Neuregulin 1-activated ERBB4 interacts with YAP to induce Hippo pathway target genes and promote cell migration

The molecular crosstalk of the hippo cascade in breast cancer: A potential central susceptibility

The incidence of breast cancer is perpetually growing globally, and it remains a major public health problem and the leading cause of mortality in women. Though the aberrant activities of the Hippo pathway have been reported to be associated with cancer, constructive knowledge of the pathway connecting the various elements of breast cancer remains to be elucidated. The Hippo transducers, yes-associated protein (YAP) and transcriptional co-activator with PDZ binding motif (TAZ), are reported to be either tumor suppressors, oncogenes, or independent prognostic markers in breast cancer. Thus, there is further need for an explicative evaluation of the dilemma with this molecular contribution of Hippo transducers in modulating breast malignancy. In this review, we summarize the intricate crosstalk of the Hippo pathway in different aspects of breast malignancy, including stem-likeness, cellular signaling, metabolic adaptations, tumor microenvironment, and immune responses. The collective data shows that Hippo transducers play an indispensable role in mammary tumor formation, progression, and dissemination. However, the cellular functions of YAP/TAZ in tumorigenesis might be largely dependent on the mechanical and biophysical cues they interact with, as well as on the cell phenotype. This review provides a glimpse into the plausible biological contributions of the cascade to the inward progression of breast carcinoma and suggests potential therapeutic prospects.

Study on the relationship between Methylation of Neuregulin (NRG) Gene and Cervical Carcinoma

Objective

To investigate the relationship between the DNA methylation state of NRG1 promoter and its expression changes, and to analyze the clinical significance of its regulatory mechanism of DNA methylation in cervical carcinoma.

Methods

This was a retrospective study. One-hundred and twenty patients from the Department of Gynecology of Cangzhou People's Hospital from September 2017 to September 2019 were selected, including 40 cases of cervical SCC, 40 cases of high grade squamous intraepithelial lesions(HSIL) and 40 cases of control cervical tissues. RT-qPCR, immunohistochemistry and DNA methylation-specific PCR(MSP) were used to detect the mRNA and protein expression of NRG1 and DNA methylation status in different tissue types.

Results

Immunohistochemical results showed that the positive protein expression rate of NRG1 gene in the SCC group was lower than that in both HSIL and Control groups. RT-qPCR results showed that the mRNA gene of NRG1 gradually decreased in expression with the increase of cervical tissue lesions, with a statistically significant difference. Similarly, it also found that the mRNA expression level of NRG1 in the SCC group was independent of patients' age (p>0.05), but significantly correlated with tumor pathological staging, surgical pathology staging and lymphatic metastasis (p<0.05). Furthermore, methylation-specific PCR results revealed a significantly higher DNA methylation rate of NRG1 gene in the SCC group than in both HSIL and Control groups, with a statistically significant difference. Moreover, the methylation degree of NRG1 gene in SCC tissues was negatively correlated with its mRNA expression (p<0.05).

Conclusions

Abnormal DNA hypermethylation of NRG1 gene inhibits the expression of mRNA and protein in the progression of cervical tissue from normal to cancerous state, which is involved in the occurrence and development of cervical carcinoma.

Comprehensive split TEV based protein-protein interaction screening reveals TAOK2 as a key modulator of Hippo signalling to limit growth

The conserved Hippo signalling pathway plays a crucial role in tumour formation by limiting tissue growth and proliferation. At the core of this pathway are tumour suppressor kinases STK3/4 and LATS1/2, which limit the activity of the oncogene YAP1, the primary downstream effector. Here, we employed a split TEV-based protein-protein interaction screen to assess the physical interactions among 28 key Hippo pathway components and potential upstream modulators. This screen led us to the discovery of TAOK2 as pivotal modulator of Hippo signalling, as it binds to the pathway's core kinases, STK3/4 and LATS1/2, and leads to their phosphorylation. Specifically, our findings revealed that TAOK2 binds to and phosphorylates LATS1, resulting in the reduction of YAP1 phosphorylation and subsequent transcription of oncogenes. Consequently, this decrease led to a decrease in cell proliferation and migration. Interestingly, a correlation was observed between reduced TAOK2 expression and decreased patient survival time in certain types of human cancers, including lung and kidney cancer as well as glioma. Moreover, in cellular models corresponding to these cancer types the downregulation of TAOK2 by CRISPR inhibition led to reduced phosphorylation of LATS1 and increased proliferation rates, supporting TAOK2's role as tumour suppressor gene. By contrast, overexpression of TAOK2 in these cellular models lead to increased phospho-LATS1 but reduced cell proliferation. As TAOK2 is a druggable kinase, targeting TAOK2 could serve as an attractive pharmacological approach to modulate cell growth and potentially offer strategies for combating cancer.

Metastatic Lymph Node 64 (MLN64) Expression in Gastric Cancer: The Clinical and Molecular Implications in Drug Resistance

BACKGROUND/AIM

Metastatic lymph node 64 (MLN64) is often co-amplified with ERBB2 (HER2) and plays a role in the progression of breast and prostate cancer. The present study explored the expression of MLN64 in clinical gastric cancer in association with the ERBB family and its impact on drug resistance in patients.

MATERIALS AND METHODS

Two independent gastric cancer cohorts (n=324; n=87) were used to explore the expression profile of MLN64 in conjunction with ERBB family members in clinical gastric cancer and its association with neoadjuvant chemotherapy responses. Gastric cancer AGS and HCG27 cells with MLN64 knockdown were generated to determine the function of MLN64 in cell behavioural changes.

RESULTS

Gastric tumor tissues expressed significantly higher levels of MLN64 compared with normal tissues (p<0.01); however, MLN64 alone was a weak prognostic indicator. An integrated co-expression of MLN64, ERBB4, and NRG4 was a significant factor in assessing overall survival in both cohorts. MLN64 was a profound indicator of patient response to neoadjuvant chemotherapy. In vitro studies indicated a significant contribution of MLN64 to the response of gastric cancer cells to chemodrugs and Her-2 inhibitors. MLN64 knockdown also contributed to the adhesion and migration and suggested a possible mechanism mediated by the interaction between MLN64 and ERBBs.

CONCLUSION

MLN64 is an indicator of patient response to neoadjuvant chemotherapy in gastric cancer. Together with the expression pattern of ERBB4, MLN64 is a poor prognostic factor for patients with gastric cancer.

Targeted perturbation of signaling-driven condensates

Biomolecular condensates have emerged as a major organizational principle in the cell. However, the formation, maintenance, and dissolution of condensates are still poorly understood. Transcriptional machinery partitions into biomolecular condensates at key cell identity genes to activate these. Here, we report a specific perturbation of WNT-activated β-catenin condensates that disrupts oncogenic signaling. We use a live-cell condensate imaging method in human cancer cells to discover FOXO and TCF-derived peptides that specifically inhibit β-catenin condensate formation on DNA, perturb nuclear β-catenin condensates in cells, and inhibit β-catenin-driven transcriptional activation and colorectal cancer cell growth. We show that these peptides compete with homotypic intermolecular interactions that normally drive condensate formation. Using this framework, we derive short peptides that specifically perturb condensates and transcriptional activation of YAP and TAZ in the Hippo pathway. We propose a "monomer saturation" model in which short interacting peptides can be used to specifically inhibit condensate-associated transcription in disease.

Nrg1 Regulates Cardiomyocyte Migration and Cell Cycle in Ventricular Development

BACKGROUND

Cardiac ventricles provide the contractile force of the beating heart throughout life. How the primitive endocardium-layered myocardial projections called trabeculae form and mature into the adult ventricles is of great interest for biology and regenerative medicine. Trabeculation is dependent on the signaling protein Nrg1 (neuregulin-1). However, the mechanism of action of Nrg1 and its role in ventricular wall maturation are poorly understood.

METHODS

We investigated the functions and downstream mechanisms of Nrg1 signaling during ventricular chamber development using confocal imaging, transcriptomics, and biochemical approaches in mice with cardiac-specific inactivation or overexpression of Nrg1.

