Histone deacetylase inhibitor induction of epithelial-mesenchymal transitions via up-regulation of Snail facilitates cancer progression

Discovery of potent pyrrolo-pyrimidine and purine HDAC inhibitors for the treatment of advanced prostate cancer

The development of drugs for the treatment of advanced prostate cancer (PCA) remains a challenging task. In this study we have designed, synthesized and tested twenty-nine novel HDAC inhibitors based on three different zinc binding groups (trifluoromethyloxadiazole, hydroxamic acid, and 2-mercaptoacetamide). These warheads were conveniently tethered to variously substituted phenyl linkers and decorated with differently substituted pyrrolo-pyrimidine and purine cap groups. Remarkably, most of the compounds showed nanomolar inhibitory activity against HDAC6. To provide structural insights into the Structure-Activity Relationships (SAR) of the investigated compounds, docking of representative inhibitors and molecular dynamics of HDAC6-inhibitor complexes were performed. Compounds of the trifluoromethyloxadiazole and hydroxamic acid series exhibited promising anti-proliferative activities, HDAC6 targeting in PCA cells, and in vitro tumor selectivity. Representative compounds of the two series were tested for solubility, cell permeability and metabolic stability, demonstrating favorable in vitro drug-like properties. The more interesting compounds were subjected to migration assays, which revealed that compound 13 and, to a lesser extent, compound 15 inhibited the invasive behaviour of androgen-sensitive and -insensitive advanced prostate cancer cells. Compound 13 was profiled against all HDACs and found to inhibit all members of class II HDACs (except for HDAC10) and to be selective with respect to class I and class IV HDACs. Overall, compound 13 combines potent inhibitory activity and class II selectivity with favorable drug-like properties, an excellent anti-proliferative activity and marked anti-migration properties on PCA cells, making it an excellent lead candidate for further optimization.

Identification and validation of novel prognostic signatures based on m5C methylation patterns and tumor EMT profiles in head and neck squamous cell carcinoma

The role of 5-methylcytosine (m5C) in tumor initiation and progression has been increasingly recognized. However, the precise association between the regulation of m5C and the progression, metastasis, and prognosis of head and neck squamous cell carcinoma (HNSCC) has not yet been fully explored. Data from 545 HNSCC patients obtained from The Cancer Genome Atlas (TCGA) database were analyzed. Unsupervised cluster analysis was conducted using the expression levels of m5C regulatory genes. Additionally, gene set variation analysis (GSVA), single-sample gene set enrichment analysis (ssGSEA), and Cox regression analysis were utilized. Quantitative reverse transcription polymerase chain reaction (RT-qPCR), colony formation assay, transwell experiments and western blots were performed in the HNSCC cell line UM-SCC-17B to assess the expression and functional role of one of the novel signatures, CNFN. Significant expression differences were found in m5C regulatory genes between tumor and normal tissues in HNSCC. Two distinct m5C modification patterns, characterized by substantial prognostic differences, were identified. Cluster-2, which exhibited a strong association with epithelial-mesenchymal transition (EMT), was found to be associated with a poorer prognosis. Based on the m5C clusters and EMT status, differentially expressed genes (DEGs) were identified. Using DEGs, an 8-gene signature (CAMK2N1, WNT7A, F2RL1, AREG, DEFB1, CNFN, TGFBI, and CAV1) was established to develop a prognostic model. The performance of this signature was validated in both the training and external validation datasets, demonstrating its promising efficacy. Furthermore, additional investigations using RT-qPCR on clinical specimens and experimental assays in cell lines provided compelling evidence suggesting that CNFN, one of the genes in the signature, could play a role in HNSCC progression and metastasis through the EMT pathway. This study highlighted the role of m5C in HNSCC progression and metastasis. The relationship between m5C and EMT has been elucidated for the first time. A robust prognostic model was developed for accurately predicting HNSCC patients' survival outcomes. Potential molecular mechanisms underlying these associations have been illuminated through this research.

γ-Secretase Inhibitor Potentiates the Activity of Suberoylanilide Hydroxamic Acid by Inhibiting Its Ability to Induce Epithelial to Mesenchymal Transition and Stemness via Notch Pathway Activation in Triple-Negative Breast Cancer Cells

Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA), possess great therapeutic value for triple-negative breast cancer patients. However, their inherent ability to induce epithelial to mesenchymal transition in various malignancies has been of greater concern. Herein, we hypothesize that SAHA facilitates epithelial to mesenchymal transition (EMT) via activation of the Notch pathway. From the literature survey, it is evident that histone deacetylase mediates the formation of the co-repressor complex upon interacting with the DNA binding domain, thereby inhibiting the transcription of the Notch downstream genes. Hence, we hypothesize that the use of SAHA facilitates the transcriptional activation of the Notch target genes, by disrupting the co-repressor complex and recruiting the coactivator complex, thereby facilitating EMT. In this study, we have observed that SAHA upregulates the expression profile of the Notch downstream proteins (such as Notch intracellular domain, Hes-1, c-Myc, etc.) and the Notch ligands (such as Jagged-1 and Jagged-2), thereby aberrantly activating the signaling pathway. Therefore, we have focused on combination therapy using a γ-secretase inhibitor LY411575 that would enhance the efficacy of SAHA by blocking the canonical Notch pathway mediated via its intracellular domain. It was observed that co-treatment significantly mediates apoptosis, generates cellular reactive oxygen species, depolarizes mitochondria, and diminishes the stemness properties. Besides, it also mediates autophagy-independent cell death and diminishes the expression of inflammatory cytokines, along with the downregulation in the expression of the Notch downstream genes and mesenchymal markers. Altogether, our study provides a mechanistic basis for combating EMT potentiated by SAHA, which could be utilized as a rational strategy for the treatment of solid tumors, especially triple-negative breast cancer.

PI3K/AKT signaling pathway as a critical regulator of epithelial-mesenchymal transition in colorectal tumor cells

Colorectal cancer (CRC) is one of the most frequent gastrointestinal malignancies that are considered as a global health challenge. Despite many progresses in therapeutic methods, there is still a high rate of mortality rate among CRC patients that is associated with poor prognosis and distant metastasis. Therefore, investigating the molecular mechanisms involved in CRC metastasis can improve the prognosis. Epithelial-mesenchymal transition (EMT) process is considered as one of the main molecular mechanisms involved in CRC metastasis, which can be regulated by various signaling pathways. PI3K/AKT signaling pathway has a key role in CRC cell proliferation and migration. In the present review, we discussed the role of PI3K/AKT pathway CRC metastasis through the regulation of the EMT process. It has been shown that PI3K/AKT pathway can induce the EMT process by down regulation of epithelial markers, while up regulation of mesenchymal markers and EMT-specific transcription factors that promote CRC metastasis. This review can be an effective step toward introducing the PI3K/AKT/EMT axis to predict prognosis as well as a therapeutic target among CRC patients. Video Abstract.

Regulation of epithelial-mesenchymal transition by protein lysine acetylation

The epithelial-mesenchymal transition (EMT) is a vital driver of tumor progression. It is a well-known and complex trans-differentiation process in which epithelial cells undergo morphogenetic changes with loss of apical-basal polarity, but acquire spindle-shaped mesenchymal phenotypes. Lysine acetylation is a type of protein modification that favors reversibly altering the structure and function of target molecules via the modulation of lysine acetyltransferases (KATs), as well as lysine deacetylases (KDACs). To date, research has found that histones and non-histone proteins can be acetylated to facilitate EMT. Interestingly, histone acetylation is a type of epigenetic regulation that is capable of modulating the acetylation levels of distinct histones at the promoters of EMT-related markers, EMT-inducing transcription factors (EMT-TFs), and EMT-related long non-coding RNAs to control EMT. However, non-histone acetylation is a post-translational modification, and its effect on EMT mainly relies on modulating the acetylation of EMT marker proteins, EMT-TFs, and EMT-related signal transduction molecules. In addition, several inhibitors against KATs and KDACs have been developed, some of which can suppress the development of different cancers by targeting EMT. In this review, we discuss the complex biological roles and molecular mechanisms underlying histone acetylation and non-histone protein acetylation in the control of EMT, highlighting lysine acetylation as potential strategy for the treatment of cancer through the regulation of EMT.

