This review article provides an overview on the most recent advances on the role of ErbB receptors and growth factors of the epidermal growth factor (EGF)-family of peptides in cancer pathogenesis and progression. The ErbB tyrosine kinases and the EGF-like peptides form a complex system. In fact, the interactions occurring between receptors and ligands of these families affect the type and the duration of the intracellular signals that derive from receptor activation. Interestingly, activation of ErbB receptors is also driven by different classes of membrane receptor, suggesting that ErbB kinases can amplify growth promoting signals carried by different pathways. The importance of ErbB receptors and EGF-like peptides in development of organs and tissues has been demonstrated by using different mouse models. In vitro and in vivo studies have also shown that ErbB receptors and their ligands can act as transforming genes. However, evidence suggests that cooperation of different receptors and ligands is necessary to induce a fully transformed phenotype. Indeed, co-expression of different ErbB receptors and EGF-like growth factors is a common phenomenon in human primary carcinomas. This observation suggests that the growth and the survival of carcinoma cells is sustained by a network of receptors/ligands of the ErbB family. In this respect, the contemporary expression of different ErbB tyrosine kinases and/or EGF-like growth factors in human carcinomas might also affect tumor response to target based agents directed against the ErbB receptor/ligand system.
