Expression Levels Of MDR1 Research Articles

Abstract 2693: MDR1 and ERCC1 expression predict outcome in patients with locally advanced bladder cancer and adjuvant chemotherapy

Abstract Aims: Patients with locally advanced bladder cancer show a poor prognosis and can benefit from adjuvant chemotherapy. It was previously shown that expression of MDR1 and ERCC1 is linked to resistance against platinum-based chemotherapy in several cancer types. The aim of the present study was to evaluate the impact of classical histological, new immunohistochemical and molecular markers on prognosis of patients with locally advanced bladder cancer undergoing cystectomy (pT3a-4a and/or pN+) and response to chemotherapy within a randomized, multicenter, phase III trial (AUO-AB 05/95). Methods: Clinico-pathological parameters were assessed retrospectively after histopathological review in 204 patients randomized to adjuvant systemic chemotherapy with cisplatin and methotrexate (CM) vs. methotrexate, vinblastine, epirubicin, and cisplatin (M-VEC) after radical cystectomy. Tissue microarrays were constructed to study the immunohistochemical expression of ERCC1, BSG (Emmprin/CD147) CAV1, phospho-CAV1 (Y14), RRM1, BRCA1, BRCA2, BIRC5 (Survivin), and KISS1. Tumor samples from 108 patients were analyzed for MDR1 and ERCC1 mRNA expression by quantitative real-time RT-PCR using formalin-fixed and paraffin embedded tumor tissue. Results: Expression of MDR1 and ERCC1 were independently associated with overall and progression-free survival (p=0.001, 2.9 exp[b]; p=0.01, 2.24 exp[b]). In contrast to ERCC1 expression, MDR1 separated patients receiving M-VEC with higher sensitivity and specificity than those receiving CM (ROC Analysis p=0.008; [AUC]=0.71). These results could be partially confirmed by immunohistochemical analysis of 204 patients. ERCC1 and RRM1 expression correlated significantly with shorter overall survival in both therapy arms by univariate analysis. Multivariate analysis showed that ERCC1 expression was an independent prognostic factor for shorter overall survival (HR=2.3, 95%CI=1.18-4.43, p=0.014). Positive nodal status (pN1-3), histologic blood vessel invasion (V1), and positive BIRC5 immunoreactivity were significant as well. Conclusion: Our results suggest a predictive value of ERCC1 and MDR1 expression levels for therapy response and outcome in patients with locally advanced bladder cancer which allows the identification of patients who are likely to benefit from adjuvant platinum-based chemotherapy. The qPCR analysis is feasible in studying paraffin-embedded material from clinical bladder cancer trials. In addition, standard histopathological variables in combination with immunohistochemical and molecular prognostic markers can be used to predict therapy outcome in bladder cancer, irrespective of the mode of chemotherapy. Prospective studies are warranted to define a role for MDR1, ERCC1 and RRM1 in individualizing multimodality treatment in locally advanced bladder cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2693.

Effect of MDR1 polymorphism on multidrug resistance expression in breast cancer patients

One of the limitations in the treatment of cancer patients with chemotherapy is the development of multidrug resistance (MDR). A well-known mechanism responsible for drug resistance is over-expression of ABC-transporter genes such as MDR1. This gene encodes p-glycoprotein (P-gp), a transmembrane glycoprotein that transports many hydrophobic substrates and anti-cancer drugs out of the cell. MDR1 gene polymorphisms could alter the expression level of P-gp and consequently result in drug resistance. We investigated a possible association between MDR1 gene C3435T polymorphism and its expression in Iranian breast cancer patients. PCR-RFLP was used for the detection of C3435T single nucleotide polymorphism in 54 breast cancer patients and 50 healthy individuals. The expression level of MDR1 was determined by real-time quantitative PCR. We observed no difference in the frequency of C3435T polymorphism between breast cancer patients and healthy controls. However, there was a significant association between MDR1 expression levels and C3435T polymorphism in the patients. C3435T polymorphism may play a role in inducing drug resistance by altering the expression level of the MDR1 gene.

