Epithelial-mesenchymal Transition In Metastasis Research Articles

KRT14 as a potential prognostic marker for metastasis in metaplastic breast carcinoma

Metaplastic breast cancer (MBC) is an aggressive breast cancer subtype with poor prognosis. To elucidate underlying genomic aberrations driving MBC, we conducted integrated transcriptomic analyses of MBC tumors and basal breast cancer cell lines with various transitioning phases (xE = epithelial phase clone, xM = mesenchymal phase clone and xEM = Epithelial-mesenchymal clone). Differential gene expression analysis between MBC vs non-MBC samples as well as between epithelial-mesenchymal (xEM) transitioning cells vs parental cells revealed 12 commonly dysregulated genes intersected from both the datasets meditates pathways governing EMT, migration, proliferation and metastasis. Further investigation onto those genes based on multi-omics approaches that include survival analysis, correlated expression patterns and interactomics indicated KRT14 had a key role in promoting MBC aggression through Epithelial mesenchymal transition leading to metastasis. Moreover, NPR3 was found to be a possible link between KRT14 and EMT in metastasis. To our knowledge, this is the first evident gene expression study to investigate the potential association between the expression of KRT14 and NPR3 and metastasis in MBC, and their potential involvement in the epithelial-mesenchymal transition (EMT) process. These mechanistic and prognostic insights gained can lead to targeted therapeutics against this rare, refractory disease. Overall, this work highlights the effectiveness of integrated multi-omics in revealing gene expression pattern and predictive biomarkers for metaplastic breast cancer subtypes with poor prognosis.

Escape from Original Home: Do Metastatic Cells Stay Dormant or Destructive?

Metastasis is defined as tumour implants discontinuous with the primary tumour. It is responsible for most cancer-related mortality. Many factors relating to the tumour and host factors are involved in the presence of metastasis and the long-term prognosis of the disease process. This study observed available literature and aims to emphasise tumours and their interaction with the tumour microenvironment. Epigenetic and genetic influences on pathogenesis, tumour and microenvironment interaction, role of epithelial-mesenchymal transition in metastasis are essential determinants of advanced malignant diseases. Early detection of metastatic disease is an essential part. The histopathological aggressiveness of a tumour and its biological behaviour determine the probability of metastasis and advanced disease. Understanding these factors has a benefit to improving the current therapies and diagnostic approaches to an advanced level, leading to the prevention of metastasis and more successful management of patients.

How important is EMT for cancer metastasis?

Epithelial-to-mesenchymal transition (EMT), a biological phenomenon of cellular plasticity initially reported in embryonic development, has been increasingly recognized for its importance in cancer progression and metastasis. Despite tremendous progress being made in the past 2 decades in our understanding of the molecular mechanism and functional importance of EMT in cancer, there are several mysteries around EMT that remain unresolved. In this Unsolved Mystery, we focus on the variety of EMT types in metastasis, cooperative and collective EMT behaviors, spatiotemporal characterization of EMT, and strategies of therapeutically targeting EMT. We also highlight new technical advances that will facilitate the efforts to elucidate the unsolved mysteries of EMT in metastasis.

Escape from Original Home: Do Metastatic Cells Stay Dormant or Destructive?

Metastasis is defined as tumour implants discontinuous with the primary tumour. It is responsible for most cancer-related mortality. Many factors relating to the tumour and host factors are involved in the presence of metastasis and the long-term prognosis of the disease process. This study observed available literature and aims to emphasise tumours and their interaction with the tumour microenvironment. Epigenetic and genetic influences on pathogenesis, tumour and microenvironment interaction, role of epithelial-mesenchymal transition in metastasis are essential determinants of advanced malignant diseases. Early detection of metastatic disease is an essential part. The histopathological aggressiveness of a tumour and its biological behaviour determine the probability of metastasis and advanced disease. Understanding these factors has a benefit to improving the current therapies and diagnostic approaches to an advanced level, leading to the prevention of metastasis and more successful management of patients.

