Vitamin E and its anticancer effects

Abraham A, Kattoor AJ, Saldeen T, Mehta JL.

Crit Rev Food Sci Nutr. 2018 May 10:1-23. doi: 10.1080/10408398.2018.1474169. [Epub ahead of print]

Abstract

Vitamin E is a lipid soluble vitamin comprising of eight natural isoforms, namely, α, β, δ, γ isoforms of tocopherol and α, β, δ, γ isoforms of tocotrienol. Many studies have been performed to elucidate its role in cancer. Until last decade, major focus was on alpha tocopherol and its anticancer effects. However, major clinical trials using alpha-tocopherol like SELECT trial and ATBC trial did not yield meaningful results. Hence there was a shift of focus to gamma-tocopherol, delta-tocopherol and tocotrienol. Unlike alpha-tocopherol, gamma-tocopherol and delta-tocopherol can scavenge reactive nitrogen species in addition to reactive oxygen species. Antiangiogenic effect, inhibition of HMG CoA reductase enzyme and inhibition of NF-κB pathway make the anti-cancer effects of tocotrienols unique compared to other vitamin E isoforms. Preclinical research on non-alpha tocopherol isoforms of vitamin E showed promising data on their anticancer effects. In this review, we deal with the current understanding on the potential mechanisms involved in the anticancer effects of vitamin E and the controversies in this field over last three decades. We also highlight the need to conduct further research on the anticancer effects of non-alpha-tocopherol isoforms in larger population and clinical setting.

KEYWORDS:

Vitamin E and cancer; anticancer mechanisms; tocopherol; tocopherol and cancer; tocotrienol

Uchihara Y, Kidokoro T, Tago K, Mashino T, Tamura H, Funakoshi-Tago M

Eur J Pharmacol. 2018 Apr 15;825:1-9. doi: 10.1016/j.ejphar.2018.02.012. Epub 2018 Feb 11.

Abstract

Crizotinib is an inhibitor of anaplastic lymphoma kinase (ALK) and is of significant therapeutic benefit to patients with non-small cell lung cancer (NSCLC) harboring the EML4-ALK fusion gene. In the present study, we demonstrated that α-tocopherol, a major component of vitamin E, attenuated the effects of crizotinib independently of its anti-oxidant properties. α-Tocopherol significantly inhibited crizotinib-induced apoptosis in cells transformed by EML4-ALK. It also effectively attenuated the crizotinib-induced inhibition of EML4-ALK and its downstream molecules, STAT3 and ERK, and suppressed the inhibitory effects of crizotinib on EML4-ALK-mediated transformation in the focus formation assay. On the other hand, other members of the vitamin E family, namely, β-tocopherol, γ-tocopherol, δ-tocopherol, and α-tocotrienol, and a water-soluble analog of vitamin E, Trolox had no effects on the anti-tumor activity of crizotinib in cells transformed by EML4-ALK. Collectively, these results revealed the risk of the anti-tumor activity of crizotinib being attenuated when it is administrated in combination with vitamin Esupplements containing α-tocopherol as a major component.

Qureshi AA, Zuvanich EG, Khan DA, Mushtaq S, Silswal N, Qureshi N

Lipids Health Dis. 2018 Apr 2;17(1):62. doi: 10.1186/s12944-018-0697-5.

Abstract

BACKGROUND:

Cancer is second most common cause of death in the United State. There are over 100 different types of cancer associated with different human organs, predominantly breast, liver, pancreas, prostate, colon, rectum, lung, and stomach. We have recently reported properties of pro-inflammatory (for treatment of various types of cancers), and anti-inflammatory (for cardiovascular disease and diabetes) compounds. The major problem associated with development of anticancer drugs is their lack of solubility in aqueous solutions and severe side effects in cancer patients. Therefore, the present study was carried out to check anticancer properties of selected compounds, mostly aqueous soluble, in cancer cell lines from different organs.

METHODS:

The anticancer properties, anti-proliferative, and pro-apoptotic activity of novel naturally occurring or FDA approved, nontoxic, proteasome inhibitors/activators were compared. In addition to that, effect of δ-tocotrienol on expression of proteasome subunits (X, Y, Z, LMP7, LMP2, LMP10), ICAM-1, VCAM-1, and TNF-α using total RNAs derived from plasmas of hepatitis C patients was investigated.

