Role of epigenetic mechanisms in epithelial-to-mesenchymal transition of breast cancer cells

Heterozygous Knockout of ARID4B Using CRISPR/Cas9 Attenuates Some Aggressive Phenotypes in a Breast Cancer Cell Line

Breast cancer is one of the leading causes of death in women around the world. Over time, many genes and mutations that are associated with the development of this disease have been identified. However, the specific role of many genes has not yet been fully elucidated. Higher ARID4B expression has been identified as a risk factor for diverse cancer types. Silencing experiments also showed that ARID4B is associated with developing cancer-associated characteristics. However, no transcriptomic studies have shown the overall cellular effect of loss of function in breast cancer in humans. This study addresses the impact of loss-of-function mutations in breast cancer MCF-7 cells. Using the CRISPR/Cas9 system, we generated mutations that caused heterozygous truncated proteins, isolating three monoclonal lines carrying insertions and deletions in ARID4B. We observed reduced proliferation and migration in in vitro experiments. In addition, from RNA-seq assays, a differential expression analysis shows known and novel deregulated cancer-associate pathways in mutated cells supporting the impact of ARID4B. For example, we found the AKT-PI3K pathway to be altered at the transcript level but through different genes than those reported for ARID4B. Our transcriptomic results also suggest new insights into the role of ARID4B in aggressiveness by the epithelial-to-mesenchymal transition and TGF-β pathways and in metabolism through cholesterol and mevalonate pathways. We also performed exome sequencing to show that no off-target effects were apparent. In conclusion, the ARID4B gene is associated with some aggressive phenotypes in breast cancer cells.

Cancer metastasis under the magnifying glass of epigenetics and epitranscriptomics

Most of the cancer-associated mortality and morbidity can be attributed to metastasis. The role of epigenetic and epitranscriptomic alterations in cancer origin and progression has been extensively demonstrated during the last years. Both regulations share similar mechanisms driven by DNA or RNA modifiers, namely writers, readers, and erasers; enzymes responsible of respectively introducing, recognizing, or removing the epigenetic or epitranscriptomic modifications. Epigenetic regulation is achieved by DNA methylation, histone modifications, non-coding RNAs, chromatin accessibility, and enhancer reprogramming. In parallel, regulation at RNA level, named epitranscriptomic, is driven by a wide diversity of chemical modifications in mostly all RNA molecules. These two-layer regulatory mechanisms are finely controlled in normal tissue, and dysregulations are associated with every hallmark of human cancer. In this review, we provide an overview of the current state of knowledge regarding epigenetic and epitranscriptomic alterations governing tumor metastasis, and compare pathways regulated at DNA or RNA levels to shed light on a possible epi-crosstalk in cancer metastasis. A deeper understanding on these mechanisms could have important clinical implications for the prevention of advanced malignancies and the management of the disseminated diseases. Additionally, as these epi-alterations can potentially be reversed by small molecules or inhibitors against epi-modifiers, novel therapeutic alternatives could be envisioned.

EMT Features in Claudin-Low versus Claudin-Non-Suppressed Breast Cancers and the Role of Epigenetic Modifications

BACKGROUND

Breast cancers are heterogeneous and are classified according to the expression of ER, PR and HER2 receptors to distinct groups with prognostic and therapeutic implications. Within the triple-negative group, with no expression of these three receptors, molecular heterogeneity exists but is currently not exploited in the clinic. The claudin-low phenotype is present in a subset of triple-negative breast cancers and constitutes together with basal-like cancers the most extensive groups within triple-negative breast cancers. Suppression of epithelial cell adhesion molecules in claudin-low cancers is also a hallmark of Epithelial Mesenchymal Transition (EMT).

METHODS

The groups of claudin-low and claudin-non-suppressed breast cancers from the extensive publicly available genomic cohorts of the METABRIC study were examined to delineate and compare their molecular landscape. Genetic and epigenetic alterations of key factors involved in EMT and potentially associated with the pathogenesis of the claudin-low phenotype were analyzed in the two groups.

RESULTS

Claudin-low cancers displayed up-regulation of several core transcription factors of EMT at the mRNA level, compared with claudin-non-suppressed breast cancers. Global promoter DNA methylation was increased in both groups of triple-negative cancers and in claudin-low ER-positive cancers compared with the rest of ER-positive cancers. Histone modifier enzymes, including methyltransferases, demethylases, acetyltransferases and deacetylases displayed amplifications more frequently in claudin-non-suppressed triple-negative cancers than in claudin-low counterparts and the expression of some of these enzymes differed significantly between the two groups.

CONCLUSION

Claudin-low and claudin-non-suppressed triple-negative breast cancers differ in their landscape of EMT core regulators and epigenetic regulators. These differences may be explored as targets for therapeutic interventions specific to the two groups of triple-negative breast cancers.

