Pancreatic Ductal Adenocarcinoma Formation Research Articles

Fascin Is Regulated by Slug, Promotes Progression of Pancreatic Cancer in Mice, and Is Associated With Patient Outcomes

Background & AimsPancreatic ductal adenocarcinoma (PDAC) is often lethal because it is highly invasive and metastasizes rapidly. The actin-bundling protein fascin has been identified as a biomarker of invasive and advanced PDAC and regulates cell migration and invasion in vitro. We investigated fascin expression and its role in PDAC progression in mice.MethodsWe used KRasG12D p53R172H Pdx1-Cre (KPC) mice to investigate the effects of fascin deficiency on development of pancreatic intraepithelial neoplasia (PanIn), PDAC, and metastasis. We measured levels of fascin in PDAC cell lines and 122 human resected PDAC samples, along with normal ductal and acinar tissues; we associated levels with patient outcomes.ResultsPancreatic ducts and acini from control mice and early-stage PanINs from KPC mice were negative for fascin, but approximately 6% of PanIN3 and 100% of PDAC expressed fascin. Fascin-deficient KRasG12D p53R172H Pdx1-Cre mice had longer survival times, delayed onset of PDAC, and a lower PDAC tumor burdens than KPC mice; loss of fascin did not affect invasion of PDAC into bowel or peritoneum in mice. Levels of slug and fascin correlated in PDAC cells; slug was found to regulate transcription of Fascin along with the epithelial−mesenchymal transition. In PDAC cell lines and cells from mice, fascin concentrated in filopodia and was required for their assembly and turnover. Fascin promoted intercalation of filopodia into mesothelial cell layers and cell invasion. Nearly all human PDAC samples expressed fascin, and higher fascin histoscores correlated with poor outcomes, vascular invasion, and time to recurrence.ConclusionsThe actin-bundling protein fascin is regulated by slug and involved in late-stage PanIN and PDAC formation in mice. Fascin appears to promote formation of filopodia and invasive activities of PDAC cells. Its levels in human PDAC correlate with outcomes and time to recurrence, indicating it might be a marker or therapeutic target for pancreatic cancer.

Disrupting the balance between tumor epithelia and stroma is a possible therapeutic approach for pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a type of highly lethal malignant tumor. PDAC is locally invasive and is surrounded by a dense desmoplasia or fibrosis, which can involve adjacent vital structures. Previously, the effect of pancreatic stellate cells (PSCs) of stroma in the progression of PDAC has received more attention, and most in vitro and in vivo studies revealed that PSCs appear to confer biological aggressiveness. However, clinical trials targeting desmoplasia or PSCs showed disappointing results. Recent studies found that stromal components, especially activated PSCs, are able to inhibit the occurrence and progression of PDAC. Inhibition of the stroma or desmoplasia through genetic regulations or drugs accelerates the formation and progression of PDAC. Thus, we hypothesized that in various times and spaces, there is a balance between the tumor epithelia and stroma; once the balance is upset, the tumor traits may undergo certain changes. Therefore, finding the key changing points of this relationship to corrupt or influence it, instead of blindly inhibiting the stroma motivation or simply maintaining stroma activation, will destroy the cooperation or promote the competition and antagonism among cells. This approach may render tumors more vulnerable and thus unable to resist anti-cancer therapies.

Genetic Progression of Pancreatic Cancer

The progression from normal cells to invasive pancreatic ductal adenocarcinoma (PDAC) requires the accumulation of multiple inherited or acquired mutations. Activating point mutations in the KRAS oncogene are prevalent in pancreatic cancer and result in the stimulation of several pathways including the RAF-mitogen-activated protein kinase pathway and the phosphoinositide 3-kinase pathway. Other genetic alterations, including telomere shortening and the inactivation of tumor suppressor genes such as CDKN2A, TP53, and SMAD4, which encode p16, p53, and SMAD4, respectively, also contribute to the progression of pancreatic cancer. These, and other genetic events, can present at different stages in the development of PDAC at histologically defined precursor lesions known as pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasms, or mucinous cystic neoplasms. Each precursor lesion represents alternate routes to PDAC formation and has a unique presentation and somewhat distinct genetic events controlling its development. Despite the advances in the understanding of the genetics of PDAC, the prognosis for this cancer remains poor, and several important aspects of its pathogenesis must be clarified to improve therapeutics, including the timing and method of metastases, as well as the relationship of the tumor cells with the desmoplastic stroma, which is a characteristic feature of the cancer. This review discusses the principal genetic alterations in PDAC and its precursor lesions, including their effects on promoting carcinogenesis.

