Distribution of CD44 variant isoforms in human skin: differential expression in components of benign and malignant epithelia

Nodular basal cell carcinoma is associated with increased hyaluronan homeostasis

BACKGROUND

Basal cell carcinoma (BCC) is one of the most frequent forms of malignancy in humans. Although BCC is a tumour of low degree of malignancy, if left untreated, it can be locally aggressive, eat away at tissues and cause ulceration. Nodular is the most common subtype of BCC (>50%). Although apparently non-invasive, micronodular, a certain subgroup of nodular, is likely to recur. Glycosaminoglycans (GAGs), such as hyaluronic acid (HA), are extracellular matrix molecules of high importance in malignant transformation, metastasis and other complex remodelling processes.

OBJECTIVES

To investigate the expression of GAGs and their metabolizing enzymes in nodular BCC, when compared with adjacent healthy human skin tissue specimens.

METHODS

Total GAGs were isolated and purified from nodular BCC and normal adjacent human skin tissue specimens. GAGs were subsequently fractionated by electrophoresis on cellulose acetate membranes and characterized using specific GAG-degrading enzymes. The content of HA in total GAGs was measured using ELISA and the expression of HA synthases (HAS), hyaluronidases (HYAL) and HA receptors (CD44 and receptor hyaluronic acid-mediated motility (RHAMM) was assessed using RT-PCR.

RESULTS

Nodular BCC is associated with increased levels of HA concomitant with upregulation of gene expression of HAS3, HYAL3 and RHAMM, when compared with normal adjacent skin.

CONCLUSION

These results indicate that HA homeostasis in nodular BCC shows distinct features which may be helpful in understanding the complex behaviour of nodular subtype of BCC, thus eventually leading to new treatment strategies.

Evaluation of the expression of P-selectin, ICAM-1, and TNF-alpha in bacteria-free lesional skin of atopic dogs with low-to-mild inflammation

Canine atopic dermatitis (AD) is a pruritic skin condition that shares many clinical and pathophysiological features with its human counterpart. A major therapeutic challenge of AD is the control of the skin inflammatory process. A detailed knowledge of the pro-inflammatory molecules involved in cell recruitment in AD would allow for a better control of the disease. We thus have studied the protein expression of P-selectin, ICAM-1 and TNF-alpha in the lesional and non-lesional skin of atopic dogs that had been treated for bacterial infections. Despite a low-to-mild inflammatory process, P-selectin protein was clearly upregulated in the lesional skin areas when compared with non-lesional skin (four-fold average increase). This P-selectin upregulation was accompanied by signs of functional changes such as increased cell margination, and membrane-associated protein expression. Although the expression of ICAM-1 and TNF-alpha was not enhanced in the lesional versus the non-lesional skin, there was a trend towards a correlated upregulation of both molecules. Further studies will help elucidate the significance of the substantial overexpression of P-selectin in canine AD, in particular in a scenario where bacterial antigens are not contributing as pro-inflammatory stimuli.

Corticosteroids regulate epithelial cell differentiation and Hassall body formation in the human thymus

The presence of characteristic epithelial swirls called Hassall bodies within the human thymic medulla has been used as an indicator of ongoing or recent thymopoiesis. We present a case where Hassall bodies were present in the absence of current or past thymopoiesis. The patient had been treated with corticosteroids for presumed asthma before his diagnosis of X-linked SCID. Two other cases of nonimmunodeficient patients treated with high-dose corticosteroids had markedly increased numbers of thymic Hassall bodies. To determine whether corticosteroid treatment induces thymic epithelial (TE) differentiation to form Hassall bodies, mAbs reactive with specific cytokeratins (CKs), filaggrin, and involucrin were used to define distinct stages of TE cell differentiation. Treatment of primary TE monolayers with hydrocortisone in vitro induced expression of involucrin and high-molecular-mass CKs that are characteristic of TE differentiation. Treatment of thymic organ cultures with hydrocortisone induced both medullary and subcapsular cortical TE cells to express CK6, a differentiation marker that is normally expressed only by Hassall bodies in vivo. These experimental studies combined with the case observations indicate that exogenous corticosteroids can regulate terminal differentiation of TE cells both in vitro and in vivo. Thus, the presence of Hassall bodies in thymus from corticosteroid-treated patients cannot be taken as an absolute indication of previous thymopoiesis. Because corticosteroids are also made within the thymus under normal physiologic conditions, these studies support the hypothesis that endogenous corticosteroids may play a role in normal TE differentiation and Hassall body formation in vivo.

