Apical-basal polarity inhibits epithelial-mesenchymal transition and tumour metastasis by PAR-complex-mediated SNAI1 degradation

Epicardial and endothelial cell activation concurs with extracellular matrix remodeling in atrial fibrillation

BACKGROUND

Improved understanding of the interconnectedness of structural remodeling processes in atrial fibrillation (AF) in patients could identify targets for future therapies.

METHODS

We present transcriptome sequencing of atrial tissues of patients without AF, with paroxysmal AF, and persistent AF (total n = 64). RNA expression levels were validated in the same and an independent cohort with qPCR. Biological processes were assessed with histological and immunohistochemical analyses.

RESULTS

In AF patients, epicardial cell gene expression decreased, contrasting with an upregulation of epithelial-to-mesenchymal transition (EMT) and mesenchymal cell gene expression. Immunohistochemistry demonstrated thickening of the epicardium and an increased proportion of (myo)fibroblast-like cells in the myocardium, supporting enhanced EMT in AF. We furthermore report an upregulation of endothelial cell proliferation, angiogenesis, and endothelial signaling. EMT and endothelial cell proliferation concurred with increased interstitial (myo)fibroblast-like cells and extracellular matrix gene expression including enhanced tenascin-C, thrombospondins, biglycan, and versican. Morphological analyses discovered increased and redistributed glycosaminoglycans and collagens in the atria of AF patients. Signaling pathways, including cell-matrix interactions, PI3K-AKT, and Notch signaling that could regulate mesenchymal cell activation, were upregulated.

CONCLUSION

Our results suggest that EMT and endothelial cell proliferation work in concert and characterize the (myo)fibroblast recruitment and ECM remodeling of AF. These processes could guide future research toward the discovery of targets for AF therapy.

Liquid-liquid phase separation: Orchestrating cell signaling through time and space

Cell signaling is a complex process. The faithful transduction of information into specific cellular actions depends on the synergistic effects of many regulatory molecules, nurtured by their strict spatiotemporal regulation. Over the years, we have gained copious insights into the subcellular architecture supporting this spatiotemporal control, including the roles of membrane-bound organelles and various signaling nanodomains. Recently, liquid-liquid phase separation (LLPS) has been recognized as another potentially ubiquitous framework for organizing signaling molecules with high specificity and precise spatiotemporal control in cells. Here, we review the pervasive role of LLPS in signal transduction, highlighting several key pathways that intersect with LLPS, including examples in which LLPS is controlled by signaling events. We also examine how LLPS orchestrates signaling by compartmentalizing signaling molecules, amplifying signals non-linearly, and moderating signaling dynamics. We focus on the specific molecules that drive LLPS and highlight the known functional and pathological consequences of LLPS in each pathway.

Epigenetic Regulation and Post-Translational Modifications of SNAI1 in Cancer Metastasis

SNAI1, a zinc finger transcription factor, not only acts as the master regulator of epithelial-mesenchymal transition (EMT) but also functions as a driver of cancer progression, including cell invasion, survival, immune regulation, stem cell properties, and metabolic regulation. The regulation of SNAI1 occurs at the transcriptional, translational, and predominant post-translational levels including phosphorylation, acetylation, and ubiquitination. Here, we discuss the regulation and role of SNAI1 in cancer metastasis, with a particular emphasis on epigenetic regulation and post-translational modifications. Understanding how signaling networks integrate with SNAI1 in cancer progression will shed new light on the mechanism of tumor metastasis and help develop novel therapeutic strategies against cancer metastasis.

Characteristics of circRNA and its approach as diagnostic tool in melanoma

One of the most common types of cancer in the world is skin cancer, which has been divided into two groups: non-melanoma and melanoma skin cancer. Different external and internal agents are considered as risk factors for melanoma skin cancer pathogenesis but the exact mechanisms are not yet confirmed. Genetic and epigenetic changes, UV exposure, arsenic compounds, and chemical substances are contributory factors to the development of melanoma. A correlation has emerged between new therapies and the discovery of a basic molecular pattern for skin cancer patients. Circular RNAs (circRNAs) are described as a unique group of extensively expressed endogenous regulatory RNAs with closed-loop structure bonds connecting the 5' and 3' ends, which are commonly expressed in mammalian cells. In this review, we describe the biogenesis of circular RNAs and its function in cancerous conditions focusing on the crosstalk between different circRNAs and melanoma. Increasing evidence suggests that circRNAs appears to be relative to the origin and development of skin-related diseases like malignant melanoma. Different circular RNAs like hsa_circ_0025039, hsa_circRNA006612, circRNA005537, and circANRIL, by targeting different cellular and molecular targets (e.g., CDK4, DAB2IP, ZEB1, miR-889, and let-7 c-3p), can participate in melanoma cancer progression.

