Potentiation of anti-cancer effect by intravenous administration of vesiculated alpha-tocopheryl hemisuccinate on mouse melanoma in vivo

Associations of Dietary Factors with Cutaneous Melanoma: A Case-Control Study in Greece with Literature Review

INTRODUCTION

It has been postulated that nutrition may influence the risk for cutaneous melanoma (CM); therefore, we aimed to assess the associations of food groups and individual nutrient intakes with CM in a Greek population.

METHODS

In this case-control study, 151 patients with histologically confirmed CM, newly diagnosed and treated in the Oncology Department of the "Laikon" University Hospital (Athens, Greece), and 151 age- and sex-matched healthy individuals residing in the Athens metropolitan area, recruited among participants for routine health examinations, were included. All participants completed a questionnaire comprising anthropometric measurements, sociodemographic, lifestyle, and health-related variables. A validated, semiquantitative food frequency questionnaire was used to assess average consumption of 136 food items during the 12 months preceding the onset of disease. Multivariate conditional regression models were used to derive odds ratios (ORs) with 95% confidence intervals (95% CI) regarding the association of nine food groups and seven macronutrients with CM.

RESULTS

Statistically significant positive associations with CM were found with higher energy intake (OR: 1.67, 95% CI: 1.22-2.30) and intake of saturated fatty acids (OR: 2.28, 95% CI: 1.00-5.28), after adjusting for sun sensitivity, major depression history, and alcohol intake. Inverse associations with higher intake of milk and dairy products (OR: 0.65, 95% CI: 0.48-0.88), fruits (OR: 0.68, 95% CI: 0.51-0.90), added lipids (OR: 0.65, 95% CI: 0.47-0.91), and sugars and syrups (OR: 0.70, 95% CI: 0.53-0.93) were also observed.

CONCLUSIONS

Beyond intrinsic risk factors, our results support associations of CM with multiple food groups and nutrients; if confirmed by prospective studies, these findings can add further knowledge about this fatal cancer.

Intraperitoneal administration of nanoparticles containing tocopheryl succinate prevents peritoneal dissemination

Intraperitoneal administration of anticancer nanoparticles is a rational strategy for preventing peritoneal dissemination of colon cancer owing to the prolonged retention of nanoparticles in the abdominal cavity. However, instability of nanoparticles in body fluids causes inefficient retention, reducing its anticancer effects. We have previously developed anticancer nanoparticles containing tocopheryl succinate, which showed high in vivo stability and multifunctional anticancer effects. In the present study, we have demonstrated that peritoneal dissemination derived from colon cancer was prevented by intraperitoneal administration of tocopheryl succinate nanoparticles. The biodistribution of tocopheryl succinate nanoparticles was evaluated by inductively coupled plasma mass spectroscopy and imaging analysis in mice administered quantum dot encapsulated tocopheryl succinate nanoparticles. Intraperitoneal administration of tocopheryl succinate nanoparticles showed longer retention in the abdominal cavity than by its intravenous administration. Moreover, due to effective biodistribution, tumor growth was prevented by intraperitoneal administration of tocopheryl succinate nanoparticles. Furthermore, the anticancer effect was attributed to the inhibition of cancer cell proliferation and improvement of the intraperitoneal microenvironment, such as decrease in the levels of vascular endothelial growth factor A, interleukin 10, and M2-like phenotype of tumor-associated macrophages. Collectively, intraperitoneal administration of tocopheryl succinate nanoparticles is expected to have multifaceted antitumor effects against colon cancer with peritoneal dissemination.

Vitamin E succinate with multiple functions: A versatile agent in nanomedicine-based cancer therapy and its delivery strategies

Vitamin E succinate (VES), a succinic acid ester of vitamin E, is one of the most effective anticancer compounds of the vitamin E family. VES can inhibit tumor growth by multiple pathways mainly involve tumor proliferation inhibition, apoptosis induction, and metastasis prevention. More importantly, the mitochondrial targeting and damaging property of VES endows it with great potential in exhibiting synergetic effect with conventional chemotherapeutic drugs and overcoming multidrug resistance (MDR). Given the lipophilicity of VES that hinders its bioavailability and therapeutic activity, nanotechnology with multiple advantages has been widely explored to deliver VES and opened up new avenues for its in vivo application. This review aims to introduce the anticancer mechanisms of VES and summarize its delivery strategies using nano-drug delivery systems. Specifically, VES-based combination therapy for synergetic anticancer effect, MDR-reversal, and oral chemotherapy improvement are highlighted. Finally, the challenges and perspectives are discussed.

Suppression of Lipid Accumulation in 3T3-L1 Adipocytes by α-Tocopheryl Succinate

Obesity is a pathological state related to various lifestyle-related diseases, such as diabetes and dyslipidemia, that may be prevented through the development of anti-obesity treatments. Lipid accumulation in cells could be affected by vitamin E ester α-tocopheryl succinate (TS), which has various biological activities, such as anti-cancer effect, via activation of cell signaling pathways, although the antioxidative activity of TS is lost due to esterification of the phenolic OH group. In this study, we found for the first time that TS significantly suppressed lipid accumulation in mouse 3T3-L1 adipocytes. TS treatment reduced the amount of triglycerides in the culture medium, and inhibited activity of glycerol-3-phosphate dehydrogenase, a marker of lipid synthesis. Furthermore, TS accelerated lipolysis. Treatment of adipocytes with TS for 24 h induced no significant cytotoxicity. In TS-treated cells, phosphorylation of Akt, which is involved in fatty acid synthesis via sterol regulatory element-binding proteins (SREBP), was prevented, while levels of phosphorylated protein kinase A (PKA) did not change. Taken together, these results suggest that vitamin E ester TS can suppress lipid accumulation in adipocytes by regulating lipid metabolic cell signaling.

