The role of the Hippo pathway in human disease and tumorigenesis

Current understanding on the role of CCT3 in cancer research

Chaperonin containing TCP1 Subunit 3 (CCT3) is an important member of the chaperone protein family, providing a favorable environment for the correct folding of proteins in cell division, proliferation, and apoptosis pathways, which is involved in a variety of biological processes as well as the development and invasion of many malignant tumors. Many malignancies have been extensively examined with CCT3. It is presently used as a possible target for the treatment of many malignancies since it is not only a novel biomarker for the screening and diagnosis of different tumors, but it is also closely associated with tumor progression, prognosis, and survival. Recent studies have shown that the expression of CCT3 is up-regulated in some tumors, such as liver cancer, breast cancer, colon cancer, acute myeloid leukemia, etc. In this paper, we review the role of CCT3 in various tumors.

The RNA-Binding Protein HuR Posttranscriptionally Regulates the Protumorigenic Activator YAP1 in Pancreatic Ductal Adenocarcinoma

Yes-associated protein 1 (YAP1) is indispensable for the development of mutant KRAS-driven pancreatic ductal adenocarcinoma (PDAC). High YAP1 mRNA is a prognostic marker for worse overall survival in patient samples; however, the regulatory mechanisms that mediate its overexpression are not well understood. YAP1 genetic alterations are rare in PDAC, suggesting that its dysregulation is likely not due to genetic events. HuR is an RNA-binding protein whose inhibition impacts many cancer-associated pathways, including the "conserved YAP1 signature" as demonstrated by gene set enrichment analysis. Screening publicly available and internal ribonucleoprotein immunoprecipitation (RNP-IP) RNA sequencing (RNA-Seq) data sets, we discovered that YAP1 is a high-confidence target, which was validated in vitro with independent RNP-IPs and 3' untranslated region (UTR) binding assays. In accordance with our RNA sequencing analysis, transient inhibition (e.g., small interfering RNA [siRNA] and small-molecular inhibition) and CRISPR knockout of HuR significantly reduced expression of YAP1 and its transcriptional targets. We used these data to develop a HuR activity signature (HAS), in which high expression predicts significantly worse overall and disease-free survival in patient samples. Importantly, the signature strongly correlates with YAP1 mRNA expression. These findings highlight a novel mechanism of YAP1 regulation, which may explain how tumor cells maintain YAP1 mRNA expression at dynamic times during pancreatic tumorigenesis.

Calmodulin activates the Hippo signaling pathway by promoting LATS1 kinase-mediated inhibitory phosphorylation of the transcriptional coactivator YAP

The Hippo signaling pathway regulates tissue growth and cell fate, and its dysregulation can induce tumorigenesis. When Hippo is activated by cell–cell contact, extracellular signals, or cell polarity among others, the large tumor suppressor 1 (LATS1) kinase catalyzes inhibitory phosphorylation of the transcriptional coactivator Yes-associated protein (YAP) to maintain YAP in the cytoplasm or promote its degradation. Separately, calmodulin is a Ca²⁺-dependent protein that modulates the activity of target proteins and regulates several signaling cascades; however, its potential role in the Hippo pathway has not been identified. Here, using diverse experimental approaches, including in vitro binding analyses, kinase assays, RT–PCR, and confocal microscopy, we reveal that calmodulin promotes Hippo signaling. We show that purified YAP and LATS1 bind directly to calmodulin and form a Ca²⁺-dependent ternary complex in vitro. Importantly, Ca²⁺/calmodulin directly stimulated the activity of LATS1 kinase. In cultured mammalian cells, we demonstrated that endogenous YAP and LATS1 coimmunoprecipitate with endogenous calmodulin. In cells with activated Hippo signaling, we show that calmodulin antagonism significantly (i) decreases YAP phosphorylation, (ii) increases expression of two Hippo target genes (connective tissue growth factor [CTGF] and cysteine-rich angiogenic inducer 61 [CYR61]) that regulate cell proliferation and tumor progression, and (iii) enhances the interaction of YAP with its major transcription factor, thereby facilitating transcription of target genes. Collectively, our data demonstrate that calmodulin activates the Hippo kinase cascade and inhibits YAP activity via a direct interaction with LATS1 and YAP, thereby uncovering previously unidentified crosstalk between the Ca²⁺/calmodulin and Hippo signaling pathways.

PRR11 promotes ccRCC tumorigenesis by regulating E2F1 stability

Proline rich 11 (PRR11), a novel tumor-related gene, has been identified in different tumors. However, the relevant biological functions of PRR11 in human clear cell renal cell carcinoma (ccRCC) have not been studied. In this study, we first identified PRR11 as a biomarker of ccRCC and predictor of poor prognosis by bioinformatics. Then, we showed that PRR11 silencing substantially reduced ccRCC cell proliferation and migration in vitro and in vivo. Importantly, we found that PRR11 induced the degradation of the E2F1 protein through its interaction with E2F1, and PRR11 reduced the stability of the E2F1 protein in ccRCC cells, thereby affecting cell cycle progression. Further results indicated that the downregulation of E2F1 expression partially reversed the changes in ccRCC cell biology caused by PRR11 deletion. In addition, we showed that PRR11 was a target gene of c-Myc. The transcription factor c-Myc may have promoted the expression of PRR11 in ccRCC cells by binding to the PRR11 promoter region, thereby accelerating the progression of ccRCC. In summary, we found that PRR11 served as an oncogene in ccRCC, and PRR11 reduced the protein stability of E2F1 and could be activated by c-Myc.

A self-amplifying loop of YAP and SHH drives formation and expansion of heterotopic ossification

Heterotopic ossification (HO) occurs as a common complication after injury or in genetic disorders. The mechanisms underlying HO remain incompletely understood, and there are no approved prophylactic or secondary treatments available. Here, we identify a self-amplifying, self-propagating loop of Yes-associated protein (YAP)-Sonic hedgehog (SHH) as a core molecular mechanism underlying diverse forms of HO. In mouse models of progressive osseous heteroplasia (POH), a disease caused by null mutations in GNAS, we found that Gnas^-/- mesenchymal cells secreted SHH, which induced osteoblast differentiation of the surrounding wild-type cells. We further showed that loss of Gnas led to activation of YAP transcription activity, which directly drove Shh expression. Secreted SHH further induced YAP activation, Shh expression, and osteoblast differentiation in surrounding wild-type cells. This self-propagating positive feedback loop was both necessary and sufficient for HO expansion and could act independently of Gnas in fibrodysplasia ossificans progressiva (FOP), another genetic HO, and nonhereditary HO mouse models. Genetic or pharmacological inhibition of YAP or SHH abolished HO in POH and FOP and acquired HO mouse models without affecting normal bone homeostasis, providing a previously unrecognized therapeutic rationale to prevent, reduce, and shrink HO.

