Grainyhead-like 2, encoded by GRHL2, is a member of a highly conserved family of transcription factors that play essential roles during epithelial development. Haploinsufficiency for GRHL2 has been implicated in autosomal-dominant deafness, but mutations have not yet been associated with any skin pathology. We investigated two unrelated Kuwaiti families in which a total of six individuals have had lifelong ectodermal defects. The clinical features comprised nail dystrophy or nail loss, marginal palmoplantar keratoderma, hypodontia, enamel hypoplasia, oral hyperpigmentation, and dysphagia. In addition, three individuals had sensorineural deafness, and three had bronchial asthma. Taken together, the features were consistent with an unusual autosomal-recessive ectodermal dysplasia syndrome. Because of consanguinity in both families, we used whole-exome sequencing to search for novel homozygous DNA variants and found GRHL2 mutations common to both families: affected subjects in one family were homozygous for c.1192T>C (p.Tyr398His) in exon 9, and subjects in the other family were homozygous for c.1445T>A (p.Ile482Lys) in exon 11. Immortalized keratinocytes (p.Ile482Lys) showed altered cell morphology, impaired tight junctions, adhesion defects, and cytoplasmic translocation of GRHL2. Whole-skin transcriptomic analysis (p.Ile482Lys) disclosed changes in genes implicated in networks of cell-cell and cell-matrix adhesion. Our clinical findings of an autosomal-recessive ectodermal dysplasia syndrome provide insight into the role of GRHL2 in skin development, homeostasis, and human disease.
Patients with recessive dystrophic epidermolysis bullosa (RDEB) have severe, incurable skin fragility, blistering, and multiple skin wounds due to mutations in the gene encoding type VII collagen (C7), the major component of anchoring fibrils mediating epidermal-dermal adherence. Nearly 10-25% of RDEB patients carry nonsense mutations leading to premature stop codons (PTCs) that result in truncated C7. In this study, we evaluated the feasibility of using aminoglycosides to suppress PTCs and induce C7 expression in two RDEB keratinocyte cell lines (Q251X/Q251X and R578X/R906) and two primary RDEB fibroblasts (R578X/R578X and R163X/R1683X). Incubation of these cells with aminoglycosides (geneticin, gentamicin, and paromomycin) resulted in the synthesis and secretion of a full-length C7 in a dose-dependent and sustained manner. Importantly, aminoglycoside-induced C7 reversed the abnormal RDEB cell phenotype and incorporated into the dermal-epidermal junction of skin equivalents. We further demonstrated the general utility of aminoglycoside-mediated readthrough in 293 cells transiently transfected with expression vectors encoding 22 different RDEB nonsense mutations. This is the first study demonstrating that aminoglycosides can induce PTC readthrough and restore functional C7 in RDEB caused by nonsense mutations. Therefore, aminoglycosides may have therapeutic potential for RDEB patients and other inherited skin diseases caused by nonsense mutations.
We report our institution's 5-year experience with upper gastrointestinal study with small bowel follow-through (UGI-SBFT) and contrast enema (CE) for the diagnosis of a post-necrotizing enterocolitis (NEC) stricture. We hypothesized that sensitivity and specificity of UGI-SBFT and CE were <85% in diagnosing a post-NEC stricture.
Recessive dystrophic epidermolysis bullosa (RDEB) is a severe genetic skin blistering disorder caused by mutations in the gene COL7A1 encoding type VII collagen. Most of the patients' clinical severity depends in part on the nature and location of the mutations, ranging from the mild form described as RDEBother-generalized (RDEB-O) to the more aggressive phenotype described as RDEBsevere-generalized (RDEB-sev gen). However, interfamilial and interindividual differences in subjects with identical COL7A1 mutations suggest the presence of modifier elements, which may influence severity. There is a single nucleotide polymorphism (SNP) at the promoter of the MMP1 gene-encoding matrix metalloproteinase type 1, which has been studied as a genetic disease modifier in different patient cohorts with different findings.
