MEF2D Transduces Microenvironment Stimuli to ZEB1 to Promote Epithelial-Mesenchymal Transition and Metastasis in Colorectal Cancer

The crosstalk role of CDKN2A between tumor progression and cuproptosis resistance in colorectal cancer

BACKGROUND

Cuproptosis is a type of cell death characterized by excessive copper-lipid reactions in the tricarboxylic acid cycle, resulting in protein toxicity stress and cell death. Although known as a cuproptosis inhibitor through CRISPR-Cas9 screening, the role of cyclin-dependent kinase inhibitor 2A (CDKN2A) in cuproptosis resistance and its connection to tumor development remains unclear.

METHODS

In this study, we combined single-cell sequencing, spatial transcriptomics, pathological image analysis, TCGA multi-omics analysis and in vitro experimental validation to comprehensively investigate CDKN2A distribution, expression, epigenetic modification, regulation and genomic features in colorectal cancer cells. We further explored the associations between CDKN2A and cellular pathway, immune infiltration and spatial signal communication.

RESULTS

Our findings showed an increasing trend in cuproptosis in the trajectory of tumor progression, accompanied by an upward trend of CDKN2A. CDKN2A underwent transcriptional activation by MEF2D and via the SNHG7/miR-133b axis, upregulating glycolysis, copper metabolism and copper ion efflux. CDKN2A likely drives epithelial-mesenchymal transition (EMT) and progression by activating Wnt signaling. CDKN2A is associated with high genomic instability and sensitivity to radiation and chemotherapy. Tumor regions expressing CDKN2A exhibit distinctive SPP1+ tumor-associated macrophage (TAM) infiltration and MMP7 enrichment, along with unique signaling crosstalk with adjacent areas.

CONCLUSIONS

CDKN2A mediates cuproptosis resistance through regulating glycolysis and copper homeostasis, accompanied by a malignant phenotype and pro-tumor niche. Radiation and chemotherapy are expected to potentially serve as therapeutic approaches for cuproptosis-resistant colorectal cancer with high CDKN2A expression.

MEF2D facilitates liver metastasis of gastric cancer cells through directly inducing H1X under IL-13 stimulation

Liver metastasis is the most common metastatic occurrence in gastric cancer patients, although the precise mechanism behind it remains unclear. Through a combination of proteomics and quantitative RT-PCR, our study has revealed a significant correlation between the upregulation of myocyte enhancer factor-2D (MEF2D) and both distant metastasis and poor prognosis in gastric cancer patients. In mouse models, we observed that overexpressing or knocking down MEF2D in gastric cancer cells respectively promoted or inhibited liver metastasis. Furthermore, our research has demonstrated that MEF2D regulates the transcriptional activation of H1X by binding to the H1X promoter. This regulation leads to the upregulation of H1X, which, in turn, promotes the in vivo metastasis of gastric cancer cells along with the upregulation of the downstream gene β-CATENIN. Additionally, we found that the expression of MEF2D and H1X at both mRNA and protein levels can be induced by the inflammatory factor IL-13, and this induction exhibits a time gradient dependence. In human gastric cancer tissues, the expression of IL13RA1, the receptor for IL-13, positively correlates with the expression of MEF2D and H1X. IL13RA1 has been identified as an intermediate receptor through which IL-13 regulates MEF2D. In conclusion, our findings suggest that MEF2D plays a crucial role in promoting liver metastasis of gastric cancer by upregulating H1X and downstream target β-CATENIN in response to IL-13 stimulation. Targeting MEF2D could therefore be a promising therapeutic strategy for the clinical management of gastric cancer. STATEMENT OF SIGNIFICANCE: MEF2D promotes its transcriptional activation in gastric cancer cells by binding to the H1X promoter and is upregulated by IL-13-IL13RA1, thereby promoting distant metastasis of gastric cancer.

MEF2D Functions as a Tumor Suppressor in Breast Cancer

The myocyte enhancer factor 2 (MEF2) gene family play fundamental roles in the genetic programs that control cell differentiation, morphogenesis, proliferation, and survival in a wide range of cell types. More recently, these genes have also been implicated as drivers of carcinogenesis, by acting as oncogenes or tumor suppressors depending on the biological context. Nonetheless, the molecular programs they regulate and their roles in tumor development and progression remain incompletely understood. The present study evaluated whether the MEF2D transcription factor functions as a tumor suppressor in breast cancer. The knockout of the MEF2D gene in mouse mammary epithelial cells resulted in phenotypic changes characteristic of neoplastic transformation. These changes included enhanced cell proliferation, a loss of contact inhibition, and anchorage-independent growth in soft agar, as well as the capacity for tumor development in mice. Mechanistically, the knockout of MEF2D induced the epithelial-to-mesenchymal transition (EMT) and activated several oncogenic signaling pathways, including AKT, ERK, and Hippo-YAP. Correspondingly, a reduced expression of MEF2D was observed in human triple-negative breast cancer cell lines, and a low MEF2D expression in tissue samples was found to be correlated with a worse overall survival and relapse-free survival in breast cancer patients. MEF2D may, thus, be a putative tumor suppressor, acting through selective gene regulatory programs that have clinical and therapeutic significance.

A Ubiquitin-Dependent Switch on MEF2D Senses Pro-Metastatic Niche Signals to Facilitate Intrahepatic Metastasis of Liver Cancer

Effective treatment for metastasis, a leading cause of cancer-associated death, is still lacking. To seed on a distal organ, disseminated cancer cells (DCCs) must adapt to the local tissue microenvironment. However, it remains elusive how DCCs respond the pro-metastatic niche signals. Here, systemic motif-enrichment identified myocyte enhancer factor 2D (MEF2D) as a critical sensor of niche signals to regulate DCCs adhesion and colonization, leading to intrahepatic metastasis and recurrence of liver cancer. In this context, MEF2D transactivates Itgb1 (coding β1-integrin) and Itgb4 (coding β4-integrin) to execute temporally unique functions, where ITGB1 recognizes extracellular matrix for early seeding, and ITGB4 acts as a novel sensor of neutrophil extracellular traps-DNA (NETs-DNA) for subsequent chemotaxis and colonization. In turn, an integrin-FAK circuit promotes a phosphorylation-dependent USP14-orchastrated deubiquitination switch to stabilize MEF2D via circumventing degradation by the E3-ubiquitin-ligase MDM2. Clinically, the USP14(pS432)-MEF2D-ITGB1/4 feedback loop is often hyper-active and indicative of inferior outcomes in human malignancies, while its blockade abrogated intrahepatic metastasis of DCCs. Together, DCCs exploit a deubiquitination-dependent switch on MEF2D to integrate niche signals in the liver mesenchyme, thereby amplifying the pro-metastatic integrin-FAK signaling. Disruption of this feedback loop is clinically applicable with fast-track potential to block microenvironmental cues driving metastasis.

Comprehensive analysis and identification of the circ_0084615/miR-451a/MEF2D axis in benzo(a)pyrene exposed tumor cells in hepato-carcinogenesis

Hepatocellular carcinoma (HCC) is caused by genetic and epigenetic alterations, as well as abnormal lifestyle and dietary habits, including contaminated food intake. Benzo(a)pyrene (B[a]P), derived from deep-fried meats, is regarded as the main dietary factor for tumorigenesis in epidemiological investigations. Although various studies have illustrated the adverse effects of B[a]P in malignancy through cell and animal models, the correlation between B[a]P exposure and clinical data remain to be explored. In the present study, we analyzed and identified novel B[a]P-associated circular RNA (circRNA) from microarray databases of liver tumor cells and HCC patient samples. Considering that circRNA regulates mRNA as a miRNA sponge, molecular circRNA-miRNA-mRNA interactions based on the stimulation of B[a]P exposure were predicted and established. Furthermore, up-regulated circ_0084615 in B[a]P-treated tumor cells was verified as a miRNA sponge via fluorescence in situ hybridization (FISH) assays, and the repression between circ_0084615 and target miR-451a exhibited a contrasting effect on hepatocarcinogenesis. Therefore, we performed integrated bioinformatics analysis and molecular experiments to establish the circ_0084615/miR-451a/MEF2D pathway, which provided a better understanding of the adverse effects of fried food preference on human health.

