CD44 is the major peanut lectin-binding glycoprotein of human epidermal keratinocytes and plays a role in intercellular adhesion

Chondroitin/dermatan sulphate proteoglycan, desmosealin, showing affinity to desmosomes

Objective

Desmosomes are the most prominent interkeratinocyte junctions. The correct barrier function of stratified epithelia such as epidermis depends on their expression. During epidermal differentiation, the molecular composition of desmosomes evolves and so do their physical and chemical properties. Desquamation of corneocytes at the surface of the stratum corneum depends on an orderly degradation of desmosomes by endogenous enzymes. This process may be regulated by glycosylated molecules. We focused on the detection and characterization of potentially implicated players bearing ‘sugar’ characteristics.

Methods

Using an original monoclonal antibody and biochemical methods, we partially characterized a proteoglycan of the exclusively chondroitin/dermatan sulphate type, secreted into the interkeratinocyte spaces, that is incorporated into the extracellular parts of desmosomes in quantities proportional to the degree of cell differentiation, as visualized with immuno-electron microscopy.

Results

This antigen, that we named desmosealin, displays biochemical and immunocytochemical characteristics that clearly differentiate it from known desmosomal elements. Unlike so far described epidermal proteoglycans, which belong to the heparan sulphate family, desmosealin displays chondroitin/dermatan sulphate glycosaminoglycan chains. It can be detected within the extracellular ‘cores’ of desmosomes in the upper viable epidermal layers and in corneodesmosomes from the lowermost part of the stratum corneum.

Conclusion

Extensive integration of proteoglycans into the extracellular parts of desmosomes at the late stages of keratinocyte maturation is likely of functional importance. Given its biochemical profile, its pattern of expression in the epidermis and its desmosomal localization, desmosealin may emerge as a key element in the regulation of desmosome processing, epidermal cohesion and formation of a functional epidermal barrier.

Hyaluronan-Based Nanohydrogels for Targeting Intracellular S. Aureus in Human Keratinocytes

Staphylococcus aureus is one of the most significant human pathogens that is frequently isolated in a wide range of superficial and systemic infections. The ability of S. aureus to invade and survive within host cells such as keratinocytes and host immune cells has been increasingly recognized as a potential factor in persistent infections and treatment failures. The incorporation of antibiotics into hyaluronan-cholesterol nanohydrogels represents a novel paradigm in the delivery of therapeutic agents against intracellular bacteria. The work presented herein shows that NHs quickly enter human keratinocytes and accumulate into lysosomes. When used for targeting intracellular S. aureus the antimicrobial activity of loaded levofloxacin is enhanced, possibly changing the antibiotic intracellular fate from cytosol to lysosome. Indeed, gentamicin, an antibiotic that predominantly accumulates in lysosomes, shows significant and equal antibacterial activity when entrapped into NHs. These results strongly suggest that lysosomal formulations may display preferential activity toward intracellular S. aureus, opening new avenues for the use of HA-based NHs for treatment of such skin infections.

Development and characterization of new and scalable topical formulations containing N-acetyl-d-glucosamine-loaded solid lipid nanoparticles

N-Acetyl-d-glucosamine (NAG) has been recently considered for topical treatment of hyperpigmentation disorders due to its inhibitory effect on thyrosinase enzymes in melanocytes. NAG is a precursor of hyaluronic acid, increasing its amount in skin, and consequently, preserving the skin hydration and elasticity. It may also act as an emulsion stabilizer. Solid lipid nanoparticles (SLN) are advanced delivery systems successfully used in pharmaceutical and cosmetic formulations for the improvement of active molecules penetration into the skin. Therefore, this work aimed to develop and characterize stable and scalable topical formulations containing NAG-loaded SLN. NAG was incorporated in SLN which were prepared by two high shear homogenizers and characterized regarding its morphology and particle size by transmission electron microscopy and photon correlation spectroscopy, respectively. Oil emulgel and hydrogel were used as carriers of NAG-loaded SLN. Several parameters were evaluated, including the droplet size distribution, rheology, pH and topical delivery by different techniques. It was observed that SLN size was significantly dependent on NAG incorporation and homogenization process. Most tested SLN parameters appeared to be quite suitable, that is, spherical and well-defined SLN with approximately 258 nm and -30 mV. Hereafter, both gels containing SLN presented a pseudoplastic flow. Emulgel formulation containing NAG-loaded SLN allowed a higher NAG permeation through the SC compared to the respective control (about 0.8 μgcm^-2h^-1). According to the results obtained, it can be suggested that NAG acts as an emulsion stabilizer. This stabilization was also particularly dependent on the homogenizer type which is quite important for scale-up process. This study demonstrated the potential of scalable SLN formulations to improve NAG topical delivery contributing to the improvement of skin properties on several skin disorders.

Galectin-3: A Positive Regulator of Leukocyte Recruitment in the Inflamed Microcirculation

In vivo and ex vivo imaging were used to investigate the function of galectin-3 (Gal-3) during the process of leukocyte recruitment to the inflamed microcirculation. The cremasteric microcirculation of wild-type (C57BL/6), Gal-3^-/-, and CX₃CR1^gfp/+ mice were assessed by intravital microscopy after PBS, IL-1β, TNF-α, or recombinant Gal-3 treatment. These cellular responses were investigated further using flow-chamber assays, confocal microscopy, flow cytometry, PCR analysis, and proteome array. We show that mechanisms mediating leukocyte slow rolling and emigration are impaired in Gal-3^-/- mice, which could be because of impaired expression of cell adhesion molecules and an altered cell surface glycoproteome. Local (intrascrotal) administration of recombinant Gal-3 to wild-type mice resulted in a dose-dependent reduction in rolling velocity associated with increased numbers of adherent and emigrated leukocytes, ∼50% of which were Ly6G⁺ neutrophils. Intrascrotal administration of Gal-3 to CX₃CR1^gfp/+ mice confirmed that approximately equal numbers of monocytes are also recruited in response to this lectin. Exogenous Gal-3 treatment was accompanied by increased proinflammatory cytokines and chemokines within the local tissue. In conclusion, this study unveils novel biology for both exogenous and endogenous Gal-3 in promoting leukocyte recruitment during acute inflammation.

Hyaluronate-Peanut Agglutinin Conjugates for Target-Specific Bioimaging of Colon Cancer

Colon cancer is one of the most common death-related cancers in the world. For treating colon cancer, it is crucial to detect and remove malignant lesions early. Here, we developed hyaluronate (HA)-peanut agglutinin (PNA) conjugates for the bioimaging of colon cancer. The HA-PNA conjugates were successfully synthesized by the coupling reaction between aldehyde-modified HA and the N-terminal amine group of PNA. For diagnostic imaging, rhodamine B (RhoB) was chemically conjugated onto PNA in HA-PNA conjugates. After intraluminal injection of HA-PNA-RhoB conjugates into tumor-bearing mice, small-sized colon cancers could be effectively visualized by ex vivo imaging with an in vivo imaging system (IVIS) and a two-photon microscope. With these results taken together, we could confirm the feasibility of HA-PNA-RhoB conjugates as a bioimaging agent for detecting colon cancers.

Production and validation of a good manufacturing practice grade human fibroblast line for supporting human embryonic stem cell derivation and culture

Introduction

The development of reproducible methods for deriving human embryonic stem cell (hESC) lines in compliance with good manufacturing practice (GMP) is essential for the development of hESC-based therapies. Although significant progress has been made toward the development of chemically defined conditions for the maintenance and differentiation of hESCs, efficient derivation of new hESCs requires the use of fibroblast feeder cells. However, GMP-grade feeder cell lines validated for hESC derivation are not readily available.

Methods

We derived a fibroblast cell line (NclFed1A) from human foreskin in compliance with GMP standards. Consent was obtained to use the cells for the production of hESCs and to generate induced pluripotent stem cells (iPSCs). We compared the line with a variety of other cell lines for its ability to support derivation and self-renewal of hESCs.

Results

NclFed1A supports efficient rates (33%) of hESC colony formation after explantation of the inner cell mass (ICM) of human blastocysts. This compared favorably with two mouse embryonic fibroblast (MEF) cell lines. NclFed1A also compared favorably with commercially available foreskin fibroblasts and MEFs in promoting proliferation and pluripotency of a number of existing and widely used hESCs. The ability of NclFed1A to maintain self-renewal remained undiminished for up to 28 population doublings from the master cell bank.

