The Origins of Chromosomal Instability in Human Tumor Cells

描述(申请人提供)：许多人类肿瘤细胞在染色体上是不稳定的，显示出整个染色体的得失比率高于二倍体原代细胞的10-100倍。染色体不稳定性(CIN)促进了肿瘤细胞的进化，导致基因组变化，从而促进转移和化疗耐药。CIN可能在肿瘤的发生中起因果作用，并与患者预后不良有关。确定在人类癌症中导致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途径失活促进细胞增殖，是肿瘤细胞中的常见事件。有趣的是，pRb的功能失活会导致非整倍体。最近的实验表明，pRb的特异性丢失增加了染色体误分离率，使其达到与CIN肿瘤细胞非常相似的水平。这强烈地表明，在肿瘤细胞中看到的染色体不稳定的很大一部分是pRb失活的副产品。这项拨款调查了pRB失活和染色体错误分离之间令人兴奋的联系。新的研究结果表明，pRb的缺失会导致着丝粒功能和染色单体凝聚力的缺陷。我们将检验这一假设，即当pRb缺陷的细胞在有丝分裂中延迟时，凝聚和凝聚缺陷允许染色体错误分离。粘附素是染色体凝聚力的主要决定因素。在目标1中，我们将确定在没有pRB的情况下，粘附素复合体与染色质的结合是如何改变的，并将测试pRB和粘附素之间物理相互作用的功能意义。目标2中的实验将测试pRb缺陷细胞中的有丝分裂缺陷是否可以被抑制或增强。这样的实验可能会带来新的治疗机会。在目标3中，我们将把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的肿瘤细胞中被特异性移除时，着丝粒功能、染色体凝聚力和染色体错误分离率的变化。我们将确定当pRb被解除调控的cdk活性失活时，以及当pRb相关蛋白成为靶点时，是否会发生类似的变化。

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.