Valproic Acid Initiates Transdifferentiation of the Human Ductal Adenocarcinoma Cell-line Panc-1 Into α-Like Cells

Non-mesenchymal pancreatic cells are a potential source for cell replacement. Their transdifferentiation can be achieved by triggering epigenetic remodeling through e. g. post-translational modification of histones. Valproic acid, a branched-chain saturated fatty acid with histone deacetylase inhibitor activity, was linked to the expression of key transcription factors of pancreatic lineage in epithelial cells and insulin transcription. However, the potential of valproic acid to cause cellular reprogramming is not fully understood. To shed further light on it we employed next-generation RNA sequencing, real-time PCR, and protein analyses by ELISA and western blot, to assess the impact of valproic acid on transcriptome and function of Panc-1-cells. Our results indicate that valproic acid has a significant impact on the cell cycle, cell adhesion, histone H3 acetylation, and metabolic pathways as well as the initiation of epithelial-mesenchymal transition through acetylation of histone H3 resulting in α-cell-like characteristics. We conclude that human epithelial pancreatic cells can be transdifferentiated into cells with endocrine properties through epigenetic regulation by valproic acid favoring an α-cell-like phenotype.

Design and synthesis of dual inhibitors targeting snail and histone deacetylase for the treatment of solid tumour cancer

Snail and histone deacetylases (HDACs) have an important impact on cancer treatment, especially for their synergy. Therefore, the development of inhibitors targeting both Snail and HDAC might be a promising strategy for the treatment of cancers. In this work, we synthesized a series of Snail/HDAC dual inhibitors. Compound 9n displayed the most potent inhibitory activity against HDAC1 with an IC₅₀ of 0.405 μM, potent inhibition against Snail with a K_d of 0.180 μM, and antiproliferative activity in HCT-116 cell lines with an IC₅₀ of 0.0751 μM. Compound 9n showed a good inhibitory effect on NCI-H522 (GI₅₀ = 0.0488 μM), MDA-MB-435 (GI₅₀ = 0.0361 μM), and MCF7 (GI₅₀ = 0.0518 μM). Docking studies showed that compound 9n can be well docked into the active binding sites of Snail and HDAC. Further studies showed that compound 9n increased histone H4 acetylation in HCT-116 cells and decreased the expression of Snail protein to induce cell apoptosis. These findings highlight the potential for the development of Snail/HDAC dual inhibitors as anti-solid tumour cancer drugs.

SAHA induce hippo pathway in CCA cells without increasing cell proliferation

BACKGROUND

Cholangiocarcinoma is a malignant tumor originating from bile duct epithelial cells. Since tumor metastasis is associated with poor prognosis and short-term survival of patients, there is an urgent need for alternative therapeutic approaches for CCA. Because of that reason, we aimed to investigate effect of SAHA which is known as HDAC inhibitor on extrahepatic cholangiocarcinoma cell line (TFK-1).

METHODS

Cell cycle was measured by Muse Cell Analyzer. YAP, TAZ, TGF-β protein levels were determined by western-blotting method. TEAD (1-3), TIMP2 and TIMP3 genes level were determined by real-time PCR analysis.

RESULTS

We have seen the positive effects of SAHA on the TFK-1 cell line as it reduces cell viability and arresting cells in the G0/G1 phase. We also observed the negative effects of SAHA, as it increases the expression levels of YAP, TAZ, TGF-β protein and TEAD (1-3) gene. We also found that SAHA reduced the expression levels of TIMP2 and TIMP3 in TFK-1 cells, but was not statistically significant.

CONCLUSIONS

Although observing its antiproliferative effects, these negative effects may be related to the cells being resistant to the drug or the remaining cells having a more aggressive phenotype. Therefore, we think that caution should be exercised in the use of this drug for CCA treatment.

SNAIL1: Linking Tumor Metastasis to Immune Evasion

The transcription factor Snail1, a key inducer of epithelial-mesenchymal transition (EMT), plays a critical role in tumor metastasis. Its stability is strictly controlled by multiple intracellular signal transduction pathways and the ubiquitin-proteasome system (UPS). Increasing evidence indicates that methylation and acetylation of Snail1 also affects tumor metastasis. More importantly, Snail1 is involved in tumor immunosuppression by inducing chemokines and immunosuppressive cells into the tumor microenvironment (TME). In addition, some immune checkpoints potentiate Snail1 expression, such as programmed death ligand 1 (PD-L1) and T cell immunoglobulin 3 (TIM-3). This mini review highlights the pathways and molecules involved in maintenance of Snail1 level and the significance of Snail1 in tumor immune evasion. Due to the crucial role of EMT in tumor metastasis and tumor immunosuppression, comprehensive understanding of Snail1 function may contribute to the development of novel therapeutics for cancer.

HDAC inhibition induces EMT and alterations in cellular iron homeostasis to augment ferroptosis sensitivity in SW13 cells

Epithelial-to-mesenchymal transition (EMT) is an essential mechanism for development and wound healing, but in cancer it also mediates the progression and spread of aggressive tumors while increasing therapeutic resistance. Adoption of a mesenchymal state is also associated with increased iron uptake, but the relationship between EMT and the key regulators of cellular iron metabolism remains undefined. In this regard, the human adrenal cortical carcinoma SW13 cell line represents an invaluable research model as HDAC inhibitor treatment can convert them from an epithelial-like (SW13-) cell type to a mesenchymal-like (SW13+) subtype. In this study we establish SW13 cells as a model for exploring the link between iron and EMT. Increased iron accumulation following HDAC inhibitor mediated EMT is associated with decreased expression of the iron export protein ferroportin, enhanced ROS production, and reduced expression of antioxidant response genes. As availability of redox active iron and loss of lipid peroxide repair capacity are hallmarks of ferroptosis, a form of iron-mediated cell death, we next examined whether HDAC inhibitor treatment could augment ferroptosis sensitivity. Indeed, HDAC inhibitor treatment synergistically increased cell death following induction of ferroptosis. The exact mechanisms by which HDAC inhibition facilitates cell death following ferroptosis induction requires further study. As several HDAC inhibitors are already in use clinically for the treatment of certain cancer types, the findings from these studies have immediate implications for improving iron-targeted chemotherapeutic strategies.

Epigenetic control of melanoma cell invasiveness by the stem cell factor SALL4

Melanoma cells rely on developmental programs during tumor initiation and progression. Here we show that the embryonic stem cell (ESC) factor Sall4 is re-expressed in the Tyr::NrasQ61K; Cdkn2a-/- melanoma model and that its expression is necessary for primary melanoma formation. Surprisingly, while Sall4 loss prevents tumor formation, it promotes micrometastases to distant organs in this melanoma-prone mouse model. Transcriptional profiling and in vitro assays using human melanoma cells demonstrate that SALL4 loss induces a phenotype switch and the acquisition of an invasive phenotype. We show that SALL4 negatively regulates invasiveness through interaction with the histone deacetylase (HDAC) 2 and direct co-binding to a set of invasiveness genes. Consequently, SALL4 knock down, as well as HDAC inhibition, promote the expression of an invasive signature, while inhibition of histone acetylation partially reverts the invasiveness program induced by SALL4 loss. Thus, SALL4 appears to regulate phenotype switching in melanoma through an HDAC2-mediated mechanism.

Histone deacetylase inhibitor panobinostat induces antitumor activity in epithelioid sarcoma and rhabdoid tumor by growth factor receptor modulation

Background

Epithelioid sarcomas and rhabdoid tumors are rare, aggressive malignancies with poor prognosis. Both are characterized by INI1 alterations and deregulation of growth factor receptors albeit their interaction has not been elucidated.

Methods

In this study, we investigated the activity of a panel of epigenetic modulators and receptor tyrosine kinase inhibitors in vitro on respective cell lines as well as on primary patient-derived epithelioid sarcoma cells, and in vivo on xenografted mice. Focusing on histone deacetylase (HDAC) inhibitors, we studied the mechanism of action of this class of agents, its effect on growth factor receptor regulation, and changes in epithelial-to-mesenchymal transition by using cell- and RT-qPCR-based assays.

