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C3435T Polymorphism (c3435t + polymorphism)
Selected AbstractsFunctional C3435T polymorphism of MDR1 gene: an impact on genetic susceptibility and clinical outcome of childhood acute lymphoblastic leukemiaEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2004Krzysztof Jamroziak Abstract: The significance of genetic background in childhood acute lymphoblastic leukemia (ALL) is not well understood. Polymorphisms of genes encoding for xenobiotics and drug transporters are potential factors, which can influence the risk of developing ALL and its clinical outcome. P-glycoprotein (P-gp) is an adenosine triphosphate-binding cassette (ABC)-family transporter involved in protection against xenobiotics and multi-drug resistance. Recently, the single-nucleotide polymorphism C3435T of MDR1 gene has been found to be associated with altered tissue expression and function of P-gp. To evaluate whether C3435T MDR1 polymorphism is associated with the occurrence and outcome of ALL, 113 children with ALL (median age 5.1 yr) and 175 healthy individuals of Polish Caucasian origin were studied by polymerase chain reaction-restriction fragment-length polymorhism (PCR-RFLP) assay. The mutant homozygous TT genotype was found to be associated with occurrence of ALL (OR, 95% CI; 1.8, 1.1,3.1; P = 0.037). Besides, the analysis of factors influencing clinical outcome of our ALL patient cohort showed that CC genotype carriers had significantly lower event-free survival probability (pEFS) (0.62 vs. 0.87; P = 0.007) and overall survival probability (pOS) (0.72 vs. 0.91; P = 0.006). The Cox proportional hazards model-based analysis revealed that the hazard ratios for lower pEFS and lower pOS among CC homozygous subjects were 3.9 (P = 0.008) and 3.3 (P = 0.02), respectively. In conclusion, the results of the present study provide evidence that C3435T MDR1 polymorphism may involve both the susceptibility to and the clinical outcome of childhood ALL. Carriers of the TT genotype are more at risk of developing ALL than other individuals, whereas CC genotype carriers are supposed to have worse prognosis. [source] Determination of ABCB1 polymorphisms and haplotypes frequencies in a French populationFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2007Elise Jeannesson Abstract The ATP-binding cassette (ABC) transporter ABCB1, or P-glycoprotein, is a transmembrane efflux pump well known for its implication in drug transport and chemoresistance. ABCB1 substrates include either drugs, such as antiretrovirals and immunomodulators, or physiological molecules like phospholipids. Pharmacogenetic analysis of ABCB1 polymorphisms, in addition to other xenobiotic metabolizing enzymes, might help to personalize and optimize drug therapy. Indeed, some polymorphisms of ABCB1 have been implicated in susceptibility to diseases, changes in drug pharmacokinetics, and in variation of the biological response to drug treatment. In addition, variant and haplotype distributions differ depending on ethnicity. Thus, some ethnies may be at higher risk for adverse events, inefficacy of treatment or prevalence of pathologies. This study aimed to determine frequencies of ABCB1 polymorphisms and haplotypes in a sample of French healthy individuals. DNA was isolated from blood-EDTA. Polymerase chain reaction-restriction fragment length polymorphism and TaqMan single nucleotide polymorphism genotyping assays were used to genotype 227 individuals for T-129C, G-1A, A61G, G1199A, C1236T, T-76A, G2677T/A and C3435T polymorphisms. The observed frequencies of the variant allele for these eight polymorphisms are 0.04, 0.08, 0.09, 0.06, 0.42, 0.46, 0.45 and 0.46 respectively. These polymorphisms are in linkage disequilibrium and haplotype frequencies were determined, the most frequent haplotype being the one with variants at position 1236, 2677 and 3435 and wild-type alleles at the other positions. Finally, the frequencies of these eight ABCB1 polymorphisms in our French individuals supposed to be healthy population are quite similar to those described in other Caucasian populations except for the C3435T polymorphism. [source] Multidrug resistance 1 gene polymorphism and susceptibility to inflammatory bowel diseaseINFLAMMATORY BOWEL DISEASES, Issue 5 2007S. Ardizzone MD Abstract Background: Several studies have evaluated the role of the multidrug resistance 1 gene (MDR1) polymorphism, which encodes the membrane-bound efflux transporter P-glycoprotein 170, in determining susceptibility to and disease behavior in inflammatory bowel disease (IBD), but with conflicting results. Methods: A total of 211 patients with Crohn's disease (CD), 97 patients with ulcerative colitis (UC), and 212 control subjects