Genetic profiling of epithelial cells expressing E-cadherin repressors reveals a distinct role for Snail, Slug, and E47 factors in epithelial-mesenchymal transition

EZH2 inhibition promotes epithelial-to-mesenchymal transition in ovarian cancer cells

Cancer cells acquire essential characteristics for metastatic dissemination through the process of epithelial-to-mesenchymal transition (EMT), which is regulated by gene expression and chromatin remodeling changes. The enhancer of zeste homolog 2 (EZH2), the catalytic subunit of the polycomb repressive complex 2 (PRC2), catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) to repress gene transcription. Here we report the functional roles of EZH2-catalyzed H3K27me3 during EMT in ovarian cancer (OC) cells. TGF-β-induced EMT in SKOV3 OC cells was associated with decreased levels of EZH2 and H3K27me3 (P<0.05). These effects were delayed (~72 h relative to EMT initiation) and coincided with increased (>15-fold) expression of EMT-associated transcription factors ZEB2 and SNAI2. EZH2 knockdown (using siRNA) or enzymatic inhibition (by GSK126) induced EMT-like changes in OC cells. The EMT regulator ZEB2 was upregulated in cells treated with either approach. Furthermore, TGF-β enhanced expression of ZEB2 in EZH2 siRNA- or GSK126-treated cells (P<0.01), suggesting that H3K27me3 plays a role in TGF-β-stimulated ZEB2 induction. Chromatin immunoprecipitation assays confirmed that TGF-β treatment decreased binding of EZH2 and H3K27me3 to the ZEB2 promoter (P<0.05). In all, these results demonstrate that EZH2, by repressing ZEB2, is required for the maintenance of an epithelial phenotype in OC cells.

Plasminogen activator inhibitor-1 enhances radioresistance and aggressiveness of non-small cell lung cancer cells

Acquired resistance of tumor cells during treatment limits the clinical efficacy of radiotherapy. Recent studies to investigate acquired resistance under treatment have focused on intercellular communication because it promotes survival and aggressiveness of tumor cells, causing therapy failure and tumor relapse. Accordingly, a better understanding of the functional communication between subpopulations of cells within a tumor is essential to development of effective cancer treatment strategies. Here, we found that conditioned media (CM) from radioresistant non-small cell lung cancer (NSCLC) cells increased survival of radiosensitive cells. Comparative proteomics analysis revealed plasminogen activator inhibitor-1 (PAI-1) as a key molecule in the secretome that acts as an extracellular signaling trigger to strengthen resistance to radiation. Our results revealed that expression and secretion of PAI-1 in radioresistant cells was increased by radiation-induced transcription factors, including p53, HIF-1α, and Smad3. When CM from radioresistant cells was applied to radiosensitive cells, extracellular PAI-1 activated the AKT and ERK1/2 signaling pathway and inhibited caspase-3 activity. Our study also proposed that PAI-1 activates the signaling pathway in radiosensitive cells via extracellular interaction with its binding partners, not clathrin-mediated endocytosis. Furthermore, secreted PAI-1 increased cell migration capacity and expression of EMT markers in vitro and in vivo. Taken together, our findings demonstrate that PAI-1 secreted from radioresistant NSCLC cells reduced radiosensitivity of nearby cells in a paracrine manner, indicating that functional inhibition of PAI-1 signaling has therapeutic potential because it prevents sensitive cells from acquiring radioresistance.

Smad4 and epithelial-mesenchymal transition proteins in colorectal carcinoma: an immunohistochemical study

Epithelial-mesenchymal transition (EMT) plays an important role in cancer metastasis. During EMT, tumor cells acquire the capacity to migrate and invade the stroma. Activation of the transforming growth factor-b (TGF-b) signaling pathway is of major importance for the initiation of EMT. Smad4, an essential protein of this pathway, is known to complex with multiple transcription factors (e.g. Snail-1, Slug, Twist-1), in various types of cancer, promoting the repression or activation of target genes. The role of Smad4 in colorectal cancer (CRC) is not straightforward so far. In the present study forty eight resected CRC tumor specimens were immunohistochemically examined in order to assess the expression of Smad4 and its association with E-cadherin, Snail-1, Slug, Twist-1 protein expression and with various pathological parameters. Smad4 was found to be positively correlated with Snail-1, Slug and Twist-1 expression (p < 0.001). On the other hand it was negatively correlated with the expression of E-cadherin (p < 0.001). Furthermore, lymphatic invasion could be clearly associated with Smad4 expression, a finding complying with the metastatic ability of EMT cells. In conclusion, Smad4 could be considered as a central component of EMT transition in human colorectal cancer that combines with transcriptional factors to reduce E-cadherin and alter the expression of the epithelial phenotype.

Differential expression profiles of conserved Snail transcription factors in the mouse testis

Snail transcription factors are key regulators of cellular transitions during embryonic development and tumorigenesis. The closely related SNAI1 and SNAI2 proteins induce epithelial-mesenchymal transitions (EMTs), acting predominantly as transcriptional repressors, while the functions of SNAI3 are unknown. An initial examination of Snai2-deficient mice provided evidence of deficient spermatogenesis. To address the hypothesis that Snail proteins are important for male fertility, this study provides the first comprehensive cellular expression profiles of all three mammalian Snail genes in the post-natal mouse testis. To evaluate Snail transcript expression profiles, droplet digital (dd) PCR and in situ hybridization were employed. Snai1, 2 and 3 transcripts are readily detected at 7, 14, 28 days post-partum (dpp) and 7 weeks (adult). Unique cellular expression was demonstrated for each by in situ hybridization and immunohistochemistry using Western blot-validated antibodies. SNAI1 and SNAI2 are in the nucleus of the most mature germ cell types at post-natal ages 10, 15 and 26. SNAI3 is only detected from 15 dpp onwards and is localized in the Sertoli cell cytoplasm. In the adult testis, Snai1 and Snai2 transcripts are detected in spermatogonia and spermatocytes, while Snai3 is in both germ and Sertoli cells. SNAI1 protein is evident in nuclei of spermatogonia, spermatocytes, round spermatids and elongated spermatids (Stages IX-XII). SNAI2 is present in the nuclei of spermatogonia and spermatocytes, with a faint signal detected in round spermatids. SNAI3 was detected only in Sertoli cell cytoplasm, as in juvenile testes. Additionally, colocalization of SNAI1 and SNAI2 with previously identified key binding partners, LSD1 and PRC2 complex components, provides strong evidence that these important functional interactions are conserved during spermatogenesis to control gene activity. These distinct expression profiles suggest that each Snail family member has unique functions during spermatogenesis.

E-cadherin: Its dysregulation in carcinogenesis and clinical implications

E-cadherin is a transmembrane glycoprotein which connects epithelial cells together at adherens junctions. In normal cells, E-cadherin exerts its tumour suppressing role mainly by sequestering β-catenin from its binding to LEF (Lymphoid enhancer factor)/TCF (T cell factor) which serves the function of transcribing genes of the proliferative Wnt signaling pathway. Despite the ongoing debate on whether the loss of E-cadherin is the cause or effect of epithelial-mesenchymal transition (EMT), E-cadherin functional loss has frequently been associated with poor prognosis and survival in patients of various cancers. The dysregulation of E-cadherin expression that leads to carcinogenesis happens mostly at the epigenetic level but there are cases of genetic alterations as well. E-cadherin expression has been linked to the cellular functions of invasiveness reduction, growth inhibition, apoptosis, cell cycle arrest and differentiation. Studies on various cancers have shown that these different cellular functions are also interdependent. Recent studies have reported a rapid expansion of E-cadherin clinical relevance in various cancers. This review article summarises the multifaceted effect E-cadherin expression has on cellular functions in the context of carcinogenesis as well as its clinical implications in diagnosis, prognosis and therapeutics.

