deltaEF1 repressor controls selectively p53 family members during differentiation

miR-200b-3p relieved inflammation in patients with heart failure by regulating ZEB1 expression

BACKGROUND

MicroRNA-200b-3p (miR-200b-3p) plays a pivotal role in inflammatory responses and is implicated in various inflammatory disorders. In this study, we aim to explore the role of miR-200b-3p in the inflammatory response in heart failure (HF).

METHODS

Patients diagnosed with heart failure and age-matched healthy controls were studied. Peripheral blood samples from participants were collected for RNA-seq analysis to explore the expression profile of miR-200b-3p. The predictive value of miR-200b-3p and ZEB1 in the prognosis of heart failure was evaluated by analyzing the receiver operating characteristic (ROC) curve. Bioinformatics analysis and double luciferase reporter gene analysis were used to confirm the interaction between miR-200b-3p and ZEB1. Real-time quantitative polymerase chain reaction (QRT-PCR) was used to detect the expression levels of miR-200b-3p and ZEB1 in cardiopulmonary bypass. Additionally, the effects of miR-200b-3p on myocardial cell line (H9c2) injury were evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the extracardiac circulation of HF patients, miR-200b-3p expression was significantly reduced, while ZEB1 levels were notably elevated. Analysis of the ROC curve revealed that miR-200b-3p and ZEB1 have predictive value in the prognosis of HF patients. The double luciferase reporter experiment demonstrated that miR-200b-3p binds to ZEB1 and inhibits its expression. Overexpression of miR-200b-3p demonstrated a remarkable ability to alleviate inflammation and inhibit the damage to myocardial cells in vivo.

CONCLUSION

MiR-200b-3p can target and inhibit ZEB1, reducing the inflammatory reaction of myocardial cells. The miR-200b-3p/ZEB1 network may be helpful in preventing and treating HF.

Mutual regulation of TGFβ-induced oncogenic EMT, cell cycle progression and the DDR

TGFβ signaling and the DNA damage response (DDR) are two cellular toolboxes with a strong impact on cancer biology. While TGFβ as a pleiotropic cytokine affects essentially all hallmarks of cancer, the multifunctional DDR mostly orchestrates cell cycle progression, DNA repair, chromatin remodeling and cell death. One oncogenic effect of TGFβ is the partial activation of epithelial-to-mesenchymal transition (EMT), conferring invasiveness, cellular plasticity and resistance to various noxae. Several reports show that both individual networks as well as their interface affect chemo-/radiotherapies. However, the underlying mechanisms remain poorly resolved. EMT often correlates with TGFβ-induced slowing of proliferation, yet numerous studies demonstrate that particularly the co-activated EMT transcription factors counteract anti-proliferative signaling in a partially non-redundant manner. Collectively, evidence piled up over decades underscore a multifaceted, reciprocal inter-connection of TGFβ signaling / EMT with the DDR / cell cycle progression, which we will discuss here. Altogether, we conclude that full cell cycle arrest is barely compatible with the propagation of oncogenic EMT traits and further propose that 'EMT-linked DDR plasticity' is a crucial, yet intricate facet of malignancy, decisively affecting metastasis formation and therapy resistance.

The role of the ZEB1–neuroinflammation axis in CNS disorders

Zinc finger E-box binding homeobox 1 (ZEB1) is a master modulator of the epithelial–mesenchymal transition (EMT), a process whereby epithelial cells undergo a series of molecular changes and express certain characteristics of mesenchymal cells. ZEB1, in association with other EMT transcription factors, promotes neuroinflammation through changes in the production of inflammatory mediators, the morphology and function of immune cells, and multiple signaling pathways that mediate the inflammatory response. The ZEB1–neuroinflammation axis plays a pivotal role in the pathogenesis of different CNS disorders, such as brain tumors, multiple sclerosis, cerebrovascular diseases, and neuropathic pain, by promoting tumor cell proliferation and invasiveness, formation of the hostile inflammatory micromilieu surrounding neuronal tissues, dysfunction of microglia and astrocytes, impairment of angiogenesis, and dysfunction of the blood–brain barrier. Future studies are needed to elucidate whether the ZEB1–neuroinflammation axis could serve as a diagnostic, prognostic, and/or therapeutic target for CNS disorders.

Epithelial-Mesenchymal Transition Associated with Head and Neck Squamous Cell Carcinomas: A Review

Head and neck squamous cell carcinomas (HNSCCs) are aggressive, recurrent, and metastatic neoplasms with a high occurrence around the world and can lead to death when not treated appropriately. Several molecules and signaling pathways are involved in the malignant conversion process. Epithelial-mesenchymal transition (EMT) has been described in HNSCCs, a major type of aggressive carcinoma. EMT describes the development of epithelial cells into mesenchymal cells, which depends on several molecular interactions and signaling pathways that facilitate mesenchymal conversion. This is related to interactions with the microenvironment of the tumor, hypoxia, growth factors, matrix metalloproteinases, and the presence of viral infections. In this review, we focus on the main molecules related to EMT, their interactions with the tumor microenvironment, plasticity phenomena, epigenetic regulation, hypoxia, inflammation, their relationship with immune cells, and the inhibition of EMT in the context of HNSCCs.

