To ensure a steady supply of oxygen and nutrients, tumors send signals that stimulate the growth of new blood vessels. Bone marrow-derived cells called endothelial progenitor cells (EPCs) are known to be recruited to the tumor-associated growing vessels, but the presence of these cells at only very low levels in the tumor vasculature has made it difficult to assess their functional contribution. Studying mouse models of lung metastasis, Gao et al. (see the Perspective by Rafii and Lyden) show that EPCs are critical regulators of the "angiogenic switch" that helps drive the progression of dormant micrometastases to lethal metastases. Genetic manipulations that blocked EPC mobilization in tumor-bearing mice inhibited angiogenesis, impaired formation of lung metastases, and increased survival time.
D. Gao, D. J. Nolan, A. S. Mellick, K. Bambino, K. McDonnell, V. Mittal, Endothelial progenitor cells control the angiogenic switch in mouse lung metastasis. Science 319, 195-198 (2008). [Abstract] [Full Text]