Extracellular matrix protein 1 (ECM1) has angiogenic properties and is expressed by breast tumor cells

Tumor growth and metastasis are critically dependent on the formation of ne w blood vessels. The present study found that extracelluIar matrix protein 1 (ECM1), a newly described secretory glycoprotein, promotes angiogenesis. This was initially suggested by itt situ hybridization studies of mouse emb ryos indicating that the ECM1 message was associated with blood vessels and its expression pattern was similar to that of flk-1, a recognized marker f or endothelium. More direct evidence for the role of ECM1 in angiogenesis w as provided by the fact that highly purified recombinant ECM1 stimulated th e proliferation of cultured endothelial cells and promoted blood vessel for mation in the chorioallantoic membrane of chicken embryos. Immunohistochemi cal staining with specific antibodies indicated that ECM1 was expressed by the human breast cancer cell lines MDA-435 and LCC15, both of which are hig hly tumorigenic. In addition, staining of tissue sections from patients wit h breast cancer revealed that ECM1 was present in a significant proportion of primary and secondary tumors. Collectively, the results of this study su ggest that ECM1 possesses angiogenic properties that may promote tumor prog ression.