NOS2 and leukemia: Our observations are supported by previous evidence demonstrating that the introduction of NO donors or the overexpression of NOS could sensitize cells to Fas signaling,32, 33, 34 whereas direct treatment of ONOO− itself could also enhance Fas-induced apoptosis in leukemia cells.35 Interestingly, we found that ONOO− production and caspase activation induced by TRAIL in cisplatin-resistant R1 cells were interdependent events.