Epithelial Mesenchymal Plasticity In Cancer Metastasis

Recent studies have highlighted that epithelial-mesenchymal transition (EMT) is not only about cell migration and invasion, but it can also govern many other important elements such as immunosuppression, metabolic reprogramming, senescence-associated secretory phenotype (SASP), stem cell properties, therapy resistance, and tumor microenvironment interactions. With the on-going debate about the requirement of EMT for cancer metastasis, an emerging focus on intermediate states of EMT and its reverse process mesenchymal-epithelial transition (MET) offer new ideas for metastatic requirements and the dynamics of EMT/MET during the entire metastatic cascade. Therefore, we would like to initiate discussions on viewing EMT and its downstream signaling networks as a fulcrum of cellular plasticity, and a facilitator of the adaptive responses of cancer cells to distant organ microenvironments and various therapeutic assaults. We hereby invite scientists who have prominently contributed to this field, and whose valuable insights have led to the appreciation of epithelial-mesenchymal plasticity as a more comprehensive mediator of the adaptive response of cancer cells, with huge implications in metastasis, drug resistance, tumor relapse, and patient survival.

Recent studies have highlighted that epithelial-mesenchymal transition (EMT) is not only about cell migration and invasion, but it can also govern many other important elements such as immunosuppression, metabolic reprogramming, senescence-associated secretory phenotype (SASP), stem cell properties, therapy resistance, and tumor microenvironment interactions. With the on-going debate about the requirement of EMT for cancer metastasis, an emerging focus on intermediate states of EMT and its reverse process mesenchymal-epithelial transition (MET) offer new ideas for metastatic requirements and the dynamics of EMT/MET during the entire metastatic cascade. Therefore, we would like to initiate discussions on viewing EMT and its downstream signaling networks as a fulcrum of cellular plasticity, and a facilitator of the adaptive responses of cancer cells to distant organ microenvironments and various therapeutic assaults. We hereby invite scientists who have prominently contributed to this field, and whose valuable insights have led to the appreciation of epithelial-mesenchymal plasticity as a more comprehensive mediator of the adaptive response of cancer cells, with huge implications in metastasis, drug resistance, tumor relapse, and patient survival.

This book is a printed edition of the Special Issue "The Epithelial-to-Mesenchymal Transition (EMT) in Cancer" that was published in Cancers

The process of Epithelial-Mesenchymal-Transition (EMT) is known to result in a phenotype change in cells from a proliferative state to a more invasive state. EMT has been reported to drive the metastatic spread of various cancers and has also been associated with drug resistance to cytotoxics and targeted therapeutics. Recently phenotype switching akin to EMT has been reported in non-epithelial cancers such as metastatic melanoma. This process involves changes in EMT-Transcription Factors (EMT-TFs), suggesting that phenotype-switching may be common to several tumour types. It remains unclear as to whether the presence of both Epilthelial-like and Mesenchymal-like cells are a pre-requisite for phenotype switching within a tumour, how this heterogeneity is regulated, and if alteration of cell phenotype is sufficient to mediate migratory changes, or whether drivers of cell migration result in an associated phenotype switch in cancer cells. Similarly it has yet to be clarified if cells in an altered phenotype can be refractory to drug therapy or whether mediators of drug resistance induce a concurrent phenotypic change. Little is known today about the underlying genetic, epigenetic and transient changes that accompany this phenotypic switch and about the role for the tumor micro-environment in influencing it. Hence this is currently an area of speculation and keen interest in the Oncology field with wide-ranging translational implications. In this Frontiers Research Topic, we discuss our current understanding of these concepts in various cancer types including breast cancer, colorectal cancer and metastatic melanoma. This topic covers how these processes of cellular and phenotypic plasticity are regulated and how they relate to cancer initiation, progression, dormancy, metastases and response to cytotoxics or targeted therapies.