Insights on the Biomarker Potential of Exosomal Non-Coding RNAs in Colorectal Cancer: An In Silico Characterization of Related Exosomal lncRNA/circRNA–miRNA–Target Axis

Colorectal cancer (CRC) is one of the most common cancer types, ranking third after lung and breast cancers. As such, it demands special attention for better characterization, which may eventually result in the development of early detection strategies and preventive measures. Currently, components of bodily fluids, which may reflect various disease states, are being increasingly researched for their biomarker potential. One of these components is the circulating extracellular vesicles, namely, exosomes, which are demonstrated to carry various cargo. Of importance, the non-coding RNA cargo of circulating exosomes, especially long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and micro RNAs (miRNAs), may potentially serve as significant diagnostic and prognostic/predictive biomarkers. In this review, we present existing evidence on the diagnostic and prognostic/predictive biomarker value of exosomal non-coding RNAs in CRC. In addition, taking advantage of the miRNA sponging functionality of lncRNAs and circRNAs, we demonstrate an experimentally validated CRC exosomal non-coding RNA-regulated target gene axis benefiting from published miRNA sponging studies in CRC. Hence, we present a set of target genes and pathways downstream of the lncRNA/circRNA–miRNA–target axis along with associated significant Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which may collectively serve to better characterize CRC and shed light on the significance of exosomal non-coding RNAs in CRC diagnosis and prognosis/prediction.

HDAC4 in cancer: A multitasking platform to drive not only epigenetic modifications

Controlling access to genomic information and maintaining its stability are key aspects of cell life. Histone acetylation is a reversible epigenetic modification that allows access to DNA and the assembly of protein complexes that regulate mainly transcription but also other activities. Enzymes known as histone deacetylases (HDACs) are involved in the removal of the acetyl-group or in some cases of small hydrophobic moieties from histones but also from the non-histone substrate. The main achievement of HDACs on histones is to repress transcription and promote the formation of more compact chromatin. There are 18 different HDACs encoded in the human genome. Here we will discuss HDAC4, a member of the class IIa family, and its possible contribution to cancer development.

Regulation of epithelial-mesenchymal transition by tumor microenvironmental signals and its implication in cancer therapeutics

Epithelial-mesenchymal transition (EMT) has been implicated in various aspects of tumor development, including tumor invasion and metastasis, cancer stemness, and therapy resistance. Diverse stroma cell types along with biochemical and biophysical factors in the tumor microenvironment impinge on the EMT program to impact tumor progression. Here we provide an in-depth review of various tumor microenvironmental signals that regulate EMT in cancer. We discuss the molecular mechanisms underlying the role of EMT in therapy resistance and highlight new therapeutic approaches targeting the tumor microenvironment to impact EMT and tumor progression.

A reciprocal feedback between colon cancer cells and Schwann cells promotes the proliferation and metastasis of colon cancer

BACKGROUND

Research has indicated that the emergence of Schwann cells around premalignant lesions of colon cancer might be an early indicator promoting the onset of tumorigenesis. The present study explored the communication between colon cancer cells and Schwann cells.

METHODS

Immunofluorescence analyses were conducted to examine the differential distribution of Schwann cells within colon cancer tissues and normal colon tissues. CCK8 assay, colony formation assay, wound healing assay, and transwell assay were performed to investigate the interaction between colon cancer cells and Schwann cells. Exosomes derived from colon cancer cells were isolated to further explore the effect of colon cancer cells on Schwann cells. Gain- and loss-of function experiments, luciferase reporter assays, chromatin immunoprecipitation assays, and immunohistochemistry assays were performed to reveal the cross-talk between colon cancer cells and Schwann cells. Furthermore, colon cancer cells co-cultured with Schwann cells were transplanted into nude mice for evaluating their effect on tumor proliferation and metastasis in vivo.

RESULTS

The clinicopathological characteristics indicated that Schwann cells were enriched in colon cancer tissues and were associated with tumor metastasis and poor prognosis. The co-culture of Schwann cells with colon cancer cells promoted the proliferation and migration of colon cancer cells and Schwann cells, which was mediated by nerve growth factor (NGF) secreted from Schwann cells. Exosomal miR-21-5p released by colon cancer cells inhibited VHL expression in Schwann cells, which in turn stabilized the HIF-1α protein and increased the transcription of NGF. Meanwhile, the Schwann cells-derived NGF activated TrkA/ERK/ELK1/ZEB1 signaling pathway in colon cancer cells, which further enhanced the expression of exosomal miR-21-5p. Inhibition of either NGF or miR-21-5p significantly inhibited the proliferation and metastasis of transplanted colon cancer cells in nude mice. Coincidently, miR-21-5p was positively associated with the expression of NGF, p-ERK, p-ELK1, and ZEB1 in human colon cancer tissues.

CONCLUSIONS

Our results implicated a reciprocal communication between colon cancer cells and Schwan cells that promoted the proliferation and metastasis of colon cancer, and identified NGF and exosomal miR-21-5p as potential therapeutic targets for the treatment of colon cancer.

Two lncRNAs, MACC1-AS1 and UCA1, co-mediate the expression of multiple mRNAs through interaction with individual miRNAs in breast cancer cells

BACKGROUND

Increasing studies have shown that lncRNAs often play roles through interaction with miRNAs to control gene expression by inhibiting translation or facilitating degradation of target mRNAs. Here, we report that two lncRNAs, MACC1-AS1 and UCA1 are coordinately expressed in breast cancer cells and share the ability to interact with multiple miRNAs to mediate the expression of different genes.

METHODS

Targetscan, starBase and miRDB databases were used to predict the relationships of MACC1-AS1/UCA1-miRNA-mRNA network. qRT-PCR, and RNA sequencing were used to study the differential expression of lncRNAs and miRNA-targeted genes in breast cancer cells. RIP, RNA pull-down and luciferase assays were performed to confirm the molecular interactions of MACC1-AS1 or UCA1 with predicted miRNAs. The role of lncRNA-mediated miRNA-mRNA interactions in cell proliferation was examined by MTT assays following loss-of-function and gain-of-function effects.

RESULTS

We identified a lncRNA-miRNA-mRNA regulatory network in breast cancer cells, in which a number of mRNAs can be co-regulated by MACC1-AS1 and UCA1 lncRNAs. Each lncRNA possesses the capacity as a ceRNA to compete with various mRNA-targeting miRNAs. Interaction of MACC1-AS1 or UCA1 with individual miRNAs is able to increase the expression of the same target mRNAs, such as TBL1X and MEF2D, thus affecting cancer-cell growth phenotype.

CONCLUSIONS

Our study suggests that in each cell type, there is a balance of interactions between certain lncRNAs and miRNAs. Disrupting the balance would eventually affect the expression of miRNA-targeted genes and cell proliferation.

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.

Acidic Tumor Microenvironment Promotes Pancreatic Cancer through miR-451a/MEF2D Axis

Pancreatic cancer (PC), as a highly malignant and aggressive solid tumor, is common in the digestive system. The acidic microenvironment is one of the critical markers of cancer. Nonetheless, there are few studies on how the acidic microenvironment affects the development of PC. This study focused on investigating the specific molecular mechanisms of the acidic microenvironment in PC. In our study, qRT-PCR was conducted for examining microRNA (miR)-451a and myocyte enhancer factor 2D (MEF2D) expressions in PANC-1 cells. Then, detailed functional effects of an acidic environment on miR-451a and MEF2D in PANC-1 cells were detected by CCK-8, colony formation, flow cytometry, wound healing, transwell, mitochondrial functionality measurement, JC-1 staining, DCFH-DA staining, and sphere formation assays. The relationship between miR-451a and MEF2D was confirmed by luciferase reporter analysis. Under acidic conditions, the increase of proliferation, migration, and invasion of PANC-1 cells was observed. Moreover, the mitochondrial oxidative respiration-related gene miR-451a was reduced in acidic conditions. In addition, we found that, in PANC-1 cells under an acidic environment, miR-451a overexpression enhanced oxygen consumption, mitochondrial membrane potential (MMP) loss, and ROS generation and inhibited proliferation, migration, invasion, and stemness via sponging MEF2D. In a word, our results revealed that the acidic microenvironment regulated PC progression by affecting the miR-451a/MEF2D axis, indicating a novel avenue for the future treatment of PC.

The Regulatory Role of RNA Metabolism Regulator TDP-43 in Human Cancer

TAR-DNA-binding protein-43 (TDP-43) is a member of hnRNP family and acts as both RNA and DNA binding regulator, mediating RNA metabolism and transcription regulation in various diseases. Currently, emerging evidence gradually elucidates the crucial role of TDP-43 in human cancers like it is previously widely researched in neurodegeneration diseases. A series of RNA metabolism events, including mRNA alternative splicing, transport, stability, miRNA processing, and ncRNA regulation, are all confirmed to be closely involved in various carcinogenesis and tumor progressions, which are all partially regulated and interacted by TDP-43. Herein we conducted the first overall review about TDP-43 and cancers to systematically summarize the function and precise mechanism of TDP-43 in different human cancers. We hope it would provide basic knowledge and concepts for tumor target therapy and biomarker diagnosis in the future.

