Suppression of keratinocyte stratification by a dominant negative JunB mutant without blocking cell proliferation

Promotion of squamous cell carcinoma tumorigenesis by oncogene-mediated THG-1/TSC22D4 phosphorylation

Carcinoma cells possess high proliferative and invasive potentials and exhibit a resilience against stresses, metabolic disorder, and therapeutic efforts. These properties are mainly acquired by genetic alterations including driver gene mutations. However, the detailed molecular mechanisms have not been fully elucidated. Here, we provide a novel mechanism connecting oncogenic signaling and the tumorigenic properties by a transforming growth factor-β1-stimulated clone 22 (TSC-22) family protein, THG-1 (also called as TSC22D4). THG-1 is localized at the basal layer of normal squamous epithelium and overexpressed in squamous cell carcinomas (SCCs). THG-1 knockdown suppressed SCC cell proliferation, invasiveness, and xenograft tumor formation. In contrast, THG-1 overexpression promoted the EGF-induced proliferation and stratified epithelium formation. Furthermore, THG-1 is phosphorylated by the receptor tyrosine kinase (RTK)-RAS-ERK pathway, which promoted the oncogene-mediated tumorigenesis. Moreover, THG-1 involves in the alternative splicing of CD44 variants, a regulator of invasiveness, stemness, and oxidative stress resistance under the RTK pathway. These findings highlight the pivotal roles of THG-1 as a novel effector of SCC tumorigenesis, and the detection of THG-1 phosphorylation by our established specific antibody could contribute to cancer diagnosis and therapy.

ACLP Activates Cancer-Associated Fibroblasts and Inhibits CD8+ T-Cell Infiltration in Oral Squamous Cell Carcinoma

We previously showed that upregulation of adipocyte enhancer-binding protein 1 (AEBP1) in vascular endothelial cells promotes tumor angiogenesis. In the present study, we aimed to clarify the role of stromal AEBP1/ACLP expression in oral squamous cell carcinoma (OSCC). Immunohistochemical analysis showed that ACLP is abundantly expressed in cancer-associated fibroblasts (CAFs) in primary OSCC tissues and that upregulated expression of ACLP is associated with disease progression. Analysis using CAFs obtained from surgically resected OSCCs showed that the expression of AEBP1/ACLP in CAFs is upregulated by co-culture with OSCC cells or treatment with TGF-β1, suggesting cancer-cell-derived TGF-β1 induces AEBP1/ACLP in CAFs. Collagen gel contraction assays showed that ACLP contributes to the activation of CAFs. In addition, CAF-derived ACLP promotes migration, invasion, and in vivo tumor formation by OSCC cells. Notably, tumor stromal ACLP expression correlated positively with collagen expression and correlated inversely with CD8+ T cell infiltration into primary OSCC tumors. Boyden chamber assays suggested that ACLP in CAFs may attenuate CD8+ T cell migration. Our results suggest that stromal ACLP contributes to the development of OSCCs, and that ACLP is a potential therapeutic target.

Activated macrophages promote invasion by early colorectal cancer via an interleukin 1β-serum amyloid A1 axis

Submucosal invasion and lymph node metastasis are important issues affecting treatment options for early colorectal cancer (CRC). In this study, we aimed to unravel the molecular mechanism underlying the invasiveness of early CRCs. We performed RNA‐sequencing (RNA‐seq) with poorly differentiated components (PORs) and their normal counterparts isolated from T1 CRC tissues and detected significant upregulation of serum amyloid A1 (SAA1) in PORs. Immunohistochemical analysis revealed that SAA1 was specifically expressed in PORs at the invasive front of T1b CRCs. Upregulation of SAA1 in CRC cells promoted cell migration and invasion. Coculture experiments using CRC cell lines and THP‐1 cells suggested that interleukin 1β (IL‐1β) produced by macrophages induces SAA1 expression in CRC cells. Induction of SAA1 and promotion of CRC cell migration and invasion by macrophages were inhibited by blocking IL‐1β. These findings were supported by immunohistochemical analysis of primary T1 CRCs showing accumulation of M1‐like/M2‐like macrophages at SAA1‐positive invasive front regions. Moreover, SAA1 produced by CRC cells stimulated upregulation of matrix metalloproteinase‐9 in macrophages. Our data suggest that tumor‐associated macrophages at the invasive front of early CRCs promote cancer cell migration and invasion through induction of SAA1 and that SAA1 may be a predictive biomarker and a useful therapeutic target.

