Neuregulin signaling and heart failure

Machine Learning in Identifying Marker Genes for Congenital Heart Diseases of Different Cardiac Cell Types

Congenital heart disease (CHD) represents a spectrum of inborn heart defects influenced by genetic and environmental factors. This study advances the field by analyzing gene expression profiles in 21,034 cardiac fibroblasts, 73,296 cardiomyocytes, and 35,673 endothelial cells, utilizing single-cell level analysis and machine learning techniques. Six CHD conditions: dilated cardiomyopathy (DCM), donor hearts (used as healthy controls), hypertrophic cardiomyopathy (HCM), heart failure with hypoplastic left heart syndrome (HF_HLHS), Neonatal Hypoplastic Left Heart Syndrome (Neo_HLHS), and Tetralogy of Fallot (TOF), were investigated for each cardiac cell type. Each cell sample was represented by 29,266 gene features. These features were first analyzed by six feature-ranking algorithms, resulting in several feature lists. Then, these lists were fed into incremental feature selection, containing two classification algorithms, to extract essential gene features and classification rules and build efficient classifiers. The identified essential genes can be potential CHD markers in different cardiac cell types. For instance, the LASSO identified key genes specific to various heart cell types in CHD subtypes. FOXO3 was found to be up-regulated in cardiac fibroblasts for both Dilated and hypertrophic cardiomyopathy. In cardiomyocytes, distinct genes such as TMTC1, ART3, ARHGAP24, SHROOM3, and XIST were linked to dilated cardiomyopathy, Neo-Hypoplastic Left Heart Syndrome, hypertrophic cardiomyopathy, HF-Hypoplastic Left Heart Syndrome, and Tetralogy of Fallot, respectively. Endothelial cell analysis further revealed COL25A1, NFIB, and KLF7 as significant genes for dilated cardiomyopathy, hypertrophic cardiomyopathy, and Tetralogy of Fallot. LightGBM, Catboost, MCFS, RF, and XGBoost further delineated key genes for specific CHD subtypes, demonstrating the efficacy of machine learning in identifying CHD-specific genes. Additionally, this study developed quantitative rules for representing the gene expression patterns related to CHDs. This research underscores the potential of machine learning in unraveling the molecular complexities of CHD and establishes a foundation for future mechanism-based studies.

Radiation therapy, tissue radiosensitization, and potential synergism in the era of novel antibody-drug conjugates

Antibody-drug conjugates (ADCs) represent a therapeutic class of agents designed to selectively deliver cytotoxic payloads to cancer cells. With the increasingly positioning of ADCs in the clinical practice, combinations with other treatment modalities, including radiation therapy (RT), will open new opportunities but also challenges. This review evaluates ADC-RT interactions, examining therapeutic synergies and potential caveats. ADC payloads can be radiosensitizing, enhancing cytotoxicity when used in combination with RT. Antigens targeted by ADCs can have various tissue expressions, resulting in possible off-target toxicities by tissue radiosensitization. Notably, the HER-2-directed ADC trastuzumab emtansine has appeared to increase the risk of radionecrosis when used concomitantly with brain RT, as glial cells can express HER2, too. Other possible organ-specific effects are discussed, such as pulmonary and cardiac toxicities. The lack of robust clinical data on the ADC-RT combination raises concerns regarding specific side effects and the ultimate trade-off of toxicity and safety of some combined approaches. Clinical studies are needed to assess ADC-RT combination safety and efficacy.

Hyperoside Protects Trastuzumab-Induced Cardiotoxicity via Activating the PI3K/Akt Signaling Pathway

PURPOSE

Trastuzumab is a landmark agent in the treatment of human epidermal growth factor receptor-2(HER2)-positive breast cancer. Nevertheless, trastuzumab also comes with unexpected cardiac side effects. Hyperoside is a natural product that serves beneficial roles in cardiovascular disease. This study aimed to explore the effect and mechanism of hyperoside in trastuzumab-induced cardiotoxicity.

