An antigen associated with mesenchyme in human tumours that cross-reacts with brain glycoprotein

Hyaluronan and hyaluronectin in the nervous system

Hyaluronan was studied in extracts of the nervous system and in situ. Extraction yielded larger amounts at neutral or alkaline pH. Protease digestion enhanced the quantitative results obtained with an indirect enzyme immunological assay. It was shown that HA extracted from brain at neutral pH was bound to a glycoprotein component (hyaluronectin, HN) which is in part free at acid pH. Although HN is not restricted to nervous tissue it is mainly expressed in the central nervous system of adult mammals. Its main form has a molecular mass of 68 kDa and binds in vitro to HA and to HA-derived oligosaccharides down to HA10 with a Kd in the 10(-8) M range. HA-HN complexes were found in human cerebrospinal fluids. The HA concentration in cerebral tissue decreases from the fetus to the adult, whereas the HN concentration increases. HA is not however saturated by HN and still binds HN in vitro. In the rat HA decreases sharply at Days 10-11 after birth. In the rat embryo HA forms an extracellular component of the migration and proliferation areas of the cerebral cortex. In the adult typical locations were at the nodes of Ranvier and in perineuronal structures. HN was found in the same locations but seemed to be associated with a restricted category of neurons. In the cerebellum HA-HN was found mainly in the grey nuclei, the granular layer and around Purkinje cells. Cell bodies were not stained but in the electron microscope HN was seen in the cytoplasm and plasma membrane of the perisynaptic glial cell processes. A hypothesis has been proposed that HA-HN is involved in neural GABAergic transmission.

Hyaluronectin modulation of lung metastasis in nude mice

Hyaluronectin (HN) is a glycoprotein with a high affinity to hyaluronic acid (HA) and known to be a component of the extracellular matrix of tumours. Clinical studies have shown that a low level of HN correlates to tumours with poor prognosis, whereas a high level of HN correlates to tumours with good prognosis. We previously demonstrated in vitro that hyaluronidase activity, which promotes tumour progression and metastatic spread by degradation of HA into angiogenic oligosaccharides, was inhibited or promoted by HN, according to the level of HN-expression. This raises the question of the role played by HN in cancer, and particularly if high and low levels of HN-expression could trigger opposite effects on tumour growth and/or metastatic spread. To address this issue, we used a model of spontaneous lung fluorescent metastases that we characterised previously. We stably transfected the human HN cDNA into fluorescent H460MGFP cells and selected two clones characterised by different levels of HN-expression: HN110 and HN704, with a high and a low level of HN-expression, respectively. In vitro, we demonstrated that HN704 cell migration was significantly increased. Inoculation of clones to nude mice had no significant effect on tumour growth, but clearly revealed opposite effects on metastatic spread: HN110 significantly decreased the number of fluorescent metastases whereas HN704 significantly increased it. We also analysed HN, HA and hyaluronidase contents in sera and tumours. These results demonstrate that HN can play a role as either a suppressor or promoter of metastatic spread.

Localisation and cellular origin of hyaluronectin

Hyaluronectin is an extracellular matrix glycoprotein which specifically binds to hyaluronan. Isoforms of hyaluronectin are present in nervous and mesenchymal tissues but, while the nervous tissue isoform has been characterised in some detail, less is known about the mesenchymal isoform. Although its tissue localisation suggests a role in tumour development, neither its cellular origin nor its exact function are known. In this study we demonstrate hyaluronectin synthesis in fibroblasts and smooth muscle cells in vitro. The pattern of immunolocalisation of hyaluronectin in fibroblasts depended on the cell type, length of time spent by the cells in culture and cell density. Immunoreactivity in sparsely plated migratory cells was seen mainly in a patchy distribution at the attached cell surface and in the migration tracks left by the cells on the subtratum. In stationary cells a more uniform distribution associated with the attached cell surface was observed, while in confluent cultures hyaluronectin immunoreactivity was mainly seen as a network of fibrillar material above the cell. The pattern of staining was distinct from that of other hyaluronan-binding proteins. Immunoprecipitation, using antihyaluronectin antibodies, of the substratum-attached material deposited by human fetal fibroblasts revealed a family of proteins ranging from 22 to 90 kDa, the major protein being of approximately 60 kDa. These results lead us to propose that hyaluronectin plays an important role in cell migration, probably by regulation of hyaluronan distribution and binding.

