Abstract

PURPOSE: Ascorbic acid is an essential micronutrient and is considered to have an antioxidant function in living systems. For the past several decades, ascorbic acid has been the subject of considerable interest as an anticancer agent. Several studies have shown that ascorbic acid is cytotoxic to a variety of cancer cells, whereas normal cells are relatively resistant to such cytotoxic action. In this study, we propose a putative molecular mechanism that accounts for the preferential cytotoxicity of ascorbic acid against cancer cells. METHODS: Standard and lysed version of alkaline single-cell gel electrophoresis (Comet assay); ferrous oxidation-xylenol orange (FOX) assay. RESULTS: We show that ascorbic acid acts as a prooxidant and leads to oxidative DNA breakage in lymphocytes and lymphocyte nuclei. Scavengers of reactive oxygen species were able to inhibit ascorbic acid-induced DNA breakage, suggesting the involvement of reactive oxygen species in this reaction. We further show that such DNA breakage is inhibited by both iron and copper chelators in cells, whereas in nuclei, similar inhibition was achieved only by copper chelators, indicating an important role of chromatin-bound copper in the prooxidant cellular DNA breakage by ascorbic acid. CONCLUSION: We propose that the copper-dependent cellular redox status is an important element in the cytotoxic action of ascorbic acid against cancer cells. It is well established that cellular copper levels are considerably elevated in various malignancies. Therefore, cancer cells may be more subject to electron transfer between copper and ascorbate to generate reactive oxygen species. In light of these observations and those in literature, in this paper we explain that the preferential cytotoxicity of ascorbic acid against cancer cells is the result of elevated copper levels in such cells. Further, this study identifies nuclear copper as a novel molecular target for cytotoxic action of ascorbic acid, which has implications for its chemotherapeutic properties against cancer.

Abstract

Malignant mesothelioma is an asbestos-related fatal disease with no effective cure. Recently, high dose of ascorbate in cancer treatment has been reexamined. We studied whether high dose of ascorbic acid induced cell death of four human mesothelioma cell lines. High dose of ascorbic acid induced cell death of all mesothelioma cell lines in a dose-dependent manner. We further clarified the cell killing mechanism that ascorbic acid induced reactive oxygen species and impaired mitochondrial membrane potential. In vivo experiment, intravenous administration of ascorbic acid significantly decreased the growth rate of mesothelioma tumor inoculated in mice. These data suggest that ascorbic acid may have benefits for patients with mesothelioma. 2010 Elsevier Inc. All rights reserved.

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Abstract

BACKGROUND: Angiogenesis is critical to tumor growth and is therefore a potential target for cancer therapy. As many current inhibitors of angiogenesis exhibit host toxicity, natural alternatives are needed. At millimolar concentrations, ascorbate (vitamin C) inhibits migration and tubule formation by mature endothelial cells and endothelial progenitors. In the present study, we examined the effects of ascorbate, at levels relevant during intravenous infusion therapy, on angiogenesis using an ex vivo an in vivo assay. METHODS: Two assays were used to evaluate effect of high-doses ascorbic acid on angiogenesis: ex vivo rat aortic ring explant assay in Matrigel matrices and in vivo Matrigel plug assay. In aortic rings, we quantified microvessel growth, branching and vessel regression under different treatment conditions. In murine angiogenesis assay, male C57 mice 6-8 weeks old were treated by high-dose ascorbic acid and the number of microvessels was analyzed by histological method. To characterize the population of cells that formed capillary network and microvessels, the sections were stained by CD34 and CD31 antibodies. RESULTS: Results show that sprouting of endothelial tubules from aortic rings was reduced in a concentration-dependent fashion by ascorbate: while controls roughly tripled sprout densities during the study, ascorbate (1 mg/mL, 5.5 mM) actually reduced sprout density. In vivo, the ability of mice to vascularize subcutaneously implanted Matrigel plug was diminished if the mice were treated with 430 mg/kg vitamin C: numbers of vessels, and vessel densities, in plugs from treated mice were roughly 30% less than those in plugs from untreated mice. CONCLUSIONS: We conclude that the inhibition of angiogenesis by ascorbate suggested in vitro is confirmed in vivo, and that angiogenesis inhibition may be one mechanism by which intravenous ascorbate therapy shows efficacy in animal experiments and clinical case studies.

Abstract

The Supplementation in Vitamins and Mineral Antioxidants Study was a double-blind, placebo-controlled, randomized trial, in which 12,741 French adults (7,713 women aged 35-60 years and 5,028 men aged 45-60 years) received a combination of ascorbic acid (120 mg), vitamin E (30 mg), beta-carotene (6 mg), selenium (100 mug) and zinc (20 mg), or placebo daily for a median follow-up time of 7.5 years [October 1994 to September 2002]. Antioxidant supplementation decreased total cancer incidence and total mortality in men. Postintervention follow-up assessment of total cancer incidence, ischemic cardiovascular disease incidence and total mortality was carried out for 5 years [September 1, 2002, to September 1, 2007]. No late effect of antioxidant supplementation was revealed 5 years after ending the intervention neither on ischemic cardiovascular disease incidence and mortality in both genders nor on cancer incidence in women. Regarding duration of intervention effects in men, the reduced risk of total cancer incidence and total mortality was no longer evident after the 5-year postintervention follow-up. During the postsupplementation period, the relative risk (RR) for total cancer incidence (n = 126) was 0.98 (95% confidence interval [CI], 0.75-1.27) among antioxidant recipients compared to nonrecipients. For total mortality (n = 90), the RR was 0.98 (95% CI, 0.75-1.26) for men receiving antioxidants compared to nonrecipients. In conclusion, beneficial effects of antioxidant supplementation in men disappeared during postintervention follow-up.

