Basal-cell adhesion molecule (B-CAM) is induced in epithelial skin tumors and inflammatory epidermis, and is expressed at cell-cell and cell-substrate contact sites

Basal-cell adhesion molecule (B-CAM) is a 90 kDa cell surface glycoprotein of the immunoglobulin superfamily that functions as a laminin-binding receptor. B-CAM is upregulated following malignant transformation of some cell types in vivo and in vitro, thus being a candidate molecule involved in tumor progression. As cutaneous distribution and function of B-CAM are largely unknown, we have studied its expression and regulation in normal and diseased human skin. In normal skin, B-CAM was expressed by endothelial cells of dermal blood vessels. In contrast, B-CAM was strongly upregulated within the tumor tissue of both malignant and benign epithelial skin tumors, including basal cell carcinomas, squamous cell carcinomas, keratoacanthomas, and common warts. Transformation-associated upregulation was confirmed in vitro, but normal keratinocytes also expressed B-CAM under culture conditions. Interestingly, the basal epidermal layer of normal-appearing skin surrounding the tumors also expressed B-CAM, and B-CAM were induced on the basal and apicolateral surfaces of basal keratinocytes in inflammatory skin disorders suggesting transformation-independent mechanisms of epidermal induction of the B-CAM. Immunoelectron microscopy studies of cultured transformed keratinocytes revealed that B-CAM was expressed at cell-cell and cell-substrate contact sites. Halting proliferation of transformed keratinocytes through cytostatic drugs resulted in decreased B-CAM synthesis. Likewise, inducing terminal differentiation in keratinocyte cultures by increasing the Ca(2+) concentration in the medium decreased B-CAM expression. In contrast, both ultraviolet A and B irradiation of cultured human keratinocytes resulted in significantly increased expression of the B-CAM. Overall, it appears that B-CAM expression in human skin is associated with activated states of keratinocytes, and that B-CAM may be involved in cell-cell adhesion or migration, in addition to its known function as a laminin receptor. J Invest Dermatol 115:1047-1053 2000     

Immunohistochemical comparison of beta-catenin expression by human normal epidermis and epidermal tumors

beta-Catenin, a cytoplasmic protein that binds directly to the intracellular domain of cadherin, controls various functions such as cell adhesion. In many human carcinomas, E-cadherin-mediated cell-cell adhesion is lost or disturbed and related to metastasis. The purpose of this study was to compare the expression of beta-catenin in the normal epidermal keratinocytes and samples from cutaneous benign and malignant epidermal tumors in 140 patients. Our study population consisted of 140 patients with benign or malignant epidermal tumors. Using immunohistochemical methods, we compared the expression of beta-catenin in their normal epidermal keratinocytes, and in samples from 61 benign (seborrheic keratosis, n = 33; verruca vulgaris, n = 14; keratoacanthoma, n = 14), and 79 malignant (Bowen's disease, n = 18; basal cell carcinoma, n = 33; squamous cell carcinoma, n = 28) epidermal tumors. beta-Catenin was found to be expressed in the cell membrane of normal keratinocytes. Compared to other cell components of the normal epidermis, basal cells showed the strongest beta-catenin expression in all 140 patients. While absent in three of 61 benign tumors, compared to normal basal cells, the expression of beta-catenin in the other 58 tumors was not significantly different; it was reduced in 71 of 79 malignant tumors (P < 0.0001). In Bowen's disease, the expression of beta-catenin on the tumor cell membrane was reduced, however, strong expression was seen in the nuclei and cytoplasm. Our results suggest that beta-catenin expression on the membrane of keratinocytes is associated with the differentiation of normal keratinocytes but not with their stage of differentiation, nor with the proliferation ability of epidermal tumor cells.     

