Cadherin switching

Epithelial to Mesenchymal Transition in a Clinical Perspective

Tumor growth and metastatic dissemination rely on cellular plasticity. Among the different phenotypes acquired by cancer cells, epithelial to mesenchymal transition (EMT) has been extensively illustrated. Indeed, this transition allows an epithelial polarized cell to acquire a more mesenchymal phenotype with increased mobility and invasiveness. The role of EMT is quite clear during developmental stage. In the neoplastic context in many tumors EMT has been associated with a more aggressive tumor phenotype including local invasion and distant metastasis. EMT allows the cell to invade surrounding tissues and survive in the general circulation and through a stem cell phenotype grown in the host organ. The molecular pathways underlying EMT have also been clearly defined and their description is beyond the scope of this review. Here we will summarize and analyze the attempts made to block EMT in the therapeutic context. Indeed, till today, most of the studies are made in animal models. Few clinical trials are ongoing with no obvious benefits of EMT inhibitors yet. We point out the limitations of EMT targeting such tumor heterogeneity or the dynamics of EMT during disease progression.

MART-10, the vitamin D analog, is a potent drug to inhibit anaplastic thyroid cancer cell metastatic potential

The survival rate of anaplastic thyroid cancer (ATC) is still very poor due to its fast growth and high metastatic potential. Currently, no effective treatment is available. The active form of vitamin D3, 1α,25(OH)2D3, has been shown to have a anti-metastatic effect in pre-clinical studies, however induction of hypercalcemia hampered its clinical application. The new class of less-calcemic vitamin D analog, 19-nor-2α-(3-hydroxypropyl)-1α,25-dihydroxyvitamin D3 (MART-10), is much more potent than 1α,25(OH)2D3 to repress cancer growth and metastasis in a variety of cancers. In this study, we demonstrated that both 1α,25(OH)2D3 and MART-10 could effectively inhibit the migration and invasion of ATC cells, 8305C and 8505C, with MART-10 much more potent than 1α,25(OH)2D3. The anti-metastatic effect of 1α,25(OH)2D3 and MART-10 on ATC cells is mediated by reversal of cadherin switch (upregulation of E-cadherin and downregulation of N-cadherin), which led to the attenuation of EMT process, and decrease of F-actin formation. We further showed that the expressions of Slug, the EMT-related transcriptional factor, and MMP-9 were inhibited by 1α,25(OH)2D3 and MART-10 in 8505C cells, but not in 8303C cells. Since metastasis is the important cause of ATC-related death, our results strongly encourage the further in vivo study of MART-10 application against ATC.

Cadherin Switch during EMT in Neural Crest Cells Leads to Contact Inhibition of Locomotion via Repolarization of Forces

Contact inhibition of locomotion (CIL) is the process through which cells move away from each other after cell-cell contact, and it contributes to malignant invasion and developmental migration. Various cell types exhibit CIL, whereas others remain in contact after collision and may form stable junctions. To investigate what determines this differential behavior, we study neural crest cells, a migratory stem cell population whose invasiveness has been likened to cancer metastasis. By comparing pre-migratory and migratory neural crest cells, we show that the switch from E- to N-cadherin during EMT is essential for acquisition of CIL behavior. Loss of E-cadherin leads to repolarization of protrusions, via p120 and Rac1, resulting in a redistribution of forces from intercellular tension to cell-matrix adhesions, which break down the cadherin junction. These data provide insight into the balance of physical forces that contributes to CIL in cells in vivo.

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Neural crest cells acquire contact inhibition of locomotion (CIL) during EMT

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An E- to N-cadherin switch controls CIL

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E-cadherin represses CIL by controlling Rac1-dependent protrusions via p120

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During CIL, forces are redistributed from intercellular junctions to cell matrix

Overexpression of connexin 43 reduces melanoma proliferative and metastatic capacity

Background:

Alterations in connexin 43 (Cx43) expression and/or gap junction (GJ)-mediated intercellular communication are implicated in cancer pathogenesis. Herein, we have investigated the role of Cx43 in melanoma cell proliferation and apoptosis sensitivity in vitro, as well as metastatic capability and tumour growth in vivo.

Methods:

Connexin 43 expression levels, GJ coupling and proliferation rates were analysed in four different human melanoma cell lines. Furthermore, tumour growth and lung metastasis of high compared with low Cx43-expressing FMS cells were evaluated in vivo using a melanoma xenograft model.

Results:

Specific inhibition of Cx43 channel activity accelerated melanoma cell proliferation, whereas overexpression of Cx43 increased GJ coupling and reduced cell growth. Moreover, Cx43 overexpression in FMS cells increased basal and tumour necrosis factor-α-induced apoptosis and resulted in decreased melanoma tumour growth and lower number and size of metastatic foci in vivo.

Conclusions:

Our findings reveal an important role for Cx43 in intrinsically controlling melanoma growth, death and metastasis, and emphasise the potential use of compounds that selectively enhance Cx43 expression on melanoma in the future chemotherapy and/or immunotherapy protocols.

HPV-16 E6/E7 promotes cell migration and invasion in cervical cancer via regulating cadherin switch in vitro and in vivo

PURPOSE

Cadherin switch, as a key hallmark of epithelial-mesenchymal transition (EMT), is characterized by reduced E-cadherin expression and increased N-cadherin or P-cadherin expression, and has been implicated in many aggressive tumors, but the importance and regulatory mechanism of cadherin switch in cervical cancer have not been investigated. Our study aimed to explore the role of cadherin switch by regulation of HPV-16 E6/E7 in progression and metastasis of cervical cancer.

METHODS

The expressions of E-cadherin and P-cadherin were examined by immunohistochemical staining in 40 cases of high-grade cervical lesions with HPV-16 infection only in which HPV-16 E6 and E7 expression had been detected using qRT-PCR method. Through modulating E6 and E7 expression using HPV-16 E6/E7 promoter-targeting siRNAs or expressed vector in vitro, cell growth, migration, and invasion were separately tested by MTT, wound-healing and transwell invasion assays, as well as the expressions of these cadherins by western blot analyses. Finally, the expressions of these cadherins in cancerous tissues of BALB/c-nu mouse model inoculated with the stable HPV-16 E6/E7 gene silencing Siha and Caski cells were also measured by immunohistochemical staining.

RESULTS

Pearson correlation coefficient analyses showed the strongly inverse correlation of E-cadherin expression and strongly positive correlation of P-cadherin expression with E6/E7 level in 40 cases of high-grade cervical lesions. Furthermore, the modulation of HPV-16 E6/E7 expression remarkably influenced cell proliferation, migration, and invasion, as well as the protein levels of E-cadherin and P-cadherin in cervical cell lines. Finally, the reduction of HPV-16 E6/E7 expression led to up-regulated expression of E-cadherin and down-regulated expression of P-cadherin in BALB/c-nu mouse model in vivo assay.

CONCLUSIONS

Our results unraveled the possibility that HPV-16 E6/E7 could promote cell invasive potential via regulating cadherin switching, and consequently contribute to progression and metastasis of cervical cancer.

A Systematic Approach to Defining the microRNA Landscape in Metastasis

The microRNA (miRNA) landscape changes during the progression of cancer. We defined a metastasis-associated miRNA landscape using a systematic approach. We profiled and validated miRNA and mRNA expression in a unique series of human colorectal metastasis tissues together with their matched primary tumors and corresponding normal tissues. We identified an exclusive miRNA signature that is differentially expressed in metastases. Three of these miRNAs were identified as key drivers of an EMT-regulating network acting though a number of novel targets. These targets include SIAH1, SETD2, ZEB2, and especially FOXN3, which we demonstrated for the first time as a direct transcriptional suppressor of N-cadherin. The modulation of N-cadherin expression had significant impact on migration, invasion, and metastasis in two different in vivo models. The significant deregulation of the miRNAs defining the network was confirmed in an independent patient set as well as in a database of diverse malignancies derived from more than 6,000 patients. Our data define a novel metastasis-orchestrating network based on systematic hypothesis generation from metastasis tissues.

