All the mechanisms involved in resistance are mainly studied in breast cancer, but there are also Melanoma, Non-Small Cell Lung Cancer, Rhabdomyosarcoma, Glioblastoma, Gastric Cancer, Canine Lymphoma cells, Prostate, Glioblastoma, Which Remind us that CDK4/6i are being widely studied and applied in various fields. Here, CDK4 is linked to breast cancer.