CBFβ promotes colorectal cancer progression through transcriptionally activating OPN, FAM129A, and UPP1 in a RUNX2-dependent manner

Colorectal cancer (CRC) is commonly associated with aberrant transcription regulation, but characteristics of the dysregulated transcription factors in CRC pathogenesis remain to be elucidated. In the present study, core-binding factor β (CBFβ) is found to be significantly upregulated in human CRC tissues and correlates with poor survival rate of CRC patients. Mechanistically, CBFβ is found to promote CRC cell proliferation, migration, invasion, and inhibit cell apoptosis in a RUNX2-dependent way. Transcriptome studies reveal that CBFβ and RUNX2 form a transcriptional complex that activates gene expression of OPN, FAM129A, and UPP1. Furthermore, CBFβ significantly promotes CRC tumor growth and live metastasis in a mouse xenograft model and a mouse liver metastasis model. In addition, tumor-suppressive miR-143/145 are found to inhibit CBFβ expression by specifically targeting its 3'-UTR region. Consistently, an inverse correlation between miR-143/miR-145 and CBFβ expression levels is present in CRC patients. Taken together, this study uncovers a novel regulatory role of CBFβ-RUNX2 complex in the transcriptional activation of OPN, FAM129A, and UPP1 during CRC development, and may provide important insights into CRC pathogenesis.

ERK5 signalling pathway is a novel target of sorafenib: Implication in EGF biology

Sorafenib is a multikinase inhibitor widely used in cancer therapy with an antitumour effect related to biological processes as proliferation, migration or invasion, among others. Initially designed as a Raf inhibitor, Sorafenib was later shown to also block key molecules in tumour progression such as VEGFR and PDGFR. In addition, sorafenib has been connected with key signalling pathways in cancer such as EGFR/EGF. However, no definitive clue about the molecular mechanism linking sorafenib and EGF signalling pathway has been established so far. Our data in HeLa, U2OS, A549 and HEK293T cells, based on in silico, chemical and genetic approaches demonstrate that the MEK5/ERK5 signalling pathway is a novel target of sorafenib. In addition, our data show how sorafenib is able to block MEK5-dependent phosphorylation of ERK5 in the Ser218/Tyr220, affecting the transcriptional activation associated with ERK5. Moreover, we demonstrate that some of the effects of this kinase inhibitor onto EGF biological responses, such as progression through cell cycle or migration, are mediated through the effect exerted onto ERK5 signalling pathway. Therefore, our observations describe a novel target of sorafenib, the ERK5 signalling pathway, and establish new mechanistic insights for the antitumour effect of this multikinase inhibitor.

Coupling HDAC4 with transcriptional factor MEF2D abrogates SPRY4-mediated suppression of ERK activation and elicits hepatocellular carcinoma drug resistance

Hepatocellular carcinoma (HCC) lacks effective treatment, and the patients rapidly develop the acquired resistance to sorafenib with less defined mechanisms. Here, we demonstrate that transcriptional factor myocyte enhancer factor 2D (MEF2D) overexpression is detected in sorafenib-resistant HCC specimens and HCC cell lines and predicts poor prognosis of sorafenib-treated HCC patients. Mechanistically, MEF2D in complex with histone deacetylase HDAC4 directly binds to the SPRY4 promoter regions and suppresses the transcriptional expression of SPRY4, which is a negative regulator of MAPK/ERK signaling pathway. Inhibition of HDAC4 with its clinically used inhibitor induces SPRY4 expression and inhibition of ERK activity, resulting in sensitization of HCC cells to sorafenib-induced apoptosis and greatly improved inhibition of liver tumor growth in mice with sorafenib treatment. These findings highlight the critical role of coupling HDAC4 with MEF2D in activation of ERK by suppressing SPRY4 and underscore the great potential to improve HCC treatment by combined administration of sorafenib with HDAC4 inhibitors.

DYRK1A phosphorylates MEF2D and decreases its transcriptional activity

Myocyte enhancer factor 2D (MEF2D) is predominantly expressed in the nucleus and associated with cell growth, differentiation, survival and apoptosis. Previous studies verified that phosphorylation at different amino acids determined MEF2's transcriptional activity which was essential in regulating downstream target genes expression. What regulates phosphorylation of MEF2D and affects its function has not been fully elucidated. Here, we uncovered that dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A), a kinase critical in Down's syndrome pathogenesis, directly bound to and phosphorylated MEF2D at Ser251 in vitro. Phosphorylation of MEF2D by DYRK1A significantly increased MEF2D protein level but attenuated its transcriptional activity, which resulted in decreased transcriptions of MEF2D target genes. Phosphorylation mutated Ser251A MEF2D exhibited enhanced transcriptional activity compared with wild type MEF2D. MEF2D and DYRK1A were observed co-localized in HEK293 and U87MG cells. Moreover, DYRK1A-mediated MEF2D phosphorylation in vitro might influence its nuclear export upon subcellular fractionation, which partially explained the reduction of MEF2D transcriptional activity by DYRK1A. Our results indicated that DYRK1A might be a regulator of MEF2D transcriptional activity and indirectly get involved in regulation of MEF2D target genes.

KDM1A Promotes Immunosuppression in Hepatocellular Carcinoma by Regulating PD-L1 through Demethylating MEF2D

Background

Immune checkpoint inhibitor therapy targeting antiprogrammed cell death-1 (anti-PD-1) or its ligand (anti-PD-L1) is effective in the treatment of some hepatocellular carcinomas (HCC). Hence, further identification of biological targets related to PD-L1 regulation in HCC is beneficial to improve the clinical efficacy of immunotherapy. Some HCC cells express lysine-specific demethylase 1A (KDM1A), which is implicated in the reduced survival time of patients. Here, we studied whether the level of PD-L1 and the immunosuppression are regulated by KDM1A and its miRNA in HCC cells.

Methods

In the present study, we studied clinical data from The Cancer Genome Atlas (TCGA) database. We performed qPCR and western blotting assays to measure the expression level of genes of interest. PD-L1 expression was also analyzed by FACS. Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 was used to generate gene knockout cells to investigate the relationships of genes of interest. We also developed a reporter gene assay (RGA) to explore the changes in T cell-induced antitumor immunity relative to PD-L1 expression in HCC cells. The binding between proteins and promoters or miRNAs and their target genes was explored by luciferase reporter assays.

Results

The results showed that PD-L1 and KDM1A were increased in HCC patients and cells, and KDM1A promoted the expression of PD-L1 in HCC cells. Our findings showed that the enhancement of PD-L1 expression was not attributed to mitochondrial dysfunction caused by increases in KDM1A in HCC cells. Furthermore, we observed a lower level of MEF2D methylation in HCC cells than in normal human liver cells. Demethylated MEF2D could bind to the promoter of PD-L1 and activate its expression, while KDM1A interacted with MEF2D and acted as a demethylase to reduce its methylation. Moreover, a new miRNA, miR-329-3p, targeting KDM1A was found to regulate the PD-L1 expression profile in HCC cells. In the xenograft model, the tumors treated with miR-329-3p showed growth inhibition.

Conclusions

Mechanistically, miR-329-3p inhibits tumor cellular immunosuppression and reinforces the response of tumor cells to T cell-induced cytotoxic effect by targeting KDM1A mRNA and downregulating its expression, which contributed to MEF2D demethylation and activation of PD-L1 expression.

ZEB1 serves as an oncogene in acute myeloid leukaemia via regulating the PTEN/PI3K/AKT signalling pathway by combining with P53

Acute myeloid leukaemia is a complex, highly aggressive hematopoietic disorder. Currently, in spite of great advances in radiotherapy and chemotherapy, the prognosis for AML patients with initial treatment failure is still poor. Therefore, the need for novel and efficient therapies to improve AML treatment outcome has become desperately urgent. In this study, we identified the expression of ZEB1 (a transcription factor) and focused on its possible role and mechanisms in the progression of AML. According to the data provided by the Gene Expression Profiling Interactive Analysis (GEPIA), high expression of ZEB1 closely correlates with poor prognosis in AML patients. Additionally, the overexpression of ZEB1 was observed in both AML patients and cell lines. Further functional experiments showed that ZEB1 depletion can induce AML differentiation and inhibit AML proliferation in vitro and in vivo. Moreover, ZEB1 expression was negatively correlated with tumour suppressor P53 expression and ZEB1 can directly bind to P53. Our results also revealed that ZEB1 can regulate PTEN/PI3K/AKT signalling pathway. The inhibitory effect of ZEB1 silencing on PTEN/PI3K/AKT signalling pathway could be significantly reversed by P53 small interfering RNA treatment. Overall, the present data indicated that ZEB1 may be a promising therapeutic target for AML treatment or a potential biomarker for diagnosis and prognosis.

