NF-kappaB and epithelial to mesenchymal transition of cancer

Anoxia/reoxygenation induces epithelial-mesenchymal transition in human colon cancer cell lines

Epithelial-mesenchymal transition (EMT) is considered to be a crucial event in the development of cancer metastasis. Anoxia/reoxygenation (A/R) is known to occur in cancer tissues due to angiogenesis and changes in tissue pressure that occur during tumor growth. We investigated whether A/R induces EMT in the human colon cancer cell line HT-29. Colon cancer cells were exposed to anoxia (2 h) followed by reoxygenation (4-22 h) and evaluated for EMT changes using immunofluorescence and western blot analyses. We also investigated the expression of EMT-related transcription factors (Snail and ZEB1) using RT-PCR and evaluated the expression of NF-κB using ELISA. To determine whether NF-κB is involved in A/R-induced EMT, HT-29 cells were treated with proteasome inhibitors. Colon cancer cells exposed to A/R underwent EMT morphological changes; the cancer cells acquired a spindle-shaped phenotype. The expression of E-cadherin on the cell surface and the total amount of E-cadherin proteins were reduced after A/R. The expression of EMT-related transcription factors (Snail, ZEB1) was increased after A/R. Pretreatment with proteasome inhibitors significantly attenuated the downregulation of E-cadherin induced by A/R. These results indicate that A/R induces EMT in human colon cancer cells through an NF-κB-dependent transcriptional pathway.

Dynamic transcription factor networks in epithelial-mesenchymal transition in breast cancer models

The epithelial-mesenchymal transition (EMT) is a complex change in cell differentiation that allows breast carcinoma cells to acquire invasive properties. EMT involves a cascade of regulatory changes that destabilize the epithelial phenotype and allow mesenchymal features to manifest. As transcription factors (TFs) are upstream effectors of the genome-wide expression changes that result in phenotypic change, understanding the sequential changes in TF activity during EMT provides rich information on the mechanism of this process. Because molecular interactions will vary as cells progress from an epithelial to a mesenchymal differentiation program, dynamic networks are needed to capture the changing context of molecular processes. In this study we applied an emerging high-throughput, dynamic TF activity array to define TF activity network changes in three cell-based models of EMT in breast cancer based on HMLE Twist ER and MCF-7 mammary epithelial cells. The TF array distinguished conserved from model-specific TF activity changes in the three models. Time-dependent data was used to identify pairs of TF activities with significant positive or negative correlation, indicative of interdependent TF activity throughout the six-day study period. Dynamic TF activity patterns were clustered into groups of TFs that change along a time course of gene expression changes and acquisition of invasive capacity. Time-dependent TF activity data was combined with prior knowledge of TF interactions to construct dynamic models of TF activity networks as epithelial cells acquire invasive characteristics. These analyses show EMT from a unique and targetable vantage and may ultimately contribute to diagnosis and therapy.

Helicobacter pylori initiates a mesenchymal transition through ZEB1 in gastric epithelial cells

Chronic Helicobacter pylori infection provokes an inflammation of the gastric mucosa, at high risk for ulcer and cancer development. The most virulent strains harbor the cag pathogenicity island (cagPAI) encoding a type 4 secretion system, which allows delivery of bacterial effectors into gastric epithelial cells, inducing pro-inflammatory responses and phenotypic alterations reminiscent of an epithelial-to-mesenchymal transition (EMT). This study characterizes EMT features in H. pylori-infected gastric epithelial cells, and investigates their relationship with NF-κB activation. Cultured human gastric epithelial cell lines were challenged with a cagPAI+ H. pylori strain or cag isogenic mutants. Morphological changes, epithelial and mesenchymal gene expression and EMT-related microRNAs were studied. H. pylori up-regulates mesenchymal markers, including ZEB1. This transcription factor is prominently involved in the mesenchymal transition of infected cells and its up-regulation depends on cagPAI and NF-κB activation. ZEB1 expression and NF-κB activation were confirmed by immunohistochemistry in gastric mucosa from cagPAI+ H. pylori-infected patients. Gastric epithelial cell lines express high miR-200 levels, which are linked to ZEB1 in a reciprocal negative feedback loop and maintain their epithelial phenotype in non-infected conditions. However, miR-200b/c were increased upon infection, despite ZEB1 up-regulation and mesenchymal morphology. In the miR-200b-200a-429 cluster promoter, we identified a functional NF-κB binding site, recruiting NF-κB upon infection and trans-activating the microRNA cluster transcription. In conclusion, in gastric epithelial cells, cagPAI+ H. pylori activates NF-κB, which transactivates ZEB1, subsequently promoting mesenchymal transition. The unexpected N-FκB-dependent increase of miR-200 levels likely thwarts the irreversible loss of epithelial identity in that critical situation.

Spatial transcriptional profile of the chick and mouse endocardial cushions identify novel regulators of endocardial EMT in vitro

Valvular Interstitial Cells (VICs) are a common substrate for congenital and adult heart disease yet the signaling mechanisms governing their formation during early valvulogenesis are incompletely understood. We developed an unbiased strategy to identify genes important in endocardial epithelial-to-mesenchymal transformation (EMT) using a spatial transcriptional profile. Endocardial cells overlaying the cushions of the atrioventricular canal (AVC) and outflow tract (OFT) undergo an EMT to yield VICs. RNA sequencing (RNA-seq) analysis of gene expression between AVC, OFT, and ventricles (VEN) isolated from chick and mouse embryos at comparable stages of development (chick HH18; mouse E11.0) was performed. EMT occurs in the AVC and OFT cushions, but not VEN at this time. 198 genes in the chick (n=1) and 105 genes in the mouse (n=2) were enriched 2-fold in the cushions. Gene regulatory networks (GRN) generated from cushion-enriched gene lists confirmed TGFβ as a nodal point and identified NF-κB as a potential node. To reveal previously unrecognized regulators of EMT four candidate genes, Hapln1, Id1, Foxp2, and Meis2, and a candidate pathway, NF-κB, were selected. In vivo spatial expression of each gene was confirmed by in situ hybridization and a functional role for each in endocardial EMT was determined by siRNA knockdown in a collagen gel assay. Our spatial-transcriptional profiling strategy yielded gene lists which reflected the known biology of the system. Further analysis accurately identified and validated previously unrecognized novel candidate genes and the NF-κB pathway as regulators of endocardial cell EMT in vitro.

Regulation of cell migration, invasion and metastasis by IAP proteins and their antagonists

Inhibitor of apoptosis (IAP) proteins are a family comprised of a total of eight mammalian members that were initially described to act as endogenous inhibitors of caspases. In addition, extensive evidence has been accumulated over the last years showing that IAP proteins can regulate various signal transduction pathways, thereby exerting non-apoptotic functions beyond the inhibition of apoptosis. For example, IAP proteins have been implied in the control of cell motility, migration, invasion and metastasis. However, currently the question is controversially discussed whether or not they positively or negatively control these processes. As small-molecule inhibitors of IAP proteins have entered the stage of clinical evaluation as experimental cancer therapeutics, a better understanding of their various cellular effects will be critical for their rational use in the treatment of human diseases.

