CCND1 and breast cancer: After that, both the DR-BC and DS-BC cells were stimulated by high-dose Dox, and the results showed that Dox downregulated cyclin D1 and CDK2 to inhibit cell proliferation and viability, and induced apoptotic cell death in DS-BC cells, instead of DR-BC cells, indicating that the DR-BC cells were successfully established, and the DR-BC cells generated in this study behaved in similar ways to that DR-cells generated in the previous studies [32, 33].