Immunohistochemical staining for desmogleins 1 and 2 in keratinocytic neoplasms with squamous phenotype: actinic keratosis, keratoacanthoma and squamous cell carcinoma of the skin

Identifying SCC Lesions Capable of Spontaneous Regression by Using Immunohistochemistry: A Systematic Review and Meta-Analysis

INTRODUCTION

Keratoacanthoma (KA) and squamous cell carcinoma (SCC) are two cutaneous conditions with morphological resemblance, which can complicate the diagnosis in some cases. Using immunohistochemistry staining of biomarkers could be beneficial in resolving this obstacle.

OBJECTIVES

We investigated a variety of biomarkers assessed in different studies in order to find the most important and helpful biomarkers for differentiation between SCC and lesions capable of spontaneous regression.

METHODS

MEDLINE via PubMed and Google Scholar database were used to identify relevant literature up to 15 June 2022. The aim of our analyses was to determine the capability of biomarkers to distinguish between SCC and lesions capable of spontaneous regression using calculated individual and pooled odds ratios (OR) and 95% confidence intervals (CI) and I2 tests.

RESULTS

Six potential biomarkers were CD10 with pooled OR= 0.006 (95% CI: 0.001-0.057) and I2=0%; COX-2 with pooled OR=0.089 (95% CI: 0.029-0.269) and I2=17.1%; elastic fibers with pooled OR= 6.69 (95% CI: 2.928-15.281) and I2=0%; IMP-3 with pooled OR=0.145 (95% CI: 0.021-1.001) and I2=44.5%; P53 with pooled OR=0.371 (95% CI: 0.188-0.733) and I2=55.9%; AT1R with OR=0.026 (95% CI: 0.006-0.107).

CONCLUSIONS

We suggest the utilization of the following IHC biomarkers for discrimination between lesions with spontaneous regression such as KA and SCC: CD10, COX-2, and elastic fibers.

A six-gene expression signature related to angiolymphatic invasion is associated with poor survival in laryngeal squamous cell carcinoma

Purpose

Angiolymphatic invasion serves as a histopathological risk factor for unfavorable survival in head and neck squamous cell carinoma. The aim of the study was to explore  the molecular mechanisms characterizing angiolymphatic invasion and therefore identify a gene expression signature related to angiolymphatic invasion.

Methods

Gene expression analysis of head and neck squamous cell carcinoma was carried out based on clinical and whole genome expression data provided by The Cancer Genome Atlas. Results were validated in an independent cohort of laryngeal squamous cell carcinoma and confirmed by immunohistochemistry staining.

Results

A gene expression signature consisting of six genes (SHH, SLC18A3, LCE3E, LCE2B, LCE3D and DSG-1) related to angiolymphatic invasion was identified. The gene expression profile identified a subset of patients with decreased overall survival (p = 0.02, log rank test), which was most prominent for patients with laryngeal squamous cell carcinoma (p = 0.004, log rank test). Furthermore, these patients showed a significant shorter progression-free survival (p = 0.002, log rank test). By use of this gene expression signature, patients at high risk of recurrence could be identified even if morphological changes were not yet recognizable.

Conclusion

Angiolymphatic invasion is characterized by a distinct histopathological phenotype and specific gene expression signature. The newly identified signature might serve as a reliable predictor of outcome in laryngeal cancer and add additional benefit to histopathological evaluation.

Electronic supplementary material

The online version of this article (10.1007/s00405-020-06214-1) contains supplementary material, which is available to authorized users.

Identification of candidate aberrantly methylated and differentially expressed genes in Esophageal squamous cell carcinoma

Aberrant methylated genes (DMGs) play an important role in the etiology and pathogenesis of esophageal squamous cell carcinoma (ESCC). In this study, we aimed to integrate three cohorts profile datasets to ascertain aberrant methylated-differentially expressed genes and pathways associated with ESCC by comprehensive bioinformatics analysis. We downloaded data of gene expression microarrays (GSE20347, GSE38129) and gene methylation microarrays (GSE52826) from the Gene Expression Omnibus (GEO) database. Aberrantly differentially expressed genes (DEGs) were obtained by GEO2R tool. The David database was then used to perform Gene ontology (GO) analysis and Kyoto Encyclopedia of Gene and Genome pathway enrichment analyses on selected genes. STRING and Cytoscape software were used to construct a protein-protein interaction (PPI) network, then the modules in the PPI networks were analyzed with MCODE and the hub genes chose from the PPI networks were verified by Oncomine and TCGA database. In total, 291 hypomethylation-high expression genes and 168 hypermethylation-low expression genes were identified at the screening step, and finally found six mostly changed hub genes including KIF14, CDK1, AURKA, LCN2, TGM1, and DSG1. Pathway analysis indicated that aberrantly methylated DEGs mainly associated with the P13K-AKT signaling, cAMP signaling and cell cycle process. After validation in multiple databases, most hub genes remained significant. Patients with high expression of AURKA were associated with shorter overall survival. To summarize, we have identified six feasible aberrant methylated-differentially expressed genes and pathways in ESCC by bioinformatics analysis, potentially providing valuable information for the molecular mechanisms of ESCC. Our data combined the analysis of gene expression profiling microarrays and gene methylation profiling microarrays, simultaneously, and in this way, it can shed a light for screening and diagnosis of ESCC in future.

Plakophilin 1 enhances MYC translation, promoting squamous cell lung cancer

Plakophilin 1 (PKP1) is a member of the arm-repeat (armadillo) and plakophilin gene families and it is an essential component of the desmosomes. Although desmosomes have generally been associated with tumor suppressor functions, we have consistently observed that PKP1 is among the top overexpressed proteins in squamous cell lung cancer. To explore this paradox, we developed in vivo and in vitro functional models of PKP1 gain/loss in squamous cell lung cancer. CRISPR-Cas9 PKP1 knockout severely impaired cell proliferation, but it increased cell dissemination. In addition, PKP1 overexpression increased cell proliferation, cell survival, and in vivo xenograft engraftment. We further investigated the molecular mechanism of the mainly oncogenic function of PKP1 by combining transcriptomics, proteomics, and protein-nucleic acid interaction assays. Interestingly, we found that PKP1 enhances MYC translation in collaboration with the translation initiation complex by binding to the 5'-UTR of MYC mRNA. We propose PKP1 as an oncogene in SqCLC and a novel posttranscriptional regulator of MYC. PKP1 may be a valuable diagnostic biomarker and potential therapeutic target for SqCLC. Importantly, PKP1 inhibition may indirectly target MYC, a primary anticancer target.

