IGFBP5 gene structure, reporter gene constructs for the IGFBP5 promoter, and luciferase expression of the constructed promoter in different cell lines. A, Genomic structure, locations, and genotypes of two selected IGFBP5 SNPs. B, Schematic drawing of the reporter gene constructs containing a 1,337-bp IGFBP5 promoter region; the only difference between the two constructs was a T or C at the -1195 polymorphic site. C, Luciferase activity of the two IGFBP5 promoter constructs in colon cancer cell line HCT116 and two head and neck cancer cell lines: MDA1386Ln and UMSCC-17B. All constructs were co-transfected with pTK-Renilla plasmid as internal control. For each cell line, fold induction of relative luciferase activity was measured by setting reporter gene activity of construct with T allele as 1, using the data (mean ± SD) from three independent transfection experiments. * denotes P < 0.05 for the difference between alleles T and C, ** denotes P < 0.01.