Oncofetal fibronectins in oral carcinomas:

Preclinical Assessment of the Effectiveness of Magnetic Resonance Molecular Imaging of Extradomain-B Fibronectin for Detection and Characterization of Oral Cancer

PURPOSE

Oral squamous cell carcinoma (OSCC) has not seen a substantial improvement in patient survival despite therapeutic advances, making accurate detection and characterization of the disease a clinical priority. Here, we aim to demonstrate the effectiveness of magnetic resonance imaging (MRI) with the targeted MRI contrast agent MT218 specific to extradomain-B fibronectin (EDB-FN) in the tumor microenvironment for detection and characterization of aggressive OSCC tumors.

PROCEDURES

EDB-FN expression was evaluated in human normal tongue and OSCC specimens with immunohistochemistry. Invasiveness of human CAL27, HSC3, and SCC4 OSCC cells was analyzed with spheroid formation and transwell assays. EDB-FN expression in the cells was analyzed with semiquantitative real-time PCR, western blotting, and a peptide binding study with confocal microscopy. Contrast-enhanced MRI with MT218 was performed on subcutaneous OSCC mouse models at a dose of 0.04 mmol/kg, using gadoteridol (0.1 mmol/kg) as a control.

RESULTS

Strong EDB-FN expression was observed in human untreated primary and metastatic OSCC, reduced expression in treated OSCC, and little expression in normal tongue tissue. SCC4 and HSC3 cell lines demonstrated high invasive potential with high and moderate-EDB-FN expression, respectively, while CAL27 showed little invasive potential and low-EDB-FN expression. In T₁-weighted MRI, MT218 produced differential contrast enhancement in the subcutaneous tumor models in correlation with EDB-FN expression in the cancer cells. Enhancement in the high-EDB-FN tumors was greater with MT218 at 0.04 mmol/kg than gadoteridol at 0.1 mmol/kg.

CONCLUSIONS

The results suggest EDB-FN has strong potential as an imageable biomarker for aggressive OSCC. MRMI results demonstrate the effectiveness of MT218 and the potential for differential diagnostic imaging of oral cancer for improving the management of the disease.

Sweet and sour: the impact of differential glycosylation in cancer cells undergoing epithelial-mesenchymal transition

Glycosylation changes are a feature of disease states. One clear example is cancer cells, which commonly express glycans at atypical levels or with different structural attributes than those found in normal cells. Epithelial–mesenchymal transition (EMT) was initially recognized as an important step for morphogenesis during embryonic development, and is now shown to be one of the key steps promoting tumor metastasis. Cancer cells undergoing EMT are characterized by significant changes in glycosylation of the extracellular matrix (ECM) components and cell-surface glycoconjugates. Current scientific methodology enables all hallmarks of EMT to be monitored in vitro and this experimental model has been extensively used in oncology research during the last 10 years. Several studies have shown that cell-surface carbohydrates attached to proteins through the amino acids, serine, or threonine (O-glycans), are involved in tumor progression and metastasis, however, the impact of O-glycans on EMT is poorly understood. Recent studies have demonstrated that transforming growth factor-beta (TGF-β), a known EMT inducer, has the ability to promote the up-regulation of a site-specific O-glycosylation in the IIICS domain of human oncofetal fibronectin, a major ECM component expressed by cancer cells and embryonic tissues. Armed with the knowledge that cell-surface glycoconjugates play a major role in the maintenance of cell homeostasis and that EMT is closely associated with glycosylation changes, we may benefit from understanding how unusual glycans can govern the molecular pathways associated with cancer progression. This review initially focuses on some well-known changes found in O-glycans expressed by cancer cells, and then discusses how these alterations may modulate the EMT process.