Local administration of anti-hepatocyte growth factor-neutralizing antibody reverts naturally occurring periodontitis

OBJECTIVES

Periodontitis is a chronic inflammatory process associated with the loss of tooth-supporting tissue. The imbalance of epithelial-mesenchymal signaling is considered to drive disease progression, and hepatocyte growth factor (HGF) is one of the main mediators of this interaction. The aim of this study was to validate the role of HGF in the pathogenesis of periodontitis and to evaluate the effects of anti-HGF neutralizing antibodies.

METHODS

Gingival tissues from cynomolgus monkeys, which naturally develop severe periodontitis, were isolated to establish an in vitro periodontitis model. Periodontitis-affected monkeys were treated by gingival injection of anti-HGF neutralizing antibodies. The therapeutic effects were documented by clinical examination (probing depth and bleeding on probing), histological examination of tissue, and reevaluation of gingival fibroblasts in the in vitro model.

RESULTS

Periodontitis-affected monkeys contain periodontitis-associated fibroblasts (PAFs) with a pro-inflammatory phenotype that induced pronounced collagen degradation in vitro. This degradation was effectively inhibited by anti-HGF-neutralizing antibodies. Locally administered anti-HGF antibody to monkey gingiva clinically improved the severity of periodontitis. This was also reflected in the tissue histology with lower inflammatory cell infiltrates in treated gingiva than in non-treated gingiva. Moreover, fibroblasts isolated from anti-HGF-treated gingiva demonstrated reduced collagen degradation capacity.

CONCLUSIONS

Our study confirmed the central role of HGF in the pathogenesis of severe periodontitis in relevant in vitro and in vivo models. The positive effect of anti-HGF treatment provides a strong rationale for the use of anti-HGF-neutralizing antibodies for the treatment of human periodontitis.

Targeting hepatocyte growth factor in epithelial-stromal interactions in an in vitro experimental model of human periodontitis

Periodontitis is a chronic inflammatory disease leading to progressive connective tissue degradation and loss of the tooth-supporting bone. Clinical and experimental studies suggest that hepatocyte growth factor (HGF) is involved in the dysregulated fibroblast–epithelial cell interactions in periodontitis. The aim of this study was to explore effects of HGF to impact fibroblast-induced collagen degradation. A patient-derived experimental cell culture model of periodontitis was applied. Primary human epithelial cells and fibroblasts isolated from periodontitis-affected gingiva were co-cultured in a three-dimensional collagen gel. The effects of HGF neutralizing antibody on collagen gel degradation were tested and transcriptome analyses were performed. HGF neutralizing antibody attenuated collagen degradation and elicited expression changes of genes related to extracellular matrix (ECM) and cell adhesion, indicating that HGF signaling inhibition leads to extensive impact on cell–cell and cell–ECM interactions. Our study highlights a potential role of HGF in periodontitis. Antagonizing HGF signaling by a neutralizing antibody may represent a novel approach for periodontitis treatment.

Transcriptome analysis of periodontitis-associated fibroblasts by CAGE sequencing identified DLX5 and RUNX2 long variant as novel regulators involved in periodontitis

Periodontitis is affecting over half of the adult population, and represents a major public health problem. Previously, we isolated a subset of gingival fibroblasts (GFs) from periodontitis patients, designated as periodontitis-associated fibroblasts (PAFs), which were highly capable of collagen degradation. To elucidate their molecular profiles, GFs isolated form healthy and periodontitis-affected gingival tissues were analyzed by CAGE-seq and integrated with the FANTOM5 atlas. GFs from healthy gingival tissues displayed distinctive patterns of CAGE profiles as compared to fibroblasts from other organ sites and characterized by specific expression of developmentally important transcription factors such as BARX1, PAX9, LHX8, and DLX5. In addition, a novel long non-coding RNA associated with LHX8 was described. Furthermore, we identified DLX5 regulating expression of the long variant of RUNX2 transcript, which was specifically active in GFs but not in their periodontitis-affected counterparts. Knockdown of these factors in GFs resulted in altered expression of extracellular matrix (ECM) components. These results indicate activation of DLX5 and RUNX2 via its distal promoter represents a unique feature of GFs, and is important for ECM regulation. Down-regulation of these transcription factors in PAFs could be associated with their property to degrade collagen, which may impact on the process of periodontitis.

