Expression of matrix metalloproteinase (MMP)-2, MMP-9, MMP-13, and MT1-MMP in skin tumors of human papillomavirus type 8 transgenic mice

MmuPV1 E7's interaction with PTPN14 delays Epithelial differentiation and contributes to virus-induced skin disease

Human papillomaviruses (HPVs) contribute to approximately 5% of all human cancers. Species-specific barriers limit the ability to study HPV pathogenesis in animal models. Murine papillomavirus (MmuPV1) provides a powerful tool to study the roles of papillomavirus genes in pathogenesis arising from a natural infection. We previously identified Protein Tyrosine Phosphatase Non-Receptor Type 14 (PTPN14), a tumor suppressor targeted by HPV E7 proteins, as a putative cellular target of MmuPV1 E7. Here, we confirmed the MmuPV1 E7-PTPN14 interaction. Based on the published structure of the HPV18 E7/PTPN14 complex, we generated a MmuPV1 E7 mutant, E7K81S, that was defective for binding PTPN14. Wild-type (WT) and E7K81S mutant viral genomes replicated as extrachromosomal circular DNAs to comparable levels in mouse keratinocytes. E7K81S mutant virus (E7K81S MmuPV1) was generated and used to infect FoxN/Nude mice. E7K81S MmuPV1 caused neoplastic lesions at a frequency similar to that of WT MmuPV1, but the lesions arose later and were smaller than WT-induced lesions. The E7K81S MmuPV1-induced lesions also had a trend towards a less severe grade of neoplastic disease. In the lesions, E7K81S MmuPV1 supported the late (productive) stage of the viral life cycle and promoted E2F activity and cellular DNA synthesis in suprabasal epithelial cells to similar degrees as WT MmuPV1. There was a similar frequency of lateral spread of infections among mice infected with E7K81S or WT MmuPV1. Compared to WT MmuPV1-induced lesions, E7K81S MmuPV1-induced lesions had a significant expansion of cells expressing differentiation markers, Keratin 10 and Involucrin. We conclude that an intact PTPN14 binding site is necessary for MmuPV1 E7's ability to contribute to papillomavirus-induced pathogenesis and this correlates with MmuPV1 E7 causing a delay in epithelial differentiation, which is a hallmark of papillomavirus-induced neoplasia.

Expression of collagenases (matrix metalloproteinase-1, -8, -13) and tissue inhibitor of metalloproteinase-3 (TIMP-3) in naturally occurring bovine cutaneous fibropapillomas

Bovine cutaneous fibropapillomas are among the most common skin tumors in cattle; their etiology is associated with infection by bovine papillomavirus (BPV) types-1/-2 which are considered oncogenic. Degradation of the extracellular matrix (ECM), especially collagenolysis, is a key event during a series of relevant physiological processes, including tissue remodeling and repair. Various types of proteins are implicated in the regulation of ECM degradation: among these, matrix metalloproteinases (MMPs), a group of zinc-dependent endoenzymes, and tissue inhibitors of matrix metalloproteinases (TIMPs) are known to play a major role. Previous studies reported that aberrant expression of collagenolytic MMPs (MMP-1/-8/-13) and unbalancing between MMPs and TIMPs represent a critical step in tumor growth and invasion; however, studies regarding this topic in bovine cutaneous fibropapillomas are lacking. The aim of this study was to investigate the expression of the collagenases MMP-1/-8/-13 and TIMP-3 in naturally occurring fibropapillomas harboring BPV-2 DNA and normal skin samples. Here, by immunohistochemistry and western blotting analysis, we demonstrated overexpression of MMP-8/-13 along with a down-regulation of MMP-1, associated with a decrease in TIMP-3 levels in tumor compared with normal skin samples. This is the first study describing MMP-1/-8/-13 and TIMP-3 expression in bovine cutaneous fibropapillomas and our results suggest that an impaired expression of collagenases along with an imbalance between MMPs/TIMPs may contribute to an increased collagenolytic activity, which in turn could be important in ECM changes and tumors development.