Enhanced Prevention of Breast Tumor Metastasis by Nanoparticle-Delivered Vitamin E in Combination with Interferon-Gamma

Preventing cancer metastasis is one of the remaining challenges in cancer therapy. As an efficient natural product, alpha-tocopheryl succinate (α-TOS), the most effective form of vitamin E, holds great anticancer potential. To improve its efficacy and bioavailability, lipid-coated calcium carbonate/phosphate (LCCP) nanoparticles (NPs) with folic acid and PEG modification are synthesized for efficient delivery of α-TOS to 4T1 cancer cells. The optimized LCCP-FA NPs (NP-TOS15) show an α-TOS loading efficiency of around 60%, and enhanced uptake by 4T1 metastatic cancer cells. Consequently, NP-TOS15 significantly enhance the anticancer effect in combination with interferon-gamma (IFN-γ) in terms of apoptosis facilitation and migration inhibition. Importantly, NP-TOS15 upregulate the anticancer immunity via downregulating program death ligand 1 (PD-L1) expression that is initially induced by IFN-γ, and remarkably prevent the lung metastasis, particularly in combination with IFN-γ. Further investigation reveals that this combination therapy also modulates the cytotoxic lymphocyte infiltration into the tumor microenvironment for tumor elimination. Taken together, the NP delivery of α-TOS in combination with IFN-γ provides an applicable strategy for cancer therapy.

Lipocalin2 as a plasma marker for tumors with hypoxic regions

Hypoxic tumors have been identified as appropriate indicators of tumor malignancy. However, no convenient plasma marker for hypoxic tumors has been described. Therefore, to identify a novel, convenient plasma marker for hypoxic tumors, we used microarray analysis to compare gene expression profiles of normoxic and hypoxic tumor tissues of mice bearing melanomas. Among the upregulated genes detected in hypoxic tumors, we chose to study the secretory protein lipocalin2 (LCN2) as a marker for hypoxic tumors. LCN2 protein levels in the plasma of mice bearing hypoxic tumors were significantly increased compared with those in mice bearing normoxic tumors. Interestingly, LCN2 mRNA levels were 17-fold higher in HIF-1α-positive hypoxic tumors than in HIF-1α-negative normoxic tumors. Furthermore, LCN2 mRNA levels were significantly higher in the B16-F1 cells and various human tumor cells cultured under hypoxic conditions than in cells cultured under normoxic conditions, while no changes in mRNA expression were observed in nontumor NIH-3T3 cells, even under hypoxic conditions. In cultured cells, the expression pattern of LCN2 was mostly consistent with that of HIF-1α, whereas that of a conventional hypoxic marker, carbonic anhydrase IX, was not. Collectively, our data suggested that LCN2 was a useful plasma marker for hypoxic tumors.

Diet in dermatology: Part II. Melanoma, chronic urticaria, and psoriasis

The roles of dietary factors in aggravating, preventing, or treating skin diseases are common questions encountered in dermatology practice. Part II of this two-part series reviews dietary modifications that can potentially be utilized in the management of melanoma, chronic urticaria, and psoriasis patients. Specifically, we examine the effect of alcohol consumption and supplementation with vitamins D and E, polyunsaturated fatty acids, selenium, green tea, resveratrol, and lycopene on melanoma risk. The relationships between chronic urticaria symptoms and dietary pseudoallergens, gluten, and vitamin D are analyzed. We explore weight loss, reduced alcohol consumption, and gluten avoidance as means of reducing psoriasis-associated morbidity, as well as the possible utility of supplementation with polyunsaturated fatty acids, folic acid, vitamin D, and antioxidants. With proper knowledge of the role of diet in these cutaneous disease processes, dermatologists can better answer patient inquiries and consider implementation of dietary modifications as adjuncts to other treatments and preventative measures.

[Development of a novel nanocarrier focusing on the physicochemical properties of an anti-cancer therapy drug--development of anti-cancer nanoparticles containing vitamin E derivative with mulitifaceted anti-cancer effect]

Successful cancer gene therapy is dependent upon the development of nanocarriers that exhibit anti-cancer effects via delivery of nucleic acids to the target site in tumor tissue. The effectiveness of such systems has typically relied on the potency of the anti-cancer nucleic acids, as conventional carriers do not exhibit inherent anti-cancer activity, serving only as vehicles for delivery. Ideal nanocarriers for effective cancer gene therapy should not only serve as delivery systems for transporting anti-cancer nucleic acids to the target tumor tissue, but should also exhibit their own inherent anti-cancer activity. α-tocopheryl succinate (TS) has attracted attention as a unique anti-cancer agent for its ability to induce apoptosis in various cancer cells; moreover, TS readily forms nanovesicles (TS-NVs). Thus, vesicles comprised of TS represent prospective tools for use as drug delivery systems (DDS) for cancer therapy. Owing to the low vesicle stability in the presence of divalent cations or serum, however, TS-NVs are not suitable for encapsulating nucleic acids, and require passive targeting delivery to tumor tissue via an enhanced permeability and retention effect. To improve the stability of TS-NVs, we developed novel nanovesicles comprised of TS and egg phosphatidylcholine (EPC), which can form a stable lamellar structure (TS-EPC-NVs). In this review, we introduce the development of nanovesicles comprised of TS as a novel DDS carrier and demonstrate the anti-cancer activity of both the encapsulated nucleic acids and the carrier itself.

