Role of Nucleostemin in Conferring The Drug Resistance of Hepatocellular Carcinoma

 描述（由申请人提供）：高级别肿瘤对DNA损伤诱导化疗剂（C/Ts）的耐药性是癌症死亡的主要原因。肝细胞癌（HCC）是众所周知的，其先天性耐药的C/Ts，但其潜在的机制仍不清楚。最近的研究开始关注晚期乳腺癌和卵巢癌的进展和耐药性可能取决于同源重组（HR）修复途径。我的小组研究了一种由干细胞和癌细胞富集的蛋白质控制的自我更新机制，称为核干细胞蛋白（NS）。我们最近发现了NS在促进HR修复和保护癌细胞免受复制诱导的DNA损伤中的关键活性。我们还发现NS在Hep 3B（人肝癌）细胞和晚期二乙基亚硝胺（DEN）诱导的小鼠肝癌中高度表达。本R 03申请的目的是获得支持NS在人HCC样本中的临床相关性及其通过HR修复在赋予HCC耐药性方面的潜在作用的数据。我们假设NS表达与人HCC的恶性程度相关，并且NS耗竭将损害HCC细胞的基于HR的双链断裂（DSB）修复和化学抗性性质。这一假设是基于以下原因制定的：1）NS表达在Hep 3B细胞和DEN诱导的HCC中在晚期癌阶段显著上调; 2）NS是维持Hep 3B细胞持续增殖所必需的; 3）NS促进基于HR的修复并防止乳腺癌中的基因组损伤。（MDA-MB-231）和骨（U2 OS）肿瘤细胞;和4）已知HR缺陷使乳腺癌、卵巢癌、前列腺癌和胰腺癌对C/Ts敏感。为了检验我们的假设，我们将追求三个具体目标。目标1将描述以下临床相关性： 人HCC中的NS。目的#2将确定NS消耗对HCC细胞中基于HR的DSB修复的影响。目的#3将确定NS在介导HCC耐药性中的作用。作为本申请的结果，我们将通过显示人HCC样本中NS表达增加或失调来确定NS的临床重要性，确定NS表达与患者临床结局之间的关系，并提供功能证据来支持NS在促进HCC细胞中基于HR的修复和化疗耐药性中的作用，所有这些都是我们未来R 01提交的重要初步数据。如果我们的假设被证明是正确的，这将影响我们的知识，肝癌细胞如何适应过度活跃的有丝分裂状态，并避免致命的基因组不稳定性在晚期，肝癌如何发展的先天性的化疗耐药性，以及是否可以重新敏感的C/Ts通过NS消融。考虑到肝癌发生的复杂性和HCC的异质性，将C/Ts与靶向癌细胞使用的共同适应机制的治疗相结合提供了一种有吸引力的策略，以提高C/Ts的疗效和耐受性。

 DESCRIPTION (provided by applicant): Resistance of high-grade tumors to DNA damage-inducing chemotherapeutic agents (C/Ts) is a major cause of cancer mortality. Hepatocellular carcinoma (HCC) is well known for its innate resistance to C/Ts, but the underlying mechanisms remain unclear. Recent studies are beginning to home in on the notion that the progression and drug resistance of late-stage breast and ovarian cancers may depend on the homologous recombination (HR) repair pathway. My group studies a self-renewal mechanism controlled by a stem and cancer cell-enriched protein called nucleostemin (NS). We recently discovered a key activity of NS in promoting HR repair and protecting cancer cells from replication-induced DNA damage. We also found that NS is highly expressed in Hep3B (human HCC) cells and late-stage diethylnitrosamine (DEN)-induced mouse HCC. The objective of this R03 application is to obtain data to support the clinical relevance of NS in human HCC samples and its potential role in conferring HCC drug resistance via HR repair. We hypothesize that NS expression correlates with the malignancy of human HCC and that NS depletion will compromise the HR- based double-strand break (DSB) repair and chemoresistant property of HCC cells. This hypothesis is formulated based on the following reasons: 1) NS expression is significantly up-regulated in Hep3B cells and in DEN-induced HCC at the late carcinoma stage; 2) NS is required to maintain the continuous proliferation of Hep3B cells; 3) NS promotes HR-based repair and prevents genomic damage in breast (MDA-MB-231) and bone (U2OS) tumor cells; and 4) HR deficiency is known to sensitize breast, ovarian, prostate, and pancreatic cancers to C/Ts. To test our hypothesis, three specific aims will be pursued. Aim #1 will characterize the clinical relevance of NS in human HCC. Aim #2 will determine the effect of NS depletion on HR-based DSB repair in HCC cells. Aim #3 will determine the role of NS in mediating HCC drug resistance. As the outcome of this application, we will establish the clinical importance of NS by showing an increased or dysregulated NS expression in human HCC samples, define the relationship between NS expression and patients' clinical outcome, and provide functional evidence to support the role of NS in promoting the HR-based repair and chemoresistance in HCC cells, all of which are important preliminary data for our future R01 submission. If our hypothesis is proven true, it will impact on our knowledge of how HCC cells adapt to the hyperactive mitotic state and avoid fatal genomic instability at late stage, how HCC develop the innate property of chemoresistance, and whether HCC can be re-sensitized to C/Ts by NS ablation. Given the complexity of hepatocarcinogenesis and heterogeneity of HCC, combining C/Ts with a treatment that targets a common adaptive mechanism used by cancer cells offers an appealing strategy to improve the efficacy and tolerability of C/Ts.