Biol Pharm Bull, 2001 May, 24(5), 555 - 7 Increase in doxorubicin cytotoxicity by inhibition of P-glycoprotein activity with lomerizine; Shiraki N et al.; Acquired resistance to chemotherapy is a major problem during cancer treatment . One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp) . Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux . This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline . Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox . Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs . Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration . These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp. Biol Pharm Bull, 2001 May, 24(5), 474 - 9 Mechanism of resistance to oxidative stress in doxorubicin resistant cells; Furusawa S et al.; Doxorubicin (DOX) is an anthracycline drug widely used in chemotherapy for cancer patients, but it often gives rise to multidrug resistance in cancer cells . The purpose of this work was to study the effect of hydrogen peroxide in DOX-sensitive mouse P388/S leukemia cells and in the DOX-resistant cell line . Hydrogen peroxide induced a significant increase in dose- and time-response cell death in cultured P388/S cells . The degree of cell death in P388/DOX cells induced by hydrogen peroxide was less than that in P388/S cells treated with hydrogen peroxide . Parent cells exposed to 3 mM of hydrogen peroxide showed a loss of mitochondrial membrane potential correlated with cell death . Hydrogen peroxide at a concentration greater than 0.3 mM increased the intracellular Ca2+ of P388/S cells dose-dependently; however, no change following addition of hydrogen peroxide (0.3-1 mM) was observed in the resistant cells . Hydrogen peroxide (0.1 and 1 mM) treatment also induced the production of intracellular ROS in P388/S cells, while no such increase was produced by this substance in P388/DOX cells . Resistant cells also showed a significant level of glutathione (GSH) compared with the parent cells . In addition, N-acetyl-L-cysteine and reduced GSH antioxidants abolished death of P388/S cells caused by hydrogen peroxide . Therefore, it is believed that the reduced effect of oxidative stress towards the resistant cells may be related to an increase in intracellular GSH level. Brain Res, 2001 May 25, 902(1), 131 - 4 Inhibition of human multidrug resistance P-glycoprotein 1 by analogues of a potent delta-opioid antagonist; Lovekamp T et al.; Analogues Dmt-Tic (2',6'-dimethyl-L-tyrosine-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) pharmacophore, a potent delta-opioid receptor antagonist, inhibited hMDR1 P-GP expressed in a G-185 fibroblast cell line in a manner similar to verapamil . N,N(Me)2-Dmt-Tic-NH-1-adamantane, H-Dmt-Tic-NH-1-adamantane, H-Dmt-Tic-Ala-NH-1-adamantane and N,N(Me)2-Dmt-Tic-NH-tBut were highly effective inhibitors . Weaker inhibition was observed with N,N(Et)2-Dmt-Tic-OH, H-Dmt-Tic-Ala-NH-tert-butyl amide and cyclo(Dmt-Tic) . Results demonstrate that N- and C-terminal hydrophobic/lipophilic analogues of the Dmt-Tic pharmacophore inhibit hMDR1 and point to a potential role as chemosensitizing agents in chemotherapy for cancers containing hMDR1. J Clin Microbiol, 2001 Jun, 39(6), 2213 - 8 Molecular epidemiology study of exogenous reinfection in an area with a low incidence of tuberculosis; Bandera A et al.; In geographical areas with a low incidence of tuberculosis, recurrent tuberculosis is generally due to reactivation of the disease . However, the relative contribution of tuberculosis reinfection increases in parallel with the incidence of disease and is likely to depend on the epidemiological context: factors such as the spread of multidrug resistance, human immunodeficiency virus (HIV) infection, and immigration from developing countries could modify disease transmission in areas at low risk for tuberculosis . A molecular epidemiology study was performed in Lombardy, Northern Italy, where the incidence of tuberculosis is 17.5 cases per 100,000 persons . A total of 2,452 cases of culture-confirmed tuberculosis in 2,127 patients were studied . A group of 32 patients (1.5%), each of whom had two episodes of tuberculosis with cure as the outcome of the first episode and with more than 6 months between the two episodes, were studied by means of restriction fragment length polymorphism DNA fingerprinting analysis . For 5 of the 32 patients (16%), the DNA fingerprinting patterns of Mycobacterium tuberculosis strains responsible for the second episode did not match those of the corresponding isolates of the first episode, indicating exogenous reinfection . Two of these patients developed multidrug-resistant tuberculosis during the second episode, and in three cases the isolates belonged to clusters of M . tuberculosis strains spreading in the community . A fourfold-increased risk for reinfection was observed in immigrant patients compared to Italian subjects . In contrast, a higher risk of relapse rather than reinfection was evidenced in HIV-positive subjects and in patients infected with multidrug-resistant tuberculosis . Episodes of tuberculosis reinfection in areas with a low incidence of tuberculosis are rare compared to those in high-incidence geographical regions . In populations that have immigrated from high-risk areas, reinfection may represent a considerable contributor to the rate of recurrent tuberculosis . This finding emphasizes the importance of containing the spread of epidemic strains in close communities, in order to prevent changes in global tuberculosis trends for developed countries. J Biol Chem, 2001 Jul 27, 276(30), 27846 - 54 Epub 2001 May 25. Transport of the beta -O-glucuronide conjugate of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) by the multidrug resistance protein 1 (MRP1) . Requirement for glutathione or a non-sulfur-containing analog; Leslie EM et al.; Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) play a crucial role in the induction of lung cancer, and NNAL-O-glucuronide formation and elimination are important steps in detoxification of these compounds . In the present study, we investigated the ATP-binding cassette (ABC) protein, MRP1 (ABCC1), as a candidate transporter responsible for NNAL-O-glucuronide export . MRP1 mediates the active transport of numerous GSH-, sulfate-, and glucuronide-conjugated organic anions and can transport certain xenobiotics by a mechanism that may involve co-transport with GSH . Using membrane vesicles prepared from transfected cells, we found that MRP1 transports {3H}NNAL-O-glucuronide but is dependent on the presence of GSH (Km 39 microm, Vmax 48 pmol x mg(-1) x min(-1)) . We also found that the sulfur atom in GSH was dispensable because transport was supported by the GSH analog, gamma-glutamyl-alpha-aminobutyryl-glycine . Despite stimulation of NNAL-O-glucuronide transport by GSH, there was no detectable reciprocal stimulation of {3H}GSH transport . Moreover, whereas the MRP1 substrates leukotriene C4 (LTC4) and 17beta-estradiol 17beta-(d-glucuronide) (E(2)17betaG) inhibited GSH-dependent uptake of {3H}NNAL-O-glucuronide, only {3H}LTC4 transport was inhibited by NNAL-O-glucuronide (+GSH) and the kinetics of inhibition were complex . A mutant form of MRP1, which transports LTC4 but not E(2)17betaG, also did not transport NNAL-O-glucuronide suggesting a commonality in the binding elements for these two glucuronidated substrates, despite their lack of reciprocal transport inhibition . Finally, the related MRP2 transported NNAL-O-glucuronide with higher efficiency than MRP1 and unexpectedly, GSH inhibited rather than stimulated uptake . These studies provide further insight into the complex interactions of the MRP-related proteins with GSH and their conjugated organic anion substrates, and extend the range of xenotoxins transported by MRP1 and MRP2 to include metabolites of known carcinogens involved in the etiology of lung and other cancers. Clin Chem, 2001 Jun, 47(6), 1048 - 52 No influence of the MDR-1 C3435T polymorphism or a CYP3A4 promoter polymorphism (CYP3A4-V allele) on dose-adjusted cyclosporin A trough concentrations or rejection incidence in stable renal transplant recipients; von Ahsen N et al.; BACKGROUND: A substantial proportion of the variability in the absorption and clearance of cyclosporin A (CsA) after oral administration has been attributed to variability in liver cytochrome P-450 3A4 (CYP3A4) activity and intestinal P-glycoprotein (P-gp) concentration . A polymorphism in the CYP3A4 promoter region, termed "variant" allele CYP3A4-V, was postulated to be associated with altered CYP3A4 enzyme activity . A polymorphism in exon 26 (C3435T) of the multidrug resistance-1 (MDR-1) gene was correlated with intestinal expression and in vivo activity of P-gp . METHODS: We investigated the occurrence of both polymorphisms in 124 stable Caucasian renal transplant recipients (>6 months after transplantation) on CsA as the primary immunosuppressant . Real-time, rapid-cycle PCR methods were developed and used for genotyping . RESULTS: The estimated allele frequencies for the MDR-1 C3435T allele (54%) and the CYP3A4-V allele (4.8%) were similar to those reported for Caucasian populations . No significant differences were found for the CsA doses needed to maintain similar CsA trough concentrations in patients with and without the CYP3A4-V allele or in patients with different MDR-1 C3435T genotypes . Furthermore, neither of the polymorphisms investigated was associated with renal function as assessed by creatinine plasma concentration or, in a retrospective analysis, the incidence of acute rejection . CONCLUSIONS: These findings suggest that the MDR-1 C3435T mutation and the CYP3A4-V variant are not major determinants of CsA efficacy in renal transplant recipients. MMW Fortschr Med, 2001 Apr 2, 143 Suppl 1, 14 - 7 {New antiretroviral drugs . Improved pharmacokinetics and simpler dose schedules}; Arasteh K et al.; Despite of 18 licensed antiretroviral drugs in Germany, there is an increased pressure for development of new substances and new targets in the treatment of HIV positive patients . Multidrug resistance and poor pharmacokinetics are the biggest problems we have to fight with . But there is hope for resolving these challenges . Second generation drugs like FTC and DPC 083 with once a day dosage and a high resistance barrier are tested in clinical trials . In addition new classes of HIV drugs are available in phase III trials (T-20 fusion inhibitor) . So the future will provide us with some new effective arms in the battle against HIV. Zhonghua Fu Chan Ke Za Zhi, 2000 Oct, 35(10), 617 - 20 {Establishment of cisplatin-induced multidrug resistant human epithelial ovarian cancer cell line 3AO/cDDP and its expressions of multidrug resistance proteins}; Chen J et al.; OBJECTIVE: To establish multidrug resistant ovarian cancer cell line 3AO/cDDP by exposing parent cell line intervally and repeatedly to high-level concentration of cisplatin, and to detect expressions of lung resistance protein (LRP), multidrug resistance-associated protein(MRP) and P-glycoprotein (P-gp) . METHODS: Using the corresponding dose calculated from clinical chemotherapy, we established 3AO/cDDP, with 3AO exposed intervally and repeatedly to high-level concentration of cisplatin at 10 micrograms/ml for 24 hours each time; LRP, MRP and P-gp expressions were detected with flow cytometry(FCM) . RESULTS: 3AO/cDDP was established after 4.5 months with stable resistance and the drug resistant index was 1.62 which was similar to clinical resistance degree . Low expression levels of MRP and P-gp were found in both 3AO and 3AO/cDDP, and no statistical difference between the two lines (P > 0.05) . However, LRP expression level in 3AO/cDDP was significantly higher than that in 3AO with FCM detection (P < 0.01) . CONCLUSIONS: 3AO/cDDP, induced by exposing 3AO to high-level concentration of cisplatin intervally and repeatedly, is an ideal model for investigation of cisplatin resistance . Cisplatin resistance in 3AO/cDDP could be related to high LRP expression and be not associated with MRP or P-gp. Clin Pharmacol Ther, 2001 May, 69(5), 308 - 16 Pharmacokinetic and prognostic significance of intestinal MDR1 expression in recipients of living-donor liver transplantation; Hashida T et al.; BACKGROUND: Living-donor liver transplantation (LDLT) and subsequent immunosuppressive therapy with tacrolimus have been cornerstones in the recovery of patients from end-stage liver failure, but there has been no critical dosage regimen for tacrolimus therapy, especially the initial dosage . In this study, we examined whether the absorptive barriers, multidrug resistance protein (MDR1), or cytochrome P450 IIIA4 (CYP3A4) are important pharmacokinetic factors for tacrolimus and are prognostic indicators for LDLT outcome . METHODS: We used competitive polymerase chain reaction to evaluate the messenger ribonucleic acid (mRNA) expression levels of MDRL And Cyp3A4 in mucosal cells of the upper jejunum from a part of the Rroux-en- Y limb for biliary reconstruction during LDLT of recipients (n = 48) . The tacrolimus dosage was started at an oral dose of 0.075 mg/kg every 12 hours and adjusted on the basis of its whole-blood trough level by use of a semiautomated microparticle enzyme immunoassay . RESULTS: The mRNA expression level of MDR1 (r = -0.776), but not CYP3A4 (r = -0.094), was inversely related to the concentration/dose ratio of tacrolimus . High levels of MDR1, but not CYP3A4, were strongly associated with reductions in survival rates after LDLT with the Kaplan-Meier method and log-rank statistics (P =.020 and P =.135, respectively) . With use of a Cox regression procedure, high levels of MDR1 (relative risk, 12.99; 95% confidence interval, 1.64-103.23), but not CYP3A4 (relative risk, 0.93; 95% confidence interval, 0.87-1.00) appeared to be a significant prognostic indicator for poor survival . CONCLUSIONS: Intestinal MDR1 is not only a good probe with which to predict the interindividual variation in tacrolimus pharmacokinetics after LDLT but also