Results

Pan-HDAC inhibitor panobinostat exhibited potent anti-proliferative activity at low nanomolar concentrations in A204 rhabdoid tumor, and VAESBJ/GRU1 epithelioid sarcoma cell lines, strongly induced apoptosis, and resulted in significant tumor growth inhibition in VAESBJ xenografts. It differentially regulated EGFR, FGFR1 and FGFR2, leading to downregulation of EGFR in epithelioid sarcoma and to mesenchymal-to-epithelial transition whereas in rhabdoid tumor cells, EGFR was strongly upregulated and reinforced the mesenchymal phenotype. All three cell lines were rendered more susceptible towards combination with EGFF inhibitor erlotinib, further enhancing apoptosis.

Conclusions

HDAC inhibitors exhibit significant anticancer activity due to their multifaceted actions on cytotoxicity, differentiation and drug sensitization. Our data suggest that the tailored, tissue-specific combination of HDAC inhibitors with therapeutics which target cellular salvage mechanisms might increase their therapeutic relevance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08579-w.

HDAC Inhibitors: Dissecting Mechanisms of Action to Counter Tumor Heterogeneity

Intra-tumoral heterogeneity presents a major obstacle to cancer therapeutics, including conventional chemotherapy, immunotherapy, and targeted therapies. Stochastic events such as mutations, chromosomal aberrations, and epigenetic dysregulation, as well as micro-environmental selection pressures related to nutrient and oxygen availability, immune infiltration, and immunoediting processes can drive immense phenotypic variability in tumor cells. Here, we discuss how histone deacetylase inhibitors, a prominent class of epigenetic drugs, can be leveraged to counter tumor heterogeneity. We examine their effects on cellular processes that contribute to heterogeneity and provide insights on their mechanisms of action that could assist in the development of future therapeutic approaches.

The Effect of EZH2 Inhibition through DZNep on Epithelial-Mesenchymal Transition Mechanism

Although the molecular pathogenesis of hepatocellular carcinoma (HCC) is uncertain, it is known that the epithelial-mesenchymal transition (EMT) mechanism and epigenetic changes have an important role. This study was focused on evaluating the relationship of 3-Deazaneplanocin A (DZNep) with the EMT mechanism, which is a histone methyltransferase inhibitor on HCC and is also known as an enhancer of zeste homolog 2 (EZH2) inhibitor. Cell viability of HepG2 cells (HCC cell line) assessed for DZNep over 72 hours with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, colony-forming assay, apoptosis assay, RNA isolation, cDNA synthesis, and real-time PCR (RT-PCR) were performed to see the effect of DZNep on HepG2 cells. DZNep reduced cell proliferation for 72 hours, also significantly reduced colony formation in addition it increased the total apoptosis. DZNep on EZH2, E-cadherin, N-cadherin, and Vimentin (Vim) gene expressions was given different results by either decreasing or increasing the expressions. In this study, we observed a positive effect of DZNep on apoptosis and TIMP3 expression level and decreased colony formation. However, it gave complicated results with the level of gene expression E-cadherin and TIMP2, increase the level of Vim and MMP2 expression. Therefore, we think that further studies are necessary to clarify the role of DZNep.

Epithelial-Mesenchymal Transition (EMT) as a Therapeutic Target

Metastasis is the spread of cancer cells from the primary tumour to distant sites and organs throughout the body. It is the primary cause of cancer morbidity and mortality, and is estimated to account for 90% of cancer-related deaths. During the initial steps of the metastatic cascade, epithelial cancer cells undergo an epithelial-mesenchymal transition (EMT), and as a result become migratory and invasive mesenchymal-like cells while acquiring cancer stem cell properties and therapy resistance. As EMT is involved in such a broad range of processes associated with malignant transformation, it has become an increasingly interesting target for the development of novel therapeutic strategies. Anti-EMT therapeutic strategies could potentially not only prevent the invasion and dissemination of cancer cells, and as such prevent the formation of metastatic lesions, but also attenuate cancer stemness and increase the effectiveness of more classical chemotherapeutics. In this review, we give an overview about the pros and cons of therapies targeting EMT and discuss some already existing candidate drug targets and high-throughput screening tools to identify novel anti-EMT compounds.

Curcumin attenuates lncRNA H19‑induced epithelial‑mesenchymal transition in tamoxifen‑resistant breast cancer cells

The H19 long non-coding RNA is involved in the development of tamoxifen resistance in breast cancer. However, the relationship between H19 and the metastatic potential and treatment options for tamoxifen-resistant (TAMR) breast cancer is not completely understood. Curcumin inhibits cellular proliferation, migration and invasiveness in several cancer types, including pancreatic cancer, breast cancer and chronic myeloid leukemia. The present study aimed to investigate the role of H19 in MCF-7/TAMR cell epithelial-mesenchymal transition (EMT), migration and invasiveness, and to assess the ability of curcumin to inhibit H19-mediated effects. Reverse transcription-quantitative PCR and western blot analysis were conducted to detect the gene or protein expression. Cell Counting Kit-8, wound healing and Transwell invasion assays were performed to estimate the capabilities of cell viability, invasion and migration. H19 overexpression enhanced MCF-7/TAMR cell EMT, invasion and migration by upregulating Snail. Furthermore, curcumin notably decreased the expression levels of epithelial marker E-cadherin and markedly increased the expression levels of mesenchymal marker N-cadherin in MCF-7/TAMR cells compared with the control group. In addition, following treatment with curcumin for 48 h, H19 expression was decreased in a dose-dependent manner. Moreover, curcumin treatment for 48 h significantly attenuated H19-induced alterations in N-cadherin and E-cadherin expression levels. Curcumin also prevented H19-induced invasion and migration. The present study indicated that H19 may serve as a promoting factor of EMT, invasion and migration in MCF-7/TAMR cells, suggesting that curcumin may prevent H19-associated metastasis. Therefore, curcumin may serve as a promising therapeutic drug for patients with TAMR breast cancer.

Protein Post-translational Modifications in Head and Neck Cancer

Head and neck cancer (HNC) is one of the most common malignant tumors worldwide, and is prone to tumor recurrence and metastasis. At present, surgery combined with radiotherapy and chemotherapy is still the conventional treatment modality for patients with HNC. However, for patients with relapse or metastasis of HNC, the treatment outcome is not ideal, and the prognosis is poor. Thus, it is crucial to deepen the understand of tumor mechanisms. Post-translational modifications (PTMs) refer to covalent binding of small chemical molecular groups to amino-acid side-chain of proteins. Post-translational modification is an important regulator of protein function, and as such, a current research hotspot of epigenetics. In recent years, it has been found that tumor occurrence is often accompanied by the abnormality of PTMs. Indeed, the abnormality play an important role in tumor development, and can be used as a target for tumor diagnosis and treatment. To date, several types of protein PTMs involved in the development of HNC have been reported. This paper reviews the relationship between HNC and several major protein PTMs, including acetylation, methylation, and glycosylation, in order to provide clues for the future application about PTMs in diagnosis and treatment of HNC.

Effect of sodium butyrate on ABC transporters in lung cancer A549 and colorectal cancer HCT116 cells

Histone deacetylase (HDAC) inhibitors and DNA alkylators are effective components of combination chemotherapy. The aim of the present study was to investigate the possible mechanism of their synergism by detecting the effect of HDAC inhibitors on the expression levels of drug transporters that export DNA alkylators. It was demonstrated that the HDAC inhibitor sodium butyrate (NaB) induced the differential expression of multidrug resistant ATP-binding cassette (ABC) transporters in lung cancer and colorectal cancer cells. Specifically, NaB increased the mRNA expression levels of ABC subfamily B member 1 (ABCB1), ABCC10 and ABCC12, and protein expression levels of multidrug resistance-1 (MDR1), multidrug resistance-associated protein 7 (MRP7) and MRP9. Moreover, NaB decreased the expression levels of ABCC1, ABCC2 and ABCC3 mRNAs, as well as those of MRP1, MRP2 and MRP3 proteins. The molecular mechanism underlying this process was subsequently investigated. NaB decreased the expression of HDAC4, but not HDAC1, HDAC2 or HDAC3. In addition, NaB promoted histone H3 acetylation and methylation at lysine 9, as well as MDR1 acetylation, suggesting that acetylation and methylation may be involved in NaB-mediated ABC transporter expression. Thus, the present results indicated that the synergism of the HDAC inhibitors with the DNA alkylating agents may due to the inhibitory effect of MRPs by HDAC inhibitors. The findings also suggested the possibility of antagonistic effects following the combined treatment of HDAC inhibitors with MDR1 ligands.

