CDK4 and neoplasm: IHC staining of tumour sections confirmed the up‐regulation of RN181 (RN181 versus RV, p < 0.01) and CDK4 in both AGS‐RV tumour (RV + CDK4 versus RV, p < 0.01) and AGS‐RN181 tumour (RN181 + CDK4 versus RN181, p < 0.01) (Figure 4E).