Natural Tocotrienols

D. Anti-cancer & tumour suppressive

• 1. Inhibiton of Tumour Promotion by Various Palm Oil Tocotrienols

  Goh, S.H. et al.(1994), “ Inhibiton of Tumour Promotion by Various Palm Oil Tocotrienols.” Int. J. Cancer, 57(4) : 529-531.

  Inhibition of tumour promotion by various vitamin E compounds (tocopherols and tocotrienols) and some of their dimers was examined by an in vitro assay utilizing the activation of Epstein-Barr virus (EBV) early antigen (EA) expression in EBV-genome-carrying human lymphoblastoid cells. The results reveal that gamma- and delta-tocotrienols derived from palm oil exhibit a strong activity against tumour promotion by inhibiting EBV EA expression in Raji cells induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). However, alpha- and gamma-tocopherols and dimers of gamma-tocotrienol or gamma-tocopherol lack this activity.

• 2. Physiological effect of tocotrienol

  Kato, A. et al.(1985), “Physiological effect of tocotrienol”. J. Japan Oil Chem. Soc. (Yukagaku), 34(5) : 375-376.

  Antitumor effect of tocotrienol was tested on murine tumor. IMC carcinoma cells were inoculated intraperitoneally (ip) into CDF1 mouse (6 week old, female), and mice were given ip injections of tocotrienol. Ten successive injections of α-tocotrienol (> 90%) gave a increase in life span of 248% at a dose of 100 mg/kg/day, and number of 60-day survivors was 4 out of 5 mice.

• 3. Studies on the biological activity of tocotrienols.

  Komiyama, K. et al.(1989), “ Studies on the biological activity of tocotrienols”. Chem. Pharm. Bull., 37(5) : 1369-1371.

  Tocotrienols were evaluated for activity against transplantable murine tumors inoculated i.p. into mouse, and the activities of two tocotrienols and alpha-tocopherols were compared. When the compounds were injected i.p., alpha- and gamma-tocotrienols were effective against sarcoma 180, Ehrlich carcinoma, and IMC carcinoma, and gamma-tocotrienol showed a slight life-prolonging effect in mice with Meth A fibrosarcoma, but the tocotrienols had no antitumor activity against P388 leukemia at doses of 5-40 mg/kg/d. On the other hand alpha-tocopherol had only a slight effect against sarcoma 180 and IMC carcinoma. The antitumor activity of gamma-tocotrienol was higher than that of alpha-tocotrienol. Tocotrienols showed growth inhibition of human and mouse tumor cells when the cells were exposed to these agents for 72 h in vitro, whereas tocopherol did not show any marked cytotoxic activity. Alpha- and gamma-tocotrienols had inhibitory effects on lipid peroxidation of murine microsomes by adriamycin

• 4. Antitumor effects of palm carotenes and tocotrienols in HRS/J hairless female mice

  Tan, B. (1992), “Antitumour effects of Palm Carotenes and Tocotrienols in HRS/J Hairless Female Mice”. Nutrition Research, 12(1) : S163-S173.

  The effect of palm carotenes (PC) and palm tocotrienols (T3) on the development of papilloma (chemical-induced skin cancer) and lymphoma (viral-induced lymph cancer) was studied in genetically recessive HRS/J female hairless mice. The two T3 groups had delayed response (2–4 weeks) to subcutaneous lymphoma (SL) formation when compared to the +ve Control group. The order of this SL inhibition phenomenon by PC in the feed was concentration dependent; 0.3% PC > 0.1% PC > 0.05% PC groups. The onset of SL in 0.3% synthetic carotene (SC) group was sooner than the 0.3% PC group. The +ve Control mice had significantly higher (>2-fold) epithelial papilloma (EP) than the next group, 0.1% T3. All the PC groups completely inhibited EP formation after the mice were 7 months old. The “no EP” groups (0.1% PC, 0.3% PC, mixed, 0.3% SC) responded as if there was no application of DMBA-croton oil. Mechanisms of inhibition by T3 and PC were different. The T3 groups delayed but not regressed SL formation but the PC groups caused SL regression in a concentration dependent fashion. The 0.3% PC group showed the strongest antitumorigenic effect (and the least toxic effect with respect to mortality) while the 0.1% T3 group showed the least antitumorigenic effect to SL and EP formation.

• 5. Effect of tocotrienols on hepatocarcinogenesis induced by 2-acetylaminofluorene in rats

  Ngah, W. Z. et al. (1991), “Effect of tocotrienols on hepatocarcinogenesis induced by 2-Acetylaminofluorene in rats.” Am. J. Clin. Nutr. 53(4) : 1076S - 1081S.

  The effects of tocotrienols on hepatocarcinogenesis in rats fed with 2-acetylaminofluorene (AAF) were followed morphologically and histologically for a period of 20 wk. No differences between treated and control rats in the morphology and histology of their livers was observed. Cell damage was extensive in the livers of AAF-treated rats but less extensive in the AAF-tocotrienols-treated rats when compared with normal and tocotrienols-treated rats. 2-Acetylaminofluorene significantly increases the activities of both plasma and liver microsomal gamma-glutamyltranspeptidase (GGT) and liver microsomal UDP-glucuronyltransferase (UDP-GT). Tocotrienols administered together with AAF significantly decrease the activities of plasma GGT after 12 and 20 wk (P less than 0.01, P less than 0.002, respectively) and liver microsomal UDP-GT after 20 wk (P less than 0.02) when compared with the controls and with rats treated only with tocotrienols. Liver microsomal GGT also showed a similar pattern to liver microsomal UDP-GT but the decrease was not significant. These results suggest that tocotrienols administered to AAF-treated rats reduce the severity of hepatocarcinogenesis.

• 6. Glutathione S-transferase and gamma-glutamyl transpeptidase activities in cultured rat hepatocytes treated with tocotrienol and tocopherol

  Ngah, W. Z. et al. (1993), “Glutathione S-Transferase and Gamma-Glutamyl Transpeptidase Activities in Cultured Rat Hepatocytes Treated with Tocotrienol and Tocopherol”. Comp. Biochem. Physiol. C. 106(1) : 237-240.

  1. The effect of tocotrienol and tocopherol on glutathione S-transferase (GST) and gamma-glutamyl transpeptidase (GGT) activities in cultured rat hepatocytes were investigated. 2. Tocotrienol and tocopherol significantly decreased GGT activities at 5 days in culture but tocotrienol also significantly decreased GGT activities at 1-2 days. 3. Tocotrienol and tocopherol treatment significantly decreased GST activities at 3 days compared to the control but tocotrienol also decreased GST activities at 1-3 days. 4. Tocotrienol showed a more pronounced effect at a dosage of greater than 50 microM tocotrienol at 1-3 days in culture compared to the control.

• 7. Effect of Vitamin E Supplementation on the Immune Response during Chemically Induced Hepatocarcinogenesis in the Rat

  Ngah, W. Z. et al. (1994), “ Effect of Vitamin E Supplementation on the Immune Response During Chemically Induced Hepatocarcinogenesis in the Rat”. J. Clin. Biochem. Nutr. 17(3) : 161-169.

