Analyses of single nucleotide polymorphisms and haplotype linkage of the humanABCB1 (MDR1) gene in Korean

Single nucleotide polymorphisms (SNPs) in theMDR1 gene that are responsible for drug efflux can cause toxicity. Therefore, this study determined the SNPs of the KoreanMDR1 gene, and analyzed the haplotypes and a linkage disequilibrium (LD) of the SNPs determined. The frequency of 9 SNPs from theMDR1 gene was determined by PCR-RFLP analyses of 100 to 500 healthy individuals. The frequcies of the SNPs were C3435T (47.7%), G2677T (37.6%), G2677A (4.4%), T1236C (21.7%), T129C (8%), A2956G (2.5%), T307C (1.5%), A41aG (9.2%), C145G (0%), and G4030C (0%). Analyses of the haplotype structure and an estimation of the LD of the combined polymorphisms demonstrated that the frequency of the 1236T-2677G-3435T haplotype is much higher in Koreans (14.1%) than in Chinese and western black Africans and the C3435T SNP in Koreans appears to have LD with T129C in Koreans for the first time. These results provide insight into the genetic variation ofMDR1 in Koreans, and demonstrated the possibility of a new LD in this gene.     

江苏地区汉族儿童多药耐药基因3个单核苷酸多态性位点的单倍型研究

目的分析江苏汉族人群多药耐药基因-1（MDR1）的单核甘酸多态（12外显子1236C→T突变、21外显子2677G→T/A突变、26外显子3435C→T突变）及其构成的单倍型分布。方法通过多重单碱基延伸反应（SNaPshotSNP分型技术）对江苏地区170名健康儿童的MDR1C1236T、G2677T/A、C3435T的SNP位点进行基因分型,统计各基因型频率。UNPHASED软件对MDR1的SNPs（C1236T-G2677T/A-C3435T）进行单倍型分析。结果在170例儿童中,等位基因1236T、2677T、2677A、3435T频率分别为63.5%、37.4%、17.0%和35.0%。基因型频率分布符合Hardy-Weinberg平衡（HWE）,差异无统计学意义（P〉0.05）。MDR1的1236、2677、3435三个位点间（C1236T-G2677T/A-C3435T）存在连锁不平衡性,以TTT（31.8%）、TGC（25.3%）、CGC（17.7%）和CAC（16.2%）四种单倍型为主。结论江苏地区汉族人群MDR1的单核甘酸多态及单倍型分布具有自己的特点。在临床应用相关药物时,进行基因型及单倍型检测,将有助于指导临床个体化用药。     

Effects of polymorphisms of MDR1, MRP1, and MRP2 genes on their mRNA expression levels in duodenal enterocytes of healthy Japanese subjects

In the present study, we examined whether polymorphisms in the ATP-binding cassette (ABC) transporter genes, MDR1, MRP1 and MRP2, were associated with their respective mRNA expression levels in duodenal enterocytes of 13 healthy Japanese volunteers. MDR1 genotypes of T-129C, G2677(A,T) and C3435T, MRP1 genotypes of G128C, C218T, G2168A and G3173A, and MRP2 genotypes of C-24T, G1249A, C2302T, C2366T and G4348A were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or direct sequencing. Mutations T-129C, G2677(A,T) and C3435T of MDRI gene were found at allele frequencies of 2/26, 16/26 and 12/26, respectively. Mutations G2168A of the MRPI gene and C-24T of the MRP2 gene were also found at allele frequencies of 1/26 and 6/26, respectively, whereas other mutations were not detected in MRP1 and MRP2 genes. The relative concentrations (mean +/- S.E.) of MDR1 mRNA to villin mRNA were 0.38 +/- 0.15, 0.56 +/- 0.14 and 1.13 +/- 0.42 in the subjects with C/C3435, C/T(3435) and T/T(3435), respectively, which supported the lower serum concentrations of digoxin after single oral administration in the subjects with the mutant T-allele at position 3435. Genetic collaboration between positions 3435 and 2677 was suggested, and those in G/G2677, G/(A,T)(2677) and T/(A,T)(2677) were 0.16 +/- 0.05, 1.10 +/- 0.40, and 0.63 +/- 0.16, respectively (p = 0.107). However, there was no remarkable effect of the G2168A of the MRP1 gene or of C-24T of the MRP2 gene on the relative MRP1 or MRP2 mRNA concentrations, respectively.     

