Targeting the Hippo Signaling Pathway for Tissue Regeneration and Cancer Therapy

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

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

Hippo Signaling at the Hallmarks of Cancer and Drug Resistance

Originally identified in Drosophila melanogaster in 1995, the Hippo signaling pathway plays a pivotal role in organ size control and tumor suppression by inhibiting proliferation and promoting apoptosis. Large tumor suppressors 1 and 2 (LATS1/2) directly phosphorylate the Yki orthologs YAP (yes-associated protein) and its paralog TAZ (also known as WW domain-containing transcription regulator 1 [WWTR1]), thereby inhibiting their nuclear localization and pairing with transcriptional coactivators TEAD1-4. Earnest efforts from many research laboratories have established the role of mis-regulated Hippo signaling in tumorigenesis, epithelial mesenchymal transition (EMT), oncogenic stemness, and, more recently, development of drug resistances. Hippo signaling components at the heart of oncogenic adaptations fuel the development of drug resistance in many cancers for targeted therapies including KRAS and EGFR mutants. The first U.S. food and drug administration (US FDA) approval of the imatinib tyrosine kinase inhibitor in 2001 paved the way for nearly 100 small-molecule anti-cancer drugs approved by the US FDA and the national medical products administration (NMPA). However, the low response rate and development of drug resistance have posed a major hurdle to improving the progression-free survival (PFS) and overall survival (OS) of cancer patients. Accumulating evidence has enabled scientists and clinicians to strategize the therapeutic approaches of targeting cancer cells and to navigate the development of drug resistance through the continuous monitoring of tumor evolution and oncogenic adaptations. In this review, we highlight the emerging aspects of Hippo signaling in cross-talk with other oncogenic drivers and how this information can be translated into combination therapy to target a broad range of aggressive tumors and the development of drug resistance.

Transcriptomics analysis revealed that TAZ regulates the proliferation of KIRC cells through mitophagy

Transcriptional Co-Activator with PDZ-Binding Motif (TAZ, also known as WWTR1) is a downstream effector of the Hippo pathway, involved in the regulation of organ regeneration and cell differentiation in processes such as development and regeneration. TAZ has been shown to play a tumor-promoting role in various cancers. Currently, many studies focus on the role of TAZ in the process of mitophagy. However, the molecular mechanism and biological function of TAZ in renal clear cell carcinoma (KIRC) are still unclear. Therefore, we systematically analyzed the mRNA expression profile and clinical data of KIRC in The Cancer Genome Atlas (TCGA) dataset. We found that TAZ expression was significantly upregulated in KIRC compared with normal kidney tissue and was closely associated with poor prognosis of patients. Combined with the joint analysis of 36 mitophagy genes, it was found that TAZ was significantly negatively correlated with the positive regulators of mitophagy. Finally, our results confirmed that high expression of TAZ in KIRC inhibits mitophagy and promotes KIRC cell proliferation. In conclusion, our findings reveal the important role of TAZ in KIRC and have the potential to be a new target for KIRC therapy.

Tolfenamic acid negatively regulates YAP and TAZ expression in human cancer cells

Several diseases are associated with improper regulation of the Hippo pathway, which plays an important role in cell proliferation and cancer metastasis. Overactivation of the YAP and TAZ proteins accelerates cell proliferation, invasion, and migration during tumorigenesis. Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug (NSAID) that exhibits activity against various types of cancer. In this study, we observed that TA decreased YAP and TAZ protein levels in cancer cells. TA increased the phosphorylation of YAP and TAZ, leading to the degradation of YAP and TAZ in the cytoplasm and nucleus. TA predominantly affected multiple phosphodegron sites in the YAP and TAZ and lowered 14-3-3β protein expression, causing YAP and TAZ to enter the ubiquitination pathway. Proteins that affect YAP and TAZ regulation, such as NAG-1 and several YAP/TAZ E3 ligases, were not involved in TA-mediated YAP/TAZ degradation. In summary, our results indicate that TA affects phosphodegron sites on YAP/TAZ, demonstrating a novel effect of TA in tumorigenesis.

The impact of interaction between verteporfin and yes-associated protein 1/transcriptional coactivator with PDZ-binding motif-TEA domain pathway on the progression of isocitrate dehydrogenase wild-type glioblastoma

Verteporfin and 5-ALA are used for visualizing malignant tissue components in different body tumors and as photodynamic therapy in treating isocitrate dehydrogenase (IDH) wild-type glioblastoma (GBM). Additionally, verteporfin interferes with Yes-associated protein 1 (YAP)/Transcriptional coactivator with PDZ-binding motif - TEA domain (TAZ-TEAD) pathway, thus inhibiting the downstream effect of these oncogenes and reducing the malignant properties of GBM. Animal studies have shown verteporfin to be successful in increasing survival rates, which have led to the conduction of phase 1 and 2 clinical trials to further investigate its efficacy in treating GBM. In this article, we aimed to review the novel mechanism of verteporfin's action, the impact of its interaction with YAP/TAZ-TEAD, its effect on glioblastoma stem cells, and its role in inducing ferroptosis.

Emerging roles of ferroptosis-related miRNAs in tumor metastasis

Ferroptosis, a novel mode of cell death dependent on iron and reactive oxygen species, has been extensively explored during malignant tumors metastasis. Ferroptosis can interact with multiple components of the tumor microenvironment to regulate metastasis. These interactions generally include the following aspects: (1) Epithelial-mesenchymal transformation, which can help cancer cells increase their sensitivity to ferroptosis while they have multiple mechanisms to fight against it; (2) Disorder of iron metabolism in cancer stem cells which maintains their stem characteristics; (3) Polarization of M0 macrophages to M2. (4) The paradoxical effects of iron metabolism and CD8 + T cells induced by ferroptosis (5) Regulation of angiogenesis. In addition, ferroptosis can be regulated by miRNAs through the reprogramming of various intracellular metabolism processes, including the regulation of the glutathione- glutathione peroxidase 4 pathway, glutamic acid/cystine transport, iron metabolism, lipid metabolism, and oxidative stress. Therefore, there are many potential interactions between ferroptosis-related miRNAs and tumor metastasis, including interaction with cancer cells and immune cells, regulating cytokines, and angiogenesis. This review focuses on the role of ferroptosis-related miRNA in tumor metastasis, aiming to help readers understand their relationship and provide a new perspective on the potential treatment strategies of malignant tumors.

Downregulation of Yap1 during limb regeneration results in defective bone formation in axolotl

The Hippo pathway plays an imperative role in cellular processes such as differentiation, regeneration, cell migration, organ growth, apoptosis, and cell cycle. Transcription coregulator component of Hippo pathway, YAP1, promotes transcription of genes involved in cell proliferation, migration, differentiation, and suppressing apoptosis. However, its role in epimorphic regeneration has not been fully explored. The axolotl is a well-established model organism for developmental biology and regeneration studies. By exploiting its remarkable regenerative capacity, we investigated the role of Yap1 in the early blastema stage of limb regeneration. Depleting Yap1 using gene-specific morpholinos attenuated the competence of axolotl limb regeneration evident in bone formation defects. To explore the affected downstream pathways from Yap1 down-regulation, the gene expression profile was examined by employing LC-MS/MS technology. Based on the generated data, we provided a new layer of evidence on the putative roles of increased protease inhibition and immune system activities and altered ECM composition in diminished bone formation capacity during axolotl limb regeneration upon Yap1 deficiency. We believe that new insights into the roles of the Hippo pathway in complex structure regeneration were granted in this study.

