Intermediate filaments in rat pancreatic acinar tumors, human ductal carcinomas, and other gastrointestinal malignancies

Contribution of proteomics to the study of the role of cytokeratins in disease and physiopathology

Cytokeratins (CKs), the most abundant group of cytoskeletal intermediate filaments, and proteomics are strongly connected. On the one hand, proteomics has been extremely useful to uncover new features and functions of CKs, on the other, the highly abundant CKs serve as an exceptional tool to test new technological developments in proteomics. As a result, proteomics has contributed to finding valuable associations of CKs with diseases as diverse as cancer, cystic fibrosis, steatohepatitis, viral and bacterial infection, keratoconus, vitreoretinopathy, preeclampsia or the chronic fatigue syndrome, as well as to characterizing their participation in a number of physiopathological processes, including drug resistance, response to toxicants, inflammation, stem cell differentiation, embryo development, and tissue repair. In some cases, like in cystic fibrosis, CKs have been described as potential therapeutic targets. The development of a specific field of proteomics where CKs become the main subject of research aims and hypotheses is suggested.

Identification of proteins of human colorectal carcinoma cell line SW480 by two-dimensional electrophoresis and MALDI-TOF mass spectrometry

AIM: To conduct the proteomic analysis of human colorectal carcinoma cell line, SW480 by using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption /ionization-time of flight mass spectrometry (MALDI-TOFMS).

METHODS: The total proteins of human colorectal carcinoma cell line, SW480 were separated with 2-DE by using immobilized pH gradient strips and visualized by staining with silver nitrate. The gel images were acquired by scanner and 2-DE analysis software, Image Master 2D Elite. Nineteen distinct protein spots were excised from gel randomly and digested in gel by TPCK-trypsin. Mass analysis of the tryptic digest peptides mixture was performed by using MALDI-TOF MS. Peptide mass fingerprints (PMFs) obtained by the MALDI-TOF analysis were used to search NCBI, SWISS-PROT and MSDB databases by using Mascot software.

RESULTS: PMF maps of all spots were obtained by MALDI-TOF MS and thirteen proteins were preliminarily identified.

CONCLUSION: The methods of analysis and identification of protein spots of tumor cells in 2-DE gel with silver staining by MALDI-TOF MS derived PMF have been established. Protein expression profile of SW480 has been obtained. It is demonstrated that a combination of proteomics and cell culture is a useful approach to comprehend the process of colon carcinogenesis.

Expression pattern of keratin subclasses in pancreatoblastoma with special emphasis on squamoid corpuscles

Expression patterns of keratins (K), both simple epithelia-type (K7, K8, K18, K19) and complex/stratified epithelia-type (K1, K4, K5/6, K10, K13, K14, K15, K16, K17), and epithelial membrane antigen (EMA) were immunohistochemically studied in six pancreatoblastomas (PBL). In all six tumors, areas with overt acinar differentiation (AA), solid areas without any specific differentiation (SO), and squamoid corpuscles (SC) were diffusely positive for K8, K18, and K19. The AA and SO in all the tumors were diffusely positive for K7, but the SC were negative or displayed only scattered reactivity for K7. In three tumors, the AA and the SC showed scattered reactivity for K5/6. No reactivity for other complex/stratified epithelia-type K was found in any of the examined tumor. All tumors were reactive for EMA with consistent predominancy in the SC. Ultrastructurally, well-developed desmosome-tonofilament complexes were only partially observed in tumor cells comprising the SC. These results implied that (i) the SC usually lack a character of complete squamous metaplasia; and (ii) the SC have a characteristic phenotype (K8/K18/K19/EMA-positive, K7-negative or scatteredly positive) that can potentially be useful to delineate the SC in PBL.

Proteomics in pancreatic disease

Proteomics represents a novel methodological approach to investigate the expression of all proteins by a cell or organism in its entireness, similar to global strategies for DNA (genomics) and RNA (transcriptomics). This review focuses on the history of protein analysis, which made up the golden age of pancreatic physiology, the current methodology for proteomics (2D gel electrophoresis, mass spectrometry) and the few published experiences with proteomics in the field of pancreatology until now. Finally, potential applications of proteomics for the pancreas, in concert with other techniques, are cited.

