Changes in CD44 isoform expression during inflammatory skin disease

The CD44 family of cell surface glycoproteins is widely-expressed in epithelial, mesothelial and haemopoietic tissues and is thought to function primarily as adhesion molecules. The molecule has an intracellular, a trans-membrane and an extracellular domain. The membrane proximal region of the extracellular domain is of variable structure depending on which of 10 variable exons are involved in coding for this region. Both in vitro stimulated T cells and cytokine stimulated keratinocytes are known to express certain isoforms. In this study we have investigated whether specific isoforms of the CD44 molecule are expressed on epithelial cells and lymphocytes in the course of two inflammatory skin diseases, namely lupus erythematosus and lichen planus. Monoclonal antibodies, specific to the epitopes of the CD44 molecule encoded by v3, v4/5, v6 and v8/9 variable exons and a pan CD44 marker, were used on 10 lupus and 8 lichen planus frozen skin samples and compared with normal skin from 9 different body sites. Results failed to show detectable levels of variant isoforms of CD44 on lymphocytes in either inflammatory skin disease, despite evidence of T cell activation. All CD44 variant isoforms were reduced on the keratinocytes in some sections of lupus and lichen planus. The results are discussed in the context of the current models for the role of CD44 in the immune response.     

Detection of CD44 splice variants in formalin-fixed, paraffin-embedded specimens of human skin cancer

The standard form of CD44 (CD44s) and CD44 isoforms, containing sequences encoded by one or several of 10 different variant CD44 exons (v1-v10), are thought to play a crucial role in the growth and metastasis of certain human tumors. Recently, monoclonal antibodies (mAbs) directed against all CD44 isoforms (panCD44), or against epitopes encoded by specific variant exons (CD44v) have been developed, which unfortunately only stain cryopreserved tissues. We wished to develop a technique to unmask chemically CD44s and CD44v epitopes in paraffin-embedded specimens of human skin cancers, so that they would be accessible for these mAbs. To address this issue, CD44s and CD44v expression was compared in cryopreserved and in formalin-fixed, paraffin-embedded biopsies obtained from the same basal cell carcinomas (BCC), squamous cell carcinomas (SCC), primary malignant melanomas (PMM) and metastatic malignant melanomas (MMM). Formalin-fixed tumors were de-paraffinized and treated briefly with an antigen retrieval fluid (TUF™) at 95°C or left untreated. In untreated paraffin-embedded tissues, no CD44s or CD44v staining was detected. In contrast, in antigen retrieval fluid-treated biopsies CD44s and CD44v expression was identical to that in cryopreserved specimens of the same tumor with the exception of mAbs detecting v7/8 and v10. We conclude that antigen retrieval unmasks certain epitopes in formalin-fixed, paraffin-embedded tissues, thus facilitating future research on the relevance of CD44s and CD44v expression for human skin carcinogenesis.     

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.     

CD44 and hyaluronate in the differential diagnosis of dermatofibroma and dermatofibrosarcoma protuberans

The histological distinction between dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) may be extremely difficult. CD34 and Factor XIIIa have been used to differentiate DF from DFSP. However, there is an overlap and relative lack of specificity of their expressions. CD44 is a widely distributed integral membrane glycoprotein, which is expressed as a multitude of isoforms generated by alternative splicing of at least 10 different variant exons and post-translational modifications. CD44 is currently thought to be the principal cell surface receptor for hyaluronate (HA), the major component of the extracellular matrix. In this study we aimed to assess the expression of standard CD44 (CD44s) and its isoforms (CD44v3, CD44v4, CD44v5, CD44v6, CD44v7, CD44v7v8, and CD44v10), and HA in DF and DFSP. Immunohistochemical staining was performed on the biopsy specimens of 15 cases of DF and four cases of DFSP, using antibodies that recognize the CD44s, different CD44 isoforms and the hyaluronate binding protein (HABP). Tumor cells displayed a strong CD44s immunoreactivity in all cases of DF whereas a faint HA positivity was observed in the tumor stroma. The DF cells were negative for CD44v3, CD44v4, CD44v6, CD44v7 and CD44v7v8 but showed a strong reactivity for CD44v5 and CD44v10. In contrast, CD44s' expression was significantly reduced or absent in all DFSP lesions and the tumor stroma displayed strong staining for HA. Our results indicate that CD44 and HA can be used as additional diagnostic markers to distinguish DF from DFSP.     

