The Hippo pathway in normal development and cancer

Regulation of Hippo-YAP signaling by insulin-like growth factor-1 receptor in the tumorigenesis of diffuse large B-cell lymphoma

Background

Hippo-Yes-associated protein (YAP) signaling is a key regulator of organ size and tumorigenesis, yet the underlying molecular mechanism is still poorly understood. At present, the significance of the Hippo-YAP pathway in diffuse large B-cell lymphoma (DLBCL) is ill-defined.

Methods

The expression of YAP in DLBCL was determined in public database and clinical specimens. The effects of YAP knockdown, CRISPR/Cas9-mediated YAP deletion, and YAP inhibitor treatment on cell proliferation and the cell cycle were evaluated both in vitro and in vivo. RNA sequencing was conducted to detect dysregulated RNAs in YAP-knockout DLBCL cells. The regulatory effects of insulin-like growth factor-1 receptor (IGF-1R) on Hippo-YAP signaling were explored by targeted inhibition and rescue experiments.

Results

High expression of YAP was significantly correlated with disease progression and poor prognosis. Knockdown of YAP expression suppressed cell proliferation and induced cell cycle arrest in DLBCL cells. Verteporfin (VP), a benzoporphyrin derivative, exerted an anti-tumor effect by regulating the expression of YAP and the downstream target genes, CTGF and CYR61. In vitro and in vivo studies revealed that deletion of YAP expression with a CRISPR/Cas9 genome editing system significantly restrained tumor growth. Moreover, downregulation of IGF-1R expression led to a remarkable decrease in YAP expression. In contrast, exposure to IGF-1 promoted YAP expression and reversed the inhibition of YAP expression induced by IGF-1R inhibitors.

Conclusions

Our study highlights the critical role of YAP in the pathogenesis of DLBCL and uncovers the regulatory effect of IGF-1R on Hippo-YAP signaling, suggesting a novel therapeutic strategy for DLBCL.

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.

Targeted Disruption of Lats1 and Lats2 in Mice Impairs Adrenal Cortex Development and Alters Adrenocortical Cell Fate

It has recently been shown that the loss of the Hippo signaling effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in adrenocortical steroidogenic cells impairs the postnatal maintenance of the adrenal gland. To further explore the role of Hippo signaling in mouse adrenocortical cells, we conditionally deleted the key Hippo kinases large tumor suppressor homolog kinases 1 and -2 (Lats1 and Lats2, two kinases that antagonize YAP and TAZ transcriptional co-regulatory activity) in steroidogenic cells using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that developing adrenocortical cells adopt characteristics of myofibroblasts in both male and female Lats1flox/flox;Lats2flox/flox;Nr5a1-cre mice, resulting in a loss of steroidogenic gene expression, adrenal failure and death by 2 to 3 weeks of age. A marked accumulation of YAP and TAZ in the nuclei of the myofibroblast-like cell population with an accompanying increase in the expression of their transcriptional target genes in the adrenal glands of Lats1flox/flox;Lats2flox/flox;Nr5a1-cre animals suggested that the myofibroblastic differentiation could be attributed in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper adrenocortical cell differentiation and suppresses their differentiation into myofibroblast-like cells.

Polyethylenimine-dextran-coated magnetic nanoparticles loaded with miR-302b suppress osteosarcoma in vitro and in vivo

Aim: We attempted to synthesize a magnetic gene carrier with poly(ethylenimine), dextran and iron oxide nanoparticles (PDIs) for miR-302b transfection in vitro and in vivo. Materials & methods: The nanoparticles were characterized for hydrodynamic properties, ζ potential and DNA-binding ability, evaluated by transmission electron microscopy. Cellular internalization, magnetofection efficiency and anti-osteosarcoma effects were investigated in osteosarcoma (OS) cells and OS-bearing nude mice. Results: PDIs were successfully prepared and showed mild cytotoxicity. A magnetic field efficiently enabled transport of PDI/pmiR302b to OS cells in OS-bearing nude mice, exerting the anti-osteosarcoma effect of miR-302b at the tumor site. The inhibitory effect of miR-302b on osteosarcoma-bearing nude mice may be attributed to regulation of the Hippo pathway through YOD1. Conclusion: Low-cytotoxic PDIs have potential applications as a magnetic transport carrier for future osteosarcoma treatment.

