Anticancer Drugs, 2002 Jul, 13(6), 567 - 81 Among substituted 9,10-dihydro-9,10-{1,2}benzenoanthracene-1,4,5,8-tetraones, the lead antitumor triptycene bisquinone TT24 blocks nucleoside transport, induces apoptotic DNA fragmentation and decreases the viability of L1210 leukemic cells in the nanomolar range of daunorubicin in vitro; Perchellet EM et al.; In contrast to their inactive parent compound triptycene (code name TT0), several new synthetic analogs (TT code number) have antileukemic activities and remain effective in daunorubicin (DAU)-resistant tumor sublines in vitro . Among variously substituted 9,10-dihydro-9,10-{1,2}benzenoanthracene-1,4,5,8-tetraones, a total of six lead antitumor compounds have been identified, and their code names are TT2, TT13, TT16, TT19, TT21 and TT24 . These active antitumor triptych structures have bisquinone functionality, and various bromo, methoxy, methylamino and/or dimethylamino substitutions with or without longer alkyl chains on the amino function . Like the anthracycline quinone antibiotic DAU, these triptycene (TT) bisquinones also inhibit DNA synthesis and induce DNA cleavage in relation with their cytotoxic activities, but have the additional advantage of blocking the cellular transport of purine and pyrimidine nucleosides, an effect which DAU cannot do . As demonstrated by intact chromatin precipitation and agarose gel electrophoresis, the ability of TT bisquinones and DAU to induce DNA fragmentation is biphasic with a peak that shifts to lower concentrations with increasing times of drug exposure . The most effective lead antitumor compound, TT24, induces DNA cleavage in the same concentration-dependent manner as DAU at 24 h (similar peak in response to 1.6 microM) and is nearly equipotent to DAU against L1210 tumor cell viability at day 4 (IC50 values of TT24 and DAU: 48 and 25 nM, respectively) . The mechanism by which TT24 induces DNA fragmentation is inhibited by actinomycin D, cycloheximide, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, benzyloxycarbonyl-Ile-Glu-Thr-Asp-fluoromethyl ketone, N-tosyl-L-phenylalanine chloromethyl ketone and ZnSO4, suggesting that TT bisquinones trigger apoptosis by caspase and endonuclease activation . Since TT24 is cytotoxic in the nanomolar range of DAU, but might have a more versatile mechanism of action than DAU in wild-type and multidrug-resistant tumor cells, this new class of DNA-damaging quinone antitumor drugs inhibiting nucleoside transport might be valuable to develop new means of polychemotherapy. Pharmacogenetics, 2002 Aug, 12(6), 451 - 7 C3435T polymorphism in the MDR1 gene affects the enterocyte expression level of CYP3A4 rather than Pgp in recipients of living-donor liver transplantation; Goto M et al.; The bioavailability of structurally unrelated drugs is limited by active secretion via the multidrug resistance gene (MDR1) product P-glycoprotein (Pgp) from enterocyte into lumen as well as intestinal metabolism by cytochrome P450 IIIA4 (CYP3A4) . In the present study, we analyzed whether genetic polymorphism of the MDR1 had some influence on the intestinal expression levels of Pgp and CYP3A4 and the tacrolimus concentration/dose ratio over the first postoperative days in recipients of living-donor liver transplantation (LDLT) . Genotyping assays were performed for the major 10 polymorphisms in the MDR1 gene by the polymerase chain reaction-restriction enzyme length polymorphism method . The allele frequencies of variations at five positions were almost comparable with those in the former studies in Caucasians and Japanese, but there was no variation at the other five positions . Although no polymorphism correlated with the intestinal expression of MDR1 mRNA or the tacrolimus concentration/dose ratio in the LDLT recipients, the C3435T polymorphism significantly affected the intestinal expression level of CYP3A4 mRNA as follows; 3435C/C>3435C/T (P < 0.05 vs . 3435C/C)>3435T/T (P < 0.01 vs . 3435C/C) . Therefore, the identified polymorphisms including C3435T in the MDR1 gene were indicated to have no influence on the intestinal expression level of Pgp or the tacrolimus concentration/dose ratio in the recipients of LDLT . On the other hand, the C3435T polymorphism of MDR1 was suggested to correlate with the enterocyte expression of CYP3A4 rather than Pgp linking unknown genetic variation in CYP3A4 gene. Clin Cancer Res, 2002 Aug, 8(8), 2647 - 54 Cellular bases of the antitumor activity of the novel taxane IDN 5109 (BAY59-8862) on hormone-refractory prostate cancer; Cassinelli G et al.; Taxane-based therapies appear to have a significant efficacy in clinical trials on hormone-refractory prostate carcinoma . In the present study, we investigated the cellular response of androgen-independent prostate carcinoma cell lines to the novel taxane IDN 5109 (BAY 59-8862) and evaluated its antitumor activity . In previous preclinical studies, this new paclitaxel (PTX) analogue was characterized by high tolerability and antitumor efficacy, ability to overcome multidrug resistance, and activity by oral administration . Upon treatment, DU145 and PC3 prostate carcinoma cell lines underwent a transient mitotic arrest . This was followed by G1 arrest and rapid occurrence of apoptosis in DU145 cells, whereas in PC3 cells, which are defective for the postmitotic checkpoint, a slow cell death was preceded by DNA endoreduplication . At the biochemical level, such events were associated with tubulin polymerization, activation of the mitosis-promoting factor, and phosphorylation of Bcl-X(L)/Bcl-2/Raf-1 . In addition, IDN 5109 shared with PTX the ability to down-regulate the expression of the two potent angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor . These findings indicated that IDN 5109 affected the same pathways involved in the cellular response to PTX and suggested that an antiangiogenic effect mediated by inhibition of paracrine stimulation of endothelial cells might contribute to the antitumor effect of both drugs . In in vivo experiments, the new taxane displayed a superior and more persistent effect compared with PTX against DU145 tumor xenografts . Such an effect was associated with pronounced reduction of the tumor microvessel density, superior to that achieved by PTX . These results support a potential therapeutic advantage of IDN 5109 over PTX against hormone-refractory prostate carcinoma. Clin Cancer Res, 2002 Aug, 8(8), 2524 - 9 Phase I trial of the cryptophycin analogue LY355703 administered as an intravenous infusion on a day 1 and 8 schedule every 21 days; Stevenson JP et al.; The cryptophycin analogue LY355703 is a potent inhibitor of microtubule polymerization that displays in vitro and in vivo activity in cell lines and tumor xenografts displaying the multidrug-resistant phenotype . In a Phase I trial, 25 patients received LY355703 as a 2-h i.v . infusion on day 1 and day 8 repeated every 3 weeks . Doses were escalated from 0.1 to 2.22 mg/m2 using a modified continual reassessment method . Neurological toxicity was found to be dose-limiting at 1.84 and 2.22 mg/m2 . Among four patients treated at these doses, two had grade 4 constipation/ileus, one with severe myalgias, and one had grade 3 motor neuropathy . These findings were reversible . The 1.5 mg/m2 dose level was well tolerated . An amended twice-weekly schedule was pursued in 11 patients in an attempt to improve dose intensity and avoid dose-limiting neurotoxicity . Doses of >0.75 mg/m2 on a day 1, 4, 8, and 11 schedule every 21 days were not tolerated as a result of nausea/constipation, suggesting that LY335703 toxicity is not schedule dependent and is related to cumulative dose . LY355703 plasma concentrations measured by liquid chromatography with tandem mass spectrometry were evaluated using a population pharmacokinetic model . LY355703 was eliminated rapidly with a short terminal half-life that ranged from 0.8 to 3.9 h . Interpatient variability with respect to plasma clearance and volume of distribution, including covariates, was moderate at 32% and 39%, respectively . Maximum plasma concentration and area under the plasma concentration-time curve were linear over the dose range studied . A patient with non-small cell lung cancer previously treated with taxanes experienced a partial response lasting 4 months, and five patients had stable disease lasting > or =3 months . LY355703 at a dose of 1.5 mg/m2 is recommended for Phase II evaluation on a days 1 and 8 schedule . Twice-weekly dosing did not allow improvement in dose intensity or tolerability. Pharmacology, 2002 Sep, 66(1), 31 - 5 Effects of phalloidin on the biliary excretion of cholephilic compounds in rats; Ohashi M et al.; Phalloidin is known to cause cholestasis by preventing microfilament depolymerization . In addition, phalloidin is reported to inhibit the vesicular targeting of canalicular transporters . The aim of the present study was to examine the effect of phalloidin on the biliary excretion of substrates typical for various canalicular transporters in rats . Phalloidin decreased the biliary excretion of tracer amounts of taurocholate, leukotriene C(4), pravastatin, and vinblastine . Increases in bile flow and biliary bile acid excretion caused by taurocholate infusion were completely inhibited by phalloidin . These data indicate that, in addition to multidrug resistance protein 2 and P glycoprotein, the vesicular targeting of the bile salt export pump, a major canalicular bile acid transporter, is also impaired by phalloidin . The decrease of biliary excretion of glutathione may also relate to the increase in the bile acid independent canalicular bile flow in phalloidin-treated rats . Cancer Lett, 2002 Nov 28, 185(2), 211 - 8 Differentially expressed gene profiles between multidrug resistant gastric adenocarcinoma cells and their parental cells; Zhao Y et al.; To better understand the molecular mechanisms of multidrug resistance (MDR) of human cancers, we isolated differentially expressed genes from drug-resistant human gastric adenocarcinoma cell lines using a polymerase chain reaction-based subtractive hybridization technique . Sixty three genes were identified to be differentially expressed in the drug-resistant human gastric adenocarcinoma cell lines . Among the 63 up-regulated genes, 27 were known genes, of which two have been reported to be associated with MDR . The remaining ones were undefined genes or expressed sequenced tags . The results suggest that this strategy is efficient for large-scale cloning of differentially expressed genes in drug-resistant cells . Further characterization of these genes will shed more light on the understanding of molecular mechanisms of MDR of human cancer cells. Anticancer Res, 2002 May-Jun, 22(3), 1649 - 53 Involvement of multidrug resistance-associated protein 2 in in vivo cisplatin resistance of rat hepatoma AH66 cells; Itoh Y et al.; We previously showed that the rat ascites hepatoma cell line AH66 is cisplatin resistant in vivo, but not in vitro . We further found that the expression of multidrug resistance-associated protein 2 (MRP2) in AH66 cells harvested from tumor-bearing rats was markedly decreased after incubation for 48 hours in medium containing 5% fetal bovine serum (5% FBS DMEM), and that the expression recovered when the cells were re-inoculated into rats . To examine whether the in vivo cisplatin resistance of AH66 cells is related to modulation or the expression of MRP2, we used AH66 cells transfected with pBK-CMV expression vector containing MRP2 antisense DNA . The expression of MRP2 alone among the MRP transporter family was markedly decreased in the transfected cells . The uptake of cisplatin into these cells was significantly higher than that in AH66 parent cells or control vector-transfected AH66 cells . The uptake of cisplatin in AH66 parent cells and the vector control cells was increased by treatment with sodium azide or probenecid whereas the uptake in the MRP2 antisense transfectant cells was not affected . When AH66 parent cells and control transfectant cells were cultured with cisplatin in medium containing 5% ascites fluid (5% ASF DMEM) for 48 hours, the cisplatin sensitivity significantly decreased . In contrast, the cisplatin sensitivity of MRP2 antisense transfectant cells did not change after culture in 5% ASF DMEM . These results show that the cisplatin resistance of AH66 cells is dependent upon the enhanced expression of MRP2. Anticancer Res, 2002 May-Jun, 22(3), 1385 - 97 Characterization of tropane alkaloid aromatic esters that reverse the multidrug-resistance phenotype; Mi Q et al.; P-Glycoprotein (Pgp) associated multidrug-resistance (MDR) is a significant factor that can lead to the failure of cancer chemotherapy . Several new tropane alkaloid aromatic esters obtained from extracts of Erythroxylum pervillei Baillon (Erythroxylaceae) (1-8) and Erythroxylum rotundifolium Lunan (Erythroxylaceae) (9-12) by means of bioassay-directed fractionation were found to restore vinblastine sensitivity with cultured multidrug-resistant KB-VI cells . With this model, growth was not inhibited by addition of vinblastine (1 microg/ml) to the culture medium, but in combination with tropane alkaloids, inhibition was observed with IC50 values categorized as: low (ranging from 0.17-0.62 microM) for 1 {3alpha-phenylacetoxy-6beta-(3,4,5-trimethaxycinnamoyloxy)-tropane}, 3 {3alpha-(3,4,5-trimethoxybenzoyloxy)-6beta-(3,4,5-trimethoxycinnamoyloxy)tropane}, 4 {3alpha-(3,4,5-trimethoxybenzoyloxy)-6beta-(3,4,5-trimethoxycinnamoyloxy)-7beta-hydroxytropane}, 5 {3alpha,6beta-di-(3,4,5-trimethoxycinnamoyloxy)tropane}, 6 {3alpha,6beta-di-(3,4,5-trimethoxycinnamoyloxy)-7beta-hydroxytropane} and 9 {6beta-benzoyloxy-3alpha-(3,4,5-trimethoxycinnamoyloxy)tropane}; medium (2.0-3.7 microM) for 2 {3alpha-(3-hydroxyphenylacetoxy)-6beta-(3,4,5-trimethoxycinnamoyloxy)tropane} and 10 {7beta-acetoxy-6beta-benzoyloxy-3alpha-(3,4,5-trimethoxycinnamoyloxy)tropane}; or high (9.8 microM) for 11 {6beta-benzoyloxy-3alpha-(3,4,5-trimethoxycinnamoyloxy)tropane-7beta-ol} . Compounds 7 (tropane-3alpha,6beta,7beta-triol 3-phenylacetate), 8 (1alphaH, 5alphaH-tropan-3alpha-yl 3,4,5-trimethoxybenzoate) and 