Down-regulation of FXYD3 is induced by transforming growth factor-β signaling via ZEB1/δEF1 in human mammary epithelial cells

Metastasis and chemoresistance in breast cancer: Crucial function of ZEB1/2 proteins

Breast cancer remains one of the leading causes of mortality worldwide. While advancements in chemotherapy, immunotherapy, radiotherapy, and targeted therapies have significantly improved breast cancer treatment, many patients are diagnosed at advanced stages, where tumor cells exhibit aggressive behavior and therapy resistance. Understanding the mechanisms driving breast cancer progression is therefore critical. Metastasis is a major factor that drastically reduces patient prognosis and survival, accounting for most breast cancer-related deaths. ZEB proteins have emerged as key regulators of cancer metastasis. Beyond their role in metastasis, ZEB proteins also influence drug resistance. This review focuses on the role of ZEB1 and ZEB2 in regulating breast cancer metastasis. These proteins interact with components of the tumor microenvironment (TME) to drive cancer progression and metastasis. Additionally, ZEB proteins regulate angiogenesis through interactions with VEGF. Targeting ZEB proteins offers potential therapeutic benefits, particularly for aggressive breast cancer subtypes such as triple-negative breast cancer (TNBC), which often show poor therapeutic response. ZEB proteins also influence the sensitivity of breast cancer cells to chemotherapy, making them promising targets for enhancing treatment efficacy. Given their upregulation in breast cancer, ZEB proteins can serve as valuable diagnostic and prognostic markers.

Nuclear α-actinin-4 regulates breast cancer invasiveness and EMT

Epithelial-to-mesenchymal transition (EMT) is a key process where cells lose their adhesion properties and augment their invasive properties. α-Actinin4 (ACTN4) is an actin crosslinking protein that responds to mechanical stimuli and is found to be elevated in breast cancer patients. While ACTN4 has been implicated in regulating cancer invasiveness by modulating cytoskeletal organization, its nuclear functions remain much less explored. Here we address this question by first establishing a correlation between nuclear localization and invasiveness in breast cancer cells. Using cancer databases, we then establish a correlation between ACTN4 expression and EMT in breast cancer. Interestingly, TGFβ-induced EMT induction in MCF10A normal mammary epithelial cells leads to increased ACTN4 expression and nuclear enrichment. We then show that ACTN4 knockdown in MDA-MB-231 breast cancer cells, which harbor sizeable fraction of nuclear ACTN4, leads to reduced invasiveness and loss of mesenchymal traits. Similar behavior was observed in knockdown cells expressing K255E ACTN4, which is primarily localized to the cytosol. Together, our findings establish a role for nuclear ACTN4 in regulating invasiveness via modulation of EMT.

FXYD3 functionally demarcates an ancestral breast cancer stem cell subpopulation with features of drug-tolerant persisters

The heterogeneity of cancer stem cells (CSCs) within tumors presents a challenge in therapeutic targeting. To decipher the cellular plasticity that fuels phenotypic heterogeneity, we undertook single-cell transcriptomics analysis in triple-negative breast cancer (TNBC) to identify subpopulations in CSCs. We found a subpopulation of CSCs with ancestral features that is marked by FXYD domain-containing ion transport regulator 3 (FXYD3), a component of the Na+/K+ pump. Accordingly, FXYD3+ CSCs evolve and proliferate, while displaying traits of alveolar progenitors that are normally induced during pregnancy. Clinically, FXYD3+ CSCs were persistent during neoadjuvant chemotherapy, hence linking them to drug-tolerant persisters (DTPs) and identifying them as crucial therapeutic targets. Importantly, FXYD3+ CSCs were sensitive to senolytic Na+/K+ pump inhibitors, such as cardiac glycosides. Together, our data indicate that FXYD3+ CSCs with ancestral features are drivers of plasticity and chemoresistance in TNBC. Targeting the Na+/K+ pump could be an effective strategy to eliminate CSCs with ancestral and DTP features that could improve TNBC prognosis.

