Clinical and biological significance of EZH2 expression in endometrial cancer.

The objective of this study was to examine the clinical significance of EZH2 expression and the therapeutic efficacy of its silencing in endometrial cancer. EZH2 expression in clinical samples was evaluated using a tissue microarray and correlated with clinical outcomes. The biological roles of EZH2 were assayed in vitro and in vivo. Gene expression was examined to reveal the molecular mechanism underlying the roles of EZH2 in endometrial cancer. We found that EZH2 overexpression was significantly correlated with disease-free and overall survival of patients with endometrial cancer. EZH2 silencing resulted in decreased cell viability and invasiveness, and increased apoptosis. In addition, EZH2 silencing enhanced the cytotoxicity of taxanes and cisplatin in Hec-1A and Ishikawa endometrial cancer cells. EZH2 silencing using small-interfering RNA (siRNA) incorporated into chitosan nanoparticles (siRNA/CN) induced a significant anti-tumor effect compared with that observed in controls (66.6% reduction in Hec-1A cells and 63.2% reduction in Ishikawa cells, p < .05 for both). Moreover, EZH2 siRNA/CN in combination with taxanes produced more robust anti-tumor effects versus those induced by monotherapies (77.0% for Hec-1A cells and 57.7% for Ishikawa cells, p < .05 for both). These results were associated with decreased angiogenesis and cell proliferation, and enhanced apoptosis. Genomic analyses revealed that EZH2 silencing decreased the expression levels of many genes associated with tumor growth, including PRDX6. Collectively, these results support EZH2 as an attractive target for the therapeutic management of endometrial cancer.