Repurposing of Drugs Targeting YAP-TEAD Functions

Strategies that regulate Hippo signaling pathway for novel anticancer therapeutics

As a highly conserved signaling network across different species, the Hippo pathway is involved in various biological processes. Dysregulation of the Hippo pathway could lead to a wide range of diseases, particularly cancers. Extensive researches have demonstrated the close association between dysregulated Hippo signaling and tumorigenesis as well as tumor progression. Consequently, targeting the Hippo pathway has emerged as a promising strategy for cancer treatment. In fact, there has been an increasing number of reports on small molecules that target the Hippo pathway, exhibiting therapeutic potential as anticancer agents. Importantly, some of Hippo signaling pathway inhibitors have been approved for the clinical trials. In this work, we try to provide an overview of the core components and signal transduction mechanisms of the Hippo signaling pathway. Furthermore, we also analyze the relationship between Hippo signaling pathway and cancers, as well as summarize the small molecules with proven anti-tumor effects in clinical trials or reported in literatures. Additionally, we discuss the anti-tumor potency and structure-activity relationship of the small molecule compounds, providing a valuable insight for further development of anticancer agents against this pathway.

The dynamic expression of YAP is essential for the development of male germ cells derived from human embryonic stem cells

YAP plays a vital role in controlling growth and differentiation in various cell lineages. Although the expression of YAP in mice testicular and spermatogenic cells suggests its role in mammalian spermatogenesis, the role of YAP in the development of human male germ cells has not yet been determined. Using an in vitro model and a gene editing approach, we generated human spermatogonia stem cell-like cells (hSSLCs) from human embryonic stem cells (hESCs) and investigated the role of YAP in human spermatogenesis. The results showed that reducing YAP expression during the early stage of spermatogenic differentiation increased the number of PLZF+ hSSLCs and haploid spermatid-like cells. We also demonstrated that the up-regulation of YAP is essential for maintaining spermatogenic cell survival during the later stages of spermatogenic differentiation. The expression of YAP that deviates from this pattern results in a lower number of hSSLCs and an increased level of spermatogenic cell death. Taken together, our result demonstrates that the dynamic expression pattern of YAP is essential for human spermatogenesis. Modulating the level of YAP during human spermatogenesis could improve the production yield of male germ cells derived from hESCs, which could provide the optimization method for in vitro gametogenesis and gain insight into the application in the treatment of male infertility.

Reactivating Hippo by drug compounds to suppress gastric cancer and enhance chemotherapy sensitivity

The Hippo signaling pathway plays an essential role in organ size control and tumorigenesis. Loss of Hippo signal and hyper-activation of the downstream oncogenic YAP signaling are commonly observed in various types of cancers. We previously identified STRN3-containing PP2A phosphatase as a negative regulator of MST1/2 kinases (i.e., Hippo) in gastric cancer (GC), opening the possibility of selectively targeting the PP2Aa-STRN3-MST1/2 axis to recover Hippo signaling against cancer. Here, we further discovered 1) disulfiram (DSF), an FDA-approved drug, which can similarly block the binding of STRN3 to PP2A core enzyme and 2) CX-6258 (CX), a chemical inhibitor, that can disrupt the interaction between STRN3 and MST1/2, both allowing reactivation of Hippo activity to inhibit GC. More importantly, we found these two compounds, via an MST1/2 kinase-dependent manner, inhibit DNA repair to sensitize GC towards chemotherapy. In addition, we identified thiram, a structural analog of DSF, can function similarly to inhibit cancer cell proliferation or enhance chemotherapy sensitivity. Interestingly, inclusion of copper ion enhanced such effects of DSF and thiram on GC treatment. Overall, this work demonstrated that pharmacological targeting of the PP2Aa-STRN3-MST1/2 axis by drug compounds can potently recover Hippo signal for tumor treatment.

ZFP982 confers mouse embryonic stem cell characteristics by regulating expression of Nanog, Zfp42, and Dppa3

BACKGROUND

Understanding the genetic underpinnings of protein networks conferring stemness is of broad interest for basic and translational research.

METHODS

We used multi-omics analyses to identify and characterize stemness genes, and focused on the zinc finger protein 982 (Zfp982) that regulates stemness through the expression of Nanog, Zfp42, and Dppa3 in mouse embryonic stem cells (mESC).

RESULTS

Zfp982 was expressed in stem cells, and bound to chromatin through a GCAGAGKC motif, for example near the stemness genes Nanog, Zfp42, and Dppa3. Nanog and Zfp42 were direct targets of ZFP982 that decreased in expression upon knockdown and increased upon overexpression of Zfp982. We show that ZFP982 expression strongly correlated with stem cell characteristics, both on the transcriptional and morphological levels. Zfp982 expression decreased with progressive differentiation into ecto-, endo- and mesodermal cell lineages, and knockdown of Zfp982 correlated with morphological and transcriptional features of differentiated cells. Zfp982 showed transcriptional overlap with members of the Hippo signaling pathway, one of which was Yap1, the major co-activator of Hippo signaling. Despite the observation that ZFP982 and YAP1 interacted and localized predominantly to the cytoplasm upon differentiation, the localization of YAP1 was not influenced by ZFP982 localization.

