Protecting against anthracycline-induced myocardial damage: a review of the most promising strategies

Chemotherapy-Induced Cardiotoxicity: Pathophysiology and Prevention

Along with the remarkable progress registered in oncological treatment that led to increased survival of cancer patients, treatment-related comorbidities have also become an issue for these long-term survivors. Of particular interest is the development of cardiotoxic events, which, even when asymptomatic, not only have a negative impact on the patient`s cardiac prognosis, but also considerably restrict therapeutic opportunities. The pathophysiology of cytostatic-induced cardiotoxicity implies a series of complex and intricate mechanisms, whose understanding enables the development of preventive and therapeutic strategies. Securing cardiac function is an ongoing challenge for the pharmaceutical industry and the physicians who have to deal currently with these adverse reactions. This review focuses on the main mechanism of cardiac toxicity induced by anticancer drugs and especially on the current strategies applied for preventing and minimizing the cardiac side effects.

Anthracycline-related cardiotoxicity in childhood cancer survivors

PURPOSE OF REVIEW

Anthracyclines have markedly improved the survival rates of children with cancer. However, anthracycline-related cardiotoxicity is also well recognized and can compromise the long-term outcome in some patients. The challenge remains of how to balance the chemotherapeutic effects of anthracycline treatment with its potentially serious cardiovascular complications. Here, we review the pathophysiology, risk factors, clinical manifestations, prevention, and treatment of anthracycline-related cardiotoxicity.

RECENT FINDINGS

Some risk factors and biomarkers associated with an increased probability of anthracycline-related cardiotoxicity have been identified. Modifying the structural forms and dosages of anthracyclines and coadministering cardioprotective agents may prevent some of these cardiotoxic effects. Cardiovascular complications have also been treated with angiotensin-converting enzyme inhibitors, β-blockers, and growth hormone replacement therapy. Cardiac transplantation remains the treatment of last resort.

SUMMARY

Despite major advances in cancer treatment, anthracycline-related cardiotoxicity remains a major cause of morbidity and mortality in survivors of childhood cancer. Promising areas of research include: use of biomarkers for early recognition of cardiac injury in children receiving chemotherapy, development and application of cardioprotective agents for prevention of cardiotoxicity, and advancements in therapies for cardiac dysfunction in children after anthracycline treatment.

Management of ACCF/AHA Stage A and B patients

Heart failure remains a major health problem in the United States, affecting 5.8 million Americans. Its prevalence continues to rise due to the improved survival of patients. Despite advances in treatment, morbidity and mortality remain very high, with a median survival of about 5 years after the first clinical symptoms. This article describes the causes, classification, and management goals of heart failure in Stages A and B.

Differential modulation of apoptotic processes by proanthocyanidins as a dietary strategy for delaying chronic pathologies

Apoptosis is a biological process necessary for maintaining cellular homeostasis. Several diseases can result if it is deregulated. For example, inhibition of apoptotic signaling pathways is linked to the survival of pathological cells, which contributes to cancer, whereas excessive apoptosis is linked to neurodegenerative diseases, partially via oxidative stress. The activation or restoration of apoptosis via extrinsic or intrinsic pathways combined with cell signaling pathways triggered by reactive oxygen specises (ROS) formation is considered a key strategy by which bioactive foods can exert their health effects. Proanthocyanidins, a class of flavonoids naturally found in fruits, vegetables, and beverages, have attracted a great deal of attention not only because they are strong antioxidants but also because they appear to exert a different modulation of apoptosis, stimulating apoptosis in damaged cells, thus preventing cancer or reducing apoptosis in healthy cells, and as a result, preserving the integrity of normal cells and protecting against neurodegenerative diseases. Therefore, proanthocyanidins could provide a defense against apoptosis induced by oxidative stress or directly inhibit apoptosis, and they could also provide a promising treatment for a variety of diseases. Emerging data suggest that proanthocyanidins, especially those that humans can be persuaded to consume, may be used to prevent and manage cancer and mental disorders.

Early myocardial deformation abnormalities in breast cancer survivors

To evaluate the role of 2D myocardial strain (rate) imaging in the detection of early subclinical cardiotoxicity in breast cancer survivors treated with an anthracycline-based chemotherapeutic regimen. 57 adult breast cancer survivors were analyzed 1 year after therapy. All patients underwent biomarker analysis and 2D echocardiography consisting of conventional echocardiographic and strain (rate) parameters. Conventional echocardiographic values were normal. Global longitudinal strain was normal, but 18 % of patients showed a >2 SD decrease when individually compared to reference values. This subgroup showed a decrease in end-systolic and end-diastolic volumes and an increase in left ventricular mass. Radial and circumferential strain rates were significantly decreased in the whole study group. 2D myocardial strain (rate) imaging showed abnormalities in breast cancer survivors, while conventional echocardiographic values remained normal, rendering 2D myocardial strain (rate) imaging an interesting tool for the early detection of anthracycline-induced cardiotoxicity.

Cardiac complications of chemotherapy: role of biomarkers

OPINION STATEMENT

Both conventional and novel antineoplastic drugs may cause damage to the heart, ultimately affecting patients' survival and quality of life. In fact, the most frequent and typical clinical manifestation of cardiotoxicity, asymptomatic or symptomatic left ventricular dysfunction, may be induced not only by conventional cancer therapy, like anthracyclines, but also by new antitumoral targeted therapy such as trastuzumab. At present, left ventricular ejection fraction assessment represents the main standard practice for cardiac monitoring during cancer therapy, but it detects myocardial damage only when a functional impairment has already occurred, not allowing for early preventive strategies. In the last decade, a newer approach based on the measurement of cardiospecific biomarkers has been proposed, proving to have higher prognostic value than imaging modalities. In particular, cardiac troponin elevation during chemotherapy allows us to identify patients who are more prone to develop myocardial dysfunction and cardiac events during follow up. In these patients, the use of an angiotensin-converting enzyme inhibitor, such as enalapril, has shown to be effective in improving clinical outcome, giving the chance for a cardioprotective strategy in a selected population.