a powerful prognostic indicator for the outcome of LDLT. Curr Opin Pulm Med, 2001 May, 7(3), 170 - 2 Science, society, and disease: emerging perspectives; Gandy M; The understanding of tuberculosis (TB) requires effective links to be made between advances in biomedical knowledge and the wider social and economic dynamics of disease epidemiology . This review highlights some recent advances in contemporary TB research with particular emphasis on the spread of multidrug-resistant tuberculosis (MDR-TB); the prevalence of TB in prisons, urban ghettoes, and the marginalized communities of the South; and the relation between TB control and general developments in public policy making . The article also draws attention to the significance of new historical insights into the epidemiological transition of the twentieth century and the implications of new and emerging diseases for the future of public health . It is concluded that the real obstacles to the effective control of TB are political rather than scientific. Curr Opin Pulm Med, 2001 May, 7(3), 154 - 9 Molecular epidemiology of tuberculosis: recent developments and applications; Fletcher HA; The standard method for the typing of Mycobacterium tuberculosis is still IS6110 restriction fragment length polymorphism (RFLP) . This method has been widely used and has provided information on the variety and distribution of tuberculosis strain types across the globe . Recently, IS6110 RFLP has been used to investigate the question of reinfection versus reactivation, examine the existence of multiple infection, and track the spread of multidrug-resistant tuberculosis . There have also been efforts to increase our understanding of the biologic characteristics of IS6110 . These studies have resulted in a clearer understanding of fingerprinting data and increased our understanding of the evolution and pathogenicity of this organism. Curr Opin Pulm Med, 2001 May, 7(3), 148 - 53 Drug-resistant tuberculosis: worldwide trends, problems specific to Eastern Europe and other hotspots, and the threat to developing countries; Willcox PA; Although it had been appreciated that high levels of antituberculous drug resistance existed in some regions of the world, the full extent of the problem was not known . A combined initiative by the World Health Organization and the International Union Against Tuberculosis and Lung Disease was launched in 1994 to address this . A second report was issued in March 2000, in which surveillance of drug resistance had been extended to 72 countries and regions . A number of drug resistant "hotspots," where there are high levels of combined multidrug-resistant tuberculosis (> 3% prevalence), have been identified . Particular areas of concern are countries of the former Soviet Union, India, and China, because these countries have the highest burden of multidrug-resistant tuberculosis . For the first time, information on trends in global drug resistance is available. AIDS, 2001 Apr 13, 15(6), 675 - 81 Differences in the intracellular accumulation of HIV protease inhibitors in vitro and the effect of active transport; Jones K et al.; OBJECTIVES: To investigate the intracellular accumulation of HIV protease inhibitors (PI) and to assess the effect of active transport on this accumulation . METHODS: CEM cells were incubated with a PI for 18 h and the intracellular concentration determined using cell number and radioactivity . The effect of active transport was investigated using cells expressing P-glycoprotein (CEM(VBL)) and cells expressing multidrug resistance-associated protein 1 (MRP1; CEM(E1000)) . Incubations were also carried out at 4 degrees C and in the presence of 2-deoxyglucose plus rotenone to examine the effect of inhibiting active transport . RESULTS: Nelfinavir (NFV) accumulated to the greatest extent (> 80-fold) followed by saquinavir (SQV; approximately 30-fold), ritonavir (RTV; 3-7-fold) and finally indinavir (IDV; extracellular equivalent to intracellular) . In CEM(VBL) cells there was a significant reduction in the intracellular accumulation of NFV, SQV and RTV and in CEM(E1000) cells there was reduced accumulation of SQV and RTV . Inhibition of active transport processes caused a reduction in SQV and RTV accumulation but had no effect on IDV accumulation in all cell types . NFV accumulation was increased in CEM(VBL) cells as a result of inhibition of active transport . CONCLUSIONS: Marked differences can be detected in the intracellular accumulation of HIV PI drugs in vitro . Both P-glycoprotein and MRP1 may play a role in limiting the intracellular concentration of the PI and active influx mechanisms may contribute to drug accumulation. Ann Med, 2001 Apr, 33(3), 167 - 71 Multidrug-resistant bacteria: overcoming antibiotic permeability barriers of gram-negative bacteria; Savage PB; Because of the permeability barrier provided by the outer membrane (OM), gram-negative bacteria are inherently resistant to many hydrophobic antibiotics . This resistance limits the arsenal of antibiotics that are effective in treating gram-negative bacterial infections . Compounding this problem, strains of gram-negative bacteria have emerged that display specific resistance mechanisms for effective antibiotics . As a means of expanding the arsenal of effective antibiotics for gram-negative bacteria, compounds that permeabilize the OM to hydrophobic substances have been developed . These compounds are typically cationic, amphiphilic molecules that can be prepared from peptides or steroids . Effective OM permeabilizers sensitize gram-negative bacteria to hydrophobic antibiotics, including erythromycin, fusidic acid, novobiocin and rifampin . These antibiotics are generally not useful in treating gram-negative bacterial infections because they traverse the OM ineffectively . The use of OM permeabilizers, in combination with hydrophobic antibiotics, may provide additional means of controlling growth of gram-negative bacteria . This review describes classes of permeabilizers, including those derived from peptides, and recently reported examples based on steroids. AIDS Clin Care, 1995 Apr, 7(4), 27 - 9, 36 Diagnosis and detection of drug-resistant strains of M . tuberculosis; Ferraro MJ et al.; AIDS: Factors contributing to the recent upswing in tuberculosis (TB) cases in the United States include the shifting of management of TB cases from specialized hospital units to lesser-equipped outpatient settings; reduced medical school teaching of TB-related issues; large-scale immigration from regions endemic for TB; and the homelessness and AIDS cases that have created a pocket of disease in high-risk populations . At least 33 percent of current cases can be attributed to new rather than reactivated infection, and many of these are caused by the ever-increasing number of drug-resistant strains . Multidrug-resistant TB has a higher overall fatality rate and disproportionately affects immunocompromised and HIV-infected individuals . Clearly, expedient diagnosis is important in controlling the spread of tuberculosis . Sputum samples, evaluated first by direct microscopic evaluation (smear), are visualized with either the easily detected acid-fast fluorochrome dye auramine O, or the more specific Ziehl-Neelsen stain . Specimens are cultured on either solid media (Lowenstein-Jensen slant), or are grown in a liquid medium, such as the BACTEC automated radiometric system . Next, biochemical or nucleic acid probe testing is used to identify various strains . Isolates are tested for resistance to commonly used antituberculosis drugs, often by using the new method of susceptibility testing in liquid broth rather than the traditional agar dilution method . Clinical laboratories await FDA approval of two new methods employing hybridization with rRNA genes or polymerase chain reaction (PCR) that will further speed up diagnosis of TB . J Biol Chem, 2001 Jul 27, 276(30), 28562 - 9 Epub 2001 May 21. Hyperthermia-induced nuclear translocation of transcription factor YB-1 leads to enhanced expression of multidrug resistance-related ABC transporters; Stein U et al.; Genotoxic stress leads to nuclear translocation of the Y-box transcription factor YB-1 and enhanced expression of the multidrug resistance gene MDR1 . Because hyperthermia is used for the treatment of colon cancer in combination with chemoradiotherapy, we investigated the influence of hyperthermia on YB-1 activity and the expression of multidrug resistance-related genes . Here we report that hyperthermia causes YB-1 translocation from the cytoplasm into the nucleus of human colon carcinoma cells HCT15 and HCT116 . Nuclear translocation of YB-1 was associated with increased MDR1 and MRP1 gene activity, which is reflected in strong efflux pump activity . However, a combination of hyperthermia and drug treatment effectively reduced cell survival of the HCT15 and HCT116 cells . These results demonstrate that activation of MDR1 and MRP1 gene expression and increased efflux pump activity after hyperthermia were insufficient to cause an increase in drug resistance in colon cancer cell lines . The ability of hyperthermia to abrogate drug resistance in the presence of an increase in functional MDR proteins may provide an explanation for the efficacious results seen in the clinic in colon cancer patients treated with a combination of hyperthermia and chemotherapy. Cancer Lett, 2001 Jun 26, 167(2), 157 - 62 Induction of apoptosis in MDR1 expressing cells by daunorubicin with combinations of suboptimal concentrations of P-glycoprotein modulators; Aszalos A et al.; The application of most agents with the capacity to reverse multidrug resistance (MDR) via modulation of the multidrug transporter P-glycoprotein (Pgp) was shown to be associated with toxic side-effects . For this reason, we have investigated the effect of combinations of suboptimal concentrations of Pgp blockers on the induction of apoptosis and growth arrest in daunorubicin (D) treated, MDR1 gene transfected cells . We used verapamil, PSC833 and Cremophor EL as Pgp modulators, which affect the function of Pgp by different mechanisms . Treatment of NIH3T3/MDR1 cells with combinations of suboptimal concentrations of Pgp modulators in the presence of D caused apoptosis and G(2) arrest to the same extent as optimal concentrations of singly used blockers . We conclude that combinations of suboptimal concentrations of Pgp modulators may cause effective sensitization of resistant tumor cells, and at the same time, may avoid the frequently observed toxic effects experienced in clinical trials with a single modifier applied at the optimal dose. Biochem J, 2001 Jun 1, 356(Pt 2), 317 - 25 Down-regulation of intestinal scavenger receptor class B, type I (SR-BI) expression in rodents under conditions of deficient bile delivery to the intestine; Voshol PJ et al.; Scavenger receptor class B, type I (SR-BI) is expressed in the intestines of rodents and has been suggested to be involved in the absorption of dietary cholesterol . The aim of this study was to determine whether intestinal SR-BI expression is affected in animal models with altered bile delivery to the intestine and impaired cholesterol absorption . SR-BI protein and mRNA levels were determined in proximal and distal small intestine from control, bile-duct-ligated and bile-diverted rats and from control and bile-duct-ligated mice . Two genetically altered mouse models were studied: multidrug resistance-2 P-glycoprotein-deficient {Mdr2((-/-))} mice that produce phospholipid/cholesterol-free bile, and cholesterol 7alpha-hydroxylase-deficient {Cyp7a((-/-))} mice, which exhibit qualitative and quantitative changes in the bile-salt pool . Cholesterol-absorption efficiency was quantified using a dual-isotope ratio method . SR-BI was present at the apical membrane of enterocytes in control rats and mice and was more abundant in proximal than in distal segments of the intestine . In bile-duct-ligated animals, levels of SR-BI protein were virtually absent and mRNA levels were decreased by approximately 50% . Bile-diverted rats, Mdr2((-/-)) mice and Cyp7a((-/-)) mice showed decreased levels of intestinal SR-BI protein while mRNA levels were unaffected . Cholesterol absorption was reduced by >90% in bile-duct-ligated and bile-diverted animals and in Cyp7a((-/-)) mice, whereas Mdr2((-/-)) mice showed an approximately 50% reduction . This study shows that SR-BI is expressed at the apical membrane of enterocytes of rats and mice, mainly in the upper intestine where cholesterol absorption is greatest, and indicates that bile components play a role in post-transcriptional regulation of SR-BI expression . Factors associated with cholestasis appear to be involved in transcriptional control of intestinal SR-BI expression . The role of SR-BI in the cholesterol-absorption process remains to be defined. Leukemia, 2001 May, 15(5), 764 - 71 Combined action of PSC 833 (Valspodar), a novel MDR reversing agent, with mitoxantrone, etoposide and cytarabine in poor-prognosis acute myeloid leukemia; Visani G et al.; PSC 833 (Valspodar) can reverse multidrug resistance (MDR) in patients with hematologic malignancies, but alters the pharmacokinetics of concomitant anticancer agents . A phase I, dose-finding study was initiated to define a safe and effective regimen of mitoxantrone, etoposide, and cytarabine (MEC) when administered with PSC 833 to patients with early relapsed or refractory acute myeloid leukemia (AML) . Poor-prognosis AML patients refractory to first-line induction therapy or relapsing within 9 months of attaining complete remission (CR) were treated with cytarabine (1.0 g/m2/day), etoposide (30 mg/m2/day), and mitoxantrone at a dose of either 3.0 mg/m2/day (cohort 1) or 4.5 mg/m2/day (cohorts 2 and 3) for 6 days plus continuous-infusion PSC 833 (10 mg/kg/24 h with a 2.0 mg/kg loading dose) for 6 or 7 days each 21-day cycle . Patients achieving CR were given a 4-day MEC plus PSC 833 consolidation cycle . Twenty-three patients were enrolled (eight with primary refractory AML and 15 in relapse) . Dose-limiting