Response of Rb and c-Myc promoter activities in Caco-2/15 cells. (A) Rb activity was determined with an Rb-TA-Luc responsive promoter in the presence of forced α6A or α6B expression. (B) c-Myc activity was determined with a Myc-TA-luc responsive promoter. Left: Effect of forced c-Myc expression on the myc-responsive promoter. Right: Effect of forced α6A or α6B expression on the myc-responsive promoter. Mean ± SEM. ***: statistically significantly different from empty vector (EV), p < 0.001, Tukey's One Way Analysis of Variance (ANOVA). (C) Representative western blot for c-Myc expression in Caco-2/15 cells stably expressing the α6A and α6B integrin subunit or EV as in Figure 5.