Expression of matrix metalloproteinases (MMPs)−2/-7/-9/-14 and tissue inhibitors of MMPs (TIMPs)−1/-2 in bovine cutaneous fibropapillomas associated with BPV-2 infection

Introduction

Bovine papillomaviruses −1/−2 (BPVs) are small non-enveloped double-stranded DNA viruses able to infect the skin of bovids and equids, causing development of neoplastic lesions such as bovine cutaneous fibropapillomas and equine sarcoid. Matrix metalloproteinases (MMPs) are a group of zinc-dependent endopeptidases that degrade basal membrane and extracellular matrix, whose function is essential in physiological processes such as tissue remodeling and wound healing. MMPs activity is finely regulated by a balancing with expression of tissue inhibitors of MMPs (TIMPs), a process that is impaired during tumour development. BPV infection is associated with upregulation of MMPs and /or their unbalancing with TIMPs, contributing to local invasion and impairment of extracellular matrix remodeling in equine sarcoid; however, studies regarding this topic in bovine fibropapillomas are lacking.

Methods

The aim of this study was to perform an immunohistochemical and biochemical analysis on a panel of MMPs and TIMPs in BPV-2 positive bovine cutaneous fibropapillomas vs. normal skin samples.

Results

Immunohistochemistry revealed a cytoplasmic expression of MMP-2 (15/19), a cytoplasmic and perinuclear immunoreactivity of MMP-7 (19/19) and MMP-9 (19/19), along with a cytoplasmic and nuclear pattern of MMP-14 (16/19), accompanied by a cytoplasmic expression of TIMP-1 (14/19) and TIMP-2 (18/19) in tumour samples; western blotting revealed an overexpression of MMP-2 (8/9), MMP-7 (9/9) and MMP-9 (9/9), and a decreased level of MMP-14 (9/9), TIMP-1 (9/9) and TIMP-2 (9/9) in tumour versus normal skin samples. Moreover, gelatine zymography confirmed the expression of pro-active MMP-2 (9/9) and MMP-9 (9/9) and, most importantly, indicated the presence and increased activity of their active forms (82 and 62 kDa, respectively) in tumour samples.

Discussion

This is the first study describing MMPs and TIMPs in bovine cutaneous fibropapillomas and our results suggest that their unbalanced expression in presence of BPV-2 may play a significant role in tumour development. A further analysis of supplementary MMPs and TIMPs could bring new important insights into the papillomavirus induced tumours.

Molecular Mechanisms of MmuPV1 E6 and E7 and Implications for Human Disease

Human papillomaviruses (HPVs) cause a substantial amount of human disease from benign disease such as warts to malignant cancers including cervical carcinoma, head and neck cancer, and non-melanoma skin cancer. Our ability to model HPV-induced malignant disease has been impeded by species specific barriers and pre-clinical animal models have been challenging to develop. The recent discovery of a murine papillomavirus, MmuPV1, that infects laboratory mice and causes the same range of malignancies caused by HPVs provides the papillomavirus field the opportunity to test mechanistic hypotheses in a genetically manipulatable laboratory animal species in the context of natural infections. The E6 and E7 proteins encoded by high-risk HPVs, which are the HPV genotypes associated with human cancers, are multifunctional proteins that contribute to HPV-induced cancers in multiple ways. In this review, we describe the known activities of the MmuPV1-encoded E6 and E7 proteins and how those activities relate to the activities of HPV E6 and E7 oncoproteins encoded by mucosal and cutaneous high-risk HPV genotypes.

Beta HPV Deregulates Double-Strand Break Repair

Beta human papillomavirus (beta HPV) infections are common in adults. Certain types of beta HPVs are associated with nonmelanoma skin cancer (NMSC) in immunocompromised individuals. However, whether beta HPV infections promote NMSC in the immunocompetent population is unclear. They have been hypothesized to increase genomic instability stemming from ultraviolet light exposure by disrupting DNA damage responses. Implicit in this hypothesis is that the virus encodes one or more proteins that impair DNA repair signaling. Fluorescence-based reporters, next-generation sequencing, and animal models have been used to test this primarily in cells expressing beta HPV E6/E7. Of the two, beta HPV E6 appears to have the greatest ability to increase UV mutagenesis, by attenuating two major double-strand break (DSB) repair pathways, homologous recombination, and non-homologous end-joining. Here, we review this dysregulation of DSB repair and emerging approaches that can be used to further these efforts.