Structural re-arrangement and peroxidase activation of cytochrome c by anionic analogues of vitamin E, tocopherol succinate and tocopherol phosphate

Cytochrome c is a multifunctional hemoprotein in the mitochondrial intermembrane space whereby its participation in electron shuttling between respiratory complexes III and IV is alternative to its role in apoptosis as a peroxidase activated by interaction with cardiolipin (CL), and resulting in selective CL peroxidation. The switch from electron transfer to peroxidase function requires partial unfolding of the protein upon binding of CL, whose specific features combine negative charges of the two phosphate groups with four hydrophobic fatty acid residues. Assuming that other endogenous small molecule ligands with a hydrophobic chain and a negatively charged functionality may activate cytochrome c into a peroxidase, we investigated two hydrophobic anionic analogues of vitamin E, α-tocopherol succinate (α-TOS) and α-tocopherol phosphate (α-TOP), as potential inducers of peroxidase activity of cytochrome c. NMR studies and computational modeling indicate that they interact with cytochrome c at similar sites previously proposed for CL. Absorption spectroscopy showed that both analogues effectively disrupt the Fe-S(Met(80)) bond associated with unfolding of cytochrome c. We found that α-TOS and α-TOP stimulate peroxidase activity of cytochrome c. Enhanced peroxidase activity was also observed in isolated rat liver mitochondria incubated with α-TOS and tBOOH. A mitochondria-targeted derivative of TOS, triphenylphosphonium-TOS (mito-VES), was more efficient in inducing H2O2-dependent apoptosis in mouse embryonic cytochrome c(+/+) cells than in cytochrome c(-/-) cells. Essential for execution of the apoptotic program peroxidase activation of cytochrome c by α-TOS may contribute to its known anti-cancer pharmacological activity.

Co-delivery of paclitaxel and α-tocopherol succinate by novel chitosan-based polymeric micelles for improving micellar stability and efficacious combination therapy

The aim of this study was to develop chitosan derivative polymeric micelles for co-delivery of paclitaxel (PTX) and α-tocopherol succinate (α-TS) to the cancer cells to improve the therapeutic efficiency and reduce side effects of PTX. In this study, amphiphilic tocopheryl succinate-grafted chitosan oligosaccharide was synthesized and physically loaded by PTX and α-TS with entrapment efficiency of 67.9% and 73.2%, respectively. Physical incorporation of α-TS into the micelles increased the hydrophobic interaction between PTX and the micelles core, which improved micelle stability, reduced the micelle size and also sustained the PTX release from the micelles. The mean particle size and zeta potential of αTS/PTX-loaded micelles were about 133 nm and +25.2 mV, respectively, and PTX release was completed during 6-9 d from the micelles. Furthermore, the cytotoxicity of α-TS/PTX-loaded micelles against human ovarian cancer cell line cancer cell in vitro was higher than that of PTX-loaded micelles and the free drug solution. Half maximal inhibitory concentration values of PTX after 48-h exposure of the cells to the PTX-loaded micelles modified and unmodified with α-TS were 110 and 188 ng/ml, respectively.

Use of anti-cancer drugs, mitocans, to enhance the immune responses against tumors

Cytotoxic drugs in cancer therapy are used with the expectation of selectively killing and thereby eliminating the offending cancer cells. If they should die in an appropriate manner, the cells can also release danger signals that promote an immune reaction that reinforces the response against the cancer. The identity of these immune-enhancing danger signals, how they work extra- and intracellularly, and the molecular mechanisms by which some anti-cancer drugs induce cell death to bring about the release of danger signals are the major focus of this review. A specific group of mitocans, the vitamin E analogs that act by targeting mitochondria to drive ROS production and also promote a more immunogenic means of cancer cell death exemplify such anti-cancer drugs. The role of reactive oxygen species (ROS) production and the events leading to the activation of the inflammasome and pro-inflammatory mediators induced by dying cancer cell mitochondria are discussed along with the evidence for their contribution to promoting immune responses against cancer. Current knowledge of how the danger signals interact with immune cells to boost the anti-tumor response is also evaluated.

Cytotoxic activity of semi-synthetic derivatives of elatol and isoobtusol

In the present study, the in vitro cytotoxic effects of six semi-synthetic derivatives of elatol (1) and isoobtusol (2) were investigated. Chemical modifications were performed on the hydroxyl groups aiming to get derivatives of different polarity, namely the hemisuccinate, carbamate and sulfamate. The structural elucidation of the new derivatives was based on detailed NMR and MS spectroscopic analyses. The in vitro cytotoxicity of compounds 1 to 8 was evaluated against A459 and RD tumor cell lines with CC₅₀ values ranging from 4.93 to 41.53 µM. These results suggest that the structural modifications performed on both compounds could be considered a good strategy to obtain more active derivatives.

Prevention of tumor growth by needle-free jet injection of anti-C7orf24 siRNA

Chromosome 7 open reading frame 24 (C7orf24), which was identified by proteome analysis, is upregulated in various types of cancer and is associated with cellular proliferation. However, in vivo antitumor effect by knockdown of C7orf24 has not been clarified. In this study, we investigated that the antitumor effect of anti-C7orf24 small interfering RNA (siRNA) administered by needle-free jet injection (JI) on lung cancer-bearing mice. Transfection of anti-C7orf24 siRNA induced cytotoxicity in cultured human lung cancer cells through specific knockdown of C7orf24. Furthermore, JI could effectively deliver anti-C7orf24 siRNA to tumor tissues, and as a result tumor growth was significantly inhibited. Immunohistochemical analysis revealed that C7orf24 levels were significantly reduced within tumor tissues collected from anti-C7orf24 siRNA-administered mice, indicating that the knockdown of C7orf24 induced cytotoxicity in tumor tissue. In conclusion, these data show for the first time that knockdown of C7orf24 prevents tumor growth in vivo following JI-mediated the siRNA delivery.

