Regulation of E-cadherin gene expression during tumor progression: the role of a new Ets-binding site and the E-pal element

Mesenchymal-to-Epithelial Transitions in Development and Cancer

The evolutionary emergence of the mesenchymal phenotype greatly increased the complexity of tissue architecture and composition in early Metazoan species. At the molecular level, an epithelial-to-mesenchymal transition (EMT) was permitted by the innovation of specific transcription factors whose expression is sufficient to repress the epithelial transcriptional program. The reverse process, mesenchymal-to-epithelial transition (MET), involves direct inhibition of EMT transcription factors by numerous mechanisms including tissue-specific MET-inducing transcription factors (MET-TFs), micro-RNAs, and changes to cell and tissue architecture, thus providing an elegant solution to the need for tight temporal and spatial control over EMT and MET events during development and adult tissue homeostasis.

Epithelial-mesenchymal-transition-inducing transcription factors: new targets for tackling chemoresistance in cancer?

Chemoresistance remains a major complication of cancer treatments. Recent data provide strong evidence that chemoresistance is linked to epithelial-mesenchymal transition (EMT), a latent developmental process, which is re-activated during cancer progression. EMT involves transcriptional reprogramming and is driven by specific EMT transcription factors (EMT-TFs). In this review, we provide support for the idea that EMT-TFs contribute to the development of resistance against cancer therapy and discuss how EMT-TFs might be targeted to advance novel therapeutic approaches to the treatment of cancer.

Grhl3 induces human epithelial tumor cell migration and invasion via downregulation of E-cadherin

Grainyhead genes are involved in wound healing and developmental neural tube closure. Metastasis is a multistep process during which cancer cells disseminate from the site of primary tumors and establish secondary tumors in distant organs. The adhesion protein E-cadherin plays an essential role in metastasis. In light of the high degree of similarity between the epithelial-mesenchymal transition (EMT) occurring in wound-healing processes and the EMT occurring during the acquisition of invasiveness in skin or breast cancer, we investigated the role of the Grainyhead genes in cancer invasion. Here, we show that there is an inverse relationship between Grainyhead-like 3 (Grhl3) and E-cadherin expression in some epithelial tumor cell lines. Overexpression of Grhl3 in the E-cadherin-positive epithelial tumor cell line, characterized by less invasiveness, generated a transcriptional blockage of the E-cadherin gene and promoted cell migration and cell invasion. Conversely, Grhl3 depletion inhibited cell migration and cell invasion and was associated with a gain of E-cadherin expression. To further explore the mechanism by which Grhl3 regulated E-cadherin expression, an E-cadherin promoter report analysis was performed and results showed that Grhl3 repressed E-cadherin gene expression by directly or indirectly binding to the E-boxes present in the proximal E-cadherin promoter. Taken together, our findings define a major role for Grhl3 in the induction of migration and invasion by the downregulation of E-cadherin in cancer cells.

Immunohistochemical Study of Correlation Between Histologic Subtype and Expression of Epithelial-Mesenchymal Transition-Related Proteins in Synovial Sarcomas

Context.—Synovial sarcomas are mesenchymal tumors with epithelial nature and comprise biphasic and monophasic fibrous subtypes. However, factors determining epithelial or spindle cell differentiation are still unexplored. Aberrant epithelial-mesenchymal transition has been implicated in the pathogenesis of diverse human malignancies.

Objective.—To analyze the correlation between cellular phenotype and expression of proteins associated with different epithelial-mesenchymal transition-related pathways.

Design.—Immunohistochemical analysis of E-cadherin, Snail, Slug, and dysadherin, components of the Wnt/wingless and PI3K/Akt pathways, was performed on 14 biphasic and 27 monophasic fibrous tumors.

Results.—In monophasic fibrous tumors, increased expression of Snail (17 of 27; 63%), Slug (18 of 27; 67%), and dysadherin (14 of 27; 52%) and activation of Wnt (nucleocytoplasmic β-catenin accumulation in 63%; n  =  27; and positive expression of GSK3 and pGSK3 in 24 of 27 [89%] and 21 of 27 [78%], respectively) and PI3K/Akt (Akt: 22 of 27 [81%]; pAkt: 25 of 27 [93%]; and PI3K: 20 of 27 [74%]) signaling correlated significantly with inactivated E-cadherin expression (1 of 27; 4%) (all P < .05). In contrast, preserved E-cadherin expression (12 of 14; 86%) in the glandular component of the biphasic subtype was associated with significantly decreased Snail (3 of 14; 21%) (P  =  .02) and dysadherin (2 of 14; 14%) expression (P < .001).

Conclusions.—Overexpression of Snail, Slug, and dysadherin and activation of Wnt and PI3K/Akt signaling was associated with inactivated E-cadherin in the spindle cells of monophasic fibrous synovial sarcomas, further supporting the hypothesis that this subtype may have developed through neoplastic epithelial-mesenchymal transition.

Phosphorylated p68 RNA helicase activates Snail1 transcription by promoting HDAC1 dissociation from the Snail1 promoter

The nuclear p68 RNA helicase is a prototypical member of the DEAD-box family of RNA helicases. p68 RNA helicase has been implicated in cell proliferation and early organ development and maturation. However, the functional role of p68 RNA helicase in these biological processes at the molecular level is not well understood. We previously reported that tyrosine phosphorylation of p68 RNA helicase mediates the effects of platelet-derived growth factor (PDGF) in induction of epithelial mesenchymal transition by promoting β-catenin nuclear translocation. Here, we report that phosphorylation of p68 RNA helicase at Y593 upregulates transcription of the Snail1 gene. The phosphorylated p68 activates transcription of the Snail1 gene by promoting histone deacetylase (HDAC)1 dissociation from the Snail1 promoter. Our results showed that p68 interacted with the nuclear remodeling and deacetylation complex MBD3:Mi-2/NuRD. Thus, our data suggested that a DEAD-box RNA unwindase could potentially regulate gene expression by functioning as a protein 'displacer' to modulate protein-protein interactions at the chromatin-remodeling complex.

The expression of ELK transcription factors in adult DRG: Novel isoforms, antisense transcripts and upregulation by nerve damage

ELK transcription factors are known to be expressed in a number of regions in the nervous system. We show by RT-PCR that the previously described Elk1, Elk3/Elk3b/Elk3c and Elk4 mRNAs are expressed in adult dorsal root ganglia (DRG), together with the novel alternatively spliced isoforms Elk1b, Elk3d and Elk4c/Elk4d/Elk4e. These isoforms are also expressed in brain, heart, kidney and testis. In contrast to Elk3 protein, the novel Elk3d isoform is cytoplasmic, fails to bind ETS binding sites and yet can activate transcription by an indirect mechanism. The Elk3 and Elk4 genes are overlapped by co-expressed Pctk2 (Cdk17) and Mfsd4 genes, respectively, with the potential formation of Elk3/Pctaire2 and Elk4/Mfsd4 sense-antisense mRNA heteroduplexes. After peripheral nerve injury the Elk3 mRNA isoforms are each upregulated approximately 2.3-fold in DRG (P<0.005), whereas the natural antisense Pctaire2 isoforms show only a small increase (21%, P<0.01) and Elk1 and Elk4 mRNAs are unchanged.

