BRCA2 is inactivated late in the development of pancreatic intraepithelial neoplasia: evidence and implications

Precursor lesions in familial and hereditary pancreatic cancer

Infiltrating ductal adenocarcinoma of the pancreas, referred to here as "pancreatic cancer," is one of the deadliest of all of the solid malignancies. The five-year survival rate in the United States for individuals diagnosed today with pancreatic cancer is a dismal 12%. Many invasive cancers, including pancreatic cancer, however, arise from histologically and genetically well-characterized precursor lesions, and these precancers are curable. Precursor lesions therefore are an attractive target for early detection and treatment. This is particularly true for individuals with an increased risk of developing invasive cancer, such as individuals with a strong family history of pancreatic cancer, and individuals with a germline variant known to increase the risk of developing pancreatic cancer. There is therefore a need to understand the precursor lesions that can give rise to invasive pancreatic cancer in these individuals.

Genetic Signature of Human Pancreatic Cancer and Personalized Targeting

Pancreatic cancer is a highly lethal disease with a 5-year survival rate of around 11-12%. Surgery, being the treatment of choice, is only possible in 20% of symptomatic patients. The main reason is that when it becomes symptomatic, IT IS the tumor is usually locally advanced and/or has metastasized to distant organs; thus, early diagnosis is infrequent. The lack of specific early symptoms is an important cause of late diagnosis. Unfortunately, diagnostic tumor markers become positive at a late stage, and there is a lack of early-stage markers. Surgical and non-surgical cases are treated with neoadjuvant and/or adjuvant chemotherapy, and the results are usually poor. However, personalized targeted therapy directed against tumor drivers may improve this situation. Until recently, many pancreatic tumor driver genes/proteins were considered untargetable. Chemical and physical characteristics of mutated KRAS are a formidable challenge to overcome. This situation is slowly changing. For the first time, there are candidate drugs that can target the main driver gene of pancreatic cancer: KRAS. Indeed, KRAS inhibition has been clinically achieved in lung cancer and, at the pre-clinical level, in pancreatic cancer as well. This will probably change the very poor outlook for this disease. This paper reviews the genetic characteristics of sporadic and hereditary predisposition to pancreatic cancer and the possibilities of a personalized treatment according to the genetic signature.

Bioactive Compounds from Plant Origin as Natural Antimicrobial Agents for the Treatment of Wound Infections

The rising prevalence of drug-resistant bacteria underscores the need to search for innovative and nature-based solutions. One of the approaches may be the use of plants that constitute a rich source of miscellaneous compounds with a wide range of biological properties. This review explores the antimicrobial activity of seven bioactives and their possible molecular mechanisms of action. Special attention was focused on the antibacterial properties of berberine, catechin, chelerythrine, cinnamaldehyde, ellagic acid, proanthocyanidin, and sanguinarine against Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa. The growing interest in novel therapeutic strategies based on new plant-derived formulations was confirmed by the growing number of articles. Natural products are one of the most promising and intensively examined agents to combat the consequences of the overuse and misuse of classical antibiotics.

Improving the prognosis of pancreatic cancer: insights from epidemiology, genomic alterations, and therapeutic challenges

Pancreatic cancer, notorious for its late diagnosis and aggressive progression, poses a substantial challenge owing to scarce treatment alternatives. This review endeavors to furnish a holistic insight into pancreatic cancer, encompassing its epidemiology, genomic characterization, risk factors, diagnosis, therapeutic strategies, and treatment resistance mechanisms. We delve into identifying risk factors, including genetic predisposition and environmental exposures, and explore recent research advancements in precursor lesions and molecular subtypes of pancreatic cancer. Additionally, we highlight the development and application of multi-omics approaches in pancreatic cancer research and discuss the latest combinations of pancreatic cancer biomarkers and their efficacy. We also dissect the primary mechanisms underlying treatment resistance in this malignancy, illustrating the latest therapeutic options and advancements in the field. Conclusively, we accentuate the urgent demand for more extensive research to enhance the prognosis for pancreatic cancer patients.

Earlier Diagnosis of Pancreatic Cancer: Is It Possible?

Pancreatic ductal adenocarcinoma has a very high mortality rate which has been only minimally improved in the last 30 years. This high mortality is closely related to late diagnosis, which is usually made when the tumor is large and has extensively infiltrated neighboring tissues or distant metastases are already present. This is a paradoxical situation for a tumor that requires nearly 15 years to develop since the first founding mutation. Response to chemotherapy under such late circumstances is poor, resistance is frequent, and prolongation of survival is almost negligible. Early surgery has been, and still is, the only approach with a slightly better outcome. Unfortunately, the relapse percentage after surgery is still very high. In fact, early surgery clearly requires early diagnosis. Despite all the advances in diagnostic methods, the available tools for improving these results are scarce. Serum tumor markers permit a late diagnosis, but their contribution to an improved therapeutic result is very limited. On the other hand, effective screening methods for high-risk populations have not been fully developed as yet. This paper discusses the difficulties of early diagnosis, evaluates whether the available diagnostic tools are adequate, and proposes some simple and not-so-simple measures to improve it.

Microbiome and MicroRNA or Long Non-Coding RNA-Two Modern Approaches to Understanding Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of humans' most common and fatal neoplasms. Nowadays, a number of PDAC studies are being conducted in two different fields: non-coding RNA (especially microRNA and long non-coding RNA) and microbiota. It has been recently discovered that not only does miRNA affect particular bacteria in the gut microbiome that can promote carcinogenesis in the pancreas, but the microbiome also has a visible impact on the miRNA. This suggests that it is possible to use the combined impact of the microbiome and noncoding RNA to suppress the development of PDAC. Nevertheless, insufficient research has focused on bounding both approaches to the diagnosis, treatment, and prevention of pancreatic ductal adenocarcinoma. In this article, we summarize the recent literature on the molecular basis of carcinogenesis in the pancreas, the two-sided impact of particular types of non-coding RNA and the pancreatic cancer microbiome, and possible medical implications of the discovered phenomenon.