Anthracycline-induced cardiotoxicity: a review of pathophysiology, diagnosis, and treatment

OPINION STATEMENT

Anthracyclines have been widely used in children and adults to treat hematologic malignancies, soft-tissue sarcomas, and solid tumors. However, anthracyclines come with both short- and long-term cardiotoxic effects, ranging from occult changes in myocardial structure and function to severe cardiomyopathy and heart failure that may result in cardiac transplantation or death. Here, we review the progress made over the past two decades in understanding the molecular and genetic basis of anthracycline-induced cardiotoxicity; detecting and monitoring myocardial dysfunction; using adjunct cardioprotectant therapies, such as dexrazoxane; and improving cardioprotection with agents such as liposomal and pegylated doxorubicin. Despite this increased understanding, preventing drug-induced cardiotoxicity while maintaining oncologic efficacy to achieve the highest quality of life over a lifespan remain cornerstones of successful anthracycline chemotherapy during childhood.

Interindividual variability in the cardiac expression of anthracycline reductases in donors with and without Down syndrome

PURPOSE

The intracardiac synthesis of anthracycline alcohol metabolites (e.g., daunorubicinol) contributes to the pathogenesis of anthracycline-related cardiotoxicity. Cancer patients with Down syndrome (DS) are at increased risk for anthracycline-related cardiotoxicity. We profiled the expression of anthracycline metabolizing enzymes in hearts from donors with- and without- DS.

METHODS

Cardiac expression of CBR1, CBR3, AKR1A1, AKR1C3 and AKR7A2 was examined by quantitative real time PCR, quantitative immunoblotting, and enzyme activity assays using daunorubicin. The CBR1 polymorphism rs9024 was investigated by allelic discrimination with fluorescent probes. The contribution of CBRs/AKRs proteins to daunorubicin reductase activity was examined by multiple linear regression.

RESULTS

CBR1 was the most abundant transcript (average relative expression; DS: 81%, non-DS: 58%), and AKR7A2 was the most abundant protein (average relative expression; DS: 38%, non-DS: 35%). Positive associations between cardiac CBR1 protein levels and daunorubicin reductase activity were found for samples from donors with- and without- DS. Regression analysis suggests that sex, CBR1, AKR1A1, and AKR7A2 protein levels were significant contributors to cardiac daunorubicin reductase activity. CBR1 rs9024 genotype status impacts on cardiac CBR1 expression in non-DS hearts.

CONCLUSIONS

CBR1, AKR1A1, and AKR7A2 protein levels point to be important determinants for predicting the synthesis of cardiotoxic daunorubicinol in heart.

Ferritin heavy chain as main mediator of preventive effect of metformin against mitochondrial damage induced by doxorubicin in cardiomyocytes

The efficacy of doxorubicin (DOX) as an antitumor agent is greatly limited by the induction of cardiomyopathy, which results from mitochondrial dysfunction and iron-catalyzed oxidative stress in the cardiomyocyte. Metformin (MET) has been seen to have a protective effect against the oxidative stress induced by DOX in cardiomyocytes through its modulation of ferritin heavy chain (FHC), the main iron-storage protein. This study aimed to assess the involvement of FHC as a pivotal molecule in the mitochondrial protection offered by MET against DOX cardiotoxicity. The addition of DOX to adult mouse cardiomyocytes (HL-1 cell line) increased the cytosolic and mitochondrial free iron pools in a time-dependent manner. Simultaneously, DOX inhibited complex I activity and ATP generation and induced the loss of mitochondrial membrane potential. The mitochondrial dysfunction induced by DOX was associated with the release of cytochrome c to the cytosol, the activation of caspase 3, and DNA fragmentation. The loss of iron homeostasis, mitochondrial dysfunction, and apoptosis induced by DOX were prevented by treatment with MET 24h before the addition of DOX. The involvement of FHC and NF-κB was determined through siRNA-mediated knockdown. Interestingly, the presilencing of FHC or NF-κB with specific siRNAs blocked the protective effect induced by MET against DOX cardiotoxicity. These findings were confirmed in isolated primary neonatal rat cardiomyocytes. In conclusion, these results deepen our knowledge of the protective action of MET against DOX-induced cardiotoxicity and suggest that therapeutic strategies based on FHC modulation could protect cardiomyocytes from the mitochondrial damage induced by DOX by restoring iron homeostasis.

Molecular basis of cancer-therapy-induced cardiotoxicity: introducing microRNA biomarkers for early assessment of subclinical myocardial injury

Development of reliable biomarkers for early clinical assessment of drug-induced cardiotoxicity could allow the detection of subclinical cardiac injury risk in vulnerable patients before irreversible damage occurs. Currently, it is difficult to predict who will develop drug-induced cardiotoxicity owing to lack of sensitivity and/or specificity of currently used diagnostics. miRNAs are mRNA regulators and they are currently being extensively profiled for use as biomarkers due to their specific tissue and disease expression signature profiles. Identification of cardiotoxicity-specific miRNA biomarkers could provide clinicians with a valuable tool to allow prognosis of patients at risk of cardiovascular injury, alteration of a treatment regime or the introduction of an adjunct therapy in order to increase the long-term survival rate of patients treated with cardiotoxic drugs.

Left ventricular endocardial dysfunction in patients with preserved ejection fraction after receiving anthracycline

BACKGROUND

Anthracycline chemotherapy generates progressive dose-dependent left ventricular (LV) dysfunction associated with a poor prognosis. Early detection of minor LV myocardial dysfunction caused by the cardiotoxicity of anthracycline is thus important for predicting global LV dysfunction.

