Insights into recent findings and clinical application of YAP and TAZ in cancer

Activation of PAR1 contributes to ferroptosis of Schwann cells and inhibits regeneration of myelin sheath after sciatic nerve crush injury in rats via Hippo-YAP/ACSL4 pathway

OBJECTIVE

Peripheral nerve injury (PNI) is characterized by high incidence and sequela rate. Recently, there was increasing evidence that has shown ferroptosis may impede functional recovery. Our objective is to explore the novel mechanism that regulates ferroptosis after PNI.

METHODS

LC-MS/MS proteomics was used to explore the possible differential signals, while PCR array was performed to investigate the differential factors. Besides, we also tried to activate or inhibit the key factors and then observe the level of ferroptosis. Regeneration of myelin sheath was finally examined in vivo via transmission electron microscopy.

RESULTS

Proteomics analysis suggested coagulation signal was activated after sciatic nerve crush injury, in which high expression of F2 (encoding thrombin) and F2r (encoding PAR1) were observed. Both thrombin and PAR1-targeted activator TRAP6 can induce ferroptosis in RSC96 cells, which can be rescued by Vorapaxar (PAR1 targeted inhibitor) in vitro. Further PCR array revealed that activation of PAR1 induced ferroptosis in RSC96 cells by increasing expression of YAP and ACSL4. Immunofluorescence of sciatic nerve confirmed that the expression of YAP and ACSL4 were simultaneously reduced after PAR1 inhibition, which may contribute to myelin regeneration after injury in SD rats.

CONCLUSION

Inhibition of PAR1 can relieve ferroptosis after sciatic nerve crush injury in SD rats through Hippo-YAP/ACSL4 pathway, thereby regulating myelin regeneration after injury. In summary, PAR1/Hippo-YAP/ACSL4 pathway may be a promising therapeutic target for promoting functional recovery post-sciatic crush injury.

YAP/TAZ Drive Agrin-Matrix Metalloproteinase 12-Mediated Diabetic Skin Wound Healing

Macroscopic loss of extracellular matrix can lead to chronic defects in skin wound healing, but supplementation of extracellular matrix holds promise for facilitating wound closure, particularly in diabetic wound healing. We recently showed that the extracellular matrix proteoglycan agrin accelerates cutaneous wound healing by improving mechanoperception of migrating keratinocytes and allowing them to respond to mechanical stresses through matrix metalloproteinase 12 (MMP12). RNA-sequencing analysis revealed that in addition to a disorganized extracellular matrix, agrin-depleted skin cells have impaired YAP/TAZ transcriptional outcomes, leading us to hypothesize that YAP/TAZ, as central mechanosensors, drive the functionality of agrin-MMP12 signaling during cutaneous wound repair. In this study, we demonstrate that agrin activates YAP/TAZ during migration of keratinocytes after wounding in vitro and in vivo. Mechanistically, YAP/TAZ sustain agrin and MMP12 protein expression during migration after wounding through positive feedback. YAP/TAZ silencing abolishes agrin-MMP12-mediated force recognition and geometrical constraints. Importantly, soluble agrin therapy accelerates wound closure in diabetic mouse models by engaging MMP12-YAP. Because patients with diabetic foot ulcers and impaired wound healing have reduced expression of agrin-MMP12 that correlates with YAP/TAZ inactivation, we propose that timely activation of YAP/TAZ by soluble agrin therapy can accentuate mechanobiological microenvironments for efficient wound healing, under normal and diabetic conditions.

Advances towards potential cancer therapeutics targeting Hippo signaling

Decades of research into the Hippo signaling pathway have greatly advanced our understanding of its roles in organ growth, tissue regeneration, and tumorigenesis. The Hippo pathway is frequently dysregulated in human cancers and is recognized as a prominent cancer signaling pathway. Hence, the Hippo pathway represents an ideal molecular target for cancer therapies. This review will highlight recent advancements in targeting the Hippo pathway for cancer treatment and discuss the potential opportunities for developing new therapeutic modalities.

Hapalindole Q suppresses autophagosome-lysosome fusion by promoting YAP1 degradation via chaperon-mediated autophagy

Autophagy is a conserved catabolic process crucial for maintaining cellular homeostasis and has emerged as a promising therapeutic target for many diseases. Mechanistically novel small-molecule autophagy regulators are highly desirable from a pharmacological point of view. Here, we report the macroautophagy-inhibitory effect of hapalindole Q, a member of the structurally intriguing but biologically understudied hapalindole family of indole terpenoids. This compound promotes the noncanonical degradation of Yes-associated protein 1 (YAP1), the downstream effector of the Hippo signaling pathway, via chaperone-mediated autophagy, disrupting proper distribution of Rab7 and suppressing autophagosome-lysosome fusion in macroautophagy. Its binding to YAP1 is further confirmed by using biophysical techniques. A preliminary structure-activity relationship study reveals that the hapalindole Q scaffold, rather than the isothiocyanate group, is essential for YAP1 binding and degradation. This work not only identifies a macroautophagy inhibitor with a distinct mechanism of action but also provided a molecular scaffold for direct targeting of YAP1, which may benefit the development of therapeutics for both autophagy-related and Hippo-YAP-related diseases.

Targeting Yes-Associated Protein (YAP) in Breast Cancer: In Silico Molecular Dynamics, Luminescence-Based In Vitro, and In Vivo Validation of Rauvolfia tetraphylla-Derived Inhibitors

The study aims to elucidate the pharmacological mechanism of Rauvolfia tetraphylla against breast cancer through a comprehensive, multi-faceted approach. This includes molecular docking, molecular dynamics, and experimental validation. Initial screening via ADME analysis and network pharmacology identified key compounds and potential targets. Protein-protein interaction (PPI) network analysis pinpointed Yes-associated protein-1 (YAP) as a crucial target. Molecular docking revealed that three compounds-ajmaline, reserpine, and serpentine-exhibited strong binding affinities with YAP, with scores of -6.5 to -6.7 kcal/mol. Molecular dynamics simulations were conducted to assess the stability of these interactions further. Experimental validation showed R. tetraphylla inhibited breast cancer cell proliferation, with an IC50 of 348.69 μg/mL, while demonstrating cytoprotective effects on Vero cells (IC50: 1056.23 μg/mL). Migration assays indicated an 88.5% reduction in cell migration, and increased ROS levels signaled elevated stress in cancer cells. Apoptosis was confirmed by AO/EtBr staining. In vivo validation in a DMBA-induced mouse model confirmed significant tumor growth inhibition, supported by changes in YAP expression and histopathological analysis. These findings highlight R. tetraphylla as a promising therapeutic candidate against breast cancer, offering insights into its mechanisms and potential for future drug development and clinical applications.

Comprehensive review on leucine-rich pentatricopeptide repeat-containing protein (LRPPRC, PPR protein): A burgeoning target for cancer therapy

Leucine-rich pentatricopeptide repeat-containing (LRPPRC), known as the gene mutations that cause Leigh Syndrome French Canadian, encodes a high molecular weight PPR protein (157,905 Da), LRPPRC. LRPPRC binds to DNA, RNA, and proteins to regulate transcription and translation, leading to changes in cell fate. Increasing evidence indicates that LRPPRC plays a pivotal role in various human diseases, particularly cancer in recent years. Here, we review the structure, function, molecular mechanism, as well as inhibitors of LRPPRC. LRPPRC expression elevates in most cancer types and high expression of LRPPRC predicts the poor prognosis of cancer patients. Targeting LRPPRC suppresses tumor progression by affecting several cancer hallmarks, including signal transduction, cancer metabolism, and immune regulation. LRPPRC is a promising target in cancer research, serving as both a biomarker and therapeutic target. Further studies are required to extend the understanding of LRPPRC function and molecular mechanism, as well as to refine novel therapeutic strategies targeting LRPPRC in cancer therapy.

The Hippo pathway as an antitumor target: time to focus on

INTRODUCTION

The Hippo signaling governs the expression of genes critically important for cell proliferation and survival. The components of this pathway are considered antitumor drug targets. However, the design of Hippo inhibitors is a challenge given the complexity of the network and redundancy of its elements.

