Hypoxia-responsive miR-346 promotes proliferation, migration, and invasion of renal cell carcinoma cells via targeting NDRG2.

Renal cell carcinoma (RCC) is the most common malignant tumor of the kidney. In this study, we investigated the role of miR-346 in RCC cells under hypoxia. OS-RC-2 and 786-O cells were cultured in 1% O2 or normal oxygen. Cell proliferation, migration, and invasion abilities were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, transwell migration, and invasion assays, respectively. Quantitative real-time PCR (qRT-PCR) was performed to detect the expression of miR-346 and N-myc downstream-regulated gene 2 (NDRG2). Then bioinformatics analysis, dual-luciferase reporter assay, and RNA immunoprecipitation were carried out to determine the relationship between miR-346 and NDRG2. The protein expression of NDRG2 was detected by western blot assay. Hypoxia promoted cell proliferation, migration, and invasion in OS-RC-2 and 786-O cells. Meanwhile, we found that miR-346 was upregulated in RCC cells under hypoxia as relative to normoxia. miR-346 deletion could decrease the viability, migration, and invasion abilities of RCC cells under hypoxia. Besides, our data demonstrated that NDRG2 was a target gene of miR-346. The expression of NDRG2 in OS-RC-2 and 786-O cells was lower under hypoxia than under normal oxygen conditions. Moreover, NDRG2 overexpression could inhibit cell proliferation, migration, and invasion in RCC cells under hypoxia. And NDRG2 silencing reversed the inhibitory effects of the miR-346 inhibitor on the viability, migration, and invasion abilities of RCC cells in hypoxia conditions. miR-346 promoted the viability, migration, and invasion of RCC cells under hypoxia by targeting NDRG2.