A miR-130a-YAP positive feedback loop promotes organ size and tumorigenesis

Interaction of noncoding RNAs with hippo signaling pathway in cancer cells and cancer stem cells

The Hippo signaling pathway has a regulatory function in the organogenesis process and cellular homeostasis, switching the cascade reactions of crucial kinases acts to turn off/on the Hippo pathway, altering the downstream gene expression and thereby regulating proliferation, apoptosis, or stemness. Disruption of this pathway can lead to the occurrence of various disorders and different types of cancer. Recent findings highlight the importance of ncRNAs, such as microRNA, circular RNA, and lncRNAs, in modulating the Hippo pathway. Defects in ncRNAs can disrupt Hippo pathway balance, increasing tumor cells, tumorigenesis, and chemotherapeutic resistance. This review summarizes ncRNAs' inhibitory or stimulatory role in - Hippo pathway regulation in cancer and stem cells. Identifying the relation between ncRNAs and the components of this pathway could pave the way for developing new biomarkers in the treatment and diagnosis of cancers.

Expression of transforming growth factor β signalling molecules and their correlations with genes in loci linked to polycystic ovary syndrome in human foetal and adult tissues

Context Altered signalling of androgens, anti-Müllerian hormone or transforming growth factor beta (TGFβ) during foetal development have been implicated in the predisposition to polycystic ovary syndrome (PCOS) in later life, aside from its genetic predisposition. In foetal ovarian fibroblasts, TGFβ1 has been shown to regulate androgen signalling and seven genes located in loci associated with PCOS. Since PCOS exhibits a myriad of symptoms, it likely involves many different organs. Aims To identify the relationships between TGFβ signalling molecules and PCOS candidate genes in different tissues associated with PCOS. Methods Using RNA sequencing data, we examined the expression patterns of TGFβ signalling molecules in the human ovary, testis, heart, liver, kidney, brain tissue, and cerebellum from 4 to 20weeks of gestation and postnatally. We also examined the correlations between gene expression of TGFβ signalling molecules and PCOS candidate genes. Key results TGFβ signalling molecules were dynamically expressed in most tissues prenatally and/or postnatally. FBN3 , a PCOS candidate gene involved in TGFβ signalling, was expressed during foetal development in all tissues. The PCOS candidate genes HMGA2, YAP1 , and RAD50 correlated significantly (P TGFBR1 in six out of the seven tissues examined. Conclusions This study suggests that possible crosstalk occurs between genes in loci associated with PCOS and TGFβ signalling molecules in multiple tissues, particularly during foetal development. Implications Thus, alteration in TGFβ signalling during foetal development could affect many tissues contributing to the multiple phenotypes of PCOS in later life.

Repression of developmental transcription factor networks triggers aging-associated gene expression in human glial progenitor cells

Human glial progenitor cells (hGPCs) exhibit diminished expansion competence with age, as well as after recurrent demyelination. Using RNA-sequencing to compare the gene expression of fetal and adult hGPCs, we identify age-related changes in transcription consistent with the repression of genes enabling mitotic expansion, concurrent with the onset of aging-associated transcriptional programs. Adult hGPCs develop a repressive transcription factor network centered on MYC, and regulated by ZNF274, MAX, IKZF3, and E2F6. Individual over-expression of these factors in iPSC-derived hGPCs lead to a loss of proliferative gene expression and an induction of mitotic senescence, replicating the transcriptional changes incurred during glial aging. miRNA profiling identifies the appearance of an adult-selective miRNA signature, imposing further constraints on the expansion competence of aged GPCs. hGPC aging is thus associated with acquisition of a MYC-repressive environment, suggesting that suppression of these repressors of glial expansion may permit the rejuvenation of aged hGPCs.

Potential targets and therapeutics for cancer stem cell-based therapy against drug resistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common digestive malignancyin the world, which is frequently diagnosed at late stage with a poor prognosis. For most patients with advanced HCC, the therapeutic options arelimiteddue to cancer occurrence of drug resistance. Hepatic cancer stem cells (CSCs) account for a small subset of tumor cells with the ability of self-renewal and differentiationin HCC. It is widely recognized that the presence of CSCs contributes to primary and acquired drug resistance. Therefore, hepatic CSCs-targeted therapy is considered as a promising strategy to overcome drug resistance and improve therapeutic outcome in HCC. In this article, we review drug resistance in HCC and provide a summary of potential targets for CSCs-based therapy. In addition, the development of CSCs-targeted therapeuticsagainst drug resistance in HCC is summarized in both preclinical and clinical trials. The in-depth understanding of CSCs-related drug resistance in HCC will favor optimization of the current therapeutic strategies and gain encouraging therapeutic outcomes.

Non-coding RNAs as regulators of the Hippo pathway in cardiac development and cardiovascular disease

Cardiovascular diseases pose a serious threat to human health. The onset of cardiovascular diseases involves the comprehensive effects of multiple genes and environmental factors, and multiple signaling pathways are involved in regulating the occurrence and development of cardiovascular diseases. The Hippo pathway is a highly conserved signaling pathway involved in the regulation of cell proliferation, apoptosis, and differentiation. Recently, it has been widely studied in the fields of cardiovascular disease, cancer, and cell regeneration. Non-coding RNA (ncRNAs), which are important small molecules for the regulation of gene expression in cells, can directly target genes and have diverse regulatory functions. Recent studies have found that ncRNAs interact with Hippo pathway components to regulate myocardial fibrosis, cardiomyocyte proliferation, apoptosis, and hypertrophy and play an important role in cardiovascular disease. In this review, we describe the mode of action of ncRNAs in regulating the Hippo pathway, provide new ideas for further research, and identify molecules involved in the mechanism of action of ncRNAs and the Hippo pathway as potential therapeutic targets, with the aim of finding new modes of action for the treatment and prevention of cardiovascular diseases.

Carnosine regulation of intracellular pH homeostasis promotes lysosome-dependent tumor immunoevasion

Tumor cells and surrounding immune cells undergo metabolic reprogramming, leading to an acidic tumor microenvironment. However, it is unclear how tumor cells adapt to this acidic stress during tumor progression. Here we show that carnosine, a mobile buffering metabolite that accumulates under hypoxia in tumor cells, regulates intracellular pH homeostasis and drives lysosome-dependent tumor immune evasion. A previously unrecognized isoform of carnosine synthase, CARNS2, promotes carnosine synthesis under hypoxia. Carnosine maintains intracellular pH (pHi) homeostasis by functioning as a mobile proton carrier to accelerate cytosolic H+ mobility and release, which in turn controls lysosomal subcellular distribution, acidification and activity. Furthermore, by maintaining lysosomal activity, carnosine facilitates nuclear transcription factor X-box binding 1 (NFX1) degradation, triggering galectin-9 and T-cell-mediated immune escape and tumorigenesis. These findings indicate an unconventional mechanism for pHi regulation in cancer cells and demonstrate how lysosome contributes to immune evasion, thus providing a basis for development of combined therapeutic strategies against hepatocellular carcinoma that exploit disrupted pHi homeostasis with immune checkpoint blockade.

