Dysregulated serum response factor triggers formation of hepatocellular carcinoma

Identification of novel inhibitors of the transcriptional coactivator MRTF-A for HCC therapy

Myocardin-related transcription factor A (MRTF-A) is a coactivator of serum response factor (SRF), which regulates the expression of genes involved in cell proliferation, migration, and differentiation and has been implicated in hepatocellular carcinoma (HCC) progression. We recently established inhibition of the transcriptional activity of MRTF-A by NS8593 as a novel therapeutic approach for HCC therapy. NS8593 is a negative gating modulator of the transient receptor potential cation channel TRPM7. In this report, we identify an aminobenzimidazole that is highly potent in inhibiting TRPM7 and its interaction with RhoA, leading to decreased SRF transcriptional activity and enhanced nuclear export of MRTF-A, as determined by fluorescence loss in photobleaching (FLIP). This resulted in reduced expression of the MRTF/SRF target genes transforming growth factor β1 (TGF-β1) and tetraspanin 5 (TSPAN5), senescence induction, and growth arrest in HCC cells. Replacement of the tetraline core by a 3-aminophenyl substructure yielded inhibitor 10 with higher potency than inhibitor 5, and further structural modifications yielded highly potent inhibitors of SRF activity, 14 and 16. Both compounds were capable of inhibiting cell proliferation and inducing senescence in HCC cells with improved efficacy compared to NS8593. These inhibitors represent valuable tools for understanding the molecular basis of drug development targeting TRPM7 and MRTFs.

The Antitumor and Sorafenib-resistant Reversal Effects of Ursolic Acid on Hepatocellular Carcinoma via Targeting ING5

Inhibitor of growth 5 (ING5) has been reported to be involved in the malignant progression of cancers. Ursolic acid (UA) has shown remarkable antitumor effects. However, its antitumor mechanisms regarding of ING5 in hepatocellular carcinoma (HCC) remain unclear. Herein, we found that UA significantly suppressed the proliferation, anti-apoptosis, migration and invasion of HCC cells. In addition, ING5 expression in HCC cells treated with UA was obviously downregulated in a concentration- and time-dependent manner. Additionally, the pro-oncogenic role of ING5 was confirmed in HCC cells. Further investigation revealed that UA exerted antitumor effects on HCC by inhibiting ING5-mediated activation of PI3K/Akt pathway. Notably, UA could also reverse sorafenib resistance of HCC cells by suppressing the ING5-ACC1/ACLY-lipid droplets (LDs) axis. UA abrogated ING5 transcription and downregulated its expression by reducing SRF and YY1 expression and the SRF-YY1 complex formation. Alb/JCPyV T antigen mice were used for in vivo experiments since T antigen upregulated ING5 expression by inhibiting the ubiquitin-mediated degradation and promoting the T antigen-SRF-YY1-ING5 complex-associated transcription. UA suppressed JCPyV T antigen-induced spontaneous HCC through inhibiting ING5-mediated PI3K/Akt signaling pathway. These findings suggest that UA has the dual antitumoral functions of inhibiting hepatocellular carcinogenesis and reversing sorafenib resistance of HCC cells through targeting ING5, which could serve as a potential therapeutic strategy for HCC.

MRTF-A gain-of-function in mice impairs homeostatic renewal of the intestinal epithelium

The actin-regulated transcription factor MRTF-A represents a central relay in mechanotransduction and controls a subset of SRF-dependent target genes. However, gain-of-function studies in vivo are lacking. Here we characterize a conditional MRTF-A transgenic mouse model. While MRTF-A gain-of-function impaired embryonic development, induced expression of constitutively active MRTF-A provoked rapid hepatocyte ballooning and liver failure in adult mice. Specific expression in the intestinal epithelium caused an erosive architectural distortion, villus blunting, cryptal hyperplasia and colonic inflammation, resulting in transient weight loss. Organoids from transgenic mice repeatedly induced in vitro showed impaired self-renewal and defective cryptal compartments. Mechanistically, MRTF-A gain-of-function decreased proliferation and increased apoptosis, but did not induce fibrosis. MRTF-A targets including Acta2 and Pai-1 were induced, whereas markers of stem cells and differentiated cells were reduced. Our results suggest that activated MRTF-A in the intestinal epithelium shifts the balance between proliferation, differentiation and apoptosis.

