Distributions of MTHFR Gene Polymorphism according to the Location of Colon Cancer

Kim, Jong Woo; Oh, Doyeun; Chong, So Young; Yim, Dong Jin; Kim, Jin Kyeoung; Kim, Nam Keun

Abstract

PURPOSE: Colon carcinogenesis seems to vary according to the original location of tumor, especially theright and the left sides. Two common methylenetetrahydrofolate reductase (MTHFR) polymorphisms, 677C->T and 1298A->C, are now known. Especially, the TT type of the 677C->T mutation shows reduced catalytic activity at a rate 30% that of wild type. The aim of this study is to investigate the distributions of MTHFR polymorphisms of 677C->T and 1298A->C according to the location of the colon cancer.
METHODS
Blood samples were collected from 112 patients diagnosed in our hospital, as having colon cancer: 34 proximal and 78 distal cases to the splenic flexure and 448 healthy control subjects. In order to characterize MTHFR polymorphisms, we applied the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).
RESULTS
The distributions of MTHFR 677C->T polymorphisms as genotypes CC, CT, and TT were 32.4%, 53.1%, and 14.5% in the control group, and 34.8%, 58.0%, and 7.1% in the cancer group (P=0.056). In the 34 proximal cancers, the CC, CT, and TT distributions were 44.1%, 55.9%, and 0% (P<0.05), respectively. In the distal group, they were 30.8%, 59.0%, and 10.3%. The distributions of the MTHFR 1298 A->C polymorphism by genotypes, AA, AC, CC were 69.6%, 28.6%, and 1.8% in the control group, and 58.9%, 38.4%, and 2.7% in the cancer group. The proximal and the distal groups show genotype distributions of 44.1%, 53.0%, and 2.9% and 65.4%, 32.0%, and 2.6%, respectively, but the differences were not statistically significant.
CONCLUSIONS
There are no definite differences between control subjects and colon-cancer patients in the two polymorphisms 677C->T and 1298A->C. However, the TT genotype shows a lower frequency in the cancer group than in the control group with a marginal statistical value (P=0.056), which suggest a reduced risk of cancer incidence for this type, compared with a CC or a CT type.