AREAS COVERED

We review the current state-of-the-art in the structure of the Hippo pathway, the microenvironment-induced extracellular cues, the strategies to design pharmacological instruments for inactivation of the Hippo signaling using small molecular weight modulators, as well as the results of initial clinical trials.

EXPERT OPINION

One special characteristic of the Hippo signaling is the adverse role of phosphorylation: opposite to classical kinase cascades that activate the transcription factors, the Hippo kinases retain their partners in a transcriptionally inactive state. Therefore, approaches for pharmacological or genetic inhibition of Hippo protein kinases are counterproductive. The developing alternatives such as disruption of protein-protein interactions or PROTAC techniques are straightforward for preventing the Hippo signaling in cancer therapy.

YAP/TAZ Signalling Controls Epidermal Keratinocyte Fate

The paralogues Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) control cell proliferation and cell fate determination from embryogenesis to ageing. In the skin epidermis, these proteins are involved in both homeostatic cell renewal and injury-induced regeneration and also drive carcinogenesis and other pathologies. YAP and TAZ are usually considered downstream of the Hippo pathway. However, they are the central integrating link for the signalling microenvironment since they are involved in the interplay with signalling cascades induced by growth factors, cytokines, and physical parameters of the extracellular matrix. In this review, we summarise the evidence on how YAP and TAZ are activated in epidermal keratinocytes; how YAP/TAZ-mediated signalling cooperates with other signalling molecules at the plasma membrane, cytoplasmic, and nuclear levels; and how YAP/TAZ ultimately controls transcription programmes, defining epidermal cell fate.

GPRC5A promotes lung colonization of esophageal squamous cell carcinoma

Emerging evidence suggests that cancer cells may disseminate early, prior to the formation of traditional macro-metastases. However, the mechanisms underlying the seeding and transition of early disseminated cancer cells (DCCs) into metastatic tumors remain poorly understood. Through single-cell RNA sequencing, we show that early lung DCCs from esophageal squamous cell carcinoma (ESCC) exhibit a trophoblast-like 'tumor implantation' phenotype, which enhances their dissemination and supports metastatic growth. Notably, ESCC cells overexpressing GPRC5A demonstrate improved implantation and persistence, resulting in macro-metastases in the lungs. Clinically, elevated GPRC5A level is associated with poorer outcomes in a cohort of 148 ESCC patients. Mechanistically, GPRC5A is found to potentially interact with WWP1, facilitating the polyubiquitination and degradation of LATS1, thereby activating YAP1 signaling pathways essential for metastasis. Importantly, targeting YAP1 axis with CA3 or TED-347 significantly diminishes early implantation and macro-metastases. Thus, the GPRC5A/WWP1/LATS1/YAP1 pathway represents a crucial target for therapeutic intervention in ESCC lung metastases.

Hypoxia-reduced YAP phosphorylation enhances expression of Mucin5AC in nasal epithelial cells of chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is an upper respiratory disease characterized by persistent inflammation of the nasal mucosa. However, the mechanism of abnormal Mucin5AC expression by CRSwNP epithelial cells is not fully understood.

OBJECTIVE

We investigated the potential role of yes-associated protein (YAP) underlying the mechanism of excessive epithelial Mucin5AC expression in CRSwNP in a hypoxic model.

METHODS

Tissue biopsies of CRSwNP (n = 60), chronic rhinosinusitis without nasal polyps (CRSsNP) (n = 9) and healthy controls (n = 30) were investigated together with a well-established hypoxic model of primary human nasal epithelial cells (hNECs). The expression levels of hypoxia inducible factor (HIF)-1α and YAP, and the effect of the signaling axis on mucus secretion in hNECs were analyzed.

RESULTS

We observed a significant elevated expression levels of YAP in patients with CRSwNP and CRSsNP compared to controls. In addition, HIF-1α expression of CRSwNP was higher than that of control group. Under hypoxic conditions, HIF-1α was found to regulate the upregulation of YAP in hNECs. Further investigations revealed that HIF-1α facilitated the activation and nuclear localization of active-YAP by reducing the phosphorylation of YAP. This mechanism appeared to be linked to HIF-1α-mediated inhibition of LATS 1 phosphorylation and subsequent YAP degradation. HIF-1α was shown to promote the expression of P63 and the levels of Mucin5AC in hNECs by enhancing YAP activation.

CONCLUSION

Our findings indicated that hypoxia enhances YAP activation by decreasing p-LATS 1 and YAP phosphorylation. This has the potential to impact on the proliferation of basal cells and the differentiation of goblet cells in CRSwNP, ultimately leading to a pathological condition characterized by excessive Mucin5AC expression.

Circ_0002722-induced regulation of YAP promotes platinum resistance in oral squamous cell carcinoma: Implications for verteporfin therapy

Oral squamous cell carcinoma (OSCC) poses a significant public health burden due to its high prevalence and poor prognosis. Platinum resistance is one of the major challenges in OSCC treatment. Yes-associated protein (YAP) has been identified as a pivotal player in OSCC tumorigenesis and progression. Circular RNA (circRNA) has been implicated in chemoresistance in various cancers by regulation the function of microRNA. Nevertheless, the specific mechanisms linking circRNA to YAP expression in OSCC remain poorly understood. In this study, we detected the YAP and circRNA hsa_circ_0002722 (circ_0002722) expression by western blot (WB) and quantitative polymerase chain reaction (qPCR). We found that YAP and circ_0002722 were up-regulated in platinum resistance in OSCC tissues. Furthermore, transfection of circ_0002722 siRNA into platinum-resistant cells revealed that circ_0002722 acted as a regulator of miR-1305, which influenced YAP expression and thereby affected platinum sensitivity. In vivo experiments corroborated the synergistic effects of cisplatin and verteporfin (a YAP inhibitor) in combating platinum resistance. Targeting YAP emerges as a promising therapeutic strategy for addressing platinum resistance in OSCC, with circ_0002722 serving as a potential therapy target and valuable diagnostic marker. These findings shed light on the underlying mechanisms of platinum resistance, paving the way for the development of effective treatment approaches.

Crosstalk between O-GlcNAcylation and ubiquitination: a novel strategy for overcoming cancer therapeutic resistance

Developing resistance to cancer treatments is a major challenge, often leading to disease recurrence and metastasis. Understanding the underlying mechanisms of therapeutic resistance is critical for developing effective strategies. O-GlcNAcylation, a post-translational modification that adds GlcNAc from the donor UDP-GlcNAc to serine and threonine residues of proteins, plays a crucial role in regulating protein function and cellular signaling, which are frequently dysregulated in cancer. Similarly, ubiquitination, which involves the attachment of ubiquitin to to proteins, is crucial for protein degradation, cell cycle control, and DNA repair. The interplay between O-GlcNAcylation and ubiquitination is associated with cancer progression and resistance to treatment. This review discusses recent discoveries regarding the roles of O-GlcNAcylation and ubiquitination in cancer resistance, their interactions, and potential mechanisms. It also explores how targeting these pathways may provide new opportunities to overcome cancer treatment resistance in cancer, offering fresh insights and directions for research and therapeutic development.

Targeting a chemo-induced adaptive signaling circuit confers therapeutic vulnerabilities in pancreatic cancer

Advanced pancreatic ductal adenocarcinomas (PDACs) respond poorly to all therapies, including the first-line treatment, chemotherapy, the latest immunotherapies, and KRAS-targeting therapies. Despite an enormous effort to improve therapeutic efficacy in late-stage PDAC patients, effective treatment modalities remain an unmet medical challenge. To change the status quo, we explored the key signaling networks underlying the universally poor response of PDAC to therapy. Here, we report a previously unknown chemo-induced symbiotic signaling circuit that adaptively confers chemoresistance in patients and mice with advanced PDAC. By integrating single-cell transcriptomic data from PDAC mouse models and clinical pathological information from PDAC patients, we identified Yap1 in cancer cells and Cox2 in stromal fibroblasts as two key nodes in this signaling circuit. Co-targeting Yap1 in cancer cells and Cox2 in stroma sensitized PDAC to Gemcitabine treatment and dramatically prolonged survival of mice bearing late-stage PDAC, whereas simultaneously inhibiting Yap1 and Cox2 only in cancer cells was ineffective. Mechanistically, chemotherapy triggers non-canonical Yap1 activation by nemo-like kinase in 14-3-3ζ-overexpressing PDAC cells and increases secretion of CXCL2/5, which bind to CXCR2 on fibroblasts to induce Cox2 and PGE2 expression, which reciprocally facilitate PDAC cell survival. Finally, analyses of PDAC patient data revealed that patients who received Statins, which inhibit Yap1 signaling, and Cox2 inhibitors (including Aspirin) while receiving Gemcitabine displayed markedly prolonged survival compared to others. The robust anti-tumor efficacy of Statins and Aspirin, which co-target the chemo-induced adaptive circuit in the tumor cells and stroma, signifies a unique therapeutic strategy for PDAC.