  The effect of vitamin E (Vit E), both α-tocopherol (α-T) and γ-tocotrienol (γ-T3), supplementation on splenocyte proliferation and phagocytic activity of peritoneal macrophages in rats treated with diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) was investigated. Splenocyte proliferation in response to concanavalin A or phytohemagglutinin and phagocytic activity of peritoneal macrophages in the DEN/AAF-treated rats were significantly reduced compared with the control levels. In contrast, mitogenesis and phagocytic activity of peritoneal macrophages were increased significantly in the DEN/AAF-treated rats supplemented with Vit E; and the vitamin effect was dose dependent. However, the increases were not so great as those observed in the controls. The highest doses of α-T and γ-T3 used effected the highest phagocytic activity, with α-T generally showing a higher activity than γ-T3. Although long-term Vit E supplementation at half the optimum dose significantly increased mitogenesis, phagocytic activity in the DEN/AAF-treated and control rats was only marginally increased.

• 8. Effect of dietary palm oils on mammary carcinogenesis in female rats induced by 7,12-dimethylbenz(a)anthracene

  Sundram, K. et al. (1989), “Effects of Dietary Palm Oils on Mammary Carcinogenesis in Female Rats Induced by 7,12-Dimethylbenz(a)Anthracene." Cancer Res. 49(6) : 1447-1451.

  Female Sprague-Dawley rats, 50 days of age, were treated with a single dose of 5 mg of 7,12-dimethylbenz(a)anthracene intragastrically. 3 days after carcinogen treatment, the rats were put on semisynthetic diets containing 20% by weight of corn oil (CO), soybean oil (SBO), crude palm oil (CPO), refined, bleached, deodorized palm oil (RBD PO) and metabisulfite-treated palm oil (MCPO) for 5 months. During the course of experiments, rats fed on different dietary fats had similar rate of growth. Rats fed 20% CO or SBO diet have higher tumor incidence than rats fed on palm oil (PO) diets; however differences of mean tumor latency periods among the groups were not statistically significant. At autopsy, rats fed on high CO or SBO diets had significantly more tumors than rats fed on the three PO diets. Our results showed that high PO diets did not promote chemically induced mammary tumorigenesis in female rats when compared to high CO or SBO diets. CO and SBO differ greatly from the palm oils in their contents of tocopherols, tocotrienols, and carotenes. But further experiments would be required to determine whether the observed differences in tumor incidence and tumor numbers were due to the differences in these minor components or due to the unique triglyceride structure of the palm oils. Analysis of the fatty acid profiles of plasma total lipids of tumor-bearing rats and of the tumor total lipids showed that, with the exception of arachidonic acid, the fatty acid profiles reflect the nature of the dietary fats. At autopsy, there were no differences in the plasma total cholesterol contents among rats fed on different dietary fats, but rats fed on palm oil diets had a significantly higher plasma triglyceride level than that of rats fed CO or SBO diets. As for the tumor lipids, there were no significant differences in the triglyceride, diglyceride, and phospholipid levels when the CO or SBO groups were compared to the palm oil groups.

• 9. Gamma-tocotrienol induced apoptosis is associated with unfolded protein response in human breast cancer cells

  Patacsil, D. et al. (2012). Gamma-tocotrienol induced apoptosis is associated with unfolded protein response in human breast cancer cells. The journal of nutritional biochemistry. 23(1):93-100.

  Gamma-tocotrienol (γ-T3) is a member of the vitamin E family. Tocotrienols (T3s) are powerful antioxidants and possess anticancer, neuroprotective and cholesterol-lowering properties. Tocotrienols inhibit the growth of various cancer cell lines without affecting normal cells. Less is known about the exact mechanisms of action of T3s on cell death and other growth inhibitory pathways. In the present study, we demonstrate that γ-T3 induces apoptosis in MDA-MB 231 and MCF-7 breast cancer cells as evident by PARP cleavage and caspase-7 activation. Gene expression analysis of MCF-7 cells treated with γ-T3 revealed alterations in the expression of multiple genes involved in cell growth and proliferation, cell death, cell cycle, cellular development, cellular movement and gene expression. Further analysis of differentially modulated genes using Ingenuity Pathway Analysis software suggested modulation of canonical signal transduction or metabolic pathways such as NRF-2-mediated oxidative stress response, TGF-β signaling and endoplasmic reticulum (ER) stress response. Analysis of ER-stress-related proteins in MCF-7 and MDA-MB 231 cells treated with γ-T3 demonstrated activation of PERK and pIRE1α pathway to induce ER stress. Activating transcription factor 3 (ATF3) was identified as the most up-regulated gene (16.8-fold) in response to γ-T3. Activating transcription factor 3 knockdown using siRNA suggested an essential role of ATF3 in γ-T3-induced apoptosis. In summary, we demonstrate that γ-T3 modulates ER stress signaling and have identified ATF3 as a molecular target for γ-T3 in breast cancer cells.

• 10. Tocotrienols inhibit growth of ZR-75-1 breast cancer cells

  Nesaretnam K. et al. (2000). “Tocotrienols Inhibit Growth of ZR-75-1 Breast Cancer Cells.” Intl. J. Food Sci. Nutr. 51 : S95-S103.

  The vitamin E component of palm oil provides a rich source of tocotrienols which have been shown previously to be growth inhibitory to two human breast cancer cell lines: responsive MCF7 cells and unresponsive MDA-MB-231 cells. Data presented here shows that the tocotrienol-rich fraction (TRF) of palm oil and individual fractions (alpha, gamma and delta) can also inhibit the growth of another responsive human breast cancer cell line, ZR-75-1. At low concentrations in the absence of oestrogen tocotrienols stimulated growth of the ZR-75-1 cells, but at higher concentrations in the presence as well as in the absence of oestradiol, tocotrienols inhibited cell growth strongly. As for MCF7 cells, alpha-tocopherol had no effect on growth of the ZR-75-1 cells in either the absence or presence of oestradiol. In studying the effects of tocotrienols in combination with antioestrogens, it was found that TRF could further inhibit growth of ZR-75-1 cells in the presence of tamoxifen (10(-7) M and 10(-8) M). Individual tocotrienol fractions (alpha, gamma, delta) could inhibit growth of ZR-75-1 cells in the presence of 10(-8) M oestradiol and 10(-8) M pure antioestrogen ICI 164,384. The immature mouse uterine weight bioassay confirmed that TRF could not exert oestrogen antagonist action in vivo. These results provide evidence of wider growth-inhibitory effects of tocotrienols beyond MCF7 and MDA-MB-231 cells, and with an oestrogen-independent mechanism of action, suggest a possible clinical advantage in combining administration of tocotrienols with antioestrogen therapy

• 11. Induction of apoptosis in human breast cancer cells by tocopherols and tocotrienols

  Yu W. P. et al. (1999). “Induction of Apoptosis in Human Breast Cancer Cells by Tocopherols and Tocotrienols.” Nutr. Cancer. 33(1) : 26-32.

