Epigenetic Regulation of Hemidesmosome Signaling in Pancreatic Cancer

胰腺导管腺癌（PDAC）是最具侵袭性的人类癌症之一，其中少于8%的人患有胰腺癌。 确诊后存活5年以上的患者。PDAC治疗的一个关键障碍是高度的 结缔组织增生性肿瘤间质。间质中非肿瘤细胞和细胞外基质（ECM）的丰度 与促进侵袭性肿瘤生长和抑制有效药物递送有关。ECM已 长期以来认为主要由基质细胞产生，包括癌症相关成纤维细胞（CAF）。 然而，我们对异种移植肿瘤模型、CAFs和PDAC细胞的体外共培养以及激光治疗的表征， 捕获显微切割的肿瘤揭示了PDAC细胞表达大比例的ECM。 此外，这些研究揭示了PDAC细胞的CAF依赖性重编程， 在肿瘤中观察到ECM成分的表达。我们之前已经证明，BET家族 染色质衔接子在PDAC肿瘤的生长中起着关键作用，它通过调节PDAC和 基质细胞在这项工作的基础上，我们发现PDAC中ECM的表达受到以下因素的广泛调节： BET蛋白。在这些BET依赖性基因中，有半桥粒的成分， 该复合物介导从ECM到细胞的细胞骨架网络的信号传导。该提案将审查 BET蛋白介导PDAC细胞中ECM的CAF依赖性表达的机制， 定义胶原蛋白XVII的生物学作用，半桥粒的关键亚基。具体目标1 应用中，低传代PDAC细胞系和永生化PDAC衍生的CAF培养物将用于 检查CAFs介导ECM的BET依赖性表达的转录机制- PDAC细胞中的编码基因。在具体目标2中，我们将采用肿瘤模型， 胶原XVII的表达，以确定PDAC细胞中CAF诱导的胶原XVII表达是否有助于 PDAC肿瘤的生长。将在肿瘤中分析下游胶原XVII信号传导途径，以阐明 这种信号传导有助于肿瘤生物学的机制。

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human cancers, with less than 8% of patients surviving beyond five years after diagnosis. A key impediment to the treatment of PDAC is a highly desmoplastic tumor stroma. The abundance of non-neoplastic cells and extracellular matrix (ECM) in the stroma have been implicated in promoting aggressive tumor growth and inhibiting effective drug delivery. The ECM has long been thought to be primarily produced by stromal cells, including cancer associated fibroblasts (CAFs). However, our characterization of xenograft tumor models, in vitro co-cultures of CAFs and PDAC cells, and laser capture microdissected tumors has revealed that PDAC cells express a large proportion of the ECM. Furthermore, these studies revealed a CAF-dependent reprogramming of PDAC cells that allows for the expression of ECM components observed in tumors. We have previously demonstrated that the BET family of chromatin adaptors play key roles in the growth of PDAC tumors by regulating pathways in both PDAC and stromal cells. Building on this work, we have found the expression of the ECM in PDAC is broadly regulated by BET proteins. Among these BET-dependent genes are components of the hemidesmosome, a multiprotein complex that mediates signaling from the ECM to the cytoskeletal network of cells. This proposal will examine the mechanisms by which BET proteins mediate the CAF-dependent expression of the ECM in PDAC cells and define the biological role of Collagen XVII, a critical subunit of hemidesmosomes. In Specific Aim 1 of this application, low passage PDAC cell lines and immortalized PDAC-derived CAF cultures will be utilized to examine the transcriptional mechanisms by which CAFs mediate the BET-dependent expression of the ECM- encoding genes in PDAC cells. In Specific Aim 2, we will employ tumor models that temporally regulate the expression of Collagen XVII to define whether CAF-induced expression of Collagen XVII in PDAC cells contribute to PDAC tumor growth. Downstream Collagen XVII signaling pathways will be analyzed in tumors to elucidate the mechanisms by which this signaling contributes to tumor biology.