RUNX3 is a novel negative regulator of oncogenic TEAD-YAP complex in gastric cancer

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.

YAP/TAZ Initiates Gastric Tumorigenesis via Upregulation of MYC

YAP and TAZ play oncogenic roles in various organs, but the role of YAP/TAZ in gastric cancer remains unclear. Here, we show that YAP/TAZ activation initiates gastric tumorigenesis in vivo and verify its significance in human gastric cancer. In mice, YAP/TAZ activation in the pyloric stem cell led to step-wise tumorigenesis. RNA sequencing identified MYC as a decisive target of YAP, which controls MYC at transcriptional and posttranscriptional levels. These mechanisms tightly regulated MYC in homeostatic conditions, but YAP activation altered this balance by impeding miRNA processing, causing a shift towards MYC upregulation. Pharmacologic inhibition of MYC suppressed YAP-dependent phenotypes in vitro and in vivo, verifying its functional role as a key mediator. Human gastric cancer samples also displayed a significant correlation between YAP and MYC. We reanalyzed human transcriptome data to verify enrichment of YAP signatures in a subpopulation of gastric cancers and found that our model closely reflected the molecular pattern of patients with high YAP activity. Overall, these results provide genetic evidence of YAP/TAZ as oncogenic initiators and drivers for gastric tumors with MYC as the key downstream mediator. These findings are also evident in human gastric cancer, emphasizing the significance of YAP/TAZ signaling in gastric carcinogenesis.Significance: YAP/TAZ activation initiates gastric carcinogenesis with MYC as the key downstream mediator. Cancer Res; 78(12); 3306-20. ©2018 AACR.

Reciprocal regulation of YAP/TAZ by the Hippo pathway and the Small GTPase pathway

Yes-associated protein 1 (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) (YAP/TAZ) are transcriptional coactivators that regulate genes involved in proliferation and transformation by interacting with DNA-binding transcription factors. Remarkably, YAP/TAZ are essential for cancer initiation or growth of most solid tumors. Their activation induces cancer stem cell attributes, proliferation, and metastasis. The oncogenic activity of YAP/TAZ is inhibited by the Hippo cascade, an evolutionarily conserved pathway that is governed by two kinases, mammalian Ste20-like kinases 1/2 (MST1/2) and Large tumor suppressor kinase 1/2 (LATS1/2), corresponding to Drosophila's Hippo (Hpo) and Warts (Wts), respectively. One of the most influential aspects of YAP/TAZ biology is that these factors are transducers of cell structural features, including polarity, shape, and cytoskeletal organization. In turn, these features are intimately related to the cell's ability to attach to other cells and to the surrounding extracellular matrix (ECM), and are also influenced by the cell's microenvironment. Thus, YAP/TAZ respond to changes that occur at the level of whole tissues. Notably, small GTPases act as master organizers of the actin cytoskeleton. Recent studies provided convincing genetic evidence that small GTPase signaling pathways activate YAP/TAZ, while the Hippo pathway inhibits them. Biochemical studies showed that small GTPases facilitate the YAP-Tea domain transcription factor (TEAD) interaction by inhibiting YAP phosphorylation in response to serum stimulation, while the Hippo pathway facilitates the YAP-RUNX3 interaction by increasing YAP phosphorylation. Therefore, small GTPase pathways activate YAP/TAZ by switching its DNA-binding transcription factors. In this review, we summarize the relationship between the Hippo pathway and small GTPase pathways in the regulation of YAP/TAZ.

