Targeted therapies in control of EMT in carcinoma and fibrosis

Expression of Genes Associated With Epithelial-Mesenchymal Transition in Merkel Cell Polyomavirus-Negative Merkel Cell Carcinoma

Two accepted possible pathways for Merkel cell carcinoma (MCC) pathogenesis include the clonal integration of the Merkel cell polyomavirus (MCPyV) into the neoplastic cells and by UV irradiation. We hypothesize that, in UV etiology, the expression of genes associated with epithelial-mesenchymal transition (EMT) would be higher in MCPyV-negative MCCs. We compared RNA expression in 16 MCPyV-negative with that in 14 MCPyV-positive MCCs in 30 patients using NanoString panel of 760 gene targets as an exploratory method. Subsequently, we confirmed the findings with a publicly available RNA sequencing data set. The NanoString method showed that 29 of 760 genes exhibited significant deregulation. Ten genes (CD44, COL6A3, COL11A1, CXCL8, INHBA, MMP1, NID2, SPP1, THBS1, and THY1) were part of the EMT pathway. The expression of CDH1/E-cadherin, a key EMT gene, and TWIST1, regulator gene of EMT, was higher in MCPyV-negative tumors. To further investigate the expression of EMT genes in MCPyV-negative MCCs, we analyzed publicly available RNA sequencing data of 111 primary MCCs. Differential expression and gene set enrichment analysis of 35 MCPyV-negative versus 76 MCPyV-positive MCCs demonstrated significantly higher expression of EMT-related genes and associated pathways such as Notch signaling, TGF-β signaling, and Hedgehog signaling, and UV response pathway in MCPyV-negative MCCs. The significance of the EMT pathway in MCPyV-negative MCCs was confirmed independently by a coexpression module analysis. One of the modules (M3) was specifically activated in MCPyV-negative MCCs and showed significant enrichment for genes involved in EMT. A network analysis of module M3 revealed that CDH1/E-cadherin was among the most connected genes (hubs). E-cadherin and LEF1 immunostains demonstrated significantly more frequent expression in MCPvV-negative versus MCPyV-positive tumors (P < .0001). In summary, our study showed that the expression of EMT-associated genes is higher in MCPyV-negative MCC. Because EMT-related proteins can be targeted, the identification of EMT pathways in MCPyV-negative MCCs is of potential therapeutic relevance.

Basement membrane fragments in the context of the epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) enables cells of epithelial phenotype to become motile and change to a migratory mesenchymal phenotype. EMT is known to be a fundamental requisite for tissue morphogenesis, and EMT-related pathways have been described in cancer metastasis and tissue fibrosis. Epithelial structures are marked by the presence of a sheet-like extracellular matrix, the basement membrane, which is assembled from two major proteins, laminin and collagen type IV. This specialized matrix is essential for tissue function and integrity, and provides an important barrier to the potential pathogenic migration of cells. The profound phenotypic transition in EMT involves the epithelial cells disrupting the basement membrane. Matrix metalloproteinases (MMPs) are known to cleave components of basement membranes, but MMP-basement membrane crosstalk during EMT in vivo is poorly understood. However, MMPs have been reported to play a role in EMT-related processes and a variety of basement membrane fragments have been shown to be released by specific MMPs in vitro and in vivo exhibiting distinct biological activities. This review discusses general considerations regarding the basement membrane in the context of EMT, a possible role for specific MMPs in EMT and highlights biologically active basement membrane fragments liberated by MMPs.

miR-639 regulates transforming growth factor beta-induced epithelial-mesenchymal transition in human tongue cancer cells by targeting FOXC1

