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1.  Spontaneous rupture of a pancreatic acinar cell carcinoma presenting as an acute abdomen 
INTRODUCTION
Pancreatic acinar cell carcinoma is a rare malignant pancreatic neoplasm. To the best of our knowledge, there has been no report on spontaneous rupture of acinar cell carcinoma.
PRESENTATION OF CASE
A 39-year-old Azari male presented with a history of sudden onset, acute epigastric pain of 12-h duration. Eight hours later the patient's general condition rapidly deteriorated, blood pressure was decreased to 90/70 mm/Hg and heart rate was increased to 120 beat/min. Emergent abdominal computed tomography scan showed a well-defined hypo-dense, necrotic mass, measured 12 cm × 12 cm that was originating from the uncinate process of pancreas with marked free peritoneal fluid and extensive haziness of retroperitoneal and mesenteric fat compatible with marked bleeding. Emergent abdominal operation was performed and histopathology revealed acinar cell carcinoma of the pancreas.
DISCUSSION
Pancreatic acinar cell carcinoma (ACC) usually presents with abdominal pain, nausea and vomiting. To best of our knowledge, no report has been made of spontaneous rupture of ACC.
CONCLUSION
Pancreatic carcinoma may present as acute abdomen due to rupture of underlying neoplasm.
doi:10.1016/j.ijscr.2012.03.025
PMCID: PMC3356555  PMID: 22543229
Acinar cell carcinoma; Pancrease; Rupture
2.  Mixed Acinar-Neuroendocrine Carcinoma of the Pancreas with Neuroendocrine Predominance 
Case Reports in Medicine  2013;2013:705092.
Background. Pancreatic tumors are rare and could arise from either the exocrine (ductal and acinar cells) or the endocrine (neuroendocrine cells) components of the pancreas. In some instances, the occurrence of pancreatic tumors comprising both acinar cells and neuroendocrine cells, with neuroendocrine cells making up more than 30% of the tumor, has been identified. This unique entity has been referred to as mixed acinar-neuroendocrine carcinoma (MANEC). Only about 20 such cases have been reported in the literature. Case Report. We report an interesting case of MANEC with neuroendocrine cell predominance in a woman presenting with epigastric pain secondary to a pancreatic mass with acinar and endocrine differentiation. She underwent surgical resection of the tumor and was offered adjuvant treatment chemotherapy with carboplatin, etoposide, and radiotherapy for positive tumor resection margins. Conclusions. Given the paucity of the cases of MANEC, continuous reporting of these cases when identified should be encouraged to aid oncologists in understanding the disease and help establish standardized management.
doi:10.1155/2013/705092
PMCID: PMC3855931  PMID: 24348574
3.  Acinar Cell Apoptosis in Serpini2-Deficient Mice Models Pancreatic Insufficiency 
PLoS Genetics  2005;1(3):e38.
Pancreatic insufficiency (PI) when left untreated results in a state of malnutrition due to an inability to absorb nutrients. Frequently, PI is diagnosed as part of a larger clinical presentation in cystic fibrosis or Shwachman–Diamond syndrome. In this study, a mouse model for isolated exocrine PI was identified in a mouse line generated by a transgene insertion. The trait is inherited in an autosomal recessive pattern, and homozygous animals are growth retarded, have abnormal immunity, and have reduced life span. Mice with the disease locus, named pequeño (pq), exhibit progressive apoptosis of pancreatic acinar cells with severe exocrine acinar cell loss by 8 wk of age, while the islets and ductal tissue persist. The mutation in pq/pq mice results from a random transgene insertion. Molecular characterization of the transgene insertion site by fluorescent in situ hybridization and genomic deletion mapping identified an approximately 210-kb deletion on Chromosome 3, deleting two genes. One of these genes, Serpini2, encodes a protein that is a member of the serpin family of protease inhibitors. Reintroduction of only the Serpini2 gene by bacterial artificial chromosome transgenic complementation corrected the acinar cell defect as well as body weight and immune phenotypes, showing that deletion of Serpini2 causes the pequeño phenotype. Dietary supplementation of pancreatic enzymes also corrected body size, body weight, and immunodeficiency, and increased the life span of Serpini2-deficient mice, despite continued acinar cell loss. To our knowledge, this study describes the first characterized genetic animal model for isolated PI. Genetic complementation of the transgene insertion mutant demonstrates that Serpini2 deficiency directly results in the acinar cell apoptosis, malabsorption, and malnutrition observed in pq/pq mice. The rescue of growth retardation, immunodeficiency, and mortality by either Serpini2 bacterial artificial chromosome transgenic expression or by pancreatic enzyme supplementation demonstrates that these phenotypes are secondary to malnutrition in pq/pq mice.
Synopsis
Pancreatic insufficiency is defined by the inability to digest and absorb nutrients due to the loss of pancreatic enzyme function or loss of the acinar cells that produce the enzymes. In this manuscript the authors have described a mouse model of pancreatic insufficiency characterized by the specific loss of pancreatic acinar cells. This specific acinar cell loss results in mice that are unable to digest and absorb nutrients from the diet, stunting the animal's growth and giving rise to immunological anomalies. The authors have identified a serendipitous transgene insertion/deletion encompassing the mouse Serpini2 gene locus as the source of the phenotypes observed. Reintroduction of the Serpini2 gene, a member of the serpin family of serine cysteine protease inhibitors, by bacterial artificial chromosome complementation corrects the pancreatic and immunological phenotypes of the disorder, confirming Serpini2 as the responsible gene. Reintroduction of pancreatic enzymes through diet supplementation is also capable of correcting the reduction in size and weight, reduction in viability, and immunological deficiencies, indicating that these phenotypes are secondary to malnutrition alone. This work provides a new mouse model for investigation of malnutrition/malabsorption due to pancreatic insufficiency and identifies a novel function for the serpin family member Serpini2.
