Multidrug Resistance Gene MDR1 Research Articles

Detection of the ABCB11930_1931del TC Mutation in Two Suspected Ivermectin-Sensitive Cats and Their Relatives by a Novel TaqMan Allelic Discrimination Assay.

The multidrug resistance gene MDR1 (syn. ABCB1) encodes for the multidrug efflux transporter P-glycoprotein (P-gp), which is highly expressed at the blood-brain barrier and protects the brain from potentially neurotoxic compounds, such as ivermectin. MDR1 mutation in dogs is known to be linked to dramatically increased brain accumulation of ivermectin and life-threatening neurological toxicity. The present report describes two suspected ivermectin-sensitive Maine Coon cats, which exhibited neurological toxicity following subcutaneous application of therapeutic doses of ivermectin. Both cats showed a homozygous 2-bp deletion in the MDR1/ABCB1 coding sequence (ABCB11930_1931del TC, syn. MDR1 nt1930(del2)) that had previously been associated with a drug-sensitive phenotype in cats. For cat MDR1 genotyping, a novel TaqMan allelic discrimination assay was established and validated. This assay was used for ABCB11930_1931del TC genotyping of the drug-sensitive cats as well as of more than 50 relatives. About half of them had the heterozygous MDR1(+/-) genotype, while none of these related cats with former ivermectin treatment had a history of drug-sensitivity. In conclusion: The present study supports previous findings on drug-sensitivity in cats with homozygous ABCB11930_1931del TC mutation. The newly established TaqMan allelic discrimination assay provides a useful and reliable method for routine MDR1 genotyping in cats in order to identify drug-sensitive cats prior to treatment with established P-gp substrates such as ivermectin and other macrocyclic lactones and thus to improve therapeutic safety.

First Sequencing of Caprine Mdr1 (Abcb1) mRNA Due to Suspected Neurological Adverse Drug Reaction in a Thuringian Goat Following Extra-Label Use of Doramectin.

The multidrug resistance gene MDR1 encodes for an efflux transporter called P-glycoprotein (P-gp). In the canine Mdr1 gene, a nonsense mutation was identified in certain dog breeds causing increased drug sensitivity to various P-gp substrates such as antiparasitic macrocyclic lactones. Symptoms of neurologic toxicity include ataxia, depression, salivation, tremor, apparent blindness, and mydriasis. In the current report, a Thuringian goat developed similar neurological signs after treatment with doramectin, a compound from the macrocyclic lactone class. Therefore, Mdr1 might be defective in this individual goat. For diagnostic purposes, sequencing of the complete mRNA transcript coding for caprine Mdr1 was performed to investigate a potential missense mutation. The Mdr1 transcripts of two related goats without drug sensitivity were also sequenced to allow differential diagnosis and were compared to the suspected drug-sensitive goat. The only position where the Mdr1 sequence from the suspected drug-sensitive goat differed was in the 3′-untranslated region, being a heterozygous single nucleotide polymorphism c.3875C>A. It can be suspected that this variant affects the expression level, stability, or translation efficiency of the Mdr1 mRNA transcript and therefore might be associated with the suspected drug sensitivity. To clarify this, further studies are needed, particularly investigating the Mdr1 mRNA and protein expression levels from brain material of affected goats. In conclusion, Mdr1 variants may exist not only in dogs, but also in individual goats. The current report provides the first Mdr1 mRNA transcript sequence of a goat and therefore represents the basis for more detailed Mdr1 sequence and expression analyses.

Association of Multidrug Resistance Gene-1 (MDR1 C1236T) Polymorphism with the Risk of Acute Myeloid Leukemia in a Moroccan Population.

