Cardioprotective interventions for cancer patients receiving anthracyclines

Cardioprotection and Safety of Dexrazoxane in Patients Treated for Newly Diagnosed T-Cell Acute Lymphoblastic Leukemia or Advanced-Stage Lymphoblastic Non-Hodgkin Lymphoma: A Report of the Children's Oncology Group Randomized Trial Pediatric Oncology Group 9404

PURPOSE

To determine the oncologic efficacy, cardioprotective effectiveness, and safety of dexrazoxane added to chemotherapy that included a cumulative doxorubicin dose of 360 mg/m(2) to treat children and adolescents with newly diagnosed T-cell acute lymphoblastic leukemia (T-ALL) or lymphoblastic non-Hodgkin lymphoma (L-NHL).

PATIENTS AND METHODS

Patients were treated on Pediatric Oncology Group Protocol POG 9404, which included random assignment to treatment with or without dexrazoxane given as a bolus infusion immediately before every dose of doxorubicin. Cardiac effects were assessed by echocardiographic measurements of left ventricular function and structure.

RESULTS

Of 573 enrolled patients, 537 were eligible, evaluable, and randomly assigned to an arm with or without dexrazoxane. The 5-year event-free survival (with standard error) did not differ between groups: 77.2% (2.7%) for the dexrazoxane group versus 76.0% (2.7%) for the doxorubicin-only group (P = .9). The frequencies of severe grade 3 or 4 hematologic toxicity, infection, CNS events, and toxic deaths were similar in both groups (P ranged from .26 to .64). Of 11 second malignancies, eight occurred in patients who received dexrazoxane (P = .17). The mean left ventricular fractional shortening, wall thickness, and thickness-to-dimension ratio z scores measured 3 years after diagnosis were worse in the doxorubicin-alone group (n = 55 per group; P ≤ .01 for all comparisons). Mean fractional shortening z scores measured 3.5 to 6.4 years after diagnosis remained diminished and were lower in the 21 patients who received doxorubicin alone than in the 31 patients who received dexrazoxane (-2.03 v -0.24; P ≤ .001).

CONCLUSION

Dexrazoxane was cardioprotective and did not compromise antitumor efficacy, did not increase the frequencies of toxicities, and was not associated with a significant increase in second malignancies with this doxorubicin-containing chemotherapy regimen. We recommend dexrazoxane as a cardioprotectant for children and adolescents who have malignancies treated with anthracyclines.

Dexrazoxane Diminishes Doxorubicin-Induced Acute Ovarian Damage and Preserves Ovarian Function and Fecundity in Mice

Advances in cancer treatment utilizing multiple chemotherapies have dramatically increased cancer survivorship. Female cancer survivors treated with doxorubicin (DXR) chemotherapy often suffer from an acute impairment of ovarian function, which can persist as long-term, permanent ovarian insufficiency. Dexrazoxane (Dexra) pretreatment reduces DXR-induced insult in the heart, and protects in vitro cultured murine and non-human primate ovaries, demonstrating a drug-based shield to prevent DXR insult. The present study tested the ability of Dexra pretreatment to mitigate acute DXR chemotherapy ovarian toxicity in mice through the first 24 hours post-treatment, and improve subsequent long-term fertility throughout the reproductive lifespan. Adolescent CD-1 mice were treated with Dexra 1 hour prior to DXR treatment in a 1:1 mg or 10:1 mg Dexra:DXR ratio. During the acute injury period (2-24 hours post-injection), Dexra pretreatment at a 1:1 mg ratio decreased the extent of double strand DNA breaks, diminished γH2FAX activation, and reduced subsequent follicular cellular demise caused by DXR. In fertility and fecundity studies, dams pretreated with either Dexra:DXR dose ratio exhibited litter sizes larger than DXR-treated dams, and mice treated with a 1:1 mg Dexra:DXR ratio delivered pups with birth weights greater than DXR-treated females. While DXR significantly increased the "infertility index" (quantifying the percentage of dams failing to achieve pregnancy) through 6 gestations following treatment, Dexra pretreatment significantly reduced the infertility index following DXR treatment, improving fecundity. Low dose Dexra not only protected the ovaries, but also bestowed a considerable survival advantage following exposure to DXR chemotherapy. Mouse survivorship increased from 25% post-DXR treatment to over 80% with Dexra pretreatment. These data demonstrate that Dexra provides acute ovarian protection from DXR toxicity, improving reproductive health in a mouse model, suggesting this clinically available drug may provide ovarian protection for cancer patients.