Sphingosylphosphorylcholine regulates keratin network architecture and visco-elastic properties of human cancer cells

Sphingosylphosphorylcholine (SPC) is a naturally occurring bioactive lipid that is present in high density lipoproteins (HDL) particles and found at increased levels in blood and malignant ascites of patients with ovarian cancer. Here, we show that incubation of human epithelial tumour cells with SPC induces a perinuclear reorganization of intact keratin 8-18 filaments. This effect is specific for SPC, largely independent of F-actin and microtubules, and is accompanied by keratin phosphorylation. In vivo visco-elastic probing of single cancer cells demonstrates that SPC increases cellular elasticity. Accordingly, SPC stimulates migration of cells through size-limited pores in a more potent manner than lysophosphatidic acid (LPA). LPA induces actin stress fibre formation, but does not reorganize keratins in cancer cells and hence increases cellular stiffness. We propose that reorganization of keratin by SPC may facilitate biological phenomena that require a high degree of elasticity, such as squeezing of cells through membranous pores during metastasis.

A comprehensive characterization of pancreatic ductal carcinoma cell lines: towards the establishment of an in vitro research platform

There are a large number of stable pancreatic ductal carcinoma cell lines that are used by researchers worldwide. Detailed data about their differentiation status and growth features are, however, often lacking. We therefore attempted to classify commonly used pancreatic carcinoma cell lines according to defined cell biological criteria. Twelve pancreatic ductal adenocarcinoma cell lines were cultured as monolayers and spheroids and graded according to their ultrastructural features. The grading system was based on the integrity of membrane structures and on the presence of mucin granules, cell organelles, nuclear and cellular polymorphism, cell polarity, and lumen formation. On the basis of the resulting scores the cell lines were classified as well, moderately, or poorly differentiated. In addition, immunocytochemistry was performed for the markers cytokeratin 7, 8, 18, 19, carcinoembryonic antigen, MUC1 MUC2, MUC5, and MUC6. The population doubling time of monolayer cultures, determined by a tetrazolium salt based proliferation assay was correlated with the ultrastructural grade. The grading of the ultrastructural features of the monolayers, and particularly of the spheroids, revealed that Capan-1 and Capan-2 cells were well differentiated; Colo357, HPAF-2, Aspc-1, A818-4, BxPc3, and Panc89 cells were moderately differentiated and PancTu-I, Panc1, Pt45P1, and MiaPaCa-2 cells poorly differentiated. Membrane-bound MUC1 staining was a characteristic of well differentiated cell lines. The population doubling time of the monolayer cultures was related to the differentiation grade. No relationship was found between the p53, K-ras, DPC4/Smad4, or p16(INK4a) mutation status and the grade of differentiation. We conclude that the proposed ultrastructural grading system combined with the proliferative activity provides a basis for further comparative studies of pancreatic ductal adenocarcinoma cell lines.

Acinar cell carcinoma of the pancreas with and without endocrine differentiation

BACKGROUND

Acinar cell carcinoma (ACC) is a rare pancreatic neoplasm, representing 1% of exocrine tumours and containing a variable endocrine component. Three recent cases of ACC are reported.

CASE OUTLINES

A 72-year-old man with painless obstructive jaundice had a 5-cm mass in the head of pancreas resected by Whipple's operation; histopathological examination showed a typical ACC. A 33-year-old man with weight loss and abnormal liver function had a dilated biliary tree but no mass on imaging. Pylorus-preserving pancreatoduodenectomy was performed, and histology showed a mixed acinar-neuro-endocrine tumour. A 56-year-old man with weight loss and a palpable mass had a 15-cm mass in the distal body of pancreas, which was resected en bloc with the spleen and adherent stomach; it was a cystic ACC.

