p16 gene silencing along with p53 single-nucleotide polymorphism and risk of esophageal cancer in Northeast India.

The high incidence of esophageal cancer in Northeast India and the unique ethnic background and dietary habits provide a great opportunity to study the molecular genetics behind esophageal squamous cell carcinoma in this part of the region. We hypothesized that in addition to currently known environmental risk factors for esophageal cancer, genetic and epigenetic factors are also involved in esophageal carcinogenesis in Northeast India. Therefore, in this study, we explored the possible association between the two important G1 cell cycle regulatory genes p16 and p53 and environmental risk factors and risk of esophageal carcinogenesis. A total of 100 newly diagnosed esophageal cancer cases along with equal number of age-, sex-, and ethnicity-matched controls were included in this study. Methylation-specific polymerase chain reaction was used to determine the p16 promoter methylation status. Single-nucleotide polymorphism at codon 72 of p53 gene was assessed by the polymerase chain reaction-restriction fragment length polymorphism method. Aberrant methylation of p16 gene was seen in 81% of esophageal cancer cases. Hypermethylation of p16 gene was not found in healthy controls. p53 Pro/Pro genotype was found to be a risk genotype in Northeast India compared with Arg/Pro and Arg/Arg. p53 variant/polymorphism was significantly associated with esophageal cancer risk in the study population under all three genetic models, namely, dominant model (Arg/Pro + Pro/Pro vs Arg/Arg odds ratio = 2.25, confidence interval = 1.19-4.26; p = 0.012), recessive model (Arg/Arg + Arg/Pro vs Pro/Pro odds ratio = 2.35, confidence interval = 1.24-4.44; p = 0.008), and homozygous model (Pro/Pro vs Arg/Arg odds ratio = 3.33, confidence interval = 1.54-7.20; p = 0.002). However, p53 variant/polymorphism was not statistically associated with esophageal cancer risk under the heterozygous model (Pro/Pro vs Arg/Pro). In the case-only analysis based on p16 methylation, the p53 variant/polymorphism (Pro/Pro or Arg/Pro) showed significant association for esophageal cancer risk (odds ratio = 3.33, confidence interval = 1.54-7.20; p = 0.002). Gene-gene and gene-environment interaction using the case-only approach revealed a strong association between p16 methylation, p53 single-nucleotide polymorphism, and environmental factors and esophageal cancer risk. Cases with p16 methylation and p53 variant/polymorphism (Pro/Pro or Arg/Pro) along with both betel quid and tobacco chewing habit (odds ratio = 8.29, confidence interval = 1.14-60.23; p = 0.037) conferred eightfold increased risk toward esophageal cancer development. This study reveals a synergistic interaction between epigenetic, genetic, and environmental factors and risk of esophageal cancer in this high-incidence region of Northeast India. The inactivation of either p16 or p53 in a majority of esophageal cancer cases in this study suggests the possible crosstalk between the important cell cycle genes.

p16 hypermethylation: a biomarker for increased esophageal cancer susceptibility in high incidence region of North East India.

Esophageal cancer is one of the most common cancers in North East India. The molecular mechanisms of esophageal cancer susceptibility in North East India have not been fully understood. There is a need for identification of biomarkers to identify people at risk of esophageal cancer. p16 is an essential G1 cell cycle regulatory gene whose loss of function is associated with carcinogenesis. Therefore, we conducted this study to determine the prevalence of p16 gene methylation in patients with esophageal cancer to assess the feasibility of using gene methylation as a biomarker. A total of 100 newly diagnosed esophageal cancer cases along with equal number of age, sex, and ethnicity-matched controls were included in this study. Methylation-specific PCR was used to determine the p16 methylation status. Aberrant promoter methylation of the p16 gene was detected in 81 of 100 (81%) esophageal cancer cases. Hypermethylation of p16 gene was found to be influenced by lifestyle factors. Betel quid and tobacco chewing habit synergistically with p16 methylation elevated the risk for esophageal cancer development (adjusted odds ratio (OR) = 6.88, 95% confidence interval (CI) = 1.64-28.81, p = 0.003 for betel quid chewing and adjusted OR = 7.02, 95% CI = 1.87-26.38, p = 0.001 for tobacco chewing). Further, intake of green leafy vegetables and fruits lowered the risk of esophageal cancer (adjusted OR = 0.16, 95 % CI = 0.04-0.58, p = 0.05 for green leafy vegetables and adjusted OR = 0.15, 95% CI = 0.04-0.64, p = 0.01 for fruits). Thus, p16 hypermethylation may aid as a biomarker in identifying habitués at greater risk for esophageal cancer susceptibility in high incidence region of North East India.

