MDR1 C3435T Genotype Research Articles

PB2066: THE STUDY OF GSTP1 AND MDR1 GENES POLYMORPHISMS IN HODGKIN’S LYMPHOMA AND THEIR LINK WITH CHEMOTHERAPY RESPONSE.

Background: Glutathione-S-transferase P1 and ATP-dependent transporter P-glycoprotein are enzymes of the second phase of xenobiotic metabolism that participate in biotransformation of agents of standard protocol of Hodgkin’s Lymphoma chemotherapy. The polymorphism of the GSTP1 and MDR1 genes encoding these proteins causes changes in their activity, which can provide an individual patients’ response to chemotherapy. In this regard, the search for predictive genetic factors for the effectiveness of antitumor therapy is an important task. Aims: to demonstrate the association between polymorphic variants of GSTP1 (A313G, C341T) and MDR1 (C1236T, G2677T, C3435T) genes in patients with Hodgkin’s lymphoma. Methods: Overall, 77 Hodgkin’s lymphoma patients aged 18-74 years who were treated by BEACOPP and ABVD chemotherapy protocols in Oncohematological Departments of City Clinical Hospital №2 and Novosibisk State District clinical Hospital were enrolled in this study. The effectiveness of chemotherapy was evaluated after 4-6 cycles of chemotherapy in accordance with clinical guidelines. Depending on the achieved results of treatment, all patients were divided into two groups: patients with complete/partial remission and patients with progressive/refractory or relapsed lymphoma. Polymorphisms of GSTP1 (A313G, C341T) and MDR1 (C1236T, G2677T, C3435T) genes were defined by PCR method with real-time detection in the samples of peripheral blood in the Centre of Collective Usage «Proteomic analysis» FRC FTM. The odds ratio (OR) used to evaluate the link between genotypes with efficacy of chemotherapy. Results: We found the following frequencies of mutant alleles in Hodgkin’s Lymphoma patients: GSTP1313G – 31.17%, GSTP1 341T – 9.7%, MDR1 1236T – 50.00%, MDR1 2677T – 48.70%, MDR13435 ТОНН – 58.44%. Patient’s genotypes were similar to described genotypes of healthy Europeans. There was no significant difference in distribution of frequency alleles and GSTP1 A313G (χ2=0,89, p=0,34), GSTP1 C341T (χ2=0,11 R=0,74), MDR1 C1236T (χ2=0,01, p=0,93), MDR1 G2677T (χ2=0,37, p=0,54), MDR1 C3435T (χ2=0,01, р=0,97) genotypes between group of Hodgkin’s lymphoma patients with complete/partial remission and group with progressive/refractory or relapsed lymphoma. At the same time we found the significant correlation between GSTP1 A313G heterozygotes and formation of progressive/refractory and prolapsed course of disease (OR = 10.80; CI 95% = 1.23 – 496.52). There was no significant association between efficacy of chemotherapy and other studied genotypes, namely GSTP1 C341T, MDR1 C1236T, MDR1 G2677T, MDR1 C3435T genotypes. Summary/Conclusion: The observed correlation between GSTP1 A313G gene polymorphisms and formation progressive/refractory or prolapsed course of disease needs to be studied to provide safe and effective specific chemotherapy.

Effect of MDR1 and CYP3A5 gene polymorphisms on outcomes of patients receiving imatinib treatment for chronic myeloid leukemia

To study the effect of MDR1 and CYP3A5 gene polymorphisms on the outcomes of imatinib treatment in patients with chronic myeloid leukemia (CML). A total of 100 patients with CML treated with imatinib were enrolled in this study, including 50 patients with cytogenetic relapse (study group) and 50 without cytogenetic relapse (control group) during the follow-up for 45 months. For all the patients, single nucleotide polymorphisms (SNPs) of C1236T, C3435T, and G2677T/A loci in the MDR1 gene and A6986G locus in CYP3A5 gene were genotyped and the trough levels of imatinib was measured using LC-MS/MS. The relationship between SNPs of the loci and the risk of cytogenetic relapse were analyzed. The risk of cytogenetic recurrence was significantly higher in patients with CC genotypes of MDR1-C1236T and MDR1-C3435T than in those with CT + TT genotypes (P < 0.05). The median survival time of the patients with TT genotypes of MDR1-C3435T and MDR1-C1236T was significantly higher than that of patients with CC genotypes and CT genotypes (P < 0.05). The incidences of hematologic toxicity and neutropenia were significantly higher in patients with cytogenetic relapse than in those without cytogenetic relapse (P < 0.05). MDR1-C3435T genotype and imatinib concentration were independent predictors of cytogenetic relapse of CML. The risk of cytogenetic relapse of CML was significantly affected by SNPs of C1236T and C3435T loci of MDR1 gene and blood imatinib concentration. MDR1-C3435T genotype can be used as a potential biomarker for predicting cytogenetic relapse in CML patients.