Extended Exposure Topotecan Significantly Improves Long-Term Drug Sensitivity by Decreasing Malignant Cell Heterogeneity and by Preventing Epithelial-Mesenchymal Transition

Maximum tolerable dosing (MTD) of chemotherapeutics has long been the gold standard for aggressive malignancies. Recently, alternative dosing strategies have gained traction for their improved toxicity profiles and unique mechanisms of action, such as inhibition of angiogenesis and stimulation of immunity. In this article, we investigated whether extended exposure (EE) topotecan could improve long-term drug sensitivity by preventing drug resistance. To achieve significantly longer exposure times, we used a spheroidal model system of castration-resistant prostate cancer. We also used state-of-the-art transcriptomic analysis to further elucidate any underlying phenotypic changes that occurred in the malignant population following each treatment. We determined that EE topotecan had a much higher barrier to resistance relative to MTD topotecan and was able to maintain consistent efficacy throughout the study period (EE IC50 of 54.4 nM (Week 6) vs. MTD IC50 of 2200 nM (Week 6) vs. 83.8 nM IC50 for control (Week 6) vs. 37.8 nM IC50 for control (Week 0)). As a possible explanation for these results, we determined that MTD topotecan stimulated epithelial-mesenchymal transition (EMT), upregulated efflux pumps, and produced altered topoisomerases relative to EE topotecan. Overall, EE topotecan resulted in a more sustained treatment response and maintained a less aggressive malignant phenotype relative to MTD topotecan.

Next Generation of Ovarian Cancer Detection Using Aptamers

Ovarian cancer is among the seven most common types of cancer in women, being the most fatal gynecological tumor, due to the difficulty of detection in early stages. Aptamers are important tools to improve tumor diagnosis through the recognition of specific molecules produced by tumors. Here, aptamers and their potential targets in ovarian cancer cells were analyzed by in silico approaches. Specific aptamers were selected by the Cell-SELEX method using Caov-3 and OvCar-3 cells. The five most frequent aptamers obtained from the last round of selection were computationally modeled. The potential targets for those aptamers in cells were proposed by analyzing proteomic data available for the Caov-3 and OvCar-3 cell lines. Overexpressed proteins for each cell were characterized as to their three-dimensional model, cell location, and electrostatic potential. As a result, four specific aptamers for ovarian tumors were selected: AptaC2, AptaC4, AptaO1, and AptaO2. Potential targets were identified for each aptamer through Molecular Docking, and the best complexes were AptaC2-FXYD3, AptaC4-ALPP, AptaO1-TSPAN15, and AptaO2-TSPAN15. In addition, AptaC2 and AptaO1 could detect different stages and subtypes of ovarian cancer tissue samples. The application of this technology makes it possible to propose new molecular biomarkers for the differential diagnosis of epithelial ovarian cancer.

Identification of Gene Signatures and Expression Patterns During Epithelial-to-Mesenchymal Transition From Single-Cell Expression Atlas

Cancer, which refers to abnormal cell proliferative diseases with systematic pathogenic potential, is one of the leading threats to human health. The final causes for patients’ deaths are usually cancer recurrence, metastasis, and drug resistance against continuing therapy. Epithelial-to-mesenchymal transition (EMT), which is the transformation of tumor cells (TCs), is a prerequisite for pathogenic cancer recurrence, metastasis, and drug resistance. Conventional biomarkers can only define and recognize large tissues with obvious EMT markers but cannot accurately monitor detailed EMT processes. In this study, a systematic workflow was established integrating effective feature selection, multiple machine learning models [Random forest (RF), Support vector machine (SVM)], rule learning, and functional enrichment analyses to find new biomarkers and their functional implications for distinguishing single-cell isolated TCs with unique epithelial or mesenchymal markers using public single-cell expression profiling. Our discovered signatures may provide an effective and precise transcriptomic reference to monitor EMT progression at the single-cell level and contribute to the exploration of detailed tumorigenesis mechanisms during EMT.