Comprehensive Analysis of the Expression and Prognosis for Lipid Metabolism-Related Genes in Hepatocellular Carcinoma

Hao DingBackground  This study aimed to screen potential key genes associated with lipid metabolism and to evaluate their expressions and prognosis values in hepatocellular carcinoma (HCC). Methods  Data sets GSE6764, GSE14520, and GSE112790 were used to identify the common differentially expressed genes (DEGs). Protein-protein interaction (PPI) network was constructed by STRING database. Hub genes in PPI network were identified and subjected to functional enrichment analysis to screen lipid metabolism-related genes. The expressions of selected genes and their associations with prognosis were analyzed using UALCAN, The Human Protein Atlas, and Kaplan-Meier plotter databases. The transcriptional factor (TF)-gene regulatory network was constructed using NetworkAnalyst. Results  A total of 331 common DEGs including 106 upregulated and 225 downregulated genes were identified. PPI network analysis showed that 76 genes with high degrees were identified as hub genes, among which 14 genes were lipid metabolism-related genes. PON1, CYP2C9, and SPP1 were found to be the independent prognostic markers. Key TFs with close interactions with these prognostic genes, including HINFP, SRF, YY1, and NR3C1, were identified from the TF-gene regulatory network. Conclusion  This study presented evidence for the prognostic capabilities of lipid metabolism-related genes in HCC, and newly identified HINFP and NR3C1 as potential biomarkers for HCC.

Serum Response Factor-Regulated IDO1/Kyn-Ahr Pathway Promotes Tumorigenesis of Oral Squamous Cell Carcinoma

Serum response factor (SRF) regulates pro-carcinogenic genes in various cancers, but its role in oral squamous cell carcinoma (OSCC) remains unclear. SRF expression in 70 OSCC samples was detected via immunohistochemistry. Abundant SRF expressed in OSCC tissues was closely associated with tumor metastasis. SRF-overexpressing OSCC cells were constructed to evaluate how SRF affects OSCC cell tumorigenesis and epithelial-to-mesenchymal transition (EMT) in vitro and in vivo. Overexpressed SRF increased OSCC cell migration and invasion in vitro and tumor growth and invasion in vivo. This promoted EMT, characterized by decreased and increased expression of E- and N-cadherin, respectively. Furthermore, an analysis of RNA sequences of transcriptional targets of SRF showed that SRF transactivated the indoleamine 2, 3-dioxygenase 1 (IDO1)/kynurenine-aryl hydrocarbon receptor (Kyn-AhR) signaling pathway in OSCC cell lines. Direct SRF binding to the IDO1 gene promoter upregulated transcription, which was detected through chromatin immunoprecipitation and dual luciferase reporter assays. Inhibiting IDO1 or AhR impaired SRF-induced migration and invasion and prevented EMT in OSCC cells. Our results demonstrated that SRF is a critical regulator of the IDO1/Kyn-AhR signaling pathway. This in turn increases OSCC cell migration and invasion by modulating EMT, which, consequently, favors OSCC cell growth and metastasis. We revealed a novel molecular mechanism through which SRF modulates OSCC metastasis. This should provide potential targets or biomarkers for OSCC diagnosis and treatment.

RHO GTPase family in hepatocellular carcinoma

RHO GTPases are a subfamily of the RAS superfamily of proteins, which are highly conserved in eukaryotic species and have important biological functions, including actin cytoskeleton reorganization, cell proliferation, cell polarity, and vesicular transport. Recent studies indicate that RHO GTPases participate in the proliferation, migration, invasion and metastasis of cancer, playing an essential role in the tumorigenesis and progression of hepatocellular carcinoma (HCC). This review first introduces the classification, structure, regulators and functions of RHO GTPases, then dissects its role in HCC, especially in migration and metastasis. Finally, we summarize inhibitors targeting RHO GTPases and highlight the issues that should be addressed to improve the potency of these inhibitors.

Smad3 Phospho-Isoform Signaling in Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis with insulin resistance, oxidative stress, lipotoxicity, adipokine secretion by fat cells, endotoxins (lipopolysaccharides) released by gut microbiota, and endoplasmic reticulum stress. Together, these factors promote NAFLD progression from steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and eventually end-stage liver diseases in a proportion of cases. Hepatic fibrosis and carcinogenesis often progress together, sharing inflammatory pathways. However, NASH can lead to hepatocarcinogenesis with minimal inflammation or fibrosis. In such instances, insulin resistance, oxidative stress, and lipotoxicity can directly lead to liver carcinogenesis through genetic and epigenetic alterations. Transforming growth factor (TGF)-β signaling is implicated in hepatic fibrogenesis and carcinogenesis. TGF-β type I receptor (TβRI) and activated-Ras/c-Jun-N-terminal kinase (JNK) differentially phosphorylate the mediator Smad3 to create two phospho-isoforms: C-terminally phosphorylated Smad3 (pSmad3C) and linker-phosphorylated Smad3 (pSmad3L). TβRI/pSmad3C signaling terminates cell proliferation, while constitutive Ras activation and JNK-mediated pSmad3L promote hepatocyte proliferation and carcinogenesis. The pSmad3L signaling pathway also antagonizes cytostatic pSmad3C signaling. This review addresses TGF-β/Smad signaling in hepatic carcinogenesis complicating NASH. We also discuss Smad phospho-isoforms as biomarkers predicting HCC in NASH patients with or without cirrhosis.

