Intermediate-sized filament proteins (prekeratin,vimentin, desmin) in the normal parotid gland and parotid gland tumours

Summary Antibodies to different intermediate-sized filament proteins can distinguish cells and tissues of epithelial, mesenchymal, muscle, astrocytic and neural origin. Antibodies to prekeratin, vimentin and desmin have been used to distinguish cells of epithelial, mesenchymal and muscle origin in the normal human parotid gland, and in addition to study some common tumors of this gland. Prekeratin-positive and vimentin-positive cells are found among the tumor cells in the pleomorphic adenomas. In contrast the tumor cells of the mucoepidermoid tumors and squamous cell carcinomas are prekeratin-positive but vimentin-negative.Supported by the Deutsche Forschungsgemeinschaft (Ca 93/1-1) and by the Hamburger Stiftung zur Förderung der Krebsbekämpfung     

Expression of intermediate filament proteins in thyroid gland and thyroid tumors

The presence of intermediate filament proteins of cytokeratin/prekeratin type and vimentin type was evaluated in non-neoplastic thyroid glands and in different types of thyroid neoplasms. Follicular epithelium of both normal and goitrous thyroids showed a strong reaction with anticytokeratin antibodies that widely cross-react with various simple epithelia. On the other hand, in normal thyroid, there were only occasionally (in one of 12 cases) solitary cells reacting with antibodies to epidermal prekeratin. In nodular goiters, such cells were often seen (eight of 18), especially among the lining cells of cysts, and in chronic thyroiditis in all (12 of 12) cases. Only the stromal cells and intraluminal macrophages reacted with antibodies to vimentin. Neoplastic cells of papillary carcinomas showed a positive staining reaction both with antibodies to cytokeratins and to epidermal prekeratin. Follicular carcinoma cells, although positive for cytokeratins, could generally not be stained with antibodies to epidermal prekeratin. Medullary carcinoma cells also showed cytokeratin positivity and, only occasionally, positivity for epidermal prekeratin. Anaplastic carcinomas were also reactive with antibodies to cytokeratin but, for the most part, were negative for epidermal prekeratin. Interestingly, some neoplastic cells of all types of thyroid carcinomas also appeared to contain vimentin, as shown with both polyclonal and monoclonal antivimentin antibodies. In contrast to carcinomas, the intermediate filaments of thyroid sarcomas and lymphomas were only of vimentin type. Furthermore, it was found that the papillary structures in benign goiters were only reactive with cytokeratin antibodies and lacked, in contrast to papillary carcinomas, epidermal prekeratin-like immunoreactivity. Hence, the analysis of intermediate filament proteins of thyroid tumors can be utilized to differentiate between papillary and follicular carcinomas and between benign and malignant papillary lesions as well as between anaplastic thyroid carcinomas and sarcomas or lymphomas.     

The expression of different intermediate-sized filaments in human salivary glands and their tumours

The intermediate-sized filaments can be divided into several groups which are characteristic of different types of tissues (e.g.: epithelial, mesenchymal, muscle, astrocytic and neural origin). Antibodies specific for some of these filament types have been used to analyse a group of salivary gland tumours. Prekeratin-positive cells were seen in the normal gland, cystadenolymphomas, mucoepidermoid tumours, and squamous cell carcinomas which are all tumours of epithelial origin. The pleomorphic adenomas showed the presence of some cells which appeared to contain both prekeratin and vimentin. The results are discussed with respect to their histogenetic implications.     

