SOX2 knockdown slows cholangiocarcinoma progression through inhibition of transcriptional activation of lncRNA PVT1

Cholangiocarcinoma (CCA) has accounted for a high rate of mortality and morbidity in the recent years. Long non-coding RNAs (lncRNAs) play an important role in different cellular environments, including cancer. As such, they have been used as potential targets during CCA therapy. The objective of this study was to investigate the effects of lncRNA PVT1 on CCA and its mechanisms behind lncRNA PVT1 regulation. The interactions among SOX2, lncRNA PVT1, miR-186 and SEMA4D were verified by chromatin immunoprecipitation, RNA immunoprecipitation and dual luciferase reporter gene assay. Gain- and loss-of-function experiments were conducted to explore the modulatory effects of SOX2, lncRNA PVT1, miR-186 and SEMA4D on cell viability, migration and invasion of CCA by CCK-8 and Transwell assays. In vivo effects of lncRNA PVT1 or SEMA4D were studied in a nude mouse model. MiR-186 was poorly expressed while SOX2, lncRNA PVT1 and SEMA4D were highly expressed in CCA cells. SOX2 induced the transcriptional activation of lncRNA PVT1 expression to promote proliferation, migration and invasion of CCA cells. LncRNA PVT1 bound to miR-186 and miR-186 was found to target SEMA4D. The overexpression of lncRNA PVT1 and SEMA4D, as well as the inhibition of miR-186 led to elevated CCA cell proliferation, migration and invasion. In vivo experiments confirmed the inhibitory role of lncRNA PVT1 knockdown or SEMA4D knockdown in CCA. All in all, SOX2 down-regulated miR-186 through the transcriptional activation of lncRNA PVT1, whereas elevating SEMA4D expression, thus promoting the progression of CCA.