Hsa_circ_0008934 promotes the proliferation and migration of osteosarcoma cells by targeting miR-145-5p to enhance E2F3 expression

Objective: To investigate the role of hsa_circ_0008934 in osteosarcoma and the molecular mechanism involved in the regulation of the occurrence and development of osteosarcoma Methods: Differentially expressed circRNAs in the osteosarcoma cell lines SaOS2 and MG63 and in the normal human osteoblast cell line hF0B1.19 were identified via next-generation RNA sequencing. The expression and circular morphology of hsa_circ_0008934 were analyzed via quantitative real-time polymerase chain reaction (qRT-PCR) and RT-PCR analysis, respectively. Proliferation, apoptosis, cell cycle progression, migration, and invasion of SaOS2 and MG63 cells with hsa_circ_0008934 silencing or overexpression were assessed using the MTS method, colony formation assay, flow cytometry, and the transwell system, respectively. The subcellular distribution of hsa_circ_0008934 was revealed via fluorescence in situ hybridization. The binding of hsa_circ_0008934 with microRNAs was confirmed using the dual-luciferase reporter assay. The oncogenic roles of hsa_circ_0008934 in osteosarcoma were determined using an in vivo tumorigenesis assay with nude mice. qRTPCR, western blotting, TUNEL assay, and immunohistochemistry (IHC) were used to detect the tumorigenicity of hsa_circ_0008934 in osteosarcoma cells. Results: Many circRNAs were differentially expressed in SaOS2 and MG63 cells than in hFOB1.19 cells. Hsa_circ_0008934 expression was significantly elevated in SaOS2 and MG63 cells. Hsa_circ_0008934 silencing significantly reduced proliferation, enhanced apoptosis, blocked cell cycle progression, and impaired migration and invasion capacities of SaOS2 cells. Opposite cellular alterations were achieved by overexpressing hsa_circ_0008934 in MG63 cells. Hsa_circ_0008934 was mainly distributed in the cytosol and positively regulated E2F3 expression in osteosarcoma cells. In addition, it directly bound with miR-145-5p to repress E2F3 expression and enhanced the tumorigenesis of MG63 cells in nude mice. qRT-PCR revealed that the intracellular injection of hsa_circ_0008934 lentivirus resulted in hsa_circ_0008934 overexpression and miR-145-5p downregulation. Western blotting confirmed that E2F3 was upregulated. Moreover, the TUNEL assay showed that hsa_circ_0008934 overexpression inhibited the apoptosis of tumor cells. IHC detection revealed that the hsa_circ_0008934 overexpression could promote the expression of Ki67 and PCNA. Conclusion: Elevated hsa_circ_0008934 expression promotes the proliferation and migration of osteosarcoma cells by sponging miR-145-5p to enhance E2F3 expression.