Scand J Infect Dis Suppl, 2003 Dec, 35 Suppl 106, 45 - 8 Cellular issues relating to the resistance of HIV to antiretroviral agents; Turriziani O et al.; It has been proposed that the declining efficiency of antiretroviral agents in human immunodeficiency virus (HIV) infection may also depend on cellular factors at their site of action . Two in particular have been proposed: (i) the defective intracellular metabolism of NRTI in target cells and the altered uptake; and (ii) efflux of nucleoside reverse transcriptase inhibitors (NRTI) and protease inhibitors (PI) by cellular transporter molecules . Several studies have shown that: changes in the activities of various purine and pyrimidine biosynthetic enzymes may occur in lymphocytes of HIV-infected patients; HIV-infected patients on prolonged treatment with nucleoside analogues, e.g . zidovudine, show significantly decreased activity of thymidine kinase (TK) compared with untreated HIV-infected people; and NRTI and PI are substrates for the multidrug membrane transporters . With regard to the latter issue, it is known that the ATP-binding cassette transporter proteins such as the P-glycoprotein (MDR), and the newly discovered family of multidrug resistance-associated proteins (MRP1-6), promote the active extracellular efflux of a wide variety of therapeutics drugs and overexpression of some of them lowers intracellular concentration of PI . In the very near future such mechanisms, also called 'cellular drug resistance', might be taken into account, together with other immunological, virological and behavioural factors, to explain the 'drug failure' and/or the variability of response in HIV patients undergoing antiretroviral treatment. Scand J Infect Dis Suppl, 2003 Dec, 35 Suppl 106, 17 - 20 Epidemiological aspects of transmitted HIV drug resistance; Girardi E; Transmitted human immunodeficiency virus (HIV) resistance to antiretrovirals (i.e . resistance in antiretroviral naive patients) emerged during the 1990s as a potentially relevant public health problem . HIV variants resistant to all classes of approved antiretroviral agents have been identified in significant proportions antiretroviral naive patients, and this phenomenon appears as a potential threat to the effectiveness of highly active antiretroviral therapy . Available data from surveys conducted between 1996 and 2001 show the prevalence of drug resistance among newly HIV-infected individuals to range from 3%, to above 20% in North America, and from 5% to 15% in Europe . Increases in prevalence observed during the late 1990s in some studies are not confirmed by most recent data . Transmission of multidrug resistance still appears to be an uncommon occurrence . However, methodological heterogeneity and problems in study design make it difficult to compare results between different surveys and to draw firm conclusions from the results . There is a clear need to improve surveillance systems aimed at identifying patients at the time of primary infection and to standardize laboratory methods for the identification of genetic markers of resistance to be used for epidemiological purposes. Expert Rev Mol Diagn, 2004 Mar, 4(2), 209 - 17 Progress in defining multidrug resistance in leukemia; Kappelmayer J et al.; Multidrug resistance (MDR) is a naturally occurring defense phenomenon by which cells battle against chemically foreign substances (xenobiotics), including some cytotoxic drugs . Membrane transporter hyperactivity is a major contributor to MDR and is the primary target of both diagnostic and therapeutic interventions . Multi-xenobiotic resistance can be exploited as several fluorescent indicator probes are extruded by the same drug transporters, making it possible to quantitatively measure MDR activity in cell lines and clinical samples by flow cytometry . The literature on MDR is reported in a number of different formats, making it difficult to compare data from various groups . This article will briefly review the pathomechanism, then focus upon the diagnostic approach, the interpretation of results from clinical samples and correlations with other variables . The authors believe that a standardized MDR assay, as well as a suitable monitoring test, may become a prognostic marker in several types of leukemia . Copyright Future Drugs Ltd. J Pharm Sci, 2004 Apr, 93(4), 932 - 42 Drug efflux transport properties of 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and its fluorescent free acid, BCECF; Bachmeier CJ et al.; 2',7'-Bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) is a fluorescent probe used to examine multidrug resistance-associated protein (MRP) transporter activity in cells . BCECF is introduced into the cell as the nonfluorescent membrane permeable acetoxymethyl ester, BCECF-AM, where it is hydrolyzed to the membrane impermeable BCECF . The lipophilic nature of BCECF-AM suggests it may be a substrate for other drug efflux transporters such as P-glycoprotein (P-gp) and the breast cancer resistance protein (BCRP) . To assess the drug efflux transporter interactions of BCECF-AM and BCECF, accumulation studies were examined in various drug efflux-expressing cells . Inhibition of P-gp, BCRP, and/or MRP produced distinct changes in the time-dependent accumulation of BCECF in the cells . Treatment with GF120918 produced an immediate and sustained effect throughout the entire time course examined . Fumitremorgin C only affected BCECF accumulation at the early time points, whereas the impact of indomethacin on BCECF accumulation was observed only at the latter time points . Permeability studies in bovine brain microvessel endothelial cells indicated an increased basolateral-to-apical transport of BCECF, which could be reduced in the presence of either indomethacin or GF120918 . These results indicate that the intracellular accumulation and transcellular permeability of BCECF are sensitive to a variety of drug efflux interactions . These results likely reflect an interaction of the ester form with P-gp and BCRP during the initial accumulation process, and an interaction of the free acid form with MRP after hydrolysis in the cell . Hepatology, 2004 Mar, 39(3), 779 - 91 BSEP and MDR3 haplotype structure in healthy Caucasians, primary biliary cirrhosis and primary sclerosing cholangitis; Pauli-Magnus C et al.; Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are characterized by a cholestatic pattern of liver damage, also observed in hereditary or acquired dysfunction of the canalicular membrane transporters bile salt export pump (BSEP, ABCB11) and multidrug resistance protein type 3 (MDR3, ABCB4) . Controversy exists whether a genetically determined dysfunction of BSEP and MDR3 plays a pathogenic role in PBC and PSC . Therefore, 149 healthy Caucasian control individuals (control group) were compared to 76 PBC and 46 PSC patients with respect to genetic variations in BSEP and MDR3 . Sequencing spanned approximately 10,000 bp including promoter and coding regions as well as 50-350 bp of flanking intronic regions . In all, 46 and 45 variants were identified in BSEP and MDR3, respectively . No differences between the groups were detected either in the total number of variants (BSEP: control group: 37, PBC: 37, PSC: 31; and MDR3: control group: 35; PBC: 32, PSC: 30), or in the allele frequency of the common variable sites . Furthermore, there were no significant differences in haplotype distribution and linkage disequilibrium . In conclusion, this study provides an analysis of BSEP and MDR3 variant segregation and haplotype structure in a Caucasian population . Although an impact of rare variants on BSEP and MDR3 function cannot be ruled out, our data do not support a strong role of BSEP and MDR3 genetic variations in the pathogenesis of PBC and PSC. Clin Infect Dis, 2004 Mar 15, 38(6), 851 - 6 Epub 2004 Mar 01. Multidrug-resistant tuberculous meningitis in KwaZulu-Natal, South Africa; Patel VB et al.; Multidrug-resistant (MDR) pulmonary tuberculosis (TB) is well described in the literature . Reports of MDR TB meningitis (MDR-TBM), however, are limited to case reports and a single case series . During the period of 1999-2002, 350 patients with TBM were identified by cerebrospinal fluid culture for TB . Thirty patients (8.6%) had TB that was resistant to at least isoniazid and rifampicin . All 30 patients were included in this study . We reviewed hospital charts of the patients with MDR-TBM and describe our experience . Seventeen patients with MDR-TBM died, and, of those who were known to be alive, many experienced significant morbidity . Eighteen patients were HIV positive . Twenty-two patients had been treated for TB in the past, 3 patients had received no previous treatment for TB, and the history of TB treatment was unknown for 5 patients . The study highlights the prevalence of MDR-TBM and identifies new challenges in the management of affected patients. J Med Chem, 2004 Mar 11, 47(6), 1413 - 22 Synthesis and evaluation of dihydropyrroloquinolines that selectively antagonize P-glycoprotein; Lee BD et al.; In a search for improved multiple drug resistance (MDR) modulators, we identified a novel series of substituted pyrroloquinolines that selectively inhibits the function of P-glycoprotein (Pgp) without modulating multidrug resistance-related protein 1 (MRP1) . These compounds were evaluated for their toxicity toward drug-sensitive tumor cells (i.e . MCF-7, T24) and for their ability to antagonize Pgp-mediated drug-resistant cells (i.e . NCI/ADR) and MRP1-mediated resistant cells (i.e . MCF-7/VP) . Cytotoxicity and drug accumulation assays demonstrated that the dihydropyrroloquinolines inhibit Pgp to varying degrees, without any significant inhibition of MRP1 . The compound termed PGP-4008 was the most effective at inhibiting Pgp in vitro and was further evaluated in vivo . PGP-4008 inhibited tumor growth in a murine syngeneic Pgp-mediated MDR solid tumor model when given in combination with doxorubicin . PGP-4008 was rapidly absorbed after intraperitoneal administration, with its plasma concentrations exceeding the in vitro effective dose for more than 2 h . PGP-4008 did not alter the plasma distribution of concomitantly administered anticancer drugs and did not cause systemic toxicity as was observed for cyclosporin A . Because of their enhanced selectivity toward Pgp, these substituted dihydropyrroloquinolines may be effective MDR modulators in a clinical setting. J Med Chem, 2004 Mar 11, 47(6), 1339 - 50 Design and synthesis of new templates derived from pyrrolopyrimidine as selective multidrug-resistance-associated protein inhibitors in multidrug resistance; Wang S et al.; In our continued effort to identify selective MRP1 modulators, we have developed two novel templates, 3 and 4, through rational drug design by identifying the key pharmacophore interaction at the 7-position of the pyrrolopyrimidine template 1 . Further synthesis and SAR work on these novel templates gave a number of potent MRP1 modulators with great selectivity against Pgp . Additional studies to reduce the CYP3A4 inhibition are also reported . Several compounds of these classes were subjected to in vivo xenograft studies and in vivo efficacies were demonstrated. J Med Chem, 2004 Mar 11, 47(6), 1329 - 38 Studies on pyrrolopyrimidines as selective inhibitors of multidrug-resistance-associated protein in multidrug resistance; Wang S et al.; Multidrug resistance mediated by P-glycoprotein (Pgp) or multidrug-resistance-associated protein (MRP) remains a major obstacle for successful treatment of cancer . Inhibition of Pgp and MRP transport is important for high efficacy of anticancer drugs . While several Pgp inhibitors have entered clinical trials, the development of specific MRP1 inhibitors is still in its infancy . In our screening program, we have identified a pyrrolopyrimidine (4) as a novel and selective MRP1 inhibitor . Subsequent SAR work on the 4-position of the template revealed the phenethylpiperazine side chain as a potent replacement of the benzylthio group of the lead molecule . Introduction of groups at the 2-position seems to have no detrimental effect on activity . Modifications to the nitrile group at the 7-position resulted in the identification of analogues with groups, such as amides, with superior pharmacokinetic profiles . In vivo efficacy has been demonstrated by xenograft studies on selected compounds. Blood, 2004 Jun 15, 103(12), 4636 - 43 Epub 2004 Mar 02. T-cell lymphoma as a model for the use of histone deacetylase inhibitors in cancer therapy: impact of depsipeptide on molecular markers, therapeutic targets, and mechanisms of resistance; Piekarz RL et al.; Depsipeptide (FK228) is a novel histone deacetylase inhibitor currently in clinical trials and the first to demonstrate clinical activity in patients . Responses have been observed in patients with T-cell lymphomas, despite prior treatment with multiple chemotherapeutic agents . To better understand the effects of histone deacetylase inhibitors on T-cell lymphoma, the human T-cell lymphoma cell line HUT78 was tested for sensitivity and molecular response to depsipeptide . Treatment with depsipeptide, as well as other histone deacetylase inhibitors, caused induction of histone acetylation, induction of p21 expression, and substantial apoptosis without significant cell cycle arrest . Treatment with the caspase inhibitor z-VAD-fmk significantly inhibited depsipeptide-induced apoptosis, enabling detection of cell cycle arrest . Treatment with depsipeptide increased expression of the interleukin-2 (IL-2) receptor, and combination with the IL-2 toxin conjugate denileukin diftitox resulted in more than additive toxicity . Cells selected for resistance to depsipeptide overexpressed the multidrug resistance pump, P-glycoprotein (Pgp) . However, cells selected for resistance to depsipeptide in the presence of a Pgp inhibitor had a Pgp-independent mechanism of resistance . These studies confirm the activity of depsipeptide in a T-cell lymphoma model and suggest a general sensitivity of T-cell lymphoma to histone deacetylase inhibitors, an