DEPDC1 and KIF4A synergistically inhibit the malignant biological behavior of osteosarcoma cells through Hippo signaling pathway

The treatment of osteosarcoma (OS) is still mainly surgery combined with systematic chemotherapy, and gene therapy is expected to improve the survival rate of patients. This study aimed to explore the effect of DEP domain 1 protein (DEPDC1) and kinesin super-family protein 4A (KIF4A) in OS and understand its mechanism. Th expression of DEPDC1 and KIF4A in OS cells was detected by RT-PCR and western blot. The viability, proliferation, invasion and migration of OS cells and tube formation of human umbilical vein endothelial cells (HUVECs) after indicated treatment were in turn detected by CCK-8 assay, EdU staining, wound healing assay, transwell assay and tube formation assay. The interaction between DEPDC1 and KIF4A was predicted by STRING and confirmed by co-immunoprecipitation. The expression of epithelial-mesenchymal transition (EMT)-related proteins, tube formation-related proteins and Hippo signaling pathway proteins was detected by western blot. As a result, the expression of DEPDC1 and KIF4A was all increased in U2OS cells. Down-regulation of DEPDC1 suppressed the viability, proliferation, invasion and migration of U2OS cells and tube formation of HUVECs, accompanied by the increased expression of E-cadherin and decreased expression of N-cadherin, Vimentin and VEGF. DEPDC1 was confirmed to be interacted with KIF4A. Upregulation of KIF4A partially reversed the effect of DEPDC1 interference on the above biological behaviors of U2OS cells. Down-regulation of DEPDC1 promoted the expression of p-LATS1 and p-YAP in Hippo signaling pathway, which was reversed by upregulation of KIF4A. In conclusion, down-regulation of DEPDC1 inhibited the malignant biological behavior of OS cells through the activation of Hippo signaling pathway, which could be reversed by upregulation of KIF4A.

The roles of KLHL family members in human cancers

The Kelch-like (KLHL) family members consist of three domains: bric-a-brac, tramtrack, broad complex/poxvirus and zinc finger domain, BACK domain and Kelch domain, which combine and interact with Cullin3 to form an E3 ubiquitin ligase. Research has indicated that KLHL family members ubiquitinate target substrates to regulate physiological and pathological processes, including tumorigenesis and progression. KLHL19, a member of the KLHL family, is associated with tumorigenesis and drug resistance. However, the regulation and cross talks of other KLHL family members, which also play roles in cancer, are still unclear. Our review mainly explores studies concerning the roles of other KLHL family members in tumor-related regulation to provide novel insights into KLHL family members.

N-(3,4-dimethoxyphenethyl)-6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-amine inhibits bladder cancer progression by suppressing YAP1/TAZ

Bladder cancer (BlC) is the fourth most common cancer in males worldwide, but few systemic chemotherapy options for its effective treatment exist. The development of new molecularly-targeted agents against BlC is therefore an urgent issue. The Hippo signaling pathway, with its upstream LATS kinases and downstream transcriptional co-activators YAP1 and TAZ, plays a pivotal role in diverse cell functions, including cell proliferation. Recent studies have shown that overexpression of YAP1 occurs in advanced BlCs and is associated with poor patient prognosis. Accessing data from our previous screening of a chemical library of compounds targeting the Hippo pathway, we identified DMPCA (N-(3,4-dimethoxyphenethyl)-6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-amine) as an agent able to induce the phosphorylation of LATS1 and YAP1/TAZ in BlC cells, thereby suppressing their viability both in vitro and in mouse xenografts. Our data indicate that DMPCA has a potent anti-tumor effect, and raise the possibility that this agent may represent a new and effective therapeutic option for BlC.

Novel neoplasms associated with syndromic pediatric medulloblastoma: integrated pathway delineation for personalized therapy

Medulloblastoma is the most common pediatric embryonal brain tumor, and may occur in cancer predisposition syndromes. We describe novel associations of medulloblastoma with atypical prolactinoma and dural high-grade sarcoma in Li-Fraumeni syndrome (LFS), and epidural desmoid fibromatosis in familial adenomatous polyposis (FAP)/Turcot syndrome. Genomic analysis showing XRCC3 alterations suggested radiotherapy as contributing factor to the progression of LFS-associated medulloblastoma, and demonstrated different mechanisms of APC inactivation in the FAP-associated tumors. The integrated genomic-transcriptomic analysis uncovered the growth pathways driving tumorigenesis, including the prolactin-prolactin receptor (PRLR) autocrine loop and Shh pathway in the LFS-associated prolactinoma and medulloblastoma, respectively, the Wnt pathway in both FAP-associated neoplasms, and the TGFβ and Hippo pathways in the soft tissue tumors, regardless of germline predisposition. In addition, the comparative analysis of paired syndromic neoplasms revealed several growth pathways susceptible to therapeutic intervention by PARP, PRLR, and selective receptor tyrosine kinase (RTK) inhibitors. These could target the defective DNA damage repair in the LFS-associated medulloblastoma, the prolactin autocrine loop in the atypical prolactinoma, the EPHA3/7 and ALK overexpression in the FAP-associated medulloblastoma, and the multi-RTK upregulation in the soft tissue neoplasms. This study presents the spatiotemporal evolution of novel neoplastic associations in syndromic medulloblastoma, and discusses the post-radiotherapy risk for secondary malignancies in syndromic pediatric patients, with important implications for the biology, diagnosis, and therapy of these tumors.

Potential molecular mechanism in self-renewal is associated with miRNA dysregulation in sacral chordoma - A next-generation RNA sequencing study

Background

Chordoma, the most frequent malignant primary spinal neoplasm, characterized by a high rate of recurrence, is an orphan disease where the clarification of the molecular oncogenesis would be crucial to developing new, effective therapies. Dysregulated expression of non-coding RNAs, especially microRNAs (miRNA) has a significant role in cancer development.

Methods

Next-generation RNA sequencing (NGS) was used for the combinatorial analysis of mRNA-miRNA gene expression profiles in sacral chordoma and nucleus pulposus samples. Advanced bioinformatics workflow was applied to the data to predict miRNA-mRNA regulatory networks with altered activity in chordoma.

Results

A large set of significantly dysregulated miRNAs in chordoma and their differentially expressed target genes have been identified. Several molecular pathways related to tumorigenesis and the modulation of the immune system are predicted to be dysregulated due to aberrant miRNA expression in chordoma. We identified a gene set including key regulators of the Hippo pathway, which is targeted by differently expressed miRNAs, and validated their altered expression by RT-qPCR. These newly identified miRNA/RNA interactions are predicted to have a role in the self-renewal process of chordoma stem cells, which might sustain the high rate of recurrence for this tumor.

