Matrix viscoelasticity promotes liver cancer progression in the pre-cirrhotic liver.

Type 2 diabetes mellitus is a major risk factor for hepatocellular carcinoma (HCC). Changes in extracellular matrix (ECM) mechanics contribute to cancer development1,2, and increased stiffness is known to promote HCC progression in cirrhotic conditions3,4. Type 2 diabetes mellitus is characterized by an accumulation of advanced glycation end-products (AGEs) in the ECM; however, how this affects HCC in non-cirrhotic conditions is unclear. Here we find that, in patients and animal models, AGEs promote changes in collagen architecture and enhance ECM viscoelasticity, with greater viscous dissipation and faster stress relaxation, but not changes in stiffness. High AGEs and viscoelasticity combined with oncogenic ß-catenin signalling promote HCC induction, whereas inhibiting AGE production, reconstituting the AGE clearance receptor AGER1 or breaking AGE-mediated collagen cross-links reduces viscoelasticity and HCC growth. Matrix analysis and computational modelling demonstrate that lower interconnectivity of AGE-bundled collagen matrix, marked by shorter fibre length and greater heterogeneity, enhances viscoelasticity. Mechanistically, animal studies and 3D cell cultures show that enhanced viscoelasticity promotes HCC cell proliferation and invasion through an integrin-ß1-tensin-1-YAP mechanotransductive pathway. These results reveal that AGE-mediated structural changes enhance ECM viscoelasticity, and that viscoelasticity can promote cancer progression in vivo, independent of stiffness.

Inhibition of Heat Shock Factor 1 Signaling Decreases Hepatoblastoma Growth via Induction of Apoptosis.

Although rare compared with adult liver cancers, hepatoblastoma (HB) is the most common pediatric liver malignancy, and its incidence is increasing. Currently, the treatment includes surgical resection with or without chemotherapy, and in severe cases, liver transplantation in children. The effort to develop more targeted, HB-specific therapies has been stymied by the lack of fundamental knowledge about HB biology. Heat shock factor 1 (HSF1), a transcription factor, is a canonical inducer of heat shock proteins, which act as chaperone proteins to prevent or undo protein misfolding. Recent work has shown a role for HSF1 in cancer beyond the canonical heat shock response. The current study found increased HSF1 signaling in HB versus normal liver. It showed that less differentiated, more embryonic tumors had higher levels of HSF1 than more differentiated, more fetal-appearing tumors. Most strikingly, HSF1 expression levels correlated with mortality. This study used a mouse model of HB to test the effect of inhibiting HSF1 early in tumor development on cancer growth. HSF1 inhibition resulted in fewer and smaller tumors, suggesting HSF1 is needed for aggressive tumor growth. Moreover, HSF1 inhibition also increased apoptosis in tumor foci. These data suggest that HSF1 may be a viable pharmacologic target for HB treatment.

s valence electrons in cations of metal oxides serving as descriptors for electron and hole polarons.

In some metal oxides, an excess electron can give rise to the formation of a small polaron localized on a single site. However, there are still some metal oxides that exhibit the formation of a large polaron. The underlying mechanism behind this phenomenon remains unclear. In this study, we investigate polaron formation in metal oxides favorable for polaron formation using different functionals and through a review of the literature. Our findings indicate that the s valence electrons in cations could serve as a descriptor to classify the polarons in materials. In metal oxides with cations having ns (n ⩾ 5) valence electrons, excess charges trend to localize on several sites or form a two-dimensional shape, and even a large polaron, as these s electrons are delocalized in nature and have a large effect on p or d state polarons. The delocalized nature of ns (n ⩽ 4) valence electrons in cations is relatively small and does not affect the localization condition of p or d state polarons. Therefore, the excess charges in these metal oxides with ns (n ⩽ 4) valence electrons prefer to form a small polaron localizing on a single site. This work unveils the impact of the s valence in cations on polaron formation and provides a fundamental understanding of various types of polarons in metal oxides.

Post-fertilization 2-ethylhexyl-4-methoxycinnamate (EHMC) exposure affects axonal growth, muscle fiber length, and motor behavior in zebrafish embryos.