emerging new class of anticancer agents. Infect Control Hosp Epidemiol, 2004 Feb, 25(2), 162 - 4 Which strategies follow from the surveillance of multidrug-resistant bacteria to strengthen the control of their spread? A French experience; Lepelletier D et al.; Efforts to enhance standard precautions and to isolate patients with positive routine clinical cultures during 3 years were insufficient to decrease multidrug-resistant bacteria infection rates . Routine screening for carriage in high-risk patients may be necessary to halt transmission and control the hospital reservoir. Clin Ter, 2003 Sep-Oct, 154(5), 325 - 35 {MDR (multidrug resistance) in hepatocarcinoma clinical-therapeutic implications}; Petraccia L et al.; Our purpose was to summarize current knowledge on "multidrug resistance", or MDR, an intrinsic or acquired cross resistance to a variety of structurally and functionally unrelated drugs, still representing one of the major problems in the therapy of cancer and other diseases . MDR depends on various mechanisms, the best known being the activity of ABC transport proteins, mainly Pgp, MDR1 gene product,and MRPs; but also other transporters can cause resistance, for example TAP, a peptide transporter, CFTR, cystic fibrosis transmembrane regulator, ABCG2, or breast cancer resistance protein (BCRP) and LRP, lung resistance protein . MDR has been detected in nearly all types of cancer, because it affects many organs and can occur against a wide number of drugs; it is frequent even in other diseases, such as epilepsy and HIV . We focused on MDR phenomenon in HCC, one of the commonest tumors in the world, and one of the most resistant to pharmacological treatment . This characteristic might be partly determined by a link between MDR and angiogenic phenotypes . The relationship between MDR in hepatocellular carcinoma and the effectiveness of therapeutic treatments has been particularly examined . Finally, the importance to overcome the strong chemoresistance of hepatocellular carcinoma with methods alternative to drugs, namely gene therapy, which makes use of antisense oligonucleotides and anti-MDR1 ribozymes, has been pointed out. Mol Interv, 2001 Jun, 1(2), 117 - 25 Transcription of the multidrug resistance gene MDR1: a therapeutic target; Scotto KW et al.; Two decades ago, the overexpression of P-glycoprotein (Pgp) was first demonstrated to mediate the energy-dependent efflux of a variety of chemotherapeutic agents from tumor cells, resulting in the development of multidrug resistance (MDR) . Not surprisingly, this discovery triggered an ongoing search for agents that would inhibit Pgp function, with the hope that by doing so the MDR phenotype could be reversed . As our understanding of Pgp function and pharmacokinetics has increased, this quest has become more urgent, as well as more complex. Yao Xue Xue Bao, 2003 Nov, 38(11), 805 - 8 {Effects of 3-substituted aryl oxindole(PH II-7) on cell cycle of tumor cells}; Tan YH et al.; AIM: To study the antitumor mechanism of 3-substituted aryl oxindole (PH II-7) and determine its effects on cell cycle distribution of tumor cells . METHODS: The cell cycle distributions were determined with FACS . The cell cycle regulation-related proteins of K562 lysates were analyzed with Western Blot . The inhibition of PH II-7 on DNA synthesis of tumor cells were estimated though 3H-thymidine incorporation and the tyrosine kinase activity of EGFR of A431 lysates was measured with ELISA . RESULTS: PH II-7 effected cell cycle distribution of several tumor cells, including multidrug resistant tumor cell lines, and accumulation of cells in the G0-G1 stages was observed . The cell cycle regulation-related proteins CDK2, Rb and c-myc were inhibited by PH II-7 in a dose dependent manner, whereas the expression of CyclinE was increased after exposure to PH II-7 . Furthermore, PH II-7 2.0 mg.L-1 was shown to inhibit the incorporation of 3H-thymidine into DNA, and 21.89%-41.29% of the PTK activity of EGFR in A431 lysates was inhibited by PH II-7 2-8 mg.L-1 in a dose-dependant manner . CONCLUSION: PH II-7, a new anti-tumor agent, blocks the transition of cell cycle of tumor cells from G1 to S phase by inhibition CDK2. J Pathol, 2004 Mar, 202(3), 305 - 12 Expression of COX-2, mPGE-synthase1, MDR-1 (P-gp), and Bcl-xL: a molecular pathway of H pylori-related gastric carcinogenesis; Nardone G et al.; Helicobacter pylori up-regulates cyclo-oxygenase-2 (COX-2) expression, which in turn is involved in tumourigenesis . Recently, a causal link between COX-2 and multidrug resistance 1 (MDR-1) gene expression, implicated in cancer chemoresistance, has been demonstrated . Thus, the expression of COX-2 and the downstream enzyme involved in PGE2 biosynthesis, microsomal PGE-synthase1 (mPGES1), was correlated with P-gp, the product of MDR-1, and the anti-apoptotic protein, Bcl-xL, in gastric biopsies from patients with H pylori infection and in patients with gastric cancer . In a retrospective analysis of endoscopic and pathology files, 40 H pylori-negative patients (Hp-), 50 H pylori-positive patients who responded to eradication therapy (Hp+R), 84 H pylori-positive patients who did not respond to eradication therapy (Hp+NR), and 30 patients with gastric cancer (18 intestinal and 12 diffuse types) were selected . COX-2, mPGES1, P-gp, and Bcl-xL were detected by immunohistochemistry . COX-2, mPGES1, P-gp, and Bcl-xL expression was undetectable in gastric mucosa from Hp- patients . By contrast, COX-2 and mPGES1 expression was detected in 42% and 44% of Hp+R patients, respectively, and in up to 66% (range 63-66%) of Hp+NR patients (p < 0.05) . The expression of COX-2 and mPGES1 correlated significantly (p < 0.0001) with that of P-gp and Bcl-xL . High levels of COX-2, mPGES1, P-gp, and Bcl-xL expression were found in intestinal-type gastric cancer samples . In conclusion, H pylori-dependent induction of COX-2 and mPGES1 is associated with enhanced production of P-gp and Bcl-xL that may contribute to gastric tumourigenesis and resistance to therapy . J Virol, 2004 Mar, 78(6), 3123 - 32 Crystal structures of a multidrug-resistant human immunodeficiency virus type 1 protease reveal an expanded active-site cavity; Logsdon BC et al.; The goal of this study was to use X-ray crystallography to investigate the structural basis of resistance to human immunodeficiency virus type 1 (HIV-1) protease inhibitors . We overexpressed, purified, and crystallized a multidrug-resistant (MDR) HIV-1 protease enzyme derived from a patient failing on several protease inhibitor-containing regimens . This HIV-1 variant contained codon mutations at positions 10, 36, 46, 54, 63, 71, 82, 84, and 90 that confer drug resistance to protease inhibitors . The 1.8-angstrom (A) crystal structure of this MDR patient isolate reveals an expanded active-site cavity . The active-site expansion includes position 82 and 84 mutations due to the alterations in the amino acid side chains from longer to shorter (e.g., V82A and I84V) . The MDR isolate 769 protease "flaps" stay open wider, and the difference in the flap tip distances in the MDR 769 variant is 12 A . The MDR 769 protease crystal complexes with lopinavir and DMP450 reveal completely different binding modes . The network of interactions between the ligands and the MDR 769 protease is completely different from that seen with the wild-type protease-ligand complexes . The water molecule-forming hydrogen bonds bridging between the two flaps and either the substrate or the peptide-based inhibitor are lacking in the MDR 769 clinical isolate . The S1, S1', S3, and S3' pockets show expansion and conformational change . Surface plasmon resonance measurements with the MDR 769 protease indicate higher k(off) rates, resulting in a change of binding affinity . Surface plasmon resonance measurements provide k(on) and k(off) data (K(d) = k(off)/k(on)) to measure binding of the multidrug-resistant protease to various ligands . This MDR 769 protease represents a new antiviral target, presenting the possibility of designing novel inhibitors with activity against the open and expanded protease forms. Zhongguo Shi Yan Xue Ye Xue Za Zhi, 2004 Feb, 12(1), 6 - 10 {Methylation status of multidrug resistance (mdr1) gene and its correlation with expression of mdr1 gene in patients with hematologic malignancies}; Zhu Y et al.; To investigate the correlation between methylation and expression of multidrug resistance (mdr1) gene, restriction endonuclease HpaII combined with competitive PCR technique was used to quantitatively detect the methylation status of two CCGG sites located at -110 and -50 bp (region I and II) up to the transcription start site in mdr1 promoter in 54 AL and 9 MM patients . Semi-quantitative RT-PCR was used to detect the expression level of mdr1 gene . The results showed that inverse correlation between methylation rate of either region or total methylation rate and expression of mdr1 gene was observed . The correlation in the region I (r = -0.64) was closer than that in the region II (r = -0.4) . High expression rate of mdr1 ascended significantly in low methylation group (n = 36) (P < 0.001) . In comparison with chemotherapy sensitive group (n = 8), the methylation rate in refractory AL patients (n = 16) was lower (P = 0.05) in the region I, P < 0.05 in the region II and total regions . Comparing with the untreated patients (n = 36), the methylation rate in the region I and total methylation rate were lower in the patients with chemotherapy (n = 14) (P < 0.05) . The methylation rate in the region II was also decreased after chemotherapy, however, no statistical significance was shown (P > 0.05) . Increased mdr1 expression level accompanying with decreased methylation rate after chemotherapy was found, although no significant difference was shown (P = 0.06) . It is concluded that the expression level of mdr1 gene was associated with the methylation status of CCGG in -110 and -50 bp upstream to the transcription start site, especially the -110 site . In both the patients treated with chemotherapy and the refractory patients, the methylation level of mdr1 gene decreased relatively . The rising expression of mdr1 gene after chemotherapy was associated with the decrease of methylation level. Eur J Med Chem, 2004 Jan, 39(1), 59 - 67 Structure-activity relationship study of antimalarial indolo {2,1-b}quinazoline-6,12-diones (tryptanthrins) . Three dimensional pharmacophore modeling and identification of new antimalarial candidates; Bhattacharjee AK et al.; A widely applicable three-dimensional QSAR pharmacophore model for antimalarial activity was developed from a set of 17 substituted antimalarial indolo{2,1-b}quinazoline-6,12-diones (tryptanthrins) that exhibited remarkable in vitro activity (below 100 ng/mL) against sensitive and multidrug-resistant Plasmodium falciparum malaria . The pharmacophore, which contains two hydrogen bond acceptors (lipid) and two hydrophobic (aromatic) features, was found to map well onto many well-known antimalarial drug classes including quinolines, chalcones, rhodamine dyes, Pfmrk cyclin dependent kinase inhibitors, malarial FabH inhibitors, and plasmepsin inhibitors . The phamacophore allowed searches for new antimalarial candidates from multiconformer 3D databases and enabled custom designed synthesis of new potent analogues. Eur J Med Chem, 2004 Feb, 39(2), 161 - 77 Anti-calmodulin acridone derivatives modulate vinblastine resistance in multidrug resistant (MDR) cancer cells; Hegde R et al.; Multidrug resistance (MDR) is one of the main obstacles limiting the efficacy of chemotherapy treatment of tumors . Parent acridones 1A and 1B were prepared by the Ullmann reaction followed by cyclization and N-alkylation . N-(omega-Chloroalkyl) analogues were subjected to iodide catalyzed nucleophilic substitution reaction with secondary amines to get the compounds 3A-13A and 3B-13B, which enhanced the uptake of vinblastine in KBChR-8-5 cells to a greater extent (2.6-13.1-fold relative to control) than verapamil . The study on the structure-activity relationship revealed that substitution of -H at position C-4 in acridone nucleus by -OCH3 increased the cytotoxic and anti-MDR activities . The ability of acridones to inhibit calmodulin dependent cyclic AMP phosphodiesterase has been determined and the results have shown a strong positive correlation between anti-calmodulin activity and cytotoxicity in KBChR-8-5 cells or anti-MDR activity. J Nat Prod, 2004 Feb, 67(2), 245 - 56 Biological activity and chemistry of taxoids from the Japanese yew, Taxus cuspidata; Shigemori H et al.; Approximately 120 taxoids have been isolated to date from the Japanese yew, Taxus cuspidata . These taxoids possess various skeletons containing 5/7/6-, 6/10/6-, 6/5/5/6-, 6/8/6-, or 6/12-membered ring systems . Among the taxoids, some non-paclitaxel-type compounds have been shown to reduce CaCl(2)-induced depolymerization of microtubules, increase cellular accumulation of vincristine in multidrug-resistant tumor cells, and exhibit potent cytotoxicity . Chemical derivatization of taxoids of T . cuspidata is also reviewed. Clin Neuropathol, 2004 Jan-Feb, 23(1), 21 - 7 Heterogeneity in the expression of markers for drug resistance in brain tumors; Andersson U et al.; Brain tumors, in general, display a multidrug-resistant phenotype . This study evaluated the immunohistochemical expression and distribution of P-glycoprotein (Pgp), multidrug resistance protein (MRP1), lung resistance protein (LRP) and O6 methylguanine-DNA methyltransferase (MGMT) in low- and high-grade astrocytoma, oligodendroglioma and in different subgroups of meningioma . The results revealed a marked heterogeneity in the expression and distribution among the analyzed tumors . In astrocytoma and oligodendroglioma, Pgp and MRP1 were observed in the capillary endothelium and in scattered tumor cells, whereas LRP occurred only in tumor cells . A pronounced expression of MGMT was found independent of the histopathological grade . An enhanced expression of MRP1 and LRP in astrocytoma and oligodendroglioma were more