Prognostic significance of sodium-potassium ATPase regulator, FXYD3, in human hepatocellular carcinoma

The clinical significance of the sodium-potassium ATPase regulator FXYD domain-containing ion transport regulator 3 (FXYD3) has been demonstrated in a number of types of cancer. However, the role of this protein in human hepatocellular carcinoma (HCC) remains to be elucidated. In the present study, 217 HCC tissue samples were analyzed to evaluate the expression and prognostic significance of FXYD3 in HCC. Reverse transcription-quantitative polymerase chain reaction was used to analyze the mRNA expression of FXYD3 in 80 primary HCC specimens and paired non-cancerous liver tissue samples, while western blotting was used to analyze the protein expression level of FXYD3 in another 24 pairs. These analyses demonstrated that the expression level of FXYD3 was significantly increasedb at the mRNA and protein levels in HCC tumor tissues compared with adjacent non-cancerous tissues. Immunohistochemical analysis of 137 paraffin-embedded HCC tissue samples indicated that the expression of FXYD3 was associated with HCC clinicopathological characteristics. Kaplan-Meier analysis demonstrated that patients with high FXYD3 protein expression (n=60) experienced significantly poorer overall survival time compared with patients with low FXYD3 protein expression (n=77) (P<0.001). Multivariate analysis demonstrated that FYXD3 protein expression level (hazard ratio, 2.137; 95% confidence interval, 1.224–3.732; P=0.008) was an independent prognostic factor in patients with HCC. Overall, the results indicated that FXYD3 expression levels were higher in HCC tumor tissues than in adjacent non-cancerous tissues, and that the FXYD3 protein may serve as a prognostic marker for HCC.

Immune oppression array elucidating immune escape and survival mechanisms in uveal melanoma

AIM

To examine the genetic profile of primary uveal melanoma (UM) as compared to UM in immune escape.

METHODS

Dendritic cells (DC) loaded with lysates of UM cells of high metastatic potential were used to stimulate CTLs(CTLs). When CTLs co-cultured with the UM cells, most UM cells could be eliminated. Survival UM cells grew slowly and were considered to be survival variants and examined by a microarray analysis. These differential genes were analyzed further with Venn Diagrams and functions related to immune escape. We additionally examined transcriptional changes of manually selected survival variants of UM cells and of clinical UM samples by quantitative real-time polymerase chain reaction (qRT-PCR), and analyzed the correlation of these expressions and patients' survival.

RESULTS

Gene expression analyses revealed a marked up-regulation of SLAMF7 and CCL22 and a significant down-regulation of KRT10, FXYD3 and ABCC2. The expression of these genes in the relapsed UM was significantly greater than those in primary UM. UM patients with overexpression of these genes had a shorter survival period as compared with those of their underexpression.

CONCLUSION

Gene expression, in particular of SLAMF7, CCL22, KRT10, FXYD3 and ABCC2, differed between primary UM cells and survival variants of UM cells.

Epigenetic regulation of ZEB1-RAB25/ESRP1 axis plays a critical role in phenylbutyrate treatment-resistant breast cancer

Phenylbutyrate (PB) is a histone deacetylase antagonist that also exhibits antitumor activity. In this study, we used 7 breast cancer cell lines to identify biomarker candidates that predict PB sensitivity in breast cancer.