Promoter methylation of MGMT gene in serum of patients with esophageal squamous cell carcinoma in North East India.

BACKGROUND: Promoter hypermethylation is a common event in human cancer. O6-methylguanine-DNA methyltransferase (MGMT) is a gene involved in DNA repair, which is methylated in a variety of cancers. We aimed to explore the methylation status of MGMT gene among the North Eastern population where esophageal cancer incidence and exposure to carcinogens like nitrosamines is high. MATERIALS AND METHODS: A total of 100 newly diagnosed esophageal cancer cases along with equal number of age, sex and ethnicity matched controls were included in this study. Methylation specific PCR was used to determine the MGMT methylation status in serum samples. RESULTS: Aberrant promoter methylation of the MGMT gene was detected in 70% of esophageal cancer cases. Hypermethylation of MGMT gene was found to be influenced by environmental factors like betel quid and tobacco which contain potent carcinogens like nitrosamines. Tobacco chewing and tobacco smoking habit synergistically with MGMT methylation elevated the risk for esophageal cancer development [adjusted OR=5.02, 95% CI=1.35-18.74; p=0.010 for tobacco chewing and Adjusted OR=3.00, 95% CI=1.22-7.36; p=0.014 for tobacco smoking]. CONCLUSIONS: Results suggest that the DNA hypermethylation of MGMT is an important mechanism for MGMT gene silencing resulting in esophageal cancer development and is influenced by the environmental factors. Thus MGMT hypermethylation can be used as a biomarker for esophageal cancer in high incidence region of North East India.

Role of household exposure, dietary habits and glutathione S-Transferases M1, T1 polymorphisms in susceptibility to lung cancer among women in Mizoram India.

BACKGROUND: A case-control study was conducted to evaluate the effect of household exposure, dietary habits, smoking and Glutathione S-Transferases M1, T1 polymorphisms on lung cancer among women in Mizoram, India. MATERIALS AND METHODS: We selected 230 newly diagnosed primary lung cases and 460 controls from women in Mizoram. Multivariate logistic regression analysis was performed to estimate adjusted odds ratio (OR). RESULTS: Exposure of cooking oil fumes (p<0.003), wood as heating source for cooking (p=0.004), kitchen inside living room (p=0.001), improper ventilated house (p=0.003), roasting of soda in kitchen (p=0.001), current smokers of tobacco (p=0.043), intake of smoked fish (p=0.006), smoked meat (p=0.001), Soda (p<0.001) and GSTM1 null genotype (p=0.003) were significantly associated with increased risk of lung cancer among women in Mizoram. Significantly protective effect was observed for intake of bamboo shoots (p=<0.001) and egg (p<0.001). A clear increase in dose response gradient was observed for total cooking dish years. Risk for lung cancer tends to increase with collegial effect of indoor environmental sources (p=0.022). Significant correlation was also observed for interaction of GST polymorphisms with some of dietary habits. CONCLUSIONS: We confirmed the important role of exposure of cooking oil emission and wood smoke, intake of smoked meat, smoked fish and soda (an alkali preparation used as food additives in Mizoram) and tobacco consumption for increase risk of lung cancer among Women in Mizoram.

Interaction of XRCC1 and XPD gene polymorphisms with lifestyle and environmental factors regarding susceptibility to lung cancer in a high incidence population in North East India.

