Long Noncoding RNA GAS5 Accelerates Cholangiocarcinoma Progression by Regulating hsa-miR-1297

Background: Long noncoding RNAs (lncRNAs) have been reported as important molecules in cholangiocarcinoma (CCA) occurrence and development. A previous study showed that lncRNA GAS5 (GAS5) was an oncogene in some tumors. But the role of GAS5 in CCA progression reminds unclear. This research was designed to study the expression and potential effects of GAS5 in the progression of CCA. Methods: The expression of GAS5 in CCA tissues was evaluated through mining of the TCGA and GEPIA databases. qRT-PCR was applied to validate the results in our clinical samples. chi(2) test was used to analyze the association between the expression level of tissue GAS5 and different clinicopathological parameters of CCA patients. The target gene of GAS5 was predicted by bioinformatic databases, and further verified by luciferase reporter assays. Finally, the role of GAS5 in CCA cells invasion and proliferation was detected by Transwell assay and CCK-8 assay. Results: Compared to the adjacent nontumor tissues and the normal human intrahepatic biliary epithelial cell, the expression of GAS5 was markedly increased in CCA tissues (p<0.001) and cell lines (p<0.01), respectively. CCA patients with high GAS5 expression tended to present lymph node metastasis (p<0.001) and had advanced clinical stage (p=0.006). The bioinformatics analysis predicted that hsa-miR-1297 was the potential target gene of GAS5, which was validated by luciferase reporter assays. In addition, the function study showed that GAS5 acted as a "sponge" to downregulate hsa-miR-1297, thus modulating CCA cell proliferation and invasion. Conclusion: GAS5 acts as an endogenous sponge of hsa-miR-1297 to promote CCA cell proliferation and invasion, which might be a potential biomarker and therapeutic target for CCA.