Serum Metabolomic Response to Long-Term Supplementation with all-rac-α-Tocopheryl Acetate in a Randomized Controlled Trial.

Mondul AM, Moore SC, Weinstein SJ, Evans AM, Karoly ED, Männistö S, Sampson JN, Albanes D.

J Nutr Metab. 2016;2016:6158436. Published online 2016 Oct 20. doi: 10.1155/2016/6158436


Background. The Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, a randomized controlled cancer prevention trial, showed a 32% reduction in prostate cancer incidence in response to vitamin E supplementation. Two other trials were not confirmatory, however. Objective. We compared the change in serum metabolome of the ATBC Study participants randomized to receive vitamin E to those who were not by randomly selecting 50 men from each of the intervention groups (50 mg/day all-racα-tocopheryl acetate (ATA), 20 mg/day β-carotene, both, placebo). Methods. Metabolomic profiling was conducted on baseline and follow-up fasting serum (Metabolon, Inc.). Results. After correction for multiple comparisons, five metabolites were statistically significantly altered (β is the change in metabolite level expressed as number of standard deviations on the log scale): α-CEHC sulfate (β = 1.51, p = 1.45 × 10-38), α-CEHC glucuronide (β = 1.41, p = 1.02 × 10-31), αtocopherol (β = 0.97, p = 2.22 × 10-13), γtocopherol(β = -0.90, p = 1.76 × 10-11), and βtocopherol (β = -0.73, p = 9.40 × 10-8). Glutarylcarnitine, beta-alanine, ornithine, and N6-acetyllysine were also decreased by ATA supplementation (β range 0.40 to -0.36), but not statistically significantly. Conclusions. Comparison of the observed metabolite alterations resulting from ATA supplementation to those in other vitamin E trials of different populations, dosages, or formulations may shed light on the apparently discordant vitamin E-prostate cancer risk findings.

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Dietary tocopherols inhibit PhIP-induced prostate carcinogenesis in CYP1A-humanized mice.

Chen JX, Li G, Wang H, Liu A, Lee MJ, Reuhl K, Suh N, Bosland MC, Yang CS.

Cancer Lett. 2016 Feb 1;371(1):71-8. doi: 10.1016/j.canlet.2015.11.010.


Tocopherols, the major forms of vitamin E, exist as alpha-tocopherol (α-T), β-T, γ-T and δ-T. The cancer preventive activity of vitamin Eis suggested by epidemiological studies, but recent large-scale cancer prevention trials with high dose of α-T yielded disappointing results. Our hypothesis that other forms of tocopherols have higher cancer preventive activities than α-T was tested, herein, in a novel prostate carcinogenesis model induced by 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), a dietary carcinogen, in the CYP1A-humanized (hCYP1A) mice. Treatment of hCYP1A mice with PhIP (200 mg/kg b.w., i.g.) induced high percentages of mouse prostatic intraepithelial neoplasia (mPIN), mainly in the dorsolateral glands. Supplementation with a γ-T-rich mixture of tocopherols (γ-TmT, 0.3% in diet) significantly inhibited the development of mPIN lesions and reduced PhIP-induced elevation of 8-oxo-deoxyguanosine, COX-2, nitrotyrosine, Ki-67 and p-AKT, and the loss of PTEN and Nrf2. Further studies with purified δ-T, γ-T or α-T (0.2% in diet) showed that δ-T was more effective than γ-T or α-T in preventing mPIN formations and p-AKT elevation. These results indicate that γ-TmT and δ-T could be effective preventive agents of prostate cancer.

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Synergistic inhibition of cancer cell proliferation with a combination of δ-tocotrienol and ferulic acid.