Comprehensive gene expression profiles were compared using microarrays, and the importance of the identified genes to PB sensitivity was confirmed in gene transfection experiments. CRL and MDAMB453 cells were identified as PB-sensitive, while MDAMB231 cells were PB-resistant.RAB25 and ESRP1 were identified as key regulators of PB sensitivity, while ANKD1, ETS1, PTRF, IFI16 and KIAA1199 acted as PB resistance-related genes. Expression of these genes was dramatically altered by DNA demethylation treatments. RAB25 expression inhibited IFI16 and PTRF, while ESRP1 expression suppressed ANKRD1, ETS1, and KIAA1199. Both RAB25 and ESRP1 were suppressed by ZEB1, which was in turn regulated via epigenetic mechanisms. Thus, PB sensitivity is influenced by epigenetic expression alteration of ZEB1. The genes associated with PB sensitivity are downstream targets of ZEB1. Epigenetic regulation of ZEB1 may prove valuable as a critical biomarker for predicting resistance to breast cancer therapies.

The impact of hypoxia on intestinal epithelial cell functions: consequences for invasion by bacterial pathogens

The maintenance of oxygen homeostasis in human tissues is mediated by several cellular adaptations in response to low-oxygen stress, called hypoxia. A decrease in tissue oxygen levels is initially counteracted by increasing local blood flow to overcome diminished oxygenation and avoid hypoxic stress. However, studies have shown that the physiological oxygen concentrations in several tissues are much lower than atmospheric (normoxic) conditions, and the oxygen supply is finely regulated in individual cell types. The gastrointestinal tract has been described to subsist in a state of physiologically low oxygen level and is thus depicted as a tissue in the state of constant low-grade inflammation. The intestinal epithelial cell layer plays a vital role in the immune response to inflammation and infections that occur within the intestinal tissue and is involved in many of the adaptation responses to hypoxic stress. This is especially relevant in the context of inflammatory disorders, such as inflammatory bowel disease (IBD). Therefore, this review aims to describe the intestinal epithelial cellular response to hypoxia and the consequences for host interactions with invading gastrointestinal bacterial pathogens.

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.

Silencing overexpression of FXYD3 protein in breast cancer cells amplifies effects of doxorubicin and γ-radiation on Na(+)/K(+)-ATPase and cell survival

FXYD3, also known as mammary tumor protein 8, is overexpressed in several common cancers, including in many breast cancers. We examined if such overexpression might protect Na(+)/K(+)-ATPase and cancer cells against the high levels of oxidative stress characteristic of many tumors and often induced by cancer treatments. We measured FXYD3 expression, Na(+)/K(+)-ATPase activity and glutathionylation of the β1 subunit of Na(+)/K(+)-ATPase, a reversible oxidative modification that inhibits the ATPase, in MCF-7 and MDA-MB-468 cells. Expression of FXYD3 was suppressed by transfection with FXYD3 siRNA. A colorimetric end-point assay was used to estimate cell viability. Apoptosis was estimated by caspase 3/7 (DEVDase) activation using a Caspase fluorogenic substrate kit. Expression of FXYD3 in MCF-7 breast cancer cells was ~eightfold and ~twofold higher than in non-cancer MCF-10A cells and MDA-MB-468 cancer cells, respectively. A ~50 % reduction in FXYD3 expression increased glutathionylation of the β1 Na(+)/K(+)-ATPase subunit and reduced Na(+)/K(+)-ATPase activity by ~50 %, consistent with the role of FXYD3 to facilitate reversal of glutathionylation of the β1 subunit of Na(+)/K(+)-ATPase and glutathionylation-induced inhibition of Na(+)/K(+)-ATPase. Treatment of MCF-7 and MDA-MB- 468 cells with doxorubicin or γ-radiation decreased cell viability and induced apoptosis. The treatments upregulated FXYD3 expression in MCF-7 but not in MDA-MB-468 cells and suppression of FXYD3 in MCF-7 but not in MDA-MB-468 cells amplified effects of treatments on Na(+)/K(+)-ATPase activity and treatment-induced cell death and apoptosis. Overexpression of FXYD3 may be a marker of resistance to cancer treatments and a potentially important therapeutic target.

