Effect of the acylation of TEAD4 on its interaction with co-activators YAP and TAZ

Direct and selective pharmacological disruption of the YAP-TEAD interface by IAG933 inhibits Hippo-dependent and RAS-MAPK-altered cancers

The YAP-TEAD protein-protein interaction mediates YAP oncogenic functions downstream of the Hippo pathway. To date, available YAP-TEAD pharmacologic agents bind into the lipid pocket of TEAD, targeting the interaction indirectly via allosteric changes. However, the consequences of a direct pharmacological disruption of the interface between YAP and TEADs remain largely unexplored. Here, we present IAG933 and its analogs as potent first-in-class and selective disruptors of the YAP-TEAD protein-protein interaction with suitable properties to enter clinical trials. Pharmacologic abrogation of the interaction with all four TEAD paralogs resulted in YAP eviction from chromatin and reduced Hippo-mediated transcription and induction of cell death. In vivo, deep tumor regression was observed in Hippo-driven mesothelioma xenografts at tolerated doses in animal models as well as in Hippo-altered cancer models outside mesothelioma. Importantly this also extended to larger tumor indications, such as lung, pancreatic and colorectal cancer, in combination with RTK, KRAS-mutant selective and MAPK inhibitors, leading to more efficacious and durable responses. Clinical evaluation of IAG933 is underway.

Leveraging the Fragment Molecular Orbital and MM-GBSA Methods in Virtual Screening for the Discovery of Novel Non-Covalent Inhibitors Targeting the TEAD Lipid Binding Pocket

The Hippo pathway controls organ size and homeostasis and is linked to numerous diseases, including cancer. The transcriptional enhanced associate domain (TEAD) family of transcription factors acts as a receptor for downstream effectors, namely yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), which binds to various transcription factors and is essential for stimulated gene transcription. YAP/TAZ-TEAD facilitates the upregulation of multiple genes involved in evolutionary cell proliferation and survival. TEAD1-4 overexpression has been observed in different cancers in various tissues, making TEAD an attractive target for drug development. The central drug-accessible pocket of TEAD is crucial because it undergoes a post-translational modification called auto-palmitoylation. Crystal structures of the C-terminal TEAD complex with small molecules are available in the Protein Data Bank, aiding structure-based drug design. In this study, we utilized the fragment molecular orbital (FMO) method, molecular dynamics (MD) simulations, shape-based screening, and molecular mechanics-generalized Born surface area (MM-GBSA) calculations for virtual screening, and we identified a novel non-covalent inhibitor-BC-001-with IC50 = 3.7 μM in a reporter assay. Subsequently, we optimized several analogs of BC-001 and found that the optimized compound BC-011 exhibited an IC50 of 72.43 nM. These findings can be used to design effective TEAD modulators with anticancer therapeutic implications.

Natural compounds targeting YAP/TAZ axis in cancer: Current state of art and challenges

Cancer has become a burgeoning global healthcare concern marked by its exponential growth and significant economic ramifications. Though advancements in the treatment modalities have increased the overall survival and quality of life, there are no definite treatments for the advanced stages of this malady. Hence, understanding the diseases etiologies and the underlying molecular complexities, will usher in the development of innovative therapeutics. Recently, YAP/TAZ transcriptional regulation has been of immense interest due to their role in development, tissue homeostasis and oncogenic transformations. YAP/TAZ axis functions as coactivators within the Hippo signaling cascade, exerting pivotal influence on processes such as proliferation, regeneration, development, and tissue renewal. In cancer, YAP is overexpressed in multiple tumor types and is associated with cancer stem cell attributes, chemoresistance, and metastasis. Activation of YAP/TAZ mirrors the cellular "social" behavior, encompassing factors such as cell adhesion and the mechanical signals transmitted to the cell from tissue structure and the surrounding extracellular matrix. Therefore, it presents a significant vulnerability in the clogs of tumors that could provide a wide window of therapeutic effectiveness. Natural compounds have been utilized extensively as successful interventions in the management of diverse chronic illnesses, including cancer. Owing to their capacity to influence multiple genes and pathways, natural compounds exhibit significant potential either as adjuvant therapy or in combination with conventional treatment options. In this review, we delineate the signaling nexus of YAP/TAZ axis, and present natural compounds as an alternate strategy to target cancer.

The tumor suppressor NF2 modulates TEAD4 stability and activity in Hippo signaling via direct interaction

As an output effector of the Hippo signaling pathway, the TEAD transcription factor and co-activator YAP play crucial functions in promoting cell proliferation and organ size. The tumor suppressor NF2 has been shown to activate LATS1/2 kinases and interplay with the Hippo pathway to suppress the YAP-TEAD complex. However, whether and how NF2 could directly regulate TEAD remains unknown. We identified a direct link and physical interaction between NF2 and TEAD4. NF2 interacted with TEAD4 through its FERM domain and C-terminal tail and decreased the protein stability of TEAD4 independently of LATS1/2 and YAP. Furthermore, NF2 inhibited TEAD4 palmitoylation and induced the cytoplasmic translocation of TEAD4, resulting in ubiquitination and dysfunction of TEAD4. Moreover, the interaction with TEAD4 is required for NF2 function to suppress cell proliferation. These findings reveal an unanticipated role of NF2 as a binding partner and inhibitor of the transcription factor TEAD, shedding light on an alternative mechanism of how NF2 functions as a tumor suppressor through the Hippo signaling cascade.

Allosteric Modulation of the YAP/TAZ-TEAD Interaction by Palmitoylation and Small-Molecule Inhibitors

The Hippo signaling pathway is a highly conserved signaling network that plays a central role in regulating cellular growth, proliferation, and organ size. This pathway consists of a kinase cascade that integrates various upstream signals to control the activation or inactivation of YAP/TAZ proteins. Phosphorylated YAP/TAZ is sequestered in the cytoplasm; however, when the Hippo pathway is deactivated, it translocates into the nucleus, where it associates with TEAD transcription factors. This partnership is instrumental in regulating the transcription of progrowth and antiapoptotic genes. Thus, in many cancers, aberrantly hyperactivated YAP/TAZ promotes oncogenesis by contributing to cancer cell proliferation, metastasis, and therapy resistance. Because YAP and TAZ exert their oncogenic effects by binding with TEAD, it is critical to understand this key interaction to develop cancer therapeutics. Previous research has indicated that TEAD undergoes autopalmitoylation at a conserved cysteine, and small molecules that inhibit TEAD palmitoylation disrupt effective YAP/TAZ binding. However, how exactly palmitoylation contributes to YAP/TAZ-TEAD interactions and how the TEAD palmitoylation inhibitors disrupt this interaction remains unknown. Utilizing molecular dynamics simulations, our investigation not only provides detailed atomistic insight into the YAP/TAZ-TEAD dynamics but also unveils that the inhibitor studied influences the binding of YAP and TAZ to TEAD in distinct manners. This discovery has significant implications for the design and deployment of future molecular interventions targeting this interaction.

