γ-tocotrienol inhibits angiogenesis-dependent growth of human hepatocellular carcinoma through abrogation of AKT/mTOR pathway in an orthotopic mouse model

// Kodappully Sivaraman Siveen 1,* , Kwang Seok Ahn 2,* , Tina H. Ong 3 , Muthu K. Shanmugam 1 , Feng Li 1 , Wei Ney Yap 1,4 , Alan Prem Kumar 1,4,5,6 , Chee Wai Fong 7 , Vinay Tergaonkar 8 , Kam M Hui 3,8,9,10 and Gautam Sethi 1,4 1 Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 2 College of Korean Medicine, Kyung Hee University, Seoul 130-701, Republic of Korea 3 Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre, Singapore 4 Cancer Science Institute of Singapore, Centre for Translational Medicine, 14 Medical Drive, #11-01M, Singapore 5 School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Western Australia 6009, Australia 6 Department of Biological Sciences, University of North Texas, Denton, Texas, 76203, USA 7 Davos Life Science Pte Ltd, 3 Biopolis Drive; #04-19 Synapse, Singapore 8 Institute of Molecular and Cell Biology, A*STAR, Biopolis Drive Proteos, Singapore 9 Cancer and Stem Cell Biology Program, Duke–National University of Singapore Graduate Medical School, Singapore 10 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore * contributed equally to this work Correspondence: Gautam Sethi, email: // Kam M Hui, email: // Keywords : γ-tocotrienol, HCC, angiogenesis, AKT/mTOR, orthotopic model. Received : January 6, 2014 Accepted :March 30, 2014 Published : March 31, 2014 Abstract Angiogenesis is one of the key hallmarks of cancer. In this study, we investigated whether γ-tocotrienol can abrogate angiogenesis-mediated tumor growth in hepatocellular carcinoma (HCC) and if so, through what molecular mechanisms. We observed that γ-tocotrienol inhibited vascular endothelial growth factor (VEGF)-induced migration, invasion, tube formation and viability of HUVECs in vitro . Moreover, γ-tocotrienol reduced the number of capillary sprouts from matrigel embedded rat thoracic aortic ring in a dose-dependent manner. Also, in chick chorioallantoic membrane assay, γ-tocotrienol significantly reduced the blood vessels formation. We further noticed that γ-tocotrienol blocked angiogenesis in an in vivo matrigel plug assay. Furthermore, γ-tocotrienol inhibited VEGF-induced autophosphorylation of VEGFR2 in HUVECs and also suppressed the constitutive activation of AKT/mammalian target of rapamycin (mTOR) signal transduction cascades in HUVECs as well as in HCC cells. Interestingly, γ-tocotrienol was also found to significantly reduce the tumor growth in an orthotopic HCC mouse model and inhibit tumor-induced angiogenesis in HCC patient xenografts through the suppression of various biomarkers of proliferation and angiogenesis. Taken together, our findings strongly suggest that γ-tocotrienol might be a promising anti-angiogenic drug with significant antitumor activity in HCC.