ZEB1 in Pancreatic Cancer. Cancers (Basel). 2010;2:1617-1628. [PMID: 24281177 DOI: 10.3390/cancers2031617]

Intricate relationship between cancer stemness, metastasis, and drug resistance

Cancer stem cells (CSCs) are widely acknowledged as the drivers of tumor initiation, epithelial-mesenchymal transition (EMT) progression, and metastasis. Originating from both hematologic and solid malignancies, CSCs exhibit quiescence, pluripotency, and self-renewal akin to normal stem cells, thus orchestrating tumor heterogeneity and growth. Through a dynamic interplay with the tumor microenvironment (TME) and intricate signaling cascades, CSCs undergo transitions from differentiated cancer cells, culminating in therapy resistance and disease recurrence. This review undertakes an in-depth analysis of the multifaceted mechanisms underlying cancer stemness and CSC-mediated resistance to therapy. Intrinsic factors encompassing the TME, hypoxic conditions, and oxidative stress, alongside extrinsic processes such as drug efflux mechanisms, collectively contribute to therapeutic resistance. An exploration into key signaling pathways, including JAK/STAT, WNT, NOTCH, and HEDGEHOG, sheds light on their pivotal roles in sustaining CSCs phenotypes. Insights gleaned from preclinical and clinical studies hold promise in refining drug discovery efforts and optimizing therapeutic interventions, especially chimeric antigen receptor (CAR)-T cell therapy, cytokine-induced killer (CIK) cell therapy, natural killer (NK) cell-mediated CSC-targeting and others. Ultimately use of cell sorting and single cell sequencing approaches for elucidating the fundamental characteristics and resistance mechanisms inherent in CSCs will enhance our comprehension of CSC and intratumor heterogeneity, which ultimately would inform about tailored and personalized interventions.

Lack of basic rationale in epithelial-mesenchymal transition and its related concepts

Epithelial-mesenchymal transition (EMT) is defined as a cellular process during which epithelial cells acquire mesenchymal phenotypes and behavior following the downregulation of epithelial features. EMT and its reversed process, the mesenchymal-epithelial transition (MET), and the special form of EMT, the endothelial-mesenchymal transition (EndMT), have been considered as mainstream concepts and general rules driving developmental and pathological processes, particularly cancer. However, discrepancies and disputes over EMT and EMT research have also grown over time. EMT is defined as transition between two cellular states, but it is unanimously agreed by EMT researchers that (1) neither the epithelial and mesenchymal states nor their regulatory networks have been clearly defined, (2) no EMT markers or factors can represent universally epithelial and mesenchymal states, and thus (3) EMT cannot be assessed on the basis of one or a few EMT markers. In contrast to definition and proposed roles of EMT, loss of epithelial feature does not cause mesenchymal phenotype, and EMT does not contribute to embryonic mesenchyme and neural crest formation, the key developmental events from which the EMT concept was derived. EMT and MET, represented by change in cell shapes or adhesiveness, or symbolized by EMT factors, are biased interpretation of the overall change in cellular property and regulatory networks during development and cancer progression. Moreover, EMT and MET are consequences rather than driving factors of developmental and pathological processes. The true meaning of EMT in some developmental and pathological processes, such as fibrosis, needs re-evaluation. EMT is believed to endow malignant features, such as migration, stemness, etc., to cancer cells. However, the core property of cancer (tumorigenic) cells is neural stemness, and the core EMT factors are components of the regulatory networks of neural stemness. Thus, EMT in cancer progression is misattribution of the roles of neural stemness to the unknown mesenchymal state. Similarly, neural crest EMT is misattribution of intrinsic property of neural crest cells to the unknown mesenchymal state. Lack of basic rationale in EMT and related concepts urges re-evaluation of their significance as general rules for understanding developmental and pathological processes, and re-evaluation of their significance in scientific research.

Aberrant expression of PELI1 caused by Jagged1 accelerates the malignant phenotype of pancreatic cancer

Pancreatic cancer is one of the most aggressive cancers. PELI1 has been reported to promote cell survival and proliferation in multiple cancers. As of now, the role of PELI1 in pancreatic cancer is largely unknown. Here, we found that the PELI1 mRNA was higher expressed in pancreatic tumor tissues than in adjacent normal tissues, and the high PELI1 level in pancreatic cancer patients had a short survival time compared with the low level. Moreover, the results showed that PELI1 promoted cell proliferation, migration, and invasion, and inhibited apoptosis in vitro. Xenograft tumor experiments were used to determine the biological function of PELI1, and the results showed that PELI1 promoted tumor growth in vivo. Additionally, we found that Jagged1 activated PELI1 transcription in pancreatic cancer cells. To sum up, our results show that PELI1 affects the malignant phenotype of pancreatic cancer.

The role of zinc finger proteins in malignant tumors

Zinc finger proteins (ZNFs) are the largest family of transcriptional factors in mammalian cells. Recently, their role in the development, progression, and metastasis of malignant tumors via regulating gene transcription and translation processes has become evident. Besides, their possible involvement in drug resistance has also been found, indicating that ZNFs have the potential to become new biological markers and therapeutic targets. In this review, we summarize the oncogenic and suppressive roles of various ZNFs in malignant tumors, including lung, breast, liver, gastric, colorectal, pancreatic, and other cancers, highlighting their role as prognostic markers, and hopefully provide new ideas for the treatment of malignant tumors in the future.

ZEB1 Is Regulated by K811 Acetylation to Promote Stability, NuRD Complex Interactions, EMT, and NSCLC Metastasis

Epithelial-to-mesenchymal transition results in loss of specialized epithelial cell contacts and acquisition of mesenchymal invasive capacity. The transcription repressor zinc finger E-box-binding homeobox 1 (ZEB1) binds to E-boxes of gene promoter regions to suppress the expression of epithelial genes. ZEB1 has inconsistent molecular weights, which have been attributed to posttranslational modifications (PTM). We performed mass spectrometry and identified K811 acetylation as a novel PTM in ZEB1. To define the role of ZEB1 acetylation in regulating function, we generated ZEB1 acetyl-mimetic (K811Q) and acetyl-deficient (K811R) mutant-expressing non-small cell lung cancer cell lines (NSCLC). We demonstrate that the K811R ZEB1 (125 kDa) has a shorter protein half-life than wild-type (WT) ZEB1 and K811Q ZEB1 (∼225 kDa), suggesting that lack of ZEB1 acetylation in the lower molecular weight form affects protein stability. Further, the acetylated form of ZEB1 recruits the nucleosome remodeling and deacetylase (NuRD) complex to bind the promoter of its target genes mir200c-141 and SEMA3F. RNA-sequencing revealed that WT ZEB1 and K811Q ZEB1 downregulate the expression of epithelial genes to promote lung adenocarcinoma invasion and metastasis, whereas the K811R ZEB1 does not. Our findings establish that the K811 acetylation promotes ZEB1 protein stability, interaction with other protein complexes, and subsequent invasion/metastasis of lung adenocarcinoma via epithelial-to-mesenchymal transition.

IMPLICATIONS

The molecular mechanisms by which ZEB1 is regulated by K811 acetylation to promote protein stability, NuRD complex and promoter interactions, and function are relevant to the development of treatment strategies to prevent and treat metastasis in patients with NSCLC.

