ErbB receptors, their ligands, and the consequences of their activation and inhibition in the myocardium

HB-EGF promotes progenitor cell proliferation and sensory neuron regeneration in the zebrafish olfactory epithelium

Maintenance and regeneration of the zebrafish olfactory epithelium (OE) are supported by two distinct progenitor cell populations that occupy spatially discrete stem cell niches and respond to different tissue conditions. Globose basal cells (GBCs) reside at the inner and peripheral margins of the sensory OE and are constitutively active to replace sporadically dying olfactory sensory neurons (OSNs). In contrast, horizontal basal cells (HBCs) are uniformly distributed across the sensory tissue and are selectively activated by acute injury conditions. Here we show that expression of the heparin-binding epidermal growth factor-like growth factor (HB-EGF) is strongly and transiently upregulated in response to OE injury and signals through the EGF receptor (EGFR), which is expressed by HBCs. Exogenous stimulation of the OE with recombinant HB-EGF promotes HBC expansion and OSN neurogenesis in a pattern that resembles the tissue response to injury. In contrast, pharmacological inhibition of HB-EGF membrane shedding, HB-EGF availability, and EGFR signaling strongly attenuate or delay injury-induced HBC activity and OSN restoration without affecting maintenance neurogenesis by GBCs. Thus, HB-EGF/EGFR signaling appears to be a critical component of the signaling network that controls HBC activity and, consequently, repair neurogenesis in the zebrafish OE.

Efficacy of tyrosine kinase inhibitors examined by a combination of Raman micro-spectroscopy and a deep wavelet scattering-based multivariate analysis framework

HER2 is a crucial therapeutic target in breast cancer, and the survival rate of breast cancer patients has increased because of this receptor's inhibition. However, tumors have shown resistance to this therapeutic strategy due to oncogenic mutations that decrease the binding of several HER2-targeted drugs, including lapatinib, and confer resistance to this drug. Neratinib can overcome this drug resistance and effectively inhibit HER2 signaling and tumor growth. In the present study, we examined the efficacy of lapatinib and neratinib using breast cancer cells by Raman microscopy combined with a deep wavelet scattering-based multivariate analysis framework. This approach discriminated between control cells and drug-treated cells with high accuracy, compared to classical principal component analysis. Both lapatinib and neratinib induced changes in the cellular biochemical composition. Furthermore, the Raman results were compared with the results of several in vitro assays. For instance, drug-treated cells exhibited (i) inhibition of ERK and AKT phosphorylation, (ii) inhibition of cellular proliferation, (iii) cell-cycle arrest, and (iv) apoptosis as indicated by western blotting, real-time cell analysis (RTCA), cell-cycle analysis, and apoptosis assays. Thus, the observed Raman spectral changes are attributed to cell-cycle arrest and apoptosis. The results also indicated that neratinib is more potent than lapatinib. Moreover, the uptake and distribution of lapatinib in cells were visualized through its label-free marker bands in the fingerprint region using Raman spectral imaging. These results show the prospects of Raman microscopy in drug evaluation and presumably in drug discovery.

Cardiotoxicity of breast cancer chemotherapy

Breast cancer is one of the leading causes of malignancy affecting women in the United States. Although many effective treatments are available, most come with notable side effects that providers and patients must take into consideration. Various classes of chemotherapeutic agents, including anthracyclines and human epidermal growth factor receptor-2 antagonists, are known to be toxic to myocardial tissue. In this review article, we discuss what is reported in the literature regarding the cardiotoxicity of these agents as well as how to monitor and prevent cardiac injury and dysfunction.

Cardio-Oncology Rehabilitation-Present and Future Perspectives

Recent advances in cancer therapy have led to increased survival rates for cancer patients, but also allowed cardiovascular complications to become increasingly evident, with more than 40% of cancer deaths now being attributed to cardiovascular diseases. Cardiotoxicity is the most concerning cardiovascular complication, one caused mainly due to anti-cancer drugs. Among the harmful mechanisms of these drugs are DNA damage, endothelial dysfunction, and oxidative stress. Cancer patients can suffer reduced cardiorespiratory fitness as a secondary effect of anti-cancer therapies, tumor burden, and deconditioning. In the general population, regular exercise can reduce the risk of cardiovascular morbidity, mortality, and cancer. Exercise-induced modifications of gene expression result in improvements of cardiovascular parameters and an increased general fitness, influencing telomere shortening, oxidative stress, vascular function, and DNA repair mechanisms. In cancer patients, exercise training is generally safe and well-tolerated; it is associated with a 10-15% improvement in cardiorespiratory fitness and can potentially counteract the adverse effects of anti-cancer therapy. It is well known that exercise programs can benefit patients with heart disease and cancer, but little research has been conducted with cardio-oncology patients. To date, there are a limited number of effective protective treatments for preventing or reversing cardiotoxicity caused by cancer therapy. Cardiac rehabilitation has the potential to mitigate cardiotoxicity based on the benefits already proven in populations suffering from either cancer or heart diseases. Additionally, the fact that cardiotoxic harm mechanisms coincide with similar mechanisms positively affected by cardiac rehabilitation makes cardiac rehabilitation an even more plausible option for cardio-oncology patients. Due to unstable functional capacity and fluctuating immunocompetence, these patients require specially tailored exercise programs designed collaboratively by cardiologists and oncologists. As the digital era is here, with the digital world and the medical world continuously intertwining, a remote, home-based cardio-oncology rehabilitation program may be a solution for this population.

MiR-146a-5p, targeting ErbB4, promotes 3T3-L1 preadipocyte differentiation through the ERK1/2/PPAR-γ signaling pathway

Background

MicroRNAs (MiRNAs) are known to participate in preadipocyte differentiation, but the manner in which miR-146a-5p participates in this process remains unclear. This study was performed to examine the participation of miR-146a-5p in 3T3-L1 cell differentiation.

Material and Methods

miR-146a-5p expression was upregulated and down-regulated to examine effects on 3T3-L1 cell differentiation. Bioinformatics analysis was performed to predict its target genes, and the signaling pathway it regulates was identified by qRT-PCR and Western blotting. The expression of miR-146a-5p in epididymal adipose tissue from obese mice and in an obese mouse adipose cell model was examined by qRT-PCR.

Results

3T3-L1 cells differentiated into mature adipocytes successfully, as verified by increased areas of intracellular lipid droplets and elevated expression of mature adipocyte markers, and these cells had elevated miR-146a-5p expression. The intracellular lipid droplet and triglyceride contents and the expression of mature adipocyte markers were significantly increased in miR-146a-5p–overexpressing 3T3-L1 cells and markedly decreased in miR-146a-5p–inhibited 3T3-L1 cells. ErbB4 was a predicted target gene of miR-146a-5p. In miR-146a-5p–overexpressing 3T3-L1 cells, ErbB4 expression and ERK1/2 phosphorylation were decreased and the expression of PPAR-γ was increased; the opposite was observed in miR-146a-5p–inhibited 3T3-L1 cells. In addition, miR-146a-5p expression was significantly increased in the mouse epididymal adipose tissue and adipose cell model.

Conclusions

Upregulated miR-146a-5p expression was related to 3T3-L1 cell differentiation. MiR-146a-5p promoted 3T3-L1 cell differentiation by targeting ErbB4 and via the ERK1/2/PPAR-γ signaling pathway.

Supplementary information

The online version contains supplementary material available at 10.1186/s12944-022-01662-6.

Hypoxic pulmonary endothelial cells release epidermal growth factor leading to vascular smooth muscle cell arginase-2 expression and proliferation

The hallmark of pulmonary hypertension (PH) is vascular remodeling. We have previously shown that human pulmonary microvascular endothelial cells (hPMVEC) respond to hypoxia with epidermal growth factor (EGF) mediated activation of the receptor tyrosine kinase, EGF receptor (EGFR), resulting in arginase-2 (Arg2)-dependent proliferation. We hypothesized that the release of EGF by hPMVEC could result in the proliferation of human pulmonary arterial smooth muscle cells (hPASMC) via activation of EGFR on the hPASMC leading to Arg2 up-regulation. To test this hypothesis, we used conditioned media (CM) from hPMVEC grown either in normoxia (NCM) or hypoxia (HCM). Human PASMC were incubated in normoxia with either HCM or NCM, and HCM caused significant induction of Arg2 and viable cell numbers. When HCM was generated with either an EGF-neutralizing antibody or an EGFR blocking antibody the resulting HCM did not induce Arg2 or increase viable cell numbers in hPASMC. Adding an EGFR blocking antibody to HCM, prevented the HCM-induced increase in Arg2 and viable cell numbers. HCM induced robust phosphorylation of hPASMC EGFR. When hPASMC were transfected with siRNA against EGFR the HCM-induced increase in viable cell numbers was prevented. When hPASMC were treated with the arginase antagonist nor-NOHA, the HCM-induced increase in viable cell numbers was prevented. These data suggest that hypoxic hPMVEC releases EGF, which activates hPASMC EGFR leading to Arg2 protein expression and an increase in viable cell numbers. We speculate that EGF neutralizing antibodies or EGFR blocking antibodies represent potential therapeutics to prevent and/or attenuate vascular remodeling in PH associated with hypoxia.