METHODS

A female C57BL/6 mice cardiotoxicity model was established via intraperitoneally injecting with trastuzumab (10 mg/kg/day, once every other day, cumulative dosage to 40 mg/kg) with or without hyperoside (15 or 30 mg/kg/day) administration. In vitro, the H9c2 cells were exposed to 1 μM trastuzumab with or without hyperoside (100 or 200 μM) administration. Cardiac function was evaluated by echocardiographic, myocardial enzymes levels, and pathological section examinations. TUNEL staining and Annexin V-FITC/ propidium iodide flow cytometry were used to analyze the cardiomyocyte apoptosis.

RESULTS

Compared to the control group, the LVEF, LVFS was decreased and the concentrations of cTnT, CK, CK-MB and LDH in mice were significantly increased after treatment with trastuzumab. Collagen deposition and cardiomyocyte hypertrophy were observed in the myocardium of the trastuzumab group. However, these changes were all reversed by different doses of hyperoside. In addition, hyperoside attenuated trastuzumab-induced myocardium apoptosis and H9c2 cells apoptosis through inhibiting the expressions of cleaved caspase-3 and Bax. Trastuzumab abolished the PI3K/Akt signaling pathway in mice and H9c2 cells, while co-treatment of hyperoside effectively increased the ratio of p-Akt/Akt.

CONCLUSION

Hyperoside inhibited trastuzumab-induced cardiotoxicity through activating the PI3K/Akt signaling pathway. Hyperoside may be a promising therapeutic approach to trastuzumab-induced cardiotoxicity.

Genetic polymorphisms and correlation with treatment induced cardiotoxicity and prognosis in breast cancer patients

BACKGROUND

Cardiac toxicity is a serious complication of HER2-directed therapies and anthracyclines. HER2 codon 655 and SLC28A3 gene polymorphisms have been reported to be associated with cardiac toxicity from anti-HER2 and anthracycline therapy, respectively. Association of the polymorphism at HER2 codon 655 with prognosis has also been reported.

METHODS

Whole blood samples from patients treated on a randomized adjuvant breast cancer trial (BCIRG-006) that compared anthracycline-based chemotherapy to trastuzumab plus either anthracycline or non-anthracycline chemotherapy were tested for genetic polymorphisms in HER2 codon 655 and SLC28A3 Genotypes were correlated with cardiac function and disease-free survival (DFS) outcomes.

RESULTS

Of 3,222 patients enrolled in BCIRG-006, 662 patient samples were successfully genotyped for the rs1136201 allele in HER2 (codon 655): 424 (64%) were AA, 30 (4.5%) were GG, and 208 (31%) were AG genotype. Additionally, 665 patient samples were successfully genotyped for the rs7853758 allele in the SLC28A3 gene: 19 (3%) were AA, 475 (71%) were GG, and 171 (26%) were AG genotype. Follow up time was 10 years. No correlation between DFS, cardiac event rate or mean left ventricular ejection fraction (LVEF) and rs1136201 genotype was seen in the trastuzumab treated or non-trastuzumab treated patients. Moreover, mean LVEF and cardiac event rates were similar in all rs7853758 genotype groups treated with anthracycline-based therapy.

CONCLUSIONS

In the largest study to date to evaluate whether two polymorphisms are associated with DFS and/or cardiac toxicity in HER2 positive breast cancer treated with trastuzumab and/or anthracyclines, we observed no correlation.

The Research Progress of Trastuzumab-Induced Cardiotoxicity in HER-2-Positive Breast Cancer Treatment

In recent years, the incidence of breast cancer has been increasing on an annual basis. Human epidermal growth factor receptor-2 (HER-2) is overexpressed in 15-20% human breast cancers, which is associated with poor prognosis and a high recurrence rate. Trastuzumab is the first humanized monoclonal antibody against HER-2. The most significant adverse effect of trastuzumab is cardiotoxicity, which has become an important factor in limiting the safe use of the drug. Unfortunately, the mechanism causing this cardiotoxicity is still not completely understood, and the use of preventive interventions remains controversial. This article focuses on trastuzumab-induced cardiotoxicity, reviewing the clinical application, potential cardiotoxicity, mechanism and discussing the potential interventions through summarizing related researches over the past tens of years.