Nutrition and melanoma prevention

Melanoma has continued to rise in incidence despite public efforts to promote sun protection behaviors. Because sunscreen use does not completely prevent skin cancer induced by ultraviolet radiation, additional chemopreventive methods for protecting against and reversing the effects of ultraviolet photodamage need evaluation. Recent years have brought increased interest in dietary factors, such as natural botanicals and vitamins, for the prevention of melanoma. This contribution provides a narrative review of the relevant, nutrition-related literature found by searching the keywords "melanoma chemoprevention," "nutrition and melanoma," "dietary botanicals and melanoma prevention," "green tea and melanoma," "vitamin D and melanoma," and "vitamin E and melanoma" in the PubMed database. Although randomized controlled trials of humans are lacking, basic science and epidemiologic studies show promising benefits of many natural products in chemoprevention for melanoma. Future studies, hopefully, will yield concrete answers and clarify the role of commonly available dietary nutrients in melanoma chemoprevention.

Noninvasive and efficient transdermal delivery of CpG-oligodeoxynucleotide for cancer immunotherapy

Oligodeoxynucleotides containing unmethylated cytosine-phosphate-guanosine motifs (CpG-ODN) possess immunostimulatory effects and potential antitumor activity. Since the skin is an easily available site of administration of CpG-ODN due to its accessibility and the presence of abundant antigen presenting cells, it is expected that the application of CpG-ODN to the skin would induce systemic immune response and antitumor activity. However, it is difficult to deliver hydrophilic macromolecules including CpG-ODN through the skin. We have previously demonstrated that small interfering RNA (siRNA) was efficiently delivered into rat epidermis by iontophoresis. In this report, we investigate the effect of transdermal iontophoretic delivery of CpG-ODN on the induction of immune responses and antitumor activity against B16F1 melanoma in mice. Iontophoresis promoted CpG-ODN delivery into the epidermis and dermis. Furthermore, iontophoretic delivery of CpG-ODN to the skin induced the expression of proinflammatory and Th1-type cytokines in the skin and draining lymph node. Finally, transdermal iontophoretic delivery of CpG-ODN led to antitumor activity against B16F1 melanoma. Interestingly, the CpG-ODN administration site is not restricted to the tumor area. In conclusion, CpG-ODN delivered transdermally induced potent antitumor activity, and our system is expected to serve as a simple and noninvasive approach for cancer immunotherapy.

Outpatient Follow-up and Secondary Prevention for Melanoma Patients

Health care providers and their patients jointly participate in melanoma prevention, surveillance, diagnosis, and treatment. This paper reviews screening and follow-up strategies for patients who have been diagnosed with melanoma, based on current available evidence, and focuses on methods to assess disease recurrence and second primary occurrence. Secondary prevention, including the roles of behavioral modification and chemoprevention are also reviewed. The role of follow-up dermatologist consultation, with focused physical examinations complemented by dermatoscopy, reflectance confocal microscopy, and/or full-body mapping is discussed. Furthermore, we address the inclusion of routine imaging and laboratory assessment as components of follow-up and monitoring of advanced stage melanoma. The role of physicians in addressing the psychosocial stresses associated with a diagnosis of melanoma is reviewed.

A redox-silent analogue of tocotrienol acts as a potential cytotoxic agent against human mesothelioma cells

AIMS

Malignant mesothelioma is an aggressive cancer with no effective treatment options. A redox-silent analogue of alpha-tocotrienol, 6-O-carboxypropyl-alpha-tocotrienol (T3E) is a new potential anti-carcinogenic agent with less toxic effect on non-tumorigenic cells. Here, we evaluated the effect of T3E on killing of chemoresistant mesothelioma cell (H28).

MAIN METHODS

The cytotoxic effect of T3E was evaluated by a WST-1 assay, and cell cycle and apoptosis analysis were done by FACS. Each signal molecule's activity was determined by protein array and immunoblot analysis.

KEY FINDINGS

T3E effectively inhibited H28 cell growth at practical pharmacological concentrations (10-20 muM) without any effect on non-tumorigenic mesothelial cell (Met-5A). Inhibition of H28 cell growth by T3E mediated through G2/M arrest in cell cycle and induction of apoptosis. Protein array and immunoblot analyses revealed that T3E inhibited the activation of epidermal growth factor receptor (EGFR) via the inactivation of the Src family of protein tyrosine kinases (Src). However, the blockade of the EGFR signaling was not associated with the T3E-dependent H28 cell growth control. In addition to Src inactivation, T3E inhibited signal transduction and activation of transcription Stat3. A combination of an Src inhibitor, PP2, and a Stat3 inhibitor, AG490, induced G2/M arrest and enhanced apoptosis compared with PP2 alone. These results suggest that T3E suppresses H28 cell growth via the inhibition of Src activation and Src-independent Stat3 activation.

SIGNIFICANCE

T3E can be a new effective therapeutic agent against chemoresistant mesothelioma cells.

