Histone acetylation-mediated regulation of the Hippo pathway

Targeting Stem Cells and Dysplastic Features With Dual MEK/ERK and STAT3 Suppression in Gastric Carcinogenesis

BACKGROUNDS & AIMS

Precancerous metaplasia progression to dysplasia can increase the risk of gastric cancers. However, effective strategies to specifically target these precancerous lesions are currently lacking. To address this, we aimed to identify key signaling pathways that are upregulated during metaplasia progression and critical for stem cell survival and function in dysplasia.

METHODS

To assess the response to chemotherapeutic drugs, we used metaplastic and dysplastic organoids derived from Mist1-Kras mice and 20 human precancerous organoid lines established from patients with gastric cancer. Phospho-antibody array analysis and single-cell RNA-sequencing were performed to identify target cell populations and signaling pathways affected by pyrvinium, a putative anticancer drug. Pyrvinium was administered to Mist1-Kras mice to evaluate drug effectiveness in vivo.

RESULTS

Although pyrvinium treatment resulted in growth arrest in metaplastic organoids, it induced cell death in dysplastic organoids. Pyrvinium treatment significantly downregulated phosphorylation of ERK and signal transducer and activator of transcription 3 (STAT3) as well as STAT3-target genes. Single-cell RNA-sequencing data analyses revealed that pyrvinium specifically targeted CD133+/CD166+ stem cell populations, as well as proliferating cells in dysplastic organoids. Pyrvinium inhibited metaplasia progression and facilitated the restoration of normal oxyntic glands in Mist1-Kras mice. Furthermore, pyrvinium exhibited suppressive effects on the growth and survival of human organoids with dysplastic features, through simultaneous blocking of the MEK/ERK and STAT3 signaling pathways.

CONCLUSIONS

Through its dual blockade of MEK/ERK and STAT3 signaling pathways, pyrvinium can effectively induce growth arrest in metaplasia and cell death in dysplasia. Therefore, our findings suggest that pyrvinium is a promising chemotherapeutic agent for reprogramming the precancerous milieu to prevent gastric cancer development.

Inflammatory pathways and cholangiocarcinoma risk mechanisms and prevention

Cholangiocarcinoma (CCA), a neoplasm burdened by a poor prognosis and currently lacking adequate therapeutic treatments, can originate at different levels of the biliary tree, in the intrahepatic, hilar, or extrahepatic area. The main risk factors for the development of CCA are the presence of chronic cholangiopathies of various etiology. To date, the most studied prodromal diseases of CCA are primary sclerosing cholangitis, Caroli's disease and fluke infestations, but other conditions, such as metabolic syndrome, nonalcoholic fatty liver disease and obesity, are emerging as associated with an increased risk of CCA development. In this review, we focused on the analysis of the pro-inflammatory mechanisms that induce the development of CCA and on the role of cells of the immune response in cholangiocarcinogenesis. In very recent times, these cellular mechanisms have been the subject of emerging studies aimed at verifying how the modulation of the inflammatory and immunological responses can have a therapeutic significance and how these can be used as therapeutic targets.

SAHA induce hippo pathway in CCA cells without increasing cell proliferation

BACKGROUND

Cholangiocarcinoma is a malignant tumor originating from bile duct epithelial cells. Since tumor metastasis is associated with poor prognosis and short-term survival of patients, there is an urgent need for alternative therapeutic approaches for CCA. Because of that reason, we aimed to investigate effect of SAHA which is known as HDAC inhibitor on extrahepatic cholangiocarcinoma cell line (TFK-1).

METHODS

Cell cycle was measured by Muse Cell Analyzer. YAP, TAZ, TGF-β protein levels were determined by western-blotting method. TEAD (1-3), TIMP2 and TIMP3 genes level were determined by real-time PCR analysis.

RESULTS

We have seen the positive effects of SAHA on the TFK-1 cell line as it reduces cell viability and arresting cells in the G0/G1 phase. We also observed the negative effects of SAHA, as it increases the expression levels of YAP, TAZ, TGF-β protein and TEAD (1-3) gene. We also found that SAHA reduced the expression levels of TIMP2 and TIMP3 in TFK-1 cells, but was not statistically significant.

