CDKN1A and breast cancer: To further examine the connection of P21 and P27 expression in breast cancer, patients from the Cancer Genome Atlas (TCGA) invasive breast carcinoma cancer study were examined to determine whether expressions of Cdkn1a (P21) and Cdkn1b (P27) genes were inhibited in breast cancer tumors (TCGA, Nature 2012) [26, 27].