Low-dose radiation-induced epithelial-mesenchymal transition through NF-κB in cervical cancer cells

Cervical cancer is the leading cause of death from cancer among women. Radiotherapy for cervical cancer is an effective treatment method; however, the response to radiotherapy varies among patients. Epithelial-mesenchymal transition (EMT) is a morphogenesis process involved in embryonic and organismal development. During tumour progression, EMT may enhance cancer cell invasion, promoting tumour metastasis. We hypothesised that EMT was involved in the enhanced invasiveness of cervical cancer cells after low-dose radiation and aimed to elucidate the underlying mechanism of this process in low-dose radiation of cervical cancer. The irradiated cells (FIR cells) were derived from the parental cells (N cells) with a cumulative dose of 75 Gy. After resting and reorganisation, the effect of low-dose radiation on the FIR cells was analysed. The expression of E-cadherin, N-cadherin and p65 was detected by real-time qPCR and western blotting in parental cancer cells and irradiated cancer cells. Motility was detected using the migration/invasion assay. After silencing of NF-κB p65 expression using siRNA against p65, the expression of E-cadherin and N-cadherin was examined by real‑time qPCR and western blotting. We found that low-dose radiation induced morphological changes of cells. The expression of epithelial markers was downregulated and mesenchymal markers were induced in irradiated cells, both of which are characteristics of EMT. Additionally, in irradiated cells, migration and invasion were enhanced and the expression of p65 was increased. To investigate whether p65 was involved in EMT, we silenced the expression of p65 in irradiated cells using siRNA and found that the features of EMT were suppressed. In summary, p65-regulated EMT induced by low-dose irradiation of cervical cancer cell lines promoted the invasiveness and metastasis of cervical cancer cells. The reversal of EMT may be a new therapeutic target for improving the effectiveness of radiotherapy for cervical cancer.

Emerging phytochemicals for prevention of melanoma invasion

Cutaneous malignant melanoma is the leading cause of death from skin diseases due to its propensity to metastasize. Once diagnosed with metastatic melanoma, most patients will die of their disease within 2years. As suppression of metastases requires long-term interventions, potential anti-metastatic agents must not only be efficacious but also have low toxicity. Many phytochemicals used in traditional medicine have low toxicity and recent studies suggest that some are promising candidates for the prevention or treatment of metastatic melanoma. Here, we review the recent literature regarding phytochemicals that have shown inhibitory effects on melanoma cell migration or invasion.

Epithelial-mesenchymal Transition---A Hallmark of Breast Cancer Metastasis

Epithelial-mesenchymal transition (EMT) is a highly conserved cellular program that converts polarized, immotile epithelial cells to migratory mesenchymal cells. In addition, EMT was initially recognized as a key step for morphogenesis during embryonic development. Emerging evidences indicate that this important developmental program promotes metastasis, drug resistance, and tumor recurrence, features that are associated with a poor clinical outcome for patients with breast cancer. Therefore, better understanding of regulation and signaling pathways in EMT is essential to develop novel targeted therapeutics. In this review, we present updated developments underlying EMT in tumor progression and metastasis, and discuss the challenges remaining in breast cancer research.

Functional roles of tumor necrosis factor-related apoptosis-inducing ligand-DR5 interaction in B16F10 cells by activating the nuclear factor-κB pathway to induce metastatic potential

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been recognized as a promising target for cancer therapy because it can induce apoptotic cell death in tumor cells but not normal cells. Although TRAIL shows specific tumoricidal activity, resistance to TRAIL-induced apoptosis in some tumor cells has been considered a clinical obstacle of its application. It has been shown that TRAIL provides inflammatory signals that may contribute to the TRAIL-resistance of cancer cells; however, it is not known whether TRAIL itself is involved in malignant cancer cell behavior. In the present study, we examined the functional role of TRAIL in B16F10 mouse melanoma cells, which are totally insensitive to TRAIL-induced apoptosis. By establishing B16F10 cells stably expressing the nuclear factor-κB (NFκB)-luciferase reporter gene, we found that TRAIL can activate NFκB through its death receptor DR5 in B16F10 cells. Furthermore, TRAIL-DR5 interaction not only promoted malignant behaviors of B16F10 cells, such as cell proliferation and MMP-9 production, but also induced lung metastasis of B16F10 cells in vivo. These findings may imply a contrary role for the TRAIL-DR5 pathway in the inflammatory tumor microenvironment, in its ability to induce the metastatic potential of B16F10 melanoma cells instead of inducing apoptosis.

Keratin 8 and 18 loss in epithelial cancer cells increases collective cell migration and cisplatin sensitivity through claudin1 up-regulation

Keratins 8 and 18 (K8/18) are simple epithelial cell-specific intermediate filament proteins. Keratins are essential for tissue integrity and are involved in intracellular signaling pathways that regulate cell response to injuries, cell growth, and death. K8/18 expression is maintained during tumorigenesis; hence, they are used as a diagnostic marker in tumor pathology. In recent years, studies have provided evidence that keratins should be considered not only as markers but also as regulators of cancer cell signaling. The loss of K8/18 expression during epithelial-mesenchymal transition (EMT) is associated with metastasis and chemoresistance. In the present study, we investigated whether K8/18 expression plays an active role in EMT. We show that K8/18 stable knockdown using shRNA increased collective migration and invasiveness of epithelial cancer cells without modulating EMT markers. K8/18-depleted cells showed PI3K/Akt/NF-κB hyperactivation and increased MMP2 and MMP9 expression. K8/18 deletion also increased cisplatin-induced apoptosis. Increased Fas receptor membrane targeting suggests that apoptosis is enhanced via the extrinsic pathway. Interestingly, we identified the tight junction protein claudin1 as a regulator of these processes. This is the first indication that modulation of K8/18 expression can influence the phenotype of epithelial cancer cells at a transcriptional level and supports the hypothesis that keratins play an active role in cancer progression.

An integrated expression profiling reveals target genes of TGF-β and TNF-α possibly mediated by microRNAs in lung cancer cells

EMT (epithelial-mesenchymal transition) is crucial for cancer cells to acquire invasive phenotypes. In A549 lung adenocarcinoma cells, TGF-β elicited EMT in Smad-dependent manner and TNF-α accelerated this process, as confirmed by cell morphology, expression of EMT markers, capacity of gelatin lysis and cell invasion. TNF-α stimulated the phosphorylation of Smad2 linker region, and this effect was attenuated by inhibiting MEK or JNK pathway. Comprehensive expression analysis unraveled genes differentially regulated by TGF-β and TNF-α, such as cytokines, chemokines, growth factors and ECM (extracellular matrices), suggesting the drastic change in autocrine/paracrine signals as well as cell-to-ECM interactions. Integrated analysis of microRNA signature enabled us to identify a subset of genes, potentially regulated by microRNAs. Among them, we confirmed TGF-β-mediated induction of miR-23a in lung epithelial cell lines, target genes of which were further identified by gene expression profiling. Combined with in silico approaches, we determined HMGN2 as a downstream target of miR-23a. These findings provide a line of evidence that the effects of TGF-β and TNF-α were partially mediated by microRNAs, and shed light on the complexity of molecular events elicited by TGF-β and TNF-α.

Class 3 semaphorins: physiological vascular normalizing agents for anti-cancer therapy

Findings from preclinical and clinical studies show that vascular normalization represents a novel strategy to enhance the efficacy of and overcome the acquired resistance to anti-angiogenic therapies in cancer. Several mechanisms of tumour vessel normalization have been revealed. Amongst them, secreted class 3 semaphorins (Sema3), which regulate axon guidance and angiogenesis, have been recently identified as novel vascular normalizing agents that inhibit metastatic dissemination by restoring vascular function. Here, we discuss the different biological functions and mechanisms of action of Sema3 in the context of tumour vascular normalization, and their impact on the different cellular components of the tumour microenvironment.

