Immunofluorescence analysis shows that the tumors in Pdgfrbfl/fl and Tie2-Cre;Pdgfrbfl/fl mice exhibited similar patterns of NG-2+ pericyte distribution and PDGFR-β expression (Supplementary Fig. 8), verifying the EC specificity of Tie2-Cre system in these tumor models. The gene discussed is PDGFRB; the disease is neoplasm.