SAGE profiling of UV-induced mouse skin squamous cell carcinomas, comparison with acute UV irradiation effects

A Review on Caspases: Key Regulators of Biological Activities and Apoptosis

Caspases are proteolytic enzymes that belong to the cysteine protease family and play a crucial role in homeostasis and programmed cell death. Caspases have been broadly classified by their known roles in apoptosis (caspase-3, caspase-6, caspase-7, caspase-8, and caspase-9 in mammals) and in inflammation (caspase-1, caspase-4, caspase-5, and caspase-12 in humans, and caspase-1, caspase-11, and caspase-12 in mice). Caspases involved in apoptosis have been subclassified by their mechanism of action as either initiator caspases (caspase-8 and caspase-9) or executioner caspases (caspase-3, caspase-6, and caspase-7). Caspases that participate in apoptosis are inhibited by proteins known as inhibitors of apoptosis (IAPs). In addition to apoptosis, caspases play a role in necroptosis, pyroptosis, and autophagy, which are non-apoptotic cell death processes. Dysregulation of caspases features prominently in many human diseases, including cancer, autoimmunity, and neurodegenerative disorders, and increasing evidence shows that altering caspase activity can confer therapeutic benefits. This review covers the different types of caspases, their functions, and their physiological and biological activities and roles in different organisms.

Programmed gene expression change in mouse skin after ultraviolet radiation damage

Ultraviolet (UV) radiation is a major cause of skin damage and carcinogenesis. Here, we systematically analyse the acute gene expression change in skin in vivo after UV exposure, aiming to establish the common C57BL/6 mouse strain as a convenient model for future pathological research and drug discovery. The back fur of C57BL/6 mice was depilated, and a mixed UV light source was used to irradiate the skin. Full-thickness skin samples were collected at 0, 0.5, 2, 6, 12 and 24 h. Total RNAs were extracted and subjected to RNA sequencing analysis. We found that the gene expression change in mouse skin is highly similar to previous reports in human skin. These include down-regulation of differentiation-related genes and extracellular matrix genes, and up-regulation of cytokine/chemokine genes. An early wave of activator protein 1 (AP-1) expression is induced, whereas activation of the p53 pathway is not significant. The impact of the AP-1 transcription factors and the antioxidant tea polyphenols is discussed. The analysis of acute gene expression change in skin after UV irradiation provides a starting point to investigate how the skin responds to genotoxic stress.

Solar UVR and Variations in Systemic Immune and Inflammation Markers

The characterization of the effects of solar UVR on a broad set of circulating markers in systemic immunity and inflammation may provide insight into the mechanisms responsible for the UVR associations observed for several benign and malignant diseases. We examined the associations between exposure to solar UVR and circulating levels of 78 markers among 1,819 individuals aged 55–74 years who participated in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial using multiplex assays. Solar UVR was derived by linking the geocoded locations of 10 screening centers across the continental United States and the date of blood draw to the National Solar Radiation Database from 1993 to 2005. We assessed associations between ambient solar UVR and dichotomized marker levels using adjusted weighted logistic regression models and applied a 5% false discovery rate criterion to P-values. UVR exposure was associated (P < 0.05) with 9 of the 78 markers. CCL27, CCL4, FGF2, GM-CSF, IFN-γ, soluble IL4R, IL-7, and IL-11 levels were lower with increasing UVR tertile, with adjusted ORs ranging from 0.66 to 0.80, and the significant association for CCL27 withstood multiple comparison correction. In contrast, CRP levels were elevated with increasing UVR. Solar UVR was associated with alterations in systemic immune and inflammation marker levels.

Desmosomes as Signaling Hubs in the Regulation of Cell Behavior

Desmosomes are intercellular junctions, which preserve tissue integrity during homeostatic and stress conditions. These functions rely on their unique structural properties, which enable them to respond to context-dependent signals and transmit them to change cell behavior. Desmosome composition and size vary depending on tissue specific expression and differentiation state. Their constituent proteins are highly regulated by posttranslational modifications that control their function in the desmosome itself and in addition regulate a multitude of desmosome-independent functions. This review will summarize our current knowledge how signaling pathways that control epithelial shape, polarity and function regulate desmosomes and how desmosomal proteins transduce these signals to modulate cell behavior.

Caspase-14-From Biomolecular Basics to Clinical Approach. A Review of Available Data

Caspase-14 is a unique member of the caspase family-a family of molecules participating in apoptosis. However, it does not affect this process but regulates another form of programmed cell death-cornification, which is characteristic of the epidermis. Therefore, it plays a crucial role in the formation of the skin barrier. The cell death cycle has been a subject of interest for researchers for decades, so a lot of research has been done to expand the understanding of caspase-14, its role in cell homeostasis and processes affecting its expression and activation. Conversely, it is also an interesting target for clinical researchers searching for its role in the physiology of healthy individuals and its pathophysiology in particular diseases. A summary was done in 2008 by Denecker et al., concentrating mostly on the biotechnological aspects of the molecule and its physiological role. However, a lot of new data have been reported, and some more practical and clinical research has been conducted since then. The majority of studies tackled the issue of clinical data presenting the role of caspase in the etiopathology of many diseases such as retinal dysfunctions, multiple malignancies, and skin conditions. This review summarizes the available knowledge on the molecular and, more interestingly, the clinical aspects of caspase-14. It also presents how theoretical science may pave the way for medical research. Methods: The authors analyzed publications available on PubMed until 21 March 2021, using the search term "caspase 14".

