cytoplasmic distribution of DNR was carried out using scanning confocal microspectrofluorometry . This technique allows determination of nuclear accumulation of anthracyclines . Our results show that nuclear accumulation of DNR in K-H30 and A549 cells was increased by NBD, BSO and VPL while in K-H300 cells, only VPL was able to increase nuclear accumulation of DNR . Similarly, NBD, BSO and VPL could reverse DNR resistance in K-H30 cells whereas, in K-H300 cells, only VPL increased the sensitivity of these cells . These data suggest a requirement for GSH in MRP-mediated resistance and suggest that even if vesicular sequestration can happen in cells overexpressing MRP and Pgp proteins, probably only the MRP protein is able to extrude the drug through intracellular vesicles and efflux . Finally, NBD and BSO might be a useful agents in facilitating discrimination between Pgp and MRP phenotypes and prognosis in patients. J Perinatol, 1998 Sep-Oct, 18(5), 389 - 94 Congenital and perinatal tuberculosis: discussion of difficult issues in diagnosis and management; Hageman JR; Tuberculosis (TB) has become more prevalent in women of childbearing age and, as well, more frequent in their children . This has occurred for a number of reasons, including: (1) women and children who have immigrated to this country from areas where TB is endemic, such as Mexico and Southeast Asia; (2) the development of multidrug-resistant organisms; (3) the increase seen in patients who live in congregate areas who are at higher risk for acquisition of TB; (4) more difficult access to adequate medical care; and (5) increases in adults and children who have become infected with human immunodeficiency virus . The focus of this review is on congenital and perinatally acquired TB including discussion of epidemiology, the stages of TB, the effects of TB infection and disease during pregnancy on the fetus and mother, congenital and perinatal TB, the potential role of the use of BCG vaccine in infants, and the emergence of multidrug-resistant TB on therapy of the pregnant mother and her fetus and the mother and her infant after delivery. Mol Pharmacol, 1998 Oct, 54(4), 623 - 30 Analysis of random recombination between human MDR1 and mouse mdr1a cDNA in a pHaMDR-dihydrofolate reductase bicistronic expression system; Shoshani T et al.; Human P-glycoprotein (Pgp) confers multidrug resistance (MDR) to otherwise sensitive cells . The homologous mouse Pgps, which are encoded by mouse mdr1a (also known as mdr3) and mdr1b (also known as mdr1), confer different degrees of resistance to the same MDR drugs and inhibitors . To create recombinants for the study of sequences responsible for these differences in drug-resistance, chimeric cDNA libraries can be constructed by homologous recombination of pools of related sequences . This mutagenesis approach is called DNA shuffling . To select for chimeric Pgp with an altered resistance profile, DNA shuffling between the homologous but not identical drug interacting transmembrane domains 5 and 6 of human MDR1 and mouse mdr1a was used . The chimeric proteins were expressed in human KB-3-1 cells . One recombinant Pgp (clone 3-4) with a novel phenotype was analyzed in detail . Inhibitors of Pgp, including verapamil and cyclosporin A, were less effective in reversing resistance of the chimeric Pgp compared with wild-type Pgp, for certain drugs . However, {125I}iodoarylazidoprazosin photoaffinity labeling of the chimeric Pgp and its binding competition with cyclosporin A, showed that cyclosporin A competed for the photoaffinity labeling . The chimeric Pgp cells stained less well with human-specific anti-Pgp mAb MRK16 than wild-type Pgp, despite having the described epitopes for MRK16 . Staining with human-specific mAb UIC2 was increased when the chimeric protein was compared with wild-type Pgp . These results suggest an alteration in exposure of human Pgp specific epitopes in this chimeric Pgp, as well as a change in the interaction of reversing agents with the chimeric protein. Br J Cancer, 1998 Oct, 78(7), 885 - 92 Reversal of P-glycoprotein-mediated multidrug resistance by XR9051, a novel diketopiperazine derivative; Dale IL et al.; XR9051 (N-(4-(2-(6,7-Dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phe nyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-pipera zinylidene) methylbenzamide) was identified as a potent modulator of P-glycoprotein-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound . The activity of XR9051 was determined using a panel of human and murine drug-resistant cell lines (H69/LX4, 2780AD, EMT6/AR 1.0, MC26 and P388/DX Johnson) . XR9051 was able to reverse resistance to a variety of cytotoxic drugs, including doxorubicin, etoposide and vincristine, which are associated with classical MDR . At a concentration of 0.3-0.5 microM, XR9051 was able to fully sensitize resistant cells to cytotoxics, whereas little or no effect was observed on the corresponding parental cell lines . No effect of XR9051 was observed on the response of