Proteasome Inhibition and ER Stress

描述（由申请方提供）：目前正在评价基于蛋白酶体抑制剂（PI）的联合化疗用于治疗胰腺癌和其他实体恶性肿瘤。我们的假设是PI引起癌细胞中的内质网（ER）应激，这种应激介导细胞杀伤。此外，我们已经获得了初步证据表明，PI对细胞死亡的影响是高度异质性的，并与它们是否诱导eIF 21磷酸化有关，eIF 21是介导抑制全球蛋白质合成的未折叠蛋白反应（UPR）的一个组成部分。具体而言，PI促进对PI诱导的细胞凋亡具有相对抗性的细胞系中eIF 21磷酸化的强烈磷酸化，但它们在最敏感的细胞系中不能这样做（或减弱翻译）。确定这种异质性的生物化学基础可以使前瞻性识别的肿瘤是最有可能响应PI为基础的联合化疗，并应产生新的治疗干预的目标。我们还希望更好地定义参与细胞凋亡的分子机制，所述细胞凋亡是由最有前途的基于PI的组合方案之一诱导的，即硼替佐米加组蛋白脱乙酰酶（HDAC）抑制剂的组合。我们已经获得了很好的初步证据，HDAC抑制剂促进蛋白酶体介导的细胞凋亡，破坏细胞保护结构称为侵略者，似乎起到缓解ER压力。基因沉默研究已经证明，负责攻击性基因组破坏的HDAC是HDAC 6，并且可能的是，更有选择性的HDAC 6抑制剂将产生比泛HDAC抑制剂（如SAHA）相当或更好的肿瘤细胞杀伤，具有更低的毒性。为了直接验证我们的假设，我们提出了以下具体目标。(1)定义控制硼替佐米诱导eIF 21磷酸化的分子机制。我们将测试的假设，PI抑制PERK激活诱导表达的分子伴侣（HSP 70？）阻断药物敏感细胞中PERK的同质聚集;（2）确定ER应激在PI诱导的细胞凋亡中的作用。在此，我们将评估ROS、Ca 2+、JNK、Noxa和半胱天冬酶-4对PI诱导的细胞凋亡的贡献;（3）：确定在异种移植物中PI和HDAC抑制剂的组合疗法的毒性和抗肿瘤功效。我们将比较PI加SAHA（一种泛HDAC抑制剂）、tubacin（HDAC 6选择性）或SNDX-275（I型HDAC特异性）的联合治疗在体外和来源于敏感和耐药细胞系的原位肿瘤中的效果。我们还将研究是否可以在这些动物的外周血中测量药物-靶点相互作用和生物学反应的药效学标志物，并将这些方法应用于在胰腺癌患者的II期临床试验中测量硼替佐米加SAHA治疗的效果。 公共卫生相关性：临床试验已经证明，常规和研究性癌症疗法的效果是显著异质的，并且目前正在努力将疗法与与对它们的响应性相关的特定分子特征相匹配，以更好地利用它们的效果（“个性化医学”）。本文提出的研究的总体目标是更好地了解两类有前途的研究性癌症治疗（蛋白酶体抑制剂和组蛋白脱乙酰酶抑制剂）诱导的细胞杀伤机制，以便在临床前模型中注意到的这些药物的有前途的作用可以在患者中得到最好的利用。我们将直接比较两种蛋白酶体抑制剂和三种HDAC抑制剂的效果，这些抑制剂要么已经获得FDA批准，要么正在临床试验中进行评估，要么正在开发用于人类临床应用，在我们的第三个具体目标，我们将开发和应用药效学测定来测量药物-靶向相互作用和有效药物靶向的生物学后果，在患者的II期临床试验的背景下。

DESCRIPTION (provided by applicant): Proteasome inhibitor (PI)-based combination chemotherapy is currently being evaluated for the treatment of pancreatic cancer and other solid malignancies. Our hypothesis is that PIs cause endoplasmic reticular (ER) stress in cancer cells and this stress mediates cell killing. Furthermore, we have obtained preliminary evidence that the effects of PIs on cell death are highly heterogeneous and are linked to whether or not they induce phosphorylation of eIF21, a component of the unfolded protein response (UPR) that mediates suppression of global protein synthesis. Specifically, PIs promote strong phosphorylation of eIF21 phosphorylation in the cell lines that are relatively resistant to PI-induced apoptosis, but they fail to do so (or attenuate translation) in the cell lines that are most sensitive. Identifying the biochemical basis for this heterogeneity could enable the prospective identification of tumors that are most likely to respond to PI-based combination chemotherapy and should yield new targets for therapeutic intervention. We also wish to better define the molecular mechanisms involved in the apoptosis that is induced by one of the most promising PI-based combination regimens, namely, the combination of bortezomib plus histone deacetylase (HDAC) inhibitors. We have obtained good preliminary evidence that HDAC inhibitors promote proteasome inhibitor-mediated apoptosis by disrupting cytoprotective structures known as aggresomes that appear to function to alleviate ER stress. Gene silencing studies have demonstrated that the HDAC responsible for aggresome disruption is HDAC6, and it is possible that more selective HDAC6 inhibitors will yield comparable or better tumor cell killing than pan HDAC inhibitors (like SAHA) with less toxicity. To directly test our hypotheses we propose the following Specific Aims. (1) Define the molecular mechanisms that control bortezomib-induced phosphorylation of eIF21. We will test the hypothesis that PIs inhibit PERK activation by inducing the expression of a molecular chaparone (HSP70?) that blocks PERK homoaggregation in drug-sensitive cells; (2) Determine role of ER stress in PI-induced apoptosis. Here we will assess the contributions of ROS, Ca2+, JNK, Noxa, and caspase-4 ot PI-induced apoptosis; (3): Determine the toxicity and anti-tumor efficacy of combination therapy with PIs and HDAC inhibitors in xenografts. We will compare the effects of combination therapy with PIs plus SAHA (a pan HDAC inhibitor), tubacin (HDAC6-selective), or SNDX-275 (type I HDAC-specific) in vitro and in orthotopic tumors derived from sensitive and resistant cell lines. We will also investigate whether or not pharmacodynamic markers of drug-target interaction and biological response can be measured in the peripheral blood of these animals and apply these methods to measure the effects of therapy with bortezomib plus SAHA within the context of a Phase II clinical trial in patients with pancreatic cancer. PUBLIC HEALTH RELEVANCE: Clinical trials have demonstrated that the effects of conventional and investigational cancer therapies are remarkably heterogeneous, and efforts are currently underway to match therapies to the specific molecular features associated with responsiveness to them in an effort to better exploit their effects ("personalized medicine"). The overall goal of the research proposed here is to better understand the mechanisms involved in cell killing induced by two promising classes of investigational cancer therapies (proteasome inhibitors and histone deacetylase inhibitors) so that the promising effects of these drugs that have been noted in preclinical models can be best exploited in patients. We will be directly comparing the effects of two proteasome inhibitors and three HDAC inhibitors that are either already FDA-approved, being evaluated in clinical trials, or being developed for clinical application in humans, and in our third Specific Aim we will develop and apply pharmacodynamic assays to measure drug-target interactions and the biological consequences of effective drug targeting within the context of a Phase II clinical trial in patients.