Synergistic role of Sprouty2 inactivation and c-Met up-regulation in mouse and human hepatocarcinogenesis

NEDD4 and NEDD4L: Ubiquitin Ligases Closely Related to Digestive Diseases

Protein ubiquitination is an enzymatic cascade reaction and serves as an important protein post-translational modification (PTM) that is involved in the vast majority of cellular life activities. The key enzyme in the ubiquitination process is E3 ubiquitin ligase (E3), which catalyzes the binding of ubiquitin (Ub) to the protein substrate and influences substrate specificity. In recent years, the relationship between the subfamily of neuron-expressed developmental downregulation 4 (NEDD4), which belongs to the E3 ligase system, and digestive diseases has drawn widespread attention. Numerous studies have shown that NEDD4 and NEDD4L of the NEDD4 family can regulate the digestive function, as well as a series of related physiological and pathological processes, by controlling the subsequent degradation of proteins such as PTEN, c-Myc, and P21, along with substrate ubiquitination. In this article, we reviewed the appropriate functions of NEDD4 and NEDD4L in digestive diseases including cell proliferation, invasion, metastasis, chemotherapeutic drug resistance, and multiple signaling pathways, based on the currently available research evidence for the purpose of providing new ideas for the prevention and treatment of digestive diseases.

Loss of TP53 cooperates with c-MET overexpression to drive hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a deadly malignancy with high genetic heterogeneity. TP53 mutation and c-MET activation are frequent events in human HCCs. Here, we discovered that the simultaneous mutations in TP53 and activation of c-MET occur in ~20% of human HCCs, and these patients show a poor prognosis. Importantly, we found that concomitant deletion of Trp53 and overexpression of c-MET (c-MET/sgp53) in the mouse liver led to HCC formation in vivo. Consistent with human HCCs, RNAseq showed that c-MET/sgp53 mouse HCCs were characterized by activated c-MET and Ras/MAPK cascades and increased tumor cell proliferation. Subsequently, a stably passaged cell line derived from a c-MET/sgp53 HCC and corresponding subcutaneous xenografts were generated. Also, in silico analysis suggested that the MEK inhibitor trametinib has a higher inhibition score in TP53 null human HCC cell lines, which was validated experimentally. We consistently found that trametinib effectively inhibited the growth of c-MET/sgp53 HCC cells and xenografts, supporting the possible usefulness of this drug for treating human HCCs with TP53-null mutations. Altogether, our study demonstrates that loss of TP53 cooperates with c-MET to drive hepatocarcinogenesis in vivo. The c-MET/sgp53 mouse model and derived HCC cell lines represent novel and useful preclinical tools to study hepatocarcinogenesis in the TP53 null background.

Targeting the effect of sofosbuvir on selective oncogenes expression level of hepatocellular carcinoma Ras/Raf/MEK/ERK pathway in Huh7 cell line

Direct acting antiviral agents are emerging line of treatment to eradicate Hepatitis C virus. Recent controversy over whether direct acting antiviral agents increase rate of hepatocellular carcinoma in HCV patients or prevent it, has increased the need to elaborate underlying mechanisms on molecular basis. This work was aimed to investigate the effect of sofosbuvir on the expression of selected oncogenes from the Ras/Raf/MEK/ERK pathway in Huh7 cell line. Results found concrete molecular evidence that sofosbuvir has significantly altered the expression of selected genes when huh7 cell line was treated with sofosbuvir. Nine genes related to HCC were found to be affected by sofosbuvir in a mixed effect manner. The relative expression of growth factors (VEGF, PDGFRB and HGF) was increased in sofosbuvir treated cell lines. The kinase family genes H-RAS, B-RAF, MET except MAPK1 were downregulated. Similarly, DUSP1 was upregulated and SPRY2 was slightly downregulated; both were negative feedback inhibitors of ERK signalling cascade. Sofosbuvir upregulated the growth factors and MAPK1 which suggests it to be a carcinogen. The downregulation of kinases and upregulation of DUSP1 make it an anticancer drug. Hence, the results from this study are important to prove that sofosbuvir neither reduce nor induce hepatocellular carcinoma.

DYRK1A inhibitors for disease therapy: Current status and perspectives

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is a conserved protein kinase that plays essential roles in various biological processes. It is located in the region q22.2 of chromosome 21, which is involved in the pathogenesis of Down syndrome (DS). Moreover, DYRK1A has been shown to promote the accumulation of amyloid beta (Aβ) peptides leading to gradual Tau hyperphosphorylation, which contributes to neurodegeneration. Additionally, alterations in the DRK1A expression are also associated with cancer and diabetes. Recent years have witnessed an explosive increase in the development of DYRK1A inhibitors. A variety of novel DYRK1A inhibitors have been reported as potential treatments for human diseases. In this review, the latest therapeutic potential of DYRK1A for different diseases and the novel DYRK1A inhibitors discoveries are summarized, guiding future inhibitor development and structural optimization.

Integrative Bioinformatics approaches to therapeutic gene target selection in various cancers for Nitroglycerin

Integrative Bioinformatics analysis helps to explore various mechanisms of Nitroglycerin activity in different types of cancers and help predict target genes through which Nitroglycerin affect cancers. Many publicly available databases and tools were used for our study. First step in this study is identification of Interconnected Genes. Using Pubchem and SwissTargetPrediction Direct Target Genes (activator, inhibitor, agonist and suppressor) of Nitroglycerin were identified. PPI network was constructed to identify different types of cancers that the 12 direct target genes affected and the Closeness Coefficient of the direct target genes so identified. Pathway analysis was performed to ascertain biomolecules functions for the direct target genes using CluePedia App. Mutation Analysis revealed Mutated Genes and types of cancers that are affected by the mutated genes. While the PPI network construction revealed the types of cancer that are affected by 12 target genes this step reveals the types of cancers affected by mutated cancers only. Only mutated genes were chosen for further study. These mutated genes were input into STRING to perform NW Analysis. NW Analysis revealed Interconnected Genes within the mutated genes as identified above. Second Step in this study is to predict and identify Upregulated and Downregulated genes. Data Sets for the identified cancers from the above procedure were obtained from GEO Database. DEG Analysis on the above Data sets was performed to predict Upregulated and Downregulated genes. A comparison of interconnected genes identified in step 1 with Upregulated and Downregulated genes obtained in step 2 revealed Co-Expressed Genes among Interconnected Genes. NW Analysis using STRING was performed on Co-Expressed Genes to ascertain Closeness Coefficient of Co-Expressed genes. Gene Ontology was performed on Co-Expressed Genes to ascertain their Functions. Pathway Analysis was performed on Co-Expressed Genes to identify the Types of Cancers that are influenced by co-expressed genes. The four types of cancers identified in Mutation analysis in step 1 were the same as the ones that were identified in this pathway analysis. This further corroborates the 4 types of cancers identified in Mutation analysis. Survival Analysis was done on the co-expressed genes as identified above using Survexpress. BIOMARKERS for Nitroglycerin were identified for four types of cancers through Survival Analysis. The four types of cancers are Bladder cancer, Endometrial cancer, Melanoma and Non-small cell lung cancer.

Epigenetic DNA Modifications Upregulate SPRY2 in Human Colorectal Cancers

Conventional wisdom is that Sprouty2 (SPRY2), a suppressor of Receptor Tyrosine Kinase (RTK) signaling, functions as a tumor suppressor and is downregulated in many solid tumors. We reported, for the first time, that increased expression of SPRY2 augments cancer phenotype and Epithelial-Mesenchymal-Transition (EMT) in colorectal cancer (CRC). In this report, we assessed epigenetic DNA modifications that regulate SPRY2 expression in CRC. A total of 4 loci within SPRY2 were evaluated for 5mC using Combined Bisulfite Restriction Analysis (COBRA). Previously sequenced 5hmC nano-hmC seal data within SPRY2 promoter and gene body were evaluated in CRC. Combined bioinformatics analyses of SPRY2 CRC transcripts by RNA-seq/microarray and 450K methyl-array data archived in The Cancer Genome Atlas (TCGA) and GEO database were performed. SPRY2 protein in CRC tumors and cells was measured by Western blotting. Increased SPRY2 mRNA was observed across several CRC datasets and increased protein expression was observed among CRC patient samples. For the first time, SPRY2 hypomethylation was identified in adenocarcinomas in the promoter and gene body. We also revealed, for the first time, increases of 5hmC deposition in the promoter region of SPRY2 in CRC. SPRY2 promoter hypomethylation and increased 5hmC may play an influential role in upregulating SPRY2 in CRC.