Modulatory role of miRNAs in thyroid and breast cancer progression and insights into their therapeutic manipulation

Over the past few decades, thyroid cancer has become one of the most common types of endocrine cancer, contributing to an increase in prevalence. In the year 2020, there were 586,202 newly diagnosed cases of thyroid cancer around the world. This constituted approximately 3.0% of all patients diagnosed with cancer. The World Health Organization reported that there will be 2.3 million women receiving treatment for breast cancer in 2020, with 685,000. Despite the fact that carcinoma is one of the world's leading causes of death, there is still a paucity of information about its biology. MicroRNAs (miRNAs; miRs) are non-coding RNAs that can reduce gene expression by cleaving the 3' untranslated regions of mRNA. These factors make them a potential protein translation inhibitor. Diverse biological mechanisms implicated in the genesis of cancer are modulated by miRNA. The investigation of global miRNA expression in cancer showed regulatory activity through up regulation and down-regulation in several cancers, including thyroid cancer and breast cancer. In thyroid cancer, miRNA influences several cancers related signaling pathways through modulating MAPK, PI3K, and the RAS pathway. In breast cancer, the regulatory activity of miRNA was played through the cyclin protein family, protein kinases and their inhibitors, and other growth promoters or suppressors, which modulated cell proliferation and cell cycle progression. This article's goal is to discuss key miRNA expressions that are involved in the development of thyroid and breast cancer as well as their therapeutic manipulation for these two specific cancer types.

miR-205-5p Downregulation and ZEB1 Upregulation Characterize the Disseminated Tumor Cells in Patients with Invasive Ductal Breast Cancer

Background: Dissemination of breast cancer (BC) cells through the hematogenous or lymphogenous vessels leads to metastatic disease in one-third of BC patients. Therefore, we investigated the new prognostic features for invasion and metastasis. Methods: We evaluated the expression of miRNAs and epithelial-to-mesenchymal transition (EMT) genes in relation to CDH1/E-cadherin changes in samples from 31 patients with invasive ductal BC including tumor centrum (TU-C), tumor invasive front (TU-IF), lymph node metastasis (LNM), and CD45-depleted blood (CD45-DB). Expression of miRNA and mRNA was quantified by RT-PCR arrays and associations with clinico-pathological characteristics were statistically evaluated by univariate and multivariate analysis. Results: We did not verify CDH1 regulating associations previously described in cell lines. However, we did detect extremely high ZEB1 expression in LNMs from patients with distant metastasis, but without regulation by miR-205-5p. Considering the ZEB1 functions, this overexpression indicates enhancement of metastatic potential of lymphogenously disseminated BC cells. In CD45-DB samples, downregulated miR-205-5p was found in those expressing epithelial and/or mesenchymal markers (CTC+) that could contribute to insusceptibility and survival of hematogenously disseminated BC cells mediated by increased expression of several targets including ZEB1. Conclusions: miR-205-5p and potentially ZEB1 gene are promising candidates for markers of metastatic potential in ductal BC.

Translocation of intracellular CD24 constitutes a triggering event for drug resistance in breast cancer

The capacity of tumor cells to shift dynamically between different states could be responsible for chemoresistance and has been commonly linked to the acquisition of stem cell properties. Here, we have evaluated the phenotype switching associated with drug resistance in breast cancer cell lines and cell lineage obtained from Brazilian patients. We have highlighted the role of the cancer stem cell marker CD24 in the dynamics of cell plasticity and the acquirement of drug resistance. We showed that the translocation of CD24 from cytosol to cell membrane is a triggering event for the phenotype change of breast tumor cells exposed to drug stress. Here, we provide evidence that the phenotype switching is due to the presence of a cytosolic pool of CD24. Importantly, the cellular localization of CD24 was correlated with the changes in the dynamics of p38 MAPK activation. A strong and continuous phosphorylation of the p38 MAPK led to the overexpression of Bcl-2 after treatment in persistent cells presenting high density of CD24 on cell membrane. This phenotype enabled the cells to enter in slow-down of cell cycle, after which several weeks later, the dormant cells proliferated again. Importantly, the use of a p38 activity inhibitor sensitized cells to drug treatment and avoided chemoresistance.

