Expression of the SPRR cornification genes is differentially affected by carcinogenic transformation

TGFA expression is associated with poor prognosis and promotes the development of cervical cancer

Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) are the second most common cancers in women aged 20-39. While HPV screening can help with early detection of cervical cancer, many patients are already in the medium to late stages when they are identified. As a result, searching for novel biomarkers to predict CESC prognosis and propose molecular treatment targets is critical. TGFA is a polypeptide growth factor with a high affinity for the epidermal growth factor receptor. Several studies have shown that TGFA can improve cancer growth and progression, but data on its impact on the occurrence and advancement of CESC is limited. In this study, we used clinical data analysis and bioinformatics techniques to explore the relationship between TGFA and CESC. The results showed that TGFA was highly expressed in cervical cancer tissues and cells. TGFA knockdown can inhibit the proliferation, migration and invasion of cervical cancer cells. In addition, after TGFA knockout, the expression of IL family and MMP family proteins in CESC cell lines was significantly reduced. In conclusion, TGFA plays an important role in the occurrence and development of cervical cancer. Therefore, TGFA may become a new target for cervical cancer treatment.

The identification, adaptive evolutionary analyses and mRNA expression levels of homeobox (hox) genes in the Chinese mitten crab Eriocheir sinensis

BACKGROUND

Arthropods are the largest group in the animal kingdom and are morphologically characterized by heterorhythmic segments. Brachyuran decapod crustaceans undergo brachyurization metamorphosis in the early developmental process, characterized by a reduced abdomen that is folded beneath the cephalothorax and inserted between the pereiopods or in a special cavity. As the main cause of major alterations in the evolution of animal body plans, Hox genes encode transcription factors and are involved in bilaterian anterior-posterior axis patterning.

RESULTS

We found eight Hox genes (labial, proboscipedia, Deformed, zerknüllt, Sex combs reduced, Antennapedia, Ultrabithorax, fushi tarazu, abdominal-A and Abdominal-B) in Eriocheir sinensis. The phylogenetic topology of 13 arthropod Hox genes was closely related to traditional taxonomic groupings. Genome collinearity analysis was performed using genomic data and chromosomal location data of E. sinensis and Portunus trituratus. We found that their chromosomes were highly collinear, and there was a corresponding collinear relationship between the three Hox genes (lab, ftz and Abd-B). The mRNA expression levels of Scr and Antp fluctuated significantly in different developmental stages of E. sinensis, especially in the brachyurization stages. Evolutionary analysis indicated the presence of positively selected sites in Ubx.

CONCLUSIONS

In this study, we used genome-wide analysis to identify and analyze all members of the Hox genes in E. sinensis. Our data will contribute to a better understanding of Hox genes in E. sinensis and provide useful molecular evolutionary information for further investigation on their roles in the brachyurization of crabs.

Small Proline-Rich Protein 2B Facilitates Gastric Adenocarcinoma Proliferation via MDM2-p53/p21 Signaling Pathway

Background

The small proline-rich protein 2B (SPRR2B) was firstly reported as a member of the cross-linked envelope protein in keratinocytes. The effect of SPRR2B in gastric adenocarcinoma (GC) remains unclear. This study initially explored the clinical significance of SPRR2B in GC patients as well as its role in tumor progression.

Methods

Immunohistochemistry was performed to characterize the expression of SPRR2B in GC tissues and adjacent tissues. The relationship between SPRR2B expression and clinicopathological features of GC patients was analyzed by Chi-square test. Kaplan-Meier method and Cox regression analyses were utilized to identify the prognostic factors of GC. Overexpression and knockdown assays were conducted to investigate possible signaling pathways downstream of SPRR2B. Flow cytometry assays were performed to evaluate cell cycle and apoptosis. Xenograft experiments were performed to validate tumor-related role of SPRR2B in vivo.

Results

Both mRNA and protein levels of SPRR2B in cancerous tissue were significantly higher than those in non-cancerous tissues. Meanwhile, SPRR2B expression was significantly associated with tumor size and tumor stage. Survival analysis revealed SPRR2B as one of the independent prognosis factors for overall survival of GC patients. Cellular and xenografts data implicated that silencing SPRR2B blocked the cell cycle of GC cells perhaps through MDM2-p53/p21-CDK1 pathway, while overexpressing SPRR2B exhibited opposite effects.

Conclusion

Our data suggest that SPRR2B may serve as a novel prognostic marker in GC, which functions at least partially by MDM2-p53/p21-CDK1 signaling pathway.

Transcriptome reprogramming by cancer exosomes: identification of novel molecular targets in matrix and immune modulation

BACKGROUND

Exosomes are extracellular vesicles released by almost all cell types, including cancer cells, into bodily fluids such as saliva, plasma, breast milk, semen, urine, cerebrospinal fluid, amniotic fluid, synovial fluid and sputum. Their key function being intercellular communication with both neighbouring as well as distant cells. Cancer exosomes have been shown to regulate organ-specific metastasis. However, little is known about the functional differences and molecular consequences of normal cells responding to exosomes derived from normal cells compared to those derived from cancer cells.

METHODS

Here, we characterised and compared the transcriptome profiles of primary human normal oral keratinocytes (HNOK) in response to exosomes isolated from either primary HNOK or head and neck squamous cell carcinoma (HNSCC) cell lines.

