Cancer cell identity and plasticity are required in transition states, such as epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET), in primary tumor initiation, progression and metastasis. The functional roles of EMT, MET and partial state (referred to as p-EMT) may vary based upon the type of tumor, state of dissemination and degree of metastatic colonization. Herein, we review EMT, MET, pEMT and plasticity in the context of tumor metastasis.

The two major isoforms of the paired-related homeodomain transcription factor 1 (Prrx1), Prrx1a and Prrx1b, are involved in pancreatic development, pancreatitis, and carcinogenesis, although the biological role that these isoforms serve in the systemic dissemination of pancreatic ductal adenocarcinoma (PDAC) has not been investigated. An epithelial-mesenchymal transition (EMT) is believed to be important for primary tumor progression and dissemination, whereas a mesenchymal-epithelial transition (MET) appears crucial for metastatic colonization. Here, we describe novel roles for both isoforms in the metastatic cascade using complementary in vitro and in vivo models. Prrx1b promotes invasion, tumor dedifferentiation, and EMT. In contrast, Prrx1a stimulates metastatic outgrowth in the liver, tumor differentiation, and MET. We further demonstrate that the switch from Prrx1b to Prrx1a governs EMT plasticity in both mouse models of PDAC and human PDAC. Last, we identify hepatocyte growth factor ( HGF) as a novel transcriptional target of Prrx1b. Targeted therapy of HGF in combination with gemcitabine in a preclinical model of PDAC reduces primary tumor volume and eliminates metastatic disease. Overall, we provide new insights into the isoform-specific roles of Prrx1a and Prrx1b in primary PDAC formation, dissemination, and metastatic colonization, allowing for novel therapeutic strategies targeting EMT plasticity.

The most common subtype of pancreatic cancer is pancreatic ductal adenocarcinoma (PDAC). pDac resembles duct cells morphologically and, to some extent, at a molecular level. recently, genetic-lineage labeling has become popular in the field of tumor biology in order to study cell-fate decisions or to trace cancer cells in the mouse. However, certain biological questions require a nongenetic labeling approach to purify a distinct cell population in the pancreas. Here we describe a protocol for isolating mouse pancreatic ductal epithelial cells and duct-like cells directly in vivo using ductal-specific Dolichos biflorus agglutinin (DBA) lectin labeling followed by magnetic bead separation. Isolated cells can be cultured (in two or three dimensions), manipulated by lentiviral transduction to modulate gene expression and directly used for molecular studies. this approach is fast (∼4 h), affordable, results in cells with high viability, can be performed on the bench and is applicable to virtually all genetic and nongenetic disease models of the pancreas.

The regulation of metastatic organotropism in pancreatic ductal a denocarcinoma (PDAC) remains poorly understood. We demonstrate, using multiple mouse models, that liver and lung metastatic organotropism is dependent upon p120catenin (p120ctn)-mediated epithelial identity. Mono-allelic p120ctn loss accelerates Kras-driven pancreatic cancer formation and liver metastasis. Importantly, one p120ctn allele is sufficient for E-CADHERIN-mediated cell adhesion. By contrast, cells with bi-allelic p120ctn loss demonstrate marked lung organotropism; however, rescue with p120ctn isoform 1A restores liver metastasis. In a p120ctn-independent PDAC model, mosaic loss of E-CADHERIN expression reveals selective pressure for E-CADHERIN-positive liver metastasis and E-CADHERIN-negative lung metastasis. Furthermore, human PDAC and liver metastases support the premise that liver metastases exhibit predominantly epithelial characteristics. RNA-seq demonstrates differential induction of pathways associated with metastasis and epithelial-to-mesenchymal transition in p120ctn-deficient versus p120ctn-wild-type cells. Taken together, P120CTN and E-CADHERIN mediated epithelial plasticity is an addition to the conceptual framework underlying metastatic organotropism in pancreatic cancer.

Pancreatic ductal adenocarcinoma is one of the most aggressive forms of cancer, and the third leading cause of cancer-related mortality in the United States. Although important advances have been made in the last decade, the mortality rate of pancreatic ductal adenocarcinoma has not changed appreciably. This review summarizes a rapidly emerging model of pancreatic cancer research, focusing on 3-dimensional organoids as a powerful tool for several applications, but above all, representing a step toward personalized medicine.