Abstract

Cervical cancer is one of the most common gynecological malignancies in Korea, although the incidence has been declining in recent years. This study explored whether antioxidant vitamin intakes influenced the risk of cervical cancer. The association between antioxidant vitamin intakes and cervical cancer risk was calculated for 144 cervical cancer cases and 288 age-matched, hospital-based controls using unconditional logistic regression models. Cases reported statistically lower mean dietary intakes of vitamin A, beta -carotene, and vitamin C than did controls. Total intakes of vitamins A and E, which included both dietary and supplement intake, were also lower in cases. Those patients in the highest quartiles of dietary vitamin A, beta -carotene, and vitamin C intakes had statistically significantly lower cervical cancer risks than those in the lowest quartiles for vitamin A, beta -carotene, and vitamin C: odds ratio (OR) = 0.36 [95% confidence interval (CI) = 0.19-0.69), OR = 0.48 (CI = 0.26-0.88), and OR = 0.36 (CI = 0.18-0.69), respectively. Total intakes of vitamins A, C, and E were strongly inversely associated with cervical cancer risk: OR = 0.35 (CI = 0.19-0.65), OR = 0.35 (CI = 0.19-0.66), and OR = 0.53 (CI = 0.28-0.99), respectively. The findings support a role for increased antioxidant vitamin intake in decreasing the risk of cervical cancer. These associations need to be assessed in large prospective studies with long-term follow-up.

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Abstract

The role of plant antioxidants as factors of civilization diseases prevention was described. The free-radical theory as a mechanism of action of antioxidants was mentioned. The main substances e.g. polyphenols including flavonoids, ascorbic acid, carotenoids and tocoferols were presented. Resveratrol of wine, as an example of possible health beneficial agent was stressed. On the other handsome doubts of beneficial effects of antioxidants e.g. beta-carotene, as supplement of diet, were mentioned. It is possible, that supplementation with flavonoids might create some health risk. But there was highlighted, that vegetables as a source of natural antioxidants are beneficial for health.

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Abstract

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by defined factors. However, the low efficiency and slow kinetics of the reprogramming process have hampered progress with this technology. Here we report that a natural compound, vitamin C (Vc), enhances iPSC generation from both mouse and human somatic cells. Vc acts at least in part by alleviating cell senescence, a recently identified roadblock for reprogramming. In addition, Vc accelerates gene expression changes and promotes the transition of pre-iPSC colonies to a fully reprogrammed state. Our results therefore highlight a straightforward method for improving the speed and efficiency of iPSC generation and provide additional insights into the mechanistic basis of the reprogramming process. Copyright 2010 Elsevier Inc. All rights reserved.

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Abstract

Gefitinib is an orally active, selective epidermal growth factor receptor-tyrosine kinase inhibitor. The present study was aimed at evaluating the antitumor activity of gefitinib alone or in combination with other antitumor agents. Gefitinib showed higher cytotoxicity against five human tumor cell lines (HSC-2, HSC-3, HSC-4, T98G and U87MG) than against three human normal oral cells (gingival fibroblast HGF, pulp cell HPC and periodontal ligament fibroblast HPLF). Gefitinib showed little or no growth stimulation effects at lower concentrations (so-called hormetic effect). Non-cytotoxic concentration of gefitinib effectively enhanced the cytotoxicity of docetaxel against HSC-2 and T98G cell, but failed to enhance the cytotoxicity of other antitumor agents (mitoxantrone, doxorubicin, methotrexate, cisplatin, sodium ascorbate, sodium fluoride) or herbal extracts (Drynaria baronii, Angelica sinensis and Cornus officinalis Sieb. et Zucc). Gefitinib alone and combined with docetaxel induced internucleosomal DNA fragmentation and caspase-3 activation in human promyelocytic leukemia HL-60 cells, but not in HSC-2 or T98G cells. Combination treatment with gefitinib and docetaxel induced the formation of acidic organelles (stained with acridine orange) and mitochondrial shrinkage, vacuolization and production of autophagosome and the loss of cell surface microvilli, without destruction of cell surface and nuclear membranes in HSC-2 and T98G cells (demonstrated by transmission electron microscopy), suggesting the induction of autophagy in HSC-2 and T98G cells.

