Figure 4.

Response of MCF-7 breast cancer cells to cholera toxin and to cholera toxin and human recombinant β galactoside binding protein (Hu-r-βGBP), and effect of Hu-r-βGBP and phosphoinositide 3-kinase (PI3K) inhibitors on akt gene expression. (a-c) Extracellular signal-regulated kinase (ERK) levels, growth curves and Akt mRNA levels in naïve cells and in cells treated with 100 ng/ml cholera toxin added at the time of seeding. (a) Phosphorylated ERK and total ERK assessed at 48 h during mitogenic expansion. (b) Naïve cells (open circles); cells treated with 100 ng/ml cholera toxin added at the time of seeding (closed circles). Values are means of triplicate cultures ± standard error of the mean (SEM). (c) akt mRNA and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA levels. (d) Growth curves in response to treatment with Hu-r-βGBP in naïve cells (open circles) and in cells treated with 100 ng/ml cholera toxin (closed circles) added at time of seeding. Hu-r-βGBP (20 nM) was added 3 h after seeding. Values are means from triplicate cultures ± SEM. (e-g) Effect on downregulation of PI3K activity and akt mRNA in MCF-7^CTx cells treated with 20 nM Hu-r-βGBP, 10 nM wortmannin or 20 nM LY294002 added at 3 h after seeding. Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) values are means of triplicate readings ± SEM. The data are representative of three separate experiments.