Quantification of vessels by platelet/endothelial cell adhesion molecule-1 (PECAM-1+) staining and BMDC infiltration by GFP+ cell quantification on B16F10 tumour sections showed no statistically significant difference in vascularization or BMDC infiltration in the primary tumour of control mice compared with Id1-overexpressing mice implanted with B16F10 melanoma (Supplementary Fig. 4A,B). Here, PECAM1 is linked to melanoma.