Targeting a tumor-specific laminin domain critical for human carcinogenesis

Matrikines in the skin: Origin, effects, and therapeutic potential

The extracellular matrix (ECM) represents a complex multi-component environment that has a decisive influence on the biomechanical properties of tissues and organs. Depending on the tissue, ECM components are subject to a homeostasis of synthesis and degradation, a subtle interplay that is influenced by external factors and the intrinsic aging process and is often disturbed in pathologies. Upon proteolytic cleavage of ECM proteins, small bioactive peptides termed matrikines can be formed. These bioactive peptides play a crucial role in cell signaling and contribute to the dynamic regulation of both physiological and pathological processes such as tissue remodeling and repair as well as inflammatory responses. In the skin, matrikines exert an influence for instance on cell adhesion, migration, and proliferation as well as vasodilation, angiogenesis and protein expression. Due to their manifold functions, matrikines represent promising leads for developing new therapeutic options for the treatment of skin diseases. This review article gives a comprehensive overview on matrikines in the skin, including their origin in the dermal ECM, their biological effects and therapeutic potential for the treatment of skin pathologies such as melanoma, chronic wounds and inflammatory skin diseases or for their use in anti-aging cosmeceuticals.

The development of in vitro organotypic 3D vulvar models to study tumor-stroma interaction and drug efficacy

BACKGROUND

Vulvar squamous cell carcinoma (VSCC) is a rare disease with a poor prognosis. To date, there's no proper in vitro modeling system for VSCC to study its pathogenesis or for drug evaluation.

METHODS

We established healthy vulvar (HV)- and VSCC-like 3D full thickness models (FTMs) to observe the tumor-stroma interaction and their applicability for chemotherapeutic efficacy examination. VSCC-FTMs were developed by seeding VSCC tumor cell lines (A431 and HTB117) onto dermal matrices harboring two NF subtypes namely papillary fibroblasts (PFs) and reticular fibroblasts (RFs), or cancer-associated fibroblasts (CAFs) while HV-FTMs were constructed with primary keratinocytes and fibroblasts isolated from HV tissues.

RESULTS

HV-FTMs highly resembled HV tissues in terms of epidermal morphogenesis, basement membrane formation and collagen deposition. When the dermal compartment shifted from PFs to RFs or CAFs in VSCC-FTMs, tumor cells demonstrated more proliferation, EMT induction and stemness. In contrast to PFs, RFs started to lose their phenotype and express robust CAF-markers α-SMA and COL11A1 under tumor cell signaling induction, indicating a favored 'RF-to-CAF' transition in VSCC tumor microenvironment (TME). Additionally, chemotherapeutic treatment with carboplatin and paclitaxel resulted in a significant reduction in tumor-load and invasion in VSCC-FTMs.

CONCLUSION

We successfully developed in vitro 3D vulvar models mimicking both healthy and tumorous conditions which serve as a promising tool for vulvar drug screening programs. Moreover, healthy fibroblasts demonstrate heterogeneity in terms of CAF-activation in VSCC TME which brings insights in the future development of novel CAF-based therapeutic strategies in VSCC.

The basement membrane in epidermal polarity, stemness, and regeneration

The epidermis is a specialized epithelium that constitutes the outermost layer of the skin, and it provides a protective barrier against environmental assaults. Primarily consisting of multilayered keratinocytes, the epidermis is continuously renewed by proliferation of stem cells and the differentiation of their progeny, which undergo terminal differentiation as they leave the basal layer and move upward toward the surface, where they die and slough off. Basal keratinocytes rest on a basement membrane at the dermal-epidermal junction that is composed of specific extracellular matrix proteins organized into interactive and mechanically supportive networks. Firm attachment of basal keratinocytes, and their dynamic regulation via focal adhesions and hemidesmosomes, is essential for maintaining major skin processes, such as self-renewal, barrier function, and resistance to physical and chemical stresses. The adhesive integrin receptors expressed by epidermal cells serve structural, signaling, and mechanosensory roles that are critical for epidermal cell anchorage and tissue homeostasis. More specifically, the basement membrane components play key roles in preserving the stem cell pool, and establishing cell polarity cues enabling asymmetric cell divisions, which result in the transition from a proliferative basal cell layer to suprabasal cells committed to terminal differentiation. Finally, through a well-regulated sequence of synthesis and remodeling, the components of the dermal-epidermal junction play an essential role in regeneration of the epidermis during skin healing. Here too, they provide biological and mechanical signals that are essential to the restoration of barrier function.

Expanded Basal Compartment and Disrupted Barrier in Vocal Fold Epithelium Infected with Mouse Papillomavirus MmuPV1

Laryngeal infection with low-risk human papillomaviruses can cause recurrent respiratory papillomatosis (RRP), a disease with severe effects on vocal fold epithelium resulting in impaired voice function and communication. RRP research has been stymied by limited preclinical models. We recently reported a murine model of laryngeal MmuPV1 infection and disease in immunodeficient mice. In the current study, we compare quantitative and qualitative measures of epithelial proliferation, apoptosis, differentiation, and barrier between mice with MmuPV1-induced disease of the larynx and surrounding tissues and equal numbers of uninfected controls. Findings supported our hypothesis that laryngeal MmuPV1 infection recapitulates many features of RRP. Like RRP, MmuPV1 increased proliferation in infected vocal fold epithelium, expanded the basal compartment of cells, decreased differentiated cells, and altered cell–cell junctions and basement membrane. Effects of MmuPV1 on apoptosis were equivocal, as with RRP. Barrier markers resembled human neoplastic disease in severe MmuPV1-induced disease. We conclude that MmuPV1 infection of the mouse larynx provides a useful, if imperfect, preclinical model for RRP that will facilitate further study and treatment development for this intractable and devastating disease.

Fibrous stroma: Driver and passenger in cancer development

Cumulative evidence shows that fibrogenic stroma and stiff extracellular matrix (ECM) not only result from tumor growth but also play pivotal roles in cellular transformation and tumor initiation. This emerging concept may largely account for the increased cancer risk associated with environmental fibrogenic agents, such as asbestos and silica, and with chronic conditions that are fibrogenic, such as obesity and diabetes. It may also contribute to poor outcomes in patients treated with certain chemotherapeutics that can promote fibrosis, such as bleomycin and methotrexate. Although the mechanistic details of this phenomenon are still being unraveled, we provide an overview of the experimental evidence linking fibrogenic stroma and tumor initiation. In this Review, we will summarize the causes and consequences of fibrous stroma and how this stromal cue is transmitted to the nuclei of parenchymal cells through a physical continuum from the ECM to chromatin, as well as ECM-dependent biochemical signaling that contributes to cellular transformation.