RasV12; scrib-/- Tumors: A Cooperative Oncogenesis Model Fueled by Tumor/Host Interactions

The phenomenon of how oncogenes and tumor-suppressor mutations can synergize to promote tumor fitness and cancer progression can be studied in relatively simple animal model systems such as Drosophila melanogaster. Almost two decades after the landmark discovery of cooperative oncogenesis between oncogenic Ras^V12 and the loss of the tumor suppressor scribble in flies, this and other tumor models have provided new concepts and findings in cancer biology that has remarkable parallels and relevance to human cancer. Here we review findings using the Ras^V12; scrib^-/- tumor model and how it has contributed to our understanding of how these initial simple genetic insults cooperate within the tumor cell to set in motion the malignant transformation program leading to tumor growth through cell growth, cell survival and proliferation, dismantling of cell-cell interactions, degradation of basement membrane and spreading to other organs. Recent findings have demonstrated that cooperativity goes beyond cell intrinsic mechanisms as the tumor interacts with the immediate cells of the microenvironment, the immune system and systemic organs to eventually facilitate malignant progression.

Harnessing Carcinoma Cell Plasticity Mediated by TGF-β Signaling

Simple Summary

This review describes mechanisms driving epithelial plasticity in carcinoma mediated by transforming growth factor beta (TGF-β) signaling. Plasticity in carcinoma is frequently induced through epithelial–mesenchymal transition (EMT), an evolutionary conserved process in the development of multicellular organisms. The review explores the multifaceted functions of EMT, particularly focusing on the intermediate stages, which provide more adaptive responses of carcinoma cells in their microenvironment. The review critically considers how different intermediate or hybrid EMT stages confer carcinoma cells with stemness, refractoriness to therapies, and ability to execute all steps of the metastatic cascade. Finally, the review provides examples of therapeutic interventions based on the EMT concept.

Abstract

Epithelial cell plasticity, a hallmark of carcinoma progression, results in local and distant cancer dissemination. Carcinoma cell plasticity can be achieved through epithelial–mesenchymal transition (EMT), with cells positioned seemingly indiscriminately across the spectrum of EMT phenotypes. Different degrees of plasticity are achieved by transcriptional regulation and feedback-loops, which confer carcinoma cells with unique properties of tumor propagation and therapy resistance. Decoding the molecular and cellular basis of EMT in carcinoma should enable the discovery of new therapeutic strategies against cancer. In this review, we discuss the different attributes of plasticity in carcinoma and highlight the role of the canonical TGFβ receptor signaling pathway in the acquisition of plasticity. We emphasize the potential stochasticity of stemness in carcinoma in relation to plasticity and provide data from recent clinical trials that seek to target plasticity.

Getting started for migration: A focus on EMT cellular dynamics and mechanics in developmental models

The conversion of epithelial cells into mesenchymal ones, through a process known as epithelial-mesenchymal transition (or EMT) is a reversible process involved in critical steps of animal development as early as gastrulation and throughout organogenesis. In pathological conditions such as aggressive cancers, EMT is often associated with increased drug resistance, motility and invasiveness. The characterisation of the upstream signals and main decision takers, such as the EMT-transcription factors, has led to the identification of a core molecular machinery controlling the specification towards EMT. However, the cellular execution steps of this fundamental shift are poorly described, especially in cancerous cells. Here we review our current knowledge regarding the stepwise nature of EMT in model organisms as diverse as sea urchin, Drosophila, zebrafish, mouse or chicken. We focus on the cellular dynamics and mechanics of the transitional stages by which epithelial cells progressively become mesenchymal and leave the epithelium. We gather the currently available pieces of the puzzle, including the overlooked property of EMT cells to produce mechanical forces along their apico-basal axis before detaching from their neighbours. We discuss the interplay between EMT and the surrounding tissue. Finally, we propose a conceptual framework of EMT cell dynamics from the very first hint of epithelial cell reorganisation to the successful exit from the epithelial sheet.

Orchestration of tissue-scale mechanics and fate decisions by polarity signalling

Eukaryotic development relies on dynamic cell shape changes and segregation of fate determinants to achieve coordinated compartmentalization at larger scale. Studies in invertebrates have identified polarity programmes essential for morphogenesis; however, less is known about their contribution to adult tissue maintenance. While polarity-dependent fate decisions in mammals utilize molecular machineries similar to invertebrates, the hierarchies and effectors can differ widely. Recent studies in epithelial systems disclosed an intriguing interplay of polarity proteins, adhesion molecules and mechanochemical pathways in tissue organization. Based on major advances in biophysics, genome editing, high-resolution imaging and mathematical modelling, the cell polarity field has evolved to a remarkably multidisciplinary ground. Here, we review emerging concepts how polarity and cell fate are coupled, with emphasis on tissue-scale mechanisms, mechanobiology and mammalian models. Recent findings on the role of polarity signalling for tissue mechanics, micro-environmental functions and fate choices in health and disease will be summarized.

RNA N 6-Methyladenosine in Cancer Metastasis: Roles, Mechanisms, and Applications

Cancer metastasis is a symptom of adverse prognosis, a prime origin of therapy failure, and a lethal challenge for cancer patients. N⁶-methyladenosine (m⁶A), the most prevailing modification in messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs) of higher eukaryotes, has attracted increasing attention. Growing studies have verified the pivotal roles of m⁶A methylation in controlling mRNAs and ncRNAs in diverse physiological processes. Remarkably, recent findings have showed that aberrant methylation of m⁶A-related RNAs could influence cancer metastasis. In this review, we illuminate how m⁶A modifiers act on mRNAs and ncRNAs and modulate metastasis in several cancers, and put forward the clinical application prospects of m⁶A methylation.