Atypical Response of Xeroderma Pigmentosum to 5‐Fluorouracil: A Histopathological Image Analysis Study Reveals New Insight into Etiopathogenesis

The histological distinction between dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) may be difficult. CD34 and Factor XIIIa have been used to differentiate DF from DFSP, but there is a lack of specificity. CD44 is a membrane glycoprotein which has multiple isoforms generated by alternative splicing of variant exons. CD44 is the principal cell surface receptor for hyaluronate (HA). In this study we explored the expression of standard CD44 (CD44s) and its isoforms (CD44v3, CD44v4, CD44v5, CD44v6, CD44v7, CD44v7v8, and CD44v10), and HA in DF and DFSP. Immunohistochemistry was performed on the biopsy specimens of 15 cases of DF and 4 cases of DFSP, using antibodies for the CD44s and its isoforms, and hyaluronate binding protein (HABP). Tumor cells displayed a strong CD44s immunoreactivity in all cases of DF whereas a faint HA positivity was observed in the tumor stroma. DF cells were negative for CD44v3, CD44v4, CD44v6, CD44v7 and CD44v7v8 but they showed a strong reactivity for CD44v5 and CD44v10. CD44s expression was significantly reduced or absent in all DFSP lesions and the tumor stroma displayed a strong staining for HA. Our results indicate that CD44 and HA can be used as additional diagnostic markers to distinguish DF from DFSP.     

CD44 and variants in melanocytic skin neoplasms

Expression of cell surface molecules that mediate cell-matrix and cell-cell interactions largely contributes to the ability of melanoma cells to migrate and spread beyond the primary site of the tumor. CD44, the principal cell-surface receptor for hyaluronate, and its numerous splice variants have been reported to play a crucial role in invasion and the metastatic process of different human neoplasms, including primary malignant melanoma (PMM). The aim of this study was to clarify which isoforms of CD44 (standard CD44 and CD44 variants) are distributed in PMM with a vertical tumor thickness of >1.4 mm. Staining of CD44 standard (CD44s) and splice variants was further examined for diagnostic and prognostic relevance in a panel of melanocytic skin lesions. Ten cases of PMM with Breslow >1.4 mm were analysed by immunohistochemistry using monoclonal antibodies specific for CD44s and the splice variants v3, v5, v6, v7, v7-8, and v10. In addition, using anti-CD44s, v5, and v6 antibodies, 55 meianocytic lesions, including dermal nevi (n=12), Clark nevi (dysplastic nevi) (CN; n=11), melanoma in situ (Mis; n=8), PMM (n=18), and cutaneous metastasis of malignant melanoma (cM-MM; n=6) were assessed. Staining intensities were scored visually and evaluated by means of a staining index. In ten cases of PMM with a Breslow index >1.4 mm positive staining was ascertained for CD44s, v5 and for v6 in three cases. No staining was found for v3, v7, v7-8, and v10. Examination of CD44s, v5, and v6 in 55 melanocytic skin lesions revealed a high index for CD44s in all specimens and a weak staining of v5 in Mis; dermal nevi and CN did not stain for v5. However, in PMM and cMMM we found v5 to be strongly positive. The isoform v6 showed a variable index only in PMM, but without connection to established prognostic criteria. We conclude that CD44s and splice variants can not be regarded as indicators for tumor progression in malignant melanomas. However, v5 may potentially serve as a diagnostic marker for meianocytic skin lesions.     