E-cadherin, beta-catenin, and ZEB1 in malignant progression of cancer

The embryonic program 'epithelial-mesenchymal transition' (EMT) is activated during tumor invasion in disseminating cancer cells. Characteristic to these cells is a loss of E-cadherin expression, which can be mediated by EMT-inducing transcriptional repressors, e.g. ZEB1. Consequences of a loss of E-cadherin are an impairment of cell-cell adhesion, which allows detachment of cells, and nuclear localization of beta-catenin. In addition to an accumulation of cancer stem cells, nuclear beta-catenin induces a gene expression pattern favoring tumor invasion, and mounting evidence indicates multiple reciprocal interactions of E-cadherin and beta-catenin with EMT-inducing transcriptional repressors to stabilize an invasive mesenchymal phenotype of epithelial tumor cells.

Progressive tumor features accompany epithelial-mesenchymal transition induced in mitochondrial DNA-depleted cells

The growth of LNCaP, a human prostate adenocarcinoma cell line, and MCF-7, a human breast adenocarcinoma cell line, is initially hormone dependent. We previously demonstrated that LNrho0-8 and MCFrho0, derived from LNCaP and MCF-7 by depleting mitochondrial DNA (mtDNA), exhibited hormone-independent growth that led to progressed phenotypes. Here, we demonstrate that LNrho0-8 and MCFrho0 have invasive characters as evaluated by the ability of invasion through the extracellular matrix (ECM) in vitro. In addition, the induction of vimentin and the repression of E-cadherin expression in rho0 cells indicate that they are mesenchymal cells. Since LNrho0-8 and MCFrho0 were derived from epithelial cancer cell lines, LNCaP and MCF-7 must have lost epithelial features and gained the mesenchymal phenotype by epithelial-mesenchymal transition (EMT) during the mtDNA depletion. In the rho0 cell lines, the Raf/MAPK signaling cascade was highly activated together with the expressions of transforming growth factor-beta (TGF-beta) and type I TGF-beta receptor (TGF-betaRI). EMT requires cooperation of TGF-beta signaling with activation of the Raf/MAPK cascade, suggesting that EMT was induced in mtDNA depleted cells resulting in the acquisition of progressive tumor features, such as higher invasiveness and loss of hormone dependent growth. Our results indicate that decreasing mtDNA content induces EMT, enabling the progressive phenotypes observed in cancer.

Transitions between epithelial and mesenchymal states in development and disease

The ancestors of modern Metazoa were constructed in large part by the foldings and distortions of two-dimensional sheets of epithelial cells. This changed approximately 600 million years ago with the evolution of mesenchymal cells. These cells arise as the result of epithelial cell delamination through a reprogramming process called an epithelial to mesenchymal transition (EMT) [Shook D, Keller R. Mechanisms, mechanics and function of epithelial-mesenchymal transitions in early development. Mech Dev 2003;120:1351-83; Thiery JP, Sleeman JP. Complex networks orchestrate epithelial-mesenchymal transitions. Nat Rev Mol Cell Biol 2006;7:131-42]. Because mesenchymal cells are free to migrate through the body cavity, the evolution of the mesenchyme opened up new avenues for morphological plasticity, as cells evolved the ability to take up new positions within the embryo and to participate in novel cell-cell interactions; forming new types of internal tissues and organs such as muscle and bone [Thiery JP, Sleeman, JP. Complex networks orchestrate epithelial-mesenchymal transitions. Nat Rev Mol Cell Biol 2006;7:131-42; Hay ED, Zuk A. Transformations between epithelium and mesenchyme: normal, pathological, and experimentally induced. Am J Kidney Dis 1995;26:678-90]. After migrating to a suitable site, mesenchymal cells coalesce and re-polarize to form secondary epithelia, in a so-called mesenchymal-epithelial transition (MET). Such switches between mesenchymal and epithelial states are a frequent feature of Metazoan gastrulation [Hay ED, Zuk A. Transformations between epithelium and mesenchyme: normal, pathological, and experimentally induced. Am J Kidney Dis 1995;26:678-90] and the neural crest lineage [Duband JL, Monier F, Delannet M, Newgreen D. Epitheliu-mmesenchyme transition during neural crest development. Acta Anat 1995;154:63-78]. Significantly, however, when hijacked during the development of cancer, the ability of cells to undergo EMT, to leave the primary tumor and to undergo MET at secondary sites can have devastating consequences on the organism, allowing tumor cells derived from epithelia to invade surrounding tissues and spread through the host [Thiery JP, Sleeman JP. Complex networks orchestrate epithelial-mesenchymal transitions. Nat Rev Mol Cell Biol 2006;7:131-42; Hay ED, Zuk A. Transformations between epithelium and mesenchyme: normal, pathological, and experimentally induced. Am J Kidney Dis 1995;26:678-90]. Thus, the molecular and cellular mechanisms underpinning EMT are both an essential feature of Metazoan development and an important area of biomedical research. In this review, we discuss the common molecular and cellular mechanisms involved in EMT in both cases.

ID1-, ID2-, and ID3-regulated gene expression in E2A positive or negative prostate cancer cells

BACKGROUND

The inhibitor of differentiation (Id) proteins are expressed in prostate cancer (PCA). However, there is a general lack of Id isoform-specific downstream effectors.

METHODS

Id1, Id2, or Id3 were silenced in PCA cell lines LNCaP, DU145, and PC3 using gene-specific small interfering RNA (siRNA). The effect of Id gene silencing on representative genes involved in apoptosis (p53, SNAIL2), proliferation (p21, p16), and tumor invasion (E-cadherin and MMP9) was investigated by real-time PCR. Expression of E-proteins, the primary Id interaction partners was also evaluated to understand the molecular mechanism of action.

RESULTS

The Id proteins regulated the expression of CDKNIs p16 and p21 even in the absence of E-proteins. Loss of Id1 and Id3 up- or downregulated E-cadherin expression in E-protein negative or positive PCA cell lines, respectively. The effect of Id genes on cell proliferation was also independent of CDKNIs in p16 and p21 null PC3 cells. The p53-independent anti-apoptotic effect of Id2 was mediated in part by transcriptional repressor SNAI2. MMP9 seems to be the common target of all three Id genes (Id1, Id2, and Id3).

CONCLUSIONS

The overall effect of Id proteins on proliferation and apoptosis is independent of E-proteins. E-proteins can however determine the magnitude of response or in some cases even reverse the Id-mediated target gene expression. Evaluating E-protein expression in conjunction with Id proteins will allow better understanding of the molecular mechanism of action of Id proteins and increase their prognostic significance in PCA.

