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和其他癌细胞的常见特征，在致癌过程中对基因组的不稳定起重要作用。最具特征的分离缺陷之一是多极纺锤体的形成。当纺锤体有两个以上的两极时，染色体不能平均分离，因此，两个子细胞遗传的染色体数目之间存在差异。改变染色体数目导致促进或抑制癌细胞表型的基因拷贝数的变化。多极纺锤体是纺锤体极复制和组织变化的结果。纺锤体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，动力蛋白在纺锤体中缺失。在一些但不是所有情况下，动力蛋白被NuMA的过表达所取代。当NuMA被siRNA敲低时，动力蛋白返回纺锤体，多极性得到纠正。因此，动力蛋白的置换被证明是测试的癌细胞中纺锤体多极化的主要原因。动力蛋白的单独缺失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，除非细胞具有过度复制的中心体，否则不会诱导多极化。这个提议的长期目标是检验这样一个假设，即在肿瘤细胞中观察到的多极纺锤体和随后的非整倍体是由涉及中心体过度折叠和分离的两步过程引起的。本提案的具体目的是测试和确认该纺锤体多极模型，确定NuMA是否可以抑制细胞和溶液中的动力蛋白，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性的意义。阐明多极纺锤体形成和随之而来的染色体不稳定性背后的病因是至关重要的，我们的生物学的癌细胞表型的理解。本研究的结果可能导致预防、早期检测、治疗和/或根除携带多极纺锤体的肿瘤细胞的靶向方法。

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.