EGR-1 forms a complex with YAP-1 and upregulates Bax expression in irradiated prostate carcinoma cells

Early growth response 1 regulates dual‑specificity protein phosphatase 1 and inhibits cell migration and invasion of tongue squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumors in the head and neck, and among the OSCCs, tongue squamous cell carcinoma (TSCC) is one of the most common types. Although therapy strategies have recently advanced, the prognosis of TSCC has not substantially improved. Metastasis is one of the main causes of patient mortality in TSCC; therefore, it is necessary to elucidate the mechanism by which TSCC metastasis is regulated. In the present study, the early growth response 1 (Egr-1) expression in TSCC was analyzed based on GEO datasets and the effect of Egr-1 in TSCC tumor cell migration and invasion was measured using Transwell assay. By overexpressing dual-specificity protein phosphatase 1 (DUSP1) in cells with Egr-1 knockdown using lentivirus infection, the role of DUSP1 in Egr-1-regulated TSCC cell migration and invasion was determined. By using luciferase and ChIP assays, the mechanism behind how DUSP1 is regulated by Egr-1 was detected. In the present study, it was demonstrated that Egr-1 was downregulated in TSCC and the knockdown of Egr-1 increased TSCC cell migration and invasion. The expression of Egr-1 was also correlated with DUSP1. The overexpression of DUSP1 in Egr-1 knockdown cells, reduced the level of cell migration and invasion. Furthermore, it was demonstrated that knockdown of Egr-1 inhibited the promoter activity of DUSP1 and the site through which Egr-1 regulates DUSP1 transcription was identified. In conclusion, the present study demonstrated that Egr-1 regulates TSCC cell migration and invasion through modulating DUSP1, suggesting the potential of Egr-1 and DUSP1 as therapy targets for TSCC.

Attenuating Epithelial-to-Mesenchymal Transition in Cancer through Angiopoietin-Like 4 Inhibition in a 3D Tumor Microenvironment Model

Epithelial-to-mesenchymal transition (EMT) plays a crucial role in metastatic cancer progression, and current research, which relies heavily on 2D monolayer cultures, falls short in recapitulating the complexity of a 3D tumor microenvironment. To address this limitation, a transcriptomic meta-analysis is conducted on diverse cancer types undergoing EMT in 2D and 3D cultures. It is found that mechanotransduction is elevated in 3D cultures and is further intensified during EMT, but not during 2D EMT. This analysis reveals a distinct 3D EMT gene signature, characterized by extracellular matrix remodeling coordinated by angiopoietin-like 4 (Angptl4) along with other canonical EMT regulators. Utilizing hydrogel-based 3D matrices with adjustable mechanical forces, 3D cancer cultures are established at varying physiological stiffness levels. A YAP:EGR-1 mediated up-regulation of Angptl4 expression is observed, accompanied by an upregulation of mesenchymal markers, at higher stiffness during cancer EMT. Suppression of Angptl4 using antisense oligonucleotides or anti-cAngptl4 antibodies leads to a dose-dependent abolishment of EMT-mediated chemoresistance and tumor self-organization in 3D, ultimately resulting in diminished metastatic potential and stunted growth of tumor xenografts. This unique programmable 3D cancer cultures simulate stiffness levels in the tumor microenvironment and unveil Angptl4 as a promising therapeutic target to inhibit EMT and impede cancer progression.

Chlamydial YAP activation in host endocervical epithelial cells mediates pro-fibrotic paracrine stimulation of fibroblasts

IMPORTANCE

Chronic or repeated infection of the female upper genital tract by C. trachomatis can lead to severe fibrotic sequelae, including tubal factor infertility and ectopic pregnancy. However, the molecular mechanisms underlying this effect are unclear. In this report, we define a transcriptional program specific to C. trachomatis infection of the upper genital tract, identifying tissue-specific induction of host YAP-a pro-fibrotic transcriptional cofactor-as a potential driver of infection-mediated fibrotic gene expression. Furthermore, we show that infected endocervical epithelial cells stimulate collagen production by fibroblasts and implicate chlamydial induction of YAP in this effect. Our results define a mechanism by which infection mediates tissue-level fibrotic pathology via paracrine signaling and identify YAP as a potential therapeutic target for the prevention of Chlamydia-associated scarring of the female genital tract.

CNN2 silencing inhibits colorectal cancer development through promoting ubiquitination of EGR1

Colorectal cancer (CRC) is one of the most commonly diagnosed malignant tumors of the digestive tract. H2-calponin (CNN2), an actin cytoskeleton-binding protein, is an isoform of the calponin protein family whose role in CRC is still unknown. Research based on clinical samples showed the up-regulation of CNN2 in CRC and its association with tumor development, metastasis, and poor prognosis of patients. Both in vitro loss-of-function and gain-of-function experiments showed that CNN2 participates in CRC development through influencing malignant cell phenotypes. In vivo, xenografts formed by CNN2 knockdown cells also showed a slower growth rate and smaller final tumors. Furthermore, EGR1 was identified as a downstream of CNN2, forming a complex with CNN2 and YAP1 and playing an essential role in the CNN2-induced regulation of CRC development. Mechanistically, CNN2 knockdown down-regulated EGR1 expression through enhancing its ubiquitination, thus decreasing its protein stability in a YAP1-dependent manner. In summary, CNN2 plays an EGR1-dependent promotion role in the development and progression of CRC, which may be a promising therapeutic target for CRC treatment.

Chlamydial YAP activation in host endocervical epithelial cells mediates pro-fibrotic paracrine stimulation of fibroblasts

Infection of the female genital tract by Chlamydia trachomatis can produce severe fibrotic sequelae, including tubal factor infertility and ectopic pregnancy. While infection demonstrably mediates a pro-fibrotic response in host cells, it remains unclear if intrinsic properties of the upper genital tract exacerbate chlamydial fibrosis. The relatively sterile environment of the upper genital tract is primed for a pro-inflammatory response to infection, potentially enhancing fibrosis - however, subclinical C. trachomatis infections still develop fibrosis-related sequelae. Here, we compare infection-associated and steady-state gene expression of primary human cervical and vaginal epithelial cells. In the former, we observe enhanced baseline expression and infection-mediated induction of fibrosis-associated signal factors (e.g. TGFA , IL6 , IL8 , IL20 ), implying predisposition to Chlamydia -associated pro-fibrotic signaling. Transcription factor enrichment analysis identified regulatory targets of YAP, a transcriptional cofactor induced by infection of cervical epithelial cells, but not vaginal epithelial cells. YAP target genes induced by infection include secreted fibroblast-activating signal factors; therefore, we developed an in vitro model involving coculture of infected endocervical epithelial cells with uninfected fibroblasts. Coculture enhanced fibroblast expression of type I collagen, as well as prompting reproducible (albeit statistically insignificant) induction of α-smooth muscle actin. Fibroblast collagen induction was sensitive to siRNA-mediated YAP knockdown in infected epithelial cells, implicating chlamydial YAP activation in this effect. Collectively, our results present a novel mechanism of fibrosis initiated by Chlamydia, wherein infection-mediated induction of host YAP facilitates pro-fibrotic intercellular communication. Chlamydial YAP activation in cervical epithelial cells is thus a determinant of this tissue's susceptibility to fibrosis.

Importance

Chronic or repeated infection of the female upper genital tract by C. trachomatis can lead to severe fibrotic sequelae, including tubal factor infertility and ectopic pregnancy. However, the molecular mechanisms underlying this effect are unclear. In this report, we define a transcriptional program specific to C. trachomatis infection of the upper genital tract, identifying tissue-specific induction of host YAP - a pro-fibrotic transcriptional cofactor - as a potential driver of infection-mediated fibrotic gene expression. Further, we show that infected endocervical epithelial cells stimulate collagen production by fibroblasts, and implicate chlamydial induction of YAP in this effect. Our results define a mechanism by which infection mediates tissue-level fibrotic pathology via paracrine signaling, and identify YAP as a potential therapeutic target for prevention of Chlamydia -associated scarring of the female genital tract.