RESULTS

Two patients are alive and free of disease at 30 months and 15 months, while the third patient with locally advanced disease died of myocardial infarction at 9 weeks.

DISCUSSION

Acinar structures are the hallmark of this neoplasm, which carries a better survival rate than ductal cancer. Surgical excision prolongs survival and offers the best chance of cure.

Cytokeratins 7, 17, and 20 reactivity in pancreatic and ampulla of vater adenocarcinomas. Percentage of positivity and distribution is affected by the cut-point threshold

We studied reactivity of cytokeratins (CK) 7, 17, and 20 in 64 pancreaticobiliary adenocarcinomas to examine the effect of different cut-point thresholds on "positive" results, compare ampulla of Vater and pancreas adenocarcinomas, and provide additional experience with CK17 reactivity. Almost all neoplasms had extensive CK7 reactivity. The number of CK20-positive cases decreased from 29 (45%; any stained cells) to 19 (30%; > 25% staining) to 14 (22%; > 50% staining) with an increasing threshold of reactive cells. Similar shifts in the distribution of CK7 and CK20 reactivity occurred when different thresholds of reactivity were used for a positive result. There were no differences in CK7 or CK20 reactivity in pancreas only, ampulla only, and neoplasms involving both sites. Of 64 adenocarcinomas, 29 (45%) had no or single-cell CK17 reactivity, and 19 (30%) had reactivity in more than 50% of neoplastic cells. Ampulla of Vater and pancreas adenocarcinomas have similar CK immunophenotypes that cannot assist in distinguishing ampullary from pancreatic neoplasms on endoscopically procured tissue. CK17 staining occurs in approximately 50% of pancreaticobiliary adenocarcinomas and is usually patchy. Single antibody staining results, especially CK7 and CK20 coordinate reactivity, are influenced by the reactivity threshold used.

Effects of keratin filament disruption on exocrine pancreas-stimulated secretion and susceptibility to injury

Disruption or absence of hepatocyte keratins 8 and 18 is associated with chronic hepatitis, marked hepatocyte fragility, and a significant predisposition to stress-induced liver injury. In contrast, pancreatic keratin disruption in transgenic mice that express keratin 18 Arg89 --> Cys (K18C) is not associated with an obvious pancreatic pathology. We compared the effects of keratin filament disruption on pancreatic acini or acinar cell viability, and on cholecystokinin (CCK)-stimulated secretion, in transgenic mice that overexpress wild-type keratin 18 and harbor normal extended keratin filaments (TG2) and K18C mice. We also compared the response of these mice to pancreatitis induced by a choline-deficient ethionine-supplemented diet or by caerulein. Despite extensive cytoplasmic keratin filament disruption, the apicolateral keratin filament bundles appear intact in the acinar pancreas of K18C mice, as determined ultrastructurally and by light microscopy. No significant pancreatitis-associated histologic, serologic, or F-actin/keratin apicolateral redistribution differences were noted between TG2 and K18C mice. Acinar cell viability and yield after collagenase digestion were lower in K18C than in TG2 mice, but the yields of intact acini and their (125)I-CCK uptake and responses to CCK-stimulated secretion were similar. Our results indicate that keratin filament reorganization is a normal physiologic response to pancreatic cell injury, but an intact keratin cytoplasmic filament network is not as essential in protection from cell injury as in the liver. These findings raise the possibility that the abundant apicolateral acinar keratin filaments, which are not as evident in hepatocytes, may play the cytoprotective role that is seen in liver and other tissues. Alternatively, identical keratins may function differently in different tissues.

Detection of extrapancreatic nerve plexus invasion of pancreatic adenocarcinoma. Cytokeratin 19 staining and K-ras mutation

BACKGROUND

Neural invasion is known to be one of the aggressive characteristics of pancreatic adenocarcinoma. However, there have been no systematic studies on intraoperative examination of neural invasion of pancreatic carcinomas after wide dissection of the retroperitoneum, particularly at the surgical margin.