The human multidrug resistance MDR1 gene plays a crucial role in the absorption, transport, metabolism and elimination of harmful compounds. An impaired metabolism of these compounds related to genetic polymorphism may cause cancer such as acute myeloid leukemia AML. Objective:The present study investigated the relationship between C1236T polymorphism and the risk of AML development in a sample of Moroccan population. Methods:The present case-control study included 131 AML patients and 136 healthy controls. The MDR1 C1236T polymorphism was identified by PCR-RFLP method. Meta-analysis was performed to discuss our results. Statistical analyses were performed using SPSS, MetaGenyo and MedCalc. Results:A positive association was found between the 1236TT mutant genotype and the risk of AML (OR 2.39; 95% CI 1.02-5.57, p= 0.04) compared to the wild type 1236CC. In addition, the recessive model revealed that carriers of 1236TT mutant genotype were more exposed to develop AML when compared to the combined 1236CC/CT genotype (OR: 2.27, CI: 1.01–5.05, p=0.04). The clinical parameters of AML showed no significant association. Meta-analysis demonstrated no statistically significant association between this polymorphism and AML susceptibility. Conclusion:Our study suggests that the MDR1C1236T polymorphism appears to be associated with the risk of AML. Further studies, including a large sample size, are needed to confirm these findings.

Graviola leaves extract enhances the anticancer effect of cisplatin on various cancer cell lines

Cisplatin (CIS) is widely applied as an anticancer drug for various cancer types, including liver, breast, colorectal, and pancreatic cancers; however, its usage is limited due to side effects. We investigated whether combined therapy of Graviola (Annona muricata) leaves extract (GLE) and CIS could reduce CIS doses without decreasing its anticancer potential. The MCF7, HepG2, CaCo2, or PANC1 cells were divided into four groups for each cell line as follows: group1 (G1): untreated cells, G2: cells treated with GLE, G3: cells treated with CIS, and G4: cells treated with GLE, after 2 h treated with CIS. All combinations were prepared as non-constant ratio from GLE. The cytotoxicity, gene expression, cell cycle arrest were determined by MTT assay, real-time PCR, and cell flow cytometry, respectively. Treatment with GLE and/or CIS-induced cytotoxic effect on HepG2, MCF7, CaCo2, and PANC1 cancer cells with the best effect of combined therapy. All twelve non-constant ratio combinations (GLE + CIS) for each cell line resulted in a significant higher cytotoxic effect than single drug treatment. The combination index (CI) values for all combinations were less than one, indicating the presence of synergistic cytotoxic effect between CIS and GLE against the four cancer cell lines. This anticancer effect was triggered through mitochondrial-dependent apoptosis with the downregulation of caspase3, Bax, and p53 and upregulation of Bcl2. GLE also shifted G0/G1 phase of cell cycle arrest induced by CIS to S and G2/M phases. Interestingly, this combined therapy did not affect oxidative stress (indicated by higher malondialdehyde level and lower activities of SOD, CAT, and GPX) induced by CIS; however, it downregulated the expression of MAPK1 and multidrug resistance gene MDR1. These results demonstrate that Graviola leaves extract optimizes the antitumor potential of cisplatin and could be utilized as a natural adjuvant to decrease cisplatin side effects.

Genotypic and allelic frequencies of MDR1 gene in dogs in Italy.

BackgroundA mutation in the canine multidrug resistance MDR1 gene (also referred as ABCB1), encoding for the multidrug resistance (MDR) P-glycoprotein (P-gp) transponder, causes a pathological condition known as ‘ivermectin toxicosis’. The causative mutation, known since 2001, has been described to affects sheep herding breeds related to collie lineage. The present study is a retrospective investigation of the presence of MDR1 mutated allele in Italian dog populations in a 5 years’ time lapse. The aim of the research is to offer a deep knowledge in MDR1 allelic and genotypic frequencies in canine breeds and populations raised in Italy.MethodsGenotype data for the 4-bp deletion (c296_299del4) in MDR1 gene from 811 dogs belonging to 32 breeds/populations were collected.ResultsThe mutated allele has been found in 9 out of 31 breeds: Rough Collie, Smooth Collie, Border Collie, Bearded Collie, Shetland Sheepdog, Australian Shepherd, White Swiss Shepherd, Old English Sheepdog, Whippet and also in crossbreed. The breeds with the highest allelic mutation frequency are Smooth and Rough Collies with 75 per cent and 66 per cent of mutant MDR1 allele, respectively.ConclusionsThe results support the usefulness of this genetic analysis to optimise medical care in dogs at risk of multidrug resistance and to create an objective basis in breeding programme definition and in the risk evaluation in different breeds.