Establishment of highly metastatic KRAS mutant lung cancer cell sublines in long-term three-dimensional low attachment cultures

Decreased cell-substratum adhesion is crucially involved in metastasis. Previous studies demonstrated that lung cancer with floating cell clusters in histology is more likely to develop metastasis. In the present study, we investigated whether cancer cells in long-term, three-dimensional low attachment cultures acquire high metastatic potential; these cells were then used to examine the mechanisms underlying metastasis. Two KRAS-mutated adenocarcinoma cell lines (A549 and H441) were cultured and selected on ultra-low attachment culture dishes, and the resulting cells were defined as FL (for floating) sublines. Cancer cells were inoculated into NOD/SCID mice via an intracardiac injection, and metastasis was evaluated using luciferase-based imaging and histopathology. In vitro cell growth (in attachment or suspension cultures), migration, and invasion were assayed. A whole genomic analysis was performed to identify key molecular alterations in FL sublines. Upon detachment on low-binding dishes, parental cells initially formed rounded spheroids with limited growth activity. However, over time in cultures, cells gradually formed smaller spheroids that grew slowly, and, after 3–4 months, we obtained FL sublines that regained prominent growth potential in suspension cultures. On ordinary dishes, FL cells reattached and exhibited a more spindle-shaped morphology than parental cells. No marked differences were observed in cell growth with attachment, migration, or invasion between FL sublines and parental cell lines; however, FL cells exhibited markedly increased growth potential under suspended conditions in vitro and stronger metastatic abilities in vivo. A genomic analysis identified epithelial-mesenchymal transition (EMT) and c-Myc amplification in A549-FL and H441-FL cells, respectively, as candidate mechanisms for metastasis. The growth potential of FL cells was markedly inhibited by lentiviral ZEB1 knockdown in A549-FL cells and by the inhibition of c-Myc through lentiviral knockdown or the pharmacological inhibitor JQ1 in H441-FL cells. Long-term three-dimensional low attachment cultures may become a useful method for investigating the mechanisms underlying metastasis mediated by decreased cell-substratum adhesion.

Differential expression of circulating biomarkers of tumor phenotype and outcomes in previously treated non-small cell lung cancer patients receiving erlotinib vs. cytotoxic chemotherapy

Background

The objective of this study was to identify serum biomarkers capable of predicting clinical outcomes in previously-treated NSCLC patients with wild-type for EGFR activating mutations or insufficient tissue for mutation status determination.

Methods

Sixty-six Luminex immunoassays representative of biological themes that emerged from a re-analysis of transcriptome data from the Cancer Genome Atlas (TCGA) were evaluate against pretreatment serum specimens from previously-treated advanced NSCLC patients received either cytotoxic chemotherapy (n=32) or erlotinib (n=79). Known EGFR mutation positive cases were excluded from analysis. Associations of biomarkers with outcome parameters and their differential interaction with treatment for survival outcomes were assessed using multivariate Cox PH analyses.

Results

Our EMT-based transcriptomic analysis revealed a range of biological processes associated with angiogenesis, apoptosis, cachexia, inflammation, and metabolism emerging as those most highly associated with patient outcome. These processes were evaluated via surrogate serum biomarkers. A treatment-biomarker interaction analysis revealed that higher pretreatment levels of c-Met signaling biomarkers (i.e. HGF levels), pro-inflammatory/ pro-cachexia (e.g. IL-8, sIL-2Rα, FGF-2) processes and a pro-angiogenic (e.g. TGF-α, IL-8, VEGF) milieu were associated with inferior survival (HR=0.35, 0.29, 0.58, 0.50, 0.61, 0.45, respectively; all p<0.05) for patients receiving chemotherapy, relative to erlotinib. In contrast, high levels of decoy receptor for IL-1, sIL-1RII, and a high tissue vimentin/E-cadherin ratio were associated with a poor OS (HR=3.78; p=0.00055) in the erlotinib cohort.

Conclusions

Contemporary precision medicine initiatives that pair patient tumor characteristics with the optimal therapy type may maximize the use of agents targeting EGFR in the treatment of NSCLC.

Pellino-1 promotes lung carcinogenesis via the stabilization of Slug and Snail through K63-mediated polyubiquitination

Pellino-1 is an E3 ubiquitin ligase acting as a critical mediator for a variety of immune receptor signaling pathways, including Toll-like receptors, interleukin-1 receptor and T-cell receptors. We recently showed that the Pellino-1-transgenic (Tg) mice developed multiple tumors with different subtypes in hematolymphoid and solid organs. However, the molecular mechanism underlying the oncogenic role of Pellino-1 in solid tumors remains unknown. Pellino-1-Tg mice developed adenocarcinoma in the lungs, and Pellino-1 expression was higher in human lung adenocarcinoma cell lines compared with non-neoplastic bronchial epithelial cell lines. Pellino-1 overexpression increased the cell proliferation, survival, colony formation, invasion and migration of lung adenocarcinoma cells, whereas Pellino-1 knock-down showed the opposite effect. Pellino-1 overexpression activated PI3K/Akt and ERK signaling pathways and elicited an epithelial–mesenchymal transition (EMT) phenotype of lung adenocarcinoma cells. Pellino-1-mediated EMT was demonstrated through morphology, the upregulation of Vimentin, Slug and Snail expression and the downregulation of E-cadherin and β-catenin expression. Notably, Pellino-1 had a direct effect on the overexpression of Snail and Slug through Lys63-mediated polyubiquitination and the subsequent stabilization of these proteins. Pellino-1 expression level was significantly correlated with Snail and Slug expression in human lung adenocarcinoma tissues, and lung tumors from Pellino-1-Tg mice showed Snail and Slug overexpression. The Pellino-1-mediated increase in the migration of lung adenocarcinoma cells was mediated by Snail and Slug expression. Taken together, these results show that Pellino-1 contributes to lung tumorigenesis by inducing overexpression of Snail and Slug and promoting EMT. Pellino-1 might be a potential therapeutic target for lung cancer.

Pathologically decreased expression of miR-193a contributes to metastasis by targeting WT1-E-cadherin axis in non-small cell lung cancers

Background

The metastatic cascade is a complex and multistep process with many potential barriers. Recently, miR-193a has been reported to be a suppressive miRNA in multiple types of cancers, but its underlying anti-oncogenic activity in non-small cell lung cancers (NSCLC) is not fully elucidated.

Methods

The expressions of miR-193a (miR-193a-5p) in human lung cancer tissues and cell lines were detected by real-time PCR. Dual-luciferase reporter assay was used to identify the direct target of miR-193a. Cell proliferation, apoptosis, and metastasis were assessed by CCK-8, flow cytometry, and Transwell assay, respectively.

Results

The expression of miR-193a in lung cancer tissues was decreased comparing to adjacent non-tumor tissues due to DNA hypermethylation in lung cancer tissues. Ectopic expression of miR-193a inhibited cell proliferation, colony formation, migration, and invasion in A549 and H1299 cells. Moreover, overexpression of miR-193a partially reversed tumor growth factor-β1 (TGF-β1)-induced epithelial-to-mesenchymal transition (EMT) in NSCLC cells. Mechanistically, miR-193a reduced the expression of WT1, which negatively regulated the protein level of E-cadherin, suggesting that miR-193a might prevent EMT via modulating WT1-E-cadherin axis. Importantly, knockdown of WT1 resembled the anti-cancer activity by miR-193a and overexpression of WT1 partially reversed miR-193a-induced anti-cancer activity, indicating that WT1 plays an important role in miR-193a-induced anti-cancer activity. Finally, overexpression of miR-193a decreased the growth of tumor xenografts in mice.

Conclusion

Collectively, our results have revealed an important role of miR-193a-WT1-E-cadherin axis in metastasis, demonstrated an important molecular cue for EMT, and suggested a therapeutic strategy of restoring miR-193a expression in NSCLC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0450-8) contains supplementary material, which is available to authorized users.

TEL2 suppresses metastasis by down-regulating SERPINE1 in nasopharyngeal carcinoma

Metastasis is the major cause of treatment failure in patients with nasopharyngeal carcinoma (NPC). However, the molecular mechanisms of NPC metastasis are poorly understood. Here, using our customized gene microarray containing all of the known human transcription factors and the current markers for epithelial-mesenchymal transition, we report that TEL2 was down-regulated in highly metastatic NPC cells and the metastatic tissues in lymph node. Mechanistically, TEL2 inhibits the cell migration and invasion in vitro and metastasis in vivo by releasing its direct suppression on the SERPINE1 promoter in NPC. Consistently, an inverse correlation was observed between the protein levels of TEL2 and SERPINE1 using clinical NPC samples. Collectively, we have provided the first evidence that TEL2 plays a key role in NPC metastasis by directly down-regulating SERPINE1, and that this novel axis of TEL2 / SERPINE1 may be valuable to develop new strategies for treating NPC patients with metastasis.