Decreased eIF3e Expression Can Mediate Epithelial-to-Mesenchymal Transition through Activation of the TGFβ Signaling Pathway

The eIF3e protein is a component of the multisubunit eIF3 complex, which is essential for cap-dependent translation initiation. Decreased eIF3e expression is often observed in breast and lung cancer and has been shown to induce epithelial-to-mesenchymal transition (EMT) in breast epithelial cells by an unknown mechanism. Here, we study the effect of decreased eIF3e expression in lung epithelial cells by creating stable clones of lung epithelial cells (A549) that express an eIF3e-targeting shRNA. Our data indicate that decreased eIF3e expression in lung epithelial cells leads to EMT, as it does in breast epithelial cells. Importantly, we show that decreased eIF3e expression in both lung and breast epithelial cells leads to the overproduction of the TGFβ cytokine and that inhibition of TGFβ signaling can reverse eIF3e-regulated EMT in lung epithelial cells. In addition, we discovered that several mRNAs that encode important EMT regulators are translated by a cap-independent mechanism when eIF3e levels are reduced. These findings indicate that EMT mediated by a decrease in eIF3e expression may be a general phenomenon in epithelial cells and that it requires activation and maintenance of the TGFβ signaling pathway.

IMPLICATIONS

These results indicate that inhibition of TGFβ signaling could be an efficient way to prevent metastasis in patients with NSCLC that display reduced eIF3e expression.

Estradiol-mediated hepatocyte growth factor is involved in the implantation of endometriotic cells via the mesothelial-to-mesenchymal transition in the peritoneum

The pathogenesis of endometriosis, a chronic painful gynecological disease characterized by the presence of endometrial tissue located outside of the uterus and often adhering to the peritoneum, is known to be estrogen dependent. However, the precise pathophysiology of endometriosis remains elusive. Recent studies indicate that the epithelial-to-mesenchymal transition (EMT) of human endometrial cells is important for the progression of endometriosis, and another previous study has implicated hepatocyte growth factor (HGF) in endometriosis progression. The aim of the present study was to examine the role of estradiol in the regulation of HGF production and progression of peritoneal endometriosis, focusing on the interactions between the peritoneum and endometriotic cells. Consequently, estradiol was found to promote the proliferation, invasion, and migration of immortalized human endometrial epithelial cells (hEECs) via HGF upregulation, and the estradiol-induced direct binding of estrogen receptor-α to the HGF promoter was confirmed on a chromatin immunoprecipitation (ChIP) assay. Estradiol also induced the EMT in hEECs by promoting HGF production. Furthermore, human mesothelial cells underwent the mesothelial-to-mesenchymal transition (MMT) during culture with estradiol-stimulated hEEC conditioned medium. Importantly, estradiol itself did not induce the MMT, and the estradiol-stimulated hEEC-conditioned medium in the presence of HGF antibodies reversed the MMT process. These results, which were obtained using immortalized hEECs, indicate that estradiol-induced HGF production may play a crucial role in the peritoneal implantation of human endometriotic cells by exerting proliferative and invasive effects via the EMT in hEECs and promoting the MMT in mesothelial cells.

miR-203 inhibits arecoline-induced epithelial-mesenchymal transition by regulating secreted frizzled-related protein 4 and transmembrane-4 L six family member 1 in oral submucous fibrosis

Oral submucous fibrosis (OSF) is a potentially malignant disease predominantly found in Asian people. The areca nut has been implicated in this disease. Arecoline, one of the areca alkaloids, induces epithelial-mesenchymal transition (EMT)-related factors in primary human buccal mucosal fibroblasts. Yet, the mechanisms of the underlying arecoline-induced EMT in OSF remain unknown. In the present study, we aimed to investigate the role of microRNAs (miRNAs) in arecoline-induced EMT in HaCaT cells. We found that miR-203 was significantly downregulated in OSF tissues compared to that in normal buccal mucosa tissues, and that miR-203 negatively regulated secreted frizzled-related protein 4 (SFRP4) and positively regulated transmembrane-4 L six family member 1 (TM4SF1). We observed that upregulation of miR-203 significantly decreased the cell proliferation of HaCaT cells, and significantly upregulated the expression of cytokeratin 19 (CK19) and E-cadherin proteins, whereas it significantly downregulated the expression of N-cadherin and vimentin compared to these levels in the vehicle control cells. Thus, we provide evidence to illustrate that miR-203 plays a role in the pathogenesis of OSF, which may be a target for OSF management.

Cooperation of distinct Rac-dependent pathways to stabilise E-cadherin adhesion

The precise mechanisms via which Rac1 is activated by cadherin junctions are not fully known. In keratinocytes Rac1 activation by cadherin junctions requires EGFR signalling, but how EGFR does so is unclear. To address which activator could mediate E-cadherin signalling to Rac1, we investigated EGFR and two Rac1 GEFs, SOS1 and DOCK180. EGFR RNAi prevented junction-induced Rac1 activation and led to fragmented localization of E-cadherin at cadherin contacts. In contrast, depletion of another EGFR family member, ErbB3, did not interfere with either process. DOCK180 RNAi, but not SOS1, prevented E-cadherin-induced Rac1 activation. However, in a strong divergence from EGFR RNAi phenotype, DOCK180 depletion did not perturb actin recruitment or cadherin localisation at junctions. Rather, reduced DOCK180 levels impaired the resistance to mechanical stress of pre-formed cell aggregates. Thus, within the same cell type, EGFR and DOCK180 regulate Rac1 activation by newly-formed contacts, but control separate cellular events that cooperate to stabilise junctions.

N-cadherin, a novel prognostic biomarker, drives malignant progression of colorectal cancer

Recent studies have indicated that the epithelial-mesenchymal transition (EMT) is a key molecular mechanism involved in the development of colorectal cancer (CRC). N-cadherin is a mesenchymal marker of the EMT and has been closely linked to several human malignancies. However, its role in CRC has remained elusive. In the present study, qRT-PCR and western blot analysis indicated that N-cadherin expression was higher in tumor tissues than in that in their adjacent normal tissues. Immunohistochemical evaluation of N-cadherin and E-cadherin (an epithelial marker of the EMT), indicated that N-cadherin expression was significantly associated with tumor differentiation, tumor size as well as tumor, nodes and metastasis stage. Correlation analysis suggested the expression of N-cadherin was negatively correlated with that of E-cadherin in CRC tissues. Kaplan-Meier analysis indicated that patients with high N-cadherin expression had a significantly lower overall survival and disease-free survival rate than those with low N-cadherin expression, while the opposite was found for E-cadherin. Of note, the present study found that high N-cadherin expression was an independent prognostic factor for CRC. In vitro assays showed that N-cadherin was widely expressed in CRC cell lines and silencing of N-cadherin suppressed the proliferation and migration of the CRC cell line HT-29 by upregulating E-cadherin, suggesting a potential role of N-cadherin in inducing EMT. In conclusion, the present study suggested that N-cadherin has the potential of serving as a novel prognostic predictor and a promising therapeutic target for CRC.

Epigenetic-Mediated Downregulation of μ-Protocadherin in Colorectal Tumours

Carcinogenesis involves altered cellular interaction and tissue morphology that partly arise from aberrant expression of cadherins. Mucin-like protocadherin is implicated in intercellular adhesion and its expression was found decreased in colorectal cancer (CRC). This study has compared MUPCDH (CDHR5) expression in three key types of colorectal tissue samples, for normal mucosa, adenoma, and carcinoma. A gradual decrease of mRNA levels and protein expression was observed in progressive stages of colorectal carcinogenesis which are consistent with reports of increasing MUPCDH 5′ promoter region DNA methylation. High MUPCDH methylation was also observed in HCT116 and SW480 CRC cell lines that revealed low gene expression levels compared to COLO205 and HT29 cell lines which lack DNA methylation at the MUPCDH locus. Furthermore, HCT116 and SW480 showed lower levels of RNA polymerase II and histone H3 lysine 4 trimethylation (H3K4me3) as well as higher levels of H3K27 trimethylation at the MUPCDH promoter. MUPCDH expression was however restored in HCT116 and SW480 cells in the presence of 5-Aza-2′-deoxycytidine (DNA methyltransferase inhibitor). Results indicate that μ-protocadherin downregulation occurs during early stages of tumourigenesis and progression into the adenoma-carcinoma sequence. Epigenetic mechanisms are involved in this silencing.

