Pancreatic intraepithelial neoplasia and ductal adenocarcinoma induced by DMBA in mice: effects of alcohol and caffeine

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.

THE ROLE OF IMMUNOINFLAMMATORY MARKERS IN THE PROGNOSIS AND RESECTABILITY OF PANCREATIC ADENOCARCINOMA

BACKGROUND

Pancreatic adenocarcinoma has a high mortality rate. A prognostic tool is essential for a better risk stratification. The neutrophil/lymphocyte ratio and adaptations and the platelet/lymphocyte ratio seem promising for this purpose.

AIM

Evaluate the prognostic value of neutrophil/lymphocyte ratio, derived neutrophil/lymphocyte ratio and platelet/lymphocyte ratio, analyze the ideal cutoff values and investigate their utility in predicting resectability.

METHODS

Data were collected of patients with pancreatic adenocarcinoma in Hospital de Clínicas de Porto Alegre between 2003 and 2013. The studied ratios were determined by blood count collected at hospital admission and after two cycles of palliative chemotherapy.

RESULTS

Basal neutrophil/lymphocyte ratio, derived neutrophil/lymphocyte ratio and platelet/lymphocyte ratio did not have prognostic impact in survival (p=0.394, p=0.152, p=0.177 respectively). In subgroup analysis of patients submitted to palliative chemotherapy, neutrophil/lymphocyte ratio, derived neutrophil/lymphocyte ratio and platelet/lymphocyte ratio determined after two cycles of chemotherapy were prognostic for overall survival (p=0.003, p=0.009, p=0.001 respectively). The ideal cutoff values found were 4,11 for neutrophil/lymphocyte ratio (sensitivity 83%, specificity 75%), 2,8 for derived neutrophil/lymphocyte ratio (sensitivity 87%, specificity 62,5%) and 362 for platelet/lymphocyte ratio (sensitivity 91%, specificity 62,5%), Neutrophil/lymphocyte ratio, derived neutrophil/lymphocyte ratio and platelet/lymphocyte ratio were not able to predict resectability (p=0.88; p=0.99; p=0.64 respectively).

CONCLUSIONS

Neutrophil/lymphocyte ratio, derived neutrophil/lymphocyte ratio and platelet/lymphocyte ratio are useful as prognostic markers of overall survival in patients with pancreatic adenocarcinoma submitted to palliative chemotherapy. Its use as resectability predictor could not be demonstrated.

Alcohol and Cancer: Mechanisms and Therapies

Several scientific and clinical studies have shown an association between chronic alcohol consumption and the occurrence of cancer in humans. The mechanism for alcohol-induced carcinogenesis has not been fully understood, although plausible events include genotoxic effects of acetaldehyde, cytochrome P450 2E1 (CYP2E1)-mediated generation of reactive oxygen species, aberrant metabolism of folate and retinoids, increased estrogen, and genetic polymorphisms. Here, we summarize the impact of alcohol drinking on the risk of cancer development and potential underlying molecular mechanisms. The interactions between alcohol abuse, anti-tumor immune response, tumor growth, and metastasis are complex. However, multiple studies have linked the immunosuppressive effects of alcohol with tumor progression and metastasis. The influence of alcohol on the host immune system and the development of possible effective immunotherapy for cancer in alcoholics are also discussed here. The conclusive biological effects of alcohol on tumor progression and malignancy have not been investigated extensively using an animal model that mimics the human disease. This review provides insights into cancer pathogenesis in alcoholics, alcohol and immune interactions in different cancers, and scope and future of targeted immunotherapeutic modalities in patients with alcohol abuse.