Snail promotes resistance to enzalutamide through regulation of androgen receptor activity in prostate cancer

Treatment with androgen-targeted therapies can induce upregulation of epithelial plasticity pathways. Epithelial plasticity is known to be important for metastatic dissemination and therapeutic resistance. The goal of this study is to elucidate the functional consequence of induced epithelial plasticity on AR regulation during disease progression to identify factors important for treatment-resistant and metastatic prostate cancer. We pinpoint the epithelial plasticity transcription factor, Snail, at the nexus of enzalutamide resistance and prostate cancer metastasis both in preclinical models of prostate cancer and in patients. In patients, Snail expression is associated with Gleason 9-10 high-risk disease and is strongly overexpressed in metastases as compared to localized prostate cancer. Snail expression is also elevated in enzalutamide-resistant prostate cancer cells compared to enzalutamide-sensitive cells, and downregulation of Snail re-sensitizes enzalutamide-resistant cells to enzalutamide. While activation of Snail increases migration and invasion, it is also capable of promoting enzalutamide resistance in enzalutamide-sensitive cells. This Snail-mediated enzalutamide resistance is a consequence of increased full-length AR and AR-V7 expression and nuclear localization. Downregulation of either full-length AR or AR-V7 re-sensitizes cells to enzalutamide in the presence of Snail, thus connecting Snail-induced enzalutamide resistance directly to AR biology. Finally, we demonstrate that Snail is capable of mediating-resistance through AR even in the absence of AR-V7. These findings imply that increased Snail expression during progression to metastatic disease may prime cells for resistance to AR-targeted therapies by promoting AR activity in prostate cancer.

Slug Is Increased in Vascular Remodeling and Induces a Smooth Muscle Cell Proliferative Phenotype

Objective

Previous studies have confirmed Slug as a key player in regulating phenotypic changes in several cell models, however, its role in smooth muscle cells (SMC) has never been assessed. The purpose of this study was to evaluate the expression of Slug during the phenotypic switch of SMC in vitro and throughout the development of vascular remodeling.

Methods and Results

Slug expression was decreased during both cell-to-cell contact and TGFβ1 induced SMC differentiation. Tumor necrosis factor-α (TNFα), a known inductor of a proliferative/dedifferentiated SMC phenotype, induces the expression of Slug in SMC. Slug knockdown blocked TNFα-induced SMC phenotypic change and significantly reduced both SMC proliferation and migration, while its overexpression blocked the TGFβ1-induced SMC differentiation and induced proliferation and migration. Genome-wide transcriptomic analysis showed that in SMC, Slug knockdown induced changes mainly in genes related to proliferation and migration, indicating that Slug controls these processes in SMC. Notably, Slug expression was significantly up-regulated in lungs of mice using a model of pulmonary hypertension-related vascular remodeling. Highly remodeled human pulmonary arteries also showed an increase of Slug expression compared to less remodeled arteries.

Conclusions

Slug emerges as a key transcription factor driving SMC towards a proliferative phenotype. The increased Slug expression observed in vivo in highly remodeled arteries of mice and human suggests a role of Slug in the pathogenesis of pulmonary vascular diseases.

Down-regulation of microRNAs of the miR-200 family and up-regulation of Snail and Slug in inflammatory bowel diseases - hallmark of epithelial-mesenchymal transition

Fibrosis is an important feature of inflammatory bowel diseases (IBD), particularly Crohn's disease (CD), but its pathogenesis is poorly understood. To determine the postulated involvement of epithelial−mesenchymal transition (EMT) in the development of fibrosis in IBD, we analysed the expression profiles of the miR‐200 family which has been shown to induce EMT in experimental models and various human diseases. We also analysed the expression of Snail and Slug, postulated targets of the investigated microRNAs. Ten patients with ulcerative colitis (UC) and 10 patients with CD who underwent colon resection were included. From each, two tissue samples were chosen (one with the most severely and one with the least affected or normal mucosa) for analysis of microRNAs expression using real‐time polymerase chain reaction, and Snail and Slug expression using immunohistochemistry. We found significant down‐regulation of all investigated microRNAs in CD, and of three investigated microRNAs in UC, in comparison to the normal or the least affected mucosa. Comparing UC and CD, four microRNAs were significantly more down‐regulated in CD than in UC. Snail and Slug were expressed in the injured epithelium and occasionally in mesothelial cells and submesothelial fibroblasts. Our finding of down‐regulation of the miR‐200 family and up‐regulation of transcription repressors Snail and Slug supports the postulated role of EMT in the pathogenesis of fibrosis in IBD. The described expression patterns are consistent with the notion that fibrosis does not occur only in CD but also in UC, being much more severe in CD.

Mechanisms of polarity protein expression control

Polarity is a universal feature of cells during division and often at other stages of the cell cycle or after post-mitotic differentiation. A conserved machinery, present in all animals, initiates and maintains polarity. Multi-cellular animals organize themselves with respect to the axes of symmetry of the organism through the process of planar cell polarity, but many tissues also express a cell-intrinsic form of polarity, for instance to segregate the apical and basolateral membranes of epithelial cells. Although the genes and proteins involved in apical-basal polarity have been known for many years, the regulation of their expression remains ill-defined. Maintenance of the correct expression levels is essential for normal cell lineage allocation, tissue morphogenesis and cell survival. Here we summarize what is known about the transcriptional and post-transcriptional regulation of polarity protein expression, and discuss areas that remain to be understood.

Effects of the lifestyle habits in breast cancer transcriptional regulation

Through research carried out in the last 25 years about the breast cancer etiology, it has been possible to estimate that less than 10 % of patients who are diagnosed with the condition are carriers of some germline or somatic mutation. The clinical reports of breast cancer patients with healthy twins and the development of disease in women without high penetrance mutations detected, warn the participation more factors in the transformation process. The high incidence of mammary adenocarcinoma in the modern woman and the urgent need for new methods of prevention and early detection have demanded more information about the role that environment and lifestyle have on the transformation of mammary gland epithelial cells. Obesity, alcoholism and smoking are factors that have shown a close correlation with the risk of developing breast cancer. And although these conditions affect different cell regulation levels, the study of its effects in the mechanisms of transcriptional and epigenetic regulation is considered critical for a better understanding of the loss of identity of epithelial cells during carcinogenesis of this tissue. The main objective of this review was to establish the importance of changes occurring to transcriptional level in the mammary gland as a consequence of acute or chronic exposure to harmful products such as obesity-causing foods, ethanol and cigarette smoke components. At analyze the main studies related to topic, it has concluded that the understanding of effects caused by the lifestyle factors in performance of the transcriptional mechanisms that determine gene expression of the mammary gland epithelial cells, may help explain the development of this disease in women without genetic propensity and different phenotypic manifestations of this cancer type.

Overcoming Resistance to Endocrine Therapy in Breast Cancer: New Approaches to a Nagging Problem

In the majority of women, breast cancer progresses through increased transcriptional activity due to over-expressed oestrogen receptors (ER). Therapeutic strategies include: (i) reduction of circulating ovarian oestrogens or of peripherally produced oestrogen (in postmenopausal women) with aromatase inhibitors and (ii) application of selective ER modulators for receptor blockade. The success of these interventions is limited by the variable but persistent onset of acquired resistance and by an intrinsic refractiveness which manifests despite adequate levels of ER in about 50% of patients with advanced metastatic disease. Loss of functional ER leads to endocrine insensitivity, loss of cellular adhesion and polarity, and increased migratory potential due to trans-differentiation of the epithelial cancer cells into a mesenchymal-like phenotype (epithelial-mesenchymal transition; EMT). Multiple mechanisms contributing to therapeutic failure have been proposed: (i) loss or modification of ER expression including epigenetic mechanisms, (ii) agonistic actions of selective ER modulators that may be enhanced through an increased expression of co-activators, (iii) attenuation of the tamoxifen metabolism through expression of genetic variants of P450 cytochromes which leads to more or less active metabolites and (iv) increased growth factor signalling particularly through epidermal growth factor receptor activation of pathways involving keratinocyte growth factor, platelet-derived growth factor, and nuclear factor x03BA;B. In addition, the small non-coding microRNAs, recently recognized as critical gene regulators, exhibit differential expression in tamoxifen-sensitive versus resistant cell lines. Several studies suggest the potential of using these either as targets or as therapeutic agents to modulate EMT regulators as a means of reversing the aggressive metastatic phenotype by reversal of the EMT, with the added benefit of re-sensitization to anti-oestrogens.