Expression of double-stranded RNA-activated protein kinase in keratinocytes and keratinocytic neoplasia

Double-stranded RNA-activated protein kinase (PKR) is a interferon-induced protein initially known for its inhibitory effects on cellular and viral protein synthesis. In recent studies, PKR has been shown to be an important participant in a broad array of cellular processes, including signal transduction, differentiation, apoptosis, cell growth, and tumorigenesis. The expression of PKR in normal human keratinocytes (NHEK) was examined, and its expression in several skin lesions was compared immunohistochemically with that of proliferating cell nuclear antigen (PCNA). Expression of PKR mRNA was detected in NHEK without IFNgamma treatment; the level of PKR mRNA increased with IFNgamma treatment for two hours. Immunoblot analysis revealed that the monoclonal anti-PKR antibody reacted specifically with a 68kDa PKR protein in extracts from NHEK. Immunohistochemistry revealed that PKR protein was expressed in normal epidermis and mucosa. PKR expression was not restricted only to suprabasal cells but was also observed in basal cells positive for PCNA. In psoriatic plaques, PKR expression was lower in basal and parabasal keratinocytes and comparable in suprabasal keratinocytes to the levels in normal skin. PKR was partially detected in atypical cells in non-invasive keratinocytic neoplasia but was completely absent from undifferentiated tumor cells of squamous cell carcinoma. The present study demonstrated that PKR protein is constitutively expressed in epidermal and epithelial keratinocytes of normal skin and mucosa and indicated that a loss of PKR is not associated with the malignant transformation itself but with the increased cell proliferative activity and the altered differentiation of keratinocytes.     

Expression of 38-kD cell-surface glycoprotein in transformed human keratinocyte cell lines, basal cell carcinomas, and epithelial germs

In this study, we attempted to identify and characterize transformation-induced cell-surface glycoproteins of human keratinocytes. Therefore, we first searched for glycoproteins which are significantly elevated in human keratinocytes after transformation and immortalization by SV40 virus and which are also found at high levels in keratinocytic cell lines derived from squamous cell carcinomas of the skin. Out of at least 80 different cell-surface antigenic systems of human tumor cells, only three glycoproteins showed elevated expression in transformed keratinocytes. Among these, a 38-kD glycoprotein (gp 38) was highly increased in all transformed keratinocyte cell lines tested, but was not elevated in transformed fibroblasts. The expression of gp 38 was further characterized in normal epidermis and in its benign and malignant hyperproliferative disorders: gp 38 was generally not expressed in normal epidermis and in benign hyperproliferative disorders. In contrast, strong and homogeneous reactivity was found in solid and fibrosing basal cell carcinomas whereas no or low reactivity was detected in squamous cell carcinomas and in those parts of BCC revealing keratotic differentiation. Interestingly, high expression of gp 38 was also found in primary epithelial germs of fetal skin, secondary germ cells of the telogenic hair follicle and secretory tubules of sweat glands. The immunohistologic data suggest that gp 38 is preferentially expressed by epidermal cells which lack squamous and pilosebaceous differentiation.     

Expression of the nm23 metastasis-suppressor gene product in skin tumors

Nm23 is a gene with a putative metastasis-suppressor function, whose expression is inversely correlated with die metastatic potential of some solid malignancies. Because very few data exist concerning the role of nm23 in skin tumors, we studied the immunohistochemical expression of nm23 gene product in frozen sections of normal skin and of 104 cutaneous benign or malignant, epithelial and mesenchymal tumors. Nm23 was found expressed within basal cells of the epidermis and its appendages. All basal cell carcinomas showed diffuse immunoreactivity predominating within cells located at the periphery of tumor masses; in contrast, most squamous cell carcinomas, premalignant lesions and the benign epithelial lesions studied showed very weak, if any, immunoreactivity. Benign nevi and most malignant melanomas expressed nm23 immunoreactivity and the pattern observed was similar between primary and metastatic lesions. These results show that nni23 is differentially expressed in cutaneous tumors. It seems likely that the strong immunoreactivity of basal cell carcinomas, contrasting with the almost non-expression in squamous cell carcinomas, reflects the different metastatic potential of these two types of tumors. In melanomas, no direct correlation between the metastatic phenotype and nm23 expression could be detected. Our results suggest that the nm23 gene is involved in cutaneous carcinogenesis; its precise role deserves further study.     