12 (6beta-(3,4,5-trimethoxybenzoyloxy)-3alpha-(3,4,5-trimethoxycinnamoyloxy)tropane-7beta-ol) were not active . Among the active compounds, 1 and 3-6 were further tested with drug-resistant CEM/VLB100 cells . In the presence of modulator, sensitivity to vinblastine increased by 50-5,000-fold . Treatment of KB-V1 cells with 1 or 3-6 enhanced the intracellular accumulation of fluorescence dye (rhodamine 123) . Visualization by confocal microscopy confirmed the intracellular accumulation of rhodamine 123 in drug-resistant KB-V1 cells was significantly less than drug-sensitive KB-3 cells, while treatment of KB-V1 cells with 10 microM 4 significantly increased intracellular accumulation . The molecular characteristics of the isolates were then determined and compared with their potential to reverse drug resistance . ClogP and molar refractivity were weakly correlated with their potential to reverse MDR Eur Respir J Suppl, 2002 Jul, 36, 66s - 77s Strategies against multidrug-resistant tuberculosis; Loddenkemper R et al.; The rise of multidrug-resistant tuberculosis (MDR-TB), defined as tuberculosis showing resistance to at least isoniazid and rifampicin, is a serious threat to tuberculosis control in some high prevalence countries and may have some impact on low prevalence regions as well . The World Health Organization estimates that 50 million people worldwide are infected with MDR-TB, and that, in the year 2000, 273,000 (3.1%) MDR-TB cases were among the 8.7 million new tuberculosis cases . In 1998, the highest MDR-TB rates among new cases and the highest combined (new and previously treated cases) MDR-TB rates were found in Estonia (14.1 and 18.1%), Henan province in China (10.8 and 15.1%), Latvia (9.0 and 12.0%), and Ivanovo Oblast (9.0 and 12.3%) and Tomsk Oblast (6.5 and 13.7%) in the Russian Federation . The risk factors for MDR-TB are previous treatment or relapse, originating from "hot spot" areas, a history of imprisonment, homelessness and possibly also human immunodeficiency virus . The treatment of multidrug-resistant tuberculosis is difficult due to side-effects and a treatment duration of up to 3 yrs, which is expensive and often unsuccessful . Therefore, strategies for the treatment and prevention of multidrug-resistant tuberculosis are urgently required . This requires functioning tuberculosis control programmes (directly observed treatment short course), and, in some high prevalence countries, the introduction of second-line drugs on the basis of appropriate susceptibility testing (directly observed treatment short course-Plus) . Only the future will show whether this "ticking time bomb" can be defused. Gen Physiol Biophys, 2002 Mar, 21(1), 103 - 9 Pentoxifylline influences drug transport activity of P-glycoprotein and decreases mdrl gene expression in multidrug resistant mouse leukemic L1210/VCR cells; Drobna Z et al.; The effects of pentoxifylline (PTX) on intracellular accumulation of doxorobicin (DOX), DOX cytotoxicity and expression of Pgp in multidrug resistant L1210/VCR cell line were investigated . PTX (100 mg/l) was able to enhance the DOX accumulation in resistant cells . The maximum intracellular levels of DOX were reached after treatment with PTX for 24 hours (total duration of PTX-treatment was 72 hours) . The levels of mdrl mRNA (measured by RT-PCR method) were decreased 2-fold in the presence of 100 mg/l PTX (minimum reached within 48 hours) in comparison to control cells. N Engl J Med, 2002 Aug 8, 347(6), 385 - 94 Antiretroviral-drug resistance among patients recently infected with HIV; Little SJ et al.; BACKGROUND: Among persons in North America who are newly infected with the human immunodeficiency virus (HIV), the prevalence of transmitted resistance to antiretroviral drugs has been estimated at 1 to 11 percent . METHODS: We performed a retrospective analysis of susceptibility to antiretroviral drugs before treatment and drug-resistance mutations in HIV in plasma samples from 377 subjects with primary HIV infection who had not yet received treatment and who were identified between May 1995 and June 2000 in 10 North American cities . Responses to treatment could be evaluated in 202 subjects . RESULTS: Over the five-year period, the frequency of transmitted drug resistance increased significantly . The frequency of high-level resistance to one or more drugs (indicated by a value of more than 10 for the ratio of the 50 percent inhibitory concentration {IC50} for the subject's virus to the IC50 for a drug-sensitive reference virus) increased from 3.4 percent during the period from 1995 to 1998 to 12.4 percent during the period from 1999 to 2000 (P=0.002), and the frequency of multidrug resistance increased from 1.1 percent to 6.2 percent (P=0.01) . The frequency of resistance mutations detected by sequence analysis increased from 8.0 percent to 22.7 percent (P<0.001), and the frequency of multidrug resistance detected by sequence analysis increased from 3.8 percent to 10.2 percent (P=0.05) . Among subjects infected with drug-resistant virus, the time to viral suppression after the initiation of antiretroviral therapy was longer (P=0.05), and the time to virologic failure was shorter (P=0.05) . CONCLUSIONS: The proportion of new HIV infections that involve drug-resistant virus is increasing in North America . Initial antiretroviral therapy is more likely to fail in patients who are infected with drug-resistant virus . Testing for resistance to drugs before therapy begins is now indicated even for recently infected patients . Biochem Pharmacol, 2002 Aug 15, 64(4), 573 - 82 Modulation of P-glycoprotein expression and function by curcumin in multidrug-resistant human KB cells; Anuchapreeda S et al.; Multidrug resistance (MDR) is a phenomenon that is often associated with decreased intracellular drug accumulation in the tumor cells of a patient, resulting from enhanced drug efflux . It is often related to the overexpression of P-glycoprotein (Pgp) on the surface of tumor cells, thereby reducing drug cytotoxicity . In this study, curcumin was tested for its potential ability to modulate the expression and function of Pgp in the multidrug-resistant human cervical carcinoma cell line KB-V1 . Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) showed that treatment with 1, 5, and 10 microM curcumin for up to 72hr was able to significantly lower Pgp expression in KB-V1 cells . Curcumin (1-10 microM) decreased Pgp expression in a concentration-dependent manner and was also found to have the same effect on MDR1 mRNA levels . The effect of curcumin on Pgp function was demonstrated by rhodamine 123 (Rh123) accumulation and efflux in Pgp-expressing KB-V1 cells . Curcumin increased Rh123 accumulation in a concentration-dependent manner (1-55 microM) and inhibited the efflux of Rh123 from these cells, but did not affect the efflux of Rh123 from the wild-type drug-sensitive KB-3-1 cells . Treatment of drug-resistant KB-V1 cells with curcumin increased their sensitivity to vinblastine, which was consistent with an increased intracellular accumulation of Rh123 . In addition, curcumin inhibited verapamil-stimulated ATPase activity and the photoaffinity labeling of Pgp with the prazosin analog {125I}iodoarylazidoprazosin in a concentration-dependent manner, demonstrating that curcumin interacts directly with the transporter . Thus, curcumin seems to be able to modulate the in vitro expression and function of Pgp in multidrug-resistant human KB-V1 cells . In summary, this study describes the duel modulation of MDR1 expression and Pgp function by the phytochemical curcumin, which may be an attractive new agent for the chemosensitization of cancer cells. Eur J Pharmacol, 2002 Aug 9, 449(3), 197 - 205 Effect of cyclophosphamide on gene expression of cytochromes p450 and beta-actin in the HL-60 cell line; Xie HJ et al.; Many studies have demonstrated that cyclophosphamide (CPA) can affect hepatic cytochrome p450 (CYP) isoenzyme activity in animals . We have investigated the effect of CPA on gene expression of various CYP enzymes as well as beta-actin in the human acute promyelocytic leukemia cell line (HL-60S) and its multidrug-resistant (MDR) phenotype HL-60R . Cells were incubated at different concentrations of CPA ranging between 50 micro g/ml and 5 mg/ml . In determination of cytotoxicity and resistance factor (RF: IC(50) HL-60R/IC(50) HL-60S), concentrations of 100 and 500 micro g/ml CPA were selected to treat HL-60S and HL-60R up to 72 h . CYP gene expression in the cells prior to and after treatment with CPA was determined using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR . Unexposed cell lines did not contain measurable levels of mRNA for CYP2B6, CYP3A4, CYP2C9 and CYP2C19 and no induction was observed after exposure . However, CYP1B1-specific mRNA, which is predominantly expressed in HL-60 cell line, was suppressed after exposure to CPA in a concentration-dependent manner . Beta-actin gene expression was also decreased . The HL-60 RF to CPA was calculated to 0.71, indicating that the multidrug-resistant (MDR) phenotype is not involved in the mechanism of resistance to CPA . No CYPs were induced by CPA in vitro, which probably indicates that the CYP inducibility in blood cells is poor . Our study suggests that suppression of beta-actin gene expression contributes or is involved in the CPA cytotoxicity. Toxicology, 2002 Sep 16, 178(3), 209 - 19 Expression of rat Multidrug Resistance Protein 2 (Mrp2) in male and female rats during normal and pregnenolone-16alpha-carbonitrile (PCN)-induced postnatal ontogeny; Johnson DR et al.; The normal maturation of biliary organic anion excretion in newborn rats can be enhanced by microsomal enzyme-inducing chemical treatment, yet the mechanism for this phenomenon is not known . Multidrug Resistance Protein 2 (Mrp2) is a biliary efflux transporter that is inducible by select microsomal enzyme-inducing chemicals . Thus, the aims of this study were to compare the normal and pregnenolone-16alpha-carbonitrile (PCN)-induced postnatal ontogeny of Mrp2 in male and female rats . Mrp2 protein increased in an age-dependent manner in both sexes between 0 and 90 days of age . At birth, Mrp2 protein in both male and female rats was the same, approximately 70% of adult levels . Mrp2 protein in both sexes reached maximal expression levels that were higher than adult levels (male: days 25-40; female: day 45), then decreased to adult levels, at which age Mrp2 protein expression in male and female rats was the same . Second, male and female rats of various ages were treated with PCN (75 mg/kg, ip) or corn oil for 4 days, after which livers were removed and analyzed for Mrp2 protein and mRNA expression . PCN accelerated the expression of Mrp2 protein in male and female rats as early as 10 days of age, whereas, PCN did not affect male and female Mrp2 mRNA ontogeny . These data suggest that PCN increased Mrp2 protein by a sex-independent posttranscriptional mechanism. Cancer Genet Cytogenet, 2002 Jul 1, 136(1), 66 - 72 Aneuploidy theory explains tumor formation, the absence of immune surveillance, and the failure of chemotherapy; Rasnick D; The autocatalyzed progression of aneuploidy accounts for all cancer-specific phenotypes, the Hayflick limit of cultured cells, carcinogen-induced tumors in mice, the age distribution of human cancer, and multidrug-resistance . Here aneuploidy theory addresses tumor formation . The logistic equation, phi(n)(+1) = rphi(n) (1 - phi(n)), models the autocatalyzed progression of aneuploidy in vivo and in vitro . The variable phi(n)(+1) is the average aneuploid fraction of a population of cells at the n+1 cell division and is determined by the value at the nth cell division . The value r is the growth control parameter . The logistic equation was used to compute the probability distribution for values of phi after numerous divisions of aneuploid cells . The autocatalyzed progression of aneuploidy follows the laws of deterministic chaos, which means that certain values of phi are more probable than others . The probability map of the logistic equation shows that: 1) an aneuploid fraction of at least 0.30 is necessary to sustain a population of cancer cells; and 2) the most likely aneuploid fraction after many population doublings is 0.70, which is equivalent to a DNA(index)=1.7, the point of maximum disorder of the genome that still sustains life . Aneuploidy theory also explains the lack of immune surveillance and the failure of chemotherapy. Bull World Health Organ, 2002, 80(7), 538 - 45 Therapeutic efficacy of sulfadoxine-pyrimethamine, amodiaquine and the sulfadoxine-pyrimethamine-amodiaquine combination against uncomplicated Plasmodium falciparum malaria in young children in Cameroon; Basco LK et al.; OBJECTIVE: To evaluate the therapeutic efficacy of sulfadoxine-pyrimethamine, amodiaquine, and the sulfadoxine-pyrimethamine-amodiaquine combination for the treatment of uncomplicated Plasmodium falciparum malaria in young children in Cameroon . METHODS: In a randomized study we evaluated the effectiveness and tolerance of (i) sulfadoxine-pyrimethamine (SP) (25 mg/kg body weight of sulfadoxine and 1.25 mg/kg of pyrimethamine in a single oral dose), (ii) amodiaquine (AQ) (30 mg/kg body weight in three divided daily doses), and (iii) the sulfadoxine-pyrimethamine-amodiaquine combination (SP+AQ) (same doses as in the other two treatment groups, given simultaneously on day 0) in young children in southern Cameroon . The parasitological and clinical responses were studied until day 28 in accordance with the modified 1996 WHO protocol for the evaluation of the therapeutic efficacy of antimalarial drugs . FINDINGS: Of 191 enrolled patients, 6 and 8 were excluded or lost to follow-up before day 14 and between day 14 and day 28, respectively . For the AQ-treated patients, parasitological and clinical evaluation on day 14 showed late treatment failure in 2 of 61 (3.3%) and adequate clinical response with parasitological failure in one (1.6%) . There was an adequate clinical response in all patients treated with SP or SP+AQ . Therapeutic failure rates on day 28 were 13.6%, 10.2% and 0% in the