Distribution of XRCC1 genotypes in north Indian population.

BACKGROUND & OBJECTIVES: XRCC1, a major DNA repair gene, acts as a scaffold of different activities involved in repair by interacting with components of base excision repair (BER) at the site of damage. Polymorphisms in this gene are associated with variations in the repair efficiency which might predispose an individual to cancer risk. To associate a gene polymorphism with disease risk, it is imperative to have the data for its genotype distribution in normal population. The present study was therefore carried out to find distribution of XRCC1 polymorphisms (codons 194, 280 and 399) in normal north Indian population. METHODS: Healthy volunteers hailing from north India (150) were enrolled in the study. DNA was isolated from blood samples and genotyping of codons 194, 280 and 399 of XRCC1 gene was done by PCR- restriction fragment length polymorphism (RFLP), using specific primers. RESULTS: The frequencies obtained for heterozygous genotype of codons 194 and 399 were 45 and 49 per cent respectively and were higher than wild and variant genotypes. For codon 280, the highest frequency (59%) was obtained for the wild genotype. Frequencies of the variant genotypes of codons 194 and 399 were higher in males and females respectively. The allele frequencies also followed the similar trends. INTERPRETATION & CONCLUSIONS: A significant distribution of variant and heterozygous XRCC1 genotypes was noticed that warrants further studies on the association between these genotypes and disease risk in our study population.

Low folate transport across intestinal basolateral surface is associated with down-regulation of reduced folate carrier in in vivo model of folate malabsorption.

The process of folate transport regulation across biological membranes is of considerable interest because of its ultimate role in providing one-carbon moieties for key cellular metabolic reactions and exogenous requirement of the vitamin in mammals. Although, intestinal folate malabsorption is established phenomena in alcoholism; however, there is no knowledge regarding the mechanism of folate exit across intestinal basolateral membrane (BLM) to circulation during alcohol associated malabsorption. In the present study, male Wistar rats were fed 1 g/kg body weight/day ethanol (20% solution) orally for 3 months and regulatory characteristics of folate transport at BLM surface were evaluated. The folate transport was found to be carrier mediated, saturable, with pH optima at 7.0, besides exhibiting Na(+) independence. The chronic alcohol ingestion resulted in alteration of transport kinetics, shifting the process to K(+) dependent one besides affecting the status of S--S linkage of the transport system. Importantly, chronic ethanol ingestion reduced the folate exit across the BLM by decreasing the affinity of transporter (high K(m)) for substrate and by decreasing the number of transporter molecules (low V(max)) on the surface. The decreased basolateral transport activity was associated with down-regulation of the reduced folate carrier (RFC) which resulted in decreased RFC protein levels in BLM in rat model of alcoholism. The study suggests that during alcohol ingestion, RFC mediated deregulated folate transport across BLM also attributes to folate malabsorption.

Polymorphism of DNA repair gene XRCC1 and hepatitis-related hepatocellular carcinoma risk in Indian population.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the life-threatening malignancies worldwide with hepatitis B and C virus infection as the major risk factor. The risk of HCC might also increase because of the hereditary genetic defects in DNA repair genes. In this regard, X-ray cross-complementing group 1 gene (XRCC1) is a major DNA repair gene involved in base excision repair (BER). AIM: The present study was designed with an aim to find out any possible association between XRCC1 (codons 194, 280, and 399) polymorphisms and the risk of developing hepatitis virus-related HCC in Indian population. METHODS: A total of 407 subjects comprising (170 controls, 174 chronic viral hepatitis, and 63 HCC subjects) were included in the study. PCR-RFLP was used for the genotyping of the three codons of XRCC1. RESULTS: The study revealed that two genotypes Arg194Trp and Arg280His increased the risk of HCC by 2.27- (95% CI = 1.01-5.08; P < 0.001) and 4.95-folds (95% CI = 2.48-9.89; P < 0.001), respectively. Interestingly, the risk for HCC was further enhanced by 35.96 (95% CI = 11.64-110.91; P < 0.001) and 5.28 times (95% CI = 2.81-9.09; P < 0.001) when the genotype Arg280His was found in association with Arg194Trp and Arg399Gln, respectively. CONCLUSION: These preliminary results suggest a positive association of XRCC1 genotypes and risk of hepatitis virus-related HCC in India.

Microsomal Epoxide Hydrolase Polymorphisms and Haplotypes as Determinants of Hepatitis B Virusand Hepatitis C Virus-related Liver Disease in Indian Population.