Presence of Circadian oscillation of Multidrug Resistance Gene 1 in KB-C2 cell line

Many physiological, biochemical and behavioral processes are under circadian regulation, which is generated by an internal time-keeping mechanism referred to as biological clock in almost all organisms from bacteria to mammals. Although the substantial evidences that the circadian clock could modulate the morbidity and efficacy of anticancer therapy have been proposed, underlying mechanisms for chronotherapy has been only poorly elucidated, and it has not been popular in clinic. The aim of this study was to determine the relationship between the expression of P-glycoprotein (P-gp)/MDR1, which is one of the important molecules in anti-cancer drug resistance, and circadian rhythm in KB-C2 cells. The present study demonstrated that both MDR1 expression level and its promoter activity oscillated after treatment with high concentration of fetal bovine serum. Moreover, cytotoxic effect of taxol were dependent on the fluctuated levels of MDR1. These results suggest that the circadian rhythm of MDR1 may have an influential effect on cytotoxicity of anti-cancer drug and could be available for chemotherapy in clinic.

MDR1 Expression and Pre-Treatment Tumor Load Predict Molecular Response in CML Patients On Nilotinib Therapy After Imatinib Failure.

Abstract 2615▪▪This icon denotes an abstract that is clinically relevant.Poster Board II-591 Introduction:The majority of patients with chronic myeloid leukemia (CML) in chronic phase achieve and maintain complete cytogenetic remission after frontline therapy with imatinib mesylate. In case of resistance or intolerance to imatinib, a switch to second generation tyrosine kinase inhibitors, such as nilotinib or dasatinib, is recommended. Mutations in the BCR-ABL kinase domain and various BCR-ABL independent mechanisms, e.g. clonal evolution and pathways bypassing BCR-ABL are considered as leading causes of resistance. Efficacy of imatinib and nilotinib depends on intracellular drug levels, which are influenced by the activity of the efflux transporter protein multidrug resistance 1 (MDR1, ABCB1 or P-gp). MDR1 involvement in the pathogenesis of resistance to nilotinib was postulated (Mahon et al., Cancer Res 2008). Aim:Hence, we evaluated the predictive impact of MDR1 expression levels as well as pre-treatment BCR-ABL load from imatinib resistant CML patients on molecular responses during second line therapy with nilotinib. Patients and Methods:Imatinib resistant patients in chronic phase CML treated with nilotinib (n=94) were investigated. Baseline BCR-ABL mutations were detected by D-HPLC and direct sequencing. MDR1 and BCR-ABL mRNA expression levels were determined by quantitative reverse transcription PCR (qRT-PCR) using LightCycler™ technology, normalized against beta-glucuronidase (GUS) expression and standardized according to the international scale (IS). Log-rank tests were performed to analyze and compare the time to achieve major (MMR, BCR-ABL IS ≤0.1%) or good molecular response (BCR-ABL IS ≤1%). Results:Within 12 or 24 months of nilotinib therapy, 22% and 27% of patients achieved MMR, and 37% and 41% of patients attained good molecular response, respectively. After 12 or 24 months, patients with MDR1/GUS ratios ≥2.5 (60%) achieved MMR in an estimated rate of 45% and 53%, whereas those with initial MDR1/GUS ratios <2.5 (40%) showed MMR in 14% and 14%, respectively (p=0.034). Good molecular response was attained in 52% vs 49% and 63% vs 66% after 12 and 24 months (ns). Further, BCR-ABL load prior to nilotinib revealed a significant impact on consecutive molecular response. BCR-ABL IS <28% separated best concerning prediction of MMR after 12 and 24 months (53% vs 25% and 53% vs 34%, p=0.002) and good molecular response (62% vs 44% and 85% vs 51%, p=0.004). Combining the two methods implied the definition of a low risk group (20%; pre-treatment BCR-ABL IS <28% and MDR1/GUS ratios ≥2.5) in contrast to a high risk group (27%; pre-treatment BCR-ABL IS ≥28% and MDR1/GUS <2.5) achieving MMR in 67% vs 6% of the patients after 24 months (p=0.0004). No relevant differences were found looking at subgroups of patients bearing BCR-ABL mutations. Conclusions:Pre-treatment expression levels of MDR1 and BCR-ABL tumor load predicts molecular responses of imatinib resistant chronic phase CML patients within the first two years of treatment with nilotinib. Disclosures:Woodman:Novartis Oncology: Employment. Hochhaus:Novartis : Research Funding.