Histone deacetylase inhibitors promote epithelial-mesenchymal transition in Hepatocellular Carcinoma via AMPK-FOXO1-ULK1 signaling axis-mediated autophagy

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer-related deaths globally because of high metastasis and recurrence rates. Elucidating the molecular mechanisms of HCC recurrence and metastasis and developing effective targeted therapies are expected to improve patient survival. The promising anti-cancer agents for the treatment of hematological malignancies, histone deacetylase inhibitors (HDIs), have limited effects against epithelial cell-derived cancers, including HCC, the mechanisms involved have not been elucidated. Herein, we studied the molecular mechanisms underlying HDI-induced epithelial-mesenchymal transition (EMT) involving FOXO1-mediated autophagy. Methods: The biological functions of HDIs in combination with autophagy inhibitors were examined both in vitro and in vivo. Cell autophagy was assessed using the generation of mRFP-GFP-LC3-expressing cells and fluorescent LC3 puncta analysis, Western blotting, and electron microscopy. An orthotopic hepatoma model was established in mice for the in vivo experiments. Results: Our study provided novel mechanistic insights into HDI-induced EMT mediated by the autophagy AMPK-FOXO1-ULK1-Snail signaling axis. We demonstrated that autophagy served as a pro-metastasis mechanism in HDI-treated hepatoma cells. HDIs induced autophagy via a FOXO1-dependent pathway, and FOXO1 inhibition promoted HDI-mediated apoptosis in hepatoma cells. Thus, our findings provided novel insights into the molecular mechanisms underlying HDI-induced EMT involving FOXO1-mediated autophagy and demonstrated that a FOXO1 inhibitor exerted a synergistic effect with an HDI to inhibit cell growth and metastasis in vitro and in vivo. Conclusion: We demonstrated that HDIs triggers FOXO1-dependent autophagy, which ultimately promotes EMT, limiting the clinical outcome of HDI-based therapies. Our study suggests that the combination of an HDI and a FOXO1 inhibitor is an effective therapeutic strategy for the treatment of HCC.

Understanding Failure and Improving Treatment Using HDAC Inhibitors for Prostate Cancer

Novel treatment regimens are required for castration-resistant prostate cancers (CRPCs) that become unresponsive to standard treatments, such as docetaxel and enzalutamide. Histone deacetylase (HDAC) inhibitors showed promising results in hematological malignancies, but they failed in solid tumors such as prostate cancer, despite the overexpression of HDACs in CRPC. Four HDAC inhibitors, vorinostat, pracinostat, panobinostat and romidepsin, underwent phase II clinical trials for prostate cancers; however, phase III trials were not recommended due to a majority of patients exhibiting either toxicity or disease progression. In this review, the pharmacodynamic reasons for the failure of HDAC inhibitors were assessed and placed in the context of the advancements in the understanding of CRPCs, HDACs and resistance mechanisms. The review focuses on three themes: evolution of androgen receptor-negative prostate cancers, development of resistance mechanisms and differential effects of HDACs. In conclusion, advancements can be made in this field by characterizing HDACs in prostate tumors more extensively, as this will allow more specific drugs catering to the specific HDAC subtypes to be designed.

Histone deacetylases, Mbd3/NuRD, and Tet2 hydroxylase are crucial regulators of epithelial-mesenchymal plasticity and tumor metastasis

An epithelial-mesenchymal transition (EMT) represents a basic morphogenetic process of high cell plasticity underlying embryogenesis, wound healing, cancer metastasis and drug resistance. It involves a profound transcriptional and epigenetic reprogramming of cells. A critical role of epigenetic modifiers and their specific chromatin modifications has been demonstrated during EMT. However, it has remained elusive whether epigenetic control differs between the dynamic cell state transitions of reversible EMT and the fixed differentiation status of irreversible EMT. We have employed varying EMT models of murine breast cancer cells to identify the key players establishing epithelial-mesenchymal cell plasticity during reversible and irreversible EMT. We demonstrate that the Mbd3/NuRD complex and the activities of histone deacetylases (HDACs), and Tet2 hydroxylase play a critical role in keeping cancer cells in a highly metastatic mesenchymal state. Combinatorial interference with their functions leads to mesenchymal-epithelial transition (MET) and efficiently represses metastasis formation by invasive murine and human breast cancer cells in vivo.

Valproic acid promotes the epithelial-to-mesenchymal transition of breast cancer cells through stabilization of Snail and transcriptional upregulation of Zeb1

Histone deacetylases (HDACs) can regulate cancer progression and its inhibitors (HDACIs) have been widely used for cancer therapy. Valproic acid (VPA, 2-propylpentanoic acid) can inhibit the class I HDAC and suppress the malignancy of solid cancers. Our present study revealed that 1 mM VPA, which has no effect on cell proliferation, can significantly increase the migration and induce epithelial to mesenchymal transition (EMT) like properties of breast cancer cells. Further, VPA increased the expression of EMT-transcription factors (EMT-TFs) Snail and Zeb1. Knockdown of Snail and Zeb1 can attenuate VPA induced cell migration and EMT. Mechanistically, VPA increased the protein stability of Snail via suppression its phosphorylation at Ser 11. As to Zeb1, VPA can increase its promoter activity and transcription via a HDAC2 dependent manner. Over expression of HDAC2 can block VPA induced expression of Zeb1. Collectively, our data revealed that VPA can trigger the EMT of breast cancer cells via upregulation of Snail and Zeb1. It indicated that more attention should be paid to the effects of VPA on the clinical therapy of breast cancer.

Dysregulation of histone deacetylases in carcinogenesis and tumor progression: a possible link to apoptosis and autophagy

Dysregulation of the epigenome and constitutional epimutation lead to aberrant expression of the genes, which regulate cancer initiation and progression. Histone deacetylases (HDACs), which are highly conserved in yeast to humans, are known to regulate numerous proteins involved in the transcriptional regulation of chromatin structures, apoptosis, autophagy, and mitophagy. In addition, a non-permissive chromatin conformation is created by HDACs, preventing the transcription of the genes encoding the proteins associated with tumorigenesis. Recently, an expanding perspective has been reported from the clinical trials with HDACis (HDAC inhibitors), which has emerged as a determining target for the study of the detailed mechanisms underlying cancer progression. Therefore, the present review focuses on the comprehensive lucubration of post-translational modifications and the molecular mechanisms through which HDACs alter the ambiguities associated with epigenome, with particular insights into the initiation, progression, and regulation of cancer.

Transcriptional Regulation of Epithelial to Mesenchymal Transition Related Genes by Lipopolysaccharide in Human Cervical Cancer Cell Line HeLa

Objective:

Cancer is one of the common diseases in the world, and cervical cancer is the fourth one. In this type of cancer, many risk factors, especially infectious diseases, such as human papilloma virus (HPV) and gram-negative bacteria can have important effects on the expression of epithelial to mesenchymal transition related genes like Snail,E-cadherin, and ZEB-1, responsible for connecting cell tissues. In this study, we have investigated the effect of Escherichia coli O111:B4 Lipopolysaccharide (LPS) on HPV positive cell line (HeLa), the expression level of the (Snail, E-cadherin, and ZEB-1), HPV oncogenes (E6, E7) and also microRNA-9, 192.

Materials and Methods:

HeLa cell line was treated with LPS to analyze Snail, E-cadherin, ZEB-1, E6, E7 and also microRNA-9, 192 expression by quantitative real-time PCR in 24, 48 and 72 hours.

Results:

Quantitative real-time PCR revealed a significant reduction in E-cadherin mRNA level at 10ug/L of LPS in three time-points and after 24 hours at 5ug/L of LPS; however, ZEB-1 at 10ug/L of LPS and Snail at 5, 10ug/L of LPS are up-regulated. E7 also illustrated a slight increase, but we did not find any relationship between E7 and LPS treatment. Additionally, there are upward trends in microRNA-9, 192 levels.

Conclusion:

The result of this study, LPS is able to reduce E-cadherin expression, caused by increase in repressor E-cadherin protein expression and some microRNAs, probably. Since bacterial infection can be in cervical site, it is likely to be effective in reducing the E-cadherin expression in the EMT and enhance cancer process, therefore; removing these infections by using the appropriate antibiotics may result in slowing down this process, which requires more research.

