To address the potential role of ROS in the regulation of the transcriptional activity of NF-ATC2 and NF-κB, we transiently transfected the CLL-derived human B cell line MEC-1 (28) with constructs encoding firefly luciferase under the control of a trimer of the either a NF-AT or a NF-κB binding site. The gene discussed is NFKB1; the disease is B-cell chronic lymphocytic leukemia.