JNK inhibition enhances cell-cell adhesion impaired by desmoglein 3 gene disruption in keratinocytes

c-Jun NH2-terminal protein kinase (JNK) and p38 are stress-activated mitogen-activated protein kinases (MAPK) that are phosphorylated by various stimuli. It has been reported that the loss of desmoglein (DSG) 3, a desmosomal transmembrane core molecule, in keratinocytes impairs cell-cell adhesion accompanied by p38 MAPK activation. To understand the biological role of DSG3 in desmosomes and its relationship with stress-activated MAPKs, we established DSG3 knockout keratinocytes (KO cells). Wild-type cells showed a linear localization of DSG1 to cell-cell contacts, whereas KO cells showed a remarkable reduction despite the increased protein levels of DSG1. Cell-cell adhesion in KO cells was impaired over time, as demonstrated by dispase-based dissociation assays. The linear localization of DSG1 to cell-cell contacts and the strength of cell-cell adhesion were promoted by the pharmacological inhibition of JNK. Conversely, pharmacological activation of JNK, but not p38 MAPK, in wild-type cells reduced the linear localization of DSG1 in cell-cell contacts. Our data indicate that DSG1 and DSG2 in KO cells cannot compensate for the attenuation of cell-cell adhesion strength caused by DSG3 deficiency and that JNK inhibition restores the strength of cell-cell adhesion by increasing the linear localization of DSG1 in cell-cell contacts in KO cells. Inhibition of JNK signaling may improve cell-cell adhesion in diseases in which DSG3 expression is impaired.

Homozygous deletion of the DSG3 terminal exon associated with acantholytic blistering of the oral and laryngeal mucosa

We report a novel homozygous 49.6 kb deletion of chromosome 18q12.1 involving the last exon of DSG3 in dizygotic twins with phenotype consistent with acantholytic blistering of the oral and laryngeal mucosa (ABOLM). The twin siblings presented predominantly with friability of the laryngeal and respiratory mucosa. This is only the second report in the literature of this unusual autosomal recessive blistering disorder. The diagnosis explains the mucosal phenotype of a pemphigus-like disorder without evidence of autoimmune dysfunction. The exclusion of an autoimmune basis has management implications. The deletion also involved the DSG2 gene, which is associated with arrhythmogenic right ventricular dysplasia (ARVD). The affected siblings and heterozygous parents do not show any cardiac phenotype at this time. Functional studies would further clarify how deletions resulting in loss of function of DSG3 may cause the reported phenotypes of DSG3-related ABOLM.

Type 2 T-Cell Responses against Distinct Epitopes of the Desmoglein 3 Ectodomain in Pemphigus Vulgaris

Pemphigus vulgaris (PV) is an autoimmune blistering disorder of the skin and/or mucous membranes caused by IgG autoantibodies that predominantly target two transmembrane desmosomal cadherins: desmoglein (DSG)1 and DSG3. DSG-specific T cells play a central role in PV pathogenesis because they provide help to autoreactive B cells for autoantibody production. In this study, we characterized DSG3-specific peripheral T cells in a cohort of 52 patients with PV and 41 healthy controls with regard to cytokine profile and epitope specificity. By ELISpot analysis, type 2 T cells reactive with the DSG3 ectodomain were significantly increased in patients with PV compared with those in healthy controls. By dextramer analysis, CD4+ T cells specific for an epitope within the extracellular domain of DSG3, DSG3(206-220), were found at significantly higher frequencies in patients with PV than in HLA-matched healthy controls. T-cell recognition of two distinct DSG3 epitopes, that is, DSG3(206-220) and DSG3(378-392), correlated significantly, suggesting a synergistic effect in B-cell help. Immunization of HLA-DRB1∗04:02-transgenic mice with PV with the same set of DSG3 peptides induced pathogenic DSG3-specific IgG antibodies, which induced loss of keratinocyte adhesion in vitro. Thus, DSG3 peptide-specific T cells are of particular interest as surrogate markers of disease activity and potential therapeutic targets in PV.

Comparative Transcriptome Analysis Identifies Desmoglein-3 as a Potential Oncogene in Oral Cancer Cells

The role of desmoglein-3 (DSG3) in oncogenesis is unclear. This study aimed to uncover molecular mechanisms through comparative transcriptome analysis in oral cancer cells, defining potential key genes and associated biological processes related to DSG3 expression. Four mRNA libraries of oral squamous carcinoma H413 cell lines were sequenced, and 599 candidate genes exhibited differential expression between DSG3-overexpressing and matched control lines, with 12 genes highly significantly differentially expressed, including 9 upregulated and 3 downregulated. Genes with known implications in cancer, such as MMP-13, KRT84, OLFM4, GJA1, AMOT and ADAMTS1, were strongly linked to DSG3 overexpression. Gene ontology analysis indicated that the DSG3-associated candidate gene products participate in crucial cellular processes such as junction assembly, focal adhesion, extracellular matrix formation, intermediate filament organisation and keratinocyte differentiation. Validation of RNA-Seq was performed through RT-qPCR, Western blotting and immunofluorescence analyses. Furthermore, using transmission electron microscopy, we meticulously examined desmosome morphology and revealed a slightly immature desmosome structure in DSG3-overexpressing cells compared to controls. No changes in desmosome frequency and diameter were observed between the two conditions. This study underscores intricate and multifaceted alterations associated with DSG3 in oral squamous carcinoma cells, implying a potential oncogenic role of this gene in biological processes that enable cell communication, motility and survival.