Systems biology approaches to adverse drug effects: the example of cardio-oncology

Increased awareness of the cardiovascular toxic effects of chemotherapy has led to the emergence of cardio-oncology (or onco-cardiology), which focuses on screening, monitoring and treatment of patients with cardiovascular dysfunctions resulting from chemotherapy. Anthracyclines, such as doxorubicin, and HER2 inhibitors, such as trastuzumab, both have cardiotoxic effects. The biological rationale, mechanisms of action and cardiotoxicity profiles of these two classes of drugs, however, are completely different, suggesting that cardiotoxic effects can occur in a range of different ways. Advances in genomics and proteomics have implicated several genomic variants and biological pathways that can influence the susceptibility to cardiotoxicity from these, and other drugs. Established pathways include multidrug resistance proteins, energy utilization pathways, oxidative stress, cytoskeletal regulation and apoptosis. Gene-expression profiles that have revealed perturbed pathways have vastly increased our knowledge of the complex processes involved in crosstalk between tumours and cardiac function. Utilization of mathematical and computational modelling can complement pharmacogenomics and improve individual patient outcomes. Such endeavours should enable identification of variations in cardiotoxicity, particularly in those patients who are at risk of not recovering, even with the institution of cardioprotective therapy. The application of systems biology holds substantial potential to advance our understanding of chemotherapy-induced cardiotoxicity.

Late Mortality After Dexrazoxane Treatment: A Report From the Children's Oncology Group

PURPOSE

Given concerns that dexrazoxane may reduce treatment efficacy, induce second cancers, and thus compromise overall survival among children, we examined long-term overall and cause-specific mortality and disease relapse rates from three randomized clinical trials.

PATIENTS AND METHODS

Children's Oncology Group trials P9404 (T-cell acute lymphoblastic leukemia/lymphoma; n = 537), P9425 (intermediate/high-risk Hodgkin lymphoma; n = 216), and P9426 (low-risk Hodgkin lymphoma; n = 255) were conducted between 1996 and 2001. Each trial randomly assigned patients to doxorubicin with or without dexrazoxane. The dexrazoxane:doxorubicin dose ratio was 10:1, and the cumulative protocol-specified doxorubicin dose was 100 to 360 mg/m(2). Dexrazoxane was given as an intravenous bolus before each doxorubicin dose. Data from all three trials were linked with the National Death Index to determine overall and cause-specific mortality by dexrazoxane status.

RESULTS

Among 1,008 patients (507 received dexrazoxane) with a median follow-up of 12.6 years (range, 0 to 15.5 years), 132 died (67 received dexrazoxane). Overall mortality did not vary by dexrazoxane status (12.8% with dexrazoxane at 10 years v 12.2% without; hazard ratio [HR], 1.03; 95% CI, 0.73 to 1.45). Findings were similar when each trial was examined separately. Dexrazoxane also was not significantly associated with differential causes of death. The original cancer caused 76.5% of all deaths (HR, 0.90; 95% CI, 0.61 to 1.32) followed by second cancers (13.6% of deaths; HR, 1.24; 95% CI, 0.49 to 3.15). Specifically, dexrazoxane was not associated with deaths from acute myeloid leukemia/myelodysplasia or cardiovascular events.

CONCLUSION

Among pediatric patients with leukemia or lymphoma, after extended follow-up, dexrazoxane use did not seem to compromise long-term survival.

