Kinetics and viability of circulating endothelial cells as surrogate angiogenesis marker in an animal model of human lymphoma

Circulating endothelial cells (CECs) were evaluated by flow cytometry in im munodeficient mice bearing human lymphoma. A trend toward higher CEC values was observed on days 7 and 14 after transplant, and differences versus con trols were highly significant on day 21 (P = 0.0061). A strong correlation was found between CEC and tumor volume (r, 0.942; P = 0.004) and between CE C and tumor-generated VEGF (r, 0.669; P = 0.02), In mice given cyclophospha mide, most of the circulating apoptotic cells were hematopoietic and not en dothelial. Conversely, in mice given endostatin, all of the increase in apo ptotic cells was in the endothelial cell compartment. CEC evaluation is pro mising as a noninvasive, surrogate angiogenesis marker.