SHMT1 1420 and MTHFR 677 variants are associated with rectal but not colon cancer.

BMC Cancer 10(1):525 (2010) PMID 20920350

ABSTRACT: BACKGROUND: Association between rectal or colon cancer risk and serine hydroxymethyltransferase 1 (SHMT1) C1420T or methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms was assessed. The serum total homocysteine (HCY), marker of folate metabolism was also investigated. METHODS: The SHMT1 and MTHFR genotypes were determined by real-time PCR and PCR-RFLP, respectively in 476 patients with rectal, 479 patients with colon cancer and in 461 and 478, respective controls matched for age and sex. Homocysteine levels were determined by HPLC kit. The association between polymorphisms and cancer risk was evaluated by logistic regression analysis adjusted for age, sex and body mass index. The population stratification bias was also estimated. RESULTS: There was no association of genotypes or diplotypes with colon cancer. The rectal cancer risk was significantly lower for SHMT1 TT (OR=0.57, 95% confidence interval (CI) 0.36-0.89) and higher for MTHFR CT genotypes (OR=1.4, 95%CI 1.06-1.84). A gene-dosage effect was observed for SHMT1 with progressively decreasing risk with increasing number of T allele (p=0.014). The stratified analysis according to age and sex revealed that the association is mainly present in the younger ( stage C and D. Further studies need to clarify why SHMT1 and MTHFR polymorphisms are associated only with rectal and not colon cancer risk.