3D organotypic cultures of epithelial cells on a matrix embedded with mesenchymal cells are widely used to study epithelial cell differentiation and invasion. Rat tail type I collagen and/or matrix derived from Engelbreth-Holm-Swarm mouse sarcoma cells have been traditionally employed as the substrates to model the matrix or stromal microenvironment into which mesenchymal cells (usually fibroblasts) are populated. Although experiments using such matrices are very informative, it can be argued that due to an overriding presence of a single protein (such as in type I Collagen) or a high content of basement membrane components and growth factors (such as in matrix derived from mouse sarcoma cells), these substrates do not best reflect the contribution to matrix composition made by the stromal cells themselves. To study native matrices produced by primary dermal fibroblasts isolated from patients with a tumor prone, genetic blistering disorder (recessive dystrophic epidermolysis bullosa), we have adapted an existing native matrix protocol to study tumor cell invasion. Fibroblasts are induced to produce their own matrix over a prolonged period in culture. This native matrix is then detached from the culture dish and epithelial cells are seeded onto it before the entire coculture is raised to the air-liquid interface. Cellular differentiation and/or invasion can then be assessed over time. This technique provides the ability to assess epithelial-mesenchymal cell interactions in a 3D setting without the need for a synthetic or foreign matrix with the only disadvantage being the prolonged period of time required to produce the native matrix. Here we describe the application of this technique to assess the ability of a single molecule expressed by fibroblasts, type VII collagen, to inhibit tumor cell invasion.
Squamous cell carcinoma (SCC) represents one of the most frequently diagnosed tumours and contributes significant mortality worldwide. Recent deep sequencing of cancer genomes has identified common mutations in SCC arising across different tissues highlighting perturbation of squamous differentiation as a key event. At the same time significant data have been accumulating to show that common tumour-stroma interactions capable of driving disease progression are also evident when comparing SCC arising in different tissues. We and others have shown altered matrix composition surrounding SCC can promote tumour development. This review focuses on some of the emerging data with particular emphasis on SCC of head and neck and skin with discussion on the potential tumour suppressive properties of a normal microenvironment. Such data indicate that regardless of the extent and type of somatic mutation it is in fact the tumour context that defines metastatic progression.
Cutaneous SCC (cSCC) is the most frequently occuring skin cancer with metastatic potential and can manifest rapidly as a common side effect in patients receiving systemic kinase inhibitors. Here, we use massively parallel exome and targeted level sequencing of 132 sporadic cSCCs and of 39 squamoproliferative lesions and cSCCs arising in patients receiving the BRAF inhibitor vemurafenib, as well as 10 normal skin samples, to identify NOTCH1 mutation as an early event in squamous cell carcinogenesis. Bisected vemurafenib-induced lesions revealed surprising heterogeneity with different activating HRAS and NOTCH1 mutations identified in two halves of the same cSCC, suggesting polyclonal origin. Immunohistochemical analysis using an antibody specific to nuclear NOTCH1 correlates with mutation status in sporadic cSCCs, and regions of NOTCH1 loss or downregulation are frequently observed in normal-looking skin. Our data indicate that NOTCH1 acts as a gatekeeper in human cSCC.
Type VII collagen is the main component of anchoring fibrils, structures integral to basement membrane homeostasis in skin. Mutations in the gene encoding type VII collagen, COL7A1, cause recessive dystrophic epidermolysis bullosa (RDEB) an inherited skin blistering condition complicated by frequent aggressive cutaneous squamous cell carcinoma (cSCC). OATP1B3, encoded by the gene SLCO1B3, is a member of the OATP (organic anion transporting polypeptide) superfamily responsible for transporting a wide range of endogenous and xenobiotic compounds. OATP1B3 expression is limited to the liver in healthy tissues but is frequently detected in multiple cancer types and is reported to be associated with differing clinical outcome. The mechanism and functional significance of tumour specific OATP1B3 expression has yet to be determined. Here, we identify SLCO1B3 (encoding OATP1B3) expression in tumour keratinocytes isolated from RDEB and UV induced cSCC and demonstrate that SLCO1B3 expression and promoter activity are modulated by type VII collagen. We demonstrate that reduction of SLCO1B3 expression upon full length type VII collagen expression in RDEB cSCC coincides with acquisition of front to rear polarity and increased organisation of 3D spheroid cultures. In addition we show that type VII collagen positively regulates the abundance of markers implicated in cellular polarity, namely ELMO2, PAR3, E-cadherin, B-catenin, ITGA6 and Ln332.
