This indicated downregulation of DKK2 mRNA in the tumor tissues (Fig. 5b), which was confirmed by western blotting (Fig. 5c), together with a negative correlation between DKK2 downregulation and miR-657 levels (Fig. 5e; r =  − 0.5362, P < 0.0001). This evidence concerns the gene DKK2 and neoplasm.