A murine tumor progression model for pancreatic cancer recapitulating the genetic alterations of the human disease

A comprehensive review of pancreatic cancer and its therapeutic challenges

Pancreatic cancer is a devastating and lethal human malignancy with no curable chemo-treatments available thus far. More than 90% of pancreatic tumors are formed from ductal epithelium as pancreatic ductal adenocarcinoma (PDAC), which often accompany with the expression of mutant K-ras. The incidences of pancreatic cancer are expected to increase rapidly worldwide in the near future, due to environmental pollution, obesity epidemics and etc. The dismal prognosis of this malignancy is contributed to its susceptibility to tumor micro-metastasis from inception and the lack of methods to detect precursor lesions at very early stages of the onset until clinical symptoms occur. In recent years, basic and clinical studies have been making promising progresses for discovering markers to determine the subtypes or stages of this malignancy, which allow effectively implementing personalized therapeutic interventions. The purpose of this review is to discuss the existing knowledge of the molecular mechanisms of pancreatic cancer and the current state of treatment options with the emphasis on targeting therapeutic approaches. The specific focuses are on the molecular mechanisms of the disease, identifications of drug resistance, establishment of immune escaping mechanisms as well as potential of targeting identified pathways in combinations with existing chemo-drugs.

Clinical significance of pancreatic ductal metaplasia

Pancreatic ductal metaplasia (PDM) is the stepwise replacement of differentiated somatic cells with ductal or ductal-like cells in the pancreas. PDM is usually triggered by cellular and environmental insults. PDM development may involve all cell lineages of the pancreas, and acinar cells with the highest plasticity are the major source of PDM. Pancreatic progenitor cells are also involved as cells of origin or transitional intermediates. PDM is heterogeneous at the histological, cellular, and molecular levels and only certain subsets of PDM develop further into pancreatic intraepithelial neoplasia (PanIN) and then pancreatic ductal adenocarcinoma (PDAC). The formation and evolution of PDM is regulated at the cellular and molecular levels through a complex network of signaling pathways. The key molecular mechanisms that drive PDM formation and its progression into PanIN/PDAC remain unclear, but represent key targets for reversing or inhibiting PDM. Alternatively, PDM could be a source of pancreas regeneration, including both exocrine and endocrine components. Cellular aging and apoptosis are obstacles to PDM-to-PanIN progression or pancreas regeneration. Functional identification of the cellular and molecular events driving senescence and apoptosis in PDM and its progression would help not only to restrict the development of PDM into PanIN/PDAC, but may also facilitate pancreatic regeneration. This review systematically assesses recent advances in the understanding of PDM physiology and pathology, with a focus on its implications for enhancing regeneration and prevention of cancer. © 2022 The Pathological Society of Great Britain and Ireland.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

B-Lymphocytes in the Pathophysiology of Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is highly infiltrated by B lymphocytes but the relevance of these immune cells in tumor development has been surprisingly overlooked until recently. Based on available evidence from other solid tumors, interaction between B lymphocytes and neoplastic cells is probably not uniformly stimulatory or inhibitory. Although presentation of tumor antigens to T cells and production of antitumor immunoglobulins might intuitively suggest a prominent tumor suppressive activity, specific subsets of B lymphocytes can secrete growth factors for neoplastic cells and immunosuppressive cytokines thus promoting escape from immunosurveillance and cancer progression. Because many of these mechanisms might also be implicated in the development of PDAC, and immune-modulation of B-cell activity is nowadays possible at different levels, determining the role of B-lymphocytes in this lethal cancer becomes of utmost importance to design novel therapeutic strategies. This review aims to discuss the emerging role of B cells in PDAC tumorigenesis, progression, and associated stromal reaction.

Activation of the GPR35 pathway drives angiogenesis in the tumour microenvironment

OBJECTIVE

Primary sclerosing cholangitis (PSC) is in 70% of cases associated with inflammatory bowel disease. The hypermorphic T108M variant of the orphan G protein-coupled receptor GPR35 increases risk for PSC and ulcerative colitis (UC), conditions strongly predisposing for inflammation-associated liver and colon cancer. Lack of GPR35 reduces tumour numbers in mouse models of spontaneous and colitis associated cancer. The tumour microenvironment substantially determines tumour growth, and tumour-associated macrophages are crucial for neovascularisation. We aim to understand the role of the GPR35 pathway in the tumour microenvironment of spontaneous and colitis-associated colon cancers.

DESIGN

Mice lacking GPR35 on their macrophages underwent models of spontaneous colon cancer or colitis-associated cancer. The role of tumour-associated macrophages was then assessed in biochemical and functional assays.

RESULTS

Here, we show that GPR35 on macrophages is a potent amplifier of tumour growth by stimulating neoangiogenesis and tumour tissue remodelling. Deletion of Gpr35 in macrophages profoundly reduces tumour growth in inflammation-associated and spontaneous tumour models caused by mutant tumour suppressor adenomatous polyposis coli. Neoangiogenesis and matrix metalloproteinase activity is promoted by GPR35 via Na/K-ATPase-dependent ion pumping and Src activation, and is selectively inhibited by a GPR35-specific pepducin. Supernatants from human inducible-pluripotent-stem-cell derived macrophages carrying the UC and PSC risk variant stimulate tube formation by enhancing the release of angiogenic factors.

CONCLUSIONS

Activation of the GPR35 pathway promotes tumour growth via two separate routes, by directly augmenting proliferation in epithelial cells that express the receptor, and by coordinating macrophages' ability to create a tumour-permissive environment.

Employing Novel Porcine Models of Subcutaneous Pancreatic Cancer to Evaluate Oncological Therapies

Immunocompromised mice are commonly utilized to study pancreatic cancer and other malignancies. The ability to xenograft tumors in either subcutaneous or orthotopic locations provides a robust model to study diverse biological features of human malignancies. However, there is a dire need for large animal models that better recapitulate human anatomy in terms of size and physiology. These models will be critical for biomedical device development, surgical optimization, and drug discovery. Here, we describe the generation and application of immunocompromised pigs lacking RAG2 and IL2RG as a novel model for human xenograft studies. These SCID-like pigs closely resemble NOD scid gamma mice and are receptive to human tumor tissue, cell lines, and organoid xenografts. However, due to their immunocompromised nature, these immunocompromised animals require housing and maintenance under germfree conditions. In this protocol, we describe the use of these pigs in a subcutaneous tumor injection study with human PANC1 cells. The tumors demonstrate a steady, linear growth curve, reaching 1.0 cm within 30 days post injection. The model described here is focused on subcutaneous injections behind the ear. However, it is readily adaptable for other locations and additional human cell types.