Insidious changes in stromal matrix fuel cancer progression

Reciprocal interactions between tumor and stromal cells propel cancer progression and metastasis. A complete understanding of the complex contributions of the tumor stroma to cancer progression necessitates a careful examination of the extracellular matrix (ECM), which is largely synthesized and modulated by cancer-associated fibroblasts. This structurally supportive meshwork serves as a signaling scaffold for a myriad of biologic processes and responses favoring tumor progression. The ECM is a repository for growth factors and cytokines that promote tumor growth, proliferation, and metastasis through diverse interactions with soluble and insoluble ECM components. Growth factors activated by proteases are involved in the initiation of cell signaling pathways essential to invasion and survival. Various transmembrane proteins produced by the cancer stroma bind the collagen and fibronectin-rich matrix to induce proliferation, adhesion, and migration of cancer cells, as well as protease activation. Integrins are critical liaisons between tumor cells and the surrounding stroma, and with their mechano-sensing ability, induce cell signaling pathways associated with contractility and migration. Proteoglycans also bind and interact with various matrix proteins in the tumor microenvironment to promote cancer progression. Together, these components function to mediate cross-talk between tumor cells and fibroblasts ultimately to promote tumor survival and metastasis. These stromal factors, which may be expressed differentially according to cancer stage, have prognostic utility and potential. This review examines changes in the ECM of cancer-associated fibroblasts induced through carcinogenesis, and the impact of these changes on cancer progression. The implication is that cancer progression, even in epithelial cancers, may be based in large part on changes in signaling from cancer-associated stromal cells. These changes may provide early prognostic indicators to further stratify patients during treatment or alter the timing of their follow-up visits and observations.

When tissue antigens and antibodies get along: revisiting the technical aspects of immunohistochemistry--the red, brown, and blue technique

Once focused mainly on the characterization of neoplasms, immunohistochemistry (IHC) today is used in the investigation of a broad range of disease processes with applications in diagnosis, prognostication, therapeutic decisions to tailor treatment to an individual patient, and investigations into the pathogenesis of disease. This review addresses the technical aspects of immunohistochemistry (and, to a lesser extent, immunocytochemistry) with attention to the antigen-antibody reaction, optimal fixation techniques, tissue processing considerations, antigen retrieval methods, detection systems, selection and use of an autostainer, standardization and validation of IHC tests, preparation of proper tissue and reagent controls, tissue microarrays and other high-throughput systems, quality assurance/quality control measures, interpretation of the IHC reaction, and reporting of results. It is now more important than ever, with these sophisticated applications, to standardize the entire IHC process from tissue collection through interpretation and reporting to minimize variability among laboratories and to facilitate quantification and interlaboratory comparison of IHC results.

Influences of tumor stroma on the malignant phenotype

BACKGROUND

The microenvironment makes a significant contribution to the progression of oral carcinomas. Many different stromal events, such as vascularization, fibroblast activation, myofibroblast differentiation, and the presence of specific stromal proteins, such as proteolytic enzymes, fibronectin and laminin 5 are all characteristics of the tumor stroma. Less is, however, known of the significance of the biophysical properties of the tumor stroma. The purpose of the present study was to investigate how cellular and mechanical properties of the three-dimensional collagen matrix may influence cell proliferation and invasion of oral carcinoma cell lines.

METHOD

Oral cancer cells were cultured in an organotypic culture system on different collagen concentrations, and invasion was measured. Furthermore, the presence of cancer associated proteins such as glycosylated oncofetal fibronectin and laminin 5 was investigated.

RESULTS

We found that expression of glycosylated oncofetal fibronectin was increased in the invasive phenotype of oral carcinoma cell lines. Furthermore we demonstrated that certain concentrations of collagen in the connective tissue equivalent, appears to stimulate invasiveness of oral carcinoma cells.

IIICS de novo glycosylated fibronectin as a marker for invasiveness in urothelial carcinoma of the urinary bladder (UBC)

PURPOSE

The urothelial carcinoma is the most frequent malignancy of the urinary bladder (UBC). The transition into invasive growth is accompanied by several histological changes including an oncofoetal reorganization of the extracellular matrix. Recently, the occurrence of oncofoetal fibronectin with an O-linked glycosylation in the IIICS region (oncf Fn) was shown to be present in urine from UBC patients and was recommended as a tumour marker. Until now there are no data available regarding the source and distribution of oncf Fn in UBC and its value for the assessment of invasiveness.