SP, AQ, and SP+AQ groups, respectively . Anaemia improved in all three regimens . AQ produced faster fever clearance but was associated with more transient minor side-effects than SP . SP+AQ reduced the risk of recrudescence between day 14 and day 28 but increased the incidence of minor side-effects . CONCLUSION: SP+AQ can be recommended as a temporary means of slowing the spread of multidrug resistance in Plasmodium falciparum in Africa while the introduction of other combinations, including artemisinin derivatives, is awaited. Biochem Biophys Res Commun, 2002 Aug 16, 296(2), 388 - 94 Nucleotide triphosphatase activity of the N-terminal nucleotide-binding domains of the multidrug resistance proteins P-glycoprotein and MRP1; Wilkes DM et al.; The multidrug resistance proteins P-glycoprotein (Pgp) and MRP1 are drug-efflux pumps . In this study, we compared the nucleotide triphosphatase activities of the isolated N-terminal nucleotide binding domains (NBD1) of Pgp and MRP1, and explored the potential role of the phosphorylation target domain of Pgp on the regulation of Pgp NBD1 ATPase activity . We found that: (1) the NBD1s of Pgp and MRP1 have ATPase and GTPase activities, (2) the K(m)s of Pgp NBD1 for ATP and GTP hydrolysis are identical, while the K(m) of MRP1 NBD1 for ATP is lower than that for GTP, and (3) phosphorylation of MLD by PKA or PKC produces a marginal increase of V(max) for ATP hydrolysis, without affecting the affinity for ATP . These results show efficient GTP hydrolysis by the NBD1s of Pgp and MRP1, and a minor role of phosphorylation in the control of Pgp NBD1 ATPase activity. Clin Pharmacokinet, 2002, 41(10), 751 - 90 Enterohepatic circulation: physiological, pharmacokinetic and clinical implications; Roberts MS et al.; Enterohepatic recycling occurs by biliary excretion and intestinal reabsorption of a solute, sometimes with hepatic conjugation and intestinal deconjugation . Cycling is often associated with multiple peaks and a longer apparent half-life in a plasma concentration-time profile . Factors affecting biliary excretion include drug characteristics (chemical structure, polarity and molecular size), transport across sinusoidal plasma membrane and canniculae membranes, biotransformation and possible reabsorption from intrahepatic bile ductules . Intestinal reabsorption to complete the enterohepatic cycle may depend on hydrolysis of a drug conjugate by gut bacteria . Bioavailability is also affected by the extent of intestinal absorption, gut-wall P-glycoprotein efflux and gut-wall metabolism . Recently, there has been a considerable increase in our understanding of the role of transporters, of gene expression of intestinal and hepatic enzymes, and of hepatic zonation . Drugs, disease and genetics may result in induced or inhibited activity of transporters and metabolising enzymes . Reduced expression of one transporter, for example hepatic canalicular multidrug resistance-associated protein (MRP) 2, is often associated with enhanced expression of others, for example the usually quiescent basolateral efflux MRP3, to limit hepatic toxicity . In addition, physiologically relevant pharmacokinetic models, which describe enterohepatic recirculation in terms of its determinants (such as sporadic gall bladder emptying), have been developed . In general, enterohepatic recirculation may prolong the pharmacological effect of certain drugs and drug metabolites . Of particular importance is the potential amplifying effect of enterohepatic variability in defining differences in the bioavailability, apparent volume of distribution and clearance of a given compound . Genetic abnormalities, disease states, orally administered adsorbents and certain coadministered drugs all affect enterohepatic recycling. Bioorg Med Chem Lett, 2002 Sep 2, 12(17), 2277 - 9 In vivo active antimalarial isonitriles; Singh C et al.; Building on the lead from antimalarial isonitriles 1-4 of marine origin, several easily accessible synthetic isonitriles were assessed for their antimalarial activity against Plasmodium falciparum (in vitro) and multidrug resistant Plasmodium yoelii in Swiss mice model (in vivo) . Isonitrile 11 has shown promising activity in both these assays. CMAJ, 2002 Jul 23, 167(2), 131 - 6 Adverse events associated with pyrazinamide and levofloxacin in the treatment of latent multidrug-resistant tuberculosis; Papastavros T et al.; BACKGROUND: The current Canadian and US guidelines for the treatment of multidrug-resistant latent tuberculosis infection advocate the use of pyrazinamide and a fluoroquinolone as a first-line treatment option . However, there is very little information in the literature that describes the use of these agents together . This case series describes the probable association between multiple adverse events and the use of pyrazinamide and levofloxacin in the treatment of individuals with suspected latent multidrug-resistant tuberculosis infection . METHODS: We studied a case series of 17 individuals with suspected latent multidrug-resistant tuberculosis infection in Hamilton, Ont., who were being treated with pyrazinamide and levofloxacin . The Naranjo scale was used to assess patients for musculoskeletal, central nervous system, gastrointestinal and dermatological adverse events . Hepatocellular events were assessed and defined using criteria established by the Council for International Organizations of Medical Sciences . Laboratory abnormalities and adverse events that were documented during combination drug therapy were evaluated to determine the likelihood of an association . RESULTS: Fourteen individuals developed musculoskeletal adverse effects (11 were deemed to be probably related to combination therapy) . There were 8 reports of central nervous system effects (5 of which were assessed as being probably associated with therapy) . Hyperuricemia and gastrointestinal and dermatological effects were also common; the use of pyrazinamide and levofloxacin was believed to be probably responsible for the emergence of these adverse effects . There were 5 cases of hepatocellular injury . Therapy was discontinued in all individuals . INTERPRETATION: The combination of pyrazinamide and levofloxacin appears to be a poorly tolerated regimen . The mechanism of a possible interaction is not yet understood . Given the severity of some of the adverse events, a better understanding of dosing and clearer guidelines for monitoring therapy are imperative if these drugs are to be prescribed together. Can J Public Health, 2002 Jul-Aug, 93(4), 264 - 6 Tuberculosis control in Alberta . A federal, provincial and regional public health partnership; Long R; The number of cases of tuberculosis in Alberta or Canada may not be large, but the public health and medical costs of just a few cases can be prohibitive . For example, the costs of managing cases of multidrug-resistant tuberculosis and their contacts, can exceed the entire annual budget of a program . This was evident in New York City in the late 1980s and early 1990s, when $1 billion in public funds were spent reversing a major resurgence of drug-resistant and susceptible tuberculosis . In Canada, the Walkerton Inquiry has identified an apparent failure of provincial public policy to adequately address public health needs . This has resulted in decreased public confidence and potential liabilities for the policy-makers . In the design of the Tuberculosis Control Program of Alberta, the notion of a quasicentralized or quasidecentralized program is rejected . Rather there is an appeal to the notion of a partnership of responsibility that recognizes jurisdictional and non-jurisdictional public health, case management and epidemiologic realities, the integral contribution of each level of government and the need to be accountable to the public's health and purse . For levels of government not to properly discharge their responsibilities may be perceived as an abrogation of the public trust and a disregard of the Tuberculosis Control Policy Package and operational directives of the World Health Organization. Cancer Res, 2002 Aug 1, 62(15), 4206 - 11 Action of a novel anticancer agent, CHS 828, on mouse fibroblasts: increased sensitivity of cells lacking poly (ADP-Ribose) polymerase-1; Lovborg H et al.; We observed stronger cytotoxic effect of CHS 828 on poly(ADP-ribose) polymerase-1(PARP-1) knock-out cells as compared with the normal counterpart . The proliferation of PARP-1 -/- cells was inhibited by a drug concentration approximately 3-fold lower than that in the normal cells . The monitoring of p53 levels revealed that CHS 828 induced p53 response in a dose-dependent manner in only normal cells . The drug, however, failed to activate the p53 protein in PARP-1-deficient cells even after combined treatment with multidrug-resistant modulators . These results show that the PARP-1 inactivation sensitizes cells to the novel anticancer drug CHS 828 and that the drug is able to activate different cellular pathways depending on PARP-1 status. J Neurochem, 2002 Aug, 82(3), 716 - 9 Expression of mRNAs of multidrug resistance proteins (Mrps) in cultured rat astrocytes, oligodendrocytes, microglial cells and neurones; Hirrlinger J et al.; Multidrug resistance proteins (Mrps) are ATP-driven export pumps that mediate the export of organic anions from cells . So far only little information is available on expression and physiological functions of Mrps in brain . The expression of mRNAs of six Mrp paralogs in rat brain, as well as in rat cultures enriched for neurones, astrocytes, oligodendrocytes and microglial cells, was studied by qualitative and semiquantitative RT-PCR analysis . In adult rat brain as well as in neural cell cultures the mRNAs coding for Mrp1, Mrp3, Mrp4 and Mrp5 were detected . Semiquantitative analysis revealed that the mRNAs coding for Mrp1 and Mrp5 were more abundant in the four cell culture types than mRNAs of the other Mrps . mRNAs coding for Mrp3 and Mrp4 were found at significant levels in cultured astrocytes and microglial cells, whereas cultures of neurones and oligodendrocytes contained only marginal quantities of these mRNAs . Putative physiological functions of Mrps in brain cells are discussed. J Neurochem, 2002 Aug, 82(3), 458 - 67 Effects of dopamine on the glutathione metabolism of cultured astroglial cells: implications for Parkinson's disease; Hirrlinger J et al.; To investigate the effects of dopamine (DA) on the release of glutathione (GSH) from astrocytes, we used astroglia-rich primary cultures from the brains of newborn rats . In the absence of DA, GSH accumulated in the medium of these cultures with a constant rate . In contrast, during incubation of the cells with 50 micro m DA extracellular GSH was not detectable anymore . This disappearance of extracellular GSH was prevented by superoxide dismutase, indicating that DA does not affect GSH release but rather reacts with the released GSH in a superoxide-dependent reaction . Incubation of astroglial cultures with 0.5 and 1 mm DA established almost constant extracellular concentrations of H2O2 of 5 microm and 15 microm, respectively . Under these conditions astroglial cultures release glutathione disulphide (GSSG) . This GSSG export was blocked by catalase and by MK571, an inhibitor of the multidrug resistance protein 1 . The effects of DA on the extracellular accumulations of GSH and GSSG were not modulated by inhibitors of DA receptors, DA transport, and monoamine oxidases . The other catecholamines adrenaline and noradrenaline showed similar effects on the accumulation of GSH and GSSG in the medium compared with those obtained for DA . In conclusion, the data presented demonstrate that DA affects astroglial GSH metabolism by two mechanisms: (i) directly by chemical reaction with extracellular GSH, and (ii) indirectly by generation of hydrogen peroxide that leads to the efflux of GSSG from astroglial cells . These observations are discussed in the context of the brain's GSH metabolism in Parkinson's disease. Leuk Lymphoma, 2002 Apr, 43(4), 875 - 9 Messenger RNA analysis of the multidrug resistance related protein (MRP1) and the lung resistance protein (LRP) in de novo and relapsed childhood acute lymphoblastic leukemia; Sauerbrey A et al.; In this study, 86 children (58 initial ALL and 28 children with relapsed disease) were investigated for lung resistance protein (LRP) and multidrug resistance related protein (MRPI)-mRNA expression by semiquantitative RT-PCR . The majority of investigated cases demonstrated variable LRP and MRP1 mRNA expression, when normalized for beta-microglobulin expression . LRP and MRPI mRNA expression may be coordinately regulated, as expression of both transcripts was found to be significantly correlated (p = 0.0001) . No differences of LRP and MRP expression were observed between initial and relapsed stage patients (LRP: p = 0.89 and for MRP: p = 0.09) . The prognostic value of both resistance mechanisms was subjected to Kaplan-Meier analysis for event-free survival . For this analysis the patients were divided into groups with high or low LRP or MRPI mRNA expression by utilizing the median value as the cut-off point . Overexpression of both resistance mechanisms had no prognostic significance in our retrospective study (log-rank test for LRP: p = 0.12 and for MRPI: p = 0.95), however, patients who showed high LRP expression exhibited a lower tendency of remaining in continuous first remission. Leuk Lymphoma, 2002 Apr, 43(4), 711 - 7 "Pros and cons" on how to measure multidrug resistance in leukemias; Kappelmayer J et al.; Drug resistance is one of the most significant challenges in the treatment of various types of malignancies, however most of the experimental and clinical data in multidrug resistance (MDR) has been obtained in leukemias . MDR is the term that describes innate or acquired resistance of tumor cells to a wide range of anticancer drugs . As its presence determines treatment outcome in several forms of leukemias, it is imperative that clinical laboratories provide the most useful data on its expression . Here, a brief review is provided on the pathomechanism and diagnostics of MDR . From the diagnostic point of view it is fortunate that MDR proteins display similar effluxing activity towards many dissimilar agents some of which can be used in fluorescent assays . These tests mimic the real clinical problem i.e . the extrusion activity of MDR proteins towards xenobiotics . Thus, we believe that functional assays when carried out in a standardized way and particularly combined with labeling for various surface markers can be recommended as a front-line test in MDR measurement. Leuk Lymphoma, 2002 Apr, 43(4), 685 - 701 The role of drug efflux pumps in acute myeloid leukemia; van der Kolk DM et al.; A major problem in the treatment of patients with acute myeloid leukemia (AML) is the occurrence of resistance to structurally and functionally unrelated chemotherapeutic agents, called multidrug resistance (MDR) . One of the known MDR mechanisms is the overexpression of adenosine triphosphate (ATP)-dependent efflux pumps . Permeability-glycoprotein (P-gp), the best characterized of the human drug efflux pumps, has been shown to be associated with poor treatment outcome in AML patients . Besides P-gp, in addition the multidrug resistance protein 1 (MRP1) appeared to contribute to the observed resistance in AML . Alternative transporter proteins, such as the MRP1 homologues MRP2, MRP3, MRP5 and MRP6, and the breast cancer resistance protein (BCRP), have been shown to be expressed at variable levels in AML patient cells . The latter proteins have been described to confer resistance to chemotherapeutic agents, such as daunorubicin, mitoxantrone, etoposide and 6-mercaptopurine, which are generally used in the treatment of AML patients; however, theyhave not yet proven to play a role in drug resistance in AML . The present review gives an overview of the current knowledge concerning these drug transporters, with a focus on the role of the transporter proteins in AML. Mol Biol Rep, 2001, 28(4), 209 - 15 Profiling methyl-CpG specific determinants on transcriptionally silent chromatin; El-Osta A et al.; Transcriptional activity is closely associated with DNA methylation and chromatin remodelling . Evidence is emerging that a family of methylation specific (methyl-CpG binding domain, MBD) proteins have the capacity to bind to methylated sequences and repress transcription . Recent advances in this area reveal that many of the MBD proteins are associated with histone deacetylase (HDAC) dependant repression . The capacity of MBD association to repress transcription would largely be defined by promoter structure and this is best explained by the position and density of DNA methylation . The mechanism of specific targeting of MBD family members to methylated sequences remains largely unknown . In order to understand the mechanistic details of silencing the current challenge is to identify and map these molecular determinants assembled on native chromatin in model systems of human development and disease . Downstream targets such as the methylated Fragile X Mental Retardation gene 1 (FMR1) gene and tumour suppressor genes are likely candidates . In this article, we describe a powerful strategy that involves the immunoprecipitation of in vivo formaldehyde fixed chromatin to identify MBD binding complexes directly isolated from the natural chromosomal environment . We demonstrate the methylated human Multidrug Resistance gene 1 (MDR1) is enriched with transcriptional repressors that belong to the MBD family and this would account for transcriptional silencing. Leuk Lymphoma, 2002 Jun, 43(6), 1221 - 8 P-glycoprotein in acute myeloid leukaemia: therapeutic implications of its association with both a multidrug-resistant and an apoptosis-resistant phenotype; Pallis M et al.; P-glycoprotein (Pgp) expression is an independent prognostic factor for response to remission-induction chemotherapy in acute myeloblastic leukaemia, particularly in the elderly . There are several potential agents for modulating Pgp-mediated multi-drug resistance, such as cyclosporin A and PSC833, which are currently being evaluated in clinical trials . An alternative therapeutic strategy is to increase the use of drugs which are unaffected by Pgp . However, in this review, we explain why this may be more difficult than it appears . Evidence from in vitro studies of primary AML blasts supports the commonly held supposition that chemoresistance may be linked to apoptosis-resistance . We have found that Pgp has a drug-independent role in the inhibition of in vitro apoptosis in AML blasts . Modulation of cytokine efflux, signalling lipids and intracellular pH have all been suggested as ways by which Pgp may affect cellular resistance to apoptosis; these are discussed in this review . For a chemosensitising agent to be successful, it may be more important for it to enhance apoptosis than to increase drug uptake. Obstet Gynecol, 2002 Aug, 100(2), 281 - 7 Low proliferation activity may be associated with chemoresistance in clear cell carcinoma of the ovary; Itamochi H et al.; OBJECTIVE: To estimate whether and how the biologic behavior of clear cell carcinoma contributes to the chemoresistance mechanism . METHODS: Forty-one patients with clear cell carcinoma and 90 patients with serous adenocarcinoma, who had measurable disease after initial surgery, were examined . All patients underwent cytoreductive surgery followed by platinum-based chemotherapy . P-glycoprotein, multidrug resistance-associated protein, and Ki-67 expression were determined by immunohistochemical staining . RESULTS: The 5-year survival rate for patients with clear cell carcinoma was significantly poorer, compared with serous adenocarcinoma (20.0% versus 31.9%) . Response rate to chemotherapy was 14.6% for clear cell carcinoma and 72.2% for serous adenocarcinoma . The expression of P-glycoprotein and multidrug resistance-associated protein did not differ between responders and nonresponders in both tumor types . The Ki-67 labeling index (LI) in clear cell carcinoma was significantly lower than serous adenocarcinoma (18.4% versus 38.8%) . The LI for responders was significantly higher than that for nonresponders in both tumor types . In clear cell carcinoma, the mean value of LI was 15.3% for nonresponders, but that for responders was 30.2%, which was similar to that for serous adenocarcinoma . When the cutoff value of LI was set at 18.4% (mean value), the 5-year survival rate for high LI (over 18.4%) patients was significantly greater than that for low LI patients (46.3% versus 9.2%) . Multivariable analysis revealed that LI and residual tumor size were the independent prognostic factors . CONCLUSION: Lower proliferation of tumor may be a behavior of clear cell carcinoma of the ovary that contributes to its resistance to chemotherapy. Lancet Infect Dis, 2002 Aug, 2(8), 472 - 8 The immune response to Plasmodium falciparum malaria; Malaguarnera L et al.; Malaria is still a major cause of severe disease which is responsible for millions of deaths, mostly in children under 5 years old, in tropical countries, especially sub-Saharan Africa . Complications of severe anaemia and cerebral malaria are thought to be the major cause of morbidity and mortality but recent evidence suggests that the host's immunological response could also contribute to the pathophysiology of the disease in human beings . Intensive studies of the immune response to malaria parasites in human beings have provided a wealth of information about the cells and cytokines implicated in the pathophysiology of survival and fatal outcome in severe infections . This review focuses on the pivotal role of macrophages and other important cellular effectors, molecules, and cytokines involved in the activation of the immune response at the different stages of human falciparum malaria . Our understanding of the putative mechanisms by which cytokines may mediate beneficial and harmful effects, through activation of phagocytic cells, could help to develop new treatment strategies, regardless of the emergence of parasite multidrug resistance. Medicina (B Aires), 2002, 62(3), 221 - 5 {Infectiousness and virulence of multidrug-resistant and drug susceptible tuberculosis in adult contacts}; Palmero D et al.; Patients carrying multidrug-resistant (MDR) strains of Mycobacterium tuberculosis have been considered traditionally as presenting a diminished epidemiological risk according to animal experimentation results . The experience obtained from the MDRTB/AIDS related epidemics showed MDRTB transmission to immunocompetent health care workers and adults close contacts . In this retrospective study, the infectiousness (measured as the frequency of intradermal test with PPD 2TU over 10 mm) and virulence (cases bacteriologically confirmed) among close contacts of patients with MDR and susceptible TB were evaluated . A total of 97 contacts of 37 MDRTB patients vs . 356 contacts of 100 patients with susceptible TB were studied . No statistical differences were found in PPD 2 UT positivity and TB cases between both contact groups, nor in relation to HIV seropositivity of index cases . According to these observations, MDR strains of M . tuberculosis present similar infectiousness and virulence compared with susceptible strains. J Clin Oncol, 2002 Aug 1, 20(15), 3282 - 92 Expression of multidrug resistance genes MVP, MDR1, and MRP1 determined sequentially before, during, and after hyperthermic isolated limb perfusion of soft tissue sarcoma and melanoma patients; Stein U et al.; PURPOSE: Isolated, hyperthermic limb perfusion (ILP) with recombinant human tumor necrosis factor alpha and melphalan is a highly effective treatment for advanced soft tissue sarcoma (STS) and locoregional metastatic malignant melanoma . Multidrug resistance (MDR)-associated genes are known to be inducible by heat and drugs; expression levels of the major vault protein (MVP), MDR1, and MDR-associated protein 1 (MRP1) were determined sequentially before, during, and after ILP of patients . PATIENTS AND METHODS: Twenty-one STS or malignant melanoma patients were treated by ILP . Tumor tissue temperatures were recorded continuously and ranged from 33.4 degrees C initially to peak values of 40.4 degrees C during ILP . Serial true-cut biopsy specimens from tumor tissues were routinely microdissected . Expression analyses for MDR genes were performed by real-time reverse transcriptase polymerase chain reaction and immunohistochemistry . RESULTS: In 83% of the patients, MVP expression was induced during hyperthermic ILP . MVP-mRNA inductions often paralleled the increase in temperature during ILP . Increased MVP protein expressions either were observed simultaneously with the MVP-mRNA induction or were delayed until after the induction at the transcriptional level . Inductions of MDR1 and MRP1 were observed in only 13% and 27% of the specimens analyzed . Temperatures and drugs applied preferentially led to an induction of MVP and were not sufficient to induce MDR1 and MRP1 in the majority of tumors . CONCLUSION: This study is the first to analyze the expression of MDR-associated genes sequentially during ILP of patients and demonstrates that treatment might lead to increased levels of MVP, whereas enhanced levels of MDR1 and MRP1 remain rare events. Blood, 2002 Aug 15, 100(4), 1224 - 32 Phase 3 study of the multidrug resistance modulator PSC-833 in previously untreated patients 60 years of age and older with acute myeloid leukemia: Cancer and Leukemia Group B Study 9720; Baer MR et al.; The Cancer and Leukemia Group B conducted a phase 3 trial of the P-glycoprotein modulator PSC-833 in untreated acute myeloid leukemia patients aged 60 years and older . Patients were randomized to 1 of 2 regimens, with doses determined in a prior phase 1 study, consisting of cytarabine 100 mg/m(2)/d by 7-day infusion, with daunorubicin 60 mg/m(2) and etoposide 100 mg/m(2) daily for 3 days (ADE), or daunorubicin 40 mg/m(2) and etoposide 60 mg/m(2) for 3 days with PSC-833, 2.8 mg/kg over 2 hours, and then 10 mg/kg/d by 3-day infusion (ADEP) . The ADEP arm was closed after randomization of 120 patients (61 to ADE and 59 to ADEP) because of excessive early mortality . Rates of complete remission, nonresponse, and death were 46%, 34%, and 20% for ADE, versus 39%, 17%, and 44% for ADEP (P =.008) . Nevertheless, disease-free survival (median 7 vs 8 months; P =.38) and overall survival (approximately 33% alive at 1 year) did not differ and were similar to historical results . Although the number of patients was limited, ADE patients whose pretreatment cells exhibited PSC-833-modulated dye efflux in vitro (n = 22) had worse outcomes than those without efflux (n = 11) (complete remission, nonresponse, and death rates of 41%, 41%, and 18%, compared with 91%, 9%, and 0%; P =.03), but with ADEP outcomes were nearly identical . Moreover, for patients with PSC-833-modulated efflux, median disease-free survival was 5 months with ADE and 14 months with ADEP (P =.07) . Further modulation trials in older patients must await the design of less-toxic regimens. Biochemistry, 2002 Aug 6, 41(31), 10123 - 32 Evidence for the role of glycosylation in accessibility of the extracellular domains of human MRP1 (ABCC1); Muller M et al.; To enable cell surface localization of the human multidrug resistance protein (MRP1, ABCC1) and to assess the role of the extracellular domains of this transporter, the FLAG epitope tag was introduced into different extracellular loops of the three membrane-spanning domains (MSDs) of the transporter . We constructed and expressed various partially and fully glycosylation-deficient, FLAG-tagged MRP1 proteins in a Vaccinia virus-based transient expression system, and the cell surface expression level of MRP1 on intact cells was followed by flow cytometry, using the FLAG tag specific monoclonal antibody M2 . We also expressed the wild-type MRP1 protein and some of the FLAG-tagged mutants in stably transfected HEK293 cells, and followed the cell surface expression and the transport function of MRP1 both by monitoring the efflux of fluorescent substrate and by their ability to confer resistance to HEK293 transfectants to anticancer agents such as