Nucleolar and spindle‑associated protein 1 promotes non‑small cell lung cancer progression and serves as an effector of myocyte enhancer factor 2D

As a potential oncogene, nucleolar and spindle‑associated protein 1 (NUSAP1) is involved in the regulation of tumor cell proliferation, metastasis and drug resistance. However, the role of NUSAP1 in non‑small cell lung cancer (NSCLC) remains unclear. The present study aimed to investigate the biological function and underlying molecular mechanisms of NUSAP1 in NSCLC. NUSAP1 expression was measured in NSCLC tissues and cell lines via immunohistochemistry and western blotting, respectively. NSCLC cell lines stably inhibiting NUSAP1 were established to investigate its effects on cell proliferation, colony formation and invasion, and on in vivo tumorigenicity. Additionally, the upstream and downstream mechanisms of NUSAP1 in regulating NSCLC progression were investigated. The results indicated that NUSAP1 expression was upregulated in NSCLC tissues and cell lines. High NUSAP1 expression was associated with tumor size, TNM stage, lymph node metastasis and poor patient survival, whereas knockdown of NUSAP1 inhibited NSCLC cell proliferation, colony formation and invasion. Furthermore, downregulation of NUSAP1 decreased the growth of NSCLC xenografts in vivo. In addition, myocyte enhancer factor 2D (MEF2D) directly targeted the NUSAP1 promoter, thereby enhancing the mRNA and protein expression levels of NUSAP1. Moreover, the results demonstrated that MEF2D expression was upregulated in NSCLC tissues and was positively correlated with NUSAP1 expression. MEF2D‑knockdown decreased NSCLC cell proliferation, colony formation and invasion. NUSAP1 upregulation reversed the effects of MEF2D‑knockdown on NSCLC progression. Furthermore, it was observed that MEF2D‑knockdown inhibited the accumulation and nuclear translocation of β‑catenin, thereby repressing the activation of the Wnt/β‑catenin signaling pathway in NSCLC cells, whereas NUSAP1 upregulation rescued the effects of MEF2D‑knockdown on the activation of the Wnt/β‑catenin signaling pathway. In conclusion, the findings of the present study indicated that the MEF2D/NUSAP1 signaling pathway promoted NSCLC progression by inducing the activation of Wnt/β‑catenin signaling, and this novel mechanism may represent a potential treatment target for patients with NSCLC.

Targeting PAK4 to reprogram the vascular microenvironment and improve CAR-T immunotherapy for glioblastoma

Malignant solid tumors are characterized by aberrant vascularity that fuels the formation of an immune-hostile microenvironment and induces resistance to immunotherapy. Vascular abnormalities may be driven by pro-angiogenic pathway activation and genetic reprogramming in tumor endothelial cells (ECs). Here, our kinome-wide screening of mesenchymal-like transcriptional activation in human glioblastoma (GBM)-derived ECs identifies p21-activated kinase 4 (PAK4) as a selective regulator of genetic reprogramming and aberrant vascularization. PAK4 knockout induces adhesion protein re-expression in ECs, reduces vascular abnormalities, improves T cell infiltration and inhibits GBM growth in mice. Moreover, PAK4 inhibition normalizes the tumor vascular microenvironment and sensitizes GBM to chimeric antigen receptor-T cell immunotherapy. Finally, we reveal a MEF2D/ZEB1- and SLUG-mediated mechanism by which PAK4 reprograms the EC transcriptome and downregulates claudin-14 and VCAM-1 expression, enhancing vessel permeability and reducing T cell adhesion to the endothelium. Thus, targeting PAK4-mediated EC plasticity may offer a unique opportunity to recondition the vascular microenvironment and strengthen cancer immunotherapy.

MEF2A transcriptionally upregulates the expression of ZEB2 and CTNNB1 in colorectal cancer to promote tumor progression

Colorectal cancer (CRC) is one of the leading cancers worldwide, accounting for high morbidity and mortality. The mechanisms governing tumor growth and metastasis in CRC require detailed investigation. The results of the present study indicated that the transcription factor (TF) myocyte enhancer factor 2A (MEF2A) plays a dual role in promoting proliferation and metastasis of CRC by inducing the epithelial-mesenchymal transition (EMT) and activation of WNT/β-catenin signaling. Aberrant expression of MEF2A in CRC clinical specimens was significantly associated with poor prognosis and metastasis. Functionally, MEF2A directly binds to the promoter region to initiate the transcription of ZEB2 and CTNNB1. Simultaneous activation of the expression of EMT-related TFs and Wnt/β-catenin signaling by MEF2A overexpression induced the EMT and increased the frequency of tumor formation and metastasis. The present study identified a new critical oncogene involved in the growth and metastasis of CRC, providing a potential novel therapeutic target for CRC intervention.

Context specificity of the EMT transcriptional response

Epithelial–mesenchymal plasticity contributes to many biological processes, including tumor progression. Various epithelial–mesenchymal transition (EMT) responses have been reported and no common, EMT-defining gene expression program has been identified. Here, we have performed a comparative analysis of the EMT response, leveraging highly multiplexed single-cell RNA sequencing (scRNA-seq) to measure expression profiles of 103,999 cells from 960 samples, comprising 12 EMT time course experiments and independent kinase inhibitor screens for each. We demonstrate that the EMT is vastly context specific, with an average of only 22% of response genes being shared between any two conditions, and over half of all response genes were restricted to 1–2 time course experiments. Further, kinase inhibitor screens revealed signaling dependencies and modularity of these responses. These findings suggest that the EMT is not simply a single, linear process, but is highly variable and modular, warranting quantitative frameworks for understanding nuances of the transition.

It is unclear if a common EMT expression program exists. Here, the authors perform multiplexed single-cell RNA sequencing across 12 EMT time courses and 16 kinase inhibitor screens, and find that EMT transcriptional responses are context specific and EMT is not a single, linear transition.

Disruption of SIRT7 Increases the Efficacy of Checkpoint Inhibitor via MEF2D Regulation of Programmed Cell Death 1 Ligand 1 in Hepatocellular Carcinoma Cells

BACKGROUND & AIMS

Immune checkpoint inhibitors have some efficacy in the treatment of hepatocellular carcinoma (HCC). Programmed cell death 1 ligand 1 (PD-L1), expressed on some cancer cells, binds to the receptor programmed cell death 1 (PDCD1, also called PD1) on T cells to prevent their proliferation and reduce the antigen-tumor immune response. Immune cells that infiltrate some types of HCCs secrete interferon gamma (IFNG). Some HCC cells express myocyte enhancer factor 2D (MEF2D), which has been associated with shorter survival times of patients. We studied whether HCC cell expression of MEF2D regulates expression of PD-L1 in response to IFNG.

METHODS

We analyzed immune cells from 20 fresh HCC tissues by flow cytometry. We analyzed 225 fixed HCC tissues (from 2 cohorts) from patients in China by immunohistochemistry and obtained survival data. We created mice with liver-specific knockout of MEF2D (MEF2D^LPC-KO mice). We knocked out or knocked down MEF2D, E1A binding protein p300 (p300), or sirtuin 7 (SIRT7) in SMMC-7721, Huh7, H22, and Hepa1-6 HCC cell lines, some incubated with IFNG. We analyzed liver tissues from mice and cell lines by RNA sequencing, immunoblot, dual luciferase reporter, and chromatin precipitation assays. MEF2D protein acetylation and proteins that interact with MEF2D were identified by coimmunoprecipitation and pull-down assays. H22 cells, with MEF2D knockout or without (controls), were transplanted into BALB/c mice, and some mice were given antibodies to deplete T cells. Mice bearing orthotopic tumors grown from HCC cells, with or without knockout of SIRT7, were given injections of an antibody against PD1. Growth of tumors was measured, and tumors were analyzed by immunohistochemistry and flow cytometry.

