Pancreatic intraepithelial neoplasia and pancreatic tumorigenesis: of mice and men

New avenues for the treatment of immunotherapy-resistant pancreatic cancer

Pancreatic cancer (PC) is characterized by its extremely aggressive nature and ranks 14th in the number of new cancer cases worldwide. However, due to its complexity, it ranks 7th in the list of the most lethal cancers worldwide. The pathogenesis of PC involves several complex processes, including familial genetic factors associated with risk factors such as obesity, diabetes mellitus, chronic pancreatitis, and smoking. Mutations in genes such as KRAS, TP53, and SMAD4 are linked to the appearance of malignant cells that generate pancreatic lesions and, consequently, cancer. In this context, some therapies are used for PC, one of which is immunotherapy, which is extremely promising in various other types of cancer but has shown little response in the treatment of PC due to various resistance mechanisms that contribute to a drop in immunotherapy efficiency. It is therefore clear that the tumor microenvironment (TME) has a huge impact on the resistance process, since cellular and non-cellular elements create an immunosuppressive environment, characterized by a dense desmoplastic stroma with cancer-associated fibroblasts, pancreatic stellate cells, extracellular matrix, and immunosuppressive cells. Linked to this are genetic mutations in TP53 and immunosuppressive factors that act on T cells, resulting in a shortage of CD8+ T cells and limited expression of activation markers such as interferon-gamma. In this way, finding new strategies that make it possible to manipulate resistance mechanisms is necessary. Thus, techniques such as the use of TME modulators that block receptors and stromal molecules that generate resistance, the use of genetic manipulation in specific regions, such as microRNAs, the modulation of extrinsic and intrinsic factors associated with T cells, and, above all, therapeutic models that combine these modulation techniques constitute the promising future of PC therapy. Thus, this study aims to elucidate the main mechanisms of resistance to immunotherapy in PC and new ways of manipulating this process, resulting in a more efficient therapy for cancer patients and, consequently, a reduction in the lethality of this aggressive cancer.

Oral bacteria accelerate pancreatic cancer development in mice

OBJECTIVE

Epidemiological studies highlight an association between pancreatic ductal adenocarcinoma (PDAC) and oral carriage of the anaerobic bacterium Porphyromonas gingivalis, a species highly linked to periodontal disease. We analysed the potential for P. gingivalis to promote pancreatic cancer development in an animal model and probed underlying mechanisms.

DESIGN

We tracked P. gingivalis bacterial translocation from the oral cavity to the pancreas following administration to mice. To dissect the role of P. gingivalis in PDAC development, we administered bacteria to a genetically engineered mouse PDAC model consisting of inducible acinar cell expression of mutant Kras (Kras +/LSL-G12D; Ptf1a-CreER, iKC mice). These mice were used to study the cooperative effects of Kras mutation and P. gingivalis on the progression of pancreatic intraepithelial neoplasia (PanIN) to PDAC. The direct effects of P. gingivalis on acinar cells and PDAC cell lines were studied in vitro.

RESULTS

P. gingivalis migrated from the oral cavity to the pancreas in mice and can be detected in human PanIN lesions. Repetitive P. gingivalis administration to wild-type mice induced pancreatic acinar-to-ductal metaplasia (ADM), and altered the composition of the intrapancreatic microbiome. In iKC mice, P. gingivalis accelerated PanIN to PDAC progression. In vitro, P. gingivalis infection induced acinar cell ADM markers SOX9 and CK19, and intracellular bacteria protected PDAC cells from reactive oxygen species-mediated cell death resulting from nutrient stress.

CONCLUSION

Taken together, our findings demonstrate a causal role for P. gingivalis in pancreatic cancer development in mice.

Is Surgery in Autoimmune Pancreatitis Always a Failure?

Autoimmune pancreatitis is a rare form of chronic pancreatitis of presumed autoimmune etiology. Due to significant overlap in clinical and imaging characteristics, misdiagnosis as a pancreatic malignancy is common. As a result, a significant number of patients undergo a major pancreatic resection, associated with considerable morbidity, for a disease process that generally responds well to corticosteroid therapy. In the past ten years, important advances have been made in understanding the disease. Several diagnostic criteria have been developed to aid in diagnosis. Despite this, pancreatic resection may still be required in a subset of patients to reliably exclude pancreatic malignancy and establish a definite diagnosis of autoimmune pancreatitis. This article aimed to define the role of surgery in autoimmune pancreatitis, if any. For this purpose, published case series of patients with a diagnosis of autoimmune pancreatitis, based on the histopathological examination of surgical specimens, were reviewed and patients' clinical, radiological and serological details were assessed. At the end, histopathologic examinations of patients who underwent pancreatic resection at our department in the last 10 years were retrospectively reviewed in order to identify patients with autoimmune pancreatitis and assess their clinical characteristics.

Risk Assessment and Pancreatic Cancer: Diagnostic Management and Artificial Intelligence

Pancreatic cancer (PC) is one of the deadliest cancers, and it is responsible for a number of deaths almost equal to its incidence. The high mortality rate is correlated with several explanations; the main one is the late disease stage at which the majority of patients are diagnosed. Since surgical resection has been recognised as the only curative treatment, a PC diagnosis at the initial stage is believed the main tool to improve survival. Therefore, patient stratification according to familial and genetic risk and the creation of screening protocol by using minimally invasive diagnostic tools would be appropriate. Pancreatic cystic neoplasms (PCNs) are subsets of lesions which deserve special management to avoid overtreatment. The current PC screening programs are based on the annual employment of magnetic resonance imaging with cholangiopancreatography sequences (MR/MRCP) and/or endoscopic ultrasonography (EUS). For patients unfit for MRI, computed tomography (CT) could be proposed, although CT results in lower detection rates, compared to MRI, for small lesions. The actual major limit is the incapacity to detect and characterize the pancreatic intraepithelial neoplasia (PanIN) by EUS and MR/MRCP. The possibility of utilizing artificial intelligence models to evaluate higher-risk patients could favour the diagnosis of these entities, although more data are needed to support the real utility of these applications in the field of screening. For these motives, it would be appropriate to realize screening programs in research settings.

