MicroRNA-92b promotes tumor growth and activation of NF-κB signaling via regulation of NLK in oral squamous cell carcinoma

Abstract

miR-92b has been reported to be dysregulated in many types of human cancers. However, the role of miR-92b in oral squamous cell carcinoma (OSCC) is unknown. The aim of the present study was to investigate the function and mechanism of miR-92b in human OSCC. Using quantitative reverse-transcription PCR (qRT-PCR), we found that the miR-92b level in primary tumors (n=85) was significantly elevated compared with that in the adjacent normal tissues (p<0.001). A high level of miR-92b was significantly associated with a large tumor size (p=0.005), advanced tumor stage (p<0.001) and poorer prognosis (p=0.04). Functionally, miR-92b was shown to not only promote the proliferation of OSCC cells in MTT and colony formation and xenograft assays, but also to inhibit cell apoptosis in a flow cytometric assay. In western blotting and luciferase assay, NLK was identified as a direct and functional target of miR-92b. We also found that NLK was involved in miR-92b-induced cell proliferation, and its protein level was obviously downregulated in the miR-92b-overexpressing xenograft tumors. Finally, luciferase reporter assay and fluorescent immunostaining revealed that miR-92b activated the NF-κB signaling pathway, which may be responsible for the effects of miR-92b on cell proliferation. Taken together, our results indicate that miR-92b upregulation accelerates tumor growth and present a novel mechanism of miRNA-mediated NF-κB activation in OSCC.