The von Hippel-Lindau Tumor Suppressor Gene and Kidney Cancer: Insights into Oxygen Sensing and Treating Cancers Caused by Undruggable Mutations

VHL肿瘤抑制蛋白（pVHL）失活是最常见的肿瘤细胞中通常的起始（“主干”）事件。 肾透明细胞癌（ccRCC）。pVHL形成一种泛素连接酶，其靶向 HIF转录因子降解。HIF 2而不是HIF 1促进ccRCC。与pVHL的结合需要 HIF α亚基被3种氧敏感性EglN脯氨酰羟化酶之一脯氨酰羟化， 是2-酮戊二酸（2-OG）依赖性双加氧酶（如泰特DNA脱甲基酶和KDM组蛋白 脱甲基酶）。IDH突变型癌症积累2-OG竞争者2-羟基戊二酸（2-HG）。我们的工作 有助于开发用于ccRCC的VEGF抑制剂/HIF 2抑制剂和用于IDH的2-HG抑制剂 突变型白血病我们发现沙利度胺重编程cereblon破坏IKZF 1/3骨髓瘤 癌蛋白也引起了人们对小分子降解剂的兴趣。 并非所有ccRCC都对VEGF抑制剂/HIF 2抑制剂有反应，2-HG抑制剂对 IDH突变型神经胶质瘤。合成杀伤力（SL）应该成为此类肿瘤的替代药物靶点的来源，并且 更普遍的是，对于与“不可治愈的”突变相关的癌症。我们已经确定了新的潜在SL交互作用者 对于VHL（CDK 4/6和ITGAV）和突变IDH（DHODH和GSK 3b），现在提出进一步验证， 机械研究。有趣的是，CDK 4/6的伴侣细胞周期蛋白D1是ccRCC中的HIF 2靶点，但SL VHL和CDK 4/6之间的关系不是HIF 2依赖性的。我们还着手在果蝇细胞中进行SL筛选 因为旁腺代偿可能会在人类细胞的基因筛选中导致许多假阴性。 我们创建了一个“向上”筛选，用于筛选可以降解感兴趣的蛋白质的化学物质和基因敲除。我们 用它来发现Spaetron-1是一种不依赖于大脑的IKZF 1降解剂，并正在寻找潜在的 机制我们还将其应用于各种不可药物化的癌蛋白（例如，c-Myc、K-Ras、b-连环蛋白）。 未能下调细胞周期蛋白D1导致VHL-/- ccRCC对pRB中HIF 2抑制剂的耐药性。 独立的方式。我们正在使用生物化学方法来识别相关的细胞周期蛋白D1底物。 我们出乎意料地发现，HIF 1和HIF 2与几乎相同的基因组位点结合，但招募 不同的蛋白质我们正在生物化学和功能测定中验证这些相关蛋白质。我们 还使用底物捕获条件回收非HIF EglN底物和非组蛋白KDM底物。 我们正在继续努力使用CRISPR的体细胞基因编辑来制作HIF 2 - 1的小鼠模型。 依赖性VHL-/- ccRCC。我们还鉴定了新的pVHL依赖性分泌蛋白，包括PTH-LH， 这可能导致在一些ccRCC患者中看到的恶病质和高钙血症。 ccRCC具有高度免疫原性，但原因尚不清楚。我们发现，HIF 2驱动了 许多内源性逆转录病毒，其中一些可以翻译并呈现为HLA结合肽。我们 正在检查其他ccRCC细胞系和肿瘤中的这些肽，以及它们是否具有免疫原性。

VHL tumor suppressor protein (pVHL) inactivation is the usual initiating (“truncal”) event in the most common form of kidney cancer, clear cell renal cell carcinoma (ccRCC). pVHL forms a ubiquitin ligase that targets the HIF transcription factor for degradation. HIF2, but not HIF1, promotes ccRCC. Binding to pVHL requires that the HIFalpha subunit be prolyl hydroxylated by one of the 3 oxygen-sensitive EglN prolyl hydroxylases, which are 2-oxoglutarate (2-OG)-dependent dioxygenases (as are the TET DNA demethylases and KDM histone demethylases). IDH mutant cancers accumulate the 2-OG competitor 2-hydroxyglutarate (2-HG). Our work contributed to the development of VEGF inhibitors/HIF2 inhibitors for ccRCC and 2-HG inhibitors for IDH mutant leukemia. Our discovery that thalidomide reprograms cereblon to destroy the IKZF1/3 myeloma oncoproteins has also galvanized interest in small molecule degraders. Not all ccRCCs respond to VEGF inhibitors/HIF2 inhibitors and 2-HG inhibitors are fairly inactive against IDH mutant gliomas. Synthetic lethality (SL) should be a source of alternative drug targets for such tumors, and more generally, for cancers linked to “undruggable” mutations. We have identified new potential SL interactors for VHL (CDK4/6 and ITGAV) and mutant IDH (DHODH and GSK3b) and now propose further validation and mechanistic studies. Intriguingly, Cyclin D1, the partner for CDK4/6, is a HIF2 target in ccRCC, but the SL between VHL and CDK4/6 is not HIF2-dependent. We also embarked on SL screens in Drosophila cells because paralog compensation likely causes many false-negatives in genetic screens with human cells. We created an “up” screen for chemicals and gene knockouts that can degrade a protein of interest. We used it to discover that Spautin-1 is a cereblon-independent IKZF1 degrader and are pursuing the underlying mechanism. We are also applying it to various undruggable oncoproteins (e.g., c-Myc, K-Ras, b-Catenin). Failure to downregulate Cyclin D1 causes resistance of VHL-/- ccRCC to HIF2 inhibitors in a pRB- independent manner. We are using biochemical approaches to identify the relevant Cyclin D1 substrate(s). We unexpectedly found that HIF1 and HIF2 bind to approximately the same genomic sites, yet recruit different proteins. We are validating these associated proteins in biochemical and functional assays. We are also using substrate-trapping conditions to recover non-HIF EglN substrates and non-histone KDM substrates. We are continuing our efforts to use somatic gene editing with CRISPR to make a murine model of HIF2- dependent VHL-/- ccRCC. We have also identified new pVHL-dependent secreted proteins including PTH-LH, which might cause the cachexia and hypercalcemia seen in some ccRCC patients. ccRCC is highly immunogenic, but the reason is unknown. We found that HIF2 drives the expression of many endogenous retroviruses, some of which can be translated and presented as HLA-bound peptides. We are examining additional ccRCC cell lines and tumors for such peptides and whether they are immunogenic.