A Novel Irreversible TEAD Inhibitor, SWTX-143, Blocks Hippo Pathway Transcriptional Output and Causes Tumor Regression in Preclinical Mesothelioma Models

The Hippo pathway and its downstream effectors, the YAP and TAZ transcriptional coactivators, are deregulated in multiple different types of human cancer and are required for cancer cell phenotypes in vitro and in vivo, while largely dispensable for tissue homeostasis in adult mice. YAP/TAZ and their main partner transcription factors, the TEAD1-4 factors, are therefore promising anticancer targets. Because of frequent YAP/TAZ hyperactivation caused by mutations in the Hippo pathway components NF2 and LATS2, mesothelioma is one of the prime cancer types predicted to be responsive to YAP/TAZ-TEAD inhibitor treatment. Mesothelioma is a devastating disease for which currently no effective treatment options exist. Here, we describe a novel covalent YAP/TAZ-TEAD inhibitor, SWTX-143, that binds to the palmitoylation pocket of all four TEAD isoforms. SWTX-143 caused irreversible and specific inhibition of the transcriptional activity of YAP/TAZ-TEAD in Hippo-mutant tumor cell lines. More importantly, YAP/TAZ-TEAD inhibitor treatment caused strong mesothelioma regression in subcutaneous xenograft models with human cells and in an orthotopic mesothelioma mouse model. Finally, SWTX-143 also selectively impaired the growth of NF2-mutant kidney cancer cell lines, suggesting that the sensitivity of mesothelioma models to these YAP/TAZ-TEAD inhibitors can be extended to other tumor types with aberrations in Hippo signaling. In brief, we describe a novel and specific YAP/TAZ-TEAD inhibitor that has potential to treat multiple Hippo-mutant solid tumor types.

A covalent inhibitor of the YAP-TEAD transcriptional complex identified by high-throughput screening

Yes-associated protein (YAP), the master transcriptional effector downstream of the Hippo pathway, regulates essential cell growth and regenerative processes in animals. However, the activation of YAP observed in cancers drives cellular proliferation, metastasis, chemoresistance, and immune suppression, making it of key interest in developing precision therapeutics for oncology. As such, pharmacological inhibition of YAP by targeting its essential co-regulators, TEA domain transcription factors (TEADs) would likely promote tumor clearance in sensitive tumor types. From a fluorescence polarization-based high throughput screen of over 800 000 diverse small molecules, here we report the identification of a pyrazolopyrimidine-based scaffold that inhibits association of YAP and TEADs. Medicinal chemistry-based optimization identified mCMY020, a potent, covalent inhibitor of TEAD transcriptional activity that occupies a conserved, central palmitoylation site on TEADs.

Chloroacetamide fragment library screening identifies new scaffolds for covalent inhibition of the TEAD·YAP1 interaction

Transcriptional enhanced associate domain (TEAD) binding to co-activator yes-associated protein (YAP1) leads to a transcription factor of the Hippo pathway. TEADs are regulated by S-palmitoylation of a conserved cysteine located in a deep well-defined hydrophobic pocket outside the TEAD·YAP1 interaction interface. Previously, we reported the discovery of a small molecule based on the structure of flufenamic acid that binds to the palmitate pocket, forms a covalent bond with the conserved cysteine, and inhibits TEAD4 binding to YAP1. Here, we screen a fragment library of chloroacetamide electrophiles to identify new scaffolds that bind to the palmitate pocket of TEADs and disrupt their interaction with YAP1. Time- and concentration-dependent studies with wild-type and mutant TEAD1-4 provided insight into their reaction rates and binding constants and established the compounds as covalent inhibitors of TEAD binding to YAP1. Binding pose hypotheses were generated by covalent docking revealing that the fragments and compounds engage lower, middle, and upper sub-sites of the palmitate pocket. Our fragments and compounds provide new scaffolds and starting points for the design of derivatives with improved inhibition potency of TEAD palmitoylation and binding to YAP1.

Diverse Roles of Protein Palmitoylation in Cancer Progression, Immunity, Stemness, and Beyond

Protein S-palmitoylation, a type of post-translational modification, refers to the reversible process of attachment of a fatty acyl chain-a 16-carbon palmitate acid-to the specific cysteine residues on target proteins. By adding the lipid chain to proteins, it increases the hydrophobicity of proteins and modulates protein stability, interaction with effector proteins, subcellular localization, and membrane trafficking. Palmitoylation is catalyzed by a group of zinc finger DHHC-containing proteins (ZDHHCs), whereas depalmitoylation is catalyzed by a family of acyl-protein thioesterases. Increasing numbers of oncoproteins and tumor suppressors have been identified to be palmitoylated, and palmitoylation is essential for their functions. Understanding how palmitoylation influences the function of individual proteins, the physiological roles of palmitoylation, and how dysregulated palmitoylation leads to pathological consequences are important drivers of current research in this research field. Further, due to the critical roles in modifying functions of oncoproteins and tumor suppressors, targeting palmitoylation has been used as a candidate therapeutic strategy for cancer treatment. Here, based on recent literatures, we discuss the progress of investigating roles of palmitoylation in regulating cancer progression, immune responses against cancer, and cancer stem cell properties.

YAP/TAZ: Molecular pathway and disease therapy

The Yes-associated protein and its transcriptional coactivator with PDZ-binding motif (YAP/TAZ) are two homologous transcriptional coactivators that lie at the center of a key regulatory network of Hippo, Wnt, GPCR, estrogen, mechanical, and metabolism signaling. YAP/TAZ influences the expressions of downstream genes and proteins as well as enzyme activity in metabolic cycles, cell proliferation, inflammatory factor expression, and the transdifferentiation of fibroblasts into myofibroblasts. YAP/TAZ can also be regulated through epigenetic regulation and posttranslational modifications. Consequently, the regulatory function of these mechanisms implicates YAP/TAZ in the pathogenesis of metabolism-related diseases, atherosclerosis, fibrosis, and the delicate equilibrium between cancer progression and organ regeneration. As such, there arises a pressing need for thorough investigation of YAP/TAZ in clinical settings. In this paper, we aim to elucidate the signaling pathways that regulate YAP/TAZ and explore the mechanisms of YAP/TAZ-induce diseases and their potential therapeutic interventions. Furthermore, we summarize the current clinical studies investigating treatments targeting YAP/TAZ. We also address the limitations of existing research on YAP/TAZ and propose future directions for research. In conclusion, this review aims to provide fresh insights into the signaling mediated by YAP/TAZ and identify potential therapeutic targets to present innovative solutions to overcome the challenges associated with YAP/TAZ.

Searching for Novel Biomarkers in Thymic Epithelial Tumors: Immunohistochemical Evaluation of Hippo Pathway Components in a Cohort of Thymic Epithelial Tumors

Given the pivotal role of the Hippo pathway in different facets of tumorigenesis, which has been vigorously established in multiple heterogenous malignancies, we attempted to evaluate its potential utility as a prognostic-predictive biomarker in thymic epithelial tumors (TETs). For this purpose, we performed a comprehensive immunohistochemical analysis of four Hippo cascade components (YAP, TAZ, TEAD4 and LATS1) in a sizeable cohort of TETs and attempted to identify possible correlations of their H-score with various clinicopathological parameters. TAZ and TEAD4 displayed both cytoplasmic and nuclear immunoreactivity in almost equal frequency, with their cytoplasmic H-score being strongly associated with more aggressive high-grade tumors (type B3, thymic carcinoma) and more advanced pathological stages. On the other hand, a primarily nuclear staining pattern was encountered in both YAP and LATS1, with the YAP nuclear H-score being higher in more indolent (type A) and earlier stage tumors. Interestingly, none of the four examined factors displayed any statistically significant correlation with patient overall (OS) or disease-free survival (DFS). In summary, our results provide some initial insight into the expression profile of these core Hippo pathway components in thymic neoplasms and point towards some clear associations with tumor characteristics, which are of paramount translational-clinical research with profound implications in therapeutic targeting of this pathway in the context of precision medicine.

