BCL2 and cancer: P53 is a key tumor suppressor that plays an irreplaceable role in cancer prevention and development [86], Stimuli such as DNA damage, hypoxia and expression of certain oncoproteins (e.g. Myc, Ras) activate the p53 signaling pathway, which in turn activates pro-apoptotic factors (e.g. Bax) in its downstream targets while inhibiting anti-apoptotic factors (e.g. Bcl-2) to induce apoptosis in cancer cells.