PCNA and cancer: As a powerful antioxidant melatonin inhibits ROS-induced activation of extracellular-regulated protein kinases (ERKs) and Akt pathways which are involved in the cancer cell survivor; inactivation of ROS-dependent Akt signaling contributes to the down-regulation of cyclin D1, PCNA, and Bcl-2 and up-regulation of Bax in cancer cells [48].