Background
Accumulating articles demonstrate that circular RNAs play pivotal functions in tumorigenesis. However, the working mechanism of circ_0136666 in osteosarcoma (OS) progression remains to be further clarified.
Conclusion
Circ_0136666 silencing inhibited OS progression partly by targeting miR-1244/CEP55 signaling. Silencing circ_0136666 and CEP55 or restoring miR-1244 level might be a potential therapeutic strategy for OS.
Methods
Real time-quantitative polymerase chain reaction and western blot assay were applied to determine RNA and protein expression, respectively. Cell proliferation was assessed by 5-Ethynyl-2'-deoxyuridine assay and colony formation assay. Transwell assays were carried out to assess cell migration and invasion abilities. Flow cytometry was performed to analyze cell apoptosis. Cell glycolysis was evaluated by analyzing the uptake of glucose and the production of lactate using the corresponding kits. Dual-luciferase reporter assay and biotinylated RNA-pull down assay were performed to confirm the target interaction between microRNA-1244 (miR-1244) and circ_0136666 or centrosomal protein 55 (CEP55). Xenograft tumor model was utilized to explore the role of circ_0136666 in tumor growth in vivo.
Results
Circ_0136666 expression was prominently elevated in OS tissues and cell lines. Circ_0136666 absence restrained the proliferation, migration, invasion and glycolytic metabolism and promoted the apoptosis of OS cells. Circ_0136666 negatively regulated miR-1244 expression by binding to it in OS cells. MiR-1244 overexpression suppressed the malignant behaviors of OS cells. CEP55 was a target of miR-1244 in OS cells. Circ_0136666 positively regulated CEP55 expression partly by sequestering miR-1244 in OS cells. CEP55 overexpression largely reversed circ_0136666 silencing-mediated influences in OS cells. Circ_0136666 silencing significantly suppressed tumor growth in vivo.