Emerging role for the Serum Response Factor (SRF) as a potential therapeutic target in cancer

INTRODUCTION

The Serum Response Factor (SRF) is a transcription factor involved in three hallmarks of cancer: the promotion of cell proliferation, cell death resistance and invasion and metastasis induction. Many studies have demonstrated a leading role in the development and progression of multiple cancer types, thus highlighting the potential of SRF as a prognostic biomarker and therapeutic target, especially for cancers with poor prognosis.

AREAS COVERED

This review examines the role of SRF in several cancers in promoting cellular processes associated with cancer development and progression. SRF co-factors and signalling pathways are discussed as possible targets to inhibit SRF in a tissue and cancer-specific way. Small-molecule inhibitors of SRF, such as the CCGs series of compounds and lestaurtinib, which could be used as cancer therapeutics, are also discussed.

EXPERT OPINION

Targeting of SRF and its co-factors represents a promising therapeutic approach. Further understanding of the molecular mechanisms behind the action of SRF could provide a pipeline of novel molecular targets and therapeutic combinations for cancer. Basket clinical trials and the use of SRF immunohistochemistry as companion diagnostics will help testing of these new targets in patients.

Identification and expression pattern analysis of miRNAs in pectoral muscle during pigeon (Columba livia) development

MicroRNAs (miRNAs) are a group of crucial regulators in the process of animal growth and development. However, little is known about the expression and function of miRNAs in pigeon muscles. To identify the miRNAs participating in the rapid development of pigeon pectoral muscles and quantitate their expression levels of pectoral muscles in different age stages, we performed miRNA transcriptome analysis in pigeon pectoral muscles by sequencing small RNAs over three different age stages (1-day old, 28 days old, and 2 years old). Dual-luciferase reporter assay was applied to validate the interaction between miRNA and its target gene. We identified 304 known miRNAs, 201 conserved miRNAs, and 86 novel miRNAs in pigeon pectoral muscles. 189 differentially expressed (DE) miRNAs were screened out during pigeon development. A short time-series expression miner (STEM) analysis indicated 89 DE miRNAs were significantly clustered in a progressively decreasing expression profile, and mainly enriched in biosynthesis-related GO categories and signaling pathways for MAPK and TGF-β. Dual-luciferase reporter assay indicated that a progressively down-regulated miRNA (miR-20b-5p) could directly target Krüppel-like factor 3 (KLF3) gene. To sum-up, our data expand the repertoire of pigeon miRNAs and enhance understanding of the mechanisms underlying rapid development in squabs.

Serum Response Factor (SRF) Drives the Transcriptional Upregulation of the MDM4 Oncogene in HCC

Different molecular mechanisms support the overexpression of the mouse double minute homolog 4 (MDM4), a functional p53 inhibitor, in human hepatocellular carcinoma (HCC). However, the transcription factors (TFs) leading to its transcriptional upregulation remain unknown. Following promoter and gene expression analyses, putative TFs were investigated using gene-specific siRNAs, cDNAs, luciferase reporter assays, chromatin immunoprecipitation, and XI-011 drug treatment in vitro. Additionally, MDM4 expression was investigated in SRF-VP16iHep transgenic mice. We observed a copy-number-independent upregulation of MDM4 in human HCCs. Serum response factor (SRF), ELK1 and ELK4 were identified as TFs activating MDM4 transcription. While SRF was constitutively detected in TF complexes at the MDM4 promoter, presence of ELK1 and ELK4 was cell-type dependent. Furthermore, MDM4 was upregulated in SRF-VP16-driven murine liver tumors. The pharmacological inhibitor XI-011 exhibited anti-MDM4 activity by downregulating the TFs driving MDM4 transcription, which decreased HCC cell viability and increased apoptosis. In conclusion, SRF drives transcriptional MDM4 upregulation in HCC, acting in concert with either ELK1 or ELK4. The transcriptional regulation of MDM4 may be a promising target for precision oncology of human HCC, as XI-011 treatment exerts anti-MDM4 activity independent from the MDM4 copy number and the p53 status.

Molecular Mechanisms to Target Cellular Senescence in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has emerged as a major cause of cancer-related death and is the most common type of liver cancer. Due to the current paucity of drugs for HCC therapy there is a pressing need to develop new therapeutic concepts. In recent years, the role of Serum Response Factor (SRF) and its coactivators, Myocardin-Related Transcription Factors A and B (MRTF-A and -B), in HCC formation and progression has received considerable attention. Targeting MRTFs results in HCC growth arrest provoked by oncogene-induced senescence. The induction of senescence acts as a tumor-suppressive mechanism and therefore gains consideration for pharmacological interventions in cancer therapy. In this article, we describe the key features and the functional role of senescence in light of the development of novel drug targets for HCC therapy with a focus on MRTFs.