Potential Therapeutic Significance of Laminin in Head and Neck Squamous Carcinomas

Simple Summary

Head and neck cancers (HNC) account for approximately 500,000 new cases of tumors annually worldwide and are represented by upper aerodigestive tract malignant neoplasms, which particularly arise in oral cavity, larynx, and pharynx tissues. Thus, due to the biological diversity between the upper aerodigestive organs, and to the heterogeneity of risk factors associated with their malignant transformation, HNC behavior, and prognosis seem to strongly vary according to the tumor site. However, despite to the heterogeneity which characterizes head and neck tumors, squamous cell carcinomas (SCC) represent the predominant histopathologic HNC subtype. In this sense, it has been reported that SCC tumor biology is strongly associated with deregulations within the extracellular matrix compartment. Accordingly, it has been shown that laminin plays a remarkable role in the regulation of crucial events associated with head and neck squamous cell carcinomas (HNSCC) progression, which opens the possibility that laminin may represent a convergence point in HNSCC natural history.

Abstract

Head and neck squamous cell carcinomas (HNSCC) are among the most common and lethal tumors worldwide, occurring mostly in oral cavity, pharynx, and larynx tissues. The squamous epithelia homeostasis is supported by the extracellular matrix (ECM), and alterations in this compartment are crucial for cancer development and progression. Laminin is a fundamental component of ECM, where it represents one of the main components of basement membrane (BM), and data supporting its contribution to HNSCC genesis and progression has been vastly explored in oral cavity squamous cell carcinoma. Laminin subtypes 111 (LN-111) and 332 (LN-332) are the main isoforms associated with malignant transformation, contributing to proliferation, adhesion, migration, invasion, and metastasis, due to its involvement in the regulation of several pathways associated with HNSCC carcinogenesis, including the activation of the EGFR/MAPK signaling pathway. Therefore, it draws attention to the possibility that laminin may represent a convergence point in HNSCC natural history, and an attractive potential therapeutic target for these tumors.

A novel mechanism in wound healing: Laminin 332 drives MMP9/14 activity by recruiting syndecan-1 and CD44

Re-epithelialization describes the resurfacing of a skin wound with new epithelium. In response to various stimuli including that of growth factors, cytokines and extracellular matrix (ECM), wound edge epidermal keratinocytes undergo cytoskeleton rearrangements compatible with their motile behavior and develop protrusive adhesion contacts. Matrix metalloproteinases (MMP) expression is crucial for proper cell movement and ECM remodeling; however, their deposition mechanism is unknown in keratinocytes. Here, we show that similar to cytokine IL-1ß, the precursor laminin 332 pro-migratory fragment G45 induces expression of the MMP-9 pro-enzyme, which together with MMP-14, further exerts its proteolytic activity within epithelial podosomes. This event strictly depends on the expression of the proteoglycan receptor syndecan-1 that was found in a ring surrounding the podosome core, co-localised with CD44. Our findings uncover that by directly recruiting both syndecan-1 and CD44, the laminin-332 G45 domain plays a major role in regulating mechanisms underlying keratinocyte / ECM remodeling during wound repair.

Loss of the laminin subunit alpha-3 induces cell invasion and macrophage infiltration in cutaneous squamous cell carcinoma

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common cancer that invades the dermis through the basement membrane. The role of the basement membrane in poorly differentiated cSCC is not well understood.

OBJECTIVES

To study the effect that loss of the laminin subunit alpha-3 (α3) chain from the tumour microenvironment has on tumour invasion and inflammatory cell recruitment.

METHODS

We examined the role of the basement membrane proteins laminin subunits α3, β3 and γ2 in SCC invasion and inflammatory cell recruitment using immunohistochemistry, short hairpin RNA knockdown, RNA-Seq, mouse xenograft models and patient tumour samples.

RESULTS

Analysis of SCC tumours and cell lines using antibodies specific to laminin chains α3, β3 and γ2 identified a link between poorly differentiated SCC and reduced expression of laminin α3 but not the other laminin subunits investigated. Knockdown of laminin α3 increased tumour invasion both in vitro and in vivo. Western blot and immunohistochemical staining identified increased phosphorylated myosin light chain with loss of laminin α3. Inhibition of ROCK (rho-associated protein kinase) but not Rac1 significantly reduced the invasive potential of laminin α3 knockdown cells. Knockdown of laminin subunits α3 and γ2 increased monocyte recruitment to the tumour microenvironment. However, only the loss of laminin α3 correlated with increased tumour-associated macrophages both in xenografted tumours and in patient tumour samples.

CONCLUSIONS

These data provide evidence that loss of the laminin α3 chain in cSCC has an effect on both the epithelial and immune components of cSCC, resulting in an aggressive tumour microenvironment.

Laminin 332 in cancer: When the extracellular matrix turns signals from cell anchorage to cell movement

Laminin 332 is crucial in the biology of epithelia. This large extracellular matrix protein consists of the heterotrimeric assembly of three subunits - α3, β3, and γ2 - and its multifunctionality relies on a number of extracellular proteolytic processing events. Laminin 332 is central to normal epithelium homeostasis by sustaining cell adhesion, polarity, proliferation, and differentiation. It also supports a major function in epithelial tissue formation, repair, and regeneration by buttressing cell migration and survival and basement membrane assembly. Interest in this protein increased after the discovery that its expression is perturbed in tumor cells, cancer-associated fibroblasts, and the tumor microenvironment. This review summarizes current knowledge regarding the established involvement of the laminin 332 γ2 chain in tumor invasiveness and discusses the role of its α3 and β3 subunits.

Multiple Skin Squamous Cell Carcinomas in Junctional Epidermolysis Bullosa Due to Altered Laminin-332 Function

Variably reduced expression of the basement membrane component laminin-332 (α3aβ3γ2) causes junctional epidermolysis bullosa generalized intermediate (JEB-GI), a skin fragility disorder with an increased susceptibility to squamous cell carcinoma (SCC) development in adulthood. Laminin-332 is highly expressed in several types of epithelial tumors and is central to signaling pathways that promote SCC tumorigenesis. However, laminin-332 mutations and expression in individuals affected by JEB-GI and suffering from recurrent SCCs have been poorly characterized. We studied a JEB-GI patient who developed over a hundred primary cutaneous SCCs. Molecular analysis combined with gene expression studies in patient skin and primary keratinocytes revealed that the patient is a functional hemizygous for the p.Cys1171* mutant allele which is transcribed in a stable mRNA encoding for a β3 chain shortened of the last two C-terminal amino acids (Cys1171-Lys1172). The lack of the Cys1171 residue involved in the C-terminal disulphide bond to γ2 chain did not prevent assembly, secretion, and proteolytic processing of the heterotrimeric molecule. Immunohistochemistry of SCC specimens revealed accumulation of mutant laminin-332 at the epithelial-stromal interface of invasive front. We conclude that the C-terminal disulphide bond is a structural element crucial for laminin-332 adhesion function in-vivo. By saving laminin-332 amount, processing, and signaling role the p.Cys1171* mutation may allow intrinsic pro-tumorigenic properties of the protein to be conveyed, thus contributing to invasiveness and recurrence of SCCs in this patient.