Gottron's papules exhibit dermal accumulation of CD44 variant 7 (CD44v7) and its binding partner osteopontin: a unique molecular signature

The accumulated mucin in non-Gottron's dermatomyositis (DM) lesions is primarily chondroitin-4-sulfate (C4S), which is immunomodulatory in vitro. Gottron's papules are a particularly resistant manifestation of DM that often persist after other lesions have resolved with therapy. We examined non-Gottron's DM lesions and Gottron's papule skin biopsies for C4S, CD44 variant 7 (CD44v7), a chondroitin sulfate-binding isoform causally implicated in autoimmunity, and osteopontin (OPN), a CD44v7 ligand implicated in chronic inflammation. Gottron's papule dermis contained more C4S and CD44v7 than non-Gottron's lesions. Normal skin showed less CD44v7 over joints relative to Gottron's lesions. All DM dermis had increased OPN compared with healthy skin. Mechanically stretching cultured fibroblasts for 6?hours induced CD44v7 mRNA and protein, whereas IFN-γ treatment induced OPN mRNA and protein. OPN alone did not induce CD44v7, but stretching dermal fibroblasts in the presence of OPN increased human acute monocytic leukemia cell line (THP-1) monocyte binding, which is blunted by anti-CD44v7 blocking antibody. C4S, CD44v7, and OPN are three molecules uniquely present in Gottron's papules that contribute to inflammation individually and in association with one another. We propose that stretch-induced CD44v7 over joints, in concert with dysregulated OPN levels in the skin of DM patients, increases local inflammatory cell recruitment and contributes to the pathogenesis and resistance of Gottron's papules.     

Hyaluronan-independent adhesion of CD44H+ and CD44v10+ lymphocytes to dermal microvascular endothelial cells and keratinocytes.

We have recently shown the CD44 variant isoform 10 (CD44v10) to be expressed on reactive as well as malignant cutaneous lymphocytes; however, the functional consequences of CD44v10 expression on lymphocytes are not elucidated. By using appropriately transfected lymphatic cells we analyzed the role of CD44v10 on lymphocytes in cell-matrix adhesion and homotypic and heterotypic cell-cell adhesion assays. Despite a low binding affinity to hyaluronan, CD44v10-expressing lymphocytes exhibited heterotypic cell-cell adhesion to inflamed dermal microvascular endothelium and keratinocytes, as indicated by Stamper-Woodruff assays on tissue sections of delayed type hypersensitivity reactions and adhesion assays with cultured keratinocytes and cytokine-stimulated human dermal microvascular endothelial cells. Antibody-blocking assays excluded interaction of CD44v10 with the principal CD44 ligand hyaluronan as well as involvement of selectins or integrins in these heterotypic cell-cell adhesion assays. In contrast, cellular aggregation assays with fluorescence-labeled CD44v10- and CD44H-expressing lymphocytes revealed homotypic CD44v10/CD44v10 binding as well as binding of CD44v10 with CD44H. Heterotypic cell-cell adhesion assays with ultraviolet-A-irradiated CD44v-negative cytokine-stimulated endothelial cells demonstrated binding kinetics of CD44v10-expressing lymphocytes paralleling those of endothelial CD44H expression. These results imply that a hyaluronan-independent CD44v10/CD44H-mediated pathway is involved in lymphocyte infiltration into the dermis and epidermis of inflamed skin and suggest modulation of CD44H expression on inflamed dermal microvascular endothelium as a mechanism of ultraviolet-A-induced therapeutic effects on the skin.     

Expression of S100A2 and S100B proteins in epithelial tumors of the skin

BACKGROUND: The purpose of this study was to evaluate the expression of Ca2+-binding S100 proteins, S100A2 and S100B, in normal skin. These immunohistochemical stain patterns were compared with those in a variety of epithelial tumors. METHODS: Paraffin-embedded tissues of 38 skin tumors were evaluated immunohistochemically with S100A2 and S100B antibodies. RESULTS: Epidermal basal cells, epithelial cells of sebaceous glands, hair follicle epithelia, and eccrine ducts reacted strongly with S100A2 antibody. Langerhans' cells and melanocytes were labeled by S100B. Varying types of skin appendage tumors and most peripheral cells in tumor nests of basal cell carcinoma and squamous cell carcinoma showed positive S100A2 immunoreactivity in neoplastic cells. Basophilic cells of calcifying epithelioma were occasionally stained with S100A2 antibody. Chondroid syringoma containing neoplastic myoepithelial cells stained strongly for both S100A2 and S100B. CONCLUSIONS: We conclude that S100A2 can be a specific marker of epithelial cells in the different skin tumors. However, these antibodies are not of much help in classifying skin appendage tumors.     

