Pathophysiology and diagnosis of cancer drug induced cardiomyopathy

An integrative review of nonobvious puzzles of cellular and molecular cardiooncology

Oncologic patients are subjected to four major treatment types: surgery, radiotherapy, chemotherapy, and immunotherapy. All nonsurgical forms of cancer management are known to potentially violate the structural and functional integrity of the cardiovascular system. The prevalence and severity of cardiotoxicity and vascular abnormalities led to the emergence of a clinical subdiscipline, called cardiooncology. This relatively new, but rapidly expanding area of knowledge, primarily focuses on clinical observations linking the adverse effects of cancer therapy with deteriorated quality of life of cancer survivors and their increased morbidity and mortality. Cellular and molecular determinants of these relations are far less understood, mainly because of several unsolved paths and contradicting findings in the literature. In this article, we provide a comprehensive view of the cellular and molecular etiology of cardiooncology. We pay particular attention to various intracellular processes that arise in cardiomyocytes, vascular endothelial cells, and smooth muscle cells treated in experimentally-controlled conditions in vitro and in vivo with ionizing radiation and drugs representing diverse modes of anti-cancer activity.

Pharmacovigilance Analysis of Heart Failure Associated With Anti-HER2 Monotherapies and Combination Regimens for Cancer

Background

Trastuzumab improves outcomes in patients with HER2-overexpressing malignancies but is associated with decreases in left ventricular ejection fraction. Heart failure (HF) risks from other anti-HER2 therapies are less clear.

Objectives

Using World Health Organization pharmacovigilance data, the authors compared HF odds across anti-HER2 regimens.

Methods

In VigiBase, 41,976 patients had adverse drug reactions (ADRs) with anti-HER2 monoclonal antibodies (trastuzumab, n = 16,900; pertuzumab, n = 1,856), antibody-drug conjugates (trastuzumab emtansine [T-DM1], n = 3,983; trastuzumab deruxtecan, n = 947), and tyrosine kinase inhibitors (afatinib, n = 10,424; lapatinib, n = 5,704; neratinib, n = 1,507; tucatinib, n = 655); additionally, 36,052 patients had ADRs with anti-HER2-based combination regimens. Most patients had breast cancer (monotherapies, n = 17,281; combinations, n = 24,095). Outcomes included comparison of HF odds with each monotherapy relative to trastuzumab, within each therapeutic class, and among combination regimens.

Results

Of 16,900 patients with trastuzumab-associated ADRs, 2,034 (12.04%) had HF reports (median time to onset 5.67 months; IQR: 2.85-9.32 months) compared with 1% to 2% with antibody-drug conjugates. Trastuzumab had higher odds of HF reporting relative to other anti-HER2 therapies collectively in the overall cohort (reporting OR [ROR]: 17.37; 99% CI: 14.30-21.10) and breast cancer subgroup (ROR: 17.10; 99% CI: 13.12-22.27). Pertuzumab/T-DM1 had 3.4 times higher odds of HF reporting than T-DM1 monotherapy; tucatinib/trastuzumab/capecitabine had similar odds as tucatinib. Among metastatic breast cancer regimens, HF odds were highest with trastuzumab/pertuzumab/docetaxel (ROR: 1.42; 99% CI: 1.17-1.72) and lowest with lapatinib/capecitabine (ROR: 0.09; 99% CI: 0.04-0.23).

Conclusions

Trastuzumab and pertuzumab/T-DM1 had higher odds of HF reporting than other anti-HER2 therapies. These data provide large-scale, real-world insight into which HER2-targeted regimens would benefit from left ventricular ejection fraction monitoring.

Angiotensin-(1-7) reduces doxorubicin-induced aortic arch dysfunction in male and female juvenile Sprague Dawley rats through pleiotropic mechanisms

Doxorubicin (Dox), an effective chemotherapeutic, can cause cumulative dose-dependent cardiovascular toxicity, which may manifest as vascular dysfunction leading to long-term end-organ damage. Currently, there are no effective treatments to mitigate Dox-induced vascular damage in cancer patients, particularly pediatric patients. We showed that angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide hormone, mitigated cardiac damage in Dox-treated juvenile rats. In this study assessing aortic stiffness, juvenile male and female rats were administered a clinically equivalent dose of Dox (21-24 mg/kg) over 6 weeks, in the presence and absence of Ang-(1-7) [24 µg/kg/h]. Aortic function was measured using echocardiography. Ang-(1-7) reduced the Dox-mediated increase in pulse wave velocity, a measure of arterial stiffness (males: p < 0.05; females: p < 0.001) as compared in control animals. Dox decreased aortic lumen diameter (p < 0.0001) and increased wall thickness (p < 0.01) in males, which was attenuated by Ang-(1-7). In male but not female aortic arches, Dox increased media hypertrophy (p < 0.05) and reduced elastin content (p < 0.001), which were prevented by Ang-(1-7). Conversely, Dox increased fibrosis (p < 0.0001) in juvenile female rats, which was reduced by Ang-(1-7). Adjunct Ang-(1-7) prevented the Dox-induced increase in total cell and nuclear pERK1/2 in the aortic intima and media of male rats and nuclear pSMAD2 in the intimal and medial regions of the aortic arches of both sexes. These results demonstrate that Ang-(1-7) attenuated Dox-induced aortic dysfunction in both sexes of juvenile rats, albeit through different mechanisms, suggesting that Ang-(1-7) may serve as an effective adjuvant to ameliorate cardiovascular and long-term end-organ damage in pediatric patients produced by anthracyclines.

Systems analysis of miRNA biomarkers to inform drug safety

microRNAs (miRNAs or miRs) are short non-coding RNA molecules which have been shown to be dysregulated and released into the extracellular milieu as a result of many drug and non-drug-induced pathologies in different organ systems. Consequently, circulating miRs have been proposed as useful biomarkers of many disease states, including drug-induced tissue injury. miRs have shown potential to support or even replace the existing traditional biomarkers of drug-induced toxicity in terms of sensitivity and specificity, and there is some evidence for their improved diagnostic and prognostic value. However, several pre-analytical and analytical challenges, mainly associated with assay standardization, require solutions before circulating miRs can be successfully translated into the clinic. This review will consider the value and potential for the use of circulating miRs in drug-safety assessment and describe a systems approach to the analysis of the miRNAome in the discovery setting, as well as highlighting standardization issues that at this stage prevent their clinical use as biomarkers. Highlighting these challenges will hopefully drive future research into finding appropriate solutions, and eventually circulating miRs may be translated to the clinic where their undoubted biomarker potential can be used to benefit patients in rapid, easy to use, point-of-care test systems.