often evident in older patients (> 50 years) . Survival analysis suggested a markedly decreased overall survival for patients suffering from low-grade glioma overexpressing Pgp . In meningioma, a heterogeneous expression of Pgp, MRP1, LRP and MGMT was seen with the most prominent staining localized to the capillary endothelium . Pgp was significantly more often overexpressed (p < 0.05) in transitional compared to meningothelial meningioma . The marked heterogeneity in the expression suggests that analysis of these factors can be of importance in the selection of individualized chemotherapy, regardless of tumor type. Biochem Biophys Res Commun, 2004 Mar 19, 315(4), 991 - 7 Effects of tributyltin on barrier functions in human intestinal Caco-2 cells; Tsukazaki M et al.; The effect of tributyltin (TBT) on human intestinal epithelial cell functions was investigated by using human intestinal Caco-2 cell monolayers . We paid particular attention to the effect of TBT on two barrier functions: the tight junction as a physical barrier and MDR1/P-glycoprotein as a biological barrier . A loss of monolayer integrity was apparent from the TBT treatment and the paracellular permeability was increased by TBT . On the other hand, the activity of P-glycoprotein, which was examined by measuring the accumulation of Rhodamine-123 and daunomycin, was increased by prolonged TBT treatment in a concentration-dependent manner (1-100 nM) . Furthermore, it was clarified by Western and Northern blots that this increase was accompanied by the increased expression of MDR1 mRNA and protein . The activation of a multidrug resistance transporter P-glycoprotein by TBT would cause a disorder of the human intestines by changing the drug pharmacokinetics. Biochem Biophys Res Commun, 2004 Mar 19, 315(4), 942 - 9 Distinct groups of multidrug resistance modulating agents are distinguished by competition of P-glycoprotein-specific antibodies; Nagy H et al.; P-glycoprotein (Pgp) is one of the ABC transporters responsible for the multidrug resistance of cancer cells . The conformational changes of Pgp that occur in the presence of substrates/modulators or ATP depletion are accompanied by the up-shift of UIC2 monoclonal antibody (mAb) binding . In the case of cyclosporin A, vinblastine or valinomycin, this up-shift was found to be concomitant with the near-complete suppression of labeling with other mAbs specific for Pgp epitopes overlapping with UIC2, while pre-treatment with verapamil or Tween 80 brings about a modest suppression . Here we have extended these observations to 44 Pgp interacting agents, and found that only 8 fall into the cyclosporin-like category, inducing a conformational state characterized by the complete UIC2 dominance . The rest of the drugs either did not affect antibody competition or had a modest effect . Thus, Pgp substrates/modulators can be classified into distinct modalities based on the conformational change they elicit. Pediatr Neurol, 2004 Feb, 30(2), 102 - 6 Multidrug resistance proteins in tuberous sclerosis and refractory epilepsy; Lazarowski A et al.; Tuberous sclerosis is an autosomal dominant syndrome characterized by seizures that are refractory to medication in severely affected individuals . The mechanism involved in drug resistance in tuberous sclerosis is unknown . The proteins MDR-1 (multidrug resistance) and MRP-1 (multidrug resistance-associated protein-1) are linked to chemotherapy resistance in tumor cells . However, the relationship between refractoriness to antiepileptic drugs and MDR-1 or MRP-1 brain expression has been poorly studied . We have previously described a case of tuberous sclerosis with refractory epilepsy that expressed multidrug resistance gene (MDR-1) in tuber cells from epileptogenic brain lesion . In this retrospective study, we describe the expression of MDR-1 and MRP-1 in the epileptogenic cortical tubers of three pediatric patients with tuberous sclerosis and refractory epilepsy surgically treated . Monoclonal antibodies for MDR-1 and MRP-1 proteins were used for immunohistochemistry . In epileptogenic cortical tuber brain specimens, MDR-1 and MRP-1 proteins were strongly immunoreactive in abnormal balloon cells, dysplastic neurons, astrocytes, microglial cells, and some blood-brain vessels . A more extensive MDR-1 immunoreactivity was observed . These data suggest that refractory epilepsy phenotype in tuberous sclerosis can be associated with the expression of both multidrug resistance MDR-1 and MRP-1 transporters in epileptogenic cortical tubers. Proc Natl Acad Sci U S A, 2004 Feb 24, 101(8), 2470 - 5 Bilirubin protects astrocytes from its own toxicity by inducing up-regulation and translocation of multidrug resistance-associated protein 1 (Mrp1); Gennuso F et al.; Unconjugated bilirubin (UCB) causes encephalopathy in severely jaundiced neonates by damaging astrocytes and neurons . Astrocytes, which help defend the brain against cytotoxic insults, express the ATP-dependent transporter, multidrug resistance-associated protein 1 (Mrp1), which mediates export of organic anions, probably including UCB . We therefore studied whether exposure to UCB affects the expression and intracellular localization of Mrp1 in cultured mouse astroglial cells (>95% astrocytes) . Mrp1 was localized and quantitated by confocal laser scanning microscopy and double immunofluorescence labeling by using specific antibodies against Mrp1 and the astrocyte marker glial fibrillary acidic protein, plus the Golgi marker wheat germ agglutinin (WGA) . In unexposed astrocytes, Mrp1 colocalized with WGA in the Golgi apparatus . Exposure to UCB at a low unbound concentration (Bf) of 40 nM caused rapid redistribution of Mrp1 from the Golgi throughout the cytoplasm to the plasma membrane, with a peak 5-fold increase in Mrp1 immunofluorescence intensity from 30 to 120 min . Bf above aqueous saturation produced a similar but aborted response . Exposure to this higher Bf for 16 h markedly decreased Trypan blue exclusion and methylthiazoletetrazoilum activity and increased apoptosis 5-fold by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay . These toxic effects were modestly increased by inhibition of Mrp1 activity with 3-({3-(2-{7-chloro-2-quinolinyl}ethenyl)phenyl-(3-dimethylamino-3-oxopropyl)-thio-methyl}thio)propanoic acid (MK571) . By contrast, Bf=40 nM caused injury only if Mrp1 activity was inhibited by MK571, which also blocked translocation of Mrp1 . Our conclusion is that in astrocytes, UCB up-regulates expression of Mrp1 and promotes its trafficking from the Golgi to the plasma membrane, thus moderating cytotoxicity from UCB, presumably by limiting its intracellular accumulation. Antimicrob Agents Chemother, 2004 Mar, 48(3), 954 - 60 Plasmodium falciparum-based bioassay for measurement of artemisinin derivatives in plasma or serum; Teja-Isavadharm P et al.; Artemisinin and its derivatives, artesunate and artemether, are rapidly acting antimalarials that are used for the treatment of severe and uncomplicated multidrug-resistant falciparum malaria . To optimize treatment regimens that use this new class of antimalarials, there is a need for readily available and reproducible assays to monitor drug levels closely in patients . A sensitive and reproducible bioassay for the measurement of the concentrations of artemisinin derivatives in plasma and serum is described . By modifying the in vitro drug susceptibility test, it was found that antimalarial activity in plasma or serum containing an unknown concentration of drug could be equated to the known concentrations of dihydroartemisinin (DHA) required to inhibit parasite growth . Dose-response curves for a Plasmodium falciparum clone (clone W2) and DHA were used as a standard for each assay . Assays with plasma or serum spiked with DHA proved to be reproducible (coefficient of variation, <or=10.9%), with a lower limit of quantitation equivalent to 2.5 ng of DHA per ml . For plasma spiked with artesunate or artemether, there was good agreement of the results obtained by the bioassay and the concentrations measured by high-performance liquid chromatography (HPLC) with electrochemical detection . The bioassay for measurement of the antimalarial activities of artemisinin derivatives in body fluids requires a smaller volume of plasma or serum and is more sensitive than the presently available HPLC methods, can provide pharmacodynamic parameters for determination of activity against the parasite, and should enhance the design of more appropriate dosage regimens for artemisinin drugs. Antimicrob Agents Chemother, 2004 Mar, 48(3), 809 - 14 Possible involvement of the drug transporters P glycoprotein and multidrug resistance-associated protein Mrp2 in disposition of azithromycin; Sugie M et al.; P glycoprotein and multidrug resistance-associated protein 2 (Mrp2), ATP-dependent membrane transporters, exist in a variety of normal tissues and play important roles in the disposition of various drugs . The present study seeks to clarify the contribution of P glycoprotein and/or Mrp2 to the disposition of azithromycin in rats . The disappearance of azithromycin from plasma after intravenous administration was significantly delayed in rats treated with intravenous injection of cyclosporine, a P-glycoprotein inhibitor, but was normal in rats pretreated with intraperitoneal injection erythromycin, a CYP3A4 inhibitor . When rats received an infusion of azithromycin, cyclosporine and probenecid, a validated Mrp2 inhibitor, significantly decreased the steady-state biliary clearance of azithromycin to 5 and 40% of the corresponding control values, respectively . However, both inhibitors did not alter the renal clearance of azithromycin, suggesting the lack of renal tubular secretion of azithromycin . Tissue distribution experiments showed that azithromycin is distributed largely into the liver, kidney, and lung, whereas both inhibitors did not alter the tissue-to-plasma concentration ratio of azithromycin . Significant reduction in the biliary excretion of azithromycin was observed in Eisai hyperbilirubinemic rats, which have a hereditary deficiency in Mrp2 . An in situ closed-loop experiment showed that azithromycin was excreted from the blood into the gut lumen, and the intestinal clearance of azithromycin was significantly decreased by the presence of cyclosporine in the loop . These results suggest that azithromycin is a substrate for both P glycoprotein and Mrp2 and that the biliary and intestinal excretion of azithromycin is mediated via these two drug transporters. Med Mycol, 2004 Feb, 42(1), 59 - 71 Profiling gene expression in Coccidioides posadasii; Delgado N et al.; Coccidioides posadasii is a dimorphic fungal pathogen which grows as a filamentous saprobe in the soil and multicellular parasitic form in host lung tissue . Studies of gene expression profiles during saprobic and parasitic phase development can provide clues about morphogenetic regulation and may lead to the discovery of molecular targets for novel antifungal drugs . Suppression-subtractive hybridization (SSH) and quantitative real-time polymerase chain reaction (QRT-PCR) were used to identify and quantify differential gene expression during in vitro growth of Coccidioides . DNA fragments obtained from the subtraction of cDNA pools derived from the saprobic and parasitic phase RNA preparations were each cloned into an appropriate vector and subjected to sequence analysis . Semi-quantitative, reverse transcription polymerase chain reaction (RT-PCR) experiments were first conducted to assess whether these inserts represented differentially expressed genes . Nucleotide sequences of the partial and full-length genes selected by RT-PCR were obtained by genome walking and rapid amplification of cDNA ends (RACE) methods . QRT-PCR analysis of the expression of these genes during saprobic and parasitic cell growth was then conducted using DNA standard curves normalized to a constitutively expressed control gene . Four C . posadasii genes whose expression is essentially restricted to the parasitic cycle were discovered using this approach . These genes include homologues of OPS1 (encodes opsin-related protein), MDR1 (multidrug resistance protein), ALDR1 (aldehyde reductase), and PSP1 (hypothetical lipid transporter/flippase protein) . The combined applications of SSH and QRT-PCR permit global analysis of gene expression patterns in C . posadasii. Anticancer Res, 2003 Nov-Dec, 23(6C), 4781 - 7 Conjugated bilirubin induces multidrug resistance-associated protein 2 mRNA expression and in vivo cisplatin resistance in rat hepatoma AH66 cells; Tamai M et al.; In vivo cisplatin resistance of rat ascites hepatoma AH66 cells is suggested to result from the induction of multidrug resistance-associated protein 2 (MRP2) expression by ascites fluid (ASF) in the peritoneal cavity . The in vitro cisplatin sensitivity of AH66 cells grown in assay medium containing 5% fetal bovine serum in Dulbecco's modified Eagle's medium (5% FBS DMEM) did not change when the cells were treated with probenecid, an inhibitor of anion transporters, while the decreased cisplatin sensitivity of AH66 cells cultured in an assay medium containing 5% ASF (5% ASF DMEM) was restored by probenecid . Furthermore, in an in vivo study, the survival span (%ILS) of AH66-bearing rats was markedly extended by combination therapy with cisplatin and probenecid, compared with either agent alone . The expression of MRP2 mRNA was increased when AH66 cells were cultured in medium containing 5% ASF or 5% bile for 24 h . The induction of MRP2 mRNA expression in AH66 cells was also observed in the presence of heat-denatured ASF . The bilirubin content in ASF was characteristically higher than that in FBS, normal rat serum or AH66-bearing rat serum . Unconjugated bilirubin did not change the expression of MRP2 mRNA, whereas conjugated bilirubin markedly increased it . The cisplatin uptake in AH66 cells after culture in 5% FBS DMEM containing conjugated bilirubin was about half that of the cells cultured in 5% FBS DMEM alone (p < 0.01) . In addition, the cisplatin