Knocking down DDX21 by treatment with DOX in mice xenografted with BE(2)‐C cells containing DOX‐inducible DDX21 shRNA‐1 or Kelly cells containing DOX‐inducible DDX21 shRNA‐2 cells led to tumor shrinkage and a significant delay in relapse, with increased overall survival by up to 68 and 24 days, respectively. This evidence concerns the gene DDX21 and neoplasm.