FXYD1 negatively regulates Na(+)/K(+)-ATPase activity in lung alveolar epithelial cells

Acute respiratory distress syndrome (ARDS) is clinical syndrome characterized by decreased lung fluid reabsorption, causing alveolar edema. Defective alveolar ion transport undertaken in part by the Na(+)/K(+)-ATPase underlies this compromised fluid balance, although the molecular mechanisms at play are not understood. We describe here increased expression of FXYD1, FXYD3 and FXYD5, three regulatory subunits of the Na(+)/K(+)-ATPase, in the lungs of ARDS patients. Transforming growth factor (TGF)-β, a pathogenic mediator of ARDS, drove increased FXYD1 expression in A549 human lung alveolar epithelial cells, suggesting that pathogenic TGF-β signaling altered Na(+)/K(+)-ATPase activity in affected lungs. Lentivirus-mediated delivery of FXYD1 and FXYD3 allowed for overexpression of both regulatory subunits in polarized H441 cell monolayers on an air/liquid interface. FXYD1 but not FXYD3 overexpression inhibited amphotericin B-sensitive equivalent short-circuit current in Ussing chamber studies. Thus, we speculate that FXYD1 overexpression in ARDS patient lungs may limit Na(+)/K(+)-ATPase activity, and contribute to edema persistence.

Estrogen and tamoxifen up-regulate FXYD3 on breast cancer cells: assessing the differential roles of ER α and ZEB1

Increased expression of the FXYD3 family of proteins has been associated with lung, colorectal, bladder and pancreatic cancers, and recent evidence suggests that elevated FXYD3 may promote tumor cell proliferation in breast cancer as well. However, factors involved in up-regulating the expression of FXYD3 in breast cancer have not been identified. We evaluated whether estrogen and the selective estrogen receptor modulator tamoxifen could regulate the expression of FXYD3 on breast cancer cells. Estrogen receptor (ER) α-positive MCF-7 and ER α-negative MDA-MB-231 human breast cancer cells used in our studies were treated with estrogen, tamoxifen or the combination of these agents. Relative expression of FXYD3 was assessed using fluorochrome-tagged antibodies and a fluorescence cytometer. We found that estrogen and tamoxifen, used alone or in combination, significantly increased FXYD3 on MCF-7 cells. FXYD3 levels did not increase compared to the control samples when ER α-negative 231 cells were treated with estrogen or tamoxifen, alone or in combination, indicating that ER α was required for the increased FXYD3 response. We showed that ER α associates with the transcription factor ZEB1 in MCF-7 cells, and that decreasing ZEB1 protein expression using siRNA disrupts the ability of estrogen, but not tamoxifen, to increase FXYD3 in MCF-7 cells. Our results indicate that there may be two mechanisms, both involving ER α and one requiring ZEB1, through which FXYD3 may be increased by estrogen and tamoxifen in breast cancer cells. Ongoing research endeavors are focusing on identifying cellular components through which estrogen and tamoxifen, alone or in combination, differentially regulate FXYD3 expression in human breast cancer cells.

Inflammatory factors of the tumor microenvironment induce plasticity in nontransformed breast epithelial cells: EMT, invasion, and collapse of normally organized breast textures

Nontransformed breast epithelial cells that are adjacent to tumor cells are constantly exposed to tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β), two inflammatory cytokines identified as having pro-tumoral causative roles. We show that continuous stimulation of nontransformed breast epithelial cells by TNFα + IL-1β for 2 to 3 weeks induced their spreading and epithelial-to-mesenchymal transition (EMT). The mechanistic bases for this slow induction of EMT by TNFα + IL-1β are: 1) it took 2 to 3 weeks for the cytokines to induce the expression of the EMT activators Zeb1 and Snail; 2) although Twist has amplified the EMT-inducing activities of Zeb1 + Snail, its expression was reduced by TNFα + IL-1β; however, the lack of Twist was compensated by prolonged stimulation with TNFα + IL-1β that has potentiated the EMT-inducing activities of Zeb1 + Snail. Stimulation by TNFα + IL-1β has induced the following dissemination-related properties in the nontransformed cells: 1) up-regulation of functional matrix metalloproteinases; 2) induction of migratory and invasive capabilities; 3) disruption of the normal phenotype of organized three-dimensional acini structures typically formed only by nontransformed breast cells and spreading of nontransformed cells out of such acini. Our findings suggest that TNFα + IL-1β induce dissemination of nontransformed breast epithelial cells and their reseeding at the primary tumor site; if, then, such detached cells are exposed to transforming events, they may form secondary malignant focus and lead to disease recurrence. Thus, our study reveals novel pathways through which the inflammatory microenvironment may contribute to relapsed disease in breast cancer.

