Chemical Genetic Dissection of Aurora A in Promoting EMT and Stem Cells Phenotype

描述(申请人提供)：胰腺癌(PC)是一种极其致命的疾病。诊断前的早期转移、肿瘤复发和对当前化疗放射治疗的抵抗在PC患者中很常见。最近的证据表明，在PC肿瘤中获得上皮向间充质转化(EMT)和诱导肿瘤干细胞(CSC)表型是这些发生的重要潜在原因。然而，导致EMT和CSC表型的机制仍不清楚。这一信息对于发现治疗PC的新的靶向疗法是至关重要的，这些疗法提供了更好的结果。长期目标是确定治疗PC的有效药物靶点。我们最近未发表的数据揭示了Aurora A(AA)激酶在促进PC的EMT和CSC中的关键作用。AA在PC中表达上调，在肿瘤的发生和转移中起重要作用；然而，其分子机制尚不清楚。利用一种创新的化学遗传筛选，FOXM1转录因子被鉴定为高度恶性的AsPC1细胞中AA的直接靶点。AA在S361直接磷酸化FOXM1，稳定其水平。反过来，FOXM1还稳定AA水平，从而触发一个互惠的正反馈循环。已知FOXM1上调可促进PC细胞的EMT和CSC表型。这项建议的目的是确定FOXM1作为AA的关键效应因子在PC肿瘤中促进EMT和CSC表型的作用。中心假设是AA和FOXM1是潜在的药物靶点，协同促进PC中的侵袭性致癌途径。这一假说将通过追求三个具体目标来检验：1)确定AA在促进PC细胞的EMT和CSC方面的潜在作用。2)确定AA介导的FOXM1磷酸化对PC细胞多种致癌途径的影响。3)测定临床标本中AA和FOXM1的水平及其与临床结局的相关性。这种方法是创新的，因为中心假说是基于一种新的AA底物FOXM1提出的，该底物是使用一种强大的化学遗传学方法发现的。在PC中还没有发现AA的癌症特异性底物。到目前为止，AA尚未链接到CSC或EMT。此外，在人类PC组织中，FOXM1或AA的水平还没有被同时分析。这项拟议的研究具有重要意义，因为FOXM1作为AA底物的有效性将提供一个有效的工具来抑制转移性PC中FOXM1的去调控。AA和FOXM1水平与不同的临床结果的相关性有望揭示PC的潜在预后和诊断生物标志物。我们工作的积极影响将是确认AA作为治疗/预防EMT、CSC和化疗耐药的潜在药物靶点，无论是单独使用还是与FOXM1抑制剂联合使用。

DESCRIPTION (provided by applicant): Pancreatic cancer (PC) is extremely lethal. Early metastasis prior to diagnosis, tumor recurrence and resistance towards current chemo-radiation therapies are common among PC patients. Recent evidence indicates that the acquisition of epithelial-to-mesenchymal transition (EMT) and induction of cancer stem cell (CSC) phenotypes in PC tumors are important underlying causes for these occurrences. However, the mechanisms leading to EMT and CSC phenotypes remain unclear. This information is critical for the discovery of novel targeted therapies for the treatment of PC that offer superior outcome. The long term goal is to identify therapeutically effective drug targets in PC. Our recent unpublished data have uncovered a critical role of Aurora A (AA) kinase in promoting EMT and CSC in PC. AA is upregulated in PC and contributes significantly to tumorigenesis and metastasis; however, the molecular mechanisms remain unknown. Using an innovative chemical genetic screen, FOXM1 transcription factor was identified as a direct target of AA in highly malignant AsPC1 cells. AA directly phosphorylates FOXM1 at S361 stabilizing its levels. In turn, FOXM1 also stabilizes AA levels, thereby triggering a reciprocal positive feedback loop. FOXM1 upregulation is known to promote EMT and CSC phenotypes in PC cells. The objective in this proposal is to determine the contribution of FOXM1 as a critical effector of AA by which it promotes EMT and CSC phenotype in PC tumors. The central hypothesis is that AA and FOXM1 are potential drug targets which promote aggressive oncogenic pathways in PC synergistically. This hypothesis will be tested by pursuing three specific aims: 1) Determine a potential role of AA in promoting EMT and CSC in PC cells. 2) Determine the consequences of AA-mediated phosphorylation of FOXM1 on various oncogenic pathways in PC cells. 3) Determine AA and FOXM1 levels in tandem in human clinical samples and their correlation with clinical outcomes. The approach is innovative because the central hypothesis was formulated based on a novel AA substrate, FOXM1, discovered using a powerful chemical genetic approach. No cancer-specific substrate of AA has been identified in PC. AA has not been linked to CSC or EMT to date. Furthermore, FOXM1 or AA levels have not been analyzed in tandem in human PC tissues. The proposed research is significant because validation of FOXM1 as an AA substrate will provide a potent tool to inhibit FOXM1 deregulation in metastatic PC. Correlation of AA and FOXM1 levels with divergent clinical outcomes are expected to reveal potential prognostic and diagnostic biomarkers for PC. The positive impact of our work will be the validation of AA as a potential drug target for treating/preventing EMT, CSC and chemoresistance, either alone or in combination with FOXM1 inhibitors.