METHODS

Fifty patients with preserved ejection fraction (all ≥55%) after receiving anthracycline chemotherapy were recruited for this study. Two-dimensional speckle tracking was used to assess global radial and circumferential strains from mid-LV short-axis views and global longitudinal strain from the apical four- and two-chamber view as peak global strain curves. Three-dimensional (3D) radial, circumferential, and longitudinal myocardial function was quantified as a peak global strain curve using 3D speckle tracking from all 16 LV segments. 3D speckle tracking imaging was used to evaluate LV endocardial area change ratio (area strain) quantified as peak global area strain curve (3D-GAS) to determine LV endocardial function. Twenty age-, gender-, and EF-matched normal volunteers were studied for comparisons.

RESULTS

Only 3D-GAS and peak 3D global circumferential strains of the anthracycline group were significantly worse than those of the control group (-43.3 ± 3.1 vs. -45.8 ± 4.3% and -31.6 ± 3.5% vs. -34.4 ± 4.2%, respectively; P = 0.008, P = 0.004) even though global LV systolic and diastolic functions were similar. 3D-GAS correlated significantly with the cumulative doxorubicin dose (r = 0.316, P = 0.026). It was noteworthy that multivariate analysis showed only 3D-GAS (β = 0.323, P = 0.025) was independently associated with cumulative doxorubicin dose.

CONCLUSIONS

Three-dimensional speckle tracking area strain was found useful for early detection of minor LV endocardial dysfunction associated with the use of anthracycline, and may thus prove to be clinically useful for predicting global LV dysfunction.

Treatment-related cardiotoxicity in survivors of childhood cancer

Treatment advances and higher participation rates in clinical trials have rapidly increased the number of survivors of childhood cancer. However, chemotherapy and radiation treatments are cardiotoxic and can cause cardiomyopathy, conduction defects, myocardial infarction, hypertension, stroke, pulmonary oedema, dyspnoea and exercise intolerance later in life. These cardiotoxic effects are often progressive and irreversible, emphasizing a need for effective prevention and treatment to reduce or avoid cardiotoxicity. Medical interventions, such as angiotensin-converting enzyme inhibitors, β-blockers, and growth hormone therapy, might be used to treat cardiotoxicity in childhood cancer survivors. Preventative strategies should include the use of dexrazoxane, which provides cardioprotection without reducing the oncological efficacy of doxorubicin chemotherapy; less-toxic anthracycline derivatives and the use of antioxidant nutritional supplements might also be beneficial. Continuous-infusion doxorubicin provides no benefit over bolus infusion in children. Identifying patient-related (for example, obesity and hypertension) and drug-related (for example, cumulative dose) risk factors for cardiotoxicity could help tailor treatments to individual patients. However, all survivors of childhood cancer are at increased risk of cardiotoxicity, suggesting that survivor screening recommendations for assessment of global risk of premature cardiovascular disease should apply to all survivors. Optimal, evidence-based monitoring strategies and multiagent preventative treatments still need to be identified.

Catalytic inhibitors of topoisomerase II differently modulate the toxicity of anthracyclines in cardiac and cancer cells

Anthracyclines (such as doxorubicin or daunorubicin) are among the most effective anticancer drugs, but their usefulness is hampered by the risk of irreversible cardiotoxicity. Dexrazoxane (ICRF-187) is the only clinically approved cardioprotective agent against anthracycline cardiotoxicity. Its activity has traditionally been attributed to the iron-chelating effects of its metabolite with subsequent protection from oxidative stress. However, dexrazoxane is also a catalytic inhibitor of topoisomerase II (TOP2). Therefore, we examined whether dexrazoxane and two other TOP2 catalytic inhibitors, namely sobuzoxane (MST-16) and merbarone, protect cardiomyocytes from anthracycline toxicity and assessed their effects on anthracycline antineoplastic efficacy. Dexrazoxane and two other TOP2 inhibitors protected isolated neonatal rat cardiomyocytes against toxicity induced by both doxorubicin and daunorubicin. However, none of the TOP2 inhibitors significantly protected cardiomyocytes in a model of hydrogen peroxide-induced oxidative injury. In contrast, the catalytic inhibitors did not compromise the antiproliferative effects of the anthracyclines in the HL-60 leukemic cell line; instead, synergistic interactions were mostly observed. Additionally, anthracycline-induced caspase activation was differentially modulated by the TOP2 inhibitors in cardiac and cancer cells. Whereas dexrazoxane was upon hydrolysis able to significantly chelate intracellular labile iron ions, no such effect was noted for either sobuzoxane or merbarone. In conclusion, our data indicate that dexrazoxane may protect cardiomyocytes via its catalytic TOP2 inhibitory activity rather than iron-chelation activity. The differential expression and/or regulation of TOP2 isoforms in cardiac and cancer cells by catalytic inhibitors may be responsible for the selective modulation of anthracycline action observed.

Occult cardiotoxicity in childhood cancer survivors exposed to anthracycline therapy

BACKGROUND

More than 50% of >270 000 childhood cancer survivors in the United States have been treated with anthracyclines and are therefore at risk of developing cardiotoxicity. Cardiac magnetic resonance (CMR) has demonstrated utility to detect diffuse interstitial fibrosis and changes in regional myocardial function. We hypothesized that CMR would identify occult cardiotoxicity characterized by structural and functional myocardial abnormalities in a cohort of asymptomatic pediatric cancer survivors with normal global systolic function.