  The apoptosis-inducing properties of RRR-alpha-, beta-, gamma-, and delta-tocopherols, alpha-, gamma-, and delta-tocotrienols, RRR-alpha-tocopheryl acetate (vitamin E acetate), and RRR-alpha-tocopheryl succinate (vitamin E succinate) were investigated in estrogen-responsive MCF7 and estrogen-nonresponsive MDA-MB-435 human breast cancer cell lines in culture. Apoptosis was characterized by two criteria: 1) morphology of 4,6-diamidino-2-phenylindole-stained cells and oligonucleosomal DNA laddering. Vitamin E succinate, a known inducer of apoptosis in several cell lines, including human breast cancer cells, served as a positive control. The estrogen-responsive MCF7 cells were more susceptible than the estrogen-nonresponsive MDA-MB-435 cells, with concentrations for half-maximal response for tocotrienols (alpha, gamma, and delta) and RRR-delta-tocopherol of 14, 15, 7, and 97 micrograms/ml, respectively. The tocotrienols (alpha, gamma, and delta) and RRR-delta-tocopherol induced MDA-MB-435 cells to undergo apoptosis, with concentrations for half-maximal response of 176, 28, 13, and 145 micrograms/ml, respectively. With the exception of RRR-delta-tocopherol, the tocopherols (alpha, beta, and gamma) and the acetate derivative of RRR-alpha-tocopherol (RRR-alpha-tocopheryl acetate) were ineffective in induction of apoptosis in both cell lines when tested within the range of their solubility, i.e., 10-200 micrograms/ml. In summary, these studies demonstrate that naturally occurring tocotrienols and RRR-delta-tocopherol are effective apoptotic inducers for human breast cancer cells.

• 12. Tocotrienols inhibit the growth of human breast cancer cells irrespective of estrogen receptor status

  Nesaretnam K. et al. (1998). “Tocotrienols Inhibit the Growth of Human Breast Cancer Cells Irrespective of Estrogen Receptor Status.” Lipids. 33(5) : 461-69.

  Potential antiproliferative effects of tocotrienols, the major vitamin E component in palm oil, were investigated on the growth of both estrogen-responsive (ER+) MCF7 human breast cancer cells and estrogen-unresponsive (ER-) MDA-MB-231 human breast cancer cells, and effects were compared with those of alpha-tocopherol (alphaT). The tocotrienol-rich fraction (TRF) of palm oil inhibited growth of MCF7 cells in both the presence and absence of estradiol with a nonlinear dose-response but such that complete suppression of growth was achieved at 8 microg/mL. MDA-MB-231 cells were also inhibited by TRF but with a linear dose-response such that 20 microg/mL TRF was needed for complete growth suppression. Separation of the TRF into individual tocotrienols revealed that all fractions could inhibit growth of both ER+ and ER- cells and of ER+ cells in both the presence and absence of estradiol. However, the gamma- and delta-fractions were the most inhibitory. Complete inhibition of MCF7 cell growth was achieved at 6 microg/mL of gamma-tocotrienol/delta-tocotrienol (gammaT3/deltaT3) in the absence of estradiol and 10 microg/mL of deltaT3 in the presence of estradiol, whereas complete suppression of MDA-MB-231 cell growth was not achieved even at concentrations of 10 microg/mL of deltaT3. By contrast to these inhibitory effects of tocotrienols, alphaT had no inhibitory effect on MCF7 cell growth in either the presence or the absence of estradiol, nor on MDA-MB-231 cell growth. These results confirm studies using other sublines of human breast cancer cells and demonstrate that tocotrienols can exert direct inhibitory effects on the growth of breast cancer cells. In searching for the mechanism of inhibition, studies of the effects of TRF on estrogen-regulated pS2 gene expression in MCF7 cells showed that tocotrienols do not act via an estrogen receptor-mediated pathway and must therefore act differently from estrogen antagonists. Furthermore, tocotrienols did not increase levels of growth-inhibitory insulin-like growth factor binding proteins (IGFBP) in MCF7 cells, implying also a different mechanism from that proposed for retinoic acid inhibition of estrogen-responsive breast cancer cell growth. Inhibition of the growth of breast cancer cells by tocotrienols could have important clinical implications not only because tocotrienols are able to inhibit the growth of both ER+ and ER- phenotypes but also because ER+ cells could be growth-inhibited in the presence as well as in the absence of estradiol. Future clinical applications of TRF could come from potential growth suppression of ER+ breast cancer cells otherwise resistant to growth inhibition by antiestrogens and retinoic acid.

• 13. Inhibition of proliferation of estrogen receptor-negative MDA-MB-435 and -positive MCF-7 human breast cancer cells by palm oil tocotrienols and tamoxifen, alone and in combination

  Guthrie N. et al. (1997). “Inhibition of Proliferation of Estrogen Receptor-Negative MDA-MB-435 and -positive MCF-7 Human Breast Cancer Cells by Palm Oil Tocotrienols and Tamoxifen, Alone and In Combination.” J. Nutr. 127(3) : 544S-548S.

  Tocotrienols are a form of vitamin E, having an unsaturated isoprenoid side-chain rather than the saturated side-chain of tocopherols. The tocotrienol-rich fraction (TRF) from palm oil contains alpha-tocopherol and a mixture of alpha-, gamma- and delta-tocotrienols. Earlier studies have shown that tocotrienols display anticancer activity. We previously reported that TRF, alpha-, gamma- and delta-tocotrienols inhibited proliferation of estrogen receptor-negative MDA-MB-435 human breast cancer cells with 50% inhibitory concentrations (IC50) of 180, 90, 30 and 90 microg/mL, respectively, whereas alpha-tocopherol had no effect at concentrations up to 500 microg/mL. Further experiments with estrogen receptor-positive MCF-7 cells showed that tocotrienols also inhibited their proliferation, as measured by [3H] thymidine incorporation. The IC50s for TRF, alpha-tocopherol, alpha-, gamma- and delta-tocotrienols were 4, 125, 6, 2 and 2 microg/mL, respectively. Tamoxifen, a widely used synthetic antiestrogen inhibits the growth of MCF-7 cells with an IC50 of 0.04 microg/mL. We tested 1:1 combinations of TRF, alpha-tocopherol and the individual tocotrienols with tamoxifen in both cell lines. In the MDA-MB-435 cells, all of the combinations were found to be synergistic. In the MCF-7 cells, only 1:1 combinations of gamma- or delta-tocotrienol with tamoxifen showed a synergistic inhibitory effect on the proliferative rate and growth of the cells. The inhibition by tocotrienols was not overcome by addition of excess estradiol to the medium. These results suggest that tocotrienols are effective inhibitors of both estrogen receptor-negative and -positive cells and that combinations with tamoxifen should be considered as a possible improvement in breast cancer therapy

• 14. Palm oil tocotrienols and plant flavonoids act synergistically with each other and with Tamoxifen in inhibiting proliferation and growth of estrogen receptor-negative MDA-MB-435 and -positive MCF-7 human breast cancer cells in culture

  Guthrie N. et al. (1997). “Palm Oil Tocotrienols and Plant Flavanoids Act Synergistically with Each Other and with Tamofixen in Inhibiting Proliferation and Growth of Estrogen Receptor-Negative MD-MB-435 and -Positive MCF-7 Human Breast Cancer Cells in Culture.” Asia Pacific J. Clin Nutr. 6(1) : 41-45.

