MKI67 and neoplasm: In subcutaneous xenograft tumor models, the p21 protein levels in the UBE2S knockdown group (UBE2S‐shRNA) were significantly increased compared with those in the control‐shRNA group, while there were fewer Ki67‐positive cells in the UBE2S knockdown group than in the control‐shRNA group (Figure 6A,B).