The role of microtubule dynamics in cell division and chromosome segregation

癌细胞比健康细胞更容易变形，而且变形能力可能与它们的转移潜力有关。例如，众所周知，组织的硬度和弹性在肿瘤存在时会发生变化；但不太清楚的是，这些变化在亚细胞水平上的起源以及这些变化与肿瘤细胞生物学的关系。细胞骨架是由微管、肌动蛋白和中间丝组成的复杂复合体，有助于维持细胞的刚性，对需要细胞运动和变形的过程至关重要。细胞骨架的稳定性由多种调节蛋白控制。微管解聚运动蛋白MCAK(KIF2C)是微管细胞骨架的主要调节因子。在健康细胞中，MCAK在调节微管长度方面发挥着重要作用，特别是在有丝分裂和减数分裂过程中，它还在纠正染色体-微管附着错误方面发挥作用。与健康细胞相比，MCAK基因敲除对癌细胞的影响更大，表达的变化介导了对抗微管癌症治疗的敏感性。MCAK在乳腺癌、结直肠癌和胃癌中高表达，且高表达与转移增加和患者预后不良相关。我们假设，癌细胞中MCAK水平的升高导致微管细胞骨架的不稳定，增加了细胞的变形能力，进而增加了转移潜力。因此，本项目的总体目标是研究通过操纵MCAK活性来干扰微管细胞骨架对细胞机械性能的影响。将使用两种不同但互补的物理技术来量化单个细胞的机械性能，并将这些测量结果与现有的细胞生物学测试结果进行比较，后者报告细胞的运动性、变形性和增殖。尽管有大量证据表明MCAK的过度表达与癌症的进展有关，但MCAK活性与细胞机械性能之间的联系尚未得到研究。因此，有必要和及时地利用现有的生物工具来滴定MCAK的活性，并将其与报道细胞力学的尖端物理技术相结合，以揭示MCAK在癌细胞中的表达与转移潜能增加和/或患者预后不良的关系。MCAK是新的化疗药物开发的靶点，特别是在对抗当前抗微管肿瘤药物的耐药性方面。这项拟议的工作将增加我们对MCAK在癌细胞中的影响的了解，并有助于开发针对MCAK活性的药物。此外，该项目将帮助开发尖端生物物理技术，促进细胞机械特性作为一种新的无标记生物标记物和诊断工具在癌症治疗中的使用。

Cancer cells are more deformable than healthy cells and deformability is likely linked to their metastatic potential. For instance, it is well-known that stiffness and elasticity of tissues change upon the presence of a tumour; what is less clear is the origin of these changes at the subcellular level and how these relate to the biology of a tumour cell. The cytoskeleton is a complex composite of microtubules, actin and intermediate filaments which helps to maintain the rigidity of cells and is critical to processes requiring movement and deformation of cells. The stability of the cytoskeleton is controlled by a variety of regulatory proteins. The microtubule depolymerizing kinesin, MCAK (KIF2C) is a major regulator of the microtubule cytoskeleton. In healthy cells, MCAK plays an important role in regulating microtubule length, particularly during mitosis and meiosis, where it also has a role in correction of chromosome-microtubule attachment errors. Knockdown of MCAK has a greater impact on cancer cells than healthy cells and alteration in expression mediates sensitivity to anti-microtubule cancer therapies. MCAK is overexpressed in breast, colorectal and gastric cancers and elevated expression correlates with increased metastasis and poor patient prognosis. We hypothesise that elevated levels of MCAK in cancer cells leading to destabilisation of the microtubule cytoskeleton increases cell deformability and in turn, metastatic potential. Hence, the overall aim of this project is to study the effect of perturbing the microtubule cytoskeleton, through manipulation of MCAK activity, on the mechanical properties of cells. Two different but complementary physical techniques will be used to quantify the mechanical properties of individual cells and these measurements compared with results from established cell biological assays which report on cell motility, deformability and proliferation. Although a body of evidence exists to connect overexpression of MCAK to progression of cancer, the link between MCAK activity and the mechanical properties of cells has not been investigated. Therefore, it is necessary and timely to use the biological tools now available to titrate MCAK activity and combine these with cutting edge physical techniques that report on cell mechanics to uncover the relationship between MCAK expression in cancer cells and increased metastatic potential and/or poor patient prognosis. MCAK is a target for new chemotherapeutic development, particularly to combat resistance to current anti-microtubule cancer drugs. The proposed work will add to our knowledge of the impact of MCAK in cancer cells and assist the development of drugs targeting MCAK activity. Further, the project will aid development of cutting edge biophysical techniques which will advance the use of cell mechanical properties as a novel label-free biomarker and diagnostic tool in the treatment of cancer.