Pharmacogenetics (Pharmacogenetics)

Publications in this journal

• Article: Pharmacogenetics and herb-drug interactions: experience with Ginkgo biloba and omeprazole.

  Ophelia Q P Yin, Brian Tomlinson, Mary M Y Waye, Albert H L Chow, Moses S S Chow
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  ABSTRACT: 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. 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. 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. 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.
  Pharmacogenetics 01/2005; 14(12):841-50.
• Article: The human serotonin receptor 2B: coding region polymorphisms and association with vulnerability to illegal drug abuse.

  Zhicheng Lin, Donna Walther, Xiao-Ying Yu, Tomas Drgon, George R Uhl
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  ABSTRACT: 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. 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). Our data are the first suggesting that HTR2B contributes to brain architecture and pathways that are involved in illegal drug reward.
  Pharmacogenetics 01/2005; 14(12):805-11.
• Article: Functional comparison of the endothelial nitric oxide synthase Glu298Asp polymorphic variants in human endothelial cells.

  Denise M McDonald, Nicholas J Alp, Keith M Channon
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  ABSTRACT: 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.
  Pharmacogenetics 01/2005; 14(12):831-9.
• Article: Upstream and coding region CYP2C9 polymorphisms: correlation with warfarin dose and metabolism.

  Barry P King, Tayyaba I Khan, Guruprasad P Aithal, Farhad Kamali, Ann K Daly
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  ABSTRACT: 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. CYP2C9 exons, intron-exon boundaries and 3 kb of upstream sequence in 20 patients requiring <or= 1.5 mg warfarin per day and with apparently homozygous wild-type or heterozygous CYP2C9*2 genotypes were screened for novel polymorphisms by single-strand conformational polymorphism analysis. PCR-based genotyping assays for novel upstream and other known polymorphisms were used to screen a larger patient population of known CYP2C9*2 and *3 genotype requiring a range of warfarin doses. 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. 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.
  Pharmacogenetics 01/2005; 14(12):813-22.
• Article: Methylenetetrahydrofolate reductase gene polymorphisms and response to fluorouracil-based treatment in advanced colorectal cancer patients.

  Marie-Christine Etienne, Jean-Louis Formento, Maurice Chazal, Mireille Francoual, Nicolas Magné, Patricia Formento, André Bourgeon, Jean-François Seitz, Jean-Robert Delpero, Christian Letoublon, Denis Pezet, Gérard Milano
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  ABSTRACT: 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.
  Pharmacogenetics 01/2005; 14(12):785-92.
• Article: Response to micronized fenofibrate treatment is associated with the peroxisome-proliferator-activated receptors alpha G/C intron7 polymorphism in subjects with type 2 diabetes.

  Christelle Foucher, Stephanie Rattier, David M Flavell, Philippa J Talmud, Steve E Humphries, John J P Kastelein, Amir Ayyobi, Simon Pimstone, Jiri Frohlich, Jean-Claude Ansquer, George Steiner
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  ABSTRACT: 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. 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. 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. 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.
  Pharmacogenetics 01/2005; 14(12):823-9.
• Article: No evidence of a role for PPARgamma Pro12Ala polymorphism in endometrial cancer susceptibility.

  Randi A Paynter, Susan E Hankinson, Graham A Colditz, David J Hunter, Immaculata De Vivo
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  ABSTRACT: 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.
  Pharmacogenetics 01/2005; 14(12):851-6.
• Article: The T341C (Ile114Thr) polymorphism of N-acetyltransferase 2 yields slow acetylator phenotype by enhanced protein degradation.