sensitivity of the cells was significantly lowered by the addition of conjugated bilirubin . The expression of MRP2 mRNA in rat normal hepatocytes was also increased after culture in medium containing 5% ASF or 5% bile . These results indicated that conjugated bilirubin, a component of ASF, induces the mRNA expression of MRP2, which is a determinant of the in vivo cisplatin resistance of AH66 cells. Anticancer Res, 2003 Nov-Dec, 23(6C), 4737 - 46 Differential control of cholesterol and fatty acid biosynthesis in sensitive and multidrug-resistant LoVo tumor cells; Santini MT et al.; Multidrug resistance (MDR) describes the decrease in sensitivity of tumor cells to a wide variety of cytotoxic compounds . Although a central role has been ascribed to the P-glycoprotein (Pgp) pump in MDR, lipids also appear to be extremely important . However, their precise role in MDR is not yet fully understood . It was the aim of the present paper to gain a deeper understanding of intracellular lipid equilibrium in both sensitive and MDR tumor cells . In particular, intracellular cholesterol biosynthesis and cholesterol esterification were examined in LoVo-sensitive and Pgp-overexpressing resistant cells . The data presented seem to suggest that the higher synthesis of cholesteryl ester and triglyceride observed in resistant with respect to wild-type cells is due to a greater production of fatty acids in these cells . The results are discussed in view of the possible roles of sterol regulatory element-binding proteins and Pgp in these phenomena. Anticancer Res, 2003 Nov-Dec, 23(6C), 4607 - 11 P-glycoprotein modulation improves in vitro chemosensitivity in malignant pediatric liver tumors; Warmann S et al.; BACKGROUND: Multidrug resistance (MDR) is a major reason for the poor outcome of advanced pediatric liver malignancies . The P-glycoprotein (P-gP), which contributes to this phenomenon, has been potently antagonized in other tumors . Our aim was to investigate the influence of P-gP antagonizers on the chemotherapy of pediatric liver malignancies in vitro . MATERIALS AND METHODS: One hepatocellular carcinoma (HCC) and three hepatoblastoma (HB) cell lines were incubated with doxorubicin or cisplatin . Additional effects of three P-gP-modulators were determined in a cytotoxicity assay . Expression levels of the MDR1 gene were determined using rT-PCR . RESULTS: Modulation of P-gP improved chemotherapy results in all HB cell lines, more effectively in the more highly differentiated tumors . Combined treatment of the HCC cell line was only more efficient using doxorubicin and PSC 833 . CONCLUSION: Modulation of P-gP can overcome MDR in HCC and HB in vitro . Our data encourage further studies analyzing this effect under in vivo conditions. Leukemia, 2004 Mar, 18(3), 513 - 20 Efficient inhibition of multidrug-resistant human tumors with a recombinant bispecific anti-P-glycoprotein x anti-CD3 diabody; Gao Y et al.; Overexpressing of P-glycoprotein (Pgp) has been shown to be responsible for cancer resistance to multiple chemotherapeutic agents . Immunotherapy with biological agents, such as bispecific antibodies (BsAbs), may represent a promising approach to overcome the emergence of drug resistance . Here we constructed a recombinant BsAb, a diabody, with specificities to both CD3 on human T-lymphocyte and Pgp on cancer cells . The diabody was produced in Escherichia coli in a soluble functional form and purified by an affinity chromatography with a yield of >4 mg/l culture medium in shaker flask . The diabody binds to both CD3 on T-lymphocytes and Pgp on multidrug-resistant (MDR) tumor cells with affinities that are comparable to its respective parental single chain Fv molecules . In the presence of activated human peripheral blood lymphocytes (PBLs), the diabody mediates effectively the lysis of the Pgp-overexpressing human leukemia K562/A02 and epidermoid carcinoma KBv(200) cells, but is much less potent in mediating the lysis of the parent K562 and KB cells . Further, the diabody localized selectively within the K562/A02 xenografts in mice . When combined with activated PBL, the diabody significantly inhibited the growth of K562/A02 and KBv(200), but had no effect on K562 and KB xenografts . In contrast, treatment with doxorubicin, a standard chemotherapeutic agent, only inhibited the growth of K562 and KB, but had no effect on K562/A02 and KBv(200) xenografts . Taken together, our results suggest that the anti-Pgp x anti-CD3 diabody may have a great potential in the treatment of various MDR cancers. Bioorg Med Chem, 2004 Mar 1, 12(5), 1177 - 82 Synthesis and antimalarial activity of a new series of trioxaquines; Singh C et al.; Trioxanes 8a-b, easily accessible in two steps from allylic alcohol 6a-b, on reductive amination with 4-aminoquinolines 4a-c furnish a new series of trioxaquines 9a-b, 10a-b, 11a-b in 32-77% yields . Dicitrate salts of these trioxaquines have been evaluated for antimalarial activity against multidrug resistant Plasmodium yoelii in mice model. Zhonghua Gan Zang Bing Za Zhi, 2004 Feb, 12(2), 95 - 8 {Establishment of human hepatocellular carcinoma multidrug-resistance cell line (HepG2/Adm) and study apoptosis induced by low-frequency pulse ultrasound exposure}; Zhai BJ et al.; OBJECTIVE: To establish human hepatocellular carcinoma multidrug-resistance cell line (HepG2/ADM) and to determine the effect of low-frequency pulse ultrasound (US) on MDR cells and investigate its mechanism . METHODS: Using gradual increase of adriamycin (ADM) concentrations in culture, an adriamycin-resistant human hepatocellular carcinoma cell sub line (HepG2/ADM) was established in vitro . HepG2/ADM cells were cultured in vitro and randomly divided into 4 groups: the control group (HepG2/ADM only), the group ADM by 1.0 mug/ml adriamycin for 1 h, the group US by low-frequency pulse ultrasound for 10 min, and the group US by low-frequency pulse ultrasound and treated with adriamycin simultaneously at same time . A sonication at a frequency of 0.8 MHz, was delivered with an intensity level of 0.5W/cm2, with continuous exposure of 10 min was applied . The ability of US to induce the apoptosis of MDR was evaluated by analyses of fluorescence microscopy, DNA fragmentation assay and flow cytometry assay . RESULTS: HepG2/Adm was resistant to many anti-tumor agents, and its IC50 of ADM was 26 times higher than that of parent cell line HepG2 . Significant over expressions of P-gp, MRP, LRP and GSTs were detected . HepG2/ADM cells radiated by US had the typical characteristics of apoptosis . Compared with the control group (HepG2/ADM, 3.47%); the apoptosis rates were higher in US (12.23%) . The therapeutic alliance of US with ADM for MDR cells, have a significant change in the ratio of apoptosis (18.81%, t=1.46 to 5.36, P<0.01) . CONCLUSION: HepG2/ADM could have the biological characteristics of human multidrug-resistance cell line . The US sonication of 0.8 MHz could induce apoptosis of HepG2/ADM cell in vitro, and could act synergistically with Adriamycin. Zhonghua Gan Zang Bing Za Zhi, 2004 Feb, 12(2), 85 - 7 {Reversal of multidrug resistance gene MDR1 and MRP of drug-resistant human hepatocellular carcinoma cells SMMC-7721/ADM with antisense phosphorothioate oligonucleotides}; Luo HY et al.; OBJECTIVES: To investigate the reversal effect of gene MDR1 and MRP with combinational antisense phosphorothioate oligonucleotide on Drug-resistant human hepatocellular carcinoma cells SMMC-7721/ADM . METHODS: SMMC-7721/ADM was transfected with synthetic antisense phosphorothioate oligonucleotides complementary to gene MDR1 and MRP mediated by Lipofectamine . Drug sensitivity was measured by MTT assay, Fluorescence intensity of cells was determined by flow cytometric analysis, RH123 and DNR retention was assayed by confocal scanning laser microscopy . RESULTS: ASODN of MDR1+MRP increased the sensitivity of SMMC-7721/ADM to chemotherapeutic drug more significantly than that any of MDR1 and MRP did separately . But they did not enhance the inhibition expression of protein of p190 or p170 . CONCLUSION: Drug-resistance could be reversed significantly when antisense phosphorothioate oligonucleotide of MDR1+MRP were transfected into drug-resistant human hepatocellular carcinoma cells SMMC-7721/ADM together. Biochemistry, 2004 Mar 2, 43(8), 2345 - 52 Glutathione S-transferases (GSTs) inhibit transcriptional activation by the peroxisomal proliferator-activated receptor gamma (PPAR gamma) ligand, 15-deoxy-delta 12,14prostaglandin J2 (15-d-PGJ2); Paumi CM et al.; 15-Deoxy-Delta(12,14)prostaglandin J(2) (15-d-PGJ(2)), a terminal metabolite of the J-series cyclopentenone prostaglandins, influences a variety of cellular processes including gene expression, differentiation, growth, and apoptosis . As a ligand of peroxisomal proliferator-activated receptor gamma (PPAR gamma), 15-d-PGJ(2) can transactivate PPAR gamma-responsive promoters . Previously, we showed that multidrug resistance proteins MRP1 and MRP3 attenuate cytotoxic and transactivating activities of 15-d-PGJ(2) in MCF7 breast cancer cells . Attenuation was glutathione-dependent and was associated with formation of the glutathione conjugate of 15-d-PGJ(2), 15-d-PGJ(2)-SG, and its active efflux by MRP . Here we have investigated whether the glutathione S-transferases (GST) can influence biological activities of 15-d-PGJ(2) . MCF7 cells were stably transduced with human cytosolic GST isozymes M1a, A1, or P1a . These GSTs had no effect on 15-d-PGJ(2) cytotoxicity when expressed either alone or in combination with MRP1 . However, expression of any of the three GSTs significantly inhibited 15-d-PGJ(2)-dependent transactivation of a PPAR gamma-responsive reporter gene . The degree of inhibition correlated with the level of GST expressed . Under physiologic conditions, the nonenzymatic rate of 15-d-PGJ(2) conjugation with glutathione was significant . Of the three GST isozymes, only GSTM1a-1a further stimulated the rate of 15-d-PGJ(2)-SG formation . Moreover, GSTM1a-1a rate enhancement was only a transient burst that was complete within 15 s . Hence, catalysis plays little, if any, role in GST inhibition of 15-d-PGJ(2)-dependent transactivation . In contrast, inhibition of transactivation was associated with strong GST/15-d-PGJ(2) interactions . Potent inhibition by 15-d-PGJ(2) and 15-d-PGJ(2)-SG of GST activity was observed with K(i) in the 0.15-2.0 microM range for the three GST isozymes, results suggesting avid associations between GST and 15-d-PGJ(2) or 15-d-PGJ(2)-SG . Electrospray ionization mass spectrometry (ESI/MS) studies revealed no stable adducts of GST and 15-d-PGJ(2) indicating that GST/15-d-PGJ(2) interactions are primarily noncovalent . These results are consistent with a mechanism of GST-mediated inhibition of transactivation in which GST binds 15-d-PGJ(2) and 15-d-PGJ(2)-SG thereby sequestering the ligands in the cytosol away from their nuclear target, PPAR gamma. No Shinkei Geka, 2004 Jan, 32(1), 19 - 26 {Report of two cases with germinoma treated by individual adjuvant chemotherapy based on the mRNA expression of drug-resistance gene}; Kunishio K et al.; We reported two cases with germ cell tumor in which new preliminary treatment trials were performed by chemotherapy using anti-cancer drug selected on the basis of multidrug resistance gene mRNA expression, such as MDR1, MRP1, MRP2, MXR1, MGMT, GST pi and TopoII alpha, from RT-PCR assay . A 28-year-old male had gradually developed DI . MR imaging revealed enhanced tumors in the medulla oblongata, the pineal region and the suprasella region . Biopsy of tumor in the medulla oblongata demonstrated germinoma histologically . RT-PCR assay of this tissue revealed overexpression of MRP1, MGMT and GST pi mRNA, but neither MDR1, MRP2 nor MXR1 was observed . The patient was successfully given carboplatin, mitoxanthrone and ifosphamide after irradiation . A 15-year-old male was admitted to our hospital with high intracranial pressure syndrome . MR imaging revealed enhanced tumor in the pineal region . The tumor was diagnosed as a malignant germ cell tumor, histopathologically . RT-PCR assay of this tissue revealed overexpression of MRP1, MRP2, MXR1, MGMT and GST pi mRNA . Only MDR1 was not expressed . The patient was treated by irradiation including radiosurgery combined with chemotherapy, given cisplatin, etoposide and ifosphamide (ICE regimen), but he died because of progressive disease such as CSF dissemination . It seems that preliminary individual adjuvant chemotherapy based on mRNA expression of drug-resistance gene is available for the treatment of germ cell tumors. Mol Pharmacol, 2004 Mar, 65(3), 675 - 84 The molecular basis of the action of disulfiram as a modulator of the multidrug resistance-linked ATP binding cassette transporters MDR1 (ABCB1) and MRP1 (ABCC1); Sauna ZE et al.; The overexpression of multidrug resistance protein 1 (MDR1) and multidrug resistance protein 1 (MRP1) gene products is a major cause of multidrug resistance in cancer cells . A recent study suggested that disulfiram, a drug used to treat alcoholism, might act as a modulator of P-glycoprotein . In this study, we investigated the molecular and chemical basis of disulfiram as a multidrug resistance modulator . We demonstrate that in intact cells, disulfiram reverses either MDR1- or MRP1-mediated efflux of fluorescent drug substrates . Disulfiram inhibits ATP hydrolysis and the binding of {alpha-32P}8-azidoATP to P-glycoprotein and MRP1, with inhibition curves comparable with those of N-ethylmaleimide, a cysteine-modifying agent . However, if the ATP sites are protected with excess ATP, disulfiram stimulates ATP hydrolysis by both transporters in a concentration-dependent manner . Thus, in addition to modifying cysteines at the ATP sites, disulfiram may interact with the drug-substrate binding site . We demonstrate that disulfiram, but not N-ethylmaleimide, inhibits in a concentration-dependent manner the photoaffinity labeling of the multidrug transporter with 125I-iodoarylazidoprazosin and {3H}azidopine . This suggests that the interaction of disulfiram with