title: Soluble HER-2/neu neutralizes biologic effects of anti-HER-2/neu antibody on breast cancer cells in vitro.
abstract: Amplification and over-expression of the HER-2/neu proto-oncogene are associated with poor prognosis in women with both node-positive and node-negative breast cancer. Therefore, the encoded surface glycoprotein represents an attractive target for cancer immunotherapies. Furthermore, the extracellular domain of HER-2/neu is released from the cell surface by proteolytic cleavage. In the present experiments, we investigated the potential biologic effects of soluble HER-2/neu with particular emphasis on its interaction with anti-HER-2/neu antibodies. A monoclonal antibody specific for the extracellular domain of HER-2/neu dose dependently inhibited the proliferation of highly HER-2/neu-expressing SK-BR-3 and BT-474 breast cancer cells but had no effect on the proliferation of weakly to moderately HER-2/neu-expressing MCF-7, HBL-100 and ZR-75-1 breast cells. Addition of SK-BR-3 or BT-474 cell supernatants with high concentrations of soluble HER-2/neu led to a neutralization of anti-HER-2/neu antibody-mediated inhibition of proliferation due to a binding of soluble HER-2/neu by the antibody, which could be demonstrated by immunoprecipitation. Furthermore, the ability of anti-HER-2/neu antibodies to mediate antibody-dependent cellular cytotoxicity (ADCC) by lymphokine-activated killer cells was assessed. Cytolysis of SK-BR-3 tumor cells was increased significantly in the presence of anti-HER-2/neu antibodies. Similar to the proliferation inhibition, ADCC was neutralized by addition of soluble HER-2/neu-containing supernatants. Our data suggest that tumors rich in HER-2/neu might thus escape certain steps of immunologic control by neutralizing biologic activities of anti HER-2/neu antibodies due to the presence of soluble HER-2/neu.
authors.affiliation: Clinical Division of Oncology, University Hospital, Vienna, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Brodowicz
authors.forename: C
authors.initials: C
authors.lastname: Wiltschke
authors.forename: A C
authors.initials: AC
authors.lastname: Budinsky
authors.forename: M
authors.initials: M
authors.lastname: Krainer
authors.forename: G G
authors.initials: GG
authors.lastname: Steger
authors.forename: C C
authors.initials: CC
authors.lastname: Zielinski
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000627:therapeutic use*; D000920:Antibody-Dependent Cell Cytotoxicity; D001940:Breast / Q000166:cytology / Q000276:immunology; D001943:Breast Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D002455:Cell Division; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D005260:Female; D006801:Humans; D007167:Immunotherapy; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis / Q000276:immunology* / Q000502:physiology*; D012995:Solubility; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D017077:Culture Media, Conditioned; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases; C000715470:MAS1 protein, human