STK39 promotes breast cancer invasion and metastasis by increasing SNAI1 activity upon phosphorylation

SNAI1 is widely regarded as a master driver of epithelial-mesenchymal transition (EMT) and associated with breast cancer progression and metastasis. This pro-malignant role is strongly linked to posttranslational modification, especially phosphorylation, which controls its protein levels and subcellular localization. While multiple kinases are implicated in regulation of SNAI1 stability, the precise mechanism by which SNAI1 is stabilized in tumors remains to be fully elucidated.

Methods: A series of in vitro and in vivo experiments were conducted to reveal the regulation of SNAI1 by Serine/Threonine Kinase 39 (STK39) and the role of STK39 in breast cancer metastasis.

Results: We identified STK39, a member of Stem 20-like serine/threonine kinase family, as a novel posttranslational regulator that enhances the stability of SNAI1. Inhibition of STK39 via knockdown or use of a specific inhibitor resulted in SNAI1 destabilization. Mechanistically, STK39 interacted with and phosphorylated SNAI1 at T203, which is critical for its nuclear retention. Functionally, STK39 inhibition markedly impaired the EMT phenotype and decreased tumor cell migration, invasion, and metastasis both in vitro and in vivo. These effects were rescued by ectopic SNAI1 expression. In addition, depletion of STK39 dramatically enhanced sensitivity to chemotherapeutic agents.

Conclusions: Our study demonstrated that STK39 is a key mediator of SNAI1 stability and is associated with the pro-metastatic cellular process, highlighting the STK39-SNAI1 signaling axis as promising therapeutic targets for treatments of metastatic breast cancer.

DDIT3 Directs a Dual Mechanism to Balance Glycolysis and Oxidative Phosphorylation during Glutamine Deprivation

Extracellular glutamine represents an important energy source for many cancer cells and its metabolism is intimately involved in maintaining redox homeostasis. The heightened metabolic activity within tumor tissues can result in glutamine deficiency, necessitating metabolic reprogramming responses. Here, dual mechanisms involving the stress-responsive transcription factor DDIT3 (DNA damage induced transcript 3) that establishes an interrelationship between glycolysis and mitochondrial respiration are revealed. DDIT3 is induced during glutamine deprivation to promote glycolysis and adenosine triphosphate production via suppression of the negative glycolytic regulator TIGAR. In concert, a proportion of the DDIT3 pool translocates to the mitochondria and suppresses oxidative phosphorylation through LONP1-mediated down-regulation of COQ9 and COX4. This in turn dampens the sustained levels of reactive oxygen species that follow glutamine withdrawal. Together these mechanisms constitute an adaptive survival mechanism permitting tumor cells to survive metabolic stress induced by glutamine starvation.

Heterogeneous Circulating Tumor Cells in Sarcoma: Implication for Clinical Practice

Simple Summary

The present review is aimed to discuss the relevance of assaying for the presence and isolation of circulating tumor cells (CTCs) in patients with sarcoma. Just a few studies have been performed to detect and enumerate viable CTCs in sarcoma and a majority of them still represent proof-of-concept studies, while more frequently tumor cells have been detected in the circulation by using the PCR-based method. Nevertheless, recent advances in technologies allowed detection of epithelial–mesenchymal transitioned CTCs from patients with mesenchymal malignancies, despite results being mostly preliminary. The possibility to identify CTCs holds a great promise for both applications of liquid biopsy in sarcoma for precision medicine, and for research purposes to pinpoint the mechanism of the metastatic process through the characterization of tumor mesenchymal cells. Coherently, clinical trials in sarcoma have been designed accordingly to detect CTCs, for diagnosis, identification of novel therapeutic targets and resistance mechanisms of systemic therapies, and patient stratification.

Abstract

Bone and soft tissue sarcomas (STSs) represent a group of heterogeneous rare malignant tumors of mesenchymal origin, with a poor prognosis. Due to their low incidence, only a few studies have been reported addressing circulating tumor cells (CTCs) in sarcoma, despite the well-documented relevance for applications of liquid biopsy in precision medicine. In the present review, the most recent data relative to the detection and isolation of viable and intact CTCs in these tumors will be reviewed, and the heterogeneity in CTCs will be discussed. The relevance of epithelial–mesenchymal plasticity and stemness in defining the phenotypic and functional properties of these rare cells in sarcoma will be highlighted. Of note, the existence of dynamic epithelial–mesenchymal transition (EMT)-related processes in sarcoma tumors has only recently been related to their clinical aggressiveness. Also, the presence of epithelial cell adhesion molecule (EpCAM)-positive CTC in sarcoma has been weakly correlated with poor outcome and disease progression, thus proving the existence of both epithelial and mesenchymal CTC in sarcoma. The advancement in technologies for capturing and enumerating all diverse CTCs phenotype originating from these mesenchymal tumors are presented, and results provide a promising basis for clinical application of CTC detection in sarcoma.