Human Satellite 3 DNA encodes megabase-scale transcription factor binding platforms

Eukaryotic genomes are frequently littered with large arrays of tandem repeats, called satellite DNA, which underlie the constitutive heterochromatin often found around centromeric regions. While some satellite DNA types have well-established roles in centromere biology, other abundant satellite DNAs have poorly characterized functions. For example, Human Satellite 3 (HSat3), which makes up roughly 2% of the human genome, forms enormous arrays up to tens of megabases, but these arrays play no known roles in centromere function and were almost fully excluded from genome assemblies until recently. As a result, these massive genomic regions have remained relatively understudied, and the potential functional roles of HSat3 have remained largely unknown. To address this, we performed a systematic screen for novel HSat3 binding factors. Our work revealed HSat3 arrays contain high densities of transcription factor (TF) motifs that are bound by factors related to multiple, highly conserved signaling pathways. Unexpectedly, the most enriched TFs in HSat3 belong to the Hippo pathway transcription effector family TEAD. We found that TEAD recruits the co-activator YAP to HSat3 regions in a cell-state specific manner. Using RNA polymerase-I reporter assays, targeted repression of HSat3, inducible degradation of YAP, and super-resolution microscopy, we show that HSat3 arrays can localize YAP/TEAD inside the nucleolus, where YAP regulates RNA Polymerase-I activity. Beyond revealing a direct relationship between the Hippo pathway and ribosomal DNA regulation, this work demonstrates that satellite DNA can encode multiple transcription factor binding motifs, defining a new role for these enormous genomic elements.

Advancements of anticancer agents by targeting the Hippo signalling pathway: biological activity, selectivity, docking analysis, and structure-activity relationship

The Hippo signalling pathway is prominent and governs cell proliferation and stem cell activity, acting as a growth regulator and tumour suppressor. Defects in Hippo signalling and hyperactivation of its downstream effector's Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) play roles in cancer development, implying that pharmacological inhibition of YAP and TAZ activity could be an effective cancer treatment strategy. Conversely, YAP and TAZ can also have beneficial effects in promoting tissue repair and regeneration following damage, therefore their activation may be therapeutically effective in certain instances. Recently, a complex network of intracellular and extracellular signalling mechanisms that affect YAP and TAZ activity has been uncovered. The YAP/TAZ-TEAD interaction leads to tumour development and the protein structure of YAP/TAZ-TEAD includes three interfaces and one hydrophobic pocket. There are clinical and preclinical trial drugs available to inhibit the hippo signalling pathway, but these drugs have moderate to severe side effects, so researchers are in search of novel, potent, and selective hippo signalling pathway inhibitors. In this review, we have discussed the hippo pathway in detail, including its structure, activation, and role in cancer. We have also provided the various inhibitors under clinical and preclinical trials, and advancement of small molecules their detailed docking analysis, structure-activity relationship, and biological activity. We anticipate that the current study will be a helpful resource for researchers.

Biocompatibility characterisation of CMOS-based Lab-on-Chip electrochemical sensors for in vitro cancer cell culture applications

Lab-on-Chip electrochemical sensors, such as Ion-Sensitive Field-Effect Transistors (ISFETs), are being developed for use in point-of-care diagnostics, such as pH detection of tumour microenvironments, due to their integration with standard Complementary Metal Oxide Semiconductor (CMOS) technology. With this approach, the passivation of the CMOS process is used as a sensing layer to minimise post-processing, and Silicon Nitride (Si3N4) is the most common material at the microchip surface. ISFETs have the potential to be used for cell-based assays however, there is a poor understanding of the biocompatibility of microchip surfaces. Here, we quantitatively evaluated cell adhesion, morphogenesis, proliferation and mechano-responsiveness of both normal and cancer cells cultured on a Si3N4, sensor surface. We demonstrate that both normal and cancer cell adhesion decreased on Si3N4. Activation of the mechano-responsive transcription regulators, YAP/TAZ, are significantly decreased in cancer cells on Si3N4 in comparison to standard cell culture plastic, whilst proliferation marker, Ki67, expression markedly increased. Non-tumorigenic cells on chip showed less sensitivity to culture on Si3N4 than cancer cells. Treatment with extracellular matrix components increased cell adhesion in normal and cancer cell cultures, surpassing the adhesiveness of plastic alone. Moreover, poly-l-ornithine and laminin treatment restored YAP/TAZ levels in both non-tumorigenic and cancer cells to levels comparable to those observed on plastic. Thus, engineering the electrochemical sensor surface with treatments will provide a more physiologically relevant environment for future cell-based assay development on chip.

GL-V9 Promotes Autophagy-Mediated YAP1 Degradation and Activates Mitochondrial Apoptosis in PDAC Cells

Background: Pancreatic ductal adenocarcinoma (PDAC) is among the most aggressive forms of pancreatic cancer with a poor prognosis. YAP1 expression is markedly elevated in PDAC, but how it works is not clear. GL-V9, a derivative of the natural compound wogonin, effectively fights a variety of tumors; however, its effect on PDAC has not yet been studied. Methods: TCGA database analysis, Western blots, immunofluorescence, and real-time PCR were used to evaluate GL-V9's effect on YAP1 expression and mRNA levels. Immunofluorescence was used to examine the co-location of YAP1 with LAMP2 and p62. Co-immunoprecipitation was used to assess the binding of YAP1 to ubiquitin, p62, and TEAD1. A PDAC graft tumor model was used to test GL-V9's pharmacological effects. Western blots and immunohistochemistry were used to measure apoptosis- and autophagy-related protein expression. Results: GL-V9 effectively promoted the degradation of YAP1, reduced YAP1 nuclear localization, and induced mitochondrial apoptosis in PDAC cells. YAP1 overexpression led to the upregulation of Bcl-2 and attenuated the caspase cascade induced by GL-V9. Furthermore, we demonstrated that GL-V9 induced autophagosome-lysosome fusion via the AKT/mTOR/TFEB pathway, leading to mitochondrial apoptosis in PDAC cells. In vivo studies also confirmed that GL-V9 exerts anti-tumor effects by suppressing YAP1 expression, while also activating autophagy and inducing mitochondrial apoptosis in BXPC-3-bearing BALB/c nude mice. Conclusions: Our findings underscore the importance of autophagy-mediated YAP1 degradation in PDAC, providing a novel molecular rationale (GL-V9) as a promising treatment for this disease.

Notch-Driven Cholangiocarcinogenesis Involves the Hippo Pathway Effector TAZ via METTL3-m6A-YTHDF1

BACKGROUND & AIMS

Notch and TAZ are implicated in cholangiocarcinogenesis, but whether and how these oncogenic molecules interact remain unknown.

METHODS

The development of cholangiocarcinoma (CCA) was induced by hydrodynamic tail vein injection of oncogenes (Notch1 intracellular domain [NICD]/AKT) to the FVB/NJ mice. CCA xenograft was developed by inoculation of human CCA cells into the livers of SCID mice. Tissues and cells were analyzed using quantitative reverse transcription polymerase chain reaction, Western blotting analyses, immunohistochemistry, chromatin immunoprecipitation-quantitative polymerase chain reaction and WST-1 cell proliferation assay.

