Moesin and CD44 expression in cutaneous melanocytic tumours

Bioinformatics analysis of lncRNA‑associated ceRNA network in melanoma

Melanoma is an extremely malignant tumor with early metastasis and high mortality. Little is known about the process of by which melanoma occurs, as its mechanism is very complex and only limited data are available on its long non-coding RNA (lncRNA)-associated competing endogenous RNAs (ceRNAs). The purpose of this study was to screen out potential prognostic molecules and identify a ceRNA network related to the occurrence of melanoma. We screened 169 differentially expressed mRNAs (DEmRNAs) from E-MTAB-1862 and GSE3189; gene ontology (GO) enrichment analysis showed that these genes were closely related to the development of skin. In the protein-protein interaction network, we screened out a total of 19 hub genes. Furthermore, we predicted the microRNAs (miRNAs) that regulate hub genes using the miRWalk database and then intersected these with GSE35579, resulting in nine DEmiRNAs. We also predicted the lncRNAs that regulate the miRNAs using the LncBasev.2 database. According to the ceRNA hypothesis, and based on the intersection of the DElncRNAs with merged GTEx and TCGA data, we obtained 20 DElncRNAs. A total of four DEmRNAs, nine DEmiRNAs, and 20 DElncRNAs were included in the ceRNA network. Based on Cox stepwise regression and survival analysis, we identified five biomarkers, ZSCAN16-AS1, LINC00520, XIST, DTL, and let-7a-5p, and obtained risk scores. The results showed that most of the differentially expressed genes were related to epithelial-mesenchymal transition (EMT) in melanoma. Finally, we obtained a LINC00520/let-7a-5p/DTL molecular regulatory network. These results suggest that ceRNA networks have an important role in evaluating the prognosis of patients with melanoma and provide a new experimental basis for exploring the EMT process in the development of melanoma.

β-Catenin and CD44 Expression in Keratoacanthoma and Squamous Cell Carcinoma of the Skin

CD44 and β-catenin are adhesion molecules expressed on a wide variety of cells. Failure of this expression is believed to lead to disruption of cell-cell adhesion and to neoplasia. The aim of this study was to investigate the staining intensity of CD44 and β-catenin in keratoacanthomas and squamous cell carcinomas of the skin. The proliferation index, PCNA staining, was also evaluated in these cases. The abnormal expression of β-catenin significantly predominated in squamous cell carcinomas (n = 20, 76.9%) compared with keratoacanthomas (P = 0.002, χ2 = 7.8). Most keratoacanthomas (n = 11, 61.1%) more frequently showed strong staining intensity with CD44 compared with squamous cell carcinoma (P = 0.001, χ2 = 13.7). The proliferation index was higher in squamous cell carcinoma (P = 0.000, χ2 = 12.8). These findings suggest that CD44 and β-catenin expression may have an important role in the development of malignancy and in the determination of biological features of keratoacanthoma and squamous cell carcinoma of the skin.

Moesin overexpression is a unique biomarker of adenomyosis

Adenomyosis is characterized by extension of endometrial glands and stromal cells into the myometrium. Here we proved that 'moesin' is a unique biomarker of adenomyosis. We selected two cases of adenomyosis that had been surgically resected and fixed with formalin. Proteins were extracted from the infiltrating adenomyosis lesions and normal endometrium by tissue microdissection. The extracted proteins were examined using a LC-MS/MS system and the expression profiles of each region were compared. Two hundred and sixty proteins were detected, among which 73 were expressed more in adenomyosis than in normal endometrium. Among these proteins, we focused on overexpression of moesin in adenomyosis. Expression of moesin estimated semiquantitatively using an immunohistochemistry score was higher in adenomyosis than in normal endometrium. In particular, moesin was significanly overexpressed in stromal cells of adenomyosis than in those of normal endometrium. Relative to normal endometrium, moesin was also overexpressed at the RNA level in 9 of 14 cases of adenomyosis and at the protein level in all 14 cases. We also detected activated (phosphorylated) moesin in adenomyosis lesions. The present findings suggest that moesin is characteristically overexpressed and activated in adenomyosis, and that moesin activation may be related to extension of adenomyosis in the myometrium.