A Targeted Metabolomics-Based Assay Using Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Identifies Structural and Functional Cardiotoxicity Potential

Implementing screening assays that identify functional and structural cardiotoxicity earlier in the drug development pipeline has the potential to improve safety and decrease the cost and time required to bring new drugs to market. In this study, a metabolic biomarker-based assay was developed that predicts the cardiotoxicity potential of a drug based on changes in the metabolism and viability of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). Assay development and testing was conducted in 2 phases: (1) biomarker identification and (2) targeted assay development. In the first phase, metabolomic data from hiPSC-CM spent media following exposure to 66 drugs were used to identify biomarkers that identified both functional and structural cardiotoxicants. Four metabolites that represent different metabolic pathways (arachidonic acid, lactic acid, 2'-deoxycytidine, and thymidine) were identified as indicators of cardiotoxicity. In phase 2, a targeted, exposure-based biomarker assay was developed that measured these metabolites and hiPSC-CM viability across an 8-point concentration curve. Metabolite-specific predictive thresholds for identifying the cardiotoxicity potential of a drug were established and optimized for balanced accuracy or sensitivity. When predictive thresholds were optimized for balanced accuracy, the assay predicted the cardiotoxicity potential of 81 drugs with 86% balanced accuracy, 83% sensitivity, and 90% specificity. Alternatively, optimizing the thresholds for sensitivity yields a balanced accuracy of 85%, 90% sensitivity, and 79% specificity. This new hiPSC-CM-based assay provides a paradigm that can identify structural and functional cardiotoxic drugs that could be used in conjunction with other endpoints to provide a more comprehensive evaluation of a drug's cardiotoxicity potential.

Disparities in Cardiovascular Disease Risk Among Hispanic Breast Cancer Survivors in a Population-Based Cohort

Background

Breast cancer is the leading cause of cancer death among Hispanic women. The aim of our study was to estimate cardiovascular disease (CVD) risk among Hispanic and non-Hispanic White (NHW) breast cancer survivors compared with their respective general population cohorts.

Methods

Cohorts of 17 469 breast cancer survivors (1774 Hispanic and 15 695 NHW) in the Utah Cancer Registry diagnosed between 1997 and 2016, and 65 866 women (6209 Hispanic and 59 657 NHW) from the general population in the Utah Population Database were identified. Cox proportional hazards models were used to estimate hazard ratios (HRs) for CVD.

Results

The risk of diseases of the circulatory system was higher in Hispanic than NHW breast cancer survivors 1-5 years after cancer diagnosis, in comparison with their respective general population cohorts (HR_Hispanic = 1.94, 99% confidence interval [CI] = 1.49 to 2.53; H_NHW = 1.38, 99% CI = 1.33 to 1.43; 2-sided P_{heterogeneity} = .01, respectively). Increased risks were observed for both Hispanic and NHW breast cancer survivors for diseases of the heart and the veins and lymphatics, compared with the general population cohorts. More than 5 years after cancer diagnosis, elevated risk of diseases of the veins and lymphatics persisted in both ethnicities. The CVD risk due to chemotherapy and hormone therapy was higher in Hispanic than NHW breast cancer survivors but did not differ for distant stage, higher baseline comorbidities, or baseline smoking.

Conclusions

We observed a risk difference for diseases of the circulatory system between Hispanic and NHW breast cancer survivors compared with their respective general population cohorts but only within the first 5 years of cancer diagnosis.

Role of Oxidative Stress in the Mechanisms of Anthracycline-Induced Cardiotoxicity: Effects of Preventive Strategies

Anthracycline-induced cardiotoxicity (AIC) persists as a significant cause of morbidity and mortality in cancer survivors. Although many protective strategies have been evaluated, cardiotoxicity remains an ongoing threat. The mechanisms of AIC remain unclear; however, several pathways have been proposed, suggesting a multifactorial origin. When the central role of topoisomerase 2β in the pathophysiology of AIC was described some years ago, the classical reactive oxygen species (ROS) hypothesis shifted to a secondary position. However, new insights have reemphasized the importance of the role of oxidative stress-mediated signaling as a common pathway and a critical modulator of the different mechanisms involved in AIC. A better understanding of the mechanisms of cardiotoxicity is crucial for the development of treatment strategies. It has been suggested that the available therapeutic interventions for AIC could act on the modulation of oxidative balance, leading to a reduction in oxidative stress injury. These indirect antioxidant effects make them an option for the primary prevention of AIC. In this review, our objective is to provide an update of the accumulated knowledge on the role of oxidative stress in AIC and the modulation of the redox balance by potential preventive strategies.

Global Longitudinal Strain: Is It Time to Change the Preoperative Cardiac Assessment of Oncology Patients?

The introduction of new anticancer treatment modalities has improved survival rates, transforming cancer into a chronic disease in many instances. One of the most devastating complications of cancer treatment is cancer therapy-related cardiac dysfunction. Adequate preoperative assessment of any significant cancer therapy-related cardiac impairment is critical, and may be missed with conventional measures. The assessment of global longitudinal strain by speckle-tracking echocardiography is more sensitive for the early detection of cardiac contractility before a decline in ejection fraction can be discovered. Global longitudinal strain can also predict postoperative cardiac dysfunction, which makes it a good alternative for preoperative cardiac assessment in the oncology population when cancer therapies have been administered that can alter normal performance.

p38δ genetic ablation protects female mice from anthracycline cardiotoxicity

The efficacy of an anthracycline antibiotic doxorubicin (DOX) as a chemotherapeutic agent is limited by dose-dependent cardiotoxicity. DOX is associated with activation of intracellular stress signaling pathways including p38 MAPKs. While previous studies have implicated p38 MAPK signaling in DOX-induced cardiac injury, the roles of the individual p38 isoforms, specifically, of the alternative isoforms p38γ and p38δ, remain uncharacterized. We aimed to determine the potential cardioprotective effects of p38γ and p38δ genetic deletion in mice subjected to acute DOX treatment. Male and female wild-type (WT), p38γ-/-, p38δ-/-, and p38γ-/-δ-/- mice were injected with 30 mg/kg DOX and their survival was tracked for 10 days. During this period, cardiac function was assessed by echocardiography and electrocardiography and fibrosis by Picro Sirius Red staining. Immunoblotting was performed to assess the expression of signaling proteins and markers linked to autophagy. Significantly improved survival was observed in p38δ-/- female mice post-DOX relative to WT females, but not in p38γ-/- or p38γ-/-δ-/- male or female mice. The improved survival in DOX-treated p38δ-/- females was associated with decreased fibrosis, increased cardiac output and LV diameter relative to DOX-treated WT females, and similar to saline-treated controls. Structural and echocardiographic parameters were either unchanged or worsened in all other groups. Increased autophagy, as suggested by increased LC3-II level, and decreased mammalian target of rapamycin activation was also observed in DOX-treated p38δ-/- females. p38δ plays a crucial role in promoting DOX-induced cardiotoxicity in female mice by inhibiting autophagy. Therefore, p38δ targeting could be a potential cardioprotective strategy in anthracycline chemotherapy.NEW & NOTEWORTHY This study for the first time identifies the sex-specific roles of the alternative p38γ and p38δ MAPK isoforms in promoting doxorubicin (DOX) cardiotoxicity. We show that p38δ and p38γ/δ systemic deletion was cardioprotective in female but not in male mice. Cardiac structure and function were preserved in DOX-treated p38δ-/- females and autophagy marker was increased.