Cellular origin and differentiation of renal carcinomas. A fluorescence microscopic study with kidney-specific antibodies, antiintermediate filament antibodies, and lectins

Frozen sections of human renal carcinomas were studied in indirect immunofluorescence using antibodies against intermediate filaments of cytokeratin, desmin and vimentin type, and against proximal tubular brush border and distal tubular Tamm-Horsfall glycoprotein antigens, as well as with fluorochrome-labeled lectins in an attempt to study the origin and stage of differentiation of renal carcinomas. Eighty per cent of the renal carcinomas expressed the brush border antigens, whereas the Tamm-Horsfall glycoprotein could not be found. Antibodies against epidermal cytokeratins reacted only with collecting ducts in normal kidney, whereas antibodies against cytokeratins of Madin-Darby canine kidney epithelial cell line also reacted with glomerular and tubular epithelium. In 93% of the carcinomas tumor cells showed reactivity with both types of antikeratin antibodies. Vimentin, the cytoskeletal protein of mesenchymal cells, was present in the carcinoma cells of 53% of the tumors, although it was not present in normal tubular epithelium. Moreover, vimentin was expressed together with cytokeratin in the carcinoma cells in 57% of the keratin-positive samples as judged by double immunostaining, whereas the muscle type of intermediate filament protein, desmin, was not seen in the malignant cells. Binding sites for Lotus tetragonolobus agglutinin and soybean agglutinin, normally present in the cells of proximal tubules, were lacking or only faintly detectable in the neoplastic cells. Dolichos biflorus agglutinin, normally present in collecting ducts, was not detected in the tumors. The results show that most renal carcinomas express cytokeratin antigens as a sign of their epithelial origin and also show characteristics of proximal tubular cells. On the other hand, the results indicate that lectin-binding sites typical for normal differentiated tubular cells are profoundly modified in renal carcinomas. Ulex europaeus agglutinin did not bind to the malignant cells but decorated the endothelial cells of the tumors.     

Differential diagnosis of benign epithelial proliferations and carcinomas of the breast using antibodies to cytokeratins

The immunohistochemical reactivity on frozen sections of diverse benign and malignant epithelial proliferations of human breast tissue from 156 patients was examined using antibodies to different cytokeratins. Antibodies recognizing cytokeratins 18 and 19 reacted with luminal epithelial cells but not with myoepithelial cells of normal mammary gland, cystic disease, adenosis, papilloma, and fibroadenoma or with a subpopulation of proliferating cells in sclerosing adenosis and epitheliosis. These antibodies reacted with the tumor cells of all in situ and invasive carcinomas. KA1 antibody, which by one- and two-dimensional gel electrophoresis and immunoblotting was shown to bind preferentially to cytokeratin 14 in a complex with cytokeratin 5, reacted with the nonproliferating myoepithelium of normal gland, cystic disease, adenosis, papilloma, fibroadenoma, and in situ carcinoma; it also reacted with a subpopulation of proliferating cells in sclerosing adenosis and epitheliosis (papillomatosis) but was negative with the tumor cells of all preinvasive and most invasive carcinomas. In adenotic and epitheliotic proliferations, groups of cells were identified that reacted strongly with KA1 antibody in addition to antibodies to cytokeratins 18 and 19. The data are discussed with respect to epithelial cell heterogeneity in the breast. We show that by using such antibodies, benign epithelial proliferations are clearly distinguished from carcinomas.     

Cytokeratins, smooth muscle actin and vimentin in human normal salivary gland and pleomorphic adenomas. Immunohistochemical studies with particular reference to myoepithelial and basal cells.