The foggy world(s) of p63 isoform regulation in normal cells and cancer

The p53 family member p63 exists as two major protein variants (TAp63 and ΔNp63) with distinct expression patterns and functional properties. Whilst downstream target genes of p63 have been studied intensively, how p63 variants are themselves controlled has been relatively neglected. Here, we review advances in understanding ΔNp63 and TAp63 regulation, highlighting their distinct pathways. TAp63 has roles in senescence and metabolism, and in germ cell genome maintenance, where it is activated post-transcriptionally by phosphorylation cascades after DNA damage. The function and regulation of TAp63 in mesenchymal and haematopoietic cells is less clear but may involve epigenetic control through DNA methylation. ΔNp63 functions to maintain stem/progenitor cells in various epithelia and is overexpressed in squamous and certain other cancers. ΔNp63 is transcriptionally regulated through multiple enhancers in concert with chromatin modifying proteins. Many signalling pathways including growth factors, morphogens, inflammation, and the extracellular matrix influence ΔNp63 levels, with inconsistent results reported. There is also evidence for reciprocal regulation, including ΔNp63 activating its own transcription. ΔNp63 is downregulated during cell differentiation through transcriptional regulation, while post-transcriptional events cause proteasomal degradation. Throughout the review, we identify knowledge gaps and highlight discordances, providing potential explanations including cell-context and cell-matrix interactions. Identifying individual p63 variants has roles in differential diagnosis and prognosis, and understanding their regulation suggests clinically approved agents for targeting p63 that may be useful combination therapies for selected cancer patients. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

MiR-326 mediates malignant biological behaviors of lung adenocarcinoma by targeting ZEB1

MiR-326 functions as an antioncogene in the several types of cancer. However, the underling mechanisms through which miRNA-326 regulates the anti-carcinogenesis of lung adenocarcinoma have remained elusive. The aim of this study was to explore the role and regulatory mechanism of miR-326 in cell proliferation, invasion, migration and apoptosis in lung adenocarcinoma. Quantitative real-time PCR (qRT-PCR) was used to detect the expression pattern of miR-326 in human bronchial epithelial cells (HBES-2B), 4 kinds of lung adenocarcinoma cell lines (H23, H1975, H2228, H2085) and 20 lung adenocarcinoma tissues. Then, H23 cells were infected with miR-326 mimics, miR-326 inhibitors and si-ZEB1 to build up-regulated miR-326 cell lines, down-regulated ZEB1(zinc-finger-enhancer binding protein 1)cell lines, simultaneous down-regulated ZEB1 and miR-326 cell lines. Moreover, CCK-8 assay, transwell invasion assay, wound healing assay and flow cytometry assay were employed to examine the effects of miR-326 and ZEB1 on the proliferation, invasion, migration and apoptosis abilities of H23 cells. Western blot was performed to explore the effects of miR-326 and ZEB1 on the expression of invasion and migration related proteins N-cadherin, E-cadherin, MMP7, MMP13, SLUG and apoptotic proteins PARP, BAX. On the mechanism, a dual-luciferase reporter gene was used to measure the target relationship between miR-326 and ZEB1. MiR-326 expression was significantly downregulated in lung adenocarcinoma tissues and cells. Overexpression of miR-326 significantly inhibited the malignant behaviors of H23 cells. Mechanically, luciferase reporter assay showed that ZEB1 was a direct target of miR-326. MiR-326 mimic downregulated the expression of ZEB1. Furthermore, knocking down ZEB1 strongly inhibited the proliferation, invasion and migration of H23 cells but promoted apoptosis. MiR-326 could target ZEB1 to inhibit the proliferation, invasion and migration of lung adenocarcinoma cells and promote apoptosis, which is a potential therapeutic target for lung adenocarcinoma.

Pleiotropic Roles for ZEB1 in Cancer

ZEB1 is a prime element of a network of transcription factors that controls epithelial-to-mesenchymal transition (EMT), a reversible embryonic transdifferentiation program that allows partial or complete transition from an epithelial to a mesenchymal state. Aberrant expression of ZEB1 has been reported in a variety of human cancers, where it is generally believed to foster migration, invasion, and metastasis. Over the past few years, in vitro and in vivo observations have highlighted unsuspected intrinsic oncogenic functions of ZEB1 that impact tumorigenesis from its earliest stages. Located downstream of regulatory processes that integrate microenvironmental signals and directly implicated in feedback loops controlled by miRNAs, ZEB1 appears to be a central switch that determines cell fate. Its expression fosters malignant transformation through the mitigation of critical oncosuppressive pathways and through the conferment of stemness properties. ZEB1 is also a key determinant of cell plasticity, endowing cells with the capacity to withstand an aberrant mitogenic activity, with a profound impact on the genetic history of tumorigenesis, and to adapt to the multiple constraints encountered over the course of tumor development. Cancer Res; 78(1); 30-35. ©2017 AACR.

Prognostic significance of ZEB1 and ZEB2 in digestive cancers: a cohort-based analysis and secondary analysis

BACKGROUND

Digestive cancers are common malignancies worldwide, however there are few effective prognostic markers available. In this study we comprehensively investigated the prognostic significance of ZEB1 and ZEB2 in digestive cancers.

METHODS

Electronic databases were searched and studies met the selection criteria were included. Study information was recorded and quality assessment was performed according to the REMARK guideline. Hazard ratios and its corresponding 95% confidence intervals were extracted and pooled. Sensitivity analyses, subgroup analyses, cumulative meta-analyses and secondary analyses were also performed to increase the stability and reliability of our results.

RESULTS

24 cohort studies were included in the study. High ZEB1 and ZEB2 levels predicted poor overall survival, meanwhile high ZEB2 levels predicted poor disease free survival for digestive cancer patients. From subgroup analyses we observed ZEB1 was found to be significantly associated with poor overall survival for patients with pancreatic cancer, gastric cancer and colorectal cancer, while ZEB2 was found to be significantly associated with poor overall survival for patients with hepatocellular carcinoma and gastric cancer. Furthermore, by conducting secondary analyses we confirmed both ZEB1 and ZEB2 played important roles in gastric cancer prediction. In addition, we found high ZEB1 and ZEB2 expression were significantly associated with depth of invasion, lymph node metastasis and TNM stage in digestive cancer patients.

CONCLUSIONS

The present study validated the prognostic value and clinicopathological association of ZEB1 and ZEB2 in digestive cancers, especially in gastric cancer.