Engineered gene networks enable non‐genetic drug resistance and enhanced cellular robustness

Drug resistance complicates the treatment of cancer and infectious diseases, and often arises from the elevated expression of a gene that neutralises or reduces drug activity. To investigate this and other expression-based mechanisms of drug resistance, the authors engineered a set of gene regulatory networks in the eukaryotic model organism Saccharomyces cerevisiae to control a homologue of the cancer-related human multidrug resistance gene MDR1. Using this system, they explored experimentally how different gene regulatory network features, also called genetic network motifs, contribute to gene expression dynamics and cellular fitness. They observed that coherent feedforward and positive feedback motifs enable rapid and self-sustained activation of gene expression, and enhance cell survival in the presence of a cytotoxic drug. These observations underscore that genetic network motifs can be critical for drug resistance and that genetic network engineering can be used to enhance cellular tolerance to cytotoxins or other environmental stresses.

The role of intercellular transfer of P-glycoprotein in tumor drug resistance

Multidrug resistance is a major cause of clinical failure of tumor chemotherapy, study on the mechanisms of tumor multidrug resistance has been becoming a fascinating area in the field of tumor chemotherapy. The tumor multidrug resistance is generally considered to be due to the gene mutation, amplification or epigenetic changes that affect the uptake, metabolism or excretion of tumor drugs. P-glycoprotein is a transmembrane glycoprotein encoded by multidrug resistance gene MDR1, which leads to the principal contributor to tumor multidrug resistance. Research suggests that P-glycoprotein can metastasize through the tumor cells, thereby affecting tumor resistance. This article reviews the role of intercellular transfer of P-glycoprotein in tumor drug resistance. Key words: P-glycoprotein; Drug resistance, neoplasm; Membranin transfer

Role of DDX53 in taxol-resistance of cervix cancer cells in vitro

Cancer/Testis antigen DDX53 shows high expression level in various tumors and is involved in anti-cancer drug resistance. However, the functional study of DDX53 in cervix cancer remains unknown. In this study, the role of DDX53 in taxol-resistance of cervix cancer cells was investigated. In taxol-resistant HelaTR cells, DDX53 was significantly increased as compared to the parental HeLa cells. HelaTR cells also showed upregulation of multidrug resistant gene MDR1, invasive characteristics and decreased apoptosis. In addition, increased autophagy level was observed in HelaTR cells. Overexpression of DDX53 in HeLa and SiHa markedly led to greater resistance to taxol and cisplatin, whereas knockdown of DDX53 in HelaTR cells restored sensitivity, demonstrating that DDX53 regulated taxol resistance in cervix cancer cells. DDX53 overexpression in HeLa and SiHa cells enhanced invasion, migration and anchorage independent growth, DDX53 knockdown showed inverse effects in HeLaTR cells. When DDX53 expression was suppressed by siRNA, autophagic flux and drug resistance of HelaTR cells were decreased. In addition, DDX53 was upregulated in cervix cancer tissues from patient with a glassy cell carcinoma of cervix. Taken together, these results suggest that DDX53 plays a critical role in taxol-resistance by activating autophagy and a potential therapeutic target for the treatment of taxol-resistant cervix cancer.

Prognostic, predictive, and pharmacogenomic assessments of CDX2 refine stratification of colorectal cancer.