Novel Allosteric Effectors Targeting Human Transcription Factor TEAD

The Hippo pathway is an evolutionary conserved signaling network involved in several cellular regulatory processes. Dephosphorylation and overexpression of Yes-associated proteins (YAPs) in the Hippo-off state are common in several types of solid tumors. YAP overexpression results in its nuclear translocation and interaction with transcriptional enhanced associate domain 1-4 (TEAD1-4) transcription factors. Covalent and non-covalent inhibitors have been developed to target several interaction sites between TEAD and YAP. The most targeted and effective site for these developed inhibitors is the palmitate-binding pocket in the TEAD1-4 proteins. Screening of a DNA-encoded library against the TEAD central pocket was performed experimentally to identify six new allosteric inhibitors. Inspired by the structure of the TED-347 inhibitor, chemical modification was performed on the original inhibitors by replacing secondary methyl amide with a chloromethyl ketone moiety. Various computational tools, including molecular dynamics, free energy perturbation, and Markov state model analysis, were employed to study the effect of ligand binding on the protein conformational space. Four of the six modified ligands were associated with enhanced allosteric communication between the TEAD4 and YAP1 domains indicated by the relative free energy perturbation to original molecules. Phe229, Thr332, Ile374, and Ile395 residues were revealed to be essential for the effective binding of the inhibitors.

Therapeutic targeting of TEAD transcription factors in cancer

The Hippo signaling pathway inhibits the activity of the oncogenic YAP (Yes-associated protein)/TAZ (transcriptional co-activator with PDZ-binding motif)-TEAD (TEA/ATTS domain) transcriptional complex. In cancers, inactivating mutations in upstream Hippo components and/or enhanced activity of YAP/TAZ and TEAD have been observed. The activity of this transcriptional complex can be effectively inhibited by targeting the TEAD family of transcription factors. The development of TEAD inhibitors has been driven by the discovery that TEAD has druggable hydrophobic pockets, and is currently at the clinical development stage. Three small molecule TEAD inhibitors are currently being tested in Phase I clinical trials. In this review, we highlight the role of TEADs in cancer, discuss various avenues through which TEAD activity can be inhibited, and outline the opportunities for the administration of TEAD inhibitors.

Small-Molecule Cyanamide Pan-TEAD·YAP1 Covalent Antagonists

Transcriptional enhanced associate domains (TEADs) are transcription factors that bind to cotranscriptional activators like the yes-associated protein (YAP) or its paralog transcriptional coactivator with a PDZ-binding motif (TAZ). TEAD·YAP/TAZ target genes are involved in tissue and immune homeostasis, organ size control, tumor growth, and metastasis. Here, we report isoindoline and octahydroisoindole small molecules with a cyanamide electrophile that forms a covalent bond with a conserved cysteine in the TEAD palmitate-binding cavity. Time- and concentration-dependent studies against TEAD1-4 yielded second-order rate constants k_inact/K_I greater than 100 M^-1 s^-1. Compounds inhibited YAP1 binding to TEADs with submicromolar IC₅₀ values. Cocrystal structures with TEAD2 enabled structure-activity relationship studies. In mammalian cells, compounds suppressed CTGF mRNA levels and inhibited TEAD1-4 transcriptional activity with submicromolar IC₅₀ values. Inhibition of TEAD binding to YAP1 in mammalian cells was also observed. Several compounds inhibited the cell viability of sarcoma, hepatocellular carcinoma, glioblastoma, and breast cancer cells with single-digit micromolar IC₅₀ values.

TEAD4 is a master regulator of high-risk nasopharyngeal carcinoma

The molecular basis underlying nasopharyngeal carcinoma (NPC) remains unclear. Recent progress in transcriptional regulatory network analysis helps identify the master regulator (MR) proteins that transcriptionally define malignant tumor phenotypes. Here, we investigated transcription factor-target interactions and identified TEA domain transcription factor 4 (TEAD4) as an MR of high-risk NPC. Precisely, TEAD4 promoted NPC migration, invasion and cisplatin resistance, depending on its autopalmitoylation. Mechanistically, YTHDF2 (YTH domain family 2) recognized WTAP (Wilms tumor 1-associating protein)-mediated TEAD4 m⁶A methylation to facilitate its stability and led to aberrant up-regulation of TEAD4. Up-regulated TEAD4 further drove NPC progression by transcriptionally activating BZW2 (basic leucine zipper and W2 domains 2) to induce the oncogenic AKT pathway. Moreover, the transcriptional activity of TEAD4 was independent of its canonical coactivators YAP/TAZ. Clinically, TEAD4 serves as an independent predictor of unfavorable prognosis and cisplatin response in NPC. Our data revealed the crucial role of TEAD4 in driving tumor malignancy, thus, may provide therapeutic vulnerability in NPC.

N-terminal β-strand in YAP is critical for stronger binding to scalloped relative to TEAD transcription factor

The yes-associated protein (YAP) regulates the transcriptional activity of the TEAD transcription factors that are key in the control of organ morphogenesis. YAP interacts with TEAD via three secondary structure elements: a β-strand, an α-helix, and an Ω-loop. Earlier results have shown that the β-strand has only a marginal contribution in the YAP:TEAD interaction, but we show here that it significantly enhances the affinity of YAP for the Drosophila homolog of TEAD, scalloped (Sd). Nuclear magnetic resonance shows that the β-strand adopts a more rigid conformation once bound to Sd; pre-steady state kinetic measurements show that the YAP:Sd complex is more stable. Although the crystal structures of the YAP:TEAD and YAP:Sd complexes reveal no differences at the binding interface that could explain these results. Molecular Dynamics simulations are in line with our experimental findings regarding β-strand stability and overall binding affinity of YAP to TEAD and Sd. In particular, RMSF, correlated motion and MMGBSA analyses suggest that β-sheet fluctuations play a relevant role in YAP53-57 β-strand dissociation from TEAD4 and contribute to the lower affinity of YAP for TEAD4. Identifying a clear mechanism leading to the difference in YAP's β-strand stability proved to be challenging, pointing to the potential relevance of multiple modest structural changes or fluctuations for regulation of binding affinity.

