SKP2 cooperates with N-Ras or AKT to induce liver tumor development in mice

Development of a prognostic model for anoikis and identifies hub genes in hepatocellular carcinoma

Considering the high fatality of hepatocellular carcinoma (HCC), current prognostic systems are insufficient to accurately forecast HCC patients' outcomes. In our study, nine anoikis‑related genes (PTRH2, ITGAV, ANXA5, BIRC5, BDNF, BSG, DAP3, SKP2, and EGF) were determined to establish a risk scoring model using LASSO regression, which could be validated in ICGC dataset. Kaplan-Meier curves and time-dependent receiver operating characteristic (ROC) curve analysis confirmed the risk score possessed an accurate predictive value for the prognosis of HCC patients. The high-risk group showed a higher infiltration of aDCs, macrophages, T-follicular helper cells, and Th2 cells. Besides, PD-L1 was significantly higher in the high-risk group compared to the low-risk group. Several anoikis‑related genes, such as ANX5, ITGAV, BDNF and SKP2, were associated with drug sensitivity in HCC. Finally, we identified BIRC5 and SKP2 as hub genes among the nine model genes using WGCNA analysis. BIRC5 and SKP2 were over-expressed in HCC tissues, and their over-expression was associated with poor prognosis, no matter in our cohort by immunohistochemical staining or in the TCGA cohort by mRNA-Seq. In our cohort, BIRC5 expression was highly associated with the T stage, pathologic stage, histologic grade and AFP of HCC patients. In general, our anoikis-related risk model can enhance the ability to predict the survival outcomes of HCC patients and provide a feasible therapeutic strategy for immunotherapy and drug resistance in HCC. BIRC5 and SKP2 are hub genes of anoikis‑related genes in HCC.

RSK2 inactivation cooperates with AXIN1 inactivation or β-catenin activation to promote hepatocarcinogenesis

BACKGROUND & AIMS

Recurrent somatic mutations of the RPS6KA3 gene encoding for the serine/threonine kinase RSK2 were identified in hepatocellular carcinomas (HCCs), suggesting its tumour-suppressive function. Our goal was to demonstrate the tumour suppressor role of RSK2 in the liver and investigate the functional consequences of its inactivation.

METHODS

We analysed a series of 1,151 human HCCs for RSK2 mutations and 20 other driver genetic alterations. We then modelled RSK2 inactivation in mice in various mutational contexts recapitulating or not those naturally found in human HCC, using transgenic mice and liver-specific carcinogens. These models were monitored for liver tumour appearance and subjected to phenotypic and transcriptomic analyses. Functional consequences of RSK2 rescue were also investigated in a human RSK2-deficient HCC cell line.

RESULTS

RSK2-inactivating mutations are specific to human HCC and frequently co-occur with AXIN1-inactivating or β-catenin-activating mutations. Modelling of these co-occurrences in mice showed a cooperative effect in promoting liver tumours with transcriptomic profiles recapitulating those of human HCCs. By contrast, there was no cooperation in liver tumour induction between RSK2 loss and BRAF-activating mutations chemically induced by diethylnitrosamine. In human liver cancer cells, we also showed that RSK2 inactivation confers some dependency to the activation of RAS/MAPK signalling that can be targeted by MEK inhibitors.

CONCLUSIONS

Our study demonstrates the tumour suppressor role of RSK2 and its specific synergistic effect in hepatocarcinogenesis when its loss of function is specifically combined with AXIN1 inactivation or β-catenin activation. Furthermore, we identified the RAS/MAPK pathway as a potential therapeutic target for RSK2-inactivated liver tumours.

IMPACT AND IMPLICATIONS

This study demonstrated the tumour suppressor role of RSK2 in the liver and showed that its inactivation specifically synergises with AXIN1 inactivation or β-catenin activation to promote the development of HCC with similar transcriptomic profiles as found in humans. Furthermore, this study highlights that activation of the RAS/MAPK pathway is one of the key signalling pathways mediating the oncogenic effect of RSK2 inactivation that can be targeted with already available anti-MEK therapies.