HPV8 Reverses the Transcriptional Output in Lrig1 Positive Cells to Drive Skin Tumorigenesis

K14-HPV8-CER transgenic mice express the complete early genome region of human papillomavirus type 8 (HPV8) and develop skin tumours attributed to the expansion of the Lrig1+ stem cell population. The correlation between HPV8-induced changes in transcriptional output in the stem cell compartment remains poorly understood. To further understand the oncogenic pathways underlying skin tumour formation we examined the gene expression network in skin tumours of K14-HPV8-CER mice and compared the differentially expressed genes (DEG) with those of the Lrig1-EGFP-ires-CreERT2 mice. Here, we report 397 DEGs in skin tumours of K14-HPV8-CER mice, of which 181 genes were up- and 216 were down-regulated. Gene ontology and KEGG pathway enrichment analyses suggest that the 397 DEGs are acting in signalling pathways known to be involved in skin homeostasis. Interestingly, we found that HPV8 early gene expression subverts the expression pattern of 23 cellular genes known to be expressed in Lrig1+ keratinocytes. Furthermore, we identified putative upstream regulating transcription factors as well as miRNAs in the control of these genes. These data provide strong evidence that HPV8 mediated transcriptional changes may contribute to skin tumorigenesis, offering new insights into the mechanism of HPV8 driven oncogenesis.

The HPV-18 E7 CKII phospho acceptor site is required for maintaining the transformed phenotype of cervical tumour-derived cells

The Human Papillomavirus E7 oncoprotein plays an essential role in the development and maintenance of malignancy, which it achieves through targeting a number of critical cell control pathways. An important element in the ability of E7 to contribute towards cell transformation is the presence of a Casein Kinase II phospho-acceptor site within the CR2 domain of the protein. Phosphorylation is believed to enhance E7 interaction with a number of different cellular target proteins, and thereby increase the ability of E7 to enhance cell proliferation and induce malignancy. However, there is little information on how important this site in E7 is, once the tumour cells have become fully transformed. In this study, we have performed genome editing of the HPV-18 E7 CKII recognition site in C4-1 cervical tumour-derived cells. We first show that mutation of HPV18 E7 S32/S34 to A32/A34 abolishes CKII phosphorylation of E7, and subsequently we have isolated C4-1 clones containing these mutations in E7. The cells continue to proliferate, but are somewhat more slow-growing than wild type cells, reach lower saturation densities, and are also more susceptible to low nutrient conditions. These cells are severely defective in matrigel invasion assays, partly due to downregulation of matrix metalloproteases (MMPs). Mechanistically, we find that phosphorylation of E7 plays a direct role in the ability of E7 to activate AKT signaling, which in turn is required for optimal levels of MMP secretion. These results demonstrate that the E7 CKII phospho-acceptor site thus continues to play an important role for E7's activity in cells derived from cervical cancers, and suggests that blocking this activity of E7 could be expected to have therapeutic potential.

NF-κB signaling and crosstalk during carcinogenesis

Transcription factors (TFs) are proteins that control the transcription of genetic information from DNA to mRNA by binding to specific DNA sequences either on their own or with other proteins as a complex. TFs thus support or suppress the recruitment of the corresponding RNA polymerase. In general, TFs are classified by structure or function. The TF, Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), is expressed in all cell types and tissues. NF-κB signaling and crosstalk are involved in several steps of carcinogenesis including in sequences involving pathogenic stimulus, chronic inflammation, fibrosis, establishment of its remodeling to the precancerous niche (PCN) and transition of a normal cell to a cancer cell. Triggered by various inflammatory cytokines, NF-κB is activated along with other TFs with subsequent stimulation of cell proliferation and inhibition of apoptosis. The involvement of NF-κB in carcinogenesis provides an opportunity to develop anti-NF-κB therapies. The complexity of these interactions requires that we elucidate those aspects of NF-κB interactions that play a role in carcinogenesis, the sequence of events leading to cancer.

Cutaneous Papillomaviruses and Non-melanoma Skin Cancer: Causal Agents or Innocent Bystanders?

