Putative SBEs in the LAMB3 and LAMC2 promoters prove non-functional. Normalized and averaged promoter activity obtained from three experiments in Smad4-negative, Smad4-reexpressing and TGFβ treated Smad4-positive SW480 cells. While the -2 kb LAMB3 promoter did not confer TGFβ responsiveness (a) and the mutation construct of the SBE at position -1.41 kb did not alter promoter responses (b), the -4 kb promoter displayed TGFβ induction (c). Mutational inactivation of both of the SBE sites at positions -2.66 and -3.67 kb did not significantly alter reporter responses in transient transfections (d, e). The -4 kb LAMC2 promoter (a') as well as the -2 kb (c') and the -0.8 kb (e') promoter constructs reflected endogenous gene responses; all of them retained TGFβ responsiveness. Correspondingly, mutations of the upstream SBE sites did not significantly affect TGFβ induction (b', d').