circIPO7 dissociates caprin-1 from ribosomes and inhibits gastric cancer cell proliferation by suppressing EGFR and mTOR

Abstract

AbstractCircular RNA (circRNA) is a novel RNA molecule characterized by covalently closed loop structure. Since its discovery, researchers have shown that circRNA is not “splicing noise” but a participant of various pathophysiological processes through unique mechanisms. circIPO7, which was identified as an independent prognostic factor in gastric cancer (GC) patients, was downregulated in GC tissues and cells compared to paracarcinoma tissues and normal epithelial cells. circIPO7 overexpression significantly suppressed GC cell proliferation in vitro and in vivo. Mechanistically, circIPO7 directly binds with caprin-1, an RNA-binding protein involved in mRNA translation, sharing overlapping binding sites with G3BP1. Thus, the complex containing overexpressed circIPO7 blocked the caprin-1-G3BP1 interaction and dissociated caprin-1 and its target mRNAs (EGFR and mTOR) from ribosomes, resulting in their translational inhibition, followed by PI3K/AKT/mTOR pathway inactivation. We uncovered a novel molecular mechanism for circRNAs in GC development, identifying circIPO7 as a potential target for cancer treatment.