p53 functions mainly as a transcription factor, promoting the expression of p21Cip1 protein (encoded by the cdkn1a gene) to inhibit the cyclin–CDK complex and cause cell cycle arrest [14,15], as well as stimulating the expression of bax, noxa, and puma to lead to cancer cell apoptosis [16,17,18,19]. Here, CDKN1A is linked to cancer.