doi:10.1371/journal.pgen.0010038
PMCID: PMC1231717  PMID: 16184191
4.  Proliferative lesions of the exocrine pancreas in male F344/N rats. 
While the rat pancreas is susceptible to experimental cancer induction, the spontaneous incidence of pancreatic cancer in this species is reported to be very low. However, we observed unusually high incidences of focal acinar hyperplasia and acinar adenoma in vehicle control male F344/N rats of some NCI/NTP 2-year toxicological studies. The vehicle in these studies was corn oil given by gavage. Focal acinar hyperplasia, acinar adenoma, and acinar carcinoma (found rarely) represent a continuous spectrum of proliferative lesions of the exocrine pancreas. While the carcinomas have clear morphological indications of malignancy, the biological behavior of focal acinar hyperplasia and acinar adenoma is not known. Although induction of acinar carcinomas is considered clear evidence of carcinogenicity of a test chemical, significantly increased incidences in treated rats of acinar adenomas but not carcinomas provides some evidence of carcinogenicity. The association of acinar hyperplasia and adenoma with vegetable oil gavage complicates the interpretation when marginally elevated incidences of these lesions are observed in rats administered the test chemical in vegetable oil vehicle. Studies of the biological behavior of exocrine pancreatic lesions in male rats would be helpful in assessing the significance of their presence when found after test compound administration.
Images
PMCID: PMC1568212  PMID: 6434300
5.  Histogenesis of pancreatic carcinogenesis in the hamster: ultrastructural evidence. 
Pancreatic carcinogenesis in the Syrian hamster, induced by beta-oxidized derivatives of N-nitroso-di-n-propylamine, constitutes a valuable model of human cancer of the exocrine pancreas. In both species the majority of tumors are adenocarcinomas: superficially, on the basis of their histological appearance, these appear to be ductal in origin. However, sequential analysis, by electron microscopy, of the development of pancreatic neoplasia in the hamster model indicates that acinar cells may participate in the histogenesis of "ductal" adenomas and carcinomas. Acinar cells appear to undergo changes in differentiation, including pseudoductular transformation, giving rise to a new population of cells that resemble ductular or centroacinar types. This new population may then proliferate to form, first, cystic foci and subsequently cystadenomas and adenocarcinomas. Mucous metaplasia appears to develop at late stages of tumor development. Although the participation of ductular and centroacinar cells in pancreatic carcinogenesis cannot be excluded, very few tumors arise from the ductal epithelium. It is possible that some human pancreatic adenocarcinomas may also have their origin from dysplastic acinar cells, by analogy with the hamster model: focal acinar dysplasia being common in human pancreatic cancer patients.
Images
PMCID: PMC1568208  PMID: 6383797
6.  Wnt/β-catenin signaling is required for development of the exocrine pancreas 
Background
β-catenin is an essential mediator of canonical Wnt signaling and a central component of the cadherin-catenin epithelial adhesion complex. Dysregulation of β-catenin expression has been described in pancreatic neoplasia. Newly published studies have suggested that β-catenin is critical for normal pancreatic development although these reports reached somewhat different conclusions. In addition, the molecular mechanisms by which loss of β-catenin affects pancreas development are not well understood. The goals of this study then were; 1] to further investigate the role of β-catenin in pancreatic development using a conditional knockout approach and 2] to identify possible mechanisms by which loss of β-catenin disrupts pancreatic development. A Pdx1-cre mouse line was used to delete a floxed β-catenin allele specifically in the developing pancreas, and embryonic pancreata were studied by immunohistochemistry and microarray analysis.
Results
Pdx1-cre floxed β-catenin animals were viable but demonstrated small body size and shortened median survival. The pancreata from knockout mice were hypoplastic and histologically demonstrated a striking paucity of exocrine pancreas, acinar to duct metaplasia, but generally intact pancreatic islets containing all lineages of endocrine cells. In animals with extensive acinar hypoplasia, putative hepatocyte transdifferention was occasionally observed. Obvious and uniform pancreatic hypoplasia was observed by embryonic day E16.5. Transcriptional profiling of Pdx1-cre floxed β-catenin embryonic pancreata at E14.5, before there was a morphological phenotype, revealed significant decreases in the β-catenin target gene N-myc, and the basic HLH transcription factor PTF1, and an increase of several pancreatic zymogens compared to control animals. By E16.5, there was a dramatic loss of exocrine markers and an increase in Hoxb4, which is normally expressed anterior to the pancreas.
Conclusion
We conclude that β-catenin expression is required for development of the exocrine pancreas, but is not required for development of the endocrine compartment. In contrast, β-catenin/Wnt signaling appears to be critical for proliferation of PTF1+ nascent acinar cells and may also function, in part, to maintain an undifferentiated state in exocrine/acinar cell precursors. Finally, β-catenin may be required to maintain positional identity of the pancreatic endoderm along the anterior-posterior axis. This data is consistent with the findings of frequent β-catenin mutations in carcinomas of acinar cell lineage seen in humans.
doi:10.1186/1471-213X-7-4
PMCID: PMC1783845  PMID: 17222338
7.  Apoptosis and proliferation of acinar and islet cells in chronic pancreatitis: evidence for differential cell loss mediating preservation of islet function 
Gut  2002;50(4):542-548.
Background: Chronic pancreatitis is characterised clinically by early exocrine insufficiency, with diabetes mellitus occurring as a late phenomenon. This is mirrored pathologically by extensive acinar cell destruction and islet preservation. The mechanisms underlying this differential rate of cellular destruction are unknown.