Conclusions

Our results can significantly contribute to the designation of possible targets for the development of anti-chordoma therapies.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

An Integrative Pan-Cancer Analysis Revealing MLN4924 (Pevonedistat) as a Potential Therapeutic Agent Targeting Skp2 in YAP-Driven Cancers

Background: YAP, coded by YAP1 gene, is critical in the Hippo pathway. It has been reported to be involved in the tumorigenesis and progression of several cancers. However, its roles on tumor cell proliferation in diverse cancers remain to be elucidated. And there is currently no clinically feasible drug that can directly target YAP in cancers. This research aimed to explore the regulatory mechanism of YAP in promoting tumor proliferation of multiple cancers, in order to find new strategies for inhibiting the overgrowth of YAP-driven cancers.

Methods: We investigated the expression pattern of YAP1 in pan-cancer across numerous databases and our cohorts. First, univariate Cox regression analysis and survival analysis were used to evaluate the effect of YAP1 on the prognosis of cancer patients. Second, TIMER was used to explore the relationship between YAP1 expression and tumor cell proliferation. Third, functional and pathway enrichment was performed to search for targets of YAP involved in cell cycle in cancers. At last, GDSC and CCLE datasets were used to assess the correlation between SKP2 expression and MLN4924 IC50 values.

Results: Differential expression analysis of multiple databases and qPCR validation showed that YAP1 was generally overexpressed in pan-cancers. Survival analysis revealed that YAP1 over-expression was significantly related to poor prognosis of patients with PAAD. The expression level of YAP1 was positively correlated with the proliferation in varieties of tumors. Further, SKP2 was confirmed as a target of YAP in promoting tumor cell proliferation. In addition, SKP2 expression was negatively correlated with MLN4924 IC50 values in almost all cancer types.

Conclusion:YAP1 is frequently overexpressed in human cancers. YAP promoted tumor cell proliferation by up-regulating SKP2 expression in multiple cancers. The comprehensive pan-cancer analysis suggested that inhibition of Skp2 with MLN4924 might be an effective therapeutic strategy for attenuating tumor cell proliferation in YAP-driven cancers.

Role of YAP in early ectodermal specification and a Huntington's Disease model of human neurulation

The Hippo pathway, a highly conserved signaling cascade that functions as an integrator of molecular signals and biophysical states, ultimately impinges upon the transcription coactivator Yes-associated protein 1 (YAP). Hippo-YAP signaling has been shown to play key roles both at the early embryonic stages of implantation and gastrulation, and later during neurogenesis. To explore YAP's potential role in neurulation, we used self-organizing neuruloids grown from human embryonic stem cells on micropatterned substrates. We identified YAP activation as a key lineage determinant, first between neuronal ectoderm and nonneuronal ectoderm, and later between epidermis and neural crest, indicating that YAP activity can enhance the effect of BMP4 stimulation and therefore affect ectodermal specification at this developmental stage. Because aberrant Hippo-YAP signaling has been implicated in the pathology of Huntington's Disease (HD), we used isogenic mutant neuruloids to explore the relationship between signaling and the disease. We found that HD neuruloids demonstrate ectopic activation of gene targets of YAP and that pharmacological reduction of YAP's transcriptional activity can partially rescue the HD phenotype.

Genomic Hippo Pathway Alterations and Persistent YAP/TAZ Activation: New Hallmarks in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) represents a highly prevalent and deadly malignancy worldwide. The prognosis for locoregionally advanced HNSCC has not appreciably improved over the past 30 years despite advances in surgical, radiation, and targeted therapies and less than 20% of HNSCC patients respond to recently approved immune checkpoint inhibitors. The Hippo signaling pathway, originally discovered as a mechanism regulating tissue growth and organ size, transduces intracellular and extracellular signals to regulate the transcriptional co-activators YAP and TAZ. Alterations in the Hippo pathway resulting in persistent YAP and TAZ activation have emerged as major oncogenic drivers. Our analysis of the human HNSCC oncogenome revealed multiple genomic alterations impairing Hippo signaling and activating YAP and TAZ, which in turn contribute to HNSCC development. This includes mutations and deletions of the FAT1 gene (29%) and amplification of the WWTR1 (encoding TAZ, 14%) and YAP1 genes (8%), together representing one of the most genetically altered signaling mechanisms in this malignancy. Here, we discuss key elements of the mammalian Hippo pathway, detail mechanisms by which perturbations in Hippo signaling promote HNSCC initiation and progression and outline emerging strategies to target Hippo signaling vulnerabilities as part of novel multimodal precision therapies for HNSCC.

The Hippo pathway in cancer: YAP/TAZ and TEAD as therapeutic targets in cancer

Tumorigenesis is a highly complex process, involving many interrelated and cross-acting signalling pathways. One such pathway that has garnered much attention in the field of cancer research over the last decade is the Hippo signalling pathway. Consisting of two antagonistic modules, the pathway plays an integral role in both tumour suppressive and oncogenic processes, generally via regulation of a diverse set of genes involved in a range of biological functions. This review discusses the history of the pathway within the context of cancer and explores some of the most recent discoveries as to how this critical transducer of cellular signalling can influence cancer progression. A special focus is on the various recent efforts to therapeutically target the key effectors of the pathway in both preclinical and clinical settings.

Targeted inhibition of YAP/TAZ alters the biological behaviours of keloid fibroblasts

Abnormal activation of fibroblasts plays a crucial role in keloid development. However, the mechanism of fibroblast activation remains to be determined. YAP/TAZ are key molecules in the Hippo signalling pathway that promote cell proliferation and inhibit apoptosis. Here, we show that keloid fibroblasts have higher levels of YAP/TAZ mRNA and proteins on primary culture. Targeted knockdown of endogenous YAP or TAZ significantly inhibited cell proliferation, reduced cell migration, induced cell apoptosis and down-regulated collagen1a1 production by keloid fibroblasts. Moreover, we demonstrate that verteporfin, an inhibitor of YAP/TAZ, has similar but stronger inhibitory effects on fibroblasts compared to YAP/TAZ knockdown. Our study provides evidence that YAP/TAZ may be involved in the pathogenesis of keloids. Targeted inhibition of YAP/TAZ could change the biological behaviours of fibroblasts and can potentially be used as therapy for keloids.

