ATDC is required for the initiation of KRAS-induced pancreatic tumorigenesis.

Pancreatic adenocarcinoma (PDA) is an aggressive disease driven by oncogenic KRAS and characterized by late diagnosis and therapeutic resistance. Here we show that deletion of the ataxia-telangiectasia group D-complementing (Atdc) gene, whose human homolog is up-regulated in the majority of pancreatic adenocarcinoma, completely prevents PDA development in the context of oncogenic KRAS. ATDC is required for KRAS-driven acinar-ductal metaplasia (ADM) and its progression to pancreatic intraepithelial neoplasia (PanIN). As a result, mice lacking ATDC are protected from developing PDA. Mechanistically, we show ATDC promotes ADM progression to PanIN through activation of ß-catenin signaling and subsequent SOX9 up-regulation. These results provide new insight into PDA initiation and reveal ATDC as a potential target for preventing early tumor-initiating events.

Novel Approach for Pancreas Transcriptomics Reveals the Cellular Landscape in Homeostasis and Acute Pancreatitis.

BACKGROUND & AIMS: Acinar cells produce digestive enzymes that impede transcriptomic characterization of the exocrine pancreas. Thus, single-cell RNA-sequencing studies of the pancreas underrepresent acinar cells relative to histological expectations, and a robust approach to capture pancreatic cell responses in disease states is needed. We sought to innovate a method that overcomes these challenges to accelerate study of the pancreas in health and disease. METHODS: We leverage FixNCut, a single-cell RNA-sequencing approach in which tissue is reversibly fixed with dithiobis(succinimidyl propionate) before dissociation and single-cell preparation. We apply FixNCut to an established mouse model of acute pancreatitis, validate findings using GeoMx whole transcriptome atlas profiling, and integrate our data with prior studies to compare our method in both mouse and human pancreas datasets. RESULTS: FixNCut achieves unprecedented definition of challenging pancreatic cells, including acinar and immune populations in homeostasis and acute pancreatitis, and identifies changes in all major cell types during injury and recovery. We define the acinar transcriptome during homeostasis and acinar-to-ductal metaplasia and establish a unique gene set to measure deviation from normal acinar identity. We characterize pancreatic immune cells, and analysis of T-cell subsets reveals a polarization of the homeostatic pancreas toward type-2 immunity. We report immune responses during acute pancreatitis and recovery, including early neutrophil infiltration, expansion of dendritic cell subsets, and a substantial shift in the transcriptome of macrophages due to both resident macrophage activation and monocyte infiltration. CONCLUSIONS: FixNCut preserves pancreatic transcriptomes to uncover novel cell states during homeostasis and following pancreatitis, establishing a broadly applicable approach and reference atlas for study of pancreas biology and disease.

The E3 ubiquitin ligase TRIP12 is required for pancreatic acinar cell plasticity and pancreatic carcinogenesis.

The E3 ubiquitin ligase thyroid hormone receptor interacting protein 12 (TRIP12) has been implicated in pancreatic adenocarcinoma (PDAC) through its role in mediating the degradation of pancreas transcription factor 1a (PTF1a). PTF1a is a transcription factor essential for the acinar differentiation state that is notably diminished during the early steps of pancreatic carcinogenesis. Despite these findings, the direct involvement of TRIP12 in the onset of pancreatic cancer has yet to be established. In this study, we demonstrated that TRIP12 protein was significantly upregulated in human pancreatic preneoplastic lesions. Furthermore, we observed that TRIP12 overexpression varied within PDAC samples and PDAC-derived cell lines. We further demonstrated that TRIP12 was required for PDAC-derived cell growth and for the expression of E2F-targeted genes. Acinar-to-ductal cell metaplasia (ADM) is a reversible process that reflects the high plasticity of acinar cells. ADM becomes irreversible in the presence of oncogenic Kras mutations and leads to the formation of preneoplastic lesions. Using two genetically modified mouse models, we showed that a loss of TRIP12 prevented acini from developing ADM in response to pancreatic injury. With two additional mouse models, we further discovered that a depletion of TRIP12 prevented the formation of KrasG12D-induced preneoplastic lesions and impaired metastasis formation in the presence of mutated KrasG12D and Trp53R172H genes. In summary our study identified an overexpression of TRIP12 from the early stages of pancreatic carcinogenesis and proposed this E3 ubiquitin ligase as a novel regulator of acinar plasticity with an important dual role in initiation and metastatic steps of PDAC. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

CD73-generated extracellular adenosine promotes resolution of neutrophil-mediated tissue injury and restrains metaplasia in pancreatitis.