  Palm oil, unlike many other dietary oils, does not increase the yield of chemically-induced mammary tumors in rats when fed at high levels in the diet. This difference appears to be due to the vitamin E fraction of palm oil, which is rich in tocotrienols, since palm oil stripped of this fraction does increase tumor yields. Experiments in our laboratory have shown that tocotrienols inhibit proliferation and growth of both MDA-MB-435 and MCF-7 cells in culture much more effectively than a-tocopherol. In addition, it was found that combinations of tocotrienols with Tamoxifen, a drug widely used for treatment of breast cancer, inhibit these cells more effectively than either tocotrienols or Tamoxifen alone. The present studies have now shown synergistic effects between tocotrienols and a number of other flavonoids from various plant sources, including citrus fruits, in the inhibition of both MDA-MB-435 and MCF-7 cells (IC50s 0.05-25 and 0.02-5 mg/mL respectively). In the MCF-7 cells, 1:1:1 combinations of tocotrienols, flavonoids and Tamoxifen were even more effective, with the best combination being d-tocotrienol, hesperetin and Tamoxifen (IC50 0.0005 mg/mL). These results suggest that diets containing palm oil may reduce the risk of breast cancer, particularly when eaten with other plant foods containing flavonoids, and may also enhance the effectiveness of Tamoxifen for treatment of breast cancer.

• 15. Effect of tocotrienols on the growth of a human breast cancer cell line in culture

  Nesaretnam K. et al. (1995). “Effects of Tocotrienols on the Growth of A Human Breast Cancer Cell Line in Culture.” Lipids. 30(12) : 1139-43.

  The tocotrienol-rich fraction (TRF) of palm oil consists of tocotrienols and some alpha-tocopherol (alpha-T). Tocotrienols are a form of vitamin E having an unsaturated side-chain, rather than the saturated side-chain of the more common tocopherols. Because palm oil has been shown not to promote chemically-induced mammary carcinogenesis, we tested effects of TRF and alpha-T on the proliferation, growth, and plating efficiency (PE) of the MDA-MB-435 estrogen-receptor-negative human breast cancer cells. TRF inhibited the proliferation of these cells with a concentration required to inhibit cell proliferation by 50% of 180 microgram/mL whereas alpha-T had no effect at concentrations up to 1000 microgram/mL as measured by incorporation of [3H]thymidine. The effects of TRF and alpha-T also were tested in longer-term growth experiments, using concentrations of 180 and 500 microgram/mL. We found that TRF inhibited the growth of these cells by 50%, whereas alpha-T did not. Their effect on the ability of these cells to form colonies also was studied, and it was found that TRF inhibited PE, whereas alpha T had no effect. These results suggest that the inhibition is due to the presence of tocotrienols in TRF rather than alpha T.

• 16(a). Effect of γ-Tocotrienol and α-Tocopherol on Blood Glutathione and Tumor Marker Enzymes during Chemical Hepatocarcinogenesis in the Rat

  Asmah R. et al. (1993). “Effect of gamma-Tocotrienols and alpha-Tocopherol on Blood Glutathione and Tumor Marker Enzymes during Chemical Hepatocarcinogenesis in the Rat.” J. Clin. Biochem. Nutr. 15(3) : 195-202.

  The protective effect of two types of vitamin E (α-tocopherol and γ-tocotrienol) in rats treated with diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) were studied by determination of plasma alkaline phosphatase (ALP), plasma and liver microsomal γ-glutamyl transpeptidase (GGT) activities, and blood glutathione (GSH). Rats treated with DEN/AAF had significantly elevated plasma and microsomal GGT, plasma ALP activities, and blood GSH levels compared with the normal controls (p<0.05). Supplementation with vitamin E of normal controls did not affect the enzyme activities or blood GSH. In rats treated with DEN/AAF, vitamin E supplementation attenuated GGT and ALP activities and blood GSH levels. The optimum dose required for highest attenuation of the tumor marker enzyme activities was 34mg/kg diet for α-tocopherol and 30mg/kg diet for γ-tocotrienol. Higher doses of the vitamin did not show further attenuation in the level of the tumor marker enzyme activities.

• 16(b). Long-term administration of tocotrienols and tumor-marker enzyme activities during hepatocarcinogenesis in rats

  Asmah R. et al. (1993). “Long-Term Administration of Tocotrienols and Tumor-Marker Enzyme Activities during Hepatocarcinogenesis in Rats. Nutr. 9(3) : 229-32.

  The effects of long-term administration of tocotrienol on hepatocarcinogenesis in rats induced by diethylnitrosamine (DEN) and 2-acetylaminofluorene (AAF) were investigated by determining the activities of gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), glutathione S-transferases (GSTs), and glutathione (GSH) levels in blood and liver. Twenty-eight male 7- to 8-wk-old Rattus norwegicus rats, weighing 120-160 g, were used in this study. The rats were divided into four treatment groups: a control group on a basal diet, a group fed a basal diet supplemented with tocotrienol (30 mg/kg food), a group treated with DEN/AAF, and a group treated with DEN/AAF and fed a diet supplemented with tocotrienol (30 mg/kg food). Blood was collected monthly, and GGT, ALP, and GSH levels were determined. The rats were killed after 9 mo, and the livers were examined morphologically. Grayish white nodules (2/liver) were found in all the DEN/AAF-treated rats (n = 10), but only one of the rats treated with DEN/AAF and supplemented with tocotrienol (n = 6) had liver nodules. A significant increase in the level of blood and liver GSH, ALP, and GGT activities was observed in the DEN/AAF-treated rats. Liver GSTs were similarly increased with DEN/AAF treatment. Tocotrienol supplementation attenuated the impact of the carcinogens in the rats.

• 16(c). Long-term tocotrienol supplementation and glutathione-dependent enzymes during hepatocarcinogenesis in the rat

  Asmah R. et al. (1993). “Long-Term Tocotrienol Supplementation and Glutathione-Dependent Enzyme during Hepatocarcinogenesis in Rats. “ Nutr. 9(2) : 129-34.