RESULTS

In recipient HNOK cells, we found that regardless of normal or cancer derived, exosomes altered molecular programmes involved in matrix modulation (MMP9), cytoskeletal remodelling (TUBB6, FEZ1, CCT6A), viral/dsRNA-induced interferon (OAS1, IFI6), anti-inflammatory (TSC22D3), deubiquitin (OTUD1), lipid metabolism and membrane trafficking (BBOX1, LRP11, RAB6A). Interestingly, cancer exosomes, but not normal exosomes, modulated expression of matrix remodelling (EFEMP1, DDK3, SPARC), cell cycle (EEF2K), membrane remodelling (LAMP2, SRPX), differentiation (SPRR2E), apoptosis (CTSC), transcription/translation (KLF6, PUS7). We have also identified CEP55 as a potential cancer exosomal marker.

CONCLUSIONS

In conclusion, both normal and cancer exosomes modulated unique gene expression pathways in normal recipient cells. Cancer cells may exploit exosomes to confer transcriptome reprogramming that leads to cancer-associated pathologies such as angiogenesis, immune evasion/modulation, cell fate alteration and metastasis. Molecular pathways and biomarkers identified in this study may be clinically exploitable for developing novel liquid-biopsy based diagnostics and immunotherapies.

ZNF750 Expression Is a Potential Prognostic Biomarker in Esophageal Squamous Cell Carcinoma

OBJECTIVE

ZNF750, a transcriptional regulator of epidermal differentiation, has been identified as a tumor suppressor in esophageal squamous cell carcinoma (ESCC). The aim of the present study was to investigate the clinical and prognostic significance of ZNF750 expression and to evaluate the effect of ZNF750 knockdown on cell proliferation, migration, and invasion in ESCC.

METHODS

A total of 124 patients with ESCC who underwent curative esophagectomy were evaluated in this study. The expression of ZNF750 in surgical specimens was immunohistochemically assessed and used in the analysis of clinicopathological features and overall survival (OS). The molecular role of ZNF750 was investigated by ZNF750 knockdown using small interfering RNA (siRNA) in ESCC cell lines.

RESULTS

Low ZNF750 expression had a significant correlation with positive lymph node metastasis (p = 0.028). Furthermore, there was a significant relationship between low expression of ZNF750 in ESCC and a poor OS, and a multivariate analysis showed that low ZNF750 expression was an independent prognostic factor (p = 0.020). The cell growth, migration, and invasion were significantly increased by downregulation of ZNF750.

CONCLUSIONS

The low expression of ZNF750 was significantly associated with a poor prognosis, and ZNF750 expression may, therefore, be a reliable prognostic biomarker in ESCC.

CRCT1 regulated by microRNA-520 g inhibits proliferation and induces apoptosis in esophageal squamous cell cancer

Cysteine-rich C-terminal 1 (CRCT1) is encoded by the epidermal differentiation complex (EDC), a gene cluster that was recently linked to esophageal cancer. However, the role of CRCT1 in esophageal squamous cell cancer (ESCC) and the underlying mechanism remain unclear. In the present study, we show that CRCT1 is downregulated in ESCC in association with TNM stage and lymph node metastasis. Restoring CRCT1 in ESCC cells by lentivirus-mediated gene transfer inhibited cell proliferation and xenograft tumor formation. CRCT1 overexpression promoted ESCC cell apoptosis and upregulated the expression of apoptosis-related proteins. CRCT1 expression was inversely correlated with the levels of microRNA-520 g (miR-520 g) in ESCC tissues, and CRCT1 was identified as a direct target gene of miR-520 g in ESCC cells. Consistent with the effects of CRCT1 overexpression, knockdown of miR-520 g inhibited growth and induced apoptosis in ESCC cells. Our results suggest that CRCT1 functions as a tumor suppressor gene in ESCC and is regulated by miR-520 g, providing potential therapeutic targets for the treatment of ESCC.

Activation of a PGC-1-related coactivator (PRC)-dependent inflammatory stress program linked to apoptosis and premature senescence

PGC-1-related coactivator (PRC), a growth-regulated member of the PGC-1 coactivator family, contributes to the expression of the mitochondrial respiratory apparatus. PRC also orchestrates a robust response to metabolic stress by promoting the expression of multiple genes specifying inflammation, proliferation, and metabolic reprogramming. Here, we demonstrate that this PRC-dependent stress program is activated during apoptosis and senescence, two major protective mechanisms against cellular dysfunction. Both PRC and its targets (IL1α, SPRR2D, and SPRR2F) were rapidly induced by menadione, an agent that promotes apoptosis through the generation of intracellular oxidants. Menadione-induced apoptosis and the PRC stress program were blocked by the antioxidant N-acetylcysteine. The PRC stress response was also activated by the topoisomerase I inhibitor 7-ethyl-10-hydroxycamptothecin (SN-38), an inducer of premature senescence in tumor cells. Cells treated with SN-38 displayed morphological characteristics of senescence and express senescence-associated β-galactosidase activity. In contrast to menadione, the SN-38 induction of the PRC program occurred over an extended time course and was antioxidant-insensitive. The potential adaptive function of the PRC stress response was investigated by treating cells with meclizine, a drug that promotes glycolytic energy metabolism and has been linked to cardio- and neuroprotection against ischemia-reperfusion injury. Meclizine increased lactate production and was a potent inducer of the PRC stress program, suggesting that PRC may contribute to the protective effects of meclizine. Finally, c-MYC and PRC were coordinately induced under all conditions tested, implicating c-MYC in the biological response to metabolic stress. The results suggest a general role for PRC in the adaptive response to cellular dysfunction.