Pancreatitis is currently the leading cause of gastrointestinal hospitalizations in the US. This condition occurs in response to abdominal injury, gallstones, chronic alcohol consumption or, less frequently, the cause remains idiopathic. CD73 is a cell surface ecto-5'-nucleotidase that generates extracellular adenosine, which can contribute to resolution of inflammation by binding adenosine receptors on infiltrating immune cells. We hypothesized genetic deletion of CD73 would result in more severe pancreatitis due to decreased generation of extracellular adenosine. CD73 knockout (CD73-/- ) and C57BL/6 (wild type, WT) mice were used to evaluate the progression and response of caerulein-induced acute and chronic pancreatitis. In response to caerulein-mediated chronic or acute pancreatitis, WT mice display resolution of pancreatitis at earlier timepoints than CD73-/- mice. Using immunohistochemistry and analysis of single-cell RNA-seq (scRNA-seq) data, we determined CD73 localization in chronic pancreatitis is primarily observed in mucin/ductal cell populations and immune cells. In murine pancreata challenged with caerulein to induce acute pancreatitis, we compared CD73-/- to WT mice and observed a significant infiltration of Ly6G+, MPO+, and Granzyme B+ cells in CD73-/- compared to WT pancreata and we quantified a significant increase in acinar-to-ductal metaplasia demonstrating sustained metaplasia and inflammation in CD73-/- mice. Using neutrophil depletion in CD73-/- mice, we show neutrophil depletion significantly reduces metaplasia defined by CK19+ cells per field and significantly reduces acute pancreatitis. These data identify CD73 enhancers as a potential therapeutic strategy for patients with acute and chronic pancreatitis as adenosine generation and activation of adenosine receptors is critical to resolve persistent inflammation in the pancreas.

Genetic ablation of Smoothened in pancreatic fibroblasts increases acinar-ductal metaplasia.

The contribution of the microenvironment to pancreatic acinar-to-ductal metaplasia (ADM), a preneoplastic transition in oncogenic Kras-driven pancreatic cancer progression, is currently unclear. Here we show that disruption of paracrine Hedgehog signaling via genetic ablation of Smoothened (Smo) in stromal fibroblasts in a Kras(G12D) mouse model increased ADM. Smo-deleted fibroblasts had higher expression of transforming growth factor-α (Tgfa) mRNA and secreted higher levels of TGFα, leading to activation of EGFR signaling in acinar cells and increased ADM. The mechanism involved activation of AKT and noncanonical activation of the GLI family transcription factor GLI2. GLI2 was phosphorylated at Ser230 in an AKT-dependent fashion and directly regulated Tgfa expression in fibroblasts lacking Smo Additionally, Smo-deleted fibroblasts stimulated the growth of Kras(G12D)/Tp53(R172H) pancreatic tumor cells in vivo and in vitro. These results define a non-cell-autonomous mechanism modulating Kras(G12D)-driven ADM that is balanced by cross-talk between Hedgehog/SMO and AKT/GLI2 pathways in stromal fibroblasts.

Pancreatic fibroblasts smoothen their activities via AKT-GLI2-TGFα.

Pancreatic stromal fibroblasts provide structural support. Activated fibroblasts are critical in the tumor microenvironment. In this issue of Genes & Development, Liu and colleagues (pp. 1943-1955) unravel the finding that depletion of Smoothened (Smo) in pancreatic stromal fibroblasts results in AKT activation and noncanonical GLI2 activation with subsequent TGFα secretion, activation of EGFR in pancreatic epithelial cells, and augmentation of acinar-ductal metaplasia. Additionally, Smo-mediated signaling has proproliferative effects on pancreatic tumor cells.

Estrogen-Related Receptor γ Maintains Pancreatic Acinar Cell Function and Identity by Regulating Cellular Metabolism.