Organic UV filters, which are often found in the environment, have been the focus of much public health concern. 2-ethylhexyl-4-methoxycinnamate (EHMC) is one of the most common organic UV filters present in the environment. However, few studies have investigated its developmental neurotoxic (DNT) effects and the underlying molecular mechanisms. In the present study, zebrafish embryos were exposed to low concentration of EHMC (0, 0.01, 0.1, 1 mg/L) in static water starting from 6 h post-fertilization (hpf). Results showed that EHMC exposure caused a reduction in somite count at 13 hpf, a diminishment in head-trunk angle at 30 hpf, a delay in hatching at 48 hpf, and a decrease in head depth and head length at both 30 and 48 hpf. Additionally, EHMC led to abnormal motor behaviors at various developmental stages including altered spontaneous movement at both 23 and 24 hpf, and decreased touch response at 30 hpf. Consistent with these morphological changes and motor behavior deficits, EHMC inhibited axonal growth of primary motor neurons at 30 and 48 hpf, and yielded subtle changes in muscle fiber length at 48 hpf, suggesting the functional relevance of structural changes. Moreover, EHMC exposure induced excessive cell apoptosis in the head and spinal cord regions, increased the production of reactive oxygen species (ROS) and malondialdehyde (MDA), and reduced the level of glutathione (GSH). Defects of lateral line system neuromasts were also observed, but no structural deformity of blood vessels was seen in developing zebrafish. Abnormal expression of axonal growth-related genes (gap43, mbp, shha, and α1-tubulin) and apoptosis-related genes (bax/bcl-2 and caspase-3) revealed potential molecular mechanisms regarding the defective motor behaviors and aberrant phenotype. In summary, our findings indicate that EHMC induced developmental neurotoxicity in zebrafish, making it essential to assess its risks and provide warnings regarding EHMC exposure.

Chronic arsenite exposure induced skeletal muscle atrophy by disrupting angiotensin II-melatonin axis in rats.

Arsenic is a well-known environmental toxicant and emerging evidence suggests that arsenic exposure has potential skeletal muscle toxicity; however, the underlying mechanism has not yet been clarified. The aim of this study was to investigate the correlation among adverse effects of subchronic and chronic environmental arsenic exposure on skeletal muscle as well as specific myokines secretion and angiotensin II (AngII)-melatonin (MT) axis in rats. Four-week-old rats were exposed to arsenite (iAs) in drinking water at environmental relevant concentration of 10 ppm for 3 or 9 months. Results indicated that the gastrocnemius muscle had atrophied and its mass was decreased in rats exposed to arsenite for 9 months, whereas, they had no significant changes in rats exposed to arsenite for 3 months. The levels of serum-specific myokine irisin and gastrocnemius muscle insulin-like growth factor-1 (IGF-1) were increased in 3-month exposure group and decreased in 9-month exposure group, while serum myostatin (MSTN) was increased significantly in 9-month exposure group. In addition, serum AngII level increased both in 3- and 9-month exposure groups, while serum MT level increased in 3-month exposure group and decreased in 9-month exposure group. Importantly, the ratio of AngII to MT level in serum increased gradually with the prolongation of arsenite exposure. It showed a certain correlation between AngII-MT axis and gastrocnemius muscle mass, gastrocnemius muscle level of IGF-1 or serum levels of irisin and MSTN. In conclusion, the disruption of AngII-MT axis balance may be a significant factor for skeletal muscle atrophy induced by chronic environmental arsenic exposure.

NOTCH-YAP1/TEAD-DNMT1 Axis Drives Hepatocyte Reprogramming Into Intrahepatic Cholangiocarcinoma.

