E2FI induces LSINCT5 transcriptional activity and promotes gastric cancer progression by affecting the epithelial-mesenchymal transition

Background: Long noncoding RNAs (lncRNAs) have been shown to play important regulatory roles in human cancer. We previously verified that the lncRNA long stress-induced noncoding transcript 5 (LSINCT5) is overexpressed in gastric cancer (GC) cells and closely correlated with cell proliferation and patient prognosis. However, whether aberrant LSINCT5 expression has an important effect on GC progression is unclear, and the potential mechanisms remain unknown. In GC, E2F1 expression is also aberrant, but the biological functions of E2F1 are controversial, and the correlation between E2F1 and lncRNAs remains unknown. Materials and methods: Expression of LSINCT5 was analyzed in metastatic CC tissues compared with nonmetastatic tissues using quantitative real-time PCR (qRT-PCR) assays. Gain and loss of function approaches were used to investigate the biological role of LSINCTS in GC cell migration and invasion. A computational screen of LSINCT5 promoter was conducted to search for transcription factor-binding sites. LSINCTS promoter activities were examined by ChIP and luciferase reporter assays. qRT-PCR and western blotting assays were performed to detect the expression of multiple EMT markers in cells in which LSINCT5 was overexpressed or knocked down. Results: An integrated quantitative analysis revealed that LSINCT5 was significantly overexpressed in metastatic GC tissues. Forced LSINCT5 expression promoted cell migration and invasion, whereas loss of LSINCT5 function decreased cell migration and invasion. Mechanistic investigations showed that LSINCT5 is a direct transcriptional target of E2F1. Moreover, LSINCT5 overexpression was found to play an important role in the epithelial-to-mesenchymal transition by regulating the expression of E-cadherin, N-cadherin, vimentin, and matrix metalloproteinase-2. Conclusion: These data suggest that E2F1-mediated activation of LSINCTS, a regulator of cell migration and invasion, constitute the mechanistic link between the E2F1-mediated pathway and lncRNA that regulates cell migration and invasion. Thus, LSINCTS may be a target for new GC therapies.