Decreased Plasma Ascorbate Levels in Stage IV Melanoma Patients T. Schleich1, S. Rodemeister1, S. Venturelli2, T. Sinnberg3, C. Garbe3, C. Busch3
1Department of Pediatrics, University of Tuebingen, Germany
2Institute of Biological Chemistry and Nutrition, University of Hohenheim, Germany
3Department of Internal Medicine I, University of Tuebingen, Germany
4Department of Dermatology, Section of Dermato-Oncology, University of Tuebingen, Germany
Abstract It has been reported that cancer patients frequently express low ascorbate (ascorbic acid, vitamin C) blood levels. However, so far this was not shown for melanoma patients.
Total ascorbate (TAA) levels were determined in plasma of healthy control individuals (n=31, mean age: 47.3 years, TAA: 64.86 µM) and in 126 melanoma patients (stage I: n=30, mean age: 51 years, TAA: 59.95 µM; stage II: n=30, mean age: 46.8 years, TAA: 58.85 µM; stage III: n=32, mean age: 48.6 years, TAA: 57.27 µM; stage IV: n=34, mean age: 51.1 years, TAA: 47.16 µM). Plasma TAA levels in stage IV patients were significantly reduced by 27.3% when compared to healthy individuals (p=0.0001, t-test). The reduced plasma TAA levels in stage IV patients negatively correlated with increased S100 and lactate dehydrogenase (LDH) levels. Further, plasma TAA levels were determined in additional 9 stage IV patients directly before and 24 h after intravenous polychemotherapy (carboplatin+paclitaxel, n=5) or immunotherapy (ipilimumab, n=4). TAA levels significantly decreased 24 h after therapy (mean TAA before therapy: 48.7 µM; mean TAA after therapy: 43.0 µM; 11.4% reduction, p<0.05, t-test).
Ascorbate levels in the plasma of 126 melanoma patients were significantly decreased in the cohort of stage IV patients and were further decreased by polychemo- or immunotherapy in stage IV patients. Considering the importance of adequate ascorbate supply, ascorbate substitution in physiological doses could be considered for late-stage melanoma patients.
Vitamin C: A Concentration-Function Approach Yields Pharmacology and Therapeutic Discoveries1,2 Mark Levine,* Sebastian J. Padayatty, and Michael Graham Espey
Molecular and Clinical Nutrition Section, Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1372
A concentration-function approach to vitamin C (ascorbate) has yielded new physiology and pharmacology discoveries. To determine the range of vitamin C concentrations possible in humans, pharmacokinetics studies were conducted. They showed that when vitamin C is ingested by mouth, plasma and tissue concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, vitamin C plasma concentrations do not exceed 100 mmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasma concentrations are always <250 mmol/L and frequently <150 mmol/L. By contrast, when ascorbate is i.v. injected, tight control is bypassed until excess ascorbate is eliminated by glomerular filtration and renal excretion. With i.v. infusion, pharmacologic ascorbate concentrations of 25–30 mmol/L are safely achieved. Pharmacologic ascorbate can act as a pro-drug for hydrogen peroxide (H2O2) formation, which can lead to extracellular fluid at concentrations as high as 200 mmol/L. Pharmacologic ascorbate can elicit cytotoxicity toward cancer cells and slow the growth of tumors in experimental murine models. The effects of pharmacologic ascorbate should be further studied in diseases, such as cancer and infections, which may respond to generation of reactive oxygen species via H2O2
Chemoprevention of Gastric Dysplasia: Randomized Trial of Antioxidant Supplements and Anti-Helicobacter pylori Therapy Pelayo Correa, Elizabeth T. H. Fontham, Juan C. Bravo, Luis E. Bravo, Bernardo Ruiz, Guillermo Zarama, J. Luis Realpe, Gray T. Malcom, Daner Li, William D. Johnson, Robertino Mera
Background: Previous research has identified a high risk of gastric carcinoma as well as a high prevalence of cancer precursor lesions in rural populations living in the province of Nariño, Colombia, in the Andes Mountains. Methods: A randomized, controlled chemoprevention trial was conducted in subjects with confirmed histologic diagnoses of multifocal nonmetaplastic atrophy and/or intestinal metaplasia, two precancerous lesions. Individuals were assigned to receive anti-Helicobacter pylori triple therapy and/or dietary supplementation with ascorbic acid, β-carotene, or their corresponding placebos. Gastric biopsy specimens taken at baseline were compared with those taken at 72 months. Relative risks of progression, no change, and regression from multifocal nonmetaplastic atrophy and intestinal metaplasia were analyzed with multivariate polytomous logistic regression models to estimate treatment effects. All statistical tests were two-sided.