The novel FAT4 activator jujuboside A suppresses NSCLC tumorigenesis by activating HIPPO signaling and inhibiting YAP nuclear translocation

FAT atypical cadherin 4 (FAT4) has been identified as a tumor suppressor in lung cancers. However, no agent for lung cancer treatment targeting FAT4 has been used in the clinic. Jujuboside A (JUA) is a major active compound in Semen Ziziphi Spinosae. Semen Ziziphi Spinosae is a traditional Chinese herbal medicine used clinically for tumor treatment to improve patients' quality of life. However, the anti-lung cancer activity and the underlying mechanisms of JUA are not yet fully understood. Here, we demonstrated the anti-lung cancer activity of JUA in two lung cancer mice models and three non-small cell lung cancer (NSCLC) cell lines, and further illustrated its underlying mechanisms. JUA suppressed the occurrence and development of lung cancer and extended mice survival in vivo, and suppressed NSCLC cell activities through cell cycle arrest, proliferation suppression, stemness inhibition and senescence promotion. Moreover, JUA directly bound with and activated FAT4, subsequently activating FAT4-HIPPO signaling and inhibiting YAP nuclear translocation. Knockdown of FAT4 diminished JUA's effects on HIPPO signaling, YAP nuclear translocation, cell proliferation and cellular senescence. In conclusion, JUA significantly suppressed NSCLC tumorigenesis by regulating FAT4-HIPPO-YAP signaling. Our findings suggest that JUA is a novel FAT4 activator that can be developed as a promising NSCLC therapeutic agent targeting the FAT4-HIPPO-YAP pathway.

The Hippo Pathway: A Master Regulatory Network Important in Cancer

The Hippo pathway is pervasively activated and has been well recognized to play critical roles in human cancer. The deregulation of Hippo signaling involved in cancer development, progression, and resistance to cancer treatment have been confirmed in several human cancers. Its biological significance and deregulation in cancer have drawn increasing interest in the past few years. A fundamental understanding of the complexity of the Hippo pathway in cancer is crucial for improving future clinical interventions and therapy for cancers. In this review, we try to clarify the complex regulation and function of the Hippo signaling network in cancer development, including its role in signal transduction, metabolic regulation, and tumor development, as well as tumor therapies targeting the Hippo pathway.

Estrogens in Hepatocellular Carcinoma: Friends or Foes?

Simple Summary

Today, we know that estrogen hormones are required for the development and function of many organs, such as the liver, in both males and females. However, in some circumstances, estrogen excess may be implicated in the appearance of various chronic diseases, including cancer. This review will inspect the results of several studies to better understand the mechanisms responsible for estrogens to change from protective into harmful hormones in human liver.

Abstract

Estrogens are recognized as key players in physiological regulation of various, classical and non-classical, target organs, and tissues, including liver development, homeostasis, and function. On the other hand, multiple, though dispersed, experimental evidence is highly suggestive for the implication of estrogen in development and progression of hepatocellular carcinoma. In this paper, data from our own studies and the current literature are reviewed to help understanding this apparent discrepancy.

Hippo Signaling Pathway in Gliomas

The Hippo signaling pathway is a highly conserved pathway involved in tissue development and regeneration that controls organ size through the regulation of cell proliferation and apoptosis. The core Hippo pathway is composed of a block of kinases, MST1/2 (Mammalian STE20-like protein kinase 1/2) and LATS1/2 (Large tumor suppressor 1/2), which inhibits nuclear translocation of YAP/TAZ (Yes-Associated Protein 1/Transcriptional co-activator with PDZ-binding motif) and its downstream association with the TEAD (TEA domain) family of transcription factors. This pathway was recently shown to be involved in tumorigenesis and metastasis in several cancers such as lung, breast, or colorectal cancers but is still poorly investigated in brain tumors. Gliomas are the most common and the most lethal primary brain tumors representing about 80% of malignant central nervous system neoplasms. Despite intensive clinical protocol, the prognosis for patients remains very poor due to systematic relapse and treatment failure. Growing evidence demonstrating the role of Hippo signaling in cancer biology and the lack of efficient treatments for malignant gliomas support the idea that this pathway could represent a potential target paving the way for alternative therapeutics. Based on recent advances in the Hippo pathway deciphering, the main goal of this review is to highlight the role of this pathway in gliomas by a state-of-the-art synthesis.

Hippo pathway effectors YAP1/TAZ induce an EWS-FLI1-opposing gene signature and associate with disease progression in Ewing sarcoma

YAP1 and TAZ (WWTR1) oncoproteins are the final transducers of the Hippo tumor suppressor pathway. Deregulation of the pathway leads to YAP1/TAZ activation fostering tumorigenesis in multiple malignant tumor types, including sarcoma. However, oncogenic mutations within the core components of the Hippo pathway are uncommon. Ewing sarcoma (EwS), a pediatric cancer with low mutation rate, is characterized by a canonical fusion involving the gene EWSR1 and FLI1 as the most common partner. The fusion protein is a potent driver of oncogenesis, but secondary alterations are scarce, and little is known about other biological factors that determine the risk of relapse or progression. We have observed YAP1/TAZ expression and transcriptional activity in EwS cell lines. Analyses of 55 primary human EwS samples revealed that high YAP1/TAZ expression was associated with progression of the disease and predicted poorer outcome. We did not observe recurrent SNV or copy number gains/losses in Hippo pathway-related loci. However, differential CpG methylation of the RASSF1 locus (a regulator of the Hippo pathway) was observed in EwS cell lines compared with mesenchymal stem cells, the putative cell of origin of EwS. Hypermethylation of RASSF1 correlated with the transcriptional silencing of the tumor suppressor isoform RASFF1A, and transcriptional activation of the pro-tumorigenic isoform RASSF1C, which promotes YAP1/TAZ activation. Knockdown of YAP1/TAZ decreased proliferation and invasion abilities of EwS cells and revealed that YAP1/TAZ transcription activity is inversely correlated with the EWS-FLI1 transcriptional signature. This transcriptional antagonism could be explained partly by EWS-FLI1-mediated transcriptional repression of TAZ. Thus, YAP1/TAZ may override the transcriptional program induced by the fusion protein, contributing to the phenotypic plasticity determined by dynamic fluctuation of the fusion protein, a recently proposed model for disease dissemination in EwS. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

High expression of chaperonin-containing TCP1 subunit 3 may induce dismal prognosis in multiple myeloma

The prognosis role of CCT3 in MM and the possible pathways it involved were studied in our research. By analyzing ten independent datasets (including 48 healthy donors, 2220 MM, 73 MGUS, and 6 PCL), CCT3 was found to express higher in MM than healthy donors, and the expression level was gradually increased from MGUS, SMM, MM to PCL (all P < 0.01). By analyzing three independent datasets (GSE24080, GSE2658, and GSE4204), we found that CCT3 was a significant indicator of poor prognosis (all P < 0.01). KEGG and GSEA analysis showed that CCT3 expression was associated with JAK-STAT3 pathway, Hippo signaling pathway, and WNT signaling pathway. In addition, different expressed genes analysis revealed MYC, which was one of the downstream genes regulated by JAK-STAT3 pathway, was upregulated in MM. This confirms that JAK-STAT3 signaling pathway may promote the progress of disease which was regulated by CCT3 expression. Our study revealed that CCT3 may play a supporting role at the diagnosis of myeloid, and high expression of CCT3 suggested poor prognosis in MM. CCT3 expression may promote the progression of MM mainly by regulating MYC through JAK-STAT3 signaling pathway.

