Fig. 1. Diverse regulatory mechanisms of circRNAs and Wnt/β-catenin signaling pathway. Circ_0006427 inactivates Wnt/β-catenin pathway by upregulating Dkk1 in a miR-6783-3p-dependent manner; Circ_ITCH may increase the expression of protein ITCH by binding to miR-7, miR-20, and miR-124. Subsequently, overexpressed ITCH downregulates Dvl, which reduces β-catenin degradation and activates this pathway. Three circRNAs (circRNA_NEK6, circ_CBFB and circ_0067934) upregulate frizzled (FZD) expression by sponging corresponding miRNAs (miR-370-3p, miR-607 and miR-1324), and thereby activating the pathway. Hsa_circ_009361 and hsa_circ_0002052 also increase APC2 expression by sponging miR-582 and miR-1205, which inactivates Wnt/β-catenin cascade. Circβ-catenin encodes a β-catenin isoform, termed “β-catenin-370-aa”, to enhance the stability of β-catenin by reducing GSK3β-induced β-catenin phosphorylation and degradation, and thereby activating Wnt/β-catenin signaling pathway. CircRNA cZNF292 directly upregulates the expression of β-catenin, thereby activating Wnt/β-catenin signaling pathway, but it also suppresses some inhibitors of this pathway, such as APC and Axin. CircRNA_102171 reduces the level of CTNNBIP1 in the nucleus, and enhances the association between β-catenin and TCF/LEF to upregulate Wnt/β-catenin signaling pathway.