Epithelial Mesenchymal Transition: The Ultimate Driver of Cancer on Difficult Paths

Metastasis is the perilous aspect of cancer and is responsible for 90% of deaths due to cancer. It represents an enigmatic and complex biological cascade that is poorly understood. The constant development in cancer research and the advent of new principles in metastasis have discovered some of the molecular keystones like epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) of this cascade. Acknowledgment of the communications between cancer cells and their micro-environment enlightens the biology of metastasis and allows us to understand the mechanism of EMT induction and its role in governing invasion, migration, plasticity, colonization, and therapeutic resistance. EMT is the principal reason behind the cancer cells’ complex behavior, tremendous plasticity, survival, and adoption in a constantly changing environment. Thus, EMT is a perfect driver mechanism to execute metastasis and develop resistance against conventional and targeted therapies. Studies have also discovered the role of EMT in CSCs generation and offered us prospects for evolving more effective treatments to target metastasis and improved patient prognosis. Our primary aim in the present review is to summarize the induction and role of EMT in cancer. This review not only discusses the role of EMT in metastasis but also uncovers the role of EMT in survival, metabolism, and CSCs generation. Further, in this review, we also discuss the strategy to target the EMT for the development of new and effective therapeutics for cancer management.

The Significance of Cancer Stem Cells and Epithelial-Mesenchymal Transition in Metastasis and Anti-Cancer Therapy.

Cancer stem cells (CSCs) have been identified and characterized in both hematopoietic and solid tumors. Their existence was first predicted by Virchow and Cohnheim in the 1870s. Later, many studies showed that CSCs can be identified and isolated by their expression of specific cell markers. The significance of CSCs with respect to tumor biology and anti-cancer treatment lies in their ability to maintain quiescence with very slow proliferation, indefinite self-renewal, differentiation, and trans-differentiation such as epithelial-mesenchymal transition (EMT) and its reverse process mesenchymal-epithelial transition (MET). The ability for detachment, migration, extra- and intravasation, invasion and thereby of completing all necessary steps of the metastatic cascade highlights their significance for metastasis. CSCs comprise the cancer cell populations responsible for tumor growth, resistance to therapies and cancer metastasis. In this review, the history of the CSC theory, their identification and characterization and their biology are described. The contribution of the CSC ability to undergo EMT for cancer metastasis is discussed. Recently, novel strategies for drug development have focused on the elimination of the CSCs specifically. The unique functional and molecular properties of CSCs are discussed as possible therapeutic vulnerabilities for the development of novel anti-metastasis treatments. Prospectively, this may provide precise personalized anti-cancer treatments with improved therapeutic efficiency with fewer side effects and leading to better prognosis.

VEGF-C mediates tumor growth and metastasis through promoting EMT-epithelial breast cancer cell crosstalk.

It is well established that a subset of cells within primary breast cancers can undergo an epithelial to mesenchymal transition (EMT), although the role of EMT in metastasis remains controversial. We previously demonstrated that breast cancer cells that had undergone an oncogenic EMT could increase metastasis of neighboring cancer cells via non-canonical paracrine-mediated activation of GLI activity that is dependent on SIX1 expression in the EMT cancer cells. However, the mechanism by which these SIX1-expressing EMT cells activate GLI signaling remained unclear. In this study, we demonstrate a novel mechanism for activation of GLI-mediated signaling in epithelial breast tumor cells via EMT cell-induced production and secretion of VEGF-C. We show that VEGF-C, secreted by breast cancer cells that have undergone an EMT, promotes paracrine-mediated increases in proliferation, migration and invasion of epithelial breast cancer cells, via non-canonical activation of GLI-signaling. We further show that the aggressive phenotypes, including metastasis, imparted by EMT cells on adjacent epithelial cancer cells can be disrupted by either inhibiting VEGF-C in EMT cells or by knocking down NRP2, a receptor which interacts with VEGF-C, in neighboring epithelial cancer cells. Interrogation of TCGA and GEO public datasets supports the relevance of this pathway in human breast cancer, demonstrating that VEGF-C strongly correlates with activation of Hedgehog signaling and EMT in the human disease. Our study suggests that the VEGF-C/NRP2/GLI axis is a novel and conserved paracrine means by which EMT cells enhance metastasis, and provides potential targets for therapeutic intervention in this heterogeneous disease.