Overexpression of PRR11 promotes tumorigenic capability and is associated with progression in esophageal squamous cell carcinoma

INTRODUCTION

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies of gastrointestinal tract in the world, and the long-term prognosis for ESCC patients still remains dismal due to the lack of effective early diagnosis biomarkers.

MATERIALS AND METHODS

Western blot and immunochemistry were used to determine the expression of PRR11 in 201 clinicopathologically characterized ESCC specimens. The effects of PRR11 on stem cell-like traits and tumorigenicity were examined by tumor sphere formation assay and SP assays in vitro and by a tumorigenesis model in vivo. The mechanism by which PRR11 mediated Wnt/β-catenin signaling was explored using luciferase reporter, immuno-chemistry, and real time-PCR (RT-PCR) assays.

RESULTS

We found that PRR11 was markedly upregulated, at the level of both transcription and translation, in ESCC cell lines as compared with normal esophageal epithelial cells (NECCs). Immunohistochemical analysis showed that 69.2% paraffin-embedded archival ESCC specimens exhibited high levels of PRR11 expression, and multivariate analysis revealed that PRR11 upregulation might be an independent prognostic indicator for the survival of patients with ESCC. Furthermore, overexpression of PRR11 dramatically enhanced, whereas inhibition of PRR11 reduced the capability of cancer stem cell (CSC)-like phenotypes and tumorigenicity of ESCC cells both in vitro and in vivo. Mechanically, we demonstrated PRR11-enhanced tumorigenicity of ESCC cells via activating Wnt/β-catenin signaling, and PRR11 expression is found to be significantly correlated with β-catenin nuclear location in ESCC.

CONCLUSION

Our findings suggest that the PRR11 might represent a novel and valuable prognostic marker for ESCC progression and play a role during the development and progression of this malignancy.

Gαs signaling in skeletal development, homeostasis and diseases

Skeletal development is exquisitely controlled both spatially and temporally by cell signaling networks. Gα_s is the stimulatory α-subunit in a heterotrimeric G protein complex transducing the signaling of G-protein-coupled receptors (GPCRs), responsible for controlling both skeletal development and homeostasis. Gα_s, encoded by the GNAS gene in humans, plays critical roles in skeletal development and homeostasis by regulating commitment, differentiation and maturation of skeletal cells. Gα_s-mediated signaling interacts with the Wnt and Hedgehog signaling pathways, both crucial regulators of skeletal development, remodeling and injury repair. Genetic mutations that disrupt Gα_s functions cause human disorders with severe skeletal defects, such as fibrous dysplasia of bone and heterotopic bone formation. This chapter focuses on the crucial roles of Gα_s signaling during skeletal development and homeostasis, and the pathological mechanisms underlying skeletal diseases caused by GNAS mutations.

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

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

Tumor suppressive role of rottlerin in cancer therapy

Cancer as a major public health problem is a big trouble to be cured at present in the world. Thus, it is essential to discover better anticancer drugs to treat cancer patients. It has been reported that rottlerin, a natural polyphenolic compound from the mature fruits of Mallotus philippinensis, possesses multiple anti-cancer biological activities. Rottlerin exhibited its antitumor property in a variety of human cancers, suggesting that rottlerin could be a potential agent for treating cancers. In this review we discuss the recent literature regarding the biological functions and tumor suppressive mechanisms of rottlerin in cancers. We hope rottlerin will be further exploited for potential treatment of human cancers.

Expression of the Hippo signalling effectors YAP and TAZ in canine mammary gland hyperplasia and malignant transformation of mammary tumours

Canine mammary tumours (CMTs) are common neoplasms in dogs that feature many of the clinical, genetic and molecular characteristics of human breast cancer. Despite their high metastatic potential, few adjuvant chemotherapeutic treatment options exist for malignant CMTs, and the development of novel, targeted pharmacological approaches will require a better understanding of their pathogenesis. As recent evidence suggests that dysregulated Hippo signalling is involved in the development and progression of breast cancer, we sought to determine if this pathway could also play a role in CMT. The expression of the Hippo signalling effectors YAP and TAZ was analysed by immunoblotting and immunohistochemistry in samples including normal mammary gland, lobular hyperplasia, benign tumours and malignant tumours of all grades. We found a significant increase in TAZ (but not YAP) expression occurred in lobular hyperplasia relative to normal mammary gland, suggesting a role for TAZ in non-neoplastic epithelial proliferation. Nuclear expression of both TAZ and YAP were significantly higher in malignant tumours than in benign ones, suggesting that Hippo dysregulation could play a role in CMT malignant transformation. No differences in YAP or TAZ expression were detected between grades of malignant tumours. Together, our results indicate that alterations in Hippo signalling may play a role in the pathogenesis of CMT, in a manner similar to breast cancer. Hippo pathway components may therefore represent targets for the development of novel chemotherapeutic agents that could be useful for the treatment of both the human and canine diseases.

STK3 is a therapeutic target for a subset of acute myeloid leukemias

Acute myeloid leukemia (AML) is characterized by uncontrolled proliferation and accumulation of immature myeloblasts, which impair normal hematopoiesis. While this definition categorizes the disease into a distinctive group, the large number of different genetic and epigenetic alterations actually suggests that AML is not a single disease, but a plethora of malignancies. Still, most AML patients are not treated with targeted medication but rather by uniform approaches such as chemotherapy. The identification of novel treatment options likely requires the identification of cancer cell vulnerabilities that take into account the different genetic and epigenetic make-up of the individual tumors. Here we show that STK3 depletion by knock-down, knock-out or chemical inhibition results in apoptotic cells death in some but not all AML cell lines and primary cells tested. This effect is mediated by a premature activation of cyclin dependent kinase 1 (CDK1) in presence of elevated cyclin B1 levels. The anti-leukemic effects seen in both bulk and progenitor AML cells suggests that STK3 might be a promising target in a subset of AML patients.

