Overall, as statistical analysis have showed a significant correlation between p53 and BCL2 expression in leukemia cells (Sahu and Jena, 2011), we guess that up regulation of p53 expression after exposure with 5-AZA in turn led to the BCL2 down regulation, which finally triggered apoptosis in MOLT4 and Jurkat cells. The gene discussed is TP53; the disease is leukemia.