HMGB1 and leukemia: To address whether secreted HMGB1 triggered by ULMW-HA stimulation can directly kill leukemia cells, we examined changes in the viability of KOPB26 cells by dye exclusion test after 4-day culture in the presence of human recombinant HMGBI, and found that exogenously added HMGB1 itself could not kill leukemia cells even at a concentration as high as 1 μg/ml.