CDw60, which identifies the acetylated form of GD3 gangliosides, is strongly expressed in human basal cell carcinoma

The monoclonal antibody UM4D4, assigned to the CDw60 cluster of differentiation, identities an epilope expressed on a subset of normal T cells, some malignant T cells, melanocytes, malignant melanoma cells and hyperproliferative psoriatic keratinocytes. CDw60 antibodies bind to the acetylated form of G_D3 gangliosides. These gangliosides have been implicated in the control of cellular proliferation. Because the acetylated form of G_D3 has been demonstrated in basal cell carcinomas, we determined whether the CDw60 epitope was expressed in basal cell carcinomas (n= 24) and squamous cell carcinomas (n= 2). Biopsies of these tumours were sectioned on a cryostat, and stained with anti-CDw60 using a sensitive indirect immunoperoxidase technique. A mean of 74±4% (mean ± SEM) of the basal cell carcinoma cells expressed CDw60. In contrasl, CDw60 expression in normal skin was confined to melanocytes and a few scattered keratinocytes at the basal cell layer. CDw60 expression in basal cell carcinomas was highly upregulated at the tumour front in most of the lesions, whereas the squamous cell carcinomas showed uniform CDw60 expression in all areas.     

Expression of vascular endothelial growth factor in basal cell carcinoma and cutaneous squamous cell carcinoma of the head and neck

BACKGROUND: Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) can both arise from any cutaneous epithelial surface. BCC are slow growing and rarely metastasise, whereas SCC are usually more aggressive. It is likely that the angiogenic process plays a key role in determining rate of growth and propensity for dissemination. Angiogenesis is a complex process requiring many factors and a pivotal group of proteins involved in this process is vascular endothelial growth factor (VEGF). METHODS: Immunohistochemical expression of VEGF was assessed in 44 cases of BCC and 41 cases of cutaneous SCC from the head and neck region. RESULTS: VEGF was expressed by blood vessel endothelial cells in both adjacent skin and tumour, and in the basal keratinocyte layer of epidermis. In BCC, VEGF was expressed by tumour epithelial cells, predominantly at the invasive tumour front, in 24/44 cases and its expression was significantly greater than in adjacent skin (p = 0.038). More widespread VEGF expression was found in 32/41 cases of SCC, and it was significantly associated with the degree of tumour differentiation (p < 0.001). CONCLUSIONS: The patterns of VEGF expression in BCC and SCC may help to explain the different behaviour that is usually seen with these tumours.     

银屑病患者角质形成细胞VEGF表达的研究

目的　研究银屑病发病与血管内皮生长因子 (VEGF)的关系 ,探讨银屑病可能的发病机制。方法　①用免疫组化法检测银屑病患者皮损和非皮损处皮肤、正常健康人皮肤及体外培养的银屑病患者和正常人角质形成细胞(KC)VEGF的表达 ;②用双抗体夹心ELISA法检测银屑病患者及正常人KC培养上清液中VEGF含量。结果　①银屑病皮损处VEGF表达明显高于非皮损处和正常人皮肤 (P均 <0 .0 0 1) ,非皮损处与正常人皮肤VEGF表达也有显著性差异 (P <0 .0 5 ) ;②体外培养的银屑病皮损处和非皮损处KCVEGF表达明显高于正常人 (P均 <0 .0 0 1) ;银屑病皮损处KC与非皮损处KC相比VEGF表达也有显著性差异 (P <0 .0 5 ) )。结论　VEGF可能参与银屑病的发病。     

