Down-regulation of microRNA-146b-5p repress proliferation of thyroid carcinoma cells by enhancing autophagy activity

Abstract

Objective To investigate the influence of autophagy on proliferation of human papillary thyroid carcinoma cells (TPC-1) repressed by down-regulation of microRNA (miRNA, miR)-146b-5p. Methods TPC-1 cells were transient transfected by Lipofectmine 2000, and then cells were devided into four groups: as-miR, as-NC, co-transfection (as-miR-146b-5p+ siBeclin1) and co-transfection for control (as-miR-146b-5p+ siNC). Then the transfection efficiency was determined by invert fluorescence microscope and real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR). Western blotting and RT-qPCR were used to analyzed the protein and mRNA levels of Beclin1 of the transfected cells, respectively. Transmission electron microscopy was used to evaluated the expression of autophagsome of the transfected cells. And cell counting kit-8 and colony formation assay were used to detected the proliferation of the transfected cells. Results Compared with those treated with as-NC, miR-146b-5p expression was decreased to (0.380±0.021), and the protein and mRNA levels of Beclin1 were increased to (0.612±0.014), (0.413±0.005) respectively, and the absorbance at 72 h and amount of colony foci was decreased to (1.470±0.062, P=0.007), (29.000±3.610)% (P=0.031) respectively, and the autophagsome expression was significantly increased in TPC-1 cells treated with as-miR-146b-5p after 24 h. Compared with those co-transfected with as-miR-146b-5p+ siNC, the protein and mRNA levels of Beclin1 were decreased to (0.286±0.027), (0.265±0.025, P=0.006) respectively, and the absorbance at 72 h and amount of colony foci was increased to (2.564±0.050), (49.000±2.821)% respectively (P=0.027), and autophagsome expression was significantly decreased in TPC-1 cells co-transfected with as-miR-146b-5p+ siBeclin1 after 36 h. Conclusion Down-regulation of miR-146b-5p inhibit the viability of TPC-1 cells via strengthening autophagy activity. Key words: MicroRNA-146b-5p; Papillary thyroid carcinoma; Atophagy; Beclin1