Epithelial-Mesenchymal Transition (EMT) and Regulation of EMT Factors by Steroid Nuclear Receptors in Breast Cancer: A Review and in Silico Investigation

Steroid Nuclear Receptors (SNRs) are transcription factors of the nuclear receptor super-family. Estrogen Receptor (ERα) is the best-studied and has a seminal role in the clinic both as a prognostic marker but also as a predictor of response to anti-estrogenic therapies. Progesterone Receptor (PR) is also used in the clinic but with a more debatable prognostic role and the role of the four other SNRs, ERβ, Androgen Receptor (AR), Glucocorticoid Receptor (GR) and Mineralocorticoid Receptor (MR), is starting only to be appreciated. ERα, but also to a certain degree the other SNRs, have been reported to be involved in virtually every cancer-enabling process, both promoting and impeding carcinogenesis. Epithelial-Mesenchymal Transition (EMT) and the reverse Mesenchymal Epithelial Transition (MET) are such carcinogenesis-enabling processes with important roles in invasion and metastasis initiation but also establishment of tumor in the metastatic site. EMT is governed by several signal transduction pathways culminating in core transcription factors of the process, such as Snail, Slug, ZEB1 and ZEB2, and Twist, among others. This paper will discuss direct regulation of these core transcription factors by SNRs in breast cancer. Interrogation of publicly available databases for binding sites of SNRs on promoters of core EMT factors will also be included in an attempt to fill gaps where other experimental data are not available.

MicroRNA Regulation of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is a central regulatory program that is similar in many aspects to several steps of embryonic morphogenesis. In addition to its physiological role in tissue repair and wound healing, EMT contributes to chemo resistance, metastatic dissemination and fibrosis, amongst others. Classically, the morphological change from epithelial to mesenchymal phenotype is characterized by the appearance or loss of a group of proteins which have come to be recognized as markers of the EMT process. As with all proteins, these molecules are controlled at the transcriptional and translational level by transcription factors and microRNAs, respectively. A group of developmental transcription factors form the backbone of the EMT cascade and a large body of evidence shows that microRNAs are heavily involved in the successful coordination of mesenchymal transformation and vice versa, either by suppressing the expression of different groups of transcription factors, or otherwise acting as their functional mediators in orchestrating EMT. This article dissects the contribution of microRNAs to EMT and analyzes the molecular basis for their roles in this cellular process. Here, we emphasize their interaction with core transcription factors like the zinc finger enhancer (E)-box binding homeobox (ZEB), Snail and Twist families as well as some pluripotency transcription factors.

Translating epithelial mesenchymal transition markers into the clinic: Novel insights from proteomics

The growing understanding of the molecular mechanisms underlying epithelial-to-mesenchymal transition (EMT) may represent a potential source of clinical markers. Despite EMT drivers have not yet emerged as candidate markers in the clinical setting, their association with established clinical markers may improve their specificity and sensitivity. Mass spectrometry-based platforms allow analyzing multiple samples for the expression of EMT candidate markers, and may help to diagnose diseases or monitor treatment efficiently. This review highlights proteomic approaches applied to elucidate the differences between epithelial and mesenchymal tumors and describes how these can be used for target discovery and validation.

Analysis of Epithelial-Mesenchymal Transition Induced by Transforming Growth Factor β

In recent years, the importance of the cell biological process of epithelial-mesenchymal transition (EMT) has been established via an exponentially growing number of reports. EMT has been documented during embryonic development, tissue fibrosis, and cancer progression in vitro, in animal models in vivo and in human specimens. EMT relates to many molecular and cellular alterations that occur when epithelial cells undergo a switch in differentiation that generates mesenchymal-like cells with newly acquired migratory and invasive properties. In addition, EMT relates to a nuclear reprogramming similar to the one occurring in the generation of induced pluripotent stem cells. Via such a process, EMT is gradually established to promote the generation and maintenance of adult tissue stem cells which under disease states such as cancer, are known as cancer stem cells. EMT is induced by developmental growth factors, oncogenes, radiation, and hypoxia. A prominent growth factor that causes EMT is transforming growth factor β (TGF-β).A series of molecular and cellular techniques can be applied to define and characterize the state of EMT in diverse biological samples. These methods range from DNA and RNA-based techniques that measure the expression of key EMT regulators and markers of epithelial or mesenchymal differentiation to functional assays of cell mobility, invasiveness and in vitro stemness. This chapter focuses on EMT induced by TGF-β and provides authoritative protocols and relevant reagents and citations of key publications aiming at assisting newcomers that enter this prolific area of biomedical sciences, and offering a useful reference tool to pioneers and aficionados of the field.

Krüppel-Like Factor 4 Inhibits the Transforming Growth Factor-β1-Promoted Epithelial-to-Mesenchymal Transition via Downregulating Plasminogen Activator Inhibitor-1 in Lung Epithelial Cells

Transforming growth factor-β (TGF-β) signaling and TGF-β-promoted epithelial-to-mesenchymal transition (EMT) have been postulated to be the common pathway causing pulmonary fibrosis. However, the up- or downstreaming markers of TGF-β-induced EMT still need to be further recognized. In the present study, we investigated the regulation on Krüppel-like factor 4 (KLF-4) and plasminogen activator inhibitor-1 (PAI-1) by TGF-β in the murine lung epithelial LA-4 cells and then examined the regulation of both markers in the TGF-β-induced EMT by the PAI-1 knockdown or the KLF-4 overexpression. Our study indicated that TGF-β induced EMT in mouse LA-4 lung epithelial cells via reducing E-cadherin, while promoting Collagen I and α-SMA. And PAI-1 was upregulated, whereas KLF-4 was downregulated in the TGF-β-induced EMT model in LA-4 cells. Moreover, the siRNA-mediated PAI-1 knockdown inhibited the TGF-β-induced EMT, whereas the adenovirus-medicated KLF-4 overexpression markedly reduced the PAI-1 expression and inhibited the TGF-β-induced EMT in LA-4 cells. In conclusion, our study confirmed the downregulation of KLF-4 in the TGF-β-induced EMT in LA-4 cells. And the KLF-4 overexpression significantly reduced the TGF-β-induced PAI-1 and thus inhibited the TGF-β-induced EMT in mouse lung epithelial LA-4 cells. It implies that KLF-4 might be a promising target for effective control of the pulmonary fibrosis.

Role of an SNP in Alternative Splicing of Bovine NCF4 and Mastitis Susceptibility

Neutrophil cytosolic factor 4 (NCF4) is component of the nicotinamide dinucleotide phosphate oxidase complex, a key factor in biochemical pathways and innate immune responses. In this study, splice variants and functional single-nucleotide polymorphism (SNP) of NCF4 were identified to determine the variability and association of the gene with susceptibility to bovine mastitis characterized by inflammation. A novel splice variant, designated as NCF4-TV and characterized by the retention of a 48 bp sequence in intron 9, was detected in the mammary gland tissues of infected cows. The expression of the NCF4-reference main transcript in the mastitic mammary tissues was higher than that in normal tissues. A novel SNP, g.18174 A>G, was also found in the retained 48 bp region of intron 9. To determine whether NCF4-TV could be due to the g.18174 A>G mutation, we constructed two mini-gene expression vectors with the wild-type or mutant NCF4 g.18174 A>G fragment. The vectors were then transiently transfected into 293T cells, and alternative splicing of NCF4 was analyzed by reverse transcription-PCR and sequencing. Mini-gene splicing assay demonstrated that the aberrantly spliced NCF4-TV with 48 bp retained fragment in intron 9 could be due to g.18174 A>G, which was associated with milk somatic count score and increased risk of mastitis infection in cows. NCF4 expression was also regulated by alternative splicing. This study proposes that NCF4 splice variants generated by functional SNP are important risk factors for mastitis susceptibility in dairy cows.