METHODS

We performed intraoperative immunostaining on the frozen sections of several excised plexus specimens, using peroxidase-labeled anti-cytokeratin 19 antibody in 17 cases of resectable pancreatic carcinoma. Postoperatively, we also tried to detect occult micrometastasis by direct sequencing of the K-ras gene in the same samples.

RESULTS

Intraoperative staining for cytokeratin 19 was positive in 4 of 17 (23.5%) cases. Patients with margin-positive neural invasion had significantly worse prognosis than patients who were margin negative (P < 0.05). One patient had micrometastasis in the nerve plexus, revealed by K-ras mutation, whereas neither cytokeratin 19 staining nor postoperative pathological investigation detected involvement of the analyzed portion. In the four patients margin-positive for cytokeratin 19 staining, the diagnosis of neural invasion by cytokeratin 19 staining was in agreement with the K-ras gene analysis.

CONCLUSION

Intraoperative staining for cytokeratin 19 is useful for detecting pancreatic cancer involvement of the neural plexus margin. The results can be also utilized as a prognostic indicator during the follow-up period.

Proteins expressed by pancreatic duct cells and their relatives

Significant progress has been made in the characterization of the structure and function of pancreatic ductal cells. Our understanding at this point in time extends to knowledge of specific molecules that provide for the structural composition of the ductal cells, their interactions with the local environment, and the regulation of their growth and properties of differentiation. Knowledge of the molecular composition and structure of the secretory products of epithelial cells in the pancreas also has increased so that we now understand the individual contributions of several secretory products to the overall function of pancreatic juice. Further study of these parameters will give us important insight into the normal function of the ductal cells and into how these processes are altered during the development and progression of diseases of the pancreas such as pancreatitis and cancer.

Undifferentiated carcinoma of the pancreas: analysis of intermediate filament profile and Ki-ras mutations provides evidence of a ductal origin

Undifferentiated carcinomas and osteoclast-like giant cell tumours of the pancreas commonly contain foci of neoplastic ductal glands. To test the hypothesis that undifferentiated carcinomas and osteoclast-like giant cell tumours have a ductal origin, the immunocytochemical cytokeratin pattern and the frequency and type of Ki-ras mutations at colon 12 were studied in a series of 17 undifferentiated carcinomas and two osteoclast-like giant cell tumours. The cytokeratin features of undifferentiated carcinomas and osteoclast-like giant cell tumours were compared with those found in 10 ductal adenocarcinomas, 20 acinar cell carcinomas, 25 neuroendocrine tumours, and 15 solid-pseudopapillary tumours. All undifferentiated carcinomas and osteoclast-like giant cell tumours stained with at least one cytokeratin antibody, and 13/19 of them with antibodies against cytokeratins 7, 8, 18, and 19. The latter cytokeratins were expressed in all ductal adenocarcinomas, but only in 15/20 acinar cell carcinomas, 2/25 neuroendocrine tumours, and 1/15 solid-pseudopapillary tumours. In addition to cytokeratin, 15/19 undifferentiated carcinomas/osteoclast-like giant cell tumours were positive for vimentin. Ki-ras mutations at codon 12 were found in 10 undifferentiated carcinomas and one osteoclast-like giant cell tumour from which DNA could be successfully amplified. The Ki-ras mutation patterns were analysed in six tumours and corresponded to those typical of ductal adenocarcinomas. In tumours with ductal and anaplastic components, both components revealed identical mutation patterns. From these findings, it is concluded that both undifferentiated carcinomas and osteoclast-like giant cell tumours belong to the pancreatic tumours that show a ductal phenotype. Since undifferentiated carcinomas and osteoclast-like giant cell tumours share the same cytokeratin and Ki-ras features, they are probably derived from the same cell lineage.