Desmoglein-Specific B-Cell-Targeted Single-Cell Analysis Revealing Unique Gene Regulation in Patients with Pemphigus

Autoreactive B cells are assumed to play a critical role in pemphigus; however, the characteristics of these cells are not yet fully understood. In this study, 23 pemphigus vulgaris or pemphigus foliaceus samples were used to isolate circulating desmoglein (DSG)-specific B cells. Transcriptome analysis of the samples was performed at the single-cell level to detect genes involved in disease activity. DSG1- or DSG3-specific B cells from three patients' differentially expressed genes related to T cell costimulation (CD137L) as well as B-cell differentiation (CD9, BATF, TIMP1) and inflammation (S100A8, S100A9, CCR3), compared with nonspecific B cells from the same patients. When the DSG1-specific B cells before and after treatment transcriptomes of the patient with pemphigus foliaceus were compared, there were changes in several B-cell activation pathways not detected in non-DSG1-specific B cells. This study clarifies the transcriptomic profile of autoreactive B cells in patients with pemphigus and documents the gene expression related to disease activity. Our approach can be applied to other autoimmune diseases and has the potential for future detection of disease-specific autoimmune cells.

Plasma Exosomal microRNA Profile Reveals miRNA 148a-3p Downregulation in the Mucosal-Dominant Variant of Pemphigus Vulgaris

The mucosal-dominant variant of pemphigus vulgaris (MPV) is an autoimmune disease characterized by oral mucosal blistering and circulating pathogenic IgG antibodies against desmoglein 3 (Dsg3), resulting in life-threatening bullae and erosion formation. Recently, microRNAs (miRNAs) have emerged as promising players in the diagnosis and prognosis of several pathological states. For the first time, we have identified a different expression profile of miRNAs isolated from plasma-derived exosomes (P-EVs) of MPV patients positive for antibodies against Dsg3 (Dsg3-positive) compared to healthy controls. Moreover, a dysregulated miRNA profile was confirmed in MPV tissue biopsies. In particular, a strong downregulation of the miR-148a-3p expression level in P-EVs of MPV patients compared to healthy controls was demonstrated. Bioinformatics prediction analysis identifies metalloproteinase-7 (MMP7) as a potential miR-148a-3p target. An in vitro acantholysis model revealed that the miR-148a-3p expression level was dramatically downregulated after treatment with Dsg3 autoantibodies, with a concomitant increase in MMP7 expression. The increased expression of MMP7 leads to the disruption of intercellular and/or extracellular matrix adhesion in an in vitro cellular model of MPV, with subsequent cell dissociation. Overexpression of miR-148a-3p prevented cell dissociation and regressed MMP7 upregulation. Our findings suggest a pivotal role of P-EV cargo in regulating molecular mechanisms involved in MPV pathogenesis and indicate them as potential MPV therapeutic targets.

Evidence for the Desmosomal Cadherin Desmoglein-3 in Regulating YAP and Phospho-YAP in Keratinocyte Responses to Mechanical Forces

Desmoglein 3 (Dsg3) plays a crucial role in cell-cell adhesion and tissue integrity. Increasing evidence suggests that Dsg3 acts as a regulator of cellular mechanotransduction, but little is known about its direct role in mechanical force transmission. The present study investigated the impact of cyclic strain and substrate stiffness on Dsg3 expression and its role in mechanotransduction in keratinocytes. A direct comparison was made with E-cadherin, a well-characterized mechanosensor. Exposure of oral and skin keratinocytes to equiaxial cyclic strain promoted changes in the expression and localization of junction assembly proteins. The knockdown of Dsg3 by siRNA blocked strain-induced junctional remodeling of E-cadherin and Myosin IIa. Importantly, the study demonstrated that Dsg3 regulates the expression and localization of yes-associated protein (YAP), a mechanosensory, and an effector of the Hippo pathway. Furthermore, we showed that Dsg3 formed a complex with phospho-YAP and sequestered it to the plasma membrane, while Dsg3 depletion had an impact on both YAP and phospho-YAP in their response to mechanical forces, increasing the sensitivity of keratinocytes to the strain or substrate rigidity-induced nuclear relocation of YAP and phospho-YAP. Plakophilin 1 (PKP1) seemed to be crucial in recruiting the complex containing Dsg3/phospho-YAP to the cell surface since its silencing affected Dsg3 junctional assembly with concomitant loss of phospho-YAP at the cell periphery. Finally, we demonstrated that this Dsg3/YAP pathway has an influence on the expression of YAP1 target genes and cell proliferation. Together, these findings provide evidence of a novel role for Dsg3 in keratinocyte mechanotransduction.

Desmoglein-3 acts as a pro-survival protein by suppressing reactive oxygen species and doming whilst augmenting the tight junctions in MDCK cells

Kidney disease prevalence increases with age, with a common feature of the disease being defects in the epithelial tight junctions. Emerging evidence suggests that the desmosomal adhesion protein Desmoglein-3 (Dsg3) functions beyond the desmosomal adhesion and plays a role in regulating the fundamental pathways that govern cell fate decisions in response to environmental chemical and mechanical stresses. In this study, we explored the role of Dsg3 on dome formation, reactive oxygen species (ROS) production and transepithelial electrical resistance (TER) in MDCK cells, a kidney epithelial cell model widely used to study cell differentiation and tight junction formation and integrity. We show that overexpression of Dsg3 constrained nuclear ROS production and cellular doming in confluent cell cultures and these features coincided with augmented TER and enhanced tight junction integrity. Conversely, cells expressing dominant-negative Dsg3ΔC mutants exhibited heightened ROS production and accelerated doming, accompanied by increased apoptosis, as well as cell proliferation, with massive disruption in F-actin organization and accumulation, and alterations in tight junctions. Inhibition of actin polymerization and protein synthesis was able to sufficiently block dome formation in mutant populations. Taken together, these findings underscore that Dsg3 has a role in controlling cellular viability and differentiation as well as the functional integrity of tight junctions in MDCK cells.

