Natural forms of vitamin E and metabolites-regulation of cancer cell death and underlying mechanisms

Different Roles of Tocopherols and Tocotrienols in Chemoprevention and Treatment of Prostate Cancer

The vitamin E family contains α-tocopherol (αT), βT, γT, and δT and α-tocotrienol (TE), βTE, γTE, and δTE. Research has revealed distinct roles of these vitamin E forms in prostate cancer (PCa). The ATBC trial showed that αT at a modest dose significantly decreased PCa mortality among heavy smokers. However, other randomized controlled trials including the Selenium and Vitamin E Cancer Prevention Trial (SELECT) indicate that supplementation of high-dose αT (≥400 IU) does not prevent PCa among nonsmokers. Preclinical cell and animal studies also do not support chemopreventive roles of high-dose αT and offer explanations for increased incidence of early-stage PCa reported in the SELECT. In contrast, accumulating animal studies have demonstrated that γT, δT, γTE, and δTE appear to be effective for preventing early-stage PCa from progression to adenocarcinoma in various PCa models. Existing evidence also support therapeutic roles of γTE and its related combinations against advanced PCa. Mechanistic and cell-based studies show that different forms of vitamin E display varied efficacy, that is, δTE ≥ γTE > δT ≥ γT >> αT, in inhibiting cancer hallmarks and enabling characteristics, including uncontrolled cell proliferation, angiogenesis, and inflammation possibly via blocking 5-lipoxygenase, nuclear factor κB, hypoxia-inducible factor-1α, modulating sphingolipids, and targeting PCa stem cells. Overall, existing evidence suggests that modest αT supplement may be beneficial to smokers and γT, δT, γTE, and δTE are promising agents for PCa prevention for modest-risk to relatively high-risk population. Despite encouraging preclinical evidence, clinical research testing γT, δT, γTE, and δTE for PCa prevention is sparse and should be considered.

Chemopreventive effects of α-tocopherol and its long-chain metabolites α-13'-hydroxy- and α-13'-carboxychromanol in LT97 colon adenoma cells

Anticancer effects of vitamin E (tocopherols) have been studied extensively. While in vitro and animal studies showed promising results regarding anticancer effects of tocopherols, human intervention studies failed to reproduce these results. In vivo, α-tocopherol (α-TOH) is metabolized to the long-chain metabolites (LCM) 13'-hydroxychromanol (α-13'-OH) and 13'-carboxychromanol (α-13'-COOH), which likely reach the large intestine. The LCM showed antiproliferative effects in different colon cancer cell lines, but the exact mechanism of action remains unclear. To further clarify the chemopreventive action of the LCM, premalignant LT97 colon adenoma cells were treated with α-TOH, α-13'-OH and α-13'-COOH to study their impact on growth, apoptosis, antigenotoxicity, and ROS-scavenging capacity as well as expression of selected genes involved in detoxification and the cell cycle. Growth inhibitory potential was observed for α-13'-OH (IC50: 37.4 μM) and α-13'-COOH (IC50: 5.8 μM) but not for α-TOH in the tested concentrations. Levels of caspase-3 activity and expression of genes regulating the cell cycle and detoxification remained unchanged. However, α-TOH, α-13'-OH and α-13'-COOH exhibited antigenotoxic and partly ROS-scavenging capacity. The results indicate that the LCM exert chemopreventive effects via ROS-scavenging capacity, the protection against DNA damage and the induction of cell death via caspase-independent mechanisms in premalignant colon cells.

Vitamin A, D, E, and K as Matrix Metalloproteinase-2/9 Regulators That Affect Expression and Enzymatic Activity

Fat-soluble vitamins (vitamin A, D, E, and K) assume a pivotal role in maintaining human homeostasis by virtue of their enzymatic functions. The daily inclusion of these vitamins is imperative to the upkeep of various physiological processes including vision, bone health, immunity, and protection against oxidative stress. Current research highlights fat-soluble vitamins as potential therapeutics for human diseases, especially cancer. Fat-soluble vitamins exert their therapeutic effects through multiple pathways, including regulation of matrix metalloproteinases' (MMPs) expression and enzymatic activity. As MMPs have been reported to be involved in the pathology of various diseases, such as cancers, cardiovascular diseases, and neurological disorders, regulating the expression and/or activity of MMPs could be considered as a potent therapeutic strategy. Here, we summarize the properties of fat-soluble vitamins and their potential as promising candidates capable of effectively modulating MMPs through multiple pathways to treat human diseases.

Interaction between vitamin E intake and a COMT gene variant on colorectal cancer risk among Korean adults: a case-control study

OBJECTIVES

Previous human trials have not supported the anticarcinogenic effect of vitamin E despite biological plausibility and considerable epidemiological evidence. A possible explanation for this inconsistency is the interactive effect of the catechol-O-methyltransferase (COMT) gene and supplemental vitamin E on cancer. We examined whether a COMT gene variant modulates the effect of dietary vitamin E intake on colorectal cancer (CRC) risk.