Aims: To test the hypothesis that acinar loss and islet preservation in chronic pancreatitis occurs due to differential epithelial kinetics and investigate the role of inflammatory cells and cell cycle associated molecules.
Methods: Archival tissue from six chronic pancreatitis cases was compared with six normal controls using TUNEL and immunohistochemistry for CD3, CD20, CD68, MIB-1, Bcl-2, Bax, Fas, Fas ligand, retinoblastoma protein (Rb), and tissue inhibitor of metalloproteinases 1 (TIMP-1) and 2 (TIMP-2).
Results: The acinar cell apoptotic index (AI) and proliferation index were higher in chronic pancreatitis than controls. T lymphocytes diffusely infiltrated fibrous bands and acini but rarely islets. Acinar Bcl-2 expression exceeded islet expression in chronic pancreatitis and controls while Bax was strongly expressed by a subset of islet cells and weakly by centroacinar cells. Islet Fas and Fas ligand expression exceeded acinar expression in chronic pancreatitis and controls. Acinar Rb expression was higher in chronic pancreatitis than in controls. Islets in chronic pancreatitis and controls showed intense TIMP-1 and TIMP-2 expression.
Conclusion: Apoptosis plays a significant role in acinar loss in chronic pancreatitis. Acinar Bcl-2 and islet Bax expression indicates complex AI control. Increased acinar Rb expression in chronic pancreatitis may differentially promote acinar loss. Fas ligand expression may be restricted to islet cell membranes through TIMP-1 expression and inhibit islet damage by promoting apoptosis of cytotoxic T lymphocytes.
PMCID: PMC1773161  PMID: 11889077
chronic pancreatitis; apoptosis; proliferation; cell cycle; Fas/Fas ligand
8.  Molecular and cellular regulation of pancreatic acinar cell function 
Purpose of review
This review focuses on studies from the past year that have greatly advanced our understanding of molecular and cellular regulation of pancreatic acinar cell function.
Recent findings
Recent advances focus on signals dictating pancreatic development, acinar cell fate, pancreatic growth, and secretion. Regeneration of acinar cells after pancreatitis depends on expression of embryonic signals in mature acinar cells. In this setting, acinar cells can also transdifferentiate into adipose cells. With the forced induction of certain early and endocrine-driving transcription factors, acinar cells can also transdifferentiate into β-cells. There has also been an increased understanding of acinar-to-ductal metaplasia and the subsequent formation of pancreatic intraepithelial neoplasia lesions. Multiple proteins involved in secretion have been characterized, including small guanosine triphosphate-binding proteins, soluble N-ethylmaleimide-sensitive factor attachment proteins, and ion channels.
Summary
These findings demonstrate the regenerative potential of the acinar cell to mitigate injurious states such as pancreatitis. The ability of acinar cells to transdifferentiate into β-cells could potentially provide a treatment for diabetes. Finally, the results might be helpful in preventing malignant transformation events arising from the acinar cell. Developments in proteomics and computer modeling could expand our view of proteins mediating acinar cell function.
doi:10.1097/MOG.0b013e32832ebfac
PMCID: PMC3030806  PMID: 19571746
calcium signaling; growth; regeneration; secretion; transdifferentiation
9.  Pancreatic Ductal Bicarbonate Secretion: Challenge of the Acinar Acid Load 
Acinar and ductal cells of the exocrine pancreas form a close functional unit. Although most studies contain data either on acinar or ductal cells, an increasing number of evidence highlights the importance of the pancreatic acinar-ductal functional unit. One of the best examples for this functional unit is the regulation of luminal pH by both cell types. Protons co-released during exocytosis from acini cause significant acidosis, whereas, bicarbonate secreted by ductal cells cause alkalization in the lumen. This suggests that the first and probably one of the most important role of bicarbonate secretion by pancreatic ductal cells is not only to neutralize the acid chyme entering into the duodenum from the stomach, but to neutralize acidic content secreted by acinar cells. To accomplish this role, it is more than likely that ductal cells have physiological sensing mechanisms which would allow them to regulate luminal pH. To date, four different classes of acid-sensing ion channels have been identified in the gastrointestinal tract (transient receptor potential ion channels, two-pore domain potassium channel, ionotropic purinoceptor and acid-sensing ion channel), however, none of these have been studied in pancreatic ductal cells. In this mini-review, we summarize our current knowledge of these channels and urge scientists to characterize ductal acid-sensing mechanisms and also to investigate the challenge of the acinar acid load on ductal cells.
doi:10.3389/fphys.2011.00036
PMCID: PMC3139102  PMID: 21808623
pancreatic duct; bicarbonate
10.  Zebrafish reporter lines reveal in vivo signaling pathway activities involved in pancreatic cancer 
Disease Models & Mechanisms  2014;7(7):883-894.