  Yu Zang, Shuang Zhao, Mark A Doll, J Christopher States, David W Hein
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  ABSTRACT: Human N-acetyltransferase 2 (NAT2) plays a significant role in the clearance and biotransformation of many drugs and carcinogens. A TC (Ile114Thr) single nucleotide polymorphism (SNP) of NAT2 is commonly found in slow acetylators, leading to altered drug response and toxicity and possibly cancer susceptibility from carcinogens. The objective of this study was to investigate the mechanism by which this SNP causes slow acetylator phenotype. A cDNA expression system was used to compare the NAT2*4 reference allele with an identical one possessing the TC SNP in COS-1 cells. The recombinant human NAT2 enzymes were compared in regard to catalytic activity, kinetic parameters, thermostability, immunoreactive protein level, mRNA level and in-vivo protein degradation. The TC (Ile114Thr) SNP significantly reduced enzyme activity without changing the apparent kinetic parameters Km and Vmax (normalized for NAT2 protein), indicating that Ile114Thr did not change substrate or cofactor binding affinities or catalytic efficiency. Furthermore, no significant difference in NAT2 mRNA level was observed, indicating no impairment of transcription. The TC (Ile114Thr) SNP did not alter thermostability of NAT2 at either 37 or 50 degrees C. However, this SNP significantly reduced cytosolic NAT2 immunoreactive protein through enhanced protein degradation. This is the first report indicating that protein degradation is an important mechanism of human NAT2 slow acetylator phenotype.
  Pharmacogenetics 12/2004; 14(11):717-23.
• Article: Functionality of allelic variations in human alcohol dehydrogenase gene family: assessment of a functional window for protection against alcoholism.

  Shou-Lun Lee, Jan-Olov Höög, Shih-Jiun Yin
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  ABSTRACT: Alcohol dehydrogenase (ADH) catalyses the rate-determining reaction in ethanol metabolism. Genetic association studies of diverse ethnic groups have firmly demonstrated that the allelic variant ADH1B*2 significantly protects against alcoholism but that ADH1C*1, which is in linkage with ADH1B*2, produces a negligible protection. The influence of other potential candidate genes/alleles within the human ADH family, ADH1B*3 and ADH2, remains unclear or controversial. To address this question, functionalities of ADH1B3 and ADH2 were assessed at a physiological level of coenzyme and substrate range. Ethanol-oxidizing activities of recombinant ADH1B1, ADH1B2, ADH1B3, ADH1C1, ADH1C2 and ADH2 were determined at pH 7.5 in the presence of 0.5 mm NAD with 2-50 mm ethanol. The activity differences between ADH1B2 and ADH1B1 were taken as a threshold for effective protection against alcoholism and those between ADH1C1 and ADH1C2 as a threshold for null protection. Over 2-50 mm ethanol, the activities of ADH1B3 were found 2.9-23-fold lower than those of ADH1B2, largely attributed to the Km effect (ADH1B2, 1.8 mm; ADH1B3, 61 mm). Strikingly, the ADH1B3 activity was only 84% that of ADH1B1 at a low ethanol concentration, 2 mm, but increased 10-fold at 50 mm. Corrected for relative expression levels of the enzyme in liver, the hepatic ADH2 activities were estimated to be 18-97% those of ADH1B1 over 2-50 mm ethanol and were 28-140% of the activity differences between ADH1C1 and ADH1C2. The assessment based on the proposed functional window for the human ADH gene family indicates that ADH1B*3 may show some degree of protection against alcoholism and that the ADH2 functional variants appear to be negligible for this protection.
  Pharmacogenetics 12/2004; 14(11):725-32.
• Article: Identification of non-functional allelic variant of CYP1A2 in dogs.

  Masashi Mise, Takanori Hashizume, Satoshi Matsumoto, Yoshiaki Terauchi, Toshihiko Fujii
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  ABSTRACT: Recently, we reported that AC-3933, a novel cognitive enhancer, is polymorphically hydroxylated in beagle dogs and that dogs could be phenotyped as extensive metabolizers (EM) or poor metabolizers (PM). AC-3933 polymorphic hydroxylation is caused by polymorphic expression of CYP1A2 protein in dog liver. In order to clarify the mechanism of polymorphic expression of CYP1A2 protein in beagle dogs, we investigated, in this study, the sequence of CYP1A2 cDNA in EM and PM dogs. In PM dogs CYP1A2 gene, we discovered a nonsense mutation (C1117T) that induces a premature termination, and is associated with PM phenotype for AC-3933 hydroxylation. All PM dogs studied were homozygote of the mutant allele (m/m) and seemed to be CYP1A2-null phenotype as they lacked the heme-binding region in CYP1A2. These results indicate that the polymorphic expression of CYP1A2 protein observed in our previous study is caused by a single nucleotide polymorphism on CYP1A2 coding region. Furthermore, we developed a genotyping method for the mutant allele using a mismatch PCR-restriction fragment length polymorphism, and carried out frequency analysis in 149 beagle dogs. Our results indicate that more than 10% of the dogs studied were CYP1A2-null. Because CYP1A2-null phenotype in dogs affects the results of pharmacokinetic, toxicological and pharmacological studies of drug candidates, these findings are important in the pharmaceutical and the veterinary fields.
  Pharmacogenetics 12/2004; 14(11):769-73.
• Article: HLA-B*5701 and abacavir hypersensitivity.

