Mitochondrial metabolism is the key source for abundant ROS in chronic lymphocytic leukemia (CLL) cells. Here, we detected significantly lower superoxide anion (O₂⁻) levels with increased accumulation of hydrogen peroxide (H₂O₂) in CLL cells vs. normal B-cells. Further analysis indicated that mitochondrial superoxide dismutase (SOD)2, which converts O₂⁻ into H₂O₂ remained deacetylated in CLL cells due to SIRT3 overexpression resulting its constitutive activation. In addition, catalase expression was also reduced in CLL cells suggesting impairment of H₂O₂-conversion into water and O₂ which may cause H₂O₂-accumulation. Importantly, we identified two CpG-islands in the catalase promoter and discovered that while the distal CpG-island (−3619 to −3765) remained methylated in both normal B-cells and CLL cells, variable degrees of methylation were discernible in the proximal CpG-island (−174 to −332) only in CLL cells. Finally, treatment of CLL cells with a demethylating agent increased catalase mRNA levels. Functionally, ROS accumulation in CLL cells activated the AXL survival axis while upregulated SIRT3, suggesting that CLL cells rapidly remove highly reactive O₂⁻ to avoid its cytotoxic effect but maintain increased H₂O₂-level to promote cell survival. Therefore, abrogation of aberrantly activated cell survival pathways using antioxidants can be an effective intervention in CLL therapy in combination with conventional agents.

线粒体代谢是慢性淋巴细胞白血病 (CLL) 细胞中大量 ROS 的关键来源。在这里，我们检测到CLL 细胞与正常 B 细胞相比，随着过氧化氢 (H ₂ O ₂ )积累的增加，超氧阴离子 (O ₂ ^- ) 水平显着降低。进一步分析表明，由于 SIRT3 过表达导致其组成型激活，将 O ₂ ^-转化为 H ₂ O _{2 的}线粒体超氧化物歧化酶 (SOD)2在 CLL 细胞中保持去乙酰化。此外，过氧化氢酶在 CLL 细胞中的表达也降低，表明 H ₂ O ₂向水和 O ₂转化的障碍这可能会导致H ₂ O _{2 -}积累。重要的是，我们在过氧化氢酶启动子中发现了两个 CpG 岛，并发现虽然远端 CpG 岛（-3619 至 -3765）在正常 B 细胞和 CLL 细胞中都保持甲基化，但在近端 CpG 中可辨别不同程度的甲基化-岛（-174 至 -332）仅在 CLL 细胞中。最后，用去甲基化剂处理 CLL 细胞增加了过氧化氢酶 mRNA 水平。在功能上，CLL 细胞中的 ROS 积累激活了 AXL 存活轴，同时上调了 SIRT3，这表明 CLL 细胞快速去除高反应性 O ₂ ^-以避免其细胞毒性作用但保持增加的 H ₂ O ₂-水平促进细胞存活。因此，使用抗氧化剂消除异常激活的细胞存活途径可能是与常规药物联合治疗 CLL 的有效干预措施。