RUNX1 and RUNX3 protect against YAP-mediated EMT, stem-ness and shorter survival outcomes in breast cancer

Hippo pathway target, YAP has emerged as an important player in solid tumor progression. Here, we identify RUNX1 and RUNX3 as novel negative regulators of oncogenic function of YAP in the context of breast cancer. RUNX proteins are one of the first transcription factors identified to interact with YAP. RUNX1 or RUNX3 expression abrogates YAP-mediated pro-tumorigenic properties of mammary epithelial cell lines in an interaction dependent manner. RUNX1 and RUNX3 inhibit YAP-mediated migration and stem-ness properties of mammary epithelial cell lines by co-regulating YAP-mediated gene expression. Analysis of whole genome expression profiles of breast cancer samples revealed significant co-relation between YAP-RUNX1/RUNX3 expression levels and survival outcomes of breast cancer patients. High RUNX1/RUNX3 expression proved protective towards YAP-dependent patient survival outcomes. High YAP in breast cancer patients' expression profiles co-related with EMT and stem-ness gene signature enrichment. High RUNX1/RUNX3 expression along with high YAP reflected lower enrichment of EMT and stem-ness signatures. This antagonistic activity of RUNX1 and RUNX3 towards oncogenic function of YAP identified in mammary epithelial cells as well as in breast cancer expression profiles gives a novel mechanistic insight into oncogene-tumor suppressor interplay in the context of breast cancer progression. The novel interplay between YAP, RUNX1 and RUNX3 and its significance in breast cancer progression can serve as a prognostic tool to predict cancer recurrence.

The Hippo pathway as a drug target in gastric cancer

The Hippo tumor suppressor pathway is critical for balancing cellular differentiation and proliferation in response to cell-cell contact, mechanical signals and diffusible signals such as lysophosphatidic acid. Hippo pathway signaling is frequently dysregulated in gastric cancer (GC), as well as many other kinds of solid tumors, contributing to multiple aspects of malignant progression including unchecked cell division and metastasis. Considering the importance of this Hippo pathway in cancer, its pharmacological disruption may be of huge benefit in the fight against this disease. In this review, we summarize the components of the Hippo pathway, its crosstalk with other major oncogenic signaling pathways, common mechanisms of its dysregulation, as well as potential therapeutic approaches of targeting this pathway for cancer treatment, specifically in a GC context.

PIWIL1/piRNA-DQ593109 Regulates the Permeability of the Blood-Tumor Barrier via the MEG3/miR-330-5p/RUNX3 Axis

The blood-tumor barrier (BTB) restricts the efficient delivery of anti-glioma drugs to cranial glioma tissues. Increased BTB permeability may allow greater delivery of the therapeutic agents. Increasing evidence has revealed that PIWI proteins and PIWI-interacting RNAs (piRNAs) play an important role in tumor progression. However, whether PIWI proteins and piRNAs regulate BTB permeability remains unclear. In the present study, we demonstrated that the PIWIL1/piRNA-DQ593109 (piR-DQ593109) complex was the predominant regulator of BTB permeability. Briefly, PIWIL1 was upregulated in glioma endothelial cells (GECs). Furthermore, piR-DQ593109 was also overexpressed in GECs, as revealed via a piRNA microarray. Downregulation of PIWIL1 or piR-DQ593109 increased the permeability of the BTB. Moreover, PIWIL1 and piR-DQ593109, which formed a piRNA-induced silencing complex, degraded the long non-coding RNA maternally expressed 3 (MEG3) in a sequenced-dependent manner. Furthermore, restoring MEG3 released post-transcriptional inhibition of Runt related transcription factor 3 (RUNX3) by sponging miR-330-5p. In addition, RUNX3 bounded to the promoter regions and reduced the promoter activities of ZO-1, occludin, and claudin-5, which significantly impaired the expression levels of ZO-1, occludin, and claudin-5. In conclusion, downregulating PIWIL1 and piR-DQ593109 increased BTB permeability through the MEG3/miR-330-5p/RUNX3 axis. These data may provide insight into glioma treatment.