Loss of polarity protein Par3, via transcription factor Snail, promotes bladder cancer metastasis

Bladder cancer (BLCA) remains the leading cause of cancer‐related mortality among genitourinary malignancies worldwide. BLCA metastasis represents the primary reason for its poor prognosis. In this study, we report that decreased expression of partitioning defective 3 (Par3), a polarity protein (encoded by PARD3), is associated with tumor aggressive phenotypes and poor prognosis in BLCA patients. Consistently, ablation of Par3 promotes the metastasis and invasion of BLCA cells in vitro and in vivo. Further studies reveal that zinc finger protein Snail represses the expression of Par3 by binding to E2‐box (CAGGTG) of PARD3 promoter‐proximal. Inhibition of GSK‐3β promotes the expression and nuclear localization of Snail and then reduces the expression of Par3, resulting in the metastasis and invasion of BLCA cells. Moreover, we detected the interaction between Par3 (936‐1356 aa) and ZO‐1 (1372‐1748 aa), which is involved in the maintenance of tight junction. Together, our results demonstrate that the GSK‐3β/Snail/Par3/ZO‐1 axis regulates BLCA metastasis, and Snail is a major regulator for Par3 protein expression in BLCA.

Linking EMT programmes to normal and neoplastic epithelial stem cells

Epithelial stem cells serve critical physiological functions in the generation, maintenance and repair of diverse tissues through their ability to self-renew and spawn more specialized, differentiated cell types. In an analogous fashion, cancer stem cells have been proposed to fuel the growth, progression and recurrence of many carcinomas. Activation of an epithelial-mesenchymal transition (EMT), a latent cell-biological programme involved in development and wound healing, has been linked to the formation of both normal and neoplastic stem cells, but the mechanistic basis underlying this connection remains unclear. In this Perspective, we outline the instances where aspects of an EMT have been implicated in normal and neoplastic epithelial stem cells and consider the involvement of this programme during tissue regeneration and repair. We also discuss emerging concepts and evidence related to the heterogeneous and plastic cell states generated by EMT programmes and how these bear on our understanding of cancer stem cell biology and cancer metastasis. A more comprehensive accounting of the still-elusive links between EMT programmes and the stem cell state will surely advance our understanding of both normal stem cell biology and cancer pathogenesis.

SCRIB Promotes Proliferation and Metastasis by Targeting Hippo/YAP Signalling in Colorectal Cancer

The complex in which scribble planar cell polarity protein (SCRIB) is located is one of the three main polar protein complexes that play an important role in maintaining epithelial polarity and affecting tumour growth. However, the role of SCRIB in colorectal cancer (CRC) remains largely unknown. This study used date from The Cancer Genome Atlas (TCGA) and clinical samples to determine the expression of SCRIB in CRC and explored its mechanism through bioinformatics analysis and in vivo and in vitro experiments. In this study, SCRIB was found to be highly expressed in CRC patients, and it was often associated with malignant characteristics, such as proliferation, apoptosis, and epithelial-mesenchymal transition (EMT). Furthermore, we found that SCRIB may interact with the Hippo signalling pathway and affect the phosphorylation of YAP and its distribution inside and outside of the nucleus. We concluded that increased expression of SCRIB is likely to inhibit the Hippo signalling pathway by promoting YAP phosphorylation. This role of SCRIB in the progression of CRC provides an important information for the treatment of CRC.

The epithelial-mesenchymal transition and the cytoskeleton in bioengineered systems

The epithelial-mesenchymal transition (EMT) is intrinsically linked to alterations of the intracellular cytoskeleton and the extracellular matrix. After EMT, cells acquire an elongated morphology with front/back polarity, which can be attributed to actin-driven protrusion formation as well as the gain of vimentin expression. Consequently, cells can deform and remodel the surrounding matrix in order to facilitate local invasion. In this review, we highlight recent bioengineering approaches to elucidate EMT and functional changes in the cytoskeleton. First, we review transitions between multicellular clusters and dispersed individuals on planar surfaces, which often exhibit coordinated behaviors driven by leader cells and EMT. Second, we consider the functional role of vimentin, which can be probed at subcellular length scales and within confined spaces. Third, we discuss the role of topographical patterning and EMT via a contact guidance like mechanism. Finally, we address how multicellular clusters disorganize and disseminate in 3D matrix. These new technologies enable controlled physical microenvironments and higher-resolution spatiotemporal measurements of EMT at the single cell level. In closing, we consider future directions for the field and outstanding questions regarding EMT and the cytoskeleton for human cancer progression. Video Abstract.