Application of omics technologies in dermatological research and skin management

BACKGROUND

"Omics" are usually based on the use of high-throughput analysis methods for global analysis of biological samples and the discovery of biomarkers, and may provide new insights into biological phenomena. Over the last few years, the development of omics technologies has considerably accelerated the pace of dermatological research.

AIMS

The purpose of this article was to review the development of omics in recent decades and their application in dermatological research.

METHODS

An extensive literature search was conducted on omics technologies since the first research on omics.

RESULTS

This article summarizes the history and main research methods of the six omics technologies, including genomics, transcriptomics, proteomics, metabolomics, lipidomics, and microbiomics. Their application in certain skin diseases and cosmetics research and development are also summarized.

CONCLUSIONS

This information will help to understand the mechanism of some skin diseases and the discovery of potential biomarkers, and provide new insights for skin health management and cosmetics research and development.

Time dependent ultrastructural alterations on the skin, eye, barbel and fins of the spawn of Clarias batrachus (Linn. 1758) exposed to UV-B radiation

Present study highlighted the ultramicroscopic (SEM) alterations of the skin, eye, barbel, and fins of spawn of an air-breathing teleost (Clarias batrachus, Linn. 1758) induced by UV-B radiation (280-320 nm) at a dose (@4.07 × 10^-20J/photon/m²) under the time-frame of 5, 10 and 15 min/d in the laboratory condition for the periods of 5 and 10 days. Limnological parameters revealed no significant changes throughout the period of experimentation which were measured by PCS Testr 35 Multi-Parameter. Morphometric analysis revealed that during the extended exposure period of 10 days the spawn size and weight were reduced as analysed through Specific Growth Rate (SGR). SGR values in terms of weight for 5 and 10 days under 3 time-frames were 17.12%, 12.52%, 11.46% and 9.09%, 6.43%, 6.09% respectively, which revealed a declined trend along with the exposure days. In the skin of C. batrachus, the compact regular orientation of the stratified epithelial cells and mucous cells became distorted and the microridges and double-ridged structures showed destruction and fragmentations. The body striations and microfolds became shrinked and swollen and finally degenerated to form a mass. The distribution of mucous cells throughout the epidermis was disorganised and releasing secretory contents on the surface through small pores. Appearance of huge quantity of biogenic semi-hexagonal plate like crystals (guanine platelets) on the skin surface of the body was the most significant observations during UV-B radiation. In the developmental phases the eyeball showed shrinkage loosing normal regular concave structure and to become a dome-shaped one. The supportive connective infoldings became loosened. The choroid coat displayed deformities and the iris deformed the pupil. The fibroblast on the epithelium and melanocytes depicted dispersed arrangement. The pairs of ventral barbels near the mouth depicted the presence of taste buds that became severely damaged exposing the sensory as well as neuroepithelial cells. Compact regular arrangement of the SECs was completely destroyed leaving long and deep channels inbetween them; the disintegrated concentric MRs also showed a mass.

Important role of kallikrein 6 for the development of keratinocyte proliferative resistance to topical glucocorticoids

One of the major adverse effects of topical glucocorticoids is cutaneous atrophy often followed by development of resistance to steroids (tachyphylaxis). Previously we showed that after two weeks, interfollicular mouse keratinocytes acquired resistance to anti-proliferative effects of glucocorticoid fluocinolone acetonide (FA). One of the top genes activated by FA during tachyphylaxis was Klk6 encoding kallikrein-related peptidase 6, known to enhance keratinocyte proliferation. KLK6 was also strongly induced by chronic glucocorticoids in human skin. Double immunostaining showed that KLK6⁺ keratinocytes, localized in suprabasal layer of mouse skin, were frequently adjacent to proliferating 5-bromo-2'-deoxyuridine-positive basal keratinocytes. We used KLK6 knockout (KO) mice to evaluate KLK6 role in skin regeneration after steroid-induced atrophy. KLK6 KOs had thinner epidermis and decreased keratinocyte proliferation. The keratinocytes in wild type and KLK6 KO epidermis were equally sensitive to acute anti-proliferative effect of FA. However, the development of proliferative resistance during chronic treatment was reduced in KO epidermis. This was not due to the changes in glucocorticoid receptor (GR) expression or function as GR protein level and induction of GR-target genes were similar in wild type and KLK6 KO skin. Overall, these results suggest a novel mechanism of epidermal regeneration after glucocorticoid-induced atrophy via KLK6 activation.

