Abstract
PURPOSE: Circular RNA (circRNA) is involved in the development of various cancers. However, whether circRNA can inhibit the tumorigenesis of non-small cell lung cancer (NSCLC) is still unclear. We aimed to explore the epigenetic function of tumor-suppressive circRNA (hsa_circ_RNA_0011780) and its downstream regulatory factors in NSCLC. PATIENTS AND METHODS: Quantitative polymerase chain reaction (qPCR) was used to evaluate hsa_circ_11780 expression in NSCLC tissues and cell lines. The impact of high hsa_circ_11780 expression on overall survival in patients with NSCLC was tested using the Log rank test. The association between decreased hsa_circ_11780 expression and clinicopathological features in patients with NSCLC was analyzed using the Chi-squared test. In vitro cell proliferation and apoptosis were assayed using the cell counting kit-8 (CCK-8) and flow cytometry, respectively. Mice xenograft models were used to determine the tumor promoting effects of hsa_circ_11780 on NSCLC in vivo. The underlying regulatory mechanism was predicted by bioinformatics and verified by a dual-luciferase reporter assay, RNA transfection, qPCR, and Western blotting. The correlation between miR-544a and hsa_circ_11780 expression was verified using Spearman correlation coefficient. RESULTS: The expression of hsa_circ_11780 in NSCLC tissues and cell lines strongly declined. Low hsa_circ_11780 expression is more likely to present in patients with a large tumor size (>3cm), distant metastasis, and poor overall survival. hsa_circ_11780 overexpression strongly inhibited proliferation, migration, and invasion of NSCLC cells (H226 and A549) in vitro and inhibited tumor growth in vivo. Furthermore, hsa_circ_11780 repressed miR-544a function by competitively binding to the complementary sites of miR-544a. miR-544a released by the declining expression of hsa_circ_11780 reduced the protein concentration of F-Box and WD repeat domain containing 7 (FBXW7) in NSCLC cells. CONCLUSION: FBXW7 expression mediated by the hsa_circ_11780/miR-544a axis is markedly associated with the proliferation, migration, and invasion of NSCLC, resulting in decreased survival. These findings suggest that this regulatory axis may serve as a novel therapeutic target in NSCLC.