Osteopontin Promotes EZH2 Expression and Tumor Progression in Nasopharyngeal Carcinoma

OBJECTIVE: To evaluate the possible mechanism of osteopontin (OPN) in the tumor progression of nasopharyngeal carcinoma (NPC). METHODS: Twenty NPC specimens and 10 normal biopsy specimens were analyzed, and the expression of OPN and enhancer of zeste homolog 2 (EZH2) was examined by immunohistochemical staining. Moreover, the expression of EZH2 in NPC cell lines was examined using quantitative reverse transcription polymerase chain reaction and Western blot analysis in the presence of recombinant human (rh) OPN and specific inhibitors. NPC cell migration and invasion were evaluated using a transwell chamber in the presence of rhOPN and/or EZH2 siRNA. RESULTS: The immunoreactivity of OPN and EZH2 was significantly enhanced in NPC specimens compared with the normal controls (p < 0.05). EZH2 expression in NPC specimens was significantly associated with OPN expression and tumor stage (p < 0.05). Moreover, rhOPN significantly stimulated EZH2 expression in the NPC cell line through a MAPK-mediated pathway and significantly stimulated migration and invasion of the NPC cell line (p < 0.05), which was notably inhibited by EZH2 siRNA transfection (p < 0.05). CONCLUSION: Our findings suggest that OPN may promote tumor progression of NPC through an EZH2-dependent pathway.