Expression and function of Fas ligand in human leukemia cells

Objective: To determine whether human leukemia cells express high levels of functional FasL and whether FasL might be a novel and effective approach for leukemia immune escape. Methods: FasL expression was investigated in peripheral blood mononuclear cells from 10 healthy individuals and 48 patients with leukemia by Strept Avidin-Biotin-enzyme Complex-alkaly phosphatase (SABC-AP) immunohistochemical method. Jurkat T cells were co-cultivated with varying numbers of effector leukemic cells for 24 hours. FasL function of inducing Jurkat cells to apoptosis was investigated by MTT and DNA fragment electrophoresis. Results: Leukemia cells expressed more FasL than that expressed in the healthy individuals. FasL expression was significantly higher in non-remission patients than those in completely/partial remission (CR/PR) group. After leukemia cells were co-cultivated with Jurkat cells for 24 hours, they induced more Jurkat cells to apoptosis. The more effective cells there were, the more apoptosis of target cells. Conclusion: Human leukemia cells express high levels of functional FasL that can kill Jurkat T-cells (Fas positive) by apoptosis. FasR-FasL system might be a novel and effective approach for leukemia immune escape.