MTHFR 677C>T genotype and folate status were generally not associated with DNA methylation in the colon of a folate-replete population without neoplasia.
In the tumour sites subgroup analysis, only the protective effects of Leu84Phe polymorphism were found in colorectal cancer, under CT versus CC comparison.
We observed a positive association between the PARP codon 940 Lys/Arg and Arg/Arg genotypes and colorectal cancer risk [odds ratio (OR), 1.8; 95% confidence interval (95% CI), 1.1-3.1], and an inverse association between the MGMT codon 84 Leu/Phe or Phe/Phe genotypes and colon cancer risk (OR, 0.6; 95% CI, 0.3-0.9), but not rectal cancer (test of heterogeneity by tumor site, P=0.027).
Dietary folate intake in combination with MTHFR C677T genotype and promoter methylation of tumor suppressor and DNA repair genes in sporadic colorectal adenomas.
Our main finding is that the presence of only the A allele at the rs34180180 SNP in the tumor was significantly associated with shorter OS, independently of the MGMT methylation status.