Kinetics and apoptotic profile of circulating endothelial cells as prognostic factors for induction treatment failure in newly diagnosed acute myeloid leukemia patients

The circulating endothelial cells (CEC) are proposed to be a noninvasive marker of angiogenesis. Recent data suggest that endothelial cells may enhance the survival and proliferation of leukemic blasts and mediate chemotherapy resistance in acute myeloid leukemia (AML). We analyzed CEC count by the four-color flow cytometry in AML and healthy subjects. We evaluated the kinetics of mature CEC, both resting (rCEC) and activated (aCEC), as well as progenitor (CEPC) and apoptotic CEC (CEC^AnnV+) in AML patients treated with standard chemotherapy and their influence on response to treatment and overall survival. We found significantly higher numbers of aCEC, rCEC, CEPC, and CEC^AnnV+ in AML patients than in healthy controls. The elevated CEPC and absolute blood counts in peripheral blood as well as the low CEC^AnnV+ number were associated with higher probability of induction treatment failure. aCEC, rCEC, CEPC, and CEC^AnnV+ counts determined in complete remission (CR) were significantly lower than those found at diagnosis. In those CR patients, a significant decrease in the CEC count and increase in the number of CEC^AnnV+ were observed already 24h after the first dose of chemotherapy. In refractory AML, the aCEC, rCEC, CEPC, and CEC^AnnV+ counts assessed before and after induction chemotherapy did not differ significantly, and a significant decrease in CEC count and increase in CEC^AnnV+ number were noted only after the last dose of chemotherapy. The number of CEC is significantly higher in AML patients than in healthy subjects and correlates with response to treatment. The evaluation of CEC kinetics and apoptotic profile may be a promising tool to select AML patients with poor response to chemotherapy who may benefit from antiangiogenic therapies.