TP53 and cancer: The ROS-mediated mitochondrial pathway of apoptosis in Y2O3NPs treated A-431 cancer cells was further confirmed through the noticed significant increases in the expression of the apoptotic gene p53 in conjunction with significant decreases in the expression of the anti-apoptotic gene Bcl2 because overexpression of the tumor suppressor p53 gene also stimulate apoptosis through direct interaction with the anti-apoptotic Bcl-2 genes leading to mitochondrial membrane depolarization and increasing the release of apoptotic signals.