toxicity occurred in one of six patients in cohort 2 (grade 4 mucositis) and one of seven patients in cohort 3 (grade 4 hyperbilirubinemia) . The maximum tolerated dose of mitoxantrone was defined as 4.5 mg/m2/day . Clinically significant grade 4 hyperbilirubinemia, possibly related to PSC 833, occurred in four patients . Hematologic toxicities were as expected in this patient population, but were not dose limiting . Mild to moderate cerebellar ataxia and paresthesia occurred in six (26%) and five (22%) patients, respectively, but were not dose limiting . Overall, six of 23 (26%) patients achieved CR, including five patients with demonstrated P-glycoprotein expression and/or function . The median overall survival was 4 months . All six patients with a CR were alive and four (17%) patients were disease free at 12 months . Blood levels of PSC 833 were well above the target level of 1000 ng/ml, a concentration that is known to reverse MDR in vitro . PSC 833 reduced the clearance of etoposide by approximately two-fold . No correlation was observed between the mitoxantrone or etoposide area under the curve and response . In conclusion, the MEC plus PSC 833 tested regimen was well tolerated and the 26% CR rate warrants further testing of this regimen in a randomized, phase III trial. AIDS Treat News, 1999 Oct 1, (No 328), 1 - 2 ABT-378 early access program begins; Raising the stakes at Retro '99 or amplified diversity; AIDS: The 6th Conference on Retroviruses and Opportunistic Infections raised serious concerns about the development of multidrug-resistant strains of HIV . There are press reports of HIV-positive men increasingly engaging in unprotected anal sex and who are seeking thrills by engaging in high risk behavior . This behavior may be attributed to the view that acquiring the virus no longer seems like a death sentence . Data from studies of HIV-positive people demonstrate how the disease spreads within a population and show that close adherence correlates with viral suppression in patients taking protease inhibitors (PIs) . Other topics covered at the conference included the importance of the thymus in HAART responders, treatment interruption failures, IL-2 trials and uses, stopping cytomegalovirus (CMV) and Pneumocystis carinii pneumonia (PCP) treatment, and CD4+ cell survival versus viral fitness . Also addressed were risk factors associated with PIs, and salvage regimens . Results from a number of drug trials are summarized . Contact information is provided . J Int Assoc Physicians AIDS Care, 1999 Jan, 5(1), 10 - 30 Therapeutic options or antiretroviral anarchy? Mascolini M. AIDS: The number of drug combinations being used to treat HIV infections may produce a public health nightmare by creating multidrug resistance . The issue of whether to use aggressive multidrug combinations early in the infectious cycle or whether to delay treatment as long as possible remains controversial and unresolved . The use of viral markers to track disease progression is discussed . Tables illustrate the relationships between CD4+ counts and opportunistic infections, disease progression, and long-term viral load reduction . The effectiveness of different drugs combinations is discussed . Results of various clinical trials are presented . BETA . 1998 Oct;:18-25. Tuberculosis; Highleyman L; AIDS: Approximately one-third of the world's population is infected with tuberculosis (TB), and TB kills more people worldwide than any other infectious disease . TB infection, however, is not the same as active TB disease . Nine out of ten people with healthy immune systems who are infected with TB do not develop active TB disease; the rate at which people who are coinfected with HIV and TB develop active TB is 100 times higher . The history and epidemiology of the disease are outlined . In 1990, epidemiologists began seeing new strains of TB that are drug-resistant . This multidrug-resistant TB (MDRTB) is especially dangerous for HIV-positive persons . Symptoms of active TB disease include lung fluid expulsion, fatigue, weakness, malaise, fever, and chills . Untreated TB can lead to severe wasting and death . TB prevention, transmission, and treatment are described . A table is included which lists the major drugs used to prevent and treat TB, and describes the primary side effects associated with each . A resource list is provided . AIDS Alert . 1998 Jun;13(6):68. Reporting of co-infection still limited; Looking down the drug pipeline; AIDS: Reports at the 5th Conference on Retroviruses and Opportunistic Infections addressed new anti-HIV agents in primary phases of development that offer treatment alternatives to people with little or no treatment history and individuals with few treatment choices . FTC, a new nucleoside analog produced by Triangle Pharmaceuticals, is an alternative to 3TC . F-ddA (lodenosine), a nucleoside analog licensed by US Bioscience, is structurally similar to ddI and is reported to have good bioavailability, once-a-day dosing, and no bone marrow suppression . F-ddA has also shown in vitro activity against multidrug-resistant strains of HIV . Adult and pediatric studies are currently being conducted by the National Cancer Institute (NCI) and US Bioscience . Oral versus IV PMPA shows promising results as a possible alternative for 3TC- and AZT-experienced patients . Further testing is being done by Gilead Sciences and HIV Network for Prevention Trials (HIVNET) . Abbott Laboratories is developing a second-generation protease inhibitor, ABT-378, which has a ten-fold greater antiviral activity in vitro than the original, ritonavir . It is administered with ritonavir to increase ABT-378 levels in the blood, but has no food requirements, and less severe side effects . Two trials are being conducted: one for patients who are treatment-naive and the second for patients who are failing other protease inhibitors . Immune-based therapies, such as Leukine (GM-CSF), are used to handle neutropenia and offset bone marrow toxicities from drugs . Concerns that GM-CSF may increase viral replication may be balanced by using highly active antiretroviral therapy . FP-21399, developed by Lexigen Pharmaceuticals, is being tested as an HIV fusion inhibitor . AIDS Alert, 1995 Jul, 10(7), 91 - 3 Prolonging survival among MDR-TB AIDS patients; Second National Retrovirus conference: a further report; AIDS: It was reported at the 1995 Second National Retrovirus Conference that AIDS has now surpassed unintentional injury as the leading cause of death for male Americans between the ages of 25 to 44, and for women, AIDS is fourth behind unintentional injury . A study of multidrug resistant tuberculosis that showed improved survival rates as long as appropriate therapy began within four weeks of diagnosis was also presented . The current recommendation is to consider the PPD skin test positive in persons with HIV if the bump that appears is over five millimeters in diameter . A new ganciclovir implant study demonstrated the implant's effectiveness in preventing CMV disease progression with low rates of complications, suggesting implants should probably replace intravenous ganciclovir as maintenance therapy . Another study demonstrated the effectiveness of cidofovir as a treatment for CMV infection, indicating that cidofovir was appropriate as a salvage therapy for those failing ganciclovir and foscarnet . In vitro studies involving Taxol and Kaposi's sarcoma (KS) show partial responses (55 percent), and some disease stabilization (40 percent) . Four of five patients with pulmonary KS responded with clearance of tumor lesions . The first randomized trial involving Loviride with zidovudine has shown a sustained increase in CD4 cells with headache, nausea, and diarrhea as the most common side effects . Preliminary assessments reveal a reduction in viral load using the combination as opposed to monotherapy . Additional Loviride combination trials are being planned in Europe . AIDS Alert, 1995 Apr, 10(4), 58 - 9 Tuberculosis rising in areas with high HIV rates; Regulation of the hepatic multidrug resistance gene expression by endotoxin and inflammatory cytokines in mice; Faculty of Pharmacy, University of Toronto, Ontario, CanadaP-glycoprotein (PGP), an ATP-dependent membrane transporter is found in epithelial tissues of the liver, kidneys, intestine and blood-brain barrier . In tumor cells, PGP is often overexpressed and confers multidrug resistance toward cancer chemotherapeutics . It has been previously shown in rats that induction of an inflammatory response evokes a decrease in hepatic expression of PGP . In order to identify the inflammatory mediators involved in this phenomenon, we examined the influence of experimentally induced inflammation and pro-inflammatory cytokines (interleukin (IL)-6, IL-1beta and tumor necrosis factor (TNF)-alpha) on the hepatic expression of PGP in mice . A significant reduction in the hepatic expression of mdr1a, mdr1b, mdr2 and spgp genes were seen in endotoxin (lipopolysaccharide (LPS)) and turpentine-treated mice . Similarly, IL-6-treated mice displayed a 70% reduction in protein expression and a 40-70% reduction in the mRNA levels of all PGP mdr isoforms . Administration IL-1beta caused an increase in both mdr1b mRNA and protein expression, however, mRNA levels of mdr1a, mdr2 and spgp were significantly reduced . Administration of TNF-alpha also caused increases in mdr1b mRNA . These findings indicate that IL-6 plays a principal role in the downregulation of PGP that is observed in the livers of mice during an inflammatory response. Cancer Res, 2001 May 15, 61(10), 4030 - 7 Pervilleine A, a novel tropane alkaloid that reverses the multidrug-resistance phenotype; Mi Q et al.; P-Glycoprotein-mediated drug efflux can yield a multidrug-resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy . Pervilleine A, a novel tropane alkaloid obtained from a chloroform extract of Erythroxylum pervillei as the result of bioactivity-guided fractionation, was found to restore the vinblastine sensitivity of cultured multidrug-resistant KB-V1 and CEM/VLB(100) cells, with IC(50) values of 0.36 and 0.02 microM, respectively . Similarly, the chemosensitivity of KB-8-5 cells to colchicine was restored with an IC(50) value of 0.61 microM . The mechanism of this response was evaluated with a number of model systems . First, incubation of multidrug-resistant KB-V1 and CEM/VLB(100) cells with up to 45 microM pervilleine A for 72 h did not significantly affect either the transcription of MDR1, as revealed by reverse transcriptional-PCR-based analysis of MDR1 mRNA, or levels of P-glycoprotein, as shown by Western blots . ATP-dependent binding of {(3)H}vinblastine observed with isolated multidrug-resistant KB-V1 cell membrane vesicles was inhibited by pervilleine A in a dose-dependent manner, and kinetic analysis indicted competitive inhibition with respect to vinblastine binding with a K(i) of 7.3 microM . Consistent with this effect, intracellular accumulation of {(3)H}vinblastine was increased from 0.18 pmol {(3)H}vinblastine/50 x 10(4) cells to approximately 5 pmol {(3)H}vinblastine/50 x 10(4) cells in the presence of 40 microM pervilleine A . To explore the potential relevance of these responses, KB-V1 or KB-8-5 cells were placed in hollow fibers and implanted into NCr nu/nu mice . Cell growth was not significantly inhibited when vinblastine or pervilleine A were administered as single agents, but when used in combination, inhibition of up to 75% was observed . Equimolar doses of verapamil were less effective . These data suggest that pervilleine A is an effective inhibitor of P-glycoprotein and should be further evaluated for clinical utility. Blood Cells Mol Dis, 2001 Jan-Feb, 27(1), 165 - 80 Erythrocyte membrane ATP binding cassette (ABC) proteins: MRP1 and CFTR as well as CD39 (ecto-apyrase) involved in RBC ATP transport and elevated blood plasma ATP of cystic fibrosis; Abraham EH et al.; In addition to the better-known roles of the erythrocyte in the transport of oxygen and carbon dioxide, the concept that the red blood cell is involved in the transport and release of ATP has been evolving (J . Luthje, Blut 59, 367, 1989; G . R . Bergfeld and T . Forrester, Cardiovasc . Res . 26, 40, 1992; M . L . Ellsworth et al., Am . J . Physiol . 269, H2155, 1995; R . S . Sprague et al., Am . J . Physiol . 275, H1726, 1998) . Membrane proteins involved in the release of ATP from erythrocytes now appear to include members of the ATP binding cassette (ABC) family (C . F . Higgins, Annu . Rev . Cell Biol . 