Astrocytic YAP Promotes the Formation of Glia Scars and Neural Regeneration after Spinal Cord Injury

Yes-associated protein (YAP) transcriptional coactivator is negatively regulated by the Hippo pathway and functions in controlling the size of multiple organs, such as liver during development. However, it is not clear whether YAP signaling participates in the process of the formation of glia scars after spinal cord injury (SCI). In this study, we found that YAP was upregulated and activated in astrocytes of C57BL/6 male mice after SCI in a Hippo pathway-dependent manner. Conditional knockout (KO) of yap in astrocytes significantly inhibited astrocytic proliferation, impaired the formation of glial scars, inhibited the axonal regeneration, and impaired the behavioral recovery of C57BL/6 male mice after SCI. Mechanistically, the bFGF was upregulated after SCI and induced the activation of YAP through RhoA pathways, thereby promoting the formation of glial scars. Additionally, YAP promoted bFGF-induced proliferation by negatively controlling nuclear distribution of p27^Kip1 mediated by CRM1. Finally, bFGF or XMU-MP-1 (an inhibitor of Hippo kinase MST1/2 to activate YAP) injection indeed activated YAP signaling and promoted the formation of glial scars and the functional recovery of mice after SCI. These findings suggest that YAP promotes the formation of glial scars and neural regeneration of mice after SCI, and that the bFGF-RhoA-YAP-p27^Kip1 pathway positively regulates astrocytic proliferation after SCI.SIGNIFICANCE STATEMENT Glial scars play critical roles in neuronal regeneration of CNS injury diseases, such as spinal cord injury (SCI). Here, we provide evidence for the function of Yes-associated protein (YAP) in the formation of glial scars after SCI through regulation of astrocyte proliferation. As a downstream of bFGF (which is upregulated after SCI), YAP promotes the proliferation of astrocytes through negatively controlling nuclear distribution of p27^Kip1 mediated by CRM1. Activation of YAP by bFGF or XMU-MP-1 injection promotes the formation of glial scar and the functional recovery of mice after SCI. These results suggest that the bFGF-RhoA-YAP-p27^Kip1 axis for the formation of glial scars may be a potential therapeutic strategy for SCI patients.

YAP1 is an independent prognostic marker in pancreatic cancer and associated with extracellular matrix remodeling

BACKGROUND

Pancreatic cancer is a major cause of cancer-related mortality. The identification of effective biomarkers is essential in order to improve management of the disease. Yes-associated protein 1 (YAP1) is a downstream effector of the Hippo pathway, a signal transduction system implicated in tissue repair and regeneration, as well as tumorigenesis. Here we evaluate the biomarker potential of YAP1 in pancreatic cancer tissue.

METHODS

YAP1 was selected as a possible biomarker for pancreatic cancer from global protein sequencing of fresh frozen pancreatic cancer tissue samples and normal pancreas controls. The prognostic utility of YAP1 was evaluated using mRNA expression data from 176 pancreatic cancer patients in The Cancer Genome Atlas (TCGA), as well as protein expression data from immunohistochemistry analysis of a local tissue microarray (TMA) cohort comprising 140 pancreatic cancer patients. Ingenuity Pathway Analysis was applied to outline the interaction network for YAP1 in connection to the pancreatic tumor microenvironment. The expression of YAP1 target gene products was evaluated after treatment of the pancreatic cancer cell line Panc-1 with three substances interrupting YAP-TEAD interaction, including Super-TDU, Verteporfin and CA3.

RESULTS

Mass spectrometry based proteomics showed that YAP1 is the top upregulated protein in pancreatic cancer tissue when compared to normal controls (log2 fold change 6.4; p = 5E-06). Prognostic analysis of YAP1 demonstrated a significant correlation between mRNA expression level data and reduced overall survival (p = 0.001). In addition, TMA and immunohistochemistry analysis suggested that YAP1 protein expression is an independent predictor of poor overall survival [hazard ratio (HR) 1.870, 95% confidence interval (CI) 1.224-2.855, p = 0.004], as well as reduced disease-free survival (HR 1.950, 95% CI 1.299-2.927, p = 0.001). Bioinformatic analyses coupled with in vitro assays indicated that YAP1 is involved in the transcriptional control of target genes, associated with extracellular matrix remodeling, which could be modified by selected substances disrupting the YAP1-TEAD interaction.

CONCLUSIONS

Our findings indicate that YAP1 is an important prognostic biomarker for pancreatic cancer and may play a regulatory role in the remodeling of the extracellular matrix.