Activation of NF-kappaB by Akt upregulates Snail expression and induces epithelium mesenchyme transition

Carcinoma progression is associated with the loss of epithelial features, and the acquisition of mesenchymal characteristics and invasive properties by tumour cells. The loss of cell-cell contacts may be the first step of the epithelium mesenchyme transition (EMT) and involves the functional inactivation of the cell-cell adhesion molecule E-cadherin. Repression of E-cadherin expression by the transcription factor Snail is a central event during the loss of epithelial phenotype. Akt kinase activation is frequent in human carcinomas, and Akt regulates various cellular mechanisms including EMT. Here, we show that Snail activation and consequent repression of E-cadherin may depend on AKT-mediated nuclear factor-kappaB (NF-kappaB) activation, and that NF-kappaB induces Snail expression. Expression of the NF-kappaB subunit p65 is sufficient for EMT induction, validating this signalling module during EMT. NF-kappaB pathway activation is associated with tumour progression and metastasis of several human tumour types; E-cadherin acts as a metastasis suppressor protein. Thus, this signalling and transcriptional network linking AKT, NF-kappaB, Snail and E-cadherin during EMT is a potential target for antimetastatic therapeutics.

Id-1 is induced in MDCK epithelial cells by activated Erk/MAPK pathway in response to expression of the Snail and E47 transcription factors

Id-1, a member of the helix-loop-helix transcription factor family has been shown to be involved in cell proliferation, angiogenesis and invasion of many types of human cancers. We have previously shown that stable expression of E47 and Snail repressors of the E-cadherin promoter in MDCK epithelial cell line triggers epithelial mesenchymal transition (EMT) concomitantly with changes in gene expression. We show here that both factors activate the Id-1 gene promoter and induce Id-1 mRNA and protein. The upregulation of the Id-1 gene occurs through the transactivation of the promoter by the Erk/MAPK signaling pathway. Moreover, oncogenic Ras is also able to activate Id-1 promoter in MDCK cells in the absence of both E47 and Snail transcription factors. Several transcriptionally active regulatory elements have been identified in the proximal promoter, including AP-1, Sp1 and four putative E-boxes. By EMSA, we only detected an increased binding to Sp1 and AP-1 elements in E47- and Snail-expressing cells. Binding is affected by the treatment of cells with PD 98059 MEK inhibitor, suggesting that MAPK/Erk contributes to the recruitment or assembly of proteins to Id-1 promoter. Small interfering RNA directed against Sp1 reduced Id-1 expression and the upregulation of the promoter, indicating that Sp1 is required for Id-1 induction in E47- and Snail-expressing cells. Our results provide new insights into how some target genes are activated during and/or as a consequence of the EMT triggered by both E47 and Snail transcription factors.

Slug is overexpressed in gastric carcinomas and may act synergistically with SIP1 and Snail in the down-regulation of E-cadherin

Epithelial-mesenchymal transition (EMT) involving down-regulation of E-cadherin is known to play an important role in tumour progression. The aim of our study was to investigate the mRNA expression of two EMT regulators-Slug and E12/E47-in primary human gastric carcinomas and to compare this with the expression of E-cadherin and other EMT regulators (Snail, Twist, and SIP1). We studied a series of 59 gastric carcinomas by real-time quantitative RT-PCR in formalin-fixed and paraffin-embedded tissues. Thirty-four cases (58%) showed Slug up-regulation in the tumour; reduced or negative expression of E-cadherin was present in 24 of these (71%, p<0.0001). Twenty-one cases (36%) showed E12/E47 up-regulation that was not significantly associated with E-cadherin down-regulation (p=0.5734). Slug up-regulation accompanied by E-cadherin down-regulation correlated with the presence of distant metastases (p=0.0029) and with advanced pTNM stages (p=0.0424). A statistically significant association was found between Slug up-regulation and the expression of SIP1 in intestinal (p=0.0014) and Snail in diffuse (p=0.0067) carcinomas. We present the first study integrating the analysis of several EMT regulators in primary gastric carcinomas and conclude that Slug up-regulation is associated with E-cadherin down-regulation in diffuse and intestinal-type gastric carcinoma, and that this effect could be complemented by the presence of other EMT regulators.

Regulatory mechanisms controlling human E-cadherin gene expression

In cancer cells, loss of E-cadherin gene expression caused dysfunction of the cell-cell junction system, triggering cancer invasion and metastasis. Therefore, E-cadherin is an important tumor-suppressor gene. To understand how E-cadherin gene expression is regulated in cancer cells, we have used E-cadherin-positive and -negative expressing cells to find out the possible up- or down regulating transcription factors in human E-cadherin regulatory sequences. Functional analysis of human E-cadherin regulatory sequences constructs indicated that AML1, Sp1, and p300 may play important roles in promoting E-cadherin expression. In addition, we found there are four HNF3-binding sites in human E-cadherin regulatory sequences. The exogenous HNF3 can enhance the E-cadherin promoter activity in metastatic breast cancer cells and the metastatic breast cancer cells stably transfected with HNF3 showed re-expression of E-cadherin. The HNF3 stable transfectants changed from mesenchymal-like into epithelial morphology. The transwell assays showed the re-expressed E-cadherin reduced cell motility of metastatic breast cancer cells. These results suggested HNF3 may play important roles in the upregulation of the E-cadherin promoter, with the consequent re-expression of E-cadherin, thus reducing the metastatic potential of breast cancer cells. These findings suggested HNF3 plays important roles in the upregulation of the E-cadherin gene and may be able to reduce the motility of metastatic breast cancer cells.

Epithelial-mesenchymal transition in development and cancer: role of phosphatidylinositol 3' kinase/AKT pathways

Epithelial-mesenchymal transition (EMT) is an important process during development by which epithelial cells acquire mesenchymal, fibroblast-like properties and show reduced intercellular adhesion and increased motility. Accumulating evidence points to a critical role of EMT-like events during tumor progression and malignant transformation, endowing the incipient cancer cell with invasive and metastatic properties. Several oncogenic pathways (peptide growth factors, Src, Ras, Ets, integrin, Wnt/beta-catenin and Notch) induce EMT and a critical molecular event is the downregulation of the cell adhesion molecule E-cadherin. Recently, activation of the phosphatidylinositol 3' kinase (PI3K)/AKT axis is emerging as a central feature of EMT. In this review, we discuss the role of PI3K/AKT pathways in EMT during development and cancer with a focus on E-cadherin regulation. Interactions between PI3K/AKT and other EMT-inducing pathways are presented, along with a discussion of the therapeutic implications of modulating EMT in order to achieve cancer control.

