p53 regulates epithelial-mesenchymal transition induced by transforming growth factor β

Simultaneous screening of overexpressed genes in breast cancer for oncogenic drivers and tumor dependencies

There are hundreds of genes typically overexpressed in breast cancer cells and it's often assumed that their overexpression contributes to cancer progression. However, the precise proportion of these overexpressed genes contributing to tumorigenicity remains unclear. To address this gap, we undertook a comprehensive screening of a diverse set of seventy-two genes overexpressed in breast cancer. This systematic screening evaluated their potential for inducing malignant transformation and, concurrently, assessed their impact on breast cancer cell proliferation and viability. Select genes including ALDH3B1, CEACAM5, IL8, PYGO2, and WWTR1, exhibited pronounced activity in promoting tumor formation and establishing gene dependencies critical for tumorigenicity. Subsequent investigations revealed that CEACAM5 overexpression triggered the activation of signaling pathways involving β-catenin, Cdk4, and mTOR. Additionally, it conferred a growth advantage independent of exogenous insulin in defined medium and facilitated spheroid expansion by inducing multiple layers of epithelial cells while preserving a hollow lumen. Furthermore, the silencing of CEACAM5 expression synergized with tamoxifen-induced growth inhibition in breast cancer cells. These findings underscore the potential of screening overexpressed genes for both oncogenic drivers and tumor dependencies to expand the repertoire of therapeutic targets for breast cancer treatment.

Opposing Roles of Wild-type and Mutant p53 in the Process of Epithelial to Mesenchymal Transition

The central role of an aberrantly activated EMT program in defining the critical features of aggressive carcinomas is well documented and includes cell plasticity, metastatic dissemination, drug resistance, and cancer stem cell-like phenotypes. The p53 tumor suppressor is critical for leashing off all the features mentioned above. On the molecular level, the suppression of these effects is exerted by p53 via regulation of its target genes, whose products are involved in cell cycle, apoptosis, autophagy, DNA repair, and interactions with immune cells. Importantly, a set of specific mutations in the TP53 gene (named Gain-of-Function mutations) converts this tumor suppressor into an oncogene. In this review, we attempted to contrast different regulatory roles of wild-type and mutant p53 in the multi-faceted process of EMT.

MicroRNA-34a: A Novel Therapeutic Target in Fibrosis

Fibrosis can occur in many organs, and severe cases leading to organ failure and death. No specific treatment for fibrosis so far. In recent years, microRNA-34a (miR-34a) has been found to play a role in fibrotic diseases. MiR-34a is involved in the apoptosis, autophagy and cellular senescence, also regulates TGF-β1/Smad signal pathway, and negatively regulates the expression of multiple target genes to affect the deposition of extracellular matrix and regulate the process of fibrosis. Some studies have explored the efficacy of miR-34a-targeted therapies for fibrotic diseases. Therefore, miR-34a has specific potential for the treatment of fibrosis. This article reviews the important roles of miR-34a in fibrosis and provides the possibility for miR-34a as a novel therapeutic target in fibrosis.

Single-cell RNA sequencing reveals PDGFRα+ stromal cell subpopulations that promote proacinar cell differentiation in embryonic salivary gland organoids

Stromal cells can direct the differentiation of epithelial progenitor cells during organ development. Fibroblast growth factor (FGF) signaling is essential for submandibular salivary gland development. Through stromal fibroblast cells, FGF2 can indirectly regulate proacinar cell differentiation in organoids, but the mechanisms are not understood. We performed single-cell RNA-sequencing and identified multiple stromal cell subsets, including Pdgfra+ stromal subsets expressing both Fgf2 and Fgf10. When combined with epithelial progenitor cells in organoids, magnetic-activated cell-sorted PDGFRα+ cells promoted proacinar cell differentiation similarly to total stroma. Gene expression analysis revealed that FGF2 increased the expression of multiple stromal genes, including Bmp2 and Bmp7. Both BMP2 and BMP7 synergized with FGF2, stimulating proacinar cell differentiation but not branching. However, stromal cells grown without FGF2 did not support proacinar organoid differentiation and instead differentiated into myofibroblasts. In organoids, TGFβ1 treatment stimulated myofibroblast differentiation and inhibited the proacinar cell differentiation of epithelial progenitor cells. Conversely, FGF2 reversed the effects of TGFβ1. We also demonstrated that adult salivary stromal cells were FGF2 responsive and could promote proacinar cell differentiation. These FGF2 signaling pathways may have applications in future regenerative therapies.

CCT8 recovers WTp53-suppressed cell cycle evolution and EMT to promote colorectal cancer progression

LIM and SH3 protein 1 (LASP1) is a metastasis-related protein reported to enhance tumor progression in colorectal cancer (CRC). However, the underlying mechanism is still elusive. The chaperonin protein containing TCP1 (CCT) is a cellular molecular chaperone complex, which is necessary for the correct folding of many proteins. It contains eight subunits, CCT1-8. CCT8 is overexpressed in many cancers, however, studies on CCT8 are limited and its role on CRC development and progression remains elusive. In this study, we confirmed that CCT8 and LASP1 can interact with each other and express positively in CRC cells. CCT8 could recover the ability of LASP1 to promote the invasion of CRC; CCT8 could significantly promote the proliferation, invasion, and metastasis of colorectal cells in vivo and in vitro. Mechanically, CCT8 inhibited the entry of WTp53 into the nucleus, and there was a negative correlation between the expression of CCT8 and the nuclear expression of WTp53 in clinical colorectal tissues. CCT8 promoted the cell cycle evolution and EMT progression of CRC by inhibiting the entry of WTp53 into the nucleus. Clinically, CCT8 was highly expressed in CRC. More importantly, the overall survival of CRC patients with high expression of CCT8 was worse than that of patients with low expression of CCT8. These findings indicate that as LASP1-modulated proteins, CCT8 plays a key role in promoting the progression of colorectal cancer, which provides a potential target for clinical intervention in patients with colorectal cancer.