Epidermolysis Bullosa-Associated Squamous Cell Carcinoma: From Pathogenesis to Therapeutic Perspectives

Epidermolysis bullosa (EB) is a heterogeneous group of inherited skin disorders determined by mutations in genes encoding for structural components of the cutaneous basement membrane zone. Disease hallmarks are skin fragility and unremitting blistering. The most disabling EB (sub)types show defective wound healing, fibrosis and inflammation at lesional skin. These features expose patients to serious disease complications, including the development of cutaneous squamous cell carcinomas (SCCs). Almost all subjects affected with the severe recessive dystrophic EB (RDEB) subtype suffer from early and extremely aggressive SCCs (RDEB-SCC), which represent the first cause of death in these patients. The genetic determinants of RDEB-SCC do not exhaustively explain its unique behavior as compared to low-risk, ultraviolet-induced SCCs in the general population. On the other hand, a growing body of evidence points to the key role of tumor microenvironment in initiation, progression and spreading of RDEB-SCC, as well as of other, less-investigated, EB-related SCCs (EB-SCCs). Here, we discuss the recent advances in understanding the complex series of molecular events (i.e., fibrotic, inflammatory, and immune processes) contributing to SCC development in EB patients, cross-compare tumor features in the different EB subtypes and report the most promising therapeutic approaches to counteract or delay EB-SCCs.

Mechanism of anchorage-independency and tumor formation of cancer cells: possible involvement of cell membrane-bound laminin-332

Cancer cells are characterized by anchorage-independency and tumor formation. Involvement of laminin-332 in the pathogenesis of cancer has also been reported. I present a theory that can explain these characteristics together. Proliferating keratinocytes in wound healing produce and deposit laminin-332, which is shown in the provisional basement membrane of a wound. In association with wound closure, expression of LG4/5 domain on the α3 chain of laminin-332 disappears, implicating cleavage of LG4/5 domain. LG4/5 domain expression indicates that laminin-332 prior to the cleavage is bound to the cell membrane, because LG4/5 domain is a cell binding site. In this binding, heparan sulfate proteoglycan on the cell surface seems to be the acceptor for LG4/5 domain. I named this laminin "cell membrane-bound laminin-332" (ML332). ML332 would then bind to integrin α3β1 via LG1-3 domain, the integrin binding site, and activate FAK and the following Ras/MAPK pathway. Therefore, ML332 eliminates the need for proliferating keratinocytes to bind to processed laminin-332 secreted and deposited into the basement membrane for their proliferation (anchorage-independency). This may hold true of every proliferating epithelial cell, either benign or malignant. Whereas wound closure deprives keratinocytes of anchorage-independency, such events do not occur in cancer cells, and cancer cells maintain anchorage-independency. In the basement membrane formation by epithelial cells, short arms of laminin-332 anchored to the cell membrane bind each other and generate a meshwork polymer. This is the three-arm interaction model. In a similar manner, short-arm interactions between adjacent cancer cells may occur and induce tumor formation.

PAC-5 Gene Expression Signature for Predicting Prognosis of Patients with Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma (PAC) is one of the most aggressive malignancies. Intratumoural molecular heterogeneity impedes improvement of the overall survival rate. Current pathological staging system is not sufficient to accurately predict prognostic outcomes. Thus, accurate prognostic model for patient survival and treatment decision is demanded. Using differentially expressed gene analysis between normal pancreas and PAC tissues, the cancer-specific genes were identified. A prognostic gene expression model was computed by LASSO regression analysis. The PAC-5 signature (LAMA3, E2F7, IFI44, SLC12A2, and LRIG1) that had significant prognostic value in the overall dataset was established, independently of the pathological stage. We provided evidence that the PAC-5 signature further refined the selection of the PAC patients who might benefit from postoperative therapies. SLC12A2 and LRIG1 interacted with the proteins that were implicated in resistance of EGFR kinase inhibitor. DNA methylation was significantly involved in the gene regulations of the PAC-5 signature. The PAC-5 signature provides new possibilities for improving the personalised therapeutic strategies. We suggest that the PAC-5 genes might be potential drug targets for PAC.

Laminin 332 expression and prognosis in breast cancer

The purpose of this study was to determine the distribution of and potential significance of laminin 332 (LM332) in breast cancer. Specimens from a population-based cohort (N = 297) from 1994 to 1995 were stained for estrogen receptor (ER), progesterone receptor (PgR), HER2 and the LM332 β3 chain. Seventy-five tumors were LM332-positive and 222 were negative. LM332 β3 stained 16.0% of ER and/or PgR-positive tumors and 73.2% of triple-negative breast cancers (TNBC). Immunoblotting revealed LM332 in TNBC and HER2-positive samples, but not in an ER-positive breast carcinoma or a phyllodes tumor. After 20 years, 172 patients were alive, 43 had died of breast cancer and 82 of other causes. Patients with LM332-positive tumors had significantly worse 5 (P < .0001) and 10-year (P < .05) overall and breast cancer specific survival. Among patients with LM332 β3-expressing and ER/PgR-negative carcinomas, 10-year survival was significantly reduced (P < .0450). In a multivariate analysis LM332-positive patients had significant hazard ratios of 3.9 with 95% confidence intervals (CI) of 2.0-7.7 and 2.2 with 95% CI of 1.3-3.8 for 5 and 10-year overall survival, respectively. Because tumor cell motility is required for metastasis, the effect of LM332 on MDA-MB-231 migration was determined using siRNA. Knockdown of LM332-specific β3 and γ2 chains reduced motility without affecting viability. Our observation that LM332 in breast carcinoma is associated with decreased survival provides evidence that LM332 may have a role in the aggressive phenotype of some breast cancers.

Migration of breast cancer cell lines in response to pulmonary laminin 332

Because tumor cell motility is a requirement for metastasis, we hypothesized that lung tissue harbors substances that induce tumor cell migration. MCF-7 breast carcinoma cells exposed to small airway epithelial cells and conditioned medium exhibited dose-dependent tumor cell migration. Among the extracellular matrix proteins in the conditioned medium identified by mass spectrometry, laminin 332 (LM332) had the greatest contribution to the migration of MCF-7 cells. Immunoblotting and immunohistochemistry for LM332-specific chains identified LM332 in the lung and in pulmonary epithelial cells. Antibodies to either LM332 or its integrin receptor inhibited MCF-7 motility, and knockdown of LM332 chains also reduced its migration-inducing activity. Taken together, these findings implicate LM332 as a component of lung tissue that can induce motility in breast carcinoma cells that have been transported to lung during metastasis. Earlier studies on LM332 in tumor progression have examined LM332 expression in tumor cells. This investigation, in comparison, provides evidence that the tumor promoting potential of LM332 may originate in the lung microenvironment rather than in tumor cells alone. Furthermore, this study provides evidence that the motility-inducing properties of the microenvironment can reside in epithelial cells. The findings raise the possibility that LM332 plays a role in the pulmonary metastases of breast carcinoma and may provide a target for antimetastasis therapy.