Effects of Lewis Y antigen on the gene expression of multiple drug resistance-associated proteins in human ovarian cancer RMG-I-H cells

The effects of Lewis Y antigen on the gene expression of multiple drug resistance-associated proteins in human ovarian cancer RMG-I-H cells were unclear by now. In this study, we detected the gene expression of multiple drug resistance-associated proteins (MRP) in RMG-I-H cells and RMG-I-H cells treated with anti-Lewis Y monoclonal antibody to investigate the association between Lewis Y antigen and the gene expression of drug resistance-associated proteins. Compared with RMG-I cells, the expression of MRP1, MRP2, protein kinase C-alpha (PKC-alpha), and topoisomerase I (Topo I) mRNAs in RMG-I-H cells were significantly upregulated, while the MDR-1 mRNA was downregulated. Immunochemistry analyses indicated that the in vitro and in vivo expression levels of MDR-1 protein (P-gp) in RMG-I-H cells were significantly higher than those in RMG-I cells. After RMG-I-H cells were treated with anti-Lewis Y monoclonal antibody, the expression levels of MDR-1, MRP1, MRP2, PKC-alpha, and Topo I mRNAs gradually decreased with the prolongation of treatment duration. In contrast, no obvious changes were noted in the expression levels of these mRNAs in the non-treatment group. At 6 h after treatment, the relative levels of MDR-1, MRP1, MRP2, PKC-alpha, and Topo I mRNAs in the antibody treatment group were significantly lower than those in the non-treatment group. In conclusion, Lewis Y antigen is closely associated with regulating the gene expression of multiple drug resistance-associated proteins.

Effect of magnetic nanoparticles of Fe3O4 and 5-bromotetrandrine on reversal of multidrug resistance in K562/A02 leukemic cells

This study aims to evaluate the multidrug resistance (MDR) reversal activity by magnetic nanoparticles of Fe3O4 (MNPs-Fe3O4) and 5-bromotetrandrine (BrTet) MDR cell line K562/A02 solitarily or symphysially. The proliferation of K562 and K562/A02 cells and the cytotoxicity on peripheral blood mononuclear cells (PMBCs) were evaluated by MTT assay. Cellular accumulation of daunorubicin (DNR) was analyzed by flow cytometry. Real-time polymerase chain reaction and Western blotting analyses were performed to examine the mRNA and protein levels of mdr1, respectively. The results showed that the combination of MNPs-Fe3O4 and BrTet with effective concentrations significantly increased cytotoxicity against MDR cell line K562/A02. Both BrTet and MNPs-Fe3O4 increased the intracellular DNR accumulation in the K562/A02 cell line, and downregulated the level of mdr1 gene and expression of P-glycoprotein. Furthermore, the combination did not have significant cytotoxicity in PMBCs. We propose that MNPs-Fe3O4 conjugated with DNR and BrTet probably have synergetic effects on MDR reversal.

Reversal effect of Raf-1/Mdr-1 siRNAs co-transfection on multidrug resistance in KBv200 cell line

