The Hippo Signaling Pathway in Regenerative Medicine

Activated TAZ induces liver cancer in collaboration with EGFR/HER2 signaling pathways

Background

Liver cancer is a major global health concern due to the steady increases in its incidence and mortality. Transcription factors, yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) have emerged as critical regulators in human hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC), the two major types of primary liver cancer. However, our study as well as other previous reports have shown that activation of YAP and TAZ (YAP/TAZ) in adult murine livers is insufficient for the development of liver cancer, suggesting a requirement for an additional oncogenic collaborator for liver carcinogenesis in adulthood. Therefore, we sought to identify the oncogenic partners of YAP/TAZ that promote hepatocarcinogenesis in adults.

Methods

Data analysis of the transcriptome of patients with liver cancer was performed using the national center for biotechnology information (NCBI) gene expression omnibus (GEO) database and the cancer genome atlas (TCGA). The cancer therapeutics response portal (CTRP) was used to investigate the correlation between sensitivity to chemicals and the copy number of TAZ in human cancer cell lines. Transposons encoding constitutively activated forms of TAZ (TAZ^S89A), BRAF (BRAF^V600E), and PIK3CA (PI3K^E545K) were used for hydrodynamic tail vein injection. Mice were monitored at least twice per week and sacrificed when moribund. Tumor-bearing livers were formalin fixed for hematoxylin–eosin staining and immunohistochemistry.

Results

Through database analyses, we identified EGFR/HER2 signaling to be essential in human cancers with high TAZ activity. Furthermore, immunohistochemical analyses showed that human HCC and CC tissues with high YAP/TAZ activities exhibited concomitant activation of EGFR/HER2 signaling pathways. To demonstrate that EGFR/HER2 signaling promotes YAP/TAZ-mediated hepatocarcinogenesis, TAZ^S89A was simultaneously expressed in murine adult livers with BRAF^V600E or PI3K^E545K, activated forms of effector molecules downstream of EGFR/HER2 signaling pathways. Expression of TAZ^S89A plus BRAF^V600E induced HCC, whereas TAZ^S89A and PI3K^E545K led to the development of CC-like cancer.

Conclusions

Our study demonstrates that TAZ collaborates with EGFR/HER2 signaling pathways to induce both HCC and CC.

Supplementary information

The online version contains supplementary material available at 10.1186/s12885-022-09516-1.

The molecular view of mechanical stress of brain cells, local translation, and neurodegenerative diseases

The assumption that chronic mechanical stress in brain cells stemming from intracranial hypertension, arterial hypertension, or mechanical injury is a risk factor for neurodegenerative diseases was put forward in the 1990s and has since been supported. However, the molecular mechanisms that underlie the way from cell exposure to mechanical stress to disturbances in synaptic plasticity followed by changes in behavior, cognition, and memory are still poorly understood. Here we review (1) the current knowledge of molecular mechanisms regulating local translation and the actin cytoskeleton state at an activated synapse, where they play a key role in the formation of various sorts of synaptic plasticity and long-term memory, and (2) possible pathways of mechanical stress intervention. The roles of the mTOR (mammalian target of rapamycin) signaling pathway; the RNA-binding FMRP protein; the CYFIP1 protein, interacting with FMRP; the family of small GTPases; and the WAVE regulatory complex in the regulation of translation initiation and actin cytoskeleton rearrangements in dendritic spines of the activated synapse are discussed. Evidence is provided that chronic mechanical stress may result in aberrant activation of mTOR signaling and the WAVE regulatory complex via the YAP/TAZ system, the key sensor of mechanical signals, and influence the associated pathways regulating the formation of F actin filaments and the dendritic spine structure. These consequences may be a risk factor for various neurological conditions, including autistic spectrum disorders and epileptic encephalopathy. In further consideration of the role of the local translation system in the development of neuropsychic and neurodegenerative diseases, an original hypothesis was put forward that one of the possible causes of synaptopathies is impaired proteome stability associated with mTOR hyperactivity and formation of complex dynamic modes of de novo protein synthesis in response to synapse-stimulating factors, including chronic mechanical stress.

Metformin suppresses interleukin-22 induced hepatocellular carcinoma by upregulating Hippo signaling pathway

BACKGROUND AND AIMS

Epidemiological studies have shown direct associations between type 2 diabetes and the risk of cancers. Accumulating evidence indicates that metformin is profoundly implicated in preventing tumor development. However, the exact mechanism underlying the antitumor effects of metformin in hepatocellular carcinoma (HCC) is still not clear.

METHODS

In this study, we investigated the effects of metformin on a mouse HCC model and interleukin-22 (IL-22)-associated carcinogenesis in vitro.