Cardiotoxicity of Anticancer Drugs: Molecular Mechanisms and Strategies for Cardioprotection

Chemotherapy and targeted therapies have significantly improved the prognosis of oncology patients. However, these antineoplastic treatments may also induce adverse cardiovascular effects, which may lead to acute or delayed onset of cardiac dysfunction. These common cardiovascular complications, commonly referred to as cardiotoxicity, not only may require the modification, suspension, or withdrawal of life-saving antineoplastic therapies, with the risk of reducing their efficacy, but can also strongly impact the quality of life and overall survival, regardless of the oncological prognosis. The onset of cardiotoxicity may depend on the class, dose, route, and duration of administration of anticancer drugs, as well as on individual risk factors. Importantly, the cardiotoxic side effects may be reversible, if cardiac function is restored upon discontinuation of the therapy, or irreversible, characterized by injury and loss of cardiac muscle cells. Subclinical myocardial dysfunction induced by anticancer therapies may also subsequently evolve in symptomatic congestive heart failure. Hence, there is an urgent need for cardioprotective therapies to reduce the clinical and subclinical cardiotoxicity onset and progression and to limit the acute or chronic manifestation of cardiac damages. In this review, we summarize the knowledge regarding the cellular and molecular mechanisms contributing to the onset of cardiotoxicity associated with common classes of chemotherapy and targeted therapy drugs. Furthermore, we describe and discuss current and potential strategies to cope with the cardiotoxic side effects as well as cardioprotective preventive approaches that may be useful to flank anticancer therapies.

Osimertinib and anti-HER3 combination therapy engages immune dependent tumor toxicity via STING activation in trans

Over the past decade, immunotherapy delivered novel treatments for many cancer types. However, lung cancer still leads cancer mortality, and non-small-cell lung carcinoma patients with mutant EGFR cannot benefit from checkpoint inhibitors due to toxicity, relying only on palliative chemotherapy and the third-generation tyrosine kinase inhibitor (TKI) osimertinib. This new drug extends lifespan by 9-months vs. second-generation TKIs, but unfortunately, cancers relapse due to resistance mechanisms and the lack of antitumor immune responses. Here we explored the combination of osimertinib with anti-HER3 monoclonal antibodies and observed that the immune system contributed to eliminate tumor cells in mice and co-culture experiments using bone marrow-derived macrophages and human PBMCs. Osimertinib led to apoptosis of tumors but simultaneously, it triggered inositol-requiring-enzyme (IRE1α)-dependent HER3 upregulation, increased macrophage infiltration, and activated cGAS in cancer cells to produce cGAMP (detected by a lentivirally transduced STING activity biosensor), transactivating STING in macrophages. We sought to target osimertinib-induced HER3 upregulation with monoclonal antibodies, which engaged Fc receptor-dependent tumor elimination by macrophages, and STING agonists enhanced macrophage-mediated tumor elimination further. Thus, by engaging a tumor non-autonomous mechanism involving cGAS-STING and innate immunity, the combination of osimertinib and anti-HER3 antibodies could improve the limited therapeutic and stratification options for advanced stage lung cancer patients with mutant EGFR.

Smad7 effects on TGF-β and ErbB2 restrain myofibroblast activation and protect from postinfarction heart failure

Repair of the infarcted heart requires TGF-β/Smad3 signaling in cardiac myofibroblasts. However, TGF-β-driven myofibroblast activation needs to be tightly regulated in order to prevent excessive fibrosis and adverse remodeling that may precipitate heart failure. We hypothesized that induction of the inhibitory Smad, Smad7, may restrain infarct myofibroblast activation, and we examined the molecular mechanisms of Smad7 actions. In a mouse model of nonreperfused infarction, Smad3 activation triggered Smad7 synthesis in α-SMA+ infarct myofibroblasts, but not in α-SMA-PDGFRα+ fibroblasts. Myofibroblast-specific Smad7 loss increased heart failure-related mortality, worsened dysfunction, and accentuated fibrosis in the infarct border zone and in the papillary muscles. Smad7 attenuated myofibroblast activation and reduced synthesis of structural and matricellular extracellular matrix proteins. Smad7 effects on TGF-β cascades involved deactivation of Smad2/3 and non-Smad pathways, without any effects on TGF-β receptor activity. Unbiased transcriptomic and proteomic analysis identified receptor tyrosine kinase signaling as a major target of Smad7. Smad7 interacted with ErbB2 in a TGF-β-independent manner and restrained ErbB1/ErbB2 activation, suppressing fibroblast expression of fibrogenic proteases, integrins, and CD44. Smad7 induction in myofibroblasts serves as an endogenous TGF-β-induced negative feedback mechanism that inhibits postinfarction fibrosis by restraining Smad-dependent and Smad-independent TGF-β responses, and by suppressing TGF-β-independent fibrogenic actions of ErbB2.

Nrg1/ErbB signaling-mediated regulation of fibrosis after myocardial infarction

Appropriate fibrotic tissue formation after myocardial infarction (MI) is crucial to the maintenance of the heart's structure. M2-like macrophages play a vital role in post-MI fibrosis by activating cardiac fibroblasts. Because the mechanism by which post-MI cardiac fibrosis is regulated is not fully understood, we investigated, in vitro and in vivo, the cellular and molecular mechanisms of post-MI fibrotic tissue formation, especially those related to the regulation of cellular senescence and apoptosis. CD206⁺ F4/80⁺ CD11b⁺ M2-like macrophages collected from mouse hearts on post-MI day 7 showed increased expression of neuregulin 1 (Nrg1). Nrg1 receptor epidermal growth factor receptors ErbB2 and ErbB4 were expressed on cardiac fibroblasts in the infarct area. M2-like macrophage-derived Nrg1 suppressed both hydrogen peroxide-induced senescence and apoptosis of fibroblasts, whereas blockade of ErbB function significantly accelerated both processes. M2-like macrophage-derived Nrg1/ErbB/PI3K/Akt signaling, shown to be related to anti-senescence, was activated in damaged cardiac fibroblasts. Interestingly, systemic blockade of ErbB function in MI model mice enhanced senescence and apoptosis of cardiac fibroblasts and exacerbated inflammation. Further, increased accumulation of M2-like macrophages resulted in excessive post-MI progression of fibrosis in mice hearts. The molecular mechanism underlying the regulation of fibrotic tissue formation in the infarcted myocardium was shown in part to be attenuation of apoptosis and senescence of cardiac fibroblasts by the activation of Nrg1/ErbB/PI3K/Akt signaling. M2-like macrophage-mediated regulation of Nrg1/ErbB signaling has a substantial effect on fibrotic tissue formation in the infarcted adult mouse heart and is critical for suppressing the progression of senescence and apoptosis of cardiac fibroblasts.

The Role of Epidermal Growth Factor Receptor Family of Receptor Tyrosine Kinases in Mediating Diabetes-Induced Cardiovascular Complications

Diabetes mellitus is a major debilitating disease whose global incidence is progressively increasing with currently over 463 million adult sufferers and this figure will likely reach over 700 million by the year 2045. It is the complications of diabetes such as cardiovascular, renal, neuronal and ocular dysfunction that lead to increased patient morbidity and mortality. Of these, cardiovascular complications that can result in stroke and cardiomyopathies are 2- to 5-fold more likely in diabetes but the underlying mechanisms involved in their development are not fully understood. Emerging research suggests that members of the Epidermal Growth Factor Receptor (EGFR/ErbB/HER) family of tyrosine kinases can have a dual role in that they are beneficially required for normal development and physiological functioning of the cardiovascular system (CVS) as well as in salvage pathways following acute cardiac ischemia/reperfusion injury but their chronic dysregulation may also be intricately involved in mediating diabetes-induced cardiovascular pathologies. Here we review the evidence for EGFR/ErbB/HER receptors in mediating these dual roles in the CVS and also discuss their potential interplay with the Renin-Angiotensin-Aldosterone System heptapeptide, Angiotensin-(1-7), as well the arachidonic acid metabolite, 20-HETE (20-hydroxy-5, 8, 11, 14-eicosatetraenoic acid). A greater understanding of the multi-faceted roles of EGFR/ErbB/HER family of tyrosine kinases and their interplay with other key modulators of cardiovascular function could facilitate the development of novel therapeutic strategies for treating diabetes-induced cardiovascular complications.