Pancreatic cancer evolution and heterogeneity: integrating omics and clinical data

Pancreatic ductal adenocarcinoma (PDAC), already among the deadliest epithelial malignancies, is rising in both incidence and contribution to overall cancer deaths. Decades of research have improved our understanding of PDAC carcinogenesis, including characterizing germline predisposition, the cell of origin, precursor lesions, the sequence of genetic alterations, including simple and structural alterations, transcriptional changes and subtypes, tumour heterogeneity, metastatic progression and the tumour microenvironment. These fundamental advances inform contemporary translational efforts in primary prevention, screening and early detection, multidisciplinary management and survivorship, as prospective clinical trials begin to adopt molecular-based selection criteria to guide targeted therapies. Genomic and transcriptomic data on PDAC were also included in the international pan-cancer analysis of approximately 2,600 cancers, a milestone in cancer research that allows further insight through comparison with other tumour types. Thus, this is an ideal time to review our current knowledge of PDAC evolution and heterogeneity, gained from the study of preclinical models and patient biospecimens, and to propose a model of PDAC evolution that takes into consideration findings from varied sources, with a particular focus on the genomics of human PDAC.

Deregulation of Transcription Factor Networks Driving Cell Plasticity and Metastasis in Pancreatic Cancer

Pancreatic cancer is a very aggressive disease with 5-year survival rates of less than 10%. The constantly increasing incidence and stagnant patient outcomes despite changes in treatment regimens emphasize the requirement of a better understanding of the disease mechanisms. Challenges in treating pancreatic cancer include diagnosis at already progressed disease states due to the lack of early detection methods, rapid acquisition of therapy resistance, and high metastatic competence. Pancreatic ductal adenocarcinoma, the most prevalent type of pancreatic cancer, frequently shows dominant-active mutations in KRAS and TP53 as well as inactivation of genes involved in differentiation and cell-cycle regulation (e.g. SMAD4 and CDKN2A). Besides somatic mutations, deregulated transcription factor activities strongly contribute to disease progression. Specifically, transcriptional regulatory networks essential for proper lineage specification and differentiation during pancreas development are reactivated or become deregulated in the context of cancer and exacerbate progression towards an aggressive phenotype. This review summarizes the recent literature on transcription factor networks and epigenetic gene regulation that play a crucial role during tumorigenesis.

Diagnostic, Predictive and Prognostic Molecular Biomarkers in Pancreatic Cancer: An Overview for Clinicians

Simple Summary

Pancreatic cancer is the fourth most common cancer-related cause of death in the United States and is usually asymptomatic in early stages. There is a scarcity of tests that facilitate early diagnosis or accurately predict the disease progression. To this end, biomarkers have been identified as important tools in the diagnosis and management of pancreatic cancer. Despite the increasing number of biomarkers described in the literature, most of them have demonstrated moderate sensitivity and/or specificity and are far from being considered as screening tests. More efficient non-invasive biomarkers are needed to facilitate early-stage diagnosis and interventions. Multi-disciplinary collaboration might be required to facilitate the identification of such markers.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy and is associated with aggressive tumor behavior and poor prognosis. Most patients with PDAC present with an advanced disease stage and treatment-resistant tumors. The lack of noninvasive tests for PDAC diagnosis and survival prediction mandates the identification of novel biomarkers. The early identification of high-risk patients and patients with PDAC is of utmost importance. In addition, the identification of molecules that are associated with tumor biology, aggressiveness, and metastatic potential is crucial to predict survival and to provide patients with personalized treatment regimens. In this review, we summarize the current literature and focus on newer biomarkers, which are continuously added to the armamentarium of PDAC screening, predictive tools, and prognostic tools.

The genetics of ductal adenocarcinoma of the pancreas in the year 2020: dramatic progress, but far to go

The publication of the "Pan-Cancer Atlas" by the Pan-Cancer Analysis of Whole Genomes Consortium, a partnership formed by The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC), provides a wonderful opportunity to reflect on where we stand in our understanding of the genetics of pancreatic cancer, as well as on the opportunities to translate this understanding to patient care. From germline variants that predispose to the development of pancreatic cancer, to somatic mutations that are therapeutically targetable, genetics is now providing hope, where there once was no hope, for those diagnosed with pancreatic cancer.

The Impact of obesity and diabetes mellitus on pancreatic cancer: Molecular mechanisms and clinical perspectives

The incidence of obesity and type 2 diabetes (T2DM) in the Western world has increased dramatically during the recent decades. According to the American Cancer Society, pancreatic cancer (PC) is the fourth leading cause of cancer‐related death in the United States. The relationship among obesity, T2DM and PC is complex. Due to increase in obesity, diabetes, alcohol consumption and sedentary lifestyle, the mortality due to PC is expected to rise significantly by year 2040. The underlying mechanisms by which diabetes and obesity contribute to pancreatic tumorigenesis are not well understood. Furthermore, metabolism and microenvironment within the pancreas can also modulate pancreatic carcinogenesis. The risk of PC on a population level may be reduced by modifiable lifestyle risk factors. In this review, the interactions of diabetes and obesity to PC development were summarized, and novel strategies for the prevention and treatment of diabetes and PC were discussed.

How do mutations affecting the breast cancer genes BRCA1 and BRCA2 cause cancer susceptibility?

The inheritance of monoallelic germline mutations affecting BRCA1 or BRCA2 predisposes with a high penetrance to several forms of epithelial malignancy. The large, nuclear-localized BRCA proteins act as custodians of chromosome integrity through distinct functions in the assembly and activity of macromolecular complexes that mediate DNA repair, replication reactivation and mitotic progression. The loss of these tumour suppressive functions following biallelic BRCA gene inactivation has long been thought to provoke genomic instability and carcinogenesis. However, recent studies not only identify new functions for BRCA1 and BRCA2 in the regulation of transcription and RNA processing potentially relevant to their tumour suppressive activity, but also suggest that monoallelic BRCA2 gene mutations suffice for carcinogenesis. This emerging evidence opens fresh lines of enquiry concerning tissue-specific cancer evolution in BRCA mutation carriers. Collectively, these insights engender new models to explain how BRCA gene mutations cause cancer susceptibility in specific tissues.

Combating pancreatic cancer with PI3K pathway inhibitors in the era of personalised medicine

Pancreatic ductal adenocarcinoma (PDAC) is among the most deadly solid tumours. This is due to a generally late-stage diagnosis of a primarily treatment-refractory disease. Several large-scale sequencing and mass spectrometry approaches have identified key drivers of this disease and in doing so highlighted the vast heterogeneity of lower frequency mutations that make clinical trials of targeted agents in unselected patients increasingly futile. There is a clear need for improved biomarkers to guide effective targeted therapies, with biomarker-driven clinical trials for personalised medicine becoming increasingly common in several cancers. Interestingly, many of the aberrant signalling pathways in PDAC rely on downstream signal transduction through the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways, which has led to the development of several approaches to target these key regulators, primarily as combination therapies. The following review discusses the trend of PDAC therapy towards molecular subtyping for biomarker-driven personalised therapies, highlighting the key pathways under investigation and their relationship to the PI3K pathway.