The distribution of immunostaining in normal major salivary gland and in 12 pleomorphic adenomas was studied using monospecific monoclonal antibodies to a number of cytokeratins, including cytokeratin 14, to smooth muscle actin and vimentin. A number of these antibodies enabled a distinction to be made between structural components of the normal gland, and to relate this to the different structures of pleomorphic adenomas. In the normal gland, the luminal duct cells expressed cytokeratins 7, 8, 18 and 19. Three antibodies were of particular value for the characterization of normal myoepithelial and basal cells; while the antibody to smooth muscle actin and the cytokeratin antibody Ks8.12 mutually exclusively stained the myoepithelial (basket) cells and the basal duct (light) cells, respectively, the recently established monospecific antibodies to cytokeratin 14 showed specific immunostaining with both cell types. These three antibodies left luminal cells virtually unstained. Ck 13 was found occasionally in single luminal excretory duct cells. Antibodies to cytokeratins 1/2, 10 and 10/11 did not show any staining in the normal gland. In the pleomorphic adenomas, the staining pattern of the two-layered tubular formation resembled that of the normal gland ducts: tumour luminal cells showed the characteristic, although more irregular, expression of cytokeratins 7, 8, 18 and 19; the outer cells resembled normal ductal basal cells with their anti-cytokeratin 14/Ks8.12-epitope staining and in that they virtually lacked staining for smooth muscle actin. Trabecular formations and cells in myxoid areas were reactive with Ks8.12 and for cytokeratin 14, occasionally also for cytokeratins 7, 18 and 19. Epidermoid cell islets expressed mainly cytokeratin 14 and inconsistently the squamous epithelial cytokeratin 13 and the epidermal cytokeratin 10/11. Vimentin was found in cells of myxoid areas. The results support the postulate that some of the normal duct basal cells act as reserve cells and can give rise to tumour formation with a primitive myxoid or trabecular pattern and a more differentiated tubular or epidermoid configuration.     

A novel monoclonal antibody to cytokeratin 18 with reactivity toward lung squamous cell carcinomas and adenocarcinomas of various sites.

Antibodies to cytokeratins (CKs) have found extensive application in the differential diagnosis of epithelial tumors. The chain-specific anti-CK reagents appear to be of practical value for further subtyping of carcinomas. The authors have produced a novel anti-CK 18 monoclonal antibody (ACK-156) using a modified immunization procedure that included sequential injections of human epidermal keratin, cyclophosphamide, and enriched cytoskeletal extracts from a human lung carcinoma cell line. This protocol effectively amplified clones with reactivity toward CK epitopes not present in epidermal keratin. Monospecificity of the antibody was confirmed by immunoblot analysis using both total cell lysates and cytoskeletal extracts as antigens. Immunoperoxidase staining of adenocarcinomas from a variety of sites, including lung, was strongly positive. Squamous cell carcinomas of lung were also strongly stained whereas squamous cell carcinomas of head and neck origin were stained focally or not at all. In contrast, several commercially available anti-CK 18 monoclonal antibodies did not distinguish squamous cell carcinomas of lung from those of head and neck origin. Immunoblot analysis of tumor lysates corroborated the tissue staining results and revealed that the commercially available antibodies that were tested recognize at least one other low molecular weight peptide in addition to the CK 18 peptide recognized by ACK-156.     

Distribution of TPA and cytokeratins in gastrointestinal carcinomas as revealed by immunohistochemistry

Summary The presence and distribution of tissue polypeptide antigen (TPA) were assessed in gastrointestinal carcinomas of different origin, morphology and degree of differentiation. Immunocytochemistry was employed, using the PAP technique on formalin-fixed, paraffin-embedded material and compared with the results obtained with antibodies to cytokeratins. Like cytokeratins, TPA was a reliable marker of epithelial differentiation and showed tissue distribution patterns similar to cytokeratins, as revealed by antibodies with broad-range cytokeratin immunoreactivity. In most carcinomas, TPA-specific immunostaining was less intense than in non-neoplastic tissue. No direct relationship between intensity of TPA staining and morphological degree of differentiation and proliferation was found. TPA staining was most pronounced at the periphery of the cells. In stratified epithelium, i.e. oesophageal mucosa, basally located cells exceeded superficial cells in TPA immunoreactivity in contrast to the cytokeratin antibodies which decorated the more superficially placed cell layers. TPA and cytokeratin staining patterns were similar in neoplastic and non-neoplastic gastric, intestinal mucosa, as well as in biliary tract epithelium. Antral and cardial mucoid glands of the stomach as well as gastric carcinomas of the pylorocardial type remained unstained with both types of antibodies. Similar staining with TPA and cytokeratin antibodies was also observed in pancreatic and liver tissue. In this study, hepatocytes were, although weakly, stained by TPA antibodies and an identical staining was found with benign and malignant hepatocellular neoplasms. Ductal and ductular TPA-staining was most conspicuous and so was the immunoreactivity of cholangiocellular carcinomas. A comparison between TPA and cytokeratins was also made by immunoblotting which revealed immunoreactivity of antibodies to TPA with cytokeratin polypeptides of different species (man, mouse) and organs (epidermis, liver), particularly with the cytokeratin component 8 of human liver and the related component A of mouse liver. The significance of this finding is uncertain until the pertinent epitopes have been revealed by monoclonal mapping of the components which exhibit similar molecular weights by SDS polyacrylamide gel electrophoresis.     