We aimed to refine the value of CDX2 as an independent prognostic and predictive biomarker in colorectal cancer (CRC) according to disease stage and chemotherapy sensitivity in preclinical models. CDX2 expression was evaluated in 1045 stage I–IV primary CRCs by gene expression (n = 403) or immunohistochemistry (n = 642) and in relation to 5‐year relapse‐free survival (RFS), overall survival (OS), and chemotherapy. Pharmacogenomic associations between CDX2 expression and 69 chemotherapeutics were assessed by drug screening of 35 CRC cell lines. CDX2 expression was lost in 11.6% of cases and showed independent poor prognostic value in multivariable models. For individual stages, CDX2 was prognostic only in stage IV, independent of chemotherapy. Among stage I–III patients not treated in an adjuvant setting, CDX2 loss was associated with a particularly poor survival in the BRAF‐mutated subgroup, but prognostic value was independent of microsatellite instability status and the consensus molecular subtypes. In stage III, the 5‐year RFS rate was higher among patients with loss of CDX2 who received adjuvant chemotherapy than among patients who did not. The CDX2‐negative cell lines were significantly more sensitive to chemotherapeutics than CDX2‐positive cells, and the multidrug resistance genes MDR1 and CFTR were significantly downregulated both in CDX2‐negative cells and in patient tumors. Loss of CDX2 in CRC is an adverse prognostic biomarker only in stage IV disease and appears to be associated with benefit from adjuvant chemotherapy in stage III. Early‐stage patients not qualifying for chemotherapy might be reconsidered for such treatment if their tumor has loss of CDX2 and mutated BRAF.

A barcode of multilocus nuclear DNA identifies genetic relatedness in pre- and post-Artemether/Lumefantrine treated Plasmodium falciparum in Nigeria

BackgroundThe decline in the efficacy of artemisinin-based combination treatment (ACT) in some endemic regions threatens the progress towards global elimination of malaria. Molecular surveillance of drug resistance in malaria-endemic regions is vital to detect the emergence and spread of mutant strains.MethodsWe observed 89 malaria patients for the efficacy of artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum infections in Lagos, Nigeria and determined the prevalence of drug resistant strains in the population. Parasite clearance rates were determined by microscopy and the highly sensitive var gene acidic terminal sequence (varATS) polymerase chain reaction for 65 patients with samples on days 0, 1, 3, 7, 14, 21 and 28 after commencement of treatment. The genomic finger print of parasite DNA from pre- and post-treatment samples were determined using 24 nuclear single nucleotide polymorphisms (SNP) barcode for P. falciparum. Drug resistance associated alleles in chloroquine resistance transporter gene (crt-76), multidrug resistance genes (mdr1–86 and mdr1–184), dihydropteroate synthase (dhps-540), dihydrofolate reductase (dhfr-108) and kelch domain (K-13580) were genotyped by high resolution melt analysis of polymerase chain reaction (PCR) fragments.ResultsBy varATS qPCR, 12 (18.5%) of the participants had detectable parasite DNA in their blood three days after treatment, while eight (12.3%) individuals presented with genotypable day 28 parasitaemia. Complexity of infection (CoI) was 1.30 on day 0 and 1.34 on day 28, the mean expected heterozygosity (HE) values across all barcodes were 0.50 ± 0.05 and 0.56 ± 0.05 on days 0 and 28 respectively. Barcode (π) pairwise comparisons showed high genetic relatedness of day 0 and day 28 parasite isolates in three (37.5%) of the eight individuals who presented with re-appearing infections. Crt-76 mutant allele was present in 38 (58.5%) isolates. The mdr1–86 mutant allele was found in 56 (86.2%) isolates. No mutation in the K-13580 was observed.ConclusionsPersistence of DNA-detectable parasitaemia in more than 18% of cases after treatment and indications of genetic relatedness between pre- and post-treatment infections warrants further investigation of a larger population for signs of reduced ACT efficacy in Nigeria.

Mechanism of the enhancing effects of miR-93 on resistance of breast cancer MCF-7 cells to adriamycin.