8, 67, 1992; C . F . Higgins, Cell 82, 693, 1995) . In addition to defining physiologically the presence of ABC proteins in RBCs, accumulating gel electrophoretic evidence suggests that the cystic fibrosis transmembrane conductance regulator (CFTR) and the multidrug resistance-associated protein (MRP1), respectively, constitute significant proteins in the red blood cell membrane . As such, this finding makes the mature erythrocyte compartment a major mammalian repository of these important ABC proteins . Because of its relative structural simplicity and ready accessibility, the erythrocyte offers an ideal system to explore details of the physiological functions of ABC proteins . Moreover, the presence of different ABC proteins in a single membrane implies that interaction among these proteins and with other membrane proteins may be the norm and not the exception in terms of modulation of their functions . Urology, 2001 May, 57(5), 993 - 8 Increased intracellular doxorubicin by anti-FAS monoclonal antibody: a mechanism that enhances the cytotoxicity in renal cell carcinoma cells; Wu X et al.; OBJECTIVES: To investigate the effect of anti-Fas monoclonal antibody (mAb) on the intracellular concentration of doxorubicin in renal cell carcinoma (RCC) cells . Little is known about the influence of anti-Fas mAb on the intracellular concentration of chemotherapeutic agents . METHODS: The concentration of intracellular doxorubicin was determined by high-performance liquid chromatography . The mRNA and protein levels of multidrug resistance-associated protein gene were evaluated by reverse transcriptase-polymerase chain reaction and immunocytochemistry, respectively . RESULTS: An increased concentration of doxorubicin inside the cells was found: 2.4-fold in ACHN cells (a human RCC cell line) after treatment with doxorubicin combined with anti-Fas mAb compared with doxorubicin alone . Of the five cases of freshly derived RCC cells treated with doxorubicin and anti-Fas mAb, the intracellular concentration of doxorubicin was increased 2.3 and 2.7-fold in two of them, respectively . Furthermore, both the mRNA and the protein levels of the multidrug resistance-associated protein gene were downregulated after treatment of ACHN cells with anti-Fas mAb . Treatment of ACHN cells with a combination of anti-Fas mAb and doxorubicin resulted in a potentiation of the doxorubicin-mediated cytotoxicity . CONCLUSIONS: The increased intracellular concentration of doxorubicin by anti-Fas mAb might be one of the mechanisms responsible for the enhancement of doxorubicin-mediated cytotoxicity in RCC cells. J Pharmacol Exp Ther, 2001 Jun, 297(3), 1137 - 43 Expression of P-glycoprotein in human placenta: relation to genetic polymorphism of the multidrug resistance (MDR)-1 gene; Tanabe M et al.; To evaluate whether mutations in the human multidrug resistance (MDR)-1 gene correlate with placental P-glycoprotein (PGP) expression, we sequenced the MDR-1 cDNA and measured PGP expression by Western blotting in 100 placentas obtained from Japanese women . Nine single nucleotide polymorphisms (SNPs) were observed with an allelic frequency of 0.005 to 0.420 . Of these SNPs, G2677A (allelic frequency = 0.18) and G2677T (0.39) in exon 21 were associated with an amino acid conversion from Ala to Thr and to Ser, respectively . Sixty-one of 65 samples (93.8%), which had a C3435T allele, also had a mutant G2677(A,T) allele, suggesting an association between the two SNPs . Correlations of mutations with expression levels were observed; individuals having the G2677(A,T) and/or T-129C (p < 0.05) allele had less placental PGP . Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based genotyping tests were developed for the detection of these SNPs . The PCR, in which genomic DNAs obtained from healthy subjects (n = 48) are used as samples, was successful . The frequency of mutations in placental cDNA was identical with that in genomic DNA . When genotype results were compared between Caucasians and Japanese, ethnic differences in the frequency of polymorphism in the MDR-1 gene were suspected . Although it remains to be determined whether these SNPs influence the pharmacokinetic and dynamic properties of clinically useful drugs that are substrates of PGP, the polymorphism of the MDR-1 gene presented here may provide useful information in in vivo study of these issues. Endocrinology, 2001 Jun, 142(6), 2686 - 94 Multidrug resistance P-glycoprotein hampers the access of cortisol but not of corticosterone to mouse and human brain; Karssen AM et al.; In the present study, we investigated the role of the multidrug resistance (mdr) P-glycoprotein (Pgp) at the blood-brain barrier in the control of access of cortisol and corticosterone to the mouse and human brain . {(3)H}Cortisol poorly penetrated the brain of adrenalectomized wild-type mice, but the uptake was 3.5-fold enhanced after disruption of Pgp expression in mdr 1a(-/-) mice . In sharp contrast, treatment with {(3)H}corticosterone revealed high labeling of brain tissue without difference between both genotypes . Interestingly, human MDR1 Pgp also differentially transported cortisol and corticosterone . LLC-PK1 monolayers stably transfected with MDR1 complementary DNA showed polar transport of {(3)H}cortisol that could be blocked by a specific Pgp blocker, whereas {(3)H}corticosterone transport did not differ between transfected and host cells . Determination of the concentration of both steroids in extracts of human postmortem brain tissue using liquid chromatography mass spectrometry revealed that the ratio of corticosterone over cortisol in the brain was significantly increased relative to plasma . In conclusion, the data demonstrate that in both mouse and human brain the penetration of cortisol is less than that of corticosterone . This finding suggests a more prominent role for corticosterone in control of human brain function than hitherto recognized. Best Pract Res Clin Haematol, 2001 Mar, 14(1), 211 - 33 Chemotherapy resistance in acute myeloid leukaemia; Sonneveld P et al.; The development of refractory disease in acute myeloid leukaemia (AML) is frequently associated with the expression of one or several multidrug resistance (MDR) genes . MDR1, MRP1 and LRP have been identified as important adverse prognostic factors in AML . Recently it has become possible to reverse clinical multidrug resistance by blocking P-glycoprotein-mediated drug efflux . The potential relevance of MDR and new approaches to treat refractory disease, are discussed . J Cancer Res Clin Oncol, 2001 May, 127(5), 301 - 13 Exploring the mechanisms of action of FB642 at the cellular level; Hammond LA et al.; FB642(methyl-2-benzimidazolecarbamate, carbendazim) is a systemic fungicide belonging to the benzimidazole family with antitumor activity against a broad spectrum of tumors both in vitro and in vivo such as pancreas, prostate, colon, and breast . Although the preclinical antitumor activity of FB642 has been well explored, its mechanism of action has not been as well delineated . Previous studies indicate that FB642 may interfere with mitosis and thus may disrupt or inhibit microtubule function resulting in apoptosis . This study seeks to determine if FB642 is a sufficiently novel agent worthy of further development by examining the effect of FB642 on apoptosis, the cell cycle, p53-positive and -negative tumors, and drug-resistant and MDR cell lines . The results of this present study indicate that FB642 increases the degree of apoptosis in all examined tumor cell lines, may induce G2/M uncoupling, may selectively kill p53 abnormal cells, and exhibits antitumor activity in drug- and multidrug-resistant cell lines . The induction of apoptosis by FB642, particularly in p53-deficient cells, its impressive in vivo activity against a broad spectrum of murine and human tumors, as well as an acceptable toxicity profile in animals, make FB642 an excellent candidate for further evaluation in clinical trials in cancer patients. J Gastroenterol Hepatol, 2001 Apr, 16(4), 460 - 6 Modulation of doxorubicin sensitivity by cyclosporine A in hepatocellular carcinoma cells and their doxorubicin-resistant sublines; Shiraga K et al.; BACKGROUND AND AIMS: Cyclosporine A (Cys) and verapamil (Ver) sensitize multidrug-resistant (MDR) cells to various anticancer drugs by interacting with membrane glycoproteins involved in the drug efflux . In the present study, we assessed the effect of Cys on the modulation of doxorubicin (DOR) sensitivity in hepatocellular carcinoma (HCC) cell lines, and their DOR-resistant sublines . METHODS: The sensitivity to DOR and the chemosensitizing effects of Cys were assessed by using two human HCC cell lines, PLC/PRF/5 and Hep-3B, and their DOR-resistant sublines, PLC/DOR and 3B/DOR . The expression of multidrug resistance 1 (MDR1) and multidrug resistance-associated protein (MRP) mRNA in these cells were detected by using a RT-PCR . The HCC cell lines grown in individual wells of 24-well plates were incubated with DOR that were sequentially diluted in culture medium in combination with 5 micromol/L Cys for 24 h . The cell viability in each well was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay . RESULTS: The mRNA of MDR1 and that of MRP were readily detectable in the HCC cell lines by RT-PCR . When 5 micromol/L Cys was added to the culture, the 50% inhibiting concentration (IC50) of DOR was reduced from 0.93 +/- 0.29 microg/mL to 0.32 +/- 0.10 microg/mL in PLC/PRF/5, and from 0.25 +/- 0.07 microg/mL to 0.09 +/- 0.04 microg/mL in Hep-3B . Furthermore, in the presence of 5 micromol/L Cys, the IC50 of DOR was reduced from 48.63 +/- 17.04 microg/mL to 0.49 +/- 0.14 microg/mL in PLC/DOR, and from 4.60 +/- 1.22 microg/mL to 0.15 +/- 0.06 microg/mL in 3B/DOR . The amounts of PCR products of MDR1 mRNA in PLC/DOR and 3B/DOR were greater than those in PLC/PRF/5 and Hep-3B, respectively . CONCLUSIONS: In HCC, the amplification of MDR1 mRNA is probably the main mechanism underlying acquired DOR resistance . Cyclosporine is also indicated to be highly active in potentiating the anticancer activity of DOR in HCC cells and their DOR-resistant sublines. Mol Pharmacol, 2001 Jun, 59(6), 1433 - 40 Nephrotoxicants induce endothelin release and signaling in renal proximal tubules: effect on drug efflux; Terlouw SA et al.; We previously used killifish proximal tubules, fluorescent substrates, and confocal microscopy to demonstrate that transport mediated by the multidrug resistance protein (Mrp2) and by P-glycoprotein was reduced by nanomolar concentrations of endothelin-1 (ET), acting through a basolateral B-type ET receptor and protein kinase C (PKC) . Here we show that representatives of two classes of nephrotoxicants decrease transport by activating the endothelin-PKC signaling pathway . Exposing tubules to radiocontrast agents (iohexol, diatrizoate) or aminoglycoside antibiotics (gentamicin, amikacin) reduced Mrp2-mediated fluorescein methotrexate (FL-MTX) transport from cell to tubular lumen . Pretreating the tubules with an ET(B)-receptor antagonist or with PKC-selective inhibitors abolished these effects . The nephrotoxicants activated signaling by inducing release of ET from the tubules, because adding of an antibody against ET to the medium abolished the effects . Elevating medium Ca(2+) also reduced FL-MTX transport; this reduction was abolished when tubules were pretreated with an ET antibody, an ET(B)-receptor antagonist, PKC-selective inhibitors, or the Ca(2+) channel blocker, nifedipine . None of these drugs by themselves affected FL-MTX transport . Importantly, nifedipine also blocked the ET(B)-receptor/PKC-dependent reduction in FL-MTX transport caused by gentamicin and diatrizoate . These results for two classes of structurally unrelated nephrotoxicants suggest that Ca(2+)-dependent ET release and subsequent action through an autocrine mechanism may be an early response to tubular injury. Antimicrob Agents Chemother, 2001 Jun, 45(6), 1836 - 42 Genotypic and phenotypic resistance patterns of human immunodeficiency virus type 1 variants with insertions or deletions in the reverse transcriptase (RT): multicenter study of patients treated with RT inhibitors; Masquelier B et al.; Genomic rearrangements in the 5' part of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) have been involved in multidrug resistance to nucleoside RT inhibitors (NRTI) . We carried out a retrospective, multicenter study to investigate the prevalence, variability, and phenotypic consequences of such rearrangements . Data concerning the HIV-1 RT genotype and the biological and clinical characteristics of NRTI-treated patients were collected from 10 virology laboratories . Sensitivities of the different HIV-1 variants to RT inhibitors were analyzed in a single-cycle recombinant virus assay . Fifty-two of 2,152 (2.4%) RT sequences had a rearrangement in the 5' part of the RT, with an extensive molecular variation . The number of codons inserted between positions 68 and 69 ranged from 1 (3 samples) or 2 (41 samples) to 5 and 11 in one case each . In four cases, codon 67 was deleted . High levels of phenotypic resistance to zidovudine (AZT), lamivudine (3TC), stavudine (d4T), abacavir (ABC), and didanosine (ddI) were found in 95, 92, 72, 62, and 15% of the 40 samples analyzed, respectively . Resistance to AZT, d4T, and ABC could be found in the absence of the T215Y/F mutations . Resistance to 3TC could develop in the absence of specific mutations . Low-level resistance to ddI was noticed in 40% of the patients . The deletions of codon 67 seemed to have little effect on NRTI sensitivity . Most of the rearrangements were shown to contribute to cross-resistance to NRTI . The results regarding susceptibility to ddI raise the question of the interpretation of the phenotypic data concerning this drug. Antimicrob Agents Chemother, 2001 Jun, 45(6), 1746 - 50 In vitro activities of antibiotics against Plasmodium falciparum are inhibited by iron; Pradines B et al.; The in vitro activities of cyclines (tetracycline, doxycycline, minocycline, oxytetracycline, and rolitetracycline), macrolides (erythromycin, spiramycin, roxithromycin, and lincomycin), quinolones (norfloxacin and ofloxacin), rifampin, thiamphenicol, tobramycin, metronidazole, vancomycin, phosphomycin, and cephalosporins (cephalexin, cefaclor, cefamandole, cefuroxime, ceftriazone, cefotaxime, and cefoxitin) were evaluated on Plasmodium falciparum clones, using an isotopic, micro-drug susceptibility test . Only tetracyclines, macrolides, quinolones, and rifampin demonstrated in vitro activity against P . falciparum, which increased after a prolonged exposure (96 or 144 h) . In the presence of iron (FeCl(3)), only the activities of tetracyclines and norfloxacin were decreased . Their in vitro activity against intraerythrocytic stages of multidrug-resistant P . falciparum and their efficacy in vivo favor the use of antibiotics as antimalarial drugs . However, due to their slow antimalarial action and to the fact that they act better after prolonged contact, they probably need to be administered in conjunction with a rapidly acting antimalarial drug, such as a short course of chloroquine or quinine. Am J Physiol Gastrointest Liver Physiol, 2001 Jun, 280(6), G1261 - 73 Expression of multidrug resistance-associated protein 2 in small intestine from pregnant and postpartum rats; Mottino AD et al.; We analyzed the expression of multidrug resistance-associated protein 2 (mrp2) in the small intestine of control female rats and in rats during late pregnancy (19-20 days of pregnancy) and lactation (2-4, 10-14, and 21 days after delivery) . Western blot analysis was performed on brush-border membranes prepared from different regions of the small intestine . Expression of mrp2 was maximal in the proximal segments for all experimental groups, was preserved in pregnant rats, and increased by 100% in postpartum rats by late lactation with respect to control animals . Northern blot analysis of mrp2 mRNA revealed a positive correlation with protein levels . Transport of S-glutathione-dinitrophenol (DNP-SG) from the intestinal cell to the lumen was analyzed in the everted intestinal sac model . Secretion of DNP-SG was not altered in pregnant rats but increased in lactating animals by late lactation . Intestinal mrp2 mRNA, protein, and transport activity are increased in lactating rats, suggesting that this may represent an adaptive mechanism to minimize the toxicity of dietary xenobiotics in response to increased postpartum food consumption. Int J Cancer, 2001 Jun 15, 92(6), 777 - 83 Role of glutathione S-transferase P1, P-glycoprotein and multidrug resistance-associated protein 1 in acquired doxorubicin resistance; Harbottle A et al.; While P-glycoprotein (Pgp) and multidrug resistance-associated protein 1 (MRP1) are known to be important in acquired doxorubicin resistance, the role of glutathione S-transferases (GST) remains unclear . Our study assessed roles of these 3 factors in a human drug-sensitive carcinoma cell line (HEp2), a subclone made resistant by prolonged incubation in doxorubicin (HEp2A), and HEp2 cells stably transfected with human GSTP1 . Drug-resistant HEp2A cells showed greater total GST activity, GSTP class enzyme expression, Pgp expression, MRP1 transcript expression, drug efflux and at least 13-fold greater resistance to doxorubicin than the parent HEp2 cell line . GSTM class enzyme expression was similar in both cell types, while GSTA class enzymes were not detected . In the resistant HEp2A cells, cytotoxicity was markedly enhanced by the Pgp/MRP inhibitor verapamil at low doxorubicin concentrations . The GST inhibitor curcumin also enhanced cytotoxicity in HEp2A cells when the Pgp/MRP efflux barrier had been reversed by verapamil or overcome by high doxorubicin concentrations . In addition, curcumin had a chemosensitising effect at low doxorubicin concentrations in HEp2 cells . Stable transfection of HEp2 cells with human GSTP1 increases doxorubicin resistance 3-fold over control cells . Our study indicates involvement of GSTP enzymes as well as efflux mechanisms in the acquired doxorubicin-resistance phenotype . Clin Cancer Res, 2001 May, 7(5), 1429 - 37 BMS-247550: a novel epothilone analog with a mode of action similar to paclitaxel but possessing superior antitumor efficacy; Lee FY et al.; BMS-247550, a novel epothilone derivative, is being developed by Bristol-Myers Squibb Company (BMS) as an anticancer agent for the treatment of patients with malignant tumors . BMS-247550 is a semisynthetic analogue of the natural product epothilone B and has a mode of action analogous to that of paclitaxel (i.e., microtubule stabilization) . In vitro, it is twice as potent as paclitaxel in inducing tubulin polymerization . Like paclitaxel, BMS-247550 is a highly potent cytotoxic agent capable of killing cancer cells at low nanomolar concentrations . Importantly, BMS-247550 retains its antineoplastic activity against human cancers that are naturally insensitive to paclitaxel or that have developed resistance to paclitaxel, both in vitro and in vivo . Tumors for which BMS-247550 demonstrated significant antitumor activity encompass both paclitaxel-sensitive and -refractory categories, i.e., (a) paclitaxel-resistant: HCT116/VM46 colorectal (multidrug resistant), Pat-21 breast and Pat-7 ovarian carcinoma (clinical isolates; mechanisms of resistance not fully known), and A2780Tax ovarian carcinoma (tubulin mutation); (b) paclitaxel-insensitive: Pat-26 human pancreatic carcinoma (clinical isolate) and M5076 murine fibrosarcoma; and (c) paclitaxel sensitive: A2780 ovarian, LS174T, and HCT116 human colon carcinoma . In addition, BMS-247550 is p.o . efficacious against preclinical human tumor xenografts grown in immunocompromised mice or rats . Schedule optimization studies indicate that BMS-247550 is efficacious when administered frequently (every 2 days x 5) or intermittently (every 4 days x 3 or every 8 days x 2) . These efficacy data demonstrate that BMS-247550 has the potential to surpass Taxol in both clinical efficacy and ease of use (i.e., less frequent treatment schedule and/or oral administration). Clin Cancer Res, 2001 May, 7(5), 1221 - 9 A phase I trial of doxorubicin, paclitaxel, and valspodar (PSC 833), a modulator of multidrug resistance; Advani R et al.; PURPOSE: P-glycoprotein is an efflux pump for many drugs including doxorubicin and paclitaxel . This study evaluated the coadministration of these drugs with the P-glycoprotein inhibitor valspodar (PSC 833) with the aim of determining: (a) maximum tolerated doses (MTDs) of doxorubicin followed by paclitaxel (DP); (b) the MTD of DP combined with PSC 833 (DPV), without and with filgrastim (G-CSF); and (c) the pharmacokinetic interactions of PSC 833 with doxorubicin and paclitaxel . EXPERIMENTAL DESIGN: For the first cycle, patients received doxorubicin as a 15-min infusion followed by paclitaxel as a 1-h infusion . For the second cycle, patients received reduced doses of DP with PSC 833 at 5 mg/kg p.o., four times a day for 12 doses . RESULTS: Thirty-three patients with various refractory malignancies were enrolled and assessable . The MTD of DP without PSC 833 was 35 mg/m(2) doxorubicin and 150 mg/m(2) paclitaxel . The MTD of DPV without G-CSF was 12.5 mg/m(2) doxorubicin and 70 mg/m(2) paclitaxel . The dose-limiting toxicity for both DP and DPV was neutropenia without thrombocytopenia . With G-CSF, the MTD for DPV was 20 mg/m(2) doxorubicin and 90 mg/m(2) paclitaxel . No grade 4 nonhematological toxicities were observed . Five partial and two minor tumor remissions were observed . Paired pharmacokinetics with and without PSC 833 revealed substantial drug interactions with both doxorubicin and paclitaxel . CONCLUSIONS: PSC 833 can be administered safely with doxorubicin and paclitaxel . The pharmacokinetic profiles of these drugs are significantly affected by PSC 833, requiring approximately 60% dose reductions for equivalent degrees of myelosuppression. Br J Pharmacol, 2001 May, 133(2), 306 - 14 Effects of chemically modified tetracyclines (CMTs) in sensitive, multidrug resistant and apoptosis resistant leukaemia cell lines; Tolomeo M et al.; Recently discovered chemically modified tetracyclines (CMTs) have shown in vitro and in vivo anti-proliferative and anti-tumour activities . Here, we evaluated in vitro the anti-proliferative and apoptotic activity of six different dedimethylamino chemically modified tetracyclines (CMT-1, CMT-3, CMT-5, CMT-6, CMT-7 and CMT-8) in sensitive and multidrug resistant myeloid leukaemia cells (HL60 and HL60R) in vitro . Three of these compounds (CMT-5, CMT-6, CMT-7) showed low cytotoxic activity both in sensitive and in resistant cells, CMT-3 was endowed with a high anti-proliferative activity only in sensitive cells and was moderately effective as apoptosis inducing agent, with an activity similar to that shown by doxycycline . On the contrary, CMT-1 and CMT-8 were very effective as programmed cell death inducing agents . The apoptotic pathway activated by these compounds involved the activation of caspases, especially caspase-9 and, for CMT-1, also the activation of FAS: Interestingly CMT-8, but not CMT-1, was able to induce apoptosis in multidrug resistant HL60R and in Fas-ligand resistant HUT78B1 cell lines . These properties, together with others previously described (e.g . anti-metastatic and anti-osteolytic activities), suggest that CMT-8 may have important applications in the clinical management of cancer . The comparative analysis of structure-activity relationship of CMT-8 and doxycycline suggests that the C-5 hydroxy moiety may play an important role in conferring activity in multidrug resistant cells . These findings appear to support the hypothesis that CMT-8 may represent an interesting lead for the development of a new class of potent apoptosis inducer agents active in multidrug resistant and Fas-ligand resistant malignancies. Hepatol Res, 2001 Jun, 20(2), 221 - 231 Biliary excretion of phenolphthalein glucuronide in the rat; Ogasawara T et al.; To examine the substrate specificity of an ATP-dependent organic anion transporter, the multidrug resistance protein 2, we examined the effects of various bile acid conjugates and organic anions on the biliary excretion of phenolphthalein glucuronide, a hydrophilic glucuronide conjugate, in rats . Biliary phenolphthalein glucuronide excretion was markedly inhibited by taurolithocholate-3-sulfate and ursodeoxycholate-3-O-glucuronide . In contrast, ursodeoxycholate-3,7-disulfate and pravastatin only slightly inhibited and cefpiramide did not inhibit biliary phenolphthalein glucuronide excretion . Biliary excretion of sulfobromophthalein, leukotriene C(4) and pravastatin was inhibited by phenolphthalein glucuronide infusion to some extent . These findings suggest that phenolphthalein glucuronide is a relatively low affinity substrate for the multidrug resistance protein 2. Hepatol Res, 2001 Jun, 20(2), 216 - 220 Biliary excretion of temocapril in zone 1- and zone 3-injured rat; Takikawa H et al.; Temocapril is a prodrug of an angiotensin-converting enzyme inhibitor, temocaprilat, a substrate of multidrug resistance protein 2 . Hepatocytes in zone 1 play a role in the uptake and biliary excretion of bile acids under physiological condition, and those in zone 3 may play a role only with their high-dose load . To investigate the pharmacokinetics of temocapril in liver injury, biliary excretion of temocapril was studied in zone 1- and zone 3-injured rats, caused by allyl alcohol and bromobenzene, respectively . Biliary excretion of a tracer dose of radiolabeled temocapril was delayed both in zone 1 and the zone 3 injury, but the extent of inhibition was more prominent in zone 3 injury . Since biliary excretion of organic anions was decreased only in zone 1 injury in our previous study, the present findings indicate that decreased biliary excretion of temocaprilat in zone 3 injury is caused by the inhibition of the metabolism from temocapril to temocaprilat. Farmaco, 2001 Jan-Feb, 56(1-2), 145 - 8 Physicochemical properties in pharmacokinetic lead optimization; Kramer SD et al.; The ADME (absorption, distribution in the body, metabolism and elimination from the body) profile of a drug determines its pharmacokinetics in the body . Modern drug design includes the modeling of pharmacokinetically favorable behavior . The pharmacokinetic parameters of most interest concern intestinal absorption, blood-brain barrier (BBB) passage and metabolism . Traditionally, experimental parameters such as partition coefficients and chromatographic capacity factors have been used for the estimation of intestinal absorption or BBB passage of newly synthesized compounds . Several studies have shown a sigmoidal relationship between intestinal absorption and lipophilicity . The latter is usually expressed by the apparent partition coefficient log D in a biphasic system at physiological pH or by the affinity to a lipophilic phase determined by chromatographic techniques . In contrast, structure-based descriptors need no experimental investigation of the compound studied . The most relevant descriptors give information on hydrogen-bonding characteristics and molecular volume . In recent years, attempts have been made to recognize substrates for multidrug resistance proteins by their structure characteristics without crucial success . There is evidence that multidrug resistance is not only driven by direct protein-substrate recognition, but also by the behavior of the compound in the lipid environment of the protein. Folia Med (Plovdiv), 2000, 42(3), 5 - 10 Cytogenetic abnormalities in chronic lymphocytic leukemia; Karnolsky IN; Trisomy of chromosome 12 is one of the commonest cytogenetic abnormalities in the karyotype in chronic lymphocytic leukemia (CLL) . It is associated with atypical morphology of lymphocytes, progressing disease and poor survival . A high incidence abnormality in the B-cell CLL is deletion of chromosome 13 (13q14) detected by using modern diagnostic methods such as southern blot hybridization and fluorescence in situ hybridization . It occurs in 51% of the CLL patients and in as much as 70% in mantle-cell lymphoma . The deletion of 13q14.3 affects a locus telomeric to the RB1 gene (retinoblastoma gene) and the marker D13S25 which bear relation to a candidate tumour suppressor gene . Also common are the chromosome 14 abnormalities which are expressed as the translocation t(11;14)(q13;q32) and which correlate with a high leukocytes count, adverse response to cytostatic therapy and increased risk of prolymphocytic proliferation . The oncogene BCL-1 is activated in this translocation . Deletions of the long arm of chromosome 18 (18q21)(q32;q13.1) activate the BCL-2 oncogene, while the translocation t(14;19)(q32;q13.1) activates the BCL-3 oncogene . Essential role in the pathogenesis of CLL is played by the aberrations in chromosome 17 and the p53 mutations (17p13.1) . The gene p53 is defined as a tumour suppressor gene; mutations of this gene leads to a CLL characterized with rapid progression, aggressive course, poor prognosis and low survival . The deletions in chromosome 7 are associated with the multidrug resistance gene which causes resistance to doxorubicin, vinblastine and colchicine . All these abnormalities are characteristic of the B-cell chronic lymphocytic leukemia . In the T-cell leukemia characteristic deletions are 11q22-q23, a.14q23.1, as well as the inversion inv(14)(11q32) and some rarer aberrations. Cancer, 2001 May 15, 91(10), 1940 - 8 Expression of