Targeting tumor marker genes by RNA trans-splicing is a promising means to induce tumor cell-specific death. Using a screening system we designed RNA trans-splicing molecules (RTM) specifically binding the pre-mRNA of SLCO1B3, a marker gene in epidermolysis bullosa associated squamous cell carcinoma (EB-SCC). Specific trans-splicing, results in the fusion of the endogenous target mRNA of SLCO1B3 and the coding sequence of the suicide gene, provided by the RTM. SLCO1B3-specific RTMs containing HSV-tk were analyzed regarding their trans-splicing potential in a heterologous context using a SLCO1B3 expressing minigene (SLCO1B3-MG). Expression of the chimeric SLCO1B3-tk was detected by semi-quantitative RT-PCR and Western blot analysis. Cell viability and apoptosis assays confirmed that the RTMs induced suicide gene-mediated apoptosis in SLCO1B3-MG expressing cells. The lead RTM also showed its potential to facilitate a trans-splicing reaction into the endogenous SLCO1B3 pre-mRNA in EB-SCC cells resulting in tk-mediated apoptosis. We assume that the pre-selection of RTMs by our inducible cell-death system accelerates the design of optimal RTMs capable to induce tumor specific cell death in skin cancer cells.
Bullous pemphigoid antigen 1 (BPAG1-e, also known as BP230) is a member of the plakin family of hemidesmosome cytoskeletal linker proteins that is encoded by an isoform of the dystonin (DST) gene. Recently, we reported two unrelated families with homozygous nonsense mutations in this DST isoform that led to ultrastructural loss of hemidesmosomal inner plaques and clinical features of trauma-induced skin fragility. We now demonstrate that keratinocytes isolated from these individuals have significant defects in adhesion, as well as increased cell spreading and migration. These mutant keratinocytes also display reduced levels of ?4 integrins at the cell surface but increased total protein levels of keratin-14 and ?1 integrins. These alterations in cell behavior and protein expression were not seen in control keratinocytes in which BPAG1-e expression had been silenced by stable expression of short hairpin RNA to target DST. The failure of knockdown approaches to recapitulate the changes in morphology, adhesion, and migration seen in patient cells therefore suggests such approaches are not appropriate to study loss of this protein in vivo. The contrasting findings in keratinocytes harboring naturally occurring mutations, however, demonstrate a previously unappreciated key role for BPAG1-e in regulating keratinocyte adhesion and migration and suggest a requirement for this protein in controlling functional switching between integrin types in epithelial cells.Journal of Investigative Dermatology advance online publication, 17 October 2013; doi:10.1038/jid.2013.382.
Autosomal-dominant diffuse nonepidermolytic palmoplantar keratoderma is characterized by the adoption of a white, spongy appearance of affected areas upon exposure to water. After exome sequencing, missense mutations were identified in AQP5, encoding water-channel protein aquaporin-5 (AQP5). Protein-structure analysis indicates that these AQP5 variants have the potential to elicit an effect on normal channel regulation. Immunofluorescence data reveal the presence of AQP5 at the plasma membrane in the stratum granulosum of both normal and affected palmar epidermis, indicating that the altered AQP5 proteins are trafficked in the normal manner. We demonstrate here a role for AQP5 in the palmoplantar epidermis and propose that the altered AQP5 proteins retain the ability to form open channels in the cell membrane and conduct water.
