Extracellular traps are released from leukemic cells.

Abstract

<p>Three leukemic cell lines (U937, THP-1, HL-60) were cultured in DMEM with 10% fetal calf serum without medium exchange for 5 days. (A) The numbers of autonomously proliferated cells are expressed as mean ± SEM of 4 experiments. (B, C) The levels of the histone–DNA complex and cell-free dsDNA were measured in the corresponding culture supernatants. (D) U937 cells (fresh or cultured for 5 days) were stained with SYTOX green and DAPI and observed using a confocal laser microscope. Images shown are representative of 3 independent experiments. (E) Total ROS activity was measured in lysates of U937 cells prepared before and after culturing for 5 days (mean±SEM of 3 experiments). (F) U937 cells were pretreated with an inhibitor of extracellular trap formation (200 μM Cl-amidine) or with antioxidants (ATA, 100 μM; quercetin, 100 μM; NAC, 50 μM; or APDC, 100 μM) and the histone–DNA complex levels were measured in the supernatants after 5 day-culture. *<i>P</i> < 0.05 versus each leukemic cell line at 0 h. ^#<i>P</i> < 0.05 versus no inhibitor.</p