YAP1 is essential for malignant mesothelioma tumor maintenance

Malignant pleural mesothelioma, a tumor arising from the membrane covering the lungs and the inner side of the ribs, is a cancer in which genetic alterations of genes encoding proteins that act on or are part of the Hippo-YAP1 signaling pathway are frequent. Dysfunctional Hippo signaling may result in aberrant activation of the transcriptional coactivator protein YAP1, which binds to and activates transcription factors of the TEAD family. Recent studies have associated elevated YAP1 protein activity with a poor prognosis of malignant mesothelioma and its resistance to current therapies, but its role in tumor maintenance is unclear. In this study, we investigate the dependence of malignant mesothelioma on YAP1 signaling to maintain fully established tumors in vivo. We show that downregulation of YAP1 in a dysfunctional Hippo genetic background results in the inhibition of YAP1/TEAD-dependent gene expression, the induction of apoptosis, and the inhibition of tumor cell growth in vitro. The conditional downregulation of YAP1 in established tumor xenografts leads to the inhibition of YAP1-dependent gene transcription and eventually tumor regression. This effect is only seen in the YAP1-activated MSTO-211H mesothelioma xenograft model, but not in the Hippo-independent HCT116 colon cancer xenograft model. Our data demonstrate that, in the context of a Hippo pathway mutated background, YAP1 activity alone is enough to maintain the growth of established tumors in vivo, thus validating the concept of inhibiting the activated YAP1-TEAD complex for the treatment of malignant pleural mesothelioma patients.

Aurintricarboxylic acid is a canonical disruptor of the TAZ-TEAD transcriptional complex

Disrupting the formation of the oncogenic YAP/TAZ-TEAD transcriptional complex holds substantial therapeutic potential. However, the three protein interaction interfaces of this complex cannot be easily disrupted using small molecules. Here, we report that the pharmacologically active small molecule aurintricarboxylic acid (ATA) acts as a disruptor of the TAZ-TEAD complex. ATA was identified in a high-throughput screen using a TAZ-TEAD AlphaLISA assay that was tailored to identify disruptors of this transcriptional complex. We further used fluorescence polarization assays both to confirm disruption of the TAZ-TEAD complex and to demonstrate that ATA binds to interface 3. We have previously shown that cell-based models that express the oncogenic TAZ-CAMTA1 (TC) fusion protein display enhanced TEAD transcriptional activity because TC functions as an activated form of TAZ. Utilizing cell-based studies and our TC model system, we performed TC/TEAD reporter, RNA-Seq, and qPCR assays and found that ATA inhibits TC/TEAD transcriptional activity. Further, disruption of TC/TEAD and TAZ/TEAD interaction by ATA abrogated anchorage-independent growth, the phenotype most closely linked to dysregulated TAZ/TEAD activity. Therefore, this study demonstrates that ATA is a novel small molecule that has the ability to disrupt the undruggable TAZ-TEAD interface.

Toward the Design of Ligands Selective for the C-Terminal Domain of TEADs

The Hippo signaling pathway plays a fundamental role in the control of organ growth, cell proliferation, and stem cell characters. TEADs are the main transcriptional output regulators of the Hippo signaling pathway and bind to YAP and TAZ co-activators. TEAD1-4 are expressed differently, depending on the tissue and developmental level, and can be overexpressed in certain pathologies. TEAD ligands mainly target the internal pocket of the C-terminal domain of TEAD, and the first ligands selective for TEAD1 and TEAD3 have been recently reported. In this paper, we focus on the topographic homology of the TEAD C-terminal domain both externally and in the internal pocket to highlight the possibility of rationally designing ligands selective for one of the TEAD family members. We identified a novel TEAD2-specific pocket and reported its first ligand. Finally, AlphaFold2 models of full-length TEADs suggest TEAD autoregulation and emphasize the importance of the interface 2.

The role of lysine palmitoylation/myristoylation in the function of the TEAD transcription factors

The TEAD transcription factors are the most downstream elements of the Hippo pathway. Their transcriptional activity is modulated by different regulator proteins and by the palmitoylation/myristoylation of a specific cysteine residue. In this report, we show that a conserved lysine present in these transcription factors can also be acylated, probably following the intramolecular transfer of the acyl moiety from the cysteine. Using Scalloped (Sd), the Drosophila homolog of human TEAD, as a model, we designed a mutant protein (Glu352Gln^Sd) that is predominantly acylated on the lysine (Lys350^Sd). This protein binds in vitro to the three Sd regulators—Yki, Vg and Tgi—with a similar affinity as the wild type Sd, but it has a significantly higher thermal stability than Sd acylated on the cysteine. This mutant was also introduced in the endogenous locus of the sd gene in Drosophila using CRISPR/Cas9. Homozygous mutants reach adulthood, do not present obvious morphological defects and the mutant protein has both the same level of expression and localization as wild type Sd. This reveals that this mutant protein is both functional and able to control cell growth in a similar fashion as wild type Sd. Therefore, enhancing the lysine acylation of Sd has no detrimental effect on the Hippo pathway. However, we did observe a slight but significant increase of wing size in flies homozygous for the mutant protein suggesting that a higher acylation of the lysine affects the activity of the Hippo pathway. Altogether, our findings indicate that TEAD/Sd can be acylated either on a cysteine or on a lysine, and suggest that these two different forms may have similar properties in cells.

Recent Therapeutic Approaches to Modulate the Hippo Pathway in Oncology and Regenerative Medicine

The Hippo pathway is an evolutionary conserved signaling network that regulates essential processes such as organ size, cell proliferation, migration, stemness and apoptosis. Alterations in this pathway are commonly found in solid tumors and can lead to hyperproliferation, resistance to chemotherapy, compensation for mKRAS and tumor immune evasion. As the terminal effectors of the Hippo pathway, the transcriptional coactivators YAP1/TAZ and the transcription factors TEAD1–4 present exciting opportunities to pharmacologically modulate the Hippo biology in cancer settings, inflammation and regenerative medicine. This review will provide an overview of the progress and current strategies to directly and indirectly target the YAP1/TAZ protein–protein interaction (PPI) with TEAD1–4 across multiple modalities, with focus on recent small molecules able to selectively bind to TEAD, block its autopalmitoylation and inhibit YAP1/TAZ–TEAD-dependent transcription in cancer.

Discovery of a cryptic site at the interface 2 of TEAD - Towards a new family of YAP/TAZ-TEAD inhibitors

The Hippo pathway is involved in organ size control and tissue homeostasis by regulating cell growth, proliferation and apoptosis. It controls the phosphorylation of the transcription co-activator YAP (Yes associated protein) and TAZ (Transcriptional coactivator with PDZ-binding motif) in order to control their nuclear import and their interaction with TEAD (Transcriptional Enhanced Associated Domain). YAP, TAZ and TEADs are dysregulated in several cancers making YAP/TAZ-TEAD interaction a new emerging anti-cancer target. We report the synthesis of a set of trisubstituted pyrazoles which bind to hTEAD2 at the interface 2 revealing for the first time a cryptic pocket created by the movement of the phenol ring of Y382. Compound 6 disrupts YAP/TAZ-TEAD interaction in HEK293T cells and inhibits TEAD target genes and cell proliferation in MDA-MB-231 cells. Compound 6 is therefore the first inhibitor of YAP/TAZ-TEAD targeting interface 2. This molecule could serve with other pan-TEAD inhibitors such as interface 3 ligands, for the delineation of the relative importance of VGLL vs YAP/TAZ in a given cellular model.