Modulation of c-kit expression in pancreatic adenocarcinoma: A novel stem cell marker responsible for the progression of the disease

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers because of late symptoms and resistance to chemotherapy and radiation therapy. We have investigated the appearance of c-kit, a stem cell marker, in both normal adult pancreatic tissue and in cancerous tissue. Apart from some very pale staining of islets of Langerhans, normal pancreas was devoid of staining with antibodies to c-kit. In contrast, in cancerous tissue that still preserves the overall integrity of the pancreatic tissue, there was a clear labeling in islets of Langerhans, which seemed to be co-localized with insulin containing β cells. In other cases, where the pancreatic tissue was completely deteriorated, intensive labeling was clearly evident in remnants of both the exocrine and the endocrine tissues. The duct cells of the adenocarcinoma were moderately but clearly labeled with antibodies to c-kit. In contrast, in metastasis of PDAC, very intensive labeling of c-kit was evident. The location of KRAS, which is strongly associated with PDAC, was also analyzed at the initial stages of the disease, when islets of Langerhans still preserve their integrity to a large extent. KRAS was found exclusively in islets of Langerhans and overlapped in its location with insulin and c-kit expressing cells. It is suggested that the modulation of the expression of c-kit, visualized by antibodies to the oncogene molecule, may play an important role in the formation and progression of PDAC. The absence of c-kit in normal pancreas and its appearance in PDAC is probably due to a mutational event, which probably allows conversion of the β cells into cancer stem cells (CSC). Co-expression of both c-kit and KRAS, typical markers for CSC with overlapping with insulin in islets of Langerhans, strongly support the notion that β-cells play a central role in the development of PDAC. The use of specific drugs that can attenuate the kinase activity of c-kit or target KRAS expressing cancer cells should be tested in order to attenuate the progression of this lethal disease.

A transposon-based tumor resection model of pancreatic ductal adenocarcinoma (PDAC) with extrahepatic distant metastases

A transposon-based tumor resection model of pancreatic ductal adenocarcinoma (PDAC) with extrahepatic distant metastases

ADH2 gene polymorphism and alcohol consumption style in chronic pancreatitis

s / Pancreatology 13 (2013) S2–S98 S57 Introduction:Masses in the head of the pancreas due to neuroimmune inflammation and hypertension inWirsung duct are two known reasons of severe abdominalgia in chronic pancreatitis (CP). Other reasons of a pain is a controversial. Aims: Demonstrate that so called «calcinates» into the parenchyma of the pancreas is really a stones in the tributary ducts. They are create a peripheral ductal hypertension. Patients m Izbicki (n1⁄42) and Berne’s modification of Beger procedure (n1⁄485). From 2010 yr for the first time in the world we carried out 13 antegrade double balloon enteroscopy (DBE) investigations of pancreaticojejunoanastomoses (PJA) lumen after elective surgery of CP. Results: Estimation of the results of the laser lithotripsy and cavitation during resection of pancreatic tissue (n1⁄435), morphology of latter and DBE data of PJA lumen examination (n1⁄413) allowed us to receive six evidences of the role of tributaryliths in the creation of peripheral ductal hypertension (PDH). This new reason of abdominal pain in CP was explained earlier as «peripheral parenchymal pressure». We proposed and introduced longitudinal pancreatotomyand laser cylindricwirsungectomy (n1⁄48) forelimination of PDH with restoration free outflow of pancreatic juce from tributary ducts. Conclusion: Detected by MRI, CT or US stones in parenchyma of the pancreas body («calcinates» earlier) are the indication for elimination of the PDH and abdominal pain. For the primary surgery of CP most effective was cylindric wirsungectomy.Izbicki. After Pargtingtone-Rochelle or classical Frey procedures indicated V-shaped resection of pancreas by Izbicki. PII-13 Abstract id: 116. Interferon gamma and transforming growth factor 1 beta levels in chronic pancreatitis patients with and without cholelithiasis I.N. Grigorieva , T.I. Romanova , E.V. Logvinenko , M.P. Grishaev , A.Yu. Yamlichanova . 1 Institute of Internal Medicine, Russia 2 JSC “Vector-Best”, Russia Introduction: Transforming growth factor beta 1 (TGF-beta1) plays a key role in promoting fi-brosis by stimulation the expression and deposition of extracellularmatrix and inhibition its degradation. Proinflammatory effect of interferon-gamma (IFN-gamma) proved an enhancement of its blood sera level in chronic pancreatitis (CP) exacerbation. IFN-gamma treatment strongly increased severity of pancreatic le-sions. Aims: To determine the IFN-gamma and TGF-beta 1 levels in the blood serum of CP patients (CPP) with or without cholelithiasis (CL). Materials m 1 – 9,6%, 2 – 90,4%. Alcohol consumption was not significantly different in CPP with ADH1B*1*2 and 2*2 genotypes, respectively: wine 84,0 74,3 and 47,8 26,6 ml/day, beer 469,3 169,1 and 443,5 112,2 ml/day, vermouth 10,0 0,1 and 13,2 2,4 ml/day, liquor 5,0 0,1 and5,5 0,5ml/day, vodka15,3 4,7 and25,7 7,0ml/day (p>0,05 inall cases). Conclusion: Among the surveyed CPP did not found ADH1B*1 homozygote. We found no significant differences in the dose of alcohol consumed by CPP in different ADH1B genotypes, but it should be noted that CPP with 2*2 genotype use higher doses of liquor and vodka, compared to those with 1*2 genotype. PII-16 Abstract id: 329. Loss of Ppar-gamma promotes KrasG12D-driven pancreatic ductal adenocarcinoma formation by inhibiting p53 function Wilhelm Sch€ onherr, Bo Kong, Sina Fritzsche, Nora Behler, Manja Thorwirth, Susanne Raulefs, Ivonne Regel, J€ org Kleeff, Christoph W.

