Circular RNA circRAB31 acts as a miR-885-5psponge to suppress gastric cancer progressionvia the PTEN/PI3K/AKT pathway

Emerging evidence indicated that circular RNAs (circRNAs) play essential roles in cancer progression. A large number of circRNAs have been reported to modulate cancer carcinogenesis. However, the underlying mechanisms by which circRNAs regulate gastric cancer remain largely unclear. By using circRNA microarray, we identified that circRAB31 may serve as a tumor suppressor. circRAB31 was downregulated in gastric cancer tissues and gastric cancer cell lines compared with normal tissues and a human gastric epithelial cell line (GES-1). Overexpression of circRAB31 suppressed gastric cancer proliferation and metastasis in vitro and in vivo, whereas silencing of circRAB31 had the opposite effects. Bioinformatic analysis as well as pull-down and luciferase assays revealed that circRAB31 exerted tumor-suppressive functions by binding directly to miR-885-5p. In addition, we demonstrated that circRAB31 could suppress PI3K/AKT signaling via the phosphatase and tensin homologue (PTEN)—a downstream target gene of miR-885-5p. In summary, our results demonstrated that circRAB31 could serve as a sponge of miR-885-5p to regulate gastric cancer cell proliferation, migration, and invasion by affecting the PTEN/PI3K/AKT signaling.