New insights into the ambivalent role of YAP/TAZ in human cancers

Hippo signaling was first identified in Drosophila as a key controller of organ size by regulating cell proliferation and anti-apoptosis. Subsequent studies have shown that this pathway is highly conserved in mammals, and its dysregulation is implicated in multiple events of cancer development and progression. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) (hereafter YAP/TAZ) are the downstream effectors of the Hippo pathway. YAP/TAZ overexpression or activation is sufficient to induce tumor initiation and progression, as well as recurrence and therapeutic resistance. However, there is growing evidence that YAP/TAZ also exert a tumor-suppressive function in a context-dependent manner. Therefore, caution should be taken when targeting Hippo signaling in clinical trials in the future. In this review article, we will first give an overview of YAP/TAZ and their oncogenic roles in various cancers and then systematically summarize the tumor-suppressive functions of YAP/TAZ in different contexts. Based on these findings, we will further discuss the clinical implications of YAP/TAZ-based tumor targeted therapy and potential future directions.

Radiation-Induced Nephropathy in the Murine Model Is Ameliorated by Targeting Heparanase

Agents used to reduce adverse effects common in cancer treatment modalities do not typically possess tumor-suppressing properties. We report that heparanase, an extracellular matrix-degrading enzyme, is a promising candidate for preventing radiation nephropathy. Heparanase promotes tumor development and progression and is upregulated in tumors found in the abdominal/pelvic cavity, whose radiation treatment may result in radiation nephropathy. Additionally, heparan sulfate degradation by heparanase has been linked to glomerular and tubular/interstitial injury in several kidney disorders. In this study, heparanase mRNA levels were measured in HK-2- and HEK-293-irradiated kidney cells and in a murine radiation nephropathy model by qRT-PCR. Roneparstat (specific heparanase inhibitor) was administered to irradiated mice, and 24 h urinary albumin was measured. Kidneys were harvested and weighed 30 weeks post-irradiation. Clinically relevant doses of ionizing radiation upregulated heparanase expression in both renal cells and mice kidneys. A murine model of abdominal radiation therapy revealed that Roneparstat abolished radiation-induced albuminuria—the hallmark of radiation nephropathy. Given the well-documented anti-cancer effects of heparanase inhibition, our findings attest this enzyme to be a unique target in cancer therapy due to its dual action. Targeting heparanase exerts not only direct anti-tumor effects but protects against radiation-induced kidney damage—the backbone of cancer therapy across a range of malignancies.

Chlamydia trachomatis induces the transcriptional activity of host YAP in a Hippo-independent fashion

Introduction

The obligate intracellular pathogen Chlamydia trachomatis is the causative agent of the most common bacterial sexually transmitted disease worldwide. While the host response to infection by this pathogen has been well characterized, it remains unclear to what extent host gene expression during infection is the product of Chlamydia-directed modulation of host transcription factors.

Methods

To identify transcription factors potentially modulated by Chlamydia during infection, we infected immortalized endocervical epithelial cells (End1/E6E7) with the anogenital C. trachomatis serovar L2, harvesting polyadenylated RNA for bulk RNA-sequencing. Subsequent experiments elucidating the mechanism of infection-mediated YAP activation assayed YAP target gene expression via qRT-PCR, YAP nuclear translocation via quantitative immunofluorescence, and YAP phosphorylation via Western blotting.

Results

RNA sequencing of Chlamydia-infected endocervical epithelial cells revealed gene expression consistent with activity of YAP, a transcriptional coactivator implicated in cell proliferation, wound healing, and fibrosis. After confirming induction of YAP target genes during infection, we observed an infection-dependent increase in YAP nuclear translocation sensitive to inhibition of bacterial protein synthesis. While Hippo-mediated phosphoinhibition of YAP at S127 was unaffected by C. trachomatis infection, Hippo-independent phosphorylation at Y357 was increased. Infection did not enhance nuclear translocation of Y357F mutant YAP, illustrating a requirement for phosphorylation at this residue. Pharmacological inhibition of host Src-family kinase activity attenuated YAP Y357 phosphorylation, but not nuclear translocation - which was instead sensitive to inhibition of Abl.

Discussion

Our results define a transcriptome-altering mechanism of pathogen-directed YAP activation that bypasses canonical inhibition by the Hippo kinase cascade, with a potential link to chlamydial fibrosis and other advanced disease sequelae. Additional study is required to determine the specific role of infection-associated Y357 phosphorylation and Abl activity in chlamydial induction of YAP.

Hippo pathway dysregulation in gastric cancer: from Helicobacter pylori infection to tumor promotion and progression

The Hippo pathway plays a critical role for balancing proliferation and differentiation, thus regulating tissue homeostasis. The pathway acts through a kinase cascade whose final effectors are the Yes-associated protein (YAP) and its paralog transcriptional co‑activator with PDZ‑binding motif (TAZ). In response to a variety of upstream signals, YAP and TAZ activate a transcriptional program that modulates cellular proliferation, tissue repair after injury, stem cell fate decision, and cytoskeletal reorganization. Hippo pathway signaling is often dysregulated in gastric cancer and in Helicobacter pylori-induced infection, suggesting a putative role of its deregulation since the early stages of the disease. In this review, we summarize the architecture and regulation of the Hippo pathway and discuss how its dysregulation fuels the onset and progression of gastric cancer. In this setting, we also focus on the crosstalk between Hippo and other established oncogenic signaling pathways. Lastly, we provide insights into the therapeutic approaches targeting aberrant YAP/TAZ activation and discuss the related clinical perspectives and challenges.

Genetic Alterations and Deregulation of Hippo Pathway as a Pathogenetic Mechanism in Bone and Soft Tissue Sarcoma

The Hippo pathway is an evolutionarily conserved modulator of developmental biology with a key role in tissue and organ size regulation under homeostatic conditions. Like other signaling pathways with a significant role in embryonic development, the deregulation of Hippo signaling contributes to oncogenesis. Central to the Hippo pathway is a conserved cascade of adaptor proteins and inhibitory kinases that converge and regulate the activity of the oncoproteins YAP and TAZ, the final transducers of the pathway. Elevated levels and aberrant activation of YAP and TAZ have been described in many cancers. Though most of the studies describe their pervasive activation in epithelial neoplasms, there is increasing evidence pointing out its relevance in mesenchymal malignancies as well. Interestingly, somatic or germline mutations in genes of the Hippo pathway are scarce compared to other signaling pathways that are frequently disrupted in cancer. However, in the case of sarcomas, several examples of genetic alteration of Hippo members, including gene fusions, have been described during the last few years. Here, we review the current knowledge of Hippo pathway implication in sarcoma, describing mechanistic hints recently reported in specific histological entities and how these alterations represent an opportunity for targeted therapy in this heterogeneous group of neoplasm.

Combined role for YAP-TEAD and YAP-RUNX2 signalling in substrate-stiffness regulation of cardiac fibroblast proliferation

Cardiac fibrosis is associated with increased stiffness of the myocardial extracellular matrix (ECM) in part mediated by increased cardiac fibroblast proliferation However, our understanding of the mechanisms regulating cardiac fibroblast proliferation are incomplete. Here we characterise a novel mechanism involving a combined activation of Yes-associated protein (YAP) targets RUNX Family Transcription Factor 2 (RUNX2) and TEA Domain Transcription Factor (TEAD). We demonstrate that cardiac fibroblast proliferation is enhanced by interaction with a stiff ECM compared to a soft ECM. This is associated with activation of the transcriptional co-factor, YAP. We demonstrate that this stiffness induced activation of YAP enhances the transcriptional activity of both TEAD and RUNX2 transcription factors. Inhibition of either TEAD or RUNX2, using gene silencing, expression of dominant-negative mutants or pharmacological inhibition, reduces cardiac fibroblast proliferation. Using mutants of YAP, defective in TEAD or RUNX2 activation ability, we demonstrate a dual role of YAP-mediated activation of TEAD and RUNX2 for substrate stiffness induced cardiac fibroblast proliferation. Our data highlights a previously unrecognised role of YAP mediated RUNX2 activation for cardiac fibroblast proliferation in response to increased ECM stiffness.

Interplay of Developmental Hippo-Notch Signaling Pathways with the DNA Damage Response in Prostate Cancer

Prostate cancer belongs in the class of hormone-dependent cancers, representing a major cause of cancer incidence in men worldwide. Since upon disease onset almost all prostate cancers are androgen-dependent and require active androgen receptor (AR) signaling for their survival, the primary treatment approach has for decades relied on inhibition of the AR pathway via androgen deprivation therapy (ADT). However, following this line of treatment, cancer cell pools often become resistant to therapy, contributing to disease progression towards the significantly more aggressive castration-resistant prostate cancer (CRPC) form, characterized by poor prognosis. It is, therefore, of critical importance to elucidate the molecular mechanisms and signaling pathways underlying the progression of early-stage prostate cancer towards CRPC. In this review, we aim to shed light on the role of major signaling pathways including the DNA damage response (DDR) and the developmental Hippo and Notch pathways in prostate tumorigenesis. We recapitulate key evidence demonstrating the crosstalk of those pathways as well as with pivotal prostate cancer-related 'hubs' such as AR signaling, and evaluate the clinical impact of those interactions. Moreover, we attempt to identify molecules of the complex DDR-Hippo-Notch interplay comprising potentially novel therapeutic targets in the battle against prostate tumorigenesis.