daunorubicin and etoposide . When we inserted the FLAG epitope in extracellular loops of the MSD1 or MSD3, the tag was accessible upon removal of N-glycosylation sites (N --> Q at positions 17, 23, and 1006, respectively), whereas the FLAG epitope placed in the MSD2 was not accessible even after removal of all three N-glycosylation sites, indicating that MSD2 region is deeply buried in the plasma membrane . However, all FLAG tagged MRP1 mutants were expressed at the cell surface to the same extent as the wild-type protein and also exhibited normal transport function . Our results demonstrate that the accessibility of the external FLAG epitope is strongly dependent on the position of the tag and the glycosylation state of the different FLAG-tagged MRP1s, and the conformation of extracellular loops in MSD1 and MDS3 does not appear to contribute to the functional status of MRP1. Proc Natl Acad Sci U S A, 2002 Aug 6, 99(16), 10347 - 52 Epub 2002 Jul 26. The multidrug transporter, P-glycoprotein, actively mediates cholesterol redistribution in the cell membrane; Garrigues A et al.; P-glycoprotein (P-gp) is a plasma membrane ATP-binding cassette transporter, responsible for multidrug resistance in tumor cells . P-gp catalyzes the ATP hydrolysis-dependent efflux of numerous amphiphilic compounds of unrelated chemical structures . In the absence of any identified substrate, P-gp exhibits an apparently futile, basal ATPase activity . By using native membrane vesicles containing high amounts of P-gp, we show here that (i) this basal ATPase activity is tightly dependent on the presence of cholesterol in the membrane; (ii) the stimulation of P-gp ATPase activity by drugs transported by P-gp is higher in the absence than in the presence of cholesterol and, conversely, the stimulation of P-gp ATPase activity by cholesterol is higher in the absence than in the presence of known P-gp substrates; (iii) P-gp mediates the ATP-dependent relocation of cholesterol from the cytosolic leaflet to the exoplasmic leaflet of the plasma membrane; and (iv) the decrease of the cholesterol dependence of P-gp ATPase activity induced by known P-gp substrates is correlated with the inhibition of the ATP-dependent cholesterol redistribution within the membrane . These data are highly evocative of a coupling between the basal ATPase activity of P-gp and its intramembrane cholesterol-redistribution function, and they are fully consistent with the possibility that P-gp may actively translocate cholesterol in the membrane . Finally, this P-gp-mediated cholesterol redistribution in the cell membrane makes it likely that P-gp contributes in stabilizing the cholesterol-rich microdomains, rafts and caveolae, and that it is involved in the regulation of cholesterol trafficking in cells. Gynecol Oncol, 2002 Aug, 86(2), 171 - 6 Multidrug resistance gene-1 is a useful predictor of Paclitaxel-based chemotherapy for patients with ovarian cancer; Kamazawa S et al.; OBJECTIVE: The objective of this study was to determine the relationship between multidrug resistance and sensitivity to paclitaxel (PTX) in ovarian cancer . METHODS: We used human ovarian adenocarcinoma cell lines, KF, a PTX-resistant cell line (KFTx), SK-OV-3, and KOC7c . Additionally, 27 patients with ovarian cancer who had residual disease were examined . All patients underwent postoperative chemotherapy consisting of 175 mg/m(2) PTX and area under curve (AUC) 5 carboplatin . The sensitivity of the cells to PTX or cisplatin (CDDP) was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay . mRNA expression of multidrug resistance gene-1 (MDR-1) and multidrug resistance-associated protein-1 (MRP-1) and MRP-2 was determined by reverse transcription-polymerase chain reaction . beta-Tubulin polymerization and Bcl-2 phosphorylation were examined by Western blot analysis . RESULTS: Compared with KF, the IC(50) to PTX was 5.5-fold higher for KFTx, 0.3-fold for SK-OV-3, and 52.1-fold for KOC7c . The IC(50) to CDDP was 0.7-, 4.2-, and 5.8-fold, respectively . Expression of the MDR-1 gene was clearly observed in KFTx and KOC7c . Expression of MRP-1 was observed in SK-OV-3 and KOC7c . Expression of MRP-2 was detected only in KOC7c . CDDP enhanced beta-tubulin polymerization induced by PTX in CDDP-sensitive cells . Bcl-2 phosphorylation appeared after exposure to IC(50) PTX in all cells . Twenty-one patients responded to chemotherapy and six did not . Expression of the MDR-1 gene for nonresponders was significantly higher than that for responders (260.0 +/- 191.6 vs 9.3 +/- 21.8) . With the cutoff value of MDR-1 expression at 100, the predictive value for chemoresponse was 96% . Expression of the MRP-1 and MRP-2 genes did not differ between nonresponders and responders . CONCLUSION: MDR-1 gene expression may be a useful predictor for PTX-based chemotherapy. Cancer Lett, 2002 Nov 8, 185(1), 103 - 9 The gain of function of the p53 mutant Asp281Gly is dependent on its ability to form tetramers; Atema A et al.; The influence of tetramerisation on the properties of the p53 mutants is poorly understood . We describe here the influence of the tetramerisation on the properties of the oncogenic mutant Asp281Gly . We show that despite being both nuclear the tetrameric Asp281Gly and the monomeric Asp281GlyLeu344Pro proteins have different properties: only Asp281Gly stimulates the transcription of the multidrug resistance-1 gene promoter and induces cisplatin resistance in Saos-2 cells . Moreover, we identify a 130-kDa protein that specifically interacts with Asp281Gly but not with Asp281GlyLeu344Pro . This suggests that tetramerisation is important for the properties of the p53 mutants and that these properties might be mediated via protein-protein interactions. Cancer Lett, 2002 Nov 8, 185(1), 79 - 85 Basal expression of the multidrug resistance gene 1 (MDR-1) is associated with the TT genotype at the polymorphic site C3435T in mammary and ovarian carcinoma cell lines; Sauer G et al.; Resistance to established drugs for cancer therapy is in many cases associated with overexpression of the multidrug resistance gene 1 (MDR-1) . Regulation of basal expression of MDR-1 and mechanisms of induction as a result of exposure to cytotoxic substances are still not completely understood . Recent reports have suggested an association of the C3435T polymorphism in exon 26 of the MDR-1 gene with MDR-1 expression in duodenal mucosa cells of healthy individuals . We analyzed the C3435T and G2677T genotypes of 38 mammary and ovarian carcinoma cell lines and measured basal MDR-1 expression by real-time reverse transcriptase-polymerase chain reaction . Cell lines were classified as non-expressing or showing weak basal expression that was found to be significantly associated (six/seven versus 13/31 expressing cell lines; P=0.0448, Fisher's exact test) with the TT genotype at position 3435 of the MDR-1 gene. Eur J Cancer, 2002 Aug, 38(12), 1661 - 70 Structure-activity relationship of indomethacin analogues for MRP-1, COX-1 and COX-2 inhibition . identification of novel chemotherapeutic drug resistance modulators; Touhey S et al.; We report the screening of analogues of indomethacin to investigate the structure-activity relationship (SAR) of indomethacin-mediated multidrug resistance associated protein-1 (MRP-1) inhibition . By examining the activities of compounds with minor variations of the parent structure, we were able to separate MRP-1, glutathione-S-transferase (GST), cyclooxygenase (COX)-1 and COX-2 inhibitory activities . Combination cytotoxicity assays were utilised to identify agents which possess synergistic potential in MRP-1-expressing cell lines . MRP-1 Inside Out Vesicles (IOVs) were utilised to demonstrate the ability of the indomethacin analogues to inhibit the pump directly . Most of the indomethacin analogues active as MRP-1 inhibitors were poor GST inhibitors when compared with the GST-inhibitory activity of indomethacin . Two of the MRP-1 inhibitory analogues were found to have no COX-1 inhibitory activity and low COX-2 inhibitory activity, suggesting potentially reduced clinical toxicity . One MRP-1 inhibitory indomethacin analogue was also found to have low COX-1 inhibitory activity, but significant COX-2 inhibitory activity, making this analogue again interesting in terms of low potential toxicity, but with the possibility of direct inhibitory effects on tumour growth. J Biotechnol, 2002 Sep 25, 98(2-3), 215 - 26 The multidrug resistance transporters of the major facilitator superfamily, 6 years after disclosure of Saccharomyces cerevisiae genome sequence; Sa-Correia I et al.; The emergence of multidrug resistance (MDR) plays a crucial role in the failure of treatments of tumors and infectious diseases and in the control of plant pathogens, weeds and food-poisoning and food-spoilage microorganisms . Among the mechanisms underlying the MDR phenomenon in various organisms is the action of transmembrane transport proteins that presumably catalyse the active expulsion of structurally and functionally unrelated cytotoxic compounds out of the cell or their intracellular partitioning . On the basis of the complete genome sequence of Saccharomyces cerevisiae, numerous established and putative multidrug transporters were identified in this non-pathogenic, easy to manipulate eukaryotic model system . In yeast, the putative drug:H(+)-antiporters belong to the major facilitator superfamily; they comprise at least 23 proteins that have largely escaped characterisation by classical approaches . Other MDR determinants are membrane transporters belonging to the ATP binding cassette (ABC) superfamily, that utilize the energy of ATP hydrolysis for activity, and factors for transcriptional regulation of all the MDR transporters . This work reviews the current status of knowledge on the poorly characterized H(+)-antiporters, with 12 and 14 predicted spans, DHA12 and DHA14, drug efflux families . Consideration is given to the inventory and phylogenetic characterization, role as MDR determinants, regulation of gene expression, subcellular localisation and activity as solute transporters . Most of the present knowledge on these putative drug:H(+)-antiporters was driven by disclosure of S . cerevisiae genome sequence, in April 1996, being a paradigm of post-genomic research. Emerg Infect Dis, 2002 Aug, 8(8), 843 - 9 Worldwide occurrence of Beijing/W strains of Mycobacterium tuberculosis: a systematic review; Glynn JR et al.; Strains of the Beijing/W genotype family of Mycobacterium tuberculosis have caused large outbreaks of tuberculosis, sometimes involving multidrug resistance . This genetically highly conserved family of M . tuberculosis strains predominates in some geographic areas . We have conducted a systematic review of the published reports on these strains to determine their worldwide distribution, spread, and association with drug resistance . Sixteen studies reported prevalence of Beijing strains defined by spoligotyping; another 10 used other definitions . Beijing strains were most prevalent in Asia but were found worldwide . Associations with drug resistance varied: in New York, Cuba, Estonia, and Vietnam, Beijing strains were strongly associated with drug resistance, but elsewhere the association was weak or absent . Although few reports have measured trends in prevalence, the ubiquity of the Beijing strains and their frequent association with outbreaks and drug resistance underline their importance. J Nat Prod, 2002 Jul, 65(7), 1061 - 4 A new cytotoxic epothilone from modified polyketide synthases heterologously expressed in Myxococcus xanthus; Arslanian RL et al.; A new epothilone, 10,11-didehydroepothilone D (5), was isolated from a strain of the heterologous host Myxococcus xanthus genetically engineered to produce epothilone D (4) . The structure of 5 was determined from NMR and MS data . The epothilone polyketide synthase was further modified in a recombinant M . xanthus strain to produce 5 as the major epothilone-related metabolite . The cytotoxicity of 5 against a panel of tumor cell lines, including several with multidrug resistance, and its effect on tubulin polymerization were comparable to epothilone D (4). Oncogene, 2002 Aug 1, 21(33), 5160 - 74 Proteinase-3, a serine protease which mediates doxorubicin-induced apoptosis in the HL-60 leukemia cell line, is downregulated in its doxorubicin-resistant variant; Wu CH et al.; We report here that expression of proteinase 3 (PR3), a serine protease, is down-regulated in the HL60/ADR multidrug resistant variant of the human myelogenous leukemia cell line HL-60, and that down-regulation of PR3 is associated with doxorubicin (DOX) resistance in these cells . To determine whether PR3 is involved in DOX-induced apoptosis in HL-60 cells, and whether its loss causes resistance to DOX, we inhibited PR3 expression by an anti-sense PR3 oligodeoxynucleotide and showed that inhibition of PR3 expression results in a significant reduction in DOX-induced DNA fragmentation and increased resistance to DOX-induced apoptosis . Our results revealed that PR3-mediated DOX-induced apoptosis in HL-60 cells is independent of the loss of mitochondrial membrane potential (deltapsi(m)) and activation of the caspase-8 and -9 pathways . Moreover, while PR3 is involved in the cleavage of caspase-3, PR3-mediated DOX-induced DNA fragmentation and apoptosis were not prevented by a specific inhibitor of caspase-3 . These data suggest that activation of caspase-3 alone is not sufficient to trigger PR3-mediated DOX-induced apoptosis . Treatment with an anti-PR3 oligomer significantly decreased reactive oxygen species (ROS) generation in cells treated with low concentrations of DOX, revealing a role for PR3 in enhancing production of DOX-induced ROS . Moreover, DOX-induced apoptosis at 0.001-0.01 microM was only inhibited in HL-60 cells pre-treated with the antioxidant N-acetyl-cysteine in the absence of anti-PR3, revealing that DOX-induced apoptosis in these cells is PR3- and ROS-dependent . Our results show that PR3 is involved in DOX-induced ROS-dependent apoptosis and that its loss is associated with resistance to DOX in HL-60 cells. Biotechniques . 