In breast and lung cancers, treatment of cell lines with the demethylating agent 5-aza-2′-deoxycytidine led to the re-expression of S100A2 mRNA, indicating that the lack of S100A2 expression may be at least partially associated with aberrant methylation of the promoter region [7, 8, 9]. The gene discussed is S100A2; the disease is lung cancer.