METHODS

In this case-control study of Korean adults (975 cases and 975 age- and sex-matched controls), dietary vitamin E density (mg/1,000 kcal) was measured using a semiquantitative food frequency questionnaire, COMT single nucleotide polymorphism (SNP) rs740603 (A>G) was genotyped, and CRC was verified histologically. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression models with adjustments for potential confounders.

RESULTS

Higher vitamin E density was associated with a lower risk of CRC (highest vs. lowest quartiles: OR, 0.72; 95% CI, 0.55 to 0.96; p-for-trend=0.002). When stratified by COMT SNP rs740603 genotype, the inverse association between vitamin E density and CRC risk was confined to those with at least 1 A allele (≥median vs.

CONCLUSIONS

Our findings support a role for a genetic polymorphism in COMT in modifying the association between dietary vitamin E intake and CRC.

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Key Words

• Case-control studies
• Catechol-O-methyltransferase
• Colorectal cancer
• Gene-environment interaction
• Single nucleotide polymorphism
• Vitamin E

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MESH Headings

• Adult
• Humans
• Catechol O-Methyltransferase/genetics
• Case-Control Studies
• Polymorphism, Single Nucleotide
• Vitamin E
• Logistic Models
• Colorectal Neoplasms/epidemiology
• Colorectal Neoplasms/genetics
• Republic of Korea/epidemiology
• Risk Factors

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Grants

• National Research Foundation of Korea
• 2021R1A6A3A01087058 Ministry of Education
• 2021R1A2C2008439 Ministry of Science and ICT

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Affiliation(s)

Shinyoung Jun Department of Cancer Biomedical Science, National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea
Madhawa Gunathilake Department of Cancer Biomedical Science, National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea
Jeonghee Lee Department of Cancer Biomedical Science, National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea
Jae Hwan Oh Center for Colorectal Cancer, National Cancer Center, Goyang, Korea
Hee Jin Chang Center for Colorectal Cancer, National Cancer Center, Goyang, Korea
Dae Kyung Sohn Center for Colorectal Cancer, National Cancer Center, Goyang, Korea
Aesun Shin Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea Cancer Research Institute, Seoul National University, Seoul, Korea
Jeongseon Kim Department of Cancer, AI & Digital Health, National Cancer Center Graduate School of Cancer Science and Policy, Goyang, Korea

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The altered metabolic pathways of diffuse large B-cell lymphoma not otherwise specified

Altered metabolic fingerprints of Diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS) may offer novel opportunities to identify new biomarkers and improve the understanding of its pathogenesis. This study aimed to investigate the modified metabolic pathways in extranodal, germinal center B-cell (GCB) and non-GCB DLBCL NOS from the head and neck. Formalin-fixed paraffin-embedded (FFPE) tissues from eleven DLBCL NOS classified according to Hans' algorithm using immunohistochemistry, and five normal lymphoid tissues (LT) were analyzed by high-performance liquid chromatography-mass spectrometry-based untargeted metabolomics. Partial Least Squares Discriminant Analysis showed that GCB and non-GCB DLBCL NOS have a distinct metabolomics profile, being the former more similar to normal lymphoid tissues. Metabolite pathway enrichment analysis indicated the following altered pathways: arachidonic acid, tyrosine, xenobiotics, vitamin E metabolism, and vitamin A. Our findings support that GCB and non-GCB DLBCL NOS has a distinct metabolomic profile, in which GCB possibly shares more metabolic similarities with LT than non-GCB DLBCL NOS.

α-tocopherol as a selective modulator of toxicogenic damage induced by antineoplastic agents cyclophosphamide and doxorubicin

The aim of this study was to determine the oxidative/antioxidative effects, modulatory and selective potential of α-tocopherol (vitamin E) on antineoplastic drug-induced toxicogenetic damage. The toxicity, cytotoxicity and genotoxicity induced by antineoplastic agents cyclophosphamide (CPA) and doxorubicin (DOX) was examined utilizing as models Saccharomyces cerevisiae, Allium cepa, Artemia salina and human peripheral blood mononuclear cells (PBMCs) in the presence of α-tocopherol. For these tests, concentrations of α- tocopherol 100 IU/ml (67mg/ml), CPA 20 µg/ml, DOX 2 µg/ml were used. The selectivity of α-tocopherol was assessed by the MTT test using human mammary gland non-tumor (MCF10A) and tumor (MCF-7) cell lines. Data showed cytoplasmic and mitochondrial oxidative damage induced by CPA or DOX was significantly diminished by α-tocopherol in S. cerevisiae. In addition, the toxic effects on A. salina and cytotoxic and mutagenic effects on A. cepa were significantly reduced by α-tocopherol. In PBMCs, α-tocopherol alone did not markedly affect these cells, and when treated in conjunction with CPA or DOX, α-tocopherol reduced the toxicogenetic effects noted after antineoplastic drug administration as evidenced by decreased chromosomal alterations and lowered cell death rate. In human mammary gland non-tumor and tumor cell lines, α-tocopherol produced selective cytotoxicity with 2-fold higher effect in tumor cells. Evidence indicates that vitamin E (1) produced anti-cytotoxic and anti-mutagenic effects against CPA and DOX (2) increased higher selectivity toward tumor cells, and (3) presented chemoprotective activity in PBMCs.