RESULTS

Analysis of cardiac-specific Nrg1 mutant mice showed that the transcriptional program underlying cardiomyocyte-oriented cell division and trabeculae formation depends on endocardial Nrg1 to myocardial ErbB2 (erb-b2 receptor tyrosine kinase 2) signaling and phospho-Erk (phosphorylated extracellular signal-regulated kinase; pErk) activation. Early endothelial loss of Nrg1 and reduced pErk activation diminished cardiomyocyte Pard3 and Crumbs2 (Crumbs Cell Polarity Complex Component 2) protein and altered cytoskeletal gene expression and organization. These alterations are associated with abnormal gene expression related to mitotic spindle organization and a shift in cardiomyocyte division orientation. Nrg1 is crucial for trabecular growth and ventricular wall thickening by regulating an epithelial-to-mesenchymal transition-like process in cardiomyocytes involving migration, adhesion, cytoskeletal actin turnover, and timely progression through the cell cycle G2/M phase. Ectopic cardiac Nrg1 overexpression and high pErk signaling caused S-phase arrest, sustained high epithelial-to-mesenchymal transition-like gene expression, and prolonged trabeculation, blocking compact myocardium maturation. Myocardial trabecular patterning alterations resulting from above- or below-normal Nrg1-dependent pErk activation were concomitant with sarcomere actin cytoskeleton disorganization. The Nrg1 loss- and gain-of-function transcriptomes were enriched for Yap1 (yes-associated protein-1) gene signatures, identifying Yap1 as a potential downstream effector. Furthermore, biochemical and imaging data reveal that Nrg1 influences pErk activation and Yap1 nuclear-cytoplasmic distribution during trabeculation.

CONCLUSIONS

These data establish the Nrg1-ErbB2/ErbB4-Erk axis as a crucial regulator of cardiomyocyte cell cycle progression and migration during ventricular development.

Cellular responses after (neratinib plus pemetrexed) exposure in NSCLC cells

We previously demonstrated that neratinib interacted with pemetrexed to kill non-small cell lung cancer (NSCLC) cells. From developing other drug combinations, we observed that several days following exposure, cells activated survival mechanisms to counteract drug toxicity. The present studies attempted to define mechanisms that evolve to reduce the efficacy of neratinib and pemetrexed. Neratinib and pemetrexed synergized to kill NSCLC cells expressing wild-type RAS proteins, mutant KRAS (G12S; Q61H; G12A and G12C) or mutant NRAS (Q61K) or mutant ERBB1 (L858R; L858R T790M and exon 19 deletion). Neratinib and pemetrexed interacted in a greater than additive fashion to kill after 24 h, and after a further 24 h culture in the absence of drugs. Mutant KRAS G12V was more cytoprotective than either activated MEK1 or activated AKT. Knockdown of mutant KRAS reduced drug combination killing at the 48 h timepoint. Despite culture for 24 h in the absence of the drugs, the expression and activities of ERBB1, ERBB2 and ERBB4 remained significantly lower as did the activities of mammalian target of rapamycin (mTOR) C1 and mTORC2. The drug combination reduced KRAS and NRAS levels for 24 h, however, in the absence of the drugs, RAS levels had normalized by 48 h. Expression of Beclin1 and ATG5 remained elevated and of MCL1 and BCL-XL lower. No evolutionary activations of survival signaling by ERBB3, c-KIT, c-MET or PDGFRβ or in intracellular signaling pathways were observed. These findings argue against the development of 'early' resistance mechanisms after neratinib and pemetrexed exposure. Future studies will be required to understand how NSCLC cells become resistant to neratinib and pemetrexed.

Neonatal Cardiovascular-Progenitor-Cell-Derived Extracellular Vesicles Activate YAP1 in Adult Cardiac Progenitor Cells

New stem cell and extracellular-vesicle-based therapies have the potential to improve outcomes for the increasing number of patients with heart failure. Since neonates have a significantly enhanced regenerative ability, we hypothesized that extracellular vesicles isolated from Islet-1+ expressing neonatal human cardiovascular progenitors (CPCs) will induce transcriptomic changes associated with improved regenerative capability when co-cultured with CPCs derived from adult humans. In order to test this hypothesis, we isolated extracellular vesicles from human neonatal Islet-1+ CPCs, analyzed the extracellular vesicle content using RNAseq, and treated adult CPCs with extracellular vesicles derived from neonatal CPCs to assess their functional effect. AKT, ERBB, and YAP1 transcripts were elevated in adult CPCs treated with neonatal CPC-derived extracellular vesicles. YAP1 is lost after the neonatal period but can stimulate cardiac regeneration. Our results demonstrate that YAP1 and additional transcripts associated with improved cardiovascular regeneration, as well as the activation of the cell cycle, can be achieved by the treatment of adult CPCs with neonatal CPC-derived extracellular vesicles. Progenitor cells derived from neonates secrete extracellular vesicles with the potential to stimulate and potentially improve functional effects in adult CPCs used for cardiovascular repair.

Unlocking cardiomyocyte renewal potential for myocardial regeneration therapy

Cardiovascular disease remains the leading cause of mortality worldwide. Cardiomyocytes are irreversibly lost due to cardiac ischemia secondary to disease. This leads to increased cardiac fibrosis, poor contractility, cardiac hypertrophy, and subsequent life-threatening heart failure. Adult mammalian hearts exhibit notoriously low regenerative potential, further compounding the calamities described above. Neonatal mammalian hearts, on the other hand, display robust regenerative capacities. Lower vertebrates such as zebrafish and salamanders retain the ability to replenish lost cardiomyocytes throughout life. It is critical to understand the varying mechanisms that are responsible for these differences in cardiac regeneration across phylogeny and ontogeny. Adult mammalian cardiomyocyte cell cycle arrest and polyploidization have been proposed as major barriers to heart regeneration. Here we review current models about why adult mammalian cardiac regenerative potential is lost including changes in environmental oxygen levels, acquisition of endothermy, complex immune system development, and possible cancer risk tradeoffs. We also discuss recent progress and highlight conflicting reports pertaining to extrinsic and intrinsic signaling pathways that control cardiomyocyte proliferation and polyploidization in growth and regeneration. Uncovering the physiological brakes of cardiac regeneration could illuminate novel molecular targets and offer promising therapeutic strategies to treat heart failure.

Human epidermal growth factor receptor 3 serves as a novel therapeutic target for acral melanoma

Acral melanoma (AM) is a rare, life-threatening skin cancer. Since AM bears unique features, existing therapies for other types of malignant melanomas have limited effects and the establishment of effective treatments for AM is strongly desired. Human epidermal growth factor receptor 3 (HER3) is a receptor tyrosine kinase that is frequently elevated in tumors and contributes to tumor progression, so it is considered a promising therapeutic target for tumors. This study was established to evaluate the potential of HER3-targeted therapy to treat AM by investigating the expression and function of HER3. HER3 expression was immunohistochemically analyzed in AM lesions of 72 patients and in AM cell lines. To investigate function of HER3, effects of HER3 inhibition on cell proliferation, apoptosis/survival, anchorage-independent growth, and underlying signals were assessed. HER3 was expressed in patients' AM tissues with various intensities and HER3 expression was significantly correlated with patient's disease-free survival. In vitro analyses revealed that HER3 is more highly expressed in AM cells than in normal epidermal melanocytes. AM cells were also shown to be sensitive to the cytotoxic part of a HER3-targeted antibody-drug conjugate. Inhibition of HER3 did not affect cell proliferation, whereas it decreased the anchorage-independent growth of AM cells likely through affecting the nuclear translocation of Yes-associated protein. It is implied that HER3 may serve as a novel therapeutic target for AM.

Aortic Stress Activates an Adaptive Program in Thoracic Aortic Smooth Muscle Cells That Maintains Aortic Strength and Protects Against Aneurysm and Dissection in Mice

BACKGROUND

When aortic cells are under stress, such as increased hemodynamic pressure, they adapt to the environment by modifying their functions, allowing the aorta to maintain its strength. To understand the regulation of this adaptive response, we examined transcriptomic and epigenomic programs in aortic smooth muscle cells (SMCs) during the adaptive response to AngII (angiotensin II) infusion and determined its importance in protecting against aortic aneurysm and dissection (AAD).

METHODS

We performed single-cell RNA sequencing and single-cell sequencing assay for transposase-accessible chromatin (scATAC-seq) analyses in a mouse model of sporadic AAD induced by AngII infusion. We also examined the direct effects of YAP (yes-associated protein) on the SMC adaptive response in vitro. The role of YAP in AAD development was further evaluated in AngII-infused mice with SMC-specific Yap deletion.