Crosslink between p53 and metastasis: focus on epithelial-mesenchymal transition, cancer stem cell, angiogenesis, autophagy, and anoikis

INTRODUCTION

P53, as a tumor suppressor gene, is believed to be one of the most mutated genes in cancer cells. The mutant forms of this protein often play a tumorigenic role in cancer cells. Recent evidence shows that p53 plays a critical role in the migration, metastasis, and invasion of cancer cells. The present article aims to investigate the molecular mechanism that induces metastasis in cancer cells generated by the mutant P53, and to highlight the compounds targeting mutant-p53 together with their clinical applications.

METHODS

A detailed literature search was conducted to find information about the role of the mutant-p53 in the processes involved in metastasis in various databases.

RESULTS

A growing body of evidence suggests that Mutant-p53 enhances tumor metastasis affecting the Epithelial-mesenchymal transition (EMT) process, cancer stem cells, angiogenesis, autophagy, anoikis, and any other mechanisms regarding metastasis.

CONCLUSIONS

Taken together, targeting mutant-p53 by altering the processes involved in metastasis could be a potential therapeutic strategy in the treatment of metastatic cancer.

Genomic Instability Is an Early Event in Aluminium-Induced Tumorigenesis

Genomic instability is generally considered as a hallmark of tumorigenesis and a prerequisite condition for malignant transformation. Aluminium salts are suspected environmental carcinogens that transform mammary epithelial cells in vitro through unknown mechanisms. We report here that long-term culture in the presence of aluminium chloride (AlCl₃) enables HC11 normal mouse mammary epithelial cells to form tumours and metastases when injected into the syngeneic and immunocompetent BALB/cByJ strain. We demonstrate that AlCl₃ rapidly increases chromosomal structural abnormalities in mammary epithelial cells, while we failed to detect direct modulation of specific mRNA pathways. Our observations provide evidence that clastogenic activity—a well-recognized inducer of genomic instability—might account in part for the transforming abilities of aluminium in mammary epithelial cells.

Differential mechanisms underlying methotrexate-induced cell death and epithelial-mesenchymal transition in A549 cells

Epithelial-mesenchymal transition (EMT), a biological process through which epithelial cells transdifferentiate into mesenchymal cells, is involved in several pathological events, such as cancer progression and organ fibrosis. So far, we have found that methotrexate (MTX), an anticancer drug, induced EMT in the human A549 alveolar adenocarcinoma cell line. However, the relationship between EMT and the cytotoxicity induced by MTX remains unclear. In this study, we compared the processes of MTX-induced EMT and apoptosis in A549 cells. Q-VD-Oph, a caspase inhibitor, suppressed MTX-induced apoptosis, but not the increase in mRNA expression of α-smooth muscle actin (SMA), a representative EMT marker. In addition, SB431542, an EMT inhibitor, did not inhibit MTX-induced apoptosis. By using isolated clonal cells from wild-type A549 cells, the induction of EMT and apoptosis by MTX in each clone was analyzed, and no significant correlation was observed between the MTX-induced increase in α-SMA mRNA expression and the proportion of cells undergoing apoptosis. Furthermore, the increase in the mRNA expression of α-SMA was well correlated with cyclin-dependent kinase inhibitor 1A, a cell cycle arrest marker, but not with BCL-2 binding component 3 and Fas cell surface death receptor, which are both pro-apoptotic factors, indicating that the MTX-induced EMT may be related to cell cycle arrest, but not to apoptosis. These findings suggested that different mechanisms were involved in the MTX-induced EMT and apoptosis.

p53 Loss in Breast Cancer Leads to Myc Activation, Increased Cell Plasticity, and Expression of a Mitotic Signature with Prognostic Value

Loss of p53 function is invariably associated with cancer. Its role in tumor growth was recently linked to its effects on cancer stem cells (CSCs), although the underlying molecular mechanisms remain unknown. Here, we show that c-myc is a transcriptional target of p53 in mammary stem cells (MaSCs) and is activated in breast tumors as a consequence of p53 loss. Constitutive Myc expression in normal mammary cells leads to increased frequency of MaSC symmetric divisions, extended MaSC replicative-potential, and MaSC-reprogramming of progenitors, whereas Myc activation in breast cancer is necessary and sufficient to maintain the expanding pool of CSCs. Concomitant p53 loss and Myc activation trigger the expression of 189 mitotic genes, which identify patients at high risk of mortality and relapse, independently of other risk factors. Altogether, deregulation of the p53:Myc axis in mammary tumors increases CSC content and plasticity and is a critical determinant of tumor growth and clinical aggressiveness.

•

Myc is overexpressed and deregulated in breast tumors because of p53 signaling attenuation

•

Myc activation favors SC symmetric divisions and SC reprogramming of progenitors

•

Myc activation is necessary and sufficient to sustain the cancer SC phenotype

•

Expression of 189 mitotic p53:Myc targets identifies high-risk breast cancer patients

p53-Mediated Tumor Suppression: DNA-Damage Response and Alternative Mechanisms

The tumor suppressor p53 regulates different cellular pathways involved in cell survival, DNA repair, apoptosis, and senescence. However, according to an increasing number of studies, the p53-mediated canonical DNA damage response is dispensable for tumor suppression. p53 is involved in mechanisms regulating many other cellular processes, including metabolism, autophagy, and cell migration and invasion, and these pathways might crucially contribute to its tumor suppressor function. In this review we summarize the canonical and non-canonical functions of p53 in an attempt to provide an overview of the potentially crucial aspects related to its tumor suppressor activity.