Molecular regulation of trophoblast stem cell self-renewal and giant cell differentiation by the Hippo components YAP and LATS1

Background

Trophoblast stem cells (TSCs), the precursors of trophoblast cells of placenta, possess the potential to differentiate into various trophoblastic subtypes in vitro. Establishment of extraembryonic trophoblastic lineage is preceded by the “outside versus inside” positional information in preimplantation embryos, critically synchronized by the Hippo components. Abundant expression of Hippo effector YAP in TSCs and differentiated cells with paucity of information on Hippo regulation of TSC proliferation/differentiation led us test the hypothesis that Hippo dynamics is one of the regulators of  TSC proliferation/differentiation.

Methods

Blastocyst-derived murine TSCs were used. Dynamics of Hippo components were analyzed using immunofluorescence, western blotting, immunoprecipitation, qRT-PCR. Interaction studies were performed using full-length and deletion constructs. BrdU incorporation assay, flow cytometry-based polyploidy analysis and confocal microscopy were used to decipher the underlying mechanism.

Results

YAP translocates to the nucleus in TSCs and utilizes its WW₂ domain to interact with the PPQY motif of the stemness factor, CDX2. YAP limits TSC proliferation with associated effect on CDX2 target CyclinD1. Trophoblast giant cells (TGC) differentiation is associated with cytoplasmic retention of YAP, heightened pYAP^Ser127, decrease in the level of the core Hippo component, LATS1, which thereby impedes LATS1-LIMK2 association. Decreased LATS1-LIMK2 complex formation in TGCs was associated with elevated pLIMK2^Thr505 as well as its target pCOFILIN^Ser3. Precocious overexpression of LATS1 during trophoblast differentiation decreased TGC marker, Prl2c2, diminished pLIMK2^Thr505 and inactive COFILIN (pCOFILIN^Ser3) while COFILIN-phosphatase, CHRONOPHIN remained unchanged. LATS1 overexpression inhibited trophoblast endoreduplication with smaller-sized TGC-nuclei, lower ploidy level and disintegrated actin filaments. Inhibition of LIMK2 activity recapitulated the effects of LATS1 overexpression in trophoblast cells.

Conclusion

These results unveil a multilayered regulation of trophoblast self-renewal and differentiation by the Hippo components.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02844-w.

Lipolysis-Stimulated Lipoprotein Receptor Impairs Hepatocellular Carcinoma and Inhibits the Oncogenic Activity of YAP1 via PPPY Motif

Purpose

Lipolysis-stimulated lipoprotein receptor (LSR) is a type I single-pass transmembrane protein which is mainly expressed in the liver. In this study, we investigated if and how LSR is involved in the carcinogenesis of hepatocellular carcinoma (HCC).

Experimental Design

To evaluate if LSR was abnormally expressed in human HCC tissues, and how its expression was associated with the survival probability of patients, we obtained data from Gene Expression Omnibus and The Cancer Genome Atlas Program. To investigate if and how LSR regulates tumor growth, we knocked down and overexpressed LSR in human HCC cell lines. In addition, to evaluate the interaction between LSR and yes-associated protein1 (YAP1), we mutated LSR at PPPY motif, a binding site of YAP1.

Results

Totally, 454 patients were enrolled in the present study, and high expression of LSR significantly decreased the probability of death. Knockdown of LSR significantly increased the expansion of HCC cells and significantly promoted tumor growth. In addition, downregulation of LSR increased the nuclear accumulation and transcriptional function of YAP1. Conversely, overexpression of LSR impairs this function of YAP1 and phosphorylates YAP1 at serine 127. Of note, mutation of LSR at the PPPY motif could block the interaction between LSR and YAP1, and restore the transcriptional ability of YAP1.

Conclusions

The present study suggests that LSR binds to YAP1 via the PPPY motif. Thus, LSR increases the phosphorylation of YAP1 and impairs the growth of HCC. This highlights that targeting LSR might be a promising therapeutic strategy for HCC.

Early Growth Response 1 Strengthens Pol-III-Directed Transcription and Transformed Cell Proliferation by Controlling PTEN/AKT Signalling Activity

RNA polymerase III (Pol III) products play essential roles in ribosome assembly, protein synthesis, and cell survival. Deregulation of Pol-III-directed transcription is closely associated with tumorigenesis. However, the regulatory pathways or factors controlling Pol-III-directed transcription remain to be investigated. In this study, we identified a novel role of EGR1 in Pol-III-directed transcription. We found that Filamin A (FLNA) silencing stimulated EGR1 expression at both RNA and protein levels. EGR1 expression positively correlated with Pol III product levels and cell proliferation activity. Mechanistically, EGR1 downregulation dampened the occupancies of Pol III transcription machinery factors at the loci of Pol III target genes. Alteration of EGR1 expression did not affect the expression of p53, c-MYC, and Pol III general transcription factors. Instead, EGR1 activated RhoA expression and inhibited PTEN expression in several transformed cell lines. We found that PTEN silencing, rather than RhoA overexpression, could reverse the inhibition of Pol-III-dependent transcription and cell proliferation caused by EGR1 downregulation. EGR1 could positively regulate AKT phosphorylation levels and is required for the inhibition of Pol-III-directed transcription mediated by FLNA. The findings from this study indicate that EGR1 can promote Pol-III-directed transcription and cell proliferation by controlling the PTEN/AKT signalling pathway.

YAP signaling in preovulatory granulosa cells is critical for the functioning of the EGF network during ovulation

Failure to ovulate is a major cause of infertility. The critical pathway that induces ovulation involves the EGF and MAPK phosphorylation, but studies in rodents have suggested that the Hippo activator, YAP, is also involved. It is unknown whether YAP-dependent transcriptional activity is important for the LH- or EGF-induced ovulatory cascade in monovulatory species such as the cow. Using a well-defined preovulatory GC culture system, we employed pharmacological inhibitors to demonstrate that YAP signaling is critical for expression of EGFR and downstream target genes EREG, EGR1 and TNFAIP6. Most importantly, by using an ultrasound guided follicle injection system, we also showed that the classic Hippo signaling inhibitor Verteporfin inhibits GnRH-induced ovulation in vivo in cattle. In conclusion, YAP transcriptional activity is critical for EGF-like cascade induced by LH to promote ovulation in a monovulatory species.

Identification of a Prognostic Signature Model with Tumor Microenvironment for predicting Disease-free Survival after Radical Prostatectomy

Background: The tumor microenvironment (TME) and immune checkpoint inhibitors have been shown to promote active immune responses through different mechanisms. We attempted to identify the important prognostic genes and prognostic characteristics related to TME in prostate cancer (PCa).

Methods: The gene transcriptome profiles and clinical information of PCa patients were obtained from The Cancer Genome Atlas (TCGA) database, and the immune and stromal scores were calculated by the ESTIMATE algorithm. We evaluated the prognostic value of the risk score (RS) model based on univariate Cox analysis and least absolute shrinkage and selection operation (LASSO) Cox regression analysis and established a nomogram to predict disease-free survival (DFS) in PCa patients. The GSE70768 dataset was utilized for external validation. Twenty-two subsets of tumor-infiltrating immune cells were analyzed using the CIBERSORT algorithm.

Results: In this study, the patients with higher immune/stromal scores were associated with a worse DFS, higher Gleason score, and higher pathological T stage. Based on the immune and stromal scores, 515 differentially expressed genes (DEGs) were identified. The univariate Cox and LASSO Cox regression models were employed to select 18 DEGs from 515 DEGs and construct an RS model. The DFS of the high-RS group was significantly lower than that of the low-RS group (P<0.001). The AUCs for the 1-year, 3-year and 5-year DFS rates in the RS model were 0.890, 0.877 and 0.841, respectively. A nomogram of DFS was established based on the RS and Gleason score, and the AUCs for the 1-year, 3-year and 5-year DFS rates in the nomogram were 0.907, 0.893, and 0.872, respectively. These results were further validated in the GSE70768 dataset. In addition, the proportion of Tregs was determined to be higher in high-RS patients (P<0.05), and the expression levels of five immune checkpoints (CTLA-4, PD-1, LAG-3, TIM-3 and TIGIT) were observed to be higher in high-RS patients (P<0.05).