Tumor suppressive microRNA-133a regulates novel targets: moesin contributes to cancer cell proliferation and invasion in head and neck squamous cell carcinoma

Recently, many studies suggest that microRNAs (miRNAs) contribute to the development, invasion and metastasis of various types of human cancers. Our recent study revealed that expression of microRNA-133a (miR-133a) was significantly reduced in head and neck squamous cell carcinoma (HNSCC) and that restoration of miR-133a inhibited cell proliferation, migration and invasion in HNSCC cell lines, suggesting that miR-133a function as a tumor suppressor. Genome-wide gene expression analysis of miR-133a transfectants and TargetScan database showed that moesin (MSN) was a promising candidate of miR-133a target gene. MSN is a member of the ERM (ezrin, radixin and moesin) protein family and ERM function as cross-linkers between plasma membrane and actin-based cytoskeleton. The functions of MSN in cancers are controversial in previous reports. In this study, we focused on MSN and investigated whether MSN was regulated by tumor suppressive miR-133a and contributed to HNSCC oncogenesis. Restoration of miR-133a in HNSCC cell lines (FaDu, HSC3, IMC-3 and SAS) suppressed the MSN expression both in mRNA and protein level. Silencing study of MSN in HNSCC cell lines demonstrated significant inhibitions of cell proliferation, migration and invasion activities in si-MSN transfectants. In clinical specimen with HNSCC, the expression level of MSN was significantly up-regulated in cancer tissues compared to adjacent non-cancerous tissues. These data suggest that MSN may function as oncogene and is regulated by tumor suppressive miR-133a. Our analysis data of novel tumor-suppressive miR-133a-mediated cancer pathways could provide new insights into the potential mechanisms of HNSCC oncogenesis.

TRPM1 (Melastatin-1/MLSN1) mRNA expression in Spitz nevi and nodular melanomas

The transient receptor potential cation channel, subfamily M, member 1 (TRPM1/Melastatin-1/MLSN-1) expression has been shown to have prognostic utility in the evaluation of primary cutaneous melanoma. We analyzed a series of spindled and epithelioid cell nevi (Spitz) and primary cutaneous nodular melanomas to determine whether the expression of TRPM1 mRNA may be useful in distinguishing between Spitz nevi and nodular melanomas and to further examine the patterns of TRPM1 mRNA expression in cutaneous melanocytic proliferations. Formalin-fixed, paraffin-embedded tissues from 95 Spitz nevi and 33 nodular melanomas were analyzed for the expression of TRPM1 mRNA by in situ hybridization using (35)S-labeled riboprobes. Ubiquitous melanocytic expression of TRPM1 mRNA was observed in 56 of 95 (59%) Spitz nevi and 4 of 33 (12%) nodular melanomas. Diffusely scattered loss of TRPM1 mRNA was identified in 38 of 95 (40%) Spitz nevi and 2 of 33 (6%) nodular melanomas. Regional loss of the TRPM1 mRNA expression by a significant subset of dermal tumor cells or a complete absence of TRPM1 expression by the dermal tumor was identified in 27 of 33 (82%) nodular melanomas, but only 1 of 95 (1%) Spitz nevi. These findings suggest that the pattern of TRPM1 mRNA expression may be helpful in the differentiation of Spitz nevi and nodular melanomas. Of the 16 patients who experienced metastasis, 15 (94%) had primary tumors that displayed reduced MLSN mRNA expression by all or a part of the dermal tumor.

Tumor necrosis is associated with increased alphavbeta3 integrin expression and poor prognosis in nodular cutaneous melanomas

Background

Tumor necrosis and apoptotic activity are considered important in cancer progression, but these features have not been much studied in melanomas. Our hypothesis was that rapid growth in cutaneous melanomas of the vertical growth phase might lead to tissue hypoxia, alterations in apoptotic activity and tumor necrosis. We proposed that these tumor characteristics might be associated with changes in expression of cell adhesion proteins leading to increased invasive capacity and reduced patient survival.