Cardiac Damage in Anthracyclines Therapy: Focus on Oxidative Stress and Inflammation

Significance: Despite their serious side effects, anthracyclines (ANTs) are the most prescribed chemotherapeutic drugs because of their strong efficacy in both solid and hematological tumors. A major limitation to ANTs clinical application is the severe cardiotoxicity observed both acutely and chronically. The mechanism underlying cardiac dysfunction under chemotherapy is mainly dependent on the generation of oxidative stress and systemic inflammation, both of which lead to progressive cardiomyopathy and heart failure. Recent Advances: Over the years, the iatrogenic ANTs-induced cardiotoxicity was believed to be simply given by iron metabolism and reactive oxygen species production; however, several experimental data indicate that ANTs may use alternative damaging mechanisms, such as topoisomerase 2β inhibition, inflammation, pyroptosis, immunometabolism, and autophagy. Critical Issues: In this review, we aimed at discussing ANTs-induced cardiac injury from different points of view, updating and focusing on oxidative stress and inflammation, since these pathways are not exclusive or independent from each other but they together importantly contribute to the complexity of ANTs-induced multifactorial cardiotoxicity. Future Directions: A deeper understanding of the mechanistic signaling leading to ANTs side effects could reveal crucial targeting molecules, thus representing strategic knowledge to promote better therapeutic efficacy and lower cardiotoxicity during clinical application.

Angiotensin-(1–7) reduces doxorubicin-induced cardiac dysfunction in male and female Sprague-Dawley rats through antioxidant mechanisms

Doxorubicin (Dox) is an effective chemotherapeutic for a variety of pediatric malignancies. Unfortunately, Dox administration often results in a cumulative dose-dependent cardiotoxicity that manifests with marked oxidative stress, leading to heart failure. Adjunct therapies are needed to mitigate Dox cardiotoxicity and enhance quality of life in pediatric patients with cancer. Angiotensin-(1–7) [Ang-(1–7)] is an endogenous hormone with cardioprotective properties. This study investigated whether adjunct Ang-(1–7) attenuates cardiotoxicity resulting from exposure to Dox in male and female juvenile rats. Dox significantly reduced body mass, and the addition of Ang-(1–7) had no effect. However, adjunct Ang-(1–7) prevented Dox-mediated diastolic dysfunction, including markers of decreased passive filling as measured by reduced early diastole mitral valve flow velocity peak ( E) ( P < 0.05) and early diastole mitral valve annulus peak velocity ( e′; P < 0.001) and increased E/e′ ( P < 0.001), an echocardiographic measure of diastolic dysfunction. Since Dox treatment increases reactive oxygen species (ROS), the effect of Ang-(1–7) on oxidative by-products and enzymes that generate or reduce ROS was investigated. In hearts of male and female juvenile rats, Dox increased NADPH oxidase 4 ( P < 0.05), a major cardiovascular NADPH oxidase isozyme that generates ROS, as well as 4-hydroxynonenal ( P < 0.001) and malondialdehyde ( P < 0.001), markers of lipid peroxidation; Ang-(1–7) prevented these effects of Dox. Cotreatment with Dox and Ang-(1–7) increased the antioxidant enzymes SOD1 (male: P < 0.05; female: P < 0.01) and catalase ( P < 0.05), which likely contributed to reduced ROS. These results demonstrate that Ang-(1–7) prevents diastolic dysfunction in association with a reduction in ROS, suggesting that the heptapeptide hormone may serve as an effective adjuvant to improve Dox-induced cardiotoxicity.

NEW & NOTEWORTHY Ang-(1–7) is a clinically safe peptide hormone with cardioprotective and antineoplastic properties that could be used as an adjuvant therapy to improve cancer treatment and mitigate the long-term cardiotoxicity associated with doxorubicin in pediatric patients with cancer.

Cardiac Adverse Events in EGFR-Mutated Non-Small Cell Lung Cancer Treated With Osimertinib

OBJECTIVES

The purpose of this study was to assess osimertinib-associated cardiac adverse events (AEs) in a real-world setting, using a retrospective single-center cohort study in Japan.

BACKGROUND

Cases of osimertinib-associated cardiac AEs have been reported but remain poorly understood.

METHODS

A total of 123 cases of advanced non-small cell lung cancer (NSCLC) with confirmed EGFR mutations who received osimertinib monotherapy from 2014 to 2019 at the Osaka International Cancer Institute (Osaka, Japan) were evaluated. Cardiac AEs were defined according to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Changes in left ventricular ejection fraction (LVEF) and rates of cancer therapeutics-related cardiac dysfunction (CTRCD), defined as a ≥10 % absolute decline in LVEF from baseline to a value of <53%, were further assessed in 36 patients in whom serial measurements of LVEF were obtained before and during osimertinib treatment.

RESULTS

Severe cardiac AEs (CTCAE grade 3 or higher) occurred in 6 patients (4.9%) after osimertinib administration. These AEs included acute myocardial infarction (n = 1), heart failure with reduced LVEF (n = 3), and valvular heart disease (n = 2). Five of the 6 patients had a history of cardiovascular risk factors or disease. Myocardial biopsies in 2 of the patients showed cardiomyocyte hypertrophy and lipofuscin deposition. In 36 patients assessed with serial LVEF, LVEF declined from 69.4 ± 4.2% to 63.4 ± 10.5% with osimertinib therapy (p < 0.001). CTRCD occurred in 4 patients with a nadir LVEF of 40.3 ± 9.1% with osimertinib.

CONCLUSIONS

In this retrospective cohort analysis, the incidence of cardiac AEs in patients treated with osimertinib was 4.9%. Additional prospective data collected from patients with NSCLC treated with osimertinib will be important in understanding the incidence, pathophysiology, and management of cardiac AEs with osimertinib.

Role of oxidative stress in cardiotoxicity of antineoplastic drugs

Tumors and heart disease are two of the leading causes of human death. With the development of anti-cancer therapy, the survival rate of cancer patients has been significantly improved. But at the same time, the incidence of cardiovascular adverse events caused by cancer treatment has also been considerably increased, such as arrhythmia, left ventricular (LV) systolic and diastolic dysfunction, and even heart failure (HF), etc., which seriously affects the quality of life of cancer patients. More importantly, the occurrence of adverse events may lead to the adjustment or the cessation of anti-cancer treatment, which affects the survival rate of patients. Understanding the mechanism of cardiotoxicity (CTX) induced by antineoplastic drugs is the basis of adequate protection of the heart without impairing the efficacy of antineoplastic therapy. Based on current research, a large amount of evidence has shown that oxidative stress (OS) plays an essential role in CTX induced by antineoplastic drugs and participates in its toxic reaction directly and indirectly. Here, we will review the mechanism of action of OS in cardiac toxicity of antineoplastic drugs, to provide new ideas for researchers, and provide further guidance for clinical prevention and treatment of cardiac toxicity of anti-tumor drugs in the future.

