半胱氨酸是蛋白质合成、抗氧化谷胱甘肽的生成以及合成非蛋白氨基酸牛磺酸所需的非必需氨基酸。在这里，我们强调白血病干细胞和祖细胞对半胱氨酸消耗的广泛敏感性。通过 CRISPR/Cas9 介导的胱硫醚-γ-裂解酶 (CTH)（胱硫醚到半胱氨酸的转化酶）的敲除，以及通过半胱氨酸上游的代谢物补充研究，我们从功能上证明了急性髓系白血病 (AML) 中的半胱氨酸不是由蛋氨酸合成的细胞。因此，虽然在营养上可能不是必需的，但必须输入半胱氨酸才能使这些特定细胞类型生存。胱氨酸的消耗增加了活性氧（ROS）水平，并且细胞死亡主要是由于谷胱甘肽缺乏而引起的。 NADPH 氧化酶 (NOX) 抑制有力地挽救了半胱氨酸耗尽后的活力，突显其是 AML 中 ROS 的重要来源。 ROS 诱导的细胞死亡是通过铁死亡介导的，而抑制 GPX4（其功能是减少脂质过氧化物）也具有剧毒，因此我们认为 GPX4 可能是介导谷胱甘肽抗氧化活性的关键。同样，用金诺芬抑制 ROS 清除剂硫氧还蛋白还原酶也会损害细胞活力，因此我们发现，特别是 OXPHOS 驱动的 AML 亚型高度依赖于硫氧还蛋白介导的铁死亡保护。虽然用柳氮磺吡啶抑制胱氨酸输入蛋白 xCT 作为单一疗法无效，但其与 L-丁硫氨酸-亚磺酰亚胺 (BSO) 的组合进一步改善了 AML 铁死亡的诱导。我们建议将柳氮磺吡啶或抗氧化机制抑制剂与 ROS 诱导剂（例如 BSO 或化疗）结合使用，以进行进一步的临床前测试。版权所有 © 2023 美国血液学会。

Cysteine is a non-essential amino acid required for protein synthesis, the generation of the anti-oxidant glutathione and for synthesizing the non-proteinogenic amino acid taurine. Here, we highlight the broad sensitivity of leukemic stem and progenitor cells to cysteine depletion. By CRISPR/Cas9-mediated knockout of cystathionine-γ-Lysase (CTH), the cystathionine to cysteine converting enzyme, and by metabolite supplementation studies upstream of cysteine, we functionally prove that cysteine is not synthesized from methionine in acute myeloid leukemia (AML) cells. Therefore, while perhaps nutritionally non-essential, cysteine must be imported for survival of these specific cell types. Depletion of cyst(e)ine increased reactive oxygen species (ROS) levels and cell death was induced predominantly as a consequence of glutathione deprivation. NADPH oxidase (NOX) inhibition strongly rescued viability following cysteine depletion, highlighting this as an important source of ROS in AML. ROS-induced cell death was mediated via ferroptosis, and inhibition of GPX4, which functions to reduce lipid peroxides, was also highly toxic and we therefore propose that GPX4 is likely key in mediating the antioxidant activity of glutathione. In line, inhibition of the ROS scavenger thioredoxin reductase with Auranofin also impaired cell viability, whereby we find that in particular OXPHOS-driven AML subtypes are highly dependent on thioredoxin-mediated protection against ferroptosis. While inhibition of the cystine importer xCT with Sulfasalazine was ineffective as a monotherapy, its combination with L-buthionine-sulfoximine (BSO) further improved AML ferroptosis induction. We propose the combination of either Sulfasalazine or anti-oxidant machinery inhibitors along with ROS inducers such as BSO or chemotherapy for further pre-clinical testing.Copyright © 2023 American Society of Hematology.