Chemically induced mammary gland adenomyoepitheliomas and myoepithelial carcinomas of mice. Immunohistochemical and ultrastructural features.

Myoepithelial cell tumors of the mammary gland have been observed in several mammalian species and are composed of a single cell type (myoepithelium) or, more often, present as a biphasic process including neoplastic ductal epithelial cells. In dogs, these are common tumors, but in humans they are rare neoplasms of the breast, and little is yet known of their pathogenesis, particularly with respect to myoepithelial origin. The present report describes bicellular mammary gland tumors arising from the duct epithelium that were induced in (C57BL/6NCr X DBA/2NCr)F1 (B6D2F1) mice by four weekly oral applications of 1 mg 7,12-dimethylbenz[a]anthracene (DMBA) starting at 8 weeks of age. Mammary tumors developed 7 to 8 months later in 14 of 57 mice, and most showed great morphologic resemblance to human adenomyoepitheliomas and myoepithelial carcinomas. Ultrastructurally, the induced tumors were composed of cuboidal epithelium with a microvillous border originating from the lining duct epithelium and plump oval or highly elongated cells that were identified as myoepithelial in origin. These spindle cells contained abundant microfilaments in parallel orientation, some with focal densities and intermediate filaments that frequently formed loose bundles or compact tonofibrils. The myoepithelial cells possessed well-developed desmosomes and plasma membrane caveolae and were regularly bordered by single or reduplicated basement membranes. By immunohistochemistry, strong immunoreactivity was observed for actin in the myoepithelial tumor component only, whereas cytokeratin was variably present in both duct epithelium and myoepithelium. Neoplastic myoepithelial cells stained purple with phosphotungstic acid hematoxylin (PTAH) and brilliant red with Masson's trichrome. It is suggested that DMBA-induced mouse mammary gland adenomyoepitheliomas and myoepithelial carcinomas may serve as very useful animal models to study myoepithelial tumorigenesis.     

Cytokeratin expression during neoplastic progression of human transitional cell carcinomas as detected by a monoclonal and a polyclonal antibody

Antibodies to intermediate filament proteins were used to study different cell layers in normal human transitional epithelium, 16 human transitional cell carcinomas, and two cell lines derived from human bladder carcinomas. Conventional rabbit antisera to human skin keratins stained all layers of the transitional epithelium from bladder, ureter, and kidney. A slightly higher staining intensity was found in the basal and superficial layers as compared with the intermediate cell layers. A monoclonal antibody to cytokeratin 18 (RGE 53), however, stained only the superficial cell layer of transitional epithelium, the so-called umbrella cells. In well-differentiated (grade I) transitional cell carcinomas, RGE 53 stained only the superficial cells of papillary structures. In higher grade papillary tumors, RGE 53 also stained cells within the basal and intermediate layers, whereas in high-grade, invasive tumors almost all tumor cells were RGE 53 positive. These results show that monoclonal antibodies to cytokeratins can provide both an indication of processes involved in neoplastic progression of bladder tumors and a means of studying the molecular relationship of the tumor cells to normal cells.     

An immunohistological comparison of primary lung carcinosarcoma and sarcoma.