2002 Jul;33(1):196, 198, 200 passim. Semi-quantitative RT-PCR method to estimate full-length mRNA levels of the multidrug resistance gene; Yang Z et al.; Expression levels of P-glycoprotein (P-gp), the transporter encoded by the human multidrug resistance gene (MDR1), may play an important role in drug disposition . The ability to quantitate full-length MDR1 mRNA levels may be predictive of P-gp expression and function . Therefore, a semi-quantitative RT-PCR assay was developed to assess full-length MDR1 mRNA levels . Levels offull-length 3.8-kb MDR1 mRNA were estimated by comparing PCR amplification of the RNA extract with that of an internal standard, deltaMDR1 . The 2.9-kb deltaMDR1 competitor RNA standard was constructed by deleting 965 bpfrom the interior of MDR1 mRNA . The full-length MDR1 and deltaMDR1 share identical 5' and 3'primer binding sequences, allowing for their simultaneous amplification in the same RT-PCR . With this approach, MDR1 mRNA levels can be sensitively and reliably estimated with a detection limit of 2000 copies . Full-length MDR1 mRNA levels in various human cell lines and lymphocytes from leukemia patients varied over 100-fold, ranging from 0.3 to 36.5 x 10(5) copies/microg total RNA . The semi-quantitative full-length RT-PCR assay may be useful in estimating MDR1 mRNA levels to assess P-gp expression, which may be important in studying the role of P-gp in drug disposition and cancer chemotherapy efficacy. Infect Control Hosp Epidemiol, 2002 Jul, 23(7), 377 - 81 An outbreak of mediastinitis among heart transplant recipients apparently related to a change in the united network for organ sharing guidelines; Samuel R et al.; OBJECTIVE: To describe an outbreak of mediastinitis in heart transplant recipients . DESIGN: Retrospective and contemporaneous cohort SETTING: Urban tertiary-care university hospital with a large cardiac transplantation program . PATIENTS: Heart transplant recipients . INTERVENTIONS: Modifications of donor harvest technique; procedures aimed at decreasing skin and mucosal bacterial colonization; strict aseptic technique in the intensive care unit; and aggressive policing of established infection control practices . RESULTS: In April 1999, mediastinitis rates among heart transplant recipients increased abruptly from a baseline of 6 cases per 100 procedures to sequential quarterly rates of 22, 31, and 50 cases per 100 procedures, whereas infection rates in other cardiac operations were unchanged . Bacteria causing these infections were multidrug-resistant "nosocomial" organisms . The epidemic occurred 2 months after a change in the United Network for Organ Sharing organ allocation algorithm . This change resulted in an increase in the duration of preoperative hospitalization from a median of 52 to 79 days (P = .008) and may have promoted prolonged hospitalization of patients with high illness severity . Aggressive multidisciplinary interventions were temporally associated with a return to preoperative mediastinitis rates without changing length of hospitalization prior to transplantation . CONCLUSIONS: Changes in organ allocation for transplant that prolong waiting time in the hospital and alter illness acuity may lead to increased rates of postoperative infection . Measures to limit bacterial colonization may be a helpful countervailing strategy. Oncology, 2002, 62(4), 349 - 53 Mechanisms of cisplatin resistance in clear cell carcinoma of the ovary; Itamochi H et al.; Resistance of clear cell carcinoma (CCC) of the ovary to platinum-based chemotherapy is associated with a poor prognosis . However, the mechanism underlying the resistance of CCC to platinum has not yet been understood . We conducted the present study to clarify the mechanism of cisplatin (CDDP) resistance in CCC cells . Eleven CCC and 5 serous adenocarcinoma (SAC) cell lines were used in this study . The IC(50) to CDDP ranged from 1.3 to 18.0 microM for CCC cells and from 2.2 to 13.0 microM for SAC cells . There was no correlation between multidrug resistance-associated protein expression and the sensitivity to CDDP in CCC cells . In contrast, the doubling time for CCC cells was significantly longer than that for SAC cells (61.4 vs . 29.8 h) . A significant reverse correlation between the S-phase fraction and the response to CDDP was observed (r = 0.647, p < 0.05) . The present study suggests that the resistance of CCC to CDDP may be caused by low cell proliferation . Oncology, 2002, 62(4), 305 - 12 Prognostic value of multidrug resistance 1, glutathione-S-transferase-pi and p53 in advanced nasopharyngeal carcinoma treated with systemic chemotherapy; Hsu CH et al.; OBJECTIVE: Nasopharyngeal carcinoma (NPC) is one of the dominant cancers in South China and Taiwan . Although NPC is highly chemosensitive, the use of chemotherapy for treating patients with recurrent or metastatic NPC has not been very successful . The emergence of drug resistance may be one of the major reasons . However, the mechanisms of drug resistance of NPC have never been addressed before . In this study, we sought to clarify the role of classical drug resistance markers in predicting the chemosensitivity and the prognosis of patients with advanced NPC . METHODS: In a cohort of 202 consecutive patients diagnosed at the Department of Pathology of the National Taiwan University Hospital, 44 patients with adequately preserved pretreatment tumor tissues and complete clinical information regarding the details of chemotherapy and tumor response were identified . The expression of multidrug resistance (MDR1), glutathione-S-transferase-pi (GSTpi), and p53 were determined by immunohistochemistry . Tumor response to chemotherapy and survival of the patients were the endpoints of this analysis . RESULTS: Thirty-four patients received cisplatin-based regimens, and 28 of them were enrolled in a prospective trial using a doxorubicin-containing regimen . The overall response rate was 70% . Expression of MDR1 was seen in only 5 cases (11%) and was associated with a significantly worse overall survival, yet did not appear to predict chemoresistance to the doxorubicin-containing regimen . Overexpression of p53 was seen in 22 patients, and surprisingly, was correlated with chemoresponse and a trend towards better survival . GSTpi expression was demonstrated in 13 cases (30%) and was not correlated with chemoresistance to cisplatin-containing regimens and overall survival . CONCLUSION: In this relatively small cohort, positive MDR1 immunostaining predicted a poor overall survival for recurrent or metastatic NPC patients receiving chemotherapy . Overexpression of p53 by immunohistochemical staining, however, was associated with a better response rate to systemic chemotherapy and a trend towards better survival . J Biol Chem, 2002 Oct 11, 277(41), 38915 - 20 Epub 2002 Jul 22. Regulation of MDR-1 (P-glycoprotein) by cyclooxygenase-2; Patel VA et al.; Cyclooxygenase-2 (Cox-2), an inducible form of the enzyme that catalyzes the first step in the synthesis of prostanoids, has been shown to be overexpressed in a wide range of tumors and possesses proangiogenic and antiapoptotic properties . To understand the molecular mechanism of Cox-2 action we used adenovirus-mediated transfer of rat Cox-2 cDNA into renal rat mesangial cells and determined the differential gene expression using cDNA microarrays . One of the several genes that were highly up-regulated by over expressed Cox-2 was MDR1 . MDR1 or P-glycoprotein (P-gp), the product of the MDR1 gene, is implicated as the primary cause of multidrug resistance (MDR) in tumors where it acts as an efflux pump for chemotherapeutic agents . It is also expressed in normal tissues of the liver and kidney where it functions to actively transport lipophilic xenobiotics . Reverse transcriptase-PCR analysis confirmed the results of the microarray, showing increased mRNA levels for MDR1 in Cox-2 overexpressing cells . This increase in mRNA translated to an increase in MDR1 protein expression, which was dose-dependent on Cox-2 expression . Furthermore, using rhodamine 123 efflux assay we observed a significant increase in P-gp activity in Cox-2 overexpressing renal mesangial cells . The specific Cox-2 inhibitor NS398 was able to block the Cox-2-mediated increase in MDR1 expression and activity, suggesting that Cox-2 products may be implicated in this response . These results prove the existence of a causal link between Cox-2 and P-gp activity, which would have implications for kidney function and multidrug resistance in tumors where Cox-2 is overexpressed. J Biol Chem, 2002 Sep 20, 277(38), 35225 - 31 Epub 2002 Jul 22. Photolabeling of human and murine multidrug resistance protein 1 with the high affinity inhibitor {125I}LY475776 and azidophenacyl-{35S}glutathione; Qian YM et al.; Multidrug resistance protein 1 (MRP1/ABCC1) is an ATP-dependent transporter of structurally diverse organic anion conjugates . The protein also actively transports a number of non-conjugated chemotherapeutic drugs and certain anionic conjugates by a presently poorly understood GSH-dependent mechanism . LY475776is a newly developed (125)I-labeled azido tricyclic isoxazole that binds toMRP1 with high affinity and specificity in a GSH-dependent manner . The compound has also been shown to photolabel a site in the COOH-proximal region of MRP1's third membrane spanning domain (MSD) . It is presently not known where GSH interacts with the protein . Here, we demonstrate that the photactivateable GSH derivative azidophenacyl-GSH can substitute functionally for GSH in supporting the photolabeling of MRP1 by LY475776 and the transport of another GSH-dependent substrate, estrone 3-sulfate . In contrast to LY475776, azidophenacyl-{(35)S} photolabels both halves of the protein . Photolabeling of the COOH-proximal site can be markedly stimulated by low concentrations of estrone 3-sulfate, suggestive of cooperativity between the binding of these two compounds . We show that photolabeling of the COOH-proximal site by LY475776 and the labeling of both NH(2)- and COOH- proximal sites by azidophenacyl-GSH requires the cytoplasmic linker (CL3) region connecting the first and second MSDs of the protein, but not the first MSD itself . Although required for binding, CL3 is not photolabeled by azidophenacyl-GSH . Finally, we identify non-conserved amino acids in the third MSD that contribute to the high affinity with which LY475776 binds to MRP1. Curr Opin Investig Drugs, 2002 Jun, 3(6), 848 - 52 AZD-2563 AstraZeneca; Johnson AP; AstraZeneca is developing AZD-2563, an oxazolidinone with a novel mechanism of action, for the potential treatment of gram-positive bacterial infections, including those caused by multidrug-resistant strains {349551}, {399542} . As of December 2001, AZD-2563 had completed an escalating-dose phase I trial in the UK and was being developed in the US {433897}; at this time, AstraZeneca did not expect launch until after 2004 {431673} . In October 2001, Morgan Stanley estimated launch in 2004 with sales of US $20 million in that year, rising to US $46 million in following years {429700}. Acta Biochim Pol, 2002, 49(1), 87 - 92 The ability to overcome multidrug resistance of tumor cell lines by novel acridine cytostatics with condensed heterocyclic rings; Bontemps-Gracz MM et al.; Two recently synthesized groups of acridine cytostatics containing fused heterocyclic ring(s): pyrazoloacridines (PAC) and pyrazolopyrimidoacridines (PPAC) were tested in regard to their in vitro cytotoxic activity towards a panel of sensitive and resistant human tumor cell lines . The obtained results corroborate our earlier hypothesis on the essential role of heterocyclic ring fused to the acridine moiety in the ability of acridine cytostatics to overcome multidrug resistance of tumor cells . The presence, location and kind of substituents considerably influenced both the cytotoxic activity of the derivatives and their ability to overcome multidrug resistance . The same factors also affected the cytostatics ability to differentiate between tumor cell lines with various types of drug exporting pumps. Cancer Biother Radiopharm, 2002 Jun, 17(3), 291 - 302 Modulation of the multidrug resistance of glioma by glutathione levels depletion--interaction with Tc-99M-Sestamibi and Tc-99M-Tetrofosmin; Perek N et al.; We have investigated the effect of glutathione (GSH) depletion on the chemosensitivity of human malignant glioma cell lines: G111, G5 and G152 . All the cell lines showed a multidrug resistant (MDR) phenotype associated with MRP1 expression, high intracellular levels of GSH, and depolarized plasma membranes . Tc-99M-Sestamibi (MIBI) and Tc-99M-Tetrofosmin (Tfos) were used for monitoring the MDR mechanisms . Modulation of GSH content was performed with butoxysulfoximide (BSO) pre-treatment alone or in combination with GSH ethyl ester . MIBI and Tfos accumulation in the cells was inversely correlated to the GSH content, a higher accumulation was found after BSO pre-treatment and addition of GSH ethyl ester reversed this process . BSO could therefore play a role as a chemosensitizing drug and thus help to overcome MDR . However, higher accumulation of MIBI and Tfos was observed even in the sensitive cells suggesting another effect of BSO on the cell physiological characteristics . No sign of apoptosis has been found indicating a possible direct effect on the plasma membrane fluidity and permeability . MIBI and Tfos don't follow the expected behavior of a MDR probe in the glioma cells and given the particular morpho-physiological characteristics of these types of tumors, Tfos could be rather used as a marker of the tumor growth and proliferation. J Cancer Res Clin Oncol, 2002 Jul, 128(7), 349 - 57 Epub 2002 Jun 26. Multiple mechanisms confer different drug-resistant phenotypes in pancreatic carcinoma cells; Lage H et al.; PURPOSE: Drug-resistant phenotypes of cancer cells may be caused by complex multimodal mechanisms of resistance . In order to gain further insighte into these mechanisms, a P-glycoprotein-mediated multidrug-resistant phenotype induced by daunorubicin-selection and an alternative drug resistance due to treatment