  The effects of long-term administration of tocotrienol on hepatocarcinogenesis in rats induced by diethyl nitrosamine (DEN) and 2-acetylaminofluorene (AAF) were investigated by the determination of plasma and liver gamma-glutamyl transpeptidase (GGT), cytosolic glutathione reductase (GSSG-Rx), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST). Twenty-eight male Rattus norwegicus rats (120-160g) were divided according to treatments into four groups: control group, tocotrienol - supplemented diet group (30mg/kg food), DEN/AAF-treated group and DEN/AAF treated plus tocotrienol-supplemented-diet group (30mg/kg food). The rats were sacrificed after nine months. The results obtained indicated no difference in the morphology and histology of the livers of control and tocotrienol-treated rats. Greyish-white neoplastic nodules (two per liver) were found in all the DEN/ AAF treated rats (n-10) whereas only one nodule was found in one of the carcinogen treated rats receiving tocotrienol supplementation (n-6). Histological examination showed obvious cellular damage for both the DEN/AAF-treated rats and the tocotrienol-supplemented rats but were less severe in the latter. Treatment with DEN/AAF caused increases in GGT, GSH-Px, GST and GSSG-Rx activities when compared to controls. These increases were also observed when tocotrienol was supplemented with DEN/AAF but the increases were less when compared to the rats receiving DEN/AAF only

• 17. The effect of vitamin E tocotrienols from palm oil on chemically induced mammary carcinogenesis in female rats

  Nesaretnam K. et al. (1992). “The Effect of Vitamin E Tocotrienols from Palm Oil on Chemically-Induced Mammary Carcinogenesis in Female Rats.” Nutr Res. 12(7) : 63-75.

  In the DMBA induced rat mammary tumor model, palm oil appeared to be less tumourigenic than corn oil, soybean oil, beef tallow and lard. Palm oil is a rich source of tocotrienols which have been reported to have antitumour activity against certain types of transplantable murine tumors. Results of the present experiments showed that palm oil stripped of its vitamin E tocopherols and tocotrienols (EFPO) enhanced tumorigenesis compared to palm oil containing vitamin E. In view of this a second experiment was designed to determine whether addition of a tocotrienol rich fraction (TRF) of palm oil to corn oil was able to inhibit development of mammary tumors in the DMBA treated rat model. One hundred female Sprague Dawley rats at 50 days of age were treated with a single dose of 5 mg of DMBA. They were then divided into 5 groups and fed semi-synthetic diets containing 20% by weight (40 en%) of either corn oil (CO), refined bleached and deodorized palm oil (RBDPO), corn oil + 500 ppm TRF, corn oil + 1000 ppm TRF or CO + 135 ppm α-tocopherol. The experiment was terminated 5 months after DMBA treatment. The RBD palm oil group had the lowest tumor incidence, tumor count and tumors per rat compared to animals fed the CO diet. This suggests that CO has a greater tumor promoting effect than palm oil. Supplementation of TRF at 500 ppm to corn oil did not provide protection. However at the higher concentration of 1000 ppm of TRF, the corn oil fed animals had significantly greater median latency period, lower tumor incidence and tumor count than the corn oil fed group as well as the group supplemented with either 500 ppm of TRF or 135 ppm α-tocopherol. The results appear to indicate that supplementation of corn oil with adequate amounts of TRF may give some protection against the cancer promoting effect of corn oil. The results also suggest that the favourable effects observed on a palm oil diet maybe attributed to the presence of naturally occurring tocotrienols in palm oil.

• 18. Effect of tocotrienols on hepatocarcinogenesis induced by 2-acetylaminofluorene in rats

  Wan Zurinah WN. et al. (1991).” Effect of Tocotrienol on Hepatocarcinogenesis Induced by 2-Acetylaminofluorene in Rats.” Am. J. Clin. Nutr. 53(4) : 1076S-81S.

  The effects of tocotrienols on hepatocarcinogenesis in rats fed with 2-acetylaminofluorene (AAF) were followed morphologically and histologically for a period of 20 wk. No differences between treated and control rats in the morphology and histology of their livers was observed. Cell damage was extensive in the livers of AAF-treated rats but less extensive in the AAF-tocotrienols-treated rats when compared with normal and tocotrienols-treated rats. 2-Acetylaminofluorene significantly increases the activities of both plasma and liver microsomal gamma-glutamyltranspeptidase (GGT) and liver microsomal UDP-glucuronyltransferase (UDP-GT). Tocotrienols administered together with AAF significantly decrease the activities of plasma GGT after 12 and 20 wk (P less than 0.01, P less than 0.002, respectively) and liver microsomal UDP-GT after 20 wk (P less than 0.02) when compared with the controls and with rats treated only with tocotrienols. Liver microsomal GGT also showed a similar pattern to liver microsomal UDP-GT but the decrease was not significant. These results suggest that tocotrienols administered to AAF-treated rats reduce the severity of hepatocarcinogenesi

• 19. Tocotrienol-rich fraction from palm oil and gene expression in human breast cancer cells

  Neseratnam et al. (2004), “Tocotrienol-rich fraction from palm oil and gene expression in human breast cancer cells”. Ann. N.Y. Acad. Sci. 1031 : 143-157.

  Vitamin E is important not only for its cellular antioxidant and lipid-lowering properties, but also as an antiproliferating agent. It has also been shown to contribute to immunoregulation, antibody production, and resistance to implanted tumors. It has recently been shown that tocotrienols are the components of vitamin E responsible for growth inhibition in human breast cancer cells in vitro as well as in vivo through estrogen-independent mechanisms. Although tocotrienols act on cell proliferation in a dose-dependent manner and can induce programmed cell death, no specific gene regulation has yet been identified. In order to investigate the molecular basis of the effect of a tocotrienol-rich fraction (TRF) from palm oil, we performed a cDNA array analysis of cancer-related gene expression in estrogen-dependent (MCF-7) and estrogen-independent (MDA-MB-231) human breast cancer cells. The human breast cancer cells were incubated with or without 8 mug/mL of tocotrienols for 72 h. RNA was subsequently extracted and subjected to reverse transcription before being hybridized onto cancer arrays. Tocotrienol supplementation modulated significantly 46 out of 1200 genes in MDA-MB-231 cells. In MCF-7 cells, tocotrienol administration was associated with a lower number of affected genes. Interestingly, only three were affected in a similar fashion in both cell lines: c-myc binding protein MM-1, 23-kDa highly basic protein, and interferon-inducible protein 9-27 (IFITM-1). These proteins are most likely involved in the cell cycle and can exert inhibitory effects on cell growth and differentiation of the tumor cell lines. These data suggest that tocotrienols are able to affect cell homeostasis, possibly independent of their antioxidant activity.

• 20. γ-tocotrienol inhibits neoplastic mammary epithelial cell proliferation by decreasing Akt and nuclear factor κB activity

  Sylvester et al. (2005), “γ-tocotrienol from palm oil inhibits neoplastic mammary epithelial cell proliferation by decreasing in Akt and Nuclear factor kB activity”. Submitted for Soc Experimen Bio and Med, 230 : 235-241.