CONCLUSIONS

Although observing its antiproliferative effects, these negative effects may be related to the cells being resistant to the drug or the remaining cells having a more aggressive phenotype. Therefore, we think that caution should be exercised in the use of this drug for CCA treatment.

Pharmaco-transcriptomic correlation analysis reveals novel responsive signatures to HDAC inhibitors and identifies Dasatinib as a synergistic interactor in small-cell lung cancer

BACKGROUND

Histone acetylation/deacetylase process is one of the most studied epigenetic modifications. Histone deacetylase inhibitors (HDACis) have shown clinical benefits in haematological malignancies but failed in solid tumours due to the lack of biomarker-driven stratification.

METHODS

We perform integrative pharmaco-transcriptomic analysis by correlating drug response profiles of five pan-HDACis with transcriptomes of solid cancer cell lines (n=659) to systematically identify generalizable gene signatures associated with HDACis sensitivity and resistance. The established signatures are then applied to identify cancer subtypes that are potentially sensitive or resistant to HDACis, and drugs that enhance the efficacy of HDACis. Finally, the reproductivity of the established HDACis signatures is evaluated by multiple independent drug response datasets and experimental assays.

FINDINGS

We successfully delineate generalizable gene signatures predicting sensitivity (containing 46 genes) and resistance (containing 53 genes) to all five HDACis, with their reproductivity confirmed by multiple external sources and independent internal assays. Using the gene signatures, we identify low-grade glioma harbouring isocitrate dehydrogenase 1/2 (IDH1/2) mutation and non-YAP1-driven subsets of small-cell lung cancer (SCLC) that particularly benefit from HDACis monotherapy. Further, based on the resistance gene signature, we identify clinically-approved Dasatinib as a synthetic lethal drug with HDACi, synergizing in inducing apoptosis and reactive oxygen species on a panel of SCLC. Finally, Dasatinib significantly enhances the therapeutic efficacy of Vorinostat in SCLC xenografts.

INTERPRETATION

Our work establishes robust gene signatures predicting HDACis sensitivity/resistance in solid cancer and uncovers combined Dasatinib/HDACi as a synthetic lethal combination therapy for SCLC.

FUNDING

This work was supported by the National Natural Science Foundation of China (82072570 to F. Yao; 82002941 to B. Sun).

Central and peripheral emetic loci contribute to vomiting evoked by the Akt inhibitor MK-2206 in the least shrew model of emesis

Akt (protein kinase B) signaling is frequently activated in diverse cancers. Akt inhibitors such as perifosine and MK-2206 have been evaluated as potential cancer chemotherapeutics. Although both drugs are generally well tolerated, among their most common side-effects vomiting is a major concern. Here we investigated whether these Akt inhibitors evoke emesis in the least shrew model of vomiting. Indeed, both perifosine and MK-2206 induced vomiting with maximal efficacies of 90% at 50 mg/kg (i.p.) and 100% at 10 mg/kg (i.p.), respectively. MK-2206 (10 mg/kg, i.p.) increased c-Fos immunoreactivity both centrally in the shrew brainstem dorsal vagal complex (DVC) emetic nuclei, and peripherally in the jejunum. MK-2206 also evoked phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in both the DVC emetic nuclei and the enteric nervous system in the jejunum. The ERK1/2 inhibitor U0126 suppressed MK-2206-induced emesis dose-dependently. We then evaluated the suppressive efficacy of diverse antiemetics against MK-2206-evoked vomiting including antagonists/inhibitors of the: L-type Ca²⁺ channel (nifedipine at 2.5 mg/kg, subcutaneously (s.c.)); glycogen synthase kinase 3 (GSK-3) (AR-A014418 at 10 mg/kg and SB216763 at 0.25 mg/kg, i.p.); 5-hydroxytryptamine 5-HT₃ receptor (palonosetron at 0.5 mg/kg, s.c.); substance P neurokinin NK₁ receptor (netupitant at 10 mg/kg, i.p.) and dopamine D_2/3 receptor (sulpride at 8 mg/kg, s.c.). All tested antagonists/blockers attenuated emetic parameters to varying degrees. In sum, this is the first study to demonstrate how pharmacological inhibition of Akt evokes vomiting via both central and peripheral mechanisms, a process which involves multiple emetic receptors.