RESULTS

In human HCC specimens, we found an inverse correlation between level of MEF2D and numbers of CD4⁺ and CD8⁺ T cells; level of MEF2D correlated with percentages of PD1-positive or TIM3-positive CD8⁺ T cells. Knockout of MEF2D from H22 cells reduced their growth as allograft tumors in immune-competent mice but not in immune-deficient mice or mice with depletion of CD8⁺ T cells. When MEF2D-knockout cells were injected into immune-competent mice, they formed smaller tumors that had increased infiltration and activation of T cells compared with control HCC cells. In human and mouse HCC cells, MEF2D knockdown or knockout reduced expression of PD-L1. MEF2D bound the promoter region of the CD274 gene (encodes PD-L1) and activated its transcription. Overexpression of p300 in HCC cells, or knockout of SIRT7, promoted acetylation of MEF2D and increased its binding, along with acetylated histones, to the promoter region of CD274. Exposure of HCC cells to IFNG induced expression of p300 and its binding MEF2D, which reduced the interaction between MEF2D and SIRT7. MEF2D-induced expression of PD-L1 upon IFNG exposure was independent of interferon-regulatory factors 1 or 9. In HCC cells not exposed to IFNG, SIRT7 formed a complex with MEF2D that attenuated expression of PD-L1. Knockout of SIRT7 reduced proliferation of HCC cells and growth of tumors in immune-deficient mice. Compared with allograft tumors grown from control HCC cells, in immune-competent mice, tumors grown from SIRT7-knockout HCC cells expressed higher levels of PD-L1 and had reduced infiltration and activation of T cells. In immune-competent mice given antibodies to PD1, allograft tumors grew more slowly from SIRT7-knockout HCC cells than from control HCC cells.

CONCLUSIONS

Expression of MEF2D by HCC cells increases their expression of PD-L1, which prevents CD8⁺ T-cell-mediated antitumor immunity. When HCC cells are exposed to IFNG, p300 acetylates MEF2D, causing it to bind the CD274 gene promoter and up-regulate PD-L1 expression. In addition to promoting HCC cell proliferation, SIRT7 reduced acetylation of MEF2D and expression of PD-L1 in HCC cells not exposed to IFNG. Strategies to manipulate this pathway might increase the efficacy of immune therapies for HCC.

ZEB1 activated-VPS9D1-AS1 promotes the tumorigenesis and progression of prostate cancer by sponging miR-4739 to upregulate MEF2D

Prostate cancer (PCa) is a destructive malignancy with a bad prognosis. LncRNA VPS9D1-AS1 has recently been delineated as an oncogene in some kinds of tumor, whereas, the function of VPS9D1-AS1 in PCa remains to be clarified. In this study, we researched its underlying role in PCa. The expression of VPS9D1-AS1 was conspicuously upregulated in PCa tissues and cells. And absence of VPS9D1-AS1 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis in PCa. In addition, VPS9D1-AS1 overexpression led to opposite results. Furthermore, VPS9D1-AS1/MEF2D could sponge with miR-4739. VPS9D1-AS1/MEF2D and miR-4739 were inversely correlated in tumor cells. And the expression of miR-4739 is markedly downregulated in PCa, meanwhile, that of MEF2D exhibited the opposite tendency. However, MEF2D was positively regulated by VPS9D1-AS1. Moreover, MEF2D upregulation offset the suppressive effects of VPS9D1-AS1 deficiency on cell proliferation, migration and invasion in PCa. Additionally, ZEB1 contained the binding sites of VPS9D1-AS1 promoter, and there existed positive relation between them. Taken together, above results illustrated that ZEB1 activated-VPS9D1-AS1 promotes the tumorigenesis and progression of PCa by sponging miR-4739 to upregulate MEF2D, which offering a new useful reference for studying the development process of PCa.

PLAGL2 promotes epithelial-mesenchymal transition and mediates colorectal cancer metastasis via β-catenin-dependent regulation of ZEB1

Background

We previously demonstrated that the pleomorphic adenoma gene like-2 (PLAGL2) is involved in the pathogenesis of Hirschsprung disease. Enhanced PLAGL2 expression was observed in several malignant tumours. However, the exact function of PLAGL2 and its underlying mechanism in colorectal cancer (CRC) remain largely unknown.

Methods

Immunohistochemical analysis of PLAGL2 was performed. A series of in vitro and in vivo experiments were conducted to reveal the role of PLAGL2 in the progression of CRC.

Results

Enhanced PLAGL2 expression was significantly associated with EMT-related proteins in CRC. The data revealed that PLAGL2 promotes CRC cell proliferation, migration, invasion and EMT both in vitro and in vivo. Mechanistically, PLAGL2 promoted the expression of ZEB1. PLAGL2 enhanced the expression and nuclear translocation of β-catenin by decreasing its phosphorylation. The depletion of β-catenin neutralised the regulation of ZEB1 that was caused by enhanced PLAGL2 expression. The small-molecule inhibitor PNU-74654, also impaired the enhancement of ZEB1 that resulted from the modified PLAGL2 expression. The depletion of ZEB1 could block the biological function of PLAGL2 in CRC cells.

Conclusions

Collectively, our findings suggest that PLAGL2 mediates EMT to promote colorectal cancer metastasis via β-catenin-dependent regulation of ZEB1.

The integrative knowledge base for miRNA-mRNA expression in colorectal cancer

"miRNA colorectal cancer" (https://mirna-coadread.omics.si/) is a freely available web application for studying microRNA and mRNA expression and their correlation in colorectal cancer. To the best of our knowledge, "miRNA colorectal cancer" has the largest knowledge base of miRNA-target gene expressions and correlations in colorectal cancer, based on the largest available sample size from the same source of data. Data from high-throughput molecular profiling of 295 colon and rectum adenocarcinoma samples from The Cancer Genome Atlas was analyzed and integrated into our knowledge base. The objective of developing this web application was to help researchers to discover the behavior and role of miRNA-target gene interactions in colorectal cancer. For this purpose, results of differential expression and correlation analyses of miRNA and mRNA data collected in our knowledge base are available through web forms. To validate our knowledge base experimentally, we selected genes FN1, TGFB2, RND3, ZEB1 and ZEB2 and miRNAs hsa-miR-200a/b/c-3p, hsa-miR-141-3p and hsa-miR-429. Both approaches revealed a negative correlation between miRNA hsa-miR-200b/c-3p and its target gene FN1 and between hsa-miR-200a-3p and its target TGFB2, thus supporting the usefulness of the developed knowledge base.

Long noncoding RNA NEAT1 drives aggressive endometrial cancer progression via miR-361-regulated networks involving STAT3 and tumor microenvironment-related genes

BACKGROUND

High-grade endometrioid and serous endometrial cancers (ECs) are an aggressive subtype of ECs without effective therapies. The reciprocal communication between tumor cells and their surrounding microenvironment drives tumor progression. Long noncoding RNAs (lncRNAs) are key mediators of tumorigenesis and metastasis. However, little is known about the role of lncRNAs in aggressive EC progression and tumor microenvironment remodeling.

METHODS

We performed an array-based lncRNA analysis of a parental HEC-50 EC cell population and derivatives with highly invasive, sphere-forming, and paclitaxel (TX)-resistant characteristics. We characterized the roles of the lncRNA NEAT1 in mediating aggressive EC progression in vitro and in vivo and explored the molecular events downstream of NEAT1.

RESULTS

We identified 10 lncRNAs with upregulated expression (NEAT1, H19, PVT1, UCA1, MIR7-3HG, SNHG16, HULC, RMST, BCAR4 and LINC00152) and 10 lncRNAs with downregulated expression (MEG3, GAS5, DIO3OS, MIR155HG, LINC00261, FENDRR, MIAT, TMEM161B-AS1, HAND2-AS1 and NBR2) in the highly invasive, sphere-forming and TX-resistant derivatives. NEAT1 expression was markedly upregulated in early-stage EC tissue samples, and high NEAT1 expression predicted a poor prognosis. Inhibiting NEAT1 expression with small hairpin RNAs (shRNAs) diminished cellular proliferation, invasion, sphere formation, and xenograft tumor growth and improved TX response in aggressive EC cells. We showed that NEAT1 functions as an oncogenic sponge for the tumor suppressor microRNA-361 (miR-361), which suppresses proliferation, invasion, sphere formation and TX resistance by directly targeting the oncogene STAT3. Furthermore, miR-361 also suppressed the expression of multiple prometastatic genes and tumor microenvironment-related genes, including MEF2D, ROCK1, WNT7A, VEGF-A, PDE4B, and KPNA4.

