The Effect of Silencing Hox Transcript Antisense Intergenic RNA (HOTAIR)/microRNA (miR)-137/Heart Development Protein with EGF Like Domains 1 [(Human)] (HEG1) Signal Axis on Endoplasmic Reticulum Stress-Induced Apoptosis in Non-Small Cell Lung Cancer, an in Vitro Study

Abstract

Background: Long noncoding RNA hox transcript antisense intergenic RNA (HOTAIR) is an oncogene of non-small cell lung cancer (NSCLC), which shows the effect of enhancing cancer cell activity and inhibiting apoptosis. However, its specific regulatory mechanism is not clear. The aim of study was to clarify the role and downstream molecular signals of HOTAIR in the regulation of endoplasmic reticulum stress (ERS) and apoptosis in NSCLC cells. Methods: The interaction between HOTAIR and microRNA (miR)-137, heart development protein with EGF (epidermal growth factor) like domains 1 [(human)] (HEG1) and recombinant activating transcription factor 6 (ATF6) was verified using bioinformatics analysis, RNA pull down and immunocoprecipitation (IP) techniques. Real time-quantitative r polymerase chain reaction (RT-qPCR) and western blotting were used to verify the regulatory effects of HOTAIR and miR-137 on downstream proteins HEG1, ATF6, B-cell lymphoma-2 (Bcl-2), Caspase-8 and TNF-related apoptosis-inducing ligand (TRAIL). 3-(4,5)-Dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and terminal deoxynucleotidyl transferase dUTP (2’-deoxyuridine 5’-triphosphate) nick end labeling (TUNEL) methods were used to detect the effects of HOTAIR and miR-137 on the proliferation and apoptosis of A549. Results: HOTAIR was highly expressed in NSCLC cell line (p < 0.001). Up-regulation of HOTAIR or down-regulation of miR-137 can significantly promote cell proliferation, inhibit cell apoptosis (upregulated Bcl-2, downregulated Caspase 8 and TRAIL (Tumor Necrosis Factor (TNF)-Related Apoptosis Inducing Ligand)), endoplasmic reticulum stress (downregulated ATF6) and HEG1 expression (p < 0.05). However, siHOTAIR (HOTAIR siRNA) or miR-137 mimic transfection showed an opposite role in A549 cells. HOTAIR was significantly enriched in the pull-down miR-137 and inhibited miR-137 expression (p < 0.05). HEG1 and ATF6 were co expressed in A549. Conclusions: The HOTAIR/miR-137 axis significantly inhibits cell apoptosis, endoplasmic reticulum stress and the expression of HEG1, and promotes cell proliferation, exerting a significant pro-cancer effect.