Autocrine CXCL8-dependent invasiveness triggers modulation of actin cytoskeletal network and cell dynamics

Glioblastoma (GB) is the most representative form of primary malignant brain tumour. Several studies indicated a pleiotropic role of CXCL8 in cancer due to its ability to modulate the tumour microenvironment, growth and aggressiveness of tumour cell. Previous studies indicated that CXCL8 by its receptors (CXCR1 and CXCR2) induced activation of the PI3K/p-Akt pathway, a crucial event in the regulation of cytoskeleton rearrangement and cell mobilization. Human GB primary cell culture and U-87MG cell line were used to study the effects of CXCR1 and CXCR2 blockage, by a dual allosteric antagonist, on cell migration and cytoskeletal dynamics. The data obtained point towards a specific effect of autocrine CXCL8 signalling on GB cell invasiveness by the activation of pathways involved in cell migration and cytoskeletal dynamics, such as PI3K/p-Akt/p-FAK, p-cortactin, RhoA, Cdc42, Acetylated α-tubulin and MMP2. All the data obtained support the concept that autocrine CXCL8 signalling plays a key role in the activation of an aggressive phenotype in primary glioblastoma cells and U-87MG cell line. These results provide new insights about the potential of a pharmacological approach targeting CXCR1/CXCR2 pathways to decrease migration and invasion of GB cells in the brain parenchyma, one of the principal mechanisms of recurrence.

Gli1 interacts with YAP1 to promote tumorigenesis in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the predominant esophageal cancer type in China. The aberrant activation of glioma-associated oncogene homolog1 (Gli1), a key factor in Hedgehog (Hh) signaling pathway, has been found in esophageal carcinoma. Moreover, Yes-associated protein 1 (YAP1), the major mediator of Hippo signaling pathway, has been linked to esophageal carcinoma progression. However, the precise roles and the underlying mechanism of both Gli1 and YAP1 in ESCC are unclear. Here, we found that Gli1 and YAP1 are overexpressed in ESCC and are associated with poor prognosis. In addition, we confirmed that knockdown of Gli1 or YAP1 suppresses ESCC cell growth, migration, and invasion in ESCC TE1 and EC109 cells. Significantly, Gli1 interacts with YAP1 in ESCC cells. Both Gli1 and YAP1 proteins are closely correlated with each other in human ESCC samples. Mechanistically, Gli1 upregulates YAP1 in a LATS1-independent manner. Conversely, YAP1 induces Gli1 by regulating phosphoinositide 3-kinase (PI3K)/AKT signaling pathway. Most importantly, we demonstrated that the interaction between Gli1 and YAP1 promotes ESCC tumor growth in vitro and in vivo. Our findings established a novel signaling mechanism by which the interaction between Gli1 and YAP1 promotes ESCC cell growth. This signaling regulation of the tumorigenesis provides a new therapeutic strategy for highly lethal ESCC.

Resveratrol Inhibits the Tumorigenesis of Follicular Thyroid Cancer via ST6GAL2-Regulated Activation of the Hippo Signaling Pathway

Follicular thyroid carcinoma (FTC) is a common endocrine malignancy with highly aggressive features. In this study, next-generation sequencing technology was used to identify aberrant expression of sialyltransferase (ST) family members in FTC. Aberrant high expression of alpha-2,6-sialyltransferase 2 (ST6GAL2) was demonstrated to promote tumorigenesis of FTC in vitro and in vivo. Furthermore, ST6GAL2 promoted tumorigenesis by inactivating the Hippo signaling pathway. Resveratrol is a native compound extracted from Vitis species, and many studies have confirmed its protective cardiovascular and antineoplastic effects. Here we found that resveratrol can inhibit the tumorigenesis of FTC by suppressing the expression of ST6GAL2, further activating the Hippo pathway. In summary, this study revealed the role of the ST6GAL2-Hippo signaling pathway in FTC tumorigenesis and indicated that resveratrol, a commonly found antineoplastic compound, could inhibit tumorigenesis of FTC by regulating the abovementioned pathways.

Melatonin triggers autophagic cell death by regulating RORC in Hodgkin lymphoma

Melatonin (Mel) has been shown to involve in many essential cell functions via modulating many signaling pathways. We for the first time investigated that Mel exerted anti-tumor activities in Hodgkin lymphoma (HL) via inhibiting cell proliferation and promoting cell apoptosis. Further study revealed that Mel treatment increased expression of LC3-II and decreased p62 proteins with the enhanced production of autolysosome, indicating it induced activation of autophagy. Nevertheless, Mel treatment together with autophagy inhibitors 3-MA or CQ exacerbated the damage effect of Mel in HL cells, which means autophagy plays a protective role in this process. Furthermore, we found Mel treatment increased the expression of G protein-coupled receptors MT2 and retinoic acid-related orphan receptors (RORs), eg. RORA, RORB and RORC. While RORC has the highest increase in Mel treated HL cells. In addition, RORC overexpression induced autophagy activation. Therefore, Mel showed tumor-suppressive role due to an increased level of RORC induced autophagy in HL.