with mitoxantrone were investigated in pancreatic carcinoma-derived cells . METHODS: For assessing cross-resistance against various drugs, cell proliferation assays were performed . Drug accumulation was measured by flow cytometry . Messenger RNA expression was analyzed by Northern blot and RT-PCR, whereas protein expression was determined by Western blot . Catalytic activity of DNA-topoisomerases (Topo) II was determined by the decatenation assay . RESULTS: In mitoxantrone-selected EPP85-181RNOV cells a decreased accumulation of mitoxantrone and daunorubicin was observed in the absence of P-glycoprotein, multidrug resistance protein or breast cancer resistance protein over-expression . An approximately twofold decrease of DNA topoisomerase II catalytic activity could be observed in both drug-resistance-exhibiting cell lines . The reduction of Topo II catalytic activity was reflected by decreased expression of Topo IIalpha and IIbeta mRNAs and proteins . CONCLUSIONS: The decreased drug accumulation in EPP85-181RNOV cells indicates that alternative transport events are occurring . The decreased catalytic activity and expression of Topo II indicate that modulation of Topo II catalytic activity contributes to both drug-resistant phenotypes in pancreatic carcinoma cells. Drug Resist Updat, 2002 Apr, 5(2), 61 - 4 Multidrug resistance: can different keys open the same lock? Kaur P. Multidrug resistance (MDR), resulting from the energy-dependent efflux of structurally unrelated lipophilic compounds, is a major clinical problem . An important question concerns the number and nature of the drug-binding sites in the MDR proteins . A recent report on the high-resolution structure of QacR, a protein that regulates expression of an MDR protein, shows the presence of several independent, but linked binding sites within a single multifaceted drug-binding pocket . This report, for the first time, provides a basis for the specific binding of multiple drugs to a single protein . The significance of these findings and their relevance to the field of drug resistance is discussed . Eur J Biochem, 2002 Jul, 269(14), 3470 - 8 S-decyl-glutathione nonspecifically stimulates the ATPase activity of the nucleotide-binding domains of the human multidrug resistance-associated protein, MRP1 (ABCC1); Cool RH et al.; The human multidrug resistance-associated protein(MRP1) is an ATP-dependent efflux pump that transports anionic conjugates, and hydrophobic compounds in a glutathione dependent manner . Similar to the other, well-characterized multidrug transporter P-gp, MRP1 comprises two nucleotide-binding domains (NBDs) in addition to transmembrane domains . However, whereas the NBDs of P-gp have been shown to be functionally equivalent, those of MRP1 differ significantly . The isolated NBDs of MRP1 have been characterized in Escherichia coli as fusions with either the glutathione-S-transferase (GST) or the maltose-binding domain (MBP) . The nonfused NBD1 was obtained by cleavage of the fusion protein with thrombin . The GST-fused forms of NBD1 and NBD2 hydrolyzed ATP with an apparent K(m) of 340 microm and a V(max) of 6.0 nmol P(I) x mg-1 x min-1, and a K(m) of 910 microm ATP and a V(max) of 7.5 nmol P(I) x mg-1 x min-1, respectively . Remarkably, S-decyl-glutathione, a conjugate specifically transported by MRP1 and MRP2, was able to stimulate the ATPase activities of the isolated NBDs more than 2-fold in a concentration-dependent manner . However,the stimulation of the ATPase activity was found to coincide with the formation of micelles by S-decyl-glutathione . Equivalent stimulation of ATPase activity could be obtained by surfactants with similar critical micelle concentrations. J R Soc Health, 2002 Jun, 122(2), 78 - 81 The global emergency of tuberculosis: what is the cause? Grange JM, Zumla A. The treatment of tuberculosis is cheap and highly effective, yet worldwide the disease remains a serious cause of illness and death; so serious as to have been declared a 'global emergency' in 1993 . It is principally a disease of poverty, with 95% of cases and 98% of deaths occurring in developing countries . The incidence of tuberculosis is increasing worldwide, partly due to poverty and inequity and partly to the HIV/AIDS pandemic, which greatly increases the risk of infection proceeding to overt disease . Around 30% of AIDS-related deaths are due to tuberculosis . The emergence of multidrug resistant tuberculosis (MDRTB) is an increasing threat to tuberculosis control . Although treatable with alternative drugs, the cost is enormous and, accordingly, not undertaken in many poor nations . While the overall global incidence of MDRTB is low, it occurs in certain 'hotspots' including Russian prisons . Due to adverse socio-economic factors, London has not escaped the general rise in incidence and, without the introduction of active control strategies, there could be a serious epidemic as occurred in New York City ten years ago which required an enormous financial outlay for its control . In view of the global emergency of tuberculosis, the WHO 'Stop TB' campaign has called for the universal adoption of its directly observed therapy, short course (DOTS) strategy . Also, though the Massive Effort Against Diseases of Poverty, several international agencies are urging the establishment of effective control programmes worldwide . London should take the lead and set an example. J Infect Dis, 2002 Aug 1, 186(3), 332 - 40 Epub 2002 Jul 08. Differential effects of p-glycoprotein and multidrug resistance protein-1 on productive human immunodeficiency virus infection; Speck RR et al.; P-glycoprotein (P-gp) and multidrug-resistance protein-1 (MRP-1) are adenosine triphosphate-binding cassette proteins that may decrease intracellular concentrations of anti-human immunodeficiency virus (HIV) drugs . After HIV-1(IIIB) infection, HIV-1 protein and infectious virus production were decreased by at least 70-fold in CEM cells overexpressing P-gp but were increased by at least 50-fold in CEM cells overexpressing MRP-1, compared with control CEM cells . After transfection with the HIV-1(IIIB) genome, cells overexpressing P-gp and MRP-1 expressed similar amounts of HIV protein . Selective inhibitors of MRP-1 and P-gp partially reversed the effect of these transporters in a concentration-dependent manner . P-gp preferentially associated with glycolipid-enriched membrane (GEM) domains, which may be an important site for cellular binding and egress of HIV . In contrast, MRP-1 was not preferentially found in GEM domains . These results suggest that the inhibition of HIV productive infection by P-gp and augmentation by MRP-1 occur predominantly at a preintegration step but act through different mechanisms. J Biol Chem, 2002 Oct 4, 277(40), 37855 - 62 Epub 2002 Jul 19. A novel membrane protein, Ros3p, is required for phospholipid translocation across the plasma membrane in Saccharomyces cerevisiae; Kato U et al.; Ro09-0198 (Ro) is a tetracyclic peptide antibiotic that binds specifically to phosphatidylethanolamine (PE) and causes cytolysis . To investigate the molecular basis of transbilayer movement of PE in biological membranes, we have isolated a series of budding yeast mutants that are hypersensitive to the Ro peptide . One of the most sensitive mutants, designated ros3 (Ro-sensitive 3), showed no significant change in the cellular phospholipid composition or in the sensitivity to amphotericin B, a sterol-binding polyene macrolide antibiotic . These results suggest that the mutation of ros3 affects the PE organization on the plasma membrane, rather than PE synthesis or overall organization of the membrane structures . By functional complementation screening, we identified the gene ROS3 affected in the mutant, and we showed that the hypersensitive phenotype was caused by the defective expression of the ROS3 gene product, Ros3p, an evolutionarily conserved protein with two putative transmembrane domains . Disruption of the ROS3 gene resulted in a marked decrease in the internalization of fluorescence-labeled analogs of PE and phosphatidylcholine, whereas the uptake of fluorescence-labeled phosphatidylserine and endocytic markers was not affected . Neither expression levels nor activities of ATP-binding cassette transporters of the ros3Delta cells differed from those of wild type cells, suggesting that Ros3p is not related to the multidrug resistance activities . Immunochemical analyses of the structure and subcellular localization showed that Ros3p was a glycosylated membrane protein localized in both the plasma membrane and the endoplasmic reticulum, and that a part of Ros3p was associated with the detergent-insoluble glycolipid-enriched complexes . These results indicate that Ros3p is a membrane glycoprotein that plays an important role in the phospholipid translocation across the plasma membrane. Biochem J, 2002 Nov 15, 368(Pt 1), 325 - 32 Impaired 2',3'-dideoxy-3'-thiacytidine accumulation in T-lymphoblastoid cells as a mechanism of acquired resistance independent of multidrug resistant protein 4 with a possible role for ATP-binding cassette C11; Turriziani O et al.; Cellular factors may contribute to the decreased efficacy of chemotherapy in HIV infection . Indeed, prolonged treatment with nucleoside analogues, such as azidothymidine (AZT), 2',3'-deoxycytidine or 9-(2-phosphonylmethoxyethyl)adenine, induces cellular resistance . We have developed a human T lymphoblastoid cell line (CEM 3TC) that is selectively resistant to the antiproliferative effect of 2',3'-dideoxy-3'-thiacytidine (3TC) because the CEM 3TC cells were equally sensitive to AZT, as well as the antimitotic agent, vinblastine . The anti-retroviral activity of 3TC against HIV-1 was also severely impaired in the CEM 3TC cells . Despite similar deoxycytidine kinase activity and unchanged uptake of nucleosides such as AZT and 2'-deoxycytidine, CEM 3TC had profoundly impaired 3TC accumulation . Further studies indicated that CEM 3TC retained much less 3TC . However, despite a small overexpression of multidrug resistance protein (MRP) 4, additional studies with cells specifically engineered to overexpress MRP4 demonstrated there was no impact on either 3TC accumulation or efflux . Finally, an increased expression of the MRP5 homologue, ATP-binding cassette C11 (ABCC11) was observed in the CEM 3TC cells . We speculate that the decreased 3TC accumulation in the CEM 3TC might be due to the upregulation of ABCC11. Bull World Health Organ, 2002, 80(6), 489 - 95; discussion 495-500 Controlling multidrug-resistant tuberculosis and access to expensive drugs: a rational framework; Pablos-Mendez A et al.; The emergence and spread of multidrug-resistant tuberculosis (MDR-TB), i.e . involving resistance to at least isoniazid and rifampicin, could threaten the control of TB globally . Controversy has emerged about the best way of confronting MDR-TB in settings with very limited resources . In 1999, the World Health Organization (WHO) created a working group on DOTS-Plus, an initiative exploring the programmatic feasibility and cost-effectiveness of treating MDR-TB in low-income and middle-income countries, in order to consider the management of MDR-TB under programme conditions . The challenges of implementation have proved more daunting than those of access to second-line drugs, the prices of which are dropping . Using data from the WHO/International Union Against Tuberculosis and Lung Disease surveillance project, we have grouped countries according to the proportion of TB patients completing treatment successfully and the level of MDR-TB among previously untreated patients . The resulting matrix provides a reasonable framework for deciding whether to use second-line drugs in a national programme . Countries in which the treatment success rate, i.e . the proportion of new patients who complete the scheduled treatment, irrespective of whether bacteriological cure is documented, is below 70% should give the highest priority to introducing or improving DOTS, the five-point TB control strategy recommended by WHO and the International Union Against Tuberculosis and Lung Disease . A poorly functioning programme can create MDR-TB much faster than it can be treated, even if unlimited resources are available . There is no single prescription for controlling MDR-TB but the various tools available should be applied wisely . Firstly, good DOTS and infection control; then appropriate use of second-line drug treatment . The interval between the two depends on the local context and resources . As funds are allocated to treat MDR-TB, human and financial resources should be increased to expand DOTS worldwide. Bull World Health Organ, 2002, 80(6), 471 - 6 The research agenda for improving health policy, systems performance, and service delivery for tuberculosis control: a WHO perspective; Nunn P et al.; The development of WHO's DOTS strategy for the control of tuberculosis (TB) in 1995 led to the expansion, adaptation and improvement of operational research in this area . From being a patchwork of small-scale studies concerned with aspects of service delivery, TB operational research shifted to larger-scale, often multicountry projects that were also concerned with health policy and the needs of health systems . The results are now being put into practice by national TB control programmes . In 1998 an ad hoc committee identified the chief factors inhibiting the expansion of DOTS: lack of political will and commitment, poor financial support for TB control, poor organization and management of health services, inadequate human resources, irregular drug supplies, the HIV epidemic, and the rise of multidrug resistance . An analysis of current operational research on TB is presented on the basis of these constraints, and examples of successful projects are outlined in the article . We discuss the prerequisites for success, the shortcomings of this WHO- supported programme, and future challenges and needs. J Vet Med Sci, 2002 Jun, 64(6), 531 - 3 Immunohistochemical detection of P-glycoprotein (PGP) and multidrug resistance-associated protein (MRP) in canine cutaneous mast cell tumors; Miyoshi N