[Frontiers in Bioscience 16, 3183-3195, June 1, 2011]

Tocotrienol combination therapy results in synergistic anticancer response

Paul W. Sylvester, Vikram B. Wali, Sunitha V. Bachawal, Amit B. Shirode, Nehad M. Ayoub, Mohamed R. Akl

College of Pharmacy, 700 University Avenue, University of Louisiana at Monroe, Monroe, LA 71209-0470

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Vitamin E compounds
4. Tocotrienols as anticancer agents
5. Mechanisms mediating the antiproliferative effects of tocotrienols
6. Mechanisms mediating the apoptotic effects of tocotrienols
7. Benefits of combination therapy
8. Combination treatment of tocotrienols with traditional cancer chemotherapy
9. Combination treatment of tocotrienols with statins
10. Combination treatment of tocotrienols with receptor tyrosine kinase inhibitors
11. Combination treatment of tocotrienols with cyclooxygenase-2 (COX-2) inhibitors
12. Conclusions
13. Acknowledgements
14. References

1. ABSTRACT

Vitamin E represents a family of compounds that is divided into two subgroups called tocopherols and tocotrienols, which act as important antioxidants that regulate peroxidation reactions and control free-radical production within the body. However, many of the biological effects of vitamin E are mediated independently of its antioxidant activity. Although tocopherols and tocotrienols have the same basic chemical structure characterized by a long phytyl chain attached to a chromane ring, only tocotrienols display potent anticancer activity, by modulating multiple intracellular signaling pathways associated with tumor cell proliferation and survival, and combination therapy with other chemotherapeutic agents result in a synergistic anticancer response. Combination therapy is most effective when tocotrienols are combined with agents that have complementary anticancer mechanisms of action. These findings strongly suggest that the synergistic antiproliferative and apoptotic effects demonstrated by combined low dose treatment of g-tocotrienol with other chemotherapeutic agents may provide significant health benefits in the prevention and/or treatment of breast cancer in women, while at the same time avoiding tumor resistance and toxic side effects associated with high dose monotherapy.