There is still controversy in the scientific field about whether certain types of cutaneous human papillomaviruses (HPVs) are causally involved in the development of non-melanoma skin cancer (NMSC). Deciphering the etiological role of cutaneous HPVs requires - besides tissue culture systems - appropriate preclinical models to match the obtained results with clinical data from affected patients. Clear scientific evidence about the etiology and underlying mechanisms involved in NMSC development is fundamental to provide reasonable arguments for public health institutions to classify at least certain cutaneous HPVs as group 1 carcinogens. This in turn would have implications on fundraising institutions and health care decision makers to force - similarly as for anogenital cancer - the implementation of a broad vaccination program against "high-risk" cutaneous HPVs to prevent NMSC as the most frequent cancer worldwide. Precise knowledge of the multi-step progression from normal cells to cancer is a prerequisite to understand the functional and clinical impact of cofactors that affect the individual outcome and the personalized treatment of a disease. This overview summarizes not only recent arguments that favor the acceptance of a viral etiology in NMSC development but also reflects aspects of causality in medicine, the use of empirically meaningful model systems and strategies for prevention.

Molecular Mechanisms of Human Papillomavirus Induced Skin Carcinogenesis

Infection of the cutaneous skin with human papillomaviruses (HPV) of genus betapapillomavirus (βHPV) is associated with the development of premalignant actinic keratoses and squamous cell carcinoma. Due to the higher viral loads of βHPVs in actinic keratoses than in cancerous lesions, it is currently discussed that these viruses play a carcinogenic role in cancer initiation. In vitro assays performed to characterize the cell transforming activities of high-risk HPV types of genus alphapapillomavirus have markedly contributed to the present knowledge on their oncogenic functions. However, these assays failed to detect oncogenic functions of βHPV early proteins. They were not suitable for investigations aiming to study the interactive role of βHPV positive epidermis with mesenchymal cells and the extracellular matrix. This review focuses on βHPV gene functions with special focus on oncogenic mechanisms that may be relevant for skin cancer development.

HPV16-E2 protein modifies self-renewal and differentiation rate in progenitor cells of human immortalized keratinocytes

BACKGROUND

Cervical cancer is the fourth cause of death worldwide by cancer in women and is a disease associated to persistent infection with human papillomavirus (HPV), particularly from two high-risk types HPV16 and 18. The virus initiates its replicative cycle infecting cells located in the basal layer of the epithelium, where a small population of epithelial stem cells is located performing important functions of renewal and maintenance of the tissue. Viral E2 gene is one of the first expressed after infection and plays relevant roles in the replicative cycle of the virus, modifying fundamental processes in the infected cells. Thus, the aim of the present study was to demonstrate the presence of hierarchic subpopulations in HaCaT cell line and evaluate the effect of HPV16-E2 expression, on their biological processes.

METHODS

HaCaT-HPV16-E2 cells were generated by transduction of HaCaT cell line with a lentiviral vector. The α6-integrin-CD71 expression profile was established by immunostaining and flow cytometric analysis. After sorting, cell subpopulations were analyzed in biological assays for self-renewal, clonogenicity and expression of stemness factors (RT-qPCR).

RESULTS

We identified in HaCaT cell line three different subpopulations that correspond to early differentiated cells (α6-integrin^dim), transitory amplifying cells (α6-integrin^bri/CD71^bri) and progenitor cells (α6-integrin^bri/CD71^dim). The last subpopulation showed stem cell characteristics, such as self-renewal ability, clonogenicity and expression of the well-known stem cell factors SOX2, OCT4 and NANOG, suggesting they are stem-like cells. Interestingly, the expression of HPV16-E2 in HaCaT cells changed its α6-integrin-CD71 immunophenotype modifying the relative abundance of the cell subpopulations, reducing significantly the percentage of α6-integrin^bri/CD71^dim cells. Moreover, the expression of the stem cell markers was also modified, increasing the expression of SOX2 and NANOG, but decreasing notably the expression of OCT4.

CONCLUSIONS

Our data demonstrated the presence of a small subpopulation with epithelial "progenitor cells" characteristics in the HaCaT cell line, and that HPV16-E2 expression on these cells induces early differentiation.