Exosomes derived from adipose tissues accelerate fibroblasts and keratinocytes proliferation and cutaneous wound healing via miR-92a/Hippo-YAP axis

Delayed wound healing is an urgent clinical issue. Cellular communication involving exosome-borne cargo such as miRNA is a critical mechanism involved in wound healing. This study isolated and identified human adipose tissue-derived exosomes (Exo-ATs). The specific effects of Exo-ATs on keratinocytes and fibroblasts were examined. Enriched miRNAs in Exo-ATs were analyzed, and miR-92a-3p was selected. The transfer of Exo-ATs-derived miR-92a-3p to keratinocytes and fibroblasts was verified. miR-92a-3p binding to LATS2 was examined and the dynamic effects of the miR-92a-3p/LATS2 axis were investigated. In a dorsal skin wound model, the in vivo effects of Exo-ATs on wound healing were examined. Exo-AT incubation increased keratinocytes and fibroblast proliferation, migration, and extracellular matrix (ECM) accumulation. miR-92a-3p, enriched in Exo-ATs, could be transferred to keratinocytes and fibroblasts, resulting in enhanced proliferation, migration, and ECM accumulation. Large tumor suppressor kinase 2 (LATS2) was a direct target of miR-92a-3p. miR-92a-3p inhibitor effects on keratinocytes and fibroblasts could be partially reversed by LATS2 knockdown. In a dorsal skin wound model, Exo-ATs accelerated wound healing through enhanced cell proliferation, collagen deposition, re-epithelialization, and YAP/TAZ activation. In conclusion, Exo-ATs improve skin wound healing by promoting keratinocyte and fibroblast migration and proliferation and collagen production by fibroblast, which could be partially eliminated by miR-92a inhibition through its downstream target LATS2 and the YAP/TAZ signaling.

Identification of BRCC3 and BRCA1 as Regulators of TAZ Stability and Activity

TAZ (WWTR1) is a transcriptional co-activator regulated by Hippo signaling, mechano-transduction, and G-protein couple receptors. Once activated, TAZ and its paralogue, YAP1, regulate gene expression programs promoting cell proliferation, survival, and differentiation, thus controlling embryonic development, tissue regeneration, and aging. YAP and TAZ are also frequently activated in tumors, particularly in poorly differentiated and highly aggressive malignancies. Yet, mutations of YAP/TAZ or of their upstream regulators do not fully account for their activation in cancer, raising the possibility that other upstream regulatory pathways, still to be defined, are altered in tumors. In this work, we set out to identify novel regulators of TAZ by means of a siRNA-based screen. We identified 200 genes able to modulate the transcriptional activity of TAZ, with prominence for genes implicated in cell-cell contact, cytoskeletal tension, cell migration, WNT signaling, chromatin remodeling, and interleukins and NF-kappaB signaling. Among these genes we identified was BRCC3, a component of the BRCA1 complex that guards genome integrity and exerts tumor suppressive activity during cancer development. The loss of BRCC3 or BRCA1 leads to an increased level and activity of TAZ. Follow-up studies indicated that the cytoplasmic BRCA1 complex controls the ubiquitination and stability of TAZ. This may suggest that, in tumors, inactivating mutations of BRCA1 may unleash cell transformation by activating the TAZ oncogene.

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

Decades of research have mapped out the basic mechanics of the Hippo pathway. The paralogues Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), as the central transcription control module of the Hippo pathway, have long been implicated in the progression of various human cancers. The current literature regarding oncogenic YAP and TAZ activities consists mostly of context-specific mechanisms and treatments of human cancers. Furthermore, a growing number of studies demonstrate tumour-suppressor functions of YAP and TAZ. In this Review we aim to synthesize an integrated perspective of the many disparate findings regarding YAP and TAZ in cancer. We then conclude with the various strategies for targeting and treating YAP- and TAZ-dependent cancers.

Genes in loci genetically associated with polycystic ovary syndrome are dynamically expressed in human fetal gonadal, metabolic and brain tissues

Background

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder, affecting around 10% of women of reproductive age, with infertility, depression or anxiety, obesity, insulin resistance and type 2 diabetes as risk factors. The cause of PCOS is not known but there is a predisposition to developing PCOS in adult life that arises during fetal or perinatal life. PCOS also has a genetic predisposition and a number of genetic loci associated with PCOS have been identified. These loci contain 25 candidate genes which are currently being studied to define the syndrome. Although the name PCOS suggests a syndrome of the ovary, PCOS has also been associated with the central nervous system and other organ systems in the body due to the wide variety of symptoms it presents.

Methods

Here, we examined the expression patterns of PCOS candidate genes in gonadal (ovary and testis), metabolic (heart, liver and kidney) and brain (brain and cerebellum) tissues during the first half of human fetal development and postnatally until adulthood using public RNA sequencing data. This study is an initial step for more comprehensive and translational studies to define PCOS.

Results

We found that the genes were dynamically expressed in the fetal tissues studied. Some genes were significantly expressed in gonadal tissues, whilst others were expressed in metabolic or brain tissues at different time points prenatally and/or postnatally. HMGA2, FBN3 and TOX3 were highly expressed during the early stages of fetal development in all tissues but least during adulthood. Interestingly, correlation between expression of HMGA2/YAP1 and RAD50/YAP1 were significant in at least 5 of the 7 fetal tissues studied. Notably, DENND1A, THADA, MAPRE1, RAB5B, ARL14EP, KRR1, NEIL2 and RAD50 were dynamically expressed in all postnatal tissues studied.

Conclusions

These findings suggest that these genes have tissue- or development-specific roles in multiple organs, possibly resulting in the various symptoms associated with PCOS. Thus the fetal origin of a predisposition to PCOS in adulthood could arise via the effects of PCOS candidate genes in the development of multiple organs.

Secreted protease PRSS35 suppresses hepatocellular carcinoma by disabling CXCL2-mediated neutrophil extracellular traps

Hepatocytes function largely through the secretion of proteins that regulate cell proliferation, metabolism, and intercellular communications. During the progression of hepatocellular carcinoma (HCC), the hepatocyte secretome changes dynamically as both a consequence and a causative factor in tumorigenesis, although the full scope of secreted protein function in this process remains unclear. Here, we show that the secreted pseudo serine protease PRSS35 functions as a tumor suppressor in HCC. Mechanistically, we demonstrate that active PRSS35 is processed via cleavage by proprotein convertases. Active PRSS35 then suppresses protein levels of CXCL2 through targeted cleavage of tandem lysine (KK) recognition motif. Consequently, CXCL2 degradation attenuates neutrophil recruitment to tumors and formation of neutrophil extracellular traps, ultimately suppressing HCC progression. These findings expand our understanding of the hepatocyte secretome's role in cancer development while providing a basis for the clinical translation of PRRS35 as a therapeutic target or diagnostic biomarker.

Interaction of miR-200a-3p with YAP regulates cell proliferation and metastasis differentially in HPV-positive and HPV-negative cervical cancer cells

BACKGROUND

Although evidence has revealed that miR-200a-3p is involved in the malignant progression of various tumors, the regulatory mechanism of miR-200a-3p in the development of cervical cancer (CC) cells with different HPV statuses remains unknown. The present study was to investigate the differential effects of either miR-200a-3p or YAP on tumorous cells' fate in vitro in HPV-negative and HPV-positive cervical cancer cell models, and to explore if the changes in proliferation, migration, and invasion of the CC cells with different HPV statuses could be attributed to the differential interactions between miR-200a-3p and YAP.

METHODS

The colony formation assays, EDU assays and Transwell assays were performed for CC cell proliferation, migration and invasion capacities analysis. The prediction of downstream targets of miR-200a-3p was performed by bioinformatical databases. The dual-luciferase reporter assays were used to validate the binding sites of miR-200a-3p and YAP. The qRT-PCR assays were performed to quantify the mRNA expression of miR-200a-3p and YAP, and the protein levels of YAP were examined by Western blot analysis.