Methods

A well characterized series of nodular melanoma (originally 202 cases) and other benign and malignant melanocytic tumors (109 cases) were examined for the presence of necrosis, apoptotic activity (TUNEL assay), immunohistochemical expression of hypoxia markers (HIF-1 α, CAIX, TNF-α, Apaf-1) and cell adhesion proteins (α_vβ₃ integrin, CD44/HCAM and osteopontin). We hypothesized that tumor hypoxia and necrosis might be associated with increased invasiveness in melanoma through alterations of tumor cell adhesion proteins.

Results

Necrosis was present in 29% of nodular melanomas and was associated with increased tumor thickness, tumor ulceration, vascular invasion, higher tumor proliferation and apoptotic index, increased expression of α_vβ₃ integrin and poor patient outcome by multivariate analysis. Tumor cell apoptosis did also correlate with reduced patient survival. Expression of TNF-α and Apaf-1 was significantly associated with tumor thickness, and osteopontin expression correlated with increased tumor cell proliferation (Ki-67).

Conclusion

Tumor necrosis and apoptotic activity are important features of melanoma progression and prognosis, at least partly through alterations in cell adhesion molecules such as increased α_vβ₃ integrin expression, revealing potentially important targets for new therapeutic approaches to be further explored.

The molecular basis of melanomagenesis and the metastatic phenotype

The last two decades have seen spectacular advances in our understanding of the biology of melanoma and, in particular, have elucidated the mechanisms operative in disease initiation and progression. With respect to the former, the genetics of melanoma and in particular the impact of genetic defects on dysregulation of the cell cycle are key issues in malignant transformation and are a major focus of this review. With respect to the latter, consideration also is given to the acquisition of growth factor autonomy and the capacity for invasion and metastasis from the standpoint of cell adhesion, motility, and matrix digestion. These events have specific morphologic correlates that will be briefly addressed. Where relevant, we will address certain of the modern pharmacogenetic strategies that flow from these novel observations concerning melanoma biology.

Ezrin in primary cutaneous melanoma

Ezrin is a member of the ezrin-radixin-moesin family of proteins that link the actin-containing cytoskeleton to the plasma membrane. Ezrin is also connected to signaling molecules involved in the regulation of cell survival, proliferation and migration. Here, we examined the expression of ezrin in 95 primary cutaneous melanomas and correlated ezrin expression with conventional prognostic factors and biomarkers. From 12 patients metastatic tissue samples were also examined. In addition to ezrin staining, Mib-1 proliferation antigen, p53 and Bcl-2 were evaluated. Ezrin immunoreactivity was seen in most tumors; only 19 (20%) melanomas were negative. A total of 48 (51%) tumors had weak immunoreactivity and 28 (29%) strong immunoreactivity. The intensity of ezrin immunoreactivity was associated with tumor thickness (Breslow, P=0.0008) and with tumor invasion level (Clark, P=0.004), thicker tumors having stronger immunoreactivity. Also, there was a correlation between higher Mib-1 index in tumors and strong ezrin expression. All metastatic samples (n=12) showed positive ezrin immunoreactivity. In univariate analysis of survival, patients (n=76) with positive ezrin immunoreactivity had worse clinical disease behavior than those (n=19) without ezrin immunoreactivity, but the difference was not significant (P=0.19). In multivariate analysis of survival, the ezrin immunoreactivity was not a significant marker. The results indicate that ezrin is expressed in most primary melanomas of the skin and in all metastatic tumors. Ezrin expression correlates with tumor thickness and level of invasion suggesting an association between ezrin expression and tumor progression.