Rottlerin exhibits antitumor activity via down-regulation of TAZ in non-small cell lung cancer

Rottlerin, a polyphenolic compound derived from Mallotus philipinensis, has been reported to exhibit anti-tumor activities in a variety of human malignancies including NSCLC (non-small cell lung cancer). TAZ (transcriptional co-activator with PDZ-binding motif), one of the key activators in Hippo pathway, has been characterized as an oncoprotein. Therefore, inhibition of TAZ could be useful for the treatment of human cancers. In the current study, we aimed to explore whether rottlerin inhibits the expression of TAZ in NSCLC, leading to its anti-cancer activity. Multiple approaches were applied for determining the mechanism of rottlerin-mediated anti-tumor function, including cell growth assay, Flow cytometry, wound healing assay, invasion assay, Western blotting, and transfection. We found that rottlerin inhibited cell growth, triggered apoptosis, arrested cell cycle, and retarded cell invasion in NSCLC cells. Moreover, our results showed that overexpression of TAZ enhanced cell growth, stimulated apoptosis, and promoted cell migration and invasion. Consistently, inhibition of TAZ exhibited anti-tumor activity in NSCLC cells. Notably, we validated that rottlerin exerted its tumor suppressive function via inactivation of TAZ in NSCLC cells. Taken together, our study indicates that inhibition of TAZ by rottlerin could be a promising strategy for the prevention and therapy of NSCLC.

Rheb may complex with RASSF1A to coordinate Hippo and TOR signaling

The TOR pathway is a vital component of cellular homeostasis that controls the synthesis of proteins, nucleic acids and lipids. Its core is the TOR kinase. Activation of the TOR pathway suppresses autophagy, which plays a vital but complex role in tumorigenesis. The TOR pathway is regulated by activation of the Ras-related protein Rheb, which can bind mTOR. The Hippo pathway is a major growth control module that regulates cell growth, differentiation and apoptosis. Its core consists of an MST/LATS kinase cascade that can be activated by the RASSF1A tumor suppressor. The TOR and Hippo pathways may be coordinately regulated to promote cellular homeostasis. However, the links between the pathways remain only partially understood. We now demonstrate that in addition to mTOR regulation, Rheb also impacts the Hippo pathway by forming a complex with RASSF1A. Using stable clones of two human lung tumor cell lines (NCI-H1792 and NCI-H1299) with shRNA-mediated silencing or ectopic overexpression of RASSF1A, we show that activated Rheb stimulates the Hippo pathway, but is suppressed in its ability to stimulate the TOR pathway. Moreover, by selectively labeling autophagic vacuoles we show that RASSF1A inhibits the ability of Rheb to suppress autophagy and enhance cell growth. Thus, we identify a new connection that impacts coordination of Hippo and TOR signaling. As RASSF1A expression is frequently lost in human tumors, the RASSF1A status of a tumor may impact not just its Hippo pathway status, but also its TOR pathway status.

Loss of large tumor suppressor 1 promotes growth and metastasis of gastric cancer cells through upregulation of the YAP signaling

Accumulating evidence shows that large tumor suppressor 1 (LATS1) as a novel resident governor of cellular homeostasis is implicated in multiple tumorigenic properties including cell growth, apoptosis and metastasis. However, the contribution of LATS1 to gastric carcinoma (GC) remains unclear. The correlation of LATS1 expression with clinicopathologic characteristics, GC prognosis and recurrence was analyzed by immunohistochemistry, Univariate and Kaplan-Meier analysis. Functional experiments were performed to investigate biological behaviors of GC cells and underlying molecular mechanisms. Tumor growth and metastasis was assessed in vivo using orthotopic implantation GC models in severe combined immune deficiency (SCID) mice. Consequently, decreased LATS1 expression was significantly associated with the lymph node metastasis, poor prognosis and recurrence. Ectopic expression of LATS1 decreased GC cell proliferation and invasion in vitro and inhibited tumor growth and liver metastasis in vivo, but depletion of LATS1 expression restored the invasive phenotype. Further observation indicated that YAP pathway was required for LATS1-induced inhibition of cell growth and invasion, and LATS1 restrained nuclear transfer of YAP, downregulated YAP, PCNA, CTGF, MMP-2, MMP-9, Bcl-2 and CyclinD1 expression and upregulated p-YAP and Bax expression. Our findings suggest that LATS1 is a potential candidate tumor suppressor and inhibits the growth and metastasis of GC cells via downregulation of the YAP signaling.

Rottlerin inhibits cell growth, induces apoptosis and cell cycle arrest, and inhibits cell invasion in human hepatocellular carcinoma

Rottlerin, a polyphenolic compound, has been demonstrated to exhibit antitumor activity in various types of human cancer. Several studies have revealed that rottlerin exerts its anticancer function through PKC‑dependent and independent pathways. The transcriptional co‑activator with PDZ‑binding motif (TAZ) oncopreotein is an important molecule in regulation of the Hippo pathway in human cancer. The present study investigated whether rottlerin has a tumor suppressive role via inhibiting the expression of TAZ, using cell viability assay, apoptosis and cell cycle analyses, western blot analysis and Tanswell invasion assay. The results demonstrated that rottlerin suppressed cell growth, triggered cell apoptosis and induced cell cycle arrest. In addition, rottlerin inhibited cell migration and invasion in hepatocellular carcinoma (HCC) cells. Mechanistically, the results demonstrated that rottlerin exerted its antitumor activity partly through the inhibition of TAZ. In addition, the depletion of TAZ led to inhibited cell growth and invasion, whereas the overexpression of TAZ enhanced cell growth and invasion in the HCC cells. Taken together, these findings indicated that the inhibition of TAZ by rottlerin may be a novel strategy for treating HCC.

Significant association of YAP1 and HSPC111 proteins with poor prognosis in Chinese gastric cancer patients

Hippo-YAP1 is a tumor-suppressor signaling pathway that inhibits cell proliferation and accelerates apoptosis. However, the role of YAP1 in gastric cancer (GC) is still in dispute. Ribosomal biogenesis is closely correlated with human malignancies. HBV pre-S2 trans-regulated protein 3 (HSPC111) is a portion of an RNA-dependent complex and plays a crucial role in ribosome biosynthesis. Nevertheless, little is known about the expression and function of this factor in GC. In the present study, we evaluated the significance of YAP1 together with HSPC111 in gastric cancer. According to The Cancer Genome Atlas database, high YAP1 mRNA expression was significantly associated with poor prognosis of GC patients, and dramatically increased mRNA levels of HSPC111 are observed in GC tissues. Consistent with these findings, we detected increased expression of both YAP1 and HSPC111 in GC cell lines and clinical samples. Notably, nuclear expression of YAP1 was positively correlated with clinical stage (P = 0.041), tumor size (P = 0.023), and lymph node metastasis (P = 0.007), while HSPC111 expression was correlated with lymph node metastasis (P = 0.014). Our analyses also detected a correlation between HSPC111 expression and nuclear and cytoplasmic YAP1 in clinical samples (nuclear: r = 0.2615, P = 0.004; cytoplasm: r = -0.3721, P < 0.001) and cell lines. Finally, we showed that patients who were HSPC111- and nuclear YAP1-positive were associated with the worst prognosis (34.5 ± 4.8 months, p = 0.001), and that nuclear expression of YAP1 might act as an independent prognostic factor for GC patients.