RESULTS

The results demonstrated that miR-200a-3p overexpression suppressed proliferation, migration, and invasion of the HPV-negative C33A cells but promoted the growth and metastasis of HPV-positive CC cells, while YAP promoted the cell growth and metastasis not only in HPV-negative but also in the HPV-positive CC cells. The suppressive role of miR-200a-3p in C33A cells appeared to be mediated partially by direct interaction with YAP, and YAP might participate in miR-200a-3p-mediated cellular changes in CC cells differing from not only the presence or absence of HPV but even also the subtypes of HPV of CC cells. Meanwhile, we preliminarily revealed that the expression level of miR-200a-3p was significantly decreased in HPV-negative, but not in HPV16-positive cervical neoplasm mucus samples.

CONCLUSION

miR-200a-3p-mediated functional changes of YAP exhibited regulatory effects on cells' fate differentially in HPV-negative and HPV-positive cervical cancer cells.

The interplay between noncoding RNA and YAP/TAZ signaling in cancers: molecular functions and mechanisms

The Hippo signaling pathway was found coordinately modulates cell regeneration and organ size. Its dysregulation contributes to uncontrolled cell proliferation and malignant transformation. YAP/TAZ are two critical effectors of the Hippo pathway and have been demonstrated essential for the initiation or growth of most tumors. Noncoding RNAs (ncRNAs), including miRNAs, lncRNAs, and circRNAs, have been shown to play critical roles in the development of many cancers. In the past few decades, a growing number of studies have revealed that ncRNAs can directly or indirectly regulate YAP/TAZ signaling. YAP/TAZ also regulate ncRNAs expression in return. This review summarizes the interactions between YAP/TAZ signaling and noncoding RNAs together with their biological functions on cancer progression. We also try to describe the complex feedback loop existing between these components.

The role of YAP1 in liver cancer stem cells: proven and potential mechanisms

YAP1 (Yes-associated protein 1) is one of the principal factors that mediates oncogenesis by acting as a driver of gene expression. It has been confirmed to play an important role in organ volume control, stem cell function, tissue regeneration, tumorigenesis and tumor metastasis. Recent research findings show that YAP1 is correlated with the stemness of liver cancer stem cells, and liver cancer stem cells are closely associated with YAP1-induced tumor initiation and progression. This article reviews the advancements made in research on the mechanisms by which YAP1 promotes liver cancer stem cells and discusses some potential mechanisms that require further study.

Hsa_circ_0006427 Suppresses Multiplication, Migration and Invasion of Non-Small Cell Lung Cancer Cells through miR-346/VGLL4 Pathway

Objective

Circular RNAs (circRNAs) are identified as key modulators in cancer biology. Nonetheless, the role of circ_0006427 in non-small cell lung cancer (NSCLC) and its modulatory mechanism are undefined. This study aimed to investigate the potential function and mechanism of circ_0006427 in NSCLC.

Materials and Methods

In this experimental study, circ_0006427, miR-346 and vestigial like family member 4 (VGLL4) mRNA expressions were analyzed in NSCLC tissues and cells, using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Multiplication, migration and invasion of NSCLC cells were examined using the CCK-8 method and Transwell experiment, respectively. Dual-luciferase reporter gene experiments were conducted to identify the paring relationship between circ_0006427 and miR-346. Western blot was employed to determine expressions of VGLL4 and epithelial-mesenchymal transition (EMT) markers on protein levels. Immuno-histochemistry (IHC) method was adopted to assess VGLL4 protein expression in NSCLC tissues.

Results

Circ_0006427 expression was down-regulated in NSCLC tissues and cells, and circ_0006427 suppressed multiplication, migration, invasion and EMT of NSCLC cells. miR-346 expression was upregulated in NSCLC tissues and cells, and miR-346 worked as a target of circ_0006427. VGLL4 was down-regulated in NSCLC tissues and cells, and knockdown of VGLL4 accelerated multiplication, migration, invasion and EMT of NSCLC cells. Circ_0006427 enhanced VGLL4 expression by competitively binding with miR-346.

Conclusion

Circ_0006427/miR-346/VGLL4 axis regulated NSCLC progression.

Circular RNA circ_0067741 regulates the Hippo/YAP pathway to suppress lung adenocarcinoma progression by targeting microRNA-183-5p

To discuss the effect and molecular mechanism of circular RNA circ_0067741 on the occurrence and development of lung adenocarcinoma (LUAD). QRT-PCR was utilized to detect circ_0067741, microRNA-183-5p (miR-183-5p) and large tumor suppressor 1 (LATS1) expressions in tumor tissues of 30 LUAD patients and LUAD cell lines (A549, Calu-3, H1299 and H1975). After overexpression or knockdown of circ_0067741-1 or miR-183-5p in H1299 and A549 cells, respectively, cell proliferation, viability, apoptosis, invasion and migration ability and angiogenesis ability were detected by MTT, cell cloning, flow cytometry, transwell and tube formation assays, respectively. The targeted relationship between miR-183-5p and circ_0067741 or LATS1 was validated using dual-luciferase reporter assay. We found that circ_0067741 expression was notably declined in LUAD cells and tissues. Overexpression of circ_0067741 inhibited the proliferation, migration, invasion, and angiogenesis of LUAD cells and promoted apoptosis. Moreover, circ_0067741 could sponge miR-183-5p to regulate LATS1 expression and then activate the Hippo/YAP pathway. Downregulation of LATS1 reversed the effects of circ_0067741 on the Hippo/YAP pathway and LUAD cells progression. In conclusion, circ_0067741 sponges miR-183-5p, and regulates LATS1 to activate Hippo/YAP pathway, thereby inhibiting the process of LUAD cells. And the circ_0067741/miR-183-5p/LATS1 axis can be a potential target for early diagnosis and targeted treatment of LUAD.

Towards an integrative understanding of cancer mechanobiology: calcium, YAP, and microRNA under biophysical forces

An increasing number of studies have demonstrated the significant roles of the interplay between microenvironmental mechanics in tissues and biochemical-genetic activities in resident tumor cells at different stages of tumor progression. Mediated by molecular mechano-sensors or -transducers, biomechanical cues in tissue microenvironments are transmitted into the tumor cells and regulate biochemical responses and gene expression through mechanotransduction processes. However, the molecular interplay between the mechanotransduction processes and intracellular biochemical signaling pathways remains elusive. This paper reviews the recent advances in understanding the crosstalk between biomechanical cues and three critical biochemical effectors during tumor progression: calcium ions (Ca²⁺), yes-associated protein (YAP), and microRNAs (miRNAs). We address the molecular mechanisms underpinning the interplay between the mechanotransduction pathways and each of the three effectors. Furthermore, we discuss the functional interactions among the three effectors in the context of soft matter and mechanobiology. We conclude by proposing future directions on studying the tumor mechanobiology that can employ Ca²⁺, YAP, and miRNAs as novel strategies for cancer mechanotheraputics. This framework has the potential to bring insights into the development of novel next-generation cancer therapies to suppress and treat tumors.

ENO1 suppresses cancer cell ferroptosis by degrading the mRNA of iron regulatory protein 1

α-Enolase 1 (ENO1) is a critical glycolytic enzyme whose aberrant expression drives the pathogenesis of various cancers. ENO1 has been indicated as having additional roles beyond its conventional metabolic activity, but the underlying mechanisms and biological consequences remain elusive. Here, we show that ENO1 suppresses iron regulatory protein 1 (IRP1) expression to regulate iron homeostasis and survival of hepatocellular carcinoma (HCC) cells. Mechanistically, we demonstrate that ENO1, as an RNA-binding protein, recruits CNOT6 to accelerate the messenger RNA decay of IRP1 in cancer cells, leading to inhibition of mitoferrin-1 (Mfrn1) expression and subsequent repression of mitochondrial iron-induced ferroptosis. Moreover, through in vitro and in vivo experiments and clinical sample analysis, we identified IRP1 and Mfrn1 as tumor suppressors by inducing ferroptosis in HCC cells. Taken together, this study establishes an important role for the ENO1-IRP1-Mfrn1 pathway in the pathogenesis of HCC and reveals a previously unknown connection between this pathway and ferroptosis, suggesting a potential innovative cancer therapy.

