Long non-coding RNA MEG3 induces cell apoptosis in esophageal cancer through endoplasmic reticulum stress

Long non-coding RNAs (lncRNAs) play important roles in diverse biological processes, such as cell growth, apoptosis and migration. Although downregulation of lncRNA MEG3 has been identified in several cancers, little is known about its role in esophageal squamous cell carcinoma (ESCC). The aim of the present study was to detect MEG3 expression in clinical ESCC tissues, investigate its biological functions and the endoplasmic reticulum (ER) stress-relative mechanism. MEG3 expression levels were detected by qRT-PCR in both tumor tissues and adjacent non-tumor tissues from 28 ESCC patients. pcDNA3.1-MEG3 recombinant plasmids were constructed and transfected to EC109 cells. Cell growth was analyzed by CCK-8 assay. Cell apoptosis was analyzed by fluorescence microscope and Annexin V/PI assay. The protein expression was determined by western blot analysis. The results showed that MEG3 decreased significantly in ESCC tissues relative to adjacent normal tissues. pcDNA3.1-MEG3 plasmids were successfully constructed and the expression level of MEG3 significantly increased after MEG3 transfection to EC109 cells. Ectopic expression of MEG3 inhibited EC109 cell proliferation and induced apoptosis in vitro. MEG3 overexpression increased the expression of ER stress-related proteins (GRP78, IRE1, PERK, ATF6, CHOP and cleaved-caspase-3). Our results first demonstrate that MEG3 is downregulated in ESCC tissues. MEG3 was able to inhibit cell growth and induced apoptosis in EC109 cells, most probably via activation of the ER stress pathway.