Lineage tracing: technology tool for exploring the development, regeneration, and disease of the digestive system

Lineage tracing is the most widely used technique to track the migration, proliferation, and differentiation of specific cells in vivo. The currently available gene-targeting technologies have been developing for decades to study organogenesis, tissue injury repairing, and tumor progression by tracing the fates of individual cells. Recently, lineage tracing has expanded the platforms available for disease model establishment, drug screening, cell plasticity research, and personalized medicine development in a molecular and cellular biology perspective. Lineage tracing provides new views for exploring digestive organ development and regeneration and techniques for digestive disease causes and progression. This review focuses on the lineage tracing technology and its application in digestive diseases.

Identification of key miRNAs in the progression of hepatocellular carcinoma using an integrated bioinformatics approach

Backgroud

It has been shown that aberrant expression of microRNAs (miRNAs) and transcriptional factors (TFs) is tightly associated with the development of HCC. Therefore, in order to further understand the pathogenesis of HCC, it is necessary to systematically study the relationship between the expression of miRNAs, TF and genes. In this study, we aim to identify the potential transcriptomic markers of HCC through analyzing common microarray datasets, and further establish the differential co-expression network of miRNAs-TF-mRNA to screen for key miRNAs as candidate diagnostic markers for HCC.

Method

We first downloaded the mRNA and miRNA expression profiles of liver cancer from the GEO database. After pretreatment, we used a linear model to screen for differentially expressed genes (DEGs) and miRNAs. Further, we used weighed gene co-expression network analysis (WGCNA) to construct the differential gene co-expression network for these DEGs. Next, we identified mRNA modules significantly related to tumorigenesis in this network, and evaluated the relationship between mRNAs and TFs by TFBtools. Finally, the key miRNA was screened out in the mRNA-TF-miRNA ternary network constructed based on the target TF of differentially expressed miRNAs, and was further verified with external data set.

Results

A total of 465 DEGs and 215 differentially expressed miRNAs were identified through differential genes expression analysis, and WGCNA was used to establish a co-expression network of DEGs. One module that closely related to tumorigenesis was obtained, including 33 genes. Next, a ternary network was constructed by selecting 256 pairs of mRNA-TF pairs and 100 pairs of miRNA-TF pairs. Network mining revealed that there were significant interactions between 18 mRNAs and 25 miRNAs. Finally, we used another independent data set to verify that miRNA hsa-mir-106b and hsa-mir-195 are good classifiers of HCC and might play key roles in the progression of HCC.

Conclusion

Our data indicated that two miRNAs-hsa-mir-106b and hsa-mir-195-are identified as good classifiers of HCC.

The correlation and role analysis of COL4A1 and COL4A2 in hepatocarcinogenesis

Liver fibrosis biomarker, Type IV collagen, may function as hepatocarcinogenesis niche. However, among the six isoforms, the isoforms providing tumor microenvironment and their regulatory network are still unclarified. Based on bioinformatics analysis of hundreds of HCC transcriptome datasets from public databases, we found that COL4A1/2 expressions were significantly correlated with hepatocarcinogenesis, progression, and prognosis. The expressions of COL4A1/2 were significantly upregulated in the preneoplastic and HCC tissues compared with normal tissues. Moreover, the overexpression of COL4A2 was highly correlated with shorter progression-free survival in HCC patients. Bioinformatics analysis also generates an interactive regulatory network in which COL4A1/2 directly binding to integrin alpha-2/beta-1 initiates a sequentially and complicated signaling transduction, to accelerate cell cycle and promote tumorigenesis. Among those pathways, the PI3K-Akt pathway is significantly enriched in cooperative mutations and correlation analysis. This suggests that the key activated signaling is PI3K-Akt pathway which severing as the centerline linked with other pathways (Wnt and MAPK signaling) and cell behaviors signaling (cell cycle control and cytoskeleton change). Switching extracellular matrix collagen isoform may establish pro-tumorigenic and metastatic niches. The findings of COL4A1/2 and related signaling networks are valuable to be further investigated that may provide druggable targets for HCC intervention.