LncRNA SFTA1P mediates positive feedback regulation of the Hippo-YAP/TAZ signaling pathway in non-small cell lung cancer

Long non-coding RNAs (lncRNAs) regulate numerous biological processes involved in both development and carcinogenesis. Hippo-YAP/TAZ signaling, a critical pathway responsible for organ size control, is often dysregulated in a variety of cancers. However, the nature and function of YAP/TAZ-regulated lncRNAs during tumorigenesis remain largely unexplored. By profiling YAP/TAZ-regulated lncRNAs, we identified SFTA1P as a novel transcriptional target and a positive feedback regulator of YAP/TAZ signaling. Using non-small cell lung cancer (NSCLC) cell lines, we show that SFTA1P is transcriptionally activated by YAP/TAZ in a TEAD-dependent manner. Functionally, knockdown of SFTA1P in NSCLC cell lines inhibited proliferation, induced programmed cell death, and compromised their tumorigenic potential. Mechanistically, SFTA1P knockdown decreased TAZ protein abundance and consequently, the expression of YAP/TAZ transcriptional targets. We provide evidence that this phenomenon could potentially be mediated via its interaction with TAZ mRNA to regulate TAZ translation. Our results reveal SFTA1P as a positive feedback regulator of Hippo-YAP/TAZ signaling, which may serve as the molecular basis for lncRNA-based therapies against YAP/TAZ-driven cancers.

miR-497-5p/SALL4 axis promotes stemness phenotype of choriocarcinoma and forms a feedback loop with DNMT-mediated epigenetic regulation

Choriocarcinoma stem-like cells (CSLCs) might be at the origin of choriocarcinoma development associated with drug resistance or relapse. Spalt-like transcription factor 4 (SALL4), which is considered to be a stemness-related gene, can be regulated by miRNAs. In this study, SALL4 result is associated with progression-free survival of choriocarcinoma patients and CSLC's stemness characteristics. In addition, it could be downregulated by miR-497-5p by direct binding. miR-497-5p silencing by hypermethylation promoted malignant CSLC phenotype in vitro and in vivo. Furthermore, increased DNA methyltransferases (DNMTs) by SALL4 upregulation inhibited miR-497-5p expression via hypermethylation promotion. SALL4 appeared to be a key factor in promoting stemness phenotype of choriocarcinoma. Silencing miR-497-5p and SALL4 promotes choriocarcinoma progression and forms a feedback loop with DNMT-mediated epigenetic regulation, playing a crucial role in stemness maintenance in choriocarcinoma.

Transcriptional regulation of miR-30a by YAP impacts PTPN13 and KLF9 levels and Schwann cell proliferation

The Hippo pathway is a key regulatory pathway that is tightly regulated by mechanical cues such as tension, pressure, and contact with the extracellular matrix and other cells. At the distal end of the pathway is the yes-associated protein (YAP), a well-characterized transcriptional regulator. Through binding to transcription factors such as the TEA Domain TFs (TEADs) YAP regulates expression of several genes involved in cell fate, proliferation and death decisions. While the function of YAP as direct transcriptional regulator has been extensively characterized, only a small number of studies examined YAP function as a regulator of gene expression via microRNAs. We utilized bioinformatic approaches, including chromatin immunoprecipitation sequencing and RNA-Seq, to identify potential new targets of YAP regulation and identified miR-30a as a YAP target gene in Schwann cells. We find that YAP binds to the promoter and regulates the expression of miR-30a. Moreover, we identify several YAP-regulated genes that are putative miR-30a targets and focus on two of these, protein tyrosine pohosphatase non-receptor type 13 (PTPN13) and Kruppel like factor 9. We find that YAP regulation of Schwann cell proliferation and death is mediated, to a significant extent, through miR-30a regulation of PTPN13 in Schwann cells. These findings identify a new regulatory function by YAP, mediated by miR-30a, to downregulate expression of PTPN13 and Kruppel like factor 9. These studies expand our understanding of YAP function as a regulator of miRNAs and illustrate the complexity of YAP transcriptional functions.

Downregulation of MicroRNA-130a Inhibits Oral Squamous Cell Carcinoma Proliferation and Metastasis via the Hippo-YAP Pathway

Introduction

Oral squamous cell carcinoma (OSCC) means oral epithelial cell injury caused by multiple genetic mutations of the cells. Dysregulation of microRNAs (miRs) can disrupt the progression of OSCC. This study explored the mechanism of miR-130a in OSCC progression.

Methods

miR-130a expression in OSCC cell lines was analyzed. Functional assays were utilized to test the alterations of OSCC cell proliferation, apoptosis and epithelial–mesenchymal transition (EMT) with downregulated miR-130a, shRNA-PTEN or/and YAP inhibitor verteporfin. Then, dual-luciferase reporter gene assay was performed to clarify the targeting relation between miR-130a and PTEN. After that, Hippo-YAP pathway-related protein levels were tested. Moreover, xenograft transplantation was applied to confirm the in vitro experiments.

Results

Highly expressed miR-130a was observed in OSCC cell lines. Silenced miR-130a reduced OSCC proliferation, metastasis, invasion and EMT while propelled apoptosis. Furthermore, miR-130a targeted PTEN to promote the OSCC progression. Downregulation of PTEN reversed the inhibition of silencing miR-130a on proliferation and migration of SCC-4 cells. miR-130a targeted PTEN to inactivate the Hippo-YAP axis. OSCC progression was notably promoted by a combination of YAP inhibitor verteporfin and miR-130a inhibitor. Additionally, silenced miR-130a inhibited OSCC progression in vivo.

Discussion

Silencing miR-130a inhibited OSCC progression by targeting PTEN and activating the Hippo-YAP axis. This investigation may provide novel insight for OSCC treatment.

Activation of yes-associated protein mediates sphingosine-1-phosphate-induced proliferation and migration of pulmonary artery smooth muscle cells and its potential mechanisms

The aims of the present study were to examine the molecular mechanisms underlying sphingosine-1-phosphate (S1P)-induced rat pulmonary artery smooth muscle cells (PASMCs) proliferation/migration and to determine the effect of yes-associated protein (YAP) activation on S1P-induced PASMCs proliferation/migration and its potential mechanisms. S1P induced YAP dephosphorylation and nuclear translocation, upregulated microRNA-130a/b (miR-130a/b) expression, reduced bone morphogenetic protein receptor 2 (BMPR2), and inhibitor of DNA binding 1(Id1) expression, and promoted PASMCs proliferation and migration. Pretreatment of cells with Rho-associated protein kinase (ROCK) inhibitor Y27632 suppressed S1P-induced YAP activation, miR-130a/b upregulation, BMPR2/Id1 downregulation, and PASMCs proliferation/migration. Knockdown of YAP using small interfering RNA also suppressed S1P-induced alterations of miR-130a/b, BMPR2, Id1, and PASMCs behavior. In addition, luciferase reporter assay indicated that miR-130a/b directly regulated BMPR2 expression in PASMCs. Inhibition of miR-130a/b functions by anti-miRNA oligonucleotides attenuated S1P-induced BMPR2/Id1 downregulation and the proliferation and migration of PASMCs. Taken together, our study indicates that S1P induces activation of YAP through ROCK signaling and subsequently increases miR-130a/b expression, which, in turn, downregulates BMPR2 and Id1 leading to PASMCs proliferation and migration.