RESULTS

We found that metformin significantly suppressed the incidence and tumor burden of HCC in the diethyl-nitrosamine-induced HCC mouse model. As expected, the expression of IL-22, an important factor involved in HCC progression, was markedly reduced by metformin. Treatment of HCC cells with metformin inhibited IL-22 induced cell proliferation, migration, and invasion, and promoted cell apoptosis. Furthermore, ectopic expression of IL-22 makes HCC more aggressive, whereas metformin largely compromised it in vitro and in vivo. Mechanistically, the whole transcriptome analysis and functional analysis revealed that Hippo signaling pathway was involved in the antitumor ability of metformin. Consistent with this, metformin directly inhibited LATS1/2 and activated Mst1/2, phosphorylated YAP1 in vitro. After blocking the Hippo pathway by XMU-MP-1, the inhibitor of MST1/2, the inhibitory effects by metformin were dramatically attenuated as shown by in vitro study.

CONCLUSIONS

Collectively, our findings illuminate a new regulatory mechanism, metformin activates Hippo signaling pathway to regulate IL-22 mediated HCC progression and provide new insights into its tumor-suppressive roles.

Exploring the influence of cytosolic and membrane FAK activation on YAP/TAZ nuclear translocation

Membrane binding and unbinding dynamics play a crucial role in the biological activity of several nonintegral membrane proteins, which have to be recruited to the membrane to perform their functions. By localizing to the membrane, these proteins are able to induce downstream signal amplification in their respective signaling pathways. Here, we present a 3D computational approach using reaction-diffusion equations to investigate the relation between membrane localization of focal adhesion kinase (FAK), Ras homolog family member A (RhoA), and signal amplification of the YAP/TAZ signaling pathway. Our results show that the theoretical scenarios in which FAK is membrane bound yield robust and amplified YAP/TAZ nuclear translocation signals. Moreover, we predict that the amount of YAP/TAZ nuclear translocation increases with cell spreading, confirming the experimental findings in the literature. In summary, our in silico predictions show that when the cell membrane interaction area with the underlying substrate increases, for example, through cell spreading, this leads to more encounters between membrane-bound signaling partners and downstream signal amplification. Because membrane activation is a motif common to many signaling pathways, this study has important implications for understanding the design principles of signaling networks.

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

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

Hydrogen peroxide is necessary during tail regeneration in juvenile axolotl

BACKGROUND

Hydrogen peroxide (H₂ O₂ ) is a key reactive oxygen species (ROS) generated during appendage regeneration among vertebrates. However, its role during tail regeneration in axolotl as redox signaling molecule is unclear.

RESULTS

Treatment with exogenous H₂ O₂ rescues inhibitory effects of apocynin-induced growth suppression in tail blastema cells leading to cell proliferation. H₂ O₂ also promotes recruitment of immune cells, regulate the activation of AKT kinase and Agr2 expression during blastema formation. Additionally, ROS/H₂ O₂ regulates the expression and transcriptional activity of Yap1 and its target genes Ctgf and Areg.

CONCLUSIONS

These results show that H₂ O₂ is necessary and sufficient to promote tail regeneration in axolotls. Additionally, Akt signaling and Agr2 were identified as ROS targets, suggesting that ROS/H₂ O₂ is likely to regulate epimorphic regeneration through these signaling pathways. In addition, ROS/H₂ O₂ -dependent-Yap1 activity is required during tail regeneration.

Silencing SAPCD2 Represses Proliferation and Lung Metastasis of Fibrosarcoma by Activating Hippo Signaling Pathway

The primary problem associated with fibrosarcoma is its high potential to metastasize to the lung. Aberrant expression of SAPCD2 has been widely reported to be implicated in the progression and metastasis in multiple cancer types. However, the clinical significance and biological roles of SAPCD2 in fibrosarcoma remain unknown. Here, we reported that SAPCD2 expression was markedly elevated in fibrosarcoma tissues, and its expression was differentially upregulated in fibrosarcoma cell lines compared with that in several primary fibroblast cell lines. Kaplan-Meier survival analysis revealed that SAPCD2 overexpression was significantly correlated with early progression and metastasis, and poor prognosis in fibrosarcoma patients. Our results further showed that silencing SAPCD2 inhibited the proliferation and increased the apoptosis of fibrosarcoma cells in vitro. Importantly, silencing SAPCD2 repressed lung metastasis of fibrosarcoma cells in vivo. Mechanistic investigation further demonstrated that silencing SAPCD2 inhibited the proliferation and lung metastasis of fibrosarcoma cells by activating the Hippo signaling pathway, as evidenced by the finding that constitutively active YAP1, YAP1-S127A, significantly reversed the inhibitory effect of SAPCD2 downregulation on the colony formation and anchorage-independent growth capabilities of fibrosarcoma cells, as well as the stimulatory effect on the apoptotic ratio of fibrosarcoma cells. In conclusion, SAPCD2 promotes the proliferation and lung metastasis of fibrosarcoma cells by regulating the activity of Hippo signaling, and this mechanism represents a potential therapeutic target for the treatment of lung metastatic fibrosarcoma.

