Population attributable risks of esophageal and gastric cancers

Identification of genetic variants in base excision repair pathway and their associations with risk of esophageal squamous cell carcinoma

The etiology of esophageal squamous cell carcinoma (ESCC) has been shown to be associated with genetic and certain environmental factors that produce DNA damage. Base excision repair (BER) genes are responsible for repair of DNA damage caused by reactive oxygen species and other electrophiles and therefore are good candidate susceptibility genes for ESCC. We first screened eight BER genes for new and potential functional polymorphisms by resequencing 27 DNA samples. We then identified and genotyped for important tagging single nucleotide polymorphisms (SNPs) in a case-control study of 419 patients with newly diagnosed esophageal cancer and 480 healthy controls by frequency matching on age and sex. The association between genotypes and ESCC risk was estimated by unconditional multivariate logistic regression analysis, and stepwise regression procedure was used for constructing the final logistic regression model. We identified 129 SNPs in the eight BER genes, including 18 SNPs that cause amino acid changes. In the final model, 4 SNPs, including 2 in the coding regions (ADPRT Val762Ala and MBD4 Glu346Lys) and others in noncoding regions (LIG3 A3704G and XRCC1 T-77C), remained as significant predictors for the risk of ESCC. The adjusted odd ratios were 1.25 [95% confidence interval (CI) 1.02-1.53] for the ADPRT 762Ala allele, 1.25 (95% CI 1.02-1.53) for the MBD4 346 Lys allele, 0.78 (95% CI 0.63-0.97) for the LIG3 3704G allele, and 1.38 (95% CI 1.01-1.89) for the XRCC1-77C allele. In addition, we observed a significant gene-gene interaction between XRCC1 Gln399Arg and ADPRT Val762Ala. The results suggest that the polymorphisms in five BER genes may be associated with the susceptibility to ESCC in a Chinese population.

Polymorphisms of death pathway genes FAS and FASL in esophageal squamous-cell carcinoma

BACKGROUND

The FAS receptor-ligand system is a key regulator of apoptotic cell death, and loss of FAS expression and gain of FAS ligand (FASL) expression play important roles in the development and progression of cancer. Single-nucleotide polymorphisms in the promoter region of the FAS (G or A at position -1377 [FAS -1377G/A] and A or G at position -670 [FAS -670A/G]) and FASL (T or C at position -844 [FASL -844T/C]) genes alter the transcriptional activity of these genes. We examined the association between these polymorphisms and risk of the development and metastasis of esophageal squamous-cell carcinoma.

METHODS

Genotypes of 588 case patients with esophageal squamous-cell carcinoma and 648 control subjects were determined by polymerase chain reaction-based restriction fragment length polymorphism. Associations with the risk of esophageal squamous-cell carcinoma were estimated by logistic regression. All statistical tests were two-sided.

RESULTS

We observed a statistically significantly increased risk of esophageal squamous-cell carcinoma associated with the FAS -1377AA (odds ratio [OR] = 1.79, 95% confidence interval [CI] = 1.29 to 2.48; P<.001) or FAS -670GG (OR = 1.72, 95% CI = 1.26 to 2.34; P<.001) genotype, which are in strong linkage disequilibrium compared with the FAS -1377GA or GG or the FAS -670AG or AA genotype, respectively. An increased risk of esophageal squamous-cell carcinoma was also associated with the FASL -844CC genotype (OR = 2.06, 95% CI = 1.64 to 2.59; P<.001) compared with the FASL -844CT or TT genotype. Gene-gene interactions of FAS and FASL polymorphisms increased the risk of esophageal squamous-cell carcinoma in a multiplicative manner (OR for the presence of both FAS -1377AA and FASL -844CC genotypes = 4.55, 95% CI = 2.75 to 7.48; P =.001, test for homogeneity). Statistically significant interactions were found between these polymorphisms in FAS and FASL and tobacco smoking. None of the polymorphisms was associated with risk of differentiation or metastasis of esophageal squamous-cell carcinoma at diagnosis.

CONCLUSION

Genetic polymorphisms in the death pathway genes FAS and FASL appear to be associated with an increased risk of developing esophageal squamous-cell carcinoma.