The Molecular Mechanisms of Cardiotoxicity Induced by HER2, VEGF, and Tyrosine Kinase Inhibitors: an Updated Review

AIM

In recent decades, there has been a revolutionary decrease in cancer-related mortality and an increase in survival due to the introduction of novel targeted drugs. Nevertheless, drugs targeting human epidermal growth factor receptor 2 (HER-2), angiogenesis, and other tyrosine kinases also come with unexpected cardiac side effects, including heart failure, hypertension, arterial thrombosis, and arrhythmias, and have mechanisms that are unlike those of classic chemotherapeutic agents. In addition, it is challenging to address some problems, as the existing guidelines need to be more specific, and further large-scale clinical trials and experimental studies are required to confirm the benefit of administering cardioprotective agents to patients treated with targeted therapies. Therefore, an improved understanding of cardiotoxicity becomes increasingly important to minimize the pernicious effects and maximize the beneficial effects of targeted agents.

METHODS

"Cardiotoxicity", "targeted drugs", "HER2", "trastuzumab", "angiogenesis inhibitor", "VEGF inhibitor" and "tyrosine kinase inhibitors" are used as keywords for article searches.

RESULTS

In this article, we report several targeted therapies that induce cardiotoxicity and update knowledge of the clinical evidence, molecular mechanisms, and management measures.

Cardioprotective Effect of Statins in Patients With HER2-Positive Breast Cancer Receiving Trastuzumab Therapy

BACKGROUND

Statins can reduce the risk of anthracycline-induced cardiotoxicity. Whether such cardioprotective effects can be seen in trastuzumab-treated patients has not been explored.

METHODS

Consecutive women with HER2+ breast cancer who received trastuzumab with or without anthracyclines were identified retrospectively. Patients receiving statins before and during cancer treatment were matched with 2 patients of the same age (± 2 years) and anthracycline exposure status but without statin treatment. The primary outcome was final left ventricular ejection fraction (LVEF). Analysis of covariance (ANCOVA) was used to assess the relationship between statin exposure and the final LVEF. A logistic regression model was constructed to assess the relationship between statin exposure and cardiotoxicity (secondary outcome).

RESULTS

Included were 129 patients (62 ± 9 years). Forty-three received statins during cancer treatment. The median trastuzumab exposure time was 11.8 (interquartile range [IQR] 11 to 12) months. Seventy-two (56%) patients received anthracyclines. Compared with controls, patients treated with statins were more likely to have diabetes (37.2% vs 4.7%, P < 0.001), hypertension (58.1% vs 22.1%, P < 0.001), and coronary artery disease (11.6% vs 2.3%, P = 0.04). Within a median cardiac follow-up duration of 11 (IQR 9 to 18) months, the adjusted final LVEF was lower in the control group (61.2% vs 64.6%, P = 0.034). A significant change in LVEF was observed in the control group (median -6%, IQR -10% to -1% P < 0.001) but not in the statin group (median 0%, IQR -5% to +3%, P = 0.27). Upon adjusted analysis, statin treatment was independently associated with a lower risk of cardiotoxicity (odds ratio [OR] 0.32, 95% confidence interval [CI], 0.10-0.99, P = 0.049).

CONCLUSIONS

In women with HER2+ breast cancer receiving trastuzumab-based therapy with or without anthracyclines, concomitant use of statins was associated with a lower risk of cardiotoxicity.

