Heterogeneity within a tumour increases its ability to adapt to constantly changing constraints, but adversely affects a patient's prognosis, therapy response and clinical outcome. Intratumoural ...heterogeneity results from a combination of extrinsic factors from the tumour microenvironment and intrinsic parameters from the cancer cells themselves, including their genetic, epigenetic and transcriptomic traits, their ability to proliferate, migrate and invade, and their stemness and plasticity attributes. Cell plasticity constitutes the ability of cancer cells to rapidly reprogramme their gene expression repertoire, to change their behaviour and identities, and to adapt to microenvironmental cues. These features also directly contribute to tumour heterogeneity and are critical for malignant tumour progression. In this article, we use breast cancer as an example of the origins of tumour heterogeneity (in particular, the mutational spectrum and clonal evolution of progressing tumours) and of tumour cell plasticity (in particular, that shown by tumour cells undergoing epithelial-to-mesenchymal transition), as well as considering interclonal cooperativity and cell plasticity as sources of cancer cell heterogeneity. We review current knowledge on the functional contribution of cell plasticity and tumour heterogeneity to malignant tumour progression, metastasis formation and therapy resistance.
Although major progress has been achieved in treating breast cancer patients, metastatic breast cancer still remains a deadly disease. A full understanding of the process of systemic cancer cell ...dissemination is therefore critical to develop next generation therapies. A plethora of experimental data points toward a central role of an epithelial to mesenchymal transition (EMT) in the multistep cascade of metastasis formation. However, in patients the data are based on correlative studies which often, but not always, tie the expression of EMT markers to cancer invasion, metastasis and poor clinical outcome. Moreover, the notion that cancer cells are able to switch between different modes of migration asks for a thorough review of the actual relevance of EMT in cancer metastasis.
Cell migration and invasion are critical parameters in the metastatic dissemination of cancer cells and the formation of metastasis, the major cause of death in cancer patients. Migratory cancer ...cells undergo dramatic molecular and cellular changes by remodeling their cell-cell and cell-matrix adhesion and their actin cytoskeleton, molecular processes that involve the activity of various signaling networks. Although in the past years, we have substantially expanded our knowledge on the cellular and molecular processes underlying cell migration and invasion in experimental systems, we still lack a clear understanding of how cancer cells disseminate in metastatic cancer patients. Different types of cancer cell migration seem to exist, including single-cell mesenchymal or amoeboid migration and collective cell migration. In most epithelial cancers, loss of the cell-cell adhesion molecule E-cadherin and gain of mesenchymal markers and promigratory signals underlie the conversion of epithelial, differentiated cells to mesenchymal, migratory, and invasive cells, a process referred to as the epithelial-to-mesenchymal transition. Although solitary migrating epithelial cancer cells have mostly undergone epithelial-to-mesenchymal transition (mesenchymal migration), and sometimes even lose their cell-matrix adhesion (amoeboid migration), collective migration of cancer cells in cell sheets, clusters, or streams is also frequently observed. The molecular mechanisms defining the different modes of cancer cell migration remain in most parts to be delineated.
Abstract Epithelial cancers make up the vast majority of cancer types and, during the transition from benign adenoma to malignant carcinoma and metastasis, epithelial tumor cells acquire a ...de-differentiated, migratory and invasive behavior. This process of epithelial–mesenchymal transition (EMT) goes along with dramatic changes in cellular morphology, the loss and remodeling of cell–cell and cell–matrix adhesions, and the gain of migratory and invasive capabilities. EMT itself is a multistage process, involving a high degree of cellular plasticity and a large number of distinct genetic and epigenetic alterations, as fully differentiated epithelial cells convert into poorly differentiated, migratory and invasive mesenchymal cells. In the past years, a plethora of genes have been identified that are critical for EMT and metastasis formation. Notably, the EMT process not only induces increased cancer cell motility and invasiveness but also allows cancer cells to avoid apoptosis, anoikis, oncogene addiction, cellular, senescence and general immune defense. Notably, EMT seems to play a critical role in the generation and maintenance of cancer stem cells, highly consistent with the notion that metastatic cells carry the ability to initiate new tumors.