In Vitro Validation of the Hippo Pathway as a Pharmacological Target for Canine Mammary Gland Tumors

Canine mammary tumors (CMTs) are the most common neoplasms in intact female dogs. Some clinical and molecular similarities between certain CMT subtypes and breast cancer make them a potential model for the study of the human disease. As misregulated Hippo signaling is thought to play an important role in breast cancer development and also occurs in CMTs, we sought to determine if Hippo represents a valid pharmacological target for the treatment of CMTs. Six CMT cell lines were assessed for their expression of the Hippo pathway effectors YAP and TAZ and for their sensitivity to verteporfin, an inhibitor of YAP-mediated transcriptional coactivation. Four cell lines that expressed YAP (CMT-9, -12, -28, -47) were found to be very sensitive to verteporfin treatment, which killed the cells through induction of apoptosis with ED50 values of 14-79 nM. Conversely, two YAP-negative cell lines (CF-35, CMT-25) were an order of magnitude more resistant to verteporfin. Verteporfin suppressed the expression of YAP/TAZ target genes, particularly CYR61 and CTGF, which play important roles in breast cancer development. Verteporfin was also able to inhibit cell migration and anchorage-independent growth. Likewise, verteporfin efficiently suppressed tumor cell invasiveness in the CMT-28 and -47 lines, but not in CF-35 cells. Together, our findings provide proof of principle that pharmacological targeting of the Hippo pathway compromises the viability and attenuates the malignant behavior of CMT cells. These results will serve as the basis for the development of novel chemotherapeutic approaches for CMTs that could translate to human medicine.

MiR-590-3p promotes proliferation and metastasis of colorectal cancer via Hippo pathway

Studies reported that miR-590-3p was involved in human cancer progression. However, its roles of oncogene or anti-oncogene in malignancies still remain elusive. This study was aimed to investigate the effect of miR-590-3p on the cell proliferation and metastasis via Hippo pathway in colorectal cancer (CRC). In our study, miR-590-3p was demonstrated highly expressed in CRC tissues, compared with adjacent normal tissues (P<0.05). In addition, miR-590-3p was positively associated with TNM stage and distant metastasis. Survival analysis showed that high miR-590-3p was related with poor overall survival rate. Then, over-expressed miR-590-3p was demonstrated to promote proliferation, invasion and migration of colon caner cells. What’s more, MST1, LATS1 and SAV1 mRNA were showed lowly expressed and YAP1 expression in mRNA and protein levels were highly expressed in CRC tissues, compared with adjacent normal tissues (all P<0.05). miR-590-3p expression was negatively associated with LATS1 and SAV1 mRNA respectively and positively related with YAP1 mRNA in CRC tissues, meanwhile, there was no relationship between miR-590-3p and MST1 mRNA. Furthermore, over-expressing miR-590-3p inhibited expressions of LATS1 and SAV1, promoted YAP1 expression and didn’t effect MST1 expression in colon cancer cells. And luciferase assay showed that miR-590-3p over-expression inhibited the luciferase activity of LATS1 and SAV1 3’UTR, meanwhile it had no effect on the mutated form of these two plasmids. Taken together, these data suggest that highly-expressed miR-590-3p promotes biological effect of proliferation and metastasis via targeting Hippo pathway, and predicts worse clinical outcomes of CRC patients.

Verteporfin Inhibits Cell Proliferation and Induces Apoptosis in Human Leukemia NB4 Cells without Light Activation

Background and Aims: Verteporfin (VP), clinically used in photodynamic therapy for neovascular macular degeneration, has recently been proven a suppressor of yes-associated protein (YAP) and has shown potential in anticancer treatment. However, its anti-human leukemia effects in NB4 cells remain unclear. In this study, we investigated the effects of VP on proliferation and apoptosis in human leukemia NB4 cells. Methods: NB4 cells were treated with VP for 24 h. The effects of VP on cell proliferation were determined using a Cell-Counting Kit-8 assay (CCK-8) assay and colony forming assay. Apoptosis and cell cycle were evaluated by flow cytometry (FCM). The protein levels were detected by western blot. Results: We found that VP inhibited the proliferation of NB4 cells in a concentration and time-dependent manner. FCM analysis showed that VP induced apoptosis in a concentration dependent manner and that VP treatment led to cell cycle arrest at G0/G1 phase. Moreover, VP significantly decreased the protein expression of YAP, p-YAP, Survivin, c-Myc, cyclinD1, p-ERK, and p-AKT. In addition, VP increased the protein expression of cleaved caspase3, cleaved PARP, Bax, and p-p38 MAPK. Conclusions: VP inhibited the proliferation and induced apoptosis in NB4 cells.

Regulatory roles of epigenetic modulators, modifiers and mediators in lung cancer

Lung cancer as the leading cause of cancer-related deaths can be initiated and progressed by the interaction between dynamically genetic and epigenetic elements, although mechanisms mediating lung cancer development and progression remain unclear. Tumor progenitor genes may contribute to lung carcinogenesis and cancer progression, are epigenetically disrupted at the early stages of malignancies even before mutations, and alter cell differentiation throughout tumor evolution. The present review explores potential roles and mechanisms of epigenetic modulators, modifiers and mediators in the development of lung cancer. We also overviewed potential mechanisms by which epigenetic modulators, modifiers and mediators control and regulate 3D nuclear architectures, and discussed translational efforts to epigenetic modifications for treatment of lung cancer. Deep understanding of epigenetic modulators, modifiers and mediators will benefit the discovery and development of new diagnostics and therapies for lung cancer.

Curcumin enhances temsirolimus-induced apoptosis in human renal carcinoma cells through upregulation of YAP/p53

Curcumin has frequently been used as a therapeutic agent in the treatment of various types of disease and is known to enhance the drug sensitivity of cells. In the present study, the combined effect of curcumin and temsirolimus treatment on apoptosis in human renal cell carcinoma (RCC) cells was investigated. Temsirolimus is an inhibitor of the mechanistic target of rapamycin signaling pathway and used in the first-line treatment of metastatic RCC. It was demonstrated that curcumin combined with temsirolimus markedly induced apoptosis in RCC cells, however this effect was not observed following curcumin or temsirolimus treatment alone. Co-treatment with temsirolimus and curcumin led to the activation of cleaved poly ADP-ribose polymerase and caspase 3, upregulation of p53 expression and nuclear translocation, and downregulation of B-cell lymphoma 2 protein expression. Furthermore, curcumin treatment was demonstrated to increase Yes-associated protein (YAP) expression in a time-dependent manner, which was concurrent with the curcumin-induced expression pattern of p53 after 2 h. In addition, knockdown of YAP by small interfering RNA caused the attenuation of curcumin-induced increased p53 expression in RCC cells. In conclusion, the present results indicate that combined curcumin and temsirolimus treatment has a synergistic effect on apoptosis in human RCC cells, through the activation of p53. Mechanistically, YAP is essential in the induction of p53 expression by curcumin. Furthermore, the results suggest that pre-treatment or co-treatment of cells with low concentration curcumin enhances the response to targeted drugs, and this presents a potentially novel and efficient strategy to overcome drug resistance in human RCC.

