Prognostic significance of flow cytometric quantification of circulating endothelial cells in chronic lymphocytic leukemia

Background: Accumulating evidences have supported the role of angiogenesis in the pathogenesis and progression of chronic lymphocytic leukemia (CLL). Detection of peripheral blood circulating endothelial cells (CECs) by flow cytometry is proposed to be a noninvasive indirect marker of angiogenesis. This work aimed to quantify CECs and endothelial progenitor cells (EPCs) by flow cytometry in patients with newly diagnosed CLL compared with healthy individuals, study their relationship with established risk predictors of the disease, and assess their prognostic significance.Materials and methods: Flow cytometric quantification of CECs and EPCs was carried out for 50 newly diagnosed B-CLL patients and 20 healthy controls. Patients were followed up for assessment of the time to first treatment, response to therapy, and disease outcome.Results: Patients with CLL had higher counts of CECs (median, 24.6×106/l) and EPCs (median, 22.7×106/l) compared with the controls (median, 2.8 and 1.9×106/l for CECs and EPCs, respectively; P 0.001). CLL patients were subdivided according to the median values of CECs and EPCs into high and low CEC and EPC subgroups. Although high levels of CECs and EPCs were not related to established risk predictors of CLL (P 0.05), they were significantly related to higher white blood cell counts (P 0.001), shorter time to first treatment, and poor response to therapy (P 0.05).Conclusion: This study shows that flow cytometric detection of peripheral blood CECs is a feasible indicator of abnormal angiogenesis in CLL that might be utilized as a biologic prognostic marker of a more aggressive disease course with a poor clinical outcome.