Exploitation of RAS signaling to develop therapy and early detection strategies for PDA

描述(申请人提供)：我们解决的治疗问题是如何抑制IPMN(导管内乳头状粘液性肿瘤)、Panin(胰腺上皮内肿瘤)和PDA(胰腺导管腺癌)的发展和进展。生物学上的问题是确定启动和传播IPMN、Panin和PDA的关键信号通路。该领域的一个中心争论是，PDA是起源于胰腺前体细胞，还是伴随着实质腺泡细胞向祖细胞样导管细胞的去分化，这一过程被称为腺泡至导管化生(ADM)。腺泡细胞识别的转录因子主调节因子(MRS)的功能在这一过程中是关键的，但翻译后通过受体酪氨酸激酶(RTK)和G蛋白偶联受体(GPCR)信号调节其活性是完全未知的。G蛋白信号转导调节蛋白(RGS)整合RTK和GPCRs的多种胞内信号，反馈调节GI和GQ蛋白信号。我们已经开发了一种GFP报告程序(RGS16：GFP)，使我们能够监测IPMN、Panin和PDA小鼠模型中早期阶段的肿瘤形成和肿瘤形成。将RGS16：GFP报告与IPMN、Panin和PDA的小鼠模型相结合，为这些肿瘤的发展提供了洞察力，并为这一过程的抑制剂提供了一种新颖和快速的体内筛选。我们发现了抑制IPMN向浸润性癌发展的RGS基因。基于这些模型的初步分析，我们发现IPMN和Panin在离散的导管前体细胞中启动，以响应胰腺腺泡或内分泌室的压力。这一解释挑战了目前流行的PDA从经历了ADM的细胞启动的范式，而我们认为慢性ADM刺激了导管中先前存在的祖细胞的增殖。我们发现RTK Axl在胰腺导管中表达，并且在原代培养的PDA前体细胞中与RGS16：GFP一起高表达。我们的假设是，基质中表达的Axl配体Gas6在上皮祖细胞中激活Axl信号，并有助于激活KrasG12D，翻译后控制MR水平和/或活动，PDA的启动和进展。在我们对抑制PDA进展的新疗法的初步体内筛选中，我们确定，阻断Gas6诱导的AXL激活的华法林与标准护理标准吉西他滨和阿布拉沙尼(GA)相结合，显著减缓了PDA的进展。这项建议的具体目标是：1)确定最佳药物组合，包括Ax1信号通路的抑制剂，以抑制PDA。2)确定血浆IPMN、Panin、PDA的早期标志物。3)确定PDA中Gas6-Axl的功能。这项拟议的项目如果成功，将通过以下方面对癌症产生重大影响：i)识别PDA的早期血液标志物，可能还有其他上皮性癌症；ii)引入一种新颖、通用和快速的体内筛选技术，以寻找抑制PDA进展的新药物组合；iii)提供新的基因工具来确定PDA是否起始于胰管内的祖细胞；IV)确定先前未知的MR转录因子的调控机制。

DESCRIPTION (provided by applicant): The therapeutic problem we address is how to inhibit the development and progression of IPMN (intraductal papillary mucinous neoplasm), PanIN (Pancreatic Intraepithelial Neoplasia) and PDA (pancreatic ductal adenocarcinoma). The biological problem is to identify key signaling pathways that initiate and propagate IPMN, PanIN and PDA. A central debate in the field is whether PDA initiates in pancreatic progenitor cells or with dedifferentiation of parenchymal acinar cells to progenitor-like ductal cells, in a process termed acinar to ductal metaplasia (ADM). The function of the transcription factor Master Regulators (MRs) of acinar cell identity is critical to this process but post-translational regulaton of their activity through receptor tyrosine kinase (RTK) and G protein coupled receptor (GPCR) signaling is completely unexplored. Regulators of G protein signaling (RGS) proteins integrate multiple intracellular signals from RTKs and GPCRs to feedback regulate Gi and Gq protein signaling. We have developed a GFP reporter (Rgs16:GFP) that allows us to monitor neoplasia and tumor formation from early stages in in vivo mouse models of IPMN, PanIN and PDA. Combining the Rgs16:GFP reporter with mouse models for IPMN, PanIN and PDA is providing insights into development of these tumors and a novel and rapid in vivo screen for inhibitors of this process. We discovered RGS genes that suppress progression of IPMN to invasive carcinoma. Based on preliminary analyses using these models, we find that IPMN and PanIN initiate in discrete ductal progenitor cells in response to stress in the acinar or endocrine compartments of the pancreas. This interpretation challenges the currently favored paradigm that PDA initiates with cells that underwent ADM whereas we propose that chronic ADM stimulates proliferation of pre-existing progenitor cells in ducts. We find that the RTK Axl is expressed in pancreatic ducts and is highly expressed with Rgs16:GFP in PDA progenitor cells in primary culture. Our hypothesis is that the Axl-ligand Gas6 expressed in stroma evokes Axl signaling in epithelial progenitor cells and contributes to activation of KrasG12D, post-translational control of MR levels and/or activity, PDA initiation and progression. In our preliminary in vivo screens of new therapeutics to inhibit PDA progression, we determined that warfarin, which blocks Gas6 induced activation of Axl, combined with the standard of care Gemcitabine and Abraxane (GA), significantly reduced PDA progression. The Specific Aims of this proposal are 1) Identify optimal drug combinations, including inhibitors of Axl signaling, to inhibit PDA. 2) Identify early markers of IPMN, PanIN and PDA in plasma. 3) Determine Gas6-Axl function in PDA. The proposed project, if successful, will have a major impact on cancer by i) identifying early blood markers of PDA, and perhaps other epithelial cancers, ii) introducing a novel, general and rapid in vivo screening technique to find novel drug combinations that inhibit PDA progression, iii) providing novel genetic tools to determine if PDA initiates in progenitor cells in the pancreatic duct, Iv) identify previously unknown regulatory mechanisms of the MR transcription factors.