Altered Cell-Cycle Control, Inflammation, and Adhesion in High-Risk Persistent Bronchial Dysplasia

Persistent bronchial dysplasia is associated with increased risk of developing invasive squamous cell carcinoma (SCC) of the lung. In this study, we hypothesized that differences in gene expression profiles between persistent and regressive bronchial dysplasia would identify cellular processes that underlie progression to SCC. RNA expression arrays comparing baseline biopsies from 32 bronchial sites that persisted/progressed to 31 regressive sites showed 395 differentially expressed genes [ANOVA, FDR ≤ 0.05). Thirty-one pathways showed significantly altered activity between the two groups, many of which were associated with cell-cycle control and proliferation, inflammation, or epithelial differentiation/cell-cell adhesion. Cultured persistent bronchial dysplasia cells exhibited increased expression of Polo-like kinase 1 (PLK1), which was associated with multiple cell-cycle pathways. Treatment with PLK1 inhibitor induced apoptosis and G2-M arrest and decreased proliferation compared with untreated cells; these effects were not seen in normal or regressive bronchial dysplasia cultures. Inflammatory pathway activity was decreased in persistent bronchial dysplasia, and the presence of an inflammatory infiltrate was more common in regressive bronchial dysplasia. Regressive bronchial dysplasia was also associated with trends toward overall increases in macrophages and T lymphocytes and altered polarization of these inflammatory cell subsets. Increased desmoglein 3 and plakoglobin expression was associated with higher grade and persistence of bronchial dysplasia. These results identify alterations in the persistent subset of bronchial dysplasia that are associated with high risk for progression to invasive SCC. These alterations may serve as strong markers of risk and as effective targets for lung cancer prevention.Significance: Gene expression profiling of high-risk persistent bronchial dysplasia reveals changes in cell-cycle control, inflammatory activity, and epithelial differentiation/cell-cell adhesion that may underlie progression to invasive SCC. Cancer Res; 78(17); 4971-83. ©2018 AACR.

Gene expression profiling of idiopathic interstitial pneumonias (IIPs): identification of potential diagnostic markers and therapeutic targets

BACKGROUND

Chronic fibrosing idiopathic interstitial pneumonia (IIP) is characterized by alveolar epithelial damage, activation of fibroblast proliferation, and loss of normal pulmonary architecture and function. This study aims to investigate the genetic backgrounds of IIP through gene expression profiling and pathway analysis, and to identify potential biomarkers that can aid in diagnosis and serve as novel therapeutic targets.

METHODS

RNA extracted from lung specimens of 12 patients with chronic fibrosing IIP was profiled using Illumina Human WG-6 v3 BeadChips, and Ingenuity Pathway Analysis was performed to identify altered functional and canonical signaling pathways. For validating the results from gene expression analysis, immunohistochemical staining of 10 patients with chronic fibrosing IIP was performed.

RESULTS

Ninety-eight genes were upregulated in IIP patients relative to control subjects. Some of the upregulated genes, namely desmoglein 3 (DSG3), protocadherin gamma-A9 (PCDHGA9) and discoidin domain-containing receptor 1 (DDR1) are implicated in cell-cell interaction and/or adhesion; some, namely collagen type VII, alpha 1 (COL7A1), contactin-associated protein-like 3B (CNTNAP3B) and mucin-1 (MUC1) are encoding the extracellular matrix molecule or the molecules involved in cell-matrix interactions; and the others, namely CDC25C and growth factor independent protein 1B (GFI1B) are known to affect cell proliferation by affecting the progression of cell cycle or regulating transcription. According to pathway analysis, alternated pathways in IIP were related to cell death and survival and cellular growth and proliferation, which are more similar to cancer than to inflammatory response and immunological diseases. Using immunohistochemistry, we further validate that DSG3, the most highly upregulated gene, shows higher expression in chronic fibrosing IIP lung as compared to control lung.

CONCLUSION

We identified several genes upregulated in chronic fibrosing IIP patients as compared to control, and found genes and pathways implicated in cancer, rather than in inflammatory or immunological disease to play important roles in the pathogenesis of IIPs. Moreover, DSG3 is a novel potential biomarker for chronic fibrosing IIP with its significantly high expression in IIP lung.

Epithelial antigenic specificities of circulating autoantibodies in mucosal lichen planus

BACKGROUND

Mucosal lichen planus (LP) is an inflammatory disease of the mucous membranes of unknown origin. The antigen-specific autoantibodies or T cells responsible for this disease have not yet been established.

OBJECTIVES

This study was designed to study the antigenic specificities of circulating antibodies in patients with mucosal LP and to review previous findings on this topic.

METHODS

We tested a series of consecutive cases of mucosal LP in our clinic by enzyme-linked immunosorbent assay using desmoglein 3 (Dsg3) and BP180 fusion proteins.

RESULTS

Three of 22 patients were positive for anti-NC16A antibodies. Interestingly, we found a middle-aged woman with severe disease with circulating anti-Dsg3 antibodies at high levels, typical of pemphigus vulgaris. Levels of these antibodies positively correlated with the severity of clinical manifestations. We failed to detect anti-desmoglein antibodies in any other patient in our series and in the literature review.