  Tocotrienols, a subgroup within the vitamin E family of compounds, have been shown to display potent anticancer activity and inhibit preneoplastic and neoplastic mammary epithelial cell proliferation at treatment doses that have little or no effect on normal cell growth and function. However, the specific intracellular mechanisms mediating the antiproliferative effects of tocotrienols are presently unknown. Because Akt and nuclear factor κB (NFκB) are intimately involved in mammary tumor cell proliferation and survival, studies were conducted to determine the effects of γ-tocotrienol on Akt and NFκB activity in neoplastic þSA mammary epithelial cells in vitro. Treatment with 0–8 lM γ-tocotrienol for 0–3 days caused a dose-responsive inhibition in +SA cell growth and mitotic activity, as determined by MTT colorimetric assay and proliferating cell nuclear antigen immunocytochemical staining, respectively. Studies also showed that treatment with 4 lM γ-tocotrienol, a dose that inhibited +SA cell growth by more than 50% compared with that of untreated control cells, decreased intracellular levels of activated phosphotidylinositol 3-kinase-dependent kinase (PI3K)-dependent kinase 1 (phospho-PDK-1) and Akt, and reduced phospho-Akt kinase activity. Furthermore, these effects were not found to be associated with an increase in either phosphatase and tensin homologue deleted from chromosome 10 (PTEN) or protein phosphatase type 2A phosphatase activity. In addition, γ-tocotrienol treatment was shown to decrease NFκB transcriptional activity, apparently by suppressing the activation of IκB-kinase-a/b, an enzyme associated with inducing NFκB activation. In summary, these findings demonstrate that the antiproliferative effects of γ-tocotrienol result, at least in part, from a reduction in Akt and NFκB activity in neoplastic +SA mammary epithelial cells.

• 21. Anti-angiogenic potential of tocotrienol in vitro

  Miyazawa et al. (2004), “Anti-angiogenic potential of tocotrienols in vitro”. Biochemistry (Moscow), 69(1) : 67-69.

  Modulation of angiogenesis is now a recognized strategy for the prevention of various angiogenesis-mediated disorders. We investigated, using well-characterized in vitro systems, the anti-angiogenic property of vitamin E compounds, with particular emphasis on tocotrienol, a natural analog of tocopherol. Tocotrienol, but not tocopherol, inhibited the proliferation of bovine aortic endothelial cells in dose dependent manner at half-maximal concentrations in the low micromolar range. Tocotrienol also significantly inhibited the formation of networks of elongated endothelial cells within 3D collagen gels. From these results, we suggest that tocotrienol is a potential candidate for the development of useful therapeutic agents or preventive food factors for tumor angiogenesis

• 22. Long-chain carboxychromanols are the major metabolites of tocopherols and tocotrienols in A549 lung epithelial cells but not HepG2 cells

  You et al. (2005), “Long-chain carboxychromanols are the major metabolites of tocopherols and tocotrienols in A549 lung epithelial cells but not HepG2 cells”. J. Nutr. 135(2) : 227-32.

  Human lung type II cell derived A549 epithelial cancer cells and HepG2 hepatocytes constitutively express cytochrome P4504F2, a P450 we previously identified as a tocopherol-omega-hydroxylase. To determine if A549 cells would metabolize tocochromanols via the omega-hydroxylase pathway, we compared the metabolism of tocopherols (alpha-, gamma-, delta-TOH) and tocotrienols (alpha-, gamma-, delta-T3) in these 2 cell lines. Cultures were incubated with alpha-, gamma-, or delta-TOH, or the analogous T3s, and synthesis of their metabolites quantitated by GC-MS. A549 cells metabolized all tocochromanols 2-3 times more extensively than HepG2 cells (P < 0.001) except alpha-TOH, a difference not related to cell uptake of substrate but rather was reflective of greater microsomal TOH-omega-hydroxylase enzyme activity. Notably, 9'-carboxychromanols were the major metabolites of all gamma- and delta-TOHs and T3s in A549 cultures, whereas 3'- and 5'-carboxychromanols predominated in HepG2 cultures. Accumulation of 9'-carboxychromanols in A549 cultures was due to their inefficient conversion to 7'-carboxychromanols relative to HepG2 cells. Sesamin inhibited tocochromanol metabolism in both cells types, and neither cell type exhibited evidence of alternative (sesamin-insensitive) pathways of metabolism. TOH-omega-hydroxylase activity was undetectable in rat primary lung type II cells, suggesting that expression of activity was associated with transformation of normal type II cells to cancer cells. Long-chain carboxychromanol metabolites of gamma-TOH and other forms of vitamin E can be biosynthesized in A549 cultures for assessment of their biological activity, including their potential inhibition of synthesis of inflammatory mediators

• 23. Intracellular signaling mechanisms mediating the antiproliferative and apoptotic effects of gamma-tocotrienol in neoplastic mammary epithelial cells

  Sylvester et al. (2005). Intracellular signaling mechanisms mediating the antiproliferative and apoptotic effects of gamma-tocotrienol in neoplastic mammary epithelial cells. J. Plant Pyhsiol. 162(7) : 803-10.

  Tocotrienols, a subgroup within the vitamin E family of compounds, display potent antiproliferative and apoptotic activity against neoplastic mammary epithelial cells at treatment doses that have little or no effect on normal cell growth and function. Recent studies have shown that treatment with a growth inhibitory, but non-cytotoxic dose (4 microM) of gamma-tocotrienol inhibits phosphatidylinositol-3-kinase-dependent kinase (Pl3K)/Pl3K-dependent kinase 1 (PDK-1)/mitogenic signaling over a 2-3 day period following treatment exposure, and these effects were not found to be associated with an increased in either phosphatase and tensin homologue deleted from chromosome 10 (PTEN) or protein phosphatase type 2A (PP2A) phosphatase activity. In addition, this treatment caused a large decrease in NFKB transcriptional activity, apparently by suppressing I kappa B-kinase (IKK)-alpha/beta activation, an enzyme associated with inducing NFKB activation. Since Akt and NFkappaB are intimately involved in mammary tumor cell proliferation and survival, these findings strongly suggest that the antiproliferative effects of gamma-tocotrienol result, at least in part, from a reduction in Akt and NFkappa B activity. In contrast, treatment with 20 microM gamma-tocotrienol (cytotoxic dose) resulted in caspase-8 and -3 activation and apoptosis. It was also shown that this same treatment caused a rapid and large decrease in Pl3K/PDK/Akt signaling within 2-4h following treatment exposure, and a corresponding decrease in intracellular levels of FLIP, an antiapoptotic protein that inhibits caspase-8 activation. In summary, both the antiproliferative and apoptotic effects of gamma-tocotrienol appear to be mediated by a reduction in the Pl3K/PDK-1 /Akt signaling, an important pathway associated with cell proliferation and survival in neoplastic mammary epithelial cells.

• 24. Tocotrienols fight cancer by targeting multiple cell signaling pathways

  Kannappan et al. (2011). Tocotrienols fight cancer by targeting multiple cell signaling pathways. Genes & Nutrition. 7:43-52.