Essential Oil from Pinus Koraiensis Pinecones Inhibits Gastric Cancer Cells via the HIPPO/YAP Signaling Pathway

Pinecone is a traditional folk herb, which has been used in China for many years. In this paper, the essential oil from Pinus koraiensis pinecones (PEO) was obtained by hydrodistillation and 41 compounds were identified by gas chromatography–mass spectrometry (GC-MS), mainly including α-Pinene (40.91%), Limonene (24.82%), and β-Pinene (7.04%). The purpose of this study was to investigate the anti-tumor activity of PEO on MGC-803 cells and its mechanism. Anti-tumor experiments in vitro showed PEO could significantly inhibit the proliferation and migration of MGC-803 cells, and it also could arrest the cell cycle in the G2/M phase, decrease the mitochondrial membrane potential, and induce apoptosis. Finally, the effects of PEO on genes expression on MGC-803 cells were analyzed by RNA sequencing, and results showed that after treatment with PEO, 100 genes were up-regulated, and 57 genes were down-regulated. According to the KEGG pathway and GSEA, FAT4, STK3, LATS2, YAP1, and AJUBA were down-regulated, which were related to HIPPO signaling pathway. Real-time PCR and western blot further confirmed the results of RNA sequencing. These results indicated that PEO may exert anti-tumor activity via the HIPPO/YAP signaling pathway. The anti-tumor mechanism of this oil can be further studied, which is important for the development of anti-tumor drugs.

Targeting YAP to overcome acquired resistance to ALK inhibitors in ALK-rearranged lung cancer

Clinical benefit of ALK tyrosine kinase inhibitors (ALK‐TKIs) in ALK‐rearranged lung cancer has been limited by the inevitable development of acquired resistance, and bypass‐molecular resistance mechanisms remain poorly understood. We investigated a novel therapeutic target through screening FDA‐approved drugs in ALK‐TKI‐resistant models. Cerivastatin, the rate‐limiting enzyme inhibitor of the mevalonate pathway, showed anti‐cancer activity against ALK‐TKI resistance in vitro/in vivo, accompanied by cytoplasmic retention and subsequent inactivation of transcriptional co‐regulator YAP. The marked induction of YAP‐targeted oncogenes (EGFR, AXL, CYR61, and TGFβR2) in resistant cells was abolished by cerivastatin. YAP silencing suppressed tumor growth in resistant cells, patient‐derived xenografts, and EML4‐ALK transgenic mice, whereas YAP overexpression decreased the responsiveness of parental cells to ALK inhibitor. In matched patient samples before/after ALK inhibitor treatment, nuclear accumulation of YAP was mainly detected in post‐treatment samples. High expression of YAP in pretreatment samples was correlated with poor response to ALK‐TKIs. Our findings highlight a crucial role of YAP in ALK‐TKI resistance and provide a rationale for targeting YAP as a potential treatment option for ALK‐rearranged patients with acquired resistance to ALK inhibitors.

Identification of Celastrol as a Novel YAP-TEAD Inhibitor for Cancer Therapy by High Throughput Screening with Ultrasensitive YAP/TAZ-TEAD Biosensors

The Hippo pathway has emerged as a key signaling pathway that regulates a broad range of biological functions, and dysregulation of the Hippo pathway is a feature of a variety of cancers. Given this, some have suggested that disrupting the interaction of the Hippo core component YAP and its paralog TAZ with transcriptional factor TEAD may be an effective strategy for cancer therapy. However, there are currently no clinically available drugs targeting the YAP/TAZ–TEAD interaction for cancer treatment. To facilitate screens for small molecule compounds that disrupt the YAP–TEAD interaction, we have developed the first ultra-bright NanoLuc biosensor to quantify YAP/TAZ–TEAD protein–protein interaction (PPI) both in living cells and also in vitro using biosensor fusion proteins purified from bacteria. Using this biosensor, we have performed an in vitro high throughput screen (HTS) of small molecule compounds and have identified and validated the drug Celastrol as a novel inhibitor of YAP/TAZ–TEAD interaction. We have also demonstrated that Celastrol can inhibit cancer cell proliferation, transformation, and cell migration. In this study, we describe a new inhibitor of the YAP/TAZ–TEAD interaction warranting further investigation and offer a novel biosensor tool for the discovery of other new Hippo-targeting drugs in future work.

