Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CD44”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed1998

Metastasis suppression by the standard CD44 isoform does not require the binding of prostate cancer cells to hyaluronate.

Previous studies from this laboratory have demonstrated that down-regulation of the standard CD44 isoform at the mRNA and protein level is associated with the acquisition of high metastatic ability within the Dunning R-3327 system of rat prostate cancers. Additional studies demonstrated that transfection-induced enhanced expression of the standard CD44 isoform suppresses the metastatic ability of the AT3.1 Dunning subline without suppressing tumorigenicity. The standard CD44 isoform is a major cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronate. In this study, an investigation was made to resolve whether the ability of the standard CD44 isoform to suppress metastasis of the AT3.1 prostate cancer cells critically requires enhanced hyaluronate binding. Highly metastatic Dunning AT3.1 rat prostate cancer cells were transfected with expression plasmids encoding either the wild-type or mutant standard CD44 isoform. The mutant standard CD44 isoform construct encoded a protein unable to bind to hyaluronate. Transfectants were isolated and characterized with regard to their level of standard CD44 isoform expression, hyaluronate binding, tumorigenicity, and metastatic ability. Expression of the wild-type standard CD44 isoform increased the hyaluronate binding of prostate cancer cells and suppressed their metastatic ability without suppressing their tumorigenicity. Expression of the mutant CD44 standard isoform did not increase hyaluronate binding; however, it equally suppressed the metastatic ability of the AT3.1 prostate cancer cells. These results demonstrate that the metastasis suppression by the standard CD44 isoform is independent of its ability to bind to hyaluronate.

Animals↗
PubMed2006

Hyaluronan-CD44 promotes phospholipase C-mediated Ca2+ signaling and cisplatin resistance in head and neck cancer.

OBJECTIVE: To investigate whether hyaluronan (HA)-CD44 promotes head and neck squamous cell carcinoma (HNSCC) cisplatin resistance and whether HA-CD44 promotes phospholipase C (PLC)-mediated Ca2+ signaling to alter cisplatin sensitivity in HNSCC. DESIGN: Cell line study. MAIN OUTCOME MEASURES: Tumor cell growth with the chemotherapeutic drug cisplatin was measured in the presence or absence of HA, anti-CD44 antibody plus HA, and other inhibitors of the PLC-mediated Ca2+ signaling pathway. Ca2+ mobilization was measured with fluorescence spectrophotometry using the Ca2+ binding dye Fura/2AM. RESULTS: In the absence of HA, cisplatin inhibited tumor cell growth. The addition of HA, but not HA plus anti-CD44 antibody, resulted in a 5-fold reduced ability of cisplatin to cause HNSCC cell death, suggesting that HA can promote CD44-dependent cisplatin resistance. Fluorescence spectrophotometry demonstrated that HA can promote CD44-dependent Ca2+ mobilization in HNSCC. On the other hand, the presence of U73122, a PLC inhibitor, and 2-aminoethoxydiphenyl borate, an inositol-1,4,5-triphosphate receptor inhibitor, eliminated HA-mediated Ca2+ mobilization and HA-mediated cisplatin resistance in these cell lines. CONCLUSIONS: Our results indicate that HA-CD44 signaling influences cisplatin sensitivity in HNSCC cell growth. In particular, HA-CD44 promotion of PLC-mediated Ca2+ signaling plays a role in cisplatin resistance in HNSCC cells. Perturbation of this HA-CD44-mediated signaling pathway may be a promising target to overcome cisplatin resistance in HNSCC.

Antineoplastic Agents↗
PubMed1998

CD44 and CD44v6 downregulation in clinical prostatic carcinoma: relation to Gleason grade and cytoarchitecture.

BACKGROUND: Altered expression of CD44 has been implicated in tumor progression and metastasis in multiple neoplasms. METHODS: CD44 expression in archival tissues of prostate carcinoma was examined by immunohistochemistry with monoclonal antibodies against core CD44 and the RNA splice variant CD44v6 (v6). RESULTS: Core CD44 expression was reduced in the majority of primary neoplastic foci (n = 94) and loss of expression correlated with increasing Gleason grade. Staining for v6 was absent in most carcinomas and metastases. Expression of core CD44 in pelvic lymph node (n = 27) and bone metastases (n = 21) was significantly reduced. In addition, CD44 expression correlated with cytoarchitecture. Tall columnar tumor cells typically stained positively, yet more rounded cells forming cribiform structures or nests showed reduced expression. All cases of high-grade prostatic intraepithelial neoplasia were positive for core CD44 yet, there was decreased expression in cribiform and micropapillary variants. CONCLUSIONS: The majority of clinically relevant human prostatic carcinomas and metastases downregulate expression of CD44. Additional studies to determine whether CD44 cell surface expression relates to clinical outcome independent of other established clinicopathologic risk factors are warranted.