Cabozantinib-based combination therapy for the treatment of hepatocellular carcinoma

OBJECTIVE

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with limited treatment options. Cabozantinib, an orally bioavailable multikinase inhibitor is now approved by Food and Drug Administration (FDA) for HCC patients. We evaluated the therapeutic efficacy of cabozantinib, either alone or in combination, in vitro and in vivo.

DESIGN

Human HCC cell lines and HCC mouse models were used to assess the therapeutic efficacy and targeted molecular pathways of cabozantinib, either alone or in combination with the pan-mTOR inhibitor MLN0128 or the checkpoint inhibitor anti-PD-L1 antibody.

RESULTS

Cabozantinib treatment led to stable disease in c-Met/β-catenin and Akt/c-Met mouse HCC while possessing limited efficacy on Akt/Ras and c-Myc liver tumours. Importantly, cabozantinib effectively inhibited c-MET and ERK activity, leading to decreased PKM2 and increased p21 expression in HCC cells and in c-Met/β-catenin and Akt/c-Met HCC. However, cabozantinib was ineffective in inhibiting the Akt/mTOR cascade. Intriguingly, a strong inhibition of angiogenesis by cabozantinib occurred regardless of the oncogenic drivers. However, cabozantinib had limited impact on other tumour microenvironment parameters, including tumour infiltrating T cells, and did not induce programmed death-ligand 1 (PD-L1) expression. Combining cabozantinib with MLN0128 led to tumour regression in c-Met/β-catenin mice. In contrast, combined treatment with cabozantinib and the checkpoint inhibitor anti-PD-L1 antibody did not provide any additional therapeutic benefit in the four mouse HCC models tested.

CONCLUSION

c-MET/ERK/p21/PKM2 cascade and VEGFR2-induced angiogenesis are the primary targets of cabozantinib in HCC treatment. Combination therapies with cabozantinib and mTOR inhibitors may be effective against human HCC.

MAPK/ERK Signaling Pathway in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a major health concern worldwide, and its incidence is increasing steadily. Recently, the MAPK/ERK signaling pathway in HCC has gained renewed attention from basic and clinical researchers. The MAPK/ERK signaling pathway is activated in more than 50% of human HCC cases; however, activating mutations in RAS and RAF genes are rarely found in HCC, which are major genetic events leading to the activation of the MAPK/ERK signaling pathway in other cancers. This suggests that there is an alternative mechanism behind the activation of the signaling pathway in HCC. Here, we will review recent advances in understanding the cellular and molecular mechanisms involved in the activation of the MAPK/ERK signaling pathway and discuss potential therapeutic strategies targeting the signaling pathway in the context of HCC.

NEDD4 Induces K48-Linked Degradative Ubiquitination of Hepatitis B Virus X Protein and Inhibits HBV-Associated HCC Progression

Neural precursor cell expressed developmentally downregulated gene 4 (NEDD4) plays two opposite roles in carcinogenesis. It has been reported that NEDD4 inhibits hepatocellular carcinoma (HCC) progression; however, little is known about its potential function and molecular mechanism in HCC in the context of hepatitis B virus (HBV) infection. In this study, we analyzed NEDD4 expression in 199 HCC specimens with or without HBV infection and observed that NEDD4 expression was unrelated to HBV exposure in HCC tumor tissue but that high NEDD4 expression conferred better overall survival (OS) and progression-free survival (PFS) than low NEDD4 expression in patients with HBV-associated HCC. Upregulation of NEDD4 inhibited proliferation, migration and invasion in HBV-related HCC cell lines. We demonstrated that NEDD4 interacts with HBV X protein (HBx) and that HBx upregulation could reverse the suppression of proliferation and mobility induced by NEDD4 overexpression. Furthermore, we confirmed that NEDD4 induced the degradation of HBx in a ubiquitin/proteasome-dependent manner via K48-linked ubiquitination. Our findings suggest that NEDD4 exerts a tumor-suppressive effect in HBV-associated HCC by acting as an E3 ubiquitin ligase for HBx degradation and provide new insights into the function of NEDD4.

NEDD4 E3 ligase: Functions and mechanism in human cancer

A growing amount of evidence indicates that the neuronally expressed developmentally downregulated 4 (NEDD4, also known as NEDD4-1) E3 ligase plays a critical role in a variety of cellular processes via the ubiquitination-mediated degradation of multiple substrates. The abnormal regulation of NEDD4 protein has been implicated in cancer development and progression. In this review article, we briefly delineate the downstream substrates and upstream regulators of NEDD4, which are involved in carcinogenesis. Moreover, we succinctly elucidate the functions of NEDD4 protein in tumorigenesis and progression, including cell proliferation, apoptosis, cell cycle, migration, invasion, epithelial mesenchymal transition (EMT), cancer stem cells, and drug resistance. The findings regarding NEDD4 functions are further supported by knockout mouse models and human tumor tissue studies. This review could provide a promising and optimum anticancer therapeutic strategy via targeting the NEDD4 protein.

Licocoumarone induces BxPC-3 pancreatic adenocarcinoma cell death by inhibiting DYRK1A

Protein kinases play an indispensable role in signaling pathways that regulate tumor cell functions, which represent potent therapeutic targets in cancers. Dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) as a serine/threonine kinase has recently been reported to be upregulated in pancreatic ductal adenocarcinoma (PDAC) and show protumorigenic effect. By activity-guided phytochemical investigation of the extracts from Glycyrrhiza uralensis Fisch, we expect to find the effective constituents that can suppress pancreatic cancer cell proliferation and/or induce cells apoptotic by inhibiting DYRK1A. Eight isopentenyl-substituted compounds (1-8), including four coumarins (1-4), one benzofuran (5), and three flavonoids (6-8), were isolated and identified from G. uralensis Fisch. Among them, licocoumarone (LC, 5) showed effective inhibitory activity against DYRK1A with an IC50 value of 12.56 μM. Molecular docking analysis suggested that LC completely occupied the whole pocket of DYRK1A and formed obvious hydrophobic interactions and hydrogen bonds with DYRK1A residues. Further in vitro validation, including Microscale Thermophoresis (MST) and drug affinity responsive target stability (DARTS) techniques, demonstrated the specific combining capacity of LC to DYRK1A. Meanwhile, LC induced significant cytotoxicity against DYRK1A-overexpressing BxPC-3 cells with an IC50 value of 50.77 μM. Mechanism studies revealed that LC reduced c-MET protein level by inhibiting DYRK1A. These findings provide preliminary evidences that LC as a natural DYRK1A inhibitor suppresses human pancreatic adenocarcinoma BxPC-3 cell proliferation and induces cell apoptotic, which might present new options and possibilities for targeted therapies in pancreatic cancer therapy.

