Engineered embryonic endothelial progenitor cells as therapeutic Trojan horses

While the hematogenic contribution of circulating endothelial cells to tumor angiogenesis is not entirely understood, one can exploit this phenomenon as a therapeutic strategy. In this issue of Cancer Cell, Wei et al. (2004) show that murine embryonic endothelial progenitor cells preferentially home to sites of lung metastases, evade immunological rejection, and can exert a bystander antitumor effect when modified to contain a suicide gene construct that activates a prodrug. Treatment with the prodrug led to improved survival in syngeneic and nonsyngeneic tumor-bearing mouse models. The conceptual advance put forward by this study might result in translational applications.