CONCLUSIONS

Together, our study identified ZFP982 as a transcriptional regulator of early stemness genes, and since ZFP982 is under the control of the Hippo pathway, underscored the importance of the context-dependent Hippo signals for stem cell characteristics.

An updated review of YAP: A promising therapeutic target against cardiac aging?

The transcriptional co-activator Yes-associated protein (YAP) functions as a downstream effector of the Hippo signaling pathway and plays a crucial role in cardiomyocyte survival. In its non-phosphorylated activated state, YAP binds to transcription factors, activating the transcription of downstream target genes. It also regulates cell proliferation and survival by selectively binding to enhancers and activating target genes. However, the upregulation of the Hippo pathway in human heart failure inhibits cardiac regeneration and disrupts astrogenesis, thus preventing the nuclear translocation of YAP. Existing literature indicates that the Hippo/YAP axis contributes to inflammation and fibrosis, potentially playing a role in the development of cardiac, vascular and renal injuries. Moreover, it is a key mediator of myofibroblast differentiation and fibrosis in the infarcted heart. Given these insights, can we harness YAP's regenerative potential in a targeted manner? In this review, we provide a detailed discussion of the Hippo signaling pathway and consolidate concepts for the development and intervention of cardiac anti-aging drugs to leverage YAP signaling as a pivotal target.

YAP/TEAD-induced PRIM1 contributes to the progression and poor prognosis of gastric carcinoma

Gastric carcinoma has a poor prognosis and low survival rate. PRIM1 is closely associated with the origin of DNA replication and serves as a carcinogenic factor in multiple tumors. This study aimed to explore the functions of PRIM1 in the progression of gastric carcinoma. The luciferase reporter assay examined the regulatory effect of YAP1/TEAD4 on PRIM1. A xenograft tumor mouse model was constructed to observe cancer cell proliferation in vivo. The upregulation of PRIM1 was found in gastric carcinoma cells and tissues, and it was associated with poor prognosis. Silencing PRIM1 inhibited cell proliferation, arrested the cell cycle, and upregulated Cdc25, Cyclin B, and Cdc2 expression. In addition, apoptosis was increased upon PRIM1 knockdown, accompanied by increased protein levels of cleaved caspase-3 and caspase-8. In vivo, knockdown of PRIM1 suppressed the growth of xenograft tumors formed by gastric carcinoma cells. Moreover, PRIM1 silencing elevated the chemosensitivity of gastric carcinoma cells. By investigating molecular events downstream of the Hippo signaling pathway, we found that PRIM1 was a target gene of the YAP1/TEAD4 transcriptional regulatory complex. PRIM1 represents a novel target for gastric carcinoma therapeutic approaches.

The Telluride YAP/TAZ and TEAD Workshop: A Small Meeting with a Big Impact

Funding the research needed to advance our understanding of rare cancers is very challenging [...].

ΔNp63α in cancer: importance and therapeutic opportunities

Our understanding of cancer and the key pathways that drive cancer survival has expanded rapidly over the past several decades. However, there are still important challenges that continue to impair patient survival, including our inability to target cancer stem cells (CSCs), metastasis, and drug resistance. The transcription factor p63 is a p53 family member with multiple isoforms that carry out a wide array of functions. Here, we discuss the critical importance of the ΔNp63α isoform in cancer and potential therapeutic strategies to target ΔNp63α expression to impair the CSC population, as well as to prevent metastasis and drug resistance to improve patient survival.

N6-methyladenosine-modified DBT alleviates lipid accumulation and inhibits tumor progression in clear cell renal cell carcinoma through the ANXA2/YAP axis-regulated Hippo pathway

BACKGROUND

The mechanism of metabolism reprogramming is an unsolved problem in clear cell renal cell carcinoma (ccRCC). Recently, it was discovered that the Hippo pathway altered tumor metabolism and promoted tumor progression. Thus, this study aimed at identifying key regulators of metabolism reprogramming and the Hippo pathway in ccRCC and pinpointing potential therapeutic targets for ccRCC patients.

METHODS

Hippo-related gene sets and metabolic gene sets were used to screen potential regulators of the Hippo pathway in ccRCC. Public databases and samples from patients were applied to investigate the association of dihydrolipoamide branched chain transacylase E2 (DBT) with ccRCC and Hippo signaling. The role of DBT was confirmed by gain or loss of function assays in vitro and in vivo. Mechanistic results were yielded by luciferase reporter assay, immunoprecipitation, mass spectroscopy, and mutational studies.