  Maria E Watson, Jeanne M Pimenta, William R Spreen, Jaime E Hernandez
  Pharmacogenetics 12/2004; 14(11):783-4; author reply 784.
• Article: Complex haplotype structure of the human GNAS gene identifies a recombination hotspot centred on a single nucleotide polymorphism widely used in association studies.

  Wanling Yang, Brook White, Eleanor K Spicer, Benjamin L Weinstein, John D Hildebrandt
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  ABSTRACT: The alpha subunit of the heterotrimeric G protein Gs (Gsalpha) is involved in numerous physiological processes and is a primary determinant of cellular responses to extracellular signals. Genetic variations in the Gsalpha gene may play an important role in complex diseases and drug responses. To characterize the genetic diversity in this locus, we resequenced exons and flanking introns of the gene in 44 genomic samples and analysed the haplotype structure of the gene in an additional 50 African-Americans and 50 Caucasians. Significant differences in allele frequency for nearly all the genotyped single nucleotide polymorphism (SNPs) were detected between the two ethnic groups. Linkage disequilibrium (LD) analysis of this locus revealed two haplotype blocks characterized by strong LD and reduced haplotype diversity, especially in Caucasians. Between the two blocks is a narrow (approximately 3 kb) recombination hotspot centred on exons 4 and 5, and a widely used genetic marker in association studies in this region (rs7121) was in linkage equilibrium with the rest of the gene. The haplotype structure of the GNAS locus warrants reevaluation of previous association studies that used marker rs7121 and affects choice of SNP markers to be used in future studies of this locus.
  Pharmacogenetics 12/2004; 14(11):741-7.
• Article: The Arg389Gly beta1-adrenoceptor gene polymorphism determines contractile response to catecholamines.

  Karl La Rosée, Michael Huntgeburth, Stephan Rosenkranz, Michael Böhm, Petra Schnabel
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  ABSTRACT: Recently, the Arg389Gly beta1-adrenoceptor (beta1AR) gene polymorphism has been detected. The Arg variant exhibited increased responsiveness to agonist-induced stimulation in vitro. Functional studies in isolated human atrial muscle strips and in-vivo studies revealed contradictory results regarding the functional relevance of this polymorphism. We sought to characterize the functional consequences of the Arg389Gly beta1-AR polymorphism in 30 consecutive healthy male volunteers in vivo. beta1-AR genotype was determined by PCR and restriction analysis, which was confirmed by DNA sequencing. We compared heart rate, blood pressure, and contractile response of the various genotype carriers with a modified dobutamine stress echocardiography protocol. Subjects homozygous for the Arg389 beta1AR showed a significantly higher increase in fractional shortening upon cumulative doses of dobutamine as compared to subjects carrying one or two copies of the Gly389 allele. A statistically significant difference was observed at a dobutamine dose of 10 microg/kg/min (46.5 +/- 1.3 vs. 41.8 +/- 1.0 %; P = 0.023) and was maximal at 40 microg/kg/min (61.9 +/- 1.4 vs. 52.8 +/- 1.6; P = 0.001). As a result, the systolic blood pressure response to dobutamine was significantly enhanced in individuals homozygous for the Arg389 allele, whereas the effect on heart rate did not differ between the two groups. Normalization for changing afterload conditions by calculating the pressure-dimension ratio revealed similar effects, indicating that the beta1AR-mediated effects are mainly a result of increased myocardial inotropy. These data indicate that the Arg389Gly beta1AR polymorphism is functionally relevant in vivo and determines contractile responsiveness to catecholamines in humans.
  Pharmacogenetics 12/2004; 14(11):711-6.
• Article: Functional analysis of single nucleotide polymorphisms of hepatic organic anion transporter OATP1B1 (OATP-C).

