Neoplastic pancreas cells enter a quasi-mesenchymal state with increased oncogenic potential following transient TGF-β exposure. Mus musculus

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease and a major health problem in the United States. While the cytokine TGF-β has been implicated in PDAC development, it can exert bot pro- and anti-tumorigenic effects that are highly context dependent and incompletely understood. To better characterize the responses of neoplastic pancreas cells to TGF-β, three-dimensional (3D) cultures of KrasG12D-expressing mouse pancreatic epithelial cells were employed. While active exposure to exogenous TGF-β caused the KrasG12D cells to growth arrest, its subsequent removal allowed the cells to enter a hyper-proliferative, quasi-mesenchymal (QM) and progenitor-like state. This transition was highly stable and maintained by autocrine TGF-β signaling. Transient pulses of TGF-β have been observed during pancreatitis, a major risk factor for PDAC, and may therefore serve to convert pre-existing KrasG12D-expressing cells into QM cells. While untreated KrasG12D cells formed simple cysts in vivo, QM cells formed ductal structures resembling human PanINs. Furthermore, markers of the QM state are expressed in human PDAC and are associated with worse outcomes. These data suggest that the QM state plays a role in PDAC development and may selectively contribute to more aggressive PDAC subtypes. This work therefore provides novel molecular insights into both PDAC development and the complex role of TGF-β in tumorigenesis. Overall design: Three technical replicates per experimental group from one isolate were analyzed by RNA sequencing

胰腺导管腺癌（Pancreatic ductal adenocarcinoma, PDAC）是一种致命性疾病，也是美国境内的主要公共卫生难题之一。尽管细胞因子转化生长因子-β（transforming growth factor-β, TGF-β）已被证实与PDAC的发生发展相关，但其既可发挥促肿瘤生成作用，亦可发挥抗肿瘤生成作用，这种双重效应具有高度的情境依赖性，目前尚未被完全阐明。为了更好地表征胰腺肿瘤细胞对TGF-β的应答反应，本研究采用了表达KrasG12D的小鼠胰腺上皮细胞的三维（3D）培养体系。持续暴露于外源性TGF-β可使KrasG12D细胞发生生长停滞，而随后移除外源性TGF-β则可促使这些细胞进入过度增殖、类间充质（quasi-mesenchymal, QM）及祖细胞样状态。这种状态转变具有高度稳定性，并可通过自分泌TGF-β信号通路得以维持。在胰腺炎（PDAC的主要危险因素之一）的发生过程中，已观测到TGF-β的瞬时脉冲式表达，因此这一现象可能促使已存在的KrasG12D阳性细胞转化为QM细胞。未经过处理的KrasG12D细胞在体内可形成简单囊肿，而QM细胞则可形成类似于人类胰腺上皮内瘤变（Pancreatic Intraepithelial Neoplasia, PanIN）的导管样结构。此外，QM状态的标志物在人类PDAC组织中均有表达，且与不良预后密切相关。上述研究结果表明，QM状态在PDAC的发生发展中发挥了一定作用，并可能选择性地促成侵袭性更强的PDAC亚型的形成。因此，本研究为PDAC的发生发展以及TGF-β在肿瘤生成过程中的复杂调控作用提供了全新的分子层面的见解。实验设计：本次研究通过RNA测序技术，对单一分离株的每个实验组进行了三次技术重复分析。