A recommended practical approach to the management of anthracycline-based chemotherapy cardiotoxicity: an opinion paper of the working group on drug cardiotoxicity and cardioprotection, Italian Society of Cardiology

Anthracyclines are the mainstay of treatment of a variety of haematological malignancies and solid tumours. Unfortunately, the clinical use of these drugs is limited by cumulative, dose-related cardiotoxicity which may ultimately lead to a severe and irreversible form of cardiomyopathy. Thus, there is an increasing need for close cooperation among cardiologists, oncologists and haemato-oncologists. As anthracyclines save lives, the logical goal of this cooperation, besides preventing or mitigating cardiotoxicity, is to promote an acceptable balance between the potential cardiac side effects and the vital benefit of anticancer treatment. This manuscript, which is specifically addressed to the cardiologist who has not accumulated much experience in the field of cancer therapy, focuses on several topics, that is old and new mechanisms of cardiac toxicity, late cardiac toxicity, the importance of overall risk assessment, the key role of a cardiology consult before starting cancer therapy, and the pros and cons of primary and secondary prevention programmes.

Protective Effect of Tetrandrine on Doxorubicin-Induced Cardiotoxicity in Rats

Aims and background

Doxorubicin (Dox) is effective in curative and adjuvant chemotherapy of malignant tumors. Cardiotoxicity is the chief toxic effect that limits the clinical use of Dox. We studied the effects of tetrandrine (Tet) on doxorubicin-induced cardiotoxicity in rats and its protective activity.

Materials and methods

Sprague-Dawley rats were randomly divided into the following 4 groups: a control group (received only saline), Dox group (received only Dox), Tet/Dox group (received Tet plus Dox), and Tet group (received only Tet). Rats were injected intravenously with 2 mg/kg Dox once a week for 7 weeks and 50 mg/kg Tet was administered intraperitoneally weekly for 7 weeks. Measurements of cardiac contractile parameters including LSVP, +dP/dt max and -dP/dt max, and assessment of electrocardiograms were carried out. Mitochondrial oxidation and phosphorylation state 3 (S3) and state 4 (S4) respiration were measured. Respiration control rate (RCR) and the ADP/O ratio were calculated. Cardiac ultrastructure was examined by electron microscopy.

Results

Dox induced significant cardiotoxicity in this rat model. The values of LSVP, +dP/dt max, and -dP/dt max in the Tet/Dox group increased as compared to the Dox group (P <0.05). The cardiac contraction and relaxation improved on Tet administration. Tet inhibited the prolonged QT interval on the electrocardiogram in Dox-treated rats. Compared to the Dox group, the values of S3, RCR, and ADP/O increased by more than 28%, 48%, and 27%, respectively, in the Tet/Dox group. Significant cardiac morphological protection was observed in the Tet/Dox-treated rats.

Conclusion

Tet can improve the reduced cardiac function caused by Dox treatment and prevent Dox-induced mitochondrial impairment in rat cardiotoxicity.

Exposure to Amphetamines Leads to Development of Amphetamine Type Stimulants Associated Cardiomyopathy (ATSAC)

With rapidly rising prevalence of exposure to Amphetamine Type Stimulants (ATS), novel insights into cardiotoxic effects of this substance are being presented in the literature and remarkably ATS Associated Cardiomyopathy (ATSAC) is emerging as a novel cardiovascular condition with its distinctive pathogenesis, risk factors, clinical features and prognosis. A comprehensive systematic review was performed to explore and analyze the current evidence on the association between ATS exposure and development of cardiomyopathy, biological mechanisms involved in pathogenesis of ATSAC, risk factors, clinical features and course of patients with ATSAC. Several animal studies, case reports, case series and case-control studies support the association between ATS exposure and ATSAC. Oxidative stress, accelerated apoptosis, increased p53 activity, cardiomyocyte necrosis, perfusion defects, fatty acid toxicity, altered gene expression, abnormal cardiac protein synthesis and function in addition to defects in intracellular calcium hemostasis present themselves as likely mechanisms of cardiotoxicity in ATSAC. Majority of patients with ATSAC were found to be male, young and presented late with severe dilated cardiomyopathy. Female ATS users predominantly develop Takotsubo type of ATSAC and in particular its atypical basal variant. Overall, cessation of ATS exposure seems to be associated with some degree of reversibility and recovery in ATSAC sufferers.

Incidence, Diagnosis, and Treatment of Cardiac Toxicity from Trastuzumab in Patients with Breast Cancer

PURPOSE OF REVIEW

Treatment with trastuzumab is a cornerstone of human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer treatment, but carries an unfortunate risk of toxicity to the cardiovascular system. Here we review recent findings on trastuzumab-associated cardiotoxicity, focusing on its incidence, diagnosis, and treatment.

RECENT FINDINGS

Screening with multigated acquisition scan (MUGA) or echocardiogram (ECHO) is recommended to assess cardiac function prior to and during trastuzumab therapy. Because trastuzumab-induced cardiotoxicity is typically reversible, cessation of trastuzumab and/or administration of first line heart failure agents effectively restores cardiac function in most cases. Severe trastuzumab-induced cardiotoxicity is rare enough that the risk-benefit ratio still weighs in favor of its use in the vast majority of patients with HER2+ breast cancer.

SUMMARY

An improved understanding of the pathophysiology underlying trastuzumab-induced cardiotoxicity and the identification of patients at highest risk will allow us to continue to safely administer trastuzumab in patients with breast cancer.

Doxorubicin enhances oxysterol levels resulting in a LXR-mediated upregulation of cardiac cholesterol transporters

The anthracycline-mediated cardiotoxicity is still not completely understood. To examine the impact of cholesterol metabolism and transport in this context, cholesterol and oxysterol levels as well as the expression of the cholesterol transporters ABCA1 and ABCG1 were analyzed in doxorubicin-treated HL-1 murine cardiomyocytes as well as in mouse model for acute doxorubicin-induced cardiotoxicity. Doxorubicin-treated HL-1 cells exhibited enhanced cholesterol (153±20% of control), oxysterol (24S-hydroxycholesterol: 206±29% of control) and cholesterol precursor levels (lathosterol: 122±12% of control; desmosterol: 188±10% of control) indicating enhanced cholesterol synthesis. Moreover, abca1 and abcg1 were upregulated on mRNA, protein and functional level caused by a doxorubicin-mediated activation of the nuclear receptor LXR. In addition, the oxysterols not only induced the abca1 and abcg1 in HL-1 cells but also enhanced the expression of endothelin-1 and transforming growth factor-β, which have already been identified as important factors in doxorubicin-induced cardiotoxicity. These in vitro findings were verified in a murine model for acute doxorubicin-induced cardiotoxicity, demonstrating elevated cardiac (2.1±0.2vs. 3.6±1.0ng/mg) and systemic cholesterol levels (105.0±8.4vs. 130.0±4.3mg/dl), respectively, as well as enhanced oxysterol levels such as cardiac 24S-hydroxycholesterol (2.1±0.2vs. 3.6±1.0ng/mg). In line with these findings cardiac mRNA expression of abca1 (303% of control) and abcg1 (161% of control) was induced. Taken together, our data demonstrate enhanced cholesterol and oxysterol levels by doxorubicin, resulting in a LXR-dependent upregulation of abca1 and abcg1. In this context, the cytotoxic effects of oxysterols and their impact on cardiac gene expression should be considered as an important factor in doxorubicin-induced cardiotoxicity.