Fixed, paraffin-embedded (FPE) tissues are a potentially rich resource for studying the role of NOTCH1 in cancer and other pathologies, but tests that reliably detect activated NOTCH1 (NICD1) in FPE samples have been lacking. Here, we bridge this gap by developing an immunohistochemical (IHC) stain that detects a neoepitope created by the proteolytic cleavage event that activates NOTCH1. Following validation using xenografted cancers and normal tissues with known patterns of NOTCH1 activation, we applied this test to tumors linked to dysregulated Notch signaling by mutational studies. As expected, frequent NICD1 staining was observed in T lymphoblastic leukemia/lymphoma, a tumor in which activating NOTCH1 mutations are common. However, when IHC was used to gauge NOTCH1 activation in other human cancers, several unexpected findings emerged. Among B cell tumors, NICD1 staining was much more frequent in chronic lymphocytic leukemia than would be predicted based on the frequency of NOTCH1 mutations, while mantle cell lymphoma and diffuse large B cell lymphoma showed no evidence of NOTCH1 activation. NICD1 was also detected in 38% of peripheral T cell lymphomas. Of interest, NICD1 staining in chronic lymphocytic leukemia cells and in angioimmunoblastic lymphoma was consistently more pronounced in lymph nodes than in surrounding soft tissues, implicating factors in the nodal microenvironment in NOTCH1 activation in these diseases. Among carcinomas, diffuse strong NICD1 staining was observed in 3.8% of cases of triple negative breast cancer (3 of 78 tumors), but was absent from 151 non-small cell lung carcinomas and 147 ovarian carcinomas. Frequent staining of normal endothelium was also observed; in line with this observation, strong NICD1 staining was also seen in 77% of angiosarcomas. These findings complement insights from genomic sequencing studies and suggest that IHC staining is a valuable experimental tool that may be useful in selection of patients for clinical trials.
Squamous cell carcinomas (SCCs) are one of the most frequent forms of human malignancy, but, other than TP53 mutations, few causative somatic aberrations have been identified. We identified NOTCH1 or NOTCH2 mutations in ~75% of cutaneous SCCs and in a lesser fraction of lung SCCs, defining a spectrum for the most prevalent tumor suppressor specific to these epithelial malignancies. Notch receptors normally transduce signals in response to ligands on neighboring cells, regulating metazoan lineage selection and developmental patterning. Our findings therefore illustrate a central role for disruption of microenvironmental communication in cancer progression. NOTCH aberrations include frameshift and nonsense mutations leading to receptor truncations as well as point substitutions in key functional domains that abrogate signaling in cell-based assays. Oncogenic gain-of-function mutations in NOTCH1 commonly occur in human T-cell lymphoblastic leukemia/lymphoma and B-cell chronic lymphocytic leukemia. The bifunctional role of Notch in human cancer thus emphasizes the context dependency of signaling outcomes and suggests that targeted inhibition of the Notch pathway may induce squamous epithelial malignancies.
Maintenance of a mitotically inactive feeder layer which is able to provide extracellular matrix and growth factors can be critical in establishing and maintaining primary tumor cells. How feeder cells are handled and processed is crucial for providing trouble-free support for primary tumor cells and spontaneously immortalized lines.
Cutaneous squamous cell carcinoma (SCC) keratinocytes readily grow, expand in culture, and continuously passage, suggesting either spontaneous immortalisation at the early stage of culture or inherent proliferative capacity. One feature of SCC keratinocytes is genomic DNA rearrangement and single-nucleotide polymorphism studies of fresh frozen primary tumour, early and late passage SCC keratinocytes suggest that these rearrangements are stable in culture and retain the parental tumour lesions. SCC keratinocytes are isolated using standard primary culture techniques and become feeder cell independent with little or no observed "crisis" period. SCC keratinocytes readily form tumours in vivo, which retain histological features of the parental tumour, making them an excellent model for the study and development of cancer therapies.