CONCLUSIONS

NEAT1 initiates a miR-361-mediated network to drive aggressive EC progression. These data support a rationale for inhibiting NEAT1 signaling as a potential therapeutic strategy for overcoming aggressive EC progression and chemoresistance.

m6A-induced lncRNA RP11 triggers the dissemination of colorectal cancer cells via upregulation of Zeb1

Background

Long noncoding RNAs (lncRNAs) have emerged as critical players in cancer progression, but their functions in colorectal cancer (CRC) metastasis have not been systematically clarified.

Methods

lncRNA expression profiles in matched normal and CRC tissue were checked using microarray analysis. The biological roles of a novel lncRNA, namely RP11-138 J23.1 (RP11), in development of CRC were checked both in vitro and in vivo. Its association with clinical progression of CRC was further analyzed.

Results

RP11 was highly expressed in CRC tissues, and its expression increased with CRC stage in patients. RP11 positively regulated the migration, invasion and epithelial mesenchymal transition (EMT) of CRC cells in vitro and enhanced liver metastasis in vivo. Post-translational upregulation of Zeb1, an EMT-related transcription factor, was essential for RP11-induced cell dissemination. Mechanistically, the RP11/hnRNPA2B1/mRNA complex accelerated the mRNA degradation of two E3 ligases, Siah1 and Fbxo45, and subsequently prevented the proteasomal degradation of Zeb1. m⁶A methylation was involved in the upregulation of RP11 by increasing its nuclear accumulation. Clinical analysis showed that m⁶A can regulate the expression of RP11, further, RP11 regulated Siah1-Fbxo45/Zeb1 was involved in the development of CRC.

Conclusions

m⁶A-induced lncRNA RP11 can trigger the dissemination of CRC cells via post-translational upregulation of Zeb1. Considering the high and specific levels of RP11 in CRC tissues, our present study paves the way for further investigations of RP11 as a predictive biomarker or therapeutic target for CRC.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-1014-2) contains supplementary material, which is available to authorized users.

Alteration of the tumor suppressor SARDH in sporadic colorectal cancer: A functional and transcriptome profiling-based study

Sporadic colorectal cancer (sCRC) is one of the leading causes of cancer death worldwide. As a highly heterogeneous complex disease, the currently reported classical genetic markers for sCRC, including APC, KRAS, BRAF, and TP53 gene mutations and epigenetic alterations, can explain only some sCRC patients. Here, we first reported a deleterious c.551C>T mutation in SARDH in sCRC. SARDH was identified as a novel tumor suppressor gene and was abnormally decreased in sCRC at both the transcriptional and the translational level. SARDH mRNA levels were also down-regulated in oesophageal cancer, lung cancer, liver cancer, and pancreatic cancer in the TCGA database. SARDH overexpression inhibited the proliferation, migration, and invasion of CRC cell lines, whereas its depletion improved these processes. SARDH overexpression was down-regulated in multiple pathways, especially in the chemokine pathway. The SARDH transcript level was positively correlated with the methylation states of CXCL1 and CCL20. Therefore, we concluded that SARDH depletion is involved in the development of sCRC.

Comprehensive profiling of JMJD3 in gastric cancer and its influence on patient survival

Histone methylation is thought to control the regulation of genetic program and the dysregulation of it has been found to be closely associated with cancer. JMJD3 has been identified as an H3K27 demethylase and its role in cancer development is context specific. The role of JMJD3 in gastric cancer (GC) has not been examined. In this study, JMJD3 expression was determined. The prognostic significance of JMJD3 and its association with clinical parameters were evaluated. JMJD3 dysregulation mechanism and targets were analyzed. The effect of JMJD3 mutation was determined by functional study. Results showed that JMJD3 was overexpressed in different patient cohorts and also by bioinformatics analysis. High JMJD3 expression was correlated with shortened overall survival in patients with GC and was an independent prognosis predictor. Genetic aberration and DNA methylation might be involved in the deregulation of JMJD3 in GC. Downstream network of JMJD3 was analyzed and several novel potential targets were identified. Furthermore, functional study discovered that both demethylase-dependent and demethylase-independent mechanisms were involved in the oncogenic role of JMJD3 in GC. Importantly, histone demethylase inhibitor GSK-J4 could reverse the oncogenic effect of JMJD3 overexpression. In conclusion, our study report the oncogenic role of JMJD3 in GC for the first time. JMJD3 might serve as an important epigenetic therapeutic target and/or prognostic predictor in GC.

Alteration of tumor suppressor BMP5 in sporadic colorectal cancer: a genomic and transcriptomic profiling based study

Background

Although the genetic spectrum of human colorectal cancer (CRC) is mainly characterized by APC, KRAS and TP53 mutations, driver genes in tumor initiation have not been conclusively demonstrated. In this study, we aimed to identify novel markers for CRC.

Methods

We performed exome analysis of sporadic colorectal cancer (sCRC) coding regions to screen loss of function (LoF) mutation genes, and carried out systems-level approaches to confirm top rank gene in this study.

Results

We identified loss of BMP5 is an early event in CRC. Deep sequencing identified BMP5 was mutated in 7.7% (8/104) of sCRC samples, with 37.5% truncating mutation frequency. Notably, BMP5 negative expression and its prognostic value is uniquely significant in sCRC but not in other tumor types. Furthermore, BMP5 expression was positively correlated with E-cadherin in CRC patients and its dysregulation play a vital role in epithelial-mesenchymal transition (EMT), thus triggering tumor initiation and development. RNA sequencing identified, independent of BMP/Smads pathway, BMP5 signaled though Jak-Stat pathways to inhibit the activation of oncogene EPSTI1.

Conclusions

Our result support a novel concept that the importance of BMP5 in sCRC. The tumor suppressor role of BMP5 highlights its crucial role in CRC initiation and development.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0925-7) contains supplementary material, which is available to authorized users.

Genomic and regulatory characteristics of significant transcription factors in colorectal cancer metastasis

The dysregulation of transcription factors has an important impact on the oncogenesis and tumor progression. Nonetheless, its functions in colorectal cancer metastasis are still unclear. In this study, four transcription factors (HNF4A, HSF1, MECP2 and RAD21) were demonstrated to be associated with the metastasis of colorectal cancer in both RNA and protein levels. To comprehensively explore the intrinsic mechanisms, we profiled the molecular landscape of these metastasis-related transcription factors from multiple perspectives. In particular, as the crucial factors affecting genome stability, both copy number variation and DNA methylation exerted their strengths on the expression of these transcription factors (except MECP2). Additionally, based on a series of bioinformatics analyses, putative long non-coding RNAs were identified as functional regulators. Besides that, rely on the ATAC-Seq and ChIP-Seq profiles, we detected the target genes regulated by each transcription factor in the active chromatin zones. Finally, we inferred the associations between the target genes by Bayesian networks and identified LMO7 and ARL8A as potential clinical biomarkers. Taken together, our research systematically characterized the regulatory cascades of HNF4A, HSF1, MECP2 and RAD21 in colorectal cancer metastasis.

Epigenetic suppression of E-cadherin expression by Snail2 during the metastasis of colorectal cancer

Background

The transcription factor Snail2 is a repressor of E-cadherin expression during carcinogenesis; however, the specific mechanisms involved in this process in human colorectal cancer (CRC) remain largely unknown.

Method

We checked the expression of Snail2 in several clinical CRC specimens. Then, we established Snail2-overexpressing and knockdown cell lines to determine the function of Snail2 during EMT and metastasis processes in CRC. In addition, we used luciferase reporter assay to explore how Snail2 inhibits the expression of E-cadherin and induces EMT.

Results

We found that the expression of Snail2 was higher in clinical specimens of colorectal cancer (CRC) compared to non-cancerous tissues. Overexpression of Snail2 induced migration and metastatic properties in CRC cells in vitro and in vivo. Furthermore, overexpression of Snail2 promoted the occurrence of the epithelial–mesenchymal transition (EMT), downregulating the expression of E-cadherin and upregulating that of vimentin. Specifically, Snail2 could interact with HDAC6 and then recruited HDAC6 and PRC2 to the promoter of E-cadherin and thus inhibited the expression of E-cadherin, promoting EMT and inducing invasion and metastasis of CRC.

Conclusion

Our study reveals that Snail2 might epigenetically suppress the expression of E-cadherin during CRC metastasis.