IDENTIFICATION OF FUNCTIONAL SNPs OF MDR1 GENE AMONG NEPHROTIC SYNDROME CHILDREN IN SOUTH INDIA

Objective: This study was conducted to determine the frequency of C3435T and G2677T/C single nucleotide polymorphisms of multi drug resistancegene -1 (MDR1) in nephrotic syndrome (NS) children in relation to healthy subjects. The role and association of these SNPs were also determined,whether response and/or resistance to steroid treatment in children with NS in south India.Methods: Genomic DNA was isolated from 371 blood samples collected from children with NS and controls. Among 173 cases, categorized intosteroid-resistant NS (SRNS) were 90 and steroid-sensitive NS (SSNS) were 83 and 198 blood samples were included as controls. All samples weresubjected to DNA extraction, and polymerase chain reaction followed by restriction fragment length polymorphism for identification of C3435T andG2677T/C genomic variations.Results: The frequencies of MDR-1 C3435T, CT, TT, and CC genotypes and SNP G2677T/C GG and G allele genotypes were observed in this study group.In SRNS, children showed significantly higher frequencies of MDR-1 C3435T, CT, TT, and TT+CC genotypes were observed than SRNS and controls.The allele frequencies of SRNS children showed CC - 4%, CT - 32% and TT - 12% and in SSNS children, CC - 10.98%, CT - 27.2% and TT - 13.9% wereobserved. Furthermore, increased frequencies of MDR-1 C3435T CT, TT, TT+CC genotypes, or T allele were observed in children aged &lt;9 years old.There were no different genotype and allele frequency observed in G2677T/C genotypes NS children and controls.Conclusion: Based on these data, we are suggesting that MDR-1 C3435T gene polymorphisms are risk factors of increased susceptibility, earlieronset of NS as well as leads to steroid resistance. Whereas SNP G2677T/C gene polymorphisms do not have significant role observed in this studypopulation.Keywords: Nephrotic syndrome, Steroid-sensitive nephrotic syndrome, Steroid-resistant nephrotic syndrome, Multidrug resistance gene-1,Polymerase chain reaction followed by restriction fragment length polymorphism.

Influence of Genotype and Haplotype of MDR1 (C3435T, G2677A/T, C1236T) on the Incidence of Breast Cancer--a Case-Control Study in Jordan.

Breast cancer is the leading cause of cancer death among women and the second in humans worldwide. Many published studies have suggested an association between MDR1 polymorphisms and breast cancer risk. Our aim was to study the association between genetic polymorphism of MDR1 at three sites (C3435T, G2677A/T, and C1236T) and their haplotype and the risk of breast cancer in Jordanian females. A case-control study involving 150 breast cancer cases and 150 controls was conducted. Controls were age-matched to cases. The polymerase chain reaction/restriction fragment length polymorphism (PCR- RFLP) technique and sequencing were performed to analyse genotypes. The distribution of MDR1 C3435T genotypes differed between cases and controls [cases, CC 45.3%, CT 41.3%, and TT 13.3%; controls, CC 13.4%, CT 43.3%, and TT 30.2%, p < 0.001]. Similarly, the distribution of G2677A/T significantly differed [cases, GG 43.1 %, GT+GA 50.9% and AA+TT 6%; controls, GG 29.6 %, GT+GA 50.9%, and AA+TT 19.4%, p = 0.004]. On the other hand, genotype and allelotype distribution of C1236T was not statistically different between cases and controls (p=0.56 and 0.26, respectively). The CGC haplotype increased the risk to breast cancer by 2.5-fold compared to others, while TGC and TTC haplotypes carried 2.5- and 5-fold lower risk of breast cancer, respectively. Genetic polymorphisms of MDR1 C3435T and G2677A/T, but not C1236T, are associated with increased risk of breast cancer. In addition, CGC, TGC and TTC haplotypes have different impacts on the risk of breast cancer. Future, larger studies are needed to validate these findings.

Association of MDR1 gene (C3435T) polymorphism and gene expression profiling in lung cancer patients treated with platinum-based chemotherapy.

Chemotherapy is the standard and recommended treatment for lung cancer apart from surgery and radiotherapy. Chemotherapy is administered as mono-agents or as combination therapy. In this study, we examined the role of MDR1 C3435T polymorphisms in lung cancer patients undergoing chemotherapy. We genotyped 126 cases with lung cancer and 111 healthy controls, using the polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Frequencies of MDR1 C3435C, C3435T and T3435T genotypes were 61, 16 and 23% in lung cancer patients and 86, 9 and 5% in the controls, respectively. The T3435T genotypes had a 5.23-fold increased risk for lung cancer. (OR 5.23; 95% CI 2.082-13.146; p=0.0004). Patients with TT genotypes were more frequent in stage IV and were significantly associated with the disease (p=0.05). Habitual smoker lung cancer patients were 50% CC genotypes whereas TT genotypes were 34%. The non-smokers had 46% CC genotypes and 23% TT genotypes. Furthermore, we collected tissue biopsy samples for expression analysis from 20 patients (for controls we used the non-cancerous region of the same tissue). The present study showed mRNA expression of MDR1 was up-regulated in 80% of the cancer group in comparison with the control group (p=0.0002). We also correlated the association between MDR1 genotypes with different combinations of chemotherapy. The combinations and genotype distributions in the group receiving paclitaxel+cisplatin were as follows: CC (67%), CT (24%) and TT (9%) genotypes, respectively, and the group receiving carboplatin+gemcitabine CC (46%), CT (19%) and TT (35%) genotypes, respectively. We found that MDR1 (rs1045642) C3435T polymorphism and gene expression was significantly associated with the clinical outcome in lung carcinoma patients. In conclusion, it is suggested that MDR1 TT genotypes had higher risk for the development of lung cancer. Also, this polymorphism could be used as a genetic marker for predicting the clinical outcome of lung cancer patients.

