BioScience Trends. 2020;14(6):399-407. (DOI: 10.5582/bst.2020.03310)

Depletion of circ-BIRC6, a circular RNA, suppresses non-small cell lung cancer progression by targeting miR-4491

Jin Z, Gao B, Gong Y, Guan L

Circular RNAs (circRNAs) are non-coding RNAs molecules consisting of a covalently closed continuous loop which have no 5'-3' polarity and contain no polyA tail. Accumulating evidence demonstrates that circRNAs are involved in the initiation and progression of human malignancies. In this study, we explored the expression profile and regulatory role of circ-baculoviral IAP repeatcontaining 6 (circ-BIRC6), a circular RNA, in malignant behaviors in non-small cell lung cancer (NSCLC). Expression levels of circ-BIRC6 and miR-4491 were examined in NSCLC patient samples and cell lines using quantitative real time PCR (qRT-PCR). In vitro roles of circ-BIRC6 knockdown on cell viability, colony formation, and apoptosis were assessed using the CCK-8, colony formation assay, and flow cytometry, respectively. The interactions between circ-BIRC6 and miR-449 were assessed using luciferase reporter and qRT-PCR assays. The in vivo role of circ-BIRC6 knockdown on tumor growth and apoptosis was evaluated in a xenograft mouse model of NSCLC. We found that expression levels of circ-BIRC6 in NSCLC patient samples and cell lines were elevated. Small interfering RNA (siRNA)-mediated circ-BIRC6 knockdown suppressed cell proliferation, colony formation, migration and invasion, and promoted apoptosis in NCI-H460 and A549 cells. In addition, miR-4491 was identified as a tumor-suppressor miRNA in NSCLC and circ-BIRC6 functions as a molecular sponge for miR-4491. Furthermore, circ-BIRC6 knockdown suppressed Wnt2B/β-catenin pathway. In vivo assay showed that depletion of circ-BIRC6 suppressed tumor growth, enhanced apoptosis, and decreased miR-4491 levels in a mouse xenograft model. These findings demonstrate that circ-BIRC6 functions as a critical regulator of proliferation and apoptosis via binding to and negatively regulating miR-4491, suggesting that circ-BIRC6 might be a potential target for treatment of NSCLC.

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