Expression of E-cadherin in human epidermal non-melanoma cutaneous tumours

Summary E-cadherin is a calcium-sensitive, cell-to-cell, adhesion molecule that is expressed widely in normal human epithelial tissue. Abnormal expression has been described in colorectal, breast and nasopharyngeal squamous cell carcinomas, where loss of E-cadherin is associated with an increased metastatic potential. We have examined, by standard immunohistochemical techniques using the monoclonal antibody HECD-1 (E-cadherin monoclonal antibody), the distribution of E-cadherin in normal human skin and in non-melanoma neoplastic lesions. In the normal epidermis, E-cadherin was strongly expressed on the surface of keratinocytes and specialized epithelial structures. Staining was absent from the lower pole of basal keratinocytes in contact with the basement membrane. Weak cytoplasmic staining was also noted in basal keratinocytes. No reactivity was demonstrated in dermal structures. The assessment of cutaneous tumours demonstrated an altered pattern of staining in most cases. Cell surface expression was reduced in 28 of 30 cases of basal cell carcinomas (BCC). Twenty showed an additional feature of positive staining on the dermal aspect of peripheral cells of tumour lobules. In squamous cell carcinomas (SCC) ( n = 16), surface expression was attenuated in eight and absent in a further four. Strong surface expression, similar to normal skin was seen in all examples of Bowen's disease ( n = 6), viral wart ( n = 3), seborrhoeic keratosis ( n = 3) and actinic keratosis ( n = 4). This study demonstrates that, in BCC and SCC, but not in premalignant lesions, cell-surface expression of E-cadherin is reduced, consistent with the observation that the loss of E-cadherin is associated with tumour invasion.     

Expression of vascular endothelial growth factor (VEGF) in various compartments of the human hair follicle

Abstract Hair follicle vascularization appears to be closely related to the processes involved in hair cycle regulation, in which growth factors, cytokines and other bioactive molecules are involved. In particular, vascular endothelial growth factor (VEGF), essential for angiogenesis and vascular permeability, may be responsible for maintaining proper vasculature around the hair follicle during the anagen growth phase. The aim of our study was to compare the in vitro angiogenic capacity, i.e. the steady-state expression of the VEGF gene, of different cultured cell types derived from normal human hair follicles, corresponding to different follicular compartments. Human dermal papilla cells (DPC), fibrous sheath fibroblasts, dermal fibroblasts, and follicular and interfollicular keratinocytes were cultured and studied in vitro for VEGF expression at the mRNA level using RT-PCR, and for VEGF protein synthesis by radioimmunoprecipitation and immunocytochemistry. In vivo examination for VEGF expression in human terminal hair follicles was performed using immunohistochemical methods. In the present report the expression of four different VEGF molecular isoforms, differing in their angiogenic capacity, are described in different cultured follicular cell types for the first time. Cultured follicular cells strongly expressed mRNA of four VEGF molecular species identified as the 121-, 145-, 165- and 189-amino acid splice variants, the most prominent being the 121-amino acid molecule. DPC, and also other mesenchymal cells such as fibrous sheath fibroblasts and dermal fibroblasts, in vivo and in vitro strongly expressed VEGF mRNA and synthesized a 46-kDa VEGF protein, whereas follicular and interfollicular keratinocytes in vitro expressed lower levels of VEGF mRNA and proteins than mesenchymal cells. As the highest expression of VEGF was found in DPC, we suggest that DPC are mainly responsible for angiogenic processes possibly related to the human hair cycle. Received: 14 January 1998 / Received after revision: 16 July 1998 / Accepted: 30 July 1998     

Expression and localization of thymidine phosphorylase/platelet-derived endothelial cell growth factor in skin and cutaneous tumors

