Comparative analysis of the distribution of laminin chains in the basement membranes in some malignant epithelial tumors: the alpha1 chain of laminin shows a selected expression pattern in human carcinomas.
Laminins (Ln), together with Type IV collagen and nidogen-1, form the structural integrity of the basement membranes (BM). In this study we used immunohistochemistry to show the distribution of laminin chains alpha1, alpha3, alpha5, beta1, beta2, beta3, gamma1, gamma2, as well as Type IV collagen, in various types of carcinomas and in normal tissues. Except for diffuse gastric carcinomas and infiltrative breast carcinomas, the malignant epithelial tumor clusters were surrounded by quite a continuous BM in most tumors. These BMs comprised most abundantly Ln alpha5, beta1, and gamma1 chains. Conversely, the Ln alpha1 chain, a component of laminins-1 and -3, showed the most restricted distribution in BMs of both normal tissues and malignancies, being moderately present in carcinomas of thyroid gland and ovary and in intraductal carcinomas of breast. In other types of carcinomas, immunoreactivity for Ln alpha1 chain was found more randomly and was practically negative in carcinomas of tongue, stomach, and colon. These findings were comparable to those observed by in situ hybridization, which showed that carcinomas of thyroid gland and intraductal carcinomas of breast constitutively expressed Ln alpha1 mRNA and that the epithelial tumor cells were the main producers of it. The results suggest that epithelial malignancies, except for infiltrative breast and diffuse gastric carcinomas, produce more notable amounts of BM macromolecules in their growth substratum than has previously been anticipated. Corroborating their widespread distribution in normal epithelial tissues, the chains of Lns-5 and -10 are the most abundant Ln molecules in the corresponding carcinomas.
Carbonic anhydrase isozyme XII (CA XII) is a novel membrane-associated protein with a potential role in von Hippel-Lindau carcinogenesis. Although Northern blotting has revealed positive signal for CA XII in normal human kidney, this is the first study to demonstrate its cellular and subcellular localization along the human nephron and collecting duct. Immunohistochemistry with a polyclonal antibody (PAb) raised against truncated CA XII revealed distinct staining in the basolateral plasma membrane of the epithelial cells in the thick ascending limb of Henle and distal convoluted tubules, and in the principal cells of the collecting ducts. A weak basolateral signal was also detected in the epithelium of the proximal convoluted tubules. In addition to the normal kidney specimens, this immunohistochemical study included 31 renal tumors. CA XII showed moderate or strong plasma membrane-associated expression in most oncocytomas and clear-cell carcinomas. The segmental, cellular, and subcellular distribution of CA XII along the human nephron and collecting duct suggests that it may be one of the key enzymes involved in normal renal physiology, particularly in the regulation of water homeostasis. High expression of CA XII in some renal carcinomas may contribute to its role in von Hippel-Lindau carcinogenesis.
Cellular (c) fibronectins (Fn) differ biochemically, immunologically, and functionally from plasma fibronectins (pFn). Most existing data on Fn distribution in the normal and diseased liver require revision because those studies were based on reagents that did not distinguish pFn from cFn and predated the development of specific cFn monoclonal antibodies (Mabs). We immunostained cryosections of normal adult livers (n = 5), cirrhotic livers (n = 20), and livers with hepatocellular carcinoma (HCC) (n = 10) by the avidin-biotin-complex method with specific Mabs to the extradomains A and B (EDA, EDB) and oncofetal (Onc) isoforms of cFn. Selected samples were stained with an antiserum to pFn; fetal livers served as controls. Normal and cirrhotic livers showed EDA-cFn staining in the portal, septal, and perisinusoidal matrix; its distribution was more restricted than that of pFn. In cirrhosis, EDA-cFn reactions were strongest at sites of piecemeal necrosis and around proliferating ductules in biliary cirrhosis. EDA-cFn reactions were consistently most intense in the matrix of HCC. Distinct from adult normal and cirrhotic livers, reactions for EDB- and Onc-cFn were noted exclusively in most cases of HCC. We conclude that the only cFn isoform indigenous to the normal adult liver matrix is EDA-cFn. Enhanced EDA-cFn in cirrhotic livers may serve as indicator of active stromal remodeling. The restriction of EDB- and Onc-cFn to a large subset of HCC and the putative role of cFn in modulating cell-matrix adhesive interactions would suggest that the emergence of these molecules may be related to the variably invasive and metastatic properties of these tumors.