Epithelial-to-mesenchymal transition (EMT) is implicated in embryonic development and various pathological events. Transforming growth factor beta (TGFβ) has been reported to induce EMT in tumor cells, which is a critical step in the process of metastasis leading to cancer spreading and treatment failure. However, the involvement of microRNA during the EMT process in tongue squamous cell carcinoma (TSCC) remains to be determined. To address this question, TSCC cell lines SCC9 and CAL27 were treated with human recombinant TGFβ1 for 48 h. miRNA microarray illustrated that miR-639 was significantly downregulated in TGFβ-treated SCC9 cells. Ectopic expression of miR-639 with miRNA mimics effectively blocked TGFβ-induced EMT in SCC9 and CAL27 cells, but inhibition of miR-639 in SCC9 and CAL27 cells with antisense oligonucleotides induced EMT. Computational microRNA target predictions detected a conserved sequence matching to the seed region of miR-639 in the 3′-UTR of FOXC1 mRNA. Luciferase reporter assays revealed that miR-639 targets FOXC1. Ectopic expression of FOXC1 induces EMT in TSCC cells. Silencing FOXC1 expression blocked TGFβ-induced EMT in SCC9 cells. Clinically, reduced miR-639 expression was associated with metastasis in TSCC and poor patient survival. The data from the present study suggest that reduced expression of miR-639 underscores the mechanism of TGFβ-induced EMT in TSCC by targeting FOXC1 and may serve as therapeutic targets in the process of metastasis.

Biomechanics of TGFβ-induced epithelial-mesenchymal transition: implications for fibrosis and cancer

Fibrosis, a disease that results in loss of organ function, contributes to a significant number of deaths worldwide and sustained fibrotic activation has been suggested to increase the risk of developing cancer in a variety of tissues. Fibrogenesis and tumor progression are regulated in part through the activation and activity of myofibroblasts. Increasing evidence links myofibroblasts found within fibrotic lesions and the tumor microenvironment to a process termed epithelial-mesenchymal transition (EMT), a phenotypic change in which epithelial cells acquire mesenchymal characteristics. EMT can be stimulated by soluble signals, including transforming growth factor (TGF)-β, and recent studies have identified a role for mechanical cues in directing EMT. In this review, we describe the role that EMT plays in fibrogenesis and in the progression of cancer, with particular emphasis placed on biophysical signaling mechanisms that control the EMT program. We further describe specific TGFβ-induced intracellular signaling cascades that are affected by cell- and tissue-level mechanics. Finally, we highlight the implications of mechanical induction of EMT on the development of treatments and targeted intervention strategies for fibrosis and cancer.

Epithelial-to-mesenchymal transition in renal neoplasms

Epithelial-to-mesenchymal transition (EMT) describes a phenotypical change induced in epithelial cells that lose their cell-cell basement membrane contacts and their structural polarity to become spindle-shaped and morphologically similar to mesenchymal/myofibroblast cell. The abnormal induction of EMT has been demonstrated to contribute to cancer dissemination and progression. Renal cell carcinoma (RCC) with sarcomatoid differentiation (sarcomatoid RCC) represents a good example of EMT both morphologically and immunohistochemically. Early spindle cell changes can at times be identified in RCC and likely represent an early step toward EMT. Herein, we present a review of the current understanding of EMT in renal neoplasms including some known signaling regulation, the association of sarcomatoid differentiation in RCC with aggressive behavior and dismal prognosis, and EMT-related tumor biology in sarcomatoid RCC. A better perception of the EMT may contribute toward an improved understanding of the development of sarcomatoid RCC. In addition, a distinct signature for sarcomatoid RCC may have utility in the differential diagnosis for prognostic stratification as well as in identifying novel genes and pathway targets for therapeutic intervention.

The dual PI3K/mTOR inhibitor NVP-BEZ235 prevents epithelial-mesenchymal transition induced by hypoxia and TGF-β1

Epithelial-mesenchymal transition (EMT) is regarded as the most important mechanism behind the initiation of cancer metastasis. Though there has been great interest in developing therapies aimed at impairing the process of EMT, only few molecules have been identified to orchestrate it so far. Here we report that the dual PI3K/mTOR inhibitor NVP-BEZ235 is capable of preventing human ovarian cancer cell line SKOV-3 and prostatic cancer cell line PC-3 from hypoxia- and TGF-β1-induced EMT. The addition of NVP-BEZ235 reverses the EMT-like morphologic changes, down-regulation of E-cadherin, and enhancement of cell migration induced by 1% O2 partially through interfering with the expression and transcriptional activity of Hif-1α via PI3K/mTOR pathway. In addition, NVP-BEZ235 inhibits TGF-β1-induced phosphorylation of Smad2/3 and Akt/GSK-3β, reduces the expression of Snail both in transcriptional and post-translational level, and consequently prevents the repression of E-cadherin expression as well as the increase of cell motility caused by TGF-β1. Moreover, in nude mice bearing SKOV-3 ovarian cancer xenografts, NVP-BEZ235 significantly increases the mRNA level of E-cadherin. Taken together, our study demonstrates, for the first time, NVP-BEZ235 can prevent microenvironment and growth factor induced EMT, which suggests this agent as a potential candidate for cancer metastasis treatment.