Thymidine phosphorylase/platelet-derived endothelial cell growth factor (TPase/PD-ECGF) is a catabolic enzyme that has been shown to be chemotactic for endothelial cells in vitro and angiogenic in vivo. TPase/PD-ECGF expression is increased in a variety of tumors. In the skin, TPase is active in normal keratinocytes in vitro and in vivo. Our objective was to study the expression and localization of TPase/PD-ECGF by immunohistochemical analysis in normal skin and cutaneous tumors and to correlate this information with enzymatic activity of TPase. TPase/PD-ECGF expression was observed in keratinocytes with intense staining of the infundibulum of hair follicles but no staining of hair bulbs. Expression localized primarily to the nucleus of keratinocytes in the basal layer but was more intense and cytoplasrmic in suprabasal keratinocytes. Increased expression of TPase/PD-ECGF in differentiated cells was confirmed by in vitro studies of TPase activity. In cutaneous tumors, there was positive staining for TPase/ PD-ECGF in squamous cell carcinomas (10/10), eccrine poromas (3/4), eccrine syringomas (4/4), trichoepitheliomas (1/3), and tumors of the follicular infundibulum (2/3) and melanomas (5/8). There was no staining of any intradermal nevi (0/2), basal cell carcinomas (0/10) or Merkel cell carcinoma (0/1). We conclude TPase/PD-ECGF is found throughout the epidermis and its expression increases with differentiation of keratinocytes. In cutaneous tumors, expression of TPase/PD-ECGF may be linked to the cell of origin of the tumor as well as the tumor's degree of differentiation.     

Differential expression of calgranulin A and B in various epithelial cell lines and reconstructed epidermis.

The monoclonal antibody F12, raised against epidermal cells from a psoriatic lesion, decorated antigens highly expressed in psoriatic epidermis and in cultured normal human keratinocytes. In normal human skin, F12 reacted only with follicular keratinocytes. Characterization of the immunoprecipitated antigens by two-dimensional gel electrophoresis revealed their identity with calgranulin A and B. A semiquantitative study with various established epithelial cell lines demonstrated that the expression of calgranulin A and B in hyperproliferative keratinocytes correlates with their potential to undergo terminal differentiation. In epidermis reconstructed in vitro, the antigen expression was stimulated by retinoids and suppressed under vitamin A starvation.     

Identification of novel genes for secreted and membrane-anchored proteins in human keratinocytes

BACKGROUND: Both intercellular and intracellular signals are transduced primarily by interactions of secreted and/or membrane-anchored polypeptides, and they play a pivotal role in regulating proliferation, differentiation and apoptosis of keratinocytes within the epidermis. Despite recent identification of these polypeptides, it is likely that several important molecules remain undisclosed. OBJECTIVES: To identify novel genes encoding secreted or membrane-anchored polypeptides expressed by human keratinocytes. METHODS: We employed a signal sequence (SS) trap of a 5'-end-enriched cDNA library prepared from primary cultured human keratinocytes. Gene expression analysis was performed using Northern blotting. R Screening of 4018 cDNA clones yielded 82 positive clones (57 independent genes), most of which encoded SSs in their N-termini. Most of the positive clones were known genes registered in the GenBank database. Seven genes were identified in the EST database, four of which encoded novel membrane-anchored polypeptides with features of type I transmembrane proteins; the other three genes encoded novel non-type I transmembrane polypeptides. These EST genes were expressed differentially by keratinocytes subjected to low vs. high calcium concentrations and by basal vs. squamous cell carcinomas. CONCLUSIONS: Using the SS trap, we isolated many genes known to be involved in constituting epidermal structures and others that had not previously been associated with keratinocytes. In addition, we identified novel genes (EST genes) that differ in kinetics of gene expression in keratinocyte differentiation. Our results validate the effective use of this SS trap method for identifying secreted and membrane-anchored polypeptides expressed by human keratinocytes. The identification will better illuminate the molecular mechanisms responsible for co-ordinated regulation of epidermal homeostasis.     

Increased expression of platelet-derived growth factor receptor alpha and beta and vascular endothelial growth factor in the skin of patients with chronic venous insufficiency