The glycosyltransferase LARGE2 is repressed by Snail and ZEB1 in prostate cancer

Reductions in both expression of the dystroglycan core protein and functional glycosylation of the α-dystroglycan (αDG) subunit have been reported in a number of cancers and may contribute to disease progression. In the case of prostate cancer, one mechanism that contributes to αDG hypoglycosylation is transcriptional down-regulation of LARGE2 (GYLTY1B), a glycosyltransferase that produces the functional (laminin-binding) glycan on αDG, but the mechanism(s) underlying reduction of LARGE2 mRNA remain unclear. Here, we show that αDG hypoglycosylation is associated with epithelial-to-mesenchymal transition (EMT)-like status. We examined immunoreactivity for both functionally-glycosylated αDG and E-cadherin by flow cytometry and the relative expression of ZEB1 mRNA and the αDG glycosyltransferase LARGE2 mRNA in prostate and other cancer cell lines by quantitative RT-PCR. To study the role of ZEB1 and other transcription factors in the regulation of LARGE2, we employed overexpression and knockdown approaches. Snail- or ZEB1-driven EMT caused αDG hypoglycosylation by repressing expression of the LARGE2 mRNA, with both ZEB1-dependent and -independent mechanisms contributing to Snail-mediated LARGE2 repression. To examine the direct regulation of LARGE2 by Snail and ZEB1 we employed luciferase reporter and chromatin immunoprecipitation assays. Snail and ZEB1 were found to bind directly to the LARGE2 promoter, specifically to E/Z-box clusters. Furthermore, analysis of gene expression profiles of clinical samples in The Cancer Genome Atlas reveals negative correlation of LARGE2 and ZEB1 expression in various cancers. Collectively, our results suggest that LARGE2 is negatively regulated by Snail and/or ZEB1, revealing a mechanistic basis for αDG hypoglycosylation during prostate cancer progression and metastasis.

Mathematical Modelling of Molecular Pathways Enabling Tumour Cell Invasion and Migration

Understanding the etiology of metastasis is very important in clinical perspective, since it is estimated that metastasis accounts for 90% of cancer patient mortality. Metastasis results from a sequence of multiple steps including invasion and migration. The early stages of metastasis are tightly controlled in normal cells and can be drastically affected by malignant mutations; therefore, they might constitute the principal determinants of the overall metastatic rate even if the later stages take long to occur. To elucidate the role of individual mutations or their combinations affecting the metastatic development, a logical model has been constructed that recapitulates published experimental results of known gene perturbations on local invasion and migration processes, and predict the effect of not yet experimentally assessed mutations. The model has been validated using experimental data on transcriptome dynamics following TGF-β-dependent induction of Epithelial to Mesenchymal Transition in lung cancer cell lines. A method to associate gene expression profiles with different stable state solutions of the logical model has been developed for that purpose. In addition, we have systematically predicted alleviating (masking) and synergistic pairwise genetic interactions between the genes composing the model with respect to the probability of acquiring the metastatic phenotype. We focused on several unexpected synergistic genetic interactions leading to theoretically very high metastasis probability. Among them, the synergistic combination of Notch overexpression and p53 deletion shows one of the strongest effects, which is in agreement with a recent published experiment in a mouse model of gut cancer. The mathematical model can recapitulate experimental mutations in both cell line and mouse models. Furthermore, the model predicts new gene perturbations that affect the early steps of metastasis underlying potential intervention points for innovative therapeutic strategies in oncology.

Sanguiin H6 suppresses TGF-β induction of the epithelial-mesenchymal transition and inhibits migration and invasion in A549 lung cancer

In the epithelial-mesenchymal transition (EMT), an important cellular process, epithelial cells become mesenchymal cells. This process is also critically involved in cancer metastasis. Sanguiin H6 is a compound derived from ellagitannin, which is found in berries. Sanguiin H6 shows various pharmacological properties, including anti-angiogenic activity. Because the possible role of sanguiin H6 in the EMT and the underlying molecular mechanisms are unclear, we investigated the effect of sanguiin H6 on the EMT. Transforming growth factor-beta 1 (TGF-β1) induces the EMT and promotes lung adenocarcinoma migration and invasion through the Smad2/3 signaling pathway. Thus, to understand the inhibitory effects of sanguiin H6 on lung cancer migration and invasion, we investigated the ability of sanguiin H6 to inhibit TGF-β1-induced EMT in the A549 cell line. We found that sanguiin H6 significantly prevented the activation of Smad2/3 signaling pathway by TGF-β1. Additionally, sanguiin H6 increased the expression of the epithelial marker E-cadherin and repressed the expression of Snail and the mesenchymal marker N-cadherin during TGF-β1-induced EMT. Moreover, sanguiin H6 regulated the expression of EMT-dependent genes induced by TGF-β1. Finally, sanguiin H6 inhibited the migration and invasion of TGF-β1-stimulated A549 cells. Taken together, our findings provide new evidence that sanguiin H6 suppresses lung cancer migration and invasion in vitro by inhibiting TGF-β1 induction of the EMT.

Specific expression patterns of epithelial to mesenchymal transition factors in gestational molar disease

INTRODUCTION

The epithelial to mesenchymal transition, a well-known and re-emerging model in pathology, has not been completely investigated in the field of gestational pathology. This study aims at improving the comprehension of this process in molar disease, even looking for new possible immunohistochemical markers.

MATERIALS AND METHODS

We have analysed the immunohistochemical expression of Twist1 and Snai2, two of the most important transcription factors involved in epithelial to mesenchymal transition, in formalin-fixed paraffin-embedded samples of 23 spontaneous abortive pregnancies, 22 molar pregnancies (10 partial and 12 complete) and 7 term placentas.

RESULTS

Twist1 and Snai2 were highly expressed in stromal villi cells of molar disease. Particularly, Twist1 was highly expressed in complete moles compared to both abortive pregnancies (p < 0.001) and partial moles (p < 0.05). Also Snai2 was more expressed by complete moles, differentiating them from non-molar abortions (p < 0.05).

DISCUSSION

On the basis of the known cadherins and claudins expression in these pathologies, our new findings reinforce the hypothesis of the involvement of epithelial to mesenchymal transition in early molar pregnancies and above all in complete moles. Furthermore, we highlighted that in molar disease not only the trophoblast, but even the villi stromal cells, are involved. Thanks to their specificity, furthermore, these Twist1 and Snai2 could be used as additional immunohistochemical tool in the diagnosis of complete molar disease, with Twist1 as the first choice.

Coronin 2A (CRN5) expression is associated with colorectal adenoma-adenocarcinoma sequence and oncogenic signalling

BACKGROUND

Coronin proteins are known as regulators of actin-based cellular processes, and some of them are associated with the malignant progression of human cancer. Here, we show that expression of coronin 2A is up-regulated in human colon carcinoma.

METHODS

This study included 26 human colon tumour specimens and 9 normal controls. Expression and localisation of coronin 2A was studied by immunohistochemistry, immunofluorescence imaging, cell fractionation, and immunoblotting. Functional roles of coronin 2A were analysed by over-expression and knock-down of the protein. Protein interactions were studied by co-immunoprecipitation and pull-down experiments, mass spectrometry analyses, and in vitro kinase and methylation assays.

RESULTS

Histopathological investigation revealed that the expression of coronin 2A in colon tumour cells is up-regulated during the adenoma-adenocarcinoma progression. At the subcellular level, coronin 2A localised to multiple compartments, i.e. F-actin stress fibres, the front of lamellipodia, focal adhesions, and the nuclei. Over-expression of coronin 2A led to a reduction of F-actin stress fibres and elevated cell migration velocity. We identified two novel direct coronin 2A interaction partners. The interaction of coronin 2A with MAPK14 (mitogen activated protein kinase 14 or MAP kinase p38α) led to phosphorylation of coronin 2A and also to activation of the MAPK14 pathway. Moreover, coronin 2A interacted with PRMT5 (protein arginine N-methyltransferase 5), which modulates the sensitivity of tumour cells to TRAIL-induced cell death.

CONCLUSIONS

We show that increased expression of coronin 2A is associated with the malignant phenotype of human colon carcinoma. Moreover, we linked coronin 2A to MAPK14 and PRMT5 signalling pathways involved in tumour progression.