the drug-binding site is independent of its role as a cysteine-modifying agent . Finally, we have exploited MRP4 (ABCC4) to demonstrate that disulfiram can inhibit ATP binding by forming disulfide bonds between cysteines located in the vicinity of, although not in, the active site . Taken together, our results suggest that disulfiram has unique molecular interactions with both the ATP and/or drug-substrate binding sites of multiple ATP binding cassette transporters, which are associated with drug resistance, and it is potentially an attractive agent to combat multidrug resistance. J Pharmacol Exp Ther, 2004 Jun, 309(3), 1029 - 35 Epub 2004 Feb 20. Cyclosporin A, but not tacrolimus, inhibits the biliary excretion of mycophenolic acid glucuronide possibly mediated by multidrug resistance-associated protein 2 in rats; Kobayashi M et al.; The onset of diarrhea after the administration of mycophenolate mofetil (MMF) is possibly associated with the biliary excretion of its metabolite, mycophenolic acid glucuronide (MPAG) . This study was undertaken to clarify the mechanism underlying the biliary excretion of MPAG . Intravenously administered mycophenolic acid (MPA, 5 mg/kg) rapidly disappeared from plasma and was efficiently excreted as MPAG in the bile of Wistar (26% of dose) and Sprague-Dawley rats (21% of dose) over 1 h . On the other hand, in spite of the rapid disappearance of MPA from plasma, the biliary excretion of MPAG was very limited in Eisai hyperbilirubinemic rats (EHBRs), which display mutations in multidrug resistance-associated protein 2 (Mrp2)/canalicular multispecific organic anion transporter, and constituted only 0.5% of dose . Instead, high levels of MPA were noted in the plasma of EHBRs . Intravenous administration of CsA (5 mg/kg) to Wistar rats significantly lowered the biliary excretion of MPAG . However, intravenously administered tacrolimus (0.1 mg/kg) failed to produce such effect . In conclusion, it is suggested that there is an efficient MPAG transport mediated by Mrp2 on the bile canalicular membrane of rat hepatocytes and that the therapeutic range of CsA potentially interferes with Mrp2 . However, the therapeutic range of tacrolimus does not inhibit the transporter . Thus, it should be noted that MMF coadministered with tacrolimus instead of CsA might increase the occurrence of diarrhea related to the biliary excretion of MPAG in transplant recipients. Toxicol Sci, 2004 May, 79(1), 189 - 95 Epub 2004 Feb 19. Biliary secretory function in rats chronically intoxicated with aluminum; Gonzalez MA et al.; The effects of a chronic aluminum (Al) exposure on biliary secretory function, with special emphasis on hepatic handling of non-bile salt organic anions, was investigated . Male Wistar rats received, intraperitoneally, either 27 mg/kg body weight of Al, as Al hydroxide {Al (+) rats}, or the vehicle saline {Al (-) rats} three times a week for 3 months . Serum and hepatic Al levels were increased by the treatment (approximately 9- and 4-fold, respectively) . This was associated with enhanced malondialdehyde formation (+110%) and a reduction in GSH content (-17%) and in the activity of the antioxidant enzymes catalase (-84%) and GSH peroxidase (-46%) . Bile flow (-23%) and the biliary output of bile salts (-39%), cholesterol (-43%), and proteins (-38%) also decreased . Compartmental analysis of the plasma decay of the model organic anion bromosulphophthalein revealed that sinusoidal uptake and canalicular excretion of the dye were significantly decreased in Al (+) rats (-53 and -43%, respectively) . Expression of multidrug resistance-associated protein 2 (Mrp2), the main, multispecific transporter involved in the canalicular excretion of organic anions, was also decreased (-40%), which was associated with a significant decrease in the cumulative biliary excretion of the Mrp2 substrate, dinitrophenyl-S-glutathione (-50%) . These results show that chronic Al exposure leads to oxidative stress, cholestasis, and impairment of the hepatic handling of organic anions by decreasing both sinusoidal uptake and canalicular excretion . The alteration of the latter process seems to be causally related to impairment of Mrp2 expression . We have addressed some possible mechanisms involved in these deleterious effects. Biochem Biophys Res Commun, 2004 Mar 12, 315(3), 719 - 25 Mapping of the MRPm5 epitope to the cytosolic region between transmembrane helices 13 and 14 in the drug and organic anion transporter, MRP1 (ABCC1); Koike K et al.; Multidrug resistance in human tumour cells is often associated with increased expression of the 190kDa multidrug resistance protein, MRP1, that belongs to the ATP-binding cassette superfamily of transport proteins . MRP1 is also an efficient transporter of many organic anions . In the present study, we have mapped the epitope of the MRP1-specific murine monoclonal antibody (MAb) MRPm5 to the decapeptide (1063)FFERTPSGNL(1072) located in the cytoplasmic loop (CL6) linking transmembrane helices 13 and 14 in the third membrane spanning domain of the protein . Several amino acids in the cytoplasmic loops of MRP1 have been reported to be important for its transport function; nevertheless, MAb MRPm5 does not inhibit vesicular uptake of the high affinity substrate leukotriene C(4) . None of the other MRP1-reactive MAbs described to date map to CL6 of MRP1 which in turn enhances the utility of MAb MRPm5 for both clinical and experimental investigations of this transporter. Int J Tuberc Lung Dis, 2004 Jan, 8(1), 52 - 8 Identifying early treatment failure on category I therapy for pulmonary tuberculosis in Lima Ciudad, Peru; Chavez Pachas AM et al.; SETTING: Ambulatory, public tuberculosis treatment facilities, central Lima, Peru . OBJECTIVE: To identify risk factors for failure on directly observed Category I therapy . DESIGN: Case-control study . All failures of Category I (2HREZ/4H2R2) therapy in 2000 (2.9% of smear-positive TB patients) were included as cases; two controls per case were matched on health center and approximate time of treatment initiation . RESULTS: The study included 38 cases and 76 controls, all new smear-positive, pulmonary TB patients treated with Category I therapy in central Lima in 2000 . Neither treatment irregularity nor incidence of adverse events predicted failure in the study group . Mean baseline body mass index was lower in cases than in controls (P = 0.06) . Cases gained less weight during therapy (P = 0.01) . Smear positivity at 2 months of therapy was strongly associated with failure (OR 11.7; 95%CI 2.4-57.5) . No controls had positive smears at or after 3 months of therapy (OR {corrected} 144.9; 95%CI 8.4-2500) . Nearly 75% of cases with isolates tested for susceptibility to first-line drugs had multidrug-resistant TB (MDR-TB) . CONCLUSION: A large proportion of failures on Category I therapy can be identified early . As three-quarters of patients with susceptibility results have MDR-TB, early referral for culture and drug susceptibility testing is critical for prompt initiation of appropriate therapy and improved outcomes. Int J Tuberc Lung Dis, 2004 Jan, 8(1), 31 - 8 Development of acquired drug resistance in recurrent tuberculosis patients with various previous treatment outcomes; Yoshiyama T et al.; SETTING: Chiang Rai province, Northern Thailand . OBJECTIVE: To study the probability of acquiring drug resistance to isoniazid (H) and rifampicin (R) on recurrence after treatment success, default and failure, among sputum smear-positive pulmonary tuberculosis (TB) patients treated with standardised short-course chemotherapy . DESIGN: Retrospective analysis of registration records of TB patients from May 1996 to December 2000 in Chiang Rai, where routine drug susceptibility testing (DST) is conducted for surveillance purposes . Patients registered twice or more were examined . RESULTS: Of 59 cases treated with HRZE/HR who underwent DST at the time of registration, 31 were fully susceptible to H and R at first registration, of whom four acquired drug resistance to H or R . Of 13 cases resistant to H or R at first registration, 11 became multidrug-resistant (MDR) . The remaining 15 patients were original MDR cases . Among 28 MDR or H- or R-resistant cases, six reverted from resistant to susceptible . DISCUSSION: A high proportion of patients with H- or R-resistant TB became MDR after treatment with 2HRZE/HR . Using this regimen, MDR may increase in a population with a high prevalence of H or R resistance . We are unable to explain why some drug-resistant cases became drug-susceptible . Further investigation is necessary. Int J Tuberc Lung Dis, 2004 Jan, 8(1), 23 - 30 Drug resistance monitoring: combined rates may be the best indicator of programme performance; Van Deun A et al.; SETTING: Greater Mymensingh District, Bangladesh . OBJECTIVES: To determine changes in prevalence of drug resistance of Mycobacterium tuberculosis under DOTS . DESIGN: Drug susceptibility testing of systematic samples of M . tuberculosis isolated from all sputum smear-positive cases newly registered in sentinel centres during 1995 and 2001 . Continuous monitoring of retreatment registrations and resistance of strains from relapse and failure cases . RESULTS: Of 942 strains from the new cases in 2001, 10.8% showed resistance to any drug, 6.2% to isoniazid, 0.4% to rifampicin (all of them multidrug-resistant, MDR), 7.1% to streptomycin, and 1.0% to ethambutol . Corresponding rates for 99 strains from previously treated cases were 32%, 20%, 3%, 20% and 2%, respectively . Although most rates of resistance had decreased since 1995, increased streptomycin resistance was the only significant change when new and previously treated cases were considered separately . However, combined resistance for any drug, isoniazid, rifampicin and MDR had decreased significantly . CONCLUSION: As suggested by monitoring of resistance in failure and relapse cases and by routine programme reports, drug resistance had decreased . Combined resistance demonstrated changes between periodic surveys better than its subgroups, and may be a more reliable and comprehensive indicator . However, continuous monitoring of the pool of resistant retreatment cases is a more efficient strategy. Int J Tuberc Lung Dis, 2004 Jan, 8(1), 15 - 22 Study of resistance to anti-tuberculosis drugs in five districts of Equatorial Guinea: rates, risk factors, genotyping of gene mutations and molecular epidemiology; Tudo G et al.; SETTING: Five districts in Equatorial Guinea, March 1999 to February 2001 . OBJECTIVES: To determine tuberculosis drug resistance among new and previously treated cases, the risk factors associated with resistance, and the mutations associated with isoniazid and rifampicin (katG, inhA and rpoB genes) resistance, and to genotype resistant strains . RESULTS: A positive culture identified as Mycobacterium tuberculosis complex was obtained in 240/499 patients . Susceptibility testing was performed in 236 strains . The overall resistance rate in new cases was 16.9% compared to 41.6% in previously treated cases . Isoniazid resistance was the most frequent (respectively 12.5% and 16.6%) in the two groups, while multidrug resistance was observed in 1.7% and 25% of new and previously treated cases, respectively . Female sex was statistically associated with resistance in new cases . Of 41 isoniazid-resistant strains, 33 (80.5%) had mutations in the inhA gene; none had mutations in the katG gene and eight had no mutations in either gene . All strains had low-level isoniazid resistance . Of eight strains resistant to rifampicin, six had mutations in the rpoB gene . Genotyping defined seven clusters . CONCLUSIONS: Moderate resistance was found in new cases . Low-level isoniazid resistance predominated among mutations in the inhA gene, with a high percentage of clustering in resistant strains. Cancer Res, 2004 Feb 15, 64(4), 1242 - 6 Pheophorbide a is a specific probe for ABCG2 function and inhibition; Robey RW et al.; Pheophorbide a (PhA), a chlorophyll catabolite, was shown to be an ABCG2 substrate based on Abcg2(-/-) knockout mouse studies (J . W . Jonker et al., Proc . Natl . Acad . Sci . USA, 99: 15649-15654, 2002) . We developed a functional assay for ABCG2 using PhA and the ABCG2 inhibitor fumitremorgin C . In selected cell lines expressing high levels of P-glycoprotein, multidrug resistance-associated protein 1, or ABCG2, PhA transport was observed only in cells expressing ABCG2 . Fumitremorgin C-inhibitable PhA transport was found to correlate with cell surface ABCG2 expression as measured by the anti-ABCG2 antibody 5D3 . We found that 100 micro M of the cyclin-dependent kinase inhibitor UCN-01 or 1 micro M of the P-glycoprotein inhibitor tariquidar inhibited ABCG2-mediated PhA transport . In 4-day cytotoxicity assays, ABCG2-mediated resistance to SN-38 and topotecan was abrogated in ABCG2-transfected HEK-293 cells treated with 1 micro M tariquidar, and ABCG2-transfected cells were 6-7-fold resistant to UCN-01 . PhA is an ABCG2-specific substrate with potential value in measuring ABCG2 function and expression in clinical samples. J Bacteriol, 2004 Mar, 186(5), 1423 - 9 Role of histone-like protein H-NS in multidrug resistance of Escherichia coli; Nishino K et al.; The histone-like protein H-NS is a major component of the bacterial nucleoid and plays a crucial role in global gene regulation of enteric bacteria . It is known that the expression of a variety of genes is repressed by H-NS, and mutations in hns result in various phenotypes, but the role of H-NS in the drug resistance of Escherichia coli has not been known . Here we present data showing that H-NS contributes to multidrug resistance by regulating the expression of multidrug exporter genes . Deletion of the hns gene from the DeltaacrAB mutant increased levels of resistance against antibiotics, antiseptics, dyes, and detergents . Decreased accumulation of ethidium bromide and rhodamine 6G in the hns mutant compared to that in the parental strain was observed, suggesting the increased expression of some drug exporter(s) in this