BACKGROUND & AIMS: Intrahepatic cholangiocarcinoma (ICC) is a devastating liver cancer with extremely high intra- and inter-tumoral molecular heterogeneity, partly due to its diverse cellular origins. We investigated clinical relevance and the molecular mechanisms underlying hepatocyte (HC)-driven ICC development. METHODS: Expression of ICC driver genes in human diseased livers at risk for ICC development were examined. The sleeping beauty and hydrodynamic tail vein injection based Akt-NICD/YAP1 ICC model was used to investigate pathogenetic roles of SRY-box transcription factor 9 (SOX9) and yes-associated protein 1 (YAP1) in HC-driven ICC. We identified DNA methyltransferase 1 (DNMT1) as a YAP1 target, which was validated by loss- and gain-of-function studies, and its mechanism addressed by chromatin immunoprecipitation sequencing. RESULTS: Co-expression of AKT and Notch intracellular domain (NICD)/YAP1 in HC yielded ICC that represents 13% to 29% of clinical ICC. NICD independently regulates SOX9 and YAP1 and deletion of either, significantly delays ICC development. Yap1 or TEAD inhibition, but not Sox9 deletion, impairs HC-to-biliary epithelial cell (BEC) reprogramming. DNMT1 was discovered as a novel downstream effector of YAP1-TEAD complex that directs HC-to-BEC/ICC fate switch through the repression of HC-specific genes regulated by master regulators for HC differentiation, including hepatocyte nuclear factor 4 alpha, hepatocyte nuclear factor 1 alpha, and CCAAT/enhancer-binding protein alpha/beta. DNMT1 loss prevented NOTCH/YAP1-dependent HC-driven cholangiocarcinogenesis, and DNMT1 re-expression restored ICC development following TEAD repression. Co-expression of DNMT1 with AKT was sufficient to induce tumor development including ICC. DNMT1 was detected in a subset of HCs and dysplastic BECs in cholestatic human livers prone to ICC development. CONCLUSION: We identified a novel NOTCH-YAP1/TEAD-DNMT1 axis essential for HC-to-BEC/ICC conversion, which may be relevant in cholestasis-to-ICC pathogenesis in the clinic.

Matrix in River Water, Sediments, and Biofilms Mitigates Mercury Toxicity to Medaka (Oryzias Latipes).

Impacts of an environmental matrix on mercury (Hg) bioavailability and toxicity to medaka (Oryzias latipes) were investigated in matrix-free controls and treatments with a stepwise increased environmental matrix of river water, sediments, and biofilms. Generally, river water enhanced but the presence of sediments and biofilms reduced Hg bioavailability to medaka up to 105 times, so that Hgtotal concentrations/amounts among different environmental media cannot mirror Hg availability and toxicity to medaka. On average, 12.9 and 12.4% of Hg in medaka was, respectively, methylated to methylmercury (MeHg) in matrix-free and -containing treatments, indicating no influence of the environmental matrix on Hg methylation in medaka. All oxidative stress, inflammatory injury, and malformation parameters correlated strongly and significantly with Hgtotal and MeHg concentrations in medaka, notably with steeper slopes in matrix-free controls than in matrix-containing treatments, highlighting that the environmental matrix mitigated Hg and MeHg toxicity to medaka. Moreover, oxidative stress was more strongly mitigated than inflammatory injury according to the stronger decreases of the regression line slopes from matrix-free to -containing treatments. Here, we have newly identified that the potential of the environmental matrix to decrease Hg bioavailability and mitigate Hg toxicity to fish together could buffer Hg ecotoxicity in the aquatic environment.

Environmentally relevant concentrations of organic (benzophenone-3) and inorganic (titanium dioxide nanoparticles) UV filters co-exposure induced neurodevelopmental toxicity in zebrafish.

UV filters, widely used in personal care products, are ubiquitous environmental pollutants detected and pose a significant public health concern. Benzophenone-3 (BP3) and titanium dioxide nanoparticles (nano-TiO2) are the predominant organic and inorganic UV filters in environmental media. However, few studies have explored the combined developmental neurotoxic (DNT) effects and the underlying mechanisms when co-exposed to BP3 and nano-TiO2. In the present study, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations of BP3 (10 µg/L), nano-TiO2 (100 µg/L), and mixtures starting from 6 h post fertilization (hpf), respectively. Developmental indicators and motor behaviors were investigated at various developmental stages. Our results showed that BP3 alone or co-exposed with nano-TiO2 increased spontaneous movement at 24 hpf, co-exposure decreased touch response at 30 hpf and hatching rate at 60 hpf. Consistent with these motor deficits, co-exposure to BP3 and nano-TiO2 inhibited relative axon length of primary motor neuron during the early developmental stages, disturbed the expression of axonal growth-related genes at 30 and 48 hpf, increased cell apoptosis on the head region and mRNA levels of apoptosis-related genes, and also increased reactive oxygen species (ROS) levels in zebrafish, suggesting the functional relevance of structural changes. Taken together, our findings demonstrated that BP3 alone or in combination with nano-TiO2 at environmentally relevant concentrations induced evident neurotoxic effects on the developing embryos in zebrafish.

Role of Lipogenesis Rewiring in Hepatocellular Carcinoma.