Identification of Pparγ-modulated miRNA hubs that target the fibrotic tumor microenvironment

Liver fibrosis interferes with normal organ function and supports tumor development in the liver. We uncovered a role of miRNAs in controlling liver fibrosis. In a comprehensive and systematic analysis we specify miRNA activities in targeting the fibrotic cellular microenvironment of the liver, in both mice and humans. We reveal and validate a complex network of 8 functionally connected miRNAs and 54 target genes to regulate structural, signaling, and remodeling components of the fibrotic extracellular matrix. We identify expression of this miRNA network to be controlled by the transcription factor Pparγ. Thus, we expand the antifibrotic function of Pparγ to controlling the synthesis of an antifibrotic miRNA network. This network may serve as a therapeutic target in antifibrotic therapies.

Liver fibrosis interferes with normal liver function and facilitates hepatocellular carcinoma (HCC) development, representing a major threat to human health. Here, we present a comprehensive perspective of microRNA (miRNA) function on targeting the fibrotic microenvironment. Starting from a murine HCC model, we identify a miRNA network composed of 8 miRNA hubs and 54 target genes. We show that let-7, miR-30, miR-29c, miR-335, and miR-338 (collectively termed antifibrotic microRNAs [AF-miRNAs]) down-regulate key structural, signaling, and remodeling components of the extracellular matrix. During fibrogenic transition, these miRNAs are transcriptionally regulated by the transcription factor Pparγ and thus we identify a role of Pparγ as regulator of a functionally related class of AF-miRNAs. The miRNA network is active in human HCC, breast, and lung carcinomas, as well as in 2 independent mouse liver fibrosis models. Therefore, we identify a miRNA:mRNA network that contributes to formation of fibrosis in tumorous and nontumorous organs of mice and humans.

Inhibition of TRPM7 blocks MRTF/SRF-dependent transcriptional and tumorigenic activity

Myocardin-related transcription factors A and B (MRTFs) are coactivators of Serum Response Factor (SRF) that mediates the expression of genes involved in cell proliferation, migration and differentiation. There is mounting evidence that MRTFs and SRF represent promising targets for hepatocellular carcinoma (HCC) growth. Since MRTF-A nuclear localization is a prerequisite for its transcriptional activity and oncogenic properties, we searched for pharmacologically active compounds able to redistribute MRTF-A to the cytoplasm. We identified NS8593, a negative gating modulator of the transient receptor potential cation channel TRPM7, as a novel inhibitor of MRTF-A nuclear localization and transcriptional activity. Using a pharmacological approach and targeted genome editing, we investigated the functional contribution of TRPM7, a unique ion channel containing a serine-threonine kinase domain, to MRTF transcriptional and tumorigenic activity. We found that TRPM7 function regulates RhoA activity and subsequently actin polymerization, MRTF-A-Filamin A complex formation and MRTF-A/SRF target gene expression. Mechanistically, TRPM7 signaling relies on TRPM7 channel-mediated Mg²⁺ influx and phosphorylation of RhoA by TRPM7 kinase. Pharmacological blockade of TRPM7 results in oncogene-induced senescence of hepatocellular carcinoma (HCC) cells in vitro and in vivo in HCC xenografts. Hence, inhibition of the TRPM7/MRTF axis emerges as a promising strategy to curb HCC growth.

Myoferlin, a Membrane Protein with Emerging Oncogenic Roles

Myoferlin (MYOF), initially identified in muscle cells, is a member of the Ferlin family involved in membrane fusion, membrane repair, and membrane trafficking. Dysfunction of this protein is associated with muscular dysfunction. Recently, a growing body of studies have identified MYOF as an oncogenic protein. It is overexpressed in a variety of human cancers and promotes tumorigenesis, tumor cell motility, proliferation, migration, epithelial to mesenchymal transition, angiogenesis as well as metastasis. Clinically, MYOF overexpression is associated with poor outcome in various cancers. It can serve as a prognostic marker of human malignant disease. MYOF drives the progression of cancer in various processes, including surface receptor transportation, endocytosis, exocytosis, intercellular communication, fit mitochondrial structure maintenance and cell metabolism. Depletion of MYOF demonstrates significant antitumor effects both in vitro and in vivo, suggesting that targeting MYOF may produce promising clinical benefits in the treatment of malignant disease. In the present article, we reviewed the physiological function of MYOF as well as its role in cancer, thus providing a general understanding for further exploration of this protein.

An IKK/NF-κB Activation/p53 Deletion Sequence Drives Liver Carcinogenesis and Tumor Differentiation

Background: Most liver tumors arise on the basis of chronic liver diseases that trigger inflammatory responses. Besides inflammation, subsequent defects in the p53-signaling pathway frequently occurs in liver cancer. In this study, we analyzed the consequences of inflammation and p53 loss in liver carcinogenesis. Methods: We used inducible liver-specific transgenic mouse strains to analyze the consequences of NF-κB/p65 activation mimicking chronic inflammation and subsequent p53 loss. Results: Ikk2^ca driven NF-κB/p65 activation in mice results in liver fibrosis, the formation of ectopic lymphoid structures and carcinogenesis independent of p53 expression. Subsequent deletion of Trp53 led to an increased tumor formation, metastasis and a shift in tumor differentiation towards intrahepatic cholangiocarcinoma. In addition, loss of Trp53 in an inflammatory liver resulted in elevated chromosomal instability and indicated a distinct aberration pattern. Conclusions: In conclusion, activation of NF-κB/p65 mimicking chronic inflammation provokes the formation of liver carcinoma. Collateral disruption of Trp53 supports tumor progression and influences tumor differentiation and heterogeneity.