mutant . The increased drug resistance and decreased drug accumulation caused by the hns deletion were completely suppressed by deletion of the multifunctional outer membrane channel gene tolC . At least eight drug exporter systems require TolC for their functions . Among these, increased expression of acrEF, mdtEF, and emrKY was observed in the Deltahns strain by quantitative real-time reverse transcription-PCR analysis . The Deltahns-mediated multidrug resistance pattern is quite similar to that caused by overproduction of the AcrEF exporter . Deletion of the acrEF gene greatly suppressed the level of Deltahns-mediated multidrug resistance . However, this strain still retained resistance to some compounds . The remainder of the multidrug resistance pattern was similar to that conferred by overproduction of the MdtEF exporter . Double deletion of the mdtEF and acrEF genes completely suppressed Deltahns-mediated multidrug resistance, indicating that Deltahns-mediated multidrug resistance is due to derepression of the acrEF and mdtEF drug exporter genes. Mol Cell Biochem, 2004 Jan, 255(1-2), 11 - 8 Toxicokinetic and genomic analysis of chronic arsenic exposure in multidrug-resistance mdr1a/1b(-/-) double knockout mice; Xie Y et al.; Multidrug-resistance gene knockout mdr1a/1b(-/-) mice, which are deficient in P-glycoproteins, are more sensitive than wild-type (WT) mice to acute arsenic toxicity . This study assessed toxic manifestations of chronic oral arsenic in mdr1a/1b(-/-) mice, including oxidative stress and altered gene expression, and investigated altered toxicokinetics as a potential basis of enhanced arsenic toxicity . Thus, mdr1a/1b(-/-) and WT mice were exposed to sodium arsenite (0-80 ppm as arsenic) in the drinking water for 10 weeks at which time hepatic arsenic accumulation, lipid peroxidation (LPO), redox status and change in gene expression level were assessed . All mice survived the arsenic exposure, but body weight gain in the highest dose group was reduced in both mdr1a/1b(-/-) and WT mice . Arsenic induced pathological changes, elevated LPO levels and enhanced glutathione S-transferase (GST) activity, in the liver to a greater extent in mdr1a/1b(-/-) than in WT mice . Arsenic also decreased Cu/Zn superoxide dismutase activity in both mdr1a/1b(-/-) and WT mice . The expressions of certain genes, such as those encoding cell proliferation, GST, acute-phase proteins and metabolic enzymes, were modestly altered in arsenic-exposed mice . The expression of cyclin D1, a potential hepatic oncogene, was enhanced in arsenic-exposed mdr1a/1b(-/-) mice only . At the highest level of exposure, hepatic arsenic content was higher in mdr1a/1b(-/-) than in WT mice, suggesting that enhanced accumulation due to transport deficiency may, in part, account for the enhanced toxicity in these mice . In summary, this study shows that chronic arsenic toxicity, including liver pathology and oxidative stress, is enhanced in mdr1a/1b(-/-) mice, possibly due to enhanced accumulation of arsenic as a result of transport system deficiency. Proc Natl Acad Sci U S A, 2004 Mar 2, 101(9), 2852 - 7 Epub 2004 Feb 17. Structure of the multidrug resistance efflux transporter EmrE from Escherichia coli; Ma C et al.; Multidrug resistance efflux transporters threaten to reverse the progress treating infectious disease by extruding a wide range of drug and other cytotoxic compounds . One such drug transporter, EmrE, from the small multidrug resistance family, utilizes proton gradients as an energy source to drive substrate translocation . In an effort to understand the molecular structural basis of this transport mechanism, we have determined the structure of EmrE from Escherichia coli to 3.8 A . EmrE is a tetramer comprised of two conformational heterodimers related by a pseudo two-fold symmetry axis perpendicular to the cell membrane . Based on the structure and biochemical evidence, we propose a mechanism by which EmrE accomplishes multidrug efflux by coupling conformational changes between two heterodimers with proton gradient . Because of its simplicity and compact size, the structure of EmrE can serve as an ideal model for understanding the general structural basis of proton:drug antiport for other drug efflux systems. Am J Physiol Renal Physiol, 2004 Jul, 287(1), F33 - 8 Epub 2004 Feb 17. Involvement of guanylyl cyclase and cGMP in the regulation of Mrp2-mediated transport in the proximal tubule; Notenboom S et al.; In killifish renal proximal tubules, endothelin-1 (ET-1), acting through a basolateral ET(B) receptor, nitric oxide synthase (NOS), and PKC, decreases cell-to-lumen organic anion transport mediated by the multidrug resistance protein isoform 2 (Mrp2) . In the present study, we examined the roles of guanylyl cyclase and cGMP in ET signaling to Mrp2 . Using confocal microscopy and quantitative image analysis to measure Mrp2-mediated transport of the fluorescent drug fluorescein methotrexate (FL-MTX), we found that oxadiazole quinoxalin (ODQ), an inhibitor of NO-sensitive guanylyl cyclase, blocked ET-1 signaling . ODQ was also effective when signaling was initiated by nephrotoxicants (gentamicin, amikacin, diatrizoate, HgCl(2), and CdCl(2)), which appear to stimulate ET release from the tubules themselves . ODQ blocked the effects of the NO donor sodium nitroprusside but not of the phorbol ester that activates PKC . Exposing tubules to 8-bromo-cGMP (8-BrcGMP), a cell-permeable cGMP analog, decreased luminal FL-MTX accumulation . This effect was abolished by bisindoylmaleimide (BIM), a PKC inhibitor, but not by N(G)-methyl-l-arginine, a NOS inhibitor . Together, these data indicate that ET regulation of Mrp2 involves activation of guanylyl cyclase and generation of cGMP . Signaling by cGMP follows NO release and precedes PKC activation. J Lipid Res, 2004 May, 45(5), 933 - 40 Epub 2004 Feb 16. Oligonucleotides blocking glucosylceramide synthase expression selectively reverse drug resistance in cancer cells; Liu YY et al.; High glucosylceramide synthase (GCS) activity is one factor contributing to multidrug resistance (MDR) in breast cancer . Enforced GCS overexpression has been shown to disrupt ceramide-induced apoptosis and to confer resistance to doxorubicin . To examine whether GCS is a target for cancer therapy, we have designed and tested the effects of antisense oligodeoxyribonucleotides (ODNs) to GCS on gene expression and chemosensitivity in multidrug-resistant cancer cells . Here, we demonstrate that antisense GCS (asGCS) ODN-7 blocked cellular GCS expression and selectively increased the cytotoxicity of anticancer agents . Pretreatment with asGCS ODN-7 increased doxorubicin sensitivity by 17-fold in MCF-7-AdrR (doxorubicin-resistant) breast cancer cells and by 10-fold in A2780-AD (doxorubicin-resistant) ovarian cancer cells . In MCF-7 drug-sensitive breast cancer cells, asGCS ODN-7 only increased doxorubicin sensitivity by 3-fold, and it did not influence doxorubicin cytotoxicity in normal human mammary epithelial cells . asGCS ODN-7 was shown to be more efficient in reversing drug resistance than either the GCS chemical inhibitor d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol or the P-glycoprotein blocking agents verapamil and cyclosporin A . Experiments defining drug transport and lipid metabolism parameters showed that asGCS ODN-7 overcomes drug resistance mainly by enhancing drug uptake and ceramide-induced apoptosis . This study demonstrates that a 20-mer asGCS oligonucleotide effectively reverses MDR in human cancer cells. Chem Res Toxicol, 2004 Feb, 17(2), 158 - 64 Multidrug resistance-associated protein 2 (MRP2) enhances 4-hydroxynonenal-induced toxicity in Madin-Darby canine kidney II cells; Ji B et al.; 4-Hydroxy-trans-2,3-nonenal (HNE) is a toxic end product of lipid peroxidation . This multifunctional aldehyde reacts with proteins, phospholipids, and nucleic acids, consequently activating/inactivating enzymes, affecting signal transduction and gene expression . HNE is mainly detoxified by glutathione (GSH) conjugation . In our previous report, we showed that GSH conjugates of 4-hydroxynonenal (HNE-SG) are substrates of multidrug resistance-associated protein 2 (MRP2) . MRP2 has been shown to export HNE-SG conjugates into the extracellular space . In the present study, the role of MRP2 in the detoxification of HNE was studied using Madin-Darby canine kidney II (MDCK II) cells expressing human MRP2 . MRP2 reduced the intracellular accumulation of HNE-SG conjugate but unexpectedly increased the susceptibility of cells to HNE . The viability of cells was reduced to approximately 70% in the presence of 62.5 microM HNE in MDCK II cells expressing MRP2, whereas MDCK II cells remained unaffected . MRP2 accelerated the elimination of intracellular GSH via a conjugation reaction with HNE (half-life of GSH was 30.1 and 12.2 min for MDCK II cells and MDCK II cells expressing MRP2, respectively) . Moreover, the consumption of GSH was unlimited in MDCK II cells expressing MRP2, finally resulting in necrosis . These results indicate that MRP2 has an adverse effect during the detoxification of HNE in MDCK II cells and suggest that expression of MRP2 may enhance the damage caused by oxidative stress. Neoplasia, 2003 Nov-Dec, 5(6), 475 - 80 Bypass of tumor drug resistance by antivascular therapy; Preise D et al.; Multidrug resistance (MDR) presents a major obstacle for the successful chemotherapy of cancer . Its emergence during chemotherapy is attributed to a selective process, which gives a growth advantage to MDR cells within the genetically unstable neoplastic cell population . The pleiotropic nature of clinical MDR poses a great difficulty for the development of treatment strategies that aim at blocking MDR at the tumor cell level . Targeting treatment to the nonmalignant vascular network-the lifeline of the tumor-is a promising alternative for the treatment of drug-resistant tumors . The present study demonstrates that MDR in cancer can be successfully circumvented by photodynamic therapy (PDT) using an antivascular treatment protocol . We show that, although P-glycoprotein-expressing human HT29/MDR colon carcinoma cells in culture are resistant to PDT with Pd-bacteriopheophorbide (TOOKAD), the same treatment induces tumor necrosis with equal efficacy (88% vs 82%) in HT29/MDR-derived xenografts and their wild type counterparts, respectively . These results are ascribed to the rapid antivascular effects of the treatment, supporting the hypothesis that MDR tumors can be successfully eradicated by indirect approaches that bypass their inherent drug resistance . We suggest that with progress in ongoing clinical trials, TOOKAD-PDT may offer a novel option for local treatment of MDR tumors. Curr Pharm Des, 2004, 10(6), 647 - 57 Cyclooxygenase-2: potential role in regulation of drug efflux and multidrug resistance phenotype; Sorokin A; Multidrug resistance (MDR) of cancer cells to cytostatic agents is the major obstacle for the succesfull chemotherapy . One of the causes of the development of cellular resistance to a wide variety of drugs is the elevated expression of membrane transporter proteins such as members of ATP binding cassette (ABC) protein superfamily . Expression of the ABC transporter MDR1, also termed P-glycoprotein (P-gp), seems to correlate with drug resistance of tumors to chemotherapy . Cyclooxygenase-2, an inducible isoform of enzyme, responsible for generation of prostaglandins from arachidonic acid, is constitutively expressed in a number of cancer cells . Anti-cancer potency of cyclooxygenase inhibitors is established, but the mechanism of Cox-2-dependent potentiation of tumor growth is a subject of intense discussion . Here we focus on the discussion of potential link between Cox-2 expression and development of multidrug resistance phenotype . Our observation, that enforced expression of Cox-2 causes enhancement in MDR1 expression and functional activity suggests the existence of causal link between Cox-2 activity and MDR1 expression . The use of Cox-2 inhibitors to decrease function of MDR1 may enhance accumulation of chemotherapy agents and decrease resistance of tumors to chemotherapeutic drugs. Curr Drug Metab, 2004 Feb, 5(1), 21 - 53 The MRP-related and BCRP/ABCG2 multidrug resistance proteins: biology, substrate specificity and regulation; Haimeur A et al.; Several members of different families of the ATP-binding cassette (ABC) superfamily of transport proteins are capable of transporting an extraordinarily structurally diverse array of endo- and xenobiotics and their metabolites across cell membranes . Together, these transporters play an important role in the absorption, disposition and elimination of these chemicals in the body . In tumor cells, increased expression of these drug transporters is associated with resistance to multiple chemotherapeutic agents . In this review, current knowledge of the biochemical, physiological and pharmacological properties of nine members of the multidrug resistance protein (MRP)-related ABCC family (MRP1, MRP2, MRP3, MRP4, MRP5, MRP6, MRP7, ABCC11 and ABCC12) as well as the G family member, ABCG2/BCRP, are summarized . A focus is placed on the structural similarities and differences of these drug transporters as well as the molecular determinants of their substrate specificities and transport activities . Factors that regulate expression of the MRP-related proteins and ABCG2/BCRP are also reviewed. Curr Drug Metab, 2004 Feb, 5(1), 11 - 9 The role of MDR1 genetic polymorphisms in interindividual variability in P-glycoprotein expression and function; Woodahl EL et al.; The human multidrug resistance gene (MDR1), spanning greater than 200 kb, encodes for the ATP-dependent membrane efflux transporter, P-glycoprotein (Pgp) . Significant progress has been made in the discovery of MDR1 polymorphisms and the assessment of allelic frequencies . The search for key genetic determinants that predispose individuals to drugs that are substrates or inhibitors of Pgp has just begun . Reports in the literature, particularly focusing on the C3435T