Eitsuka T, Tatewaki N, Nishida H, Kurata T, Nakagawa K, Miyazawa T

Biochem Biophys Res Commun. 2014 Oct 5


Rice bran consists of many functional compounds and thus much attention has been focused on the health benefits of its components. Here, we investigated the synergistic inhibitory effects of its components, particularly δ-tocotrienol (δ-T3) and ferulic acid (FA), against the proliferation of an array of cancer cells, including DU-145 (prostate cancer), MCF-7 (breast cancer), and PANC-1 (pancreatic cancer) cells. The combination of δ-T3 and FA markedly reduced cell proliferation relative to δ-T3 alone, and FA had no effect when used alone. Although δ-T3 induced G1 arrest by up-regulating p21 in PANC-1 cells, more cells accumulated in G1 phase with the combination of δ-T3 and FA. This synergistic effect was attributed to an increase in the cellular concentration of δ-T3 by FA. Our results suggest that the combination of δ-T3 and FA may present a new strategy for cancer prevention and therapy.

Polysaccharopeptide enhanced the anti-cancer effect of gamma-tocotrienol through activation of AMPK.

Liu J, Lau EY, Chen J, Yong J, Tang KD, Lo J, Ng IO, Lee TK, Ling MT.


Prostate cancer (PCa) frequently relapses after hormone ablation therapy. Unfortunately, once progressed to the castration resistant stage, the disease is regarded as incurable as prostate cancer cells are highly resistant to conventional chemotherapy.


We recently reported that the two natural compounds polysaccharopeptide (PSP) and Gamma-tocotrienols (gamma-T3) possessed potent anti-cancer activities through targeting of CSCs. In the present study, using both prostate cancer cell line and xenograft models, we seek to investigate the therapeutic potential of combining gamma-T3 and PSP in the treatment of prostate cancer.Result: We showed that in the presence of PSP, gamma-T3 treatment induce a drastic activation of AMP-activated protein kinase (AMPK). This was accompanied with inactivation of acetyl-CoA carboxylase (ACC), as evidenced by the increased phosphorylation levels at Ser 79. In addition, PSP treatment also sensitized cancer cells toward gamma-T3-induced cytotoxicity. Furthermore, we demonstrated for the first time that combination of PSP and gamma-T3 treaments significantly reduced the growth of prostate tumor in vivo.


Our results indicate that PSP and gamma-T3 treaments may have synergistic anti-cancer effect in vitro and in vivo, which warrants further investigation as a potential combination therapy for the treatment of cancer.

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Induction of DNA Damage and Caspase-Independent Programmed Cell Death by Vitamin E

Constantinou C, Neophytou CM, Vraka P, Hyatt JA, Papas KA, Constantinou AI.

Nutr Cancer. 2012;64(1):136-52. Epub 2011 Dec 15.

Vitamin E comprises 8 functionally unique isoforms and may be a suitable candidate for the adjuvant treatment of prostate cancer. In this study, we examined the ability of 2 vitamin E isoforms [α-tocotrienol (γ-TT) and δ-tocotrienol (δ-TT)] and 4 synthetic derivatives [γ- and δ-tocotrienol succinate (γ-TS, δ-TS), α-tocopheryl polyethylene glycol succinate (TPGS), and α-tocopheryl polyethylene glycol ether (TPGS-e)] of vitamin E to induce cell death in AR- (DU145 and PC-3) and AR+ (LNCaP) prostate cancer cell lines. Our results show that δ-TT and TPGS-e are the most effective isoform and synthetic derivative, respectively, of all compounds examined. Overall, the results of our study suggest that isoforms and synthetic derivatives of vitamin E have the potency to trigger both caspase-dependent and -independent DNA damage and dominant caspase-independent programmed cell death. The capacity of vitamin E to trigger caspase-independent programmed cell death suggests that it may be useful in the chemotherapy of prostate cancer since it may prevent the tumor resistance commonly associated with the use of classical chemotherapeutic agents that trigger caspase-dependent programmed cell death.