Metabolic rewiring is one of the hallmarks of cancer. Altered de novo lipogenesis is one of the pivotal metabolic events deregulated in cancers. Sterol regulatory element-binding transcription factor 1 (SREBP1) controls the transcription of major enzymes involved in de novo lipogenesis, including ACLY, ACACA, FASN, and SCD. Studies have shown the increased de novo lipogenesis in human hepatocellular carcinoma (HCC) samples. Multiple mechanisms, such as activation of the AKT/mechanistic target of rapamycin (mTOR) pathway, lead to high SREBP1 induction and the coordinated enhanced expression of ACLY, ACACA, FASN, and SCD genes. Subsequent functional analyses have unraveled these enzymes' critical role(s) and the related de novo lipogenesis in hepatocarcinogenesis. Importantly, targeting these molecules might be a promising strategy for HCC treatment. This paper comprehensively summarizes de novo lipogenesis rewiring in HCC and how this pathway might be therapeutically targeted.

The Role of Fibroblast Growth Factor 19 in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common type of cancer and the third leading cause of cancer-related deaths worldwide. Liver resection or liver transplantation is the most effective therapy for HCC because drugs approved by the US Food and Drug Administration to treat patients with unresectable HCC have an unfavorable overall survival rate. Therefore, the development of biomarkers for early diagnosis and effective therapy strategies are still necessary to improve patient outcomes. Fibroblast growth factor (FGF) 19 was amplified in patients with HCC from various studies, including patients from The Cancer Genome Atlas. FGF19 plays a syngeneic function with other signaling pathways in primary liver cancer development, such as epidermal growth factor receptor, Wnt/ß-catenin, the endoplasmic reticulum-related signaling pathway, STAT3/IL-6, RAS, and extracellular signal-regulated protein kinase, among others. The current review presents a comprehensive description of the FGF19 signaling pathway involved in liver cancer development. The use of big data and bioinformatic analysis can provide useful clues for further studies of the FGF19 pathway in HCC, including its application as a biomarker, targeted therapy, and combination therapy strategies.

Nuclear factor erythroid 2-related factor 2 and ß-Catenin Coactivation in Hepatocellular Cancer: Biological and Therapeutic Implications.

BACKGROUND AND AIMS: HCC remains a major unmet clinical need. Although activating catenin beta-1 (CTNNB1) mutations are observed in prominent subsets of HCC cases, these by themselves are insufficient for hepatocarcinogenesis. Coexpression of mutant CTNNB1 with clinically relevant co-occurrence has yielded HCCs. Here, we identify cooperation between ß-catenin and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling in HCC. APPROACH AND RESULTS: Public HCC data sets were assessed for concomitant presence of CTNNB1 mutations and either mutations in nuclear factor erythroid-2-related factor-2 (NFE2L2) or Kelch like-ECH-associated protein 1 (KEAP1), or Nrf2 activation by gene signature. HCC development in mice and similarity to human HCC subsets was assessed following coexpression of T41A-CTNNB1 with either wild-type (WT)-, G31A-, or T80K-NFE2L2. Based on mammalian target of rapamycin complex 1 activation in CTNNB1-mutated HCCs, response of preclinical HCC to mammalian target of rapamycin (mTOR) inhibitor was investigated. Overall, 9% of HCC cases showed concomitant CTNNB1 mutations and Nrf2 activation, subsets of which were attributable to mutations in NFE2L2/KEAP1. Coexpression of mutated CTNNB1 with mutant NFE2L2, but not WT-NFE2L2, led to HCC development and mortality by 12-14 weeks. These HCCs were positive for ß-catenin targets, like glutamine synthetase and cyclin-D1, and Nrf2 targets, like NAD(P)H quinone dehydrogenase 1 and peroxiredoxin 1. RNA-sequencing and pathway analysis showed high concordance of preclinical HCC to human HCC subset showing activation of unique (iron homeostasis and glioblastoma multiforme signaling) and expected (glutamine metabolism) pathways. NFE2L2-CTNNB1 HCC mice were treated with mTOR inhibitor everolimus (5-mg/kg diet ad libitum), which led to >50% decrease in tumor burden. CONCLUSIONS: Coactivation of ß-catenin and Nrf2 is evident in 9% of all human HCCs. Coexpression of mutant NFE2L2 and mutant CTNNB1 led to clinically relevant HCC development in mice, which responded to mTOR inhibitors. Thus, this model has both biological and therapeutic implications.

