美国研究人员8月4日在新一期美国《国家科学院院刊》（PNAS）上发表论文指出，给患有癌症的实验鼠注射大剂量的维生素C，可以明显减缓肿瘤生长。
来自美国国家卫生研究所的一个科研小组介绍说，肌体内很多关键酶都需要维生素C才能正常工作，长期缺乏维生素C可能导致坏血病。维生素C还起到抗氧化剂的作用，能保护细胞免受自由基的危害。但是他们发现，当维生素C被大剂量注入实验鼠体内时，反而会起到“促氧化剂”的作用，导致形成过氧化氢，它可以杀死癌细胞。
研究小组负责人马克·莱文等人最初对43种癌症细胞系和5种正常细胞系进行的实验显示，高浓度的维生素C对75%的癌细胞系都有抑制效果，并且不会影响正常的细胞系。他们随后用患癌实验鼠进行实验并发现，大剂量注射维生素C可使肿瘤重量和生长速度分别降低41%和53%。
研究人员分析认为，维生素C之所以有抗癌功效，是由于它能在围绕癌细胞的细胞外液中促使形成过氧化氢，正是过氧化氢杀死了一些癌细胞。
研究小组称，这些动物实验数据表明，应该继续推进维生素C在人类癌症治疗领域的应用。医学界早年曾一度掀起研究用维生素C治疗癌症的热潮，后来由于有些临床试验得出结论认为，口服高剂量维生素C对于癌症患者没有明显益处，研究热潮逐渐降温。而莱文等人指出，只有通过注射，人体内的维生素C才能达到可发挥抗癌效果的水平。他们已经在设计新的人体临床试验，以进一步研究维生素C在人体中的抗癌功效。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS，doi: 10.1073/pnas.0804226105，Qi Chen, Mark Levine
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*,‡
+Author Affiliations
*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
↵ †Q.C. and M.G.E. contributed equally to this work.
Edited by Bruce N. Ames, Children's Hospital Oakland Research Institute, Oakland, CA, and approved June 6, 2008 (received for review May 1, 2008)
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.