were investigated for the presence of MDR1 G2677T/A and C3435T polymorphisms. Genotype frequencies of CD and UC patients were compared to those observed in a control population. Genotype,phenotype correlations with major clinical features were also established and estimated risks (odds ratio [OR] with 95% confidence interval [CI]) for the mutations were calculated by a logistic regression analysis and multiple correspondent analysis. Results: No significant difference was observed for genotype frequencies for both MDR1 G2677T/A and C3435T polymorphisms on overall disease susceptibility for either CD or UC patients compared with control subjects. A significant association was found between the MDR1 C3435T polymorphism and patients with ileo-colonic CD (OR = 3.34; 95% CI: 1.34,8.27). Interestingly, a negative association was found between MDR1 C3435T polymorphism in patients with a positive family history for IBD (OR = 0.44; 95% CI: 0.20,0.95) and articular manifestations (OR = 0.29; 95% CI: 0.13,0.68). Both susceptible and protective effects were identified. No significant association between G2677T/A polymorphism and any specific subphenotypes was found, nor was there any association with subphenotypic categories of UC and both single nucleotide polymorphisms. Conclusions: The results of our study suggest that MDR1 gene polymorphism could have a role in determining susceptibility to IBD. The variability of this possible effect in the several studies reported so far may be the indirect expression of the complex role played by the MDR1 gene and its product, P-glycoprotein 170, in the regulation of host,bacteria interactions and in the pathogenesis of IBD. (Inflamm Bowel Dis 2007) [source] Gefitinib,phenytoin interaction is not correlated with the 14C-erythromycin breath test in healthy male volunteersBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2 2009Stephanie Chhun WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , The response to gefitinib is variable and could be explained partly by the interindividual variability in gefitinib exposure. , Gefitinib is mainly metabolized by CYP3A4 and CYP2D6, and is to a lesser extent a P-glycoprotein (P-gp) substrate. , Patients with cancer are at high risk of drug,drug interactions, such as with phenytoin, a potent CYP3A4 inducer. WHAT THIS STUDY ADDS , The reduced systemic exposure of gefitinib with multiple-dose phenytoin treatment. , An effect attributed to the possible induction of intestinal CYP3A4 because of the lack of correlation between changes in gefitinib disposition and the erythromycin breath test and the lack of association between allelic variant in the ABCB1 gene and baseline and induced oral gefitinib clearance. , The CYP2D6 extensive metabolizer seems to be less sensitive to the interaction with phenytoin, as the magnitude of induction of gefitinib clearance was greater in CYP2D6 poor metabolizers than in CYP2D6 extensive metabolizers. AIMS We aimed to describe the pharmacokinetic interaction between phenytoin, a potent CYP3A4 and P-glycoprotein (P-gp) (ABCB1) inducer, and gefitinib, a CYP3A4, CYP2D6 and P-gp substrate. METHODS An open-label, randomized, two-phase crossover study was conducted. Eighteen healthy male volunteers (nine homozygous CC and nine homozygous TT as determined by their ABCB1 C3435T polymorphism in exon 26) received a single oral dose of 250 mg gefitinib alone or after 5 days treatment with phenytoin (5 mg kg,1 daily). Gefitinib plasma concentrations were determined by high-performance liquid chromatography. Hepatic CYP3A4 activity was evaluated by the 14C-erythromycin breath test (ERMBT) and the ABCB1 and CYP2D6 genetic polymorphisms were determined by the TaqMan allelic discrimination assay and long polymerase chain reaction, respectively. RESULTS Following treatment with phenytoin, mean gefitinib Cmax and AUC0,, decreased by 26 ± 44% [95% confidence interval (CI) for the difference 5,48%, P= 0.005] and 47 ± 26% (95% CI for the difference 34,60%, P= 0.001), respectively, and apparent oral clearance increased by 126 ± 93% (95% CI for the difference 80,172%, P= 0.004). Concomitantly, phenytoin increased the mean ERMBT by 91 ± 44% (95% CI 75,105%, P < 0.001) from baseline, but the extent of liver CYP3A4 induction was not correlated to the extent of interaction. Furthermore, this interaction was independent of ABCB1 genetic polymorphism. The CYP2D6 genotype was slightly but significantly related to gefitinib clearance (P= 0.04) during the control phase. CONCLUSIONS The significant interaction between gefitinib and phenytoin was not correlated with the erythromycin breath test and was independent of ABCB1 polymorphism, but may involve presystemic CYP3A-mediated intestinal first-pass. [source] Minimal