Axis inhibition protein 1 (Axin1) Deletion-Induced Hepatocarcinogenesis Requires Intact β-Catenin but Not Notch Cascade in Mice

Inactivating mutations of axis inhibition protein 1 (AXIN1), a negative regulator of the Wnt/β-Catenin cascade, are among the common genetic events in human hepatocellular carcinoma (HCC), affecting approximately 10% of cases. In the present manuscript, we sought to define the genetic crosstalk between Axin1 mutants and Wnt/β-catenin as well as Notch signaling cascades along hepatocarcinogenesis. We discovered that c-MET activation and AXIN1 mutations occur concomitantly in ~3%-5% of human HCC samples. Subsequently, we generated a murine HCC model by means of CRISPR/Cas9-based gene deletion of Axin1 (sgAxin1) in combination with transposon-based expression of c-Met in the mouse liver (c-Met/sgAxin1). Global gene expression analysis of mouse normal liver, HCCs induced by c-Met/sgAxin1, and HCCs induced by c-Met/∆N90-β-Catenin revealed activation of the Wnt/β-Catenin and Notch signaling in c-Met/sgAxin1 HCCs. However, only a few of the canonical Wnt/β-Catenin target genes were induced in c-Met/sgAxin1 HCC when compared with corresponding lesions from c-Met/∆N90-β-Catenin mice. To study whether endogenous β-Catenin is required for c-Met/sgAxin1-driven HCC development, we expressed c-Met/sgAxin1 in liver-specific Ctnnb1 null mice, which completely prevented HCC development. Consistently, in AXIN1 mutant or null human HCC cell lines, silencing of β-Catenin strongly inhibited cell proliferation. In striking contrast, blocking the Notch cascade through expression of either the dominant negative form of the recombinant signal-binding protein for immunoglobulin kappa J region (RBP-J) or the ablation of Notch2 did not significantly affect c-Met/sgAxin1-driven hepatocarcinogenesis. Conclusion: We demonstrated here that loss of Axin1 cooperates with c-Met to induce HCC in mice, in a β-Catenin signaling-dependent but Notch cascade-independent way.

CRISPR-Cas9-mediated knockout of SPRY2 in human hepatocytes leads to increased glucose uptake and lipid droplet accumulation

BACKGROUND

The prevalence of obesity and its comorbidities, including type 2 diabetes mellitus (T2DM), is dramatically increasing throughout the world; however, the underlying aetiology is incompletely understood. Genome-wide association studies (GWAS) have identified hundreds of genec susceptibility loci for obesity and T2DM, although the causal genes and mechanisms are largely unknown. SPRY2 is a candidate gene identified in GWAS of body fat percentage and T2DM, and has recently been linked to insulin production in pancreatic β-cells. In the present study, we aimed to further understand SPRY2 via functional characterisation in HepG2 cells, an in vitro model of human hepatocytes widely used to investigate T2DM and insulin resistance.

METHODS

CRISPR-Cas9 genome editing was used to target SPRY2 in HepG2 cells, and the functional consequences of SPRY2 knockout (KO) and overexpression subsequently assessed using glucose uptake and lipid droplet assays, measurement of protein kinase phosphorylation and RNA sequencing.

RESULTS

The major functional consequence of SPRY2 KO was a significant increase in glucose uptake, along with elevated lipid droplet accumulation. These changes were attenuated, but not reversed, in cells overexpressing SPRY2. Phosphorylation of protein kinases across key signalling pathways (including Akt and mitogen activated protein kinases) was not altered after SPRY2 KO. Transcriptome profiling in SPRY2 KO and mock (control) cells revealed a number of differentially expressed genes related to cholesterol biosynthesis, cell cycle regulation and cellular signalling pathways. Phospholipase A2 group IIA (PLA2G2A) mRNA level was subsequently validated as significantly upregulated following SPRY2 KO, highlighting this as a potential mediator downstream of SPRY2.

CONCLUSION

These findings suggest a role for SPRY2 in glucose and lipid metabolism in hepatocytes and contribute to clarifying the function of this gene in the context of metabolic diseases.

DYRK1A modulates c-MET in pancreatic ductal adenocarcinoma to drive tumour growth

BACKGROUND AND AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumour with a poor prognosis using current treatments. Targeted therapies may offer a new avenue for more effective strategies. Dual-specificity tyrosine regulated kinase 1A (DYRK1A) is a pleiotropic kinase with contradictory roles in different tumours that is uncharacterised in PDAC. Here, we aimed to investigate the role of DYRK1A in pancreatic tumorigenesis.

DESIGN

We analysed DYRK1A expression in PDAC genetic mouse models and in patient samples. DYRK1A function was assessed with knockdown experiments in pancreatic tumour cell lines and in PDAC mouse models with genetic reduction of Dyrk1a dosage. Furthermore, we explored a mechanistic model for DYRK1A activity.

RESULTS

We showed that DYRK1A was highly expressed in PDAC, and that its protein level positively correlated with that of c-MET. Inhibition of DYRK1A reduced tumour progression by limiting tumour cell proliferation. DYRK1A stabilised the c-MET receptor through SPRY2, leading to prolonged activation of extracellular signal-regulated kinase signalling.

CONCLUSIONS

These findings reveal that DYRK1A contributes to tumour growth in PDAC, at least through regulation of c-MET accumulation, suggesting that inhibition of DYRK1A could represent a novel therapeutic target for PDAC.

Genome-wide promoter DNA methylation profiling of hepatocellular carcinomas arising either spontaneously or due to chronic exposure to Ginkgo biloba extract (GBE) in B6C3F1/N mice

Epigenetic modifications, such as DNA methylation, play an important role in carcinogenesis. In a recent NTP study, chronic exposure of B6C3F1/N mice to Ginkgo biloba extract (GBE) resulted in a high incidence of hepatocellular carcinomas (HCC). Genome-wide promoter methylation profiling on GBE-exposed HCC (2000 mg/kg group), spontaneous HCC (vehicle-control group), and age-matched vehicle control liver was performed to identify differentially methylated genes in GBE-exposed HCC and spontaneous HCC. DNA methylation alterations were correlated to the corresponding global gene expression changes. Compared to control liver, 1296 gene promoters (719 hypermethylated, 577 hypomethylated) in GBE-exposed HCC and 738 (427 hypermethylated, 311 hypomethylated) gene promoters in spontaneous HCC were significantly differentially methylated, suggesting an impact of methylation on GBE-exposed HCC. Differential methylation of promoter regions in relevant cancer genes (cMyc, Spry2, Dusp5) and their corresponding differential gene expression was validated by quantitative pyrosequencing and qRT-PCR, respectively. In conclusion, we have identified differentially methylated promoter regions of relevant cancer genes altered in GBE-exposed HCC compared to spontaneous HCC. Further study of unique sets of differentially methylated genes in chemical-exposed mouse HCC could potentially be used to differentiate treatment-related tumors from spontaneous-tumors in cancer bioassays and provide additional understanding of the underlying epigenetic mechanisms of chemical carcinogenesis.

The Molecular Chaperone Heat Shock Protein 70 Controls Liver Cancer Initiation and Progression by Regulating Adaptive DNA Damage and Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase Signaling Pathways

Delineating the mechanisms that drive hepatic injury and hepatocellular carcinoma (HCC) progression is critical for development of novel treatments for recurrent and advanced HCC but also for the development of diagnostic and preventive strategies. Heat shock protein 70 (HSP70) acts in concert with several cochaperones and nucleotide exchange factors and plays an essential role in protein quality control that increases survival by protecting cells against environmental stressors. Specifically, the HSP70-mediated response has been implicated in the pathogenesis of cancer, but the specific mechanisms by which HSP70 may support malignant cell transformation remains to be fully elucidated. Here, we show that genetic ablation of HSP70 markedly impairs HCC initiation and progression by distinct but overlapping pathways. This includes the potentiation of the carcinogen-induced DNA damage response, at the tumor initiation stage, to increase the p53-dependent surveillance response leading to the cell cycle exit or death of genomically damaged differentiated pericentral hepatocytes, and this may also prevent their conversion into more proliferating HCC progenitor cells. Subsequently, activation of a mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) negative feedback pathway diminishes oncogenic signals, thereby attenuating premalignant cell transformation and tumor progression. Modulation of HSP70 function may be a strategy for interfering with oncogenic signals driving liver cell transformation and tumor progression, thus providing an opportunity for human cancer control.