The ability of cancer cells to break out of tissue compartments and invade locally gives solid tumours a defining deadly characteristic. One of the first steps of invasion is the remodelling of the surrounding tissue or extracellular matrix (ECM) and a major part of this process is the over-expression of proteolytic enzymes, such as the urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs), by the cancer cells to break down ECM proteins. Degradation of the matrix enables the cancer cells to migrate through the tissue and subsequently to spread to secondary sites in the body, a process known as metastasis. In this paper we undertake an analysis of a mathematical model of cancer cell invasion of tissue, or ECM, which focuses on the role of the urokinase plasminogen activation system. The model consists of a system of five reaction-diffusion-taxis partial differential equations describing the interactions between cancer cells, uPA, uPA inhibitors, plasmin and the host tissue. Cancer cells react chemotactically and haptotactically to the spatio-temporal effects of the uPA system. The results obtained from computational simulations carried out on the model equations produce dynamic heterogeneous spatio-temporal solutions and using linear stability analysis we show that this is caused by a taxis-driven instability of a spatially homogeneous steady-state. Finally we consider the biological implications of the model results, draw parallels with clinical samples and laboratory based models of cancer cell invasion using three-dimensional invasion assay, and go on to discuss future development of the model.
Familial primary localized cutaneous amyloidosis (FPLCA) is an autosomal dominant disorder associated with chronic itching and skin lichenification. In lesional skin, there are apoptotic basal keratinocytes and deposits of amyloid material on degenerate keratin filaments in the upper dermis. The genetic basis of FPLCA involves mutations in the OSMR and IL31RA genes but the disease pathophysiology is not fully understood. In this study, we identified new pathogenic heterozygous missense mutations in the OSMR gene (p.Val631Leu and p.Asp647Tyr) in two Dutch FPLCA families. We then compared gene expression profiles between FPLCA lesional skin (n = 4) and site-matched control skin (n = 6). There was twofold or greater upregulation of 34 genes and downregulation of 43 genes. Most changes in gene expression (verified by quantitative RT-PCR) reflected alterations in epidermal differentiation and proliferation consistent with lichenification, but we also noted a reduction in several interfollicular keratinocyte stem cell markers in FPLCA skin. Differences in gene expression were also noted for proteins involved in apoptosis and nerve conduction. Collectively, this study expands the molecular basis of FPLCA and provides new insight into the skin pathology of this condition.
Desmoplakin is a ubiquitous component of desmosomes and desmosome-like structures, such as the cardiomyocyte area composita. Two major isoforms, desmoplakin I (DSPI) and desmoplakin II (DSPII) are encoded by alternative mRNA transcripts differentially spliced from the same gene. The resulting proteins are identical in amino acid sequence with the exception that DSPII contains only one third of the central alpha-helical rod domain present in DSPI. Here we describe a novel minor isoform of desmoplakin that is also produced by alternative splicing of the desmoplakin gene and that we name desmoplakin Ia (DSPIa). DSPIa is an alternatively spliced DSPI mRNA with a unique splice donor site that is 90% homologous to and downstream of the DSPII specific donor. The resulting DSPIa mRNA is in-frame and encodes a protein that has a central alpha-helical rod domain of intermediate size and that is 156 amino acids larger than DSPII and 443 amino acids smaller than DSPI. We demonstrate, through recombinant expression and short interfering RNA knockdown, that the DSPIa protein is readily detectable, albeit at substantially lower levels than the dominant isoforms, DSPI and DSPII. DSPIa mRNA has a similar tissue distribution to that of DSPI and of DSPII.
