TP53 may also suppress ferroptosis by directly inhibiting the enzymatic activity of membrane-bound glycoprotein dipeptidyl peptidase 4 (DPP4, also known as CD26)153 or by increasing the expression of cell-cycle regulator cyclin-dependent kinase inhibitor 1A (CDKN1A, also known as p21).154 This has been observed in some cancers, in particular colorectal carcinoma, suggesting a context-dependent role of TP53 in the regulation of ferroptosis.155 An African-specific coding region variant of TP53, namely Pro47Ser, also affects ferroptosis senstivity and tumor supression.156. This evidence concerns the gene CDKN1A and neoplasm.