MTHFR and neoplasm: Polymorphisms on the gene encoding the methylenetetrahydrofolate reductase (MTHFR) enzyme, which plays a key role in the folate-mediated one-carbon metabolism, also affects proliferation rates and disease progression, as tumor cells frequently rely on the folate metabolism as a major source of one-carbon units for anabolic processes, nucleic acid synthesis and DNA methylation [13, 21–26].