Cysteine Depletion-induced Ferroptosis as a Therapeutic Vulnerability i

胶质母细胞瘤是最恶性和最常见的原发于成人的脑肿瘤。 令人沮丧的中位总生存期为14至16个月。2005年，Stupp方案改变了临床 注意发现化疗药物替莫唑胺(TMZ)，加上 手术和放射治疗可以延长患者的存活期。然而，新的治疗途径已经 仍然停滞不前，没有二线治疗选择显示出显著改善 在复发的基底膜肿瘤中，对TMZ的耐药性通常是致命的。为此，我们试图更好地 了解TMZ耐药疾病的分子机制为患者提供潜在的 二线治疗方案，重点是半胱氨酸耗竭所致的TMZ铁下垂- 抗性GBM。铁下垂是一种铁依赖的细胞死亡形式，最近获得了 关注是根除抗药性癌细胞的一个有吸引力的途径。我们的 初步数据支持一种以前未确定的代谢酶在 诱导半胱氨酸耗竭所致的铁性下垂。我们的发现强烈表明伽马 (γ)-谷氨酰基酶(γ-谷氨酰环转移酶；GGCT)回收半胱氨酸，防止 谷胱甘肽的产生--γ-谷氨酰途径的主要目标。我们进一步表明， TMZ耐药细胞的变化与对铁下垂诱导的敏感性一致，如 活性氧(ROS)、半胱氨酸摄取和半胱氨酸/谷氨酸逆向转运体增加 -XCT，以及错位的核周线粒体。因此，我们试图改变用途 Ebselen，一种以前被描述为神经保护剂的药物，被认为是谷胱甘肽 过氧化物酶4(Gpx4)是一种模拟酶，但最近因其硒离子能够 共价结合半胱氨酸。我们发现神经保护剂ebselen已经 已被证明可以跨越血脑屏障--治疗GBM的一个主要障碍--特别是 体外靶向耐TMZ的GBM细胞。基于这些结果，我们建议进一步研究 半胱氨酸通过GGCT循环的作用及其作为治疗易损性的治疗潜力 在患者来源的异种移植(PDX)中，抗TMZ的GBM原位临床前动物模型。 最后，我们试图通过一种方法建立这种异常的半胱氨酸循环的预后生物标志物。 临床胶质瘤标本中GGCTs酶活性的代谢副产物。总体而言，这 该提案将为耐药的GBM提供一种诱导铁下垂的新途径，以及 可能为其他耐药患者半胱氨酸剥夺所致的铁性下垂铺平道路 癌症。

Glioblastoma is the most malignant and commonly diagnosed primary brain tumor in adults with a dismal median overall survival of 14 to 16 months. In 2005 the Stupp regimen changed clinical care with the discovery that the chemotherapeutic drug temozolomide (TMZ), with the addition of surgery and radiation, could extend patient survival. However, new therapeutic avenues have remained stagnant and with no second-line therapeutic options showing significant improvement in recurrent GBM tumors, resistance to TMZ is uniformly fatal. To this end we sought to better understand the molecular mechanisms of TMZ-resistant disease to provide patients a potential second-line therapeutic option with a focus on cysteine depletion-induced ferroptosis in TMZ- resistant GBM. Ferroptosis is an iron-dependent form of cell death which has recently gained attention as an attractive avenue to eradicate otherwise drug resistant cancer cells. Our preliminary data support the role of a previously uncharacterized metabolic enzyme in the induction of cysteine depletion-induced ferroptosis. Our findings strongly suggest that the gamma (γ)-glutamyl enzyme (γ-glutamylcyclotransferase; GGCT) recycles cysteine and prevents glutathione (GSH) production – the main goal of the γ-glutamyl pathway. We further show that TMZ-resistant cells have changes consistent with a sensitivity to ferroptosis induction such as an increase in reactive oxygen species (ROS), cysteine uptake and the cysteine/glutamate antiporter – xCT, as well as mislocalized perinuclear mitochondria. Therefore, we sought to repurpose ebselen, a previously characterized neuroprotective agent that was thought to be a glutathione peroxidase 4 (GPX4) mimetic but has recently garnered attention for its selenium ion’s ability to covalently bind cysteines. We show that the neuroprotective agent ebselen which has already been shown to cross the blood brain barrier – a major hurdle for GBM treatment – specifically targets TMZ-resistant GBM cells in vitro. Based on these results, we propose to further investigate the role of cysteine recycling via GGCT and its therapeutic potential as a treatment vulnerability in patient-derived xenograft (PDX) TMZ-resistant GBM orthotopic pre-clinical animal models. Lastly, we seek to establish prognostic biomarkers of this aberrant cysteine recycling through a metabolic byproduct of GGCTs enzymatic activity in clinical glioma specimens. Overall, this proposal will give insight into a new avenue of ferroptosis induction in drug resistant GBM, and potentially pave the way for cysteine deprivation-induced ferroptosis in other drug resistant cancers.