Therapeutic effect of palbociclib in chondrosarcoma: implication of cyclin-dependent kinase 4 as a potential target

BACKGROUND: Chondrosarcoma is a malignant cartilaginous neoplasm of the bone which resistant to radiation therapy and chemotherapy. Cyclin-dependent kinase 4 (CKD4) is highly expressed in human cancer, and palbociclib, the inhibitor of CDK4 has been used clinically under FDA approval for application in cancer therapeutic remedies. However, the level of CDK4 and the treatment possibility in chondrosarcoma require further exploration. Thus, we aim to investigate the level of CDK4 and accompanying therapeutic effects of palbociclib in chondrosarcoma. METHODS: We used immunohistochemistric analysis to evaluate human CDK4 productions in chondrosarcoma tissues. The inhibitory expression of CDK4 by siRNA or palbociclib on cell proliferation, invasion, migration, apoptosis and cycle arrest of chondrosarcoma were determined by MTT, wound healing, transwell and flow cytometry. CDK4/Rb signaling pathway were determined by western blot and Immunofluorescence assay. The inhibition effect of palbociclib on tumor growth within the bone were determined by bioluminescence imaging in vivo. RESULTS: CDK4 was found to express significantly in human chondrosarcoma samples. The enhanced levels of CDK4 were interlinked with malignant metastasis and undesirable prognosis of chondrosarcoma patients. CDK4 was also highly expressed in human chondrosarcoma cell lines and its inhibition by specific siRNA and palbociclib lead to a decrease in cell proliferation, accompanied by the phosphorylation of Rb. Furthermore, palbociclib also induced cell cycle arrest in G1 phase and decreased cell migration and invasion via CDK4/Rb signaling pathway. Administration of palbociclib in vivo could reduce tumor burden in chondrosarcoma. CONCLUSIONS: In summary, these data highlight CDK4 inhibitors, such as palbociclib, as potential promising therapeutics in the treatment of human chondrosarcoma.