CONCLUSIONS

Some patients with mucosal LP may present with circulating anti-BP180 antibodies at low levels. We also report the first case with positive anti-Dsg3 antibodies. The pathogenic relevance of these autoantibodies remains unknown.

A spontaneous deletion within the desmoglein 3 extracellular domain of mice results in hypomorphic protein expression, immunodeficiency, and a wasting disease phenotype

Desmoglein 3 is a transmembrane component of desmosome complexes that mediate epidermal cell-to-cell adhesion and tissue integrity. Antibody blockade of desmoglein 3 function in pemphigus vulgaris patients leads to skin blistering (acantholysis) and oral mucosa lesions. Desmoglein 3 deficiency in mice leads to a phenotype characterized by cyclic alopecia in addition to the dramatic skin and mucocutaneous acantholysis observed in pemphigus patients. In this study, mice that developed an overt squeaky (sqk) phenotype were identified with obstructed airways, cyclic hair loss, and severe immunodeficiency subsequent to the development of oral lesions and malnutrition. Single-nucleotide polymorphism-based quantitative trait loci mapping revealed a genetic deletion that resulted in expression of a hypomorphic desmoglein 3 protein with a truncation of an extracellular cadherin domain. Because hypomorphic expression of a truncated desmoglein 3 protein led to a spectrum of severe pathology not observed in mice deficient in desmoglein 3, similar human genetic alterations may also disrupt desmosome function and induce a disease course distinct from pathogenesis of pemphigus vulgaris.

Altered expression and localization of desmoglein 3 in esophageal squamous cell carcinoma

Desmoglein 3 (DSG3), a transmembrane cadherin of the desmosomal cell-cell adhesion structure, plays vital roles in the maintenance of normal epithelial tissue architecture. Reports implicating a role for DSG3 expression in cancer are few and contradictory. In this study, immunohistochemical staining was employed to investigate DSG3 expression and subcellular localization in esophageal squamous cell carcinoma (ESCC), and to correlate changes with clinical characteristics. Results indicate that in normal squamous cell epithelia, strong DSG3 immunoreactivity was observed in the Stratum spinosum, and localization occurred only at the cell membrane. In ESCC, DSG3 immunoreactivity displayed an abnormal cytoplasmic localization that was correlated with cell differentiation (P=0.018). Most strikingly, in 74.1% of the tumors, DSG3 expression was up-regulated and correlated with regional lymph node metastasis (P=0.036). Moreover, in patients without lymph node metastasis, cytoplasmic localization of DSG3 correlated with poor prognosis (P=0.044). These results suggest that DSG3 is involved in the development of ESCC and imply that DSG3 overexpression is likely to be an essential contributor to the aggressive features of esophageal cancer.

Prognostic significance of desmoglein 2 and desmoglein 3 in esophageal squamous cell carcinoma

OBJECTIVE

Desmogleins (DSGs) are major members among the desmosomal cadherins critically involved in cell-cell adhesion and the maintenance of normal tissue architecture in epithelia. Reports exploring links of DSG family member expression with cancers are few and vary. The aim of this study was to investigate the ratio of DSG2 and DSG3 mRNA expression in esophageal squamous cell carcinoma (ESCC) tissue to normal tissue (T/N ratio) and evaluate correlations with clinical parameters.

METHODS

The mRNA expression of DSGs, as well as γ-catenin and desmoplakin, was detected by real-time quantitative RT-PCR in 85 cases of ESCC tissue specimens.

RESULTS

The expression level of DSG3 mRNA was significantly higher than that of DSG2 in ESCC specimens (p = 0.000). DSG3 mRNA expression highly correlated with histological grade (p = 0.009), whereas that of DSG2 did not significantly relate to any clinicopathologic parameter. Kaplan-Meier survival analysis showed that only DSG3 expression had an impact on the survival curve, with negative DSG3 expression indicating worse survival (p = 0.038). Multivariate Cox regression analysis demonstrated DSG3 to be an independent prognostic factor for survival. Furthermore, correlation analysis demonstrated the mRNA level of DSG3 to highly correlate with those of γ-catenin and desmoplakin in ESCC samples (p=0.000), implying that the expression of desmosomal components might be regulated by the same upstream regulatory molecules.

CONCLUSIONS

Our findings suggest that DSG3 may be involved in the progression of ESCC and serve as a prognostic marker, while expression of DSG2 cannot be used as a predictor of ESCC patient outcome.

Evaluation of patients with nasal polyps about the possible association of desmosomal junctions, RORA and PDE4D gene

OBJECTIVES

Nasal polyposis is chronic inflammatory disease of the nasal mucosa of the nose and sinuses, often associated with chronic non-allergic rhinitis, aspirin intolerance and non-allergic asthma. The etiology of nasal polyposis is unknown. Multiple factors contribute to the development of nasal polyps including genetic predisposition.

PATIENTS AND METHODS

This study was conducted on patients applied due to nasal polyps. Blood samples were collected peripheral vein and stored at 4°C until analysis for DNA extraction. Genomic DNA was extracted from peripheral blood by a standard method, samples were studied in real time PCR. All patients were evaluated about the possible association of DSG1 (rs7236477-G, 96 rxn), DSG3 (rs1941184-C, 96 rxn), PDE4D (rs1588265) and RORA (rs11071559) gene.

RESULTS

32 patients (17 male, 15 female) with nasal polyposis were included to the study. The mean age was 34.9 ± 17.7 years, ranging between 18 and 55 years. Control group was consisted with 50 healthy volunteers without a history of nasal polyp. DSG1, DSG3 and RORA values of the study group were not statistically different from control group (p > 0.05). PDE4D values of the study group were significantly different from control group (p < 0.05).