Tumor RNA disruption predicts survival benefit from breast cancer chemotherapy

In a prior substudy of the CAN-NCIC-MA.22 clinical trial (ClinicalTrials.gov identifier NCT00066443), we observed that neoadjuvant chemotherapy reduced tumor RNA integrity in breast cancer patients, a phenomenon we term "RNA disruption." The purpose of the current study was to assess in the full patient cohort the relationship between mid-treatment tumor RNA disruption and both pCR post-treatment and, subsequently, disease-free survival (DFS) up to 108 months post-treatment. To meet these objectives, we developed the RNA disruption assay (RDA) to quantify RNA disruption and stratify it into 3 response zones of clinical importance. Zone 1 is a level of RNA disruption inadequate for pathologic complete response (pCR); Zone 2 is an intermediate level, while Zone 3 has high RNA disruption. The same RNA disruption cut points developed for pCR response were then utilized for DFS. Tumor RDA identified >fourfold more chemotherapy non-responders than did clinical response by calipers. pCR responders were clustered in RDA Zone 3, irrespective of tumor subtype. DFS was about 2-fold greater for patients with tumors in Zone 3 compared to Zone 1 patients. Kaplan-Meier survival curves corroborated these findings that high tumor RNA disruption was associated with increased DFS. DFS values for patients in zone 3 that did not achieve a pCR were similar to that of pCR recipients across tumor subtypes, including patients with hormone receptor positive tumors that seldom achieve a pCR. RDA appears superior to pCR as a chemotherapy response biomarker, supporting the prospect of its use in response-guided chemotherapy.

Unbalanced upregulation of ryanodine receptor 2 plays a particular role in early development of daunorubicin cardiomyopathy

Calcium release channel on the sarcoplasmic reticulum of cardiomyocytes (ryanodine receptor type 2, RyR2) plays a critical role in the regulation of calcium and was identified as a crucial factor for development of chronic anthracycline cardiomyopathy. Its early stages are less well described although these determine the later development. Hence, we tested the effect of repeated, short-term anthracycline (daunorubicin) administration on cardiac performance, cardiomyocyte function and accompanied changes in calcium regulating proteins expression. Ten-twelve weeks old male Wistar rats were administered with 6 doses of daunorubicin (DAU, 3 mg/kg, i.p., every 48 h), controls (CON) received vehicle. Left ventricular function (left ventricular pressure, LVP; rate of pressure development, +dP/dt and decline, -dP/dt) was measured using left ventricular catheterization under tribromethanol anaesthesia (15 ml/kg b.w.). Cell shortening was measured in enzymatically isolated cardiomyocytes. The expressions of RyR2 and associated intracellular calcium regulating proteins, cytoskeletal proteins (alpha-actinin, alpha-tubul in) as well as oxidative stress regulating enzymes (gp91phox, MnSOD) were detected in ventricular tissue samples using immunoblotting. mRNA expressions of cardiac damage markers (Nppa and Nppb, atrial and brain natriuretic peptides; Myh6, Myh7 and Myh7b, myosin heavy chain alpha and beta) were detected using RT-PCR. Thiobarbituric acid reactive substances concentration was measured to estimate oxidative stress. DAU rats exhibited significantly depressed left ventricular features (LVP by 14%, +dP/dt by 36% and -dP/dt by 30%; for all P<0.05), in line with concomitant increase in Nppa and Nppb gene expressions (3.23- and 2.18-fold, for both P<0.05), and a 4.34-fold increase in Myh7 (P<0.05). Controversially, we observed increased cell shortening of isolated cardiac cells by 31% (p<0.05). DAU administration was associated with a twofold upregulation of RyR2 (P<0.05), but not of other examined Ca(2+) regulating proteins remained. In addition, we observed a significant reduction in alpha-tubulin (by 46% when compared to CON P<0.05). Indicators of oxidative injury were unaffected. In conclusion, unbalanced RyR2 overexpression plays a particular role in early development of daunorubicin cardiomyopathy characterized by discrepant in situ versus in vitro cardiac performance.

Dissecting the Mechanisms of Doxorubicin and Oxidative Stress-Induced Cytotoxicity: The Involvement of Actin Cytoskeleton and ROCK1