Nucleus-encoded regulators of mitochondrial function: integration of respiratory chain expression, nutrient sensing and metabolic stress

Nucleus-encoded regulatory factors are major contributors to mitochondrial biogenesis and function. Several act within the organelle to regulate mitochondrial transcription and translation while others direct the expression of nuclear genes encoding the respiratory chain and other oxidative functions. Loss-of-function studies for many of these factors reveal a wide spectrum of phenotypes. These range from embryonic lethality and severe respiratory chain deficiency to relatively mild mitochondrial defects seen only under conditions of physiological stress. The PGC-1 family of regulated coactivators (PGC-1α, PGC-1β and PRC) plays an important integrative role through their interactions with transcription factors (NRF-1, NRF-2, ERRα, CREB, YY1 and others) that control respiratory gene expression. In addition, recent evidence suggests that PGC-1 coactivators may balance the cellular response to oxidant stress by promoting a pro-oxidant environment or by orchestrating an inflammatory response to severe metabolic stress. These pathways may serve as essential links between the energy generating functions of mitochondria and the cellular REDOX environment associated with longevity, senescence and disease. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.

PGC-1-related coactivator (PRC), a sensor of metabolic stress, orchestrates a redox-sensitive program of inflammatory gene expression

PGC-1-related coactivator (PRC) is a growth-regulated transcriptional cofactor that activates many nuclear genes specifying mitochondrial respiratory function. Stable PRC silencing in U2OS cells results in a complex phenotype typical of mitochondrial dysfunction including abundant abnormal mitochondria, reduced respiratory subunit expression, diminished respiratory enzymes and ATP levels, and elevated lactate production. The PRC response to metabolic stress was investigated by subjecting cells to metabolic insults including treatment with the uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP), expression of a dominant negative allele of nuclear respiratory factor 1 (NRF-1), and glucose deprivation. These treatments led to constitutively elevated PRC protein levels, a departure from its normal transient expression upon the initiation of cell growth. A microarray screen identified 45 genes that require PRC for their induction by CCCP. A subset of these genes specific to inflammation and cell stress was also induced by dominant negative NRF-1 and by glucose deprivation, suggesting that diverse metabolic insults converge on the same PRC-dependent inflammatory program. The PRC-dependent inflammatory response was inhibited by N-acetylcysteine, suggesting that PRC may contribute to the inflammatory microenvironment linked to oxidant signaling. The induction of this PRC-dependent program may be an early event in adaptations linked to cancer and degenerative diseases.

Regulation of antimicrobial peptide expression in human gingival keratinocytes by interleukin-1α

In the oral cavity, mucosal keratinocytes resist bacterial infection, in part, by producing broad-spectrum antimicrobial peptides (AMPs) including defensin, adrenomedullin and calprotectin. Epidermal keratinocyte expression of many AMPs increases in response to interleukin-1α (IL-1α). IL-1α is produced by epidermal keratinocytes and regulates cell differentiation. To better understand innate immunity in the oral cavity, we sought to determine how IL-1α might regulate expression of AMPs by human gingival keratinocytes (HGKs) using DNA microarray and Western blot analyses. HGKs from three subjects expressed eleven AMPs, including S100A7, S100A8, S100A9, S100A12, secretory leucocyte protease inhibitor, lipocalin 2 (LCN2), cystatin C and β-defensin 2. Of the expressed AMPs, S100A7, S100A12 and LCN2 were up-regulated by IL-1α (inducible AMPs); the other AMPs were considered to be constitutive. Human gingival keratinocytes, therefore, express constitutive and IL-1α-inducible AMPs to provide a rapid and robust innate response to microbial infection.

Quantitative evaluation of SPRR3 expression in esophageal squamous cell carcinoma by qPCR and its potential use as a biomarker

Esophageal squamous cell carcinoma (ESCC) is highly fatal due to late diagnosis and inefficient treatment. Early disease detection could improve diagnosis and patient survival. Esophageal squamous epithelial cells express SPRR3, a member of the small proline-rich protein family, which is downregulated in ESCC. Therefore, SPRR3 expression may be used as a biomarker to follow the transition from healthy mucosa to ESCC. Both SPRR3 mRNA splice variants, v1 and v2, were evaluated by real time PCR in tumor and histologically normal adjacent tissue biopsies from 84 ESCC patients and 18 healthy controls. SPRR3-v1 was most highly expressed in the esophageal mucosa of healthy subjects, with an increasingly lower expression in the adjacent mucosa of ESCC patients and in tumors, respectively. SPRR3-v2 expression was low in normal mucosa and in tumors but it was higher in the adjacent mucosa of ESCC patients. In addition, we found a significant correlation between a lower SPRR3-v1 and SPRR3-v2 expression and age and alcohol consumption, respectively. SPRR3 protein expression presented a good correlation with SPRR3 mRNA expression. Cut-off points to discriminate between healthy mucosa, tumor and adjacent mucosa were determined with receiver operating characteristic (ROC) curves. This analysis showed that SPRR3-v1 expression discriminates the esophageal mucosa of healthy subjects from the adjacent mucosa and the tumor of ESCC patients with high sensitivity and specificity. Our data shows that the quantitative analysis of SPRR3 mRNA is a robust and reliable method to monitor the malignant transformation of the healthy esophageal mucosa into ESCC.