MicroRNAs Regulating Hippo-YAP Signaling in Liver Cancer

Liver cancer is one of the most common cancers worldwide, and its prevalence and mortality rate are increasing due to the lack of biomarkers and effective treatments. The Hippo signaling pathway has long been known to control liver size, and genetic depletion of Hippo kinases leads to liver cancer in mice through activation of the downstream effectors yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). Both YAP and TAZ not only reprogram tumor cells but also alter the tumor microenvironment to exert carcinogenic effects. Therefore, understanding the mechanisms of YAP/TAZ-mediated liver tumorigenesis will help overcome liver cancer. For decades, small noncoding RNAs, microRNAs (miRNAs), have been reported to play critical roles in the pathogenesis of many cancers, including liver cancer. However, the interactions between miRNAs and Hippo-YAP/TAZ signaling in the liver are still largely unknown. Here, we review miRNAs that influence the proliferation, migration and apoptosis of tumor cells by modulating Hippo-YAP/TAZ signaling during hepatic tumorigenesis. Previous findings suggest that these miRNAs are potential biomarkers and therapeutic targets for the diagnosis, prognosis, and treatment of liver cancer.

YAP1 and its fusion proteins in cancer initiation, progression and therapeutic resistance

YAP1 is a transcriptional co-activator whose activity is controlled by the Hippo signaling pathway. In addition to important functions in normal tissue homeostasis and regeneration, YAP1 has also prominent functions in cancer initiation, aggressiveness, metastasis, and therapy resistance. In this review we are discussing the molecular functions of YAP1 and its roles in cancer, with a focus on the different mechanisms of de-regulation of YAP1 activity in human cancers, including inactivation of upstream Hippo pathway tumor suppressors, regulation by intersecting pathways, miRNAs, and viral oncogenes. We are also discussing new findings on the function and biology of the recently identified family of YAP1 gene fusions, that constitute a new type of activating mutation of YAP1 and that are the likely oncogenic drivers in several subtypes of human cancers. Lastly, we also discuss different strategies of therapeutic inhibition of YAP1 functions.

The Hippo Pathway in Liver Homeostasis and Pathophysiology

Studies of the regenerative capacity of the liver have converged on the Hippo pathway, a serine/threonine kinase cascade discovered in Drosophila and conserved from unicellular organisms to mammals. Genetic studies of mouse and rat livers have revealed that the Hippo pathway is a key regulator of liver size, regeneration, development, metabolism, and homeostasis and that perturbations in the Hippo pathway can lead to the development of common liver diseases, such as fatty liver disease and liver cancer. In turn, pharmacological targeting of the Hippo pathway may be utilized to boost regeneration and to prevent the development and progression of liver diseases. We review current insights provided by the Hippo pathway into liver pathophysiology. Furthermore, we present a path forward for future studies to understand how newly identified components of the Hippo pathway may control liver physiology and how the Hippo pathway is regulated in the liver.

Regulatory role of microRNAs in cancer through Hippo signaling pathway

Cancer is the major cause of death worldwide in countries of all income levels. The Hippo signaling pathway is a Drosophila kinase gene that was identified to regulate organ size, cell regeneration, and contribute to tumorigenesis. A huge variety of extrinsic and intrinsic signals regulate the Hippo signaling pathway. The Hippo signaling pathway consists of a wide array of components that merge numerous signals such as mechanical signals to address apoptosis resistance, cell proliferation, cellular outputs of growth, cell death and survival at cellular and tissue level. Recent studies have shed new light on the regulatory role of microRNAs in Hippo signaling and how they contribute to cancer progression. MicroRNAs influence various cancer-related processes such as, apoptosis, proliferation, migration, cell cycle and metabolism. Inhibition and overexpression of miRNAs via miRNA mimics and miRNA inhibitors, respectively, can uncover a hopeful and reliable insight for treatment and early diagnosis of cancer patients. In this review we will discuss our current understanding of regulatory role of miRNAs in Hippo signaling pathway.

Regulation of Body Size and Growth Control

The control of body and organ growth is essential for the development of adults with proper size and proportions, which is important for survival and reproduction. In animals, adult body size is determined by the rate and duration of juvenile growth, which are influenced by the environment. In nutrient-scarce environments in which more time is needed for growth, the juvenile growth period can be extended by delaying maturation, whereas juvenile development is rapidly completed in nutrient-rich conditions. This flexibility requires the integration of environmental cues with developmental signals that govern internal checkpoints to ensure that maturation does not begin until sufficient tissue growth has occurred to reach a proper adult size. The Target of Rapamycin (TOR) pathway is the primary cell-autonomous nutrient sensor, while circulating hormones such as steroids and insulin-like growth factors are the main systemic regulators of growth and maturation in animals. We discuss recent findings in Drosophila melanogaster showing that cell-autonomous environment and growth-sensing mechanisms, involving TOR and other growth-regulatory pathways, that converge on insulin and steroid relay centers are responsible for adjusting systemic growth, and development, in response to external and internal conditions. In addition to this, proper organ growth is also monitored and coordinated with whole-body growth and the timing of maturation through modulation of steroid signaling. This coordination involves interorgan communication mediated by Drosophila insulin-like peptide 8 in response to tissue growth status. Together, these multiple nutritional and developmental cues feed into neuroendocrine hubs controlling insulin and steroid signaling, serving as checkpoints at which developmental progression toward maturation can be delayed. This review focuses on these mechanisms by which external and internal conditions can modulate developmental growth and ensure proper adult body size, and highlights the conserved architecture of this system, which has made Drosophila a prime model for understanding the coordination of growth and maturation in animals.

The Drosophila MLR COMPASS-like complex regulates bantam miRNA expression differentially in the context of cell fate

The conserved MLR COMPASS-like complexes are histone modifiers that are recruited by a variety of transcription factors to enhancer regions where they act as necessary epigenetic tools for enhancer establishment and function. A critical in vivo target of the Drosophila MLR complex is the bantam miRNA that regulates cell survival and functions in feedback regulation of cellular signaling pathways during development. We determine that loss of Drosophila MLR complex function in developing wing and eye imaginal discs results in growth and patterning defects that are sensitive to bantam levels. Consistent with an essential regulatory role in modulating bantam transcription, the MLR complex binds to tissue-specific bantam enhancers and contributes to fine-tuning expression levels during larval tissue development. In wing imaginal discs, the MLR complex attenuates bantam enhancer activity by negatively regulating expression; whereas, in differentiating eye discs, the complex exerts either positive or negative regulatory activity on bantam transcription depending on cell fate. Furthermore, while the MLR complex is not required to control bantam levels in undifferentiated eye cells anterior to the morphogenetic furrow, it serves to prepare critical enhancer control of bantam transcription for later regulation upon differentiation. Our investigation into the transcriptional regulation of a single target in a developmental context has provided novel insights as to how the MLR complex contributes to the precise timing of gene expression, and how the complex functions to help orchestrate the regulatory output of conserved signaling pathways during animal development.

Interaction of non-coding RNAs and Hippo signaling: Implications for tumorigenesis

Hippo signaling is an evolutionarily conserved pathway that controls organ size by regulating cell proliferation, apoptosis, and stem cell self-renewal by "turning off" or "turning on" the kinase cascade chain reaction to manipulate the expression of downstream genes. Dysregulation of the Hippo pathway contributes to cancer development and metastasis. Emerging evidence has revealed new insights into tumorigenesis through the interplay between the Hippo pathway and non-coding RNAs (ncRNAs), especially microRNA, long non-coding RNA and circular RNA. Here, we reviewed the interactions between the Hippo pathway and ncRNAs and their implication for a variety of tumor-promoting or tumor-repressing effects. These interactions have the potential to serve as cancer biomarkers and therapeutic targets in clinical applications.