Synthetic molecules targeting yes associated protein activity as chemotherapeutics against cancer

The Hippo signaling pathway extorts several signals that concomitantly target the activity of transcriptional cofactor yes associated protein (YAP). YAP is a key regulator that elicits signature gene expression by coupling with transcriptional enhanced associate domain (TEAD) family of transcriptional factors. The YAP-TEAD complex via target gene expression gets associated with the development, proliferation, and progression of cancerous cells. Moreover, YAP adorns cells with several oncogenic traits such as inhibition of apoptosis, enhanced proliferation, drug resistance, and immune response suppression, which later became associated with various diseases, particularly cancer. Therefore, inhibition of the YAP activity is an appealing and viable therapeutic target for cancer treatment. This review highlights the recent advances in existing and novel synthetic therapeutics targeting YAP inhibition and regulation. The synthetically produced YAP^D93A belonging to cyclic peptides and DC-TEADin02 and vinyl sulfonamide class of compounds are the most potent compounds to inhibit the YAP-TEAD expression by targeting protein-protein interaction (IC₅₀  = 25 nM) and palmitate binding central pocket of TEAD (IC₅₀  = 197 nM), respectively. On the other hand, Chlorpromazine belonging to phenothiazines class has the least potential to suppress YAP via proteasomal degradation (cell viability value of <20% at 40 µM).

Emerging roles for the YAP/TAZ transcriptional regulators in brain tumour pathology and targeting options

The transcriptional co-activators Yes-associated protein 1/transcriptional co-activator with PDZ-binding motif (YAP/TAZ) have emerged as significant regulators of a wide variety of cellular and organ functions with impact in early embryonic development, especially during the expansion of the neural progenitor cell pool. YAP/TAZ signalling regulates organ size development, tissue homeostasis, wound healing and angiogenesis by participating in a complex network of various pathways. However, recent evidence suggests an association of these physiologic regulatory effects of YAP/TAZ with pro-oncogenic activities. Herein, we discuss the physiological functions of YAP/TAZ as well as the extensive network of signalling pathways that control their expression and activity, leading to brain tumour development and progression. Furthermore, we describe current targeting approaches and drug options including direct YAP/TAZ and YAP-TEA domain transcription factor (TEAD) interaction inhibitors, G-protein coupled receptors (GPCR) signalling modulators and kinase inhibitors, which may be used to successfully attack YAP/TAZ-dependent tumours.

A Yes-Associated Protein (YAP) and Insulin-Like Growth Factor 1 Receptor (IGF-1R) Signaling Loop Is Involved in Sorafenib Resistance in Hepatocellular Carcinoma

The role of a YAP-IGF-1R signaling loop in HCC resistance to sorafenib remains unknown.

METHOD

Sorafenib-resistant cells were generated by treating naïve cells (HepG2215 and Hep3B) with sorafenib. Different cancer cell lines from databases were analyzed through the ONCOMINE web server. BIOSTORM-LIHC patient tissues (46 nonresponders and 21 responders to sorafenib) were used to compare YAP mRNA levels. The HepG2215_R-derived xenograft in SCID mice was used as an in vivo model. HCC tissues from a patient with sorafenib failure were used to examine differences in YAP and IGF-R signaling.

RESULTS

Positive associations exist among the levels of YAP, IGF-1R, and EMT markers in HCC tissues and the levels of these proteins increased with sorafenib failure, with a trend of tumor-margin distribution in vivo. Blocking YAP downregulated IGF-1R signaling-related proteins, while IGF-1/2 treatment enhanced the nuclear translocation of YAP in HCC cells through PI3K-mTOR regulation. The combination of YAP-specific inhibitor verteporfin (VP) and sorafenib effectively decreased cell viability in a synergistic manner, evidenced by the combination index (CI).

CONCLUSION

A YAP-IGF-1R signaling loop may play a role in HCC sorafenib resistance and could provide novel potential targets for combination therapy with sorafenib to overcome drug resistance in HCC.

The hippo pathway: A master regulator of liver metabolism, regeneration, and disease

The liver is the only visceral organ in the body with a tremendous capacity to regenerate in response to insults that induce inflammation, cell death, and injury. Liver regeneration is a complicated process involving a well-orchestrated activation of non-parenchymal cells in the injured area and proliferation of undamaged hepatocytes. Furthermore, the liver has a Hepatostat, defined as adjustment of its volume to that required for homeostasis. Understanding the mechanisms that control different steps of liver regeneration is critical to informing therapies for liver repair, to help patients with liver disease. The Hippo signaling pathway is well known for playing an essential role in the control and regulation of liver size, regeneration, stem cell self-renewal, and liver cancer. Thus, the Hippo pathway regulates dynamic cell fates in liver, and in absence of its downstream effectors YAP and TAZ, liver regeneration is severely impaired, and the proliferative expansion of liver cells blocked. We will mainly review upstream mechanisms activating the Hippo signaling pathway following partial hepatectomy in mouse model and patients, its roles during different steps of liver regeneration, metabolism, and cancer. We will also discuss how targeting the Hippo signaling cascade might improve liver regeneration and suppress liver tumorigenesis.

Hippo Signaling Pathway as a New Potential Target in Non-Melanoma Skin Cancers: A Narrative Review

Non-melanoma skin cancers (NMSCs), including basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC), are the most frequently diagnosed cancers in humans, however, their exact pathogenesis is not fully understood. In recent years, it has been hypothesized that the recently discovered Hippo pathway could play a detrimental role in cutaneous carcinogenesis, but no direct connections have been made. The Hippo pathway and its effector, YAP, are responsible for tissue growth by accelerating cell proliferation, however, YAP upregulation and overexpression have also been reported in numerous types of tumors. There is also evidence that disrupted YAP/Hippo signaling is responsible for cancer growth, invasion, and metastasis. In this short review, we will explore whether the Hippo pathway is an important regulator of skin carcinogenesis and if it could be a promising target for future therapies.

Small-molecule inhibition of Lats kinases may promote Yap-dependent proliferation in postmitotic mammalian tissues

Hippo signaling is an evolutionarily conserved pathway that restricts growth and regeneration predominantly by suppressing the activity of the transcriptional coactivator Yap. Using a high-throughput phenotypic screen, we identified a potent and non-toxic activator of Yap. In vitro kinase assays show that the compound acts as an ATP-competitive inhibitor of Lats kinases-the core enzymes in Hippo signaling. The substance prevents Yap phosphorylation and induces proliferation of supporting cells in the murine inner ear, murine cardiomyocytes, and human Müller glia in retinal organoids. RNA sequencing indicates that the inhibitor reversibly activates the expression of transcriptional Yap targets: upon withdrawal, a subset of supporting-cell progeny exits the cell cycle and upregulates genes characteristic of sensory hair cells. Our results suggest that the pharmacological inhibition of Lats kinases may promote initial stages of the proliferative regeneration of hair cells, a process thought to be permanently suppressed in the adult mammalian inner ear.