Neural induction drives body axis formation during embryogenesis, but a neural induction-like process drives tumorigenesis in postnatal animals

Characterization of cancer cells and neural stem cells indicates that tumorigenicity and pluripotency are coupled cell properties determined by neural stemness, and tumorigenesis represents a process of progressive loss of original cell identity and gain of neural stemness. This reminds of a most fundamental process required for the development of the nervous system and body axis during embryogenesis, i.e., embryonic neural induction. Neural induction is that, in response to extracellular signals that are secreted by the Spemann-Mangold organizer in amphibians or the node in mammals and inhibit epidermal fate in ectoderm, the ectodermal cells lose their epidermal fate and assume the neural default fate and consequently, turn into neuroectodermal cells. They further differentiate into the nervous system and also some non-neural cells via interaction with adjacent tissues. Failure in neural induction leads to failure of embryogenesis, and ectopic neural induction due to ectopic organizer or node activity or activation of embryonic neural genes causes a formation of secondary body axis or a conjoined twin. During tumorigenesis, cells progressively lose their original cell identity and gain of neural stemness, and consequently, gain of tumorigenicity and pluripotency, due to various intra-/extracellular insults in cells of a postnatal animal. Tumorigenic cells can be induced to differentiation into normal cells and integrate into normal embryonic development within an embryo. However, they form tumors and cannot integrate into animal tissues/organs in a postnatal animal because of lack of embryonic inducing signals. Combination of studies of developmental and cancer biology indicates that neural induction drives embryogenesis in gastrulating embryos but a similar process drives tumorigenesis in a postnatal animal. Tumorigenicity is by nature the manifestation of aberrant occurrence of pluripotent state in a postnatal animal. Pluripotency and tumorigenicity are both but different manifestations of neural stemness in pre- and postnatal stages of animal life, respectively. Based on these findings, I discuss about some confusion in cancer research, propose to distinguish the causality and associations and discriminate causal and supporting factors involved in tumorigenesis, and suggest revisiting the focus of cancer research.

ZEB1-activated Notch1 promotes circulating tumor cell migration and invasion in lung squamous cell carcinoma

BACKGROUND

Lung squamous cell carcinoma (LUSC) is recognized as the major subtypes of non-small cell lung cancer (NSCLC). Circulating tumor cells (CTCs) are critical players in tumor metastasis. A molecular profiling of CTCs has previously identified notch receptor 1 (Notch1) as an important mediator in NSCLC. Therefore, we investigate Notch1 roles in LUSC and its related mechanisms.

METHODS

The serum levels of Notch1 were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The CTCs isolated from blood samples were characterized via an immunofluorescence method. Cell motion was determined using Transwell chambers. The regulatory relationship between Notch1 and zinc finger E-box-binding homeobox 1 (ZEB1) was verified by chromatin immunoprecipitation (ChIP) and luciferase reporter assays. The protein levels were detected by western blotting.

RESULTS

Higher Notch1 expression in patients with LUSC than that in normal controls was observed. Notch1 knockdown inhibited cell motion and epithelial-mesenchymal transition (EMT). ZEB1 transcriptionally activated Notch1. ZEB1 upregulation exacerbated the malignant phenotypes of CTCs.

CONCLUSION

ZEB1-activated Notch1 promotes malignant phenotypes of CTCs in LUSC and indicates poor prognosis.

microRNAs Associated with Gemcitabine Resistance via EMT, TME, and Drug Metabolism in Pancreatic Cancer

Despite extensive research, pancreatic cancer remains a lethal disease with an extremely poor prognosis. The difficulty in early detection and chemoresistance to therapeutic agents are major clinical concerns. To improve prognosis, novel biomarkers, and therapeutic strategies for chemoresistance are urgently needed. microRNAs (miRNAs) play important roles in the development, progression, and metastasis of several cancers. During the last few decades, the association between pancreatic cancer and miRNAs has been extensively elucidated, with several miRNAs found to be correlated with patient prognosis. Moreover, recent evidence has revealed that miRNAs are intimately involved in gemcitabine sensitivity and resistance through epithelial-to-mesenchymal transition, the tumor microenvironment, and drug metabolism. Gemcitabine is the gold standard drug for pancreatic cancer treatment, but gemcitabine resistance develops easily after chemotherapy initiation. Therefore, in this review, we summarize the gemcitabine resistance mechanisms associated with aberrantly expressed miRNAs in pancreatic cancer, especially focusing on the mechanisms associated with epithelial-to-mesenchymal transition, the tumor microenvironment, and metabolism. This novel evidence of gemcitabine resistance will drive further research to elucidate the mechanisms of chemoresistance and improve patient outcomes.

Post-Translational Modification of ZEB Family Members in Cancer Progression

Post-translational modification (PTM), the essential regulatory mechanisms of proteins, play essential roles in physiological and pathological processes. In addition, PTM functions in tumour development and progression. Zinc finger E-box binding homeobox (ZEB) family homeodomain transcription factors, such as ZEB1 and ZEB2, play a pivotal role in tumour progression and metastasis by induction epithelial-mesenchymal transition (EMT), with activation of stem cell traits, immune evasion and epigenetic reprogramming. However, the relationship between ZEB family members' post-translational modification (PTM) and tumourigenesis remains largely unknown. Therefore, we focussed on the PTM of ZEBs and potential therapeutic approaches in cancer progression. This review provides an overview of the diverse functions of ZEBs in cancer and the mechanisms and therapeutic implications that target ZEB family members' PTMs.

Regulation of ZEB1 Function and Molecular Associations in Tumor Progression and Metastasis

Zinc finger E-box binding homeobox 1 (ZEB1) is a pleiotropic transcription factor frequently expressed in carcinomas. ZEB1 orchestrates the transcription of genes in the control of several key developmental processes and tumor metastasis via the epithelial-to-mesenchymal transition (EMT). The biological function of ZEB1 is regulated through pathways that influence its transcription and post-transcriptional mechanisms. Diverse signaling pathways converge to induce ZEB1 activity; however, only a few studies have focused on the molecular associations or functional changes of ZEB1 by post-translational modifications (PTMs). Due to the robust effect of ZEB1 as a transcription repressor of epithelial genes during EMT, the contribution of PTMs in the regulation of ZEB1-targeted gene expression is an active area of investigation. Herein, we review the pivotal roles that phosphorylation, acetylation, ubiquitination, sumoylation, and other modifications have in regulating the molecular associations and behavior of ZEB1. We also outline several questions regarding the PTM-mediated regulation of ZEB1 that remain unanswered. The areas of research covered in this review are contributing to new treatment strategies for cancer by improving our mechanistic understanding of ZEB1-mediated EMT.

A Comparative Endocrine Trans-Differentiation Approach to Pancreatic Ductal Adenocarcinoma Cells with Different EMT Phenotypes Identifies Quasi-Mesenchymal Tumor Cells as Those with Highest Plasticity