Nonproliferative and Proliferative Lesions of the Gastrointestinal Tract, Pancreas and Salivary Glands of the Rat and Mouse

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) project is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature and diagnostic criteria for nonproliferative and proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and diagnostic criteria for classifying lesions in the digestive system including the salivary glands and the exocrine pancreas of laboratory rats and mice. Most lesions are illustrated by color photomicrographs. The standardized nomenclature, the diagnostic criteria, and the photomicrographs are also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and age related lesions as well as lesions induced by exposure to test items. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature and diagnostic criteria for the digestive system will decrease misunderstandings among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Orthotopic inflammation-related pancreatic carcinogenesis in a wild-type mouse induced by combined application of caerulein and dimethylbenzanthracene

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies, with a poor long-term prognosis, and effective therapeutic options are lacking. Observing the dynamics of the pathogenesis of pancreatic intraepithelial neoplasia (PanIN) and PDAC in tumor models can facilitate understanding of the molecular mechanisms involved in early PDAC. Furthermore, it can compensate for the research limitations associated with analyzing clinical specimens of late-stage PDAC. In this study, we orthotopically treated the pancreas with dimethylbenzanthracene (DMBA) combined with caerulein in wild-type C57BL/6 J mice to induce inflammation-related pancreatic carcinogenesis. We observed that DMBA and caerulein treatment induced a chronic consumptive disease, which caused a decrease in the relative body and pancreas weights, diminishing the health status of the mice and enhancing the inflammation-related histological changes. Moreover, mid-dose and high-frequency treatment with caerulein caused prolonged inflammatory damage to the pancreas and contributed to a permissive environment for the development of PDAC. CXCL12/CXCR4, CCL2/CCR2, and several cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were upregulated in the tumor tissue of DMBA and caerulein-induced PDAC mice. This orthotopic mouse pancreatic carcinogenesis model mimic human disease because it reproduces a spectrum of pathological changes observed in human PDAC, ranging from inflammatory lesions to pancreatic intraepithelial neoplasia. Thus, this mouse model may improve the understanding of molecular mechanisms underlying the injury-inflammation-cancer pathway in the early stages of pancreatic carcinogenesis.

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.

Involvement of inflammatory factors in pancreatic carcinogenesis and preventive effects of anti-inflammatory agents

Chronic inflammation is known to be a risk for many cancers, including pancreatic cancer. Heavy alcohol drinking and cigarette smoking are major causes of pancreatitis, and epidemiological studies have shown that smoking and chronic pancreatitis are risk factors for pancreatic cancer. Meanwhile, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) are elevated in pancreatitis and pancreatic cancer tissues in humans and in animal models. Selective inhibitors of iNOS and COX-2 suppress pancreatic cancer development in a chemical carcinogenesis model of hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). In addition, hyperlipidemia, obesity, and type II diabetes are also suggested to be associated with chronic inflammation in the pancreas and involved in pancreatic cancer development. We have shown that a high-fat diet increased pancreatic cancer development in BOP-treated hamsters, along with aggravation of hyperlipidemia, severe fatty infiltration, and increased expression of adipokines and inflammatory factors in the pancreas. Of note, fatty pancreas has been observed in obese and/or diabetic cases in humans. Preventive effects of anti-hyperlipidemic/anti-diabetic agents on pancreatic cancer have also been shown in humans and animals. Taking this evidence into consideration, modulation of inflammatory factors by anti-inflammatory agents will provide useful data for prevention of pancreatic cancer.

Beta-adrenergic signaling in the development and progression of pulmonary and pancreatic adenocarcinoma

Small airway epithelial cells from, which most pulmonary adenocarcinomas (PACs) derive, and pancreatic duct epithelia, from which pancreatic ductal adenocarcinomas (PDACs) originate, share the ability to synthesize and release bicarbonate. This activity is stimulated in both cell types by the α7nicotinic acetylcholine receptor (α7nAChR)-mediated release of noradrenaline and adrenaline, which in turn activate β-adrenergic receptor (β-AR) signaling, leading to the cAMP-dependent release of bicarbonate. The same signaling pathway also stimulates a complex network of intracellular signaling cascades which regulate the proliferation, migration, angiogenesis and apoptosis of PAC and PDAC cells. The amino acid neurotransmitter γ-aminobutyric acid (GABA) serves as the physiological inhibitor of this cancer stimulating network by blocking the activation of adenylyl cyclase. This review summarizes experimental, epidemiological and clinical data that have identified risk factors for PAC and PDAC such as smoking, alcoholism, chronic non neoplastic diseases and their treatments as well as psychological stress and analyzes how these factors increase the cancer-stimulating effects of this regulatory cascade in PAC and PDAC. This analysis identifies the careful maintenance of balanced levels in stimulatory stress neurotransmitters and inhibitory GABA as a key factor for the prevention of PDAC and suggests the marker-guided use of beta-blockers, GABA or GABA-B receptor agonists as well as psychotherapeutic or pharmacological stress reduction as important tools that may render currently ineffective cancer intervention of PAC and PDAC more successful.