We have recently reported that ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has superior anti-apoptotic and pro-survival effects than antioxidants against doxorubicin, a chemotherapeutic drug. Although oxidative stress is the most widely accepted mechanism, our studies suggest that ROCK1-dependent actin cytoskeleton remodeling plays a more important role in mediating doxorubicin cytotoxicity on MEFs. To further explore the contributions of ROCK1-dependent actin cytoskeleton remodeling in response to stress, this study investigates the mechanistic differences between the cytotoxic effects of doxorubicin versus hydrogen peroxide (H2O2), with a focus on cytoskeleton alterations, apoptosis and necrosis induction. We found that both types of stress induce caspase activation but with different temporal patterns and magnitudes in MEFs: H2O2 induces the maximal levels (2 to 4-fold) of activation of caspases 3, 8, and 9 within 4 h, while doxorubicin induces much higher maximal levels (15 to 25-fold) of caspases activation at later time points (16-24 h). In addition, necrosis induced by H2O2 reaches maximal levels within 4 h while doxorubicin-induced necrosis largely occurs at 16-24 h secondary to apoptosis. Moreover, both types of stress induce actin cytoskeleton remodeling but with different characteristics: H2O2 induces disruption of stress fibers associated with cytosolic translocation of phosphorylated myosin light chain (p-MLC) from stress fibers, while doxorubicin induces cortical F-actin formation associated with cortical translocation of p-MLC from central stress fibers. Furthermore, N-acetylcysteine (an antioxidant) is a potent suppressor for H2O2-induced cytotoxic effects including caspase activation, necrosis, and cell detachment, but shows a much reduced inhibition on doxorubicin-induced changes. On the other hand, ROCK1 deficiency is a more potent suppressor for the cytotoxic effects induced by doxorubicin than by H2O2. These results support the notion that doxorubicin induces caspase activation, necrosis, and actin cytoskeleton alterations largely through ROCK1-dependent and oxidative stress-independent pathways.

Chemotherapy-related Cardiomyopathy

Advances in chemotherapeutic agents have resulted in significantly improved cancer survival rates. Cardiac toxicity, however, has emerged as a leading cause of morbidity, both during and years after treatment. One of the most common manifestations of cardiotoxicity is that of heart failure and left ventricular systolic dysfunction. In this review, current opinions and guidelines in this field are discussed, with particular focus on the most common culprits, the anthracyclines, and the monoclonal antibody, trastuzumab.

The prevention, detection and management of cancer treatment-induced cardiotoxicity: a meta-review

BACKGROUND

The benefits associated with some cancer treatments do not come without risk. A serious side effect of some common cancer treatments is cardiotoxicity. Increased recognition of the public health implications of cancer treatment-induced cardiotoxicity has resulted in a proliferation of systematic reviews in this field to guide practice. Quality appraisal of these reviews is likely to limit the influence of biased conclusions from systematic reviews that have used poor methodology related to clinical decision-making. The aim of this meta-review is to appraise and synthesise evidence from only high quality systematic reviews focused on the prevention, detection or management of cancer treatment-induced cardiotoxicity.

METHODS

Using Cochrane methodology, we searched databases, citations and hand-searched bibliographies. Two reviewers independently appraised reviews and extracted findings. A total of 18 high quality systematic reviews were subsequently analysed, 67 % (n = 12) of these comprised meta-analyses.

RESULTS

One systematic review concluded that there is insufficient evidence regarding the utility of cardiac biomarkers for the detection of cardiotoxicity. The following strategies might reduce the risk of cardiotoxicity: 1) The concomitant administration of dexrazoxane with anthracylines; 2) The avoidance of anthracyclines where possible; 3) The continuous administration of anthracyclines (>6 h) rather than bolus dosing; and 4) The administration of anthracycline derivatives such as epirubicin or liposomal-encapsulated doxorubicin instead of doxorubicin. In terms of management, one review focused on medical interventions for treating anthracycline-induced cardiotoxicity during or after treatment of childhood cancer. Neither intervention (enalapril and phosphocreatine) was associated with statistically significant improvement in ejection fraction or mortality.

CONCLUSION

This review highlights the lack of high level evidence to guide clinical decision-making with respect to the detection and management of cancer treatment-associated cardiotoxicity. There is more evidence with respect to the prevention of this adverse effect of cancer treatment. This evidence, however, only applies to anthracycline-based chemotherapy in a predominantly adult population. There is no high-level evidence to guide clinical decision-making regarding the prevention, detection or management of radiation-induced cardiotoxicity.