Pan-Cancer Analysis of the Expression and Prognostic Value of S-Phase Kinase-Associated Protein 2

BACKGROUND: S-Phase Kinase-Associated Protein 2 (SKP2) is essential in modulating metabolism processes, cell proliferation, and carcinogenesis DUE to its capacity to ubiquitinate and degrade various tumor-suppressive substrates. However, the actual biological and mechanism significance of SKP2 in the development of tumors and as a possible therapeutic target remains to be completely understood. AIM: This study aimed to explore the potential roles of the SKP2 gene in the oncologic pathogenesis of various cancers through an in-depth pan-cancer analysis including gene expression assessment, survival analysis, genetic alteration, and enrichment analysis. METHODS: Public databases including the Cancer Genome Atlas database, Genotype-Tissue Expression Project database, cBioPortal database, Gene Expression Profiling Interactive Analysis 2 database, Tumor Immune Estimation Resource version 2.0 database, and STRING database were used to detect the SKP2 expression, molecular mechanism, and its association with the prognosis across pan-cancer. RESULTS: SKP2 was significantly highly expressed in most types of cancers and was substantially correlated to the poor survival of patients with specific cancers based on the log-rank test. SKP2 had the highest frequency of alteration in lung cancer and amplification was the most common genetic alteration type. Finally, SKP2-related genes were identified and enrichment analyses were conducted. CONCLUSION: This study presented the first demonstration of the pan-cancer landscape of abnormal SKP2 expression, it could potentially serve as a predictive indicator and prospective therapeutic target.

BRD4 Inhibition Protects Against Myocardial Ischemia/Reperfusion Injury by Suppressing Inflammation and Oxidative Stress Through the PI3K/AKT Signaling Pathway

ABSTRACT

This study aims to investigate the effect and the related mechanisms of bromodomain-containing protein 4 (BRD4) inhibition on myocardial ischemia/reperfusion (I/R) injury. In vivo and in vitro myocardial I/R models were constructed. Expression of BRD4 was examined by RT-qPCR and Western blot. I/R injury was evaluated by analyzing cardiac function and the activity of biochemical markers of myocardial injury. Inflammation and oxidative stress were determined by measuring the levels of myeloperoxidase, TNF-α, IL-6, malondialdehyde, and superoxide dismutase. The activation of the PI3K/AKT signaling pathway was tested by the phosphorylation of p85 and AKT. We found BRD4 was significantly increased in the myocardial tissues after myocardial I/R injury. BRD4 inhibition suppressed the indices of cardiac function and the biochemical markers of myocardial injury. I/R-induced inflammation and oxidative stress were suppressed by shBRD4 in vivo and in vitro. In addition, BRD4 inhibition significantly increased the relative protein expression levels of p-p85, p-AKT T308, and p-AKT S473. In conclusion, this study for the first time demonstrated the protective effect of BRD4 inhibition on myocardial I/R injury in vivo and in vitro, and this effect was related to the suppression of inflammation and oxidative stress through the activation of the PI3K/AKT signaling pathway.

GINS1 Induced Sorafenib Resistance by Promoting Cancer Stem Properties in Human Hepatocellular Cancer Cells

Hepatocellular carcinoma (HCC) is characterized by a high rate of incidence and recurrence, and resistance to chemotherapy may aggravate the poor prognosis of HCC patients. Sorafenib resistance is a conundrum to the treatment of advanced/recurrent HCC. Therefore, studies on the molecular pathogenesis of HCC and the resistance to sorafenib are of great interest. Here, we report that GINS1 was highly expressed in HCC tumors, associated with tumor grades, and predicted poor patient survival using Gene Expression Omnibus (GEO) databases exploration. Cell cycle, cell proliferation assay and in vivo xenograft mouse model indicated that knocking down GINS1 induced in G1/S phase cell cycle arrest and decreased tumor cells proliferation in vitro and in vivo. Spheroid formation assay results showed that GINS1 promoted the stem cell activity of HCC tumor cells. Furthermore, GEO database (GSE17112) analysis showed that HRAS oncogenic gene set was enriched in GINS1 high-expressed cancer cells, and quantitative real-time PCR, and Western blot results proved that GINS1 enhanced HCC progression through regulating HRAS signaling pathway. Moreover, knocking down endogenous GINS1 with shGINS1 increased the sensitivity of HCC cells to sorafenib, and restoring HRAS or stem associated pathway partly recovered the sorafenib resistance. Overall, the collective findings highlight GINS1 functions in hepatocarcinogenesis and sorafenib resistance, and indicate its potential use of GINS1 in drug-resistant HCC.