Adipose-derived mesenchymal stem cells induced PAX8 promotes ovarian cancer cell growth by stabilizing TAZ protein

Our previous studies have shown that the Adipose‐derived mesenchymal stem cells (ADSCs) can regulate metastasis and development of ovarian cancer. However, its specific mechanism has yet to be fully revealed. In this study, an RNA‐seq approach was adopted to compare the differences in mRNA levels in ovarian cancer cells being given or not given ADSCs. The mRNA level of paired box 8 (PAX8) changed significantly and was confirmed as an important factor in tumour‐inducing effect of ADSCs. In comparison with the ovarian cancer cells cultured in the common growth medium, those cultured in the medium supplemented with ADSCs showed a significant increase of the PAX8 level. Moreover, the cancer cell growth could be restricted, even in the ADSC‐treated group (P < .05), by inhibiting PAX8. In addition, an overexpression of PAX8 could elevate the proliferation of ovarian cancer cells. Moreover, Co‐IP assays in ovarian cancer cells revealed that an interaction existed between endogenous PAX8 and TAZ. And the PAX8 levels regulated the degradation of TAZ. The bioluminescence images captured in vivo manifested that the proliferation and the PAX8 expression level in ovarian cancers increased in the ADMSC‐treated group, and the effect of ADSCs in promoting tumours was weakened through inhibiting PAX8. Our findings indicate that the PAX8 expression increment could contribute a role in promoting the ADSC‐induced ovarian cancer cell proliferation through TAZ stability regulation.

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.

Small Extracellular Vesicles from Human Fetal Dermal Cells and Their MicroRNA Cargo: KEGG Signaling Pathways Associated with Angiogenesis and Wound Healing

The use of cell secreted factors in clinical settings could be an alternative to conventional cell therapy, with the advantage of limiting concerns generally associated with traditional cell transplantation, such as tumorigenicity, immunoreactivity, and carrying of infections. Based on our published data, we predict a potential role for extracellular vesicles (EVs) in contributing to the proangiogenic activity of human fetal dermal cell secretome. Depletion of nanosized EVs from secretome significantly impaired its ability to induce formation of mesh-like structures in vitro. The isolated EVs were characterized for size and concentration by nanoparticle tracking analysis, and for protein markers (Rab5⁺, Alix⁺, CD63⁺, and calnexin⁻). The microRNA profile of EVs revealed 87 microRNAs significantly upregulated (≥15-fold increase) in fetal compared to adult dermal cell-derived EVs. Interestingly, these upregulated microRNAs included microRNAs with a validated role in angiogenesis according to literature. Moreover, the DIANA-TarBase v7.0 analysis confirmed enrichment in the KEGG signaling pathways associated with angiogenesis and wound healing, with the identification of putative target genes including thrombospondin 1. To validate the in silico data, EVs were also characterized for total protein contents. When tested in in vitro angiogenesis, fetal dermal cell-derived EVs were more effective than their adult counterpart in inducing formation of complete mesh-like structures. Furthermore, treatment of fibroblasts with fetal dermal-derived EVs determined a 4-fold increase of thrombospondin 1 protein amounts compared with the untreated fibroblasts. Finally, visualization of CSFE-labeled EVs in the cytosol of target cells suggested a successful uptake of these particles at 4-8 hours of incubation. We conclude that EVs are important contributors of the proangiogenic effect of fetal dermal cell secretome. Hence, EVs could also serve as vehicle for a successful delivery of microRNAs or other molecules of therapeutic interest to target cells.

microRNA-10 and -221 modulate differential expression of Hippo signaling pathway in human astroglial tumors

Gliomas represent over 70% of all brain tumors, they are highly invasive and structurally vascular neoplasms. Despite the latest technological advance in neuro-surgery the survival of patients with high-grade glioma remains poor. The lack of robust treatment options has propelled the search for new markers that may able allow the identification of patients who can benefit from molecularly targeted therapies. The Hippo signaling pathway is considered as a key regulator of tissue homeostasis, cell proliferation and apoptosis, and alterations of this pathway seem to contribute to tumorigenesis. Yes-associated protein (YAP1) is a downstream target of the Hippo pathway which acts as a transcription co-activator. In cancer, YAP1 has been reported to function either as an oncogene or tumor suppressor, depending on the cell context. The aim of this study was to examine the expression of YAP1, Survivin and LATS1 kinase activity in human astroglial tumors with different grades of malignancy. Moreover, we also investigated the expression of miR-221 and miR-10b and their relationship with core molecules of the Hippo pathway. Our results showed the overexpression of YAP1 and Survivin as well as a decreased activity of large tumor suppressor 1 (LATS1) in high-grade glioblastoma versus anaplastic astrocytoma and low-grade glioma. Furthermore, we also demonstrated that miR-221 and miR-10b are specifically involved in Hippo signaling via LATS1 regulation and that their knockdown significantly decreased glioma cell proliferation. This preliminary data confirmed the crucial role of the Hippo pathway in cancer and suggested that miR-221 and miR-10b could be potential therapeutic targets for glioma treatment.

Yes‑associated protein protects and rescues SH‑SY5Y cells from ketamine‑induced apoptosis

Ketamine is a widely used intravenous anesthetic; however, basic and clinical studies have demonstrated that prolonged exposure can cause irreversible injury to the immature human brain. Yes-associated protein (YAP) is the main effector of the Hippo signaling pathway, which serves an important role in regulating tissue homeostasis and organ size during development. However, whether YAP mediates ketamine-induced apoptosis is not completely understood. Based on the functions of YAP during apoptosis resistance and cell self-renewal regulation, the present study hypothesized that YAP serves a role during ketamine-induced apoptosis. An in vitro model was utilized to investigate the effects of ketamine on neurotoxicity and to further investigate the role of YAP in ketamine-induced apoptosis using techniques including CCK-8 assay, flow cytometry and western blotting. The present study assessed the effects of YAP overexpression and knockdown on the expression of typical apoptotic markers in SH-SY5Y cells. Ketamine induced apoptosis in a dose-dependent manner, which was regulated by YAP. Following YAP overexpression, ketamine-treated SH-SY5Y cells displayed increased activity and viability, whereas expression levels of the apoptotic markers were decreased compared with the negative control group. By contrast, ketamine-induced apoptosis was enhanced following YAP knockdown. Collectively, the results of the present study indicated that YAP may serve an important role during ketamine-induced neurotoxicity, and alterations to YAP signaling may counteract ketamine-induced apoptosis. The neuroprotective effect of YAP activation may serve as a novel pharmacological target for the treatment of ketamine-induced neurotoxicity via neurogenesis normalization.

The Hippo in the room: Targeting the Hippo signalling pathway for osteosarcoma therapies

Osteosarcoma (OS) is a primary malignant bone tumour which usually occurs in children and adolescents. OS is primarily a result of chromosomal aberrations, a combination of acquired genetic changes and, hereditary, resulting in the dysregulation of cellular functions. The Hippo signalling pathway regulates cell and tissue growth by modulating cell proliferation, differentiation, and migration in developing organs. Mammalian STE20-like 1/2 (MST1/2) protein kinases are activated by neurofibromatosis type 2, Ras association domain family member 2, kidney and brain protein, or other factors. Interactions between MST1/2 and salvador family WW domain-containing protein 1 activate large tumour suppressor kinase 1/2 proteins, which in turn phosphorylate the downstream Yes-associated protein 1/transcriptional coactivator with PDZ-binding motif (YAP/TAZ). Moreover, dysregulation of this pathway can lead to aberrant cell growth, resulting in tumorigenesis. Interestingly, small molecules targeting the Hippo signalling pathways, through affecting YAP/TAZ cellular localisation and their interaction with members of the TEA/ATTS domain family of transcriptional enhancers are being developed and hold promise for the treatment of OS. This review discusses the existing knowledge about the involvement of the Hippo signalling cascade in OS and highlights several small molecule inhibitors as potential novel therapeutics.