Multidrug resistance (MDR) is a major barrier for chemotherapy of many cancers. Mdr-1 plays a key role in the development of MDR as extensively verified. However, the role of Raf-1 overexpression in the development of multidrug resistance in human squamous carcinoma (KBv200) cells remains largely unknown. The aim of this study was to investigate the correlation of Raf-1 overexpression with the development of multidrug resistance in KBv200 cells. Furthermore, we explored the reversal effect of Raf-1 siRNA transfection and Raf-1/Mdr-1 siRNAs co-transfection on the multidrug resistance of KBv200 cells and potential mechanism of reversing the multidrug resistance. MTT and flow cytometry assay were used to investigate the reversal effect of single transfection with either Raf-1 or Mdr-1 siRNA and double transfection with Raf-1/Mdr-1 siRNAs to vincristine of KBv200 cells. RT-PCR, immunofluorescence and Western Blot were used to detect mRNA and protein expression of Raf-1 and multidrug-resistant gene Mdr-1. The results of gene detection showed that the expression levels of both Raf-1 and Mdr-1 were greatly decreased upon Raf-1 silencing alone or in combination with Mdr-1 silencing. Raf-1 or Mdr-1 siRNA single transfection could reverse the multidrug resistance of KBv200 cells effectively. Compared with single transfection, Raf-1/Mdr-1 siRNAs co-transfection can significantly reduce IC(50) values and increase the apoptotic rates of KBv200 cells. The above results suggested that Raf-1 gene may be a novel target for reversing the multidrug resistance of human squamous carcinoma cells. Raf-1/Mdr-1 siRNAs co-transfection might be a promising approach to abrogate the multidrug resistance of cancer cells. The potential mechanism may be via inhibiting the multidrug-resistant gene Mdr-1 expression efficiently.

Altered Expression of Proliferation-Inducing and Proliferation-Inhibiting Genes Might Contribute to Acquired Doxorubicin Resistance in Breast Cancer Cells

This study was designed to investigate the molecular changes that may develop during exposure of breast cancer cells to anticancer agents and that may lead to acquired resistance. We used two breast cancer cell lines, a parental (MCF7/WT) and a doxorubicin-resistant (MCF7/DOX) one. Cell survival, cell cycle distribution and RT-PCR expression level of genes involved in DNA damage response, MDR1, GST and TOPOIIalpha were measured. MCF7/DOX cells were five-fold more resistant to doxorubicin (DOX) than the MCF7/WT cells. DOX treatment causes arrest of MCF7/DOX cells in G1 and G2 phases of cell cycle whereas MCF7/WT cells were arrested in S-phase. The molecular changes in both cell lines due to DOX treatment could be classified into: (1) the basal level of p53, p21, BRCA1, GST and TOPOIIalpha mRNA was higher in MCF7/DOX than MCF7/WT. During DOX treatment, the expression level of these genes decreased in both cell lines but the rate of down-regulation was faster in MCF7/WT than MCF7/DOX cells. (2) The expression level of MDR1 was the same in both cell lines but 48 and 72 h of drug treatment, MDR1 disappeared in MCF7/WT but still expressed in MCF7/DOX. (3) There was no change in the expression level of BAX, FAS and BRCA2 in both cell lines. Conclusively, after validation in clinical samples, overexpression of genes like BRCA1, p53, p21, GST, MDR1 and TOPOIIalpha could be used as a prognostic biomarker for detection of acquired resistance in breast cancer and as therapeutic targets for the improvement of breast cancer treatment strategies.

Mechanism of Action of Tetrandrine, a Natural Inhibitor of &lt;i&gt;Candida albicans&lt;/i&gt; Drug Efflux Pumps

Synergistic effects have previously been observed for a natural compound, tetrandrine (TET), with fluconazole (FLC) in vitro and in the treatment of Candida albicans-infected mice. To investigate the mechanisms of these synergistic effects, 16 strains of C. albicans from the same parent but with different FLC sensitivities were examined using flow cytometry and fluorescent spectrophotometry. Rhodamine 123 (Rh123)-positive cells and intracellular Rh123 fluorescence intensity were determined in accumulation/efflux experiments involving no or a noncytotoxic dose of TET. Total RNA extracted from each strain was used to compare the expressions of drug efflux pump genes in FLC-susceptible, -susceptible dose-dependent, and -resistant strains before and 24 h after TET administration. Accumulation experiments determined that mean percentages of Rh123-positive cells were 26.65% (TET-free) and 70.99% (TET 30 microg/ml), and mean respective intracellular Rh123 fluorescence intensities were 11.34 and 18.00. Efflux experiments showed that percentages of Rh123-positive cells were 1.79% (TET free) and 42.57% (TET 30 microg/ml), respectively, and respective mean intracellular Rh123 fluorescence intensities were 0.74 and 2.19. Differences in MDR1, FLU1, CDR1, and CDR2 expression levels in the absence of TET were statistically significant (p<0.05) between FLC-susceptible, -susceptible dose-dependent, and -resistant strains. Compared with TET-free conditions, 24 h TET-treated strains showed statistically different (p<0.05) expression of MDR1 (FLC-resistant strain), FLU1 (FLC-susceptible dose-dependent and -resistant strains), and CDR1 and CDR2 (FLC-susceptible, -susceptible dose-dependent, and -resistant strains). Thus TET can inhibit the C. albicans drug efflux system and reduce drug efflux. Its mechanism of action is related to the inhibition of expression of the drug efflux pump genes MDR1, FLU1, CDR1, and CDR2.