Emerging roles of PDGF-D in EMT progression during tumorigenesis

Platelet-derived growth factor-D (PDGF-D) signaling pathway has been reported to be involved in regulating various cellular processes, such as cell growth, apoptotic cell death, migration, invasion, angiogenesis and metastasis. Recently, multiple studies have shown that PDGF-D plays a critical role in governing epithelial-to-mesenchymal transition (EMT), although the underlying mechanism of PDGF-D-mediated acquisition of EMT is largely unclear. Therefore, this mini review will discuss recent advances in our understanding of the role of PDGF-D in the acquisition of EMT during tumorigenesis. Furthermore, we will summarize the function of chemical inhibitors and natural compounds that are known to inactivate PDGF-D signaling pathway, which leads to the reversal of EMT. In summary, inactivation of PDGF-D could be a novel strategy for achieving better treatment outcome of patients inflicted with cancers.

Transglutaminase 2 and NF-κB: an odd couple that shapes breast cancer phenotype

Owing to numerous pro-survival target genes, aberrant activation of the NF-κB transcription factor is associated with a drug-resistant phenotype and aggressive breast tumor behavior. Transglutaminase 2 (TG2), a ubiquitously expressed protein cross-linking enzyme, activates NF-κB through a non-conventional mechanism that disables the IκBα inhibitor. Our group has recently documented that the TG2 gene (termed TGM2) is a direct transcriptional target of NF-κB. These developments uncover a novel self-reinforcing molecular feedback loop where TG2 activates NF-κB and, in turn, NF-κB directly upregulates the transcription of TGM2. This manuscript reviews the literature that supports the existence of the TG2/NF-κB signaling loop, the nature of the signal transduction that activates this loop, and the phenotypic consequences stemming from the aberrant activation of this novel signaling mechanism in breast cancer.

Epithelial-mesenchymal transition in breast cancer progression and metastasis

Breast cancer is the most common cancer in women, and approximately 90% of breast cancer deaths are caused by local invasion and distant metastasis of tumor cells. Epithelial-mesenchymal transition (EMT) is a vital process for large-scale cell movement during morphogenesis at the time of embryonic development. Tumor cells usurp this developmental program to execute the multi-step process of tumorigenesis and metastasis. Several transcription factors and signals are involved in these events. In this review, we summarize recent advances in breast cancer researches that have provided new insights in the molecular mechanisms underlying EMT regulation during breast cancer progression and metastasis. We especially focus on the molecular pathways that control EMT.

CXCL1/GROα increases cell migration and invasion of prostate cancer by decreasing fibulin-1 expression through NF-κB/HDAC1 epigenetic regulation

Inflammatory tumor microenvironments play pivotal roles in the development of cancer. Inflammatory cytokines such as CXCL1/GROα exert cancer-promoting activities by increasing tumor angiogenesis. However, whether CXCL1/GROα also plays a role in the progression of prostate cancer, particularly in highly invasive castration-resistant prostate cancer (CRPC), has not been investigated. We explored whether CXCL1/GROα enhances cell migration and invasion in PC-3 and DU145 CRPC. Induction of PC-3 and DU145 cancer progression by CXCL1/GROα is associated with increased AKT activation and IκB kinase α (IKKα) phosphorylation, resulting in nuclear factor-kappaB (NF-κB) activation. Activated NF-κB interacts with histone deacetylase 1 (HDAC1) to form a gene-silencing complex, which represses the expression of fibulin-1D by decreasing the acetylation of histone H3 and H4 on the NF-κB-binding site of the fibulin-1D promoter. Blockade of AKT2 by small hairpin RNA (shRNA) decreases IKKα phosphorylation, NF-κB nuclear translocation and cell migration, indicating that AKT is required in CXCL1/GROα-mediated NF-κB activation and cell migration. In addition, NF-κB and HDAC1 shRNA decrease the effect of CXCL1/GROα on fibulin-1D downregulation, migration and invasion, suggesting that the NF-κB/HDAC1 complex is also involved in CXCL1/GROα-mediated cancer progression. Our findings provide the first evidence that CXCL1/GROα decreases fibulin-1D expression in prostate cancer cells and also reveals novel insights into the mechanism by which CXCL1/GROα regulates NF-κB activation through the AKT pathway. Our results also clearly establish that co-operation of NF-κB and HDAC1 regulates fibulin-1D expression by epigenetic modification. Our study suggests that inhibition of CXCL1/GROα-mediated AKT/NF-κB signaling may be an attractive therapeutic target for CRPC.

Overexpression of pro-inflammatory genes and down-regulation of SOCS-1 in human PTC and in hypoxic BCPAP cells

Hypoxia-inducible factor-1α (HIF-1α) is frequently overexpressed and activated in many cancer types. However, its regulation and function in thyroid carcinomas are only partially known. Aim of our study was to demonstrate that adaptation to the hypoxic micro-environment by human papillary thyroid carcinoma (PTC) cells, in the absence of leukocyte infiltrate, induces a "molecular inflammation" process characterized by the expression of a large set of genes normally involved in inflammation. To address this, tumor, peritumor or normal host tissue from eleven human PTC surgical samples, were separated by laser capture microdissection (LCMD) and studied by real-time quantitative PCR and Western blot. In such condition, we observed an increased expression and activation of HIF-1α, NF-kB and pro-inflammatory genes only in tumor tissues. Importantly, an anti-inflammatory gene such as SOCS-1 was markedly down-regulated in tumor tissue compared to surrounding normal host tissue. Similar results were found in fine-needle aspiration biopsy (FNAB)-derived specimens from PTC and in hypoxic human papillary thyroid tumor cell line, BCPAP. Moreover, we also detected an elevated expression of metalloproteinase-9 (MMP9) both in solid tumor and in hypoxic-treated BCPAP cells. Our findings reveal that, in human PTC tumor, hypoxic conditions are accompanied by up-regulation of pro-inflammatory genes, down-regulation of anti-inflammatory genes and increased expression of MMP9. We propose that a better understanding of the pro- and anti-inflammatory pathways involved in the "molecular inflammation" process even in the absence of leukocyte, may help to clarify progression toward malignancy and may prove useful for new anti-tumor strategy.

Grape seed proanthocyanidins inhibit migration potential of pancreatic cancer cells by promoting mesenchymal-to-epithelial transition and targeting NF-κB

Here we explore the effect of grape seed proanthocyanidins (GSPs) on pancreatic cancer cell migration and the molecular mechanisms underlying these effects. Treatment of human pancreatic cancer cell lines Miapaca-2, PANC-1 and AsPC-1 with GSPs resulted in inhibition of cell migration (19-82%, P<0.01-0.001), which was associated with decreased phosphorylation of ERK1/2 and inactivation of NF-κB. Treatment of cells with UO126, an inhibitor of MEK, and caffeic acid phenethyl ester, an inhibitor of NF-κB, also inhibited the migration of cells (40-80%, P<0.01-0.001). Inhibition of cell migration by GSPs was associated with reversal of the epithelial-to-mesenchymal transition. This was associated with upregulation of E-cadherin and desmoglein-2 and down-regulation of fibronectin, N-cadherin and vimentin.

Role of emmprin in endometrial cancer

Background

Extracellular matrix metalloproteinase inducer (Emmprin/CD147) is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. Enriched on the surface of many tumor cells, emmprin promotes tumor growth, invasion, metastasis and angiogenesis. We evaluated the clinical importance of emmprin and investigated its role in endometrial cancer.

Methods

Emmprin expression was examined in uterine normal endometrium, endometrial hyperplasia and cancer specimens by immunohistochemistry. In addition, the biological functions and inhibitory effects of an emmprin knockdown were investigated in HEC-50B and KLE endometrial cancer cell lines.