Multiple functions of p21 in cell cycle, apoptosis and transcriptional regulation after DNA damage

An appropriate control over cell cycle progression depends on many factors. Cyclin-dependent kinase (CDK) inhibitor p21 (also known as p21(WAF1/Cip1)) is one of these factors that promote cell cycle arrest in response to a variety of stimuli. The inhibitory effect of P21 on cell cycle progression correlates with its nuclear localization. P21 can be induced by both p53-dependent and p53-independent mechanisms. Some other important functions attributed to p21 include transcriptional regulation, modulation or inhibition of apoptosis. These functions are largely dependent on direct p21/protein interactions and also on p21 subcellular localizations. In addition, p21 can play a role in DNA repair by interacting with proliferating cell nuclear antigen (PCNA). In this review, we will focus on the multiple functions of p21 in cell cycle regulation, apoptosis and gene transcription after DNA damage and briefly discuss the pathways and factors that have critical roles in p21 expression and activity.

Transforming growth factor β1 antagonizes the transcription, expression and vascular signaling of guanylyl cyclase/natriuretic peptide receptor A - role of δEF1

The objective of this study was to determine the role of transforming growth factor β1 (TGF-β1) in transcriptional regulation and function of the guanylyl cyclase A/natriuretic peptide receptor A gene (Npr1) and whether cross-talk exists between these two hormonal systems in target cells. After treatment of primary cultured rat thoracic aortic vascular smooth muscle cells and mouse mesangial cells with TGF-β1, the Npr1 promoter construct containing a δ-crystallin enhancer binding factor 1 (δEF1) site showed 85% reduction in luciferase activity in a time- and dose-dependent manner. TGF-β1 also significantly attenuated luciferase activity of the Npr1 promoter by 62%, and decreased atrial natriuretic peptide-mediated relaxation of mouse denuded aortic rings ex vivo. Treatment of cells with TGF-β1 increased the protein levels of δEF1 by 2.4-2.8-fold, and also significantly enhanced the phosphorylation of Smad 2/3, but markedly reduced Npr1 mRNA and receptor protein levels. Over-expression of δEF1 showed a reduction in Npr1 promoter activity by 75%, while deletion or site-directed mutagenesis of δEF1 sites in the Npr1 promoter eliminated the TGF-β1-mediated repression of Npr1 transcription. TGF-β1 significantly increased the expression of α-smooth muscle actin and collagen type I α2 in rat thoracic aortic vascular smooth muscle cells, which was markedly attenuated by atrial natriuretic peptide in cells over-expressing natriuretic peptide receptor A. Together, the present results suggest that an antagonistic cascade exists between the TGF-β1/Smad/δEF1 pathways and Npr1 expression and receptor signaling that is relevant to renal and vascular remodeling, and may be critical in the regulation of blood pressure and cardiovascular homeostasis.

Zeb2: A multifunctional regulator of nervous system development

Zinc finger E-box binding homeobox (Zeb) 2 is a transcription factor, identified due its ability to bind Smad proteins, and consists of multiple functional domains which interact with a variety of transcriptional co-effectors. The complex nature of the Zeb2, both at its genetic and protein levels, underlie its multifunctional properties, with Zeb2 capable of acting individually or as part of a transcriptional complex to repress, and occasionally activate, target gene expression. This review introduces Zeb2 as an essential regulator of nervous system development. Zeb2 is expressed in the nervous system throughout its development, indicating its importance in neurogenic and gliogenic processes. Indeed, mutation of Zeb2 has dramatic neurological consequences both in animal models, and in humans with Mowat-Wilson syndrome, which results from heterozygous ZEB2 mutations. The mechanisms by which Zeb2 regulates the induction of the neuroectoderm (CNS primordium) and the neural crest (PNS primordium) are reviewed herein. We then describe how Zeb2 acts to direct the formation, delamination, migration and specification of neural crest cells. Zeb2 regulation of the development of a number of cerebral regions, including the neocortex and hippocampus, are then described. The diverse molecular mechanisms mediating Zeb2-directed development of various neuronal and glial populations are reviewed. The role of Zeb2 in spinal cord and enteric nervous system development is outlined, while its essential function in CNS myelination is also described. Finally, this review discusses how the neurodevelopmental defects of Zeb2 mutant mice delineate the developmental dysfunctions underpinning the multiple neurological defects observed in Mowat-Wilson syndrome patients.

Pathway Regulation of p63, a Director of Epithelial Cell Fate

The p53-related gene p63 is required for epithelial cell establishment and its expression is often altered in tumor cells. Great strides have been made in understanding the pathways and mechanisms that regulate p63 levels, such as the Wnt, Hedgehog, Notch, and EGFR pathways. We discuss here the multiple signaling pathways that control p63 expression as well as transcription factors and post-transcriptional mechanisms that regulate p63 levels. While a unified picture has not emerged, it is clear that the fine-tuning of p63 has evolved to carefully control epithelial cell differentiation and fate.

EVI1 targets ΔNp63 and upregulates the cyclin dependent kinase inhibitor p21 independent of p53 to delay cell cycle progression and cell proliferation in colon cancer cells

Several lines of evidence suggest that specific transcriptional events are involved in cell cycle, proliferation and differentiation processes; however, their deregulation by proto-oncogenes are involved in the development of leukemia and tumors. One such proto-oncogene is ecotropic viral integration site I which can differentially effect cell cycle progression and proliferation, in cell types of different origin. Our data for the first time shows that ecotropic viral integration site I binds to ΔNp63 promoter element directly and down regulates its expression. Down regulation of ΔNp63 induces the expression of p21 in HT-29 cells and also in colon carcinoma cells that do not express p53 including patient samples expressing low level of p53, that eventually delay cell cycle progression at G0/G1 phase. Concomitant silencing of ecotropic viral integration site I from the cells or introduction of ΔNp63 to the cells significantly rescued this phenotype, indicating the growth defect induced by ΔNp63 deficiency to be, at least in part, attributable to ecotropic viral integration site I function. The mutual regulation between ecotropic viral integration site I and ΔNp63 may constitute a novel axis which might affect the downstream pathways in cells that do not express functional p53.