NT5DC2 promotes leiomyosarcoma tumour cell growth via stabilizing unpalmitoylated TEAD4 and generating a positive feedback loop

5'-Nucleotidase Domain Containing 2 (NT5DC2) is a novel oncoprotein, the regulatory effects of which have not been well characterized. This study aimed to investigate the expression profile and functional regulation of NT5DC2 and its potential interplay with TEAD4 in leiomyosarcoma (LMS). Bioinformatic analysis was conducted using data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) program. LMS cell lines SK-LMS-1 and SK-UT-1 were used for both in vitro and in vivo analysis. Results showed that NT5DC2 is aberrantly upregulated in LMS. Its overexpression was associated with unfavourable survival. Deletion of NT5DC2 significantly reduced the expression of cyclin B1, cyclin A2, cyclin E1 and CDK1 and increased G1 phase arrest in LMS cell lines, and suppressed their proliferation both in vitro and in vivo. NT5DC2 interacted with unpalmitoylated TEAD4, and this association reduced TEAD4 degradation via the ubiquitin-proteasome pathway. TRIM27 is a novel E3 ubiquitin ligase that induces K27/48-linked ubiquitination of unpalmitoylated TEAD4 at Lys278. TEAD4 inhibition significantly suppressed LMS cell growth both in vitro and in vivo. Dual-luciferase assay demonstrated that TEAD4 could bind to the NT5DC2 promoter and activate its transcription. Based on these findings, we infer that the NT5DC2-TEAD4 positive feedback loop plays an important role in LMS development and might serve as a potential therapeutic target.

Development of LM98, a Small-Molecule TEAD Inhibitor Derived from Flufenamic Acid

The YAP-TEAD transcriptional complex is responsible for the expression of genes that regulate cancer cell growth and proliferation. Dysregulation of the Hippo pathway due to overexpression of TEAD has been reported in a wide range of cancers. Inhibition of TEAD represses the expression of associated genes, demonstrating the value of this transcription factor for the development of novel anti-cancer therapies. We report herein the design, synthesis and biological evaluation of LM98, a flufenamic acid analogue. LM98 shows strong affinity to TEAD, inhibits its autopalmitoylation and reduces the YAP-TEAD transcriptional activity. Binding of LM98 to TEAD was supported by ¹⁹ F-NMR studies while co-crystallization experiments confirmed that LM98 is anchored within the palmitic acid pocket of TEAD. LM98 reduces the expression of CTGF and Cyr61, inhibits MDA-MB-231 breast cancer cell migration and arrests cell cycling in the S phase during cell division.

Biochemical properties of VGLL4 from Homo sapiens and Tgi from Drosophila melanogaster and possible biological implications

The TEAD (Sd in drosophila) transcription factors are essential for the Hippo pathway. Human VGLL4 and drosophila Tgi bind to TEAD/Sd via two distinct binding sites. These two regions are separated by few amino acids in VGLL4 but they are very distant from each other in Tgi. This difference prompted us to study whether it influences the interaction with TEAD4/Sd. We show that the full-length VGLL4/Tgi proteins behave as intrinsically disordered proteins. They have a similar affinity for TEAD4/Sd revealing that the length of the region between the two binding sites has little effect on the interaction. One of their two binding sites (high-affinity site) binds to TEAD4/Sd 100 times more tightly than to the other site, and size exclusion chromatography experiments reveal that VGLL4/Tgi only form trimeric complexes with TEAD4/Sd at high protein concentrations. In solution, therefore, VGLL4/Tgi may predominantly interact with TEAD4/Sd via their high-affinity site to create dimeric complexes. In contrast, when TEAD4/Sd molecules are immobilized on sensor chips used in Surface Plasmon Resonance experiments, one VGLL4/Tgi molecule can bind simultaneously with an enhanced affinity to two immobilized molecules. This effect, due to a local increase in protein concentration triggered by the proximity of the immobilized TEAD4/Sd molecules, suggests that in vivo VGLL4/Tgi could bind with an enhanced affinity to two nearby TEAD/Sd molecules bound to DNA. The presence of two binding sites in VGLL4/Tgi might only be required for the function of these proteins when they interact with TEAD/Sd bound to DNA.

The interaction of TEA domain transcription factor 4 (TEAD4) and Yes-associated protein 1 (YAP1) promoted the malignant process mediated by serum/glucocorticoid regulated kinase 1 (SGK1)

TEA domain transcription factor 4 (TEAD4) has been investigated to be implicated in the progression of various cancers, and it plays a role in the esophageal squamous cell carcinoma (ESCC). The study was designed to investigate how TEAD4 affected the progression of ESCC through Hippo signaling pathway in vitro and in vivo. The interaction of TEAD4 and Yes-associated protein (YAP) was detected though immunoprecipitation assay (IP). Following the treatment of TED-347, which was able to suppress the interaction of TEAD4 and YAP1, the malignant behaviors of cells including proliferation, invasion, and migration were assessed by EDU staining, wound healing, and transwell assay in vitro, while tumor growth was measured. Luciferase reporter plasmids containing the enhancer and promoter region of serum/glucocorticoid regulated kinase 1 (SGK1) were constructed to analyze how TEAD4 affected the transcription of SGK1. The above cell behaviors were further analyzed after the silencing of SGK1. Results showed that TED-347 hindered the promoting effect of TEAD4 overexpression on the malignant behaviors of ESCC cells, and this effect was related to the suppression of the TEAD4/YAP1 complex. Moreover, the promoter activity of SGK1 was obviously inhibited by TED-347. Decreased expression of SGK1 suppressed the above behaviors of cells and destroyed the effects of increased expression of TEAD4. Collectively, TEAD4/YAP promotes the malignant process of ESCC cells, which was inhibited by the interference of SGK1. Targeting TEAD4/YAP1 complex or SGK1 could find application in the treatment of esophageal squamous cell carcinoma.

Study of the TEAD-binding domain of the YAP protein from animal species

The Hippo signaling pathway, which plays a central role in the control of organ size in animals, is well conserved in metazoans. The most downstream elements of this pathway are the TEAD transcription factors that are regulated by their association with the transcriptional coactivator YAP. Therefore, the creation of the binding interface that ensures the formation of the YAP:TEAD complex is a critical molecular recognition event essential for the development/survival of many living organisms. In this report, using the available structural information on the YAP:TEAD complex, we study the TEAD‐binding domain of YAP from different animal species. This analysis of more than 400 amino acid sequences reveals that the residues from YAP involved in the formation of the two main contact regions with TEAD are very well conserved. Therefore, the binding interface between YAP and TEAD, as found in humans, probably appeared at an early evolutionary stage in metazoans. We find that, in contrast to most other animal species, several Actinopterygii species possess YAP variants with a different TEAD‐binding domain. However, these variants bind to TEAD with a similar affinity. Our studies show that the protein identified as a YAP homolog in Caenorhabditis elegans does not contain the TEAD‐binding domain found in YAP of other metazoans. Finally, we do not identify in non‐metazoan species, amino acid sequences containing both a TEAD‐binding domain, as in metazoan YAP, and WW domain(s).

