C677T and A1298C MTHFR Polymorphisms and Fluoropyrimidine Effectiveness in Metastatic Colon Cancer

Fluoropyrimidines are the backbone of chemotherapy regimes used to treat metastatic colorectal cancer (CRC). These drugs act in different pathways of folate metabolism altering DNA synthesis mainly by inhibition of the tymidylate synthase. For this reaction the 5,10-methylenetetrahydrofolate acts as cofactor. It has been demonstrated that A1298C and C677T polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene result in reduced enzyme activity that leads to reduced availability of this important cofactor. Hence, we hypothesized that the presence of these polymorphisms are related to the efficacy and toxicity of fluoropyrimidines in patients with CRC.