The main findings in our study were that Ang2 was specifically expressed in the tumour vasculature, but not in RCC tumour cells, Ang2 expression in the primary tumours correlated with tumour vascular density and that the high baseline endothelial Ang2 levels were associated with an initial beneficial response to first-line sunitinib. The gene discussed is ANGPT2; the disease is renal cell carcinoma.