Disassembling a cancer puzzle: Cell junctions and plasma membrane as targets for anticancer therapy

Despite an enhanced permeability and retention effect typical of many solid tumors, drug penetration is not always sufficient. Possible strategies for the drug delivery improvement are a modification of the tumor cell-to-cell junctions and usage of cell membrane permeabilization proteins. In this review we discuss epithelial cell junctions as targets for a combined anticancer therapy and propose new possible sources of such agents. We suggest considering viral and bacterial pathogens disrupting epithelial layers as plentiful sources of new therapeutic agents for increasing tumor permeability for other effector agents. We also observe the application of pore forming proteins and peptides of different origin for cytoplasmic delivery of anti-cancer agents and consider the main obstacles of their use in vivo.

Keratoacanthoma (KA): An update and review

Keratoacanthoma (KA) is a common but underreported tumor of the skin. Two striking features of KA are its clinical behavior with spontaneous regression after rapid growth and its nosological position on the border between benignity and malignancy. We review current knowledge on the clinical, histopathological, and dermoscopic features of KA to ensure a proper diagnosis and describe its variants, including different types of multiple KAs. We highlight current concepts of KA ethiopathogenesis with special emphasis on the genetic background of multiple familial KA, the role of Wnt signaling pathway, and induction of KA by BRAF inhibitors and procedures of esthetic dermatology. Finally, treatment strategies are presented with surgical excision as a first option, followed by other modalities, including intralesional chemotherapy, topical and systemic agents, lasers, cryotherapy, and photodynamic therapy.

Mucin1 expression in focal epidermal dysplasia of actinic keratosis

BACKGROUND

Actinic keratoses (AKs) are generally considered as premalignant skin lesions that can progress into squamous cell carcinoma (SCC) in situ and invasive SCC. However, its progression to SCC is still matter of debate. A transmembrane glycoprotein that contributes to the progression of certain premalignant and malignant lesions is mucin1 (MUC1). Nevertheless, their functions in the skin lesions are not yet fully clear. Therefore, the aim of this study is to ascertain whether MUC1 is present in the focal epidermal dysplasia of AK.

METHODS

Fourteen skin biopsies from patients diagnosed with AK were selected. They were classified according to the degree of dysplasia in keratinocyte intraepidermal neoplasia (KIN) I, KIN II, and KIN III. In five biopsies the three degrees were present, in two biopsies both KIN I and KIN II, in four biopsies only KIN I, and in three biopsies only KIN III. The presence of MUC1 was assessed by immunofluorescence staining using confocal laser scanning microscopy.

RESULTS

Immunostaining revealed that MUC1 was present over the entire cell surface of only a few atypical basal keratinocytes confined to the lower third of the epidermis (KIN I). While in KIN II where atypical keratinocytes occupy the lower two thirds, MUC1 was localized at the apical surface of some atypical keratinocytes and over the entire cell surface of some of them. Interestingly, in KIN III where the atypical keratinocytes extend throughout the full thickness, MUC1 was localized at the apical surface and over the entire cell surface of many of these cells. Conversely, MUC1 expression was not detected in the epidermis of normal skin.

CONCLUSIONS

Our findings suggest that the expression of MUC1 in AK would be induced by alteration of keratinocyte stratification and differentiation and associated to the degree of dysplasia rather than the thickness of the epidermis.

Immunohistochemical expression of matrix metalloproteinase-1, matrix metalloproteinase-2 and matrix metalloproteinase-9, myofibroblasts and Ki-67 in actinic cheilitis and lip squamous cell carcinoma

Matrix metalloproteinases (MMPs), myofibroblasts (MFs) and epithelial proliferation have key roles in neoplastic progression. In this study immunoexpression of MMP-1, MMP-2 and MMP-9, presence of MFs and the epithelial proliferation index were investigated in actinic cheilitis (AC), lip squamous cell carcinoma (LSCC) and mucocele (MUC). Thirty cases of AC, thirty cases of LSCC and twenty cases of MUC were selected for immunohistochemical investigation of the proteins MMP-1, MMP-2, MMP-9, α-smooth muscle actin (α-SMA) and Ki-67. The MMP-1 expression in the epithelial component was higher in the AC than the MUC and LSCC. In the connective tissue, the expression was higher in the LSCC. MMP-2 showed lower epithelial and stromal immunostaining in the LSCC when compared to the AC and MUC. The epithelial staining for MMP-9 was higher in the AC when compared to the LSCC. However, in the connective tissue, the expression was lower in the AC compared to other lesions. The cell proliferation rate was increased in proportion to the severity of dysplasia in the AC, while in the LSCC it was higher in well-differentiated lesions compared to moderately differentiated. There were no statistically significant differences in number of MFs present in the lesions studied. The results suggest that MMPs could affect the biological behaviour of ACs and LSCCs inasmuch as they could participate in the development and progression from premalignant lesions to malignant lesions.

Mouse models of nonmelanoma skin cancer

The skin is the largest organ of the mammalian body, made up of multiple layers, which include the epidermis, dermis, and subcutis (Alam and Ratner, N Engl J Med 344(13):975-983, 2001). The human interfollicular epidermis can be subdivided into five different layers: (1) stratum basale, (2) stratum spinosum, (3) stratum granulosum, (4) stratum lucidum, and (5) stratum corneum, all originating from basal keratinocytes by differentiation (Hameetman et al., BMC cancer 13:58, 2013; Ramirez et al., Differentiation 58(1):53-64, 1994). The epidermis is also able to generate different appendages: hair follicles (HF) and their associated sebaceous glands (Sibilia et al., Cell 102(2):211-220, 2000) as well as sweat glands (Luetteke et al., Genes Dev 8(4):399-413, 1994). The skin has important functions in several biological processes like environmental barrier, tissue regeneration, hair cycling, and wound repair. During these processes, stem cells from the interfollicular epidermis and from the hair follicle bulge are activated to renew the epidermis or hair. The epidermis and hair undergo continuous homeostatic regeneration and mutations, upon mutations which disturb the balance of homeostatic regeneration of epidermis and hair and lead to enhanced proliferation of keratinocytes, development of skin cancer is developed. Tumors that arise in the skin are mainly of three types: malignant melanoma, arising from melanocytes, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC), the latter two both arising from keratinocytes or hair follicle cells. In this chapter, we will describe some genetically engineered mouse models (GEMM) that aim at modeling human BCC and SCC and their respective precancerous lesions. We will describe the experimental approaches used in our laboratory to analyze tumor-bearing mice focusing on methods necessary for the induction of tumor growth as well as for the molecular and histological analysis of tumor tissue.

