Pharmacogenetics最新文献

Methylenetetrahydrofolate reductase (MTHFR) controls intracellular CH2FH4 concentrations (required for optimal fluoropyrimidine efficacy) by irreversibly converting CH2FH4 into 5-methyltetrahydrofolate. MTHFR 677C>T and 1298A>C polymorphisms are linked to altered enzyme activity. Thus, mutated MTHFR tumours should, in theory, be more sensitive to 5-fluorouracil (5FU) than wild-type tumours. MTHFR polymorphisms in position 677 and 1298 were analysed in 98 colorectal cancer patients with unresectable liver metastases (57 men, 41 women, mean age 64 years) receiving 5FU-folinic acid. 677C>T and 1298A>C genotypes were determined simultaneously by melting curve analyses on liver metastases. 677C>T genotype distribution was 46.9% wt/wt, 34.7% wt/mut and 18.4% mut/mut; that of 1298A>C was 52.0% wt/wt, 35.7% wt/mut and 12.3% mut/mut. The response rate was not related to 1298A>C genotype but was significantly linked to 677C>T genotype (response rate: 40%, 21% and 56% in wt/wt, wt/mut and mut/mut, respectively; P = 0.040), with an increased response rate in mut/mut tumours relative to wt/wt (odds ratio = 1.88). Thymidylate synthase activity measured in metastases was a significant predictor of 5FU responsiveness and the addition of the 677C>T genotype improved model prediction. MTHFR 1298A>C polymorphism was significantly linked to specific survival, with homozygous mutated patients having the worst prognosis (P = 0.009, relative risk = 2.48 in mut/mut versus wt/wt). MTHFR 1298A>C genotype remained a significant predictor in a multivariate analysis including metastasis characteristics. The results suggest that MTHFR genotypes are relevant and independent factors of patient outcome in 5FU-based treatment of advanced colorectal cancer.

Objectives: To assess whether CYP2C9 alleles other than CYP2C9*2 and *3 are associated with a low-warfarin dose requirement and the relevance of upstream CYP2C9 polymorphisms to dose requirement and metabolism.

Methods: CYP2C9 exons, intron-exon boundaries and 3 kb of upstream sequence in 20 patients requiring

Results: Polymorphisms at eight different upstream sites were found, five of which were already described. We found that the majority of the upstream polymorphisms were in complete linkage disequilibrium with previously described coding region polymorphisms. However, two polymorphisms, T-1188C and the novel DeltaG-2664DeltaT-2665, occurred both in individuals who were otherwise wild-type and in individuals positive for coding region polymorphisms. Evidence for 11 haplotypes, including 8 with frequencies >or= 0.01, was obtained. In individuals negative for coding region polymorphisms, neither individual genotypes for T-1188C or DeltaG-2664DeltaT-2665 or particular combinations of haplotype pairs were predictive of dose requirement or S-warfarin total clearance, suggesting neither upstream polymorphism was functionally significant. Dose requirements in CYP2C9*11 heterozygotes were not statistically significantly different from homozygous wild-type individuals.

Conclusions: The coding region non-synonymous polymorphisms associated with the CYP2C9*2 and CYP2C9*3 alleles are the major CYP2C9-related factor affecting warfarin dose in UK Caucasians. Upstream CYP2C9 polymorphisms do not appear to be important independent determinants of dose requirement.

Objective: The association between polymorphisms in candidate genes related to lipoprotein metabolism and the reduction in plasma triglyceride (TG) in response to fenofibrate treatment was evaluated in subjects with type 2 diabetes treated with micronized fenofibrate (200 mg/day) for at least 3 years in the Diabetes Atherosclerosis Intervention Study.

Methods: The cholesteryl ester transfer protein Taq1B, LPL S447X, hepatic lipase -514 C-->T, peroxisome-proliferator-activated receptors alpha (PPARA) L162V and G/C intron 7 polymorphisms and the apolipoprotein E2/E3/E4 alleles were genotyped using PCR and restriction enzyme digestion. Subjects were divided into high TG-responders (with > 30% TG relative reduction after treatment) and low TG-responders.

Results: The frequency of the PPARA intron 7 G/G genotype was higher in high TG-responders than in low TG-responders (85% vs. 69%, P < 0.05). There was no significant difference between the percentage of high TG-responders and low TG-responders for any of the other genetic polymorphisms examined. In stepwise logistic regression, baseline TG and only the PPARA intron 7 polymorphism among the others were selected in the model as significant predictors of TG-response (odds ratio: 3.10, 95% CI: 1.28-7.52, P = 0.012 for PPARA polymorphism). With age, gender, body mass index, smoking status and HbA1c as additional factors, baseline TG (P< 0.0001), intron 7 (P = 0.013), body mass index (P = 0.040) and LPL-S447X (P = 0.084) were significant predictors of TG-response.

Conclusion: These results indicate that elevated baseline TG levels and PPARA gene intron 7 G/G genotype were associated with TG reduction > 30% after fenofibrate treatment in patients with type 2 diabetes.