Cardiac Nonmyocyte Cell Functions and Crosstalks in Response to Cardiotoxic Drugs

The discovery of the molecular mechanisms involved in the cardiac responses to anticancer drugs represents the current goal of cardio-oncology research. The oxidative stress has a pivotal role in cardiotoxic responses, affecting the function of all types of cardiac cells, and their functional crosstalks. Generally, cardiomyocytes are the main target of research studies on cardiotoxicity, but recently the contribution of the other nonmyocyte cardiac cells is becoming of growing interest. This review deals with the role of oxidative stress, induced by anticancer drugs, in cardiac nonmyocyte cells (fibroblasts, vascular cells, and immune cells). The alterations of functional interplays among these cardiac cells are discussed, as well. These interesting recent findings increase the knowledge about cardiotoxicity and suggest new molecular targets for both diagnosis and therapy.

Myocardial ischemia/reperfusion upregulates the transcription of the Neuregulin1 receptor ErbB3, but only postconditioning preserves protein translation: Role in oxidative stress

BACKGROUND

Neuregulin1 (Nrg1) and its receptors ErbB are crucial for heart development and for adult heart structural maintenance and function and Nrg1 has been proposed for heart failure treatment. Infarct size is the major determinant of heart failure and the mechanism of action and the role of each ErbB receptor remain obscure, especially in the post-ischemic myocardium. We hypothesized that Nrg1 and ErbB are affected at transcriptional level early after ischemia/reperfusion (I/R) injury, and that the protective postconditioning procedure (PostC, brief cycles of ischemia/reperfusion carried out after a sustained ischemia) can influence this pathway.

METHODS AND RESULTS

The Langendorff's heart was used as an ex-vivo model to mimic an I/R injury in the whole rat heart; after 30min of ischemia and 2h of reperfusion, with or without PostC, Nrg1 and ErbB expression were analysed by quantitative real-time PCR and Western blot. While no changes occur for ErbB2, ErbB4 and Nrg1, an increase of ErbB3 expression occurs after I/R injury, with and without PostC. However, I/R reduces ErbB3 protein, whereas PostC preserves it. An in vitro analysis with H9c2 cells exposed to redox-stress indicated that the transient over-expression of ErbB3 alone is able to increase cell survival (MTT assay), limiting mitochondrial dysfunction (JC-1 probe) and apoptotic signals (Bax/Bcl-2 ratio).

CONCLUSIONS

This study suggests ErbB3 as a protective factor against death pathways activated by redox stress and supports an involvement of this receptor in the pro-survival responses.

Cancer drug related cardiotoxicity during breast cancer treatment

INTRODUCTION

Breast cancer (BC) is the most common cancer in women. Although therapeutic armamentarium like chemotherapy, endocrine and target agents have increased survival, cardiovascular side effects have been observed. A comprehensive risk assessment, early detection and management of cardiac adverse events is therefore needed.

AREAS COVERED

In this review we focus on cardiotoxicity data deriving from Phase III randomized trials, systematic reviews and meta-analysis in BC patients. We provide insight into advances that have been made in the molecular mechanisms, clinical presentation and management of such adverse event.

EXPERT OPINION

Despite the large number of data from Phase III trials about cardiac events incidence, there are poor evidences for detection, monitoring and management of cardiotoxicity during BC treatment. Future cardiotoxicity-oriented clinical cancer research can help to predict the risk of cardiac adverse events and improve patients' outcome. Multidisciplinary approach as well as integration of blood biomarkers with imaging will be desirable.

Trastuzumab and target-therapy side effects: Is still valid to differentiate anthracycline Type I from Type II cardiomyopathies?

