Whether normal or malignant, cells possess within their repertoire of epigenetic programs the ability to undergo a process of cellular suicide, termed programmed cell death. This programmed cell death process involves an epigenetic reprogramming of the cell that results in an energy-dependent cascade of biochemical and morphologic changes within the cell (also termed apoptosis), resulting in its death and elimination. Activation of programmed cell death is controlled by a series of endogenous cell-type-specific signals. In addition, various exogenous cell-damaging treatments (eg, radiation, chemicals, and viruses) can activate this pathway if sufficient injury to the cell occurs.