Pterostilbene prevents hepatocyte epithelial-mesenchymal transition in fructose-induced liver fibrosis through suppressing miR-34a/Sirt1/p53 and TGF-β1/Smads signalling

BACKGROUND AND PURPOSE

Excessive fructose consumption is a risk factor for liver fibrosis. Pterostilbene protects against liver fibrosis. Here, we investigated the potential role and the mechanisms underlying the hepatocyte epithelial-mesenchymal transition (EMT) in fructose-induced liver fibrosis and protection by pterostilbene.

EXPERIMENTAL APPROACH

Characteristic features of liver fibrosis in 10% fructose-fed rats and EMT in 5 mM fructose-exposed BRL-3A cells with or without pterostilbene and the change of miR-34a/Sirt1/p53 and transforming growth factor-β1 (TGF-β1)/Smads signalling were examined. MiR-34a inhibitor, miR-34a minic, or p53 siRNA were used to explore the role of miR-34a/Sirt1/p53 signalling in fructose-induced EMT and the action of pterostilbene.

KEY RESULTS

Pterostilbene prevented fructose-induced liver injury with fibrosis in rats. Fructose caused hepatocyte undergoing EMT, gaining fibroblast-specific protein 1 and vimentin, and losing E-cadherin, effects attenuated by pterostilbene. Moreover, fructose induced miR-34a overexpression in hepatocytes with down-regulated Sirt1, increased p53 and ac-p53, and activated TGF-β1/Smads signalling, whereas these disturbances were suppressed by miR-34a inhibitor. Additionally, miR-34a inhibitor and p53 siRNA prevented TGF-β1-driven hepatocyte EMT under fructose exposure. Pterostilbene down-regulated miR-34a, up-regulated Sirt1, and suppressed p53 activation and TGF-β1/Smads signalling in fructose-stimulated animals and cells but showed no additional effects with miR-34a inhibitor on miR-34a/Sirt1/p53 signalling in fructose-exposed hepatocytes.

CONCLUSIONS AND IMPLICATIONS

These results strongly suggest that activation of miR-34a/Sirt1/p53 signalling is required for fructose-induced hepatocyte EMT mediated by TGF-β1/Smads signalling, contributing to liver fibrosis in rats. Pterostilbene exhibits a protective effect against liver fibrosis at least partly through inhibiting miR-34a/Sirt1/p53 signalling activation.

Signaling roadmap to epithelial-mesenchymal transition in pterygium, TWIST1 centralized

Pterygium as a complex disease shares common features with other malignant cells in its onset recurrence and especially epithelial-mesenchymal transition (EMT) transition. Although using different approaches including conjunctival autografts, amniotic membrane, radiotherapy, mitomycin C (MMC) has shown promising insights in the inhibition of pterygium recurrence, it needs to be investigated in more details in molecular pathways to present adjuvant target therapy. In this study, we aimed to evaluate the expression of and then illustrate the role of signaling pathways on EMT in pterygium. Using real-time polymerase chain reaction, the twist-related protein 1 (TWIST1) expression was compared in primary pterygium and normal conjunctiva. This study assessed the mRNA expression, as well as the association between the clinicopathological indices and the gene expression level. The expression level of TWIST1 was overexpressed in 36% of our cohort ( n = 76). There was a significant positive correlation between recurrence with grade T, grade V and a significant negative correlation with growth activity. Our vast literature review on different signaling pathways in pterygium showed that EMT has centralization role in recurrence of this disease. Our data confirmed that EMT is important in the recurrence of pterygium samples and different signaling pathways end up activating the EMT markers. It is suggested to evaluate the environmental factors and their correlation with molecular markers to select favorable treatment for this kind of diseases.

Epithelial-Mesenchymal Transition and Metastasis under the Control of Transforming Growth Factor β

Metastasis of tumor cells from primary sites of malignancy to neighboring stromal tissue or distant localities entails in several instances, but not in every case, the epithelial-mesenchymal transition (EMT). EMT weakens the strong adhesion forces between differentiated epithelial cells so that carcinoma cells can achieve solitary or collective motility, which makes the EMT an intuitive mechanism for the initiation of tumor metastasis. EMT initiates after primary oncogenic events lead to secondary secretion of cytokines. The interaction between tumor-secreted cytokines and oncogenic stimuli facilitates EMT progression. A classic case of this mechanism is the cooperation between oncogenic Ras and the transforming growth factor β (TGFβ). The power of TGFβ to mediate EMT during metastasis depends on versatile signaling crosstalk and on the regulation of successive waves of expression of many other cytokines and the progressive remodeling of the extracellular matrix that facilitates motility through basement membranes. Since metastasis involves many organs in the body, whereas EMT affects carcinoma cell differentiation locally, it has frequently been debated whether EMT truly contributes to metastasis. Despite controversies, studies of circulating tumor cells, studies of acquired chemoresistance by metastatic cells, and several (but not all) metastatic animal models, support a link between EMT and metastasis, with TGFβ, often being a common denominator in this link. This article aims at discussing mechanistic cases where TGFβ signaling and EMT facilitate tumor cell dissemination.