Uncertain Beginnings: Acinar and Ductal Cell Plasticity in the Development of Pancreatic Cancer

The pancreas consists of several specialized cell types that display a remarkable ability to alter cellular identity in injury, regeneration, and repair. The abundant cellular plasticity within the pancreas appears to be exploited in tumorigenesis, with metaplastic, dedifferentiation, and transdifferentiation processes central to the development of pancreatic intraepithelial neoplasia and intraductal papillary neoplasms, precursor lesions to pancreatic ductal adenocarcinoma. In the face of shifting cellular identity, the cell of origin of pancreatic cancer has been difficult to elucidate. However, with the extensive utilization of in vivo lineage-traced mouse models coupled with insights from human samples, it has emerged that the acinar cell is most efficiently able to give rise to both intraductal papillary neoplasms and pancreatic intraepithelial neoplasia but that acinar and ductal cells can undergo malignant transformation to pancreatic ductal adenocarcinoma. In this review, we discuss the cellular reprogramming that takes place in both the normal and malignant pancreas and evaluate the current state of evidence that implicate both the acinar and ductal cell as context-dependent origins of this deadly disease.

Development of thymic tumor in [LSL:KrasG12D; Pdx1-CRE] mice, an adverse effect associated with accelerated pancreatic carcinogenesis

Pancreatic Ductal AdenoCarcinoma (PDAC) represents about 90% of pancreatic cancers. It is one of the most aggressive cancer, with a 5-year survival rate below 10% due to late diagnosis and poor therapeutic efficiency. This bad prognosis thus encourages intense research in order to better understand PDAC pathogenesis and molecular basis leading to the development of innovative therapeutic strategies. This research frequently involves the KC (LSL:KrasG12D;Pdx1-CRE) genetically engineered mouse model, which leads to pancreatic cancer predisposition. However, as frequently encountered in animal models, the KC mouse model also exhibits biases. Herein, we report a new adverse effect of KrasG12D mutation in KC mouse model. In our hands, 10% of KC mice developed clinical signs reaching pre-defined end-points between 100- and 150-days post-parturition, and associated with large thymic mass development. Histological and genetic analyses of this massive thymus enabled us (1) to characterize it as a highly proliferative thymic lymphoma and (2) to detect the unexpected recombination of the Lox-STOP-Lox cassette upstream KrasG12D allele and subsequent KRASG12D protein expression in all cells composing thymic masses. Finally, we highlighted that development of such thymic tumor was associated with accelerated pancreatic carcinogenesis, immune compartment disorganization, and in some cases, lung malignancies.

Toll-like receptor 3 expression in myeloid cells is essential for efficient regeneration after acute pancreatitis in mice

Stringent regulation of the inflammatory response is crucial for normal tissue regeneration. Here, we analyzed the role of Toll-like receptor 3 (TLR3) in pancreatic regeneration after acute pancreatitis (AP). AP was induced by caerulein treatment in mice with global TLR3 deficiency (TLR3^OFF ) or in mice re-expressing TLR3 exclusively in the myeloid cell lineage (TLR3^Mye ). Compared to WT mice, TLR3^OFF mice had a markedly increased formation of acinar-to-ductal metaplasia (ADM) that persisted until day 7 after initiation of AP. Pancreatic tissue of WT mice was completely regenerated after 5 days with no detectable ADM structures. The enhancing effect of TLR3-deficiency on ADM formation was closely linked with an increased and prolonged accumulation of macrophages in pancreata of TLR3^OFF mice. Importantly, the phenotype of TLR3^OFF mice was rescued in TLR3^Mye mice, demonstrating the causative role of myeloid cell selective TLR3 signaling. Moreover, in vitro stimulation of macrophages through TLR3 initiated cell death by a caspase-8-associated mechanism. Therefore, these findings provide evidence that TLR3 signaling in myeloid cells is sufficient to limit inflammation and ADM formation and to promote regeneration after AP. Notably, resolution of inflammation after AP was associated with macrophage sensitivity to TLR3-mediated cell death.

Differential impact of the ERBB receptors EGFR and ERBB2 on the initiation of precursor lesions of pancreatic ductal adenocarcinoma

Earlier diagnosis of pancreatic ductal adenocarcinoma (PDAC) requires better understanding of the mechanisms driving tumorigenesis. In this context, depletion of Epidermal Growth Factor Receptor (EGFR) is known to impair development of PDAC-initiating lesions called acinar-to-ductal metaplasia (ADM) and Pancreatic Intraepithelial Neoplasia (PanIN). In contrast, the role of v-erb-b2 erythroblastic leukemia viral oncogene homolog 2 (ERBB2), the preferred dimerization partner of EGFR, remains poorly understood. Here, using a mouse model with inactivation of Erbb2 in pancreatic acinar cells, we found that Erbb2 is dispensable for inflammation- and KRas^G12D-induced development of ADM and PanIN. A mathematical model of EGFR/ERBB2-KRAS signaling, which was calibrated on mouse and human data, supported the observed roles of EGFR and ERBB2. However, this model also predicted that overexpression of ERBB2 stimulates ERBB/KRAS signaling; this prediction was validated experimentally. We conclude that EGFR and ERBB2 differentially impact ERBB signaling during PDAC tumorigenesis, and that the oncogenic potential of ERBB2 is only manifested when it is overexpressed. Therefore, the level of ERBB2, not only its mere presence, needs to be considered when designing therapies targeting ERBB signaling.

The Use of Genetically Engineered Mouse Models for Studying the Function of Mutated Driver Genes in Pancreatic Cancer

Pancreatic cancer is often treatment-resistant, with the emerging standard of care, gemcitabine, affording only a few months of incrementally-deteriorating survival. Reflecting on the history of failed clinical trials, genetically engineered mouse models (GEMMs) in oncology research provides the inspiration to discover new treatments for pancreatic cancer that come from better knowledge of pathogenesis mechanisms, not only of the derangements in and consequently acquired capabilities of the cancer cells, but also in the aberrant microenvironment that becomes established to support, sustain, and enhance neoplastic progression. On the other hand, the existing mutational profile of pancreatic cancer guides our understanding of the disease, but leaves many important questions of pancreatic cancer biology unanswered. Over the past decade, a series of transgenic and gene knockout mouse modes have been produced that develop pancreatic cancers with features reflective of metastatic pancreatic ductal adenocarcinoma (PDAC) in humans. Animal models of PDAC are likely to be essential to understanding the genetics and biology of the disease and may provide the foundation for advances in early diagnosis and treatment.

Animal Models: Challenges and Opportunities to Determine Optimal Experimental Models of Pancreatitis and Pancreatic Cancer

At the 2018 PancreasFest meeting, experts participating in basic research met to discuss the plethora of available animal models for studying exocrine pancreatic disease. In particular, the discussion focused on the challenges currently facing the field and potential solutions. That meeting culminated in this review, which describes the advantages and limitations of both common and infrequently used models of exocrine pancreatic disease, namely, pancreatitis and exocrine pancreatic cancer. The objective is to provide a comprehensive description of the available models but also to provide investigators with guidance in the application of these models to investigate both environmental and genetic contributions to exocrine pancreatic disease. The content covers both nongenic and genetically engineered models across multiple species (large and small). Recommendations for choosing the appropriate model as well as how to conduct and present results are provided.