High expression of the transcriptional coactivator TAZ is associated with a worse prognosis and affects cell proliferation in patients with medulloblastoma

The transcriptional coactivator tafazzin (TAZ) serves pivotal roles in organ development, tumor initiation and tumor progression. However, to the best of our knowledge, the expression of TAZ and its clinical significance in human medulloblastoma have not been defined. The present study aimed to clarify the clinical and biological significance of TAZ expression in human medulloblastoma. Immunohistochemical staining for TAZ was performed with 72 medulloblastoma and three normal brain tissue samples. A high expression level of TAZ was detected in 65.28% of medulloblastoma tissues, whereas low expression was identified in the normal brain tissues. TAZ expression was significantly associated with medulloblastoma recurrence. However, the expression of TAZ was not associated with sex, age, tumor location, tumor maximal diameter and tumor histology. Furthermore, both the overall survival and tumor-free survival rate of patients with high levels of expression of TAZ were shorter compared with those of patients with tumors expressing low levels of TAZ. In univariate and multivariate Cox regression analyses, TAZ expression was identified as a significant prognostic factor for patients with medulloblastoma. Functionally, downregulation of TAZ inhibited the proliferation and tumor formation of medulloblastoma cells and the expression of cell-cycle associated proteins in Daoy cells. In conclusion, high expression of TAZ may serve as a prognostic marker for patients with medulloblastoma and TAZ may be a potential target for medulloblastoma therapy.

A New Regulatory Mechanism Between P53 And YAP Crosstalk By SIRT1 Mediated Deacetylation To Regulate Cell Cycle And Apoptosis In A549 Cell Lines

Background

Yes-associated protein (YAP) is downstream of the Hippo signaling pathway, which regulates several cellular processes. P53 is a key transcriptional regulator that responds to a variety of cellular stresses and regulates key cellular processes such as DNA repair, cell-cycle progression, angiogenesis, and apoptosis. Overexpression of YAP antagonizes P53 activity and targets its expression. However, the mechanism that underlies the post-transcriptional crosstalk between P53 and YAP has not been well dissected.

Methods

We performed an integrated analysis and found that SIRT1 is a key candidate that connects YAP and P53 by modulating their acetylation.

Results

We found that YAP promotes P53 deacetylation, promotes cell survival by inhibiting P53-induced G0/G1 arrest and apoptosis in A549 cells. Conversely, P53 enhances YAP acetylation, and decreases A549 cell survival by strengthening YAP acetylation-induced G0/G1 arrest and apoptosis both in vitro and in vivo.

Conclusion

Our results demonstrate that SIRT1 is responsible for YAP and P53 deacetylation of specific residues, and reveal for the first time, a new regulatory mechanism of P53 and YAP crosstalk by SIRT1-mediated deacetylation, which may be involved in lung tumorigenesis.

Post-translational inhibition of YAP oncogene expression by 4-hydroxynonenal in bladder cancer cells

The transcriptional regulator YAP plays an important role in cancer progression and is negatively controlled by the Hippo pathway. YAP is frequently overexpressed in human cancers, including bladder cancer. Interestingly, YAP expression and activity can be inhibited by pro-oxidant conditions; moreover, YAP itself can also affect the cellular redox status through multiple mechanisms. 4-Hydroxynonenal (HNE), the most intensively studied end product of lipid peroxidation, is a pro-oxidant agent able to deplete GSH and has an anti-tumoral effect by affecting multiple signal pathways, including the down-regulation of oncogene expressions. These observations prompted us to investigate the effect of HNE on YAP expression and activity. We demonstrated that HNE inhibited YAP expression and its target genes in bladder cancer cells through a redox-dependent mechanism. Moreover, the YAP down-regulation was accompanied by an inhibition of proliferation, migration, invasion, and angiogenesis, as well as by an accumulation of cells in the G2/M phase of cell cycle and by an induction of apoptosis. We also established the YAP role in inhibiting cell viability and inducing apoptosis in HNE-treated cells by using an expression vector for YAP. Furthermore, we identified a post-translational mechanism for the HNE-induced YAP expression inhibition, involving an increase of YAP phosphorylation and ubiquitination, leading to proteasomal degradation. Our data established that HNE can post-translationally down-regulate YAP through a redox-dependent mechanism and that this modulation can contribute to determining the specific anti-cancer effects of HNE.

Knockdown of YAP inhibits growth in Hep-2 laryngeal cancer cells via epithelial-mesenchymal transition and the Wnt/β-catenin pathway

BACKGROUND

Yes-associated protein (YAP) plays a crucial role in tumour development and it is the main effector of the Hippo signalling pathway. However, the mechanism underlying YAP downregulation in laryngeal cancer is still unclear. In our previous study, we found that YAP, compared with adjacent tissues, was expressed higher in laryngeal cancer and was also closely associated with histological differentiation, TNM stage and poor prognosis.

METHODS

In this study, we attempted to determine whether silenced YAP could downregulate human laryngeal carcinoma Hep-2 cells progression. YAP was downregulated in Hep-2 cells by shRNA, and the malignant ability of Hep-2 was assessed in vitro and in vivo.