The effects of adriamycin on E-cadherin mediated cell-cell adhesion and apoptosis during early kidney development

Adriamycin (ADR) is strongly teratogenic. We investigated the effects of ADR on apoptosis and the intensity of E-cadherin expression in developing kidneys. An experimental group of rats was given 2 mg/kg/day ADR on days 6-9 of gestation and a control group was given saline on the same schedule. Embryos were decapitated on days 13, 15, 17 and 19 of gestation, and processed and embedded in paraffin for routine light microscopy. Kidney specimens were stained with hematoxylin and eosin or periodic acid-Schiff, or immunostained for E-cadherin. Apoptosis was assessed using the TUNEL method. Weight loss and developmental deficiency were determined in embryos of the experimental group. ADR damaged or destroyed tubule epithelial cells, which caused apparent dilatation of the tubule lumen. Also, the brush borders of proximal tubules were damaged and glomerular spaces were dilated. ADR caused apoptosis of kidney tissue by days 15, 17 and 19 of development and E-cadherin expression was up-regulated during kidney development compared to controls. We found that ADR can cause apoptosis and increased E-cadherin expression in the developing rat kidney. E-cadherin expression and apoptosis may contribute to the development of ADR nephrotoxicity.

The calcium-sensing receptor suppresses epithelial-to-mesenchymal transition and stem cell- like phenotype in the colon

BACKGROUND

The calcium sensing receptor (CaSR), a calcium-binding G protein-coupled receptor is expressed also in tissues not directly involved in calcium homeostasis like the colon. We have previously reported that CaSR expression is down-regulated in colorectal cancer (CRC) and that loss of CaSR provides growth advantage to transformed cells. However, detailed mechanisms underlying these processes are largely unknown.

METHODS AND RESULTS

In a cohort of 111 CRC patients, we found significant inverse correlation between CaSR expression and markers of epithelial-to-mesenchymal transition (EMT), a process involved in tumor development in CRC. The colon of CaSR/PTH double-knockout, as well as the intestine-specific CaSR knockout mice showed significantly increased expression of markers involved in the EMT process. In vitro, stable expression of the CaSR (HT29(CaSR)) gave a more epithelial-like morphology to HT29 colon cancer cells with increased levels of E-Cadherin compared with control cells (HT29(EMP)). The HT29(CaSR) cells had reduced invasive potential, which was attributed to the inhibition of the Wnt/β-catenin pathway as measured by a decrease in nuclear translocation of β-catenin and transcriptional regulation of genes like GSK-3β and Cyclin D1. Expression of a spectrum of different mesenchymal markers was significantly down-regulated in HT29(CaSR) cells. The CaSR was able to block upregulation of mesenchymal markers even in an EMT-inducing environment. Moreover, overexpression of the CaSR led to down-regulation of stem cell-like phenotype.

CONCLUSIONS

The results from this study demonstrate that the CaSR inhibits epithelial-to-mesenchymal transition and the acquisition of a stem cell-like phenotype in the colon of mice lacking the CaSR as well as colorectal cancer cells, identifying the CaSR as a key molecule in preventing tumor progression. Our results support the rationale to develop new strategies either preventing CaSR loss or reversing its silencing.

DACH1 inhibits SNAI1-mediated epithelial-mesenchymal transition and represses breast carcinoma metastasis

Epithelial-mesenchymal transition (EMT) has a major role in cancer progression and metastasis. However, the specific mechanism of transcriptional repression involved in this process remains largely unknown. Dachshund homologue 1 (DACH1) expression is lost in invasive breast cancer with poor prognosis, and the role of DACH1 in regulating breast cancer metastasis is poorly understood. In this study, significant correlation between the expression of DACH1 and the morphology of breast cancer cells was observed. Subsequent investigation into the relationship between DACH1 and EMT showed that overexpression of DACH1 in ZR-75-30 cells induced a shift towards epithelial morphology and cell-cell adhesion, as well as increased the expression of the epithelial marker E-cadherin and suppressed cell migration and invasion. In contrast, silencing DACH1 in MCF-7 and T47D cells disrupted the epithelial morphology and cell-cell contact, reduced the expression of E-cadherin, and induced cell migration and invasion. DACH1 also specifically interacted with SNAI1, but not SNAI2, to form a complex, which could bind to the E-box on the E-cadherin promoter in an SNAI1-dependent manner. DACH1 inhibited the transcriptional activity of SNAI1, leading to the activation of E-cadherin in breast cancer cells. Furthermore, the level of DACH1 also correlated with the extent of metastasis in a mouse model. DACH1 overexpression significantly decreased the metastasis and growth of 4T1/Luc cells in BALB/c mice. Analysis of tissue samples taken from human breast cancers showed a significant correlation between the expression of DACH1 and E-cadherin in SNAI1-positive breast cancer. Collectively, our data identified a new mechanistic pathway for the regulation of EMT and metastasis of breast cancer cells, one that is based on the regulation of E-cadherin expression by direct DACH1-SNAI1 interaction.

Adhesion in mammary development: novel roles for E-cadherin in individual and collective cell migration

Epithelial tissues are essential for barrier function, secretion, and regulation of fluid transport. Their function requires cell polarity and cell-cell adhesion, mediated through intercellular junctions. Conversely, disruption of adhesion and polarity is thought to drive cancer progression. The mammary gland is an important model for cell adhesion due to its postnatal hormonally regulated development; ducts undergo branching morphogenesis in response to steroid hormones during puberty. These hormonal signals induce a transition from simple to stratified architecture, initiated by asymmetric luminal cell divisions. Ductal elongation is accomplished by this multilayered, low-polarity epithelium, and polarity is reestablished as elongation ceases. The requirement for cell adhesion has been tested in 3D culture and in vivo, using gene deletion, knockdown, and misexpression in both developmental and homeostatic contexts. Attention has focused on E-cadherin, the major classical cadherin in luminal epithelial cells. Classic studies revealed a requirement for E-cadherin during lactation, and E-cadherin loss is widely posited to promote metastasis. However, recent findings demonstrated a broader requirement for E-cadherin during branching morphogenesis and homeostasis and also, surprisingly, in epithelial dissemination. These studies suggest that long-standing models of the role of adhesion in epithelial biology need to be revisited. Advances in inducible gene expression and knockdown, CRISPR/Cas9 technology, and fluorescent labeling of genetically modified cells offer the opportunity to test the roles of diverse adhesion systems and to develop a mechanistic understanding of how cell adhesion regulates development and cancer.

Regulation of epithelial-mesenchymal transition in breast cancer cells by cell contact and adhesion

Epithelial-mesenchymal transition (EMT) is a physiological program that is activated during cancer cell invasion and metastasis. We show here that EMT-related processes are linked to a broad and conserved program of transcriptional alterations that are influenced by cell contact and adhesion. Using cultured human breast cancer and mouse mammary epithelial cells, we find that reduced cell density, conditions under which cell contact is reduced, leads to reduced expression of genes associated with mammary epithelial cell differentiation and increased expression of genes associated with breast cancer. We further find that treatment of cells with matrix metalloproteinase-3 (MMP-3), an inducer of EMT, interrupts a defined subset of cell contact-regulated genes, including genes encoding a variety of RNA splicing proteins known to regulate the expression of Rac1b, an activated splice isoform of Rac1 known to be a key mediator of MMP-3-induced EMT in breast, lung, and pancreas. These results provide new insights into how MMPs act in cancer progression and how loss of cell-cell interactions is a key step in the earliest stages of cancer development.

