Fig. 7. Schematic model for signal transduction pathways in serum-starved 5637 cells. In carcinoma 5637 cells, serum starvation promotes signaling events involving EGFR ligands, EGFR, SFKs (e.g. Src) and p145^met to suppress activation of caspase-like proteases. Serum-starved cells can therefore survive and proliferate. In this study, several materials are used to validate this scheme: positive regulators such as conditioned medium and purified EGF, but not HGF; negative regulators such as a neutralizing anti-EGFR antibody (mAb528), PP2, SU6656, AG99 and downregulation of p145^met, but not K252a. See text for details.