Furthermore, damage to mitochondrial membrane potential leads to the release of cytochrome c from mitochondria to the cytoplasm, further leading to the activation of two caspase systems called caspase 3 and caspase 9; caspase-3 further triggers proteolytic cleavage of one of its substrates called PARP which induces the activation of apoptosis in cancer cells in a mitochondrial-induced pathway (Li and Dewson, 2015; Zhao et al., 2015; Shen et al., 2016). The gene discussed is PARP1; the disease is cancer.