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. Ong³, Muthu K. Shanmugam¹, Feng Li¹, Wei Ney Yap^1,4, Alan Prem Kumar^1,4,5,6, Chee Wai Fong⁷, Vinay Tergaonkar⁸, 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 Oriental 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

Oncotarget, Vol. 5, No. 7
www.impactjournals.com/oncotarget/
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.

Keywords:

γ-tocotrienol, HCC, angiogenesis, AKT/mTOR, orthotopic model.