Results

The levels of emmprin expression were significantly increased in the endometrial cancer specimens compared with the normal endometrium and endometrial hyperplasia specimens (p < 0.05). The disease-free survival (DFS) and overall survival (OS) rates of patients with high emmprin expression were significantly higher than those of patients with low emmprin expression (DFS: p < 0.001; OS: p < 0.001). Emmprin knockdown by the siRNA led to cell proliferation, migration and invasion through TGF-β, EGF, NF-κB, VEGF, MMP-2, and MMP-9 expression, which in turn resulted in increased levels of E-cadherin and reduced levels of Vimentin and Snail in endometrial cancer.

Conclusions

The present findings suggest that low emmprin expression might be a predictor of favorable prognosis in endometrial cancer patients, and that emmprin may represent a potential therapeutic target for endometrial cancer.

Microbes-induced EMT at the crossroad of inflammation and cancer

It is noteworthy that bacterial or viral infections, and the resulting chronic inflammation, have been shown to predispose individuals to certain types of cancer. Remarkably, these microbes upregulated some transcription factors involved in the regulation of the epithelial to mesenchymal transition, referred herein as EMT. EMT is a cellular process that consists in the conversion of epithelial cell phenotype to a mesenchymal phenotype. Under physiological conditions EMT is clearly important for embryogenesis, organ development, wound repair and tissue remodeling. However, EMT may also be activated under pathologic conditions, more particularly in carcinogenesis and metastatic progression. In this review, we make a parallel between microbes- and growth factors- induced transcription factors. A unifying EMT model then emerges that may help in understanding the development of microbial pathogenesis and in defining new potential future therapeutic strategy in treating diseases linked to infections.

Semaphorin 3A overcomes cancer hypoxia and metastatic dissemination induced by antiangiogenic treatment in mice

Cancer development, progression, and metastasis are highly dependent on angiogenesis. The use of antiangiogenic drugs has been proposed as a novel strategy to interfere with tumor growth, but cancer cells respond by developing strategies to escape these treatments. In particular, animal models show that antiangiogenic drugs currently used in clinical settings reduce tumor tissue oxygenation and trigger molecular events that foster cancer resistance to therapy. Here, we show that semaphorin 3A (Sema3A) expression overcomes the proinvasive and prometastatic resistance observed upon angiogenesis reduction by the small-molecule tyrosine inhibitor sunitinib in both pancreatic neuroendocrine tumors (PNETs) in RIP-Tag2 mice and cervical carcinomas in HPV16/E2 mice. By improving cancer tissue oxygenation and extending the normalization window, Sema3A counteracted sunitinib-induced activation of HIF-1α, Met tyrosine kinase receptor, epithelial-mesenchymal transition (EMT), and other hypoxia-dependent signaling pathways. Sema3A also reduced tumor hypoxia and halted cancer dissemination induced by DC101, a specific inhibitor of the VEGF pathway. As a result, reexpressing Sema3A in cancer cells converts metastatic PNETs and cervical carcinomas into benign lesions. We therefore suggest that this strategy could be developed to safely harnesses the therapeutic potential of the antiangiogenic treatment.

Ubiquitination and the Ubiquitin-Proteasome System as regulators of transcription and transcription factors in epithelial mesenchymal transition of cancer

Epithelial to Mesenchymal Transition (EMT) in cancer is a process that allows cancer cells to detach from neighboring cells, become mobile and metastasize and shares many signaling pathways with development. Several molecular mechanisms which regulate oncogenic properties in neoplastic cells such as proliferation, resistance to apoptosis and angiogenesis through transcription factors or other mediators are also regulators of EMT. These pathways and downstream transcription factors are, in their turn, regulated by ubiquitination and the Ubiquitin-Proteasome System (UPS). Ubiquitination, the covalent link of the small 76-amino acid protein ubiquitin to target proteins, serves as a signal for protein degradation by the proteasome or for other outcomes such as endocytosis, degradation by the lysosome or directing these proteins to specific cellular compartments. This review discusses aspects of the regulation of EMT by ubiquitination and the UPS and underlines its complexity focusing on transcription and transcription factors regulating EMT and are being regulated by ubiquitination.

Twist modulates human trophoblastic cell invasion via regulation of N-cadherin

The invasion of extravillous cytotrophoblasts (EVT) into the underlying maternal tissues and vasculature is a key step in human placentation. The molecular mechanisms involved in the development of the invasive phenotype of EVT include many that were first discovered for their role in cancer cell metastasis. Previous studies have demonstrated that N-cadherin and its regulatory transcription factor Twist play important roles in the onset and progression of cancers, but their roles in human trophoblastic cell invasion is not clear. The goal of the study was to examine the role of Twist and N-cadherin in human trophoblastic cell invasion. Twist and N-cadherin mRNA and protein levels were determined by RT-PCR and Western blotting in human placental tissues, highly invasive EVT, and poorly invasive JEG-3 and BeWo cells. Whether IL-1β and TGF-β1 regulate Twist mRNA and protein levels in the EVT was also examined. A small interfering RNA strategy was employed to determine the role of Twist and N-cadherin in HTR-8/SVneo cell invasion. Matrigel assays were used to assess cell invasion. Twist and N-cadherin were highly expressed in EVT but were poorly expressed in JEG-3 and BeWo cells. IL-1β and TGF-β1 differentially regulated Twist expression in EVT in a time- and concentration-dependent manner. Small interfering RNA specific for Twist decreased N-cadherin and reduced invasion of HTR-8/SVneo cells. Similarly, a reduction in N-cadherin decreased the invasive capacity of HTR-8/SVneo cells. Twist is an upstream regulator of N-cadherin-mediated invasion of human trophoblastic cells.

Grape seed proanthocyanidins inhibit the invasiveness of human HNSCC cells by targeting EGFR and reversing the epithelial-to-mesenchymal transition

Head and neck squamous cell carcinoma (HNSCC) is responsible for approximately 20,000 deaths per year in the United States. Most of the deaths are due to the metastases. To develop more effective strategies for the prevention of metastasis of HNSCC cells, we have determined the effect of grape seed proanthocyanidins (GSPs) on the invasive potential of HNSCC cell and the mechanisms underlying these effects using OSC19 cells as an in vitro model. Using cell invasion assays, we established that treatment of the OSC19 cells with GSPs resulted in a dose-dependent inhibition of cell invasion. EGFR is over-expressed in 90% of HNSCCs and the EGFR inhibitors, erlotinib and gefitinib, are being explored as therapies for this disease. We found that GSPs treatment reduced the levels of expression of EGFR in the OSC19 cells as well as reducing the activation of NF-κB/p65, a downstream target of EGFR, and the expression of NF-κB-responsive proteins. GSPs treatment also reduced the activity of ERK1/2, an upstream regulator of NF-κB and treatment of the cells with caffeic acid phenethyl ester, an inhibitor of NF-κB, inhibited cell invasion. Overexpression of EGFR and high NF-κB activity play a key role in the epithelial-to-mesenchymal transition, which is of critical importance in the processes underlying metastasis, and we found treatment with GSPs enhanced the levels of epithelial (E-cadherin, cytokeratins and desmoglein-2) and reduced the levels of mesenchymal (vimentin, fibronectin, N-cadherin and Slug) biomarkers in the OSC19 cells. These results indicate that GSPs have the ability to inhibit HNSCC cell invasion, and do so by targeting the expression of EGFR and activation of NF-κB as well as inhibiting the epithelial-to-mesenchymal transition.