Expanding horizons in iron chelation and the treatment of cancer: role of iron in the regulation of ER stress and the epithelial-mesenchymal transition

Cancer is a major public health issue and, despite recent advances, effective clinical management remains elusive due to intra-tumoural heterogeneity and therapeutic resistance. Iron is a trace element integral to a multitude of metabolic processes, including DNA synthesis and energy transduction. Due to their generally heightened proliferative potential, cancer cells have a greater metabolic demand for iron than normal cells. As such, iron metabolism represents an important "Achilles' heel" for cancer that can be targeted by ligands that bind and sequester intracellular iron. Indeed, novel thiosemicarbazone chelators that act by a "double punch" mechanism to both bind intracellular iron and promote redox cycling reactions demonstrate marked potency and selectivity in vitro and in vivo against a range of tumours. The general mechanisms by which iron chelators selectively target tumour cells through the sequestration of intracellular iron fall into the following categories: (1) inhibition of cellular iron uptake/promotion of iron mobilisation; (2) inhibition of ribonucleotide reductase, the rate-limiting, iron-containing enzyme for DNA synthesis; (3) induction of cell cycle arrest; (4) promotion of localised and cytotoxic reactive oxygen species production by copper and iron complexes of thiosemicarbazones (e.g., Triapine(®) and Dp44mT); and (5) induction of metastasis and tumour suppressors (e.g., NDRG1 and p53, respectively). Emerging evidence indicates that chelators can further undermine the cancer phenotype via inhibiting the epithelial-mesenchymal transition that is critical for metastasis and by modulating ER stress. This review explores the "expanding horizons" for iron chelators in selectively targeting cancer cells.

Sheep, wolf, or werewolf: cancer stem cells and the epithelial-to-mesenchymal transition

Multiple cancers contain subpopulations that exhibit characteristics of cancer stem cells (CSCs), the ability to self-renew and seed heterogeneous tumors. Recent evidence suggests two potentially overlapping models for these phenotypes: one where stem cells arise from multipotent progenitor cells, and another where they are created via an epithelial to mesenchymal transition. Unraveling this issue is critical, as it underlies phenomena such as metastasis and therapeutic resistance. Therefore, there is intense interest in understanding these two types of CSSs, how they differ from differentiated cancer cells, the mechanisms that drive their phenotypes, and how that knowledge can be incorporated into therapeutics.

A cell-based small molecule screening method for identifying inhibitors of epithelial-mesenchymal transition in carcinoma

Epithelial Mesenchymal Transition (EMT) is a crucial mechanism for carcinoma progression, as it provides routes for in situ carcinoma cells to dissociate and become motile, leading to localized invasion and metastatic spread. Targeting EMT therefore represents an important therapeutic strategy for cancer treatment. The discovery of oncogene addiction in sustaining tumor growth has led to the rapid development of targeted therapeutics. Whilst initially optimized as anti-proliferative agents, it is likely that some of these compounds may inhibit EMT initiation or sustenance, since EMT is also modulated by similar signaling pathways that these compounds were designed to target. We have developed a novel screening assay that can lead to the identification of compounds that can inhibit EMT initiated by growth factor signaling. This assay is designed as a high-content screening assay where both cell growth and cell migration can be analyzed simultaneously via time-course imaging in multi-well plates. Using this assay, we have validated several compounds as viable EMT inhibitors. In particular, we have identified compounds targeting ALK5, MEK, and SRC as potent inhibitors that can interfere with EGF, HGF, and IGF-1 induced EMT signaling. Overall, this EMT screening method provides a foundation for improving the therapeutic value of recently developed compounds in advanced stage carcinoma.