Fibroblast VEGF-receptor 1 expression as molecular target in periodontitis

AIM

Degradation of extracellular matrices is an integral part in periodontitis. For antagonizing this pathophysiological mechanism, we aimed at identifying gene expression profiles in disease progression contributing periodontitis-associated fibroblasts (PAFs) versus normal gingival fibroblasts to determine their molecular repertoire, and exploit it for therapeutic intervention.

MATERIALS AND METHODS

Applying an exploratory analysis using a small number of microarrays in combination with a three dimensional (3D) in vitro culture model that incorporates some aspects of periodontitis, PAFs were initially characterized by gene-expression analyses, followed by targeted gene down-regulation and pharmacological intervention in vitro. Further, immunohistochemistry was applied for phosphorylation analyses in tissue specimens.

RESULTS

PAFs were characterized by 42 genes being commonly up-regulated >1.5-fold, and by five genes that were concordantly down-regulated (<0.7-fold). Expression of vascular endothelial growth factor (VEGF)-receptor 1 (Flt-1) was highly enhanced, and was thus further explored in in vitro culture models of periodontal fibroblasts without accounting for the microbiome. Phosphorylation of the VEGF-receptor 1 was enhanced in PAFs. Receptor inhibition by a specific VEGF-receptor inhibitor or intrinsic down-regulation by RNAi of the VEGF-receptor kinase in 3D gel cultures resulted in significant reduction in collagen degradation associated with increased tissue inhibitor of metalloproteinase expression, suggesting that Flt-1 may contribute to periodontitis.

CONCLUSION

Based on the finding that VEGF-receptor kinase inhibition impaired collagen degradation pathways, Flt-1 may represent a candidate for therapeutic approaches in periodontitis.

Epoxyeicosatrienoic acids enhance embryonic haematopoiesis and adult marrow engraftment

Haematopoietic stem and progenitor cell (HSPC) transplant is a widely used treatment for life-threatening conditions such as leukaemia; however, the molecular mechanisms regulating HSPC engraftment of the recipient niche remain incompletely understood. Here we develop a competitive HSPC transplant method in adult zebrafish, using in vivo imaging as a non-invasive readout. We use this system to conduct a chemical screen, and identify epoxyeicosatrienoic acids (EETs) as a family of lipids that enhance HSPC engraftment. The pro-haematopoietic effects of EETs were conserved in the developing zebrafish embryo, where 11,12-EET promoted HSPC specification by activating a unique activator protein 1 (AP-1) and runx1 transcription program autonomous to the haemogenic endothelium. This effect required the activation of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway, specifically PI(3)Kγ. In adult HSPCs, 11,12-EET induced transcriptional programs, including AP-1 activation, which modulate several cellular processes, such as migration, to promote engraftment. Furthermore, we demonstrate that the EET effects on enhancing HSPC homing and engraftment are conserved in mammals. Our study establishes a new method to explore the molecular mechanisms of HSPC engraftment, and discovers a previously unrecognized, evolutionarily conserved pathway regulating multiple haematopoietic generation and regeneration processes. EETs may have clinical application in marrow or cord blood transplantation.

Three-dimensional Co-culture model for tumor-stromal interaction

Cancer progression (initiation, growth, invasion and metastasis) occurs through interactions between malignant cells and the surrounding tumor stromal cells. The tumor microenvironment is comprised of a variety of cell types, such as fibroblasts, immune cells, vascular endothelial cells, pericytes and bone-marrow-derived cells, embedded in the extracellular matrix (ECM). Cancer-associated fibroblasts (CAFs) have a pro-tumorigenic role through the secretion of soluble factors, angiogenesis and ECM remodeling. The experimental models for cancer cell survival, proliferation, migration, and invasion have mostly relied on two-dimensional monocellular and monolayer tissue cultures or Boyden chamber assays. However, these experiments do not precisely reflect the physiological or pathological conditions in a diseased organ. To gain a better understanding of tumor stromal or tumor matrix interactions, multicellular and three-dimensional cultures provide more powerful tools for investigating intercellular communication and ECM-dependent modulation of cancer cell behavior. As a platform for this type of study, we present an experimental model in which cancer cells are cultured on collagen gels embedded with primary cultures of CAFs.

