Abstract C259: Olive phenolics as c-Met inhibitors: Molecular mechanisms mediating the anticancer effects of oleocanthal in breast cancer cells.

The Mediterranean countries have lower cancer incidence compared to the rest of European countries and the United States. Olive oil is a key ingredient of the Mediterranean diet. Olive oil secoiridoids have showed antiproliferative and apoptotic activity in HER2 overexpressing cancer cells. In addition, oleocanthal, a minor phenolic secoiridoid in extra-virgin olive oil, displays protective activity against inflammatory and Alzheimer9s disease. It has been shown that oleocanthal treatment inhibited the growth, migration, and invasion of human breast and prostate cancer cell lines. Oleocanthal was identified via a computer-assisted study as a c-Met activation inhibitor hit, targeting its ATP binding site, and stabilizing the kinase domain in its inactive conformation. It has been reported that oleocanthal competitively inhibited the phosphorylation of c-Met kinase in vitro in the Z’-LYTE assay, however, the exact antiproliferative, antimigratory, and pro-apoptotic mechanisms of oleocanthal are not well understood. In this study, the effects of oleocanthal on cell proliferation, migration and apoptosis in human breast cancer cells were evaluated. Oleocanthal treatment showed a dose-dependent inhibition of HGF-induced cell proliferation as shown by MTT, and Ki-67 immunostaining assay. Additional studies were conducted to determine the intracellular mechanisms mediating oleocanthal9s anticancer activity in breast cancer cells. Flow cytometry analysis showed that oleocanthal treatment increased the percentage of cells in G1 phase as compared to the vehicle-treated control group. Western blot studies revealed that blockade in cell cycle progression is associated with regulating the expression of various important G1/S modulators. Additional Western blot experiments showed that oleocanthal treatment caused a marked, dose-dependent decrease of HGF-induced c-Met receptor phosphorylation. Furthermore, oleocanthal treatment was associated with a relatively large suppression in HGF-induced of Erk1/2, Akt, PTK6 phosphorylation as compared to vehicle-treated control group. Additional studies were conducted to investigate whether the growth inhibitory effects of the oleocanthal treatment is associated with a concomitant activation of apoptotic pathways. Results of MTT assay showed that the oleocanthal treatment induced apoptosis at 25 µM. Activation of apoptosis by oleocanthal in MDA-MB-231 cells seemed to be initiated through induction of Fas ligand, which resulted in activation of caspase-8, caspase-3, and poly(ADPribose) polymerase(PARP). Additional studies showed that oleocanthal treatment inhibited HGF-induced migration of cancer cells, and suppressed HGF-induced epithelial-to-mesenchymal transition (EMT), as indicated by wound healing assay and a characteristic increased expression of epithelial cellular markers (E-cadherin, β-catenin) and a corresponding decrease in mesenchymal cellular markers (vimentin). These results suggest that oleocanthal is a promising hit with potential therapeutic use for the control of c-Met-dependent malignancies. This study was supported by the National Cancer Institute, grant number 1R15CA167475-01. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C259. Citation Format: Mohamed R. Akl, Belnaser A. Busnena, Mohamed M. Mohyeldin, Khalid El Sayed. Olive phenolics as c-Met inhibitors: Molecular mechanisms mediating the anticancer effects of oleocanthal in breast cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C259.