Vitamin E succinate induces NAG-1 expression in a p38 kinase-dependent mechanism

NAG-1 (nonsteroidal anti-inflammatory drug-activated gene), a member of the transforming growth factor-beta superfamily, is involved in many cellular processes, such as inflammation, apoptosis/survival, and tumorigenesis. Vitamin E succinate (VES) is the succinate derivative of alpha-tocopherol and has antitumorigenic activity in a variety of cell culture and animal models. In the current study, the regulation and role of NAG-1 expression in PC-3 human prostate carcinoma cells by VES was examined. VES treatment induced growth arrest and apoptosis as well as an increase in NAG-1 protein and mRNA levels in a time- and concentration-dependent manner. VES treatment induced nuclear translocation and activation of p38 kinase. Pretreatment with p38 kinase inhibitor blocked the VES-induced increase in NAG-1 protein and mRNA levels, whereas an inhibition of protein kinase C, Akt, c-Jun NH(2)-terminal kinase, or MEK activity had no effect on VES-induced NAG-1 levels. Forced expression of constitutively active MKK6, an upstream kinase for p38, induced an increase in NAG-1 promoter activity, whereas p38 kinase inhibitor blocked MKK6-induced increase in NAG-1 promoter activity. VES treatment resulted in >3-fold increase in the half-life of NAG-1 mRNA in a p38 kinase-dependent manner and transient transfection experiment showed that VES stabilizes NAG-1 mRNA through AU-rich elements in 3'-untranslated region of NAG-1 mRNA. The inhibition of NAG-1 expression by small interfering RNA significantly blocked VES-induced poly(ADP-ribose) polymerase cleavage, suggesting that NAG-1 may play an important role in VES-induced apoptosis. These results indicate that VES-induced expression of NAG-1 mRNA/protein is regulated by transcriptional/post-transcriptional mechanism in a p38 kinase-dependent manner and NAG-1 can be chemopreventive/therapeutic target in prostate cancer.

Dietary administration of the proapoptotic vitamin E analogue alpha-tocopheryloxyacetic acid inhibits metastatic murine breast cancer

The ability of the vitamin E (RRR-alpha-tocopherol) derivatives alpha-tocopheryl succinate (alpha-TOS) and alpha-tocopheryloxyacetic acid (alpha-TEA) to suppress tumor growth in preclinical animal models has recently led to increased interest in their potential use for treating human cancer. To make the use of these vitamin E analogues more clinically relevant, we compared the antitumor efficacy of orally and i.p. delivered forms of alpha-TEA and alpha-TOS against a murine mammary cancer (4T1) that bears resemblance to human breast cancer because of its poor immunogenicity and high metastatic potential. In cell culture studies, we showed that both compounds inhibited tumor colony formation and induced apoptotic death of tumor cells. To avoid solubility concerns associated with the hydrophobicity of alpha-TEA and alpha-TOS, we used the vesiculated forms of alpha-TEA (V alpha-TEA) and alpha-TOS (V alpha-TOS) for the in vivo tumor studies. Both compounds inhibited the growth of preestablished 4T1 tumors when given i.p. However, when given by oral gavage, only the esterase-resistant V alpha-TEA was able to suppress primary tumor growth and reduce lung metastasis. To make this approach more translatable to the clinic, alpha-TEA was incorporated into the diet and fed to tumor-bearing mice. We report here for the first time that dietary alpha-TEA delivery significantly inhibited primary tumor growth and dramatically reduced spontaneous metastatic spread to the lung in prophylactic and therapeutic settings. This study suggests that dietary alpha-TEA could prove useful as a relatively easy and effective modality for treating metastatic breast cancer.

Melanoma chemoprevention

BACKGROUND

Despite efforts to promote sun protection behaviors, melanoma incidence continues to increase. The prognosis of advanced melanoma remains extremely poor in spite of treatment advances, emphasizing the importance of exploring additional preventive measures.

OBJECTIVE

We sought to summarize the results of published research on candidate chemoprevention agents for melanoma.

METHODS

We conducted a narrative review of the literature.

RESULTS

Investigation into a possible role in melanoma chemoprevention continues for multiple agents, including sunscreen, lipid-lowering medications, nonsteroidal anti-inflammatory drugs, dietary nutrients, immunomodulators, and other drugs, including retinoids, difluoromethylornithine, and T4 endonuclease V.

LIMITATIONS

Systematic review of the literature was not performed.

CONCLUSION

Because no agent yet emerges as a clear choice for effective melanoma chemoprevention, sun avoidance and sun protection remain the mainstay of melanoma prevention for persons at high risk.

α-Tocopheryl Succinate Induces Apoptosis in Prostate Cancer Cells in Part through Inhibition of Bcl-xL/Bcl-2 Function

Although the antitumor effect of alpha-tocopheryl succinate (vitamin E succinate) has been well demonstrated, its underlying mechanism remains elusive. This study provides evidence that inhibition of Bcl-xL/Bcl-2 function represents a major pathway whereby alpha-tocopheryl succinate mediates apoptosis induction in prostate cancer cells. In vitro data indicate that alpha-tocopheryl succinate was able to disrupt the binding of Bak BH3 peptide to Bcl-xL and Bcl-2 with IC50 of 26 microm, in line with its potency in antiproliferation. Treatment of PC-3 cells with this agent led to reduced association of Bcl-2 and Bcl-xL with Bak, leading to caspase-dependent apoptosis. Moreover, overexpression of Bcl-xL protected LNCaP cells from the apoptosis induction. This mechanistic finding provided a basis to develop potent Bcl-xL/Bcl-2 inhibitors. Docking of alpha-tocopheryl succinate into the Bak peptide-binding site indicates that it adopted a unique hairpin-shaped conformation for protein interactions. We rationalized that the hemisuccinate and the two proximal isopranyl units of the side chain played a crucial role in ligand anchoring and protein-ligand complex stabilization, respectively. However, exposure of the distal isopranyl unit to a polar environment might diminish the binding affinity of alpha-tocopheryl succinate. This premise was corroborated by a structure-activity analysis of a series of derivatives with truncated side chains and/or altered carboxyl terminus. This computer model predicted that the removal of the distal isopranyl unit from the side chain would improve binding affinity, leading to two agents with significantly higher potency in inhibiting Bak peptide binding and in suppressing prostate cancer cell proliferation.

