PECAM1 and melanoma: We chose three representative melanoma cells from patients (MeMI, MePA and MeTA) and SKMEL28 cell line and we observed that they were negative for the expression of human CD31, a marker of endothelial cells (Figure 2A and Supplementary Table S1), but that they expressed CD144 and VEGFR-2 (Figure 2B, 2C and Supplementary Table S1).