MTHFD1 is an enzyme involved in folate metabolism [115,116,117], and although it was reported as a potential stem cell marker by Maguire et al. and Bhattacharya et al. [51,118], there is no other knowledge in regard to its role in stem cell pluripotency, while its polymorphisms have been associated with therapeutic response to methotrexate in childhood acute lymphoblastic leukemia [119,120,121]. This evidence concerns the gene MTHFD1 and acute lymphoblastic leukemia.