We wished to assess the antigenic expression of primary lung tumors diagnosed as either carcinosarcoma or sarcoma in order to determine whether this information would be useful in distinguishing the two. We therefore immunohistochemically analyzed six pulmonary carcinosarcomas and five primary lung sarcomas for the presence of carcinoembryonic antigen (CEA), S100 protein, cytokeratin and vimentin using commercially available monoclonal and polyclonal antibodies on formalin fixed tissues. Six of six carcinosarcomas stained positively for cytokeratin while none of the sarcomas stained. In three carcinosarcomas both the carcinomatous and sarcomatous areas were positive while in three only the carcinomatous areas were positive. CEA staining was present in five carcinosarcomas and absent in all the sarcomas. CEA positivity was strong and not confined to those tumors with obvious gland formation. Staining for S100 protein was positive in two carcinosarcomas but only in those areas showing chondroid differentiation. Immunohistochemical staining for vimentin using two different monoclonal antibodies gave inconsistent results. We conclude that in differentiating between a carcinosarcoma and a sarcoma of the lung, immunohistochemical staining for both cytokeratin and CEA are useful with cytokeratin marginally preferable. The data indicate that carcinosarcoma of the lung, like that of the upper aerodigestive tract, expresses antigens suggesting both epithelial and mesenchymal differentiation.     

Antibodies to intermediate filaments as diagnostic tools: human gastrointestinal carcinomas express prekeratin

Twenty-five primary gastrointestinal carcinomas have been studied using immunofluorescence microscopy with affinity-purified antibodies to prekeratin and to vimentin. The tissues were alcohol fixed and paraffin embedded before use. In all cases (i.e., one case of esophagal carcinoma, seven stomach carcinomas, and 17 large bowel carcinomas) the tumor cells are stained by antibodies to prekeratin. In cases in which only very few tumor cells are present, such as signet ring carcinoma, immunofluorescence with prekeratin antibody provides an easy way to visualize single tumor cells. When the same specimens were tested with antibodies to vimentin, the tumor cells were unstained, and only the fibroblasts and vessels of the stroma were decorated. Four of the tumors were also negative when tested with antibodies specific for either desmin, or glial fibrillary acidic protein or neurofilaments. Three metastases to the abdominal region from tumors originating in the ovary, stomach, and large bowel were like the primary tumors in that the tumor cells were positive when stained with antibodies to prekeratin and negative when tested with the antibodies to vimentin.     

Immunohistochemical distinction of human carcinomas by cytokeratin typing with monoclonal antibodies.

Carcinomas of different origin have been tested in immunofluorescence microscopy with the monoclonal murine antibodies CK1-CK4, which recognize a single cytokeratin polypeptide (human cytokeratin No. 18) present in simple but not in stratified squamous epithelia, and with the monoclonal antibody KG8.13 and guinea pig kerA antibodies, both of which recognize a variety of cytokeratins common to almost all epithelial cell types. Tumors derived from simple epithelia, including adenocarcinomas and some other tumors such as ductal breast carcinomas, were strongly stained by all three antibodies. So was a transitional carcinoma of the bladder. In contrast, basal cell epithelioma, cloacogenic carcinoma, and squamous cell carcinoma of skin, tongue, and esophagus appeared negative with CK1-CK4 but positive with the other two antibodies. Other squamous cell carcinomas derived from epiglottis and cervix uteri showed a mixture of positive and negative cells when tested with CK1-CK4, although all tumor cells were positive when tested with KG8.13 and with kerA. Thus, use of an appropriate collection of cytokeratin antibodies with different specificities not only allows tumors of epithelial origin to be distinguished from other tumor types but, in addition, allows a further subdivision of carcinomas in relation to their histologic origin.     