ZEB1 imposes a temporary stage-dependent inhibition of muscle gene expression and differentiation via CtBP-mediated transcriptional repression

Skeletal muscle development is orchestrated by the myogenic regulatory factor MyoD, whose activity is blocked in myoblasts by proteins preventing its nuclear translocation and/or binding to G/C-centered E-boxes in target genes. Recent evidence indicates that muscle gene expression is also regulated at the cis level by differential affinity for DNA between MyoD and other E-box binding proteins during myogenesis. MyoD binds to G/C-centered E-boxes, enriched in muscle differentiation genes, in myotubes but not in myoblasts. Here, we used cell-based and in vivo Drosophila, Xenopus laevis, and mouse models to show that ZEB1, a G/C-centered E-box binding transcriptional repressor, imposes a temporary stage-dependent inhibition of muscle gene expression and differentiation via CtBP-mediated transcriptional repression. We found that, contrary to MyoD, ZEB1 binds to G/C-centered E-boxes in muscle differentiation genes at the myoblast stage but not in myotubes. Its knockdown results in precocious expression of muscle differentiation genes and acceleration of myotube formation. Inhibition of muscle genes by ZEB1 occurs via transcriptional repression and involves recruitment of the CtBP corepressor. Lastly, we show that the pattern of gene expression associated with muscle differentiation is accelerated in ZEB1(-/-) mouse embryos. These results set ZEB1 as an important regulator of the temporal pattern of gene expression controlling muscle differentiation.

miR-205 regulates basement membrane deposition in human prostate: implications for cancer development

The basement membrane (BM) is a layer of specialized extracellular matrix that surrounds normal prostate glands and preserves tissue integrity. Lack or discontinuity of the BM is a prerequisite for tumor cell invasion into interstitial spaces, thus favoring metastasis. Therefore, BM maintenance represents a barrier against cancer development and progression. In the study, we show that miR-205 participates in a network involving ΔNp63α, which is essential for maintenance of the BM in prostate epithelium. At the molecular level, ΔNp63α is able to enhance miR-205 transcription by binding to its promoter, whereas the microRNA can post-transcriptionally limit the amount of ΔNp63α protein, mostly by affecting ΔNp63α proteasomal degradation rather than through a canonical miRNA/target interaction. Functionally, miR-205 is able to control the deposition of laminin-332 and its receptor integrin-β4. Hence, pathological loss of miR-205, as widely observed in prostate cancer, may favor tumorigenesis by creating discontinuities in the BM. Here we demonstrate that therapeutic replacement of miR-205 in prostate cancer (PCa) cells can restore BM deposition and 3D organization into normal-like acinar structures, thus hampering cancer progression.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

ZEB1 drives prometastatic actin cytoskeletal remodeling by downregulating miR-34a expression

Metastatic cancer is extremely difficult to treat, and the presence of metastases greatly reduces a cancer patient's likelihood of long-term survival. The ZEB1 transcriptional repressor promotes metastasis through downregulation of microRNAs (miRs) that are strong inducers of epithelial differentiation and inhibitors of stem cell factors. Given that each miR can target multiple genes with diverse functions, we posited that the prometastatic network controlled by ZEB1 extends beyond these processes. We tested this hypothesis using a mouse model of human lung adenocarcinoma metastasis driven by ZEB1, human lung carcinoma cells, and human breast carcinoma cells. Transcriptional profiling studies revealed that ZEB1 controls the expression of numerous oncogenic and tumor-suppressive miRs, including miR-34a. Ectopic expression of miR-34a decreased tumor cell invasion and metastasis, inhibited the formation of promigratory cytoskeletal structures, suppressed activation of the RHO GTPase family, and regulated a gene expression signature enriched in cytoskeletal functions and predictive of outcome in human lung adenocarcinomas. We identified several miR-34a target genes, including Arhgap1, which encodes a RHO GTPase activating protein that was required for tumor cell invasion. These findings demonstrate that ZEB1 drives prometastatic actin cytoskeletal remodeling by downregulating miR-34a expression and provide a compelling rationale to develop miR-34a as a therapeutic agent in lung cancer patients.

ZEB1 drives prometastatic actin cytoskeletal remodeling by downregulating miR-34a expression

Metastatic cancer is extremely difficult to treat, and the presence of metastases greatly reduces a cancer patient's likelihood of long-term survival. The ZEB1 transcriptional repressor promotes metastasis through downregulation of microRNAs (miRs) that are strong inducers of epithelial differentiation and inhibitors of stem cell factors. Given that each miR can target multiple genes with diverse functions, we posited that the prometastatic network controlled by ZEB1 extends beyond these processes. We tested this hypothesis using a mouse model of human lung adenocarcinoma metastasis driven by ZEB1, human lung carcinoma cells, and human breast carcinoma cells. Transcriptional profiling studies revealed that ZEB1 controls the expression of numerous oncogenic and tumor-suppressive miRs, including miR-34a. Ectopic expression of miR-34a decreased tumor cell invasion and metastasis, inhibited the formation of promigratory cytoskeletal structures, suppressed activation of the RHO GTPase family, and regulated a gene expression signature enriched in cytoskeletal functions and predictive of outcome in human lung adenocarcinomas. We identified several miR-34a target genes, including Arhgap1, which encodes a RHO GTPase activating protein that was required for tumor cell invasion. These findings demonstrate that ZEB1 drives prometastatic actin cytoskeletal remodeling by downregulating miR-34a expression and provide a compelling rationale to develop miR-34a as a therapeutic agent in lung cancer patients.

