The role of PP2A B56a in pancreatic tumorigenesis

项目摘要 大多数胰腺导管腺癌（PDA）患者表现为晚期转移性疾病 通常对治疗有抵抗力，导致极低的存活率。了解机制 调节PDA的早期启动和进展对于开发新的，更重要的 准确的胰腺癌模型，用于识别生物标志物和新的治疗靶点。蛋白 磷酸酶是细胞信号传导途径（包括MAPK和PI 3 K途径）的主要调节剂。 我们实验室和其他实验室的研究表明，PDA肿瘤的PP 2A表达增加， 抑制剂和PP 2A功能的相应降低，表明PP 2A的抑制是常见的 PDA进展事件。活性PP 2A全酶由三种蛋白质组成，包括一种催化蛋白质， 亚基、支架亚基和提供靶特异性的调节（B）亚基。虽然PP 2A 被认为具有肿瘤抑制因子的功能，即特定B亚单位对疾病的个体贡献 进展仍然知之甚少。我们已经鉴定出PP 2A B亚基B56 β是一个重要的 KRAS驱动途径的调节剂，包括癌蛋白c-MYC的稳定。鉴于KRAS 突变发生在90-95%的PDA患者中，B56 β对该途径的调节代表了一个重要的空白， 知识在我们的初步研究中，小鼠中B56 β的缺失加速了胰腺前体的形成， 病变和增加参与细胞命运和转移的转录因子的表达。所以我 假设B56 β在介导胰腺细胞可塑性中起关键作用， 将增加胰腺细胞对致癌突变的易感性，驱动PDA的启动， 转型这一假设将通过以下三个具体目标来解决：1）确定 致癌性KRAS对PP 2A-B56激酶复合物形成和功能影响，2）检查B56激酶的缺失是否 加速体外和体内癌前病变的进展，和3）确定是否治疗 PP 2A-B56 β的激活可以抑制PDA过程中发生的转录和表观遗传变化， 入会仪式这些研究将利用诸如单细胞表观遗传分析、小鼠遗传学分析、小鼠遗传学分析等技术。 PDA的建模，以及使用循环免疫荧光分析人PDA肿瘤中的PP 2A组成 以提供PDA发展与磷酸酶功能相关的深入分子理解。 重要的是，在肿瘤早期，参与细胞可塑性的因子的转录失调 发展已被证明对晚期肿瘤异质性、亚型和 治疗反应因此，这些研究的结果将为未来提供强有力的基础 询问早期和晚期疾病，扩大我的独立科学计划， 支持我的长期目标，了解PDA的分子基础。

Project Summary The majority of pancreatic ductal adenocarcinoma (PDA) patients present with late-stage, metastatic disease that is often resistant to therapeutics, resulting in extremely low survival rates. Understanding the mechanisms that regulate the early initiation and progression of PDA is critically important to the development of new, more accurate pancreatic cancer models for the identification of biomarkers and novel therapeutic targets. Protein phosphatases are master regulators of cell signaling pathways, including the MAPK and PI3K pathways. Studies from our lab and others have demonstrated that PDA tumors have increased expression of PP2A inhibitors and a corresponding decrease in PP2A function, suggesting that the inhibition of PP2A is a common event in PDA progression. The active PP2A holoenzyme is composed of three proteins including a catalytic subunit, a scaffolding subunit, and a regulatory (B) subunit that provides target specificity. While PP2A is thought to function as a tumor suppressor, the individual contribution of specific B subunits to disease progression is still poorly understood. We have identified the PP2A B subunit, B56, as being an important regulator of KRAS driven pathways, including the stabilization of the oncoprotein c-MYC. Given that KRAS mutations occur in 90-95% of PDA patients, regulation of this pathway by B56 represents an important gap in knowledge. In our preliminary studies, loss of B56 in mice accelerated the formation of pancreatic precursor lesions and increased the expression of transcription factors involved in cell fate and metastasis. Therefore, I hypothesize that B56 plays a critical role in mediating pancreatic cell plasticity, and that suppression of B56 will increase the susceptibility of pancreatic cells to oncogenic mutation, driving PDA initiation and transformation. This hypothesis will be addressed through the following three Specific Aims: 1) Determine the impact of oncogenic KRAS on PP2A-B56 complex formation and function, 2) Examine whether loss of B56 accelerates the progression of premalignant lesions in vitro and in vivo, and 3) Determine if therapeutic activation of PP2A-B56 can suppress the transcriptional and epigenetic changes that occur during PDA initiation. These studies will take advantage of techniques such as single cell epigenetic analysis, mouse modeling of PDA, and analysis of PP2A composition in human PDA tumors using cyclic immunofluorescence in order to provide a deep molecular understanding of PDA development in relation to phosphatase function. Importantly, the transcriptional deregulation of factors involved in cellular plasticity during early tumor development has been shown to have a significant impact on late stage tumor heterogeneity, subtype, and therapeutic response. Therefore, results from these studies will provide a strong basis for the future interrogation of both early and late stage disease, expanding my independent scientific program and supporting my long-term goal of understanding the molecular basis of PDA.