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Research Articles: Therapeutics, Targets, and Development

Mitogen-activated protein kinase kinase signaling promotes growth and vascularization of fibrosarcoma

Laboratories of ¹ Cancer and Developmental Cell Biology, ² Analytical, Cellular and Molecular Microscopy, ³ Cancer Genetics, ⁴ Noninvasive Imaging and Radiation Biology, and ⁵ Computational Biology, Van Andel Research Institute, Grand Rapids, Michigan and ⁶ Cancer Research Institute of Scott & White Memorial Hospital, Temple, Texas

Requests for reprints: Nicholas S. Duesbery, Laboratory of Cancer and Developmental Cell Biology, Van Andel Research Institute, 333 Bostwick Avenue Northeast, Grand Rapids, MI 49503. Phone: 616-234-5258; Fax: 616-234-5259. E-mail: duesbery{at}vai.org

Abstract

We hypothesized that signaling through multiple mitogen-activated protein kinase (MAPK) kinase (MKK) pathways is essential for the growth and vascularization of soft-tissue sarcomas, which are malignant tumors derived from mesenchymal tissues. We tested this using HT-1080, NCI, and Shac fibrosarcoma-derived cell lines and anthrax lethal toxin (LeTx), a bacterial toxin that inactivates MKKs. Western blots confirmed that LeTx treatment reduced the levels of phosphorylated extracellular signal-regulated kinase and p38 MAPK in vitro. Although short treatments with LeTx only modestly affected cell proliferation, sustained treatment markedly reduced cell numbers. LeTx also substantially inhibited the extracellular release of angioproliferative factors including vascular endothelial growth factor, interleukin-8, and basic fibroblast growth factor. Similar results were obtained with cell lines derived from malignant fibrous histiocytomas, leiomyosarcomas, and liposarcomas. In vivo, LeTx decreased MAPK activity and blocked fibrosarcoma growth. Growth inhibition correlated with decreased cellular proliferation and extensive necrosis, and it was accompanied by a decrease in tumor mean vessel density as well as a reduction in serum expression of angioproliferative cytokines. Vital imaging using high-resolution ultrasound enhanced with contrast microbubbles revealed that the effects of LeTx on tumor perfusion were remarkably rapid (<24 h) and resulted in a marked reduction of perfusion within the tumor but not in nontumor tissues. These results are consistent with our initial hypothesis and lead us to propose that MKK inhibition by LeTx is a broadly effective strategy for targeting neovascularization in fibrosarcomas and other similar proliferative lesions. [Mol Cancer Ther 2008;7(3):648–58]

Grant support: NIH/National Cancer Institute RO1 grant CA 109308 (N.S. Duesbery).

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.

⁷ Supplementary material for this article is available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

Received 10/25/07; accepted 12/ 4/07.