Recent advances in preclinical model systems for papillomaviruses

Preclinical model systems to study multiple features of the papillomavirus life cycle have greatly aided our understanding of Human Papillomavirus (HPV) biology, disease progression and treatments. The challenge to studying HPV in hosts is that HPV along with most PVs are both species and tissue restricted. Thus, fundamental properties of HPV viral proteins can be assessed in specialized cell culture systems but host responses that involve innate immunity and host restriction factors requires preclinical surrogate models. Fortunately, there are several well-characterized and new animal models of papillomavirus infections that are available to the PV research community. Old models that continue to have value include canine, bovine and rabbit PV models and new rodent models are in place to better assess host-virus interactions. Questions arise as to the strengths and weaknesses of animal PV models for HPV disease and how accurately these preclinical models predict malignant progression, vaccine efficacy and therapeutic control of HPV-associated disease. In this review, we examine current preclinical models and highlight the strengths and weaknesses of the various models as well as provide an update on new opportunities to study the numerous unknowns that persist in the HPV research field.

Nuclear export of cutaneous HPV8 E7 oncoprotein is mediated by a leucine-rich nuclear export signal via a CRM1 pathway

We recently determined that the nuclear import of cutaneous beta genus HPV8 E7 oncoprotein it is mediated by its zinc-binding domain via direct hydrophobic interactions with the FG nucleoporins Nup62 and Nup153 (Onder and Moroianu, 2014). Here we investigated the nuclear export of HPV8 E7 oncoprotein using confocal microscopy after transfections of HeLa cells with EGFP-8cE7 and mutant plasmids and treatment with Ratjadone A nuclear export inhibitor. We determined that HPV8 E7 contains a leucine-rich nuclear export signal (NES), 76IRTFQELLF84, within its zinc-binding domain that mediates its nuclear export via a CRM1 pathway. We found that HPV8 E7 interacts with CRM1 and that the hydrophobic amino acid residues I76, F79 and L82 of the NES are essential for this interaction and for nuclear export of HPV8 E7 oncoprotein.

Matrix metalloproteinases and genetic mouse models in cancer research: a mini-review

Carcinogenesis is a multistep and also a multifactorial process that involves agents like genetic and environmental factors. Matrix metalloproteinases (MMPs) are major proteolytic enzymes which are involved in cancer cell migration, invasion, and metastasis. Genetic variations in genes encoding the MMPs were shown in human studies to influence cancer risk and phenotypic features of a tumor. The complex role of MMPs seems to be important in the mechanism of carcinogenesis, but it is not well recognized. Rodent studies concentrated particularly on the better understanding of the biological functions of the MMPs and their impact on the pathological process, also through the modification of Mmp genes. This review presents current knowledge and the existing evidence on the importance of selected MMPs in genetic mouse models of cancer and human genetic association studies. Further, this work can be useful for scientists studying the role of the genetic impact of MMPs in carcinogenesis.

Nuclear import of cutaneous beta genus HPV8 E7 oncoprotein is mediated by hydrophobic interactions between its zinc-binding domain and FG nucleoporins

We have previously discovered and characterized the nuclear import pathways for the E7 oncoproteins of mucosal alpha genus HPVs, type 16 and 11. Here we investigated the nuclear import of cutaneous beta genus HPV8 E7 protein using confocal microscopy after transfections of HeLa cells with EGFP-8E7 and mutant plasmids and nuclear import assays in digitonin-permeabilized HeLa cells. We determined that HPV8 E7 contains a nuclear localization signal (NLS) within its zinc-binding domain that mediates its nuclear import. Furthermore, we discovered that a mostly hydrophobic patch 65LRLFV69 within the zinc-binding domain is essential for the nuclear import and localization of HPV8 E7 via hydrophobic interactions with the FG nucleoporins Nup62 and Nup153. Substitution of the hydrophobic residues within the 65LRLFV69 patch to alanines, and not R66A mutation, disrupt the interactions between the 8E7 zinc-binding domain and Nup62 and Nup153 and consequently inhibit nuclear import of HPV8 E7.

The papillomavirus E2 proteins

The papillomavirus E2 proteins are pivotal to the viral life cycle and have well characterized functions in transcriptional regulation, initiation of DNA replication and partitioning the viral genome. The E2 proteins also function in vegetative DNA replication, post-transcriptional processes and possibly packaging. This review describes structural and functional aspects of the E2 proteins and their binding sites on the viral genome. It is intended to be a reference guide to this viral protein.

Host-derived MMP-13 exhibits a protective role in lung metastasis of melanoma cells by local endostatin production

Background:

Although matrix metalloproteinases (MMPs) are implicated in tumourigenesis and cancer progression, the role of MMP-13 in melanoma cell metastases is poorly understood.