Abstract Growth factors produced by a variety of cells act as signalling peptides through specific cell surface receptor pathways. Functions such as cell proliferation, migration and differentiation have been assigned to each of them. Here, we report alterations of platelet-derived growth factor receptor alpha (PDGFR-α) and beta (PDGFR-β) and vascular endothelial growth factor (VEGF) expression patterns in the progressive clinical stages of chronic venous insufficiency (CVI). A total of 30 punch biopsies were taken from patients with CVI, and VEGF and PDGFR were detected by indirect immunofluorescence and immunoperoxidase techniques. PDGFR-α and PDGFR-β expression was strongly increased in endothelial cells of capillaries, pericapillary cells and connective tissue cells in the stroma of the skin of venous eczema and venous leg ulcer patients, and to a smaller extend in the dermis of those with lipodermatosclerosis. VEGF staining showed a similar expression pattern in the progressive CVI stages. However, staining of vessels in particular might simply reflect binding of VEGF, secreted by keratinocytes or fibroblasts, to its receptors. Growth factor and receptor expression in specimens from telangiectases and reticular veins, and from pigmented areas, resembled that of normal skin. We conclude that PDGFR-α, PDGFR-β and VEGF play an important role in mediating inflammation and epithelial hyperproliferation in venous eczema, inducing connective tissue sclerosis in lipodermatosclerosis, and causing the reduced reepithelialization tendency in venous ulcers. We speculate that endothelial proliferation with chronic venous hypertension might be mediated by these growth factors. Received: 1 April 1997     

Neuronatin is related to keratinocyte differentiation by up-regulating involucrin

BackgroundNeuronatin (Nnat), which is a neuronal developmental and differentiation molecule, is expressed in the endoplasmic reticulum of non-neuronal cells and is involved in insulin secretion from pancreatic β-cells by plausibly modulating their intracellular calcium concentration. However, the role of Nnat in keratinocyte differentiation remains unclear.ObjectiveTo unveil a possible integration of Nnat in controlling the keratinocyte differentiation markers such as involucrin, cytokeratin1, filaggrin, loricrin and S100A7.MethodsImmunohistological staining was done using psoriasis, chronic eczema, lichen planus and normal skin. Immunofluorescence staining, Western blotting and semi-quantitative real-time PCR were performed for detecting Nnat, involucrin, cytokeratin1, filaggrin, loricrin and S100A7 using human keratinocytes with or without Nnat gene transfection. Small interference RNA was applied to knockdown the Nnat gene expression.ResultsNnat existed in normal human epidermis and cultured keratinocytes. In the hyperplastic epidermis of psoriasis, chronic eczema and lichen planus, over-expression of Nnat was evident along with involucrin and cytokeratin1 expression. Coordinate up-regulation of Nnat and involucrin, but not cytokeratin1, was demonstrated in cultured keratinocytes under differentiation stimuli such as extracellular calcium elevation, exposure to phorbol myristate acetate, and increased cell density. Transfection of small intereference RNA for Nnat decreased the mRNA levels of Nnat and involucrin, but not of cytokeratin1. Furthermore, a gene transfection assay showed increased involucrin expression in the Nnat-transfected keratinocytes than in mock-transfected counterparts, without any appreciable influence on cytokeratin1, filaggrin, loricrin and S100A7 expression.ConclusionThese data indicate that Nnat is related to keratinocyte differentiation by up-regulating involucrin expression.     

Differences of expression of cytokeratin polypeptides in various epithelial skin tumors

Summary In normal skin, cytokeratin polypeptides are expressed in different cell-type-specific patterns, in the keratinocytes of the different epidermal cell strata as well as in different lateral epithelial domains. Using light microscopically controlled microdissection of defined regions from frozen sections of biopsies, we have prepared cytoskeletons of various benign and malignant keratinocyte-derived tumors of human skin and analyzed their cytokeratin polypeptide patterns by two-dimensional gel electrophoresis. Premalignant fibro-epitheliomas and basal cell epitheliomas display a relatively simple cytokeratin pattern (cytokeratins nos. 5, 14, 15, and 17). Pseudocarcinomatous hyperplasia, some squamous cell carcinomas, and a certain subtype of condylomata acuminata present a hair-follicle-like pattern (nos. 5, 6, 14, 16, 17). In addition to these components, variable, mostly low amounts of cytokeratins nos. 1 (M_r 68,000), and 11 are detected in most squamous cell carcinomas, in keratoacanthomas, verruca vulgaris, and another type of condylomata acuminata. In molluscum contagiosum, verruca plana, solar keratosis, and seborrheic keratosis, the cytokeratin expression is shifted more towards the normal epidermal pattern (polypeptides nos. 1, 2, 5, 10, 11, 14, 15 and traces of nos. 6 and 16 in the latter two tumors). No tumor-specific cytokeratins have been found. We conclude that keratinocyte-derived skin tumors contain various combinations of cytokeratins of the subset typical for normal keratinocytes of skin, but no cytokeratins typical for internal, simple epithelia. Different groups of tumors can be distinguished by their specific cytokeratin patterns. Possible applications of cytokeratin typing in clinical diagnosis are discussed.     