Loss of Ppar-gamma promotes KrasG12D-driven pancreatic ductal adenocarcinoma formation by inhibiting p53 function

Loss of Ppar-gamma promotes KrasG12D-driven pancreatic ductal adenocarcinoma formation by inhibiting p53 function

Interferon gamma and transforming growth factor 1 beta levels in chronic pancreatitis patients with and without cholelithiasis

s / Pancreatology 13 (2013) S2–S98 S57 Introduction:Masses in the head of the pancreas due to neuroimmune inflammation and hypertension inWirsung duct are two known reasons of severe abdominalgia in chronic pancreatitis (CP). Other reasons of a pain is a controversial. Aims: Demonstrate that so called «calcinates» into the parenchyma of the pancreas is really a stones in the tributary ducts. They are create a peripheral ductal hypertension. Patients m Izbicki (n1⁄42) and Berne’s modification of Beger procedure (n1⁄485). From 2010 yr for the first time in the world we carried out 13 antegrade double balloon enteroscopy (DBE) investigations of pancreaticojejunoanastomoses (PJA) lumen after elective surgery of CP. Results: Estimation of the results of the laser lithotripsy and cavitation during resection of pancreatic tissue (n1⁄435), morphology of latter and DBE data of PJA lumen examination (n1⁄413) allowed us to receive six evidences of the role of tributaryliths in the creation of peripheral ductal hypertension (PDH). This new reason of abdominal pain in CP was explained earlier as «peripheral parenchymal pressure». We proposed and introduced longitudinal pancreatotomyand laser cylindricwirsungectomy (n1⁄48) forelimination of PDH with restoration free outflow of pancreatic juce from tributary ducts. Conclusion: Detected by MRI, CT or US stones in parenchyma of the pancreas body («calcinates» earlier) are the indication for elimination of the PDH and abdominal pain. For the primary surgery of CP most effective was cylindric wirsungectomy.Izbicki. After Pargtingtone-Rochelle or classical Frey procedures indicated V-shaped resection of pancreas by Izbicki. PII-13 Abstract id: 116. Interferon gamma and transforming growth factor 1 beta levels in chronic pancreatitis patients with and without cholelithiasis I.N. Grigorieva , T.I. Romanova , E.V. Logvinenko , M.P. Grishaev , A.Yu. Yamlichanova . 1 Institute of Internal Medicine, Russia 2 JSC “Vector-Best”, Russia Introduction: Transforming growth factor beta 1 (TGF-beta1) plays a key role in promoting fi-brosis by stimulation the expression and deposition of extracellularmatrix and inhibition its degradation. Proinflammatory effect of interferon-gamma (IFN-gamma) proved an enhancement of its blood sera level in chronic pancreatitis (CP) exacerbation. IFN-gamma treatment strongly increased severity of pancreatic le-sions. Aims: To determine the IFN-gamma and TGF-beta 1 levels in the blood serum of CP patients (CPP) with or without cholelithiasis (CL). Materials m 1 – 9,6%, 2 – 90,4%. Alcohol consumption was not significantly different in CPP with ADH1B*1*2 and 2*2 genotypes, respectively: wine 84,0 74,3 and 47,8 26,6 ml/day, beer 469,3 169,1 and 443,5 112,2 ml/day, vermouth 10,0 0,1 and 13,2 2,4 ml/day, liquor 5,0 0,1 and5,5 0,5ml/day, vodka15,3 4,7 and25,7 7,0ml/day (p>0,05 inall cases). Conclusion: Among the surveyed CPP did not found ADH1B*1 homozygote. We found no significant differences in the dose of alcohol consumed by CPP in different ADH1B genotypes, but it should be noted that CPP with 2*2 genotype use higher doses of liquor and vodka, compared to those with 1*2 genotype. PII-16 Abstract id: 329. Loss of Ppar-gamma promotes KrasG12D-driven pancreatic ductal adenocarcinoma formation by inhibiting p53 function Wilhelm Sch€ onherr, Bo Kong, Sina Fritzsche, Nora Behler, Manja Thorwirth, Susanne Raulefs, Ivonne Regel, J€ org Kleeff, Christoph W.