DSS1 promoter hypomethylation and overexpression predict poor prognosis in melanoma and squamous cell carcinoma patients

Previous studies have found a link between high expression levels of the Deleted in Split hand/Split foot 1 (DSS1) gene and cancer progression. The aim of this study was to examine whether overexpression of DSS1 is a feature of melanoma and squamous cell carcinoma (SCC) and if any epigenetic modifications are involved. Evaluation of DSS1 expression profile indicated that the gene is overexpressed in 112 of 130 cutaneous melanomas (86.1%), 41 of 64 uveal melanomas (64.1%), 67 of 82 mucosal melanomas (81.7%), and 61 of 75 SCC samples (81.3%), relative to normal skin. An inverse correlation between DSS1 expression and methylation status of the promoter was found. In vitro studies showed that treatment of DSS1-methylated melanoma and SCC cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine significantly increased DSS1 expression at mRNA and protein levels. Interestingly, a significant association between high DSS1 expression levels and some clinicopathological variables, such as metastasis, ulceration, and reduced overall/disease-free survival was observed. In summary, these data suggest that the extent of promoter methylation plays a role in modulating DSS1 gene expression and highlight that promoter hypomethylation is a frequent event in melanoma and SCC closely linked to poor prognosis.

Cross-species identification of genomic drivers of squamous cell carcinoma development across preneoplastic intermediates

Cutaneous squamous cell carcinoma (cuSCC) comprises 15-20% of all skin cancers, accounting for over 700,000 cases in USA annually. Most cuSCC arise in association with a distinct precancerous lesion, the actinic keratosis (AK). To identify potential targets for molecularly targeted chemoprevention, here we perform integrated cross-species genomic analysis of cuSCC development through the preneoplastic AK stage using matched human samples and a solar ultraviolet radiation-driven Hairless mouse model. We identify the major transcriptional drivers of this progression sequence, showing that the key genomic changes in cuSCC development occur in the normal skin to AK transition. Our data validate the use of this ultraviolet radiation-driven mouse cuSCC model for cross-species analysis and demonstrate that cuSCC bears deep molecular similarities to multiple carcinogen-driven SCCs from diverse sites, suggesting that cuSCC may serve as an effective, accessible model for multiple SCC types and that common treatment and prevention strategies may be feasible.

Desmosomes: regulators of cellular signaling and adhesion in epidermal health and disease

Desmosomes are intercellular junctions that mediate cell-cell adhesion and anchor the intermediate filament network to the plasma membrane, providing mechanical resilience to tissues such as the epidermis and heart. In addition to their critical roles in adhesion, desmosomal proteins are emerging as mediators of cell signaling important for proper cell and tissue functions. In this review we highlight what is known about desmosomal proteins regulating adhesion and signaling in healthy skin-in morphogenesis, differentiation and homeostasis, wound healing, and protection against environmental damage. We also discuss how human diseases that target desmosome molecules directly or interfere indirectly with these mechanical and signaling functions to contribute to pathogenesis.

Aberrant expression of caspase 14 in salivary gland carcinomas

OBJECTIVES

Caspase 14 is reduced in adenocarcinomas of the stomach and colon. In contrast, breast and lung adenocarcinomas frequently show an overexpression of caspase 14. Salivary gland adenocarcinomas have not been evaluated for potential aberrant caspase 14 expression.

MATERIALS AND METHODS

Samples from salivary gland carcinomas (n = 43) were analysed by immunohistochemistry (caspase 14, filaggrin, GATA3 and Ki67) and fluorescence in situ hybridization.

RESULTS

Caspase 14 is not expressed in normal salivary glands, while in a subfraction of carcinomas (32%) an aberrant expression was found. Filaggrin could not be detected. Caspase 14 staining was not associated with tumour dedifferentiation, GATA3 expression or amplification of gene locus 19p13.

CONCLUSION

In summary, aberrant expression of caspase 14 can be found in a subfraction of salivary gland carcinomas but could not be used as a biomarker for a specific carcinoma subtype of the salivary gland.

The desmosomal protein desmoglein 1 aids recovery of epidermal differentiation after acute UV light exposure

Epidermal structure is damaged by exposure to UV light, but the molecular mechanisms governing structural repair are largely unknown. UVB (290-320 nm wavelengths) exposure before induction of differentiation reduced expression of differentiation-associated proteins, including desmoglein 1 (Dsg1), desmocollin 1 (Dsc1), and keratins 1 and 10 (K1/K10), in a dose-dependent manner in normal human epidermal keratinocytes (NHEKs). The UVB-induced reduction in both Dsg1 transcript and protein was associated with reduced binding of the p63 transcription factor to previously unreported enhancer regulatory regions of the Dsg1 gene. As Dsg1 promotes epidermal differentiation in addition to participating in cell-cell adhesion, the role of Dsg1 in aiding differentiation after UVB damage was tested. Compared with controls, depleting Dsg1 via short hairpin RNA resulted in further reduction of Dsc1 and K1/K10 expression in monolayer NHEK cultures and in abnormal epidermal architecture in organotypic skin models recovering from UVB exposure. Ectopic expression of Dsg1 in keratinocyte monolayers rescued the UVB-induced differentiation defect. Treatment of UVB-exposed monolayer or organotypic cultures with trichostatin A, a histone deacetylase inhibitor, partially restored differentiation marker expression, suggesting a potential therapeutic strategy for reversing UV-induced impairment of epidermal differentiation after acute sun exposure.

