Taneli Tani

Anchoring complex components laminin-5 and type VII collagen in intestine: association with migrating and differentiating enterocytes.

Anchoring complex component laminin-5 and its subunits laminin (Ln)-alpha3 and Ln-beta3 chains, Type VII collagen, and integrin chains alpha3, alpha6, and beta4 were studied in developing and adult human intestine and compared with findings on Ln-alpha1 and Ln-alpha2 chains. In adult human duodenum, jejunum, and ileum, Ln-5 detected with a polyclonal antiserum and Ln-alpha3 and Ln-beta3 chains, detected with monoclonal antibodies (MAbs), were restricted to the epithelial basement membranes (BMs) of villi, whereas Ln-alpha2 chain was seen only focally in crypt bottoms. In double labeling experiments, the stretch of crypt BM corresponding to the proliferative cell compartment was found to be devoid of both Ln-alpha3 and Ln-alpha2 chains. Double labeling for Ln-5 and proliferating cell nuclear antigen also showed an abrupt onset of Ln-5 expression exactly at the upper edge of the proliferative cell compartment. Type VII collagen was negligible in duodenum and showed a rising duodenal-ileal gradient localizing to villar BMs. Double labeling for Ln-5 and Type VII collagen, however, indicated only partial co-distribution in the intestine. Electron microscopy of ileum revealed both anchoring filaments and anchoring fibrils but no hemidesmosomal plaques. Our results demonstrate the expression of Ln-5 in BMs outside of stratified epithelia and indicate that Ln-5 in the intestine is associated with the compartment of migrating and differentiating enterocytes. Absence of hemidesmosomes and the presence of other anchoring complex components, such as Ln-5, Type VII collagen, and integrin chains alpha3, alpha6, and beta4, suggests unique properties for epithelial cell attachment in the intestine.

Expression of type IV collagen α1(IV)–α6(IV) polypeptides in normal and developing human kidney and in renal cell carcinomas and oncocytomas

Type IV collagen trimer is a major component of basement membranes (BMs). It is composed of polypeptides named α1(IV)–α6(IV) chains. Chains α1,2(IV) are widely expressed in BMs while α3(IV)–α6(IV) are more restricted in human tissues. We have now studied by immunohistochemical means the distribution of collagen IV chains in fetal and adult human kidney, in oncocytomas, in renal cell carcinomas (RCCs) and their metastases and in experimental xenografts of human tumors. α1,2(IV) chains were found in all BMs of fetal and adult kidney as well as of renal tumors, while α3(IV)–α6(IV) chains were found in BMs of distal segments of developing and mature tubules. α3(IV)–α5(IV) chains were seen also in BMs of developing fetal glomeruli after the capillary loop stage. Most of the RCCs and their metastases showed occasional expression of α3(IV)–α6(IV) with papillary variants showing only expression of α5(IV) chain. There was a distinct expression of α3(IV)–α5(IV) chains in BMs of 3 oncocytomas. In 2 of them a variable expression of the α6(IV) chain was seen. In 3 of 4 xenografts, immunoreactivity for human‐specific monoclonal antibody (MAb) for α1,2(IV) was seen in the BM‐like structures. No α3–α6(IV) was seen in any of the xenografts, while polyclonal antiserum for type IV collagen presented immunoreactivity in BMs of all xenografts. Our results show that oncocytomas and most of the RCCs express scarce variants of type IV collagen containing α3(IV)–α6(IV) chains. In experimental xenograft tumors, both implanted RCC cells and host stromal cells have a capacity to produce type IV collagen. Int. J. Cancer 72:43–49, 1997.

Laminins, tenascin and type VII collagen in colorectal mucosa

SummaryThe distribution of different laminin polypeptides, type VII collagen and tenascin has been studied in adult and foetal colorectal mucosa by using the indirect immunofluorescence technique. Immunoreactivity for laminin α1 chain was located to basement membranes of epithelia, muscularis mucosae, and blood vessels, respectively in different segments of adult colon and rectum. Laminin β1 and γ1 chains were additionally expressed in lamina propria. Laminin α2 chain was also found in lamina propria around the pericyptal fibrollasts. Immunoreactivity for laminin β2 chain was restricted to basement membranes in the muscularis mucosae and arteries. Laminin α3 and β3 chains, suggestive for laminin-5, were confined especially to surface epithelial basement membranes. Immunoreactivity for type VII collagen was confined to basement membrane of surface epithelium in a punctate manner, while that for tenascin was seen slightly more broadly in the basement membrane zone and also in the muscular layer. The distribution of laminin chains in 16-week-foetal colon mostly resembled that of corresponding adult tissue, although immunoreactivities for laminin α2 and β2 chains were lacking. Type VII collagen and the high molecular weight isoform of tenascin also absent from the foetal colon. The results show that the basement membrane of the surface epithelium of colon and rectum express the components of epithelial adhesion complex, laminin-5 (α3-β3-γ2) and type VII collagen, resembling in this respect small intestine and stomach while laminin-2 (α2-β1-γ1) appears to be associated with pericryptal fibroblasts, and laminin-1 (α1-β1-γ1) widely in most basement membranes.