Isolation and characterisation of a hyaluronan binding protein, hyaluronectin, from human placenta and its colocalisation with hyaluronan

Hyaluronan (HA) is a major component of the extracellular matrix and is known to influence cell behaviour and to play a role in angiogenesis, morphogenesis and tissue remodelling, although little is known concerning the regulation of these effects. Until now its detection in the placenta has been by indirect methods, which has led to conflicting conclusions as to its distribution and hence its role. Hyaluronectin (HN) is one of a group of proteins with HA binding ability which may regulate the effects of HA. Although nervous tissue HN has been partly characterised with regard to its distribution, structure and biochemistry, little is known about the mesenchymal isoform and its distribution in placenta has not previously been reported. Using specific probes we have characterised the distribution of HA and HN in human placental tissue. At all stages of development studied (8, 10, 12, 30 and 38 wk gestation) HA and HN were unequivocally colocalised, being distributed in the extracellular matrix of stromal tissue of placental villi, chorioallantoic membranes and umbilical cord. Particularly strong immunoreactivity was observed in the villous stroma immediately adjacent to fibrinoid depositions at sites of denudation of the trophoblast layer. Extraction and characterisation of the HN from placental villi have revealed 4 major glycoproteins of 47, 52, 57 and 67 kDa, this being a different pattern and smaller molecular range than observed for the nervous tissue form. This is the first direct demonstration of the presence of HA and HN in the placenta and identifies an abundant new source of mesenchymal HN. The functions of mesenchymal HN are unknown but may include ion exchange, immunosuppression and regulation of the effects of HA in such roles as maintenance of tissue architecture, cell migration and angiogenesis.

Hyaluronan (hyaluronic acid) and hyaluronectin in the extracellular matrix of human breast carcinomas: comparison between invasive and non-invasive areas

We performed quantitative determination of the distribution of hyaluronan (hyaluronic acid, HA) and the HA-binding protein, hyaluronectin (HN), 2 components of the extracellular matrix of tumor desmoplasia, within 71 human breast carcinomas. Results showed that HA and HN were more elevated in tumoral than in non-tumoral adjacent tissue, and that the peripheral invasive area of tumors contained increased levels of HA and HN as compared with the central non-invasive area (p less than 10(-3) and p less than 10(-5) respectively). HN and HA levels of 61 ductal carcinomas were related to the histological grade of tumors; no significant difference was found between grades for HA; HN was found to be significantly lower in grade III than in grade II tumors (p less than 0.01). HA and HN rates were correlated in grade I and grade II tumors and were not correlated in grade III. Mean percentage of HA saturation level by HN for whole tumors was found to be less than 4%, indicating that HA is essentially free of proteins and could be used as a target for cancer diagnosis or therapy.

Differential expression of the fibronectin isoform containing the ED-B oncofetal domain in normal human fibroblast cell lines originating from different tissues

Fibronectin (FN) polymorphism is due both to alternative splicing of three sequences (ED-A, ED-B, and IIICS) of the primary transcript and to post-translational modifications. The FN isoform containing the ED-B sequence (B-FN), while having an extremely restricted distribution in normal adult tissues, has a high expression in fetal and tumor tissues. On a panel of non-fetal skin, fetal skin, and fetal lung fibroblast cell lines we have studied, through S1-nuclease protection analysis, the expression of the ED-B containing FN mRNA as well as the expression of the ED-B containing FN isoform through immunoblotting and immunofluorescence techniques, using domain specific monoclonal antibodies. The results show that the expression of B-FN in the different fibroblast cell lines has an extremely great variability depending on the developmental stage of the donor and on the tissue of origin. Moreover, we found that SV-40-transformed fibroblasts present a higher expression of B-FN mRNA with respect to their normal counterparts. An increase in the relative amount of the B-FN isoform in normal human fibroblasts was also obtained by treatment with transforming growth factor-beta.

Characterization of a hyaluronic acid-binding protein from sheep brain comparison with human brain hyaluronectin

1. A hyaluronic acid (HA)-binding glycoprotein from sheep brain was characterized. 2. The specific affinity for HA was shown in vitro by high performance liquid chromatography, polyacrylamide gel electrophoresis and ELISA methods. 3. The KD for high molecular weight HA was 5.4 10(-9) M at 37 degrees C and lower than 10(-10) M at 4 degrees C. 4. No link protein was found and HA molecules could bind up to 10 times their weight of the glycoprotein. 5. The specific site for interaction was the HA-derived decasaccharide HA10. 6. The protein is composed of one polypeptidic chain. Tryptophan and lysine play a prominent role in the conformation of the binding site to HA. 7. Enzyme analysis indicated that the protein different forms are due to differences in glycosylation and that N- and O-linkages coexist in the molecules. 8. Immunohistochemistry localized the glycoprotein at the nodes of Ranvier and at the periphery of neurons. The perineuronal labeling was seen around all neurons studied in the cerebellum whereas it was almost undetectable in the cerebral hemispheres. 9. HA is not saturated by hyaluronectin (HN) in the sheep nervous system. 10. The glycoprotein is largely similar to human brain HN, and different from the hyaluronate-binding protein characterized in the cartilage.