cells to non-MDR cytotoxics such as methotrexate and 5-fluorouracil . XR9051 was consistently more potent than cyclosporin A (CsA) and verapamil (Vpm) in all assays used . XR9051 inhibited the efflux of {3H}daunorubicin from preloaded cells and, unlike CsA and Vpm, remained active for several hours after removal of resistance-modifying agent . In photoaffinity labelling experiments employing {3H}azidopine, XR9051 was able to displace binding to P-glycoprotein . In binding studies using {3H}vinblastine, XR9051 was shown to be a potent inhibitor of the binding of the cytotoxic to P-glycoprotein (EC50 = 1.4 +/- 0.5 nM) . Taken together, the results indicate that XR9051 reverses the MDR phenotype through direct interaction with P-glycoprotein. Trans R Soc Trop Med Hyg, 1998 Mar-Apr, 92(2), 207 - 11 Artesunate and mefloquine in the treatment of uncomplicated multidrug-resistant hyperparasitaemic falciparum malaria; Price R et al.; Oral artesunate is the most effective treatment for uncomplicated hyperparasitaemia in falciparum malaria . To assess the contribution of mefloquine to therapeutic efficacy in an area endemic for mefloquine-resistant Plasmodium falciparum, an open randomized comparison of a 5 d course of oral artesunate (total dose 12 mg/kg) with and without a single dose of mefloquine (25 base mg/kg) was conducted in 100 adults and children with uncomplicated hyperparasitaemia (> 4% parasitized red blood cells) . Both regimens were well tolerated and gave equally rapid clinical responses (84% of patients were aparasitaemic and 96% were afebrile within 48 h), but the recrudescence rate assessed at day 42 was 6% in those receiving artesunate with mefloquine compared to 36% in those receiving artesunate alone (adjusted hazard ratio 7, 95% confidence interval {95% CI} 2-32; P < 0.01) . In addition, the efficacy of a 7 d course of artesunate, with and without the addition of mefloquine, was monitored in 178 patients who were not part of the randomized comparison . The failure rate was again lower in those receiving artesunate and mefloquine--7% (95% CI 2-13) compared with 26% (95% CI 8-44) in patients treated with artesunate alone . An oral regimen of 5 d or more of artesunate, together with mefloquine (25 mg/kg) given on day 2, is an effective treatment for uncomplicated hyperparasitaemic falciparum malaria in this area of high level multidrug resistance. Trans R Soc Trop Med Hyg, 1998 Mar-Apr, 92(2), 201 - 6 Efficacy and pharmacokinetics of atovaquone and proguanil in children with multidrug-resistant Plasmodium falciparum malaria; Sabchareon A et al.; A trial was conducted in 32 Thai children with uncomplicated multidrug-resistant falciparum malaria to assess the efficacy, safety and pharmacokinetics of atovaquone and proguanil; plasma concentrations of atovaquone, proguanil and its metabolite, cycloguanil, were measured in a subset of 9 children . The children received atovaquone (17 mg/kg/d for 3 d) plus proguanil (7 mg/kg/d for 3 d) . Twenty-six children who had only Plasmodium falciparum infection and remained in hospital for 28 d were assessed for drug efficacy . The combination regimen produced a cure rate of 100% . Parasite and fever clearance times were 47 h (range 8-75) and 50 h (range 7-111), respectively . Atovaquone and proguanil were rapidly absorbed, with median time to peak concentrations of 6 h (range 6-24) and 6 h (range 6-12), respectively . Peak concentrations of cycloguanil were achieved between 6 and 12 h (median 6) after administration of proguanil . Mean peak plasma concentration of atovaquone on day 3 was 5.1 micrograms/mL (SD = 2.1) . The day 3 mean peak plasma concentration of proguanil was 306 ng/mL (SD = 108) compared with 44.3 ng/mL (SD = 27.3) for cycloguanil . Mean values for the AUC (area under plasma concentration-time curve) were 161.8 micrograms/mL.h (SD = 126.9) for atovaquone, 4646 ng/mL.h (SD = 1226) for proguanil, and 787 ng/mL.h (SD = 397) for cycloguanil . Terminal elimination half-lives of atovaquone, proguanil and cycloguanil were estimated as 31.8 h (SD = 8.9), 14.9 h (SD = 3.3) and 14.6 h (SD = 2.6), respectively . No major adverse effect was attributable to the study drugs . Atovaquone/proguanil combination is safe and highly effective, and should be especially valuable for treatment of multidrug-resistant falciparum malaria. Bull World Health Organ, 1998, 76 Suppl 1, 9 - 19 Interventions to improve the use of antimalarials in south-east Asia: an overview; Gomes M et al.; There are few drugs for malaria, and those which are available for use are subject to rapid development of resistance . Curiously, little effort has been made to improve drug use in malaria-endemic countries and to assess the benefits of such improvements . Advances can be made in public understanding of the value of ingesting a full regimen of antimalarials, in order to achieve complete cure, and in improving simple technologies (blister packaging) to achieve the same result . Better efforts can be made to reduce the availability of