Have molecular hybrids delivered effective anti-cancer treatments and what should future drug discovery focus on?

INTRODUCTION

Cancer continues to be a big threat and its treatment is a huge challenge among the medical fraternity. Conventional anti-cancer agents are losing their efficiency which highlights the need to introduce new anti-cancer entities for treating this complex disease. A hybrid molecule has a tendency to act through varied modes of action on multiple targets at a given time. Thus, there is the significant scope with hybrid compounds to tackle the existing limitations of cancer chemotherapy.

AREA COVERED

This perspective describes the most significant hybrids that spring hope in the field of cancer chemotherapy. Several hybrids with anti-proliferative/anti-tumor properties currently approved or in clinical development are outlined, along with a description of their mechanism of action and identified drug targets.

EXPERT OPINION

The success of molecular hybridization in cancer chemotherapy is quite evident by the number of molecules entering into clinical trials and/or have entered the drug market over the past decade. Indeed, the recent advancements and co-ordinations in the interface between chemistry, biology, and pharmacology will help further the advancement of hybrid chemotherapeutics in the future.List of abbreviations: Deoxyribonucleic acid, DNA; national cancer institute, NCI; peripheral blood mononuclear cells, PBMC; food and drug administration, FDA; histone deacetylase, HDAC; epidermal growth factor receptor, EGFR; vascular endothelial growth factor receptor, VEGFR; suberoylanilide hydroxamic acid, SAHA; farnesyltransferase inhibitor, FTI; adenosine triphosphate, ATP; Tamoxifen, TAM; selective estrogen receptor modulator, SERM; structure activity relationship, SAR; estrogen receptor, ER; lethal dose, LD; half maximal growth inhibitory concentration, GI₅₀; half maximal inhibitory concentration, IC₅₀.

TAZ Represses the Neuronal Commitment of Neural Stem Cells

The mechanisms involved in regulation of quiescence, proliferation, and reprogramming of Neural Stem Progenitor Cells (NSPCs) of the mammalian brain are still poorly defined. Here, we studied the role of the transcriptional co-factor TAZ, regulated by the WNT and Hippo pathways, in the homeostasis of NSPCs. We found that, in the murine neurogenic niches of the striatal subventricular zone and the dentate gyrus granular zone, TAZ is highly expressed in NSPCs and declines with ageing. Moreover, TAZ expression is lost in immature neurons of both neurogenic regions. To characterize mechanistically the role of TAZ in neuronal differentiation, we used the midbrain-derived NSPC line ReNcell VM to replicate in a non-animal model the factors influencing NSPC differentiation to the neuronal lineage. TAZ knock-down and forced expression in NSPCs led to increased and reduced neuronal differentiation, respectively. TEADs-knockdown indicated that these TAZ co-partners are required for the suppression of NSPCs commitment to neuronal differentiation. Genetic manipulation of the TAZ/TEAD system showed its participation in transcriptional repression of SOX2 and the proneuronal genes ASCL1, NEUROG2, and NEUROD1, leading to impediment of neurogenesis. TAZ is usually considered a transcriptional co-activator promoting stem cell proliferation, but our study indicates an additional function as a repressor of neuronal differentiation.

Transcriptional Co-activator Functions of YAP and TAZ Are Inversely Regulated by Tyrosine Phosphorylation Status of Parafibromin

YAP and TAZ, the Hippo signal-regulated transcriptional co-activators, play crucial roles in morphogenesis and organogenesis. Here we report that the YAP/TAZ activities are stimulated upon complex formation with Parafibromin, which undergoes tyrosine phosphorylation and dephosphorylation by kinases such as PTK6 and phosphatases such as SHP2, respectively. Furthermore, TAZ and the Wnt effector β-catenin interact cooperatively with tyrosine-dephosphorylated Parafibromin, which synergistically stimulates the co-activator functions of TAZ and β-catenin. On the other hand, YAP is selectively activated through binding with tyrosine-phosphorylated Parafibromin, which does not interact with β-catenin and thus cannot co-activate YAP and β-catenin. These findings indicate that Parafibromin inversely regulates the activities of YAP and TAZ depending on its tyrosine phosphorylation status. They also suggest that YAP and TAZ exert their redundant and non-redundant biological actions through mutually exclusive interaction with Parafibromin, which is regulated by a balance of kinase and phosphatase activities toward Parafibromin.