MDR1 C3435T polymorphism is predictive of later onset of ulcerative colitis in Japanese

Recently, a silent polymorphism of C3435T of the MDR1 gene, encoding the multidrug resistant transporter MDR1/P-glycoprotein, has been found to be associated with susceptibility to ulcerative colitis (UC), but this remains controversial. This study was conducted to find a possible reason for the discrepancies, and it was suggested that the age of onset was important for the association, namely, C3435T was predictive of susceptibility to later onset UC, but not for early onset UC. Linkage disequilibrium of C3435T with T-129C, C1236T and G2677A, T was suggested to be altered in UC, but the analysis of their haplotype provided no advantage in terms of prediction over that with only C3435T. The effect of C3435T on susceptibility could not be explained by that on mRNA expression in rectal mucosa, but it was greater in the C(3435)-noncarriers in the early onset group, allowing the individualization of steroid-based pharmacotherapy.     

Pharmacokinetics of paclitaxel in ovarian cancer patients and genetic polymorphisms of CYP2C8, CYP3A4, and MDR1

Interindividual differences in the pharmacokinetics of paclitaxel and its metabolites in Japanese ovarian cancer patients were investigated in relation to genetic polymorphisms of the CYP2C8, CYP3A4, and MDR1 genes. The area under the concentration-time curve (AUC) ratios of paclitaxel/6alpha-hydroxypaclitaxel and paclitaxel/3 -p-hydroxypaclitaxel calculated as the metabolic index of CYP2C8 and CYP3A4 showed 13- and 12-fold interindividual variations, respectively. No patient had any CYP2C8 variants, while 2 patients were heterozygotes of CYP3A4*16. For the MDR1 gene, the frequencies of -129C, 1236C, 2677T, 2677A, and 3435T alleles were 2.2%, 8.7%, 56.5%, 4.4%, and 52.2%, respectively. Subjects possessing the 3435T allele had a significantly (P < .05) higher AUC of 3'- p-hydroxypaclitaxel compared to those possessing the 3435C allele. Leukocytopenia was significantly (P < .05) related to the AUC of paclitaxel. Genotyping of the CYP2C8, CYP3A4, and MDR1 genes might not be essential to predict adverse effects of paclitaxel in Japanese patients, although an allelic variant of MDR1 may functionally affect the pharmacokinetics of its metabolite.     

C1236T、 G2677T/A 和C3435T 基因多态性与乳腺癌分子分型的关系及意义

摘要： 目的 观察多药耐药基因 1 （MDR1） 第 12、 21 及 26 外显子 C1236T、 G2677T/A 和 C3435T 基因多态性在乳腺癌患者外周血中的分布, 分析其与分子分型的关系。方法 应用高分辨熔解曲线 （HRM） 技术检测 400 例乳腺癌患者 C1236T、 G2677T/A 及 C3435T 基因多态性。采用 Hardy-Weinberg 遗传平衡检验进行基因型分布遗传平衡吻合度检验。参照 2013 年 St.Gallen 国际专家乳腺癌分子分型共识。分析乳腺癌患者中 C1236T、 G2677T/A 和 C3435T 基因型分布特点, 并探讨其与分子分型的关系。结果 （1）400 例乳腺癌患者中 C1236T、 G2677T/A 和 C3435T 中分别有 2 例、 3 例和 2 例标本未得出基因分型结果, C1236T 位点 CC、 CT 和 TT 基因型分别占 16.08% （64/398）、 44.22% （176/398） 和 39.70% （158/398）; G2677T/A 位点 GG、 GT、 GA、 TT 和 AT 基因型分别占 16.62% （66/397）、 44.33% （176/ 397）、 7.05% （28/397）、 27.46% （109/397） 和 4.54% （18/397）; C3435T 位点 CC、 CT 和 TT 基因型分别占 21.11% （84/ 398）、 56.03% （223/398） 和 22.86% （91/398）。经 Hardy-Weinberg 遗传平衡检验, 认为 C1236T、 G2677T/A 和 C3435T 基因多态性具有群体代表性 （P > 0.05）。（2） 分子分型显示, 11例人类表皮生长因子受体2 （HER-2, 2+） 患者未行荧光原位杂交 （FISH） 检测予以剔除, 其中Luminal A型占41.90% （163/389）, Luminal B型占32.65% （127/389）, HER-2过表达型占13.62% （53/389）, 三阴型占11.83% （46/389）。（3） C3435T位点CT/TT基因型在Luminal A型患者中的频率高于其在HER-2过表达型和三阴型患者中的频率 （χ2 =12.011, P=0.001; χ2 =13.976, P < 0.001）, C1236T和G2677T/A基因多态性在不同分子分型中的分布差异无统计学意义 （P > 0.05）。结论 MDR1基因C3435T位点多态性可以为乳腺癌异质性提供更合理的补充, 不同乳腺癌分子分型患者中CT/TT基因表型可能对药物治疗更敏感。     