Role of focal adhesion kinase in oocyte-follicle communication

Germ cells require communication with associated somatic cells for normal gametogenesis, as exemplified by an oocyte that interacts with granulosa cells via paracrine factors as well as gap junctions located at sites of contact between these two cell types. The objective of the present study was to define the mechanisms by which cell-cell contact with the oocyte is controlled and to determine the extent that the oocyte actively participates in this association. Proline-rich tyrosine kinase 2 (PTK2), a focal adhesion kinase, was found to be activated at sites of contact between the oocyte and trans-zonal cell processes from the surrounding granulosa cells. In order to determine the functional significance of oocyte-derived PTK2 signaling in oocyte-follicle communication, an oocyte-specific Ptk2 knockout was produced through a breeding strategy pairing a floxed Ptk2-CAT-eGFP mouse with the Zp3-Cre line. Since Ptk2-null mice never develop to birth, this represents the first opportunity to define the role of PTK2 in oocyte-follicle communication. Ablation of Ptk2 within the developing oocyte resulted in lower fertility with reduced numbers of pups, lower rates of blastocyst formation, and reduced cell numbers per blastocyst. Follicles containing Ptk2-null oocytes exhibited reduced oocyte diameter, reduced numbers of connexin 37 and 43 foci at the oocyte surface, and impaired dye coupling between oocyte and granulosa cells. These findings are consistent with a model in which PTK2 plays a critical role in establishing or maintaining oocyte-granulosa cell contacts that are essential for gap junction-mediated communication between granulosa cells and the oocyte.

Cell fusion between gastric epithelial cells and mesenchymal stem cells results in epithelial-to-mesenchymal transition and malignant transformation

BACKGROUND

The discovery of cancer stem cells and tumor heterogeneity prompted the exploration of additional mechanisms aside from genetic mutations for carcinogenesis and cancer progression. The aim of the present study was to investigate the effect of cell fusion between mesenchymal stem cells and the gastric epithelial cells in tumorigenesis.

METHODS

Cell fusion between cord blood mesenchymal stem cells and human gastric epithelial cells was performed in vitro. Cell scratch and transwell assays were performed to determine migration and invasion abilities of the hybrids. The expressions of epithelial-mesenchymal transition-related proteins and genes were analyzed by immunocytochemistry and real time quantitative PCR. Tumorigenesis of the hybrids was evaluated through in vivo inoculation in nude mice.

RESULTS

Hybrids expressed the phenotypes of both donor cells. Aneuploidy was observed in 84.1% of cells. The hybrids showed increased proliferation, migration and invasion abilities compared with the parental cells. In addition, the expression of N-cadherin and vimentin in the hybrids was significantly higher than that of the epithelial cells, and the mRNA expression of the epithelial-mesenchymal transition-related genes, Twist and Slug, in the hybrids was also increased compared with that of the parental epithelial cells. Furthermore, the hybrids formed masses of epithelial origin with glandular structures in BALB/c nude mice.

CONCLUSIONS

These findings suggest that cell fusion between gastric epithelial cells and mesenchymal stem cells may result in epithelial to mesenchymal transition and malignant transformation.

DNMT3B7 expression promotes tumor progression to a more aggressive phenotype in breast cancer cells

Epigenetic changes, such as DNA methylation, have been shown to promote breast cancer progression. However, the mechanism by which cancer cells acquire and maintain abnormal DNA methylation is not well understood. We have previously identified an aberrant splice form of a DNA methyltransferase, DNMT3B7, expressed in virtually all cancer cell lines but at very low levels in normal cells. Furthermore, aggressive MDA-MB-231 breast cancer cells have been shown to express increased levels of DNMT3B7 compared to poorly invasive MCF-7 cells, indicating that DNMT3B7 may have a role in promoting a more invasive phenotype. Using data gathered from The Cancer Genome Atlas, we show that DNMT3B7 expression is increased in breast cancer patient tissues compared to normal tissue. To determine the mechanism by which DNMT3B7 was functioning in breast cancer cells, two poorly invasive breast cancer cell lines, MCF-7 and T-47D, were stably transfected with a DNMT3B7 expression construct. Expression of DNMT3B7 led to hypermethylation and down-regulation of E-cadherin, altered localization of β-catenin, as well as increased adhesion turnover, cell proliferation, and anchorage-independent growth. The novel results presented in this study suggest a role for DNMT3B7 in the progression of breast cancer to a more aggressive state and the potential for future development of novel therapeutics.

Jag1b is essential for patterning inner ear sensory cristae by regulating anterior morphogenetic tissue separation and preventing posterior cell death

The sensory patches of the vertebrate inner ear, which contain hair cells and supporting cells, are essential for hearing and balance functions. How the stereotypically organized sensory patches are formed remains to be determined. In this study, we isolated a zebrafish mutant in which the jag1b gene is disrupted by an EGFP insertion. Loss of Jag1b causes cell death in the developing posterior crista and results in downregulation of fgf10a in the posterior prosensory cells. Inhibition of FGFR activity in wild-type embryos also causes loss of the posterior crista, suggesting that Fgf10a mediates Jag1b activity. By contrast, in the anterior prosensory domain, Jag1b regulates separation of a single morphogenetic field into anterior and lateral cristae by flattening cells destined to form a nonsensory epithelium between the two cristae. MAPK activation in the nonsensory epithelium precursors is required for the separation. In the jag1b mutant, MAPK activation and cell flattening are extended to anterior crista primordia, causing loss of anterior crista. More importantly, inhibition of MAPK activity, which blocks the differentiation of nonsensory epithelial cells, generated a fused large crista and extra hair cells. Thus, Jag1b uses two distinct mechanisms to form three sensory cristae in zebrafish.

N-cadherin mediates the migration of MCF-10A cells undergoing bone morphogenetic protein 4-mediated epithelial mesenchymal transition

Epithelial-mesenchymal transition (EMT) of mammary epithelial cells is important in both normal morphogenesis of mammary glands and metastasis of breast cancer. Cadherin switching from E-cadherin to N-cadherin plays important roles in EMT. We found that cadherin switching is important in bone morphogenetic protein 4 (BMP4)-induced EMT in MCF-10A cells. BMP4 increased the phosphorylation of SMAD proteins in MCF-10A cells. Canonical BMP4 signaling decreased the expression of E-cadherin and disrupted the polarity of the tight junction protein ZO-1 in MCF-10A cells. However, the expression of N-cadherin and SNAI2 was up-regulated in BMP4-treated MCF-10A cells. MCF-10A cells that expressed N-cadherin migrated into type I collagen gels in response to BMP4 when evaluated using three-dimensional culture assays. Thus, active canonical BMP4 signaling is important for the migration and EMT of mammary epithelial cells. Moreover, the decrease in E-cadherin and/or increase in N-cadherin may be required for BMP4-induced migration and EMT.

Cranial placodes: models for exploring the multi-facets of cell adhesion in epithelial rearrangement, collective migration and neuronal movements

Key to morphogenesis is the orchestration of cell movements in the embryo, which requires fine-tuned adhesive interactions between cells and their close environment. The neural crest paradigm has provided important insights into how adhesion dynamics control epithelium-to-mesenchyme transition and mesenchymal cell migration. Much less is known about cranial placodes, patches of ectodermal cells that generate essential parts of vertebrate sensory organs and ganglia. In this review, we summarise the known functions of adhesion molecules in cranial placode morphogenesis, and discuss potential novel implications of adhesive interactions in this crucial developmental process. The great repertoire of placodal cell behaviours offers new avenues for exploring the multiple roles of adhesion complexes in epithelial remodelling, collective migration and neuronal movements.

Activation of c-Src tyrosine kinase mediated the degradation of occludin in ventilator-induced lung injury

BACKGROUND

Ventilator-induced lung injury (VILI) is characterized by increased alveolar permeability, pulmonary edema. The tyrosine kinase, c-Src, is involved in VILI but its role has not been fully elucidated. This study examined the relationship between c-Src activation and occludin levels in VILI both in vitro and in vivo.