USP10 Promotes Proliferation of Hepatocellular Carcinoma by Deubiquitinating and Stabilizing YAP/TAZ

Yes-associated protein (YAP) and its paralog, transcriptional coactivator with PDZ-binding motif (TAZ), play pivotal roles in promoting the progression of hepatocellular carcinoma. However, the regulatory mechanism underpinning aberrant activation of YAP/TAZ in hepatocellular carcinoma remains unclear. In this study, we globally profiled the contribution of deubiquitinating enzymes (DUB) to both transcriptional activity and protein abundance of YAP/TAZ in hepatocellular carcinoma models and identified ubiquitin-specific peptidase 10 (USP10) as a potent YAP/TAZ-activating DUB. Mechanistically, USP10 directly interacted with and stabilized YAP/TAZ by reverting their proteolytic ubiquitination. Depletion of USP10 enhanced polyubiquitination of YAP/TAZ, promoted their proteasomal degradation, and ultimately arrested the proliferation of hepatocellular carcinoma in vitro and in vivo. Expression levels of USP10 positively correlated with the abundance of YAP/TAZ in hepatocellular carcinoma patient samples as well as in N-nitrosodiethylamine (DEN)-induced liver cancer mice models. Collectively, this study establishes the causal link between USP10 and hyperactivated YAP/TAZ in hepatocellular carcinoma cells and provides a rationale for potential therapeutic interventions in the treatment of patients with hepatocellular carcinoma harboring a high level of YAP/TAZ. SIGNIFICANCE: These findings identify USP10 as a DUB of YAP/TAZ and its role in hepatocellular carcinoma progression, which may serve as a potential therapeutic target for hepatocellular carcinoma treatment.

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

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

Hippo-YAP/TAZ signalling in organ regeneration and regenerative medicine

The Hippo pathway and its downstream effectors, the transcriptional co-activators Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), regulate organ growth and cell plasticity during animal development and regeneration. Remarkably, experimental activation of YAP/TAZ in the mouse can promote regeneration in organs with poor or compromised regenerative capacity, such as the adult heart and the liver and intestine of old or diseased mice. However, therapeutic YAP/TAZ activation may cause serious side effects. Most notably, YAP/TAZ are hyperactivated in human cancers, and prolonged activation of YAP/TAZ triggers cancer development in mice. Thus, can the power of YAP/TAZ to promote regeneration be harnessed in a safe way? Here, we review the role of Hippo signalling in animal regeneration, examine the promises and risks of YAP/TAZ activation for regenerative medicine and discuss strategies to activate YAP/TAZ for regenerative therapy while minimizing adverse side effects.

PRPH2 Activates Hippo Signalling and Suppresses the Invasion and Anoikis Inhibition of Laryngeal Cancer

Introduction

Laryngeal cancer is the most common head and neck cancer worldwide. It is urgent to identify the mechanisms underlying laryngeal cancer pathogenesis. In the present study, we investigated the biological functions of Peripherin 2 (PRPH2) in laryngeal cancer and uncovered the molecular mechanism underlying this disease.

Methods

Laryngeal cancer tissues were used to analyze the expression of PRPH2. In vitro transwell matrigel invasion assay and annexin V anoikis assay in laryngeal cancer cells were conducted to investigate PRPH2 related biological functions. Quantitative real-time PCR and Western blotting were performed to investigate the expression and mechanism of PRPH2 in laryngeal cancer.

Results

We found that the expression of PRPH2 was significantly downregulated in laryngeal cancer tissues. Overexpression of PRPH2 suppressed the invasion and anoikis inhibition of laryngeal cancer cells. Furthermore, PRPH2 overexpression increased the phosphorylation of YAP and LATS1 and decreased the activities of Rho GTPases, while PRPH2 knockdown had opposite effects. Inhibitors of the Hippo pathway abrogated PRPH2 knockdown-induced laryngeal cancer cell invasion and anoikis inhibition.

Discussion

These results suggested that PRPH2 suppresses laryngeal cancer cell invasion and anoikis inhibition by activating Hippo signalling. PRPH2 may serve as a potential therapeutic target for laryngeal cancer in the future.

Recent Advances of the Hippo/YAP Signaling Pathway in Brain Development and Glioma

The Hippo signaling pathway is highly conserved from Drosophila melanogaster to mammals and plays a crucial role in organ size control, tissue regeneration, and tumor suppression. The Yes-associated protein (YAP) is an important transcriptional co-activator that is negatively regulated by the Hippo signaling pathway. The Hippo signaling pathway is also regulated by various upstream regulators, such as cell polarity, adhesion proteins, and other signaling pathways (the Wnt/β-catenin, Notch, and MAPK pathways). Recently, accumulated evidence suggests that the Hippo/YAP signaling pathway plays important roles in central nervous system development and brain tumor, including glioma. In this review, we summarize the results of recent studies on the physiological effect of the Hippo/YAP signaling pathway in neural stem cells, neural progenitor cells, and glial cells. In particular, we also focus on the expression of MST1/2, LATS1/2, and the downstream effector YAP, in glioma, and offer a review of the latest research of the Hippo/YAP signaling pathway in glioma pathogenesis. Finally, we also present future research directions and potential therapeutic strategies for targeting the Hippo/YAP signaling in glioma.

Integrin signaling: linking mechanical stimulation to skeletal muscle hypertrophy

The α₇β₁-integrin is a transmembrane adhesion protein that connects laminin in the extracellular matrix (ECM) with actin in skeletal muscle fibers. The α₇β₁-integrin is highly expressed in skeletal muscle and is concentrated at costameres and myotendious junctions, providing the opportunity to transmit longitudinal and lateral forces across the membrane. Studies have demonstrated that α₇-integrin subunit mRNA and protein are upregulated following eccentric contractions as a mechanism to reinforce load-bearing structures and resist injury with repeated bouts of exercise. It has been hypothesized for many years that the integrin can also promote protein turnover in a manner that can promote beneficial adaptations with resistance exercise training, including hypertrophy. This review provides basic information about integrin structure and activation and then explores its potential to serve as a critical mechanosensor and activator of muscle protein synthesis and growth. Overall, the hypothesis is proposed that the α₇β₁-integrin can contribute to mechanical-load induced skeletal muscle growth via an mammalian target of rapamycin complex 1-independent mechanism.