Arsenic trioxide inhibits liver cancer stem cells and metastasis by targeting SRF/MCM7 complex

Hepatocellular carcinoma (HCC) has a high mortality rate due to the lack of effective treatments and drugs. Arsenic trioxide (ATO), which has been proved to successfully treat acute promyelocytic leukemia (APL), was recently reported to show therapeutic potential in solid tumors including HCC. However, its anticancer mechanisms in HCC still need further investigation. In this study, we demonstrated that ATO inhibits tumorigenesis and distant metastasis in mouse models, corresponding with a prolonged mice survival time. Also, ATO was found to significantly decrease the cancer stem cell (CSC)-associated traits. Minichromosome maintenance protein (MCM) 7 was further identified to be a potential target suppressed dramatically by ATO, of which protein expression is increased in patients and significantly correlated with tumor size, cellular differentiation, portal venous emboli, and poor patient survival. Moreover, MCM7 knockdown recapitulates the effects of ATO on CSCs and metastasis, while ectopic expression of MCM7 abolishes them. Mechanistically, our results suggested that ATO suppresses MCM7 transcription by targeting serum response factor (SRF)/MCM7 complex, which functions as an important transcriptional regulator modulating MCM7 expression. Taken together, our findings highlight the importance of ATO in the treatment of solid tumors. The identification of SRF/MCM7 complex as a target of ATO provides new insights into ATO’s mechanism, which may benefit the appropriate use of this agent in the treatment of HCC.

Modulation of YrdC promotes hepatocellular carcinoma progression via MEK/ERK signaling pathway

Accumulating evidence suggested that YrdC involved in growth, telomere homeostasis, translation and the N6-threonylcarbamoylation (t6A) of tRNA was abnormally expressed in the progression of tumor. However, the role of YrdC in hepatocellular carcinoma remained elusive. Our study aimed to investigate the clinical significance and oncogenic phenotypes of YrdC in hepatocellular carcinoma, and to determine its related mechanism of this disease. With the usage of GEO datasets, we analyzed the expression of YrdC in hepatocellular carcinoma (HCC). Kaplan-Meier survival analysis was used to evaluate the prognostic significance of hepatocellular carcinoma patients in TCGA. Gain- and loss-of-function analyses in vitro of YrdC were also performed to evaluate its effects on oncogenic phenotypes and relevant signaling pathways. YrdC expression was not only dysregulated in hepatocellular carcinoma tissue but also related to the prognosis of patients with hepatocellular carcinoma. In addition, YrdC depletion suppressed the capability of proliferation, migration and invasion of huh7 cells, while there was opposite result for YrdC overexpression. Our data also unraveled that YrdC promoted the progression of HCC by activating MEK/ERK signaling pathways. Together, our findings indicated that YrdC was a potential prognosis marker for hepatocellular carcinoma, and therapeutic strategies targeting YrdC might hold promise in improving the treatment of hepatocellular carcinoma.

Epilepsy Associates with Decreased HIF-1α/STAT5b Signaling in Glioblastoma

Epilepsy at presentation is an independent favorable prognostic factor in glioblastoma (GBM). In this study, we analyze the oncologic signaling pathways that associate with epilepsy in human GBMs, and that can underlie this prognostic effect. Following ethical approval and patient consent, fresh frozen GBM tissue was obtained from 76 patient surgeries. Hospital records were screened for the presence of seizures at presentation of the disease. mRNA and miRNA expression-based and gene set enrichment analyses were performed on these tissues, to uncover candidate oncologic pathways that associate with epilepsy. We performed qPCR experiments and immunohistochemistry on tissue microarrays containing 286 GBMs to further explore the association of these candidate pathways and of markers of mesenchymal transformation (NF-κB, CEBP-β, STAT3, STAT5b, VEGFA, SRF) with epilepsy. Gene sets involved in hypoxia/HIF-1α, STAT5, CEBP-β and epithelial-mesenchymal transformation signaling were significantly downregulated in epileptogenic GBMs. On confirmatory protein expression analyses, epileptogenic tumors were characterized by a significant downregulation of phospho-STAT5b, a target of HIF-1α. Epilepsy status did not associate with molecular subclassification or miRNA expression patterns of the tumors. Epileptogenic GBMs correlate with decreased hypoxia/ HIF-1α/STAT5b signaling compared to glioblastomas that do not present with epilepsy.

