Delphinidin, a major anthocyanidin in pigmented fruits and vegetables inhibits HGF/Met- mediated proliferation and invasion in immortalized MCF10A cells

4203 Hepatocyte growth factor (HGF) is a pleiotropic cytokine that promotes survival and proliferation in a wide variety of cells. Increased expression of HGF and its receptor Met has been linked to invasive human cancer and metastasis. Delphinidin , an anthocyanidin present in pigmented fruits and vegetables possesses potent anti-oxidant, anti-inflammatory and anti-angiogenic properties. We have recently shown that ‘ delphinidin protects against UVB-mediated oxidative stress and apoptosis in immortalized HaCaT cells’ (J Invest Dermatol.; 2006, In press). Here, we assessed the anti-proliferative and anti-invasive effect of delphinidin on HGF-mediated responses in the immortalized, nontumorigenic breast cell line, MCF10A. Exposure of MCF10A cells to exogenous HGF (40 nM; 30 min) resulted in tyrosyl-phosphorylation and increased expression of the Met receptor that was completely abolished by treatment of cells with delphinidin (5-40 μM; 3h). The functional involvement of PI3/AKT and Raf/MAPK pathway in HGF activation plays an important role in carcinogenesis. Immunoblot analysis shows that delphinidin treatment completely inhibited HGF-mediated activation of Raf/ MEK/ ERK pathway in MCF10A cells resulting in decreased phosphorylation of (i) Raf-1, MEK-1 and ERK1/2 MAPKs, (ii) JNK and p38 MAPKs; and (iii) increased expression of RasGap protein. Delphinidin treatment further resulted in the downregulation of HGF-mediated (i) activation of PI3K/AKT, (ii) phosphorylation of mTOR and its downstream target p70S6Kinase, and (iii) increased expression of MMPs 2 and 9. Oncogenic signals involve activation of kinases that transduce signals, leading to cell proliferation or inhibition of apoptosis by activating NFκB family of transcription factors. Our studies show that HGF-activated NFκB transcription in MCF10A cells was repressed by delphinidin treatement resulting in a decrease in HGF-mediated (i) phosphorylation of IKKα/β and IκBα, and (ii) activation and nuclear translocation of NFκB/p65. Delphinidin treatment to MCF10A cells resulted in nuclear translocation of PKCα, a serine/threonine kinase central to a variety of cellular functions including proliferation, motility, and inflammation. Cell invasion studies showed that delphinidin treatment resulted in attenuation of HGF-mediated enhanced migration of cells across the matrigel in a dose-dependent manner. A requirement of STAT3 signaling for HGF/Met mediated tumorigenesis has been reported. HGF stimulation of MCF10A cells resulted in activation of STAT3, and delphinidin-mediated ablation of STAT3 expression may in part be responsible for a reduction of Met-driven invasiveness. In conclusion, our results strongly suggest a potential inhibitory role of delphinidin in preventing HGF-mediated activation of various signaling pathways implicated in breast cancer.