Cardiac regenerative capacity: an evolutionary afterthought?

Cardiac regeneration is the outcome of the highly regulated interplay of multiple processes, including the inflammatory response, cardiomyocyte dedifferentiation and proliferation, neovascularization and extracellular matrix turnover. Species-specific traits affect these injury-induced processes, resulting in a wide variety of cardiac regenerative potential between species. Indeed, while mammals are generally considered poor regenerators, certain amphibian and fish species like the zebrafish display robust regenerative capacity post heart injury. The species-specific traits underlying these differential injury responses are poorly understood. In this review, we will compare the injury induced processes of the mammalian and zebrafish heart, describing where these processes overlap and diverge. Additionally, by examining multiple species across the animal kingdom, we will highlight particular traits that either positively or negatively affect heart regeneration. Last, we will discuss the possibility of overcoming regeneration-limiting traits to induce heart regeneration in mammals.

The Multifunctional Contribution of FGF Signaling to Cardiac Development, Homeostasis, Disease and Repair

The current focus on cardiovascular research reflects society’s concerns regarding the alarming incidence of cardiac-related diseases and mortality in the industrialized world and, notably, an urgent need to combat them by more efficient therapies. To pursue these therapeutic approaches, a comprehensive understanding of the mechanism of action for multifunctional fibroblast growth factor (FGF) signaling in the biology of the heart is a matter of high importance. The roles of FGFs in heart development range from outflow tract formation to the proliferation of cardiomyocytes and the formation of heart chambers. In the context of cardiac regeneration, FGFs 1, 2, 9, 16, 19, and 21 mediate adaptive responses including restoration of cardiac contracting rate after myocardial infarction and reduction of myocardial infarct size. However, cardiac complications in human diseases are correlated with pathogenic effects of FGF ligands and/or FGF signaling impairment. FGFs 2 and 23 are involved in maladaptive responses such as cardiac hypertrophic, fibrotic responses and heart failure. Among FGFs with known causative (FGFs 2, 21, and 23) or protective (FGFs 2, 15/19, 16, and 21) roles in cardiac diseases, FGFs 15/19, 21, and 23 display diagnostic potential. The effective role of FGFs on the induction of progenitor stem cells to cardiac cells during development has been employed to boost the limited capacity of postnatal cardiac repair. To renew or replenish damaged cardiomyocytes, FGFs 1, 2, 10, and 16 were tested in (induced-) pluripotent stem cell-based approaches and for stimulation of cell cycle re-entry in adult cardiomyocytes. This review will shed light on the wide range of beneficiary and detrimental actions mediated by FGF ligands and their receptors in the heart, which may open new therapeutic avenues for ameliorating cardiac complications.

LncRNA AK020546 protects against cardiac ischemia-reperfusion injury by sponging miR-350-3p

Long non-coding RNAs (lncRNAs) have been implicated in the development of cardiovascular diseases. We observed that lncRNA AK020546 was downregulated following ischemia/reperfusion injury to the myocardium and following H2O2 treatment in H9c2 cardiomyocytes. In vivo and in vitro studies showed that AK020546 overexpression attenuated the size of the ischemic area, reduced apoptosis among H9c2 cardiomyocytes, and suppressed the release of reactive oxygen species, lactic acid dehydrogenase, and malondialdehyde. AK020546 served as a competing endogenous RNA for miR-350-3p and activated the miR-350-3p target gene ErbB3. MiR-350-3p overexpression reversed the effects of AK020546 on oxidative stress injury and apoptosis in H9c2 cardiomyocytes. Moreover, ErbB3 knockdown alleviated the effects of AK020546 on the expression of ErbB3, Bcl-2, phosphorylated AKT, cleaved Caspase 3, and phosphorylated Bad. These findings suggest lncRNA AK020546 protects against ischemia/reperfusion and oxidative stress injury by sequestering miR-350-3p and activating ErbB3, which highlights its potential as a therapeutic target for ischemic heart diseases.

Comprehensive bioinformatics analysis reveals kinase activity profiling associated with heart failure

Heart failure is a complex clinical syndrome originating from cardiac injury, which leads to considerable morbidity and mortality. Among the dynamic molecular adaptations occurring in heart failure development, aggravation of the disease is often attributed to global or local abnormality of the kinase. Therefore, the overall monitoring of kinase activity is indispensable. In this study, a bioinformatics analysis method was developed to conduct deep mining of transcriptome and phosphoproteome in failing heart tissue. A total of 982 differentially expressed genes and 9781 phosphorylation sites on 3252 proteins were identified. Via upstream regulator relations and kinase-substrate relations, a dendrogram of kinases can be constructed to monitor its abnormality. The results show that, on the dendrogram, the distribution of kinases demonstrated complex kinase activity changes and certain rules that occur during heart failure. Finally, we also identified the hub kinases in heart failure and verified the expression of these kinases by reverse-transcription polymerase chain reaction and Western blot analysis. In conclusion, for the first time, we have systematically analyzed the differences in kinases during heart failure and provided an unprecedented breadth of multi-omics data. These results can bring about a sufficient data foundation and novel research perspectives.

PET and SPECT Imaging of the EGFR Family (RTK Class I) in Oncology

The human epidermal growth factor receptor family (EGFR-family, other designations: HER family, RTK Class I) is strongly linked to oncogenic transformation. Its members are frequently overexpressed in cancer and have become attractive targets for cancer therapy. To ensure effective patient care, potential responders to HER-targeted therapy need to be identified. Radionuclide molecular imaging can be a key asset for the detection of overexpression of EGFR-family members. It meets the need for repeatable whole-body assessment of the molecular disease profile, solving problems of heterogeneity and expression alterations over time. Tracer development is a multifactorial process. The optimal tracer design depends on the application and the particular challenges of the molecular target (target expression in tumors, endogenous expression in healthy tissue, accessibility). We have herein summarized the recent preclinical and clinical data on agents for Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) imaging of EGFR-family receptors in oncology. Antibody-based tracers are still extensively investigated. However, their dominance starts to be challenged by a number of tracers based on different classes of targeting proteins. Among these, engineered scaffold proteins (ESP) and single domain antibodies (sdAb) show highly encouraging results in clinical studies marking a noticeable trend towards the use of smaller sized agents for HER imaging.

S100A4 in Spinal Substantia Gelatinosa from Dorsal Root Ganglia Modulates Neuropathic Pain in a Rodent Spinal Nerve Injury Model

Purpose

To detect the spatio-temporal expression of S100A4 in a spinal nerve ligation (SNL) rat model. Also to figure out which other molecules directly interact with S100A4 to explore the possible mechanisms which might be involved in neuropathic pain.

Methods

Seven-week-old male SD rats were used for the SNL model construction. Immunofluorescence and Western blotting were used to detect the spatio-temporal expression of S100A4 in the model. S100A4 was co-labeled with a number of related molecules and marker molecules that can distinguish between cell types. After intrathecal injection of S100A4 neutralizing antibody, the behavioral changes of SNL rats were recorded, and molecular changes compared. The direct interaction between S100A4 and other related molecules was verified by co-immunoprecipitation (co-IP) to explore its possible mechanism.

Results

After spinal nerve ligation, the content of S100A4 in the dorsal root ganglion (DRG) and spinal dorsal horn increased significantly. Intrathecal injection of S100A4 neutralizing antibody could effectively relieve the mechanical pain in rats. co-IP revealed a direct interaction between S100A4 and RAGE.

Conclusion

The content of S100A4 in the DRG and spinal dorsal horn of SNL rats increased, compared with that of the control group. Intrathecal injection of S100A4 neutralizing antibody could effectively relieve the mechanical pain in SNL rats. S100A4 may be involved in the production of neuropathic pain through RAGE or other ways, but the specific mechanism needs to be further studied.