RESULTS

In wild-type mice, AngII infusion increased medial thickness in the thoracic aorta. Single-cell RNA sequencing analysis revealed an adaptive response in thoracic SMCs characterized by upregulated genes with roles in wound healing, elastin and collagen production, proliferation, migration, cytoskeleton organization, cell-matrix focal adhesion, and PI3K-PKB/Akt (phosphoinositide-3-kinase-protein kinase B/Akt) and TGF-β (transforming growth factor beta) signaling. ScATAC-seq analysis showed increased chromatin accessibility at regulatory regions of adaptive genes and revealed the mechanical sensor YAP/transcriptional enhanced associate domains as a top candidate transcription complex driving the expression of these genes (eg, Lox, Col5a2, Tgfb2). In cultured human aortic SMCs, cyclic stretch activated YAP, which directly bound to adaptive gene regulatory regions (eg, Lox) and increased their transcript abundance. SMC-specific Yap deletion in mice compromised this adaptive response in SMCs, leading to an increased AAD incidence.

CONCLUSIONS

Aortic stress triggers the systemic epigenetic induction of an adaptive response (eg, wound healing, proliferation, matrix organization) in thoracic aortic SMCs that depends on functional biomechanical signal transduction (eg, YAP signaling). Our study highlights the importance of the adaptive response in maintaining aortic homeostasis and preventing AAD in mice.

TAZ/YAP fusion proteins: mechanistic insights and therapeutic opportunities

The Hippo pathway is dysregulated in many different cancers, but point mutations in the pathway are rare. Transcriptional co-activator with PDZ-binding motif (TAZ) and Yes-associated protein (YAP) fusion proteins have emerged in almost all major cancer types and represent the most common genetic mechanism by which the two transcriptional co-activators are activated. Given that the N termini of TAZ or YAP are fused to the C terminus of another transcriptional regulator, the resultant fusion proteins hyperactivate a TEAD transcription factor-based transcriptome. Recent advances show that the C-terminal fusion partners confer oncogenic properties to TAZ/YAP fusion proteins by recruiting epigenetic modifiers that promote a hybrid TEAD-based transcriptome. Elucidating these cooperating epigenetic complexes represents a strategy to identify new therapeutic approaches for a pathway that has been recalcitrant to medical therapy.

Neuronal-epithelial cross-talk drives acinar specification via NRG1-ERBB3-mTORC2 signaling

Acinar cells are the principal secretory units of multiple exocrine organs. A single-cell, layered, lumenized acinus forms from a large cohort of epithelial progenitors that must initiate and coordinate three cellular programs of acinar specification, namely, lineage progression, secretion, and polarization. Despite this well-known outcome, the mechanism(s) that regulate these complex programs are unknown. Here, we demonstrate that neuronal-epithelial cross-talk drives acinar specification through neuregulin (NRG1)-ERBB3-mTORC2 signaling. Using single-cell and global RNA sequencing of developing murine salivary glands, we identified NRG1-ERBB3 to precisely overlap with acinar specification during gland development. Genetic deletion of Erbb3 prevented cell lineage progression and the establishment of lumenized, secretory acini. Conversely, NRG1 treatment of isolated epithelia was sufficient to recapitulate the development of secretory acini. Mechanistically, we found that NRG1-ERBB3 regulates each developmental program through an mTORC2 signaling pathway. Thus, we reveal that a neuronal-epithelial (NRG1/ERBB3/mTORC2) mechanism orchestrates the creation of functional acini.

Amyloidogenesis: What Do We Know So Far?

The study of protein aggregation, and amyloidosis in particular, has gained considerable interest in recent times. Several neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD) show a characteristic buildup of proteinaceous aggregates in several organs, especially the brain. Despite the enormous upsurge in research articles in this arena, it would not be incorrect to say that we still lack a crystal-clear idea surrounding these notorious aggregates. In this review, we attempt to present a holistic picture on protein aggregation and amyloids in particular. Using a chronological order of discoveries, we present the case of amyloids right from the onset of their discovery, various biophysical techniques, including analysis of the structure, the mechanisms and kinetics of the formation of amyloids. We have discussed important questions on whether aggregation and amyloidosis are restricted to a subset of specific proteins or more broadly influenced by the biophysiochemical and cellular environment. The therapeutic strategies and the significant failure rate of drugs in clinical trials pertaining to these neurodegenerative diseases have been also discussed at length. At a time when the COVID-19 pandemic has hit the globe hard, the review also discusses the plausibility of the far-reaching consequences posed by the virus, such as triggering early onset of amyloidosis. Finally, the application(s) of amyloids as useful biomaterials has also been discussed briefly in this review.

ERBB and P-glycoprotein inhibitors break resistance in relapsed neuroblastoma models through P-glycoprotein

Chemotherapy resistance is a persistent clinical problem in relapsed high-risk neuroblastomas. We tested a panel of 15 drugs for sensitization of neuroblastoma cells to the conventional chemotherapeutic vincristine, identifying tariquidar, an inhibitor of the transmembrane pump P-glycoprotein (P-gp/ABCB1), and the ERBB family inhibitor afatinib as the top resistance breakers. Both compounds were efficient in sensitizing neuroblastoma cells to vincristine in trypan blue exclusion assays and in inducing apoptotic cell death. The evaluation of ERBB signaling revealed no functional inhibition, that is, dephosphorylation of the downstream pathways upon afatinib treatment but direct off-target interference with P-gp function. Depletion of ABCB1, but not ERRB4, sensitized cells to vincristine treatment. P-gp inhibition substantially broke vincristine resistance in vitro and in vivo (zebrafish embryo xenograft). The analysis of gene expression datasets of more than 50 different neuroblastoma cell lines (primary and relapsed) and more than 160 neuroblastoma patient samples from the pediatric precision medicine platform INFORM (Individualized Therapy For Relapsed Malignancies in Childhood) confirmed a pivotal role of P-gp specifically in neuroblastoma resistance at relapse, while the ERBB family appears to play a minor part.

Neuregulin-1, a potential therapeutic target for cardiac repair

NRG1 (Neuregulin-1) is an effective cardiomyocyte proliferator, secreted and released by endothelial vascular cells, and affects the cardiovascular system. It plays a major role in heart growth, proliferation, differentiation, apoptosis, and other cardiovascular processes. Numerous experiments have shown that NRG1 can repair the heart in the pathophysiology of atherosclerosis, myocardial infarction, ischemia reperfusion, heart failure, cardiomyopathy and other cardiovascular diseases. NRG1 can connect related signaling pathways through the NRG1/ErbB pathway, which form signal cascades to improve the myocardial microenvironment, such as regulating cardiac inflammation, oxidative stress, necrotic apoptosis. Here, we summarize recent research advances on the molecular mechanisms of NRG1, elucidate the contribution of NRG1 to cardiovascular disease, discuss therapeutic approaches targeting NRG1 associated with cardiovascular disease, and highlight areas for future research.

Estrogen Regulates the Expression and Localization of YAP in the Uterus of Mice

The dynamics of uterine endometrium is important for successful establishment and maintenance of embryonic implantation and development, along with extensive cell differentiation and proliferation. The tissue event is precisely and complicatedly regulated as several signaling pathways are involved including two main hormones, estrogen and progesterone signaling. We previously showed a novel signaling molecule, Serine/threonine protein kinase 3/4 (STK3/4), which is responded to hormone in the mouse uterine epithelium. However, the role and regulation of its target, YES-associated protein (YAP) remains unknown. In this study, we investigated the expression and regulation of YAP in mouse endometrium. We found that YAP was periodically expressed in the endometrium during the estrous cycle. Furthermore, periodic expression of YAP was shown to be related to the pathway under hormone treatment. Interestingly, estrogen was shown to positively modulate YAP via endometrial epithelial receptors. In addition, the knockdown of YAP showed that YAP regulated various target genes in endometrial cells. The knockdown of YAP down-regulated numerous targets including ADAMTS1, AMOT, AMOTL1, ANKRD1, CTNNA1, MCL1. On the other hand, the expressions of AREG and AXL were increased by its knockdown. These findings imply that YAP responds via Hippo signaling under various intrauterine signals and is considered to play a role in the expression of factors important for uterine endometrium dynamic regulation.