CD44 variant expression in cutaneous T-cell lymphoma

Expression of the lymphocyte homing receptor CD44 and its splice variants have been linked to tumour dissemination and poor prognosis in non-Hodgkin's lymphoma. Specifically, the in vitro expression of variant exon V6 confers metastatic potential in rat pancreatic carcinoma cell lines. In this study, we investigated the expression of CD44 splice variants in cutaneous T-cell lymphomas, including patients with mycosis fungoides (MF), Sezary syndrome (SS), large-cell anaplastic lymphoma (LCAL) and HTLV1-associated cutaneous lymphoma. In addition, 4 involved lymph nodes from 2 patients with MF and 1 patient with SS were examined. Inflammatory dermatoses, lichen planus and psoriasis, and normal skin were also studied. Immunohistochemistry was performed using a panel of monoclonal antibodies, including those with specificity for CD44H (standard isoform) and variant exons V3, V6 and V8-9. Normal epidermal keratinocytes were consistently CD44H and CD44 V3, V6 and V8-9 positive. In all the different clinicopathological subtypes and stages of cutaneous T-cell lymphomas, including involved lymph nodes, tumour cells consistently expressed CD44H, but were CD44 V3 and V6 negative. CD44 V8-9 was expressed on a majority of tumour cells in 2/5 LCAL and on occasional tumour cells in 2/5 LCAL. Occasional V8-9 positive tumour cells were also identified in 6/13 MF, 1/4 SS and 3/4 HTLV1. In 2/3 lymph node samples from 2 patients with tumour-stage MF, CD44 V8-9 expression was found on a small percentage of atypical mono-nuclear cells. Scattered V8-9 positive dermal mononuclear cells were present in sections of lichen planus and psoriasis. We have found no evidence to suggest that the metastasis-associated CD44 variant exon (V6) is expressed in cutaneous T-cell lymphoma, or that CD44H expression is associated with an adverse prognostic group. It is not clear whether the strong expression of CD44 V8-9 in 2 patients with CD30 positive LCAL reflects activation status or metastatic potential.     

CD44 and melanocytic tumors: a possible role for standard CD44 in the epidermotropic spread of melanoma

CD44 is a polymorphic family of cell membrane glycoproteins that mediate cell-matrix and cell-cell interactions involved in the mechanisms of tumor invasion and metastasis, and are subject to differential regulation during normal and malignant cell growth. We have investigated immunohistochemically the expression of CD44S and the variant isoforms CD44v3 and CD44v6 in paraffin-embedded tissue from 5 Spitz nevi, 3 compound melanocytic nevi, 2 blue nevi, 6 primary melanomas, 15 cutaneous metastases (three epidermotropic, nine dermal and three ulcerated) and 10 lymph node metastases of melanoma. Melanocytes were extensively positive for CD44S in primary melanomas and benign melanocytic proliferations. Among 15 cases of cutaneous metastases of melanoma, the three epidermotropic metastases, as well as one of the three ulcerated ones were positive for CD44S. CD44S expression was diminished or totally absent in six of the nine dermal metastases, in two of the ulcerated metastases and in seven of the ten lymph node metastases. CD44v3 and CD44v6 melanocytic expression was absent in all the lesions studied.
According to our results, selective retention of CD44S expression by melanocytes in epidermotropic metastases of melanoma seems to indicate that preservation of CD44S may contribute to the intraepidermal spread of melanoma.     

Expression of CD44 isoforms in basal cell carcinomas

The expression of CD44 isoforms (CD44std, CD44v6, CD44v10) was investigated by an immuno-histochemical technique in 42 basal cell carcinomas (BCC) of the superficial and nodular variety. All BCCs studied displayed very low amounts of CD44std, a receptor for hyaluronic acid. Except for single CD44std-positive cells located preferentially in the central parts of the BCC nests, the bulk of the tumour formations were CD44std-negative. CD44v6 showed a heterogeneous distribution pattern accentuated in the peripheral palisading tumour cells. In superficial BCCs, the labelling intensity for CD44v6) increased with the size of the tumour nests. CD44v10 was not detectable in BCCs Our findings support the notion that CD44v6 is not linked to the metastatic proclivity of tumours originating from keratinocytes. We suggest that the very low expression of the receptor for hyaluronic acid (CD44std) may be one of the factors which block the formation of metastases from BCCs.     

