Taccalonolides: Mechanisms of Action and Cellular Resistance

描述（申请人提供）：微管稳定剂是治疗癌症的重要药物。本项目的重点是一类新的植物来源的微管稳定剂，塔卡隆内酯。塔卡洛内酯具有独特的作用机制。它们是第一个在细胞中具有紫杉醇样作用的微管稳定剂，但它们不与微管蛋白结合。全面的研究提出，以确定细胞机制的作用和耐药性的塔卡洛内酯。这些研究有望确定稳定微管的新靶点，从而产生抗肿瘤作用。从这些研究中获得的信息还将确定化学和生物多样性微管稳定剂引发有丝分裂停止和随后的细胞凋亡的信号通路。这有望导致发现新的癌症治疗靶点。这些靶点可能提供了紫杉烷的抗癌功效，以及规避紫杉烷耐药和微管蛋白相关毒性的能力。这项工作的第一个目标是确定塔卡卡内酯的细胞结合位点。我们将验证塔卡洛内酯结合并抑制细胞内固有的微管不稳定因素导致微管稳定的假设。第二个目标是阐明塔卡卡内酯阻断有丝分裂信号导致有丝分裂阻滞和细胞凋亡的机制。我们将检验塔卡洛内酯抑制极光A表达和活性的假设。耐药性是癌症治疗中的一个严重问题。我们将确定细胞对他卡洛内酯耐药的性质，并测试这些化合物可以在临床中规避导致紫杉烷耐药的耐药机制的假设。将测试他卡洛内酯绕过p糖蛋白表达、微管蛋白改变和pxr介导的耐药的能力。将评估暴露于他卡洛内酯产生的细胞系，以确定获得性他卡洛内酯耐药的机制。最终目的是确定塔卡洛内酯的作用机制和耐药性的结构基础。将确定对最佳细胞毒性和效力、抗有丝分裂作用和抗肿瘤活性具有重要作用的特定化学成分。

DESCRIPTION (provided by applicant): Microtubule stabilizing agents are important drugs used in the treatment of cancer. The focus of this project is a new class of plant-derived microtubule stabilizers, the taccalonolides. The taccalonolides have a unique mechanism of action. They are the first microtubule stabilizers identified that have Taxol-like effects in cells but they do not bind to tubulin. Comprehensive studies are presented to identify the cellular mechanisms of action and resistance of the taccalonolides. These studies are expected to identify new targets for stabilizing microtubules that can lead to antitumor effects. Information gained from these studies will also identify the signaling pathways invoked by chemically and biologically diverse microtubule stabilizers to initiate mitotic arrest and subsequent apoptosis. This is expected to lead to the identification of new therapeutic targets for cancer. These targets could provide the anticancer efficacy of the taxanes and the ability to circumvent taxane drug resistance and tubulin-related toxicity. The first goal of this effort is to identify the cellular binding site of the taccalonolides. We will test the hypothesis that the taccalonolides bind and inhibit an intrinsic cellular microtubule destabilizing factor resulting in microtubule stabilization. A second goal is to elucidate the mechanisms by which the taccalonolides interrupt mitotic signaling leading to mitotic arrest and apoptosis. We will test the hypothesis that the taccalonolides inhibit Aurora A expression and activity. Drug resistance is a serious problem in the treatment of cancer. We will identify the nature of cellular resistance to the taccalonolides and test the hypothesis that these compounds can circumvent resistance mechanisms that contribute to taxane resistance in the clinic. The ability of the taccalonolides to bypass resistance due to P-glycoprotein expression, tubulin alterations and PXR-mediated resistance will be tested. Cell lines generated by taccalonolide exposure will be evaluated to identify the mechanisms of acquired taccalonolide resistance. The final aim will identify the structural basis for the taccalonolides mechanisms of action and resistance. Specific chemical constituents important for optimal cytotoxic efficacy and potency, antimitotic actions and antitumor activities will be determined.