CONCLUSIONS

Multiple factors contribute to the pathogenesis of nasal polyps including genetic predisposition. The PDE4D family has gained interest in the complex pathogenesis of nasal polyposis. This is likely linked to the mucosal inflammatory response.

DSG3 facilitates cancer cell growth and invasion through the DSG3-plakoglobin-TCF/LEF-Myc/cyclin D1/MMP signaling pathway

Desmoglein 3 (DSG3) is a component of the desmosome, which confers strong cell-cell adhesion. Previously, an oncogenic function of DSG3 has been found in head neck cancer (HNC). Here, we investigated how this molecule contributes to the malignant phenotype. Because DSG3 is associated with plakoglobin, we examined whether these phenotypic alterations were mediated through the plakoglobin molecule. Immunoprecipitation and immunofluorescence staining revealed that DSG3 silencing disrupted its interaction with plakoglobin and induced plakoglobin translocation from the cytoplasm to the nucleus. Knockdown of DSG3 significantly increased the interaction of plakoglobin with the transcriptional factor TCF and suppressed the TCF/LEF transcriptional activity. These effects further conferred to reduced expression of the TCF/LEF downstream target genes, including c-myc, cyclin D1, and MMP-7. Functional analyses showed that DSG3 silencing reduced cell growth and arrested cells at G0/G1 phase. Besides, cell migration and invasion abilities were also decreased. These cellular results were confirmed using tumor xenografts in mice, as DSG3 silencing led to the suppressed tumor growth, plakoglobin translocation and reduced expression of TCF/LEF target genes in tumors. Therefore, our study shows that the desmosomal protein DSG3 additionally functions to regulate malignant phenotypes via nuclear signaling. In conclusion, we found that DSG3 functions as an oncogene and facilitates cancer growth and invasion in HNC cells through the DSG3-plakoglobin-TCF/LEF pathway.

Unimpaired skin carcinogenesis in Desmoglein 3 knockout mice

The contribution of adherens junction inactivation, typically by downregulation or mutation of the transmembrane core component E-cadherin, to cancer progression is well recognized. In contrast, the role of the desmosomal cadherin components of the related cell-cell adhesion junction, the desmosome, in cancer development has not been well explored. Here, we use mouse models to probe the functional role of desmosomal cadherins in carcinogenesis. Because mice lacking the desmosomal cadherin Desmoglein 3 (Dsg3) have revealed a crucial role for Dsg3 in cell-cell adhesion in stratified epithelia, we investigate the consequence of Dsg3 loss in two models of skin carcinogenesis. First, using Dsg3−/− keratinocytes, we show that these cells display adhesion defects in vitro and compromised tumor growth in allograft assays, suggesting that Dsg3 enables tumor formation in certain settings. In contrast, using an autochthonous model for SCC development in response to chronic UVB treatment, we discover a surprising lack of enhanced tumorigenesis in Dsg3−/− mice relative to controls, unlike mice lacking the desmosomal component Perp. Accordingly, there is no defect in the apoptotic response to UVB or enhanced immune cell infiltration upon Dsg3 loss that could promote tumorigenesis. Thus, Dsg3 does not display a clear function as a tumor suppressor in these mouse skin cancer models. Continued unraveling of the roles of Dsg3 and other desmosomal constituents in carcinogenesis in different contexts will be important for ultimately improving cancer diagnosis, prognostication, and treatment.

Aire-dependent thymic expression of desmoglein 3, the autoantigen in pemphigus vulgaris, and its role in T-cell tolerance

In the mechanism of thymus-induced central tolerance, the transcription factor Aire has been demonstrated to promote the expression of a wide range of peripheral organ-specific antigens (Ags) in the medullary thymic epithelial cells (mTECs), which serve as self-Ags in negative selection. We examined the expression of desmoglein 3 (Dsg3), the autoantigen in pemphigus vulgaris (PV), in mouse thymus and the involvement of Aire in tolerance to Dsg3. Immunofluorescence and in situ hybridization revealed Dsg3 in single cells or in clusters in ∼3% of mTECs near the cortico-medullary junction of the thymus in C57BL/6 mice. Dsg3-expressing mTECs also expressed some Ags of skin-unrelated peripheral organs simultaneously. In contrast, Dsg3-positive mTECs were not detected in the Aire(-/-) thymus. Adoptive transfer of splenocytes from Aire(-/-) mice immunized with Dsg3 did not induce anti-Dsg3 IgG production or PV phenotype in Rag2(-/-) recipient mice. However, Aire(-/-) CD4(+) T cells, but not Aire(+/+) CD4(+) T cells, induced low levels of anti-Dsg3 IgG production when transferred with Dsg3(-/-) B cells. These findings indicate that Aire has an important role in Dsg3 expression as well as in selection of T cells that help B cells to produce anti-Dsg3 IgG in thymus.

Relationship between target antigens and major histocompatibility complex (MHC) class II genes in producing two pathogenic antibodies simultaneously

In this report,we present 15 patients with histological and immunopathologically proven pemphigus vulgaris (PV). After a mean of 80 months since the onset of disease, when evaluated serologically, they had antibodies typical of PV and pemphigoid (Pg). Similarly, 18 patients with bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP) were diagnosed on the basis of histology and immunopathology.After a mean of 60 months since the onset of disease, when their sera were evaluated they were found to have Pg and PV autoantibodies. In both groups of patients the diseases were characterized by a chronic course, which included several relapses and recurrences and were non-responsive to conventional therapy. The major histocompatibility complex class II (MHC II) genes were studied in both groups of patients and phenotypes associated typically with them were observed. Hence, in 33 patients, two different pathogenic autoantibodies were detected simultaneously. The authors provide a computer model to show that each MHC II gene has relevant epitopes that recognize the antigens associated with both diseases. Using the databases in these computer models, the authors present the hypothesis that these two autoantibodies are produced simultaneously due to the phenomena of epitope spreading.