Pancreatic adenocarcinoma, one of the worst malignancies of the exocrine pancreas, is a solid tumor with increasing incidence and mortality in industrialized countries. This condition is usually driven by oncogenic KRAS point mutations and evolves into a highly aggressive metastatic carcinoma due to secondary gene mutations and unbalanced expression of genes involved in the specific signaling pathways. To examine in vivo the effects of KRASG12D during pancreatic cancer progression and time correlation with cancer signaling pathway activities, we have generated a zebrafish model of pancreatic adenocarcinoma in which eGFP-KRASG12D expression was specifically driven to the pancreatic tissue by using the GAL4/UAS conditional expression system. Outcrossing the inducible oncogenic KRASG12D line with transgenic zebrafish reporters, harboring specific signaling responsive elements of transcriptional effectors, we were able to follow TGFβ, Notch, Bmp and Shh activities during tumor development. Zebrafish transgenic lines expressing eGFP-KRASG12D showed normal exocrine pancreas development until 3 weeks post fertilization (wpf). From 4 to 24 wpf we observed several degrees of acinar lesions, characterized by an increase in mesenchymal cells and mixed acinar/ductal features, followed by progressive bowel and liver infiltrations and, finally, highly aggressive carcinoma. Moreover, live imaging analysis of the exocrine pancreatic tissue revealed an increasing number of KRAS-positive cells and progressive activation of TGFβ and Notch pathways. Increase in TGFβ, following KRASG12D activation, was confirmed in a concomitant model of medulloblastoma (MDB). Notch and Shh signaling activities during tumor onset were different between MDB and pancreatic adenocarcinoma, indicating a tissue-specific regulation of cell signaling pathways. Moreover, our results show that a living model of pancreatic adenocarcinoma joined with cell signaling reporters is a suitable tool for describing in vivo the signaling cascades and molecular mechanisms involved in tumor development and a potential platform to screen for novel oncostatic drugs.
doi:10.1242/dmm.014969
PMCID: PMC4073277  PMID: 24878567
Zebrafish; Pancreatic adenocarcinoma; Medulloblastoma; KRAS; Reporters; TGFβ; Notch; Shh
11.  Nr5a2 maintains acinar cell differentiation and constrains oncogenic Kras-mediated pancreatic neoplastic initiation 
Gut  2013;63(4):656-664.
Objectives
Emerging evidence from mouse models suggests that mutant Kras can drive the development of pancreatic ductal adenocarcinoma (PDA) precursors from acinar cells by enforcing ductal de-differentiation at the expense of acinar identity. Recently, human genome-wide association studies have identified NR5A2, a key regulator of acinar function, as a susceptibility locus for human PDA. We investigated the role of Nr5a2 in exocrine maintenance, regeneration and Kras driven neoplasia.
Design
To investigate the function of Nr5a2 in the pancreas, we generated mice with conditional pancreatic Nr5a2 deletion (PdxCrelate; Nr5a2c/c). Using this model, we evaluated acinar differentiation, regeneration after caerulein pancreatitis and Kras driven pancreatic neoplasia in the setting of Nr5a2 deletion.
Results
We show that Nr5a2 is not required for the development of the pancreatic acinar lineage but is important for maintenance of acinar identity. Nr5a2 deletion leads to destabilisation of the mature acinar differentiation state, acinar to ductal metaplasia and loss of regenerative capacity following acute caerulein pancreatitis. Loss of Nr5a2 also dramatically accelerates the development of oncogenic Kras driven acinar to ductal metaplasia and PDA precursor lesions.
Conclusions
Nr5a2 is a key regulator of acinar plasticity. It is required for maintenance of acinar identity and re-establishing acinar fate during regeneration. Nr5a2 also constrains pancreatic neoplasia driven by oncogenic Kras, providing functional evidence supporting a potential role as a susceptibility gene for human PDA.
doi:10.1136/gutjnl-2012-304287
PMCID: PMC3883808  PMID: 23645620
12.  Aberrant Innate Immune Activation following Tissue Injury Impairs Pancreatic Regeneration 
PLoS ONE  2014;9(7):e102125.
Normal tissue architecture is disrupted following injury, as resident tissue cells become damaged and immune cells are recruited to the site of injury. While injury and inflammation are critical to tissue remodeling, the inability to resolve this response can lead to the destructive complications of chronic inflammation. In the pancreas, acinar cells of the exocrine compartment respond to injury by transiently adopting characteristics of progenitor cells present during embryonic development. This process of de-differentiation creates a window where a mature and stable cell gains flexibility and is potentially permissive to changes in cellular fate. How de-differentiation can turn an acinar cell into another cell type (such as a pancreatic β-cell), or a cell with cancerous potential (as in cases of deregulated Kras activity) is of interest to both the regenerative medicine and cancer communities. While it is known that inflammation and acinar de-differentiation increase following pancreatic injury, it remains unclear which immune cells are involved in this process. We used a combination of genetically modified mice, immunological blockade and cellular characterization to identify the immune cells that impact pancreatic regeneration in an in vivo model of pancreatitis. We identified the innate inflammatory response of macrophages and neutrophils as regulators of pancreatic regeneration. Under normal conditions, mild innate inflammation prompts a transient de-differentiation of acinar cells that readily dissipates to allow normal regeneration. However, non-resolving inflammation developed when elevated pancreatic levels of neutrophils producing interferon-γ increased iNOS levels and the pro-inflammatory response of macrophages. Pancreatic injury improved following in vivo macrophage depletion, iNOS inhibition as well as suppression of iNOS levels in macrophages via interferon-γ blockade, supporting the impairment in regeneration and the development of chronic inflammation arises from aberrant activation of the innate inflammatory response. Collectively these studies identify targetable inflammatory factors that can be used to influence the development of non-resolving inflammation and pancreatic regeneration following injury.
doi:10.1371/journal.pone.0102125
PMCID: PMC4092101  PMID: 25010227
13.  Pancreas-Specific Deletion of Prox1 Affects Development and Disrupts Homeostasis of the Exocrine Pancreas 
Gastroenterology  2011;142(4):999-1009.e6.
BACKGROUND & AIMS
The exocrine portion of the pancreas functions in digestion and preserves pancreatic homeostasis. Learning how this tissue forms during embryogenesis could improve our understanding of human pancreatic diseases. Expression of the homeo-box gene Prox1 in the exocrine pancreas changes throughout development in mice. We investigated the role of Prox1 in development of the exocrine pancreas in mice.