Narrower insight to SIRT1 role in cancer: A potential therapeutic target to control epithelial-mesenchymal transition in cancer cells

The epithelial-mesenchymal transition (EMT) is a highly networked cellular process which involves cell transition from the immotile epithelial to the motile mesenchymal phenotype, whereby cells lose their cell-cell adhesion and cell polarity. This important process is one of the underlying mechanisms for enabling invasion and metastasis of cancer cells which is considered as malignant phase of tumor progression. However, the molecular mechanisms of this process are not fully clarified. It is reported that Sirtuin1 (SIRT1), a NAD+ dependent class III histone deacetylase is associated with tumor metastasis through positive regulation of EMT in several types of cancers. Recent studies confirmed that up and down regulation of SIRT1 expression remarkably change the migration ability of different cancer cells in vitro and tumor metastasis in vivo. Also, according to this fact that carcinomas as the main human solid tumors, originate from different epithelial cell types, SIRT1 role in EMT has received a great attention due to its potential role in tumor development and metastasis. Therefore, SIRT1 has been proposed as a key regulator of cancer metastasis by promoting EMT, although little is known about the cleared effect of SIRT1 in this transition. Our aim in this review is to explain in more detail the role of SIRT1 in various signaling pathways related to carcinogenesis, with the focus on the promoting role of SIRT1 in EMT as a potential therapeutic target to control EMT and to prevent cancer progression.

Tumor-Suppressor Inactivation of GDF11 Occurs by Precursor Sequestration in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous carcinoma in which various tumor-suppressor genes are lost by mutation, deletion, or silencing. Here we report a tumor-suppressive mode of action for growth-differentiation factor 11 (GDF11) and an unusual mechanism of its inactivation in TNBC. GDF11 promotes an epithelial, anti-invasive phenotype in 3D triple-negative cultures and intraductal xenografts by sustaining expression of E-cadherin and inhibitor of differentiation 2 (ID2). Surprisingly, clinical TNBCs retain the GDF11 locus and expression of the protein itself. GDF11 bioactivity is instead lost because of deficiencies in its convertase, proprotein convertase subtilisin/kexin type 5 (PCSK5), causing inactive GDF11 precursor to accumulate intracellularly. PCSK5 reconstitution mobilizes the latent TNBC reservoir of GDF11 in vitro and suppresses triple-negative mammary cancer metastasis to the lung of syngeneic hosts. Intracellular GDF11 retention adds to the concept of tumor-suppressor inactivation and reveals a cell-biological vulnerability for TNBCs lacking therapeutically actionable mutations.

Carnosol controls the human glioblastoma stemness features through the epithelial-mesenchymal transition modulation and the induction of cancer stem cell apoptosis

A high cell proliferation rate, invasiveness and resistance to chemotherapy are the main features of glioblastoma (GBM). GBM aggressiveness has been widely associated both with a minor population of cells presenting stem-like properties (cancer stem-like cells, CSCs) and with the ability of tumor cells to acquire a mesenchymal phenotype (epithelial-mesenchymal transition, EMT). Carnosol (CAR), a natural inhibitor of MDM2/p53 complex, has been attracted attention for its anti-cancer effects on several tumor types, including GBM. Herein, the effects of CAR on U87MG-derived CSC viability and stemness features were evaluated. CAR decreased the rate of CSC formation and promoted the CSC apoptotic cell death through p53 functional reactivation. Moreover, CAR was able to control the TNF-α/TGF-β-induced EMT, counteracting the effects of the cytokine on EMT master regulator genes (Slug, Snail, Twist and ZEB1) and modulating the activation of miR-200c, a key player in the EMT process. Finally, CAR was able to increase the temozolomide (TMZ) anti-proliferative effects. These findings demonstrate that CAR affected the different intracellular mechanism of the complex machinery that regulates GBM stemness. For the first time, the diterpene was highlighted as a promising lead for the development of agents able to decrease the stemness features, thus controlling GBM aggressiveness.

Transcriptome of the GSH-Depleted Lens Reveals Changes in Detoxification and EMT Signaling Genes, Transport Systems, and Lipid Homeostasis

Purpose

To understand the effects of glutathione (GSH)-deficiency on genetic processes that regulate lens homeostasis and prevent cataractogenesis.

Methods

The transcriptome of lens epithelia and fiber cells was obtained from C57BL/6 LEGSKO (lens GSH-synthesis knockout) and buthionine sulfoximine (BSO)-treated LEGSKO mice and compared to C57BL/6 wild-type mice using RNA-Seq. Transcriptomic data were confirmed by qPCR and Western blot/ELISA on a subset of genes.

Results

RNA-Seq results were in excellent agreement with qPCR (correlation coefficients 0.87-0.94 and P < 5E-6 for a subset of 36 mRNAs). Of 24,415 transcripts mapped to the mouse genome, 441 genes showed significantly modulated expression. Pathway analysis indicated major changes in epithelial-mesenchymal transition (EMT) signaling, visual cycle, small molecule biochemistry, and lipid metabolism. GSH-deficient lenses showed upregulation of detoxification genes, including Aldh1a1, Aldh3a1 (aldehyde dehydrogenases), Mt1, Mt2 (metallothioneins), Ces1g (carboxylesterase), and Slc14a1 (urea transporter UT-B). Genes in canonical EMT pathways, including Wnt10a, showed upregulation in lens epithelia samples. Severely GSH-deficient lens epithelia showed downregulation of vision-related genes (including crystallins). The BSO-treated LEGSKO lens epithelia transcriptome has significant correlation (r = 0.63, P < 0.005) to that of lens epithelia undergoing EMT. Protein expression data correlated with transcriptomic data and confirmed EMT signaling activation.