Structural Basis for the Functional Changes by EGFR Exon 20 Insertion Mutations

Activating somatic mutations of the epidermal growth factor receptor (EGFR) are frequently implicated in non-small cell lung cancer (NSCLC). While L858R and exon 19 deletion mutations are most prevalent, exon 20 insertions are often observed in NSCLC. Here, we investigated the structural implications of two common EGFR exon 20 insertions in NSCLC, V769insASV and D770insNPG. The active and inactive conformations of wild-type, D770insNPG and V769insASV EGFRs were probed with molecular dynamics simulations to identify local and global alterations that the mutations exert on the EGFR kinase domain, highlighting mechanisms for increased enzymatic activity. In the active conformation, the mutations increase interactions that stabilize the αC helix that is essential for EGFR activity. Moreover, the key Lys745-Glu762 salt bridge was more conserved in the insertion mutations. The mutants also preserved the state of the structurally critical aspartate-phenylalanine-glycine (DFG)-motif and regulatory spine (R-spine), which were altered in wild-type EGFR. The insertions altered the structure near the ATP-binding pocket, e.g., the P-loop, which may be a factor for the clinically observed tyrosine kinase inhibitor (TKI) insensitivity by the insertion mutants. The inactive state simulations also showed that the insertions disrupt the Ala767-Arg776 interaction that is key for maintaining the "αC-out" inactive conformation, which could consequently fuel the transition from the inactive towards the active EGFR state.

Regulation of cardiomyocyte fate plasticity: a key strategy for cardiac regeneration

With the high morbidity and mortality rates, cardiovascular diseases have become one of the most concerning diseases worldwide. The heart of adult mammals can hardly regenerate naturally after injury because adult cardiomyocytes have already exited the cell cycle, which subseqently triggers cardiac remodeling and heart failure. Although a series of pharmacological treatments and surgical methods have been utilized to improve heart functions, they cannot replenish the massive loss of beating cardiomyocytes after injury. Here, we summarize the latest research progress in cardiac regeneration and heart repair through altering cardiomyocyte fate plasticity, which is emerging as an effective strategy to compensate for the loss of functional cardiomyocytes and improve the impaired heart functions. First, residual cardiomyocytes in damaged hearts re-enter the cell cycle to acquire the proliferative capacity by the modifications of cell cycle-related genes or regulation of growth-related signals. Additionally, non-cardiomyocytes such as cardiac fibroblasts, were shown to be reprogrammed into cardiomyocytes and thus favor the repair of damaged hearts. Moreover, pluripotent stem cells have been shown to transform into cardiomyocytes to promote heart healing after myocardial infarction (MI). Furthermore, in vitro and in vivo studies demonstrated that environmental oxygen, energy metabolism, extracellular factors, nerves, non-coding RNAs, etc. play the key regulatory functions in cardiac regeneration. These findings provide the theoretical basis of targeting cellular fate plasticity to induce cardiomyocyte proliferation or formation, and also provide the clues for stimulating heart repair after injury.

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.

Non-coding RNAs: emerging players in cardiomyocyte proliferation and cardiac regeneration

Soon after birth, the regenerative capacity of the mammalian heart is lost, cardiomyocytes withdraw from the cell cycle and demonstrate a minimal proliferation rate. Despite improved treatment and reperfusion strategies, the uncompensated cardiomyocyte loss during injury and disease results in cardiac remodeling and subsequent heart failure. The promising field of regenerative medicine aims to restore both the structure and function of damaged tissue through modulation of cellular processes and regulatory mechanisms involved in cardiac cell cycle arrest to boost cardiomyocyte proliferation. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) are functional RNA molecules with no protein-coding function that have been reported to engage in cardiac regeneration and repair. In this review, we summarize the current understanding of both the biological functions and molecular mechanisms of ncRNAs involved in cardiomyocyte proliferation. Furthermore, we discuss their impact on the structure and contractile function of the heart in health and disease and their application for therapeutic interventions.

The role of endothelial autocrine NRG1/ERBB4 signaling in cardiac remodeling

Neuregulin-1 (NRG1) is a paracrine growth factor, secreted by cardiac endothelial cells (ECs) in conditions of cardiac overload/injury. The current concept is that the cardiac effects of NRG1 are mediated by activation of erythroblastic leukemia viral oncogene homolog (ERBB)4/ERBB2 receptors on cardiomyocytes. However, recent studies have shown that paracrine effects of NRG1 on fibroblasts and macrophages are equally important. Here, we hypothesize that NRG1 autocrine signaling plays a role in cardiac remodeling. We generated EC-specific Erbb4 knockout mice to eliminate endothelial autocrine ERBB4 signaling without affecting paracrine NRG1/ERBB4 signaling in the heart. We first observed no basal cardiac phenotype in these mice up to 32 wk. We next studied these mice following transverse aortic constriction (TAC), exposure to angiotensin II (ANG II), or myocardial infarction in terms of cardiac performance, myocardial hypertrophy, myocardial fibrosis, and capillary density. In general, no major differences between EC-specific Erbb4 knockout mice and control littermates were observed. However, 8 wk following TAC both myocardial hypertrophy and fibrosis were attenuated by EC-specific Erbb4 deletion, albeit these responses were normalized after 20 wk. Similarly, 4 wk after ANG II treatment, myocardial fibrosis was less pronounced compared with control littermates. These observations were supported by RNA-sequencing experiments on cultured endothelial cells showing that NRG1 controls the expression of various hypertrophic and fibrotic pathways. Overall, this study shows a role of endothelial autocrine NRG1/ERBB4 signaling in the modulation of hypertrophic and fibrotic responses during early cardiac remodeling. This study contributes to understanding the spatiotemporal heterogeneity of myocardial autocrine and paracrine responses following cardiac injury.NEW & NOTEWORTHY The role of NRG1/ERBB signaling in endothelial cells is not completely understood. Our study contributes to the understanding of spatiotemporal heterogeneity of myocardial autocrine and paracrine responses following cardiac injury and shows a role of endothelial autocrine NRG1/ERBB4 signaling in the modulation of hypertrophic and fibrotic responses during early cardiac remodeling.

Neuregulin-1 triggers GLUT4 translocation and enhances glucose uptake independently of insulin receptor substrate and ErbB3 in neonatal rat cardiomyocytes

During stress conditions such as pressure overload and acute ischemia, the myocardial endothelium releases neuregulin-1β (NRG-1), which acts as a cardioprotective factor and supports recovery of the heart. Recently, we demonstrated that recombinant human (rh)NRG-1 enhances glucose uptake in neonatal rat ventricular myocytes via the ErbB2/ErbB4 heterodimer and PI3Kα. The present study aimed to further elucidate the mechanism whereby rhNRG-1 activates glucose uptake in comparison to the well-established insulin and to extend the findings to adult models. Combinations of rhNRG-1 with increasing doses of insulin did not yield any additive effect on glucose uptake measured as ³H-deoxy-d-glucose incorporation, indicating that the mechanisms of the two stimuli are similar. In c-Myc-GLUT4-mCherry-transfected neonatal rat cardiomyocytes, rhNRG-1 increased sarcolemmal GLUT4 by 16-fold, similar to insulin. In contrast to insulin, rhNRG-1 did not phosphorylate IRS-1 at Tyr⁶¹², indicating that IRS-1 is not implicated in the signal transmission. Treatment of neonatal rats with rhNRG-1 induced a signaling response comparable with that observed in vitro, including increased ErbB4-pTyr¹²⁸⁴, Akt-pThr³⁰⁸ and Erk1/2-pThr²⁰²/Tyr²⁰⁴. In contrast, in adult cardiomyocytes rhNRG-1 only increased the phosphorylation of Erk1/2 without having any significant effect on Akt and AS160 phosphorylation and glucose uptake, suggesting that rhNRG-1 function in neonatal cardiomyocytes differs from that in adult cardiomyocytes. In conclusion, our results show that similar to insulin, rhNRG-1 can induce glucose uptake by activating the PI3Kα-Akt-AS160 pathway and GLUT4 translocation. Unlike insulin, the rhNRG-1-induced effect is not mediated by IRS proteins and is observed in neonatal, but not in adult rat cardiomyocytes.

Mechanisms of the Multitasking Endothelial Protein NRG-1 as a Compensatory Factor During Chronic Heart Failure

Heart failure is a complex syndrome whose phenotypic presentation and disease progression depends on a complex network of adaptive and maladaptive responses. One of these responses is the endothelial release of NRG (neuregulin)-1—a paracrine growth factor activating ErbB2 (erythroblastic leukemia viral oncogene homolog B2), ErbB3, and ErbB4 receptor tyrosine kinases on various targets cells. NRG-1 features a multitasking profile tuning regenerative, inflammatory, fibrotic, and metabolic processes. Here, we review the activities of NRG-1 on different cell types and organs and their implication for heart failure progression and its comorbidities. Although, in general, effects of NRG-1 in heart failure are compensatory and beneficial, translation into therapies remains unaccomplished both because of the complexity of the underlying pathways and because of the challenges in the development of therapeutics (proteins, peptides, small molecules, and RNA-based therapies) for tyrosine kinase receptors. Here, we give an overview of the complexity to be faced and how it may be tackled.

