Ferroptosis, a form of iron-dependent cell death driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated as a tumor-suppressor function for cancer therapy. Recent advance revealed that the sensitivity to ferroptosis is tightly linked to numerous biological processes, including metabolism of amino acid and the biosynthesis of glutathione. Here, by using a high-throughput CRISPR/Cas9-based genetic screen in HepG2 hepatocellular carcinoma cells to search for metabolic proteins inhibiting ferroptosis, we identified a branched-chain amino acid aminotransferase 2 (BCAT2) as a novel suppressor of ferroptosis. Mechanistically, ferroptosis inducers (erastin, sorafenib, and sulfasalazine) activated AMPK/SREBP1 signaling pathway through iron-dependent ferritinophagy, which in turn inhibited BCAT2 transcription. We further confirmed that BCAT2 as the key enzyme mediating the metabolism of sulfur amino acid, regulated intracellular glutamate level, whose activation by ectopic expression specifically antagonize system Xc^– inhibition and protected liver and pancreatic cancer cells from ferroptosis in vitro and in vivo. On the contrary, direct inhibition of BCAT2 by RNA interference, or indirect inhibition by blocking system Xc^– activity, triggers ferroptosis. Finally, our results demonstrate the synergistic effect of sorafenib and sulfasalazine in downregulating BCAT2 expression and dictating ferroptotic death, where BCAT2 can also be used to predict the responsiveness of cancer cells to ferroptosis-inducing therapies. Collectively, these findings identify a novel role of BCAT2 in ferroptosis, suggesting a potential therapeutic strategy for overcoming sorafenib resistance.

铁死亡是一种由细胞代谢和铁依赖性脂质过氧化驱动的铁依赖性细胞死亡形式，已被认为是癌症治疗的肿瘤抑制功能。最近的进展表明，对铁死亡的敏感性与许多生物过程密切相关，包括氨基酸的代谢和谷胱甘肽的生物合成。在这里，通过在 HepG2 肝细胞癌细胞中使用基于 CRISPR/Cas9 的高通量基因筛选来寻找抑制铁死亡的代谢蛋白，我们确定了一种支链氨基酸氨基转移酶 2 (BCAT2) 作为一种新型的铁死亡抑制剂。从机制上讲，铁死亡诱导剂（erastin、索拉非尼和柳氮磺吡啶）通过铁依赖性铁蛋白吞噬激活 AMPK/SREBP1 信号通路，进而抑制 BCAT2 转录。^–在体外和体内抑制和保护肝脏和胰腺癌细胞免于铁死亡。相反，通过 RNA 干扰直接抑制 BCAT2，或通过阻断系统 Xc活性间接抑制，会引发铁死亡^。最后，我们的结果证明了索拉非尼和柳氮磺吡啶在下调 BCAT2 表达和指示铁死亡方面的协同作用，其中 BCAT2 也可用于预测癌细胞对铁死亡诱导疗法的反应。总的来说，这些发现确定了 BCAT2 在铁死亡中的新作用，表明了克服索拉非尼耐药性的潜在治疗策略。