MiR-93-5p promotes gastric cancer-cell progression via inactivation of the Hippo signaling pathway

MiR-93-5p has been previously found to be associated with gastric cancer (GC) tumorigenesis; however, the current understanding of its function in this context remains largely incomplete. In the present study, we showed that miR-93-5p was upregulated in GC tissues. We also demonstrated that miR-93-5p overexpression promoted the proliferation, migration, invasion, and chemoresistance of SGC-7901 cells in vitro, and conversely, that endogenously silencing miR-93-5p expression induced the opposite effects in HGC-27 cells. Overexpression of miR-93-5p was found to inactivate the Hippo pathway, and furthermore, miR-93-5p knockdown activated Hippo signaling. MiR-93-5p upregulation was also shown to inhibit the expression of two well-characterized Hippo pathway regulators, protocadherin Fat 4 (FAT4), and large tumor suppressors 2 (LATS2), at both the mRNA and protein level. Additionally, the results of bioinformatics analyses and luciferase reporter assays indicated that miR-93-5p directly targets the 3'-UTR of FAT4 and LATS2. Taken together, these results demonstrate that miR-93-5p promotes GC-cell progression via the inactivation of the Hippo signaling pathway, and thus, represents a potential therapeutic target for the treatment of GC.

Roles of RUNX in Solid Tumors

All RUNX genes have been implicated in the development of solid tumors, but the role each RUNX gene plays in the different tumor types is complicated by multiple interactions with major signaling pathways and tumor heterogeneity. Moreover, for a given tissue type, the specific role of each RUNX protein is distinct at different stages of differentiation. A regulatory function for RUNX in tissue stem cells points sharply to a causal effect in tumorigenesis. Understanding how RUNX dysregulation in cancer impinges on normal biological processes is important for identifying the molecular mechanisms that lead to malignancy. It will also indicate whether restoration of proper RUNX function to redirect cell fate is a feasible treatment for cancer. With the recent advances in RUNX research, it is time to revisit the many mechanisms/pathways that RUNX engage to regulate cell fate and decide whether cells proliferate, differentiate or die.

The prognostic impacts of TEA domain (TEAD) transcription factor polymorphisms in Chinese hepatocellular carcinoma patients

TEA domain (TEAD) transcription factors play an important role in hepatocellular carcinoma (HCC) development and progression by regulating the expression of a number of genes. However, the association of their genetic variations with HCC prognosis remains elusive. Seven potentially functional single nucleotide polymorphisms in TEAD1-4 (rs2304733, rs10831923, rs12104362, rs3745305, rs11756089, rs2076173, rs7135838) were genotyped from 331 hepatitis B virus positive HCC patients using the Sequenom MassARRAY iPLEX platform. The TEAD3 rs2076173 C allele and rs11756089 T allele were identified as protective alleles as they were significantly associated with longer median overall survival time (MST). The T allele of rs2076173 was significantly associated with HCC survival independent of age, gender, smoking and drinking status, BCLC stage, and chemotherapy or TACE status (HR = 0.73, 95% CI = 0.56-0.93, P = 0.012). This protective effect was more prominent for patients who were non-drinkers (P for multiplicative interaction = 0.002). Patients had more than one of these protective alleles had significant longer MST of 19.25 months than those had none (MST=12.85 months, adjusted HR = 0.56, 95% CI = 0.33-0.95, P=0.030), especially for those non-drinkers (adjusted HR = 0.48, 95% CI = 0.32-0.74, P = 0.001). These findings suggested that rs2076173 and rs11756089 in TEAD3 gene could serve as genetic markers for favorable survival in the Chinese HCC patients.

YAP signaling in gastric cancer-derived mesenchymal stem cells is critical for its promoting role in cancer progression

Cancer-associated mesenchymal stem cells (MSCs) are critically involved in tumor development and progression. However, the mechanisms of action for MSCs in cancer remain largely unknown. Herein, we reported that the expression of Yes-associated protein 1 (YAP) was higher in gastric cancer derived mesenchymal stem cells (GC-MSCs) than that in bone marrow derived MSCs (BM-MSCs). YAP knockdown not only inhibited the growth, migration and invasion, and stemness of GC-MSCs, but also suppressed their promoting effect on gastric cancer growth in vitro and in vivo. In addition, the interference of YAP expression in GC-MSCs also attenuated the promoting role of gastric cancer cells in endothelial cell tube formation and migration. Mechanistically, YAP knockdown reduced the activation of β-catenin and its target genes in gastric cancer cells by GC-MSCs. Taken together, these findings suggest that YAP activation in GC-MSCs plays an important role in promoting gastric cancer progression, which may represent a potential target for gastric cancer therapy.