KLF16 promotes pancreatic adenocarcinoma cell proliferation and migration by positively regulating SMAD6

BACKGROUND

Pancreatic adenocarcinoma (PAAD) is a cancerous tumor with an extremely poor 5-year survival rate. The exploration of biomarkers for the diagnosis and treatment of PAAD is crucial in clinical practice. Krüppel-like factors (KLFs) are involved in a variety of biological functions in cells. According to multiple studies, KLF16 behave as an oncogene in prostate, breast and gastric cancers. However, no research has been done on the significance of KLF16 in PAAD.

AIM

To explore the molecular mechanisms of KLF16 in PAAD.

METHODS

KLF16 was identified in the tumor specimens and normal tissues by GEPIA database and verified by quantitative real-time PCR (qRT-PCR). Knockdown or exogenous expression of KLF16, combined with in vitro and in vivo assays, was performed to show the functional significance of KLF16. The molecular mechanism of KLF16 was demonstrated by qRT-PCR, western blotting, immunoprecipitation assay and flow cytometry.

RESULTS

We showed that KLF16 was highly expressed in PAAD patients based on the GEPIA database. KLF16 silencing suppressed while KLF16 overexpression promoted the malignant function of PAAD cells. Based on RNA sequencing, we discovered that KLF16 potentiated the expression of SMAD6 in PAAD cells. SMAD6 transcript abundance was increased and positively correlated with KLF16 expression in PAAD samples. In addition, inhibiting SMAD6 was able to mitigate the effects of KLF16 overexpression on PAAD cell processes, suggesting the importance of SMAD6 in the development of KLF16-triggered PAAD.

CONCLUSION

KLF16/SMAD6 axis might be explored as a therapeutic target for PAAD therapy.

Targeted transcriptome and KRAS mutation analysis improve the diagnostic performance of EUS-FNA biopsies in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) carries a poor prognosis, and current diagnostic tests have suboptimal sensitivity. Incorporating standard cytology with targeted transcriptomic and mutation analysis may improve the accuracy of diagnostic biopsies, thus reducing the burden of repeat procedures and delays to treatment initiation.

METHODS

We reviewed the accuracy of 308 EUS-FNA PDAC biopsies using a large multicenter clinical and biospecimen database, then performed RNA sequencing on 134 EUS-FNA biopsies spanning all stages of disease. We identified a transcriptomic diagnostic gene signature which was validated using external datasets and 60 further diagnostic EUS-FNAs. KRAS ddPCR analysis was performed and correlated with signature gene expression.

RESULTS

The sensitivity of EUS-FNA cytology in diagnosing solid pancreatic masses in our retrospective cohort (n=308) was 78.6% (95% CI 73.2 to 83.2%). KRAS mutation analysis and our custom transcriptomic signature significantly improved upon the diagnostic accuracy of standard cytology to 91.3% in external validation sets and 91.6% in our validation cohort (n=60). Exploratory ddPCR analysis of KRAS mutant allele fraction (MAF%) correlated with signature performance and may represent a novel surrogate marker of tumour cellularity in EUS-FNA biopsies.

CONCLUSIONS

Our findings support EUS-FNA biopsies as a feasible tissue source for integrated genomic and transcriptomic analysis of PDAC across all tumour stages, including cases with non-diagnostic cytology. Our transcriptome-derived genetic signature in combination with tissue KRAS mutation analysis significantly improves upon the diagnostic accuracy of current standard procedures, and has potential clinical utility in improving the speed and accuracy of diagnosis for patients presenting with PDAC.

CXCL10 is a Tumor Microenvironment and Immune Infiltration Related Prognostic Biomarker in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is the 10th most common cancer worldwide and the outcomes for patients with the disease remain extremely poor. Precision biomarkers are urgently needed to increase the efficiency of early diagnosis and to improve the prognosis of patients. The tumor microenvironment (TME) and tumor immune infiltration are thought to impact the occurrence, progression, and prognosis of PAAD. Novel biomarkers excavated originating from the TME and immune infiltration may be effective in predicting the prognosis of PAAD patients. In the current study, the ESTIMATE and CIBERSORT algorithms were applied to estimate the division of immune and stromal components and the proportion of tumor-infiltrating immune cells in 182 PAAD cases downloaded from The Cancer Genome Atlas database. Intersection analyses of the Protein-Protein Interaction networks and Cox regression analysis identified the chemokine (CXC-motif) ligand 10 (CXCL10) as a predictive biomarker. We verified that CXCL10 in the TME negatively correlates with prognosis in PAAD and positively correlates with tumor cell differentiation. GSE62452 from the GEO database and cumulative survival analysis were performed to validate CXCL10 expression as an independent prognostic indicator. We also found that memory B cells, regulatory T cells, and macrophages M0 and M1 were correlated with the expression of CXCL10 indicating that expression of CXCL10 influenced the immune activity of the TME. Our data suggest that CXCL10 is beneficial as a prognostic indicator in PAAD patients and highlights the potential for immune targeted therapy in the treatment of PAAD.