Methods:

Lung metastases of mouse melanoma B16BL6 cells were analysed in MMP-13 knockout (KO) and wild-type (WT) mice after intravenous injection. The mRNA and protein expression of MMP-13 in lung tissues was analysed by RT–PCR, real-time PCR, immunoblotting and immunohistochemistry. The expression of SDF-1α, CXCR4 and endostatin, and effects of endostatin to cultured melanoma cells and lung metastases were also studied.

Results:

Lung metastases of B16BL6 cells were significantly higher by 2.5–5.7-fold in MMP-13 KO mice than in WT mice. The expression of MMP-13 in WT mouse lung tissue was stimulated on day 1 after intravenous injection of the melanoma cells and MMP-13 was immunolocalised to vascular endothelial cells in the lungs. Endostatin formation, but not degradation of SDF-1α, in the lung tissue was associated with reduced lung metastasis in WT mice. Endostatin significantly inhibited migration of B16BL6 cells in monolayer wounding assay and remarkably suppressed Matrigel invasion and transendothelial invasion of the cells. In addition, lung metastases of melanoma cells in MMP-13 KO mice were reduced by intraperitoneal administration of endostatin.

Conclusion:

Our results suggest that MMP-13 is overproduced by endothelial cells in the lungs with melanoma cells and has a protective role in lung metastasis by local generation of endostatin.

The E2 protein of human papillomavirus type 8 increases the expression of matrix metalloproteinase-9 in human keratinocytes and organotypic skin cultures

Non-melanoma skin cancer (NMSC) is the most frequent human cancer of Caucasian populations. Although the ultraviolet irradiation is a key contributor to the establishment of this keratinocyte malignancy, the infection by some types of human papillomavirus (HPV) has also been implicated in NMSC development. Cancers occur as a result of a complex series of interactions between the cancer cell and its surrounding matrix. The matrix metalloproteinases (MMPs) play a role in degrading the extracellular matrix. MMP9 is an important gelatinase involved in processes such as cell migration, invasion and metastasis. In this report, we demonstrated by EMSA experiments that the MMP9 promoter contains a binding site for the transcriptional regulator E2 of HPV8. Transient reporter gene assays showed that HPV8-E2 activated the MMP9 promoter in a dose-dependent manner in human epidermal keratinocytes. An E2 transactivation-defective mutant (I73L) as well as a DNA-binding deficient mutant (R433K) demonstrated no activation of the MMP9 promoter, suggesting that both an intact transactivation and DNA-binding domain are required for E2 activation of the MMP9-promoter. The functional role of the E2 binding site within the MMP9 promoter was also confirmed by mutating the E2 binding site. In organotypic cultures of human skin, an overexpression of MMP9 was observed in suprabasal layers of the HPV8 E2-expressing epidermis thus confirming the results of the monolayer cultures. These results demonstrate that the early gene E2 of HPV8 is able to increase the expression of MMP9 by direct activation of the MMP9-promoter.

Lgl2 executes its function as a tumor suppressor by regulating ErbB signaling in the zebrafish epidermis

Changes in tissue homeostasis, acquisition of invasive cell characteristics, and tumor formation can often be linked to the loss of epithelial cell polarity. In carcinogenesis, the grade of neoplasia correlates with impaired cell polarity. In Drosophila, lethal giant larvae (lgl), discs large (dlg), and scribble, which are components of the epithelial apico-basal cell polarity machinery, act as tumor suppressors, and orthologs of this evolutionary conserved pathway are lost in human carcinoma with high frequency. However, a mechanistic link between neoplasia and vertebrate orthologs of these tumor-suppressor genes remains to be fully explored at the organismal level. Here, we show that the pen/lgl2 mutant phenotype shares two key cellular and molecular features of mammalian malignancy: cell autonomous epidermal neoplasia and epithelial-to-mesenchymal-transition (EMT) of basal epidermal cells including the differential expression of several regulators of EMT. Further, we found that epidermal neoplasia and EMT in pen/lgl2 mutant epidermal cells is promoted by ErbB signalling, a pathway of high significance in human carcinomas. Intriguingly, EMT in the pen/lgl2 mutant is facilitated specifically by ErbB2 mediated E-cadherin mislocalization and not via canonical snail-dependent down-regulation of E-cadherin expression. Our data reveal that pen/lgl2 functions as a tumor suppressor gene in vertebrates, establishing zebrafish pen/lgl2 mutants as a valuable cancer model.