This study aimed to investigate the effects of miR-93 on resistance of breast cancer MCF-7 cells to adriamycin, and to explore the possible mechanism. Expression of miR-93 in breast cancer cell lines MCF-7 and MCF-7/ADM was detected by reverse transcription-quantitative PCR (RT-qPCR). miR-93 mimics and inhibitors were transfected into MCF-7/ADM and MCF-7 cells, and MTT assay was used to detect the resistance of cells to adriamycin after transfection. Western blot analysis was used to detect the expression of anti-apoptotic protein Bcl-2 and multidrug resistance gene MDR1 related P-gp protein in MCF-7/ADM and MCF-7 cells before and after the transfection of miR-93 mimics. Expression level of miR-93 in MCF-7/ADM cells was decreased, and was 40% of that in MCF-7 cells (0.39±0.04, p<0.05). Before transfection, IC50 value of MCF-7 cells to adriamycin (11.02±0.95) was lower than that of MCF-7/ADM cells (21.29±1.83, p<0.05). IC50 value of MCF-7/ADR cells at 72 h after transfection with miR-93 mimics (13.55±0.86) was lower than that of the negative control group (24.67±1.51, p<0.05). IC50 value of MCF-7 cells 72 h after transfection with miR-93 inhibitor (19.88±1.28) was higher than that of negative control group (11.02±0.95, p<0.05). Expression levels of Bcl-2 and P-gp proteins in MCF-7/ADM cells were 1.63±0.24 and 1.76±0.22 times that of MCF-7 cells, respectively (p<0.05). At 72 h after transfection of miR-93 mimics, expression levels of Bcl-2 and P-gp proteins in MCF-7/ADM cells were 0.27±0.06 and 0.39±0.05, respectively, compared with the negative control group (p<0.05). At 72 h after transfection with miR-93 inhibitor, expression levels of Bcl-2 and P-gp protein in MCF-7 cells were 1.48±0.10 and 1.56±0.11 times of the negative control group, respectively (p<0.05). miR-93 can increase the apoptosis of MCF-7/ADM cells and their resistance to adriamycin by inhibiting the expression of Bcl-2 and P-gp proteins.

Drug resistance genes: pvcrt-o and pvmdr-1 polymorphism in patients from malaria endemic South Western Coastal Region of India

BackgroundMalaria is highly prevalent in many parts of India and is mostly caused by the parasite species Plasmodium vivax followed by Plasmodium falciparum. Chloroquine (CQ) is the first-line treatment for blood stage P. vivax parasites, but cases of drug resistance to CQ have been reported from India. One of the surveillance strategies which is used to monitor CQ drug resistance, is the analysis of single nucleotide polymorphisms (SNPs) of the associated gene markers. Susceptibility to CQ can also be determined by copy number assessment of multidrug resistant gene (mdr-1). The current study has examined the prevalence of SNPs in P. vivax orthologs of P. falciparum chloroquine resistant and multi-drug resistant genes (pvcrt-o and pvmdr-1, respectively) and pvmdr-1 copy number variations in isolates from the highly endemic Mangaluru city near the South Western Coastal region of India.MethodsA total of 140 blood samples were collected from P. vivax infected patients attending Wenlock Hospital Mangaluru during July 2014 to January 2016. Out of these 140 samples, sequencing was carried out for 54 (38.5%) and 85 (60.7%) isolates for pvcrt-o and pvmdr-1, respectively. Single nucleotide polymorphisms (SNPs) in the pvcrt-o and pvmdr-1 genes were analysed by direct sequencing method, while copy number variations of 60 isolates (42. 8%) were determined by real time PCR.ResultsOut of 54 clinical isolates analysed for pvcrt-o, three (5.6%) showed K10 insertion and the rest had wild type sequence. This is the first report to show K10 insertion in P. vivax isolates from India. Further, out of 85 clinical isolates of P. vivax analysed for mutations in pvmdr-1 gene, only one isolate had wild type sequence (~ 1%) while the remaining (99%) carried mutant alleles. Seven non-synonymous mutations with two novel mutations (I946V and Y1028C) were observed. Of all the observed mutations in pvmdr-1 gene, T958M was most highly prevalent (present in 90% of samples) followed by F1076L (76%), and Y976F (7%). Amplification of pvmdr-1 gene was observed in 31.6% of the isolates, out of 60 amplified.ConclusionThe observed variations both in pvmdr-1 and pvcrt-o genes indicate a trend towards parasite acquiring CQ resistance in this endemic area.