Verteporfin, a suppressor of YAP-TEAD complex, presents promising antitumor properties on ovarian cancer

Yes-associated protein (YAP) is a key transcriptional coactivator of Hippo pathway and has been shown to be an oncoprotein in ovarian cancer (OC). Verteporfin (VP), clinically used in photodynamic therapy for neovascular macular degeneration, has been recently proven to be a suppressor of YAP–TEAD complex and has shown potential in anticancer treatment. In this study, we aimed to explore the potential effect of VP in the treatment of OC. Our results showed that VP led to inhibition of proliferation in a time- and dose-dependent manner and to the suppression of migratory and invasive capacities of OC cells. Western blot and real-time polymerase chain reaction demonstrated that VP induced YAP cytoplasmic retention and deregulated inducible YAP and CCNs in OC cells. In vivo, VP exerted a significant effect on tumor growth in OVCAR8 xenograft mice, resulting in tumor nodules with lower average weight and reduced volume of gross ascites. In addition, VP treatment remarkably upregulated cytoplasmic YAP and phosphorylation YAP and downregulated CCN1 and CCN2, but exerted little effect on YAP-upstream components in Hippo pathway. In conclusion, our results suggested that VP may be a promising agent for OC, acting by suppressing YAP–TEAD complex.

A comparison of foamy and lentiviral vector genotoxicity in SCID-repopulating cells shows foamy vectors are less prone to clonal dominance

Hematopoietic stem cell (HSC) gene therapy using retroviral vectors has immense potential, but vector-mediated genotoxicity limits use in the clinic. Lentiviral vectors are less genotoxic than gammaretroviral vectors and have become the vector of choice in clinical trials. Foamy retroviral vectors have a promising integration profile and are less prone to read-through transcription than gammaretroviral or lentiviral vectors. Here, we directly compared the safety and efficacy of foamy vectors to lentiviral vectors in human CD34(+) repopulating cells in immunodeficient mice. To increase their genotoxic potential, foamy and lentiviral vectors with identical transgene cassettes with a known genotoxic spleen focus forming virus promoter were used. Both vectors resulted in efficient marking in vivo and a total of 825 foamy and 460 lentiviral vector unique integration sites were recovered in repopulating cells 19 weeks after transplantation. Foamy vector proviruses were observed less often near RefSeq gene and proto-oncogene transcription start sites than lentiviral vectors. The foamy vector group were also more polyclonal with fewer dominant clones (two out of six mice) than the lentiviral vector group (eight out of eight mice), and only lentiviral vectors had integrants near known proto-oncogenes in dominant clones. Our data further support the relative safety of foamy vectors for HSC gene therapy.

Understanding the Multifaceted Role of Human Down Syndrome Kinase DYRK1A

The dual-specificity tyrosine (Y) phosphorylation-regulated kinase DYRK1A, also known as Down syndrome (DS) kinase, is a dosage-dependent signaling kinase that was originally shown to be highly expressed in DS patients as a consequence of trisomy 21. Although this was evident some time ago, it is only in recent investigations that the molecular roles of DYRK1A in a wide range of cellular processes are becoming increasingly apparent. Since initial knowledge on DYRK1A became evident through minibrain mnb, the Drosophila homolog of DYRK1A, this review will first summarize the scientific reports on minibrain and further expand on the well-established neuronal functions of mammalian and human DYRK1A. Recent investigations across the current decade have provided rather interesting and compelling evidence in establishing nonneuronal functions for DYRK1A, including its role in infection, immunity, cardiomyocyte biology, cancer, and cell cycle control. The latter part of this review will therefore focus in detail on the emerging nonneuronal functions of DYRK1A and summarize the regulatory role of DYRK1A in controlling Tau and α-synuclein. Finally, the emerging role of DYRK1A in Parkinson's disease will be outlined.

Markers of Hippo-Pathway Activity in Tumor Forming Liver Lesions

Hepatocellular Carcinoma (HCC) is a lethal cancer worldwide. Recently, the hippo signaling pathway has been implicated in tumorigenesis of HCC and other malignant tumors. Aim of the study was therefore to evaluate the hippo signaling pathway activity and its clinico-pathological associations and crosstalk in different tumor forming hepatocellular lesions (HCC, hepatocellular adenoma (HCA), focal nodular hyperplasia (FNH) and cirrhosis). A tissue micro array (TMA) from paired human tumorous and non-tumorous (NT) tissue samples of HCC (n = 92), HCA (n = 25), FNH (n = 28) and cirrhosis (n = 28; no NT) was constructed. The hippo-pathway related proteins of MST1/2, (nuclear(n)/cytoplasmic(c)) YAP and (phospho(p)) TAZ and interactors as Glypican3, RASSF1a, pAKT, pERK and pP70S6K were evaluated by immunohistochemistry (IHC). Proliferation was assessed by Ki67-IHC and apoptosis by TUNEL-technique. MST1/2- and nYAP-immunoreactivity was associated with lymph node status (p = 0.048, p = 0.001), higher grading (p = 0.012, p = 0.24) and unfavorable relapse-free survival (p = 0.004, p = 0.003). MST1/2, c/nYAP and pTAZ were significantly different between HCC/NT (p < 0.001, p = 0.029, p < 0.001, p < 0.001) and mono-/polyclonal hepatocellular lesions (HCC/HCA vs. FNH/cirrhosis; all p ≤ 0.001). Phospho-TAZ-negativity and nYAP-positivity were almost exclusively and MST1/2 exclusively detected in HCC. MST1/2 correlated with pP70S6K (p = 0.002), pERK (p = 0.042), RASSF1a-IRS (p = 0.002) and GPC3 (p < 0.001) and nYAP with GPC3 (p = 0.025), higher Ki67-indices (p = 0.016) and lower apoptosis rate (p = 0.078). MST1/2 and nYAP are unfavorable prognostic markers associated with an aggressive tumor-phenotype in HCC. Positive nYAP- and negative pTAZ-immunostaining were strong indicators of a monoclonal hepatocellular lesion. The unexpected findings for MST1/2 remain to be elucidated.

SnoN Antagonizes the Hippo Kinase Complex to Promote TAZ Signaling during Breast Carcinogenesis

SnoN regulates multiple signaling pathways, including TGF-β/Smad and p53, and displays both pro-oncogenic and anti-oncogenic activities in human cancer. We have observed previously that both its intracellular localization and expression levels are sensitive to cell density, suggesting that it may crosstalk with Hippo signaling. Here we report that, indeed, SnoN interacts with multiple components of the Hippo pathway to inhibit the binding of Lats2 to TAZ and the subsequent phosphorylation of TAZ, leading to TAZ stabilization. Consistently, SnoN enhances the transcriptional and oncogenic activities of TAZ, and reducing SnoN decreases TAZ expression as well as malignant progression of breast cancer cells. Interestingly, SnoN itself is downregulated by Lats2 that is activated by the Scribble basolateral polarity protein. Thus, SnoN is a critical component of the Hippo regulatory network that receives signals from the tissue architecture and polarity to coordinate the activity of intracellular signaling pathways.