Mouse Model for Hepatocellular Carcinoma and Cholangiocarcinoma Originated from Mature Hepatocytes

Liver cancer consists of two main histological subtypes, hepatocellular carcinoma and cholangiocarcinoma, both of which have poor prognosis. Therefore, in searching for new therapeutic targets, adequate mouse models to develop and validate therapeutic strategies are urgently needed. Although there are mouse models of liver cancer, each model has shortcomings. To overcome these shortcomings, a mouse model using a hydrodynamic tail vein injection and the Sleeping Beauty transposon was developed. By inducing stable expression of oncogenes in mouse hepatocytes in vivo, the model can easily induce liver cancer with specific characteristics that depend on the oncogenes used to induce carcinogenesis. Here, we describe the details of the methods to induce hepatocellular carcinoma or cholangiocarcinoma from mouse hepatocytes.

Oncogenic potential of N-terminal deletion and S45Y mutant β-catenin in promoting hepatocellular carcinoma development in mice

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide with limited treatment options. Mutation of β-catenin is one of the most frequent genetic events along hepatocarcinogenesis. β-catenin mutations can be in the form of point mutation or large N-terminal deletion. Studies suggested that different β-catenin mutations might have distinct oncogenic potential.

METHODS

We tested the oncogenic activity of β-cateninS45Y, one of the most frequent point mutations of β-catenin, and ∆N90-β-catenin, a form of β-catenin with a large N-terminal deletion, in promoting HCC development in mice. Thus, we co-expressed β-cateninS45Y or ∆N90-β-catenin together with c-Met into the mouse liver using hydrodynamic injection.

RESULTS

We found that both β-catenin mutations were able to induce HCC formation in combination with c-Met at the same latency and efficiency. Tumors showed similar histological features and proliferation rates. However, immunohistochemistry showed predominantly nuclear staining of β-catenin in c-Met/∆N90-β-catenin HCC, but membrane immunoreactivity in c-Met/β-cateninS45Y HCC. qRT-PCR analysis demonstrated that both ∆N90-β-catenin and β-cateninS45Y induced the same effectors, although at somewhat different levels. In cultured cells, both ∆N90-β-catenin and β-cateninS45Y were capable of inducing TCF/LEF reporter expression, promoting proliferation, and inhibiting apoptosis.

CONCLUSIONS

Our study suggests that β-cateninS45Y and ∆N90-β-catenin, in combination with the c-Met proto-oncogene, have similar oncogenic potential. Furthermore, nuclear staining of β-catenin does not always characterize β-catenin activity.

SPRY2 is a novel MET interactor that regulates metastatic potential and differentiation in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a predominantly pediatric soft-tissue cancer where the tumor cells exhibit characteristics of the developing skeletal muscle, and the two most common sub-types are embryonal and alveolar RMS. Elevated activation of the receptor tyrosine kinase (RTK) MET is frequent in RMS and is thought to cause increased tumor metastasis and lack of differentiation. However, the reasons underlying dysregulated MET expression and activation in RMS are not well understood. Therefore, we explored the role of Sprouty 2 (SPRY2), a modulator of RTK signaling, in regulating MET. We identify SPRY2 as a novel MET interactor that colocalizes with and binds MET in both embryonal and alveolar RMS. We find that depletion of SPRY2 leads to MET degradation, resulting in reduced migratory and clonogenic potential, and induction of differentiation in both embryonal and alveolar RMS, outcomes that are identical to depletion of MET. Activation of the ERK/MAPK pathway, known to be crucial for regulating cell migration and whose inhibition is required for myogenic differentiation, was downregulated upon depletion of MET or SPRY2. This provides a direct connection to the decreased migration and induction of differentiation upon depletion of MET or SPRY2. Thus, these data indicate that SPRY2 interacts with MET and stabilizes it in order to maintain signaling downstream of MET, which keeps the ERK/MAPK pathway active, resulting in metastatic potential and inhibition of differentiation in RMS. Our results identify a novel mechanism by which MET signaling is stabilized in RMS, and is a potential target for therapeutic intervention in RMS.

An in vivo transfection system for inducible gene expression and gene silencing in murine hepatocytes

BACKGROUND

Hydrodynamic tail vein injection (HTVI) of transposon-based integration vectors is an established system for stably transfecting mouse hepatocytes in vivo that has been successfully employed to study key questions in liver biology and cancer. Refining the vectors for transposon-mediated hepatocyte transfection will further expand the range of applications of this technique in liver research. In the present study, we report an advanced transposon-based system for manipulating gene expression in hepatocytes in vivo.

METHODS

Transposon-based vector constructs were generated to enable the constitutive expression of inducible Cre recombinase (CreER) together with tetracycline-inducible transgene or miR-small hairpin RNA (shRNA) expression (Tet-ON system). Transposon and transposase expression vectors were co-injected into R26R-mTmG reporter mice by HTVI. Cre-mediated gene recombination was induced by tamoxifen, followed by the administration of doxycycline to drive tetracycline-inducible gene or shRNA expression. Expression was visualized by immunofluorescence staining in livers of injected mice.

RESULTS

After HTVI, Cre recombination by tamoxifen led to the expression of membrane-bound green fluorescent protein in transfected hepatocytes. Activation of inducible gene or shRNA expression was detected by immunostaining in up to one-third of transfected hepatocytes, with an efficiency dependent on the promoter driving the Tet-ON system.

CONCLUSIONS

Our vector system combines Cre-lox mediated gene mutation with inducible gene expression or gene knockdown, respectively. It provides the opportunity for rapid and specific modification of hepatocyte gene expression and can be a useful tool for genetic screening approaches and analysis of target genes specifically in genetically engineered mouse models.

Loss of Pten synergizes with c-Met to promote hepatocellular carcinoma development via mTORC2 pathway

Hepatocellular carcinoma (HCC) is a deadly malignancy with limited treatment options. Activation of the AKT/mTOR cascade is one of the most frequent events along hepatocarcinogenesis. mTOR is a serine/threonine kinase and presents in two distinct complexes: mTORC1 and mTORC2. While mTORC1 has been extensively studied in HCC, the functional contribution of mTORC2 during hepatocarcinogenesis has not been well characterized, especially in vivo. Pten expression is one of the major mechanisms leading to the aberrant activation of the AKT/mTOR signaling. Here, we show that concomitant downregulation of Pten and upregulation of c-Met occurs in a subset of human HCC, mainly characterized by poor prognosis. Using CRISPR-based gene editing in combination with hydrodynamic injection, Pten was deleted in a subset of mouse hepatocytes (sgPten). We found that loss of Pten synergizes with overexpression of c-Met to promote HCC development in mice (sgPten/c-Met). At the molecular level, sgPten/c-Met liver tumor tissues display increased AKT and mTOR signaling. Using Rictor conditional knockout mice, we demonstrate that sgPten/c-Met-driven HCC development strictly depends on an intact mTORC2 complex. Our findings therefore support the critical role of mTORC2 in hepatocarcinogenesis. sgPten/c-Met mouse model represents a novel valuable system that can be used for the development of targeted therapy against this deadly malignancy.

Glucose Catabolism in Liver Tumors Induced by c-MYC Can Be Sustained by Various PKM1/PKM2 Ratios and Pyruvate Kinase Activities

Different pyruvate kinase isoforms are expressed in a tissue-specific manner, with pyruvate kinase M2 (PKM2) suggested to be the predominant isoform in proliferating cells and cancer cells. Because of differential regulation of enzymatic activities, PKM2, but not PKM1, has been thought to favor cell proliferation. However, the role of PKM2 in tumorigenesis has been recently challenged. Here we report that increased glucose catabolism through glycolysis and increased pyruvate kinase activity in c-MYC-driven liver tumors are associated with increased expression of both PKM1 and PKM2 isoforms and decreased expression of the liver-specific isoform of pyruvate kinase, PKL. Depletion of PKM2 at the time of c-MYC overexpression in murine livers did not affect c-MYC-induced tumorigenesis and resulted in liver tumor formation with decreased pyruvate kinase activity and decreased catabolism of glucose into alanine and the Krebs cycle. An increased PKM1/PKM2 ratio by ectopic PKM1 expression further decreased glucose flux into serine biosynthesis and increased flux into lactate and the Krebs cycle, resulting in reduced total levels of serine. However, these changes also did not affect c-MYC-induced liver tumor development. These results suggest that increased expression of PKM2 is not required to support c-MYC-induced tumorigenesis in the liver and that various PKM1/PKM2 ratios and pyruvate kinase activities can sustain glucose catabolism required for this process. Cancer Res; 77(16); 4355-64. ©2017 AACR.