Blockade of leukemia inhibitory factor as a therapeutic approach to KRAS driven pancreatic cancer

KRAS mutations are present in over 90% of pancreatic ductal adenocarcinomas (PDAC), and drive their poor outcomes and failure to respond to targeted therapies. Here we show that Leukemia Inhibitory Factor (LIF) expression is induced specifically by oncogenic KRAS in PDAC and that LIF depletion by genetic means or by neutralizing antibodies prevents engraftment in pancreatic xenograft models. Moreover, LIF-neutralizing antibodies synergize with gemcitabine to eradicate established pancreatic tumors in a syngeneic, Kras^G12D-driven, PDAC mouse model. The related cytokine IL-6 cannot substitute for LIF, suggesting that LIF mediates KRAS-driven malignancies through a non-STAT-signaling pathway. Unlike IL-6, LIF inhibits the activity of the Hippo-signaling pathway in PDACs. Depletion of YAP inhibits the function of LIF in human PDAC cells. Our data suggest a crucial role of LIF in KRAS-driven pancreatic cancer and that blockade of LIF by neutralizing antibodies represents an attractive approach to improving therapeutic outcomes.

KRAS mutations are frequent in pancreatic ductal adenocarcinoma, leading to bad prognosis and resistance to targeted therapies. Here, the authors show that LIF expression is specifically induced by KRAS and constitutes a potential target to treat these KRAS-mutated cancers.

Mesenchymal stromal cells modulate the molecular pattern of healing process in tissue-engineered urinary bladder: the microarray data

BACKGROUND

Molecular mechanisms underlying the regenerative process induced by stem cells in tissue-engineered urinary bladder are poorly explained. The study was performed to explore the pathways associated with regeneration process in the urinary bladder reconstructed with adipose tissue-derived mesenchymal stromal cells (ASCs).

METHODS

Rat urinary bladders were reconstructed with bladder acellular matrix (BAM) (n = 52) or BAM seeded with adipose tissue-derived mesenchymal stromal cells (ASCs) (n = 52). The process of bladder healing was analyzed at 7, 30, 90, and 180 days postoperatively using macroscopic histologic and molecular techniques. Gene expression was analyzed by microarrays and confirmed by real-time PCR.

RESULTS

Numerous differentially expressed genes (DEGs) were identified between the bladders augmented with BAM seeded with ASCs or BAM only. Pathway analysis of DEGs allows to discover numerous pathways among them Hedgehog, TGF-β, Jak-STAT, PI3-Akt, and Hippo modulated by ASCs during the healing process of tissue-engineered urinary bladder. Real-time PCR analysis confirmed upregulation of genes involved in the Hedgehog signaling pathway including Shh, Gli1, Smo, Bmp2, Bmp4, Wnt2, Wnt2b, Wnt4, Wnt5a, and Wnt10 in urinary bladders reconstructed with ASC-seeded grafts.

CONCLUSION

The study provided the unequivocal evidence that ASCs change the molecular pattern of healing in tissue-engineered urinary bladder and indicated which signaling pathways triggered by ASCs can be associated with the regenerative process. These pathways can be used as targets in the future studies on induced urinary bladder regeneration. Of particular interest is the Hedgehog signaling pathway that has been upregulated by ASCs during healing of tissue-engineered urinary bladder.

MTA2 promotes HCC progression through repressing FRMD6, a key upstream component of hippo signaling pathway

Discerning oncogenic drivers from passengers remains a major effort in understanding of the essence of the initiation and development of hepatocellular carcinoma (HCC), the most common primary liver malignancy and the third leading cause of cancer mortality worldwide. Here we report that MTA2, Metastasis Associated 1 Family Member 2, is significantly up-regulated in HCC. We show that high level of MTA2 expression is strongly correlated with advanced pathological stages and poor overall survival of the patients. Genome-wide identification of the transcriptional targets of MTA2 by ChIP-seq indicates that MTA2 represses a cohort of genes including FRMD6 that are critically involved in the growth and mobility of HCC. We demonstrate that the MTA2 promotes the proliferation and metastasis of HCC in vitro and in vivo through suppressing Hippo signaling pathway. Together, these results reveal a key role for the MTA2-FRDM6-Hippo axis in human hepatocarcinogenesis.

CTGF expression is indicative of better survival rates in patients with medulloblastoma

Medulloblastoma (MB) is the most frequent malignant brain tumor in children and it is subgrouped into 4 entities (SHH, WNT, Group 3, and Group 4). Molecular pathways involved in these different subgroups still are evolving and can be of clinical relevance to therapy. The YAP1-CTGF axis is known to regulate cell proliferation, differentiation, and cell death; however, its role in MB is poorly explored. We aimed to investigate the role of YAP1 gene in the MB SHH cell line DAOY and evaluate cell proliferation, doubling time and 3D spheroids invasion and its consequence on CTGF regulation. We assessed CTGF expression from 22 children with MB. Lastly, we validated our findings through in silico analysis in large cohorts dataset of patients. We observed an increased invasion rate of DAOY cells and CTGF downregulation under YAP1 knockdown (p < 0.0001). Additionally CTGF is overexpressed in MB with extensive nodularity subtype and an indicative of higher survival rates in pediatric MB (p < 0.05). Interestingly, no difference of CTGF expression was observed between molecular subgroups. These results provide new evidence ofCTGF as a potential prognostic marker for MB, corroborating to the role of YAP1 in restricting MB cell.

Antiproliferative and Antimigratory Effects of a Novel YAP-TEAD Interaction Inhibitor Identified Using in Silico Molecular Docking

The Hippo pathway is an important regulator of cell growth, proliferation, and migration. TEAD transcription factors, which lie at the core of the Hippo pathway, are essential for regulation of organ growth and wound repair. Dysregulation of TEAD and its regulatory cofactor Yes-associated protein (YAP) have been implicated in numerous human cancers and hyperproliferative pathological processes. Hence, the YAP–TEAD complex is a promising therapeutic target. Here, we use in silico molecular docking using Bristol University Docking Engine to screen a library of more than 8 million druglike molecules for novel disrupters of the YAP–TEAD interaction. We report the identification of a novel compound (CPD3.1) with the ability to disrupt YAP–TEAD protein–protein interaction and inhibit TEAD activity, cell proliferation, and cell migration. The YAP–TEAD complex is a viable drug target, and CPD3.1 is a lead compound for the development of more potent TEAD inhibitors for treating cancer and other hyperproliferative pathologies.

HTRF® Total and Phospho-YAP (Ser127) Cellular Assays

The YAP protein is a co-transcription factor increasing the expression of genes involved in cell proliferation and repressing the expression of genes important for cell differentiation and apoptosis. It is regulated by several inputs, like the Hippo pathway, through the action of kinases that phosphorylate YAP on several residues. The level of phosphorylation of the residues serine 127 (S127) of YAP is generally assessed in cellular models, native tissues, and organs, as a marker of YAP activity and location, and is regulated by numerous partners. This phosphorylation event is classically detected using a western blot technical approach. Here, we describe a novel approach to detect both the relative amount of total YAP (T-YAP assay) and the phosphorylation of the residue S127 of YAP (S127-P-YAP assay) using a HTRF^®-based method. This easy-to-run method can easily be miniaturized and allows for a high-throughput analysis in 96/384-well plate format, requiring less cellular material and being more rapid than other approaches.