Recommendations for cardiomyopathy surveillance for survivors of childhood cancer: a report from the International Late Effects of Childhood Cancer Guideline Harmonization Group

Survivors of childhood cancer treated with anthracycline chemotherapy or chest radiation are at an increased risk of developing congestive heart failure. In this population, congestive heart failure is well recognised as a progressive disorder, with a variable period of asymptomatic cardiomyopathy that precedes signs and symptoms. As a result, several clinical practice guidelines have been developed independently to help with detection and treatment of asymptomatic cardiomyopathy. These guidelines differ with regards to definitions of at-risk populations, surveillance modality and frequency, and recommendations for interventions. Differences between these guidelines could hinder the effective implementation of these recommendations. We report on the results of an international collaboration to harmonise existing cardiomyopathy surveillance recommendations using an evidence-based approach that relied on standardised definitions for outcomes of interest and transparent presentation of the quality of the evidence. The resultant recommendations were graded according to the quality of the evidence and the potential benefit gained from early detection and intervention.

The catalytic topoisomerase II inhibitor dexrazoxane induces DNA breaks, ATF3 and the DNA damage response in cancer cells

BACKGROUND AND PURPOSE

The catalytic topoisomerase II inhibitor dexrazoxane has been associated not only with improved cancer patient survival but also with secondary malignancies and reduced tumour response.

EXPERIMENTAL APPROACH

We investigated the DNA damage response and the role of the activating transcription factor 3 (ATF3) accumulation in tumour cells exposed to dexrazoxane.

KEY RESULTS

Dexrazoxane exposure induced topoisomerase IIα (TOP2A)-dependent cell death, γ-H2AX accumulation and increased tail moment in neutral comet assays. Dexrazoxane induced DNA damage responses, shown by enhanced levels of γ-H2AX/53BP1 foci, ATM (ataxia telangiectasia mutated), ATR (ATM and Rad3-related), Chk1 and Chk2 phosphorylation, and by p53 accumulation. Dexrazoxane-induced γ-H2AX accumulation was dependent on ATM. ATF3 protein was induced by dexrazoxane in a concentration- and time-dependent manner, which was abolished in TOP2A-depleted cells and in cells pre-incubated with ATM inhibitor. Knockdown of ATF3 gene expression by siRNA triggered apoptosis in control cells and diminished the p53 protein level in both control and dexrazoxane -treated cells. This was accompanied by increased γ-H2AX accumulation. ATF3 knockdown also delayed the repair of dexrazoxane -induced DNA double-strand breaks.

CONCLUSIONS AND IMPLICATIONS

As with other TOP2A poisons, dexrazoxane induced DNA double-strand breaks followed by activation of the DNA damage response. The DNA damage-triggered ATF3 controlled p53 accumulation and generation of double-strand breaks and is proposed to serve as a switch between DNA damage and cell death following dexrazoxane treatment. These findings suggest a mechanistic explanation for the diverse clinical observations associated with dexrazoxane.

Individual prediction of heart failure among childhood cancer survivors

PURPOSE

To create clinically useful models that incorporate readily available demographic and cancer treatment characteristics to predict individual risk of heart failure among 5-year survivors of childhood cancer.

PATIENTS AND METHODS

Survivors in the Childhood Cancer Survivor Study (CCSS) free of significant cardiovascular disease 5 years after cancer diagnosis (n = 13,060) were observed through age 40 years for the development of heart failure (ie, requiring medications or heart transplantation or leading to death). Siblings (n = 4,023) established the baseline population risk. An additional 3,421 survivors from Emma Children's Hospital (Amsterdam, the Netherlands), the National Wilms Tumor Study, and the St Jude Lifetime Cohort Study were used to validate the CCSS prediction models.

RESULTS

Heart failure occurred in 285 CCSS participants. Risk scores based on selected exposures (sex, age at cancer diagnosis, and anthracycline and chest radiotherapy doses) achieved an area under the curve of 0.74 and concordance statistic of 0.76 at or through age 40 years. Validation cohort estimates ranged from 0.68 to 0.82. Risk scores were collapsed to form statistically distinct low-, moderate-, and high-risk groups, corresponding to cumulative incidences of heart failure at age 40 years of 0.5% (95% CI, 0.2% to 0.8%), 2.4% (95% CI, 1.8% to 3.0%), and 11.7% (95% CI, 8.8% to 14.5%), respectively. In comparison, siblings had a cumulative incidence of 0.3% (95% CI, 0.1% to 0.5%).