Regulation of HIF-1 alpha by the proprotein convertases furin and PC7 in human squamous carcinoma cells

Proprotein convertases (PC), a family of serine proteases, process cancer-related substrates such as growth factors, growth factor receptors, cell adhesion molecules, metalloproteinases, etc. HIF-1α is a major transcription factor involved in tumorigenesis by sensing intratumoral hypoxia. Furin (PCSK3) is one of the numerous target genes regulated by HIF-1α transactivation and its distribution into endosomal compartments and onto the cell surface can be triggered by hypoxia via HIF-1α. siRNAs to knockdown PCs were transfected into cells alone or in combination with different drug treatments. Protein and RNA expression levels were analyzed by Western blotting or RT-PCR, respectively. PC7 (PCSK7) and furin siRNAs upregulated HIF-1α protein under normoxic condition to a level similar to that obtained by cobalt chloride treatment, eventually leading to activation of VEGF-A synthesis in two human head and neck squamous cell carcinoma cell lines. The unchanged levels of HIF-1α mRNA expression under siRNA treatment and the additive HIF-1α induction of PC siRNAs and either cobalt chloride or the 26S ribosome inhibitor, MG-132, suggested a post-transcriptional PC-mediated regulation. Furthermore, cycloheximide chase showed that PC7/furin siRNA regulation occurred at the level of HIF-1α translation. A specific IGF-1R signaling inhibitor was able to attenuate the PC siRNA induction of HIF-1α, suggesting the involvement of the IGF-1R pathway. Thus, the data show that PCs regulate HIF-1α. Furin and PC7 siRNAs induced HIF-1α protein by increasing its translation, resulting in upregulation of VEGF-A. This finding may provide insight into intricate PC functions that seem to be independent from their substrate-processing activity.

Identification of the deleted in split hand/split foot 1 protein as a novel biomarker for human cervical cancer

The morphological detection of early neoplastic transformation leading to cervical cancer remains problematic. In this work, we have identified deleted in split hand/split foot 1 protein (DSS1) as an early biomarker that is specifically upregulated in premalignant and malignant cervical epithelial cells, but is low or undetectable in non-malignant cells. DSS1 mRNA and protein levels are significantly increased in cultured human cervical carcinoma cell lines originating from primary and metastatic tumors. In fact, > 96% of patient tumor tissues were found to have cells with elevated DSS1 when compared with tumor-adjacent normal cells. In histological sections of cervical tissue containing either invasive cervical carcinoma or its precursor lesions, DSS1 was readily detected in the tumor cells. Steady-state DSS1 expression by immortalized cervical cancer cell lines was found to be necessary for maintenance of their transformed phenotype, since stable shRNA-mediated depletion of DSS1 in HeLa cells inhibited their proliferation and colony-forming activity in monolayer cultures and prevented division of these cells in soft agar. When DSS1 levels are reduced using shRNA, the cells ultimately undergo apoptosis via activation of p53 and the p53 downstream targets, and cleavage of apoptosis-associated proteins including CPP32/caspase-3, poly(ADP-ribose)polymerase and DNA-PKcs. In addition, silencing of DSS1 makes cervical cancer cells sensitive to cell death after treatment with cisplatin. We conclude that the DSS1 protein is critically involved in the maintenance of the transformed phenotype in cervical cancer cells, and that it might be a specific, robust and reliable marker for early detection, diagnosis and treatment.

Serum and tissue CTACK/CCL27 chemokine levels in early mycosis fungoides may be correlated with disease-free survival following treatment with interferon alfa and psoralen plus ultraviolet A therapy

BACKGROUND

Neoplastic T-cell recruitment into the skin is a critical step in the pathogenesis of mycosis fungoides (MF), and the cutaneous T-cell attracting chemokine, CTACK/CCL27, might be involved.

OBJECTIVES

To investigate the clinical and prognostic significance of CTACK/CCL27 levels in patients with early-stage MF.

METHODS

Serum samples and skin biopsy specimens were collected from 15 patients at the time of diagnosis and after the end of treatment with psoralen plus ultraviolet A/interferon alfa-2b combination therapy. Serum samples were also collected from 20 healthy donors as controls. CTACK/CCL27 serum levels were analysed by enzyme-linked immunosorbent assays. CTACK/CCL27 tissue expression was determined by immunohistochemistry on skin biopsy specimens taken at diagnosis and after therapy. Event-free survival was taken as the primary clinical outcome.

RESULTS

In patients with MF at diagnosis, CTACK/CCL27 serum levels were not significantly different from healthy controls, whereas CTACK/CCL27 expression in the skin was increased in 87% of cases compared with normal controls. After therapy, all patients obtained a clinical complete remission, serum levels did not change significantly and tissue expression remained abnormal in 80% of patients, even if complete histological remission was recorded. Serum levels were not significantly different in cases with different intensity of cutaneous immunostaining. Eight patients experienced a relapse: the combination of high CTACK/CCL27 levels both in sera and skin increased the probability of experiencing an event at 51 months from 36% to 83%.

CONCLUSIONS

Our data seem to indicate that CTACK/CCL27 levels in skin and sera after therapy might be correlated with risk of recurrence.