Hypoxia inducible factors regulate the transcription of the sprouty2 gene and expression of the sprouty2 protein

Receptor Tyrosine Kinase (RTK) signaling plays a major role in tumorigenesis and normal development. Sprouty2 (Spry2) attenuates RTK signaling and inhibits processes such as angiogenesis, cell proliferation, migration and survival, which are all upregulated in tumors. Indeed in cancers of the liver, lung, prostate and breast, Spry2 protein levels are markedly decreased correlating with poor patient prognosis and shorter survival. Thus, it is important to understand how expression of Spry2 is regulated. While prior studies have focused on the post-translation regulation of Spry2, very few studies have focused on the transcriptional regulation of SPRY2 gene. Here, we demonstrate that in the human hepatoma cell line, Hep3B, the transcription of SPRY2 is inhibited by the transcription regulating hypoxia inducible factors (HIFs). HIFs are composed of an oxygen regulated alpha subunit (HIF1α or HIF2α) and a beta subunit (HIF1β). Intriguingly, silencing of HIF1α and HIF2α elevates SPRY2 mRNA and protein levels suggesting HIFs reduce the transcription of the SPRY2 promoter. In silico analysis identified ten hypoxia response elements (HREs) in the proximal promoter and first intron of SPRY2. Using chromatin immunoprecipitation (ChIP), we show that HIF1α/2α bind near the putative HREs in the proximal promoter and intron of SPRY2. Our studies demonstrated that not only is the SPRY2 promoter methylated, but silencing HIF1α/2α reduced the methylation. ChIP assays also showed DNA methyltransferase1 (DNMT1) binding to the proximal promoter and first intron of SPRY2 and silencing HIF1α/2α decreased this association. Additionally, silencing of DNMT1 mimicked the HIF1α/2α silencing-mediated increase in SPRY2 mRNA and protein. While simultaneous silencing of HIF1α/2α and DNMT1 increased SPRY2 mRNA a little more, the increase was not additive suggesting a common mechanism by which DNMT1 and HIF1α/2α regulate SPRY2 transcription. Together these data suggest that the transcription of SPRY2 is inhibited by HIFs, in part, via DNMT1- mediated methylation.

Sprouty2 Protein Regulates Hypoxia-inducible Factor-α (HIFα) Protein Levels and Transcription of HIFα-responsive Genes

The α-subunits of hypoxia-inducible factors (HIF1α and HIF2α) promote transcription of genes that regulate glycolysis and cell survival and growth. Sprouty2 (Spry2) is a modulator of receptor tyrosine kinase signaling and inhibits cell proliferation by a number of different mechanisms. Because of the seemingly opposite actions of HIFα subunits and Spry2 on cellular processes, we investigated whether Spry2 regulates the levels of HIF1α and HIF2α proteins. In cell lines from different types of tumors in which the decreased protein levels of Spry2 have been associated with poor prognosis, silencing of Spry2 elevated HIF1α protein levels. Increases in HIF1α and HIF2α protein levels due to silencing of Spry2 also up-regulated HIFα target genes. Using HIF1α as a prototype, we show that Spry2 decreases HIF1α stability and enhances the ubiquitylation of HIF1α by a von Hippel-Lindau protein (pVHL)-dependent mechanism. Spry2 also exists in a complex with HIF1α. Because Spry2 can also associate with pVHL, using a mutant form of Spry2 (3P/3A-Spry2) that binds HIF1α, but not pVHL, we show that WT-Spry2, but not the 3P/3A-Spry2 decreases HIF1α protein levels. In accordance, expression of WT-Spry2, but not 3P/3A-Spry2 results in a decrease in HIF1α-sensitive glucose uptake. Together our data suggest that Spry2 acts as a scaffold to bring more pVHL/associated E3 ligase in proximity of HIF1α and increase its ubiquitylation and degradation. This represents a novel action for Spry2 in modulating biological processes regulated by HIFα subunits.

[(11)C]acetate PET Imaging is not Always Associated with Increased Lipogenesis in Hepatocellular Carcinoma in Mice

PURPOSE

Altered metabolism, including increased glycolysis and de novo lipogenesis, is one of the hallmarks of cancer. Radiolabeled nutrients, including glucose and acetate, are extensively used for the detection of various tumors, including hepatocellular carcinomas (HCCs). High signal of [(11)C]acetate positron emission tomography (PET) in tumors is often considered to be associated with increased expression of fatty acid synthase (FASN) and increased de novo lipogenesis in tumor tissues. Defining a subset of tumors with increased [(11)C]acetate PET signal and thus increased lipogenesis was suggested to help select a group of patients, who may benefit from lipogenesis-targeting therapies.

PROCEDURES

To investigate whether [(11)C]acetate PET imaging is truly associated with increased de novo lipogenesis along with hepatocarcinogenesis, we performed [(11)C]acetate PET imaging in wild-type mice as well as two mouse HCC models, induced by myrAKT/Ras(V12) (AKT/Ras) and PIK3CA(1047R)/c-Met (PI3K/Met) oncogene combinations. In addition, we analyzed FASN expression and de novo lipogenesis rate in these mouse liver tissues.

RESULTS

We found that while HCCs induced by AKT/Ras co-expression showed high levels of [(11)C]acetate PET signal compared to normal liver, HCCs induced by PI3K/Met overexpression did not. Intriguingly, elevated FASN expression and increased de novo lipogenesis rate were observed in both AKT/Ras and PI3K/Met HCCs.

CONCLUSION

Altogether, our study suggests that [(11)C]acetate PET imaging can be a useful tool for imaging of a subset of HCCs. However, at molecular level, the increased [(11)C]acetate PET imaging is not always associated with increased FASN expression or de novo lipogenesis.

Co-activation of AKT and c-Met triggers rapid hepatocellular carcinoma development via the mTORC1/FASN pathway in mice

Activation of the AKT/mTOR cascade and overexpression of c-Met have been implicated in the development of human hepatocellular carcinoma (HCC). To elucidate the functional crosstalk between the two pathways, we generated a model characterized by the combined expression of activated AKT and c-Met in the mouse liver. Co-expression of AKT and c-Met triggered rapid liver tumor development and mice required to be euthanized within 8 weeks after hydrodynamic injection. At the molecular level, liver tumors induced by AKT/c-Met display activation of AKT/mTOR and Ras/MAPK cascades as well as increased lipogenesis and glycolysis. Since a remarkable lipogenic phenotype characterizes liver lesions from AKT/c-Met mice, we determined the requirement of lipogenesis in AKT/c-Met driven hepatocarcinogenesis using conditional Fatty Acid Synthase (FASN) knockout mice. Of note, hepatocarcinogenesis induced by AKT/c-Met was fully inhibited by FASN ablation. In human HCC samples, coordinated expression of FASN, activated AKT, and c-Met proteins was detected in a subgroup of biologically aggressive tumors. Altogether, our study demonstrates that co-activation of AKT and c-Met induces HCC development that depends on the mTORC1/FASN pathway. Suppression of mTORC1 and/or FASN might be highly detrimental for the growth of human HCC subsets characterized by concomitant induction of the AKT and c-Met cascades.

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.

