CDKN1A and breast carcinoma: EGR1 has also been shown to act as a TSG in several human tumors, including breast carcinomas and non-small cell lung cancer.27 Recently, Egr1 has been shown to be a direct transcriptional regulator of many known TSGs, e.g., Tp53, Cdkn1a/p21, Tgfb and Pten. 27