METHODS
Mice with pancreas-specific deletion of Prox1 (Prox1ΔPanc) were generated and their pancreatic tissues were analyzed using immunohistochemistry, transmission electron microscopy, histologic techniques, quantitative real-time polymerase chain reaction, immunoblotting, and morphometric analysis.
RESULTS
Loss of Prox1 from the pancreas led to multiple exocrine alterations, most notably premature acinar cell differentiation, increased ductal cell proliferation, altered duct morphogenesis, and imbalanced expression of claudin proteins. Prox1ΔPanc mice also had some minor alterations in islet cells, but beta-cell development was not affected. The exocrine congenital defects of Prox1ΔPanc pancreata appeared to initiate a gradual process of deterioration that resulted in extensive loss of acinar cells, lipomatosis, and damage to ductal tissue in adult mice.
CONCLUSIONS
Pancreas-specific deletion of Prox1 causes premature differentiation of acinar cells and poor elongation of epithelial branches; these defects indicate that Prox1 controls the expansion of tip progenitors in the early developing pancreas. During later stages of embryogenesis, Prox1 appears to regulate duct cell proliferation and morphogenesis. These findings identify Prox1 as an important regulator of pancreatic exocrine development.
doi:10.1053/j.gastro.2011.12.007
PMCID: PMC3398795  PMID: 22178591
Transcription; Regulation; Organogenesis; Mouse Model
14.  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. Genetically engineered mouse models of pancreatic neoplasia develop acinar-to-ductal metaplasia prior to the development of pancreatic intraepithelial neoplasia suggesting that acinar-to-ductal metaplasias can be an early precursor lesion to pancreatic cancer. Some human pancreatic intraepithelial neoplasias 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 pancreatic intraepithelial neoplasias. Since the earliest known genetic lesions of pancreatic intraepithelial neoplasias is shortened telomeres we compared the telomere lengths of acinar-to-ductal metaplasia lesions, pancreatic intraepithelial neoplasias and adjacent normal cells of human pancreata to determine if acinar-to-ductal metaplasias could be precursors to pancreatic intraepithelial neoplasia. 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 pancreatic intraepithelial neoplasias associated with acinar-to-ductal metaplasias, and 12 pancreatic intraepithelial neoplasias. 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 pancreatic intraepithelial neoplasia-associated acinar-to-ductal metaplasias, and 1.6±1.9 in pancreatic intraepithelial neoplasias, respectively (p<0.001, ANOVA with randomized block design). Telomeres were significantly shorter in pancreatic intraepithelial neoplasia-associated acinar-to-ductal metaplasias (p<0.05, post-hoc Duncan test) and in pancreatic intraepithelial neoplasias (p<0.05), than in normal cells, or isolated acinar-to-ductal metaplasias. Thus, shortened telomeres are found in pancreatic intraepithelial neoplasia-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 pancreatic intraepithelial neoplasia, and support the hypothesis that pancreatic intraepithelial neoplasia-associated acinar-to-ductal metaplasias arise secondary to pancreatic intraepithelial neoplasia lesions.
doi:10.1038/modpathol.2010.181
PMCID: PMC3166222  PMID: 20871595
15.  Acinar cell neoplasms of the exocrine pancreas. 
Journal of Clinical Pathology  1977;30(2):103-112.
The pathological features of 12 acinar cell neoplasms of the pancreas are described; these comprise 11 carcinomas, of which seven were pure acinar cell growths and four were mixed acinar and ductal carcinomas, and one adenoma. These tumors occurred in a series of 105 during the period 162-75. Thrombotic endocarditis developed in three out the 11 carcinoma cases. The distinctive histological features of these neoplasms and the means of differentiating them from anaplastic carcinomas and certain other carcinomas, for example, islet cell carcinoma, oat cell carcinomas, and carcinoid tumours, are discussed. The poor prognosis of pancreatic cancers is emphasized, and reasons are put forward for believing that future epidemiological studies may need to take account of the histological types of pancreatic carcinoma.
Images
PMCID: PMC476331  PMID: 845259
16.  Liver metastases of pancreatic acinar cell carcinoma with marked nuclear atypia and pleomorphism diagnosed by EUS FNA cytology: a case report with emphasis on FNA cytological findings 
CytoJournal  2006;3:29.
Background
Acinar cell carcinoma of the pancreas is a rare neoplasm. Although this tumor has been well characterized histologically, the morphological patterns in Fine Needle Aspiration Cytology have not been well defined. Unlike ductal adenocarcinomas, endocrine tumors, and solid pseudopapillary tumors of the pancreas with their characteristic FNA cytological features, acinar cell carcinomas pose a particular diagnostic challenge by sharing many cytomorphologic features with endocrine tumors of the pancreas.
Case presentation
A 37-year-old man presented with lower chest and left upper quadrant abdominal pain. Computed tomography revealed a 7.8 × 7.3 cm irregular, partially cystic mass in the body and tail of the pancreas, and two lesions in the liver compatible with metastases. Subsequently, the patient underwent endoscopic ultrasound-guided fine needle aspiration on one of the two metastatic liver masses.
FNA cytology revealed abundant, loosely cohesive clusters of malignant epithelial cells with vaguely acinar and trabecular formations. The pleomorphic nuclei had fine granular chromatin and occasionally small nucleoli. There were scant to moderate amounts of cytoplasm. Scattered, strikingly large tumor cells with giant nuclei, prominent mitoses and associated necrosis were evident. A pancreatic endocrine tumor was suspected initially, but acinar cell carcinoma of the pancreas was confirmed by immunohistochemistry, cytochemical and ultrastructural studies.
