In vitro reporter assays. Luciferase reporter constructs were used to evaluate induction of the Egr1 promoter by IR or cisplatin. Minimal LA was detectable following transfection with either the pGL3 basic (negative control) or the pGL3 660 plasmid (minimal Egr1 promoter) constructs. (a) In Seg-1 cells transfected with pGL3 425, a 2.4-fold increase (P = 0.005) in relative LA was observed following exposure to IR (20 Gy), and a 2.0-fold increase (P = 0.005) was seen following exposure to cisplatin (50 μM). (b) In PROb cells transfected with pGL3 425, there was a 4.2-fold increase (P = 0.004) in relative LA following exposure to IR (20 Gy), and a 3.6-fold increase (P = 0.01) following exposure to cisplatin (50 μM). Data are reported as mean ± SEM.