Alternative Splicing↗
PubMed1997

Common pattern of CD44 isoforms is expressed in morphogenetically active epithelia.

CD44 is a widely distributed cell surface glycoprotein that is expressed as many isoforms arising from a single gene by alternative splicing. An important ligand for the widespread CD44 isoform, CD44s (standard form of CD44), is hyaluronan but ligands for the numerous variant isoforms are not as well characterized. Although it has been documented that CD44 is present at critical sites and stages of morphogenesis of several organs, the nature of the isoforms expressed and their precise localization have not been described. In this study we have determined the identity and distribution of CD44 isoforms expressed during development of several embryonic mouse organs by a combination of immunohistochemistry, in situ hybridization, reverse transcription-polymerase chain reaction, and DNA sequencing. As expected from previous studies, numerous CD44 variants are expressed by actively proliferating and invaginating epithelia at sites of epithelial-mesenchymal interaction, e.g., in the developing tooth, nose and hair follicle. Our results show that most prominent amongst these variants at these sites are CD44(v3-v10), CD44(v4-v10), and CD44(v6-v10), as was also found previously in the apical ectodermal ridge of the developing limb (Yu et al. [1996]). The common pattern of expression of these three particular variants in active epithelia implies that they play an important role in morphogenesis. Also very prominent in morphogenetically active epithelia is CD44s; hyaluronan is uniformly absent from these epithelia and often also from associated mesenchyme with which they interact, supporting the previously documented role of CD44s in endocytic removal of hyaluronan.

Animals↗
PubMed1996

Evaluation of CD44 transcription variants in human digestive tract carcinomas and normal tissues.

We generated DNA probes for CD44 variable region exons 11 (v6) to 14 (v9) and also for intronic sequences and examined the expression of aberrant CD44 transcripts in digestive tract carcinomas, colorectal adenomas and intestinal metaplasia of the stomach. The study used the reverse transcription-polymerase chain reaction/Southern blot technique. Among the probes generated, the CD44 intron 9 probe was the best for distinguishing cancer tissue from normal tissue in adenocarcinomas of the colorectum or stomach. All the colorectal adenocarcinomas revealed overexpression of CD44 variants containing the intron 9 sequence compared with the corresponding normal colorectal mucosa. The overexpression of such abnormal CD44 variants was observed from an early stage in colorectal cancer and did not correlate with nodal or distant metastatic status. In intestinal metaplasia of the stomach, aberrant CD44 transcripts with characteristic 2 or 3 peaks containing intron 9 were observed. On the other hand, in oral and esophageal squamous cell carcinomas and corresponding normal squamous epithelia, overexpression of CD44 variants with variable exons and retained intron 9 sequence was frequently observed in both cancer tissue and corresponding normal mucosa. Examination of the expression of CD44 variants in a screening panel of normal tissues from the whole body revealed that overexpression of transcripts containing exon 11 and 14 as well as of the intron 9 sequence was constantly observed in tissues with squamous epithelia like skin, oral mucosa, esophagus and uterine cervix. Expression of these variants was also found in urinary bladder, respiratory tract, pancreas and salivary glands. Our results overall indicate that detecting the overexpression of abnormal CD44 transcripts, especially ones containing the intron 9 sequence, could be a powerful indicator for the presence of adenocarcinomas in the digestive tract. However, it is not applicable for the diagnosis of malignancies originating from squamous epithelia.

Adenoma↗
PubMed2001

Antisense inhibition of CD44 tailless splice variant in human articular chondrocytes promotes hyaluronan internalization.

