The Origins of Chromosomal Instability in Human Tumor Cells

描述（由申请人提供）：许多人肿瘤细胞染色体不稳定，显示出整个染色体的获得和丢失率升高，比二倍体原代细胞高10-100倍。染色体不稳定性（CIN）增强了肿瘤细胞的进化，导致基因组变化，可促进转移和化疗耐药性。CIN可在肿瘤发生中起因果作用，并且与患者预后不良相关。确定导致人类癌症CIN的突变，并了解它们为什么会降低有丝分裂的保真度，是癌症研究的重要目标。 pRB途径的失活促进细胞增殖，并且是肿瘤细胞中的常见事件。有趣的是，pRB的功能失活导致非整倍体。最近的实验表明，pRB的特异性丢失将染色体错误分离的速率增加到与CIN肿瘤细胞非常相似的水平。这强烈表明，在肿瘤细胞中观察到的染色体不稳定性的显著部分是pRB失活的副产物。 该基金研究了pRB失活和染色体错误分离之间令人兴奋的联系。最新的研究结果表明，pRB的缺失导致了着丝粒功能和染色单体凝聚力的缺陷。我们将检验这样的假设，即当pRB缺陷细胞在有丝分裂中延迟时，内聚和凝聚缺陷允许染色体错误分离。凝聚素是染色体凝聚的主要决定因素。在目标1中，我们将确定如何改变的pRB的情况下，与染色质的粘附复合物的协会，并将测试pRB和粘附之间的物理相互作用的功能意义。目标2中的实验将测试是否可以抑制或增强pRB缺陷细胞中的有丝分裂缺陷。这些实验可能会带来新的治疗机会。在目标3中，我们将这些研究扩展到癌细胞，并将测量和比较当功能性pRB重新引入缺乏它的肿瘤细胞或从具有功能性pRB的肿瘤细胞中特异性去除时，着丝粒功能，染色体凝聚力和染色体错误分离率的变化。我们将确定是否发生类似的变化时，pRB是失活的cdk活性失调，当pRB相关的蛋白质的目标。

DESCRIPTION (provided by applicant): Many human tumor cells are chromosomally unstable, showing an elevated rate of gains and losses of whole chromosomes that is 10-100 times higher than that seen in diploid primary cells. Chromosome instability (CIN) enhances the evolution of tumor cells causing genomic changes that can promote metastasis and chemotherapeutic resistance. CIN can have a causal role in tumorigenesis and it correlates with poor patient prognosis. Identifying the mutations that cause CIN in human cancer, and understanding why they reduce the fidelity of mitosis, are important objectives in cancer research. The inactivation of the pRB pathway promotes cell proliferation and is a common event in tumor cells. Interestingly, the functional inactivation of pRB causes aneuploidy. Recent experiments show that the specific loss of pRB increases rates of chromosome mis-segregation to levels that are remarkably similar to CIN tumor cells. This strongly suggests that a significant fraction of the chromosome instability seen in tumor cells is a byproduct of the inactivation of pRB. This grant investigates the exciting link between pRB inactivation and chromosome mis-segregation. Newly obtained results show that the loss of pRB causes defects in centromere function and chromatid cohesion. We will test the hypothesis that defects in cohesion and condensation allow chromosome mis-segregation when pRB-deficient cells are delayed in mitosis. Cohesin is the primary determinant of chromosome cohesion. In Aim 1 we will determine how the association of cohesin complexes with chromatin is altered in the absence pRB, and will test the functional significance of physical interactions between pRB and cohesin. The experiments in Aim 2 will test whether the mitotic defects in pRB-deficient cells can be either suppressed or enhanced. Such experiments may lead to new therapeutic opportunities. In Aim 3 we will extend these studies to cancer cells and will measure and compare the changes in centromere function, chromosome cohesion, and the rates of chromosome mis-segregation seen when functional pRB is re-introduced into tumor cells that lack it, or is specifically removed from tumor cells with functional pRB. We will determine whether similar changes occur when pRB is inactivated by deregulated cdk activity and when pRB-related proteins are targeted.