RESULTS

DBT was confirmed as a Hippo-related marker with significant prognostic predictive value, and its downregulation was caused by methyltransferase-like-3 (METTL3)-mediated N6-methyladenosine (m⁶ A) modification in ccRCC. Functional studies specified DBT as a tumor suppressor for inhibiting tumor progression and correcting the lipid metabolism disorder in ccRCC. Mechanistic findings revealed that annexin A2 (ANXA2) interacted with the lipoyl-binding domain of DBT to activate Hippo signaling which led to decreased nuclear localization of yes1-associated transcriptional regulator (YAP) and transcriptional repression of lipogenic genes.

CONCLUSIONS

This study demonstrated a tumor-suppressive role for the DBT/ANXA2/YAP axis-regulated Hippo signaling and suggested DBT as a potential target for pharmaceutical intervention in ccRCC.

Fingolimod exerts in vitro anticancer activity against hepatocellular carcinoma cell lines via YAP/TAZ suppression

Hepatocellular carcinoma (HCC) remains a notably global health challenge with high mortality rates and poor prognosis. The deregulation of the Hippo signalling pathway, especially the overexpression and activation of downstream effector Yes-associated protein (YAP), has been demonstrated to result in the rapid malignant evolution of HCC. In this context, multiple efforts have been dedicated to targeting YAP for HCC therapy, but effective YAP inhibitors are still lacking. In this study, through a YAP-TEAD (8×GTIIC) luciferase reporter assay, we identified fingolimod, an immunomodulatory drug approved for the treatment of multiple sclerosis, as a novel YAP inhibitor. Fingolimod suppressed the proliferation of HCC cell lines by downregulating the protein levels as well as the trans-activating function of YAP. Overall, our current study not only identifies fingolimod as a novel YAP-targeting in hibitor, but also indicates that this clinically-approved drug could be utilized as a potential and feasible therapeutic drug for HCC.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

Hippo in Gastric Cancer: From Signalling to Therapy

The Hippo pathway is one of the most important ones in mammals. Its key functions in cell proliferation, tissue growth, repair, and homeostasis make it the most crucial one to be controlled. Many means have been deployed for its regulation, since this pathway is not only composed of core regulatory components, but it also communicates with and regulates various other pathways, making this signalisation even more complex. Its role in cancer has been studied more and more over the past few years, and it presents YAP/TAZ as the major oncogenic actors. In this review, we relate how vital this pathway is for different organs, and how regulatory mechanisms have been bypassed to lead to cancerous states. Most studies present an upregulation status of YAP/TAZ, and urge the need to target them. A focus is made here on gastric carcinogenesis, its main dysregulations, and the major strategies adopted and tested to counteract Hippo pathway disbalance in this disease. Hippo pathway targeting can be achieved by various means, which are described in this review. Many studies have tested different potential molecules, which are detailed hereby. Though not all tested in gastric cancer, they could represent a real interest.

Identification of a Quinone Derivative as a YAP/TEAD Activity Modulator from a Repurposing Library

The transcriptional regulators YAP (Yes-associated protein) and TAZ (transcriptional co-activator with PDZ-binding motif) are the major downstream effectors in the Hippo pathway and are involved in cancer progression through modulation of the activity of TEAD (transcriptional enhanced associate domain) transcription factors. To exploit the advantages of drug repurposing in the search of new drugs, we developed a similar approach for the identification of new hits interfering with TEAD target gene expression. In our study, a 27-member in-house library was assembled, characterized, and screened for its cancer cell growth inhibition effect. In a secondary luciferase-based assay, only seven compounds confirmed their specific involvement in TEAD activity. IA5 bearing a p-quinoid structure reduced the cytoplasmic level of phosphorylated YAP and the YAP–TEAD complex transcriptional activity and reduced cancer cell growth. IA5 is a promising hit compound for TEAD activity modulator development.

Repurposing the Trypanosomatidic GSK Kinetobox for the Inhibition of Parasitic Pteridine and Dihydrofolate Reductases

Three open-source anti-kinetoplastid chemical boxes derived from a whole-cell phenotypic screening by GlaxoSmithKline (Tres Cantos Anti-Kinetoplastid Screening, TCAKS) were exploited for the discovery of a novel core structure inspiring new treatments of parasitic diseases targeting the trypansosmatidic pteridine reductase 1 (PTR1) and dihydrofolate reductase (DHFR) enzymes. In total, 592 compounds were tested through medium-throughput screening assays. A subset of 14 compounds successfully inhibited the enzyme activity in the low micromolar range of at least one of the enzymes from both Trypanosoma brucei and Lesihmania major parasites (pan-inhibitors), or from both PTR1 and DHFR-TS of the same parasite (dual inhibitors). Molecular docking studies of the protein–ligand interaction focused on new scaffolds not reproducing the well-known antifolate core clearly explaining the experimental data. TCMDC-143249, classified as a benzenesulfonamide derivative by the QikProp descriptor tool, showed selective inhibition of PTR1 and growth inhibition of the kinetoplastid parasites in the 5 μM range. In our work, we enlarged the biological profile of the GSK Kinetobox and identified new core structures inhibiting selectively PTR1, effective against the kinetoplastid infectious protozoans. In perspective, we foresee the development of selective PTR1 and DHFR inhibitors for studies of drug combinations.