MDR1基因多态性和单倍体对肾移植术后稳定期患者他克莫司浓度/剂量比值的影响

目的 探讨MDR1 C1236T、G2677T/A和C3435T 基因多态性和单倍体对中国汉族肾移植术后稳定期患者他克莫司浓度/剂量比值的影响,为他克莫司个体化用药提供依据。方法 采用PCR-基因测序法检测104例肾移植术后稳定期患者MDR1 C1236T、G2677T/A和C3435T 的基因多态性,采用均相酶免疫测定方法(EMIT法)测定他克莫司的谷浓度,比较不同基因型患者之间他克莫司血药浓度/(剂量×体质量)(C/D)比值。结果 104例患者中,MDR1 C1236T、G2677T/A和C3435T突变频率分别为56.73%、55.77%和33.17%。MDR1 C3435T、MDR1 TTT单倍体与他克莫司C/D比值具有相关性(P<0.05)。CYP3A5*3*3患者中,MDR1 TTT单倍体与他克莫司C/D比值仍存在显著相关(P<0.05)。MDR1 C1236T、G2677T/A、CGC单倍体与他克莫司C/D比值无显著性差异(P>0.05)。结论 MDR1 C3435T、MDR1 TTT单倍体与中国汉族肾移植术后稳定期患者他克莫司C/D比值具有显著相关性,是影响肾移植患者他克莫司浓度个体化差异的重要因素。     

Genetic variability and haplotype profile of MDR1 (ABCB1) in Roma and Hungarian population samples with a review of the literature

The genetic variability, haplotype profile and ethnic differences of MDR1 polymorphisms in healthy Roma and Hungarian populations were analyzed and the results were compared with those of other populations available from the literature. Healthy subjects (465 Roma and 503 Hungarian) were genotyped for C1236T, G2677T/A and C3435T variants of MDR1 by PCR-RFLP assay. Differences were found between the Roma and Hungarian populations in the frequencies of MDR1 1236 CC (20.7 vs. 33.2%) and TT genotypes (30.8 vs. 21.9%), in T allele frequency (0.551 vs. 0.443) (p < 0.002), and in 3435T allele frequency (0.482 vs. 0.527, p < 0.04). Furthermore, the frequency of CGC, CGT and CTT haplotypes was significantly higher in the Hungarian population than in Roma (41.4 vs. 35.3%, 9.04 vs. 6.02% and 2.88 vs. 1.08%, respectively; p < 0.009), whereas the frequency of TGC and TTC haplotypes was higher in the Roma population than in the Hungarian (7.31 vs. 1.68% and 6.67 vs. 2.08%, respectively; p < 0.001). The prevalence of MDR1 polymorphisms in the Hungarian population is similar to that of other European populations; however, some differences were observed in the haplotype structures. In contrast, the Roma population differs from Hungarians, from Caucasians and from populations from India in the incidence of MDR1 common variants and haplotypes.     