Comparative Histopathology of Grey-Horse-Melanoma and Human Malignant Melanoma

Equine melanoma shows striking features particularly with regard to clinical development in grey horses: in contrast to malignant melanoma in humans and in solid coloured horses that are characterized by early onset of metastasis, pigment cell tumours display almost benign clinical features in ageing grey horses. Through evolution, grey horses appear to be in a favourable position in regard to the biological behaviour of melanomas. Yet unknown factors inhibiting or retarding early melanoma metastasis may be responsible for this phenomenon. In this study, immunostaining profiles and histopathologic patterns of equine vs. human melanotic tumours were compared. In addition, the expression of melanoma markers currently used in human melanoma detection and characterization were evaluated for their applicability in equine melanoma diagnosis. Immunohistopathologic investigations revealed that benign grey horse melanomas share common features with human blue nevi and with human malignant desmoplastic melanomas, whereas their resemblance to other types of human cutaneous malignant melanomas is less pronounced. Our data equally underline that S-100, proliferating cell nuclear antigen (PCNA), HMB-45, Ki-67, T-311 and CD44 can serve as reliable markers for horse melanomas. Further investigations aiming at identifying factors retarding metastasis in affected grey horses are needed, as they may contribute to the development of novel treatment strategies for human malignant melanoma.

Proteomic analysis of melanoma-derived exosomes by two-dimensional polyacrylamide gel electrophoresis and mass spectrometry

Exosomes are 40-100 nm vesicles released by numerous cell types and are thought to have a variety of roles depending on their origin. Exosomes derived from antigen presenting cells have been shown to be capable of initiating immune responses in vivo and eradicating established tumours in murine models. Tumour-derived exosomes can be utilised as a source of tumour antigen for cross-priming to T-cells and are thus of interest for use in anti-tumour immunotherapy. Further exploration into the protein composition of exosomes may increase our understanding of their potential roles in vivo and this study has examined the proteome of exosomes purified from cell supernatants of the melanoma cell lines MeWo and SK-MEL-28. The vesicular nature and size (30-100 nm) of the purified exosomes was confirmed by electron microscopy and sucrose density gradient centrifugation. Western blotting demonstrated the absence of calnexin and cytochrome c, verifying the purity of the exosome preparations, as well as enrichment of MHC class I and the tumour-associated antigens Mart-1 and Mel-CAM. The two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) protein profiles of exosomes from the two cell lines were highly comparable and strikingly different from the profiles of the total cell lysates. Mass spectrometric sequencing identified proteins present in 49 protein spots in the exosome lysates. Several of these have been identified previously in exosomes but some are novel, including p120 catenin, radixin, and immunoglobulin superfamily member 8 (PGRL). Proteins present in whole-cell lysates that were significantly reduced or excluded from exosomes were also identified and included several mitochondrial and lysosomal proteins, again confirming the proposed endosomal origin of exosomes. This study presents a starting point for future more in-depth protein studies of tumour-derived exosomes which will aid the understanding of their biogenesis and targeting for use in anti-tumour immunotherapy protocols.

Clinical Significance of Cellular Distribution of Moesin in Patients with Oral Squamous Cell Carcinoma

PURPOSE

Moesin is a linking protein of the submembraneous cytoskeleton and plays a key role in the control of cell morphology, adhesion, and motility. The aim of the present study was to elucidate the clinical significance of expression patterns of moesin in patients with oral squamous cell carcinoma (OSCC).

EXPERIMENTAL DESIGN

Immunohistochemistry for moesin monoclonal antibody was performed on 103 paraffin-embedded specimens from patients with primary OSCC, including 30 patients with locoregional lymph node metastasis, and in the sections from nude mice transplanted with two cell lines derived from a single human tongue cancer (SQUU-A and SQUU-B).

RESULTS

Expression patterns of moesin in OSCCs were divided into three groups: membranous pattern; mixed pattern; and cytoplasmic pattern. These expression patterns correlated with tumor size, lymph node metastasis, mode of invasion, differentiation, and lymphocytic infiltration. In about two-thirds of the patients with metastatic lymph node, homogeneous cytoplasmic expression was detected in the metastatic lymph nodes. In addition, SQUU-B with high metastatic potential showed more reduced levels of membrane-bound moesin than SQUU-A with low metastatic potential. A multivariate analysis demonstrated that expression patterns of moesin can be an independent prognostic factor.

CONCLUSIONS

Our results suggest that moesin expression contributed to discriminating between patients with the potentiality for locoregional lymph node metastasis and those with a better prognosis and might improve the definition of suitable therapy for each.