Influence of MDR1 C3435T Genotype, Sokal Score and Hasford Score on the Overall Survival of Chronic Myelid Leukemia Patients Treated with Imatinib

Aim: Imatinib is considered as the first-line drug of choice for the treatment of CML who is positive for Philadelphia chromosome. To correlate various prognostic scores (Sokal, Hasford and Eutos) and pharmacogenetic markers like ABCG2 421 C>A, SLC22A1 1386C>A, SLC22A1 1022C>T, SLC22A1 1222A>G, ABCB1 3435T>C, ABCB1 2677 G>T/A with the overall and progression-free survival in CML patients.Methods: The patients who were started on imatinib from December 2009 to January 2014 at Regional Cancer Centre (RCC), JIPMER, Puducherry, India were recruited into the study. DNA was extracted from peripheral blood using phenol-chloroform method. The genotype status was identified using RT-PCR technique (AB7300, Applied Biosystems) using validated SNP genotyping kits. The influence of various factor on OS and PFS was determined using log-rank test (SPSS Ver 20.0).Results: A total of 119 patients was identified as BCR/ABL positive and started on Imatinib treatment. Out of this 113 patients were in Chronic phase and six were in Accelerated phase. The median age of the patient group wad 39 years (18-74). The median overall survival and progression-free survival was found to be 25 months and 19 months respectively. The three yr overall survival was 94.5%. None of the prognostic scores or genotypes correlated with progression-free survival of the patients in this study cohort. The low-risk category of Sokal and Hasford groups had a statistically better overall survival compared to intermediate and high-risk groups (p value 0.030 and 0.014 using log-rank test analysis). The Mutant alleles for MDR1 C3435T had a better overall survival compared to other genotypes (p value <0.001 using log-rank test).Conclusion: The Sokal score and Hasford score, not the Eutos score were better predictors of overall survival in our study. Out of the pharmacogenetic markers analyzed, MDR1 C3435T polymorphism had an influence on the overall survival.Acknowledgments: The study was supported by the Science and Engineering Research Board (SERB) research grant (SB/FT/LS-147/2012). DisclosuresNo relevant conflicts of interest to declare.

Relationship Between Response to Colchicine Treatment and MDR1 Polymorphism in Familial Mediterranean Fever Patients

Investigate the relationship between MDR1 C3435T polymorphism and colchicine response in Familial Mediterranean fever (FMF) patients. Patients (n=50) who received colchicine regularly, were willing to participate in the study, and attended control visits were included in the study. MDR1 C3435T genotype was defined by the real-time polymerase chain reaction method. Patients were divided into three groups. Patients, who recovered from episodes with standard colchicine treatment, and had no attack in the last 1 year were accepted as complete; patients whose episode number and intensity were decreased with the ongoing standard treatment as partial; and patients whose episodes were not decreased despite the standard treatment as nonresponders. MDR1 C and T allele frequencies of FMF patients with colchicine responses of complete, partial, and nonresponders were C=0.75 and T=0.25; C=0.56 and T=0.44; and C=0.50 and T=0.50, respectively. When complete responding patients were compared with the partial responding patients, subjects with CT genotype had 6.18 times more increased risk than with CC genotype (OR=6.18; p=0.015). Poor response risk of subjects with the T allele was increased 2.45 times more when compared with the C allele (p=0.03). MDR1 gene C3435T polymorphism enacts an important role on colchicine response in FMF; good response to colchicine treatment was related to the C allele, whereas poor response was related to the T allele in FMF.

Is There a Role for MDR1, EPHX1 and Protein Z Gene Variants in Modulation of Warfarin Dosage? A Study on a Cohort of the Egyptian Population