ZEB/miR-200 feedback loop: at the crossroads of signal transduction in cancer

Embryonic differentiation programs of epithelial-mesenchymal and mesenchymal-epithelial transition (EMT and MET) represent a mechanistic basis for epithelial cell plasticity implicated in cancer. Transcription factors of the ZEB protein family (ZEB1 and ZEB2) and several microRNA species (predominantly miR-200 family members) form a double negative feedback loop, which controls EMT and MET programs in both development and tumorigenesis. In this article, we review crosstalk between the ZEB/miR-200 axis and several signal transduction pathways activated at different stages of tumor development. The close association of ZEB proteins with these pathways is indirect evidence for the involvement of a ZEB/miR-200 loop in tumor initiation, progression and spread. Additionally, the configuration of signaling pathways involving ZEB/miR-200 loop suggests that ZEB1 and ZEB2 may have different, possibly even opposing, roles in some forms of human cancer.

The miR-200 and miR-221/222 microRNA families: opposing effects on epithelial identity

Carcinogenesis is a complex process during which cells undergo genetic and epigenetic alterations. These changes can lead tumor cells to acquire characteristics that enable movement from the primary site of origin when conditions become unfavorable. Such characteristics include gain of front-rear polarity, increased migration/invasion, and resistance to anoikis, which facilitate tumor survival during metastasis. An epithelial to mesenchymal transition (EMT) constitutes one way that cancer cells can gain traits that promote tumor progression and metastasis. Two microRNA (miRNA) families, the miR-200 and miR-221 families, play crucial opposing roles that affect the differentiation state of breast cancers. These two families are differentially expressed between the luminal A subtype of breast cancer as compared to the less well-differentiated triple negative breast cancers (TNBCs) that exhibit markers indicative of an EMT. The miR-200 family promotes a well-differentiated epithelial phenotype, while high miR-221/222 results in a poorly differentiated, mesenchymal-like phenotype. This review focuses on the mechanisms (specific proven targets) by which these two miRNA families exert opposing effects on cellular plasticity during breast tumorigenesis and metastasis.

Androgen Receptor Regulates Transcription of the ZEB1 Transcription Factor

The zinc finger E-box binding protein 1 (ZEB1) transcription factor belongs to a two-member family of zinc-finger homeodomain proteins involved in physiological and pathological events mostly relating to cell migration and epithelial to mesenchymal transitions (EMTs). ZEB1 (also known as δEF1, zfhx1a, TCF8, and Zfhep) plays a key role in regulating such diverse processes as T-cell development, skeletal patterning, reproduction, and cancer cell metastasis. However, the factors that regulate its expression and consequently the signaling pathways in which ZEB1 participates are poorly defined. Because it is induced by estrogen and progesterone and is high in prostate cancer, we investigated whether tcf8, which encodes ZEB1, is regulated by androgen. Data herein demonstrate that tcf8 is induced by dihydrotestosterone (DHT) in the human PC-3/AR prostate cancer cell line and that this induction is mediated by two androgen response elements (AREs). These results demonstrate that ZEB1 is an intermediary in androgen signaling pathways.

BRCA1-associated epigenetic regulation of p73 mediates an effector pathway for chemosensitivity in ovarian carcinoma

The majority of tumors arising in BRCA1 mutation carriers exhibit inactivation of p53, a key effector of cell death after DNA damage. Despite the loss of p53, BRCA1-deficient tumor cells exhibit increased sensitivity to cisplatin, and patients with BRCA1-associated ovarian carcinomas experience improved outcomes with platinum-based chemotherapy compared with sporadic cases. Although it is known that chemosensitivity in BRCA1-associated cancers is associated with unrepaired DNA damage, the specific effector pathway mediating the cellular response to platinum-induced damage in these tumors is poorly understood. Here, we show that the p53-related gene p73, encoding a proapoptotic protein that is linked to chemosensitivity in many settings, is upregulated through a novel epigenetic mechanism in both human and murine models of BRCA1-associated ovarian carcinoma. BRCA1-deficient ovarian carcinoma cells exhibit hypermethylation within a p73 regulatory region, which includes the binding site for the p73 transcriptional repressor ZEB1, leading to the abrogation of ZEB1 binding and increased expression of transactivating p73 isoforms (TAp73). Cisplatin chemotherapy induces TAp73 target genes specifically in BRCA1-deficient cells, and knockdown of TAp73 in these cells causes chemoresistance while having little or no effect on BRCA1-expressing tumor cells. In primary ovarian carcinomas, ZEB1 binding site methylation and TAp73 expression correlate with BRCA1 status and with clinical response. Together, these findings uncover a novel regulatory mechanism that supports the contribution of TAp73 as an important mediator of the response to platinum chemotherapy in a subset of ovarian carcinomas. TAp73 might represent a response predictor and potential therapeutic target for enhancing chemosensitivity in this disease.

The tumor suppressors p53, p63, and p73 are regulators of microRNA processing complex

The tumor suppressors p53, p73, and p63 are known to function as transcription factors. They promote either growth arrest or apoptosis, depending upon the DNA damage. A number of microRNAs (miRNAs) have been shown to function as transcriptional targets of p53 and they appear to aid p53 in promoting growth arrest and apoptosis. However, the question of p53/p63/p73 regulating the miRNA processing complex has not been addressed in depth so far. Comparative/computational genomic analysis was performed using Target scan, Mami, and Diana software to identify miRNAs that regulate the miRNA processing complex. Here, I present evidence for the first time that the tumor suppressors p53, p63, and p73 function as both positive and negative regulators of the miRNA processing components. Curated p53-dependent miRNA expression data was used to identify p53-miRs that target the components of the miRNA-processing complex. This analysis suggests that most of the components (mRNAs' 3'UTR) of the miRNA processing complex are targeted by p53-miRs. Remarkably, this data revealed the conserved nature of p53-miRs in targeting a number of components of the miRNA processing complex. p53/p73/p63 appears to regulate the major components of the miRNA processing, such as Drosha-DGCR8, Dicer-TRBP2, and Argonaute proteins. In particular, p53/p73/p63 appears to regulate the processing of miRNAs, such as let-7, miR-200c, miR-143, miR-107, miR-16, miR-145, miR-134, miR-449a, miR-503, and miR-21. Interestingly, there seems to be a phenotypic similarity between p63(-/-) and dicer(-/-) mice, suggesting that p63 and dicer could regulate each other. In addition, p63, p73, and the DGCR8 proteins contain a conserved interaction domain. Further, promoters of a number of components of the miRNA processing machinery, including dicer and P2P-R, contain p53-REs, suggesting that they could be direct transcriptional targets of p63/p73/p53. Together, this study provides mechanistic insights into how p53, p63, and p73 regulate the components of the miRNA processing; and how p53, TA-p63, and TA-p73 regulated miRNAs inhibit tumorigenesis, EMT, metastasis, and cancer stem cell proliferation.