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancer types with the quasi-mesenchymal (QM) subtype of PDAC having the worst prognosis. De-differentiation of the ductal tumor cells to a mesenchymal phenotype occurs as a result of epithelial–mesenchymal transition (EMT), a process associated with the acquisition of stem cell traits. While QM tumor cells are highly metastatic and drug-resistant, their increased plasticity opens a window of opportunity for trans-differentiation into non-malignant pancreatic cells. In this study we compared established PDAC-derived cell lines of either epithelial (E) or QM phenotype for their potential to be differentiated to pancreatic endocrine cells. We found that QM cells responded more strongly than E cells with transcriptional activation of a pancreatic progenitor or pancreatic β cell-specific program. Our results bear strong implications for a novel type of targeted therapy, namely EMT-based trans-differentiation of highly metastatic PDAC cells in vivo to non-malignant endocrine cells.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and therapy-resistant cancer types which is largely due to tumor heterogeneity, cancer cell de-differentiation, and early metastatic spread. The major molecular subtypes of PDAC are designated classical/epithelial (E) and quasi-mesenchymal (QM) subtypes, with the latter having the worst prognosis. Epithelial–mesenchymal transition (EMT) and the reverse process, mesenchymal-epithelial transition (MET), are involved in regulating invasion/metastasis and stem cell generation in cancer cells but also early pancreatic endocrine differentiation or de-differentiation of adult pancreatic islet cells in vitro, suggesting that pancreatic ductal exocrine and endocrine cells share common EMT programs. Using a panel of PDAC-derived cell lines classified by epithelial/mesenchymal expression as either E or QM, we compared their trans-differentiation (TD) potential to endocrine progenitor or β cell-like cells since studies with human pancreatic cancer cells for possible future TD therapy in PDAC patients are not available so far. We observed that QM cell lines responded strongly to TD culture using as inducers 5′-aza-2′-deoxycytidine or growth factors/cytokines, while their E counterparts were refractory or showed only a weak response. Moreover, the gain of plasticity was associated with a decrease in proliferative and migratory activities and was directly related to epigenetic changes acquired during selection of a metastatic phenotype as revealed by TD experiments using the paired isogenic COLO 357-L3.6pl model. Our data indicate that a QM phenotype in PDAC coincides with increased plasticity and heightened trans-differentiation potential to activate a pancreatic β cell-specific transcriptional program. We strongly assume that this specific biological feature has potential to be exploited clinically in TD-based therapy to convert metastatic PDAC cells into less malignant or even benign cells.

Non-coding RNAs in pancreatic ductal adenocarcinoma: New approaches for better diagnosis and therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies with a 5-year survival rate less than 8%, which has remained unchanged over the last 50 years. Early detection is particularly difficult due to the lack of disease-specific symptoms and a reliable biomarker. Multimodality treatment including chemotherapy, radiotherapy (used sparingly) and surgery has become the standard of care for patients with PDAC. Carbohydrate antigen 19-9 (CA 19-9) is the most common diagnostic biomarker; however, it is not specific enough especially for asymptomatic patients. Non-coding RNAs are often deregulated in human malignancies and shown to be involved in cancer-related mechanisms such as cell growth, differentiation, and cell death. Several micro, long non-coding and circular RNAs have been reported to date which are involved in PDAC. Aim of this review is to discuss the roles and functions of non-coding RNAs in diagnosis and treatments of PDAC.

The Identification of Stemness-Related Genes in the Risk of Head and Neck Squamous Cell Carcinoma

Objectives

This study aimed to identify genes regulating cancer stemness of head and neck squamous cell carcinoma (HNSCC) and evaluate the ability of these genes to predict clinical outcomes.

Materials and Methods

The stemness index (mRNAsi) was obtained using a one-class logistic regression machine learning algorithm based on sequencing data of HNSCC patients. Stemness-related genes were identified by weighted gene co-expression network analysis and least absolute shrinkage and selection operator analysis (LASSO). The coefficient of LASSO was applied to construct a diagnostic risk score model. The Cancer Genome Atlas database, the Gene Expression Omnibus database, Oncomine database and the Human Protein Atlas database were used to validate the expression of key genes. Interaction network analysis was performed using String database and DisNor database. The Connectivity Map database was used to screen potential compounds. The expressions of stemness-related genes were validated using quantitative real‐time polymerase chain reaction (qRT‐PCR).

Results

TTK, KIF14, KIF18A and DLGAP5 were identified. Stemness-related genes were upregulated in HNSCC samples. The risk score model had a significant predictive ability. CDK inhibitor was the top hit of potential compounds.

Conclusion

Stemness-related gene expression profiles may be a potential biomarker for HNSCC.

Promoter G-quadruplex favours epigenetic reprogramming-induced atypical expression of ZEB1 in cancer cells

BACKGROUND

Aberrant expression of Zinc-finger E-box binding homeobox 1 (ZEB1), which remains repressed in normal cells, is frequently associated with cancer aggressiveness. However, transcriptional mechanism underlying such atypical ZEB1 expression in cancer is not yet well-understood.

METHODS

ZEB1 promoter G-quadruplexes were studied and modeled extensively using circular dichroism, fluorescence spectroscopy, ITC and DMS protection assay. Luciferase assay, qPCR, FAIRE, ChIP, western blotting, confocal microscopy was used to access the regulation of ZEB1 transcription.

RESULTS

Our study unravels the occupancy of nucleolin to ZEB1 promoter as a crucial determinant which facilitates the binding of SP1 transcription factor to chromatin, by locally remodelling the region. SP1, subsequently, recruits P300 acetyl transferase leading to enriched acetyl-histone H3 at promoter and activates ZEB1 transcription. ZEB1 promoter analysis identifies presence of four putative G-quadruplex (G4) forming motifs within 700 bp of TSS; each quadruplex is characterized structurally in details with an array of biophysical techniques. Surprisingly, stabilization of G4 with cationic porphyrin TMPyP4 represses its transcription and eventually impedes cell invasiveness.

CONCLUSIONS

TMPyP4 binding to a selected G4 motif (5' -534/-511-3' from TSS), where nucleolin/SP1/P300 co-occupies, prevents the association of nucleolin which consequently hinders SP1 binding, leading to chromatin compactness and transcriptional repression.

GENERAL SIGNIFICANCE

Our findings demonstrate an epigenetic mechanism of ZEB1 reactivation where dynamic occupancy of transcription regulators encompassing a G4 motif is crucial and thus, small molecule induced G-quadruplex stabilization may act as a potential molecular switch to turn-off gene expression.

MiR-4269 suppresses the tumorigenesis and development of pancreatic cancer by targeting ZEB1/OTX1 pathway

As one of the most prevalent malignant tumors, pancreatic cancer (PC) is a leading fatal cancer worldwide. Surging evidence has unraveled that miRNAs are involved in the occurrence and progression of multiple cancers, including PC. The tumor suppressor effects of miR-4269 have been certified in gastric carcinoma. However, the potential function of miR-4269 remains largely unclear, which drives us to identify the role of miR-4269 in PC development. In the present study, we determined the expression pattern of miR-4269 in PC cells and normal cells. Results of RT-qPCR analysis illuminated that miR-4269 expression level in PC cells was lower than that in normal cells. Functional assays demonstrated that up-regulation of miR-4269 obviously inhibited the proliferation, migration and invasion of PC cells. In order to elucidate the mechanism governing miR-4269 in PC, we carried out bioinformatics analysis and further experimental investigations. Our results validated that ZEB1 was a direct target of miR-4269. Additionally, ZEB1 activated the transcription of OXT1. More importantly, miR-4269 attenuated the expression level of OXT1 via targeting ZEB1. Ultimately, our findings confirmed that miR-4269 served as a cancer suppressor in PC through regulation of ZEB1/OTX1 pathway, which suggested that miR-4269 might represent a promising target for the clinical treatment of PC.

Alternative splicing modulates cancer aggressiveness: role in EMT/metastasis and chemoresistance

Enhanced metastasis and disease recurrence accounts for the high mortality rates associated with cancer. The process of Epithelial-Mesenchymal Transition (EMT) contributes towards the augmentation of cancer invasiveness along with the gain of stem-like and the subsequent drug-resistant behavior. Apart from the well-established transcriptional regulation, EMT is also controlled post-transcriptionally by virtue of alternative splicing (AS). Numerous genes including Fibroblast Growth Factor receptor (FGFR) as well as CD44 are differentially spliced during this trans-differentiation process which, in turn, governs cancer progression. These splicing alterations are controlled by various splicing factors including ESRP, RBFOX2 as well as hnRNPs. Here, we have depicted the mechanisms governing the splice isoform switching of FGFR and CD44. Moreover, the role of the splice variants generated by AS of these gene transcripts in modulating the metastatic potential and stem-like/chemoresistant behavior of cancer cells has also been highlighted. Additionally, the involvement of splicing factors in regulating EMT/invasiveness along with drug-resistance as well as the metabolic properties of the cells has been emphasized. Tumorigenesis is accompanied by a remodeling of the cellular splicing profile generating diverse protein isoforms which, in turn, control the cancer-associated hallmarks. Therefore, we have also briefly discussed about a wide variety of genes which are differentially spliced in the tumor cells and promote cancer progression. We have also outlined different strategies for targeting the tumor-associated splicing events which have shown promising results and therefore this approach might be useful in developing therapies to reduce cancer aggressiveness in a more specific manner.