RESULTS

Our experimental findings show that TAZ is indispensable in NICD-driven cholangiocarcinogenesis. Notch activation induces the expression of methyltransferase like-3 (METTL3), which catalyzes N6-methyladenosine modification of TAZ mRNA and that this mechanism plays a central role in the crosstalk between Notch and TAZ in CCA cells. Mechanistically, Notch regulates the expression of METTL3 through the binding of NICD to its downstream transcription factor CSL in the promoter region of METTL3. METTL3 in turn mediates N6-methyladenosine modification of TAZ mRNA, which is recognized by the m6A reader YTHDF1 to enhance TAZ protein translation. We observed that inhibition of Notch signaling decreased the protein levels of both MELLT3 and TAZ. Depletion of METTL3 by short hairpin RNAs or by the next generation GapmeR antisense oligonucleotides decreased the level of TAZ protein and inhibited the growth of human CCA cells in vitro and in mice.

CONCLUSIONS

This study describes a novel Notch-METTL3-TAZ signaling cascade, which is important in CCA development and progression. Our experimental results provide new insight into how the Notch pathway cooperates with TAZ signaling in CCA, and the findings may have important therapeutic implications.

Direct Inhibition of the YAP : TEAD Interaction: An Unprecedented Drug Discovery Challenge

The Hippo pathway, which is key in organ morphogenesis, is frequently deregulated in cancer. The TEAD (TEA domain family member) transcription factors are the most distal elements of this pathway, and their activity is regulated by proteins such as YAP (Yes-associated protein). The identification of inhibitors of the YAP : TEAD interaction is one approach to develop novel anticancer drugs: the first clinical candidate (IAG933) preventing the association between these two proteins by direct competition has just been reported. The discovery of this molecule was particularly challenging because the interface between these two proteins is large (~3500 Å2 buried in complex formation) and made up of distinct contact areas. The most critical of these involves an omega-loop (Ω-loop), a secondary structure element rarely found in protein-protein interactions. This review summarizes how the knowledge gained from structure-function studies of the interaction between the Ω-loop of YAP and TEAD was used to devise the strategy to identify potent low-molecular weight compounds that show a pronounced anti-tumor effect.

A highly sensitive reporter system to monitor endogenous YAP1/TAZ activity and its application in various human cells

The activation of yes-associated protein 1 (YAP1) and transcriptional co-activator with PDZ-binding motif (TAZ) has been implicated in both regeneration and tumorigenesis, thus representing a double-edged sword in tissue homeostasis. However, how the activity of YAP1/TAZ is regulated or what leads to its dysregulation in these processes remains unknown. To explore the upstream stimuli modulating the cellular activity of YAP1/TAZ, we developed a highly sensitive YAP1/TAZ/TEAD-responsive DNA element (YRE) and incorporated it into a lentivirus-based reporter cell system to allow for sensitive and specific monitoring of the endogenous activity of YAP1/TAZ in terms of luciferase activity in vitro and Venus fluorescence in vivo. Furthermore, by replacing YRE with TCF- and NF-κB-binding DNA elements, we demonstrated the applicability of this reporter system to other pathways such as Wnt/β-catenin/TCF- and IL-1β/NF-κB-mediated signaling, respectively. The practicality of this system was evaluated by performing cell-based reporter screening of a chemical compound library consisting of 364 known inhibitors, using reporter-introduced cells capable of quantifying YAP1/TAZ- and β-catenin-mediated transcription activities, which led to the identification of multiple inhibitors, including previously known as well as novel modulators of these signaling pathways. We further confirmed that novel YAP1/TAZ modulators, such as potassium ionophores, Janus kinase inhibitors, platelet-derived growth factor receptor inhibitors, and genotoxic stress inducers, alter the protein level or phosphorylation of endogenous YAP1/TAZ and the expression of their target genes. Thus, this reporter system provides a powerful tool to monitor endogenous signaling activities of interest (even in living cells) and search for modulators in various cellular contexts.

Disrupting YAP1-mediated glutamine metabolism induces synthetic lethality alongside ODC1 inhibition in osteosarcoma

PURPOSE

Osteosarcoma, a highly malignant primary bone tumor primarily affecting adolescents, frequently develops resistance to initial chemotherapy, leading to metastasis and limited treatment options. Our study aims to uncover novel therapeutic targets for metastatic and recurrent osteosarcoma.

METHODS

In this study, we proved the potential of modulating the YAP1-regulated glutamine metabolic pathway to augment the response of OS to DFMO. We initially employed single-cell transcriptomic data to gauge the activation level of polyamine metabolism in MTAP-deleted OS patients. This was further substantiated by transcriptome sequencing data from recurrent and non-recurrent patient tissues, confirming the activation of polyamine metabolism in progressive OS. Through high-throughput drug screening, we pinpointed CIL56, a YAP1 inhibitor, as a promising candidate for a combined therapeutic strategy with DFMO. In vivo, we utilized PDX and CDX models to validate the therapeutic efficacy of this drug combination. In vitro, we conducted western blot analysis, qPCR analysis, immunofluorescence staining, and PuMA experiments to monitor alterations in molecular expression, distribution, and tumor metastasis capability. We employed CCK-8 and colony formation assays to assess the proliferative capacity of cells in the experimental group. We used flow cytometry and reactive oxygen probes to observe changes in ROS and glutamine metabolism within the cells. Finally, we applied RNA-seq in tandem with metabolomics to identify metabolic alterations in OS cells treated with a DFMO and CIL56 combination. This enabled us to intervene and validate the role of the YAP1-mediated glutamine metabolic pathway in DFMO resistance.

RESULTS

Through single-cell RNA-seq data analysis, we pinpointed a subset of late-stage OS cells with significantly upregulated polyamine metabolism. This upregulation was further substantiated by transcriptomic profiling of recurrent and non-recurrent OS tissues. High-throughput drug screening revealed a promising combination strategy involving DFMO and CIL56. DFMO treatment curbs the phosphorylation of YAP1 protein in OS cells, promoting nuclear entry and initiating the YAP1-mediated glutamine metabolic pathway. This reduces intracellular ROS levels, countering DFMO's anticancer effect. The therapeutic efficacy of DFMO can be amplified both in vivo and in vitro by combining it with the YAP1 inhibitor CIL56 or the glutaminase inhibitor CB-839. This underscores the significant potential of targeting the YAP1-mediated glutamine metabolic pathway to enhance efficacy of DFMO.

CONCLUSION

Our findings elucidate YAP1-mediated glutamine metabolism as a crucial bypass mechanism against DFMO, following the inhibition of polyamine metabolism. Our study provides valuable insights into the potential role of DFMO in an "One-two Punch" therapy of metastatic and recurrent osteosarcoma.

Liquid-liquid phase separation: a new perspective on respiratory diseases

Liquid-liquid phase separation (LLPS) is integral to various biological processes, facilitating signal transduction by creating a condensed, membrane-less environment that plays crucial roles in diverse physiological and pathological processes. Recent evidence has underscored the significance of LLPS in human health and disease. However, its implications in respiratory diseases remain poorly understood. This review explores current insights into the mechanisms and biological roles of LLPS, focusing particularly on its relevance to respiratory diseases, aiming to deepen our understanding and propose a new paradigm for studying phase separation in this context.

The actin-binding protein drebrin disrupts NF2-LATS kinases complex assembly to facilitate liver tumorigenesis

BACKGROUND AND AIMS

The Hippo signaling has emerged as a crucial regulator of tissue homeostasis, regeneration, and tumorigenesis, representing a promising therapeutic target. Neurofibromin 2 (NF2), a component of Hippo signaling, is directly linked to human cancers but has been overlooked as a target for cancer therapy.