Dynamic and physical clustering of gene expression during epidermal barrier formation in differentiating keratinocytes

The mammalian epidermis is a continually renewing structure that provides the interface between the organism and an innately hostile environment. The keratinocyte is its principal cell. Keratinocyte proteins form a physical epithelial barrier, protect against microbial damage, and prepare immune responses to danger. Epithelial immunity is disordered in many common diseases and disordered epithelial differentiation underlies many cancers. In order to identify the genes that mediate epithelial development we used a tissue model of the skin derived from primary human keratinocytes. We measured global gene expression in triplicate at five times over the ten days that the keratinocytes took to fully differentiate. We identified 1282 gene transcripts that significantly changed during differentiation (false discovery rate <0.01%). We robustly grouped these transcripts by K-means clustering into modules with distinct temporal expression patterns, shared regulatory motifs, and biological functions. We found a striking cluster of late expressed genes that form the structural and innate immune defences of the epithelial barrier. Gene Ontology analyses showed that undifferentiated keratinocytes were characterised by genes for motility and the adaptive immune response. We systematically identified calcium-binding genes, which may operate with the epidermal calcium gradient to control keratinocyte division during skin repair. The results provide multiple novel insights into keratinocyte biology, in particular providing a comprehensive list of known and previously unrecognised major components of the epidermal barrier. The findings provide a reference for subsequent understanding of how the barrier functions in health and disease.

Gene expression pattern and hormonal regulation of small proline-rich protein 2 family members in the female mouse reproductive system during the estrous cycle and pregnancy

Small proline-rich proteins (SPRR) are known to construct the cornified cell envelope (CE) in the stratified squamous epithelial cell. Their functions in the simple epithelium such as the uterine epithelium are not clear hitherto. In the present study, the mRNA expression patterns of sprr2 family members in the mouse uterus and vagina during the estrous cycle and pregnancy as well as their regulation by steroids were investigated. Using semi-quantitative RT-PCR, it was revealed that the transcripts of sprr2b, 2e and 2g genes were up-regulated in the proestrous and estrous uteri, and sprr2d was up-regulated only in the estrous uterus. In the vagina, transcription of sprr2a, 2b, 2d, 2e and 2k genes were up-regulated at the metestrous stage. Northern blot analysis demonstrated that the overall expression of sprr2 was highly up-regulated in the estrous uterus and the metestrous vagina. During pregnancy, the sprr2 mRNA in the uterus was sharply repressed from day 3 postcoitus on, and began to be induced around labor time. In situ hybridization showed that the sprr2 transcripts were localized in uterine luminal and glandular epithelial cells as well as vaginal stratified epithelial cells. In ovariectomized mice, the expression of sprr2a, 2d, 2e and 2f genes in the uterus were induced by estrogen, and the effect of estrogen on sprr2d and 2e expression could be partly abolished by progesterone. The data indicate that the sprr2 genes have unique regulation patterns in different reproductive tissues under different physiological conditions, and the encoded proteins might play diverse functions in the female reproductive system.

Downstream targets of Nm23-H1: gene expression profiling of CAL 27 cells using DNA microarray

The human nm23-H1 was discovered as a tumor metastasis suppressor based on its reduced expression in melanoma cell lines with low versus high metastatic potential. It encodes for one of two subunits of the nucleoside-diphosphate kinase. Besides its role in the maintenance of the cells NTP pool, nm23 plays a key role in different cellular processes. The role of nm23-H1 in these processes still has to be elucidated. Our goal was to identify Nm23-H1 downstream targets by subjecting Nm23-H1 overexpressing CAL 27 cells oral squamous cell carcinoma (OSSC) to microarray analysis. The genes with changed expression patterns could be clustered into several groups: transforming growth factor beta (TGFbeta) signaling pathway, cell adhesion, invasion and motility, proteasome machinery, cell-cycle, epithelial structural and related molecules and others. Based on the expression patterns observed we presume that nm23-H1 might have a role in OSSCs, which should be confirmed by future experiments.

The immunogenetics of asthma and eczema: a new focus on the epithelium

Asthma and eczema (atopic dermatitis) are the most common chronic diseases of childhood. These diseases are characterized by the production of high levels of immunoglobulin E in response to common allergens. Their development depends on both genetic and environmental factors. Over the past few years, several genes and genetic loci that are associated with increased susceptibility to asthma and atopic dermatitis have been described. Many of these genes are expressed in the mucosa and epidermis, indicating that events at epithelial-cell surfaces might be driving disease processes. This review describes the mechanisms of innate epithelial immunity and the role of microbial factors in providing protection from disease development. Understanding events at the epithelial-cell surface might provide new insights for the development of new treatments for inflammatory epithelial disease.

SPRR1B overexpression enhances entry of cells into the G0 phase of the cell cycle

Many studies have established the role of SPRR1B during squamous differentiation of skin and respiratory epithelial cells. However, its role in nonsquamous cells is largely unknown. We reported that expression of SPRR1B in Chinese hamster ovary (CHO) cells is increased as they enter the G0 phase of the cell cycle. The purpose of this study was to further investigate the SPRR1B expression pattern in nonsquamous tumors and to study its role in these cells. Expression of SPRR1B was detected by Northern blotting in a higher percentage of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced compared with beryllium metal-induced rat lung adenocarcinomas. In situ hybridizations confirmed that SPRR1B is expressed in individual or clusters of cells of nonsquamous cells from mouse, rat, and human adenocarcinomas. The same pattern of expression was observed in adenocarcinomas formed in nude mice from cell lines established from adenocarcinomas. SPRR1B expression was downregulated in the cell lines derived from adenocarcinoma when cells were enriched in G0 at low confluence. Tetraploidy was induced in CHO, mouse, and human tumor cell lines by stably overexpressing SPRR1B, whereas control cells showed no change in ploidy. Inducible expression of this protein for shorter periods using the ecdyson system did not affect growth rate or the ploidy of CHO cells but accelerated entry into G0/G1 compared with controls. These findings indicate that SPRR1B is likely coupled primarily to signals responsible for withdrawal from the proliferative state rather than the final stages of cellular quiescence and that its overexpression for prolonged periods may disrupt the normal progression of mitosis.

