Several reports have shown that various RB-deficient tumors are drug resistant.4, 5, 51 For instance, tamoxifen (TAM)-resistant breast cancer cells display stem cell-like traits and loss of RB function.4, 5 Statins can re-sensitize those TAM-resistant breast cancer cells to chemo-drugs.52, 53 Our work present here may provide a clue for exploring the mechanisms by which statins inhibit proliferation of TAM-resistant breast cancer cells or other chemo-drug-resistant tumor cells in the process of tumor therapy. This evidence concerns the gene RB1 and breast carcinoma.