effect of MDR1 and CYP3A5 genetic polymorphisms on the pharmacokinetics of indinavir in HIV-infected patientsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 3 2007Caroline Solas What is already known about this subject ,,Before this study, few data were available on the potential effect of genetic variants of P-glycoprotein or the CYP3A5 enzyme on the pharmacokinetic variability of protease inhibitors (PI). ,,MDR1 C3435T polymorphism was often linked with the pharmacokinetic variability of nelfinavir. CYP3A5*3 polymorphism was linked with the pharmacokinetic variability of calcineurin inhibitors and was therefore strongly suspected of being one of the key factors in the pharmacokinetic variability of other CYP3A susbtrates. What this study adds ,,Our results showed that both MDR1 C3435T and CYP3A5*3 polymorphisms are involved in the pharmacokinetic variability of the absorption or elimination of indinavir, but probably jointly with other factors. ,,The potent CYP3A inhibitory effect of ritonavir may hide the variability linked to genetic differences in the CYP3A5 gene, thereby reducing the overall pharmacokinetic variability of the boosted protease inhibitor. ,,Genotyping MDR1 and/or CYP3A5 does not appear to be a clinically relevant factor in optimizing protease inhibitor boosted regimens. Aims The protease inhibitor indinavir is characterized by an important interindividual pharmacokinetic variability, which results from the actions of the metabolizing enzymes cytochrome P450 (CYP) 3A and the multidrug efflux pump P-glycoprotein (P-gp), encoded by MDR1. Using a population pharmacokinetic approach, we investigated the effect of several MDR1 and CYP3A5 polymorphisms on the pharmacokinetic parameters of indinavir in HIV-infected patients. Methods Twenty-eight patients receiving indinavir alone or together with ritonavir were included. Indinavir pharmacokinetics were studied over a 12 h interval. Genetic polymorphisms were assessed by real-time PCR assays and direct sequencing for MDR1 and by PCR-SSCP analysis for CYP3A5. Results The pharmacokinetics of indinavir were best described by a one-compartment model with first-order absorption. In the final model, the MDR1 C3435T genotype and ritonavir were identified as statistically significant covariates (P , 0.001) for the absorption rate constant (95% confidence interval on the difference between CC and CT genotype 0.37, 5.53) and for clearance (95% confidence interval on the difference 5.8, 26.2), respectively. Patients with the CYP3A5*3/*3 genotype receiving indinavir alone had a 31% decrease in the indinavir clearance rate compared with patients carrying the CYP3A5*1/*3 genotype. Conclusions The MDR1 C3435T genotype affects the absorption constant of indinavir suggesting that P-gp may be implicated in its pharmacokinetic variability. Through its inhibition of CYP3A and P-gp, ritonavir could attenuate the pharmacokinetic variability linked to genetic differences, reducing significantly the interindividual variability of indinavir. However, genotyping MDR1 and/or CYP3A5 to optimize protease inhibitor boosted regimens does not seem clinically relevant. [source] Determination of ABCB1 polymorphisms and haplotypes frequencies in a French populationFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2007Elise Jeannesson Abstract The ATP-binding cassette (ABC) transporter ABCB1, or P-glycoprotein, is a transmembrane efflux pump well known for its implication in drug transport and chemoresistance. ABCB1 substrates include either drugs, such as antiretrovirals and immunomodulators, or physiological molecules like phospholipids. Pharmacogenetic analysis of ABCB1 polymorphisms, in addition to other xenobiotic metabolizing enzymes, might help to personalize and optimize drug therapy. Indeed, some polymorphisms of ABCB1 have been implicated in susceptibility to diseases, changes in drug pharmacokinetics, and in variation of the biological response to drug treatment. In addition, variant and haplotype distributions differ depending on ethnicity. Thus, some ethnies may be at higher risk for adverse events, inefficacy of treatment or prevalence of pathologies. This study aimed to determine frequencies of ABCB1 polymorphisms and haplotypes in a sample of French healthy individuals. DNA was isolated from blood-EDTA. Polymerase chain reaction-restriction fragment length polymorphism and TaqMan single nucleotide polymorphism genotyping assays were used to genotype 227 individuals for T-129C, G-1A, A61G, G1199A, C1236T, T-76A, G2677T/A and C3435T polymorphisms. The observed frequencies of the variant allele for these eight polymorphisms are 0.04, 0.08, 0.09, 0.06, 0.42, 0.46, 0.45 and 0.46 respectively. These polymorphisms are