The improvement in cancer therapy and the increasing number of long term survivors unearth the issue of cardiovascular side effects of anticancer treatments. As a paradox in cancer survivors, delayed cardiotoxicity has emerged as a significant problem. Two categories of cardiotoxic side effects of antineoplastic drugs have been previously proposed: Type I cardiotoxicity, defined as permanent cardiotoxicity, is usually caused by anthracyclines; Type II cardiotoxicity, considered as reversible cardiotoxicity, has been mainly related to monoclonal antibodies. The cardiotoxicity of antibodies has been associated to trastuzumab, a humanized anti-ErbB2 monoclonal antibody currently in clinical use for the therapy of breast carcinomas, which induces cardiac dysfunction when used in monotherapy, or in combination with anthracyclines. Furthermore, recent retrospective studies have shown an increased incidence of heart failure and/or cardiomyopathy in patients treated with trastuzumab, that can persist many years after the conclusion of the therapy, thus suggesting that the side toxic effects are not always reversible as it was initially proposed. On the other hand, early detection and prompt therapy of anthracycline associated cardiotoxicity can lead to substantial recovery of cardiac function. On the basis of these observations, we propose to find a new different classification for cardiotoxic side effects of drugs used in cancer therapy.

Progress in neuregulin/ErbB signaling and chronic heart failure

Heart failure is one of the leading causes of death today. It is a complex clinical syndrome in which the heart has a reduced contraction ability and decreased viable myocytes. Novel approaches to the clinical management of heart failure have been achieved through an understanding of the molecular pathways necessary for normal heart development. Neuregulin-1 (NRG-1) has emerged as a potential therapeutic target based on the fact that mice null for NRG-1 or receptors mediating its activity, ErbB2 and ErbB4, are embryonic lethal and exhibit severe cardiac defects. Preclinical studies performed with animal models of heart failure demonstrate that treatment with NRG-1 significantly improves heart function and survival. Clinical data further support NRG-1 as a promising drug candidate for the treatment of cardiac dysfunction in patients. Recent studies have revealed the mechanism underlying the therapeutic effects of NRG-1/ErbB signaling in the treatment of heart failure. Through activation of upstream signaling molecules such as phosphoinositide 3-kinase, mitogen-activated protein kinase, and focal adhesion kinase, NRG-1/ErbB pathway activation results in increased cMLCK expression and enhanced intracellular calcium cycling. The former is a regulator of the contractile machinery, and the latter triggers cell contraction and relaxation. In addition, NRG-1/ErbB signaling also influences energy metabolism and induces epigenetic modification in cardiac myocytes in a way that more closely resembles healthy heart. These observations reveal potentially new treatment options for heart failure.

The roles of neuregulin-1 in cardiac development, homeostasis, and disease

Neuregulin-1 (NRG-1) and its signaling receptors, erythroblastic leukemia viral oncogene homologs (ErbB) 2, 3, and 4, have been implicated in both cardiomyocyte development and disease, as well as in homeostatic cardiac function. NRG-1/ErbB signaling is involved in a multitude of cardiac processes ranging from myocardial and cardiac conduction system development to angiogenic support of cardiomyocytes, to cardioprotective effects upon injury. Numerous studies of NRG-1 employ a variety of platforms, including in vitro assays, animal models, and human clinical trials, with equally varying and, sometimes, contradictory outcomes. NRG-1 has the potential to be used as a therapeutic tool in stem cell therapies, tissue engineering applications, and clinical diagnostics and treatment. This review presents a concise summary of the growing body of literature to highlight the temporally persistent significance of NRG-1/ErbB signaling throughout development, homeostasis, and disease in the heart, specifically in cardiomyocytes.

The Src homology and collagen A (ShcA) adaptor protein is required for the spatial organization of the costamere/Z-disk network during heart development

Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere.

Neuregulin-1 protects myocardial cells against H2 O2 -induced apoptosis by regulating endoplasmic reticulum stress

Neuregulin-1 (NRG-1) is a stress-mediated growth factor secreted by cardiovascular endothelial cells and provides the protection to myocardial cells, but the underlying mechanisms are not fully understood. This study aimed to demonstrate that NRG-1 protects myocardial cells exposed to oxidative damage by regulating endoplasmic reticulum (ER) stress. Neonatal rat cardiac myocytes (NRCMs) were isolated and treated with H2 O2 as a cellular model of ER stress. NRCMs were pretreated with different concentrations of NRG-1. We found that NRG-1 increased the viability and reduced the apoptosis of NRCMs treated by H2 O2 . Moreover, NRG-1 reduced lactate dehydrogenase level, increased superoxide dismutase activity and decreased malondialdehyde content in NRCMs treated by H2 O2 . Finally, we demonstrated that NRG-1 alleviated ER stress and decreased CHOP and GRP78 protein levels in NRCMs treated by H2 O2 . Taken together, these data indicate that NRG-1 relieves oxidative and ER stress in NRCMs and suggest that NRG-1 is a promising agent for cardioprotection.