ETS transcription factors and targets in tumour invasion, angiogenesis and bone metastasis

The ETS gene family encodes unique transcription regulators that have a common ETS DNA binding domain. At least 25 distinct ETS related genes have been isolated from various species. The ETS family transcription factors are known to regulate genetic programs essential for differentiation and development processes and play diverse roles in a number of biological processes such as organogenesis and tissue remodelling during murine development, hematopoiesis, B-cell development, activation of T-cells and signal transduction, as well as osteogenesis, osteoblast differentiation and extracellular matrix mineralization. Based on the observation of overexpression of ETS related genes in various primary and metastatic tumors, their utility as potential therapeutic targets has been suggested. Antisense oligonucleotides, transdominant, and dominant-negative mutants have been exploited to target and inhibit ETS gene expression selectively. These ETS-targeted studies are being pursued to assess their antitumour effect, and hold the potential that such specific ETS-targeted inhibitors may become a viable option for cancer therapy. Collectively, these studies also demonstrate that Ets factors can regulate multiple aspects of the malignant phenotype of many tumor cells in particular neoangiogenesis and extracellular matrix-regulated (ECM-regulated) cell proliferation, motility and invasiveness.

Snail and E47 repressors of E-cadherin induce distinct invasive and angiogenic properties in vivo

The transcription factors Snail and E47 are direct repressors of E-cadherin, with both inducing a full epithelial-mesenchymal transition and invasive behaviour in vitro when expressed in the prototypic epithelial MDCK cell line. The role of these repressors in the invasive process and in other tumorigenic properties is, nevertheless, still poorly understood. However, organotypic cultures and in vivo transplantation assays indicate that cells expressing MDCK-Snail and MDCK-E47 exhibit significant differences. MDCK-Snail cells have a higher infiltrative potential than MDCK-E47 cells. Interestingly, both cell types induce angiogenesis of the host stromal tissue in transplantation assays, but this property is greatly enhanced in transplants of MDCK-E47 cells. Xenografted tumours induced in nude mice also show signs of strong angiogenic potential, again markedly increased in tumours induced by MDCK-E47 which exhibit a higher vessel density and proliferation rate than those induced by MDCK-Snail cells. These results suggest differential roles for Snail and E47 E-cadherin repressors in tumour progression where Snail is implicated in promoting the initial invasion and E47 plays an active role in tumour cell growth by promoting angiogenesis.

Tumor-associated E-cadherin mutations do not induce Wnt target gene expression, but affect E-cadherin repressors

E-cadherin is a cell-cell adhesion molecule and tumor invasion suppressor gene that is frequently altered in human cancers. It interacts through its cytoplasmic domain with beta-catenin which in turn interacts with the Wnt (wingless) signaling pathway. We have compared the effects of different tumor-derived E-cadherin variants with those of normal E-cadherin on Wnt signaling and on genes involved in epithelial mesenchymal transition. We established an in-house cDNA microarray composed of 1105 different, sequence verified cDNA probes corresponding to 899 unique genes that represent the majority of genes known to be involved in cadherin-dependent cell adhesion and signaling ('Adhesion/Signaling Array'). The expression signatures of E-cadherin-negative MDA-MB-435S cancer cells transfected with E-cadherin variants (in frame deletions of exon 8 or 9, D8 or D9, respectively, or a point mutation in exon 8 (D370A)) were compared to that of wild-type E-cadherin (WT) transfected cells. From the differentially expressed genes, we selected 38 that we subsequently analyzed by quantitative real-time RT-PCR and/or Northern Blot. A total of 92% of these were confirmed as differentially expressed. Most of these genes encode proteins of the cytoskeleton, cadherins/integrins, oncogenes and matrix metalloproteases. No significant expression differences of genes downstream of the Wnt-pathway were found, except in E-cadherin D8 transfected cells where upregulation of three Tcf/Lef-transcribed genes was seen. One possible reason for the lack of expression differences of the Tcf/Lef-regulated genes is upregulation of SFRP1 and SFRP3; both of which are competitive inhibitors of the Wnt proteins. Interestingly, known E-cadherin transcriptional repressors, such as SLUG (SNAI2), SIP1 (ZEB2), TWIST1, SNAIL (SNAI1) and ZEB1 (TCF8), but not E12/E47 (TCF3), had a lack of upregulation in cells expressing mutated E-cadherin compared to WT. In conclusion, E-cadherin mutations have no influence on expression of genes involved in Wnt-signaling, but they may promote their own expression by blocking upregulation of E-cadherin repressors.

E-cadherin mutation and Snail overexpression as alternative mechanisms of E-cadherin inactivation in synovial sarcoma

We have recently reported frequent E-cadherin gene mutations in synovial sarcoma (SS), suggesting mutational inactivation of E-cadherin as a potential mechanism of spindle cell morphology in SS, a spindle cell sarcoma that shows areas of glandular epithelial differentiaton in some cases (biphasic SS) and only pure spindle cell morphology in most cases (monophasic SS). However, the mechanism of downregulation of E-cadherin in SS remains unknown. To further address this issue, we analysed the mechanisms of E-cadherin silencing in 40 SS. Genetic and epigenetic changes in the E-cadherin gene, and the expression level of its transcriptional repressor Snail were examined by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP), methylation-specific PCR, and real-time quantitative PCR, respectively. Expression of E-cadherin was examined by RT-PCR and immunohistochemistry. We also examined ELF3, a transcription factor associated with epithelial differentiation in SS in a previous cDNA microarray, by RT-PCR. E-cadherin and ELF3 transcripts were detected, respectively, in 27/40 (67.5%) and in 25/40 (62.5%) of SS, and these epithelial-related genes were almost always coexpressed. Hypermethylation of the promoter of the E-cadherin gene was detected in five cases (12.5%) in SS; however, E-cadherin was silenced at mRNA level in only one of the five cases. E-cadherin missense mutations were observed in five cases (12.5%) of SS. In SS, all five cases with E-cadherin missense mutations had the SYT-SSX1 fusion and were monophasic tumors, suggesting a relationship between the SYT-SSX fusion type and E-cadherin missense mutation (P=0.07). E-cadherin mRNA expression in SS was associated with reduced Snail expression level (P=0.03). E-cadherin membranous expression was observed in 14/40 (35.0%) of SS, and was also correlated with SYT-SSX1 fusion type and biphasic histology. ELF3 was confirmed to be more highly expressed in biphasic than monophasic SS by real-time quantitative PCR. These results suggest that in SS the loss of E-cadherin expression occurs either by Snail trans-repression or by inactivating mutations. Thus, E-cadherin downregulation is associated with the loss or absence of glandular epithelial differentiation in certain SS.