Genetic and epigenetic regulation of cardiomyocytes in development, regeneration and disease

Embryonic and postnatal life depend on the uninterrupted function of cardiac muscle cells. These cells, termed cardiomyocytes, display many fascinating behaviors, including complex morphogenic movements, interactions with other cell types of the heart, persistent contractility and quiescence after birth. Each of these behaviors depends on complex interactions between both cardiac-restricted and widely expressed transcription factors, as well as on epigenetic modifications. Here, we review recent advances in our understanding of the genetic and epigenetic control of cardiomyocyte differentiation and proliferation during heart development, regeneration and disease. We focus on those regulators that are required for both heart development and disease, and highlight the regenerative principles that might be manipulated to restore function to the injured adult heart.

Dual Role of a C-Terminally Truncated Isoform of Large Tumor Suppressor Kinase 1 in the Regulation of Hippo Signaling and Tissue Growth

The considerable amount of experimental evidence has defined the Hippo pathway as a tumor suppressive pathway and increased expression and/or activity of its oncogenic effectors is frequently observed in cancer. However, clinical studies have failed to attribute cancer development and progression to mutations in the pathway. In explaining this conundrum, we investigated the expression and functions of a C-terminally truncated isoform of large tumor suppressor kinase 1 (LATS1) called short LATS1 (sLATS1) in human cell lines and Drosophila. Intriguingly, through overexpression of sLATS1, we demonstrated that sLATS1 either activates or suppresses the activity of Yes-associated protein (YAP), one of the effectors of the Hippo pathway, in a cell type-specific manner. The activation is mediated through inhibition of full-length LATS1, whereas suppression of YAP is accomplished through sLATS1-YAP interaction. In HEK293T cells, the former mechanism may affect the cellular response more dominantly, whereas in U2OS cells and developing tissues in Drosophila, the latter mechanism may be solely carried out. Finally, to find the clinical relevance of this molecule, we examined the expression of sLATS1 in breast cancer patients. The transcriptome analysis showed that the ratio of sLATS1 to LATS1 was increased in tumor tissues comparing to their adjacent normal tissues.

Overexpression of Rac GTPase Activating Protein 1 Contributes to Proliferation of Cancer Cells by Reducing Hippo Signaling to Promote Cytokinesis

BACKGROUND & AIMS

Agents designed to block or alter cytokinesis can kill or stop proliferation of cancer cells. We aimed to identify cytokinesis-related proteins that are overexpressed in hepatocellular carcinoma (HCC) cells and might be targeted to slow liver tumor growth.

METHODS

Using the Oncomine database, we compared the gene expression patterns in 16 cancer microarray datasets and assessed gene enrichment sets using gene ontology. We performed immunohistochemical analysis of an HCC tissue microarray and identified changes in protein levels that are associated with patient survival times. Candidate genes were overexpressed or knocked down with small hairpin RNAs in SMMC7721, MHCC97H, or HCCLM3 cell lines; we analyzed their proliferation, viability, and clone-formation ability and their growth as subcutaneous or orthotopic xenograft tumors in mice. We performed microarray analyses to identify alterations in signaling pathways and immunoblot and immunofluorescence assays to detect and localize proteins in tissues. Yeast 2-hybrid screens and mass spectrometry combined with co-immunoprecipitation experiments were used to identify binding proteins. Protein interactions were validated with co-immunoprecipitation and proximity ligation assays. Chromatin immunoprecipitation, promoter luciferase activity, and quantitative real-time polymerase chain reaction analyses were used to identify factors that regulate transcription of specific genes.

RESULTS

The genes that were most frequently overexpressed in different types of cancer cells were involved in cell division processes. We identified 3 cytokinesis-regulatory proteins among the 10 genes most frequently overexpressed by all cancer cell types. Rac GTPase activating protein 1 (RACGAP1) was the cytokinesis-regulatory protein that was most highly overexpressed in multiple cancers. Increased expression of RACGAP1 in tumor tissues was associated with shorter survival times of patients with cancer. Knockdown of RACGAP1 in HCC cells induced cytokinesis failure and cell apoptosis. In microarray analyses, we found knockdown of RACGAP1 in SMMC7721 cells to reduce expression of genes regulated by yes-associated protein (YAP) and WW domain containing transcription regulator 1 (WWTR1 or TAZ). RACGAP1 reduced activation of the Hippo pathway in HCC cells by increasing activity of RhoA and polymerization of filamentous actin. Knockdown of YAP reduced phosphorylation of RACGAP1 and redistribution at the anaphase central spindle. We found transcription of the translocated promoter region, nuclear basket protein (TPR) to be regulated by YAP and coordinately expressed with RACGAP1 to promote proliferation of HCC cells. TPR redistributed upon nuclear envelope breakdown and formed complexes with RACGAP1 during mitosis. Knockdown of TPR in HCC cells reduced phosphorylation of RACGAP1 by aurora kinase B and impaired their redistribution at the central spindle during cytokinesis. STAT3 activated transcription of RACGAP in HCC cells.

CONCLUSIONS

In an analysis of gene expression patterns of multiple tumor types, we found RACGAP1 to be frequently overexpressed, which is associated with shorter survival times of patients. RACGAP1 promotes proliferation of HCC cells by reducing activation of the Hippo and YAP pathways and promoting cytokinesis in coordination with TPR.

LMO3 promotes hepatocellular carcinoma invasion, metastasis and anoikis inhibition by directly interacting with LATS1 and suppressing Hippo signaling

Background

In this research, we aimed to investigate the biological functions of LIM domain only 3 (LMO3) in hepatocellular carcinoma (HCC) and uncover the underlying molecular mechanism in it.

Methods

HCC tissue microarray (n = 180) was used to analyze the correlation between LMO3 expression and clinicopathological findings. In vitro transwell matrigel invasion assay and annexin V anoikis assay in HCC cells were conducted to investigate LMO3 related biological functions. In vivo intrahepatic and lung metastasis models were used to determine the role of LMO3 in HCC metastasis. Quantitative real-time PCR, western blotting and immunohistochemical staining were performed to investigate the expression and mechanism of LMO3 in HCC.

Results

We found that the expression of LMO3 was significantly upregulated in HCC tissues, and it was closely related to clinicopathological findings and patient prognoses. Knockdown of LMO3 suppressed the invasion and anoikis inhibition of HCC cells in vitro. Meanwhile, the metastasis of SMMC-7721 cells was also suppressed by LMO3 knockdown in vivo. Furthermore, we found that LMO3 knockdown increased the phosphorylation of YAP and LATS1, and decrease Rho GTPases activities. LMO3 directly interacted with LATS1, and thus suppressed Hippo signaling. Recombinant LMO3 (rLMO3) protein administration decreased the phosphorylation of YAP and LATS1, and increased Rho GTPases activities. The inhibitors of the Hippo pathway abrogated rLMO3 protein-induced HCC cell invasion and anoikis inhibition.

Conclusions

These results suggest that LMO3 promotes HCC cell invasion and anoikis inhibition by interacting with LATS1 and suppressing Hippo signaling. LMO3 may serve as a potential therapeutic target for HCC in future.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0903-3) contains supplementary material, which is available to authorized users.

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.