Structural characterization of EGFR exon 19 deletion mutation using molecular dynamics simulation

Epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor important in diverse biological processes including cell proliferation and survival. Upregulation of EGFR activity due to over-expression or mutation is widely implicated in cancer. Activating somatic mutations of the EGFR kinase are postulated to affect the conformation and/or stability of the protein, shifting the EGFR inactive-active state equilibrium towards the activated state. Here, we examined a common EGFR deletion mutation, Δ⁷⁴⁶ELREA⁷⁵⁰, which is frequently observed in non-small cell lung cancer patients. By using molecular dynamics simulation, we investigated the structural effects of the mutation that lead to the experimentally reported increases in kinase activity. Simulations of the active form wild-type and ΔELREA EGFRs revealed the deletion stabilizes the αC helix of the kinase domain, which is located adjacent to the deletion site, by rigidifying the flexible β3-αC loop that accommodates the ELREA sequence. Consequently, the αC helix is stabilized in the “αC-in” active conformation that would prolong the time of the activated state. Moreover, in the mutant kinase, a salt bridge between E762 and K745, which is key for EGFR activity, was also stabilized during the simulation. Additionally, the interaction between EGFR and ATP was favored by ΔELREA EGFR over wild-type EGFR, as reflected by the number of hydrogen bonds formed and the free energy of binding. Simulation of inactive EGFR suggested the deletion would promote a shift from the inactive conformation towards active EGFR, which is supported by the inward movement of the αC helix. The MDS results also align with the effects of tyrosine kinase inhibitors on ΔELREA and wild-type EGFR lung cancer cell lines, where more pronounced inhibition was observed against ΔELREA than for wild-type EGFR by inhibitors recognizing the active kinase conformation.

The heart of a hibernator: EGFR and MAPK signaling in cardiac muscle during the hibernation of thirteen-lined ground squirrels, Ictidomys tridecemlineatus

Background

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) experience dramatic changes in physiological and molecular parameters during winter hibernation. Notably, these animals experience reduced blood circulation during torpor, which can put numerous stresses on their hearts. The present study evaluates the role played by the epidermal growth factor receptor (EGFR) in signal transduction during hibernation at low body temperature to evaluate signaling mechanisms. By investigating the regulation of intracellular mitogen activated protein kinase (MAPK) pathway responses, anti-apoptosis signals, downstream transcription factors, and heat shock proteins in cardiac muscle we aim to determine the correlation between upstream tyrosine phosphorylation events and downstream outcomes.

Methods

Protein abundance of phosphorylated EGFR, MAPKs and downstream effector proteins were quantified using immunoblotting and Luminex^® multiplex assays.

Results

Monitoring five time points over the torpor/arousal cycle, EGFR phosphorylation on T654, Y1068, Y1086 was found to increase significantly compared with euthermic control values particularly during the arousal process from torpor, whereas phosphorylation at Y1045 was reduced during torpor. Phosphorylation of intracellular MAPK targets (p-ERK 1/2, p-JNK, p-p38) also increased strongly during the early arousal stage with p-p38 levels also rising during prolonged torpor. However, of downstream MAPK effector kinases that were measured, only p-Elk-1 levels changed showing a decrease during interbout arousal (IA). Apoptosis markers revealed a strong reduction of the pro-apoptotic p-BAD protein during entrance into torpor that remained suppressed through torpor and IA. However, active caspase-9 protein rose strongly during IA. Levels of p-AKT were suppressed during the transition phases into and out of torpor. Of four heat shock proteins assessed, only HSP27 protein levels changed significantly (a 40% decrease) during torpor.

Conclusion

We show evidence of EGFR phosphorylation correlating to activation of MAPK signaling and downstream p-ELK1 suppression during hibernation. We also demonstrate a reduction in p-BAD mediated pro-apoptotic signaling during hibernation with active caspase-9 protein levels increasing only during IA. I. tridecemlineatus has natural mechanisms of tissue protection during hibernation that is largely due to cellular regulation through phosphorylation-mediated signaling cascade. We identify a possible link between EGFR and MAPK signaling via p-ERK, p-p38, and p-JNK in the cardiac muscle of these hibernating mammals that correlates with an apparent reduction in caspase-9 apoptotic signaling. This reveals a piece of the mechanism behind how these mammals are resilient to cardiac stresses during hibernation that would otherwise be damaging.

Modulation of cardiac AKT and STAT3 signalling in preclinical cancer models and their impact on the heart

BACKGROUND

Advanced cancer induces fundamental cardiac changes and promotes body wasting and heart failure. We evaluated the impact of cancer on major cardiac signalling pathways, and resulting consequences for the heart.

METHODS AND RESULTS

Metastatic melanoma disease was induced in male C57BL/6 N mice by intraperitoneal injection of the melanoma cell line B16F10 and lead to cardiac atrophy and heart failure. Analyses of key cardiac signalling pathways in left ventricular tissue revealed increased activation of STAT3 and reduced activation of AKT, p38 and ERK1/2. Markers of the ubiquitin proteasomal system (UPS: Atrogin-1) and of mitophagy/autophagy (LC3b, BNIP3) were upregulated. Tumour-bearing C57BL/6 N mice with a cardiomyocyte-specific overexpression of a constitutively active AKT transgene (AKTtg) displayed less cardiac atrophy and dysfunction and normalized Atrogin-1, LC3b and BNIP3 expression while the cardiomyocyte-specific knockout of STAT3 (CKO) had no major effect on these parameters compared to WT.

CONCLUSION

Cancer alters major cardiac signalling pathways and subsequently the UPS, mitophagy and autophagy. The present study suggests that cancer-induced reduction of cardiomyocyte AKT contributes to these alterations as they were attenuated in tumour-bearing AKTtg mice. In turn, increased cardiomyocyte STAT3 activation appears less relevant, as tumour-induced impairment on the heart was largely similar in CKO and WT mice. Since oncologic therapies frequently target AKT and/or STAT3, their impact on the heart might be different in tumour-bearing mice compared to healthy mice, a feature suggesting to test tumour therapies also in tumour disease models and not only under healthy conditions. This article is part of a Special Issue entitled: Cardiomyocyte biology: new pathways of differentiation and regeneration edited by Marijke Brink, Marcus C. Schaub, and Christian Zuppinger.

Molecular switch model for cardiomyocyte proliferation

This review deals with the human adult cardiomyocyte proliferation as a potential source for heart repair after injury. The mechanism to regain the proliferative capacity of adult cardiomyocytes is a challenge. However, recent studies are promising in showing that the ‘locked’ cell cycle of adult cardiomyocytes could be released through modulation of cell cycle checkpoints. In support of this are the signaling pathways of Notch, Hippo, Wnt, Akt and Jak/Stat that facilitate or inhibit the transition at cell cycle checkpoints. Cyclins and cyclin dependant kinases (CDKs) facilitate this transition which in turn is regulated by inhibitory action of pocket protein e.g. p21, p27 and p57. Transcription factors e.g. E2F, GATA4, TBx20 up regulate Cyclin A, A2, D, E, and CDK4 as promoters of cell cycle and Meis-1 and HIF-1 alpha down regulate cyclin D and E to inhibit the cell cycle. Paracrine factors like Neuregulin-1, IGF-1 and Oncostatin M and Extracellular Matrix proteins like Agrin have been involved in cardiomyocyte proliferation and dedifferentiation processes.

A molecular switch model is proposed that transforms the post mitotic cell into an actively dividing cell. This model shows how the cell cycle is regulated through on- and off switch mechanisms through interaction of transcription factors and signaling pathways with proteins of the cell cycle checkpoints. Signals triggered by injury may activate the right combination of the various pathways that can ‘switch on’ the proliferation signals leading to myocardial regeneration.