Gelsolin gene silencing involving unusual hypersensitivities to dimethylsulfate and KMnO4 in vivo footprinting on its promoter region

We previously reported that gelsolin gene expression is reduced in various tumors. In an effort to gain further insights into the mechanism of gelsolin downregulation in tumors, we examined the in vivo properties of the gelsolin promoter in urinary bladder cancer cell lines. Neither mutation nor hypermethylation was responsible for gene silencing at the promoter. After exposure to trichostatin A (TSA), a histone deacetylase inhibitor, gelsolin promoter activity was markedly enhanced in the cancer cells, not in cells derived from normal tissue. Chromatin immunoprecipitation assays revealed that both histones H3 and H4 were hypoacetylated in the promoter region of the cancer cells, and the accumulation of acetylated histones was detected by TSA treatment. In vivo footprinting analysis revealed the presence of dimethylsulfate (DMS) hypersensitive site in the untranslated region around nucleotide--35 only in the cancer cells but not in cells derived from normal tissue, and analysis of KMnO4 reactive nucleotides showed that the stem loop structure could be formed in vivo of the cancer cells. This novel stem loop structure may play a part in regulating the transcription of the gelsolin gene in the cancer cells. These results suggest that nucleosome accessibility through histone deacetylation and structural changes (DMS hypersensitivity and stem loop structure) in the promoter region form the basis of the mechanism leading to the silencing of gelsolin gene in human bladder cancer.

Disregulation of E-cadherin in transgenic mouse models of liver cancer

E-cadherin is a cell-cell adhesion molecule that plays a pivotal role in the development and maintenance of cell polarity. Disruption of E-cadherin-mediated adhesion represents a key step toward the invasive phenotype in a variety of solid tumors, including hepatocellular carcinoma (HCC). Here, we investigate whether deregulation of E-cadherin occurs along the multistep process of hepatocarcinogenesis in transgenic mouse models, including c-Myc, E2F1, c-Myc/TGF-alpha and c-Myc/E2F1 mice. Liver tumors from the transgenic mouse lines could be divided into two categories based on E-cadherin levels. Of 28, 20 (71.4%) c-Myc HCCs showed marked reduction of E-cadherin expression when compared with wild-type livers. In contrast, all of c-Myc/TGF-alpha and the majority of E2F1 and c-myc/E2F1 preneoplastic and neoplastic lesions exhibited overexpression of E-cadherin. Downregulation of E-cadherin was associated with promoter hypermethylation in seven of 20 c-Myc HCCs (35%), while no loss of heterozygosity at the E-cadherin locus was detected. Nuclear accumulation of beta-catenin did not correlate with E-cadherin downregulation. Furthermore, c-Myc HCCs with reduced E-cadherin displayed upregulation of hypoxia-inducible factor-1alpha and vascular endothelial growth factor proteins. Importantly, loss of E-cadherin was associated with increased cell proliferation and higher microvessel density in c-Myc tumors. Taken together, these data suggest that loss of E-cadherin might favor tumor progression in relatively more benign HCC from c-Myc transgenic mice by stimulating neoplastic proliferation and angiogenesis under hypoxic conditions.

Altered expression of adhesion molecules and epithelial-mesenchymal transition in silica-induced rat lung carcinogenesis

Loss of the epithelial phenotype and disruption of adhesion molecules is a hallmark in the epithelial-mesenchymal transition (EMT) reported in several types of cancer. Most of the studies about the relevance of adhesion and junction molecules in lung cancer have been performed using established tumors or in vitro models. The sequential molecular events leading to EMT during lung cancer progression are still not well understood. We have used a rat model for multistep lung carcinogenesis to study the status of adherens and tight junction proteins and mesenchymal markers during EMT. After silica-induced chronic inflammation, rats sequentially develop epithelial hyperplasia, preneoplastic lesions, and tumors such as adenocarcinomas and squamous cell carcinomas. In comparison with normal and hyperplastic bronchiolar epithelium and with hyperplastic alveolar type II cells, the expression levels of E-cadherin, alpha-catenin and beta-catenin were significantly reduced in adenomatoid preneoplastic lesions and in late tumors. The loss of E-cadherin in tumors was associated with its promoter hypermethylation. alpha- and beta-catenin dysregulation lead to cytoplasmic accumulation in some carcinomas. No nuclear beta-catenin localization was found at any stage of any preneoplastic or neoplastic lesion. Zonula occludens protein-1 was markedly decreased in 66% of adenocarcinomas and in 100% squamous cell carcinomas. The mesenchymal-associated proteins N-cadherin and vimentin were analyzed as markers for EMT. N-cadherin was de novo expressed in 32% of adenocarcinomas and 33% of squamous cell carcinomas. Vimentin-positive tumor cells were found in 35% of adenocarcinomas and 88% of squamous cell carcinomas. Mesenchymal markers were absent in precursor lesions, both hyperplastic and adenomatoid. The present results show that silica-induced rat lung carcinogenesis is a good model to study EMT in vivo, and also provide in vivo evidence suggesting that the changes in cell-cell adhesion molecules are an early event in lung carcinogenesis, while EMT occurs at a later stage.

Ets-1 regulates TNF-alpha-induced matrix metalloproteinase-9 and tenascin expression in primary bronchial fibroblasts

Increased subepithelial deposition of extracellular matrix proteins is a key feature in bronchial asthma. Matrix metalloproteinase-9 (MMP-9) is a proteolytic enzyme that degrades the extracellular matrix. Tenascin is an extracellular matrix glycoprotein that is abundant in thickened asthmatic subbasement membrane. The expression of MMP-9 and tenascin reflects disease activity in asthma and airway remodeling. The molecular mechanisms regulating the expression of these proteins remain unknown. Both MMP-9 and tenascin promoters contain an Ets binding site, suggesting control by Ets-1. Thus, we hypothesized that Ets-1 expression is increased in asthma and that it contributed to enhanced MMP-9 and tenascin expression. To test this hypothesis, we determined the expression of Ets-1 in bronchial biopsies obtained from asthmatic subjects and determined the expression of Ets-1, MMP-9, and tenascin by bronchial fibroblasts activated ex vivo. We observed that nuclear extracts from TNF-alpha-activated fibroblasts showed increased Ets-binding activity. In addition, TNF-alpha-activated fibroblasts had increased expression of Ets-1 mRNA and protein, which preceded an increase in MMP-9 and tenascin mRNA. Furthermore, treatment of fibroblasts with Ets-1 antisense oligonucleotides down-regulated TNF-alpha-induced Ets-1, MMP-9, and, to a lesser extent, tenascin protein expression or activity. Taken together, these data demonstrate that TNF-alpha increases MMP-9 and tenascin expression in bronchial fibroblasts via the transcription factor Ets-1, and suggest a role for Ets-1 in airway remodeling in asthma.