fake or substandard drugs in the marketplace . In this article, we describe the outcome of a concerted effort to improve drug compliance and drug quality in an area of multidrug resistance for malaria . These research efforts, guided by the Task Force for Improved Use of Antimalarials, characterized the problems in drug compliance in South-East Asia, and developed interventions to improve drug use in the various countries . Interventions involved drug packaging, public information campaigns, and assessments of drug quality . Results show that blister packaging worked best to improve drug compliance and that the increased cost of packaged medication did not limit its use . Drug quality was a major problem in unregulated countries and should be improvedPIP: Except for the artemisinin derivatives recently deployed in southeast Asia, resistance has emerged to all antimalarial drugs . The Task Force for Improved Use of Antimalarials was created within the UNDP/World Bank/WHO Special Program for Research and Training in Tropical Diseases (TDR) in 1993, with the purpose of establishing, through research, measures to take to protect the few existing antimalarials in the southeast Asian region . Research was conducted in China, Myanmar, Cambodia, Thailand, Laos, and Viet Nam . The task force characterized the problems in drug compliance in southeast Asia, and developed interventions to improve drug use in the various countries . Interventions involved drug packaging, public information campaigns, and assessments of drug quality . It was found that blister packaging worked best in improving drug compliance and that the increased cost of packaged medication did not limit its use . Poor drug quality is a major problem in unregulated countries which should be improved . Biochem Pharmacol, 1998 Aug 15, 56(4), 497 - 502 S9788 modulation of P-glycoprotein- and Multidrug-related protein-mediated multidrug resistance by Servier 9788 in doxorubicin-resistant MCF7 cells; Bichat F et al.; Inherent or acquired resistance to multiple natural drugs, termed multidrug resistance (MDR), represents a major obstacle to chemotherapy . Expression of P-glycoprotein (P-gp) in MCF7mdr and MCF7R resistant cells was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis . MCF7R, but not the MDR1 gene-transfected MCF7mdr cells, expressed multidrug-related protein (MRP) concomitantly . Efficacy of an MDR modulator, designated as Servier 9788 (S9788), was estimated by doxorubicin (Dox) sensitization, Dox incorporation, and functional rhodamine 123 assay on MCF7 cell lines . Results showed that S9788 modulates the P-gp-associated MDR of MCF7mdr cells as well as the Multidrug-related protein-associated MDR of MCF7R cells. Biochem Pharmacol, 1998 Aug 15, 56(4), 451 - 7 Modifications of oxido-reductase activities in adriamycin-resistant leukaemia K562 cells; Denis-Gay M et al.; Adriamycin (ADR), a well-known antitumoral drug, interacts with DNA (nuclear and mitochondrial) and cardiolipin . Moreover, ADR induces numerous mitochondrial modifications in sensitive cells . However, no results have yet been obtained as to the repercussions of drug effects on oxido-reductase activities in ADR-resistant cells . To analyze mitochondrial damage induced by ADR treatment, we investigated lactate content, oxygen consumption, respiratory chain activities, and cytochrome content in ADR-sensitive K562 cells and two ADR-resistant variants (K562/R0.2 and K562/R0.5 cells) . Biochemical investigations in ADR-resistant cells showed several mitochondrial modifications (in comparison to the parental cell line) according to the variant line and the physiologic state . More particularly, in K562/R0.5 cells cytochrome c (cyt c) oxidase (COX; EC 1.9.3.1) activity and cytochrome aa3 content dramatically decreased since cells enter into the stationary phase . Regardless of the number of multidrug-resistant cell subcultures in ADR-free medium, the cytochrome c oxidase activity in the stationary phase remained unchanged, indicating an irreversible effect of the drug . These alterations could correspond to several modifications of the nuclear and/or mitochondrial genome(s) following acquisition of the ADR resistance phenotype by K562 cells. Biochem Mol Biol Int, 1998 Sep, 45(6), 1227 - 41 Glutathione metabolism and glutathione S-conjugate export ATPase (MRP1/GS-X pump) activity in cancer . I . Differential expression in human cancer cell lines; de Bittencourt Junior PI et al.; Mg(2+)-dependent vanadate-sensitive glutathione S-conjugate ATPase (GS-X pump) activity is a common feature of some ATP-binding cassette (ABC) transporters, such as the multidrug resistance-associated protein (MRP1) gene product, that exports biologically active electrophiles after their conjugation with intracellular glutathione (GSH) from normal and cancer cells . Antitumor electrophiles (e.g . naturally occurring cyclopentenone prostaglandins and anticancer chemicals) can be intracellularly conjugated with GSH via a glutathione S-transferase catalyzed