Germline Variants and Risk for Pancreatic Cancer: A Systematic Review and Emerging Concepts

Pancreatic cancer requires many genetic mutations. Combinations of underlying germline variants and environmental factors may increase the risk of cancer and accelerate the oncogenic process. We systematically reviewed, annotated, and classified previously reported pancreatic cancer-associated germline variants in established risk genes. Variants were scored using multiple criteria and binned by evidence for pathogenicity, then annotated with published functional studies and associated biological systems/pathways. Twenty-two previously identified pancreatic cancer risk genes and 337 germline variants were identified from 97 informative studies that met our inclusion criteria. Fifteen of these genes contained 66 variants predicted to be pathogenic (APC, ATM, BRCA1, BRCA2, CDKN2A, CFTR, CHEK2, MLH1, MSH2, NBN, PALB2, PALLD, PRSS1, SPINK1, TP53). Pancreatic cancer risk genes were organized into key biological mechanisms that promote pancreatic oncogenesis within an oncogenic model. Development of precision medicine approaches requires updated variant information within the framework of an oncogenic progression model. Complex risk modeling may improve interpretation of early biomarkers and guide pathway-specific treatment for pancreatic cancer in the future. Precision medicine is within reach.

A mouse model for pain and neuroplastic changes associated with pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) continues to be one of the deadliest human malignancies and is associated with excruciating pain, which is a serious complication and severely impacts the quality of life in patients. In human patients, poor survival prognosis is linked to remarkable remodeling of intrapancreatic nerves, which, in turn, is correlated to increased pain intensity. Understanding mechanisms underlying pain associated with PDAC has been hampered by the lack of animal models which replicate all germane aspects of the disease and importantly, enable analyses of pain associated with PDAC. In this study, we describe an immunocompetent orthotopic mouse model of PDAC involving intrapancreatic growth of K8484 mouse PDAC cells, which reliably exhibits a large number of key characteristics of human PDAC, including its unique histopathology and neuroplastic changes. We observed that tumor-bearing mice demonstrated significant abdominal mechanical hypersensitivity to von Frey stimuli as well as on-going pain in the conditioned place preference paradigm. Moreover, a myriad of other behavioral tests revealed that indicators of overall well-being were significantly reduced in tumor-bearing mice as compared to sham mice. Morphological and immunohistochemical analyses revealed structural remodeling in several different types of sensory and autonomic nerve fibers. Finally, perineural invasion of tumor cells, a cardinal manifestation in human PDAC, was also observed in our orthotopic mouse model. Thus, we describe a validated tumor model for quantitatively testing hypersensitivity and pain in PDAC, which lays a crucial basis for interrogating tumor-nerve interactions and the molecular and cellular mechanisms underlying pain in PDAC.

Pancreatic acinar cell carcinoma presenting with panniculitis, successfully treated with FOLFIRINOX: A case report

Pancreatic acinar cell carcinoma (PACC) is a rare tumor of the exocrine pancreas, representing only 1% of all pancreatic malignancies. A 50-year-old man presented with edema of the thumb joints bilaterally, followed by an appearance of masses in the bilateral lower extremities and fever (38°C). The masses were diagnosed as panniculitis by skin biopsy, and multiple intraperitoneal masses were incidentally detected on pelvic magnetic resonance imaging performed to investigate the leg abnormalities. The patient was referred to the Kyushu University Hospital for further investigation, and fluorodeoxyglucose-positron emission tomography/computed tomography (CT) revealed high-uptake tumors in the pancreatic tail, in the periphery of the liver, and in the pelvis. Laboratory examinations revealed high serum concentrations of pancreatic exocrine enzymes, such as lipase, trypsin, elastase 1 and pancreatic phospholipase A2. Histological examination of a bioptic specimen obtained from a hepatic lesion revealed proliferation of atypical cells arranged in a tubular or glandular pattern. Immunohistochemical staining revealed that the atypical cells were positive for cytokeratin (CK)7, CK19 and lipase, but negative for CK20 and thyroid transcription factor-1, leading to a final diagnosis of acinar cell carcinoma of the pancreatic tail (T4bN0M1, stage IV according to the 7th edition of the TNM Classification of Malignant Tumors). Combined chemotherapy with oxaliplatin, irinotecan and fluorouracil (FOLFIRINOX) was administered and fever was soon alleviated. The serum levels of lipase also declined and panniculitis completely resolved. As of the start of the 8th course of chemotherapy, the levels of the pancreatic exocrine enzymes were within normal ranges and CT revealed partial response. Therefore, the severe lipase hypersecretion syndrome was well controlled by the FOLFIRINOX regimen and shrinkage of the mass was also achieved. Thus, the FOLFIRINOX regimen may represent an effective treatment option for advanced PACC.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Cellular and molecular aspects of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy that affects nearly 50,000 patients each year. The overall 5-year survival rate for this malignancy remains the lowest of any cancer at around 7% due to limited diagnostic methods, disease aggressiveness and a lack of targeted therapeutic interventions. This review highlights the successes achieved over the past several decades as well as the significant cellular and molecular hurdles that remain in combatting this deadly disease at a translational level.

Peroxisome proliferator activated receptors at the crossroad of obesity, diabetes, and pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth cause of cancer death with an overall survival of 5% at five years. The development of PDAC is characteristically associated to the accumulation of distinctive genetic mutations and is preceded by the exposure to several risk factors. Epidemiology has demonstrated that PDAC risk factors may be non-modifiable risks (sex, age, presence of genetic mutations, ethnicity) and modifiable and co-morbidity factors related to the specific habits and lifestyle. Recently it has become evident that obesity and diabetes are two important modifiable risk factors for PDAC. Obesity and diabetes are complex systemic and intertwined diseases and, over the years, experimental evidence indicate that insulin-resistance, alteration of adipokines, especially leptin and adiponectin, oxidative stress and inflammation may play a role in PDAC. Peroxisome proliferator activated receptor-γ (PPARγ) is a nuclear receptor transcription factor that is implicated in the regulation of metabolism, differentiation and inflammation. PPARγ is a key regulator of adipocytes differentiation, regulates insulin and adipokines production and secretion, may modulate inflammation, and it is implicated in PDAC. PPARγ agonists are used in the treatment of diabetes and oxidative stress-associated diseases and have been evaluated for the treatment of PDAC. PPARγ is at the cross-road of diabetes, obesity, and PDAC and it is an interesting target to pharmacologically prevent PDAC in obese and diabetic patients.

