Circusp34 Promotes Osteosarcoma Proliferation and Invasion by Sponging Mir-16-5p: An in Vivo and in Vitro Analysis

Abstract

Background Osteosarcoma (OS) is a primary and highly malignant mesenchymal tissue tumor. Although it has achieved a significant breakthrough in therapeutic administration, the specific pathological mechanism remains unclear. CircRNAs are a type of covalently circular RNA with a head-to-tail junction site. Several studies have reported that abnormal expression of circRNAs is closely associated with tumorigenesis and progression. CircRNAs promote or inhibit the progression of OS by sponging miRNAs. In this study, we aimed to investigate the endogenous competition between circRNAs and miRNAs in OS. Methods CircUSP34 expression was detected by qRT-PCR in KHOS and 143B cells. To confirm the effect of circRNAs and miRNAs, function assays including CCK8, EdU, wound healing, transwell, and western blot were performed in OS cells. FISH and dual-luciferase reporter assays were performed to confirm the sponging mechanism of circUSP34 and miR-16-5p. Additionally, qRT-PCR, immunohistochemistry, HE staining, and western blot were used to confirm the expression of proteins and genes in tumor tissues from mice. Results In the present study, we found that circUSP34 promoted OS proliferation, migration, and invasion in vitro and in vivo. circUSP34 and miR-16-5p were upregulated and downregulated, respectively, in OS cells. OS cells’ biological behaviors, such as proliferation, migration, and invasion, were inhibited after circUSP34 knockdown. Western blot results also showed that Vimentin and Ki-67 expression levels were decreased. Similarly, miR-16-5p mimic compromised OS cell proliferation and migration. FISH assay indicated that circUSP34 and miR-16-5p were colocalized in the cytoplasm. The dual-luciferase reporter assay showed that miR-16-5p was sponged by circUSP34. Interestingly, the miR-16-5p mimic partly reversed the inhibitory effect of sh-circUSP34 on the malignancy of OS cells. Finally, animal experiment results about IHC indicated that Vimentin, N-cadherin, and Ki-67 protein expression decreased, but E-cadherin protein expression increased. Conclusion Collectively, circUSP34 promoted OS proliferation, migration, and invasion by sponging miR-16-5p. It can serve as a potential therapeutic target and biomarker.