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Anti‐epidermal growth factor receptor monoclonal antibodies affecting signal transduction
Author(s) -
Reins HansAlbert,
Steinhilber Gerhard,
Freiberg Brigitte,
Anderer F. Alfred
Publication year - 1993
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240510215
Subject(s) - autophosphorylation , epitope , epidermal growth factor , epidermal growth factor receptor , monoclonal antibody , microbiology and biotechnology , tyrosine kinase , a431 cells , phosphorylation , signal transduction , chemistry , tyrosine phosphorylation , biology , biochemistry , protein kinase a , receptor , antibody , cell , cell cycle , immunology , molecular medicine
Monoclonal antibodies prepared against tyrosine phosphorylated epidermal growth factor receptor (EGFR) were tested for their effects on transmembrane signal transduction in A431 tumor cells. Monoclonal antibodies (mab) defined by SDS‐sensitive epitopes, i.e., epitopes with conformational specificity, were most effective. Mab 5‐‐125 reacting with a site of the extracellular EGFR domain blocked EGF‐binding and cell proliferation in vitro, as well as tumor growth in vivo. However, this mab appeared not to be internalized upon binding to EGFR and did not trigger EGFR autophosphorylation. In contrast, mab 5‐D43, also defined by an SDS‐sensitive epitope and reacting with an extracellular EGFR site, did not block EGF binding but was readily internalized after binding to EGFR of untreated A431 cells. This mab induced EGFR tyrosine phosphorylation in cell lysates and tyrosine‐specific autophosphorylation of insolubilized EGFR immune complexes. Cell growth in vitro was greatly stimulated in the presence of mab 5‐D43. Since interaction of mab 5‐D43 with EGFR induced most EGF‐specific functions, although it did not bind to the EGF‐specific site of EGFR, we have to assume that binding of mab 5‐D43 to EGFR induced a conformational shift that activated the cytoplasmic EGFR kinase site. On the other hand, activation and/or accessibility of the EGFR kinase site could be blocked by mab 1‐594, which is defined by an SDS‐insensitive protein epitope of the cytoplasmic EGFR domain. Blocking of the EGFR kinase site by mab 1‐594 also abolished EGF‐induced tyrosine phosphorylation of endogenous cellular substrates with molecular masses of 145, 97, 85, 37, and 32 kDa, as well as of exogenous substrates such as GAT copolymer. © 1993 Wiley‐Liss, Inc.