Target cell movement in tumor and cardiovascular diseases based on the epithelial-mesenchymal transition concept

Epithelial-mesenchymal transition (EMT) is a fundamental mechanism in development driving body plan formation. EMT describes a transition process wherein polarized epithelial cells lose their characteristics and acquire a mesenchymal phenotype. The apico-basal polarity of epithelial cells is replaced by a front-rear polarity in mesenchymal cells which favor cell-extracellular matrix than intercellular adhesion. These events serve as a prerequisite to the context-dependent migratory and invasive functions of mesenchymal cells. In solid tumors, carcinoma cells undergoing EMT not only invade and metastasize but also exhibit cancer stem cell-like properties, providing resistance to conventional and targeted therapies. In cardiovascular systems, epicardial cells engaged in EMT contribute to myocardial regeneration. Conversely, cardiovascular endothelial cells undergoing EMT cause cardiac fibrosis. Growing evidence has shed light on the potential development of novel therapeutics that target cell movement by applying the EMT concept, and this may provide new therapeutic strategies for the treatment of cancer and heart diseases.

The ins and outs of the epithelial to mesenchymal transition in health and disease

The epithelial to mesenchymal transition (EMT) converts epithelial cells into migratory and invasive cells and is a fundamental event in morphogenesis. Although its relevance in the progression of cancer and organ fibrosis had been debated until recently, the EMT is now established as an important step in the metastatic cascade of epithelial tumors. The similarities between pathological and developmental EMTs validate the embryo as the best model to understand the molecular and cellular mechanisms involved in this process, identifying those that are hijacked during the progression of cancer and organ degeneration. Our ever-increasing understanding of how transcription factors regulate the EMT has revealed complex regulatory loops coupled to posttranscriptional and epigenetic regulatory programs. The EMT is now integrated into the systemic activities of whole organisms, establishing links with cell survival, stemness, inflammation, and immunity. In addition, the EMT now constitutes a promising target for the treatment of cancer and organ-degenerative diseases.

MiR-200b and miR-15b regulate chemotherapy-induced epithelial-mesenchymal transition in human tongue cancer cells by targeting BMI1

Chemotherapy has been reported to induce epithelial-mesenchymal transition (EMT) in tumor cells, which is a critical step in the process of metastasis leading to cancer spreading and treatment failure. However, the underlying mechanisms of chemotherapy-induced EMT remain unclear, and the involvement of microRNAs (miRNA) in this process is poorly understood. To address these questions, we established stable chemotherapy-resistant tongue squamous cell carcinoma (TSCC) cell lines CAL27-res and SCC25-res by exposing the parental CAL27 and SCC25 lines to escalating concentrations of cisplatin for 6 months. CAL27-res and SCC25-res cells displayed mesenchymal features with enhanced invasiveness and motility. MiRNA microarray illustrated that miR-200b and miR-15b were the most significantly downregulated microRNAs in CAL27-res cells. Ectopic expression of miR-200b and miR-15b with miRNA mimics effectively reversed the phenotype of EMT in CAL27-res and SCC25-res cells, and sensitized them to chemotherapy, but inhibition of miR-200b and miR-15b in the sensitive lines with anti-sense oligonucleotides induced EMT and conferred chemoresistance. Retrieving the expression of B lymphoma Mo-MLV insertion region 1 homolog (BMI1), a target for miR-200b and miR-15b, in the presence of the miRNA mimics by transfecting CAL27-res cells with pcDNA3.1-BMI1-carrying mutated seed sequences of miR-200b or miR-15b at its 3'-UTR recapitulated chemotherapy-induced EMT. In vivo, enforced miR-200b or miR-15b expression suppressed metastasis of TSCC xenografts established by CAL27-res cells. Clinically, reduced miR-200b or miR-15b expression was associated with chemotherapeutic resistance in TSCCs and poor patient survival. Our data suggest that reduced expression of miR-200b and miR-15b underscores the mechanisms of chemotherapy-induced EMT in TSCC, and may serve as therapeutic targets to reverse chemotherapy resistance in tongue cancers.