Noninvasive functional imaging of P-glycoprotein-mediated doxorubicin resistance in a mouse model of hereditary breast cancer to predict response, and assign P-gp inhibitor sensitivity

Using a "spontaneous" mammary mouse tumor model we set out to develop diagnostic approaches for non-invasive P-glycoprotein (P-gp) staging and response prediction. (99m)Tc-MIBI efflux rates were measured using a gamma camera in three Brca1 (-/-); p53 (-/-) mouse mammary tumors that have different Mdr1a/b expression levels. The efflux rates were quantified in the 10-30-min period after injection. In addition to the P-gp-mediated efflux measurements in untreated tumors, efflux measurements were performed in the presence of the P-gp inhibitor tariquidar. Volumetric doxorubicin response patterns for the different tumors were determined and correlated with the efflux rates. Combined pre- and post-inhibitor treatment imaging of P-gp-mediated efflux correlated with Mdr1a/b expression: basal (0.0026, p = 0.16), 3-fold Mdr1a/b (0.0074, p = 0.02), and 17-fold Mdr1a and 46-fold Mdr1b (0.012, p = 0.002). Based on the doxorubicin response of these tumors, we generated a computer-aided diagnosis model that predicts the likelihood of drug resistance. Quantified (99m)Tc-MIBI efflux has potential to: (1) noninvasively assign Mdr1 expression levels, (2) predict the therapeutic impact of a P-gp inhibitor, and (3) noninvasively assess the probability of drug resistance.

CD34 expression is associated with poor survival in pediatric T‐cell acute lymphoblastic leukemia

Children with T-lineage acute lymphoblastic leukemia (T-ALL) have an inferior outcome with combination chemotherapy compared to B-lineage ALL, and still about 30% of the patients relapse within the first 2 years following diagnosis. As CD34 has been related with poor outcome in ALL in general, we investigated the prognostic significance of the stem cell marker CD34, as well as the association of CD34 positivity with the expression of several multidrug resistance (MDR) genes. In this retrospective study, we investigated the prognostic significance of the expression of the early T-cell differentiation marker CD34 and the expression of MDR genes in relation to outcome in a cohort of 72 newly diagnosed pediatric T-ALL patients. CD34 expression was related to a poor 5-year disease-free-survival and a poor 5-year overall survival. Using the Cox proportional hazard model, CD34 expression predicted for increased risk for relapse and death. Expression of CD34 was associated with elevated MDR1 and MRP1 mRNA expression levels. For the entire T-ALL cohort, these expression levels of MDR1 or MRP1 did not independently predict for poor outcome. We conclude that CD34-positive T-ALL has a relatively poor survival that is not explained by the mRNA expression levels of MDR1, LRP, or MRP1.

