To further test the suppressive effect of WIP1 and miR-21 inhibition on breast tumor growth in vivo, HER18R cells expressing doxycycline (Dox)-inducible control, WIP1, miR-21 or DDX5 short-hairpin RNAs (shRNAs) (>70% knockdown efficiency) were injected to mouse mammary fat pads to establish xenograft breast tumor models in female nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. This evidence concerns the gene PPM1D and breast neoplasm.