Gene transfer of human neuregulin-1 attenuates ventricular remodeling in diabetic cardiomyopathy rats

Neuregulin-1 (NRG-1) is a cardioactive growth factor released from endothelial cells. However, the effect of NRG-1 on ventricular remodeling in diabetic cardiomyopathy (DCM) remains unclear. The aim of the present study was to investigate the pathophysiological role of NRG-1 in a rat model of DCM. Rat cardiac microvascular endothelial cells (CMECs) were transfected with human NRG-1 (hNRG-1) lentivirus. The hNRG-1 medium was utilized to culture rat cardiomyocytes. The cardiomyocytes were counted with a hemacytometer to determine the proliferation index and Annexin V/propidium iodide double staining was employed to examine the apoptotic rate. A rat model of DCM was induced by an intraperitoneal injection of streptozotocin. The hNRG-1 lentivirus was injected into the myocardium of the DCM model rats. Four weeks after the lentiviral injection, cardiac catheterization was performed to evaluate the cardiac function. Apoptotic cells were determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. Left ventricular sections were stained with Masson’s trichrome to investigate the myocardial collagen content. The expression levels of related genes and proteins were analyzed. The results indicated that hNRG-1 conditioned medium stimulated the proliferation and counteracted the apoptosis of cardiomyocytes in vitro. In the rats with DCM, gene transfer of hNRG-1 to the myocardium improved heart function, as indicated by invasive hemodynamic measurements. In addition, hNRG-1 reduced the number of apoptotic cells, decreased the expression of bax and increased the expression of bcl-2 in the myocardium of the DCM model rats. Myocardial fibrosis and type I and III pro-collagen mRNA levels in the myocardium were significantly reduced by hNRG-1. hNRG-1 also increased the expression of phospho-Akt and phospho-eNOS in the myocardium. In conclusion, the gene transfer of hNRG-1 ameliorates cardiac dysfunction in diabetes. Although further studies are required, NRG-1 appears to protect cardiomyocytes against apoptosis and to reduce the extent of myocardial interstitial fibrosis.

The HER2 Receptor in Breast Cancer: Pathophysiology, Clinical Use, and New Advances in Therapy

Human epidermal growth factor receptor 2 (HER2) is overexpressed in around 20-30% of breast cancer tumors. It is associated with a more aggressive disease, higher recurrence rate, and increased mortality. Trastuzumab is a HER2 receptor blocker that has become the standard of care for the treatment of HER2 positive breast cancer. The effectiveness of Trastuzumab has been well validated in research as well as in clinical practice. The addition of Trastuzumab to standard of care chemotherapy in clinical trials has been shown to improve outcomes for early stage as well as metastatic HER2 positive breast cancer. The most clinically significant side effect of Trastuzumab is the risk of cardiac myocyte injury, leading to the development of congestive heart failure. The emergence of patterns of resistance to Trastuzumab has led to the discovery of new monoclonal antibodies and other targeted agents aimed at overcoming Trastuzumab resistance and improving survival in patients diagnosed with HER2 positive breast cancers.

Breast cancer treatment and adverse cardiac events: what are the molecular mechanisms?