"Shedding" light on HER4 signaling in normal and malignant breast tissues

Receptor Tyrosine Kinases of the Epidermal Growth Factor Receptor Family play a pivotal role as drivers of carcinogenesis and uncontrolled cell growth for a variety of malignancies, not least for breast cancer. Besides the estrogen receptor, the HER2 receptor was and still is a representative marker for advanced taxonomic sub-differentiation of breast cancer and emerged as one of the first therapeutic targets for antibody based therapies. Since the approval of trastuzumab for the therapy of HER2-positive breast cancer in 1998 anti-HER2 treatment strategies are being modified, refined, and successfully combined with complementary treatments, nevertheless there is still potential for improvement. The HER2 relatives, namely HER1 (i.e., EGFR), HER3 and HER4 share a high degree of molecular homology and together form a functional unit for signal transmission. Under regular conditions, receptor coexpression patterns and receptor interaction represent key parameters for signaling robustness, which ensures cellular growth control and enables tissue differentiation. In addition, treatment efficiency of e.g., an anti-HER2 targeting is substantially determined by the expression pattern of HER receptors on target cells. Within the receptor family, the HER4 plays a particular role and is engaged in exceptional signaling activities. A favorable prognostic impact has been attributed to HER4 expression in breast cancer under specific molecular conditions. HER4-specific cellular effects are initially determined by a ligand-dependent or -independent receptor activation. Essential processes as cell growth and proliferation, cell differentiation, and apoptotic cell death can be initiated by this receptor. This review gives an overview of the role of HER4 in normal and malignant breast epithelial cells and tissues. Specific mechanism of HER4 activation and subsequent intracellular signaling will be described by taking a focus on effects provoked by receptor shedding. HER4 activities and specific effects will be correlated to breast cancer subtypes and the impact of HER4 on course and outcome of disease will be considered. Moreover, current and potential therapeutic approaches will be discussed.

YAP1 maintains active chromatin state in head and neck squamous cell carcinomas that promotes tumorigenesis through cooperation with BRD4

Analysis of The Cancer Genome Atlas and other published data of head and neck squamous cell carcinoma (HNSCC) reveals somatic alterations of the Hippo-YAP pathway in approximately 50% of HNSCC. Better strategies to target the YAP1 transcriptional complex are sought. Here, we show that FAT1, an upstream inhibitor of YAP1, is mutated either by missense or by truncating mutation in 29% of HNSCC. Comprehensive proteomic and drug-screening studies across pan-cancer models confirm that FAT1-mutant HNSCC exhibits selective and higher sensitivity to BRD4 inhibition by JQ1. Epigenomic analysis reveals an active chromatin state in FAT1-mutant HNSCC cells that is driven by the YAP/TAZ transcriptional complex through recruitment of BRD4 to deposit active histone marks, thereby maintaining an oncogenic transcriptional state. This study reveals a detailed cooperative mechanism between YAP1 and BRD4 in HNSCC and suggests a specific therapeutic opportunity for the treatment of this subset of head and neck cancer patients.

The HER family as therapeutic targets in colorectal cancer

The human epidermal growth factor receptor (HER, ErbB) family has four members, epidermal growth factor receptor (EGFR), HER2, HER3, and HER4. Although distinct in ligands and functions, all of the HER family members are receptor tyrosine kinases playing important roles in the pathogenesis of cancers. In the era of precision medicine, the HER family is one of the most important and successful cancer therapeutic targets, hallmarked by the approval of anti-EGFR therapies for the treatment of colorectal cancer and non-small cell lung cancer, and anti-HER2 therapies for the treatment of breast cancer and gastric cancer. This review briefly discusses how HER family members were discovered, their functions and roles in cancer, and most importantly, the developmental history and recent updates of therapies targeting HER family members, with colorectal cancer as a focus. We also discussed the patient selection and drug resistance to anti-EGFR therapies in the treatment of colorectal cancer.

An overview of the crosstalk between YAP and cGAS-STING signaling in non-small cell lung cancer: it takes two to tango

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is recognized as a main mediator bridging innate and adaptive immunity, recent advances have expanded its roles to anti-tumor immunity and carcinogenesis. Loss of cGAS-STING signaling in non-small cell lung cancer (NSCLC) leads to enhanced tumorigenicity and decreased cytotoxic T lymphocyte infiltration. Apart from its anticancer response, persistent overreaction of cGAS-STING signaling promotes progression of certain inflammation-aggravated cancers. Activation of the pro-inflammatory nucleic acid sensing pathway can trigger Hippo pathway, which mediates the inactivation of Yes-associated protein 1 (YAP1) and its paralogue transcriptional co-regulators with PDZ-binding motif (TAZ, also known as WWTR1), and subsequent suppression of tumorigenesis. Active YAP acts as a transcriptional driver in bolstering immunosuppressive cytokines to evade immune surveillance and promote occurrence of preneoplasia. It is reasonable that aggressive tumors co-opt these regulators to generate few immunogenic antigens and drive tumorigenic behaviors via a highly cooperative manner. Given their multifaced roles, we profile the molecular biology characteristic and current status underpinning oncogenic YAP, review its crosstalk roles with cGAS/STING pathway in NSCLC, and summarize the major clinical investigations in NSCLC with TCGA database.

Hippo Signaling in the Endometrium

The uterus is essential for embryo implantation and fetal development. During the estrous cycle, the uterine endometrium undergoes dramatic remodeling to prepare for pregnancy. Angiogenesis is an essential biological process in endometrial remodeling. Steroid hormones regulate the series of events that occur during such remodeling. Researchers have investigated the potential factors, including angiofactors, involved in endometrial remodeling. The Hippo signaling pathway discovered in the 21st century, plays important roles in various cellular functions, including cell proliferation and cell death. However, its role in the endometrium remains unclear. In this review, we describe the female reproductive system and its association with the Hippo signaling pathway, as well as novel Hippo pathway genes and potential target genes.

ErbB4 alternative splicing mediates fetal mouse alveolar type II cell differentiation in vitro

BACKGROUND

Alternative splicing (AS) creates different protein isoforms, an important mechanism regulating cell-specific function. Little is known about AS in lung development, particularly in alveolar type II (ATII) cells. ErbB4 receptor isoforms Jma and Jmb have significant and opposing functions in the brain, heart, and lung development and/or disease. However, the regulators of ErbB4 AS are unknown. ErbB4 AS regulators in fetal mouse ATII cells control its function in ATII cell maturation.

METHODS

Candidate ErbB4 AS regulators were found using in silico analysis. Their developmental expression was studied in fetal mouse ATII cells. The effects of splice factor downregulation and upregulation on ATII cell maturation were analyzed.

RESULTS

ErbB4-Jma increased significantly in ATII cells after gestation E16.5. In silico analysis found four candidate splice factors: FOX2, CUG/CELF1, TIAR, and HUB. Fetal ATII cells expressed these factors in distinct developmental profiles. HUB downregulation in E17.5 ATII cells increased Jma isoform levels and Sftpb gene expression and decreased Jmb. HUB overexpression decreased Jma and Sftpb.

CONCLUSIONS

ErbB4 AS is developmentally controlled by HUB in fetal ATII cells, promoting ATII differentiation. Regulated AS expression during ATII cell differentiation suggests novel therapeutic strategies to approach human disease.

IMPACT

Alternative splicing (AS) of the ErbB4 receptor, involving mutually exclusive exon inclusion, creates Jma and Jmb isoforms with distinct differences in receptor processing and function. The Jma isoform of ErbB4 promotes differentiation of fetal lung alveolar type II cells. The AS is mediated in part by the RNA-binding protein HUB. The molecular mechanism of AS for ErbB4 has not been previously described. The regulation of ErbB4 AS has important implications in the development of organs, such as the lung, brain, and heart, and for disease, including cancer.

Context-dependent transcriptional regulations of YAP/TAZ in cancer

As the downstream effectors of Hippo pathway, YAP/TAZ are identified to participate in organ growth, regeneration and tumorigenesis. However, owing to lack of a DNA-binding domain, YAP/TAZ usually act as coactivators and cooperate with other transcription factors or partners to mediate their transcriptional outputs. In this article, we first present an overview of the core components and the upstream regulators of Hippo-YAP/TAZ signaling in mammals, and then systematically summarize the identified transcription factors or partners that are responsible for the downstream transcriptional output of YAP/TAZ in various cancers.