Potential Anticancer Activity of Pomegranate (Punica granatum L.) Fruits of Different Color: In Vitro and In Silico Evidence

Pomegranate (PMG; Punica granatum L.) fruits possess a well-balanced nutrient/phytochemical composition, with proven adjuvant benefits in experimental cancer chemotherapy; however, such bioactivity could be affected by PMG's phenogenotype (varietal). Here, the chemical and phytochemical (UPLC-DAD-MS2) composition, antioxidant capacity and anticancer potential [in vitro (MTT assay) and in silico (foodinformatics)] of three PMG fruits of different aryl color [red (cv. Wonderful), pink (cv. Molar de Elche), and white (cv. Indian)] were evaluated. The macro/micronutrient (ascorbic acid, tocols, carotenoids), organic acid (citric/malic), and polyphenol content were changed by PMG's varietal and total antioxidant activity (ABTS, alcoholic > hexane extract) in the order of red > pink > white. However, their in vitro cytotoxicity was the same (IC50 > 200 μg.mL-1) against normal (retinal) and cancer (breast, lung, colorectal) cell lines. Sixteen major phytochemicals were tentatively identified, four of them with a high GI absorption/bioavailability score [Ellagic (pink), vanillic (red), gallic (white) acids, D-(+)-catechin (white)] and three of them with multiple molecular targets [Ellagic (52) > vanillic (32) > gallic (23)] associated with anticancer (at initiation and promotion stages) activity. The anticancer potential of the PMG fruit is phenogenotype-specific, although it could be more effective in nutraceutical formulations (concentrates).

Vitamin E in Cancer Treatment: A Review of Clinical Applications in Randomized Control Trials

Vitamin E, along with other vitamins and micronutrients play a range of physiologic roles in the homeostasis of the body. Moreover, they also have postulated therapeutic roles that are often incompletely studied and understood. In this scoping review, we explored the recent randomized control trials (RCTs) of Vitamin E in the context of cancer, to investigate whether Vitamin E has a therapeutic role. We searched major bibliographic electronic databases to identify sixteen RCTs studying the role of Vitamin E in cancer management that have been published in the last ten years. These studies had different methodological qualities, including some that used Vitamin E in combination with other treatments. Furthermore, due to the heterogenous results, it is difficult to make a consensus statement on the effectiveness of Vitamin E in cancer therapeutics. In some cases, there were even suggestion of detriment with Vitamin E supplementation. Therefore, well designed, large, prospective RCTs are needed studying pure isoforms of Vitamin E to establish the safety and efficacy of this dietary supplement.

Vitamin E and Metabolic Health: Relevance of Interactions with Other Micronutrients

A hundred years have passed since vitamin E was identified as an essential micronutrient for mammals. Since then, many biological functions of vitamin E have been unraveled in both cell and animal models, including antioxidant and anti-inflammatory properties, as well as regulatory activities on cell signaling and gene expression. However, the bioavailability and physiological functions of vitamin E have been considerably shown to depend on lifestyle, genetic factors, and individual health conditions. Another important facet that has been considered less so far is the endogenous interaction with other nutrients. Accumulating evidence indicates that the interaction between vitamin E and other nutrients, especially those that are enriched by supplementation in humans, may explain at least some of the discrepancies observed in clinical trials. Meanwhile, increasing evidence suggests that the different forms of vitamin E metabolites and derivates also exhibit physiological activities, which are more potent and mediated via different pathways compared to the respective vitamin E precursors. In this review, possible molecular mechanisms between vitamin E and other nutritional factors are discussed and their potential impact on physiological and pathophysiological processes is evaluated using published co-supplementation studies.