RESULTS:

Our data demonstrated that following compounds are very effective in inducing apoptosis of cancer cells: Thiostrepton, dexamethasone, 2-methoxyestradiol, δ-tocotrienol, quercetin, amiloride, and quinine sulfate have significant anti-proliferation properties in Hela cells (44% – 87%) with doses of 2.5-20 μM, compared to respective controls. Anti-proliferation properties of thiostrepton, 2-methoxyestradiol, δ-tocotrienol, and quercetin were 70% – 92%. However, thiostrepton, dexamethasone, 2-methoxyestradiol, δ-tocotrienol, quercetin, and quinine sulphate were effective in pancreatic, prostate, breast, lungs, melanoma, Β-lymphocytes, and T-cells (Jurkat: 40% to 95%) compared to respective controls. In lung cancer cells, these compounds were effective between 5 and 40 μM. The IC₅₀ values of anti-proliferation properties of thiostrepton in most of these cell lines were between doses of 2.5-5 μM, dexamethasone 2.5-20 μM, 2-methoxyestradiol 2.5-10 μM, δ-tocotrienol 2.5-20 μM, quercetin 10-40 μM, and (-) Corey lactone 40-80 μM. In hepatitis C patients, δ-tocotrienol treatment resulted in significant decrease in the expression of pro-inflammatory cytokines.

CONCLUSIONS:

These data demonstrate effectiveness of several natural-occurring compounds with anti-proliferative properties against cancer cells of several organs of humans. Thiostrepton, dexamethasone, 2-methoxyestradiol, δ-tocotrienol and quercetin are very effective for apoptosis of cancer cells in liver, pancreas, prostate, breast, lung, melanoma, Β-lymphocytes and T-cells. The results have provided an opportunity to test these compounds either individually or in combination as dietary supplements in humans for treatment of various types of cancers.

KEYWORDS:

B-lymphocytes; Breast; Inflammatory biomarkers; Liver; Lung; Melanoma; Pancreas; Potent anticancer compounds; Prostate; Several cancer cell lines (Hela; T-cells)

Abubakar IB, Lim SW, Loh HS.

Trop Life Sci Res. 2018 Mar;29(1):229-238. doi: 10.21315/tlsr2018.29.1.15. Epub 2018 Mar 2.

Abstract

Kajian terbaru mencadangkan bahawa pendekatan gabungan rawatan boleh digunakan untuk meningkatkan potensi antikanser dan menghindari batasan pemberian tocotrienol dos tinggi. Acalypha wilkesiana adalah tumbuhan ubatan yang telah digunakan sebagai rawatan tambahan untuk kanser dalam perubatan tradisional. Di sini, kesan rawatan tunggal dan gabungan β-, γ-dan δ-tocotrienols dan ekstrak etil asetat (9EA) daripada Acalypha wilkesiana pada paru-paru (A549) dan sel-sel kanser otak (U87MG) telah disiasat. γ-dan δ-tocotrienols menunjukkan kesan antiproliferatif yang lebih tinggi terhadap A549 (12.1 μg/ml dan 13.6 μg/ml) dan sel U87MG (3.3 μg/ml dan 5.2 μg/ml) berbanding β-tocotrienols (9.4 μg/ml), masing-masing. Sedangkan, 9EA merangsang kesan antiproliferatif yang kuat terhadap sel U87MG sahaja (2.0 μg/ml). Rawatan terapi tocotrienols dan 9EA mencetuskan perencatan pertumbuhan sinergis sehingga pengurangan 8.4 kali ganda dalam dos yang kuat dari β-, γ-dan δ-tocotrienols pada sel A549. Ciri-ciri apoptotik juga dibuktikan pada sel-sel A549 yang menerima rawatan tunggal dan gabungan. Sinergi ini boleh meningkatkan hasil terapeutik untuk kanser paru-paru.

Recent studies suggested that combined treatment approaches can be used to improve anticancer potency and circumvent the limitations of high-dose tocotrienols administration. Acalypha wilkesiana is a medicinal plant that has been used as an adjunct treatment for cancers in traditional medicine. Herein, the effects of single and combined treatments of β-, γ- and δ-tocotrienols and ethyl acetate extract (9EA) of Acalypha wilkesiana on lung (A549) and brain (U87MG) cancer cells were investigated. γ- and δ-tocotrienols exhibited higher potent antiproliferative effects against A549 (12.1 μg/ml and 13.6 μg/ml) and U87MG cells (3.3 μg/ml and 5.2 μg/ml) compared to β-tocotrienols (9.4 μg/ml and 92.4 μg/ml), respectively. Whereas, 9EA induced potent antiproliferative effects against U87MG cells only (2.0 μg/ml). Combined treatments of tocotrienols and 9EA induced a synergistic growth inhibition with up to 8.4-fold reduction in potent doses of β-, γ- and δ-tocotrienols on A549 cells. Apoptotic features were also evidenced on A549 cells receiving single and combined treatments. The synergism may greatly improve the therapeutic outcome for lung cancer.