Molecular basis for hair loss in mice carrying a novel nonsense mutation (Hrrh-R ) in the hairless gene (Hr)

Animal models carrying mutations in the hairless (Hr) gene provide a rich resource for study of hair follicle biology. A spontaneous mouse mutant with a phenotype strikingly similar to rhino mutants of Hr arose spontaneously in the mouse facility at Oak Ridge National Laboratory. Sequence analysis of Hr in these mutants uncovered a nonsense mutation in exon 12, designated as Hr(rh-R) (rhino, Oak Ridge). The mutation led to significant reduction in Hr mRNA levels, predicted to be due to nonsense-mediated decay. Histological analysis indicated dilated hair follicle infundibula at 14 days of age that rapidly became filled with cornified material. Microarray analyses revealed that expression levels of many genes involved in keratinocyte differentiation, epidermal regeneration, and wound healing were significantly upregulated before morphological detection of the phenotype, suggesting their role in onset of the Hr(rh-R) phenotype. Identification of this new Hr allele and the underlying molecular alterations allows further understanding of the role of Hr in hair follicle biology.

Response of heterogeneous ribonuclear proteins (hnRNP) to ionising radiation and their involvement in DNA damage repair

PURPOSE

To determine the relationship between heterogeneous nuclear ribonucleoproteins (hnRNP) and DNA repair, particularly in response to ionising radiation (IR).

MATERIALS AND METHODS

The literature was examined for papers related to the topics of hnRNP, IR and DNA repair.

RESULTS

HnRNP orchestrate the processing of mRNA to which they are bound in response to IR. HnRNP A18, B1, C1/C2 and K interact with important proteins from DNA Damage Response (DDR) pathways, binding DNA-dependent protein kinase (DNA-PK), the Ku antigen (Ku) and tumour suppressor protein 53 (p53) respectively. Notably, irregularities in the expression of hnRNP A18, B1, K, P2 and L have been linked to cancer and radiosensitivity. Sixteen different hnRNP proteins have been reported to show either mRNA transcript or protein quantity changes following IR. Various protein modifications of hnRNP in response to IR have also been noted: hnRNP A18, C1/C2 and K are phosphorylated; hnRNP C1/C2 is a target of apoptotic proteases; and hnRNP K degradation is controlled by murine double minute ubiquitin ligase (MDM2). Evidence points to a role for hnRNP A1, A18, A2/B1, C1/C2, K and P2 in regulating double-stranded break (DSB) repair pathways by promoting either homologous recombination (HR) or non-homologous end rejoining (NHEJ) repair pathways following IR.

CONCLUSIONS

HnRNP proteins play a pivotal role in coordinating repair pathways following exposure to IR, through protein-protein interactions and transcript regulation of key repair and stress response mRNA. In particular, several hnRNP proteins are critical in coordinating the choice of HR or NHEJ to repair DSB caused by IR.

Changes in S100A8 expression in UV-irradiated and aged human skin in vivo

S100A8, a calcium-binding protein, is associated with keratinocyte differentiation, inflammation and wound healing. S100A8 is induced by various skin stresses and diseases, which suggests that S100A8 plays a role in those processes. However, it has not been reported how the expression of S100A8 is affected during skin aging or whether S100A8 plays a role in the skin aging process. In this study, we investigated the changes in S100A8 mRNA and protein following acute UV irradiation to human buttock skin and by intrinsic aging and photoaging in human sun-protected (upper-inner arm) and sun-exposed (forearm) skin of elderly subjects. Real-time PCR, western blot and immunohistochemical staining analyses of UV-irradiated young buttock skin revealed that S100A8 protein expression was increased at 24 h (3.0-fold) and 48 h (4.4-fold) after UV irradiation. S100A8 mRNA and protein were more highly expressed by 2.3- and 4.0-fold, respectively, in the sun-protected skin of elderly people than in that of young people. In addition, the sun-exposed skin of elderly expressed more S100A8 mRNA and protein than the sun-protected skin of the same individuals. In immunohistochemical staining, facial (photoaged) skin > or = 72 years showed higher epidermal expression of S100A8 than that of the other age groups. Based on the above results, our data suggest that the expression of S100A8 is affected by acute UV irradiation, intrinsic aging and photoaging processes.

The hairless mouse in skin research

The hairless (Hr) gene encodes a transcriptional co-repressor highly expressed in the mammalian skin. In the mouse, several null and hypomorphic Hr alleles have been identified resulting in hairlessness in homozygous animals, characterized by alopecia developing after a single cycle of relatively normal hair growth. Mutations in the human ortholog have also been associated with congenital alopecia. Although a variety of hairless strains have been developed, outbred SKH1 mice are the most widely used in dermatologic research. These unpigmented and immunocompetent mice allow for ready manipulation of the skin, application of topical agents, and exposure to UVR, as well as easy visualization of the cutaneous response. Wound healing, acute photobiologic responses, and skin carcinogenesis have been extensively studied in SKH1 mice and are well characterized. In addition, tumors induced in these mice resemble, both at the morphologic and molecular levels, UVR-induced skin malignancies in man. Two limitations of the SKH1 mouse in dermatologic research are the relatively uncharacterized genetic background and its outbred status, which precludes inter-individual transplantation studies.