METHODS AND RESULTS

Forty-six long-term childhood cancer survivors with a cumulative anthracycline dose ≥200 mg/m(2) and normal systolic function were studied 2.5 to 26.9 years after anthracycline exposure. Subjects underwent transthoracic echocardiography, CMR with routine cine acquisition, tissue characterization, and left ventricular strain analysis using a modified 16-segment model. Extracellular volume was measured in 27 subjects, all of whom were late gadolinium enhancement negative. End-systolic fiber stress was elevated in 45 of 46 subjects. Low average circumferential strain magnitude (εcc) -14.9±1.4; P<0.001, longitudinal strain magnitude (εll) -13.5±1.9; P<0.001, and regional peak circumferential strain were seen in multiple myocardial segments, despite normal global systolic function by transthoracic echocardiography and CMR. The mean T1 values of the myocardium were significantly lower than that of control subjects at 20 minutes (458±69 versus 487±44 milliseconds; P=0.01). Higher mean extracellular volume was observed in female subjects (0.34 versus 0.22; P=0.01).

CONCLUSIONS

Asymptomatic postchemotherapy pediatric patients have abnormal myocardial characteristics and strain parameters by CMR despite normal global cardiac function by standard transthoracic echocardiography and CMR measures.

Topoisomerase 2β: a promising molecular target for primary prevention of anthracycline-induced cardiotoxicity

Anthracyclines are powerful chemotherapy agents that are still widely used today. However, their clinical use is limited by the development of dose-dependent cardiotoxicity. Recently, we showed that topoisomerase 2β (Top2β) is required for anthracycline to induce DNA double-strand breaks and changes in the transcriptome, leading to mitochondrial dysfunction and generation of reactive oxygen species. Furthermore, deleting Top2β from cardiomyocytes prevented the development of anthracycline-induced cardiotoxicity in mice. On the basis of this molecular insight, new strategies should be developed to prevent anthracycline-induced cardiotoxicity. First, Top2α-specific anthracyclines should be tested to determine whether they will spare the heart. Second, Top2β should be studied as a potential biomarker to predict risk of developing cardiotoxicity before anthracycline treatment. Third, inhibiting and deleting Top2β in the heart should also be tested as primary prevention strategies. We propose that Top2β is a promising molecular target that can be used to design interventions to prevent anthracycline-induced cardiotoxicity.

Temporal changes in standard and tissue Doppler imaging echocardiographic parameters after anthracycline chemotherapy in women with breast cancer

Anthracyclines are established cardiotoxic agents; however, the exact extent and time course of such cardiotoxicity has not been appraised in detail. We aimed to exploit serial measurements of standard and tissue Doppler imaging (TDI) echocardiographic parameters collected in a prospective clinical trial to clarify the outlook of cardiac function during and long after anthracycline chemotherapy. Women enrolled in a randomized trial focusing on liposomal doxorubicin-based chemotherapy for breast cancer and providing ≥4 separate echocardiographic assessments were included. Repeat-measure nonparametric analyses were used to appraise changes over time in the standard and tissue Doppler imaging echocardiographic parameters. A total of 39 patients with serial imaging evaluations were enrolled. Significant temporal changes were found for the left ventricular ejection fraction and diastolic parameters, despite different temporal trends. Specifically, the left ventricular ejection fraction exhibited a V-shaped trend, decreasing initially from 63% to 61% but then recovering to 64% (p <0.001), with a similar trend in the TDI E/Em ratio (p = 0.011). In contrast, persistent impairments typical of an L-shaped trend were found for the E wave (p = 0.006), TDI lateral Em wave (p = 0.001), and TDI septal Em wave (p = 0.001). In conclusion, subclinical temporal changes in the standard and TDI echocardiographic parameters after anthracycline chemotherapy showed a distinctive pattern of transient impairment followed by full recovery of the left ventricular ejection fraction versus a persistent impairment of the diastolic parameters, which must be taken into account in the everyday treatment of such patients.

Cardiac toxicity of anticancer agents

Modern cancer therapies are highly effective in the treatment of various malignancies, but their use is limited by the potential for cardiotoxicity. The most frequent and typical clinical manifestation of cardiotoxicity is left ventricular dysfunction, induced not only by cytotoxic conventional cancer therapy like anthracyclines, but also by new antitumor targeted therapy such as trastuzumab. The current standard for monitoring cardiac function, based on periodic assessment of left ventricular ejection fraction detects cardiotoxicity only when a functional impairment has already occurred, precluding any chance of preventing its development. A novel approach, based on the use of cardiac biomarkers has emerged in the last decade, resulting in a cost-effective diagnostic tool for early, real-time identification, assessment and monitoring of cardiotoxicity. In particular, prophylactic treatment with enalapril in patients with an early increase in troponin after chemotherapy has been shown to be very effective in preventing left ventricular dysfunction and associated cardiac events. In patients developing cancer treatment induced-cardiomyopathy, complete left ventricular ejection fraction recovery and a reduction of cardiac events may be achieved only when left ventricular dysfunction is detected early after the end of cancer treatment and treatment with angiotensin-converting enzyme inhibitors, possibly in combination with beta-blockers, is promptly initiated.

