Circular RNA circEZH2 Promotes Lung Adenocarcinoma Progression by Regulating microRNA-495-3p/Tumor Protein D52 Axis and Activating Nuclear Factor-Kappa B Pathway

Background: It has been increasingly recognized that circular RNAs (circRNAs) act as a pivotal factor in the onset and progression of human malignancies. Yet, the specific activities and mechanistic roles of these RNAs in the context of lung adenocarcinoma (LUAD) are not fully understood.<br /> Methods: Microarray analysis identified a novel LUAD-associated circular RNA, termed hsa_circ_0006357 (also referred to as circEZH2). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was utilized for the analysis of circEZH2 expression in tissues and cell lines. The characteristics of circEZH2 were verified by RNase R treatment and fluorescence in situ hybridization (FISH) assays. The functions of circEZH2 were detected by Cell Counting Kit-8 (CCK-8), colony formation, wound healing, and Transwell assays. The molecular mechanism of circEZH2 was clarified through bioinformatics analysis as well as RNA pulldown, dual-luciferase reporter, RT-qPCR, and immunoblotting assays. The role of circEZH2 in vivo was investigated using a xenograft model.<br /> Results: This investigation revealed that circEZH2 expression was elevated in LUAD cell lines and tumor samples. This elevation was associated with enhanced cell proliferation, migratory capacity, epithelial-mesenchymal transition (EMT), and invasion in vitro. Conversely, silencing of circEZH2 in vivo resulted in a notable decrease in LUAD tumorigenesis, whereas its overexpression led to the opposite effects. Mechanistically, circEZH2 appeared to act as a sponge for miR-495-3p, facilitating the upregulation of tumor protein D52 (TPD52) and triggering the nuclear factor kappa B (NF-kappa B) signaling pathway, thus contributing to the progression of LUAD.<br /> Conclusion: These findings indicate that circEZH2 may function as a competitive endogenous RNA (ceRNA), driving the progression of LUAD by manipulating the miR-495-3p/TPD52 axis and activating the NF-kappa B pathway.