There is considerable inter-individual variability in warfarin dosages necessary to achieve target therapeutic anticoagulation. Polymorphisms in genes, which master warfarin pharmacokinetics and pharmacodynamics, might influence warfarin dose variation. Genes encoding drug transporters, such as human multidrug resistance (MDR1), as well as epoxide hydrolase 1 (EPHX1), which is a putative subunit of the vitamin K epoxide reductase, and Protein Z (PZ), which is a vitamin K-dependent plasma glycoprotein, are among those candidate genes. The purpose of this study was to investigate the contribution of MDR1 C3435T, EPHX1 H139R and PZ A-13G gene polymorphisms in warfarin dose variation in a cohort of the Egyptian population. Eighty-four patients whose international normalized ratio (INR) was in the range of 2-3, 41 males and 43 females, with a mean (±SD) age of 40.9 (13.3) years were recruited into this study. MDR1 C3435T, EPHX1 H139R and PZ A-13G gene polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism. Primarily, linear regression analysis, including the variables age, gender, MDR1 C3435T, EPHX1 H139R and combined MDR1 C3435T, EPHX1 H139R and PZ A-13G genotypes, was used to assess the effective factors for warfarin maintenance dose. Secondly, the previously examined cytochrome P450 (CYP) 2C9 A1075C and vitamin K epoxide reductase complex subunit 1 (VKORC1) C1173T were added to the regression analysis. Warfarin dose/week was not influenced by each of the MDR1 C3435T, EPHX1 H139R, and PZ A-13G gene polymorphisms when examined separately. However, when these single nucleotide polymorphisms (SNPs) were combined, MDR1 TT/EPHX1 RH,RR/PZ AA subjects showed statistically significant increase in warfarin dose/week when compared with MDR1 CC/EPHX1 RH,RR/PZ AA subjects [median (25th-75th percentiles): 49.0 (42.0-59.5) vs. 35.0 (24.5-42.0)mg/week, respectively] (p=0.014). In contrast, in the presence of wild-type EPHX1 HH, there was a decrease in warfarin dose/week in MDR1 TT subjects when compared with CT and CC subjects [median (25th-75th percentiles): 22.0 (17.5-30.6), 42.0 (35.0-49.0) and 42.0 (28.0-54.3)mg/week, respectively] (p=0.005 and 0.030, respectively). Age had a significant contribution (p=0.048) to the overall variability in warfarin dose. Calculated weekly dose=52.928-(0.289×age)+(9.709×combined genotype). The multivariate linear regression equation of warfarin maintenance dose accounted for about 8% of variation in dose (R (2)=0.079), age accounted for 5% of variation, while combined genotypes added the extra 3%. However, the new regression equation accounted for 20.9% of variation in dose. Age accounted for 5%, while VKORC1 C1173T accounted for an extra 13% of variation and MDR1 C3435T accounted for the remaining 3% of variation. Calculated dose=64.909-(0.282×age)-(13.390×VKORC1)-(7.164×MDR1). Correlation analysis showed a close and significant relationship between the calculated and actual warfarin dose (r=0.457; p<0.0005). Warfarin dose/week was significantly influenced by the combined MDR1 C3435T and EPHX1 H139R gene polymorphism since no polymorphism of PZ A-13G SNP was detected in our studied Egyptian population. Future studies with larger sample size will be needed to confirm our findings before definitive conclusions can be made.

Abstract P2-09-21: Effect of MDR1 Gene Polymorphisms and Haplotypes on Taxanes-Based Chemotherapy Responses in Chinese Han Patients with Breast Cancer

Abstract Background: In recent years, taxanes play an important role in chemotherapy of breast cancer patients, and its response rate is about 50%. Taxanes is primarily metabolized by CYP450 in liver microsome, and it also is a substrate for P-glycoprotein (the coded product of MDR1 gene). The interindividual heterogeneity in drug-metabolizing enzymes and transporters has contributed to the variability on anti-cancer efficacy of taxanes in breast cancer patients. Several studies showed that the pharmacokinetics of taxanes was influenced by the MDR1 polymorphisms. The aim of this study is to investigate the relationship between MDR1 gene polymorphisms and taxanes-based chemotherapy responses, and provides useful information for clinical personalized medicine and prognostic judgment. Material and Methods: Genotyping of MDR1 variants was determined in the blood samples from 142 Chinese Han patients with breast cancer, by PCR-RFLP. The association of the gene polymorphisms of MDR1 C1236T at exon 12, G2677T/A at exon 21 and C3435T at exon 26 with chemotherapy responses was analyzed on the 63 patients, who received taxanes-based neoadjuvant chemotherapy [56 cases with TA (taxanes and anthracycline), 7 cases with TAC (C: cyclophosphamide)] and had the intact treatment follow-up information. Results: In the 142 breast cancer patients, the frequencies of C1236T, G2677T, G2677A and C3435T variant alleles was 70.7%,52.1%,2.5% and 46.5%, respectively, and the frequency of 3435T allele was significantly higher in comparison with that in healthy subjects (34.7%). In the 63 patients with neoadjuvant chemotherapy, the overall clinical response rate (CR+PR) to chemotherapy was 66.7%. 3435TT genotype was showed to be related to taxanes-based chemotherapy, and its efficient rate was 23.1%, significantly lower than that of patients carrying C allele (73.5%; x2 = 9.125, P=0.003). The 3 SNPs were in linkage disequilibrium, and the 4 haplotypes TTT, TGC, CGC and TTC were 90.6 % of all. The patients who carrying 2677G-3435C haplotype showed better response to chemotherapy compared with those with the other haplotypes combined (72.1% vs 40.0%;x2=9.125, P=0.003). The response rate of the patients with 2677T-3435T haplotype or 1236T-3435T haplotype (54.3% or 54.9%) were lower than that of the patients harboring the other haplotypes (82.4% or 91.7%;x2=4.128 and x2=4.118, P =0.042 for both) respectively, and the efficient rate of the patients with 1236T-2677T-3435T (54.3%) were also lower than that of the patients with other haplotypes combined (82.4%;x2=4.128, P=0.042). Conclusion: C1236T, G2677T/A and C3435T of MDR1 gene were polymorphic with different frequency in breast cancer patients. The analyses of MDR1 C3435T genotype and its haplotypes with C1236T or G2677T/A are valuable for predicting the taxanes-based chemotherapy responses in breast cancer patients, which deserve the further study. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-21.