Epithelial-mesenchymal transition (EMT) is a transient, reversible process of cell de-differentiation where cancer cells transit between various stages of an EMT continuum, including epithelial, ...partial EMT, and mesenchymal cell states. We have employed Tamoxifen-inducible dual recombinase lineage tracing systems combined with live imaging and 5-cell RNA sequencing to track cancer cells undergoing partial or full EMT in the MMTV-PyMT mouse model of metastatic breast cancer. In primary tumors, cancer cells infrequently undergo EMT and mostly transition between epithelial and partial EMT states but rarely reach full EMT. Cells undergoing partial EMT contribute to lung metastasis and chemoresistance, whereas full EMT cells mostly retain a mesenchymal phenotype and fail to colonize the lungs. However, full EMT cancer cells are enriched in recurrent tumors upon chemotherapy. Hence, cancer cells in various stages of the EMT continuum differentially contribute to hallmarks of breast cancer malignancy, such as tumor invasion, metastasis, and chemoresistance.
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•Lineage tracing of partial and full EMT cells in breast cancer metastasis•Partial EMT cells cycle between hybrid EMT and epithelial stages•Partial, but not full, EMT cells are required for metastasis formation•Both partial and full EMT cells contribute to chemoresistance
Lüönd et al. establish genetic lineage tracing systems to monitor mammary tumor cells undergoing early partial and late full epithelial-mesenchymal transition (EMT). They demonstrate that partial EMT cells, but not full EMT cells, are required for lung metastasis, while both contribute to the development of chemoresistance.
Most cancer deaths are due to the systemic dissemination of cancer cells and the formation of secondary tumors (metastasis) in distant organs. Recent years have brought impressive progress in ...metastasis research, yet we still lack sufficient insights into how cancer cells migrate out of primary tumors and invade into neighboring tissue, intravasate into the blood or the lymphatic circulation, survive in the blood stream, and target specific organs to initiate metastatic outgrowth. While a large number of cellular and animal models of cancer have been crucial in delineating the molecular mechanisms underlying tumor initiation and progression, experimental models that faithfully recapitulate the multiple stages of metastatic disease are still scarce. The advent of sophisticated genetic engineering in mice, in particular the ability to manipulate gene expression in specific tissue and at desired time points at will, have allowed to rebuild the metastatic process in mice. Here, we describe a selection of cellular experimental systems, tumor transplantation mouse models and genetically engineered mouse models that are used for monitoring specific processes involved in metastasis, such as cell migration and invasion, and for investigating the full metastatic process. Such models not only aid in deciphering the pathomechanisms of metastasis, but are also instrumental for the preclinical testing of anti-metastatic therapies and further refinement and generation of improved models.
► We describe currently used cellular and ex vivo assays of metastasis. ► We discuss syngeneic and xenograft transplantation mouse models of metastasis. ► We illustrate genetically engineered mice that recapitulate metastatic cancer. ► Mouse models are valuable tools for dissecting the multistage process of metastasis. ► Novel technologies are available to monitor and investigate tumor metastasis.
Understanding the mechanisms underlying evasive resistance in cancer is an unmet medical need to improve the efficacy of current therapies. In this study, a combination of shRNA‐mediated synthetic ...lethality screening and transcriptomic analysis revealed the transcription factors YAP/TAZ as key drivers of Sorafenib resistance in hepatocellular carcinoma (HCC) by repressing Sorafenib‐induced ferroptosis. Mechanistically, in a TEAD‐dependent manner, YAP/TAZ induce the expression of SLC7A11, a key transporter maintaining intracellular glutathione homeostasis, thus enabling HCC cells to overcome Sorafenib‐induced ferroptosis. At the same time, YAP/TAZ sustain the protein stability, nuclear localization, and transcriptional activity of ATF4 which in turn cooperates to induce SLC7A11 expression. Our study uncovers a critical role of YAP/TAZ in the repression of ferroptosis and thus in the establishment of Sorafenib resistance in HCC, highlighting YAP/TAZ‐based rewiring strategies as potential approaches to overcome HCC therapy resistance.
SYNOPSIS
Resistance to therapy occurs in most liver cancer patients treated with Sorafenib, and patients succumb to the disease. A synthetic lethal screen identified a regulatory circuit, which prevents ferroptosis and promotes cancer cell survival, thus promoting resistance to Sorafenib.
The transcription factors YAP and TAZ stabilize ATF4 by promoting its nuclear import to cooperatively induce expression of SLC7A11, a cystine importer critical for glutathione synthesis.