Metabolic Plasticity and Epithelial-Mesenchymal Transition

A major transcriptional and phenotypic reprogramming event during development is the establishment of the mesodermal layer from the ectoderm through epithelial-mesenchymal transition (EMT). EMT is employed in subsequent developmental events, and also in many physiological and pathological processes, such as the dissemination of cancer cells through metastasis, as a reversible transition between epithelial and mesenchymal states. The remarkable phenotypic remodeling accompanying these transitions is driven by characteristic transcription factors whose activities and/or activation depend upon signaling cues and co-factors, including intermediary metabolites. In this review, we summarize salient metabolic features that enable or instigate these transitions, as well as adaptations undergone by cells to meet the metabolic requirements of their new states, with an emphasis on the roles played by the metabolic regulation of epigenetic modifications, notably methylation and acetylation.

Targeting prostate cancer cells with enzalutamide-HDAC inhibitor hybrid drug 2-75

BACKGROUND

The progression of castration-resistant prostate cancer (CRPC) still relies on the function of androgen receptor (AR), achieved by evolving mechanisms to reactivate AR signaling under hormonal therapy. Histone deacetylase inhibitors (HDACis) disrupt cytoplasmic AR chaperone heat shock protein 90 (Hsp90) via HDAC6 inhibition, leading to AR degradation and growth suppression of prostate cancer (PCa) cells. However, current HDACis are not effective in clinical trials treating CRPC.

METHODS

We designed hybrid molecules containing partial chemical scaffolds of AR antagonist enzalutamide (Enz) and HDACi suberoylanilide hydroxamic acid (SAHA) as new anti-PCa agents. We previously demonstrated that Enz-HDACi hybrid drug 2-75 targets both AR and Hsp90, which inhibits the growth of Enz-resistant C4-2 cells. In the current study, we further investigate the molecular and cellular actions of 2-75 and test its anti-PCa effects in vivo.

RESULTS

Compared with Enz, 2-75 had greater AR antagonistic effects by decreasing the stability, transcriptional activity, and nuclear translocation of intracellular AR. In addition to inhibition of full-length AR (FL AR), 2-75 downregulated the AR-V7 variant in multiple PCa cell lines. Mechanistic studies indicated that the AR affinity of 2-75 retains the drug in the cytoplasm of AR + PCa cells and further directs 2-75 to the AR-associated protein complex, which permits localized effects on AR-associated Hsp90. Further, unlike pan-HDACi SAHA, the cytoplasm-retaining property allows 2-75 to significantly inhibit cytoplasmic HDAC6 with limited impact on nuclear HDACs. These selective cytoplasmic actions of 2-75 overcome the unfavorable resistance and toxicity properties associated with classical AR antagonists, HDACis, and Hsp90 inhibitors. Finally, 2-75 showed greater antitumor activities than Enz in vivo on SQ xenografts derived from LNCaP cells.

CONCLUSIONS

Novel therapeutic strategy using newly designed 2-75 and related AR antagonist-HDACi hybrid drugs has great potential for effective treatment of CRPC.

Effects of histone deacetylase inhibitors on ATP-binding cassette transporters in lung cancer A549 and colorectal cancer HCT116 cells

Histone deacetylase (HDAC) inhibitors and DNA alkylators are effective components used in combination chemotherapy. In the present study, the effects of HDAC inhibitors on the expression of ATP-binding cassette (ABC) transporters were investigated. It was observed that HDAC inhibitors induced the expression of multidrug-resistant ABC transporters differently in lung cancer A549 cells than in colorectal cancer HCT116 cells. In these two cell lines, the HDAC inhibitors suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) significantly increased ABCB1 expression at the mRNA and protein levels, whereas they had no evident effect on ABCG2 protein expression. SAHA and TSA decreased ABCG2 mRNA expression in A549 cells and had no evident effect on ABCG2 mRNA expression in HCT116 cells. Notably, SAHA and TSA increased the mRNA expression levels of ABCC5, ABCC6, ABCC10, ABCC11 and ABCC12, as well as the protein expression levels of ABCC2, ABCC10 and ABCC12. By contrast, these inhibitors decreased the mRNA expression levels of ABCC1, ABCC2, ABCC3 and ABCC4, as well as the expression of ABCC1 and ABCC3 proteins. Furthermore, SAHA and TSA were found to downregulate HDAC3 and HDAC4, but not HDAC1 and HDAC2. Taken together, the results suggested that HDAC inhibitors work synergistically with DNA alkylators, in part, due to the inhibitory effect of these inhibitors on ABCC1 expression, which translocates these alkylators from inside to outside of cancer cells. These results further suggested the possibility of antagonism when HDAC inhibitors are combined with anthracyclines and other ABCB1 drug ligands in chemotherapy.

Combination chemotherapy of valproic acid (VPA) and gemcitabine regulates STAT3/Bmi1 pathway to differentially potentiate the motility of pancreatic cancer cells

BACKGROUND

Gemcitabine is the standard first-line chemotherapy regimen for pancreatic cancer. However, its therapeutic value is substantially limited in pancreatic cancer patients due to occurrence of resistance towards gemcitabine. A strategy of combined chemo-regimens is widely employed in clinical settings in attempt to reduce the chance of developing therapeutic resistance. Valproic acid (VPA) has been reported as a promising anticancer drug in various clinical trials and studies. However, the clinical value and potential dose-effect of VPA in combination with gemcitabine for pancreatic cancer treatment are under investigated.

RESULTS

In this study, we determined the synergistic effect of VPA and gemcitabine and found that high-dose VPA significantly and dose-dependently enhanced the sensitivity of pancreatic cancer cells to gemcitabine. Intriguingly, low-dose VPA potentiated the migration and invasion of pancreatic cancer cells that already showed gemcitabine-induced motility. Moreover, low-dose VPA increased the reactive oxygen species (ROS) production, which activated AKT to further stimulate the activation of STAT3, Bmi1 expression and eventually promoted the migration and invasion of pancreatic cancer cells induced by gemcitabine. Whereas high-dose VPA stimulated excessive ROS accumulation that promoted p38 activation, which suppressed the activation of STAT3 and Bmi1.

CONCLUSION

Pancreatic cancer cells respond differentially towards low- or high-dose of VPA in combination with gemcitabine, and a low VPA further potentiate pancreatic cancer cell to migrate and invade. Our results suggest that STAT3/Bmi1 signaling cascade, which is regulated by ROS-dependent, AKT- or p38-modulated pathways, primarily mediated the sensitivity and motility of pancreatic cancer cells towards combined gemcitabine and VPA regimen. These findings suggest a highly clinically relevant new mechanism of developing resistance against combined chemo-regimens, warranting further mechanistic and translational exploration for VPA in combination with gemcitabine and other chemotherapies.

Downregulation of HDAC3 by ginsenoside Rg3 inhibits epithelial-mesenchymal transition of cutaneous squamous cell carcinoma through c-Jun acetylation

The metastatic rate of human cutaneous squamous cell carcinoma (CSCC) has increased in recent years. Despite the current advances in therapies, effective treatments remain lacking. Ginsenoside 20(R)-Rg3 is an effective antitumor monomer extracted from ginseng, but the role of Rg3 in CSCC remains unknown. It has been reported that aberrantly elevated histone deacetylase 3 (HDAC3) is involved in tumor malignancy in multiple malignant tumors. However, the effects of HDAC3 on the regulation of c-Jun acetylation in tumor epithelial-mesenchymal transition (EMT) and migration have not been clearly illuminated. In our research, the immunohistochemistry staining results of skin tissue microarrays showed that HDAC3 staining was increased in CSCC compared with the normal dermal tissue. Then, we found that Rg3 treatment (25 and 50 μg/ml) inhibited CSCC cell (A431 and SCC12 cells) EMT through increasing E-cadherin and decreasing N-cadherin, vimentin, and Snail expression. Wound-healing and transwell assays showed that Rg3 could inhibit migration. Meanwhile, Rg3 significantly downregulated the expression of HDAC3 in CSCC cells as detected by real-time quantitative PCR, western blot, and immunofluorescence. Importantly, c-Jun acetylation was increased by the downregulation of HDAC3 with HDAC3 shRNA, and the downregulation was associated with CSCC cell EMT inhibition. Collectively, our results showed that downregulation of HDAC3 by Rg3 or shHDAC3 treatment resulted in c-Jun acetylation, which in turn inhibited CSCC cell EMT. These results indicate that HDAC3 could potentially serve as a therapeutic target therapeutic target for CSCC. Rg3 is an attractive and efficient agent that has oncotherapeutic effects and requires further investigation.