BACKGROUND & AIMS: Mitochondrial dysfunction disrupts the synthesis and secretion of digestive enzymes in pancreatic acinar cells and plays a primary role in the etiology of exocrine pancreas disorders. However, the transcriptional mechanisms that regulate mitochondrial function to support acinar cell physiology are poorly understood. Here, we aim to elucidate the function of estrogen-related receptor γ (ERRγ) in pancreatic acinar cell mitochondrial homeostasis and energy production. METHODS: Two models of ERRγ inhibition, GSK5182-treated wild-type mice and ERRγ conditional knock-out (cKO) mice, were established to investigate ERRγ function in the exocrine pancreas. To identify the functional role of ERRγ in pancreatic acinar cells, we performed histologic and transcriptome analysis with the pancreas isolated from ERRγ cKO mice. To determine the relevance of these findings for human disease, we analyzed transcriptome data from multiple independent human cohorts and conducted genetic association studies for ESRRG variants in 2 distinct human pancreatitis cohorts. RESULTS: Blocking ERRγ function in mice by genetic deletion or inverse agonist treatment results in striking pancreatitis-like phenotypes accompanied by inflammation, fibrosis, and cell death. Mechanistically, loss of ERRγ in primary acini abrogates messenger RNA expression and protein levels of mitochondrial oxidative phosphorylation complex genes, resulting in defective acinar cell energetics. Mitochondrial dysfunction due to ERRγ deletion further triggers autophagy dysfunction, endoplasmic reticulum stress, and production of reactive oxygen species, ultimately leading to cell death. Interestingly, ERRγ-deficient acinar cells that escape cell death acquire ductal cell characteristics, indicating a role for ERRγ in acinar-to-ductal metaplasia. Consistent with our findings in ERRγ cKO mice, ERRγ expression was significantly reduced in patients with chronic pancreatitis compared with normal subjects. Furthermore, candidate locus region genetic association studies revealed multiple single nucleotide variants for ERRγ that are associated with chronic pancreatitis. CONCLUSIONS: Collectively, our findings highlight an essential role for ERRγ in maintaining the transcriptional program that supports acinar cell mitochondrial function and organellar homeostasis and provide a novel molecular link between ERRγ and exocrine pancreas disorders.

Acinar-to-Ductal Metaplasia (ADM): On the Road to Pancreatic Intraepithelial Neoplasia (PanIN) and Pancreatic Cancer.

Adult pancreatic acinar cells show high plasticity allowing them to change in their differentiation commitment. Pancreatic acinar-to-ductal metaplasia (ADM) is a cellular process in which the differentiated pancreatic acinar cells transform into duct-like cells. This process can occur as a result of cellular injury or inflammation in the pancreas. While ADM is a reversible process allowing pancreatic acinar regeneration, persistent inflammation or injury can lead to the development of pancreatic intraepithelial neoplasia (PanIN), which is a common precancerous lesion that precedes pancreatic ductal adenocarcinoma (PDAC). Several factors can contribute to the development of ADM and PanIN, including environmental factors such as obesity, chronic inflammation and genetic mutations. ADM is driven by extrinsic and intrinsic signaling. Here, we review the current knowledge on the cellular and molecular biology of ADM. Understanding the cellular and molecular mechanisms underlying ADM is critical for the development of new therapeutic strategies for pancreatitis and PDAC. Identifying the intermediate states and key molecules that regulate ADM initiation, maintenance and progression may help the development of novel preventive strategies for PDAC.

Akt1 signalling supports acinar proliferation and limits acinar-to-ductal metaplasia formation upon induction of acute pancreatitis.

Molecular signalling mediated by the phosphatidylinositol-3-kinase (PI3K)-Akt axis is a key regulator of cellular functions. Importantly, alteration of the PI3K-Akt signalling underlies the development of different human diseases, thus prompting the investigation of the pathway as a molecular target for pharmacologic intervention. In this regard, recent studies showed that small molecule inhibitors of PI3K, the upstream regulator of the pathway, reduced the development of inflammation during acute pancreatitis, a highly debilitating and potentially lethal disease. Here we investigated whether a specific reduction of Akt activity, by using either pharmacologic Akt inhibition, or genetic inactivation of the Akt1 isoform selectively in pancreatic acinar cells, is effective in ameliorating the onset and progression of the disease. We discovered that systemic reduction of Akt activity did not protect the pancreas from initial damage and only transiently delayed leukocyte recruitment. However, reduction of Akt activity decreased acinar proliferation and exacerbated acinar-to-ductal metaplasia (ADM) formation, two critical events in the progression of pancreatitis. These phenotypes were recapitulated upon conditional inactivation of Akt1 in acinar cells, which resulted in reduced expression of 4E-BP1, a multifunctional protein of key importance in cell proliferation and metaplasia formation. Collectively, our results highlight the critical role played by Akt1 during the development of acute pancreatitis in the control of acinar cell proliferation and ADM formation. In addition, these results harbour important translational implications as they raise the concern that inhibitors of PI3K-Akt signalling pathways may negatively affect the regeneration of the pancreas. Finally, this work provides the basis for further investigating the potential of Akt1 activators to boost pancreatic regeneration following inflammatory insults. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A critical role for Akt1 signaling in acute pancreatitis progression†.