Multiple Roles of Vestigial-Like Family Members in Tumor Development

Vestigial-like family (VGLL) members are mammalian orthologs of vestigial gene in Drosophila, and they consist of four homologs (VGLL1–4). VGLL members have TDU motifs that are binding regions to TEA/ATSS-DNA-binding domain transcription factor (TEAD). Through TDU motifs, VGLL members act as transcriptional cofactors for TEAD. VGLL1-3 have single TDU motif, whereas VGLL4 has two tandem TDU motifs, suggesting that VGLL4 has distinct molecular functions among this family. Although molecular and physiological functions of VGLL members are still obscure, emerging evidence has shown that these members are involved in tumor development. Gene alterations and elevated expression of VGLL1-3 were observed in various types of tumors, and VGLL1-3 have been shown to possess tumorigenic functions. In contrast, down-regulation of VGLL4 was detected in various tumors, and the tumor-suppressing role of VGLL4 has been demonstrated. In this review, we summarize the recently identified multiple roles of VGLL members in tumor development and provide important and novel insights regarding tumorigenesis.

[Emerging roles of Hippo signaling pathway in gastrointestinal cancers and its molecular mechanisms]

Hippo signaling pathway is highly conservative in evolution. MST1/2, LATS1/2, and the effector protein YAP/TAZ are the core members of this signaling pathway in mammalian cells. There have been many studies on YAP/TAZ and its downstream, however, the upstream regulatory factors of the Hippo signaling pathway remain unclear, and become one of the hot research directions of this pathway at present. In addition, Hippo signaling pathway can cross-talk with other signaling pathways such as Wnt and Notch signaling pathways, and plays an important role in controlling organ size, maintaining tissue homeostasis, and promoting tissue repair and regeneration. Abnormal Hippo signaling pathway may lead to the occurrence of a variety of tumors, especially gastrointestinal cancers such as liver cancer, colorectal cancer and gastric cancer. The abnormal expression of its members in gastrointestinal cancers is related to cancer cell proliferation, apoptosis, invasion and migration. Hippo signaling pathway is vital for liver repair and regeneration. Its inactivation will lead to the occurrence of primary liver cancer. The mechanism of YAP in liver cancer mainly depends on TEAD-mediated gene transcription. Hippo signaling pathway is also important for maintaining intestinal homeostasis, and its imbalance can lead to the occurrence and recurrence of colorectal cancer. In primary and metastatic gastric cancer, the expression of YAP/TAZ is significantly up-regulated, but the specific molecular mechanism is unclear. This article summarizes the recent progress on Hippo signaling pathway and its upstream regulatory factors, its roles in the development of gastrointestinal cancers and related molecular mechanisms; and also discusses the future research directions of Hippo signaling pathway.

Regulation and functions of the Hippo pathway in stemness and differentiation

The Hippo pathway plays important roles in organ development, tissue regeneration, and human diseases, such as cancer. In the canonical Hippo pathway, the MST1/2-LATS1/2 kinase cascade phosphorylates and inhibits transcription coactivators Yes-associated protein and transcription coactivator with PDZ-binding motif and thus regulates transcription of genes important for cell proliferation and apoptosis. However, recent studies have depicted a much more complicate picture of the Hippo pathway with many new components and regulatory stimuli involving both chemical and mechanical signals. Furthermore, accumulating evidence indicates that the Hippo pathway also plays important roles in the determination of cell fates, such as self-renewal and differentiation. Here, we review regulations of the Hippo pathway and its functions in stemness and differentiation emphasizing recent discoveries.

The YAP/TAZ Pathway in Osteogenesis and Bone Sarcoma Pathogenesis

YAP and TAZ are intracellular messengers communicating multiple interacting extracellular biophysical and biochemical cues to the transcription apparatus in the nucleus and back to the cell/tissue microenvironment interface through the regulation of cytoskeletal and extracellular matrix components. Their activity is negatively and positively controlled by multiple phosphorylation events. Phenotypically, they serve an important role in cellular plasticity and lineage determination during development. As they regulate self-renewal, proliferation, migration, invasion and differentiation of stem cells, perturbed expression of YAP/TAZ signaling components play important roles in tumorigenesis and metastasis. Despite their high structural similarity, YAP and TAZ are functionally not identical and may play distinct cell type and differentiation stage-specific roles mediated by a diversity of downstream effectors and upstream regulatory molecules. However, YAP and TAZ are frequently looked at as functionally redundant and are not sufficiently discriminated in the scientific literature. As the extracellular matrix composition and mechanosignaling are of particular relevance in bone formation during embryogenesis, post-natal bone elongation and bone regeneration, YAP/TAZ are believed to have critical functions in these processes. Depending on the differentiation stage of mesenchymal stem cells during endochondral bone development, YAP and TAZ serve distinct roles, which are also reflected in bone tumors arising from the mesenchymal lineage at different developmental stages. Efforts to clinically translate the wealth of available knowledge of the pathway for cancer diagnostic and therapeutic purposes focus mainly on YAP and TAZ expression and their role as transcriptional co-activators of TEAD transcription factors but rarely consider the expression and activity of pathway modulatory components and other transcriptional partners of YAP and TAZ. As there is a growing body of evidence for YAP and TAZ as potential therapeutic targets in several cancers, we here interrogate the applicability of this concept to bone tumors. To this end, this review aims to summarize our current knowledge of YAP and TAZ in cell plasticity, normal bone development and bone cancer.

Targeting YAP1/LINC00152/FSCN1 Signaling Axis Prevents the Progression of Colorectal Cancer

As a transcription coactivator, Yes-associated protein 1 (YAP1)'s role in tumorigenesis is well established. However, the mechanism of YAP1-regulating long noncoding RNAs (lncRNA) in tumors is still largely unknown. Here, a YAP1 target gene, long intergenic noncoding RNA 00152 (LINC00152), which is highly expressed in colorectal cancer (CRC), is identified. The oncogenic functions of LINC00152 in CRC are demonstrated by a panel of in vitro and in vivo experiments. Further studies reveal the potential downstream mechanisms of LINC00152, which can act as a competing endogenous RNA sponging with miR-632 and miR-185-3p to regulate Fascin actin-bundling protein 1 (FSCN1) expression and thus promote the malignant proliferation and metastasis in CRC cells. Targeting the YAP1/LINC00152/FSCN1 axis inhibits the progression of CRC. This finding provides a new regulatory model of the "YAP1-lncRNA" in CRC, which gives rise to a new perspective, "YAP1/LINC00152/miR-632-miR-185-3p/FSCN1," to explore the cancer-promoting mechanism of YAP1 involved in CRC.

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.

MicroRNAs in Drosophila Cancer Models

MiRNAs are post-transcriptional regulators of gene expression which have been implicated in virtually all biological processes. MiRNAs are frequently dysregulated in human cancers. However, the functional consequences of aberrant miRNA levels are not well understood. Drosophila is emerging as an important in vivo tumor model, especially in the identification of novel cancer genes. Here, we review Drosophila studies which functionally dissect the roles of miRNAs in tumorigenesis. Ultimately, these advances help to understand the implications of miRNA dysregulation in human cancers.

