Enhancement of antibody-dependent cellular cytotoxicity of cetuximab by a chimeric protein encompassing interleukin-15

Maria Carmen Ochoa,Luna Minute,Ascensión López,Elisabeth Pérez-Ruiz,Celia Gomar,Marcos Vasquez,Susana Inoges,Iñaki Etxeberria,Inmaculada Rodriguez,Saray Garasa,Jan-Peter Andreas Mayer,Peter Wirtz,Ignacio Melero,Pedro Berraondo

doi:10.1080/2162402x.2017.1393597

Abstract

ABSTRACTEnhancement of antibody-dependent cellular cytotoxicity (ADCC) may potentiate the antitumor efficacy of tumor-targeted monoclonal antibodies. Increasing the numbers and antitumor activity of NK cells is a promising strategy to maximize the ADCC of standard-of-care tumor-targeted antibodies. For this purpose, we have preclinically tested a recombinant chimeric protein encompassing the sushi domain of the IL15Rα, IL-15, and apolipoprotein A-I (Sushi-IL15-Apo) as produced in CHO cells. The size-exclusion purified monomeric fraction of this chimeric protein was stable and retained the IL-15 and the sushi domain bioactivity as measured by CTLL-2 and Mo-7e cell proliferation and STAT5 phosphorylation in freshly isolated human NK and CD8+ T cells. On cell cultures, Sushi-IL15-Apo increases NK cell proliferation and survival as well as spontaneous and antibody-mediated cytotoxicity. Scavenger receptor class B type I (SR-B1) is the receptor for ApoA-I and is expressed on the surface of tumor cells. SR-B1 can adsorb the chimeric protein on tumor cells and can transpresent IL-15 to NK and CD8+ T cells. A transient NK-humanized murine model was developed to test the increase of ADCC attained by the chimeric protein in vivo. The EGFR+ human colon cancer cell line HT-29 was intraperitoneally inoculated in immune-deficient Rag2−/−γc−/− mice that were reconstituted with freshly isolated PBMCs and treated with the anti-EGFR mAb cetuximab. The combination of the Sushi-IL15-Apo protein and cetuximab reduced the number of remaining tumor cells in the peritoneal cavity and delayed tumor engraftment in the peritoneum. Furthermore, Sushi-IL15-Apo increased the anti-tumor effect of a murine anti-EGFR mAb in Rag1−/− mice bearing subcutaneous MC38 colon cancer transfected to express EGFR. Thus, Sushi-IL15-Apo is a potent tool to increase the number and the activation of NK cells to promote the ADCC activity of antibodies targeting tumor antigens.

Highlights

Tumor-targeting monoclonal antibodies recognize cell surface tumor antigens and elicit tumor cell death by direct or indirect mechanisms
SR-B1 can adsorb the chimeric protein on tumor cells and can transpresent Interleukin 15 (IL-15) to NK and CD8C T cells
The EGFRC human colon cancer cell line HT-29 was intraperitoneally inoculated in immune-deficient Rag2¡/¡gc¡/¡ mice that were reconstituted with freshly isolated PBMCs and treated with the anti-epidermal growth factor receptor (EGFR) mAb cetuximab

Summary

Introduction

Tumor-targeting monoclonal antibodies recognize cell surface tumor antigens and elicit tumor cell death by direct or indirect mechanisms. The complement cascade can be activated by recruitment of C1q to the Fc region of appropriate IgG subclasses.[1] Secondly, NK and macrophage cytotoxic activity can be triggered against tumor cells by activating Fc-receptor CD16A (FcgRIIIA). This mechanism is termed antibody-dependent cellular-mediated cytotoxicity (ADCC).[2]. ADCC has been exploited therapeutically since the discovery of anti-tumor associated antigen directed monoclonal antibodies One of these approved monoclonal antibodies is cetuximab,[3] which targets the epidermal growth factor receptor (EGFR) and is used for treatment of head and neck and colon cancer. In addition to a direct antitumor effect impairing intrinsic EGFR tyrosine kinase signaling,[4] cetuximab is able to mediate ADCC.[5]

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