TP53 and cancer: On the other hand, p53 mediates expression of the tumor suppressor cyclin-dependent kinase inhibitor 1A (CDKN1A/p21), which is a key mediator of p53-dependent cell cycle arrest after DNA damage, delays the onset of ferroptosis in response to cystine deprivation in cancer cells, and increases p53 expression by using the MDM2 inhibitor nutlin-3 that blocks erastin-induced ferroptosis in HT-1080 cells (58).