Gene expression profiles in human non-small and small-cell lung cancers

Suppression subtractive hybridisation (SSH) was performed comparing normal bronchial epithelial cells with a lung squamous cell carcinoma (SCC) and a metastatic small-cell lung carcinoma (SCLC). The sequence analysis of four cDNA libraries revealed 869 individual sequences. Of these, 342 were tested using northern blots of lung cancer cell lines representing the three major subtypes (SCC, adenocarcinoma, SCLC) which confirmed the differential expression of 236 cDNAs. The extended analysis of 31 randomly chosen fragments confirmed the validity of the approach to identify genes associated with lung cancer development. Additionally, five novel full-length cDNA were isolated encoding the microtubule-associated proteins 1A/1B light chain 3, the epithelial V-like antigen 1 (EVA1), the GTP-binding protein SAR1, a new member of the S100-type calcium binding protein family and a new homeobox-containing gene.

Genetics and genomics of asthma and allergic diseases

Asthma and eczema (atopic dermatitis) are characterized by a number of unexplained phenomena: the familial aggregation of disease, the initiation of disease by apparently trivial exposure to allergens, the preferential transmission of disease from affected mothers and the large increase in prevalence of disease in Westernized societies in the last century. A number of genes and chromosomal regions have been identified that consistently show linkage to asthma and its related phenotypes. Known loci modify the strength of the atopic response, nonspecific inflammation, the ability to respond to particular allergens and nonspecific airway reactivity. Eczema has been shown to be due to a different set of genetic loci that are shared with other skin diseases such as psoriasis and leprosy. Genetic and genomic studies both provide evidence that epithelial surfaces are active in the induction of allergic disease.

Activation of the esophagin promoter during esophageal epithelial cell differentiation

Esophagin is a member of the small proline-rich protein family of cell envelope precursor proteins, which are expressed during squamous cell differentiation. Esophagin is expressed at high levels in normal esophageal epithelium, but its expression is absent from esophageal squamous cell carcinomas and adenocarcinomas. Moreover, loss of esophagin expression is present in areas of dysplasia or normal mucosa adjacent to carcinomas, suggesting that absence of esophagin may constitute a harbinger of early esophageal malignant transformation. A greater understanding of transcriptional control of esophagin may provide valuable insights into esophageal malignancy. Therefore, this study was undertaken in order to isolate and carry out initial characterization of a functional promoter for esophagin. A genomic clone containing esophagin was isolated and sequenced, including 2.7 kb of the esophagin promoter region. Esophagin expression was studied in response to various treatments of primary cultured human esophageal epithelial cells and squamous cell carcinoma cell lines. Calcium was the strongest inducer of the endogenous esophagin promoter, with induction occurring at 12-72 hours. In primary cultured esophageal epithelial cells, a region spanning 116 bp upstream of the transcriptional start site to 45 bp downstream was sufficient to direct low, basal, in vitro esophagin expression. However, responsiveness of primary esophageal cells to calcium required inclusion of promoter elements 1688 bp upstream of the transcriptional start site. Site-directed mutagenesis studies suggested a putative role for C/EBP-beta, OCT-1, and OCT-3 transcription factor binding sites in the minimal promoter region. In conjunction with published human in vivo studies, these data support the hypothesis that esophagin is a biomarker of esophageal squamous cell differentiation and provide an in vitro model to evaluate regulatory factors involved in this differentiation process.

Keratins and the keratinocyte activation cycle

In wound healing and many pathologic conditions, keratinocytes become activated: they turn into migratory, hyperproliferative cells that produce and secrete extracellular matrix components and signaling polypeptides. At the same time, their cytoskeleton is also altered by the production of specific keratin proteins. These changes are orchestrated by growth factors, chemokines, and cytokines produced by keratinocytes and other cutaneous cell types. The responding intracellular signaling pathways activate transcription factors that regulate expression of keratin genes. Analysis of these processes led us to propose the existence of a keratinocyte activation cycle, in which the cells first become activated by the release of IL-1. Subsequently, they maintain the activated state by autocrine production of proinflammatory and proliferative signals. Keratins K6 and K16 are markers of the active state. Signals from the lymphocytes, in the form of Interferon-gamma, induce the expression of K17 and make keratinocytes contractile. This enables the keratinocytes to shrink the provisional fibronectin-rich basement membrane. Signals from the fibroblasts, in the form of TGF-beta, induce the expression of K5 and K14, revert the keratinocytes to the healthy basal phenotype, and thus complete the activation cycle.

