bromochloroacetic-acid and Adenoma--Islet-Cell

Topics: Adenocarcinoma; Adenoma, Islet Cell; Animals; Antibodies, Monoclonal; Breast Neoplasms; Carcinoma, Small Cell; Carcinoma, Squamous Cell; Cytoskeletal Proteins; Desmoplakins; Desmosomes; Electrophoresis, Polyacrylamide Gel; Granulosa Cell Tumor; Humans; Immunosorbent Techniques; Intermediate Filament Proteins; Intermediate Filaments; Keratins; Kidney Neoplasms; Lung Neoplasms; Melanoma; Membrane Proteins; Meningioma; Mesothelioma; Microscopy, Electron; Microscopy, Fluorescence; Neoplasms; Neurosecretory Systems; Skin Neoplasms

Twelve cases of gastrointestinal neuroendocrine tumors, including eight carcinoids and four pancreatic islet cell tumors or their metastases, were immunohistochemically analyzed for the expression of different types of intermediate filament proteins. All of the tumors showed cytokeratin positivity in immunostaining, and the Western blotting technique revealed 45- and 52-kilodalton cytokeratins in carcinoid tumors. Three of the islet cell tumors, but none of the carcinoid tumors, showed, in addition, varying numbers of neurofilament-positive tumor cells when evaluated with rabbit and mouse monoclonal antineurofilament antibodies. The presence of only the 70-kilodalton neurofilament and cytokeratin polypeptides in an islet cell tumor was revealed also by using the Western blotting technique. On the other hand, both fetal and adult pancreatic islet cells showed only cytokeratin positivity. Neurofilament-positive epithelial cells were not found in normal small intestines either. The results show epithelial characteristics in normal gastrointestinal neuroendocrine cells and neuroendocrine tumors by their expression of cytokeratin. In addition, some islet cell tumors display the 70-kilodalton neurofilament protein which suggests the acquisition of a new type of intermediate filament during the neoplastic change.

Topics: Adenoma, Islet Cell; Carcinoid Tumor; Cytoskeleton; Gastric Mucosa; Gastrointestinal Neoplasms; Humans; Intestinal Mucosa; Keratins; Pancreas; Zollinger-Ellison Syndrome

This report describes the cytoskeleton nature of a 60,000-mol-wt protein, P60, previously shown to undergo Ca2+ influx-induced phosphorylation concomitant with insulin release in hamster insulinoma cells. Four lines of evidence suggest that P60 is an intermediate filament protein of the keratin class. (a) As previously described (Schubart, U.K., 1982, J. Biol. Chem. 257:12231-12238), Triton X-100-insoluble cytoskeletons are enriched for P60; (b) these cytoskeletons contain 7-11-nm filaments as determined by negative staining; (c) immunoblot analysis revealed that all proteins detected in the insulinoma cell cytoskeletons are recognized by a monoclonal antibody that interacts with a common determinant in all intermediate filament proteins; and (d) P60 was shown, by its identical migration on two-dimensional electrophoresis and by its immunologic relatedness, to be analogous to a known keratin present in HeLa cells. An antibody specific for P60, as judged by immunoblotting, was developed in a rabbit. In indirect immunofluorescence studies on insulinoma cells, this anti-P60 antibody produced a filamentous staining pattern. The antibody also permitted the identification of P60 in normal pancreatic islets as determined both by immunoblotting of hamster islet proteins resolved by two-dimensional electrophoresis and by indirect immunofluorescence microscopy on cryostat sections of hamster pancreas. In addition, the antibody recognized an antigen in the epithelial layer of pancreatic exocrine ducts, as determined by indirect immunofluorescence. The data have implications for the embryonic origin of pancreatic islets. Together with the phosphorylation data, these findings suggest that this islet cell cytokeratin may be involved in the regulation of insulin release.

Topics: Adenoma, Islet Cell; Animals; Calcium; Cricetinae; Cytoskeleton; HeLa Cells; Humans; Insulinoma; Intermediate Filament Proteins; Islets of Langerhans; Keratins; Phosphoproteins