Pharmacological vitamin C (VC) has gained attention for its pro-oxidant characteristics and selective ability to induce cancer cell death. However, defining its role in cancer has been challenging due to its complex redox properties. In this study, using a human osteosarcoma (OS) model, we show that the redox-active property of VC is critical for inducing non-apoptotic cancer cell death via intracellular reactive oxygen species (ROS)-iron-calcium crosstalk and mitochondrial dysfunction. In both 2D and 3D OS cell culture models, only the oxidizable form of VC demonstrated potent dose-dependent cytotoxicity, while non-oxidizable and oxidized VC derivatives had minimal effects. Live-cell imaging showed that only oxidizable VC caused a surge in cytotoxic ROS, dependent on iron rather than copper. Inhibitors of ferroptosis, a form of iron-dependent cell death, along with classical apoptosis inhibitors, were unable to completely counteract the cytotoxic effects induced by VC. Further pharmacological and genetic inhibition analyses showed that VC triggers calcium release through inositol 1,4,5-trisphosphate receptors (IP3Rs), leading to mitochondrial ROS production and eventual cell death. RNA sequencing revealed down-regulation of genes involved in the mitochondrial electron transport chain and oxidative phosphorylation upon pharmacological VC treatment. Consistently, high-dose VC reduced mitochondrial membrane potential, oxidative phosphorylation, and ATP levels, with ATP reconstitution rescuing VC-induced cytotoxicity. In vivo OS xenograft studies demonstrated reduced tumor growth with high-dose VC administration, concomitant with the altered expression of mitochondrial ATP synthase (MT-ATP). These findings emphasize VC's potential clinical utility in osteosarcoma treatment by inducing mitochondrial metabolic dysfunction through a vicious intracellular ROS-iron-calcium cycle.

中文翻译：

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氧化还原活性维生素 C 通过触发细胞内 ROS-铁-钙信号串扰和线粒体功能障碍来抑制人骨肉瘤生长


药理学维生素 C (VC) 因其促氧化特性和诱导癌细胞死亡的选择性能力而受到关注。然而，由于其复杂的氧化还原特性，定义其在癌症中的作用一直具有挑战性。在这项研究中，使用人类骨肉瘤（OS）模型，我们表明VC的氧化还原活性特性对于通过细胞内活性氧（ROS）-铁-钙串扰和线粒体功能障碍诱导非凋亡癌细胞死亡至关重要。在 2D 和 3D OS 细胞培养模型中，只有可氧化形式的 VC 表现出有效的剂量依赖性细胞毒性，而不可氧化和氧化的 VC 衍生物的影响最小。活细胞成像表明，只有可氧化的 VC 才会导致细胞毒性 ROS 激增，依赖于铁而不是铜。铁死亡抑制剂（铁依赖性细胞死亡的一种形式）与经典的细胞凋亡抑制剂一起，无法完全抵消 VC 诱导的细胞毒性作用。进一步的药理学和遗传抑制分析表明，VC 通过肌醇 1,4,5-三磷酸受体 (IP3R) 触发钙释放，导致线粒体 ROS 产生并最终细胞死亡。 RNA 测序揭示了药物 VC 治疗后参与线粒体电子传递链和氧化磷酸化的基因下调。一致地，高剂量 VC 降低了线粒体膜电位、氧化磷酸化和 ATP 水平，而 ATP 重建可挽救 VC 诱导的细胞毒性。体内 OS 异种移植研究表明，高剂量 VC 给药可减少肿瘤生长，同时改变线粒体 ATP 合酶 (MT-ATP) 的表达。 这些发现强调了 VC 通过恶性细胞内 ROS-铁-钙循环诱导线粒体代谢功能障碍，在骨肉瘤治疗中的潜在临床用途。