Conclusions: Our study established and validated an 18-gene prognostic signature model associated with TME, which might serve as a prognosis stratification tool to predict DFS in PCa patients after radical prostatectomy.

New insights in Hippo signalling alteration in human papillomavirus-related cancers

The persistent infection with high-risk human papillomavirus (HPV) is an etiologic factor for the development of different types of cancers, mainly attributed to the continuous expression of E6 and E7 HPV oncoproteins, which regulate several cell signalling pathways including the Hippo pathway. It has been demonstrated that E6 proteins promote the increase of the Hippo elements YAP, TAZ and TEAD, at protein level, as well as their transcriptional targets. Also, E6 and E7 oncoproteins promote nuclear YAP localization and a decrease in YAP negative regulators such as MST1, PTPN14 or SOCS6. Interestingly, Hippo signalling components modulate HPV activity, such as TEAD1 and the transcriptional co-factor VGLL1, induce the activation of HPV early and late promoters, while hyperactivation of YAP in specific cells facilitates virus infection by increasing putative HPV receptors and by evading innate immunity. Additionally, alterations in Hippo signalling elements have been found in HPV-related cancers and particularly, the involvement of HPV oncoproteins on the regulation of some of these Hippo components has been also proposed, although the precise mechanisms remain unclear. The present review addresses the recent findings describing the interplay between HPV and Hippo signalling in HPV-related cancers, a fact that highlights the importance of developing more in-depth studies in this field to establish key therapeutic targets.

Gone Caving: Roles of the Transcriptional Regulators YAP and TAZ in Skeletal Development

PURPOSE OF REVIEW

The development of the skeleton is controlled by cellular decisions determined by the coordinated activation of multiple transcription factors. Recent evidence suggests that the transcriptional regulator proteins, Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), could have important roles in directing the activity of these transcriptional programs. However, in vitro evidence for the roles of YAP and TAZ in skeletal cells has been hopelessly contradictory. The goals of this review are to provide a cross-sectional view on the state of the field and to synthesize the available data toward a unified perspective.

RECENT FINDINGS

YAP and TAZ are regulated by diverse upstream signals and interact downstream with multiple transcription factors involved in skeletal development, positioning YAP and TAZ as important signal integration nodes in an hourglass-shaped signaling pathway. Here, we provide a survey of putative transcriptional co-effectors for YAP and TAZ in skeletal cells. Synthesizing the in vitro data, we conclude that TAZ is consistently pro-osteogenic in function, while YAP can exhibit either pro- or anti-osteogenic activity depending on cell type and context. Synthesizing the in vivo data, we conclude that YAP and TAZ combinatorially promote developmental bone formation, bone matrix homeostasis, and endochondral fracture repair by regulating a variety of transcriptional programs depending on developmental stage. Here, we discuss the current understanding of the roles of the transcriptional regulators YAP and TAZ in skeletal development, and provide recommendations for continued study of molecular mechanisms, mechanotransduction, and therapeutic implications for skeletal disease.

The Hippo pathway in the heart: pivotal roles in development, disease, and regeneration. Nat Rev Cardiol. 2018;15:672-684. [PMID: 30111784 DOI: 10.1038/s41569-018-0063-3]

The Hippo-YAP (Yes-associated protein) pathway is an evolutionarily and functionally conserved regulator of organ size and growth with crucial roles in cell proliferation, apoptosis, and differentiation. This pathway has great potential for therapeutic manipulation in different disease states and to promote organ regeneration. In this Review, we summarize findings from the past decade revealing the function and regulation of the Hippo-YAP pathway in cardiac development, growth, homeostasis, disease, and regeneration. In particular, we highlight the roles of the Hippo-YAP pathway in endogenous heart muscle renewal, including the pivotal role of the Hippo-YAP pathway in regulating cardiomyocyte proliferation and differentiation, stress response, and mechanical signalling. The human heart lacks the capacity to self-repair; therefore, the loss of cardiomyocytes after injury such as myocardial infarction can result in heart failure and death. Despite substantial advances in the treatment of heart failure, an enormous unmet clinical need exists for alternative treatment options. Targeting the Hippo-YAP pathway has tremendous potential for developing therapeutic strategies for cardiac repair and regeneration for currently intractable cardiovascular diseases such as heart failure. The lessons learned from cardiac repair and regeneration studies will also bring new insights into the regeneration of other tissues with limited regenerative capacity.

EGR1 regulates angiogenic and osteoclastogenic factors in prostate cancer and promotes metastasis

Early growth response-1 (EGR1) is a transcription factor correlated with prostate cancer (PC) progression in a variety of contexts. For example, EGR1 levels increase in response to suppressed androgen receptor signaling or loss of the tumor suppressor, PTEN. EGR1 has been shown to regulate genes influencing proliferation, apoptosis, immune cell activation, and matrix degradation, among others. Despite this, the impact of EGR1 on PC metastatic colonization is unclear. We demonstrate using a PC model (DU145/RasB1) of bone and brain metastasis that EGR1 expression regulates angiogenic and osteoclastogenic properties of metastases. We have shown previously that FN14 (TNFRSF12A) and downstream NF-κB signaling is required for metastasis in this model. Here we demonstrate that FN14 ligation also leads to NF-κB-independent, MEK-dependent EGR1 expression. EGR1-depletion in DU145/RasB1 cells reduced both the number and size of metastases but did not affect primary tumor growth. Decreased EGR1 expression led to reduced blood vessel density in brain and bone metastases as well as decreased osteolytic bone lesion area and reduced numbers of osteoclasts at the bone-tumor interface. TWEAK (TNFSF12) induced several EGR1-dependent angiogenic and osteoclastogenic factors (e.g. PDGFA, TGFB1, SPP1, IL6, IL8, and TGFA, among others). Consistent with this, in clinical samples of PC, the level of several genes encoding angiogenic/osteoclastogenic pathway effectors correlated with EGR1 levels. Thus, we show here that EGR1 has a direct effect on prostate cancer metastases. EGR1 regulates angiogenic and osteoclastogenic factors, informing the underlying signaling networks that impact autonomous and microenvironmental mechanisms of cancer metastases.

The lncRNA MIR2052HG regulates ERα levels and aromatase inhibitor resistance through LMTK3 by recruiting EGR1

Background

Our previous genome-wide association study using the MA.27 aromatase inhibitors adjuvant trial identified SNPs in the long noncoding RNA MIR2052HG associated with breast cancer-free interval. MIR2052HG maintained ERα both by promoting AKT/FOXO3-mediated ESR1 transcription and by limiting ubiquitin-mediated ERα degradation. Our goal was to further elucidate MIR2052HG’s mechanism of action.

Methods

RNA-binding protein immunoprecipitation assays were performed to demonstrate that the transcription factor, early growth response protein 1 (EGR1), worked together with MIR2052HG to regulate that lemur tyrosine kinase-3 (LMTK3) transcription in MCF7/AC1 and CAMA-1 cells. The location of EGR1 on the LMTK3 gene locus was mapped using chromatin immunoprecipitation assays. The co-localization of MIR2052HG RNA and the LMTK3 gene locus was determined using RNA-DNA dual fluorescent in situ hybridization. Single-nucleotide polymorphisms (SNP) effects were evaluated using a panel of human lymphoblastoid cell lines.

Results

MIR2052HG depletion in breast cancer cells results in a decrease in LMTK3 expression and cell growth. Mechanistically, MIR2052HG interacts with EGR1 and facilitates its recruitment to the LMTK3 promoter. LMTK3 sustains ERα levels by reducing protein kinase C (PKC) activity, resulting in increased ESR1 transcription mediated through AKT/FOXO3 and reduced ERα degradation mediated by the PKC/MEK/ERK/RSK1 pathway. MIR2052HG regulated LMTK3 in a SNP- and aromatase inhibitor-dependent fashion: the variant SNP increased EGR1 binding to LMTK3 promoter in response to androstenedione, relative to wild-type genotype, a pattern that can be reversed by aromatase inhibitor treatment. Finally, LMTK3 overexpression abolished the effect of MIR2052HG on PKC activity and ERα levels.

Conclusions

Our findings support a model in which the MIR2052HG regulates LMTK3 via EGR1, and LMTK3 regulates ERα stability via the PKC/MEK/ERK/RSK1 axis. These results reveal a direct role of MIR2052HG in LMTK3 regulation and raise the possibilities of targeting MIR2052HG or LMTK3 in ERα-positive breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1130-3) contains supplementary material, which is available to authorized users.