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YAP and TAZ co-activators bind to the nuclear tyrosine phosphoprotein Parafibromin

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TAZ is functionally activated through binding with dephosphorylated Parafibromin

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YAP activity is stimulated upon binding with tyrosine-phosphorylated Parafibromin

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Dephosphorylated Parafibromin co-stimulates TAZ and β-catenin via complex formation

Hippo pathway deregulation: implications in the pathogenesis of haematological malignancies

The Hippo pathway participates in the regulation of cell proliferation, differentiation and apoptosis. It is composed by a large array of proteins whose deregulation has been associated with pro-oncogenic and antioncogenic processes. The present review focuses on the Hippo pathway signalling network and discusses its dual role in oncogenesis, particularly in haematological malignancies.

HDACi Valproic Acid (VPA) and Suberoylanilide Hydroxamic Acid (SAHA) Delay but Fail to Protect against Warm Hepatic Ischemia-Reperfusion Injury

BACKGROUND

Histone deacetylases (HDAC) catalyze N-terminal deacetylation of lysine-residues on histones and multiple nuclear and cytoplasmic proteins. In various animal models, such as trauma/hemorrhagic shock, ischemic stroke or myocardial infarction, HDAC inhibitor (HDACi) application is cyto- and organoprotective and promotes survival. HDACi reduce stress signaling, cell death and inflammation. Hepatic ischemia-reperfusion (I/R) injury during major liver resection or transplantation increases morbidity and mortality. Assuming protective properties, the aim of this study was to investigate the effect of the HDACi VPA and SAHA on warm hepatic I/R.

MATERIAL AND METHODS

Male Wistar-Kyoto rats (age: 6-8 weeks) were randomized to VPA, SAHA, vehicle control (pre-) treatment or sham-groups and underwent partial no-flow liver ischemia for 90 minutes with subsequent reperfusion for 6, 12, 24 and 60 hours. Injury and regeneration was quantified by serum AST and ALT levels, by macroscopic aspect and (immuno-) histology. HDACi treatment efficiency, impact on MAPK/SAPK-activation and Hippo-YAP signaling was determined by Western blot.

RESULTS

Treatment with HDACi significantly enhanced hyperacetylation of Histone H3-K9 during I/R, indicative of adequate treatment efficiency. Liver injury, as measured by macroscopic aspect, serum transaminases and histology, was delayed, but not alleviated in VPA and SAHA treated animals. Importantly, tissue destruction was significantly more pronounced with VPA. SAPK-activation (p38 and JNK) was reduced by VPA and SAHA in the early (6h) reperfusion phase, but augmented later on (JNK, 24h). Regeneration appeared enhanced in SAHA and VPA treated animals and was dependent on Hippo-YAP signaling.

CONCLUSIONS

VPA and SAHA delay warm hepatic I/R injury at least in part through modulation of SAPK-activation. However, these HDACi fail to exert organoprotective effects, in this setting. For VPA, belated damage is even aggravated.

Loss of histone deacetylase HDAC1 induces cell death in Drosophila epithelial cells through JNK and Hippo signaling

Inactivation of HDAC1 and its homolog HDAC2 or addition of HDAC inhibitors in mammalian systems induces apoptosis, cell cycle arrest, and developmental defects. Although these phenotypes have been extensively characterized, the precise underlying mechanisms remain unclear, particularly in in vivo settings. In this study, we show that inactivation of Rpd3, the only HDAC1 and HDAC2 ortholog in Drosophila, induced apoptosis and clone elimination in the developing eye and wing imaginal discs. Depletion of Rpd3 by RNAi cell-autonomously increased JNK activities and decreased activities of Yki, the nuclear effecter of Hippo signaling pathway. In addition, inhibition of JNK activities largely rescued Rpd3 RNAi-induced apoptosis, but did not affect its inhibition of Yki activities. Conversely, increasing the Yki activities largely rescued Rpd3 RNAi-induced apoptosis, but did not affect its induction of JNK activities. Furthermore, inactivation of Mi-2, a core component of the Rpd3-containing NuRD complex strongly induced JNK activities; while inactivation of Sin3A, a key component of the Rpd3-containing Sin3 complex, significantly inhibited Yki activities. Taken together, these results reveal that inactivation of Rpd3 independently regulates JNK and Yki activities and that both Hippo and JNK signaling pathways contribute to Rpd3 RNAi-induced apoptosis.