APPROACH AND RESULTS

Through a high-content RNA interference genome-wide screen, the actin-binding protein Drebrin (DBN1) has been identified as a novel modulator of YAP localization. Further investigations have revealed that DBN1 directly interacts with NF2, disrupting the activation of large tumor suppressor kinases (LATS1/2) by competing with LATS kinases for NF2 binding. Consequently, DBN1 knockout considerably promotes YAP nuclear exclusion and repression of target gene expression, thereby preventing cell proliferation and liver tumorigenesis. We identified three lysine residues (K238, K248, and K252) essential for DBN1-NF2 interaction and developed a mutant DBN1 (DBN1-3Kmut) that is defective in NF2 binding and incompetent to trigger NF2-dependent YAP activation and tumorigenesis both in vitro and in vivo. Furthermore, BTP2, a DBN1 inhibitor, successfully restored NF2-LATS kinase binding and elicited potent antitumor activity. The combination of sorafenib and BTP2 exerted synergistic inhibitory effects against HCC.

CONCLUSIONS

Our study identifies a novel DBN1-NF2-LATS axis, and pharmacological inhibition of DBN1 represents a promising alternative intervention targeting the Hippo pathway in cancer treatment.

Ku70 Binding to YAP Alters PARP1 Ubiquitination to Regulate Genome Stability and Tumorigenesis

Yes-associated protein (YAP) is a central player in cancer development, with functions extending beyond its recognized role in cell growth regulation. Recent work has identified a link between YAP/transcriptional coactivator with PDZ-binding motif (TAZ) and the DNA damage response. Here, we investigated the mechanistic underpinnings of the cross-talk between DNA damage repair and YAP activity. Ku70, a key component of the nonhomologous end joining pathway to repair DNA damage, engaged in a dynamic competition with TEAD4 for binding to YAP, limiting the transcriptional activity of YAP. Depletion of Ku70 enhanced interaction between YAP and TEAD4 and boosted YAP transcriptional capacity. Consequently, Ku70 loss enhanced tumorigenesis in colon cancer and hepatocellular carcinoma (HCC) in vivo. YAP impeded DNA damage repair and elevated genome instability by inducing PARP1 degradation through the SMURF2-mediated ubiquitin-proteasome pathway. Analysis of samples from patients with HCC substantiated the link between Ku70 expression, YAP activity, PARP1 levels, and genome instability. In conclusion, this research provides insight into the mechanistic interactions between YAP and key regulators of DNA damage repair, highlighting the role of a Ku70-YAP-PARP1 axis in preserving genome stability. Significance: Increased yes-associated protein transcriptional activity stimulated by loss of Ku70 induces PARP1 degradation by upregulating SMURF2 to inhibit DNA damage, driving genome instability and tumorigenesis.

Synergistic effects of combined BET and FAK inhibition against Vestibular Schwannomas in NF2-related Schwannomatosis

Neurofibromatosis type 2 (NF2) is a rare disorder that causes vestibular schwannomas (VS), meningiomas and ependymomas. To date, there is no FDA approved drug-based treatment for NF2. We have previously identified that BET inhibition can selectively reduce growth of the NF2-null schwannoma and Schwann cells in vitro and tumorigenesis in vivo and, separately, reported that inhibition of Focal Adhesion Kinase 1 (FAK1) via crizotinib has antiproliferative effects in NF2-null Schwann cells. The current study was aimed at determining whether combined BET and FAK inhibition can synergize and to identify the mechanisms of action. A panel of normal and NF2-null Schwann and schwannoma cell lines were used to characterize the effects of combined BET and FAK inhibition in vitro and in vivo using pharmacological and genetic approaches. The mechanism of action was explored by chromatin immunoprecipitation, ChIP-PCR, western blotting, and functional approaches. We find that combined BET and FAK inhibition are synergistic and inhibit the proliferation of NF2-null schwannoma and Schwann cell lines in vitro and in vivo, by arresting cells in the G1/S and G2/M phases of the cell cycle. Further, we identify the mechanism of action through the downregulation of FAK1 transcription by BET inhibition, which potentiates inhibition of FAK by 100-fold. Our findings suggest that combined targeting of BET and FAK1 may offer a potential therapeutic option for the treatment of NF2-related schwannomas.

Bioactive sphingolipids as emerging targets for signal transduction in cancer development

Sphingolipids, crucial components of cellular membranes, play a vital role in maintaining cellular structure and signaling integrity. Disruptions in sphingolipid metabolism are increasingly implicated in cancer development. Key bioactive sphingolipids, such as ceramides, sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glycosphingolipids, profoundly impact tumor biology. They influence the behavior of tumor cells, stromal cells, and immune cells, affecting tumor aggressiveness, angiogenesis, immune modulation, and extracellular matrix remodeling. Furthermore, abnormal expression of sphingolipids and their metabolizing enzymes modulates the secretion of tumor-derived extracellular vesicles (TDEs), which are key players in creating an immunosuppressive tumor microenvironment, remodeling the extracellular matrix, and facilitating oncogenic signaling within in situ tumors and distant pre-metastatic niches (PMNs). Understanding the role of sphingolipids in the biogenesis of tumor-derived extracellular vesicles (TDEs) and their bioactive contents can pave the way for new biomarkers in cancer diagnosis and prognosis, ultimately enhancing comprehensive tumor treatment strategies.

Regulation of YAP translocation by myeloid Pten deficiency alleviates acute lung injury via inhibition of oxidative stress and inflammation

BACKGROUND

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is intricately involved in modulating the inflammatory response in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Nevertheless, the myeloid PTEN governing Hippo-YAP pathway mediated oxidative stress and inflammation in lipopolysaccharide (LPS)-induced ALI remains to be elucidate.

METHODS

The floxed Pten (PtenFL/FL) and myeloid-specific Pten knockout (PtenM-KO) mice were intratracheal instill LPS (5 mg/kg) to establish ALI, then Yap siRNA mix with the mannose-conjugated polymers was used to knockdown endogenous macrophage YAP in some PtenM-KO mice before LPS challenged. The bone marrow-derived macrophages (BMMs) from PtenFL/FL and PtenM-KO mice were obtained, and BMMs were transfected with CRISPR/Cas9-mediated glycogen synthase kinase 3 Beta (GSK3β) knockout (KO) or Yes-associated protein (YAP) KO vector subjected to LPS (100 ng/ml) challenged or then cocultured with MLE12 cells.

RESULTS

Here, our findings demonstrate that myeloid-specific PTEN deficiency exerts a protective against LPS-induced oxidative stress and inflammation dysregulated in ALI model. Moreover, ablation of the PTEN-YAP axis in macrophages results in reduced nuclear factor-E2-related factor-2 (NRF2) expression, a decrease in antioxidant gene expression, augmented levels of free radicals, lipid and protein peroxidation, heightened generation of pro-inflammatory cytokines, ultimately leading to increased apoptosis in MLE12 cells. Mechanistically, it is noteworthy that the deletion of myeloid PTEN promotes YAP translocation and regulates NRF2 expression, alleviating LPS-induced ALI via the inhibition of GSK3β and MST1 binding.

CONCLUSIONS

Our study underscores the crucial role of the myeloid PTEN-YAP-NRF2 axis in governing oxidative stress and inflammation dysregulated in ALI, indicating its potential as a therapeutic target for ALI.

Retinoic acid-induced protein 14 links mechanical forces to Hippo signaling

Cells sense and respond to various mechanical forces from the extracellular matrix primarily by modulating the actin cytoskeleton. Mechanical forces can be translated into biochemical signals in a process called mechanotransduction. Yes-associated protein (YAP) is an effector of Hippo signaling and a mediator of mechanotransduction, but how mechanical forces regulate Hippo signaling is still an open question. We propose that retinoic acid-induced protein 14 (RAI14) responds to mechanical forces and regulates Hippo signaling. RAI14 positively regulates the activity of YAP. RAI14 interacts with NF2, a key component of the Hippo pathway, and the interaction occurs on filamentous actin. When mechanical forces are kept low in cells, NF2 dissociates from RAI14 and filamentous actin, resulting in increased interactions with LATS1 and activation of the Hippo pathway. Clinical data show that tissue stiffness and expression of RAI14 and YAP are upregulated in tumor tissues and that RAI14 is strongly associated with adverse outcome in patients with gastric cancer. Our data suggest that RAI14 links mechanotransduction with Hippo signaling and mediates Hippo-related biological functions such as cancer progression.