RESULTS

In vitro, CCK-8, colony formation and wound healing assays showed that downregulation of YAP significantly reduced the rates of proliferation, migration, and invasion in Hep-2 cells. Downregulation of YAP distinctly induced G2/M cycle arrest and increased the rate of apoptosis. Accordingly, western blot assay suggested that the expression of DKK1, vimentin and β-catenin was significantly decreased after YAP downregulated treatment, thereby indicating that YAP mediated the EMT programme and the Wnt/β-catenin signalling pathway in carcinoma of the larynx. Furthermore, silencing of YAP suppressed Hep-2 cell tumourigenesis and metastasis in vivo.

CONCLUSION

In summary, our findings demonstrated the proliferation of YAP downregulation and the invasion of Hep-2 cells via downregulating the Wnt/β-catenin pathway in vitro and in vivo, suggesting that YAP may provide a potential therapeutic strategy for the treatment of laryngeal cancer.

PLEKHO1 knockdown inhibits RCC cell viability in vitro and in vivo, potentially by the Hippo and MAPK/JNK pathways

Renal cell carcinoma (RCC) is the most common type of kidney cancer. By analysing The Cancer Genome Atlas (TCGA) database, 16 genes were identified to be consistently highly expressed in RCC tissues compared with the matched para‑tumour tissues. Using a high‑throughput cell viability screening method, it was found that downregulation of only two genes significantly inhibited the viability of 786‑O cells. Among the two genes, pleckstrin homology domain containing O1 (PLEKHO1) has never been studied in RCC, to the best of our knowledge, and its expression level was shown to be associated with the prognosis of patients with RCC in TCGA dataset. The upregulation of PLEKHO1 in RCC was first confirmed in 30 paired tumour and para‑tumour tissues. Then, the effect of PLEKHO1 on cell proliferation and apoptosis was assessed in vitro. Additionally, xenograft tumour models were established to investigate the function of PLEKHO1 in vivo. The results showed that PLEKHO1 knockdown significantly inhibited cell viability and facilitated apoptosis in vitro and impaired tumour formation in vivo. Thus, PLEKHO1 is likely to be associated with the viability of RCC cells in vitro and in vivo. Further gene expression microarray and co‑expression analyses showed that PLEKHO1 may be involved in the serine/threonine‑protein kinase hippo and JNK signalling pathways. Together, the results of the present study suggest that PLEKHO1 may contribute to the development of RCC, and therefore, further study is needed to explore its potential as a therapeutic target.

Jiedu Sangen Decoction Inhibits the Invasion and Metastasis of Colorectal Cancer Cells by Regulating EMT through the Hippo Signaling Pathway

Colorectal cancer (CRC) is one of the most common malignant tumors affecting the digestive tract. Moreover, the invasion and metastasis of CRC are the main reason therapy is usually inefficient. Decreased intercellular adhesion and enhanced cell motility induced by epithelial-mesenchymal transition (EMT) provide the basic conditions for the invasion and metastasis of the epithelial tumor cells of CRC. The Jiedu Sangen Decoction (JSD) is a prescription that has been used for more than 50 years in the treatment of CRC in the Zhejiang Hospital of Traditional Chinese Medicine. The aim of this study was to investigate the mechanism of JSD-triggered inhibition of invasion and metastasis in colon cancer. In vitro, the EMT model of the SW480 cells was induced by using epithelial growth factor (50 ng/mL). In vivo, the murine model of liver metastasis was constructed by inoculating mice with the SW480 cells. The effects of JSD on cell migration, invasion, and proliferation were determined using the transwell assay and CCK-8 assay. Moreover, the proteins related to the EMT process and the Hippo signaling pathway in the cancerous tissues and cell lines were determined by western blotting and immunostaining. JSD could significantly inhibit the proliferation, migration, and invasion of CRC cells and reverse their EMT status (all, P < 0.05). Moreover, after intervention with JSD, the levels of E-Cadherin (E-cad) increased, whereas the expression levels of N-Cadherin (N-cad), Yes-associated protein (YAP), and the transcriptional coactivator with the PDZ-binding motif (TAZ) decreased in both the SW480 cells and the tumor tissues. In summary, JSD reversed EMT and inhibited the invasion and metastasis of CRC cells through the Hippo signaling pathway.

SOX9 promotes epithelial-mesenchymal transition via the Hippo-YAP signaling pathway in gastric carcinoma cells

SRY-box 9 (SOX9) is overexpressed in a number of human tumors, including gastric cancer (GC). However, the function of SOX9 in the development of GC remains unknown. In the present study, SOX9 activated the Hippo-yes-associated protein (YAP) signaling pathway to enhance the epithelial-mesenchymal transition in GC cell lines. The results suggested that SOX9 knockdown inhibited invasion, proliferation and migration of GC cells. Furthermore, SOX9 silencing upregulated the expression of E-cadherin, an epithelial marker, and downregulated the expression of mesenchymal markers, including snail family transcriptional repressor 1, vimentin and N-cadherin. SOX9 overexpression increased the expression of the aforementioned markers. SOX9 significantly affected YAP phosphorylation and total YAP protein levels, suggesting that SOX9 is involved in the Hippo-YAP signaling pathway. The current study revealed that SOX9 may be involved in the pathogenesis of GC, and further elucidation of the pathways involved may support the development of novel therapeutic options for the treatment of GC.