Reversal effect of resveratrol on multidrug resistance in KBv200 cell line

A multidrug-resistant clone of human oral epidermoid carcinoma KB cells was isolated by stepwise selection on exposure to increasing doses of vincristine. The final clone, KBv200, obtained after ethylmethane sulfonate mutagenesis showed 156-fold higher resistance to vincristine than KB cells. The cells were also cross-resistant to paclitaxel and adriamycin. The aim of this study was to explore the reversal effect and potential mechanism of resveratrol on KBv200 cells. MTT assay was used to investigate the reversal index of resveratrol to vincristine, adriamycin and paclitaxel. Cell apoptosis was measured by flow cytometry. RT-PCR and western blot were used to detect mRNA and protein expression of multidrug-resistant gene MDR1 and apoptosis-suppressing gene Bcl-2. Resveratrol produced a synergistic effect combined with the chemotherapeutic agents and reversed the multidrug-resistant phenotype of KBv200 cells. Flow cytometry confirmed that the percentage of apoptotic cell increased when KBv200 cells were exposed to resveratrol. The results of gene detection showed that the expression levels of MDR1 and Bcl-2 were decreased upon resveratrol treatment. Resveratrol can efficiently reverse multidrug resistance in KBv200 cells. The potential mechanism may be via inhibiting the multidrug-resistant gene expressions and/or promoting cell apoptosis.

Expression of MDR1, MRP2 and BCRP mRNA in tissues of turkeys

MDR1, MRP2 and BCRP are members of the superfamily of ABC membrane transporters that export a large variety of structurally diverse substances out of the cell, hence being an integral part of various biological barriers. Here we report for the first time the tissue distribution of these ABC efflux transporters in the gastrointestinal tract (crop, proventriculus, duodenum, proximal and distal jejunum, ileum, caecum, colon) as well as in liver, kidney, lung, brain, adrenal gland, ovaries, oviduct and testes in BUT9 turkeys. MDR1 and BCRP mRNA expression was detected in all tissue samples, and the highest levels were measured in the small intestines. The tissue distribution of MRP2 mRNA was less consistent and some tissues seemed to lack any significant expression. Moreover, in consideration of previous findings suggesting that fluoroquinolones are substrates and modulators of ABC transporters, the effect of orally administered danofloxacin mesylate on the levels of MDR1, MRP2 and BCRP mRNA expression was investigated. Danofloxacin treatment resulted in a significant up-regulation of the measured transporters at the transcriptional level in the upper part of gastro-intestinal tract, liver and kidneys as well as in barrier-protected organs, such as the brain. However, despite this significant increase in the transcription levels, the pharmacokinetic parameters after repeated application of danofloxacin mesylate were not significantly altered.

Inhibit multidrug resistance and induce apoptosis by using glycocholic acid and epirubicin

Cancer-cell resistance to chemotherapy limits the efficacy of cancer treatment. The primary mechanisms of multidrug resistance (MDR) are “pump” and “non-pump” resistance. We evaluated the effects and mechanisms of glycocholic acid (GC), a bile acid, on inhibiting pump and non-pump resistance, and increasing the chemosensitivity of epirubicin in human colon adenocarcinoma Caco-2 cells and rat intestine. GC increased the cytotoxicity of epirubicin, significantly increased the intracellular accumulation of epirubicin in Caco-2 cells and the absorption of epirubicin in rat small intestine, and intensified epirubicin-induced apoptosis. GC and epirubicin significantly reduced mRNA expression levels of human intestinal MDR1, MDR-associated protein (MRP)1, and MRP2; downregulated the MDR1 promoter region; suppressed the mRNA expression of Bcl-2; induced the mRNA expression of Bax; and significantly increased the Bax-to-Bcl-2 ratio and the mRNA levels of p53, caspase-9 and -3. This suggests that GC- and epirubicin-induced apoptosis was mediated through the mitochondrial pathway. We conclude that simultaneous suppression of pump and non-pump resistance dramatically increased the chemosensitivity of epirubicin. A combination of anticancer drugs with GC can control MDR via a mechanism that involves modulating P-gp and MRPs as well as regulating apoptosis-related pathways.

Functional Polymorphism of the Human Multidrug Resistance Gene (MDR1) and Polydipsia–Hyponatremia in Schizophrenia