The Anticancer Effects of Flavonoids through miRNAs Modulations in Triple-Negative Breast Cancer

Triple- negative breast cancer (TNBC) incidence rate has regularly risen over the last decades and is expected to increase in the future. Finding novel treatment options with minimum or no toxicity is of great importance in treating or preventing TNBC. Flavonoids are new attractive molecules that might fulfill this promising therapeutic option. Flavonoids have shown many biological activities, including antioxidant, anti-inflammatory, and anticancer effects. In addition to their anticancer effects by arresting the cell cycle, inducing apoptosis, and suppressing cancer cell proliferation, flavonoids can modulate non-coding microRNAs (miRNAs) function. Several preclinical and epidemiological studies indicate the possible therapeutic potential of these compounds. Flavonoids display a unique ability to change miRNAs' levels via different mechanisms, either by suppressing oncogenic miRNAs or activating oncosuppressor miRNAs or affecting transcriptional, epigenetic miRNA processing in TNBC. Flavonoids are not only involved in the regulation of miRNA-mediated cancer initiation, growth, proliferation, differentiation, invasion, metastasis, and epithelial-to-mesenchymal transition (EMT), but also control miRNAs-mediated biological processes that significantly impact TNBC, such as cell cycle, immune system, mitochondrial dysregulation, modulating signaling pathways, inflammation, and angiogenesis. In this review, we highlighted the role of miRNAs in TNBC cancer progression and the effect of flavonoids on miRNA regulation, emphasizing their anticipated role in the prevention and treatment of TNBC.

Expression and significance of c-kit and epithelial-mesenchymal transition (EMT) molecules in thymic epithelial tumors (TETs)

Background

To investigate the expression and significance of c-kit and epithelial-mesenchymal transition (EMT) molecules (E-cadherin, N-cadherin, Twist, Snail) in thymic epithelial tumors (TETs).

Methods

The tissue microarray technology and immunohistochemistry MaxVisionTM-use kit were used to detect the expression of c-kit and EMT molecular markers in 150 cases of paraffin sections of TET tissue and analysis the correlation between c-kit and EMT molecules and explore the malignancy and the relationship of clinicopathological parameters between c-kit, EMT molecules and TETs.

Results

The expression difference of c-kit and EMT molecular markers (E-cadherin, N-cadherin, Snail, Twist) in TETs subtypes was statistically significant (P<0.01) and their positive expression rate of thymic carcinoma was significantly higher than that in thymoma, and the difference was statistically significant, respectively (P<0.01). There is a negative correlation between the expression of c-kit and E-cadherin as well as a positive correlation between the expression level of c-kit, N-cadherin, Twist, and Snail. Furthermore, E-cadherin was negatively correlated with N-cadherin, Twist, and Snail while N-cadherin expression was positively correlated with Twist, Snail.

Conclusions

Five indicators (c-kit, E-cadherin, N-cadherin, Twist, and Snail) may determine the malignancy of TETs, especially for distinguishing thymoma and thymic carcinoma.

MicroRNAs Contribute to Breast Cancer Invasiveness

Cancer statistics in 2018 highlight an 8.6 million incidence in female cancers, and 4.2 million cancer deaths globally. Moreover, breast cancer is the most frequent malignancy in females and twenty percent of these develop metastasis. This provides only a small chance for successful therapy, and identification of new molecular markers for the diagnosis and prognostic prediction of metastatic disease and development of innovative therapeutic molecules are therefore urgently required. Differentially expressed microRNAs (miRNAs) in cancers cause multiple changes in the expression of the tumorigenesis-promoting genes which have mostly been investigated in breast cancers. Herein, we summarize recent data on breast cancer-specific miRNA expression profiles and their participation in regulating invasive processes, in association with changes in cytoskeletal structure, cell-cell adhesion junctions, cancer cell-extracellular matrix interactions, tumor microenvironments, epithelial-to-mesenchymal transitions and cancer cell stem abilities. We then focused on the epigenetic regulation of individual miRNAs and their modified interactions with other regulatory genes, and reviewed the function of miRNA isoforms and exosome-mediated miRNA transfer in cancer invasiveness. Although research into miRNA’s function in cancer is still ongoing, results herein contribute to improved metastatic cancer management.

MicroRNAs and Epigenetics Strategies to Reverse Breast Cancer

Breast cancer is a sporadic disease with genetic and epigenetic components. Genomic instability in breast cancer leads to mutations, copy number variations, and genetic rearrangements, while epigenetic remodeling involves alteration by DNA methylation, histone modification and microRNAs (miRNAs) of gene expression profiles. The accrued scientific findings strongly suggest epigenetic dysregulation in breast cancer pathogenesis though genomic instability is central to breast cancer hallmarks. Being reversible and plastic, epigenetic processes appear more amenable toward therapeutic intervention than the more unidirectional genetic alterations. In this review, we discuss the epigenetic reprogramming associated with breast cancer such as shuffling of DNA methylation, histone acetylation, histone methylation, and miRNAs expression profiles. As part of this, we illustrate how epigenetic instability orchestrates the attainment of cancer hallmarks which stimulate the neoplastic transformation-tumorigenesis-malignancy cascades. As reversibility of epigenetic controls is a promising feature to optimize for devising novel therapeutic approaches, we also focus on the strategies for restoring the epistate that favor improved disease outcome and therapeutic intervention.