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Abstract

Oxidative stress is one major factor in upper aerodigestive tract carcinogenesis. Reactive oxygen species derived from environmental sources, cigarette smoke or cellular metabolism, constantly attack large molecules within the cell. While damaged lipids and proteins can be replaced, oxidative DNA damage needs to be repaired. Damage exceeding DNA repair capacity might lead to permanent mutations. Ascorbic acid, zinc and N-acetylcysteine are widely used as supplementations during upper aerodigestive tract infections. Therefore we chose to investigate their potential in DNA protection. We produced so called “mini-organ” cultures of nasal mucosa, three-dimensional tissue cubes coated with ciliated epithelium, for repeated incubation with ascorbic acid, zinc and N-acetylcysteine at different concentrations. This model has several advantages with respect to repeated incubations, metabolic competence of cells and standardized conditions compared to cell line experiments or animal models. After washing twice, oxidative damage was induced by hydrogen peroxide. Resulting DNA fragmentation was analyzed using the FPG-comet assay, a special modification of the alkaline single-cell microgel electrophoresis for the detection of the most prevalent oxidative DNA base modification. DNA damage was reduced within a range of 45-60%. Cell viability after incubations with hydrogenperoxide was >90%. Our results show strong DNA protective effects of the substances tested in accordance with epidemiological studies linking a diet rich in antioxidative micronutrients with a lowered risk for cancer development. The reasons for the failure of large antioxidant supplementation interventional trials need to be further investigated.

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Abstract

BACKGROUND: The purpose of this study was to compare plasma levels of antioxidants and oxidative stress biomarkers in head and neck squamous cell carcinoma (HNSCC) patients with healthy controls. Furthermore, the effect of radiotherapy on these biomarkers and their association with survival in HNSCC patients were investigated. METHODS: Seventy-eight HNSCC patients and 100 healthy controls were included in this study. Follow-up samples at the end of radiotherapy were obtained in 60 patients. Fifteen antioxidant biomarkers (6 carotenoids, 4 tocopherols, ascorbic acid, total antioxidant capacity, glutathione redox potential, total glutathione and total cysteine) and four oxidative stress biomarkers (total hydroperoxides, gamma-glutamyl transpeptidase, 8-isoprostagladin F2alpha and ratio of oxidized/total ascorbic acid) were measured in plasma samples. Analysis of Covariance was used to compare biomarkers between patients and healthy controls. Kaplan-Meier plots and Cox’ proportional hazards models were used to study survival among patients. RESULTS: Dietary antioxidants (carotenoids, tocopherols and ascorbic acid), ferric reducing antioxidant power (FRAP) and modified FRAP were lower in HNSCC patients compared to controls and dietary antioxidants decreased during radiotherapy. Total hydroperoxides (d-ROMs), a marker for oxidative stress, were higher in HNSCC patients compared to controls and increased during radiotherapy. Among the biomarkers analyzed, high levels of plasma carotenoids before radiotherapy are associated with a prolonged progression-free survival (hazard rate ratio: 0.42, 95% CI: 0.20-0.91, p = 0.03). Additionally, high relative increase in plasma levels of d-ROMs (hazard rate ratio: 0.31, 95% CI: 0.13-0.76, p = 0.01) and high relative decrease in FRAP (hazard rate ratio: 0.42, 95% CI: 0.17-0.998, p = 0.05) during radiotherapy are also positively associated with survival. CONCLUSIONS: Biomarkers of antioxidants and oxidative stress are unfavourable in HNSCC patients compared to healthy controls, and radiotherapy affects many of these biomarkers. Increasing levels of antioxidant biomarkers before radiotherapy and increasing oxidative stress during radiotherapy may improve survival indicating that different factors/mechanisms may be important for survival before and during radiotherapy in HNSCC patients. Thus, the therapeutic potential of optimizing antioxidant status and oxidative stress should be explored further in these patients.

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Abstract

The pathogenesis of hemangiomas is still largely unknown and the current therapy, such as systemic corticosteroid, vincristine, and interferon-alpha, is toxic and remains unsatisfactory. A nutrient mixture (NM) containing lysine, proline, ascorbic acid and green tea extract has shown significant anti-angiogenic and anti-tumor effect against a number of cancer cell lines. Aim: Using a mouse hemangioendothelioma model, we investigated the efficacy of NM. We also tested the effect of NM in vitro, evaluating cell viability, MMP secretion, invasion, morphology and apoptosis. METHODS: Athymic nude mice, 5-6 weeks old, were inoculated with 3 x10(6) EOMA cells subcutaneously and randomly divided into two groups; group A was fed a regular diet and group B – a regular diet supplemented with 0.5% NM. Four weeks later, the mice were sacrificed and their tumors were excised, weighed and processed for histology. We also tested the effect of NM in vitro. RESULTS: NM inhibited the growth of tumors by 50%. In vitro, NM exhibited dose response cytotoxicity with 10%, 30% and 55% at 10, 100 and 1000 microg/ml. Invasion through Matrigel was inhibited at 50, 100 and 500 microg/ml by 25%, 30% and 100% respectively. NM induced dose-dependent apoptosis of EOMA cells. CONCLUSIONS: These results suggest that NM may have therapeutic potential in treating infantile hemangioendotheliomas and, perhaps, other cutaneous vascular tumors.

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