A new perspective on the interaction between the Vg/VGLL1-3 proteins and the TEAD transcription factors

The most downstream elements of the Hippo pathway, the TEAD transcription factors, are regulated by several cofactors, such as Vg/VGLL1-3. Earlier findings on human VGLL1 and here on human VGLL3 show that these proteins interact with TEAD via a conserved amino acid motif called the TONDU domain. Surprisingly, our studies reveal that the TEAD-binding domain of Drosophila Vg and of human VGLL2 is more complex and contains an additional structural element, an Ω-loop, that contributes to TEAD binding. To explain this unexpected structural difference between proteins from the same family, we propose that, after the genome-wide duplications at the origin of vertebrates, the Ω-loop present in an ancestral VGLL gene has been lost in some VGLL variants. These findings illustrate how structural and functional constraints can guide the evolution of transcriptional cofactors to preserve their ability to compete with other cofactors for binding to transcription factors.

Structural and Functional Overview of TEAD4 in Cancer Biology

TEA domain transcription factor 4 (TEAD4) is an important member of the TEAD family. As a downstream effector of the Hippo pathway, TEAD4 has essential roles in cell proliferation, cell survival, tissue regeneration, and stem cell maintenance. TEAD4 contains a TEA DNA binding domain that binds the promoters of target genes and a Yes-associated protein/transcriptional co-activator with PDZ-binding motif (YAP/TAZ) binding domain that associates with transcriptional cofactors. TEAD4 coordinates with YAP, TAZ, VGLL, and other transcription factors to regulate different cellular processes in cancer via its transcriptional output. Moreover, TEAD4 undergoes post-translational modifications and subcellular translocations, and both processes have been shown to shed new insights on how TEAD transcriptional activity can be modified. In summary, TEAD4 has important roles in cancer, including epithelial-mesenchymal transition (EMT), metastasis, cancer stem cell dynamics, and chemotherapeutic drug resistance, suggesting that TEAD4 may be a promising prognostic biomarker in cancer.

Discovery of Covalent Inhibitors Targeting the Transcriptional Enhanced Associate Domain Central Pocket

Transcriptional enhanced associate domain (TEAD) transcription factors together with coactivators and corepressors modulate the expression of genes that regulate fundamental processes, such as organogenesis and cell growth, and elevated TEAD activity is associated with tumorigenesis. Hence, novel modulators of TEAD and methods for their identification are in high demand. We describe the development of a new “thiol conjugation assay” for identification of novel small molecules that bind to the TEAD central pocket. The assay monitors prevention of covalent binding of a fluorescence turn-on probe to a cysteine in the central pocket by small molecules. Screening of a collection of compounds revealed kojic acid analogues as TEAD inhibitors, which covalently target the cysteine in the central pocket, block the interaction with coactivator yes-associated protein with nanomolar apparent IC₅₀ values, and reduce TEAD target gene expression. This methodology promises to enable new medicinal chemistry programs aimed at the modulation of TEAD activity.

TEAD4 transcriptional regulates SERPINB3/4 and affect crosstalk between keratinocytes and T cells in psoriasis

Psoriasis is a common chronic inflammatory disease with the prevalence rate of approximately 1-3 %. Currently, it is generally believed that the pathogenesis of psoriasis is a T-cell immune-mediated skin disease mediated by multiple genes and factors, and the interaction between keratinocytes and T cells. TEA domain family member 4 (TEAD4) is a transcription factor which regulates the expression of downstream genes in Hippo pathway and affects several biological processes, such as regulating cell differentiation and embryonic development. However, few studies have reported the role of TEAD4 in psoriasis and its possible regulatory mechanism. In this study, we found the expression level of TEAD4 in the skin of psoriasis was significantly higher than that of normal skin. In patients with the pathological keratinocytes, TEAD4 can transcriptionally regulate the expression of SERPINB3/4 and affect the secretion of chemokines, and the depletion of SERPINB3/4 inhibited the secretion of chemokines. In addition, the supernatant of keratinocytes of patients can significantly increase the migration ability of T cells, and the supernatant of T cells cultured by the supernatant of keratinocytes of patients can significantly enhance the proliferation ability of keratinocytes. Therefore, our results suggested that TEAD4 is a key regulatory factor in progression of psoriasis, and the crosstalk between keratinocytes and T cells mediated by TEAD4 plays a critical role in the psoriasis pathogenesis.

Determination of the migration effect and molecular docking of verteporfin in different subtypes of breast cancer cells

Breast cancer is one of the most aggressive malignant tumors in women. According to the expression differences of estrogen receptor, progesterone receptor, human epidermal growth factor receptor-2 (HER-2) and cell proliferation antigen Ki-67, breast cancer can be divided into four molecular subtypes: Luminal A, Luminal B, HER-2 overexpression and Basal-like. Yes-associated protein (YAP), a downstream effector of the Hippo pathway, is overexpressed in human cancers and is associated with proliferation, apoptosis, migration, invasion and resistance to chemotherapy drugs in breast cancer cells. Verteporfin (VP) is used as a photosensitizer in the treatment of neovascular macular degeneration. VP is also identified as an inhibitor of YAP/TEA domain transcription factor (TEAD) interaction in the absence of light activation. However, detailed structural information about VP and YAP interactions is relatively scarce and VP research targeting YAP in different molecular subtypes of breast cancer cells is also rare. The aims of the present study were to structurally describe the VP binding site in the YAP crystal structure and to verify the non-photoreactive VP effect targeting YAP on the migration of different molecular subtypes of breast cancer cells. The crystal structure of VP and YAP was calculated by AutoDock 4.2 and the result was illustrated using PyMOL. The non-photoactivated VP effect on the migration of Luminal A MCF-7, Luminal B BT-474 and triple-negative breast cancer BT-549 breast cancer cells was evaluated by wound healing and Transwell migration experiments. Results from molecular docking experiments demonstrated that VP could interact through hydrogen bonds and hydrophobic interactions with important YAP residues involved in TEADs binding (Gln82, Val84, Met86 and Arg89). Migration experiments revealed that the non-photoinduced VP could inhibit the migration of different molecular subtypes of breast cancer cells. The results of the present study indicated that VP may be a novel repositioned drug for breast cancer treatment in the future.

Therapeutic Targeting of Signaling Pathways Related to Cancer Stemness

The theory of cancer stem cells (CSCs) proposes that the different cells within a tumor, as well as metastasis deriving from it, are originated from a single subpopulation of cells with self-renewal and differentiation capacities. These cancer stem cells are supposed to be critical for tumor expansion and metastasis, tumor relapse and resistance to conventional therapies, such as chemo- and radiotherapy. The acquisition of these abilities has been attributed to the activation of alternative pathways, for instance, WNT, NOTCH, SHH, PI3K, Hippo, or NF-κB pathways, that regulate detoxification mechanisms; increase the metabolic rate; induce resistance to apoptotic, autophagic, and senescence pathways; promote the overexpression of drug transporter proteins; and activate specific stem cell transcription factors. The elimination of CSCs is an important goal in cancer therapeutic approaches because it could decrease relapses and metastatic dissemination, which are main causes of mortality in oncology patients. In this work, we discuss the role of these signaling pathways in CSCs along with their therapeutic potential.