CONCLUSION

Using information available to clinicians soon after completion of childhood cancer therapy, individual risk for subsequent heart failure can be predicted with reasonable accuracy and discrimination. These validated models provide a framework on which to base future screening strategies and interventions.

Dexrazoxane abrogates acute doxorubicin toxicity in marmoset ovary

Preservation of ovarian function following chemotherapy for nonovarian cancers is a formidable challenge. For prepubescent girls, the only option to prevent chemotherapy damage to the ovary is ovarian tissue cryopreservation, an experimental procedure requiring invasive surgeries to harvest and reimplant tissue, which carries the risk of cancer reintroduction. Drugs that block the primary mechanism of chemotherapy insult, such as dexrazoxane (Dexra) in the context of anthracycline chemotherapy, provide a novel approach for ovarian protection and have the potential to overcome current limitations to oncofertility treatment. Dexra is a catalytic topoisomerase 2 inhibitor that protects the mouse ovary from acute doxorubicin (DXR) chemotherapy toxicity in vitro by preventing DXR-induced DNA damage and subsequent gammaH2AX activation. To translate acute DXR ovarian insult and Dexra protection from mouse to nonhuman primate, freshly obtained marmoset ovarian tissue was cultured in vitro and treated with vehicle or 20 μM Dexra 1 h prior to 50 nM DXR. Cultured ovarian tissue was harvested at 2, 4, or 24 h post-DXR treatment. Dexra prevented DXR-induced DNA double-strand breaks as quantified by the neutral comet assay. DXR treatment for 24 h increased gammaH2AX phosphorylation, specifically increasing the number of foci-positive granulosa cells in antral follicles, while Dexra pretreatment inhibited DXR-induced gammaH2AX phosphorylation foci formation. Additionally, Dexra pretreatment trended toward attenuating DXR-induced AKT1 phosphorylation and caspase-9 activation as assayed by Western blots of ovarian tissue lysates. The combined findings suggest Dexra prevents primary DXR-induced DNA damage, the subsequent cellular response to DNA damage, and may diminish early apoptotic signaling in marmoset ovarian tissue. This study provides initial translation of Dexra protection against acute ovarian DXR toxicity from mice to marmoset monkey tissue.

Dexrazoxane may prevent doxorubicin-induced DNA damage via depleting both topoisomerase II isoforms

BACKGROUND

The bisdioxopiperazine dexrazoxane (DRZ) prevents anthracycline-induced heart failure, but its clinical use is limited by uncertain cardioprotective mechanism and by concerns of interference with cancer response to anthracyclines and of long-term safety.

METHODS

We investigated the effects of DRZ on the stability of topoisomerases IIα (TOP2A) and IIβ (TOP2B) and on the DNA damage generated by poisoning these enzymes by the anthracycline doxorubicin (DOX).

RESULTS

DRZ given i.p. transiently depleted in mice the predominant cardiac isoform Top2b. The depletion was also seen in H9C2 cardiomyocytes and it was attenuated by mutating the bisdioxopiperazine binding site of TOP2B. Consistently, the accumulation of DOX-induced DNA double strand breaks (DSB) by wild-type, although not by mutant TOP2B, was reduced by DRZ. In contrast, the DRZ analogue ICRF-161, which is capable of iron chelation but not of TOP2B binding and cardiac protection, did not deplete TOP2B and did not prevent the accumulation of DOX-induced DSB. TOP2A, re-expressed in cultured cardiomyocytes by fresh serum, was depleted by DRZ along with TOP2B. DRZ depleted TOP2A also from fibrosarcoma-derived cells, but not from lung cancer-derived and human embryo-derived cells. DRZ-mediated TOP2A depletion reduced the accumulation of DOX-induced DSB.

CONCLUSIONS

Taken together, our data support a model of anthracycline-induced heart failure caused by TOP2B-mediated DSB and of its prevention by DRZ via TOP2B degradation rather than via iron chelation. The depletion of TOP2B and TOP2A suggests an explanation for the reported DRZ interference with cancer response to anthracyclines and for DRZ side-effects.

Use of biomarkers for the assessment of chemotherapy-induced cardiac toxicity

OBJECTIVES

To review the evidence for the use of various biomarkers in the detection of chemotherapy associated cardiac damage.