Vitamin E in foodstuff: Nutritional, analytical, and food technology aspects

Vitamin E is a group of isoprenoid chromanols with different biological activities. It comprises eight oil-soluble compounds: four tocopherols, namely, α-, β-, γ-, and δ-tocopherols; and four tocotrienols, namely, α-, β-, γ, and δ-tocotrienols. Vitamin E isomers are well-known for their antioxidant activity, gene-regulation effects, and anti-inflammatory and nephroprotective properties. Considering that vitamin E is exclusively synthesized by photosynthetic organisms, animals can only acquire it through their diet. Plant-based food is the primary source of vitamin E; hence, oils, nuts, fruits, and vegetables with high contents of vitamin E are mostly consumed after processing, including industrial processes and home-cooking, which involve vitamin E profile and content alteration during their preparation. Accordingly, it is essential to identify the vitamin E content and profile in foodstuff to match daily intake requirements. This review summarizes recent advances in vitamin E chemistry, metabolism and metabolites, current knowledge on their contents and profiles in raw and processed plant foods, and finally, their modern developments in analytical methods.

How vitamin E and its derivatives regulate tumour cells via the MAPK signalling pathway?'

In tumour cells, vitamin E and its derivatives play a critical role in the regulation of multiple signalling pathways through their oxidative and nonoxidative functions. To date, there are 8 known natural vitamin E forms and many kinds of derivatives, among which VES and α-TEA have excellent anticancer activities. The MAPK pathway consists of a complex cascade of proteins that control the proliferation, differentiation and apoptosis of tumour cells. The MAPK pathway includes four subfamilies, ERK1/2, JNK1/2, p38 MAPK, and ERK5. Most of the proteins in these subfamilies interact with each other in a complex manner. The anticancer function of vitamin E and its derivatives is closely related to the MAPK cascade. Studies have shown that in tumour cells, α-T/γ-T/γ-T3/δ-T3/VES/α-TEA regulated ERK1/2, prevent tumorigenesis, inhibit tumour cell growth and metastasis and induce cell differentiation, apoptosis, and cell cycle arrest; γ-T3/δ-T3/VES/α-TEA regulates JNK1/2, induce apoptosis, reduce ceramide synthesis and inhibit proliferation; and γ-T3/δ-T3/VES regulate p38 MAPK and induce apoptosis. This paper reviews the role of vitamin E and its derivatives in the MAPK cascade, and tumour cells are used as a model in an attempt to explore the mechanism of their interactions.

Vitamins as Possible Cancer Biomarkers: Significance and Limitations

The Western-style diet, which is common in developed countries and spreading into developing countries, is unbalanced in many respects. For instance, micronutrients (vitamins A, B complex, C, D, E, and K plus iron, zinc, selenium, and iodine) are generally depleted in Western food (causing what is known as ‘hidden hunger’), whereas some others (such as phosphorus) are added beyond the daily allowance. This imbalance in micronutrients can induce cellular damage that can increase the risk of cancer. Interestingly, there is a large body of evidence suggesting a strong correlation between vitamin intake as well as vitamin blood concentrations with the occurrence of certain types of cancer. The direction of association between the concentration of a given vitamin and cancer risk is tumor specific. The present review summarized the literature regarding vitamins and cancer risk to assess whether these could be used as diagnostic or prognostic markers, thus confirming their potential as biomarkers. Despite many studies that highlight the importance of monitoring vitamin blood or tissue concentrations in cancer patients and demonstrate the link between vitamin intake and cancer risk, there is still an urgent need for more data to assess the effectiveness of vitamins as biomarkers in the context of cancer. Therefore, this review aims to provide a solid basis to support further studies on this promising topic.

Phytochemicals from Indian Ethnomedicines: Promising Prospects for the Management of Oxidative Stress and Cancer

Oxygen is indispensable for most organisms on the earth because of its role in respiration. However, it is also associated with several unwanted effects which may sometimes prove fatal in the long run. Such effects are more evident in cells exposed to strong oxidants containing reactive oxygen species (ROS). The adverse outcomes of oxidative metabolism are referred to as oxidative stress, which is a staple theme in contemporary medical research. Oxidative stress leads to plasma membrane disruption through lipid peroxidation and has several other deleterious effects. A large body of literature suggests the involvement of ROS in cancer, ageing, and several other health hazards of the modern world. Plant-based cures for these conditions are desperately sought after as supposedly safer alternatives to mainstream medicines. Phytochemicals, which constitute a diverse group of plant-based substances with varying roles in oxidative reactions of the body, are implicated in the treatment of cancer, aging, and all other ROS-induced anomalies. This review presents a summary of important phytochemicals extracted from medicinal plants which are a part of Indian ethnomedicine and Ayurveda and describes their possible therapeutic significance.