P-glycoprotein (P-gp), which is coded by the MDR1 gene, in the brain capillary endothelial cell limits the entry of many drugs including antipsychotics into the brain. The aim of this study is to examine whether a functional polymorphism, a C to T substitution at position 3435 in exon 26 of the MDR1 gene, is associated with susceptibility to polydipsia-hyponatremia in schizophrenia (SCZ) in a Japanese case-control sample. It has been reported that individuals homozygous for this polymorphism had significantly lower MDR1 expression levels and dysfunction of MDR1 (PNAS 97:3473-3478, 2000). Furthermore, the brain entry of risperidone and 9-hydroxyrisperidone has been shown to be greatly limited by P-gp (Int J Neuropsychopharmacol 7:415-419, 2004). In order to our knowledge, this is the first association study between the MDR1 polymorphism and polydipsia-hyponatremia in SCZ. Our sample includes 331 patients with SCZ (DSM-IV) (84 with polydipsics and 247 non-polydipsic controls). The common C3435T polymorphism of the MDR1 was genotyped for both groups and differences in genotype and allele frequency between cases and controls were evaluated using the chi(2)-test. A significant association between the MDR1 C3435T polymorphism and polydipsia was found (chi(2) = 4.43, d.f. = 1, P = 0.035; OR = 1.46; 95%CI = 1.03-2.07). Our results suggest that the MDR1 C3435T polymorphism may confer susceptibility to polydipsia in SCZ.

Reversal effect of Ganoderma lucidum polysaccharide on multidrug resistance in K562/ADM cell line

To investigate the reversal effect of Ganoderma lucidum polysaccharides (Gl-PS) on multidrug resistance (MDR) in the adriamycin (ADM)-resistant leukemic cell line K562/ADM. Cytotoxicity was assayed by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide method; the ADM concentration in cells was determined by flow cytometry and confocal laser scanning microscopy techniques; the expression of P-glycoprotein was assayed by flow cytometry; and the mRNA expression levels of MDR-1 and MDR-associated protein (MRP)1 were determined by RT-PCR. Gl-PS reversed MDR in K562/ADM cells. Gl-PS obviously reversed the resistance of K562/ADM to doxorubicin. The reversing factors of Gl-PS at 10 and 20 mg/L were 6.46 and 6.80, respectively. MDR-1 and MRP1 transcription were downregulated by 10 and 50 mg/L Gl-PS. Gl-PS can reverse the MDR by downregulating the expression of MDR-1 and MRP1 in K562/ADM cells.

Expression levels of MDR1, MRP1, MRP4, and MRP5 in peripheral blood mononuclear cells from HIV infected patients failing antiretroviral therapy

The aim of the study was to evaluate the mRNA expression of four relevant ABC-transporter genes [MDR1 (P-glycoprotein; Pgp), MRP1, MRP4, and MRP5] in HIV-positive individuals failing treatment and analyze the association between the levels of their expression and viral load, CD4 cell count, and therapeutic history. Ninety-eight HIV-positive samples and 20 samples from healthy donors were analyzed, retrospectively. Peripheral blood mononuclear cells (PBMCs) from HIV1-positive individuals were collected at the time of virological failure. Expression of mRNA of Pgp, MRP1, MRP4, and MRP5 in PBMCs was evaluated by real-time PCR. A high inter-individual variability was observed in both HIV-positive individuals and healthy donors but the expression levels of all mRNA analyzed were significantly higher in the HIV-infected group (P < 0.05). A weak but significant inverse correlation was observed between CD4 cell counts and expression levels of MRP4 and MRP5. Comparison of mRNA expression between individuals with different therapeutic histories showed that expression of MRP4 and MRP5 genes in patients who were both protease inhibitor (PI) and non-nucleoside reverse transcriptase inhibitor (NNRTI)-experienced was significantly higher than in patients who were PI experienced but NNRTI-naïve. In conclusion, the mRNA expression of Pgp, MRP1, MRP4, and MRP5 varies among HIV-infected patients and healthy donors but is significantly higher in HIV-positive patients than in donors. The expression of MRP4 and MRP5 seems to correlate with CD4 cell counts. The same protein seems to be overexpressed in patients receiving NNRTIs.