P-glycoprotein, multidrug resistance-associated protein 1, and lung resistance-related protein in human soft tissue sarcomas before and after hyperthermic isolated limb perfusion with tumor necrosis factor-alpha and melphalan; Komdeur R et al.; BACKGROUND: Multidrug resistance (MDR) is associated with expression of P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1), and lung resistance-related protein (LRP) . Tumor necrosis factor (TNF-alpha) is able to modify the expression of these three proteins in different cell types . The effect of TNF-alpha in the clinical situation on patients with soft tissue sarcomas (STS) is indeterminate . METHODS: Thirty-seven patients with a locally advanced extremity STS underwent hyperthermic isolated limb perfusion (HILP) with TNF-alpha and melphalan; 15 patients received additional interferon gamma . Clinical and histologic responses were documented and used to define the overall response . Samples before and after HILP were analyzed immunohistochemically for P-gp, MRP1, and LRP . Samples were scored as negative or positive (< or = 5% or > 5% positive tumor cells) . RESULTS: Six patients had an overall complete response, 25 patients had a partial response, and 4 patients with STS revealed no change; in 2 patients, the response remained unclear . The percentage STS samples that were positive for all three proteins dropped from 92% before HILP to 85% after HILP . P-gp positive samples were encountered more often than MRP1 positive samples (P < 0.05) . The percentage of samples that were negative for all three MDR proteins increased after HILP from 6% to 16% . MDR status had no significant correlation with tumor response . CONCLUSIONS: HILP with TNF-alpha and melphalan results in excellent overall tumor response in patients with locally advanced STS . STS more often are positive for P-gp than for MRP1 . MDR status in patients with STS is not predictive for tumor response after HILP . Data from the current study suggest that the combination of TNF-alpha and melphalan does not induce MDR positive STS: a result with clinical importance when consecutive, adjuvant, doxorubicin-containing chemotherapy is considered . Jpn J Cancer Res, 2001 Apr, 92(4), 452 - 8 Expression of multidrug resistance-related transporters in human breast carcinoma; Kanzaki A et al.; The expression levels of mRNA for multidrug resistance 1 (MDR1) gene, multidrug resistance protein 1 (MRP1), lung resistance-related protein (LRP) and breast cancer resistance protein (BCRP), which confer multidrug resistance in vitro, were examined in 43 untreated breast carcinoma patients, of whom 38 subsequently received doxorubicin-based chemotherapy after surgery, in order to elucidate the roles of these genes in drug resistance in vivo . The mRNA levels were determined using a semi-quantitative reverse-transcription polymerase chain reaction method in breast carcinoma tissues including at least 80% carcinoma cells . The expression level of BCRP gene was low and did not vary markedly in comparison with that of MDR1, MRP1 or LRP gene . The expressions of MDR1 and MRP1 genes were correlated with each other, but the expression of BCRP or LRP gene did not correlate with that of other genes . These four gene expressions were independent of age, TNM categories and the status of progesterone or estrogen receptor . The expression levels of these four genes were not related to the relapse or prognosis of the 38 patients treated with doxorubicin-based chemotherapy . P-glycoprotein (P-gp) / MDR1, MRP1 and LRP may play more important roles than BCRP in chemotherapy of human breast carcinoma. Cancer Chemother Pharmacol, 2001 Apr, 47(4), 327 - 32 Continuous infusion prochlorperazine: pharmacokinetics, antiemetic efficacy, and feasibility of high-dose therapy; Morgan RJ Jr et al.; PURPOSE: The purpose of these sequential phase I studies was to evaluate the antiemetic efficacy and pharmacokinetics of high-dose continuous infusion prochlorperazine . METHODS: A total of 52 patients with advanced cancer were treated in two sequential phase I studies utilizing high-dose prochlorperazine . In study 1, designed to investigate the antiemetic effects of dose-intensive prochlorperazine, various cisplatin-based multiagent chemotherapeutic regimens were administered in combination with escalating doses of prochlorperazine . In study 2, a fixed dose of cisplatin (60 mg/m2) was administered over 24 h as a continuous intravenous infusion in combination with infusional high-dose prochlorperazine . Antiemetic efficacy in the first trial was assessed in terms of the number of episodes of nausea, retching, and/or emesis during the 24 h following cisplatin administration . The pharmacokinetics of high-dose prochlorperazine were evaluated in eight patients treated in study 2 at the two dose levels below those at which dose-limiting toxicity was noted . RESULTS: The maximally tolerated dose of prochlorperazine in combination with cisplatin (60 mg/m2 administered as a continuous infusion over 24 h) was 24 mg/h . The dose-limiting toxicity was grade 4 agitation and confusion noted in one patient treated at 26 mg/h . This patient died 3 days following cessation of chemotherapy due to the toxicity of the regimen in combination with the debilitating pulmonary effects of the disease . The mean end of infusion prochlorperazine level at the 24 mg/h dose level was 1.1 microM, a concentration previously reported to be consistent with the reversal of the multidrug resistance phenotype . Two partial responses were observed in study 2 . CONCLUSIONS: We conclude that the antiemetic efficacy of high-dose infusional prochlorperazine does not appear to be improved over more convenient bolus administration . However, prochlorperazine levels consistent with those required in vitro for drug resistance reversal are attainable within the dose range having a tolerable toxicity profile. Hepatology, 2001 May, 33(5), 1194 - 205 Etiologic significance of defects in cholesterol, phospholipid, and bile acid metabolism in the liver of patients with intrahepatic calculi; Shoda J et al.; Intrahepatic calculi, highly prevalent in the Far East, including Japan, are characterized clinically by chronic proliferative cholangitis with frequent stone recurrences . Intrahepatic calculi consist of 2 groups, i.e., brown pigment stones, including a high cholesterol content, and cholesterol stones, with the former predominating . To gain insights into the pathogenesis of intrahepatic calculi, cholesterol and bile acid biosynthesis, as well as alterations in intracellular transport and/or canalicular secretion of phospholipid and bile acid were investigated in liver of patients with intrahepatic calculi . Enzyme activities of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase were increased (12.8 +/- 1.9 pmol/min/mg protein, mean +/- SEM vs . 5.5 +/- 0.4 in controls; P < .01) and cholesterol 7 alpha-hydroxylase activities were decreased (1.3 +/- 0.4 vs . 4.9 +/- 0.6; P < .01) in liver specimens of patients with brown pigment stones . In addition, messenger RNA (mRNA) levels of multidrug resistance P-glycoprotein 3 (MDR3 Pgp) and phosphatidylcholine transfer protein (PCTP) were markedly low in the liver specimens compared with the levels in specimens of control subjects, gallbladder stone patients, and patients with obstructive cholestasis . The protein levels and the immunohistochemical staining were decreased for MDR3 Pgp and PCTP in the liver . Consistently, the concentrations of phospholipid were markedly reduced in the hepatic bile from both affected and unaffected hepatic segments . In patients with intrahepatic calculi, biliary cholesterol supersaturation and the formation of cholesterol-rich brown pigment as well as cholesterol stones may be attributed to decreased hepatic transport and biliary secretion of phospholipids, in the setting of increased cholesterogenesis and decreased bile acid synthesis. J Infect Dis, 2001 Jun 1, 183(11), 1688 - 93 Epub 2001 Apr 23. Vertical transmission of multidrug-resistant human immunodeficiency virus type 1 (HIV-1) and continued evolution of drug resistance in an HIV-1-infected infant; Johnson VA et al.; To confirm the vertical transmission of multidrug-resistant (MDR) human immunodeficiency virus type 1 (HIV-1) and to assess its impact on further evolution of drug-resistant virus in an infant, proviral DNA amplified from infected peripheral blood mononuclear cell cultures was sequenced to identify reverse transcriptase (RT) and protease (PR) mutations . The infant had proviral DNA with evidence of RT mutations (M41L, L74V, and T215Y) and 3 PR substitutions (K20R, M36I, and V82A) . After delivery, the mother's proviral DNA had the same substitutions . Phylogenetic analyses of these HIV-1 RT and PR sequences indicated epidemiological linkage . Plasma drug susceptibility was determined by using a recombinant virus assay . Plasma HIV-1 obtained after the infant's birth demonstrated reduced susceptibility to zidovudine and ritonavir . Thus, vertical transmission of MDR HIV-1 was demonstrated in the setting of detectable maternal plasma viremia . Further accumulation of broad MDR in the infant's virus to 3 antiretroviral classes occurred, despite postnatal therapy. Biochim Biophys Acta, 2001 Feb 9, 1510(1-2), 414 - 25 Trifluoperazine induces domain formation in zwitterionic phosphatidylcholine but not in charged phosphatidylglycerol bilayers; Hendrich AB et al.; The interaction of trifluoperazine with the zwitterionic lipids dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine and with anionic dimyristoylphosphatidylglycerol was studied by means of microcalorimetry and fluorescence spectroscopy . Intercalation of drug molecules into the lipid bilayers was confirmed by the observed differential scanning calorimetry peak broadening and the decrease in chain-melting temperatures . For trifluoperazine:lipid mole ratios higher than 0.4 and 0.6 (for dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine, respectively) the deconvolution of transition profiles into two Gaussian components was possible, which suggests phase separation in the studied mixtures . Deconvolution of the thermograms was not possible for any of the drug:dimyristoylphosphatidylglycerol mole ratios studied . To confirm the existence of phase separation in trifluoperazine-phosphatidylcholine mixtures fluorescence spectroscopy experiments were performed using Laurdan as a probe . From the generalised polarisation versus excitation wavelength dependences, recorded at different temperatures, we conclude that a phase separation occurs in the gel state of the studied trifluoperazine-phosphatidylcholine mixtures . We attribute the existence of domains in the bilayer to the dissimilar interactions of two protonation forms of trifluoperazine with phosphatidylcholine molecules . Structural defects present at domain boundaries could be related to the trifluoperazine induced increase of membrane permeability and fluidity . This may partially explain the mechanism of multidrug resistance modulation by trifluoperazine. Orv Hetil, 2001 Apr 22, 142(16), 833 - 7 {Molecular biology examination in chronic lymphocytic leukemia}; Telek B et al.; Chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia characterised by the accumulation of monoclonal CD5 + B-lymphocytes . The pathogenesis and the biology of CLL is complex and many details are still unknown . Several molecular biological methods have been used in the investigation of CLL, among them the study of apoptosis appears to be one of the most important . Initial experiences obtained by the spontaneous and fludarabine induced apoptosis, multidrug resistance (MDR)-test and fluorescent in situ hybridization (FISH) are reported by the authors . Apoptosis of CLL cells could be induced by fludarabine, while more studies should be performed to determine the exact role of MDR-test and FISH. Pharmacogenetics, 2001 Apr, 11(3), 217 - 21 MDR1 pharmacogenetics: frequency of the C3435T mutation in exon 26 is significantly influenced by ethnicity; Ameyaw MM et al.; P-glycoprotein (PGP), the product of the multidrug resistance gene (MDR1), acts as an energy-dependent efflux pump that exports its substrates out of the cell . PGP expression is an important factor regulating absorption of a wide variety of medications . It has also been associated with intrinsic and acquired cross resistance to a number of structurally unrelated anticancer drugs . A single nucleotide polymorphism (SNP) in exon 26 of the MDR1 gene, C3435T, was recently correlated with PGP protein levels and substrate uptake . Individuals homozygous for the T allele have more than four-fold lower PGP expression compared with CC individuals . As overexpression of PGP has been associated with altered drug absorption, therapy-resistant malignancies, and lower concentrations of HIV-1 protease inhibitors, this SNP may provide a useful approach to individualize therapy . To facilitate clinical application throughout the world, 1280 subjects from 10 different ethnic groups were evaluated for this SNP using the polymerase chain reaction-restriction fragment length polymorphism assay and the genotype and allele frequency for each group were ascertained . Marked differences in genotype and allele frequency were apparent between the African populations and the Caucasian/Asian populations (P < 0.0001) . The Ghanaian, Kenyan, African American and Sudanese populations studied had frequencies of 83%, 83%, 84% and 73%, respectively, for the C allele . The British Caucasian, Portuguese, South-west Asian, Chinese, Filipino and Saudi populations had lower frequencies of the C allele compared to the African group (48%, 43%, 34%, 53%, 59%, and 55%, respectively) . The high frequency of the C allele in the African group implies overexpression of PGP and may have important therapeutic and prognostic implications for use of PGP dependent drugs in individuals of African origin. J Nucl Med, 2001 Apr, 42(4), 646 - 54 In vitro and in vivo tracer characteristics of an established multidrug-resistant