Cyclotrisiloxan and β-Sitosterol rich Cassia alata (L.) flower inhibit HT-115 human colon cancer cell growth via mitochondrial dependent apoptotic stimulation

Cancer traits dependent chemo and radiotherapy display acute toxicity and long-term side effects. Since last two decades, researchers investigated a new anticancer agents derived from plants. Cassia alata (L.) is a medicinal herb distributed in the tropical and humid regions. In this study, C. alata flower methanol extract (CME) have been prepared using cold percolation method and the phytochemical components were identified using GC–MS analysis. CME have been used to study the antiproliferative and apoptosis properties against human colon cancer HT-115 colon cancer cells, its molecular mechanism have been explored. 0.2 mg/mL dose of CME, inhibited 50% of HT-115 colon cancer cell growth after 48hr was confirmed the significant antiproliferation effect. In normal cells such as Vero cells and hMSCs, 0.2 mg/mL dose of CME shown only 4% and 5% growth inhibition confirmed the HT-115 cell specific cytotoxic effect. This effect might be due to the availability of phytoactive biomolecules in CME such as, cyclotrisiloxan, beta-sitosterol and alpha-tocopherol have been confirmed by GC–MS. Most interestingly, PI and AO/ErBr staining of CME treated HT-115 cells shown early (25%), pro (17%) and late (8%) apoptotic and 3% necrotic cells after 48 hr. Treatment with CME extract showed potential effect on the inhibition of protumorigenic inflammatory and oxidative stress genes. Protumorigenic COX-2/PGE-2 and TNF-α/NF-κB immune axis were normalized after CME treatment. Amounts of both apoptosis related mRNA p53, Bax, caspase 3 and p21 genes were upregulated, whereas it resulted in significant reduction in the anti-apoptotic marker mdm2 and Bcl-2 genes. In conclusion, bioactive compounds present in CME potentially inhibit HT-115 colon cancer cell proliferation via an inhibition of protumorigenic immune axis and stimulation of mitochondria dependent apoptotic pathway without necrotic effect.

Tocopherols and Tocotrienols-Bioactive Dietary Compounds; What Is Certain, What Is Doubt?

Tocopherols and tocotrienols are natural compounds of plant origin, available in the nature. They are supplied in various amounts in a diet, mainly from vegetable oils, some oilseeds, and nuts. The main forms in the diet are α- and γ-tocopherol, due to the highest content in food products. Nevertheless, α-tocopherol is the main form of vitamin E with the highest tissue concentration. The α- forms of both tocopherols and tocotrienols are considered as the most metabolically active. Currently, research results indicate also a greater antioxidant potential of tocotrienols than tocopherols. Moreover, the biological role of vitamin E metabolites have received increasing interest. The aim of this review is to update the knowledge of tocopherol and tocotrienol bioactivity, with a particular focus on their bioavailability, distribution, and metabolism determinants in humans. Almost one hundred years after the start of research on α-tocopherol, its biological properties are still under investigation. For several decades, researchers' interest in the biological importance of other forms of vitamin E has also been growing. Some of the functions, for instance the antioxidant functions of α- and γ-tocopherols, have been confirmed in humans, while others, such as the relationship with metabolic disorders, are still under investigation. Some studies, which analyzed the biological role and mechanisms of tocopherols and tocotrienols over the past few years described new and even unexpected cellular and molecular properties that will be the subject of future research.

Antioxidant vitamins promote anticancer effects on low-concentration methotrexate-treated glioblastoma cells via enhancing the caspase-3 death pathway

Vitamin C and vitamin E are well-known antioxidant vitamins, both of which are also applied as adjunct treatments for cancer therapy. Methotrexate (MTX) is a clinical drug that is used widely for rheumatoid arthritis and cancer treatment. Human glioblastoma multiforme (GBM) is an aggressive malignant brain tumor; the mean survival time for GBM patients is <2 years with traditional therapies. Developing and investigating novel treatments are important for clinical GBM therapy. Therefore, the aim of this study was to investigate whether combined treatment with vitamin C/E and MTX can display anticancer activities on GBM. Our studies showed that MTX displays anticancer effects on GBM in a dose-dependent manner, while vitamins C and E are not cytotoxic to glioblastoma. Importantly, this study showed that vitamins C and E can promote anticancer effects on low-concentration methotrexate-treated glioblastoma. Additionally, this study suggested that MTX alone or combined with vitamins C/E inhibits GBM cell growth via the caspase-3 death pathway.

Evaluation of common genetic variants in vitamin E-related pathway genes and colorectal cancer susceptibility

Vitamin E is effective for preventing the risk of cancer. However, few studies have elucidated the mechanism of vitamin E in cancer occurrence. Herein, we aimed to identify the genetic variants in vitamin E-related pathway genes associated with colorectal cancer risk. We applied logistic regression models to assess the association between single-nucleotide polymorphisms (SNPs) in vitamin E-related pathway genes and colorectal cancer risk in the Chinese and European population. The false discovery rate (FDR) method was used to correct multiple comparisons. The mRNA and protein expression analysis were evaluated in public database and in-house RNA-Seq data. SCARB1 rs73227586 was identified significantly increased risk of colorectal cancer in the Chinese population (odd ratio (OR) = 1.46, 95% confidence interval (CI) = 1.22-1.75, P = 2.99 × 10^-5). This finding was further validated in the European population (OR = 1.11, 95% CI = 1.02-1.20, P = 1.44 × 10^-2). Additionally, the mRNA and protein expression of SCARB1 were markedly up-regulated in colorectal tumor tissues. Moreover, rs73227586 T allele could increase the minimum free energy (MFE) and weaken binding ability to transcription factor ELL2. Our findings indicated that SCARB1 may play a carcinogenic role in colorectal cancer. Genetic variants in vitamin E-related pathway genes may concern to be predictors of colorectal cancer risk.

