Hypoxia and Anticancer Drug Action

描述（由申请人提供）：实体瘤存在于细胞生长的应激环境中。即使是最小的肿瘤生长，它们也会迅速超过新血管的形成，导致灌注不良和缺氧。由缺氧诱导的基因允许癌细胞通过切换到无氧代谢来适应恶劣的缺氧环境，减少整体蛋白质合成，引起对细胞死亡的抵抗，产生增加从现有脉管系统形成新血管（血管生成）的因子，并增加转移。肿瘤细胞还经常发展调节低氧应激反应的基因的组成性上调。这些组成性和适应性变化使肿瘤具有侵袭性，对放疗和化疗具有抗性，并导致患者预后不良。低氧应激反应是胚胎发育早期的正常生理过程，但在灌注良好的正常成体组织中作用有限。尽管这些变化导致了侵袭性的耐药肿瘤，但它们也为选择性攻击肿瘤提供了致命弱点，因为没有它们，癌细胞就会死亡。因此，我们的研究所基于的假设是，了解调节肿瘤对缺氧应激的反应的途径及其对肿瘤生长的影响，将提供新的靶点和选择性治疗癌症的药物的开发。研究最多的介导癌细胞对缺氧的反应的机制是缺氧诱导因子-1（HIF-11）转录因子水平的增加。我们提供的证据表明，一个新的途径HIF-11的调节内质网（ER）未折叠蛋白反应（UPR）介导的HIF-11和其他应激蛋白在缺氧的合成。我们还鉴定了HAF/SART-1介导的HIF-11降解的一种新的氧非依赖性途径，我们已经证明HAF/SART-1是HIF-11的一种新的E3泛素连接酶。我们将研究HAF/SART-1诱导的HIF-11降解的机制和调控，为治疗干预提供新的靶点。有足够的临床和实验证据表明，HIF-11独立的机制，维持肿瘤生长的缺氧。已知尽管在缺氧期间蛋白质翻译被普遍抑制，但HIF-11和其它应激存活蛋白的合成被维持或甚至增加。了解这种机制可以提供新的药物靶点来抑制肿瘤对缺氧的生存反应。我们研究的总体目标是了解有助于在缺氧中维持肿瘤生长的机制，涉及HIF-11和其他应激蛋白，这将为治疗癌症提供新的药物靶点和治疗策略。

DESCRIPTION (provided by applicant): Solid tumors exist in a stressed environment for cell growth. As even the smallest tumors grow they rapidly outstrip new blood vessel formation leading to poor perfusion and hypoxia. Genes induced by hypoxia allow the cancer cell to adapt to the hostile hypoxic environment by switching to anaerobic metabolism, decreasing overall protein synthesis, causing resistance to cell death, producing factors that increase the formation of new blood vessels from the existing vasculature (angiogenesis), and increased metastasis. Tumor cells also frequently develop constitutive upregulation of genes that regulate the hypoxic stress response. These constitutive and adaptive changes make tumors aggressive, resistant to radiation and chemotherapy, and lead to a poor patient prognosis. The hypoxic stress response is a normal physiological process employed in the early stages of embryogenesis but with a limited role in well perfused normal adult tissues. Although the changes result in aggressive, drug-resistant tumors they also provide an Achilles heel for selectively attacking the tumor, because without them the cancer cells will die. Thus, the hypothesis upon which our studies are based is that understanding the pathways that regulate the tumor's response to the stress of hypoxia and the consequences this has for tumor growth, will provide novel targets and the development of agents to selectively treat cancer. The most studied mechanism mediating the cancer cell's response to hypoxia is an increase in the levels of the hypoxia inducible factor-1 (HIF-11) transcription factor. We provide evidence for a new pathway of HIF-11 regulation by the endoplasmic reticulum (ER) unfolded protein response (UPR) that mediates the synthesis of HIF-11 and other stress proteins in hypoxia. We have also identified a novel oxygen independent pathway for HIF-11 degradation mediated by HAF/SART-1 which we have shown to be a novel E3 ubiquitin ligase for HIF-11. We will investigate the mechanisms and regulation of the HAF/SART-1-induced degradation of HIF-11 to provide novel targets for therapeutic intervention. There is ample clinical and experimental evidence for a HIF-11 independent mechanism for maintaining tumor growth in hypoxia. It is known that despite a general inhibition of protein translation during hypoxia the synthesis of HIF-11 and of other stress survival proteins is maintained or even increased. Understanding this mechanism could provide novel drug targets to inhibit the tumor's survival response to hypoxia. The overall goal of our studies is to understand mechanisms that contribute to the maintenance of tumor growth in hypoxia, involving both HIF-11 and other stress proteins that will provide new drug targets and therapeutic strategies for treating cancer.