human colon cancer cell line; Lorke DE et al.; 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) has been suggested as a tracer for the scintigraphic detection of multidrug resistance (MDR) . The aim of this study was to compare MDR characteristics in vitro and in vivo by immunohistochemic and functional uptake assays in established tumor cell lines cultured and grown in severe combined immunodeficient (SCID) mice . METHODS: The presence of MDR was assessed in vitro in drug-resistant HT-29(mdr1) colon carcinoma cells and in nonresistant HT-29(par) cells by JSB-1 immunohistochemistry, uptake of the fluorescent dye Rhodamine 123, and quantitative measurement of 99mTc-MIBI accumulation . For in vivo imaging, SCID mice bearing subcutaneous xenografts of these cell lines were injected with 99mTc-MIBI and 18F-FDG for scintigraphic and PET examination . After imaging, tumors were analyzed by immunohistochemistry and electron microscopy . RESULTS: All HT-29(mdr1) cells cultured in vitro exhibited distinct JSB-1 immunoreactivity, although to a variable degree, whereas HT-29(par) cells were completely devoid of JSB-1 staining . Rhodamine 123 accumulated poorly in HT-29(mdr1) cells but strongly in HT-29(par) cells . Accumulation of 99mTc-MIBI was 0.05% +/- 0.01% of the activity of the external medium in HT-29(mdr1) cells, but about eight times higher in HT-29(par) cells (0.40% +/- 0.09%), a very low percentage compared with other tumor cell lines . No difference in 201TlCl accumulation was observed between both cell lines . In vivo, neither HT-29(par) nor HT-29(mdr1) tumors grown in SCID mice could be detected by 99mTc-MIBI scintigraphy . In FDG PET, both HT-29(mdr1) and HT-29(par) tumors were clearly visible . FDG uptake was, however, markedly higher in HT-29(par) than in HT-29(mdr1) tumors . Both tumor types were poorly vascularized, as shown histologically . JSB-1 immunoreactivity was absent in all HT-29(par) tumors examined, whereas the majority of HT-29(par) tumor cells were stained . Electron microscopy showed that HT-29(par) tumors contained significantly less mitochondria than hepatocytes of the SCID mouse liver, which displayed high 99mTc-MIBI uptake in our scintigraphy studies . CONCLUSION: Sufficient 99mTc-MIBI uptake is the major prerequisite for distinguishing successfully between drug-resistant and sensitive cells . Negative 99mTc-MIBI scintigrams are not necessarily associated with MDR expression . In some tumors, FDG may be an in vivo marker for MDR as suggested by PET. Biochem J, 2001 May 15, 356(Pt 1), 71 - 5 Role of glycine-534 and glycine-1179 of human multidrug resistance protein (MDR1) in drug-mediated control of ATP hydrolysis; Szakacs G et al.; The human multidrug resistance protein (MDR1) (P-glycoprotein), a member of the ATP-binding cassette (ABC) family, causes multidrug resistance by an active transport mechanism, which keeps the intracellular level of hydrophobic compounds below a cell-killing threshold . Human MDR1 variants with mutations affecting a conserved glycine residue within the ABC signature of either or both ABC units (G534D, G534V, G1179D and G534D/G1179D) were expressed and characterized in Spodoptera frugiperda (Sf9) cell membranes . These mutations caused a loss of measurable ATPase activity but still allowed ATP binding and the formation of a transition-state intermediate (nucleotide trapping) . In contrast with the wild-type protein, in which substrate drugs accelerate nucleotide trapping, in the ABC signature mutants nucleotide trapping was inhibited by MDR1-substrate drugs, suggesting a miscommunication between the drug-binding site(s) and the catalytic domains . Equivalent mutations of the two catalytic sites resulted in a similar effect, indicating the functional equivalence of the two sites . On the basis of these results and recent structural information on an ABC-ABC dimer {Hopfner, Karcher, Shin, Craig, Arthur, Carney and Tainer (2000) Cell 101, 789-800}, we propose a key role of these glycine residues in the interdomain communication regulating drug-induced ATP hydrolysis. Pharm Res, 2001 Jan, 18(1), 39 - 44 A human lymphocyte based ex vivo assay to study the effect of drugs on P-glycoprotein (P-gp) function; Parasrampuria DA et al.; PURPOSE: The effect of drugs on P-glycoprotein (P-gp) is normally studied in transfected or overexpressing cell lines derived from tumor cells or animal tissue . We wanted to develop an assay using normal healthy human tissue to study and characterize the drug-transporter interaction . METHODS: Lymphocytes were isolated from healthy human blood . The effect of inhibitors of P-gp (cyclosporine, tacrolimus, verapamil, quinidine, vinblastine) and of other transporters (indomethacin, probenecid, sulfinpyrazone) on intracellular accumulation of rhodamine 123 was evaluated by flow cytometry . RESULTS: The efflux of rhodamine 123 was inhibited by P-gp inhibitors in a saturable, concentration-dependent manner . The potency of inhibition of P-gp was cyclosporine > tacrolimus > quinidine > verapamil > vinblastine . Vinblastine inhibited P-gp at lower concentrations, whereas at high concentrations, there was an activation of rhodamine 123 efflux from lymphocytes . The multidrug resistance associated protein (MRP) inhibitors, sulfinpyrazone and probenecid, did not have any significant effect on intracellular accumulation of rhodamine 123, but indomethacin caused a concentration-dependent increase in retention of rhodamine 123, indicating the involvement of other uncharacterized transporters . CONCLUSIONS: Lymphocytes can serve as a model tissue for studying modulation of P-gp activity by drugs . Both inhibitors and inducers of P-gp activity can be evaluated. Int J Tuberc Lung Dis, 2001 May, 5(5), 413 - 8 Risk factors for nosocomial transmission of multidrug-resistant tuberculosis due to Mycobacterium bovis among HIV-infected patients; Cobo J et al.; OBJECTIVE: To identify risk factors for transmission of multidrug-resistant tuberculosis (MDR-TB) among hospitalized human immunodeficiency virus (HIV) infected patients exposed during a nosocomial outbreak . DESIGN: Case control study . Cases were HIV-infected patients with MDR-TB due to Mycobacterium bovis (MDR-TBMb) who acquired the disease after exposure to an MDR-TBMb patient in an hospital ward . Controls were HIV-infected patients exposed to a case of MDR-TBMb in an hospital ward but who did not develop MDR-TBMb during the follow-up . RESULTS: Nineteen cases and 31 controls were included . CD4 cell counts were significantly lower among cases . Exposure in the infectious diseases ward or exposure to the index patient were associated with development of MDR-TBMb, while exposure during a single-room hospital stay and exposure in the respiratory isolation ward were associated with non-development of MDR-TBMb . A multiple regression logistic model showed that only a CD4 cell count below 50/microL and exposure to the index patient increased the risk of developing MDR-TBMb (P < 0.05) . Hospitalization in a single room seemed to protect HIV-infected patients from developing nosocomial MDR-TBMb (P = 0.052) . CONCLUSIONS: Over classic risk factors, such as length of exposure or sharing a room with a case, severe immunosuppression independently increases the risk of MDR-TB transmission in the context of a nosocomial MDR-TB outbreak among HIV-infected patients . This information must be considered in the management of tuberculosis outbreaks . Patients with CD4 cell counts below 50/microL should be the principal group targeted for prevention strategies in nosocomial outbreaks. Anticancer Drugs, 2001 Apr, 12(4), 359 - 67 Antitumor activity of XR5944, a novel and potent topoisomerase poison; Stewart AJ et al.; Inhibitors of topoisomerases are widely used in the treatment of cancer, including inhibitors of topoisomerase I (camptothecin analogs such as irinotecan and topotecan) and topoisomerase II (etoposide and doxorubicin) . The novel bis-phenazine, XR5944, is a joint inhibitor of topoisomerase I and II as shown by the stabilization of topoisomerase-dependent cleavable complexes . XR5944 demonstrated exceptional activity against human and murine tumor cells in vitro and in vivo . In a range of cell lines XR5944 (IC50 0.04-0.4 nM) was significantly more potent than TAS-103, originally proposed as a joint topoisomerase I and II inhibitor, as well as agents specific for topoisomerase I or II (topotecan, doxorubicin and etoposide) . In addition, XR5944 was unaffected by atypical drug resistance and retained significant activity in cells overexpressing P-glycoprotein or multidrug resistance-associated protein . Antitumor efficacy of XR5944 was demonstrated in human carcinoma xenograft models (H69 small cell lung cancer and HT29 colon) . In the HT29 model, which is relatively unresponsive to chemotherapy, XR5944 (15 mg/kg i.v., q4dx3) induced tumor regression in the majority of animals (six of eight), whereas TAS-103, dosed at its maximum tolerated dose (45 mg/kg i.v., q7dx3), only induced a delay in tumor growth compared with control animals . In the H69 model, low doses of XR5944 (5 mg/kg i.v., qdx5/week for 2 weeks or 10-15 mg/kg i.v., q4dx3), induced complete tumor regression in the majority of animals . In contrast, topotecan (20 mg/kg i.v., q4dx3) or etoposide (30 mg/kg i.v., q5dx5) only slowed the tumor growth rate . These studies show that XR5944 is a highly active novel anticancer agent that is well tolerated at efficacious doses. Eur J Cancer, 2001 May, 37(8), 1041 - 52 Selection with melphalan or paclitaxel (Taxol) yields variants with different patterns of multidrug resistance, integrin expression and in vitro invasiveness; Liang Y et al.; A melphalan-resistant variant (Roswell Park Memorial Institute (RPMI)-2650Ml) and a paclitaxel-resistant variant (RPMI-2650Tx) of the drug-sensitive human nasal carcinoma cell line, RPMI-2650, were established . The multidrug resistance (MDR) phenotype in the RPMI-2650Tx appeared to be P-glycoprotein (PgP)-mediated . Overexpression of multidrug resistant protein (MRP) family members was observed in the RPMI-2650Ml cells, which were also much more invasive in vitro than the parental cell line or the paclitaxel-resistant variant . Increased expression of alpha(2), alpha(5), alpha(6), beta(1) and beta(4) integrin subunits, decreased expression of alpha(4) integrin subunit, stronger adhesion to collagen type IV, laminin, fibronectin and matrigel, increased expression of MMP-2 and MMP-9 and significant motility compared with the parental cells were observed, along with a high invasiveness in the RPMI-2650Ml cells . Decreased expression of the alpha(2) integrin subunit, decreased attachment to collagen type IV, absence of cytokeratin 18 expression, no detectable expression of gelatin-degrading proteases and poor motility may be associated with the non-invasiveness of the RPMI-2650Tx variant . These results suggest that melphalan exposure can result in not only a MDR phenotype, but could also make cancer cells more invasive, whereas paclitaxel exposure resulted in MDR without increasing the in vitro invasiveness in the RPMI-2650 cells. Int J Tuberc Lung Dis, 2001 Apr, 5(4), 329 - 38 Evaluation of tuberculosis control by periodic or routine susceptibility testing in previously treated cases; Van Deun A et al.; SETTING: A national tuberculosis control programme (NTP) disposing of baseline drug resistance rates and using 2EHRZ/6TH in the treatment of new cases . OBJECTIVE: To estimate the extent of drug resistance created by the NTP . DESIGN: Resistance rates in 2EHRZ/6TH failure and relapse cases were compared to baseline, and resistance profiles of repeat isolates were checked . Numbers of observed resistant failures were compared to numbers expected due to pre-existing resistance . Trends of resistance in combined new and previously treated cases were extrapolated . RESULTS: High drug resistance rates were observed . Changes in resistance to streptomycin, the virtual absence of documented acquired resistance and a close match of observed with expected resistant failures all indicated accumulation of primary drug resistance as the main mechanism . Resistance in relapse/failure cases showed a significantly declining trend, and estimated combined drug resistance decreased rapidly . CONCLUSIONS: Drug resistance in previously treated cases seems to consist of passed-on primary rather than true acquired resistance . A one-time survey is thus confusing, but continuous routine testing may constitute the best drug resistance monitoring method . Cases previously treated with short-course chemotherapy may show drug resistance much more frequently than generally assumed, and all should receive a re-treatment regimen . The 2EHRZ/6TH regimen proved very safe under field conditions, causing no 'amplification' towards multidrug resistance and almost no acquired isoniazid resistance . Implementation of this regimen, together with a standardised re-treatment regimen, seemed to rapidly reduce isoniazid as well as multidrug resistance levels, despite the fact that directly observed treatment was not strictly applied. Int J Tuberc Lung Dis, 2001 Apr, 5(4), 321 - 8 Infection and disease among household contacts of patients with multidrug-resistant tuberculosis; Teixeira L et al.; SETTING: Urban public teaching and referral hospital in Espirito Santo, Brazil . OBJECTIVE: To assess whether rates of infection and progression to active tuberculosis (TB) differed between household contacts of patients with multidrug-resistant (MDR) and drug susceptible (DS) pulmonary tuberculosis . DESIGN: Household contacts were assessed for evidence of TB infection and disease by purified protein derivative (PPD) skin testing, physical examination, chest X-ray, and sputum smear and culture . RESULTS: Among 133 close contacts of patients with MDR-TB, 44% were PPD-positive (> or =10 mm) compared to 37% of 231 contacts of the DS-TB cases (P = 0.18, chi2 test, OR 1.2, 95%CI 0.8-2) . In a multivariate logistic regression analysis, after allowance for between-household