The CDK4/6 inhibitors (which block the activity of the cyclin-dependent kinases 4 and 6, which play a role in the regulation of the cell cycle) [6], HER2 inhibitors (which block the activity of the HER2 protein, which is overexpressed in some types of BC) [7], and luteinizing hormone-releasing hormone (LHRH) agonists (a class of drugs that lower estrogen levels by inhibiting the production of luteinizing hormone, which is needed for the ovaries to produce estrogen) [8] also have found a place in BC therapy. This evidence concerns the gene CDK4 and breast cancer.