Objective To explore the role of chloride intracellular channel 5 (CLIC5) in the development of lung adenocarcinoma (LUAD).

Methods The expression levels of CLIC5 in LUAD samples were determined using bioinformatics and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The correlation between CLIC5 expression and LUAD progression was revealed through survival analysis and clinicopathological feature analysis. After the knockdown and overexpression of CLIC5 in the LUAD cells, cell proliferation was assessed through colony formation assay, cell apoptosis rate by flow cytometry, and cell migration and invasion by scratch and Transwell invasion assay. The protein levels of vimentin and Snail were detected by Western blot.

Results Bioinformatics analysis results showed low CLIC5 expression levels in the LUAD samples. This finding was associated with the aggressive progression of LUAD and the poor survival of patients with LUAD. The qRT-PCR results confirmed that CLIC5 was mainly expressed in the cytoplasm of the LUAD cells. CLIC5 overexpression inhibited cell activity and proliferation and promoted the apoptosis of LUAD cells. The knockdown of CLIC5 exhibited the opposite effect. CLIC5 overexpression inhibited the migration and invasion of LUAD cells, downregulated Bcl-2, vimentin, and Snail and upregulated Bax, cleaved caspase-3 and E-cadherin in the LUAD cells. CLIC5 knockdown exhibited opposite effects.

Conclusions CLIC5 overexpression promotes cell apoptosis and inhibits cell proliferation and invasion, thereby inhibiting the development of LUAD. Hence, CLIC5 is a novel biomarker of prognosis and therapeutic target for LUAD.