Role of Merlin/NF2 inactivation in tumor biology

Merlin (Moesin-ezrin-radixin-like protein, also known as schwannomin) is a tumor suppressor protein encoded by the neurofibromatosis type 2 gene NF2. Loss of function mutations or deletions in NF2 cause neurofibromatosis type 2 (NF2), a multiple tumor forming disease of the nervous system. NF2 is characterized by the development of bilateral vestibular schwannomas. Patients with NF2 can also develop schwannomas on other cranial and peripheral nerves, as well as meningiomas and ependymomas. The only potential treatment is surgery/radiosurgery, which often results in loss of function of the involved nerve. There is an urgent need for chemotherapies that slow or eliminate tumors and prevent their formation in NF2 patients. Interestingly NF2 mutations and merlin inactivation also occur in spontaneous schwannomas and meningiomas, as well as other types of cancer including mesothelioma, glioma multiforme, breast, colorectal, skin, clear cell renal cell carcinoma, hepatic and prostate cancer. Except for malignant mesotheliomas, the role of NF2 mutation or inactivation has not received much attention in cancer, and NF2 might be relevant for prognosis and future chemotherapeutic approaches. This review discusses the influence of merlin loss of function in NF2-related tumors and common human cancers. We also discuss the NF2 gene status and merlin signaling pathways affected in the different tumor types and the molecular mechanisms that lead to tumorigenesis, progression and pharmacological resistance.

Targeting the Hippo pathway: Clinical implications and therapeutics

The Hippo pathway plays a critical role in tissue and organ size regulation by restraining cell proliferation and apoptosis under homeostatic conditions. Deregulation of this pathway can promote tumorigenesis in multiple malignant human tumor types, including sarcoma, breast, lung and liver cancers. In this review, we summarize the current understanding of Hippo pathway function, it's role in human cancer, and address the potential of Hippo pathway member proteins as therapeutic targets for a variety of tumors.

Cancer Biomarkers from Genome-Scale DNA Methylation: Comparison of Evolutionary and Semantic Analysis Methods

DNA methylation profiling exploits microarray technologies, thus yielding a wealth of high-volume data. Here, an intelligent framework is applied, encompassing epidemiological genome-scale DNA methylation data produced from the Illumina’s Infinium Human Methylation 450K Bead Chip platform, in an effort to correlate interesting methylation patterns with cancer predisposition and, in particular, breast cancer and B-cell lymphoma. Feature selection and classification are employed in order to select, from an initial set of ~480,000 methylation measurements at CpG sites, predictive cancer epigenetic biomarkers and assess their classification power for discriminating healthy versus cancer related classes. Feature selection exploits evolutionary algorithms or a graph-theoretic methodology which makes use of the semantics information included in the Gene Ontology (GO) tree. The selected features, corresponding to methylation of CpG sites, attained moderate-to-high classification accuracies when imported to a series of classifiers evaluated by resampling or blindfold validation. The semantics-driven selection revealed sets of CpG sites performing similarly with evolutionary selection in the classification tasks. However, gene enrichment and pathway analysis showed that it additionally provides more descriptive sets of GO terms and KEGG pathways regarding the cancer phenotypes studied here. Results support the expediency of this methodology regarding its application in epidemiological studies.

Hippo circuitry and the redox modulation of hippo components in cancer cell fate decisions

Meticulous and precise control of organ size is undoubtedly one of the most pivotal processes in mammalian development and regeneration along with cell differentiation, morphogenesis and programmed cell death. These processes are strictly regulated by complex and highly coordinated mechanisms to maintain a steady growth state. There are a number of extrinsic and intrinsic factors that dictate the total number and/or size of cells by influencing growth, proliferation, differentiation and cell death. Multiple pathways, such as those involved in promoting organ size and others that restrict disproportionate tissue growth act simultaneously to maintain cellular and tissue homeostasis. Aberrations at any level in these organ size-regulating processes can lead to various pathological states with cancers being the most formidable one (Yin and Zhang, 2011). Extensive research in the realm of growth control has led to the identification of the Hippo-signaling pathway as a critical network in modulating tissue growth via its effect on multiple signaling pathways and through intricate crosstalk with proteins that regulate cell polarity, adhesion and cell-cell interactions (Zhao et al., 2011b). The Hippo pathway controls cell number and organ size by transducing signals from the plasma membrane to the nucleus to regulate the expression of genes involved in cell fate determination (Shi et al., 2015). In this review, we summarize the recent discoveries concerning Hippo pathway, its diversiform regulation in mammals as well as its implications in cancers, and highlight the possible role of oxidative stress in Hippo pathway regulation.

Alterations in the NF2/LATS1/LATS2/YAP Pathway in Schwannomas

Schwannomas are benign nerve sheath tumors composed of well-differentiated Schwann cells. Other than frequent NF2 (neurofibromatosis type 2) mutations (50%-60%), their molecular pathogenesis is not fully understood. LATS1 and LATS2 are downstream molecules of NF2 and are negative regulators of the yes-associated protein (YAP) oncogene in the Hippo signaling pathway. We assessed mutations of the NF2, LATS1, and LATS2 genes, promoter methylation of LATS1 and LATS2, and expression of YAP and phosphorylated YAP in 82 cases of sporadic schwannomas. Targeted sequencing using the Ion Torrent Proton instrument revealed NF2 mutations in 45 cases (55%), LATS1 mutations in 2 cases (2%), and LATS2 mutations in 1 case (1%) of schwannoma. Methylation-specific polymerase chain reaction showed promoter methylation of LATS1 and LATS2 in 14 cases (17%) and 25 cases (30%), respectively. Overall, 62 cases (76%) had at least 1 alteration in the NF2, LATS1, and/or LATS2 genes. Immunohistochemistry revealed nuclear YAP expression in 18 of 42 cases of schwannoma (43%) and reduced cytoplasmic phosphorylated YAP expression in 15 of 49 cases of schwannoma (31%), all of which had at least 1 alteration in the NF2, LATS1, and/or LATS2 genes. These results suggest that an abnormal Hippo signaling pathway is involved in the pathogenesis of most sporadic schwannomas.

