FOXO3 and esophageal squamous cell carcinoma: The regulating mechanism of circRNA in cancer was investigated in several studies: in esophageal squamous cell carcinoma (ESCC), cir-ITCH acted as sponge of miRNAs to both increase the level of ITCH and inhibit the Wnt/β-catenin pathway, therefore inhibiting ESCC (14); in breast cancer cells (MDA-MB-231), circ-Foxo3 (hsa_circRNA_104170) bonded with 8 miRNAs (miR-22, miR-136, miR-138, miR-149, miR-433, miR-762, miR-3614-5, and miR-3622b-5p) to promote the translation of Foxo3 mRNA, thus inhibiting cell proliferation (22).