Identification of a specific motif of the DSS1 protein required for proteasome interaction and p53 protein degradation

Deleted in Split hand/Split foot 1 (DSS1) was previously identified as a novel 12-O-tetradecanoylphorbol-13-acetate (TPA)-inducible gene with possible involvement in early event of mouse skin carcinogenesis. The mechanisms by which human DSS1 (HsDSS1) exerts its biological effects via regulation of the ubiquitin-proteasome system (UPS) are currently unknown. Here, we demonstrated that HsDSS1 regulates the human proteasome by associating with it in the cytosol and nucleus via the RPN3/S3 subunit of the 19S regulatory particle (RP). Molecular anatomy of HsDSS1 revealed an RPN3/S3-interacting motif (R3IM), located at amino acid residues 15 to 21 of the NH(2) terminus. Importantly, negative charges of the R3IM motif were demonstrated to be required for proteasome interaction and binding to poly-ubiquitinated substrates. Indeed, the R3IM motif of HsDSS1 protein alone was sufficient to replace the ability of intact HsDSS1 protein to pull down proteasome complexes and protein substrates with high-molecular mass ubiquitin conjugates. Interestingly, this interaction is highly conserved throughout evolution from humans to nematodes. Functional study, lowering the levels of the endogenous HsDSS1 using siRNA, indicates that the R3IM/proteasome complex binds and targets p53 for ubiquitin-mediated degradation via gankyrin-MDM2/HDM2 pathway. Most significantly, this work indicates that the R3IM motif of HsDSS1, in conjunction with the complexes of 19S RP and 20S core particle (CP), regulates proteasome interaction through RPN3/S3 molecule, and utilizes a specific subset of poly-ubiquitinated p53 as a substrate.

Caspase-14 reveals its secrets

Caspase-14 is a unique member of the evolutionarily conserved family of cysteinyl aspartate-specific proteinases, which are mainly involved in inflammation and apoptosis. However, recent evidence also implicates these proteases in proliferation and differentiation. Although most caspases are ubiquitously expressed, caspase-14 expression is confined mainly to cornifying epithelia, such as the skin. Moreover, caspase-14 activation correlates with cornification, indicating that it plays a role in terminal keratinocyte differentiation. The determination of in vitro conditions for caspase-14 activity paved the way to identifying its substrates. The recent development of caspase-14-deficient mice underscored its importance in the correct degradation of (pro)filaggrin and in the formation of the epidermal barrier that protects against dehydration and UVB radiation. Here, we review the current knowledge on caspase-14 in skin homeostasis and disease.

Ultraviolet B regulation of transcription factor families: roles of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) in UVB-induced skin carcinogenesis

Prolonged and repeated exposure of the skin to ultraviolet light (UV) leads not only to aging of the skin but also increases the incidence of non-melanoma skin cancer (NMSC). Damage of cells induced by ultraviolet B (UVB) light both at the DNA level and molecular level initiates the activation of transcription factor pathways, which in turn regulate the expression of a number of genes termed the "UV response genes". Two such transcription factor families that are activated in this way are those of the nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) families. These two transcription factor families have been identified to be involved in the processes of cell proliferation, cell differentiation and cell survival and therefore play important roles in tumorigenesis. The study of these two transcription factor pathways and the cross-talk between them in response to UVB exposure may help with the development of new chemopreventive strategies for the prevention of UVB-induced skin carcinogenesis.

Ultraviolet radiation stimulates expression of Snail family transcription factors in keratinocytes

The related zinc finger transcription factors Slug and Snail modulate epithelial mesenchymal transformation (EMT), the conversion of sessile epithelial cells into migratory fibroblast-like cells. EMT occurs during development, wound healing, and tumor progression. Growth factors, acting through mitogen-activated protein kinase (MAPK) cascades, regulate expression of Slug and Snail. Expression of Snail family transcription factors appears to be elevated in UVR-induced murine squamous cell carcinomas (SCC). We report here that ultraviolet radiation (UVR), which activates MAPK cascades, also stimulates Snail and Slug expression in epidermal keratinocytes. UVR exposure transiently elevated Slug and Snail mRNA expression in human keratinocytes in vitro and mouse epidermis in vivo. This induction was mediated, at least in part, through the ERK and p38 MAPK cascades, as pharmacological inhibition of these cascades partially or completely blocked Slug and Snail induction by UVR. On the other hand, UVR induction of Slug and Snail was enhanced by inhibition of JNK. Slug appears to play a functional role in the acute response of keratinocytes to UVR, as UVR induction of keratin 6 in the epidermis of Slug knockout mice was markedly delayed compared to wild-type mice. Slug and Snail are known to regulate molecules important in the cytoskeleton, intercellular adhesion, cell motility, and apoptosis, thus it seems probable that transiently or persistently elevated expression of these factors fosters the progression of UVR-induced SCC.

