TRANSFORMING GROWTH FACTOR-ALPHA - AN ONCODEVELOPMENTAL GROWTH-FACTOR

Transforming growth factor-alpha-(TGF-alpha) is a 5-amino-acid mitogenic peptide that is structurally and, in some cases, functionally related to members of the epidermal growth factor (EGF) family of peptides. TGF-alpha is initially synthesized as a high-molecular-weight, glycosylated, membrane-associated precursor of approximately-160 amino acids. The low-molecular-weight TGF-alpha-peptide as well as the precursor are biologically active in a number of systems and can function as transforming proteins when overexpressed. TGF-alpha-binds to and activates the EGF receptor, and TGF-alpha and the EGF receptor are coexpressed in a number of human and rodent tumors and tumor cell lines - which suggests that TGF-alpha-can function as an autocrine or paracrine growth factor. TGF-alpha is transiently expressed in some fetal and adjacent maternal tissues during development and is also expressed in a number of adult tissues; this pattern of expression suggests that the growth factor is involved in several distinct physiological functions.