Diverse Natural Products That Stabilize Microtubules

描述（由申请人提供）：我们研究的长期目标是全面了解紫杉醇的作用机制和耐药性机制，紫杉醇是一种已知可有效治疗人类癌症的抗肿瘤药物。药物开发的强烈兴趣现在集中在埃博霉素和discodermolide，其化学结构与紫杉醇不同的天然产物，但其作用机制和耐药性与紫杉醇相似，但肯定不相同。我们的计划是剖析这三种微管稳定药物之间的异同。与紫杉醇相比，埃博霉素和/或discodermolide可具有上级临床活性，特别是在对紫杉烷类有抗性的肿瘤中。这项资助申请的一个压倒一切的主题是低剂量的紫杉醇、埃博霉素和discodermolide在杀死癌细胞中的作用。这种强调低药物剂量是我们实验室的一个新焦点，因为很明显，紫杉醇是在低剂量药物下导致细胞死亡的原因，而这种药物并不阻止细胞的有丝分裂。毫无疑问，低剂量的紫杉醇通过多种途径杀死癌细胞。临床前数据的可用性是必不可少的，必须有助于决定将药物转入临床试验。这项建议的具体目标是：1.确定用低浓度紫杉醇处理的细胞逃避纺锤体检查点的机制。HeLa细胞将用MAD 2（一种检查点组分）转染，以确定其过表达是否可以从细胞死亡中拯救那些逃离有丝分裂检查点的细胞。蛋白质CENP-E（有丝分裂检查点的一个组分）的过表达与耐药性之间的关系也将被研究。2.检测p53依赖性细胞凋亡对低浓度紫杉醇引起的细胞毒性的作用。确定异常有丝分裂是否导致p53依赖性细胞凋亡。DNA微阵列将用于调查和比较用不同浓度的微管稳定药物处理的A549细胞的基因表达谱。3.研究癌细胞中微管调节蛋白stathmin和MAP 4的表达水平和磷酸化状态如何与微管稳定剂的差异敏感性相关，以及这些药物如何影响这些蛋白质的表达谱。

DESCRIPTION (provided by applicant): The long-term objectives of our research are to acquire a thorough understanding of the mechanisms of action and of resistance to Taxol, an antitumor agent that is known to be efficacious in the treatment of human cancer. An intense interest in drug development is now concentrated on the epothilones and discodermolide, natural products whose chemical structures are distinct from Taxol but whose mechanisms of action and resistance have similarities, but are definitely not identical, to those of Taxol. Our plan is to dissect the similarities and differences between these three microtubule stabilizing drugs. The epothilones and/or discodermolide may have superior clinical activity compared to Taxol, particularly in tumors resistant to taxanes. An overriding theme of this grant application is the role that low doses of Taxol, the epothilones and discodermolide play in the killing of cancer cells. This emphasis on low drug dosage is a new focus for our laboratory that developed as it became clear that Taxol was responsible for cell death at low doses of drug that did not block cells in mitosis. There are undoubtedly diverse pathways by which low doses of Taxol kill cancer cells. The availability of preclinical data is essential and must contribute to the decision to move drugs into clinical trials. The specific aims of this proposal are to: 1. Determine the mechanism(s) by which cells treated with low concentrations of Taxol escape the spindle checkpoint. HeLa cells will be transfected with MAD2, a checkpoint component, to determine if its overexpression can rescue from cell death, those cells that escape from the mitotic checkpoint. The relationship between overexpression of the protein CENP-E, a component of the mitotic checkpoint, and drug resistance will also be investigated. 2. Examine the contribution of p53-dependent apoptosis to cytotoxicity caused by low concentrations of Taxol. Determine if aberrant mitosis leads to p53-dependent apoptosis. DNA microarrays will be used to survey and compare gene expression profiles of A549 cells treated with different concentrations of microtubule stabilizing drugs. 3. Investigate how the expression level and the phosphorylation status of the microtubule regulatory proteins stathmin and MAP4 in cancer cells relate to differential sensitivity to microtubule-stabilizing agents, and how these agents affect the expression profile of these proteins.