E6/E7 expression of human papillomavirus type 20 (HPV-20) and HPV-27 influences proliferation and differentiation of the skin in UV-irradiated SKH-hr1 transgenic mice

The functional role of UV irradiation, in combination with the E6 and E7 proteins of the cutaneous human papillomavirus (HPV) types in the malignant conversion of benign papillomatous lesions, has not been elucidated. Transgenic SKH-hr1 hairless mice expressing HPV-20 and HPV-27 E6 and E7 proteins in the suprabasal compartment were generated and exposed to chronic UV irradiation. Histological and immunohistochemical examination of skin samples revealed enhanced proliferation of the epidermal layers and papilloma formation in both transgenic strains in comparison to what was observed with nontransgenic mice. Squamous cell carcinoma developed in the HPV-20 E6/E7 transgenic line as well as in the HPV-27 E6/E7 transgenic line. Several weeks after cessation of UV-B exposure, enhanced proliferation, as measured by BrdU incorporation, was maintained only in HPV-20 transgenic skin. Keratin 6 expression was increased in the transgenic mice throughout all cell layers. Expression of the differentiation markers involucrin and loricrin was reduced and disturbed. p63alpha expression was differentially regulated with high levels of cytoplasmic expression in clusters of cells in the granular layer of the skin in the transgenic lines 20 weeks after cessation of UV-B exposure, in contrast to uninterrupted staining in the nontransgenic lines. p53 was expressed in clusters of cells in nontransgenic and HPV-27 transgenic mice, in contrast to an even distribution in a higher number of cells in HPV-20 transgenic animals.

Presence of circulating CCR10+ T cells and elevated serum CTACK/CCL27 in the early stage of mycosis fungoides

PURPOSE

Mycosis fungoides (MF), a common type of cutaneous T cell lymphoma with an indolent clinical course, has the characteristic that malignant T cell clones are recruited into the skin from the early disease stages. The mechanisms of recruitment have been suggested from our knowledge of various chemokine-chemokine receptor interactions. Recently, CCR10 and CTACK/CCL27 were proposed to play a role in the recruitment of other types of cutaneous T cell lymphoma. We examined the expression of CCR10 in peripheral blood and serum CTACK/CCL27 levels in patients with MF.

EXPERIMENTAL DESIGN

Eighteen patients with MF, six patients with atopic dermatitis, and nine healthy volunteers were enrolled in our investigation. We investigated the differences in CCR10+ CD4+ expression in peripheral blood mononuclear cells by flow cytometry. Serum CTACK/CCL27 levels were determined using a CTACK/CCL27 ELISA assay kit.

RESULTS

The number of circulating CCR10+ CD4+ cells was significantly higher in MF peripheral blood than in controls, even during the early stages. In lesional MF skin, infiltrating tumor cells also showed extensive expression of CCR10. The serum level of CTACK/CCL27 was higher in patients with MF than normal controls, but no statistical difference was found compared with atopic dermatitis patients.

CONCLUSIONS

CCR10-CTACK/CCL27 interactions between circulating T cells and keratinocytes would seem to play an important role in the pathophysiology of MF from the early disease stages.

CDDO-Imidazolide inhibits growth and survival of c-Myc-induced mouse B cell and plasma cell neoplasms

Background

Gene-targeted iMyc^Eμ mice that carry a His₆-tagged mouse Myc(c-myc)cDNA, Myc^His, just 5' of the immunoglobulin heavy-chain enhancer, Eμ, are prone to B cell and plasma cell neoplasms, such as lymphoblastic B-cell lymphoma (LBL) and plasmacytoma (PCT). Cell lines derived from Myc-induced neoplasms of this sort may provide a good model system for the design and testing of new approaches to prevent and treat MYC-driven B cell and plasma cell neoplasms in human beings. To test this hypothesis, we used the LBL-derived cell line, iMyc^Eμ-1, and the newly established PCT-derived cell line, iMyc^Eμ-2, to evaluate the growth inhibitory and death inducing potency of the cancer drug candidate, CDDO-imidazolide (CDDO-Im).

Methods

Morphological features and surface marker expression of iMyc^Eμ-2 cells were evaluated using cytological methods and FACS, respectively. mRNA expression levels of the inserted Myc^His and normal Myc genes were determined by allele-specific RT-PCR and qPCR. Myc protein was detected by immunoblotting. Cell cycle progression and apoptosis were analyzed by FACS. The expression of 384 "pathway" genes was assessed with the help of Superarray^© cDNA macroarrays and verified, in part, by RT-PCR.

Results

Sub-micromolar concentrations of CDDO-Im caused growth arrest and apoptosis in iMyc^Eμ-1 and iMyc^Eμ-2 cells. CDDO-Im-dependent growth inhibition and apoptosis were associated in both cell lines with the up-regulation of 30 genes involved in apoptosis, cell cycling, NFκB signaling, and stress and toxicity responses. Strongly induced (≥10 fold) were genes encoding caspase 14, heme oxygenase 1 (Hmox1), flavin-containing monooxygenase 4 (Fmo4), and three members of the cytochrome P450 subfamily 2 of mixed-function oxygenases (Cyp2a4, Cyp2b9, Cyp2c29). CDDO-Im-dependent gene induction coincided with a decrease in Myc protein.

Conclusion

Growth arrest and killing of neoplastic mouse B cells and plasma cells by CDDO-Im, a closely related derivative of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid, appears to be caused, in part, by drug-induced stress responses and reduction of Myc.