Mitophagy and Oxidative Stress in Cancer and Aging: Focus on Sirtuins and Nanomaterials

Mitochondria are the cellular center of energy production and of several important metabolic processes. Mitochondrion health is maintained with a substantial intervention of mitophagy, a process of macroautophagy that degrades selectively dysfunctional and irreversibly damaged organelles. Because of its crucial duty, alteration in mitophagy can cause functional and structural adjustment in the mitochondria, changes in energy production, loss of cellular adaptation, and cell death. In this review, we discuss the dual role that mitophagy plays in cancer and age-related pathologies, as a consequence of oxidative stress, evidencing the triggering stimuli and mechanisms and suggesting the molecular targets for its therapeutic control. Finally, a section has been dedicated to the interplay between mitophagy and therapies using nanoparticles that are the new frontier for a direct and less invasive strategy.

The Ambivalent Function of YAP in Apoptosis and Cancer

Yes-associated protein, a core regulator of the Hippo-YAP signaling pathway, plays a vital role in inhibiting apoptosis. Thus, several studies and reviews suggest that yes-associated protein is a good target for treating cancer. Unfortunately, more and more evidence demonstrates that this protein is also an essential contributor of p73-mediated apoptosis. This questions the concept that yes-associated protein is always a good target for developing novel anti-cancer drugs. Thus, the aim of this review was to evaluate the clinical relevance of yes-associated protein for cancer pathophysiology. This review also summarized the molecules, processes and drugs, which regulate Hippo-YAP signaling and discusses their effect on apoptosis. In addition, issues are defined, which should be addressed in the future in order to provide a solid basis for targeting the Hippo-YAP signaling pathway in clinical trials.

Biomechanical Characterization at the Cell Scale: Present and Prospects

The rapidly growing field of mechanobiology demands for robust and reproducible characterization of cell mechanical properties. Recent achievements in understanding the mechanical regulation of cell fate largely rely on technological platforms capable of probing the mechanical response of living cells and their physico–chemical interaction with the microenvironment. Besides the established family of atomic force microscopy (AFM) based methods, other approaches include optical, magnetic, and acoustic tweezers, as well as sensing substrates that take advantage of biomaterials chemistry and microfabrication techniques. In this review, we introduce the available methods with an emphasis on the most recent advances, and we discuss the challenges associated with their implementation.

Loss of HACE1 promotes colorectal cancer cell migration via upregulation of YAP1

Colorectal cancer (CRC) is the third-leading cause of cancer mortality worldwide. HACE1 function as a tumor-suppressor gene and is downregulated in several kinds of cancers. However, the distribution and clinical significance of HACE1 in CRC is still not clarified. In this study, we found that the HACE1 expression is greatly downregulated in CRC tissues and cell lines. Moreover, the HACE1 expression was significantly associated with inhibition of CRC cell proliferation, metastasis, and invasion. HACE1 inhibited epithelial-mesenchymal transition in CRC cells. Furthermore, we found that HACE1 altered the protein expression of the Hippo pathway by downregulation of YAP1. HACE1 suppresses the invasive ability of CRC cells by negatively regulating the YAP1 pathway. Our data indicates that HACE1 directly targets YAP1 and induces downregulation of YAP1, thereby increasing the activity of the Hippo pathway. In summary, these findings demonstrated that HACE1-YAP1 axis had an important part in the CRC development and progression.

Monitoring Hippo Signaling Pathway Activity Using a Luciferase-based Large Tumor Suppressor (LATS) Biosensor

The Hippo signaling pathway is a conserved regulator of organ size and has important roles in the development and cancer biology. Due to technical challenges, it remains difficult to assess the activity of this signaling pathway and interpret it within a biological context. The existing literature on large tumor suppressor (LATS) relies on methods that are qualitative and cannot easily be scaled-up for screening. Recently, we have developed a bioluminescence-based biosensor to monitor the kinase activity of LATS-a core component of the Hippo kinase cascade. Here, we describe procedures for how this LATS biosensor (LATS-BS) can be used to characterize Hippo pathway regulators. First, we provide a detailed protocol for investigating the effect of an overexpressed protein candidate (e.g., VEGFR2) on LATS activity using the LATS-BS. Then, we show how the LATS-BS can be used for a small-scale kinase inhibitor screen. This protocol can feasibly be scaled-up to perform larger screens, which undoubtedly will identify novel regulators of the Hippo pathway.