OBJECTIVE: To determine whether alternatively spliced variants of CD44, in particular a short, intracellular tail CD44 isoform, are used by articular chondrocytes to modulate the functions of this matrix receptor. METHODS: Normal human articular chondrocytes were cultured with or without interleukin-1alpha (IL-1alpha), and the relative expression of CD44 exon 19 and CD44 exon 20, hyaluronan synthase 2, aggrecan, and GAPDH messenger RNA (mRNA) was determined using reverse transcriptase-polymerase chain reaction. Next, CD44 exon 19 mRNA was selectively inhibited by the use of antisense oligonucleotides. The effects of exon 19 loss were analyzed by matrix assembly and hyaluronan internalization assays. RESULTS: Human articular chondrocytes express varying levels of exon 19 (short tail)- and exon 20 (long tail)-containing CD44 mRNA. Both CD44 mRNA are up-regulated by IL-1alpha. Selective inhibition of CD44 exon 19 results in enhanced hyaluronan internalization and smaller cell-associated matrices. CONCLUSION: The expression of a natural CD44 decoy-like receptor by articular chondrocytes modulates the function of this matrix receptor.

Aggrecans↗
PubMed1994

Binding and degradation of hyaluronan by human breast cancer cell lines expressing different forms of CD44: correlation with invasive potential.

In the present study, we examined a panel of human breast cancer cell lines with regard to their expression of CD44 and ability to bind and degrade hyaluronan. The cell lines expressed varying amounts of different molecular weight forms of CD44 (85-200 kDa) and, in general, those that expressed the greatest amounts of CD44 were the most invasive as judged by in vitro assays. In addition, the ability to bind and degrade hyaluronan was restricted to the cell lines expressing high levels of CD44, and both these functions were blocked by an antibody to CD44 (Hermes-1). Moreover, the rate of [3H]hyaluronan degradation was highly correlated with the amount of CD44 (r = 0.951, P < 0.0001), as well as with the invasive potential of the cells. Scatchard analysis of the [3H]hyaluronan binding of these cells revealed the existence of significant differences in both their binding capacity and their dissociation constant. To determine the source of this deviation, the different molecular weight forms of CD44 were partially separated by gel filtration chromatography. In all cell lines, the 85 kDa form was able to bind hyaluronan, although with different affinities. In contrast, not all of the high molecular weight forms of CD44 had this ability. These results illustrate the diversity of CD44 molecules in invasive tumor cells, and suggest that one of their major functions is to degrade hyaluronan.

Blotting, Western↗
PubMed1996

Spatial distribution of CD44 and hyaluronan in the proximal tibia of the growing rat.

CD44 has been described as a cell surface hyaluronan receptor present on a variety of different cells, and it is generally assumed to be prevalent in most connective tissues that contain hyaluronan. A major aim of this study was to test that presumption by localizing CD44 and hyaluronan within several tissues of the proximal tibia of the growing rat. Comparison of these profiles would reveal whether CD44 and hyaluronan co-localize with high fidelity, as would be expected if CD44 were a major hyaluronan binding protein. Using in situ hybridization and immunohistochemistry, CD44 was identified on osteoclasts, chondroclasts, osteocytes, hematopoietic marrow cells, synovial cells, and connective tissue fibroblasts (ligaments, tendons, and fascia). Although the majority of osteocytes expressed CD44, reduced expression was observed for osteoblasts and ostcoprogenitor cells. Additionally. CD44 was not detected on chondrocytes from epiphyseal and metaphyseal growth cartilages or in meniscal fibrocartilage. Using biotinylated G1 domain from aggrecan and link protein, hyaluronan was observed in the maturational and hypertrophic zones of all growth cartilages, the synovium and other fibroblastic connective tissues, regional areas of the periosteum and endosteum (around osteoblasts, osteoprogenitor cells, and osteoclasts), osteocyte lacunae, and surrounding blood vessels. In regions of co-localization for CD44 and hyaluronan, it seems that CD44 is a likely hyaluronan binding protein in several tissues of the proximal tibia. However, it does not appear to be the predominant hyaluronan binding protein in growing cartilages of the weanling rat.

Aggrecans↗
PubMed1995

Binding of cell-surface expressed CD44 to hyaluronate is dependent on splicing and cell type.

CD44 is a major cell-surface receptor for hyaluronate (HA). By alternative RNA-splicing a large number of CD44 variants are generated. To explore the role of CD44 splicing in the regulation of cell binding to HA, three different isoforms of CD44 were transfected in the CD44 negative B-cell lymphoma line Namalwa and in the fibroblastoid cell line COS7. We observed that whereas the standard form of CD44 (CD44s) mediated adhesion of Namalwa to HA, Namalwa transfected with CD44v3-10 or CD44v8-10 was unable to bind to either immobilized or soluble HA. After stimulation of CD44 with an activating anti-CD44 mAb or with phorbol ester, the binding of CD44s to HA was 5- to 10-fold higher than that of the other two isoforms. By contrast, COS7 cells transfected with CD44s, CD44v8-v10, or CD44v3-v10 bound equally effectively to HA. Hence, in addition to alternative splicing, cell type determines CD44 binding to HA.

