CDK4 and breast cancer: The combination of CDK4/6 inhibitors and endocrine therapy substantially improves the survival outcomes of patients with advanced HR+/HER2− breast cancer, the emergence of drug resistance limits their clinical efficacy.[26] Therefore, identifying the biomarkers for predicting efficacy and exploring the molecular basis of resistance to the combination of CDK4/6 inhibitors plus endocrine therapy is crucial for screening patients who may not benefit from the therapy and providing more effective alternative treatments.