Desmosomes are intercellular adhesive junctions and attachment sites for the intermediate filament (IF) cytoskeleton, prominent in tissues subject to high levels of mechanical stress such as the epidermis and heart. The obligate desmosomal constituent, plakoglobin (PG), is involved in coupling transmembrane desmosomal components with IFs. PG also contributes to intercellular adhesion through adherens junctions and has additional signaling roles. To date, two mutations in the gene encoding PG, JUP, have been described, and in both instances, patients harboring pathogenic mutations suffered from arrhythmogenic right ventricular cardiomyopathy with or without skin abnormalities. We describe homozygous nonsense mutation, p.S24X, and homozygous splice site mutation, c.468G>A, in the JUP gene that results in skin fragility, diffuse palmoplantar keratoderma, and woolly hair with no symptoms of cardiomyopathy. We show barely detectable levels of PG immunostaining in skin sections from patients harboring these mutations and show that an alternative AUG codon in p.S24X mRNA translates a 42-amino-acid N-terminal truncation. We conclude that PG is required for correct maintenance of skin integrity, and the absence of heart phenotype in patients suggests that aberrant PG expression does not compromise normal human heart development in children. Our findings provide new insight into the distinct roles that PG has in the epidermis and heart.
Kindler syndrome is an autosomal recessive disorder characterized by skin atrophy and blistering. It results from loss-of-function mutations in the FERMT1 gene encoding the focal adhesion protein, fermitin family homolog-1. How and why deficiency of fermitin family homolog-1 results in skin atrophy and blistering are unclear. In this study, we investigated the epidermal basement membrane and keratinocyte biology abnormalities in Kindler syndrome. We identified altered distribution of several basement membrane proteins, including types IV, VII, and XVII collagens and laminin-332 in Kindler syndrome skin. In addition, reduced immunolabeling intensity of epidermal cell markers such as beta1 and alpha6 integrins and cytokeratin 15 was noted. At the cellular level, there was loss of beta4 integrin immunolocalization and random distribution of laminin-332 in Kindler syndrome keratinocytes. Of note, active beta1 integrin was reduced but overexpression of fermitin family homolog-1 restored integrin activation and partially rescued the Kindler syndrome cellular phenotype. This study provides evidence that fermitin family homolog-1 is implicated in integrin activation and demonstrates that lack of this protein leads to pathological changes beyond focal adhesions, with disruption of several hemidesmosomal components and reduced expression of keratinocyte stem cell markers. These findings collectively provide novel data on the role of fermitin family homolog-1 in skin and further insight into the pathophysiology of Kindler syndrome.
Type VII collagen (ColVII) is the main component of anchoring fibrils, attachment structures within the lamina densa of the basement membrane that are responsible for attachment of the epidermis to the dermis in skin. Mutations in the human ColVII gene, COL7A1, cause the severe inherited blistering disorder recessive dystrophic epidermolysis bullosa (RDEB) affecting skin and mucosae, associated with a greatly increased risk of skin cancer. In this study, we examined the effect of loss of ColVII on squamous cell carcinoma (SCC) tumourigenesis using RNAi in a 3D organotypic skin model. Our findings suggest that loss of ColVII promotes SCC migration and invasion as well as regulating cell differentiation with evidence for concomitant promotion of epithelial-mesenchymal transition (EMT). Immunostaining of RDEB skin and a tissue array of sporadic cutaneous SCCs confirmed that loss of ColVII correlates with decreased involucrin expression in vivo. Gene-expression-array data and immunostaining demonstrated that loss of ColVII increases expression of the chemokine ligand-receptor CXCL10-CXCR3 and downstream-associated PLC signalling, which might contribute to the increased metastatic potential of SCCs with reduced or absent ColVII expression. Together, these findings may explain the aggressive behaviour of SCCs in RDEB patients and may also be relevant to non-RDEB skin cancer, as well as other tumours from organs where ColVII is expressed.
Using vital records and census data representing 165,136 singleton births from 2003-2006, geospatial filtering and density estimates enabled the calculation of preterm birth rates at each geographical point within three urban Ohio counties. Adjusted attributable risk calculations were used to identify risk factors associated with regions of high and low rates of preterm birth. Among the three counties, affected populations varied in size as well as in demographic composition. Variation in the risk factors from one region to another suggests that a single one size fits all intervention strategy would be unlikely to efficiently or effectively impact the complex preterm birth problem. Although more useful in areas with a heterogeneous distribution of preterm birth, application of the presented approach supports the development of efficient community-level health intervention strategies by identifying communities with the highest potential impact and allowing for the prioritization of efforts on specific risk factors within those communities.
