Knocking down DDX21 almost completely abolished clonogenicity in the DOX‐inducible DDX21 shRNA‐1 and DDX21 shRNA‐2 BE(2)‐C and Kelly cells, compared with the DOX‐inducible control shRNA cells (Fig. 3F–G), indicating that DDX21 plays a crucial role in neuroblastoma tumorigenesis. This evidence concerns the gene DDX21 and neuroblastoma.