Conclusion
We describe a case of pancreatic acinar cell carcinoma with unusual cytomorphologic features mimicking an endocrine tumor of pancreas, encountered in endoscopic ultrasound-guided fine needle aspiration of a metastatic liver mass and discuss the diagnostic approach for this unusual pancreatic tumor in fine needle aspiration cytology.
doi:10.1186/1742-6413-3-29
PMCID: PMC1779360  PMID: 17196112
17.  Murine ES-derived pancreatic acinar cells recapitulate features of early pancreatic differentiation 
Gastroenterology  2008;135(4):1301-1310.e5.
Background & Aims
Acinar cells constitute 90% of the pancreas epithelium, are polarized, and secrete digestive enzymes. These cells play a crucial role in pancreatitis and pancreatic cancer. However, there are no models to study normal acinar cell differentiation in vitro. The aim of this work was to generate and characterize purified populations of pancreatic acinar cells from embryonic stem cells (ES).
Methods
Reporter ES cells (Ela-pur) were generated that stably expressed both beta-galactosidase and puromycin resistance genes under the control of the elastase I promoter. Directed differentiation was achieved by incubation with conditioned media (CM) of cultured foetal pancreatic rudiments and adenoviral-mediated co-expression of p48/Ptf1a and Mist1, two bHLH transcription factors crucial for normal pancreatic acinar development and differentiation.
Results
Selected cells expressed multiple markers of acinar cells, including digestive enzymes and proteins of the secretory pathway, indicating activation of a coordinated differentiation program. The genes coding for digestive enzymes were not regulated as a single module, thus recapitulating what occurs during in vivo pancreatic development. The generated cells displayed transient agonist-induced Ca2+ mobilization and exhibited a typical response to physiologic concentrations of secretagogues, including enzyme synthesis and secretion. Importantly, these effects did not imply the acquisition of a mixed acinar-ductal phenotype.
Conclusions
These studies allow for the first time to generate almost pure acinar-like cells from ES cells. This is the first normal cell-based model allowing the study of the acinar differentiation program in vitro.
doi:10.1053/j.gastro.2008.06.049
PMCID: PMC2586982  PMID: 18725222
18.  An Effective Personalized Approach to a Rare Tumor: Prolonged Survival in Metastatic Pancreatic Acinar Cell Carcinoma Based on Genetic Analysis and Cell Line Development 
Journal of Cancer  2011;2:142-152.
Acinar cell carcinoma of the pancreas is an uncommon malignancy, accounting for less than 1% of all pancreatic neoplasms. Because of its rarity, only a few retrospective studies are available to help guide management. We report the case of a patient with metastatic ACC who achieved prolonged survival as a result of personalized treatment designed in part on the basis of molecular and in-vitro data collected on analysis of the tumor and a cell line developed from the liver metastasis. To our knowledge, this represents the first human cell line of ACC. The molecular findings on this case and this patient's cell line may be of use in the management of future cases of this rare tumor and allow the identification of potential novel targets for the effective treatment of this disease.
PMCID: PMC3053537  PMID: 21475719
acinar cell pancreatic cancer; prolonged survival; personalized medicine; cell line
19.  Acinar Cell Carcinoma of the Pancreas: New Genetic and Treatment Insights into a Rare Malignancy 
The Oncologist  2011;16(12):1714-1720.
A series of 40 consecutive cases of acinar cell carcinoma of the pancreas treated at Memorial Sloan-Kettering Cancer Center is presented, with an emphasis on evaluation of activity to new therapeutic agents.
Background.
Acinar cell carcinoma (ACC) of the pancreas is a rare neoplasm, accounting for 1% of all pancreatic neoplasms. There remains a lack of data regarding the use of systemic therapy in this disease. We present a series of 40 consecutive cases of ACC of the pancreas treated at Memorial Sloan-Kettering Cancer Center, with an emphasis on evaluation of activity of new therapeutic agents.
Methods.
Patients reviewed at our institution from January 2000 through January 2011 were identified from an institutional database with prior institutional review board approval. Pathology was confirmed in all cases as ACC or a closely related entity.
Results.
Forty patients were identified; 29 were male (73%). The median age at diagnosis was 65 years (range, 16–87 years). The median overall survival (OS) time for patients with localized, resectable disease was 56.9 months and the OS time for patients with metastatic ACC (n = 18) was 19.6 months. Six patients with metastatic or recurrent ACC had a partial response to chemotherapy and five patients had stable disease for ≥6 months on systemic chemotherapy. Clinical observation was made of a patient with ACC and hereditary nonpolyposis colorectal cancer and a patient with ACC and a BRCA1 germline mutation.
Conclusions.
ACC is moderately chemoresponsive to agents that have activity in pancreatic adenocarcinoma and colorectal carcinoma. A potential association between germline mutations in DNA mismatch repair genes and ACC warrants further evaluation.
doi:10.1634/theoncologist.2011-0231
PMCID: PMC3248770  PMID: 22042785
Pancreas; Acinar; Genetics; BRCA
20.  Mouse Pancreas Tissue Slice Culture Facilitates Long-Term Studies of Exocrine and Endocrine Cell Physiology in situ 
PLoS ONE  2013;8(11):e78706.