Managing cardiotoxicity of chemotherapy

OPINION STATEMENT

The increase in survivorship of cancer patients makes the understanding of the available options for prevention and treatment of cardiotoxicity induced by antineoplastic agents a crucial topic both for cardiologists and oncologists. The most frequent and typical clinical manifestation of cardiotoxicity is asymptomatic or symptomatic left ventricular dysfunction, which may progress to overt heart failure. It may be induced not only by conventional cancer therapy, like anthracyclines, but also by new antitumoral targeted therapy such as trastuzumab. The current standard for monitoring cardiac damage during antineoplastic treatment, mainly based on the quantification of left ventricular ejection fraction, detects cardiac toxicity only when a functional impairment has already occurred. Evaluation of cardiac biomarkers such as troponin, however, has shown excellent sensitivity in the early detection of cardiotoxicity by the identification of patients with subclinical cardiac injury that precedes the development of cardiac dysfunction. The use of angiotensin-converting enzyme inhibitors in patients with troponin elevation during chemotherapy may be an effective tool to prevent left ventricular ejection fraction reduction and late cardiac events. There are no well established recommendations for treatment of cancer patients who develop cardiac dysfunction. Angiotensin-converting enzyme inhibitors and beta-blockers have proven to be effective in this setting. However, there are concerns in using these medications in cancer patients, and therefore the tendency is to treat patients only if symptomatic. However, the clinical benefit of these medications may be more evident in asymptomatic patients, and the recovery of cardiac function strongly depends on the amount of time elapsed from the end of chemotherapy to the start of heart failure therapy. This observation suggests that the early detection of cardiac damage is crucial and early use of angiotensin-converting enzyme inhibitors and beta-blockers should be considered in patients with left ventricular dysfunction induced by antineoplastic agents.

Enalaprilat increases PPARβ/δ expression, without influence on PPARα and PPARγ, and modulate cardiac function in sub-acute model of daunorubicin-induced cardiomyopathy

Anthracycline therapy is limited by a cardiotoxicity that may eventually lead to chronic heart failure which is thought to be prevented by ACE inhibitors (ACEi). However, the protective effect of ACEi in early stages of this specific injury remains elusive. Activated nuclear transcription factors peroxisome proliferator-activated receptors (PPAR) regulate cellular metabolism, but their involvement in anthracycline cardiomyopathy has not been investigated yet. For this purpose, Wistar rats were administered with daunorubicin (i.p., 3 mg/kg, in 48 h intervals) or co-administered with daunorubicine and enalaprilat (i.p., 5 mg/kg in 12 h intervals). Control animals received vehicle. Left ventricular function was measured invasively under anesthesia. Cell-shortening was measured by videomicroscopy in isolated cardiomyocytes. Expression of PPARs mRNA in cardiac tissue was measured by Real-Time PCR. Although the hemodynamic parameters of daunorubicin-treated rats remained altered upon ACEi co-administration, ACEi normalized daunorubicin-induced QT prolongation. On cellular level, ACEi normalized altered basal and isoproterenol-stimulated cardiac cell shortening in daunorubicine-treated group. Moreover, anthracycline administration significantly up-regulated heart PPARα mRNA and its expression remained increased after ACEi co-administration. On the other hand, the expression of cardiac PPARβ/δ was not altered in anthracycline-treated animals, whereas co-administration of ACEi increased its expression. Conclusively, effect of ACEi can be already detected in sub-acute phase of anthracycline-induced cardiotoxicity. Altered expression of heart PPARs may suggest these nuclear receptors as a novel target in anthracycline cardiomyopathy.

Using cardiac biomarkers and treating cardiotoxicity in cancer

Cardiotoxicity is a frequent and serious adverse effect of both conventional and novel anticancer treatments, affecting patient survival and quality of life. The current standard for cardiac monitoring during cancer therapy, mainly based on left ventricular ejection fraction assessment, detects myocardial damage only when a functional impairment has already occurred, not allowing for early preventive strategies. Measurement of cardiospecific biomarkers has proven to have higher prognostic value than imaging modalities. In particular, cardiac troponin elevation during chemotherapy allows the identification of patients who are more prone to develop myocardial dysfunction and cardiac events during follow-up. In these patients, the use of an angiotensin-converting enzyme inhibitor such as enalapril has shown to be effective in improving clinical outcome, giving the chance for a cardioprotective strategy in a selected population. Once left ventricular dysfunction occurs, heart failure therapies currently used for other forms of left ventricular dysfunction, particularly angiotensin-converting enzyme inhibitors and β-blockers, seem to be effective. However, their use in cancer patients is still undervalued.

An engineered bivalent neuregulin protects against doxorubicin-induced cardiotoxicity with reduced proneoplastic potential

BACKGROUND

Doxorubicin (DOXO) is an effective anthracycline chemotherapeutic, but its use is limited by cumulative dose-dependent cardiotoxicity. Neuregulin-1β is an ErbB receptor family ligand that is effective against DOXO-induced cardiomyopathy in experimental models but is also proneoplastic. We previously showed that an engineered bivalent neuregulin-1β (NN) has reduced proneoplastic potential in comparison with the epidermal growth factor-like domain of neuregulin-1β (NRG), an effect mediated by receptor biasing toward ErbB3 homotypic interactions uncommonly formed by native neuregulin-1β. Here, we hypothesized that a newly formulated, covalent NN would be cardioprotective with reduced proneoplastic effects in comparison with NRG.

METHODS AND RESULTS

NN was expressed as a maltose-binding protein fusion in Escherichia coli. As established previously, NN stimulated antineoplastic or cytostatic signaling and phenotype in cancer cells, whereas NRG stimulated proneoplastic signaling and phenotype. In neonatal rat cardiomyocytes, NN and NRG induced similar downstream signaling. NN, like NRG, attenuated the double-stranded DNA breaks associated with DOXO exposure in neonatal rat cardiomyocytes and human cardiomyocytes derived from induced pluripotent stem cells. NN treatment significantly attenuated DOXO-induced decrease in fractional shortening as measured by blinded echocardiography in mice in a chronic cardiomyopathy model (57.7±0.6% versus 50.9±2.6%, P=0.004), whereas native NRG had no significant effect (49.4±3.7% versus 50.9±2.6%, P=0.813).

CONCLUSIONS

NN is a cardioprotective agent that promotes cardiomyocyte survival and improves cardiac function in DOXO-induced cardiotoxicity. Given the reduced proneoplastic potential of NN versus NRG, NN has translational potential for cardioprotection in patients with cancer receiving anthracyclines.

