We found that the expression levels SHMT2, PSAT1, PHGDH, PSPH, CBS, DAO, MAOA, AOC2, GNMT, PIPOX, ALAS2, AOC3 and MAOB were significantly increased in colon cancer tissues compared with those in normal tissues (Supplemental Fig. 2B). Here, PIPOX is linked to malignant colon neoplasm.