Characterization of Gastrointestinal Drug Absorption in Cynomolgus Monkeys

Possible factors of species differences in gastrointestinal drug absorption between cynomolgus monkeys and humans were examined using several commercial drugs. Oral bioavailability (BA) of acetaminophen, furosemide, and propranolol in cynomolgus monkeys was significantly lower than that in humans. From the pharmacokinetic analysis, these drugs were found to show the low fraction absorbed into portal vein (FaFg), suggesting that the low BA in cynomolgus monkeys was attributed mainly to the gastrointestinal absorption processes. The gastric emptying rate (GER) calculated from plasma concentration profiles after oral administration of acetaminophen in cynomolgus monkeys was similar in humans. The gastrointestinal transit time (GITT) in cynomolgus monkeys was only slightly shorter than that in humans. On the other hand, it was demonstrated that the apparent intestinal permeability (Papp) of five drugs to cynomolgus monkey intestine was lower than that to rat intestine; especially propranolol and furosemide showed the remarkably low Papp. The expression levels of mRNAs of efflux transporters analyzed by real-time RT-PCR indicated that mRNA expression levels of MDR1, MRP2, and BCRP in monkey intestine were significantly higher than those in human intestine. This result suggested that low oral absorption of furosemide in cynomolgus monkeys was attributed to the high activities of efflux transporters in its intestinal membrane. Results of in vivo PK analysis clearly showed that FaFg values of propranolol and acetaminophen in cynomolgus monkeys were markedly lower than those in humans. Since propranolol and acetaminophen were the drug with high membrane permeability, it was considered that the high first-pass metabolism in the enterocytes was a main factor of their low FaFg in cynomolgus monkeys. In conclusion, it was demonstrated that the high activities of efflux transporters and/or metabolizing enzymes in the intestinal membrane are possible factors to cause poor oral absorption of drugs in cynomolgus monkeys.

CD34+ leukemic subpopulation predominantly displays lower spontaneous apoptosis and has higher expression levels of Bcl-2 and MDR1 genes than CD34− cells in childhood AML

In view of obscure clinical and biological significance of leukemic cells heterogeneity, we studied the efficacy of apoptosis, proliferation, and expression levels of the Bcl-2, MDR1, LRP, and BCRP genes in sorted CD34+ and CD34- subpopulations of childhood AML leukemic samples. In five out of nine cases, CD34+ cells were less sensitive to spontaneous apoptosis and had from 1.2- to 5.0-fold higher expression levels of Bcl-2 (eight of ten) and from 1.5- to 28.7-fold higher expression levels of MDR1 (eight of ten). The expression levels of the LRP gene were from 1.1- to 1.8-fold higher in CD34+ subpopulations (five of ten cases), and the expression levels of the BCRP gene were from 1.1- to 22.4-fold higher in CD34+ leukemic cells (six of ten). In all M4 cases, the expression levels of LRP were higher in the CD34- subpopulation. Significant differences in the patterns of genes expression between patients do not allow us to conclude that the CD34+ fractions have more resistant phenotype than the CD34- subpopulations. Nevertheless, distinctions between CD34+ and CD34- cells may lead to different chemosensitivities between leukemic subpopulations in vivo and may determine the alteration of the leukemic immunophenotype during treatment and in relapse.

Inhibition of MDR1 expression by retinol treatment increases sensitivity to etoposide (VP16) in human neoplasic cell line

Multidrug resistance (MDR) is the major obstacle to cancer chemotherapy. MDR phenotype is mainly related to the over-expression of MDR1 gene, being responsible for tumor resistance to several chemotherapeutic drugs. It has been suggested that MDR1 expression is redox-regulated and we have recently described a pro-oxidative effect of retinol. Here we tested the therapeutic use of retinol as a modulator of MDR1 gene expression in tumor cell lines, and verified in situ the enhancement of anticancer drug efficacy. Two human colorectal adenocarcinoma cell lines (HT29, SW620) with different degrees of MDR1 expression were used. Cells were pre-treated with a sublethal dose of retinol and then challenged with the etoposide (VP16) drug. The drug GI50 was assessed by SRB method and levels of MDR1 expression were determined by semi-quantitative rtPCR. Retinol treatment caused a 40% decrease in MDR1 expression and increased VP16 toxicity. MDR1 expression and drug sensitivity were restored to control values when mannitol (a hydroxyl radical scavenger) was co-administrated. Our data point a role to the use of retinol as an adjuvant in the treatment of tumors with MDR phenotype.