Inhibition of ZEB1 expression induces redifferentiation of adult human β cells expanded in vitro

In-vitro expansion of functional adult human β-cells is an attractive approach for generating insulin-producing cells for transplantation. However, human islet cell expansion in culture results in loss of β-cell phenotype and epithelial-mesenchymal transition (EMT). This process activates expression of ZEB1 and ZEB2, two members of the zinc-finger homeobox family of E-cadherin repressors, which play key roles in EMT. Downregulation of ZEB1 using shRNA in expanded β-cell-derived (BCD) cells induced mesenchymal-epithelial transition (MET), β-cell gene expression, and proliferation attenuation. In addition, inhibition of ZEB1 expression potentiated redifferentiation induced by a combination of soluble factors, as judged by an improved response to glucose stimulation and a 3-fold increase in the fraction of C-peptide-positive cells to 60% of BCD cells. Furthermore, ZEB1 shRNA led to increased insulin secretion in cells transplanted in vivo. Our findings suggest that the effects of ZEB1 inhibition are mediated by attenuation of the miR-200c target genes SOX6 and SOX2. These findings, which were reproducible in cells derived from multiple human donors, emphasize the key role of ZEB1 in EMT in cultured BCD cells and support the value of ZEB1 inhibition for BCD cell redifferentiation and generation of functional human β-like cells for cell therapy of diabetes.

Searching the Human Genome for Snail and Slug With DNA@Home

DNA@Home is a volunteer computing project that aims to use Gibbs Sampling for the identification and location of DNA control signals on full genome-scale datasets. A fault tolerant and asynchronous implementation of Gibbs sampling using the Berkeley Open Infrastructure for Network Computing (BOINC) was used to identify the location of binding sites of the SNAI1 (Snail) and SNAI2 (Slug) transcription factors across the human genome. Genes regulated by Slug but not Snail, and genes regulated by Snail but not Slug provided two datasets with known motifs. These datasets contained up to 994 DNA sequences which to our knowledge is largest scale use of Gibbs sampling for discovery of binding sites. 1000 parallel sampling walks were used to search for the presence of 1, 2 or 3 possible motifs using small, medium, and full size sets of these sequences. These runs were performed over a period of two months using over 1500 volunteered computing hosts and generated over 2.2 Terabytes of sampling data. High performance computing resources were used for post processing. This paper presents intra and inter walk analyses used to determine walk convergence. The results were validated against current biological knowledge of the Snail and Slug promoter regions and present avenues for further biological study.

PAK5-mediated E47 phosphorylation promotes epithelial-mesenchymal transition and metastasis of colon cancer

The p21-activated kinase 5 (PAK5) is overexpressed in advanced cancer and the transcription factor E47 is a direct repressor of E-cadherin and inducer of epithelial-mesenchymal transition (EMT). However, the relationship between PAK5 and E47 has not been explored. In this study, we found that PAK5-mediated E47 phosphorylation promoted EMT in advanced colon cancer. PAK5 interacted with E47 and phosphorylated E47 on Ser39 under hepatocyte growth factor (HGF) stimulation, which decreased cell-cell cohesion, increased cell migration and invasion in vitro and promoted metastasis in a xenograft model. Furthermore, phosphorylation of E47 facilitated its accumulating in nucleus in an importin α-dependent manner, and enhanced E47 binding to E-cadherin promoter directly, leading to inhibition of E-cadherin transcription. In contrast, PAK5-knockdown resulted in blockage of HGF-induced E47 phosphorylation, attenuated association of E47 with importin α and decreased E47 binding to E-cadherin promoter. In addition, we demonstrated a close correlation between PAK5 and phospho-Ser39 E47 expression in colon cancer specimens. More importantly, high expression of phospho-E47 was associated with an aggressive phenotype of colon cancer and nuclear phospho-E47 staining was found in certain cases of colon cancer with metastasis. Collectively, E47 is a novel substrate of PAK5, and PAK5-mediated phosphorylation of E47 promotes EMT and metastasis of colon cancer, suggesting that phosphorylated E47 on Ser39 may be a potential therapeutic target in progressive colon cancer.

[Advances in the molecular mechanisms and prognostic significance of EMT in non-small cell lung cancer]

上皮细胞-间叶细胞转化（epithelial to mesenchymal transition, EMT）不仅在胚胎的发育过程中起着十分重要的作用，还参与非小细胞肺癌（non-small cell lung cancer, NSCLC）的转移过程。近期的研究发现，发生EMT的细胞不仅出现了形态的改变，还出现了相关表型的改变。既往有关EMT发生机制的研究多数是针对其他肿瘤的，因此很有必要研究NSCLC中是否有类似发生机制。随着研究的进展，EMT相关的基础研究逐渐被用于预测NSCLC的预后。本文将对NSCLC中EMT的发生机制及其临床应用的研究进展进行探讨。

SLUG: Critical regulator of epithelial cell identity in breast development and cancer

SLUG, a member of the SNAIL family of transcriptional repressors, is known to play a diverse number of roles in the cell, and its deregulation has been observed in a variety of cancers including breast. Here, we focus on SLUG's role as a master regulator of mammary epithelial cell (MEC) fate and lineage commitment in the normal mammary gland, and discuss how aberrant SLUG expression can influence breast tumor formation, phenotype, and progression. Specifically, we discuss SLUG's involvement in MEC differentiation, stemness, cellular plasticity, and the epithelial to mesenchymal transition (EMT), and highlight the complex connection between these programs during development and disease progression. Undoubtedly, delineating how molecular factors influence lineage identity and cell-state dynamics in the normal mammary gland will contribute to our understanding of breast tumor heterogeneity.

FH535 inhibited metastasis and growth of pancreatic cancer cells

FH535 is a small-molecule inhibitor of the Wnt/β-catenin signaling pathway, which a substantial body of evidence has proven is activated in various cancers, including pancreatic cancer. Activation of the Wnt/β-catenin pathway plays an important role in tumor progression and metastasis. We investigated the inhibitory effect of FH535 on the metastasis and growth of pancreatic cancer cells. Western blotting and luciferase reporter gene assay indicated that FH535 markedly inhibited Wnt/β-catenin pathway viability in pancreatic cancer cells. In vitro wound healing, invasion, and adhesion assays revealed that FH535 significantly inhibited pancreatic cancer cell metastasis. We also observed the inhibitory effect of FH535 on pancreatic cancer cell growth via the tetrazolium and plate clone formation assays. Microarray analyses suggested that changes in the expression of multiple genes could be involved in the anti-cancer effect of FH535 on pancreatic cancer cells. Our results indicate for the first time that FH535 inhibits pancreatic cancer cell metastasis and growth, providing new insight into therapy of pancreatic cancer.

TNF-related weak inducer of apoptosis (TWEAK) regulates junctional proteins in tubular epithelial cells via canonical NF-κB pathway and ERK activation

The tubular epithelium may be intrinsically involved in promoting kidney injury by junctional instability, epithelial-mesenchymal transition (EMT) and extracellular matrix remodelling. In this work, we investigated whether the pleiotropic and proinflammatory cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK), could be able to disturb junctional protein expression and to induce EMT of tubular cells. In cultured murine proximal tubular cells TWEAK induced phenotypic changes that were accompanied by F-actin redistribution, loss of epithelial adherent (E-cadherin, Cadherin-16, β-catenin) and tight junction (ZO-1) proteins, and re-expression of the mesenchymal protein Vimentin. The transcriptional repressors Snail and HNF1β were also modulated by TWEAK. In a murine model of obstructive renal pathology, TWEAK expression correlated with the appearance of the mesenchymal marker αSMA in kidney tubular cells. Mechanistically, the epithelial changes induced by TWEAK, including loss of epithelial integrity and EMT, via Fn14 were TGF-β1 independent, but mediated by several intracellular signaling systems, including the canonical NF-κB, ERK activation and the vitamin D receptor modulation. These results highlight potential contributions of TWEAK-induced inflammatory mechanisms that could unveil new pathogenic effects of TWEAK starting tubulointerstitial damage and fibrosis.

SIRT7 inactivation reverses metastatic phenotypes in epithelial and mesenchymal tumors

Metastasis is responsible for over 90% of cancer-associated mortality. In epithelial carcinomas, a key process in metastatic progression is the epigenetic reprogramming of an epithelial-to-mesenchymal transition-like (EMT) change towards invasive cellular phenotypes. In non-epithelial cancers, different mechanisms must underlie metastatic change, but relatively little is known about the factors involved. Here, we identify the chromatin regulatory Sirtuin factor SIRT7 as a key regulator of metastatic phenotypes in both epithelial and mesenchymal cancer cells. In epithelial prostate carcinomas, high SIRT7 levels are associated with aggressive cancer phenotypes, metastatic disease, and poor patient prognosis, and depletion of SIRT7 can reprogram these cells to a less aggressive phenotype. Interestingly, SIRT7 is also important for maintaining the invasiveness and metastatic potential of non-epithelial sarcoma cells. Moreover, SIRT7 inactivation dramatically suppresses cancer cell metastasis in vivo, independent of changes in primary tumor growth. Mechanistically, we also uncover a novel link between SIRT7 and its family member SIRT1, providing the first demonstration of direct interaction and functional interplay between two mammalian sirtuins. Together with previous work, our findings highlight the broad role of SIRT7 in maintaining the metastatic cellular phenotype in diverse cancers.

