J Hakulinen1, S Meri. 1. Department of Bacteriology and Immunology, University of Helsinki, Finland.
Abstract
BACKGROUND: Normal human cells resist the lytic activity of homologous complement (C) by expressing inhibitory molecules on their cell membranes. Recently, it has become increasingly evident that information on C inhibitors on malignant tumor cells is crucial before considering any immunotherapeutic attempts with C-activating antibodies. As one of the most potent inhibitors of C lysis is protectin (CD59), we have examined its expression and function on human breast cancer cells. EXPERIMENTAL DESIGN: Immunofluorescence microscopy was used to detect protectin expression on solid breast tumor samples (N = 12). Using immunoaffinity chromatography, protectin was isolated from the membranes of cultured MCF7 and T47D breast cancer cells. The purified proteins were incorporated into heterologous cells to study their C inhibitory activities. The reactivity of tumor cell protectins with terminal C complexes was examined by sucrose density ultracentrifugation analysis. A chromium release assay was used to study the effects of protectin neutralization on the sensitivity of MCF7 and T47D cells to C-mediated cytotoxicity. RESULTS: Protectin was found to be strongly expressed by all human breast cancer tumors examined. The affinity-purified protectins had a glycophosphoinositollipid anchor and migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as glycosylated smears of 19 to 25 kilodaltons. Protectin isolated from T47D cells bound to nascent C5b-9 complexes generated in human sera and inhibited C lysis of guinea pig erythrocytes when incorporated into their cell membranes. C-mediated killing of breast cancer cells could be significantly enhanced after treatment of the cells with F(ab')2 fragments of the anti-protectin monoclonal antibody YTH53.1. CONCLUSIONS: Human breast cancer cells resist C membrane attack by expressing protectin on their cell membranes. Neutralization of protectin on the surface of the tumor cells increases their sensitivity to C lysis.
BACKGROUND: Normal human cells resist the lytic activity of homologous complement (C) by expressing inhibitory molecules on their cell membranes. Recently, it has become increasingly evident that information on C inhibitors on malignant tumor cells is crucial before considering any immunotherapeutic attempts with C-activating antibodies. As one of the most potent inhibitors of C lysis is protectin (CD59), we have examined its expression and function on humanbreast cancer cells. EXPERIMENTAL DESIGN: Immunofluorescence microscopy was used to detect protectin expression on solid breast tumor samples (N = 12). Using immunoaffinity chromatography, protectin was isolated from the membranes of cultured MCF7 and T47D breast cancer cells. The purified proteins were incorporated into heterologous cells to study their C inhibitory activities. The reactivity of tumor cell protectins with terminal C complexes was examined by sucrose density ultracentrifugation analysis. A chromium release assay was used to study the effects of protectin neutralization on the sensitivity of MCF7 and T47D cells to C-mediated cytotoxicity. RESULTS:Protectin was found to be strongly expressed by all humanbreast cancer tumors examined. The affinity-purified protectins had a glycophosphoinositollipid anchor and migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as glycosylated smears of 19 to 25 kilodaltons. Protectin isolated from T47D cells bound to nascent C5b-9 complexes generated in human sera and inhibited C lysis of guinea pig erythrocytes when incorporated into their cell membranes. C-mediated killing of breast cancer cells could be significantly enhanced after treatment of the cells with F(ab')2 fragments of the anti-protectin monoclonal antibody YTH53.1. CONCLUSIONS:Humanbreast cancer cells resist C membrane attack by expressing protectin on their cell membranes. Neutralization of protectin on the surface of the tumor cells increases their sensitivity to C lysis.
Authors: L I Brasoveanu; E Fonsatti; A Visintin; M Pavlovic; I Cattarossi; F Colizzi; A Gasparollo; S Coral; V Horejsi; M Altomonte; M Maio Journal: J Clin Invest Date: 1997-09-01 Impact factor: 14.808
Authors: Y T Konttinen; A Ceponis; S Meri; A Vuorikoski; P Kortekangas; T Sorsa; A Sukura; S Santavirta Journal: Ann Rheum Dis Date: 1996-12 Impact factor: 19.103