The Rab GTPase Rab27B and one of its effector proteins, Slac2-b (also known as EXPH5, exophilin-5), have putative roles in intracellular vesicle trafficking but their relevance to human disease is not known. By using whole-exome sequencing, we identified a homozygous frameshift mutation in EXPH5 in three siblings with inherited skin fragility born to consanguineous Iraqi parents. All three individuals harbor the mutation c.5786delC (p.Pro1929Leufs(?)8) in EXPH5, which truncates the 1,989 amino acid Slac2-b protein by 52 residues. The clinical features comprised generalized scale-crusts and occasional blisters, mostly induced by trauma, as well as mild diffuse pigmentary mottling on the trunk and proximal limbs. There was no increased bleeding tendency, no neurologic abnormalities, and no increased incidence of infection. Analysis of an affected persons skin showed loss of Slac2-b immunostaining (C-terminal antibody), disruption of keratinocyte adhesion within the lower epidermis, and an increased number of perinuclear vesicles. A role for Slac2-b in keratinocyte biology was supported by findings of cytoskeletal disruption (mainly keratin intermediate filaments) and decreased keratinocyte adhesion in both keratinocytes from an affected subject and after shRNA knockdown of Slac2-b in normal keratinocytes. Slac2-b was also shown to colocalize with Rab27B and ?4 integrin to early adhesion initiation sites in spreading normal keratinocytes. Collectively, our findings identify an unexpected role for Slac2-b in inherited skin fragility and expand the clinical spectrum of human disorders of GTPase effector proteins.
Patients with the genetic skin blistering disease recessive dystrophic epidermolysis bullosa (RDEB) develop aggressive cutaneous squamous cell carcinoma (cSCC). Metastasis leading to mortality is greater in RDEB than in other patient groups with cSCC. Here we investigate the dermal component in RDEB using mRNA expression profiling to compare cultured fibroblasts isolated from individuals without cSCC and directly from tumor matrix in RDEB and non-RDEB samples. Although gene expression of RDEB normal skin fibroblasts resembled that of cancer-associated fibroblasts, RDEB cancer-associated fibroblasts exhibited a distinct and divergent gene expression profile, with a large proportion of the differentially expressed genes involved in matrix and cell adhesion. RDEB cancer-associated fibroblasts conferred increased adhesion and invasion to tumor and nontumor keratinocytes. Reduction of COL7A1, the defective gene in RDEB, in normal dermal fibroblasts led to increased type XII collagen, thrombospondin-1, and Wnt-5A, while reexpression of wild type COL7A1 in RDEB fibroblasts decreased type XII collagen, thrombospondin-1, and Wnt-5A expression, reduced tumor cell invasion in organotypic culture, and restricted tumor growth in vivo. Overall, our findings show that matrix composition in patients with RDEB is a permissive environment for tumor development, and type VII collagen directly regulates the composition of matrix proteins secreted by dermal and cancer-associated fibroblasts.
Desmosomes are intercellular junctions specialised for strong adhesion that are prominent in the epidermis and heart muscle. Defective desmosomal function due to inherited mutations in the constitutive desmosomal gene desmoplakin (DSP) causes skin or heart disorders and in some instances both. Different mutations have different disease-causing molecular mechanisms as evidenced by the varying phenotypes resulting from mutations affecting different domains of the same protein, but the majority of these mechanisms remain to be determined. Here, we studied two mutations in DSP that lead to different dosages of the two major DSP splice variants, DSPI and DSPII, and compared their molecular mechanisms. One of the mutations results in total DSP haploinsufficiency and is associated with autosomal dominant striate palmoplantar keratoderma (PPK). The other leads to complete absence of DSPI and the minor isoform DSPIa but normal levels of DSPII, and is associated with autosomal recessive epidermolytic PPK, woolly hair and severe arrhythmogenic dilated cardiomyopathy. Using siRNA treatments to mimic these two mutations and additionally a DSPII-specific siRNA, we found striking differences between DSP isoforms with respect to keratinocyte adhesion upon cellular stress with DSPII being the key component in intermediate filament (IF) stability and desmosome-mediated adhesion. In addition, reduction in DSP expression reduced the amount of plakophilin 1, desmocollin (DSC) 2 and DSC3 with DSPI having a greater influence than DSPII on the expression levels of DSC3. These results suggest that the two major DSP splice variants are not completely redundant in function and that DSPII dosage is particularly important for desmosomal adhesion in the skin.