B-Myb enhances proliferation and suppresses differentiation of keratinocytes in three-dimensional cell culture

B-Myb (Mybl2) is a member of the Myb gene family of transcription factors involved in the control of cell growth, differentiation, and apoptosis. The effects of B-Myb on keratinocyte proliferation and differentiation have not yet been clarified. The present study was performed to examine the role of B-Myb in proliferation and differentiation of the spontaneously immortalized human skin keratinocyte cell line HaCaT and normal human keratinocytes with formation of a stratified epidermoid structure in air-liquid interface three-dimensional culture. B-Myb was expressed specifically in undifferentiated normal keratinocytes and downregulated during differentiation. The constitutive overexpression of B-Myb in HaCaT cells during air exposure-induced differentiation resulted in an undifferentiated phenotype, i.e., thickening of the stratified layers, suppression of differentiation marker expression, and retention of proliferative activity with activation of cell cycle regulatory proteins in the S and G2/M phases. In contrast, suppression of B-Myb caused their downregulation and constrained proliferation with retention of differentiation capacity. These findings suggested that B-Myb plays an important role in maintenance of the undifferentiated phenotype of keratinocytes in the basal epidermal layer.

Podoplanin is expressed at the invasive front of esophageal squamous cell carcinomas and is involved in collective cell invasion

The expression of podoplanin is reportedly involved in collective cell invasion, which is independent from the epithelial-mesenchymal transition (EMT). We focused on the expression of podoplanin in esophageal squamous cell carcinomas (ESCC) and investigated the correlation of podoplanin and EMT-related markers, and evaluated its prognostic significance. Five ESCC cell lines were subjected to western blot analysis for podoplanin and EMT markers. The effects of podoplanin on EMT and carcinoma invasion were evaluated with wound healing assays, invasion assays and 3-D culture. Transfection of ectopic podoplanin into a podoplanin-negative ESCC cell line (TE-15) induced cell migration and invasive activity (P < 0.001 and P < 0.05, respectively) without downregulation of E-cadherin. In contrast, transfection of si-podoplanin RNA into a podoplanin-positive ESCC cell line (TE-13) reduced cell migration and invasive activity (P < 0.05). We reviewed 101 patients who had undergone esophagectomy for ESCC. Podoplanin expression was observed in 58 patients (57.4%), and positive expression was positively correlated with expression of E-cadherin (P < 0.01), deeper wall invasion (P < 0.01), venous invasion (P < 0.05) and poorer prognosis (P < 0.01). Multivariate Cox analysis revealed that expression of podoplanin was a significant and independent unfavorable predictor of survival (P < 0.05). These data suggest that podoplanin is significantly associated with and likely contributes to ESCC invasion in the absence of EMT.

Role of JunB in adenosine A2B receptor-mediated vascular endothelial growth factor production

Interstitial adenosine stimulates neovascularization in part through A2B adenosine receptor-dependent upregulation of vascular endothelial growth factor (VEGF). In the current study, we tested the hypothesis that A2B receptors upregulate JunB, which can contribute to stimulation of VEGF production. Using the human microvascular endothelial cell line, human mast cell line, mouse cardiac Sca1-positive stromal cells, and mouse Lewis lung carcinoma (LLC) cells, we found that adenosine receptor-dependent upregulation of VEGF production was associated with an increase in VEGF transcription, activator protein-1 (AP-1) activity, and JunB accumulation in all cells investigated. Furthermore, the expression of JunB, but not the expression of other genes encoding transcription factors from the Jun family, was specifically upregulated. In LLC cells expressing A2A and A2B receptor transcripts, only the nonselective adenosine agonist NECA (5'-N-ethylcarboxamidoadenosine), but not the selective A2A receptor agonist CGS21680 [2-p-(2-carboxyethyl) phenylethylamino-5'-N-ethylcarboxamidoadenosine], significantly increased JunB reporter activity and JunB nuclear accumulation, which were inhibited by the A2B receptor antagonist PSB603 [(8-[4-[4-((4-chlorophenzyl)piperazide-1-sulfonyl)phenyl]]-1-propylxanthine]. Using activators and inhibitors of intracellular signaling, we demonstrated that A2B receptor-dependent accumulation of JunB protein and VEGF secretion share common intracellular pathways. NECA enhanced JunB binding to the murine VEGF promoter, whereas mutation of the high-affinity AP-1 site (-1093 to -1086) resulted in a loss of NECA-dependent VEGF reporter activity. Finally, NECA-dependent VEGF secretion and reporter activity were inhibited by the expression of a dominant negative JunB or by JunB knockdown. Thus, our data suggest an important role of the A2B receptor-dependent upregulation of JunB in VEGF production and possibly other AP-1-regulated events.