Mieap suppresses murine intestinal tumor via its mitochondrial quality control

Mieap, a novel p53-inducible protein, plays a key role in maintaining healthy mitochondria in various pathophysiological states. Here, we show that Mieap deficiency in Apc^Min/+ mice is strikingly associated with the malignant progression of murine intestinal tumors. To understand the role that Mieap plays in in vivo tumorigenesis, we generated Mieap heterozygous (Apc^Min/+ Mieap^+/−) and homozygous (Apc^Min/+ Mieap^−/−) Apc^Min/+ mice. Interestingly, the Apc^Min/+ mice with the Mieap^+/− and Mieap^−/− genetic background revealed remarkable shortening of the lifetime compared to Apc^Min/+ mice because of severe anemia. A substantial increase in the number and size of intestinal polyps was associated with Mieap gene deficiency. Histopathologically, intestinal tumors in the Mieap-deficient Apc^Min/+ mice clearly demonstrated advanced grades of adenomas and adenocarcinomas. We demonstrated that the significant increase in morphologically unhealthy mitochondria and trace accumulations of reactive oxygen species may be mechanisms underlying the increased malignant progression of the intestinal tumors of Mieap-deficient Apc^Min/+ mice. These findings suggest that the Mieap-regulated mitochondrial quality control plays a critical role in preventing mouse intestinal tumorigenesis.

Yes-associated protein (Yap) is necessary for ciliogenesis and morphogenesis during pronephros development in zebrafish (Danio Rerio)

The Hippo signaling pathway and its transcriptional co-activator Yap are known as essential regulators for cell proliferation and organ size. However, little is known about their roles in kidney development and ciliogenesis. We examined expression of Yap during zebrafish embryogenesis, and its transcripts were detected in pronephric duct, while Yap protein was found to be localized in the cytoplasm and apical membrane in kidney epithelium cells. By morpholino (MO) knockdown of yap expression in zebrafish, the injected larve exhibits pronephic cysts and many aspects of ciliopathy, which can be rescued by full-length yap mRNA, but not yap^S127A mRNA. With transgenic Tg(Na⁺/K⁺ ATPase:EGFP), we found that lacking Yap led to expansion and discontinuities of pronephric duct, as well as disorganization of cloaca during pronephros morphogenesis. Mis-located Na⁺/K⁺ ATPase and ciliary abnormalities are also detected in pronephric duct of yap morphants. In addition, genetic analysis suggests that yap interacts with ift20, ift88 and arl13b in pronephric cyst formation. Taken together, our data reveals that Yap is required for pronephric duct integrity, maintenance of baso-lateral cell polarity, and ciliogenesis during zebrafish kidney development.

Hippo Component TAZ Functions as a Co-repressor and Negatively Regulates ΔNp63 Transcription through TEA Domain (TEAD) Transcription Factor

Transcriptional co-activator with a PDZ binding domain (TAZ) is a WW domain-containing transcriptional co-activator and a core component of an emerging Hippo signaling pathway that regulates organ size, tumorigenesis, metastasis, and drug resistance. TAZ regulates these biological functions by up-regulating downstream cellular genes through transactivation of transcription factors such as TEAD and TTF1. To understand the molecular mechanisms underlying TAZ-induced tumorigenesis, we have recently performed a gene expression profile analysis by overexpressing TAZ in mammary cells. In addition to the TAZ-up-regulated genes that were confirmed in our previous studies, we identified a large number of cellular genes that were down-regulated by TAZ. In this study, we have confirmed these down-regulated genes (including cytokines, chemokines, and p53 gene family members) as bona fide downstream transcriptional targets of TAZ. By using human breast and lung epithelial cells, we have further characterized ΔNp63, a p53 gene family member, and shown that TAZ suppresses ΔNp63 mRNA, protein expression, and promoter activity through interaction with the transcription factor TEAD. We also show that TEAD can inhibit ΔNp63 promoter activity and that TAZ can directly interact with ΔNp63 promoter-containing TEAD binding sites. Finally, we provide functional evidence that down-regulation of ΔNp63 by TAZ may play a role in regulating cell migration. Altogether, this study provides novel evidence that the Hippo component TAZ can function as a co-repressor and regulate biological functions by negatively regulating downstream cellular genes.

New insights into the pathophysiology of the tuberous sclerosis complex: Crosstalk of mTOR- and hippo-YAP pathways in cell growth

Tuberous Sclerosis Complex (TSC) is a genetic disease causing uncontrolled growth of hamartomas involving different organ systems. In the last decade, dysregulation of the mTORC1 pathway was shown to be a main driver of tumor growth in TSC. Recently, a new crosstalk was detected between the mTORC1 and the Hippo-YAP pathway, another major cell signaling cascade controlling cell growth and organ size. Elucidating this connection is an important step in understanding the complexity of TSC, enabling new pharmacological targets and therapeutical options.

The cancer COMPASS: navigating the functions of MLL complexes in cancer

The mixed-lineage leukemia family of histone methyltransferases (MLL1-4, or KMT2A-D) were previously linked to cancer through the founding member, MLL1/KMT2A, which is often involved in translocation-associated gene fusion events in childhood leukemias. However, in recent years, a multitude of tumor exome sequencing studies have revealed that orthologues MLL3/KMT2C and MLL2/KMT2D are mutated in a significant percentage of a large variety of malignancies, particularly solid tumors. These unexpected findings necessitate a deeper inspection into the activities and functional differences between the MLL/KMT2 family members. This review provides an overview of this protein family and its relation to cancers, focusing on the recent links between MLL3/KMT2C and MLL2/4/KMT2D and their potential roles as tumor suppressors in an assortment of cell types.

Hippo pathway in mammary gland development and breast cancer

Accumulated evidence suggests that the Hippo signaling pathway plays crucial roles in mammary gland development and breast cancer. Key components of the Hippo pathway regulate breast epithelial cell proliferation, migration, invasion, and stemness. Additionally, the Hippo pathway regulates breast tumor growth, metastasis, and drug resistance. It is expected that the Hippo pathway will provide novel therapeutic targets for breast cancer. This review will discuss and summarize the roles of several core components of the Hippo pathway in mammary gland development and breast cancer.

Automated analysis of immunohistochemistry images identifies candidate location biomarkers for cancers

Molecular biomarkers are changes measured in biological samples that reflect disease states. Such markers can help clinicians identify types of cancer or stages of progression, and they can guide in tailoring specific therapies. Many efforts to identify biomarkers consider genes that mutate between normal and cancerous tissues or changes in protein or RNA expression levels. Here we define location biomarkers, proteins that undergo changes in subcellular location that are indicative of disease. To discover such biomarkers, we have developed an automated pipeline to compare the subcellular location of proteins between two sets of immunohistochemistry images. We used the pipeline to compare images of healthy and tumor tissue from the Human Protein Atlas, ranking hundreds of proteins in breast, liver, prostate, and bladder based on how much their location was estimated to have changed. The performance of the system was evaluated by determining whether proteins previously known to change location in tumors were ranked highly. We present a number of candidate location biomarkers for each tissue, and identify biochemical pathways that are enriched in proteins that change location. The analysis technology is anticipated to be useful not only for discovering new location biomarkers but also for enabling automated analysis of biomarker distributions as an aid to determining diagnosis.