A surrogate marker to monitor angiogenesis at last

The first angiogenesis inhibitor has recently been approved for cancer treatment. Nonetheless, optimizing the dose of novel angiogenesis inhibitors remains a formidable challenge—primarily because we lack reliable surrogate markers of tumor angiogenesis. In this issue, Shaked et al. provide evidence that the levels of circulating endothelial precursor cells (CEPs), which contribute to the formation of tumor vessels, are genetically predetermined and regulated by angiogenic factors, and reflect the antitumor efficacy of angiogenesis inhibitors. These findings highlight the potential usefulness of CEPs as a surrogate marker to monitor and adjust antiangiogenic therapy.