Regulation of S100A2 expression by TGF-β-induced MEK/ERK signalling and its role in cell migration/invasion

S100A2, an EF hand calcium-binding protein, is a potential biomarker in several cancers and is also a TGF-β (transforming growth factor-β)-regulated gene in melanoma and lung cancer cells. However, the mechanism of S100A2 regulation by TGF-β and its significance in cancer progression remains largely unknown. In the present study we report the mechanism of S100A2 regulation by TGF-β and its possible role in TGF-β-mediated tumour promotion. Characterization of the S100A2 promoter revealed an AP-1 (activator protein-1) element at positions -1161 to -1151 as being the most critical factor for the TGF-β1 response. Chromatin immunoprecipitation and electrophoretic mobility-shift assays confirmed the functional binding of the AP-1 complex, predominantly JunB, to the S100A2 promoter in response to TGF-β1 in HaCaT keratinocytes. JunB overexpression markedly stimulated the S100A2 promoter which was blocked by the dominant-negative JunB and MEK1 [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase 1] inhibitor, PD98059. Intriguingly, despite the presence of a putative SMAD-binding element, S100A2 regulation by TGF-β1 was found to be SMAD3 independent. Interestingly, p53 protein and TGF-β1 show synergistic regulation of the S100A2 promoter. Finally, knockdown of S100A2 expression compromised TGF-β1-induced cell migration and invasion of Hep3B cells. Together our findings highlight an important link between the TGF-β1-induced MAPK and p53 signalling pathways in the regulation of S100A2 expression and pro-tumorigenic actions.

Characterization of human lung cancer-associated fibroblasts in three-dimensional in vitro co-culture model

Lung cancer is the most common cause of cancer-related death worldwide. Stromal cancer-associated fibroblasts (CAFs) play crucial roles in carcinogenesis, proliferation, invasion, and metastasis of non-small cell lung carcinoma, and targeting of CAFs could be a novel strategy for cancer treatment. However, the characteristics of human CAFs still remain to be better defined. In this study, we established patient-matched CAFs and normal fibroblasts (NFs), from tumoral and non-tumoral portions of resected lung tissue from lung cancer patients. CAFs showed higher α-smooth muscle actin (α-SMA) expression than NFs, and CAFs clearly enhanced collagen gel contraction. Furthermore, we employed three-dimensional co-culture assay with A549 lung cancer cells, where CAFs were more potent in inducing collagen gel contraction. Hematoxylin and eosin staining of co-cultured collagen gel revealed that CAFs had the potential to increase invasion of A549 cells compared to NFs. These observations provide evidence that lung CAFs have the tumor-promoting capacity distinct from NFs.

MicroRNA-203 functions as a tumor suppressor in basal cell carcinoma

Basal cell carcinoma (BCC) of the skin represents the most common malignancy in humans. MicroRNAs (miRNAs), small regulatory RNAs with pleiotropic function, are commonly misregulated in cancer. Here we identify miR-203, a miRNA abundantly and preferentially expressed in skin, to be downregulated in BCCs. We show that activation of the Hedgehog (HH) pathway, critically involved in the pathogenesis of BCCs, as well as the EGFR/MEK/ERK/c-JUN signaling pathway suppresses miR-203. We identify c-JUN, a key effector of the HH pathway, as a novel direct target for miR-203 in vivo. Further supporting the role of miR-203 as a tumor suppressor, in vivo delivery of miR-203 mimics in a BCC mouse model results in the reduction of tumor growth. Our results identify a regulatory circuit involving miR-203 and c-JUN, which provides functional control over basal cell proliferation and differentiation. We propose that miR-203 functions as a ‘bona fide' tumor suppressor in BCC, whose suppressed expression contributes to oncogenic transformation via derepression of multiple stemness- and proliferation-related genes, and its overexpression could be of therapeutic value.

Expression of laminin 5-γ2 chain in cutaneous squamous cell carcinoma and its role in tumour invasion

Background:

Laminin-5 (Ln5), a heterotrimer composed of three chains (α3, β3, and γ2), is a major component of the basement membrane in most adult tissues. One of the chains, Ln5-γ2, is a marker of invasive tumours because it is frequently expressed as a monomer in malignant tumours. Recent studies from our laboratories detected higher levels of Ln5-γ2 expression in basal cell carcinoma (BCC) than in trichoblastoma. Furthermore, Ln5-γ2 overexpression tended to correlate with aggressiveness in BCC.