METHODS

oncf Fn was analysed in noninvasive and invasive UBC using immunohistochemistry and western blot. Additionally, the mRNA expression of the IIICS splicing region was evaluated by quantitative real time RT-PCR.

RESULTS

Immunohistochemical results reveal a highly significant correlation of oncf Fn to invasiveness. Papillary tumours regularly show no positivity. In western blot, invasive UBC show a strongly increased amount of the 250 kDa oncf Fn. Additionally, several smaller bands could be shown suggesting a proteolytic processing of Fn. The mRNA of the IIICS region shows a 21.5-fold increase in invasive UBC compared with noninvasive carcinomas.

CONCLUSIONS

In summary, immunohistochemistry of oncf Fn is a valuable histological marker for invasiveness of urothelial carcinoma of the urinary bladder. The restricted and invasion-associated tissue distribution of immunoreactivity enables to monitor the recurrence of invasive UBC by a quantitative evaluation of IIICS O-linked glycosylated Fn in urine.

Structural insights into fibronectin type III domain-mediated signaling

The alternatively spliced type III extradomain B (EIIIB) of fibronectin (FN) is expressed only during embryogenesis, wound healing and tumorigenesis. The biological function of this domain is unclear. We describe here the first crystal structure of the interface between alternatively spliced EIIIB and its adjacent FN type III domain 8 (FN B-8). The opened CC' loop of EIIIB, and the rotation and tilt of EIIIB allow good access to the FG loop of FN-8, which is normally hindered by the CC' loop of FN-7. In addition, the AGEGIP sequence of the CC'' loop of EIIIB replaces the NGQQGN sequence of the CC' loop of FN-7. Finally, the CC'' loop of EIIIB forms an acidic groove with FN-8. These structural findings warrant future studies directed at identifying potential binding partners for FN B-8 interface, linking EIIIB to skeletal and cartilaginous development, wound healing, and tumorigenesis, respectively.

Molecular basis for the presence of glycosylated onco-foetal fibronectin in oral carcinomas: the production of glycosylated onco-foetal fibronectin by carcinoma cells

Glycosylated onco-foetal fibronectin (GOF) deposited in the stroma of oral squamous cell carcinomas correlates with survival. One of the two polypeptide GalNAc-transferases, GalNAc-T3 or GalNAc-T6, is required for the biosynthesis of GOF by the initiation of a unique O-glycan in the alternative spliced IIICS region. Using cell culture experiments, immunohistochemical staining of primary tissue, and RT-PCR of tumour cells isolated by laser capture techniques we have examined the molecular basis for the production of GOF in oral carcinomas. Immuno-histochemical investigation confirmed the stromal deposition of GOF in oral carcinomas. However, neither GalNAc-T3 nor GalNAc-T6 could be detected in stromal fibroblasts. In contrast both transferases were present in the oral squamous carcinoma cells, suggesting that GOF is produced by the oral cancer cells and not only the stromal cells. RT-PCR analysis of RNA isolated from carcinoma cells provided further support for this conclusion by demonstrating in-splicing of the alternative spliced IIICS domain in GOF.

Technical aspects of immunohistochemistry

Immunohistochemistry is an integral technique in many veterinary laboratories for diagnostic and research purposes. In the last decade, the ability to detect antigens (Ags) in tissue sections has improved dramatically, mainly by countering the deleterious effects of formaldehyde with antigen retrieval (AR) and increasing sensitivity of the detection systems. In this review, I address these topics and provide an overview of technical aspects of immunohistochemistry, including those related to antibodies (Abs) and Ags, fixation, AR, detection methods, background, and troubleshooting. Microarray technology and the use of rabbit monoclonal Abs in immunohistochemistry are also discussed.

