High number of peripheral blood circulating endothelial progenitor cells (EPCs) in a patient with erythropoietin (EPO) producing renal carcinoma (RC)

9707 Background: RC is a clinical and laboratory model to study tumor angiogenesis. Methods: A 76-year-old patient presented with secondary erythrocytosis associated with EPO producing RC. At the initial diagnosis, hematocrit (Hct) was 55% and blood EPO level was 54 IU/L. The patient developed metastatic disease 9 months after nephrectomy. At that time, Hct was 54% and EPO was 329 IU/L. Four weeks following the initiation of an immunotherapy with interferon, Hct and EPO were 53% and 182 IU/L, respectively. Another 4 weeks later, because of a clinical picture of hyperviscosity despite a stable Hct level at 54%, a bloodletting was performed. A total of 400 ml of blood was removed into a sterile bag in which 500 IU of heparin was injected prior to the procedure in order to avoid clotting. This blood sample was then analyzed for the presence of colony forming unit EPCs (CFU-EPCs). Mononuclear cells were obtained by density gradient centrifugation. Cells were then plated on collagen-I coated Petri dishes at a ...