ORN: Inferring patient-specific dysregulation status of pathway modules in cancer with OR-gate Network.

Pathway level understanding of cancer plays a key role in precision oncology. However, the current amount of high-throughput data cannot support the elucidation of full pathway topology. In this study, instead of directly learning the pathway network, we adapted the probabilistic OR gate to model the modular structure of pathways and regulon. The resulting model, OR-gate Network (ORN), can simultaneously infer pathway modules of somatic alterations, patient-specific pathway dysregulation status, and downstream regulon. In a trained ORN, the differentially expressed genes (DEGs) in each tumour can be explained by somatic mutations perturbing a pathway module. Furthermore, the ORN handles one of the most important properties of pathway perturbation in tumours, the mutual exclusivity. We have applied the ORN to lower-grade glioma (LGG) samples and liver hepatocellular carcinoma (LIHC) samples in TCGA and breast cancer samples from METABRIC. Both datasets have shown abnormal pathway activities related to immune response and cell cycles. In LGG samples, ORN identified pathway modules closely related to glioma development and revealed two pathways closely related to patient survival. We had similar results with LIHC samples. Additional results from the METABRIC datasets showed that ORN could characterize critical mechanisms of cancer and connect them to less studied somatic mutations (e.g., BAP1, MIR604, MICAL3, and telomere activities), which may generate novel hypothesis for targeted therapy.

Polaron formation and transport in Bi2WO6 studied by DFT+U and hybrid PBE0 functional approaches.

Bi2WO6 (BWO) is considered as a promising material for photocatalytic water splitting. Its unique layered structure leads the charge separation, and transport is different from other materials. However, the charge transport mechanisms in BWO are not well understood. In this work, we investigated polaron formation and transport in BWO using the DFT+U and hybrid PBE0 functional approaches. We found that the electron will form 2-dimensional (2D)-shaped polarons among W sites in the ab plane of BWO with approximately 55% polaron density state on the central W site. This type of polaron is similar to the electron polarons in WO3. For other W-based materials, the electrons may also form a 2D-shaped polaron. We found that the W 6s orbital plays an important role in these 2D-shaped electron polarons. The calculated mobility of electron polarons in BWO was consistent with experimental findings. For the hole state, it could form a small hole polaron on the O site with O 2p in character. However, it will not form a polaron on the Bi site, which is quite different from BiVO4. This study provides insight for understanding polaron formation and transport in materials with W and Bi ions. It also provides understanding regarding charge separation and transport for materials with layered structures.

Phosphorylated Ezrin (Thr567) Regulates Hippo Pathway and Yes-Associated Protein (Yap) in Liver.

The activation of CD81 [the portal of entry of hepatitis C virus (HCV)] by agonistic antibody results in phosphorylation of Ezrin via Syk kinase and is associated with inactivation of the Hippo pathway and increase in yes-associated protein (Yap1). The opposite occurs when glypican-3 or E2 protein of HCV binds to CD81. Hepatocyte-specific glypican-3 transgenic mice have decreased levels of phosphorylated (p)-Ezrin (Thr567) and Yap, increased Hippo activity, and suppressed liver regeneration. The role of Ezrin in these processes has been speculated, but not proved. We show that Ezrin has a direct role in the regulation of Hippo pathway and Yap. Forced expression of plasmids expressing mutant Ezrin (T567D) that mimics p-Ezrin (Thr567) suppressed Hippo activity and activated Yap signaling in hepatocytes in vivo and enhanced activation of pathways of ß-catenin and leucine rich repeat containing G protein-coupled receptor 4 (LGR4) and LGR5 receptors. Hepatoma cell lines JM1 and JM2 have decreased CD81 expression and Hippo activity and up-regulated p-Ezrin (T567). NSC668394, a p-Ezrin (Thr567) antagonist, significantly decreased hepatoma cell proliferation. We additionally show that p-Ezrin (T567) is controlled by epidermal growth factor receptor and MET. Ezrin phosphorylation, mediated by CD81-associated Syk kinase, is directly involved in regulation of Hippo pathway, Yap levels, and growth of normal and neoplastic hepatocytes. The finding has mechanistic and potentially therapeutic applications in hepatocyte growth biology, hepatocellular carcinoma, and HCV pathogenesis.

