In human breast cancer cell lines, MCF-7 and MDA-MB-231, it has been shown that fangchinoline significantly inhibited the expression of cyclins D1, 3, and E, the kinase activities of CDK2, 4, and 6 (which are over-expressed in breast cancer) and increased the expression of cyclin-dependent kinase (CDK) inhibitors p21/WAF1, and p27/KIP1 [27,78]. This evidence concerns the gene CDK2 and breast cancer.