Relationship between a 7-mRNA signature of the pancreatic adenocarcinoma microenvironment and patient prognosis (a STROBE-compliant article)

The potential association between the prognosis of the pancreatic adenocarcinoma (PAAD) and its microenvironment is unclear. This study aims to construct a prognostic index (PI) model of the PAAD microenvironment to predict PAAD patient survival outcomes.The mRNA sequencing and the clinical parameters data were obtained from The Cancer Genome Atlas. Immune and stromal scores were computed using the expression data algorithm to capture infiltration of immune and stromal cells in the PAAD tissue, where patients were categorized as high and low score groups according to these scores. Differentially expressed genes were identified using the R package LIMMA. Univariate and multivariate Cox regression analysis were conducted to select candidate survival-correlated gene signatures from the tumor microenvironment for constructing a model. The Kaplan-Meier method was used to access overall survival of the primary and validation cohorts. The immunological features of the PI model was explored using the Tumor Immune Estimation Resource (TIMER) database. Bioinformatic analyses were conducted based on the DAVID database.A total of 1266 overlapping differentially expressed genes and 49 prognosis-associated genes were identified. A 7-mRNA signature (GBP5, BICC1, SLC7A14, CYSLTR1, P2RY6, VENTX, and RAB39B) was screened for the construction of a PI model (area under the curve = 0.791). In both the primary and validation cohorts, Kaplan Meier analysis revealed that the overall survival of the high-risk group was significantly worse compared to the low-risk group (P < .0001, P = .0028 respectively). The TIMER database described that the 7 signature genes were correlated with immune infiltrating cells and tumor purity. Bioinformatic analyses revealed that these prognosis-associated genes were significantly enriched during inflammation, the defense response, would response, calcium ion transport, and plasma membrane part.A list of the prognosis-correlated genes was generated based on the PAAD microenvironment. A 7-mRNA PI model may be used for predicting the prognosis of PAAD patients.

Early Detection of Pancreatic Intraepithelial Neoplasias (PanINs) in Transgenic Mouse Model by Hyperpolarized 13C Metabolic Magnetic Resonance Spectroscopy

While pancreatic cancer (PC) survival rates have recently shown modest improvement, the disease remains largely incurable. Early detection of pancreatic cancer may result in improved outcomes and therefore, methods for early detection of cancer, even premalignant lesions, may provide more favorable outcomes. Pancreatic intraepithelial neoplasias (PanINs) have been identified as premalignant precursor lesions to pancreatic cancer. However, conventional imaging methods used for screening high-risk populations do not have the sensitivity to detect PanINs. Here, we have employed hyperpolarized metabolic imaging in vivo and nuclear magnetic resonance (¹H-NMR) metabolomics ex vivo to identify and understand metabolic changes, towards enabling detection of early PanINs and progression to advanced PanINs lesions that precede pancreatic cancer formation. Progression of disease from tissue containing predominantly low-grade PanINs to tissue with high-grade PanINs showed a decreasing alanine/lactate ratio from high-resolution NMR metabolomics ex vivo. Hyperpolarized magnetic resonance spectroscopy (HP-MRS) allows over 10,000-fold sensitivity enhancement relative to conventional magnetic resonance. Real-time HP-MRS was employed to measure non-invasively changes of alanine and lactate metabolites with disease progression and in control mice in vivo, following injection of hyperpolarized [1-¹³C] pyruvate. The alanine-to-lactate signal intensity ratio was found to decrease as the disease progressed from low-grade PanINs to high-grade PanINs. The biochemical changes of alanine transaminase (ALT) and lactate dehydrogenase (LDH) enzyme activity were assessed. These results demonstrate that there are significant alterations of ALT and LDH activities during the transformation from early to advanced PanINs lesions. Furthermore, we demonstrate that real-time conversion kinetic rate constants (k_PA and k_PL) can be used as metabolic imaging biomarkers of pancreatic premalignant lesions. Findings from this emerging HP-MRS technique can be translated to the clinic for detection of pancreatic premalignant lesion in high-risk populations.

NMR-based metabolic profiling of urine, serum, fecal, and pancreatic tissue samples from the Ptf1a-Cre; LSL-KrasG12D transgenic mouse model of pancreatic cancer

Pancreatic cancer is the third leading cause of cancer deaths in the United States with more than 53,000 expected to be diagnosed with the disease in 2018. The median survival time after diagnosis is four to six months. The poor survival statistics are due in part to the fact that pancreatic cancer is typically asymptomatic until it reaches advanced stages of the disease. Although surgical resection provides the best chance of survival, pancreatic cancer is rarely detected when surgery is still possible due, in part, to lack of effective biomarkers for early detection. The goal of the research reported here was to determine if it was possible to identify metabolic biomarkers for detection of pre-cancerous pancreatic intraepithelial neoplasia (PanIN) that precede pancreatic adenocarcinoma. The transgenic Ptf1a-Cre; LSL-KrasG12D mouse strain was used as a model of pancreatic cancer progression. Nuclear magnetic resonance (NMR) spectroscopy was employed to compare metabolic profiles of urine, sera, fecal extracts, and pancreatic tissue extracts collected from control and study mice aged 5, 11, and 15 months, including 47 mice with tumors. We were able to identify the following potential biomarkers: decreased 3-indoxylsulfate, benzoate and citrate in urine, decreased glucose, choline, and lactate in blood, and decreased phenylalanine and benzoate and increased acetoin in fecal extracts. Potential biomarkers were validated by p-values, PLS-DA VIP scores, and accuracies based on area under ROC curve analyses. Essentially, all of the metabolic profiling changes could be explained as being associated with the consequences of bicarbonate wasting caused by a complete substitution of the normal pancreatic acinar tissue by tissue entirely composed of PanIN. Given the nature of the mouse model used here, our results indicate that it may be possible to use NMR-based metabolic profiling to identify biomarkers for detection of precancerous PanIN that immediately precede pancreatic cancer.