The Hippo Effector Transcriptional Coactivator with PDZ-Binding Motif Cooperates with Oncogenic ß-Catenin to Induce Hepatoblastoma Development in Mice and Humans.

Hepatoblastoma (HB) is the most common pediatric liver tumor. Though Wnt/ß-catenin and Hippo cascades are implicated in HB development, studies on crosstalk between ß-catenin and Hippo downstream effector transcriptional coactivator with PDZ-binding motif (TAZ) in HB are lacking. Expression levels of TAZ and ß-catenin in human HB specimens were assessed by immunohistochemistry. Functional interplay between TAZ and ß-catenin was determined by overexpression of an activated form of TAZ (TAZS89A), either alone or combined with an oncogenic form of ß-catenin (ΔN90-ß-catenin), in mouse liver via hydrodynamic transfection. Activation of TAZ often co-occurred with that of ß-catenin in clinical specimens. Although the overexpression of TAZS89A alone did not induce hepatocarcinogenesis, concomitant overexpression of TAZS89A and ΔN90-ß-catenin triggered the development of HB lesions exhibiting both epithelial and mesenchymal features. Mechanistically, TAZ/ß-catenin-driven HB development required TAZ interaction with transcriptional enhanced associate domain factors. Blockade of the Notch cascade did not inhibit TAZ/ß-catenin-dependent HB formation in mice but suppressed the mesenchymal phenotype. Neither Yes-associated protein nor heat shock factor 1 depletion affected HB development in TAZ/ß-catenin mice. In human HB cell lines, silencing of TAZ resulted in decreased cell growth, which was further reduced when TAZ knockdown was associated with suppression of either ß-catenin or Yes-associated protein. Overall, our study identified TAZ as a crucial oncogene in HB development and progression.

Primary resistance to first-generation EGFR-TKIs induced by MDM2 amplification in NSCLC.

INTRODUCTION: Targeted therapy for NSCLC is rapidly evolving. EGFR-TKIs benefit NSCLC patients with sensitive EGFR mutations and significantly prolong survival. However, 20-30% of patients demonstrate primary resistance to EGFR-TKIs, which leads to the failure of EGFR-TKI treatment. The mechanisms of primary resistance to EGFR-TKIs require further study. METHODS: Targeted sequencing was used for the detection of genomic alterations among patients in our center. Regular cell culture and transfection with plasmids were used to establish NSCLC cell lines over-expressing MDM2 and vector control. We used the MTT assays to calculate the inhibition rate after exposure to erlotinib. Available datasets were used to determine the role of MDM2 in the prognosis of NSCLC. RESULTS: Four patients harboring concurrent sensitive EGFR mutations and MDM2 amplifications demonstrated insensitivity to EGFR-TKIs in our center. In vitro experiments suggested that MDM2 amplification induces primary resistance to erlotinib. Over-expressed MDM2 elevated the IC50 value of erlotinib in HCC2279 line and reduced the inhibition rate. In addition, MDM2 amplification predicted a poor prognosis in NSCLC patients and was associated with a short PFS in those treated with EGFR-TKIs. The ERBB2 pathway was identified as a potential pathway activated by MDM2 amplification could be the focus of further research. CONCLUSION: MDM2 amplification induces the primary resistance to EGFR-TKIs and predicts poor prognosis in NSCLC patients. MDM2 may serve as a novel biomarker and treatment target for NSCLC. Further studies are needed to confirm the mechanism by which amplified MDM2 leads to primary resistance to EGFR-TKIs.

TEA Domain Transcription Factor 4 Is the Major Mediator of Yes-Associated Protein Oncogenic Activity in Mouse and Human Hepatoblastoma.