Glutathione synthesis and homeostasis are required to repress ferroptosis and to maintain Sorafenib resistance in liver cancer cells.
Inhibition of Glutathione synthesis re‐sensitizes Sorafenib‐resistant cancer cells to Sorafenib therapy, which then induces ferroptosis and represses tumor growth in murine liver cancer models.
Pharmacological repression of the anti‐oxidant pathways regulated by YAP/TAZ and ATF4 could re‐sensitize therapy‐resistant liver cancers to Sorafenib treatment.
Resistance to therapy occurs in most liver cancer patients treated with Sorafenib, and patients succumb to the disease. A synthetic lethal screen identified a regulatory circuit, which prevents ferroptosis and promotes cancer cell survival, thus promoting resistance to Sorafenib.
Epithelial-mesenchymal transition (EMT) encompasses dynamic changes in cellular organization from epithelial to mesenchymal phenotypes, which leads to functional changes in cell migration and ...invasion. EMT occurs in a diverse range of physiological and pathological conditions and is driven by a conserved set of inducing signals, transcriptional regulators and downstream effectors. With over 5,700 publications indexed by Web of Science in 2019 alone, research on EMT is expanding rapidly. This growing interest warrants the need for a consensus among researchers when referring to and undertaking research on EMT. This Consensus Statement, mediated by 'the EMT International Association' (TEMTIA), is the outcome of a 2-year-long discussion among EMT researchers and aims to both clarify the nomenclature and provide definitions and guidelines for EMT research in future publications. We trust that these guidelines will help to reduce misunderstanding and misinterpretation of research data generated in various experimental models and to promote cross-disciplinary collaboration to identify and address key open questions in this research field. While recognizing the importance of maintaining diversity in experimental approaches and conceptual frameworks, we emphasize that lasting contributions of EMT research to increasing our understanding of developmental processes and combatting cancer and other diseases depend on the adoption of a unified terminology to describe EMT.
An epithelial to mesenchymal transition (EMT) is an embryonic dedifferentiation program which is aberrantly activated in cancer cells to acquire cellular plasticity. This plasticity increases the ...ability of breast cancer cells to invade into surrounding tissue, to seed metastasis at distant sites and to resist to chemotherapy. In this study, we have observed a higher expression of interferon-related factors in basal-like and claudin-low subtypes of breast cancer in patients, known to be associated with EMT. Notably, Irf1 exerts essential functions during the EMT process, yet it is also required for the maintenance of an epithelial differentiation status of mammary gland epithelial cells: RNAi-mediated ablation of Irf1 in mammary epithelial cells results in the expression of mesenchymal factors and Smad transcriptional activity. Conversely, ablation of Irf1 during TGFβ-induced EMT prevents a mesenchymal transition and stabilizes the expression of E-cadherin. In the basal-like murine breast cancer cell line 4T1, RNAi-mediated ablation of Irf1 reduces colony formation and cell migration in vitro and shedding of circulating tumor cells and metastasis formation in vivo. This context-dependent dual role of Irf1 in the regulation of epithelial-mesenchymal plasticity provides important new insights into the functional contribution and therapeutic potential of interferon-regulated factors in breast cancer.
Gene expression profiling has uncovered the transcription factor Sox4 with upregulated activity during TGF-β-induced epithelial-mesenchymal transition (EMT) in normal and cancerous breast epithelial ...cells. Sox4 is indispensable for EMT and cell survival in vitro and for primary tumor growth and metastasis in vivo. Among several EMT-relevant genes, Sox4 directly regulates the expression of Ezh2, encoding the Polycomb group histone methyltransferase that trimethylates histone 3 lysine 27 (H3K27me3) for gene repression. Ablation of Ezh2 expression prevents EMT, whereas forced expression of Ezh2 restores EMT in Sox4-deficient cells. Ezh2-mediated H3K27me3 marks associate with key EMT genes, representing an epigenetic EMT signature that predicts patient survival. Our results identify Sox4 as a master regulator of EMT by governing the expression of the epigenetic modifier Ezh2.
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•Sox4 is critical for EMT and for experimental primary tumor growth and metastasis•Sox4 directly regulates EMT-relevant genes, among them Ezh2•Ezh2 function and thus H3K27me3 are required for EMT•The expression of Ezh2-regulated genes is predictive for patient survival
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