Developing Novel Means to Inhibit Metastasis Through Targeting Tumor Heterogeneity and EMT

It is well established that a subset of cells within primary breast cancers can undergo an epithelial to mesenchymal transition (EMT), although the role of EMT in metastasis remains controversial. We previously demonstrated a novel mechanism by which EMT contributes to metastasis, via mediating tumor cell crosstalk. In this seminar, I will discuss how breast cancer cells that have undergone an oncogenic EMT can increase metastasis of neighboring epithelial cancer cells via non‐canonical paracrine‐mediated activation of GLI activity that is dependent on Six1 expression in the EMT cancer cells. I will discuss how VEGF‐C, secreted by breast cancer cells that have undergone an EMT, promotes paracrine‐mediated increases in proliferation, migration, invasion, and metastasis of epithelial breast cancer cells, via non‐canonical activation of GLI‐signaling. Importantly, the aggressive phenotypes imparted by EMT cells on adjacent epithelial cancer cells can be disrupted by either inhibiting VEGF‐C in EMT cells or by knocking down NRP2, which interacts with VEGF‐C, in neighboring epithelial cancer cells both in vitro and in vivo. Interrogation of TCGA and GEO public datasets supports the relevance of this pathway in human breast cancer, as VEGF‐C and GLI pathway genes significantly positively correlate. Our study suggests that the VEGF‐C/NRP2/GLI axis may be a novel and conserved paracrine means by which EMT cells enhance metastasis, and provides potential targets for therapeutic intervention in this heterogeneous disease. In addition, because SIX1 activates VEGF‐C expression which leads to enhancement of metastasis via cell autonomous and non‐cell autonomous means, we have developed an inhibitor that targets SIX1 action and thereby inhibits metastatic disease. We describe results using this inhibitor in cell culture, where it inhibits SIX1 function and EMT, and in animals, where it inhibits metastasis without an effect on primary tumor growth.Support or Funding InformationColorado Cancer Translational Research Accelerator (CCTRA) PI Heide L. Ford, Co‐I Rui ZhaoNCI R01 CA224867 PIs Heide L. Ford and Michael T. Lewis

Differential Contributions of Pre- and Post-EMT Tumor Cells in Breast Cancer Metastasis.

Metastases are responsible for the majority of breast cancer-associated deaths. The contribution of epithelial-to-mesenchymal transition (EMT) in the establishment of metastases is still controversial. To obtain in vivo evidence of EMT in metastasis, we established an EMT lineage tracing (Tri-PyMT) model, in which tumor cells undergoing EMT would irreversibly switch their fluorescent marker from RFP+ to GFP+ due to mesenchymal-specific Cre expression. Surprisingly, we found that lung metastases were predominantly derived from the epithelial compartment of breast tumors. However, concerns were raised on the fidelity and sensitivity of RFP-to-GFP switch of this model in reporting EMT of metastatic tumor cells. Here, we evaluated Tri-PyMT cells at the single-cell level using single-cell RNA-sequencing and found that the Tri-PyMT cells exhibited a spectrum of EMT phenotypes, with EMT-related genes concomitantly expressed with the activation of GFP. The fluorescent color switch in these cells precisely marked an unequivocal change in EMT status, defining the pre-EMT and post-EMT compartments within the tumor. Consistently, the pre-EMT cells played dominant roles in metastasis, while the post-EMT cells were supportive in promoting tumor invasion and angiogenesis. Importantly, the post-EMT (GFP+) cells in the Tri-PyMT model were not permanently committed to the mesenchymal phenotype; they were still capable of reverting to the epithelial phenotype and giving rise to secondary tumors, suggesting their persistent EMT plasticity. Our study addressed major concerns with the Tri-PyMT EMT lineage tracing model, which provides us with a powerful tool to investigate the dynamic EMT process in tumor biology. SIGNIFICANCE: These findings confirm the fidelity and sensitivity of the EMT lineage tracing (Tri-PyMT) model and highlight the differential contributions of pre- and post-EMT tumor cells in breast cancer metastasis.See related commentary by Bunz, p. 153.