Lymphocyte migration into the skin: the role of lymphocyte homing receptor (CD44) and endothelial cell antigen (HECA-452).

Lymphocyte migration into the lymphoid organs and sites of inflammation is controlled by lymphocyte-endothelial cell interaction at sites where lymphocytes exit from the blood. Expression of Hermes-defined CD44 class of lymphocyte homing receptor and HECA-452 antigen specific for high-endothelium-mediating physiologic lymphocyte extravasation was studied in dermatitis herpetiformis, celiac disease, psoriasis, mycosis fungoides, lymphocytosis cutis, atopic dermatitis, and allergic contact dermatitis. Also, duodenal biopsies of patients suffering from dermatitis herpetiformis or celiac disease were studied for existence of these antigens. Infiltrating lymphocytes in the skin and in the duodenal area expressed homing receptor molecules when studied with monoclonal antibodies, Hermes-1 and Hermes-3, that recognize the CD44 class of molecules involved in lymphocyte binding to high endothelial venules in peripheral lymph nodes, mucosa-associated lymphatic tissues, and inflamed synovium. However, the HECA-452 antigen was not detected on the venules, neither in the skin nor in the duodenum. Even the venules possessing high endothelium morphologically were HECA-452 negative. These findings suggest the CD44 class of lymphocyte homing receptor(s) is also involved in lymphocyte homing to inflamed skin and the duodenal area of the gut. However, on the basis of HECA-452 staining, high endothelial venules in inflamed skin and duodenum are not antigenically identical with high endothelial venules in organized lymphoid tissues. This finding indirectly supports the idea that molecules and/or mechanisms mediating lymphocyte extravasation might be distinct in these organs.     

Transient CD44 variant isoform expression and reduction in CD4(+)/CD25(+) regulatory T cells in C3H/HeJ mice with alopecia areata

Alopecia areata, an autoimmune disease affecting anagen stage hair follicles, can be induced by grafting spontaneous alopecia areata affected skin to normal-haired C3H/HeJ mice. As the onset of alopecia areata can be significantly retarded by anti-CD44 variant isoform 10 treatment, it was interesting to explore the underlying disease mechanism. Two weeks after transplanting alopecia areata affected skin, expression of CD44 variant isoforms 3, 6, 7, and 10 was strikingly upregulated as compared with sham-grafted mice. By 6 wk after grafting, CD44 variant isoform levels had returned to normal, whereas in draining lymph nodes, CD44 variant isoform expression was slightly decreased. Leukocytes in the skin of mice with chronic alopecia areata expressed a hematopoietic isoform of CD44 and CD44 variant isoform 6 at an elevated level, but CD44 variant isoform 3 expression was reduced. Cytokine expression in leukocytes of chronic alopecia areata affected skin was higher than in normal-haired controls. Cytokine expression also increased postsurgery in sham and alopecia areata grafted mice, but remained elevated only in mice receiving alopecia areata affected skin. Finally, from the skin of mice with chronic alopecia areata and of mice transplanted with alopecia areata affected skin, an increased number of CD4(+) and CD8(+) cells, but a strongly decreased number of CD4(+)/CD25(+) regulatory T cells was recovered. Thus, expression of CD44 variant isoforms is important for the migration of leukocytes during the initial period of alopecia areata. CD44, however, is apparently not involved in the maintenance of the disease state, which is characterized by high cytokine expression levels, an increased number of CD4(+) and CD8+ cells, but a low level of CD4(+)/CD25(+) suppressor cells.     