WW Domain-Containing Proteins YAP and TAZ in the Hippo Pathway as Key Regulators in Stemness Maintenance, Tissue Homeostasis, and Tumorigenesis

The Hippo pathway is a conserved signaling pathway originally defined in Drosophila melanogaster two decades ago. Deregulation of the Hippo pathway leads to significant overgrowth in phenotypes and ultimately initiation of tumorigenesis in various tissues. The major WW domain proteins in the Hippo pathway are YAP and TAZ, which regulate embryonic development, organ growth, tissue regeneration, stem cell pluripotency, and tumorigenesis. Recent reports reveal the novel roles of YAP/TAZ in establishing the precise balance of stem cell niches, promoting the production of induced pluripotent stem cells (iPSCs), and provoking signals for regeneration and cancer initiation. Activation of YAP/TAZ, for example, results in the expansion of progenitor cells, which promotes regeneration after tissue damage. YAP is highly expressed in self-renewing pluripotent stem cells. Overexpression of YAP halts stem cell differentiation and yet maintains the inherent stem cell properties. A success in reprograming iPSCs by the transfection of cells with Oct3/4, Sox2, and Yap expression constructs has recently been shown. In this review, we update the current knowledge and the latest progress in the WW domain proteins of the Hippo pathway in relevance to stem cell biology, and provide a thorough understanding in the tissue homeostasis and identification of potential targets to block tumor development. We also provide the regulatory role of tumor suppressor WWOX in the upstream of TGF-β, Hyal-2, and Wnt signaling that cross talks with the Hippo pathway.

Quantitative Real-Time PCR to Measure YAP/TAZ Activity in Human Cells

Transcription coactivators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ, also known as WWTR1) are homologs of the Drosophila Yorkie (Yki) protein and are major downstream effectors of the evolutionarily conserved Hippo pathway. YAP/TAZ play critical roles in regulation of cell proliferation, apoptosis, and stemness, thus mediate functions of the Hippo pathway in organ size control and tumorigenesis. The Hippo pathway inhibits YAP/TAZ through phosphorylation, which leads to YAP/TAZ cytoplasmic retention and degradation. Dephosphorylated and nuclear-localized YAP/TAZ bind to transcription factors, especially the TEAD family proteins, thus transactivate the expression of specific genes. Therefore, measuring the expression level of YAP/TAZ target genes is a critical approach to assess Hippo pathway activity. Through gene expression profiling in different tissues and cells using techniques such as microarray and RNA-seq, many target genes of YAP/TAZ have been identified. Some of these genes were confirmed to be direct YAP/TAZ targets by chromatin immunoprecipitation (ChIP)-PCR or ChIP-seq. These works made it possible to quickly determine YAP/TAZ activity by measuring the mRNA levels of several YAP/TAZ target genes, such as CTGF, CYR61, and miR-130a by quantitative real-time PCR (qPCR). In this chapter, we demonstrate the use of qPCR to measure YAP/TAZ activity in MCF10A cells.

CircFAT1 sponges miR-375 to promote the expression of Yes-associated protein 1 in osteosarcoma cells

Background

There is an urgent need to identify new molecular targets for treatment of osteosarcoma. Circular RNAs are a class of endogenous RNAs that are extensively found in mammalian cells and exert critical functions in the regulation of gene expression, but in osteosarcoma the underlying molecular mechanism of circular RNAs remain poorly understood. Here we assessed the tumorigenesis properties of a circular RNA, circFAT1 in osteosarcoma.

Methods

The effects of circFAT1/miR-375/YAP1 was evaluated on human osteosarcoma cells growth, apoptosis, migration, invasion and tumorigenesis. Signaling pathways were analyzed by western blotting, qRT-PCR, fluorescence in situ hybridization, chromogenic in situ hybridization,RNA Binding Protein Immunoprecipitation and immunofluorescence. The consequence of circFAT1 short hairpin RNA combined or not with miR-375 sponge was evaluated in mice bearing 143B xenografts on tumor growth.

Results

In this study, we observed significant upregulation of circFAT1 originating from exon 2 of the FAT1 gene in human osteosarcoma tissues and cell lines. Inhibition of circFAT1 effectively prevented the migration, invasion, and tumorigenesis of osteosarcoma cells in vitro and repressed osteosarcoma growth in vivo. Mechanistic studies revealed that circFAT1 contains a binding site for the microRNA-375 (miR-375) and can abundantly sponge miR-375 to upregulate the expression of Yes-associated protein 1. Moreover, inhibition of miR-375 reversed attenuation of cell proliferation, migration, and invasion, which was induced by circFAT1 knockdown, and therefore promoted tumorigenesis.

Conclusions

Our findings demonstrate a novel function of circFAT1 in tumorigenesis and suggest a new therapeutic target for the treatment of osteosarcoma.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0917-7) contains supplementary material, which is available to authorized users.

The Hippo Signaling Network and Its Biological Functions

Hippo signaling is an evolutionarily conserved network that has a central role in regulating cell proliferation and cell fate to control organ growth and regeneration. It promotes activation of the LATS kinases, which control gene expression by inhibiting the activity of the transcriptional coactivator proteins YAP and TAZ in mammals and Yorkie in Drosophila. Diverse upstream inputs, including both biochemical cues and biomechanical cues, regulate Hippo signaling and enable it to have a key role as a sensor of cells' physical environment and an integrator of growth control signals. Several components of this pathway localize to cell-cell junctions and contribute to regulation of Hippo signaling by cell polarity, cell contacts, and the cytoskeleton. Downregulation of Hippo signaling promotes uncontrolled cell proliferation, impairs differentiation, and is associated with cancer. We review the current understanding of Hippo signaling and highlight progress in the elucidation of its regulatory mechanisms and biological functions.

NUAK2 is a critical YAP target in liver cancer

The Hippo-YAP signaling pathway is a critical regulator of proliferation, apoptosis, and cell fate. The main downstream effector of this pathway, YAP, has been shown to be misregulated in human cancer and has emerged as an attractive target for therapeutics. A significant insufficiency in our understanding of the pathway is the identity of transcriptional targets of YAP that drive its potent growth phenotypes. Here, using liver cancer as a model, we identify NUAK2 as an essential mediator of YAP-driven hepatomegaly and tumorigenesis in vivo. By evaluating several human cancer cell lines we determine that NUAK2 is selectively required for YAP-driven growth. Mechanistically, we found that NUAK2 participates in a feedback loop to maximize YAP activity via promotion of actin polymerization and myosin activity. Additionally, pharmacological inactivation of NUAK2 suppresses YAP-dependent cancer cell proliferation and liver overgrowth. Importantly, our work here identifies a specific, potent, and actionable target for YAP-driven malignancies.

Hippo-YAP pathway plays an important role in cancers; however the in vivo relevance of YAP/TAZ target genes is unclear. Here, the authors show that NUAK2 is a target of YAP and participates in a feedback loop to maximize YAP activity. Inhibition of NUAK2 suppresses YAP-driven hepatomegaly and liver cancer growth, offering a new target for cancer therapy.

Loss of VGLL4 suppresses tumor PD-L1 expression and immune evasion

Targeting immune checkpoints, such as PD-L1 and its receptor PD-1, has opened a new avenue for treating cancers. Understanding the regulatory mechanism of PD-L1 and PD-1 will improve the clinical response rate and efficacy of PD-1/PD-L1 blockade in cancer patients and the development of combinatorial strategies. VGLL4 inhibits YAP-induced cell proliferation and tumorigenesis through competition with YAP for binding to TEADs. However, whether VGLL4 has a role in anti-tumor immunity is largely unknown. Here, we found that disruption of Vgll4 results in potent T cell-mediated tumor regression in murine syngeneic models. VGLL4 deficiency reduces PD-L1 expression in tumor cells. VGLL4 interacts with IRF2BP2 and promotes its protein stability through inhibiting proteasome-mediated protein degradation. Loss of IRF2BP2 results in persistent binding of IRF2, a transcriptional repressor, to PD-L1 promoter. In addition, YAP inhibits IFNγ-inducible PD-L1 expression partially through suppressing the expression of VGLL4 and IRF1 by YAP target gene miR-130a. Our study identifies VGLL4 as an important regulator of PD-L1 expression and highlights a central role of VGLL4 and YAP in the regulation of tumor immunity.