Overexpression of ERBB4 rejuvenates aged mesenchymal stem cells and enhances angiogenesis via PI3K/AKT and MAPK/ERK pathways

The age-related functional exhaustion limits potential efficacy of mesenchymal stem cells (MSC) in treating cardiovascular disease. Therefore, rejuvenation of aged MSC in the elderly population is of great interest. We have previously reported that Erb-B2 receptor tyrosine kinase 4 ( ERBB4) plays a critical role in regulating MSC survival under hypoxia. The aim of this study was to investigate whether ERBB4 rejuvenates aged MSC and how ERBB4 enhances therapeutic efficacy of aged MSC in treating myocardial infarction (MI). Compared with vector aged MSC (aged-MSC), ERBB4-engineered aged MSC (ER4-aged-MSC) conferred resistance to oxidative stress-induced cell death and ameliorated the senescent phenotype in vitro. Four weeks after MI, the ER4-aged-MSC group exhibited enhanced blood vessel density, reduced cardiac remodeling and apoptosis with improved heart function compared with the aged-MSC group. Overexpression of ERBB4 caused an increase in phosphorylated v-akt murine thymoma viral oncogene homolog 1 (AKT), and phosphorylated ERK expression under hypoxia. ER4-aged-MSC secreted higher levels of angiopoietin, epithelial neutrophil activating peptide 78, VEGF, and fibroblast growth factor 2, and enhanced tube formation in HUVEC. The impact of ERBB4 on protein expression, proangiogenesis, cell behavior, and cytokine secretion was abolished by inhibiting PI3K/AKT and MAPK/ERK signaling pathway.-Liang, X., Ding, Y., Lin, F., Zhang, Y., Zhou, X., Meng, Q., Lu, X., Jiang, G., Zhu, H., Chen, Y., Lian, Q., Fan, H., Liu, Z. Overexpression of ERBB4 rejuvenates aged mesenchymal stem cells and enhances angiogenesis via PI3K/AKT and MAPK/ERK pathways.

Phytoestrogens and mycoestrogens interacting with breast cancer proteins

Breast cancer is a highly heterogeneous disease influenced by the hormonal microenvironment and the most common malignancy in women worldwide. Some phytoestrogens and mycoestrogens have been epidemiologically linked as risk factors or protectors, however their mechanisms of action are complex and not fully understood. The aim of this study was to predict the potential of 36 natural xenoestrogens to interact with 189 breast cancer proteins using AutoDock Vina. In order to validate our protocol, an in silico docking pose and binding site determination was compared with the crystallographic structure and the power of prediction to distinguish between ligand and decoys was evaluated through a receiver operating characteristic curve (ROC) of the resultant docking affinities and in vitro data. The best affinity score was obtained for glyceollin III interacting with the sex hormone binding globulin (-11.9 Kcal/mol), a plasma steroid transport protein that regulates sex steroids bioavailability. Other natural xenoestrogens such as beta-carotene, chrysophanol 8-O-beta-d-glucopyranoside and glyceollin I, also presented good affinity for proteins related to this disease and the validation was successful. This study may help to prioritize compounds for toxicity tests or drug development from natural scaffolds, and to elucidate their mechanisms of action.

Hypoxic-induction of arginase II requires EGF-mediated EGFR activation in human pulmonary microvascular endothelial cells

We have previously shown that hypoxia-induced proliferation of human pulmonary microvascular endothelial cells (hPMVEC) depends on arginase II, and that epidermal growth factor receptor (EGFR) is necessary for hypoxic-induction of arginase II. However, it remains unclear how hypoxia activates EGFR-mediated signaling in hPMVEC. We hypothesized that hypoxia results in epidermal growth factor (EGF) production and that EGF binds to EGFR to activate the signaling cascade leading to arginase II induction and proliferation in hPMVEC. We found that hypoxia significantly increased the mRNA levels of EGF, EGFR, and arginase in hPMVEC. Hypoxia significantly increased pEGFR(Tyr845) protein levels and an EGF neutralizing antibody prevented the hypoxic induction of pEGFR. Inhibiting EGFR activation prevented hypoxia-induced arginase II mRNA and protein induction. Treatment of hPMVEC with exogenous EGF resulted in greater levels of arginase II protein both in normoxia and hypoxia. An EGF neutralizing antibody diminished hypoxic induction of arginase II and resulted in fewer viable cells in hPMVEC. Similarly, siRNA against EGF prevented hypoxic induction of arginase II and resulted in fewer viable cells. Finally, conditioned media from hypoxic hPMVEC induced proliferation in human pulmonary artery smooth muscle cells (hPASMC), however, conditioned media from a group of hypoxic hPMVEC in which EGF were knocked down did not promote hPASMC proliferation. These findings demonstrate that hypoxia-induced arginase II expression and cellular proliferation depend on autocrine EGF production leading to EGFR activation in hPMVEC. We speculate that EGF-EGFR signaling may be a novel therapeutic target for pulmonary hypertensive disorders associated with hypoxia.

Neddylation mediates ventricular chamber maturation through repression of Hippo signaling

During development, ventricular chamber maturation is a crucial step in the formation of a functionally competent postnatal heart. Defects in this process can lead to left ventricular noncompaction cardiomyopathy and heart failure. However, molecular mechanisms underlying ventricular chamber development remain incompletely understood. Neddylation is a posttranslational modification that attaches ubiquitin-like protein NEDD8 to protein targets via NEDD8-specific E1-E2-E3 enzymes. Here, we report that neddylation is temporally regulated in the heart and plays a key role in cardiac development. Cardiomyocyte-specific knockout of NAE1, a subunit of the E1 neddylation activating enzyme, significantly decreased neddylated proteins in the heart. Mice lacking NAE1 developed myocardial hypoplasia, ventricular noncompaction, and heart failure at late gestation, which led to perinatal lethality. NAE1 deletion resulted in dysregulation of cell cycle-regulatory genes and blockade of cardiomyocyte proliferation in vivo and in vitro, which was accompanied by the accumulation of the Hippo kinases Mst1 and LATS1/2 and the inactivation of the YAP pathway. Furthermore, reactivation of YAP signaling in NAE1-inactivated cardiomyocytes restored cell proliferation, and YAP-deficient hearts displayed a noncompaction phenotype, supporting an important role of Hippo-YAP signaling in NAE1-depleted hearts. Mechanistically, we found that neddylation regulates Mst1 and LATS2 degradation and that Cullin 7, a NEDD8 substrate, acts as the ubiquitin ligase of Mst1 to enable YAP signaling and cardiomyocyte proliferation. Together, these findings demonstrate a role for neddylation in heart development and, more specifically, in the maturation of ventricular chambers and also identify the NEDD8 substrate Cullin 7 as a regulator of Hippo-YAP signaling.

Determination of the Relative Efficacy of Eicosapentaenoic Acid and Docosahexaenoic Acid for Anti-Cancer Effects in Human Breast Cancer Models

Epidemiological studies have associated high fish oil consumption with decreased risk of breast cancer (BC). n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found in fish and fish oils exert anti-cancer effects. However, few studies have examined the relative efficacy of EPA and DHA alone and in mixtures on BC subtypes. This was the objective of the present review, as this research is a necessity for the translation of findings to human health and disease. The literature suggests that DHA has a greater anti-cancer effect in triple negative BC (TNBC). In estrogen positive (ER+) BC, DHA has a greater effect on cell viability, while both fatty acids have similar effects on apoptosis and proliferation. These effects are associated with preferential uptake of DHA into TNBC lipid rafts and EPA in ER+ BC. EPA:DHA mixtures have anti-cancer activity; however, the ratio of EPA:DHA does not predict the relative incorporation of these two fatty acids into membrane lipids as EPA appears to be preferentially incorporated. In summary, DHA and EPA should be considered separately in the context of BC prevention. The elucidation of optimal EPA:DHA ratios will be important for designing targeted n-3 LCPUFA treatments.

Kinome and Transcriptome Profiling Reveal Broad and Distinct Activities of Erlotinib, Sunitinib, and Sorafenib in the Mouse Heart and Suggest Cardiotoxicity From Combined Signal Transducer and Activator of Transcription and Epidermal Growth Factor Receptor Inhibition

BACKGROUND

Most novel cancer therapeutics target kinases that are essential to tumor survival. Some of these kinase inhibitors are associated with cardiotoxicity, whereas others appear to be cardiosafe. The basis for this distinction is unclear, as are the molecular effects of kinase inhibitors in the heart.

METHODS AND RESULTS

We administered clinically relevant doses of sorafenib, sunitinib (cardiotoxic multitargeted kinase inhibitors), or erlotinib (a cardiosafe epidermal growth factor receptor inhibitor) to mice daily for 2 weeks. We then compared the effects of these 3 kinase inhibitors on the cardiac transcriptome using RNAseq and the cardiac kinome using multiplexed inhibitor beads coupled with mass spectrometry. We found unexpectedly broad molecular effects of all 3 kinase inhibitors, suggesting that target kinase selectivity does not define either the molecular response or the potential for cardiotoxicity. Using in vivo drug administration and primary cardiomyocyte culture, we also show that the cardiosafety of erlotinib treatment may result from upregulation of the cardioprotective signal transducer and activator of transcription 3 pathway, as co-treatment with erlotinib and a signal transducer and activator of transcription inhibitor decreases cardiac contractile function and cardiomyocyte fatty acid oxidation.

