Origin of Spindle Multipolarity in Oral Cancer Cells

描述(申请人提供)：染色体分离缺陷是口腔和其他癌症细胞的共同特征，在癌症发生过程中对破坏基因组的稳定起着重要作用。最典型的偏析缺陷之一是多极纺锤形的形成。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量存在差异。改变染色体数目会导致促进或抑制癌细胞表型的基因的拷贝数发生变化。多极主轴是主轴磁极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和微管运动胞浆动力蛋白之间的相互作用，在口腔癌细胞和其他类型的肿瘤细胞中，动力蛋白从纺锤体中缺失。在某些情况下，但不是所有情况下，dynein被nuA的过度表达所取代。当nuA被siRNA击倒时，dynein回到纺锤体，多极被纠正。因此，动力蛋白的置换被证明是被测试的癌细胞中纺锤体多极化的主要原因。动力蛋白本身的丢失不足以导致多极纺锤波。当NUMA过度表达，或动力蛋白被相关多肽过度表达抑制时，除非细胞有过度复制的中心体，否则不会诱导多极。这一提议的长期目标是检验一种假设，即肿瘤细胞中出现的多极纺锤体和随之而来的非整倍体是涉及中心体过度复制和分离的两步过程的结果。这项建议的具体目的是测试和确认这一纺锤体多极化模型，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过度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背后的病因学对于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导致有针对性的方法来预防、早期发现、治疗和/或根除含有多极纺锤体的肿瘤细胞。

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.