Department of Internal Medicine, University of Oulu, Oulu; Department of Anatomy, Institute of Biomedicine, University of Helsinki; and Finnish Institute of Occupational Health, Helsinki, Finland. email@example.com
Fibronectin (Fn) and tenascin (Tn) are two major extracellular matrix (ECM) glycoproteins that may have important roles both in fibrotic lung diseases and in lung tumors. The significance of Fn and Tn in human pleural mesothelial cells and pleural diseases is unclear. Transformed human pleural mesothelial cells (Met5A), primary cultures of mesothelial cells, and cultured mesothelioma cell lines were investigated for Fn and Tn immunoreactivity. Mesothelial cells were exposed for 48 to 96 h to transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha), amosite asbestos fibers, or oxidants (H2O2 and menadione, a compound that auto-oxidizes to produce superoxide). Immunofluorescence and Western blotting with monoclonal anti-Fn and anti-Tn antibodies, and Northern blotting with a complementary DNA (cDNA) probe for Tn showed that mesothelial cells are capable of producing Fn and Tn. The mRNA level and immunoreactivity of Tn was enhanced by TGF-beta and TNF-alpha, whereas Fn was intensified only by TGF-beta. A wide range of amosite, H2O2, or menadione concentrations had no clear effect on Fn or Tn reactivity. Fn and Tn were present at low or undetectable concentrations in five of six mesothelioma cell lines, whereas the organization of Fn immunoreactivity in these cell lines was variable. Furthermore, results obtained with the tumor tissue of these same mesothelioma patients suggested that Fn and Tn expressions do not necessarily parallel either each other or results obtained with the cultured cells.
The distribution of tenascin immunoreactivity was analyzed in nonneoplastic lung tissue, benign lung tumors, and different types of lung carcinomas. In nonneoplastic lung tissue, tenascin could be observed in the basement membranes of the bronchial epithelium and endothelial cells, smooth muscle cells, and bronchial cartilage. Strong tenascin immunoreactivity was seen in the stroma of all the carcinomas of various histologic types. The staining intensity was stronger in the stroma of squamous cell carcinomas than in the stroma of the other types of lung carcinomas. In 10 of 27 squamous cell carcinomas, a granular intracytoplasmic reactivity could also be observed in a subpopulation of tumor cells. Similar intracytoplasmic reactivity was observed in 2 of 27 adenocarcinomas and in both adenosquamous carcinomas. In other types of lung tumors, individual cells did not have intracytoplasmic tenascin, except for one case of leiomyoma, which showed a weak, linear, intracytoplasmic tenascin reactivity. In lung hamartomas, tenascin could be seen in the cartilaginous component of the tumor and in the areas of basement membranes of the bronchial epithelium. In the carcinoid tumors, the stroma displayed a faint positivity for tenascin. These results show that tenascin is widely expressed in the stroma of lung carcinomas. A proportion of lung carcinomas also expressed intracytoplasmic tenascin immunoreactivity, suggesting that tumor cells may be able to synthesize tenascin. In the lung, tenascin positivity is not, however, restricted to malignant neoplasms, as evidenced by the presence of tenascin in nonneoplastic lung parenchyma and in some benign lung tumors.
AIMS: To determine the distribution of tenascin in normal and pathological bone marrow. METHODS: 48 different bone marrow lesions were studied immunohistochemically using a monoclonal antibody to tenascin. RESULTS: Tenascin immunoreactivity was found in lesions with increased fibrosis and high numbers of reticular fibres. The strongest immunoreactivity was found in myelofibrosis. Bone marrow from acute and chronic myeloid and lymphatic leukaemias showed weak or moderate immunoreactivity. In hyperplasias inconsistent reticular tenascin immunoreactivity was found; in normal bone marrow, only a few scattered positive fibres were occasionally seen. CONCLUSIONS: Tenascin was generally observed in conditions in which megakaryocytic hyperplasia was a feature. This is in line with the notion that tenascin synthesis in bone marrow fibroblasts is stimulated by TGF-beta which is synthesised by the megakaryocytic lineage. Tenascin also contains EGF-like repeats. It might therefore function as a growth promoter and in this way could also stimulate synthesis of other matrix components. On the other hand, tenascin could function as an adhesive molecule to some cells of the bone marrow. The presence of tenascin in many pathological states of the bone marrow suggests that it may have a role in their pathogenesis and that it also could be a potential marker of disease.
The distribution of tenascin immunoreactivity was analysed in salivary gland tissue and in various benign and malignant tumours of the salivary gland. In the non-neoplastic tissue, tenascin was seen in the areas of basement membranes of the ductal epithelium. No immunoreactivity could be observed in the serous or mucous glands. In pleomorphic adenomas, tenascin immunoreactivity could be seen in the stromal compartment. It was more pronounced in the dense stromal areas and chondroid elements than in the myxoid area. In Warthin's tumours, strong tenascin immunoreactivity could be observed in the basement membrane zone of the epithelial component. In the lymphatic component, faint reticular staining could be seen. In adenoid cystic carcinomas, acinic cell tumours and mucoepidermoid carcinomas, tenascin showed a linear stromal distribution. No intracytoplasmic immunoreactivity could be seen in any of the cases. The widespread tenascin positivity in salivary gland tumours suggests that tenascin may play a role in the induction and progression of salivary gland tumours, presumably by interfering with the normal parenchymal-mesenchymal interaction.