The Hippo pathway in cancer: YAP/TAZ and TEAD as therapeutic targets in cancer

Tumorigenesis is a highly complex process, involving many interrelated and cross-acting signalling pathways. One such pathway that has garnered much attention in the field of cancer research over the last decade is the Hippo signalling pathway. Consisting of two antagonistic modules, the pathway plays an integral role in both tumour suppressive and oncogenic processes, generally via regulation of a diverse set of genes involved in a range of biological functions. This review discusses the history of the pathway within the context of cancer and explores some of the most recent discoveries as to how this critical transducer of cellular signalling can influence cancer progression. A special focus is on the various recent efforts to therapeutically target the key effectors of the pathway in both preclinical and clinical settings.

YAP/TAZ in Bone and Cartilage Biology

YAP and TAZ were initially described as the main regulators of organ growth during development and more recently implicated in bone biology. YAP and TAZ are regulated by mechanical and cytoskeletal cues that lead to the control of cell fate in response to the cellular microenvironment. The mechanical component represents a major signal for bone tissue adaptation and remodelling, so YAP/TAZ contributes significantly in bone and cartilage homeostasis. Recently, mice and cellular models have been developed to investigate the precise roles of YAP/TAZ in bone and cartilage cells, and which appear to be crucial. This review provides an overview of YAP/TAZ regulation and function, notably providing new insights into the role of YAP/TAZ in bone biology.

ErbB4-mediated regulation of vasculogenic mimicry capability in breast cancer cells

ErbB4 is a member of the ErbB receptor tyrosine kinase family. It has both pro- and anti-oncogenic activities in tumors. Vasculogenic mimicry (VM), a phenomenon in which cancer cells form capillary-like structures without endothelial cells, has been recognized to be a cause of malignant phenotypes in some solid tumors. Here, we used an in vitro VM formation assay, and demonstrated that ErbB4 negatively regulated VM formation in human breast cancer cells. By using CRISPR/Cas9-mediated gene knockout, we verified that the depletion of endogenous ErbB4 improved the VM formation capability. Although treatment with neuregulin 1 (NRG1), a ligand of ErbB4, induced the phosphorylation of ErbB4 and promoted VM formation in a dose-dependent manner, it did not induce such activities in kinase-dead K751M ErbB4-expressing breast cancer cells. Moreover, we examined the effect of the missense mutation E872K of ErbB4, which has been reported in multiple tumors, on VM formation, and found that the mutation enhanced the basal phosphorylation level and ErbB4-mediated VM formation in the absence of NRG1 stimulation. While NRG1 stimulated VM formation, excessive activation of ErbB4 induced a negative effect. In E872K ErbB4-overexpressing cells, but not in wild-type ErbB4-overexpressing cells, the number of VM tubes was significantly decreased by low-dose treatment with the ErbB inhibitor afatinib. Taken together, our findings demonstrated the significance of ErbB4-mediated VM formation, and suggested the possibility of ErbB4 mutations as effective targets in breast cancer.

Mechano-Signaling Aspects of Hepatocellular Carcinoma

HCC is one of the leading causes of cancer related death worldwide and comprises about 90% of the cases of primary liver cancer. It is generally accompanied by chronic liver fibrosis characterised by deposition of collagen fibres, which, in turn, causes enhanced stiffness of the liver tissue. Changes of tissue stiffness give rise to alterations of signalling pathways that are associated to mechanical properties of the cells and the extracellular matrix, and that can be subsumed as "mechano-signaling pathways", like, e.g., the YAP/TAZ pathway, or the SRF pathway. Stiffness of the liver tissue modulates mechanical regulation of many genes involved in HCC progression. However, mechano-signaling is still rather underrepresented in our concepts of cancer in comparison to "classical" biochemical signalling pathways. This review aims to give an overview of various stiffness induced mechano-biological aspects of HCC.

Yes-Associated Protein in Atherosclerosis and Related Complications: A Potential Therapeutic Target That Requires Further Exploration

Atherosclerosis and its complications diseases remain leading causes of cardiovascular morbidity and mortality, bringing a massive burden on public health worldwide. Atherosclerosis is recognized as chronic inflammation, and involves several highly correlated processes, including lipid metabolism dysfunction, endothelial cell dysfunction, inflammation, oxidative stress, vascular smooth muscle cell activation, platelet activation, thrombosis, altered matrix metabolism, and vascular remodeling. Within the past few decades, accumulating evidence has shown that the Yes-associated protein (YAP), the major effector of the Hippo pathway, can play a crucial role in pathogenesis and development of atherosclerosis. Activation of YAP-related pathways, which are induced by alerting flow pattern and matrix stiffness among others, can regulate processes including vascular endothelial cell dysfunction, monocyte infiltration, and smooth muscle cell migration, which contribute to atherosclerotic lesion formation. Further, YAP potentially modulates atherosclerotic complications such as vascular calcification and intraplaque hemorrhage, which require further investigation. Here, we summarized the relevant literature to outline current findings detailing the relationship between of YAP and atherosclerosis and highlight areas for future research.

The roles of signaling pathways in cardiac regeneration

In recent years, knowledge of cardiac regeneration mechanisms has dramatically expanded. Regeneration can replace lost parts of organs, common among animal species. The heart is commonly considered an organ with terminal development, which has no reparability potential during post-natal life; however, some intrinsic regeneration capacity has been reported for cardiac muscle, which opens novel avenues in cardiovascular disease treatment. Different endogenous mechanisms were studied for cardiac repairing and regeneration in recent decades. Survival, proliferation, inflammation, angiogenesis, cell-cell communication, cardiomyogenesis, and anti-aging pathways are the most important mechanisms that have been studied in this regard. Several in vitro and animal model studies focused on proliferation induction for cardiac regeneration reported promising results. These studies have mainly focused on promoting proliferation signaling pathways and demonstrated various signaling pathways such as Wnt, PI3K/Akt, IGF-1, TGF-β, Hippo, and VEGF signaling cardiac regeneration. Therefore, in this review, we intended to discuss the connection between different critical signaling pathways in cardiac repair and regeneration.

MicroRNAs in blood act as biomarkers of colorectal cancer and indicate potential therapeutic targets

Association studies have linked alterations of blood-derived microRNAs (miRNAs) with colorectal cancer (CRC). Here, we performed a microarray-based comparison of the profiles of 2549 miRNAs in 80 blood samples from healthy donors and patients with colorectal adenomas, colorectal diverticulitis and CRC at different stages. Confirmation by quantitative real-time PCR (RT-PCR) was complemented by validation of identified molecules in another 36 blood samples. No variations in miRNA levels were observed in samples from patients with colorectal adenomas and diverticulitis or from healthy donors. However, there were 179 CRC-associated miRNAs of differential abundance compared to healthy controls. Only three - miR-1225-5p, miR-1207-5p and miR-4459 - exhibited increased levels at all CRC stages. Most deregulated miRNAs (128/179, 71%) specifically predicted metastatic CRC. Pathway analysis found several cancer-related pathways to which the miRNAs contribute in various ways. In conclusion, miRNA levels in blood vary throughout CRC progression and affect cellular functions relevant to haematogenous CRC progression and dissemination. The identified biomarker and therapeutic candidates require further confirmation of their clinical relevance.

Emerging Principles in the Transcriptional Control by YAP and TAZ

Simple Summary

YAP and TAZ are transcriptional cofactors that integrate several upstream signals to generate context-dependent transcriptional responses. This requires extensive integration with epigenetic regulators and other transcription factors. The molecular and genomic characterization of YAP and TAZ nuclear function has broad implications both in physiological and pathological settings.

Abstract

Yes-associated protein (YAP) and TAZ are transcriptional cofactors that sit at the crossroad of several signaling pathways involved in cell growth and differentiation. As such, they play essential functions during embryonic development, regeneration, and, once deregulated, in cancer progression. In this review, we will revise the current literature and provide an overview of how YAP/TAZ control transcription. We will focus on data concerning the modulation of the basal transcriptional machinery, their ability to epigenetically remodel the enhancer–promoter landscape, and the mechanisms used to integrate transcriptional cues from multiple pathways. This reveals how YAP/TAZ activation in cancer cells leads to extensive transcriptional control that spans several hallmarks of cancer. The definition of the molecular mechanism of transcriptional control and the identification of the pathways regulated by YAP/TAZ may provide therapeutic opportunities for the effective treatment of YAP/TAZ-driven tumors.