Studies on pancreatic cell physiology rely on the investigation of exocrine and endocrine cells in vitro. Particularly, in the case of the exocrine tissue these studies have suffered from a reduced functional viability of acinar cells in culture. As a result not only investigations on dispersed acinar cells and isolated acini were limited in their potential, but also prolonged studies on pancreatic exocrine and endocrine cells in an intact pancreatic tissue environment were unfeasible. To overcome these limitations, we aimed to establish a pancreas tissue slice culture platform to allow long-term studies on exocrine and endocrine cells in the intact pancreatic environment. Mouse pancreas tissue slice morphology was assessed to determine optimal long-term culture settings for intact pancreatic tissue. Utilizing optimized culture conditions, cell specificity and function of exocrine acinar cells and endocrine beta cells were characterized over a culture period of 7 days. We found pancreas tissue slices cultured under optimized conditions to have intact tissue specific morphology for the entire culture period. Amylase positive intact acini were present at all time points of culture and acinar cells displayed a typical strong cell polarity. Amylase release from pancreas tissue slices decreased during culture, but maintained the characteristic bell-shaped dose-response curve to increasing caerulein concentrations and a ca. 4-fold maximal over basal release. Additionally, endocrine beta cell viability and function was well preserved until the end of the observation period. Our results show that the tissue slice culture platform provides unprecedented maintenance of pancreatic tissue specific morphology and function over a culture period for at least 4 days and in part even up to 1 week. This analytical advancement now allows mid -to long-term studies on the cell biology of pancreatic disorder pathogenesis and therapy in an intact surrounding in situ.
doi:10.1371/journal.pone.0078706
PMCID: PMC3817072  PMID: 24223842
21.  Induced Mist1 Expression Promotes Remodeling of Mouse Pancreatic Acinar Cells 
Gastroenterology  2012;143(2):469-480.
BACKGROUND & AIMS
Early embryogenesis involves cell fate decisions that define the body axes and establish pools of progenitor cells. Development does not stop once lineages are specified; cells continue to undergo specific maturation events, and changes in gene expression patterns lead to their unique physiological functions. Secretory pancreatic acinar cells mature postnatally to synthesize large amounts of protein, polarize, and communicate with other cells. The transcription factor MIST1 is expressed by only secretory cells and regulates maturation events. MIST1-deficient acinar cells in mice do not establish apical-basal polarity, properly position zymogen granules, or communicate with adjacent cells, disrupting pancreatic function. We investigated whether MIST1 directly induces and maintains the mature phenotype of acinar cells.
METHODS
We analyzed the effects of Cre-mediated expression of Mist1 in adult Mist1– deficient (Mist1KO) mice. Pancreatic tissues were collected and analyzed by light and electron microscopy, immunohistochemistry, real-time polymerase chain reaction analysis, and chromatin immunoprecipitation. Primary acini were isolated from mice and analyzed in amylase secretion assays.
RESULTS
Induced expression of Mist1 in adult Mist1KO mice restored wild-type gene expression patterns in acinar cells. The acinar cells changed phenotypes, establishing apical-basal polarity, increasing the size of zymogen granules, reorganizing the cytoskeletal network, communicating intercellularly (by synthesizing gap junctions), and undergoing exocytosis.
CONCLUSIONS
The exocrine pancreas of adult mice can be remodeled by re-expression of the transcription factor MIST1. MIST1 regulates acinar cell maturation and might be used to repair damaged pancreata in patients with pancreatic disorders.
doi:10.1053/j.gastro.2012.04.011
PMCID: PMC3664941  PMID: 22510200
DIMM; Exocrine Pancreas Disease; Secretion; Transcription
22.  Lesions induced in rodent pancreas by azaserine and other pancreatic carcinogens. 
Focal proliferative changes in the acinar cells of the pancreas of rats have been induced by several systemically administered carcinogens including azaserine, N-nitrosobis(2-oxopropyl)amine, N-nitroso-(2-hydroxypropyl) (2-oxopropyl)amine, and N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine (MNCO). Foci, nodules, and adenomas induced by these carcinogens are usually made up of atypical-appearing acinar cells that maintain a high degree of differentiation, but a minority of these lesions exhibit anaplastic cellular changes that suggest the development of malignant potential. Such anaplasia may occupy the whole of smaller lesions or may occur as a secondary focal change within larger nodules or adenomas. Many foci and nodules per pancreas have been induced by single or multiple exposures to these known genotoxic carcinogens, but relatively few of them develop into carcinomas. Azaserine and MNCO have induced acinar cell carcinomas in rats. Those induced by azaserine have exhibited a broad spectrum of histologic variants, including ductlike cystic, and undifferentiated patterns. Higher doses of MNCO have induced a second pattern of change in the pancreatic lobules of rats, which includes cystic and tubular ductlike structures that have been called cystic and tubular ductal complexes. MNCO has also induced focal acinar cell lesions, cystic and tubular ductal complexes, and adenocarcinomas in the pancreas of Syrain golden hamsters. In this species, ductal complexes are much more numerous than are proliferative lesions of acinar cells, and the histologic appearance of the carcinomas is ductlike. Hyperplasia and atypical changes were also seen in the epithelium of the intralobular ducts of hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)
Images
PMCID: PMC1568198  PMID: 6332732
23.  Fluorescence In Situ Hybridization to Visualize Genetic Abnormalities in Interphase Cells of Acinar Cell Carcinoma, Ductal Adenocarcinoma, and Islet Cell Carcinoma of the Pancreas 
Mayo Clinic Proceedings  2009;84(9):801-810.
OBJECTIVE: To use fluorescence in situ hybridization (FISH) to visualize genetic abnormalities in interphase cell nuclei (interphase FISH) of acinar cell carcinoma, ductal adenocarcinoma, and islet cell carcinoma of the pancreas.
PATIENTS AND METHODS: Between April 4, 2007, and December 4, 2008, interphase FISH was used to study paraffin-embedded preparations of tissue obtained from 18 patients listed in the Mayo Clinic Biospecimen Resource for Pancreas Research with a confirmed diagnosis of acinar cell carcinoma, ductal adenocarcinoma, islet cell carcinoma, or pancreas without evidence of neoplasia. FISH probes were used for chromosome loci of APC (see glossary at end of article for expansion of all gene symbols), BRCA2, CTNNB1, EGFR, ERBB2, CDKN2A, TP53, TYMP, and TYMS. These FISH probes were used with control probes to distinguish among various kinds of chromosome abnormalities of number and structure.