Mechanistic Insights into Self-Reinforcing Processes Driving Abnormal Histogenesis During the Development of Pancreatic Cancer

Pancreatic ductal adenocarcinoma, one of the most feared lethal and painful diseases, is increasing in incidence. The poor prognosis of pancreatic ductal adenocarcinoma-affected patients primarily is owing to our inability to develop effective therapies. Mechanistic studies of genetic, epigenetic, and cell-to-cell signaling events are providing clues to molecular pathways that can be targeted in an attempt to cure this disease. The current review article seeks to draw inferences from available mechanistic knowledge to build a theoretical framework that can facilitate these approaches. This conceptual model considers pancreatic cancer as a tissue disease rather than an isolated epithelial cell problem, which develops and progresses in large part as a result of three positive feedback loops: i) genetic and epigenetic changes in epithelial cells modulate their interaction with mesenchymal cells to generate a dynamically changing process of abnormal histogenesis, which drives more changes; ii) the faulty tissue architecture of neoplastic lesions results in unsynchronized secretion of signaling molecules by cells, which generates an environment that is poor in oxygen and nutrients; and iii) the increased metabolic needs of rapidly dividing cells serve as an evolutionary pressure for them to adapt to this adverse microenvironment, leading to the emergence of resistant clones. We discuss how these concepts can guide mechanistic studies, as well as aid in the design of novel experimental therapeutics.

KDM2B promotes pancreatic cancer via Polycomb-dependent and -independent transcriptional programs

Epigenetic mechanisms mediate heritable control of cell identity in normal cells and cancer. We sought to identify epigenetic regulators driving the pathogenesis of pancreatic ductal adenocarcinoma (PDAC), one of the most lethal human cancers. We found that KDM2B (also known as Ndy1, FBXL10, and JHDM1B), an H3K36 histone demethylase implicated in bypass of cellular senescence and somatic cell reprogramming, is markedly overexpressed in human PDAC, with levels increasing with disease grade and stage, and highest expression in metastases. KDM2B silencing abrogated tumorigenicity of PDAC cell lines exhibiting loss of epithelial differentiation, whereas KDM2B overexpression cooperated with KrasG12D to promote PDAC formation in mouse models. Gain- and loss-of-function experiments coupled to genome-wide gene expression and ChIP studies revealed that KDM2B drives tumorigenicity through 2 different transcriptional mechanisms. KDM2B repressed developmental genes through cobinding with Polycomb group (PcG) proteins at transcriptional start sites, whereas it activated a module of metabolic genes, including mediators of protein synthesis and mitochondrial function, cobound by the MYC oncogene and the histone demethylase KDM5A. These results defined epigenetic programs through which KDM2B subverts cellular differentiation and drives the pathogenesis of an aggressive subset of PDAC.

