Vascular Endothelial Growth Factor-Trap Decreases Tumor Burden, Inhibits Ascites, and Causes Dramatic Vascular Remodeling in an Ovarian Cancer Model Annette T. Byrne, 1,2,3 Leorah Ross, 2,4 Joceyln Holash, 4 Mikiye Nakanishi, 1 Limin Hu, 1 Judith I. Hofmann, 1 George D. Yancopoulos, 4 and Robert B. Jaffe 1 1 Center for Reproductive Sciences, University of California, San Francisco, San Francisco, California, and 4 Regeneron Pharmaceuticals Inc., Tarrytown, New York ABSTRACT Ovarian cancer is the most lethal gynecological malig- nancy and the fifth most common cause of cancer in women. It is characterized by diffuse peritoneal carcinomatosis and often by large volumes of i.p. ascites. Because vascular en- dothelial growth factor (VEGF), also known as vascular permeability factor, increases vascular permeability and stimulates endothelial cell growth, its role in ovarian cancer has been evaluated in a number of studies. However, ques- tions remain regarding the ability of VEGF alone to cause ascites formation and the ability of VEGF blockade to in- hibit the growth of disseminated cancer. We have used retroviral technology to create cell populations that over- produce VEGF and report that enforced expression of VEGF by ovarian carcinoma cells dramatically reduces the time to onset of ascites formation. In fact, even tumor-free peritoneal overexpression of VEGF, created by using adeno- viral vectors, is sufficient to cause ascites to accumulate. We have found that systemic administration of the VEGF-Trap, a recently described high-affinity soluble decoy receptor for VEGF, prevents ascites accumulation and also inhibits the growth of disseminated cancer. Remarkably, much as is observed in s.c. tumor models, VEGF blockade results in dramatic remodeling of the blood vessels in disseminated ovarian carcinoma. The potent effects of the VEGF-Trap in reducing both ascites and tumor burden suggest that it will be of value in a regimen for treatment of women with ovarian cancer and ascites. INTRODUCTION Angiogenesis, the development of new capillaries from existing vasculature, is an important component of tumor growth because many types of tumors are associated with grow- ing blood vessels, whereas others cannot grow more than 2–3 mm without developing a new blood supply (1). VEGF 5 is a potent angiogenic factor whose receptors, including VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1), are selectively located on vascular endothelial cells. By activating its receptors, VEGF, which also is known as vascular permeability factor, both exerts a mitogenic effect on endothelial cells (2–5) and increases vessel permeability (6, 7). It is expressed in increased amounts in ovarian cancers and other solid tumors (8 –14). Although the value of quantifying serum levels of VEGF as a prognostic indicator of ovarian cancer is unclear (15–22), substantial evi- dence suggests that VEGF promotes the formation of ascites. It is present at very high levels in the ascites of patients with advanced ovarian cancer and is similarly present in animals inoculated with human ovarian tumor cells; furthermore, VEGF blockade in animal models dramatically reduces ascites forma- tion (23–30). Previously, we and others have found that VEGF blockade inhibits ascites formation in a SKOV-3 ovarian carcinoma model. Unfortunately, due to the dispersion and invasiveness of the tumor cells in this model, tumor burden was difficult to evaluate, and we could not demonstrate significant, reproducible decreases in tumor burden (28). In similar models, however, less specific tyrosine kinase inhibitors have been shown to decrease tumor burden (31–33), raising the question of whether VEGF blockade on its own is inadequate to block tumor growth, or whether VEGF-specific blocking agents tested to date have lacked potency. When considering the therapeutic potential of VEGF blockade in ovarian cancer, it is important to distinguish whether VEGF blockade alone has the potential to reduce both ascites formation and tumor burden, or whether it will block only ascites formation (suggesting that the success of tyrosine kinase inhibitors is attributable to their ability to block multiple kinases). Because resolving this question may provide guidance in planning future clinical trials, we felt additional studies with a potent, yet specific, VEGF blocking agent were warranted. We designed the present studies to further substantiate that Received 5/7/03; revised 8/1/03; accepted 8/5/03. Grant support: Supported, in part, by National Cancer Institute SPORE grant CA083639. 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. Requests for reprints: Dr. Robert B. Jaffe, Center for Reproductive Sciences, University of California, San Francisco, 505 Parnassus Ave- nue, Room H5W-1671, San Francisco, California 94143-0556. Phone: 415-476-6130; Fax: 415-502-7866; E-mail: jaffer@obgyn.ucsf.edu. 2 Both authors contributed equally to this work. 3 Present address: Pharmacyclics Inc., 995 E: Arques Avenue, Sunny- vale, California 94085-4521. 5 The abbreviations used are: VEGF, vascular endothelial growth factor; VEGFR, VEGF receptor; MCS, multi-cloning site; GFP, enhanced green fluorescent protein; mVEGF, mouse VEGF; FACS, fluorescence- activated cell sorting. 5721 Vol. 9, 5721–5728, November 15, 2003 Clinical Cancer Research Cancer Research. on January 21, 2016. © 2003 American Association for clincancerres.aacrjournals.org Downloaded from