RESULTS: FISH abnormalities were observed in 12 (80%) of 15 patients with pancreatic cancer: 5 of 5 patients with acinar cell carcinoma, 5 of 5 patients with ductal adenocarcinoma, and 2 (40%) of 5 patients with islet cell carcinoma. All 3 specimens of pancreatic tissue without neoplasia had normal FISH results. Gains of CTNNB1 due to trisomy 3 occurred in each tumor with acinar cell carcinoma but in none of the other tumors in this study. FISH abnormalities of all other cancer genes studied were observed in all forms of pancreatic tumors in this investigation.
CONCLUSION: FISH abnormalities of CTNNB1 due to trisomy 3 were observed only in acinar cell carcinoma. FISH abnormalities of genes implicated in familial cancer, tumor progression, and the 5-fluorouracil pathway were common but were not associated with specific types of pancreatic cancer.
Fluorescence in situ hybridization abnormalities of CTNNB1 due to trisomy 3 were observed only in acinar cell carcinoma. Fluorescence in situ hybridization abnormalities of genes implicated in familial cancer, tumor progression, and the 5-fluorouracil pathway were common, but they were not associated with specific types of pancreatic cancer.
PMCID: PMC2735430  PMID: 19720778
24.  Extensive Pancreas Regeneration Following Acinar-Specific Disruption of Xbp1 in Mice 
Gastroenterology  2011;141(4):1463-1472.
Background & Aims
Progression of diseases of the exocrine pancreas, which include pancreatitis and cancer, is associated with increased levels of cell stress. Pancreatic acinar cells are involved in development of these diseases and, because of their high level of protein output, they require an efficient, unfolded protein response (UPR), which mediates recovery from endoplasmic reticulum (ER) stress following the accumulation of misfolded proteins.
Methods
To study recovery from ER stress in the exocrine organ, we generated mice with conditional disruption of Xbp1 (a principle component of the UPR) in most adult pancreatic acinar cells (Xbp1fl/fl). We monitored the effects of constitutive ER stress in the exocrine pancreas of these mice.
Results
Xbp1-null acinar cells underwent extensive apoptosis, followed by a rapid phase of recovery in the pancreas that included expansion of the centroacinar cell compartment, formation of tubular complexes that contained Hes1- and Sox9-expressing cells, and regeneration of acinar cells that expressed Mist1 from the residual, surviving Xbp1+ cell population.
Conclusions
XBP1 appears to be required for homeostatisis of acinar cells in mice; ER stress induces a regenerative response in the pancreas that involves acinar and centroacinar cells and promotes organ recovery from exocrine pancreas disease.
doi:10.1053/j.gastro.2011.06.045
PMCID: PMC3186847  PMID: 21704586
endoplasmic reticulum stress; pancreatic progenitor cells; protein folding; tissue regeneration
25.  Regulated Exocytosis in the Pancreatic Acinar Cell 
The studies reported here will summarize the major events taking place during the synthesis, intracellular transport and discharge of secretory proteins from the pancreatic acinar cell. We will summarize the work that led to the definition of the regulated secretory pathway in the acinar cell followed by an update of the major steps in the pathway to incorporate new information on vesicular transport that has been gathered over the past 10 years from a number of laboratories. These studies arise from an amazing convergence of information derived from studies on the simpler eukaryote, S. cerevisiae, from biochemical analysis of neurotransmitter release, and from in vitro membrane fusion systems that have allowed for the dissection of the proteins involved in membrane recognition and fusion. Taken together, these studies have shown that the major proteins involved in membrane targeting and fusion, and the accessory proteins that control these events, are highly conserved over vast periods of evolutionary time. Thus, information derived from each of these systems and approaches can be transferred directly to regulated exocytosis in the pancreatic acinar cell — a system that has superimposed on it the complexities of organization into a polarized epithelium and control from the extracellular milieu via neurohormones. The ensuing hypothesis that integrates this body of information is termed the SNARE hypothesis. According to this hypothesis, the core complex of NSF (N-ethylmaleimide sensitive fusion protein) and SNAPs (soluble NSF attachment proteins) pair with their cognate receptors, SNAREs, present on the vesicles (v-SNARE) and the target membrane (t-SNARE) to form a complex that can lead to specific docking and fusion of the vesicles with their target membranes. This process is believed to be controlled by a variety of accessory proteins including synaptotagmin, a Ca2+ binding clamp for exocytosis and members of the rab family of low molecular weight GTP-binding proteins. Several of these proteins have been found by us to be present in the pancreatic acinar cell and are likely involved in similar processes that have been worked out in simpler systems. For example, we have shown that rab3D is uniquely associated with the cytosolic side of zymogen granule membranes as an integral membrane protein and that peptides from the effector domain of the rab proteins are able to induce secretion from permeabilized acinar cells, suggesting a role for this process in regulated exocytosis. These types of approaches are being used to define the localizaiton and function of members of the SNARE family of proteins and of proteins that control formation of the SNARE complex with a particular emphasis on their role in hormonally-elicited secretion. In our presentations, we will also discuss the acquisition of stimulus secretion coupling during the perinatal period in the developing rat pancreas since this system provides the possibility of defining, in a system that does not require exogenous transfection, the sequential expression of factors involved in membrane targeting and fusion. For example, during secretogenesis, rab3D is initially cytosolic at a time when the machinery of exocytosis is present but not functional, and only becomes associated with zymogen granule membranes after birth when stimulus-secretion coupling is acquired.
PMCID: PMC2589129

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