Clinical Evolution of Epithelial-Mesenchymal Transition in Human Carcinomas.

The significance of the phenotypic plasticity afforded by epithelial-mesenchymal transition (EMT) for cancer progression and drug resistance remains to be fully elucidated in the clinic. We evaluated epithelial-mesenchymal phenotypic characteristics across a range of tumor histologies using a validated, high-resolution digital microscopic immunofluorescence assay (IFA) that incorporates β-catenin detection and cellular morphology to delineate carcinoma cells from stromal fibroblasts and that quantitates the individual and colocalized expression of the epithelial marker E-cadherin (E) and the mesenchymal marker vimentin (V) at subcellular resolution ("EMT-IFA"). We report the discovery of β-catenin+ cancer cells that coexpress E-cadherin and vimentin in core-needle biopsies from patients with various advanced metastatic carcinomas, wherein these cells are transitioning between strongly epithelial and strongly mesenchymal-like phenotypes. Treatment of carcinoma models with anticancer drugs that differ in their mechanism of action (the tyrosine kinase inhibitor pazopanib in MKN45 gastric carcinoma xenografts and the combination of tubulin-targeting agent paclitaxel with the BCR-ABL inhibitor nilotinib in MDA-MB-468 breast cancer xenografts) caused changes in the tumor epithelial-mesenchymal character. Moreover, the appearance of partial EMT or mesenchymal-like carcinoma cells in MDA-MB-468 tumors treated with the paclitaxel-nilotinib combination resulted in upregulation of cancer stem cell (CSC) markers and susceptibility to FAK inhibitor. A metastatic prostate cancer patient treated with the PARP inhibitor talazoparib exhibited similar CSC marker upregulation. Therefore, the phenotypic plasticity conferred on carcinoma cells by EMT allows for rapid adaptation to cytotoxic or molecularly targeted therapy and could create a form of acquired drug resistance that is transient in nature. SIGNIFICANCE: Despite the role of EMT in metastasis and drug resistance, no standardized assessment of EMT phenotypic heterogeneity in human carcinomas exists; the EMT-IFA allows for clinical monitoring of tumor adaptation to therapy.

Epithelial-Mesenchymal Transition: Role in Cancer Progression and the Perspectives of Antitumor Treatment.

About 90% of all malignant tumors are of epithelial nature. The epithelial tissue is characterized by a close interconnection between cells through cell–cell interactions, as well as a tight connection with the basement membrane, which is responsible for cell polarity. These interactions strictly determine the location of epithelial cells within the body and are seemingly in conflict with the metastatic potential that many cancers possess (the main criteria for highly malignant tumors). Tumor dissemination into vital organs is one of the primary causes of death in patients with cancer. Tumor dissemination is based on the so-called epithelial–mesenchymal transition (EMT), a process when epithelial cells are transformed into mesenchymal cells possessing high mobility and migration potential. More and more studies elucidating the role of the EMT in metastasis and other aspects of tumor progression are published each year, thus forming a promising field of cancer research. In this review, we examine the most recent data on the intracellular and extracellular molecular mechanisms that activate EMT and the role they play in various aspects of tumor progression, such as metastasis, apoptotic resistance, and immune evasion, aspects that have usually been attributed exclusively to cancer stem cells (CSCs). In conclusion, we provide a detailed review of the approved and promising drugs for cancer therapy that target the components of the EMT signaling pathways.

