Sinnberg Tobias, Noor Seema, Venturelli Sascha, Berger Alexander, Schuler Paul, Garbe Claus, Busch Christian
Division of Dermatologic Oncology, Department of Dermatology and Allergology, University of Tuebingen, Tuebingen, Germany.
J Cell Mol Med. 2014 Mar;18(3):530-41. doi: 10.1111/jcmm.12207. Epub 2013 Dec 14.
Intravenous application of high-dose ascorbate is used in complementary palliative medicine to treat cancer patients. Pharmacological doses of ascorbate in the mM range induce cytotoxicity in cancer cells mediated by reactive oxygen species (ROS), namely hydrogen peroxide and ascorbyl radicals. However, little is known about intrinsic or extrinsic factors modulating this ascorbate-mediated cytotoxicity. Under normoxia and hypoxia, ascorbate IC50 values were determined on the NCI60 cancer cells. The cell cycle, the influence of cobalt chloride-induced hypoxia-inducible factor-1α (HIF-1α) and the glucose transporter 1 (GLUT-1) expression (a pro-survival HIF-1α-downstream-target) were analysed after ascorbate exposure under normoxic and hypoxic conditions. The amount of ascorbyl radicals increased with rising serum concentrations. Hypoxia (0.1% O2 ) globally increased the IC50 of ascorbate in the 60 cancer cell lines from 4.5 ± 3.6 mM to 10.1 ± 5.9 mM (2.2-fold increase, P < 0.001, Mann-Whitney t-test), thus inducing cellular resistance towards ascorbate. This ascorbate resistance depended on HIF-1α-signalling, but did not correlate with cell line-specific expression of the ascorbate transporter GLUT-1. However, under normoxic and hypoxic conditions, ascorbate treatment at the individual IC50 reduced the expression of GLUT-1 in the cancer cells. Our data show a ROS-induced, HIF-1α- and O2 -dependent cytotoxicity of ascorbate on 60 different cancer cells. This suggests that for clinical application, cancer patients should additionally be oxygenized to increase the cytotoxic efficacy of ascorbate.
大剂量静脉注射抗坏血酸用于辅助姑息医学中治疗癌症患者。毫摩尔范围内的药理学剂量抗坏血酸可诱导癌细胞产生由活性氧（ROS）介导的细胞毒性，即过氧化氢和抗坏血酸自由基。然而，关于调节这种抗坏血酸介导的细胞毒性的内在或外在因素知之甚少。在常氧和缺氧条件下，测定了NCI60癌细胞的抗坏血酸IC50值。在常氧和缺氧条件下抗坏血酸暴露后，分析了细胞周期、氯化钴诱导的缺氧诱导因子-1α（HIF-1α）的影响以及葡萄糖转运蛋白1（GLUT-1）的表达（一种促生存的HIF-1α下游靶点）。抗坏血酸自由基的量随血清浓度升高而增加。缺氧（0.1% O2）使60种癌细胞系中抗坏血酸的IC50从4.5±3.6 mM整体增加到10.1±5.9 mM（增加2.2倍，P<0.001，曼-惠特尼t检验），从而诱导细胞对抗坏血酸产生抗性。这种抗坏血酸抗性依赖于HIF-1α信号传导，但与抗坏血酸转运蛋白GLUT-1的细胞系特异性表达无关。然而，在常氧和缺氧条件下，以个体IC50进行抗坏血酸处理可降低癌细胞中GLUT-1的表达。我们的数据显示抗坏血酸对60种不同癌细胞具有ROS诱导的、HIF-1α和O2依赖性细胞毒性。这表明在临床应用中，癌症患者应额外进行吸氧以提高抗坏血酸的细胞毒性疗效。
