(a) Tumour volume (mm3) post-subcutaneous injections of MDA-MB-231 cells; *P < 0.05 (n=5 mice per group). MDA-MB-231 cells silenced with control, Skp2 shRNAs, or Skp2 shRNAs plus CDK8 overexpression were injected into nude mice (n=5 for each group) and followed up for tumourigenesis (see Methods). The lysate of tumour cells were subjected to immunoblotting (left panel). A photo of five tumours aligned together were presented (middle panel). The results were calculated as mean values ± s.d. *p<0.05, **p<0.01 using Student’s t-test (right panel). (b) Histological analysis of Skp2, mH2A1.1, mH2A1.2 and CDK8 expressions in patients with low or high grade of breast invasive ductal carcinoma. Scale bar represents 200µm. (c-e) Skp2 expression was negatively correlated with mH2A1.1 (r=−0.624, p<0.001) (c), but positively associated with CDK8 (r=0.661, p<0.001) (d). mH2A1.1 negatively correlated with CDK8 expression (r=−0.638, p<0.001) (e). (f-h), Kaplan-Meier plot analysis of overall survival of 189 cases of breast invasive ductal carcinoma patients with low or high expression of Skp2 (f), mH2A1.1 (g) or CDK8 (h) P-value in all case is < 0.01 by using Mann-Whitney U test.