Haplotypes and a Novel Defective Allele of CES2 Found in a Japanese Population

ABSTRACT: Human carboxylesterase 2 (hCE-2) is a member of the serine esterase superfamily and is responsible for hydrolysis of a wide variety of xenobiotic and endogenous esters. hCE-2 also activates an anticancer drug, irinotecan (7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin, CPT-11), into its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). In this study, a comprehensive haplotype analysis of the CES2 gene, which encodes hCE-2, in a Japanese population was conducted. Human carboxylesterases are members of the serine esterase superfamily and are responsible for hydrolysis of a wide variety of xenobiotic and endogenous esters. They metabolize esters, thioesters, carbamates, and amides to yield soluble acids and alcohols or amines Although both hCE-1 and hCE-2 show broad substrate specificities, hCE-2 is relatively specific for heroin, cocaine (benzoyl ester), 6-acetylmorphine, procaine, and oxybutynin 1865 camptothecin (SN-38), a topoisomerase inhibitor, by carboxylesterases Previously, 12 exons and their flanking regions of CES2 were sequenced from 153 Japanese subjects, who received irinotecan or steroidal drugs, and 12 novel SNPs, including the nonsynonymous SNP, 100CϾT (Arg 34 Trp), and the SNP at the splice acceptor site of intron 8 (IVS8-2AϾG) were found Materials and Methods Chemicals. Irinotecan, SN-38, and SN-38G were kindly supplied by Yakult Honsha Co. Ltd. (Tokyo, Japan). Patients. A total of 262 Japanese subjects analyzed in this study consisted of 85 patients with allergies who received steroidal drugs and 177 patients with cancer who received irinotecan. The ethical review boards of the National Cancer Center, National Center for Child Health and Development, and National Institute of Health Sciences approved this study. Written informed consent was obtained from all participants. DNA Sequencing. Total genomic DNA was extracted from blood leukocytes or Epstein-Barr virus-transformed lymphocytes and used as a template in the polymerase chain reaction (PCR). Sequence data of the CES2 gene from 72 patients and 81 cancer patients were described previously Linkage Disequilibrium and Haplotype Analyses. LD analysis was performed by the SNPAlyze software (version 5.1; Dynacom Co., Yokohama, Japan), and a pairwise two-dimensional map between SNPs was obtained for the DЈ and rho square (r 2 ) values. All allele frequencies were in HardyWeinberg equilibrium. Some haplotypes were unambiguously assigned in the subjects with homozygous variations at all sites or a heterozygous variation at only one site. Separately, the diplotype configurations (combinations of haplotypes) were inferred by LDSUPPORT software, which determines the posterior probability distribution of the diplotype configuration for each subject on the basis of estimated haplotype frequencies Administration of Irinotecan and Pharmacokinetic Analysis. The demographic data and eligibility criteria for 177 cancer patients who received irinotecan in the National Cancer Center Hospitals (Tokyo and Chiba, Japan) were described elsewhere Each patient received a 90-min i.v. infusion at doses of 60 to 150 mg/m 2 , which varied depending on regimens/coadministered drugs: i.e., irinotecan dosages were 100 or 150 mg/m 2 for monotherapy and combination with 5-FU, 150 mg/m 2 for combination with mitomycin C (MMC), and 60 (or 70) mg/m 2 for combination with platinum anticancer drugs. Heparinized blood was collected before administration of irinotecan and at 0 min (end of infusion), 20 min, 1 h, 2 h, 4 h, 8 h, and 24 h after infusion. Plasma concentrations of irinotecan, SN-38, and SN-38G were determined as described previously Expression of Wild-Type and Variant CES2 Proteins in COS-1 Cells. Expression of wild-type and variant CES2 proteins in COS-1 cells was examined as described previously and ZERO-Dscan software (Raytest, Straubenhardt, Germany). The relative expression levels are shown as the means Ϯ S.D. of three separate transfection experiments. Determination of CES2 mRNA by Real-Time RT-PCR. Total RNA was isolated from transfected COS-1 cells using the RNeasy Mini Kit (QIAGEN, Tokyo, Japan). After RNase-free DNase treatment of samples to minimize plasmid DNA contamination, first-strand cDNA was prepared from 1 g of total RNA using the High-Capacity cDNA Archive Kit (Applied Biosystems, Foster City, CA) with random primers. Real-time PCR assays were performed with the ABI7500 Real Time PCR System (Applied Biosystems) using the TaqMan Gene Expression Assay for CES2 (Hs01077945_m1; Applied Biosystems) according to the manufacturer's instructions. The relative mRNA levels were determined using calibration curves obtained from serial dilutions of the pooled wild-type CES2 cDNA. Samples without reverse transcriptase were routinely included in the RT-PCR reactions to measure possible contributions of contaminating DNA, which was usually less than 1% of the mRNA-derived amplification. Transcripts of ␤-actin were quantified as internal controls using TaqMan ␤-Actin Control Reagent (Applied Biosystems), and normalization of CES2 mRNA levels were based on ␤-actin concentrations. Enzyme Assay. CPT-11 hydrolyzing activity of the postmitochondrial supernatants (microsomal fraction plus cytosol) was assayed over the substrate concentration range of 0.25 to 50 M as described previously Statistical Analysis. Statistical analysis of the differences in the AUC ratios among CES2 diplotypes, coadministered drugs. or irinotecan dosages was performed using the Kruskal-Wallis test, Mann-Whitney test, or Spearman rank correlation test (Prism 4.0, GraphPad Software, Inc., San Diego, CA). The t test (Prism 4.0) was applied to the comparison of the average values of protein expression and mRNA levels between wild-type and variant CES2. Results CES2 Variations Detected in a Japanese Population. Previously, the promoter region, all 12 exons, and their flanking introns of the CES2 gene were sequenced from 72 allergic patients and 81 cancer patients and resulted in the identification of 12 novel SNPs The nonsynonymous SNP 424GϾA (V142M) reported by our group LD and Haplotype Analysis. Using the detected SNPs, LD analysis was performed, and the pairwise values of r 2 and DЈ were obtained. A perfect linkage (r 2 ϭ 1.00) was observed between SNPs Ϫ363CϾG and IVS10-87GϾA. A close association (r 2 ϭ 0.85) was found between SNPs IVS10-108GϾA and 1749AϾG. Other associations were much lower (r 2 Ͻ 0.1). Therefore, the entire CES2 gene was analyzed as one LD block. The determined/inferred haplotypes are summarized i

