Epigenetic gene silencing of tumor suppresser genes through promoter DNA hypermethylation is a common feature in human cancers, whereas cancer-specific methylation is a relatively rare event.[4,5] We have developed pharmacologic reversal of epigenetic silencing and thereby uncovered a myriad of transcriptionally repressed genes in human cancers.[6] Using this technique, we have identified novel tumor suppressor gene candidates including the cysteine dioxygenase type1 (CDO1) gene. The gene discussed is CDO1; the disease is cancer.