Acute pancreatitis (AP) is an inflammatory disease of the pancreas that causes significant morbidity and mortality worldwide. Unfortunately, there is no specific treatment available to date. Several studies have previously shown that inhibitors of the PI3K/Akt axis downregulate the degree of inflammation in animal models of AP. However, studies on in vivo side-effects of such inhibitors are still lacking. In a recent issue of The Journal of Pathology, Chen, Malagola et al investigated if inhibition of Akt signaling plays a negative role in the regenerative phase of AP. They showed that treating AP mice with an Akt inhibitor (MK2206) impaired acinar regeneration and increased the development of acinar-to-ductal metaplasia. This is the first study to highlight the negative impact of an Akt inhibitor on cellular regeneration while simultaneously inhibiting inflammation in AP. The authors also suggested combining Akt activators to recover pancreatic regeneration. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

GRP78 haploinsufficiency suppresses acinar-to-ductal metaplasia, signaling, and mutant Kras-driven pancreatic tumorigenesis in mice.

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal disease in critical need of new therapeutic strategies. Here, we report that the stress-inducible 78-kDa glucose-regulated protein (GRP78/HSPA5), a key regulator of endoplasmic reticulum homeostasis and PI3K/AKT signaling, is overexpressed in the acini and PDAC of Pdx1-Cre;KrasG12D/+;p53f/+ (PKC) mice as early as 2 mo, suggesting that GRP78 could exert a protective effect on acinar cells under stress, as during PDAC development. The PKC pancreata bearing wild-type Grp78 showed detectable PDAC by 3 mo and rapid subsequent tumor growth. In contrast, the PKC pancreata bearing a Grp78f/+ allele (PKC78f/+ mice) expressing about 50% of GRP78 maintained normal sizes during the early months, with reduced proliferation and suppression of AKT, S6, ERK, and STAT3 activation. Acinar-to-ductal metaplasia (ADM) has been identified as a key tumor initiation mechanism of PDAC. Compared with PKC, the PKC78f/+ pancreata showed substantial reduction of ADM as well as pancreatic intraepithelial neoplasia-1 (PanIN-1), PanIN-2, and PanIN-3 and delayed onset of PDAC. ADM in response to transforming growth factor α was also suppressed in ex vivo cultures of acinar cell clusters isolated from mouse pancreas bearing targeted heterozygous knockout of Grp78 (c78f/+ ) and subjected to 3D culture in collagen. We further discovered that GRP78 haploinsufficiency in both the PKC78f/+ and c78f/+ pancreata leads to reduction of epidermal growth factor receptor, which is critical for ADM initiation. Collectively, our studies establish a role for GRP78 in ADM and PDAC development.

Establishment and Characterization of Immortalized Miniature Pig Pancreatic Cell Lines Expressing Oncogenic K-RasG12D.

In recent decades, many studies on the treatment and prevention of pancreatic cancer have been conducted. However, pancreatic cancer remains incurable, with a high mortality rate. Although mouse models have been widely used for preclinical pancreatic cancer research, these models have many differences from humans. Therefore, large animals may be more useful for the investigation of pancreatic cancer. Pigs have recently emerged as a new model of pancreatic cancer due to their similarities to humans, but no pig pancreatic cancer cell lines have been established for use in drug screening or analysis of tumor biology. Here, we established and characterized an immortalized miniature pig pancreatic cell line derived from primary pancreatic cells and pancreatic cancer-like cells expressing K-rasG12D regulated by the human PTF1A promoter. Using this immortalized cell line, we analyzed the gene expression and phenotypes associated with cancer cell characteristics. Notably, we found that acinar-to-ductal transition was caused by K-rasG12D in the cell line constructed from acinar cells. This may constitute a good research model for the analysis of acinar-to-ductal metaplasia in human pancreatic cancer.