Identification, Characterization, and Regulatory Mechanisms of a Novel EGR1 Splicing Isoform

EGR1 is a transcription factor expressed in many cell types that regulates genes involved in different biological processes including growth, proliferation, and apoptosis. Dysregulation of EGR1 expression has been associated with many pathological conditions such as tumors and brain diseases. Known molecular mechanisms underlying the control of EGR1 function include regulation of transcription, mRNA and protein stability, and post-translational modifications. Here we describe the identification of a splicing isoform for the human EGR1 gene. The newly identified splicing transcript encodes a shorter protein compared to the canonical EGR1. This isoform lacks a region belonging to the N-terminal activation domain and although it is capable of entering the nucleus, it is unable to activate transcription fully relative to the canonical isoform.

Involvement of CTCF in transcription regulation of EGR1 at early G1 phase as an architecture factor

Early growth response 1 (EGR1) is a transcription factor and regulates cellular processes such as proliferation, differentiation, and apoptosis. The expression of EGR1 is rapidly induced in response to several stimuli, and it activates the expression of downstream target genes involved in signaling cascades. EGR1 gene is also known to be transcribed in early G1 phase. However, the regulation of EGR1 transcription in early G1 phase is not clarified well. Here we found that CCCTC-binding factor (CTCF), a chromatin binding protein, is required to transcribe EGR1 gene at the onset of early G1 phase. We found that CTCF mediated the formation of higher-order chromatin structures among CTCF binding sites located in the EGR1 locus. Disruption of the CTCF-dependent higher-order chromatin structure using nuclease-dead Cas9 (dCas9)-mediated interference reduced the EGR1 transcription in early G1 phase. Collectively, we propose that CTCF has functional roles for the temporal expression of EGR1 in early G1 phase through regulation of higher-order chromatin structure organization.

Identification of genes involved in the regulation of TERT in hepatocellular carcinoma

Telomerase reverse transcriptase (TERT) promotes immortalization by protecting telomeres in cancer cells. Mutation of the TERT promoter is one of the most common genetic alterations in hepatocellular carcinoma (HCC), indicating that TERT upregulation is a critical event in hepatocarcinogenesis. Regulators of TERT transcription are, therefore, predicted to be plausible targets for HCC treatment. We undertook a genome‐wide shRNA library screen and identified C15orf55 and C7orf43 as regulators of TERT expression in HepG2 cells. Promoter assays showed that C15orf55‐ and C7orf43‐responsive sites exist between base pairs −58 and +36 and −169 and −59 in the TERT promoter, respectively. C15orf55 upregulates TERT expression by binding to two GC motifs in the SP1 binding site of the TERT promoter. C7orf43 upregulates TERT expression through Yes‐associated protein 1. The expression levels of C15orf55 and C7orf43 also correlated with that of TERT, and were significantly increased in both HCC tissues and their adjacent non‐tumor tissues, compared to normal liver tissues from non‐HCC patients. Analysis of 377 HCC patients in The Cancer Genome Atlas dataset showed that overall survival of patients with low levels of C15orf55 and C7orf43 expression in tumor tissues was better compared with patients with high levels of C15orf55 and/or high C7orf43 expression. These results indicate that C15orf55 and C7orf43 are involved in the incidence and progression of HCC by upregulating TERT. In conclusion, we identified C15orf55 and C7orf43 as positive regulators of TERT expression in HCC tissues. These genes are promising targets for HCC treatment.

GCN5 inhibition prevents IL-6-induced prostate cancer metastases through PI3K/PTEN/Akt signaling by inactivating Egr-1

General control non-derepressible 5 (GCN5) is ectopically expressed in different types of human cancer and association with the carcinogenesis, development, and poor prognosis of cancers. The present study was aimed to investigate the potential role and related mechanisms of GCN5 in IL-6–treated prostate cancer (PCa) cell. The results showed that an elevated GCN5 expression was stimulated by IL-6. Knockdown of GCN5 significantly inhibited IL-6–driven proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT). Moreover, early growth response-1 (Egr-1) expression was elevated by IL-6 treatment and GCN5 siRNA down-regulated the expression of Egr-1. Furthermore, overexpression of Egr-1 attenuated the effects of GCN5 silence on cell proliferation, migration, invasion, and EMT in PCa. Besides, knockdown of GCN5 resulted in the down-regulation of p-Akt and up-regulation of PTEN, which was partly impeded by Egr-1 overexpression. The effects of GCN5 overexpression on cell proliferation and invasion were suppressed by LY294002, In conclusion, these data demonstrated the negative effect of up-regulated GCN5 in IL-6-induced metastasis and EMT in PCa cells through PI3K/PTEN/Akt signaling pathway down-regulating Egr-1 expression.

The Ambivalent Function of YAP in Apoptosis and Cancer

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

DNA binding partners of YAP/TAZ

Hippo signaling plays critical roles in regulation of tissue homeostasis, organ size, and tumorigenesis by inhibiting YES-associated protein (YAP) and PDZ-binding protein TAZ through MST1/2 and LATS1/2 pathway. It is also engaged in cross-talk with various other signaling pathways, including WNT, BMPs, Notch, GPCRs, and Hedgehog to further modulate activities of YAP/TAZ. Because YAP and TAZ are transcriptional coactivators that lack DNA-binding activity, both proteins must interact with DNA-binding transcription factors to regulate target gene’s expression. To activate target genes involved in cell proliferation, TEAD family members are major DNA-binding partners of YAP/TAZ. Accordingly, YAP/TAZ were originally classified as oncogenes. However, YAP might also play tumor-suppressing role. For example, YAP can bind to DNA-binding tumor suppressors including RUNXs and p73. Thus, YAP might act either as an oncogene or tumor suppressor depending on its binding partners. Here, we summarize roles of YAP depending on its DNA-binding partners and discuss context-dependent functions of YAP/TAZ.

Immediate-Early Promoter-Driven Transgenic Reporter System for Neuroethological Research in a Hemimetabolous Insect

Genes expressed in response to increased neuronal activity are widely used as activity markers in recent behavioral neuroscience. In the present study, we established transgenic reporter system for whole-brain activity mapping in the two-spotted cricket Gryllus bimaculatus, a hemimetabolous insect used in neuroethology and behavioral ecology. In the cricket brain, a homolog of early growth response-1 (Gryllus egr-B) was rapidly induced as an immediate-early gene (IEG) in response to neuronal hyperexcitability. The upstream genomic fragment of Gryllus egr-B contains potential binding sites for transcription factors regulated by various intracellular signaling pathways, as well as core promoter elements conserved across insect/crustacean egr-B homologs. Using the upstream genomic fragment of Gryllus egr-B, we established an IEG promoter-driven transgenic reporter system in the cricket. In the brain of transgenic crickets, the reporter gene (a nuclear-targeted destabilized EYFP) was induced in response to neuronal hyperexcitability. Inducible expression of reporter protein was detected in almost all neurons after neuronal hyperexcitability. Using our novel reporter system, we successfully detected neuronal activation evoked by feeding in the cricket brain. Our IEG promoter-driven activity reporting system allows us to visualize behaviorally relevant neural circuits at cellular resolution in the cricket brain.

Quinacrine induces the apoptosis of human leukemia U937 cells through FOXP3/miR-183/β-TrCP/SP1 axis-mediated BAX upregulation

Quinacrine, which is clinically used as an antimalarial drug, has anti-cancer activity. However, mechanism underlying its cytotoxic effect remains to be completely elucidated. In the present study, we investigated the cytotoxic effect of quinacrine on human leukemia U937 cells. Quinacrine-induced apoptosis of U937 cells was accompanied with ROS generation, mitochondrial depolarization, and BAX upregulation. Quinacrine-treated U937 cells showed ROS-mediated p38 MAPK activation and ERK inactivation, which in turn upregulated FOXP3 transcription. FOXP3-mediated miR-183 expression decreased β-TrCP mRNA stability and suppressed β-TrCP-mediated SP1 degradation, thus increasing SP1 expression in U937 cells. Upregulated SP1 expression further increased BAX expression. BAX knock-down attenuated quinacrine-induced mitochondrial depolarization and increased the viability of quinacrine-treated cells. Together, our data indicate that quinacrine-induced apoptosis of U937 cells is mediated by mitochondrial alterations triggered by FOXP3/miR-183/β-TrCP/SP1 axis-mediated BAX upregulation.

