A novel approach for the selective inhibition of HIF-2a in kidney cancer

透明细胞型肾细胞癌是最常见和最具侵袭性的肾癌， 是对治疗最抗拒的实体肿瘤之一。CcRCC通常通过停用VON来启动 Hippel Lindau(VHL)肿瘤抑制基因，导致低氧诱导的结构性激活 因子：低氧诱导因子-1α和低氧诱导因子-2α。肾细胞癌的进展是由低氧诱导因子-2α唯一驱动的，而低氧诱导因子-1α起肿瘤作用 抑制者角色。因此，HIF-2α是治疗肾细胞癌的一个有吸引力的靶点。通过高吞吐量 筛选活动中，我们已经鉴定了一系列选择性降低HIF-2α蛋白和 活性，而不影响缺氧诱导因子-1α。我们发现这些化合物通过增强铁的结合而起作用。 调节蛋白-1对缺氧诱导因子-2α5‘非翻译区中铁反应元件的作用 抑制缺氧诱导因子-2α的翻译。使用无偏见的全球蛋白质组筛选，我们确认了铁-硫 簇组装2(ISCA2)作为这些化合物的分子靶标。ISCA2规定成立为 铁-硫簇形成IRP-1，调节其IRE结合活性。ISCA2是非转录的 由低氧诱导，是pVHL的假定靶点，提示ISCA2可能发挥低氧-或ccRCC- 特定的角色。我们观察到，与配对相比，ISCA2和细胞铁在ccRCC中均上调 肾功能正常，与肾功能显著相关。抑制IscA2选择性降低HIF-2α蛋白 而不影响HIF-1α，并且不依赖于HIF-2α来消耗细胞内的铁。值得注意的是，通过抑制ISCA2 小分子抑制CCRCC移植瘤生长，减少瘤内HIF-2α蛋白表达。因此，我们的 假说是：ISCA2在促进HIF-2α和驱动细胞铁的升高方面起着中心作用 CcRCC进展。因此，ISCA2的靶向为特异性抑制HIF提供了一种新的策略。 2α和细胞铁耗竭治疗肾细胞癌“。我们的首要目标是找出 低氧诱导IscA_2的表达及其在HIF-2、α和铁调节中的作用 慢性肾细胞癌中的代谢。我们的第二个目标是研究ISCA2调制对ccRCC的影响 使用体外和体内模型的进展，并使用临床来确定其生理相关性 人肾细胞癌样本(取自600名患者)。我们的第三个目标是调查 抑制IscA2对缺氧诱导因子-2α和胞浆铁的影响及其在治疗中的应用 Ccrcc。我们研究的总体目标是确定ISCA2、HIF-2α和 铁代谢的放松有助于CRCC的进展；并确定ISCA2抑制是否 将为慢性肾癌患者带来更多的治疗益处。

Clear cell type renal cell carcinoma (CCRCC) is the most common and aggressive form of kidney cancer, and is among the most resistant of solid tumors to therapy. CCRCC is typically initiated by inactivation of the von Hippel Lindau (VHL) tumor suppressor gene, resulting in the constitutive activation of the hypoxia inducible factors, HIF-1α and HIF-2α. CCRCC progression is uniquely driven by HIF-2α, whereas HIF-1α plays a tumor suppressor role. Thus, HIF-2α is an attractive therapeutic target for CCRCC. Through a high throughput screening campaign, we have identified a series of compounds that selectively decrease HIF-2α protein and activity without affecting HIF-1α. We show that these compounds act by enhancing the binding of iron regulatory protein (IRP)-1 to the iron-responsive element (IRE) within the 5' untranslated region of HIF-2α mRNA, which inhibits HIF-2α translation. Using an unbiased global proteomic screen, we confirm Iron-sulfur Cluster Assembly 2 (ISCA2) as the molecular target of these compounds. ISCA2 regulates the incorporation of the iron-sulfur cluster into IRP-1, which modulates its IRE-binding activity. ISCA2 is non-transcriptionally induced by hypoxia, and is a putative pVHL target, suggesting that ISCA2 may play a hypoxia- or CCRCC- specific role. We observe that both ISCA2 and cellular iron are upregulated in CCRCC compared to paired normal kidney, and are significantly correlated. Inhibition of ISCA2 selectively decreases HIF-2α protein without affecting HIF-1α, and depletes cellular iron independently of HIF-2α. Significantly, ISCA2 inhibition by small molecules inhibits CCRCC xenograft growth, and decreases intra-tumoral HIF-2α protein. Thus, our hypothesis is that “ISCA2 plays a central role in promoting the elevation of HIF-2α and cellular iron that drive CCRCC progression. Hence, the targeting of ISCA2 provides a novel strategy for the specific inhibition of HIF- 2α and depletion of cellular iron for the treatment of CCRCC”. Our first aim is to identify the mechanisms mediating ISCA2 induction in hypoxia; and to characterize its role in the regulation of HIF-2α and iron metabolism in CCRCC. Our second aim is to investigate the impact of ISCA2 modulation on CCRCC progression using in vitro and in vivo models, and to determine its physiological relevance using clinical samples of human CCRCC (samples from 600 patients obtained). Our third aim is to investigate the therapeutic impact of ISCA2 inhibition on HIF-2α and cytoplasmic iron, and to explore its use for the treatment of CCRCC. The overall goal of our studies is to identify the mechanisms by which ISCA2, HIF-2α and the deregulation of iron metabolism contribute to CRCC progression; and to determine whether ISCA2 inhibition will yield increased therapeutic benefit for patients with CCRCC.