A key regulator of cholesterol homeostasis, SREBP-2, can be targeted in prostate cancer cells with natural products

James R. Krycer, Lisa Phan, Andrew J. Brown

Biochem J. 2012 Sep 1;446(2):191-201

There is growing evidence showing prostate cancer cells have perturbed cholesterol homeostasis, accumulating cholesterol to promote cell-growth. Consequently, cholesterol lowering drugs like statins are being evaluated in prostate cancer treatment. Furthermore, natural products such as betulin (from birch tree bark) and tocotrienol (a minor form of Vitamin E) have been shown to lower cholesterol levels. Using these drugs and oxysterols, we determine which aspects of cholesterol homeostasis should be targeted in prostate cancer –e.g., cellular cholesterol levels are increased by the transcription factor Sterol-Regulatory Element Binding Protein isoform 2 (SREBP-2), whereas the Liver X Receptor (LXR) promotes cholesterol efflux. Whilst betulin exerted non-specific effects on cell viability, tocotrienols produced a strong direct correlation between SREBP-2 activity and cell viability. Mechanistically, tocotrienols lowered SREBP-2 activity by degrading mature SREBP-2 independently of the proteasome. In contrast, no correlation was seen between LXR activity and cell viability, implying SREBP-2 is a better target than LXR for prostate cancer treatment. Lastly, androgen-dependent and -independent LNCaP cells were both sensitive to tocotrienols. Overall, this suggests that tocotrienols and other drugs targeting the SREBP-2 pathway are a potential therapeutic option for prostate cancer.

Gamma-tocotrienol induces apoptosis and autophagy in prostate cancer cells by increasing intracellular dihydrosphingosine and dihydroceramide

Jiang Q, Rao X, Kim CY, Freiser H, Zhang Q, Jiang Z, Li G.

Int J Cancer. 2012 Feb 1;130(3):685-93.

Although cell-based studies have shown that gamma-tocotrienol (gammaTE) exhibits stronger anticancer activities than other forms of vitamin E including gamma-tocopherol (gammaT), the molecular bases underlying gammaTE-exerted effects remains to be elucidated. Here we showed that gammaTE treatment promoted apoptosis, necrosis and autophagy in human prostate PC-3 and LNCaP cancer cells. In search of potential mechanisms of gammaTE-provoked effects, we found that gammaTE treatment led to marked increase of intracellular dihydroceramide and dihydrosphingosine, the sphingolipid intermediates in de novo sphingolipid synthesis pathway but had no effects on ceramide or sphingosine. The elevation of these sphingolipids by gammaTE preceded or coincided with biochemical and morphological signs of cell death and was much more pronounced than that induced by gammaT, which accompanied with much higher cellular uptake of gammaTE than gammaT. The importance of sphingolipid accumulation in gammaTE-caused fatality was underscored by the observation that dihydrosphingosine and dihydroceramide potently reduced the viability of both prostate cell lines and LNCaP cells, respectively. In addition, myriosin, a specific inhibitor of de novo sphingolipid synthesis, counteracted gammaTE-induced cell death. In agreement with these cell-based studies, gammaTE inhibited LNCaP xenograft growth by 53% (p < 0.05), compared to 33% (p = 0.07) by gammaT, in nude mice. These findings provide a molecular basis of gammaTE-stimulated cancer cell death and support the notion that elevation of intracellular dihydroceramide and dihydrosphingosine is likely a novel anticancer mechanism.

Gamma-tocotrienol as an effective agent in targeting prostate cancer stem cell-like population

Luk, S. U.,Yap, W. N.,Chiu, Y. T.,Lee, D. T.,Ma, S.,Lee, T. K.,Vasireddy, R. S.,Wong, Y. C.,Ching, Y. P.,Nelson, C.,Yap, Y. L.,Ling, M. T.