Conclusions

The human fibroblast line Ncl1Fed1A, produced in compliance with GMP standards and qualified for derivation and maintenance of hESCs, is a useful resource for the advancement of progress toward hESC-based therapies in regenerative medicine.

Synergistic effect of hyaluronate fragments in retinaldehyde-induced skin hyperplasia which is a Cd44-dependent phenomenon

BACKGROUND

CD44 is a polymorphic proteoglycan and functions as the principal cell-surface receptor for hyaluronate (HA). Heparin-binding epidermal growth factor (HB-EGF) activation of keratinocyte erbB receptors has been proposed to mediate retinoid-induced epidermal hyperplasia. We have recently shown that intermediate size HA fragments (HAFi) reverse skin atrophy by a CD44-dependent mechanism.

METHODOLOGY AND PRINCIPAL FINDINGS

Treatment of primary mouse keratinocyte cultures with retinaldehyde (RAL) resulted in the most significant increase in keratinocyte proliferation when compared with other retinoids, retinoic acid, retinol or retinoyl palmitate. RAL and HAFi showed a more significant increase in keratinocyte proliferation than RAL or HAFi alone. No proliferation with RAL was observed in CD44-/- keratinocytes. HA synthesis inhibitor, 4-methylumbelliferone inhibited the proliferative effect of RAL. HB-EGF, erbB1, and tissue inhibitor of MMP-3 blocking antibodies abrogated the RAL- or RAL- and HAFi-induced keratinocyte proliferation. Topical application of RAL or RAL and HAFi for 3 days caused a significant epidermal hyperplasia in the back skin of wild-type mice but not in CD44-/- mice. Topical RAL and HAFi increased epidermal CD44 expression, and the epidermal and dermal HA. RAL induced the expression of active HB-EGF and erbB1. However, treatment with RAL and HAFi showed a more significant increase in pro-HB-EGF when compared to RAL or HAFi treatments alone. We then topically applied RAL and HAFi twice a day to the forearm skin of elderly dermatoporosis patients. After 1 month of treatment, we observed a significant clinical improvement.

CONCLUSIONS AND SIGNIFICANCE

Our results indicate that (i) RAL-induced in vitro and in vivo keratinocyte proliferation is a CD44-dependent phenomenon and requires the presence of HA, HB-EGF, erbB1 and MMPs, (ii) RAL and HAFi show a synergy in vitro and in vivo in mouse skin, and (iii) the combination of RAL and HAFi seems to have an important therapeutic effect in dermatoporosis.

Clinical significance of pAKT and CD44v6 overexpression with breast cancer

PURPOSE

CD44v6 contributes to apoptosis resistance and metastasis via upregulated activity of the PI3K/AKT pathway. The purpose of this study was to investigate the expression patterns and predictive value of phosphorylated AKT (pAKT) and CD44v6 in breast cancer tissues.

METHODS

Expression of pAkt and CD44v6 protein was detected using immunohistochemistry in breast cancer tissues and lymph node tissues in 98 patients. The correlation between the expression of pAkt, CD44v6 and other disease-related characteristics was investigated. The prognostic value of pAKT and CD44v6 overexpression for overall survival (OS) and disease free survival (DFS) was determined.

RESULTS

37 cases (37.8%) were observed as positive for pAkt expression, and 38 cases (38.8%) for CD44V6 overexpression. Staining was positive for pAKT in 20 of 38 (52.6%) CD44v6(+) and 17 of 60 (28.3%) CD44v6(-) (P = 0.016). A progressively increased trend of CD44v6 overexpression was observed from node(-) primary breast cancer tissues to node(+) primary cancer tissues to node(+) lymph tissues (P = 0.000). In univariate analysis lymph node status, pAKT and CD44V6 were significantly associated with a decreased OS and DFS. Multivariate analysis revealed that CD44v6 status was associated with a reduced OS (P = 0.003), and pAKT and CD44v6 with a shorter DFS (P = 0.012 and 0.016, respectively).

CONCLUSIONS

Our data suggested that there had an intensive relationship between pAKT and CD44v6 expression in breast cancer tissues. The overexpression of CD44v6 was an independent prognostic marker for predicting OS and DFS of breast cancer patients.

RON-expressing MCF-10A breast epithelial cells exhibit alterations of hyaluronan expression, promoting RON-mediated early adhesion events

The receptor tyrosine kinase known as RON appears to play a role in the progression of human carcinomas, and is associated with a poor patient prognosis. Our current study demonstrates that RON expression in MCF-10A breast epithelial cells lead to an alteration of cell-surface hyaluronan compared to the parental cells. We found that hyaluronan was important for initial cell attachment to poly-d-lysine-coated coverslips, but did not contribute to the process of cell spreading. Previous data implied that the Src kinase was important for spreading but not the initial attachment of 10A cells, and here we demonstrate Src activation was also not necessary for hyaluronan production in these cells.

CD44 is overexpressed in basal-like breast cancers but is not a driver of 11p13 amplification

Overexpression and alternative splicing of CD44 have been implicated in tumour progression. Here we describe the identification of a high level amplification of human 11p13, encompassing the CD44 gene, in primary breast cancers and cell lines and test whether CD44 acts as the driver of this amplicon. aCGH analysis revealed 11p13 amplification in 3% (3/100) of primary breast carcinomas and in two cell lines. The minimal region of amplification was 34.38-37.62 Mb. Amplification was confirmed by dual-colour FISH in these cell lines and further validated by CISH in an independent tumour cohort. CD44 expression in primary breast cancers was significantly associated with features of basal-like breast cancer. Detection of CD44 expression in breast cancer cell lines confirmed moderate to high expression in basal-like cell lines and minimal expression in luminal cell lines. In both, primary breast cancers and cell lines, 11p13 amplification was associated with high levels of CD44 mRNA expression. CD44 alternative splicing was detected in four of nine cell lines and in tumour samples, irrespective of the amplification status. RNAi mediated knock down of CD44 failed to reveal an increased dependence on CD44 expression for proliferation or survival in amplified cell lines. Given that expression of CD44 is not an absolute requirement for the survival of cells harbouring CD44 gene amplification, CD44 is unlikely to be a driver of the 11p13 amplicon.

Variant CD44 expression by human fibroblasts

CD44 is a cell surface glycoprotein with roles in tumour invasion and metastasis. CD44 is variably spliced from ten variant exons and mis-splicing is a biomarker for detection of colon, urothelial and other carcinomas. Fibroblasts are normally considered to lack variant exons and thus should not generate false-positive signals. Transcription of variant exons by fibroblasts was investigated by exon-specific reverse transcription-polymerase chain reaction (RT-PCR) for variant exons v2-v10 using normal primary fibroblasts, immortalized and experimentally transformed fibroblasts. Flow cytometry, immunocytochemistry and Western blotting were used to determine expression. All types of fibroblasts, including normal primary culture fibroblasts, transcribed low levels of variant exon mRNA. Expression could not be detected by blotting or immunocytochemistry but flow cytometry revealed minor expression of some exons by all three types of cultured fibroblast. Fibroblasts do transcribe and express small amounts of variant exon CD44. This may need to be considered when using exon splicing as a biomarker for malignancy in clinical samples containing connective tissue.

Molecular mechanism of systemic delivery of neural precursor cells to the brain: assembly of brain endothelial apical cups and control of transmigration by CD44

Systemically injected neural precursor cells (NPCs) were unexpectedly shown to reach the cerebral parenchyma and induce recovery in various diffuse brain pathologies, including animal models of multiple sclerosis. However, the molecular mechanisms supporting NPC migration across brain endothelium remain elusive. Brain endothelium constitutes the blood-brain barrier, which uniquely controls the access of drugs and trafficking of cells, including leukocytes, from the blood to the brain. Taking advantage of the availability of in vitro models of human and rat blood-brain barrier developed in our laboratory and validated by us and others, we show here that soluble hyaluronic acid, the major ligand of the adhesion molecule CD44, as well as anti-CD44 blocking antibodies, largely prevents NPC adhesion to and migration across brain endothelium in inflammatory conditions. We present further evidence that NPCs, surprisingly, induce the formation of apical cups at the surface of brain endothelial cells, enriched in CD44 and other adhesion molecules, thus hijacking the endothelial signaling recently shown to be involved in leukocyte extravasation. These results demonstrate the pivotal role of CD44 in the trans-endothelial migration of NPCs across brain endothelial cells: we propose that they may help design new strategies for the delivery of therapeutic NPCs to the brain by systemic administration.

