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Research Articles: Therapeutics

Cytokines fused to antibodies and their combinations as therapeutic agents against different peritoneal HER2/neu expressing tumors

¹ Division of Surgical Oncology, Department of Surgery; ² Department of Microbiology, Immunology, and Molecular Genetics; and ³ Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, at Los Angeles, Los Angeles, California

Requests for reprints: Manuel L. Penichet, Division of Surgical Oncology, Department of Surgery, University of California, Los Angeles, Box 167817, Los Angeles, CA 90095-1678. Phone: 310-825-1304; Fax: 310-825-6192. E-mail: penichet{at}microbio.ucla.edu

Abstract

We have previously generated antihuman HER2/neu–humanized IgG3 fused to interleukin-2 (IL-2), IL-12, or granulocyte macrophage colony-stimulating factor (GM-CSF) [monofunctional fusion proteins (mono-AbFP)] or fused to IL-2 and IL-12 or IL-12 and GM-CSF [bifunctional fusion proteins (bi-AbFP)]. These AbFPs retained cytokine and antigen-binding activities. We have now further characterized the AbFPs and determined the heparin-binding activity of the fused cytokines, their ability to trigger IFN- secretion and natural killer (NK) activation, and their direct antitumor efficacy. Flow cytometry revealed heparin-binding activity in the AbFPs containing IL-12 and IL-2, although this activity seems to be decreased in the bi-AbFPs. However, both bi-AbFPs retained the capacity to stimulate IL-12-dependent IFN- secretion in the NK cell line KY-1, and IL-12/IL-2 bi-AbFP induced NK activity in splenocytes. The antitumor effectiveness of bi-AbFPs and mono-AbFP combinations was studied in mice challenged i.p. with three different human HER2/neu murine syngeneic models (D2F2/E2, CT26-HER2/neu, and MC38-HER2/neu). Although a significant variability in the profile of antitumor response was observed in the different tumor models, the combination of IL-12 and GM-CSF mono-AbFPs protected 100% of D2F2/E2-challenged and 75% of CT26-HER2/neu–challenged mice. In contrast, bi-AbFPs protected less than the combination of mono-AbFPs and, in some models, even less than mono-AbFPs alone. However, in all cases, most of long-term survivors showed protection after s.c. rechallenge with the tumors and later with the parental tumors not expressing HER2/neu. These results show that, although the pattern of protection is tumor model dependent, treatments with AbFPs can effectively generate high levels of protection against peritoneal tumors expressing HER2/neu, which may be relevant in patients with primary or metastatic peritoneal carcinomatosis that may be observed in ovarian, colon, stomach, bladder, lung, and breast cancers. [Mol Cancer Ther 2006;5(4):1029–40]

Grant support: National Cancer Institute/NIH grants CA86915 and CA107023 and the 2002 AACR-California Department of Health Services Career Development Award in Gender-Related Cancer Research.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

⁴ Supplementary material for this article is available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

⁵ Unpublished results.

Received 11/28/05; revised 12/24/05; accepted 1/25/06.