Roles of E-cadherin and Noncoding RNAs in the Epithelial-mesenchymal Transition and Progression in Gastric Cancer

The epithelial–mesenchymal transition (EMT) is thought to be at the root of invasive and metastatic cancer cell spreading. E-cadherin is an important player in this process, which forms the structures that establish and maintain cell–cell interactions. A partial or complete loss of E-cadherin expression in the EMT is presumably mediated by mechanisms that block the expression of E-cadherin regulators and involve the E-cadherin-associated transcription factors. The protein is involved in several oncogenic signaling pathways, such as the Wnt/β-catenin, Rho GTPase, and EGF/EGFR, whereby it plays a role in many tumors, including gastric cancer. Such noncoding transcripts as microRNAs and long noncoding RNAs—critical components of epigenetic control of gene expression in carcinogenesis—contribute to regulation of the E-cadherin function by acting directly or through numerous factors controlling transcription of its gene, and thus affecting not only cancer cell proliferation and metastasis, but also the EMT. This review focuses on the role of E-cadherin and the non-coding RNAs-mediated mechanisms of its expressional control in the EMT during stomach carcinogenesis.

Overview on Epigenetic Re-programming: A Potential Therapeutic Intervention in Triple Negative Breast Cancers

Breast cancer treatments leads to variable responses. Hormonal therapy is beneficial to receptor positive breast cancer subtypes and display better clinical outcome than triple negative breast cancers (TNBCs) with FEC (5-Fluorouracil, Epirubicin and Cyclophosphamide) the mainstay chemotherapy regiment. Owning to their negative expressions of estrogen (ER), progesterone (PR) and HER2 receptors, disease recurrence and metastasis befalls some patients indicating resistance to FEC. Involvement of epigenetic silencing through DNA methylation, histone methylation, acetylation and sumoylation may be the key player in FEC chemoresistance. Epigenetic and molecular profiling successfully classified breast cancer subtypes, indicating potential driver mechanisms to the progression of TNBCs but functional mechanisms behind chemoresistance of these molecular markers are not well defined. Several epigenetic inhibitors and drugs have been used in the management of cancers but these attempts are mainly beneficial in hematopoietic cancers and not specifically favourable in solid tumours. Hypothetically, upon administration of epigenetic drugs, recovery of tumour suppressor genes is expected. However, high tendency of switching on global metastatic genes is predicted. Polycomb repressive complex (PRC) such as EZH2, SETD1A, DNMT, is known to have repressive effects in gene regulation and shown to inhibit cell proliferation and invasion in breast cancers. Individual epigenetic regulators may be an option to improve chemo-drug delivery in cancers. This review discussed on molecular signatures of various breast cancer subtypes and on-going attempts in understanding underlying molecular mechanisms of epigenetic regulators as well as providing insights on possible ways to utilize epigenetic enzymes/inhibitors with responses to chemotherapeutic drugs to re-program cellular and biological outcome in TNBCs.

Fisetin Inhibited Growth and Metastasis of Triple-Negative Breast Cancer by Reversing Epithelial-to-Mesenchymal Transition via PTEN/Akt/GSK3β Signal Pathway

Triple negative breast cancer (TNBC), characterized by its highly aggressive and metastatic features, is associated with poor prognosis and high mortality partly due to lack of effective treatment. Fisetin, a natural flavonoid compound, has been demonstrated to possess anti-cancer effects in various cancers. However, the effects and mechanisms of fisetin on metastasis of TNBC remain uncovered. In this study, we found that fisetin dose-dependently inhibited cell proliferation, migration and invasion in TNBC cell lines MDA-MB-231 and BT549 cells. In addition, fisetin reversed epithelial to mesenchymal transition (EMT) as evaluated by cell morphology and EMT markers in MDA-MB-231 and BT549 cells. Furthermore, fisetin suppressed phosphoinositol 3-kinase (PI3K)-Akt-GSK-3β signaling pathway but upregulated the expression of PTEN mRNA and protein in a concentration-dependent manner. Further, silence of PTEN by siRNA abolished these benefits of fisetin on proliferation and metastasis of TNBCs. In vivo, using the metastatic breast cancer xenograft model bearing MDA-MB-231 cells, we found that fisetin dramatically inhibited growth of primary breast tumor and reduced lung metastasis, meanwhile, the expression of EMT molecules and PTEN/Akt/GSK-3β in primary and metastatic tissues changed in the same way as those in vitro experiments. In conclusion, all these results indicated that fisetin could effectively suppress proliferation and metastasis of TNBC and reverse EMT process, which might be mediated by PTEN/Akt/GSK-3β signaling pathway.