The developing story of Sprouty and cancer

Sprouty proteins are evolutionarily conserved modulators of MAPK/ERK pathway. Through interacting with an increasing number of effectors, mediators, and regulators with ultimate influence on multiple targets within or beyond ERK, Sprouty orchestrates a complex, multilayered regulatory system and mediates a crosstalk among different signaling pathways for a coordinated cellular response. As such, Sprouty has been implicated in various developmental and physiological processes. Evidence shows that ERK is aberrantly activated in malignant conditions. Accordingly, Sprouty deregulation has been reported in different cancer types and shown to impact cancer development, progression, and metastasis. In this article, we have tried to provide an overview of the current knowledge about the Sprouty physiology and its regulatory functions in health, as well as an updated review of the Sprouty status in cancer. Putative implications of Sprouty in cancer biology, their clinical relevance, and their proposed applications are also revisited. As a developing story, however, role of Sprouty in cancer remains to be further elucidated.

Sprouty2 protein is downregulated in human squamous cell carcinoma of the head and neck and suppresses cell proliferation in vitro

Sprouty2 is known for its tumor-suppressing effect in various human malignant diseases. In head and neck squamous cell carcinoma (HNSCC), the role of sprouty2 in tumorigenesis and clinical implication remains elusive. The aim of the present study was to investigate the expression of sprouty2 in patients with HNSCC and its function in vitro. Quantitative analysis of mRNA expression of sprouty2 was performed on frozen tumor samples from 42 patients with HNSCC and 19 with oral verrucous hyperplasia (OVH) with paired counterparts of normal mucosa. Downregulation of sprouty2 expression was demonstrated in 79% of HNSCC samples and in 58% of OVH samples compared with paired samples of normal mucosa. Enhanced expression of sprouty2 protein suppressed the growth of HNSCC cells and signaling of the phosphorylated AKT pathway. Following transfection of the sprouty2 plasmid, HNSCC cells were more sensitive to sorafenib, a tyrosine kinase inhibitor of Raf and vascular endothelial growth factor receptor. The present study suggested that sprouty2 expression was downregulated and behaved as a tumor suppressor in HNSCC. Sprouty2 expression in tumor cells enhanced sensitivity to sorafenib. Further studies are required to define the clinical impact of sprouty2 in patients with HNSCC.

NEDD4 controls the expression of GUCD1, a protein upregulated in proliferating liver cells

Liver regeneration is a unique means of studying cell proliferation in vivo. Screening of a large cDNA library from regenerating liver has previously allowed us to identify and characterize a cluster of genes encoding proteins with important roles in proliferative processes. Here, by examining different rat and human tissues as well as cell lines, we characterized a highly conserved gene, guanylyl cyclase domain containing 1 (GUCD1), whose modulation occurs in liver regeneration and cell cycle progression in vitro. High-level expression of GUCD1 transcripts was observed in livers from patients with hepatocellular carcinoma. A yeast two-hybrid interaction assay, aimed at identifying any relevant interaction partners of GUCD1, revealed direct interactions with NEDD4-1 (E3 ubiquitin protein ligase neural precursor cell expressed, developmentally downregulated gene 4), resulting in control of GUCD1 stability. Thus, we have characterized expression and function of a ubiquitous protein, GUCD1, which might have a role in regulating normal and abnormal cell growth in the liver.

Fibroblast growth factor signaling in liver carcinogenesis

Fibroblast growth factors, or FGFs, are a large family of polypeptide cytokines exhibiting a pleiotropy of functions, from cell growth to angiogenesis, wound healing, and tissue repair. This review broadly covers the genetics and protein expression of the FGF family members and the signaling pathways involved in FGF-mediated growth regulation. We emphasize the role of FGFs in the pathogenesis of hepatocellular carcinoma (HCC), including their effects on regulation of the tumor microenvironment and angiogenesis. Finally, we present current views on FGF's potential role as a prognostic marker in clinical practice, as well as its potential as a therapeutic target in HCC.

Hydrodynamic transfection for generation of novel mouse models for liver cancer research

Primary liver cancers, including hepatocellular carcinoma and intrahepatic cholangiocarcinoma, are leading causes of cancer-related death worldwide. Recent large-scale genomic approaches have identified a wide number of genes whose deregulation is associated with hepatocellular carcinoma and intrahepatic cholangiocarcinoma development. Murine models are critical tools to determine the oncogenic potential of these genes. Conventionally, transgenic or knockout mouse models are used for this purpose. However, several limitations apply to the latter models. Herein, we review a novel approach for stable gene expression in mouse hepatocytes by hydrodynamic injection in combination with Sleeping Beauty-mediated somatic integration. This method represents a flexible, reliable, and cost-effective tool to generate preclinical murine models for liver cancer research. Furthermore, it can be used as an in vivo transfection method to study biochemical cross talks among multiple pathways along hepatocarcinogenesis and to test the therapeutic potential of drugs against liver cancer.

C1GALT1 enhances proliferation of hepatocellular carcinoma cells via modulating MET glycosylation and dimerization

Altered glycosylation is a hallmark of cancer. The core 1 β1,3-galactosyltransferase (C1GALT1) controls the formation of mucin-type O-glycans, far overlooked and underestimated in cancer. Here, we report that C1GALT1 mRNA and protein are frequently overexpressed in hepatocellular carcinoma tumors compared with nontumor liver tissues, where it correlates with advanced tumor stage, metastasis, and poor survival. Enforced expression of C1GALT1 was sufficient to enhance cell proliferation, whereas RNA interference-mediated silencing of C1GALT1 was sufficient to suppress cell proliferation in vitro and in vivo. Notably, C1GALT1 attenuation also suppressed hepatocyte growth factor (HGF)-mediated phosphorylation of the MET kinase in hepatocellular carcinoma cells, whereas enforced expression of C1GALT1 enhanced MET phosphorylation. MET blockade with PHA665752 inhibited C1GALT1-enhanced cell viability. In support of these results, we found that the expression level of phospho-MET and C1GALT1 were associated in primary hepatocellular carcinoma tissues. Mechanistic investigations showed that MET was decorated with O-glycans, as revealed by binding to Vicia villosa agglutinin and peanut agglutinin. Moreover, C1GALT1 modified the O-glycosylation of MET, enhancing its HGF-induced dimerization and activation. Together, our results indicate that C1GALT1 overexpression in hepatocellular carcinoma activates HGF signaling via modulation of MET O-glycosylation and dimerization, providing new insights into how O-glycosylation drives hepatocellular carcinoma pathogenesis.

Functional crosstalk between AKT/mTOR and Ras/MAPK pathways in hepatocarcinogenesis: implications for the treatment of human liver cancer

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide, with limited treatment options. AKT/mTOR and Ras/MAPK pathways are frequently deregulated in human hepatocarcinogenesis. Recently, we generated an animal model characterized by the co-expression of activated forms of AKT and Ras in the mouse liver. We found that concomitant activation of AKT/mTOR and Ras/MAPK cascades leads to rapid liver tumor development in AKT/Ras mice, mainly through mTORC1 induction. To further define the role of mTORC1 cascade in AKT/Ras induced HCC development, the mTORC1 inhibitor Rapamycin was administered to AKT/Ras mice at the time when small tumors started to emerge in the liver. Of note, Rapamycin treatment significantly delayed hepatocarcinogenesis in AKT/Ras mice. However, some microscopic lesions persisted in the livers of AKT/Ras mice despite the treatment and rapidly gave rise to HCC following Rapamycin withdrawal. Mechanistically, Rapamycin inhibited mTORC1 and mTORC2 pathways, lipogenesis and glycolysis, resulting in inhibition of proliferation in the treated livers. However, activated ERK and its downstream effectors, Mnk1 and eIF4E, were strongly upregulated in the residual lesions. Concomitant suppression of AKT/mTOR and Ras/MAPK pathways was highly detrimental for the growth of AKT/Ras cells in vitro. The study indicates the existence of a complex interplay between AKT/mTOR and Ras/MAPK pathways during hepatocarcinogenesis, with important implications for the understanding of HCC pathogenesis as well as for its prevention and treatment.