Emerging role of Hippo signalling pathway in bladder cancer

Bladder cancer (BC) is one of the most common cancers worldwide with a high progression rate and poor prognosis. The Hippo signalling pathway is a conserved pathway that plays a crucial role in cellular proliferation, differentiation and apoptosis. Furthermore, dysregulation and/or malfunction of the Hippo pathway is common in various human tumours, including BC. In this review, an overview of the Hippo pathway in BC and other cancers is presented. We focus on recent data regarding the Hippo pathway, its network and the regulation of the downstream co-effectors YAP1/TAZ. The core components of the Hippo pathway, which induce BC stemness acquisition, metastasis and chemoresistance, will be emphasized. Additional research on the Hippo pathway will advance our understanding of the mechanism of BC as well as the development and progression of other cancers and may be exploited therapeutically.

TEAD1/4 exerts oncogenic role and is negatively regulated by miR-4269 in gastric tumorigenesis

TEA domain (TEAD) transcription factors are key components of the Hippo–YAP1 signaling pathway, but their functional role and regulatory mechanisms remain unclear. This study aims to comprehensively explore the expression pattern and functional role of TEAD family in gastric carcinogenesis and investigate its regulation by microRNAs (miRNAs). The mRNA and protein expression of TEAD family were examined by quantitative reverse transcription–PCR (qRT–PCR) and western blot. Their functional roles were determined by in vitro and in vivo studies. The clinicopathological association of TEAD4 in gastric cancer (GC) was studied using immunohistochemistry on tissue microarray. The prediction of miRNAs, which potentially target TEAD1/4, was performed by TargetScan and miRDB. The regulation of TEAD1/4 by miRNAs was confirmed by qRT–PCR, western blot and luciferase assays. TEAD1/4 were overexpressed in GC cell lines and primary GC tissues. Knockdown of TEAD1/4 induced a significant anticancer effect in vitro and in vivo. TEAD1 was confirmed to be a direct target of miR-377-3p and miR-4269, while TEAD4 was negatively regulated by miR-1343-3p and miR-4269. Among them, miR-4269 was the most effective inhibitor of TEAD1/4. Ectopic expression of these miRNAs substantiated their tumor-suppressive effects. In primary GC tumors, downregulation of miR-4269 was associated with poor disease-specific survival and showed a negative correlation with TEAD4. TEAD1 and TEAD4 are oncogenic factors, whose aberrant activation are, in part, mediated by the silence of miR-377-3p, miR-1343-3p and miR-4269. For the first time, the nuclear accumulated TEAD4 and downregulated miR-4269 are proposed to serve as novel prognostic biomarkers in GC.

Identification of a novel YAP-14-3-3ζ negative feedback loop in gastric cancer

Growing evidence indicates that 14-3-3ζ and yes-associated protein (YAP) substantially promote tumorigenesis and tumor development. However, the regulatory mechanism underlying these two proteins remains unknown. Herein, we report a new regulatory role of 14-3-3ζ in the phosphorylation of YAP and the feedback inhibition of 14-3-3ζ by YAP. YAP and 14-3-3ζ expression exhibited a negative correlation in gastric cancer (GC) tissues. Moreover, patients with higher YAP and lower 14-3-3ζ expression had poor prognoses. Studies have revealed that 14-3-3ζ promotes cytoplasmic retention and suppresses the transcriptional activity of YAP by inducing its phosphorylation. Furthermore, we observed that the overexpression of YAP significantly reduced the expression of 14-3-3ζ by inducing its ubiquitination. YAP, 14-3-3ζ, and mouse double minute 2 homolog (MDM2) were colocalized, and the knockdown of MDM2 by siRNA attenuated the YAP-induced decrease of 14-3-3ζ. The binding of 14-3-3ζ and MDM2 was also restrained when the expression of YAP was interfered. Our results indicated the presence of a 14-3-3ζ–YAP negative regulatory feedback loop, which has a crucial role in cell proliferation and survival and is a potential target for the clinical treatment of GC.

