Downregulated circular RNA hsa_circ_0001649 regulates proliferation, migration and invasion in cholangiocarcinoma cells.

Cholangiocarcinoma (CCA) is one of the most aggressive malignancies with increasing worldwide incidence and is characterized by unfavorable prognosis due to its early invasive characteristics and poor response to chemotherapy or radiotherapy. Accumulating evidence has indicated that aberrantly expressed circular RNAs (circRNAs) are involved in cancer development and progression. However, their clinical values and biological roles in CCA remain unclear. Hsa_circ_0001649, a novel cancer-related circRNA, has been previously reported to be downregulated in hepatocellular carcinoma and gastric cancer. In the present study, qRT-PCR was carried out to measure the expression of hsa_circ_0001649 in CCA tissue samples and cell lines, and the correlation between hsa_circ_0001649 expression and clinicopathologic features was analyzed. The biological functions of hsa_circ_0001649 in CCA cells were evaluated both in vitro and in vivo. As a result, hsa_circ_0001649 was aberrantly downregulated in CCA tissues and cells, and this downregulation was associated with tumor size and differentiation grade in CCA. In addition, hsa_circ_0001649 overexpression caused tumor suppressive effects via inhibiting cell proliferation, migration and invasion; inducing cell apoptosis in KMBC and Huh-28 cells. On the contrary, silencing of hsa_circ_0001649 caused the opposite phenotypes. Furthermore, tumor xenograft study confirmed the in vitro results. Collectively, our findings suggest that hsa_circ_0001649 might be a rational CCA-related therapeutic target.