HIF-alpha-independent Druggable Targets in Renal Cell Carcinoma

 描述(由申请人提供)： 肾皮质癌被称为肾细胞癌(RCC)，约占所有原发肾脏肿瘤的80%-85%。透明细胞变种占所有RCC的85%，预计2014年美国将导致约6.4万例新病例和约1.4万人死亡。透明细胞肾细胞癌是一种随着年龄增长而增加的疾病，在男性中更常见，因此是退伍军人癌症相关发病率和死亡率的常见来源。这种疾病在晚期转移阶段是致命的。尽管包括小分子酪氨酸激酶抑制剂和雷帕霉素类似物在内的几种新疗法已经获得监管部门的批准，但它们对生存率的总体影响并不大，转移性透明细胞肾癌患者的中位生存期仅为~24个月。遗传性和散发性透明细胞肾癌的分子特征是vonHippel-Lindau(Vhl)抑癌基因的双等位基因失活，该基因是E3泛素连接酶的底物识别单元，以缺氧诱导因子α(HIFα)为靶标，介导蛋白酶的降解。重要的是，超过90%的散发性透明细胞肾细胞癌病例表现出VHL失活。虽然VHL基因的蛋白产物pVHL的表达恢复可以抑制肿瘤的发生，但抑制HIFα的表达、基因替代治疗和开发小分子转录因子抑制物如HIFαS并不容易用于临床翻译。我们提出的研究的首要目标是验证非依赖于缺氧诱导因子的VHL缺失效应作为透明细胞肾癌可行的治疗靶点。具体地说，我们建议产生临床前数据，以确定一种被称为转化生长因子β激活激酶(TAK1)的MAP激酶是药物开发和转化到临床的合适靶点。我们已经证实TAK1驱动c-jun氨基末端激酶(Jnk)和核因子kappaB(nf-B)的激活，在pVHL缺失的RCC中，这两个通路都是促肿瘤和结构性激活的。因此，我们的假设是，TAK1抑制代表了一个潜在的治疗靶点，通过下游激活NF-B和JNK通路来介导肾脏肿瘤的发生。基于这一背景和我们的初步研究，我们提出了三个目标：目的1.建立TAK1抑制在体内外预防和延缓pVHL缺陷性肾癌生长的作用。目的2.阐明在pVHL缺陷细胞中允许同时、结构性地激活核因子-JNK B和通路的潜在分子机制。根据初步研究，我们推测pVHL缺陷的RCC获得的分子适应对于pVHL缺陷细胞正在进行的、结构性的JNK激活至关重要。目的3.建立肾细胞癌患者肾透明细胞癌组织中存在结构性Tak1，同时存在核转录因子B和JNK1激活的机制。作为分子靶标临床前验证过程的关键组成部分，确认相关通路确实在患者标本中以与我们的临床前模型一致的方式激活是至关重要的。 建议的AIMS的成功实施将为验证TAK1作为临床开发的分子靶点奠定基础。TAK1是一种由于VHL丢失而被过度激活的“可药物”激酶。通过这种方式，我们的长期目标是将我们的发现转化为晚期透明细胞肾癌的治疗，这是退伍军人中相对常见的一种恶性肿瘤。

 DESCRIPTION (provided by applicant): Cancers of the renal cortex are known as renal cell carcinomas (RCC) and represent ~80-85% of all primary renal neoplasms. The clear cell variant comprises up to 85% of all RCCs, which are expected to result in ~64,000 new cases and ~14,000 deaths in the U.S. in 2014. Clear cell RCC is a disease that increases with age and is more common in men, and as such represents a common source of cancer-related morbidity and mortality amongst our Veterans. The disease is lethal at the advanced, metastatic stage. Although several novel treatments, including small molecule tyrosine kinase inhibitors and rapamycin analogs, have received regulatory approval, their overall impact on survival is modest, and median survival for patients with metastatic clear cell RCC remains at only ~24 months. The molecular hallmark of hereditary and sporadic clear cell RCC is the biallelic inactivation of the vonHippel-Lindau (VHL) tumor suppressor gene, which is most well characterized for its role as the substrate recognition unit of an E3 ubiquitin ligase that targets hypoxia-inducible factor alpha (HIFα) for proteasomemediated degradation. Importantly, upwards of 90% of sporadic cases of clear cell RCC manifest VHL inactivation. Although restoration of the expression pVHL, the protein product of the VHL gene, suppresses tumorigenesis as does inhibition of HIFα expression, gene replacement therapy and the development of small molecule inhibitors of transcription factors such as HIFα s not readily feasible for clinical translation. The overarching goal of our proposed research is to validate HIF-independent effects of VHL loss as viable therapeutic targets for clear cell RCC. Specifically, we propose to generate the pre-clinical data to establish that a MAP kinase kinase kinase known as transforming growth factor β activated kinase (TAK1), which is hyperactivated in response to pVHL deficiency, is a suitable target for drug development and translation into the clinic. We have already established that TAK1 drives the activation of the c-Jun N-terminal kinase (JNK) and nuclear factor kappa B (NF-B) pathways, both of which are pro-tumorigenic and constitutively activated in pVHL-deficient RCCs. Thus, our hypothesis is that TAK1 inhibition represents a potential therapeutic target that mediates renal oncogenesis through downstream activation of the NF-B and JNK pathways. Based on this background and our preliminary studies, many of which have been published, we have proposed three aims: Aim 1. To establish that TAK1 inhibition prevents and retards the growth of pVHL-deficient RCCs in vitro and in vivo. Aim 2. To elucidate the underlying molecular mechanisms that are permissive for concurrent, constitutive activation of the NF-B and JNK pathways in pVHL-deficient cells. Based on preliminary studies, we postulate that molecular adaptations acquired by pVHL-deficient RCCs are critical to the ongoing, constitutive JNK activation that characterizes pVHL-deficient cells. Aim 3. To establish that constitutive TAK1 and concurrent NF-B and JNK activation occur in clear cell RCC patient specimens. As a critical component to the process of pre-clinical validation of a molecular target, it is vital to confirm that the relevant pathways ar indeed activated in patient specimens in a fashion that is consistent with our pre-clinical models. Successful execution of the proposed aims will lay the groundwork for the validation of TAK1, a "druggable" kinase that is hyperactivated as a consequence of VHL loss, as a molecular target for clinical development. In this fashion, our long-term goal is to translate our findings to the management of advanced clear cell RCC, a relatively common malignancy amongst our Veterans.