ESX induces transformation and functional epithelial to mesenchymal transition in MCF-12A mammary epithelial cells

ESX is an epithelial-restricted member of a large family of transcription factors known as the Ets family. ESX expression has been shown to be correlated with Her2/neu proto-oncogene amplification in highly aggressive breast cancers and induced by Her2/neu in breast cell lines, but its role in tumorigenesis is unknown. Previously, we have shown that ESX enhances breast cell survival in colony-formation assays. In order to determine whether ESX can act as a transforming gene, we stably transfected MCF-12A human mammary epithelial cells with the ESX expression vector, pCGN2-HA-ESX. The MCF-12A cell line is immortalized, but nontransformed, and importantly, these cells fail to express endogenous ESX protein. We used pCGN2-HA-Ets-2 and pSVRas expression vectors as positive controls for transformation. Like HA-Ets-2 and V12-Ras, stable expression of ESX induced EGF-independent proliferation, serum-independent MAPK phosphorylation and growth in soft agar. Additionally, stable ESX expression conferred increased cell adhesion, motility and invasion in two-dimensional and transwell filter assays, and an epithelial to mesenchymal morphological transition. In three-dimensional cultures, parental and vector control (pCGN2) cells formed highly organized duct-like structures with evidence of cell polarity, ECM adhesion-dependent proliferation and cell survival, and lack of cellular invasion into surrounding matrix. Remarkably, the ESX stable cells formed solid, disorganized structures, with lack of cell polarity, loss of adhesion junctions and cytokeratin staining and loss of dependence on ECM adhesion for cell proliferation and survival. In addition, ESX cells invaded the surrounding matrix, indicative of a transformed and metastatic phenotype. Taken together, these data show that ESX expression alone confers a transformed and in vitro metastatic phenotype to otherwise normal MCF-12A cells.

Snail mediates E-cadherin repression by the recruitment of the Sin3A/histone deacetylase 1 (HDAC1)/HDAC2 complex

The transcription factor Snail has been described as a direct repressor of E-cadherin expression during development and carcinogenesis; however, the specific mechanisms involved in this process remain largely unknown. Here we show that mammalian Snail requires histone deacetylase (HDAC) activity to repress E-cadherin promoter and that treatment with trichostatin A (TSA) is sufficient to block the repressor effect of Snail. Moreover, overexpression of Snail is correlated with deacetylation of histones H3 and H4 at the E-cadherin promoter, and TSA treatment in Snail-expressing cells reverses the acetylation status of histones. Additionally, we demonstrate that Snail interacts in vivo with the E-cadherin promoter and recruits HDAC activity. Most importantly, we demonstrate an interaction between Snail, histone deacetylase 1 (HDAC1) and HDAC2, and the corepressor mSin3A. This interaction is dependent on the SNAG domain of Snail, indicating that the Snail transcription factor mediates the repression by recruitment of chromatin-modifying activities, forming a multimolecular complex to repress E-cadherin expression. Our results establish a direct causal relationship between Snail-dependent repression of E-cadherin and the modification of chromatin at its promoter.

The epithelial-specific ETS transcription factor ESX/ESE-1/Elf-3 modulates breast cancer-associated gene expression

Several members of the ETS family of transcription factors contribute to tumorigenesis in many different tissues, including breast epithelium. The ESX gene is an epithelial-specific Ets member that is particularly relevant to breast cancer. ESX is amplified in early breast cancers, it is overexpressed in human breast ductal carcinoma in situ, and there may be a positive feedback loop between the HER2/neu proto-oncogene and ESX. Despite this progress in our understanding of ESX, its ability to regulate tumor-related gene expression and to modulate breast cell survival, remain unknown. Here we show that HA-ESX stimulates the collagenase and HER2/neu promoters, but fails to activate an intact stromelysin promoter. However, HA-ESX activates, in a dose-dependent manner, a heterologous promoter containing eight copies of the Ets binding site derived from the stromelysin gene (p8Xpal-CAT). Analysis of the ability of constructs encoding nine Ets family members to activate the HER2/neu promoter revealed three patterns of gene activation: (1) no effect or repressed promoter activity (Elk-1 and NET); (2) intermediate activity (ER81, GABP, ESX, and HA-Ets-2); and, (3) maximal activity (Ets-1, VP-16-Ets-1, and EHF). Based on these observations, we also determined whether ESX is capable of conferring a survival phenotype upon immortalized, but nontransformed and ESX negative MCF-12A human breast cells. Using a colony formation assay, we found that HA-ESX and HA-Ets-2, mediated MCF-12A cell survival rates that approached those generated by oncogenic V12 Ras, whereas empty vector resulted in negligible colony formation. By contrast, in immortalized and transformed T47D breast cancer cells, which express both HER2/neu and ESX, we found that antisense and dominant-negative HA-ESX inhibited T47D colony formation, whereas control vector allowed formation of many colonies. These results are significant because they show that HA-ESX is able to differentially activate several malignancy-associated gene promoters, and that ESX expression is required for cellular survival of nontransformed MCF-12A and transformed T47D human mammary cells.

The transcription factor Slug represses E-cadherin expression and induces epithelial to mesenchymal transitions: a comparison with Snail and E47 repressors

Transcriptional repression mechanisms have emerged as one of the crucial processes for the downregulation of E-cadherin expression during development and tumour progression. Recently, several E-cadherin transcriptional repressors have been characterized (Snail, E12/E47, ZEB-1 and SIP-1) and shown to act through an interaction with proximal E-boxes of the E-cadherin promoter. We have analyzed the participation of another member of the Snail family, Slug, and observed that it also behaves as a repressor of E-cadherin expression. Stable expression of Slug in MDCK cells leads to the full repression of E-cadherin at transcriptional level and triggers a complete epithelial to mesenchymal transition. Slug-induced repression of E-cadherin is mediated by its binding to proximal E-boxes, particularly to the E-pal element of the mouse promoter. Detailed analysis of the binding affinity of different repressors to the E-pal element indicates that Slug binds with lower affinity than Snail and E47 proteins. These results, together with the known expression patterns of these factors in embryonic development and carcinoma cell lines, support the idea that the in vivo action of the different factors in E-cadherin repression can be modulated by their relative concentrations as well as by specific cellular or tumour contexts.

Differential expression of the epithelial-mesenchymal transition regulators snail, SIP1, and twist in gastric cancer

Epithelial-mesenchymal transition (EMT) involving down-regulation of E-cadherin is thought to play a fundamental role during early steps of invasion and metastasis of carcinoma cells. The aim of our study was to elucidate the role of EMT regulators Snail, SIP1 (both are direct repressors of E-cadherin), and Twist (an activator of N-cadherin during Drosophila embryogenesis), in primary human gastric cancers. Expression of Snail, SIP1, and Twist was analyzed in 48 gastric carcinomas by real-time quantitative RT-PCR in paraffin-embedded and formalin-fixed tissues. The changes of expression levels of these genes in malignant tissues compared to matched non-tumorous tissues were correlated with the expression of E- and N-cadherin. From 28 diffuse-type gastric carcinomas analyzed reduced E-cadherin expression was detected in 11 (39%) cases compared to non-tumorous tissues. Up-regulated Snail could be found in 6 cases with reduced or negative E-cadherin expression. However, there was no correlation to increased SIP1 expression. Interestingly, we could detect abnormal expression of N-cadherin mRNA in 6 cases, which was correlated with Twist overexpression in 4 cases. From 20 intestinal-type gastric cancer samples reduced E-cadherin expression was found in 12 (60%) cases, which was correlated to up-regulation of SIP1, since 10 of these 12 cases showed elevated mRNA levels, whereas Snail, Twist, and N-cadherin were not up-regulated. We present the first study investigating the role of EMT regulators in human gastric cancer and provide evidence that an increase in Snail mRNA expression is associated with down-regulation of E-cadherin in diffuse-type gastric cancer. We detected abnormally positive or increased N-cadherin mRNA levels in the same tumors, probably due to overexpression of Twist. SIP1 overexpression could not be linked to down-regulated E-cadherin in diffuse-type tumors, but was found to be involved in the pathogenesis of intestinal-type gastric carcinoma. We conclude that EMT regulators play different roles in gastric carcinogenesis depending on the histological subtype.

