ABSTRACT
Growth factors and other extracellular signaling agents such as hormones and regulatory peptides have an important role in the regulation of cell proliferation and differentiation, two processes that are critically altered in neoplasia. Growth factors may participate in oncogenic processes in vivo, contributing to the proliferation of neoplastically transformed cells, the vascularization of the mass of tumor cells through the formation of new vessels (angiogenesis), and the dissemination of the tumor cells through the body by the invasion and metastatization of normal body tissues. The interactions that exist between growth factors and oncoproteins are of great importance in relation to the development of tumors in both human and nonhuman species. 1 Clinical studies on different human cancers indicate that these interactions may contribute to determining the presentation and pathological characteristics of human tumors and may define, at least in part, the prognosis of different tumors. 2-6 Inhibition of specific signaling pathways involving growth factors and oncoproteins may be useful for cancer therapy. 7