Vesiculated alpha-tocopheryl succinate enhances the anti-tumor effect of dendritic cell vaccines

Alpha tocopheryl succinate (alpha-TOS) is a non-toxic vitamin E analog under study for its anti-cancer properties. In an earlier study, we showed that alpha-TOS, when used in combination with non-matured dendritic cells (nmDC) to treat pre-established tumors, acts as an effective adjuvant. In this study, we have used vesiculated alpha-TOS (Valpha-TOS), a more soluble form of alpha-TOS that is relevant for clinical use, in combination with dendritic cells to treat pre-established murine tumors. We demonstrate that Valpha-TOS kills tumor cells in vitro and inhibits the growth of pre-established murine lung carcinoma (3LLD122) as effectively as alpha-TOS. The combination of Valpha-TOS plus non-matured or TNF-alpha-matured DC is more effective at inhibiting the growth of established tumors than Valpha-TOS alone. We also observed that Valpha-TOS induces expression of heat shock proteins in tumor cells and that co-incubation of non-matured DC with lysate derived from Valpha-TOS-treated tumor cells leads to DC maturation evidenced by up-regulation of co-stimulatory molecules and secretion of IL-12p70. This study therefore demonstrates the immunomodulatory properties of Valpha-TOS that may account for its adjuvant effect when combined with DC vaccines to treat established tumors.

Chemo-Immunotherapy of Breast Cancer Using Vesiculated α-Tocopheryl Succinate in Combination With Dendritic Cell Vaccination

In this study, we evaluated the efficacy of vesiculated alpha-tocopheryl succinate (Valpha-TOS) in combination with non-antigen pulsed, nonmatured dendritic cells (nmDC) to treat pre-established tumors of the highly metastatic murine mammary cancer cell line 4T1. We demonstrated that Valpha-TOS in combination with non-antigen pulsed nmDC significantly inhibits the growth of established tumors in vivo and prolongs survival of treated mice. In addition, when initiated after resection of the established primary tumor, the combination treatment dramatically inhibits residual metastatic disease. The clinical response achieved with the combination therapy was correlated with increased interferon-gamma and interleukin-4 (IL-4) production by splenic lymphocytes and draining lymph node cells. Interestingly, when used in combination with Valpha-TOS, nmDC were as effective as tumor necrosis factor-alpha matured DC at inhibiting the growth of pre-established tumors. Valpha-TOS-induced cellular factors collected by high-speed centrifugation of supernatant from Valpha-TOS-treated tumor cells caused maturation of DC as evidenced by the up-regulation of co-stimulatory molecules and secretion of IL-12p70. These results demonstrate the potential usefulness of Valpha-TOS + DC chemo-immunotherapy in treating established primary mammary tumors as well as residual metastatic disease.

α-Tocopheryl succinate selectively induces apoptosis in neuroblastoma cells: potential therapy of malignancies of the nervous system?

Vitamin E (VE) analogues, epitomized by alpha-tocopheryl succinate (alpha-TOS), are potent inducers of apoptosis and anti-cancer agents. Here, we tested their effect on the highly malignant N-type neuroblastoma (Nb) cells and their differentiated, neurone-like counterparts. Nb cells were highly susceptible to several VE analogues, while differentiated Nb cells were relatively resistant to alpha-TOS. The importance of caspase-9 rather than caspase-8, as judged by specific siRNAs studies, together with the loss of the inner mitochondrial potential, suggests that alpha-TOS triggers apoptosis in Nb cells via the mitochondrial pathway. Cultured Nb cells were sensitized to alpha-TOS by pre-treatment with Bcl-2, Bcl-xL or Mcl-1 siRNAs, while the malignant cell line was more resistant to the vitamin E analogue when Bax was knocked down. In contrast, overexpression of Bcl-2 in Nb cells rendered them more resistant to alpha-TOS-induced apoptosis. The resistance of differentiated Nb cells to alpha-TOS-mediated apoptosis occurred via two modes: first, by up-regulation of the anti-apoptotic Bcl-2 family proteins and second, by accumulation of decreased levels of reactive oxygen species when challenged with alpha-TOS. We conclude that alpha-TOS is highly selective in killing malignant brain cancer cells while relatively inert toward differentiated neuronal cells, and that vitamin E analogues may be novel therapeutics for the treatment of tumours such as neuroblastomas.

α-Tocopheryl Succinate Inhibits Malignant Mesothelioma byDisrupting the Fibroblast Growth Factor Autocrine Loop

We have studied the potential effect against human malignant mesotheliomas (MM) of alpha-tocopheryl succinate (alpha-TOS), a redox-silent vitamin E analog with strong pro-apoptotic and anti-cancer activity. alpha-TOS at sub-apoptotic levels inhibited proliferation of MM cell lines, while being nontoxic to nonmalignant mesothelial cells. Because MM cells are typified by a highly metastatic phenotype, we investigated the effect of alpha-TOS on genes playing a major role in MM progression. Of these, alpha-TOS down regulated fibroblast growth factor (FGF)-1 and, in particular, FGF-2 on the transcriptional level in MM cells, and this was not observed in their nonmalignant counterparts. FGF-2 short interfering RNA suppressed proliferation of MM cells. Down-regulation of FGF-2 was likely because of inhibition of the egr-1 transcription activity that was decreased in MM cells via oxidative stress induced by alpha-TOS, as evidenced by EPR spectroscopy, whereas nonmalignant cells did not show this response. Treatment of MM cells with egr-1 short interfering RNA suppressed proliferation, which was overridden by exogenously added recombinant FGF-1 and, in particular, FGF-2. An analog of coenzyme Q targeted to mitochondria and superoxide dismutase overrode inhibition of MM cell proliferation by alpha-TOS as well as alpha-TOS-induced inhibition of egr-1-dependent transactivation. Finally, alpha-TOS significantly suppressed experimental MM in immunocompromised mice. Our data suggest that alpha-TOS suppresses MM cell proliferation by disrupting the FGF-FGF receptor autocrine signaling loop by generating oxidative stress and point to the agent as a selective drug against thus far fatal mesotheliomas.

