FLT1 and neoplasm: In a study on angiogenic-defective tumor-resistant Id-mutant mice, the restoration of tumor angiogenesis, after transplantation of wild-type BM or VEGF-mobilized stem cells, was associated not only with the uptake of BM-derived VEGF-R2+-endothelial precursor cells in the blood vessels, but also with the incorporation of BM-derived myeloid cells into perivascular sites of the tumor microenvironment, these cells being characterized by the expression of VEGF-R1 [45].