The Mouse Model of Pancreatic Cancer Atlas (MMPCA) for classification of pancreatic cancer lesions: A large histological investigation of the Ptf1aCre/+;LSL-KrasG12D/+ transgenic mouse model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading forms of cancer related deaths in the United States. With limited treatment options and unreliable diagnostic methods, long-term survival rates following a diagnosis of pancreatic cancer remain poor. Pancreatic intraepithelial neoplasia (PanIN) are precancerous lesions that precede progression towards PDAC. PanIN occur in increasing complexity as the disease progresses and the description of PanIN plays a critical role in describing, staging and diagnosing PDAC. Inconsistencies in PanIN classifications exist even amongst leading pathologists. This has led to debate and confusion among researchers and pathologists involved in pancreatic cancer research, diagnosis and treatment. We have sought to initiate a discussion with leading pathologists with a goal of increasing consensus in the interpretation of PanIN and associated structures within the precancerous pancreas. Toward achieving this goal, we are in the process of conducting an extensive study of over 1000 male and female pancreata in varying stages of PanIN progression isolated from the Ptf1a^Cre/+;LSL-Kras^G12D/+ transgenic mouse model of pancreatic cancer. Using this extensive database, we have established the Mouse Model of Pancreatic Cancer Atlas (MMPCA) to serve as a platform for meaningful and interactive discussion among researchers and pathologists who study pancreatic disease. We hope that the MMPCA will be an effective tool for promoting a more consistent and accurate consensus of PanIN classifications in the future.

HMGA1 expression levels are elevated in pancreatic intraepithelial neoplasia cells in the Ptf1a-Cre; LSL-KrasG12D transgenic mouse model of pancreatic cancer

BACKGROUND

Pancreatic cancer is currently the third leading cause of cancer deaths in the United States and it is predicted to become the second by the year 2030. High-mobility group A1 protein (HMGA1) is an oncogenic transcription factor, localised and active in cell nuclei, that is linked to tumour progression in many human cancers, including pancreatic cancer. Overexpression of HMGA1 renders cancer cells resistant to chemotherapy. Although the Ptf1a-Cre; LSL-KrasG12D transgenic mouse is perhaps the most widely utilised animal model for human pancreatic cancer, expression levels of HMGA1 in pancreata from this mouse model have not been characterised.

METHODS

Quantitative immunohistochemical analysis was used to determine nuclear HMGA1 levels in pancreatic tissue sections from Ptf1a-Cre; LSL-KrasG12D mice aged 5, 11, and 15 months. The H Score method was used for quantitative analysis.

RESULTS

The HMGA1 levels were significantly elevated in pancreatic intraepithelial neoplasia (PanIN) epithelia compared with untransformed acinar tissues or fibroinflammatory stroma.

CONCLUSIONS

The PanINs have long been regarded as precancerous precursors to pancreatic adenocarcinoma. Significantly elevated HMGA1 levels observed in the nuclei of PanINs in Ptf1a-Cre; LSL-KrasG12D mice validate this animal model for investigating the role that HMGA1 plays in cancer progression and testing therapeutic approaches targeting HMGA1 in human cancers.

Genomic Variations in Pancreatic Cancer and Potential Opportunities for Development of New Approaches for Diagnosis and Treatment

Human pancreatic cancer has a very poor prognosis with an overall five-year survival rate of less than 5% and an average median survival time of six months. This is largely due to metastatic disease, which is already present in the majority of patients when diagnosed. Although our understanding of the molecular events underlying multi-step carcinogenesis in pancreatic cancer has steadily increased, translation into more effective therapeutic approaches has been inefficient in recent decades. Therefore, it is imperative that novel and targeted approaches are designed to facilitate the early detection and treatment of pancreatic cancer. Presently, there are numerous ongoing studies investigating the types of genomic variations in pancreatic cancer and their impact on tumor initiation and growth, as well as prognosis. This has led to the development of therapeutics to target these genetic variations for clinical benefit. Thus far, there have been minimal clinical successes directly targeting these genomic alterations; however research is ongoing to ultimately discover an innovative approach to tackle this devastating disease. This review will discuss the genomic variations in pancreatic cancer, and the resulting potential diagnostic and therapeutic implications.

Pancreatic Cancer Chemoprevention Translational Workshop: Meeting Report

Pancreatic cancer is the fourth leading cause of cancer related deaths in the United States with a 5-year survival rate of less than 10%. The Division of Cancer Prevention of the National Cancer Institute sponsored the Pancreatic Cancer Chemoprevention Translational Workshop on September 10 to 11, 2015. The goal of the workshop was to obtain information regarding the current state of the science and future scientific areas that should be prioritized for pancreatic cancer prevention research, including early detection and intervention for high-risk precancerous lesions. The workshop addressed the molecular/genetic landscape of pancreatic cancer and precursor lesions, high-risk populations and criteria to identify a high-risk population for potential chemoprevention trials, identification of chemopreventative/immunopreventative agents, and use of potential biomarkers and imaging for assessing short-term efficacy of a preventative agent. The field of chemoprevention for pancreatic cancer is emerging, and this workshop was organized to begin to address these important issues and promote multi-institutional efforts in this area. The meeting participants recommended the development of an National Cancer Institute working group to coordinate efforts, provide a framework, and identify opportunities for chemoprevention of pancreatic cancer.

Molecular Biomarkers of Pancreatic Intraepithelial Neoplasia and Their Implications in Early Diagnosis and Therapeutic Intervention of Pancreatic Cancer

Lack of early detection and effective interventions is a major reason for the poor prognosis and dismal survival rates for pancreatic cancer. Pancreatic intraepithelial neoplasia (PanIN) is the most common precursor of invasive pancreatic ductal adenocarcinoma (PDAC). Each stage in the progression from PanIN to PDAC is well characterized by multiple significant genetic alterations affecting signaling pathways. Understanding the biological behavior and molecular alterations in the progression from PanIN to PDAC is crucial to the identification of noninvasive biomarkers for early detection and diagnosis and the development of preventive and therapeutic strategies for control of pancreatic cancer progression. This review focuses on molecular biomarkers of PanIN and their important roles in early detection and treatment of pancreatic cancer.

