DNMT1 and neoplasm: In addition, preclinical studies have verified that drugs targeting the DNMT action substrate (azacitidine) and the DNMT cofactor SAM (sinefungin) as well as the anti-SAM metabolite neplanosin, and the non-competitive non-nucleotide transmethylase inhibitor procainamide can reverse the abnormal methylation in tumour cells, re-express the inactivated genes, and suppress cancer cell proliferation and invasion [39–41].