The contribution of epithelia-mesenchyme interaction to normal development (eg., tissue formation) and to neoplasia has become a subject of increasing interest to scientists because of recent progress in deciphering the molecular signals that mediate this interaction. Clearly, some of the same types of molecules (eg., growth factors and their receptors, proteolytic enzymes, cell adhesion molecules, and structural proteins of the extracellular matrix) mediate exchange of information between epithelia and mesenchyme during normal development and malignant growth. However, defects in the regulation of this exchange appear to contribute to malignancy by allowing growth promoting, invasogenic, and angiogenic factors to accumulate within the microenvironment of the tumor. For example, recent studies suggest that abnormal interactions between tumor epithelial cells and stromal mesenchymal cells contribute to the overproduction and accumulation of scatter factor (hepatocyte growth factor), an invasogenic and angiogenic cytokine, in certain types of tumor. The production and and activation of type IV collagenase, a matrix-degrading enzyme required for tumor cell invasion, appears to require intimate cooperation between tumor and stromal cells. The material contained in this volume highlights the state-of-the-art of knowledge of the molecular mechanisms by which epithelia and mesenchyme collaborate, and the abnormalities in these mechanisms that may lead to the development of cancer.

This book compiles the latest research and key findings about the role of circulating tumor cells (CTCs) in Breast Cancer progression, both from the research and clinical standpoint. Based on latest advancements, the content of the book is set out to provide a clear overview about the biology and use of CTCs as a tool for the monitoring and management of breast cancer patients. This work covers basic concepts about the process of metastasis, the biology of CTCs and their potential applications as a biomarker in breast cancer. It will enable readers to delve into the process of epithelial-mesenchymal plasticity (EMP), mechanisms and clinical implications of tumor cell dormancy and minimal residual disease, and into the phenotypical and molecular heterogeneity of CTCs and CTC clusters, including the epigenetic characterization of CTCs. Readers will find out about the key technologies used for the isolation of CTCs as well as the latest advances towards the characterization of CTCs, involving single cell analyses and patient-derived models. It will discuss the evidences about the use of CTCs as a tool to monitor breast cancer progression and therapy response, as well as to unravel mechanisms of resistance to therapy and to identify new therapeutic targets favoring the development of novel anticancer drugs. Lastly, it will discuss ongoing clinical trials and try to foresee the future of CTCs in terms of clinical application and implementation in the clinical routine. The topic of this book is particularly relevant for cancer researchers and oncologist with an interest in the field, looking to refresh or to broaden their knowledge and understanding about the use of CTCs as a diagnostic biomarker in breast cancer.

This book is aimed to summarise the key aspects of the role of circulating tumour cells (CTCs) in breast cancer, with special attention to their contribution to tumour progression and establishment of metastatic disease. We aim to give a clear overview of the knowledge about CTCs, framed in the context of breast cancer, by analysing basic and clinical research carried out so far. In a broader sense, we will address what are the main clinical needs of this disease based on its molecular heterogeneity (subtypes) and lay out the knowledge and understanding that CTCs are giving about it and how they are contributing and can still improve the better monitoring and management of breast cancer patients. We will discuss the evidences of the use of CTCs as a tool to monitor cancer progression and therapy response, based on the prognostic and predictive value they have, as well as a tool to unravel mechanisms of resistance to therapy and to identify new biomarkers allowing to predict therapy success. Moreover, we will analyse the main aspects of ongoing clinical trials and how they can contribute to determine the clinical utility of CTCs as a breast cancer biomarker. We will also touch upon general knowledge or basic notions of the biology of the metastatic process in epithelial cancers, in order to understand the origin and biology of CTCs. In this sense, we will pay special attention to EMT (epithelial to mesenchymal transition), dormancy and minimal residual disease, three key aspects that determine the outcome of the disease. We will also cover general aspects on the isolation and characterization techniques applies to the study of CTCs, and also the possibilities that the study of CTCs, as a biomarker with biological function, is opening in terms of understanding the biology of metastatic cells and the identification of therapeutic targets based on the functional and molecular characterization of CTCs. Lastly, we will try to foresee the future of CTCs in terms of clinical application and implementation in the clinical routine.