Evaluation of the antimetastatic and anticancer activities of morin in HER2-overexpressing breast cancer SK-BR-3 cells

Morin (2 ',3,4 ',5,7-pentahydroxyflavone), a flavonoid isolated from members of the Moraceae family and the leaves of Cudranaia tricuspidata Buread, is a well-known natural substance with anti-inflammatory, antioxidative, antimetastasis, and anticancer effects. However, its anticancer activity has not been comprehensively investigated in human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer cells. Here, we evaluated the effects of morin on metastasis and cell viability in HER-2-overexpressing human breast cancer SK-BR-3 cells. Our results revealed that morin (150-200 mu M) prevented endothelial growth factor (EGF)-induced metastatic potential and suppressed cell migration and MMP-9 activity by inhibiting the EGFR signaling pathway in SK-BR-3 cells by gelatin zymography, wound healing assay and western blotting. Interestingly, morin-induced reductions in cell viability were found to be associated with inhibition of the HER2/EGFR signaling pathway by sulforhodamine B assay and western blotting. Morin also induced the phosphorylation of H2A.X and downregulated the expression levels of RAD51 and survivin, which implied morin-induced DNA damage and that this damage accumulated in HER-2-overexpressing SK-BR-3 cells. Western blot analysis and fluorescent immunocytochemisty showed that morin also activated autophagy after 24 h of treatment and this was maintained at 48 h when activation of apoptosis via PARP cleavage resulted in the activation of caspase-3 and -7, which was associated with the release of cytochrome c to the cytosol from mitochondria. In addition, the phosphorylation of p38 and JNK was enhanced in the HER-2-overexpressing SK-BR-3 cells by morin after 24 and 48 h of treatment, which suggested p38 and JNK participate in morin-induced cell death. Taken together, the present investigation indicates that morin is a powerful therapeutic candidate for the treatment of HER2-overexpressing breast cancer because it suppresses the EGFR signaling pathway, induces cell death by inhibiting the HER2/EGFR signaling pathway, and suppresses metastatic potential.