1. ¹Laboratory of Cancer Biology and Genetics, NCI, NIH, Bethesda, MD, USA
2. ²Division of Oncology, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain
3. ³Department of Histology and Pathology, University of Navarra, Pamplona, Spain
4. ⁴Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, USA
5. ⁵Department of Oncology, University Clinic of Navarra, Pamplona, Spain
6. ⁶Pathology and Histology Laboratory, Frederick Cancer and Research Development Center, SAIC, Frederick, MD, USA

Correspondence: Dr MD Johnson, Lombardi Cancer Center, Georgetown University, The Research Building, W325, 3970 Reservoir Rd., NW, Washington, DC 20057, USA. E-mail: Johnsom@georgetown.edu; Dr JE Green, Dr Laboratory of Cancer Biology and Genetics, National Cancer Institute, NIH, Building 37, Room 4054, 37 Convent Drive, Bethesda, MD 20892, USA. E-mail: jegreen@nih.gov

⁷These authors contributed equally to this work.

⁸This paper is dedicated to the memory of Dr Robert Dickson.

⁹Contributed equally as senior authors.

Received 16 October 2007; Revised 19 March 2008; Accepted 28 March 2008; Published online 26 May 2008.

Abstract

Metastasis is the primary cause of death in patients with breast cancer. Overexpression of c-myc in humans correlates with metastases, but transgenic mice only show low rates of micrometastases. We have generated transgenic mice that overexpress both c-myc and vascular endothelial growth factor (VEGF) (Myc/VEGF) in the mammary gland, which develop high rates of pulmonary macrometastases. Gene expression profiling revealed a set of deregulated genes in Myc/VEGF tumors compared to Myc tumors associated with the increased metastatic phenotype. Cross-comparisons between this set of genes with a human breast cancer lung metastasis gene signature identified five common targets: tenascin-C(TNC), matrix metalloprotease-2, collagen-6-A1, mannosidase--1A and HLA-DPA1. Signaling blockade or knockdown of TNC in MDA-MB-435 cells resulted in a significant impairment of cell migration and anchorage-independent cell proliferation. Mice injected with clonal MDA-MB-435 cells with reduced expression of TNC demonstrated a significant decrease (P<0.05) in (1) primary tumor growth; (2) tumor relapse after surgical removal of the primary tumor and (3) incidence of lung metastasis. Our results demonstrate that VEGF induces complex alterations in tissue architecture and gene expression. The TNC signaling pathway plays an important role in mammary tumor growth and metastases, suggesting that TNC may be a relevant target for therapy against metastatic breast cancer.