Conclusions

These results show that GSH-deficiency in the lens leads to expression of detoxifying genes and activation of EMT signaling, in addition to changes in transport systems and lipid homeostasis. These data provide insight into the adaptation and consequences of GSH-deficiency in the lens and suggest that GSH plays an important role in lenticular EMT pathology.

miR-21 Promotes Fibrogenesis in Peritoneal Dialysis

Peritoneal dialysis (PD) is a life-saving form of renal replacement therapy for those with end-stage kidney disease. Mesothelial cells (MCs) line the peritoneal cavity and help define peritoneal response to treatment-associated injury, a major reason for treatment failure. miRNAs are important regulators, but their roles in peritoneal fibrosis are largely unknown. In this study, miR-21 was one of the most abundant miRNAs in primary MCs, and was up-regulated by the profibrotic cytokine transforming growth factor-β1 and in PD effluent-derived MCs exhibiting mesenchymal phenotypic change. Increased miR-21 was found in peritoneal membrane biopsy specimens from PD patients compared to healthy controls (PD biocompatible, 5.86×, P = 0.0001; PD conventional, 7.09×, P < 0.0001, n = 11 per group). In PD effluent from a cohort of 230 patients, miR-21 was higher in those receiving the therapy long-term compared to new starters (n = 230, miR-21 3.26×, P = 0.001) and associated with icodextrin use (R = 0.52; 95% CI, 0.20-0.84), peritonitis count (R = 0.16; 95% CI, 0.03-0.29), and dialysate cytokines. miR-21 down-regulated programmed cell death 4 and programmed cell death 4 protein was decreased in peritoneal membrane biopsy specimens from PD patients compared to healthy controls. New miR-21 targets were identified that may be important during PD fibrogenesis. These data identify miR-21 as an important effector of fibrosis in the peritoneal membrane, and a promising biomarker in the dialysis effluent for membrane change in patients receiving PD.

Switching Roles of TGF-β in Cancer Development: Implications for Therapeutic Target and Biomarker Studies

TGF-β induces complicated and even opposite responses in numerous biological processes, e.g., tumor suppression in pre-malignant cells and metastasis promotion in cancer cells. However, the cellular contextual determinants of these different TGF-β roles remain elusive, and the driver genes triggering the determinants’ changes have not been identified. Recently, however, several findings have provided new insights on the contextual determinants of Smads in TGF-β’s biological processes. These novel switches and their effectors may serve as prognostic biomarkers and therapeutic targets of TGF-β-mediated cancer progression.

Silencing of ASC in Cutaneous Squamous Cell Carcinoma

Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an important adaptor protein for inflammasome activation, mediating the secretion of protumorigenic innate cytokines. However, ASC is also known to trigger apoptosis in tumor cells, acting as a tumor-suppressor gene, which is lost in several human cancers. The aim of this study was to evaluate the clinical significance of ASC in human cutaneous squamous cell carcinoma (SCC). Initially, ASC expression was immunohistochemically evaluated in non-metastic and metastatic SCC. While ASC expression does not correlate with metastatic potential, it correlates with the degree of dedifferentiation. Using methylation specific PCR we were able to demonstrate ASC silencing by promotor specific methylation and impaired inflammasome function in methylated cell lines, linking epigenetic modifications to innate immune activation in keratinocytes. Interestingly, upon ASC restoration by treatment with demethylating agents, we were able to restore AIM2 and NLRP3 activation. In summary, loss of ASC driven tumor development is counterbalanced in the identical cell by the inhibition of pro-tumorigenic inflammation in the tumor cell itself.

TGF-β induces p53/Smads complex formation in the PAI-1 promoter to activate transcription

Transforming growth factor β (TGF-β) signaling facilitates tumor development during the advanced stages of tumorigenesis, but induces cell-cycle arrest for tumor suppression during the early stages. However, the mechanism of functional switching of TGF-β is still unknown, and it is unclear whether inhibition of TGF-β signaling results amelioration or exacerbation of cancers. Here we show that the tumor suppressor p53 cooperates with Smad proteins, which are TGF-β signal transducers, to selectively activate plasminogen activator inhibitor type-1 (PAI-1) transcription. p53 forms a complex with Smad2/3 in the PAI-1 promoter to recruit histone acetyltransferase CREB-binding protein (CBP) and enhance histone H3 acetylation, resulting in transcriptional activation of the PAI-1 gene. Importantly, p53 is required for TGF-β-induced cytostasis and PAI-1 is involved in the cytostatic activity of TGF-β in several cell lines. Our results suggest that p53 enhances TGF-β-induced cytostatic effects by activating PAI-1 transcription, and the functional switching of TGF-β is partially caused by p53 mutation or p53 inactivation during cancer progression. It is expected that these findings will contribute to optimization of TGF-β-targeting therapies for cancer.

Hsa-miR-520d converts fibroblasts into CD105+ populations

BACKGROUND

We have previously shown that hsa-miR-520d-5p can convert cancer cells into induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs) via a dedifferentiation by a demethylation mechanism.

METHODS

We tested the effect of miR-520d-5p on human fibroblasts to determine whether it could be safely used in normal cells for future clinical therapeutic applications. After we transfected the microRNA into fibroblasts, we analyzed the phenotypic changes, gene expression levels, and stemness induction in vitro, and we evaluated tumor formation in an in vivo xenograft model.

RESULTS

The transfected fibroblasts turned into CD105+ cell populations, survived approximately 24 weeks, and exhibited increases in both the collagen-producing ability and in differentiation. Combinatorial transfection of small interfering RNAs for miR-520d-5p target genes (ELAVL2, GATAD2B, and TEAD1) produced similar results to miR-520d-5p transfection. These molecules converted normal cells into MSCs and not iPSCs.