Reciprocal Regulation of Hippo and WBP2 Signalling-Implications in Cancer Therapy

Cancer is a global health problem. The delineation of molecular mechanisms pertinent to cancer initiation and development has spurred cancer therapy in the form of precision medicine. The Hippo signalling pathway is a tumour suppressor pathway implicated in a multitude of cancers. Elucidation of the Hippo pathway has revealed an increasing number of regulators that are implicated, some being potential therapeutic targets for cancer interventions. WW domain-binding protein 2 (WBP2) is an oncogenic transcriptional co-factor that interacts, amongst others, with two other transcriptional co-activators, YAP and TAZ, in the Hippo pathway. WBP2 was recently discovered to modulate the upstream Hippo signalling components by associating with LATS2 and WWC3. Exacerbating the complexity of the WBP2/Hippo network, WBP2 itself is reciprocally regulated by Hippo-mediated microRNA biogenesis, contributing to a positive feedback loop that further drives carcinogenesis. Here, we summarise the biological mechanisms of WBP2/Hippo reciprocal regulation and propose therapeutic strategies to overcome Hippo defects in cancers through targeting WBP2.

Discovery of a subtype-selective, covalent inhibitor against palmitoylation pocket of TEAD3

The TEA domain (TEAD) family proteins (TEAD1‒4) are essential transcription factors that control cell differentiation and organ size in the Hippo pathway. Although the sequences and structures of TEAD family proteins are highly conserved, each TEAD isoform has unique physiological and pathological functions. Therefore, the development and discovery of subtype selective inhibitors for TEAD protein will provide important chemical probes for the TEAD-related function studies in development and diseases. Here, we identified a novel TEAD1/3 covalent inhibitor (DC-TEADin1072) with biochemical IC₅₀ values of 0.61 ± 0.02 and 0.58 ± 0.12 μmol/L against TEAD1 and TEAD3, respectively. Further chemical optimization based on DC-TEAD in 1072 yielded a selective TEAD3 inhibitor DC-TEAD3in03 with the IC₅₀ value of 0.16 ± 0.03 μmol/L, which shows 100-fold selectivity over other TEAD isoforms in activity-based protein profiling (ABPP) assays. In cells, DC-TEAD3in03 showed selective inhibitory effect on TEAD3 in GAL4-TEAD (1–4) reporter assays with the IC₅₀ value of 1.15 μmol/L. When administered to zebrafish juveniles, experiments showed that DC-TEAD3in03 reduced the growth rate of zebrafish caudal fins, indicating the importance of TEAD3 activity in controlling proportional growth of vertebrate appendages.

New Insights into the Clinical Implications of Yes-Associated Protein in Lung Cancer: Roles in Drug Resistance, Tumor Immunity, Autophagy, and Organoid Development

Simple Summary

Innovative advancements in lung cancer treatment have developed over the past decade with the advent of targeted and immune therapies. Yes-associated protein (YAP), an effector of the Hippo pathway, promotes the resistance of these targeted drugs and modulates tumor immunity in lung cancer. YAP is involved in autophagy in lung cancer and plays a prominent role in forming the tubular structure in lung organoids and alveolar differentiation. In this review, we discuss the central roles of YAP in lung cancer and present YAP as a novel target for treating resistance to targeted therapies and immunotherapies in lung cancer.

Abstract

Despite significant innovations in lung cancer treatment, such as targeted therapy and immunotherapy, lung cancer is still the principal cause of cancer-associated death. Novel strategies to overcome drug resistance and inhibit metastasis in cancer are urgently needed. The Hippo pathway and its effector, Yes-associated protein (YAP), play crucial roles in lung development and alveolar differentiation. YAP is known to mediate mechanotransduction, an important process in lung homeostasis and fibrosis. In lung cancer, YAP promotes metastasis and confers resistance against chemotherapeutic drugs and targeted agents. Recent studies revealed that YAP directly controls the expression of programmed death-ligand 1 (PD-L1) and modulates the tumor microenvironment (TME). YAP not only has a profound relationship with autophagy in lung cancer but also controls alveolar differentiation, and is responsible for tubular structure formation in lung organoids. In this review, we discuss the various roles and clinical implications of YAP in lung cancer and propose that targeting YAP can be a promising strategy for treating lung cancer.