METHODS

For the in vivo study, Wistar rats were randomly divided into five groups: control (group C); normal tidal volume (group M); normal tidal volume + c-Src inhibitor (PP2) (group M + P); high tidal volume (group H); and high tidal volume + c-Src inhibitor (PP2) (group H + P). Rats in all groups but group C underwent mechanical ventilation for 4 h. For the in vitro study, MLE-12 cells pretreated with PP2 and siRNA underwent cyclic stretching at 8% or 20% for 0, 1, 2 and 4 h. The expressions of occludin, c-Src, and p-c-Src were analyzed by western blotting, hematoxylin and eosin (HE) staining, and immunofluorescence.

RESULTS

For the in vivo study, rats in group H showed decreased occludin expression and activated c-Src compared with group C. HE staining and lung injury score showed more severe lung injury and alveolar edema in group H compared with group M and group C. Group H + P had less pulmonary edema induced by the high tidal volume ventilation. For the in vitro study, occludin expression decreased and c-Src activation increased as indicated by the phosphorylation of c-Src over time. Consistently, PP2 could restore occludin levels.

CONCLUSIONS

Mechanical ventilation can activate c-Src by phosphorylation and increase the degradation of occludin. c-Src inhibitor can ameliorate barrier function and lung injury by up-regulating occludin.

Angiomotin is a novel component of cadherin-11/β-catenin/p120 complex and is critical for cadherin-11-mediated cell migration

Loss of E-cadherin and up-regulation of mesenchymal cadherins, a hallmark of the epithelial-mesenchymal transition, contributes to migration and dissemination of cancer cells. Expression of human cadherin-11 (Cad11), also known as osteoblast cadherin, in prostate cancer increases the migration of prostate cancer cells. How Cad11 mediates cell migration is unknown. Using the human Cad11 cytoplasmic domain in pulldown assays, we identified human angiomotin (Amot), known to be involved in cell polarity, migration, and Hippo pathway, as a component of the Cad11 protein complex. Deletion analysis showed that the last C-terminal 10 amino acids in Cad11 cytoplasmic domain are required for Amot binding. Further, Cad11 preferentially interacts with Amot-p80 than Amot-p130 isoform and binds directly to the middle domain of Amot-p80. Cad11-Amot interaction affects Cad11-mediated cell migration, but not homophilic adhesion, as deletion of Amot binding motif of Cad11 (Cad11-ΔAmot) did not abolish Cad11-mediated cell-cell adhesion of mouse L cells, but significantly reduced Cad11-mediated cell migration of human C4-2B4 and PC3-mm2 prostate cancer cells and human HEK293T cells. Together, our studies identified Amot-p80 as a novel component of the Cad11 complex and demonstrated that Amot-p80 is critical for Cad11-mediated cell migration.

SDF-1/CXCR4 signaling up-regulates survivin to regulate human sacral chondrosarcoma cell cycle and epithelial-mesenchymal transition via ERK and PI3K/AKT pathway

Human sacral chondrosarcoma, the most common one of malignant tumors, has a potent capacity to invade locally and metastasize. Notably, CXCR4 and survivin are widely recommended as a candidate of the molecule-targeted therapy. However, the roles and associations of CXCR4 and survivin in sacral chondrosarcoma have not been well characterized. Here, we investigated CXCR4 and survivin expression in human sacral chondrosarcoma. Resected sacral chondrosarcoma specimens were available from 30 patients. In vitro human chondrosarcoma cell lines SW1353 was used. Immunohistochemistry, Western blot, RNA interference, and cell cycle analyses were conducted. Immunohistochemistry revealed that CXCR4 and survivin expressed in 83.3 and 86.7 % of sacral chondrosarcoma tissues, respectively, and both were closely associated with grade and recurrence (p < 0.05). Western blot revealed that survivin expression in SW1353 increased in a dose- and time-dependent manner following SDF-1 treatment. However, the interference with MEK/ERK and PI3K/AKT pathway affected SDF-1-induced up-regulation of survivin. Besides survivin siRNA affected cell cycle progression and the expression of epithelial-mesenchymal transition (EMT) biomarkers: Snail and N-cadherin, when compared with those of non-transfection. In conclusion, the present study shows that SDF-1/CXCR4 signaling up-regulates survivin via MEK/ERK and PI3K/AKT pathway, leading to cell cycle and EMT occurrence in human sacral chondrosarcoma. The antagonizing of CXCR4 and/or survivin might benefit patients with sacral chondrosarcoma.

Prognostic and diagnostic value of epithelial to mesenchymal transition markers in pulmonary neuroendocrine tumors

Background

Pulmonary neuroendocrine tumors (Pulmonary NETs) include a wide spectrum of tumors, from the low-grade typical carcinoid (TC) and the intermediate-grade atypical carcinoid (AC), to the high-grade large-cell neuroendocrine carcinoma (LCNEC) and the small-cell carcinoma (SCLC). Epithelial Mesenchymal Transition (EMT) is a process initially recognised during several critical stages of embryonic development, which has more recently been implicated in promoting carcinoma invasion and metastasis. The initial stage of the EMT process begins with the deregulation of adhesion molecules, such as E-cadherin, due to transcriptional repression carried out by factors such as Snail family members, Twist and Foxc2.

Methods

Immunohistochemistry for EMT markers and E-cadherin/ β-catenin complex in 134 patients with pulmonary NETs between 1990 – 2009. Analysis of potential associations with clinicopathological variables and survival.

Results

Pulmonary NETs of high malignant potential (LCNEC and SCLC) had reduced expression of the adhesion molecules and high level expression of transcriptional repressors (Snail1, Snail2, Twist and Foxc2). Snail high expression levels and the loss of E-cadherin/β-catenin complex integrity had the strongest negative effect on the five-year survival rates. E-cadherin/β-catenin complex integrity loss independently predicted lymph node involvement and helped in Atypical Carcinoid (AC) vs Typical Carcinoid (TC) differential diagnosis. Importantly, among the TC group, the loss of E-cadherin/β-catenin complex integrity identified patients with an adverse clinical course despite favourable clinicopathological features.

Conclusion

The immunohistochemical determination of E-cadherin/β-catenin complex integrity loss and EMT markers in the clinical setting might be a potential useful diagnostic and prognostic tool especially among the TC patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-855) contains supplementary material, which is available to authorized users.

DDX3X induces primary EGFR-TKI resistance based on intratumor heterogeneity in lung cancer cells harboring EGFR-activating mutations

The specific mechanisms how lung cancer cells harboring epidermal growth factor receptor (EGFR) activating mutations can survive treatment with EGFR-tyrosine kinase inhibitors (TKIs) until they eventually acquire treatment-resistance genetic mutations are unclear. The phenotypic diversity of cancer cells caused by genetic or epigenetic alterations (intratumor heterogeneity) confers treatment failure and may foster tumor evolution through Darwinian selection. Recently, we found DDX3X as the protein that was preferentially expressed in murine melanoma with cancer stem cell (CSC)-like phenotypes by proteome analysis. In this study, we transfected PC9, human lung cancer cells harboring EGFR exon19 deletion, with cDNA encoding DDX3X and found that DDX3X, an ATP-dependent RNA helicase, induced CSC-like phenotypes and the epithelial-mesenchymal transition (EMT) accompanied with loss of sensitivity to EGFR-TKI. DDX3X expression was associated with upregulation of Sox2 and increase of cancer cells exhibiting CSC-like phenotypes, such as anchorage-independent proliferation, strong expression of CD44, and aldehyde dehydrogenase (ALDH). The EMT with switching from E-cadherin to N-cadherin was also facilitated by DDX3X. Either ligand-independent or ligand-induced EGFR phosphorylation was inhibited in lung cancer cells that strongly expressed DDX3X. Lack of EGFR signal addiction resulted in resistance to EGFR-TKI. Moreover, we found a small nonadherent subpopulation that strongly expressed DDX3X accompanied by the same stem cell-like properties and the EMT in parental PC9 cells. The unique subpopulation lacked EGFR signaling and was highly resistant to EGFR-TKI. In conclusion, our data indicate that DDX3X may play a critical role for inducing phenotypic diversity, and that treatment targeting DDX3X may overcome primary resistance to EGFR-TKI resulting from intratumor heterogeneity.