Molecular Targeted Intervention for Pancreatic Cancer

Pancreatic cancer (PC) remains one of the worst cancers, with almost uniform lethality. PC risk is associated with westernized diet, tobacco, alcohol, obesity, chronic pancreatitis, and family history of pancreatic cancer. New targeted agents and the use of various therapeutic combinations have yet to provide adequate treatments for patients with advanced cancer. To design better preventive and/or treatment strategies against PC, knowledge of PC pathogenesis at the molecular level is vital. With the advent of genetically modified animals, significant advances have been made in understanding the molecular biology and pathogenesis of PC. Currently, several clinical trials and preclinical evaluations are underway to investigate novel agents that target signaling defects in PC. An important consideration in evaluating novel drugs is determining whether an agent can reach the target in concentrations effective to treat the disease. Recently, we have reported evidence for chemoprevention of PC. Here, we provide a comprehensive review of current updates on molecularly targeted interventions, as well as dietary, phytochemical, immunoregulatory, and microenvironment-based approaches for the development of novel therapeutic and preventive regimens. Special attention is given to prevention and treatment in preclinical genetically engineered mouse studies and human clinical studies.

Mutations in the p16 gene in DMBA-induced pancreatic intraepithelial neoplasia and pancreatic cancer in rats

BACKGROUND

7, 12-dimethylbenzanthracene (DMBA)-induced pancreatic intraepithelial neoplasia (PanIN) and pancreatic cancer in rats provide a classic model for uncovering the molecular mechanisms underlying pancreatic cancer. However, this model has not been characterized genetically, and in particular, the major genetic alterations in the p16 gene are unknown.

METHODS

Lesions of PanIN and pancreatic cancer were induced with DMBA implantation in 40 rats, and control pancreatic tissue was obtained from 10 age-matched rats without exposure to DMBA. Pancreatic tissue was harvested three months after DMBA implantation and DNA was extracted. Homozygous deletions and point mutations of the p16 (exons 1 and 2) gene were detected by PCR amplification and direct sequencing.

RESULTS

DMBA implantation in the 40 rats induced 26 PanINs and 9 carcinomas. The overall frequency of p16 alterations in the pancreatic tissue of these rats was 42.86% (15/35), and the changes were point mutations, not homozygous deletions. p16 mutations were present in 30.77% (8/26) of the rats with PanIN and 77.78% (7/9) of the rats with carcinoma (P<0.05). The increasing incidence of p16 alterations was detected in 20.00% (1/5) of PanIN-1, 28.57% (2/7) of PanIN-2 and 35.71% (5/14) of PanIN-3 lesions.

CONCLUSION

Our findings indicated that p16 alteration is a common event in the carcinogenesis of this model and that the mutation pattern is analogous to that of human lesions.

Somatic mutations in exocrine pancreatic tumors: association with patient survival

KRAS mutations are major factors involved in initiation and maintenance of pancreatic tumors. The impact of different mutations on patient survival has not been clearly defined. We screened tumors from 171 pancreatic cancer patients for mutations in KRAS and CDKN2A genes. Mutations in KRAS were detected in 134 tumors, with 131 in codon 12 and only 3 in codon 61. The GGT>GAT (G12D) was the most frequent mutation and was present in 60% (80/134). Deletions and mutations in CDKN2A were detected in 43 tumors. Analysis showed that KRAS mutations were associated with reduced patient survival in both malignant exocrine and ductal adenocarcinomas (PDAC). Patients with PDACs that had KRAS mutations showed a median survival of 17 months compared to 30 months for those without mutations (log-rank P = 0.07) with a multivariate hazard ratio (HR) of 2.19 (95%CI 1.09-4.42). The patients with G12D mutation showed a median survival of 16 months (log-rank-test P = 0.03) and an associated multivariate HR 2.42 (95%CI 1.14-2.67). Although, the association of survival in PDAC patients with CDKN2A aberrations in tumors was not statistically significant, the sub-group of patients with concomitant KRAS mutations and CDKN2A alterations in tumors were associated with a median survival of 13.5 months compared to 22 months without mutation (log-rank-test P = 0.02) and a corresponding HR of 3.07 (95%CI 1.33-7.10). Our results are indicative of an association between mutational status and survival in PDAC patients, which if confirmed in subsequent studies can have potential clinical application.

Molecular markers in pancreatic cancer diagnosis

Pancreatic ductal adenocarcinoma (PDAC) represents a fatal neoplasia with a high mortality rate. Effective early detection methods are needed since this is the best way to cure this disease. During the last several years, many investigations focused on determining relevant biomarkers that may be present during early stages of pancreatic tumor development. Although several biomarkers have been proposed for pancreatic cancer detection, the clinical applicability has been confusing. Currently, although CA19-9 is one test used, the sensitivity and specificity for the disease are less than optimal. Here, we review several new potential serum, plasma and stool markers that are currently under evaluation. Although these have not been sufficiently validated for routine clinical use, these markers could prove valuable with further investigations. We keep the hope that a combination of some of these novel biomarkers can be a useful tool for early PDAC diagnosis before image techniques and/or patient's symptoms reveal disease in an incurable state.