Rationale and design of the multidisciplinary team IntervenTion in cArdio-oNcology study (TITAN)

BACKGROUND

Cancer is the leading cause of premature death in Canada. In the last decade, important gains in cancer survival have been achieved by advances in adjuvant treatment. However, many oncologic treatments also result in cardiovascular "toxicity". Furthermore, cardiac risk factors such as hypertension, dyslipidemia, and diabetes mellitus are known to contribute to the progression of cardiac damage and clinical cardiotoxicity. As such, for many survivors, the risk of death from cardiac disease exceeds that of recurrent cancer. While provision of care by multidisciplinary teams has been shown to reduce mortality and hospitalizations among heart failure patients, the effect of assessments and interventions by multidisciplinary specialists in cancer patients receiving cardiotoxic chemotherapy regimens is currently unknown. Accordingly, we will examine the effect of a multi-disciplinary team interventions in the early assessment, identification and treatment of cardiovascular risk factors in cancer patients receiving adjuvant systemic therapy. Our main hypothesis is to determine if the incidence of LV dysfunction in cancer patients undergoing adjuvant therapy can be reduced through a multidisciplinary team approach.

METHODS/DESIGN

This is a randomized study comparing intensive multidisciplinary team intervention to usual care in the prevention of LV remodeling in patients receiving anthracycline or trastuzumab-based chemotherapy. Main objectives include early detection strategies for cardiotoxicity using novel biomarkers that reflect myocardial injury, remodeling and/or dysfunction; early identification and intensive treatment of cardiovascular risk factors; and early intervention with supportive care strategies including nutritional and pharmacist counselling, exercise training and cardiology team support. Secondary objectives include correlation of novel biomarkers to clinical outcomes; correlation of multidisciplinary interventions to adverse clinical outcomes; relationship of multidisciplinary interventions and chemotherapy dose density; preservation of lean muscle mass; and patient reported outcomes (symptom intensity and quality of life).

DISCUSSION

Cardiac toxicity as a result of cancer therapies is now recognized as a significant health problem of increasing prevalence. To our knowledge, TITAN will be the first randomized trial examining the utility of multidisciplinary team care in the prevention of cardiotoxicity. We expect our results to inform comprehensive and holistic care for patients at risk for negative cancer therapy mediated sequelae.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01621659 Registration Date 4 June 2012.

Nilotinib reverses ABCB1/P-glycoprotein-mediated multidrug resistance but increases cardiotoxicity of doxorubicin in a MDR xenograft model

The BCR-Abl tyrosine kinase inhibitor (TKI), nilotinib, was developed to surmount resistance or intolerance to imatinib in patients with Philadelphia-positive chronic myelogenous leukemia. Recent studies have shown that nilotinib induces potent sensitization to anticancer agents by blocking the functions of ABCB1/P-glycoprotein (P-gp) in multidrug resistance (MDR). However, changes in P-gp expression or function affect the cardiac disposition and prolong the presence of both doxorubicin (DOX) and doxorubicinol (DOXol) in cardiac tissue, thus, enhancing the risk of cardiotoxicity. In this study, we used a MDR xenograft model to evaluate the antitumor activity, tissue distribution and cardiotoxicity of DOX when co-administered with nilotinib. This information will provide more insight into the pharmacological role of nilotinib in MDR reversal and the risk of DOX cardiotoxicity. Our results showed that nilotinib significantly enhanced DOX cytotoxicity and increased intracellular rhodamine 123 accumulation in MG63/DOX cells in vitro and strongly enhanced DOX inhibition of growth of P-gp-overexpressing MG63/DOX cell xenografts in nude mice. Additionally, nilotinib significantly increased DOX and DOXol accumulation in serum, heart, liver and tumor tissues. Importantly, nilotinib induced a disproportionate increase in DOXol in cardiac tissue. In the co-administration group, CBR1 and AKR1A1 protein levels were significantly increased in cardiac tissue, with more severe necrosis and vacuole formation. These results indicate that nilotinib reverses P-gp- mediated MDR by blocking the efflux function and potentiates DOX-induced cardiotoxicity. These findings represent a guide for the design of future clinical trials and studies of pharmacokinetic interactions and may be useful in guiding the use of nilotinib in combination therapy of cancer in clinical practice.

Doxorubicin induced heart failure: Phenotype and molecular mechanisms

Long term survival of childhood cancers is now more than 70%. Anthracyclines, including doxorubicin, are some of the most efficacious anticancer drugs available. However, its use as a chemotherapeutic agent is severely hindered by its dose-limiting toxicities. Most notably observed is cardiotoxicity, but other organ systems are also degraded by doxorubicin use. Despite the years of its use and the amount of information written about this drug, an understanding of its cellular mechanisms is not fully appreciated. The mechanisms by which doxorubicin induces cytotoxicity in target cancer cells have given insight about how the drug damages cardiomyocytes. The major mechanisms of doxorubicin actions are thought to be as an oxidant generator and as an inhibitor of topoisomerase 2. However, other signaling pathways are also invoked with significant consequences for the cardiomyocyte. Further the interaction between oxidant generation and topoisomerase function has only recently been appreciated and the consequences of this interaction are still not fully understood. The unfortunate consequences of doxorubicin within cardiomyocytes have promoted the search for new drugs and methods that can prevent or reverse the damage caused to the heart after treatment in cancer patients. Alternative protocols have lessened the impact on newly diagnosed cancer patients. However the years of doxorubicin use have generated a need for monitoring the onset of cardiotoxicity as well as understanding its potential long-term consequences. Although a fairly clear understanding of the short-term pathologic mechanisms of doxorubicin actions has been achieved, the long-term mechanisms of doxorubicin induced heart failure remain to be carefully delineated.