polymorphism, have provided discordant results with respect to functional modification in vitro, and Pgp expression and disposition of probe drugs in vivo . Due to the large size of the MDR1 gene, genotyping based on individual single nucleotide polymorphism (SNPs) analysis is not sufficient to predict functional consequences . Strong linkage disequilibrium has been detected between several MDR1 polymorphisms, and discrepancies in the literature may be due to the focus on the influence of single nucleotide variations instead of on linked nucleotide variations . Multiple SNPs found on the same chromosome are assigned to a specific haplotype, and some attempts have been made to determine the role of MDR1 haplotypes in Pgp variability . Most of the data for MDR1 haplotype have been predicted based on computational or mathematical models . However, molecular haplotyping techniques, analysis of linkages on the same chromosome directly by biophysical and biochemical means, may be needed to characterize haplotypes in individuals with a highly polymorphic and large gene like MDR1 . Haplotype identification may prove to be vital in identifying the functional significance of MDR1 polymorphisms on disease susceptibility and drug disposition. Clin Nephrol, 2004 Jan, 61(1), 25 - 9 Mycophenolate mofetil in children with multidrug-resistant nephrotic syndrome; Bayazit AK et al.; AIM: The aim of the present study is to report our clinical experiences with MMF in problematic children with chronic glomerulonephritis resistant to corticosteroids and/or other immunosuppressive drugs . PATIENTS AND METHODS: Ten patients with chronic glomerulonephritis resistant to treatment with corticosteroids and other immunosuppressive drugs were treated with mycophenolate mofetil (MMF) . Causes of chronic glomerulonephritis were mesangial proliferative glomerulonephritis (4), membranoproliferative glomerulonephritis (3), chronic sclerosing glomerulonephritis (1), focal segmental glomerulosclerosis (1), diffuse endo- and extracapillary proliferative glomerulonephritis (1) . MMF 15 mg/kg was used in combination with low-dose corticosteroids and angiotensin-converting enzyme inhibitors . RESULTS: During 24 weeks of MMF therapy, no significant changes were detected in mean serum creatinine, albumin and proteinuria . Severe leukopenia was seen in 1 patient . Additional adverse effects, including nausea and diarrhea, were observed in another patient when the dosage was increased to 20 mg/kg per day . During MMF treatment proteinuria decreased slightly without remission in 6 of 10 patients . CONCLUSION: Further data and clinical trials are needed to evaluate the possible role of MMF in the treatment of chronic glomerulonephritis of similar etiologies in pediatric patients. Blood, 2004 Jun 1, 103(11), 4276 - 84 Epub 2004 Feb 12. The peripheral benzodiazepine receptor ligand PK11195 overcomes different resistance mechanisms to sensitize AML cells to gemtuzumab ozogamicin; Walter RB et al.; The antibody-targeted therapeutic, gemtuzumab ozogamicin (GO, Mylotarg), is approved for treatment of relapsed acute myeloid leukemia (AML) . We previously showed that AML blasts from GO refractory patients frequently express the drug transporters P-glycoprotein (Pgp) and/or multidrug resistance protein (MRP) . We also previously reported that inhibition of drug transport by the Pgp modulator, cyclosporine A (CSA), can increase GO sensitivity in Pgp(+) AML cells and that the peripheral benzodiazepine receptor ligand, PK11195, sensitizes AML cells to standard chemotherapeutics both by inhibiting Pgp-mediated efflux and by promoting mitochondrial apoptosis . We now show that PK11195 also can overcome multiple resistance mechanisms to increase GO sensitivity in AML cells, including resistance associated with expression of drug transporters and/or antiapoptotic proteins . PK11195 substantially increases GO cytotoxicity in AML cells from many different cell lines and primary patient samples, often more effectively than CSA . We also show that PK11195 is nontoxic in NOD/SCID mice and can sensitize xenografted human AML cells to GO . Since PK11195 is well tolerated in humans as a single agent, its further study as a multifunctional chemosensitizer for anti-AML therapies, including GO-based therapies, is warranted. Eur J Cancer, 2004 Mar, 40(4), 606 - 13 Inhibition of multidrug resistance by immunisation with synthetic P-glycoprotein-derived peptides; Pawlak-Roblin C et al.; Overexpression of the membrane glycoprotein (P170) represents the most common multidrug resistance (MDR) mechanism in cancer therapy . Specific auto-antibodies to extracellular loops 1, 2 and 4 of murine P170 were elicited in mice using palmitoylated synthetic peptides reconstituted in liposomes, with or without Lipid A, and resuspended in alum . IgM antibodies were detected 14 days following the first injection and IgG1 became predominant after the third challenge . Animals did not show any auto-immune symptoms or induced toxicity up to 18 months after the immunisation . Previous immunisations of mice using liposomes with MDR1 peptides increases the efficacy of chemotherapy treatments with doxorubicin and vinblastine against P388 R cells with increase of 77% in the survival half time in the immunised group . Sera from the immunised mice were also effective in reducing cellular resistance to vinblastine and doxorubicin in vitro . Taken together, these data suggest that this immunisation approach might have potential clinical applications. Lancet, 2004 Feb 7, 363(9407), 474 - 81 Programmes and principles in treatment of multidrug-resistant tuberculosis; Mukherjee JS et al.; Multidrug-resistant tuberculosis (MDR-TB) presents an increasing threat to global tuberculosis control . Many crucial management issues in MDR-TB treatment remain unanswered . We reviewed the existing scientific research on MDR-TB treatment, which consists entirely of retrospective cohort studies . Although direct comparisons of these studies are impossible, some insights can be gained: MDR-TB can and should be addressed therapeutically in resource-poor settings; starting of treatment early is crucial; aggressive treatment regimens and high-end dosing are recommended given the lower potency of second-line antituberculosis drugs; and strategies to improve treatment adherence, such as directly observed therapy, should be used . Opportunities to treat MDR-TB in developing countries are now possible through the Global Fund to Fight AIDS, TB, and Malaria, and the Green Light Committee for Access to Second-line Anti-tuberculosis Drugs . As treatment of MDR-TB becomes increasingly available in resource-poor areas, where it is needed most, further clinical and operational research is urgently needed to guide clinicians in the management of this disease. Eur J Haematol, 2004 Jan, 72(1), 45 - 51 Significant co-expression of WT1 and MDR1 genes in acute myeloid leukemia patients at diagnosis; Galimberti S et al.; A high expression of Wilms' tumor gene (WT1) in acute myeloid leukemia (AML) seems to correlate with a poor outcome and its increased levels can be predictive of an impending relapse . WT1 has been shown in vitro to interact with the promoter of the MDR1, a gene involved in the multidrug resistance phenomenon . The aim of this study was to measure, by real-time polymerase chain reaction, levels of WT1 and MDR1 expression, in order to find a possible association between these genes, in a series of 50 newly diagnosed AML cases . Twenty-five percent of patients carried very high (>75 degrees percentile) MDR1- and 23.3%WT1-mRNA levels . Interestingly, high levels of WT1 were significantly correlated with correspondent high levels of MDR1 gene . Nevertheless, the co-expression of these genes did not significantly influence the complete response rate to the induction therapy . Reported data confirm the existence of a co-expression of WT1 and MDR1 genes even in vivo; this may be relevant because one consequence could be the positive selection by chemotherapeutic regimens of cells with higher MDR1 levels already present before treatment . Thus, the association between these genes could suggest avoiding the use of drugs involved in the multidrug resistance (MDR) phenomenon in patients carrying high levels of WT1 at diagnosis. Leuk Lymphoma, 2003 Dec, 44(12), 2109 - 16 Physiological oxidants induce apoptosis and cell cycle arrest in a multidrug-resistant natural killer cell line, NK-YS; Than TA et al.; Natural-killer (NK) cell-derived malignant tumors, such as angiocentric lymphoma, is often resistant to various chemotherapeutic agents and follows an aggressive clinical course . We report the effects of physiological oxidants (hydrogen peroxide, H2O2; sodium hypochlorite, NaOCl and monochloramine, NH2Cl) on the cell growth and cell death in a multidrug-resistant NK tumor cell line, NK-YS . Among the oxidants tested, NH2Cl was most cytotoxic, in which more than 90% of the cells died at 150 nmol/1 x 10(6) cells . H2O2 was less cytotoxic, whereas NaOCl showed no significant cell death at this dose . The cell death induced by NH2Cl was accompanied by DNA cleavage and caspase activation, which suggested apoptosis . In addition, lower dose of NH2Cl (70 nmol/1 x 10(6) cells) retarded cell growth and inhibited the cell cycle transition from G1 to S . This cell cycle arrest accompanied a decrease in the phosphorylation of retinoblastoma tumor suppressor protein at serine 795 . These observations suggest that NH2Cl may induce apoptotic cell death and growth arrest in multidrug-resistant NK cell tumors. J Biol Chem, 2004 Apr 23, 279(17), 17134 - 41 Epub 2004 Feb 09. RNA helicase A in the MEF1 transcription factor complex up-regulates the MDR1 gene in multidrug-resistant cancer cells; Zhong X et al.; RNA helicase A (RHA) is a member of the DEAD/H family of RNA helicases and unwinds duplex RNA and DNA . Recent studies have shown that RHA regulates the activity of gene promoters . However, little information is available about the in vivo relevance of RHA in the regulation of natural genes . We previously characterized a nuclear protein (MEF1) that binds to the proximal promoter of the multidrug resistance gene (MDR1) and up-regulates the promoter activity . In the present study, we isolated and identified RHA as a component of the MEF1 complex by using DNA-affinity chromatography and mass spectrometry . The antibody against RHA specifically disrupted the complex formation in electrophoretic mobility shift assay, confirming the identity of RHA . Western blotting showed that RHA in drug-resistant cells had a higher molecular weight than that in drug-sensitive cells . Similar results were obtained when FLAG-tagged RHA was overexpressed in these cells . This size difference probably reflects posttranslational modification(s) of RHA in drug-resistant cells . Chromatin immunoprecipitation revealed that RHA occupies the MDR1 promoter in vivo . Overexpression of RHA enhanced expression of the MDR1 promoter/reporter construct and endogenous P-glycoprotein (P-gp), the MDR1 gene product, and increased drug resistance of drug-resistant cells but not the drug-sensitive counterpart . Introduction of short interfering RNA targeting the RHA gene sequence selectively knocked-down RHA expression and concomitantly reduced P-gp level . Thus, our study demonstrates, for the first time, the involvement of RHA in up-regulation of the MDR1 gene . Interactions of RHA with other protein factors in the MEF1 complex bound to the promoter element may contribute to P-gp overexpression and multidrug resistance phenotype in drug-resistant cancer cells. Oncol Rep, 2004 Mar, 11(3), 641 - 5 Chemotherapeutic potential of plant alkaloids and multidrug resistance mechanisms in malignant fibrous histiocytoma of the heart; Reinecke P et al.; Primary malignant fibrous histiocytoma (MFH) of the heart is a rare and highly malignant soft tissue tumor, which is largely resistant to conventional chemotherapy and radiotherapy . Therefore, we analyzed growth inhibitory effects of different chemotherapeutic agents and mechanisms of drug resistance in the recently established cell line MFH-H derived from a human primary cardiac MFH . The growth inhibitory effects of etoposide, vincristine, and paclitaxel were tested using the MTT assay . The expression and function of multidrug resistance-related proteins, i.e . the P-glycoprotein, the multidrug resistance-associated protein (MRP) and the lung resistance-related protein (LRP) were determined by FACScan and functional assays of cellular drug efflux . The concentration required for a 50% inhibition of growth (IC50) was 0.001 microM for etoposide and 0.035 microM for vincristine . Paclitaxel dissolved in Cremophor EL/ethanol inhibited the cell growth of MFH-H cells more intensively (IC50: 0.27 microM) than paclitaxel dissolved in DMSO (IC50: 11.09 microM) suggesting that Cremophor EL is contributing to the inhibitory effects of paclitaxel . The response of MFH-H to etoposide, vincristine and paclitaxel/Taxol could not be predicted by the expression and function of P-glycoprotein, MRP and LRP . This study demonstrates that etoposide and to a lesser extent vincristine can effectively inhibit the growth of MFH-H cells, irrespective of the multidrug resistance phenotype . MFH-H cells are relatively insensitive to paclitaxel dissolved in DMSO, in contrast to paclitaxel dissolved in Cremophor EL/ethanol indicating that the diluent Cremophor contributes to the antiproliferative effects of the taxane paclitaxel. J Biol Chem, 2004 Apr 30, 279(18), 18256 - 61 Epub 2004 Feb 06. Cytoprotective effect of glucosylceramide synthase inhibition against daunorubicin-induced apoptosis in human leukemic cell lines; Grazide S et al.; Several studies have shown that ceramide (CER) glucosylation contributes to drug resistance in multidrug-resistant cells and that inhibition of glucosylceramide synthase sensitizes cells to various drug treatments . However, the role of glucosylceramide synthase has not been studied in drug-sensitive cancer cells . We have demonstrated