Plasma, Prostate and Urine Levels of Tocopherols and Metabolites in Men after Supplementation with a γ-Tocopherol-Rich Vitamin E Mixture

The vitamin E forms γ- and δ-tocopherols (T) inhibit carcinogenesis in animal models; nevertheless, their cancer preventive activities in humans are uncertain. As an initial step to address this issue, we conducted a pilot phase 0 trial to determine the levels of tocopherols and their metabolites in prostate cancer patients undergoing radical prostatectomy. The patients were randomized to no supplementation or two capsules of a γ-T-rich vitamin E mixture daily for 7 or 14 day prior to prostatectomy. Blood and urine samples were collected before supplementation and on the day of surgery, along with prostate tissue, for analysis of tocopherols and their metabolites. Estimated blood loss during surgery was not significantly different across treatment arms and there were no reported adverse events. Prostate tissue levels of γ-T and δ-T were increased after 14 day of supplementation. Their side-chain degradation metabolites (CEHCs and CMBHCs) were significantly elevated in plasma, prostate and urine samples after supplementation for 7 or 14 day. In conclusion, supplementation with γ-T-rich vitamin E increased the prostate levels of γ-T and δ-T. The use of pure γ-T, δ-T or tocopherol mixtures with higher ratio of γ-T or δ-T to α-T is recommended for future studies.

The pleiotropic role of transcription factor STAT3 in oncogenesis and its targeting through natural products for cancer prevention and therapy

Signal transducer and activator of transcription 3 (STAT3) is one of the crucial transcription factors, responsible for regulating cellular proliferation, cellular differentiation, migration, programmed cell death, inflammatory response, angiogenesis, and immune activation. In this review, we have discussed the classical regulation of STAT3 via diverse growth factors, cytokines, G-protein-coupled receptors, as well as toll-like receptors. We have also highlighted the potential role of noncoding RNAs in regulating STAT3 signaling. However, the deregulation of STAT3 signaling has been found to be associated with the initiation and progression of both solid and hematological malignancies. Additionally, hyperactivation of STAT3 signaling can maintain the cancer stem cell phenotype by modulating the tumor microenvironment, cellular metabolism, and immune responses to favor drug resistance and metastasis. Finally, we have also discussed several plausible ways to target oncogenic STAT3 signaling using various small molecules derived from natural products.

UPLC-MS/MS method for determination of retinol and α-tocopherol in serum using a simple sample pretreatment and UniSpray as ionization technique to reduce matrix effects

Background

Our goal was to develop a simple, rapid and precise ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of retinol and α-tocopherol in serum. Currently published LC-MS/MS methods either require complex extraction procedures (liquid-liquid or solid-phase) or do not meet desirable specifications for imprecision in serum (coefficient of variation [CV] <6.8% and 6.9%, respectively).

Methods

Sample preparation consisted of a simple protein precipitation with ethanol and acetonitrile. Stable isotope-labeled internal standards (IS) and a homemade calibration curve were used for quantification. The analysis was performed using an Acquity I-class Xevo TQ XS LC-MS/MS. Chromatographic runtime was 6.0 min using a reversed phase gradient elution. UniSpray (US) as an ionization technique was compared to electrospray ionization (ESI). Analytical validation included matrix effect, recovery and trueness compared to National Institute of Standards and Technology (NIST) standards and United Kingdom National External Quality Assessment Service (UK NEQAS) samples.

Results

Intra- and inter-run CVs were <4.9% for retinol and <1.7% for α-tocopherol, both complying with desirable specifications for imprecision. Bias compared to NIST standards was <3.1% for both compounds. The method was linear over the entire tested range. The lower limit of quantification (LLOQ) with US was lower than with ESI for both retinol (0.022 vs. 0.043 mg/L) and α-tocopherol (0.22 vs. 0.87 mg/L). Matrix effects were not significant (<15%) for retinol. However, for α-tocopherol matrix effects of on average 54.0% were noted using ESI, but not with US.

Conclusions

We developed a fast, precise and accurate UPLC-MS/MS method for the determination of retinol and α-tocopherol in human serum using a single-step sample pretreatment. Ionization using US eliminated the matrix effects for α-tocopherol.

