miR-26b is downregulated in human tongue squamous cell carcinoma and regulates cell proliferation and metastasis through a COX-2-dependent mechanism

MicroRNAs (miRNAs) are important gene regulators that play a profound role in tumorigenesis. Previous studies have revealed that miR-26b is downregulated in a wide range of malignant tumors and plays an important role in the regulation of carcinogenesis and tumor progression. In the present study, we revealed that miR-26b expression was decreased in human tongue squamous cell carcinoma and was associated with clinical stage, lymph node metastasis and survival prognosis. Ectopic expression of miR-26b suppressed the proliferation and metastasis of human tongue squamous cell carcinoma cells. Using a luciferase reporter assay, combined with western blot analysis results, we identified PTGS2 (prostaglandin-endoperoxide synthase-2, encoding COX-2) as the functional target of miR-26b. Specific inhibition of COX-2 activity by nimesulide further confirmed that miR-26b was able to regulate the cell proliferation and metastasis of the human tongue squamous cell carcinoma cells through a COX-2-dependent mechanism. Taken together, these results suggest that miR-26b serves as a tumor suppressor by targeting COX-2 and calls for the use of miR-26b as a potential therapeutic tool for human tongue squamous cell carcinoma, where COX-2 is often hyperactivated.