Association analysis of three ABCB1 (MDR1) gene variants (C1236T,G2677A/T and C3435T) and their genotype/haplotype combinations with the familial Mediterranean fever

Abstract

1. Familial Mediterranean fever (FMF) is considered an autosomal recessive disorder, associated with a single gene named Mediterranean fever (MEFV). The aim of this study was to perform genotyping and haplotyping analysis of the multidrug resistance (ATP-binding cassette, subfamily B, member 1 – ABCB1) gene in FMF patients.

2. Three ABCB1 gene polymorphisms (C1236T, G2677T/A and C3435T) were analyzed in 309 FMF patients and 250 healthy control subjects. All subjects were genotyped by PCR–restriction fragment length polymorphism analysis, and statistical analysis was performed using the Arlequin 3.1.1 and SPSS 16.0 software packages.

3. The CT genotype frequency of the C3435T polymorphism (p?=?0.003), the CT–GT–CT (C1236T–G2677T/A–C3435T) triple genotype (p?=?0.001) and the C–G (C1236T–G2677T/A) haplotype (p?=?0.030) were more common in the FMF patients. The CT–GG–CC triple genotype and T–G–C, C–T–T and T–G–T haplotypes (C1236T–G2677T/A–C3435T) were higher in the control subjects (p?=?0.011, 0.001, 0.009 and 0.000, respectively). The CT–GG binary genotype and C–T and T–G haplotypes for C1236T–G2677T/A polymorphisms may have a high degree of protective effect against FMF (p?=?0.0005, 0.002 and 0.000, respectively).

4. Our study showed that genotypes and haplotypes of ABCB1 gene polymorphisms may affect patients’ FMF susceptibility.     

MDR1 gene polymorphism in Japanese patients with schizophrenia and mood disorders including depression

P-Glycoprotein (ABCB1-type P-gp), a membrane protein encoded by the multi drug resistant gene (MDR1), expressing on the blood brain barrier protects the brain from many drugs including dexamethasone. Psychiatric disorders, schizophrenia and depression, have known to have abnormal hypothalamus-pituitary-adrenal (HPA) activity, which is assessed by non-suppression of cortisol in dexamethasone suppression test. The poor response to dexamethasone in these patients' population suggested the impaired activity on dexamethasone penetration into the brain via P-gp, which was associated with MDR1 polymorphisms. We, therefore, examined five SNPs of the MDR1 gene, -1517 T>C (promoter), -41 A>G (intron -1), -129 T>C (exon 1b), 2677 G>A,T (exon 21) and 3435 C>T (exon 26), in Japanese patients with schizophrenia (n=121) and mood disorders (n=62), and compared with the control subjects (n=160). The frequency of MDR1 mutant alleles at -1517, -41 and -129 in patients with mood disorders was significantly lower (2.4, 5.6, 2.4%, respectively) than those of controls (7.8, 13.7, 7.8%, respectively) (p<0.05). The frequencies of MDR1 2677 G/A and A/A genotype in mood disorders was significantly higher (17.7, 6.5%, respectively) than controls (11.2, 0%, respectively) (p<0.05). The 2677A allele frequency in mood disorders (20.2%) was significant higher than controls (10.9%) (p<0.05). Haplotype of 129-2677-3435 (T-A-C) in mood disorders was significantly higher (14.4%) than controls (8.0%) (p<0.05). There was no significant difference in allele and genotype frequencies between the patients with schizophrenia and controls. These findings suggested that predispose to mood disorders, not schizophrenia, was associated with possible alteration of P-gp activities corresponding MDR1 polymorphism at least partly.     

Simultaneous determination of single nucleotide polymorphisms of MDR1 genes by electrochemical DNA chip

The on-chip genotyping system ("the electrochemical DNA chip") has been developed as a more cost-effective genotyping system and was applied to MDR1 genotyping in the present study, which is required for wide use in clinical application and for personalized medication based on genotype. The electrochemical DNA chip was optimized and applied to simultaneous genotyping of four MDR1 polymorphisms (T-129C, C1236T, G2677(A,T) and C3435T) using synthetic model oligonucleotide DNA and human genomic DNA. The electrochemical DNA chip successfully gave the T-129C, C1236T, G2677(A,T) and C3435T genotypes, which were completely consistent with those determined by direct sequencing. In conclusion, the electrochemical DNA chip is useful for simultaneous determination of some genotypes and haplotypes, and efficient genotyping using this system can support future genotype-phenotype studies at a large scale.     

