PARP1 and cancer: Melatonin inhibits cancer cell growth by increasing cell cycle arrest in the G2/M phase, which this effect is coincident with the induction of apoptosis through up-regulating the expression of p53, p21, caspase-3/8/9, PARP, cytochrome c, Bax, JNK 1,-2 and -3 and p38 MAPKs in cancer cells [115].