Zinc finger E-box binding homeobox 1 and atherosclerosis: New insights and therapeutic potential

Zinc finger E-box binding homeobox 1 (ZEB1), an important transcription factor belonging to the ZEB family, plays a crucial role in regulating gene expression required for both normal physiological and pathological processes. Accumulating evidence has shown that ZEB1 participates in the initiation and progression of atherosclerotic cardiovascular disease. Recent studies suggest that ZEB1 protects against atherosclerosis by regulation of endothelial cell angiogenesis, endothelial dysfunction, monocyte-endothelial cell interaction, macrophage lipid accumulation, macrophage polarization, monocyte-vascular smooth muscle cell (VSMC) interaction, VSMC proliferation and migration, and T cell proliferation. In this review, we summarize the recent progress of ZEB1 in the pathogenesis of atherosclerosis and provide insights into the prevention and treatment of atherosclerotic cardiovascular disease.

RAC1B Regulation of TGFB1 Reveals an Unexpected Role of Autocrine TGFβ1 in the Suppression of Cell Motility

Autocrine transforming growth factor (TGF)β has been implicated in epithelial-mesenchymal transition (EMT) and invasion of several cancers including pancreatic ductal adenocarcinoma (PDAC) as well as triple-negative breast cancer (TNBC). However, the precise mechanism and the upstream inducers or downstream effectors of endogenous TGFB1 remain poorly characterized. In both cancer types, the small GTPase RAC1B inhibits cell motility induced by recombinant human TGFβ1 via downregulation of the TGFβ type I receptor, ALK5, but whether RAC1B also impacts autocrine TGFβ signaling has not yet been studied. Intriguingly, RNA interference-mediated knockdown (RNAi-KD) or CRISPR/Cas-mediated knockout of RAC1B in TGFβ1-secreting PDAC-derived Panc1 cells resulted in a dramatic decrease in secreted bioactive TGFβ1 in the culture supernatants and TGFB1 mRNA expression, while the reverse was true for TNBC-derived MDA-MB-231 cells ectopically expressing RAC1B. Surprisingly, the antibody-mediated neutralization of secreted bioactive TGFβ or RNAi-KD of the endogenous TGFB1 gene, was associated with increased rather than decreased migratory activities of Panc1 and MDA-MB-231 cells, upregulation of the promigratory genes SNAI1, SNAI2 and RAC1, and downregulation of the invasion suppressor genes CDH1 (encoding E-cadherin) and SMAD3. Intriguingly, ectopic re-expression of SMAD3 was able to rescue Panc1 and MDA-MB-231 cells from the TGFB1 KD-induced rise in migratory activity. Together, these data suggest that RAC1B favors synthesis and secretion of autocrine TGFβ1 which in a SMAD3-dependent manner blocks EMT-associated gene expression and cell motility.

The Small GTPase RAC1B: A Potent Negative Regulator of-and Useful Tool to Study-TGFβ Signaling

RAC1 and its alternatively spliced isoform, RAC1B, are members of the Rho family of GTPases. Both isoforms are involved in the regulation of actin cytoskeleton remodeling, cell motility, cell proliferation, and epithelial-mesenchymal transition (EMT). Compared to RAC1, RAC1B exhibits a number of distinctive features with respect to tissue distribution, downstream signaling and a role in disease conditions like inflammation and cancer. The subcellular locations and interaction partners of RAC1 and RAC1B vary depending on their activation state, which makes RAC1 and RAC1B ideal candidates to establish cross-talk with cancer-associated signaling pathways-for instance, interactions with signaling by transforming growth factor β (TGFβ), a known tumor promoter. Although RAC1 has been found to promote TGFβ-driven tumor progression, recent observations in pancreatic carcinoma cells surprisingly revealed that RAC1B confers anti-oncogenic properties, i.e., through inhibiting TGFβ-induced EMT. Since then, an unexpected array of mechanisms through which RAC1B cross-talks with TGFβ signaling has been demonstrated. However, rather than being uniformly inhibitory, RAC1B interacts with TGFβ signaling in a way that results in the selective blockade of tumor-promoting pathways, while concomitantly allowing tumor-suppressive pathways to proceed. In this review article, we are going to discuss the specific interactions between RAC1B and TGFβ signaling, which occur at multiple levels and include various components such as ligands, receptors, cytosolic mediators, transcription factors, and extracellular inhibitors of TGFβ ligands.

Morphologic and Molecular Landscape of Pancreatic Cancer Variants as the Basis of New Therapeutic Strategies for Precision Oncology

To date, pancreatic cancer is still one of the most lethal cancers in the world, mainly due to the lack of early diagnosis and personalized treatment strategies. In this context, the possibility and the opportunity of identifying genetic and molecular biomarkers are crucial to improve the feasibility of precision medicine. In 2019, the World Health Organization classified pancreatic ductal adenocarcinoma cancer (the most common pancreatic tumor type) into eight variants, according to specific histomorphological features. They are: colloid carcinoma, medullary carcinoma, adenosquamous carcinoma, undifferentiated carcinoma, including also rhabdoid carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, hepatoid carcinoma, and signet-ring/poorly cohesive cells carcinoma. Interestingly, despite the very low incidence of these variants, innovative high throughput genomic/transcriptomic techniques allowed the investigation of both somatic and germline mutations in each specific variant, paving the way for their possible classification according also to specific alterations, along with the canonical mutations of pancreatic cancer (KRAS, TP53, CDKN2A, SMAD4). In this review, we aim to report the current evidence about genetic/molecular profiles of pancreatic cancer variants, highlighting their role in therapeutic and clinical impact.

A Comprehensive Molecular Characterization of the Pancreatic Neuroendocrine Tumor Cell Lines BON-1 and QGP-1

Experimental models of neuroendocrine tumor disease are scarce, with only a few existing neuroendocrine tumor cell lines of pancreatic origin (panNET). Their molecular characterization has so far focused on the neuroendocrine phenotype and cancer-related mutations, while a transcription-based assessment of their developmental origin and malignant potential is lacking. In this study, we performed immunoblotting and qPCR analysis of neuroendocrine, epithelial, developmental endocrine-related genes as well as next-generation sequencing (NGS) analysis of microRNAs (miRs) on three panNET cell lines, BON-1, QGP-1, and NT-3. All three lines displayed a neuroendocrine and epithelial phenotype; however, while insulinoma-derived NT-3 cells preferentially expressed markers of mature functional pancreatic β-cells (i.e., INS, MAFA), both BON-1 and QGP-1 displayed high expression of genes associated with immature or non-functional β/δ-cells genes (i.e., NEUROG3), or pancreatic endocrine progenitors (i.e., FOXA2). NGS-based identification of miRs in BON-1 and QGP-1 cells revealed the presence of all six members of the miR-17–92 cluster, which have been implicated in β-cell function and differentiation, but also have roles in cancer being both oncogenic or tumor suppressive. Notably, both BON-1 and QGP-1 cells expressed several miRs known to be negatively associated with epithelial–mesenchymal transition, invasion or metastasis. Moreover, both cell lines failed to exhibit migratory activity in vitro. Taken together, NT-3 cells resemble mature functional β-cells, while both BON-1 and QGP-1 are more similar to immature/non-functional pancreatic β/δ-cells or pancreatic endocrine progenitors. Based on the recent identification of three transcriptional subtypes in panNETs, NT-3 cells resemble the “islet/insulinoma tumors” (IT) subtype, while BON-1 and QGP-1 cells were tentatively classified as “metastasis-like/primary” (MLP). Our results provide a comprehensive characterization of three panNET cell lines and demonstrate their relevance as neuroendocrine tumor models.