TSC2Loss in Lymphangioleiomyomatosis Cells Correlated with Expression of CD44v6, a Molecular Determinant of Metastasis

Lymphangioleiomyomatosis (LAM), a rare multisystem disease found primarily in women of childbearing age, is characterized by the proliferation of abnormal smooth muscle-like cells, LAM cells, that form nodules in the pulmonary interstitium. Proliferation of LAM cells results, in part, from dysfunction in tuberous sclerosis complex (TSC) genes TSC1 (hamartin) and/or TSC2 (tuberin). Identification of LAM cells in donor lungs, their isolation from blood, and their presence in urine, chylous ascites, and pleural effusions are consistent with their ability to metastasize. Here, we investigated the presence on LAM cells of the hyaluronic acid receptor CD44 and its splice variants associated with metastasis. The heterogeneous populations of cells grown from lungs of 12 LAM patients contain cells expressing mRNA for the variant CD44v6. Histologically, CD44v6 was present in LAM lung nodules, but not in normal vascular smooth muscle cells. CD44v6-positive sorted cells showed loss of heterozygosity at the TSC2 locus; binding of CD44v6 antibody resulted in loss of cell viability. Levels of CD44 were higher in cultured Eker rat (Tsc2-/-) cells than in Tsc2+/+ cells, but unlike human LAM cells, the Tsc2-/- Eker rat cells did not contain CD44v6 splice variant mRNA. CD44 splicing and signaling is regulated by osteopontin. Plasma from LAM patients contained higher concentrations of osteopontin than plasma of healthy, age-, and sex-matched volunteers (P = 0.00003) and may be a biomarker for LAM. The cell surface receptor CD44 and its splice variant CD44v6 may contribute to the metastatic potential of LAM cells.

Identification of the decay-accelerating factor CD55 as a peanut agglutinin-binding protein and its alteration in non-small cell lung cancers

PURPOSE

Peanut agglutinin (PNA) recognizes tumor-associated carbohydrates. In this study, we aimed to identify the core protein harboring PNA-binding sugars in the human lung and to explore the relationship with the pathology of primary non-small cell lung cancers (NSCLC).

EXPERIMENTAL DESIGN

PNA lectin blotting was used to detect PNA-binding proteins in the microsomal fraction of lung tissue from 24 patients with NSCLC. The 55- to 65-kDa core peptide PNA-binding protein was characterized by enzymatic treatment and identified by immunoprecipitation and affinity chromatography. The expression level and increase in size of the 55- to 65-kDa PNA-binding protein/decay-accelerating factor (DAF) were compared between normal and tumor regions of the tumor tissue by Western blotting and quantitative PCR.

RESULTS

The 55- to 65-kDa PNA-binding protein was observed in human lung. This was a glycosylphosphatidylinositol-anchored membrane protein carrying O-linked carbohydrates. This core protein was identified as DAF, one of the complementary regulatory proteins. DAF was enlarged to 65 to 75 kDa in NSCLC tumor lesions due to sialylation in the sugar moiety. At the transcription level, DAF levels were significantly lower in tumor regions, suggesting its down-regulation in NSCLC cells.

CONCLUSIONS

DAF was identified as a new PNA-binding protein in the human lung. The down-regulation and heavy sialylation of DAF was associated with pathology in NSCLC, and these alterations make this protein a potential marker for NSCLC.

Glycoconjugate profiling of primary melanoma and its sentinel node and distant metastases: implications for diagnosis and pathophysiology of metastases

Aiming at more precise detection of melanoma cells in sentinel lymph nodes and better understanding of the mechanisms underlying metastatic spread, expression of L1, CEACAM1, and binding of the lectins HPA, ML-I and PNA, was assessed in benign nevi (n=12), primary melanomas (PTs: n=67), their corresponding sentinel lymph nodes (SLNs: n=40), and distant metastases (DMs: n=35). Sensitivity and specificity of CEACAM1 (95-97%; 66%) and L1 (90-93%; 100%) exceeded that of the standard markers MelanA, S100, and HMB45 in single marker use. Lectin binding was found in PTs and DMs (HPA: 69% and 77%; ML-I: 82% and 77%, respectively), but rarely in SLNMs (HPA: 20%, ML-I: 20%, PNA: 5%, respectively). The highly specific and sensitive L1-11A against L1 and 4D1/C2 against CEACAM1 antibodies are a worthy completion to standard antibody panels for diagnosis of melanoma cells. Both CAMs seem to be functionally involved in lymphatic and haematogenous spread, and are thus promising target molecules for immunotoxins.

Comparison of the zones of the human prostate with the seminal vesicle: morphology, immunohistochemistry, and cell kinetics

BACKGROUND

The prostate contains three glandular zones (central, peripheral, transition) with widely differing susceptibilities to cancer and benign prostatic hyperplasia (BPH). Most of the prostate is derived from urogenital sinus, but the central zone may be derived from Wolffian duct, in common with the seminal vesicles (SV). The peripheral zone is the most frequent site of cancer and the transition zone is the almost exclusive site of BPH.

METHOD

We compared the histology and immunohistochemistry of the SV with those of the prostate zones in order to identify differences associated with susceptibility to disease or different embryological origins. Sections from the prostates of nine organ donors (aged 15-36) were stained for tissue-specific markers, antigens previously shown to stain differentially between the zones and markers of cell proliferation and cell death.

RESULTS

Neuroendocrine cells were absent from the SV and significantly fewer neuroendocrine cells were seen in the central zone compared to the peripheral zone. Most of the SV epithelium stained for lactoferrin, compared to approximately one-third of central zone and only 2% of peripheral zone epithelial cells. The proliferative index of the central zone was approximately 50% lower and the incidence of apoptotic cells approximately half that of the peripheral and transition zones.

CONCLUSIONS

The central zone has features in common with both the SV and the other zones of the prostate. The higher incidence of proliferative diseases in the transition and peripheral zones may be associated with the higher rate of cell turnover observed in these zones.

Expression of E-cadherin, and CD44s and CD44v6 and its association with prognosis in head and neck cancer

OBJECTIVES

In the current study, the expression of E-cadherin, CD44s, and CD44v6 has been noted as markers for tumor metastasis and prognosis in several tumors, so we examined whether or not E-cadherin, CD44s, and CD44v6 are useful markers for evaluating the prognosis of mesopharyngeal cancer patients.

METHODS

The expression of E-cadherin, CD44s, and CD44v6, was evaluated immunohistochemically using monoclonal antibodies against epitopes of standard and variant proteins, in paraffin-embedded mesopharyngeal cancer tissues from 57 patients who had received curative therapy.

RESULTS

Tumor tissues from 47 (82.5%) patients showed positive immunoreactivity with monoclonal antibody against E-cadherin, 43 (75.4%) patients showed positive expression with CD44, and 45 (78.9%) patients showed positive expression with CD44v6. The expression of CD44v6 was slightly correlated with tumor volume, and lymph node metastasis, and stage classification (P > 0.05). However, there was no significant correlation between the expression of E-cadherin, CD44s and CD44v6 and clinicopathological characteristics. Concerning the prognosis, the survival period of patients with CD44s positive tumors was shorter than that of patients with CD44s negative tumors (18.2% versus 52.1%, 5-year survival, P > 0.05). The survival period of patients with CD44v6 positive tumors was also shorter than that of patients with CD44v6 negative tumors (12.8% versus 55.6%, 5-year survival, P > 0.05).

CONCLUSION

These results suggest that CD44v6 may be related to tumor invasion and metastasis, and both CD44s and CD44v6 may be useful markers for poor prognosis in head and neck cancer.