EB-D fibronectin expression in squamous cell carcinoma of the head and neck

ED-B fibronectin (ED-B FN), a glycoprotein involved in cell adhesion and migration, is expressed in fetal and neoplastic tissues and absent in their normal counterparts. The aim of this study is to evaluate the expression of this glycoprotein in relation to the histological and clinical data and to determine whether it has a prognostic value in patients with head and neck squamous cell carcinoma (HNSCC). Ninety-five cases were assessed for ED-B FN expression using immunohistochemistry. Positive ED-B FN expression was significantly associated with tumor grade (p=0.06) and primary tumor site (p=0.02). The larynx was the tumor site associated with the least ED-B FN expression. In univariate analysis, there was no association with disease-free survival (p=0.48), but the mean time to progression was clearly shorter in tumors with positive ED-B FN expression than in those with negative expression (6 vs. 11 months). Patients having tumors expressing the ED-B FN had a trend to a significant lower overall survival in the multivariate analysis (p=0.06). Our study showed that ED-B FN expression might have a prognostic value in patients with HNSCC.

Expression of the extra domain B of fibronectin, a marker of angiogenesis, in head and neck tumors

OBJECTIVES/HYPOTHESIS

The extra domain B (ED-B) of fibronectin, a naturally occurring marker of tissue remodeling and angiogenesis, is expressed in the majority of aggressive solid human tumors, whereas it is not detectable in normal vessels and tissues.

STUDY DESIGN

In view of the diagnostic and therapeutic clinical applications of the L19 antibody, which is specific for the ED-B domain of fibronectin, a prospective immunohistochemical analysis of different head and neck tumors was performed.

METHODS

In all, 82 head and neck tissue biopsy specimens were immunohistochemically analyzed using the L19 antibody. They consisted of 53 different malignant tumors, 8 benign tumors, 10 nontumoral lesions, and 11 normal control tissues.

RESULTS

A strong positive staining with the L19 antibody could be observed in 87% of the investigated malignant tumors, in only 38% of the benign tumors, and in 20% of the nontumoral lesions (P <.0001). The extra domain B was completely absent in the normal control tissue samples.

CONCLUSIONS

The results show that ED-B is abundantly expressed around the neovasculature and in the stroma of the majority of malignant tumors of the head and neck but is undetectable in normal tissues. The ED-B domain of fibronectin is a good-quality tumor-stroma-associated antigen that warrants clinical trials with antibody-based pharmaceuticals, including immunoscintigraphic investigations and radioimmunoguided surgery with the radiolabeled L19 antibody.

Oncofetal fibronectin and oral squamous cell carcinoma

Fibronectin is a cell matrix glycoprotein, which exists as a number of isoforms that are often found within the cell matrix that surrounds tumours. Collectively these tumour-associated isomers of fibronectin have been termed oncofetal fibronectin (OFFN). We looked for expression of OFFN within oral squamous cell carcinomas (SCC) and related its presence to prognosis. The investigation used a monoclonal antibody (MoAb 5C10) to the glycosylated variant of OFFN, and 100 archival specimens of oral SSC. Immunostaining for OFFN was intense in the adjacent stroma of 43 squamous carcinomas, weak in 27 and absent in 30. Cervical metastases were found in 17/27 (63%) specimens that stained intensely, 6/17 (35%) that stained weakly and 3/13 (23%) that did not stain. Of the 21 cases which had extracapsular lymph node spread, 81% were from those that stained intensely, 19% from those that stained weakly and none from those that did not stain for OFFN expression. Also, 21/44 patients (49%) died in group with intense OFFN staining, 6/26 (23%) in the group with weak staining and 3/30 (10%) in the group that did not stain. The presence of OFFN glycoprotein in oral SCC as evaluated by immunostaining with MoAb 5C10 correlates strongly with the presence of metastatic lymph node involvement, particularly extracapsular involvement, and mortality. We therefore suggest that the degree of expression of OFFN in tumours is a valuable prognostic indicator.

