Iron, Ferroptosis and Ovarian Cancer

总结 在美国，卵巢癌导致的死亡人数比任何其他妇科癌症都多。的悲观预测 在过去的30年里，晚期疾病患者的情况几乎没有变化。需要采取新的办法。 在上一个资助周期中，我们的实验室发现卵巢肿瘤细胞和卵巢癌肿瘤启动 细胞（“癌症干细胞”）获得并保留比其非恶性对应物多得多的铁- 我们称之为“铁瘾”。这种增强的铁的获取和保留促进了 卵巢癌然而，我们发现这种增强的铁保留也使卵巢癌细胞 对引发铁凋亡的药物敏感，这是一种依赖铁的细胞死亡形式。 尽管铁是铁下垂的核心，但人们对铁如何实际赋予这种易感性知之甚少。在这 应用，我们测试的假设，铁起着关键的，新颖的，以前未描述的作用， 铁凋亡，我们最近发现的铁凋亡途径中的新靶点可能导致 卵巢癌的治疗方法我们以两个广泛的目标来处理这个问题：1）更好地 了解铁在铁凋亡中的作用; 2）确定将增强铁活性的特定靶点。 通过在卵巢癌本身和卵巢癌组织中促进促铁凋亡途径， 卵巢癌微环境 我们的具体目标是针对这些目标。在目标1中，我们进行了初步观察， 触发信号网络，促进多不饱和脂质过氧化物（近端 铁性上睑下垂的“刽子手”）。我们认为铁凋亡是通过以下两种途径传播的：1）转录激活， 增加不稳定铁的铁依赖性促铁蛋白，和2）前馈环的接合， 使我们最近发现的铁依赖性脂质去饱和酶SCD 1失效，该酶可防止铁凋亡。我们 将使用细胞培养以及卵巢癌小鼠模型来验证我们的假设。在目标2中，我们使用状态- 最先进的NanoSIMS成像和MALDI-MSI来探测铁凋亡死亡信号的起源位点， 使铁与氧化脂质一起定位，这是典型的铁凋亡症。我们证实并扩大这些发现， 细胞器靶向铁螯合剂。在目标3中，我们评估了卵巢肿瘤微环境中的细胞如何改变 卵巢癌对诱导铁凋亡的药物的反应。我们专注于巨噬细胞和成纤维细胞， 我们在初步研究中发现，卵巢癌转移中的关键细胞， 旁分泌对脂质和铁代谢的影响，显著影响卵巢中铁下垂的程度 癌细胞 总的来说，这些实验将提高对卵巢癌铁代谢的认识，探索铁代谢的调控机制， 以前与铁凋亡无关的途径，并定义了肿瘤微环境对铁凋亡的贡献。 ferroptosis -努力将有助于指导更有效地使用ferroptosis诱导剂在卵巢癌治疗。

Summary Ovarian cancer causes more deaths than any other gynecologic cancer in the US. The dismal prognosis of patients with advanced disease remains little changed in the past 30 years. New approaches are needed. In the last grant cycle, our laboratory discovered that ovarian tumor cells and ovarian cancer tumor-initiating cells (`cancer stem cells') acquire and retain substantially more iron than their non-malignant counterparts – a phenomenon we named “iron addiction”. This enhanced iron acquisition and retention facilitates growth of ovarian cancer. However, we found that this enhanced iron retention also makes ovarian cancer cells exquisitely susceptible to drugs that trigger ferroptosis, an iron-dependent form of cell death. Although iron is central to ferroptosis, little is known about how iron actually confers this susceptibility. In this application, we test the hypothesis that iron plays critical, novel, and previously undescribed roles in ferroptosis, and that new targets in the ferroptosis pathway that we recently discovered might lead to successful interventions in ovarian cancer. We approach this problem with two broad objectives: 1) to better understand the role of iron in ferroptosis; 2) to identify specific targets that will enhance the activity of ferroptosis inducers by fostering pro-ferroptotic pathways both in ovarian cancers themselves and in the ovarian cancer microenvironment. Our Specific Aims are directed at these goals. In Aim 1, we pursue pilot observations that ferroptosis inducers trigger a signaling network that fosters the generation of polyunsaturated lipid peroxides (the proximal `executioners' of ferroptosis). We propose that ferroptosis is propagated by both 1) transcriptional activation of iron-dependent pro-ferroptotic proteins that increase labile iron, and 2) engagement of a feed forward loop that disables the iron-dependent lipid desaturase SCD1 that we recently showed protects against ferroptosis. We will test our hypothesis using cell culture as well as murine models of ovarian cancer. In Aim 2, we use state- of-the-art NanoSIMS imaging and MALDI-MSI to probe the sites of origin of the ferroptotic death signal, co- localizing iron with the oxidized lipids that typify ferroptosis. We confirm and expand these findings using organelle-targeted iron chelators. In Aim 3, we assess how cells in the ovarian tumor microenvironment modify the response of ovarian cancers to drugs that induce ferroptosis. We focus on macrophages and fibroblasts, cells that are critically involved in ovarian cancer metastasis, which we discovered in pilot studies exert paracrine effects on lipid and iron metabolism that dramatically affect the degree of ferroptosis in ovarian cancer cells. Collectively, these experiments will enhance knowledge of ovarian cancer iron metabolism, explore regulatory pathways not previously linked to ferroptosis, and define the contribution of the tumor microenvironment to ferroptosis - efforts that will help to direct more effective use of ferroptosis inducers in ovarian cancer therapy.