Triclosan potentiates epithelial-to-mesenchymal transition in anoikis-resistant human lung cancer cells

Alteration of cancer cell toward mesenchymal phenotype has been shown to potentiate tumor aggressiveness by increasing cancer cell metastasis. Herein, we report the effect of triclosan, a widely used antibacterial agent found in many daily products, in enhancing the epithelial-to-mesenchymal transition (EMT) in aggressive anoikis resistant human H460 lung cancer cells. EMT has been long known to increase abilities of the cells to increase migration, invasion, and survival in circulating system. The present study reveals that treatment of the cancer cells with triclosan at the physiologically related concentrations significantly increased the colony number of the cancer cells assessed by tumor formation assay. Also, the mesenchymal-like morphology and decrease in cell-to-cell adhesion were observed in triclosan-treated cells. Importantly, western blot analysis revealed that triclosan-treated cells exhibited decreased E-cadherin, while the levels of EMT markers, namely N-cadherin, vimentin, snail and slug were found to be significantly up-regulated. Furthermore, EMT induced by triclosan treatment was accompanied by the activation of focal adhesion kinase/ATP dependent tyrosine kinase (FAK/Akt) and Ras-related C3 botulinum toxin substrate 1 (Rac1), which enhanced the ability of the cells to migrate and invade. In conclusion, we demonstrated for the first time that triclosan may potentiate cancer cells survival in detached condition and motility via the process of EMT. As mentioned capabilities are required for success in metastasis, the present study provides the novel toxicological information and encourages the awareness of triclosan use in cancer patients.

Pan-Bcl-2 inhibitor obatoclax delays cell cycle progression and blocks migration of colorectal cancer cells

Despite the fact that new treatment regimes have improved overall survival of patients challenged by colorectal cancer (CRC), prognosis in the metastatic situation is still restricted. The Bcl-2 family of proteins has been identified as promising anti cancer drug target. Even though small molecules targeting Bcl-2 proteins are in clinical trials, little is known regarding their effects on CRC. The aim of this study was to preclinically investigate the value of ABT-737 and Obatoclax as anticancer drugs for CRC treatment. The effects of the BH3-mimetics ABT-737 and Obatoclax on CRC cells were assessed using viability and apoptosis assays. Wound healing migration and boyden chamber invasion assays were applied. 3-dimensional cell cultures were used for long term assessment of invasion and proliferation. Clinically relevant concentrations of pan-Bcl-2 inhibitor Obatoclax did not induce cell death. In contrast, the BH3-mimetic ABT-737 induced apoptosis in a dose dependent manner. Obatoclax caused a cell line specific slowdown of CRC cell growth. Furthermore, Obatoclax, but not ABT-737, recovered E-Cadherin expression and led to impaired migration and invasion of CRC cells. The proliferative capacity and invasiveness of CRC cells was strikingly inhibited by low dose Obatoclax in long term 3-dimensional cell cultures. Obatoclax, but not ABT-737, caused a G1-phase arrest accompanied by a downregulation of Cyclin D1 and upregulation of p27 and p21. Overexpression of Mcl-1, Bcl-xL or Bcl-2 reversed the inhibitory effect of Obatoclax on migration but failed to restore the proliferative capacity of Obatoclax-treated CRC cells. The data presented indicate broad and multifaceted antitumor effects of the pan-Bcl-2 inhibitor Obatoclax on CRC cells. In contrast to ABT-737, Obatoclax inhibited migration, invasion and proliferation in sublethal doses. In summary, this study recommends pan-Bcl-2 inhibition as a promising approach for clinical trials in CRC.

Chordoma: the entity

Chordomas are malignant tumors of the axial skeleton, characterized by their locally invasive and slow but aggressive growth. These neoplasms are presumed to be derived from notochordal remnants with a molecular alteration preceding their malignant transformation. As these tumors are most frequently observed on the skull base and sacrum, patients suffering from a chordoma present with debilitating neurological disease, and have an overall 5-year survival rate of 65%. Surgical resection with adjuvant radiotherapy is the first-choice treatment modality in these patients, since chordomas are resistant to conventional chemotherapy. Even so, management of chordomas can be challenging, as chordoma patients often present with recurrent disease. Recent advances in the understanding of the molecular events that contribute to the development of chordomas are promising; the most novel finding being the identification of brachyury in the disease process. Here we present an overview of the current paradigms and summarize relevant research findings.

CCL21/CCR7 axis activating chemotaxis accompanied with epithelial-mesenchymal transition in human breast carcinoma

Secondary lymphoid tissue chemokine (SLC/CCL21) and its receptor CCR7 have been implicated in lymph node metastasis, whereas the mechanism of which remains unclear. Epithelial-mesenchymal transition (EMT) plays an important role in invasion and migration of cancer cells. We presumed that CCL21/CCR7 axis activates EMT process to induce cancer cell invasion and metastasis. Firstly, the expressions of CCR7 and EMT markers were examined by immunohistochemical staining in the primary breast carcinoma tissues from 60 patients who underwent radical mastectomy. Then, we investigated whether CCL21/CCR7 induces EMT process during mediating cancer cell invasion or migration in vitro. By immunohistolochemistry, high expressions of CCR7, Slug and N-cadherin were seen in 60, 65, and 76.67 % of tumors, respectively, and significantly associated with lymph node metastases as well as clinical pathological stage. Furthermore, the CCR7 expression was significantly correlated to Slug and N-cadherin. In vitro, stimulating breast cancer cell lines 1428, MCF-7 and MDA-MB-231 with CCL21, the invasion and migration of tumor cells were promoted, and simultaneously, EMT phenotype of tumor cells was enhanced, including down-regulation of E-cadherin, up-regulation of Slug, Vimentin and N-cadherin at both protein and mRNA levels. Inversely, knockdown of CCR7 by shRNA suppressed tumor cell invasion, migration and EMT phenotype induced by CCL21. These results indicated that CCL21/CCR7 axis could activate EMT process during chemotaxis of breast carcinoma cells.

Cadherin 6 promotes neural crest cell detachment via F-actin regulation and influences active Rho distribution during epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) is a complex change in cell phenotype that is important for cell migration, morphogenesis and carcinoma metastasis. Loss of epithelial cell adhesion and tight regulation of cadherin adhesion proteins are crucial for EMT. Cells undergoing EMT often display cadherin switching, where they downregulate one cadherin and induce expression of another. However, the functions of the upregulated cadherins and their effects on cell motility are poorly understood. Neural crest cells (NCCs), which undergo EMT during development, lose N-cadherin and upregulate Cadherin 6 (Cdh6) prior to EMT. Cdh6 has been suggested to suppress EMT via cell adhesion, but also to promote EMT by mediating pro-EMT signals. Here, we determine novel roles for Cdh6 in generating cell motility during EMT. We use live imaging of NCC behavior in vivo to show that Cdh6 promotes detachment of apical NCC tails, an important early step of EMT. Furthermore, we show that Cdh6 affects spatiotemporal dynamics of F-actin and active Rho GTPase, and that Cdh6 is required for accumulation of F-actin in apical NCC tails during detachment. Moreover, Cdh6 knockdown alters the subcellular distribution of active Rho, which is known to promote localized actomyosin contraction that is crucial for apical NCC detachment. Together, these data suggest that Cdh6 is an important determinant of where subcellular actomyosin forces are generated during EMT. Our results also identify mechanisms by which an upregulated cadherin can generate cell motility during EMT.