Integrins alpha5beta1, alphavbeta1, and alphavbeta6 collaborate in squamous carcinoma cell spreading and migration on fibronectin

The expression of alphavbeta6 fibronectin/tenascin receptor integrin is induced in malignant transformation of oral epithelium. In this study, we demonstrate the contribution of alphavbeta6 as well as other fibronectin receptor integrins in squamous cell carcinoma (SCC) cell adhesion and migration. Of 11 SCC cell lines isolated from the head and neck area, 8 (73%) expressed alphavbeta6 integrin on the cell surface. Three cell lines were chosen for further functional experiments: 1 with relatively high, 1 with moderate, and 1 with minimal surface expression of alphavbeta6 integrin. In addition to alphavbeta6, all 3 cell lines expressed alpha5beta1 and alphavbeta1 fibronectin receptor integrins. Function-blocking experiments with inhibitory anti-integrin antibodies showed that all these three integrins were functional in SCC cell spreading on fibronectin. Integrin alphavbeta6, however, was not used as a primary but as an alternative fibronectin receptor by SCC cells, as the inhibitory anti-beta6 integrin antibody alone had no effect on spreading. In migration, however, alphavbeta6, alpha5beta1, and alphavbeta1 integrins were all used in cooperation. The presence of alphavbeta1 integrin in SCC cells is a novel finding as is its contribution to SCC cell migration. When one or two of these three receptors were blocked, the cells demonstrated an adaptive ability to remain migratory using integrins that were not targeted by antibodies. Utilization of a combination of receptors of different affinities may be beneficial for SCC cell migration versatility.

Distribution of laminin and fibronectin isoforms in oral mucosa and oral squamous cell carcinoma

The expression of laminin and fibronectin isoforms varies with cellular maturation and differentiation and these differences may well influence cellular processes such as adhesion and motility. The basement membrane (BM) of fetal oral squamous epithelium contains the laminin chains, alpha2, alpha3, alpha5, beta1, beta2, beta3, gamma1 and gamma2. The BM of adult normal oral squamous epithelium comprises the laminin chains, alpha3, alpha5, beta1, beta3, gamma1 and gamma2. A re-expression of the laminin alpha2 and beta2 chains could be shown in adult hyperproliferative, dysplastic and carcinomatous lesions. In dysplasia and oral squamous cell carcinoma (OSCC), multifocal breaks of the BM are present as indicated by laminin chain antibodies. These breaks correlate to malignancy grade in their extent. Moreover, in the invasion front the alpha3 and gamma2 chain of laminin-5 can immunohistochemically be found outside the BM within the cytoplasm of budding carcinoma cells and in the adjacent stroma. The correlation between the morphological pattern of invasive tumour clusters and a laminin-5 immunostaining in the adjacent stroma may suggest, first, that a laminin-5 deposition outside the BM is an immunohistochemical marker for invasion and second, that OSCC invasion is guided by the laminin-5 matrix. Expression of oncofetal fibronectins (IIICS de novo glycosylated fibronectin and ED-B fibronectin) could be demonstrated throughout the stromal compartment. However, the ED-B fibronectin synthesizing cells (RNA/RNA in situ hybridization) are confined to small stroma areas and to single stroma and inflammatory cells in the invasion front. A correlation of the number of ED-B fibronectin synthesizing cells to malignancy grade could not be seen. ED-B fibronectin mRNA-positive cells seem to be concentrated in areas of fibrous stroma recruitment with a linear alignment of stromal fibro-/myofibroblasts (desmoplasia). Double staining experiments (ED-B fibronectin in situ hybridization and alpha-smooth muscle actin immunohistochemistry) indicated that the stroma myofibroblasts are a preferential source of ED-B fibronectin. In conclusion, in OSCC, a fetal extracellular matrix conversion is demonstrable. Tumour cells (laminin alpha2 and beta2 chain) and recruited stromal myofibroblasts (oncofetal ED-B fibronectin) contribute to the fetal extracellular matrix milieu.