Roles for growth factors and mutations in metastatic dissemination

Cancer is initiated largely by specific cohorts of genetic aberrations, which are generated by mutagens and often mimic active growth factor receptors, or downstream effectors. Once initiated cells outgrow and attract blood vessels, a multi-step process, called metastasis, disseminates cancer cells primarily through vascular routes. The major steps of the metastatic cascade comprise intravasation into blood vessels, circulation as single or collectives of cells, and eventual colonization of distant organs. Herein, we consider metastasis as a multi-step process that seized principles and molecular players employed by physiological processes, such as tissue regeneration and migration of neural crest progenitors. Our discussion contrasts the irreversible nature of mutagenesis, which establishes primary tumors, and the reversible epigenetic processes (e.g. epithelial-mesenchymal transition) underlying the establishment of micro-metastases and secondary tumors. Interestingly, analyses of sequencing data from untreated metastases inferred depletion of putative driver mutations among metastases, in line with the pivotal role played by growth factors and epigenetic processes in metastasis. Conceivably, driver mutations may not confer the same advantage in the microenvironment of the primary tumor and of the colonization site, hence phenotypic plasticity rather than rigid cellular states hardwired by mutations becomes advantageous during metastasis. We review the latest reported examples of growth factors harnessed by the metastatic cascade, with the goal of identifying opportunities for anti-metastasis interventions. In summary, because the overwhelming majority of cancer-associated deaths are caused by metastatic disease, understanding the complexity of metastasis, especially the roles played by growth factors, is vital for preventing, diagnosing and treating metastasis.

Aberrant epithelial polarity cues drive the development of precancerous airway lesions

Molecular events that drive the development of precancerous lesions in the bronchial epithelium, which are precursors of lung squamous cell carcinoma (LUSC), are poorly understood. We demonstrate that disruption of epithelial cellular polarity, via the conditional deletion of the apical determinant Crumbs3 (Crb3), initiates and sustains precancerous airway pathology. The loss of Crb3 in adult luminal airway epithelium promotes the uncontrolled activation of the transcriptional regulators YAP and TAZ, which stimulate intrinsic signals that promote epithelial cell plasticity and paracrine signals that induce basal-like cell growth. We show that aberrant polarity and YAP/TAZ-regulated gene expression associates with human bronchial precancer pathology and disease progression. Analyses of YAP/TAZ-regulated genes further identified the ERBB receptor ligand Neuregulin-1 (NRG1) as a key transcriptional target and therapeutic targeting of ERBB receptors as a means of preventing and treating precancerous cell growth. Our observations offer important molecular insight into the etiology of LUSC and provides directions for potential interception strategies of lung cancer.

Endothelial YAP/TAZ Signaling in Angiogenesis and Tumor Vasculature

Solid tumors are dependent on vascularization for their growth. The hypoxic, stiff, and pro-angiogenic tumor microenvironment induces angiogenesis, giving rise to an immature, proliferative, and permeable vasculature. The tumor vessels promote tumor metastasis and complicate delivery of anti-cancer therapies. In many types of tumors, YAP/TAZ activation is correlated with increased levels of angiogenesis. In addition, endothelial YAP/TAZ activation is important for the formation of new blood and lymphatic vessels during development. Oncogenic activation of YAP/TAZ in tumor cell growth and invasion has been studied in great detail, however the role of YAP/TAZ within the tumor endothelium remains insufficiently understood, which complicates therapeutic strategies aimed at targeting YAP/TAZ in cancer. Here, we overview the upstream signals from the tumor microenvironment that control endothelial YAP/TAZ activation and explore the role of their downstream targets in driving tumor angiogenesis. We further discuss the potential for anti-cancer treatments and vascular normalization strategies to improve tumor therapies.

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

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

6-Gingerol suppresses tumor cell metastasis by increasing YAPser127 phosphorylation in renal cell carcinoma

According to the World Health Organization, the incidence and mortality rates of renal cell carcinoma (RCC) are rapidly increasing worldwide. Serious side effects caused by immune therapy and resistance to targeted drug therapy are urgent clinical problems facing kidney treatment. There is increasing global interest in developing natural products with a reduced number of side effects as adjunctive therapeutic options for RCC. Ginger is a spice and herbal remedy used worldwide, and 6-gingerol is a major pharmacologically active ingredient in ginger. In our study, we found that 6-gingerol suppressed RCC cell migration and metastasis in vitro and in vivo. Moreover, reduction in MMP2, Slug, and Vimentin protein levels was observed following 6-gingerol treatment of 786-O and ACHN cells. Furthermore, we revealed the mechanisms underlying the ability of 6-gingerol to inhibit RCC cell migration and metastasis. 6-Gingerol increased yes-associated protein (YAP)ser127 phosphorylation and reduced YAP levels in cell nuclei. We also used a series of loss-of-function and gain-of-function experiments to support our results. Western blot results showed that MMP2, Slug, and Vimentin protein expression was downregulated in YAP-silenced cells and upregulated in YAP-overexpressing cells. Transwell data demonstrated that YAP suppressed RCC migration ability. Immunofluorescence images showed that 6-gingerol decreased YAP levels, leading to disordered F-actin and a reduction in cell lamellipodia. Overall, our results indicated that 6-gingerol is a potential antimetastatic compound for use in kidney therapy.

Protective role of ErbB3 signaling in myeloid cells during adaptation to cardiac pressure overload

BACKGROUND

Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood. This study investigated the role of ErbB3 receptors in the regulation of early adaptive response using a mouse model of transverse aortic constriction (TAC) for non-ischemic cardiomyopathy.

METHODS AND RESULTS

TAC surgery was performed in groups of age- and sex-matched myeloid cell-specific ErbB3-deficient mice (ErbB3^MyeKO) and control animals (ErbB3^MyeWT). The number of cardiac CD45 immune cells, CD11b myeloid cells, Ly6G neutrophils, and Ly6C monocytes was determined using flow cytometric analysis. Five days after TAC, survival was dramatically reduced in male but not female ErbB3^MyeKO mice or control animals. The examination of lung weight to body weight ratio suggested that acute pulmonary edema was present in ErbB3^MyeKO male mice after TAC. To determine the cellular and molecular mechanisms involved in the increased mortality in ErbB3^MyeKO male mice, cardiac cell populations were examined at day 3 post-TAC using flow cytometry. Myeloid cells accumulated in control but not in ErbB3^MyeKO male mouse hearts. This was accompanied by increased proliferation of Sca-1 positive non-immune cells (endothelial cells and fibroblasts) in control but not ErbB3^MyeKO male mice. No significant differences in intramyocardial accumulation of myeloid cells or proliferation of Sca-1 cells were found between the groups of ErbB3^MyeKO and ErbB3^MyeWT female mice. An antibody-based protein array analysis revealed that IGF-1 expression was significantly downregulated only in ErbB3^MyeKO mice hearts compared to control animals after TAC.

CONCLUSION

Our data demonstrate the crucial role of myeloid cell-specific ErbB3 signaling in the cardiac accumulation of myeloid cells, which contributes to the activation of cardiac endothelial cells and fibroblasts and development of an early adaptive response to cardiac pressure overload in male mice.

Transcriptional co-activators YAP/TAZ: Potential therapeutic targets for metastatic breast cancer

Breast cancer is the most commonly diagnosed cancer among women. Although routine and targeted therapies have improved the survival rate, there are still considerable challenges in the treatment of breast cancer. Metastasis is the leading cause of death in patients diagnosed with breast cancer. Yes-associated protein (YAP) and/or PDZ binding motif (TAZ) are usually abnormally activated in breast cancer leading to a variety of effects on tumour promotion, such as epithelial-mesenchymal transition, cancer stem cell production and drug-resistance. The abnormal activation of YAP/TAZ can affect metastasis-related processes and promote cancer progression and metastasis by interacting with some metastasis-related factors and pathways. In this article, we summarise the evidence that YAP/TAZ regulates breast cancer metastasis, its post-translational modification mechanisms, and the latest advances in the treatment of YAP/TAZ-related breast cancer metastasis, besides providing a new strategy of YAP/TAZ-based treatment of human breast cancer.

