Institute of Virology, Department of Medical Microbiology and Hygiene, University Medical Center, Freiburg, Germany.
Redox Biol. 2015 Aug;5:415-416. doi: 10.1016/j.redox.2015.09.018. Epub 2015 Dec 30.
Oncogenic transformation depends on the activation of membrane-associated NADPH oxidase. The resultant extracellular superoxide anions control the proliferation of malignant cells, but they also drive two intercellular signaling pathways that cause selective apoptosis induction in malignant cells, i. e. the HOCl and the NO/peroxynitrite pathway. Tumor progression requires the establishment of resistance against these apoptosis-inducing pathways through expression of membrane-associated catalase that interferes with HOCl signaling through decomposition of HO and with NO/peroxynitrite through oxidation of NO and decomposition of peroxynitrite.
We aimed to establish the biochemical basis for novel therapeutic approaches that target tumor cell protective catalase and thus cause reactivation of intercellular reactive oxygen/nitrogen species-dependent apoptotic signaling of tumor cells.
We used cells from defined stages of multistep oncogenesis, i. e. nontransformed, transformed and bona vide tumor cells. Intercellular apoptosis-inducing ROS/RNS signaling was studied using defined inhibitors/scavengers, reconstitution experiments and small interfering RNA directed against relevant targets.
Direct inhibition of tumor cell catalase by neutralizing antibodies or its direct inactivation by extracellular singlet oxygen caused efficient reactivation of apoptosis-inducing signaling. Interestingly, the increase in cell-derived NO through addition of arginine, inhibition of arginase, inhibition of NO dioxygenase or induction of NO synthase by interferon led to the generation of extracellular singlet oxygen that triggered a complex self-amplificatory system. As a result, high concentrations of cell-derived singlet oxygen inactivated catalase and reactivated apoptosis inducing intercellular signaling.
Modulation of the cellular NO concentration causes extracellular singlet oxygen generation and inactivation of tumor cell protective catalase.
致癌转化依赖于膜相关 NADPH 氧化酶的激活。由此产生的细胞外超氧阴离子控制恶性细胞的增殖，但它们也驱动两种细胞间信号通路，导致恶性细胞的选择性凋亡诱导，即次氯酸（HOCl）和一氧化氮/过氧亚硝酸盐途径。肿瘤进展需要通过表达膜相关过氧化氢酶来建立对这些凋亡诱导途径的抗性，该酶通过分解 HO 干扰 HOCl 信号，并通过氧化 NO 和分解过氧亚硝酸盐来干扰 NO/过氧亚硝酸盐。
我们旨在确定针对肿瘤细胞保护性过氧化氢酶的新治疗方法的生化基础，从而导致肿瘤细胞细胞间活性氧/氮物种依赖性凋亡信号的重新激活。
我们使用多步致癌作用中定义的阶段的细胞，即非转化、转化和真正的肿瘤细胞。使用定义的抑制剂/清除剂、重建实验和针对相关靶标的小干扰 RNA 研究细胞间凋亡诱导 ROS/RNS 信号。
通过中和抗体直接抑制肿瘤细胞过氧化氢酶或通过细胞外单线态氧直接失活，可有效重新激活凋亡诱导信号。有趣的是，通过添加精氨酸、抑制精氨酸酶、抑制一氧化氮双加氧酶或干扰素诱导一氧化氮合酶，增加细胞衍生的一氧化氮会导致细胞外单线态氧的产生，从而引发复杂的自我放大系统。结果，细胞衍生的单线态氧的高浓度会使过氧化氢酶失活并重新激活诱导凋亡的细胞间信号。
细胞内一氧化氮浓度的调节会导致细胞外单线态氧的产生和肿瘤细胞保护性过氧化氢酶的失活。