Differential expression of CD44 during human prostate epithelial cell differentiation

CD44 is a polymorphic transmembrane glycoprotein that binds hyaluronan and growth factors. Multiple isoforms of the protein can be generated by alternative splicing but little is known about the expression and function of these isoforms in normal development and differentiation. We have investigated the expression of CD44 during normal prostate epithelial cell differentiation. A conditionally immortalized prostate epithelial cell line, Pre2.8, was used as a model system. These cells proliferate at 33C but at 39C stop dividing and undergo changes consistent with early stages of cell differentiation. During the differentiation of these cells, the expression of the CD44 isoform v3-v10 was upregulated. Two layers of epithelial cells can clearly be distinguished in the human prostate, a basal layer expressing keratins 5/14 and a luminal layer expressing keratins 8/18. In prostate tissue the v3-v10 isoform was found predominantly in basal cells but also in keratin 14-negative, keratin 19-positive cells intermediate between the two layers. CD44 v3-v10 was also expressed in other keratin 14-negative prostate tissues, the ejaculatory ducts and prostatic urethra. Therefore, CD44 v3-v10 may be important as a cell surface marker for differentiating cells in the prostate epithelium.

Adhesion molecule CD44 expression in non-tumour epithelium adjacent to tongue cancer

An immunohistochemical study was performed of changes in the expression of adhesion molecule CD44 in 32 adjacent non-tumour epithelia (ANTE) to lingual carcinomas and in the tumour tissue, using anti-CD44 monoclonal antibody DF1485. The aim was to evaluate the importance of these changes as an early event in lingual carcinogenesis. The ANTE was histologically normal in 22 cases (68.8%) and presented epithelial dysplasia in 10 (32.2%). Three cases of normal and dysplastic ANTE, respectively, were CD44- (9.4%). Negative CD44 expression was significantly more frequent in tumours with lower percentages of CD44+ cancer cells, both in normal (P=0.014) and dysplastic (P=0.033) ANTE. The expression in normal ANTE was also significantly associated with clinical stage (P=0.040) and presence of extracapsular nodal spread (P=0.013). Therefore, loss of CD44 expression in ANTE can be considered an early event in lingual carcinogenesis and a marker of major alterations of CD44 expression in the derived tumour tissue.

CD44: from adhesion molecules to signalling regulators

Cell-adhesion molecules, once believed to function primarily in tethering cells to extracellular ligands, are now recognized as having broader functions in cellular signalling cascades. The CD44 transmembrane glycoprotein family adds new aspects to these roles by participating in signal-transduction processes--not only by establishing specific transmembrane complexes, but also by organizing signalling cascades through association with the actin cytoskeleton. CD44 and its associated partner proteins monitor changes in the extracellular matrix that influence cell growth, survival and differentiation.

CD44 is required for two consecutive steps in HGF/c-Met signaling

The tyrosine kinase receptor c-Met and its ligand HGF/SF, ezrin, and splice variants of CD44 have independently been identified as tumor metastasis-associated proteins. We now show that these proteins cooperate. A CD44 isoform containing variant exon v6 sequences is strictly required for c-Met activation by HGF/SF in rat and human carcinoma cells, in established cell lines as well as in primary keratinocytes. CD44v6-deficient tumor cells were unable to activate c-Met unless they were transfected with a CD44v6-bearing isoform. Antibodies to two v6-encoded epitopes inhibited autophosphorylation of c-Met by interfering with the formation of a complex formed by c-Met, CD44v6, and HGF/SF. In addition, signal transduction from activated c-Met to MEK and Erk required the presence of the cytoplasmic tail of CD44 including a binding motif for ERM proteins. This suggests a role for ERM proteins and possibly their link to the cortical actin cytoskeleton in signal transfer.

Cell adhesion molecules and oral cancer

Cell adhesion molecules (CAMs) are found on the surfaces of all cells, where they bind to extracellular matrix molecules or to receptors on other cells. As well as having a structural role, CAMs function as signaling receptors, transducing signals initiated by cellular interactions which regulate many diverse processes, including cell division, migration, and differentiation. Cell adhesion molecules are essential for maintaining stable tissue structure. However, cell adhesion must be dynamic to facilitate the mobility and turnover of cells. In dynamic situations, cells alter their cell-cell and cell-matrix interactions by virtue of altered expression and function of CAMs. The expression of CAMs is normally tightly regulated, thereby controlling cell proliferation, mobility, differentiation, and survival. Many of these processes are misregulated in malignant tumors, and it has been shown that many of the characteristics of tumor cells are attributable to the aberrant expression or function of CAMs. Integrins and E-cadherin are the most important CAMs expressed by stratified squamous epithelium. Altered expression of these molecules has been found in oral carcinoma, where loss of CAM expression is often seen in poorly differentiated lesions. However, up-regulation of certain integrins, such as alphavbeta6, has consistently been found in oral cancer, suggesting that it may play an active role in disease progression.

Cell surface-expressed Thomsen-Friedenreich antigen in colon cancer is predominantly carried on high molecular weight splice variants of CD44

Increased mucosal expression of TF, the Thomsen-Friedenreich oncofetal blood group antigen (galactose beta1-3 N-acetylgalactosamine alpha-) occurs in colon cancer and colitis. This allows binding of TF-specific lectins, such as peanut agglutinin (PNA), which is mitogenic to the colorectal epithelium. To identify the cell surface TF-expressing glycoprotein(s), HT29 and Caco2 colon cancer cells were surface-labeled with Na[(125)I] and subjected to PNA-agarose affinity purification and electrophoresis. Proteins, approximately 110-180 kDa, present in HT29 but not Caco2 were identified by Western blotting as high molecular weight splice variants of CD44 (CD44v). Selective removal of TF antigen by Streptococcus pneumoniae endo-alpha-N-acetylgalactosaminidase substantially reduced PNA binding to CD44v. Immunoprecipitated CD44v from HT29 cell extracts also expressed sialyl-Tn (sialyl 2-6 N-acetylgalactosaminealpha-). Incubation of PNA 15 microg/ml with HT29 cells caused no additional proliferative effect in the presence of anti-CD44v6 mAb. In colon cancer tissue extracts (N = 3) PNA bound to CD44v but not to standard CD44. These data show that CD44v is a major PNA-binding glycoprotein in colon cancer cells. Because CD44 high molecular weight splice variants are present in colon cancer and inflammatory bowel disease tissue but are absent from normal mucosa, these results may also explain the increased PNA reactivity in colon cancer and inflammatory bowel disease. The coexpression of oncofetal carbohydrate antigens TF and sialyl-Tn on CD44 splice variants provides a link between cancer-associated changes in glycosylation and CD44 splicing, both of which correlate with increased metastatic potential.

Glycoconjugate distribution in early human notochord and axial mesenchyme

Glycosylation patterns of cells and tissues give insights into spatially and temporally regulated developmental processes and can be detected histochemically using plant lectins with specific affinities for sugar moieties. The early development of the vertebral column in man is a process which has never been investigated by lectin histochemistry. Therefore, we studied binding of several lectins (AIA, Con A, GSA II, LFA, LTA, PNA, RCA I, SBA, SNA, WGA) in formaldehyde-fixed sections of the axial mesenchyme of 5 human embryos in Carnegie stages 12-15. During these developmental stages, an unsegmented mesenchyme covers the notochord. Staining patterns did not show striking temporal variations except for SBA which stained the cranial axial mesenchyme only in the early stage 12 embryo and for PNA, of which the staining intensity in the mesenchyme decreased with age. The notochord appeared as a highly glycosylated tissue. Carbohydrates detected may correspond to adhesion molecules or to secreted substances like proteoglycans or proteins which could play an inductive role, for example, for the neural tube. The axial perinotochordal unsegmented mesenchyme showed strong PNA binding. Therefore, its function as a PNA-positive "barrier" tissue is discussed. The endoderm of the primitive gut showed a lectin-binding pattern that was similar to that of the notochord, which may correlate with interactions between these tissues during earlier developmental stages.

