In 2019, Cheng et al. (2019) indicated that icariin can significantly downregulate CDK2, CDK4, cyclin D1, and Bcl-2 and upregulate cleaved caspase-3 and PARP, thereby inducing apoptosis of the tamoxifen-resistant MCF-7/TAM BC cell line. This evidence concerns the gene CCND1 and breast cancer.