Effects of IPTG and α-lactose on the transient expression of luciferase and green fluorescent protein (GFP) activity after transfection of SW480 cells with luciferase-containing and GFP-containing plasmids, respectively. (A) Effects of inducers on the transient expression of luciferase activity; lysates were derived from SW480 cells transfected with luciferase-containing plasmids and incubated for 48 h before harvesting. Data are presented as relative activity of Firefly luciferase to Renilla luciferase in order to normalize transfection efficiency among different wells. Different letters represent significant difference, P < 0.05. (B) Qualitative analysis of inducer effect on transient expression of GFP activity. a–e: FACS analysis of cells transfected with vectors shown (A-E, A:pGL3-basic, B: pHMLacO, C: pNLacI and pHMLacO, D: inducer IPTG, E: inducer α-lactose). The percentage of cells exhibiting strong fluorescence (date marked area) was calculated as the number of cells exhibiting fluorescence.