PTPN14 aggravates neointimal hyperplasia via boosting PDGFRβ signaling in smooth muscle cells

Smooth muscle cell (SMC) phenotypic modulation, primarily driven by PDGFRβ signaling, is implicated in occlusive cardiovascular diseases. However, the promotive and restrictive regulation mechanism of PDGFRβ and the role of protein tyrosine phosphatase non-receptor type 14 (PTPN14) in neointimal hyperplasia remain unclear. Our study observes a marked upregulation of PTPN14 in SMCs during neointimal hyperplasia. PTPN14 overexpression exacerbates neointimal hyperplasia in a phosphatase activity-dependent manner, while SMC-specific deficiency of PTPN14 mitigates this process in mice. RNA-seq indicates that PTPN14 deficiency inhibits PDGFRβ signaling-induced SMC phenotypic modulation. Moreover, PTPN14 interacts with intracellular region of PDGFRβ and mediates its dephosphorylation on Y692 site. Phosphorylation of PDGFRβY692 negatively regulates PDGFRβ signaling activation. The levels of both PTPN14 and phospho-PDGFRβY692 are correlated with the degree of stenosis in human coronary arteries. Our findings suggest that PTPN14 serves as a critical modulator of SMCs, promoting neointimal hyperplasia. PDGFRβY692, dephosphorylated by PTPN14, acts as a self-inhibitory site for controlling PDGFRβ activation.

Targeting of mutant-p53 and MYC as a novel strategy to inhibit oncogenic SPAG5 activity in triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive disease which currently has no effective therapeutic targets and prominent biomarkers. The Sperm Associated antigen 5 (SPAG5) is a mitotic spindle associated protein with oncogenic function in several human cancers. In TNBC, increased SPAG5 expression has been associated with tumor progression, chemoresistance, relapse, and poor clinical outcome. Here we show that high SPAG5 expression in TNBC is regulated by coordinated activity of YAP, mutant p53 and MYC. Depletion of YAP or mutant p53 proteins reduced SPAG5 expression and the recruitment of MYC onto SPAG5 promoter. Targeting of MYC also reduced SPAG5 expression and concomitantly tumorigenicity of TNBC cells. These effects of MYC targeting were synergized with cytotoxic chemotherapy and markedly reduced TNBC oncogenicity in SPAG5-expression dependent manner. These results suggest that mutant p53-MYC-SPAG5 expression can be considered as bona fide predictors of patient's outcome, and reliable biomarkers for effective anticancer therapies.

Insights gained from computational modeling of YAP/TAZ signaling for cellular mechanotransduction

YAP/TAZ signaling pathway is regulated by a multiplicity of feedback loops, crosstalk with other pathways, and both mechanical and biochemical stimuli. Computational modeling serves as a powerful tool to unravel how these different factors can regulate YAP/TAZ, emphasizing biophysical modeling as an indispensable tool for deciphering mechanotransduction and its regulation of cell fate. We provide a critical review of the current state-of-the-art of computational models focused on YAP/TAZ signaling.

Hippo signaling modulation and its biological implications in urological malignancies

Although cancer diagnosis and treatment have rapidly advanced in recent decades, urological malignancies, which have high morbidity and mortality rates, are among the most difficult diseases to treat. The Hippo signaling is an evolutionarily conserved pathway in organ size control and tissue homeostasis maintenance. Its downstream effectors, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), are key modulators of numerous physiological and pathological processes. Recent work clearly indicates that Hippo signaling is frequently altered in human urological malignancies. In this review, we discuss the disparate viewpoints on the upstream regulators of YAP/TAZ and their downstream targets and systematically summarize the biological implications. More importantly, we highlight the molecular mechanisms involved in Hippo-YAP signaling to improve our understanding of its role in every stage of prostate cancer, bladder cancer and kidney cancer progression. A better understanding of the biological outcomes of YAP/TAZ modulation will contribute to the establishment of future therapeutic approaches.

Regulation of Hippo-YAP signaling axis by Isoalantolactone suppresses tumor progression in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a devastating malignancy characterized by aggressive tumor growth and limited treatment options. Dysregulation of the Hippo signaling pathway and its downstream effector, Yes-associated protein (YAP), has been implicated in CCA development and progression. In this study, we investigated the effects of Isoalantolactone (IALT) on CCA cells to elucidate its effect on YAP activity and its potential clinical significance. Our findings demonstrate that IALT exerts cytotoxic effects, induces apoptosis, and modulates YAP signaling in SNU478 cells. We further confirmed the involvement of the canonical Hippo pathway by generating LATS1/LATS2 knockout cells, highlighting the dependence of IALT-mediated apoptosis and YAP phosphorylation on the Hippo-LATS signaling axis. In addition, IALT suppressed cell growth and migration, partially dependent on YAP-TEAD activity. These results provide insights into the therapeutic potential of targeting YAP in CCA and provide a rationale for developing of YAP-targeted therapies for this challenging malignancy.

The Prognostic Biomarker RAB7A Promotes Growth and Metastasis of Liver Cancer Cells by Regulating Glycolysis and YAP1 Activation

Activating transcription factor 6 (ATF6) and its downstream genes are involved in progression of hepatocellular carcinoma (HCC). Herein, we demonstrated that sulfhydration of Ras-related protein Rab-7a (RAB7A) was regulated by ATF6. High expression of RAB7A indicated poor prognosis of HCC patients. RAB7A overexpression contributed to proliferation, colony formation, migration, and invasion of HepG2 and Hep3B cells. Furthermore, we found that RAB7A enhanced aerobic glycolysis in HepG2 cells, indicating a higher degree of tumor malignancy. Mechanistically, RAB7A suppressed Yes-associated protein 1 (YAP1) binding to 14-3-3 and conduced to YAP1 nuclear translocation and activation, promoting its downstream gene expression, thereby promoting growth and metastasis of liver cancer cells. In addition, knocking down RAB7A attenuated the progression of orthotopic liver tumors in mice. These findings illustrate the important role of RAB7A in regulating HCC progression. Thus, RAB7A may be a potential innovative target for HCC treatment.

Stearoylation cycle regulates the cell surface distribution of the PCP protein Vangl2

Defects in planar cell polarity (PCP) have been implicated in diverse human pathologies. Vangl2 is one of the core PCP components crucial for PCP signaling. Dysregulation of Vangl2 has been associated with severe neural tube defects and cancers. However, how Vangl2 protein is regulated at the posttranslational level has not been well understood. Using chemical reporters of fatty acylation and biochemical validation, here we present that Vangl2 subcellular localization is regulated by a reversible S-stearoylation cycle. The dynamic process is mainly regulated by acyltransferase ZDHHC9 and deacylase acyl-protein thioesterase 1 (APT1). The stearoylation-deficient mutant of Vangl2 shows decreased plasma membrane localization, resulting in disruption of PCP establishment during cell migration. Genetically or pharmacologically inhibiting ZDHHC9 phenocopies the effects of the stearoylation loss of Vangl2. In addition, loss of Vangl2 stearoylation enhances the activation of oncogenic Yes-associated protein 1 (YAP), serine-threonine kinase AKT, and extracellular signal-regulated protein kinase (ERK) signaling and promotes breast cancer cell growth and HRas G12V mutant (HRasV12)-induced oncogenic transformation. Our results reveal a regulation mechanism of Vangl2, and provide mechanistic insight into how fatty acid metabolism and protein fatty acylation regulate PCP signaling and tumorigenesis by core PCP protein lipidation.

Targeted Treatment against Cancer Stem Cells in Colorectal Cancer

The cancer stem cell (SC) theory proposes that a population of SCs serves as the driving force behind fundamental tumor processes, including metastasis, recurrence, and resistance to therapy. The standard of care for patients with stage III and high-risk stage II colorectal cancer (CRC) includes surgery and adjuvant chemotherapy. Fluoropyrimidines and their combination with oxaliplatin increased the cure rates, being able to eradicate the occult metastatic SC in a fraction of patients. The treatment for unresectable metastatic CRC is based on chemotherapy, antibodies to VEGF and EGFR, and tyrosine-kinase inhibitors. Immunotherapy is used in MSI-H tumors. Currently used drugs target dividing cells and, while often effective at debulking tumor mass, these agents have largely failed to cure metastatic disease. SCs are generated either due to genetic and epigenetic alterations in stem/progenitor cells or to the dedifferentiation of somatic cells where diverse signaling pathways such as Wnt/β-catenin, Hedgehog, Notch, TGF-β/SMAD, PI3K/Akt/mTOR, NF-κB, JAK/STAT, DNA damage response, and Hippo-YAP play a key role. Anti-neoplastic treatments could be improved by elimination of SCs, becoming an attractive target for the design of novel agents. Here, we present a review of clinical trials assessing the efficacy of targeted treatment focusing on these pathways in CRC.