服用他克莫司的肾移植患者ABCB1基因多态性与术后感染的相关性

目的:观察服用他克莫司(Tacrolimus)的肾移植受者ABCB1基因多态性对于术后感染发生的影响。方法:选取行肾移植手术并服用他克莫司的患者90例,根据术后是否存在感染分为感染组和对照组,检测所有患者的ABCB1基因型3435C>T,1236C>T和2677G>A/T。采用χ²检验,方差分析和独立样本T检验的方法对患者的基本临床资料进行检验。采用卡方检验比较感染组和未感染组的基因多态性频率分布差异。结果:患者C1236T,C3435T,G2677A/T等位基因频率,均符合Hardy-Weinberg平衡。感染组和非感染组患者的年龄,性别,体质量,临床诊断,吗替麦考酚酯(Mycophenolate Mofetil)的用量均没有显著性差异。2组患者的平均血药谷浓度在一年内均无统计学差异。C1236T单核苷酸多态性对肾移植术后感染发生的影响具有统计学意义(P=0.034)。G2677A/T突变的发生对肾移植术后感染发生的影响具有统计学意义(P=0.010)。结论:ABCB1基因多态性中,仅C1236T的SNP多态性与G2677A/T的突变对肾移植术后感染发生的影响具有统计学意义。     

MDR1 genetic polymorphisms and comparison of MDR1 haplotype profiles in Korean and Vietnamese populations

Two representative genetic variants of the MDR1 gene, 3435C>T and 2677G>T/A, show wide interethnic differences in its genetic polymorphism. In this study, the authors evaluated the genetic polymorphisms of MDR1 and directly compared MDR1 haplotype profiles of the Korean and Vietnamese populations. The 3435C>T and 2677G>T/A variations were analyzed in 632 Koreans and 142 Vietnamese using pyrosequencing. The allelic frequencies of 3435C>T did not significantly differ between the Korean (39.3%) and Vietnamese (36.6%) groups. However, the frequencies of mutant alleles at 2677 locus (T or A allele) showed a significant difference between Koreans (56.2%) and Vietnamese (41.9%), as the frequency of 2677A allele in the Korean subjects (17.1%) was much higher than that of the Vietnamese subjects (6.3%). Linkage analysis revealed that 2677A allele is closely linked to 3435C allele. The frequency of 2677A-3435C haplotype in Koreans was 15.4%, which was significantly higher than that found in Vietnamese subjects (6.3%). In conclusion, the frequencies of MDR1 variants and haplotype profiles showed significant differences between the Korean and Vietnamese populations, especially with respect to the 2677G>T/A variants. Because the 2677A allele was recently found to be functional in vivo and was detected at a high frequency in Koreans, the genotyping of this variant is necessary for pharmacogenetic studies of MDR1 in this population. In addition, by virtue of strong linkage disequilibrium, 2677A-3435C haplotype may help improve the predictability of MDR1 genetic polymorphism for MDR1 functional changes.     

肝移植中他克莫司的血药浓度与多药耐药基因多态性的关系

目的探讨肝移植术后患者的多药耐药基因（MDR1）C3435T、G2677T／A和C1236T位点的基因多态性对他克莫司（F1〈506）血药浓度的影响。方法使用荧光偏振免疫分析法（AxSYM）测定42例肝移植患者在术后1周和1个月时FK506的血药浓度,使用等位基因特异扩增法（ASA-PCR）对患者进行MDR1基因分型,比较不同基因型之间FK506的浓度／剂量比的差异。结果在42例患者中,C3435T中CC型16例（38．1％）,CT型23例（54．8％）,TT型3例（7．1％）;G2677T／A中CA;型4例（9．5％）,GT型13例（31．O％）,TT型8例（19．0％）,GA型7例（16．7％）,AT型10例（23．8％）;C1236T中CC型6例（14．3％）,CT型19例（45．2％）,TT型17例（40．5％）。根据移植术后第1周和第1个月的记录,在C1236T中CC型患者的浓度／剂量比小于CT型和TT型,且差异有统计学意义（P〈0．05）。在C3435T和G2677T／A中不同基因型之间的浓度／剂量比的差异无统计学意义（P〉0．05）。结论在肝移植患者中MDR1多态性与FK506血药浓度具有相关性,C1236TCC型患者拟取得相似的血药浓度要比CT型和TT型患者服用更高剂量的FK506。     