Evidence that GTP-binding domain but not catalytic domain of transglutaminase 2 is essential for epithelial-to-mesenchymal transition in mammary epithelial cells

INTRODUCTION

The expression of proinflammatory protein tissue transglutaminase 2 (TG2) is frequently upregulated in multiple cancer cell types. However, the exact role of TG2 in cancer cells is not well-understood. We recently initiated studies to determine the significance of TG2 in cancer cells and observed that sustained expression of TG2 resulted in epithelial-to-mesenchymal transition (EMT) and promoted cancer stem cell (CSC) traits in mammary epithelial cells. These results suggested that TG2 could serve as a promising therapeutic target for overcoming chemoresistance and inhibiting metastatic spread of cancer cells.

METHODS

Using various mutant constructs, we analyzed the activity of TG2 that is essential for promoting the EMT-CSC phenotype.

RESULTS

Our results suggest that catalytically inactive TG2 (TG2-C277S) is as effective as wild-type TG2 (TG2-WT) in inducing the EMT-CSC in mammary epithelial cells. In contrast, overexpression of a GTP-binding-deficient mutant (TG2-R580A) was completely incompetent in this regard. Moreover, TG2-dependent activation of the proinflammatory transcription factor NF-κB is deemed essential for promoting the EMT-CSC phenotype in mammary epithelial cells.

CONCLUSIONS

Our results suggest that the transamidation activity of TG2 is not essential for promoting its oncogenic functions and provide a strong rationale for developing small-molecule inhibitors to block GTP-binding pockets of TG2. Such inhibitors may have great potential for inhibiting the TG2-regulated pathways, reversing drug resistance and inhibiting the metastasis of cancer cells.

The p65 subunit of NF-κB and PARP1 assist Snail1 in activating fibronectin transcription

Snail1 is a transcriptional repressor of E-cadherin that triggers epithelial-mesenchymal transition (EMT). Here, we report assisted Snail1 interaction with the promoter of a typical mesenchymal gene, fibronectin (FN1), both in epithelial cells undergoing EMT and in fibroblasts. Together with Snail1, the p65 subunit of NF-κB and PARP1 bound to the FN1 promoter. We detected nuclear interaction of these proteins and demonstrated the requirement of all three for FN1 transcription. Moreover, other genes involved in cell movement mimic FN1 expression induced by Snail1 or TGF-β1 treatment and recruit p65NF-κB and Snail1 to their promoters. The molecular cooperation between Snail1 and NF-κB in transcription activation provides a new insight into how Snail1 can modulate a variety of cell programs.

Inhibition of Epithelial-to-Mesenchymal Transition (EMT) in Cancer by Nitric Oxide: Pivotal Roles of Nitrosylation of NF-κB, YY1 and Snail

Treatment of cancer cell lines with high levels of nitric oxide (NO) via NO donors, such as DETANONOate, inhibits cell growth and survival pathways and sensitizes resistant tumor cells to apoptosis by chemoimmunotherapeutic drugs. In addition, we recently have reported that NO also inhibits the epithelial-to-mesenchymal transition (EMT) phenotype in metastatic cancer cell lines via dysregulation of the nuclear factor (NF)-κB/Snail/Yin Yang 1 (YY1)/Raf kinase inhibitor protein circuitry. The mechanism underlying NO-mediated dysregulation of this circuit was investigated, namely, NO-mediated inhibition of the activity of the transcription factors NF-κB, Snail, and YY1. We hypothesized that one mechanism of NO-mediated inhibition may invoke the NO-induced S-nitrosylation of these transcription factors. We demonstrate in metastatic and EMT⁺ human prostate carcinoma cell lines that treatment with NO results in the S-nitrosylation of NF-κB (p50), Snail, and YY1 and inhibits their activities, resulting in the reversal of the EMT phenotype into a mesenchymal-to-epithelial transition phenotype. These findings suggest that NO donors may be potential therapeutic agents in both the reversal of resistance and the inhibition of EMT and metastasis.

Grape seed proanthocyanidins inhibit the invasive potential of head and neck cutaneous squamous cell carcinoma cells by targeting EGFR expression and epithelial-to-mesenchymal transition

Background

Head and neck squamous cell carcinoma (HNSCC) is responsible for over 20,000 deaths every year in United States. Most of the deaths are due, in large part, to its propensity to metastasize. We have examined the effect of bioactive component grape seed proanthocyanidins (GSPs) on human cutaneous HNSCC cell invasion and the molecular mechanisms underlying these effects using SCC13 cell line as an in vitro model.

Methods

The therapeutic effects of GSPs on cancer cell invasion were studied using Boyden chamber and wound healing assays. The effects of GSPs on the levels of various proteins related with cancer cell invasion were determined using western blot analysis.

Results

Using in vitro cell invasion assays, we observed that treatment of SCC13 cells with GSPs resulted in a concentration-dependent inhibition of cell invasion of these cells, which was associated with a reduction in the levels of epidermal growth factor receptor (EGFR). Treatment of cells with gefitinib and erlotinib, inhibitors of EGFR, or transient transfection of SCC13 cells with EGFR small interfering RNA, also inhibited invasion of these cells. The inhibition of cell invasion by GSPs was associated with the inhibition of the phosphorylation of ERK1/2, a member of mitogen-activated protein kinase family. Treatment of cells with UO126, an inhibitor of MEK, also inhibited the invasion potential of SCC13 cells. Additionally, inhibition of human cutaneous HNSCC cell invasion by GSPs was associated with reversal of epithelial-to-mesenchymal transition (EMT) process, which resulted in an increase in the levels of epithelial biomarker (E-cadherin) while loss of mesenchymal biomarkers (vimentin, fibronectin and N-cadherin) in cells. Similar effect on EMT biomarkers was also observed when cells were treated with erlotinib.

Conclusion

The results obtained from this study indicate that grape seed proanthocyanidins have the ability to inhibit the invasion of human cutaneous HNSCC cells by targeting the EGFR expression and reversing the process of epithelial-to-mesenchymal transition. These data suggest that GSPs can be developed as a complementary and alternative medicine for the prevention of invasion/metastasis of HNSCC cells.

The p65 subunit of NF-κB and PARP1 assist Snail1 in activating fibronectin transcription

Snail1 is a transcriptional repressor of E-cadherin that triggers epithelial–mesenchymal transition (EMT). Here, we report assisted Snail1 interaction with the promoter of a typical mesenchymal gene, fibronectin (FN1), both in epithelial cells undergoing EMT and in fibroblasts. Together with Snail1, the p65 subunit of NF-κB and PARP1 bound to the FN1 promoter. We detected nuclear interaction of these proteins and demonstrated the requirement of all three for FN1 transcription. Moreover, other genes involved in cell movement mimic FN1 expression induced by Snail1 or TGF-β1 treatment and recruit p65NF-κB and Snail1 to their promoters. The molecular cooperation between Snail1 and NF-κB in transcription activation provides a new insight into how Snail1 can modulate a variety of cell programs.