Wnt5a is one of the so-called non-canonical Wnt ligands which do not act through ?-catenin. In normal development, Wnt5a is secreted and directs the migration of target cells along concentration gradients. The effect of Wnt5a on target cells is regulated by many factors, including the expression level of inhibitors and receptors. Dysregulated Wnt5a signalling facilitates invasion of multiple tumor types into adjacent tissue. However, the expression and distribution of Wnt5a in cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), as well as the effect of Wnt5a on keratinocyte migration has not been studied in detail to date. We here report that Wnt5a is upregulated in SCC and BCC and localised to the leading edge of tumors, as well as tumor-associated fibroblasts. The Wnt5a-triggered bundling of its receptor Fzd3 provides evidence of Wnt5a concentration gradients projecting into the tumor. In vitro migration assays show that Wnt5a concentration gradients determine its effect on keratinoctye migration: While chemotactic migration is inhibited by Wnt5a present in homogenous concentrations, it is enhanced in the presence of a Wnt5a gradient. Expression profiling of the Wnt pathway shows that the upregulation of Wnt5a in SCC is coupled to repression of canonical Wnt signalling. This is confirmed by immunohistochemistry showing lack of nuclear ?-catenin, as well as absent accumulation of Axin2. Since both types of Wnt signalling act mutually antogonistically at multiple levels, the concurrent repression of canonical Wnt signalling suggests hyper-active Wnt5a signal transduction. Significantly, this combination of gene dysregulation is not observed in the benign hyperproliferative inflammatory skin disease psoriasis. Collectively, our data strongly suggest that Wnt5a signalling contributes to tissue invasion by non-melanoma skin cancer.
Recent deep sequencing of cancer genomes has produced an explosion of new data implicating Notch signaling in several human cancers. Unlike most other pathways, these data indicate that Notch signaling can be either oncogenic or tumor suppressive, depending on the cellular context. In some instances, these relationships were predicted from mouse models or presaged by developmental roles for Notch, but in other cases were unanticipated. This review discusses the pathogenic and translational significance of these new findings.
Tylosis esophageal cancer (TOC) is an autosomal-dominant syndrome characterized by palmoplantar keratoderma, oral precursor lesions, and a high lifetime risk of esophageal cancer. We have previously localized the TOC locus to a small genomic interval within chromosomal region 17q25. Using a targeted capture array and next-generation sequencing, we have now identified missense mutations (c.557T>C [p.Ile186Thr] and c.566C>T [p.Pro189Leu] in RHBDF2, which encodes the inactive rhomboid protease RHBDF2 (also known as iRhom2), as the underlying cause of TOC. We show that the distribution of RHBDF2 in tylotic skin is altered in comparison with that in normal skin, and immortalized tylotic keratinocytes have decreased levels of total epidermal growth factor receptor (EGFR) and display an increased proliferative and migratory potential relative to normal cells, even when normal cells are stimulated with exogenous epidermal growth factor. It would thus appear that EGFR signaling is dysregulated in tylotic cells. Furthermore, we also show an altered localization of RHBDF2 in both tylotic and sporadic squamous esophageal tumors. The elucidation of a role of RHBDF2 in growth-factor signaling in esophageal cancer will help to determine whether targeting this pathway in chemotherapy for this and other squamous cell carcinomas will be effective.
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