Methylenetetrahydrofolate reductase (MTHFR) regulates the flow of folate groups between DNA synthesis and DNA methylation. A common C677T substitution (Ala222Val) in exon 4 of the MTHFR gene has been linked with the risk of colorectal cancer (CRC). To assess this risk in the Macedonian population, we conducted a case-control study of 413 randomly selected CRC patients and 185 controls without a clinical diagnosis of CRC. We found a statistically significant inverse association between the MTHFR T allele (35.35% for the patients and 41.35% for the controls) and the CRC risk [odds ratio (OR) 0.776; 95% confidence interval (95% CI) 0.603-0.997; p = 0.047). The prevalence of the MTHFR T allele is lower in patients with advanced CRC (Duke’ s stage C and D) and with microsatellite instable tumors (MSI+), indicating the inverse association with the CRC aggressiveness and MSI status. This effect seems to be independent of gender, age of onset and localization. We concluded that the MTHFR 677T allele is more likely to have a protective effect on CRC development and progression in the Macedonian population.

      Key words: Methylenetetrahydrofolate reductase (MTHFR); C677T polymorphism; Colorectal cancer (CRC)