Circular RNAs are a large class of noncoding RNAs. Smad5 functions in cell differentiation

cell proliferation and metastasis. It has been reported that lnc-Smad5 can inhibit the proliferation of diffuse large B cell lymphoma. However

the function of circ-Smad5 has not yet been reported. Lentivirus vectors were constructed to establish circ-Smad5 upregulated and circ-Smad5 downregulated cell models. A CCK-8 assay was used to detect the proliferation of JB6 cells. FACS was used to analyze the cell cycle in the cell models. Western blot

immunofluorescence staining and TOP/FOP flash dual luciferase activity assays were used to determine the activity of the Wnt signaling pathway. The results revealed that the expression level of circ-Smad5 in JB6 cells was significantly lower than the expression level of linearized-Smad5. Compared with the control group

the percentage of S phase cells and the expression level of cyclin D1 protein were significantly higher in the sh-circ-Smad5 group. In the sh-circ-Smad5 group

β-catenin and LEF-1 were significantly increased

p-β-catenin was significantly decreased

and the relative activity of the TOP/FOP reporter gene was higher compared to the control group levels. These phenomena could be reversed by treating with Wnt signaling inhibitor PNU-74654. We conclude that the circ-Smad5 retards the proliferation and the cell cycle progression of JB6 cells. Thus

circ-Smad5 may function by inhibiting the activation of Wnt/β-catenin/Lef 1 signaling

which inhibits the expression of cyclin D1. To the best of our knowledge

we are the first to report the function of circ-Smad5.