The roles of ZEB1 in tumorigenic progression and epigenetic modifications

Highly expressed Zinc-finger E-box binding protein 1 (ZEB1) is significantly associated with the malignancy of various cancers. Signal transduction and activation of ZEB1 play important roles in cancer transformation and epithelial-mesenchymal transition (EMT). Emerging evidence suggests that ZEB1 drives the induction of EMT with activation of stem cell traits, immune evasion and epigenetic reprogramming. As an ideal target for EMT research, ZEB1 has been extensively studied for decades. However, the link between ZEB1 and epigenetic regulation of EMT has only recently been discovered. ZEB1 facilitates the epigenetic silencing of E-cadherin by recruiting multiple chromatin enzymes of E-cadherin promoter, such as histone deacetylases (HDACs), DNA methyltransferase (DNMT) and ubiquitin ligase. Destruction of the connection between ZEB1 and these chromatin-modifying enzymes may represent an efficient for treating cancer. In this review, we outlined the biological function of ZEB1 in tumorigenic progression and epigenetic modifications and elucidate its transcriptional network, which is a suitable potential target for the design of novel anticancer drugs.

A comprehensive look at the role of hyperlipidemia in promoting colorectal cancer liver metastasis

Colorectal cancer (CRC) is one of the most malignant cancers, and it tends to migrate to the liver and has a high mortality rate. Several mechanisms behind the metastasis of CRC have been identified, including hyperlipidemia. For example, hyperlipidemia can lead to enhanced stemness and neutrophil infiltration, which increases CRC metastasis. There are three primary aspects to the relationship between hyperlipidemia and CRC metastasis: hyperlipidemia (1) promotes the initial metastatic properties of CRC, (2) stimulates CRC cells to leave the vasculature, and (3) facilitates the development of CRC metastasis. In this study, we provide a comprehensive overview of the role that hyperlipidemia played in CRC metastasis to help reduce the mortality associated with CRC metastasis from the standpoint of metabolic. We also review cancer metastasis.

MEF2 and the tumorigenic process, hic sunt leones

While MEF2 transcription factors are well known to cooperate in orchestrating cell fate and adaptive responses during development and adult life, additional studies over the last decade have identified a wide spectrum of genetic alterations of MEF2 in different cancers. The consequences of these alterations, including triggering and maintaining the tumorigenic process, are not entirely clear. A deeper knowledge of the molecular pathways that regulate MEF2 expression and function, as well as the nature and consequences of MEF2 mutations are necessary to fully understand the many roles of MEF2 in malignant cells. This review discusses the current knowledge of MEF2 transcription factors in cancer.

Absent expression of miR-30a promotes the growth of lung cancer cells by targeting MEF2D

The microRNA (miR)-30 family has been reported to be aberrantly expressed in several types of cancer. However, its contributions to lung cancer remain to be fully elucidated. Myocyte enhancer factor 2D (MEF2D), an oncogene in liver cancer, has been shown to be aberrantly expressed in lung cancer. In the present study, it was found that MEF2D and miR-30a were inversely correlated in lung cancer samples. Using an online database, it was predicted that miR-30a targeted the 3' untranslated region (UTR) of MEF2D mRNA. The activity of luciferase with MEF2D 3'UTR was suppressed by transfecting cells with miR-30a mimics. The results of western blot analysis showed that the miR-30a mimics also suppressed the MEF2D protein. The miR-30a mimics were able to reduce the growth and colonies of lung cancer cells by suppressing MEF2D. The results of FACS and western blot assays showed that the apoptotic rate was reduced by transfection with the miR-30a mimics. Collectively, the aberrant expression of miR-30a in lung cancer promoted the expression of MEF2D protein. miR-30a inhibited the growth and colony formation of the lung cancer cells by promoting apoptosis.

Anti-cancer effect of Aquaporin 5 silencing in colorectal cancer cells in association with inhibition of Wnt/β-catenin pathway

Aquaporin 5 (AQP5) is a water channel protein that is over-expressed in many tumors. Elevated expression of AQP5 is associated with poor prognosis of colorectal cancer. Yet, whether AQP5 plays a role in epithelial-mesenchymal transition (EMT) of colorectal cancer has not been reported until now. Here we aim to investigate the function of AQP5 in the EMT process of colorectal cancer. We transfected HCT116 and SW480 cells with AQP5-specific shRNA and verified the knockdown efficiency through western blotting and real-time PCR. Afterwards, scratch wound healing assay, invasion assay, gelatin zymography, immunofluorescence staining and immunoblotting were performed to assess the effect of AQP5 silencing in these two cells. The ability of migration and invasion of colorectal cancer cells was significantly impaired after AQP5 silencing. Correspondingly, the activity and expression of Matrix Metallopeptidase (MMP)-2 and MMP-9 were reduced. Moreover, the expression levels of EMT-related factors were altered: E-cadherin, Tissue Inhibitor Of Metalloproteinases (TIMP)-1 and TIMP-2 were upregulated, whereas Vimentin, N-cadherin, Plasminogen Activator, Urokinase (uPA) and Snail were downregulated following knockdown of AQP5 in colorectal cancer cells. Furthermore, the expression of Wnt1 and β-catenin was markedly decreased after AQP5 knockdown. Interestingly, the alteration of EMT-related factors mediated by AQP5 knockdown could be reversed by upregulation of β-catenin. Taken together, silencing of AQP5 restrained the migration and invasion of colorectal cancer cells, and regulated the expression of EMT-related molecules in them by inhibiting Wnt/β-catenin pathway.

RHBDD1 promotes colorectal cancer metastasis through the Wnt signaling pathway and its downstream target ZEB1

BACKGROUND

40-50% of colorectal cancer (CRC) patients develop metastatic disease; the presence of metastasis hinders the effective treatment of cancer through surgery, chemotherapy and radiotherapy, which makes 5-year survival rate extremely low; therefore, studying CRC metastasis is crucial for disease therapy. In the present study, we investigated the role of rhomboid domain containing 1 (RHBDD1) in tumor metastasis of CRC.

METHODS

The expression of RHBDD1 was analyzed in 539 colorectal tumor tissues for its correlation with lymphatic metastasis and distal metastasis. Transwell assay in vitro and pleural metastasis analysis in vivo were performed to determine the functions of RHBDD1 during CRC cells metastasis. RNA-seq analysis, TOP/FOP flash reporter assay, western blot and transwell assay were performed to investigate the underlying mechanism for the function of RHBDD1 on Wnt signaling pathway. Bioinformatics analysis was conducted to investigate epithelial-mesenchymal transition (EMT) and stemness in HCT-116 cells. Tissue microarray analysis, Q-PCR and western blot were performed to determine the correlation of RHBDD1 and Zinc Finger E-Box Binding Homeobox 1 (ZEB1).

RESULTS

In this study, we found that RHBDD1 expression was positively correlated with lymphatic metastasis and distal metastasis in 539 colorectal tumor tissues. RHBDD1 expression can promote CRC cells metastasis in vitro and in vivo. RNA-Seq analysis showed that the Wnt signaling pathway played a key role in this metastatic regulation. RHBDD1 mainly regulated ser552 and ser675 phosphorylation of β-catenin to activate the Wnt signaling pathway. Rescuing ser552 and ser675 phosphorylation of β-catenin resulted in the recovery of signaling pathway activity, migration, and invasion in CRC cells. RHBDD1 promoted EMT and a stem-like phenotype of CRC cells. RHBDD1 regulated the Wnt/β-catenin target gene ZEB1, a potent EMT activator, at the RNA and protein levels. Clinically, RHBDD1 expression was positively correlated with ZEB1 at the protein level in 71 colon tumor tissues.

CONCLUSIONS

Our findings therefore indicated that RHBDD1 can promote CRC metastasis through the Wnt signaling pathway and ZEB1. RHBDD1 may become a new therapeutic target or clinical biomarker for metastatic CRC.

MEF2 transcription factors in human placenta and involvement in cytotrophoblast invasion and differentiation

Development of the human placenta and its trophoblast cell types is critical for a successful pregnancy. Defects in trophoblast invasion and differentiation are associated with adverse pregnancy outcomes, including preeclampsia. The members of myocyte enhancer factor-2 (MEF2) family of transcription factors are key regulators of cellular proliferation, differentiation, and invasion in various cell types and tissues and might play a similarly important role in regulating trophoblast proliferation, invasion, and differentiation during human placental development. In the present study, using human cytotrophoblast cell lines (HTR8/SVneo and BeWo) and primary human cytotrophoblasts (CTBs), we show that members of the MEF2 family are differentially expressed in human placental CTBs, with MEF2B and MEF2D being highly expressed in first trimester extravillous CTBs. Overexpression of MEF2D results in cytotrophoblast proliferation and enhances the invasion and migration of extravillous-like HTR8/SVneo cells. This invasive property is blocked by overexpression of a dominant negative MEF2 (dnMEF2). In contrast, MEF2A is the principal MEF2 isoform expressed in term CTBs, MEF2C and MEF2D being expressed more weakly, and MEF2B expression being undetected. Overexpression of MEF2A induces cytotrophoblast differentiation and syncytium formation in BeWo cells. During in vitro differentiation of primary CTBs, MEF2A expression is associated with CTB differentiation into syncytiotrophoblast. Additionally, the course of p38 MAPK and ERK5 activities parallels the increase in MEF2A expression. These findings suggest individual members of MEF2 family distinctively regulate cytotrophoblast proliferation, invasion, and differentiation. Dysregulation of expression of MEF2 family or of their upstream signaling pathways may be associated with placenta-related pregnancy disorders.

