Figure 1.

Schematic representation of molecular players involved in paracrine and autocrine VEGF secretion. Tumour cells are the major source of VEGF production, but alternative cells are currently credited as important sources to release VEGF. VEGF receptors expressed in endothelial cells have pivotal role in cancer angiogenesis and angiopoietin 1, and Tie2 receptor support the new vessel stabilization, whereas Ang-2 is thought to antagonize the stabilizing action of Ang-1. Tie-2 receptor was recently recognised to critically participate on breast cancer development and bone metastasis.