Circ_0008287 promotes immune escape of gastric cancer cells through impairing microRNA-548c-3p-dependent inhibition of CLIC1

Background: Analyses in silico suggested the upregulation of a circular RNA (circRNA), circ_0008287, in gastric cancer and possible interactions among microRNA (miR)-548c-3p, circ_0008287, and intracellular chloride channel protein 1 (CLIC1). This study aims to testify whether circ_0008287 can affect the immune escape of gastric cancer cells by regulating miR-548c-3p and CLIC1.

Methods: RT-qPCR was performed to determine the expression pattern of circ_0008287 in gastric cancer cells. Gain- and loss-of function assays were then performed to assess the effects of circ_0008287 on malignant phenotypes of cancer cells. Interactions among circ_0008287, miR-548c-3p and CLIC1 were verified by dual luciferase reporter gene, RIP and FISH assays. Effects of CLIC1 on IFN-γ secretion and apoptosis in CD8 + T cells were evaluated by flow cytometry following co-culture of CD8 + T cells with cancer cells overexpressing/silencing CLIC1. A gastric cancer mouse model was further developed for in vivo investigation on effects of circ_0008287 on tumorigenesis and tumor metastasis.

Results: circ_0008287, an upregulated circRNA in gastric cancer cells, augmented the viability as well as invasive and migratory potentials of gastric cancer cells. By competitively binding to miR-548c-3, circ_0008287 increased the expression of CLIC1, which impaired the function of CD8 + T cells and promoted their apoptosis. After downregulation of circ_0008287, in vivo tumorigenesis and metastasis were suppressed.

Conclusion: Hence, this study suggests the promotive role of circ_0008287 in gastric cancer progression and immune escape and further elucidates the underlying circ_0008287/miR-548c-3p/CLIC1 regulatory axis.