Identification and characterization of a highly metastatic epithelial cancer cell line from rat tongue cancer

OBJECTIVES

Tongue squamous cell carcinoma (TSCC) is a clinically devastating disease. However, most established TSCC cell lines currently show undesirable malignant behaviours. The purpose of this study is to establish a highly metastatic TSCC cell line to serve as a useful tool for basic research.

MATERIALS AND METHODS

TSCCs were induced by 4-nitroquinoline-1-oxide (4NQO) in Sprague-Dawley rats. Tumor cells were obtained from the cancer tissues by primary culture and were then purified by an in vitro invasion assay and a limiting dilution assay. The growth rate, cell cycle distribution, apoptotic rate, tumorigenicity and distant metastatic phenotypes of the rat tongue cancer cells were fully investigated and characterized.

RESULTS

To date, the rat tongue cancer cell line, named Rca-T, has been continuously cultured in vitro for over 210 passages and exhibit a long spindle-shaped morphology, adherent growth, and a stable epithelial phenotype. The population doubling time of Rca-T cells is 23.35 h. Approximately 39.8% of these cells are in S phase, and the apoptosis rate of Rca-T cells is 7.46%. Furthermore, in immunodeficient nude mice, both the xenograft rate and the incidence of experimental lung metastasis are 100%. The in vitro assays further reveal the highly malignant and epithelial-mesenchymal transition-like properties of Rca-T cells.

CONCLUSION

In this study, the tumorigenic and highly distant metastatic TSCC cell line Rca-T was established. The malignant features of this cell line, especially its metastatic potential, will enable a wealth of functional studies on the molecular mechanisms of TSCC metastasis in the future.

Functional Role of Non-Coding RNAs during Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a key biological process involved in a multitude of developmental and pathological events. It is characterized by the progressive loss of cell-to-cell contacts and actin cytoskeletal rearrangements, leading to filopodia formation and the progressive up-regulation of a mesenchymal gene expression pattern enabling cell migration. Epithelial-to-mesenchymal transition is already observed in early embryonic stages such as gastrulation, when the epiblast undergoes an EMT process and therefore leads to the formation of the third embryonic layer, the mesoderm. Epithelial-to-mesenchymal transition is pivotal in multiple embryonic processes, such as for example during cardiovascular system development, as valve primordia are formed and the cardiac jelly is progressively invaded by endocardium-derived mesenchyme or as the external cardiac cell layer is established, i.e., the epicardium and cells detached migrate into the embryonic myocardial to form the cardiac fibrous skeleton and the coronary vasculature. Strikingly, the most important biological event in which EMT is pivotal is cancer development and metastasis. Over the last years, understanding of the transcriptional regulatory networks involved in EMT has greatly advanced. Several transcriptional factors such as Snail, Slug, Twist, Zeb1 and Zeb2 have been reported to play fundamental roles in EMT, leading in most cases to transcriptional repression of cell⁻cell interacting proteins such as ZO-1 and cadherins and activation of cytoskeletal markers such as vimentin. In recent years, a fundamental role for non-coding RNAs, particularly microRNAs and more recently long non-coding RNAs, has been identified in normal tissue development and homeostasis as well as in several oncogenic processes. In this study, we will provide a state-of-the-art review of the functional roles of non-coding RNAs, particularly microRNAs, in epithelial-to-mesenchymal transition in both developmental and pathological EMT.

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.

In bone metastasis miR-34a-5p absence inversely correlates with Met expression, while Met oncogene is unaffected by miR-34a-5p in non-metastatic and metastatic breast carcinomas

The highlight of the molecular basis and therapeutic targets of the bone-metastatic process requires the identification of biomarkers of metastasis colonization. Here, we studied miR-34a-5p expression, and Met-receptor expression and localization in bone metastases from ductal breast carcinomas, and in ductal carcinomas without history of metastasis (20 cases). miR-34a-5p was elevated in non-metastatic breast carcinoma, intermediate in the adjacent tissue and practically absent in bone metastases, opposite to pair-matched carcinoma. Met-receptor biomarker was highly expressed and inversely correlated with miR-34a-5p using the same set of bone-metastasis tissues. The miR-34a-5p silencing might depend on aberrant-epigenetic mechanisms of plastic-bone metastases, since in 1833 cells under methyltransferase blockade miR-34a-5p augmented. In fact, 1833 cells showed very low endogenous miR-34a-5p, in respect to parental MDA-MB231 breast carcinoma cells, and the restoration of miR-34a-5p with the mimic reduced Met and invasiveness. Notably, hepatocyte growth factor (HGF)-dependent Met stabilization was observed in bone-metastatic 1833 cells, consistent with Met co-distribution with the ligand HGF at plasma membrane and at nuclear levels in bone metastases. Met-protein level was higher in non-metastatic (low grade) than in metastatic (high grade) breast carcinomas, notwithstanding miR-34a-5p-elevated expression in both the specimens. Thus, mostly in non-metastatic carcinomas the elevated miR-34a-5p unaffected Met, important for invasive/mesenchymal phenotype, while possibly targeting some stemness biomarkers related to metastatic phenotype. In personalized therapies against bone metastasis, we suggest miR-34a-5p as a suitable target of epigenetic reprogramming leading to the accumulation of miR-34a-5p and the down-regulation of Met-tyrosine kinase, a key player of the bone-metastatic process.

