癌细胞由于癌基因活化、核苷酸生物合成以及生长因子受体信号通路的影响而经历了升高的氧化应激水平。线粒体通过在电子传递链（ETC）中产生反应性氧分子（ROS）并释放到基质和膜间隙中，为这种氧化应激作出了贡献。评估线粒体ROS在癌细胞中的贡献具有技术难度，因为ETC抑制剂既可以增加也可以减少ROS的产生，同时也会阻止氧化磷酸化和ATP合成。线粒体靶向抗氧化化合物可以清除基质区域的ROS，但不能作用于释放到膜间隙中的ROS。我们通过在143B骨肉瘤和HCT116结直肠癌细胞系中稳定表达一种过氧化氢清除剂——过氧化氢酶-5（IMS-Prdx5），并将其定位在线粒体膜间隙中，评估了线粒体ROS对肿瘤细胞增殖、存活和肿瘤异种移植生长的重要性。IMS-Prdx5可以在无氧和缺氧培养条件下减弱缺氧诱导的ROS信号，独立评估细胞质和膜间隙中的HIF-1α稳定和活性，以及细胞增殖。它还抑制了体内肿瘤生长。在IMS-Prdx5表达细胞中稳定表达不能降解的HIF-1α仅能部分恢复增殖，表明线粒体H2O2信号通过HIF依赖和HIF非依赖机制促进了肿瘤细胞的增殖和存活。版权所有©2023作者，由Elsevier Inc.出版。保留所有权利。

Cancer cells experience increased levels of oxidant stress as a consequence of oncogene activation, nucleotide biosynthesis, and growth factor receptor signaling. Mitochondria contribute to this redox stress by generating reactive oxygen species (ROS) along the electron transport chain (ETC), which are released to the matrix and the intermembrane space (IMS). Assessing the contribution of mitochondrial ROS in cancer cells is technically difficult, as ETC inhibitors can increase or decrease ROS generation, while they also block oxidative phosphorylation and ATP synthesis. Mitochondria-targeted antioxidant compounds can scavenge ROS in the matrix compartment, but do not act on ROS released to the intermembrane space. We assessed the importance of mitochondrial ROS for tumor cell proliferation, survival, and for tumor xenograft growth by stably expressing a hydrogen peroxide (H2O2) scavenger, peroxiredoxin-5, in the mitochondrial IMS (IMS-Prdx5) in 143B osteosarcoma and HCT116 colorectal cancer cell lines. IMS-Prdx5 attenuates hypoxia-induced ROS signaling as assessed independently in cytosol and IMS, HIF-1α stabilization and activity, and cellular proliferation under normoxic and hypoxic culture conditions. It also suppressed tumor growth in vivo. Stable expression of non-degradable HIF-1α only partially rescued proliferation in IMS-Prdx5-expressing cells, indicating that mitochondrial H2O2 signaling contributes to tumor cell proliferation and survival through HIF-dependent and HIF-independent mechanisms.Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.