CDKN1A and neoplasm: For instance, P53 directly suppresses the activity of dipeptidyl peptidase 4 (DPP4) and increases the expression of cyclin dependent kinase inhibitor 1A, also known as p21WAF1/Cip1 (CDKN1A/p21).64,65 These studies indicate that the interaction between ferroptosis and lipid metabolism contributes to P53-mediated tumor suppression.