Inhibition of BRD4 suppresses the malignancy of breast cancer cells via regulation of Snail

The mechanistic action of bromodomain-containing protein 4 (BRD4) in cancer motility, including epithelial-mesenchymal transition (EMT), remains largely undefined. We found that targeted inhibition of BRD4 reduces migration, invasion, in vivo growth of patient-derived xenograft (PDX), and lung colonization of breast cancer (BC) cells. Inhibition of BRD4 rapidly decreases the expression of Snail, a powerful EMT transcription factor (EMT-TF), via diminishing its protein stability and transcription. Protein kinase D1 (PRKD1) is responsible for BRD4-regulated Snail protein stability by triggering phosphorylation at Ser11 of Snail and then inducing proteasome-mediated degradation. BRD4 inhibition also suppresses the expression of Gli1, a key transductor of Hedgehog (Hh) required to activate the transcription of SNAI1, in BC cells. The GACCACC sequence (-341 to -333) in the SNAI1 promoter is responsible for Gli1-induced transcription of SNAI1. Clinically, BRD4 and Snail levels are increased in lung-metastasized, estrogen receptor-negative (ER-), and progesterone receptor-negative (PR-) breast cancers and correlate with the expression of mesenchymal markers. Collectively, BRD4 can regulate malignancy of breast cancer cells via both transcriptional and post-translational regulation of Snail.

RNA m6A methylation regulates the epithelial mesenchymal transition of cancer cells and translation of Snail

N6-Methyladenosine (m6A) modification has been implicated in the progression of several cancers. We reveal that during epithelial-mesenchymal transition (EMT), one important step for cancer cell metastasis, m6A modification of mRNAs increases in cancer cells. Deletion of methyltransferase-like 3 (METTL3) down-regulates m6A, impairs the migration, invasion and EMT of cancer cells both in vitro and in vivo. m6A-sequencing and functional studies confirm that Snail, a key transcription factor of EMT, is involved in m6A-regulated EMT. m6A in Snail CDS, but not 3'UTR, triggers polysome-mediated translation of Snail mRNA in cancer cells. Loss and gain functional studies confirm that YTHDF1 mediates m6A-increased translation of Snail mRNA. Moreover, the upregulation of METTL3 and YTHDF1 act as adverse prognosis factors for overall survival (OS) rate of liver cancer patients. Our study highlights the critical roles of m6A on regulation of EMT in cancer cells and translation of Snail during this process.

SATB2-AS1 Suppresses Colorectal Carcinoma Aggressiveness by Inhibiting SATB2-Dependent Snail Transcription and Epithelial-Mesenchymal Transition

Accumulating evidence suggests that long noncoding RNA (lncRNA) plays important regulatory roles in cancer biology. However, the involvement of lncRNA in colorectal carcinoma progression remains largely unknown, especially in colorectal carcinoma metastasis. In this study, we investigated the changes in lncRNA expression in colorectal carcinoma and identified a new lncRNA, the antisense transcript of SATB2 (SATB2-AS1), as a key regulator of colorectal carcinoma progression. SATB2-AS1 was frequently downregulated in colorectal carcinoma cells and tissues, and patients whose tumors expressed SATB2-AS1 at low levels had a shorter overall survival and poorer prognosis. Downregulation of SATB2-AS1 significantly promoted cell proliferation, migration, and invasion in vitro and in vivo, demonstrating that it acts as a tumor suppressor in colorectal carcinoma. SATB2-AS1 suppressed colorectal carcinoma progression by serving as a scaffold to recruit p300, whose acetylation of H3K27 and H3K9 at the SATB2 promoter upregulated expression of SATB2, a suppressor of colorectal carcinoma growth and metastasis. SATB2 subsequently recruited HDAC1 to the Snail promoter, repressing Snail transcription and inhibiting epithelial-to-mesenchymal transition. Taken together, these data reveal SATB2-AS1 as a novel regulator of the SATB2-Snail axis whose loss facilitates progression of colorectal carcinoma. SIGNIFICANCE: These data show that the lncRNA SATB2-AS1 mediates epigenetic regulation of SATB2 and Snail expression to suppress colorectal cancer progression.See related commentary by Li, p. 3536.

Drug resistance profiling of a new triple negative breast cancer patient-derived xenograft model

Background

Triple-negative breast cancer (TNBC) represents an aggressive subtype with limited therapeutic options. Experimental preclinical models that recapitulate their tumors of origin can accelerate target identification, thereby potentially improving therapeutic efficacy. Patient-derived xenografts (PDXs), due to their genomic and transcriptomic fidelity to the tumors from which they are derived, are poised to improve the preclinical testing of drug-target combinations in translational models. Despite the previous development of breast and TNBC PDX models, those derived from patients with demonstrated health-disparities are lacking.

Methods

We use an aggressive TNBC PDX model propagated in SCID/Beige mice that was established from an African-American woman, TU-BcX-2 K1, and assess its metastatic potential and drug sensitivities under distinct in vitro conditions. Cellular derivatives of the primary tumor or the PDX were grown in 2D culture conditions or grown in mammospheres 3D culture. Flow cytometry and fluorescence staining was used to quantify cancer stem cell-like populations. qRT-PCR was used to describe the mesenchymal gene signature of the tumor. The sensitivity of TU-BcX-2 K1-derived cells to anti-neoplastic oncology drugs was compared in adherent cells and mammospheres. Drug response was evaluated using a live/dead staining kit and crystal violet staining.

Results

TU-BcX-2 K1 has a low propensity for metastasis, reflects a mesenchymal state, and contains a large burden of cancer stem cells. We show that TU-BcX-2 K1 cells have differential responses to cytotoxic and targeted therapies in 2D compared to 3D culture conditions insofar as several drug classes conferred sensitivity in 2D but not in 3D culture, or cells grown as mammospheres.

Conclusions

Here we introduce a new TNBC PDX model and demonstrate the differences in evaluating drug sensitivity in adherent cells compared to mammosphere, or suspension, culture.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5401-2) contains supplementary material, which is available to authorized users.

Nodal Promotes the Migration and Invasion of Bladder Cancer Cells via Regulation of Snail

Urinary bladder cancer is one of commonly diagnosed malignancies worldwide, especially in males. Understanding the mechanisms of advanced metastasis in bladder cell is important for therapy and drug development. Nodal, an important embryonic morphogen, has been reported to modulate tumorigenesis. We found that the expression of Nodal was upregulated in bladder cancer cells and tissues as compared to their corresponding controls. Knockdown of Nodal can suppress the migration, invasion, and epithelial-to-mesenchymal transition (EMT) of bladder cancer cells. Nodal can positively regulate the expression of Snail, one powerful EMT transcription factors, in bladder cancer cells. Overexpression of Snail can attenuate the si-Nodal suppressed cell migration and invasion. Nodal can increase the transcription and protein stability of Snail in bladder cancer cells. YY1, which can be activated by Nodal, is responsible for Nodal induced transcription of Snail. ATM, which can stabilize Snail by phosphorylation on Serine-100, was involved in Nodal upregulated protein stability of Snail. Collectively, our data showed that Nodal can trigger the malignancy of bladder cancer cells via increasing the transcription and protein stability of Snail. It indicated that Nodal might be a potential therapeutic target for bladder cancer treatment.

