We previously showed that simvastatin, an agent for the treatment of hypercholesterolemia16, 17, reduces the expression of MCM7 and causes a significant upregulation of γH2AX expression; therefore, we proposed that simvastatin may cause DNA damage in tamoxifen-resistant breast cancer cells in which p-Rb expression is low via downregulation of MCM7. The gene discussed is RB1; the disease is breast cancer.