previously that the anthracycline daunorubicin (DNR) rapidly induces interphasic apoptosis through neutral sphingomyelinase-mediated CER generation in human leukemic cell lines . We now report that inhibition of glucosylceramide synthase using d,l-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) or 1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP) protected U937 and HL-60 cells from DNR-induced apoptosis . Moreover, blocking CER glucosylation did not lead to increased CER levels but to increased CER galactosylation . We also observed that pretreating cells with galactosylceramide (GalCER) significantly inhibited DNR-induced apoptosis . Finally, we show that GalCER-enriched lymphoblast cells (Krabbe's disease) were significantly more resistant to DNR- and cytosine arabinoside-induced apoptosis as compared with normal lymphoblasts, whereas glucosylceramide-enriched cells (Gaucher's disease) were more sensitive . In conclusion, this study suggests that sphingomyelin-derived CER in itself is not a second messenger but rather a precursor of both an apoptosis second messenger (GD3) and an apoptosis "protector" (GalCER). J Clin Microbiol, 2004 Feb, 42(2), 891 - 4 Genotypic and phenotypic characterization of drug-resistant Mycobacterium tuberculosis isolates from rural districts of the Western Cape Province of South Africa; Streicher EM et al.; Genotypic and phenotypic analysis of drug-resistant Mycobacterium tuberculosis isolates from the Western Cape Province of South Africa showed that drug resistance is widespread and recently transmitted . Multidrug-resistant (MDR) isolates comprise 40% of this collection, and a large pool of isoniazid monoresistance may be a future source of MDR tuberculosis. J Biol Chem, 2004 Apr 23, 279(17), 17090 - 100 Epub 2004 Feb 06. JNK regulates HIPK3 expression and promotes resistance to Fas-mediated apoptosis in DU 145 prostate carcinoma cells; Curtin JF et al.; Elevated endogenous JNK activity and resistance to Fas receptor-mediated apoptosis have recently been implicated in progression of prostate cancer and can promote resistance to apoptosis in response to chemotherapeutic drugs . In addition, JNK has been demonstrated to promote transformation of epithelial cells by increasing both proliferation and survival . Although numerous studies have reported a role for JNK in promoting Fas receptor-mediated apoptosis, there is a paucity in the literature studying the antiapoptotic function of JNK during Fas receptor-mediated apoptosis . Consequently, we have used the recently described specific JNK inhibitor SP600125 and RNA interference to inhibit endogenous JNK activity in the prostate carcinoma cell line DU 145 . We demonstrated that endogenous JNK activity increased the expression of a kinase, HIPK3, that has previously been implicated in multidrug resistance in a number of tumors . HIPK3 has also been reported to phosphorylate FADD . The interaction between FADD and caspase-8 was inhibited, but abrogation of JNK activity or HIPK3 expression was found to restore this interaction and increased the sensitivity of DU 145 cells to Fas receptor-mediated apoptosis . In conclusion, we present novel evidence that JNK regulates the expression of HIPK3 in prostate cancer cells, and this contributes to increased resistance to Fas receptor-mediated apoptosis by reducing the interaction between FADD and caspase-8. Natl Med J India, 2003 Nov-Dec, 16(6), 321 - 7 Beyond DOtS: avenues ahead in the management of tuberculosis; Chaudhury RR et al.; India has almost 30% of the global burden of tuberculosis (TB)--one person dies of the disease every minute in our country . India has mounted the second-largest DOTS programme in the world to control this disease . However, DOTS has its limitations and newer approaches have been developed over the years to overcome the global burden of tuberculosis . Problems with health facilities, patients, drugs and the disease itself constitute some of the hurdles in the implementation of the DOTS programme . In an attempt to go beyond DOTS, the WHO launched the 'Stop TB Initiative' in 1988 . Against the background of irrational antituberculosis drug use, which contributes to increasing drug resistance, the effective involvement of private healthcare providers is imperative to achieve better geographical and patient coverage for the implementation of DOTS . The WHO is currently addressing the issue of involving private practitioners in tuberculosis control in a programme called Public-Private Mix DOTS (PPM DOTS) . The Stop TB Initiative is also active in the area of dual infection with HIV and tuberculosis, and the initiatives that have been taken in this area include 'ProTEST', community contribution to tuberculosis care, and development and dissemination of training materials and guidelines . The DOTS-Plus strategy for the management of multidrug resistant (MDR)-TB and the establishment of the Green Light Committee to review project applications in this area are initiatives taken to curb the problem of drug resistance in tuberculosis . Even decades after the introduction of the DOTS strategy, much needs to be done to expand the services to the entire population; it is now essential to develop strategies that go beyond DOTS. Planta Med, 2004 Jan, 70(1), 81 - 4 Pubescenes, jatrophane diterpenes, from Euphorbia pubescens, with multidrug resistance reversing activity on mouse lymphoma cells; Valente C et al.; The macrocyclic jatrophane diterpene polyesters, pubescenes A - D ( 1 - 4) were isolated from the whole dried plant of Euphorbia pubescens, and evaluated for multidrug resistance (MDR) reversing activity on mouse lymphoma cells . All the compounds displayed very strong activity compared with the positive control verapamil . Pubescene D ( 4) is a new compound, whose structure was established as 3beta,9alpha,-diacetoxy-7beta-benzoyloxy-15beta-hydroxy-14-oxo-2beta H-jatropha-5 E,12 E-diene by spectroscopic methods, including (1)H- (1)H COSY, HMQC, HMBC and NOESY. Planta Med, 2004 Jan, 70(1), 45 - 9 Rearranged jatrophane-type diterpenes from euphorbia species . Evaluation of their effects on the reversal of multidrug resistance; Madureira AM et al.; The rearranged jatrophane-type diterpenes ( 1 - 3), isolated from the Me (2)CO extracts of Euphorbia portlandica and Euphorbia segetalis, were examined for their effects on multidrug resistance (MDR) in mouse lymphoma cells . Compounds 2 and 3 revealed to be active with the latter being more active than the positive control verapamil, a known resistance modifier . The new compound 1, named portlandicine, was isolated from Euphorbia portlandica and its structure characterised by high-field NMR spectroscopic methods including 2D NMR techniques: COSY, HMQC, HMBC and NOESY . The known diterpene 2, together with aleuritolic acid ( 4), oleanolic acid ( 5), and betulin diacetate ( 6), were also isolated from the same species. JPEN J Parenter Enteral Nutr, 2004 Jan-Feb, 28(1), 1 - 6 Hepatic P-glycoprotein changes with total parenteral nutrition administration; Tazuke Y et al.; BACKGROUND: The mechanism(s) responsible for the development of parenteral nutrition-associated liver disease (PNALD) is unknown . Recently, a number of bile canalicular transport proteins have been identified that transport bile components out of hepatocytes . One group of these genes, multidrug resistance 1 (mdr1) and mdr2, encode P-glycoproteins . Mice lacking mdr2 expression develop liver disease that appears similar to PNALD . This study investigated the alteration in the expression of these transport proteins during the administration of total parenteral nutrition (TPN) . METHODS: Mice received either physiologic saline and standard chow or TPN . Mice were sacrificed on day 7, and hepatic DNA and RNA content, mRNA expression, and levels of mdr1 and mdr2 proteins were measured . RESULTS: TPN administration led to a significant (p < .05) decline in mdr2 mRNA expression and an increase in mdr1 mRNA expression . Mdr2 protein expression declined by 66% in the TPN-treated group, and mdr1 protein expression significantly increased by 58% . Histology and biochemical parameters showed no evidence of liver injury . Serum bile acid levels were elevated in the TPN group, suggesting the development of early cholestasis . CONCLUSIONS: The decline in mdr2 and rise in mdr1 mRNA and protein expression with TPN administration occurred before the development of liver injury but during an early state of cholestasis . This suggests that alterations in mdr gene expression may be a causative factor in the development of PNALD. Biosci Rep, 2003 Aug, 23(4), 199 - 212 Mitotracker green is a P-glycoprotein substrate; Marques-Santos LF et al.; P-glycoprotein has a widespread expression on normal tissues . The protein has also been strongly associated with the multidrug resistance phenotype (MDR) on tumor cells . The employment of flow cytometry and confocal microscopy has contributed to the discovery and application of new particular fluorescent dyes . Nevertheless, several studies are being performed in different cellular types neglecting the expression/activity of MDR proteins . Because many fluorochromes have been reported as P-glycoprotein substrates, an especial attention must be given to the properties of new dyes in the presence of MDR proteins . Flow cytometric analyzes of Mitotracker Green (MTG) fluorescence profile were performed in a human erythroleukemic cell line and its resistant counterpart . In this report we demonstrated that MTG, a probe used to evaluate the mitochondrial mass, is a P-glycoprotein substrate and its staining profile is dependent on the activity of this protein . In vitro studies on a human erythroleukemic cell line and its resistant counterpart revealed that MDR modulators (Cyclosporin A, Verapamil, and Trifluoperazine) alter the MTG fluorescence pattern on a resistant cell line . The findings suggest that attention should be given to the expression of P-glycoprotein when performing an evaluation of mitochondria properties with MTG. Curr Opin Investig Drugs, 2003 Dec, 4(12), 1416 - 21 Multidrug resistance in cancer therapy: role of the microenvironment; Galmarini CM et al.; Despite advances in the design of chemotherapeutic agents, and although many of these effective agents are now available for clinical use, most human cancers are resistant to therapy at presentation or become resistant after an initial response . The effectiveness of chemotherapy is compromised by several microenvironmental factors that affect the bioavailability and efficacy of chemotherapeutic agents . These factors vary from one tumor to another, and from one location to another, within the same tumor . A better comprehension of microenvironmental multidrug resistance mechanisms would lead to a clearer understanding of the reason for chemotherapeutic failure . This improved knowledge will permit a more rational utilization of chemotherapy. J Pharmacol Exp Ther, 2004 Jun, 309(3), 1221 - 9 Epub 2004 Feb 04. Multidrug resistance protein (MRP) 4- and MRP 5-mediated efflux of 9-(2-phosphonylmethoxyethyl)adenine by microglia; Dallas S et al.; The pathogenesis of human immunodeficiency virus (HIV)-associated dementia has been linked to microglial responses after infection . We have recently confirmed expression of several ATP-dependent efflux transporters in microglia, namely, multidrug resistance protein 1 (MRP1) and P-glycoprotein (P-gp) . In the present study, we investigated whether cultured rat microglia express two additional MRP family members, rMRP4 and rMRP5 . Using reverse transcriptase-polymerase chain reaction, rMRP4 and rMRP5 mRNA was detected in primary cultures of microglia and in a rat microglia cell line, MLS-9 . Western blot analysis further confirmed protein expression of the two MRP isoforms in MLS-9 cells . Bis(pivaloxymethyl)-9-(2-phosphonylmethoxyethyl)adenine {bis(POM)PMEA}, a lipophilic ester prodrug of the well characterized MRP4 and 5 substrate 9-(2-phosphonylmethoxyethyl)adenine (PMEA), was chosen to examine transport characteristics in MLS-9 . Using thin layer chromatography, we verified that more than 90% of radioactivity recovered in MLS-9 loaded with 1 microM {(3)H}bis(POM)PMEA for 1 h under ATP-depleting conditions was converted to PMEA . Efflux of PMEA by MLS-9 cell monolayers was ATP-dependent, glutathione-independent, and significantly inhibited by several MRP inhibitors (i.e., sulfinpyrazone, genistein, indomethacin, and probenecid) as well as the antiretroviral drug azidothymidine-monophosphate . Similar results were not observed in MRP1- or P-gp-overexpressing cell lines, suggesting that PMEA is not a substrate for either P-gp or MRP1 . These studies provide further evidence that microglia express multiple subfamilies of ATP-binding cassette transporters (i.e., P-gp, MRP1, MRP4, and MRP5) that could restrict permeation of several different classes of antiretroviral drugs in a brain cellular target of HIV-1 infection. Zhonghua Xue Ye Xue Za Zhi, 2003 Dec, 24(12), 617 - 20 {CIK cells acquired multidrug resistance and maintained cytotoxic activity to tumor cells after mdr1 gene transfection}; Yang YH et al.; OBJECTIVE: To investigate whether the cytokine-induced killer (CIK) cells could acquire multidrug resistance and maintain the original cytotoxic activity after multidrug resistance (mdr1) genes transfection . METHODS: CIK cells were generated from peripheral blood cultured with IFN-gamma, CD(3) monoclonal antibody, IL-2, IL-1 and transfected with a plasmid (pHamdr) containing human mdr1 gene via electroporation . RT-PCR method was used to assay mRNA expression of mdr1 gene in transfected CIK cells, flow cytometry with anti-P-gp monoclonal antibody to detect P-glycoprotein (P-gp) expression on CIK cells membrane, and MTT assay to compare both the multidrug resistance to doxorubicin and colchicines and cytotoxic activity to human mammary cancer cell line MCF7 between transfected and non-transfected CIK cells . RESULTS: mdr1 expression was detected in the transfected CIK cells . There was a strong expression of P-gp on the t