Activating transcription factor 3 is crucial for antitumor activity and to strengthen the antiviral properties of Onconase

Onconase is a ribonuclease that presents both antitumor and antiviral properties linked to its ribonucleolytic activity and represents a new class of RNA-damaging drugs. It has reached clinical trials for the treatment of several cancers and human papilloma virus warts. Onconase targets different RNAs in the cell cytosol but Onconase-treated cells present features that are different from a simple arrest of protein synthesis. We have used microarray-derived transcriptional profiling to identify Onconase-regulated genes in two ovarian cancer cell lines (NCI/ADR-RES and OVCAR-8). RT-qPCR analyses have confirmed the microarray findings. We have identified a network of up-regulated genes implicated in different signaling pathways that may explain the cytotoxic effects exerted by Onconase. Among these genes, activating transcription factor 3 (ATF3) plays a central role in the key events triggered by Onconase in treated cancer cells that finally lead to apoptosis. This mechanism, mediated by ATF3, is cell-type independent. Up-regulation of ATF3 may also explain the antiviral properties of this ribonuclease because this factor is involved in halting viral genome replication, keeping virus latency or preventing viral oncogenesis. Finally, Onconase-regulated genes are different from those affected by nuclear-directed ribonucleases.

EGR-1/ASPP1 inter-regulatory loop promotes apoptosis by inhibiting cyto-protective autophagy

The decrease of ASPP1 (Apoptosis-Stimulating Protein of p53 1), a known p53 activator, has been linked to carcinogenesis and the cytotoxic resistance in various cancers, yet the underlying mechanisms of ASPP1 expression and its complex functions are not yet clear. Here, we report that ASPP1 forms an inter-regulatory loop with Early Growth Response 1 (EGR-1), and promotes apoptosis via inhibiting cyto-protective autophagy, independent of the well-documented p53-dependent mechanisms. We show that ASPP1 mRNA and protein were remarkably elevated by ectopic EGR-1 expression or endogenous EGR-1 activation, in cells with different tissue origins and p53 status. Conversely, RNAi-mediated EGR-1 knockdown suppressed ASPP1. The further mechanism studies revealed that ASPP1 promoter, mapped to -283/+88, which contained three conserved EGR-1 binding sites, was required for both binding and transactivity of EGR-1. In addition, we demonstrate that ASPP1 promoted EGR-1 in a positive feedback loop by preventing proteasome-mediated EGR-1 degradation or promoting EGR-1 nuclear import in response to anticancer natural compound Quercetin. Furthermore, albeit activating p53 in the nucleus is the well-studied function of ASPP1, we found that ASPP1 was predominately localized in the cytoplasm. Interestingly, the cytoplasmic ASPP1 retained its pro-apoptosis capability. Mechanistically, ASPP1 suppressed Atg5-Atg12 and also bound with Atg5-Atg12 to prevent its further complex formation with Atg16, resulting in the inhibition of cyto-protective autophagy. In conclusion, our results provide new insights into EGR-1/ASPP1 regulatory loop in sensitizing Quercetin-induced apoptosis. EGR-1/ASPP1, therefore, may be potentially used as therapeutic targets to improve cancer's response to pro-apoptosis treatments.

ETS (E26 transformation-specific) up-regulation of the transcriptional co-activator TAZ promotes cell migration and metastasis in prostate cancer

Prostate cancer is a very common malignant disease and a leading cause of death for men in the Western world. Tumorigenesis and progression of prostate cancer involves multiple signaling pathways, including the Hippo pathway. Yes-associated protein (YAP) is the downstream transcriptional co-activator of the Hippo pathway, is overexpressed in prostate cancer, and plays a vital role in the tumorigenesis and progression of prostate cancer. However, the role of the YAP paralog and another downstream effector of the Hippo pathway, transcriptional co-activator with PDZ-binding motif (TAZ), in prostate cancer has not been fully elucidated. Here, we show that TAZ is a basal cell marker for the prostate epithelium. We found that overexpression of TAZ promotes the epithelial-mesenchymal transition (EMT), cell migration, and anchorage-independent growth in the RWPE1 prostate epithelial cells. Of note, knock down of TAZ in the DU145 prostate cancer cells inhibited cell migration and metastasis. We also found that SH3 domain binding protein 1 (SH3BP1), a RhoGAP protein that drives cell motility, is a direct target gene of TAZ in the prostate cancer cells, mediating TAZ function in enhancing cell migration. Moreover, the prostate cancer-related oncogenic E26 transformation-specific (ETS) transcription factors, ETV1, ETV4, and ETV5, were required for TAZ gene transcription in PC3 prostate cancer cells. MAPK inhibitor U0126 treatment decreased TAZ expression in RWPE1 cells, and ETV4 overexpression rescued TAZ expression in RWPE1 cells with U0126 treatment. Our results show a regulatory mechanism of TAZ transcription and suggest a significant role for TAZ in the progression of prostate cancer.

Lipopolysaccharide Induces Human Pulmonary Micro-Vascular Endothelial Apoptosis via the YAP Signaling Pathway

Gram-negative bacterial lipopolysaccharide (LPS) induces a pathologic increase in lung vascular leakage under septic conditions. LPS-induced human pulmonary micro-vascular endothelial cell (HPMEC) apoptosis launches and aggravates micro-vascular hyper-permeability and acute lung injury (ALI). Previous studies show that the activation of intrinsic apoptotic pathway is vital for LPS-induced EC apoptosis. Yes-associated protein (YAP) has been reported to positively regulate intrinsic apoptotic pathway in tumor cells apoptosis. However, the potential role of YAP protein in LPS-induced HPMEC apoptosis has not been determined. In this study, we found that LPS-induced activation and nuclear accumulation of YAP accelerated HPMECs apoptosis. LPS-induced YAP translocation from cytoplasm to nucleus by the increased phosphorylation on Y357 resulted in the interaction between YAP and transcription factor P73. Furthermore, inhibition of YAP by small interfering RNA (siRNA) not only suppressed the LPS-induced HPMEC apoptosis but also regulated P73-mediated up-regulation of BAX and down-regulation of BCL-2. Taken together, our results demonstrated that activation of the YAP/P73/(BAX and BCL-2)/caspase-3 signaling pathway played a critical role in LPS-induced HPMEC apoptosis. Inhibition of the YAP might be a potential therapeutic strategy for lung injury under sepsis.

p53-dependent and -independent mechanisms are involved in (E)-1-(2-hydroxyphenyl)-3-(2-methoxynaphthalen-1-yl)prop-2-en-1-one (HMP)-induced apoptosis in HCT116 colon cancer cells

(E)-1-(2-hydroxyphenyl)-3-(2-methoxynaphthalen-1-yl)prop-2-en-1-one (HMP) is a novel synthetic naphthal chalcone derivative. The aim of this study was to investigate the mode of action underlying the antitumor activity of HMP. We found that treatment with HMP potently inhibited the clonogenicity and triggered cell death in HCT116 colon cancer cells. Flow cytometry showed that HMP induced an increase in the population of sub-G₀/G₁-phase cells. Annexin V binding assay revealed that HMP triggered apoptotic cell death. Furthermore, HMP stimulated the cleavages of caspase-7 and its substrate poly (ADP-ribose) polymerase (PARP). HMP promoted γ-H2AX formation and the production of reactive oxygen species (ROS), and up-regulated expression of the tumor suppressor p53. Interestingly, HMP-induced caspase-7 processing was not completely abrogated in p53-null (p53^-/-) HCT116 cells, suggesting that p53-dependent and -independent mechanisms are involved in HMP-induced apoptosis. Egr-1, a zinc finger transcription factor, was upregulated by HMP. Silencing of Egr-1 by shRNA significantly reduced HMP-induced caspase-7 and PARP cleavages, regardless of p53 status. These results suggest that HMP triggers caspase-mediated apoptosis through two distinct mechanisms involving p53-dependent and p53-independent, Egr-1-dependent pathways.