Effects of human papillomavirus type 16 E5 deletion mutants on epithelial morphology: functional characterization of each transmembrane domain

Human papillomavirus type 16 (HPV-16) is the cause of cervical cancer. The HPV genome encodes three transforming proteins, E5, E6 and E7. E6 and E7 are the main transforming proteins of HPV, while the role of E5 is still poorly understood. Using three dimensional organotypic raft cultures we show that HaCaT human keratinocytes expressing HPV-16 E5 form a very perturbed epithelium, with simultaneous hyperkeratinization of some cells and defective differentiation of other cells. The basal layer is disturbed and many cells invade the collagen matrix. Many cells among the differentiated layers show characteristics of basal cells: progression through the cell cycle, expression of cytokeratin 14, lack of cytokeratin 1 and production of matrix metalloproteases (MMP). Using deletion mutants which encompass the three hydrophobic domains of E5, we have assigned the ability to promote invasion of the matrix to the first hydrophobic domain, and the capacity to induce MMP9 to the C-terminal four amino acids. We also show that invasion and production of MMP9 can be dissociated, as mutants that are still capable of invasion do not produce MMP9 and vice versa.

Mechanical stretching modulates growth direction and MMP-9 release in human keratinocyte monolayer

Cells within human skin are exposed to mechanical stretching that is considered a trigger stimulus for keratinocyte proliferation, while its effect on keratinocyte migration has been poorly investigate. In order to explore the effect of stretching on keratinocyte migration spontaneously immortalized human keratinocyte (HaCaT) monolayers seeded onto collagen I-coated silicon sheets were stimulated 3 times for 1 hour every 24 hours (total time = 72 hours) by mechanical stretching increasing substrate deformations (10%) applied both as static (0 Hz) and cyclic (0.17 Hz) uniaxial stretching. At the end of stimulations monolayer areas measured in both static and cyclic samples appeared reduced and strongly oriented in a direction perpendicular to the stress direction compared to unstimulated ones. Moreover during the mechanical stimulation period HaCaT monolayers strongly increased the release in the medium of matrix metalloproteinase 9 (MMP-9), a proteolytic enzyme necessary for keratinocyte migration.

Stromal expression of MMP-13 is required for melanoma invasion and metastasis

Tumor invasion and metastasis of malignant melanoma have been shown to require proteolytic degradation of the extracellular environment achieved primarily by enzymes of the matrix metalloproteinases (MMP) family. We have earlier shown that increased enzyme activity is localized at the border of tumor cells and the adjacent peritumoral connective tissue, emphasizing the importance of tumor-stroma interactions in the regulation of MMP activity. To confirm the role of stroma-derived MMP-13 in the invasion process, we investigated the invasiveness of melanoma cells upon intradermal injection in mice with complete inactivation of MMP-13. Tumor growth was significantly impaired in mmp-13(-/-) mice and most significant at early time points as compared with wild-type littermates. Moreover, metastasis to various organs was reduced to 17.6 vs 30% in lungs, 2.9 vs 30% in the liver. Strikingly, ablation of MMP-13 completely abrogated formation of metastasis in the heart (0 vs 40%). Notably, decreased tumor growth in mmp-13(-/-) mice was associated with reduced blood vessel density. In addition, decreased blood vessel permeability in the tumors was measured by magnetic resonance imaging of tumor-bearing animals. These data suggest an important role of MMP-13 in tumor growth and an unexpected role in organ-specific metastasis of melanoma cells.

Ets1 induces dysplastic changes when expressed in terminally-differentiating squamous epidermal cells

BACKGROUND

Ets1 is an oncogene that functions as a transcription factor and regulates the activity of many genes potentially important for tumor initiation and progression. Interestingly, the Ets1 oncogene is over-expressed in many human squamous cell cancers and over-expression is highly correlated with invasion and metastasis. Thus, Ets1 is believed to mainly play a role in later stages of the oncogenic process, but not early events.