An expert opinion on pharmacologic approaches to reducing the cardiotoxicity of childhood acute lymphoblastic leukemia therapies

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the most common hematologic malignancy in children. Treatment-related cardiac damage is progressive and often difficult to reverse. Strategies to minimize cardiotoxicity during treatment are crucial to prevent severe lasting effects on health and quality of life.

AREAS COVERED

This comprehensive review covers the pathophysiology and various presentations, both clinical and subclinical, of treatment-induced cardiotoxicity and characteristics associated with increased risk of cardiac dysfunction in childhood ALL survivors. Additionally, contemporary prevention strategies such as limiting cumulative anthracycline dose, altering drug administration schedule, the use of anthracycline structural analogs, liposomal encapsulated anthracyclines, cardioprotective agents and nutritional supplements are critically analyzed. Finally, this review covers the management options of chemotherapy-induced damage and other treatment-related cardiotoxicity.

EXPERT OPINION

Higher lifetime cumulative doses of anthracyclines, younger age at diagnosis, longer follow-up, female sex, higher dose rates and cranial irradiation are associated with more severe cardiotoxic effects. Long-term adverse effects of both anthracycline and non-anthracycline chemotherapeutic agents are becoming an increasing focus during treatment of childhood malignancies. There must be a careful balance between achieving remission of childhood ALL while avoiding the development of another often-fatal illness, heart failure.

Strategies to prevent and treat cardiovascular risk in cancer patients

Cardiotoxicity due to cancer treatment is of rising concern, for both cardiologists and oncologists, because it may have a significant impact on cancer patient management and outcome. The most typical manifestation of cardiotoxicity is a hypokinetic cardiomyopathy leading to heart failure. However, the spectrum of the toxic effects that can impair the cardiovascular system may also include acute coronary syndromes, hypertension, arrhythmias, and thromboembolic events. Patients undergoing cancer treatment are more vulnerable to cardiovascular injuries, and their risk of premature cardiovascular disease and death is higher than that of the general population. Prevention of cardiotoxicity remains the most important strategy, and several measures, including cardiac function monitoring, limitation of chemotherapy dose, use of anthracycline analogues and cardioprotectants, and early detection of myocardial cell injury by biomarkers, have been proposed. The response to modern heart failure therapy of cancer treatment-induced cardiomyopathy has never been evaluated in clinical trials, and currently there are no definitive guidelines. Although it is likely that medications used for other forms of cardiomyopathy, particularly angiotensin-converting enzyme inhibitors and β-blockers, may be highly effective, there is still some unjustified concern regarding their use in cancer patients. Specific guidelines that take cardiologic conditions of cancer patients into account are currently lacking and need to be developed.

Involvement of ferritin heavy chain in the preventive effect of metformin against doxorubicin-induced cardiotoxicity

Doxorubicin is a wide-spectrum chemotherapeutic agent, although a cumulative dose may cause cardiac damage and lead to heart failure. Doxorubicin cardiotoxicity is dependent on the intracellular iron pool and manifests itself by increasing oxidative stress. Our group has recently shown the ability of metformin, an oral antidiabetic with cardiovascular benefits, to protect cardiomyocytes from doxorubicin-induced damage. This work aimed to study whether metformin is able to modulate the expression of ferritin, the major intracellular iron storage protein, in cardiomyocytes and whether it is involved in their protection. The addition of metformin to adult mouse cardiomyocytes (HL-1 cell line) induced both gene and protein expression of the ferritin heavy chain (FHC) in a time-dependent manner. The silencing of FHC expression with siRNAs inhibited the ability of metformin to protect cardiomyocytes from doxorubicin-induced damage, in terms of the percentage of cell viability, the levels of reactive oxygen species, and the activity of antioxidant enzymes (catalase, glutathione peroxidase, and superoxide dismutase). In addition, metformin induced the activation of NF-κB in HL-1 cells, whereas preincubation with SN50, an inhibitor of NF-κB, blocked the upregulation of the FHC and the protective effect mediated by metformin. Taken together, these results provide new knowledge on the protective actions of metformin against doxorubicin-induced cardiotoxicity by identifying FHC and NF-κB as the major mediators of this beneficial effect.

Oxidative stress, redox signaling, and metal chelation in anthracycline cardiotoxicity and pharmacological cardioprotection

SIGNIFICANCE

Anthracyclines (doxorubicin, daunorubicin, or epirubicin) rank among the most effective anticancer drugs, but their clinical usefulness is hampered by the risk of cardiotoxicity. The most feared are the chronic forms of cardiotoxicity, characterized by irreversible cardiac damage and congestive heart failure. Although the pathogenesis of anthracycline cardiotoxicity seems to be complex, the pivotal role has been traditionally attributed to the iron-mediated formation of reactive oxygen species (ROS). In clinics, the bisdioxopiperazine agent dexrazoxane (ICRF-187) reduces the risk of anthracycline cardiotoxicity without a significant effect on response to chemotherapy. The prevailing concept describes dexrazoxane as a prodrug undergoing bioactivation to an iron-chelating agent ADR-925, which may inhibit anthracycline-induced ROS formation and oxidative damage to cardiomyocytes.

RECENT ADVANCES

A considerable body of evidence points to mitochondria as the key targets for anthracycline cardiotoxicity, and therefore it could be also crucial for effective cardioprotection. Numerous antioxidants and several iron chelators have been tested in vitro and in vivo with variable outcomes. None of these compounds have matched or even surpassed the effectiveness of dexrazoxane in chronic anthracycline cardiotoxicity settings, despite being stronger chelators and/or antioxidants.

CRITICAL ISSUES

The interpretation of many findings is complicated by the heterogeneity of experimental models and frequent employment of acute high-dose treatments with limited translatability to clinical practice.