Coexisting YAP expression and TP53 missense mutations delineates a molecular scenario unexpectedly associated with better survival outcomes in advanced gastric cancer

We have previously reported that nuclear expression of the Hippo transducer TAZ in association with Wnt pathway mutations negatively impacts survival outcomes in advanced gastric cancer (GC) patients. Here, we extended these previous findings by investigating another oncogenic cooperation, namely, the interplay between YAP, the TAZ paralogue, and p53. The molecular output of the YAP-p53 cooperation is dependent on TP53 mutational status. In the absence of mutations, the YAP-p53 crosstalk elicits a pro-apoptotic response, whereas in the presence of TP53 mutations it activates a pro-proliferative transcriptional program. In order to study this phenomenon, we re-analyzed data from 83 advanced GC patients treated with chemotherapy whose tissue samples had been characterized for YAP expression (immunohistochemistry, IHC) and TP53 mutations (deep sequencing). In doing so, we generated a molecular model combining nuclear YAP expression in association with TP53 missense variants (YAP+/TP53^mut(mv)). Surprisingly, this signature was associated with a decreased risk of disease progression (multivariate Cox for progression-free survival: HR 0.53, 95% CI 0.30–0.91, p = 0.022). The YAP+/TP53^mut(mv) model was also associated with better OS in the subgroup of patients who received chemotherapy beyond the first-line setting (multivariate Cox: HR 0.36, 95% CI 0.16–0.81, p = 0.013). Collectively, our findings suggest that the oncogenic cooperation between YAP and mutant p53 may translate into better survival outcomes. This apparent paradox can be explained by the pro-proliferative program triggered by YAP and mutant p53, that supposedly renders cancer cells more vulnerable to cytotoxic therapies.

The role of YAP/TAZ activity in cancer metabolic reprogramming

In contrast to normal cells, which use the aerobic oxidation of glucose as their main energy production method, cancer cells prefer to use anaerobic glycolysis to maintain their growth and survival, even under normoxic conditions. Such tumor cell metabolic reprogramming is regulated by factors such as hypoxia and the tumor microenvironment. In addition, dysregulation of certain signaling pathways also contributes to cancer metabolic reprogramming. Among them, the Hippo signaling pathway is a highly conserved tumor suppressor pathway. The core oncosuppressive kinase cascade of Hippo pathway inhibits the nuclear transcriptional co-activators YAP and TAZ, which are the downstream effectors of Hippo pathway and oncogenic factors in many solid cancers. YAP/TAZ function as key nodes of multiple signaling pathways and play multiple regulatory roles in cancer cells. However, their roles in cancer metabolic reprograming are less clear. In the present review, we examine progress in research into the regulatory mechanisms of YAP/TAZ on glucose metabolism, fatty acid metabolism, mevalonate metabolism, and glutamine metabolism in cancer cells. Determining the roles of YAP/TAZ in tumor energy metabolism, particularly in relation to the tumor microenvironment, will provide new strategies and targets for the selective therapy of metabolism-related cancers.

A Hippo Pathway-Related GCK Controls Both Sexual and Vegetative Developmental Processes in the Fungus Sordaria macrospora

The supramolecular striatin-interacting phosphatases and kinases (STRIPAK) complex is conserved from yeast to human, and regulates a variety of key biological processes. In animals, this complex consists of the scaffold protein striatin, the protein phosphatase 2A, and kinases, such as germinal center kinase (GCK) III and GCKIV family members, as well as other associated proteins. The STRIPAK complex was identified as a negative regulator of the Hippo pathway, a large eukaryotic signaling network with a core composed of a GCK and a nuclear Dbf2-related kinase. The signaling architecture of the Hippo core resembles the fungal septation initiation network (SIN) that regulates cytokinesis in fission yeast as well as septation in filamentous fungi. In the filamentous model fungus Sordaria macrospora, core components of the STRIPAK complex have been functionally described and the striatin homolog PRO11 has been shown to interact with the GCK SmKIN3. However, the exact role of SmKIN3 in fungal development has not yet been fully elucidated. Here, we provide comprehensive genetic and functional analysis of SmKIN3 from S. macrospora Using deletion mutants and site-directed mutagenesis, along with phenotypic and phylogenetic analysis, we provide compelling evidence that SmKIN3 is involved in fruiting body formation, hyphal fusion, and septation. Strains carrying the ATP-binding mutant SmKIN3K39R, as well as a double-deletion strain lacking SmKIN3 and the core STRIPAK subunit PRO11, also revealed severe developmental defects. Collectively, this study suggests that SmKIN3 links both the SIN and STRIPAK complex, thereby regulating multiple key cellular processes.