Chemopreventive effect of dietary d-alpha-tocopheryl succinate supplementation on precancer colon aberrant crypt formation and vitamin E analogue levels in young and old rats

This study examined the effects of dietary d-alpha-tocopheryl succinate (TS) in female rats, 20 mo (OLD) or 2 mo (YNG) of age, on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) and tissue distribution of d-alpha-tocopherol (alphaT), d-gamma-tocopherol (gammaT), and alphaTS. Rats were fed a commercial rodent chow supplemented with or without 1 (YNG) or 2 (OLD) g alphaTS/kg diet for 1 week prior to ip administration of AOM to induce colon ACF. The animals were sacrificed after 49 days of exposure. The results showed that OLD rats had significantly fewer ACF than YNG animals, and the percent body fat and serum triglycerides were significantly higher in the OLD group compared with the YNG. However, only OLD animals receiving alphaTS had significantly reduced numbers of larger ACF and significantly higher levels of colonic alphaT, gammaT, and alphaTS. These data support previous studies demonstrating that dietary alphaTS administration is protective against intestinal cancer. Also, this is the first study to show that alphaTS accumulates in most tissues following dietary exposure. We hypothesize that increased colon accumulation of fat-soluble vitamin E compounds and subsequent chemoprevention may be related to greater percent body fat and serum triglycerides in OLD animals receiving dietary TS.

Hepatic processing determines dual activity of α-tocopheryl succinate: a novel paradigm for a shift in biological activity due to pro-vitamin-to-vitamin conversion

Redox-silent vitamin E analogues, represented by alpha-tocopheryl succinate, are potent anti-cancer drugs with potential secondary bioactivity due to their processing in vivo. Here we verified the hypothesis that hepatic processing of these agents determines the secondary effect. Mice were repeatedly injected with alpha-tocopheryl succinate, and their systemic and hepatic vein blood was assessed for alpha-tocopheryl succinate and its hydrolysis product, vitamin E (alpha-tocopherol). While levels of alpha-tocopherol doubled compared to control mice and alpha-tocopheryl succinate accumulated in the systemic blood, no alpha-tocopheryl succinate was detected in blood draining the liver. We conclude that hepatic processing endows compounds like alpha-tocopheryl succinate with a secondary, anti-oxidant/anti-inflammatory activity due to converting it to the redox-active alpha-tocopherol. Our finding epitomises a novel, general paradigm, according to which a drug can be converted in the liver into a product that has a different beneficial bioactivity.

Pharmacokinetics and tissue distribution ofd-alpha-tocopheryl succinate formulations following intravenous administration in the rat

Unlike d-alpha tocopherol (T), d-alpha tocopheryl succinate (TS) has the unique ability to selectively kill tumor cells while protecting normal tissue from toxic oxidative stress. The pharmacokinetics of TS and the serum and tissue disposition of TS were studied in male Sprague-Dawley rats to delineate formulation dependent disposition between TS administered as the Tris salt (TS-T) (a liposomal formulation) or as the free acid (TS-FA) dissolved in polyethylene glycol (PEG) 400. The pharmacokinetics of TS was studied after single intravenous (i.v.) equimolar doses of 124 mg/kg TS-T and 100 mg/kg of TS-FA. Serial blood samples were collected via a catheter inserted into the right jugular vein and serum samples were analysed for TS and T levels using a reverse phase HPLC method. Terminal tissue samples were also collected at 24 and 48 h. After an acute i.v. dose of TS-T, serum AUC, t(1/2), Cl and V(d) of TS were 2601.0 +/- 351.7 microg h/ml, 9.98 +/- 1.02 h, 0.049 +/- 0. 0073 l/h/kg and 0.7 +/- 0.14 l/kg (mean +/- SD), respectively. The acute i.v. administration of TS-FA (PEG formulation) yielded results similar to those observed for TS-T, with a serum AUC, t(1/2), Cl and V(d) of 2553.3 +/- 166.4 microg h/ml, 9.83 +/- 0.86 h, 0.039 +/- 0.0027 l/h/kg and 0.56 +/- 0.09 l/kg (mean +/- SD), respectively. Distribution into tissues and a low Cl was apparent, with the highest concentrations of TS in the liver and lung, regardless of formulation. As expected, baseline endogenous concentrations of T were present in both groups, with a net increase in T levels, occurring as TS was hydrolysed to T, which slowly peaked in serum between 7-8 h post-dose. Intravenous TS administration, regardless of formulation, also resulted in significant T accumulation in all tissues examined, which was especially abundant in the liver and lung. Likewise, there was a lack of significant effect of formulation on the pharmacokinetics and tissue distribution of TS. The only significant formulation difference was a small but significant increase in serum T and liver T levels in the TS in PEG formulation group. These results indicate that TS may be especially useful for the targeted delivery of T and TS to the lung and liver for anti-oxidant and anti-cancer activity.

Structural characteristic of terminal dicarboxylic moiety required for apoptogenic activity of alpha-tocopheryl esters

alpha-Tocopheryl succinate (TS) is known to induce apoptosis in various cells and has attracted attention as a chemotherapeutic agent. Recently, we reported the structural significance of the terminal dicarboxylic moiety for the action of TS [J. Nutr. Sci. Vitaminol. 49 (2003) 310-314]. In this study, to determine details of the relationship between the structure and the function of the terminal ester moiety of alpha-tocopherol (alpha-T), we synthesized four novel esters, alpha-tocopheryl oxalate (TO), alpha-tocopheryl malonate (TM), alpha-tocopheryl pimelate (TP) and alpha-tocopheryl succinate ethyl ester (TSE), and compared their apoptogenic activities with those of TS, alpha-T, gamma-tocopherol (gamma-T) and two commercially available alpha-T derivatives, alpha-tocopheryl nicotinate (TN) and alpha-tocopheryl acetate (TA), in vascular smooth muscle cells and a mouse breast cancer cell line C127I. TO and TM in addition to TS, but not the others, induced apoptosis in both cells. Particularly, TO was the most potent of all alpha-T derivatives used. The addition of exogenous superoxide dismutase (SOD) significantly prevented the apoptosis induced by TM as well as that by TS as reported previously, but did not affect TO-induced apoptosis. These results suggest that O(2)(-) generated exogenously participates in TM-induced apoptosis but not in TO-induced apoptosis. The difference in their apoptotic effects is attributed to structural properties of the terminal dicarboxylic moiety, which has an inflexible plane conformation in TO, while it is highly flexible in TM and TS.