Highly sensitive detection of invasive lung cancer cells by novel antibody against amino-terminal domain of laminin γ2 chain

The laminin γ2 chain, a subunit of laminin-332 (α3β3γ2), is a molecular marker for invasive cancer cells, but its pathological roles in tumor progression remain to be clarified. It was recently found that the most N-terminal, domain V (dV) of γ2 chain has activities to bind CD44 and stimulate tumor cell migration and vascular permeability. In the present study, we prepared a mAb recognizing γ2 dV. Immunoblotting with this antibody, for the first time, showed that proteolytic fragments containing dV in a range of 15-80 kDa were highly produced in various human cancer cell lines and lung cancer tissues. In immunohistochemistry of adenocarcinomas and squamous cell carcinomas of the lung, this antibody immunostained the cytoplasm of invasive tumor cells and adjacent stroma much more strongly than a widely used antibody recognizing the C-terminal core part of the processed γ2 chain. This suggests that the dV fragments are highly accumulated in tumor cells and stroma compared to the processed γ2 protein. The strong tumor cell staining with the dV antibody correlated with the tumor malignancy grade. We also found that the laminin β3 and α3 chains were frequently overexpressed in tumor cells and tumor stroma, respectively. The cytoplasmic dV detection was especially prominent in tumor cells infiltrating stroma, but low in the cells surrounded by basement membranes, suggesting that the active tumor-stroma interaction is critical for the aberrant γ2 expression. The present study suggests important roles of laminin γ2 N-terminal fragments in tumor progression.

Tension in Cancer

Integrins represent a large family of cell receptors that mediate adhesion to the extracellular matrix (ECM), thereby modulating a variety of cellular functions that are required for proliferation, migration, malignant conversion and invasiveness. During tumorigenesis the conversion of a tumor cell from sessile, stationary phenotype to an invasive phenotype requires the ability of tumor cells to interact with their environment in order to transduce signals from the ECM into the cells. Hence, there is increasing evidence that changes in the composition, topography and tension of tumor matrix can be sensed by integrin receptors, leading to the regulation of intracellular signalling events which subsequently help to fuel cancer progression. The fact that intracellular signals perceived from integrin ligand binding impact on almost all steps of tumor progression, including tumor cell proliferation, survival, metastatic dissemination and colonization of a metastatic niche, renders integrins as ideal candidates for the development of therapeutic agents. In this review we summarize the role of integrins in cancer with the special focus on cancer therapies and the recent progress that has been made in the understanding of “integrin-induced tension in cancer”. Finally, we conclude with clinical evidence for the role of integrin-mediated mechanotransduction in the development of therapy-resistant tumors.

Autoimmunity against laminins

Laminins are ubiquitous constituents of the basement membranes with major architectural and functional role as supported by the fact that absence or mutations of laminins lead to either lethal or severely impairing phenotypes. Besides genetic defects, laminins are involved in a wide range of human diseases including cancer, infections, and inflammatory diseases, as well as autoimmune disorders. A growing body of evidence implicates several laminin chains as autoantigens in blistering skin diseases, collagenoses, vasculitis, or post-infectious autoimmunity. The current paper reviews the existing knowledge on autoimmunity against laminins referring to both experimental and clinical data, and on therapeutic implications of anti-laminin antibodies. Further investigation of relevant laminin epitopes in pathogenic autoimmunity would facilitate the development of appropriate diagnostic tools for thorough characterization of patients' antibody specificities and should decisively contribute to designing more specific therapeutic interventions.

Matricryptins Network with Matricellular Receptors at the Surface of Endothelial and Tumor Cells

The extracellular matrix (ECM) is a source of bioactive fragments called matricryptins or matrikines resulting from the proteolytic cleavage of extracellular proteins (e.g., collagens, elastin, and laminins) and proteoglycans (e.g., perlecan). Matrix metalloproteinases (MMPs), cathepsins, and bone-morphogenetic protein-1 release fragments, which regulate physiopathological processes including tumor growth, metastasis, and angiogenesis, a pre-requisite for tumor growth. A number of matricryptins, and/or synthetic peptides derived from them, are currently investigated as potential anti-cancer drugs both in vitro and in animal models. Modifications aiming at improving their efficiency and their delivery to their target cells are studied. However, their use as drugs is not straightforward. The biological activities of these fragments are mediated by several receptor families. Several matricryptins may bind to the same matricellular receptor, and a single matricryptin may bind to two different receptors belonging or not to the same family such as integrins and growth factor receptors. Furthermore, some matricryptins interact with each other, integrins and growth factor receptors crosstalk and a signaling pathway may be regulated by several matricryptins. This forms an intricate 3D interaction network at the surface of tumor and endothelial cells, which is tightly associated with other cell-surface associated molecules such as heparan sulfate, caveolin, and nucleolin. Deciphering the molecular mechanisms underlying the behavior of this network is required in order to optimize the development of matricryptins as anti-cancer agents.

Extracellular matrix structure

Extracellular matrix (ECM) is a non-cellular three-dimensional macromolecular network composed of collagens, proteoglycans/glycosaminoglycans, elastin, fibronectin, laminins, and several other glycoproteins. Matrix components bind each other as well as cell adhesion receptors forming a complex network into which cells reside in all tissues and organs. Cell surface receptors transduce signals into cells from ECM, which regulate diverse cellular functions, such as survival, growth, migration, and differentiation, and are vital for maintaining normal homeostasis. ECM is a highly dynamic structural network that continuously undergoes remodeling mediated by several matrix-degrading enzymes during normal and pathological conditions. Deregulation of ECM composition and structure is associated with the development and progression of several pathologic conditions. This article emphasizes in the complex ECM structure as to provide a better understanding of its dynamic structural and functional multipotency. Where relevant, the implication of the various families of ECM macromolecules in health and disease is also presented.

E-cadherin-defective gastric cancer cells depend on Laminin to survive and invade

Epithelial-cadherin (Ecad) deregulation affects cell-cell adhesion and results in increased invasiveness of distinct human carcinomas. In gastric cancer, loss of Ecad expression is a common event and is associated with disease aggressiveness and poor prognosis. However, the molecular mechanisms underlying the invasive process associated to Ecad dysfunction are far from understood. We hypothesized that deregulation of cell-matrix interactions could play an important role during this process. Thus, we focussed on LM-332, which is a major matrix component, and in Ecad/LM-332 crosstalk in the process of Ecad-dependent invasion. To verify whether matrix deregulation was triggered by Ecad loss, we used the Drosophila model. To dissect the key molecules involved and unveil their functional significance, we used gastric cancer cell lines. The relevance of this relationship was then confirmed in human primary tumours. In vivo, Ecad knockdown induced apoptosis; nonetheless, at the invasive front, cells ectopically expressed Laminin A and βPS integrin. In vitro, we demonstrated that, in two different gastric cancer cell models, Ecad-defective cells overexpressed Laminin γ2 (LM-γ2), β1 and β4 integrin, when compared with Ecad-competent ones. We showed that LM-γ2 silencing impaired invasion and enhanced cell death, most likely via pSrc and pAkt reduction, and JNK activation. In human gastric carcinomas, we found a concomitant decrease in Ecad and increase in LM-γ2. This is the first evidence that ectopic Laminin expression depends on Ecad loss and allows Ecad-dysfunctional cells to survive and invade. This opens new avenues for using LM-γ2 signalling regulators as molecular targets to impair gastric cancer progression.