Design, Synthesis and Evaluation of a Series of 1,5-Diaryl-1,2,3-triazole-4-carbohydrazones as Inhibitors of the YAP-TAZ/TEAD Complex

Starting from our previously reported hit, a series of 1,5-diaryl-1,2,3-triazole-4-carbohydrazones were synthesized and evaluated as inhibitors of the YAP/TAZ-TEAD complex. Their binding to hTEAD2 was confirmed by nanodifferential scanning fluorimetry, and some of the compounds were also found to moderately disrupt the YAP-TEAD interaction, as assessed by a fluorescence polarization assay. A TEAD luciferase gene reporter assay performed in HEK293T cells and RTqPCR measurements in MDA-MB231 cells showed that these compounds inhibit YAP/TAZ-TEAD activity to cells in the micromolar range. In spite of the cytotoxic effects displayed by some of the compounds of this series, they are still good starting points and can be suitably modified into an effective and viable YAP-TEAD disruptor in the future.

Imaging methods in mechanosensing: a historical perspective and visions for the future

Over the past three decades, as mechanobiology has become a distinct area of study, researchers have developed novel imaging tools to discover the pathways of biomechanical signaling. Early work with substrate engineering and particle tracking demonstrated the importance of cell–extracellular matrix interactions on the cell cycle as well as the mechanical flux of the intracellular environment. Most recently, tension sensor approaches allowed directly measuring tension in cell–cell and cell–substrate interactions. We retrospectively analyze how these various optical techniques progressed the field and suggest our vision forward for a unified theory of cell mechanics, mapping cellular mechanosensing, and novel biomedical applications for mechanobiology.

TGFβ promotes YAP-dependent AXL induction in mesenchymal-type lung cancer cells

The acquisition of chemoresistance remains a major cause of cancer mortality due to the limited accessibility of targeted or immune therapies. However, given that severe alterations of molecular features during epithelial-to-mesenchymal transition (EMT) lead to acquired chemoresistance, emerging studies have focused on identifying targetable drivers associated with acquired chemoresistance. Particularly, AXL, a key receptor tyrosine kinase that confers resistance against targets and chemotherapeutics, is highly expressed in mesenchymal cancer cells. However, the underlying mechanism of AXL induction in mesenchymal cancer cells is poorly understood. Our study revealed that the YAP signature, which was highly enriched in mesenchymal-type lung cancer, was closely correlated to AXL expression in 181 lung cancer cell lines. Moreover, using isogenic lung cancer cell pairs, we also found that doxorubicin treatment induced YAP nuclear translocation in mesenchymal-type lung cancer cells to induce AXL expression. Additionally, the concurrent activation of TGFβ signaling coordinated YAP-dependent AXL expression through SMAD4. These data suggest that crosstalk between YAP and the TGFβ/SMAD axis upon treatment with chemotherapeutics might be a promising target to improve chemosensitivity in mesenchymal-type lung cancer.

MiR-133 Targets YES1 and Inhibits the Growth of Triple-Negative Breast Cancer Cells

Triple-negative breast cancer shows worse outcome compared with other subtypes of breast cancer. The discovery of dysregulated microRNAs and their roles in the progression of triple-negative breast cancer provide novel strategies for the treatment of patients with triple-negative breast cancer. In this study, we identified the significant reduction of miR-133 in triple-negative breast cancer tissues and cell lines. Ectopic overexpression of miR-133 suppressed the proliferation, colony formation, and upregulated the apoptosis of triple-negative breast cancer cells. Mechanism study revealed that the YES Proto-Oncogene 1 was a target of miR-133. miR-133 bound the 3′-untranslated region of YES Proto-Oncogene 1 and decreased the level of YES Proto-Oncogene 1 in triple-negative breast cancer cells. Consistent with miR-133 downregulation, YES1 was significantly increased in triple-negative breast cancer, which was inversely correlated with the level of miR-133. Restoration of YES Proto-Oncogene 1 attenuated the inhibitory effects of miR-133 on the proliferation and colony formation of triple-negative breast cancer cells. Consistent with the decreased expression of YES Proto-Oncogene 1, overexpression of miR-133 suppressed the phosphorylation of YAP1 in triple-negative breast cancer cells. Our results provided novel evidence for the role of miR-133/YES1 axis in the development of triple-negative breast cancer, which indicated miR-133 might be a potential therapeutic strategy for triple-negative breast cancer.

Association of subcellular localization of TEAD transcription factors with outcome and progression in pancreatic ductal adenocarcinoma

BACKGROUND

Transcriptional enhanced associated domain (TEAD) transcription factors are nuclear effectors of several oncogenic signalling pathways including Hippo, WNT, TGF-ß and EGFR pathways that interact with various cancer genes. The subcellular localization of TEAD regulates the functional output of these pathways affecting tumour progression and patient outcome. However, the impact of the TEAD family on pancreatic ductal adenocarcinoma (PDAC) and its clinical progression remain elusive.

METHODS

A cohort of 81 PDAC patients who had undergone surgery was established. Cytoplasmic and nuclear localization of TEAD1, TEAD2, TEAD3 and TEAD4 was evaluated with the immunoreactive score (IRS) by immunohistochemistry (IHC) using paraffin-embedded tissue. Results were correlated with clinicopathological data, disease-free and overall survival.

RESULTS

Nuclear staining of all four TEADs was increased in pancreatic cancer tissue. Patients suffering from metastatic disease at time of surgery showed a strong nuclear staining of TEAD2 and TEAD3 (p < 0.05). Furthermore, a nuclear > cytoplasmic ratio of TEAD2 and TEAD3 was associated with a shorter overall survival and TEAD2 emerged as an independent prognostic factor for disease-free survival.

CONCLUSION

Our study underlines the importance of TEAD transcription factors in PDAC as a nuclear localization was found to be associated with metastatic disease and an unfavourable prognosis after surgical resection.

The YAP/TEAD Axis as a New Therapeutic Target in Osteosarcoma: Effect of Verteporfin and CA3 on Primary Tumor Growth

Although some studies suggested that disruption of the Hippo signaling pathway is associated with osteosarcoma progression, the molecular mechanisms by which YAP regulates primary tumor growth is not fully clarified. In addition, the validation of YAP as a therapeutic target through the use of inhibitors in a preclinical model must be demonstrated. RNA-seq analysis and Kaplan-Meier assays identified a YAP signature in osteosarcoma patients and a correlation with patients' outcomes. Molecular and cellular analysis (RNAseq, PLA, immunoprecipitation, promoter/specific gene, proliferation, cell cycle assays) using overexpression of mutated forms of YAP able or unable to interact with TEAD, indicate that TEAD is crucial for YAP-driven cell proliferation and in vivo tumor growth. In addition, in vivo experiments using an orthotopic mice model of osteosarcoma show that two YAP/TEAD inhibitors, verteporfin and CA3, reduce primary tumor growth. In this context, in vitro experiments demonstrate that these inhibitors decrease YAP expression, YAP/TEAD transcriptional activity and cell viability mainly by their ability to induce cell apoptosis. We thus demonstrate that the YAP/TEAD signaling axis is a central actor in mediating primary tumor growth of osteosarcoma, and that the use of YAP inhibitors may be a promising therapeutic strategy against osteosarcoma tumor growth.

Regulation of Hippo signaling pathway in cancer: A MicroRNA perspective

Recent studies have suggested that Hippo signaling is not only involved in controlling organ size in Drosophila but can also regulate cell proliferation, tissue homeostasis, differentiation, apoptosis and regeneration. Any dysregulation of Hippo signaling, especially the hyper activation of its downstream effectors YAP/TAZ, can lead to uncontrolled cell proliferation and malignant transformation. In majority of cancers, expression of YAP/TAZ is extremely high and this increased expression of YAP/TAZ has been shown to be an independent predictor of prognosis and indicator of increased cell proliferation, metastasis and poor survival. In this review, we have summarized the most recent findings about the cross talk of Hippo signaling pathway with other signaling pathways and its regulation by different miRNAs in various cancer types. Recent evidence has suggested that Hippo pathway is also involved in mediating the resistance of different cancer cells to chemotherapeutic drugs and in a few cancer types, this is brought about by regulating miRNAs. Therefore, the delineation of the underlying mechanisms regulating the chemotherapeutic resistance might help in developing better treatment options. This review has attempted to provide an overview of different drugs/options which can be utilized to target oncogenic YAP/TAZ proteins for therapeutic interventions.

Biomimicking Fiber Platform with Tunable Stiffness to Study Mechanotransduction Reveals Stiffness Enhances Oligodendrocyte Differentiation but Impedes Myelination through YAP-Dependent Regulation

A key hallmark of many diseases, especially those in the central nervous system (CNS), is the change in tissue stiffness due to inflammation and scarring. However, how such changes in microenvironment affect the regenerative process remains poorly understood. Here, a biomimicking fiber platform that provides independent variation of fiber structural and intrinsic stiffness is reported. To demonstrate the functionality of these constructs as a mechanotransduction study platform, these substrates are utilized as artificial axons and the effects of axon structural versus intrinsic stiffness on CNS myelination are independently analyzed. While studies have shown that substrate stiffness affects oligodendrocyte differentiation, the effects of mechanical stiffness on the final functional state of oligodendrocyte (i.e., myelination) has not been shown prior to this. Here, it is demonstrated that a stiff mechanical microenvironment impedes oligodendrocyte myelination, independently and distinctively from oligodendrocyte differentiation. Yes-associated protein is identified to be involved in influencing oligodendrocyte myelination through mechanotransduction. The opposing effects on oligodendrocyte differentiation and myelination provide important implications for current work screening for promyelinating drugs, since these efforts have focused mainly on promoting oligodendrocyte differentiation. Thus, the platform may have considerable utility as part of a drug discovery program in identifying molecules that promote both differentiation and myelination.