Cloning and characterization of a close homologue of human UDP-N-acetyl-alpha-D-galactosamine:Polypeptide N-acetylgalactosaminyltransferase-T3, designated GalNAc-T6. Evidence for genetic but not functional redundancy

The UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase, designated GalNAc-T3, exhibits unique functions. Specific acceptor substrates are used by GalNAc-T3 and not by other GalNAc-transferases. The expression pattern of GalNAc-T3 is restricted, and loss of expression is a characteristic feature of poorly differentiated pancreatic tumors. In the present study, a sixth human UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase, designated GalNAc-T6, with high similarity to GalNAc-T3, was characterized. GalNAc-T6 exhibited high sequence similarity to GalNAc-T3 throughout the coding region, in contrast to the limited similarity that exists between homologous glycosyltransferase genes, which is usually restricted to the putative catalytic domain. The genomic organizations of GALNT3 and GALNT6 are identical with the coding regions placed in 10 exons, but the genes are localized differently at 2q31 and 12q13, respectively. Acceptor substrate specificities of GalNAc-T3 and -T6 were similar and different from other GalNAc-transferases. Northern analysis revealed distinct expression patterns, which were confirmed by immunocytology using monoclonal antibodies. In contrast to GalNAc-T3, GalNAc-T6 was expressed in WI38 fibroblast cells, indicating that GalNAc-T6 represents a candidate for synthesis of oncofetal fibronectin. The results demonstrate the existence of genetic redundancy of a polypeptide GalNAc-transferase that does not provide full functional redundancy.

Blood-group-related carbohydrates are expressed in organotypic cultures of human skin and oral mucosa

Cellular maturation and migration are usually associated with changes in cell-surface carbohydrates, but the relationship between these changes and cell behaviour is at present largely unknown. To investigate whether an organotypic culture system can be used as an in vitro model to study the function of cell-surface carbohydrates, we established organotypic cultures of skin and buccal mucosa. In these cultures, keratinocytes are grown at the air-liquid interface on a supporting matrix consisting of homologous fibroblasts embedded in a collagen type I gel. We examined the expression of blood-group-related carbohydrate structures, including Lewis x, sialylated Lewis x, Lewis y, Lewis a, and Lewis b, on the surface of epithelial cells in the cultures. We compared the results with the expression of more well-established markers, including cytokeratins, integrins, bullous pemphigoid antigen and laminin, in the same cultures. The organotypic skin and oral mucosa cultures showed a histological differentiation pattern analogous to that of normal skin and buccal mucosa, and a tissue-specific expression of carbohydrate structures and cytokeratins. However, both types of organotypic cultures also expressed markers which are normally seen during wound healing, including Lewis y, cytokeratin 16, and cytokeratin 19. We conclude that the organotypic cultures of oral mucosa and skin are suitable models for future studies of the function of cell-surface carbohydrates, although the expression of wound healing markers has to be taken into consideration.

Measurement of the expression of oncofetal fibronectin mRNA in thyroid carcinomas by competitive reverse transcription-polymerase chain reaction

Abundant expression of oncofetal fibronectin mRNA has been observed in thyroid papillary and anaplastic carcinomas. In this study, we measured relative expression levels of oncofetal fibronectin mRNA in thyroid cancer tissues by competitive reverse transcription polymerase chain reaction (RT-PCR) using thyroglobulin mRNA as an internal control. By this method, all papillary and anaplastic carcinomas and 3 of 6 follicular carcinomas were distinguished from benign tissues, such as normal thyroid tissues, follicular adenomas, and adenomatous goiters. Furthermore, 2 anaplastic carcinomas were clearly distinguished from differentiated carcinomas. These results suggest the possibility of establishing a more accurate preoperative or postoperative diagnosis of papillary and anaplastic carcinomas by measuring the relative expression level of oncofetal fibronectin to thyroglobulin in thyroid tumors.