Comparative Analysis on Abnormal Methylome of Differentially Expressed Genes and Disease Pathways in the Immune Cells of RA and SLE

We identified abnormally methylated, differentially expressed genes (DEGs) and pathogenic mechanisms in different immune cells of RA and SLE by comprehensive bioinformatics analysis. Six microarray data sets of each immune cell (CD19⁺ B cells, CD4⁺ T cells and CD14⁺ monocytes) were integrated to screen DEGs and differentially methylated genes by using R package “limma.” Gene ontology annotations and KEGG analysis of aberrant methylome of DEGs were done using DAVID online database. Protein-protein interaction (PPI) network was generated to detect the hub genes and their methylation levels were compared using DiseaseMeth 2.0 database. Aberrantly methylated DEGs in CD19⁺ B cells (173 and 180), CD4⁺ T cells (184 and 417) and CD14⁺ monocytes (193 and 392) of RA and SLE patients were identified. We detected 30 hub genes in different immune cells of RA and SLE and confirmed their expression using FACS sorted immune cells by qPCR. Among them, 12 genes (BPTF, PHC2, JUN, KRAS, PTEN, FGFR2, ALB, SERB-1, SKP2, TUBA1A, IMP3, and SMAD4) of RA and 12 genes (OAS1, RSAD2, OASL, IFIT3, OAS2, IFIH1, CENPE, TOP2A, PBK, KIF11, IFIT1, and ISG15) of SLE are proposed as potential biomarker genes based on receiver operating curve analysis. Our study suggests that MAPK signaling pathway could potentially differentiate the mechanisms affecting T- and B- cells in RA, whereas PI3K pathway may be used for exploring common disease pathways between RA and SLE. Compared to individual data analyses, more dependable and precise filtering of results can be achieved by integrating several relevant data sets.

Targeting Akt in Hepatocellular Carcinoma and Its Tumor Microenvironment

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related deaths worldwide, and its incidence is rising. HCC develops almost exclusively on the background of chronic liver inflammation, which can be caused by chronic alcohol consumption, viral hepatitis, or an unhealthy diet. The key role of chronic inflammation in the process of hepatocarcinogenesis, including in the deregulation of innate and adaptive immune responses, has been demonstrated. The inhibition of Akt (also known as Protein Kinase B) directly affects cancer cells, but this therapeutic strategy also exhibits indirect anti-tumor activity mediated by the modulation of the tumor microenvironment, as demonstrated by using Akt inhibitors AZD5363, MK-2206, or ARQ 092. Moreover, the isoforms of Akt converge and diverge in their designated roles, but the currently available Akt inhibitors fail to display an isoform specificity. Thus, selective Akt inhibition needs to be better explored in the context of HCC and its possible combination with immunotherapy. This review presents a compact overview of the current knowledge concerning the role of Akt in HCC and the effect of Akt inhibition on the HCC and liver tumor microenvironment.

Signal transduction pathway mutations in gastrointestinal (GI) cancers: a systematic review and meta-analysis

The present study was conducted to evaluate the prevalence of the signaling pathways mutation rate in the Gastrointestinal (GI) tract cancers in a systematic review and meta-analysis study. The study was performed based on the PRISMA criteria. Random models by confidence interval (CI: 95%) were used to calculate the pooled estimate of prevalence via Metaprop command. The pooled prevalence indices of signal transduction pathway mutations in gastric cancer, liver cancer, colorectal cancer, and pancreatic cancer were 5% (95% CI: 3–8%), 12% (95% CI: 8–18%), 17% (95% CI: 14–20%), and 20% (95% CI: 5–41%), respectively. Also, the mutation rates for Wnt pathway and MAPK pathway were calculated to be 23% (95% CI, 14–33%) and 20% (95% CI, 17–24%), respectively. Moreover, the most popular genes were APC (in Wnt pathway), KRAS (in MAPK pathway) and PIK3CA (in PI3K pathway) in the colorectal cancer, pancreatic cancer, and gastric cancer while they were beta-catenin and CTNNB1 in liver cancer. The most altered pathway was Wnt pathway followed by the MAPK pathway. In addition, pancreatic cancer was found to be higher under the pressure of mutation compared with others based on pooled prevalence analysis. Finally, APC mutations in colorectal cancer, KRAS in gastric cancer, and pancreatic cancer were mostly associated gene alterations.