Desmoglein-3/γ-catenin and E-cadherin/ß-catenin differential expression in oral leukoplakia and squamous cell carcinoma

OBJECTIVE

The purpose of this study was to investigate gene/protein expression alterations of intercellular connections' components in oral leukoplakia (OLs) and squamous-cell carcinoma (OSCCs).

MATERIALS AND METHODS

Expression of desmogleins-2,3 (Dsg2/Dsg3), E-cadherin, and their cytoplasmic ligand, β/γ-catenins were quantitatively assessed in HSC-3 cells growing as monolayer cultures (ML)/multicellular aggregates (MCAs), using RT-PCR/Western blot, whereas their localization was detected by immunofluorescence. Furthermore, their expression was semi-quantitatively investigated in tissues from 25 OLs/25 OSCCs, using automated immunohistochemistry.

RESULTS

The steady-state levels of Dsg3 RNA transcripts increased as HSC-3 cells enter their exponential phase of growth, before a dramatic decrease to be observed as cells reached their plateau phase especially in MCAs. Upon the same period of time, Dsg2 levels have been increased. The expression of γ-catenin but not that of β-catenin was increased after 48 h in both MLs and MCAs. In clinical samples, Dsg3, Ε-cadherin, β/γ-catenin down-regulation was observed to be associated with the grade of OLs-dysplasia and OSCCs. Importantly, a membrane-to-cytoplasmic switch of expression and strong perinuclear aggregation of Dsg3/γ-catenin was seen in both HSC-3 cells and OLs/OSCCs.

CONCLUSIONS

The altered expression of Dsg3/γ-catenin and E-cadherin/β-catenin, in vitro and in ODs/OSCC imply their involvement in growth regulation and phenotype of dysplastic/malignant oral epithelial cells, contributing to the better understanding of epithelial dysplasia and OSCCs.

CLINICAL RELEVANCE

The observed alterations of their expression suggest a role of Dsg3 and γ-catenin (additionally to E-cadherin/β-catenin) as biomarkers of malignant transformation risk of oral dysplasia and the biological behavior (aggressiveness) of oral cancer, respectively.

Expression patterns of α2,3-sialyltransferase I and α2,6-sialyltransferase I in human cutaneous epithelial lesions

Skin tumors have become one of the most common cancers in the world and their carcinogenesis is frequently associated with altered glycosylation patterns. The aberrant sialylation, a type of glycosylation, can mediate pathophysiological key events during various stages of tumor progression, including invasion and metastasis. Sialyltransferases play a key role in a variety of biological processes, including cell-cell communication, cell-matrix interaction, adhesion, and protein targeting. In this study, it was evaluated the expression of ST3Gal I and ST6Gal I in cutaneous epithelial lesions that include actinic keratosis (n=15), keratoacanthoma (n=9), squamous cell carcinoma (n=22) and basal cell carcinoma (n=28) in order to evaluate if sialyltransferases expression is different in premalignant and in malignant tumors. The expression of ST3Gal I was observed in actinic keratosis (53%), keratoacanthoma (78%), squamous cell carcinoma (73%) and basal cell carcinoma (32%) with statistic differences between basal cell carcinoma and keratoacanthoma (P=0.0239) and basal cell carcinoma and squamous cell carcinoma (P=0.0096); for ST6Gal I, cytoplasmic expression was noted in actinic keratosis (40%), heterogeneous and cytoplasmic expression was noted in keratoacanthoma (67%), squamous cell carcinoma (41%) and basal cell carcinoma (7%) with statistic differences between basal cell carcinoma and squamous cell carcinoma (P=0.0061) and basal cell carcinoma and keratoacanthoma (P=0.0008). In summary, our results showed that the high expression of ST3Gal I and ST6Gal I, in skin tumors, is associated with tumors with greater potential for invasion and metastasis, as in the case of squamous cell carcinoma, and this may be related to their behavior.

Decreased expression of kallikrein-related peptidase 13: possible contribution to metastasis of human oral cancer

The human kallikrein-related peptidase family is comprised of 15 serine protease genes on chromosome 19q13.4. Our previous microarray analyses showed that the gene kallikrein-related peptidase 13 (KLK13) was down-regulated in oral squamous cell carcinoma (OSCC) cell lines. We evaluated the expression status of KLK13 in primary OSCCs and performed functional molecular experiments in OSCC cell lines. In 102 primary tumors studied, KLK13 expression significantly (P < 0.05) decreased compared with matched normal counterparts. Interestingly, KLK13-negative cases correlated significantly (P < 0.05) with regional lymph node metastasis. In vitro, cells overexpressing KLK13 (oeKLK13) had decreased invasiveness and motility and up-regulation of adhesion molecules (E-cadherin, α-catenin, β-catenin, junction plakoglobin, plakophilin4, desmocollin2, desmoglein3, and desmoplakin) compared with control cells. A rescue experiment that transfected oeKLK13 cells with siRNA against KLK13 restored invasiveness and migration activities with down-regulated adhesion molecules. Based on our results, we concluded that KLK13 may play an important role in regulating cellular migration and invasiveness, making the loss of KLK13 a potential biomarker for early detection of lymph node metastasis in OSCCs.

From prediction to experimental validation: desmoglein 2 is a functionally relevant substrate of matriptase in epithelial cells and their reciprocal relationship is important for cell adhesion

Accurate identification of substrates of a protease is critical in defining its physiological functions. We previously predicted that Dsg-2 (desmoglein-2), a desmosomal protein, is a candidate substrate of the transmembrane serine protease matriptase. The present study is an experimental validation of this prediction. As demanded by our published method PNSAS [Prediction of Natural Substrates from Artificial Substrate of Proteases; Venkatraman, Balakrishnan, Rao, Hooda and Pol (2009) PLoS ONE 4, e5700], this enzyme-substrate pair shares a common subcellular distribution and the predicted cleavage site is accessible to the protease. Matriptase knock-down cells showed enhanced immunoreactive Dsg-2 at the cell surface and formed larger cell clusters. When matriptase was mobilized from intracellular storage deposits to the cell surface there was a decrease in the band intensity of Dsg-2 in the plasma membrane fractions with a concomitant accumulation of a cleaved product in the conditioned medium. The exogenous addition of pure active recombinant matriptase decreased the surface levels of immunoreactive Dsg-2, whereas the levels of CD44 and E-cadherin were unaltered. Dsg-2 with a mutation at the predicted cleavage site is resistant to cleavage by matriptase. Thus Dsg-2 seems to be a functionally relevant physiological substrate of matriptase. Since breakdown of cell-cell contact is the first major event in invasion, this reciprocal relationship is likely to have a profound role in cancers of epithelial origin. Our algorithm has the potential to become an integral tool for discovering new protease-substrate pairs.

