MicroRNA (miR) are short non-coding RNA that bind to the 3'-untranslational region of their target genes, inhibiting translation and causing mRNA degradation. miR deregulation has been implicated in human cancer; however, the detailed regulatory mechanism of miR-137 in osteosarcoma (OS) remains largely unknown. In the present study, miR-137 and enhancer of zeste homologue 2 (EZH2) mRNA and protein expression levels were analyzed using reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. MTT and transwell assays were performed to evaluate cell viability and invasion capacities and a luciferase reporter gene assay was used to determine the targeting relationship. The results of the current study indicated that miR-137 expression was significantly downregulated in OS tissues and cell lines (P<0.01). Moreover, it was observed that low miR-137 expression levels were significantly associated with lung metastasis and advanced TMN stage (P<0.05), but not associated with age, gender, tumor size, location, serum lactate dehydrogenase or serum alkaline phosphatase. Increasing levels of miR-137 significantly inhibited U2OS cell viability and invasion (P<0.01). By contrast, knockdown of miR-137 markedly increased U2OS cell viability and invasion. EZH2 was identified as a direct target gene of miR-137 in U2OS cells by luciferase reporter assay and EZH2 expression was found to be significantly increased in OS tissues and cell lines (P<0.01). EZH2 was significantly downregulated following miR-137 overexpression (P<0.01), and was upregulated following miR-137 knockdown in U2OS cells. Furthermore, EZH2 overexpression significantly attenuated the suppressive effects of miR-137 on U2OS cell viability and invasion (P<0.01), suggesting that miR-137 inhibits the viability and invasion of OS cells by targeting EZH2. Therefore, the results of the current study suggest that the miR-137/EZH2 axis may be a potential target for novel potential therapeutic strategies to treat OS.
Keywords: enhancer of zeste homolog 2; microRNA-137; osteosarcoma; tumor suppressor.