The receptor for advanced glycation end products promotes pancreatic carcinogenesis and accumulation of myeloid-derived suppressor cells

Pancreatic ductal adenocarcinoma (PDA) has an aggressive natural history and is resistant to therapy. The receptor for advanced glycation end products (RAGE) is a pattern recognition receptor for many damage-associated molecular pattern molecules. RAGE is overexpressed in both human and murine models of PDA as well as most advanced epithelial neoplasms. The immunosuppressive nature of the PDA microenvironment is facilitated, in part, by the accumulation of regulatory immune cell infiltrates such as myeloid-derived suppressor cells (MDSCs). To study the role of RAGE expression in the setting of mutant Ras-promoted pancreatic carcinogenesis (KC), a triple-transgenic model of spontaneous murine PDA in a RAGE-null background (KCR) was generated. KCR mice had markedly delayed pancreatic carcinogenesis and a significant diminution of MDSCs compared with KC mice at comparable time points postweaning. Although RAGE was not required for the development or suppressor activity of MDSCs, its absence was associated with temporally limited pancreatic neoplasia and altered phenotype and function of the myeloid cells. In lieu of MDSCs, KCR animals at comparable time points exhibited mature CD11b(+)Gr1(-)F4/80(+) cells that were not immunosuppressive in vitro. KCR mice also maintained a significantly less suppressive milieu evidenced by marked decreases in CCL22 in relation to CXCL10 and diminished serum levels of IL-6.

Overexpressed galectin-3 in pancreatic cancer induces cell proliferation and invasion by binding Ras and activating Ras signaling

Pancreatic cancer (PDAC) is a lethal disease with a five-year survival of 3–5%. Mutations in K-Ras are found in nearly all cases, but K-Ras mutations alone are not sufficient for the development of PDAC. Additional factors contribute to activation of Ras signaling and lead to tumor formation. Galectin-3 (Gal-3), a multifunctional β-galactoside-binding protein, is highly expressed in PDAC. We therefore investigated the functional role of Gal-3 in pancreatic cancer progression and its relationship to Ras signaling. Expression of Gal-3 was determined by immunohistochemistry, Q-PCR and immunoblot. Functional studies were performed using pancreatic cell lines genetically engineered to express high or low levels of Gal-3. Ras activity was examined by Raf pull-down assays. Co-immunoprecipitation and immunofluorescence were used to assess protein-protein interactions. In this study, we demonstrate that Gal-3 was highly up-regulated in human tumors and in a mutant K-Ras mouse model of PDAC. Down-regulation of Gal-3 by lentivirus shRNA decreased PDAC cell proliferation and invasion in vitro and reduced tumor volume and size in an orthotopic mouse model. Gal-3 bound Ras and maintained Ras activity; down-regulation of Gal-3 decreased Ras activity as well as Ras down-stream signaling including phosphorylation of ERK and AKT and Ral A activity. Transfection of Gal-3 cDNA into PDAC cells with low-level Gal-3 augmented Ras activity and its down-stream signaling. These results suggest that Gal-3 contributes to pancreatic cancer progression, in part, by binding Ras and activating Ras signaling. Gal-3 may therefore be a potential novel target for this deadly disease.

Incidentally discovered benign pancreatic cystic neoplasms not communicating with the ductal system: MR/MRCP imaging appearance and evolution

PURPOSE

The authors sought to determine magnetic resonance/magnetic resonance cholangiopancreatography (MR/MRCP) imaging features of incidentally discovered benign, noncommunicating cystic neoplasms (BNCNs) of the pancreas to assess their evolution over time and identify MR/MRCP imaging features predictive of tumour growth.

MATERIAL AND METHODS

This was a retrospective study, so informed consent was waived. Sixty-two patients with a diagnosis of BNCN were assessed. Inclusion criteria were incidentally discovered cystic neoplasm of the pancreas with nonmeasurable walls, no mural nodules and no communication with the pancreatic ductal system and who underwent ≥ 1 MR/MRCP examination. Image analysis, performed at diagnosis and during follow-up, included macroscopic pattern (microcystic/macrocystic/mixed), number of cysts (unicystic/oligocystic/multicystic), BNCN maximum diameter and tumour growth rates.

RESULTS

A total of 64 BNCNs was detected. Macroscopic pattern was mixed in 31/64 (48%), microcystic in 28/64 (44%) and macrocystic in 5/64 (8%). BNCNs appeared multicystic in 38/64 (59%) cases, oligocystic in 22/64 (35%) and unicystic in 4/64(6%). All qualitative parameters remained unchanged during follow-up. At diagnosis, the median maximum BNCN diameter was 35.0 mm and 38.0 mm at the final examination (p<0.001). BNCNs showed a tumour growth rate of 2 mm/year.

CONCLUSIONS

Mixed and microcystic patterns were the most common, accounting for 48% and 44% of cases, respectively, and showed no change over time. MR/MRCP features predictive of lesion enlargement were a mixed/ macrocystic pattern, and lesion size was >3 cm (both p<0.001).

Pancreatic ductal adenocarcinoma in hereditary diffuse gastric cancer. A case report

Hereditary diffuse gastric cancer is an autosomal dominant cancer syndrome characterized by highly penetrant diffuse gastric cancer. It is caused by germ line mutations in CDH1, encoding the cell-cell adhesion protein E-cadherin. Pancreatic ductal adenocarcinoma is one of the most dismal malignancies in humans. Although absent E-cadherin expression in pancreatic ductal adenocarcinoma is related to a higher tumor grade and a worse prognosis, there have been no reports of pancreatic ductal adenocarcinoma associated with hereditary diffuse gastric cancer. Here, we describe a patient with hereditary diffuse gastric cancer who was subsequently diagnosed with pancreatic ductal adenocarcinoma. To investigate if the previously identified CDH1 germ line mutation initiated pancreatic ductal adenocarcinoma development, we performed mutational and proteomic analyses. We conclude that the pancreatic ductal adenocarcinoma did not occur in the context of the germ line CDH1 mutation but rather appeared as a sporadic event. Immunohistochemistry ultimately proved to be the most valuable tool of investigation as persistent CDH1 staining in the pancreatic ductal adenocarcinoma unequivocally revealed E-cadherin expression.