Ras farnesylation inhibitor FTI-277 restores the E-cadherin/catenin cell adhesion system in human cancer cells and reduces cancer metastasis

The E-cadherin/catenin cell adhesion system is often down-regulated in epithelial tumors. This is thought to play an important role in cancer invasion and metastasis, and restoration of this system may suppress metastatic spread of cancer. In this study, the effects of a Ras farnesylation inhibitor (FTI-277) on E-cadherin-mediated cell-cell adhesion and metastatic potential were examined. In cell aggregation assays, FTI-277 stimulated aggregation of colon, liver and breast cancer cells. In vitro cultures of cancer cells showed that FTI-277 induced strong cell-cell contact. Immunoblotting analysis showed that FTI-277 increased E-cadherin/catenin (alpha, beta and gamma) expression and strongly stabilized E-cadherin/catenin with the actin cytoskeleton. Northern blotting studies indicated that the observed increase in the E-cadherin/catenin protein content was due to increased expression of their genes. After inoculation of the spleens of mice with severe combined immunodeficiency (SCID) with cancer cells, FTI-277 treatment for 3 weeks markedly reduced splenic primary tumor growth and the rate of liver metastasis compared with control counterparts. Our data demonstrate that FTI-277 can activate functioning of the E-cadherin-mediated cell adhesion system, which is associated with suppression of cancer cell metastasis. Therefore, selective inhibition of Ras activation may be useful for preventing cancer metastasis.

Calcium modulation of adherens and tight junction function: a potential mechanism for blood-brain barrier disruption after stroke

BACKGROUND

This review deals with the role of calcium in endothelial cell junctions of the blood-brain barrier (BBB). Calcium is critical for adherens junction function, but it appears that calcium is also important in regulating tight junction function necessary for the barrier characteristics of cerebral microvessels.

SUMMARY OF REVIEW

The BBB is critical for brain homeostasis and is located at the cerebral microvessel endothelial cells. These endothelial cells maintain their barrier characteristics via cell-cell contacts made up of adherens and tight junctions. Adherens junctions are calcium dependent; recent evidence suggests that calcium also affects tight junctions. After stroke, there is a disruption of the BBB. Interfering with calcium flux under hypoxic conditions can prevent BBB breakdown. Calcium may alter BBB junction integrity by a number of different signal transduction cascades, as well as via direct interaction of calcium ions with junction proteins. It remains to be determined whether clinical use of calcium channel antagonists is a viable means to reduce BBB disruption after stroke.

CONCLUSIONS

With the widespread use of calcium channel blockers as clinical treatments for hypertension, which is a risk factor for stroke, the exact role of calcium in modulating BBB integrity needs to be elucidated.

Inactivation of the transcription factor Elf3 in mice results in dysmorphogenesis and altered differentiation of intestinal epithelium

BACKGROUND & AIMS

The mammalian small intestine is lined by a highly specialized epithelium that functions in the digestion and absorption of nutrients. The molecular mechanisms that direct intestinal epithelial cell morphogenesis and terminal differentiation are poorly understood. We have previously identified Elf3 (E74-like factor-3) as a member of the ETS transcription factor family strongly expressed in small intestinal epithelium. The aim of this study is to investigate the biological roles of Elf3 in vivo.

METHODS

Mice with a null mutation of Elf3 were generated through targeted gene disruption. Characterization of intestinal development was performed by histologic and immunohistochemical techniques.

RESULTS

Targeted disruption of Elf3 resulted in fetal lethality of about 30% at around embryonic day 11.5. Seventy percent of the Elf3-deficent progeny were born and displayed severe alterations of tissue architecture in the small intestine, manifested by poor villus formation and abnormal morphogenesis and terminal differentiation of absorptive enterocytes and mucus-secreting goblet cells. Crypt cell proliferation, however, appeared intact in Elf3-deficient mice.Elf3-deficient enterocytes express markedly reduced levels of the transforming growth factor beta type II receptor (TGF-beta RII), an inducer of intestinal epithelial differentiation.

CONCLUSIONS

Elf3 is an important regulator of morphogenesis and terminal differentiation of epithelial cell lineages in the small intestine.

A new role for E12/E47 in the repression of E-cadherin expression and epithelial-mesenchymal transitions

Down-regulation of E-cadherin expression is a determinant of tumor cell invasiveness, an event frequently associated with epithelial-mesenchymal transitions. Here we show that the mouse E12/E47 basic helix-loop-helix transcription factor (the E2A gene product) acts as a repressor of E-cadherin expression and triggers epithelial-mesenchymal transitions. The mouse E47 factor was isolated in a one-hybrid system designed to isolate repressors of the mouse E-cadherin promoter. Epithelial cells ectopically expressing E47 adopt a fibroblastic phenotype and acquire tumorigenic and migratory/invasive properties, concomitant with the suppression of E-cadherin expression. Suppression of E-cadherin expression under stable or inducible expression of E47 in epithelial cells occurs at the transcriptional level and is dependent on the E-boxes of the E-cadherin promoter. Interestingly, analysis of endogenous E2A expression in murine and human cell lines illustrated its presence in E-cadherin-deficient, invasive carcinoma cells but its absence from epithelial cell lines. This expression pattern is consistent with that observed in early mouse embryos, where E2A mRNA is absent from epithelia but strongly expressed in the mesoderm. These results implicate E12/E47 as a repressor of E-cadherin expression during both development and tumor progression and indicate its involvement in the acquisition and/or maintenance of the mesenchymal phenotype.

