δ-Tocotrienol treatment is more effective against hypoxic tumor cells than normoxic cells: potential implications for cancer therapy.

Abstract

Tocotrienols, unsaturated forms of vitamin E, inhibit the proliferation of a variety of cancer cells and suppress angiogenesis. However, the mechanisms underlying those effects on cancer cell growth remain unclear especially under hypoxic conditions. In this study, we demonstrated that δ-tocotrienol (δ-T3) could be used as a novel anticancer agent against human colorectal adenocarcinoma (DLD-1) cells under both normoxic and hypoxic conditions. δ-T3 inhibited the growth of DLD-1 cells in a dose-dependent fashion by inducing cell cycle arrest and apoptosis. This effect was more potent under hypoxic than normoxic conditions. The anticancer effect of δ-T3 was achieved by its up-regulation of cyclin-dependent kinase inhibitors (p21 and p27), the activation of caspases and the suppression of phosphorylation of protein kinase B (Akt) at Thr(308) and Ser(473). In in vivo studies, oral administration of rice bran tocotrienol (RBT3, mainly γ-T3) (10 mg/mouse/day) significantly inhibited tumor growth in nude mice. In tumor analyses, RBT3 activated p21, p27, caspase-3 and caspase-9 and decreased Akt phosphorylation. Furthermore, immunostaining revealed that RBT3 decreased the number of cells positive for CD31/platelet endothelial cell adhesion molecule-1 in microvessels in the tumor. Taken together, these data suggest that tocotrienols are potent antitumor agents capable of inducing apoptosis and inhibiting angiogenesis under both hypoxic and normoxic conditions. Tocotrienols could have significant therapeutic potential in the clinical treatment of tumors.

• Authors: Akira Shibata, Kiyotaka Nakagawa, Tsuyoshi Tsuduki, Teruo Miyazawa
• Journal: The Journal of nutritional biochemistry (J Nutr Biochem) Vol. 26 Issue 8 Pg. 832-40 (Aug 2015) ISSN: 1873-4847 [Electronic] United States
• PMID: 25979648 (Publication Type: Journal Article)
• Copyright: Copyright © 2015 Elsevier Inc. All rights reserved.

Chemical References

• Angiogenesis Inhibitors
• Antineoplastic Agents
• Cyclin-Dependent Kinase Inhibitor p21
• Vitamin E
• Cyclin-Dependent Kinase Inhibitor p27
• tocotrienol, delta
• Cyclin-Dependent Kinases
• Casp3 protein, mouse
• Casp9 protein, mouse
• Caspase 3
• Caspase 9

Topics

• Angiogenesis Inhibitors (pharmacology)
• Animals
• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects)
• Caspase 3 (genetics, metabolism)
• Caspase 9 (genetics, metabolism)
• Cell Cycle Checkpoints (drug effects)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Colorectal Neoplasms (drug therapy)
• Cyclin-Dependent Kinase Inhibitor p21 (genetics, metabolism)
• Cyclin-Dependent Kinase Inhibitor p27 (genetics, metabolism)
• Cyclin-Dependent Kinases (genetics, metabolism)
• Humans
• Male
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• Phosphorylation
• Up-Regulation
• Vitamin E (analogs & derivatives, pharmacology)