The extracellular matrix of the central and peripheral nervous systems: structure and function

The extracellular matrix (ECM) is the naturally occurring substrate upon which cells migrate, proliferate, and differentiate. The ECM functions as a biological adhesive that maintains the normal cytoarchitecture of different tissues and defines the key spatial relationships among dissimilar cell types. A loss of coordination and an alteration in the interactions between mesenchymal cells and epithelial cells separated by an ECM are thought to be fundamental steps in the development and progression of cancer. Although a substantial body of knowledge has been accumulated concerning the role of the ECM in most other tissues, much less is known of the structure and function of the ECM in the nervous system. Recent experiments in mammalian systems have shown that an increased knowledge of the ECM in the nervous system can lead to a better understanding of complex neurobiological processes under developmental, normal, and pathological conditions. This review focuses on the structure and function of the ECM in the peripheral and central nervous systems and on the importance of ECM macromolecules in axonal regeneration, cerebral edema, and cerebral neoplasia.

Interaction of hyaluronectin with hyaluronic acid oligosaccharides

Hyaluronic acid was digested by bovine testicular hyaluronidase, and oligomers were fractionated by gel permeation using AcA 202 Ultrogel, an acrylamide-agarose matrix. Oligosaccharides composed of from two to six disaccharide repeating units were isolated. Two nonasaccharides were prepared by enzymatic or chemical modification of the decasaccharide. Oligosaccharides were compared by a competitive inhibition in the enzyme-linked immunosorbent assay for their ability to inhibit the interaction of hyaluronectin (a hyaluronic acid-binding brain glycoprotein) with hyaluronic acid. Among these oligosaccharides, decasaccharides were the smallest fragments that strongly inhibited the interaction. Octasaccharides inhibited with 700-fold lower affinity than decasaccharides. Dodecasaccharides had the same effect as decasaccharides. Nonasaccharides obtained by beta-glucuronidase splitting of decasaccharides inhibited the interaction more than nonasaccharides prepared by an alkaline treatment.

Immunolocalization of monoclonal antibody-defined extracellular matrix antigens in human brain tumors

The extracellular matrix is involved in many aspects of tumor cell biology, including tumor invasion and metastasis. 2A6 and 81C6 are murine monoclonal antibodies that identify glioma-mesenchymal extracellular matrix antigens. The 81C6 antigen is a high molecular weight glycoprotein composed of Mr 230,000 subunits. The expression of 2A6 antigen, 81C6 glycoprotein, fibronectin (FN), and laminin (LN) was examined immunohistochemically in ten malignant gliomas (MG) and four medulloblastomas (MBT). 2A6 and 81C6 were expressed in similar patterns by the neoplastic neuroepithelial cells in 9/10 MG and 1/4 MBT. The staining was typically diffuse and amorphous, without visualization of distinct cell bodies or processes. Less frequently, antigen was detected within tumor cell cytoplasm. In most tumors the staining was greatest in the perivascular regions. In two MG, 2A6 and 81C6 were expressed only by a subpopulation of neoplastic cells. Although intense staining was also associated with hyperplastic vascular and mesenchymal cells, many small and medium size blood vessels stained weakly or not at all. In contrast, FN and LN were expressed uniformly and intensely in the tumor vasculature, but were not expressed by neoplastic neuroepithelial cells. The 2A6 antigen and 81C6 glycoprotein are immunohistochemically distinct from FN and LN. These monoclonal antibody-defined antigens are heterogeneously expressed by neoplastic neuroepithelial cells and hyperplastic vascular-mesenchymal elements in MG and MBT. The 2A6 and 81C6 monoclonal antibodies will be useful reagents in the investigation of the extracellular matrix of malignant neuroepithelial neoplasms.

Expression of hyaluronic acid-binding glycoprotein, hyaluronectin, in the developing rat embryo

Immunological and histological methods have been applied to the developing rat embryo to study the distribution of hyaluronectin (HN, a glycoprotein with hyaluronic acid-binding properties) previously shown to be present in the nervous system and in desmoplasias. HN was absent in the morula and the blastula and was first detected in the mesenchyme bordering the neural tube and somites on Day 10, i.e., at a time when hyaluronic acid is already widely dispersed in the mesenchyme. At this stage HN appeared to be closely associated with the basement membrane around the epithelial structures (somites, notochord, ectoderm) whereas the intercellular areas of mesenchyme were less strongly strained. The delineation of basement membranes decreased progressively, while the accumulation of HN increased in the cell-free areas of mesenchyme, giving a continuous, diffuse pattern. Differentiation of mesenchyme into vertebral cartilage and gut smooth muscle was accompanied by a progressive disappearance of HN. Even after streptomyces hyaluronidase or chondroitinase digestion the antigen was not unmasked in these tissues. The results are in agreement with the few observations made in the human. They suggest that HN could play a role, in association with fibronectin and glycosaminoglycans (hyaluronic acid), in the physiology of the embryonic extracellular matrix. HN appeared at a later stage in the embryonic nervous tissue; its distribution was extracellular in areas where both cell migration and proliferation occur.