Reduced expression of CD44 variant 9 is related to lymph node metastasis and poor survival in squamous cell carcinoma of tongue

Expression of CD44v9 was immunohistochemically studied in 120 biopsy specimens from primary squamous cell carcinoma (SCC) of the tongue and correlated with clinicopathological findings of the SCCs. The tumors were classified into three groups according to immunostaining pattern of CD44v9; 53 cases with distinct positivity in all cancer cells except for those in the central part of nests (Group 1, non-reduced group), 42 cases with reduced expression in peripheral cells of nests (Group 2, reduced group), and 25 cases with complete disappearance of the expression in one or more nests (Group 3, negative group). Nineteen of 25 (76%) tumors in Group 3 and 14 of 42 (33%) in Group 2 exhibited lymph node metastasis, compared with only 8 of 53 (15%) in Group 1. The average survival time in Groups 1, 2 and 3 was 4496+/-204, 3866+/-379 and 2719+/-359 days, respectively and became shorter with the reduction of CD44v9 expression. These results suggest that the down-regulation of CD44v9 in SCC of the tongue may relate to the detachment of tumor cells from primary lesions, establishment of lymph node metastasis and consequently the death of patients.

Lectin ligands on human dendritic cells and identification of a peanut agglutinin positive subset in blood

As only a few cell surface markers for dendritic cells (DC) have been identified to date, this study examined the expression of ligands for lectin on different human DC populations. The ability of Concanavalin A (Con A), Wheat Germ Agglutinin (WGA), peanut agglutinin (PNA), and Helix pomatia (HPA) to bind to cell lines and PBMC and DC populations was analyzed by flow cytometry and specificity of binding confirmed using inhibitory and noninhibitory sugars. The cell lines showed non-lineage-restricted binding with Con A and WGA, independent of sialidase treatment. HPA and PNA bound to a restricted number of lines, but showed broad reactivity after sialidase treatment. The peripheral blood mononuclear cells (PBMC) and directly isolated blood DC, activated CD83(+) blood DC, epidermal Langerhans cells (LC), and monocyte-derived DC (Mo-DC) showed strong binding of Con A and WGA, both before and after sialidase treatment. No HPA binding ligands were detected on PBMC populations, including directly isolated blood DC. Following sialidase treatment CD3(+), CD16(+), and a subset of CD19(+) lymphocytes bound HPA. The lectin PNA bound weakly to CD14(+) monocytes and a subpopulation of circulating DC that were HLA-DR(hi)CDw123 Dr(hi)CDw123(dim)/(neg)CD11c(+). The HLA-DR(mod)CDw123(hi)CD11c(neg) subpopulation did not bind PNA. Without sialidase treatment LC expressed both HPA and PNA ligands, but these were either absent on activated CD83(+) blood DC or weakly expressed on Mo-DC. Following sialidase treatment PBMC populations, activated CD83(+) blood DC, and Mo-DC became PNA positive. Thus human DC express several lectin ligands and PNA binding identifies a subset of blood DC. That may reflect discrete changes associated with stages of DC development or functional maturation.

Expression of E-cadherin, alpha- & beta-catenin, and CD44V6 and the subcellular localization of E-cadherin and CD44V6 in normal epidermis and basal cell carcinoma

Basal cell carcinoma (BCC) of the skin is a locally invasive, rarely metastasizing epithelial tumor. In the current study, the expression of E-cadherin, alpha- and beta-catenin and CD44V6 in normal epidermis and on BCC cells were investigated. A significantly reduced expression of alpha-catenin and CD44V6 and a slightly reduced expression of E-cadherin on BCC cells were observed compared with the overlying epidermis. Immunoelectron microscopy was used to investigate whether the decreased expression of E-cadherin and CD44V6 was due to either an absence or downregulation of specific membrane structures or due to an overall downregulation of these adhesion molecules in all membrane structures in BCC. E-cadherin and CD44V6 were expressed in adherens junctions, desmosomes, and complex interdigitating membrane structures both in normal epidermis and in BCC. A quantitative analysis showed that only a percentage of desmosomes was stained. In addition, the effect of pro-inflammatory cytokines, such as interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), was investigated in biopsy specimens of normal skin and BCC, using a biopsy culture system and immunohistochemistry. The expression of E-cadherin and CD44V6 was not significantly decreased after culturing BCC or normal skin biopsy specimens for 48 hours with or without recombinant human (rHu)IFN-gamma or rHuTNF-alpha. It may be concluded that the decreased expression of both E-cadherin and CD44V6, observed in light microscopy, was not attributable to the absence of specific specialized structures in BCC and most likely also not caused by downregulation by local cytokines, but rather by generic downregulation of both of these adhesion molecules during malignant transformation.

Characterization of CD44v6 isoforms in head-and-neck squamous-cell carcinoma

CD44 splice variants, especially those containing the v6 domain, are assumed to play a critical role in the malignant progression of many human tumors. This concept was based on (i) the aberrant expression of CD44v6 in malignant cells, often encoded by alternatively spliced transcripts, and (ii) the absence of CD44v6 expression in corresponding normal tissues. Remarkably, data on CD44v6 expression in squamous cells do not support this hypothesis: the v6 domain is highly expressed in normal squamous tissues and down-regulation has been described in the majority of squamous-cell carcinomas of the head and neck (HNSCC). In this study, we have compared the expression of v6 in normal oral mucosa and HNSCC in a qualitative and quantitative way. Immuno-histochemistry was performed with 3 different anti-v6 antibodies (U36, U39 and VFF18) on a large panel of HNSCC cell lines and tumors. The v6-encoding splice variants were characterized by screening a cDNA library of a human HNSCC cell line and by RT-PCR on HNSCC cell lines, microdissected normal mucosa and primary as well as metastatic HNSCC tissue. The results revealed that there is no, or only marginal, down-regulation of CD44v6 in HNSCC. About 97% of the primary HNSCC tumors exhibited a high and homogeneous staining pattern (U36, 270/277; U39, 268/277 tumors with more than 50% positive cells). Furthermore, the v6-containing CD44 splice variants present in HNSCC primary tumors and metastases were identical to those expressed in normal mucosa. Our data indicate that v6-containing CD44 splice variants do not play a role in the malignant progression of HNSCC.

Prognostic importance of the expression of CD44 splice variants in oral squamous cell carcinomas

Considering squamous cell carcinomas (SCCs) of the oral cavity and oropharynx the molecular mechanisms underlying the infiltration and destruction of adjacent tissue as well as the metastatic spread are largely unknown. In this context, the detection of defective expression of cellular adhesion molecules in the tumour cells, e.g. CD44, might be important and correlated with prognosis. Paraffin-embedded tumour-tissue from 99 patients with primary oral and oropharyngeal SCC, additionally including corresponding lymph-node metastases in nine cases, was analysed for expression of the CD44 splice variants v4, v5, v6, v7, and v9 by means of immunohistochemistry. A diminution of at least one of the examined CD44 isoforms compared to the normal oral epithelium was observed in 39.4% of the squamous cell carcinomas. No correlations could be found between CD44 expression and pT- or pN-stage. However, decreased expression of v9 was correlated with higher histological grade (p < 0.001). Moreover, reduced CD44 expression was a statistically significant independent predictor for shorter survival time (p = 0.002) as well as shorter recurrence-free interval (p = 0.004) in addition to pT- and pN-stage. The separate analysis showed that particularly the decreased v7 (p = 0.04) and v9 (p < 0.02) expression in the tumour cells was associated negatively with survival.

Growth and differentiation regulate CD44 expression on human keratinocytes

Several members of the CD44 family of hyaluronan receptors are expressed on keratinocytes. To identify factors that might be important in regulating CD44 expression, we studied CD44 expression on keratinocytes growing in vitro under a variety of conditions and on cells isolated directly from epidermis. Using Western immunoblots and metabolic labeling, we showed that the pattern of CD44 proteins expressed by keratinocytes was strongly influenced by growth and differentiation. Many protein forms of CD44 are expressed on proliferating keratinocytes in preconfluent cultures, whereas only a few forms are expressed on differentiated cells and in confluent cultures. In preconfluent monolayers, at least four splice variants were identified, including epican, CD44H, CD44E, and a 180-kDa variant. In differentiated cells or in confluent cultures, by contrast, only epican and the 180-kDa protein variant were found. Synthesis of all variants is strongly downregulated when keratinocytes become confluent or when they differentiate. Epican is the predominant form of CD44 on keratinocytes under all conditions and is expressed as a heparan, chondroitin, or keratan sulfate proteoglycan. Preconfluent basal keratinocytes, but not confluent or differentiated keratinocytes, also express chondroitin sulfate proteoglycan forms of CD44E and of the 180-kDa core protein. The modal size of the epican expressed on differentiated keratinocytes is smaller than the size of the epican expressed on basal keratinocytes. Thus, cell confluence and differentiation regulate several aspects of CD44 expression on keratinocytes, suggesting nuances in function for the different protein forms.