Talking Genes in Breast and Pancreatic Malignancies

Introduction:

Both breast and pancreatic cancers have high mortality rates. Breast cancer is the second leading cause of cancer death in females, while pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer death. Almost 4-16 % of individuals with pancreatic cancer have a family history of the disease. Intra-ductal papillary mucinous neoplasms (IPMNs) are cystic lesions that received more attention lately due to their associations with PDAC and other solid organ tumors, such as breast cancer.

Aim:

The purpose of this article is to discuss the association of the familiar pancreatic cancer (FPC), sporadic pancreatic cancer, and IPMNs with the breast cancer.

Results:

Mutations in BRCA2, BRCA1, p16 and PALB2 play a major role in the genetic etiologies of familial pancreatic cancer. In familial and sporadic pancreatic cancers, mutations in BRCA2 are associated with a high incidence of PDAC, while mutations in BRCA1have shown inconsistent results. Data is insufficient to prove an association between IPMNs and breast cancer.

Conclusion:

The familial clustering of PDAC is not well understood. Further studies are required for greater comprehension of the genetic basis of PDAC and the association between IPMNs and breast cancer.

Clinical Outcome of Resected Remnant Pancreatic Cancer After Resection of the Primary Pancreatic Cancer

Purpose: Pancreatic cancer (PC) has high morbidity and mortality rates, with a poor prognosis and frequent recurrence. The postresection survival rate has increased but remains low, and remnant PC is becoming more common. This review evaluates the current literature pertaining to the clinical outcomes of patients with resected remnant PC. Material and Methods: We reviewed publications on remnant PC that included repeated and completion pancreatectomy. Clinicophysiological data were analyzed, and survival rates were calculated using the Kaplan-Meier method. Remnant PC was defined by negative margins at the initial operation, a cancer-free interval >1 year, and presence in the remnant pancreas. Results: Forty-nine cases of remnant PC selected from the literature were examined. Primary and remnant PCs had the same histopathological features in 29 of 45 patients (64.4%). The median disease-free interval was 44.3 months (12-143 months). The 1- and 3-year survival rates after repeat pancreatectomy were 81.5% and 50%, respectively, and the median survival time was 32 months. The age of the patient at the time of the first operation independently predicted survival in a multivariate analysis. Conclusion: In long-term survivors after curative resection for PC, resectable remnant PCs should be aggressively removed to improve prognosis.

Genetics of pancreatic cancer and implications for therapy

Pancreatic cancer is a highly lethal disease with a dismal 5-year prognosis. Knowledge of its genetics may help in identifying new methods for patient screening, and cancer treatment. In this review, we will describe the most common mutations responsible for the genesis of pancreatic cancer and their impact on screening, patterns of disease progression, and therapy.

Inflammatory responses and inflammation-associated diseases in organs

Inflammation is a biological response of the immune system that can be triggered by a variety of factors, including pathogens, damaged cells and toxic compounds. These factors may induce acute and/or chronic inflammatory responses in the heart, pancreas, liver, kidney, lung, brain, intestinal tract and reproductive system, potentially leading to tissue damage or disease. Both infectious and non-infectious agents and cell damage activate inflammatory cells and trigger inflammatory signaling pathways, most commonly the NF-κB, MAPK, and JAK-STAT pathways. Here, we review inflammatory responses within organs, focusing on the etiology of inflammation, inflammatory response mechanisms, resolution of inflammation, and organ-specific inflammatory responses.

Inflammatory responses and inflammation-associated diseases in organs

Inflammation is a biological response of the immune system that can be triggered by a variety of factors, including pathogens, damaged cells and toxic compounds. These factors may induce acute and/or chronic inflammatory responses in the heart, pancreas, liver, kidney, lung, brain, intestinal tract and reproductive system, potentially leading to tissue damage or disease. Both infectious and non-infectious agents and cell damage activate inflammatory cells and trigger inflammatory signaling pathways, most commonly the NF-κB, MAPK, and JAK-STAT pathways. Here, we review inflammatory responses within organs, focusing on the etiology of inflammation, inflammatory response mechanisms, resolution of inflammation, and organ-specific inflammatory responses.

Targeting reactive nitrogen species suppresses hereditary pancreatic cancer

Germline mutation of BRCA2 induces hereditary pancreatic cancer. However, how BRCA2 mutation specifically induces pancreatic tumorigenesis remains elusive. Here, we have examined a mouse model of Brca2-deficiency-induced pancreatic tumors and found that excessive reactive nitrogen species (RNS), such as nitrite, are generated in precancerous pancreases, which induce massive DNA damage, including DNA double-strand breaks. RNS-induced DNA lesions cause genomic instability in the absence of Brca2. Moreover, with the treatment of antioxidant tempol to suppress RNS, not only are DNA lesions significantly reduced, but also the onset of pancreatic cancer is delayed. Thus, this study demonstrates that excess RNS are a nongenetic driving force for Brca2-deficiency-induced pancreatic tumors. Suppression of RNS could be an important strategy for pancreatic cancer prevention.

Tumor Dormancy and Relapse: From a Natural Byproduct of Evolution to a Disease State

Species evolve by mutations and epigenetic changes acting on individuals in a population; tumors evolve by similar mechanisms at a cellular level in a tissue. This article reviews growing evidence about tumor dormancy and suggests that (i) cellular malignancy is a natural byproduct of evolutionary mechanisms, such as gene mutations and epigenetic modifications, which is manifested in the form of tumor dormancy in healthy individuals as well as in cancer survivors; (ii) cancer metastasis could be an early dissemination event that could occur during malignant dormancy even before primary cancer is clinically detectable; and (iii) chronic inflammation is a key factor in awakening dormant malignant cells at the primary site, leading to primary cancer development, and at distant sites, leading to advanced stage diseases. On the basis of this evidence, it is reasonable to propose that we are all cancer survivors rather than cancer-free individuals because of harboring dormant malignant cells in our organs. A better understanding of local and metastatic tumor dormancy could lead to novel cancer therapeutics for the prevention of cancer. Cancer Res; 77(10); 2564-9. ©2017 AACR.

The Role of BRCA2 Mutation Status as Diagnostic, Predictive, and Prognosis Biomarker for Pancreatic Cancer

Pancreatic cancer is one of the deadliest cancers worldwide, and life expectancy after diagnosis is often short. Most pancreatic tumours appear sporadically and have been highly related to habits such as cigarette smoking, high alcohol intake, high carbohydrate, and sugar consumption. Other observational studies have suggested the association between pancreatic cancer and exposure to arsenic, lead, or cadmium. Aside from these factors, chronic pancreatitis and diabetes have also come to be considered as risk factors for these kinds of tumours. Studies have found that 10% of pancreatic cancer cases arise from an inherited syndrome related to some genetic alterations. One of these alterations includes mutation in BRCA2 gene. BRCA2 mutations impair DNA damage response and homologous recombination by direct regulation of RAD51. In light of these findings that link genetic factors to tumour development, DNA damage agents have been proposed as target therapies for pancreatic cancer patients carrying BRCA2 mutations. Some of these drugs include platinum-based agents and PARP inhibitors. However, the acquired resistance to PARP inhibitors has created a need for new chemotherapeutic strategies to target BRCA2. The present systematic review collects and analyses the role of BRCA2 alterations to be used in early diagnosis of an inherited syndrome associated with familiar cancer and as a prognostic and predictive biomarker for the management of pancreatic cancer patients.

Can Molecular Biomarkers Change the Paradigm of Pancreatic Cancer Prognosis?

Pancreatic ductal adenocarcinoma is one of the most lethal types of tumour, and its incidence is rising worldwide. Although survival can be improved when these tumours are detected at an early stage, this cancer is usually asymptomatic, and the disease only becomes apparent after metastasis. The only prognostic biomarker approved by the FDA to date is carbohydrate antigen 19-9 (CA19-9); however, the specificity of this biomarker has been called into question, and diagnosis is usually based on clinical parameters. Tumour size, degree of differentiation, lymph node status, presence of distant metastasis at diagnosis, protein levels of KI-67 or C-reactive protein, and mutational status of P53, KRAS, or BRCA2 are the most useful biomarkers in clinical practice. In addition to these, recent translational research has provided evidence of new biomarkers based on different molecules involved in endoplasmic reticulum stress, epithelial-to-mesenchymal transition, and noncoding RNA panels, especially microRNAs and long noncoding RNAs. These new prospects open new paths to tumour detection using minimally or noninvasive techniques such as liquid biopsies. To find sensitive and specific biomarkers to manage these patients constitutes a challenge for the research community and for public health policies.

MicroRNA-506 is up-regulated in the development of pancreatic ductal adenocarcinoma and is associated with attenuated disease progression

BACKGROUND

MicroRNA-506 (miR-506) has been reported to function in several tumors as a tumor suppressor gene or oncogene. However, the expression and role of miR-506 in pancreatic ductal adenocarcinoma (PDAC) remains unclear. In this study, we aimed to evaluate the phenotype of miR-506 in PDAC.

METHODS

Using miRNA in situ hybridization, we examined the expression of miR-506 in 113 PDACs and 87 paired normal pancreatic tissues. We evaluated miR-506 expression in PDAC cells, normal pancreatic ducts, and acinus/islands, and we analyzed the associations between miR-506 expression and the clinicopathologic characteristics of PDAC patients.

RESULTS

miR-506 expression was higher in PDAC than in matched normal pancreatic ductal cells (P < 0.001). On the other hand, the combined group of well and moderately differentiated PDACs showed higher levels of miR-506 than the poorly differentiated ones (P = 0.023). Moreover, miR-506 expression was negatively associated with pathologic T category (P = 0.004) and lymph node metastasis (P = 0.033), suggesting that miR-506 might inhibit the progression of PDAC.

CONCLUSIONS

Our results suggest that miR-506 either plays a role as an oncogene in the tumorigenesis and a tumor suppressor in the progression or serves as a house-keeping, tumor-suppressing miRNA, whose expression can be activated by oncogenic signals in early development to hinder the progression of PDAC.

Second primary pancreatic ductal carcinoma in the remnant pancreas after pancreatectomy for pancreatic ductal carcinoma: High cumulative incidence rates at 5 years after pancreatectomy

OBJECTIVES

The aim of this study was to determine the incidence rate and clinical features of second primary pancreatic ductal carcinoma (SPPDC) in the remnant pancreas after pancreatectomy for pancreatic ductal carcinoma (PDC).

METHODS

Data of patients undergoing R0 resection for PDC at a single high-volume center were reviewed. SPPDC was defined as a tumor in the remnant pancreas after R0 resection for PDC, and SPPDC met at least one of the following conditions: 1) the time interval between initial pancreatectomy and development of a new tumor was 3 years or more; 2) the new tumor was not located in contact with the pancreatic stump. We investigated the clinical features and treatment outcomes of patients with SPPDC.

RESULTS

This study included 130 patients who underwent surgical resection for PDC between 2005 and 2014. Six (4.6%) patients developed SPPDC. The cumulative 3- and 5-year incidence rates were 3.1% and 17.7%, respectively. Four patients underwent remnant pancreatectomy for SPPDC. They were diagnosed with the disease in stage IIA or higher and developed recurrence within 6 months after remnant pancreatectomy. One patient received carbon ion radiotherapy and survived 45 months. One patient refused treatment and died 19 months after the diagnosis of SPPDC.

CONCLUSIONS

The incidence rate of SPPDC is not negligible, and the cumulative 5-year incidence rate of SPPDC is markedly high. Post-operative surveillance of the remnant pancreas is critical for the early detection of SPPDC, even in long-term survivors after PDC resection.

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.

Interplay between menin and Dnmt1 reversibly regulates pancreatic cancer cell growth downstream of the Hedgehog signaling pathway

Menin, the product of the Men1 gene, which is frequently mutated in pancreatic neuroendocrine tumors, acts as a chromatin-remodeling factor to modulate the transcription of cell cycle regulators by interacting with histone modification factors. However, the function of menin and its underlying mechanisms in pancreatic ductal adenocarcinoma remain unknown. Here, we found that menin inhibited pancreatic cancer cell growth in vitro and in vivo and that its expression was gradually lost during pancreatic carcinogenesis. Menin overexpression significantly activated the expression of the cyclin-dependent kinase (CDK) inhibitors p18 and p27, accompanied with a decrease in DNA methylation levels of p18 and p27 promoters. Mechanistically, we found that interaction of menin with DNA methyltransferase 1 (Dnmt1) competitively pulled down Dnmt1 from p18 and p27 promoters, leading to the downregulation of DNA methylation levels. Moreover, menin expression was suppressed by Dnmt1 downstream of the Hedgehog signaling pathway, and menin overexpression strongly antagonized the promotion effect of hedgehog signaling on pancreatic cancer cell proliferation. Taken together, the interaction between menin and Dnmt1 reversibly regulates pancreatic cancer cell growth downstream of Hedgehog pathways with complex mutual modulation networks, suggesting that the Hedgehog/Dnmt1/menin axis is a potential molecular target for pancreatic cancer therapy.

Molecular signature of pancreatic adenocarcinoma: an insight from genotype to phenotype and challenges for targeted therapy

INTRODUCTION

Pancreatic adenocarcinoma remains one of the most clinically challenging cancers despite an in-depth characterization of the molecular underpinnings and biology of this disease. Recent whole-genome-wide studies have elucidated the diverse and complex genetic alterations which generate a unique oncogenic signature for an individual pancreatic cancer patient and which may explain diverse disease behavior in a clinical setting.

AREAS COVERED

In this review article, we discuss the key oncogenic pathways of pancreatic cancer including RAS-MAPK, PI3KCA and TGF-β signaling, as well as the impact of these pathways on the disease behavior and their potential targetability. The role of tumor suppressors particularly BRCA1 and BRCA2 genes and their role in pancreatic cancer treatment are elaborated upon. We further review recent genomic studies and their impact on future pancreatic cancer treatment.

EXPERT OPINION

Targeted therapies inhibiting pro-survival pathways have limited impact on pancreatic cancer outcomes. Activation of pro-apoptotic pathways along with suppression of cancer-stem-related pathways may reverse treatment resistance in pancreatic cancer. While targeted therapy or a 'precision medicine' approach in pancreatic adenocarcinoma remains an elusive challenge for the majority of patients, there is a real sense of optimism that the strides made in understanding the molecular underpinnings of this disease will translate into improved outcomes.

The Emerging Genetic Basis and Its Clinical Implication in Pancreatic Cancer

<b><i>Background:</i></b> Pancreatic cancer is one of the most devastating diseases without early detection, effective screening biomarkers and therapeutic treatments. In the past decades, genetic studies have indicated various genes related to this malignancy. <b><i>Summary:</i></b> Genetic alterations have been involved in the initiation, progression and invasion of pancreatic cancer, which might indicate promising targets for early screening, diagnosis and future intervention. Here we will review genetic changes in pancreatic cancer and analyze their correlations with several common precursors and familial syndromes. <b><i>Key Message:</i></b> Genetic analysis for pancreatic cancer or its precursors might help us to characterize patients into subtype individuals in the future and have significant implications for individualized treatments. <b><i>Practical Implications:</i></b> At present, pancreatic cancer is regarded as a disease with a wide range of genetic alterations, including germline and somatic mutations. Some genetic alterations such as <i>KRAS</i>, <i>p16</i>^{<i>CDKN2A</i>}, <i>TP53</i> and <i>SMAD4</i> were specifically correlated with different types of histological precursors of pancreatic cancer and some familial syndromes highly related to pancreatic cancer. Moreover, genetic changes also predict drug sensitivity and implicate novel therapeutic targets.

Pancreatic intraepithelial neoplasia arising from an ectopic pancreas in the small bowel

BACKGROUND

Ectopic pancreatic tissue is relatively uncommon, and is characterized as pancreatic tissue with no contact with the normal pancreas, and with its own ductal system and blood supply. It is usually asymptomatic, and can be incidentally diagnosed by conventional imaging studies.

METHOD

A 69-year-old woman with a prior history of bilateral breast carcinoma presented with ectopic pancreatic intraepithelial neoplasia (PanIN) that was identified incidentally in the small bowel during an oncological resection of a synchronous primary pancreatic adenocarcinoma, and renal cell carcinoma.

RESULTS

The patient underwent subtotal pancreatectomy with splenectomy, regional lymphadenectomy, radical left nephrectomy, and small bowel resection with primary anastomosis of ectopic PanIN-2. She had an uneventful hospitalization and was discharged home on postoperative day 7.

CONCLUSIONS

The occurrence of ectopic PanIN is extremely unusual with only few cases previously reported in the literature. The need for negative margins after surgical resection of ectopic PanIN lesions remains controversial.

Identification of dysregulated pathways associated with pancreatic cancer by survival analysis

In order to identify the dysregulated pathways associated with pancreatic cancer, the fourth leading cause of cancer mortality in the United States, tumor and non-tumor samples were systematically analyzed in the present study. Initially, dysregulated genes in pancreatic cancer were identified using paired t-test. Subsequently, dysregulated biological pathways involved in the development of pancreatic cancer were identified by enrichment analysis. Finally, individual survival analysis of the significantly dysregulated functions was conducted at the pathway level. Our results indicated that the pathway named ̔Pathways in cancer was significantly correlated with survival time. In addition, the mean survival time of individual and genetic variation demonstrated a significantly negative correlation, that is, the lower the genetic variation, the longer the survival time. Furthermore, detailed analysis of genes on the pathway named ̔Pathways in cancer denoted that this pathway involved multiple cancer hallmark signals and several dysregulated cancer genes, including tumor protein p53, myelocytomatosis, Kirsten rat sarcoma, phosphatidylinositol 3-kinase, v-raf murine sarcoma viral oncogene homolog B1 and cyclin-dependent kinase inhibitor 2A. According to the DrugBank database, certain oncogenes have been validated to be the targets of drugs, including Sorafenib, Trastuzumab, Imatinib and Paclitaxel or were under investigation. An improved understanding of the pathophysiology of pancreatic cancer has been achieved based on our results and the present study aimed to provide guidance for the development of drugs to treat pancreatic cancer.

Pancreatic cancer genomes: toward molecular subtyping and novel approaches to diagnosis and therapy

Pancreatic neoplasms represent a broad range of clinical entities, many of which have drastic effects on the lives of patients. Recently, high-throughput sequencing analyses have been performed in many pancreatic neoplasms, providing deep insights into the underlying biology of these neoplasms as well as novel approaches to diagnosis and treatment. This review discusses the molecular alterations underlying pancreatic neoplasms as well as the clinical impact of these alterations for diagnosis and treatment.

Genetic determinants and potential therapeutic targets for pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer deaths in both men and women in the United States, carrying a 5-year survival rate of approximately 5%, which is the poorest prognosis of any solid tumor type. Given the dismal prognosis associated with PDAC, a more thorough understanding of risk factors and genetic predisposition has important implications not only for cancer prevention, but also for screening techniques and the development of personalized therapies. While screening of the general population is not recommended or practicable with current diagnostic methods, studies are ongoing to evaluate its usefulness in people with at least 5- to 10-fold increased risk of PDAC. In order to help identify high-risk populations who would be most likely to benefit from early detection screening tests for pancreatic cancer, discovery of additional pancreatic cancer susceptibility genes is crucial. Thus, specific gene-based, gene-product, and marker-based testing for the early detection of pancreatic cancer are currently being developed, with the potential for these to be useful as potential therapeutic targets as well. The goal of this review is to provide an overview of the genetic basis for PDAC with a focus on germline and familial determinants. A discussion of potential therapeutic targets and future directions in screening and treatment is also provided.

High prevalence of BRCA1 and BRCA2 germline mutations with loss of heterozygosity in a series of resected pancreatic adenocarcinoma and other neoplastic lesions

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is associated with the breast ovarian cancer syndrome (BRCA1/BRCA2) mutations. It is unknown if this association is causal.

EXPERIMENTAL DESIGN

This is a single-site study of patients who underwent surgical pancreatic tumor resection and self-identified as Ashkenazi Jewish. DNA from normal pancreatic tissue was genotyped for the three Ashkenazi Jewish BRCA1/2 founder mutations BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT, and loss of heterozygosity (LOH) was determined by sequencing DNA from microdissected tumor. When additional tumor tissue was available, p53 immunohistochemistry (IHC) was conducted.

RESULTS

Thirty-seven patients underwent surgery for PDAC, seven for intraductal papillary mucinous neoplasm (IPMN), and 19 for other diseases. A high prevalence of BRCA1/2 mutations was found in the surgical cohort (12/63; 19.0%; P < 0.001), PDAC cohort (8/37; 21.6%; P < 0.001), and IPMN cohort (2/7; 28.6%; P = .01) compared with published control mutation frequency. A high prevalence of BRCA1 185delAG (8.1%; P < 0.001) and BRCA2 6174delT (10.8%; P < 0.001) in Ashkenazi Jewish patients with PDAC was shown. BRCA1/2 LOH was found in 2 of 4 BRCA1-associated PDACs and 3 of 4 BRCA2-associated PDACs. Positive p53 IHC was found in 5 of 8 BRCA1/2 PDACs.

CONCLUSIONS

We show a high prevalence of BRCA1/2 mutations with LOH in an Ashkenazi Jewish cohort of surgically resected PDAC and neoplastic lesions, suggesting that these germline mutations are causal in selected individuals.

Met receptor tyrosine kinase signaling induces secretion of the angiogenic chemokine interleukin-8/CXCL8 in pancreatic cancer

At diagnosis, the majority of pancreatic cancer patients present with advanced disease when curative resection is no longer feasible and current therapeutic treatments are largely ineffective. An improved understanding of molecular targets for effective intervention of pancreatic cancer is thus urgent. The Met receptor tyrosine kinase is one candidate implicated in pancreatic cancer. Notably, Met is over expressed in up to 80% of invasive pancreatic cancers but not in normal ductal cells correlating with poor overall patient survival and increased recurrence rates following surgical resection. However the functional role of Met signaling in pancreatic cancer remains poorly understood. Here we used RNA interference to directly examine the pathobiological importance of increased Met signaling for pancreatic cancer. We show that Met knockdown in pancreatic tumor cells results in decreased cell survival, cell invasion, and migration on collagen I in vitro. Using an orthotopic model for pancreatic cancer, we provide in vivo evidence that Met knockdown reduced tumor burden correlating with decreased cell survival and tumor angiogenesis, with minimal effect on cell growth. Notably, we report that Met signaling regulates the secretion of the pro-angiogenic chemokine interleukin-8/CXCL8. Our data showing that the interleukin-8 receptors CXCR1 and CXCR2 are not expressed on pancreatic tumor cells, suggests a paracrine mechanism by which Met signaling regulates interleukin-8 secretion to remodel the tumor microenvironment, a novel finding that could have important clinical implications for improving the effectiveness of treatments for pancreatic cancer.

Genetic evolution of pancreatic cancer: lessons learnt from the pancreatic cancer genome sequencing project

Pancreatic cancer is a disease caused by the accumulation of genetic alterations in specific genes. Elucidation of the human genome sequence, in conjunction with technical advances in the ability to perform whole exome sequencing, have provided new insight into the mutational spectra characteristic of this lethal tumour type. Most recently, exomic sequencing has been used to clarify the clonal evolution of pancreatic cancer as well as provide time estimates of pancreatic carcinogenesis, indicating that a long window of opportunity may exist for early detection of this disease while in the curative stage. Moving forward, these mutational analyses indicate potential targets for personalised diagnostic and therapeutic intervention as well as the optimal timing for intervention based on the natural history of pancreatic carcinogenesis and progression.

Genome-wide somatic copy number alterations in low-grade PanINs and IPMNs from individuals with a family history of pancreatic cancer

PURPOSE

Characterizing the earliest chromosomal alterations of pancreatic precursor neoplasms from individuals with a familial aggregation of pancreatic cancer may provide clues as to the loci of pancreatic cancer susceptibility genes.

EXPERIMENTAL DESIGN

We used Illumina 370/660K SNP arrays to conduct genome-wide copy number analysis in 60 benign neoplasms [58 mostly low-grade pancreatic intraepithelial neoplasias (PanIN) and intraductal papillary mucinous neoplasms (IPMN) and two pancreatic neuroendocrine tumors (PNET)] and matched normal tissues from 16 individuals with a family history of pancreatic cancer. PanINs and IPMNs were analyzed for KRAS codon 12/13 mutations.

RESULTS

Of 40 benign neoplasms with adequate SNP calls and allele ratios, somatic chromosomal copy number changes were identifiable in only nine lesions, including eight of the 38 PanIN/IPMNs (two of which had identical alterations) and one of the two PNETs. Only two precursor lesions had more than one somatic copy number alteration. In contrast, the overwhelming majority (∼95%) of PanINs harbored KRAS mutations. The chromosomal alterations identified included nine chromosomal arms affected by chromosomal loss and two by chromosomal gain. Copy number loss spanning 9p21.3 was identified in three precursor lesions; two precursors had chromosomal losses affecting 6q and 17p.

CONCLUSIONS

Low- and intermediate-grade PanINs and IPMNs from patients with a family history of pancreatic cancer harbor few if any somatic chromosomal alterations. The absence of a locus of recurrent chromosomal loss in most low-grade pancreatic cancer precursor lesions supports the hypothesis that there is no one tumor suppressor gene locus consistently involved in initiating familial pancreatic neoplasia.

Evolutionary pathways in BRCA1-associated breast tumors

BRCA1-associated breast tumors display loss of BRCA1 and frequent somatic mutations of PTEN and TP53. Here we describe the analysis of BRCA1, PTEN, and p53 at the single cell level in 55 BRCA1-associated breast tumors and computational methods to predict the relative temporal order of somatic events, on the basis of the frequency of cells with single or combined alterations. Although there is no obligatory order of events, we found that loss of PTEN is the most common first event and is associated with basal-like subtype, whereas in the majority of luminal tumors, mutation of TP53 occurs first and mutant PIK3CA is rarely detected. We also observed intratumor heterogeneity for the loss of wild-type BRCA1 and increased cell proliferation and centrosome amplification in the normal breast epithelium of BRCA1 mutation carriers. Our results have important implications for the design of chemopreventive and therapeutic interventions in this high-risk patient population.

Incidence of subsequent pancreatic adenocarcinoma in patients with a history of nonpancreatic primary cancers

BACKGROUND

Several environmental risk factors are known to predispose individuals to pancreatic cancer, and up to 15% of pancreatic cancers have an inherited component. Understanding metachronous cancer associations can modify pancreas cancer risk. The objective of this study was to investigate the association of nonpancreatic cancers with subsequent pancreatic adenocarcinoma.

METHODS

The authors used data from the US Surveillance, Epidemiology, and End Results (SEER) registries to identify 1,618,834 individuals who had a primary malignancy and subsequent pancreatic adenocarcinoma (n = 4013). Standardized incidence ratios were calculated as an approximation of relative risk (RR) for the occurrence of pancreatic adenocarcinoma after another primary malignancy.

RESULTS

Among patients who were diagnosed with a first primary malignancy at ages 20 to 49 years, the risk of subsequent pancreatic adenocarcinoma was increased among patients who had cancers of the ascending colon (relative risk [RR], 4.62; 95% confidence interval [CI], 1.86-9.52), hepatic flexure (RR, 5.42; 95% CI, 1.12-15.84), biliary system (RR, 13.14; 95% CI, 4.27-30.66), breast (RR, 1.32; 95% CI, 1.09-1.59), uterine cervix (RR, 1.61; 95% CI, 1.02-2.41), testes (RR, 2.78; 95% CI, 1.83-4.05), and hematopoietic system (RR, 1.83; 95% CI, 1.28-2.53). Among patients who had a first malignancy at ages 50 to 64 years, the risk was increased after cancers of the stomach (RR, 1.88; 95% CI, 1.13-2.93), hepatic flexure (RR, 2.25; 95% CI, 1.08-4.13), lung and bronchus (RR, 1.46; 95% CI, 1.16-1.82), pharynx (RR, 2.26; 95% CI, 1.13-4.04), and bladder (RR, 1.24; 95% CI, 1.03-1.48). Among patients who had a primary cancer after age 65 years, the risk was increased after cancers of the stomach (RR, 1.79; 95% CI, 1.23-2.53), hepatic flexure (RR, 1.76; 95% CI, 1.06-2.75), biliary system (RR, 2.35; 95% CI, 1.17-4.20), and uterus (RR, 1.23; 95% CI, 1.03-1.47).

CONCLUSIONS

The results from the current population-based data set suggested that pancreatic adenocarcinoma is associated with certain primary cancers. Genetic predisposition and common environmental and behavioral risk factors all may contribute to this observation. Specific tumor associations will guide future risk-stratification efforts.

Advances in biomarker research for pancreatic cancer

Pancreatic cancer (PC) is a leading cause of cancer related deaths in United States. The lack of early symptoms results in latestage detection and a high mortality rate. Currently, the only potentially curative approach for PC is surgical resection, which is often unsuccessful because the invasive and metastatic nature of the tumor masses makes their complete removal difficult. Consequently, patients suffer relapses from remaining cancer stem cells or drug resistance that eventually lead to death. To improve the survival rate, the early detection of PC is critical. Current biomarker research in PC indicates that a serum carbohydrate antigen, CA 19-9, is the only available biomarker with approximately 90% specificity to PC. However, the efficacy of CA 19-9 for assessing prognosis and monitoring patients with PC remains contentious. Thus, advances in technology and the detection of new biomarkers with high specificity to PC are needed to reduce the mortality rate of pancreatic cancer.

RAD51 as a potential biomarker and therapeutic target for pancreatic cancer

Chemotherapy is a very important therapeutic strategy for cancer treatment. The failure of conventional and molecularly targeted chemotherapeutic regimes for the treatment of pancreatic cancer highlights a desperate need for novel therapeutic interventions. Chemotherapy often fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Overexpression of RAD51 protein, a key player in DNA repair/recombination has been observed in many cancer cells and its hyperexpression is implicated in drug resistance. Recent studies suggest that RAD51 overexpression contributes to the development, progression and drug resistance of pancreatic cancer cells. Here we provide a brief overview of the available pieces of evidence in support of the role of RAD51 in pancreatic tumorigenesis and drug resistance, and hypothesize that RAD51 could serve as a potential biomarker for diagnosis of pancreatic cancer. We discuss the possible involvement of RAD51 in the drug resistance associated with epithelial to mesenchymal transition and with cancer stem cells. Finally, we speculate that targeting RAD51 in pancreatic cancer cells may be a novel approach for the treatment of pancreatic cancer.

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.

The role of tobacco-derived carcinogens in pancreas cancer

The extremely poor outcome from pancreas cancer is well known. However, its aetiology less well appreciated, and the molecular mechanisms underlying this are poorly understood. Tobacco usage is one of the strongest risk factors for this disease, and this is a completely avoidable hazard. In addition, there are well described hereditary diseases which predispose, and familial pancreas cancer. We have sought here to summarise the role of tobacco-derived carcinogens and the mode of their tumorigenic action on the pancreas. There is compelling evidence from animal and human studies (laboratory including cell line studies and epidemiologic) that tobacco derived carcinogens cause pancreas cancer. However, the manner in which they do so is not entirely apparent. There is also compelling evidence that synergism with genetic and other life-style factors-like diet obesity-results in a multifactorial causation of the disease. Ascertaining the role of tobacco carcinogens in the development of this cancer and their interaction with other risk factors will enable novel therapeutic and preventative strategies to improve outcome from this appalling malignancy.

Inactivation of Brca2 cooperates with Trp53(R172H) to induce invasive pancreatic ductal adenocarcinomas in mice: a mouse model of familial pancreatic cancer

An inactivating germline mutation in BRCA2 is the most common known genetic basis for familial pancreatic cancer (FPC), accounting for 5-10% of inherited cases. A genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC) arising on the backdrop of Brca2 deficiency is likely to elucidate valuable diagnostic and therapeutic insights for FPC. Both Brca2 alleles were conditionally deleted during development within the pancreatic epithelium by generating Pdx1-Cre; Brca2(f/f) (CB) mice; in addition, triple transgenic Pdx1-Cre; Brca2(f/f); LSL-Trp53(R172H) (CBP) mice were generated, in order to determine the impact of p53 deregulation on Brca2-deficient carcinogenesis. Both CB and CBP mice developed non-invasive ductal precursor lesions (murine pancreatic intraepithelial neoplasia or mPanIN), although these were observed at an earlier time point (5 versus 8 months) and with higher prevalence in CBP mice. A minority of CB mice (15%) developed invasive and metastatic PDAC at a latency of 15 months or greater; in contrast, CBP mice of comparable age uniformly developed PDAC with variable histological features. Mortality in the absence of neoplasia in CB and CBP mice was associated with profound loss of pancreatic parenchyma, consistent with progressive elimination of Brca2-deficient cells. Widespread DNA damage, as evidenced by overexpression of the phosphorylated histone H(2)AX(Ser139), was observed in the non-neoplastic exocrine pancreas, as well as in the mPanIN and PDAC lesions of Brca2-deficient mice, independent of p53 status. Loss of Brca2 function predisposes the exocrine pancreas to profound DNA damage, and the frequency of invasive neoplasia is accentuated by the concomitant deregulation of p53.

Inactivation of Brca2 promotes Trp53-associated but inhibits KrasG12D-dependent pancreatic cancer development in mice

BACKGROUND & AIMS

Inherited mutations in the BRCA2 tumor suppressor have been associated with an increased risk of pancreatic cancer. To establish the contribution of Brca2 to pancreatic cancer we developed a mouse model of pancreas-specific Brca2 inactivation. Because BRCA2-inactivating mutations cause defects in repair of DNA double-strand breaks that result in chromosomal instability, we evaluated whether Brca2 inactivation induced instability in pancreatic tissue from these mice and whether associated pancreatic tumors were hypersensitive to DNA damaging agents.

METHODS

We developed mouse models that combined pancreas-specific Kras activation and Trp53 deletion with Brca2 inactivation. Development of pancreatic cancer was assessed; tumors and nonmalignant tissues were analyzed for chromosomal instability and apoptosis. Cancer cell lines were evaluated for sensitivity to DNA damaging agents.

RESULTS

In the presence of disrupted Trp53, Brca2 inactivation promoted the development of premalignant lesions and pancreatic tumors that reflected the histology of human disease. Cancer cell lines derived from these tumors were hypersensitive to specific DNA damaging agents. In contrast, in the presence of KrasG12D, Brca2 inactivation promoted chromosomal instability and apoptosis and unexpectedly inhibited growth of premalignant lesions and tumors.

CONCLUSIONS

Trp53 signaling must be modified before inactivation of the Brca2 wild-type allele, irrespective of Kras status, for Brca2-deficient cells to form tumors.

Telomeres are shortened in acinar-to-ductal metaplasia lesions associated with pancreatic intraepithelial neoplasia but not in isolated acinar-to-ductal metaplasias

Telomeres protect against chromosomal breakage, fusion, and interchromosome bridges during cell division. Shortened telomeres have been observed in the lowest grade of pancreatic intraepithelial neoplasia (PanIN). Genetically engineered mouse models of pancreatic neoplasia develop acinar-to-ductal metaplasia prior to the development of PanIN, suggesting that acinar-to-ductal metaplasias can be an early precursor lesion to pancreatic cancer. Some human PanINs are associated with acinar-to-ductal metaplasias, and it has been suggested that these acinar-to-ductal metaplasias arise as a consequence of growth of adjacent PanINs. As the earliest known genetic lesions of PanINs is shortened telomeres, we compared the telomere lengths of acinar-to-ductal metaplasia lesions, PanINs, and adjacent normal cells of human pancreata to determine whether acinar-to-ductal metaplasias could be precursors to PanIN. We used quantitative fluorescent in situ hybridization to measure the telomere length of cells from pancreatic lesions and adjacent normal pancreata from 22 patients, including 20 isolated acinar-to-ductal metaplasias, 13 PanINs associated with acinar-to-ductal metaplasias, and 12 PanINs. Normalized mean telomere fluorescence was significantly different among the cell types analyzed; 12.6 ± 10.2 units in normal acinar cells, 10.2 ± 6.4 in ductal cells, 8.4 ± 5.9 in fibroblasts, 9.4 ± 7.3 in isolated acinar-to-ductal metaplasias, 4.1 ± 2.9 in PanIN-associated acinar-to-ductal metaplasias, and 1.6 ± 1.9 in PanINs, respectively (P<0.001, ANOVA with randomized block design). Telomeres were significantly shorter in PanIN-associated acinar-to-ductal metaplasias (P<0.05, post hoc Duncan test) and in PanINs (P<0.05), than in normal cells, or isolated acinar-to-ductal metaplasias. Thus, shortened telomeres are found in PanIN-associated acinar-to-ductal metaplasias, but not in isolated acinar-to-ductal metaplasia lesions. These results indicate that isolated acinar-to-ductal metaplasias are not a precursor to PanIN, and support the hypothesis that PanIN-associated acinar-to-ductal metaplasias arise secondary to PanIN lesions.

Germline Brca2 heterozygosity promotes Kras(G12D) -driven carcinogenesis in a murine model of familial pancreatic cancer

Inherited heterozygous BRCA2 mutations predispose carriers to tissue-specific cancers, but somatic deletion of the wild-type allele is considered essential for carcinogenesis. We find in a murine model of familial pancreatic cancer that germline heterozygosity for a pathogenic Brca2 truncation suffices to promote pancreatic ductal adenocarcinomas (PDACs) driven by Kras(G12D), irrespective of Trp53 status. Unexpectedly, tumor cells retain a functional Brca2 allele. Correspondingly, three out of four PDACs from patients inheriting BRCA2(999del5) did not exhibit loss-of-heterozygosity (LOH). Three tumors from these patients displaying LOH were acinar carcinomas, which also developed only in mice with biallelic Brca2 inactivation. We suggest a revised model for tumor suppression by BRCA2 with implications for the therapeutic strategy targeting BRCA2 mutant cancer cells.

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.