Fig. 1.

The angiocrine and angiogenic switch during tumor progression. Vascular endothelial cells are capable of enhancing tumor growth and migration by secreting several cytokines and growth factors or activating the so-called angiocrine switch (bottom). This switch is activated by signals directed to ECs from their surrounding tumor cells. As a result, the activated ECs increase the production of angiocrine factors that confer many growth advantages to tumor cells. The angiocrine factors may be in the form of transmembrane ligands, secretory cytokines, or microparticle-packaged factors. There is evidence that activated ECs trough their interaction with tumor cells demonstrate some degree of plasticity toward a mesenchymal phenotype with enhanced tumor promoting potential