Metformin may antagonize Lin28 and/or Lin28B activity, thereby boosting let-7 levels and antagonizing cancer progression

Cancer cells with stem cell characteristics are harbored by most tumors, and are characterized by epithelial-mesenchymal transition (EMT) - which promotes invasive growth and metastasis - chemoresistance, and the capacity to reconstitute new tumors. Hence, the control or destruction of cancer stem cells should be a major goal of cancer management. The let-7 family of microRNAs has cancer suppressor activity, and recent evidence suggests that markedly reduced levels of let-7 are not only a typical feature of cancer stem cells, but may be largely responsible for cancer stemness. It is therefore particularly intriguing that metformin, a diabetes drug thought to have potential in the prevention and treatment of cancer, has recently been found to oppose cancer cell stemness, to markedly potentiate chemotherapeutic control of cancer in mouse xenograft models, and to notably boost let-7a levels in cancer stem cells. It is proposed that this latter effect of metformin may reflect AMPK-mediated inhibition of the expression or activity of Lin28/Lin28A, proteins which act post-transcriptionally to decrease the levels of all let-7 family members. The transcription of Lin28B is promoted by NF-kappaB and by Myc; hence, practical measures which antagonize NF-kappaB or Myc activity may complement the utility of metformin for boosting let-7 expression and controlling cancer stemness; salsalate, antioxidants, tyrosine kinase and cox-2 inhibitors, ribavirin, vitamin D, gamma-secretase inhibitors (when available), and parenteral curcumin may have some utility in this regard. Although the impact of histone deacetylase inhibitors on let-7 expression has not been assessed, there is reason to suspect that these drugs might complement let-7's impact on chemoresistance, EMT, and stemness. Multifocal strategies centering on metformin may have considerable potential for reversing cancer stemness and rendering advanced cancers more susceptible to long term control.

BI 5700, a Selective Chemical Inhibitor of IκB Kinase 2, Specifically Suppresses Epithelial-Mesenchymal Transition and Metastasis in Mouse Models of Tumor Progression

Increasing evidence suggests that processes termed epithelial-mesenchymal transitions (EMTs) play a key role in therapeutic resistance, tumor recurrence, and metastatic progression. NF-κB signaling has been previously identified as an important pathway in the regulation of EMT in a mouse model of tumor progression. However, it remains unclear whether there is a broad requirement for this pathway to govern EMT and what the relative contribution of IKK family members acting as upstream NF-κB activators is toward promoting EMT and metastasis. To address this question, we have used a novel, small-molecule inhibitor of IκB kinase 2 (IKK2/IKKβ), termed BI 5700. We investigated the role of IKK2 in a number of mouse models of EMT, including TGFβ-induced EMT in the mammary epithelial cell line EpRas, CT26 colon carcinoma cells, and 4T1 mammary carcinoma cells. The latter model was also used to evaluate in vivo activities of BI 5700.We found that BI 5700 inhibits IKK2 with an IC(50) of 9 nM and was highly selective as compared to other IKK family members (IKK1, IKKε, and TBK1) and other kinases. BI 5700 effectively blocks NF-κB activity in EpRas cells and prevents TGFβ-induced EMT. In addition, BI 5700 reverts EMT in mesenchymal CT26 cells and prevents EMT in the 4T1 model. Oral application of BI 5700 significantly interferes with metastasis after mammary fat-pad injection of 4T1 cells, yielding fewer, smaller, and more differentiated metastases as compared to vehicle-treated control animals. We conclude that IKK2 is a key regulator of both the induction and maintenance of EMT in a panel of mouse tumor progression models and that the IKK2 inhibitor BI 5700 constitutes a promising candidate for the treatment of metastatic cancers.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Antimetastatic effect and mechanism of ovatodiolide in MDA-MB-231 human breast cancer cells

Cancer metastasis is a primary cause of cancer death. Ovatodiolide, a bioactive cembrane-type diterpenoid isolated from Anisomeles indica (L.) Kuntze (Labiatae), has been shown to inhibit the growth and proliferation of cancer cells. However, the anti-metastatic effects of ovatodiolide on highly metastatic human breast cancer MDA-MB-231 cells remain unclear. In this study, we first noted that ovatodiolide inhibited MDA-MB-231 cell migration and invasion by wound-healing assay and Boyden chamber assay. Western blot, gelatin zymography and reversed transcription-PCR analysis showed that ovatodiolide significantly and selectively suppressed the expression, activation, and mRNA of matrix metalloproteinase-9 (MMP-9) in a concentration-dependent manner. Ovatodiolide significantly decreased the nuclear level of nuclear factor kappaB (NF-κB), increased inhibitor of kappaBα (IκBα) through preventing phosphorylation of upstream signal IκB kinase (IKK). Pretreatment with a specific NF-κB inhibitor (PDTC) and an IκB protease inhibitor (TPCK) also reduced MMP-9 activity, cell migration and cell invasion. Moreover, ovatodiolide can suppress activation of c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, phosphatidylinositol 3-kinase and Akt, while it did not affect phosphorylation of extracellular signal regulating kinases (ERK)1/2. Additionally, the treatment of inhibitors specific for PI3K (wortmannin), JNK (SP600125) or p38 MAPK (SB203580) to MDA-MB-231 cells could result in a reduced activation of MMP-9, concomitantly with a marked inhibition on cell migration and invasion. Taken together, these results demonstrate that ovatodiolide inhibits the metastatic ability of MDA-MB-231 cells by reducing MMP-9 activity through suppressing JNK, p38 MAPK and PI3K/Akt signaling pathways and inhibiting NF-κB activity. These results are the first to reveal the function of ovatodiolide in tumor metastasis and its underlying molecular mechanism, thus suggesting ovatodiolide to be a promising antimetastatic agent.

Green tea catechins reduce invasive potential of human melanoma cells by targeting COX-2, PGE2 receptors and epithelial-to-mesenchymal transition

Melanoma is the most serious type of skin disease and a leading cause of death from skin disease due to its highly metastatic ability. To develop more effective chemopreventive agents for the prevention of melanoma, we have determined the effect of green tea catechins on the invasive potential of human melanoma cells and the molecular mechanisms underlying these effects using A375 (BRAF-mutated) and Hs294t (Non-BRAF-mutated) melanoma cell lines as an in vitro model. Employing cell invasion assays, we found that the inhibitory effects of green tea catechins on the cell migration were in the order of (-)-epigallocatechin-3-gallate (EGCG)>(-)-epigallocatechin>(-)-epicatechin-3-gallate>(-)-gallocatechin>(-)-epicatechin. Treatment of A375 and Hs294t cells with EGCG resulted in a dose-dependent inhibition of cell migration or invasion of these cells, which was associated with a reduction in the levels of cyclooxygenase (COX)-2, prostaglandin (PG) E₂ and PGE₂ receptors (EP2 and EP4). Treatment of cells with celecoxib, a COX-2 inhibitor, also inhibited melanoma cell migration. EGCG inhibits 12-O-tetradecanoylphorbol-13-acetate-, an inducer of COX-2, and PGE₂-induced cell migration of cells. EGCG decreased EP2 agonist (butaprost)- and EP4 agonist (Cay10580)-induced cell migration ability. Moreover, EGCG inhibited the activation of NF-κB/p65, an upstream regulator of COX-2, in A375 melanoma cells, and treatment of cells with caffeic acid phenethyl ester, an inhibitor of NF-κB, also inhibited cell migration. Inhibition of melanoma cell migration by EGCG was associated with transition of mesenchymal stage to epithelial stage, which resulted in an increase in the levels of epithelial biomarkers (E-cadherin, cytokeratin and desmoglein 2) and a reduction in the levels of mesenchymal biomarkers (vimentin, fibronectin and N-cadherin) in A375 melanoma cells. Together, these results indicate that EGCG, a major green tea catechin, has the ability to inhibit melanoma cell invasion/migration, an essential step of metastasis, by targeting the endogenous expression of COX-2, PGE₂ receptors and epithelial-to-mesenchymal transition.