BACKGROUND: This study aimed to explore the role of XRCC1 (Arg399Gln) and XPD (Lys751Gln) gene polymorphisms, lifestyle and environmental factors as well as their possible interactions in propensity to develop lung cancer in a population with high incidence from North East India. MATERIALS AND METHODS: A total of 272 lung cancer cases and 544 controls were collected and XRCC1 (Arg399Gln) and XPD (Lys751Gln) genotypes were analyzed using a polymerase chain reaction based restriction fragment length polymorphism assay. Conditional multiple logistic regression analysis was used to calculate adjusted odds ratios and 95% confidence intervals after adjusting for confounding factors. RESULTS: The combined Gln/Gln genotype of XRCC1 and XPD genes (OR=2.78, CI=1.05-7.38; p=0.040) was significantly associated with increased risk for lung cancer. Interaction of XRCC1Gln/Gln genotype with exposure of wood combustion (OR=2.56, CI=1.16-5.66; p=0.020), exposure of cooking oil fumes (OR=3.45, CI=1.39-8.58; p=0.008) and tobacco smoking (OR=2.54, CI=1.21-5.32; p=0.014) and interaction of XPD with betel quid chewing (OR=2.31, CI=1.23-4.32; p=0.009) and tobacco smoking (OR=2.13, CI=1.12-4.05; p=0.022) were found to be significantly associated with increased risk for lung cancer. CONCLUSIONS: Gln/Gln alleles of both XRCC1 and XPD genes appear to amplify the effects of household exposure, smoking and betel quid chewing on lung cancer risk in the study population.

Association of a p53 codon 72 gene polymorphism with environmental factors and risk of lung cancer: a case control study in Mizoram and Manipur, a high incidence region in North East India.

BACKGROUND: A very high incidence of lung cancer is observed in Mizoram and Manipur, North East India. We conducted a population based case control study to establish associations of p53 codon 72 polymorphisms and interactions with environmental factors for this high incidence. MATERIAL AND METHODS: A total of 272 lung cancer cases and 544 controls matched for age (±5 years), sex and ethnicity were collected and p53 codon 72 polymorphism genotypes were analyzed using a polymerase chain based restriction fragment length polymorphism assay. We used conditional multiple logistic regression analysis to calculate adjusted odds ratios and 95% confidence intervals after adjusting for confounding factors. RESULTS: p53 Pro/Pro genotype was significantly associated with increased risk of lung cancer in the study population (adjusted OR=2.14, CI=1.35-3.38, p=0.001). Interactions of the p53 Pro/Pro genotype with exposure to wood smoke (adjusted OR=3.60, CI=1.85-6.98, p<0.001) and cooking oil fumes (adjusted OR=3.27, CI=1.55-6.87, p=0.002), betel quid chewing (adjusted OR=3.85, CI=1.96- 7.55, p<0.001), tobacco smoking (adjusted OR=4.42, CI=2.27-8.63, p<0.001) and alcohol consumption (adjusted OR=3.31, CI=1.10-10.03, p=0.034) were significant regarding the increased risk of lung cancer in the study population. CONCLUSIONS: The present study provided preliminary evidence that a p53 codon 72 polymorphism may effect lung cancer risk in the study population, interacting synergistically with environmental factors.

Interaction of tobacco smoking and chewing with Angiotensin converting enzyme (insertion/deletion) gene polymorphisms and risk of lung cancer in a high risk area from northeast India.

BACKGROUND: Association of angiotensin converting enzyme (ACE) gene polymorphisms with lung cancer susceptibility remains uncertain and varies with ethnicity. Northeast India represents a geographically, culturally, and ethnically isolated population. The area reports an especially high rate of tobacco usage in a variety of ways of consumption, compared with the rest of the Indian population. MATERIALS AND METHODS: We conducted a population based case control study in two major high risk region for lung cancer from Northeast India. A total of 151 consecutive lung cancer cases diagnosed histopathologically and equal numbers of controls were recruited with record of relevant sociodemographic information. Blood samples were collected and processed to identify ACE gene polymorphism. RESULTS: Significantly higher (40.4 % vs 29.1%, OR=1.97, CI=1.04-3.72; p=0.037) prevalence of the ACE II genotype was observed among lung cancer cases. Smoking was significantly associated with increased risk of lung cancer (OR=1.70, CI=1.02-2.81; p=0.041). An enhanced risk was also observed for interaction of ACE II genotype with tobacco smoking (OR=4.09, CI=1.51-11.05; p=0.005) and chewing (OR=3.68, CI=1.22-11.13; p=0.021). CONCLUSIONS: The present study indicates significant association s of the ACE II genotype with lung cancer in high risk Northeast India.