Overview on how oncogenic Kras promotes pancreatic carcinogenesis by inducing low intracellular ROS levels

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease without clearly known disease causes. Recent epidemiological and animal studies suggest that the supplementation of dietary antioxidants (e.g., vitamins C and E) decreases cancer risk, implying that increased reactive oxygen species (ROS) may play a role in pancreatic carcinogenesis. However, oncogenic Kras mutations (e.g., KrasG12D), which are present in more than 90% of PDAC, have been proven to foster low intracellular ROS levels. Here, oncogenic Kras activates expression of a series of anti-oxidant genes via Nrf2 (nuclear factor, erythroid derived 2, like 2) and also mediates an unusual metabolic pathway of glutamine to generate NADPH. This can then be used as the reducing power for ROS detoxification, leading collectively to low ROS levels in pancreatic pre-neoplastic cells and in cancer cells. In adult stem cells and cancer stem cells, low ROS levels have been associated with the formation of a proliferation-permissive intracellular environment and with perseverance of self-renewal capacities. Therefore, it is conceivable that low intracellular ROS levels may contribute significantly to oncogenic Kras-mediated PDAC formation.

KRAS above and beyond - EGFR in pancreatic cancer

KRAS above and beyond - EGFR in pancreatic cancer

Ready, Set, Go: The EGF Receptor at the Pancreatic Cancer Starting Line

Acinar-to-ductal metaplasia (ADM) results from pancreatic injury or KRAS activation, and is an early step in pancreatic cancer progression. In this issue of Cancer Cell, Ardito and colleagues and Navas and colleagues demonstrate that ADM- and KRAS-driven pancreatic cancer require EGFR signaling, revealing a mechanism for developmental reprogramming that primes tumorigenesis.

The activity of Gli transcription factors is essential for Kras-induced pancreatic tumorigenesis

Pancreatic ductal adenocarcinoma (PDAC), one of the most aggressive human malignancies, is thought to be initiated by KRAS activation. Here we find that transcriptional activation mediated by the Gli family of transcription factors, although dispensable for pancreatic development, is required for Kras-induced proliferation and survival in primary pancreatic epithelial cells in culture and for Kras-driven pancreatic intraepithelial neoplasia and PDAC formation in vivo. Further, ectopic Gli1 activation in the mouse pancreas accelerates Kras-driven tumor formation, underscoring the importance of Gli transcription factors in pancreatic tumorigenesis. Interestingly, we demonstrate Gli-regulated I-kappa-B kinase epsilon (IKBKE) and NF-κB activity in pancreatic cancer cells and show that this activity is a critical downstream mediator for Gli-dependent PDAC cell transformation and survival. Together, these studies demonstrate the requirement for Gli in Kras-dependent pancreatic epithelial transformation, suggest a mechanism of Gli-NF-κB oncogenic activation, and provide genetic evidence supporting the therapeutic targeting of Gli activity in pancreatic cancer.

Genetically-engineered mouse models for pancreatic cancer: Advances and current limitations

Recently, there has been significant progress in the development of genetically-engineered mouse (GEM) models. By introducing genetic alterations and/or signaling alterations of human pancreatic cancer into the mouse pancreas, animal models can recapitulate human disease. Pancreas epithelium-specific endogenous Kras activation develops murine pancreatic intraepithelial neoplasia (mPanIN). Additional inactivation of p16, p53, or transforming growth factor-β signaling, in the context of Kras activation, dramatically accelerates mPanIN progression to invasive pancreatic ductal adenocarcinoma (PDAC) with abundant stromal expansion and marked fibrosis (desmoplasia). The autochthonous cancer models retain tumor progression processes from pre-cancer to cancer as well as the intact tumor microenvironment, which is superior to xenograft models, although there are some limitations and differences from human PDAC. By fully studying GEM models, we can understand the mechanisms of PDAC formation and progression more precisely, which will lead us to a breakthrough in novel diagnostic and therapeutic methods as well as identification of the origin of PDAC.