Roles of RUNX in Hippo Pathway Signaling

The Runt-domain (RD) transcription factors (RUNX genes) are an important family of transcriptional mediators that interact with a variety of proteins including the Hippo pathway effector proteins, YAP and TAZ. In this chapter we focus on two examples of RUNX-TAZ/YAP interactions that have particular significance in human cancer. Specifically, recent evidence has found that RUNX2 cooperates with TAZ to promote epithelial to mesenchymal transition mediated by the soluble N-terminal ectodomain of E-Cadherin, sE-Cad. Contrastingly, in gastric cancer, RUNX3 acts as a tumor suppressor via inhibition of the YAP-TEAD complex and disruption of downstream YAP-mediated gene transcription and the oncogenic phenotype. The reports highlighted in this chapter add to the growing repertoire of instances of Hippo pathway crosstalk that have been identified in cancer. Elucidation of these increasingly complex interactions may help to identify novel strategies to target Hippo pathway dysregulation in human cancer.

Correlation of RUNX3 expression with microvessel density in colorectal adenocarcinoma tissues and clinical significance

OBJECTIVE

To study the expression of RUNX3 in colorectal adenocarcinoma tissues and its correlation with microvessel density (MVD), and investigate the clinical pathological prognostic significance of RUNX3 and MVD in patients with colorectal cancer.

METHODS

The expression value of RUNX3 and MVD in 70 specimens' colorectal adenocarcinoma tissues were detected by immunohistochemistry staining technique. The correlation between their expression and the clinicopathologic features was also investigated.

RESULTS

The expression value of RUNX3 and the positive rates of RUNX3 in colorectal adenocarcinoma tissues were 3.25 ± 1.14 and 25.71% (18/70). The expression value of MVD in colorectal adenocarcinoma tissues was 13.14 ± 3.23. Expression of RUNX3 and MVD value were correlated with CEA, serosal invasion, liver metastasis, lymph node metastasis, and TNM stage (P < 0.01). The expression value of RUNX3 had negative correlations with that of MVD.

CONCLUSIONS

The high expression of RUNX3 could inhibit tumor microvascular generation in order to have negative control response on invasion and distant metastasis.

Repair Injured Heart by Regulating Cardiac Regenerative Signals

Cardiac regeneration is a homeostatic cardiogenic process by which the sections of malfunctioning adult cardiovascular tissues are repaired and renewed employing a combination of both cardiomyogenesis and angiogenesis. Unfortunately, while high-quality regeneration can be performed in amphibians and zebrafish hearts, mammalian hearts do not respond in kind. Indeed, a long-term loss of proliferative capacity in mammalian adult cardiomyocytes in combination with dysregulated induction of tissue fibrosis impairs mammalian endogenous heart regenerative capacity, leading to deleterious cardiac remodeling at the end stage of heart failure. Interestingly, several studies have demonstrated that cardiomyocyte proliferation capacity is retained in mammals very soon after birth, and cardiac regeneration potential is correspondingly preserved in some preadolescent vertebrates after myocardial infarction. There is therefore great interest in uncovering the molecular mechanisms that may allow heart regeneration during adult stages. This review will summarize recent findings on cardiac regenerative regulatory mechanisms, especially with respect to extracellular signals and intracellular pathways that may provide novel therapeutics for heart diseases. Particularly, both in vitro and in vivo experimental evidences will be presented to highlight the functional role of these signaling cascades in regulating cardiomyocyte proliferation, cardiomyocyte growth, and maturation, with special emphasis on their responses to heart tissue injury.