Less Carcinogenic Chlorinated Estrogens Applicable to Hormone Replacement Therapy

Human estrogens prescribed for hormone replacement therapy (HRT) are known to be potent carcinogens. To find safer estrogens, several chlorinated estrogens were synthesized and their carcinogenic potential were determined. A pellet containing either 2-chloro-17β-estradiol (2-ClE2) or 4-chloro-17β-estradiol (4-ClE2) was implanted subcutaneously for 52 weeks into August Copenhagen Irish (ACI) rats, a preferred animal model for human breast cancer. 17β-Estradiol (E2) frequently induced mammary tumors while both 2-ClE2 and 4-ClE2 did not. Their 17α-ethinyl forms, thought to be orally active estrogens, were also synthesized. Neither 2-chloro-17α-ethinylestradiol (2-ClEE2) nor 4-chloro-17α-ethinylestradiol (4-ClEE2) induced tumors. The less carcinogenic effects were supported by histological examination of mammary glands of ACI rats treated with the chlorinated estrogens. A chlorine atom positioned at the 2- or 4-position of E2 may prevent the metabolic activation, resulting in reducing the carcinogenicity. 2-ClE2 and 4-ClE2 administered subcutaneously and 2-ClEE2 and 4-ClEE2 given orally to ovariectomized rats all showed uterotrophic potency, albeit slightly weaker than that of E2. Our results indicate that less carcinogenic chlorinated estrogens retaining estrogenic potential could be safer alternatives to the carcinogenic estrogens now in use for HRT

INVOLVEMENT OF HUMAN HEPATIC UGT1A1, UGT2B4, AND UGT2B7 IN THE GLUCURONIDATION OF CARVEDILOL

This article is available online at http://dmd.aspetjournals.org ABSTRACT: Carvedilol ((؎)-1-carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl]amino]-2-propanol) is metabolized primarily into glucuronide conjugates. In the present study, we identified the human UDPglucuronosyltransferase (UGT) isoforms involved in the glucuronidation of carvedilol by thin-layer chromatography using microsomes from human liver or insect cells expressing recombinant UGT isoforms. We observed two forms of carvedilol glucuronides, namely G1 and G2, in hepatic microsomes. The glucuronidation of carvedilol was catalyzed by at least three recombinant UGT isoforms: UGT1A1, UGT2B4, and UGT2B7. UGT2B4 formed both G1 and G2, whereas UGT1A1 and UGT2B7 were responsible for the formation of glucuronide G2 and G1, respectively. The enzyme kinetics for carvedilol glucuronidation by UGT1A1, UGT2B4, and UGT2B7 in addition to human liver microsomes were examined by Lineweaver-Burk analysis. The values of K m and V max for human liver microsomes were 26.6 M and 106 pmol/min/mg protein for G1, and 46.0 M and 44.5 pmol/min/mg protein for G2, respectively. The K m values for UGT1A1, UGT2B4, and UGT2B7 for G1 and G2 (22.1-55.1 M) were comparable to those of the liver microsomes, whereas the V max values were in the range of 3.33 to 7.88 pmol/min/mg protein. The K m and V max /K m values for UGT2B4 and UGT2B7 for G1 were similar, whereas UGT2B4 had lower Km and higher V max /K m values for G2 compared with those of UGT1A1. These results suggest that G1 formation is catalyzed by UGT2B4 and UGT2B7, whereas G2 is formed by UGT2B4 and UGT1A1. These three hepatic UGT isoforms may have important roles in carvedilol metabolism