KEYWORDS:

Acalypha wilkesiana; Apoptosis; Synergism; Tocotrienol

Sailo BL, Banik K, Padmavathi G, Javadi M, Bordoloi D, Kunnumakkara AB

Pharmacol Res. 2018 Feb 27. pii: S1043-6618(17)31460-3

Abstract

Despite the significant advancements in the diagnosis and treatment of cancer, it still remains one of the most fatal diseases in the world due to the lack of sensitive diagnosis methods and effective drugs. Therefore, discovering novel therapies that are safe, efficacious and affordable are required for the better management of this disease. Tocotrienols, analogues of vitamin E have gained increased attention due to their safety and efficacy. Extensive research over the past several years has strongly indicated that tocotrienols can efficiently prevent/inhibit the growth of different cancers such as cancers of blood, brain, breast, cervical, colon, liver, lung, pancreas, prostate, skin, stomach etc. This is mainly accredited to their ability to modulate various molecular targets involved in cancer cell proliferation, survival, invasion, angiogenesis, and metastasis such as NF-κB, STAT3, Akt/mTOR, etc. In addition, increasing lines of evidence has shown that tocotrienols can sensitize cancer cells to chemotherapeutic agents such as celecoxib, doxorubicin, erlotinib, gefitinib, gemcitabine, paclitaxel, statin etc. Moreover, several clinical trials have confirmed the safety and tolerability of tocotrienols in humans. This review summarizes the potential of tocotrienols for the prevention and treatment of different cancers based on the available in vitro, in vivo and clinical studies.

Malavolta M, Bracci M, Santarelli L, Sayeed MA, Pierpaoli E, Giacconi R, Costarelli L, Piacenza F, Basso A, Cardelli M, Provinciali M

Mediators Inflamm. 2018 Feb 12;2018:4159013. doi: 10.1155/2018/4159013. eCollection 2018.

Abstract

The reactivation of senescence in cancer and the subsequent clearance of senescent cells are suggested as therapeutic intervention in the eradication of cancer. Several natural compounds that activate Nrf2 (nuclear factor erythroid-derived 2-related factor 2) pathway, which is involved in complex cytoprotective responses, have been paradoxically shown to induce cell death or senescence in cancer. Promoting the cytoprotective Nrf2 pathway may be desirable for chemoprevention, but it might be detrimental in later stages and advanced cancers. However, senolytic activity shown by some Nrf2-activating compounds could be used to target senescent cancer cells (particularly in aged immune-depressed organisms) that escape immunosurveillance. We herein describe in vitro and in vivo effects of fifteen Nrf2-interacting natural compounds (tocotrienols, curcumin, epigallocatechin gallate, quercetin, genistein, resveratrol, silybin, phenethyl isothiocyanate, sulforaphane, triptolide, allicin, berberine, piperlongumine, fisetin, and phloretin) on cellular senescence and discuss their use in adjuvant cancer therapy. In light of available literature, it can be concluded that the meaning and the potential of adjuvant therapy with natural compounds in humans remain unclear, also taking into account the existence of few clinical trials mostly characterized by uncertain results. Further studies are needed to investigate the therapeutic potential of those compounds that display senolytic activity.

Abu-Fayyad A, Kamal MM, Carroll JL, Dragoi AM, Cody R, Cardelli J, Nazzal S

Int J Pharm. 2018 Jan 30;536(1):146-157. doi: 10.1016/j.ijpharm.2017.11.062. Epub 2017 Dec 2.

Abstract

Vitamin E TPGS is a tocopherol (α-T) based nonionic surfactant that was used in the formulation of the Tocosol™ paclitaxel nanoemulsion, which was withdrawn from phase III clinical trials. Unlike tocopherols, however, the tocotrienol (T₃) isomers of vitamin E were found to have innate anticancer activity and were shown to potentiate the antitumor activity of paclitaxel. The primary objective of the present study was therefore to develop a paclitaxel nanoemulsions by substituting α-T oil core of Tocosol™ with γ-T₃ in, and vitamin E TPGS with PEGylated γ-T₃ as the shell, and test the nanoemulsions against Bx-PC-3 and PANC-1 pancreatic tumor cells. A secondary objective was to test the activity of paclitaxel when directly conjugated with the γ-T₃ isomer of vitamin E. The synthesis of the conjugates was confirmed by NMR and mass spectroscopy. Developed nanoemulsions were loaded with free or lipid conjugated paclitaxel. Nanoemulsions droplets were <300 nm with fastest release observed with formulations loaded with free paclitaxel when γ-T₃ was used as the core. Substituting α-T with γ-T₃ was also found to potentiate the anticancer activity of the nanoemulsions. Although marginal increase in activity was observed when nanoemulsions were loaded with free paclitaxel, a significant increase in activity was observed when lipid conjugates were used. The results from this study suggest that the developed paclitaxel nanoemulsions with either γ-T₃, PEGylated γ-T₃, or paclitaxel lipid conjugates may represent a more promising option for paclitaxel delivery in cancer chemotherapy.

