MicroRNA-185 inhibits cell proliferation while promoting apoptosis and autophagy through negative regulation of TGF-β1/mTOR axis and HOXC6 in nasopharyngeal carcinoma.

Objective: Accumulating studies have revealed that microRNAs (miRs) play a critical role in the development and progression of nasopharyngeal carcinoma (NPC), which is a disease with a remarkable racial and geographical distribution. In our study, through the alteration in the expression of microRNA-185 (miR-185) in NPC cells by microarray-based gene expression profiling, we subsequently evaluated its ability to influence NPC cells and associated mechanism.

Methods: The expressions of miR-185 and HOXC6 in NPC and paracancerous tissues collected from patients with NPC were detected. The CNE-2 cells with the lowest miR-185 among the five NPC cell lines (CNE-1, CNE-2, HNE-1, HNE-2, and 5-8F) were selected and transfected with a series of mimic or inhibitor of miR-185, or shRNA-against HOXC6. The Kaplan-Meier method was used to analyze the survival of patients. Besides, the reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to determine the levels of related genes/proteins. By means of cell counting kit-8 (CCK-8) assay, transwell assay, flow cytometry, and AO staining, the influences miR-185 has on the processes associated with NPC, including cell proliferation, invasion, apoptosis and autophagy were evaluated.

Results: NPC was observed to decrease miR-185 but increase HOXC6. Dual luciferase reporter gene assay demonstrated that HOXC6 is a target gene of miR-185. Increased mRNA and protein levels of Bax, caspase-3, LC3 and Beclin1 and reduced levels of HOXC6, TGF-β1, mTOR, Cyclin D1, PCNA, Bcl-2 were found by overexpression of miR-185. High expression of miR-185 and low expression of HOXC6 had longer survival time of NPC patients. Overexpressed miR-185 enhanced cell apoptosis and autophagy, and reduced cell proliferation and invasion, while miR-185 inhibitor was observed to have induced effects on the CNE-2 cells.

Conclusion: Overall, the data show that miR-185 could negatively target HOXC6 to suppress cell proliferation, promotes apoptosis and autophagy through inhibiting TGF-β1/mTOR axis in NPC. Thus, miR-185 is useful strategy for the treatment of NPC.