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.

STC1 competitively binding βPIX enhances melanoma progression via YAP nuclear translocation and M2 macrophage recruitment through the YAP/CCL2/VEGFA/AKT feedback loop

This study investigates the role of Stanniocalcin-1 (STC1) in melanoma progression, with a focus on its impact on metastasis, angiogenesis, and immune evasion. Systematic bioinformatics analysis revealed the potential influence of STC1 dysregulation on prognosis, immune cell infiltration, response to immune therapy, and cellular functions. In vitro assays were conducted to assess the proliferation, invasion, migration, and angiogenesis capabilities of A375 cells. In vivo experiments utilizing C57BL/6 J mice established a lung metastasis model using B16-F10 cells to evaluate macrophage infiltration and M2 polarization. A Transwell co-culture system was employed to explore the crosstalk between melanoma and macrophages. Molecular interactions among STC1, YAP, βPIX, and CCL2 are investigated using mass spectrometry, Co-Immunoprecipitation, Dual-Luciferase Reporter Assay, and Chromatin Immunoprecipitation experiments. STC1 was found to enhance lung metastasis by promoting the recruitment and polarization of M2 macrophages, thereby fostering an immunosuppressive microenvironment. Mechanistically, STC1 competes with YAP for binding to βPIX within the KER domain in melanoma cells, leading to YAP activation and subsequent CCL2 upregulation. CCL2-induced M2 macrophages secrete VEGFA, which enhances tumor vascularization and increases STC1 expression via the AKT signaling pathway in melanoma cells, establishing a pro-metastatic feedback loop. Notably, STC1-induced YAP activation increases PD-L1 expression, promoting immune evasion. Silencing STC1 enhances the efficacy of PD-1 immune checkpoint therapy in mice. This research elucidates STC1's role in melanoma metastasis and its complex interactions with tumor-associated macrophages, proposing STC1 as a potential therapeutic target for countering melanoma metastasis and augmenting the efficacy of PD-1 immunotherapy.

TRAF6 enhances PD-L1 expression through YAP1-TFCP2 signaling in melanoma

Immunotherapy represented by programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) monoclonal antibodies has led tumor treatment into a new era. However, the low overall response rate and high incidence of drug resistance largely damage the clinical benefits of existing immune checkpoint therapies. Recent studies correlate the response to PD-1/PD-L1 blockade with PD-L1 expression levels in tumor cells. Hence, identifying molecular targets and pathways controlling PD-L1 protein expression and stability in tumor cells is a major priority. In this study, we performed a Stress and Proteostasis CRISPR interference screening to identify PD-L1 positive modulators. Here, we identified TRAF6 as a critical regulator of PD-L1 in melanoma cells. As a non-conventional E3 ubiquitin ligase, TRAF6 is inclined to catalyze the synthesis and linkage of lysine-63 (K63) ubiquitin which is related to the stabilization of substrate proteins. Our results showed that suppression of TRAF6 expression down-regulates PD-L1 expression on the membrane surface of melanoma cells. We then used in vitro and in vivo assays to investigate the biological function and mechanism of TRAF6 and its downstream YAP1/TFCP2 signaling in melanoma. TRAF6 stabilizes YAP1 by K63 poly-ubiquitination modification, subsequently promoting the formation of YAP1/TFCP2 transcriptional complex and PD-L1 transcription. Inhibition of TRAF6 by Bortezomib enhanced cytolytic activity of CD8+ T cells by reduction of endogenous PD-L1. Notably, Bortezomib enhances anti-tumor immunity to an extent comparable to anti-PD-1 therapies with no obvious toxicity. Our findings reveal the potential of inhibiting TRAF6 to stimulate internal anti-tumor immunological effect for TRAF6-PD-L1 overexpressing cancers.

Cordycepin alleviates hepatic fibrosis in association with the inhibition of glutaminolysis to promote hepatic stellate cell senescence

Cordycepin (CRD) is an active component derived from Cordyceps militaris, which possesses multiple biological activities and uses in liver disease. However, whether CRD improves liver fibrosis by regulating hepatic stellate cell (HSC) activation has remained unknown. The study aims further to clarify the activities of CRD on liver fibrosis and elucidate the possible mechanism. Our results demonstrated that CRD significantly relieved hepatocyte injury and inhibited HSC activation, alleviating hepatic fibrogenesis in the Diethyl 1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate (DDC)-induced mice model. In vitro, CRD exhibited dose-dependent repress effects on HSC proliferation, migration, and pro-fibrotic function in TGF-β1-activated LX-2 and JS-1 cells. The functional enrichment analysis of RNA-seq data indicated that the pathway through which CRD alleviates HSC activation involves cellular senescence and cell cycle-related pathways. Furthermore, it was observed that CRD accumulated the number of senescence-associated a-galactosidase positive cells and the levels of senescencemarker p21, and provoked S phasearrestof activated HSC. Remarkably, CRD treatment abolished TGF-β-induced yes-associated protein (YAP) nuclear translocation that acts upstream of glutaminolysis in activated HSC. On the whole, CRD significantly inhibited glutaminolysis of activated-HSC and induced cell senescence through the YAP signaling pathway, consequently alleviating liver fibrosis, which may be a valuable supplement for treating liver fibrosis.

VGLL2 and TEAD1 fusion proteins drive YAP/TAZ-independent transcription and tumorigenesis by engaging p300

Studies on Hippo pathway regulation of tumorigenesis largely center on YAP and TAZ, the transcriptional co-regulators of TEAD. Here, we present an oncogenic mechanism involving VGLL and TEAD fusions that is Hippo pathway-related but YAP/TAZ-independent. We characterize two recurrent fusions, VGLL2-NCOA2 and TEAD1-NCOA2, recently identified in spindle cell rhabdomyosarcoma. We demonstrate that, in contrast to VGLL2 and TEAD1, the fusion proteins are strong activators of TEAD-dependent transcription, and their function does not require YAP/TAZ. Furthermore, we identify that VGLL2 and TEAD1 fusions engage specific epigenetic regulation by recruiting histone acetyltransferase p300 to control TEAD-mediated transcriptional and epigenetic landscapes. We showed that small molecule p300 inhibition can suppress fusion proteins-induced oncogenic transformation both in vitro and in vivo. Overall, our study reveals a molecular basis for VGLL involvement in cancer and provides a framework for targeting tumors carrying VGLL, TEAD, or NCOA translocations.

Hippo pathway in non-small cell lung cancer: mechanisms, potential targets, and biomarkers

Lung cancer is the primary contributor to cancer-related deaths globally, and non-small cell lung cancer (NSCLC) constitutes around 85% of all lung cancer cases. Recently, the emergence of targeted therapy and immunotherapy revolutionized the treatment of NSCLC and greatly improved patients' survival. However, drug resistance is inevitable, and extensive research has demonstrated that the Hippo pathway plays a crucial role in the development of drug resistance in NSCLC. The Hippo pathway is a highly conserved signaling pathway that is essential for various biological processes, including organ development, maintenance of epithelial balance, tissue regeneration, wound healing, and immune regulation. This pathway exerts its effects through two key transcription factors, namely Yes-associated protein (YAP) and transcriptional co-activator PDZ-binding motif (TAZ). They regulate gene expression by interacting with the transcriptional-enhanced associate domain (TEAD) family. In recent years, this pathway has been extensively studied in NSCLC. The review summarizes a comprehensive overview of the involvement of this pathway in NSCLC, and discusses the mechanisms of drug resistance, potential targets, and biomarkers associated with this pathway in NSCLC.