Alternative Splicing↗
PubMed1993

Expression and regulation of the porcine CD44 molecule.

The expression and regulation of porcine CD44 were studied under various experimental conditions and in the context of lymphocyte differentiational and functional status. The CD44 molecule was subject to antigenic modulation by the anti-CD44 mAbs to different degrees depending on the type of cross-linking reagent and could be induced to shed from the cell surface. The reexpression of CD44 on papain-denuded lymphocytes was heterogeneous, as about half of the cells failed to resynthesize the molecule after prolonged culture, whereas the rest of the cells had a high turnover. Stimulation of lymphocytes by mitogens caused prolonged, dose-dependent elevation of the expression of CD44. Expression of CD44 on lymph node cells was found to be correlated with the expression of CD2 and sIgM. A CD2-CD4-sIgM-CD44-MHC Class IIhiCD45+ cell subset was identified, which was present in small numbers in lymph nodes but was enriched in gut-associated lymphoid tissues. In the thymus, CD44 expression seemed to be correlated with the differentiation status of thymocytes. In general, the expression of CD44 in the lymphoid tissues tested appeared to be related to their level of cell migration capacity.

Animals↗
PubMed1995

Changes in CD44 expression during B cell differentiation in the human tonsil.

CD44 is a widely distributed cell surface glycoprotein that has been implicated in a number of cellular adhesion processes and signal transduction events. These functional capabilities qualify CD44 as a potential mediator of contact-signaling events underlying the process of antigen-dependent B cell differentiation in secondary lymphoid tissues. We postulated that changes in the expression of CD44 during B cell differentiation reflect the cells' changing requirements for this receptor. It has been reported that germinal center B cells are low to negative for CD44 expression, implying that the receptor is lost upon activation. Correlation of the expression of CD44 with surface immunoglobulin and a number of B cell differentiation markers revealed a trimodal expression pattern. High levels of CD44 are expressed on resting IgD+/IgM+ cells. The receptor is still expressed at the early activation stage defined by the expression of CD23. At the early blast stage, when the blast marker CD38 appears on the cell surface and IgD and CD23 disappear, CD44 is downregulated. The majority of CD38+/IgM+ blasts and CD38+/Ig- centroblasts are CD44 low/negative. The receptor is re-upregulated at the point of transition from the centroblast to the centrocyte level. Centrocytes expressing IgG or IgA comprise CD44high and CD44low fractions. IgG+ or IgA+ cells at the postgerminal center stage express high levels of CD44. The functional implications of this expression pattern are discussed.

ADP-ribosyl Cyclase↗
PubMed1997

Tissue-specific and growth-regulated expression of CD44 variable exon determinants in the mouse.

CD44 is a polymorphic transmembrane glycoprotein widely expressed in lymphocytes and epithelial cells. CD44 polymorphism reflects both posttranslational modification and alternative splicing of up to 10 variably expressed exons in the membrane-proximal CD44 extracellular domain. An analysis of CD44 variable exon-containing isoforms in the mouse was carried out by generating a panel of monoclonal antibodies against variable region determinants of CD44. Immunohistochemical analysis demonstrated selective patterns of expression of CD44 variable exon determinants in normal tissues, and flow cytometric analysis identified expression of CD44 variable exon-dependent determinants in epithelial and lymphoid cell lines. Regulation of alternative splicing was studied by characterization of cell surface expression of CD44 variable exon determinants on HC11 mammary epithelial cells, and it was demonstrated that variably spliced isoforms are selectively regulated as a function of growth phase in vitro. These results demonstrate the tissue-specific and growth-regulated expression of the CD44 isoform at the level of cell surface protein products and identify isoform-specific determinants that can be targeted in analysis of isoform-specific function.

Animals↗
PubMed1998

Interleukins 4 and 13 upregulate expression of cd44 in human colonic epithelial cell lines.