Blueberry Anthocyanins-Enriched Extracts Attenuate Cyclophosphamide-Induced Cardiac Injury

We sought to explore the effect of blueberry anthocyanins-enriched extracts (BAE) on cyclophosphamide (CTX)-induced cardiac injury. The rats were divided randomly into five groups including normal control, CTX 100 mg/kg, BAE 80mg/kg, CTX+BAE 20mg/kg and CTX+BAE 80mg/kg groups. The rats in the three BAE-treated groups were administered BAE for four weeks. Seven days after BAE administration, rats in CTX group and two BAE-treated groups were intraperitoneally injected with a single dose of 100 mg/kg CTX. Cardiac injury was assessed using physiological parameters, Echo, morphological staining, real-time PCR and western blot. In addition, cardiotoxicity indices, inflammatory cytokines expression and oxidative stress markers were also detected. Four weeks 20mg/kg and 80mg/kg dose of BAE treatment following CTX exposure attenuated mean arterial blood pressure, heart rate and activities of heart enzymes, improved cardiac dysfunction, left ventricular hypertrophy and fibrosis. Importantly, BAE also attenuated CTX-induced LV leukocyte infiltration and inflammatory cytokines expression, ameliorated oxidative stress as well as cardiomyocyte apoptosis. In conclusion, BAE attenuated the CTX-induced cardiac injury and the protective mechanisms were related closely to the anti-inflammatory, antioxidant and anti-inflammatory characteristics of BAE.

Losartan treatment attenuates tumor-induced myocardial dysfunction

Fatigue and muscle wasting are common symptoms experienced by cancer patients. Data from animal models demonstrate that angiotensin is involved in tumor-induced muscle wasting, and that tumor growth can independently affect myocardial function, which could contribute to fatigue in cancer patients. In clinical studies, inhibitors of angiotensin converting enzyme (ACE) can prevent the development of chemotherapy-induced cardiovascular dysfunction, suggesting a mechanistic role for the renin-angiotensin-aldosterone system (RAAS). In the present study, we investigated whether an angiotensin (AT) 1-receptor antagonist could prevent the development of tumor-associated myocardial dysfunction.

METHODS AND RESULTS

Colon26 adenocarcinoma (c26) cells were implanted into female CD2F1 mice at 8weeks of age. Simultaneously, mice were administered Losartan (10mg/kg) daily via their drinking water. In vivo echocardiography, blood pressure, in vitro cardiomyocyte function, cell proliferation assays, and measures of systemic inflammation and myocardial protein degradation were performed 19days following tumor cell injection. Losartan treatment prevented tumor-induced loss of muscle mass and in vitro c26 cell proliferation, decreased tumor weight, and attenuated myocardial expression of interleukin-6. Furthermore, Losartan treatment mitigated tumor-associated alterations in calcium signaling in cardiomyocytes, which was associated with improved myocyte contraction velocity, systolic function, and blood pressures in the hearts of tumor-bearing mice.

CONCLUSIONS

These data suggest that Losartan may mitigate tumor-induced myocardial dysfunction and inflammation.

A comparison of cardiomyocyte cytotoxic mechanisms for 5-fluorouracil and its pro-drug capecitabine

1. 5-Fluorouracil (5-FU) and its prodrug capecitabine are key chemotherapeutic agents in the treatment of many gastrointestinal tract adenocarcinomas. In addition to their beneficial antitumor effects, they also possess undesired cardiac toxicity. In the present study, we investigated the cytotoxic mechanisms of 5-FU and capecitabine in freshly isolated rat cardiomyocytes. 2. 5-FU and capecitabine cytotoxicities were associated with reactive oxygen species (ROS) formation, lipid peroxidation and rapid glutathione depletion. Increased intracellular ROS could target mitochondria, and our findings confirmed that the cardiomyocytes mitochondrial membrane potential (ΔΨm) was rapidly decreased by 5-FU and capecitabine. Mitochondrial dysfunction subsequently initiates downstream events that trigger caspase-3 activation, and our results showed that 5-FU and capecitabine activated caspase-3 which leads to apoptosis or necrosis. However, 5-FU acted much more powerful than capecitabine at inducing several cytotoxicity markers in heart cardiomyocytes. In addition, 5-FU but not capecitabine caused lysosomal membrane leakiness when it was incubated with cardiomyocytes. All cytotoxicity markers were prevented by antioxidants, ROS scavengers, mitochondrial permeability transition (MPT) pore sealing agents and lysosomotropic agents. 3. Our findings showed that the cytotoxic action of 5-FU and capecitabine on cardiomyocytes are mediated by oxidative stress and subsequent mitochondrial dysfunction which causes caspase-3 activation and cell death.

Use of wave intensity analysis of carotid arteries in identifying and monitoring left ventricular systolic function dynamics in rabbits

Wave intensity analysis (WIA) of the carotid artery was conducted to determine the changes that occur in left ventricular systolic function after administration of doxorubicin in rabbits. Each randomly selected rabbit was subject to routine ultrasound, WIA of the carotid artery, cardiac catheterization and pathologic examination every week and was followed for 16 wk. The first positive peak (WI1) of the carotid artery revealed that left ventricular systolic dysfunction occurred earlier than conventional indexes of heart function. WI1 was highly, positively correlated with the maximum rate of rise in left ventricular pressure in cardiac catheterization (r = 0.94, p < 0.01) and moderately negatively correlated with the apoptosis index of myocardial cells, an indicator of myocardial damage (r = -0.69, p < 0.01). Ultrasound WIA of the carotid artery sensitively reflects early myocardial damage and cardiac function, and the result is highly consistent with cardiac catheterization findings and the apoptosis index of myocardial cells.

Anthracycline-induced cardiotoxicity: prospective cohort study from Pakistan

OBJECTIVES

To identify anthracycline-induced acute (within 1 month) and early-onset chronic progressive (within 1 year) cardiotoxicity in children younger than 16 years of age with childhood malignancies at a tertiary care centre of Pakistan.

DESIGN

Prospective cohort study.

SETTING

Aga Khan University, Karachi, Pakistan.

PARTICIPANTS

110 children (aged 1 month-16 years).

INTERVENTION

Anthracycline (doxorubicin and/or daunorubicin).

OUTCOME MEASUREMENTS

All children who received anthracycline as chemotherapy and three echocardiographic evaluations (baseline, 1 month and 1 year) between July 2010 and June 2012 were prospectively analysed for cardiac dysfunction. Statistical analysis including systolic and diastolic functions at baseline, 1 month and 1 year was carried out by repeated measures analysis of variance.

RESULTS

Mean age was 74±44 months and 75 (68.2%) were males. Acute lymphoblastic leukaemia was seen in 70 (64%) patients. Doxorubicin alone was used in 59 (54%) and combination therapy was used in 35 (32%). A cumulative dose of anthracycline <300 mg/m(2) was used in 95 (86%). Fifteen (14%) children developed cardiac dysfunction within a month and 28 (25%) children within a year. Of these 10/15 (66.6%) and 12/28 (43%) had isolated diastolic dysfunction, respectively, while 5/15 (33.3%) and 16/28 (57%) had combined systolic and diastolic dysfunction. Seven (6.4%) patients expired due to severe cardiac dysfunction. Eight of 59 (13.5%) children showed dose-related cardiotoxicity (p=<0.001). Cardiotoxicity was also high when the combination of doxorubicin and daunorubicin was used (p=0.004).

