Promising new treatments are being established and explored for the treatment of HR+ BC, including inhibitors of critical oncoproteins in the cell-cycle pathways (e.g., CDK4/6 inhibitors) and also in the PI3K-AKT-mTOR pathways, including isoform-specific PI3K inhibitor and mTORC1 inhibitor. This evidence concerns the gene CDK4 and breast cancer.