During mitosis ZEB1 "switches" from being a chromatin-bound epithelial gene repressor, to become a microtubule-associated protein

Microtubules are polymers of α/β-tubulin, with microtubule organization being regulated by microtubule-associated proteins (MAPs). Herein, we describe a novel role for the epithelial gene repressor, zinc finger E-box-binding homeobox 1 (ZEB1), that "switches" from a chromatin-associated protein during interphase, to a MAP that associates with α-, β- and γ-tubulin during mitosis. Additionally, ZEB1 was also demonstrated to associate with γ-tubulin at the microtubule organizing center (MTOC). Using confocal microscopy, ZEB1 localization was predominantly nuclear during interphase, with α/β-tubulin being primarily cytoplasmic and the association between these proteins being minimal. However, during the stages of mitosis, ZEB1 co-localization with α-, β-, and γ-tubulin was significantly increased, with the association commonly peaking during metaphase in multiple tumor cell-types. ZEB1 was also observed to accumulate in the cleavage furrow during cytokinesis. The increased interaction between ZEB1 and α-tubulin during mitosis was also confirmed using the proximity ligation assay. In contrast to ZEB1, its paralog ZEB2, was mainly perinuclear and cytoplasmic during interphase, showing some co-localization with α-tubulin during mitosis. Considering the association between ZEB1 with α/β/γ-tubulin during mitosis, studies investigated ZEB1's role in the cell cycle. Silencing ZEB1 resulted in a G₂-M arrest, which could be mediated by the up-regulation of p21^Waf1/Cip1 and p27^Kip1 that are known downstream targets repressed by ZEB1. However, it cannot be excluded the G₂/M arrest observed after ZEB1 silencing is not due to its roles as a MAP. Collectively, ZEB1 plays a role as a MAP during mitosis and could be functionally involved in this process.

Cutaneous Epithelial to Mesenchymal Transition Activator ZEB1 Regulates Wound Angiogenesis and Closure in a Glycemic Status-Dependent Manner

Epithelial to mesenchymal transition (EMT) and wound vascularization are two critical interrelated processes that enable cutaneous wound healing. Zinc finger E-box binding homeobox 1 (ZEB1), primarily studied in the context of tumor biology, is a potent EMT activator. ZEB1 is also known to contribute to endothelial cell survival as well as stimulate tumor angiogenesis. The role of ZEB1 in cutaneous wounds was assessed using Zeb1^+/- mice, as Zeb1^-/- mice are not viable. Quantitative stable isotope labeling by amino acids in cell culture (SILAC) proteomics was used to elucidate the effect of elevated ZEB1, as noted during hyperglycemia. Under different glycemic conditions, ZEB1 binding to E-cadherin promoter was investigated using chromatin immunoprecipitation. Cutaneous wounding resulted in loss of epithelial marker E-cadherin with concomitant gain of ZEB1. The dominant proteins downregulated after ZEB1 overexpression functionally represented adherens junction pathway. Zeb1^+/- mice exhibited compromised wound closure complicated by defective EMT and poor wound angiogenesis. Under hyperglycemic conditions, ZEB1 lost its ability to bind E-cadherin promoter. Keratinocyte E-cadherin, thus upregulated, resisted EMT required for wound healing. Diabetic wound healing was improved in ZEB^+/- as well as in db/db mice subjected to ZEB1 knockdown. This work recognizes ZEB1 as a key regulator of cutaneous wound healing that is of particular relevance to diabetic wound complication.

Ultraviolet A irradiation induces senescence in human dermal fibroblasts by down-regulating DNMT1 via ZEB1

In this study, we report the role of DNA methyltransferase 1 (DNMT1) in ultraviolet A (UVA)-induced senescence in human dermal fibroblasts (HDFs). We show that DNMT1 expression was significantly reduced during UVA-induced senescence, and this senescence could be alleviated or aggravated by the up- or down-regulation of DNMT1, respectively. Expression of the transcription factor zinc finger E-box binding homeobox 1(ZEB1) also decreased after UVA irradiation, following a UVA-induced increase of intracellular reactive oxygen species (ROS). We show that ZEB1 binds to the DMNT1 promoter and regulates its transcription, which, in turn, affects cellular senescence. These changes in DMNT1 and ZEB1 expression following UVA exposure were confirmed in matched skin specimens that had or had not been sun-exposed. On analyzing the promoter methylation of 24 senescence associated genes in these matched skin specimens, we discovered that p53 promoter methylation was significantly reduced in sun-exposed skin. In vitro experiments confirmed that UVA irradiation reduced p53 promoter methylation, and DNMT1 up-regulation could reverse this effect. Collectively, down-regulation of ZEB1 caused by UVA induced ROS could transcriptionally inhibit DNMT1, leading to low methylation level of senescence related proteins p53 and increase its expression, eventually result in cellar senescence.

Gemcitabine-induced epithelial-mesenchymal transition-like changes sustain chemoresistance of pancreatic cancer cells of mesenchymal-like phenotype

Growing body of evidence suggests that epithelial-mesenchymal transition (EMT) is a critical process in tumor progression and chemoresistance in pancreatic cancer (PC). The aim of this study was to analyze the role of EMT-like changes in acquisition of resistance to gemcitabine in pancreatic cells of the mesenchymal or epithelial phenotype. Therefore, chemoresistant BxPC-3, Capan-2, Panc-1, and MiaPaca-2 cells were selected by chronic exposure to increasing concentrations of gemcitabine. We show that gemcitabine-resistant Panc-1 and MiaPaca-2 cells of mesenchymal-like phenotype undergo further EMT-like molecular changes mediated by ERK-ZEB-1 pathway, and that inhibition of ERK1/2 phosphorylation or ZEB-1 expression resulted in a decrease in chemoresistance. Conversely, gemcitabine-resistant BxPC-3 and Capan-2 cells of epithelial-like phenotype did not show such typical EMT-like molecular changes although the expression of the tight junction marker occludin could be found decreased. In pancreatic cancer patients, high ZEB-1 expression was associated with tumor invasion and tumor budding. In addition, tumor budding was essentially observed in patients treated with neoadjuvant chemotherapy. These findings support the notion that gemcitabine treatment induces EMT-like changes that sustain invasion and chemoresistance in PC cells.

LncRNA XIST promotes pancreatic cancer migration, invasion and EMT by sponging miR-429 to modulate ZEB1 expression

Pancreatic cancer (PC) has become a worldwide malignancy accompanied by high metastasis and extremely poor prognosis. The critical roles of long non-coding RNAs (lncRNAs) in PC are generally summarized as molecular sponges of microRNAs (miRNAs). We intended to investigate the biological function and mechanism of lncRNA X-inactive specific transcript (XIST) in PC progression, especially in PC cell migration and invasion. qPCR was applied to detect the expression levels of XIST and miR-429 in PC tissues and cell lines. The roles of XIST and miR-429 on PC cell migration, invasion and epithelial-mesenchymal transition (EMT) were assessed by wound healing, transwell, qPCR and Western blot assays, respectively. The regulating relationship among XIST, miR-429 and zinc finger E-box binding homeobox 1 (ZEB1) was investigated in PC cells. XIST was frequently upregulated while miR-429 was commonly downregulated in PC tissues, especially in metastatic PC tissues. Knockdown of XIST in two PC cell lines caused inhibition of migration, invasion and EMT capacities. Forced expression of miR-429 exerted the similar tumor suppressing effects. XIST repressed miR-429 expression thus upregulated ZEB1, one of the targets of miR-429. ZEB1 mediated the tumor suppressing roles of XIST knockdown in PC cells. We identified the critical axis of XIST/miR-429/ZEB1 in PC cell migration, invasion and EMT, which may aid in developing new therapeutic strategies for PC.