Marzagalli M, Moretti RM, Messi E, Marelli MM, Fontana F, Anastasia A, Bani MR, Beretta G, Limonta P

Sci Rep. 2018 Jan 12;8(1):587. doi: 10.1038/s41598-017-19057-4

Abstract

The prognosis of metastatic melanoma is very poor, due to the development of drug resistance. Cancer stem cells (CSCs) may play a crucial role in this mechanism, contributing to disease relapse. We first characterized CSCs in melanoma cell lines. We observed that A375 (but not BLM) cells are able to form melanospheres and show CSCs traits: expression of the pluripotency markers SOX2 and KLF4, higher invasiveness and tumor formation capability in vivo with respect to parental adherent cells. We also showed that a subpopulation of autofluorescent cells expressing the ABCG2 stem cell marker is present in the A375 spheroid culture. Based on these data, we investigated whether δ-TT might target melanoma CSCs. We demonstrated that melanoma cells escaping the antitumor activity of δ-TT are completely devoid of the ability to form melanospheres. In contrast, cells that escaped vemurafenib treatment show a higher ability to form melanospheres than control cells. δ-TT also induced disaggregation of A375 melanospheres and reduced the spheroidogenic ability of sphere-derived cells, reducing the expression of the ABCG2 marker. These data demonstrate that δ-TT exerts its antitumor activity by targeting the CSC subpopulation of A375 melanoma cells and might represent a novel chemopreventive/therapeutic strategy against melanoma.

Das Gupta S, Patel M, Wahler J, Bak MJ, Wall B, Lee MJ, Lin Y, Shih WJ, Cai L, Yang CS, Suh N

Cancer Prev Res (Phila). 2017 Dec;10(12):694-703. doi: 10.1158/1940-6207.CAPR-17-0190. Epub 2017 Sep 28.

Abstract

Despite experimental evidence elucidating the antitumor activities of tocopherols, clinical trials with α-tocopherol (α-T) have failed to demonstrate its beneficial effects in cancer prevention. This study compared the chemopreventive efficacy of individual tocopherols (α-, δ-, and γ-T) and a γ-T-rich tocopherol mixture (γ-TmT) in the August-Copenhagen Irish (ACI) rat model of estrogen-mediated mammary cancer. Female ACI rats receiving 17β-estradiol (E2) implants were administered with 0.2% α-T, δ-T, γ-T, or γ-TmT for 30 weeks. Although α-T had no significant effects on mammary tumor growth in ACI rats, δ-T, γ-T, and γ-TmT reduced mammary tumor volume by 51% (P < 0.05), 60% (P < 0.01), and 59% (P < 0.01), respectively. Immunohistochemical analysis revealed that δ-T, γ-T, and γ-TmT reduced levels of the cell proliferation marker, proliferating cell nuclear antigen, in the rat mammary tumors. To gain further insight into the biological functions of different forms of tocopherols, RNA-seq analysis of the tumors was performed. Treatment with γ-T induced robust gene expression changes in the mammary tumors of ACI rats. Ingenuity Pathway Analysis identified “Cancer” as a top disease pathway and “Tumor growth” and “Metastasis” as the top signaling pathways modulated by γ-T. Although the results need further functional validation, this study presents an unbiased attempt to understand the differences between biological activities of individual forms of tocopherols at the whole transcriptome level. In conclusion, δ-T and γ-T have superior cancer preventive properties compared to α-T in the prevention of estrogen-mediated mammary carcinogenesis.

Kanchi MM, Shanmugam MK, Rane G, Sethi G, Kumar AP

Drug Discov Today. 2017 Dec;22(12):1765-1781. doi: 10.1016/j.drudis.2017.08.001. Epub 2017 Aug 5.

Abstract

Vitamin E family members: tocotrienols and tocopherols are widely known for their health benefits. Decades of research on tocotrienols have shown they have diverse biological activities such as antioxidant, anti-inflammatory, anticancer, neuroprotective and skin protection benefits, as well as improved cognition, bone health, longevity and reduction of cholesterol levels in plasma. Tocotrienols also modulate several intracellular molecular targets and, most importantly, have been shown to improve lipid profiles, reduce total cholesterol and reduce the volume of white matter lesions in human clinical trials. This review provides a comprehensive update on the little-known therapeutic potentials of tocotrienols, which tocopherols lack in a variety of inflammation-driven diseases.