Experimental Surgery, Department of Surgery, University of Würzburg Hospital, Germany.
BMC Complement Altern Med. 2012 May 2;12:61. doi: 10.1186/1472-6882-12-61.
Ascorbic acid demonstrates a cytotoxic effect by generating hydrogen peroxide, a reactive oxygen species (ROS) involved in oxidative cell stress. A panel of eleven human cancer cell lines, glioblastoma and carcinoma, were exposed to serial dilutions of ascorbic acid (5-100 mmol/L). The purpose of this study was to analyse the impact of catalase, an important hydrogen peroxide-detoxifying enzyme, on the resistance of cancer cells to ascorbic acid mediated oxidative stress.
Effective concentration (EC(50)) values, which indicate the concentration of ascorbic acid that reduced the number of viable cells by 50%, were detected with the crystal violet assay. The level of intracellular catalase protein and enzyme activity was determined. Expression of catalase was silenced by catalase-specific short hairpin RNA (sh-RNA) in BT-20 breast carcinoma cells. Oxidative cell stress induced apoptosis was measured by a caspase luminescent assay.
The tested human cancer cell lines demonstrated obvious differences in their resistance to ascorbic acid mediated oxidative cell stress. Forty-five percent of the cell lines had an EC(50) > 20 mmol/L and fifty-five percent had an EC(50) < 20 mmol/L. With an EC(50) of 2.6-5.5 mmol/L, glioblastoma cells were the most susceptible cancer cell lines analysed in this study. A correlation between catalase activity and the susceptibility to ascorbic acid was observed. To study the possible protective role of catalase on the resistance of cancer cells to oxidative cell stress, the expression of catalase in the breast carcinoma cell line BT-20, which cells were highly resistant to the exposure to ascorbic acid (EC(50): 94,9 mmol/L), was silenced with specific sh-RNA. The effect was that catalase-silenced BT-20 cells (BT-20 KD-CAT) became more susceptible to high concentrations of ascorbic acid (50 and 100 mmol/L).
Fifty-five percent of the human cancer cell lines tested were unable to protect themselves against oxidative stress mediated by ascorbic acid induced hydrogen peroxide production. The antioxidative enzyme catalase is important to protect cancer cells against cytotoxic hydrogen peroxide. Silenced catalase expression increased the susceptibility of the formerly resistant cancer cell line BT-20 to oxidative stress.
抗坏血酸通过生成过氧化氢（一种参与氧化细胞应激的活性氧物质）表现出细胞毒性作用。一组 11 个人类癌细胞系，包括神经胶质瘤和癌，被暴露于抗坏血酸的连续稀释液中（5-100mmol/L）。本研究的目的是分析过氧化氢解毒酶-过氧化氢酶对抗坏血酸介导的氧化应激下癌细胞耐药性的影响。
采用结晶紫法检测有效浓度（EC（50））值，该值表示使存活细胞数量减少 50%的抗坏血酸浓度。测定细胞内过氧化氢酶蛋白和酶活性水平。在 BT-20 乳腺癌细胞中，用过氧化氢酶特异性短发夹 RNA（sh-RNA）沉默过氧化氢酶表达。通过半胱天冬酶发光测定法测量氧化细胞应激诱导的细胞凋亡。
所测试的人类癌细胞系对抗坏血酸介导的氧化细胞应激的抵抗力表现出明显差异。45%的细胞系 EC（50）>20mmol/L，55%的细胞系 EC（50）<20mmol/L。本研究分析的神经胶质瘤细胞系 EC（50）为 2.6-5.5mmol/L，是最敏感的癌细胞系。观察到过氧化氢酶活性与对阿萨希丝酸敏感性之间存在相关性。为了研究过氧化氢酶在癌症细胞对氧化细胞应激的耐药性中的可能保护作用，用特异性 sh-RNA 沉默对阿萨希丝酸暴露高度耐药的乳腺癌细胞系 BT-20 中的过氧化氢酶表达。结果是，沉默过氧化氢酶的 BT-20 细胞（BT-20 KD-CAT）对高浓度的抗坏血酸（50 和 100mmol/L）变得更加敏感。
55%的测试人癌细胞系无法保护自己免受抗坏血酸诱导的过氧化氢产生的氧化应激。抗氧化酶过氧化氢酶对抗细胞毒性过氧化氢保护癌细胞很重要。沉默过氧化氢酶表达增加了先前耐药的 BT-20 癌细胞系对氧化应激的敏感性。