MDR1 C3435 Gene Polymorphism in Adult and Childhood Acute Lymphoblastic Leukemia of an Ethnic Iranian Population

Abstract Multidrug resistance protein 1 (MDR1, Pgp, ABCB1) is a membrane efflux transporter protein encoded by the MDR1 gene. The overexpression of this gene has been linked with the resistance to a variety of cancer chemotherapeutic agents in cancer patients. It also has an important role in tissue and cell defense against xenobiotics and toxic-compounds insult. A gene polymorphism in exon 26 of MDR1 (C3435T) has been reported to be associated with a decreased expression of MDR1 in TT genotype carriers compared with those of the CC genotype. In the present study, the MDR1 C3435T polymorphism of an ethnic Iranian population with acute lymphoblastic leukemia (ALL) was studied, and the incidence of the genotypes was compared among patients in different age groups: ≥ 20 years of age (A) and 1-19 years of age (B). The percent distribution of genotypes were found to be TT (A: 21.4; B: 26.0), TC (A: 57.1; B: 60.0), and CC (A: 21.4; B: 14.0). The B group ALL patients (1-19 years) were further divided into 2 groups of 1-9 (Y) and 9-19 (Z) years of age, and their MDR1 C3435T genotypes were analyzed. The distribution of the genotypes were found to be as follows: TT (Y: 27.9; Z: 23.1), TC (Y: 60.7.1; Z: 59.0), and CC (Y: 11.5; Z: 17.9). No significant differences were found among different genotypes in the studied age groups. It was concluded that in the studied population no specific genotype (either TT, TC, or CC) in MDR1 C3435T gene polymorphism was associated with the incidence of ALL. Further studies will shed light on the possible importance of these findings.

Effect of MDR1 gene promoter methylation in patients with ulcerative colitis

Altered MDR1 expression and/or function contribute to the pathogenesis of inflammatory bowel disease (IBD). DNA methylation was shown as an important mechanism in gene silencing. We investigated DNA methylation of the MDR1 gene in ulcerative colitis (UC) and its relation to MDR1 C3435T genotypes. Eighty-three UC patients were enrolled. Methylation of MDR1 promoter was determined by methylation specific polymerase (MSP) for rectal inflammatory mucosa from all patients and normal terminal ileum from 17 patients. Promoter methylation of MDR1 gene was also quantified by digital densitographic analysis following MSP. MDR1 methylation was detected in 51 (61.4%) out of 83 patients in rectal inflammatory mucosa. Mean methylation level of MDR1 gene in rectal inflammatory mucosa was significantly higher than in normal terminal ileum (p=0.021). MDR1 methylation occurred more frequently in total colitis, and total+left side colitis, compared to rectal colitis (p=0.001, 0.013, respectively). Higher methylation levels were also associated with chronic continuous type (p=0.034) and earlier onset of disease (p=0.038). The 3435 CC+CT genotype of MDR1 was associated with more than 6-fold increased risk of MDR1 methylation, especially in UC patients with 9 years and shorter duration. Both frequency and level of MDR1 methylation were higher in UC onset at younger or in middle age with the same genotype. MDR1 methylation frequently occurred in inflammatory rectal mucosa from UC patients and was influenced by MDR1 C3435T polymorphism, especially in patients with shorter duration and younger onset.

CYP2C19 Genotype Is a Major Factor Contributing to the Highly Variable Pharmacokinetics of Voriconazole

In vitro data on the metabolism of the antifungal voriconazole suggest that its pharmacokinetics might be influenced by the activity of CYP2C19, CYP2C9, and CYP3A. To elucidate the genetic influence of polymorphic enzymes on voriconazole metabolism, the authors pooled the pharmacokinetic data from 2 interaction studies in which 35 participants were enrolled according to their CYP2C19 genotype to receive a single 400-mg oral dose of voriconazole. Nine participants were homozygous for CYP2C19(*)1/(*)1, 8 heterozygous for (*)1/(*)17, 11 heterozygous for (*)1/(*)2, 2 heterozygous for (*)2/(*)17, 4 homozygous for (*)2/(*)2, and 1 with a double mutation CYP2C19(*)2/(*)2(*)17. Nine (heterozygous) individuals were carriers of the CYP2C9(*)2 or (*)3 variant alleles. Twenty-five participants did not express the CYP3A5 isozyme ((*)3/(*)3), whereas in 5 individuals, the (*)1/(*)3 combination was present (active enzyme). In addition, the CYP2D6 genotype and 2 variants of the drug transporter MDR1 (C3435T and G2677T) were determined. Multiple regression analysis of voriconazole apparent oral clearance revealed that 49% of its variance can be explained solely by the CYP2C19 polymorphism (P < .0001). Including the other polymorphisms into the regression model did not show any significant contribution. The number of variant CYP2C19 alleles therefore explains a substantial part of the wide variability of voriconazole pharmacokinetics, whereas the presence of functional CYP3A5 and the CYP2C9 genotype had no significant impact on voriconazole exposure. Some minor contribution results from the MDR1 C3435T genotype.