The antiproliferative effect of lectin from the edible mushroom (Agaricus bisporus) on human keratinocytes: preliminary studies on its use in psoriasis

Lectins or agglutinins are proteins with affinity for specific sugar residues. Peanut agglutinin (PNA) and the lectin from the edible mushroom (Agaricus bisporus, ABL) both bind to the disaccharide galactosyl beta-1,3-N-acetyl galactosamine alpha-. This is expressed in keratinocytes as an O-linked chain on CD44, a polymorphic membrane glycoprotein. Many lectins are mitogens and PNA is a mitogen for colonic epithelial cells. However, ABL reversibly inhibits proliferation of colonic cancer cell lines without cytotoxicity and thus has therapeutic potential in situations such as psoriasis where proliferation is increased. We have therefore investigated the effect of ABL on the growth of normal human cultured keratinocytes and a human papilloma virus (HPV)-transformed cell line. In a 5-day dose-response study, keratinocyte growth was greatly reduced by 1.0 microg/mL ABL and completely inhibited by 3.0 microg/mL ABL (ANOVA, P < 0.0001). Exposure to 1.0 microg/mL ABL for only 8 h gave the same growth inhibition as did continued exposure for 3 days. No cytotoxic or morphological changes were observed. An HPV-immortalized cell line was relatively resistant to ABL: in a 5-day dose-response study, exposure to 30 microg/mL was required to inhibit cell growth completely. Topical application of ABL 0.01% or 0.1% to normal human skin caused no change in skin erythema, blood flow or thickness compared with vehicle or baseline (n = 6). ABL 0. 1% in white soft paraffin was compared with vehicle in 11 psoriatic patients, using comparative contralateral plaques. Twice daily application for 2 weeks showed no significant difference from vehicle-treated sites, although the skin thickness of plaques fell from 5.3 +/- 0.4 (n = 11, mean +/- SEM) to 4.1 +/- 0.3 mm. In view of the in vitro results further studies are warranted, particularly if means can be found to improve the epidermal penetration of the relatively large ABL molecule (60 kDa).

Predominant expression of CD44 splice variant v10 in malignant and reactive human skin lymphocytes

The remarkable functional diversity of the cell surface receptor CD44 may be due to expression of multiple variant isoforms generated by alternative splicing of variant exons. Functional and correlative data implicate a role of CD44 variant isoforms in adhesion dependent processes such as lymphocyte recirculation and tumor progression and metastasis. We have analyzed 25 primary cutaneous lymphomas and 35 reactive lymphoid cell skin infiltrates or T cell-mediated skin diseases for the expression of CD44 variant isoforms. Irrespective of histologic typing, staging, and grading, cutaneous lymphomas as well as nonmalignant skin-infiltrating CD3+ CD4+ and CD8+ T and CD19+ B lymphocytes exhibited a strong expression of CD44v10 and a moderate expression of CD44v3 as determined by immunohistochemistry, immunofluorescence microscopy, and mRNA analysis. Expression of v5, v6, v7, and v9-containing CD44 variant isoforms was not detected. Furthermore, flow cytometry revealed expression of CD44v10 on a significant proportion of peripheral blood lymphocytes from Sézary's syndrome patients and a remarkable co-expression with cutaneous lymphocyte antigen. These results indicate a distinct CD44 variant isoform expression pattern associated with skin-homing lymphocytes different to lymphatic cells at noncutaneous sites. This differential expression pattern of CD44 variant isoforms may contribute to the development of lymphocyte skin infiltrates and/or the unique biologic behavior of cutaneous lymphomas.

Activation-dependent modulation of hyaluronate-receptor expression and of hyaluronate-avidity by human monocytes

During inflammation, activated monocytes (Mo) migrate into tissues where they interact with extracellular matrix components such as hyaluronate (HA), produced in high amounts at inflammatory sites. We determined whether Mo that had invaded sites of cutaneous inflammation bind HA and express the putative HA receptors CD44 isoforms, ICAM-1, or receptor for hyaluronate-mediated motility (RHAMM). In cutaneous inflammation, activated infiltrating Mo displayed high HA avidity and expressed epitopes encoded by CD44s, CD44 variant exons v3, v4, v5, v6, v7, and v9, and ICAM-1, but not RHAMM. We further investigated how activation affects the avidity of Mo for HA and which receptors were responsible for such binding. Mo freshly purified from human peripheral blood bound little HA and expressed CD44s but no epitopes encoded by CD44v exons, ICAM-1, or RHAMM. During short-term tissue culture, Mo upregulated their HA avidity and expression of ICAM-1, CD44s, and epitopes encoded by CD44v, all of which were further augmented by IFN-gamma or lipopolysaccharide, whereas RHAMM was not detectable. Thus in vitro activated Mo resembled Mo that had migrated to inflammatory sites in vivo. Lipolysaccharide or IFN-gamma-induced HA binding was inhibited by more than 90% with monoclonal antibodies directed against N-terminal HA binding domains of CD44s, but not by monoclonal antibodies against CD44v epitopes or ICAM-1. In conclusion, we show that upon in vitro or in vivo activation, Mo enhance their capacity to bind HA. This is critically dependent upon the expression ofCD44s epitopes. Regulated CD44-HA interactions may be important for the ability of Mo to migrate into and within sites of inflammation and for Mo effector functions.

Expression of CD44 variant exons by primary and metastatic oral squamous carcinomas

Abnormal CD44 expression in many neoplasms correlates with behaviour, but reports on its role in oral squamous carcinoma are contradictory. CD44 expression was characterised in a closely matched series of oral carcinomas with and without metastases in both frozen and formalin-fixed tissue and correlated with behaviour and histological grading parameters. Eleven primary oral squamous carcinomas without metastases and nine primary carcinomas with 19 matched metastases were stained immunocytochemically for CD44H and products of variant exons v3, v4/5, v6 and v9. Patterns of staining in frozen and formalin-fixed tissue were correlated with invasive front grading and behaviour using exact inferential statistics. Most primary carcinomas stained for all exons tested but some showed loss of expression of v4/5. Loss of expression was more marked in metastases, but there was no correlation between expression and behaviour or grade. Stromal surfaces of epithelial cells often expressed variant exon products reflecting loss of polarity. This, together with selective loss of v4 and v5 in primary carcinomas and their more frequent loss in metastases, suggests that CD44 may play a role in metastasis of some oral squamous carcinomas.

Reduced expression of the CD44 variant exons in oral squamous cell carcinoma and its relationship to metastasis

In the present study, we examined the expression of CD44 variant exons in human oral squamous cell carcinoma (OSCC). Of ten cell lines from OSCCs, two (KB and H357), as well as the HeLa cell line, failed to express CD44 variant exons. In surgical specimens, all normal mucosa expressed CD44v9 (both mRNA and protein). Of 40 primary OSCCs, 19 (47.5%) showed downregulation of CD44v9, which correlated with tumor cell differentiation, primary metastasis to lymph nodes and secondary metastasis to lymph nodes. The results suggest that the downregulation of CD44v9 may play a role in lymphatic metastasis of OSCC and changes in its expression may be a useful diagnostic tool to determine the metastatic potential of OSCC to lymph nodes. Moreover, three cell lines that failed to express CD44 variant exons might become a useful experimental model to study the role of variant exons in the progression of OSCC.