MAP17 is associated with the T-helper cell cytokine-induced down-regulation of filaggrin transcription in human keratinocytes

In the meta-analysis of public microarray databases for different skin diseases, we revealed seven commonly up-regulated genes, DSG3, KRT6, MAP17, PLSCR1, RPM2, SOD2 and SPRR2B. We postulated that the genes selected from the meta-analysis may be potentially associated with the abnormal keratinocyte differentiation. To demonstrate this postulation, we alternatively evaluated whether the genes of interest in the meta-analysis can be regulated by T-helper (Th) cell cytokines in normal human epidermal keratinocytes (NHEK). We found that MAP17 was significantly up-regulated in response to interferon-gamma, interleukin 4 (IL-4), IL-6, IL-17A or IL-22 in NHEK. Interestingly, MAP17 was originally reported to interact with PDZK1; in turn, the PDZK1 gene is localized within the atopic dermatitis-linked region on human chromosome 1q21. In an attempt to evaluate whether MAP17 regulates the expression of cornified envelope-associated genes at the 1q21 locus, such as filaggrin, loricrin and involucrin, we found that the over-expression of MAP17 in HaCaT keratinocytes significantly decreased the expression of filaggrin. Taken together, the Th cell cytokine-induced up-regulation of MAP17 expression may be linked to the down-regulation of filaggrin in NHEK, which may be associated with the abnormal epidermal differentiation observed in the dermatological diseases.

Antimitochondrial autoantibodies in pemphigus vulgaris: a missing link in disease pathophysiology

A loss of epidermal cohesion in pemphigus vulgaris (PV) results from autoantibody action on keratinocytes (KCs) activating the signaling kinases and executioner caspases that damage KCs, causing their shrinkage, detachment from neighboring cells, and rounding up (apoptolysis). In this study, we found that PV antibody binding leads to activation of epidermal growth factor receptor kinase, Src, p38 MAPK, and JNK in KCs with time pattern variations from patient to patient. Both extrinsic and intrinsic apoptotic pathways were also activated. Although Fas ligand neutralizing antibody could inhibit the former pathway, the mechanism of activation of the latter remained unknown. PV antibodies increased cytochrome c release, suggesting damage to mitochondria. The immunoblotting experiments revealed penetration of PVIgG into the subcellular mitochondrial fraction. The antimitochondrial antibodies from different PV patients recognized distinct combinations of antigens with apparent molecular sizes of 25, 30, 35, 57, 60, and 100 kDa. Antimitochondrial antibodies were pathogenic because their absorption abolished the ability of PVIgG to cause keratinocyte detachment both in vitro and in vivo. The downstream signaling of antimitochondrial antibodies involved JNK and late p38 MAPK activation, whereas the signaling of anti-desmoglein 3 (Dsg3) antibody involved JNK and biphasic p38 MAPK activation. Using KCs grown from Dsg3(-/-) mice, we determined that Dsg3 did not serve as a surrogate antigen allowing antimitochondrial antibodies to enter KCs. The PVIgG-induced activation of epidermal growth factor receptor and Src was affected neither in Dsg3(-/-) KCs nor due to absorption of antimitochondrial antibodies. These results demonstrated that apoptolysis in PV is a complex process initiated by at least three classes of autoantibodies directed against desmosomal, mitochondrial, and other keratinocyte self-antigens. These autoantibodies synergize with the proapoptotic serum and tissue factors to trigger both extrinsic and intrinsic pathways of cell death and break the epidermal cohesion, leading to blisters. Further elucidation of the primary signaling events downstream of PV autoantigens will be crucial for the development of a more successful therapy for PV patients.

Significance of autoimmunity to non-desmoglein targets in pemphigus

The pathogenesis of pemphigus vulgaris (PV) is a highly controversial, "hot" topic that has received considerable enrichment in recent years by both clinical and basic researchers. On the one hand, the classical view of desmogleins (Dsg) as main targets of this autoimmune disease is supported by the characterization of pathogenic anti-Dsg3 antibodies from both patients and animal models. On the other hand, fundamental doubt has been raised towards this monopathogenic view by several independent factors: (1) pemphigus lesions can be induced in Dsg3-knockout (KO) mice; (2) pemphigus sera contain multiple autoantibodies against different adhesion molecules and also cholinergic receptors; (3) experimental inhibition of PV IgG induced acantholysis can be obtained by interference with different signaling cascades regulating both calcium homeostasis and apoptosis; and (4) cholinergic agonists exhibit anti-acantholytic activity both in vitro and in vivo. The field is open for controlled clinical trials and further basic research to unfold the true story of the pemphigus enigma and provide the basis for a better treatment of pemphigus patients.