  Megumi Iwai, Hiroshi Suzuki, Ichiro Ieiri, Kenji Otsubo, Yuichi Sugiyama
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  ABSTRACT: Two kinds of single nucleotide polymorphism (SNP; Asn130Asp and Val174Ala) are frequently observed in the liver specific transporter, organic anion transporting polypeptide 1B1 (OATP1B1/OATP-C) gene. Although these two SNPs occur independently in European-Americans, Val174Ala is mostly associated with Asn130Asp in Japanese. Our previous in-vivo studies in Japanese subjects indicated that the non-renal clearance of pravastatin was decreased to 13% of that in wild-type subjects (Nishizato et al. Clin Pharmacol Ther 2003;73(6):554-564). The purpose of the present study is to characterize the function of SNPs variants of OATP1B1 in cDNA transfected cells. The localization and transport activity were analyzed in HEK293 cells stably expressing wild-type OATP1B1 (OATP1B1*1a), OATP1B1*1b (Asn130Asp), OATP1B1*5 (Val174Ala) and OATP1B1*15 (Asn130Asp and Val174Ala). To characterize the intrinsic Vmax, observed Vmax in uptake study were normalized by the expression level estimated from Western blotting. All SNP variants are predominantly located on the cell surface. No significant alteration was observed in Km values for the transport of 17beta-estradiol 17beta-d-glucuronide (E217betaG), a typical substrate of OATP1B1, among these SNP variants. However, the normalized Vmax value for OATP1B1*15 was drastically decreased to less than 30% compared with OATP1B1*1a. In contrast, the transport activity of OATP1B1*1b (Asn130Asp) and OATP1B1*5 (Val 174Ala) was similar to that of OATP1B1*1a. These results are consistent with the results of our previous clinical studies. It is thus suggested that in-vivo disposition may be predicted from in-vitro results using recombinant transporters.
  Pharmacogenetics 12/2004; 14(11):749-57.
• Article: Association between single nucleotide polymorphisms in deoxycytidine kinase and treatment response among acute myeloid leukaemia patients.

  Jing-Yi Shi, Zhan-Zhong Shi, Su-Jiang Zhang, Yong-Mei Zhu, Bai-Wei Gu, Guo Li, Xue-Tao Bai, Xiao-Dong Gao, Jiong Hu, Wei Jin, Wei Huang, Zhu Chen, Sai-Juan Chen
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  ABSTRACT: Development of resistance to 1-beta-arabinofuranosylcytosine (AraC) is a major obstacle in the treatment of patients with acute myeloid leukaemia (AML). Deficiency of functional deoxycytidine kinase (dCK) plays an important role in AraC resistance in vitro. We screened 5378 bp sequences of the dCK gene, including all exons and the 5' flanking region, and identified two single nucleotide polymorphisms (SNPs) in the regulatory region (rSNPs) with high allele frequencies. These two rSNPs (-201C>T and -360C>G) formed two major haplotypes. Genotyping with sequencing and MassARRAY system among 122 AML patients showed that those with -360CG/-201CT and -360GG/-201TT compound genotypes (n = 41) displayed a favourable response to chemotherapy whereas those with -360CC/-201CC (n = 81) tended to have a poor response (P = 0.025). Moreover, real-time quantitative reverse transcriptase-polymerase chain reaction showed that patients with -360CG/-201CT and -360GG/-201TT genotypes expressed higher level of dCK mRNA compared to those with the -360CC/-201CC genotype (P = 0.0034). Luciferase-reporter assay showed that dCK 5' regulatory region bearing -360G/-201T genotype alone had an eight-fold greater transcriptional activation activity compared to that with -360C/-201C genotype, whereas co-transfection of both -360G/-201T and -360C/-201C constructs mimicked the heterozygous genotype, which exhibited a four-fold greater activity compared to that with -360C/-201C. These results indicate that rSNP haplotypes of dCK gene may serve as a genetic marker for predicting drug responsiveness, which will be beneficial in establishing more effective AML chemotherapeutic regimens.
  Pharmacogenetics 11/2004; 14(11):759-68.
• Article: Identification of deletion-junction site of CYP2A6*4B allele lacking entire coding region of CYP2A6 in Japanese.