CONCLUSIONS

In vitro data indicate the potent usefulness of this small molecule as a therapeutic biomaterial in normal cells and cancer cells because CD105+ cells never converted to iPSCs despite repeated transfections and all types of transfectants lost their tumorigenicity. This maintenance of a benign state following miR-520d-5p transfection appears to be caused by p53 upregulation. We conclude that miR-520d-5p may be a useful biomaterial at an in vitro level.

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Reprogramming during epithelial to mesenchymal transition under the control of TGFβ

Epithelial-mesenchymal transition (EMT) refers to plastic changes in epithelial tissue architecture. Breast cancer stromal cells provide secreted molecules, such as transforming growth factor β (TGFβ), that promote EMT on tumor cells to facilitate breast cancer cell invasion, stemness and metastasis. TGFβ signaling is considered to be abnormal in the context of cancer development; however, TGFβ acting on breast cancer EMT resembles physiological signaling during embryonic development, when EMT generates or patterns new tissues. Interestingly, while EMT promotes metastatic fate, successful metastatic colonization seems to require the inverse process of mesenchymal-epithelial transition (MET). EMT and MET are interconnected in a time-dependent and tissue context-dependent manner and are coordinated by TGFβ, other extracellular proteins, intracellular signaling cascades, non-coding RNAs and chromatin-based molecular alterations. Research on breast cancer EMT/MET aims at delivering biomolecules that can be used diagnostically in cancer pathology and possibly provide ideas for how to improve breast cancer therapy.

Emerging from the shade of p53 mutants: N-terminally truncated variants of the p53 family in EMT signaling and cancer progression

The prevailing view has been that N-terminally truncated p53 family isoforms (ΔNp53, ΔNp63, and DNp73) predominantly counteract cell cycle arrest and apoptosis. Recent progress in the field extend these well-known functions and place these isoforms in the center of a comprehensive regulatory network controlling major epithelial-to-mesenchymal transition (EMT)-relevant signaling pathways [such as transforming growth factor-β (TGF-β), wingless-int (WNT), insulin-like growth factor (IGF), and signal transducer and activator of transcription (STAT)], microRNAs, and EMT-associated transcription factors that promote invasion, loss of tumor cell polarity, and metastatic behavior in conjunction with a chemoresistant phenotype. These observations add new weight to the concept that currently underappreciated truncated forms of this tumor suppressor family play an equally important role in promoting cancer aggressiveness as do mutant p53 proteins, and illustrate how the consequences of ΔN/DN expression depend on cellular contexts. The tumor microenvironment contributes to the emergence of these variants, thereby linking inflammation to the activation of the mesenchymal program. In addition, molecular connections between ΔN/DN forms and self-renewal have arisen, suggesting their potential function in the generation of cancer stem cells (CSCs) from bulk tumor cells. These intriguing insights provoke a new understanding of the acquisition of aggressive traits by carcinoma cells in the absence of p53 mutations, and may help direct the development of new therapies for a broad range of cancers.

Mutant p53 promotes epithelial-mesenchymal plasticity and enhances metastasis in mammary carcinomas of WAP-T mice

To study the postulated mutant p53 (mutp53) "gain of function" effects in mammary tumor development, progression and metastasis, we crossed SV40 transgenic WAP-T mice with mutant p53 transgenic WAP-mutp53 mice. Compared to tumors in monotransgenic WAP-T mice, tumors in bitransgenic WAP-T x WAP-mutp53 mice showed higher tumor grading, enhanced vascularization, and significantly increased metastasis. Bitransgenic tumors revealed a gene signature associated with the oncogenic epithelial-mesenchymal transition pathway (EMT gene signature). In cultures of WAP-T tumor-derived G-2 cancer cells, which are comprised of subpopulations displaying "mesenchymal" and "epithelial" phenotypes, this EMT gene signature was associated with the "mesenchymal" compartment. Furthermore, ectopic expression of mutp53 in G-2 cells sufficed to induce a strong EMT phenotype. In contrast to these in vitro effects, monotransgenic and bitransgenic tumors were phenotypically similar suggesting that in vivo the tumor cell phenotype might be under control of the tumor microenvironment. In support, orthotopic transplantation of G-2 cells as well as of G-2 cells expressing ectopic mutp53 into syngeneic mice resulted in tumors with a predominantly epithelial phenotype, closely similar to that of endogenous primary tumors. We conclude that induction of an EMT gene signature by mutp53 in bitransgenic tumors primarily promotes tumor cell plasticity, that is, the probability of tumor cells to undergo EMT processes under appropriate stimuli, thereby possibly increasing their potential to disseminate and metastasize.

Wild-type and mutant p53 differentially regulate NADPH oxidase 4 in TGF-β-mediated migration of human lung and breast epithelial cells

BACKGROUND

Transforming growth factor-beta (TGF-β) induces the epithelial-to-mesenchymal transition (EMT) leading to increased cell plasticity at the onset of cancer cell invasion and metastasis. Mechanisms involved in TGF-β-mediated EMT and cell motility are unclear. Recent studies showed that p53 affects TGF-β/SMAD3-mediated signalling, cell migration, and tumorigenesis. We previously demonstrated that Nox4, a Nox family NADPH oxidase, is a TGF-β/SMAD3-inducible source of reactive oxygen species (ROS) affecting cell migration and fibronectin expression, an EMT marker, in normal and metastatic breast epithelial cells. Our present study investigates the involvement of p53 in TGF-β-regulated Nox4 expression and cell migration.