ZEB1 and IL-6/11-STAT3 signalling cooperate to define invasive potential of pancreatic cancer cells via differential regulation of the expression of S100 proteins

Background

S100 proteins have been implicated in various aspects of cancer, including epithelial-mesenchymal transitions (EMT), invasion and metastasis, and also in inflammatory disorders. Here we examined the impact of individual members of this family on the invasion of pancreatic ductal adenocarcinoma (PDAC) cells, and their regulation by EMT and inflammation.

Methods

Invasion of PDAC cells was analysed in zebrafish embryo xenografts and in transwell invasion assays. Expression and regulation of S100 proteins was studied in vitro by immunoblotting, quantitative PCR and immunofluorescence, and in pancreatic lesions by immunohistochemistry.

Results

Whereas the expression of most S100 proteins is characteristic for epithelial PDAC cell lines, S100A4 and S100A6 are strongly expressed in mesenchymal cells and upregulated by ZEB1. S100A4/A6 and epithelial protein S100A14 respectively promote and represses cell invasion. IL-6/11-STAT3 pathway stimulates expression of most S100 proteins. ZEB1 synergises with IL-6/11-STAT3 to upregulate S100A4/A6, but nullifies the effect of inflammation on S100A14 expression.

Conclusion

EMT/ZEB1 and IL-6/11-STAT3 signalling act independently and congregate to establish the expression pattern of S100 proteins, which drives invasion. Although ZEB1 regulates expression of S100 family members, these effects are masked by IL-6/11-STAT3 signalling, and S100 proteins cannot be considered as bona fide EMT markers in PDAC.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

Expression of Epithelial-Mesenchymal Transition Markers in Treated Pancreatic Ductal Adenocarcinoma

OBJECTIVES

Epithelial-mesenchymal transition (EMT) plays an important role in the progression, metastasis, and chemoresistance of pancreatic duct adenocarcinoma (PDAC); however, the expression of EMT markers and their clinical significance in PDAC patients who received neoadjuvant therapy (NAT) are unclear.

METHODS

We examined the expression of EMT markers, including Zeb-1 (zinc finger E-box-binding homeobox 1), E-cadherin, and vimentin by immunohistochemistry in 120 PDAC patients who received NAT and pancreatectomy from 1999 to 2007. The results were correlated with clinicopathologic parameters and survival.

RESULTS

Among 120 cases, 45 (37.5%) and 14 (11.7%) were positive for Zeb-1 and vimentin, respectively, and 25 (20.8%) were E-cadherin-low. The median overall survival and disease-free survival were 35.3 (standard deviation [SD], 2.8) and 15.9 (SD, 3.6) months, respectively, in vimentin-negative group compared with 16.1 (SD, 1.1) (P = 0.03) and 7.0 (SD, 1.1) months (P = 0.02) in the vimentin-positive group. In multivariate analysis, vimentin expression was an independent predictor of shorter disease-free survival (hazard ratio, 2.50; 95% confidence interval, 1.31-4.78; P = 0.016) and overall survival (hazard ratio, 2.55; 95% confidence interval, 1.33-4.89; P = 0.01).

CONCLUSIONS

Epithelial-mesenchymal transition markers are frequently expressed in treated PDAC. Vimentin expression is a prognostic biomarker for survival in PDAC patients who received NAT.

Pancreatic cancer chemo-resistance is driven by tumor phenotype rather than tumor genotype

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the deadliest forms of cancer. A major reason for this situation is the fact that these tumors are already resistant or become rapidly resistant to all conventional therapies. Like any transformation process, initiation and development of PDCA are driven by a well known panel of genetic alterations, few of them are shared with most cancers, but many mutations are specific to PDAC and are partially responsible for the great inter-tumor heterogeneity. Importantly, this knowledge has been inefficient in predicting response to anticancer therapy, or in establishing diagnosis and prognosis. Hence, the pre-existing or rapidly acquired resistance of pancreatic cancer cells to therapeutic drugs rely on other parameters and features developed by the cells and/or the micro-environment, that are independent of their genetic profiles. This review sheds light on all major phenotypic, non genetic, alterations known to play important roles in PDAC cells resistance to treatments and therapeutic escape.

Zeb1 in Stromal Myofibroblasts Promotes Kras-Driven Development of Pancreatic Cancer

The transcription factor Zeb1 has been identified as a crucial player in Kras-dependent oncogenesis. In pancreatic ductal adenocarcinoma (PDAC), Zeb1 is highly expressed in myofibroblasts and correlates with poor prognosis. As Kras mutations are key drivers in PDAC, we aimed here to assess the necessity of Zeb1 for Kras-driven PDAC and to define the role of Zeb1-expressing myofibroblasts in PDAC development. Genetically engineered mice with conditional pancreatic Kras^G12D and Trp53 mutations (KPC) were crossed with Zeb1 haploinsufficient mice (Z^+/-). Extensive PDAC was prominent in all 20-week-old KPC;Z^+/+ mice, whereas only low-grade precursor lesions were detected in age-matched KPC;Z^+/- littermates, with PDAC developing eventually in KPC;Z^+/- aged animals. Zeb1 expression in myofibroblasts occurred early in tumorigenesis and Zeb1 haploinsufficiency retarded native expansion of stromal myofibroblasts during precursor-to-cancer progression. Zeb1 downregulation in mPSC repressed their activated gene profile, impaired their migratory and proliferative activity, and attenuated their tumor-supporting features. Conditioned media from Z^+/+ mouse-activated (myofibroblast-like) pancreatic stellate cells (mPSC) boosted Ras activity in pancreatic cancer cells carrying mutant Kras; this effect was not observed when using conditioned media from Z^+/- mPSC, revealing a paracrinal cooperative axis between Zeb1-expressing PSC and oncogenic Kras-bearing tumor cells. We conclude that Zeb1-expressing stromal myofibroblasts enable a heterotypic collaboration with the Kras-fated epithelial compartment, thus supporting pancreatic malignancy.Significance: Zeb1 expression in stromal myofibroblasts supports PDAC development via collaboration with the epithelial compartment bearing oncogenic Kras mutations. Cancer Res; 78(10); 2624-37. ©2018 AACR.

Prognostic significance of E-cadherin and ZEB1 expression in intraductal papillary mucinous neoplasm

There is an urgent need to investigate the genetic changes that occur in intraductal papillary mucinous neoplasm (IPMN), which is a well-known precursor of pancreatic cancer. In this study, gene expression profiling was performed by removing unwanted variation to determine the differentially expressed genes (DEGs) associated with malignant progression of IPMN. Among the identified DEGs, zinc finger E-box binding homeobox 1 (ZEB1) and E-cadherin, a crucial regulator of epithelial-to-mesenchymal transition (EMT), was validated among identified DEGs.

A total of 76 fresh-frozen tissues were used for gene expression profiling and formalin-fixed, paraffin-embedded blocks from 87 patients were obtained for immunohistochemical analysis. Loss of E-cadherin expression (p = 0.023, odd ratio [OR] = 4.923) and expression of ZEB1 in stromal cells (stromal ZEB1, p < 0.001, OR = 26.800) were significantly correlated with degree of dysplasia. The hazard of death was significantly increased in patients with loss of E-cadherin expression (hazard ratio [HR] = 13.718, p = 0.004), expression of epithelial ZEB1 (HR = 19.117, p = 0.001), and stromal ZEB1 (HR = 6.373, p = 0.043).