S-Phase Kinase-associated Protein-2 Rejuvenates Senescent Endothelial Progenitor Cells and Induces Angiogenesis in Vivo

Cell cycle slowdown or arrest is a prominent feature of cellular senescence. S-phase kinase-associated protein-2 (Skp2), an F-box subunit of SCF^Skp2 ubiquitin ligase, is a key regulator of G1/S transition. We investigated whether Skp2 plays a role in the regulation of endothelial progenitor cell (EPC) senescence, which is closely associated with aging-related vasculopathy. Replication-induced senescent EPCs demonstrated more pronounced senescence markers and lower Skp2 levels in comparison with those of their younger counterparts. Depletion of Skp2 induced increases in senescence-associated β-galactosidase (SA-βGal) activity and a reduction of telomere length and generated a senescent bioenergetics profile, whereas adenoviral-mediated Skp2 expression reversed the relevant senescence. EPCs isolated from older rats displayed a reduced proliferation rate and increased SA-βGal activity, both of which were significantly reversed by Skp2 ectopic expression. In addition to reversing senescence, Skp2 also rescued the angiogenic activity of senescent EPCs in the ischemic hind limbs of nude mice. The results revealed that ectopic expression of Skp2 has the potential to rejuvenate senescent EPCs and rescue their angiogenic activity and thus may be pivotal in the development of novel strategies to manage aging-related vascular disease.

Paeoniflorin inhibits cell viability and invasion of liver cancer cells via inhibition of Skp2

Paeoniflorin (PF) has been demonstrated to exert tumor suppressive functions in various types of human cancer. However, the mechanisms of PF-mediated anti-tumor activity have not been fully elucidated. S-phase kinase associated protein 2 (Skp2) has been characterized as an oncoprotein that contributes to carcinogenesis. Therefore, the inhibition of Skp2 may be a useful approach for the treatment of various types of human cancer. The present study explored whether PF inhibited the expression of Skp2 in liver cancer cells, leading to cell viability inhibition, induction of apoptosis, and suppression of migration and invasion. PF treatment led to inhibition of Skp2 expression in liver cancer cells. The overexpression of Skp2 abolished PF-mediated anti-cancer activity, whereas the downregulation of Skp2 enhanced this type of activity. The data indicated that PF may be considered as a novel inhibitor of Skp2 in liver cancer cells.

Ubiquitin-Regulated Cell Proliferation and Cancer

Ubiquitin ligases (E3) play a crucial role in the regulation of different cellular processes such as proliferation and differentiation via recognition, interaction, and ubiquitination of key cellular proteins in a spatial and temporal regulated manner. The type of ubiquitin chain formed determines the fate of the substrates. The ubiquitinated substrates can be degraded by the proteasome, display altered subcellular localization, or can suffer modifications on their interaction with functional protein complexes. Deregulation of E3 activities is frequently found in various human pathologies, including cancer. The illegitimated or accelerated degradation of oncosuppressive proteins or, inversely, the abnormally high accumulation of oncoproteins, contributes to cell proliferation and transformation. Anomalies in protein abundance may be related to mutations that alter the direct or indirect recognition of proteins by the E3 enzymes or alterations in the level of expression or activity of ubiquitin ligases. Through a few examples, we illustrate here the complexity and diversity of the molecular mechanisms related to protein ubiquitination involved in cell cycle regulation. We will discuss the role of ubiquitin-dependent degradation mediated by the proteasome, the role of non-proteolytic ubiquitination during cell cycle progression, and the consequences of this deregulation on cellular transformation. Finally, we will highlight the novel opportunities that arise from these studies for therapeutic intervention.

Experimental Models to Define the Genetic Predisposition to Liver Cancer

Hepatocellular carcinoma (HCC) is a frequent human cancer and the most frequent liver tumor. The study of genetic mechanisms of the inherited predisposition to HCC, implicating gene-gene and gene-environment interaction, led to the discovery of multiple gene loci regulating the growth and multiplicity of liver preneoplastic and neoplastic lesions, thus uncovering the action of multiple genes and epistatic interactions in the regulation of the individual susceptibility to HCC. The comparative evaluation of the molecular pathways involved in HCC development in mouse and rat strains differently predisposed to HCC indicates that the genes responsible for HCC susceptibility control the amplification and/or overexpression of c-Myc, the expression of cell cycle regulatory genes, and the activity of Ras/Erk, AKT/mTOR, and of the pro-apoptotic Rassf1A/Nore1A and Dab2IP/Ask1 pathways, the methionine cycle, and DNA repair pathways in mice and rats. Comparative functional genetic studies, in rats and mice differently susceptible to HCC, showed that preneoplastic and neoplastic lesions of resistant mouse and rat strains cluster with human HCC with better prognosis, while the lesions of susceptible mouse and rats cluster with HCC with poorer prognosis, confirming the validity of the studies on the influence of the genetic predisposition to hepatocarinogenesis on HCC prognosis in mouse and rat models. Recently, the hydrodynamic gene transfection in mice provided new opportunities for the recognition of genes implicated in the molecular mechanisms involved in HCC pathogenesis and prognosis. This method appears to be highly promising to further study the genetic background of the predisposition to this cancer.

