Anin vitro study with MOLT-4 ALL cells showed that knocking down TPMT expression did not affect sensitivity to 6MP, and that increasing the 6MMP to 6TGN ratio in the MOLT-4 ALL cell line by adding S-adenosylmethionine (SAM) decreases cytotoxicity of 6MP15,16. Here, TPMT is linked to acute lymphoblastic leukemia.