Recently, the receptor for epidermal growth factor (EGF) was identified as a downstream element in different signaling pathways. This expanded its classical function as a receptor for EGF-like ligands to a role as mediator of diverse signaling systems and as a switch point of a cellular communication network. In addition, several downstream targets, (e.g. Smad proteins and STATs) into which signals from synergistic and antagonistic signaling pathways converge, were identified.