Genetics and Genetic Testing in Pancreatic Cancer

Genetic testing of germline DNA is used in patients suspected of being at risk of pancreatic ductal adenocarcinoma (PDAC) to better define the individual's risk and to determine the mechanism of risk. A high genetic risk increases the pretest probability that a biomarker of early cancer is a true positive and warrants further investigation. The highest PDAC risk is generally associated with a hereditary predisposition. However, the majority of PDAC results from complex, progressive gene-environment interactions that currently fall outside the traditional risk models. Over many years, the combination of inflammation, exposure to DNA-damaging toxins, and failed DNA repair promote the accumulation of somatic mutations in pancreatic cells; PDAC risk is further increased by already present oncogenic germline mutations. Predictive models and new technologies are needed to classify patients into more accurate and mechanistic PDAC risk categories that can be linked to improved surveillance and preventative strategies.

NFATc1 Links EGFR Signaling to Induction of Sox9 Transcription and Acinar-Ductal Transdifferentiation in the Pancreas

BACKGROUND & AIMS

Oncogenic mutations in KRAS contribute to the development of pancreatic ductal adenocarcinoma, but are not sufficient to initiate carcinogenesis. Secondary events, such as inflammation-induced signaling via the epidermal growth factor receptor (EGFR) and expression of the SOX9 gene, are required for tumor formation. Herein we sought to identify the mechanisms that link EGFR signaling with activation of SOX9 during acinar-ductal metaplasia, a transdifferentiation process that precedes pancreatic carcinogenesis.

METHODS

We analyzed pancreatic tissues from Kras(G12D);pdx1-Cre and Kras(G12D);NFATc1(Δ/Δ);pdx1-Cre mice after intraperitoneal administration of caerulein, vs cyclosporin A or dimethyl sulfoxide (controls). Induction of EGFR signaling and its effects on the expression of Nuclear factor of activated T cells c1 (NFATc1) or SOX9 were investigated by quantitative reverse-transcription polymerase chain reaction, immunoblot, and immunohistochemical analyses of mouse and human tissues and acinar cell explants. Interactions between NFATc1 and partner proteins and effects on DNA binding or chromatin modifications were studied using co-immunoprecipitation and chromatin immunoprecipitation assays in acinar cell explants and mouse tissue.

RESULTS

EGFR activation induced expression of NFATc1 in metaplastic areas from patients with chronic pancreatitis and in pancreatic tissue from Kras(G12D) mice. EGFR signaling also promoted formation of a complex between NFATc1 and C-JUN in dedifferentiating mouse acinar cells, leading to activation of Sox9 transcription and induction of acinar-ductal metaplasia. Pharmacologic inhibition of NFATc1 or disruption of the Nfatc1 gene inhibited EGFR-mediated induction of Sox9 transcription and blocked acinar-ductal transdifferentiation and pancreatic cancer initiation in mice.

CONCLUSIONS

EGFR signaling induces expression of NFATc1 and Sox9, leading to acinar cell transdifferentiation and initiation of pancreatic cancer. Strategies designed to disrupt this pathway might be developed to prevent pancreatic cancer initiation in high-risk patients with chronic pancreatitis.

Smad4 loss synergizes with TGFα overexpression in promoting pancreatic metaplasia, PanIN development, and fibrosis

AIMS

While overexpression of TGFα has been reported in human pancreatic ductal adenocarcinoma (PDAC), mice with overexpressed TGFα develop premalignant pancreatic acinar-to-ductal metaplasia (ADM) but not PDAC. TGF-β signaling pathway is pivotal to the development of PDAC and tissue fibrosis. Here we sought to investigate the interplay between TGFα and TGF-β signaling in pancreatic tumorigenesis and fibrosis, namely via Smad4 inactivation.

METHODS

The MT-TGFα mouse was crossed with a new Smad4 conditional knock-out mouse (Smad4flox/flox;p48-Cre or S4) to generate Smad4flox/flox;MT-TGFα;p48-Cre (STP). After TGFα overexpression was induced with zinc sulfate water for eight months, the pancreata of the STP, MT-TGFα, and S4 mice were examined for tumor development and fibrotic responses. PanIN lesions and number of ducts were counted, and proliferation was measured by Ki67 immunohistochemistry (IHC). Qualitative analysis of fibrosis was analyzed by Trichrome Masson and Sirius Red staining, while vimentin was used for quantification. Expression analyses of fibrosis, pancreatitis, or desmoplasia associated markers (α-SMA, Shh, COX-2, Muc6, Col1a1, and Ctgf) were performed by IHC and/or qRT-PCR.

RESULTS

Our STP mice exhibited advanced ADM, increased fibrosis, increased numbers of PanIN lesions, overexpression of chronic pancreatitis-related marker Muc6, and elevated expression of desmoplasia-associated marker Col1A1, compared to the MT-TGFα mice. The inactivation of Smad4 in the exocrine compartment was responsible for both the enhanced PanIN formation and fibrosis in the pancreas. The phenotype of the STP mice represents a transient state from ADMs to PanINs, closely mimicking the interface area seen in human chronic pancreatitis associated with PDAC.

CONCLUSION

We have documented a novel mouse model, the STP mice, which displayed histologic presentations reminiscent to those of human chronic pancreatitis with signs of early tumorigenesis. The STP mice could be a suitable animal model for interrogating the transition of chronic pancreatitis to pancreatic cancer.

Utilizing past and present mouse systems to engineer more relevant pancreatic cancer models

The study of pancreatic cancer has prompted the development of numerous mouse models that aim to recapitulate the phenotypic and mechanistic features of this deadly malignancy. This review accomplishes two tasks. First, it provides an overview of the models that have been used as representations of both the neoplastic and carcinoma phenotypes. Second, it presents new modeling schemes that ultimately will serve to more faithfully capture the temporal and spatial progression of the human disease, providing platforms for improved understanding of the role of non-epithelial compartments in disease etiology as well as evaluating therapeutic approaches.

Galectin-1 drives pancreatic carcinogenesis through stroma remodeling and Hedgehog signaling activation

Despite some advances, pancreatic ductal adenocarcinoma (PDAC) remains generally refractory to current treatments. Desmoplastic stroma, a consistent hallmark of PDAC, has emerged as a major source of therapeutic resistance and thus potentially promising targets for improved treatment. The glycan-binding protein galectin-1 (Gal1) is highly expressed in PDAC stroma, but its roles there have not been studied. Here we report functions and molecular pathways of Gal1 that mediate its oncogenic properties in this setting. Genetic ablation of Gal1 in a mouse model of PDAC (EIa-myc mice) dampened tumor progression by inhibiting proliferation, angiogenesis, desmoplasic reaction and by stimulating a tumor-associated immune response, yielding a 20% increase in relative lifesplan. Cellular analyses in vitro and in vivo suggested these effects were mediated through the tumor microenvironment. Importantly, acinar-to-ductal metaplasia, a crucial step for initiation of PDAC, was found to be regulated by Gal1. Mechanistic investigations revealed that Gal1 promoted Hedgehog pathway signaling in PDAC cells and stromal fibroblasts as well as in Ela-myc tumors. Taken together, our findings establish a function for Gal1 in tumor-stroma crosstalk in PDAC and provide a preclinical rationale for Gal1 targeting as a microenvironment-based therapeutic strategy.