TAZ/Wnt-β-catenin/c-MYC axis regulates cystogenesis in polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, primarily caused by germline mutation of PKD1 or PKD2, leading to end-stage renal disease. There are few cures for ADPKD, although many researchers are trying to find a cure. The Hippo signaling pathway regulates organ growth and cell proliferation. Transcriptional coactivator with PDZ-binding motif (TAZ) is a Hippo signaling effector. In this study, we demonstrated that the PKD1–TAZ–Wnt–β-catenin–c-MYC signaling axis plays a critical role in cystogenesis. Endo IWR1 treatment, which inhibited β-catenin activity via AXIN stabilization, reduced cyst growth in an ADPKD model. Our findings provide a potential therapeutic target against ADPKD and would be important for clinical translation.

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, primarily caused by germline mutation of PKD1 or PKD2, leading to end-stage renal disease. The Hippo signaling pathway regulates organ growth and cell proliferation. Herein, we demonstrate the regulatory mechanism of cystogenesis in ADPKD by transcriptional coactivator with PDZ-binding motif (TAZ), a Hippo signaling effector. TAZ was highly expressed around the renal cyst-lining epithelial cells of Pkd1-deficient mice. Loss of Taz in Pkd1-deficient mice reduced cyst formation. In wild type, TAZ interacted with PKD1, which inactivated β-catenin. In contrast, in PKD1-deficient cells, TAZ interacted with AXIN1, thus increasing β-catenin activity. Interaction of TAZ with AXIN1 in PKD1-deficient cells resulted in nuclear accumulation of TAZ together with β-catenin, which up-regulated c-MYC expression. Our findings suggest that the PKD1–TAZ–Wnt–β-catenin–c-MYC signaling axis plays a critical role in cystogenesis and might be a potential therapeutic target against ADPKD.

ERBB2 drives YAP activation and EMT-like processes during cardiac regeneration

Cardiomyocyte loss after injury results in adverse remodelling and fibrosis, inevitably leading to heart failure. The ERBB2-Neuregulin and Hippo-YAP signalling pathways are key mediators of heart regeneration, yet the crosstalk between them is unclear. We demonstrate that transient overexpression of activated ERBB2 in cardiomyocytes (OE CMs) promotes cardiac regeneration in a heart failure model. OE CMs present an epithelial-mesenchymal transition (EMT)-like regenerative response manifested by cytoskeletal remodelling, junction dissolution, migration and extracellular matrix turnover. We identified YAP as a critical mediator of ERBB2 signalling. In OE CMs, YAP interacts with nuclear-envelope and cytoskeletal components, reflecting an altered mechanical state elicited by ERBB2. We identified two YAP-activating phosphorylations on S352 and S274 in OE CMs, which peak during metaphase, that are ERK dependent and Hippo independent. Viral overexpression of YAP phospho-mutants dampened the proliferative competence of OE CMs. Together, we reveal a potent ERBB2-mediated YAP mechanotransduction signalling, involving EMT-like characteristics, resulting in robust heart regeneration.

A genome-wide association study of polycystic ovary syndrome identified from electronic health records

BACKGROUND

Polycystic ovary syndrome is the most common endocrine disorder affecting women of reproductive age. A number of criteria have been developed for clinical diagnosis of polycystic ovary syndrome, with the Rotterdam criteria being the most inclusive. Evidence suggests that polycystic ovary syndrome is significantly heritable, and previous studies have identified genetic variants associated with polycystic ovary syndrome diagnosed using different criteria. The widely adopted electronic health record system provides an opportunity to identify patients with polycystic ovary syndrome using the Rotterdam criteria for genetic studies.

OBJECTIVE

To identify novel associated genetic variants under the same phenotype definition, we extracted polycystic ovary syndrome cases and unaffected controls based on the Rotterdam criteria from the electronic health records and performed a discovery-validation genome-wide association study.

STUDY DESIGN

We developed a polycystic ovary syndrome phenotyping algorithm on the basis of the Rotterdam criteria and applied it to 3 electronic health record-linked biobanks to identify cases and controls for genetic study. In the discovery phase, we performed an individual genome-wide association study using the Geisinger MyCode and the Electronic Medical Records and Genomics cohorts, which were then meta-analyzed. We attempted validation of the significant association loci (P<1×10^-6) in the BioVU cohort. All association analyses used logistic regression, assuming an additive genetic model, and adjusted for principal components to control for population stratification. An inverse-variance fixed-effect model was adopted for meta-analysis. In addition, we examined the top variants to evaluate their associations with each criterion in the phenotyping algorithm. We used the STRING database to characterize protein-protein interaction network.

RESULTS

Using the same algorithm based on the Rotterdam criteria, we identified 2995 patients with polycystic ovary syndrome and 53,599 population controls in total (2742 cases and 51,438 controls from the discovery phase; 253 cases and 2161 controls in the validation phase). We identified 1 novel genome-wide significant variant rs17186366 (odds ratio [OR]=1.37 [1.23, 1.54], P=2.8×10^-8) located near SOD2. In addition, 2 loci with suggestive association were also identified: rs113168128 (OR=1.72 [1.42, 2.10], P=5.2×10^-8), an intronic variant of ERBB4 that is independent from the previously published variants, and rs144248326 (OR=2.13 [1.52, 2.86], P=8.45×10^-7), a novel intronic variant in WWTR1. In the further association tests of the top 3 single-nucleotide polymorphisms with each criterion in the polycystic ovary syndrome algorithm, we found that rs17186366 (SOD2) was associated with polycystic ovaries and hyperandrogenism, whereas rs11316812 (ERBB4) and rs144248326 (WWTR1) were mainly associated with oligomenorrhea or infertility. We also validated the previously reported association with DENND1A1. Using the STRING database to characterize protein-protein interactions, we found both ERBB4 and WWTR1 can interact with YAP1, which has been previously associated with polycystic ovary syndrome.

CONCLUSION

Through a discovery-validation genome-wide association study on polycystic ovary syndrome identified from electronic health records using an algorithm based on Rotterdam criteria, we identified and validated a novel genome-wide significant association with a variant near SOD2. We also identified a novel independent variant within ERBB4 and a suggestive association with WWTR1. With previously identified polycystic ovary syndrome gene YAP1, the ERBB4-YAP1-WWTR1 network suggests involvement of the epidermal growth factor receptor and the Hippo pathway in the multifactorial etiology of polycystic ovary syndrome.

RNA binding proteins: Linking mechanotransduction and tumor metastasis

Mechanotransduction is the leading cellular process that mammalian cells adopted to receive and respond to various mechanical cues from their local microenvironment. Increasing evidence suggests that mechano-transduction is involved in many physiological and disease conditions, ranging from early embryonic development, organogenesis, to a variety of human diseases including cancer. Mechanotransduction is mediated through several classes of senor proteins on the cell surface, intracellular signaling mediators, and core transcriptional regulation networks. Dissecting the molecular mechanisms regulating mechanotransduction and their association with cancer metastasis has received much attention in recent years. RNA binding proteins (RBPs) are a special group of nucleic acid interacting factors that participate in many important cellular processes. In this review, we would like to summarize recent research progresses in understanding the role of RBPs-mediated regulation in mechanotransduction and cancer metastasis. Those intriguing findings will provide novel insights for the disease and guide the potential development of new therapeutic approaches.

YAP and TAZ Are Not Identical Twins

Yes-associated protein (YAP) and TAZ (WW domain containing transcription regulator 1, or WWTR1) are paralog transcriptional regulators, able to integrate mechanical, metabolic, and signaling inputs to regulate cell growth and differentiation during development and neoplastic progression. YAP and TAZ hold common and distinctive structural features, reflecting only partially overlapping regulatory mechanisms. The two paralogs interact with both shared and specific transcriptional partners and control nonidentical transcriptional programs. Although most of the available literature considers YAP and TAZ as functionally redundant, they play distinctive or even contrasting roles in different contexts. The issue of their divergent roles is currently underexplored but holds fundamental implications for mechanistic and translational studies. Here, we aim to review the available literature on the biological functions of YAP and TAZ, highlighting differential roles that distinguish these two paralogues.