Immunofluorescence study of the antigens of the basement membrane and the peritumoral stroma in human colonic adenocarcinomas

Twenty-three colonic adenocarcinomas were studied by immunofluorescence with antisera against components of the basement membrane (type IV collagen, laminin, and heparan sulfate-rich proteoglycan) as well as antisera against antigens of the connective tissue (type III collagen, fibronectin, and hyaluronectin). Marked alterations of the basement membranes were consistently observed on staining with each one of the first three antisera. In contrast, staining of the normal components of connective tissue was in most cases as intense in tumors as in normal colonic mucosa. Hyaluronectin, a marker of peritumoral stroma, was found to be present in 13 out of 16 tumors studied. In six metastatic lymph nodes, tumor foci were sometimes surrounded by antigens of the basement membrane. But these antigens were never found in the cytoplasm of cancer cells.

Localization of hyaluronectin in the nervous system

The localization of hyaluronectin was determined by immunofluorescence and immunoperoxidase methods, in the rat, the sheep and the human. The study of the peripheral nervous system revealed the localization of this protein at the node of Ranvier. It was also present at this site in the central nervous system where the appearance was less characteristic than in the peripheral nervous system. The protein was also observed around about 10% of neurones in all of the regions studied. The subcellular structures labelled could not be precisely defined with the optical microscope.

Antigens of the basement membrane and the peritumoral stroma in human colonic adenocarcinomas: an immunofluorescence study

Twenty colonic adenocarcinomas were studied by immunofluorescence with antisera against components of the basement membrane: type IV collagen, laminin and heparan sulfate-rich proteoglycan, as well as antisera against antigens of the connective tissue: type-III collagen, fibronectin and hyaluronectin. Marked alterations of the basement membranes were consistently observed on staining with each one of the first three antisera. In contrast, staining of the normal components of connective tissue was in most cases as intense as in normal colonic mucosa. Hyaluronectin, a marker of peritumoral stroma, was found to be present in 12 out 15 tumors studied.

Hyaluronectin in normal human skin and in basal cell carcinoma

The localization of hyaluronectin has been studied in normal skin and in basal cell carcinoma. In fetal skin it is abundant in the dermis but absent from the epidermis, and in adult skin it is totally absent except in the hair sheaths and bulbs. In basal cell carcinoma it is abundant only in the stroma reaction. The presence of this protein in mesenchymatous tissues seems to be linked to zones of physiological or neoplastic proliferation.

Immunochemical characterization of the hyaluronic acid-hyaluronectin interaction

The interaction between hyaluronic acid (HA) and hyaluronectin (HN) was analyzed by gel chromatography and by the effects of HA on the immunological precipitation of HN. This interaction led to formation of larger molecules, as shown by gel permeation. No inhibition of immune precipitation occurred in liquid phase after addition of HA, but the precipitates in unstained gels were rendered transparent, giving the appearance of inhibition. However, after staining of the gels the precipitates appeared normal. Moreover, a non-linear decrease of the diffusion rate in antibody-containing gel was observed as a function of HA concentration at HA:HN weight ratios of 0.75 x 10(-3) and higher. A faster movement during electrophoresis, depending on the HA:HN ratio, suppressed the precipitation line when tested by electrosyneresis and produced an increase in migration distance when tested by Laurell's electroimmunoassay. These results show that in the immunochemical detection and quantitation of NH by these techniques consideration should always be given to the amount of HA in the samples.

Organization of actin-containing cables in cultured skin fibroblasts from individuals at high risk of colon cancer

Actin-containing cables were examined by immunofluorescence in cultured skin fibroblasts from individuals genetically prone to colon cancer. The study confirmed our earlier finding of an altered distribution of actin-containing cables in skin fibroblasts of patients with hereditary adenomatosis of the colon and rectum (ACR) (Kopelovich et al., 1977). Abnormalities were also found in about one-half of the asymptomatic offspring at risk for ACR, while a polyposis-free branch of one ACR family showed a normal pattern of actin-containing cables. Persons from colon cancer-prone (CCP) families without polyposis, and normal controls, showed no disturbance in the actin patterns. The results suggest that this phenotypic marker may be useful in identifying ACR gene carriers and in probing cellular controls of carcinogenesis.