Overexpression of EZH2 is associated with the poor prognosis in osteosarcoma and function analysis indicates a therapeutic potential
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Ranran Sun1,2, Jacson Shen2, Yan Gao2, Yubing Zhou1, Zujiang Yu1, Francis Hornicek2, Quancheng Kan1, Zhenfeng Duan1,2
1Department of Infectious Diseases, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People’s Republic of China
2Sarcoma Biology Laboratory, Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Boston, MA, 02114, USA
Quancheng Kan, email: [email protected]
Zhenfeng Duan, email: [email protected]
Keywords: osteosarcoma, EZH2, tissue microarray, proliferation, apoptosis
Received: January 15, 2016 Accepted: May 08, 2016 Published: May 20, 2016
Osteosarcoma is a primary malignant bone tumor that has a poor prognosis due to local recurrence, metastasis, and chemotherapy resistance. Therefore, there is an urgent need to develop novel potential therapeutic targets for osteosarcoma. Enhancer of zeste homologue 2 (EZH2) is a member of the polycomb group of proteins, which has important functions in epigenetic silencing and cell cycle regulation. Overexpression of EZH2 has been found in several malignancies, however, its expression and the role of EZH2 in osteosarcoma is largely unknown. In this study, we examined EZH2 expression by immunohistochemistry in a large series of osteosarcoma tissues in association with tumor characteristics and patient outcomes. EZH2 expression was also analyzed in a microarray dataset of osteosarcoma. Results showed that higher expression of EZH2 was significantly associated with more aggressive tumor behavior and poor patient outcomes of osteosarcoma. We subsequently investigated the functional and therapeutic relevance of EZH2 as a target in osteosarcoma. Immunohistochemical analysis indicated that EZH2 expression was significantly associated with more aggressive tumor behavior and poorer patient outcomes of osteosarcoma. EZH2 silencing by siRNA inhibited osteosarcoma cell growth, proliferation, migration, and invasion. Moreover, suppression of EZH2 attenuated cancer stem cell functions. Similar results were observed in osteosarcoma cells treated with EZH2 specific inhibitor 3-deazaneplanocin A (DZNep), which exhausted cellular levels of EZH2. These results suggest that EZH2 is critical for the growth and metastasis of osteosarcoma, and an epigenetic therapy that pharmacologically targets EZH2 via specific inhibitors may constitute a novel approach to the treatment of osteosarcoma.
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