MDR1 haplotypes significantly minimize intracellular uptake and transcellular P-gp substrate transport in recombinant LLC-PK1 cells

To date, research on the effect of single nucleotide polymorphisms (SNPs) on P-glycoprotein (P-gp) expression and functionality has rendered inconsistent results. This study systematically evaluates the impact of MDR1 haplotypes (1236/2677, 1236/3435, 2677/3435, 1236/2677/3435) on P-gp functionality compared to individual SNPs (1236, 2677, and 3435) in validated stable recombinant epithelial cells. Recombinant LLC-PK1 cells expressing MDR1wt or its variants were developed and validated for this purpose. Intracellular accumulation and time-dependant efflux of a P-gp substrate, Rhodamine 123 (R123, 5 microM) were evaluated in control and recombinant cells. Additionally, the transepithelial transport of R123 (1 microM) and Vinca alkaloids (5 microM) was evaluated. Except for MDR1(2677T) and MDR1(1236T/2677T/3435T), cells expressing MDR1 variants displayed intermediate R123 intracellular accumulation (1.5-2-fold higher) and lower effluxed R123 (10-20% vs. 52%) compared to those expressing MDR1wt. Efflux ratios across MDR1wt expressing cells were significantly larger for R123 (3.95+/-1.1), Vinblastine (3.75+/-0.26), and Vincristine (2.8+/-0.29). Recombinant cells expressing MDR1 variants displayed 0%-22.7% P-gp activity (approximately 80%-100% efflux loss). Results suggest that MDR1 polymorphisms at the 1236, 2677, and/or 3435 positions significantly minimize P-gp functionality in vitro, the extent of which appears to be substrate dependant.     

Complex haplotypic effects of the ABCB1 gene on epilepsy treatment response

OBJECTIVES: The aim of this study was to investigate the association of the complex haplotype system of the adenosine triphosphate-binding cassette B1 (ABCB1) gene with the epilepsy treatment response. METHODS AND RESULTS: Ten polymorphisms were genotyped in 108 drug-resistant epileptic patients, 223 seizure-free patients and 287 normal controls. Highly significant linkage disequilibrium was shown among exon 12 C1236T, exon 21 G2677T and exon 26 C3435T. Haplotypic analysis demonstrated that patients with the CGC, TGC, and TTT haplotypes were more likely to be drug resistant. Further analysis of haplotype combinations demonstrated that drug-resistant patients tended to have the CGC/CGC, CGC/TGC, CGC/TTT, and TGC/TTT haplotype combinations over the seizure-free patients and controls (all p-values < 0.0001). In contrast, patients with the TTC/TTC, TTC/CGT, TTC/TGT, CGT/CGT and TGT/CGT haplotype combinations were more likely to be seizure-free (all p-values<0.0001 except CGT/CGT [p=0.0063]). CONCLUSION: Our results showed that the three loci, C1236T, G2677T and C3435T, jointly influenced the treatment response for epileptic patients. They should be regarded together as a complex polymorphic drug-response system. These findings suggest that examination of the haplotypes of the three loci could be useful in predicting drug resistance in epilepsy.     