CD44 is exposed to the extracellular matrix at invasive sites in basal cell carcinomas

We have previously shown, by light microscopy, that the level of expression of CD44 (pan-CD44, CD44v3, CD44v5, and CD44v6) in human basal cell carcinomas is related to growth pattern and invasiveness (Br J Dermatol 1099;140:17-25). We have now studied the fine distribution of these CD44 isoforms in the same tumors using immunoelectron microscopy. Despite the strong differences in the level of expression in tumor areas with different growth patterns, CD44 was consistently found almost exclusively at intercellular surfaces, with a very strong predilection for widened intercellular pouches, ie, identical to the distribution in the normal epidermis. This prevalent distribution corroborates a role for CD44 in maintaining hyaluronan-filled spaces (J Histochem Cytochem 1998;46:241-248). However, the correlation between the presence of CD44 and the presence of such pouches was not absolute, indicating that other factors are involved as well. In contrast to the prevailing literature, we also found a weak but distinct labeling of cell surfaces facing the extracellular matrix. Interestingly, this appeared significantly elevated in the thinnest, most irregular, and usually most peripheral tumor cell strands, where it was associated with tumor cell protrusions and absence of a basal lamina. Thus, the CD44(+) protrusions were in direct contact with the extracellular matrix and apparently represented sites of invasion. The mechanisms that may contribute to a role of CD44 at these sites include binding of extracellular matrix components (notably hyaluronan) and several biologically active factors such as hepatocyte growth factor/scatter factor and matrix metalloproteinase 9.

Grover's disease: clinicopathologic review of 72 cases

OBJECTIVE

To report the clinicopathologic findings in patients with Grover's disease.

MATERIAL AND METHODS

We reviewed the medical records and biopsy specimens from 72 patients with transient acantholytic dermatosis (Grover's disease) examined at Mayo Clinic Rochester. Hematoxylin-eosin-stained biopsy specimens (from all patients) were assessed. Immunohistochemistry stains BRST-2, CAM 5.2, and CD44 were used to stain eight specimens. Direct immunofluorescence reports were reviewed. Selected specimens were stained by indirect immunofluorescence to detect major basic protein.

RESULTS

Of the 72 patients, 63 (88%) were men, and the mean age was 48 years (range, 31 to 85). Lesions were distributed mainly on the trunk (in 71 patients) and proximal extremities (in 25). Heat and sweating frequently were exacerbating factors. Fifteen patients (21%) were bedbound. Concurrent nondermatologic malignant disease was present in 18 patients (25%). Two patients (3%) had acquired immunodeficiency syndrome. Follow-up in 28 patients (mean, 38 months; range, 3 months to 7 years) revealed that the disease had recurred in 13, persisted in 3, and resolved in 12. Review of the biopsy specimens showed that acantholysis was pemphigus vulgaris-like in 40 patients (56%), Darier's disease-like in 16 (22%), spongiotic in 12 (17%), pemphigus foliaceus-like in 2 (3%), and Hailey-Hailey disease-like in 2 (3%). A perivascular lymphocytic infiltrate of varied intensity in 64 specimens (89%) was associated with eosinophils in 16 (22%). In nine biopsy specimens with dermal eosinophilia stained for major basic protein, varied dermal cellular and extracellular deposition of major basic protein was present. Results of direct immunofluorescence studies, performed in 17 cases, were negative or nonspecific. CD44 stained acantholytic areas in addition to sweat glands in two of eight specimens (25%).

CONCLUSION

Further studies of the pathogenesis of Grover's disease are needed. The predisposing conditions, site of involvement, and relapsing nature of this disorder may implicate acrosyringeal dysfunction as the cause.