Int J Cancer, 2011. 128(9):2182-91

Emerging evidence supports that prostate cancer originates from a rare subpopulation of cells, namely prostate cancer stem cells (CSCs). Conventional therapies for prostate cancer are believed to mainly target the majority of differentiated tumor cells but spare CSCs, which may account for the subsequent disease relapse after treatment. Therefore, successful elimination of CSCs may be an effective strategy to achieve complete remission from this disease. Gamma-tocotrienols (gamma-T3) is one of the vitamin-E constituents, which have been shown to have anticancer effects against a wide range of human cancers. Recently, we have reported that gamma-T3 treatment not only inhibits prostate cancer cell invasion but also sensitizes the cells to docetaxel-induced apoptosis, suggesting that gamma-T3 may be an effective therapeutic agent against advanced stage prostate cancer. Here, we demonstrate for the first time that gamma-T3 can downregulate the expression of prostate CSC markers (CD133/CD44) in androgen-independent prostate cancer cell lines (PC-3 and DU145), as evident from Western blotting analysis. Meanwhile, the spheroid formation ability of the prostate cancer cells was significantly hampered by gamma-T3 treatment. In addition, pretreatment of PC-3 cells with gamma-T3 was found to suppress tumor initiation ability of the cells. More importantly, although CD133-enriched PC-3 cells were highly resistant to docetaxel treatment, these cells were as sensitive to gamma-T3 treatment as the CD133-depleted population. Our data suggest that gamma-T3 may be an effective agent in targeting prostate CSCs, which may account for its anticancer and chemosensitizing effects reported in previous studies.

γ-Tocotrienol induces growth arrest through a novel pathway with TGFβ2 in prostate cancer

Campbell SE, Rudder B, Phillips RB, Whaley SG, Stimmel JB, Leesnitzer LM, Lightner J, Dessus-Babus S, Duffourc M, Stone WL, Menter DG, Newman RA, Yang P, Aggarwal BB, Krishnan K.

Free Radic Biol Med. 2011 May 15;50(10):1344-54. Epub 2011 Feb 16.

Regions along the Mediterranean and in southern Asia have lower prostate cancer incidence compared to the rest of the world. It has been hypothesized that one of the potential contributing factors for this low incidence includes a higher intake of tocotrienols. Here we examine the potential of γ-tocotrienol (GT3) to reduce prostate cancer proliferation and focus on elucidating pathways by which GT3 could exert a growth-inhibitory effect on prostate cancer cells. We find that the γ and δ isoforms of tocotrienol are more effective at inhibiting the growth of prostate cancer cell lines (PC-3 and LNCaP) compared with the γ and δ forms of tocopherol. Knockout of PPAR-γ and GT3 treatment show inhibition of prostate cancer cell growth, through a partially PPAR-γ-dependent mechanism. GT3 treatment increases the levels of the 15-lipoxygenase-2 enzyme, which is responsible for the conversion of arachidonic acid to the PPAR-γ-activating ligand 15-S-hydroxyeicosatrienoic acid. In addition, the latent precursor and the mature forms of TGFβ2 are down-regulated after treatment with GT3, with concomitant disruptions in TGFβ receptor I, SMAD-2, p38, and NF-κB signaling.

Mixed tocotrienols inhibit prostate carcinogenesis in TRAMP mice

Barve A, Khor TO, Reuhl K, Reddy B, Newmark H, Kong AN.

Nutr Cancer. 2010;62(6):789-94. June

The biological activities of tocotrienols are receiving increasing attention. Herein, we report the efficacy of a mixed-tocotrienol diet against prostate tumorigenesis in the transgenic adenocarcinoma mouse prostate (TRAMP) mouse model. Male TRAMP mice, 8 wk old, were fed 0.1%, 0.3%, or 1% mixed tocotrienols in AIN- 76A diet up to 24 wk old. Likewise, a positive control group consisting of male TRAMP mice and a negative control group consisting of wild-type nontransgenic mice were fed regular AIN-76A diet up to 24 wk old. Our results show that mixed-tocotrienol-fed groups had a lower incidence of tumor formation along with a significant reduction in the average wet weight of genitourinary apparatus. Furthermore, mixed tocotrienols significantly reduced the levels of high-grade neoplastic lesions as compared to the positive controls. This decrease in levels of high-grade neoplastic lesions was found to be associated with increased expression of proapoptotic proteins BAD (Bcl(2) antagonist of cell death) and cleaved caspase-3 and cell cycle regulatory proteins cyclin dependent kinase inhibitors p21 and p27. In contrast, the expression of cyclins A and E were found to be decreased in mixed-tocotrienol groups. Taken together, our results show that by modulating cell cycle regulatory proteins and increasing expression of proapoptotic proteins, mixed tocotrienols suppress prostate tumorigenesis in the TRAMP mice.