Figure 1.

Tumor angiogenesis.

Notes: (A) Tumor cells produce VEGF-A and other angiogenic factors such as bFGF and angiopoietins. These stimulate endothelial cells to proliferate and migrate. (B) An additional source of angiogenic factors is the stroma. This is a heterogeneous compartment, comprising fibroblastic, inflammatory, and immune cells. VEGF-A or placental growth factor may also contribute through recruitment of BMC. Tumor cells may release stromal cell recruitment factors, such as PDGF-A, PDGF-C, or TGF-β. (C) Endothelial cells produce PDGF-β, which promotes recruitment of pericytes in the microvasculature after activation of PDGFR-β. Reprinted from Ferrara N, Kerbel RS. Angiogenesis as a therapeutic target. Nature. 2005;438:967–974⁷¹ with permission from the Nature Publishing Group.

Abbreviations: BMC, bone marrow-derived angiogenic cells; bFGF, basic fibroblast growth factor; HGF, hepatocyte growth factor; PDGF, platelet-derived growth factor; SDF-1, stromal-derived factor-1; TGF, transforming growth factor; VEGF, vascular endothelial growth factor.