The expression of CD44 glycoprotein adhesion molecules in basal cell carcinomas is related to growth pattern and invasiveness

Basal cell carcinomas (BCCs) of the skin exhibit a wide range of histological growth patterns as well as a highly variable rate of invasiveness. A large body of experimental and clinical studies supports a role for the CD44 glycoprotein family in the latter process. In the present study, we explored the distribution and the level of expression of pan-CD44, CD44v3, CD44v5 and CD44v6 in BCCs. The use of paraffin sections, combined with an antigen retrieval procedure, yielded far more detailed data than would have been possible with frozen sections. On average, the level of expression of the four CD44 isoforms studied appeared to differ relatively little. However, tumours or tumour areas consisting of thin tumour cell strands showed a significantly stronger expression of all four isoforms than those consisting of solid tumour cell groups. Furthermore, the highest CD44 expression was frequently observed in the smallest tumour cell strands in the tumour periphery. In these strands, the label seemed to be located not only at the tumour cell-tumour cell interface, as in other tumour areas, but also on the tumour cell surfaces facing the stroma. We are presently assessing the exact localization of CD44 at the cellular level by immunoelectron microscopy. In most cases, different growth patterns with significantly different levels of CD44 expression were found side by side within individual tumours. CD44 expression is therefore not a static tumour cell characteristic but is correlated with tumour architecture and tumour-stroma interaction.

Expression of moesin and its associated molecule CD44 in epithelial skin tumors

Moesin, one of the ERM (ezrin; radixin; moesin) family members, is directly associated with the cytoplasmic domain of CD44, which is now thought to be related to the metastatic potential of tumor cells. Using immunohistochemistry we investigated the expression of moesin in normal epidermis and various kinds of epithelial skin tumors: squamous cell carcinoma, verrucous carcinoma, Bowen's disease, solar keratosis, keratoacanthoma, basal cell carcinoma, and extramammary Paget's disease. Normal skin showed positive epidermal staining for moesin with the exception of the stratum corneum. The expression of moesin varied with the type of skin tumor. In basal cell carcinoma, Bowen's disease, and extramammary Paget's disease, moesin expression was either faint or negative. In contrast to Bowen's disease, invasive squamous cell carcinoma showed more intense and heterogeneous staining of the cytoplasm and the cell membrane. Verrucous carcinoma was weakly positive, with a tendency for the moesin to be distributed in the cell membrane. The staining pattern of moesin varied among the different kinds of epithelial skin tumors, and its expression was generally similar to that of the standard form of CD44. These results suggest that moesin is closely inter-related with CD44 in epithelial skin cells as seen in other cellular systems, and that the variable pattern of moesin staining among the skin tumor cells could reflect expression disorders associated with the transformation.

Hyaluronic acid capsule modulates M protein-mediated adherence and acts as a ligand for attachment of group A Streptococcus to CD44 on human keratinocytes

We used wild-type and isogenic mutant strains of group A Streptococcus (GAS) that expressed M protein, capsule, or both to study the function of M protein and the hyaluronic acid capsular polysaccharide in attachment of GAS to human keratinocytes. Types 6 and 24, but not type 18, M protein were found to mediate attachment of GAS to soft palate or skin keratinocytes, but this interaction was prevented by the hyaluronic acid capsule on highly encapsulated, or mucoid, strains. Monoclonal antibody to CD44, the principal hyaluronic acid-binding receptor on keratinocytes, inhibited attachment of both highly encapsulated and poorly encapsulated wild type strains of GAS, but not the attachment of acapsular mutants. Transfection of K562 cells with cDNA encoding human CD44 conferred the capacity to bind each of six wild-type strains of GAS, but not to bind acapsular mutants. Because, in contrast to other potential adhesins, the group A streptococcal capsule is both highly conserved and surface-exposed, it may serve as a universal adhesin for attachment of diverse strains of GAS to keratinocytes of the pharyngeal mucosa and the skin.

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 mononuclear 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.

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 deparaffinized and treated briefly with an antigen retrieval fluid (TUFTM) at 95 degrees 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.