Role of FH loss in development of HLRCC heriditary kidney cancer

具有半合子生殖系富马酸水合酶（FH）突变的个体易患肾癌。这些肿瘤主要表现出剩余野生型等位基因的功能性失活，暗示FH失活是肿瘤促进事件。缺氧诱导因子在许多癌症中表达，在透明细胞肾癌中表达增加。在常氧条件下，HIF由于依赖于VHL的蛋白酶体降解而不稳定，但在缺氧条件下，由于HIF脯氨酰羟化酶（HPH）失活而稳定，这阻止了HIF羟化和VHL识别。我们证明FH抑制，连同细胞内富马酸升高，与HIF上调相一致。此外，我们表明富马酸作为HPH的竞争性抑制剂。这些数据描述了一种新的富马酸依赖途径来调节HPH活性和HIF蛋白水平。此外，我们证明了在hlrcc来源的细胞系中FH的失活突变导致葡萄糖介导的细胞活性氧（ROS）的产生和ROS依赖的hif -1 α稳定。此外，我们还发现，在永活肾上皮细胞中，FH的稳定下调导致ros依赖性hif -1 α的稳定。这些数据表明，hhrcc中存在的专性糖酵解开关对通过ROS生成稳定HIF至关重要。我们还表明，这些细胞的专性糖酵解性质使它们对葡萄糖上瘾，并上调HSF1转录活性。我们已经确定了一种天然产物，englerin a，具有独特的抗肾癌活性，作为这些细胞中胰岛素信号传导和葡萄糖摄取的抑制剂。我们已经证明，englerin A活性的机制涉及蛋白激酶C δ的激活，使HSF1和IRS1磷酸化。

Individuals with hemizygous germline fumarate hydratase (FH) mutations are predisposed to renal cancer. These tumors predominantly exhibit functional inactivation of the remaining wild-type allele, implicating FH inactivation as a tumor-promoting event. Hypoxia-inducible factors are expressed in many cancers and are increased in clear cell renal carcinomas. Under normoxia, the HIFs are labile due to VHL-dependent proteasomal degradation, but stabilization occurs under hypoxia due to inactivation of HIF prolyl hydroxylase (HPH), which prevents HIF hydroxylation and VHL recognition. We demonstrate that FH inhibition, together with elevated intracellular fumarate, coincides with HIF upregulation. Further, we show that fumarate acts as a competitive inhibitor of HPH. These data delineate a novel fumarate-dependent pathway for regulating HPH activity and HIF protein levels. Additionally, we demonstrate that inactivating mutations of FH in an HLRCC-derived cell line result in glucose-mediated generation of cellular reactive oxygen species (ROS) and ROS-dependent HIF-1alpha stabilization. Further, we have found that stable knockdown of FH in immortalized renal epithelial cells results in ROS-dependent HIF-1alpha stabilization. These data reveal that the obligate glycolytic switch present in HLRCC is critical to HIF stabilization via ROS generation. We have also shown that the obligate glycolytic nature of these cells adicts them to glucose and to upregulated HSF1 transcriptional activity. We have identified a natural product, englerin A, with unique activity against kidney cancer, as an inhibitor of insulin signaling and glucose uptake in these cells. We have shown that the mechanism underlying this activity of englerin A involves activation of protein kinase C delta to phosphorylate HSF1 and IRS1.