CONCLUSIONS

Collectively our findings indicate that preclinical kinome and transcriptome profiling may predict the cardiotoxicity of novel kinase inhibitors, and suggest caution for the proposed therapeutic strategy of combined signal transducer and activator of transcription/epidermal growth factor receptor inhibition for cancer treatment.

Alternative Splicing in Breast Cancer and the Potential Development of Therapeutic Tools

Alternative splicing is a key molecular mechanism now considered as a hallmark of cancer that has been associated with the expression of distinct isoforms during the onset and progression of the disease. The leading cause of cancer-related deaths in women worldwide is breast cancer, and even when the role of alternative splicing in this type of cancer has been established, the function of this mechanism in breast cancer biology is not completely decoded. In order to gain a comprehensive view of the role of alternative splicing in breast cancer biology and development, we summarize here recent findings regarding alternative splicing events that have been well documented for breast cancer evolution, considering its prognostic and therapeutic value. Moreover, we analyze how the response to endocrine and chemical therapies could be affected due to alternative splicing and differential expression of variant isoforms. With all this knowledge, it becomes clear that targeting alternative splicing represents an innovative approach for breast cancer therapeutics and the information derived from current studies could guide clinical decisions with a direct impact in the clinical advances for breast cancer patients nowadays.

MicroRNA 125a-5p Inhibits Cell Proliferation and Induces Apoptosis in Hepatitis B Virus-Related Hepatocellular Carcinoma by Downregulation of ErbB3

MicroRNAs, a class of endogenous noncoding RNAs, regulate gene expression at the posttranscriptional level and thus take part in multiple biological processes. An increasing number of miRNAs have been found to be dysregulated in hepatocellular carcinoma (HCC) and are involved in liver tumorigenesis. In this study, miR-125a-5p was found to be obviously downregulated much more in hepatitis B virus (HBV)-related HCC. To investigate the effects of miR-125a-5p, miR-125a-5p was overexpressed in HepG2.2.15 and HepG3X cells. The findings have indicated that overexpression of miR-125a-5p dramatically inhibited cell proliferation and induced cell apoptosis. Furthermore, overexpression of miR-125a-5p could significantly decrease the secretion of HBsAg and HBeAg. In concordance to this, the expression of ErbB3 was upregulated in human HBV-related HCC tissue, HepG2.2.15 cells, and HepG3X cells. miR-125a-5p directly targeted ErbB3 and reduced both mRNA and protein levels of ErbB3, which promoted cell proliferation and suppressed cell apoptosis in HCC cells. Our results provide new insights into the function of miR-125a-5p in HBV-related HCC. It is beneficial to gain insight into the mechanism of HBV infection and pathophysiology of HBV-related HCC.

Functional prediction of miR-3144-5p in human cardiac myocytes based on transcriptome sequencing and bioinformatics

BACKGROUND

RAN guanine nucleotide release factor (RANGRF) encoding protein MOG1 plays an important role in cardiac arrhythmia, so we intended to investigate the regulatory miRNA of RANGRF and explore its potential regulatory mechanism in arrhythmogenesis.

METHODS

Based on bioinformatic analysis, miR-3144-5p was predicted to be a regulatory miRNA of RANGRF, which were then validated through a dual-luciferase reporter plasmid assay. Subsequently, the expression level of miR-3144-5p in human cardiac myocytes (HCMs) was detected, followed by cell transfection with miR-3144-5p mimics. Transcriptome sequencing was then performed in HCMs with or without transfection. The sequencing results were subjected to bioinformatic analyses, including differentially expressed gene (DEG) analysis, functional enrichment analysis, protein-protein interaction (PPI) network analysis, miRNA-target gene analysis, and miRNA-transcription factor (TF)-target gene coregulatory network analysis.

RESULTS

There really existed a regulatory relation between miR-3144-5p and RANGRF. The expression level of miR-3144-5p was low in HCMs. After cell transfection, miR-3144-5p expression level significantly increased in HCMs. Bioinformatic analyses of the transcriptome sequencing results identified 300 upregulated and 271 downregulated DEGs between miR-3144-5p mimic and control group. The upregulated genes ISL1 and neuregulin 1 (NRG1) were significantly enriched in cardiac muscle cell myoblast differentiation (GO:0060379). CCL21 was one of the hub genes in the PPI network and also a target gene of miR-3144-5p. Moreover, the TF of v-Myc avian myelocytomatosis viral oncogene neuroblastoma-derived homolog (MYCN) was involved in the miR-3144-5p-TF-target gene coregulatory network and interacted with the target genes of miR-3144-5p.

CONCLUSION

ISL1, NRG1, CCL21, and MYCN were differentially expressed in the miR-3144-5p mimic group, suggesting that miR-3144-5p overexpression plays a role in HCMs by regulating these genes and TF. This study may provide new insight into the mechanisms behind the progression of cardiac arrhythmia.

Cardiotoxicity of ErbB2-targeted therapies and its impact on drug development, a spotlight on trastuzumab

INTRODUCTION

Trastuzumab, a therapeutic monoclonal antibody directed against ErbB2, is often noted as a successful example of targeted therapy. Trastuzumab improved outcomes for many patients with ErbB2-positive breast and gastric cancers, however, cardiac side effects [e.g., left ventricular dysfunction and congestive heart failure (CHF)] were reported in the early phase clinical studies. This finding, subsequently corroborated by multiple clinical studies, raised concerns that the observed cardiotoxicity induced by trastuzumab might adversely impact the clinical development of other therapeutics targeting ErbB family members. Areas covered: In this review we summarize both basic research and clinical findings regarding trastuzumab-induced cardiotoxicity and assess if there has been an impact of trastuzumab-induced cardiotoxicity on the development of other agents targeting ErbB family members. Expert opinion: There are a number of scientific gaps that are critically important to address for the continued success of HER2-targeted agents. These include: 1) elucidating the molecular mechanisms contributing to cardiotoxicity; 2) developing relevant preclinical testing systems for predicting cardiotoxicity; 3) developing clinical strategies to identify patients at risk of cardiotoxicity; and 4) enhancing management of clinical symptoms of cardiotoxicity.

Neuregulin-1β induces proliferation, survival and paracrine signaling in normal human cardiac ventricular fibroblasts

Neuregulin-1β (NRG-1β) is critical for cardiac development and repair, and recombinant forms are currently being assessed as possible therapeutics for systolic heart failure. We previously demonstrated that recombinant NRG-1β reduces cardiac fibrosis in an animal model of cardiac remodeling and heart failure, suggesting that there may be direct effects on cardiac fibroblasts. Here we show that NRG-1β receptors (ErbB2, ErbB3, and ErbB4) are expressed in normal human cardiac ventricular (NHCV) fibroblast cell lines. Treatment of NHCV fibroblasts with recombinant NRG-1β induced activation of the AKT pathway, which was phosphoinositide 3-kinase (PI3K)-dependent. Moreover, the NRG-1β-induced PI3K/AKT signaling in these cells required phosphorylation of both ErbB2 and ErbB3 receptors at tyrosine (Tyr)1248 and Tyr1289 respectively. RNASeq analysis of NRG-1β-treated cardiac fibroblasts obtained from three different individuals revealed a global gene expression signature consistent with cell growth and survival. We confirmed enhanced cellular proliferation and viability in NHCV fibroblasts in response to NRG-1β, which was abrogated by PI3K, ErbB2, and ErbB3 inhibitors. NRG-1β also induced production and secretion of cytokines (interleukin-1α and interferon-γ) and pro-reparative factors (angiopoietin-2, brain-derived neurotrophic factor, and crypto-1), suggesting a role in cardiac repair through the activation of paracrine signaling.