Secretory Leukocyte Protease Inhibitor (SLPI) expression downregulates E-cadherin, induces β-catenin re-localisation and triggers apoptosis-related events in breast cancer cells

BACKGROUND INFORMATION

Epithelial cadherin (E-cadherin) is involved in cell-cell adhesion through its extracellular domain, whereas the intracellular domain interacts with adaptor proteins, i.e. β-catenin, links E-cadherin to the actin cytoskeleton and participates in signal transduction events. E-cadherin protects mammary epithelial cells from apoptosis and its loss during tumour progression has been documented. Secretory Leukocyte Protease Inhibitor (SLPI) has anti- and pro-tumourigenic activities but its role in breast cancer has not been fully elucidated. Notwithstanding its relevance, how SLPI affects E-cadherin in breast cancer is still unknown. This study evaluated the effect of SLPI upon E-cadherin/β-catenin expression and apoptosis-related markers in murine (F3II) and human (MCF-7) breast tumour cells either treated with exogenous recombinant human SLPI (rhSLPI) or stably transfected with a plasmid encoding its sequence.

RESULTS

Addition of rhSLPI to F3II cells caused a decrease (P < 0.05) in E-cadherin transcript and protein levels. Similar results were observed in SLPI-stable F3II transfectants (2C1), and treatment of 2C1 cells with a siRNA toward SLPI restored E-cadherin to control levels. SLPI-expressing cells showed disruption of E-cadherin/β-catenin complex and increased (P < 0.05) percentage of cells depicting nuclear β-catenin localisation. Associated to these changes, 2C1 cells showed increased Bax/Bcl-2 ratio and p21 protein levels, decreased c-Myc protein levels and decreased Cyclin D1 and Claudin-1 transcript levels. No differences in N- and P-cadherin were observed between SLPI-transfected cells and controls. Addition of rhSLPI to MCF-7 cells or stable transfection with SLPI caused a decrease (P < 0.05) in E-cadherin expression (transcript/protein) and its redistribution to the cytoplasm, as well as β-catenin re-localisation to the cell nucleus.

CONCLUSIONS

Expression of SLPI was associated to a decrease in E-cadherin expression and re-localisation of E-cadherin to the cell cytoplasm and β-catenin to the cell cytoplasm and nucleus, and had pro-apoptotic and cell cycle-arrest effects.

Hypoxia induces resistance to ALK inhibitors in the H3122 non-small cell lung cancer cell line with an ALK rearrangement via epithelial-mesenchymal transition

Patients with non-small cell lung cancer (NSCLC) with echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) rearrangements generally respond to ALK inhibitors such as crizotinib. However, some patients with EML4-ALK rearrangements respond poorly to crizotinib. Hypoxia is involved in the resistance to chemotherapeutic treatments in several cancers, and we investigated the association between the responses to ALK inhibitors and hypoxia. Sensitivity of the H3122 NSCLC cell line (EML4-ALK rearrangement) to ALK inhibitors (crizotinib or alectinib) was investigated during a normoxic or hypoxic state using an MTT assay. We found that the cell line was resistant to the inhibitors during hypoxia. Hypoxia mediated morphologic changes, including cell scattering and the elongation of the cell shape, that are characteristic of the epithelial-mesenchymal transition (EMT). A migration assay demonstrated that the number of migrating cells increased significantly during hypoxia, compared with during normoxia. Regarding EMT-related molecules, the expressions of slug, vimentin, and fibronectin were increased while that of E-cadherin was decreased by hypoxia. In addition, hypoxia inducible factor 1A-knockdown cancelled the hypoxia-induced EMT and resistance. Our findings indicate that hypoxia induces resistance to ALK inhibitors in NSCLC with an EML4-ALK rearrangement via the EMT.

Prognostic significance of epithelial-mesenchymal transition-related markers in extrahepatic cholangiocarcinoma: comprehensive immunohistochemical study using a tissue microarray

Background:

Epithelial–mesenchymal transition (EMT) is characterised by the loss of cell-to-cell adhesion and gaining of mesenchymal phenotypes. Epithelial–mesenchymal transition is proposed to occur in various developmental processes and cancer progression. ‘Cadherin switch', a process in which cells shift to express different isoforms of the cadherin transmembrane protein and usually refers to a switch from the expression of E-cadherin to N-cadherin, is one aspect of EMT and can have a profound effect on tumour invasion/metastasis. The aim of this study was to investigate the clinicopathological significance of EMT-related proteins and cadherin switch in extrahepatic cholangiocarcinoma (EHCC).

Methods:

We investigated the association between altered expression of 12 EMT-related proteins and clinical outcomes in patients with EHCC (n=117) using immunohistochemistry on tissue microarrays.

Results:

Univariate and multivariate analyses revealed that, in addition to N classification (P=0.0420), the expression of E-cadherin (P=0.0208), N-cadherin (P=0.0038) and S100A4 (P=0.0157) was each an independent and a significant prognostic factor. We also demonstrated that cadherin switch was independently associated with poor prognosis (P=0.0143) in patients with EHCC.

Conclusions:

These results may provide novel information for selection of patients with EHCC who require adjuvant therapy and strict surveillance.

The cytoplasmic domain of N-cadherin modulates MMP‑9 induction in oral squamous carcinoma cells

Oral squamous carcinoma is the sixth most common cancer worldwide, and one of the most common cancers in developing countries. Regional and distant metastases comprise the majority of cases at initial diagnosis and correlate with poor patient outcomes. Oral epithelia is one of many tissue types to exhibit a cadherin switch during tumor progression, in which endogenous cell adhesion proteins, such as E-cadherin, give way to those of mesenchymal origin. The mesenchymal cell adhesion protein N-cadherin is found at the invading front of oral squamous carcinomas and has been strongly correlated with poor patient prognosis. The goal of the present study was to elucidate the mechanism by which N-cadherin may increase extracellular matrix-associated proteolytic activity to facilitate invasiveness in oral tumor development. The overexpression of N-cadherin in two oral squamous carcinoma cell lines increased motility, invasive capacity and synthesis of matrix metalloproteinase-9 (MMP-9) in a manner that was independent of E-cadherin downregulation. The use of EN and NE chimeric cadherin molecules with reciprocally substituted cytoplasmic domains revealed that optimal induction of MMP-9 synthesis required the cytoplasmic region, but not the extracellular region, of N-cadherin. Utilizing an N-cadherin mutant with impaired p120 binding ability, we found that such mutation resulted in a 4-fold decrease in motility compared to wild-type N-cadherin, but did not affect either MMP-9 expression or motility-normalized invasion. Overexpression of wild-type N-cadherin produced a 27-fold increase in the transcriptional activity of β-catenin, concomitant with increases in MMP-9 transcription. These results suggest that N-cadherin may promote motility and invasiveness through distinct mechanisms, and that β-catenin may be an integral mediator of N-cadherin-dependent invasive signaling in oral epithelia.

E-cadherin can replace N-cadherin during secretory-stage enamel development

BACKGROUND

N-cadherin is a cell-cell adhesion molecule and deletion of N-cadherin in mice is embryonic lethal. During the secretory stage of enamel development, E-cadherin is down-regulated and N-cadherin is specifically up-regulated in ameloblasts when groups of ameloblasts slide by one another to form the rodent decussating enamel rod pattern. Since N-cadherin promotes cell migration, we asked if N-cadherin is essential for ameloblast cell movement during enamel development.

METHODOLOGY/PRINCIPAL FINDINGS

The enamel organ, including its ameloblasts, is an epithelial tissue and for this study a mouse strain with N-cadherin ablated from epithelium was generated. Enamel from wild-type (WT) and N-cadherin conditional knockout (cKO) mice was analyzed. μCT and scanning electron microscopy showed that thickness, surface structure, and prism pattern of the cKO enamel looked identical to WT. No significant difference in hardness was observed between WT and cKO enamel. Interestingly, immunohistochemistry revealed the WT and N-cadherin cKO secretory stage ameloblasts expressed approximately equal amounts of total cadherins. Strikingly, E-cadherin was not normally down-regulated during the secretory stage in the cKO mice suggesting that E-cadherin can compensate for the loss of N-cadherin. Previously it was demonstrated that bone morphogenetic protein-2 (BMP2) induces E- and N-cadherin expression in human calvaria osteoblasts and we show that the N-cadherin cKO enamel organ expressed significantly more BMP2 and significantly less of the BMP antagonist Noggin than did WT enamel organ.

