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Research Articles: Therapeutics, Targets, and Development

Hypoxia modulation and radiosensitization by the novel dual EGFR and VEGFR inhibitor AEE788 in spontaneous and related allograft tumor models

Departments of ¹ Radiation Oncology and ² Pathology, University Hospital Zurich, Zurich, Switzerland; and ³ Oncology Research, Novartis Institutes for Biomedical Research, Basel, Switzerland

Requests for reprints: Martin Pruschy, Laboratory for Molecular Radiobiology, Department of Radiation Oncology, Raemistr. 100, University Hospital Zurich, CH-8091 Zürich, Switzerland. Phone: 41-44-255-8549; Fax: 41-44-255-4435. E-mail: martin.pruschy{at}usz.ch

Abstract

Concomitant inhibition of ErbB1/2- and VEGF receptor-signaling synergizes when used in combination with DNA-damaging agents. Here, we investigated for the first time the combined treatment modality of the novel dual specific receptor tyrosine kinase inhibitor AEE788 with ionizing radiation and analyzed treatment-induced end points in situ as indicators for a potential sensitizing mechanism. Furthermore, we assessed tumor hypoxia in response to different antiangiogenic and antiproliferative treatment modalities. The combined treatment effect was investigated in a spontaneously growing mammary carcinoma model and against Her-2/neu-overexpressing mammary carcinoma allografts. In tumor allografts derived from murine mammary carcinoma cells of mouse mammary tumor virus/c-neu transgenic mice, a minimal treatment regimen with AEE788 and fractionated irradiation resulted in an at least additive tumor response. Treatment response in the corresponding spontaneous tumor model strongly exceeded the response induced in the isogenic allografts. Treatment-induced changes of tumor proliferation, apoptosis, and microvessel density were similar in the two tumor models. Treatment with AEE788 alone or in combination with IR strongly improved tumor oxygenation in both tumor models as determined by the detection of endogenous and exogenous markers of tumor hypoxia. Specific inhibition of the VEGF-receptor tyrosine kinase versus Erb1/2-receptor tyrosine kinase indicated that it is the antiproliferative and not the antiangiogenic potency of AEE788 that mediates the hypoxia-reducing effect of this dual kinase-specific inhibitor. Overall, we show that concomitant inhibition of ErbB- and VEGF-receptor signaling by AEE788, in combination with ionizing radiation, is a promising treatment approach, especially in hypoxic, oncogenic ErbB-driven tumors. [Mol Cancer Ther 2007;6(9):2496–504]

Grant support: Oncosuisse, the Radiumfonds, the Sassella- and the Swiss National Foundations (to C. Oehler-Jänne, O. Riesterer, and M. Pruschy).

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.

Received 4/ 9/07; revised 7/ 2/07; accepted 7/26/07.