Antitubulin drugs: Mechanisms of action and resistance

描述（由申请人提供）：我们的整体研究计划集中在了解作用的分子机制和对靶向微管（MT）细胞骨架的抗肿瘤药物的耐药性。MT靶向药物是癌症化疗中最有效的药物之一。紫杉醇是MT稳定药物的原型，其在广泛的人类肿瘤中的活性引发了对微管蛋白作为化疗靶点的强烈兴趣。然而，耐药肿瘤细胞的出现限制了紫杉醇治疗疾病的能力。紫杉醇耐药主要通过P-糖蛋白（Pgp）的过度表达和β-微管蛋白突变的存在介导。因此，虽然微管蛋白似乎是一个非常重要的化疗靶点，但对在耐药细胞中具有活性的新型MT靶向剂的需求日益增加。一种这样的药剂是discodermolide，一种海洋海绵天然产物，与紫杉醇的作用机制相似，但具有几个独特的特征。Discodermolide具有非紫杉烷的化学结构，对紫杉醇耐药细胞系（过度表达Pgp或携带β-微管蛋白突变的细胞系）具有活性。此外，discodermolide是迄今为止报道的唯一一种在各种人类癌细胞系中与紫杉醇协同作用的MT稳定药物。然而，这种协同作用的分子机制目前尚不清楚。为了更好地了解discodermolide和紫杉醇如何与它们的细胞内靶点微管蛋白相互作用，我们建立了对discodermolide和discodermolide与紫杉醇的协同组合具有抗性的人癌细胞系。我们的建议的具体目标是：（a）阐明在药物选择克隆中对discodermolide或对discodermolide/紫杉醇组合的耐药性的分子机制。(b)对discodermolide类似物进行构效关系（SAR）研究，以确定生物活性的结构要求。我们还将进行discodermolide-微管蛋白结合的分子建模和结构研究。（c）将特定的微管蛋白突变引入人类癌细胞，以研究它们对药物结合的影响。

DESCRIPTION (provided by applicant): Our overall research initiative is focused on understanding the molecular mechanism of action and resistance to antitumor drugs that target the microtubule (MT) cytoskeleton. MT- targeting drugs are among the most effective agents introduced in cancer chemotherapy. Taxol is the prototype of MT-stabilizing drugs, and its activity in a broad range of human tumors has ignited intense interest in tubulin as a chemotherapy target. The emergence of drug resistant tumor cells, however, limits Taxol's ability to cure disease. Resistance to Taxol is primarily mediated through overexpression of P-glycoprotein (Pgp) and the presence of beta-tubulin mutations. Thus, while tubulin appears to be a very important chemotherapy target, there is an increasing need for novel MT-targeting agents with activity in resistant cells. One such agent is discodermolide, a marine-sponge natural product, with a similarity to Taxol's mechanism of action but with several unique features. Discodermolide has a nontaxane chemical structure and is active against Taxol-resistance cell lines, both those that overexpress Pgp or harbor beta-tubulin mutations. In addition, discodermolide is the only MT-stabilizing drug reported to date to be synergistic with Taxol in various human cancer cell lines. The molecular mechanism of this synergistic interaction, however, is currently unknown. In an effort to better understand how discodermolide and Taxol interact with their intracellular target, tubulin, we have established human cancer cell lines resistant to discodermolide and to the synergistic combination of discodermolide and Taxol. The specific aims of our proposal are :(a) Elucidate the molecular mechanism of resistance to discodermolide or to the discodermolide/-taxol combinations in the drug selected clones. (b) Perform structure-activity relationship (SAR) studies on discodermolide analogs to determine the structural requirements for biological activity. We will also perform molecular modeling and structural studies of discodermolide-tubulin binding (c) Introduce specific tubulin mutations into human cancer cells to investigate their effect on drug-binding.