CDKN1A and breast cancer: TQ induces G0/G1 cell cycle arrest, increases the expression of p16, decreases the expression of cyclin D1 protein in DMBA-initiated TPA-promoted skin tumors in mice, inactivates CHEK1, and contributes to apoptosis in colorectal cancer cells [224,225], as well as inducing G1 phase cell cycle arrest in human breast cancer, colon cancer, and osteosarcoma cells through inhibiting the activation of cyclin E or cyclin D and upregulating p27 and p21, a cyclin-dependent kinase (Cdk) inhibitor [222].