The relationship between MDR1 gene polymorphism and long-time survival in children with acute lymphoblastic leukemia

Objective To study the frequency distribution patterns of gene polymorphism of multidrug resistance gene MDR1 in children with acute lymphoblastic leukemia(ALL), and their relationship with long-time survival. Methods A case-control study was carried out to compare the distribution of genotype and genetic frequency of MDR1 C3435T, C1236T and G2677T/A in 176 children with ALL by single nucleotide polymorphisms-shot (SNP-shot) method. Results MDR1 C3435T C/C, C/T, T/T took 67, 94 and 15 cases respectively; MDR1 C1236T C/C, C/T, T/T took 23, 82 and 71 cases respectively; G2677T/A G/T, T/T, T/A, G/G, G/A and A/A took 66, 17, 28, 37, 24 and 4 cases respectively. The overall survival rate of 176 children in this group was 77.3 % (136/176). The 5-year event-free survival (EFS) rates in children with MDR1 C3435T C/C, C/T and T/T were 79.57 %, 83.33 % and 33.33 % respectively. The EFS rate in children with T/T genotype was lower than those in C/C and C/T genotypes(χ2=15.301, P=0.002). The 5-year EFS rates in patients with MDR1 C1236T C/C, C/T and T/T were 52 %, 81.71 % and 71.93 % respectively. The EFS rate in patients with C/C genotype was lower than those in C/T and T/T genotypes (χ2=17.800, P=0.001). Conclusions The gene polymorphism of MDR1 is related to the EFS of children with ALL. The survival rates in children with MDR1 C1236T C/C and C3435T T/T genotypes are lower than those in other genotypes. Key words: Leukemia, lymphocyte, acute; Multidrug resistance gene; Gene polymorphism; Event-free survival

Identification of multidrug resistance gene MDR1 associated microRNA of salvianolic acid A reversal in lung cancer

This paper was aimed to investigate the microRNA associated with multidrug resistance gene MDR1 of salvianolic acid A reversal in lung cance. Human lung cancer A549 cells were divided into normal control group and drug group, and the MDR1 expression levels were determined by real-time quantitative PCR. MicroRNA expression profiling of normal control group and drug group were detected by using the latest microRNA microarray. Quantitative RT-PCR was used to validate the differentially expressed miRNA. Forecast of miRNA associated with MDR1 multi-resistant genes of up-regulated miRNA. Experimental results showed that the dosage of MDR1 expression level significantly lowered compared with control group. The miRNA expression spectrum analyses of human lung cancer A549 cells to drug group and the control group were detected by microRNA microarray, 426 differentially expressed miRNA were screened out. Then target prediction were performed for difference up-expression of miRNA and found that there were four obvious increase of miRNA associated with MDR1 multi-resistant genes. Real-time quantitative PCR for 4 microRNA verification, the results were consistent with the chip. So the author considered that salvianolic acid A down lung cancer multidrug resistance gene MDR1 is likely to be affected by the miRNA expression and regulation of target genes, to further clarify the traditional Chinese medicine to reverse multi-drug resistant mechanism provides the experimental basis.

Human Helicase RECQL4 Drives Cisplatin Resistance in Gastric Cancer by Activating an AKT-YB1-MDR1 Signaling Pathway.

