Overexpression of protectin (CD59) down‐modulates the susceptibility of human melanoma cells to homologous complement

Abstract

The clinical efficacy of therapeutic complement (C)-activating monoclonal antibodies (mAb) to melanoma-associated antigens can be impaired by the levels of expression of C-inhibitory molecules on neoplastic cells. Protectin (CD59) is a glycosylphosphatidylinositol (GPI)-anchored cell membrane glycoprotein, acting as terminal regulator of C cascade, which is heterogeneously expressed in melanomas and represents the main restriction factor of C-mediated lysis of melanoma cells. Thus, we investigated whether the overexpression of CD59 could influence the constitutive susceptibility of distinct melanoma cells to homologous C. Infection of CD59-positive Mel 100 and 70-W melanoma cells by a retroviral vector carrying the CD59 cDNA, significantly (P < 0.05) upregulated their constitutive expression of CD59, whereas it did not affect that of additional C-regulatory molecules. Transduced CD59 was entirely GPI-anchored and showed a molecular weight identical to native CD59. Additionally, higher amounts of soluble CD59 were detected in the conditioned media of CD59-transduced melanoma cells compared with parental cells. CD59-transduced melanoma cells, sensitized by the anti-GD3 disialoganglioside mAb R24, were significantly (P < 0.05) less susceptible to homologous C-lysis than were parental cells; this effect was fully reverted by the masking of CD59 with F(ab')(2) fragments of the anti-CD59 mAb YTH53.1. These results provide conclusive evidence demonstrating that absolute levels of CD59 expression regulate the susceptibility to homologous C of specific melanoma cells, and suggest an additional explanation for the poor clinical results obtained with C-activating mAb in the clinical setting.

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

“…38 Ectopic expression of CD59 in vitro renders melanoma cells less susceptible to mAb-mediated CDC. 39 Contradictory to previous results one immunohistochemistry study showed that the loss of CD59 is associated with aggressiveness of breast carcinomas. 40 This study however did not assess expression of CD55, which-on colorectal cancer-is inversely correlated with the expression of CD59.…”

Application of a novel inhibitor of human CD59 for the enhancement of complement-dependent cytolysis on cancer cells

“…3 Extensive clinical and experimental evidence indicates that CD59 is highly effective at protecting NHL and CLL cells from Ab (rituximab or ofatumumab)-mediated CDC. [7][8][9][10][11][12][13][14][15][16][17][18][19] Many in vivo and in vitro studies indicate that CDC plays a critical role and also interacts synergistically with Ab-dependent cell cytotoxicity in rituximab therapy. 3 To further enhance CDC activity, the human IgG1 anti-CD20 mAb ofatumumab has been developed as another new mAb therapeutic.…”

“…22 Thus, there remains a need for more effective therapies in both the upfront and the relapsed settings. Since upregulation of human CD59 (hCD59) is an important determinant of sensitivity to Ab (rituximab and ofatumumab) treatment for NHL and CLL, [7][8][9][10][11][12][13][14][15][16][17][18] it is imperative for us to develop a molecule capable of abrogating CD59 function in cancer cells and facilitating Ab-mediated cancer therapy.…”

Down-regulation of CD55 and CD46 expression by anti-sense phosphorothioate oligonucleotides (S-ODNs) sensitizes tumour cells to complement attack

“…Although mCRP-blocking experiments in vitro suggest a prominent role of CD59 in the protection of tumour cells against CDC [6,32], there are in vivo data which emphasize the role of early complement pathway regulation by CD55 and CD46. Caragine et al [33] underline the importance of recruiting cell-mediated effector mechanisms for the eradication of tumour cells in vivo by generation of C3 opsonins and by the release of inflammatory activation fragments (C3a, C5a).…”