CONCLUSIONS

Incidence of anthracycline-induced cardiotoxicity is high. Long-term follow-up is essential to diagnose its late manifestations.

Doxorubicin mediated cardiotoxicity in rats: protective role of felodipine on cardiac indices

Anthracyclines find vital uses in the treatment of solid tumors and other kind of malignancies. A typical side effect observed with few agents of this class is dose-dependent cardiotoxicity. Doxorubicin is one such agent which backs the generation of free radicals through metabolism of its quinone structure. This effect combined with induction of apoptotic and necrotic pathways leads to the development of irreversible cardiotoxicity. Reports showing the cardioprotective effects of felodipine have been published in the past. We chose to evaluate protective effect of felodipine in acute cardiotoxicity in rats induced by single dose of doxorubicin. Felodipine was assessed against doxorubicin-induced cardiotoxicity and we found that felodipine not only improves cardiac marker enzymes (P<0.001 for LDH; P<0.01 for CK-MB) but also prevents damage to myocardial tissue (20.61% necrosed area in doxorubicin intoxication; 11.52% necrosed area in felodipine treated group). Activation of apoptotic pathways is decelerated which is indicated by a significant reduction in myocardial caspase-3 activity (P<0.05) following felodipine pretreatment. Felodipine pretreatment was able to maintain normal cardiac morphology and histoarchitecture. Gravimetric analysis revealed beneficial effects following felodipine pretreatment. Abnormalities seen in the ECG after doxorubicin treatment were normalized to a significant extent (ST interval normalization was significant at P<0.01) in felodipine treated rats. In itself, felodipine was not found to have any detrimental effects on the myocardium or hemodynamic parameters of rats. Findings of the study suggest that pretreatment with felodipine prevents doxorubicin induced cardiotoxicity.

Role of oxidants on calcium and sodium movement in healthy and diseased cardiac myocytes

In this review article we give an overview of current knowledge with respect to redox-sensitive alterations in Na(+) and Ca(2+) handling in the heart. In particular, we focus on redox-activated protein kinases including cAMP-dependent protein kinase A (PKA), protein kinase C (PKC), and Ca/calmodulin-dependent protein kinase II (CaMKII), as well as on redox-regulated downstream targets such as Na(+) and Ca(2+) transporters and channels. We highlight the pathological and physiological relevance of reactive oxygen species and some of its sources (such as NADPH oxidases, NOXes) for excitation-contraction coupling (ECC). A short outlook with respect to the clinical relevance of redox-dependent Na(+) and Ca(2+) imbalance will be given.

Ionizing radiation regulates cardiac Ca handling via increased ROS and activated CaMKII

Ionizing radiation (IR) is an integral part of modern multimodal anti-cancer therapies. IR involves the formation of reactive oxygen species (ROS) in targeted tissues. This is associated with subsequent cardiac dysfunction when applied during chest radiotherapy. We hypothesized that IR (i.e., ROS)-dependently impaired cardiac myocytes’ Ca handling might contribute to IR-dependent cardiocellular dysfunction. Isolated ventricular mouse myocytes and the mediastinal area of anaesthetized mice (that included the heart) were exposed to graded doses of irradiation (sham 4 and 20 Gy) and investigated acutely (after ~1 h) as well as chronically (after ~1 week). IR induced a dose-dependent effect on myocytes’ systolic function with acutely increased, but chronically decreased Ca transient amplitudes, which was associated with an acutely unaltered but chronically decreased sarcoplasmic reticulum (SR) Ca load. Likewise, in vivo echocardiography of anaesthetized mice revealed acutely enhanced left ventricular contractility (strain analysis) that declined after 1 week. Irradiated myocytes showed persistently increased diastolic SR Ca leakage, which was acutely compensated by an increase in SR Ca reuptake. This was reversed in the chronic setting in the face of slowed relaxation kinetics. As underlying cause, acutely increased ROS levels were identified to activate Ca/calmodulin-dependent protein kinase II (CaMKII). Accordingly, CaMKII-, but not PKA-dependent phosphorylation sites of the SR Ca release channels (RyR2, at Ser-2814) and phospholamban (at Thr-17) were found to be hyperphosphorylated following IR. Conversely, ROS-scavenging as well as CaMKII-inhibition significantly attenuated CaMKII-activation, disturbed Ca handling, and subsequent cellular dysfunction upon irradiation. Targeted cardiac irradiation induces a biphasic effect on cardiac myocytes Ca handling that is associated with chronic cardiocellular dysfunction. This appears to be mediated by increased oxidative stress and persistently activated CaMKII. Our findings suggest impaired cardiac myocytes Ca handling as a so far unknown mediator of IR-dependent cardiac damage that might be of relevance for radiation-induced cardiac dysfunction.

Early detection of anthracycline-mediated cardiotoxicity: the value of considering both global longitudinal left ventricular strain and twist

Anthracyclines are important anticancer drugs, but their use is limited by cardiotoxicity. Left ventricular ejection fraction (LVEF) is often inadequate to detect myocardial disease induced by chemotherapy. Tissue Doppler and bidimensional-strain imaging could detect LV myocardial dysfunction earlier than LVEF. In drug-induced cardiotoxicity, torsional and longitudinal LV deformations [LV twist (LVtw), radial strain (GRS), global longitudinal strain (GLS)] are damaged. We assessed whether a new index, GLS×LVtw, could predict future anthracycline-induced cardiomyopathy. Echocardiography, troponin, and natriuretic peptide determination were prospectively performed in 74 patients before and after 6, 12, 24, and 52 weeks of anthracycline treatment. These patients were treated for breast cancer, Hodgkin’s or non-Hodgkin’s lymphoma, acute lymphoblastic or myeloblastic leukaemia, or osteosarcoma. At 6 weeks after initiation of chemotherapy, isovolumic relaxation time, systolic mitral annular velocity, LVGLS, LVGRS, LV apical rotation, LVtw, and GLS×LVtw deteriorated, and troponin levels became elevated (all p < 0.05 by ANOVA) before LVEF decreased. The receiver operating characteristic curves identified early deterioration of GLS×LVtw as the best predictor of later cardiotoxicity (area under curve = 0.93), followed by GLS (0.84) and LV apical rotation (0.81) deterioration. In conclusion, early change in the GLS×LVtw index seems to be a good predictor of future development of anthracycline-induced cardiotoxicity.

Role of cardioprotective therapy for prevention of cardiotoxicity with chemotherapy: a systematic review and meta-analysis

BACKGROUND

Cardiotoxicity is a well-recognised complication of chemotherapy with anthracycline and/or trastuzumab, and its prevention remains an important challenge in cancer survivorship. Several successful preventative strategies have been identified in animal trials. We sought to assemble the clinical evidence that prophylactic pharmacological interventions could prevent left ventricular (LV) dysfunction and heart failure in patients undergoing chemotherapy.