Structural organization and regulation of the small proline-rich family of cornified envelope precursors suggest a role in adaptive barrier function

The protective barrier provided by stratified squamous epithelia relies on the cornified cell envelope (CE), a structure synthesized at late stages of keratinocyte differentiation. It is composed of structural proteins, including involucrin, loricrin, and the small proline-rich (SPRR) proteins, all encoded by genes localized at human chromosome 1q21. The genetic characterization of the SPRR locus reveals that the various members of this multigene family can be classified into two distinct groups with separate evolutionary histories. Whereas group 1 genes have diverged in protein structure and are composed of three different classes (SPRR1 (2x), SPRR3, and SPRR4), an active process of gene conversion has counteracted diversification of the protein sequences of group 2 genes (SPRR2 class, seven genes). Contrasting with this homogenization process, all individual members of the SPRR gene family show specific in vivo and in vitro expression patterns and react selectively to UV irradiation. Apparently, creation of regulatory rather than structural diversity has been the driving force behind the evolution of the SPRR gene family. Differential regulation of highly homologous genes underlines the importance of SPRR protein dosage in providing optimal barrier function to different epithelia, while allowing adaptation to diverse external insults.

Identification of human epidermal differentiation complex (EDC)-encoded genes by subtractive hybridization of entire YACs to a gridded keratinocyte cDNA library

The epidermal differentiation complex (EDC) comprises a large number of genes that are of crucial importance for the maturation of the human epidermis. So far, 27 genes of 3 related families encoding structural as well as regulatory proteins have been mapped within a 2-Mb region on chromosome 1q21. Here we report on the identification of 10 additional EDC genes by a powerful subtractive hybridization method using entire YACs (950_e_2 and 986_e_10) to screen a gridded human keratinocyte cDNA library. Localization of the detected cDNA clones has been established on a long-range restriction map covering more than 5 Mb of this genomic region. The genes encode cytoskeletal tropomyosin TM30nm (TPM3), HS1-binding protein Hax-1 (HAX1), RNA-specific adenosine deaminase (ADAR1), the 34/67-kD laminin receptor (LAMRL6), and the 26S proteasome subunit p31 (PSMD8L), as well as five hitherto uncharacterized proteins (NICE-1, NICE-2, NICE-3, NICE-4, and NICE-5). The nucleotide sequences and putative ORFs of the EDC genes identified here revealed no homology with any of the established EDC gene families. Whereas database searches revealed that NICE-3, NICE-4, and NICE-5 were expressed in many tissues, no EST or gene-specific sequence was found for NICE-2. Expression of NICE-1 was up-regulated in differentiated keratinocytes, pointing to its relevance for the terminal differentiation of the epidermis. The newly identified EDC genes are likely to provide further insights into epidermal differentiation and they are potential candidates to be involved in skin diseases and carcinogenesis that are associated with this region of chromosome 1. Moreover, the extended integrated map of the EDC, including the polymorphic sequence tag site (STS) markers D1S1664, D1S2346, and D1S305, will serve as a valuable tool for linkage analyses.

Mechanism of repression of squamous differentiation marker, SPRR1B, in malignant bronchial epithelial cells: role of critical TRE-sites and its transacting factors

The overexpression of SPRR1B in bronchial epithelium is a marker for early metaplastic changes and the loss of its expression is associated with an irreversible malignant transformation. In the present study, we have used a model system consisting of normal and malignant bronchial epithelial (BE) cells to elucidate the differential transcriptional control of SPRR1B. SPRR1B expression is either detectable or PMA (phorbol 13-myristate 12-acetate) -inducible in several malignant BE cells including squamous, adeno, small and large cell carcinomas. Loss of SPRR1B expression is correlated well with the lack of strong in vivo protein-DNA interactions at the -152 bp promoter, which contains two functional TRE sites. Even though the basal level AP-1 protein DNA binding pattern is different between normal and malignant cells, PMA significantly enhances Jun and Fos binding to the consensus TRE site in both cell types. Intriguingly, the composition of AP-1 protein binding to the -152 to -86 bp SPRR1B promoter is quite different. In untreated cells, SPRR1B promoter is predominantly occupied by JunD and Fra2. PMA significantly induced binding of JunB and Fra1 in normal cells, while JunB and Fra2 bound to TREs in the malignant cells. Overexpression of fra1 in malignant cells significantly enhanced SPRR1B promoter activity. In contrast, overexpression of fra2, but not fra1, strongly reduced both basal and PMA-inducible promoter activities in normal cells. Together, these results indicate that either temporal expression and/or differential activation of AP-1 proteins, especially Fra1 and Fra2, might contribute to the dysregulation of terminal differentiation marker, SPRR1B, expression in various BE cells.

Phorbol ester-induced expression of airway squamous cell differentiation marker, SPRR1B, is regulated by protein kinase Cdelta /Ras/MEKK1/MKK1-dependent/AP-1 signal transduction pathway

