Cross‐linking tumor cells with effector cells via CD55 with a bispecific mAb induces β‐glucan‐dependent CR3‐dependent cellular cytotoxicity

Abstract

Complement (C) regulatory proteins decrease the effectiveness of immunotherapeutic anti-cancer antibodies. Bispecific mAb (bi-mAb) that target a tumor antigen and simultaneously inhibit a C regulator increase the effectiveness of such a therapy. Here we investigated the mechanism by which bi-mAb increase tumor cell lysis. Apart from Cdependent cytotoxicity, C activation can lead to complement receptor 3 (CR3)-dependent cellular cytotoxicity (CR3-DCC) by CR3-positive effector cells in the presence of b-glucan. Here we show that an anti-Ep-CAM*anti-CD55 bi-mAb induced more than threefold higher CR3-DCC (71%) of human colorectal cancer cells compared with antiEp-CAM alone (20%). This CR3-DCC was dependent on the binding of the anti-CD55 arm of tumor-bound anti-Ep-CAM*anti-CD55 bi-mAb to effector cell CD55, CR3 priming by b-glucan and the presence of iC3b on the target cell. Comparable lysis could be obtained in the absence of iC3b, when CR3 and CD55 were cross-linked on the effector cells, suggesting cooperation between CD55 and CR3 in signal transduction. Tumor cells with low antigen expression were effectively lysed via this mechanism in contrast to direct C-dependent cytotoxicity. These data imply that the effectiveness of mAb immunotherapy can be improved using anti-tumor antigen*anti-CD55 bi-mAb and b-glucan, thereby initiating CR3-DCC as an additional effector mechanism that is efficient for eradication of tumor cells with lower antigen expression.

Combined Yeast β-Glucan and Antitumor Monoclonal Antibody Therapy Requires C5a-Mediated Neutrophil Chemotaxis via Regulation of Decay-Accelerating Factor CD55

“…This drawback may be overcome by using bispecific mAb against tumor antigen with higher affinity and CD55 with lower affinity. A previous study has shown that this strategy could specifically target tumor cells with minimal binding to normal cells and increase h-glucan-mediated CR3-dependent cellular cytotoxicity (43). Indeed, bispecific mAb to epithelial cell adhesion molecule and Crry in rat has shown a significant therapeutic efficacy for a rat colorectal cancer lung metastasis model in vivo (44).…”

Complement in Cancer and Cancer Immunotherapy

“…It has been demonstrated that tumours can be sensitised to complement by removal of CD55 and CD59 by phosphatidylinositol-phospholipase C treatment (PI-PLC) (Brasoveanu et al 1996;Gelderman et al 2006). Brasoveanu and colleagues showed that using increasing doses of PI-PLC, progressively decreased cell-surface expression of CD59 and increased C-mediated lysis of cells sensitised with mAb R24.…”

“…A more recent attempt was made by Gelderman and colleagues who generated two bispecific antibodies against HLA and CD55 and anti-EpCam anti CD55. Both bispecific antibodies were able to increase C3b deposition on the surface of cervical and colorectal carcinoma cell lines substantially (Gelderman et al 2002a, b) In a subsequent study using anti-EpCamxCD55 bispecific mAb, Gelderman et al (2006) showed threefold increase in CR3-DCC by …”

Regulation of complement and modulation of its activity in monoclonal antibody therapy of cancer

“…Interaction of iC3b with CR3 on macrophages or NK cells resulted in enhanced ADCC. 7,8 Figure 1. Schematic representation of the classical complement pathway initiated by mAbs and its inhibitors.…”