Based on the results of this study, loss of E-cadherin and expression of stromal ZEB1 are associated with increased risk of malignant progression. Epithelial and stromal ZEB1, as well as E-cadherin may be strong predictors of survival in patients with IPMN. Our finding suggests that these EMT markers may be utilized as potential prognosticators and may be used to improve and personalize treatment of IPMN.

ZEB1 confers stem cell-like properties in breast cancer by targeting neurogenin-3

Cancer stem cells (CSCs) are a subpopulation of cancer cells believed to be implicated in cancer initiation, progression, and recurrence. Here, we report that ectopic expression of zinc finger E-box binding homeobox 1 protein (ZEB1) results in the acquisition of CSC properties by breast cancer cells, leading to tumor initiation and progression in vitro and in vivo. The neurogenin 3 gene (Ngn3) is a bona fide target of ZEB1, and its repression is a key factor contributing to ZEB1-induced cancer cell stemness. ZEB1 suppressed Ngn3 transcription by forming a ZEB1/DNA methyltransferase (DNMT)3B/histone deacetylase 1 (HDAC1) complex on the Ngn3 promoter, leading to promoter hypermethylation and gene silencing. The rescue of Ngn3 expression attenuated ZEB1-induced cancer stemness and symmetric CSC division. Immunohistological analysis of human breast cancer specimens revealed a strong inverse relationship between ZEB1 and NGN3 protein expression. Thus, our findings suggest ZEB1-mediated silencing of Ngn3 is required for breast tumor initiation and maintenance. Targeted therapies against the ZEB1/Ngn3 axis may be highly valuable for the prevention and treatment of breast cancer.

Epithelial/mesenchymal plasticity: how have quantitative mathematical models helped improve our understanding?

Phenotypic plasticity, the ability of cells to reversibly alter their phenotypes in response to signals, presents a significant clinical challenge to treating solid tumors. Tumor cells utilize phenotypic plasticity to evade therapies, metastasize, and colonize distant organs. As a result, phenotypic plasticity can accelerate tumor progression. A well‐studied example of phenotypic plasticity is the bidirectional conversions among epithelial, mesenchymal, and hybrid epithelial/mesenchymal (E/M) phenotype(s). These conversions can alter a repertoire of cellular traits associated with multiple hallmarks of cancer, such as metabolism, immune evasion, invasion, and metastasis. To tackle the complexity and heterogeneity of these transitions, mathematical models have been developed that seek to capture the experimentally verified molecular mechanisms and act as ‘hypothesis‐generating machines’. Here, we discuss how these quantitative mathematical models have helped us explain existing experimental data, guided further experiments, and provided an improved conceptual framework for understanding how multiple intracellular and extracellular signals can drive E/M plasticity at both the single‐cell and population levels. We also discuss the implications of this plasticity in driving multiple aggressive facets of tumor progression.

Clinicopathological significance of ZEB-1 and E-cadherin proteins in patients with oral cavity squamous cell carcinoma

Background

Zinc-finger E-box binding homeobox 1 (ZEB-1), a member of the ZFH family, plays a key role in epithelial–mesenchymal transition during tumor progression in various cancers. However, little information is available on ZEB-1 expression in oral cavity squamous cell carcinoma (OSCC).

Methods

The expression levels of ZEB-1 and E-cadherin were assessed by immunohistochemistry in a cohort of 120 patients with OSCC treated by curative operation, and then the correlations between ZEB-1 and E-cadherin expression and clinical factors were evaluated, including patient prognosis. Quantitative real-time polymerase chain reaction (qRT-PCR) assays were performed to assess mRNA levels of ZEB-1 and E-cadherin in 20 matched OSCC specimens.

Results

Patients were followed up for a median period of 66 months (range 8−116 months), and 5-year overall survival was 68.3%. Positive ZEB-1 and E-cadherin immunostaining reactivity was detected in 64 (53.3%) and 53 (44.2%) patients, respectively. There was a negative correlation between ZEB-1 expression and E-cadherin expression. In addition, overexpression of ZEB-1 was significantly associated with recurrence, lymph node metastasis, and pathologic grading of patients, loss of E-cadherin was significantly associated with lymph node metastasis and pathologic grading of patients. Univariate analysis showed that increased ZEB-1 expression, loss of E-cadherin expression, lymph node metastasis, recurrence, and pathology grade were prognostic factors. In multivariate analysis, increased ZEB-1 expression and recurrence remained independent prognostic factors. In particular, patients with both ZEB-1 positivity and loss of E-cadherin expression had a poorer prognosis. qRT-PCR showed that ZEB-1 mRNA expression was higher in OSCC compared to the adjacent nontumorous tissues, while E-cadherin mRNA expression was lower in tumor tissues.

Conclusion

This study shows that overexpression of ZEB-1 and loss of E-cadherin expression are significantly correlated with poor survival in OSCC patients, and ZEB-1 expression might serve as an independent prognostic biomarker of OSCC.

EMT and stemness: flexible processes tuned by alternative splicing in development and cancer progression

Epithelial-to-mesenchymal transition (EMT) is associated with metastasis formation as well as with generation and maintenance of cancer stem cells. In this way, EMT contributes to tumor invasion, heterogeneity and chemoresistance. Morphological and functional changes involved in these processes require robust reprogramming of gene expression, which is only partially accomplished at the transcriptional level. Alternative splicing is another essential layer of gene expression regulation that expands the cell proteome. This step in post-transcriptional regulation of gene expression tightly controls cell identity between epithelial and mesenchymal states and during stem cell differentiation. Importantly, dysregulation of splicing factor function and cancer-specific splicing isoform expression frequently occurs in human tumors, suggesting the importance of alternative splicing regulation for cancer biology.

In this review, we briefly discuss the role of EMT programs in development, stem cell differentiation and cancer progression. Next, we focus on selected examples of key factors involved in EMT and stem cell differentiation that are regulated post-transcriptionally through alternative splicing mechanisms. Lastly, we describe relevant oncogenic splice-variants that directly orchestrate cancer stem cell biology and tumor EMT, which may be envisioned as novel targets for therapeutic intervention.

African Americans with pancreatic ductal adenocarcinoma exhibit gender differences in Kaiso expression

Kaiso, a bi-modal transcription factor, regulates gene expression, and is elevated in breast, prostate, and colon cancers. Depletion of Kaiso in other cancer types leads to a reduction in markers for the epithelial-mesenchymal transition (EMT) (Jones et al., 2014), however its clinical implications in pancreatic ductal adenocarcinoma (PDCA) have not been widely explored. PDCA is rarely detected at an early stage but is characterized by rapid progression and invasiveness. We now report the significance of the subcellular localization of Kaiso in PDCAs from African Americans. Kaiso expression is higher in the cytoplasm of invasive and metastatic pancreatic cancers. In males, cytoplasmic expression of Kaiso correlates with cancer grade and lymph node positivity. In male and female patients, cytoplasmic Kaiso expression correlates with invasiveness. Also, nuclear expression of Kaiso increases with increased invasiveness and lymph node positivity. Further, analysis of the largest PDCA dataset available on ONCOMINE shows that as Kaiso increases, there is an overall increase in Zeb1, which is the inverse for E-cadherin. Hence, these findings suggest a role for Kaiso in the progression of PDCAs, involving the EMT markers, E-cadherin and Zeb1.