Hippo Component TAZ Functions as a Co-repressor and Negatively Regulates ΔNp63 Transcription through TEA Domain (TEAD) Transcription Factor

Transcriptional co-activator with a PDZ binding domain (TAZ) is a WW domain-containing transcriptional co-activator and a core component of an emerging Hippo signaling pathway that regulates organ size, tumorigenesis, metastasis, and drug resistance. TAZ regulates these biological functions by up-regulating downstream cellular genes through transactivation of transcription factors such as TEAD and TTF1. To understand the molecular mechanisms underlying TAZ-induced tumorigenesis, we have recently performed a gene expression profile analysis by overexpressing TAZ in mammary cells. In addition to the TAZ-up-regulated genes that were confirmed in our previous studies, we identified a large number of cellular genes that were down-regulated by TAZ. In this study, we have confirmed these down-regulated genes (including cytokines, chemokines, and p53 gene family members) as bona fide downstream transcriptional targets of TAZ. By using human breast and lung epithelial cells, we have further characterized ΔNp63, a p53 gene family member, and shown that TAZ suppresses ΔNp63 mRNA, protein expression, and promoter activity through interaction with the transcription factor TEAD. We also show that TEAD can inhibit ΔNp63 promoter activity and that TAZ can directly interact with ΔNp63 promoter-containing TEAD binding sites. Finally, we provide functional evidence that down-regulation of ΔNp63 by TAZ may play a role in regulating cell migration. Altogether, this study provides novel evidence that the Hippo component TAZ can function as a co-repressor and regulate biological functions by negatively regulating downstream cellular genes.

HDAC9 promotes glioblastoma growth via TAZ-mediated EGFR pathway activation

Histone deacetylase 9 (HDAC9), a member of class II HDACs, regulates a wide variety of normal and abnormal physiological functions. We found that HDAC9 is over-expressed in prognostically poor glioblastoma patients. Knockdown HDAC9 decreased proliferation in vitro and tumor formation in vivo. HDAC9 accelerated cell cycle in part by potentiating the EGFR signaling pathway. Also, HDAC9 interacted with TAZ, a key downstream effector of Hippo pathway. Knockdown of HDAC9 decreased the expression of TAZ. We found that overexpressed TAZ in HDAC9-knockdown cells abrogated the effects induced by HDAC9 silencing both in vitro and in vivo. We demonstrated that HDAC9 promotes tumor formation of glioblastoma via TAZ-mediated EGFR pathway activation, and provide the evidence for promising target for the treatment of glioblastoma.

Identification, mechanism of action, and antitumor activity of a small molecule inhibitor of hippo, TGF-β, and Wnt signaling pathways

Embryonic signaling pathways, in particular those mediated by Wnt and TGF-β, are known to play key roles in tumor progression through the induction of epithelial-mesenchymal transition (EMT). Their simultaneous targeting could therefore represent a desirable anticancer strategy. On the basis of recent findings that both Wnt and TGF-β-associated pathways are regulated by Hippo signaling in mammalian cells, we reasoned that targeting the latter would be more effective in inhibiting EMT. In a search for such inhibitors, we identified a small molecule (C19) with remarkable inhibitory activity not only against Hippo, but also against Wnt and TGF-β pathways. C19 inhibited cancer cell migration, proliferation, and resistance to doxorubicin in vitro, and exerted strong antitumor activity in a mouse tumor model. Mechanistically, C19 induced GSK3-β-mediated degradation of the Hippo transducer TAZ, through activation of the Hippo kinases Mst/Lats and the tumor suppressor kinase AMPK upstream of the degradation complex. Overall, this study identified C19 as a multi-EMT pathway inhibitor with a unique mechanism of action. The findings that both AMPK and Mst/Lats mediate the antitumor activity of C19 shed light on a potential cross-talk between metabolic and organ size control pathways in regulating cancer progression. By simultaneously targeting these two pathways, C19 may represent a new type of agents to suppress cancer progression and/or its recurrence.