Confounding influence of tamoxifen in mouse models of Cre recombinase-induced gene activity or modulation

Tamoxifen (TAM) is commonly used for cell type specific Cre recombinase-induced gene inactivation and in cell fate tracing studies. Inducing a gene knockout by TAM and using non-TAM exposed mice as controls lead to a situation where differences are interpreted as consequences of the gene knockout but in reality result from TAM-induced changes in hepatic metabolism. The degree to which TAM may compromise the interpretation of animal experiments with inducible gene expression still has to be elucidated. Here, we report that TAM strongly attenuates CCl₄-induced hepatotoxicity in male C57Bl/6N mice, even after a 10 days TAM exposure-free period. TAM decreased (p < 0.0001) the necrosis index and the level of aspartate- and alanine transaminases in CCl₄-treated compared to vehicle-exposed mice. TAM pretreatment also led to the downregulation of CYP2E1 (p = 0.0045) in mouse liver tissue, and lowered its activity in CYP2E1 expressing HepG2 cell line. Furthermore, TAM increased the level of the antioxidant ascorbate, catalase, SOD2, and methionine, as well as phase II metabolizing enzymes GSTM1 and UGT1A1 in CCl₄-treated livers. Finally, we found that TAM increased the presence of resident macrophages and recruitment of immune cells in necrotic areas of the livers as indicated by F4/80 and CD45 staining. In conclusion, we reveal that TAM increases liver resistance to CCl₄-induced toxicity. This finding is of high relevance for studies using the tamoxifen-inducible expression system particularly if this system is used in combination with hepatotoxic compounds such as CCl₄.

Transgenic expression of the RNA binding protein IMP2 stabilizes miRNA targets in murine microsteatosis

Adult expression of IMP2 is often associated with several types of disease and cancer. The RNA binding protein IMP2 binds and stabilizes the IGF2 mRNA as well as hundreds of other transcripts during development. To gain insight into the molecular action of IMP2 and its contribution to disease in context of adult cellular metabolism, we analyze transgenic overexpression of IMP2 in mouse livers, which has been shown to induce a steatosis-like phenotype and enhanced risk to develop hepatocellular carcinoma (HCC). Our data show up-regulation of several HCC marker genes and miRNAs (miR438-3p and miR151-5p). To characterize the impact of miRNAs to their targets, integrative analysis of transcriptome-and miRNAome-dynamics in combination with IMP2 target prediction was carried out. Our analyses show that targets of expressed miRNAs become accumulated in the case that these transcripts have positive IMP2 binding prediction. Therefore, our data indicates that overexpression of IMP2 alters the regulatory capacity of many miRNAs and we conclude that IMP2 competes with miRNAs for binding sites on thousands of transcripts. As a result, our data implicates that overexpression of IMP2 has distinct effects to the regulatory capacity of miRNAs with yet unknown consequences for translational efficiency.

Decreased expression of long non-coding RNA LOC728290 in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-associated mortality worldwide. Despite progress in the diagnosis and treatment of HCC, prognosis remains unfavorable. Long non-coding RNAs (lncRNAs) are emerging as important factors in tumorigenesis and cancer progression; however, the underlying molecular mechanisms and clinical significance of lncRNAs in HCC remain largely unknown. The present study examined the expression pattern and clinical significance of a novel lncRNA, LOC728290, in HCC. Expression of LOC728290 was markedly decreased in HCC tissues compared with adjacent non-tumor liver tissues, as detected using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The area under the receiver operating characteristic curve for LOC728290 was 0.728. The expression of LOC728290 was associated with the level of α-fetoprotein and microvascular invasion. Furthermore, patients with low LOC728290 expression exhibited decreased recurrence-free survival times (P<0.05) compared with those with high LOC728290 expression. The results of the present study indicated that downregulation of LOC728290 in patients with HCC may be a powerful tumor biomarker, with potential clinical applications in prognosis as well as a therapeutic target.