Background & Aims The ETS-transcription factor ETV1 is involved in the epithelial–mesenchymal transition (EMT) during pancreatic development and is induced in mouse pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDAC). We investigated the function of ETV1 in stromal expansion of PDAC and metastasis, as well as its effects on its downstream target Sparc, which encodes a matricellular protein found in the PDAC stroma that has been associated with invasiveness and metastasis and poor outcomes of patients. Methods Pancreatic ductal cells were isolated from Pdx1Cre;KrasG12D/+ mice (PanIN), Pdx1Cre;KrasG12D/+;p53fl/+ and Pdx1Cre;KrasG12D/+;p53fl/+;Rosa26YFP mice (PDAC), and Pdx1Cre;KrasG12D/+; p53fl/+;Sparc-/- mice. Cells were grown in 3-dimensional organoid culture to analyze morphology, proliferation, and invasion. Human PanIN and PDAC tissues were evaluated for ETV1 expression. Orthotopic transplants of ETV1-overexpressing PDAC and control cells were assessed in mice. Results Analyses of orthotopic xenografts revealed that ETV1 induced significantly larger primary tumors than controls, with significantly increased stromal expansion and significantly more ascites and metastases. Three-dimensional organoids that overexpressed ETV1 had a disrupted cyst architecture, underwent the EMT, and were more invasive. ETV1 expression was increased in human PanINs and even more so in primary and metastatic PDACs. We identified Sparc as a functional gene target of ETV1 by luciferase assays, and SPARC and ETV1 proteins co-localized in vivo. Disruption of Sparc reduced the phenotype of stromal expansion and metastasis found with ETV1 overexpression in vivo. We identified Has2 as another downstream factor of ETV1; it may mediate ETV1's significant expansion of hyaluronic acid. Conversely, disruption of Etv1 in PDAC mice (Pdx1Cre;KrasG12D/+;p53fl/+;Rosa26YFP;Cre;Etv1fl/fl) reduced levels of SPARC and hyaluronic acid in the stroma. Conclusions ETV1 is critical in the desmoplastic stromal expansion and metastatic progression of pancreatic cancer in mice, mediated functionally in part through SPACR2 and HAS2.

Pancreatic cancer metastasis is a leading cause of cancer-related deaths, yet very little is understood regarding the underlying biology. As a result, targeted therapies to inhibit metastasis are lacking. Here, we report that the parathyroid hormone–related protein (PTHrP encoded by PTHLH) is frequently amplified as part of the KRAS amplicon in patients with pancreatic cancer. PTHrP upregulation drives the growth of both primary and metastatic tumors in mice and is highly enriched in pancreatic ductal adenocarcinoma metastases. Loss of PTHrP—either genetically or pharmacologically—dramatically reduces tumor burden, eliminates metastasis, and enhances overall survival. These effects are mediated in part through a reduction in epithelial-to-mesenchymal transition, which reduces the ability of tumor cells to initiate metastatic cascade. Spp1, which encodes osteopontin, is revealed to be a downstream effector of PTHrP. Our results establish a new paradigm in pancreatic cancer whereby PTHrP is a driver of disease progression and emerges as a novel therapeutic vulnerability. Significance: Pancreatic cancer often presents with metastases, yet no strategies exist to pharmacologically inhibit this process. Herein, we establish the oncogenic and prometastatic roles of PTHLH, a novel amplified gene in pancreatic ductal adenocarcinoma. We demonstrate that blocking PTHrP activity reduces primary tumor growth, prevents metastasis, and prolongs survival in mice. This article is highlighted in the In This Issue feature, p. 1601

BACKGROUND & AIMS Perturbations in pancreatic ductal bicarbonate secretion cause chronic pancreatitis. The physiologic mechanism of ductal secretion is known, but its transcriptional control is not. We determine the role of the transcription factor hematopoietically expressed homeobox protein (Hhex) in ductal secretion and pancreatitis. METHODS We derived mice with pancreas-specific, Cremediated Hhex gene ablation to determine the requirement of Hhex in the pancreatic duct in early life and in adult stages. Histologic and immunostaining analyses were used to detect the presence of pathology. Pancreatic primary ductal cells were isolated to discover differentially expressed transcripts upon acute Hhex ablation on a cell autonomous level. RESULTS Hhex protein was detected throughout the embryonic and adult ductal trees. Ablation of Hhex in pancreatic progenitors resulted in postnatal ductal ectasia associated with acinar-to-ductal metaplasia, a progressive phenotype that ultimately resulted in chronic pancreatitis. Hhex ablation in adult mice, however, did not cause any detectable pathology. Ductal ectasia in young mice did not result from perturbation of expression of Hnf6, Hnf1β, or the primary cilia genes. RNA-seq analysis of Hhex-ablated pancreatic primary ductal cells showed mRNA levels of the G-protein coupled receptor natriuretic peptide receptor 3 (Npr3), implicated in paracrine signaling, up-regulated by 4.70-fold. CONCLUSIONS Although Hhex is dispensable for ductal cell function in the adult, ablation of Hhex in pancreatic progenitors results in pancreatitis. Our data highlight the critical role of Hhex in maintaining ductal homeostasis in early life and support ductal hypersecretion as a novel etiology of pediatric chronic pancreatitis.