Inhibition of epidermal growth factor/transforming growth factor-alpha-stimulated cell growth by a synthetic peptide.
Estrogen-stimulated growth of the human mammary adenocarcinoma cell line MCF-7 is significantly inhibited by monoclonal antibodies to the epidermal growth factor (EGF) receptor that act as antagonists of EGF's mitogenic events by competing for high-affinity EGF receptor binding sites. These antibodies likewise inhibit the EGF or transforming growth factor-alpha (TGF-alpha)-stimulated growth of these MCF-7 cells. An analogous pattern of specific EGF or TGF-alpha growth inhibitory activity was obtained using a synthetic peptide analog encompassing the third disulfide loop region of TGF-alpha, but containing additional modifications designed for increased membrane affinity [( Ac-D-hArg(Et)2(31),Gly32,33]HuTGF-alpha(31-43)NH2). The growth factor antagonism by this synthetic peptide was specific in that it inhibited EGF, TGF-alpha, or estrogen-stimulated growth of MCF-7 cells but did not inhibit insulin-like growth factor-1 (IGF-1)-stimulated cell growth. Altogether, these results suggest that a significant portion of the estrogen-stimulated growth of these MCF-7 cells is mediated in an autocrine/paracrine manner by release of EGF or TGF-alpha-like growth factors. The TGF-alpha peptide likewise inhibited EGF- but not fibroblast growth factor (FGF)- or platelet-derived growth factor (PDGF)-stimulated growth of NIH-3T3 cells in completely defined media; but had no effect on growth or DNA synthesis of G0-arrested cells, nor did it effect growth of NR-6 cells, which are nonresponsive to EGF. Although this synthetic peptide did not directly compete with EGF for cell surface receptor binding, it exhibited binding to a cell surface component (followed by internalization), which likewise was not competed by EGF. The peptide did not directly inhibit EGF-stimulated phosphorylation of the EGF receptor, nor did it inhibit phosphorylation of an exogenous substrate, angiotensin II, by activated EGF receptor. The TGF-alpha peptide did, however, affect the structure of laminin as manifested by laminin self-aggregation; this affect on laminin may, in turn, have a modulatory effect on EGF-mediated cell growth.
Eppstein
D A
DA
Cancer and Developmental Biology, Syntex Research, Palo Alto, California 94304.
Marsh
Y V
YV
Schryver
B B
BB
Bertics
P J
PJ
D000230:Adenocarcinoma / Q000473:pathology* / Q000648:ultrastructure; D000906:Antibodies / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D001943:Breast Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000473:pathology; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006801:Humans; D007797:Laminin / Q000378:metabolism / Q000502:physiology; D010455:Peptides / Q000494:pharmacology*; D011971:Receptors, Immunologic / Q000378:metabolism / Q000502:physiology; D017474:Receptors, Laminin; D015291:Transforming Growth Factors / Q000032:analysis / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000473:pathology / Q000648:ultrastructure
D000906:Antibodies; D004967:Estrogens; D007797:Laminin; D010455:Peptides; D011971:Receptors, Immunologic; D017474:Receptors, Laminin; D004958:Estradiol; D004815:Epidermal Growth Factor; D015291:Transforming Growth Factors; D066246:ErbB Receptors