Pemphigus vulgaris and its active disease mouse model

Pemphigus is an autoimmune disease of the skin and mucous membranes and is mediated by IgG autoantibodies against desmoglein (Dsg), a cadherin-type cell-cell adhesion molecule in desmosomes. Recently, an active disease mouse model of pemphigus vulgaris (PV) was generated with a unique approach using autoantigen knockout mice, in which selftolerance of the defective gene product is not acquired. This approach included the adoptive transfer of Dsg3-/- lymphocytes to Rag2-/- immunodeficient mice that express Dsg3- induced stable production of pathogenic anti-Dsg3 IgG for over 6 months and the phenotype of PV including oral erosion with the typical histology in recipient mice. Subsequently, AK and NAK series of anti-Dsg3 IgG monoclonal antibodies were developed from the PV model mice. These monoclonal antibodies showed pathogenic heterogeneity in blister formation, which is, at least in part, explained by their epitopes, and synergistic pathogenic effects by combining several monoclonal antibodies reacting in different parts of the molecule. Although this model does not reflect the actual triggers of autoimmune diseases, it does provide a means to investigate the roles of T and B lymphocytes in perpetuating autoantibody production and to clarify unsolved immunological mechanisms in the autoimmune diseases.

[Expression of desmoglein 3 in nasopharyngeal carcinoma: research of 22 cases]

OBJECTIVE

To investigate the expression of desmoglein 3 (DSG3), a candidate target gene in the antisense RNA (aRNA) from the purified nasopharyngeal tissues in nasopharyngeal carcinoma (NPC).

METHODS

Specimens of nasopharyngeal tissues were harvested from 22 NPC patients, aged 44 +/- 11 (NPC group), and 12 normal persons or patients with nasopharyngeal infectious diseases, aged 46 +/- 14. Microdissection technique was used to get homogenous tissue cells from which total RNA was isolated (control group). aRNA was amplified from the total RNA by "in vitro transcription" (IVT). The expression of DSG3 gene was identified using these aRNA by semi-quantitative reverse transcriptase polymerase chain reaction (sqRT-PCR).

RESULTS

The average expression level of DSG3 in the NPC group was 3.536 +/- 2.689, significantly higher than that of the control group (0.95 +/- 0.23, df = 32, t = 3.307, P = 0.002). The expression level of DSG3 in the whole expression profiling of the NPC group was 1.06 +/- 1.60, significantly higher than that of the control group (0.48 +/- 0.23, df = 16, t = 2.145, P = 0.048).

CONCLUSION

The whole genome expression profiling detected by sqRT-PCR can be used to shift the marker genes from biopsy tissue samples. DSG3 may be a tumor candidate gene in NPC.

Pemphigus IgG causes skin splitting in the presence of both desmoglein 1 and desmoglein 3

According to the desmoglein (Dsg) compensation concept, different epidermal cleavage planes observed in pemphigus vulgaris and pemphigus foliaceus have been proposed to be caused by different autoantibody profiles against the desmosomal proteins Dsg 1 and Dsg 3. According to this model, Dsg 1 autoantibodies would only lead to epidermal splitting in those epidermal layers in which no Dsg 3 is present to compensate for the functional loss of Dsg 1. We provide evidence that both pemphigus foliaceus-IgG containing Dsg 1- but not Dsg 3-specific antibodies and pemphigus vulgaris-IgG with antibodies to Dsg 1 and Dsg 3 were equally effective in causing epidermal splitting in human skin and keratinocyte dissociation in vitro. These effects were present where keratinocytes expressed both Dsg 1 and Dsg 3, demonstrating that Dsg 3 does not compensate for Dsg 1 inactivation. Rather, the cleavage plane in intact human skin caused by pemphigus autoantibodies was similar to the plane of keratinocyte dissociation in response to toxin B-mediated inactivation of Rho GTPases. Because we recently demonstrated that pemphigus-IgG causes epidermal splitting by inhibition of Rho A, we propose that Rho GTPase inactivation contributes to the mechanisms accounting for the cleavage plane in pemphigus skin splitting.

Dissecting the anti-desmoglein autoreactive B cell repertoire in pemphigus vulgaris patients

Pemphigus vulgaris (PV) encompasses two clinical phenotypes, one producing mucosal blisters and the other mucosal and skin lesions (mcPV). The mucosal blister-producing PV variant is characterized by autoantibodies against desmoglein (Dsg)3, whereas mucosal and skin lesion-producing PV is characterized by autoantibodies to Dsg3 and Dsg1. The present study was aimed at disclosing the diversity and clonality of the anti-Dsg3 response, as well as whether anti-Dsg3 B cells are Ag selected. Human-mouse heterohybridomas were generated by fusion of EBV-transformed or freshly isolated PBLs from six PV patients with mouse myeloma cells. A total of 73 anti-Dsg hybridomas (47 IgM and 26 IgG) were isolated. Over 90% are specific for both Dsg1 and Dsg3 indicating extensive cross-reactivity between these responses. V(H) gene segment use by IgM hybridomas is diverse, but is restricted among IgG hybridomas, where the majority uses one of two V(H) genes. V(L) gene segment use was diverse even among IgG hybridomas suggesting that the V(L) is less critical to defining desmoglein specificity. Additionally, the IgG hybridomas were extensively mutated and the distribution and nature of the mutations suggested that they had been Ag selected. We conclude that the potentially pathogenic IgG anti-Dsg response is restricted in V(H) use, is somatically mutated, and is Ag selected.

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.