JNK and STAT3 signaling pathways converge on Akt-mediated phosphorylation of EZH2 in bronchial epithelial cells induced by arsenic

The molecular mechanisms by which arsenic (As ( 3+) ) causes human cancers remain to be fully elucidated. Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of polycomb-repressive complexes 2 (PRC2) that promotes trimethylation of lysine 27 of histone H3, leading to altered expression of tumor suppressors or oncogenes. In the present study, we determined the effect of As ( 3+) on EZH2 phosphorylation and the signaling pathways important for As ( 3+) -induced EZH2 phosphorylation in human bronchial epithelial cell line BEAS-2B. The involvement of kinases in As ( 3+) -induced EZH2 phosphorylation was validated by siRNA-based gene silencing. The data showed that As ( 3+) can induce phosphorylation of EZH2 at serine 21 in human bronchial epithelial cells and that the phosphorylation of EZH2 requires an As ( 3+) -activated signaling cascade from JNK and STAT3 to Akt. Transfection of the cells with siRNA specific for JNK1 revealed that JNK silencing reduced serine727 phosphorylation of STAT3, Akt activation and EZH2 phosphorylation, suggesting that JNK is the upstream kinase involved in As ( 3+) -induced EZH2 phosphorylation. Because As ( 3+) is capable of inducing miRNA-21 (miR-21), a STAT3-regulated miRNA that represses protein translation of PTEN or Spry2, we also tested the role of STAT3 and miR-21 in As ( 3+) -induced EZH2 phosphorylation. Ectopic overexpression of miR-21 promoted Akt activation and phosphorylation of EZH2, whereas inhibiting miR-21 by transfecting the cells with anti-miR-21 inhibited Akt activation and EZH2 phosphorylation. Taken together, these results demonstrate a contribution of the JNK, STAT3 and Akt signaling axis to As ( 3+) -induced EZH2 phosphorylation. Importantly, these findings may reveal new molecular mechanisms underlying As ( 3+) -induced carcinogenesis.

Histone deacetylases activate hepatocyte growth factor signaling by repressing microRNA-449 in hepatocellular carcinoma cells

BACKGROUND & AIMS

Histone deacetylation regulates chromatin remodeling and transcriptional down-regulation of specific genomic regions; it is altered in many types of cancer cells. We searched for microRNAs (miRs) that are affected by histone deacetylation and investigated the effects in hepatocellular carcinoma (HCC) cells.

METHODS

HCC cell lines (HepG2, HLE, HLF, and Huh7) and immortalized liver cell lines (THLE-2 and THLE-3) were incubated with the histone deacetylase inhibitor trichostatin A. Differentially expressed messenger RNAs (mRNAs) and miRs were identified by expression profiling. Small interfering RNAs were used to reduce levels of histone deacetylases (HDAC)1-3, and HCC cell lines were transfected with miR-449. We evaluated growth of xenograft tumors from modified cells in nude mice. Cells were analyzed by immunoblot and luciferase reporter assays. We analyzed HCC samples from 23 patients.

RESULTS

HDAC1-3 were up-regulated in HCC samples from patients. In cell lines, inhibition of HDAC significantly increased levels of hsa-miR-449a. c-MET mRNA, which encodes the receptor tyrosine kinase for hepatocyte growth factor, is a target of miR-449. Incubation of HCC cells with trichostatin A or transfection with miR-449 reduced expression of c-MET and phosphorylation of extracellular signal-regulated kinases 1 and 2 (downstream effectors of c-MET), increased apoptosis, and reduced proliferation. Huh-7 cells transfected with miR-449 formed tumors more slowly in mice than cells expressing control miRs. HCC samples from patients had lower levels of miR-449 and higher levels of c-MET than human reference.

CONCLUSIONS

In HCC cells, up-regulation of HDAC1-3 reduces expression of miR-449. miR-449 binds c-MET mRNA to reduce its levels, promoting apoptosis and reducing proliferation of liver cells. Expression of miR-449 slows growth of HCC xenograft tumors in mice; this miR might function as a tumor suppressor.

Inactivation of Spry2 accelerates AKT-driven hepatocarcinogenesis via activation of MAPK and PKM2 pathways

BACKGROUND & AIMS

Aberrant activation of the AKT oncogenic pathway and downregulation of the Sprouty 2 (Spry2) tumor suppressor gene are frequently observed molecular events in human hepatocarcinogenesis. The goal of the present study was to investigate the eventual biochemical and genetic crosstalk between activated AKT and inactivation of Spry2 during liver cancer development by using in vivo and in vitro approaches.

METHODS

Activated AKT and/or Spry2Y55F, a dominant negative form of Spry2, were overexpressed in the mouse liver via hydrodynamic gene delivery. Histological and biochemical assays were applied to characterize the molecular features of AKT and AKT/Spry2Y55F liver tumors. The human HLE hepatocellular carcinoma (HCC) cell line, stably overexpressing AKT, was transfected with Spry2Y55F to study the molecular mechanisms underlying hepatocarcinogenesis driven by Spry2 loss.

RESULTS

Spry2Y55F overexpression significantly accelerated AKT-induced hepatocarcinogenesis in the mouse. AKT/Spry2Y55F liver lesions had increased proliferation and glycolysis and decreased lipogenesis when compared with AKT corresponding lesions. At the molecular level, AKT/Spry2Y55F HCCs exhibited a significantly stronger induction of activated mitogen-activated protein kinase (MAPK) and pyruvate kinase M2 (PKM2) pathways than in AKT corresponding lesions. This phenotype was reproduced in HLE cells overexpressing AKT following transfection with Spry2Y55F. Furthermore, we found that concomitant suppression of the MAPK cascade and PKM2 strongly inhibited the growth induced by Spry2Y55F in AKT-overexpressing cells.

CONCLUSIONS

Inactivation of Spry2 accelerates AKT-induced hepatocarcinogenesis via activation of MAPK and PKM2 pathways.

EGFR activation is a potential determinant of primary resistance of hepatocellular carcinoma cells to sorafenib

Sorafenib is currently the medical treatment of reference for hepatocellular carcinoma (HCC), but it is not known whether sorafenib is equally active in all HCC. Here, our aim was to explore intrinsic differences in the response of HCC cells to sorafenib, to identify potential mechanisms leading to primary resistance to this treatment. We analyzed a panel of six human HCC cell lines and compared the activity of the main oncogenic kinase cascades, their clonogenic potential, proliferation and apoptosis upon exposure to sorafenib. We report that HCC cells present important differences in their response to sorafenib, and that some cell lines are more resistant to the actions of sorafenib than others. We identify the activated epidermal growth factor receptor (EGFR) as a parameter that promotes the resistance of HCC cells to sorafenib. In resistant cells, the efficacy of sorafenib was increased when EGFR was inhibited, as was demonstrated using two chemical inhibitors (erlotinib or gefitinib), a monoclonal antibody directed against EGFR (cetuximab), and RNA interference directed against EGFR. A combination of EGFR inhibitors and sorafenib affords a better control over HCC proliferation, most likely through an improved blockade of the RAF kinases. Our findings therefore confirm the importance of RAF kinases as therapeutic targets in HCC, and identify EGFR as a determinant of the sensitivity of HCC cells to sorafenib. Our findings bear possible implications for the improvement of the efficacy of sorafenib in HCC, and might be useful for the identification of predictive biomarkers in this context.