Ethanol differentially regulates snail family of transcription factors and invasion of premalignant and malignant pancreatic ductal cells

Pancreatic cancer is one of the deadliest of cancers with a dismal 5-year survival rate. Epidemiological studies have identified chronic pancreatitis as a risk factor for pancreatic cancer. Pancreatic cancer cells also demonstrate increased expression of the transcription factor Snail, a key regulator of epithelial-mesenchymal transition. As ethanol is one of the major causes of pancreatitis, we examined the effect of ethanol on Snail family members in immortalized human pancreatic ductal epithelial (HPDE) cells and in pancreatic cancer cells. Ethanol induced Snail mRNA levels 2.5-fold in HPDE cells, with only 1.5-fold mRNA induction of the Snail-related protein slug. In contrast, ethanol increased Slug mRNA levels 1.5- to 2-fold in pancreatic cancer cells, with minimal effect on Snail. Because Snail increases invasion of cancer cells, we examined the effect of ethanol on invasion of HPDE and pancreatic cancer cells. Surprisingly, ethanol decreased invasion of HPDE cells, but had no effect on invasion of pancreatic cancer cells. Mechanistically, ethanol increased adhesion of HPDE cells to collagen and increased expression of the collagen binding α2- and β1-integrins. In contrast, ethanol did not affect collagen adhesion or integrin expression in pancreatic cancer cells. Also in contrast to HPDE cells, ethanol did not attenuate ERK1/2 phosphorylation in pancreatic cancer cells; however, inhibiting ERK1/2 decreased pancreatic cancer cell invasion. Overall, our results identify the differential effects of ethanol on premalignant and malignant pancreatic cells, and demonstrate the pleiotropic effects of ethanol on pancreatic cancer progression.

Proteomic analysis of pancreatic intraepithelial neoplasia and pancreatic carcinoma in rat models

AIM

To detect the proteomic variabilities of pancreatic intraepithelial neoplasia (PanIN) and pancreatic carcinoma (PC) induced by 7,12-dimethylbenzanthracene (DMBA) in rat models and to identify potential biomarkers.

METHODS

Sixty adult male Sprague Dawley rats were randomized into three groups. The rats had DMBA implanted into their pancreas for one (n = 20) or two months (n = 20) or assigned to the normal group (n = 20). The rats were killed after one or two months, and were evaluated histopathologically. Three tissue samples from each group of rats with either normal pancreas, PanIN (PanIN-2) or PC were examined by 2D-DIGE. The different expression spot features were analyzed by matrix-assisted laser desorption/ionization-time of flight/time of flight (MALDI-TOF/TOF) tandem mass spectrometry. The expression of enolase 1, a differentially expressed protein, was identified by immunohistochemistry.

RESULTS

There was significant difference in the proportions of neoplastic changes between the 1- and 2-mogroups (P = 0.0488). There was an increase in the frequency of adenocarcinomas in the 2-mo group compared with the 1-mo group (P = 0.0309). No neoplastic changes were observed in any of the animals in the normal group. Enolase 1, pancreatic ELA3B, necdin, Hbp23, CHD3, hnRNP A2/B1, Rap80, and Gnb2l1 were up-regulated in the PanIN and PC tissues, and CEL, TPT1, NME2, PCK2, an unnamed protein product, and glycine C-acetyltransferase were down-regulated in the PanIN and PC tissues. The immunohistochemical results showed that enolase 1 expression was up-regulated in the pancreatic cancer tissues of rats and humans.

CONCLUSION

The pancreatic protein expression changes induced by DMBA suggest potential molecular targets for the early diagnosis and treatment of PC.

