Association between MTHFR polymorphism (C677T) with nonfamilial colorectal cancer

The enzyme 5,10-methylene-tetrahydrofolate reductase (MTHFR) is linked to DNA methylation, synthesis, and repair. C677T is one of the most important polymorphisms in the MTHFR gene. The single nucleotide polymorphism C677T has been found to be associated with decreased enzyme activity and plasma folate, and thus may play a crucial role in the etiology of colorectal cancer. This decrease was observable in people with either high or low folate status. We aimed to test the hypothesis that the C677T genotype is involved in colorectal cancer. Using pyrosequencing, we analyzed the MTHFR genotypes in 234 colorectal cancer patients and 257 matched controls. We examined the polymorphisms in MTHFR and folate intake in relation to risk of colon cancer in an Iranian population-based case-control study. Our finding revealed that the CC, CT, and TT genotypes of MTHFR among the colorectal cancer patients were 50%, 29.1%, and 20.9%, respectively. On the other hand, we could find 29.5% of 677CC, 46% of 677CT and 24.5% of 677TT in the controls. A decreased risk of colon cancer for participants with wild-type genotype was observed. Interestingly, this association was stronger at higher levels of folate intake. Our study corroborates previous findings of an inverse association of the MTHFR 677TT genotype with colorectal cancer, in particular at high levels of folate.