HBx regulates transcription factor PAX8 stabilization to promote the progression of hepatocellular carcinoma

Transcription factor PAX8 expression is upregulated in several types of cancers. However, little is known about the function of PAX8 in the progression of hepatoma and its regulatory mechanisms. Here, we show that PAX8 silencing inhibits the proliferation and clonogenicity of hepatoma cells and its growth in vivo. The HBV X protein (HBx) does not directly interacts, but stabilizes PAX8 by inhibiting proteasome-dependent ubiquitination and degradation. Furthermore, the E3 ubiquitin ligase complex component Skp2 through its LRR domain directly interacts with the Prd domain of PAX8 and targets PAX8 by recognizing its lysine 275 for ubiquitination and degradation in hepatoma cells. In addition, HBx directly interacts and is colocalized with Skp2 to inhibit its recognition and subsequent ubiquitination and degradation of PAX8 in hepatoma cells. Moreover, HBx upregulates the expression and phosphorylation of Aurora A, a serine-threonine kinase, which interacts with and phosphorylates PAX8 at S209 and T277, compromising the Skp2-recognized PAX8 ubiquitination and destabilization. Thus, HBx stabilizes PAX8 protein by inhibiting the Skp2 targeted PAX8 ubiquitination and enhancing the Aurora A-mediated its phosphorylation, contributing to the progression of hepatoma. Our findings suggest that PAX8 may a new target for design of therapies and uncover new insights into the pathogenesis of hepatoma.

Functional role of SGK3 in PI3K/Pten driven liver tumor development

Background

Hepatocellular carcinoma (HCC) is a leading cause of cancer related deaths worldwide. The PI3K cascade is one of the major signaling pathways underlying HCC development and progression. Activating mutations of PI3K catalytic subunit alpha (PIK3CA) and/or loss of Pten often occur in human HCCs. Serum and glucocorticoid kinase 3 (SGK3) belongs to the SGK family of AGK kinases and functions in parallel to AKT downstream of PI3K. Previous studies have shown that SGK3 may be the major kinase responsible for the oncogenic potential of PIK3CA helical domain mutants, such as PIK3CA(E545K), but not kinase domain mutants, such as PIK3CA(H1047R).

Methods

We investigated the functional contribution of SGK3 in mediating activated PIK3CA mutant or loss of Pten induced HCC development using Sgk3 knockout mice.

Results

We found that ablation of Sgk3 does not affect PIK3CA(H1047R) or PIK3CA(E545K) induced lipogenesis in the liver. Using PIK3CA(H1047R)/c-Met, PIK3CA(E545K)/c-Met, and sgPten/c-Met murine HCC models, we also demonstrated that deletion of Sgk3 moderately delays PIK3CA(E545K)/c-Met driven HCC, while not affecting PIK3CA(H1047R)/c-Met or sgPten/c-Met HCC formation in mice. Similarly, in human HCC cell lines, silencing of SGK3 reduced PIK3CA(E545K) -but not PIK3CA(H1047R)- induced accelerated tumor cell proliferation.

Conclusion

Altogether, our data suggest that SGK3 plays a role in transducing helical domain mutant PIK3CA signaling during liver tumor development.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5551-2) contains supplementary material, which is available to authorized users.