No effect of MDR1 C3435T polymorphism on oral pharmacokinetics of telmisartan in 19 healthy Chinese male subjects

Considerable interindividual differences in both drug response and pharmacokinetics of telmisartan have been identified. This study was designed to investigate the influence of MDR1 C3435T polymorphism on pharmacokinetics of telmisartan after a single oral dose in healthy Chinese volunteers. A total of 61 unrelated male volunteers were genotyped for MDR1 C3435T polymorphism by using the polymerase chain reaction-restriction fragment length polymorphism method. Six 3435CC homozygotes, eight 3435CT heterozygotes, and five 3435TT homozygotes were randomly selected and received a single oral dose of 40 mg telmisartan. Plasma concentrations of telmisartan were determined by the high performance liquid chromatography-mass spectrometry method up to 48 h after telmisartan administration. Interindividual variation for t(max), C(max), t(1/2), AUC(0-48), AUC(0-infinity), and clearance (CL) for telmisartan was approximately 6-, 33-, 16-, 17-, 20-, and 20-fold, respectively. C(max) (p=0.010), t(1/2) (p=0.029) and CL (p=0.010) of telmisartan were not normally distributed. MDR1 3435TT homozygotes seemed to show increases in C(max), t(max), t(1/2), AUC(0-48), and AUC(0-infinity). However, no significant differences in C(max), t(max), t(1/2), AUC(0-48), AUC(0-infinity), and CL among MDR1 C3435T genotypes were observed. MDR1 C3435T polymorphism does not affect oral pharmacokinetics of telmisartan.

A polymorphism C3435T of the MDR-1 gene associated with smoking or high body mass index increases the risk of sporadic breast cancer in women

The human multidrug resistance gene 1 (MDR-1) encodes a plasma membrane P-glycoprotein (P-gp) that functions as the transmembrane efflux pump for various structurally unrelated anticancer agents and toxins. Polymorphisms in the MDR-1 gene may have an impact on the expression and function of P-gp, thereby influencing the susceptibility to various diseases, including cancer. We investigated the incidence of C3435T polymorphisms at exon 26 in the MDR-1 gene in 92 women with breast cancer and potential association of altered genotypes with smoking and high body mass index in cancer development among patients. The MDR-1C3435T allelotype and genotype analysis revealed a high incidence (75.0%) of polymorph alteration in the MDR-1 gene. The frequencies of homozygous T/T, heterozygous C/T and homozygous C/C genotypes were 25.0, 50.0 and 25.0%, respectively. The risk of breast carcinoma in patients with MDR-1 polymorphism was significantly associated with the higher body mass index, where women with BMI >30 kg/m(2) and C allele in genotype had a higher risk of disease compared to patients with lower amounts of body fat tissue (p=0.0439). The risk was highest for the homozygous carriers of C allele with BMI >30 kg/m(2) compared to patients with BMI 25.1-30 or <or=25 kg/m(2) (OR 3.65, 95% CI 0.94-14.20; or OR 2.50, 95% CI 0.55-11.41), respectively. Consistent with the results of genotyping and BMI analyses, smoking patients harboring the C/T or C/C genotype had an increased risk of cancer (OR 1.28, 95% CI 0.23-7.17; OR 1.58, 95% CI 0.28-10.44, respectively) when exposed to carcinogens in tobacco smoke, although it was not statistically significant. Our findings suggest that the MDR-1C3435T polymorphism occurs in high incidence among women with breast carcinoma where C allele carriers have increased risk of developing cancer when exposed to toxic substances. Our observations are the first that indicate this polymorphism as a modulator of health to be associated with an increased risk of breast cancer.

Minimal effect of MDR1 and CYP3A5 genetic polymorphisms on the pharmacokinetics of indinavir in HIV‐infected patients

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. 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. 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. 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.

Genotype-dependent Down-regulation of Gene Expression and Function of MDR1 in Human Peripheral Blood Mononuclear Cells under Acute Inflammation

Recent advances in pharmacogenomics have suggested the association of clinical outcome of glucocorticoid-based anti-inflammatory therapy with a single nucleotide polymorphism at position 3435 in exon 26 (C3435T) of the MDR1 gene. In the present study, the effects of the MDR1 C3435T genotype on the time-dependent profiles of gene expression and function of MDR1/P-glycoprotein were evaluated in peripheral blood mononuclear cells (PBMCs) under lipopolysaccharide (LPS)-induced experimental acute inflammation. LPS treatment resulted in the rapid elevation of IL-1beta and TNF-alpha mRNA levels relative to beta-actin mRNA at 1 h, with a subsequent slight decrease at 3 h after the treatment, while the down-regulation of the relative concentration of MDR1 mRNA was found at 3 h, not at 1 h, after LPS treatment. Here, the C3435T genotype-dependent down-regulations of MDR1 mRNA level were found for CC(3435) and CT(3435), but not for TT(3435), and were 64.1+/-10.1%, 71.4+/-5.9% and 100.0+/-22.5% (+/-S.D.), respectively, of their respective baseline levels, which were independent of C3435T (0.010+/-0.005, 0.011+/-0.013 and 0.009+/-0.006 (+/-S.D.), respectively). The C3435T genotype-dependent down-regulation was supported by the increase of the intracellular accumulation of calcein in PBMCs treated with LPS for 72 h, and the increase was more predominant for CC(3435) than TT(3435). These data suggested that glucocorticoid-based anti-inflammatory therapy might be more effective for C(3435)-allele carriers than non-carriers.

