Circular RNA Circ_0001777 Suppresses Lung Adenocarcinoma Progression In Vitro and In Vivo.

Circular RNA_0001777 (circ_0001777) is reported to be down-regulated in lung cancer. Nevertheless, the function of circ_0001777 in lung adenocarcinoma is largely unclear. We explored the role of circ_0001777 in lung adenocarcinoma progression and the underlying molecular mechanism. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were conducted to determine the expression of RNAs and proteins. 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, 5-ethynyl-20-deoxyuridine, and colony formation assays were conducted to analyze cell proliferation ability. Flow cytometry was carried out to assess cell apoptosis rate. Cell migration and invasion abilities were analyzed by wound healing assay and transwell assays. Cell glycolytic metabolism was measured using a fluorescence-based glucose assay kit and a lactate oxidase-based colorimetric assay kit. Dual-luciferase reporter assay and RNA immunoprecipitation assay were implemented to verify the intermolecular interactions. Circ_0001777 expression was reduced in lung adenocarcinoma tissues and cell lines. Circ_0001777 overexpression restrained the proliferation, migration, invasion, and glycolysis and promoted the apoptosis of lung adenocarcinoma cells. Circ_0001777 could directly bind to microRNA-942-5p (miR-942-5p). The anti-tumor effects of circ_0001777 overexpression in lung adenocarcinoma cells were reversed after miR-942-5p accumulation. miR-942-5p directly bound to the 3' untranslated region (3'UTR) of prickle planar cell polarity protein 2 (PRICKLE2), and PRICKLE2 silencing reversed the anti-tumor effects of miR-942-5p knockdown in lung adenocarcinoma cells. Circ_0001777 could regulate PRICKLE2 expression by absorbing miR-942-5p. Circ_0001777 overexpression markedly hampered tumor progression in vivo. Circ_0001777 suppressed the progression of lung adenocarcinoma by binding to miR-942-5p to induce PRICKLE2 expression.