Figure 1
From: Signaling through Raf-1 in the Neovasculature and Target Validation by Nanoparticles
How do tumors survive, grow and become resistant to drug treatment? The answer may lie in the fact that tumors secrete multiple cytokines and growth factors. A complex interplay between positive and negative factors determines the survival of tumors. The apoptotic signals exerted by "intrinsic" and "extrinsic" pathways could be rescued by bFGF and VEGF. These cytokines activate the PAK-1 and Src kinases, and phosphorylation of specific amino acid residues (indicated by the lightning symbols) within the Raf-1 kinase signals it to be targeted to the mitochondria, which promotes endothelial cell survival [adapted from Alavi, A. et al., Science 301; 94–6 (2003)].