A Potential Role of YAP/TAZ in the Interplay Between Metastasis and Metabolic Alterations

Yes-Associated Protein (YAP) and Transcriptional Co-activator with PDZ-binding Motif (TAZ) are the downstream effectors of the Hippo signaling pathway that play a crucial role in various aspects of cancer progression including metastasis. Metastasis is the multistep process of disseminating cancer cells in a body and responsible for the majority of cancer-related death. Emerging evidence has shown that cancer cells reprogram their metabolism to gain proliferation, invasion, migration, and anti-apoptotic abilities and adapt to various environment during metastasis. Moreover, it has increasingly been recognized that YAP/TAZ regulates cellular metabolism that is associated with the phenotypic changes, and recent studies suggest that the YAP/TAZ-mediated metabolic alterations contribute to metastasis. In this review, we will introduce the latest knowledge of YAP/TAZ regulation and function in cancer metastasis and metabolism, and discuss possible links between the YAP/TAZ-mediated metabolic reprogramming and metastasis.

Targeting YAP Degradation by a Novel 1,2,4-Oxadiazole Derivative via Restoration of the Function of the Hippo Pathway

Recent evidence has linked the dysregulation of the Hippo pathway to tumorigenesis and cancer progression due to its pivotal role in regulating the stability of the oncoprotein YAP. Based on an unexpected finding from the SAR study of a recently reported oxadiazole-based EGFR/c-Met dual inhibitor (compound 1), we identified a closely related derivative, compound 2, which exhibited cogent antitumor activities while devoid of compound 1's ability to promote EGFR/c-Met degradation. Compound 2 acted, in part, by facilitating YAP degradation through activation of its upstream kinase LATS1. However, it did not alter the phosphorylation status of MST1/2, a LATS1 kinase, suggesting an alternative mechanism for LATS1 activation. Orally administered compound 2 was effective in suppressing MDA-MB-231 xenograft tumor growth while exhibiting a satisfactory safety profile. From a therapeutic perspective, compound 2 might help foster new therapeutic strategies for cancer treatment by restoring the Hippo pathway regulatory function to facilitate YAP degradation.

Hippo/YAP Signaling Pathway: A Promising Therapeutic Target in Bone Paediatric Cancers?

Osteosarcoma and Ewing sarcoma are the most prevalent bone pediatric tumors. Despite intensive basic and medical research studies to discover new therapeutics and to improve current treatments, almost 40% of osteosarcoma and Ewing sarcoma patients succumb to the disease. Patients with poor prognosis are related to either the presence of metastases at diagnosis or resistance to chemotherapy. Over the past ten years, considerable interest for the Hippo/YAP signaling pathway has taken place within the cancer research community. This signaling pathway operates at different steps of tumor progression: Primary tumor growth, angiogenesis, epithelial to mesenchymal transition, and metastatic dissemination. This review discusses the current knowledge about the involvement of the Hippo signaling pathway in cancer and specifically in paediatric bone sarcoma progression.

Outcompeting cancer

The tumour microenvironment plays a critical role in determining tumour fate. Within that environment, and indeed throughout epithelial tissues, cells experience competition with their neighbours, with those less fit being eliminated by fitter adjacent cells. Herein we discuss evidence suggesting that mutations in cancer cells may be selected for their ability to exploit cell competition to kill neighbouring host cells, thereby facilitating tumour expansion. In some instances, cell competition may help host tissues to defend against cancer, by removing neoplastic and aneuploid cells. Cancer risk factors, such as high-sugar or high-fat diet and inflammation, impact cell competition-based host defences, suggesting that their effect on tumour risk may in part be accounted for by their influence on cell competition. We propose that interventions aimed at modifying the strength and direction of cell competition could induce cancer cell killing and form the basis for novel anticancer therapies.