MicroRNAs regulate the epithelial-mesenchymal transition and influence breast cancer invasion and metastasis

MicroRNAs are small RNA molecules that play a major role in the post-transcriptional regulation of genes and influence the development, differentiation, proliferation, and apoptosis of cells and the development and progression of tumors. The epithelial-mesenchymal transition is a process by which epithelial cells morphologically transform into cells with a mesenchymal phenotype. The epithelial-mesenchymal transition plays a highly important role in tumor invasion and metastasis. Increasing evidence indicates that microRNAs are tightly associated with epithelial-mesenchymal transition regulation in tumor cells. In breast cancer, various microRNA molecules have been identified as epithelial-mesenchymal transition inducers or inhibitors, which, through different mechanisms and signaling pathways, participate in the regulation of breast cancer invasion and metastasis among various biological behaviors. The epithelial-mesenchymal transition-related microRNAs in breast cancer provide valuable molecules for researching cell invasion and metastasis, and they also provide candidate targets that may be significant for the targeted therapy of breast cancer.

Epigenetic regulation of HGF/Met receptor axis is critical for the outgrowth of bone metastasis from breast carcinoma

Our translational research deals with the influence of microenvironment on the phenotype and colonization of bone metastases from breast carcinoma, and on pre-metastatic niche formation. The aim of the present study was to clarify the origin of hepatocyte growth factor (HGF), ligand of Met receptor, the control of the axis HGF/Met by DNA methylation, and its importance for the nexus supportive cells-metastatic cells and for metastasis outgrowth. In bone metastasis of the 1833-xenograft model, DNA methyltransferase blockade using the chemotherapic drug 5-aza-2′-deoxycytidine (decitabine) strongly reduced the expression of HGF/Met receptor axis and of E-cadherin, with decrease of metastasis wideness and osteolysis, prolonging mice survival. Thus, DNA methylation events acted as commanders of breast carcinoma cells metastatizing to bone influencing the epithelial phenotype. HGF emerged as a bone-marrow stimulus, and the exosomes seemed to furnish HGF to metastatic cells. In fact, decitabine treatment similarly affected some markers of these microvesicles and HGF, indicating that its supply to recipient cells was prevented. Notably, in bone metastasis the hypomethylation of HGF, Met and E-cadherin promoters did not appear responsible for their elevated expression, but we suggest the involvement of hypermethylated regulators and of Wwox oncosuppressor, the latter being affected by decitabine. Wwox expression increased under decitabine strongly localizing in nuclei of bone metastases. We hypothesize a role of Wwox in Met activity since in vitro Wwox overexpression downregulated the level of nuclear-Met protein fragment and Met stability, also under long exposure of 1833 cells to decitabine. HGF enhanced phosphoMet and the activity in nuclei, an effect partially prevented by decitabine. Altogether, the data indicated the importance to target the tumor microenvironment by blocking epigenetic mechanisms, which control critical events for colonization such as HGF/Met axis and Wwox, as therapy of bone metastasis.

From conventional therapy toward microRNA-based therapy in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a hematopoietic malignancy that is known with its special cytogenetic feature. Several studies have surveyed expression signature of microRNAs (miRNAs) in APL patients, especially patients who are treated with conventional therapy of this disease. Using miRNAs as diagnostic or prognostic biomarkers in various cancers has been widely studied. Currently, most studies are focusing on exploiting miRNAs as therapeutic tools, and promising progress has been achieved in this field. Recently, studies in the field of miRNA-based therapy in APL have been started.

Mesenchymal Stromal Cells Can Regulate the Immune Response in the Tumor Microenvironment

The tumor microenvironment is a good target for therapy in solid tumors and hematological malignancies. Indeed, solid tumor cells' growth and expansion can influence neighboring cells' behavior, leading to a modulation of mesenchymal stromal cell (MSC) activities and remodeling of extracellular matrix components. This leads to an altered microenvironment, where reparative mechanisms, in the presence of sub-acute inflammation, are not able to reconstitute healthy tissue. Carcinoma cells can undergo epithelial mesenchymal transition (EMT), a key step to generate metastasis; these mesenchymal-like cells display the functional behavior of MSC. Furthermore, MSC can support the survival and growth of leukemic cells within bone marrow participating in the leukemic cell niche. Notably, MSC can inhibit the anti-tumor immune response through either carcinoma-associated fibroblasts or bone marrow stromal cells. Experimental data have indicated their relevance in regulating cytolytic effector lymphocytes of the innate and adaptive arms of the immune system. Herein, we will discuss some of the evidence in hematological malignancies and solid tumors. In particular, we will focus our attention on the means by which it is conceivable to inhibit MSC-mediated immune suppression and trigger anti-tumor innate immunity.