Drug Metabolism and Disposition Genes in Israeli HIV Patients: MDR1 and CYP3A4 Polymorphisms May Affect Susceptibility to HIV but Not the Course of the Disease.

Background: Some studies have suggested a relationship between different alleles of the multidrug resistance gene MDR1, and the course of HIV in treated or untreated patients (pts). It is controvertial whether polymorphisms alter the susceptibility to HIV infectivity. We therefore studied the C3435T polymorphism in MDR1, which may influence HIV. The normal allele has been associated with higher MDR1 activity than the polymorphic allele (Hitzl, 2001). We also studied the A to G polymorphism in the NFSE element of the promoter of the CYP3A4 gene, which metabolizes many important drugs.Methods: 96 pts, of either Ethiopian (57) or Caucasian (39) ethnicity, and 276 controls of these ethnic groups were studied using PCR based techniques. MDR1 activity was analyzed on peripheral blood mononuclear cells of 65 pts using rhodamine extrusion. CD4 counts, clinical course and opportunistic infections were recorded at the Hadassah Hospital AIDS Center where all pts are followed. Our pts are highly compliant with medical therapy and followup. Statistical significance was determined using the Cochrane-Armitage Trends test.Results: We found that the C allele of MDR1 C3435T was highly associated with being an HIV patient (p<0.0001) as compared to controls. The reverse was true for the T allele. This association was found for all patients and also separately for each ethnic group. To analyze if this polymorphism affects the course of HIV, we compared CD4 counts in the patients of both ethnic groups according to genotypes. CD4 counts did not differ according to MDR1 C3435T genotype. Furthermore, C3435T genotypes did not affect the change in CD4 count over time in treated pts. CD4 counts rose following antiretroviral therapy in all pts. Twenty-eight of the pts were positive for HIV infection but were not yet treated. In untreated pts, the TT patients had more severe CD4 deficiency over time compared to CC pts. Our sample size is small, but this concurs with the findings of Lee who found that increased MDR1 activity correlated with decreased viral production (Lee, CG, FASEB J, 2000). Rhodamine extrusion did not vary according to MDR1 C3435T genotype. Opportunistic infections were rare and unaffected by genotype. For the CYP3A4 promoter polymorphism, we found a significantly increased probability of being infected with HIV (p<0.0001) with the presence of the C allele, both in heterozygotes and in homozygotes. There were significantly fewer T alleles among the controls as compared to HIV pts. However when analyzed by ethnic group, this association was only found to be significant for Ethiopians and not for Caucasians (Ethiopians: p< 0.0232 compared to p=0.44). There were no differences found in CD4 count, in treated or untreated patients, or in opportunistic infections according to CYP3A4 genotype.Conclusions: We conclude that for Israeli patients (Ethiopians and Caucasians), susceptibility to HIV infection may be altered according to MDR1 genotype. The C allele was highly associated with infection with HIV for both ethnic groups, as compared to normal controls. For Ethiopians, the CYP3A4 genotype may influence the predisposition to HIV infection (the C allele being associated with being a patient as compared to controls). However, the course of the disease and unsorted lymphocyte MDR1 activity were not influenced by the polymorphisms which we studied.

The impact of pharmacogenomic factors on acute persistent rejection in adult lung transplant patients

Persistent rejection in the face of treatment and multiple episodes of rejection are associated with the development of chronic rejection and graft loss in solid organ transplantation. The factors that create an environment for rejection that persists in the face of treatment are as yet not understood. The objective of this study was to evaluate the risk factors, including human multidrug resistance gene ( MDR1), cytochrome P4503A5 (CYP3A5) and cytokine gene polymorphisms, associated with acute persistent rejection (APR) in lung transplant patients. One hundred and twenty-five adult lung transplant patients were studied. MDR1 G2677T, C3435T and CYP3A5 polymorphisms were assessed by direct sequencing of the polymorphic region in patient DNA. Cytokine genotyping for five cytokines was performed using the polymerase chain reaction-sequence specific primers (PCR-SSP) technique. Multivariate regression analysis was used to identify the predictors of acute persistent rejection. The dependent variable was the presence or absence of acute persistent rejection based on lung biopsies during the first postoperative year. The independent variables were MDR1 G2677T and C3435T, CYP4503A5 and cytokine polymorphisms, survival status, age, gender, survival days and HLA mismatches. The MDR1 C3435T polymorphism and age were independently associated with acute persistent rejection ( p=0.025, odds ratio=0.29, 95% CI 0.1–0.86 and p=0.016, odds ratio=0.94, 95% CI 0.89–0.98, respectively). For the MDR1 C3435T polymorphism, 72% of patients with the C allele had acute persistent rejection in comparison to 52% for TT patients ( p=0.04). For age, a significant difference was found between the nonrejection group and the rejection group (mean±S.D. 52.1±11.2 vs. 44.4±12.3, p=0.01). This is the first report of the association of a drug disposition genotype with drug-resistant acute rejection in organ transplant patients. The major predictor of acute persistent rejection in the first postoperative year for lung transplant patients was the MDR1 C3435T genotype. This association could be due to drug resistance, altered drug disposition or other immunologic effects associated with P-glycoprotein (P-gp) function. Future prospective treatment algorithms should be developed that will incorporate the knowledge of gene polymorphisms into treatment regimens to improve the outcome following lung transplantation.