Shifts in cellular localization of moesin in normal oral epithelium, oral epithelial dysplasia, verrucous carcinoma and oral squamous cell carcinoma

BACKGROUND

Moesin, a member of ERM (ezrin/radixin/moesin) family, links actin filaments of cell surface structure to the cell membrane. The purpose of the study is to assess the shifts in cellular distribution of moesin in normal oral epithelium, oral epithelial dysplasia (OED), verrucous carcinoma (VC), and oral squamous cell carcinoma (OSCC).

METHODS

The expression of moesin was evaluated immunohistochemically in paraffin-embedded tissues of 59 specimens of OSCC, 35 specimens of OED, 17 specimens of VC, and five specimens of normal oral epithelium.

RESULTS

In the normal oral epithelia, all specimens showed a pattern of membranous expression against the anti-moesin antibody in the basal layer cells. In the OED specimens, moesin was dominantly expressed in the cell membrane except for the cornified layer. In VC and OSCC specimens, almost the whole of the carcinoma cells were stained with anti-moesin antibody. However, in OSCC samples, moesin was markedly expressed increasingly in the cytoplasm and decreasingly in the cell membrane, as compared with OED and VC. In addition, there was a significant correlation between the pattern of moesin expression and tumor differentiation in OSCC.

CONCLUSIONS

Our results suggest that it is useful to detect the moesin expression as adjunct to screening mucosal lesions in the oral cavity.

The role of the CD44/ezrin complex in cancer metastasis

CD44 is a cell adhesion molecule that was traditionally known as 'homing receptor'. This molecule is known to interact with the ezrin family (ERM family) members and form a complex that plays diverse roles within both normal and abnormal cells, particularly cancer cells. CD44 and ezrin and their respective complex have properties suggesting that they may be important in the process of tumour-endothelium interactions, cell migrations, cell adhesion, tumour progression and metastasis. This article reviews the role of CD44, ezrin family and the CD44/ezrin complex in cancer cells and their clinical impact in patients with cancer.

Ezrin, a membrane-cytoskeletal linking protein, is highly expressed in atypical endometrial hyperplasia and uterine endometrioid adenocarcinoma

We previously demonstrated that ezrin transcription was required for in vitro invasion and was involved in the acquisition of metastatic potential in endometrial cancer cells. In order to determine the functional role of ezrin in endometrial cancer, we examined ezrin protein expression in 20 cancerous and 33 non-cancerous tissues by immunohistochemistry and Western blot analysis. The specimens included 20 uterine endometrioid adenocarcinomas (UEC), seven simple endometrial hyperplasias (sH), seven complex endometrial hyperplasias (cH), seven atypical endometrial hyperplasias (aH), and 12 samples of normal endometrium (NE). Tissues of primary (P) and metastatic (M) lesions of endometrial cancers were obtained from five patients. Ezrin was specifically expressed in UEC and its precursor lesions. Ezrin expression was significantly higher in aH (P<0.05) and UEC (P<0.001) compared with NE, sH, and cH. In addition, ezrin was significantly highly expressed in M compared with P (P<0.05). Ezrin expression was associated with neither clinical stage nor histopathologic grade of UEC. In immunohistochemistry, ezrin was localized in the membrane of metastasized cancer cells, although ezrin was mainly distributed in the cytoplasm of most cancer cells and some endometrial hyperplastic cells. On Western blot analysis, ezrin was also detected in both cytosolic and membrane fractions in aH and UEC, whereas ezrin was detected in only cytosolic fraction in sH and cH. These data suggest that expression and subcellular distribution of ezrin protein play an important role in development and progression of UEC.