RAS-mediated oncogenic signaling pathways in human malignancies

Abnormally activated RAS proteins are the main oncogenic driver that governs the functioning of major signaling pathways involved in the initiation and development of human malignancies. Mutations in RAS genes and or its regulators, most frequent in human cancers, are the main force for incessant RAS activation and associated pathological conditions including cancer. In general, RAS is the main upstream regulator of the highly conserved signaling mechanisms associated with a plethora of important cellular activities vital for normal homeostasis. Mutated or the oncogenic RAS aberrantly activates a web of interconnected signaling pathways including RAF-MEK (mitogen-activated protein kinase kinase)-ERK (extracellular signal-regulated kinase), phosphoinositide-3 kinase (PI3K)/AKT (protein kinase B), protein kinase C (PKC) and ral guanine nucleotide dissociation stimulator (RALGDS), etc., leading to uncontrolled transcriptional expression and reprogramming in the functioning of a range of nuclear and cytosolic effectors critically associated with the hallmarks of carcinogenesis. This review highlights the recent literature on how oncogenic RAS negatively use its signaling web in deregulating the expression and functioning of various effector molecules in the pathogenesis of human malignancies.

Ubiquitin ligases in oncogenic transformation and cancer therapy

The cellular response to external stress signals and DNA damage depends on the activity of ubiquitin ligases (E3s), which regulate numerous cellular processes, including homeostasis, metabolism and cell cycle progression. E3s recognize, interact with and ubiquitylate protein substrates in a temporally and spatially regulated manner. The topology of the ubiquitin chains dictates the fate of the substrates, marking them for recognition and degradation by the proteasome or altering their subcellular localization or assembly into functional complexes. Both genetic and epigenetic alterations account for the deregulation of E3s in cancer. Consequently, the stability and/or activity of E3 substrates are also altered, in some cases leading to downregulation of tumour-suppressor activities and upregulation of oncogenic activities. A better understanding of the mechanisms underlying E3 regulation and function in tumorigenesis is expected to identify novel prognostic markers and to enable the development of the next generation of anticancer therapies. This Review summarizes the oncogenic and tumour-suppressor roles of selected E3s and highlights novel opportunities for therapeutic intervention.

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.

Dual inhibition of BRD4 and PI3K-AKT by SF2523 suppresses human renal cell carcinoma cell growth

Bromodomain-containing protein 4 (BRD4) and PI3K-AKT are both important for renal cell carcinoma (RCC) development and progression. SF2523 is a BRD4 and PI3K-AKT dual inhibitor. The present study demonstrated that SF2523 was cytotoxic and anti-proliferative to established RCC cell lines (786-O and A498) and primary human RCC cells. SF2523 induced activation of caspase and apoptosis in RCC cells. Further, SF2523 disrupted RCC cell cycle progression and inhibited cell migration in vitro. At the signaling level, SF2523 in-activated PI3K-AKT-mTOR, and downregulated BRD4-dependent proteins, Bcl-2 and Myc, in RCC cells. Remarkably, SF2523 was more efficient than Wortmannin (the PI3K inhibitor) and JQ1 (the BRD4 specific inhibitor) in killing RCC cells. In vivo, SF2523 administration at well-tolerated doses suppressed 786-O xenograft tumor growth in severe combined immunodeficient (SCID) mice. Together, our results suggest that concurrent blockage of BRD4 and PI3K-AKT signalings by SF2523 efficiently inhibits RCC cell growth in vitro and in vivo.

Targeting β-catenin in hepatocellular cancers induced by coexpression of mutant β-catenin and K-Ras in mice

Recently, we have shown that coexpression of hMet and mutant-β-catenin using sleeping beauty transposon/transposase leads to hepatocellular carcinoma (HCC) in mice that corresponds to around 10% of human HCC. In the current study, we investigate whether Ras activation, which can occur downstream of Met signaling, is sufficient to cause HCC in association with mutant-β-catenin. We also tested therapeutic efficacy of targeting β-catenin in an HCC model. We show that mutant-K-Ras (G12D), which leads to Ras activation, cooperates with β-catenin mutants (S33Y, S45Y) to yield HCC in mice. Affymetrix microarray showed > 90% similarity in gene expression in mutant-K-Ras-β-catenin and Met-β-catenin HCC. K-Ras-β-catenin tumors showed up-regulation of β-catenin targets like glutamine synthetase (GS), leukocyte cell-derived chemotaxin 2, Regucalcin, and Cyclin-D1 and of K-Ras effectors, including phosphorylated extracellular signal-regulated kinase, phosphorylated protein kinase B, phosphorylated mammalian target of rapamycin, phosphorylated eukaryotic translation initiation factor 4E, phosphorylated 4E-binding protein 1, and p-S6 ribosomal protein. Inclusion of dominant-negative transcription factor 4 at the time of K-Ras-β-catenin injection prevented HCC and downstream β-catenin and Ras signaling. To address whether targeting β-catenin has any benefit postestablishment of HCC, we administered K-Ras-β-catenin mice with EnCore lipid nanoparticles (LNP) loaded with a Dicer substrate small interfering RNA targeting catenin beta 1 (CTNNB1; CTNNB1-LNP), scrambled sequence (Scr-LNP), or phosphate-buffered saline for multiple cycles. A significant decrease in tumor burden was evident in the CTNNB1-LNP group versus all controls, which was associated with dramatic decreases in β-catenin targets and some K-Ras effectors, leading to reduced tumor cell proliferation and viability. Intriguingly, in relatively few mice, non-GS-positive tumors, which were evident as a small subset of overall tumor burden, were not affected by β-catenin suppression.