Expression of CD44 and CD44v6 in primary cutaneous CD30 positive T-cell lymphoproliferative disorders

BACKGROUND: Expression of the lymphocyte homing receptor CD44 and its variant form, CD44v6, have been linked to unfavorable prognosis and tumor dissemination in non-Hodgkin's lymphoma. The role of CD44 and CD44v6 in primary cutaneous lymphomas may not necessarily correlate with that observed in nodal lymphomas. Our study attempts to evaluate the expression pattern of CD44 and CD44v6 in primary cutaneous CD30 positive T-cell lymphoproliferative disorders including primary cutaneous anaplastic large cell lymphoma (cALCL) and lymphomatoid papulosis (LyP) and compared the expression between these two subgroups. METHODS: Immunohistochemical staining of CD44 and CD44v6 was performed on 10 cALCL and 18 LyP cases. RESULTS: CD44 consistently expressed in all cases of primary cutaneous CD30 positive T-cell lymphoproliferative disorders. In contrast with previous studies, our results showed that CD44v6 expressed in 46% of all cases, including 50% cALCL and 44% LyP. There was no statistic difference in expression of CD44 or CD44v6 between cALCL and LyP subgroups. CONCLUSIONS: These results provide a new evidence that CD44v6 is expressed in a subset cases of primary cutaneous CD30 positive T-cell lymphoproliferative disorders and suggest that other factors or molecules rather than CD44 or CD44v6 are responsible for the difference between cALCL and LyP.     

CD44 variant isoform v10 is expressed on tumor-infiltrating lymphocytes and mediates hyaluronan-independent heterotypic cell-cell adhesion to melanoma cells

CD44 is a family of cell-surface receptors on human lymphocytes that act as co-stimulatory molecules leading to the induction of effector functions in T cells. We have analyzed primary cutaneous malignant melanomas with clinical and histologic signs of tumor regression using immunohistochemistry and observed the predominant expression of the CD44 variant isoform v10 on CD3 CD4/CD8 co-expressing tumor-infiltrating lymphocytes (TIL). We further analyzed the role of CD44v10 in adhesion of lymphocytes to human melanoma cells. In contrast to CD44- lymphatic cells, CD44v10+ lymphatic cells strongly bound to cultured human melanoma cells and to frozen tissue samples of melanomas. Antibody blocking studies revealed a hyaluronan-, integrin-, and selectin-independent pathway of adhesion. Furthermore, CD44v10+ lymphatic cells exhibited significantly higher invasiveness in three-dimensional collagen matrices as compared with CD44H+ and CD44-negative lymphocytes. These results indicate that expression of CD44v10 on TIL may mediate adhesion to melanoma cells and result in gain of novel invasive properties.     

Hyaluronan,CD44 and versican in epidermal keratinocyte tumours

BACKGROUND: The high molecular weight polysaccharide hyaluronan is a major component of the extracellular matrix between the vital cells of human skin epidermis. The levels of hyaluronan, and those of the hyaluronan receptor CD44 and the hyaluronan binding proteoglycan versican, correlate with the aggressiveness of different human carcinomas of epithelial origin. OBJECTIVES: To study skin keratinocyte tumours for the expression of hyaluronan, the hyaluronan receptor CD44 and the hyaluronan binding proteoglycan versican. METHODS: Paraffin-embedded sections of 114 basal cell carcinomas (BCC), 31 in situ carcinomas (ISC) and 35 squamous cell carcinomas (SCC) were stained with a hyaluronan specific probe, biotinylated hyaluronan binding complex, and with monoclonal antibodies against CD44 and versican. RESULTS: Compared with normal epidermis, ISC and well differentiated SCCs showed an enhanced hyaluronan signal on carcinoma cells while CD44 expression level resembled that of normal skin. Less differentiated SCCs showed reduced and irregular expression of both hyaluronan and CD44 on carcinoma cells. In BCCs, hyaluronan and CD44 signals were absent or very low on the surface of carcinoma cells. However, hyaluronan was frequently present on BCC cell nuclei, a feature completely absent in ISC, SCC and normal epidermis. An accumulation of hyaluronan in the connective tissue stroma around the tumour was more frequent in SCCs than BCCs. Versican staining was positive around hair follicles and dermal blood vessels of normal skin. Peritumoral versican signal was present in a part of the BCCs but not in other tumours. CONCLUSIONS: The completely different hyaluronan and CD44 expression patterns in BCC and SCC probably reflect the different origins of the tumours, with BCC an undifferentiated keratinocyte and SCC a keratinocyte at an early stage in the differentiation pathway. The difference in hyaluronan and CD44 expression between these tumours may also contribute to the difference in their capacity to metastasize.     

