MTHFR and colorectal neoplasm: Mutations in the relevant sites of MTHFR gene can result in a decrease in the enzyme activity of the MTHFR protein, leading to a deficiency of methylenetetrahydrofolate, which can eventually lead to a decrease in the degree of DNA methylation and microsatellite instability, and ultimately can induce colorectal neoplasm [2, 3, 17].