Recent advances in melanoma research

Recent advancement in the research of malignant melanoma is reviewed. Among many gene alterations detected in human melanoma, defect of CDKN2A located at chromosome 9p21 seems to be most important in the earlier developmental phase, though significance of this gene in the evolution of melanoma in situ has not been confirmed yet. Deletions of PTEN/MMAC1 on 10q23.3 and AIM1 on 6q21 as well as mutations of ras gene are involved in the later progression stages of melanoma. Adhesion molecules relevant to development and progression of melanoma have been intensely investigated in recent years, revealing crucial roles of cadherins and alpha(v)beta(3) integrin in the biologic behaviors of melanoma cells. Melanoma is characterized by extremely high potential of developing metastases. Dynamic changes of matrix metalloproteinase activity during invasion and movement of melanoma cells may be a major concern in this field. Fragility of blood vessels in melanoma lesions is another important point related to hematogeneous metastases. Acral lentiginous melanoma is a unique subtype of melanoma, because, in contrast to other subtypes, ultraviolet irradiation is not a major factor in its development. Investigation of pathogenesis of acral lentiginous melanoma surely provides us with new information about mechanism of melanocyte transformation. Recent advances in the management of malignant melanoma are also briefly reviewed, such as biochemotherapy, immunotherapy, and gene therapy. Finally, the concept of molecular classification of melanoma by gene expression profile is introduced, which possibly enables us to give the tailor-made therapy for each melanoma patient in the near future.

Altered expression of the ERM proteins in lung adenocarcinoma

Radixin is a member of the ERM (ezrin/radixin/moesin) protein family that is proposed to function as a membrane-cytoskeletal linker. Using differential display analysis, we have identified radixin as a gene down-regulated in primary lung adenocarcinoma. Real-time quantitative reverse transcription polymerase chain reaction confirmed that radixin mRNA was decreased, both in 10 early-stage bronchioloalveolar carcinomas and in 16 invasive lung adenocarcinomas, by 69% (p = 0.0002) and 82% (p < 0.0001), respectively, compared with 9 nontumor lung tissues. Similarly, moesin and ezrin mRNA levels were reduced in lung adenocarcinoma. Immunohistochemistry confirmed that cancer cells expressed very little radixin and moesin, whereas non-neoplastic alveolar and bronchiolar epithelial cells, and endothelial cells, including those within the tumor stroma, were consistently positive for these two proteins. Ezrin was localized in the apical surface of non-neoplastic bronchiolar and alveolar epithelial cells and, in contrast to radixin and moesin, the majority of tumor cells retained expression of ezrin. Localization of ezrin was altered in a significant proportion of tumor cells: whereas tumor cells forming lumina displayed membranous staining on the apical side, tumor cells with disorganized structures were either negative or diffusely positive for ezrin in the cytoplasm. Furthermore, a fraction of tumor cells invading the stroma in a scattered manner were strongly positive for ezrin. In conclusion, expression of radixin and moesin is down-regulated in lung adenocarcinoma, including early-stage bronchioloalveolar carcinoma. An intriguing implication of this finding is that these two genes may function as tumor suppressors in lung adenocarcinoma oncogenesis. Although structurally related to radixin and moesin, ezrin may have a distinct function in tumor-cell invasion.

Reduced level of CD44 and hyaluronan associated with unfavorable prognosis in clinical stage I cutaneous melanoma

The cell surface glycoprotein CD44 and its ligand, hyaluronan (HA), enhance growth and metastatic capacity of melanoma cells in vitro, but their clinical significance in primary cutaneous melanoma is still unclear. Therefore, we studied whether the levels of CD44 and HA associate with disease progression and survival of cutaneous melanoma. A series of 292 clinical stage I cutaneous melanomas was analyzed by immunohistochemistry using an anti-CD44H antibody (clone 2C5). HA was demonstrated histochemically using a biotinylated HA-specific affinity probe (bHABC). The reduced staining levels of CD44 and HA were associated with each other and indicators of progressive disease. Reduced CD44 and HA level, high tumor thickness, high pT category, high Clark's level, bleeding, and male gender predicted short univariate recurrence free survival (RFS) and overall survival (OS). In Cox's multivariate analysis (N: = 251), the decreased level of CD44, high tumor thickness, and bleeding predicted independently short RFS. High tumor thickness and bleeding were associated with short OS. We conclude that the reduced cell surface CD44 and HA levels associate with poor prognosis in clinical stage I cutaneous melanoma. The notion that the decreased level of CD44 independently predicts short RFS suggests that reduced cell surface CD44 enhances the spreading potential in localized cutaneous melanoma and that quantification of CD44 offers a prognostic tool for its clinical evaluation.