Genotype-phenotype correlation of CTNNB1 mutations reveals different ß-catenin activity associated with liver tumor progression

CTNNB1 mutations activating ß-catenin are frequent somatic events in hepatocellular carcinoma (HCC) and adenoma (HCA), particularly associated with a risk of malignant transformation. We aimed to understand the relationship between CTNNB1 mutation types, tumor phenotype, and level of ß-catenin activation in malignant transformation. To this purpose, CTNNB1 mutation spectrum was analyzed in 220 HCAs, 373 HCCs, and 17 borderline HCA/HCC lesions. ß-catenin activation level was assessed in tumors by quantitative reverse-transcriptase polymerase chain reaction and immunohistochemistry (IHC), in cellulo by TOP-Flash assay. Overall, ß-catenin activity was higher in malignant mutated tumors, compared to adenomas, and this was related to a different spectrum of CTNNB1 mutations in HCCs and HCAs. In benign tumors, we defined three levels of ß-catenin activation related to specific mutations: (1) S45, K335, and N387 mutations led to weak activation; (2) T41 mutations were related to moderate activity; and (3) highly active mutations included exon 3 deletions and amino acid substitutions within the ß-TRCP binding site (D32-S37). Accordingly, in vitro, K335I and N387K mutants showed a lower activity than S33C. Tumors with highly active mutations demonstrated strong/homogeneous glutamine synthase (GS) staining and were associated with malignancy. In contrast, weak mutants demonstrated heterogeneous pattern of GS staining and were more frequent in HCAs except for the S45 mutants identified similarly in 20% of mutated HCAs and HCCs; however, in most of the HCCs, the weak S45 mutant alleles were duplicated, resulting in a final high ß-catenin activity.

CONCLUSION

High ß-catenin activity driven by specific CTNNB1 mutations and S45 allele duplication is associated with malignant transformation. Consequently, HCAs with S45 and all high/moderate mutants should be identified with precise IHC criteria or mutation screening. (Hepatology 2016;64:2047-2061).

Application of HC-AFW1 Hepatocarcinoma Cells for Mechanistic Studies: Regulation of Cytochrome P450 2B6 Expression by Dimethyl Sulfoxide and Early Growth Response 1

Various exogenous compounds, for example, the drugs bupropione and propofol, but also various cytostatics, are metabolized in the liver by the enzyme cytochrome P450 (P450) CYP2B6. Transcription from the CYP2B6 gene is regulated mainly via the transcription factors constitutive androstane receptor (CAR) and pregnane-X-receptor (PXR). Most hepatic cell lines express no or only low levels of CYP2B6 because of loss of these two regulators. Dimethyl sulfoxide (DMSO) is frequently used in liver cell cultivation and is thought to affect the expression of various P450 isoforms by inducing or preserving cellular differentiation. We studied the effects of up to 1.5% of DMSO as cell culture medium supplement on P450 expression in hepatocarcinoma cells from line HC-AFW1. DMSO did not induce differentiation of the HC-AFW1 cell line, as demonstrated by unaltered levels of selected mRNA markers important for hepatocyte differentiation, and also by the lack of a DMSO effect on a broader spectrum of P450s. By contrast, CYP2B6 mRNA was strongly induced by DMSO. This process was independent of CAR or PXR activation. Interestingly, elevated transcription of CYP2B6 was accompanied by a simultaneous induction of early growth response 1 (EGR1), a transcription factor known to influence the expression of CYP2B6. Expression of wild-type EGR1 or of a truncated, dominant-negative EGR1 mutant was able to mimic or attenuate the DMSO effect, respectively. These findings demonstrate that EGR1 is involved in the regulation of CYP2B6 by DMSO in HC-AFW1 cells.

The Ras/MAPK pathway and hepatocarcinoma: pathogenesis and therapeutic implications

BACKGROUND

Hepatocellular carcinoma (HCC) is still a major health problem, often diagnosed at an advanced stage. The multikinase inhibitor sorafenib is to date the sole approved systemic therapy. Several signalling pathways are implicated in tumour development and progression. Among these pathways, the Ras/MAPK pathway is activated in 50-100% of human HCCs and is correlated with a poor prognosis. The aim of this work was to review the main intracellular mechanisms leading to aberrant Ras pathway activation in HCC and the potential therapeutic implications.

MATERIALS AND METHODS

This review is based on the material found on PubMed up to December 2014. 'Ras signaling, Ras dysregulation, Ras inhibition, MAPK pathway, cancer, hepatocarcinoma and liver cancer' alone or in combination were the main terms used for online research.

RESULTS

Multiple mechanisms lead to the deregulation of the Ras pathway in liver cancer. Ras and Raf gene mutations are rare events in human hepatocarcinogenesis in contrast to experimental models in rodents. Downregulation of several Ras/MAPK pathway inhibitors such as GAPs, RASSF proteins, DUSP1, Sprouty and Spred proteins is largely implicated in the aberrant activation of this pathway in the context of wild-type Ras and Raf genes. Epigenetic or post-transcriptional mechanisms lead to the downregulation of these tumour suppressor genes.

CONCLUSION

Ras/MAPK pathway effectors may be considered as potential therapeutic targets in the field of HCC. In particular after the arrival of sorafenib, more Ras/MAPK inhibitors have emerged and are still in preclinical or clinical investigation for HCC therapy.