Cytokeratins and cell differentiation in the pancreas

Keratins, or cytokeratins, represent a family of more than 20 different polypeptides which are important markers of epithelial cell differentiation. This review deals with the use of keratin immunohistochemistry in the study of pancreatic cell differentiation. Exocrine acinar cells and endocrine islet cells are well-differentiated cells which express the keratin combination 8 and 18, whereas the less-differentiated cells of the ductal tree are characterized by the additional expression of keratin 7, keratin 19, and, in the rat, keratin 20. Keratin expression is stable and can be used for cell identification after isolation and culture, and in clinical or experimental injury. The intercalated ductal cells and centroacinar cells are inconspicuous unless specific immunohistochemical markers, such as keratins, are used. In conditions where there is morphogenetic differentiation such as in fetal life, or where transdifferentiation is occurring, keratins have been used to trace the origin and fate of pancreatic cells.

Mucinous tumors of the vermiform appendix and ovary, and pseudomyxoma peritonei: histogenetic implications of cytokeratin 7 expression

Cytokeratin 7 (CK-7) has been shown to be uncommonly expressed in colonic epithelial tumors, as opposed to ovarian epithelial tumors, which are always CK-7 positive. The authors investigated the expression of CK-7 in 17 appendiceal cystadenomas and carcinomas, 20 mucinous borderline tumors of the ovary, 10 cases of simultaneous mucinous tumors of the appendix and ovary, three so-called high-stage mucinous borderline tumors of the ovary, and three cases of pseudomyxoma peritonei (PP) of unknown origin. Nine appendiceal cystadenomas were CK-7 negative; two of these were associated with PP, and the peritoneal lesions were negative as well. Three cystadenomas were CK-7 positive. Three appendiceal carcinomas were CK-7 negative, and in one case the metastases were also negative. Two carcinomas were CK-7 positive. All 20 ovarian borderline tumors were CK-7 positive. Six cases of simultaneous mucinous tumors of the ovary and appendix were CK-7 negative, as were their peritoneal mucinous deposits. Four cases showed a positive reaction in both appendiceal and ovarian sites. Two of three so-called high-stage ovarian borderline tumors were CK-7 negative. All three cases of PP of unknown origin were CK-7 negative. In conclusion, appendiceal cystadenomas are often CK-7 negative, whereas ovarian mucinous borderline tumors are always CK-7 positive. The concordant staining pattern for CK-7 of simultaneous mucinous tumors involving the appendix and ovary (60% of which were CK-7 negative) supports an appendiceal origin for these tumors. Our results also support an appendiceal (or colonic) source for any CK-7-negative mucinous tumor involving the ovary or the peritoneum. Furthermore, our findings are in agreement with the assumption that mucinous borderline-like tumors in the ovary associated with PP are not ovarian in origin but are often, if not always, metastatic from an appendiceal (or other) mucinous tumor.

Cytokeratin 19 fragment in serum and tissues of patients with pancreatic diseases

CONCLUSION

The present study has shown that increased serum levels of cytokeratin 19 fragment reflect increases in the size of the pancreatic carcinomas, although the sensitivity for detecting small pancreatic carcinomas was low.

BACKGROUND

Cytokeratin is a member of the intermediate family of filaments in epithelial cells. The cytokeratin 19 fragment is an acidic cytokeratin, which is found in various epithelial tissues. Recently, the serum fragment of cytokeratin 19 has been measured and found to be a good marker for squamous cell carcinoma. Cytokeratin 19 is known to be expressed in normal pancreatic tissues and pancreatic carcinomas. However, serum cytokeratin 19 levels in pancreatic diseases have not been precisely detailed.

METHODS

In this study, we evaluated serum cytokeratin 19 levels and the immunohistochemical expression of cytokeratin 19 in various pancreatic diseases.

RESULTS

Serum cytokeratin 19 levels were high (> 2 ng/mL) in 51 of 99 (52%) cases of pancreatic duct cell carcinoma, but were low in all 24 cases of chronic pancreatitis and in 7 cases of islet cell tumors. The sensitivity of the cytokeratin 19 assay increased with increased size of the pancreatic carcinomas, but was not influenced by the presence of obstructive jaundice. Immunohistochemical studies using a monoclonal anticytokeratin 19 antibody showed that staining for cytokeratin was positive in all 38 of the pancreatic carcinomas examined and in 2 of 6 islet tumors.