Origin of Spindle Multipolarity in Oral Cancer Cells

描述（由申请人提供）：染色体分离缺陷是口腔癌细胞和其他癌细胞的共同特征，在致癌过程中对基因组的不稳定起着重要作用。最典型的偏析缺陷之一是多极纺锤的形成。当纺锤体有两个以上的极时，染色体不能均匀分离，因此，两个子细胞遗传的染色体数量存在差异。染色体数目的改变导致基因拷贝数的改变，促进或抑制癌细胞的表型。多极纺锤体是纺锤极的复制和组织变化的结果。纺锤体的组织依赖于中心体蛋白NuMA和微管运动细胞质动力蛋白之间的相互作用，在口腔癌细胞以及其他类型的肿瘤细胞中，纺锤体中缺少动力蛋白。在某些情况下，但不是所有情况下，动力蛋白被NuMA的过度表达所取代。当NuMA被siRNA敲除时，动力蛋白返回纺锤体，多极性得到纠正。因此，在测试的癌细胞中，动力蛋白的位移被证明是纺锤体多极性的主要原因。仅仅失去动力蛋白并不足以引起多极纺锤体。当NuMA过表达，或动力蛋白被相关肽的过表达抑制时，除非细胞有过度复制的中心体，否则不会诱导多极。本研究的长期目标是验证肿瘤细胞中多极纺锤体和由此产生的非整倍体是中心体过度复制和分离两步过程的结果。本课题的具体目的是对纺锤体多极性模型进行验证，确定NuMA在细胞和溶液中是否具有抑制动力蛋白的作用，并测试多极纺锤体和NuMA过表达对染色体不稳定性和非整倍体的意义。阐明多极纺锤体形成和随之而来的染色体不稳定性的病因学对我们理解癌细胞表型的生物学至关重要。这项研究的结果可能会导致有针对性的方法来预防，早期发现，治疗，和/或根除肿瘤细胞窝藏多极纺锤体。

DESCRIPTION (provided by applicant): Chromosomal segregational defects are a common feature of oral and other cancer cells and play an important role in destabilizing the genome during carcinogenesis. One of the best characterized segregational defects is the formation of multipolar spindles. When the spindle has more than two poles, the chromosomes cannot be separated equally, consequently, there is a difference between the numbers of chromosomes inherited by the two daughter cells. Altering chromosome number results in a change in the copy numbers of genes promoting or inhibiting the cancer cell phenotype. Multipolar spindles are a consequence of changes in both the replication and organization of the spindle pole. Spindle organization depends on an interaction between the centrosomal protein NuMA and the microtubule motor cytoplasmic dynein, in oral cancer cells, as well as other types of tumor cells, dynein is missing from the spindles. In some, but not all cases, dynein is displaced by overexpression of NuMA. When NuMA is knocked down by siRNA, dynein returns to the spindle and multipolarity is corrected. Thus, displacement of dynein is shown to be a major cause of spindle multipolarity in the tested cancer cells. Loss of dynein alone is not sufficient to cause multipolar spindles. When NuMA is overexpressed, or dynein is inhibited by overexpression of an associated peptide, multipolarity is not induced unless the cells have over-replicated centrosomes. The long-term objective of this proposal is to test the hypothesis that multipolar spindles and the consequent aneuploidy seen in tumor cells result from a two-step process involving centrosome overeplication and separation. The Specific Aims of this proposal are to test and confirm this model for spindle multipolarity, determine if NuMA can act to inhibit dynein in cells and in solution, and test the significance of multipolar spindles and NuMA overexpression on chromosomal instability and aneuploidy. Elucidation of the etiology behind multipolar spindle formation and the consequent chromosomal instability is critical to our understanding of the biology of the cancer cell phenotype. The results of this study may lead to targeted methods for prevention, early detection, therapy, and/or eradication of tumor cells harboring multipolar spindles.