Desmosome dynamics in migrating epithelial cells requires the actin cytoskeleton

Re-modeling of epithelial tissues requires that the cells in the tissue rearrange their adhesive contacts in order to allow cells to migrate relative to neighboring cells. Desmosomes are prominent adhesive structures found in a variety of epithelial tissues that are believed to inhibit cell migration and invasion. Mechanisms regulating desmosome assembly and stability in migrating cells are largely unknown. In this study we established a cell culture model to examine the fate of desmosomal components during scratch wound migration. Desmosomes are rapidly assembled between epithelial cells at the lateral edges of migrating cells and structures are transported in a retrograde fashion while the structures become larger and mature. Desmosome assembly and dynamics in this system are dependent on the actin cytoskeleton prior to being associated with the keratin intermediate filament cytoskeleton. These studies extend our understanding of desmosome assembly and provide a system to examine desmosome assembly and dynamics during epithelial cell migration.

Special stains in Mohs surgery

The excellent cure rates associated with Mohs micrographic surgery depend on accurate interpretation of complete and high-quality microscopic frozen sections. Reliable interpretation of microscopic slides is only possible if the surgeon can distinguish tumor cells from surrounding normal tissue. By highlighting tumor cells with a chromogen that is visible on light microscopy, immunostaining allows the Mohs surgeon to distinguish tumor from normal cells in these challenging scenarios. This article focuses on practical aspects involving the most commonly used immunostains in dermatologic surgery, including MART-1 for melanocytic neoplasms, cytokeratin stains for keratinocytic neoplasms, and CD34 stains for dermatofibrosarcoma protuberans.

Keratoacanthoma: facts and controversies

The keratoacanthoma and its variants are clinically and histologically heterogenous. Some consider the keratoacanthoma to be benign, whereas others classify it as a subtype of squamous cell carcinoma. The keratoacanthoma is generally treated rather than observed for spontaneous resolution. This hampers evaluation of the true natural history of lesions diagnosed as keratoacanthoma. In addition, studies have not found a reliable marker to differentiate keratoacanthoma from squamous cell carcinoma. It currently remains unclear how the keratoacanthoma relates to squamous cell carcinoma, and continued investigation is necessary.

Desmosomal component expression in normal, dysplastic, and oral squamous cell carcinoma

Squamous cell carcinoma (oral SCC) is the most common oral cancer in the U.S., affecting nearly 30,000 Americans each year. Despite recent advances in detection and treatment, there has been little improvement in the five-year survival rate for this devastating disease. Oral cancer may be preceded by premalignant disease that appears histologically as dysplasia. Identification of molecular markers for cellular change would assist in determining the risk of dysplasia progressing to oral squamous cell carcinoma. The goal of this study was to determine if any correlation exists between histological diagnosed dysplasia and OSCC lesions and altered expression of desmosomal cell-cell adhesion molecules in the oral epithelium. Our data showed that oral SCC tissue samples showed decreased immunoreactivity of both desmoplakin and plakophilin-1 proteins compared to normal oral epithelium. Furthermore, significant decrease in desmoplakin immunoreactivity was observed in dysplastic tissue compared to normal oral epithelium. In contrast, the level of desmoglein-1 staining was unchanged between samples however desmoglein-1 was found localized to cell borders in oral SCC samples. These data suggest that changes in expression of desmoplakin and plakophilin-1 may prove to be a useful marker for changes in tissue morphology and provide a tool for identifying pre-neoplastic lesions of the oral cavity.

Immunostaining in Mohs micrographic surgery: a review

BACKGROUND

With the advent of incorporating the immunoperoxidase staining technique into the processing of frozen tissue, the use of Mohs micrographic surgery (MMS) has been expanded to include several high-risk tumors such as lentigo maligna, malignant melanoma, and dermatofibrosarcoma protuberans.

OBJECTIVES

To thoroughly review the English medical literature pertaining to the use of immunohistochemical staining techniques on frozen sections during MMS and to summarize the basic relevant outcomes from the different relevant studies.

MATERIALS AND METHODS

Medline search was conducted, with the following words used in the search criteria: "Mohs surgery,""staining,""immunostaining," and "immunoperoxidase." RESULTS Generally, all immunostains showed advantage over the traditional hematoxylin and eosin approach. Studies of MART-1 in melanoma chemosurgery indicated that it is typically crisp and has less background staining than MEL-5 and better staining consistency than HMB-45. In cases of desmoplastic melanomas, S100 is the stain of choice.

CONCLUSION

Immunostaining offers an advantage in MMS. Large, randomized, prospective studies comparing the different immunostains are still lacking in the literature. The authors have indicated no significant interest with commercial supporters.

PGP 9.5 and Cyclin D1 Coexpression in Cutaneous Squamous Cell Carcinomas

Background: squamous cell carcinoma (SCC) consists of altered keratinocytes, presents variable differentiation, inexorably progresses, and on occasion metastasizes. Objective: to investigate the biological activity of epidermal cells in SCCs by estimating the expression of PGP 9.5 and cyclin D1 using immunohistochemistry. Methods: the sample included 13 well-differentiated cases of cutaneous SCC (grade I), 12 moderately differentiated tumors (grade II), and 7 poorly differentiated lesions (grade III). Four cases belonged to the distinct entity of pseudoadenoid SCC. Results: PGP 9.5 expression was positively correlated with tumor stage ( P < .001) and potential perineural invasion ( P < .001), whereas cyclin D1 expression correlated inversely with the degree of cellular differentiation ( P < .001) and PGP 9.5 immunostaining ( P < .001). Conclusion: PGP 9.5 and cyclin D1 coexpression was closely associated with tumor aggressiveness and can be classified as a marker for predicting the outcome of resection-treated skin cancer patients.

Increased expression of Dsg2 in malignant skin carcinomas: A tissue-microarray based study

Desmoglein 2 (Dsg2), a transmembrane cadherin of the desmosomal cell-cell adhesion structure, is downregulated with epithelial differentiation. We recently demonstrated that overexpression of Dsg2 in epidermal keratinocytes deregulates multiple signaling pathways associated with increased growth rate, anchorage-independent cell survival, and the development of skin tumors. While changes in Dsg2 expression have been observed in neoplastic lesions, the correlation of expression levels and localization of Dsg2 and the state of tumor development has not been fully established. Here we generated a highly sensitive Dsg2 antibody (Ab10) and characterized that antibody along with a previously developed Dsg2 specific antibody 10D2. Using these antibodies in immunostaining of tissue microarrays, we show a dramatic upregulation of Dsg2 expression in certain human epithelial malignancies including basal cell carcinomas (BCC; n = 12), squamous cell carcinomas (SCC; n = 57), carcinomas of sebaceous and sweat glands (n = 12), and adenocarcinomas (n = 3). Dsg2 expression was completely absent in malignant fibrosarcomas (n = 16) and melanomas (n = 15). While Dsg2 expression was consistently strong in BCC, it varied in SCC with a minor correlation between a decrease of Dsg2 expression and tumor differentiation. In summary, we have identified Dsg2 as a potential novel marker for epithelial-derived malignancies.