METHODS

We undertook a systemic review of the evidence from randomised trials and observational studies where a prophylactic intervention was compared with a control arm in patients with a normal ejection fraction and no past history of heart failure. The primary outcome was development of heart failure (HF), a drop in ejection fraction (EF) or both. A random-effects model was used to combine relative risks (RR) and 95% confidence intervals (CIs), and a meta-regression was undertaken to assess the impact of potential covariates.

FINDINGS

Data were collated from 14 published articles (n=2015 paediatric and adult patients) comprising 12 randomised controlled trials and two observational studies. The most studied chemotherapeutic agents were anthracyclines, and prophylactic agents included dexrazoxane, statins, beta-blocker and angiotensin antagonists. There were 304 cardiac events in the control arm compared to 83 in the prophylaxis arm (RR=0.31 [95% CI: 0.25-0.39], p<0.00001). Cardiac events were reduced with dexrazoxane (RR=0.35 [95% CI 0.27-0.45], p<0.00001), beta-blockade (RR=0.31 [95% CI 0.16-0.63], p=0.001), statin (RR=0.31 [95% CI 0.13-0.77], p=0.01) and angiotensin antagonists (RR=0.11 [95% CI 0.04-0.29], p<0.0001).

INTERPRETATION

Prophylactic treatment with dexrazoxane, beta-blocker, statin or angiotensin antagonists appear to have similar efficacy for reducing cardiotoxicity.

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.

CaMKII-dependent SR Ca leak contributes to doxorubicin-induced impaired Ca handling in isolated cardiac myocytes

Doxorubicin (DOX) is one of the most effective chemotherapeutic agents, but cardiotoxicity limits DOX therapy. Although the mechanisms are not entirely understood, reactive oxygen species (ROS) appear to be involved in DOX cardiotoxicity. Ca/calmodulin dependent protein kinase II (CaMKII) can be activated by ROS through oxidation and is known to contribute to myocardial dysfunction through Ca leakage from the sarcoplasmic reticulum (SR). We hypothesized that CaMKII contributes to DOX-induced defects in intracellular Ca ([Ca](i)) handling. Cardiac myocytes were isolated from wild-type (WT) adult rat hearts and from mouse hearts lacking the predominant myocardial CaMKII isoform (CaMKIIδ(-/-), KO) vs. WT. Isolated cardiomyocytes were investigated 30 min after DOX (10 μmol/L) superfusion, using epifluorescence and confocal microscopy. Intracellular ROS-generation ([ROS](i)) and [Ca](i) handling properties were assessed. In a subset of experiments, KN-93 or AIP (each 1 μmol/L) were used to inhibit CaMKII. Melatonin (Mel, 100 μmol/L) served as ROS-scavenger. Western blots were performed to determine the amount of CaMKII phosphorylation and oxidation. DOX increased [ROS](i) and led to significant diastolic [Ca](i) overload in rat myocytes. This was associated with reduced [Ca](i) transients, a 5.8-fold increased diastolic SR Ca leak and diminished SR Ca content. ROS-scavenging partially rescued Ca handling. Western blots revealed increased CaMKII phosphorylation, but not CaMKII oxidation after DOX. Pharmacological CaMKII inhibition attenuated diastolic [Ca](i) overload after DOX superfusion and led to partially restored [Ca](i) transients and SR Ca content, presumably due to reduced Ca spark frequency. In line with this concept, isoform-specific CaMKIIδ-KO attenuated diastolic [Ca](i) overload and Ca spark frequency. DOX exposure induces CaMKII-dependent SR Ca leakage, which partially contributes to impaired cellular [Ca](i) homeostasis. Pharmacological and genetic CaMKII inhibition attenuated but did not completely abolish the effects of DOX on [Ca](i). In light of the clinical relevance of DOX, further investigations seem appropriate to determine if CaMKII inhibition could reduce DOX-induced cardiotoxicity.

Acute exposure to doxorubicin results in increased cardiac P-glycoprotein expression

Doxorubicin is a frequently used anticancer drug, but its use is restricted due to the occurrence of severe side effects, namely strong cardiotoxicity. It is known from cancer cells that doxorubicin enhanced the expression of its efflux pump P-glycoprotein (P-gp), which may modulate local drug concentrations. We therefore studied the cardiac expression of P-gp in doxorubicin-treated mice. Mice were treated with doxorubicin, and P-gp expression was studied after 1, 3, and 5 days. Thereby, we could show a significant upregulation of abcb1a (162 ± 15% of control) and abcb1b (418 ± 110% of control) mRNA transcripts after 3 days. On protein level, western blot analysis and immunofluorescence staining revealed a similar finding 5 days after doxorubicin administration. In addition, these results could be confirmed by in vitro models using primary rat cardiomyocytes and the murine cardiomyocyte-like HL-1 cells. Besides an enhanced mRNA and protein expression, doxorubicin-treated HL-1 cells also demonstrated an enhanced P-gp function as assessed by a daunorubicin accumulation assay. Our in vivo and in vitro results demonstrate a cardiac upregulation of P-gp in doxorubicin-treated mice on expression and functional level. This finding may be relevant for cardiac tissue concentrations of P-gp substrates and may represent a mechanism in cardiac self-protection against xenobiotics.

[Non-pegylated doxorubicin (Myocet®) as the less cardiotoxic alternative of free doxorubicin]

Anthracyclines have probably been considered to be the most active agents for the treatment of breast cancer and some other solid tumors and hematological malignancies. However, they are associated with dose-related cardiotoxicity, which can lead to progressive myocardial damage and limits the maximal cumulative dose that can be given. This review focuses on the non-pegylated liposome-encapsulated doxorubicin (Myocet®), which has been developed to increase the therapeutic index of free doxorubicin. The encapsulation of doxorubicin within a macromolecular vector, such as a liposome ("nanoparticle based drug delivery system") reduces its distribution volume, diminishing its toxicity for healthy tissues while increasing the concentration within the neoplastic tissue. The most common adverse event is neutropenia, which is consistent with previous experience with free doxorubicin. Available evidence suggests that the incidence of hematological toxicity is lower than with conventional doxorubicin. Myocet® both as a single agent and in combination is effective and safe with an associated reduction in incidence and severity of cardiac events. Nagykálnai T. Non-pegylated doxorubicin (Myocet®) as the less cardiotoxic alternative of free doxorubicin.

Anticancer therapy induced cardiotoxicity: review of the literature

Innovative anticancer strategies have contributed to an improved survival of patients suffering from malignancies, and in some cases, have turned cancer into a chronic disease. Therefore, the early and particularly late onsets of adverse cardiovascular effects of systemic anticancer treatments are of increasing interest. Among a rapidly increasing variety of anticancer drugs, the anthracyclines and the monoclonal antibody, trastuzumab, are the agents with a well-known cardiotoxicity. The diagnostic work-up, the cardiotoxic risk of anthracyclines and trastuzumab, and additionally, cardiotoxicity as a risk factor of a multimodal therapeutic approach in breast cancer patients is discussed in this study.