3D models of epithelial-mesenchymal transition in breast cancer metastasis: high-throughput screening assay development, validation, and pilot screen

Despite advancements in therapies developed for the treatment of cancer, patient prognosis and mortality rates have improved minimally, and metastasis remains the primary cause of cancer mortality worldwide. An underlying mechanism promoting metastasis in many types of cancer is epithelial-mesenchymal transition (EMT). Here the authors report a novel 3D model of EMT and metastatic breast cancer suitable for high-throughput screening (HTS) drug discovery. The primary assay incorporates the expression of the prognostic biomarker vimentin, as a luciferase reporter of EMT, in basil-like/triple-negative MDA-MB-231 breast carcinoma spheroids. Using this model, the authors developed a number of known antitumor agents as control modulators of EMT. U0126, PKC412, PF2341066, dasatinib, and axitinib downregulated vimentin expression by 70% to 90% as compared to untreated spheroids. Counterassays were developed to measure spheroid viability and the invasive potential of MDA-MB-231 spheroids after small-molecule treatment and used to confirm hits from primary screening. Finally, the authors conducted a pilot screen to validate this model for HTS using a purified library of marine secondary metabolites. From 230 compounds screened, they obtained a Z' score of 0.64, indicative of an excellent assay, and confirmed 4 hits, including isonaamidine B, papuamine, mycalolide E, and jaspamide. This HTS model demonstrates the potential to identify small-molecule modulators of EMT that could be used to discover novel antimetastatic agents for the treatment of cancer.

Snail family regulation and epithelial mesenchymal transitions in breast cancer progression

Since its initial description, the interconversion between epithelial and mesenchymal cells (designed as epithelial-mesenchymal or mesenchymal-epithelial transition, EMT or MET, respectively) has received special attention since it provides epithelial cells with migratory features. Different studies using cell lines have identified cytokines, intercellular signaling elements and transcriptional factors capable of regulating this process. Particularly, the identification of Snail family members as key effectors of EMT has opened new ways for the study of this cellular process. In this article we discuss the molecular pathways that control EMT, showing a very tight and interdependent regulation. We also analyze the contribution of EMT and Snail genes in the process of tumorigenesis using the mammary gland as cellular model.

Epithelial-mesenchymal transitions in development and disease

The epithelial to mesenchymal transition (EMT) plays crucial roles in the formation of the body plan and in the differentiation of multiple tissues and organs. EMT also contributes to tissue repair, but it can adversely cause organ fibrosis and promote carcinoma progression through a variety of mechanisms. EMT endows cells with migratory and invasive properties, induces stem cell properties, prevents apoptosis and senescence, and contributes to immunosuppression. Thus, the mesenchymal state is associated with the capacity of cells to migrate to distant organs and maintain stemness, allowing their subsequent differentiation into multiple cell types during development and the initiation of metastasis.

Epithelial to mesenchymal transition and breast cancer

Epithelial-mesenchymal plasticity in breast carcinoma encompasses the phenotypic spectrum whereby epithelial carcinoma cells within a primary tumor acquire mesenchymal features and re-epithelialize to form a cohesive secondary mass at a metastatic site. Such plasticity has implications in progression of breast carcinoma to metastasis, and will likely influence response to therapy. The transcriptional and epigenetic regulation of molecular and cellular processes that underlie breast cancer and result in characteristic changes in cell behavior can be monitored using an increasing array of marker proteins. Amongst these markers exists the potential for emergent prognostic, predictive and therapeutic targeting.

Inflammation and EMT: an alliance towards organ fibrosis and cancer progression

Recent advances in our understanding of the molecular pathways that govern the association of inflammation with organ fibrosis and cancer point to the epithelial to mesenchymal transition (EMT) as the common link in the progression of these devastating diseases. The EMT is a crucial process in the development of different tissues in the embryo and its reactivation in the adult may be regarded as a physiological attempt to control inflammatory responses and to 'heal' damaged tissue. However, in pathological contexts such as in tumours or during the development of organ fibrosis, this healing response adopts a sinister nature, steering these diseases towards metastasis and organ failure. Importantly, the chronic inflammatory microenvironment common to fibrotic and cancer cells emerges as a decisive factor in the induction of the pathological EMT.