Focal adhesion kinase pp125FAK is associated with both intercellular junctions and matrix adhesion sites in vivo

Previous studies have characterized pp125FAK as a focal adhesion (FA)-associated non-receptor tyrosine kinase. However, there are few data available on the expression and localization of this kinase in tissues. In this study we show that in human tissues the highest expression of pp125FAK is found in some developing epithelia, where pp125FAK is associated with either intercellular junctions or with sites of adhesion to the basement membrane, whereas the same adult tissues show only a faint reactivity. Connective tissue cells do not show any reactivity for pp125FAK in vivo, but developing arterial smooth muscle expresses pp125FAK at high levels. The expression pattern in malignant tissues is variable, but most carcinomas do not express this kinase. In primary cultures of human amnion epithelial cells pp125FAK first becomes associated with the polarized adhesion lamellae, but is subsequently translocated to the forming adherens junctions (AJs). Later upon culturing pp125FAK becomes associated with prominent FAs, as in cultured cell lines. Taken together, our results suggest that the association of pp125FAK with FAs in cultured cells is principally due to a process of adaptation, whereas in vivo pp125FAK mainly functions as a regulatory component of intercellular AJs and cell-matrix adhesions of developing epithelia and also in developing arterial smooth muscle.

Expression of laminin in renal‐cell carcinomas, renal‐cell carcinoma cell lines and xenografts in nude mice

We studied the expression of laminin (Ln) chains (α1–α3, β1–β3, γ1) in human renal‐cell carcinomas (RCC), papillary renal neoplasms (PRN) and oncocytomas, in RCC cell lines and their xenografts. In RCCs the basement membranes (BM) showed immunoreactivity for chains of Ln‐1 (α1‐β1‐γ1). Only in well‐differentiated RCCs could vessel BMs be distinguished from those of carcinoma cell islets. RCCs and oncocytomas also exhibited an abundant immunoreactivity for Ln β2 chain in both vessel and tumor cell BMs, while Ln α2 chain was not seen in any renal tumors. In distinction from RCCs, PRNs presented a strong BM immunoreactivity for Ln α3 and β3 chains and for Ln‐5, as well as lack of Ln β2 chain. A more variable reactivity for Ln‐5 was seen in oncocytomas. As PRNs and oncocytomas have been suggested to originate from collecting ducts, it is notable that in normal human kidney, we could detect immunoreactivity for Ln‐5 and its chains only in BM of the tubules of the loop of Henle. In immunoprecipitation experiments, an abundant production of Ln‐1, but not of Ln‐5, was seen in cultured RCC cells, while in xenografts of the same cells BM‐confined immunoreactivity for both Ln‐1 and Ln‐5 was seen. Ln β2 chain was produced by 2 of the 4 RCC cell lines in culture but was found only in 1 of the xenografted tumors.

Laminin chains in the basement membranes of human thymus

SummaryIn recent studies, the α2 chain of laminin (Ln) has been suggested to be the only laminin α chain expressed in mouse and human thymus. We have now used chain-specific monoclonal antibodies and indirect immunofluorescence microscopy to study the expression of laminin chains in samples of foetal and 6-year-old human thymus. The subepithelial basement membrane of the capsule of foetal 16- to 18-week thymus presented a bright immunoreactivity for Ln α1, α3, β1, β3 and γ1 chains but not for α2 chain, suggesting the expression of laminins-1 and-5. Most cortical and medullary epithelial cells, including Hassalls corpuscles, however, lacked laminin immunoreactivity. Immunoreactivity for Ln β2 chain was only seen in basal laminae of larger blood vessels. In thymic specimens from 6-year-old children, immunoreactivity for the laminin α1, α3, β1, β3 and γ1 chains was invariably found in subepithelial basement membrane of the capsule and that for laminin α2 chain was now also distinct but more heterogeneous. Furthermore, the thymic subepithelial basement membrane of the capsule at all stages showed immunore-activity for collagen type VII, forming the anchoring fibres in epithelial basement membranes. The subcapsular thymic epithelium also showed immunoreactivity for the BP 230 antigen and β4 integrin subunit, both components of hemidesmosomes. The present results show that the thymic subepithelial basement membrane of the capsule presents properties which are commonly seen in stratified and combined epithelia, and are compatible with suggestions of the antigenic similarity of thymic epithelial cells and keratinocytes.

Renal cell carcinomas and pancreatic adenocarcinomas produce nidogen in vitro and in vivo

The production of nidogen by four renal cell carcinoma (RCC) and three pancreatic adenocarcinoma (PAc) cell lines has been studied in cell culture and in xenografted tumours in nude mice. In RCC cells, immunoreactivity for nidogen was seen only after exposure to monensin to induce cytoplasmic accumulation of secretory proteins. In PAc cells, immunoreaction was also detectable in control cells. Immunoblotting of control and monensin‐exposed cells and immunoprecipitation of culture media of radioactively labelled cells demonstrated the production of nidogen polypeptide of Mr ca. 150000 by six of the seven cell lines. Basement membranes (BMs) and stroma of the xenografted tumours derived from these six cell lines demonstrated immunoreactivity for both human and mouse nidogen, as revealed with species‐specific antibodies. The ability of the cells to produce nidogen in vitro and deposit in vivo was positively correlated with high histological grade of the xenografted tumours, although the small number of cell lines studied calls for further studies to confirm this. The distribution of nidogen in human RCC and PAc specimens was also studied by immunohistochemistry. There was strong immunoreactivity for nidogen in tumour stroma, BM of carcinoma cell nests, and endothelial basal lamina, but no conclusions could be drawn regarding histological grade and immunostaining patterns, because stromal production could not be ruled out. The results show that nidogen is produced by human carcinoma cells both in vitro and in vivo. Copyright