Elevation of the DNA-unwinding helicase RECQL4, which participates in various DNA repair pathways, has been suggested to contribute to the pathogenicity of various human cancers, including gastric cancer. In this study, we addressed the prognostic and chemotherapeutic significance of RECQL4 in human gastric cancer, which has yet to be determined. We observed significant increases in RECQL4 mRNA or protein in >70% of three independent sets of human gastric cancer specimens examined, relative to normal gastric tissues. Strikingly, high RECQL4 expression in primary tumors correlated well with poor survival and gastric cancer lines with high RECQL4 expression displayed increased resistance to cisplatin treatment. Mechanistic investigations revealed a novel role for RECQL4 in transcriptional regulation of the multidrug resistance gene MDR1, through a physical interaction with the transcription factor YB1. Notably, ectopic expression of RECQL4 in cisplatin-sensitive gastric cancer cells with low endogenous RECQL4 was sufficient to render them resistant to cisplatin, in a manner associated with YB1 elevation and MDR1 activation. Conversely, RECQL4 silencing in cisplatin-resistant gastric cancer cells with high endogenous RECQL4 suppressed YB1 phosphorylation, reduced MDR1 expression, and resensitized cells to cisplatin. In establishing RECQL4 as a critical mediator of cisplatin resistance in gastric cancer cells, our findings provide a therapeutic rationale to target RECQL4 or the downstream AKT-YB1-MDR1 axis to improve gastric cancer treatment. Cancer Res; 76(10); 3057-66. ©2016 AACR.

NANOG regulates epithelial-mesenchymal transition and chemoresistance through activation of the STAT3 pathway in epithelial ovarian cancer.

NANOG is a key transcription factor that is overexpressed and plays an important role in various cancers. Its overexpression is associated with highly tumorigenic, drug-resistant, and poor prognosis. However, the underlying mechanism of action of NANOG in ovarian cancer remains unclear. Epithelial-mesenchymal transition (EMT), which is a critical process in cancer invasion and metastasis, is also associated with drug resistance. We determined whether NANOG is associated with EMT and chemoresistance in epithelial ovarian cancer cells. NANOG expression was increased in epithelial ovarian cancer cells (HEY and SKOV3) compared with normal epithelial ovarian cells (Moody). Low expression of NANOG increased the expression of E-cadherin and decreased the expression of vimentin, β-catenin, and Snail. Furthermore, the cell migration and invasion abilities were decreased. The multidrug resistance genes MDR-1 and GST-π were also downregulated when NANOG was lowly expressed. The cells that were transfected with the si-NANOG plasmid were more sensitive to cisplatin compared with the cells that were transfected with empty vector. The data demonstrated that Stat3 was correlated with NANOG-mediated EMT and drug resistance. The silencing of Stat3 expression abrogated NANOG-mediated EMT changes and increased the sensitivity of the cells to chemotherapy. These results suggest that NANOG mediates EMT and drug resistance through activation of the Stat3 pathway in epithelial ovarian cancer.

Potential implications of CYP3A4, CYP3A5 and MDR-1 genetic variants on the efficacy of Lopinavir/Ritonavir (LPV/r) monotherapy in HIV-1 patients.

Introduction Several genetic single nucleotide polymorphisms (SNPs) in biotransformation enzymes (CYP3A4, CYP3A5) or transporter proteins (multidrug resistance MDR1 gene product, P-gp) are involved in PI metabolism so that PI pharmacokinetics is characterized by a large inter-individual variability. The aim of this study was: (i) to develop an in-house PCR/direct sequencing, based on DNA purification of full-length CYP3A4 and CYP3A5 genes (SNPs) and MDR1 C3435T variant; (ii) to investigate association of CYP3A4 and CYP3A5 reported or unreported genetic polymorphisms and MDR1-C3435T (CC homozygote, CT heterozygote, TT homozygote) with clinical outcome of HIV-1 infected subjects treated with PI.Methods Overall, 39 HIV-1 infected patients receiving boosted Lopinavir (LPV/r) monotherapy after virological suppression were genotyped and analyzed through PCR and direct sequencing of full-length CYP3A4 and CYP3A5 gene sequences [1] and MDR1 gene (C3435T). CD4+T-cell counts and plasma viral load were analyzed before and after LPV/r initiation; LPV/r therapeutic drug monitoring (TDM) was determined at 12-hours.Results LPV/r TDM (ng/ml) did not show significant differences among CYP3A4 or CYP3A5 SNPs, although a mean lower level of LPV/r was associated with detection of several SNPs: CYP3A5*3 rs776746; CYP3A5 rs28365088, CYP3A5 rs15524, CYP3A4 rs2687116, and a not already described polymorphism CYP3A4 nt20338. In follow-up analysis, <90% adherence was the main factor associated with virological failure of LPV/r monotherapy (83.3% of failure vs 34.4%, p<0.001 at log-rank test). Adjusting for adherence, the detection of a single CYP3A5*3 rs776746 and CYP3A5 rs15524 SNPs was associated with higher probability of LPV/r monotherapy failure (p<0.01), and in general, detection of any CYP3A5 SNP was associated with failure (26.2% vs 58.3%, p=0.067). No-association with detection of any CYP3A4 SNPs was found. MDR1 TT variants showed significant lower frequency of treatment failure (0.0% vs 47.7%, p=0.026), since non-TT homozygote patient failed LPV/r monotherapy.Conclusions Efficacy of PI monotherapy is strongly dependent from patient adherence, but, in adherent patients, genetic factors, such as CYP3A5 and MDR1-C3435T gene variants, may affect the response to treatment, though their role, as well of other genetic variants, need further investigation.