The Ets-transcription factor family in embryonic development: lessons from the amphibian and bird

This chapter reviews the expression and role of Ets-genes during embryogenesis of amphibians and birds. In addition to overlapping expression domains, some of them exhibit cell type-specific expression. Many of them are expressed in migratory cells: neural crest, endothelial, and pronephric duct cells for instance. They are also transcribed in embryonic areas affected by epithelio-mesenchymal transitions. Both processes involve modifications of cellular adhesion. Ets-family genes appear to coordinate changes in the expression of adhesion molecules and degradation of the extracellular matrix upon regulation of matrix metalloproteinases and their specific inhibitors. These functions are essential for physiological processes like tissue remodelling during embryogenesis or wound healing. Unfortunately they also play a harmful role in metastasis. Recent studies in the nervous system showed that Ets-genes contribute to the establishment of a cellular identity. This identity could rely on definite cell-surface determinants, among which cadherins could play an important role. In addition to cell-type specific expression, other factors contribute to the specificity of function of Ets-genes. These genes have a broad specificity of recognition of target sequences in gene promoters, insufficient for accurate control of gene expression. A fine tuning could arise from combinatorial interactions with other Ets- or accessory proteins.

Ets target genes: past, present and future

Ets is a family of transcription factors present in species ranging from sponges to human. All family members contain an approximately 85 amino acid DNA binding domain, designated the Ets domain. Ets proteins bind to specific purine-rich DNA sequences with a core motif of GGAA/T, and transcriptionally regulate a number of viral and cellular genes. Thus, Ets proteins are an important family of transcription factors that control the expression of genes that are critical for several biological processes, including cellular proliferation, differentiation, development, transformation, and apoptosis. Here, we tabulate genes that are regulated by Ets factors and describe past, present and future strategies for the identification and validation of Ets target genes. Through definition of authentic target genes, we will begin to understand the mechanisms by which Ets factors control normal and abnormal cellular processes.

Heterotopic expression of the Xl-Fli transcription factor during Xenopus embryogenesis: modification of cell adhesion and engagement in the apoptotic pathway

In the Xenopus laevis embryo, the overexpression of the Xl-FLI protein, a transcription factor of the ETS family, provokes severe developmental anomalies, which affect anteroposterior and dorsoventral polarities, optic cup formation, head cartilage morphogenesis, and erythrocyte differentiation. It has been proposed that these effects could be correlated to modifications of cell adhesion properties and/or to an increased engagement of cells in the apoptotic pathway during early development (Remy et al., Int. J. Dev. Biol. 40, 577-589, 1996). To address these questions, we have first analyzed the behavior of cells overexpressing the protein in both aggregation and adhesion assays. We observe perturbations of cell-cell interactions as well as perturbations of cell adhesion and spreading on fibronectin and extracellular matrix (ECM). Second, we have analyzed apoptosis of cells overexpressing the Xl-FLI protein, by testing DNA fragmentation, caspase-3 activity and by performing TUNEL assay. We show that Xl-Fli overexpression results in the appearance of hallmarks of apoptosis, including exclusion of cells from the interior of the embryo, internucleosomal fragmentation of DNA and dose-dependent induction of caspase-3, resulting in the hydrolysis of poly(ADP-ribose) polymerase. In addition, a dominant-negative mutation of BMPs receptors decreases the effects of Xl-Fli overexpression, suggesting that a modification of the BMP signalling could be responsible for increased apoptosis. The latter appears to affect predominantly ventral and ventrolateral regions of the embryo.

Patterning and nuclear beta-catenin expression in the colonic adenoma-carcinoma sequence. Analogies with embryonic gastrulation

Patterning is a process by which ordered arrangements of cells and tissue structure are attained. The term derived from developmental biology is also useful for the study of colonic carcinogenesis, in which the patterning of neoplastic tubules is necessary for properties of growth, invasion, and metastasis. Interestingly the nuclear expression and transcriptional activity of beta-catenin, a major oncoprotein in colonic carcinogenesis, is decisive for the first patterning of a tubule in embryogenesis, which creates the primitive gut and is called the gastrulation. Thus, basic patternings of embryogenesis and carcinogenesis might be linked. To test this hypothesis we compared morphological patterns and immunohistochemical beta-catenin stainings in colonic adenomas and adenocarcinomas with the gastrulation steps. Two analogies were found: 1) the patterning of invasion with reconstruction in adenocarcinomas corresponded to the epithelio-mesenchymal transition, ingression, and rearrangement of cells during the first phase of gastrulation; and 2) the patterning of tubular branching in adenomas and adenocarcinomas resembled the endodermal invagination during the second phase. The intratumorous distribution and intensity of nuclear beta-catenin expression was significantly correlated with the two patternings, similar to the findings in gastrulation. The results indicate microenvironmental regulations of nuclear beta-catenin expression and a return of neoplastic cells to embryonic transcriptional susceptibilities during colonic carcinogenesis.

The transcription factor snail controls epithelial-mesenchymal transitions by repressing E-cadherin expression

The Snail family of transcription factors has previously been implicated in the differentiation of epithelial cells into mesenchymal cells (epithelial-mesenchymal transitions) during embryonic development. Epithelial-mesenchymal transitions are also determinants of the progression of carcinomas, occurring concomitantly with the cellular acquisition of migratory properties following downregulation of expression of the adhesion protein E-cadherin. Here we show that mouse Snail is a strong repressor of transcription of the E-cadherin gene. Epithelial cells that ectopically express Snail adopt a fibroblastoid phenotype and acquire tumorigenic and invasive properties. Endogenous Snail protein is present in invasive mouse and human carcinoma cell lines and tumours in which E-cadherin expression has been lost. Therefore, the same molecules are used to trigger epithelial-mesenchymal transitions during embryonic development and in tumour progression. Snail may thus be considered as a marker for malignancy, opening up new avenues for the design of specific anti-invasive drugs.

Substance P-induced cadherin expression and its signal transduction in a cloned human corneal epithelial cell line

Although the absence of Substance P (SP), a neurotransmitter in the trigeminal nerve, has been speculated as a cause for developing neurotrophic keratitis, its exact pathogenesis is still not clarified. In a previous report, we showed with electron microscopic examination that epithelial cell attachment was weakened in denervated corneas. In this study, SV40-transformed human corneal epithelial cells (HCE-Ts) were used to explore the molecular mechanisms responsible for mediating regulation of E-cadherin expression in response to Substance P receptor stimulation. Expression of the mRNAs for specific SP receptors, neurokinin (NK)-1R, NK-2R, and NK-3R, was demonstrated with RT-PCR. The cells were treated with various concentrations of SP in vitro, and the expression of an adhesion molecule E-cadherin was analyzed by immunofluorescence, immunoblotting, and enzyme-linked immunosorbent assay (ELISA) using an anti-E-cadherin antibody. E-cadherin expression was increased by SP in a dose-dependent manner both in the cytosolic fraction and in the cell membrane fraction. This increase in E-cadherin expression was completely inhibited by Calphostin C (PKC inhibitor) and KN-62 (CaMK inhibitor), but not by H-89 (PKA inhibitor), indicating that SP-induced E-cadherin expression involves the activation of protein kinase C (PKC) and calmodulin kinase (CaMK). SP did not affect cell proliferation at all. All these findings indicate that SP induced E-cadherin expression through PKC and CaMK activation and suggest that a lack of SP may account in part for the pathogenesis of neurotrophic keratitis.