Langerhans cells, inflammation markers and human papillomavirus infections in benign and malignant epithelial tumors from transplant recipients.

Organ transplant recipients frequently develop warts which progress toward premalignant or malignant lesions after a rather long grafting period. The local immune responses of such lesions (warts, condyloma acuminata, actinic keratoses, Bowen, basal and squamous cell carcinomas) was studied in 32 frozen skin specimens taken from 15 male transplant recipients and compared to similar lesions from the normal population. We studied the expression of T cell subsets, Langerhans cell phenotype, HLA class 1 (beta 2-microglobulin), HLA class 2 (DR antigen), and intercellular adhesion molecule 1 (ICAM 1). The presence of HPV infection was also considered, using in situ hybridization with biotinylated probes in order to examine the correlation with immunological markers. In the dermis, the lesions from grafted patients showed a moderate to intense inflammatory reaction of HLA-DR-positive cells. Most of these cells were CD4+ and CD8+ without any predominance of a single T cell subset. In the epidermis, most lesions were characterized by a reduced number of CD1-positive cells; this was concomitant with a decrease or a loss of beta 2-microglobulin expression by epithelial cells. HLA-DR antigen was not expressed by keratinocytes or tumoral cells in any specimen; ICAM 1 antigen was observed in a few cases. The expression of these markers was similarly modified with or without the presence of HPV DNA. Conversely, most lesions from non-immunocompromised patients, except warts, showed intense inflammatory reactions, with a predominance of CD4-positive cells and large foci of ICAM 1-positive cells. Expression of activation markers by keratinocytes occurred mainly in condylomas and squamous cell carcinomas. In the normal population, HPV infection was only detected in papilloma lesions. These data indicate, in lesions from grafted patients, a lack of effective immune response with partial inhibition of activation markers expressed by keratinocytes. It is conceivable that immunosuppressive treatment with solar exposure may also be responsible for the local immune deficiency and thus for the conversion of benign warts toward malignant lesions in grafted patients.     

Interferon-gamma-induced 15-lipoxygenase-2 expression in normal human epidermal keratinocytes and a pathogenic link to psoriasis vulgaris

Epidermal keratinocytes contain 15-lipoxygenase, which generates 15-hydroxyeicosatetraenoic acid, a major metabolite of arachidonic acid. Although two isozymes, 15-lipoxygenase-1 and -2, exist, it remains unclear which isozyme plays an important role in inflammatory processes and proliferative skin diseases. In the present study, we demonstrated that 15-lipoxygenase-2 expression was increased in normal human epidermal keratinocytes and HaCaT cells treated with interferon-gamma (200 U/ml), while no induction of 15-lipoxygenase-1 was observed. Under the same culture conditions, no 15-lipoxygenase-2 was expressed by a carcinoma cell line, A431. Weak expression of 15-lipoxygenase-2 was observed in the basal cell layer of non-lesional psoriatic skin by in situ hybridization and immunostaining, whereas strong expression of 15-lipoxygenase-2 was observed in all living layers of psoriatic lesions. Actinic keratosis and squamous cell carcinomas showed a variable immunostaining pattern for 15-lipoxygenase-2. These results indicate that 15-lipoxygenase-2 is implicated in interferon-gamma-induced inflammatory processes in normal human epidermal keratinocytes and psoriatic skin.