Cell Development Deficiency and Gene Expression Dysregulation of Trisomy 21 Retina Revealed by Single-Nucleus RNA Sequencing

Retina is a crucial tissue for capturing and processing light stimulus. It is critical to describe the characteristics of retina at the single-cell level for understanding its biological functions. A variety of abnormalities in terms of morphology and function are present in the trisomy 21 (T21) retina. To evaluate the consequences of chromosome aneuploidy on retina development, we identified the single-cell transcriptional profiles of a T21 fetus and performed comprehensive bioinformatic analyses. Our data revealed the diversity and heterogeneity of cellular compositions in T21 retina, as well as the abnormal constitution of T21 retina compared to disomic retina. In total, we identified seven major cell types and several subtypes within each cell type, followed by the detection of corresponding molecular markers, including previously reported ones and a series of novel markers. Through the analysis of the retinal differentiation process, subtypes of retinal progenitor cells (RPCs) exhibiting the potential of different retinal cell-type commitments and certain Müller glial cells (MGs) with differentiating potency were identified. Moreover, the extensive communication networks between cellular types were confirmed, among which a few ligand–receptor interactions were related to the formation and function of retina and immunoregulatory interactions. Taken together, our data provides the first ever single-cell transcriptome profiles for human T21 retina, which facilitates the understanding on the dosage effects of chromosome 21 on the development of retina.

Interaction of the Hippo Pathway and Phosphatases in Tumorigenesis

The Hippo pathway is an emerging tumor suppressor signaling pathway involved in a wide range of cellular processes. Dysregulation of different components of the Hippo signaling pathway is associated with a number of diseases including cancer. Therefore, identification of the Hippo pathway regulators and the underlying mechanism of its regulation may be useful to uncover new therapeutics for cancer therapy. The Hippo signaling pathway includes a set of kinases that phosphorylate different proteins in order to phosphorylate and inactivate its main downstream effectors, YAP and TAZ. Thus, modulating phosphorylation and dephosphorylation of the Hippo components by kinases and phosphatases play critical roles in the regulation of the signaling pathway. While information regarding kinase regulation of the Hippo pathway is abundant, the role of phosphatases in regulating this pathway is just beginning to be understood. In this review, we summarize the most recent reports on the interaction of phosphatases and the Hippo pathway in tumorigenesis. We have also introduced challenges in clarifying the role of phosphatases in the Hippo pathway and future direction of crosstalk between phosphatases and the Hippo pathway.

Clinicopathologic significance of nuclear HER4 and phospho-YAP(S127) in human breast cancers and matching brain metastases

Background

Human epidermal growth factor receptor-4 (HER4) and yes-associated protein-1 (YAP) are candidate therapeutic targets in oncology. YAP's transcriptional coactivation function is modulated by the HER4 intracellular domain (HER4-ICD) in vitro, but the clinical relevance of this has not been established. This study investigated the potential for targeting the HER4-YAP pathway in brain metastatic breast cancer.

Methods

We performed immuno-phenotypic profiling of pathway markers in a consecutive breast cancer series with 25 years of clinical follow up (n = 371), and patient-matched breast and metastatic brain tumours (n = 91; 30 pairs).

Results

Membrane localisation of phospho-HER4 [pHER4(Y¹¹⁶²)] was infrequent in primary breast cancer, but very frequent in brain metastases (5.9% versus 75% positive), where it was usually co-expressed with pHER3(Y¹²⁸⁹) (p < 0.05). The presence of YAP in tumour cell nuclei was associated directly with nuclear pERK5(T²¹⁸/Y²¹⁰) (p = 0.003). However, relationships with disease-specific survival depended on oestrogen receptor (ER) status. Nuclear pYAP(S¹²⁷) was associated with smaller, good prognostic ER+ breast tumours (log-rank hazard-ratio 0.53; p = 9.6E^-03), but larger, poor prognostic triple-negative cancers (log-rank hazard-ratio 2.78; p = 1.7E^-02), particularly when co-expressed with nuclear HER4-ICD (p = 0.02). This phenotype was associated with stemness and mitotic instability markers (vimentin, SOX9, ID1, SPAG5, TTK, geminin; p < 0.05). YAP expression in brain metastases was higher than matched primary tumours; specifically, nuclear pYAP(S¹²⁷) in ER-negative cases (p < 0.05). Nuclear YAP was detected in ~70% of ER-negative, HER4-activated brain metastases.

Discussion

Our findings suggest that the canonical-mechanism where Hippo pathway-mediated phosphorylation of YAP ostensibly excludes it from the nucleus is dysfunctional in breast cancer. The data are consistent with pYAP(S¹²⁷) having independent transcriptional functions, which may include transducing neuregulin signals in brain metastases. Consistent with mechanistic studies implicating it as an ER co-factor, nuclear pYAP(S¹²⁷) associations with breast cancer clinical outcomes were dependent on ER status.

Conclusion

Preclinical studies investigating HER4 and nuclear YAP combination therapy strategies are warranted.

Hippo Signaling Pathway as a Central Mediator of Receptors Tyrosine Kinases (RTKs) in Tumorigenesis

The Hippo pathway plays a critical role in tissue and organ growth under normal physiological conditions, and its dysregulation in malignant growth has made it an attractive target for therapeutic intervention in the fight against cancer. To date, its complex signaling mechanisms have made it difficult to identify strong therapeutic candidates. Hippo signaling is largely carried out by two main activated signaling pathways involving receptor tyrosine kinases (RTKs)—the RTK/RAS/PI3K and the RTK-RAS-MAPK pathways. However, several RTKs have also been shown to regulate this pathway to engage downstream Hippo effectors and ultimately influence cell proliferation. In this text, we attempt to review the diverse RTK signaling pathways that influence Hippo signaling in the context of oncogenesis.

The guanine nucleotide exchange factor VAV3 participates in ERBB4-mediated cancer cell migration

ERBB4 is a member of the epidermal growth factor receptor (EGFR)/ERBB subfamily of receptor tyrosine kinases that regulates cellular processes including proliferation, migration, and survival. ERBB4 signaling is involved in embryogenesis and homeostasis of healthy adult tissues, but also in human pathologies such as cancer, neurological disorders, and cardiovascular diseases. Here, an MS-based analysis revealed the Vav guanine nucleotide exchange factor 3 (VAV3), an activator of Rho family GTPases, as a critical ERBB4-interacting protein in breast cancer cells. We confirmed the ERBB4-VAV3 interaction by targeted MS and coimmunoprecipitation experiments and further defined it by demonstrating that kinase activity and Tyr-1022 and Tyr-1162 of ERBB4, as well as the intact phosphotyrosine-interacting SH2 domain of VAV3, are necessary for this interaction. We found that ERBB4 stimulates tyrosine phosphorylation of the VAV3 activation domain, known to be required for guanine nucleotide exchange factor (GEF) activity of VAV proteins. In addition to VAV3, the other members of the VAV family, VAV1 and VAV2, also coprecipitated with ERBB4. Analyses of the effects of overexpression of dominant-negative VAV3 constructs or shRNA-mediated down-regulation of VAV3 expression in breast cancer cells indicated that active VAV3 is involved in ERBB4-stimulated cell migration. These results define the VAV GEFs as effectors of ERBB4 activity in a signaling pathway relevant for cancer cell migration.

Nuclear receptor tyrosine kinase transport and functions in cancer

Signaling functions of plasma membrane-localized receptor tyrosine kinases (RTKs) have been extensively studied after they were first described in the mid-1980s. Plasma membrane RTKs are activated by extracellular ligands and cellular stress stimuli, and regulate cellular responses by activating the downstream effector proteins to initiate a wide range of signaling cascades in the cells. However, increasing evidence indicates that RTKs can also be transported into the intracellular compartments where they phosphorylate traditional effector proteins and non-canonical substrate proteins. In general, internalization that retains the RTK's transmembrane domain begins with endocytosis, and endosomal RTK remains active before being recycled or degraded. Further RTK retrograde transport from endosome-Golgi-ER to the nucleus is primarily dependent on membranes vesicles and relies on the interaction with the COP-I vesicle complex, Sec61 translocon complex, and importin. Internalized RTKs have non-canonical substrates that include transcriptional co-factors and DNA damage response proteins, and many nuclear RTKs harbor oncogenic properties and can enhance cancer progression. Indeed, nuclear-localized RTKs have been shown to positively correlate with cancer recurrence, therapeutic resistance, and poor prognosis of cancer patients. Therefore, understanding the functions of nuclear RTKs and the mechanisms of nuclear RTK transport will further improve our knowledge to evaluate the potential of targeting nuclear RTKs or the proteins involved in their transport as new cancer therapeutic strategies.