Extracellular vesicle-associated miR-135b and -135a regulate stemness in Group 4 medulloblastoma cells by targeting angiomotin-like 2

Background

Extracellular vesicles (EVs) secreted by tumours, including exosomes, are important factors that regulate cell–cell interactions in oncogenesis. Although EV studies are ongoing, the biological understanding of EV-miRNAs derived from brain tumour spheroid-forming cells (BTSCs) of medulloblastoma is poor.

Purposes

We explored the specific cellular miRNAs and EV-miRNAs in medulloblastoma BTSCs to determine their potential biological function.

Methods

Bulk tumor cells (BTCs) and BTSCs were cultured under different conditions from medulloblastoma tissues (N = 10).

Results

Twenty-four miRNAs were simultaneously increased in both cells and EVs derived from BTSCs in comparison to BTCs. After inhibition of miR-135b or miR135a which were the most significantly increased in BTSCs, cell viability, self-renewal and stem cell marker expression decreased remarkably. Through integrated analysis of mRNAs and miRNAs data, we found that angiomotin-like 2 (AMOTL2), which was significantly decreased, was targeted by both miR-135b and miR-135a. STAT6 and GPX8 were targeted only by miR-135a. Importantly, low expression of AMOTL2 was significantly associated with overall poor survival in paediatric Group 3 and Group 4 medulloblastoma patients.

Conclusion

Our results indicated that inhibition of miR-135b or miR-135a leads to suppress stemness of BTSC through modulation of AMOTL2.

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.

Concentrated growth factor promotes gingival regeneration through the AKT/Wnt/β-catenin and YAP signaling pathways

Although concentrated growth factor (CGF) is known to promote gingival regeneration and improve the outcomes of clinical treatment, the mechanisms underlying its effects remain unknown. Therefore, this study aimed to elucidate the effects of CGF on gingival thickening. To this end, gingival mesenchymal stem cells (GMSCs) were treated with different concentrations of CGF, and the effects of CGF on cell proliferation and migration; collagen-1 (Col-1), fibronectin (FN), vascular endothelial growth factor (VEGF), and angiopoietin-1 (Ang-1) expression; and the AKT, Wnt/β-catenin, and Yes-associated protein (YAP) signalling pathways were investigated. The effects of CGF in vivo were also investigated in a rat buccal gingival injection model. GMSCs cultured with CGF showed improved cell proliferation and migration. Moreover, CGF treatment improved the levels of FN, Col-1, VEGF, and ANG-1. These effects of CGF were mediated by the AKT/Wnt and YAP pathways, with the AKT pathway possibly functioning upstream of the Wnt/β-catenin and YAP pathways. YAP was also shown to be overexpressed in the in vivo model. Thus, CGF can promote gingival regeneration, and YAP transport into the nucleus may be a key factor underlying this activity, which provides a novel perspective for gingival regeneration and further promotion of the clinical application of CGF.

Computational Structural Biology: Successes, Future Directions, and Challenges

Computational biology has made powerful advances. Among these, trends in human health have been uncovered through heterogeneous 'big data' integration, and disease-associated genes were identified and classified. Along a different front, the dynamic organization of chromatin is being elucidated to gain insight into the fundamental question of genome regulation. Powerful conformational sampling methods have also been developed to yield a detailed molecular view of cellular processes. when combining these methods with the advancements in the modeling of supramolecular assemblies, including those at the membrane, we are finally able to get a glimpse into how cells' actions are regulated. Perhaps most intriguingly, a major thrust is on to decipher the mystery of how the brain is coded. Here, we aim to provide a broad, yet concise, sketch of modern aspects of computational biology, with a special focus on computational structural biology. We attempt to forecast the areas that computational structural biology will embrace in the future and the challenges that it may face. We skirt details, highlight successes, note failures, and map directions.

High Risk of Hepatocellular Carcinoma Development in Fibrotic Liver: Role of the Hippo-YAP/TAZ Signaling Pathway

Liver cancer is the fourth leading cause of cancer-related death globally, accounting for approximately 800,000 deaths annually. Hepatocellular carcinoma (HCC) is the most common type of liver cancer, making up about 80% of cases. Liver fibrosis and its end-stage disease, cirrhosis, are major risk factors for HCC. A fibrotic liver typically shows persistent hepatocyte death and compensatory regeneration, chronic inflammation, and an increase in reactive oxygen species, which collaboratively create a tumor-promoting microenvironment via inducing genetic alterations and chromosomal instability, and activating various oncogenic molecular signaling pathways. In this article, we review recent advances in fields of liver fibrosis and carcinogenesis, and consider several molecular signaling pathways that promote hepato-carcinogenesis under the microenvironment of liver fibrosis. In particular, we pay attention to emerging roles of the Hippo-YAP/TAZ signaling pathway in stromal activation, hepatic fibrosis, and liver cancer.