Identification of FAM181A and FAM181B as new interactors with the TEAD transcription factors

The Hippo pathway is a key signaling pathway in the control of organ size and development. The most distal elements of this pathway, the TEAD transcription factors, are regulated by several proteins, such as YAP (Yes-associated protein), TAZ (transcriptional co-activator with PDZ-binding motif) and VGLL1-4 (Vestigial-like members 1-4). In this article, combining structural data and motif searches in protein databases, we identify two new TEAD interactors: FAM181A and FAM181B. Our structural data show that they bind to TEAD via an Ω-loop as YAP/TAZ do, but only FAM181B possesses the LxxLF motif (x any amino acid) found in YAP/TAZ. The affinity of different FAM181A/B fragments for TEAD is in the low micromolar range and full-length FAM181A/B proteins interact with TEAD in cells. These findings, together with a recent report showing that FAM181A/B proteins have a role in nervous system development, suggest a potential new involvement of the TEAD transcription factors in the development of this tissue.

Discovery and biological evaluation of vinylsulfonamide derivatives as highly potent, covalent TEAD autopalmitoylation inhibitors

Transcriptional enhancer associated domain family members (TEADs) are the most important downstream effectors that play the pivotal role in the development, regeneration and tissue homeostasis. Recent biochemical studies have demonstrated that TEADs could undergo autopalmitoylation that is indispensable for its function making the lipid-binding pocket an attractive target for chemical intervention. Herein, through structure-based virtual screen and rational medicinal chemistry optimization, we identified DC-TEADin02 as the most potent, selective, covalent TEAD autopalmitoylation inhibitor with the IC₅₀ value of 197 ± 19 nM while it showed minimal effect on TEAD-YAP interaction. Further biochemical counter-screens demonstrate the specific thiol reactivity and selectivity of DC-TEADin02 over the kinase family, lipid-binding proteins and epigenetic targets. Notably, DC-TEADin02 inhibited TEADs transcription activity leading to downregulation of YAP-related downstream gene expression. Taken together, our findings proved the validity of modulating transcriptional output in the Hippo signaling pathway through irreversible chemical interventions of TEADs autopalmitoylation activity, which may serve as a qualified chemical tool for TEADs palmitoylation-related studies in the future.

Fluorescence polarization assay for the identification and evaluation of inhibitors at YAP-TEAD protein-protein interface 3

The Hippo signaling pathway controls cell-cell contact, cell proliferation, as well as organ size by integrating changes in the cellular microenvironment. In recent years, the pivotal role of Hippo signaling in cancers has been well recognized. Inhibition of the pathway promotes the translocation of the major Hippo pathway effectors, the yes-associated protein (YAP) and its paralog TAZ, to the nucleus, where they interact with the transcription factor family transcriptional enhancer associate domain (TEAD), thus coactivating the expression of downstream genes, leading to cell transformation, tissue overgrowth, and tumor development. Therefore, the interruption of the YAP-TEAD transcriptional complex represents a novel opportunity for the treatment of cancer. Here, we established a fluorescence polarization (FP)-based assay for the identification and evaluation of YAP-TEAD protein-protein interface (PPI) inhibitors at the YAP Ω-loop binding region of TEAD, which is also called interface 3 at the YAP-TEAD binding surface. Furthermore, a patented small molecule (Patent-22) was evaluated by the FP assay, which confirmed that it was a YAP-TEAD PPI inhibitor at interface 3. Possessing great application value, this FP method is reliable, robust, and economical for inhibitor assessment and drug discovery.

Regulation of TEAD Transcription Factors in Cancer Biology

Transcriptional enhanced associate domain (TEAD) transcription factors play important roles during development, cell proliferation, regeneration, and tissue homeostasis. TEAD integrates with and coordinates various signal transduction pathways including Hippo, Wnt, transforming growth factor beta (TGFβ), and epidermal growth factor receptor (EGFR) pathways. TEAD deregulation affects well-established cancer genes such as KRAS, BRAF, LKB1, NF2, and MYC, and its transcriptional output plays an important role in tumor progression, metastasis, cancer metabolism, immunity, and drug resistance. To date, TEADs have been recognized to be key transcription factors of the Hippo pathway. Therefore, most studies are focused on the Hippo kinases and YAP/TAZ, whereas the Hippo-dependent and Hippo-independent regulators and regulations governing TEAD only emerged recently. Deregulation of the TEAD transcriptional output plays important roles in tumor progression and serves as a prognostic biomarker due to high correlation with clinicopathological parameters in human malignancies. In addition, discovering the molecular mechanisms of TEAD, such as post-translational modifications and nucleocytoplasmic shuttling, represents an important means of modulating TEAD transcriptional activity. Collectively, this review highlights the role of TEAD in multistep-tumorigenesis by interacting with upstream oncogenic signaling pathways and controlling downstream target genes, which provides unprecedented insight and rationale into developing TEAD-targeted anticancer therapeutics.

Adaptation of the bound intrinsically disordered protein YAP to mutations at the YAP:TEAD interface

Many interactions between proteins are mediated by intrinsically disordered regions (IDRs). Intrinsically disordered proteins (IDPs) do not adopt a stable three-dimensional structure in their unbound form, but they become more structured upon binding to their partners. In this communication, we study how a bound IDR adapts to mutations, preventing the formation of hydrogen bonds at the binding interface that needs a precise positioning of the interacting residues to be formed. We use as a model the YAP:TEAD interface, where one YAP (IDP) and two TEAD residues form hydrogen bonds via their side chain. Our study shows that the conformational flexibility of bound YAP and the reorganization of water molecules at the interface help to reduce the energetic constraints created by the loss of H-bonds at the interface. The residual flexibility/dynamic of bound IDRs and water might, therefore, be a key for the adaptation of IDPs to different interface landscapes and to mutations occurring at binding interfaces.

Cell contact and Nf2/Merlin-dependent regulation of TEAD palmitoylation and activity

The Hippo pathway is involved in regulating contact inhibition of proliferation and organ size control and responds to various physical and biochemical stimuli. It is a kinase cascade that negatively regulates the activity of cotranscription factors YAP and TAZ, which interact with DNA binding transcription factors including TEAD and activate the expression of target genes. In this study, we show that the palmitoylation of TEAD, which controls the activity and stability of TEAD proteins, is actively regulated by cell density independent of Lats, the key kinase of the Hippo pathway. The expression of fatty acid synthase and acetyl-CoA carboxylase involved in de novo biosynthesis of palmitate is reduced by cell density in an Nf2/Merlin-dependent manner. Depalmitoylation of TEAD is mediated by depalmitoylases including APT2 and ABHD17A. Palmitoylation-deficient TEAD4 mutant is unstable and degraded by proteasome through the activity of the E3 ubiquitin ligase CHIP. These findings show that TEAD activity is tightly controlled through the regulation of palmitoylation and stability via the orchestration of FASN, depalmitoylases, and E3 ubiquitin ligase in response to cell contact.

YAP/TAZ Signaling and Resistance to Cancer Therapy

Drug resistance is a major challenge in cancer treatment. Emerging evidence indicates that deregulation of YAP/TAZ signaling may be a major mechanism of intrinsic and acquired resistance to various targeted and chemotherapies. Moreover, YAP/TAZ-mediated expression of PD-L1 and multiple cytokines is pivotal for tumor immune evasion. While direct inhibitors of YAP/TAZ are still under development, FDA-approved drugs that indirectly block YAP/TAZ activation or critical downstream targets of YAP/TAZ have shown promise in the clinic in reducing therapy resistance. Finally, BET inhibitors, which reportedly block YAP/TAZ-mediated transcription, present another potential venue to overcome YAP/TAZ-induced drug resistance.