The role of ZEB1 in the inflammation-induced promotion of EMT in HNSCC

OBJECTIVES

To determine the role of ZEB1 in the inflammation-induced promotion of the epithelial-mesenchymal transition (EMT) in head and neck squamous cell carcinoma (HNSCC).

STUDY DESIGN

A molecular biology study. Real-time quantitative reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot analysis, and immunohistochemical staining of human HNSCC tissue sections were used to determine how inflammation affects the transcriptional repressor, ZEB1.

SETTING

An academic hospital laboratory.

SUBJECTS AND METHODS

Relative ZEB1 RNA levels were determined by RT-PCR, and protein expression was evaluated in situ by immunohistochemical staining of human HNSCC tissue sections.

RESULTS

IL-1beta-treated HNSCC cell lines demonstrated a significant decrease in E-cadherin mRNA and an increase in the mRNA expression of the transcriptional repressor ZEB1. IL-1beta exposure led to enhanced ZEB1 binding at the chromatin level, as determined by chromatin immunoprecipitation assays (ChIP). An inverse relationship between ZEB1 and E-cadherin was demonstrated in situ by immunohistochemical staining of human HNSCC tissue sections.

CONCLUSIONS

Our recent investigations indicate that inflammatory mediators are potent regulators of EMT in HNSCC. This is the first report indicating the role of ZEB1 in the inflammation-induced promotion of EMT in HNSCC. This newly defined pathway for transcriptional regulation of E-cadherin in HNSCC has important implications for targeted chemoprevention and therapy.

E-cadherin transcriptional down-regulation by epigenetic and microRNA-200 family alterations is related to mesenchymal and drug-resistant phenotypes in human breast cancer cells

The conversion of early stage tumors into invasive malignancies with an aggressive phenotype has been associated with the irreversible loss of E-cadherin expression. The loss of E-cadherin expression in human tumors, including breast cancer, has been attributed to promoter CpG island hypermethylation and direct inhibition by transcriptional repressors. Recent evidence demonstrates that up-regulation of E-cadherin by microRNA-200b (miR-200b) and miR-200c through direct targeting of transcriptional repressors of E-cadherin, ZEB1, and ZEB2, inhibits epithelial-to-mesenchymal transition (EMT), a crucial process in the tumor progression. We demonstrate that microRNA miR-200 family-mediated transcriptional up-regulation of E-cadherin in mesenchymal MDA-MB-231 and BT-549 cells is associated directly with translational repression of ZEB1 and indirectly with increased acetylation of histone H3 at the E-cadherin promoter. The increase in histone H3 acetylation may be attributed to the disruption of repressive complexes between ZEB1 and histone deacetylases and to the inhibition of SIRT1, a class III histone deacetylase. These events inhibit EMT and reactivate a less aggressive epithelial phenotype in cancer cells. Additionally, disruption of ZEB1-histone deacetylase repressor complexes and down-regulation of SIRT1 histone deacetylase up-regulate proapoptotic genes in the p53 apoptotic pathway resulting in the increased sensitivity of cancer cells to the chemotherapeutic agent doxorubicin.

DeltaEF1 promotes breast cancer cell proliferation through down-regulating p21 expression

Although the zinc finger-homeodomain transcription factor deltaEF1 is implied as a regulatory factor at the crossroad between proliferation and differentiation in carcinogenesis, its potential effect in the regulation of cell cycle progression has not been well elucidated. In our present study, we provide novel finding that, in breast cancer, the ectopic expression of deltaEF1 in MDA-MB-231 cells significantly promoted cell proliferation by increasing the cell number in S phase of the cell cycle. In contrast, deltaEF1 knockdown by RNA interference exhibited an opposite effect, highlighting a potent role of deltaEF1 to promote G1-S transition of breast cancer cells. Moreover, we demonstrated that deltaEF1 down-regulated p21 and concurrently up-regulated the expressions of CDK2 and CDK4 during this process. Further, deltaEF1 inhibited p21 transcription by recruiting to the E(2) box element on the p21 promoter. Depletion of endogenous deltaEF1 in MDA-MB-231 cells was sufficient to allow an inherent release of p21 expression, thus resulting in the cell cycle arrest. In addition, the stimulatory effect of deltaEF1 on cell proliferation through p21 regulation was supported by an inverse correlation of deltaEF1 and p21 expressions observed in both breast cancer cell lines and clinical tumor specimens. Taken together, these observations suggest a dual effect of deltaEF1 in promoting breast cancer cell proliferation, by differentially regulating the cell cycle regulatory proteins.

Therapeutic prospects for p73 and p63: rising from the shadow of p53

The p53 protein family consists of three transcription factors: p53, p63, and p73. These proteins share significant structural and functional similarities and each has unique biological functions as well. Although the role of p53 in cellular stress is extensively studied, many questions remain about p63 and p73. In this review we summarize current data on functional interactions within the p53 family, their regulation and roles in response to genotoxic stress. We also discuss the significance of p73 and p63 for cancer therapy and outline novel approaches in development of therapeutic drugs that specifically target the p53 family.