Methods:

In this study, we compared the expression of Ln5-γ2 in invasive squamous cell carcinoma (SCC, n=62) of the skin to that in preinvasive Bowen’s disease (BD, n=51), followed by analysis of the role of Ln5-γ2 in cancer invasion in vitro.

Results:

Immunohistochemically, the proportion of SCC cases (86%) strongly positive for Ln5-γ2 expression was higher than that of BD (16%). Real-time RT–PCR showed Ln5-γ2 overexpression in SCC cell line, A431, compared with normal keratinocyte cell line, HaCaT. Ln5-γ2 monomer and proteolytically cleaved, biologically active fragments of Ln5-γ2 were identified in SCC tumour extracts. In in vitro raft cultures, which simulate in vivo conditions, Ln5-γ2 siRNA significantly suppressed epidermal growth factor (EGF)-stimulated A431 cell invasion.

Conclusion:

Our results indicate that Ln5-γ2 has a role in cutaneous SCC invasion.

c-Jun promotes whereas JunB inhibits epidermal neoplasia

Deregulation of the activator protein 1 (AP1) family gene regulators has been implicated in a wide range of diseases, including cancer. In this study we report that c-Jun was activated in human squamous cell carcinoma (SCC) and coexpression of c-Jun with oncogenic Ras was sufficient to transform primary human epidermal cells into malignancy in a regenerated human skin grafting model. In contrast, JunB was not induced in a majority of human SCC cells. Moreover, exogenous expression of JunB inhibited tumorigenesis driven by Ras or spontaneous human SCC cells. Conversely, the dominant-negative JunB mutant (DNJunB) promoted tumorigenesis, which is in contrast to the tumor-suppressor function of the corresponding c-Jun mutant. At the cellular level, JunB induced epidermal cell senescence and slowed cell growth in a cell-autonomous manner. Consistently, coexpression of JunB and Ras induced premature epidermal differentiation concomitant with upregulation of p16 and filaggrin and downregulation of cyclin D1 and cyclin-dependent kinase 4 (CDK4). These findings indicate that JunB and c-Jun differentially regulate cell growth and differentiation and induce opposite effects on epidermal neoplasia.JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://www.nature.com/jid/journalclub.

TGF-β regulates isoform switching of FGF receptors and epithelial-mesenchymal transition

Both TGF-β and FGF signalling regulate the epithelial–mesenchymal transition. Here, TGF-β is found to promote myofibroblast differentiation, while concomitant FGF pathway activation instead drives cells towards an invasive mesenchymal fate.

The epithelial–mesenchymal transition (EMT) is a crucial event in wound healing, tissue repair, and cancer progression in adult tissues. Here, we demonstrate that transforming growth factor (TGF)-β induced EMT and that long-term exposure to TGF-β elicited the epithelial–myofibroblastic transition (EMyoT) by inactivating the MEK-Erk pathway. During the EMT process, TGF-β induced isoform switching of fibroblast growth factor (FGF) receptors, causing the cells to become sensitive to FGF-2. Addition of FGF-2 to TGF-β-treated cells perturbed EMyoT by reactivating the MEK-Erk pathway and subsequently enhanced EMT through the formation of MEK-Erk-dependent complexes of the transcription factor δEF1/ZEB1 with the transcriptional corepressor CtBP1. Consequently, normal epithelial cells that have undergone EMT as a result of combined TGF-β and FGF-2 stimulation promoted the invasion of cancer cells. Thus, TGF-β and FGF-2 may cooperate with each other and may regulate EMT of various kinds of cells in cancer microenvironment during cancer progression.

TGF-β Signaling in Gingival Fibroblast-Epithelial Interaction

The underlying mechanism and the therapeutic regimen for the transition of reversible gingivitis to irreversible periodontitis are unclear. Since transforming growth factor (TGF)-β has been implicated in differentially regulated gene expression in gingival fibroblasts, we hypothesized that TGF-β signaling is activated in periodontitis-affected gingiva, along with enhanced collagen degradation, that is reversed by TGF-β inhibition. A novel three-dimensional (3D) gel-culture system consisting of primary human gingival fibroblasts (GF) and gingival epithelial (GE) cells in collagen gels was applied. GF populations from patients with severe periodontitis degraded collagen gels, which was reduced by TGF-β-receptor kinase inhibition. Up-regulation of TGF-β-responsive genes was evident in GF/GE co-cultures. Furthermore, the TGF-β downstream transducer Smad3C was highly phosphorylated in periodontitis-affected gingiva and 3D cultures. These results imply that TGF-β signaling is involved in fibroblast-epithelial cell interaction in periodontitis, and suggest that the 3D culture system is a useful in vitro model for therapeutic drug screening for periodontitis.

