MTHFR and leukemia: On the other hand, the mechanism proposed to explain the reduced risk of leukemia[23], colorectal carcinoma[58] and other neoplasias is that impaired MTHFR activity, because of polymorphic variation, leads to an accumulation of cytosolic 5,10-methylene THF available for purine and pyrimidine synthesis, thus a lower incorporation of uracil into DNA and a lower cancer risk (Additional file 1: Figure S1).