Assembly, heterogeneity, and breaching of the basement membranes

Basement membranes are thin sheets of self-assembled extracellular matrices that are essential for embryonic development and for the homeostasis of adult tissues. They play a role in structuring, protecting, polarizing, and compartmentalizing cells, as well as in supplying them with growth factors. All basement membranes are built from laminin and collagen IV networks stabilized by nidogen/perlecan bridges. The precise composition of basement membranes, however, varies between different tissues. Even though basement membranes represent physical barriers that delimit different tissues, they are breached in many physiological or pathological processes, including development, the immune response, and tumor invasion. Here, we provide a brief overview of the molecular composition of basement membranes and the process of their assembly. We will then illustrate the heterogeneity of basement membranes using two examples, the epithelial basement membrane in the gut and the vascular basement membrane. Finally, we examine the different strategies cells use to breach the basement membrane.

Epidermal Basement Membrane in Health and Disease

Skin, as the organ protecting the individual from environmental aggressions, constantly meets external insults and is dependent on mechanical toughness for its preserved function. Accordingly, the epidermal basement membrane (BM) zone has adapted to enforce tissue integrity. It harbors anchoring structures created through unique organization of common BM components and expression of proteins exclusive to the epidermal BM zone. Evidence for the importance of its correct assembly and the nonredundancy of its components for skin integrity is apparent from the multiple skin blistering disorders caused by mutations in genes coding for proteins associated with the epidermal BM and from autoimmune disorders in which autoantibodies target these molecules. However, it has become clear that these proteins not only provide mechanical support but are also critically involved in tissue homeostasis, repair, and regeneration. In this chapter, we provide an overview of the unique organization and components of the epidermal BM. A special focus will be given to its function during regeneration, and in inherited and acquired diseases.

A syndecan-4 binding peptide derived from laminin 5 uses a novel PKCε pathway to induce cross-linked actin network (CLAN) formation in human trabecular meshwork (HTM) cells

In this study, we examined the role(s) of syndecan-4 in regulating the formation of an actin geodesic dome structure called a cross-linked actin network (CLAN) in which syndecan-4 has previously been localized. CLANs have been described in several different cell types, but they have been most widely studied in human trabecular meshwork (HTM) cells where they may play a key role in controlling intraocular pressure by regulating aqueous humor outflow from the eye. In this study we show that a loss of cell surface synedcan-4 significantly reduces CLAN formation in HTM cells. Analysis of HTM cultures treated with or without dexamethasone shows that laminin 5 deposition within the extracellular matrix is increased by glucocorticoid treatment and that a laminin 5-derived, syndecan-4-binding peptide (PEP75), induces CLAN formation in TM cells. This PEP75-induced CLAN formation was inhibited by heparin and the broad spectrum PKC inhibitor Ro-31-7549. In contrast, the more specific PKCα inhibitor Gö 6976 had no effect, thus excluding PKCα as a downstream effector of syndecan-4 signaling. Analysis of PKC isozyme expression showed that HTM cells also expressed both PKCγ and PKCε. Cells treated with a PKCε agonist formed CLANs while a PKCα/γ agonist had no effect. These data suggest that syndecan-4 is essential for CLAN formation in HTM cells and that a novel PKCε-mediated signaling pathway can regulate formation of this unique actin structure.

Classification of inflammatory skin diseases: a proposal based on the disorders of the three-layered defense systems, barrier, innate immunity and acquired immunity

The host defense system of the skin is composed of (1) a barrier, (2) innate immunity, and (3) acquired immunity. Inflammatory skin diseases can be classified into one of the disorders of these layers of the defense system, unless there is an ordinary response to specific infectious agents or internal/external injury. Any inflammatory skin disease partly simulates the response to real infections or dangers. Disorders of acquired immunity can be classified into (1) immunodeficiency, (2) immunohyperactivity (allergy), and (3) qualitative disorder (autoimmunity). Disorders of innate immunity can be classified into (1) innate immunodeficiency, (2) innate immunohyperactivity (general or local autoinflammation), and (3) qualitative disorder (general or local innate autoimmunity). The barrier of the skin is composed of (1) the physical barrier and (2) the chemical barrier. Several diseases, such as atopic dermatitis, are attributed to the disorder of these components of the barrier. Here, we propose an algorithm to classify the pathology of inflammatory skin diseases by means of what disorder in the specific layer of the host defense system is truly responsible.

A truncating mutation in the laminin-332α chain highlights the role of the LG45 proteolytic domain in regulating keratinocyte adhesion and migration

BACKGROUND

Altered function of laminin-332 (α3β3γ2) consequent to mutations in the LAMA3, LAMB3 and LAMC2 genes causes junctional epidermolysis bullosa non-Herlitz (JEB-nH). JEB-nH patients suffer from skin blistering and have an increased risk of developing aggressive skin carcinomas in adulthood. Laminin-332 is proteolytically processed and its extracellular mature form lacks the α3 chain C-terminal globules 4 and 5 (LG45). The LG45 tandem has cell adhesion and protumorigenic properties. However, mutations that affect this domain are very rare and their functional effects in patients have not been explored to date.

OBJECTIVE

To characterize molecularly an adult patient with JEB-nH and altered laminin-332 expression presenting multiple skin carcinomas, and to analyse LG45-mediated biological functions using keratinocytes from the patient.

METHODS

A mutational search in laminin-332 genes was performed by hetero-duplex analysis. LAMA3 mRNA and laminin-332 protein levels in patient keratinocytes were investigated by real-time reverse transcriptase polymerase chain reaction and radioimmunoprecipitation assay, respectively. Keratinocyte migration was examined by scratch and Boyden chamber assays.

RESULTS

We identified a homozygous LAMA3 mutation, p.Leu1648TrpfsX32, which truncates the last 45 amino acids of the carboxyl terminal LG5 subdomain. Gene expression studies revealed that the mutant transcripts were stable and even increased, precursor laminin-332 molecules were retained intracellularly and the amount of mature extracellular heterotrimers was reduced to about 50%. Finally, the patient's keratinocytes migrated faster than normal keratinocytes.

CONCLUSIONS

Structural disruption of LG5 highlights the critical functions of the LG45 proteolytic region in precursor laminin-332 secretion and keratinocyte adhesion and migration. Perturbation of LG45 function might explain the non-aggressive behaviour of carcinomas in this patient.

Amino-terminal fragments of laminin γ2 chain retract vascular endothelial cells and increase vascular permeability

Laminin γ2 (Lmγ2) chain, a subunit of laminin-332, is a typical molecular marker of invading cancer cells, and its expression correlates with poor prognosis of cancer patients. It was previously found that forced expression of Lmγ2 in cancer cells promotes their invasive growth in nude mice. However, the mechanism of the tumor-promoting activity of Lmγ2 remains unknown. Here we investigated the interaction between Lmγ2 and vascular endothelial cells. When treated with an N-terminal proteolytic fragment of γ2 (γ2pf), HUVECs became markedly retracted or shrunken. The overexpression of Lmγ2 or treatment with γ2pf stimulated T-24 bladder carcinoma cells to invade into the HUVEC monolayer and enhanced their transendothelial migration in vitro. Moreover, γ2pf increased endothelial permeability in vitro and in vivo. As the possible mechanisms, γ2pf activated ERK and p38 MAPK but inactivated Akt in HUVECs. Such effects of γ2pf led to prominent actin stress fiber formation in HUVECs, which was blocked by a ROCK inhibitor. In addition, γ2pf induced delocalization of VE-cadherin and β-catenin from the intercellular junction. As possible receptors, γ2pf interacted with heparan sulfate proteoglycans on the surface of HUVECs. Moreover, we localized the active site of γ2pf to the N-terminal epidermal growth factor-like repeat. These data suggest that the interaction between γ2pf and heparan sulfate proteoglycans induces cytoskeletal changes of endothelial cells, leading to the loss of endothelial barrier function and the enhanced transendothelial migration of cancer cells. These activities of Lmγ2 seem to support the aberrant growth of cancer cells.