Endogenous oestrogens play a crucial role in endometrial cancer pathogenesis, with most endometrial cancer risk factors causing an increase in oestrogens. Adipose tissue, where androgens are converted to oestrogens by the enzyme aromatase, is an important source of endogenous oestrogen production in the postmenopausal woman. The peroxisome proliferator-activated receptor-gamma (PPARgamma), a key transcriptional regulator of adipogenesis, may also play a role in the regulation of aromatase expression in adipose tissue. We hypothesized that the functional PPARgamma ProAla polymorphism may alter aromatase expression, ultimately affecting endometrial cancer susceptibility. We genotyped the PPARgamma ProAla polymorphism in a study of invasive endometrial cancer cases (n = 222) and matched controls (n = 666) nested within the Nurses' Health Study Cohort. We found little or no evidence of an association between the Ala allele of the PPARgamma codon 12 polymorphism and endometrial cancer risk (adjusted odds ratio = 1.18, 95% confidence interval = 0.80-1.76). Furthermore, we found no association with the PPARgamma ProAla polymorphism and the ratio of oestrone to androstenedione or oestradiol to testosterone plasma hormone levels, measures of aromatase activity. Consistent with previous findings for breast cancer, these results suggest that the PPARgamma ProAla polymorphism does not play a major role in mediating circulating oestrogen levels or endometrial cancer susceptibility.

Objective and methods: 5-Hydroxytryptamine (serotonin) receptor 2B (HTR2B) is involved in brain development. Although expressed in the human brain, HTR2B has not been investigated much for its role in higher brain functions. Here we describe a genome-scan with 391 simple sequence repeat markers in 300 Caucasians, identifying HTR2B gene as a candidate for drug abuse vulnerability.

Results: From DNA re-sequencing of 110 subjects, we discovered three novel single nucleotide polymorphisms (SNPs), two of which confer a double-mutant of the receptor protein in a drug-abusing population. Arg6, a conserved basic residue, and the conserved acidic Glu42 are mutated simultaneously into Gly, termed R6G/E42G. Furthermore, this double-mutant tends to associate with drug abuse (P = 0.08 by chi2 test). The third SNP that is a synonymous mutation in the codon of Gln11 showed significant association with drug abuse (P = 0.0335 by Fisher's exact test).

Conclusion: Our data are the first suggesting that HTR2B contributes to brain architecture and pathways that are involved in illegal drug reward.

The G894T endothelial nitric oxide synthase (eNOS) polymorphism results in a Glu to Asp substitution at position 298. This position is located externally on the protein and as the regulation of eNOS is dependent on its subcellular localization and interaction with modulatory proteins, we aimed to address whether the substitution of Asp at 298 had any effect on these mechanisms. Initially, we developed a novel method to accurately determine molar quantities of each variant by expressing them as green fluorescent protein (GFP) fusion proteins and using recombinant adenoviruses to facilitate transient infection of human microvascular endothelial cells. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting of eNOSAsp revealed a 135-kDa proteolytic fragment which was not present with eNOSGlu. This proteolysis was prevented by using LDS buffer confirming that this differential cleavage is an artefact of sample preparation and unlikely to occur intracellularly. Nitric oxide was measured following stimulation with calcium ionophore or oestrogen in the presence of varying sepiapterin concentrations. GFP fluorescence was used to quantify the amount of fusion protein and calculate intracellular specific activity. There was no significant difference in intracellular specific activity between Glu and Asp eNOS in response to calcium ionophore or oestrogen. Tetrahydrobiopterin supplementation increased eNOS activity of both variants in an identical manner. The presence of the GFP also facilitated the visualization of the variants by confocal microscopy and demonstrated that both localized to the plasma membrane and the Golgi. These findings demonstrate that the Asp substitution at 298 does not have a major effect in modulating eNOS activity in vivo.

Objective: Ginkgo biloba was found to exert a significant inductive effect on CYP2C19 activity. This study was designed to investigate the potential herb-drug interaction between G. biloba and omeprazole, a widely used CYP2C19 substrate, in subjects with different CYP2C19 genotypes.

Methods: Eighteen healthy Chinese subjects previously genotyped for CYP2C19 were selected. All subjects received a single omeprazole 40 mg at baseline and then at the end of a 12-day treatment period with G. biloba (140 mg, bid). Multiple blood samples were collected over 12 h, and 24 h urine was collected post omeprazole dosing. Plasma and urine concentrations of omeprazole and its metabolites, 5-hydroxyomeprazole and omeprazole sulfone, were determined, and their pharmacokinetics calculated non-compartmentally.

Results: Plasma concentrations of omeprazole and omeprazole sulfone were significantly decreased, and 5-hydroxyomeprazole significantly increased following G. biloba administration in comparison to baseline. A significant decrease in the ratio of area under the plasma concentration-time curve (AUC) of omeprazole to 5-hydroxyomeprazole was observed in the homozygous extensive metabolizers, heterozygous extensive metabolizers, and poor metabolizers, respectively. The decrease was greater in PMs than EMs. No significant changes in the AUC ratios of omeprazole to omeprazole sulfone were observed. Renal clearance of 5-hydroxyomeprazole was significantly decreased after G. biloba, but the change was not significantly different among the three genotype groups.

Conclusion: Our results show that G biloba can induce omeprazole hydroxylation in a CYP2C19 genotype-dependent manner and concurrently reduce the renal clearance of 5-hydroxyomeprazole. Co-administration of G. biloba with omeprazole or other CYP2C19 substrates may significantly reduce their effect, but further studies are warranted.