Expression and function of the complement membrane attack complex inhibitor protectin (CD59) on human breast cancer cells.

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.

• Authors: J Hakulinen, S Meri
• Journal: Laboratory investigation; a journal of technical methods and pathology (Lab Invest) Vol. 71 Issue 6 Pg. 820-7 (Dec 1994) ISSN: 0023-6837 [Print] United States
• PMID: 7528832 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, CD
• CD59 Antigens
• Complement Membrane Attack Complex
• Immunoglobulin Fab Fragments
• Membrane Glycoproteins
• Complement System Proteins

Topics

• Adenocarcinoma (immunology)
• Antigens, CD (biosynthesis, immunology)
• Breast Neoplasms (immunology)
• CD59 Antigens
• Carcinoma, Ductal, Breast (immunology)
• Complement Membrane Attack Complex (antagonists & inhibitors)
• Complement System Proteins (immunology)
• Cytotoxicity Tests, Immunologic (methods)
• Fluorescent Antibody Technique
• Humans
• Immunoblotting
• Immunoglobulin Fab Fragments (immunology)
• Membrane Glycoproteins (biosynthesis, immunology)
• Tumor Cells, Cultured