α-Tocopheryl succinate inhibits proliferation of mesothelioma cells by selective down-regulation of fibroblast growth factor receptors

alpha-Tocopheryl succinate (alpha-TOS), a redox-silent analogue of vitamin E, inhibits malignant mesotheliomas (MM) in a pre-clinical model. Here we investigated the underlying mechanism. Exposure of MM cells to alpha-TOS triggered apoptosis at higher and inhibited proliferation at lower concentrations, while this effect was not observed in non-malignant mesothelial cells. Sub-apoptotic doses of alpha-TOS caused down-regulation of fibroblast growth factor receptor-1 (FGFR1) selectively in MM cells, while the effect on FGFR2 was only marginal. FGF1 and FGF2 enhanced MM cell proliferation that was suppressed by alpha-TOS. Over-expression of E2F1, a transcriptional factor of FGFR1, but not its dominant-negative counterpart, partially blocked the inhibitory activity of alpha-TOS on MM cell proliferation. Our data suggest a novel mechanism by which a clinically intriguing agent selectively suppresses proliferation of cancer cells, as shown here for the untreatable mesotheliomas.

The effect of α- and γ-tocopherol and their carboxyethyl hydroxychroman metabolites on prostate cancer cell proliferation

It is known that gamma-tocopherol inhibits human prostate cancer cell proliferation via down-regulation of cyclin-related signalling but tocopherol and tocotrienol metabolites with a shortened phytyl chain, carboxyethyl hydroxychromans, were not previously investigated as anti-proliferative agents. In this study, the effect of the two main tocopherols, namely, alpha-tocopherol and gamma-tocopherol, and their corresponding metabolites (alpha- and gamma-carboxyethyl hydroxychromans) was studied on proliferation and cyclin D1 expression of the prostate cancer cell line PC-3. The hydrosoluble vitamin E analogues Trolox and alpha-tocopherol succinate were also tested. The most effective inhibitors of PC-3 proliferation were gamma-tocopherol and gamma-carboxyethyl hydroxychroman. Their effect was discernable at 1 microM and reached a plateau at concentrations > or = 10 microM with maximal inhibition values ranging between 70 and 82%. alpha-Tocopherol, alpha-carboxyethyl hydroxychroman, and the analogue Trolox were much less effective; a weak effect was observed for concentrations < or = 10 microM and a maximal inhibition of less than 45% was found at 50 microM concentration. PC-3 cells showed higher inhibition, particularly by the gamma derivatives, than HTB-82 and HECV cells. Tocopherols and carboxyethyl hydroxychromans exerted an inhibitory effect on cyclin D1 expression parallel to the retardation of cell growth. gamma-Carboxyethyl hydroxychroman and gamma-tocopherol showed effects also upstream of the cyclin modulation. Furthermore, the inhibition of cyclin D1 expression by gamma-carboxyethyl hydroxychroman was competed for by alpha-carboxyethyl hydroxychroman. In conclusion, this study shows that carboxyethyl hydroxychroman metabolites are as effective as their vitamin precursors to inhibit PC-3 growth by specific down-regulation of cyclin expression, with the gamma forms being the most effective ones. Although the inhibition of PC-3 cell growth and diminution of cyclin expression are clearly visible, more subtle mechanistic effects of tocopherols and their corresponding carboxyethyl hydroxychroman metabolites deserve further investigations.

Dynamics of antioxidant action of vitamin E

Vitamin E is the major lipophilic, radical-scavenging antioxidant in vivo and protects humans from the oxidative stress mediated by active oxygen and nitrogen species. The mechanisms of the inhibition of oxidation by vitamin E in vitro are now fairly well understood, but the dynamics of antioxidant action of vitamin E in vivo have not been well elucidated yet, primarily because of the inherent heterogeneity of biological systems. In this Account, the factors which determine the antioxidant capacity of vitamin E are discussed, and the importance of its localization and mobility in the membranes and lipoproteins is emphasized.

Vitamin E succinate and cancer treatment: a vitamin E prototype for selective antitumour activity

Great hope has been given to micronutrients as anticancer agents, since they present natural compounds with beneficial effects for normal cells and tissues. One of these is vitamin E (VE), an antioxidant and an essential component of biological membranes and circulating lipoproteins. In spite of a number of epidemiological and intervention studies, little or no correlation between VE intake and incidence of cancer has been found. Recent reports have identified a redox-silent analogue of VE, alpha-tocopheryl succinate (alpha-TOS), as a potent anticancer agent with a unique structure and pharmacokinetics in vivo. alpha-TOS is highly selective for malignant cells, inducing them into apoptotic death largely via the mitochondrial route. The molecule of alpha-TOS may be modified so that analogues with higher activity are generated. Finally, alpha-TOS and similar agents are metabolised to VE, thereby yielding a compound with a secondary beneficial activity. Thus, alpha-TOS epitomises a group of novel compounds that hold substantial promise as future anticancer drugs. The reasons for this optimistic notion are discussed in the following paragraphs.