Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, effectively halting the cell cycle and slowing cancer cell growth by preventing CDK4/6 from binding to cyclin D and stopping the phosphorylation of the retinoblastoma protein, combined endocrine therapy have made significant survival improvement in HR-positive, HER2-negative ABC [14]. This evidence concerns the gene CDK4 and cancer.