in linkage disequilibrium and haplotype frequencies were determined, the most frequent haplotype being the one with variants at position 1236, 2677 and 3435 and wild-type alleles at the other positions. Finally, the frequencies of these eight ABCB1 polymorphisms in our French individuals supposed to be healthy population are quite similar to those described in other Caucasian populations except for the C3435T polymorphism. [source] Multidrug resistance 1 gene polymorphism and susceptibility to inflammatory bowel diseaseINFLAMMATORY BOWEL DISEASES, Issue 5 2007S. Ardizzone MD Abstract Background: Several studies have evaluated the role of the multidrug resistance 1 gene (MDR1) polymorphism, which encodes the membrane-bound efflux transporter P-glycoprotein 170, in determining susceptibility to and disease behavior in inflammatory bowel disease (IBD), but with conflicting results. Methods: A total of 211 patients with Crohn's disease (CD), 97 patients with ulcerative colitis (UC), and 212 control subjects were investigated for the presence of MDR1 G2677T/A and C3435T polymorphisms. Genotype frequencies of CD and UC patients were compared to those observed in a control population. Genotype,phenotype correlations with major clinical features were also established and estimated risks (odds ratio [OR] with 95% confidence interval [CI]) for the mutations were calculated by a logistic regression analysis and multiple correspondent analysis. Results: No significant difference was observed for genotype frequencies for both MDR1 G2677T/A and C3435T polymorphisms on overall disease susceptibility for either CD or UC patients compared with control subjects. A significant association was found between the MDR1 C3435T polymorphism and patients with ileo-colonic CD (OR = 3.34; 95% CI: 1.34,8.27). Interestingly, a negative association was found between MDR1 C3435T polymorphism in patients with a positive family history for IBD (OR = 0.44; 95% CI: 0.20,0.95) and articular manifestations (OR = 0.29; 95% CI: 0.13,0.68). Both susceptible and protective effects were identified. No significant association between G2677T/A polymorphism and any specific subphenotypes was found, nor was there any association with subphenotypic categories of UC and both single nucleotide polymorphisms. Conclusions: The results of our study suggest that MDR1 gene polymorphism could have a role in determining susceptibility to IBD. The variability of this possible effect in the several studies reported so far may be the indirect expression of the complex role played by the MDR1 gene and its product, P-glycoprotein 170, in the regulation of host,bacteria interactions and in the pathogenesis of IBD. (Inflamm Bowel Dis 2007) [source] Influence of CYP3A5 and MDR1 polymorphisms on tacrolimus concentration in the early stage after renal transplantationCLINICAL TRANSPLANTATION, Issue 5 2005Xin Zhang Abstract:, Objective:, Tacrolimus is an immunosuppressive drug with a narrow therapeutic range and wide interindividual variation in its pharmacokinetics. Cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp, encoded by MDR1) play an important role in the absorption and metabolism of tacrolimus. The objective of this study was to evaluate whether or not CYP3A5*1/*3 or MDR1 C3435T polymorphisms are associated with the tacrolimus concentration per dose. Methods:, CYP3A5 and MDR1 genotypes were determined by polymerase chain reaction followed by restriction fragment length polymorphism analysis in 118 Chinese renal transplant patients receiving tacrolimus. Whole blood trough tacrolimus concentration was measured by enzyme-linked immunosorbent assay and dose-adjusted concentration (ng/mL per mg/kg/d) was calculated at 1 wk, 1 month, and 3 months after transplantation. Results:, The dose-adjusted concentration of CYP3A5*1/*1 and *1/*3 patients was significantly lower than *3/*3 patients (32.8 ± 17.7 and 41.6 ± 15.8 vs. 102.3 ± 51.2 at 1 wk; 33.1 ± 7.5 and 46.4 ± 12.9 vs. 103 ± 47.5 at 1 month; 35.3 ± 20.9 and 59.0 ± 20.6 vs. 150 ± 85.3 at 3 months after transplantation respectively). At 1 wk, 46% of the CYP3A5*1 allele carriers had a tacrolimus concentration lower than 5 ng/mL and 77% lower than 8 ng/mL, whereas 20% of the *3/*3 patients had a concentration higher than 20 ng/mL. There was a mild difference between *1/*1 homozygotes and *1/*3 heterozygotes at 1 and 3 months after transplantation. No difference was found among the MDR1 genotypes. Conclusion:, CYP3A5*1/*3 polymorphisms are associated with tacrolimus pharmacokinetics and dose requirements in renal transplant recipients. Pharmacogenetic methods could be employed prospectively to help initial dose selection and to individualize immunosuppressive therapy. [source] | ||||||||||