Hypoxic proliferation requires EGFR-mediated ERK activation in human pulmonary microvascular endothelial cells

We have previously shown that hypoxic proliferation of human pulmonary microvascular endothelial cells (hPMVECs) depends on epidermal growth factor receptor (EGFR) activation. To determine downstream signaling leading to proliferation, we tested the hypothesis that hypoxia-induced proliferation in hPMVECs would require EGFR-mediated activation of extracellular signal-regulated kinase (ERK) leading to arginase II induction. To test this hypothesis, hPMVECs were incubated in either normoxia (21% O₂, 5% CO₂) or hypoxia (1% O₂, 5% CO₂) and Western blotting was performed for EGFR, arginase II, phosphorylated-ERK (pERK), and total ERK (ERK). Hypoxia led to greater EGFR, pERK, and arginase II protein levels than did normoxia in hPMVECs. To examine the role of EGFR in these hypoxia-induced changes, hPMVECs were transfected with siRNA against EGFR or a scrambled siRNA and placed in hypoxia. Inhibition of EGFR using siRNA attenuated hypoxia-induced pERK and arginase II expression as well as the hypoxia-induced increase in viable cell numbers. hPMVECs were then treated with vehicle, an EGFR inhibitor (AG1478), or an ERK pathway inhibitor (U0126) and placed in hypoxia. Pharmacologic inhibition of EGFR significantly attenuated the hypoxia-induced increase in pERK level. Both AG1478 and U0126 also significantly attenuated the hypoxia-induced increase in viable hPMVECs numbers. hPMVECs were transfected with an adenoviral vector containing arginase II (AdArg2) and overexpression of arginase II rescued the U0126-mediated decrease in viable cell numbers in hypoxic hPMVECs. Our findings suggest that hypoxic activation of EGFR results in phosphorylation of ERK, which is required for hypoxic induction of arginase II and cellular proliferation.

Loss of ErbB2-PI3K/Akt signaling prevents zinc pyrithione-induced cardioprotection during ischemia/reperfusion

OBJECTIVES

The purpose of this study was to determine if zinc homeostasis is affected during ischemia/reperfusion, if so, whether zinc pyrithione limits myocardial cell death and improves hemodynamics when administered as an adjunct to reperfusion and if ErbB receptor tyrosine kinases that are important for the long-term structural integrity of the heart are indispensable for reperfusion salvage.

METHODS

Isolated perfused rat hearts were subjected to 35min of global ischemia and reperfused for 120min to determine the relative intracellular zinc levels by TSQ staining. The hearts were reperfused in the presence of incremental concentrations of zinc pyrithione for the first 10min during reperfusion. Silencing or blockade of ErbB2 using a monoclonal antibody, ErbB2 kinase inhibition and PI3kinase inhibition was used to study their critical role in zinc pyrithione-induced cardioprotection.

RESULTS

We found that there was a profound decrease in intracellular zinc after ischemia/reperfusion resulting in increased apoptosis, caspase-3 activation, and infarct size. A dose-dependent reduction of infarct size with zinc pyrithione in the range of 5-20μmol/l (optimal protection was seen at 10μmol/l with infarct size of 16±2% vs. I/R vehicle, 33±2%, p<0.01). Increased TUNEL staining and caspase-3 activity observed after ischemia/reperfusion were attenuated by zinc pyrithione administration during the reperfusion. Moreover, this protection was sensitive to silencing and blockade of ErbB2, inhibition of ErbB2 kinase activity or PI3-kinase activity. Western blot analysis revealed that zinc pyrithione resulted in decreased caspase-3 activation, rapid stabilization of ErbB2/ErbB1 heterodimers, and increased activation of PI3K/Akt signaling cascade.

CONCLUSIONS

Zinc pyrithione attenuates lethal perfusion-induced injury in a manner that is reliant on ErbB2/PI3K/Akt activity.

IgG-Containing Isoforms of Neuregulin-1 Are Dispensable for Cardiac Trabeculation in Zebrafish

The Neuregulin-1 (Nrg1) signaling pathway has been widely implicated in many aspects of heart development including cardiac trabeculation. Cardiac trabeculation is an important morphogenetic process where clusters of ventricular cardiomyocytes extrude and expand into the lumen of the ventricular chambers. In mouse, Nrg1 isoforms containing an immunoglobulin-like (IgG) domain are essential for cardiac trabeculation through interaction with heterodimers of the epidermal growth factor-like (EGF-like) receptors ErbB2/ErbB4. Recent reports have underscored the importance of Nrg1 signaling in cardiac homeostasis and disease, however, placental development has precluded refined evaluation of the role of this pathway in mammals. ErbB2 has been shown to have a developmentally conserved role in cardiac trabeculation in zebrafish, a vertebrate model organism with completely external development, but the requirement for Nrg1 has not been examined. We found that among the multiple Nrg1 isoforms, the IgG domain-containing, type I Nrg1 (nrg1-I) is the only isoform detectable in the heart. Then, using CRISPR/Cas9 gene editing, we targeted the IgG domain of Nrg1 to produce novel alleles, nrg1^nc28 and nrg1^nc29, encoding nrg1-I and nrg1-II truncations. Our results indicated that zebrafish deficient for nrg1-I developed trabeculae in an ErbB2-dependent manner. Further, these mutants survive to reproductive adulthood with no overt cardiovascular defects. We also found that additional EGF-like ligands were expressed in the zebrafish heart during development of trabeculae. Together, these results suggest that Nrg1 is not the primary effector of trabeculation and/or that other EGF-like ligand(s) activates the ErbB2/ErbB4 pathway, either through functioning as the primary ligand or acting in a redundant manner. Overall, our work provides an example of cross-species differences in EGF family member requirements for an evolutionary conserved process.

HER2 overexpression reverses the relative resistance of EGFR-mutant H1975 cell line to gefitinib

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) that has been demonstrated to be clinically useful for the treatment of patients with non-small cell lung cancer (NSCLC). However, ~50% of patients do not respond to EGFR TKI treatment through the emergence of mutations, such as T790M. Therefore, it is important to determine which patients are eligible for treatment with gefitinib. As a preferred dimerization partner for EGFR, the role of EGFR 2 (HER2) in mediating sensitivity to gefitinib is poorly understood. In the present study, full-length human HER2 cDNA was introduced to the NSCLC cell lines H1975 and H1299, which have a low endogenous expression level of HER2. In addition, it was observed in the present study that the H1975 cell line harbored the L858R and T790M mutations in the EGFR kinase domain. Western blot analysis and MTT assay were used to evaluate the TKI sensitivity of HER2 expression status, and the activation of HER3 and HER2 downstream effectors. The results indicated that the sensitivity of H1975 cells to gefitinib was restored by the overexpression of HER2, which stimulated HER2-driven signaling cascades accompanied by the activation of protein kinase B. By contrast, ectopic HER2 overexpression in H1299 cells did not significantly alter the sensitivity to gefitinib treatment. In conclusion, the current study results suggested that the relatively resistance of the H1975 cell line to gefitinib could be reversed by the overexpression of HER2. Therefore, the expression of HER2 could also be considered when evaluate the patients' potential response to gefitinib, particularly in the subgroup of lung cancer patients who harbor an EGFR mutation.

Epidermal Growth Factor Receptor Silencing Blunts the Slow Force Response to Myocardial Stretch

Background

Myocardial stretch increases force biphasically: the Frank‐Starling mechanism followed by the slow force response (SFR). Based on pharmacological strategies, we proposed that epidermal growth factor (EGF) receptor (EGFR or ErbB1) activation is crucial for SFR development. Pharmacological inhibitors could block ErbB4, a member of the ErbB family present in the adult heart. We aimed to specifically test the role of EGFR activation after stretch, with an interference RNA incorporated into a lentiviral vector (small hairpin RNA [shRNA]‐EGFR).

Methods and Results

Silencing capability of p‐shEGFR was assessed in EGFR‐GFP transiently transfected HEK293T cells. Four weeks after lentivirus injection into the left ventricular wall of Wistar rats, shRNA‐EGFR–injected hearts showed ≈60% reduction of EGFR protein expression compared with shRNA‐SCR–injected hearts. ErbB2 and ErbB4 expression did not change. The SFR to stretch evaluated in isolated papillary muscles was ≈130% of initial rapid phase in the shRNA‐SCR group, while it was blunted in shRNA‐EGFR–expressing muscles. Angiotensin II (Ang II)‐dependent Na+/H+ exchanger 1 activation was indirectly evaluated by intracellular pH measurements in bicarbonate‐free medium, demonstrating an increase in shRNA‐SCR–injected myocardium, an effect not observed in the silenced group. Ang II‐ or EGF‐triggered reactive oxygen species production was significantly reduced in shRNA‐EGFR–injected hearts compared with that in the shRNA‐SCR group. Chronic lentivirus treatment affected neither the myocardial basal redox state (thiobarbituric acid reactive substances) nor NADPH oxidase activity or expression. Finally, Ang II or EGF triggered a redox‐sensitive pathway, leading to p90RSK activation in shRNA‐SCR‐injected myocardium, an effect that was absent in the shRNA‐EGFR group.

Conclusions

Our results provide evidence that specific EGFR activation after myocardial stretch is a key factor in promoting the redox‐sensitive kinase activation pathway, leading to SFR development.