FUTURE DIRECTIONS

Dexrazoxane may be the key to the enigma of anthracycline cardiotoxicity, and therefore it warrants further investigation, including the search for alternative/complementary modes of cardioprotective action beyond simple iron chelation.

Current applications of cardiac troponin T for the diagnosis of myocardial damage

Biochemical markers of myocardial injury play an important role in the diagnosis of cardiovascular diseases. Measurement of cardiac biomarkers is one of the most important diagnostic tests in acute myocardial infarction (AMI), heart failure, and other cardiovascular disorders. Recently, the European Society of Cardiology, the American College of Cardiology Foundation, the American Heart Association, and the World Heart Federation have published a consensus definition of AMI that includes a detailed guideline for the assessment of biochemical markers in suspected disease. The cardiac troponins (cTI and cTnT) were recommended as preferred markers of myocardial necrosis in this setting. Herein, we review cardiac troponin biochemistry, the performance characteristics of cTnT assays, and optimal utilization of troponin in patients with proven or possible cardiovascular disease. We also discuss the use of troponin tests, with emphasis on cTnT, in different clinical situations in which its levels may be elevated.

pH-responsive hydrogels with dispersed hydrophobic nanoparticles for the oral delivery of chemotherapeutics

Amphiphilic polymer carriers were formed by polymerizing a hydrophilic, pH-responsive hydrogel composed of poly(methacrylic-grafted-ethylene glycol) (P(MAA-g-EG)) in the presence of hydrophobic PMMA nanoparticles. These polymer carriers were varied in PMMA nanoparticle content to elicit a variety of physiochemical properties which would preferentially load doxorubicin, a hydrophobic chemotherapeutic, and release doxorubicin locally in the colon for the treatment of colon cancers. Loading levels ranged from 49% to 64% and increased with increasing nanoparticle content. Doxorubicin loaded polymers were released in a physiological model where low pH was used to simulate the stomach and then stepped to more neutral conditions to simulate the upper small intestine. P(MAA-g-EG) containing nanoparticles were less mucoadhesive as determined using a tensile tester, polymer samples, and fresh porcine small intestine. The cytocompatibility of the polymer materials were assessed using cell lines representing the GI tract and colon cancer and were noncytotoxic at varying concentrations and exposure times.

Continuous Versus Bolus Infusion of Doxorubicin in Children With ALL: Long-term Cardiac Outcomes

BACKGROUND AND OBJECTIVES

Doxorubicin, effective against many malignancies, is limited by cardiotoxicity. Continuous-infusion doxorubicin, compared with bolus-infusion, reduces early cardiotoxicity in adults. Its effectiveness in reducing late cardiotoxicity in children remains uncertain. We determined continuous-infusion doxorubicin cardioprotective efficacy in long-term survivors of childhood acute lymphoblastic leukemia (ALL).

METHODS

The Dana-Farber Cancer Institute ALL Consortium Protocol 91-01 enrolled pediatric patients between 1991 and 1995. Newly diagnosed high-risk patients were randomly assigned to receive a total of 360 mg/m(2) of doxorubicin in 30 mg/m(2) doses every 3 weeks, by either continuous (over 48 hours) or bolus-infusion (within 15 minutes). Echocardiograms at baseline, during, and after doxorubicin therapy were blindly remeasured centrally. Primary outcomes were late left ventricular (LV) structure and function.

RESULTS

A total of 102 children were randomized to each treatment group. We analyzed 484 serial echocardiograms from 92 patients (n = 49 continuous; n = 43 bolus) with ≥1 echocardiogram ≥3 years after assignment. Both groups had similar demographics and normal baseline LV characteristics. Cardiac follow-up after randomization (median, 8 years) showed changes from baseline within the randomized groups (depressed systolic function, systolic dilation, reduced wall thickness, and reduced mass) at 3, 6, and 8 years; there were no statistically significant differences between randomized groups. Ten-year ALL event-free survival rates did not differ between the 2 groups (continuous-infusion, 83% versus bolus-infusion, 78%; P = .24).

CONCLUSIONS

In survivors of childhood high-risk ALL, continuous-infusion doxorubicin, compared with bolus-infusion, provided no long-term cardioprotection or improvement in ALL event-free survival, hence provided no benefit over bolus-infusion.

Transcriptome profiling of peripheral blood cells identifies potential biomarkers for doxorubicin cardiotoxicity in a rat model

Aims

Doxorubicin (DOX), a widely used anticancer agent, can cause an unpredictable cardiac toxicity which remains a major limitation in cancer chemotherapy. There is a need for noninvasive, sensitive and specific biomarkers which will allow identifying patients at risk for DOX-induced cardiotoxicity to prevent permanent cardiac damage. The aim of this study was to investigate whether the expression of specific genes in the peripheral blood can be used as surrogate marker(s) for DOX-induced cardiotoxicity.

Methods/Results

Rats were treated with a single dose of DOX similar to one single dose that is often administered in humans. The cardiac and peripheral blood mononuclear cells (PBMCs) genome-wide expression profiling were examined using Illumina microarrays. The results showed 4,409 differentially regulated genes (DRG) in the hearts and 4,120 DRG in PBMC. Of these 2411 genes were similarly DRG (SDRG) in both the heart and PBMC. Pathway analysis of the three datasets of DRG using Gene Ontology (GO) enrichment analysis and Ingenuity Pathways Analysis (IPA) showed that most of the genes in these datasets fell into pathways related to oxidative stress response and protein ubiquination. IPA search for potential eligible biomarkers for cardiovascular disease within the SDRG list revealed 188 molecules.