An overview of the complexities and subtleties of immunohistochemistry

Immunohistochemistry has the potential to be a powerful research tool. However, immunohistochemical studies are frequently undertaken without regard to the complexities and subtleties of these useful techniques. This review aims to address the problems and limitations that are often encountered, and the procedures that should be considered in both the planning and interpretation of immunohistochemical studies. Particular reference is made to the generation of functionally different protein isoforms from a single gene by alternative splicing and post-translational modifications, primary antibody selection, the effects of tissue manipulation such as fixation and antigen retrieval, the need for appropriate controls and interpretation of staining patterns.

Expression of GLUT1 in stratified squamous epithelia and oral carcinoma from humans and rats

Most cells express facilitative glucose transporters. Four isoforms (GLUT1-4) transporting D-glucose across the plasma membrane show a specific tissue distribution, which is the basis for tissue-specific patterns in glucose metabolism. GLUT1 is expressed at high levels in tissue barriers such as the blood-brain barrier, and this isoform has been suggested as an indicator of such barriers. GLUT1 has been found in basal layers of human epidermis where no such tissue barrier is present. To further clarify these issues, we examined the distribution of GLUT1 and GLUT4 in skin, different types of oral mucosa from rat and man, and a human oral carcinoma by indirect immunofluorescence microscopy. The results showed that GLUT1 was expressed in the basal and parabasal layers of the different stratified squamous epithelia, with some variations between keratinized and non-keratinized subtypes. GLUT1 was also expressed in ductal- and myoepithelial cells of minor salivary glands and perineural sheath located in the lamina propra, and furthermore in the cells of an oral carcinoma. GLUT4 was not expressed in any of the tissues examined. This distribution of GLUT1 does not fit with the idea of GLUT1 as a general indicator of tissue barriers. In contrast, our results support the prevailing, but limited knowledge of glucose metabolism in squamous stratified epithelia, a metabolism believed to depend mostly on glycolysis, especially in the basal layers. High-level expression seemed to be confined to keratinocytes without glycogen stores.

RT-PCR investigation of fibronectin mRNA isoforms in malignant, normal and reactive oral mucosa

This study aimed to establish patterns of cellular fibronectin mRNA splice variants in normal oral mucosa, oral squamous cell carcinoma, oral leukoplakias with and without atypia, and focal reactive overgrowths of oral mucosa. Particular emphasis was placed on evaluation of either the EDA or EDB domains as markers of malignancy. Total RNA was extracted from normal oral mucosa, oral squamous cell carcinoma, oral leukoplakias with and without atypia, reactive epulides, fibroepithelial polyps and denture-related hyperplasia. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to identify different fibronectin transcripts at three splice sites (EDA, EDB and IIICS). All the tissues investigated produced EDA+, EDA-, EDB+ and EDB- splice variants, and this study did not support RT-PCR-based detection of either EDA or EDB domains as markers of malignancy in oral tissues. Variations in IIICS splice patterns were observed, although these were not specific to any lesion group. In particular, there were differences in either the inclusion or omission of the domain coding for the CS-5 binding site for alpha 4 beta 1 integrin, whereas the CS-1 binding site for alpha 4 beta 1 integrin was typically present when additional domains were included at the IIICS splice site. In conclusion, complex patterns of fibronectin splice variant transcripts exist in normal and pathological oral mucosa. This may reflect the multiple biological functions identified for fibronectin proteins, although the significance of different specific fibronectin splice variants has yet to be fully elucidated.

Matrix remodelling in dilated cardiomyopathy entails the occurrence of oncofetal fibronectin molecular variants

OBJECTIVES

To investigate whether disturbance of the cellular homoeostasis and integrity of cardiomyocytes in dilated cardiomyopathy (DCM) is accompanied by alterations in cell-matrix relations as indicated by changes in the deposition of fibronectin (FN) isoforms.

DESIGN

Tissue from a case series of patients with DCM was investigated by immunohistochemistry with antibodies against FN (all variants, clone IST4), ED-A+ FN (clone IST9), ED-B+ FN (clone BC1), and oncofetal glycosylated FN (clone 5C10). The sites of de novo synthesis of FN were demonstrated by means of non-radioactive RNA in situ hybridisation (ISH) with biotinylated FN cDNA fragments as the probe.