Vitamin E and cancer prevention: Studies with different forms of tocopherols and tocotrienols

α-Tocopherol (α-T) is the major form of vitamin E (VE) in animals and has the highest activity in carrying out the essential antioxidant functions of VE. Because of the involvement of oxidative stress in carcinogenesis, the cancer prevention activity of α-T has been studied extensively. Lower VE intake or nutritional status has been shown to be associated with increased cancer risk, and supplementation of α-T to populations with VE insufficiency has shown beneficial effects in lowering the cancer risk in some intervention studies. However, several large intervention studies with α-T conducted in North America have not demonstrated a cancer prevention effect. More recent studies have centered on the γ- and δ-forms of tocopherols and tocotrienols (T3). In comparison with α-T, these forms have much lower systemic bioavailability but have shown stronger cancer-preventive activities in many studies in animal models and cell lines. γ-T3 and δ-T3 generally have even higher activities than γ-T and δ-T. In this article, we review recent results from human and laboratory studies on the cancer-preventive activities of different forms of tocopherols and tocotrienols, at nutritional and pharmacological levels. We aim to elucidate the possible mechanisms of the preventive actions and discuss the possible application of the available information for human cancer prevention by different VE forms.

Tocopherols and Tocotrienols Are Bioavailable in Rats and Primarily Excreted in Feces as the Intact Forms and 13'-Carboxychromanol Metabolites

BACKGROUND

Vitamin E α-, γ-, or δ-tocopherol (αT, γT, δT) and γ- or δ-tocotrienol (γTE, δTE) are metabolized to hydroxychromanols and carboxychromanols including 13'-carboxychromanol (13'-COOH), 11'-COOH, and carboxyethyl hydroxychroman (CEHC), some of which have unique bioactivities compared with the vitamers. However, the bioavailability of these metabolites has not been well characterized.

OBJECTIVE

We investigated the pharmacokinetics (PK) of vitamin E forms and metabolites in rats.

METHODS

Six-week-old male Wistar rats received 1-time gavage of γT-rich tocopherols (50 mg/kg) containing γT/δT/αT (57.7%, 21.9%, and 10.9%, respectively) or δTE-rich tocotrienols (35 mg/kg) containing δTE/γTE (8:1). We quantified the time course of vitamin E forms and metabolites in the plasma and their 24-h excretion to the urine and feces. The general linear model repeated measure was used for analyses of the PK data.

RESULTS

In the rats' plasma, Cmax of γT or δTE was 25.6 ± 9.1 μM (Tmax = 4 h) or 16.0 ± 2.3 μM (Tmax = 2 h), respectively, and sulfated CEHCs and sulfated 11'-COOHs were the predominant metabolites with Cmax of 0.4-0.5 μM (Tmax ∼5-7 h) or ∼0.3 μM (Tmax at 4.7 h), respectively. In 24-h urine, 2.7% of γT and 0.7% of δTE were excreted as conjugated CEHCs. In the feces, 17-45% of supplemented vitamers were excreted as unmetabolized forms and 4.9-9.2% as unconjugated carboxychromanols, among which 13'-COOHs constituted ∼50% of total metabolites and the amount of δTE-derived 13'-COOHs was double that of 13'-COOH derived from γT.

CONCLUSIONS

PK data of vitamin E forms in rats reveal that γT, δT, γTE, and δTE are bioavailable in the plasma and are mainly excreted as unmetabolized forms and long-chain metabolites including 13'-COOHs in feces, with more metabolites from tocotrienols than from tocopherols.

γ-Tocotrienol and α-Tocopherol Ether Acetate Enhance Docetaxel Activity in Drug-Resistant Prostate Cancer Cells

Prostate cancer is the second most commonly diagnosed cancer in men, and metastatic prostate cancer is currently incurable. Prostate cancer frequently becomes resistant to standard of care treatments, and the administration of chemotherapeutic drugs is often accompanied by toxic side effects. Combination therapy is one tool that can be used to combat therapeutic resistance and drug toxicity. Vitamin E (VE) compounds and analogs have been proposed as potential non-toxic chemotherapeutics. Here we modeled combination therapy using mixture design response surface methodology (MDRSM), a statistical technique designed to optimize mixture compositions, to determine whether combinations of three chemotherapeutic agents: γ-tocotrienol (γ-T3), α-tocopherol ether acetate (α-TEA), and docetaxel (DOC), would prove more effective than docetaxel alone in the treatment of human prostate cancer cells. Response surfaces were generated for cell viability, and the optimal treatment combination for reducing cell viability was calculated. We found that a combination of 20 µM γ-T3, 30 µM α-TEA, and 25 nm DOC was most effective in the treatment of PC-3 cells. We also found that the combination of γ-T3 and α-TEA with DOC decreased the amount of DOC required to reduce cell viability in PC-3 cells and ameliorated therapeutic resistance in DOC-resistant PC-3 cells.