Precursor lesions in pancreatic cancer: morphological and molecular pathology

Pancreatic cancer has a dismal prognosis and is the fourth most common cause of cancer related death in Western societies. In large part this is due to its typically late presentation, usually as locally advanced or metastatic disease. Identification of the non-invasive precursor lesions to pancreatic cancer raises the possibility of surgical treatment or chemoprevention at an early stage in the evolution of this disease, when more amenable to therapeutic interventions. Precursor lesions to pancreatic ductal adenocarcinoma, in particular pancreatic intraepithelial neoplasia (PanIN), have been recognised under a variety of synonyms for over 50 years. Over the past decade our understanding of the morphology, biological significance and molecular aberrations of these lesions has grown rapidly and there is now a widely accepted progression model integrating the accumulated morphological and molecular observations. Further progress is likely to be accelerated by improved mouse models of pancreatic cancer and by insight into the cancer genome gained by the International Cancer Genome Consortium (ICGC), in which an Australian consortium is leading the pancreatic cancer initiative. This review also outlines the morphological and molecular features of the other two precursors of pancreatic ductal adenocarcinoma, i.e., intraductal papillary mucinous neoplasms and mucinous cystic neoplasms.

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.

Precursor lesions of early onset pancreatic cancer

Early onset pancreatic cancer (EOPC) constitutes less than 5% of all newly diagnosed cases of pancreatic cancer (PC). Although histopathological characteristics of EOPC have been described, no detailed reports on precursor lesions of EOPC are available. In the present study, we aimed to describe histopathological picture of extratumoral parenchyma in 23 cases of EOPCs (definition based on the threshold value of 45 years of age) with particular emphasis on two types of precursor lesions of PC: pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasms (IPMNs). The types, grades, and densities of precursor lesions of PC were compared in patients with EOPCs, in young patients with neuroendocrine neoplasms (NENs), and in older (at the age of 46 or more) patients with PC. PanINs were found in 95.6% of cases of EOPCs. PanINs-3 were found in 39.1% of EOPC cases. Densities of all PanIN grades in EOPC cases were larger than in young patients with NENs. Density of PanINs-1A in EOPC cases was larger than in older patients with PC, but densities of PanINs of other grades were comparable. IPMN was found only in a single patient with EOPC but in 20% of older patients with PC. PanINs are the most prevalent precursor lesions of EOPC. IPMNs are rarely precursor lesions of EOPC. Relatively high density of low-grade PanINs-1 in extratumoral parenchyma of patients with EOPC may result from unknown multifocal genetic alterations in pancreatic tissue in patients with EOPCs.

Intraductal papillary-mucinous neoplasia of the pancreas: Histopathology and molecular biology

Intraductal papillary-mucinous neoplasm (IPMN) of the pancreas is a clinically and morphologically distinctive precursor lesion of pancreatic cancer, characterized by gradual progression through a sequence of neoplastic changes. Based on the nature of the constituting neoplastic epithelium, degree of dysplasia and location within the pancreatic duct system, IPMNs are divided in several types which differ in their biological properties and clinical outcome. Molecular analysis and recent animal studies suggest that IPMNs develop in the context of a field-defect and reveal their possible relationship with other neoplastic precursor lesions of pancreatic cancer.

Identification of susceptibility loci in a mouse model of KRASG12D-driven pancreatic cancer

Genetic background affects susceptibility to pancreatic ductal adenocarcinoma in the Ela-KRAS(G12D) mouse model. In this model, KRAS oncogene expression is driven by an elastase promoter in acinar cells of the pancreas on an FVB/NTac (FVB) background [FVB-Tg(Ela-KRAS(G12D))] with the transgene carried on the Y chromosome. Through linkage analysis of crosses between the C57BL/6J (B6), BALB/cJ (BALB), and DBA/2J (D2) inbred strains of mice and resistant FVB-Tg(Ela-KRAS(G12D)), we have identified six susceptibility loci that affect mean preinvasive lesion multiplicity. Markers on chromosome 2 segregated with high tumor multiplicity in all three strains; these loci were designated Prsq1-3 (pancreatic ras susceptibility quantitative trait loci 1-3; combined F2 and N2 LOD(W), 6.0, 4.1, and 2.7, respectively). Susceptibility loci on chromosome 4, designated Prsq4 and Prsq5, were identified in crosses between FVB transgenic mice and B6 or BALB mice (combined F2 and N2 LOD(W), 3.6 and 2.9, respectively). A marker on chromosome 12 segregated with tumor multiplicity in a BALB × FVB-Tg(Ela-KRAS(G12D)) cross and was designated Prsq6 (LOD(W), ∼2.5). B6-Chr Y(FVB-Tg(Ela-KRASG12D)) and BALB-Chr Y(FVB-Tg(Ela-KRASG12D)) consomics, which carry the KRAS transgene on the FVB Y chromosome on an otherwise inbred B6 or BALB background, developed ∼4-fold (B6) and ∼10-fold (BALB) more lesions than FVB-Tg(Ela-KRAS(G12D)) mice. By 12 months of age, 10% of BALB-Chr Y(FVB-Tg(Ela-KRASG12D)) mice developed invasive carcinomas. Our findings provide evidence that regions of chromosomes 2, 4, and 12 influence the development and progression of pancreatic neoplasms initiated by an oncogenic allele of KRAS in mice.

