ODC1 and neoplasm: Inhibition of polyamine synthesis by DL-α-difluoromethylornithine (DFMO), an inhibitor of ODC that catalyzes the first rate-limiting step in polyamine biosynthesis, with or without methylglyoxal-bis-guanylhydrazone (MGBG), an inhibitor of S-Adenosylmethionine (SAM) that is required for polyamine synthesis, successfully suppressed tumor growth and prolonged survival of tumor-bearing animals [43-46].