Focal adhesion complex proteins in epidermis and squamous cell carcinoma

Focal adhesions (FAs) are large, integrin-containing, multi-protein assemblies spanning the plasma membrane that link the cellular cytoskeleton to surrounding extracellular matrix. They play critical roles in adhesion and cell signaling and are major regulators of epithelial homeostasis, tissue response to injury, and tumorigenesis. Most integrin subunits and their associated FA proteins are expressed in skin, and murine genetic models have provided insight into the functional roles of FAs in normal and neoplastic epidermis. Here, we discuss the roles of these proteins in normal epidermal proliferation, adhesion, wound healing, and cancer. While many downstream signaling mechanisms remain unclear, the critically important roles of FAs are highlighted by the development of therapeutics targeting FAs for human cancer.

Tetraspanin CD151 plays a key role in skin squamous cell carcinoma

Here we provide the first evidence that tetraspanin CD151 can support de novo carcinogenesis. During two-stage mouse skin chemical carcinogenesis, CD151 reduces tumor lag time and increases incidence, multiplicity, size and progression to malignant squamous cell carcinoma (SCC), while supporting both cell survival during tumor initiation and cell proliferation during the promotion phase. In human skin SCC, CD151 expression is selectively elevated compared with other skin cancer types. CD151 support of keratinocyte survival and proliferation may depend on activation of transcription factor STAT3 (signal transducers and activators of transcription), a regulator of cell proliferation and apoptosis. CD151 also supports protein kinase C (PKC)α-α6β4 integrin association and PKC-dependent β4 S1424 phosphorylation, while regulating α6β4 distribution. CD151-PKCα effects on integrin β4 phosphorylation and subcellular localization are consistent with epithelial disruption to a less polarized, more invasive state. CD151 ablation, while minimally affecting normal cell and normal mouse functions, markedly sensitized mouse skin and epidermoid cells to chemicals/drugs including 7,12-dimethylbenz[α]anthracene (mutagen) and camptothecin (topoisomerase inhibitor), as well as to agents targeting epidermal growth factor receptor, PKC, Jak2/Tyk2 and STAT3. Hence, CD151 'co-targeting' may be therapeutically beneficial. These findings not only support CD151 as a potential tumor target, but also should apply to other cancers utilizing CD151/laminin-binding integrin complexes.

Skin basement membrane: the foundation of epidermal integrity--BM functions and diverse roles of bridging molecules nidogen and perlecan

The epidermis functions in skin as first defense line or barrier against environmental impacts, resting on extracellular matrix (ECM) of the dermis underneath. Both compartments are connected by the basement membrane (BM), composed of a set of distinct glycoproteins and proteoglycans. Herein we are reviewing molecular aspects of BM structure, composition, and function regarding not only (i) the dermoepidermal interface but also (ii) the resident microvasculature, primarily focusing on the per se nonscaffold forming components perlecan and nidogen-1 and nidogen-2. Depletion or functional deficiencies of any BM component are lethal at some stage of development or around birth, though BM defects vary between organs and tissues. Lethality problems were overcome by developmental stage- and skin-specific gene targeting or by cell grafting and organotypic (3D) cocultures of normal or defective cells, which allows recapitulating BM formation de novo. Thus, evidence is accumulating that BM assembly and turnover rely on mechanical properties and composition of the adjacent ECM and the dynamics of molecular assembly, including further "minor" local components, nidogens largely functioning as catalysts or molecular adaptors and perlecan as bridging stabilizer. Collectively, orchestration of BM assembly, remodeling, and the role of individual players herein are determined by the developmental, tissue-specific, or functional context.

A novel monoclonal antibody to human laminin α5 chain strongly inhibits integrin-mediated cell adhesion and migration on laminins 511 and 521

Laminins, a large family of αβγ heterotrimeric proteins mainly found in basement membranes, are strong promoters of adhesion and migration of multiple cell types, such as tumor and immune cells, via several integrin receptors. Among laminin α (LMα) chains, α5 displays the widest tissue distribution in adult life and is synthesized by most cell types. Here, we have generated and characterized five novel monoclonal antibodies (mAbs) to the human LMα5 chain to further study the biological relevance of α5 laminins, such as laminins 511 (α5β1γ1) and 521 (α5β2γ1). As detected by ELISA, immunohistochemistry, immunoprecipitation and Western blotting, each antibody displayed unique properties when compared to mAb 4C7, the prototype LMα5 antibody. Of greatest interest, mAb 8G9, but not any other antibody, strongly inhibited α3β1/α6β1 integrin-mediated adhesion and migration of glioma, melanoma, and carcinoma cells on laminin-511 and, together with mAb 4C7, on laminin-521. Accordingly, mAb 8G9 abolished the interaction of soluble α3β1 integrin with immobilized laminins 511 and 521. Binding of mAb 8G9 to laminin-511 was unaffected by the other mAbs to the LMα5 chain but largely hindered by mAb 4E10 to a LMβ1 chain epitope near the globular domain of laminin-511. Thus, mAb 8G9 defines a novel epitope localized at or near the integrin-binding globular domain of the LMα5 chain, which is essential for cell adhesion and migration, and identifies a potential therapeutic target in malignant and inflammatory diseases.

Laminin 332 processing impacts cellular behavior

Laminin 332, composed of the α3, β3 and γ2 chains, is an epithelial-basement membrane specific laminin variant. Its main role in normal tissues is the maintenance of epithelial-mesenchymal cohesion in tissues exposed to external forces, including skin and stratified squamous mucosa. After being secreted and deposited in the extracellular matrix, laminin 332 undergoes physiological maturation processes consisting in the proteolytic processing of domains located within the α3 and the γ2 chains. These maturation events are essential for laminin 332 integration into the basement membrane where it plays an important function in the nucleation and maintenance of anchoring structures. Studies in normal and pathological situations have revealed that laminin 332 can trigger distinct cellular events depending on the level of its proteolytic cleavages. In this review, the biological and structural characteristics of laminin 332 domains are presented and we discuss whether they trigger specific functions.

[The value of laminin-322 staining in distinguishing between keratoacanthoma, keratoacanthoma with areas of squamous cell carcinoma, and crateriform squamous cell carcinoma]

INTRODUCTION

Keratoacanthoma is a fast-growing crateriform skin tumor. Approximately 25% of such tumors undergo malignant transformation and develop areas of squamous cell carcinoma (SCC). The presence of laminin-322 has been associated with progression to invasive forms of SCC. The aim of this study was to determine whether or not immunohistochemical staining for laminin-322 would be of value in distinguishing between keratoacanthomas, keratoacanthomas with areas of squamous cell carcinoma, and SCCs.