CONCLUSIONS/SIGNIFICANCE

The E- to N-cadherin switch at the secretory stage is not essential for enamel development or for forming the decussating enamel rod pattern. E-cadherin can substitute for N-cadherin during these developmental processes. Bmp2 expression may compensate for the loss of N-cadherin by inducing or maintaining E-cadherin expression when E-cadherin is normally down-regulated. Notably, this is the first demonstration of a natural endogenous increase in E-cadherin expression due to N-cadherin ablation in a healthy developing tissue.

In vivo collective cell migration requires an LPAR2-dependent increase in tissue fluidity

Collective cell migration (CCM) and epithelial-mesenchymal transition (EMT) are common to cancer and morphogenesis, and are often considered to be mutually exclusive in spite of the fact that many cancer and embryonic cells that have gone through EMT still cooperate to migrate collectively. Here we use neural crest (NC) cells to address the question of how cells that have down-regulated cell-cell adhesions can migrate collectively. NC cell dissociation relies on a qualitative and quantitative change of the cadherin repertoire. We found that the level of cell-cell adhesion is precisely regulated by internalization of N-cadherin downstream of lysophosphatidic acid (LPA) receptor 2. Rather than promoting the generation of single, fully mesenchymal cells, this reduction of membrane N-cadherin only triggers a partial mesenchymal phenotype. This intermediate phenotype is characterized by an increase in tissue fluidity akin to a solid-like-to-fluid-like transition. This change of plasticity allows cells to migrate under physical constraints without abolishing cell cooperation required for collectiveness.

FRK inhibits migration and invasion of human glioma cells by promoting N-cadherin/β-catenin complex formation

Fyn-related kinase (FRK), a member of Src-related tyrosine kinases, is recently reported to function as a potent tumor suppressor in several cancer types. Our previous study has also shown that FRK over-expression inhibited the migration and invasion of glioma cells. However, the mechanism of FRK effect on glioma cell migration and invasion, a feature of human malignant gliomas, is still not clear. In this study, we found that FRK over-expression increased the protein level of N-cadherin, but not E-cadherin. Meanwhile, FRK over-expression promoted β-catenin translocation to the plasma membrane, where it formed complex with N-cadherin, while decreased β-catenin level in the nuclear fraction. In addition, down-regulation of N-cadherin by siRNA promoted the migration and invasion of glioma U251 and U87 cells and abolished the inhibitory effect of FRK on glioma cell migration and invasion. In summary, these results indicate that FRK inhibits migration and invasion of human glioma cells by promoting N-cadherin/β-catenin complex formation.

Adherens junction treadmilling during collective migration

Collective cell migration is essential for both physiological and pathological processes. Adherens junctions (AJs) maintain the integrity of the migrating cell group and promote cell coordination while allowing cellular rearrangements. Here, we show that AJs undergo a continuous treadmilling along the lateral sides of adjacent leading cells. The treadmilling is driven by an actin-dependent rearward movement of AJs and is supported by the polarized recycling of N-cadherin. N-cadherin is mainly internalized at the cell rear and then recycled to the leading edge where it accumulates before being incorporated into forming AJs at the front of lateral cell-cell contacts. The polarized dynamics of AJs is controlled by a front-to-rear gradient of p120-catenin phosphorylation, which regulates polarized trafficking of N-cadherin. Perturbation of the GSK3-dependent phosphorylation of p120-catenin impacts on the stability of AJs, and the polarity and speed of leading cells during collective migration.

Upregulation of the tight junction protein occludin: effects on ventilation-induced lung injury and mechanisms of action

BACKGROUND

Occludin, a tight junction protein, plays an important role in maintaining the integrity of the lung epithelial barrier; however, its role in ventilation-induced lung injury has not been explored. Here, we measured the expression of occludin with different tidal volumes. Our study indicated that the level of occludin was significantly decreased and alveolar permeability was increased owing to acute lung injury.

METHODS

Thirty healthy Wistar rats (15 female, 15 male) weighing 250-300 g, were randomly divided into 5 groups (n = 6 in each group): a control group (group C), a low tidal volume group (group L), a low tidal volume + protein kinase C(PKC) inhibitor group (group L + P), a high tidal volume group (group H) and a high tidal volume + PKC inhibitor group (group H + P). Tracheas of rats in the control group underwent incision without any special treatment. The other four groups were mechanically ventilated for 4 h. The rats in groups L + P and H + P were treated with a PKC inhibitor (bisindolylmaleimide I, 0.12 mg/kg) by intramuscular injection 1 h before anesthesia. Rats were sacrificed after mechanical ventilation. Specimens of lung tissues were harvested. Lung pathological changes were observed using an optical microscope, and lung wet/dry weight ratio was measured. The occludin protein level was assayed by immunohistochemistry and Western blotting.

RESULTS

HE staining and immunohistochemistry results showed that occludin was mainly located in alveolar epithelial cells and some alveolar endothelial cells. The lung injury and alveolar edema were more serious in high tidal volume groups than in low tidal volume groups. Occludin expression was reduced and PKC activation was increased in rats in the high tidal volume groups compared with rats in the low tidal volume groups. Rats that were pretreated with the PKC inhibitor had less pulmonary edema induced by the high tidal volume ventilation.

CONCLUSION

Mechanical ventilation can activate the PKC signaling pathway and tight junction proteins participate in this pathway. Up-regulation of occludin can reduce ventilation-induced lung injury.

Atomic force microscopy reveals a role for endothelial cell ICAM-1 expression in bladder cancer cell adherence

Cancer metastasis is a complex process involving cell-cell interactions mediated by cell adhesive molecules. In this study we determine the adhesion strength between an endothelial cell monolayer and tumor cells of different metastatic potentials using Atomic Force Microscopy. We show that the rupture forces of receptor-ligand bonds increase with retraction speed and range between 20 and 70 pN. It is shown that the most invasive cell lines (T24, J82) form the strongest bonds with endothelial cells. Using ICAM-1 coated substrates and a monoclonal antibody specific for ICAM-1, we demonstrate that ICAM-1 serves as a key receptor on endothelial cells and that its interactions with ligands expressed by tumor cells are correlated with the rupture forces obtained with the most invasive cancer cells (T24, J82). For the less invasive cancer cells (RT112), endothelial ICAM-1 does not seem to play any role in the adhesion process. Moreover, a detailed analysis of the distribution of rupture forces suggests that ICAM-1 interacts preferentially with one ligand on T24 cancer cells and with two ligands on J82 cancer cells. Possible counter receptors for these interactions are CD43 and MUC1, two known ligands for ICAM-1 which are expressed by these cancer cells.

Targeted knockdown of IQGAP1 inhibits the progression of esophageal squamous cell carcinoma in vitro and in vivo

IQGAP1 is a scaffolding protein that can regulate several distinct signaling pathways. The accumulating evidence has demonstrated that IQGAP1 plays an important role in tumorigenesis and tumor progression. However, the function of IQGAP1 in esophageal squamous cell carcinoma (ESCC) has not been thoroughly investigated. In the present study, we showed that IQGAP1 was overexpressed in ESCC tumor tissues, and its overexpression was correlated with the invasion depth of ESCC. Importantly, by using RNA interference (RNAi) technology we successfully silenced IQGAP1 gene in two ESCC cell lines, EC9706 and KYSE150, and for the first time found that suppressing IQGAP1 expression not only obviously reduced the tumor cell growth, migration and invasion in vitro but also markedly inhibited the tumor growth, invasion, lymph node and lung metastasis in xenograft mice. Furthermore, Knockdown of IQGAP1 expression in ESCC cell lines led to a reversion of epithelial to mesenchymal transition (EMT) progress. These results suggest that IQGAP1 plays crucial roles in regulating ESCC occurrence and progression. IQGAP1 silencing may therefore develop into a promising novel anticancer therapy.