Suppression of Heregulin-β1/HER2-Modulated Invasive and Aggressive Phenotype of Breast Carcinoma by Pterostilbene via Inhibition of Matrix Metalloproteinase-9, p38 Kinase Cascade and Akt Activation
Figure 6
Effects of pterostilbene on HRG-β1-mediated MMP-9 activity and expression in MCF-7 breast cancer cells. (a) Inhibition of HRG-β1-mediated MMP-9 gelatinolytic activity by pterostilbene. Serum-starved MCF-7 cells were pretreated with 0, 5, 10, 20 or 30 M of pterostilbene for 30 min followed by exposure to 20 ng/ml of HRG-β1. After 24 h of incubation, the conditioned medium was collected and subjected to zymography. (b) Inhibition of HRG-β1-mediated MMP-9 protein expression by pterostilbene. Cells were pretreated with various concentrations of pterostilbene for 30 min in serum-free media and then stimulated by 20 ng/ml of HRG-β1 for 24 h. At the end of incubation, total proteins in cellular extracts were collected and assayed by western blotting using an antibody against MMP-9. β-Actin was an internal control for equivalent protein loading. (c) Dose-related inhibition of HRG-β1-induced increase in MMP-9 protein level by pterostilbene. Serum-starved cells were stimulated with HRG-β1 (20 ng/ml) for 24 h after pretreatment of pterostilbene at the indicated concentrations. Then total RNA was isolated, and RNA expression was analyzed by RT–PCR as described in Section 2. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) cDNA was used as an internal control.