Cardiotoxicity associated with breast cancer treatment is an important concern in the oncology clinic. Different types of anti-cancer therapies have recorded high rates of cardiac dysfunction in treated patients. Cardiac dysfunction linked to anthracyclines--one of the most common conventional chemotherapies--has extensively been described and several mechanisms have been proposed, although their mode of action is not fully understood even in cancer cells. The mediation of cardiac damage by reactive oxygen species stress is a recent hypothesis that has attracted a lot of interest, since it might explain the tissue-specific toxic effects of anthracyclines in the heart. Regarding molecular targeted tyrosine kinase inhibitors used in patients with human epidermal growth factor receptor type 2+ tumours (e.g., trastuzumab, lapatinib), it is the blockage of survival pathways required for a normal heart development and function that seems to lead to cardiac pathology. Both types of breast cancer treatment appear to trigger cardiotoxicity synergically, being patients under adjuvant therapy closely monitored. Given the complex nature of heart failure and of the pathways altered by anti-cancer drugs, global gene expression regulation is key in the heart disease process. MicroRNAs have been demonstrated to be small molecules with big roles as essential gene expression modulators. The great potential of microRNAs as biomarkers in the cardio-oncology field needs to be further explored before new microRNA-based diagnostic and therapeutic tools can be developed.

Novel biomarkers in chronic heart failure

Understanding of chronic heart failure (HF) has progressed from a syndrome of disordered hemodynamics caused by alterations in the structure of the heart to one that involves intertwined molecular pathways in disarray. Accordingly, the assessment and treatment of patients with chronic HF has shifted from a focus on hemodynamics to modification of maladaptive molecular processes. Accumulating evidence shows that molecular biomarkers of disease could provide a unique window into the pathophysiology of chronic HF, potentially improving our ability to predict adverse outcomes, provide novel drug targets, and even help gauge therapeutic efficacy. The more 'traditional' biomarkers such as cardiac troponin, natriuretic peptides, and C-reactive protein have been studied in large cohorts of patients with chronic HF and have relatively established clinical applications. In this Review, we summarize the properties, clinical data, and potential applications of some emerging biomarkers that could uniquely indicate the level of biomechanical stretch, inflammation, ventricular remodeling, myocardial injury, and renal dysfunction that occurs in chronic HF. We will also discuss the potential role for these biomarkers within a multimarker-based strategy that could, in the future, lead to better care for these patients.

The ShcA phosphotyrosine docking protein uses distinct mechanisms to regulate myocyte and global heart function

RATIONALE

Although tyrosine kinases (TKs) are important for cardiac function, their relevant downstream targets in the adult heart are unknown. The ShcA docking protein binds specific phosphotyrosine (pTyr) sites on activated TKs through its N-terminal pTyr-binding (PTB) and C-terminal SH2 domains and stimulates downstream pathways through motifs such as pTyr sites in its central CH1 region. Therefore, ShcA could be a potential hub for downstream TK signaling in the myocardium.

OBJECTIVE

To define the role of ShcA, a TK scaffold, in the adult heart using a myocardial-specific knockout of murine ShcA (ShcA CKO) and domain knock-in models.

METHODS AND RESULTS

ShcA CKO mice developed a dilated cardiomyopathy phenotype involving impaired systolic function with enhanced cardiomyocyte contractility. This uncoupling of global heart and intrinsic myocyte functions was associated with altered collagen and extracellular matrix compliance properties, suggesting disruption of mechanical coupling. In vivo dissection of ShcA signaling properties revealed that selective inactivation of the PTB domain in the myocardium had effects resembling those seen in ShcA CKO mice, whereas disruption of the SH2 domain caused a less severe cardiac phenotype. Downstream signaling through the CH1 pTyr sites was dispensable for baseline cardiac function but necessary to prevent adverse remodeling after hemodynamic overload.

CONCLUSIONS

These data demonstrate a requirement for TK-ShcA PTB domain signaling to maintain cardiac function. In addition, analysis of the SH2 domain and CH1 pTyr sites reveals that ShcA mediates pTyr signaling in the adult heart through multiple distinct signaling elements that control myocardial functions and response to stresses.