Current status of molecular markers for early detection of sporadic pancreatic cancer

Pancreatic cancer (PC) is a highly lethal malignancy with near 100% mortality. This is in part due to the fact that most patients present with metastatic or locally advanced disease at the time of diagnosis. Significantly, in nearly 95% of PC patients there is neither an associated family history of PC nor of diseases known to be associated with an increased risk of PC. These groups of patients who comprise the bulk of PC cases are termed as "sporadic PC" in contrast to the familial PC cases that comprise only about 5% of all PCs. Given the insidious onset of the malignancy and its extreme resistance to chemo and radiotherapy, an abundance of research in recent years has focused on identifying biomarkers for the early detection of PC, specifically aiming at the sporadic PC cohort. However, while several studies have established that asymptomatic individuals with a positive family history of PC and those with certain heritable syndromes are candidates for PC screening, the role of screening in identifying sporadic PC is still an unsettled question. The present review attempts to assess this critical question by investigating the recent advances made in molecular markers with potential use in the early diagnosis of sporadic PC - the largest cohort of PC cases worldwide. It also outlines a novel yet simple risk factor based stratification system that could be potentially employed by clinicians to identify those individuals who are at an elevated risk for the development of sporadic PC and therefore candidates for screening.

Genomic instability at both the base pair level and the chromosomal level is detectable in earliest PanIN lesions in tissues of chronic pancreatitis

OBJECTIVE

Chronic pancreatitis (CP) is a predisposing disease for pancreatic carcinoma (PC), however, precise molecular mechanisms of cancer development in the background of CP are ill defined.

METHODS

A total of 443 laser-microdissected pancreatic intraepithelial neoplasias (PanINs), acinar-ductal metaplasia (ADM), and normal ducts from 21 patients with CP were analyzed for loss of heterozygosity (LOH) and immunohistochemical protein expression of p53, p16, and DPC4. Pancreatic intraepithelial neoplasias were analyzed for mutations in p53, p16, and Ki-ras genes by ABI sequencing. Aneuploidy was determined by fluorescence in situ hybridization with probes for chromosomes 3, 7, 8, and 17.

RESULTS

Loss of heterozygosity rate in PanIN-1 and ADM was between 1.7% (p53) and 5.8% (p16). In PanIN-3, p53 protein overexpression and loss of expression for p16 and DPC4 protein were seen. Heterozygous mutations of p53 and p16 without LOH were found in PanIN-1A and ADM, whereas homozygous mutations were found in PanIN-3. Aneuploidy increased from PanIN-1A to PanIN-3. Ki-ras mutations were discovered first in PanIN-1.

CONCLUSIONS

Heterozygous mutations of p53- and p16 genes together with chromosomal instability occur early in CP and are clonally expanded, but final inactivation mostly by LOH happens later in pancreatic carcinogenesis. Determination of aneuploidy in pancreatic juice may be of value for early detection and risk assessment in patients with long-standing CP.

Pancreatic intraepithelial neoplasia-can we detect early pancreatic cancer?

Haugk B
(2010) Histopathology 57, 503-514
Pancreatic intraepithelial neoplasia - can we detect early pancreatic cancer? Pancreatic cancer is one of the most lethal cancers, with an incidence equalling mortality. Pancreatic cancer is a heterogeneous group in which pancreatic ductal adenocarcinoma (PDAC) is the most common. It is now established that PDAC develops through stepwise progression from precursor lesions. Detection and treatment of these precursor lesions would allow curative treatment. Three precursor lesions for PDAC have been identified. Two of these - mucinous cystic neoplasms (MCNs) and intraductal papillary mucinous neoplasms (IPMNs) - are rare, radiologically detectable, cystic precursor lesions which can be cured if treated at the preinvasive stage. The third and most common precursor lesion has recently been defined as pancreatic intraepithelial neoplasia (PanIN). PanINs are microscopic lesions with no clinical correlate. They display a spectrum of cyto-architectural changes (PanIN-1, PanIN-2 and PanIN-3) mirrored in an increasing accumulation of molecular genetic changes, with PanIN-3 sharing many of the alterations with PDAC. Great advances in the understanding of pancreatic carcinogenesis have opened avenues for diagnosis and chemoprevention. However, access to the pancreas is limited, molecular tests are at the early stages and too little is known about the natural history of early PanINs to justify resection. Currently, screening focuses upon high-risk individuals only.

Binding of pro-prion to filamin A: by design or an unfortunate blunder

Over the last decades, cancer research has focused on tumor suppressor genes and oncogenes. Genes in other cellular pathways has received less attention. Between 0.5% to 1% of the mammalian genome encodes for proteins that are tethered on the cell membrane via a glycosylphosphatidylinositol (GPI)-anchor. The GPI modification pathway is complex and not completely understood. Prion (PrP), a GPI-anchored protein, is infamous for being the only normal protein that when misfolded can cause and transmit a deadly disease. Though widely expressed and highly conserved, little is known about the functions of PrP. Pancreatic cancer and melanoma cell lines express PrP. However, in these cell lines the PrP exists as a pro-PrP as defined by retaining its GPI anchor peptide signal sequence (GPI-PSS). Unexpectedly, the GPI-PSS of PrP has a filamin A (FLNA) binding motif and binds FLNA. FLNA is a cytolinker protein, and an integrator of cell mechanics and signaling. Binding of pro-PrP to FLNA disrupts the normal FLNA functions. Although normal pancreatic ductal cells lack PrP, about 40% of patients with pancreatic ductal cell adenocarcinoma express PrP in their cancers. These patients have significantly shorter survival time compared with patients whose cancers lack PrP. Pro-PrP is also detected in melanoma in situ but is undetectable in normal melanocyte, and invasive melanoma expresses more pro-PrP. In this review, we will discuss the underlying mechanisms by which binding of pro-PrP to FLNA disrupts normal cellular physiology and contributes to tumorigenesis, and the potential mechanisms that cause the accumulation of pro-PrP in cancer cells.