Age-associated up-regulation of EGR1 promotes granulosa cell apoptosis during follicle atresia in mice through the NF-κB pathway

Follicular atresia is the main process responsible for the loss of follicles and oocytes from the ovary, and it is the root cause of ovarian aging. Apoptosis of granulosa cells (GCs) is the cellular mechanism responsible for follicular atresia in mammals. Recent advances have highlighted fundamental roles for EGR1 in age-related diseases via the induction of apoptosis. In the present study, we found that the expression of EGR1 was significantly increased in aged mouse ovaries compared with young ovaries. Immunohistochemical analysis revealed strongly positive EGR1 staining in atretic follicles, especially in apoptotic granulosa cells. We further showed that EGR1 up-regulation in mouse primary granulosa cells inhibited cell proliferation and promoted apoptosis. In addition, the promotion of apoptosis in GCs by EGR1 increases over time and with reactive oxygen species (ROS) stimulation. Our mechanistic study suggested that EGR1 regulates GC apoptosis in a mitochondria-dependent manner and that this mainly occurs through the NF-κB signaling pathway. In conclusion, our results suggested that age-related up-regulation of EGR1 promotes GC apoptosis in follicle atresia during ovarian aging.

The MST/Hippo Pathway and Cell Death: A Non-Canonical Affair

The MST/Hippo signalling pathway was first described over a decade ago in Drosophila melanogaster and the core of the pathway is evolutionary conserved in mammals. The mammalian MST/Hippo pathway regulates organ size, cell proliferation and cell death. In addition, it has been shown to play a central role in the regulation of cellular homeostasis and it is commonly deregulated in human tumours. The delineation of the canonical pathway resembles the behaviour of the Hippo pathway in the fly where the activation of the core kinases of the pathway prevents the proliferative signal mediated by the key effector of the pathway YAP. Nevertheless, several lines of evidence support the idea that the mammalian MST/Hippo pathway has acquired new features during evolution, including different regulators and effectors, crosstalk with other essential signalling pathways involved in cellular homeostasis and the ability to actively trigger cell death. Here we describe the current knowledge of the mechanisms that mediate MST/Hippo dependent cell death, especially apoptosis. We include evidence for the existence of complex signalling networks where the core proteins of the pathway play a central role in controlling the balance between survival and cell death. Finally, we discuss the possible involvement of these signalling networks in several human diseases such as cancer, diabetes and neurodegenerative disorders.

Effect of YAP1 silencing on esophageal cancer

Background

YAP1, the nuclear effector of the Hippo pathway, has become an attractive target for treatment of malignancies and is a candidate oncogene in esophageal cancer (EC). We hypothesized that knockdown of YAP1 could suppress EC and could be used for targeted therapy. However, there are few reports of the effect of YAP1 knockdown in EC.

Materials and methods

Quantitative real-time polymerase chain reaction and Western blot assays were performed to determine the expression levels of YAP1 mRNA and protein in primary EC tissue samples, EC cell lines, and controls. Immunohistochemistry was also performed to detect YAP1 protein expression in primary EC tumor and matched nontumor control tissues. YAP1-knockdown cell lines were constructed using short-hairpin RNA, and MTT, flow cytometry, and transwell chamber assays were used to analyze the effect of YAP1 knockdown on EC cell proliferation, apoptosis, and invasion. In vivo tumor formation assays were used to investigate the antitumor effect of YAP1 knockdown.

Results

We found that YAP1 mRNA and protein were upregulated in EC and that YAP1 expression correlated significantly with metastasis and tumor stage. We also found that YAP1 knockdown repressed cell proliferation and invasion and promoted apoptosis of EC cell lines. In addition, animal experiments revealed that YAP1 knockdown suppressed the growth of esophageal tumors in vivo.

Conclusion

Collectively, these data confirm our hypothesis that YAP1 knockdown suppresses EC and suggest that YAP1 knockdown could be exploited in the targeted gene therapy of EC in the future.

Transforming growth factor-β1 induces cell cycle arrest by activating atypical cyclin-dependent kinase 5 through up-regulation of Smad3-dependent p35 expression in human MCF10A mammary epithelial cells

Cyclin-dependent kinases (Cdks) play important roles in control of cell division. Cdk5 is an atypical member of Cdk family with non-cyclin-like regulatory subunit, p35, but its role in cell cycle progression is still unclear. In the present study, we investigated the role of Cdk5/p35 on transforming growth factor-β1 (TGF-β1)-induced cell cycle arrest. In human MCF10A mammary epithelial cells, TGF-β1 induced cell cycle arrest at G1 phase and increased p27KIP1 expression. Interestingly, pretreatment with roscovitine, an inhibitor of Cdk5, or transfection with small interfering (si) RNAs specific to Cdk5 and p35 significantly attenuated the TGF-β1-induced p27KIP1 expression and cell cycle arrest. TGF-β1 increased Cdk5 activity via up-regulation of p35 gene at transcriptional level, and these effects were abolished by transfection with Smad3 siRNA or infection of adenovirus carrying Smad3 mutant at the C-tail (3SA). Chromatin immunoprecipitation assay further revealed that wild type Smad3, but not mutant Smad3 (3SA), binds to the region of the p35 promoter region (-1000--755) in a TGF-β1-dependent manner. These results for the first time demonstrate a role of Cdk5/p35 in the regulation of cell cycle progression modulated by TGF-β1.

Yes-associated protein (YAP) signaling regulates lipopolysaccharide-induced tissue factor expression in human endothelial cells

BACKGROUND

Sepsis-induced acute lung injury (ALI) is characterized by fibrin deposition, which indicates the local activation of coagulation. Tissue factor (TF), expressed in the pulmonary microvasculature, acts as a critical initiator of blood coagulation and ALI in sepsis. The molecular mechanism of lipopolysaccharide (LPS)-induced TF expression in endothelial cells (ECs), however, has not been determined. In this study, we implicate the Rho-associated protein kinase (ROCK)/Yes associated protein (YAP)/early growth response (Egr-1) signaling pathway in LPS-induced TF expression in vitro and in sepsis-induced ALI in vivo.

METHODS

Human umbilical vein ECs incubated with LPS were pretreated with or without the ROCK inhibitor Y-27632, a YAP small, interfering RNA (siRNA) and an Egr-1 siRNA. ROCK, YAP and Egr-1 signaling-induced protein expression was investigated by Western blot. The LPS-induced activation of YAP was analyzed by an immunofluorescent assay. Furthermore, we intratracheally injected YAP siRNA to assess septic ALI in mice by hematoxylin and eosin staining.

RESULTS

LPS rapidly induced ROCK activation and increased TF expression in ECs. LPS caused YAP shuttling into the nuclei of ECs and combined with Egr-1 via the activation of ROCK. Furthermore, the LPS-mediated TF expression increase was prevented by ROCK inactivation, YAP knockdown and Egr-1 depletion, suggesting that LPS-induced TF expression is closely associated with the ROCK/YAP/Egr-1 signaling pathway in ECs. Finally, an intratracheal injection of YAP siRNA relieved lung injury in septic mice.

CONCLUSION

This study not only suggests that ROCK/YAP/Egr-1 signaling regulates TF expression after stimulation with LPS in ECs, but it also indicates that LPS-induced activation of YAP signaling plays an important role in septic ALI in mice. Our findings provide a new insight into the pathogenic mechanism of TF expression, which is closely linked to septic ALI, and YAP signaling is considered to be a novel target for therapeutic intervention under septic conditions.

Early growth response 1 (EGR-1) is a transcriptional regulator of mitochondrial carrier homolog 1 (MTCH 1)/presenilin 1-associated protein (PSAP)

Attempts to elucidate the cellular function of MTCH1 (mitochondrial carrier homolog 1) have not yet rendered a clear insight into the function of this outer mitochondrial membrane protein. Classical biochemical and cell biology approaches have not produced the expected outcome. In vitro experiments have indicated a likely role in the regulation of cell death by apoptosis, and its reported interaction with presenilin 1 suggests a role in the cellular pathways in which this membrane protease participates, nevertheless in vivo data are missing. In an attempt to identify cellular pathways in which this protein might participate, we have studied its promoter looking for transcriptional regulators. We have identified several putative binding sites for EGR-1 (Early growth response 1; a protein involved in growth, proliferation and differentiation), in the proximal region of the MTCH1 promoter. Chromatin immunoprecipitation showed an enrichment of these sequences in genomic DNA bound to EGR-1 and transient overexpression of EGR-1 in cultured HEK293T cells induces an increase of endogenous MTCH1 levels. We also show that MTCH1 levels increase in response to treatment of cells with doxorubicin, an apoptosis inducer through DNA damage. The endogenous levels of MTCH1 decrease when EGR-1 levels are lowered by RNA interference. Our results indicate that EGR-1 is a transcriptional regulator of MTCH1 and give some clues about the cellular processes in which MTCH1 might participate.