The intermediate filament cytoskeleton of cutaneous neuroendocrine carcinoma (Merkel cell tumour)

Summary The presence and distribution of cytokeratins, neurofilament proteins, vimentin and glial fibrillary acidic protein were studied in 10 cutaneous neuroendocrine carcinomas (CNEC) by immunohistochemical techniques, using specific antibodies. In all cases tumour cells were specifically stained with antibodies to mouse liver cytokeratin component D in paraffin-embedded formalin-fixed and frozen sections. Moreover, one- and two-dimensional SDS-polyacrylamide gel electrophoresis of high salt/detergent resistant cytoskeletal residues from tumour material, isolated by microdissection from frozen sections, revealed the presence of cytokeratin components 8 and 18 which are characteristic constitutents of cytokeratin filaments of simple epithalia. Neurofilament proteins were detected by immunocytochemistry in tumour cells from 2 patients, from whom frozen material was available, and their presence was also positively identified in cytoskeletal residues by immunoblotting using specific antibodies. Glial fibrillary acidic protein and vimentin could not be demonstrated in tumour cells. Our studies did not confirm the suggested origin of CNEC from epidermal Merkel cells.This work was supported in part by Fonds zur Förderung der wissenschaftlichen Forschung, Grant P4708 to H.D.     

Conserved antigen expression in epithelial tumors recognized by monoclonal antibody 4A9 generated against canine mammary carcinoma cells

Hybridoma-derived murine monoclonal antibodies (MoAbs) were generated by fusing P3X63-Ag8.653 myeloma cells with splenic cells from BALB/c mouse which had been immunized with viable canine mammary adenocarcinoma cells, CMT-2. Fifteen MoAbs were shown to react with immunizing cells in indirect immunofluorescence (IFA) and enzyme-linked immunosorbent (ELISA) assays. The reactivity of one IgM MoAb, designated 4A9, was evaluated. The antigen recognized by 4A9 on CMT-2 cells appeared to be localized both in cell membrane and cytoplasm against fixed and unfixed preparations by IFA. The 4A9 MoAb was found to bind with four of five canine mammary carcinoma cell lines while no binding was detected with normal fibroblastic cell lines. In vivo tissue distribution of 4A9 antigen was evaluated by indirect immunoperoxidase (IP) assay against formalin-fixed, paraffin-embedded sections of normal and neoplastic tissues. 4A9 MoAb reacted strongly to moderately with 75% of mammary carcinomas, moderately to weakly with 57% of benign mammary tumors, and strongly with squamous cell and perianal gland carcinomas (100%), interstitial cell tumors (100%), transitional cell carcinomas (43%), lung adenocarcinomas (40%), colon carcinomas (33%), and pancreatic adenocarcinomas (20%). Moderate to weak staining was detected with granulosa cell tumors (25%) and apocrine gland adenocarcinomas (50%). Strong reactivity with perianal gland carcinomas contrasted to no reactivity with perianal gland adenomas. No immunostaining was detected with a large variety and number of normal adult and fetal tissues tested; negligible and very restricted staining was observed in a few adult and fetal tissues. Normal mammary gland was negative. Since the antigen is expressed on the cell surface and in the cytoplasm of most mammary carcinoma cells and a variety of other epithelial tumor cells, the 4A9 antibody may have potential application in diagnosis and management of canine mammary cancer and a variety of other epithelial tumors.     

Pulmonary adenosquamous carcinomas with amyloid-like stroma

Two unique cases of pulmonary carcinomas showing squamous and glandular differentiation and the production of excessive amounts of extracellular waxy eosinophilic material resembling amyloid are reported. Immunohistochemical studies showed strong staining of the neoplastic cells with antibodies directed at cytokeratin, epithelial membrane antigen, and carcinoembryonic antigen. Of particular interest was the simultaneous strong staining for S-100 protein and vimentin. The histology, ultrastructure, and immunohistochemical findings suggest focal myoepithelial differentiation in these mixed carcinomas and indicate an analogy to salivary gland neoplasms, particularly adenoid cystic carcinoma and dermal analog tumors.     

Immunohistochemical expression of cytokeratins 7 and 20 in malignant salivary gland tumors.