Ring1b-dependent epigenetic remodelling is an essential prerequisite for pancreatic carcinogenesis.

BACKGROUND AND AIMS: Besides well-defined genetic alterations, the dedifferentiation of mature acinar cells is an important prerequisite for pancreatic carcinogenesis. Acinar-specific genes controlling cell homeostasis are extensively downregulated during cancer development; however, the underlying mechanisms are poorly understood. Now, we devised a novel in vitro strategy to determine genome-wide dynamics in the epigenetic landscape in pancreatic carcinogenesis. DESIGN: With our in vitro carcinogenic sequence, we performed global gene expression analysis and ChIP sequencing for the histone modifications H3K4me3, H3K27me3 and H2AK119ub. Followed by a comprehensive bioinformatic approach, we captured gene clusters with extensive epigenetic and transcriptional remodelling. Relevance of Ring1b-catalysed H2AK119ub in acinar cell reprogramming was studied in an inducible Ring1b knockout mouse model. CRISPR/Cas9-mediated Ring1b ablation as well as drug-induced Ring1b inhibition were functionally characterised in pancreatic cancer cells. RESULTS: The epigenome is vigorously modified during pancreatic carcinogenesis, defining cellular identity. Particularly, regulatory acinar cell transcription factors are epigenetically silenced by the Ring1b-catalysed histone modification H2AK119ub in acinar-to-ductal metaplasia and pancreatic cancer cells. Ring1b knockout mice showed greatly impaired acinar cell dedifferentiation and pancreatic tumour formation due to a retained expression of acinar differentiation genes. Depletion or drug-induced inhibition of Ring1b promoted tumour cell reprogramming towards a less aggressive phenotype. CONCLUSIONS: Our data provide substantial evidence that the epigenetic silencing of acinar cell fate genes is a mandatory event in the development and progression of pancreatic cancer. Targeting the epigenetic repressor Ring1b could offer new therapeutic options.

Serotonin uptake is required for Rac1 activation in Kras-induced acinar-to-ductal metaplasia in the pancreas.

Pancreatic ductal adenocarcinoma (PDAC), which is the primary cause of pancreatic cancer mortality, is poorly responsive to currently available interventions. Identifying new targets that drive PDAC formation and progression is critical for developing alternative therapeutic strategies to treat this lethal malignancy. Using genetic and pharmacological approaches, we investigated in vivo and in vitro whether uptake of the monoamine serotonin [5-hydroxytryptamine (5-HT)] is required for PDAC development. We demonstrated that pancreatic acinar cells have the ability to readily take up 5-HT in a transport-mediated manner. 5-HT uptake promoted activation of the small GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1), which is required for transdifferentiation of acinar cells into acinar-to-ductal metaplasia (ADM), a key determinant in PDAC development. Consistent with the central role played by Rac1 in ADM formation, inhibition of the 5-HT transporter Sert (Slc6a4) with fluoxetine reduced ADM formation both in vitro and in vivo in a cell-autonomous manner. In addition, fluoxetine treatment profoundly compromised the stromal reaction and affected the proliferation and lipid metabolism of malignant PDAC cells. We propose that Sert is a promising therapeutic target to counteract the early event of ADM, with the potential to stall the initiation and progression of pancreatic carcinogenesis. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Baicalein inhibits acinar-to-ductal metaplasia of pancreatic acinal cell AR42J via improving the inflammatory microenvironment.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers. Recent research has demonstrated that chronic pancreatitis (CP) is associated with an increased risk of PDAC, partly due to acinar-to-ductal metaplasia (ADM). Baicalein has been shown to exert anti-inflammatory and anti-tumor effects for CP or PDAC, respectively. The aim of our study was to investigate the effect of baicalein, and the putative underlying mechanism, on inflammatory cytokines-induced ADM of rat pancreatic acinar cell line AR42J. To investigate ADM and baicalein effects in vitro, AR42J were treated with recombinant rat Tumor Necrosis Factor alpha (rTNFα) with or without baicalein for 5 days. Results showed that rTNFα-induced AR42J cells switched their phenotype from dominantly amylase-positive acinar cells to dominantly cytokeratin 19-positive ductal cells. Moreover, expression of the transcripts for TNFα or Hes-1, a Notch target, was up-regulated in these cells. Interestingly, baicalein reduced the population of ADM as well as cytokines gene expression but not Hes-1. Baicalein inhibited NF-κB activation induced by rTNFα in AR42J, but no effect on Notch 1activation. Moreover, baicalein suppressed the secretion of TNFα and Nitric Oxide (NO) in macrophages stimulated with LPS and further inhibited ADM of conditional medium-treated AR42J cells. Baicalein also suppressed the inflammatory response of LPS-activated macrophages, thereby inhibited ADM of AR42J by altering their microenvironment. Taken together, our study indicates that baicalein reduces rTNFα-induced ADM of AR42J cells by inhibiting NF-κB activation. It also sheds new light on Chinese material medica therapy of pancreatitis and thereby prevention of PDAC.