Down-regulation of human sialyltransferase gene expression during in vitro human keratinocyte cell line differentiation

Sialic acids play important roles in biological processes, such as cell-cell communication and cell-matrix interaction. Histochemical analysis using PNA and LFA lectin has shown that the expression of alpha 2,3-sialic acid linked to Gal beta 1,3GalNAc is high in basal cells and decreases following further keratinocyte differentiation. In the present study, we used an in vitro keratinocyte cell line differentiation model to study expression of alpha 2,3-sialic acid linked to Gal beta 1,3 GalNAc. Treatment of the human papillomavirus type 16-immortalized human keratinocyte (PHK16) cell line with high concentrations (1.0 mM) of Ca2+ resulted in PHK16 cell differentiation and redistribution of PNA binding glycoproteins. The synthesis of alpha 2,3-sialic acid linked to Gal beta 1,3GalNAc is mediated by three beta-galactoside alpha 2,3-sialytransferases, which are the gene products of hST30, hST30/N and hST3 Gal II. Ca2+ treatment of PHK16 cells decreased the mRNA expression of hST30/N, whereas the mRNA of hST30 and hST3Gal II was not detected by Northern blot analysis, suggesting that the hST30/N gene is responsible for sialic acid down regulation during keratinocyte differentiation. In order to examine transcriptional regulation of the hST30/N gene, we first determined the transcriptional starting sites of the hST30/N gene in PHK 16 using 5'-RACE analysis. Two kinds of type B isoforms, types B3 and BX, were identified. Type BX is a novel isoform related to the type B form, but which differs upstream of the B3 exon. The results of Northern blot analysis using a type BX-specific probe suggest that the B3 promoter may be regulated by Ca2+. Using a luciferase assay, we identified a functional DNA portion within hST30/N genomic DNA that confers negative transcriptional regulation on the hST30/N B3 promoter during Ca2+ stimulated human keratinocyte differentiation. This element contains some putative transcriptional factor binding sequence motifs such as AP2.

Ultrastructural analysis of human epidermal CD44 reveals preferential distribution on plasma membrane domains facing the hyaluronan-rich matrix pouches

We used immunogold staining and stereology to examine the ultrastructural localization and to estimate the relative content of CD44 in different strata and cell types of normal human epidermis. We found that CD44 existed almost exclusively on the plasma membranes; only rare labeling occurred on vesicular structures within the cytoplasm. Quantitation of the immunogold particles indicated that the labeling density of melanocytes corresponded to that of basal keratinocytes, and Langerhans cells displayed a labeling density of approximately 10% that of the surrounding spinous cells. Among keratinocyte strata, the highest labeling density occurred on spinous cells, suggesting upregulation of CD44 after detachment from the basement membrane. The plasma membrane distribution of CD44 was compartmentalized, with little signal on cell-cell and cell-substratum contact sites such as desmosomes, the plasma membrane domain facing the basement membrane, and the close apposition of terminally differentiating granular cells. In contrast, CD44 was abundant on plasma membrane domains facing an open intercellular space, rich in hyaluronan. This distribution is in line with a role of CD44 as a hyaluronan receptor, important in the maintenance of the intercellular space for nutritional and cell motility functions in stratified epithelia.

CD44 substituted with heparan sulfate and endo-beta-galactosidase-sensitive oligosaccharides: a major proteoglycan in adult human epidermis

CD44 is a group of cell surface glycoproteins that is generated from a single gene by mRNA splice variation. Its functions in matrix adhesion and tumor invasion are strongly influenced by glycosylation. We studied the glycosylated tissue forms of CD44 from extracts of normal adult human epidermis by using western blotting and immunoprecipitation from short-term skin organ cultures. An antibody for CD44 (Hermes 3) precipitated 7-17% of all 35SO4-labeled proteoglycans (PGs) synthesized in epidermis. Immunoprecipitates digested with heparitinase lost 40-68% of incorporated 35SO4 and 24-40% of [3H]glucosamine, indicating that heparan sulfate was the predominant glycosaminoglycan in epidermal CD44. Chondroitinase ABC released 10-25% and 6-12% of 35SO4 and [3H]glucosamine, respectively. Less than 5% of both isotopes were susceptible to keratanase. Five to 33% of 35SO4 and 26-37% of [3H]glucosamine, however, was released by endo-beta-galactosidase, implying marked substitution by oligosaccharides with N-acetyllactosamine repeats. Heparitinase pretreatment retarded, whereas endo-beta-galactosidase enhanced the mobility of the > or = 180-kDa polydisperse CD44 on agarose gel electrophoresis. On SDS-polyacrylamide gel electrophoresis, however, western blotting and fluorographs of 35SO4-labeled immunoprecipitates showed the main CD44 isoform at > or = 250 kDa and a shift to 180-200 kDa after heparitinase treatment. Keratanase, keratanase II, and chondroitinase ABC had minor effects. A less abundant form of CD44, with a core of 100 kDa, partly substituted with chondroitinase ABC- and endo-beta-galactosidase-sensitive chains, was also present. Therefore, the large heparan sulfate-substituted CD44 forms a significant part of all proteoglycans in normal human epidermis. Both the large and the 100-kDa variant of epidermal CD44 contain endo-beta-galactosidase-sensitive oligosaccharides not previously noted in other cells or tissues.

An essential role for CD44 variant isoforms in epidermal Langerhans cell and blood dendritic cell function

Upon antigen contact, epidermal Langerhans cells (LC) and dendritic cells (DC) leave peripheral organs and home to lymph nodes via the afferent lymphatic vessels and then assemble in the paracortical T cell zone and present antigen to T lymphocytes. Since splice variants of CD44 promote metastasis of certain tumors to lymph nodes, we explored the expression of CD44 proteins on migrating LC and DC. We show that upon antigen contact, LC and DC upregulate pan CD44 epitopes and epitopes encoded by variant exons v4, v5, v6, and v9. Antibodies against CD44 epitopes inhibit the emigration of LC from the epidermis, prevent binding of activated LC and DC to the T cell zones of lymph nodes, and severely inhibit their capacity to induce a delayed type hypersensitivity reaction to a skin hapten in vivo. Our results demonstrate that CD44 splice variant expression is obligatory for the migration and function of LC and DC.

Expression of heparan sulphate and small dermatan/chondroitin sulphate proteoglycans in chronically inflamed human periodontium

Proteoglycans (PGs) function in regulating aspects of cell behavior, such as proliferation, adhesion, and migration. In this report, we investigated the localization of three heparan sulphate PGs (basement membrane [BM] heparan sulphate PG, CD44, and syndecan-1) and two small dermatan/chondroitin sulphate PGs (decorin and biglycan) in chronically inflamed human periodontium. Frozen sections were analyzed by immunofluorescence microscopy. In inflamed tissue, BM heparan sulphate PG showed reduced immunostaining in subepithelial and subendothelial basement membrane. Loss of CD44 and syndecan-1 was common in epithelial cells of inflamed periodontal tissue. Suprabasal keratinocytes of epithelium expressed involucrin, a cornified envelope protein and marker for epithelial differentiation, while the expression of syndecan-1 was weak or absent. In contrast, expression of the mesenchymal variant of CD44 and syndecan-1 was strong in infiltrating lymphocytes. Small dermatan/chondroitin sulphate PGs, decorin and biglycan, were also present in markedly reduced amounts in the periodontal connective tissue in chronic inflammation. In addition, decorin localized in the connective tissue along short rod-like structures. The results suggest that proteoglycan-dependent intercellular adhesion of keratinocytes is decreased and that adhesion of lymphocytes to matrix molecules via cell surface PGs increased in chronic inflammation. Disappearance of adhesion-modulating small dermatan/chondroitin sulphate PGs may further regulate cell migration in inflamed periodontium.

