Down-Regulatory Effects of miR-211 on Long Non-Coding RNA SOX2OT and SOX2 Genes in Esophageal Squamous Cell Carcinoma

MicroRNAs (miRNAs) are a class of non-coding RNAs (ncRNAs) that tran- scriptionally or post-transcriptionally regulate gene expression through degradation of their mRNA targets and/or translational suppression. However, there are a few reports on miRNA-mediated expression regulation of long ncRNAs (lncRNAs). We have previ- ously reported a significant upregulation of the lncRNA SOX2OT and its intronic cod- ing gene, SOX2, in esophageal squamous cell carcinoma (ESCC) tissue samples. In this study, we aimed to evaluate the effect of induced overexpression of miR-211 on SOX2OT and SOX2 expression in vitro.

In this experimental study, we performed both bioinformatic and experimental analyses to examine whether these transcripts are regulated by miRNAs. From the list of potential candidate miRNAs, miR-211 was found to have complementary sequences to SOX2OT and SOX2 transcripts. To validate our finding experimentally, we transfected the NT-2 pluripotent cell line (an embryonal carcinoma stem cell) with an expression vector overexpressing miR-211. The expression chang- es of miR-211, SOX2OT, and SOX2 were then quantified by a real-time polymerase chain reaction (RT-PCR) approach.

Compared with mock-transfected cells, overexpression of miR-211 caused a significant down-regulation of both genes (P<0.05). Furthermore, flow-cytometry analysis revealed a significant elevation in sub-G1 cell population following ectopic expression of miR-211 in NT-2 cells.

We report here, for the first time, the down-regulation of SOX2OT and SOX2 genes by an miRNA. Considering the vital role of SOX2OT and SOX2 genes in pluripotency and tumorigenesis, our data suggest an important and inhibitory role for miR-211 in the aforementioned processes.