Structure and function of desmosomes

Desmosomes are prominent adhesion sites that are tightly associated with the cytoplasmic intermediate filament cytoskeleton providing mechanical stability in epithelia and also in several nonepithelial tissues such as cardiac muscle and meninges. They are unique in terms of ultrastructural appearance and molecular composition with cell type-specific variations. The dynamic assembly properties of desmosomes are important prerequisites for the acquisition and maintenance of tissue homeostasis. Disturbance of this equilibrium therefore not only compromises mechanical resilience but also affects many other tissue functions as becomes evident in various experimental scenarios and multiple diseases.

Altered expression of desmocollin 3, desmoglein 3, and beta-catenin in oral squamous cell carcinoma: correlation with lymph node metastasis and cell proliferation

Desmocollin 3 (Dsc3) and desmoglein 3 (Dsg3) are both transmembrane glycoproteins that belong to the cadherin family of calcium-dependent cell adhesion molecules. beta-Catenin is a member of the cadherin-catenin complex that mediates homotypic cell-cell adhesion and is also an important molecule in the wnt signaling pathway. In this study, we examined the simultaneous expression level of Dsc3, Dsg3, and beta-catenin in oral squamous cell carcinomas (OSCCs) and normal oral epithelia using immunohistochemistry. There was a significant correlation (p < 0.05) among the following variables in OSCCs: reduced or loss of expression of Dsc3, Dsg3, and beta-catenin compared to normal oral epithelium, reduced or loss of expression of Dsc3 and histological grade (moderately or poorly differentiated), and reduced or loss of expression of beta-catenin and lymph node metastasis. Furthermore, a positive correlation was found between reduced or loss of beta-catenin staining and reduced or loss of Dsc3 staining in lymph node metastatic cancer tissue (r = 0.734, p < 0.05). These results suggest an abnormal expression of Dsc3, Dsg3, and beta-catenin induced in the progression of oral carcinomas and that the Dsc3 expression level might be related to the regulation of beta-catenin in lymph node metastasis and cell proliferation in OSCCs.

Increased keratinocyte proliferation initiated through downregulation of desmoplakin by RNA interference

The intercellular adhesive junction desmosomes are essential for the maintenance of tissue structure and integrity in skin. Desmoplakin (Dp) is a major obligate plaque protein which plays a fundamental role in anchoring intermediate filaments to desmosomal cadherins. Evidence from hereditary human disease caused by mutations in the gene encoding Dp, e.g. Dp haploinsufficiency, suggests that alterations in Dp expression result not only in the disruption of tissue structure and integrity but also could evoke changes in keratinocyte proliferation. We have used transient RNA interference (RNAi) to downregulate Dp specifically in HaCaT keratinocytes. We showed that this Dp downregulation also caused reduced expression of several other desmosomal proteins. Increased cell proliferation and enhanced G(1)-to-S-phase entry in the cell cycle, as monitored by colonial cellular density and BrdU incorporation, were seen in Dp RNAi-treated cells. These proliferative changes were associated with elevated phospho-ERK1/2 and phospho-Akt levels. Furthermore, this increase in phospho-ERK/1/2 and phospho-Akt levels was sustained in Dp RNAi-treated cells at confluence whereas in control cells there was a significant reduction in phosphorylation of ERK1/2. This study indicates that Dp may participate in the regulation of keratinocyte cell proliferation by, in part at least, regulating cell cycle progression.

Desmoglein 3 as a prognostic factor in lung cancer

Desmoglein 3 is a desmosomal protein of the cadherin family. Our cDNA expression profile demonstrated that desmoglein 3 was highly expressed in squamous cell carcinoma of the lung but not detected in pulmonary adenocarcinoma or normal lung. To investigate the clinical significance of desmoglein 3 in lung cancer, we surveyed its expression in primary non-small-cell lung cancers and neuroendocrine tumors. We used immunohistochemical analysis to examine the expression of desmoglein 3 by using tissue microarrays containing samples from 300 surgical non-small-cell lung cancer and 183 lung neuroendocrine tumor. Staining status was determined based on the sum of the distribution score (0, 1, or 2) and the intensity score (0, 1, 2, or 3) of the staining signal. Follow-up was available for 346 cases (median follow-up of 2.8 years). We determined the survival statistical significance of desmoglein 3 by using the log-rank test, and we plotted Kaplan-Meier curves. Negative immunohistochemical staining with desmoglein 3 was associated with shorter survival for all lung cancer patients regardless of the histologic subtype (5-year survival of 20.9% versus 49.5%, P < .001) in our series. In patients with atypical carcinoid tumors, lacking desmoglein 3 expression showed a 5-year survival of 0% compared with 36.8% for desmoglein 3-positive cases (P < .001). Desmoglein 3 status indicated a poor prognosis in lung cancers and portends a more aggressive behavior for atypical carcinoid tumors.

E-cadherin is a selective and strongly dominant prognostic factor in squamous cell carcinoma: a comparison of E-cadherin with desmosomal components

E-cadherin-mediated and desmosomal cell-cell adhesion have been implicated in the suppression of invasive and metastatic behavior of squamous cell carcinomas. Whether the adhaerens junction represented by E-cadherin and the desmosomes interplay or have distinct and separate roles in squamous cell cancer progression is still unclear. We have studied a cohort of 200 primary tumors and 56 lymph node metastases from different anatomic sites of the head and neck region for changes in synthesis of E-cadherin, desmoplakin and desmoglein by immunohistochemistry (IHC). Selected cases were studied by indirect immunofluorescence (IIF) and electron microscopy (EM). Only frozen sections were evaluated since they gave stronger and reproducible staining results. IHC data obtained were compared to clinical parameters. While some reduction in immunostaining was found in virtually all invasive tumors, at least partial expression, including that of E-cadherin, persisted in most late stage tumors and in lymph node metastases. Reduced desmosomal staining correlated with desmosomes reduced in numbers, size or in structural defects by EM analysis. By univariate analysis, reduction in synthesis of both E-cadherin and the desmosomal components that were generally linked (i.e., they showed positive rank correlations) were significantly associated with clinical parameters including overall and disease-free survival. However, by multivariate analysis including a Cox proportional hazards regression model (backward selection), the desmosomal components were not significant as independent prognostic factors. By contrast, E-cadherin was strongly associated with patient prognosis. In line with the highly significant association of reduced E-cadherin synthesis with an increased relative risk of follow up events, i.e., regional lymph node (p = 0.0007) and distant metastasis (p < 0.0001), as well as local recurrences (p < 0.0001), the prognostic strength of E-cadherin was independent of and stronger than histological grading, N stage, tumor site, and even stronger than the TNM stage. Based on these results, evaluation of E-cadherin in squamous cell carcinomas by immunostaining is recommended as a significant prognostic marker.