Knockdown of E-cadherin induces cancer stem-cell-like phenotype and drug resistance in cervical cancer cells

Cervical cancer is one of the leading causes of mortality amongst women in developing countries, and resistance to therapy is the main reason for treatment failure. Recent advances suggest that cancer stem cells (CSCs) are critically involved in regulating the chemo-resistant behavior of cervical cancer cells. In our study, cells with the CSC phenotype were isolated, and we examined the expression levels of stem cell markers and genes associated with epithelial-mesenchymal transition (EMT) using different assays. However, the cells with the CSC phenotype could not be cultured for further cytotoxicity studies, so we established a model of CSC in cervical cancer cells. We performed siRNA-mediated knockdown of E-cadherin in these cells, and studied them for EMT-associated stem-cell-like properties. We also performed dose-dependent cell viability assays using clinically relevant drugs such as cisplatin, cyclopamine, and GANT58 to analyze the drug resistant behavior of these cancer cells. We found that knockdown of E-cadherin induces EMT in cervical cancer cells, imparting stem-cell like characteristics along with enhanced tumorsphere formation, cell migration, invasiveness, and drug resistance. This is the first study to establish a CSC model in cervical cancer cells by knockdown of E-cadherin, which can be used to develop anti-cancer therapies.

Nerve growth factor regulates liver cancer cell polarity and motility

Nerve growth factor (NGF), a prototypical neurotrophic factor essential for neuronal cell proliferation and survival, has been implicated as a marker of tumor progression, as well as a potential target for novel therapeutic approaches in cancer. To investigate the functional potential of NGF in liver cancer in the present study, a stable NGF-overexpressing HepG2 cell line was generated. The scratch-wound assay was used to investigate cell motility and polarity. Western blotting was performed to evaluate the expression levels of epithelial-mesenchymal transition (EMT)-related proteins, including E-cadherin, N-cadherin and vimentin. Moreover, immunofluorescence was performed to investigate the arrangement of the actin cytoskeleton. Cell anoikis resistance was examined using a suspension culture model and cell apoptosis was examined via flow cytometry. The present results indicated that NGF overexpression in HepG2 cells disrupted HepG2 cell polarity and promoted cell motility. Furthermore, NGF overexpression induced EMT and actin cytoskeleton rearrangement in HepG2 cells, as well as enhanced anoikis resistance and prevented cellular apoptosis. Notably, a tropomyosin receptor kinase A receptor inhibitor blocked NGF-induced cell motility and apoptosis. Therefore, it was suggested that NGF serves a critical role in the invasion and metastasis of liver cancer. The use of NGF as a biomarker or potential new target could lead to the development of novel factors for diagnosis or for improving therapeutic strategies in liver cancer.

Recepteur d'origine nantais contributes to the development of endometriosis via promoting epithelial-mesenchymal transition of a endometrial epithelial cells

Endometriosis is a benign, chronic inflammatory disease that commonly occurs in reproductive‐aged women. Epithelial‐mesenchymal transition (EMT) of endometrial epithelial cells plays an important role in the development of endometriosis. Recepteur d'origine nantais (RON), a receptor tyrosine kinase, has been reported to promote EMT and progression in tumours. However, whether and how RON mediates the EMT and endometriosis development is not known. Here, we found that RON activation could improve the migratory and invasive capabilities, change cellular morphologies, and decrease expression of E‐cadherin and increase expression of N‐cadherin in endometrial epithelial cells. Inhibition or knockdown of RON expression suppressed the migration and invasion of endometrial epithelial cells. Our studies also indicated that RON played its part in endometrial epithelial cells through protein kinase B (Akt) and mitogen‐activated protein kinase (MAPK) pathways. Treatment with a RON inhibitor could decrease the number of ectopic lesions in a mouse model of endometriosis and mediate expression of EMT markers in endometriotic lesions. These data suggest that RON contributed to endometriosis development by promoting EMT of endometrial epithelial cells. Therefore, RON may be a new therapeutic target for endometriosis.

Mesenchymal-to-Epithelial Transitions in Development and Cancer

The evolutionary emergence of the mesenchymal phenotype greatly increased the complexity of tissue architecture and composition in early Metazoan species. At the molecular level, an epithelial-to-mesenchymal transition (EMT) was permitted by the innovation of specific transcription factors whose expression is sufficient to repress the epithelial transcriptional program. The reverse process, mesenchymal-to-epithelial transition (MET), involves direct inhibition of EMT transcription factors by numerous mechanisms including tissue-specific MET-inducing transcription factors (MET-TFs), micro-RNAs, and changes to cell and tissue architecture, thus providing an elegant solution to the need for tight temporal and spatial control over EMT and MET events during development and adult tissue homeostasis.