Identification of genes and gene ontology processes critical to skin papilloma development in Tg.AC transgenic mice

This study analyzes gene expression associated with papilloma development in Tg.AC v-Ha-ras transgenic mice and identifies novel genes and biological processes that may be critical to skin carcinogenesis in these mice. Epidermal abrasion was used to synchronously induce epidermal regeneration in FVB/N wild type and transgenic Tg.AC mice. Skin papillomagenesis was uniquely induced in Tg.AC mice, and gene expression profiling was carried out using a 22,000 element mouse DNA microarray. Histological analysis showed that papillomas developed at a high rate by d 30 after abrasion in transgenic animals, while no papilloma developed in wild type mice. Transgene-specific differentially expressed genes were identified at d 30 postabrasion and these genes were annotated using EASE software and literature mining. Annotated and non-annotated genes associated with papilloma development were identified and clustering analysis revealed groups of genes that are coordinately expressed. A number of genes associated with differentiation and development were also physically clustered on mouse chromosome 16, including 16B3 that contains several Stefins and stefin-like genes, and 16A1 containing a number of keratin associated protein genes. Additional analyses presented here yield novel insights into the genes and processes involved in papilloma development in Tg.AC mice.

Tumor-associated alterations in caspase-14 expression in epithelial malignancies

PURPOSE

Caspase-14 is unique among caspase family proteases in that its proteolytic processing has been principally associated with epithelial cell differentiation rather than apoptosis or inflammation. We investigated caspase-14 expression in several types of human epithelial malignancy by immunohistochemistry, correlating results with stage, histologic grade, and patient survival.

EXPERIMENTAL DESIGN

Tumor-associated alterations in caspase-14 expression were observed for cervical, ovarian, breast, gastric, and colon cancers.

RESULTS

In cervical (n = 445), ovarian (n = 91), and colon (n = 106) specimens, expression of caspase-14 was significantly reduced in cancers compared with normal epithelium. Decreases in caspase-14 immunopositivity correlated with the histologic progression of cervical cancer (P < 0.0001, ANOVA). In localized gastric cancers, caspase-14 immunostaining was significantly lower in poorly differentiated tumors compared with well-differentiated tumors (P = 0.02, Pearson's chi(2) analysis). Lower caspase-14 expression was associated with advanced clinical stage in ovarian cancer (P = 0.04, ANOVA) and with shorter overall survival among ovarian cancer patients with serous tumors (n = 62) in both univariate (P = 0.005) and multivariate (P = 0.03) analysis. Lower caspase-14 expression correlated with shorter overall survival among patients with T(3)N(0)M(0) stage gastric cancers (n = 94; P = 0.006, log-rank test). In contrast to cervical, ovarian, and colon cancers, caspase-14 expression was increased in ductal carcinoma in situ and invasive cancers compared with normal mammary epithelium (P = 0.001, t test).

CONCLUSIONS

The findings reveal tumor-specific alterations in caspase-14 expression and suggest that differences in its expression may define subsets of epithelial cancers with distinct clinical behaviors.

Id2 protein is selectively upregulated by UVB in primary, but not in immortalized human keratinocytes and inhibits differentiation

Solar ultraviolet B (UVB) acts as both an initiator and promoter in models of multistage skin carcinogenesis. We found that, whereas UVB induces apoptosis in human papillomavirus-16 E6/7-immortalized keratinocytes, it inhibits markers of differentiation in human foreskin keratinocytes (HFK). Potential mechanisms for this differential response were examined by DNA microarray, which revealed that UVB alters the expression of three of the four human inhibitor of differentiation/DNA binding (Id) proteins that comprise a class of helix-loop-helix family of transcription factors involved in proliferation, differentiation, apoptosis, and carcinogenesis. These results were verified by RT-PCR and immunoblot analysis of control and UVB-irradiated primary and immortalized keratinocytes. Whereas Id1 was downregulated in both cell types, Id2 expression was upregulated in primary HFK, but not immortalized cells. In contrast, Id3 expression was significantly increased only in immortalized cells. The differential expression pattern of Id2 in response to UVB was recapitulated in reporter constructs containing the 5' regulatory regions of this gene. Id2 promoter activity increased in response to UVB in HFK, but not in immortalized cells. To identify the regulatory elements in the Id2 promoter that mediate transcriptional activation by UVB in HFK, promoter deletion/mutation analysis was performed. Deletion analysis revealed that transactivation involves a 166 bp region immediately upstream to the Id2 transcriptional start site and is independent of c-Myc. The consensus E twenty-six (ETS) binding site at -120 appears to mediate UVB transcriptional activation of Id2 because point mutations at this site completely abrogated this response. Chromatin immunoprecipitation and electrophoretic mobility-shift assays verified that the Id2 promoter interacts with known Id2 promoter (ETS) binding factors Erg1/2 and Fli1, but not with c-Myc; and this interaction is enhanced after UVB exposure. Similar to the effects of UVB exposure, ectopic expression of Id2 protein in primary HFK resulted in inhibition of differentiation, as shown by decreased levels of the terminal differentiation marker keratin K1 and inhibition of involucrin crosslinking. Reduction of Id2 expression by small interfering RNAs attenuated the UVB-induced inhibition of differentiation in these cells. These results suggest that UVB-induced inhibition of differentiation of primary HFK is at least, in part, due to the upregulation of Id2, and that upregulation of Id2 by UVB might predispose keratinocytes to carcinogenesis by preventing their normal differentiation program.