Interplay of RAP2 GTPase and the cytoskeleton in Hippo pathway regulation

The Hippo signaling is instrumental in regulating organ size, regeneration, and carcinogenesis. The cytoskeleton emerges as a primary Hippo signaling modulator. Its structural alterations in response to environmental and intrinsic stimuli control Hippo signaling pathway activity. However, the precise mechanisms underlying the cytoskeleton regulation of Hippo signaling are not fully understood. RAP2 GTPase is known to mediate the mechanoresponses of Hippo signaling via activating the core Hippo kinases LATS1/2 through MAP4Ks and MST1/2. Here we show the pivotal role of the reciprocal regulation between RAP2 GTPase and the cytoskeleton in Hippo signaling. RAP2 deletion undermines the responses of the Hippo pathway to external cues tied to RhoA GTPase inhibition and actin cytoskeleton remodeling, such as energy stress and serum deprivation. Notably, RhoA inhibitors and actin disruptors fail to activate LATS1/2 effectively in RAP2-deficient cells. RNA sequencing highlighted differential regulation of both actin and microtubule networks by RAP2 gene deletion. Consistently, Taxol, a microtubule-stabilizing agent, was less effective in activating LATS1/2 and inhibiting cell growth in RAP2 and MAP4K4/6/7 knockout cells. In summary, our findings position RAP2 as a central integrator of cytoskeletal signals for Hippo signaling, which offers new avenues for understanding Hippo regulation and therapeutic interventions in Hippo-impaired cancers.

The roles of Hippo/YAP signaling pathway in physical therapy

Cellular behavior is regulated by mechanical signals within the cellular microenvironment. Additionally, changes of temperature, blood flow, and muscle contraction also affect cellular state and the development of diseases. In clinical practice, physical therapy techniques such as ultrasound, vibration, exercise, cold therapy, and hyperthermia are commonly employed to alleviate pain and treat diseases. However, the molecular mechanism about how these physiotherapy methods stimulate local tissues and control gene expression remains unknow. Fortunately, the discovery of YAP filled this gap, which has been reported has the ability to sense and convert a wide variety of mechanical signals into cell-specific programs for transcription, thereby offering a fresh perspective on the mechanisms by which physiotherapy treat different diseases. This review examines the involvement of Hippo/YAP signaling pathway in various diseases and its role in different physical therapy approaches on diseases. Furthermore, we explore the potential therapeutic implications of the Hippo/YAP signaling pathway and address the limitations and controversies surrounding its application in physiotherapy.

Cyr61 delivery promotes angiogenesis during bone fracture repair

Compromised vascular supply and insufficient neovascularization impede bone repair, increasing risk of non-union. Cyr61, Cysteine-rich angiogenic inducer of 61kD (also known as CCN1), is a matricellular growth factor that is regulated by mechanical cues during fracture repair. Here, we map the distribution of endogenous Cyr61 during bone repair and evaluate the effects of recombinant Cyr61 delivery on vascularized bone regeneration. In vitro, Cyr61 treatment did not alter chondrogenesis or osteogenic gene expression, but significantly enhanced angiogenesis. In a mouse femoral fracture model, Cyr61 delivery did not alter cartilage or bone formation, but accelerated neovascularization during fracture repair. Early initiation of ambulatory mechanical loading disrupted Cyr61-induced neovascularization. Together, these data indicate that Cyr61 delivery can enhance angiogenesis during bone repair, particularly for fractures with stable fixation, and may have therapeutic potential for fractures with limited blood vessel supply.

Asparaginyl Endopeptidase-Mediated Peptide Cyclization for Phage Display

We report here an enzymatic strategy for asparaginyl endopeptidase-mediated peptide cyclization. Incorporation of chloroacetyl groups into the recognition sequence of OaAEP1 enabled intramolecular cyclization with Cys residues. Combining this strategy and phage display, we identified nanomolar macrocyclic peptide ligands targeting TEAD4. One of the bicyclic peptides binds to TEAD4 with a KD value of 139 nM, 16 times lower than its linear analogue, demonstrating the utility of this platform in discovering high-affinity macrocyclic peptide ligands.

Upregulation of CYR61 by TGF-β and YAP signaling exerts a counter-suppression of hepatocellular carcinoma

Transforming growth factor-β (TGF-β) and Hippo signaling are two critical pathways engaged in cancer progression by regulating both oncogenes and tumor suppressors, yet how the two pathways coordinately exert their functions in the development of hepatocellular carcinoma (HCC) remains elusive. In this study, we firstly conducted an integrated analysis of public liver cancer databases and our experimental TGF-β target genes, identifying CYR61 as a pivotal candidate gene relating to HCC development. The expression of CYR61 is downregulated in clinical HCC tissues and cell lines than that in the normal counterparts. Evidence revealed that CYR61 is a direct target gene of TGF-β in liver cancer cells. In addition, TGF-β-stimulated Smad2/3 and the Hippo pathway downstream effectors YAP and TEAD4 can form a protein complex on the promoter of CYR61, thereby activating the promoter activity and stimulating CYR61 gene transcription in a collaborative manner. Functionally, depletion of CYR61 enhanced TGF-β- or YAP-mediated growth and migration of liver cancer cells. Consistently, ectopic expression of CYR61 was capable of impeding TGF-β- or YAP-induced malignant transformation of HCC cells in vitro and attenuating HCC xenograft growth in nude mice. Finally, transcriptomic analysis indicates that CYR61 can elicit an antitumor program in liver cancer cells. Together, these results add new evidence for the crosstalk between TGF-β and Hippo signaling and unveil an important tumor suppressor function of CYR61 in liver cancer.

Endothelial H2S-AMPK dysfunction upregulates the angiocrine factor PAI-1 and contributes to lung fibrosis

Dysfunction of the vascular angiocrine system is critically involved in regenerative defects and fibrosis of injured organs. Previous studies have identified various angiocrine factors and found that risk factors such as aging and metabolic disorders can disturb the vascular angiocrine system in fibrotic organs. One existing key gap is what sense the fibrotic risk to modulate the vascular angiocrine system in organ fibrosis. Here, using human and mouse data, we discovered that the metabolic pathway hydrogen sulfide (H2S)-AMP-activated protein kinase (AMPK) is a sensor of fibrotic stress and serves as a key mechanism upregulating the angiocrine factor plasminogen activator inhibitor-1 (PAI-1) in endothelial cells to participate in lung fibrosis. Activation of the metabolic sensor AMPK was inhibited in endothelial cells of fibrotic lungs, and AMPK inactivation was correlated with enriched fibrotic signature and reduced lung functions in humans. The inactivation of endothelial AMPK accelerated lung fibrosis in mice, while the activation of endothelial AMPK with metformin alleviated lung fibrosis. In fibrotic lungs, endothelial AMPK inactivation led to YAP activation and overexpression of the angiocrine factor PAI-1, which was positively correlated with the fibrotic signature in human fibrotic lungs and inhibition of PAI-1 with Tiplaxtinin mitigated lung fibrosis. Further study identified that the deficiency of the antioxidative gas metabolite H2S accounted for the inactivation of AMPK and activation of YAP-PAI-1 signaling in endothelial cells of fibrotic lungs. H2S deficiency was involved in human lung fibrosis and H2S supplement reversed mouse lung fibrosis in an endothelial AMPK-dependent manner. These findings provide new insight into the mechanism underlying the deregulation of the vascular angiocrine system in fibrotic organs.

The Hippo signaling pathway in development and regeneration

The Hippo signaling pathway is a central growth control mechanism in multicellular organisms. By integrating diverse mechanical, biochemical, and stress cues, the Hippo pathway orchestrates proliferation, survival, differentiation, and mechanics of cells, which in turn regulate organ development, homeostasis, and regeneration. A deep understanding of the regulation and function of the Hippo pathway therefore holds great promise for developing novel therapeutics in regenerative medicine. Here, we provide updates on the molecular organization of the mammalian Hippo signaling network, review the regulatory signals and functional outputs of the pathway, and discuss the roles of Hippo signaling in development and regeneration.