  Cancer cell are distinguished by several distinct characteristic, suh as self-sufficiency in growth signal, resistance to growth inhibition, limitless replicative potential,evasion of apoptosis, sustained angiogenesis, and tissue invasion and metastasis. Tumor cells acquire these properties due to the dysergulation of multiple genes and associated cell signaling pathways, most of which are linked to inflammation. For that reason, rationally designed drugs that target a single gene product are unlikely to be of use in preventing or treating cancer. Moreover, targeted drugs can cause serious and even life-threating side effects. Therefore, there is an urgent need for safe and effective promiscous (multitargeted) drugs. "Mother Nature" produces numerous such compounds that regulate multiple cell signaling pathways, are cost effective, exhibit low toxicity, and are readily available. One among these is tocotrienol, a member of the vitamin E family, which has exhibited anticancer properties. This review summarizes data from in vitro and in vivo studies of the effects of tocotrienol on nuclear factor-ƙB, signal transducer and activator of transcription (STAT) 3, death receptors, apoptosis, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), hypoxia-inducible factor (HIF) 1, growth factor receptor kinases, and angiogenic pathways.

• 25. Metabolism of tocotrienols in animals and synergistic inhibitory actions of tocotrienols with atorvastatin in cancer cells.

  Yang, Z. et al. (2011). Metabolism of tocotrienols in animals and synergistic inhibitory actions of tocotrienols with atoevastatin in cancer cells. Genes & Nutrition. 7:11-18.

  Tocotrienols (T3s), members of the vitamin E family,exhibit potent anti-cancer, anti-oxidative, anti-inflammatory, and some other biological activities. To better understand the bioavailability and metabolism of T3s, T3s and their metabolism were identified in urine and fecal samples from mice on diet supplemented with mixed T3s using HPLC/electrochemical detection and liquid chromatography electrospray ionisation  mass spectrometry (LC–ESI–MS). Whereas the short-chain metabolites carboxyethyl hydroxychromans (CEHCs) and carboxymethylbutyl hydroxychromans (CMBHCs) were the major metabolites of T3s, several new metabolites with double bonds were also identified. Similar to tocopherols, the majority of T3 metabolites were excreted as sulfate/glucuronide conjugates in mouse urine. The distribution of γ- and δ-T3 and γ-T3 metabolites were also determined in different organs as well as in urine and fecal samples from mice on diets supplemented with corresponding T3s. The synergistic anti-cancer actions of γ-T3 and atorvastatin (ATST) were studied in HT29 and HCT116 colon cancer cell lines. The combination greatly potentiated the ability of each individual agent to inhibit cancer cell growth and to induce cell cycle arrest and apoptosis. The triple combination of γ-T3, ATST, and celecoxib exhibited synergistic actions when compared with any double combination plus the third agent. Mechanistic studies revealed that the synergistic actions of γ-T3 and ATST could be attributed to their mediation of 3-hydroxy-3-methyl-glutaryl-CoA reductase, and the subsequent inhibition of protein geranylgeranylation. It remains to be determined whether such a synergy occurs in vivo.

• 26. Why tocotrienols work better: insight into the in vitro anti-cancer mechanism of vitamin E.

  Viola, V. et al. (2011). Why tocotrienols work better: insight into the in vitro anti-cancer mechanism of vitamin E. Genes & Nutrition. 7:29-41.

  The selective constraint of liver uptake and the sustained metabolism of tocotrienols (T3) demonstrate the need for a prompt detoxication of this class of this class of lipophilic vitamers, and thus the potential for cytotoxic effects in hepatic and extra-hepatic tissues. Hypomethylated (γ and δ) forms of T3 show the highest in vitro and in vivo metabolism and are also the most potent natural xenobiotics of the entire vitamin E family of compounds. These stimulate a stress response with the induction of detoxification and antioxidant genes. Depending on the intensity of this response, these genes may confer cell protection or alternatively they stimulate a senescence-like phenotype with cell cycle inhibition or even mitochondrial toxicity and apoptosis. In cancer cells, the uptake rate and thus the cell content of these vitamers is again higher for the hypomethylated forms, and it is the critical factor that drives the dichotomy between protection and toxicity responses to different T3 forms and doses. These aspects suggest the potential for marked biological activity of hypomethylated “highly metabolized” T3 that may result in cytoprotection and cancer prevention or even chemotherapeutic effects. Cytotoxicity and metabolism of hypomethylated T3 have been extensively investigated in vitro using different cell model systems that will be discussed in this review paper as regard molecular mechanisms and possible relevance in cancer therapy.

• 27. Tocotrienols and breast cancer: the evidence to date

  Nesaretnam, K. et al. (2011). Tocotrienols and breast cancer: the evidence to date. Genes & Nutrition. 7; 3-9.

  Breast cancer is the second most frequent cancer affecting women worldwide after lung cancer. The toxicity factor associated with synthetic drugs has turned the attention toward natural compounds as the primary focus of interest as anticancer agents. Vitamin E derivatives consisting of the well-established tocopherols and their analogs namely tocotrienols have been extensively studied due to their remarkable biological properties. While tocopherols have failed to offer protection, tocotrienols, in particular, α-, δ-, and γ-tocotrienols alone and in combination have demonstrated anticancer properties. The discovery of the antiangiogenic, antiproliferative, and apoptotic effects of tocotrienols, as well as their role as an inducer of immunological functions, not only reveals a new horizon as a potent antitumor agent but also reinforces the notion that tocotrienols are indeed more than antioxidants. On the basis of a transcriptomic platform, we have recently demonstrated a novel mechanism for tocotrienol activity that involves estrogen receptor (ER) signaling. In silico simulations and in vitro binding analyses indicate a high affinity of specific forms of tocotrienols for ERβ, but not for ERα. Moreover, we have demonstrated that specific tocotrienols increase ERβ translocation into the nucleus which, in turn, activates the expression of estrogen-responsive genes (MIC-1, EGR-1 and Cathepsin D) in breast cancer cells only expressing ERβ cells (MDA-MB-231) and in cells expressing both ER isoforms (MCF-7). The binding of specific tocotrienol forms to ERβ is associated with the alteration of cell morphology, caspase-3 activation, DNA fragmentation, and apoptosis. Furthermore, a recently concluded clinical trial seems to suggest that tocotrienols in combination with tamoxifen may have the potential to extend breast cancer-specific survival.

• 28. Synergistic anticancer effects of combined γ-tocotrienol with statin or receptor tyrosine kinase inhibitor treatment

  Sylvester, P. et al. (2011). Synergistic anticancer effects of combined γ-tocotrienol with statin or receptor tyrosine kinase inhibitor treatment. 7:63-74.