The effect of sodium butyrate and cisplatin on expression of EMT markers

Histone modifications play a key role in the epigenetic regulation of gene transcription in cancer cells. Histone acetylations are regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs are increased in ovarian carcinomas and they are involved in carcinogenesis and resistance to chemotherapeutic agents. In our study we investigated anticancer effect of HDAC inhibitor sodium butyrate (NaBu) on cisplatin-sensitive and cisplatin-resistant ovarian cell lines A2780 and A2780cis. A2780 and A2780cis were treated with NaBu alone or in combination with cisplatin (CP). NaBu inhibited the growth of both cell lines and enhanced cytotoxic effect of CP. Exposure to NaBu for 24 h induced cell cycle arrest. The expressions of EMT-related genes and proteins were further investigated by qPCR and western blot analysis. Loss of E-cadherin has been shown to be crucial in ovarian cancer development. We found that NaBu dramatically induce expression of E-cadherin gene (CDH1) and protein levels in A2780 and A2780cis. We investigated correlation between transcription and methylation of CDH1gene. Methylation level analysis in 32 CpG sites in CDH1 gene (promoter/exon1 regions) was performed using bisulfite NGS (Next Generation Sequencing). We found that cisplatin-resistant cell line A2780cis cells differ from their cisplatin-sensitive counterparts in the CDH1 methylation. Methylation in A2780cis cells is elevated compared to A2780. However, NaBu-induced expression of CDH1 was not accompanied by CDH1 demethylation. NaBu treatment induced changes in expression of EMT-related genes and proteins. Interestingly E-cadherin zinc finger transcriptional repressor SNAIL1 was upregulated in both cell lines. Mesenchymal marker vimentin was downregulated. Matrix metalloproteases (MMPs) are necessary for pericellular proteolysis and facilitate migration and invasion of tumour cells. NaBu induced mRNA expression of MMPs, mild changes in activities of gelatinases MMP2 and MMP9 were detected. Our data demonstrate that NaBu sensitizes cisplatin-resistant ovarian cancer cells, re-established E-cadherin expression, but it was not able to reverse the EMT phenotype completely.

The role of DEAD-box RNA helicase p68 (DDX5) in the development and treatment of breast cancer

RNA helicase p68 or DEAD (Asp-Glu-Ala-Asp) box polypeptide 5 (DDX5) is a unique member of the highly conserved protein family, which is involved in a broad spectrum of biological processes, including transcription, translation, precursor messenger RNA processing or alternative splicing, and microRNA (miRNA) processing. It has been shown that p68 is necessary for cell growth and participates in the early development and maturation of some organs. Interestingly, p68 is a transcriptional coactivator of numerous oncogenic transcription factors, including nuclear factor-κβ (NF-κβ), estrogen receptor α (ERα), β-catenin, androgen receptor, Notch transcriptional activation complex, p53 and signal transducer, and activator of transcription 3 (STAT3). Recent studies on the role of p68 (DDX5) in multiple dysregulated cellular processes in various cancers and its abnormal expression indicate the importance of this factor in tumor development. Discussion of the precise role of p68 in cancer is complex and depends on the cellular microenvironment and interacting factors. In terms of the deregulated expression of p68 in breast cancer and the high prevalence of this cancer among women, it can be informative to review the precise function of this factor in the breast cancer. Therefore, an attempt will be made in this review to clarify the tumorigenic function of p68 in association with its targeting potential for the treatment of breast cancer.

CCR7 preservation via histone deacetylase inhibition promotes epithelial-mesenchymal transition of hepatocellular carcinoma cells

The effects of Histone deacetylase (HDAC) inhibition on epithelial-mesenchymal transition (EMT) differs in various types of cancers. However, its function in hepatocellular carcinoma (HCC) is not well-explored. In this study, we investigated the effect of HDAC inhibition on EMT in HCC cells by using trichostatin A (TSA) and valproic acid (VPA). The results showed that TSA/VPA significantly induced EMT phenotype, as demonstrated by the decreased level of E-cadherin, increased level of N-cadherin, vimentin, Twist and snail, and enhanced capacity of cell migration and invasion. In addition, CCR7 was speculated and confirmed as a function target of HDAC inhibition. CCR7 promotes the progression of HCC and is associated with poor survival. Knockdown of CCR7 significantly attenuated the effect of TSA on EMT. Moreover, our results demonstrated that HDAC inhibition up-regulates CCR7 via reversing the promoter hypoacetylation and increasing CCR7 transcription. Taken together, our study has identified the function of HDAC in EMT of HCC and suggested a novel mechanism through which TSA/VPA exerts its carcinogenic roles in HCC. HDAC inhibitors require careful caution before their application as new anticancer drugs.

HDAC1 inhibition by MS-275 in mesothelial cells limits cellular invasion and promotes MMT reversal

Peritoneal fibrosis is a pathological alteration of the peritoneal membrane occurring in a variety of conditions including peritoneal dialysis (PD), post-surgery adhesions and peritoneal metastases. The acquisition of invasive and pro-fibrotic abilities by mesothelial cells (MCs) through induction of MMT, a cell-specific form of EMT, plays a main role in this process. Aim of this study was to evaluate possible effects of histone deacetylase (HDAC) inhibitors, key components of the epigenetic machinery, in counteracting MMT observed in MCs isolated from effluent of PD patients. HDAC inhibitors with different class/isoform selectivity have been used for pharmacological inhibition. While the effect of other inhibitors was limited to a partial E-cadherin re-expression, MS-275, a HDAC1-3 inhibitor, promoted: (i) downregulation of mesenchymal markers (MMP2, Col1A1, PAI-1, TGFβ1, TGFβRI) (ii) upregulation of epithelial markers (E-cadherin, Occludin), (iii) reacquisition of an epithelial-like morphology and (iv) marked reduction of cellular invasiveness. Results were confirmed by HDAC1 genetic silencing. Mechanistically, MS-275 causes: (i) increase of nuclear histone H3 acetylation (ii) rescue of the acetylation profile on E-cadherin promoter, (iii) Snail functional impairment. Overall, our study, pinpointing a role for HDAC1, revealed a new player in the regulation of peritoneal fibrosis, providing the rationale for future therapeutic opportunities.

Histone deacetylase inhibitor SAHA-induced epithelial-mesenchymal transition by upregulating Slug in lung cancer cells

SAHA, a member of histone deacetylase inhibitors (HDACIs), which emerged as a class of novel antitumor drug, has been used in clinical treatment of cancers. However, clinical experience of SAHA in solid tumors has been disappointing. Nevertheless, the underlying mechanism of this deficiency is not clearly understood. In the present study, we found that SAHA could induce epithelial-mesenchymal transitions (EMT) in lung cancer A549 cells, which was associated with increased migration capability and cellular morphology changes. We showed that SAHA decreased epithelial marker E-cadherin's expression and increased the expression of mesenchymal marker vimentin. SAHA upregulated the protein and mRNA expression of transcription factor Slug in a time-dependent manner and promoted its nuclear translocation. We further demonstrated that SAHA upregulated Slug expression by promoting Slug acetylation but not influencing the phosphorylation of GSK-3β, a main kinase-controlled Slug expression. Finally, silencing of Slug by siRNA reversed EMT marker expressions and cellular morphology change induced by SAHA, suggesting that Slug plays a crucial role in SAHA-mediated EMT in A549 cells. Our research study provided a better understanding of treatment failure of SAHA in patients with solid tumors. Therefore, more attention should be paid to cancer treatment using SAHA and strategies for reversing EMT before using SAHA would be better if the value of SAHA in the treatment of solid tumors, especially lung cancer, is realized.

Curcumin downregulates the expression of Snail via suppressing Smad2 pathway to inhibit TGF-β1-induced epithelial-mesenchymal transitions in hepatoma cells

Hepatocellular carcinoma (HCC) remains the third cause of cancer-related mortality. Resection and transplantation are the only curative treatments available but are greatly hampered by high recurrence rates and development of metastasis, the initiation of cancer metastasis requires migration and invasion of cells, which is enabled by epithelial-mesenchymal transitions (EMT). TGF-β1 is a secreted protein that performs many cellular functions, including the control of cell growth, cell proliferation, cell differentiation and apoptosis. TGF-β1 is known as a major inducer of EMT, and it was reported that TGF-β1 induced EMT via Smad-dependent and Smad-independent pathways. However, the extrinsic signals of TGF-β1 regulated the EMT in hepatoma cells remains to be elucidated, and searching drugs to inhibit TGF-β1 induced EMT may be considered to be a potentially effective therapeutic strategy in HCC. Fortunately, in this study, we found that curcumin inhibited TGF-β1-induced EMT in hepatoma cells. Furthermore, we demonstrated that curcumin inhibited TGF-β1-induced EMT via inhibiting Smad2 phosphorylation and nuclear translocation, then suppressing Smad2 combined with the promoter of Snail which inhibited the transcriptional expression of Snail. These findings suggesting curcumin could be a useful agent for antitumor therapy and also a promising drug combined with other strategies to preventing and treating HCC.

