Long non-coding RNA MEG3 represses cholangiocarcinoma by regulating miR-361-5p/TRAF3 axis.

Abstract

The aim of this study was to investigate the effect of long non-coding RNA MEG3 (MEG3) and microRNA-361-5p (miR-361-5p) on cholangiocarcinoma cells and to explore the molecular mechanisms. The level of MEG3 and miR-361-5p was detected using quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The relationship between miR-361-5p and MEG3/TNF receptor-associated factor 3 (TRAF3) was confirmed by the Dual-Luciferase Reporter Assay. 3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry analysis were used to determine cell viability and cell apoptosis. Moreover, the protein level of TRAF3, p65, and p-p65 was measured by Western blot assay. We found that MEG3 was downregulated in CCA tissues and cell lines, especially in TFK1 and QBC939 cells. MEG3 directly bind to miR-361-5p, which was highly expressed in CCA tissues and cell lines. Further analysis indicated that MEG3-plasmid could inhibit cell viability and induce cell apoptosis in CCA cells, but these effects were significantly reversed by miR-361-5p mimic. Moreover, we proved that TRAF3 was a direct target of miR-361-5p and it was downregulated in CCA tissues and cell lines. In addition, we found that miR-361-5p downregulation significantly inhibited CCA cell viability and induced cell apoptosis, and these effects were eliminated by the knockdown of TRAF3. Further functional analysis showed that the knockdown of TRAF3 upregulated the expression of p-p65 decreased by miR-361-5p inhibitor in CCA cells. Our results suggested that MEG3 repressed cholangiocarcinoma by downregulating miR-361-5p expression. Meanwhile, the suppression of miR-361-5p might improve CCA survival by targeting TRAF3 and inhibiting the NF-κB pathway, which might help to develop new strategies for CCA therapy.