SHMT1 and lung carcinoma: Folate genes implicated in lung cancer risk include methylenetetrahydrofolate reductase (MTHFR) [7]; thymidylate synthase (TYMS) [10], [15]; serine hydroxymethyltransferase 1 (SHMT1) [11]; and cystathionine β-synthase (CBS) [8].