Dasatinib Inhibits the Development of Metastases in a Mouse Model of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly invasive and metastatic disease for which conventional treatments are of limited efficacy. A number of agents in development are potential anti-invasive and antimetastatic agents, including the Src kinase inhibitor dasatinib. The aim of this study was to assess the importance of Src in human PDAC and to use a genetically engineered mouse model of PDAC to determine the effects of dasatinib on PDAC progression. Src expression and activity was measured by immunohistochemistry in 114 human PDACs. Targeting expression of Trp53(R172H) and Kras(G12D) to the mouse pancreas results in the formation of invasive and metastatic PDAC. These mice were treated with dasatinib, and disease progression monitored. Cell lines were derived from mouse PDACs, and in vitro effects of dasatinib assessed. Src expression and activity were up-regulated in human PDAC and this correlated with reduced survival. Dasatinib inhibited the migration and invasion of PDAC cell lines, although no effects on proliferation were seen at concentrations that inhibited Src kinase activity. In addition, dasatinib significantly inhibited the development of metastases in Pdx1-Cre, Z/EGFP, LSL-Kras(G12D/+), LSL-Trp53(R172H/+) mice. However, there was no survival advantage in the dasatinib-treated animals owing to continued growth of the primary tumor. This study confirms the importance of Src in human PDAC and shows the usefulness of a genetically engineered mouse model of PDAC for assessing the activity of potential antimetastatic agents and suggests that dasatinib should be evaluated further as monotherapy after resection of localized invasive PDAC.

Abstract A76: A novel in vivo model for pancreatic restructuring and suppression of transformation

Abstract Our studies are focused on the identification and prevention of the initial transformation events associated with pancreatic ductal adenocarcinoma (PDA) development, an extremely lethal malignancy with poor prognosis and ineffective treatments. PDA initiates through activating mutations in the KRAS proto-oncogene (KrasG12D) and recent studies from our laboratory have determined that targeted expression of an endogenous KrasG12D allele in pancreatic acinar cells is sufficient to produce PDA precursor lesions (PanINs). These results suggest that PDA arises via acinar cells undergoing a process of acinar-to-ductal metaplasia (ADM) which is characterized by a loss of acinar cell properties with the acquisition of duct-like characteristics. Several studies indicate that the process of ADM requires inactivation of the acinar-specific transcription factor Mist1, since Mist1 null (Mist1KO) mice display accelerated ADM and PanIN formation upon KrasG12D expression. Additionally, acinar cell polarity is disrupted in Mist1KO mice with diffuse zymogen granule organization and mis-localization of nuclei. These results suggest that Mist1 has a key role in suppressing PDA formation by maintaining the acinar cell differentiation program. To identify the downstream genes affected by the absence of Mist1, we have generated an inducible Mist1 transgenic mouse line (LSL-Mist1myc) in which constitutive Mist1 expression is activated through Cre-mediated recombination. When LSL-Mist1myc mice are crossed to Mist1Cre-ER mice, Mist1myc expression can be induced in acinar cells upon Tamoxifen (TM) addition. Analysis of Mist1Cre-ER/Cre-ER; LSL-Mist1myc mice confirmed that exogenous Mist1myc expression is detected as early as 6 hours post-TM. Time course studies in a Mist1KO background revealed that nuclear and zymogen granule organization can be restored within 24 hours of Cre activation. We conclude that Mist1 actively controls pancreatic acinar cell organization and that induction of Mist1 in Mist1KO mice leads to complete reorganization of pancreatic tissues. Our current efforts are focused on establishing how Mist1 negatively regulates ADM and PanIN formation and to identify Mist1 targets that negatively regulate Kras-induced pancreas metaplasia and transformation. Citation Information: Cancer Res 2009;69(23 Suppl):A76.

Hedgehog/Ras interactions regulate early stages of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) constitutes a lethal disease that affects >30,000 people annually in the United States. Deregulation of Hedgehog signaling has been implicated in the pathogenesis of PDA. To gain insights into the role of the pathway during the distinct stages of pancreatic carcinogenesis, we established a mouse model in which Hedgehog signaling is activated specifically in the pancreatic epithelium. Transgenic mice survived to adulthood and developed undifferentiated carcinoma, indicating that epithelium-specific Hedgehog signaling is sufficient to drive pancreatic neoplasia but does not recapitulate human pancreatic carcinogenesis. In contrast, simultaneous activation of Ras and Hedgehog signaling caused extensive formation of pancreatic intraepithelial neoplasias, the earliest stages of human PDA tumorigenesis, and accelerated lethality. These results indicate the cooperation of Hedgehog and Ras signaling during the earliest stages of PDA formation. They also mark Hedgehog pathway components as relevant therapeutic targets for both early and advanced stages of pancreatic ductal neoplasia.