Global DNA Methylation in Cord Blood as a Biomarker for Prenatal Lead and Antimony Exposures

DNA methylation is an epigenetic mechanism for gene expression modulation and can be used as a predictor of future disease risks. A prospective birth cohort study was performed to clarify the effects of neurotoxicants on child development, namely, the Tohoku Study of Child Development, in Japan. This study aimed to evaluate the association of prenatal exposure to five toxic metals—arsenic, cadmium, mercury, lead (Pb), antimony (Sb), and polychlorinated biphenyls (PCBs, N = 166)—with global DNA methylation in umbilical cord blood DNA. DNA methylation markers, 5-methyl-2′-deoxycytidine (mC) and 5-hydroxymethyl-2′-deoxycytidine (hmC), were determined using liquid chromatography-tandem mass spectrometry. The mC content in cord blood DNA was positively correlated with Pb and Sb levels (r = 0.435 and 0.288, respectively) but not with cord blood PCBs. We also observed significant positive correlations among Pb levels, maternal age, and hmC content (r = 0.155 and 0.243, respectively). The multiple regression analysis among the potential predictors demonstrated consistent positive associations between Pb and Sb levels and mC and hmC content. Our results suggest that global DNA methylation is a promising biomarker for prenatal exposure to Pb and Sb

Global DNA Methylation in Cord Blood as a Biomarker for Prenatal Lead and Antimony Exposures

DNA methylation is an epigenetic mechanism for gene expression modulation and can be used as a predictor of future disease risks. A prospective birth cohort study was performed to clarify the effects of neurotoxicants on child development, namely, the Tohoku Study of Child Development, in Japan. This study aimed to evaluate the association of prenatal exposure to five toxic metals—arsenic, cadmium, mercury, lead (Pb), antimony (Sb), and polychlorinated biphenyls (PCBs, N = 166)—with global DNA methylation in umbilical cord blood DNA. DNA methylation markers, 5-methyl-2′-deoxycytidine (mC) and 5-hydroxymethyl-2′-deoxycytidine (hmC), were determined using liquid chromatography-tandem mass spectrometry. The mC content in cord blood DNA was positively correlated with Pb and Sb levels (r = 0.435 and 0.288, respectively) but not with cord blood PCBs. We also observed significant positive correlations among Pb levels, maternal age, and hmC content (r = 0.155 and 0.243, respectively). The multiple regression analysis among the potential predictors demonstrated consistent positive associations between Pb and Sb levels and mC and hmC content. Our results suggest that global DNA methylation is a promising biomarker for prenatal exposure to Pb and Sb

Decreased DNA Methylation in the Shati/Nat8l Promoter in Both Patients with Schizophrenia and a Methamphetamine-Induced Murine Model of Schizophrenia-Like Phenotype.

The number of patients with schizophrenia has increased over the past decade. Previously, many studies have been performed to establish its diagnostic criteria, prophylactic methods, and effective therapies. In this study, we analyzed whether the ratios of DNA methylation in CpG islands of the Shati/Nat8l is decreased in model mice of schizophrenia-like phenotype using genomic DNA collected from brain regions and peripheral blood, since the mouse model of schizophrenia-like phenotype, mice treated repeatedly with methamphetamine showed increase of Shati/Nat8l mRNA expression in our previous experiment. The ratios of Shati/Nat8l CpG island methylation were significantly decreased in both the nucleus accumbens and the peripheral blood of model mice compared with those of control mice. We also investigated Shati/Nat8l methylation in the blood of patients with schizophrenia. We found that Shati/Nat8l CpG island methylation ratios were lower in the patients with schizophrenia than in the healthy controls, which is consistent with our findings in the mice model. To our knowledge, this is the first study to show similar alterations in methylation status of a particular genomic DNA site in both the brain and peripheral blood of mice. Furthermore, the same phenomenon was observed in corresponding human genomic sequences of the DNA extracted from the peripheral blood of patients with schizophrenia. Based on our findings, DNA methylation profiles of the CpG island of Shati/Nat8l might be a diagnostic biomarker of schizophrenia