  Noritaka Ariyoshi, Hiromi Sekine, Kazuo Nakayama, Katsuhiko Saito, Atsushi Miyamoto, Tetsuya Kamataki
  Pharmacogenetics 11/2004; 14(10):701-5.
• Article: Benzydamine metabolism in vivo is impaired in patients with deficiency of flavin-containing monooxygenase 3.

  Ertan Mayatepek, Bianca Flock, Johannes Zschocke
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  ABSTRACT: Flavin-containing monooxygenase 3 (FMO3) is an important hepatic enzyme for the detoxification of xenobiotics. The pharmacogenetic relevance of FMO3 deficiency has frequently been postulated from in vitro studies but has not yet been proven in vivo. We investigated the metabolism of benzydamine (BZD) in controls as well as patients with severe FMO3 deficiency and found evidence of markedly reduced N-oxygenation capacity both in serum and urine samples. After 2 h the N-oxide/total BZD ratio in serum of the patients ranged from 3.1 to 5.6% compared to controls with a median of 13.1%. Urinary BZD was almost fully N-oxygenated in controls (> 93.7%) whilst the urinary N-oxide/total BZD ratios were 29.4-35.7% in patients. Our study is the first to confirm that severe FMO3 deficiency is associated with reduced metabolism of a drug substrate in vivo. This is relevant because of the prevalence of mild FMO3 deficiency in the general population. BZD may be also useful as a diagnostic probe for determination of FMO3 deficiency in vivo.
  Pharmacogenetics 11/2004; 14(11):775-7.
• Article: Regulation of CYP3A4 by the bile acid receptor FXR: evidence for functional binding sites in the CYP3A4 gene.

  Carmela Gnerre, Sharon Blättler, Michel R Kaufmann, Renate Looser, Urs A Meyer
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  ABSTRACT: CYP3A4, the most abundant cytochrome P450 in human liver, is responsible for the metabolism of numerous xenobiotics and endobiotics. CYP3A4 expression is highly variable and is induced by numerous compounds of exogenous and endogenous origin, including elevated concentrations of secondary bile acids via the pregnane X receptor (PXR). We show that physiological concentrations of the primary bile acid chenodeoxycholic acid regulate the expression of CYP3A4 via the bile acid receptor FXR. Experiments performed in vitro in different cell culture systems, gel-mobility shift assays and experiments performed in vivo in transgenic mice lacking FXR or PXR and treated with the synthetic FXR agonist GW4064 were undertaken to study the implication of FXR in the regulation of CYP3A. Our data provide evidence for the presence of two functional FXR recognition sites located in a 345-bp element within the 5'-flanking region of CYP3A4. Mutational analysis of these sites and experiments in transgenic mice lacking FXR or PXR support the relevance of FXR activation for CYP3A regulation. Thus, whereas elevated concentrations of precursors of bile acids and secondary bile acids induce CYP3A via PXR, primary bile acids can modulate the expression of CYP3A via FXR. These findings may explain elevated CYP3A expression in cholestasis and part of the variability of drug responsiveness and toxicity between individuals.
  Pharmacogenetics 11/2004; 14(10):635-45.
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  Article: Functional polymorphism of human glutathione transferase A3: effects on xenobiotic metabolism and steroid biosynthesis.

  Natasha Tetlow, Marjorie Coggan, Marco G Casarotto, Philip G Board
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  ABSTRACT: The alpha class glutathione transferase GSTA3-3 is involved in steroid biosynthesis and the metabolism of some xenobiotics. A bioinformatics approach was utilized to identify novel coding region polymorphisms in the glutathione transferase A3 gene (GSTA3). We describe an I71L polymorphism in GSTA3 that occurs at a low frequency in African populations. The activity of the leucine containing isoform was significantly reduced in a range of glutathione-conjugating reactions due to a diminished affinity for reduced glutathione, indicating that this allele could be implicated in disease caused by oxidative stress in steroidogenic tissue. By contrast, the delta(5)-androsten-3,17-dione isomerase activity of GSTA3-3 was not affected by this substitution, indicating that there is no direct effect on steroid synthesis. However, the L71 isoform displayed diminished stability at 45 degrees C. If this relative instability is mirrored in vivo, testosterone and progesterone synthesis may be affected in individuals carrying this allele.
  Pharmacogenetics 11/2004; 14(10):657-63.