ODC1 and lip and oral cavity carcinoma: ODC1 is linked to methyl group metabolism by the observation that interference with ODC1 enzyme activity results in accumulation of SAH and decarboxylated S-adenosylmethionine (dcSAM), which likewise acts as a competitive inhibitor of methylation reactions, resulting in genome-wide DNA demethylation, as shown e.g. in human oral cancer cells35,36.