The miRacle in Pancreatic Cancer by miRNAs: Tiny Angels or Devils in Disease Progression

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with increasing incidence and high mortality. Surgical resection is the only potentially curative treatment of patients with PDAC. Because of the late presentation of the disease, about 20 percent of patients are candidates for this treatment. The average survival of resected patients is between 12 and 20 months, with a high probability of relapse. Standard chemo and radiation therapies do not offer significant improvement of the survival of these patients. Furthermore, novel treatment options aimed at targeting oncogenes or growth factors in pancreatic cancer have proved unsuccessful. Thereby, identifying new biomarkers that can detect early stages of this disease is of critical importance. Among these biomarkers, microRNAs (miRNAs) have supplied a profitable recourse and become an attractive focus of research in PDAC. MiRNAs regulate many genes involved in the development of PDAC through mRNA degradation or translation inhibition. The possibility of intervention in the molecular mechanisms of miRNAs regulation could begin a new generation of PDAC therapies. This review summarizes the reports describing miRNAs involvement in cellular processes involving pancreatic carcinogenesis and their utility in diagnosis, survival and therapeutic potential in pancreatic cancer.

β-III tubulin modulates the behavior of Snail overexpressed during the epithelial-to-mesenchymal transition in colon cancer cells

Class III β-tubulin (TUBB3) is a marker of drug resistance expressed in a variety of solid tumors. Originally, it was described as an important element of chemoresistance to taxanes. Recent studies have revealed that TUBB3 is also involved in an adaptive response to a microenvironmental stressor, e.g. low oxygen levels and poor nutrient supply in some solid tumors, independently of the microtubule targeting agent. Furthermore, it has been demonstrated that TUBB3 is a marker of biological aggressiveness associated with modulation of metastatic abilities in colon cancer. The epithelial-to-mesenchymal transition (EMT) is a basic cellular process by which epithelial cells lose their epithelial behavior and become invasive cells involved in cancer metastasis. Snail is a zinc-finger transcription factor which is able to induce EMT through the repression of E-cadherin expression. In the presented studies we focused on the analysis of the TUBB3 role in EMT-induced colon adenocarcinoma cell lines HT-29 and LS180. We observed a positive correlation between Snail presence and TUBB3 upregulation in tested adenocarcinoma cell lines. The cellular and behavioral analysis revealed for the first time that elevated TUBB3 level is functionally linked to increased cell migration and invasive capability of EMT induced cells. Additionally, the post-transcriptional modifications (phosphorylation, glycosylation) appear to regulate the cellular localization of TUBB3 and its phosphorylation, observed in cytoskeleton, is probably involved in cell motility modulation.

ZEB1: at the crossroads of epithelial-mesenchymal transition, metastasis and therapy resistance

Zinc finger E-box binding homeobox 1 (ZEB1) is a transcription factor that promotes tumor invasion and metastasis by inducing epithelial-mesenchymal transition (EMT) in carcinoma cells. EMT not only plays an important role in embryonic development and malignant progression, but is also implicated in cancer therapy resistance. It has been hypothesized that carcinoma cells that have undergone EMT acquire cancer stem cell properties including self-renewal, chemoresistance and radioresistance. However, our recent data indicate that ZEB1 regulates radioresistance in breast cancer cells through an EMT-independent mechanism. In this Perspective, we review different mechanisms by which ZEB1 regulates tumor progression and treatment resistance. Based on studies by us and others, we propose that it is specific EMT inducers like ZEB1, but not the epithelial or mesenchymal state itself, that dictate cancer stem cell properties.

Expression of zinc finger E-box-binding homeobox factor 1 in epithelial ovarian cancer: A clinicopathological analysis of 238 patients

A growing body of evidence indicates that aberrant activation of epithelial-to-mesenchymal transition (EMT) plays a key role in tumor cell invasion and metastasis. Zinc finger E-box-binding homeobox factor 1 (ZEB1), as a crucial mediator of EMT, contributes to the malignant progression of various epithelial tumors. To determine whether ZEB1 is involved in the progression of ovarian cancer, we immunohistochemically evaluated the expression of ZEB1 in 238 cases of epithelial ovarian cancer (EOC) and analyzed its associations with clinicopathological parameters. Positive expression of ZEB1 was observed in 32.8% (78/238) of EOCs and it was found to be significantly associated with advanced tumor stage (P=0.001). The survival analysis indicated that the expression of ZEB1 was associated with a poor 5-year progression-free survival (PFS) (P=0.021). A similar tendency was also observed between the expression of ZEB1 and 5-year overall survival, although it did not reach statistical significance (P=0.118). Moreover, the multivariate analysis demonstrated that ZEB1 expression was an independent risk factor for 5-year PFS in ovarian cancer. Taken together, our data provide evidence that ZEB1 may play a crucial role in promoting aggressive ovarian carcinoma progression. Therefore, ZEB1 may serve as an effectively predictive marker and a potential target for therapeutic intervention in EOC.

Pancreatic cancer stem cells: Advances and perspectives

The evolution of certain types of malignancies including pancreatic carcinoma, as verified in mountains of literature published since the 1970s, is due in great measure to cancer stem cells located within the hierarchically organized tumor structure. However, by now, the results of numerous attempts to relate cancer stem cell theory to malignant biological behavior of cancers have appeared rather discouraging in terms of explaining and overcoming tumor heterogeneity in both in vitro and in vivo conditions. In seeking to describe the cancer stem cells in pancreatic adenocarcinoma, in the current editorial, we rely primarily on the existing evidence to gain a comprehensive perspective toward this area.

Pancreatic cancer stem cells

Studies are emerging in support of the cancer stem cells (CSCs) theory which considers that a tiny subset of cancer cells is exclusively responsible for the initiation and malignant behavior of a cancer. This cell population, also termed CSCs, possesses the capacity both to self-renew, producing progeny that have the identical tumorigenic potential, and to differentiate into the bulk of cancer cells, helping serve the formation of the tumor entities, which, altogether, build the hierarchically organized structure of a cancer. In this review, we try to articulate the complicated signaling pathways regulating the retention of the characteristics of pancreatic CSCs, and in the wake of which, we seek to offer insights into the CSCs-relevant targeted therapeutics which are, in the meantime, confronted with bigger challenges than ever.

Retinoblastoma protein determines aggressiveness in triple-negative breast cancer

Retinoblastoma protein (RB) is one of the most important tumor suppressors and functions in multiple biological pathways that are deregulated during tumor initiation and progression. Epithelial-to-mesenchymal transition (EMT) is a reversible embryonic process by which epithelial cells lose cell-cell contact and polarity, and its aberrant activation can trigger tumor progression and metastasis. Previously, it has been shown that depletion of RB initiates EMT by downregulating the adhesion molecule E-cadherin. The evaluated article suggests that RB inactivation contributes to loss of cell cycle control and also leads to downregulation of the miR-200 family, thereby causing upregulation of ZEB expression and consequently EMT by downregulation of E-cadherin. RB inactivation could be a key event underlying the mesenchymal and aggressive phenotype of triple-negative breast cancer. Furthermore, exploring links between RB inactivation and EMT might reveal new therapeutic targets for triple-negative breast cancer.

Epithelial-mesenchymal transition in pancreatic carcinoma

Pancreatic carcinoma is the fourth-leading cause of cancer death and is characterized by early invasion and metastasis. The developmental program of epithelial-mesenchymal transition (EMT) is of potential importance for this rapid tumor progression. During EMT, tumor cells lose their epithelial characteristics and gain properties of mesenchymal cells, such as enhanced motility and invasive features. This review will discuss recent findings pertinent to EMT in pancreatic carcinoma. Evidence for and molecular characteristics of EMT in pancreatic carcinoma will be outlined, as well as the connection of EMT to related topics, e.g., cancer stem cells and drug resistance.