Cullin3 promotes breast cancer cells metastasis and epithelial-mesenchymal transition by targeting BRMS1 for degradation

Metastasis is the leading cause of death in breast cancer (BC) patients. However, until now, the mechanisms of BC metastasis remain elusive. Cullin3 is a highly conserved Cullin family member present in the genomes of all eukaryotes, which has been proposed as an oncogene in many types of tumors; however, its role and underlying mechanisms in BC remain unclear. Here we show that Cullin3 is elevated in BC and its expression level is positively correlated with metastasis. Overexpression of Cullin3 in BC cells increased proliferation, epithelial-mesenchymal transition, migration and invasion in vitro, and enhanced tumorigenic and metastatic capacities in vivo. In contrast, silencing Cullin3 in aggressive and invasive BC cells inhibited these processes. Mechanistically, we found Cullin3 exerts its function through promoting BRMS1 protein degradation, which was associated with EMT, migration and invasion. BRMS1 overexpression blocked Cullin3-driven EMT, and metastasis. Our results, for the first time, portray a pivotal role of Cullin3 in stimulating metastatic behaviors of BC cells. Targeting Cullin3 may thus be a useful strategy to impede BC cell invasion and metastasis.

Epigenetic Determinants of Cancer

SUMMARYEpigenetic changes are present in all human cancers and are now known to cooperate with genetic alterations to drive the cancer phenotype. These changes involve DNA methylation, histone modifiers and readers, chromatin remodelers, microRNAs, and other components of chromatin. Cancer genetics and epigenetics are inextricably linked in generating the malignant phenotype; epigenetic changes can cause mutations in genes, and, conversely, mutations are frequently observed in genes that modify the epigenome. Epigenetic therapies, in which the goal is to reverse these changes, are now one standard of care for a preleukemic disorder and form of lymphoma. The application of epigenetic therapies in the treatment of solid tumors is also emerging as a viable therapeutic route.

Identification of epigenetic factors regulating the mesenchyme to epithelium transition by RNA interference screening in breast cancer cells

Background

In breast cancer, the epithelial to mesenchyme transition (EMT) is associated to tumour dissemination, drug resistance and high relapse risks. It is partly controlled by epigenetic modifications such as histone acetylation and methylation. The identification of genes involved in these reversible modifications represents an interesting therapeutic strategy to fight metastatic disease by inducing mesenchymal cell differentiation to an epithelial phenotype.

Methods

We designed a siRNA library based on chromatin modification-related to functional domains and screened it in the mesenchymal breast cancer cell line MDA-MB-231. The mesenchyme to epithelium transition (MET) activation was studied by following human E-CADHERIN (E-CAD) induction, a specific MET marker, and cell morphology. Candidate genes were validated by studying the expression of several differential marker genes and their impact on cell migration.

Results

The screen led to the identification of 70 gene candidates among which some are described to be, directly or indirectly, involved in EMT like ZEB1, G9a, SMAD5 and SMARCD3. We also identified the DOT1L as involved in EMT regulation in MDA-MB-231. Moreover, for the first time, KAT5 gene was linked to the maintenance of the mesenchymal phenotype.

Conclusions

A multi-parametric RNAi screening approach was developed to identify new EMT regulators such as KAT5 in the triple negative breast cancer cell line MDA-MB-231.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2683-5) contains supplementary material, which is available to authorized users.

Differentially Expressed MicroRNAs in Meningiomas Grades I and II Suggest Shared Biomarkers with Malignant Tumors

Meningiomas represent the most common primary tumors of the central nervous system, but few microRNA (miRNA) profiling studies have been reported so far. Deep sequencing of small RNA libraries generated from two human meningioma biopsies WHO grades I (benign) and II (atypical) were compared to excess dura controls. Nineteen differentially expressed miRNAs were validated by RT-qPCR using tumor RNA from 15 patients and 5 meninges controls. Tumor suppressor miR-218 and miR-34a were upregulated relative to normal controls, however, miR-143, miR-193b, miR-451 and oncogenic miR-21 were all downregulated. From 10 selected putative mRNA targets tested by RT-qPCR only four were differentially expressed relative to normal controls. PTEN and E-cadherin (CDH1) were upregulated, but RUNX1T1 was downregulated. Proliferation biomarker p63 was upregulated with nuclear localization, but not detected in most normal arachnoid tissues. Immunoreactivity of E-cadherin was detected in the outermost layer of normal arachnoids, but was expressed throughout the tumors. Nuclear Cyclin D1 expression was positive in all studied meningiomas, while its expression in arachnoid was limited to a few trabecular cells. Meningiomas of grades I and II appear to share biomarkers with malignant tumors, but with some additional tumor suppressor biomarkers expression. Validation in more patients is of importance.