Small-Molecule Covalent Modification of Conserved Cysteine Leads to Allosteric Inhibition of the TEAD⋅Yap Protein-Protein Interaction

The Hippo pathway coordinates extracellular signals onto the control of tissue homeostasis and organ size. Hippo signaling primarily regulates the ability of Yap1 to bind and co-activate TEA domain (TEAD) transcription factors. Yap1 tightly binds to TEAD4 via a large flat interface, making the development of small-molecule orthosteric inhibitors highly challenging. Here, we report small-molecule TEAD⋅Yap inhibitors that rapidly and selectively form a covalent bond with a conserved cysteine located within the unique deep hydrophobic palmitate-binding pocket of TEADs. Inhibition of TEAD4 binding to Yap1 by these compounds was irreversible and occurred on a longer time scale. In mammalian cells, the compounds formed a covalent complex with TEAD4, inhibited its binding to Yap1, blocked its transcriptional activity, and suppressed expression of connective tissue growth factor. The compounds inhibited cell viability of patient-derived glioblastoma spheroids, making them suitable as chemical probes to explore Hippo signaling in cancer.

Overexpression of TEAD4 correlates with poor prognosis of glioma and promotes cell invasion

This study aimed to reveal the correlation of increased TEA domain transcription factor 4 (TEAD4) expression and disease prognosis in glioma. The expression data of TEAD4 mRNA in glioma were collected from GEO database (GSE4290), and the expression of TEAD4 protein in glioma was confirmed using western blot and Immunohistochemistry. Kaplan-Meier analysis with the log-rank test was used to reveal the correlation of TEAD4 expression level and patients' survival. The effects of TEAD4 on migration and invasion were separately examined by Transwell assay and Boyden assay. Gene set enrichment analysis (GSEA) was performed to predict the possible biological function of TEAD4 in glioma. The results showed that TEAD4 mRNA and protein expression were upregulated in glioma tissues compared to normal brain tissues. Furthermore, overexpression of TEAD4 correlated with poor prognosis in glioma patients. Knockdown of TEAD4 markedly inhibited glioma cells migration and invasion in vitro. Consistent with the result that TEAD4 was associated with epithelial-mesenchymal transition (EMT) closely by GESA, knockdown of TEAD4 resulted in N-cadherin, vimentin and Slug downregulated but E-cadherin upregulated. Our study indicated that overexpression of TEAD4 may represent as a potential unfavorable marker for poor survival and prognosis in glioma. Knockdown of TEAD4 led to suppressed glioma migration and invasion.

Repurposing of Drugs Targeting YAP-TEAD Functions

Drug repurposing is a fast and consolidated approach for the research of new active compounds bypassing the long streamline of the drug discovery process. Several drugs in clinical practice have been reported for modulating the major Hippo pathway's terminal effectors, namely YAP (Yes1-associated protein), TAZ (transcriptional co-activator with PDZ-binding motif) and TEAD (transcriptional enhanced associate domains), which are directly involved in the regulation of cell growth and tissue homeostasis. Since this pathway is known to have many cross-talking phenomena with cell signaling pathways, many efforts have been made to understand its importance in oncology. Moreover, this could be relevant to obtain new molecular tools and potential therapeutic assets. In this review, we discuss the main mechanisms of action of the best-known compounds, clinically approved or investigational drugs, able to cross-talk and modulate the Hippo pathway, as an attractive strategy for the discovery of new potential lead compounds.

Structural and ligand-binding analysis of the YAP-binding domain of transcription factor TEAD4

The oncoprotein YAP (Yes-associated protein) requires the TEAD family of transcription factors for the up-regulation of genes important for cell proliferation. Disrupting YAP–TEAD interaction is an attractive strategy for cancer therapy. Targeting TEADs using small molecules that either bind to the YAP-binding pocket or the palmitate-binding pocket is proposed to disrupt the YAP–TEAD interaction. There is a need for methodologies to facilitate robust and reliable identification of compounds that occupy either YAP-binding pocket or palmitate-binding pocket. Here, using NMR spectroscopy, we validated compounds that bind to these pockets and also identify the residues in mouse TEAD4 (mTEAD4) that interact with these compounds. Flufenamic acid (FA) was used as a positive control for validation of palmitate-binding pocket-occupying compounds by NMR. Furthermore, we identify a hit from a fragment screen and show that it occupies a site close to YAP-binding pocket on the TEAD surface. Our results also indicate that purified mTEAD4 can catalyze autopalmitoylation. NMR studies on mTEAD4 revealed that exchanges exist in TEAD as NMR signal broadening was observed for residues close to the palmitoylation site. Mutating the palmitoylated cysteine (C360S mutant) abolished palmitoylation, while no significant changes in the NMR spectrum were observed for the mutant which still binds to YAP. We also show that FA inhibits TEAD autopalmitoylation. Our studies highlight the utility of NMR spectroscopy in identifying small molecules that bind to TEAD pockets and reinforce the notion that both palmitate-binding pocket and YAP-binding pocket are targetable.

Toward the Discovery of a Novel Class of YAP⁻TEAD Interaction Inhibitors by Virtual Screening Approach Targeting YAP⁻TEAD Protein⁻Protein Interface

Intrinsically disordered protein YAP (yes-associated protein) interacts with TEADs transcriptional factors family (transcriptional enhancer associated domain) creating three interfaces. Interface 3, between the Ω-loop of YAP and a shallow pocket of TEAD was identified as the most important TEAD zone for YAP-TEAD interaction. Using the first X-ray structure of the hYAP_50–71-hTEAD1_209–426 complex (PDB 3KYS) published in 2010, a protein-protein interaction inhibitors-enriched library (175,000 chemical compounds) was screened against this hydrophobic pocket of TEAD. Four different chemical families have been identified and evaluated using biophysical techniques (thermal shift assay, microscale thermophoresis) and in cellulo assays (luciferase activity in transfected HEK293 cells, RTqPCR in MDA-MB231 cells). A first promising hit with micromolar inhibition in the luciferase gene reporter assay was discovered. This hit also decreased mRNA levels of TEAD target genes.

Targeting the Hippo Pathway and Cancer through the TEAD Family of Transcription Factors

The Hippo pathway is a critical transcriptional signaling pathway that regulates cell growth, proliferation and organ development. The transcriptional enhanced associate domain (TEAD) protein family consists of four paralogous transcription factors that function to modulate gene expression in response to the Hippo signaling pathway. Transcriptional activation of these proteins occurs upon binding to the co-activator YAP/TAZ whose entry into the nucleus is regulated by Lats1/2 kinase. In recent years, it has become apparent that the dysregulation and/or overexpression of Hippo pathway effectors is implicated in a wide range of cancers, including prostate, gastric and liver cancer. A large body of work has been dedicated to understanding the therapeutic potential of modulating the phosphorylation and localization of YAP/TAZ. However, YAP/TAZ are considered to be natively unfolded and may be intractable as drug targets. Therefore, TEAD proteins present themselves as an excellent therapeutic target for intervention of the Hippo pathway. This review summarizes the functional role of TEAD proteins in cancer and assesses the therapeutic potential of antagonizing TEAD function in vivo.