Heat shock protein 90 antagonist-based therapy of mantle cell lymphoma

描述(申请人提供)：需要新的治疗策略来提高人类套细胞淋巴瘤(MCL)的无病存活率。热休克蛋白(HSP)90是一种依赖于三磷酸腺苷的分子伴侣，对几种客户蛋白的正确折叠和维持其天然和活性构象是必需的。格尔达那霉素的类似物，如17-AAG和17-DMAG，抑制HSP90的ATP结合和伴侣功能，导致客户蛋白的错误折叠、多泛素化和蛋白酶体降解。最近的研究表明，GAA处理会耗尽HSP90客户蛋白CDK4、c-Raf、AKT和Cyclin D1的水平，这些蛋白赋予MCL细胞生长和生存优势。此外，GAA处理耗尽了内质网应激的调节因子PKR和IRE-11。异羟肟酸类似物(HA)PAN-组蛋白脱乙酰酶抑制剂(HDI)，如伏立诺斯特(SAHA)或LBH589，可增加CDK抑制剂p21和p27的水平，诱导包括AKT和c-Raf在内的几种促凋亡和抗凋亡蛋白的表达。此外，HA-HDIs通过抑制HDAC6诱导HSP90乙酰化，从而抑制HSP90的ATP结合和伴侣功能。这导致MCL相关的HSP90客户蛋白的多泛素化、蛋白酶体降解和耗尽，以及诱导MCL细胞的生长停滞和凋亡。已知抑制HDAC6可以消除核周侵袭体的形成，核周侵袭体隔离和保护未折叠蛋白，从而触发内质网应激反应(UPR)。最近，蛋白酶体抑制剂Bortezomib通过内质网应激增加细胞内未折叠蛋白水平和毒性，被证明在复发的MCL中具有单一的药物活性。基于这些观察建立的强大的理论基础，这里提出的研究将检验这样的假设，即与Bortezomib和HSP90拮抗剂(GAA和/或HA-HDI)联合治疗将取消涉及侵袭体和基于ER的UPR的保护机制，从而在体外和体内发挥相对选择性的致命的抗MCL效应。因此，本研究的具体目的是：目的1：确定HSP90抑制剂在培养和原代人MCL细胞中抗肿瘤选择性的分子基础；目的2：确定HA-HDI、HSP90抑制剂和LBH589在培养和原代MCL细胞中相对抗肿瘤选择性的机制(S)，以及更具特异性的HDAC6抑制剂Tubacin在培养和原代MCL细胞中的选择性；目的3：确定HA-HDI/HSP90抑制剂如何介导Bortezomib诱导的ER应激导致HA-HDI/HSP90抑制剂与Bortezomib组合的抗MCL选择性；目的：检测HSP90拮抗剂17-DMAG或LBH589和/或Bortezomib对小鼠MCL模型的体内抗MCL活性。公共卫生相关性：套细胞淋巴瘤(MCL)是一种高度侵袭性的B淋巴细胞癌。利用培养的和患者来源的MCL细胞，以及MCL的小鼠模型，拟议的研究将评估MCL的分子基础和新治疗策略的有效性。这一策略涉及热休克蛋白90和蛋白酶体抑制剂的组合治疗，旨在针对MCL细胞中的蛋白质折叠和降解。

DESCRIPTION (provided by applicant): New treatment strategies are needed to improve the disease free survival in human mantle cell lymphoma (MCL). Heat shock protein (hsp) 90 is an ATP-dependent molecular chaperone required for the proper folding and maintenance of several client proteins in their native and active conformation. Analogues of geldanamycin (GAAs), e.g., 17-AAG and 17-DMAG, inhibit the ATP binding and chaperone function of hsp90, resulting in misfolding, polyubiquitylation and proteasomal degradation of the client proteins. Recent studies demonstrated that treatment with GAA depleted the levels of the hsp90 client proteins CDK4, c-Raf, AKT and cyclin D1, which confer growth and survival advantage on MCL cells. Additionally, GAA treatment depleted the mediators of endoplasmic reticulum (ER) stress PKR and IRE-11. Treatment with hydroxamic acid analogue (HA) pan-histone deacetylase inhibitor (HDI), e.g., vorinostat (SAHA) or LBH589, was shown to increase the levels of the CDK inhibitors p21 and p27, induce several pro-apoptotic and attenuate antiapoptotic proteins, including AKT and c-Raf, in MCL cells. Furthermore, by inhibiting HDAC6, HA-HDIs induced hsp90 acetylation, which inhibited ATP binding and chaperone function of hsp90. This resulted in polyubiquitylation, proteasomal degradation and depletion of the MCL-relevant hsp90 client proteins, as well as induced growth arrest and apoptosis of MCL cells. Inhibition of HDAC6 is known to abrogate the formation of perinuclear aggresome, which sequesters and protects against unfolded proteins, known to trigger ER stress response (UPR). Recently, the proteasome inhibitor bortezomib, which increases intracellular unfolded protein levels and toxicity through ER stress, was shown to have a single agent activity in relapsed MCL. Based on the strong rationale created by these observations, studies proposed here will test the hypothesis that combined treatment with bortezomib and hsp90 antagonists (GAA and/or HA-HDI) will abrogate the protective mechanisms involving the aggresome and ER-based UPR, thereby exerting a relatively selective, in vitro and in vivo, lethal, anti-MCL effect. Therefore, the specific aims of this proposal are: AIM 1: To determine the molecular basis of the anti-tumor selectivity of hsp90 inhibitors in cultured and primary human MCL cells; AIM 2: To determine the mechanism(s) of the relative anti-tumor selectivity of the HA-HDIs vorinostat and LBH589, as well as the more specific HDAC6 inhibitor tubacin in cultured and primary MCL cells; AIM 3: To determine how HA-HDI/hsp90 inhibitor-mediated abrogation of bortezomib-induced ER stress results in anti-MCL selectivity of the combination of HA-HDI/hsp90 inhibitor with bortezomib; AIM 4: To determine the in vivo anti-MCL activity of the hsp90 antagonist 17-DMAG or LBH589 and/or bortezomib against mouse models of MCL. PUBLIC HEALTH RELEVANCE: Mantle cell lymphoma (MCL) is a highly aggressive cancer of B-lymphocytes. Utilizing cultured and patient-derived MCL cells, as well as mouse models of MCL, proposed studies would evaluate the molecular underpinnings and efficacy of a novel therapeutic strategy for MCL. This strategy involves combinations of treatments with heat shock protein 90 and proteosome inhibitors designed to target protein folding and degradation in MCL cells.