Epithelial-Mesenchymal Transition and Breast Cancer

Breast cancer is the most common cancer in women and distant site metastasis is the main cause of death in breast cancer patients. There is increasing evidence supporting the role of epithelial-mesenchymal transition (EMT) in tumor cell progression, invasion, and metastasis. During the process of EMT, epithelial cancer cells acquire molecular alternations that facilitate the loss of epithelial features and gain of mesenchymal phenotype. Such transformation promotes cancer cell migration and invasion. Moreover, emerging evidence suggests that EMT is associated with the increased enrichment of cancer stem-like cells (CSCs) and these CSCs display mesenchymal characteristics that are resistant to chemotherapy and target therapy. However, the clinical relevance of EMT in human cancer is still under debate. This review will provide an overview of current evidence of EMT from studies using clinical human breast cancer tissues and its associated challenges.

Combined silencing of TGF-β2 and Snail genes inhibit epithelial-mesenchymal transition of retinal pigment epithelial cells under hypoxia

BACKGROUND

The formation of scar-like fibrous tissue in age-related macular degeneration (AMD) is associated with hypoxia. Under hypoxia, retinal pigment epithelial (RPE) cells can secret more transforming growth factor-β2 (TGF-β2), which is determined to induce epithelial-mesenchymal transition (EMT) at certain concentrations. Whether hypoxia can induce EMT by stimulating RPE cell line secrets TGF-β2 or not remains unknown. To gain a better understanding of the signaling mechanisms of fibrosis in AMD under hypoxic conditions, we investigated EMT in retinal pigment epithelial (RPE) cells and the effect of TGF-β2 and Snail in this process.

METHODS

Human RPE cell line (ARPE-19) was incubated with 5 % O2 for different periods of time. The expression of N-cadherin, α-smooth muscle actin (α-SMA), TGF-β2 , and Snail were determined by Western blot and real-time PCR. Cell proliferation was assessed by CCK8 kit. RNA interference was used for multi-gene silencing of TGF-β2 and Snail genes.

RESULTS

N-cadherin was decreased and mesenchymal cell marker α-SMA was increased after the ARPE-19 cell line was incubated with 5 % O2. Meanwhile, the proliferation capability of the cell line was increased. TGF-β2 and Snail expression were increased in a time-dependent manner under hypoxia. After multi-silencing TGF-β2 and Snail genes, N-cadherin was increased and α-SMA was reduced. Meanwhile, the proliferation of the cell line was suppressed.

CONCLUSIONS

Under hypoxic conditions, RPE cells undergo EMT. Endogenic TGF-β2 and Snail are involved in this process. Furthermore, knockdown of both TGF-β2 and Snail inhibited EMT to a greater extent than knockdown of either gene individually.

The role of EMT and MET in cancer dissemination

Metastatic cancer cells are lethal. Understanding the molecular mechanisms that bolster the conversion from benign to malignant progression is key for treating these heterogeneous and resistant neoplasms. The epithelial-mesenchymal transition (EMT) is a conserved cellular program that alters cell shape, adhesion and movement. The shift to a more mesenchymal-like phenotype can promote tumor cell intravasation of surrounding blood vessels and emigration to a new organ, yet may not be necessary for extravasation or colonization into that environment. Lymphatic dissemination, on the other hand, may not require EMT. This review presents emerging data on the modes by which tumor cells promote EMT/MET via microRNA and prepare the pre-metastatic niche via exosomes.

New targeted therapies for breast cancer: A focus on tumor microenvironmental signals and chemoresistant breast cancers

Breast cancer is the most frequent female malignancy worldwide. Current strategies in breast cancer therapy, including classical chemotherapy, hormone therapy, and targeted therapies, are usually associated with chemoresistance and serious adverse effects. Advances in our understanding of changes affecting the interactome in advanced and chemoresistant breast tumors have provided novel therapeutic targets, including, cyclin dependent kinases, mammalian target of rapamycin, Notch, Wnt and Shh. Inhibitors of these molecules recently entered clinical trials in mono- and combination therapy in metastatic and chemo-resistant breast cancers. Anticancer epigenetic drugs, mainly histone deacetylase inhibitors and DNA methyltransferase inhibitors, also entered clinical trials. Because of the complexity and heterogeneity of breast cancer, the future in therapy lies in the application of individualized tailored regimens. Emerging therapeutic targets and the implications for personalized-based therapy development in breast cancer are herein discussed.