SMAD4 and gastric cancer: We further determined the effects of hsa_circ_0004872 on Smad4 and p21 expression and found that hsa_circ_0004872 knockdown reduced the expression of Smad4 and p21 in GC cells (Fig. 4o) and the enforced expression of hsa_circ_0004872 significantly increased the p21 and Smad4 protein levels, while mutated hsa_circ_0004872 has no obvious effect on the expression of p21 and Smad4.