title: The Role of CDK4/6 Inhibition in Breast Cancer.
abstract: Imbalance of the cyclin D and cyclin-dependent kinase (CDK) pathway in cancer cells may result in diversion away from a pathway to senescence and toward a more proliferative phenotype. Cancer cells may increase cyclin D-dependent activity through a variety of mechanisms. Therapeutic inhibition of CDKs in tumors to negate their evasion of growth suppressors has been identified as a key anticancer strategy. In this review, we outline the development of CDK inhibitory therapy in breast cancer, including the initial experience with the pan-CDK inhibitor flavopiridol and the next generation of oral highly selective CDK4 and CDK6 inhibitors PD0332991 (palbociclib), LEE011 (ribociclib), and LY2835219 (abemaciclib). Data from phase I and II studies in estrogen receptor-positive (ER+) breast cancer demonstrate promising efficacy with manageable toxic effects, chiefly neutropenia. We discuss these studies and the phase III studies that are accruing or nearing completion. We describe the application of such therapy to other breast cancer settings, including HER2-positive breast cancer and the adjuvant treatment of early breast cancer. We also discuss potential concerns surrounding the combination of CDK inhibitors with chemotherapy and their effects on repair of double-strand DNA breaks in cancer cells. Oral highly selective CDK inhibitors show great promise in improving the outcomes of patients with ER+ breast cancer, although caution must apply to their combination with other agents and in the early breast cancer setting.
authors: Department of Medical Oncology, Bon Secours Hospital, Cork, Ireland; Breast Medicine Service, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University, New York, New York, USA cgmurphy@bonsecours.ie.
authors: Conleth G
authors: CG
authors: Murphy
authors: Department of Medical Oncology, Bon Secours Hospital, Cork, Ireland; Breast Medicine Service, Memorial Sloan Kettering Cancer Center, Weill Medical College of Cornell University, New York, New York, USA.
authors: Maura N
authors: MN
authors: Dickler
mesh_terms: D000631:Aminopyridines / Q000008:administration & dosage; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D002986:Clinical Trials as Topic; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors / Q000235:genetics*; D051361:Cyclin-Dependent Kinase 6 / Q000037:antagonists & inhibitors / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D047628:Estrogen Receptor alpha / Q000235:genetics; D005260:Female; D005419:Flavonoids / Q000008:administration & dosage; D006801:Humans; D010879:Piperazines / Q000008:administration & dosage; D010880:Piperidines / Q000008:administration & dosage; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D011687:Purines / Q000008:administration & dosage; D011725:Pyridines / Q000008:administration & dosage
chemical_list: D000631:Aminopyridines; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D005419:Flavonoids; D010879:Piperazines; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011687:Purines; D011725:Pyridines; C077990:alvocidib; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; C500026:palbociclib; C000589651:ribociclib
keywords: Abemaciclib; Breast neoplasms; Flavopiridol; Inhibitors of cyclin-dependent kinase 4 proteins; LEE011; Palbociclib