Challenges and advances in mouse modeling for human pancreatic tumorigenesis and metastasis

Pancreatic cancer is critical for developed countries, where its rate of diagnosis has been increasing steadily annually. In the past decade, the advances of pancreatic cancer research have not contributed to the decline in mortality rates from pancreatic cancer-the overall 5-year survival rate remains about 5% low. This number only underscores an obvious urgency for us to better understand the biological features of pancreatic carcinogenesis, to develop early detection methods, and to improve novel therapeutic treatments. To achieve these goals, animal modeling that faithfully recapitulates the whole process of human pancreatic cancer is central to making the advancements. In this review, we summarize the currently available animal models for pancreatic cancer and the advances in pancreatic cancer animal modeling. We compare and contrast the advantages and disadvantages of three major categories of these models: (1) carcinogen-induced; (2) xenograft and allograft; and (3) genetically engineered mouse models. We focus more on the genetically engineered mouse models, a category which has been rapidly expanded recently for their capacities to mimic human pancreatic cancer and metastasis, and highlight the combinations of these models with various newly developed strategies and cell-lineage labeling systems.

Macropinocytosis of protein is an amino acid supply route in Ras-transformed cells

Macropinocytosis is a highly conserved endocytic process by which extracellular fluid and its contents are internalized into cells through large, heterogeneous vesicles known as macropinosomes. Oncogenic Ras proteins have been shown to stimulate macropinocytosis but the functional contribution of this uptake mechanism to the transformed phenotype remains unknown. Here we show that Ras-transformed cells use macropinocytosis to transport extracellular protein into the cell. The internalized protein undergoes proteolytic degradation, yielding amino acids including glutamine that can enter central carbon metabolism. Accordingly, the dependence of Ras-transformed cells on free extracellular glutamine for growth can be suppressed by the macropinocytic uptake of protein. Consistent with macropinocytosis representing an important route of nutrient uptake in tumours, its pharmacological inhibition compromises the growth of Ras-transformed pancreatic tumour xenografts. These results identify macropinocytosis as a mechanism by which cancer cells support their unique metabolic needs and point to the possible exploitation of this process in the design of anticancer therapies.

Biodistribution and pharmacokinetics of EGFR-targeted thiolated gelatin nanoparticles following systemic administration in pancreatic tumor-bearing mice

The objective of this study was to evaluate qualitative and quantitative biodistribution of epidermal growth factor receptor (EGFR)-targeted thiolated type B gelatin nanoparticles in vivo in subcutaneous human pancreatic adenocarcinoma (Panc-1) bearing female SCID Beige mice. EGFR-targeted nanoparticles showed preferential and sustained accumulation in the tumor mass, especially at early time points. Higher blood concentrations and higher tumor accumulations were observed with PEG-modified and EGFR-targeted nanoparticles during the study (AUClast: 17.38 and 19.56%ID/mL·h in blood, 187 and 322%ID/g·h in tumor for PEG-modified and EGFR-targeted nanoparticles, respectively), as compared to control, unmodified particles (AUClast: 10.71%ID/mL·h in blood and 138%ID/g·h in tumor). EGFR-targeted nanoparticles displayed almost twice tumor targeting efficiency than either PEG-modified or the unmodified nanoparticles, highlighting the efficacy of the active targeting strategy. In conclusion, this study shows that EGFR-targeted and PEG-modified nanoparticles were suitable vehicles for specific systemic delivery in subcutaneous Panc-1 tumor xenograft models.

Incretin-based therapies in the treatment of type 2 diabetes--more than meets the eye?

A lot of contradictory data regarding the serious side effects of incretin-based therapies are currently available, with more being prepared or published every month. Considering the widespread use of these drugs it should be considered a priority to establish both short- and long-term risks connected with incretin treatment. We performed an extensive literature search of the PubMed database looking for articles dealing with connections between incretin-based therapies and pancreatitis, pancreatic cancer, thyroid cancer and other neoplasms. Data obtained indicate that GLP-1 agonists and DPPIV inhibitors could increase the risk of pancreatitis and pancreatic cancer, possibly due to their capacity to increase ductal cell turnover, which has previously been found to be up-regulated in patients with obesity and T2DM. GLP-1 analogues exenatide and liraglutide seem to be connected with medullary thyroid carcinoma in rat models and, surprisingly, GLP-1 receptors have been found in papillary thyroid carcinoma, currently the most common neoplasm of the thyroid gland in humans. Changes in expression of DPPIV have been described in ovarian carcinoma, melanoma, endometrial adenocarcinoma, prostate cancer, non-small cell lung cancer and in certain haematological malignancies. In most cases loss of DPPIV activity is connected with a higher grading scale, more aggressive tumour behaviour and higher metastatic potential. In conclusion animal and human studies indicate that there could be a connection between incretin-based therapies and pancreatitis, pancreatic cancer, thyroid cancer and other neoplasms. Therefore whenever such therapy is started it would be wise to proceed with caution, especially if personal history of neoplasms is present.

Animal models of pancreatic cancer for drug research

BACKGROUND

The operative and conservative results of therapy in pancreatic ductal adenocarcinoma remain appallingly poor. This underlines the demand for further research for effective anticancer drugs. The various animal models remain the essential method for the determination of efficacy of substances during preclinical phase.

OBJECTIVE

Unfortunately, most of these tested substances showed a good efficacy in pancreatic carcinoma in the animal model but were not confirmed during the clinical phase.

METHODS

The available literature in PubMed, Medline, Ovid and secondary literature was searched regarding the available animal models for drug testing against pancreatic cancer. The models were analyzed regarding their pros and cons in anticancer drug testing.

CONCLUSION

The different modifications of the orthotopic model (especially in mice) seem at present to be the best model for anticancer testing in pancreatic carcinoma. The value of genetically engineered animal model (GEM) and syngeneic models is on debate. A good selection of the model concerning the questions supposed to be clarified may improve the comparability of the results of animal experiments compared to clinical trials.

Genetically engineered mouse models of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of human cancer for which there are no effective therapies. Deep sequencing of PDAC tumors has revealed the presence of a high number of mutations (>50) that affect at least a dozen key signaling pathways. This scenario highlights the urgent need to develop experimental models that faithfully reproduce the natural history of these human tumors in order to understand their biology and to design therapeutic approaches that might effectively interfere with their multiple mutated pathways. Over the last decade, several models, primarily based on the genetic activation of resident KRas oncogenes knocked-in within the endogenous KRas locus have been generated. These models faithfully reproduce the histological lesions that characterize human pancreatic tumors. Decoration of these models with additional mutations, primarily involving tumor suppressor loci known to be also mutated in human PDAC tumors, results in accelerated tumor progression and in the induction of invasive and metastatic malignancies. Mouse PDACs also display a desmoplastic stroma and inflammatory responses that closely resemble those observed in human patients. Interestingly, adult mice appear to be resistant to PDAC development unless the animals undergo pancreatic damage, mainly in the form of acute, chronic or even temporary pancreatitis. In this review, we describe the most representative models available to date and how their detailed characterization is allowing us to understand their cellular origin as well as the events involved in tumor progression. Moreover, their molecular dissection is starting to unveil novel therapeutic strategies that could be translated to the clinic in the very near future.