A combination of molecular markers accurately detects lymph node metastasis in non-small cell lung cancer patients

Occult lymph node metastasis (micrometastasis) is a good prognostic indicator in non-small cell lung cancer (NSCLC) and could be used to direct adjuvant chemotherapy in stage I patients. This study was designed to evaluate molecular markers for detection of occult lymph node metastasis in NSCLC, define the best marker or marker combination to distinguish positive from benign lymph nodes, and evaluate these markers in lymph nodes from pathologically node-negative (pN(0)) NSCLC patients. Potential markers were identified through literature and database searches and all markers were analyzed by quantitative reverse transcription-PCR in a primary screen of six NSCLC specimens and 10 benign nodes. Selected markers were further evaluated on 21 primary NSCLC specimens, 21 positive nodes, and 21 benign nodes, and the best individual markers and combinations were identified. A combination of three markers was further validated on an independent set of 32 benign lymph nodes, 38 histologically positive lymph nodes, and 462 lymph nodes from 68 pN(0) NSCLC patients. Forty-two markers were evaluated in the primary screen and eight promising markers were selected for further analysis. A combination of three markers (SFTPB, TACSTD1, and PVA) was identified that provided perfect classification of benign and positive nodes in all sample sets. PVA and SFTPB are particularly powerful in tumors of squamous and adenocarcinoma histologies, respectively, whereas TACSTD1 is a good general marker for NSCLC metastasis. The combination of these genes identified 32 of 462 (7%) lymph nodes from 20 of 68 (29%) patients as potentially positive for occult metastasis. Long-term follow-up will determine the clinical relevance of these findings.

DSG3 is overexpressed in head neck cancer and is a potential molecular target for inhibition of oncogenesis

To identify genes that could potentially serve as molecular therapeutic markers for human head and neck cancer (HNC), we employed differential display analysis to compare the gene expression profiles between HNC and histopathologically normal epithelial tissues. Using reverse transcription-polymerase chain reaction and Western blot analysis, desmoglein 3 (DSG3) was identified as being differentially expressed at both the RNA and protein levels. Of 56 patients assayed, 34 (61%) had overexpression of DSG3, which correlated statistically with T stage (P=0.009), N stage (P=0.047), overall stage (P=0.011), tumor depth (P=0.009) and extracapsular spread in lymph nodes (P=0.044), suggesting that DSG3 participates in carcinogenesis of HNC. Consistent with the clinical findings, inhibition of DSG3 by RNA interference (RNAi) significantly reduced cell growth and colony formation to 57-21% in three HNC cell lines. Use of an in vitro wound healing and Matrigel invasion assays, we found that cell migration and invasive ability were also inhibited to 30-48% in three cell lines tested. An in vivo xenograft study showed that administration of DSG3-RNAi plasmid significantly inhibited tumor growth for 2 months in BALB/C nude mice. In conclusion, DSG3 is identified overexpressed in HNC, with the degree of overexpression associated with clinicopathologic features of the tumor. Inhibition of DSG3 significantly suppresses carcinogenic potential in cellular and in vivo animal studies. These findings suggest that DSG3 is a potential molecular target in the development of adjuvant therapy for HNC.

Evidence of an association between desmoglein 3 haplotypes and pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV, OMIM 169610) is a severe blistering disorder of the skin and mucous membranes, caused by the production of autoantibodies directed against the epithelial adhesive protein desmoglein 3. Although an association between PV and HLA class II alleles has been established, the genetic factors predisposing to the disease remain poorly understood, the rarity of PV hampering the recruitment of substantial patient cohorts.

OBJECTIVES

To investigate DSG3 as a candidate PV susceptibility gene.

METHODS

We examined five DSG3 single nucleotide polymorphisms (rs8085532, rs3911655, rs3848485, rs3794925 and rs1466379) in two case-control datasets respectively originating from the U.K. (62 PV patients, 154 controls) and northern India (28 patients, 98 controls).

RESULTS

In the U.K. sample, we observed a significant association between PV and the DSG3*TCCTC haplotype (Fisher's exact test P = 0.002). A related haplotype (DSG3*TCCCC) was associated with PV in the Indian dataset (P = 0.002). We also found that all British and Indian patients bearing DSG3 risk haplotypes carried at least one copy of a PV-associated HLA allele.

CONCLUSIONS

These results suggest that genetic variation of DSG3 may be an additive risk factor predisposing to PV and warrant further investigations of this gene.

Tolerance induction by the blockade of CD40/CD154 interaction in pemphigus vulgaris mouse model

Pemphigus vulgaris (PV) is an autoimmune blistering disease caused by IgG autoantibodies against desmoglein 3 (Dsg3). We have recently developed an active disease mouse model for PV by adoptive transfer of splenocytes from Dsg3(-/-) mice. The purpose of this study was to determine the role of CD40/CD154 interaction in the pathogenic antibody production and development of the disease in PV model mice. When anti-CD154 monoclonal antibody (mAb) was administered to recipient mice prior to adoptive transfer, anti-CD154 mAb almost completely blocked the anti-Dsg3 IgG production and prevented blister formation. The blockade of CD40/CD154 interaction induced tolerance against Dsg3 as the suppression of antibody production was observed through day 70, and it was maintained even after challenge by immunization with recombinant mouse Dsg3 or by adoptive transfer of immunized Dsg3(-/-) splenocytes. Furthermore, the tolerance to Dsg3 was transferable because cotransfer of splenocytes from anti-CD154 mAb-treated mice and naïve Dsg3(-/-) splenocytes significantly suppressed anti-Dsg3 IgG production in recipient mice. In contrast, when anti-CD154 mAb was injected after the mice had developed the PV phenotype, no significant suppression of the production of anti-Dsg3 IgG was observed. These findings indicate that the CD40/CD154 interaction is essential for the induction of pathogenic anti-Dsg3 IgG antibodies and that antigen-specific immune-regulatory cells induced by anti-CD154 mAb would hold a therapeutic option for autoimmune diseases.