CONCLUSION

Ras activation downstream of c-Met is sufficient to induce clinically relevant HCC in cooperation with mutant β-catenin. β-catenin suppression by a clinically relevant modality is effective in treatment of β-catenin-positive, GS-positive HCCs. (Hepatology 2017;65:1581-1599).

Down-regulation of the cyclin-dependent kinase inhibitor p57 is mediated by Jab1/Csn5 in hepatocarcinogenesis

Down-regulation of p57 (KIP2) cyclin-dependent kinase inhibitors accelerates the growth and invasion of hepatocellular carcinoma (HCC), suggesting that p57 may play an important role in liver carcinogenesis. However, the mechanism or oncogenic signal leading to p57 down-regulation in HCC remains to be determined. Herein, we demonstrated that Jab1/Csn5 expression is negatively correlated with p57 levels in HCC tissues. Kaplan-Meier analysis of tumor samples revealed that high Jab1/Csn5 expression with concurrent low p57 expression is associated with poor overall survival. The inverse pattern of Jab1 and p57 expression was also observed during carcinogenesis in a chemically induced rat HCC model. We also found that mechanistically, Jab1-mediated p57 proteolysis in HCC cells is dependent on 26S-proteasome inhibitors. We further demonstrated that direct physical interaction between Jab1 and p57 triggers p57 down-regulation, independently of Skp2 and Akt pathways, in HCC cells. These data suggest that Jab1 is an important upstream negative regulator of p57 and that aberrant expression of Jab1 in HCC could lead to a significant decrease in p57 levels and contribute to tumor cell growth. Furthermore, restoration of p57 levels induced by loss of Jab1 inhibited tumor cell growth and further increased cell apoptosis in HCC cells. Moreover, silencing Jab1 expression further enhanced the antitumor effects of cisplatin-induced apoptosis in HCC cells.

CONCLUSION

Jab1-p57 pathway confers resistance to chemotherapy and may represent a potential target for investigational therapy in HCC.

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.

Co-activation of PIK3CA and Yap promotes development of hepatocellular and cholangiocellular tumors in mouse and human liver

Activation of the PI3K and Yes-associated protein (Yap) signaling pathways has been independently reported in human hepatocellular carcinoma (HCC). However, the oncogenic interactions between these two cascades in hepatocarcinogenesis remain undetermined. To assess the consequences of the crosstalk between the PI3K and Yap pathways along liver carcinogenesis, we generated a mouse model characterized by combined overexpression of activated mutant forms of PIK3CA (PIK3CAH1047R) and Yap (YapS127A) in the mouse liver using hydrodynamic transfection (PIK3CA/Yap). In addition, suppression of PI3K and Yap pathways was conducted in human HCC and cholangiocarcinoma (CCA) cell lines. We found that concomitant activation of PI3K and Yap pathways triggered rapid liver tumor development in mice. Histologically, tumors were pure HCC, CCA, or mixed HCC/CCA. At the molecular level, PIK3CA/Yap tumors were characterized by activation of the mTORC1/2, ERK/MAPK, and Notch pathways. Simultaneous activation of PI3K and Yap pathways frequently occurred in human liver tumor specimens and their combined suppression was highly detrimental for the growth of HCC and CCA cell lines. In conclusion, our study demonstrates the oncogenic cooperation between PI3K and Yap pathways along liver carcinogenesis. The PIK3CA/Yap mouse represents an important preclinical liver tumor model for the development of novel therapeutics against this malignancy.