BACKGROUND: Hepatocellular carcinoma (HCC) is the fifth most common cancer and third leading cause of death worldwide. Main causes of HCC are hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. mEPHX, a xenobiotic metabolizing enzyme, exhibits a dual role of procarcinogen detoxification and activation, hence considered as a cancer risk factor as well as a protective factor. Two known polymorphic forms of mEPHX, exon in exon 3 and 4, are associated with the development of HCC. OBJECTIVE: To determine the association of genotypes and haplotypes of mEPHX with risk of HCC developments separately in HBV- and HCV-infected carriers and patients with hepatitis. METHODS: Polymerase chain reactions (PCR) were carried out using primers to amplify exon 3 (113 Tyr→His variant) and exon 4 (139 His→Arg) polymorphic sites. To distinguish the wild and variant forms, PCR amplification products were digested with restriction endonucleases EcoRV and Rsa1 for exons 3 and 4, respectively. RESULT: Exon 3 genotypes, Y113H and H113H, shared a protective association with HBV-chronic hepatitis infection (P < 0.001 and P< 0.01, respectively) as well as HBV-HCC development (P < 0.001) among HBV-carrier group, while Y113H acts as a risk factor for HCV-chronic hepatitis development (P < 0.001) as well as for HCC development (P < 0.01) with HCV-carrier group as reference. Both H139R and R139R, exon 4 genotypes, acted as a risk factor for HBV/HCV-chronic hepatitis infection and for HBV/HCV-HCC development (P ranges from < 0.05 to < 0.001) with HBV/HCV carriers as reference. 113His-139His and 113His-139Arg haplotypes shared a significant negative and positive association, respectively, with HBV hepatitis and HBV-HCC risk. 113Tyr-139Arg haplotype acted as a risk for HCV-HCC development. CONCLUSION: Polymorphic and haplotypic variant forms of mEPHX exon 3 and 4 variably determine the susceptibility to develop HCC in HBV- and HCV-carrier subjects.

Methylation profiling of tumor suppressor genes and oncogenes in hepatitis virus-related hepatocellular carcinoma in northern India.

Hepatocellular carcinoma (HCC) is the fifth most common cancer in India, and hepatitis B virus and hepatitis C virus infections are major risk factors. DNA methylation alterations have been linked to various carcinomas in different populations. Aberrant CpG island methylation of genes has been recognized in HCC, information is limited for hepatitis virus-related hepatocarcinogenesis. HCC risk has not previously been associated with gene-specific DNA methylation in India. Promoter region methylation of a panel of six tumor suppressor genes (CDKN2A, CDKN2B, CDH1, GSTP1, SOCS1, and APC) and three oncogenes (MYC, HRAS, and KRAS) was determined by methylation-specific PCR among 23 HCC samples and 20 control hepatitis samples. CDKN2B methylation frequency in HCC was double that for hepatitis, and methylation allele density of APC, GSTP1, and CDKN2B increased 2.2-, 2.3-, and 7.6-fold, respectively. Epigenetic silencing of tumor suppressor genes starts during viral infection and progresses toward HCC with the chronicity of the disease. Findings of altered methylation status support involvement of these tumor suppressor genes in HCC. MYC showed decreased methylation in HCC, relative to hepatitis. These observations on DNA methylation suggest the involvement of CDKN2B, SOCS1, CDH1, GSTP1, and MYC in pathogenesis of HCC in India and implicate altered DNA methylation in the molecular pathogenesis.

Haplotypes of microsomal epoxide hydrolase and x-ray cross-complementing group 1 genes in Indian hepatocellular carcinoma patients.

Hepatocellular carcinoma (HCC) is a life-threatening disease that is often associated with chronic infection by hepatitis B and C viruses. Genetic polymorphisms have been reported to alter the risk for HCC development. Genetic studies based on the haplotype have an increased power for detecting disease associations compared with single-nucleotide polymorphism-based analysis. There is sufficient epidemiological evidence suggesting a link between genetic polymorphism and haplotypes of microsomal epoxide hydrolase (mEPHX) and X-ray cross-complementing group 1 (XRCC1) with altered cancer risk. However, no report correlates the risk of HCC development with mEPHX and XRCC1 haplotypes. Genetic polymorphism of these genes was studied for haplotype construction in 169 control subjects, 174 hepatitis patients, and 63 HCC patients. 113Tyr-139Arg and 113His-139His haplotypes of mEPHX significantly elevated the risk for HCC by 1.4- and 1.5-folds, respectively. Arg-His-Arg haplotype of XRCC1 significantly enhanced the risk for hepatitis by 2.8-folds (p = 0.001), but not for HCC (odds ratio = 1.5; p = 0.28). mEPHX haplotypes shared a positive association with HCC risk in India.

Glutathione-S-transferase and microsomal epoxide hydrolase polymorphism and viral-related hepatocellular carcinoma risk in India.

Hepatocellular carcinoma (HCC) is the fourth most common cancer worldwide, the main etiological factors being chronic infections with hepatitis B and C viruses. Genetic polymorphic forms of glutathione-S-transferase (GST) and microsomal epoxide hydrolase (mEPHX) have been associated with risk for various malignancies. The present study was undertaken to evaluate the association of GSTT1 and GSTM1 null genotypes and mEPHX polymorphisms with hepatitis virus-related HCC risk in an Indian population. Three groups of subjects were considered, control (n = 169), chronic viral hepatitis (n = 174), and HCC (n = 63). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for this polymorphic study. Genotype distributions between categories were compared using the chi2 test; odds ratios (ORs) and 95% confidence interval were calculated to express the relative risk. GSTT1 null genotype was associated with 2.23-fold (p < 0.05) increased risk for HCC development as compared to the control group. However, GSTM1 null genotype was found to have a protective effect when hepatitis patients were considered. In case of mEPHX, R139R imposed a risk factor for HCC with both control (OR = 1.81) and chronic hepatitis-infected (OR = 2.06) subjects. Combination of heterozygous mutant genotypes at mEPHX exons 3 and 4 revealed a twofold risk (nonsignificant) for HCC. Further, combination of GSTM1 and T1 genotypes with either of exon 3 or 4 polymorphism of mEPHX displayed synergistic associations (risk or protective) for HCC development. GST and mEPHX variants share a positive association with viral-related HCC risk in Indian population, although a larger sample size is still required to confirm the results.