Expression of the ZEB1 (deltaEF1) transcription factor in human: additional insights

The zinc finger E-box binding transcription factor ZEB1 (deltaEF1/Nil-2-a/AREB6/zfhx1a/TCF8/zfhep/BZP) is emerging as an important regulator of the epithelial to mesenchymal transitions (EMT) required for development and cancer metastasis. ZEB1 promotes EMT by repressing genes contributing to the epithelial phenotype while activating those associated with the mesenchymal phenotype. TCF8 (zfhx1a), the gene encoding ZEB1, is induced by several potentially oncogenic ligands including TGF-beta, estrogen, and progesterone. TGF-beta appears to activate EMT, at least in part, by inducing ZEB1. However, our understanding of how ZEB1 contributes to signaling pathways elicited by estrogen and progesterone is quite limited, as is our understanding of its functional roles in normal adult tissues. To begin to address these questions, a human tissue mRNA array analysis was done. In adults, the highest ZEB1 mRNA expression is in bladder and uterus, whereas in the fetus highest expression is in lung, thymus, and heart. To further investigate the regulation of TCF8 by estrogen, ZEB1 mRNA was measured in ten estrogen-responsive cell lines, but it is only induced in the OV266 ovarian carcinoma line. Although high expression of ZEB1 mRNA is estrogen-dependent in normal human ovarian and endometrial biopsies, high expression is estrogen-independent in late stage ovarian and endometrial carcinomas, raising the possibility that deregulated expression promotes cancer progression. In contrast, TCF8 is at least partially deleted in 4 of 5 well-differentiated, grade I endometrial carcinomas, which may contribute to their non-aggressive phenotype. These data support the contention that high ZEB1 encourages gynecologic carcinoma progression.

Down-regulation of TCF8 is involved in the leukemogenesis of adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is caused by latent human T-lymphotropic virus-1 (HTLV-1) infection. To clarify the molecular mechanism underlying leukemogenesis after viral infection, we precisely mapped 605 chromosomal breakpoints in 61 ATLL cases by spectral karyotyping and identified frequent chromosomal breakpoints in 10p11, 14q11, and 14q32. Single nucleotide polymorphism (SNP) array-comparative genomic hybridization (CGH), genetic, and expression analyses of the genes mapped within a common breakpoint cluster region in 10p11.2 revealed that in ATLL cells, transcription factor 8 (TCF8) was frequently disrupted by several mechanisms, including mainly epigenetic dysregulation. TCF8 mutant mice frequently developed invasive CD4(+) T-cell lymphomas in the thymus or in ascitic fluid in vivo. Down-regulation of TCF8 expression in ATLL cells in vitro was associated with resistance to transforming growth factor beta1 (TGF-beta1), a well-known characteristic of ATLL cells, suggesting that escape from TGF-beta1-mediated growth inhibition is important in the pathogenesis of ATLL. These findings indicate that TCF8 has a tumor suppressor role in ATLL.

p63: defining roles in morphogenesis, homeostasis, and neoplasia of the epidermis

p63 is a member of a gene family also including the p53 tumor suppressor and p73. In contrast to p53, p63 is rarely mutated in human cancers. Rather, gene amplification and dysregulated expression of p63 protein have been observed, particularly in squamous cell carcinomas. p63 is essential for development of stratified squamous epithelium, including the epidermis. The p63 gene is expressed as multiple protein isoforms with different functional capacities, and the balance of these isoforms, along with the presence or absence of the other family members, p53 and p73, can impact biological outcome. Both gene silencing and overexpression approaches have been utilized to elucidate the contributions of specific p63 isoforms to normal epidermal morphogenesis and tissue maintenance. While numerous studies have established the essential nature of p63 in the epidermis, the basis of this requirement, and the unique, as well as, overlapping functions of the individual isoforms, remain controversial. In this review, we summarize the current understanding of roles played by specific p63 isoforms within the context of epidermal morphogenesis and homeostasis of the established epidermis, and the potential impact of p63 dysregulation on cancer development.

Important differences between human and mouse APOE gene promoters: limitation of mouse APOE model in studying Alzheimer's disease

Apolipoprotein E (ApoE), encoded by the apolipoprotein E gene (APOE), plays an important role in the pathogenesis of Alzheimer's disease (AD). The APOE epsilon4 variant is strongly associated with AD. APOE promoter polymorphisms have also been reported to associate with higher AD risk. Mouse models of APOE expression have long been used to study the pathogenesis of AD. Elucidating the role of the APOE gene in AD requires understanding of how its regulation differs between mouse and human APOE genes, and how the differences influence AD risk. We compared the structure and function of both the human APOE gene promoter (hAPOEP) and mouse APOE gene promoter (mAPOEP) regions. Homology is less than 40% at 180 bp or more upstream of the two species' transcription start site (TSS, +1). Functional analysis revealed both similarities and important differences between the two sequences, significantly affected by human versus rodent cell line origin. We likewise probed nuclear extracts from several cell lines of different origins (astrocytic, glial, and neuronal) and mouse brain with specific hAPOEP and mAPOEP fragments. Each fragment shared DNA-protein interactions with the other but, notably, also bound distinct factors, demonstrated by gel shift and southwestern analyses. We determined possible identities for these distinct factors. These results suggest that regulation of mouse and human APOE genes may be sufficiently unique to justify the use of both the human APOE promoter sequence in transgenic rodent models and non-rodent AD models for studying factors involved in AD pathogenesis.

The p53 family in differentiation and tumorigenesis

The role of p53 as a tumour suppressor is generally attributed to its ability to stop the proliferation of precancerous cells by inducing cell-cycle arrest or apoptosis. The relatives and evolutionary predecessors of p53 - p63 and p73 - share the tumour-suppressor activity of p53 to some extent, but also have essential functions in embryonic development and differentiation control. Recent evidence indicates that these ancestral functions in differentiation control contribute to the tumour-suppressor activity that the p53 family is famous for.