Organotypic Modeling of the Tumor Landscape

Cancer is a complex disease and it is now clear that not only epithelial tumor cells play a role in carcinogenesis. The tumor microenvironment is composed of non-stromal cells, including endothelial cells, adipocytes, immune and nerve cells, and a stromal compartment composed of extracellular matrix, cancer-associated fibroblasts and mesenchymal cells. Tumorigenesis is a dynamic process with constant interactions occurring between the tumor cells and their surroundings. Even though all connections have not yet been discovered, it is now known that crosstalk between actors of the microenvironment drives cancer progression. Taking into account this complexity, it is important to develop relevant models to study carcinogenesis. Conventional 2D culture models fail to represent the entire tumor microenvironment properly and the use of animal models should be decreased with respect to the 3Rs rule. To this aim, in vitro organotypic models have been significantly developed these past few years. These models have different levels of complexity and allow the study of tumor cells alone or in interaction with the microenvironment actors during the multiple stages of carcinogenesis. This review depicts recent insights into organotypic modeling of the tumor and its microenvironment all throughout cancer progression. It offers an overview of the crosstalk between epithelial cancer cells and their microenvironment during the different phases of carcinogenesis, from the early cell autonomous events to the late metastatic stages. The advantages of 3D over classical 2D or in vivo models are presented as well as the most promising organotypic models. A particular focus is made on organotypic models used for studying cancer progression, from the less complex spheroids to the more sophisticated body-on-a-chip. Last but not least, we address the potential benefits of these models in personalized medicine which is undoubtedly a domain paving the path to new hopes in terms of cancer care and cure.

Long noncoding RNA LINC01578 drives colon cancer metastasis through a positive feedback loop with the NF-κB/YY1 axis

Metastasis accounts for poor prognosis of cancers and related deaths. Accumulating evidence has shown that long noncoding RNAs (lncRNAs) play critical roles in several types of cancer. However, which lncRNAs contribute to metastasis of colon cancer is still largely unknown. In this study, we found that lncRNA LINC01578 was correlated with metastasis and poor prognosis of colon cancer. LINC01578 was upregulated in colon cancer, associated with metastasis, advanced clinical stages, poor overall survival, disease-specific survival, and disease-free survival. Gain-of-function and loss-of-function assays revealed that LINC01578 enhanced colon cancer cell viability and mobility in vitro and colon cancer liver metastasis in vivo. Mechanistically, nuclear factor kappa B (NF-κB) and Yin Yang 1 (YY1) directly bound to the LINC01578 promoter, enhanced its activity, and activated LINC01578 expression. LINC01578 was shown to be a chromatin-bound lncRNA, which directly bound NFKBIB promoter. Furthermore, LINC01578 interacted with and recruited EZH2 to NFKBIB promoter and further repressed NFKBIB expression, thereby activating NF-κB signaling. Through activation of NF-κB, LINC01578 further upregulated YY1 expression. Through activation of the NF-κB/YY1 axis, LINC01578 in turn enhanced its own promoter activity, suggesting that LINC01578 and NF-κB/YY1 formed a positive feedback loop. Blocking NF-κB signaling abolished the oncogenic roles of LINC01578 in colon cancer. Furthermore, the expression levels of LINC01578, NFKBIB, and YY1 were correlated in clinical tissues. Collectively, this study demonstrated that LINC01578 promoted colon cancer metastasis via forming a positive feedback loop with NF-κB/YY1 and suggested that LINC01578 represents a potential prognostic biomarker and therapeutic target for colon cancer metastasis.

Protein phosphatase 1 in tumorigenesis: is it worth a closer look?

Cancer cells take advantage of signaling cascades to meet their requirements for sustained growth and survival. Cell signaling is tightly controlled by reversible protein phosphorylation mechanisms, which require the counterbalanced action of protein kinases and protein phosphatases. Imbalances on this system are associated with cancer development and progression. Protein phosphatase 1 (PP1) is one of the most relevant protein phosphatases in eukaryotic cells. Despite the widely recognized involvement of PP1 in key biological processes, both in health and disease, its relevance in cancer has been largely neglected. Here, we provide compelling evidence that support major roles for PP1 in tumorigenesis.

Wnt/β-Catenin Signaling Axis Is Required for TFEB-Mediated Gastric Cancer Metastasis and Epithelial-Mesenchymal Transition

Gastric cancer remains the third leading cause of cancer-related death, and tumor metastasis is the main risk factor for poor prognosis of patients with gastric cancer. Transcription factor EB (TFEB) is a MiT family member and has been found to drive tumorigenesis in a number of tissues, whereas few studies were focused on investigating its prometastasis role and mechanism in gastric cancer. Here, we found TFEB was upregulated in gastric cancer tissues compared with adjacent normal gastric epithelial tissues. IHC analysis from gastric cancer tissue microarray revealed that TFEB in gastric cancer was correlated with depth of tumor invasion, lymph node or distant metastasis, tumor tumor-node-metastasis stage, and overall survival. Gastric cancer cells with TFEB overexpression presented an increased cell migration or invasion, and epithelial-mesenchymal transition (EMT). Furthermore, gene correlation analysis and gene set enrichment analysis enriched Wnt/β-catenin signaling pathway members in TFEB high-expression group, and the TOP/FOPflash assay verified the effect of TFEB on β-catenin transcription activity. Besides, we found that TFEB could trigger the aggregation of β-catenin in nucleus and activate its transcription, as well as facilitate the expression of Wnt/β-catenin target genes and EMT-related markers, which could be reversed by the Wnt/β-catenin inhibitor XAV-939. Collectively, TFEB enhances gastric cancer metastatic potential by activating Wnt/β-catenin signaling pathway and may become a promising therapeutic target for gastric cancer metastasis. IMPLICATIONS: Overexpressed TFEB predicts a higher rate of metastasis and worse survival in patients with gastric cancer. Mechanistically, TFEB activates Wnt/β-catenin signaling to fuel migratory and invasive activities of gastric cancer cells, as well as EMT.

