Genetic variations in the SMAD4 gene and gastric cancer susceptibility

AIM: To explore the association between mothers against decapentaplegic homolog 4 (SMAD4) gene polymorphisms and gastric cancer risk. METHODS: Five tagging single nucleotide polymorphisms (tSNPs) in the SMAD4 gene were selected and genotyped in 322 gastric cancer cases and 351 cancer-free controls in a Chinese population by using the polymerase chain reactionrestriction fragment length polymorphism method. Immunohistochemistry was used to examine SMAD4 protein expression in 10 normal gastric tissues adjacent to tumors. RESULTS: In the single-locus analysis, two significantly decreased risk polymorphisms for gastric cancer were observed: the SNP3 rs17663887 TC genotype (adjusted odds ratio = 0.38, 95% confidence interval: 0.21-0.71), compared with the wild-type TT genotype and the SNP5 rs12456284 GG genotype (0.31, 0.16-0.60), and with the wild-type AA genotype. In the combined analyses of these two tSNPs, the combined genotypes with 2-3 protective alleles (SNP3 C and SNP5 G allele) had a significantly decreased risk of gastric cancer (0.28, 0.16-0.49) than those with 0-1 protective allele. Furthermore, individuals with 0-1 protective allele had significantly decreased SMAD4 protein expression levels in the normal tissues adjacent to tumors than those with 2-3 protective alleles (P = 0.025). CONCLUSION: These results suggest that genetic variants in the SMAD4 gene play a protective role in gastric cancer in a Chinese population. (C) 2010 Baishideng. All rights reserved.