Generation of RUNX3 knockout pigs using CRISPR/Cas9-mediated gene targeting

Pigs are an attractive animal model to study the progression of cancer because of their anatomical and physiological similarities to human. However, the use of pig models for cancer research has been limited by availability of genetically engineered pigs which can recapitulate human cancer progression. Utilizing genome editing technologies such as CRISPR/Cas9 system allows us to generate genetically engineered pigs at a higher efficiency. In this study, specific CRISPR/Cas9 systems were used to target RUNX3, a known tumour suppressor gene, to generate a pig model that can induce gastric cancer in human. First, RUNX3 knockout cell lines carrying genetic modification (monoallelic or biallelic) of RUNX3 were generated by introducing engineered CRISPR/Cas9 system specific to RUNX3 into foetal fibroblast cells. Then, the genetically modified foetal fibroblast cells were used as donor cells for somatic cell nuclear transfer, followed by embryo transfer. We successfully obtained four live RUNX3 knockout piglets from two surrogates. The piglets showed the lack of RUNX3 protein in their internal organ system. Our results demonstrate that the CRISPR/Cas9 system is effective in inducing mutations on a specific locus of genome and the RUNX3 knockout pigs can be useful resources for human cancer research and to develop novel cancer therapies.

RUNX3-mediated up-regulation of miR-29b suppresses the proliferation and migration of gastric cancer cells by targeting KDM2A

RUNX3 is a transcriptional factor that has been shown to regulate protein-coding gene expression at the transcriptional level. However, the regulation of RUNX3 on miRNAs is not fully understood. In this study, we used miRNA microarray to identify the miRNAs that are regulated by RUNX3 and found that miR-29b showed the most up-regulation in RUNX3 over-expressed cells compared with the control cells. We used qRT-PCR to confirm the miRNA microarray results in several gastric cancer cells and found that RUNX3 could bind to the miR-29b promoter directly and cooperate with Smad3 to increase the promoter activity of miR-29b. In the clinical setting, both RUNX3 and miR-29b are down-regulated significantly in human gastric cancer tissues. A positive correlation between miR-29b and RUNX3 was found in the gastric cancer tissues. Additionally, we found that miR-29b suppressed the proliferation and metastasis of gastric cancer cells by directly targeting KDM2A. The miR-29b/KDM2A axis was involved in the RUNX3-mediated inhibition of gastric cancer cell proliferation and metastasis. Taken together, our results suggested that RUNX3-mediated up-regulation of miR-29b inhibited the proliferation and migration of gastric cancer cells by targeting KDM2A, representing a novel molecular mechanism for the tumor suppression action of RUNX3.

Transcription factor RUNX2 up-regulates chemokine receptor CXCR4 to promote invasive and metastatic potentials of human gastric cancer

Runt-related transcription factor 2 (RUNX2) is a regulator of embryogenesis and development, but has also been implicated in the progression of certain human cancer. This study aimed to elucidate the role of RUNX2 in the invasive and metastatic potentials of human gastric cancer (GC) and the underlying mechanisms. We found that the levels of RUNX2 expression in gastric cancer tissues were correlated with the differentiation degrees, invasion depth and lymph node metastasis. COX regression analysis indicated that RUNX2 was an independent prognostic indicator for GC patients. RUNX2 significantly increased the migration and invasion ability of GC cells in vitro and enhanced the invasion and metastatic potential of GC cells in an orthotopic GC model of nude mice. Mechanistically, RUNX2 directly bound to the promoter region of the gene coding for the chemokine receptor CXCR4 to enhance its transcription. CXCR4 knockdown or treatment with AMD3100, a CXCR4 inhibitor, attenuated RUNX2-promoted invasion and metastasis. These results demonstrate that RUNX2 promotes the invasion and metastasis of human GC by transcriptionally up-regulating the chemokine receptor CXCR4. Therefore, the RUNX2-CXCR4 axis is a potential therapeutic target for GC.