Regulation of EMT in Colorectal Cancer: A Culprit in Metastasis

Epithelial to mesenchymal transition (EMT) is a process during which cells lose their epithelial characteristics, for instance cell polarity and cell-cell contact, and gain mesenchymal properties, such as increased motility. In colorectal cancer (CRC), EMT is associated with an invasive or metastatic phenotype. In this review, we discuss recent studies exploring novel regulation mechanisms of EMT in CRC, including the identification of new CRC EMT regulators. Upregulation of inducers can promote EMT, leading to increased invasiveness and metastasis in CRC. These inducers can downregulate E-cadherin and upregulate N-cadherin and vimentin (VIM) through modulating EMT-related signaling pathways, for instance WNT/β-catenin and TGF-β, and EMT transcription factors, such as zinc finger E-box binding homeobox 1 (ZEB1) and ZEB2. In addition, several microRNAs (miRNAs), including members of the miR-34 and miR-200 families, are found to target mRNAs of EMT-transcription factors, for example ZEB1, ZEB2, or SNAIL. Downregulation of these miRNAs is associated with distant metastasis and advanced stage tumors. Furthermore, the role of EMT in circulating tumor cells (CTCs) is also discussed. Mesenchymal markers on the surface of EMT CTCs were found to be associated with metastasis and could serve as potential biomarkers for metastasis. Altogether, these studies indicate that EMT is orchestrated by a complicated network, involving regulators of different signaling pathways. Further studies are required to understand the mechanisms underlying EMT in CRC.

MEF2 signaling and human diseases

The members of myocyte Enhancer Factor 2 (MEF2) protein family was previously believed to function in the development of heart and muscle. Recent reports indicate that they are also closely associated with development and progression of many human diseases. Although their role in cancer biology is well established, the molecular mechanisms underlying their action is yet largely unknown. MEF2 family is closely associated with various signaling pathways, including Ca²⁺ signaling, MAP kinase signaling, Wnt signaling, PI3K/Akt signaling, etc. microRNAs also contribute to regulate the activities of MEF2. In this review, we summarize the known molecular mechanism by which MEF2 family contribute to human diseases.

Analyses of germline variants associated with ovarian cancer survival identify functional candidates at the 1q22 and 19p12 outcome loci

We previously identified associations with ovarian cancer outcome at five genetic loci. To identify putatively causal genetic variants and target genes, we prioritized two ovarian outcome loci (1q22 and 19p12) for further study. Bioinformatic and functional genetic analyses indicated that MEF2D and ZNF100 are targets of candidate outcome variants at 1q22 and 19p12, respectively. At 19p12, the chromatin interaction of a putative regulatory element with the ZNF100 promoter region correlated with candidate outcome variants. At 1q22, putative regulatory elements enhanced MEF2D promoter activity and haplotypes containing candidate outcome variants modulated these effects. In a public dataset, MEF2D and ZNF100 expression were both associated with ovarian cancer progression-free or overall survival time. In an extended set of 6,162 epithelial ovarian cancer patients, we found that functional candidates at the 1q22 and 19p12 loci, as well as other regional variants, were nominally associated with patient outcome; however, no associations reached our threshold for statistical significance (p<1×10-5). Larger patient numbers will be needed to convincingly identify any true associations at these loci.

Myocyte enhancer factor 2D promotes colorectal cancer angiogenesis downstream of hypoxia-inducible factor 1α

Myocyte enhancer factor 2D (MEF2D) is involved in many aspects of cancer progression, including cell proliferation, invasion, and migration. However, little is known about the role of MEF2D in tumor angiogenesis. Using clinical specimens, colorectal cancer (CRC) cell lines and a mouse model in the present study, we found that MEF2D expression was positively correlated with CD31-positive microvascular density in CRC tissues. MEF2D promoted tumor angiogenesis in vitro and in vivo and induced the expression of proangiogenic cytokines in CRC cells. MEF2D was found to be a downstream effector of hypoxia-inducible factor (HIF)-1α in the induction of tumor angiogenesis. HIF-1α transactivates MEF2D expression by binding to the MEF2D gene promoter. These results demonstrate that the HIF-1α/MEF2D axis can serve as a therapeutic target for the treatment of CRC.

The co-existence of transcriptional activator and transcriptional repressor MEF2 complexes influences tumor aggressiveness

The contribution of MEF2 TFs to the tumorigenic process is still mysterious. Here we clarify that MEF2 can support both pro-oncogenic or tumor suppressive activities depending on the interaction with co-activators or co-repressors partners. Through these interactions MEF2 supervise histone modifications associated with gene activation/repression, such as H3K4 methylation and H3K27 acetylation. Critical switches for the generation of a MEF2 repressive environment are class IIa HDACs. In leiomyosarcomas (LMS), this two-faced trait of MEF2 is relevant for tumor aggressiveness. Class IIa HDACs are overexpressed in 22% of LMS, where high levels of MEF2, HDAC4 and HDAC9 inversely correlate with overall survival. The knock out of HDAC9 suppresses the transformed phenotype of LMS cells, by restoring the transcriptional proficiency of some MEF2-target loci. HDAC9 coordinates also the demethylation of H3K4me3 at the promoters of MEF2-target genes. Moreover, we show that class IIa HDACs do not bind all the regulative elements bound by MEF2. Hence, in a cell MEF2-target genes actively transcribed and strongly repressed can coexist. However, these repressed MEF2-targets are poised in terms of chromatin signature. Overall our results candidate class IIa HDACs and HDAC9 in particular, as druggable targets for a therapeutic intervention in LMS.

The tumorigenic process is characterized by profound alterations of the transcriptional landscape, aimed to sustain uncontrolled cell growth, resistance to apoptosis and metastasis. The contribution of MEF2, a pleiotropic family of transcription factors, to these changes is controversial, since both pro-oncogenic and tumor-suppressive activities have been reported. To clarify this paradox, we studied the role of MEF2 in an aggressive type of soft-tissue sarcomas, the leiomyosarcomas (LMS). We found that in LMS cells MEF2 become oncogenes when in complex with class IIa HDACs. We have identified different sub-classes of MEF2-target genes and observed that HDAC9 converts MEF2 into transcriptional repressors on some, but not all, MEF2-regulated loci. This conversion correlates with the acquisition by MEF2 of oncogenic properties. We have also elucidated some epigenetic re-arrangements supervised by MEF2. In summary, our studies suggest that the paradoxical actions of MEF2 in cancer can be explained by their dual role as activators/repressors of transcription and open new possibilities for therapeutic interventions.

ZEB1 induced miR-99b/let-7e/miR-125a cluster promotes invasion and metastasis in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common digestive tumors in Asia. Recent researches demonstrate that miRNAs are involved in the development of ESCC. In this study, we identified a miRNA cluster, termed miR-99b/let-7e/miR-125a as pro-metastasis oncomir. Overexpression of this miRNA cluster promoted ESCC cell migration and invasion in vitro and induced an experimental metastasis in vivo. ZEB1 was discovered to bind to the promoter region of miR-99b/let-7e/miR-125a cluster and regulate the expression of miRNAs at transcriptional level. Knockdown of ZEB1 resulted in a decrease of both mature and primary miRNAs. Further research revealed AT-rich interaction domain 3A (ARID3A) as a direct target of miR-99b/let-7e/miR-125a cluster. Reduced ARID3A phenocopied miR-99b/let-7e/miR-125a overexpression, and elevated ARID3A counteracted the pro-metastasis effect of miR-99b/let-7e/miR-125a. Moreover, ARID3A was downregulated by ZEB1 in a miR-99b/let-7e/miR-125a dependent manner. Collectively, our study sheds light on the essential role of miR-99b/let-7e/miR-125a cluster in tumor metastasis.