METHODS

We investigated the effect of wild-type p53 (WT-p53) and mutant p53 proteins on TGF-β-regulated Nox4 expression and cell migration. Nox4 mRNA and protein, ROS production, cell migration, and focal adhesion kinase (FAK) activation were examined in three different cell models based on their p53 mutational status. H1299, a p53-null lung epithelial cell line, was used for heterologous expression of WT-p53 or mutant p53. In contrast, functional studies using siRNA-mediated knockdown of endogenous p53 were conducted in MDA-MB-231 metastatic breast epithelial cells that express p53-R280K and MCF-10A normal breast cells that have WT-p53.

RESULTS

We found that WT-p53 is a potent suppressor of TGF-β-induced Nox4, ROS production, and cell migration in p53-null lung epithelial (H1299) cells. In contrast, tumour-associated mutant p53 proteins (R175H or R280K) caused enhanced Nox4 expression and cell migration in both TGF-β-dependent and TGF-β-independent pathways. Moreover, knockdown of endogenous mutant p53 (R280K) in TGF-β-treated MDA-MB-231 metastatic breast epithelial cells resulted in decreased Nox4 protein and reduced phosphorylation of FAK, a key regulator of cell motility. Expression of WT-p53 or dominant-negative Nox4 decreased TGF-β-mediated FAK phosphorylation, whereas mutant p53 (R280K) increased phospho-FAK. Furthermore, knockdown of WT-p53 in MCF-10A normal breast epithelial cells increased basal Nox4 expression, whereas p53-R280K could override endogenous WT-p53 repression of Nox4. Remarkably, immunofluorescence analysis revealed MCF-10A cells expressing p53-R280K mutant showed an upregulation of Nox4 in both confluent and migrating cells.

CONCLUSIONS

Collectively, our findings define novel opposing functions for WT-p53 and mutant p53 proteins in regulating Nox4-dependent signalling in TGF-β-mediated cell motility.

Transitions between epithelial and mesenchymal states during cell fate conversions

Cell fate conversion is considered as the changing of one type of cells to another type including somatic cell reprogramming (de-differentiation), differentiation, and trans-differentiation. Epithelial and mesenchymal cells are two major types of cells and the transitions between these two cell states as epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) have been observed during multiple cell fate conversions including embryonic development, tumor progression and somatic cell reprogramming. In addition, MET and sequential EMT-MET during the generation of induced pluripotent stem cells (iPSC) from fibroblasts have been reported recently. Such observation is consistent with multiple rounds of sequential EMT-MET during embryonic development which could be considered as a reversed process of reprogramming at least partially. Therefore in current review, we briefly discussed the potential roles played by EMT, MET, or even sequential EMT-MET during different kinds of cell fate conversions. We also provided some preliminary hypotheses on the mechanisms that connect cell state transitions and cell fate conversions based on results collected from cell cycle, epigenetic regulation, and stemness acquisition.

Clinical significance of apoptosis-associated speck-like protein containing a caspase recruitment domain in oral squamous cell carcinoma

OBJECTIVES

To assess apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) expression in oral squamous cell carcinoma (OSCC) and analyze its clinical and pathological significance.

STUDY DESIGN

ASC expression was studied using immunohistochemistry in 119 OSCCs patients. The relationships between ASC expression and clinical and pathological parameters were statistically analyzed. In addition, the relationships between ASC expression and cell differentiation [IVL (involcrin) expression] and apoptosis (TUNEL [TdT-mediated dUTP nick end labeling] positive cell number) were investigated.

RESULTS

ASC expression showed significant correlations with parameters including clinical tumor stage, mode of invasion, and histological differentiation, and had a significant impact on survival of OSCC. The distribution of ASC correlated well with that of IVL. ASC expression was significantly correlated with the TUNEL-positive cell number.

CONCLUSIONS

Lower ASC expression correlates with clinical and pathological malignancy and, consequently, poor prognosis of OSCC. ASC has a close association with cell differentiation and apoptosis.

TGFβ and matrix-regulated epithelial to mesenchymal transition

BACKGROUND

The progression of cancer through stages that guide a benign hyperplastic epithelial tissue towards a fully malignant and metastatic carcinoma, is driven by genetic and microenvironmental factors that remodel the tissue architecture. The concept of epithelial-mesenchymal transition (EMT) has evolved to emphasize the importance of plastic changes in tissue architecture, and the cross-communication of tumor cells with various cells in the stroma and with specific molecules in the extracellular matrix (ECM).

SCOPE OF THE REVIEW

Among the multitude of ECM-embedded cytokines and the regulatory potential of ECM molecules, this article focuses on the cytokine transforming growth factor β (TGFβ) and the glycosaminoglycan hyaluronan, and their roles in cancer biology and EMT. For brevity, we concentrate our effort on breast cancer.

MAJOR CONCLUSIONS

Both normal and abnormal TGFβ signaling can be detected in carcinoma and stromal cells, and TGFβ-induced EMT requires the expression of hyaluronan synthase 2 (HAS2). Correspondingly, hyaluronan is a major constituent of tumor ECM and aberrant levels of both hyaluronan and TGFβ are thought to promote a wounding reaction to the local tissue homeostasis. The link between EMT and metastasis also involves the mesenchymal-epithelial transition (MET). ECM components, signaling networks, regulatory non-coding RNAs and epigenetic mechanisms form the network of regulation during EMT-MET.