Epigenetic down regulation of G protein-coupled estrogen receptor (GPER) functions as a tumor suppressor in colorectal cancer

Background

Estrogenic signals are suggested to have protection roles in the development of colorectal cancer (CRC). The G protein-coupled estrogen receptor (GPER) has been reported to mediate non-genomic effects of estrogen in hormone related cancers except CRC. Its expression and functions in CRC were investigated.

Methods

The expression of GPER and its associations with clinicopathological features were examined. The mechanisms were further investigated using cells, mouse xenograft models, and clinical human samples.

Results

GPER was significantly (p < 0.01) down regulated in CRC tissues compared with their matched adjacent normal tissues in our two cohorts and three independent investigations from Oncomine database. Patients whose tumors expressing less (n = 36) GPER showed significant (p < 0.01) poorer survival rate as compared with those with greater levels of GPER (n = 54). Promoter methylation and histone H3 deacetylation were involved in the down regulation of GPER in CRC cell lines and clinical tissues. Activation of GPER by its specific agonist G-1 inhibited proliferation, induced cell cycle arrest, mitochondrial-related apoptosis and endoplasmic reticulum (ER) stress of CRC cells. The upregulation of reactive oxygen species (ROS) induced sustained ERK1/2 activation participated in G-1 induced cell growth arrest. Further, G-1 can inhibit the phosphorylation, nuclear localization, and transcriptional activities of NF-κB via both canonical IKKα/ IκBα pathways and phosphorylation of GSK-3β. Xenograft model based on HCT-116 cells confirmed that G-1 can suppress the in vivo progression of CRC.

Conclusions

Epigenetic down regulation of GPER acts as a tumor suppressor in colorectal cancer and its specific activation might be a potential approach for CRC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0654-3) contains supplementary material, which is available to authorized users.

Adipocytes promote malignant growth of breast tumours with monocarboxylate transporter 2 expression via β-hydroxybutyrate

Adipocytes are the most abundant stromal partners in breast tissue. However, the crosstalk between breast cancer cells and adipocytes has been given less attention compared to cancer-associated fibroblasts. Here we find, through systematic screening, that primary mammary gland-derived adipocytes (MGDAs) promote growth of breast cancer cells that express monocarboxylate transporter 2 (MCT2) both in vitro and in vivo. We show that β-hydroxybutyrate is secreted by MGDAs and is required to enhance breast cancer cells malignancy in vitro. Consistently, β-hydroxybutyrate is sufficient to promote tumorigenesis of a mouse xenograft model of MCT2-expressing breast cancer cells. Mechanistically we observe that upon co-culturing with MGDAs or treatment with β-hydroxybutyrate, breast cancer cells expressing MCT2 increase the global histone H3K9 acetylation and upregulate several tumour-promoting genes. These results suggest that adipocytes promote malignancy of MCT2-expressing breast cancer via β-hydroxybutyrate potentially by inducing the epigenetic upregulation of tumour-promoting genes.

Invasion of the adipose tissue correlates with poor prognosis in breast cancer. Here, the authors show that mammary gland adipocytes promote malignancy via β-hydroxybutyrate, which acts on cancer cells through the monocarboxylate transporter MCT2 resulting in tumour-promoting epigenetic modifications.

Histone deacetylase inhibitors deplete myeloid-derived suppressor cells induced by 4T1 mammary tumors in vivo and in vitro

Myeloid-derived suppressor cells (MDSC) have been identified as a population of immature myeloid cells that suppress anti-tumor immunity. MDSC are increased in tumor-bearing hosts; thus, depletion of MDSC may enhance anti-tumor immunity. Histone deacetylase inhibitors (HDACi) are chemical agents that are primarily used against hematologic malignancies. The ability of these agents to modulate anticancer immunity has recently been extensively studied. However, the effect of HDACi on MDSC has remained largely unexplored. In the present study, we provide the first demonstration that HDACi treatment decreases MDSC accumulation in the spleen, blood and tumor bed but increases the proportion of T cells (particularly the frequency of IFN-γ- or perforin-producing CD8+ T cells) in BALB/C mice with 4T1 mammary tumors. In addition, HDACi exposure of bone marrow (BM) cells significantly eliminated the MDSC population induced by GM-CSF or the tumor burden in vitro, which was further demonstrated as functionally important to relieve the inhibitory effect of MDSC-enriched BM cells on T cell proliferation. Mechanistically, HDACi increased the apoptosis of Gr-1+ cells (almost MDSC) compared with that of Gr-1- cells, which was abrogated by the ROS scavenger N-acetylcysteine, suggesting that the HDACi-induced increase in MDSC apoptosis due to increased intracellular ROS might partially account for the observed depletion of MDSC. These findings suggest that the elimination of MDSC using an HDACi may contribute to the overall anti-tumor properties of these agents, highlighting a novel property of HDACi as potent MDSC-targeting agents, which may be used to enhance the efficacy of immunotherapeutic regimens.

Roles and epigenetic regulation of epithelial-mesenchymal transition and its transcription factors in cancer initiation and progression

The epithelial-mesenchymal transition (EMT) is a crucial developmental process by which epithelial cells undergo a mesenchymal phenotypic change. During EMT, epigenetic mechanisms including DNA methylation and histone modifications are involved in the regulation of EMT-related genes. The epigenetic gene silencing of the epithelial marker E-cadherin has been well characterized. In particular, three major transcriptional repressors of E-cadherin, Snail, ZEB, and Twist families, also known as EMT-inducing transcription factors (EMT-TFs), play a crucial role in this process by cooperating with multiple epigenetic modifiers. Furthermore, recent studies have identified the novel epigenetic modifiers that control the expression of EMT-TFs, and these modifiers have emerged as critical regulators of cancer development and as novel therapeutic targets for human cancer. In this review, the diverse functions of EMT-TFs in cancer progression, the cooperative mechanisms of EMT-TFs with epigenetic modifiers, and epigenetic regulatory roles for the expression of EMT-TFs will be discussed.

Epigenetic regulation of epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is an essential process for morphogenesis and organ development which reversibly enables polarized epithelial cells to lose their epithelial characteristics and to acquire mesenchymal properties. It is now evident that the aberrant activation of EMT is also a critical mechanism to endow epithelial cancer cells with migratory and invasive capabilities associated with metastatic competence. This dedifferentiation program is mediated by a small cohort of pleiotropic transcription factors which orchestrate a complex array of epigenetic mechanisms for the wide-spread changes in gene expression. Here, we review major epigenetic mechanisms with an emphasis on histone modifications and discuss their implications in EMT and tumor progression. We also highlight mechanisms underlying transcription regulation concerted by various chromatin-modifying proteins and EMT-inducing transcription factors at different molecular layers. Owing to the reversible nature of epigenetic modifications, a thorough understanding of their functions in EMT will not only provide new insights into our knowledge of cancer progression and metastasis, but also facilitate the development of diagnostic and therapeutic strategies for human malignancy.

Upregulation of annexin A1 expression by butyrate in human melanoma cells induces invasion by inhibiting E-cadherin expression

Epithelial to mesenchymal transition (EMT) is a critical step in the metastasis of epithelial cancer cells. Butyrate, which is produced from dietary fiber by colonic bacterial fermentation, has been reported to influence EMT. However, some studies have reported that butyrate promotes EMT, while others have reported an inhibitory effect. To clarify these controversial results, it is necessary to elucidate the mechanism by which butyrate can influence EMT. In this study, we examined the potential role of annexin A1 (ANXA1), which was previously reported to promote EMT in breast cancer cells, as a mediator of EMT regulation by butyrate. We found that ANXA1 mRNA and protein were expressed in highly invasive melanoma cell lines (A2058 and A375), but not in SK-MEL-5 cells, which are less invasive. We also showed that butyrate induced ANXA1 mRNA and protein expression and promoted EMT-related cell invasion in SK-MEL-5 cells. Downregulation of ANXA1 expression using specific small interfering RNAs in butyrate-treated SK-MEL-5 cells resulted in increased expression of the epithelial marker E-cadherin and decreased cell invasion. Moreover, overexpressing ANXA1 decreased the expression of the E-cadherin. Collectively, these results indicate that butyrate induces the expression of ANXA1 in human melanoma cells, which then promotes invasion through activating the EMT signaling pathway.