Yes-associated protein (YAP) binds to HIF-1α and sustains HIF-1α protein stability to promote hepatocellular carcinoma cell glycolysis under hypoxic stress

BACKGROUND

Hypoxia-inducible factor 1α (HIF-1α) is essential in hepatocellular carcinoma (HCC) glycolysis and progression. Yes-associated protein (YAP) is a powerful regulator and is overexpressed in many cancers, including HCC. The regulatory mechanism of YAP and HIF-1α in HCC glycolysis is unknown.

METHODS

We detected YAP expression in 54 matched HCC tissues and the adjacent noncancerous tissues. The relationship between YAP mRNA expression and that of HIF-1α was analyzed using The Cancer Genome Atlas HCC tissue data. We cultured HepG2 and Huh7 HCC cells under normoxic (20% O2) and hypoxic (1% O2) conditions, and measured the lactate and glucose levels, migration and invasive capability, and the molecular mechanism of HCC cell glycolysis and progression.

RESULTS

In this study, we detected YAP expression in 54 matched HCC tissues and the adjacent noncancerous tissues. We observed that hypoxia-induced YAP activation is crucial for accelerating HCC cell glycolysis. Hypoxia inhibited the Hippo signaling pathway and promoted YAP nuclear localization, and decreased phosphorylated YAP expression in HCC cells. YAP knockdown inhibited HCC cell glycolysis under hypoxic. Mechanistically, hypoxic stress in the HCC cells promoted YAP binding to HIF-1α in the nucleus and sustained HIF-1α protein stability to bind to PKM2 gene and directly activates PKM2 transcription to accelerate glycolysis.

CONCLUSIONS

Our findings describe a new regulatory mechanism of hypoxia-mediated HCC metabolism, and YAP might be a promising therapeutic target in HCC.

A time for YAP1: Tumorigenesis, immunosuppression and targeted therapy

YAP1 is one of the most important effectors of the Hippo pathway and has crosstalk with other cancer promoting pathways. YAP1 contributes to cancer development in various ways that include promoting malignant phenotypes, expansion of cancer stem cells and drug resistance of cancer cells. Because pharmacologic or genetic inhibition of YAP1 suppresses tumor progression and increases the drug sensitivity, targeting YAP1 may open a fertile avenue for a novel therapeutic approach in relevant cancers. Recent enormous studies have established the efficacy of immunotherapy, and several immune checkpoint blockades are in clinical use or in the phase of development to treat various cancer types. Immunosuppression in the tumor microenvironment (TME) induced by cancer cells, immune cells and associated stromal cells promotes tumor progression and causes drug resistance. Accumulated evidences of scientific efforts from the last few years suggest that YAP1 influences macrophages, myeloid-derived suppressor cells and regulatory T-cells to facilitate immunosuppressive TME. Although the underlying mechanisms is not clearly discerned, it is evident that YAP1 activating pathways in different cellular components induce immunosuppressive TME. In this review, we summarize the evidences involved in the dual roles of YAP1 in cancer development and immunosuppression in the TME. We also discuss the possibility of YAP1 as a novel therapeutic target.

MicroRNA‑130a inhibits the proliferation, migration and invasive ability of hepatocellular carcinoma cells by downregulating Rho‑kinase 2

MicroRNA‑130a (miR‑130a) has been reported to be downregulated in hepatocellular carcinoma (HCC). However, the roles and underlying tumor‑suppressive mechanisms of miR‑130a in the pathogenesis of HCC remain unclear. In the current study, reduced expression of miR‑130a was observed in tumor tissues of patients with HCC in addition to in four HCC cell lines, BEL‑7402, MHCC97H, HepG2 and Huh7. Results of methyl thiazolyl tetrazolium (MTT) assays identified decreased growth rates of MHCC97H and HepG2 cells transfected with miR‑130a mimics. The in vitro colony formation assays demonstrated that the number of colonies formed by cells transfected with miR‑130a mimics and cells transfected with miR‑130a inhibitors was lower and higher, respectively, than that formed by the cells transfected with miR‑negative control. In addition, it was identified that overexpression of miR‑130a reduced the migration and invasiveness of MHCC97H and HepG2 cells. Luciferase reporter assays demonstrated that miR‑130a directly targeted the 3'‑untranslated region of Rho‑kinase 2 (ROCK2) mRNA. Northern and western blot analyses indicated that miR‑130a could modulate the mRNA and protein expression of ROCK2. Additionally, small‑interfering RNA‑mediated knockdown of ROCK2 decreased the proliferation, migration and invasiveness of MHCC97H and HepG2 cells. Overall, these observation suggest that miR‑130a is a regulator of ROCK2 and can inhibit proliferation, migration and invasive ability of HCC cells, at least in part, by suppressing the expression of ROCK2. The current study provides further insight into the molecular mechanisms of HCC pathogenesis and suggests a new potential biotarget for HCC treatment.

VGLL4 is a transcriptional cofactor acting as a novel tumor suppressor via interacting with TEADs

Vestigial Like Family Member 4 (VGLL4) is a transcriptional cofactor of VGLL family, which includes VGLL1-4. Unlike other members of VGLL family, VGLL4 was described as a novel tumor suppressor containing two TDU motifs. VGLL4 executes its biological function through two TDU domains via interacting with TEA domain (TEAD) transcription factors. Lower expression of VGLL4 usually indicates poor survival in many cancers, such as lung cancer, gastric cancer, breast cancer, colorectal cancer, bladder cancer, pancreatic adenocarcinoma and esophageal squamous cancer. In cancer cells, the expression of VGLL4 is lower than that of normal tissues, moreover, expression level of VGLL4 is positively related to survival rate. VGLL4 is found to play an important role in several signal pathways, mainly acts as a tumor suppressor interacting with TEADs. In Hippo signaling pathway, VGLL4 competes with YAP in binding to TEADs and inhibits the downstream of YAP. In Wnt/β-catenin signaling pathway, VGLL4 negatively regulates Wnt/β-catenin signaling pathway via inhibiting β-catenin and TCF (T-cell factor). VGLL4 can also suppress epithelial-mesenchymal transition (EMT) and contribute to apoptosis signaling pathway.

YAP/TAZ Activation as a Target for Treating Metastatic Cancer

Yes-Associated Protein (YAP) and Transcriptional Co-activator with PDZ-binding Motif (TAZ) have both emerged as important drivers of cancer progression and metastasis. YAP and TAZ are often upregulated or nuclear localized in aggressive human cancers. There is abundant experimental evidence demonstrating that YAP or TAZ activation promotes cancer formation, tumor progression, and metastasis. In this review we summarize the evidence linking YAP/TAZ activation to metastasis, and discuss the roles of YAP and TAZ during each step of the metastatic cascade. Collectively, this evidence strongly suggests that inappropriate YAP or TAZ activity plays a causal role in cancer, and that targeting aberrant YAP/TAZ activation is a promising strategy for the treatment of metastatic disease. To this end, we also discuss several potential strategies for inhibiting YAP/TAZ activation in cancer and the challenges each strategy poses.