GENERAL SIGNIFICANCE

Understanding the mechanism that controls epithelial plasticity in the mammary gland promises the development of valuable biomarkers for the prognosis of breast cancer progression and even provides new ideas for a more integrative therapeutic approach against disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

p53 inactivation decreases dependence on estrogen/ERK signalling for proliferation but promotes EMT and susceptility to 3-bromopyruvate in ERα+ breast cancer MCF-7 cells

BACKGROUND

Most breast cancers express the estrogen receptor alpha (ERα(+)), harbor wt TP53, depend on estrogen/ERK signalling for proliferation, and respond to anti-estrogens. However, concomittant activation of the epidermal growth factor receptor (EGFR)/MEK pathway promotes resistance by decreasing estrogen dependence. Previously, we showed that retroviral transduction of mutant p53 R175H into wt TP53 ERα(+) MCF-7 cells induces epidermal growth factor (EGF)-independent proliferation, activation of the EGF receptor (p-EGFR) and some characteristics of epithelial-mesenchymal transition (EMT).

PURPOSE

To investigate whether p53 inactivation augments ERα(+) cell proliferation in response to restrictive estradiol, chemical MEK inhibition or metabolic inhibitors.

RESULTS

Introduction of mutant p53 R175H lowered expression of p53-dependent PUMA and p21WAF1, decreased E-cadherin and cytokeratin 18 associated with EMT, but increased the % of proliferating ERα(+)/Ki67 cells, diminishing estrogen dependence. These cells also exhibited higher proliferation in the presence of MEK-inhibitor UO126, reciprocally correlating with preferential susceptibility to the pyruvate analog 3-bromopyruvate (3-BrPA) without a comparable response to 2-deoxyglucose. p53 siRNA silencing by electroporation in wt TP53 MCF-7 cells also decreased estrogen dependence and response to MEK inhibition, while also conferring susceptibility to 3-BrPA.

CONCLUSIONS

(a) ERα(+) breast cancer cells dysfunctional for TP53 which proliferate irrespective of low estrogen and chemical MEK inhibition are likely to increase metabolic consumption becoming increasingly susceptible to 3-BrPA; (b) targeting the pyruvate pathway may improve response to endocrine therapy in ERα(+) breast cancer with p53 dysfunction.

RASSF3 downregulation increases malignant phenotypes of non-small cell lung cancer

BACKGROUND

Ras-Association Family1A (RASSF1A) is a well-established tumor suppressor. Ten RASSF homologues comprise this family, and each member is considered a tumor suppressor. RASSF3 is one of the RASSF family members, but its function has not yet been clarified. Recently, we found that RASSF3 interacts with MDM2 and facilitates its ubiquitination, which induces apoptosis through p53 stabilization. However, the role of RASSF3 in human malignancies remains largely unknown.

PATIENTS AND METHODS

Ninety-five non-small cell lung cancer (NSCLC) patients from Nagoya University Hospital and 45 NSCLC patients from Aichi Cancer Center Hospital underwent pulmonary resection at each hospital, and lung cancer and corresponding non-cancerous lung tissues were collected. The expression levels of RASSF3 were analyzed using quantitative real-time reverse transcription PCR. We performed statistical analysis to investigate the correlation with RASSF3 expression and the clinicopathological characteristics. We also transfected RASSF3-siRNA into NSCLC cells, and performed motility assays to evaluate the influence on migration ability.

RESULTS

RASSF3 expression levels were downregulated in 125 of a total 140 NSCLCs. In a multivariate logistic regression analysis, the low RASSF3 expression group below the median value was independently correlated with progressive phenotypes (lymph node metastasis and pleural invasion), non-adenocarcinoma histology and wild-type epidermal growth factor receptor (EGFR) status. In motility assays, RASSF3-knockdown NSCLC cells increased the migration rate compared to the control cells.

CONCLUSIONS

We found that the expression levels of RASSF3 were frequently downregulated in NSCLCs. Downregulation of RASSF3 strongly correlated with the progressive phenotypes of NSCLCs and EGFR wild-type status. In vitro studies also suggested that RASSF3 downregulation increases migration ability of lung cancer cells. Together, our findings indicate RASSF3 is a candidate tumor suppressor gene of NSCLCs.

DEAR1 is a chromosome 1p35 tumor suppressor and master regulator of TGF-β-driven epithelial-mesenchymal transition

Deletion of chromosome 1p35 is a common event in epithelial malignancies. We report that DEAR1 (annotated as TRIM62) is a chromosome 1p35 tumor suppressor that undergoes mutation, copy number variation, and loss of expression in human tumors. Targeted disruption in the mouse recapitulates this human tumor spectrum, with both Dear1(-/-) and Dear1(+/-) mice developing primarily epithelial adenocarcinomas and lymphoma with evidence of metastasis in a subset of mice. DEAR1 loss of function in the presence of TGF-β results in failure of acinar morphogenesis, upregulation of epithelial-mesenchymal transition (EMT) markers, anoikis resistance, migration, and invasion. Furthermore, DEAR1 blocks TGF-β-SMAD3 signaling, resulting in decreased nuclear phosphorylated SMAD3 by binding to and promoting the ubiquitination of SMAD3, the major effector of TGF-β-induced EMT. Moreover, DEAR1 loss increases levels of SMAD3 downstream effectors SNAIL1 and SNAIL2, with genetic alteration of DEAR1/SNAIL2 serving as prognostic markers of overall poor survival in a cohort of 889 cases of invasive breast cancer.

SIGNIFICANCE

Cumulative results provide compelling evidence that DEAR1 is a critical tumor suppressor involved in multiple human cancers and provide a novel paradigm for regulation of TGF-β-induced EMT through DEAR1's regulation of SMAD3 protein levels. DEAR1 loss of function has important therapeutic implications for targeted therapies aimed at the TGF-β-SMAD3 pathway.