Chaetocin as a Potential Therapy for Multiple Myeloma

描述(申请人提供)：多发性骨髓瘤是一种一致致命的浆细胞癌，仅在美国每年就有超过11,000人死亡。目前还没有治愈方法，迫切需要改进的治疗方法。我们最近发现，毛壳素是一种以前没有报道过的具有抗癌作用的天然产物，在体外、体外和体内都具有有效和选择性的抗骨髓瘤活性。令人印象深刻的是，毛壳素的抗骨髓瘤作用在对地塞米松或阿霉素耐药的骨髓瘤细胞和患者骨髓瘤样本中保持不变，这些骨髓瘤样本来自经过严格预治疗的患者，这些患者存在多种细胞遗传学变化。从机制上讲，毛霉素会在癌细胞中迅速而显著地积聚，需要完整/未还原的二硫化物才能摄取，并需要施加ROS来实现细胞毒选择性。此外，我们最近证实，在达到细胞内浓度的情况下，毛壳素是ROS缓解酶硫氧还蛋白还原酶(TrxR)的竞争底物(和抑制剂)--这导致了我们的假设，即TrxR可能代表毛壳素的细胞毒性分子靶点。综合考虑，毛壳素似乎是一种有希望作为潜在的抗骨髓瘤治疗药物进一步开发的药物。基于令人鼓舞的初步结果，我们现在提出以下具体目标：目标1：进一步评价毛壳素诱导的细胞毒性、细胞摄取和积累的机制。我们将严格评估TrxR和其他还原酶、组蛋白修饰酶(包括HDACs和HMTs)、HIF1和其他靶标对毛细管素细胞毒选择性的影响；并进一步研究细胞毛管素摄取和积累的机制。目的2：通过系统研究骨髓瘤细胞中ROS通路的不同功能，进一步阐明毛壳素的细胞毒性选择性。我们将进一步定义正常和恶性血液病细胞中毛黄素的选择性，并与目标1中的机制研究密切合作，通过阐述ROS和其他途径在成对的毛黄素敏感/耐药患者细胞和骨髓瘤细胞系中的不同活性，探索观察到的细胞毒性选择性的分子基础。目的3：进一步评价毛壳素的体内毒性和疗效。我们将优化体内配方，在异种移植和系统性骨髓瘤模型中进行毒理学、PK、PD和疗效研究，并初步探索基于AIM 1的机制研究而形成的体内生物标记物。总之，拟议的实验将促进对毛壳素的细胞效应的了解，促进其进一步发展，并为其他类似引起ROS的药物是否也可能成为作为抗骨髓瘤治疗药物的有吸引力的候选药物提供重要的见解。公共卫生相关性：多发性骨髓瘤是一种致命的骨髓癌，仅在美国每年就有超过11,000人死亡；目前还没有治愈方法，迫切需要改进的治疗方法。我们最近发现，毛壳素是从一种常见的木霉中分离出来的一种物质，以前没有报道过具有抗癌作用，但在癌细胞系、患者骨髓瘤细胞和骨髓瘤动物模型中具有有效和选择性的抗骨髓瘤活性。我们现在建议对毛壳素进行进一步的研究，旨在更好地确定其作用机制、癌症选择性和在动物模型中治疗骨髓瘤的能力，希望最终开发毛壳素作为治疗骨髓瘤患者的方法。

DESCRIPTION (provided by applicant): Multiple myeloma is a uniformly fatal plasma cell cancer that kills over 11,000 individuals annually in the U.S. alone. No cure exists, and improved therapies are desperately needed. We have recently discovered that chaetocin, a natural product previously unreported to have anti-cancer effects, has potent and selective in vitro, ex vivo and in vivo anti-myeloma activity. Impressively, the anti-myeloma effects of chaetocin are maintained in dexamethasone- or doxorubicin-resistant myeloma cells and in patient myeloma samples collected from heavily pre-treated patients harboring a diverse array of cytogenetic alterations. Mechanistically, chaetocin is rapidly and dramatically accumulated in cancer cells, requiring intact/unreduced disulfides for uptake, and imposition of ROS for cytotoxic selectivity. Moreover, we have recently established that chaetocin is a competitive substrate for (and inhibitor of) the ROS mitigation enzyme thioredoxin reductase (TrxR) at achieved intracellular concentrations - leading to our hypothesis that TrxR may represent a cytotoxic molecular target of chaetocin. Considered collectively, chaetocin appears to represent a promising agent for further development as a potential anti-myeloma therapeutic. Based upon encouraging preliminary results, we now propose the following specific aims: Aim 1: Further evaluation of the mechanisms of chaetocin-induced cytotoxicity, cellular uptake and accumulation. We will critically evaluate the contributions of effects on TrxR and other reductases, histone modifying enzymes (including HDACs and HMTs), HIF1 and other targets to the cytotoxic selectivity of chaetocin; as well as further investigate mechanisms of cellular chaetocin uptake and accumulation. Aim 2: Further clarification of the cytotoxic selectivity of chaetocin with systematic exploration of differential functions of ROS pathways in myeloma cells. We will further define the selectivity of chaetocin in normal vs. malignant hematological cells and, in close coordination with mechanistic studies in Aim 1, probe the molecular basis of observed cytotoxic selectivity through elaboration of differential activities of ROS and other pathways in paired chaetocin sensitive/resistant patient cells and myeloma cell lines. Aim 3: Further evaluation of the in vivo toxicities and efficacy of chaetocin. We will optimize in vivo formulations and conduct toxicology, PK, PD, and efficacy studies in xenograft and systemic myeloma models; as well as preliminarily explore in vivo biomarkers formulated based upon mechanistic studies of Aim 1. Collectively, proposed experiments will advance understanding of the cellular effects of chaetocin, foster its further development, and provide important insights into whether other agents that similarly induce ROS may also represent attractive candidates for further development as anti-myeloma therapeutics. PUBLIC HEALTH RELEVANCE: Multiple myeloma is a uniformly fatal bone marrow cancer that kills over 11,000 individuals annually in the U.S. alone; no cure exists, and improved therapies are desperately needed. We have recently discovered that chaetocin, a substance isolated from a common wood mold previously unreported to have anti-cancer effects, has potent and selective anti-myeloma activity in cancer cell lines, patient myeloma cells and in an animal model of myeloma. We now propose further studies of chaetocin intended to better define its mechanisms of action, cancer selectivity, and ability to treat myeloma in animal models in hopes of eventually developing chaetocin as a therapy for patients afflicted with myeloma.