The inflammatory tumor microenvironment, epithelial mesenchymal transition and lung carcinogenesis

The inflammatory tumor microenvironment (TME) has many roles in tumor progression and metastasis, including creation of a hypoxic environment, increased angiogenesis and invasion, changes in expression of microRNAs (miRNAs) and an increase in a stem cell phenotype. Each of these has an impact on epithelial mesenchymal transition (EMT), particularly through the downregulation of E-cadherin. Here we review seminal work and recent findings linking the role of inflammation in the TME, EMT and lung cancer initiation, progression and metastasis. Finally, we discuss the potential of targeting aspects of inflammation and EMT in cancer prevention and treatment.

Linoleic acid induces an EMT-like process in mammary epithelial cells MCF10A

Epidemiological studies and animal models suggest an association between high levels of dietary fat intake and an increased risk of developing breast cancer. Epithelial-mesenchymal-transition (EMT) is a process, by which epithelial cells are transdifferentiated to a mesenchymal state, and it has been implicated in cancer progression, including invasion and metastasis. Linoleic acid (LA) induces proliferation and invasion in breast cancer cells. However, the role of LA on the EMT process in human mammary epithelial cells remains to be studied. In the present study, we demonstrate that LA induces a transient down-regulation of E-cadherin expression, accompanied with an increase of Snail1, Snail2, Twist1, Twist2 and Sip1 expressions. Furthermore, LA induces FAK and NFκB activation, MMP-2 and -9 secretions, migration and invasion. In summary, our findings demonstrate, for the first time, that LA promotes an EMT-like process in MCF10A human mammary epithelial cells.

Vimentin in cancer and its potential as a molecular target for cancer therapy

Vimentin, a major constituent of the intermediate filament family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress. Vimentin is overexpressed in various epithelial cancers, including prostate cancer, gastrointestinal tumors, tumors of the central nervous system, breast cancer, malignant melanoma, and lung cancer. Vimentin's overexpression in cancer correlates well with accelerated tumor growth, invasion, and poor prognosis; however, the role of vimentin in cancer progression remains obscure. In recent years, vimentin has been recognized as a marker for epithelial-mesenchymal transition (EMT). Although EMT is associated with several tumorigenic events, vimentin's role in the underlying events mediating these processes remains unknown. By virtue of its overexpression in cancer and its association with tumor growth and metastasis, vimentin serves as an attractive potential target for cancer therapy; however, more research would be crucial to evaluate its specific role in cancer. Our recent discovery of a vimentin-binding mini-peptide has generated further impetus for vimentin-targeted tumor-specific therapy. Furthermore, research directed toward elucidating the role of vimentin in various signaling pathways would reveal new approaches for the development of therapeutic agents. This review summarizes the expression and functions of vimentin in various types of cancer and suggests some directions toward future cancer therapy utilizing vimentin as a potential molecular target.

Epithelial-Mesenchymal Transition in tumor microenvironment

The epithelial to mesenchymal transition (EMT) plays crucial roles in the formation of the body plan and also in the tumor invasion process. In addition, EMT also causes disruption of cell-cell adherence, loss of apico-basal polarity, matrix remodeling, increased motility and invasiveness in promoting tumor metastasis. The tumor microenvironment plays an important role in facilitating cancer metastasis and may induce the occurrence of EMT in tumor cells. A large number of inflammatory cells infiltrating the tumor site, as well as hypoxia existing in a large area of tumor, in addition many stem cells present in tumor microenvironment, such as cancer stem cells (CSCs), mesenchymal stem cells (MSCs), all of these may be the inducers of EMT in tumor cells. The signaling pathways involved in EMT are various, including TGF-β, NF-κB, Wnt, Notch, and others. In this review, we discuss the current knowledge about the role of the tumor microenvironment in EMT and the related signaling pathways as well as the interaction between them.

Nuclear factor-κB-dependent epithelial to mesenchymal transition induced by HIF-1α activation in pancreatic cancer cells under hypoxic conditions

BACKGROUND

Epithelial to mesenchymal transition (EMT) induced by hypoxia is one of the critical causes of treatment failure in different types of human cancers. NF-κB is closely involved in the progression of EMT. Compared with HIF-1α, the correlation between NF-κB and EMT during hypoxia has been less studied, and although the phenomenon was observed in the past, the molecular mechanisms involved remained unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we report that hypoxia or overexpression of hypoxia-inducible factor-1α (HIF-1α) promotes EMT in pancreatic cancer cells. On molecular or pharmacologic inhibition of NF-κB, hypoxic cells regained expression of E-cadherin, lost expression of N-cadherin, and attenuated their highly invasive and drug-resistant phenotype. Introducing a pcDNA3.0/HIF-1α into pancreatic cancer cells under normoxic conditions heightened NF-κB activity, phenocopying EMT effects produced by hypoxia. Conversely, inhibiting the heightened NF-κB activity in this setting attenuated the EMT phenotype.

CONCLUSIONS/SIGNIFICANCE

These results suggest that hypoxia or overexpression of HIF-1α induces the EMT that is largely dependent on NF-κB in pancreatic cancer cells.

Systemic administration of antisense oligonucleotides simultaneously targeting CK2α and α' subunits reduces orthotopic xenograft prostate tumors in mice

CK2 is a highly conserved, ubiquitous, signal responsive protein serine/threonine kinase. CK2 promotes cell proliferation and suppresses apoptosis, and increased CK2 expression is observed in all cancers examined. We previously reported that direct injection of antisense (AS) CK2α phosphorothioate oligonucleotides (PTO) into xenograft prostate tumors in mice significantly reduced tumor size. Downregulation of CK2α in tumor cells in vivo appeared to result in overexpression of CK2α' protein. This suggested that in cancer cells downregulation of CK2α might be compensated by CK2α' in vivo, prompting us to design a bispecific (bs) AS PTO (bs-AS-CK2) targeting both catalytic subunits. bs-AS-CK2 reduced CK2α and α' protein expression, decreased cell proliferation, and induced apoptosis in cultured cells. Biodistribution studies of administered bs-AS-CK2 oligonucleotide demonstrated its presence in orthotopic prostate xenograft tumors. High dose injections of bs-AS-CK2 resulted in no damage to normal liver or prostate, but induced extensive cell death in tumor tissue. Intraperitoneal treatment with bs-AS-CK2 PTO decreased orthotopic tumor size and downregulated both CK2 mRNA and protein expression. Tumor reduction was accomplished using remarkably low doses and was improved by dividing the dose using a multi-day schedule. Decreased expression of the key signaling pathway proteins NF-κB p65 and AKT was also observed. We propose that the molecular downregulation of CK2 through bispecific targeting of the two catalytic subunits may be uniquely useful for therapeutic elimination of tumors.

Overcoming drug resistance in pancreatic cancer

INTRODUCTION

Pancreatic cancer has the worst survival rate of all cancers. The current standard care for metastatic pancreatic cancer is gemcitabine, however, the success of this treatment is poor and overall survival has not improved for decades. Drug resistance (both intrinsic and acquired) is thought to be a major reason for the limited benefit of most pancreatic cancer therapies.

AREAS COVERED

Previous studies have indicated various mechanisms of drug resistance in pancreatic cancer, including changes in individual genes or signaling pathways, the influence of the tumor microenvironment, and the presence of highly resistant stem cells. This review summarizes recent advances in the mechanisms of drug resistance in pancreatic cancer and potential strategies to overcome this.

EXPERT OPINION

Increasing drug delivery efficiency and decreasing drug resistance is the current aim in pancreatic cancer treatment, and will also benefit the treatment of other cancers. Understanding the molecular and cellular basis of drug resistance in pancreatic cancer will lead to the development of novel therapeutic strategies with the potential to sensitize pancreatic cancer to chemotherapy, and to increase the efficacy of current treatments in a wide variety of human cancers.