SETTING

University hospital.

PATIENTS

Samples from 10 patients with clinical criteria and histological diagnosis of DCM and from 3 individuals with normal hearts.

INTERVENTIONS

Samples were obtained by right ventricular endomyocardial biopsy.

MAIN OUTCOME MEASURE

Distribution of oncofetal FN variants in DCM hearts.

RESULTS

Immunostaining of FN (IST4, all variants) showed a coarse interstitial network in normal and diseased myocardium. ED-A+ FN was deposited as fine interstitial spots in normal myocardium and in DCM samples. Immunostaining for oncofetal glycosylated FN and ED-B+ FN was not seen in normal adult myocardium, whereas myocardium from DCM patients showed focal and delicate staining in the interstitium. RNA ISH showed that these deposits resulted from local FN synthesis.

CONCLUSION

The results accord with de novo expression of oncofetal FN variants in hearts from patients with DCM. The oncofetal FN variants may serve as disease markers in myocardium affected by DCM.

Differential expression of fibronectin splice variants, oncofetal glycosylated fibronectin and laminin isoforms in nodular palmar fibromatosis

The tissue formation process in nodular palmar fibromatosis (Morbus Dupuytren) was investigated by the demonstration of fibronectin splice variants (ED-A and ED-B fibronectin), de novo glycosylated fibronectin and laminin isoforms (A, M, B1, B2, s chains) in association to the proliferative activity (Ki-67 antigen) and the occurrence of myofibroblast phenotype (alpha-smooth muscle actin, desmin). The proliferative noduli of the fibromatosis were characterized by a diffuse immunostaining for alpha-smooth muscle actin, and single cells positive for desmin and the Ki-67 antigen. In contrast to the surrounding aponeurosis as extracellular matrix, components of the whole proliferative noduli were defined: ED-A, ED-B and de novo glycosylated fibronectin, B1 and B2 laminin chain, tenascin and collagen type IV. The demonstration of the A and M laminin chain was restricted to a few cells of the proliferative noduli. S laminin could be visualized in the majority of palmar aponeurotic fibroblasts. As revealed by mRNA, in situ hybridization a de novo synthesis of fibronectin could only be detected within proliferative noduli. There is a positive correlation between the myofibroblast phenotype formation, cellular proliferation and the occurrence of ED-A and ED-B containing fibronectin, as well as de novo glycosylated fibronectin in Dupuytren's disease. The ultrastructural irregularities of myofibroblastic basal lamina and the heterogeneity of the myofibroblast phenotype are equivalent to the variability of laminin isoform immunostaining.

Purification and cDNA cloning of a human UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase

A UDP-GalNAc:polypeptide N-acetylgalactosaminyl-transferase (GalNAc-transferase) from human placenta was purified to apparent homogeneity using a synthetic acceptor peptide as affinity ligand. The purified GalNAc-transferase migrated as a single band with an approximate molecular weight of 52,000 by reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Based on a partial amino acid sequence, the cDNA encoding the transferase was cloned and sequenced from a cDNA library of a human cancer cell line. The cDNA sequence has a 571-amino acid coding region indicating a protein of 64.7 kDa with a type II domain structure. The deduced protein sequence showed significant similarity to a recently cloned bovine polypeptide GalNAc-transferase (Homa, F.L., Hollanders, T., Lehman, D.J., Thomsen, D.R., and Elhammer, A.P. (1993) J. Biol. Chem. 268, 12609-12616). A polymerase chain reaction construct was expressed in insect cells using a baculovirus vector. Northern analysis of eight human tissues differed clearly from that of the bovine GalNAc-transferase. Polymerase chain reaction cloning and sequencing of the human version of the bovine transferase are presented, and 98% similarity at the amino acid level was found. The data suggest that the purified human GalNAc-transferase is a novel member of a family of polypeptide GalNAc-transferases, and a nomenclature GalNAc-T1 and GalNAc-T2 is introduced to distinguish the members.