Pemphigus foliaceus masquerading as postoperative wound infection: report of a case and review of the Koebner and related phenomenon following surgical procedures

BACKGROUND

The Koebner phenomenon, also known as the isomorphic response, is the development of preexisting skin disease following trauma to uninvolved skin. Various cutaneous disorders have been described to arise at surgical wounds and scars. Moreover, dermatologic procedures, such as cold-steel and laser surgery, can evoke koebnerization.

OBJECTIVE

To describe a case of pemphigus foliaceus arising in postoperative wounds and to present a review of dermatologic disorders triggered by surgical procedures.

METHODS

We report a case of pemphigus foliaceus initially presenting at sites of Mohs' micrographic surgery, shave biopsy, and cryotherapy and, subsequently, at a nonsurgical site. We reviewed the English literature in MEDLINE from November 1955 to April 2004 for reports of Koebner and related phenomenon following surgical procedures.

RESULTS

To our knowledge, this is the first reported case of pemphigus foliaceus erupting at surgical and cryotherapy wounds. The clinical appearance can mimic wound infection. In addition to inducing preexisting disease, cutaneous procedures can also trigger the onset of new disease, which can either be limited only to the surgical site or subsequently become generalized.

CONCLUSION

Postoperative Koebner or related responses should be included in the differential diagnosis of poorly healing surgical wounds. Skin biopsies for histopathology and immunologic studies may be necessary for definitive diagnosis and optimal management.

Expression of desmosomal proteins in squamous cell carcinomas of the skin

BACKGROUND

Desmosomal proteins are well established markers of epithelial differentiation. Down-regulation of desmosomal proteins has been suggested to be a sign of reduced adhesiveness in metastasizing cells.

METHODS

We examined actinic keratoses, Bowen's disease, and squamous cell carcinoma (SCC) of the skin for the expression of desmosomal proteins using isoform-specific antibodies on paraffin-embedded sections. Evaluation was performed qualitatively in comparison to the epidermis and semiquantitatively using an area-intensity-score.

RESULTS

We found no qualitative correlation of desmoplakin or plakoglobin expression with risk of metastasis. Plakophilin 1, desmoglein 1, and the desmocollins 1-3 were found to be heterogeneously expressed in all neoplasms without significant correlation to aggressive tumor behavior. Plakophilin 2 was not expressed in any of the neoplasms examined. As most striking finding, desmoglein 2 was up-regulated qualitatively in half of all neoplasms examined and showed a significant higher proportion of positive cells in high-risk SCC than in low-risk SCC.

CONCLUSIONS

Desmosomal proteins are highly regulated in cutaneous SCC. Only desmoglein 2 expression correlates with risk of metastasis. Desmosomes may still be functional in metastasizing tumor cells.

Biological behavior of keratoacanthoma and squamous cell carcinoma: telomerase activity and COX-2 as potential markers

Distinguishing keratoacanthoma from squamous cell carcinoma is a persistent issue in pathology practice. Solitary keratoacanthoma is a self-limiting lesion as opposed to rather aggressive clinical behavior of squamous cell carcinoma. Several markers were studied to understand their biology and to separate these two lesions on a firm basis, but without much success. In this study, we plan to utilize recent markers such as telomerase activity and cyclooxygenase-2 (COX-2) along with more established marker p53 in understanding the biologic differences between keratoacanthoma and squamous cell carcinoma. We studied 17 well to moderately differentiated squamous cell carcinoma and 24 early proliferative phase keratoacanthoma by immunohistochemistry for the expression of p53 protein, COX-2 and telomerase activity. Higher telomerase activity was found in 11/17 squamous cell carcinoma (65%) compared to 4/24 (17%) of keratoacanthoma. Similarly, stronger expression of p53 and COX-2 was detected in 12 (71%) and 11 (65%) cases of squamous cell carcinoma compared to 2 (8%) and 2 (8%) cases of keratoacanthoma respectively. A highly significant 'P' value was obtained for telomerase activity (0.001), p53 (0.000), and COX-2 (0.001). Telomerase activity, COX-2, and p53 expression provide evidence that keratoacanthoma and squamous cell carcinoma are indeed distinct entities and also help in discriminating these two lesions, which closely resemble each other on conventional morphology. Although these markers present new insights into the biologic variation of keratoacanthoma and squamous cell carcinoma, they are of limited value for routine application in histological distinction of these two lesions. The differential expression of markers also explains the sustained proliferation observed in squamous cell carcinoma, compared to a shorter lifespan and involution in keratoacanthoma.

Alterations in desmosome size and number coincide with the loss of keratinocyte cohesion in skin with homozygous and heterozygous defects in the desmosomal protein plakophilin 1

Recessive mutations in the desmosomal plaque protein plakophilin 1 (PkP1) underlie ectodermal dysplasia/skin fragility syndrome (MIM 604536). We undertook an immunohistochemical and quantitative electron microscopic examination of suprabasal desmosomes from 4 skin samples from 3 PkP1 deficient patients, an unaffected carrier with a PKP1 heterozygous acceptor splice site mutation and 5 healthy control subjects. Desmosomal plaque size (>50 desmosomes per individual) and frequency (>20 high power fields, HPF) were assessed. Compared with controls, desmosomes were reduced dramatically both in size (49%) and frequency (61%) in the lower suprabasal layers (LSB) in PkP1 null patients (P<0.01). In the LSB compartment of the heterozygous carrier, corresponding reductions were 37% and 20%, respectively (P<0.01). Surprisingly, the PkP1 null patient's upper suprabasal layer, (USB), desmosome size was larger (59%, P<0.01) than the control value, and showed increased desmoglein 1 and PkP2 USB staining. The USB desmosome frequency in PKP1 null patients was similar to the LSB compartment (but reduced by 43% compared to USB controls). The carrier showed no difference in the USB desmosome size and frequency compared with the controls (P>0.05). The PKP1 null patients showed poorly developed inner and outer desmosomal plaques. Thus, both the patients and unaffected carrier showed reductions in the LSB desmosome size and number; despite only PkP1 null patients exhibiting any phenotype. These findings attest to the molecular recruiting and stabilizing roles of PkP1 in desmosome formation, particularly in the LSB compartment.