Hepatoblastoma (HB) is the most common type of pediatric liver cancer. Activation of yes-associated protein (YAP) has been implicated in HB molecular pathogenesis. The transcriptional co-activator Yap regulates downstream gene expression through interaction with the TEA domain (TEAD) proteins. Nonetheless, YAP also displays functions that are independent of its transcriptional activity. The underlying molecular mechanisms by which Yap promotes HB development remain elusive. In the current study, we demonstrated that blocking TEAD function via the dominant-negative form of TEAD2 abolishes Yap-driven HB formation in mice and restrains human HB growth in vitro. When TEAD2 DNA-binding domain was fused with virus protein 16 transcriptional activation domain, it synergized with activated ß-catenin to promote HB formation in vivo. Among TEAD genes, silencing of TEAD4 consistently inhibited tumor growth and Yap target gene expression in HB cell lines. Furthermore, TEAD4 mRNA expression was significantly higher in human HB lesions when compared with corresponding nontumorous liver tissues. Human HB specimens also exhibited strong nuclear immunoreactivity for TEAD4. Altogether, data demonstrate that TEAD-mediated transcriptional activity is both sufficient and necessary for Yap-driven HB development. TEAD4 is the major TEAD isoform and Yap partner in human HB. Targeting TEAD4 may represent an effective treatment option for human HB.

ß-Catenin and Yes-Associated Protein 1 Cooperate in Hepatoblastoma Pathogenesis.

Hepatoblastoma (HB), the most common pediatric primary liver neoplasm, shows nuclear localization of ß-catenin and yes-associated protein 1 (YAP1) in almost 80% of the cases. Co-expression of constitutively active S127A-YAP1 and ΔN90 deletion-mutant ß-catenin (YAP1-ΔN90-ß-catenin) causes HB in mice. Because heterogeneity in downstream signaling is being identified owing to mutational differences even in the ß-catenin gene alone, we investigated if co-expression of point mutants of ß-catenin (S33Y or S45Y) with S127A-YAP1 led to similar tumors as YAP1-ΔN90-ß-catenin. Co-expression of S33Y/S45Y-ß-catenin and S127A-YAP1 led to activation of Yap and Wnt signaling and development of HB, with 100% mortality by 13 to 14 weeks. Co-expression with YAP1-S45Y/S33Y-ß-catenin of the dominant-negative T-cell factor 4 or dominant-negative transcriptional enhanced associate domain 2, the respective surrogate transcription factors, prevented HB development. Although histologically similar, HB in YAP1-S45Y/S33Y-ß-catenin, unlike YAP1-ΔN90-ß-catenin HB, was glutamine synthetase (GS) positive. However, both ΔN90-ß-catenin and point-mutant ß-catenin comparably induced GS-luciferase reporter in vitro. Finally, using a previously reported 16-gene signature, it was shown that YAP1-ΔN90-ß-catenin HB tumors exhibited genetic similarities with more proliferative, less differentiated, GS-negative HB patient tumors, whereas YAP1-S33Y/S45Y-ß-catenin HB exhibited heterogeneity and clustered with both well-differentiated GS-positive and proliferative GS-negative patient tumors. Thus, we demonstrate that ß-catenin point mutants can also collaborate with YAP1 in HB development, albeit with a distinct molecular profile from the deletion mutant, which may have implications in both biology and therapy.

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

Inactivating mutations of axis inhibition protein 1 (AXIN1), a negative regulator of the Wnt/ß-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/ß-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-ß-Catenin revealed activation of the Wnt/ß-Catenin and Notch signaling in c-Met/sgAxin1 HCCs. However, only a few of the canonical Wnt/ß-Catenin target genes were induced in c-Met/sgAxin1 HCC when compared with corresponding lesions from c-Met/∆N90-ß-Catenin mice. To study whether endogenous ß-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 ß-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 ß-Catenin signaling-dependent but Notch cascade-independent way.

Advancement in research and therapy of NF1 mutant malignant tumors.

The NF1 gene encodes neurofibromin, which is one of the primary negative regulatory factors of the Ras protein. Neurofibromin stimulates the GTPase activity of Ras to convert it from an active GTP-bound form to its inactive GDP-bound form through its GTPase activating protein-related domain (GRD). Therefore, neurofibromin serves as a shutdown signal for all vertebrate RAS GTPases. NF1 mutations cause a resultant decrease in neurofibromin expression, which has been detected in many human malignancies, including NSCLC, breast cancer and so on. NF1 mutations are associated with the underlying mechanisms of treatment resistance discovered in multiple malignancies. This paper reviews the possible mechanisms of NF1 mutation-induced therapeutic resistance to chemotherapy, endocrine therapy and targeted therapy in malignancies. Then, we further discuss advancements in targeted therapy for NF1-mutated malignant tumors. In addition, therapies targeting the downstream molecules of NF1 might be potential novel strategies for the treatment of advanced malignancies.