Differential expression of laminin isoforms and beta 4 integrin epitopes in the basement membrane zone of normal human skin and basal cell carcinomas.

The basement membrane zone biology of normal human skin and basal cell carcinomas was explored by indirect immunofluorescence with monoclonal antibodies recognizing five subunit polypeptides of three different laminin isoforms as well as the beta 4 integrin epitopes. The laminin antibodies were specific for A, B1, and B2 chains of classic laminin, for the M chain of merosin, or for the S chain in S-laminin. Immunostaining of normal human skin revealed a strong signal with antibodies for A, B1, and B2 chain epitopes. A weak immunosignal was detected with an anti-M chain antibody, whereas the S-chain epitopes were undetectable, even following pretreatment of sections with hyaluronidase. Thus, the laminin at the epidermal-dermal junction of normal human skin is primarily of the classic type, with some merosin molecules being present. The staining of six nodular basal cell carcinomas revealed the presence of A, B1, and B2 chain epitopes in a linear pattern, but, in contrast to normal skin, the antibody recognizing M-chain epitopes yielded a strong immunosignal, and S-chain epitopes could also be readily detected. Staining for beta 4 integrins, potential receptors for laminin, revealed a strong staining reaction in normal skin as well as in the superficial portions of the basal cell carcinoma. However, the immunofluorescence pattern in the deeper portions of the lesions was scattered and interrupted. Thus, altered composition of the basement membrane of nodular basal cell carcinomas with respect to laminin isoforms and their interactions with putative cell-surface receptors, the beta 4 integrins, may change the containment of the tumor islands, contributing to the local aggressive behavior of basal cell carcinomas.     

Epithelial and neural localization and heparin binding of the cell-substratum adhesion molecule, epinectin

Epinectin, a cell-substratum adhesion promoting molecule, was first isolated from the extracellular matrix of A431 human squamous carcinoma cells. In order to determine the biologic significance of epinectin, we determined the distribution of epinectin in various rat epithelial tissues by indirect immunofluorescence microscopy. Polyclonal antibodies to epinectin stained basal cells and basilar regions of skin, urinary bladder, and vagina. There was predominantly cytoplasmic staining along with amorphous extracellular staining. Strong staining was also noted in sebaceous glands and hair follicles. The immunoreactivity for epinectin in the skin was distinct from that for fibronectin, laminin, and type IV collagen. Antibodies to epinectin also stained subpopulations of neurons in the cerebrum and cerebellum. Epinectin antibodies strongly stained the cytoplasm of some pineal cells and cells of the pars intermedia of the pituitary. The distribution of epinectin suggests a role not only in epithelial cell-substratum adhesion, but in neuronal cell function. Heparan sulfate is known to be involved in the binding of several adhesion promoting molecules to cell surfaces. In order to assess the mechanism of adhesion of epinectin to cells, we measured the binding of 3H-heparin to epinectin. Binding of 3H-heparin was concentration dependent and inhibitable with cold heparin.     

CD44v6 is a marker for systemic spread in cutaneous T-cell lymphomas

Adhesion molecules are involved in leukocyte recruitment, lymphocyte recirculation, and in several aspects of tumour biology. Recent discoveries of surface proteins on tumour cells involved in tumour metastasis may explain the invasive behaviour, the migration involving reversible adhesive contacts, the release into the circulation and the extravasation of tumour cells.
CD44 is a family of glycoproteins involved in cell-cell and cell-matrix interactions. The v6 (variant exon v6) form of CD44 confers a metastatic potential onto some carcinoma cells. In the present study, the expression of CD44v6 on skin biopsies of 10 inflammatory skin diseases, 30 cutaneous lymphomas (CL), 11 reactive lymph nodes, 10 primary nodal non-Hodgkin's lymphomas (NHL) and 5 secondary nodal NHL was investigated immunohistochemically.
None of the 10 nodal NHL were CD44v6 positive for the neo-plastic B- or T-cells, whereas 11/12 CL with systemic spread showed a distinct CD44vG expression in the skin. CD44v6 was not expressed on the tumour cells of skin biopsies of patients without systemic spread (18 cases of CL). In conclusion, CD44v6 expression is connected to an aggressive behaviour of CL.