Figure 7.

Molecular roles of circRNAs in the TGF-β/Smad signaling pathway. TGF-β signaling occurs via membrane-bound heteromeric serine-threonine kinase receptor complexes that are activated by TGF-β ligands and the subsequent phosphorylation of Smad family members. Smad members accumulate in the nucleus and act as transcription factors regulating target gene expression. Activation of canonical TGF-β signaling represses epithelial gene expression, and the resulting TGF-β-induced EMT has a central role in cancer metastasis. Three upregulated and 4 downregulated circRNAs are indicated; 4 circRNAs regulate the TGF-β/Smad pathway through ceRNA effects. Red: upregulated circRNAs; blue: downregulated circRNAs.