et al.; Fifty-four canine cutaneous mast cell tumors were evaluated immunohistochemically for the expression of P-glycoprotein (PGP) and multidrug-resistance-associated protein (MRP) . All tumors examined were graded according to the histological malignancy . ranging from grade I to III . The expression of PGP was confirmed in 15% (8/54) of whole, 33% (5/15) of grade I, 10% (3/31) of grade II, and 0% (0/8) of grade III tumors . The expression of MRP was found in 18% (10/54) of whole, 26% (4/15) of grade I, 19% (6/31) of grade II, and 0% (0/8) of grade III tumors . The cases positive to at least one of these 2 multidrug markers were 26%, 47%, 23% and 0% of whole and grade I to III tumors, respectively . These results indicate that at least 26% of canine cutaneous mast cell tumors express PGP and/or MRP and that these tumors may be resistant to several anti-cancer drugs. J Pharmacol Exp Ther, 2002 Aug, 302(2), 407 - 15 Regulation of expression of the multidrug resistance-associated protein 2 (MRP2) and its role in drug disposition; Gerk PM et al.; The multidrug resistance protein 2 (MRP2; ABCC2) is an ATP-binding cassette transporter accepting a diverse range of substrates, including glutathione, glucuronide, and sulfate conjugates of many endo- and xenobiotics . MRP2 generally performs excretory or protective roles, and it is expressed on the apical domain of hepatocytes, enterocytes of the proximal small intestine, and proximal renal tubular cells, as well as in the brain and the placenta . MRP2 is regulated at several levels, including membrane retrieval and reinsertion, translation, and transcription . In addition to transport of conjugates, MRP2 transports cancer chemotherapeutics, uricosurics, antibiotics, leukotrienes, glutathione, toxins, and heavy metals . Several mutagenesis studies have described critical residues for substrate binding and various naturally occurring mutations that eliminate MRP2 expression or function . MRP2 is important clinically as it modulates the pharmacokinetics of many drugs, and its expression and activity are also altered by certain drugs and disease states. Mol Pharmacol, 2002 Aug, 62(2), 304 - 12 Influence of ceramide metabolism on P-glycoprotein function in immature acute myeloid leukemia KG1a cells; Plo I et al.; Previous studies have emphasized the role of glucosylceramide (Glu-Cer) synthase in multidrug resistance (MDR) regulation . However, the mechanism by which the inhibition of this enzyme results in increased drug retention and cytotoxicity remains unclear . In this study, we investigated the respective role of ceramide (Cer) accumulation and Glu-Cer derivatives depletion in MDR reversal effect of 1-phenyl-2-decanoylamino-3-morpholino-1-propanolol (PDMP), a Glu-Cer synthase inhibitor . We show here that treatment with PDMP resulted in increased rhodamine 123 (Rh123) retention and potent chemosensitization of P-glycoprotein (P-gp)-expressing cells, including KG1a cells, KG1a/200 cells, K562/138 cells, and K562/mdr-1 cells . Metabolic studies revealed that PDMP induced not only time-dependent Cer accumulation but also reduction of all glycosylated forms of Cer, including Glu-Cer, lactosylceramide (Lac-Cer), monosialo ganglioside (GM3) and disialo ganglioside (GD3) . The influence of these metabolites on P-gp function was investigated by measuring Rh123 retention in PDMP-treated cells . P-gp function was found to be stimulated only by the addition of gangliosides in all resistant cell lines, whereas Glu-Cer, Lac-Cer, and Cer had no effect . Moreover, in KG1a/200 cells, GD3 and, to a lesser extent, GM3 were found to phosphorylate P-gp on serine residues . Altogether, these results suggest that, at least in leukemic cells, gangliosides depletion accounts for PDMP-mediated MDR reversal effect, and that gangliosides are important P-gp regulators perhaps through their capacity to modulate P-gp phosphorylation. Blood, 2002 Aug 1, 100(3), 974 - 81 MDR1 protein expression is an independent predictor of complete remission in newly diagnosed adult acute lymphoblastic leukemia; Tafuri A et al.; Little is known about the prognostic role of multidrug resistance (MDR) in adults with newly diagnosed acute lymphoblastic leukemia (ALL) . In the context of the GIMEMA ALL0496 protocol, we evaluated the impact of MDR1 (protein expression and function) on the achievement of complete remission (CR) and clinical outcome . Flow cytometric analysis of MDR1 expression (D) and function (rhodamine-123 efflux) was obtained in 203 and 158 patients, respectively . MDR1 expression was detected in 44 (21.7%) of 203 patients, and function was found in 23 (14.6%) of 158 (14.6%) patients . Expression of the multidrug resistance-associated protein 1 (MRP1) and lung-resistance protein (LRP) evaluated in 43 samples was found in 13 and 26 patients, respectively . Among the 200 patients evaluable for the clinical correlation study, 125 (79.6%) of 157 without MDR1 expression achieved CR compared with 23 (53.5%) of 43 with MDR1 expression (P =.001) . At univariate analysis, MDR1 expression was significantly associated with CR when considered as a dichotomized (P =.001) or continuous (P =.01) variable . At multivariate analysis, dichotomized evaluation of MDR1 expression independently predicted CR (P =.004) with age (P =.03) and CD34 (P =.03); as a continuous variable, MDR1 expression (P =.03) was the only significant factor other than CD34 (P =.01) . MDR1 function failed to predict achievement of CR or of MRP1 and LRP expression . MDR1 expression did not correlate with CR duration, nor did it predict for survival duration . These results demonstrate that MDR1 expression in de novo adult ALL is an independent predictor of CR achievement. Eur J Pharm Sci, 2002 Aug, 16(3), 201 - 8 Differential interaction of Sophora isoflavonoids with lipid bilayers; Hendrich AB et al.; The mechanisms of some biological effects exerted by flavonoids (e.g . activity against lipid oxidation, multidrug resistance modulation) may involve their interactions with lipid bilayers . Due to variety of substituents attached to the flavonoid nucleus individual isoflavones significantly differ in their properties; in particular they may differently interact with membranes . For this reason we have investigated the interactions of different isoflavones with lipid bilayers . The influence of four plant isoflavones on the phase transitions of dipalmitoylphosphatidylcholine (DPPC) and on liposome aggregation was studied, using microcalorimetry and absorption measurements, respectively . We found that isoflavones substituted with one or two prenyl groups less effectively induce liposome aggregation than more polar ones, possessing no prenyl groups . For aggregation-promoting compounds, rather small differences in the influence on phosphatidylcholine, phosphatidylserine and phosphatidylinositol liposomes were recorded . On the other hand, the alteration of DPPC phase transitions by prenyl-substituted isoflavones was more pronounced than changes induced by non-prenyl ones . On the basis of observed effects we conclude that prenyl-substituted isoflavones penetrate deeper into the lipid bilayer while more polar ones act closer to the membrane surface . Comparing our results with biological tests it seems that interactions with the hydrophobic core of membranes are responsible for the activity of the studied isoflavones. Eur J Pharm Sci, 2002 Aug, 16(3), 159 - 65 Effects of 12 Ca2+ antagonists on multidrug resistance, MDR1-mediated transport and MDR1 mRNA expression; Takara K et al.; The effects of 12 Ca(2+) antagonists on MDR1 were examined by two independent models: the inhibitory effect on MDR1-mediated transport of {(3)H}digoxin using MDR1-overexpressing LLC-GA5-COL150 cell monolayers and the reversal effect on cytotoxicity of vinblastine or paclitaxel using MDR1-overexpressing Hvr100-6 cells . The inhibitory effects on {(3)H}digoxin transport were assessed as the 50% inhibitory concentration during 4 h exposure, and the values were the lowest for nicardipine (4.54 microM), manidipine (4.65 microM) and benidipine (4.96 microM), followed by bepridil (10.6 microM), barnidipine (12.6 microM), efonidipine (13.0 microM), verapamil (13.2 microM) and nilvadipine (18.0 microM) . The reversal effect on cytotoxicity was assessed by the 50% growth inhibitory concentration after 3 days exposure, and the resistance to vinblastine or paclitaxel in Hvr100-6 cells was reversed by manidipine, verapamil, benidipine, barnidipine, and nicardipine, in that order . Bepridil, barnidipine, efonidipine, verapamil and nilvadipine showed similar inhibitory effects on {(3)H}digoxin transport, but barnidipine and verapamil showed a stronger effect in reversal of cytotoxicity . Real-time quantitative RT-PCR assay indicated a decrease in MDR1 mRNA expression by barnidipine and verapamil . It is concluded that Ca(2+) antagonists cannot only be direct inhibitors of MDR1 but that some may at the same time act as inhibitors of expression of MDR1 via down-regulation of MDR1 mRNA. Biochem Biophys Res Commun, 2002 Jul 26, 295(4), 832 - 40 Reversal of P-glycoprotein-mediated multidrug resistance by 5,6,7,3',4'-pentamethoxyflavone (Sinensetin); Choi CH et al.; Multidrug resistance (MDR) cells can be sensitized to anticancer drugs when treated concomitantly with chemosensitizers . In this study, chemosensitizing effects of 5,6,7,3',4'-pentamethoxyflavone (sinensetin) and its analogs were investigated with respect to in vitro efficacy and structure-activity relationship . Sinensetin reversed the resistance of P-glycoprotein (Pgp)-overexpressing AML-2/D100 to vincristine in a concentration-dependent manner . Chemosensitizing effect of sinensetin was 10- and 18-fold higher than those of 5,7,3',4'-tetramethoxyflavone and 3,7-dihydroxy-3',4'-dimethoxyflavone, respectively . Sinensetin cytotoxicity in AML-2/D100 was not changed by the complete inhibition of Pgp, suggesting that it is not a substrate for Pgp . Flow cytometry showed that sinensetin increased drug accumulation in the AML-2/D100 in a concentration-dependent manner . Unlike verapamil and cyclosporin A, the maximum non-cytotoxic concentrations of sinensetin were found to decrease the Pgp levels . Azidopine-binding assay showed that cyclosporin A or verapamil inhibited azidopine binding on Pgp partially but sinensetin did not . Taken together, these results suggest that sinensetin has a chemosensitizing effect in reversing Pgp-mediated MDR by increasing the intracellular accumulation of drugs without competition in a binding site of azidopine . Thus, sinensetin is anticipated as a novel and highly potent second-generation flavonoid chemosensitizer, since sinensetin has significant advantages of having a high therapeutic index, of being a non-transportable inhibitor, and of effecting no induction of Pgp. Aquat Toxicol, 2002 Sep 24, 59(3-4), 237 - 51 Expression of P-glycoprotein in killifish (Fundulus heteroclitus) exposed to environmental xenobiotics; Bard SM et al.; P-glycoproteins (P-gp) are transmembrane efflux flippases that prevent the cellular accumulation of moderately hydrophobic compounds and are responsible for certain multidrug resistance phenotypes in tumor cell lines and human patients . We investigated whether P-gps could be involved in a contaminant resistant phenotype observed in a population of fish exposed over generations to high levels of planar halogenated aromatic hydrocarbons (PHAHs) . Hepatic and intestinal epithelial P-gp expression was examined by immunoblot and immunohistochemistry in killifish (Fundulus heteroclitus) from New Bedford Harbor, MA (NBH), a Superfund site highly contaminated with PHAHs, and from Scorton Creek on Cape Cod, MA (SC), a relatively unpolluted site . The NBH population has developed resistance to the toxicity of PHAHs . Hepatic P-gp levels were more than 40% greater in fish freshly collected from SC than in fish freshly collected from NBH . When killifish from either site were maintained in clean water for up to 78 days to permit depuration of bioaccumulated contaminants, hepatic P-gp levels decreased approximately 50% by day 8 . P-glycoprotein expression was detected in the intestinal epithelium in 55% of freshly collected NBH fish . However, depurated NBH fish and freshly caught and depurated SC fish rarely expressed P-gp in the intestine . In an effort to determine whether environmental chemicals at the two sites might contribute to altered P-gp expression, depurated fish were exposed either to sediment collected from SC or 2,3,7,8-tetrachlorodibenzofuran, a contaminant found at the NBH site and a model aryl hydrocarbon receptor agonist . Neither exposure affected hepatic P-gp levels in killifish . Elevated intestinal P-gp in NBH fish might counter the absorption of P-gp substrates/inducers and thus limit the amount of these compounds reaching the liver, which might account for the lower hepatic P-gp levels in NBH fish compared to SC fish . The differences in hepatic P-gp levels (SC>NBH) and intestinal P-gp (NBH>SC) in freshly collected fish also might reflect environmental exposure to different anthropogenic contaminants or microbial, algal, plant or other natural products via the water column, sediment, or diet at each site. Leuk Res, 2002 Sep, 26(9), 857 - 62 NAIP-deltaEx10-11: a novel splice variant of the apoptosis inhibitor NAIP differently expressed in drug-sensitive and multidrug-resistant HL60 leukemia cells; Notarbartolo M et al.; Alterations of neuronal apoptosis inhibitory protein (NAIP), a member of the inhibitory of apoptosis protein (IAP) family of inhibitors of apoptosis, have been previously associated with different neurodegenerative disorders . This study indicated the existence of a novel NAIP splice variant . This isoform, NAIP-deltaEx10-11, was found in tumor cell lines of different origin and in normal adult brain . Analysis of the putative protein predicted that the NAIP variant lacks part of the third BIR domain as well as the COOH-terminal tail of regular NAIP . This might suggest that it is endowed with a reduced antiapoptotic activity . This view is supported by the fact that NAIP-deltaEx10-11 mRNA and