Polymorphisms in Drug Metabolism/Disposition Genes and Increased Susceptibility to Adult De Novo AML: MDR1 and CYP3A4.

Primary AML may be induced by environmental toxins in the same way as chemotherapy-induced genotoxic damage leads to therapy-related AML (t-AML). The genotypes of MDR1 and CYP3A4 genes may be important in predisposing to both primary and t-AML. Hoffmeyer et al (PNAS, 2000) found that a silent single nucleotide polymorphism, C3435T was associated with higher plasma concentrations of digoxin after oral dosing. The T allele increases effective exposure to toxins, and may predispose to renal tumors. We previously reported (ASH 2002) an association of t-AML with C3435T in a small sample (17 pts). The cytochrome P450 (CYP) enzymes including CYP3A4 metabolize drugs and toxins, and can activate procarcinogens. Some studies found that an A to G substitution in the CYP3A4 promoter (CYP3A4*1B) “protects” against t-AML, while the wild type allele was associated with t-AML (including our study, ASH 2002).Aims: To determine if either the MDR1 or CYP3A4 polymorphism affects predisposition to develop primary AML, and to determine ethnic differences in the frequency of the polymorphisms.Methods: The MDR1 C3435T polymorphism was analyzed using PCR and Sau3A1 digestion. CYP3A*1B was studied using PCR and hybridization to a wild type or mutant 19-mer oligonucleotide probe. We studied primary and t-AML patients (68 Jewish and 43 Arab for C3435T, and 81 Jewish and 37 Arab for CYP3A1*1B), and control DNA samples of the same ethnic origin (58 Caucasian Jewish and 44 Arab and 88 Ethiopian Jews).Results: The TT genotype at position 3435 of MDR1 was found more frequently in AML patients (both primary and t-AML) than in controls (p value: 0.0302). There was an additive effect of the T allele, with fewest AML patients having the CC genotype, more with CT and the most with the TT genotype (P value: 0.0015). The relative risk of primary AML is 0.5975 (C.I- (0.3135, 1.1389) for patients with the CC genotype versus those with CT/TT. The relative risk of t-leuk is 0.1180 (C.I- (0.0073 1.8952) for patients with the CC genotype versus those with CT/TT. Of 23 t-AML patients analyzed, none had the CC genotype. Because the allele may affect response to therapy, we analyzed survival. Using Kaplan-Meier analysis, we found no statistically significant difference in the survival of AML patients of different MDR1 C3435T genotypes. Among controls, there was a statistically significant difference in the frequency of the different genotypes among Arabs, Caucasian Jews and Ethiopian Jews. Arab individuals had a lower frequency of the CC genotype and more frequent TT, Ethiopian Jews had a high frequency of the CC genotype (p value: 0.0072). Among AML patients of different ethnicity, there was no difference in genotype. The CYP3A*1B polymorphism was found in approximately 15% of the Israeli population (Caucasian Jews and Arabs alike). In comparison, 52% of Ethiopian Jews carried CYP3A*1B. 9/118 primary AML patients (7%) carried CYP3A*1B and only 1 (2.4%) of 41 t-AML patients was found to carry CYP3A4*1B (p value < 0.05).Conclusions: The MDR1 C3435T polymorphism is associated with a higher risk of developing primary as well as t-AML. Arabs may be at higher risk for AML due to a high frequency of the T allele. In addition, the CYP3A4*1B polymorphism might be protective against primary AML, and we confirm previous reports that it may protect against t-AML in adults. Lastly, Ethiopian Jews have a high frequency of the C allele of the MDR1 C3435T polymorphism, and high frequency of CYP3A4*1B, which may underlie the relatively low incidence of AML in this ethnic group in Israel.

Pharmacogenetics in solid organ transplantation: present knowledge and future perspectives.

The promise of pharmacogenetics is to elucidate the inherited basis of differences between individual responses to drugs, in order to identify the right drug and dose for each patient. Genetic polymorphisms are implicated in the interindividual variability of the pharmacokinetic or pharmacodynamic characteristics of immunosuppressive drugs. The first pharmacogenetic trait identified was monogenic, and concerned the prototypic example of thiopurine methyltransferase (TPMT) implicated in azathioprine metabolism. Individuals with low TPMT activity, inherited in an autosomal codominant fashion, are at risk of drug-induced myelosuppression. TPMT activity determination and DNA-based tests are now used in clinical practice. It has been also demonstrated that there is a link between the polymorphisms of the cytochrome P450 3A5, 3A4 and the multidrug resistance-1 (MDR1) genes, and the daily dose necessary to achieve adequate blood tacrolimus levels. Analysis of MDR1 haplotypes or using the association of the different genes might further improve predictions. Since genotyping methods improve rapidly, it will soon be easy to test for thousands of single nucleotide polymorphisms in one assay. Present challenges are to determine the genes of interest and to validate such determination prospectively in clinical practice.