RNA-Seq and Network Analysis Revealed Interacting Pathways in TGF-β-Treated Lung Cancer Cell Lines

Whole transcriptome shotgun sequencing (RNA-Seq) is a useful tool for analyzing the transcriptome of a biological sample. With appropriate statistical and bioinformatic processing, this platform is capable of identifying significant differences in gene expression within the transcriptome and permits pathway and network analyses to determine how these genes interact biologically. In this study, we examined gene expression in two lung adenocarcinoma cell lines (H358 and A459) that were treated with transforming growth factor-β (TGF-β) as a model for induction of the epithelial-to-mesenchymal transition (EMT), commonly associated with disease progression. We performed this study in order to illustrate a workflow for identifying interesting genes and processes that are regulated early in EMT and to determine their gene pathway/network relationships and regulation. With this, we identified 137 upregulated and 32 downregulated genes common to both cell lines after TGF-β treatment that represent components of multiple canonical pathways and biological networks associated with the induction of EMT. These findings were also verified against reposited Affymetrix U133a expression profiles from multiple trials examining metastatic progression in patient cohorts (n = 731 total) to further establish the clinical relevance and translational significance of the model system. Together, these findings help validate the relevance of the TGF-β model for the study of EMT and provide new insights into early events in EMT.

Let-7a inhibits migration, invasion and epithelial-mesenchymal transition by targeting HMGA2 in nasopharyngeal carcinoma

BACKGROUND

Let-7a has been shown to play important roles in nasopharyngeal carcinoma (NPC) cell proliferation and apoptosis, but little is known about the function and mechanism of let-7a in nasopharyngeal carcinoma metastasis. We aimed to investigate the function and mechanism of let-7a in nasopharyngeal carcinoma metastasis and clarified the regulation of high mobility group A2 (HMGA2) by let-7a.

METHODS

The expression levels of let-7a and HMGA2 were examined in NPC clinical specimens using quantitative reverse transcription-PCR (RT-qPCR). HMGA2 was confirmed as a target of let-7a through luciferase reporter assays, RT-qPCR, and Western blotting. Furthermore, the roles of let-7a and HMGA2 in regulating NPC cells biological properties including proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) process were analyzed with let-7a mimics and si-HMGA2 transfected cells.

RESULTS

Our study demonstrated that let-7a was downregulated and inversely associated with the clinical stage, T classification and N classification, and HMGA2 was upregulated and directly associated with the clinical stage and N classification in patients with NPC. Moreover, there was an inverse correlation between let-7a expression and HMGA2 expression in NPC patient. In addition, HMGA2 was negatively regulated at the posttranscriptional level by let-7a via a binding site of HMGA2-3'UTR. In addition, synthetic let-7a mimics suppressed NPC cells migration, invasion and EMT process and knockdown of HMGA2 was consistent with the effects of let-7a in NPC cells.

CONCLUSION

Let-7a directly downregulates HMGA2 protein expression, which suppress NPC cell migration, invasion and EMT process. Let-7a could serve as a potential diagnostic marker and therapeutic target for NPC.

Zeb1 and Snail1 engage miR-200f transcriptional and epigenetic regulation during EMT

Cell plasticity is emerging as a key regulator of tumor progression and metastasis. During carcinoma dissemination epithelial cells undergo epithelial to mesenchymal transition (EMT) processes characterized by the acquisition of migratory/invasive properties, while the reverse, mesenchymal to epithelial transition (MET) process, is also essential for metastasis outgrowth. Different transcription factors, called EMT-TFs, including Snail, bHLH and Zeb families are drivers of the EMT branch of epithelial plasticity, and can be post-transcriptionally downregulated by several miRNAs, as the miR-200 family. The specific or redundant role of different EMT-TFs and their functional interrelations are not fully understood. To study the interplay between different EMT-TFs, comprehensive gain and loss-of-function studies of Snail1, Snail2 and/or Zeb1 factors were performed in the prototypical MDCK cell model system. We here describe that Snail1 and Zeb1 are mutually required for EMT induction while continuous Snail1 and Snail2 expression, but not Zeb1, is needed for maintenance of the mesenchymal phenotype in MDCK cells. In this model system, EMT is coordinated by Snail1 and Zeb1 through transcriptional and epigenetic downregulation of the miR-200 family. Interestingly, Snail1 is involved in epigenetic CpG DNA methylation of the miR-200 loci, essential to maintain the mesenchymal phenotype. The present results thus define a novel functional interplay between Snail and Zeb EMT-TFs in miR-200 family regulation providing a molecular link to their previous involvement in the generation of EMT process in vivo.

Comprehensive study of gene and microRNA expression related to epithelial-mesenchymal transition in prostate cancer

Prostate cancer is the most common cancer in men, and most patients have localized disease at the time of diagnosis. However, 4% already present with metastatic disease. Epithelial-mesenchymal transition is a fundamental process in carcinogenesis that has been shown to be involved in prostate cancer progression. The main event in epithelial-mesenchymal transition is the repression of E-cadherin by transcription factors, but the process is also regulated by microRNAs. The aim of this study was to analyze gene and microRNA expression involved in epithelial-mesenchymal transition in localized prostate cancer and metastatic prostate cancer cell lines and correlate with clinicopathological findings. We studied 51 fresh frozen tissue samples from patients with localized prostate cancer (PCa) treated by radical prostatectomy and three metastatic prostate cancer cell lines (LNCaP, DU145, PC3). The expression of 10 genes and 18 miRNAs were assessed by real-time PCR. The patients were divided into groups according to Gleason score, pathological stage, preoperative PSA, biochemical recurrence, and risk group for correlation with clinicopathological findings. The majority of localized PCa cases showed an epithelial phenotype, with overexpression of E-cadherin and underexpression of the mesenchymal markers. MiRNA-200 family members and miRNAs 203, 205, 183, 373, and 21 were overexpressed, while miRNAs 9, 495, 29b, and 1 were underexpressed. Low-expression levels of miRNAs 200b, 30a, and 1 were significantly associated with pathological stage. Lower expression of miR-200b was also associated with a Gleason score ≥ 8 and shorter biochemical recurrence-free survival. Furthermore, low-expression levels of miR-30a and high-expression levels of Vimentin and Twist1 were observed in the high-risk group. Compared with the primary tumor, the metastatic cell lines showed significantly higher expression levels of miR-183 and Twist1. In summary, miRNAs 200b, 30a, 1, and 183 and the genes Twist1 and Vimentin might play important roles in the progression of prostate cancer and may eventually become important prognostic markers.

TGF-β induces global changes in DNA methylation during the epithelial-to-mesenchymal transition in ovarian cancer cells

A key step in the process of metastasis is the epithelial-to-mesenchymal transition (EMT). We hypothesized that epigenetic mechanisms play a key role in EMT and to test this hypothesis we analyzed global and gene-specific changes in DNA methylation during TGF-β-induced EMT in ovarian cancer cells. Epigenetic profiling using the Infinium HumanMethylation450 BeadChip (HM450) revealed extensive (P < 0.01) methylation changes after TGF-β stimulation (468 and 390 CpG sites altered at 48 and 120 h post cytokine treatment, respectively). The majority of gene-specific TGF-β-induced methylation changes occurred in CpG islands located in or near promoters (193 and 494 genes hypermethylated at 48 and 120 h after TGF-β stimulation, respectively). Furthermore, methylation changes were sustained for the duration of TGF-β treatment and reversible after the cytokine removal. Pathway analysis of the hypermethylated loci identified functional networks strongly associated with EMT and cancer progression, including cellular movement, cell cycle, organ morphology, cellular development, and cell death and survival. Altered methylation and corresponding expression of specific genes during TGF-β-induced EMT included CDH1 (E-cadherin) and COL1A1 (collagen 1A1). Furthermore, TGF-β induced both expression and activity of DNA methyltransferases (DNMT) -1, -3A, and -3B, and treatment with the DNMT inhibitor SGI-110 prevented TGF-β-induced EMT. These results demonstrate that dynamic changes in the DNA methylome are implicated in TGF-β-induced EMT and metastasis. We suggest that targeting DNMTs may inhibit this process by reversing the EMT genes silenced by DNA methylation in cancer.