The transcriptional induction of SPRR1B by phorbol 12-myristate 13-acetate (PMA) is mainly mediated by the first -152-base pair 5'-flanking region containing two functional AP-1 sites. In this study, we have analyzed the signaling pathways that mediate the induction in tracheobronchial epithelial cells. PKC inhibitor ablated PMA-stimulated expression of endogenous SPRR1B and reporter gene expression driven by SPRR1B promoter. PKC activator promoted the transcription. The dominant negative protein kinase Cdelta (dn-PKCdelta) and rottlerin (PKCdelta inhibitor) completely suppressed PMA-stimulated promoter activity. dn-Ras or dn-MEKK1 inhibited PMA-stimulated promoter activity, while their corresponding constitutively active mutants augmented it. dn-c-Raf-1 did not have any effect on reporter gene expression. Since MEKK1 activates multiple parallel pathways, we examined involvement of JNK/SAPK, p38, and MKK1 in promoter regulation. Co-expression of the dominant negative forms of MKK4, MKK7, JNK/SAPK, MKK3, MKK6, or p38alpha did not suppress PMA-stimulated reporter gene expression. However, MKK1 inhibitors UO126 and PD98095 suppressed gene expression. Consistent with this, expression of dn-MKK1 strongly suppressed PMA-stimulated promoter activity, while the constitutively active MKK1 augmented it. However, MKK1-mediated induction of SPRR1B probably does not depend on extracellular signal-regulated kinases 1 and 2, suggesting the requirement of another kinase(s). dn-c-Jun mutants abolished PMA-stimulated expression supporting an important role for AP-1 proteins in SPRR1B expression. Together, these results suggest that a PKCdelta/Ras/MEKK1/MKK1-dependent/AP-1 pathway regulates the PMA-inducible expression of the SPRR1B in tracheobronchial epithelial cells.

Isolation and characterization of human and mouse ZIRTL, a member of the IRT1 family of transporters, mapping within the epidermal differentiation complex

We report the precise mapping and characterization of ZIRTL (zinc-iron regulated transporter-like) gene, the first mammalian member of an extensive family of divalent metal ion transporters, comprising IRT1 and ZIP1, ZIP2, ZIP3, and ZIP4 in plants and ZRT1 and ZRT2 in yeast. The human gene maps at the telomeric end of the epidermal differentiation complex (EDC), within chromosomal band 1q21, while the mouse gene maps within the mouse EDC, on mouse chromosome 3, between S100A9 and S100A13. The structure of the human gene has been determined, and message was detected in most adult and fetal tissues including the epidermis. The mouse gene is developmentally regulated and found expressed in fetal and adult suprabasal epidermis, osteoblasts, small intestine, and salivary gland.

Opposite effects of Ras or PKC activation on the expression of the SPRR2A keratinocyte terminal differentiation marker

Epidermal growth factor (EGF) enhances the expression of the keratinocyte terminal differentiation marker SPRR2A, when added to monolayers of basal keratinocytes, induced to stratify by increasing the extracellular calcium concentration. A similar stimulation is found during suspension-induced differentiation in methylcellulose. This effect, which is observed after several hours of EGF addition, is restricted to terminally differentiating keratinocytes and is dependent on PKC signaling. EGF also transiently activates the Ras signaling pathway, with a maximum induction after 10 min (Medema et al., 1994, Mol. Cell. Biol. 14, 7078-7085). The cellular effects of activated Ras were determined by transient transfection of Ha-ras(Leu-61) into normal human keratinocytes. Activated Ras completely inhibited PKC-mediated expression of SPRR2A. This inhibition is mediated via c-Jun as it is reversed by a dominant-negative c-Jun mutant (cJunDelta6/194) and c-Jun can substitute for activated Ras. The inhibitory effect is targeted to a 150-bp minimal promoter region, which is essential and sufficient for SPRR2A expression during keratinocyte terminal differentiation. This indicates that the Ras and PKC pathways, which both can be triggered by EGF, although at different time points, have opposite effects on SPRR2A gene expression.

Expression, regulation, and function of the SPR family of proteins. A review

The small, proline-rich (SPR) genes consist of three subclasses closely linked on human chromosome 1, a region referred to as the epidermal differentiation complex. SPR genes consist of two exons, with the second exon containing the entire open reading frame. SPRs are expressed in all squamous tissues of the skin, scalp, footpad, vaginal epithelia, and most of the epithelial lining of the digestive tract, including the lip, tongue, esophagus, and forestomach. Although SPR1 is absent in normal mucociliary epithelium of the respiratory tract, epithelia that undergo squamous differentiation in response to vitamin-A deficiency or to injury owing to exposure to environmental toxicants express SPR1. High levels of SPR1 are detected in various diseases and cancers of the skin or respiratory epithelia and in nonkeratinizing papillary adenocarcinomas. SPR expression can be regulated by transcriptional factors, by posttranscriptional factors, or by factors that affect SPR1 mRNA translation or protein turnover. Furthermore, regulation can be affected by the state of cell proliferation. The presence of SPR1 in most of these epithelia, and the absence of SPR3 in normal skin, suggest that these subclasses have distinct functions. Various approaches to the study of the cross-linked envelope (CE) components in identifying SPR1 and SPR2 and in suggesting that SPRs are one of the precursor proteins of the CE. However, expression of SPR1 in nonsquamous tissues and cell lines indicates a function not associated with squamous differentiation. Several studies have demonstrated that SPR1 antibodies react with nuclear proteins and that SPR1 is expressed in cells before entering the G0 phase of the cell cycle. Future studies should clarify the role of SPRs by modifying their contents in CE, and should identify SPR-associated proteins to clarify the cell growth-related role of SPR1.

Structure and evolution of the human SPRR3 gene: implications for function and regulation

SPRR3, a member of the SPRR family of cornified envelope precursor proteins, is expressed in oral and esophageal epithelia, where it is strictly linked to keratinocyte terminal differentiation. This gene is characterized by intragenic duplications that have created the characteristic proline-rich repeats in the coding sequence, an alternative noncoding exon, and a 200-bp polypyrimidine tract in the promoter region. Mutational analysis of the promoter region and transient transfection in normal human keratinocytes showed that in addition to the polypyrimidine tract, multiple regulatory elements are involved in differentiation-specific expression. These elements include a high-affinity Ets binding site bound by ESE-1, an AP-1 site (TRE) recognized by the Jun/Fos family of transcription factors, and an ATF/CRE bound by Jun/Fos and ATF factors. The repositioning of the SPRR3 Ets binding site during evolution has a major effect on the relative contribution of this site to promoter activity.