Glycogen synthase kinase-3ß ablation limits pancreatitis-induced acinar-to-ductal metaplasia.

Acinar-to-ductal metaplasia (ADM) is a reversible epithelial transdifferentiation process that occurs in the pancreas in response to acute inflammation. ADM can rapidly progress towards pre-malignant pancreatic intraepithelial neoplasia (PanIN) lesions in the presence of mutant KRas and ultimately pancreatic adenocarcinoma (PDAC). In the present work, we elucidate the role and related mechanism of glycogen synthase kinase-3beta (GSK-3ß) in ADM development using in vitro 3D cultures and genetically engineered mouse models. We show that GSK-3ß promotes TGF-α-induced ADM in 3D cultured primary acinar cells, whereas deletion of GSK-3ß attenuates caerulein-induced ADM formation and PanIN progression in KrasG12D transgenic mice. Furthermore, we demonstrate that GSK-3ß ablation influences ADM formation and PanIN progression by suppressing oncogenic KRas-driven cell proliferation. Mechanistically, we show that GSK-3ß regulates proliferation by increasing the activation of S6 kinase. Taken together, these results indicate that GSK-3ß participates in early pancreatitis-induced ADM and thus could be a target for the treatment of chronic pancreatitis and the prevention of PDAC progression. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Multiple roles for TGFß receptor type II in regulating the pancreatic response in acute pancreatitis.

In their recent publication in Journal of Pathology, Grabliauskaite and Sapanora and their colleagues in Zurich use a conditional ablation of the TGFß type II receptor (TBRII) to analyse its specific role in pancreatic epithelial cells in response to a caerulein-induced model of acute pancreatitis. These experiments help to clarify some confusion that has existed in the literature stemming from the use of a dominant-negative transgenic TBRII mouse. The results point to a central role for TBRII in acinar cells in mitigating the overall response of the pancreas to the damage and inflammation of acute pancreatitis.

Long-term evolution of acinar-to-ductal metaplasia and ß-cell mass after radiofrequency-assisted transection of the pancreas in a controlled large animal model.

BACKGROUND: Pancreatic duct ligation (PDL) has been used as a model of chronic pancreatitis and as a model to increase ß-cell mass. However, studies in mice have demonstrated acinar regeneration after PDL, questioning the long-term validity of the model. We aim to elucidate whether RF-assisted transection (RFAT) of the main pancreatic duct is a reliable PDL model, both in short (ST, 1-month) and long-term (LT, 6-months) follow-ups. METHODS: Eleven pigs were subjected to RFAT. Biochemical (serum/peripancreatic amylase and glucose) and histological changes (including a semiautomatic morphometric study of over 1000 images/pancreas and IHC analysis) were evaluated after ST or LT follow-up and also in fresh pancreas specimens that were used as controls for 1 (n = 4) and 6 months (n = 6). RESULTS: The distal pancreas in the ST was characterized by areas of acinar-to-ductal metaplasia (56%) which were significantly reduced at LT (21%) by fibrotic replacement and adipose tissue. The endocrine mass showed a normal increase. CONCLUSION: RFAT in the pig seems to be an appropriate PDL model without restoration of pancreatic drainage or reduction of endocrine mass.