Interleukin 4 (IL-4) inhibits carcinoma cell growth and promotes expression of differentiation-associated products by normal and malignant epithelial cells. The effects of IL-4 and IL-13 on expression of the CD44 transmembrane adhesion receptor were examined in human epithelial cell lines of colonic (HT-29, CaCo-2, DLD-1, T84), breast (MCF-7, ZR75-1) and liver (Hep-G2, PLC/PRF/5) origins as well as mitogen-activated and resting peripheral blood lymphocytes (PBL) and T cell lines (Jurkat, HUT78). Liver and Jurkat cells were negative for CD44. Colonic, breast and HUT78 cells expressed CD44 constitutively and all except DLD-1 and HUT78 also expressed CD44 splice variant (CD44v) epitopes. All cell lines expressed IL-4 receptors, but IL-4 and IL-13 induced upregulation of CD44 only in the colonic cell lines. CD44v was also upregulated, but there was no de novo induction of CD44v in variant-negative cells and no de novo expression of CD44 in the CD44(-) lines. CD44 upregulation in mitogen-activated PBL was not increased by IL-4 and IL-13 and was not inhibited by neutralizing antibodies. Other cytokines tested [interferon gamma (IFN-gamma, tumour necrosis factor alpha (TNF-alpha), transforming growth factor beta1 (TGF-beta1) and IL-6] did not affect CD44 core epitope expression in the cell lines tested.

Alternative Splicing↗
PubMed2000

MYCN-related suppression of functional CD44 expression enhances tumorigenic properties of human neuroblastoma cells.

Highly malignant neuroblastoma tumors with MYCN amplification have been shown to downregulate the expression of the CD44 adhesion receptor. We have previously shown that MYCN amplified neuroblastoma cell lines either lack CD44 expression or express a nonfunctional, nonhyaluronic acid-binding CD44 receptor. By analysis of cells with manipulated expression of either CD44 or MYCN, we demonstrate that transfection of cells with a CD44 full-length cDNA construct produced a functional receptor in single copy MYCN cells and a nonfunctional CD44 receptor in MYCN amplified cells, similar to the CD44 receptor expressed by cells with enforced MYCN. Analysis of the in vivo growth properties of the transfectants revealed that the restoration of a functional CD44 receptor in nonamplified cells resulted in the suppression of in vivo cell growth, therefore linking the MYCN-related lack of hyaluronic acid-binding function of CD44 to the highly tumorigenic properties of a subset of neuroblastoma cells.

Animals↗
PubMed1994

Preferential expression of the cell adhesion molecule CD44 in papillary thyroid carcinoma.

CD44 is a polymorphic family of immunologically related integral membrane glycoproteins associated with cell matrix adhesion, lymphocyte activation and targeting, and tumor growth and metastasis. We studied CD44 expression in 114 formalin-fixed paraffin-embedded thyroid tumors using the A3D8 anti-human CD44 monoclonal antibody. Sixty-five of 67 papillary carcinomas (97%) strongly expressed CD44 with an intense plasma membrane pattern. Thirty-seven of these cases originated from Albany, New York, and 30 cases from Russia. Immunoreactivity was also observed in 9 of 16 follicular adenomas (56%); 4 of 8 Hurthle cell neoplasms (50%); 5 of 15 medullary carcinomas (33%); and 3 of 8 follicular carcinomas (38%). These results show that among thyroid neoplasms, papillary carcinomas preferentially display the CD44 antigen (P < or = 0.001). Nonneoplastic follicular epithelium exhibited a low to moderate level of staining. To further characterize the CD44 isoform, we tested a subset of cases with the 2F10 anti-human CD44 variant 6 monoclonal antibody, which recognizes a CD44 variant exon (CD44v6) implicated in tumor metastasis. Eleven of 11 papillary carcinomas tested were 2F10 positive, and 1 of the follicular carcinomas was positive. These results suggest the hypothesis that deregulated CD44v6 expression on the plasma membrane of papillary carcinoma cells contributes to the ability of those cells to metastasize to regional lymph nodes and then to remain dormant for years. Our results suggest that human papillary thyroid cancer will be an interesting model in which to further study the role of CD44 isoforms, particularly those containing CD44v6, in tumor metastasis and lymphatic invasion.

Antibodies, Monoclonal↗
PubMed1998

Characterization of a functional hyaluronan-binding domain from the human CD44 molecule expressed in Escherichia coli.