variation in PPD responses, PPD positivity among household contacts of patients with MDR-TB remained comparable to PPD positivity in contacts of patients with DS-TB (OR 2.1, 95%CI 0.7-6.5) . Respectively six (4%) and 11 (4%) contacts of the MDR- and DS-TB cases were found to have active TB at the time of initial evaluation or during follow-up (P = 0.78, chi2 test) . Five of six contacts of MDR-TB cases and nine of nine contacts of DS-TB cases who developed TB, and for whom drug susceptibility test results were available, had the same bacterial susceptibility profiles as their index cases . DNA fingerprinting analysis of Mycobacterium tuberculosis isolates was identical between household contacts with active TB and the index MDR or DS-TB case for all 14 pairs compared . CONCLUSION: Our data suggest that the prevalence of tuberculous infection and progression to active TB among household contacts exposed to DS and MDR-TB cases is comparable, despite a longer duration of exposure of contacts to the index case in patients with MDR-TB. Int J Tuberc Lung Dis, 2001 Apr, 5(4), 313 - 20 A clinic-based molecular epidemiologic study of tuberculosis in Monterrey, Mexico; Yang ZH et al.; SETTING: A tuberculosis clinic associated with a university hospital in Monterrey, Mexico, an urban community with high tuberculosis incidence . OBJECTIVE: To determine the diversity of DNA fingerprint patterns and the extent of drug resistance of Mycobacterium tuberculosis isolates from patients who attended the clinic . DESIGN: Isolates of M . tuberculosis obtained from 186 patients during the period from 31 January 1996 to 31 March 1998 were tested for susceptibility to isoniazid, rifampicin, ethambutol and streptomycin . Demographic data and the social history of each patient were obtained prospectively by interview . The IS6110 DNA fingerprints were obtained for 166 of the 186 isolates . Secondary typing was carried out on isolates with fewer than six copies of IS6110 . RESULTS: Thirty-two per cent of the tested isolates (60/ 186) were drug-resistant, and 18% (33/186) were multidrug-resistant . Approximately 55% of the resistant isolates (33/60) were attributed to acquired resistance . A total of 106 different IS6110 fingerprint patterns were observed among the 166 fingerprinted isolates . Based on both IS6110 and pTBN12 fingerprinting, 65 (39%) of the 166 isolates were part of 22 DNA fingerprint clusters . Various drug susceptibility patterns were seen in most clusters . CONCLUSION: Fingerprint clustering indicates extensive recent transmission of tuberculosis in patients attending the clinic . The prevalence of drug-resistant tuberculosis is high. Cancer Gene Ther, 2001 Mar, 8(3), 185 - 92 Selection and characterization of a high-activity ribozyme directed against the antineoplastic drug resistance-associated ABC transporter BCRP/MXR/ABCG2; Kowalski P et al.; Breast cancer resistance protein (BCRP) is a recently identified new member of the superfamily of ATP-binding cassette transporters . BCRP is a "half transporter" that may homo- or heterodimerize to form an active transport complex . A considerable overexpression of BCRP was reported from various atypical multidrug-resistant tumor cell lines, in particular from those which were established by treatment with mitoxantrone . Thus, BCRP represents a very interesting candidate molecule for reversal of a drug-resistant phenotype . Six hammerhead ribozymes directed against the BCRP-encoding mRNA were designed and tested for their ability to cleave their target molecule . The anti-BCRP ribozymes were in vitro synthesized using bacteriophage T7 RNA polymerase and oligonucleotide primers whereby one primer contains a T7 RNA polymerase promoter sequence . BCRP-encoding substrate RNA molecules were created by a reverse transcription polymerase chain reaction using total RNA prepared from the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV exhibiting a high BCRP mRNA expression level . One anti-BCRP ribozyme was found to show a very high endoribonucleolytic cleavage activity at physiologic pH and temperature . This ribozyme was characterized in a cell-free system with regard to its specific kinetic parameters using large target molecules. Int J Lepr Other Mycobact Dis, 2000 Dec, 68(4), 452 - 5 A Mycobacterium leprae isolate resistant to dapsone, rifampin, ofloxacin and sparfloxacin; Matsuoka M et al.; Mycobacterium leprae were isolated from a Japanese patient, and susceptibility to antileprosy drugs was examined by the mouse foot pad method . The isolate was susceptible to clofazimine and clarithromycin, and resistant to dapsone, rifampin, ofloxacin and sparfloxacin . Mutations were identified in the genes associated with resistance to these drugs . The risk of the emergence of leprosy with multidrug resistance is emphasized. Biochem Pharmacol, 2001 Jun 1, 61(11), 1401 - 8 Collateral sensitivity to gemcitabine (2',2'-difluorodeoxycytidine) and cytosine arabinoside of daunorubicin- and VM-26-resistant variants of human small cell lung cancer cell lines; Bergman AM et al.; Multidrug resistance (MDR), characterized by a cross-resistance to many natural toxin-related compounds, may be caused either by overexpression of a drug efflux pump such as P-glycoprotein, (P-gP), multidrug resistance proteins MRP1-3, or BCRP/MXR or, in the case of DNA topoisomerase II active drugs, by a decrease in the enzymatic activity of the target molecule termed altered topoisomerase MDR (at-MDR) . However, human small cell lung carcinoma (SCLC) cell lines showed a collateral sensitivity to 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) and 1-beta-D-arabinofuranosylcytosine (ara-C) . H69/DAU, a daunorubicin (DAU)-resistant variant of H69 with a P-gP overexpression, and NYH/VM, a VM-26 (teniposide)-resistant variant of NYH with an at-MDR, were both 2-fold more sensitive to gemcitabine and 7- and 2-fold more sensitive to ara-C, respectively . MDR variants had a 4.3- and 2.0-fold increased activity of deoxycytidine kinase (dCK), respectively . dCK catalyzes the first rate-limiting activation step of both gemcitabine and ara-C . In addition, deoxycytidine deaminase, responsible for inactivation of dFdC and ara-C, was 9.0-fold lower in H69/DAU cells . The level of thymidine kinase 2, a mitochondrial enzyme that can also phosphorylate deoxycytidine and gemcitabine, was not significantly different between the variants . These differences most likely caused an increased accumulation of the active metabolites (dFdCTP, 2.1- and 1.6-fold in NYH/VM and H69/DAU cells, respectively) and of ara-CTP (1.3-fold in NYH/VM cells) . Ara-CTP accumulation was not detectable in either H69 variant . The pools of all ribonucleoside and deoxyribonucleoside triphosphates were at least 3- to 4-fold higher in the NYH variants compared to the H69 variants; for dCTP and dGTP this difference was even larger . The higher ribonucleotide pools might explain the >10-fold higher accumulation of dFdCTP in NYH compared to H69 variants . Since dCTP is low, H69 cells might not need a high ara-CTP accumulation to inhibit DNA polymerase . This might be related to the lack of ara-CTP in H69 variants . In addition, the increased CTP, ATP, and UTP pools in the MDR variants might explain the increased ara-CTP and dFdCTP accumulation . In conclusion, the MDR variants of the human SCLC cell lines were collaterally sensitive due to an increased dCK activity, and consequently an increased ara-CTP and dFdCTP accumulation. Biochem Pharmacol, 2001 Jun 1, 61(11), 1393 - 9 Modulation by LY335979 of P-glycoprotein function in multidrug-resistant cell lines and human natural killer cells; Green LJ et al.; Resistance to chemotherapy by some human tumors may be due to overexpression of membrane-associated transport proteins . The best characterized of these is the multidrug resistance (MDR) transporter, P-glycoprotein (Pgp) . The aim of this study was to measure the inhibitory effects of a potent new MDR modulator, (2R)-anti-5-(3-{4-(10,11-difluoromethanodibenzo-suber-5-yl) piperazin-1-yl}-2-hydroxypropoxy)quinoline trihydrochloride (LY335979), in the drug-resistant cell line HL60/VCR and in normal, human CD56(+) lymphocytes . We used flow cytometric methods to detect the accumulation of rhodamine 123 and daunorubicin, fluorescent MDR substrates, in these cells . Our results indicate that LY335979 was 500-1500 times more potent than cyclosporin A or verapamil in restoring Pgp substrate accumulation in the MDR cell line HL60/VCR . Moreover, LY335979 could effectively block Pgp function on isolated CD56(+) lymphocytes (IC(50) = 1.2 nM) or CD56(+) lymphocytes in whole blood (IC(50) = 174 nM) . We conclude that LY335979 is among the most potent Pgp inhibitors described and that it maintains significant potency in whole-human blood . These latter findings are important for establishing the dosing regimens of LY335979 for future clinical studies. Biochem Pharmacol, 2001 Jun 1, 61(11), 1387 - 91 Resistance of human multidrug resistance-associated protein 1-overexpressing lung tumor cells to the anticancer drug arsenic trioxide; Vernhet L et al.; The human multidrug-resistance protein (MRP1) confers resistance to some heavy metals such as arsenic and antimony, mainly through mediating an increased cellular efflux of metal . However, it was recently suggested that arsenic, used under its trioxide derivative form as anticancer drug, is not handled by MRP1 . The aim of the present study was to test this hypothesis in MRP1-overexpressing human lung tumor GLC4/Sb30 cells . Using the cytotoxicity MTT assay, GLC4/Sb30 cells were found to be 10.8-fold more resistant to arsenic trioxide (As2O3) than parental GLC4 cells . MK571, a potent inhibitor of MRP1 activity, almost totally reversed resistance of GLC4/Sb30 cells, but did not alter the sensitivity of GLC4 cells . Moreover, As2O3-loaded GLC4/Sb30 cells poorly accumulated arsenic through an increased MK571-sensitive efflux of metal . Finally, depletion of cellular glutathione levels in buthionine sulfoximine-treated GLC4/Sb30 cells was found to result in increased accumulation and reduced efflux of arsenic in cells exposed to As2O3, outlining the glutathione-dependence of MRP1-mediated transport of the metal . These results indicate that MRP1 overexpression in human tumor cells can confer resistance to As2O3, which may limit the clinical use of this anticancer drug for treatment of MRP1-positive tumors. J Interferon Cytokine Res, 2001 Mar, 21(3), 187 - 96 Interleukin-1 or tumor necrosis factor-alpha augmented the cytotoxic effect of mycobacteria on human fibroblasts: application to evaluation of pathogenesis of clinical isolates of Mycobacterium tuberculosis and M . avium complex; Takii T et al.; Mycobacteria-induced in vitro events reflecting human tuberculosis can contribute to the evaluation of the pathogenesis of Mycobacterium tuberculosis (MTB) . In this study, we propose such an in vitro method based on live mycobacteria-induced cytotoxicity to human cell lines . When human lung-derived normal fibroblast cell line MRC-5 was infected with various strains of mycobacteria (M . tuberculosis H(37)Rv and H(37) Ra, Mycobacterium avium 427S and 2151SmO, and Mycobacterium bovis BCG Pasteur and Tokyo), the fibroblasts were killed by mycobacteria according to the degree of virulence . Other human originated macrophage (U-937, THP-1), myeloid (HL-60), and epithelial carcinoma (A549) cell lines exhibited a similar cytotoxic response to virulent mycobacteria . MRC-5 was most susceptible to virulent mycobacteria among various human cell lines examined . The cytotoxicity was enhanced by the proinflammatory cytokines, interleukin-1 (IL-1) and tumor necrosis factor-a (TNF-alpha), which in the absence of mycobacteria stimulate the growth of normal human fibroblasts . This in vitro evaluation system was applied to clinical isolates of drug-sensitive MTB (DS-MTB), drug-resistant MTB (DR-MTB) including multidrug-resistant (MDR-MTB), and M . avium complex (MAC) . MTB strains (n = 24) exhibited strong cytotoxic activity, but MAC strains (n = 5) had only weak activity . Furthermore, there was no significant difference in cytotoxicity between DS-MTB (n = 11) and DR-MTB (n = 13) . Collectively, these results suggest that this new in vitro system is useful for evaluating the pathogenesis of mycobacteria and that there was no difference in the pathogenesis between drug-susceptible and drug-resistant clinical isolates. Biochemistry, 2001 May 8, 40(18), 5542 - 7 Hypersensitization of tumor cells to glycolytic inhibitors; Liu H et al.; The slow growth of cells in the inner core of solid tumors presents a form of multidrug resistance to most of the standard chemotherapeutic agents, which target the outer more rapidly dividing cells . However, the anaerobic environment of the more centrally located tumor cells also provides an opportunity to exploit their dependence on glycolysis for therapeutic gain . We have developed two in vitro models to investigate this possibility . Model A represents osteosarcoma wild-type (wt) cells treated with agents which inhibit mitochondrial oxidative phosphorylation (Oxphos) by interacting with complexes I, III, and V of the electron transport chain in different ways, i.e., rhodamine 123 (Rho 123), rotenone, antimycin A, and oligomycin . All of these agents were found to hypersensitize wt cells to the glycolytic inhibitor 2-deoxyglucose . Cells treated with Rho 123 also become hypersensitive to oxamate, an analogue of pyruvate, which blocks the step of glycolysis that converts pyruvate to lactic acid . Model B is rho(0) cells which have lost their mitochondrial DNA and therefore cannot undergo Oxphos . These cells are 10 and 4.9 times more sensitive to 2-deoxyglucose and oxamate, respectively, than wt cells . Lactic acid levels, which are a measure of anaerobic metabolism, were found to be > 3 times higher in rho(0) than in wt cells . Moreover, when wt cells were treated with Rho 123, lactic acid amounts increased as a function of increasing Rho 123 doses . Under similar Rho 12