Epithelial-type systemic breast carcinoma cells with a restricted mesenchymal transition are a major source of metastasis.

Carcinoma cells undergo epithelial-mesenchymal transition (EMT); however, contributions of EMT heterogeneity to disease progression remain a matter of debate. Here, we addressed the EMT status of ex vivo cultured circulating and disseminated tumor cells (CTCs/DTCs) in a syngeneic mouse model of metastatic breast cancer (MBC). Epithelial-type CTCs with a restricted mesenchymal transition had the strongest lung metastases formation ability, whereas mesenchymal-type CTCs showed limited metastatic ability. EpCAM expression served as a surrogate marker to evaluate the EMT heterogeneity of clinical samples from MBC, including metastases, CTCs, and DTCs. The proportion of epithelial-type CTCs, and especially DTCs, correlated with distant metastases and poorer outcome of patients with MBC. This study fosters our understanding of EMT in metastasis and underpins heterogeneous EMT phenotypes as important parameters for tumor prognosis and treatment. We further suggest that EpCAM-dependent CTC isolation systems will underestimate CTC numbers but will quantify clinically relevant metastatic cells.

Context-dependent EMT programs in cancer metastasis.

Epithelial-mesenchymal transition (EMT) is a developmental process whereby stationary, adherent cells acquire the ability to migrate. EMT is critical for dramatic cellular movements during embryogenesis; however, tumor cells can reactivate EMT programs, which increases their aggressiveness. In addition to motility, EMT is associated with enhanced stem cell properties and drug resistance; thus it can drive metastasis, tumor recurrence, and therapy resistance in the context of cancer. However, the precise requirements for EMT in metastasis have not been fully delineated, with different tumor types relying on discrete EMT effectors. Most tumor cells do not undergo a full EMT, but rather adopt some qualities of mesenchymal cells and maintain some epithelial characteristics. Emerging evidence suggests that partial EMT can drive distinct migratory properties and enhance the epithelial-mesenchymal plasticity of cancer cells as well as cell fate plasticity. This review discusses the diverse regulatory mechanisms and functional consequences of EMT, with an emphasis on the importance of partial EMT.

EMT in Metastasis: Finding the Right Balance

The epithelial-to-mesenchymal transition (EMT) is a key driver of cancer metastasis. In this issue of Developmental Cell, Aiello etal. (2018) demonstrate that an EMT mechanism involving protein internalization impacts cell migration, while Reichert etal. (2018) identify epithelial plasticity as a determinant of metastatic organotropism in pancreatic cancer.

Epithelial Mesenchymal Transition in Tumor Metastasis.

Metastasis is the major cause of cancer-related deaths; therefore, the prevention and treatment of metastasis are fundamental to improving clinical outcomes. Epithelial mesenchymal transition (EMT), an evolutionarily conserved developmental program, has been implicated in carcinogenesis and confers metastatic properties upon cancer cells by enhancing mobility, invasion, and resistance to apoptotic stimuli. Furthermore, EMT-derived tumor cells acquire stem cell properties and exhibit marked therapeutic resistance. Given these attributes, the complex biological process of EMT has been heralded as a key hallmark of carcinogenesis, and targeting EMT pathways constitutes an attractive strategy for cancer treatment. However, demonstrating the necessity of EMT for metastasis in vivo has been technically challenging, and recent efforts to demonstrate a functional contribution of EMT to metastasis have yielded unexpected results. Therefore, determining the functional role of EMT in metastasis remains an area of active investigation. Studies using improved lineage tracing systems, dynamic in vivo imaging, and clinically relevant in vivo models have the potential to uncover the direct link between EMT and metastasis. This review focuses primarily on recent advances in and emerging concepts of the biology of EMT in metastasis in vivo and discusses future directions in the context of novel diagnostic and therapeutic opportunities.