AP-1 and ets transcription factors regulate the expression of the human SPRR1A keratinocyte terminal differentiation marker

The 173-base pair proximal promoter of SPRR1A is necessary and sufficient for regulated expression in primary keratinocytes induced to differentiate either by increasing extracellular calcium or by 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment. Whereas calcium-induced expression depends both on an AP-1 and an Ets binding site in this region, responsiveness to TPA resides mainly (but not exclusively) on the Ets element, indicating that Ets factors are important targets for protein kinase C signaling during keratinocyte terminal differentiation. This conclusion is further substantiated by the finding that expression of ESE-1, an Ets transcription factor involved in SPRR regulation, is also induced by TPA, with kinetics similar to SPRR1A. The strict AP-1 requirement in SPRR1A for calcium-induced differentiation is not found for SPRR2A, despite the presence of an identical AP-1 consensus binding site in this gene. Binding site swapping indicates that both the nucleotides flanking the TGAGTCA core sequence and the global promoter context are essential in determining the contribution of AP-1 factors in gene expression during keratinocyte terminal differentiation. In the distal SPRR1A promoter region, a complex arrangement of positive and negative regulatory elements, which are only conditionally needed for promoter activity, are likely involved in gene-specific fine-tuning of the expression of this member of the SPRR gene family.

Epidermal signal transduction and transcription factor activation in activated keratinocytes

In the area of biology, many laboratories around the world are dissecting and characterizing signal transduction mechanisms and transcription factors responsive to various growth factors and cytokines, in various cell types. However, because of the differences in systems used, it is not clear whether these systems coexist, whether they interact meaningfully, and what their relative roles are. Epidermal keratinocytes are the perfect cell type in which to integrate this knowledge, because in these cells these mechanisms are known to be relevant. Keratinocytes both produce and respond to growth factors and cytokines, especially in pathological conditions and during wound healing, when the physiology of keratinocytes is altered in a way specified by the presence of a subset growth factors and cytokines. In fact, growth factors and cytokines cause the major changes in gene expression and keratinocyte behavior in various cutaneous diseases. In some cases, such as in wound healing, these responses are highly beneficial; in others, such as in psoriasis, they are pathological. It is not clear at present which are operating in which conditions, which are important for the healing process and which are harmful. Growth factors and cytokines affect keratinocytes sometimes simultaneously, at other times individually. In this manuscript we describe the signal transduction pathways responsible for the effects of interferons, the EGF/TGF alpha family and the TNF alpha/IL-1 family of signaling molecules. We also describe the important transcription factors known to be functional in epidermis, with particular emphasis on those factors that are activated by growth factors and cytokines. Finally, we describe what is known about transcriptional regulation of keratin genes, especially those specifically expressed in pathological processes in the epidermis. We expect that the enhanced understanding of the pathways regulating gene expression in keratinocytes will identify the pharmacological targets, the signal transducing proteins and the corresponding transcription factors, used by growth factors and cytokines. This research will led to development of compounds precisely aimed at those targets, allowing us to isolate and inhibit the harmful side effects of growth factors and cytokines. Such compounds should lead to highly specific and therefore more effective treatments of the cutaneous disorders in which these pathways play significant roles.

The expression of desmoglein isoforms in cultured human keratinocytes is regulated by calcium, serum, and protein kinase C

Three desmoglein (Dsg) isoforms are expressed in a differentiation-specific fashion in the epidermis, with Dsg2 being basal, Dsg3 (pemphigus vulgaris antigen) basal and spinous, and Dsg1 (pemphigus foliaceus antigen) predominantly granular. To better understand the mechanism(s) regulating Dsg isoform expression, we examined the expression pattern of Dsg1, Dsg2, and Dsg3 in normal human epidermal keratinocytes (NHEKs), the immortalized, nontumorigenic HaCaT cell line, and several squamous cell carcinoma cell lines (SCC-9, SCC-12F, SCC-13, and SCC-25). In all cells, the accumulation of high Dsg protein levels required calcium and was not observed in low calcium (0.05-0.07 mM) media. NHEKs expressed Dsg1 in all media tested, consistent with their normal differentiation capacity. HaCaT and SCC-25 also expressed Dsg1; however, the presence of serum in the media dramatically decreased Dsg1 protein levels. Serum also inhibited Dsg1 mRNA levels in HaCaT cells. Dsg1 was not detected in extracts from SCC-9, SCC-12F, and SCC-13 under any conditions. Since activation of protein kinase C (PKC) is involved in keratinocyte differentiation, we evaluated the effects of PKC down-regulation on Dsg isoform expression. Long-term treatment with either the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or bryostatin 1 inhibited levels of Dsg1 and Dsg3, but not Dsg2 in NHEKs and HaCaT cells. Chronic TPA also decreased Dsg1 and Dsg3 mRNA levels in NHEKs, further supporting a role for PKC activation in the expression of the suprabasal Dsg1 and Dsg3. These results identify several regulatory mechanisms by which the differentiation-specific pattern of desmosomal cadherins is established in the epidermis.