YAP and TAZ Take Center Stage in Cancer

The Hippo pathway was originally identified and named through screening for mutations in Drosophila, and the core components of the Hippo pathway are highly conserved in mammals. In the Hippo pathway, MST1/2 and LATS1/2 regulate downstream transcription coactivators YAP and TAZ, which mainly interact with TEAD family transcription factors to promote tissue proliferation, self-renewal of normal and cancer stem cells, migration, and carcinogenesis. The Hippo pathway was initially thought to be quite straightforward; however, recent studies have revealed that YAP/TAZ is an integral part and a nexus of a network composed of multiple signaling pathways. Therefore, in this review, we will summarize the latest findings on events upstream and downstream of YAP/TAZ and the ways of regulation of YAP/TAZ. In addition, we also focus on the crosstalk between the Hippo pathway and other tumor-related pathways and discuss their potential as therapeutic targets.

Quantitative mRNA expression analysis of selected genes in patients with early-stage hypothyroidism induced by treatment with iodine-131

The present study aimed to investigate the molecular markers indicative of early-stage hypothyroidism induced by treatment with iodine-131, in order to assist in further investigations of radio iodine‑induced hypothyroidism. A total of 59 patients diagnosed with hyperthyroidism (male/female, 16/43; median age, 46.4 years) and 27 healthy subjects (male/female, 7/21; median age, 44.6 years) were included in the present study. All patients were treated with appropriate doses of iodine‑131 and, three months following treatment, the patients were subdivided into two groups: A group with early‑stage hypothyroidism symptoms, and a group with non‑early‑stage hypothyroidism, including euthyroid patients and patients remaining with hyperthyroidism. Tissue samples from the patients and healthy subjects were collected by fine needle biopsies, and the mRNA expression levels of B-cell lymphoma 2 (Bcl‑2), nuclear factor (NF)‑κB, Ku70, epidermal growth factor receptor (EGFR), early growth response 1 (Egr‑1), TP53 and ataxia telangiectasia mutated were analyzed using reverse transcription‑quantitative polymerase chain reaction prior to iodine‑131 treatment. The association of the variation of target genes with susceptibility to early‑stage hypothyroidism was analyzed. Compared with normal subjects, the mRNA expression levels of Ku70 (0.768, vs. 3.304, respectively; P<0.001) and EGFR (0.859, vs. 1.752, respectively; P<0.05) were significantly higher, whereas those of NF‑κB (0.884, vs. 0.578, respectively; P<0.05) and Bcl‑2 (1.235, vs. 0.834, respectively; P<0.05) were lower in the hyperthyroid patients. Following treatment with iodine‑131, 30 of the 59 (50.8%) patients with hyperthyroidism were diagnosed with early‑stage hypothyroidism, and in the early‑stage hypothyroidism group, the mRNA expression levels of Bcl‑2 were significantly decreased (P<0.05), whereas those of Egr‑1 (P<0.05) were significantly increased, compared with the non‑early‑stage hypothyroidism group. The association between the changes in the expression levles of Bcl‑2 and Egr‑1 and susceptibility to early‑stage hypothyroidism was supported by multivariate regression analysis. No significant changes in the expression levels of the other target genes were detected. The opposing changes in the mRNA expression levels of Bcl‑2 and Egr‑1 in patients with early‑stage hypothyroidism indicates their potential as prognostic markers of early-stage hypothyroidism induced by iodine-131 treatment.

Silencing Egr1 Attenuates Radiation-Induced Apoptosis in Normal Tissues while Killing Cancer Cells and Delaying Tumor Growth

Normal tissue toxicity reduces the therapeutic index of radiotherapy and decreases the quality of life for cancer survivors. Apoptosis is a key element of the radiation response in normal tissues like the hippocampus and small intestine, resulting in neurocognitive disorders and intestinal malabsorption. The Early Growth Response 1 (Egr1) transcription factor mediates radiation-induced apoptosis by activating the transcription of proapoptosis genes in response to ionizing radiation (IR). Therefore, we hypothesized that the genetic abrogation of Egr1 and the pharmacologic inhibition of its transcriptional activity could attenuate radiation-induced apoptosis in normal tissues. We demonstrated that Egr1-null mice had less apoptosis in the hippocampus and intestine following irradiation as compared with their wild-type littermates. A similar result was achieved using Mithramycin A (MMA) to prevent binding of Egr1 to target promoters in the mouse intestine. Abolishing Egr1 expression using shRNA dampened apoptosis and enhanced the clonogenic survival of irradiated HT22 hippocampal neuronal cells and IEC6 intestinal epithelial cells. Mechanistically, these events involved an abrogation of p53 induction by IR and an increase in the ratio of Bcl-2/Bax expression. In contrast, targeted silencing of Egr1 in two cancer cell lines (GL261 glioma cells and HCT116 colorectal cancer cells) was not radioprotective, since it reduced their growth while also sensitizing them to radiation-induced death. Further, Egr1 depletion delayed the growth of heterotopically implanted GL261 and HCT116 tumors. These results support the potential of silencing Egr1 in order to minimize the normal tissue complications associated with radiotherapy while enhancing tumor control.

YAP is closely correlated with castration-resistant prostate cancer, and downregulation of YAP reduces proliferation and induces apoptosis of PC-3 cells

Yes-associated protein 65 (YAP65) has been implicated as an oncogene, and its expression is increased in human cancer. Previous studies have demonstrated that alterations in YAP activity may result in tumourigenesis of the prostate. With androgen deprivation therapies becoming progressively ineffective, often leading to life‑threatening androgen‑resistant prostate cancer (CRPC). The present study aimed to analyse the role of YAP in prostate cancer (PCa), particularly in CRPC. YAP protein was detected using immunohistochemistry and western blot analysis in different prostatic tissues. In addition, three specific RNA interference vectors targeting the human YAP gene were synthesised, and PC‑3 cells with a stable inhibition of YAP were obtained by transfection. MTT, flow cytometry, reverse transcription‑quantitative polymerase chain reaction and western blot assays were used to analyse the effects of YAP inhibition on the proliferation and apoptosis of PC‑3 cells. The frequency of cells that were positive for YAP protein in PCa (78.13%) was significantly higher, compared with para‑PCa (26.67%; P=0.007) and benign prostatic hyperplasia (0%; P=0.002). The frequency of cells, which were positive for the expression of YAP exhibited a positive correlation (P=0.008) with the Gleason score, the tumour‑node‑metastasis staging (P=0.033) and the level of prostate specific antigens (P=0.0032) in PCa. The proliferative capacity of the transfected group was significantly lower, compared with the negative control group (P=0.022). The cell‑cycle of the transfected group was arrested in the G1 stage, which was detected using flow cytometry, and there was a significant increase in the apoptosis of cells in the transfected group (P=0.002). The mRNA and protein levels of TEA domain family member 1 were inhibited in the transfected group (P=0.001 and P=0.00, respectively). Therefore, it was concluded that gene transcription and protein expression of YAP may be involved in the development of PCa, particularly CRPC, and may be a novel biomarker for investigation of the occurrence and progression of CRPC. However, the mechanism underlying the modulation of YAP in CRPC remains to be fully elucidated.

Loss of YAP protein in prostate cancer is associated with Gleason score increase

AIMS AND BACKGROUND

To investigate the expression of YAP protein by immunohistochemistry in prostate cancer tissues and hyperplasia or normal prostate tissues adjacent to cancer, and establish the correlation of YAP expression with Gleason score.

METHODS AND STUDY DESIGN

The expression of YAP protein was evaluated in tissue microarray by immunohistochemistry. The samples included 66 radical prostatectomy specimens with clinically detected prostate cancer and 54 hyperplasia or normal prostate tissues adjacent to cancer.

RESULTS

YAP expression was present mainly in the nuclei of basal cells in both prostate cancer tissues and normal prostate or hyperplasia tissues adjacent to cancer. Cytoplasmic expression of YAP was weaker than nuclear expression in both malignant and nonmalignant luminal epithelial cells. YAP expression was decreased or lost in prostate cancer tissues; hyperplasia or normal prostate tissues adjacent to cancer exhibited stronger nuclear and cytoplasmic expression of YAP (p = 0.0001). Downregulation of YAP expression in prostate cancer samples correlated with Gleason score increase (p = 0.002).

CONCLUSIONS

This immunohistochemical study expands our knowledge of the expression and localization of YAP in prostate cancer tissue and nonmalignant prostate tissue adjacent to cancer. YAP might function as a tumor suppressor in prostate cancer. Such information may provide the foundation for the treatment of preneoplastic and neoplastic lesions of the prostate.