Akt-mediated transforming growth factor-β1-induced epithelial-mesenchymal transition in cultured human esophageal squamous cancer cells

Epithelial-mesenchymal transition (EMT) has a crucial role during embryonic development and has also come under intense scrutiny as a mechanism through which esophageal squamous cell cancer (ESCC) progresses to become metastatic. Transforming growth factor beta (TGF-β)-mediated EMT has been observed in a variety of cell types and has been identified as the main inducer of EMT in many types of cancer. Akt activity is involved in TGF-β-mediated EMT; however, its precise relationship and role in EMT in ESCC has not been well explained to date. Our data demonstrated that in human ESCC tissues Akt and its activated form, phosphorylated-Akt (p-Akt), were overexpressed; in addition, Akt and p-Akt were negatively correlated with epithelial cadherin (E-cadherin). In EC-9706 cells, exogenous TGF-β1 could induce EMT and at the same time could increase the EC-9706 cell invasive and metastatic ability. Moreover, Akt knockdown by small-interfering RNA could attenuate the EMT induced by TGF-β1 by increasing the epithelial marker E-cadherin and decreasing the mesenchymal marker Vimentin. Silencing Akt expression could decrease the migration ability of EC-9706 cells efficiently. In short, Akt is likely to have a more important role in the EMT induced by TGF-β1 in EC-9706 and may contribute to the invasive and metastatic ability of EC-9706. Akt may be an effective therapeutic in advanced and metastatic ESCC.

PuF, an antimetastatic and developmental signaling protein, interacts with the Alzheimer's amyloid-β precursor protein via a tissue-specific proximal regulatory element (PRE)

BACKGROUND

Alzheimer's disease (AD) is intimately tied to amyloid-β (Aβ) peptide. Extraneuronal brain plaques consisting primarily of Aβ aggregates are a hallmark of AD. Intraneuronal Aβ subunits are strongly implicated in disease progression. Protein sequence mutations of the Aβ precursor protein (APP) account for a small proportion of AD cases, suggesting that regulation of the associated gene (APP) may play a more important role in AD etiology. The APP promoter possesses a novel 30 nucleotide sequence, or "proximal regulatory element" (PRE), at -76/-47, from the +1 transcription start site that confers cell type specificity. This PRE contains sequences that make it vulnerable to epigenetic modification and may present a viable target for drug studies. We examined PRE-nuclear protein interaction by gel electrophoretic mobility shift assay (EMSA) and PRE mutant EMSA. This was followed by functional studies of PRE mutant/reporter gene fusion clones.

RESULTS

EMSA probed with the PRE showed DNA-protein interaction in multiple nuclear extracts and in human brain tissue nuclear extract in a tissue-type specific manner. We identified transcription factors that are likely to bind the PRE, using competition gel shift and gel supershift: Activator protein 2 (AP2), nm23 nucleoside diphosphate kinase/metastatic inhibitory protein (PuF), and specificity protein 1 (SP1). These sites crossed a known single nucleotide polymorphism (SNP). EMSA with PRE mutants and promoter/reporter clone transfection analysis further implicated PuF in cells and extracts. Functional assays of mutant/reporter clone transfections were evaluated by ELISA of reporter protein levels. EMSA and ELISA results correlated by meta-analysis.