reaction and be eliminated through GS-X pumps thus threatening cancer chemotherapeutics . Since different sensitivities to antitumor electrophiles are shown by different cell types, the ability of several human cancer cell lines to produce and export S-(2,4-dinitrophenyl)-glutathione (DNP-SG) conjugate through the GS-X pump, using whole cells and inside-out membrane vesicle preparations, is investigated . Different cancer cell lines exhibited characteristically different GS-X pump activity . In particular, HEp-2 larynx carcinoma cells possess an elevated DNP-SG export rate through the GS-X pump compared with HeLa, K562, U937 or HL-60 cells, which exhibit the lowest activity . The differences in DNP-SG export rates are not due to decreased glutathione S-transferase activity or impaired de novo synthesis of GSH . The findings suggest that the GS-X pump may be involved in the modulation of the biological activity of both naturally occurring electrophiles and anticancer drugs . The differential expression of GS-X pumps may lead to an improved understanding of multidrug resistance and may be exploited in the development of new therapeutic strategies for the treatment of cancer patients. Rinsho Byori, 1998 Aug, 46(8), 745 - 58 {Mechanisms of multidrug resistance in tumor cells and analytical methods for its detection}; Takemura Y et al.; We reviewed mechanisms of multidrug resistance (MDR) phenotype in tumor cells and evaluated analytical methods for detection of clinical MDR . A well-recognized mechanism of MDR phenotype is the induction and increased expression of P-glycoprotein (P-gp) which is a 170 kDa cellular transmembrane protein encoded by a multidrug-resistance 1 gene (MDR1) and works as a drug efflux pump . Cellular MDR phenotype through P-gp/MDR1 can be detectable at protein level by: (1) using immunohistochemical method, flow cytometric assay and Western blot analysis with monoclonal antibodies against human P-gp, and (2) measuring Rhodamine 123 dye-efflux as a functional assay of P-gp . Molecular knowledge and recent technical progress enable to determine MDR1 gene expression by RT-PCR-based analytical methods as well as conventional quantification methods of gene expression such as Northern blot analysis . In the evaluation of P-gp/MDR1 expression in clinical samples, in which amount of materials was limited, utilization of simple and sensitive methods like competitive RT-PCR assay might be efficacious for its quantitative detection in clinical laboratories . Evidences which showed the positive correlation between the expression of P-gp/MDR1 and clinical resistance or refractoriness of tumor cells to anticancer drugs involved in MDR have been accumulated and support the clinical importance of its detection to circumvent resistance with alternate use of non-MDR drugs. MMWR Morb Mortal Wkly Rep, 1998 Sep 18, 47(36), 759 - 61 Acquired multidrug-resistant tuberculosis--Buenaventura, Colombia, 1998; P-glycoprotein-mediated methotrexate resistance in CCRF-CEM sublines deficient in methotrexate accumulation due to a point mutation in the reduced folate carrier gene; Children's Cancer Research Institute, Sydney Children's Hospital, NSW, AustraliaWe have previously described a series of methotrexate (MTX)-selected CCRF-CEM sublines (CEM/MTX R1-3) displaying increased resistance to drugs associated with the multidrug resistance phenotype and have provided evidence that MDR1 P-glycoprotein contributes to multifactorial MTX resistance in these cells . We have also suggested that P-glycoprotein-mediated MTX transport arises in these cells due to a deficiency in the normal MTX transport route, the reduced folate carrier (RFC) . We have now determined the nucleotide sequence of the RFC gene in CEM/MTX R1-3 cells and confirm that the carrier is defective in these cells as a result of a premature stop mutation at codon 99, which severely truncates the encoded protein . CEM/MTX R3 cells were removed from MTX, and a series of sublines with increasing MDR1 expression were derived, following selection with vincristine . These cells show increasing cross-resistance to vincristine as well as other drugs associated with the multidrug resistance phenotype . More importantly, the increased P-glycoprotein expression correlates with increased resistance to MTX, supporting the hypothesis that in cells with a defective carrier protein, MTX can become a substrate for P-glycoprotein . Our data have implications for the P-glycoprotein-mediated transport of other hydrophilic drugs in situations where the relevant carrier protein has been functionally inhibited. Parasite, 1998 Jun, 5(2), 167 - 73 Development and characterization of paromomycin-resistant Leishmania donovani promastigotes; Maarouf M et al.; Paromomycin is an antileishmanial chemotherapeutic agent . Leishmania donovani promastigotes resistant to 800 microM of paromomycin were selected by increasing drug pressure and cloned . These promastigotes did not acquire multidrug resistance . Paromomycin resistance was stable