METHODOLOGY/PRINCIPAL FINDINGS

To better define the role of Ets1 in squamous cell carcinogenesis, we generated a transgenic mouse model in which expression of the Ets1 oncogene could be temporally and spatially regulated. Upon Ets1 induction in differentiating cells of stratified squamous epithelium, these mice exhibited dramatic changes in epithelial organization including increased proliferation and blocked terminal differentiation. The phenotype was completely reversed when Ets1 expression was suppressed. In mice where Ets1 expression was re-induced at a later age, the phenotype was more localized and the lesions that developed were more invasive. Many potential Ets1 targets were upregulated in the skin of these mice with the most dramatic being the metalloprotease MMP13, which we demonstrate to be a direct transcriptional target of Ets1.

CONCLUSIONS/SIGNIFICANCE

Collectively, our data reveal that upregulation of Ets1 can be an early event that promotes pre-neoplastic changes in epidermal tissues via its regulation of key genes driving growth and invasion. Thus, the Ets1 oncogene may be important for oncogenic processes in both early and late stages of tumor development.

Heat-induced MMP-1 expression is mediated by TRPV1 through PKCalpha signaling in HaCaT cells

BACKGROUND

Matrix metalloproteinase-1 (MMP-1) is considered a key initiator of collagen degradation in inflammatory responses. A heat-gated channel, transient receptor potential vanilloid type 1 (TRPV1), induces release of proinflammatory mediators. TRPV1 channels have been localized to the epidermis and we have recently suggested that they act as mediators of heat-induced MMP-1. The aim of this study was to investigate the signaling of TRPV1 in MMP-1 regulation by heat shock in human epidermal keratinocytes.

METHODS

Heat shock-induced MMP-1 expression was decreased by treatment with TRPV1 inhibitor. The heat-induced MMP-1 expression was suppressed by Gö6976 [calcium-dependent inhibitor] and staurosporine (ST, broad-spectrum PKC inhibitor), while rottlerin (ROT, calcium-independent PKCdelta inhibitor) had no effect. Also, transfection of PKCalpha siRNA decreased MMP-1 expression, whereas MMP-1 expression was not significantly affected in cells transfected with negative control siRNA, PKCbeta siRNA or PKCdelta siRNA.

RESULTS

We demonstrated that heat shock failed to induce MMP-1 expression in HaCaT cells cultured in calcium-free media. The heat-induced [Ca(2+)](i) increase was inhibited by Gö6976 and ST, but not by ROT. We also found that heat-induced phosphorylation of ERK, JNK and p38 MAPK in HaCaT cells, but capsazepine and ruthenium red had no effect on this activation. In addition to the role of TRPV1 in heat-induced MMP-1 expression, we also found that heat increased TRPV1 proteins in human skin in vivo.

CONCLUSIONS

Our results suggest that TRPV1 mediates heat shock-induced MMP-1 expression via calcium-dependent PKCalpha signaling in HaCaT cells.

An armamentarium of wart treatments

Patients and clinicians experience the frustration of cutaneous viral warts caused by infection with the human papilloma virus (HPV).Warts appear in various forms on different sites of the body and include common warts (verruca vulgaris), plane or flat warts, myrmecia, plantar warts, coalesced mosaic warts, filiform warts, periungual warts, anogenital warts (venereal or condyloma acuminata), oral warts and respiratory papillomas. Cervical infection with HPV is now known to cause cervical cancer if untreated. A review of the medical literature reveals a huge armamentarium of wart monotherapies and combination therapies. Official evidence-based guidelines exist for the treatment of warts, but very few of the reported treatments have been tested by rigorous blinded, randomized controlled trials.Therefore, official recommendations do not often include treatments with reportedly high success rates, but they should not be ignored when considering treatment options. It is the purpose of this review to provide a comprehensive overview of the wart treatment literature to expand awareness of the options available to practitioners faced with patients presenting with problematic warts.

HPV-associated skin disease

Human papillomaviruses (HPVs) are DNA tumour viruses that induce hyperproliferative lesions in cutaneous and mucosal epithelia. The relationship between HPV and non-melanoma skin cancer (NMSC) is important clinically since NMSC is the most common form of malignancy among fair-skinned populations. It is well established that solar ultraviolet (UV) irradiation is the major risk factor for developing NMSC, but a pathogenic role for HPV in the development of NMSC has also been proposed. Recent molecular studies reveal a likely role for HPV infection in skin carcinogenesis as a co-factor in association with UV. This review summarizes the literature describing these data, highlights some of the important findings derived from these studies, and speculates on future perspectives.