Circ_0000274 contributes to renal cell carcinoma progression by regulating miR-338-3p/NUCB2 axis and JAK1/STAT3 pathway

Background: Kidney transplant recipients (KTRs) are at increased risk of developing renal cell carcinoma (RCC). Accumulating evidence has demonstrated that circular RNAs (circRNAs) are essential players in tumor advancement. However, the functions of circ_0000274 in renal cell carcinoma (RCC) are barely explored.Methods: The primary RCC cell lines 786-O and A498 were used in this study. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was employed for the RNA levels of circ_0000274, microRNA-338-3p (miR-3383p) and nucleobindin 2 (NUCB2). RNase R assay was conducted to analyze the feature of circ_0000274.Cell Counting Kit-8 (CCK-8) assay, colony formation assay, transwell assay, tube formation assay and flow cytometry analysis were conducted for cell viability, colony formation, metastasis, angiogenesis and apoptosis, respectively. Western blot assay was utilized for protein levels. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were adopted to analyze the associations of circ_0000274 RNA, miR-338-3p RNA and NUCB2 protein. Murine xenograft model was established to explore the function of circ_0000274 RNA in vivo. Immunohistochemistry (IHC) assay was used to analyze NUCB2 protein level in xenograft tumors.Results: Compared to normal tissues and cells, circ_0000274 RNA level was elevated in RCC tissues and cells. Knockdown of circ_0000274 RNA suppressed cell viability, colony formation, metastasis and tube formation and promoted apoptosis in RCC cells in vitro. Circ_0000274 RNA sponged miR-338-3p RNA to positively regulate NUCB2 protein in RCC cells. Inhibition of miR-338-3p reversed the impacts of circ_0000274 knockdown on RCC cell malignant behaviors. MiR-338-3p RNA overexpression repressed the malignant phenotypes of RCC cells, while NUCB2 protein elevation could abrogate the effect. Moreover, circ_0000274 RNA knockdown blocked tumorigenesis in vivo. Besides, circ_0000274 RNA knockdown inactivated the JAK1/STAT3 protein signaling pathway.Conclusion: Circ_0000274 RNA functioned as an oncogene in RCC development by regulating miR-338-3p RNA/ NUCB2 protein axis and activating the JAK1/STAT3 protein signaling pathway.