MATERIAL AND METHODS

Seventy-four lesions were selected from the pathology archives of our hospital and divided into 4 groups: 20 keratoacanthomas without SCC, 20 keratoacanthomas with areas of squamous cell carcinoma, 20 invasive SCCs (8 with crateriform morphology) unrelated to keratoacanthoma, and 14 problem lesions (keratoacanthomas with areas suggestive of SCC). All 74 lesions were stained for laminin-322.

RESULTS

Laminin-322 staining was strongly positive both in areas of SCC in keratoacanthomas with malignant transformation and in invasive SCCs (mostly at the invasive front of the SCC). However, in benign keratoacanthomas, it was only weakly positive and furthermore it was confined to isolated cells or small groups of cells. The 14 problem lesions were reexamined after laminin-322 staining and 8 were diagnosed as keratoacanthomas with incipient SCC and 6 as keratoacanthomas without SCC.

CONCLUSIONS

Laminin-322 staining is different in keratoacanthomas and SCCs and would thus be a useful test for differentiating keratoacanthomas from both invasive SCCs and keratoacanthomas with areas of squamous cell carcinoma. It would also be of value in diagnosing keratoacanthomas with areas suggestive of SCC or with incipient SCC.

Cell surface proteoglycans syndecan-1 and -4 bind overlapping but distinct sites in laminin α3 LG45 protein domain

Keratinocyte migration during epidermal repair depends on interactions between cellular heparan sulfate proteoglycan receptors, syndecan-1 and -4, and the C-terminal globular domains (LG45) of the extracellular matrix protein laminin 332. This study investigates the molecular basis of the binding specificity of the syndecan-1 and -4 receptors expressed by human keratinocytes. We used site-directed mutagenesis to alter a recombinant LG45 protein by substituting the most critical basic residues with glutamine. All proteins were expressed in mammalian cells, purified, and characterized biochemically. We used in vitro binding assays, including surface plasmon resonance, to examine interactions between mutated LG45 and heparan sulfates, syndecan-1 and -4. We identify a major heparin binding domain on the outer edge of a β-strand of LG45 surrounded by a track of converging low affinity residues. This domain harbors distinctive syndecan-1 and -4 binding-specific sequences. This is the first study to demonstrate a binding specificity of two proteoglycans produced by a single cell type. In addition, we found that although syndecan-1 interacts exclusively through its glycosaminoglycan chains, syndecan-4 binding relies on both its core protein and its heparan sulfate chains. These results suggest that LG45 may trigger different signals toward keratinocytes depending on its interaction with syndecan-1 or -4.

Hepatic stellate cells stimulate HCC cell migration via laminin-5 production

Activated HSCs (hepatic stellate cells) are the main source of extracellular matrix proteins present in cirrhotic liver on which HCC (hepatocellular carcinoma) commonly develops. HCC cells behave differently according to differences in the surrounding microenvironment. In the present study, we have investigated a mechanism whereby HSCs modulate the migratory activity of HCC cells. We used primary cultures of human HSCs to investigate their effect on Hep3B, Alexander, HLE and HLF HCC cells. The expression of Ln-5 (laminin-5) was documented at transcript and protein levels both in vitro and in vivo. HCC cells strongly adhere, migrate and spread in the presence of HSC-conditioned medium and of co-culture. HSCs produce and secrete Ln-5 in the CM (conditioned medium). The electrophoretic pattern of secreted Ln-5 is consistent with that of a migratory substrate, showing the presence of the γ2x fragment. Blocking antibodies against Ln-5 inhibit HCC migration in the presence of HSC-CM. HCC cells migrate very poorly in the presence of Ln-5 immunodepleted HSC-CM. HCC migration in the presence of HSCs is dependent on the MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase]/ERK pathway, but not the PI3K (phosphoinositide 3-kinase)/Akt pathway. HSC-CM, as well as Ln-5, activates the MEK/ERK but not the PI3K/Akt pathway. In human HCC tissues, Ln-5 is mainly distributed along α-SMA (smooth muscle actin)-positive cells, whereas in peritumoural tissues, Ln-5 is absent. HSCs stimulate HCC migration via the production and secretion of Ln-5.

Putative biomarker genes for grading clear cell renal cell carcinoma

OBJECTIVE

The initial objective of this renal cancer study was to identify gene sets in clear cell renal cell carcinoma (ccRCC) to support grading of ccRCC histopathology.

MATERIALS AND METHODS

Preselected ccRCC tumor tissues of grade 1 (G1, n = 14) and grade 3 (G3, n = 15) as well es 14 normal kidney tissues thereof were subjected to microarray expression analysis using Human Genome U133 Plus 2.0 Array. Event ratio scoring, hierarchical clustering and principal component analysis were used to determine gene sets that distinguish expression profiles from normal kidney tissue, G1 and G3 tumor tissues.

RESULTS

An initial set of 73 genes provided seven gene subclusters (SC01 to SC07) that distinguish RNA expression profiles from G1, G3 tumor and normal kidney tissues. A ranked list of 24 genes was determined that separated G1 from G3 tumors in high concordance with histopathological grading confirmed by immunohistochemical analysis of ceruloplasmin protein expression.

CONCLUSION

A final set of 24 genes has been determined awaiting further validation on the RNA as well as on the protein level by studying an additional cohort of ccRCC patients. A reliable separation of G1 and G3 tumor grades will be instrumental to foster and direct the administration of upcoming targeted therapeutics of ccRCC tumors in a more predictive and reliable manner.

Molecular organization of the basement membrane zone

The dermal-epidermal basement membrane is a complex assembly of proteins that provide adhesion and regulate many important processes such as development, wound healing, and cancer progression. This contribution focuses on the structure and function of individual components of the basement membrane, how they assemble together, and how they participate in human tissues and diseases, with an emphasis on skin involvement. Understanding the composition and structure of the basement membrane provides insight into the pathophysiology of inherited blistering disorders, such as epidermolysis bullosa, and acquired bullous diseases, such as the pemphigoid group of autoimmune diseases and epidermolysis bullosa acquisita.

Basement membrane components are key players in specialized extracellular matrices

More than three decades ago, basement membranes (BMs) were described as membrane-like structures capable of isolating a cell from and connecting a cell to its environment. Since this time, it has been revealed that BMs are specialized extracellular matrices (sECMs) with unique components that support important functions including differentiation, proliferation, migration, and chemotaxis of cells during development. The composition of these sECM is as unique as the tissues to which they are localized, opening the possibility that such matrices can fulfill distinct functions. Changes in BM composition play significant roles in facilitating the development of various diseases. Furthermore, tissues have to provide sECM for their stem cells during development and for their adult life. Here, we briefly review the latest research on these unique sECM and their components with a special emphasis on embryonic and adult stem cells and their niches.