Altered expression of desmosomal components in high-grade squamous intraepithelial lesions of the cervix

We have used immunohistochemistry to test the hypothesis that components of the desmosome are disrupted during neoplastic progression of squamous epithelial cells in the uterine cervix. Sections of normal cervix and squamous intraepithelial lesions (SILs) were immunostained for desmosomal proteins and glycoproteins, and results were assessed using a semi-quantitative grading system. No difference between normal cervix and low-grade SIL (LSIL) was found. A significant reduction in expression of desmogleins was seen between high-grade SIL (HSIL) and LSIL (P<0.01) and normal cervix (P<0.001). Desmocollin expression was not reduced significantly, although scores showed significantly greater variation in HSIL compared with LSIL (P<0.05) and normal cervix (P<0.05). There was no significant difference in desmoplakin expression among the three groups. The results suggest that there may be sequential disruption of desmosomal function during neoplastic progression of cervical squamous intraepithelial cells, with downregulation of desmogleins during the progression from LSIL to HSIL and loss of desmocollin expression occurring in some cases of established HSIL.

Altered cytokeratin expression in actinic cheilitis

BACKGROUND

Actinic cheilitis (AC) is a widely recognized precancerous lesion of the lip. Varying degrees of epithelial dysplasia may be present. However, no studies have correlated epithelial changes with cytokeratin expression that might reflect the disordered maturation that is probably occurring.

METHODS

Thirty-four cases diagnosed as AC were classified according to dysplasia degree, and submitted to immunohistochemical staining for the detection of cytokeratins (CKs) 7, 8, 13, 14, 16 and 19. Normal mucosa adjacent to the lesions was also evaluated.

RESULTS

The results obtained showed that CK10 immunostained only superficial keratinized epithelial layers in 11 cases, and also intermediate spinous layers in 18 cases. Cytokeratin 14 was expressed in all epithelial layers of 31 cases, in two cases its expression was in the basal and intermediate layers, and one case was negative. Cytokeratin 13 immunostained 26 cases and was negative in eight cases. In these eight cases, CK13 was apparently replaced by CK16. Cytokeratin 16, besides these eight cases, was also expressed in the spinous intermediate layers of a further eight cases. The remaining CKs tested were all negative. No relation between the degree of dysplasia and the CK expression was noted.

CONCLUSIONS

Cytokeratin expression in AC is different from that of normal oral mucosa, and is not related to the degree of dysplasia.

Carcinoma-like vascular density in atypic keratoacanthoma suggests malignant progression

Differential diagnosis between keratoacanthomas and well differentiated squamous cell carcinomas based on clinical and histomorphological data is problematic. Recent findings of cellular atypia in a large proportion of keratoacanthomas indicated that these potentially 'self-healing' cutaneous neoplasms had the potential for malignant progression. Another malignancy-associated criterion is enhanced angiogenesis with increased microvessel density. To provide further diagnostic markers for keratoacanthomas we examined microvessel density on paraffin sections of 13 keratoacanthomas in comparison with 10 normal skin biopsies and 16 late-stage skin squamous cell carcinomas by counting and by computer-assisted image analysis of CD31-immunostained vessels. A significant increase of microvessel density in 'hot spots' was observed in keratoacanthomas as compared to normal skin. Furthermore, when keratoacanthomas were subdivided into tumours with and without malignancy-associated atypic areas, only those with atypia (n=6) were significantly better vascularised than normal skin and had a mean microvessel density in the range of late-stage squamous cell carcinomas. Both keratoacanthoma subtypes revealed comparable levels of inflammatory cell infiltration, tumour cell proliferation and vascular endothelial growth factor expression (mRNA and protein). Thus, in addition to malignancy-associated cellular atypia, increased microvessel density may serve as further diagnostic parameter to discriminate keratoacanthomas with a potential to progress to malignancy.

The potential role of abnormal E-cadherin and alpha-, beta- and gamma-catenin immunoreactivity in the determination of the biological behaviour of keratoacanthoma

BACKGROUND

Failure of E-cadherin and its associated proteins alpha-, beta- and gamma-catenin is believed to lead to disruption of cell-cell adhesion and to contribute to neoplasia.

OBJECTIVES

To determine the pattern of E-cadherin and alpha-, beta- and gamma-catenin immunostaining in keratoacanthoma (KA) and to evaluate its potential value in routine histopathology in differentiating KA with benign from that with malignant biological behaviour.

METHODS

We examined the expression of E-cadherin and alpha-, beta- and gamma-catenin in KA and correlated the histopathological features with the immunohistochemical findings. Next, we compared the immunohistochemical findings of KA with those found in malignant (squamous cell carcinoma, SCC) and benign (warts) lesions. In addition to the established histopathological criteria we used the Ki-67 index, a well-known marker of cell proliferation. Immunoperoxidase staining of E-cadherin and alpha-, beta- and gamma-catenin, and Ki-67 determination, were performed in paraffin-embedded sections of 12 KAs taken from archival material. On reviewing the histology, seven of the 12 KAs were characterized as 'classical' KA, and the rest as 'borderline' KA or KA resembling SCC. Additionally, 28 well, nine moderately and five poorly differentiated SCCs and 20 warts were examined.

RESULTS

Most 'classical' KAs (79-86%) showed normal membranous immunostaining and a low Ki-67 index. The remaining 'classical' KAs showed abnormal expression, in a staining pattern resembling that of well-differentiated SCC. All 'borderline' KAs showed a high Ki-67 index (> 40%) and abnormal expression of the adhesion molecules studied, identical to that of poorly differentiated SCC. Expression of E-cadherin and alpha-, beta- and gamma-catenin was found to be more frequently abnormal in 'borderline' KA compared with that in 'classical' KA (P < 0.05). Among E-cadherin and alpha-, beta- and gamma-catenin expression and Ki-67 index, only the expression of beta-catenin was more frequently found to be abnormal in total SCC than in total KA (P < 0.05). Expression of E-cadherin and alpha-, beta- and gamma-catenin was more frequently found to be abnormal in well-differentiated SCC than in 'classical' KA (P < 0.05). In total, as well as in 'classical' or 'borderline' KA, an agreement between expression of E-cadherin and of catenins was seen.

CONCLUSIONS

These findings suggest that E-cadherin and catenins may be very helpful in distinguishing between 'classical' and 'borderline' KA, as the expression of these adhesion molecules in 'classical' KA is identical to that found in normal epidermis, overlapping with well-differentiated SCC in some cases. In 'borderline' KA, expression of adhesion molecules is identical to that in poorly differentiated SCC.