Long noncoding RNA MAPKAPK5-AS1 promotes colorectal cancer progression by cis-regulating the nearby gene MK5 and acting as a let-7f-1-3p sponge

BACKGROUND

Long noncoding RNAs (lncRNAs) are considered critical regulators in cancers; however, the clinical significance and mechanisms of MAPKAPK5-AS1 (hereinafter referred to as MK5-AS1) in colorectal cancer (CRC) remain mostly unknown.

METHODS

In this study, quantitative real-time PCR (qPCR) and western blotting were utilized to detect the levels of MK5-AS1, let-7f-1-3p and MK5 (MAPK activated protein kinase 5) in CRC tissues and cell lines. The biological functions of MK5-AS1, let-7f-1-3p and MK5 in CRC cells were explored using Cell Counting Kit-8 (CCK8), colony formation and transwell assays. The potential mechanisms of MK5-AS1 were evaluated by RNA pull-down, RNA immunoprecipitation (RIP), dual luciferase reporter assay, chromatin immunoprecipitation (ChIP) and bioinformatics analysis. The effects of MK5-AS1 and MK5 on CRC were investigated by a xenotransplantation model.

RESULTS

We confirmed that MK5-AS1 was significantly increased in CRC tissues. Knockdown of MK5-AS1 suppressed cell migration and invasion in vitro and inhibited lung metastasis in mice. Mechanistically, MK5-AS1 regulated SNAI1 expression by sponging let-7f-1-3p and cis-regulated the adjacent gene MK5. Moreover, MK5-AS1 recruited RBM4 and eIF4A1 to promote the translation of MK5. Our study verified that MK5 promoted the phosphorylation of c-Jun, which activated the transcription of SNAI1 by directly binding to its promoter.

CONCLUSIONS

MK5-AS1 cis-regulated the nearby gene MK5 and acted as a let-7f-1-3p sponge, playing a vital role in CRC tumorigenesis. This study could provide novel insights into molecular therapeutic targets of CRC.

Onion Epithelial Membrane Scaffolds Transfer Corneal Epithelial Layers in Reconstruction Surgery

Plants and their extracts have been used especially in China for more than ten centuries for preventing and treating disease. However, there are only few reports describing their use in animal cell culture and tissue transplantation. In this study, onion epithelial membranes (OEM) is used as scaffolds to support cultures of a variety of cells such as fibroblasts and epithelial cells notably; they maintain the phenotypic characteristics of corneal epithelial cells. This improvement includes preservation of the proliferative potential and stemness of rabbit corneal epithelial cells (RCECs). Such an outcome suggests that this cost-effective technology warrants further evaluation to determine if OEM is a viable candidate for use as scaffolds in corneal epithelial transplantation surgery. To test this possibility, rabbit corneal epithelial cells expanded on OEM are transplanted to treat corneal epithelial defects in limbal stem cell deficient rabbits. This procedure is successful because it shortens the time required for wound healing to restore losses in corneal epithelial integrity, and forms a more compact and stratified epithelium framework than the untreated group. Ultimately, should they be proven to be effective in other relevant animal model systems, their usefulness for treating wounds in a clinical setting warrants consideration.

Disruption of TFIIH activities generates a stress gene expression response and reveals possible new targets against cancer

Disruption of the enzymatic activities of the transcription factor TFIIH by the small molecules Triptolide (TPL) or THZ1 could be used against cancer. Here, we used the MCF10A-ErSrc oncogenesis model to compare the effect of TFIIH inhibitors between transformed cells and their progenitors. We report that tumour cells exhibited highly increased sensitivity to TPL or THZ1 and that the combination of both had a synergic effect. TPL affects the interaction between XPB and p52, causing a reduction in the levels of XPB, p52 and p8, but not other TFIIH subunits. RNA-Seq and RNAPII-ChIP-Seq experiments showed that although the levels of many transcripts were reduced, the levels of a significant number were increased after TPL treatment, with maintained or increased RNAPII promoter occupancy. A significant number of these genes encode for factors that have been related to tumour growth and metastasis, suggesting that transformed cells might rapidly develop resistance to TPL/THZ inhibitors. Some of these genes were also overexpressed in response to THZ1, of which depletion enhances the toxicity of TPL, and are possible new targets against cancer.

