Rewired Signaling at the Nexus of Melanoma Metastasis and Resistance

 描述(申请人提供)：恶性细胞持续暴露于外在(低氧、有限的营养获取、免疫监视)和内在(致癌)应激，最终导致低氧和内质网应激(ERS)反应程序的激活。肿瘤细胞对这些挑战的适应既依赖于遗传机制(获得新的突变)，也依赖于表观遗传机制(基因表达的调节)，这些机制构成了肿瘤生存、转移和治疗抵抗的基础；也称为可塑性。在过去的二十年里，我的实验室一直专注于了解细胞应激反应，特别是激酶和泛素连接酶的作用。我们的研究建立了一些应激适应的范例，对黑色素瘤和前列腺癌的发展、进展和耐药性都具有重要意义。我们定义了亚细胞定位如何决定ATF2的致癌或肿瘤抑制活性，并表明这是由AGC激酶PKC调节的。基于这一发现，我们根据改变的亚细胞定位对这种转录因子的抑制剂进行了筛选-表面上看是不可下药的靶点。我们最近发现的另一种ATF2剪接形式具有功能增益表型，这将使我们能够进一步重新定义ATF2在黑色素瘤中的功能。此外，我们确定了ERK影响JNK并伴随着对AGC激酶的主要调节因子PDK1的影响的一种重新连接的信号机制。这使得我们证明了PDK1在黑色素瘤中所起的关键作用。我们未来的研究将继续研究PDK1及其下游靶点如何与黑色素瘤转移和耐药性有关。我们发现泛素连接酶Siah1/2控制缺氧反应，揭示了它们在黑色素瘤和最具侵袭性的前列腺癌中的作用。Siah1/2还控制应激反应信号，建立了一种在缺血条件下承诺细胞死亡的机制。这为我们开发和评估针对前列腺癌和黑色素瘤转移和耐药性的一流SIAH抑制剂奠定了基础。我们最近还确定RNF5泛素连接酶调节自噬和谷氨酰胺代谢，并建立了一种新的方法来对乳腺癌患者进行分层以选择治疗方案。最后，RNF125泛素连接酶是黑色素瘤抵抗BRAF抑制剂的关键调节因子，这一发现将推动对胰腺癌的研究，其中一小部分携带突变 RNF125。总而言之，我们的发现揭示了肿瘤细胞对压力的反应，这是它们可塑性的基础，涉及到重新连接信号和遗传损伤之间的合作。我们提出的研究将建立肿瘤可塑性的新机制，使预测、监测和预防肿瘤转移和耐药的新药物的开发成为可能。

 DESCRIPTION (provided by applicant): Malignant cells are continuously exposed to extrinsic (hypoxia, limited access to nutrients, immune surveillance) and intrinsic (oncogenic insults) stresses that culminate in activation of the hypoxia and endoplasmic reticulum stress (ERS) response programs. Tumor cell adaptation to these challenges depends on both genetic (acquisition of new mutations) and epigenetic (modulation of gene expression) mechanisms that underlie tumor survival, metastasis, and resistance to therapy; also known as plasticity. Over the past two decades, my lab has focused on understanding the cellular stress response, particularly the contribution of kinases and ubiquitin ligases. Our studies established a number of paradigms in stress adaptation, with demonstrated significance for the development, progression, and drug resistance of both melanoma and prostate cancer. We defined how subcellular localization dictates the oncogenic or tumor suppressor activity of ATF2, and showed that this is regulated by the AGC kinase PKC. Based on this discovery we performed a screen for inhibitors of this transcription factor-ostensibly undruggable targets- based on altered subcellular localization. Our other recent discovery of a spliced form of ATF2 that exhibits a gain-of-function phenotype will enable us to further redefine the function of ATF2 in melanoma. Further, we identified a mechanism of rewired signaling in which ERK impacts JNK with concomitant effects on PDK1, the master regulator of AGC kinases. This led us to demonstrate the key role played by PDK1 in melanoma. Our future studies will continue to investigate how PDK1 and its downstream targets contribute to melanoma metastasis and drug resistance. Our discovery that the ubiquitin ligases Siah1/2 control the hypoxia response revealed their roles in melanoma and the most aggressive forms of prostate cancer. Siah1/2 also control stress response signaling, establishing a mechanism for commitment to cell death under ischemic conditions. This established the basis upon which we will develop and evaluate first-in-class Siah inhibitors for prostate cancer and melanoma metastasis and resistance. We also recently determined that the RNF5 ubiquitin ligase regulates both autophagy and glutamine metabolism and established a new method to stratify breast cancer patients to select therapies. Lastly, the discovery that RNF125 ubiquitin ligase is a key regulator of melanoma resistance to BRAF inhibitors will drive an investigation in pancreatic cancer, a fraction of which carry mutated RNF125. Collectively, our discoveries reveal that the tumor cell response to stress, which underlies their plasticity, involves the cooperation between rewired signaling and genetic lesions. Our proposed studies will establish novel mechanisms underlying tumor plasticity, enabling the development of novel agents for predicting, monitoring, and preventing tumor metastasis and resistance.