Grape seed proanthocyanidins inhibit melanoma cell invasiveness by reduction of PGE2 synthesis and reversal of epithelial-to-mesenchymal transition

Melanoma is the leading cause of death from skin disease due, in large part, to its propensity to metastasize. We have examined the effect of grape seed proanthocyanidins (GSPs) on melanoma cancer cell migration and the molecular mechanisms underlying these effects using highly metastasis-specific human melanoma cell lines, A375 and Hs294t. Using in vitro cell invasion assays, we observed that treatment of A375 and Hs294t cells with GSPs resulted in a concentration-dependent inhibition of invasion or cell migration of these cells, which was associated with a reduction in the levels of cyclooxygenase (COX)-2 expression and prostaglandin (PG) E(2) production. Treatment of cells with celecoxib, a COX-2 inhibitor, or transient transfection of melanoma cells with COX-2 small interfering RNA, also inhibited melanoma cell migration. Treatment of cells with 12-O-tetradecanoylphorbol-13-acetate, an inducer of COX-2, enhanced the phosphorylation of ERK1/2, a protein of mitogen-activated protein kinase family, and subsequently cell migration whereas both GSPs and celecoxib significantly inhibited 12-O-tetradecanoylphorbol-13-acetate-promoted cell migration as well as phosphorylation of ERK1/2. Treatment of cells with UO126, an inhibitor of MEK, also inhibited the migration of melanoma cells. Further, GSPs inhibited the activation of NF-κB/p65, an upstream regulator of COX-2, in melanoma cells, and treatment of cells with caffeic acid phenethyl ester, an inhibitor of NF-κB, also inhibited cell migration. Additionally, inhibition of melanoma cell migration by GSPs was associated with reversal of epithelial-mesenchymal transition process, which resulted in an increase in the levels of epithelial biomarkers (E-cadherin and cytokeratins) while loss of mesenchymal biomarkers (vimentin, fibronectin and N-cadherin) in melanoma cells. Together, these results indicate that GSPs have the ability to inhibit melanoma cell invasion/migration by targeting the endogenous expression of COX-2 and reversing the process of epithelial-to-mesenchymal transition.

Metadherin enhances the invasiveness of breast cancer cells by inducing epithelial to mesenchymal transition

The epithelial-mesenchymal transition (EMT) is a process in which polarized epithelial cells are converted into motile mesenchymal cells. During cancer development, EMT is conducive to tumor dissemination and metastatic spread. While overexpression of metadherin (MTDH) in breast cancer cell lines and tissues has been found to be associated with aggressive tumor behavior, its precise role in invasion and metastasis is largely unknown. Here we report that MTDH overexpression could significantly enhance the invasion and migration of breast cancer cells by inducing EMT. Metadherin overexpression led to upregulation of mesenchymal marker fibronectin, downregulation of epithelial marker E-cadherin, and the nuclear accumulation of beta-catenin. Also, transcription factors Snail and Slug were upregulated in breast cancer cells overexpressing MTDH. Overexpression of MTDH enhanced the invasiveness and migration ability of breast cancer cells in vitro. In addition, overexpression of MTDH led to increased acquisition of CD44(+) /CD24(-/low) markers that are characteristic of breast cancer stem cells. We also showed that NF-kappa was involved in the expression of EMT-related markers. Taken together, our results suggest that MTDH could promote EMT in breast cancer cells in driving the progression of their aggressive behavior.

Differential expression of signaling pathways in odontogenic differentiation of ectomesenchymal cells isolated from the first branchial arch

The aim of this study was to screen for differential expression of signaling pathways in odontogenic differentiation of ectomesenchymal cells isolated from the first branchial arch of embryonic day 10 (E10) mice by real time RT-PCR microarray. Observations of cellular morphology, immunocytochemistry, and RT-PCR were used to identify the cell source. A real time RT-PCR microarray was then used to detect the differential expression of signaling pathways in cells dissected from animals at two different developmental stages. These assays identified 25 up-regulated genes and 16 down-regulated genes involved in odontogenic differentiation of the ectomesenchymal cells of the first branchial arch. They represented the main members of Wnt, Hedgehog, TGF-β, NF-κB, and LDL signaling pathways. This study determined that these signaling pathways are important for odontogenic differentiation of ectomesenchymal cells of the first branchial arch.

Artificially induced epithelial-mesenchymal transition in surgical subjects: its implications in clinical and basic cancer research

Background

Surgical samples have long been used as important subjects for cancer research. In accordance with an increase of neoadjuvant therapy, biopsy samples have recently become imperative for cancer transcriptome. On the other hand, both biopsy and surgical samples are available for expression profiling for predicting clinical outcome by adjuvant therapy; however, it is still unclear whether surgical sample expression profiles are useful for prediction via biopsy samples, because little has been done about comparative gene expression profiling between the two kinds of samples.

Methodology and Findings

A total of 166 samples (77 biopsy and 89 surgical) of normal and malignant lesions of the esophagus were analyzed by microarrays. Gene expression profiles were compared between biopsy and surgical samples. Artificially induced epithelial-mesenchymal transition (aiEMT) was found in the surgical samples, and also occurred in mouse esophageal epithelial cell layers under an ischemic condition. Identification of clinically significant subgroups was thought to be disrupted by the disorder of the expression profile through this aiEMT.

Conclusion and Significance

This study will evoke the fundamental misinterpretation including underestimation of the prognostic evaluation power of markers by overestimation of EMT in past cancer research, and will furnish some advice for the near future as follows: 1) Understanding how long the tissues were under an ischemic condition. 2) Prevalence of biopsy samples for in vivo expression profiling with low biases on basic and clinical research. 3) Checking cancer cell contents and normal- or necrotic-tissue contamination in biopsy samples for prevalence.

Pancreatic cancer cells resistant to chemoradiotherapy rich in "stem-cell-like" tumor cells

BACKGROUND

Tumor resistance to chemoradiation therapy is partly attributed to the presence of apoptosis-resistant cancer stem cells (CSCs). Chemoradiation therapy can enrich CSCs by killing apoptosis-susceptible cancer cells.

AIM

Our preliminary study showed chemoradiation-resistant pancreatic cancer cells to have some CSC characteristics, and to undergo epithelial-mesenchymal transition (EMT); we aimed to verify that study's implication that chemoradiation-resistant subpopulations are enriched with "stem-cell-like" tumor cells, which may be linked to EMT.

METHODS

Four pancreatic cancer cell lines were cultured in gemcitabine with synchronous radiotherapy to obtain resistant subpopulations. Morphological changes were observed under microscope; migration and invasiveness were assessed by Transwell tests. Protein expression was determined by immunoblotting. Pancreatic CSC markers were studied using fluorescence-activated cell sorting analyses. Colony-formation tests, tumor sphere formation assays, and tumor xenografts in BALB/C nude mice were used to evaluate "stemness" in resistant cells.

RESULTS

Resistant cells expressed more antiapoptotic protein Bcl-2, apoptosis-inhibitory protein survivin, and stem cell markers Oct4, ABCG2, CD24, and CD133, were more tumorigenic in vitro and in vivo, and showed phenotypic and molecular changes consistent with EMT, including upregulation of vimentin and downregulation of E-cadherin. They were also more invasive and migratory.

CONCLUSIONS

We found chemoradiation-resistant pancreatic cancer cells to be similar to CSCs and to undergo EMT, suggesting that chemoradiation resistance-induced EMT is linked to CSC generation.