Ezrin, a membrane-cytoskeletal linking protein, is involved in the process of invasion of endometrial cancer cells

In order to study ezrin function in tumor growth and invasion, we used two cell lines of human endometrial cancers. Ishikawa, the low-metastatic endometrial cancer cell line, and its subclone (mEIIL) with high-metastatic activity and higher ezrin expression were treated with a ezrin antisense phosphorothioate oligonucleotides (ePONs) pulse four times before the in vitro growth assay and Matrigel invasion assay. ePONs significantly suppressed the number of both cells that penetrated through Matrigel membrane (inhibition rate; 40.1 +/- 7.5% (Ishikawa), 42.7 +/- 2.4% (mEIIL), mean +/- SD, n = 6, P < 0.05, Student's t-test), whereas they showed no effect on cell proliferation. Ezrin expression at the protein level was inhibited by ePONs. These data suggest that ezrin expression is required for invasion. The association of high ezrin expression in mEIIL and its higher ability to migrate through Matrigel may at least in part indicate functional significance of ezrin in endometrial cancer metastasis.

Increased synthesis of hyaluronate enhances motility of human melanoma cells

Hyaluronate plays a unique role in the cancer cell microenvironment. In particular, melanoma is the tumor type in which hyaluronate and hyaluronate recognition have been most closely linked to malignancy. In this study we show that a human melanoma cell line stably transfected with hyaluronate synthase cDNA displays enhanced motility. We used a fixed erythrocyte exclusion assay to isolate subsets of the WM793 human melanoma cell line that expressed either high or low amounts of hyaluronate. A cell line with a high level of hyaluronate on its surface (WM793H) displayed significantly higher cell motility on colloidal-gold-coated coverslips than did a line with a low level (WM793L). Next, in order to directly investigate the effects of hyaluronate on melanoma cell migration, we transfected cDNA encoding mouse hyaluronate synthase HAS1 or HAS2 into the re-cloned human melanoma cell line that produced a low amount of hyaluronate (WM793L) by the lipofection method. Several clonal transfectants differentially producing hyaluronate were obtained. There was a positive correlation between total hyaluronate synthesis and formation of the pericellular hyaluronate-rich matrix. We observed an increase in the migration ability of hyaluronate cDNA (HAS1 or HAS2)-transfected cells compared with control cells on glass plates covered with colloidal gold particles. A migration-inhibition assay with anti-CD44 monoclonal antibody showed blocking of the cell motility. It is speculated that the tumor cells might migrate through a hyaluronate-rich extracellular environment when they invade nearby host tissues and that hyaluronate production by the tumor cells could increase this migration. These results suggest that hyaluronate may play a role in the aggressiveness of human melanoma cells.

Colocalization of basic fibroblast growth factor and CD44 isoforms containing the variably spliced exon v3 (CD44v3) in normal skin and in epidermal skin cancers

Previous in vitro studies have shown CD44 isoforms containing the alternatively spliced exon v3 (CD44v3) to be modified with heparan sulphate (HS) and to bind HS-binding basic fibroblast growth factor (bFGF). Here, we demonstrate that exogenously added bFGF is also bound in vivo by CD44v3-positive keratinocytes in normal skin and by tumour cells in basal cell carcinoma and squamous cell carcinoma (SCC), two skin cancers of keratinocyte origin. bFGF binding and CD44v3 expression were colocalized in cultured human normal keratinocytes (HNK) and on the SCC cell line A431. By contrast, benign or malignant tumours of melanocyte origin failed to express CD44v3 and bound no bFGF. The bFGF binding to normal or transformed keratinocytes in vivo and in vitro was dependent on HS modification, as it was completely eliminated by pretreatment with heparitinase or by blocking with free heparin, whereas chondroitinase had no effect. In addition, specific removal of CD44v3 by antibody-induced shedding also diminished bFGF binding to keratinocytes. Furthermore, bFGF stimulated the proliferation of CD44v3-positive HNK and A431 in a dose-dependent fashion. This bFGF effect was again completely abolished by heparitinase or free heparin, but not by chondroitinase. In aggregate, our results suggest that a function of HS-modified CD44 isoforms such as CD44v3 in skin is to present the HS-binding growth factor bFGF, thereby stimulating the proliferation of normal or transformed keratinocytes.