PECAM1 and neoplasm: We therefore assessed the VEGF-A and CD31 (a marker for endothelial cell) expression in these tumor sections (Figure 1F) and found a markedly reduced staining of VEGF-A, that could explain, in part the significant reduction CD31+ endothelial cells in primary tumors from CCR2−/− when compared to tumors from WT mice.Collectively, the above observations suggest that F4/80+ tumor-associated macrophages are essential for sufficient production of angiogenic factors, including VEGF, at the tumor site.