Circ‐LAMP1 contributes to the growth and metastasis of cholangiocarcinoma via miR‐556‐5p and miR‐567 mediated YY1 activation

Dysregulation of circular RNAs (circRNAs) executes important regulatory roles in carcinogenesis. Nonetheless, few studies focused on the mechanisms of circRNAs in cholangiocarcinoma (CCA). qRT‐PCR was applied to verify the dysregulated circRNAs in CCA. Fisher's exact test, Kaplan‐Meier analysis and Cox regression model were utilized to investigate the clinical implications of circ‐LAMP1 in the patients with CCA. The viability, apoptosis, migration and invasion of CCA cells were detected after silencing/overexpression of circ‐LAMP1. Xenograft and lung metastasis assays were performed to verify the in vitro results. The regulatory networks of circ‐LAMP1 were unveiled by bioinformatic analysis, RNA immunoprecipitation (RIP), RNA pulldown and luciferase reporter assays. Up‐regulation of circ‐LAMP1 was found in CCA tissue samples and cell lines. Enhanced level of circ‐LAMP1 was linked to clinical severity, high post‐operative recurrence and poor prognosis for the patients with CCA. Gain/loss‐of‐function assays confirmed the oncogenic role of circ‐LAMP1 in mediating cell growth, apoptosis, migration and invasion. Nevertheless, the level of circ‐LAMP1 had no effect on normal biliary epithelium proliferation and apoptosis. Animal study further verified the in vitro data. Mechanistically, circ‐LAMP1 directly sponged miR‐556‐5p and miR‐567, thereby releasing their suppression on YY1 at post‐transcriptional level. Rescue assay indicated that the oncogenic role of circ‐LAMP1 is partially dependent on its modulation of YY1 in CCA. In summary, this study suggested that circ‐LAMP1 might be used as a promising biomarker/therapeutic target for CCA.