  Systemic chemotherapy is the only current method of treatment that provides some chance for long-term survival in patients with advanced or metastatic cancer. γ-Tocotrienol is a natural form of vitamin E found in high concentrations in palm oil and displays potent anticancer effects, but limited absorption and transport of by the body has made it difficult to obtain and sustain therapeutic levels in the blood and target tissues. Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase and are an example of a promising cancer chemotherapeutic agent whose clinical usefulness has been limited due to high-dose toxicity. Similarly, erlotinib and gefitinib are anticancer agents that inhibit the activation of individual HER/ErbB receptor subtypes, but have shown limited clinical success because of heterodimerization between different EGF receptor family members that can rescue cancer cells from agents directed against a single receptor subtype. Recent studies have investigated the anticancer effectiveness of low-dose treatment of various statins or EGF receptor inhibitors alone and in combination with γ-tocotrienol on highly malignant +SA mouse mammary epithelial cells in vitro. Combined treatment with subeffective doses of γ-tocotrienol with these other chemotherapeutic agents resulted in a synergistic inhibition of +SA cell growth and viability. These findings strongly suggest that combined treatment of γ-tocotrienol with other anticancer agents may not only provide an enhanced therapeutic response but also provide a means to avoid the toxicity, low bioavailability, or limited therapeutic action associated with high-dose monotherapy.

• 29. Palm tocotrienols decrease levels of pro-angiogenic markers in human umbilical vein endothelial cells (HUVEC) and murine mammary cancer cells

  Selvaduray, K. R. et al. (2011). Palm tocotrienols decrease levels of pro-angiogenic markers in human umbilical vein endothelial cells (HUVEC) and murine mammary cancer cells. Genes & Nutrition. 7: 53-61.

  Anti-angiogenic therapy is widely being used to halt tumour angiogenesis. In this study, the anti-angiogenic activity of palm tocotrienol-rich fraction (TRF) and its individual components (γ- and δ-tocotrienol) were first investigated in vitro in human umbilical vein endothelial cells (HUVEC) and 4T1 mouse mammary cancer cells. Results showed reduced levels of Interkeukin (IL)-8 and IL-6, two pro-angiogenic cytokines in HUVEC treated with palm tocotrienols compared with α-tocopherol (α-T) and control cells (P < 0.05). The production of IL-8 and IL-6 was lowest in δ-tocotrienol (δ-T3)-treated cells followed by γ-tocotrienol (γ-T3) and TRF. There was significant (P < 0.05) reduction in IL-8 and vascular endothelial growth factor (VEGF) production in 4T1 cells treated with TRF or δ-T3. There was decreased expression of VEGF and its receptors; VEGF-R1 (fms-like tyrosine kinase, Flt-1) and VEGF-R2 (Kinase-insert-domain-containing receptor, KDR/Flk-2) in tumour tissues excised from mice supplemented with TRF were observed. There was also decreased expression of VEGF-R2 in lung tissues of mice supplemented with TRF. These observations correlate with the smaller tumour size recorded in the tocotrienol-treated mice. This study confirms previous observations that palm tocotrienols exhibit anti-angiogenic properties that may inhibit tumour progression.

• 30. The value of tocotrienols in the prevention and treatment of cancer

  Sylvester, P. et al. (2010). The value of tocotrienols in the prevention and treatment of cancer. J Am Coll Nutr. 29(3): 3245-3335.

  Tocopherols and tocotrienols represent the 2 subgroups that make up the vitamin E family of compounds, but only tocotrienols display potent anticancer activity. Although in vitro experimental evidence has been very promising, oral supplementation of tocotrienols in animal and human studies has produced inconsistent results. However, recent studies have now clarified the reasons for these discrepancies observed between in vitro and in vivo studies. Oral absorption of tocotrienols into the circulation is mediated in large part by carrier transporter systems that display saturation and apparently down-regulation when exposed to high concentrations of tocotrienols. To circumvent these limitations in oral absorption of tocotrienols, investigators have developed novel prodrug derivatives and nanoparticle delivery systems that greatly enhance tocotrienol bioavailability and therapeutic responsiveness. Additional studies have also demonstrated that combined treatment of tocotrienols with other traditional chemotherapeutic agents results in a synergistic anticancer response, and this synergistic response was further enhanced when these agents were encapsulated in a nanoparticle delivery system. Taken together, these findings clarify the limitations of oral tocotrienol administration and provide novel alternative drug-delivery systems that circumvent these limitations and greatly enhance the therapeutic effectiveness of tocotrienols in the prevention and treatment of cancer.

• 31. Multitargeted therapy of cancer by tocotrienols

  Nesaretnam, K. (2008). Multitargeted therapy of cancer by tocotrienols. Cancer letter. 269(2): 388-395.

  Natural compounds with possible health benefits have become attractive targets for research in areas pertaining to human health. For both prevention and therapy of various human ailments, such compounds are preferred over synthetic ones due to their lesser toxicity. They are also easily absorbed and processed by our body. Vitamins are prominent among natural or endogenous compounds that are considered to be beneficial. The vitamin E group of compounds is among the better known of the vitamins due to their suggested health benefits including antioxidant and related protective properties. Among these, tocotrienols have gained prominence in recent years due to their potential applications and better protective effects in certain systems. These tocotrienols are vitamin E derivatives that are analogs of the more established forms of vitamin E namely tocopherols. In addition to their potent antioxidant activity, tocotrienols have other important functions, especially in maintaining a healthy cardiovascular system and a possible role in protection against cancer and other ailments.

• 32. Tocotrienols inhibit AKT and ERK activation and suppress pancreatic cancer cell proliferation by suppressing the ErbB2 pathway

  Shin-Kang, S. et al. (2011). Tocotrienols inhibit AKT and ERK activation and suppress pancreatic cancer cell proliferation by suppressing the ErbB2 pathway. Free radical biology and medicine. 51(6):1164-1174.

  Tocotrienols are members of the vitamin E family but, unlike tocopherols, possess an unsaturated isoprenoid side chain that confers superior anti-cancer properties. The ability of tocotrienols to selectively inhibit the HMG-CoA reductase pathway through posttranslational degradation and to suppress the activity of transcription factor NF-κB could be the basis for some of these properties. Our studies indicate that γ- and δ-tocotrienols have potent antiproliferative activity in pancreatic cancer cells (Panc-28, MIA PaCa-2, Panc-1, and BxPC-3). Indeed both tocotrienols induced cell death (> 50%) by the MTT cell viability assay in all four pancreatic cancer cell lines. We also examined the effects of the tocotrienols on the AKT and the Ras/Raf/MEK/ERK signaling pathways by Western blotting analysis. γ- and δ-tocotrienol treatment of cells reduced the activation of ERK MAP kinase and that of its downstream mediator RSK (ribosomal protein S6 kinase) in addition to suppressing the activation of protein kinase AKT. Suppression of activation of AKT by γ-tocotrienol led to downregulation of p-GSK-3β and upregulation accompanied by nuclear translocation of Foxo3. These effects were mediated by the downregulation of Her2/ErbB2 at the messenger level. Tocotrienols but not tocopherols were able to induce the observed effects. Our results suggest that the tocotrienol isoforms of vitamin E can induce apoptosis in pancreatic cancer cells through the suppression of vital cell survival and proliferative signaling pathways such as those mediated by the PI3-kinase/AKT and ERK/MAP kinases via downregulation of Her2/ErbB2 expression. The molecular components for this mechanism are not completely elucidated and need further investigation.