Identification of cadmium-produced lipid hydroperoxides, transcriptomic changes in antioxidant enzymes, xenobiotic transporters, and pro-inflammatory markers in human breast cancer cells (MCF7) and protection with fat-soluble vitamins

Cadmium (Cd) is a toxic metal that is regarded as a metallohormone with estrogen-like properties. The present study aimed at identification of lipid hydroperoxides produced in human breast cancer (MCF7) exposed to cadmium (Cd) at environmentally relevant levels. Cd induced cytotoxicity and oxidative stress and produced a series of 26 lipid hydroperoxide species including 14 phosphatidylcholine hydroperoxides (PC-OOH), 9 triacylglycerol hydroperoxides (TG-OOH), and 3 cholesteryl ester hydroperoxides (CE-OOH). Among these hydroperoxides, PC34:2-OOH, PC34:3-OOH, TG60:14-OOH, TG48:5-OOH, TG60:15-OOH, and CE20:4-OOH were produced in a dose-dependent manner, suggesting these as possible biomarkers for Cd exposure in MCF7 cells. In addition, Cd led to significant decreases in the gene expressions of antioxidants, detoxification enzymes, and xenobiotic transporters. In a protection trial, co-exposure of MCF7 cells to fat-soluble vitamins including vitamin A, D, and E reduced Cd-induced cytotoxicity, lipid peroxidation, oxidative stress, and inflammatory responses. Fat-soluble vitamins upregulated antioxidant and detoxification enzymes, and xenobiotic transporters. Therefore, dietary supplementation of such micronutrients is recommended for people at risk for exposure to Cd.

Scavenging of Retinoid Cation Radicals by Urate, Trolox, and α-, β-, γ-, and δ-Tocopherols

Retinoids are present in human tissues exposed to light and under increased risk of oxidative stress, such as the retina and skin. Retinoid cation radicals can be formed as a result of the interaction between retinoids and other radicals or photoexcitation with light. It has been shown that such semi-oxidized retinoids can oxidize certain amino acids and proteins, and that α-tocopherol can scavenge the cation radicals of retinol and retinoic acid. The aim of this study was to determine (i) whether β-, γ-, and δ-tocopherols can also scavenge these radicals, and (ii) whether tocopherols can scavenge the cation radicals of another form of vitamin A—retinal. The retinoid cation radicals were generated by the pulse radiolysis of benzene or aqueous solution in the presence of a selected retinoid under oxidizing conditions, and the kinetics of retinoid cation radical decays were measured in the absence and presence of different tocopherols, Trolox or urate. The bimolecular rate constants are the highest for the scavenging of cation radicals of retinal, (7 to 8) × 10⁹ M⁻¹·s⁻¹, followed by retinoic acid, (0.03 to 5.6) × 10⁹ M⁻¹·s⁻¹, and retinol, (0.08 to 1.6) × 10⁸ M⁻¹·s⁻¹. Delta-tocopherol is the least effective scavenger of semi-oxidized retinol and retinoic acid. The hydrophilic analogue of α-tocopherol, Trolox, is substantially less efficient at scavenging retinoid cation radicals than α-tocopherol and urate, but it is more efficient at scavenging the cation radicals of retinoic acid and retinol than δ-tocopherol. The scavenging rate constants indicate that tocopherols can effectively compete with amino acids and proteins for retinoid cation radicals, thereby protecting these important biomolecules from oxidation. Our results provide another mechanism by which tocopherols can diminish the oxidative damage to the skin and retina and thereby protect from skin photosensitivity and the development and/or progression of changes in blinding retinal diseases such as Stargardt’s disease and age-related macular degeneration (AMD).

Vitamin E and cancer: an update on the emerging role of γ and δ tocotrienols

Despite significant advances in the diagnosis and treatment of cancer, the latter still remains a fatal disease due to the lack of prevention, early diagnosis, and effective drugs. Radiotherapy, chemotherapy, and surgery are not only expensive but produce a number of side effects that are detrimental to the patients' quality of life. Therefore, there is a great need to discover anti-cancer therapies that are specific to cancer cells and affordable, safe, and well tolerated by the patients. Vitamin E is a potential candidate due to its safety. Accumulating evidence on the anti-cancer potency of vitamin E has shifted the focus from tocopherols (TOCs) to tocotrienols (TTs). γ-TT and δ-TT have the highest anti-cancer activities and target common molecular pathways involved in the inhibition of the cell cycle, the induction of apoptosis and autophagy, and the inhibition of invasion, metastasis, and angiogenesis. Future directions should focus on further investigating how γ-TT and δ-TT (solely or in combination) induce anti-cancer molecular pathways when used in the presence of conventional chemotherapeutic drugs. These studies should be carried out in vitro, and promising results and combinations should then be assessed in in vivo experiments and finally in clinical trials. Finally, future research should focus on further evaluating the roles of γ-TT and δ-TT in the chemoprevention of cancer.