Early Implantation Events in the Baboon (Papio anubis) with Special Reference to the Establishment of Anchoring Villi

The development of the baboon anchoring villus has been studied from day 14 to day 48 of gestation, using light and electron microscopy. At day 14, cords of trophoblast could be seen streaming into the endometrium, invading maternal vessels and forming blood-filled lacunae; by 20 days gestation some of these had differentiated into distinctive anchoring villi, with an outer covering of syncytiotrophoblast and inner cytotrophoblast cells which differed from those of floating villi in that a subpopulation detached from the syncytium to form an interconnecting network of cells within the centre of the villus. Subsequent migration of cytotrophoblast into the endometrium formed the cytotrophoblastic shell while fibrillin-like extracellular matrix biosynthesis within the body of the villus provided a firm mechanical support. At the trophoblast-decidual interface, a zone of necrosis and phagocytosis initially developed, which became less extensive with time, so that by 40 days a stable interface was evident with only residual pockets of necrosis. During this period, there was differentiation of decidual cells which by 28 days developed characteristic pedunculated cell processes, and later became surrounded by a basal lamina. The factors that control detachment of cytotrophoblast from the syncytium and the biosynthesis of the specialized, fibrillar extracellular matrix, features that are not apparent in other placental villi, require further investigation, possibly by carefully controlled in vitro experimentation.

Comparison of oncostatin M expression in keratoacanthoma and squamous cell carcinoma

Oncostatin M (OSM) is a 28-kDa glycoprotein, produced by stimulated macrophages and T lymphocytes, that inhibits the proliferation and induces differentiation of a number of different cell lines derived from solid tumors. To determine whether keratoacanthoma (KA) is unique or a variant of squamous cell carcinoma (SCC), we compared the immunohistochemical expression of OSM in the tumor cells and peri- and intratumoral macrophages of 21 mature KAs, 7 regressing KAs, and 27 SCCs. An inverse correlation was identified between OSM tumor labeling and the density of OSM-labeled tumor-associated macrophages for KAs (r = -.4; P = .09). OSM tumor expression was significantly more frequent and more intense in KAs than in SCCs (95% versus 63%; P < .01). In contrast, the density of OSM-labeled macrophages was significantly higher in SCCs compared with mature KAs (7/3 high power fields versus 4/3 high power fields; P = .02). These OSM-positive macrophages were predominantly located at the advancing, infiltrative margins of both neoplasms. Regressing KAs demonstrated a decreased level of OSM tumor expression compared with mature KAs (53% versus 95%; P = .001), but there was no difference in density of OSM-labeled macrophages. Both the above differences and the overlapping patterns of OSM expression suggest that KAs are a variant of SCC where OSM, possibly as an autocrine factor, may mediate KA's overwhelming but not absolute tendency to involute.

Changing roles of cadherins and catenins during progression of squamous intraepithelial lesions in the uterine cervix

Uterine cervix represents a convenient model for the study of the gradual transformation of normal squamous epithelium via low- to high-grade squamous intraepithelial lesions (SILs). Because SIL, on the basis of the cytokeratins expressed, are thought to originate from the reserve cells, we analyzed whether SILs also show a reserve cell phenotype with respect to intercellular interactions. The changes in expression and subcellular localization of the components of the adherens junction and desmosomal complexes were investigated in normal, metaplastic, and premalignant cervical epithelium, as well as in cell cultures derived from these tissues. The results suggest that 1) during progression of SILs, E-cadherin is suppressed, with its role in cell-cell connections diminishing; 2) P-cadherin, in contrast, becomes the predominant cadherin in high-grade SILs; 3) the level of cellular alpha-catenin is dramatically decreased in high-grade SILs; 4) the level of beta-catenin is decreased during progression of SILs, with plakoglobin suggestively becoming the predominant catenin mediating connection of cadherins to the cytoskeleton; 5) the assembly of desmosomes is affected during progression of SILs and is accompanied by a dramatically decreased expression for desmogleins and desmoplakins (I, II); and 6) expression of differentiation markers (involucrin, CK13) in high-grade SILs seems to be controlled by P-cadherin as opposed to E-cadherin in the normal tissue counterpart. We conclude that during development of cervical lesions substantial (both quantitative and qualitative) changes occur in cell-cell junctions, making the interactions of cells in lesions dissimilar from those of reserve cells, basal cells, or cells of immature squamous metaplasia, despite existing morphological similarity between all of these cell types and cells of high-grade lesions.

Loss of invasiveness in squamous cell carcinoma cells overexpressing desmosomal cadherins

The molecular and structural characteristics of intercellular adhesion were investigated in a squamous cell carcinoma (SCCA) cell line, originally derived from an oral tumor with an invasive growth pattern. The expression of adherens junction and desmosomal components were compared with that of cultured normal oral keratinocytes. Lack of membrane association in interdesmosomal areas, the disorganization of the actin cytoskeleton and the faster cell disassembly upon E-cadherin antibody binding in SCCA cells indicated decreased functional adherens junctions. These observations were supported by a significant reduction in E-, N-, and P-cadherin protein expression. In contrast, the level of desmosomal cadherin proteins, desmoglein 1/2 and desmocollin 2, were substantially upregulated and accompanied, ultrastructurally, by increased number and size of desmosomes. Since tumor invasion suppressor capacity has been proposed for desmosomal cadherins, we investigated the in vivo invasion potential of these SCCA cells by introducing them into SCID mice. Tumors developed, but with a benign phenotype. Based on these results, we hypothesize that the benign behavior of this SCCA cell line is a consequence of overexpressed desmosomal cadherins. This SCCA cell line, therefore, represents an excellent model system to further investigate the regulation and tumor invasion suppressor potential of desmosomal adhesion molecules.

Desmosomes: intercellular adhesive junctions specialized for attachment of intermediate filaments

Cell-cell adhesion is thought to play important roles in development, in tissue morphogenesis, and in the regulation of cell migration and proliferation. Desmosomes are adhesive intercellular junctions that anchor the intermediate filament network to the plasma membrane. By functioning both as an adhesive complex and as a cell-surface attachment site for intermediate filaments, desmosomes integrate the intermediate filament cytoskeleton between cells and play an important role in maintaining tissue integrity. Recent observations indicate that tissue integrity is severely compromised in autoimmune and genetic diseases in which the function of desmosomal molecules is impaired. In addition, the structure and function of many of the desmosomal molecules have been determined, and a number of the molecular interactions between desmosomal proteins have now been elucidated. Finally, the molecular constituents of desmosomes and other adhesive complexes are now known to function not only in cell adhesion, but also in the transduction of intracellular signals that regulate cell behavior.