Results: All three basic interventions resulted in statistically significant increases in the rates of regression: Relative risks were 4.8 (95% confidence interval [CI] = 1.6–14.2) for anti-H. pylori treatment, 5.1 (95% CI = 1.7–15.0) for β-carotene treatment, and 5.0 (95% CI = 1.7–14.4) for ascorbic acid treatment in subjects with atrophy. Corresponding relative risks of regression in subjects with intestinal metaplasia were 3.1 (95% CI = 1.0–9.3), 3.4 (95% CI = 1.1–9.8), and 3.3 (95% CI = 1.1–9.5). Combinations of treatments did not statistically significantly increase the regression rates. Curing the H. pylori infection (which occurred in 74% of the treated subjects) produced a marked and statistically significant increase in the rate of regression of the precursor lesions (relative risks = 8.7 [95% CI = 2.7–28.2] for subjects with atrophy and 5.4 [95% CI = 1.7–17.6] for subjects with intestinal metaplasia).
Conclusions: In the very high-risk population studied, effective anti-H. pylori treatment and dietary supplementation with antioxidant micronutrients may interfere with the precancerous process, mostly by increasing the rate of regression of cancer precursor lesions, and may be an effective strategy to prevent gastric carcinoma.
Source : JNCI J Natl Cancer Inst (2000) 92 (23): 1881-1888. doi: 10.1093/jnci/92.23.1881 LINK TO FULL ARTICLE
Pharmacologic ascorbic acid concentrations selectively kill cancer cells: Action as a pro-drug to deliver hydrogen peroxide to tissues
Qi Chen,*† Michael Graham Espey,‡ Murali C. Krishna,‡ James B. Mitchell,‡ Christopher P. Corpe,* Garry R. Buettner,§ Emily Shacter,† and Mark Levine*¶*Molecular and Clinical Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; Free Radical and Radiation Biology Program, University of Iowa, Iowa City, IA 52242-1101; and †Laboratory of Biochemistry, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892
Abstract Human pharmacokinetics data indicate that i.v. ascorbic acid (ascorbate) in pharmacologic concentrations could have an unanticipated role in cancer treatment. Our goals here were to test whether ascorbate killed cancer cells selectively, and if so, to determine mechanisms, using clinically relevant conditions. Cell death in 10 cancer and 4 normal cell types was measured by using 1-h exposures. Normal cells were unaffected by 20 mM ascorbate, whereas 5 cancer lines had EC50 values of <4 mM, a concentration easily achievable i.v. Human lymphoma cells were studied in detail because of their sensitivity to ascorbate (EC50 of 0.5 mM) and suitability for addressing mechanisms. Extracellular but not intracellular ascorbate mediated cell death, which occurred by apoptosis and pyknosis/necrosis. Cell death was independent of metal chelators and absolutely dependent on H2O2 formation. Cell death from H2O2 added to cells was identical to that found when H2O2 was generated by ascorbate treatment. H2O2 generation was dependent on ascorbate concentration, incubation time, and the presence of 0.5-10% serum, and displayed a linear relationship with ascorbate radical formation. Although ascorbate addition to medium generated H2O2, ascorbate addition to blood generated no detectable H2O2 and only trace detectable ascorbate radical. Taken together, these data indicate that ascorbate at concentrations achieved only by i.v. administration may be a pro-drug for formation of H2O2, and that blood can be a delivery system of the pro-drug to tissues. These findings give plausibility to i.v. ascorbic acid in cancer treatment, and have unexpected implications for treatment of infections where H2O2 may be beneficial.
Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo
Qi Chen,* Michael Graham Espey,† Andrew Y. Sun,* Je-Hyuk Lee,* Murali C. Krishna,† Emily Shacter,‡ Peter L. Choyke,§ Chaya Pooput,¶ Kenneth L. Kirk,¶ Garry R. Buettner,‖ and Mark Levine Molecular and Clinical Nutrition Section and ¶Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892; † Radiation Biology Branch and the §Molecular Imaging Program, National Cancer Institute, Bethesda, MD 20892; Laboratory of Biochemistry, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892; and Free Radical and Radiation Biology Program, University of Iowa, Iowa City, IA 52242
Abstract Ascorbate (ascorbic acid, vitamin C), in pharmacologic concentrations easily achieved in humans by i.v. administration, selectively kills some cancer cells but not normal cells. We proposed that pharmacologic ascorbate is a prodrug for preferential steady-state formation of ascorbate radical (Asc•−) and H2O2 in the extracellular space compared with blood. Here we test this hypothesis in vivo. Rats were administered parenteral (i.v. or i.p.) or oral ascorbate in typical human pharmacologic doses (≈0.25–0.5 mg per gram of body weight). After i.v. injection, ascorbate baseline concentrations of 50–100 μM in blood and extracellular fluid increased to peaks of >8 mM. After i.p. injection, peaks approached 3 mM in both fluids. By gavage, the same doses produced ascorbate concentrations of <150 μM in both fluids. In blood, Asc•− concentrations measured by EPR were undetectable with oral administration and always <50 nM with parenteral administration, even when corresponding ascorbate concentrations were >8 mM. After parenteral dosing, Asc•− concentrations in extracellular fluid were 4- to 12-fold higher than those in blood, were as high as 250 nM, and were a function of ascorbate concentrations. By using the synthesized probe peroxyxanthone, H2O2 in extracellular fluid was detected only after parenteral administration of ascorbate and when Asc•− concentrations in extracellular fluid exceeded 100 nM. The data show that pharmacologic ascorbate is a prodrug for preferential steady-state formation of Asc•− and H2O2 in the extracellular space but not blood. These data provide a foundation for pursuing pharmacologic ascorbate as a prooxidant therapeutic agent in cancer and infections.Keywords: ascorbic acid, cancer, vitamin C, pharmacokinetics
Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice
Qi Chen,*† Michael Graham Espey,*†‡ Andrew Y. Sun,* Chaya Pooput,§ Kenneth L. Kirk,§ Murali C. Krishna,¶ Deena Beneda Khosh,‖ Jeanne Drisko,‖ and Mark Levine*‡* Molecular and Clinical Nutrition Section and §Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, and ¶Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and ‖Program in Integrative Medicine, University of Kansas Medical Center, Kansas City, KS 66160
Abstract Ascorbic acid is an essential nutrient commonly regarded as an antioxidant. In this study, we showed that ascorbate at pharmacologic concentrations was a prooxidant, generating hydrogen-peroxide-dependent cytotoxicity toward a variety of cancer cells in vitro without adversely affecting normal cells. To test this action in vivo, normal oral tight control was bypassed by parenteral ascorbate administration. Real-time microdialysis sampling in mice bearing glioblastoma xenografts showed that a single pharmacologic dose of ascorbate produced sustained ascorbate radical and hydrogen peroxide formation selectively within interstitial fluids of tumors but not in blood. Moreover, a regimen of daily pharmacologic ascorbate treatment significantly decreased growth rates of ovarian (P < 0.005), pancreatic (P < 0.05), and glioblastoma (P < 0.001) tumors established in mice. Similar pharmacologic concentrations were readily achieved in humans given ascorbate intravenously. These data suggest that ascorbate as a prodrug may have benefits in cancers with poor prognosis and limited therapeutic options.