Epigenetic landscape change analysis during human EMT sheds light on a key EMT mediator TRIM29.

Epithelial to mesenchymal transition (EMT) is a key trans-differentiation process, which plays a critical role in physiology and pathology. Although gene expression changes in EMT have been scrutinized, study of epigenome is in its infancy. To understand epigenetic changes during TWIST-driven EMT, we used the AcceSssIble assay to study DNA methylation and chromatin accessibility in human mammary epithelial cells (HMECs). The DNA methylation changes were found to have functional significance in EMT – i.e. methylated genes were enriched for E-box motifs that can be recognized by TWIST, at the promoters suggesting a potential targeting phenomenon, whereas the demethylated regions were enriched for pro-metastatic genes, supporting the role of EMT in metastasis. TWIST-induced EMT triggers alterations in chromatin accessibility both independent of and dependent on DNA methylation changes, primarily resulting in closed chromatin conformation. By overlapping the genes, whose chromatin structure is changed during early EMT and a known “core EMT signature”, we identified 18 driver candidate genes during EMT, 14 upregulated and 4 downregulated genes with corresponding chromatin structure changes. Among 18 genes, we focused on TRIM29 as a novel marker of EMT. Although loss of TRIM29 is insufficient to suppress CDH, it is enough to induce CDH2 and VIM. Gene functional annotation analysis shows the involvement of TRIM29 in epidermal development, cell differentiation and cell migration. Taken together, our results provide a robust snapshot of chromatin state during human EMT and identify TRIM29 as a core mediator of EMT.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer.

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

Cancer metastasis through the prism of epithelial-to-mesenchymal transition in circulating tumor cells.

Metastasis of epithelial cancer cells to distant sites is a particularly critical stage of cancer progression that typically marks the incurability of the disease. It is governed by a complex series of events including invasion and intravasation of tumor cells into the stroma and blood, respectively. Epithelial‐to‐mesenchymal transition (EMT), a phenotypic change marked by the loss of epithelial characteristics and the acquisition of invasive mesenchymal properties, is implicated in the dissemination of tumor cells. Circulating tumor cells (CTCs), the precursors of metastasis, can be used to interrogate the contribution of EMT in metastasis and therapeutic responses. The analysis of these CTCs and in particular the presence of inter‐ and intrapatient heterogeneity for markers of EMT has provided new insights into the metastatic process. This review will focus on epithelial–mesenchymal plasticity in CTCs and its potential clinical implications.

Probing the Fifty Shades of EMT in Metastasis

The involvement of epithelial-to-mesenchymal transition (EMT) in metastasis has long been under debate. Recent efforts to probe the occurrence and functional significance of EMT in clinical samples and animal models have produced exciting but sometimes conflicting findings. The diversity of EMT underlies the challenge in studying its role in metastasis.

Role of EMT in Metastasis and Therapy Resistance.

Epithelial–mesenchymal transition (EMT) is a complex molecular program that regulates changes in cell morphology and function during embryogenesis and tissue development. EMT also contributes to tumor progression and metastasis. Cells undergoing EMT expand out of and degrade the surrounding microenvironment to subsequently migrate from the primary site. The mesenchymal phenotype observed in fibroblasts is specifically important based on the expression of smooth muscle actin (α-SMA), fibroblast growth factor (FGF), fibroblast-specific protein-1 (FSP1), and collagen to enhance EMT. Although EMT is not completely dependent on EMT regulators such as Snail, Twist, and Zeb-1/-2, analysis of upstream signaling (i.e., TGF-β, EGF, Wnt) is necessary to understand tumor EMT more comprehensively. Tumor epithelial–fibroblast interactions that regulate tumor progression have been identified during prostate cancer. The cellular crosstalk is significant because these events influence therapy response and patient outcome. This review addresses how canonical EMT signals originating from prostate cancer fibroblasts contribute to tumor metastasis and recurrence after therapy.