Pathogenetic and Prognostic Significance of Inactivation of RASSF Proteins in Human Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent solid tumors worldwide, with limited treatment options and a dismal prognosis. Thus, there is a strong need to expand the basic and translational research on this deadly disease in order to improve the prognosis of HCC patients. Although the etiologic factors responsible for HCC development have been identified, the molecular pathogenesis of liver cancer remains poorly understood. Recent evidence has shown the frequent downregulation of Ras association domain family (RASSF) proteins both in the early and late stages of hepatocarcinogenesis. Here, we summarize the data available on the pathogenetic role of inactivation of RASSF proteins in liver cancer, the molecular mechanisms responsible for suppression of RASSF proteins in HCC, and the possible clinical implications arising from these discoveries. Altogether, the data indicate that inactivation of the RASSF1A tumor suppressor is ubiquitous in human liver cancer, while downregulation of RASSF2 and RASSF5 proteins is limited to specific HCC subsets. Also, the present findings speak in favour of therapeutic strategies aimed at reexpressing RASSF1A, RASSF2, and RASSF5 genes and/or inactivating the RASSF cellular inhibitors for the treatment of human liver cancer.

Prognostic significance and clinical relevance of Sprouty 2 protein expression in human hepatocellular carcinoma

BACKGROUND

In vitro experiments and mice models have confirmed the importance of Sprouty 2 (Spry2) in inhibiting tumorigenesis and the progression of human cancer. However, the prognostic value of Spry2 in cancer patients remains unknown. This study is aimed to investigate the clinical relevance and prognostic significance of Spry2 expression in patients with hepatocellular carcinoma (HCC).

METHODS

With samples from 240 randomly-selected HCC patients who underwent surgery, immunohistochemistry was used to investigate Spry2 expression on tissue microarrays. The correlation of Spry2 expression with survival was estimated by the Kaplan-Meier method and univariate/multivariate Cox proportional hazard regression analysis. Spry2, ERK and phospho-ERK expression in HCC cell lines was detected by Western blotting.

RESULTS

Among the patients, 86.3% (207 of 240) exhibited down-regulation of Spry2 expression. Patients negative for Spry2 showed poorer survival (P=0.002) and increased recurrence (P=0.003). Multivariate analysis further established Spry2 as an independent predictor of postoperative recurrence in HCC patients (HR=1.47; 95% CI, 1.02-2.08; P=0.037). Down-regulation of Spry2 was associated with highly malignant phenotypes like vascular invasion and advanced tumor stages, and was positively correlated with the metastatic potential of HCC cell lines.

CONCLUSION

In the era of molecular targeted therapy, the expression of Spry2 in HCC may have relevant clinical significance and turn out to be a key factor in prognostic assessment and in treatment planning.

Down-regulation of CMTM8 induces epithelial-to-mesenchymal transition-like changes via c-MET/extracellular signal-regulated kinase (ERK) signaling

The acquisition of an invasive phenotype is a critical turning point for malignant tumor cells. CMTM8, a potential tumor suppressor, is frequently down-regulated in solid tumors, and its overexpression induces tumor cell apoptosis. Here, we identify a new role for CMTM8 in regulating tumor cell migration. Reducing CMTM8 expression in HepG2 hepatocellular carcinoma cells results in the acquisition of epithelial-to-mesenchymal transition (EMT) features, including a morphological change from organized epithelial sheets to scattered fibroblast-like shapes, reduction of the epithelial marker E-cadherin, and an increased invasive and migratory ability. These phenotypic changes are mediated in large part by the ERK-MAPK pathway, as the MEK inhibitor U0126 and shRNA-mediated knockdown of ERK2 significantly reversed these phenotypes. Hepatocyte growth factor binding to the c-MET receptor is known to induce EMT in HepG2 cells. We found that CMTM8 knockdown in HepG2 cells induced c-MET signaling and ERK activation. Inhibition of c-MET signaling with the small molecule inhibitor SU11274 or c-MET RNAi blocked the EMT-like changes following CMTM8 knockdown. CMTM8 overexpression in HepG2 cells inhibited hepatocyte growth factor-induced EMT-like morphological changes and cell motility. Down-regulation of CMTM8 also promoted an EMT-like change in MCF-10A cells, indicating a broader role for CMTM8 in regulating cellular transformation.

Regulation of cellular levels of Sprouty2 protein by prolyl hydroxylase domain and von Hippel-Lindau proteins

Sprouty (Spry) proteins modulate the actions of receptor tyrosine kinases during development and tumorigenesis. Decreases in cellular levels of Spry, especially Sprouty2 (Spry2), have been implicated in the growth and progression of tumors of the breast, prostate, lung, and liver. During development and tumor growth, cells experience hypoxia. Therefore, we investigated how hypoxia modulates the levels of Spry proteins. Hypoxia elevated the levels of all four expressed Spry isoforms in HeLa cells. Amounts of endogenous Spry2 in LS147T and HEP3B cells were also elevated by hypoxia. Using Spry2 as a prototype, we demonstrate that silencing and expression of prolyl hydroxylase domain proteins (PHD1-3) increase and decrease, respectively, the cellular content of Spry2. Spry2 also preferentially interacted with PHD1-3 and von Hippel-Lindau protein (pVHL) during normoxia but not in hypoxia. Additionally, Spry2 is hydroxylated on Pro residues 18, 144, and 160, and substitution of these residues with Ala enhanced stability of Spry2 and abrogated its interactions with pVHL. Silencing of pVHL increased levels of Spry2 by decreasing its ubiquitylation and degradation and thereby augmented the ability of Spry2 to inhibit FGF-elicited activation of ERK1/2. Thus, prolyl hydroxylase mediated hydroxylation and subsequent pVHL-elicited ubiquitylation of Spry2 target it for degradation and, consequently, provide a novel mechanism of regulating growth factor signaling.

c-Met represents a potential therapeutic target for personalized treatment in hepatocellular carcinoma

c-Met, a high-affinity receptor for hepatocyte growth factor (HGF), plays a critical role in cancer growth, invasion, and metastasis. Hepatocellular carcinoma (HCC) patients with an active HGF/c-Met signaling pathway have a significantly worse prognosis. Although targeting the HGF/c-Met pathway has been proposed for the treatment of multiple cancers, the effect of c-Met inhibition in HCC remains unclear. The human HCC cell lines Huh7, Hep3B, MHCC97-L, and MHCC97-H were used in this study to investigate the effect of c-Met inhibition using the small molecule selective c-Met tyrosine kinase inhibitor PHA665752. MHCC97-L and MHCC97-H cells demonstrate a mesenchymal phenotype with decreased expression of E-cadherin and increased expression of c-Met, fibronectin, and Zeb2 compared with Huh7 and Hep3B cells, which have an epithelial phenotype. PHA665752 treatment blocked phosphorylation of c-Met and downstream phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase/Erk pathways, inhibited cell proliferation, and induced apoptosis in c-Met-positive MHCC97-L and MHCC97-H cells. In xenograft models, administration of PHA665752 significantly inhibited c-Met-positive MHCC97-L and MHCC97-H tumor growth, and PHA665752-treated tumors demonstrated marked reduction of both c-Met phosphorylation and cell proliferation. c-Met-negative Huh7 and Hep3B cells were not affected by c-Met inhibitor treatment in vitro or in vivo. In addition, c-Met-positive MHCC97-L and MHCC97-H cells demonstrated cancer stem cell-like characteristics, such as resistance to chemotherapy, tumor sphere formation, and increased expression of CD44 and ABCG2, and PHA665752 treatment suppressed tumor sphere formation and inhibited CD44 expression.

CONCLUSION

c-Met represents a potential target of personalized treatment for HCC with an active HGF/c-Met pathway.

Management of chronic hepatitis B

Chronic hepatitis B continues to be a major global health burden. It accounts for a substantial impact on health care resources and finances in many parts of the world including Europe. Natural history and disease spectrum are varied, depending on when and how the infection is acquired. The chronic infective state increases patients' risk of progression to liver cirrhosis or hepatocellular carcinoma. Several treatment options are currently available, but their use depends on the stage of the patient's infection, which is influenced by both host and viral factors. The ultimate goals in hepatitis B treatment are to prevent disease progression, hepatic decompensation, hepatocellular carcinoma, and death. Patients with decompensated liver cirrhosis should be referred to specialized transplant centers in a timely manner.