Intestinal tumorigenesis initiated by dedifferentiation and acquisition of stem-cell-like properties

Cell-type plasticity within a tumor has recently been suggested to cause a bidirectional conversion between tumor-initiating stem cells and nonstem cells triggered by an inflammatory stroma. NF-κB represents a key transcription factor within the inflammatory tumor microenvironment. However, NF-κB's function in tumor-initiating cells has not been examined yet. Using a genetic model of intestinal epithelial cell (IEC)-restricted constitutive Wnt-activation, which comprises the most common event in the initiation of colon cancer, we demonstrate that NF-κB modulates Wnt signaling and show that IEC-specific ablation of RelA/p65 retards crypt stem cell expansion. In contrast, elevated NF-κB signaling enhances Wnt activation and induces dedifferentiation of nonstem cells that acquire tumor-initiating capacity. Thus, our data support the concept of bidirectional conversion and highlight the importance of inflammatory signaling for dedifferentiation and generation of tumor-initiating cells in vivo.

Genetically engineered mouse models of pancreatic cancer

Pancreatic ductal adenocarcinoma is the 10th most common cancer and the fourth leading cause of cancer-related death in the United States. Despite great effort, the prognosis for patients with this disease remains dismal with a 5-year survival rate of just 4% to 6%. Although several important advances have improved our understanding of the underlying biology of pancreatic cancer, this knowledge has not translated into novel therapeutic approaches and effective systemic or targeted therapies. Pancreatic cancer is one of the malignancies most difficult to treat, with remarkable intrinsic resistance to both standard and targeted chemotherapy as well as ionizing radiation. Surgical intervention remains the only potentially curative approach. However, most patients present with inoperable and/or metastatic disease and are therefore excluded from surgery. Accordingly, new therapeutic options are desperately needed. In vivo models to study innovative and alternative treatment approaches are of major importance. A variety of genetically engineered mouse models of pancreatic cancer have been developed over the last decade. However, these models display different characteristics, and not all of them are suited for preclinical studies. In this review, we aim to review the mouse models available, their experimental use, their clinical relevance and limitations, and future directions.

The role of stroma in pancreatic cancer: diagnostic and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies worldwide and survival has not improved substantially in the past 30 years. Desmoplasia (abundant fibrotic stroma) is a typical feature of PDAC in humans, and stromal activation commonly starts around precancerous lesions. It is becoming clear that this stromal tissue is not a bystander in disease progression. Cancer-stroma interactions effect tumorigenesis, angiogenesis, therapy resistance and possibly the metastatic spread of tumour cells. Therefore, targeting the tumour stroma, in combination with chemotherapy, is a promising new option for the treatment of PDAC. In this Review, we focus on four issues. First, how can stromal activity be used to detect early steps of pancreatic carcinogenesis? Second, what is the effect of perpetual pancreatic stellate cell activity on angiogenesis and tissue perfusion? Third, what are the (experimental) antifibrotic therapy options in PDAC? Fourth, what lessons can be learned from Langton's Ant (a simple mathematical model) regarding the unpredictability of genetically engineered mouse models?

The role of stroma in pancreatic cancer: diagnostic and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies worldwide and survival has not improved substantially in the past 30 years. Desmoplasia (abundant fibrotic stroma) is a typical feature of PDAC in humans, and stromal activation commonly starts around precancerous lesions. It is becoming clear that this stromal tissue is not a bystander in disease progression. Cancer-stroma interactions effect tumorigenesis, angiogenesis, therapy resistance and possibly the metastatic spread of tumour cells. Therefore, targeting the tumour stroma, in combination with chemotherapy, is a promising new option for the treatment of PDAC. In this Review, we focus on four issues. First, how can stromal activity be used to detect early steps of pancreatic carcinogenesis? Second, what is the effect of perpetual pancreatic stellate cell activity on angiogenesis and tissue perfusion? Third, what are the (experimental) antifibrotic therapy options in PDAC? Fourth, what lessons can be learned from Langton's Ant (a simple mathematical model) regarding the unpredictability of genetically engineered mouse models?

Mouse models of pancreatic cancer

Pancreatic cancer is one of the most lethal of human malignancies ranking 4th among cancer-related death in the western world and in the United States, and potent therapeutic options are lacking. Although during the last few years there have been important advances in the understanding of the molecular events responsible for the development of pancreatic cancer, currently specific mechanisms of treatment resistance remain poorly understood and new effective systemic drugs need to be developed and probed. In vivo models to study pancreatic cancer and approach this issue remain limited and present different molecular features that must be considered in the studies depending on the purpose to fit special research themes. In the last few years, several genetically engineered mouse models of pancreatic exocrine neoplasia have been developed. These models mimic the disease as they reproduce genetic alterations implicated in the progression of pancreatic cancer. Genetic alterations such as activating mutations in KRas, or TGFb and/or inactivation of tumoral suppressors such as p53, INK4A/ARF BRCA2 and Smad4 are the most common drivers to pancreatic carcinogenesis and have been used to create transgenic mice. These mouse models have a spectrum of pathologic changes, from pancreatic intraepithelial neoplasia to lesions that progress histologically culminating in fully invasive and metastatic disease and represent the most useful preclinical model system. These models can characterize the cellular and molecular pathology of pancreatic neoplasia and cancer and constitute the best tool to investigate new therapeutic approaches, chemopreventive and/or anticancer treatments. Here, we review and update the current mouse models that reproduce different stages of human pancreatic ductal adenocarcinoma and will have clinical relevance in future pancreatic cancer developments.

Aberrant signaling pathways in pancreatic cancer: a two compartment view

Pancreatic cancer is a devastating disease with historically limited success in treatment and a poor prognosis. Pancreatic cancer appears to have a progressive pathway of development, initiating from well-described pancreatic intraepithelial neoplasia lesions and concluding with invasive carcinoma. These early lesions have been shown to harbor-specific alterations in signaling pathways that remain throughout this tumorigenesis process. Meanwhile, new alterations occur during this process of disease progression to have a cumulative effect. This series of events not only impacts the epithelial cells comprising the tumor, but they may also affect the surrounding stromal cells. The result is the formation of complex signaling networks of communication between the tumor epithelial cell and the stromal cell compartments to promote a permissive and cooperative environment. This article highlights some of the most common pathway aberrations involved with this disease, and how these may subsequently affect one or both cellular compartments. Consequently, furthering our understanding of these pathways in terms of their function on the tumoral epithelial and stromal compartments may prove to be crucial to the development of targeted and more successful therapies in the future.