Laminin deposition in the extracellular matrix: a complex picture emerges

Laminins are structural components of basement membranes. In addition, they are key extracellular-matrix regulators of cell adhesion, migration, differentiation and proliferation. This Commentary focuses on a relatively understudied aspect of laminin biology: how is laminin deposited into the extracellular matrix? This topic has fascinated researchers for some time, particularly considering the diversity of patterns of laminin that can be visualized in the matrix of cultured cells. We discuss current ideas of how laminin matrices are assembled, the role of matrix receptors in this process and how laminin-associated proteins modulate matrix deposition. We speculate on the role of signaling pathways that are involved in laminin-matrix deposition and on how laminin patterns might play an important role in specifying cell behaviors, especially directed migration. We conclude with a description of new developments in the way that laminin deposition is being studied, including the use of tagged laminin subunits that should allow the visualization of laminin-matrix deposition and assembly by living cells.

Interaction of syndecan and alpha6beta4 integrin cytoplasmic domains: regulation of ErbB2-mediated integrin activation

The alpha6beta4 integrin is a laminin 332 (LN332) receptor central to the formation of hemidesmosomes in epithelial layers. However, the integrin becomes phosphorylated by keratinocytes responding to epidermal growth factor in skin wounds or by squamous cell carcinomas that overexpress/hyperactivate the tyrosine kinase ErbB2, epidermal growth factor receptor, or c-Met. We show here that the beta4-dependent signaling in A431 human squamous carcinoma cells is dependent on the syndecan family of matrix receptors. Yeast two-hybrid analysis identifies an interaction within the distal third (amino acids 1473-1752) of the beta4 cytoplasmic domain and the conserved C2 region of the syndecan cytoplasmic domain. Via its C2 region, Sdc1 forms a complex with the alpha6beta4 integrin along with the receptor tyrosine kinase ErbB2 and the cytoplasmic kinase Fyn in A431 cells. Engagement of LN332 or clustering of the alpha6beta4 integrin with integrin-specific antibodies causes phosphorylation of ErbB2, Fyn, and the beta4 subunit as well as activation of phosphatidylinositol 3-kinase and Akt and their assimilation into this complex. This leads to phosphatidylinositol 3-kinase-dependent cell spreading and Akt-dependent protection from apoptosis. This is disrupted by RNA interference silencing of Sdc1 but can be rescued by mouse Sdc1 or Sdc4 but not by syndecan mutants lacking their C-terminal C2 region. This disruption does not prevent the phosphorylation of ErbB2 or Fyn but blocks the Fyn-mediated phosphorylation of the beta4 tail. We propose that syndecans engage the distal region of the beta4 cytoplasmic domain and bring it to the plasma membrane, where it can be acted upon by Src family kinases.

Role of dermal-epidermal basement membrane zone in skin, cancer, and developmental disorders

The dermal-epidermal basement membrane zone is an important epithelial and stromal interface, consisting of an intricately organized collection of intracellular, transmembrane, and extracellular matrix proteins. The basement membrane zone has several main functions including acting as a permeability barrier, forming an adhesive interface between epithelial cells and the underlying matrix, and controlling cellular organization and differentiation. This article identifies key molecular players of the dermal-epidermal membrane zone, and highlights recent research studies that have identified structural and functional roles of these components in the context of various blistering, neoplastic, and developmental syndromes.

Understanding the pathogenesis of recessive dystrophic epidermolysis bullosa squamous cell carcinoma

Patients with recessive dystrophic epidermolysis bullosa develop numerous life-threatening skin cancers. The reasons for this remain unclear. Parallels exist with other scarring skin conditions, such as Marjolin ulcer. We summarize observational and experimental data and discuss proposed theories for the development of such aggressive skin cancers. A context-driven situation seems to be emerging, but more focused research is required to elucidate the pathogenesis of epidermolysis bullosa-associated squamous cell carcinoma.

Adhesion and migration, the diverse functions of the laminin alpha3 subunit

The laminins are a secreted family of heterotrimeric molecules essential for basement membrane formation, structure, and function. It is now well established that the alpha3 subunit of laminins-332, -321, and -311 plays an important role in mediating epidermal-dermal integrity and is essential for the skin to withstand mechanical stresses. These laminins also regulate cell migration and mechanosignal transduction. This article provides an overview of the gene, transcripts, and protein structures of laminin alpha3. Also discussed are the proposed functions for the alpha3 subunit-containing laminins.

Defining the role of laminin-332 in carcinoma

The deadly feature of cancer, metastasis, requires invasion of cells through basement membranes (BM), which normally act as barriers between tissue compartments. In the case of many epithelially-derived cancers (carcinomas), laminin-332 (Ln-332) is a key component of the BM barrier. This review provides a historical examination of Ln-332 from its discovery through identification of its functions in BM and possible role in carcinomas. Current understanding points to distinct roles for the three Ln-332 subunits (alpha3, beta3, gamma2) in cell adhesion, extracellular matrix stability, and cell signaling processes in cancer. Given the large number of studies linking Ln-332 gamma2 subunit with cancer prognosis, particular attention is given to the crucial role of this subunit in cancer invasion and to the unanswered questions in this area.

Laminins

Laminins are cell adhesion molecules that comprise a family of glycoproteins found predominantly in basement membranes, which are the thin sheets of extracellular matrix that underlie epithelial and endothelial cells and surround muscle cells, Schwann cells, and fat cells. Many laminins self-assemble to form networks that remain in close association with cells through interactions with cell surface receptors. Laminins are vital for many physiological functions. They are essential for early embryonic development and organogenesis and have crucial functions in several tissues including muscle, nerve, skin, kidney, lung, and the vasculature. A great wealth of data on laminins is available, and an in-depth description is not attempted here. In this review, I will instead provide a snapshot of laminin structure, tissue distribution, and interactions with other matrix molecules and receptors and briefly describe laminin mutations in mice and humans. Several illuminating and timely reviews are cited that can be consulted for references to original articles and more detailed information concerning laminins.

Migration of isogenic cell lines quantified by dynamic multivariate analysis of single-cell motility

Cell migration is essential in many physiological and pathological processes. To understand this complex behavior, researchers have turned to quantitative, in vitro, image-based measurements to dissect the steps of cellular motility. With the rise of automated microscopy, the bottleneck in these approaches is no longer data acquisition, but data analysis. Using time-lapse microscopy and computer-assisted image analysis, we have developed a novel, quantitative assay that extracts a multivariate profile for cellular motility. This technique measures three dynamic parameters per single cell: speed, surface area, and an in-dex of cell expansion/contraction activity (DECCA). Our assay can be used in combination with a variety of extracellular matrix components, or other soluble agents, to analyze the effects of the microenvironment on cellular migration dynamics in vitro. Our application was developed and tested using A431 and HT-1080 cell lines plated on laminin-332 or fibronectin substrates. Our results indicate that HT-1080 cells migrate faster, have a greater surface area, and have a higher DECCA index than A431 cells on both matrices (for all parameters, p < 0.05). Spearman's correlation coefficients suggest that for these cell lines and matrices, various combinations of the three measurements display low to medium-high levels of correlation. These findings compare well with previous literature. Our approach provides new tools to measure cellular migration dynamics and address questions on the relationship between cell motility and the microenvironment, using only common microscopy techniques, accessible image analysis applications, and a basic desktop computer for image processing.