SP1-activated long noncoding RNA lncRNA GCMA functions as a competing endogenous RNA to promote tumor metastasis by sponging miR-124 and miR-34a in gastric cancer

Long noncoding RNAs (lncRNAs) were demonstrated to play important roles in gene regulation and cancer progression. However, the functional roles of lncRNAs and the detailed mechanisms underlying gastric cancer (GC) progression remain largely unclear. Here, we identified a novel cancer-related lncRNA, termed lncRNA GCMA (Gastric Cancer metastasis-associated lncRNA), which was upregulated in GC tissues with lymph node metastasis (LNM) compared with tissues without LNM. High expression of GCMA was significantly associated with poor prognosis of patients with GC. Luciferase assays, bioinformatics analyses and chromatin immunoprecipitation (ChIP) assays indicated that SP1 transcription factor directly bound to the GCMA promoter region and activated its transcription. Functionally, upregulation of GCMA dramatically promoted GC cells proliferation, migration and invasion in vitro, whereas knockdown of GCMA elicited the opposite function. Consistently, stable knockdown of GCMA inhibited tumor proliferation, invasion and metastasis in vivo. Mechanistically, by using bioinformatics analyses, RNA binding protein immunoprecipitation (RIP) assays, luciferase assays and western-blot assays, GCMA was demonstrated to function as a competing endogenous RNA (ceRNA) via competitively absorbing miR-124 and miR-34a to upregulate slug and snail, thereby induced epithelial-mesenchymal transition (EMT) and GC cell metastasis in vitro and in vivo. Collectively, these results demonstrate that GCMA functions as an oncogenic lncRNA that may serve as a potential prognostic biomarker for GC and shed new lights on targeted therapy of GC in the future.

Circular RNA: A novel potential biomarker for skin diseases

Circular RNA (circRNA) has been classified as noncoding RNA with a covalent closed continuous loop, the 3'and 5' ends of which are normally joined together to increase its own stability. More recently, circRNA has been shown to encode proteins and may be involved in the regulation of gene transcription. This provides more evidence for the involvement of circRNA in disease progression. Accumulating investigations have found that the expression of many circRNAs is abnormal in plenty of skin diseases such as malignant melanoma, psoriasis, and abnormal wound healing. Herein, in addition to the summary of recent studies on the nuclear export, N⁶-methyladenosine (m⁶A) modification, degradation, and other biogenesis and properties of circRNA, we highlight the importance of circRNAin skin diseases. Although their exact roles and mechanisms in most skin disease remain preliminary, circRNAs have potential applications as diagnostic biomarkers and novel therapeutic targets for skin diseases due to its structural and functional properties (stability, specificity and sensitivity), which is worthy of deeper exploration and greater research efforts.

Guidelines and definitions for research on epithelial-mesenchymal transition

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.

In this Consensus Statement, the authors (on behalf of the EMT International Association) propose guidelines to define epithelial–mesenchymal transition, its phenotypic plasticity and the associated multiple intermediate epithelial–mesenchymal cell states. Clarification of nomenclature and definitions will help reduce misinterpretation of research data generated in different experimental model systems and promote cross-disciplinary collaboration.

Novel approaches to link apicobasal polarity to cell fate specification

Understanding the development of apicobasal polarity (ABP) is a long-standing problem in biology. The molecular components involved in the development and maintenance of APB have been largely identified and are known to have ubiquitous roles across organisms. Our knowledge of the functional consequences of ABP establishment and maintenance is far less comprehensive. Recent studies using novel experimental approaches and cellular models have revealed a growing link between ABP and the genetic program of cell lineage. This mini-review describes some of the most recent advances in this new field, highlighting examples from Caenorhabditis elegans and mouse embryos, human pluripotent stem cells, and epithelial cells. We also speculate on the most interesting and challenging avenues that can be explored.

The role of polarisation of circulating tumour cells in cancer metastasis

Metastasis is the spread of cancer cells from a primary tumour to a distant site of the body. Metastasising tumour cells have to survive and readjust to different environments, such as heterogeneous solid tissues and liquid phase in lymph- or blood circulation, which they achieve through a high degree of plasticity that renders them adaptable to varying conditions. One defining characteristic of the metastatic process is the transition of tumour cells between different polarised phenotypes, ranging from differentiated epithelial polarity to migratory front-rear polarity. Here, we review the polarisation types adopted by tumour cells during the metastatic process and describe the recently discovered single-cell polarity in liquid phase observed in circulating tumour cells. We propose that single-cell polarity constitutes a mode of polarisation of the cell cortex that is uncoupled from the intracellular polarisation machinery, which distinguishes single-cell polarity from other types of polarity identified so far. We discuss how single-cell polarity can contribute to tumour metastasis and the therapeutic potential of this new discovery.

The Dual Roles of the Atypical Protein Kinase Cs in Cancer

Atypical protein kinase C (aPKC) isozymes, PKCλ/ι and PKCζ, are now considered fundamental regulators of tumorigenesis. However, the specific separation of functions that determine their different roles in cancer is still being unraveled. Both aPKCs have pleiotropic context-dependent functions that can translate into tumor-promoter or -suppressive functions. Here, we review early and more recent literature to discuss how the different tumor types, and their microenvironments, might account for the selective signaling of each aPKC isotype. This is of clinical relevance because a better understanding of the roles of these kinases is essential for the design of new anti-cancer treatments.

Snail1: A Transcriptional Factor Controlled at Multiple Levels

Snail1 transcriptional factor plays a key role in the control of epithelial to mesenchymal transition and fibroblast activation. As a consequence, Snail1 expression and function is regulated at multiple levels from gene transcription to protein modifications, affecting its interaction with specific cofactors. In this review, we describe the different elements that control Snail1 expression and its activity both as transcriptional repressor or activator.