Acinar-to-ductal metaplasia accompanies c-myc-induced exocrine pancreatic cancer progression in transgenic rodents

Several important characteristics of exocrine pancreatic tumor pathogenesis remain incompletely defined, including identification of the cell of origin. Most human pancreatic neoplasms are ductal adenocarcinomas. However, acinar cells have been proposed as the source of some ductal neoplasms through a process of acinar-to-ductal metaplasia. The oncogenic transcription factor c-myc is associated with human pancreatic neoplasms. Transgenic mice overexpressing c-myc under control of acinar cell-specific elastase (Ela) gene regulatory elements not only develop acinar cell carcinomas but also mixed neoplasms that display both acinar-like neoplastic cells and duct-like neoplastic cells. In this report, we demonstrate that, first, c-myc is sufficient to induce acinar hyperplasia, though neoplastic lesions develop focally. Second, cell proliferation remains elevated in the neoplastic duct cell compartment of mixed neoplasms. Third, the proliferation/apoptosis ratio in cells from all lesion types remains constant, suggesting that differential regulation of these processes is not a feature of cancer progression in this model. Fourth, before the development of mixed neoplasms, there is transcriptional activation of the duct cell-specific cytokeratin-19 gene promoter in multicellular foci of amylase-positive acinar neoplasms. This observation provides direct evidence for metaplasia as the mechanism underlying development of ductal neoplastic cells within the context of an acinar neoplasm and suggests that the stimulus for this transformation acts over a multicellular domain or field within a neoplasm. Finally, focal ductal elements develop in some acinar cell carcinomas in Ela-c-myc transgenic rats, indicating that myc-associated acinar-to-ductal metaplasia is not restricted to the mouse.

Early requirement of Rac1 in a mouse model of pancreatic cancer

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease without effective chemopreventive or therapeutic approaches. Although the role of oncogenic Kras in initiating development of PDAC is well established, downstream targets of aberrant Ras signaling are poorly understood. Acinar-ductal metaplasia (ADM) appears to be an important prerequisite for development of pancreatic intraepithelial neoplasia (PanIN), a common precursor to PDAC. RAS-related C3 botulinum substrate 1 (Rac1), which controls actin reorganization, can be activated by Ras, is up-regulated in several human cancers, and is required for cerulein-induced morphologic changes in acini. We investigated effects of loss of Rac1 in Kras-induced pancreatic carcinogenesis in mice.

METHODS

Using a Cre/lox approach, we deleted Rac1 from pancreatic progenitor cells in different mouse models of PDAC and in mice with cerulein-induced acute pancreatitis. Acinar epithelial explants of mutant mice were used to investigate the role of Rac1 in vitro.

RESULTS

Rac1 expression increased in mouse and human pancreatic tumors, particularly in the stroma. Deletion of Rac1 in Kras(G12D)-induced PDAC in mice reduced formation of ADM, PanIN, and tumors and significantly prolonged survival. Pancreatic epithelial metaplasia was accompanied by apical-basolateral redistribution of F-actin, along with basal expression of Rac1. Acinar epithelial explants that lacked Rac1 or that were incubated with inhibitors of actin polymerization had a reduced ability to undergo ADM in 3-dimensional cultures.

CONCLUSIONS

In mice, Rac1 is required for early metaplastic changes and neoplasia-associated actin rearrangements in development of pancreatic cancer. Rac1 might be developed as a diagnostic marker or therapeutic target for PDAC.

Molecular biology of pancreatic ductal adenocarcinoma progression: aberrant activation of developmental pathways

Embryonic development marks a period of peak tissue growth and morphogenesis in the mammalian lifecycle. Many of the pathways that underlie cell proliferation and movement are relatively quiescent in adult animals but become reactivated during carcinogenesis. This phenomenon has been particularly well documented in pancreatic cancer, where detailed genetic studies and a robust mouse model have permitted investigators to test the role of various developmental signals in cancer progression. In this chapter, we review current knowledge regarding the signaling pathways that act during pancreatic development and the evidence that the reactivation of developmentally important signals is critical for the pathogenesis of this treatment-refractory malignancy.

Amphiregulin regulates the activation of ERK and Akt through epidermal growth factor receptor and HER3 signals involved in the progression of pancreatic cancer

Pancreatic cancer is one of the most lethal malignancies. Epidermal growth factor receptor (EGFR), HER3, Akt, and amphiregulin have been recognized as targets for pancreatic cancer therapy. Although gemcitabine + erlotinib has been the recommended chemotherapy for pancreatic cancer, the prognosis is extremely poor. The development of molecularly targeted therapies has been required for patients with pancreatic cancer. To assess the validation of amphiregulin as a target for pancreatic cancer therapy, we examined its expression in pancreatic cancer using real-time PCR analyses and ELISA. We also measured the apoptotic cell rate using TUNEL assays. In addition, alterations in signaling pathways were detected by immunoblotting analyses. Treatment with gemcitabine, which reduced the cell viability and augmented the cell apoptotic rate, activated and subsequently attenuated ERK and EGFR signals. However, gemcitabine, paclitaxel, or cisplatin treatment enhanced the Akt activation, heterodimer formation of EGFR with HER3, and secretion of amphiregulin, indicating that the presence of gemcitabine promoted the activity of targeted molecules including amphiregulin, Akt, and HER3 for pancreatic cancer therapy. Combined treatment with an inhibitor for amphiregulin and gemcitabine, paclitaxel, or cisplatin induced synergistic antitumor effects, accompanied by the suppression of Akt and ERK activation. Blockade of amphiregulin suppressed the activities of EGFR, HER3, and Akt and the expression of amphiregulin itself. According to this evidence, combination chemotherapy of conventional anticancer drugs plus an inhibitor for amphiregulin would allow us to provide more favorable clinical outcomes for patients with pancreatic cancer.