Conclusions

We report the first in-depth comparison of DOX-induced global gene expression profiles of hearts and PBMCs. The high similarity between the gene expression profiles of the heart and PBMC induced by DOX indicates that the PBMC transcriptome may serve as a surrogate marker of DOX-induced cardiotoxicity. Future directions of this research will include analysis of PBMC expression profiles of cancer patients treated with DOX-based chemotherapy to identify the cardiotoxicity risk, predict DOX-treatment response and ultimately to allow individualized anti-cancer therapy.

Incidence of heart failure or cardiomyopathy after adjuvant trastuzumab therapy for breast cancer

OBJECTIVES

The purpose of this study was to estimate heart failure (HF) and cardiomyopathy (CM) rates after adjuvant trastuzumab therapy and chemotherapy in a population of older women with early-stage breast cancer.

BACKGROUND

Newer biologic therapies for breast cancer such as trastuzumab have been reported to increase HF and CM in clinical trials, especially in combination with anthracycline chemotherapy. Elderly patients, however, typically have a higher prevalence of cardiovascular risk factors and have been underrepresented in trastuzumab clinical trials.

METHODS

Using Surveillance, Epidemiology, and End Results-Medicare data from 2000 through 2007, we identified women 67 to 94 years of age with early-stage breast cancer. We calculated 3-year incidence rates of HF or CM for the following mutually exclusive treatment groups: trastuzumab (with or without nonanthracycline chemotherapy), anthracycline plus trastuzumab, anthracycline (without trastuzumab and with or without nonanthracycline chemotherapy), other nonanthracycline chemotherapy, or no adjuvant chemotherapy or trastuzumab therapy. HF or CM events were ascertained from administrative Medicare claims. Poisson regression was used to quantify risk of HF or CM, adjusting for sociodemographic factors, cancer characteristics, and cardiovascular conditions.

RESULTS

We identified 45,537 older women (mean age: 76.2 years, standard deviation: 6.2 years) with early-stage breast cancer. Adjusted 3-year HF or CM incidence rates were higher for patients receiving trastuzumab (32.1 per 100 patients) and anthracycline plus trastuzumab (41.9 per 100 patients) compared with no adjuvant therapy (18.1 per 100 patients, p < 0.001). Adding trastuzumab to anthracycline therapy added 12.1, 17.9, and 21.7 HF or CM events per 100 patients over 1, 2, and 3 years of follow-up, respectively.

CONCLUSIONS

HF or CM are common complications after trastuzumab therapy for older women, with higher rates than those reported from clinical trials.

Development of doxorubicin-induced chronic cardiotoxicity in the B6C3F1 mouse model

Serum levels of cardiac troponins serve as biomarkers of myocardial injury. However, troponins are released into the serum only after damage to cardiac tissue has occurred. Here, we report development of a mouse model of doxorubicin (DOX)-induced chronic cardiotoxicity to aid in the identification of predictive biomarkers of early events of cardiac tissue injury. Male B6C3F(1) mice were administered intravenous DOX at 3mg/kg body weight, or an equivalent volume of saline, once a week for 4, 6, 8, 10, 12, and 14weeks, resulting in cumulative DOX doses of 12, 18, 24, 30, 36, and 42mg/kg, respectively. Mice were sacrificed a week following the last dose. A significant reduction in body weight gain was observed in mice following exposure to a weekly DOX dose for 1week and longer compared to saline-treated controls. DOX treatment also resulted in declines in red blood cell count, hemoglobin level, and hematocrit compared to saline-treated controls after the 2nd weekly dose until the 8th and 9th doses, followed by a modest recovery. All DOX-treated mice had significant elevations in cardiac troponin T concentrations in plasma compared to saline-treated controls, indicating cardiac tissue injury. Also, a dose-related increase in the severity of cardiac lesions was seen in mice exposed to 24mg/kg DOX and higher cumulative doses. Mice treated with cumulative DOX doses of 30mg/kg and higher showed a significant decline in heart rate, suggesting drug-induced cardiac dysfunction. Altogether, these findings demonstrate the development of DOX-induced chronic cardiotoxicity in B6C3F(1) mice.

Differential mitochondrial toxicity screening and multi-parametric data analysis

Early evaluation of new drug entities for their potential to cause mitochondrial dysfunction is becoming an important task for drug development. Multi-parametric high-content screening (mp-HCS) of mitochondrial toxicity holds promise as a lead in-vitro strategy for drug testing and safety evaluations. In this study, we have developed a mp-HCS and multi-parametric data analysis scheme for assessing cell responses to induced mitochondrial perturbation. The mp-HCS measurements are shown to be robust enough to allow for quantitative comparison of biological systems with different metabolic pathways simulated by alteration of growth media. Substitution of medium glucose for galactose sensitized cells to drug action and revealed novel response parameters. Each compound was quantitatively characterized according to induced phenotypic changes of cell morphology and functionality measured by fluorescent biomarkers for mitochondrial activity, plasma membrane permeability, and nuclear morphology. Descriptors of drug effects were established by generation of a SCRIT (Specialized-Cell-Response-to-Induced-Toxicity) vector, consisting of normalized statistical measures of each parameter at each dose and growth condition. The dimensionality of SCRIT vectors depends on the number of parameters chosen, which in turn depends on the hypothesis being tested. Specifically, incorporation of three parameters of response into SCRIT vectors enabled clustering of 84 training compounds with known pharmacological and toxicological activities according to the degree of toxicity and mitochondrial involvement. Inclusion of 6 parameters enabled the resolution of more subtle differences between compounds within a common therapeutic class; scoring enabled a ranking of statins in direct agreement with clinical outcomes. Comparison of drug-induced changes required variations in glucose for separation of mitochondrial dysfunction from other types of cytotoxicity. These results also demonstrate that the number of drugs in a training set, the choice of parameters used in analysis, and statistical measures are fundamental for specific hypothesis testing and assessment of quantitative phenotypic differences.