Neutralization of complement regulatory proteins augments lysis of breast carcinoma cells targeted with rhumAb anti-HER2.
The capacity of recombinant human monoclonal anti-p185HER2 IgG (rhumAb anti-HER2) to activate human complement was investigated. Complement activation by rhumAb anti-HER2 on various human breast carcinoma cell lines resulted in deposition of complement proteins on these cells. Complement activation was also observed in a solid-phase binding assay, in which purified p185HER2 was immobilized onto a microtiter plate. rhumAb anti-HER2 induced some complement-mediated tumor cell lysis by rabbit complement, but not by human complement. Analysis of membrane complement regulatory proteins (mCRP) on breast carcinoma cells revealed a heterogenous expression of CD46, CD55 and CD59. After blocking the mCRP activity with specific antibodies, rhumAb anti-HER2 induced about 15% lysis of p185HER2-expressing tumor cells. Tumor cell sensitization with rabbit polyclonal anti-tumor antiserum following mCRP neutralization, augmented cell lysis from 10 to 80%. Expression of mCRP was upregulated by treatment with PMA, and correlated with increased protection of the tumor cells from complement lysis. These results suggest that humanized antibodies like rhumAb anti-HER2 promote complement activation leading to tumor cell phagocytosis and cell-mediated cytotoxicity. They further demonstrate that a successful tumor immunotherapeutical approach, based on antibody and complement treatment, requires mCRP neutralization.
Institute of Immunology, University of Heidelberg, Germany.
K
K
Jurianz
S
S
Maslak
H
H
Garcia-Schüler
Z
Z
Fishelson
M
M
Kirschfink
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D000918:Antibody Specificity; D001943:Breast Neoplasms / Q000276:immunology / Q000378:metabolism / Q000628:therapy*; D002277:Carcinoma / Q000276:immunology / Q000378:metabolism / Q000628:therapy*; D003167:Complement Activation / Q000276:immunology*; D003165:Complement System Proteins / Q000502:physiology; D005434:Flow Cytometry; D006801:Humans; D007116:Immunization, Passive; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism; D011817:Rabbits; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D003165:Complement System Proteins; D007074:Immunoglobulin G; D009363:Neoplasm Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins