Tumor-suppressing pathways in cystic pancreatic tumors

HER2 Overexpression in Periampullary Tumors According to Anatomical and Histological Classification-A Systematic Review

Pancreatic cancer is one of the most aggressive, heterogeneous, and fatal types of human cancer; therefore, more effective therapeutic drugs are urgently needed. Human epidermal growth factor receptor 2 (HER2) overexpression and amplification have been identified as a cornerstone in this pathology. The aim of this review is to identify HER2 membrane overexpression in relation to pancreatic cancer pathways that can be used in order to develop a targeted therapy. After searching the keywords, 174 articles were found during a time span of 10 years, between 2013 and 2023, but only twelve scientific papers were qualified for this investigation. The new era of biomolecular research found a significant relationship between HER2 overexpression and pancreatic cancer cells in 25-30% of cases. The variables are dependent on tumor-derived cells, with differences in receptor overexpression between PDAC (pancreatic ductal adenocarcinoma), BTC (biliary tract cancer), ampullary carcinoma, and PNETs (pancreatic neuroendocrine tumors). HER2 overexpression is frequently encountered in human pancreatic carcinoma cell lines, and the ERBB family is one of the targets in the near future of therapy, with good results in phase I, II, and III studies evaluating downregulation and tumor downstaging, respectively.

Biological characteristics of pancreatic ductal adenocarcinoma: Initiation to malignancy, intracellular to extracellular

Pancreatic ductal adenocarcinoma (PDAC) is a highly life-threatening tumour with a low early-detection rate, rapid progression and a tendency to develop resistance to chemotherapy. Therefore, understanding the regulatory mechanisms underlying the initiation, development and metastasis of pancreatic cancer is necessary for enhancing therapeutic effectiveness. In this review, we summarised single-gene mutations (including KRAS, CDKN2A, TP53, SMAD4 and some other less prevalent mutations), epigenetic changes (including DNA methylation, histone modifications and RNA interference) and large chromosome alterations (such as copy number variations, chromosome rearrangements and chromothripsis) associated with PDAC. In addition, we discussed variations in signalling pathways that act as intermediate oncogenic factors in PDAC, including PI3K/AKT, MAPK/ERK, Hippo and TGF-β signalling pathways. The focus of this review was to investigate alterations in the microenvironment of PDAC, particularly the role of immunosuppressive cells, cancer-associated fibroblasts, lymphocytes, other para-cancerous cells and tumour extracellular matrix in tumour progression. Peripheral axons innervating the pancreas have been reported to play a crucial role in the development of cancer. In addition, tumour cells can influence the behaviour of neighbouring non-tumour cells by secreting certain factors, both locally and at a distance. In this review, we elucidated the alterations in intracellular molecules and the extracellular environment that occur during the progression of PDAC. Altogether, this review may enhance the understanding of the biological characteristics of PDAC and guide the development of more precise treatment strategies.

From somatic mutation to early detection: insights from molecular characterization of pancreatic cancer precursor lesions

Pancreatic cancer arises from noninvasive precursor lesions, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN), which are curable if detected early enough. Recently, these types of precursor lesions have been extensively characterized at the molecular level, defining the timing of critical genetic alterations in tumorigenesis pathways. The results of these studies deepen our understanding of tumorigenesis in the pancreas, providing novel insights into tumor initiation and progression. Perhaps more importantly, they also provide a rational foundation for early detection approaches that could allow clinical intervention prior to malignant transformation. In this review, we summarize the results of comprehensive molecular characterization of PanINs, IPMNs, and MCNs and discuss the implications for cancer biology as well as early detection. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Endoscopic Ultrasound Imaging for Diagnosing and Treating Pancreatic Cysts

Cystic pancreatic lesions are increasingly diagnosed owing to the abundant use of cross-sectional imaging. Given their malignant potential, true pancreatic cysts should be considered for resection or periodic follow-up. Cystic lesions of the pancreas (CLPs) require further evaluation and management. Therefore, it is important to establish a solid diagnosis at the time of detection. Endoscopic ultrasound examination is the imaging modality of choice. Fine needle aspiration provides fluid for cytologic, biochemical, and molecular assays to classify lesions and predict biological behavior. This review provides an overview of the diagnosis and management of various types of commonly encountered true CLPs.

Molecular Genetics of Pancreatic Neoplasms

Pancreatic neoplasms have a wide range of histologic types with distinct clinical outcomes. Recent advances in high-throughput sequencing technologies have greatly deepened our understanding of pancreatic neoplasms. Now, the exomes of major histologic types of pancreatic neoplasms have been sequenced, and their genetic landscapes have been revealed. This article reviews the molecular changes underlying pancreatic neoplasms, with a special focus on the genetic changes that characterize the histologic types of pancreatic neoplasms. Emphasis is also made on the molecular features of key genes that have the potential for therapeutic targets.

Role of emerging molecular markers in pancreatic cyst fluid

Cystic lesions of the pancreas (CLPs) are increasingly diagnosed due to the growing utilization of cross-sectional imaging modalities. The differentiation between true cysts (epithelial tumors) and nonepithelial lesions (such as pseudocysts) relies on clinical and imaging characteristics, but more reliably obtained by endoscopic ultrasound (EUS) fine-needle aspiration. Due to their malignant potential, some of the true pancreatic cysts require further assessment and periodic follow-up. Therefore, it is important to establish a solid diagnosis at the time of detection of the various types of pancreatic cysts. Due to the limitations of cytology and biochemical markers in accurately classifying cyst pathology, the search for specific molecular markers associated with each type of cyst is ongoing. In this chapter, we will review some of the emerging molecular markers in pancreatic cystic fluid and their potential impact on endosonography and pancreatic cyst management.

Clinicopathological Significance of CDKN2A Promoter Hypermethylation Frequency with Pancreatic Cancer

The prognosis of pancreatic cancer patients is very poor, with a 5-year survival of less than 6%. Previous studies demonstrated that the loss of function of CDKN2A is mainly caused by the hypermethylation of CDKN2A gene promoter; however, whether or not it is associated with the incidence of pancreatic cancer still remains unclear. In this study, we systematically reviewed the association between CDKN2A promoter methylation and pancreatic cancer using meta-analysis methods. The pooled data were analyzed by Review Manager 5.2. Fourteen studies eligible studies, including 418 pancreatic cancer, 155 pancreatic intraepithelial neoplasia (PanINs) and 45 chronic pancreatitis (CP) patients were analyzed. We observed that the frequency of CDKN2A methylation was significantly higher in pancreatic cancer patients than in normal healthy controls, the pooled OR = 17.19, 95% CI = 8.72–33.86, P < 0.00001. The frequency of CDKN2A methylation was also significantly higher in PanINs patients than that in normal individual controls, OR = 12.35, 95% CI = 1.70–89.89, P = 0.01. In addition, CDKN2A methylation was associated with worse survival in pancreatic cancer, HR = 4.46, 95% CI = 1.37–14.53, P = 0.01. The results strongly suggest that CDKN2A methylation is correlated with an increased risk of pancreatic cancer. CDKN2A methylation plays a critical role in pancreatic carcinogenesis and may serve as a prognostic marker.

APC alterations are frequently involved in the pathogenesis of acinar cell carcinoma of the pancreas, mainly through gene loss and promoter hypermethylation

Genetic and epigenetic alterations involved in the pathogenesis of pancreatic acinar cell carcinomas (ACCs) are poorly characterized, including the frequency and role of gene-specific hypermethylation, chromosome aberrations, and copy number alterations (CNAs). A subset of ACCs is known to show alterations in the APC/β-catenin pathway which includes mutations of APC gene. However, it is not known whether, in addition to mutation, loss of APC gene function can occur through alternative genetic and epigenetic mechanisms such as gene loss or promoter methylation. We investigated the global methylation profile of 34 tumor suppressor genes, CNAs of 52 chromosomal regions, and APC gene alterations (mutation, methylation, and loss) together with APC mRNA level in 45 ACCs and related peritumoral pancreatic tissues using methylation-specific multiplex ligation probe amplification (MS-MLPA), fluorescence in situ hybridization (FISH), mutation analysis, and reverse transcription-droplet digital PCR. ACCs did not show an extensive global gene hypermethylation profile. RASSF1 and APC were the only two genes frequently methylated. APC mutations were found in only 7 % of cases, while APC loss and methylation were more frequently observed (48 and 56 % of ACCs, respectively). APC mRNA low levels were found in 58 % of cases and correlated with CNAs. In conclusion, ACCs do not show extensive global gene hypermethylation. APC alterations are frequently involved in the pathogenesis of ACCs mainly through gene loss and promoter hypermethylation, along with reduction of APC mRNA levels.

PIK3CA mutations in mucinous cystic neoplasms of the pancreas

OBJECTIVES

Mucinous cystic neoplasms (MCNs) are rare, potentially curable, mucin-producing neoplasms of the pancreas. We have previously reported PIK3CA (phosphoinositide-3-kinase catalytic subunit, p110α) mutations in intraductal papillary mucinous neoplasms, another mucin-producing neoplasm of the pancreas. In this study, we analyzed the presence of PIK3CA and AKT1/PKB (V-akt murine thymoma viral oncogene homolog 1) hot-spot mutations in MCN specimens.

METHODS

Using the genomic DNA sequencing of tumor tissues isolated by laser capture microdissection, we evaluated 15 well-characterized MCNs for the E542K, E545K (exon 9), and H1047R (exon 20) hot-spot mutations in the PIK3CA gene and the E17K mutation in the AKT1 gene.

RESULTS

A hot-spot mutation (E545K) of the PIK3CA gene was detected in 1 of the 15 MCNs and further confirmed by a mutant-enriched method. Interestingly, this mutation was found to be present only in the high-grade but not in low-grade dysplastic epithelium obtained from this neoplasm and coexisted with a KRAS mutation. No mutations were identified in the AKT1 gene.

CONCLUSIONS

Our data, when combined with previous reports on intraductal papillary mucinous neoplasms, indicate that oncogenic activation of the PI3K pathway involving PIK3CA gene mutations can contribute to the progression of mucin-producing neoplasms but not pancreatic intraepithelial neoplasia. PIK3CA status could be useful for understanding their progression to malignancy.

Carcinogenesis of pancreatic adenocarcinoma: precursor lesions

Pancreatic adenocarcinoma displays a variety of molecular changes that evolve exponentially with time and lead cancer cells not only to survive, but also to invade the surrounding tissues and metastasise to distant sites. These changes include: genetic alterations in oncogenes and cancer suppressor genes; changes in the cell cycle and pathways leading to apoptosis; and also changes in epithelial to mesenchymal transition. The most common alterations involve the epidermal growth factor receptor (EGFR) gene, the HER2 gene, and the K-ras gene. In particular, the loss of function of tumor-suppressor genes has been documented in this tumor, especially in CDKN2a, p53, DPC4 and BRCA2 genes. However, other molecular events involved in pancreatic adenocarcinoma pathogenesis contribute to its development and maintenance, specifically epigenetic events. In fact, key tumor suppressors that are well established to play a role in pancreatic adenocarcinoma may be altered through hypermethylation, and oncogenes can be upregulated secondary to permissive histone modifications. Indeed, factors involved in tumor invasiveness can be aberrantly expressed through dysregulated microRNAs. This review summarizes current knowledge of pancreatic carcinogenesis from its initiation within a normal cell until the time that it has disseminated to distant organs. In this scenario, highlighting these molecular alterations could provide new clinical tools for early diagnosis and new effective therapies for this malignancy.

Epigenetic regulation and role of metastasis suppressor genes in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is distinguished by rapid dissemination. Thus, genetic and/or epigenetic deregulation of metastasis suppressor genes (MSG) is a likely event during early pancreatic carcinogenesis and a potential diagnostic marker for the disease. We investigated 9 known MSGs for their role in the dissemination of PDAC and examined their promoters for methylation and its use in PDAC detection.

METHODS

MRNA expression of 9 MSGs was determined in 18 PDAC cell lines by quantitative RT-PCR and promoter methylation was analyzed by Methylation Specific PCR and validated by Bisulfite Sequencing PCR. These data were compared to the cell lines' in vivo metastatic and invasive potential that had been previously established. Statistical analysis was performed with SPSS 20 using 2-tailed Spearman's correlation with P < 0.05 being considered significant.

RESULTS

Complete downregulation of MSG-mRNA expression in PDAC cell lines vs. normal pancreatic RNA occurred in only 1 of 9 investigated genes. 3 MSGs (CDH1, TIMP3 and KiSS-1) were significantly methylated. Methylation only correlated to loss of mRNA expression in CDH1 (P < 0.05). Bisulfite Sequencing PCR showed distinct methylation patterns, termed constant and variable methylation, which could distinguish methylation-regulated from non methylation-regulated genes. Higher MSG mRNA-expression did not correlate to less aggressive PDAC-phenotypes (P > 0.14).

CONCLUSIONS

Genes with metastasis suppressing functions in other tumor entities did not show evidence of assuming the same role in PDAC. Inactivation of MSGs by promoter methylation was an infrequent event and unsuitable as a diagnostic marker of PDAC. A distinct methylation pattern was identified, that resulted in reduced mRNA expression in all cases. Thus, constant methylation patterns could predict regulatory significance of a promoter's methylation prior to expression analysis and hence present an additional tool during target gene selection.

Molecular analysis of cyst fluid aspiration in the diagnosis and risk assessment of cystic lesions of the pancreas

Pancreatic cyst detection is increasing largely due to increasing use of cross-sectional imaging. The management of pancreatic cysts differs for true cysts, pseudocysts, mucinous cysts, nonmucinous cysts, and malignant lesions. Depending on the setting, diagnostic tests, such as cross-sectional imaging, endoscopic ultrasound, cyst fluid chemistry, and cytology, have moderate accuracy in characterizing the cyst subtype. Molecular analysis of cyst fluid aspirates has shown promise in preliminary studies and may require smaller fluid volumes than is needed for carcinoembryonic antigen level and cytology. This article reviews published studies in which molecular analysis was performed in the evaluation of pancreatic cysts. The molecular studies are compared with the conventional tests. Most studies have had moderate sample sizes (16-124) and have characterized a high proportion of patients with malignant cysts. Evaluation of molecular analysis as a diagnostic tool merits larger prospective trials with long-term follow-up of patients who are not sent to surgery. Larger cysts may meet size criteria for resection, and it is the smaller cysts for which molecular analysis may be of benefit if additional molecular testing results in a change in management.

Diagnosis and treatment of cystic pancreatic tumors

Cystic pancreatic tumors (CPTs) have more frequently been identified in the last decade because of increased use of cross-sectional abdominal imaging. Although serous CPTs follow an indolent course and do not necessarily require surgical resection or long-term follow-up, mucinous CPTs (mucinous cystic neoplasms and intraductal papillary mucinous neoplasms) have a greater risk for malignancy. Although most CPTs are initially detected with imaging modalities such as computed tomography or magnetic resonance imaging, these tests alone rarely permit an accurate clinical diagnosis. Endoscopic ultrasound and endoscopic ultrasound-guided, fine-needle aspiration allow real-time examination and biopsy analysis of CPTs, which increases diagnostic accuracy because cytopathology features and tumor markers in cyst fluid can be analyzed. Management of patients with mucinous CPTs by surgery or imaging surveillance is controversial, partially because of limited information about disease progression and the complexities of surgical resection. We review approaches to diagnosis and management of common CPTs.

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.

Comparative immunohistochemical study of the stroma of serous and mucinous cystic neoplasms: possible histopathogenetic relationship of the 2 entities

OBJECTIVES

Serous and mucinous cystic neoplasms (SCNs/MCNs) are the most common true cystic neoplasms of the pancreas and occur more frequently in women. The aim of this study was to characterize the stroma of SCNs to compare its phenotype with that of MCNs.

METHODS

A total of 12 SCNs and 5 MCNs were analyzed immunohistochemically using the following antisera: progesterone receptor (PR), estrogen receptor (ER), inhibin, CD10, and vimentin. Normal pancreatic tissue (17 cases) and ductal adenocarcinomas of the pancreas (3 cases) were used as controls.

RESULTS

Eight of 12 patients with SCNs and all 5 patients with MCNs were women. For SCNs, the stroma was sclerotic and paucicellular and showed focal moderate to strong reactivity for PR. Estrogen receptor, CD10, and inhibin were virtually negative. For MCNs, the stroma was more cellular and ovarianlike and showed a larger number of PR-positive cells with focal expression of ER and inhibin. Vimentin was expressed in all stromal cells in both groups.

CONCLUSIONS

Both SCNs and MCNs contain PR-positive stromal cells. In view of the aforementioned clinical and immunophenotypical similarities, we suggest that in SCNs and MCNs, the stromal framework is similar in origin and/or differentiation.

PAR-4 as a possible new target for pancreatic cancer therapy

IMPORTANCE OF THE FIELD

Pancreatic cancer (PC) is a deadly disease that is intractable to currently available treatment regimens. Although well described in different tumors types, the importance of apoptosis inducer prostate apoptosis response-4 (Par-4) in PC has not been appreciated. PC is an oncogenic kras driven disease, which is known to downregulate Par-4. Therefore, this review highlights its significance and builds a strong case supporting the role of Par-4 as a possible therapeutic target in PC.

AREAS COVERED IN THIS REVIEW

Literature-based evidence spanning the last 15 years on Par-4 and its significance in PC.

WHAT THE READER WILL GAIN

This review provides comprehensive knowledge of the significance of Par-4 and its association with kras status in PC, along with the crosstalk with crucial resistance and survival molecules NF-kappaB and Bcl-2 that ultimately are responsible for the overall poor outcome of different therapeutic approaches in this disease.

TAKE HOME MESSAGE

Par-4 holds promise as a potential therapeutic target that can be induced by chemopreventive agents and small-molecule inhibitors either alone or in combination with standard chemotherapeutics leading to selective apoptosis in PC cells. It also acts as a chemosensitizer and therefore warrants further clinical investigations in this disease.

Immunohistochemical localization of metallothionein and p53 protein in pancreatic serous cystadenomas

INTRODUCTION

The objective of this study was to determine the expression levels of metallothionein (MT) and p53 protein, recognized neoplastic transformation markers, in pancreatic serous cystadenomas (SCA) and adenomocarcinomas.

MATERIALS AND METHODS

Neoplastic pancreatic tissue was taken from 20 patients with diagnosed benign (SCA: 5 cases) or malignant tumors (adenomocarcinomas: 15 cases) and control pancreatic tissue from healthy persons who had died in car accidents. Sections were stained with hematoxylin-eosin. Immunohistochemical localization of MT and p53 protein was carried out by LSAB2-HRP using specific antibodies against MT and p53.

RESULTS

Metallothionein expression was observed only in the epithelial cells of the neoplastic tissue of SCAs. MT expression in the cystadenomas was weaker than in the healthy pancreatic tissue. No tissue was found with p53 protein expression. In the adenomocarcinomas, positive staining for MT was observed in 67% and p53 was positive in the carcinoma cells.

CONCLUSION

The weak MT expression and lack of p53 protein expression in pancreatic SCAs confirms the lack of local invasive potential of the neoplastic lesion. Increased expressions of MT and p53 were observed in the less differentiated tumors. Thus the expression of MT may be a potential prognostic marker for tumors.

Calponin is expressed in serous cystadenomas of the pancreas but not in adenocarcinomas or endocrine tumors

The diagnosis of serous microcystic adenoma (SMA) is usually straightforward. For small biopsies and/or unusual variants, the differential diagnosis includes other pancreatic or metastatic neoplasms showing cystic or clear cell features. We evaluated immunostains for potential use in the diagnosis of SMA. Cases of SMA were identified from archival files. Tissue cores (2 per block) were arrayed to create a microarray of cores measuring 2mm each. Additionally, microarrays previously constructed from 56 pancreatic adenocarcinomas (PACs) and 64 pancreatic endocrine tumors (PENs) were studied. The microarrays were stained with calponin, chromogranin, CD10, alpha-inhibin, and monoclonal neuron-specific enolase (m-NSE). Subsequently, some were stained with MUC6, melan-A, D2-40, h-caldesmon, smooth muscle actin, and smooth muscle myosin. For SMAs, staining was seen with calponin (85.2%), alpha-inhibin (96.2%), and m-NSE (96.2%). Focal weak staining was seen with MUC6 (65%). All SMAs were negative with chromogranin, CD10, melan-A, D2-40, h-caldesmon, smooth muscle actin, and smooth muscle myosin. In contrast, calponin was negative in all PACs and PENs. Staining for alpha-inhibin was absent in PACs and present in 4.1% of PENs; whereas immunoreactivity for m-NSE was present in 26.8% of PACs and 73.7% of PENs. Chromogranin staining was present in 9.1% of PACs and 100% of PENs. An immunohistochemical profile of staining with calponin, alpha-inhibin, and m-NSE and absent staining with chromogranin supports the diagnosis of SMA, and distinguishes SMA from PAC and PEN. Calponin and alpha-inhibin are the most useful positive markers for SMA, and are negative in most entities in the differential diagnosis.

Pancreatic cysts: pathologic classification, differential diagnosis, and clinical implications

CONTEXT

Cystic lesions of the pancreas are being recognized with increasing frequency and have become a more common finding in clinical practice because of the widespread use of advanced imaging modalities and the sharp drop in the mortality rate of pancreatic surgery. Consequently, in the past 2 decades, the nature of many cystic tumors in this organ has been better characterized, and significant developments have taken place in the classification and in our understanding of pancreatic cystic lesions.

OBJECTIVE

To provide an overview of the current concepts in classification, differential diagnosis, and clinical/biologic behavior of pancreatic cystic tumors.

DATA SOURCES

The authors' personal experience, based on institutional and consultation materials, combined with an analysis of the literature.

CONCLUSIONS

In contrast to solid tumors, most of which are invasive ductal adenocarcinomas with dismal prognosis, cystic lesions of the pancreas are often either benign or low-grade indolent neoplasia. However, those that are mucinous, namely, intraductal papillary mucinous neoplasms and mucinous cystic neoplasms, constitute an important category because they have well-established malignant potential, representing an adenoma-carcinoma sequence. Those that are nonmucinous such as serous tumors, congenital cysts, lymphoepithelial cysts, and squamoid cyst of pancreatic ducts have no malignant potential. Only rare nonmucinous cystic tumors that occur as a result of degenerative/necrotic changes in otherwise solid neoplasia, such as cystic ductal adenocarcinomas, cystic pancreatic endocrine neoplasia, and solid-pseudopapillary neoplasm, are also malignant and have variable degrees of aggressiveness.

Update on the molecular pathogenesis of pancreatic tumors other than common ductal adenocarcinoma

PURPOSE

Although ductal adenocarcinoma is the most common and well known pancreatic tumor type, other distinct epithelial neoplasms affecting the pancreas that show different symptoms, biological behaviors and outcomes are becoming more frequently recognized and documented. Pancreatic epithelial tumors may be separated into ductal and nonductal neoplasms. The former group includes pancreatic ductal adenocarcinoma, intraductal papillary-mucinous tumor, mucinous cystic tumor and serous cystic tumor. The latter group includes pancreatic endocrine tumor, pancreatic acinar cell carcinoma, pancreatoblastoma and solid-pseudopapillary tumor. The aim of this review is to summarize recently acquired knowledge regarding the molecular characterization of these uncommon pancreatic epithelial neoplasms.

RECENT FINDINGS

Molecular studies of uncommon pancreatic epithelial tumors suggest that the different morphological entities are associated with distinct molecular profiles, highlighting the involvement of different molecular pathways leading to the development of each subtype of pancreatic neoplasm.

CONCLUSION

The correct classification of rare pancreatic epithelial tumors and the identification of their characteristic molecular aspects is the fundamental starting point in identifying novel diagnostic molecular tools and new targets for innovative therapeutic strategies.

Cystic lesions of the pancreas

Although cystic tumors of the pancreas are relatively rare, they constitute an increasingly important category. Advances in imaging and interventional techniques and the sharp drop in the mortality rate of pancreatic surgery have rendered pancreatic biopsies and resections commonplace specimens. Consequently, in the past two decades, the nature of many cystic tumors in this organ has been better characterized. The names of some existing entities were revised; for example, what was known as papillary-cystic tumor is now regarded as solid-pseudopapillary tumor. New entities, in particular, intraductal papillary mucinous neoplasm and its variants, such as oncocytic and intestinal subtypes were recognized. The importance of clinical and pathologic correlation in the evaluation of these lesions was appreciated, in particular, with regards to the multifocality of these lesions, their association with invasive carcinomas, and thus their 'preinvasive' nature. Consensus criteria for the distinction of these from the ordinary precursors of adenocarcinoma, the pancreatic intraepithelial neoplasia, were established. The definition of mucinous cystic neoplasms was refined; ovarian-like stroma has now become almost a requirement for the diagnosis of mucinous cystic neoplasia, and defined as such, the propensity of these tumors to occur in perimenopausal women became even more striking. The validity and clinical value of classifying the pancreatic cysts of mucinous type as adenoma, borderline, CIS and invasive have been established. Related to this, the importance of thorough sampling in accurate classification of these mucinous lesions was recognized. Greater accessibility of the pancreas afforded by improved invasive as well as noninvasive modalities has also increased the detection of otherwise clinically silent cystic tumors, which has led to the recognition of more innocuous entities such as acinar cell cystadenoma and squamoid cyst of pancreatic ducts. As the significance of the cystic lesions emerged, cystic forms of otherwise typically solid tumors were also better characterized. Thus, significant developments have taken place in the classification and our understanding of pancreatic cystic tumors in the past few years, and experience with these lesions is likely to grow exponentially in the coming years.

A giant pancreatic serous microcystic adenoma with 20 years follow-up

BACKGROUND AND AIMS

There is only little information about the spontaneous course of large pancreatic serous tumours. We followed up a white woman with a giant serous microcystic adenoma over more than 20 years.

CASE REPORT

At first clinical presentation, in 1986, the tumour measured 4.5 cm in diameter. Two years later, it measured 6 cm and was considered as non-resectable at laparotomy. A biopsy was obtained, and the tumour was diagnosed as lymphangioma, based on hematoxylin and eosin-staining. During the follow-up, the tumour progressively increased in size, measuring 12 cm in diameter in 1993 and 17 cm in 2000. Thus, an average growth rate of 0.83 cm per year was calculated. Unspecific abdominal discomfort and pain were the leading clinical symptoms. A colonic resection was necessary because of compression by the tumour in 1993. Portal hypertension was detected at laparotomy. Finally, the initial biopsy specimen was re-evaluated, using immunohistochemistry, and the final diagnosis of a serous microcystic adenoma was made.

CONCLUSION

This unique case demonstrates that the spontaneous course of serous microcystic adenoma of the pancreas may be favourable even with huge tumour size and that immunohistochemistry may prove a valuable tool for differential diagnosis of cystic pancreatic lesions. Due to their size and progressive, space-occupying growth, these biologically benign tumours may cause injury to adjacent organs and thus clinical symptoms. For this reason, curative surgical resection is the treatment of choice for this tumour entity except for small, asymptomatic lesions, which do not require intervention. When radical resection is impossible, palliative surgery may improve the quality of life for several years. The risk of malignant transformation seems to be low even in the long-term course.

Preinvasive duct-derived neoplasms in pancreas of keratin 5-promoter cyclooxygenase-2 transgenic mice

BACKGROUND & AIMS

Basic research aimed at a better understanding of pancreatic carcinogenesis and improving the treatment of this disease is crucial because the majority of pancreatic cancers are highly aggressive and therapeutically nonaccessible. Cyclooxygenase (COX)-2, which is a key enzyme of prostaglandin (PG) biosynthesis, is overexpressed in around 75% of human carcinomas including those of the pancreas.

METHODS

The pathologic changes of transgenic mouse pancreas with keratin 5-promoter-driven expression and activity of COX-2 were characterized.

RESULTS

Aberrant expression of COX-2 in a few ductal cells and COX-2-mediated PG synthesis in the transgenic mice resulted in keratin 19- and mucin-positive intraductal papillary mucinous neoplasm- and pancreatic intraepithelial neoplasia-like structures, characterized by an increased proliferation index and serous cystadenomas. Moreover, Ras activation was enhanced and the HER-2/Neu receptor was overexpressed. Loss of acini, fibrosis, and inflammation were pronounced. Feeding a COX-2-selective inhibitor to the transgenic mice suppressed the accumulation of PG and the phenotype. The changes resemble the human disease in which COX-2 was overexpressed consistently.

CONCLUSIONS

We present strong evidence for a causal relationship between aberrant COX-2 overexpression and COX-2-mediated PG synthesis and the development of serous cystadenoma, intraductal papillary mucinous, and pancreatic intraepithelial neoplasms. This model offers the unique possibility of identifying molecular pathways leading to the formation and malignant progression of the various types of preinvasive lesions of pancreatic adenocarcinomas that show different dismal outcomes.

Preoperative evaluation of pancreatic cystic lesions: cost-benefit analysis and proposed management algorithm

BACKGROUND

This study was performed to develop a management algorithm that accurately predicts the necessity of operative intervention and results in significant cost savings for patients with cystic pancreatic tumors.

METHODS

We reviewed 60 patients treated between 1992 and 2003. Accuracy rates of tests used to differentiate benign from premalignant and malignant cysts were calculated. A management algorithm was generated that incorporated clinical presentation, radiologic findings, and selective use of endoscopic procedures. This algorithm was tested for predictive accuracy, and savings between actual management and proposed management were compared.

RESULTS

There was an average of 3 preoperative tests performed per patient. Endoscopic procedures included endoscopic retrograde cholangiopancreatography in 21 patients and endoscopic ultrasound in 25 patients. A cyst fluid carcinoembryonic antigen (CEA) level of 158 ng/mL or greater had an accuracy rate of 87.5% that was significantly higher than endoscopic retrograde cholangiopancreatography (72%), endoscopic ultrasound morphology (45%), or endoscopic ultrasound cytology (66.7%). There was no combination of tests that provided greater accuracy than cyst fluid CEA level alone (P < .05). The management algorithm had a positive predictive value of 81%. The average actual cost of radiographic and endoscopic procedures was dollar 8,080 per patient. The proposed cost based on the algorithm was dollar 6,677 with a savings of dollar 1,403 per patient (P = .009).

CONCLUSIONS

In patients with clinical symptoms or radiographic findings of mucinous or malignant tumors, further testing is excessive. Of endoscopic tests available, the cystic fluid CEA level most accurately predicts the presence of a mucinous neoplasm. A management algorithm based on presenting symptoms, radiographic findings, and cyst fluid CEA level provides a guideline for the evaluation of cystic lesions in the most cost-efficient manner while ensuring proper care.

Molecular Diagnosis of Solid and Cystic Lesions of the Pancreas

Pancreatic cancer presents at a clinically advanced stage. Diagnosis often is delayed in those who undergo several negative investigations, and at times, the diagnosis ultimately is made at surgery. Tumor suppressor-linked microsatellite allelic loss analysis appears to improve the diagnostic accuracy of inconclusive cytology specimens. Science, however, still suffers from the lack of a reliable biomarker for the purpose of screening and early detection. The continued study of sera and pancreatic juice hopefully will lead to the discovery of molecular biomarkers capable of diagnosing preclinical disease in at-risk groups.The ability to predict the underlying biologic behavior of pancreatic cystic neoplasia is less than ideal. Tumor suppressor-linked microsatellite allelic loss and telomerase analysis show promise, but they have not been studied extensively. Proteomic analysis of pancreatic cyst fluid, although not yet reported, also may prove valuable in guiding clinical management.

Mucinous cystic carcinoma of the pancreas: a unique cell line and xenograft model of a preinvasive lesion

Pancreatic mucinous cystic tumors (MCT) are proliferations of mucin-producing epithelia supported by an ovarian-like stroma. They are classified into adenomas (MCA), borderline (MCB) and noninvasive or invasive carcinomas (MCC). The molecular mechanisms underlying their clinical behavior are poorly understood, partly due to the lack of cellular models. We report the establishment of MCC1, the first cell line from a pancreatic MCT, deriving from the highly dysplastic cell component of a noninvasive MCC. MCC1 has mutations in codon 12 of K-RAS (GGT>GAT), codon 58 of P16 (CGA>TGA) and codon 132 of P53 (AAG>AGG). The FHIT and DPC4 genes are unaltered. Immunohistochemistry shows abnormal expression of MUC1 and p53, loss of p16 and retention of Fhit and Dpc4 in both the cell line and the highly dysplastic cells of the primary lesion. The morphological and molecular features of MCC1 and its corresponding primary tumor are consistent with a model for non-invasive MCC, where K-RAS, P16, P53 and MUC1 alterations are pre-invasive changes associated with progression of malignancy of MCT from adenoma to carcinoma. MCC1 is sensitive to 5-fluorouracil, representing the first assessment of drug sensitivity for MCC. Finally, MCC1 is a suitable model for preclinical studies, as it grows in immunodeficient mice.

Molecular diagnosis of solid and cystic lesions of the pancreas

Pancreatic cancer presents at a clinically advanced stage. Diagnosis often is delayed in those who undergo several negative investigations, and at times, the diagnosis ultimately is made at surgery. Tumor suppressor-linked microsatellite allelic loss analysis appears to improve the diagnostic accuracy of inconclusive cytology specimens. Science, however, still suffers from the lack of a reliable biomarker for the purpose of screening and early detection. The continued study of sera and pancreatic juice hopefully will lead to the discovery of molecular biomarkers capable of diagnosing pre-clinical disease in at-risk groups. The ability to predict the underlying biologic behavior of pancreatic cystic neoplasia is less than ideal. Tumor suppressor-linked microsatellite allelic loss and telomerase analysis show promise, but they have not been studied extensively. Proteomic analysis of pancreatic cyst fluid, although not yet reported, also may prove valuable in guiding clinical management.

Missense mutations of MADH4: characterization of the mutational hot spot and functional consequences in human tumors

PURPOSE AND EXPERIMENTAL DESIGN

The mutational spectrum of MADH4 (DPC4/SMAD4) opens valuable insights into the functions of this protein that confer its tumor-suppressive nature in human tumors. We present the MADH4 genetic status determined on a new set of pancreatic, biliary, and duodenal cancers with comparison to the mutational data reported for various tumor types.

RESULTS

Homozygous deletion, followed by inactivating nonsense or frameshift mutations, is the predominant form of MADH4 inactivation in pancreatic cancers. Among the naturally occurring MADH4 missense mutations, the MH2 domain is the most frequent target (77%) of missense mutations in human tumors. A mutational hot spot resides within the MH2 domain corresponding to codons 330 to 370, termed the mutation cluster region (MCR). A relationship was found between the locations of the missense mutations (the MH1 domain, the MH2-MCR, and the MH2 outside of the MCR) and the tumor types, suggesting environmental or selective influences in the development of MADH4 mutations. Immunohistochemical studies for Madh4 protein in nine archival cancers (six pancreatic cancers, two duodenal cancers, and one biliary cancer) with known missense mutations indicated that all mutations within the MH1 or MH2 domain COOH-terminal to the MCR (seven of nine cases) had negative or weak labeling, whereas two cancers with mutations within the MCR had strong positive nuclear labeling for Madh4 protein.

CONCLUSIONS

These findings have important implications for in vitro functional studies, suggesting that the majority of missense mutations inactivate Madh4 by protein degradation in contrast to those that occur within the MCR.

Serous cystic neoplasms of the pancreas: an immunohistochemical analysis revealing alpha-inhibin, neuron-specific enolase, and MUC6 as new markers

Serous cystic neoplasms (SCNs) of the pancreas include serous microcystic adenoma (SMA), serous oligocystic ill-demarcated adenoma (SOIA), solid serous adenoma (SSA), von Hippel-Lindau-associated cystic neoplasm (VHL-CN), and serous cystadenocarcinoma (SCC). These neoplasms are histologically similar but differ in their localization, gross appearance, gender distribution, and biology. A centroacinar origin is assumed but has not been proven. To clarify whether the various subtypes of SCN may be distinguished from each other by marker profiles that might also provide evidence of their origin, the immunoprofiles of 38 SCNs (21 SMAs, 13 SOIAs, 2 VHL-CNs, 1 SSA, and 1 SCC) were defined by applying antibodies against cytoskeletal, neuroendocrine, hormone receptor, and mucin markers. In addition, we examined the expression of calretinin and alpha-inhibin. The various types of SCN showed a very similar immunoprofile, characterized by positivity for cytokeratins and neuron-specific enolase and negativity for vimentin and synaptophysin. Further markers that were commonly expressed in SCNs were alpha-inhibin (SMAs: 76%, SOIAs: 92%, VHL-CNs: 100%), MUC6 (SMAs: 60%, SOIAs: 85%, VHL-CNs: 100%), and MUC1 (SMAs: 24%, SOIAs: 38%, VHL-CNs: 50%). Western blot analysis in one SMA revealed a distinct band that stained with neuron-specific enolase antiserum. Alpha-inhibin was only expressed in 4 of 11 acinar cell carcinomas and not in five ductal adenocarcinomas, five neuroendocrine tumors, one mixed ductal-endocrine carcinoma, and one acinar cell cystadenoma of the pancreas. These results suggest that, despite their biologic differences, the various types of SCNs are composed of the same (or a very similar) cell type and may therefore have a common direction of differentiation. This notion is further supported by the finding that neuron-specific enolase, alpha-inhibin, and MUC6, which may be regarded as new markers for this pancreatic tumor type, were also expressed in most SCNs. Because a number of SCNs share MUC1 and MUC6 expression with the pancreatic centroacinar cells, the possibility of a histogenetic relationship has to be considered.