Overexpression of the transcription factor Yin-Yang-1 suppresses differentiation of HaCaT cells in three-dimensional cell culture

Yin-Yang-1 (YY1) is a member of the GLI-Krüppel family of transcription factors, and both YY1 mRNA and protein expression have been identified in a number of different tissues and cell types suggesting that it is expressed both constitutively and ubiquitously. In epidermal tissue, however, we reported previously that YY1 protein is expressed at high levels in undifferentiated basal keratinocytes and is downregulated during differentiation toward the suprabasal layers. This differential expression pattern during keratinocyte differentiation suggests that YY1 may have an important role in regulating keratinocyte differentiation. In this study, we examined the role of YY1 in differentiation of the human keratinocyte cell line HaCaT using air-liquid interface three-dimensional culture. The constitutive overexpression of YY1 in HaCaT cells during air exposure-induced differentiation resulted in an undifferentiated phenotype, thickening of the stratified layers, suppression of differentiation marker expression, and retention of proliferative activity. These findings suggested that YY1 may have an important role in maintenance of the undifferentiated phenotype of keratinocytes in the basal epidermal layer, and that reduction of YY1 expression in the suprabasal layers may allow keratinocytes to differentiate and move toward the upper layers of the epidermis.

Protein kinase C delta and eta differently regulate the expression of loricrin and Jun family proteins in human keratinocytes

Barrier function of the epidermis is maintained by precise expression of keratinocyte-specific structural proteins to form the cornified cell envelope (CE). Loricrin, a major component of the CE, is expressed at the late stage of keratinocyte differentiation. In this study, we reveal the isoform-specific function of protein kinase C (PKC) in the regulation of loricrin expression. Both PKCdelta and PKCeta have been recognized as differentiation-promoting isoforms. However, loricrin expression was inversely controlled by PKCdelta and PKCeta in cultured keratinocytes and 3D skin culture; i.e. loricrin expression was decreased by PKCdelta and increased by PKCeta. To clarify the mechanisms that PKCdelta and PKCeta oppositely regulate the loricrin expression, we examined the expression of activator protein-1 (AP-1) family proteins, which modulate the transcription of loricrin and are downstream molecules of PKC. PKCdelta decreased c-Jun expression, whereas PKCeta increased JunD, which are positive regulators of loricrin transcription. These findings suggest that inverse effects of PKCdelta and PKCeta on loricrin expression attributes to the expression of c-Jun and JunD.

Protein kinase C-dependent upregulation of miR-203 induces the differentiation of human keratinocytes

Terminal differentiation of keratinocytes is a multistep process that requires a coordinated program of gene expression. We aimed to explore the possible involvement of a previously unreported class of non-coding RNA genes, microRNAs (miRNAs) in keratinocyte differentiation by using miRNA expression profiling. Out of 365 miRNAs tested, 7 showed significant change between keratinocytes cultured in low or high calcium concentration. The highest-ranked upregulated gene was miR-203, whose expression was significantly upregulated in response to calcium and other inducers of keratinocyte differentiation such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and vitamin D(3). Differentiation-induced upregulation of miR-203 expression was blocked by treatment with specific inhibitors of protein kinase C (PKC), GF109203X, and Ro31-8220. Moreover, our results showed that the activator protein-1 (AP-1) proteins c-Jun and JunB regulate miR-203 expression in keratinocytes. In contrast to inducers of keratinocyte differentiation, epidermal growth factor and keratinocyte growth factor suppressed miR-203 expression in keratinocytes below the basal level. Overexpression of miR-203 in keratinocytes resulted in enhanced differentiation, whereas inhibition of miR-203 suppressed calcium-induced terminal differentiation as judged by involucrin expression. These results suggest that upregulation of miR-203 in human keratinocytes is required for their differentiation and is dependent on the activation of the PKC/AP-1 pathway.