The hemodynamically-regulated vascular microenvironment promotes migration of the steroidogenic tissue during its interaction with chromaffin cells in the zebrafish embryo

Background

While the endothelium-organ interaction is critical for regulating cellular behaviors during development and disease, the role of blood flow in these processes is only partially understood. The dorsal aorta performs paracrine functions for the timely migration and differentiation of the sympatho-adrenal system. However, it is unclear how the adrenal cortex and medulla achieve and maintain specific integration and whether hemodynamic forces play a role.

Methodology and Principal Findings

In this study, the possible modulation of steroidogenic and chromaffin cell integration by blood flow was investigated in the teleostean counterpart of the adrenal gland, the interrenal gland, in the zebrafish (Danio rerio). Steroidogenic tissue migration and angiogenesis were suppressed by genetic or pharmacologic inhibition of blood flow, and enhanced by acceleration of blood flow upon norepinephrine treatment. Repressed steroidogenic tissue migration and angiogenesis due to flow deficiency were recoverable following restoration of flow. The regulation of interrenal morphogenesis by blood flow was found to be mediated through the vascular microenvironment and the Fibronectin-phosphorylated Focal Adhesion Kinase (Fn-pFak) signaling. Moreover, the knockdown of krüppel-like factor 2a (klf2a) or matrix metalloproteinase 2 (mmp2), two genes regulated by the hemodynamic force, phenocopied the defects in migration, angiogenesis, the vascular microenvironment, and pFak signaling of the steroidogenic tissue observed in flow-deficient embryos, indicating a direct requirement of mechanotransduction in these processes. Interestingly, epithelial-type steroidogenic cells assumed a mesenchymal-like character and downregulated β-Catenin at cell-cell junctions during interaction with chromaffin cells, which was reversed by inhibiting blood flow or Fn-pFak signaling. Blood flow obstruction also affected the migration of chromaffin cells, but not through mechanosensitive or Fn-pFak dependent mechanisms.

Conclusions and Significance

These results demonstrate that hemodynamically regulated Fn-pFak signaling promotes the migration of steroidogenic cells, ensuring their interaction with chromaffin cells along both sides of the midline during interrenal gland development.

Role of SPARC in bone remodeling and cancer-related bone metastasis

There is a growing socioeconomic recognition that clinical bone diseases such as bone infections, bone tumors and osteoporotic bone loss mainly associated with ageing, are major issues in today's society. SPARC (secreted protein, acidic and rich in cysteine), a matricellular glycoprotein, may be a promising therapeutic target for preventing or treating bone-related diseases. In fact, SPARC is associated with tissue remodeling, repair, development, cell turnover, bone mineralization and may also participate in growth and progression of tumors, namely cancer-related bone metastasis. Yet, the function of SPARC in such biological processes is poorly understood and controversial. The main objective of this work is to review the current knowledge related to the activity of SPARC in bone remodeling, tumorigenesis, and bone metastasis. Progress in understanding SPARC biology may provide novel strategies for bone regeneration and the development of anti-angiogenic, anti-proliferative, or counter-adhesive treatments specifically against bone metastasis.

Emerging role of mucins in epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) is an important and complex phenomenon that determines the aggressiveness of cancer cells. The morphological transformation of cancerous cells is accompanied by various cellular processes such as alterations in cell-cell adhesion, cell matrix degradation, down regulation of epithelial marker Ecadherin and upregulation of mesenchymal markers N-cadherin and Vimentin. Besides these markers several other important tumor antigens/mucins are also involved in the EMT process. Mainly high molecular weight glycoproteins such as mucin molecules (MUC1, MUC4 and MUC16) play a major role in the cellular transformation and signaling alteration in EMT process. In addition to these factors, EMT may be an essential process triggering the emergence or expansion of the CSC population, which slowly results in the initiation of tumor at metastatic sites. Furthermore, mucins have been demonstrated to be involved in the EMT process and also in the enrichment of cancer stem cell population. Mucin mediated EMT is very complex since the key components of tumor microenvironment are also regulating mucin molecules. In this review, we have discussed all the aforementioned factors and their mechanistic involvement for EMT process.

An AMPK-independent signaling pathway downstream of the LKB1 tumor suppressor controls Snail1 and metastatic potential

The serine/threonine kinase LKB1 is a tumor suppressor whose loss is associated with increased metastatic potential. In an effort to define biochemical signatures of metastasis associated with LKB1 loss, we discovered that the epithelial-to-mesenchymal transition transcription factor Snail1 was uniquely upregulated upon LKB1 deficiency across cell types. The ability of LKB1 to suppress Snail1 levels was independent of AMPK but required the related kinases MARK1 and MARK4. In a screen for substrates of these kinases involved in Snail regulation, we identified the scaffolding protein DIXDC1. Similar to loss of LKB1, DIXDC1 depletion results in upregulation of Snail1 in a FAK-dependent manner, leading to increased cell invasion. MARK1 phosphorylation of DIXDC1 is required for its localization to focal adhesions and ability to suppress metastasis in mice. DIXDC1 is frequently downregulated in human cancers, which correlates with poor survival. This study defines an AMPK-independent phosphorylation cascade essential for LKB1-dependent control of metastatic behavior.

Axl mediates tumor invasion and chemosensitivity through PI3K/Akt signaling pathway and is transcriptionally regulated by slug in breast carcinoma

The invasion and chemoresistance are crucial causes of morbidity and relapse for cancer patients. Axl is implicated in the modulation of cell invasion, cancer metastasis, and chemosensitivity in human breast carcinoma cell lines. Both breast cancer cell lines and tissues displayed increased expression of Axl, and it over expressed in highly metastatic breast cancer. The altered expression level of Axl was corresponding to the changed invasive phenotype and chemosensitivity of MDA-MB-231 cells both in vitro and in vivo. Further data indicated that experimental inhibition of Axl by RNAi assay inhibited phosphatidylinositol 3-kinase (PI3K)/Akt/GSK3β signaling pathway, resulted in the decrease of Slug expression, and further suppressed cell invasion properties and chemosensitivity. What is more, after the detection and statistics in human breast cancer specimens, we found the Axl expression was closely correlated with histological grade, lymph node metastasis, and clinical stage (P < 0.01). Taken together, these findings indicate that Axl exerts the role of tumor metastasis and chemosensitivity through activation of the PI3K/Akt/GSK3β signaling pathway, which is transcriptionally regulated by Slug. Our findings support the possibility that Axl is a novel regulator. It means by targeting Axl or its related signaling pathways, we can reduce the invasion and chemosensitivity of breast tumor.

Coupled reversible and irreversible bistable switches underlying TGFβ-induced epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) plays an important role in embryonic development, tissue regeneration, and cancer metastasis. Whereas several feedback loops have been shown to regulate EMT, it remains elusive how they coordinately modulate EMT response to TGF-β treatment. We construct a mathematical model for the core regulatory network controlling TGF-β-induced EMT. Through deterministic analyses and stochastic simulations, we show that EMT is a sequential two-step program in which an epithelial cell first is converted to partial EMT then to the mesenchymal state, depending on the strength and duration of TGF-β stimulation. Mechanistically the system is governed by coupled reversible and irreversible bistable switches. The SNAIL1/miR-34 double-negative feedback loop is responsible for the reversible switch and regulates the initiation of EMT, whereas the ZEB/miR-200 feedback loop is accountable for the irreversible switch and controls the establishment of the mesenchymal state. Furthermore, an autocrine TGF-β/miR-200 feedback loop makes the second switch irreversible, modulating the maintenance of EMT. Such coupled bistable switches are robust to parameter variation and molecular noise. We provide a mechanistic explanation on multiple experimental observations. The model makes several explicit predictions on hysteretic dynamic behaviors, system response to pulsed stimulation, and various perturbations, which can be straightforwardly tested.