Frequency of common MDR1 gene variants in a Polish population

P-glycoprotein (P-gp) is a transmembrane transporter playing an important role in drug efflux. There is growing evidence that P-gp activity may be related to haplotypes of MDR1 gene. In the current study, the frequencies of common functional polymorphisms in MDR1 gene (2677G > A,T and 3435C > T) were evaluated using PCR-RFLP and allele-specific amplification, in a group of 204 healthy individuals of Caucasian origin from Poland. It was found that the frequencies of the studied single nucleotide polymorphisms were similar to those reported for other Caucasian populations, and were as follows: 2677G-3435C--0.453, 2677G-3435T--0.143, 2677T-3435C--0.015, 2677T-3435T--0.370, 2677A-3435C--0.008, 2677A-3435T--0.011. The results of our study may give the basis for predicting pharmacokinetic and pharmacodynamic effects of many commonly used drugs in the Polish population.     

ABCB1基因多态性对卡马西平血药浓度的影响

目的:探讨ABCB1基因多态性对卡马西平血药浓度的影响。方法:采用荧光偏振免疫法(FPIA)测定275例口服卡马西平癫痫患者的血药浓度,聚合酶链式反应-限制性片段长度多态性方法(PCR-RFLP)或直接测序法检测ABCB1多态性位点C1236T、G2677T/A和C3435T的基因型。单因素方差分析计算各SNP位点不同基因型对应的卡马西平血药浓度是否有差异。结果:G2677T/A不同基因型对应的调整后血药浓度均值之间差别有显著性,TT基因型对应的调整后血药浓度显著高于GG型(P=0.001)。C1236T、C3435T各基因型对应的调整后血药浓度均值差别无统计学意义(P>0.05)。结论:ABCB1基因SNP位点G2677T/A的基因多态性对口服卡马西平癫痫患者的血药浓度有影响,提示TT基因型的患者可适当减少药物使用剂量。     

MDR1 haplotypes derived from exons 21 and 26 do not affect the steady-state pharmacokinetics of tacrolimus in renal transplant patients

AIM: This retrospective study investigated the influence of MDR1 haplotypes derived from the polymorphisms 2677G > T (exon 21) and 3435C > T (exon 26) on the pharmacokinetics of the immunosuppressant drug tacrolimus in 73 renal transplant patients. METHODS: Based on both variants of SNPs 2677 and 3435, four different haplotypes and eight different genotypes were identified in the study sample. Tacrolimus trough concentrations (C(0)) were compared between different SNP variants and genotypes, as well as between carriers and noncarriers of each haplotype. Additionally, CYP3A5 genotype (6956G > A) was determined. RESULTS: No significant differences were observed between groups. Differences in mean tacrolimus C(0) values between carriers and noncarriers of each haplotype ranged from -0.04 microg/litre (95% confidence interval: -0.53 to 0.60) to -23 microg/litre (-1.07 to 1.53). No association was found between CYP3A5*1/*3 genotype and tacrolimus Co concentractions. CONCLUSION: MDR1 haplotypes derived from the SNPs 2677G > T (exon 21) and 3435C > T (exon 26) do not influence the pharmacokinetics of tacrolimus in renal transplant patients.     

Functional evaluation of polymorphisms in the human ABCB1 gene and the impact on clinical responses of antiepileptic drugs

OBJECTIVE: The ABCB1 haplotype combinations have been demonstrated to be associated with epilepsy treatment outcomes. The aim of this study is to investigate whether ABCB1 haplotype combinations would affect P-glycoprotein (Pgp) function and impact the clinical responses of antiepileptic drugs (AEDs). METHODS AND RESULTS: Transport of substrate rhodamine 123 and calcein-AM by human Pgp carrying 12 haplotype combinations of 1236C>T, 2677G>T/A and 3435C>T were assayed in the absence and presence of known inhibitors and AEDs. The inhibitory potency of the tested drugs from the dose-response relationships was cyclosporin A>verapamil> phenytoin> carbamazepine> lamotrigine>phenobarbital>valproic acid, levetiracetam, gabapentin. The silent polymorphisms combination (1236T-3435T) and triple haplotypes (1236T-2677A/T-3435T) resulted in profoundly less effective inhibition against substrates with significantly lower intracellular substrate concentration. These results confirmed that ABCB1 polymorphisms were associated with clinical responses of AEDs. CONCLUSION: Our findings demonstrated that human ABCB1 polymorphisms may alter the interactions between Pgp and substrates, and provided functional evidence for ABCB1 haplotypes-associated epilepsy treatment responses.