269: Multidrug resistance gene MDR1 is transactivated by Oct4 to increase chemotherapy resistance

269: Multidrug resistance gene MDR1 is transactivated by Oct4 to increase chemotherapy resistance

Tegillarca granosa extract Haishengsu (HSS) suppresses expression of mdr1, BCR/ABL and sorcin in drug-resistant K562/ADM tumors in mice

To evaluate the effect of Haishengsu (HSS), a protein extract from Tegillarca granosa, on multidrug-resistance genes mdr1, BCR/ABL and sorcin in transplanted tumors. Mice were inoculated subcutaneously with a drug resistant leukemia cell line K562/ADM. Tumor-bearing animals were divided into control, adriamycin, HSS and combination therapy (adriamycin plus HSS) groups. Flow cytometry was used to detect apoptosis of tumor cells, and RT-PCR was used to evaluate the expression of mdr1, BCR/ABL and sorcin. The apoptosis rate in the high (71.8%), medium (72.3%) and low doses HSS group (72.4%) was higher than in control (1.2%, p<0.01), adriamycin (34.4%, p<0.05) or combination therapy group (46.4%, p<0.05). The mean optical density of mdr1, BCR/ABL and sorcin in HSS groups was lower than in control, adriamycin and combination therapy group (p<0.01). The optical density of the three genes in high HSS group was lower than in medium and low HSS group (p<0.01). Haishengsu promotes apoptosis of drug-resistant K562/ADM tumors in mice in a dose-dependent manner. The pro-apoptotic effect of Haishengsu may be related to a reduced expression of multidrug-resistance genes mdr1, BCR/ABL and sorcin.

MDR-1 genotypes and quetiapine pharmacokinetics in healthy volunteers

P-glycoprotein is an efflux transporter encoded by the multidrug-resistance MDR-1 gene, which influences the absorption and excretion of a variety of drugs. The relation between quetiapine pharmacokinetics and MDR-1 genetic polymorphisms remains controversial. Therefore, the aim of the present study was to analyze the association between quetiapine plasma concentrations and MDR-1 genetic polymorphisms in a bioequivalence trial. Quetiapine bioequivalence was studied in 24 unrelated healthy Caucasian adults with an open-label, randomized, cross-over, two-sequence and two-period design. Subjects were genotyped for 3435C>T and 1236C>T single-nucleotide polymorphisms. A linear mixed model was performed to compare pharmacokinetic parameters. Subjects with 3435T/T genotype vs. C carriers showed a higher area under the concentration-time curve from 0 to 36 h (p=0.01). Subjects classified according to 1236C>T SNP and haplotypes showed no statistically significant differences. These results suggest that the polymorphic MDR-1, in particular the 3435C>T allelic variant, might influence plasma levels of quetiapine.