DCLK1 marks a morphologically distinct subpopulation of cells with stem cell properties in preinvasive pancreatic cancer.

BACKGROUND & AIMS: As in other tumor types, progression of pancreatic cancer may require a functionally unique population of cancer stem cells. Although such cells have been identified in many invasive cancers, it is not clear whether they emerge during early or late stages of tumorigenesis. Using mouse models and human pancreatic cancer cell lines, we investigated whether preinvasive pancreatic neoplasia contains a subpopulation of cells with distinct morphologies and cancer stem cell-like properties. METHODS: Pancreatic tissue samples were collected from the KC(Pdx1), KPC(Pdx1), and KC(iMist1) mouse models of pancreatic intraepithelial neoplasia (PanIN) and analyzed by confocal and electron microscopy, lineage tracing, and fluorescence-activated cell sorting. Subpopulations of human pancreatic ductal adenocarcinoma (PDAC) cells were similarly analyzed and also used in complementary DNA microarray analyses. RESULTS: The microtubule regulator DCLK1 marked a morphologically distinct and functionally unique population of pancreatic cancer-initiating cells. These cells displayed morphological and molecular features of gastrointestinal tuft cells. Cells that expressed DCLK1 also expressed high levels of ATAT1, HES1, HEY1, IGF1R, and ABL1, and manipulation of these pathways in PDAC cell lines inhibited their clonogenic potential. Pharmacological inhibition of γ-secretase activity reduced the abundance of these cells in murine PanIN in a manner that correlated with inhibition of PanIN progression. CONCLUSIONS: Human PDAC cells and pancreatic neoplasms in mice contain morphologically and functionally distinct subpopulations that have cancer stem cell-like properties. These populations can be identified at the earliest stages of pancreatic tumorigenesis and provide new cellular and molecular targets for pancreatic cancer treatment and/or chemoprevention.

Identification and manipulation of biliary metaplasia in pancreatic tumors.

BACKGROUND & AIMS: Metaplasias often have characteristics of developmentally related tissues. Pancreatic metaplastic ducts are usually associated with pancreatitis and pancreatic ductal adenocarcinoma. The tuft cell is a chemosensory cell that responds to signals in the extracellular environment via effector molecules. Commonly found in the biliary tract, tuft cells are absent from normal murine pancreas. Using the aberrant appearance of tuft cells as an indicator, we tested if pancreatic metaplasia represents transdifferentiation to a biliary phenotype and what effect this has on pancreatic tumorigenesis. METHODS: We analyzed pancreatic tissue and tumors that developed in mice that express an activated form of Kras (Kras(LSL-G12D/+);Ptf1a(Cre/+) mice). Normal bile duct, pancreatic duct, and tumor-associated metaplasias from the mice were analyzed for tuft cell and biliary progenitor markers, including SOX17, a transcription factor that regulates biliary development. We also analyzed pancreatic tissues from mice expressing transgenic SOX17 alone (ROSA(tTa/+);Ptf1(CreERTM/+);tetO-SOX17) or along with activated Kras (ROSAtT(a/+);Ptf1a(CreERTM/+);tetO-SOX17;Kras(LSL-G12D;+)). RESULTS: Tuft cells were frequently found in areas of pancreatic metaplasia, decreased throughout tumor progression, and absent from invasive tumors. Analysis of the pancreatobiliary ductal systems of mice revealed tuft cells in the biliary tract but not the normal pancreatic duct. Analysis for biliary markers revealed expression of SOX17 in pancreatic metaplasia and tumors. Pancreas-specific overexpression of SOX17 led to ductal metaplasia along with inflammation and collagen deposition. Mice that overexpressed SOX17 along with Kras(G12D) had a greater degree of transformed tissue compared with mice expressing only Kras(G12D). Immunofluorescence analysis of human pancreatic tissue arrays revealed the presence of tuft cells in metaplasia and early-stage tumors, along with SOX17 expression, consistent with a biliary phenotype. CONCLUSIONS: Expression of Kras(G12D) and SOX17 in mice induces development of metaplasias with a biliary phenotype containing tuft cells. Tuft cells express a number of tumorigenic factors that can alter the microenvironment. Expression of SOX17 induces pancreatitis and promotes Kras(G12D)-induced tumorigenesis in mice.