A combat with the YAP/TAZ-TEAD oncoproteins for cancer therapy

The transcriptional co-regulators YAP and TAZ pair primarily with the TEAD family of transcription factors to elicit a gene expression signature that plays a prominent role in cancer development, progression and metastasis. YAP and TAZ endow cells with various oncogenic traits such that they sustain proliferation, inhibit apoptosis, maintain stemness, respond to mechanical stimuli, engineer metabolism, promote angiogenesis, suppress immune response and develop resistance to therapies. Therefore, inhibiting YAP/TAZ- TEAD is an attractive and viable option for novel cancer therapy. It is exciting to know that many drugs already in the clinic restrict YAP/TAZ activities and several novel YAP/TAZ inhibitors are currently under development. We have classified YAP/TAZ-inhibiting drugs into three groups. Group I drugs act on the upstream regulators that are stimulators of YAP/TAZ activities. Many of the Group I drugs have the potential to be repurposed as YAP/TAZ indirect inhibitors to treat various solid cancers. Group II modalities act directly on YAP/TAZ or TEADs and disrupt their interaction; targeting TEADs has emerged as a novel option to inhibit YAP/TAZ, as TEADs are major mediators of their oncogenic programs. TEADs can also be leveraged on using small molecules to activate YAP/TAZ-dependent gene expression for use in regenerative medicine. Group III drugs focus on targeting one of the oncogenic downstream YAP/TAZ transcriptional target genes. With the right strategy and impetus, it is not far-fetched to expect a repurposed group I drug or a novel group II drug to combat YAP and TAZ in cancers in the near future.

Yes-associated protein regulates podocyte cell cycle re-entry and dedifferentiation in adriamycin-induced nephropathy

Podocytes are terminally differentiated cells with little proliferative capacity. The high expression levels of cell cycle inhibitory proteins, including p21, p27, and p57, play an important role in maintaining the low level of proliferation of mature podocytes. In the present study, we aimed to explore the role of yes-associated protein (YAP) signalling in adriamycin-induced podocyte re-entry into the cell cycle and dedifferentiation. Proliferating cell nuclear antigen (PCNA)-, cyclin-dependent kinase 4 (CDK4)-, and Cyclin D1-positive podocytes were found in mice with adriamycin-induced nephropathy. In vitro, adriamycin administration increased the percentage of cells in S phase and the upregulation of mesenchymal-related marker proteins. CDK4 and cyclin D1 were significantly up-regulated after incubation with adriamycin. Overexpression of YAP in podocytes promoted their entry into the cell cycle; up-regulated cyclin D1, desmin, and snail2 expression and down-regulated Wilms’ tumour 1 (WT1) and nephrin production. Recombinant murine FGF-basic induced podocytes to re-enter the cell cycle, inhibited WT1 and nephrin, and increased desmin and snail2 expression. Pretreating podocytes with verteporfin, an inhibitor of YAP/ TEA domain transcription factor (TEAD), decreased the adriamycin-induced overexpression of cyclin D1 and reduced the ratio of S-phase podocytes. This result was further verified by knocking down YAP expression using RNA interference. In conclusion, adriamycin induced podocytes to re-enter the cell cycle via upregulation of CDK4 and cyclin D1 expression, which was at least partly mediated by YAP signalling. Re-entry into the cell cycle induced the over-expression of mesenchymal markers in podocytes.

Promoter Hypermethylation of Genes Encoding for RASSF/Hippo Pathway Members Reveals Specific Alteration Pattern in Diffuse Gliomas

Ras association domain family (RASSF)/Hippo pathway alterations are poorly characterized in diffuse gliomas. We assayed promoter methylation of LATS1/2, MST1(STK4)/MST2(STK3), RASSF1, RASSF2, Nore1A/RASSF5, RASSF6, and RASSF10 genes in 133 diffuse gliomas. The RASSF/Hippo pathway was highly silenced in gliomas, particularly RASSF1A (79.4%) and LATS2 (35.9%). The most frequent combination of promoter hypermethylation of one RASSF gene and one Hippo pathway member's gene was RASSF1/LATS2-coupled hypermethylation [n = 44 (33.08%)]. Hypermethylated profiles were related to IDH mutation, yet not randomly in IDH-mutated gliomas, because LATS2 promoter hypermethylation was more frequent in oligodendroglioma than in astrocytoma. RASSF1 and LATS2 promoter hypermethylation predicted a longer overall survival (OS). Considering hypermethylation of these two promoters, Cox proportional hazard regression analysis categorized the patients into three prognostic groups: i) high risk of death (n = 24; both RASSF1 and LATS2 unmethylated promoters; median OS, 13 months); ii) intermediate risk of death (n = 65; RASSF1 or LATS2 hypermethylated promoter; median OS, 50.5 months; HR = 3.3; 95% CI, 1.6-6.4; P = 0.001); and iii) low risk of death (n = 44; both RASSF1 and LATS2 hypermethylated promoters; median OS, 119 months; HR = 75.1; 95% CI, 3.3-15.1; P = 0.001). We have thus highlighted a simple two-gene (RASSF1/LATS2) methylation signature as a tool to stratify different prognostic groups of patients with diffuse glioma, adding further prognostic information within the IDH-mutated group.