In vitro characterization of chondrogenic cells isolated from chick embryonic muscle using peanut agglutinin affinity chromatography

Specific binding to the lectin, peanut agglutinin (PNA), has been reported in embryonic precartilage tissues, including the condensing limb bud blastema and the caudal half of the developing somite. The present study aimed to test the hypothesis that PNA-binding may be a surface characteristic of chondroprogenitor cells residing within noncartilage tissues, such as muscle, which have the potential of being induced to form cartilage, e.g., in the presence of bone matrix-derived factors. Day-14 chick embryonic pectoral muscle, which contained histochemically detectable PNA-binding cells, was dissociated into single cells (TM cells) and fractionated by PNA affinity chromatography into PNA-binding (PNA+) and nonbinding (PNA-) cells by PNA-Sepharose 6 MB affinity chromatography. The differentiation potential of the PNA-affinity fractionated cells in vitro was analyzed as a function of culture plating cell density. Immunohistochemistry of a number of cell-type-specific differentiation markers, including sarcomeric actin, collagen type II, and aggrecan core protein, demonstrated that PNA+ cells, when cultured as a micromass at high density (20 x 10(6) cells/ml), exhibited a chondrocyte-like phenotype, whereas the PNA-cells remained myogenic; however, both PNA+ and PNA- monolayer cultures (4 x 10(4) cells/ml) behaved as myoblastic cells. The expression of collagen type II mRNA was also confirmed by coupled reverse transcription/polymerase chain reaction analysis. These observations suggest that PNA binding, i.e., the presence of specific galactose-containing cell surface moieties, is likely to be one of the characteristics of chondrogenic cells residing in mesenchymally derived embryonic tissues.

Selective suppression of CD44 in keratinocytes of mice bearing an antisense CD44 transgene driven by a tissue-specific promoter disrupts hyaluronate metabolism in the skin and impairs keratinocyte proliferation

CD44 is a broadly distributed polymorphic glycoprotein that serves as the principal cell-surface receptor for hyaluronate. Although CD44-mediated cell interaction with hyaluronate has been implicated in a variety of physiologic events, including cell-cell and cell-substrate adhesion, cell migration, proliferation, and activation, as well as hyaluronate uptake and degradation, the biologic role of CD44 in vivo in various tissues remains to be determined. In the present work we have developed transgenic mice that express an antisense CD44 cDNA driven by the keratin-5 promoter. These mice lack detectable CD44 expression in skin keratinocytes and corneal epithelium and display abnormal hyaluronate accumulation in the superficial dermis and corneal stroma, distinct morphologic alterations of basal keratinocytes and cornea, and defective keratinocyte proliferation in response to mitogen and growth factors. These alterations are reflected by a decrease in skin elasticity, impaired local inflammatory response and tissue repair, delayed hair regrowth, and failure of the epidermis to undergo hyperplasia in response to carcinogen. Our observations indicate that two major functions of CD44 in skin are the regulation of keratinocyte proliferation in response to extracellular stimuli and the maintenance of local hyaluronate homeostasis.

Is the binding of the lectin Helix pomatia agglutinin (HPA) of prognostic relevance in tumours of the upper aerodigestive tract?

The lectin Helix pomatia agglutinin (HPA) has been used as a prognostic indicator in a number of clinical studies including those of breast, colorectal and gastric cancer. Binding of HPA to tissue sections was associated with a bad prognosis indicating that the carbohydrate residue recognized by this lectin is linked to metastasis. In order to investigate whether HPA binding is also of prognostic relevance in squamous cell carcinomas of the upper aerodigestive tract, 53 tumours of this region were stained with HPA. Almost all tumours (95%) bound HPA to various degrees and hence HPA binding is of no prognostic relevance in this group of tumours. These findings indicate a fundamental difference in the role of carbohydrate residues in metastasis between squamous cell carcinoma (as in our study) and in tumours derived from glandular tissues such as breast, colon and stomach.

Functional significance of CD9 association with beta 1 integrins in human epidermal keratinocytes

CD9 is a member of the tetraspan (TM4) family of proteins and is abundantly expressed in the epidermis. As CD9 forms complexes with beta 1 integrins and the integrins are known to regulate keratinocyte behaviour, we investigated CD9 expression and function in human epidermal keratinocytes. CD9 was present in all the living layers of the epidermis, whereas the beta 1 integrins were largely confined to the basal layer; the same relative distribution was found in stratified cultures of keratinocytes. There was extensive co-localisation of CD9 and beta 1 integrins on microvilli and at cell-cell borders of basal keratinocytes; however, in contrast to the integrins, CD9 was not found in focal adhesions. CD9 was detected in beta 1 integrin immunoprecipitates and also in immunoprecipitates of CD44 and syndecan, but not of cadherins. CD9 was associated with alpha 3 beta 1 but not alpha 5 beta 1; small amounts of CD9 also co-immunoprecipitated with antibodies to alpha 2 beta 1 and alpha 6 beta 4. Antibodies to CD9 did not affect the proportion of keratinocytes that adhered to laminin 1, type IV collagen and fibronectin, but did inhibit motility of keratinocytes on tissue culture plastic. Like antibodies to the beta 1 integrin subunit, anti-CD9 inhibited suspension-induced terminal differentiation. These results suggest that CD9 may play a role in regulating keartinocyte motility and differentiation.

Analysis of human articular chondrocyte CD44 isoform expression and function in health and disease

Interactions between articular chondrocytes and components of the extracellular matrix are of potential importance in the normal function of cartilage and in the pathophysiology of arthritis. Little is known of the basis of these interactions, but cell adhesive molecules such as CD44 are likely to be involved. Immunohistology using six well-characterized anti-CD44 monoclonal antibodies demonstrated standard CD44 isoform (CD44H) expression by all chondrocytes in normal and osteoarthrotic (OA) cartilage but absence of the CD44E variant. Polymerase chain reaction (PCR) of reverse transcribed mRNA from monolayer cultures of normal and OA chondrocytes using primer sequences which span the region containing variably spliced exons produced a predominant band representing the standard form of CD44, which lacks the variable exons 6-15 (v1-v10). No product was seen at the expected size of the epithelial variant of CD44 (CD44v8-10). Use of exon-specific primers, however, showed expression of variant exons resulting in multiple minor isoforms. Standard CD44 was also shown to be the predominantly expressed isoform identified by immunoprecipitation, but human articular chondrocytes did not adhere to hyaluronan in vitro. Chondrocyte CD44 may function as an adhesion receptor for other matrix molecules such as fibronectin or collagen.

A di-hydrophobic Leu-Val motif regulates the basolateral localization of CD44 in polarized Madin-Darby canine kidney epithelial cells

Both in vivo and in vitro the distribution of the resident plasma membrane adhesion protein, CD44, is restricted to the basolateral domain of polarized epithelial cells, suggesting a role in interepithelial interactions. To determine how this localization might be regulated a range of CD44 cytoplasmic domain mutations were generated and a minimal 5 amino acid sequence, His330-Leu-Val-Asn-Lys334, was identified which when deleted results in expression of CD44 on the apical microvillal membrane. Further mutagenesis throughout this regions pinpointed a critical di-hydrophobic motif, Leu331/Val332. The ability of wild type but not mutant CD44 cytoplasmic domains to redirect an apically targeted protein, placental alkaline phosphatase, to the basolateral plasma membrane demonstrates that this sequence can function as a dominant localization signal. This His330-Lys334 sequence is spatially separate from other CD44 regulatory elements and as discussed here, a comparison with known basolateral sorting sequences identified in other transmembrane proteins suggests that a distinct mechanism operates to retain resident plasma membrane proteins in their correct plasma membrane subdomains.

CD44 exon variant 6 epitope and hyaluronate synthase are expressed on HT29 human colorectal carcinoma cells in a SCID mouse model of metastasis formation

The factors which lead to the formation of metastases are generally poorly understood; however the expression of a particular variant of the cell adhesion molecule CD44 may be important in facilitating metastasis formation in colon cancer. The aim of the present study was to investigate the expression of CD44 exon v 6 (CD44v6), hyaluronate (one of its ligands), and hyaluronate synthase, in a clinically relevant animal model of metastatic colon carcinoma. HT29 human colon carcinoma cells were injected subcutaneously between the scapulae of severe combined immunodeficient (SCID) mice and left for 3 weeks (by which time the tumours had produced metastases in the lungs). Morphological observations at the tumour-host interface were consistent with the dissociation of neoplastic cells from the primary tumours, and the ability of these cells to migrate through the extracellular matrix facilitating metastasis formation. Immunohistochemically detectable hyaluronate synthase expression was increased in vivo compared with the parent cell line in vitro. CD44v6 expression and hyaluronate were increased around single cells at the periphery of tumours compared with the central regions. CD44v6 and hyaluronate snythase expression were co-expressed in the same cells. Indeed, the present study is the first to demonstrate hyaluronate synthase expression by an epithelial cell type.