Regulating p73 isoforms in human tumours

Although mutations in the TP73 gene are extremely rare in human tumours, altered expression is common. In some tumours, most notably leukaemias and lymphomas, expression of TP73 is reduced, suggesting a tumour suppressor role. In contrast, TP73 is over-expressed in many other tumour types, implying that it has oncogenic functions in human tumourigenesis. These conflicting scenarios can be reconciled by the observations that the TP73 gene produces p53-like isoforms (TAp73) and anti-p53 isoforms (DeltaTAp73). Thus, loss of TAp73 or over-expression of DeltaTAp73 should each promote oncogenic transformation, and the balance of expression of the opposing isoforms is the crucial factor. The mechanisms that regulate expression of TP73 isoforms are therefore of great interest. Recent data provide evidence for interacting roles of ZEB1, p300, and a polymorphic 73 bp deletion in intron 1 of the human TP73 gene in this process. Importantly, alterations to the proposed regulatory pathway for controlling TP73 isoform expression in colorectal cancer are associated with adverse clinico-pathological characteristics. Because p73 is also associated with tumour chemosensitivity, these new findings should provide prognostic information and have the potential to guide future therapeutic decisions.

The transcription factor ZEB1 is aberrantly expressed in aggressive uterine cancers

The transcription factor ZEB1 (deltaEF1 in mice) has been implicated in cellular processes during development and tumor progression including epithelial to mesenchymal transition. deltaEF1 null mice die at birth, but heterozygotes expressing a LacZ reporter inserted into the deltaEF1 gene live and reproduce. Using these mice, we observed ZEB1 promoter activity in the virgin myometrium, and stroma and myometrium of the pregnant uterus. ZEB1 protein is up-regulated in the myometrium and endometrial stroma after progesterone or estrogen treatment of ovariectomized mice. In the normal human uterus, ZEB1 protein is increased in the myometrium and stroma during the secretory stage of the menstrual cycle. ZEB1 is not expressed in the normal endometrial epithelium. In malignancies of the uterus, we find that ZEB1 (a) is overexpressed in malignant tumors derived from the myometrium (leiomyosarcomas), (b) is overexpressed in tumor-associated stroma of low-grade endometrioid adenocarcinomas, and (c) is aberrantly expressed in the tumor epithelial cells of aggressive endometrial cancers. Specifically, in grade 3 endometrioid adenocarcinomas and uterine papillary serous carcinomas, ZEB1 could be expressed in the epithelial-derived carcinoma cells as well as in the stroma. In malignant mixed Müllerian tumors, the sarcomatous component always expresses ZEB1, and the carcinomatous component can also be positive. In summary, ZEB1 is normally regulated by both estrogen and progesterone receptors, but in uterine cancers, it is likely no longer under control of steroid hormone receptors and becomes aberrantly expressed in epithelial-derived tumor cells, supporting a role for ZEB1 in epithelial to mesenchymal transitions associated with aggressive tumors.

Defining the regulatory elements in the proximal promoter of DeltaNp63 in keratinocytes: Potential roles for Sp1/Sp3, NF-Y, and p63

p63, a homolog of the tumor suppressor p53, plays an important role in the formation of stratified epithelium such as those in the epidermis of the skin. The p63 gene gives rise to multiple functionally distinct protein isoforms, including the DeltaNp63 class of isoforms, which lacks the N-terminal transactivation domain and is synthesized from an internal promoter. DeltaNp63 proteins are the predominant isoforms expressed in keratinocytes and are thought to be important for maintenance of the proliferative capacity of these cells. Here, we have examined the transcriptional control mechanisms that govern the expression DeltaNp63 in keratinocytes. We first performed DNase I hypersensitive site mapping and demonstrated that the promoter region of DeltaNp63 is in open chromatin state in keratinocytes. To identify the cis-elements that regulate DeltaNp63, we have performed transient transfection assays in keratinocytes with several DeltaNp63 promoter constructs. This identified a short evolutionarily conserved fragment that harbors most of the transcriptional activity of the DeltaNp63 promoter. Biochemical studies of this element have revealed critical roles for CCAAT-box-binding factor (CBF/NF-Y) and Sp1/Sp3 family of proteins. In addition, our data suggest that DeltaNp63 is recruited to and can activate its own promoter, possibly through protein-protein interactions, thus providing an auto-regulatory loop of self-regulation. These studies support the notion that unique and distinct pathways control the expression of individual p53 family members and their various isoforms.

p57Kip2 is Induced by MyoD Through a p73-dependent Pathway

The cyclin-dependent-kinase inhibitors p21 and p57 are highly expressed in skeletal muscle where they redundantly control cell cycle arrest during differentiation. We have previously shown that p57 is a target of the myogenic factor MyoD in cells lacking p21. Here we show that MyoD induces p57 at the transcriptional level through a mechanism different from that involved in p21 regulation, since it is E-box-independent and requires new synthesized protein(s). We have identified p73 family members as the factors that mediate the activation of p57 through a 165bp promoter region. The levels of p73 alpha, beta and delta isoforms increase during muscle differentiation both in MyoD-expressing fibroblasts and in spontaneously differentiating C2 myoblasts. Moreover, the expression of a p73 dominant negative mutant interferes with the induction of p57. Finally, each of the isoforms up-regulated by MyoD, even when over-expressed alone, is capable of inducing p57 in p21-lacking fibroblasts. In contrast, the same p73 isoforms, either induced by MyoD or exogenously over-expressed, are unable to activate the expression of p57 in p21-expressing fibroblasts. Our finding that a transfected p57 promoter-reporter construct, unlike the endogenous gene, is responsive to both MyoD and p73 even in these cells, suggests that a cis-acting mechanism, probably involving a repressive chromatin structure, prevents the induction of p57 in p21-expressing fibroblasts.