The CD44 molecule is a widely distributed cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronan. The ligand-binding site which is located in the membrane distal portion of the molecule encompasses a region of approximately 100 amino acids termed the Link domain, a structural unit that is conserved among members of the Hyaladherin superfamily which includes cartilage link protein, aggrecan, and tumor necrosis factor-stimulated gene-6 (TSG-6). In contrast to these other Hyaladherins, however, the ligand-binding domain of CD44 appears to extend beyond the Link domain to involve additional basic residues located toward the membrane proximal region. Furthermore, recent molecular modeling studies indicate that within the CD44 Link domain itself, the spatial arrangement of critical residues involved in HA binding is likely to differ significantly from the prototypic TSG-6 Link module. In order to obtain material to solve the CD44 solution structure we have developed an optimized method for the expression and purification of functionally active CD44 ectodomains encompassing both the Link module and the additional downstream HA-binding residues in Escherichia coli. Here we describe the details of the method which involves solubilization of recombinant CD44 from inclusion bodies in 8 M urea, followed by refolding and purification of intact monomers using size-exclusion and reverse-phase chromatography. We show the method yields CD44 molecules that (1) retain reactivity with a panel of conformation-sensitive antibodies, (2) possess similar hyaluronan-binding characteristics to authentically folded CD44 molecules expressed in eukaryotic cells, and (3) display one-dimensional NMR spectra that indicate the presence of a single conformational species. This method should enable sufficient amounts of functional CD44 Link module to be produced for comprehensive structural analyses by multidimensional NMR spectroscopy.

Binding Sites↗
PubMed1992

Distribution of hyaluronan and its CD44 receptor in the epithelia of human skin appendages.

Biotinylated hyaluronan (HA) binding complex (HABC) from bovine articular cartilage proteoglycan was used as a histological probe to study the localization of HA in human skin. The distribution of HA was compared with its presumptive cell surface receptor, CD44, using monoclonal antibodies. In epidermis both HA and CD44 were found in the basal and spinous cell layers, but neither was present in the stratum granulosum and stratum corneum. In the keratinizing parts of hair follicles, i.e. in the outer and inner epidermal root sheath, pilosebaceous duct and the actual hair, HA and CD44 were found between the vital but not the terminally differentiated cells. In the sebaceous glands a small amount of HA was found around all cells, whereas CD44 was restricted to the basal cell layer. The secretory acini of the sweat glands stained intensively with anti-CD44 antibodies but only weakly with HABC. In the sweat gland, CD44 was localized on the basal and lateral surfaces of the clear cells, whereas the dark cells and the myoepithelial cells were negative. Both the lower and upper layers of the sweat gland ducts showed a faint but constant staining for CD44 and only minor amounts of HA. While in the keratinizing skin epithelia both HA and its CD44 receptor showed an intense staining with a close co-distribution, in the sweat and sebaceous glands their distribution patterns were not similar. It is suggested that in epithelia with divergent differentiation programs the functions of CD44 and HA may be different.

Biotin↗
PubMed1995

Expression of variant CD44 epitopes in human astrocytic brain tumors.

Expression of CD44 and of specific splice-variants of CD44 has been causally related to metastatic behaviour in a variety of carcinomas and lymphomas. To elucidate whether, in principle, similar splice-variants could be involved in glioma cell invasion we examined the expression of CD44 and its splice-variants in a series of 38 primary human brain tumors (28 astrocytomas, WHO grade I-III and 10 glioblastomas, WHO grade IV) and in cell lines derived from 9 glioblastomas. All brain tumors examined showed strong immunoreactivity for an N-terminal epitope present on all CD44 isoforms known. Using a polyclonal antiserum raised against the complete sequence encoded by variant exons v3 to v10, CD44 splice-variants could be detected irrespective of the grade of malignancy in many of the tumor samples at a low level and often restricted to only a few clustered tumor cells. Thus, the N-terminal epitope probably indicates the presence of the smallest and most ubiquitous isoform CD44s. Interestingly, all glioblastomas expressed CD44 variants whereas expression in astrocytomas WHO grade I, II, and III could only be detected in about half of the tumor samples. Using reverse transcriptase-PCR we were able to detect different CD44 splice-variants in the glioblastoma cell lines and in cultured primary astrocytic cells. Glioblastoma cells analyzed by flow cytometry showed the expected binding capacity for hyaluronic acid which could be increased twofold after pretreatment with hyaluronidase. The results presented show that there is low expression of CD44 variants in human tumors of astrocytic origin. Expression of CD44 and its splice-variants could contribute to the migration capacity of neoplastic astrocytes, and may be considered as a target for new diagnostic and therapeutic approaches in the clinical management of brain tumors.

Alternative Splicing↗