On the basis of the heterogeneity of cytokeratins 7 and 20 expression in malignant epithelial tumors, the cytokeratin 7/20 immunophenotype has served as a useful diagnostic tool for discrimination of primary and/or metastatic carcinomas of unknown origin. However, the expression pattern of these cytokeratins in malignant salivary gland tumors has not been thoroughly studied. Our study material was composed of 84 malignant tumors of primary major or minor salivary gland origin. Nine histologic types of carcinoma were represented, including mucoepidermoid (26 cases), adenoid cystic (25), polymorphous low grade (11), salivary duct (8), acinic cell (4), ex mixed tumor (3), not otherwise specified (3), clear cell (2), and basal cell (2). In all, 13 cases of primary skin or mucosal squamous cell carcinoma with secondary salivary gland involvement were also examined. Immunoreactivity for cytokeratin 7 was evident in all malignant salivary gland tumors; the staining pattern was diffuse and strong in 62 cases, and focal and strong in 22 cases. In contrast, 78 cases were negative for cytokeratin 20, whereas only six cases (two mucoepidermoid, one adenoid cystic, and three salivary duct) displayed focal weak positivity. Overall, 92.9% of malignant salivary gland tumors were characterized by a cytokeratin 7 positive/20 negative immunoprofile, the remaining 7.1% of cases being positive for both cytokeratins. The latter phenotype was more common in salivary duct carcinomas (P< or =0.05). On the other hand, most squamous cell carcinomas (69%) were negative for both cytokeratins, while the remaining cases (31%) were negative for cytokeratin 20 and focally weakly positive for cytokeratin 7. We suggest that assessment of cytokeratin 7/20 immunoprofile may facilitate the differential diagnosis of (a) primary malignant salivary gland tumors from metastatic tumors, (b) metastatic salivary gland tumors, (c) primary salivary gland tumors, especially mucoepidermoid carcinomas, from squamous cell carcinomas, and (d) salivary duct carcinomas from other malignant salivary gland tumors.     

Myoepithelial cells in salivary gland tumors. An immunohistochemical study

Normal salivary glands and 55 salivary gland tumors were examined by immunostaining (immunoperoxidase [IMP] and immunofluorescence [IMF]) to identify myoepithelial cells (MCs) and speculate on their role in the histogenesis of the tumors. The classic (C) MCs of normal salivary glands stained by IMP with antibodies to cytokeratin and S100 protein and stained by IMF with the same antibodies and with antibodies to vimentin and actin. Modified (M) MCs of pleomorphic adenomas stained positively by IMP and IMF with all of the preceding antibodies. In many mucoepidermoid carcinomas, adenoid cystic carcinomas, and basal cell adenomas, variable numbers of CMCs and MMCs stained positively by IMP with anti-cytokeratin and anti-S100 protein antibodies. No MCs were detected in adenolymphomas or acinic cell carcinomas. We believe that MCs play a major role in the histogenesis of pleomorphic adenomas and may also be important in many mucoepidermoid carcinomas, adenoid cystic carcinomas, and basal cell adenomas.     

Modulation of expression of intermediate filaments during the development of established rat liver cell lines

A number of clear epithelial-like cell lines were established from the liver of fetal and neonatal rats. The intermediate filaments of these cells were investigated using polyclonal prekeratin antisera, monoclonal antibodies against a cytokeratin subfamily and vimentin by means of the indirect immunofluorescence technique and SDS-PAGE analysis. Changes in the expression of cytokeratin filaments were found during the evolution of permanent cell lines. Cells positively stained for cytokeratins could be seen near to other cells which were negative. In early passages (up to the 40th) nearly all cells were strongly stained by the different keratin antibodies. During the following subcultivation the pattern of staining considerably changed. In FRL and NP-RL cell lines keratin-negative cells could already be observed in the early passages, rapidly increasing in the later passages. Compared to this, vimentin-staining of all cells remained constant in its morphological expression. The keratin filaments were seen in thick fiber bundles arranged particularly in the perinuclear ring as well as in finer networks throughout the cytoplasm. Every cell in the established lines showed their very individual staining pattern. The vimentin filaments extended to the whole cytoplasm up to the cell margin. Our observations demonstrate the variability of the system of keratin filaments in established epithelial-like liver cells under cultural conditions.