The epidermal growth factor receptor inhibitor gefitinib prevents the progression of pancreatic lesions to carcinoma in a conditional LSL-KrasG12D/+ transgenic mouse model

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy with a dismal prognosis. Developing novel strategies to prevent or delay pancreatic cancer is currently of intense interest. The chemopreventive efficacy of gefitinib, an epidermal growth factor receptor (EGFR) inhibitor, was evaluated against the progression of pancreatic intraepithelial neoplasms (PanIN) to PDAC in conditional LSL-Kras(G12D/+) transgenic mice. LSL-Kras(G12D/+) and p48(Cre/+) mice were bred, and offspring of activated Kras(G12D/+) were generated. Six-week-old male Kras(G12D/+) (20 per group) and C57BL/6 wild-type (12 per group) mice were fed (AIN-76A) diets containing 0, 100, and 200 ppm of gefitinib for 35 weeks. At termination, pancreases were evaluated histopathologically for PanINs and PDAC, and various biomarkers were measured by immunohistochemistry, immunofluorescence, immunoblotting, and/or reverse transcription-PCR. Dietary gefitinib at 100 and 200 ppm significantly suppressed PDAC incidence by 77% and 100%, respectively (P < 0.0001) when compared with control diet. Importantly, a significant inhibition of carcinoma and a dose-dependent suppression of PanINs [PanIN-1, 37-62% (P < 0.002); PanIN-2, 38-41 (P < 0.001); and PanIN-3, 7-34% (P < 0.0141)] were observed in mice treated with gefitinib. Furthermore, mice treated with 100 and 200 ppm of gefitinib exhibited 67.6% to 77.3% of the pancreas to be free from ductal lesions. Also, gefitinib reduced EGFR, proliferating cell nuclear antigen, cyclin D1, C(2)GNT, RhoA, β-catenin, p38, phospho-extracellular signal-regulated kinase, caveolin-1, and mucin and increased cyclin B1 in the pancreatic lesions/PDAC. In summary, these results show that gefitinib can prevent the progression of pancreatic cancer precursor lesions to PDAC in a preclinical model. The present study highlights the promise of chemoprevention and the potential usefulness of EGFR inhibitors in individuals at high risk for pancreatic cancer.

The zinc-finger protein KCMF1 is overexpressed during pancreatic cancer development and downregulation of KCMF1 inhibits pancreatic cancer development in mice

Potassium channel modulatory factor 1 (KCMF1) was found upregulated in a differential screen in the metaplastic epithelium in the pancreas of transforming growth factor (TGF)-alpha transgenic mice. Expression analysis indicated broad overexpression in human cancer tissues. Therefore, we investigated the hypothesis that KCMF1 promotes metaplastic changes and tumor development. KCMF1 represents an evolutionarily highly conserved protein with a 95% identity between human and zebrafish. KCMF1 is expressed during embryonic development and in the majority of adult tissues investigated. Upregulation of nuclear KCMF1 expression is evident in preneoplastic lesions and in several epithelial malignancies, such as pancreatic cancer in mice and humans. In cell culture and in the chicken chorioallantoic membrane model, KCMF1 enhances proliferation, migration and invasion of HEK-293 and Panc1 cells. In crossbreeding experiments, KCMF1-knockdown gene trap mice showed a reduced number and size of premalignant lesions and absence of pancreatic cancer formation in TGF-alpha transgenic mice. This effect is related to the decreased expression of G1 to S cell-cycle regulators such as cyclin D and cyclin-dependent kinase (CDK) 4. Our data support the hypothesis that KCMF1 mediates pro-oncogenic functions in vitro and in vivo and downregulation of KCMF1 results in the inhibition of pancreatic cancer formation in mice. These effects are mediated through downregulation of cell-cycle control genes such as cyclin D and CDK4.

Molecular mechanism of pancreatic cancer--understanding proliferation, invasion, and metastasis

INTRODUCTION

The purpose of this review is to highlight the molecular mechanisms leading to the development and progression of pancreatic ductal adenocarcinoma (PDAC) with particular emphasis on tumor cell proliferation, local invasion, and metastasis. Recent advances in the field of PDAC biology have shed light on the molecular events that trigger PDAC initiation and maintenance.

RESULTS

It is now clear that apart from the genetic alterations within the tumor cells, interactions of the tumor with its environment are necessary for proliferation and invasion. Interestingly, a number of developmental signaling pathways are reactivated in PDAC. Progress has also been made in the understanding of the molecular events that govern the process of metastasis.

CONCLUSION

Although our understanding of the mechanisms underlying PDAC pathobiology are more advanced than ever, little progress has been made in the clinical treatment of PDAC, and successful bench-to-bedside transfer of knowledge to boost new treatment options is still unsatisfying.

Betacellulin protects from pancreatitis by activating stress-activated protein kinase

BACKGROUND & AIMS

Acute pancreatitis (AP) is a serious, unpredictable clinical problem, the pathophysiology of which is poorly understood. Here, we evaluate whether betacellulin (BTC), a ligand of the epidermal growth factor receptor also able to activate the proapoptotic ERBB4 receptor, can protect against experimental AP.

METHODS

AP was induced in transgenic mice overexpressing BTC (BTC-tg), control mice, or control mice after administration of recombinant BTC. The severity of pancreatitis was assessed by measurements of serum amylase and lipase and histologic grading. The involvement of the stress-activated protein kinase (SAPK) was evaluated by treating BTC-tg mice with an SAPK inhibitor before induction of AP.

RESULTS

BTC-tg mice showed increased apoptosis and proliferation in the exocrine pancreas, indicating an increased cell turnover. There was a marked, epidermal growth factor receptor-independent decrease in pancreas weight. After induction of AP by cerulein injection, BTC-tg mice showed a significantly lower increase in serum amylase and lipase levels as well as less pronounced tissue necrosis, edema, and inflammation, as compared to nontransgenic littermates. This protective effect, also confirmed in the L-arginine AP model, was associated with increased phosphorylation of SAPK and abrogated after treatment of BTC-tg mice with a SAPK inhibitor. Finally, the protective effect of BTC against AP was confirmed by treating nontransgenic mice with recombinant BTC.

CONCLUSIONS

These findings indicate a potential application of the BTC/ERBB4 pathway for modulating the course of AP.

Pancreatic duct replication is increased with obesity and type 2 diabetes in humans

AIMS/HYPOTHESIS

In a high-fat-fed rat model of type 2 diabetes we noted increased exocrine duct replication. This is a predisposing factor for pancreatitis and pancreatic cancer, both of which are more common in type 2 diabetes. The aim of the study reported here was to establish if obesity and/or type 2 diabetes are associated with increased pancreatic ductal replication in humans.

METHODS

We obtained pancreas at autopsy from 45 humans, divided into four groups: lean (BMI <25 kg/m(2)); obese (BMI >27 kg/m(2)); non-diabetic; and with type 2 diabetes. Pancreases were evaluated after immunostaining for the duct cell marker cytokeratin and Ki67 for replication.

RESULTS

We show for the first time that both obesity and type 2 diabetes in humans are associated with increased pancreatic ductal replication. Specifically, we report that (1) replication of pancreatic duct cells is increased tenfold by obesity, and (2) lean subjects with type 2 diabetes demonstrate a fourfold increase in replication of pancreatic duct cells compared with their lean non-diabetic controls.

CONCLUSIONS/INTERPRETATION

Pancreatic duct cell replication is increased in humans in response to both obesity and type 2 diabetes, potentially providing a mechanism for the increased risk of pancreatitis and pancreatic cancer in those with obesity and/or type 2 diabetes.