Circular RNA circNRIP1 acts as a microRNA-149-5p sponge to promote gastric cancer progression via the AKT1/mTOR pathway

CircRNA has emerged as a new non-coding RNA that plays crucial roles in tumour initiation and development. 'MiRNA sponge' is the most reported role played by circRNAs in many tumours. The AKT/mTOR axis is a classic signalling pathway in cancers that sustains energy homeostasis through energy production activities, such as the Warburg effect, and blocks catabolic activities, such as autophagy. Additionally, the AKT/mTOR axis exerts a positive effect on EMT, which promotes tumour metastasis.

We detected higher circNRIP1 expression in gastric cancer by performing RNA-seq analysis. We verified the tumour promotor role of circNRIP1 in gastric cancer cells through a series of biological function assays. We then used a pull-down assay and dual-luciferase reporter assay to identify the downstream miR-149-5p of circNRIP1. Western blot analysis and immunofluorescence assays were performed to demonstrate that the circNRIP1-miR-149-5p-AKT1/mTOR axis is responsible for the altered metabolism in GC cells and promotes GC development. We then adopted a co-culture system to trace circNRIP1 transmission via exosomal communication and RIP experiments to determine that quaking regulates circNRIP1 expression. Finally, we confirmed the tumour suppressor role of microRNA-133a-3p in vivo in PDX mouse models.