Experimental animal models of pancreatic carcinogenesis for prevention studies and their relevance to human disease

Pancreatic cancer is difficult to cure, so its prevention is very important. For this purpose, animal model studies are necessary to develop effective methods. Injection of N-nitrosobis(2-oxopropyl)amine (BOP) into Syrian golden hamsters is known to induce pancreatic ductal adenocarcinomas, the histology of which is similar to human tumors. Moreover, K-ras activation by point mutations and p16 inactivation by aberrant methylation of 5' CpG islands or by homozygous deletions have been frequently observed in common in both the hamster and humans. Thus, this chemical carcinogenesis model has an advantage of histopathological and genetic similarity to human pancreatic cancer, and it is useful to study promotive and suppressive factors. Syrian golden hamsters are in a hyperlipidemic state even under normal dietary conditions, and a ligand of peroxizome proliferator-activated receptor gamma was found to improve the hyperlipidemia and suppress pancreatic carcinogenesis. Chronic inflammation is a known important risk factor, and selective inhibitors of inducible nitric oxide synthase and cyclooxygenase-2 also have protective effects against pancreatic cancer development. Anti-inflammatory and anti-hyperlipidemic agents can thus be considered candidate chemopreventive agents deserving more attention.

Chronic administration of ethanol leads to an increased incidence of hepatocellular adenoma by promoting H-ras-mutated cells

This study used tissue samples from male B6C3F1 mice treated with ethanol in drinking water (0%, 2.5%, or 5%) for 4 or 104 weeks. We tested whether chronic alcohol drinking promotes oxidative stress in the liver and characterized the mutation profile of spontaneous and ethanol-induced tumors. We show that ethanol does not cause detectable oxidative stress in the liver at any time point and acts by promoting H-ras mutated cells.

Effect of nicotine and cigarette smoke on an experimental model of intraepithelial lesions and pancreatic adenocarcinoma induced by 7,12-dimethylbenzanthracene in mice

OBJECTIVES

To evaluate the effects of nicotine and cigarette smoke exposure on mice submitted to 7,12-dimethylbenzanthracene (DMBA) model of pancreatic carcinogenesis.

METHODS

One hundred fourteen male mice were divided into the DMBA-n and DMBA-s groups: the DMBA-n group was given 2 mg/kg per dose of nicotine ([3-(1-methyl-2-pyrrolidinyl)pyridine]) subcutaneously for 45 days, and the DMBA-s group was exposed to 100 mg/m of cigarette smoke. At day 16, 1 mg of DMBA crystals was implanted in the pancreatic head of both groups. Euthanasia was performed in all mice 30 days after the surgery. The specimens were evaluated according to the following criteria: normal ducts, reactive hyperplasia, pancreatic intraepithelial neoplasm 3 (PanIN-3), and carcinoma. For statistical analysis, DMBA-exclusive ([DMBA-e] historical control group) was included.

RESULTS

The frequency of PanIN in the 3 groups was almost the same when considering the higher-grade lesions: DMBA-e (16 [66.7%]), DMBA-s (20 [66.7%]), and DMBA-n (12 [44.4%]). Pancreatic adenocarcinoma has a higher frequency in the DMBA-n group (14 [51.9%]) than in the DMBA-e (4 [16.7%]) and DMBA-s (4, 13.3%) groups. The DMBA-s group has the highest score of PanIN-3 (40%). The differences among the groups were statistically significant (P = 0.05, Fisher exact test).

CONCLUSIONS

Nicotine but not cigarette smoke promotes pancreatic DMBA carcinogenesis in mice. Pancreatic adenocarcinomas and PanINs have the same phenotypic appearance as those that occur in humans.

[Early pancreatic cancer: can the methods currently available identify this disease?]

OBJECTIVES

Call attention of the gastroenterologists and surgeons on the patients with high risk of developing pancreatic carcinoma, and whether or not forms of surveillance and prevention of this disease, which can be applied to daily clinical practice. DATA SURVEY: It was used the database of PubMed (US National Library of Medicine), looked up the publications of recent years for the groups at risk, molecular biological testing and methods of image used in the identification of small tumors of the pancreas.

BACKGROUND

The survival rates of adenocarcinoma of the pancreas remain negligible, even after the significant advances in diagnosis by imaging, treatment and understanding of the molecular biology of this disease. Although embryonic strategies for surveillance and prevention for people with high risk of pancreatic cancer has developed.

CONCLUSIONS

This review summarizes how to identify people at high risk of developing this disease and what is the state of the art of genetic counseling and screening through techniques of image available.