CONCLUSIONS

We propose that PuF may regulate the APP gene promoter and that AD risk may be increased by interference with PuF regulation at the PRE. PuF is targeted by calcium/calmodulin-dependent protein kinase II inhibitor 1, which also interacts with the integrins. These proteins are connected to vital cellular and neurological functions. In addition, the transcription factor PuF is a known inhibitor of metastasis and regulates cell growth during development. Given that APP is a known cell adhesion protein and ferroxidase, this suggests biochemical links among cell signaling, the cell cycle, iron metabolism in cancer, and AD in the context of overall aging.

δEF1 down-regulates ER-α expression and confers tamoxifen resistance in breast cancer

Resistance to tamoxifen therapy represents a major barrier to the successful treatment of breast cancer, where a loss of or reduced ER-α level is considered a primary mechanism. Understanding how ER-α expression is regulated would provide insights into new intervention points to overcome tamoxifen resistance. In this study, we report that the expression of δEF1 is up-regulated by 17β-estradiol (E2) in MCF-7 cells in an ER-α-dependent manner, through either PI3K or NF-κB pathway. Ectopic expression of δEF1 in turn repressed ER-α transcription by binding to the E(2)-box on the ER-α promoter. At the tissue level of breast cancer, there is a strong and inverse correlation between the expression levels of δEF1 and ER-α. In MCF-7 cells, an elevated expression of δEF1 made the cells less sensitive to tamoxifen treatment, whereas overexpression of ER-α compromised the effects of δEF1 and restored the sensitivity. Also, depletion of δEF1 by RNA interference in MDA-MB-231 cells restored the expression of ER-α and tamoxifen sensitivity. In conclusion, we have identified an important role of δEF1 in the development of tamoxifen resistance in breast cancer. Inhibiting δEF1 to restore ER-α expression might represent a potential therapeutic strategy for overcoming endocrine resistance in breast cancer.

Meta-analysis of gene expression signatures defining the epithelial to mesenchymal transition during cancer progression

The epithelial to mesenchymal transition (EMT) represents a crucial event during cancer progression and dissemination. EMT is the conversion of carcinoma cells from an epithelial to a mesenchymal phenotype that associates with a higher cell motility as well as enhanced chemoresistance and cancer stemness. Notably, EMT has been increasingly recognized as an early event of metastasis. Numerous gene expression studies (GES) have been conducted to obtain transcriptome signatures and marker genes to understand the regulatory mechanisms underlying EMT. Yet, no meta-analysis considering the multitude of GES of EMT has been performed to comprehensively elaborate the core genes in this process. Here we report the meta-analysis of 18 independent and published GES of EMT which focused on different cell types and treatment modalities. Computational analysis revealed clustering of GES according to the type of treatment rather than to cell type. GES of EMT induced via transforming growth factor-β and tumor necrosis factor-α treatment yielded uniformly defined clusters while GES of models with alternative EMT induction clustered in a more complex fashion. In addition, we identified those up- and downregulated genes which were shared between the multitude of GES. This core gene list includes well known EMT markers as well as novel genes so far not described in this process. Furthermore, several genes of the EMT-core gene list significantly correlated with impaired pathological complete response in breast cancer patients. In conclusion, this meta-analysis provides a comprehensive survey of available EMT expression signatures and shows fundamental insights into the mechanisms that are governing carcinoma progression.

Transforming growth factor-β signaling in tumor initiation, progression and therapy in breast cancer: an update

Transforming growth factor-β (TGF-β) is a ubiquitous cytokine playing an essential role in cell proliferation, differentiation, apoptosis, adhesion and invasion, as well as in cellular microenvironment. In malignant diseases, TGF-β signaling features a growth inhibitory effect at an early stage but aggressive oncogenic activity at the advanced malignant state. Here, we update the current understanding of TGF-β signaling in cancer development and progression with a focus on breast cancer. We also review the current approaches of TGF-β signaling-targeted therapeutics for human malignancies.