DESIGN AND METHODS

Pubmed.gov was queried using the search words chemotherapy and cardiac biomarkers with the filters of past 10years, humans, and English language. An emphasis was placed on obtaining primary research articles looking at the utility of biomarkers for the detection of chemotherapy-mediated cardiac injury.

RESULTS

Biomarkers may help identify patients undergoing treatment who are at high risk for cardiotoxicity and may assist in identification of a low risk cohort that does not necessitate continued intensive screening. cTn assays are the best studied biomarkers in this context and may represent a promising and potentially valuable modality for detecting cardiac toxicity in patients undergoing chemotherapy. Monitoring cTnI levels may provide information regarding the development of cardiac toxicity before left ventricular dysfunction becomes apparent on echocardiography or via clinical symptoms. A host of other biomarkers have been evaluated for their utility in the field of chemotherapy related cardiac toxicity with intermittent success; further trials are necessary to determine what role they may end up playing for prediction and prognostication in this setting.

CONCLUSIONS

Biomarkers represent an exciting potential complement or replacement for echocardiographic monitoring of chemotherapy related cardiac toxicity which may allow for earlier realization of the degree of cardiac damage occurring during treatment, creating the opportunity for more timely modulation of therapy.

Cardiomyopathy associated with cancer therapy

Chemotherapy-associated cardiomyopathy is a well known cardiotoxicity of contemporary cancer treatment and a cause of increasing concern for both cardiologists and oncologists. As cancer outcomes improve, cardiovascular disease has become a leading cause of morbidity and mortality among cancer survivors. Asymptomatic or symptomatic left ventricular systolic dysfunction in the setting of cardiotoxic chemotherapy is an important entity to recognize. Early diagnosis of cardiac injury through the use of novel blood-based biomarkers or noninvasive imaging modalities may allow for the initiation of cardioprotective medications or modification of chemotherapy regimen to minimize or prevent further damage. Several clinical trials are currently underway to determine the efficacy of cardioprotective medications for the prevention of chemotherapy-associated cardiomyopathy. Implementing a strategy that includes both early detection and prevention of cardiotoxicity will likely have a significant impact on the overall prognosis of cancer survivors. Continued coordination of care between cardiologists and oncologists remains critical to maximizing the oncologic benefit of cancer therapy while minimizing any early or late cardiovascular effects.

Managing chemotherapy-related cardiotoxicity in survivors of childhood cancers

In the US, children diagnosed with cancer are living longer, but not without consequences from the same drugs that cured their cancer. In these patients, cardiovascular disease is the leading cause of non-cancer-related morbidity and mortality. Although this review focuses on anthracycline-related cardiomyopathy in childhood cancer survivors, the global lifetime risk of other cardiovascular diseases such as atherosclerosis, arrhythmias and intracardiac conduction abnormalities, hypertension, and stroke also are increased. Besides anthracyclines, newer molecularly targeted agents, such as vascular endothelial growth factor receptor and tyrosine kinase inhibitors, also have been associated with acute hypertension, cardiomyopathy, and increased risk of ischemic cardiac events and arrhythmias, and are summarized here. This review also covers other risk factors for chemotherapy-related cardiotoxicity (including both modifiable and non-modifiable factors), monitoring strategies (including both blood and imaging-based biomarkers) during and following cancer treatment, and discusses the management of cardiotoxicity (including prevention strategies such as cardioprotection by use of dexrazoxane).

An update on cardio-oncology

Over the past decades, there have been great advancements in the survival outcome of patients with cancer. As a consequence, treatment regimens are being extended to patient populations that would not have qualified in the past based on comorbidities and age. Furthermore, the anti-cancer regimens, which have been and are being used, can cause considerable morbidity and even mortality. In fact, new drugs such as tyrosine kinase inhibitors have yielded unanticipated side effects in frequency and severity. The cardiovascular disease spectrum is an important element in all of these. In order to optimize the outcome of cancer patients with cardiovascular diseases existing prior to cancer treatment or developing as a consequence of it, a new discipline called "cardio-oncology" has evolved over the past few years. Herein, we review the latest developments in this field including cardiotoxicities, vascular toxicities, and arrhythmias. This field is taking on more shape as cardiologists, oncologists, and hematologists are forming alliances, programs, and clinics, supported by the development of expert consensus statements on best management approaches and care of the cancer patient with cardiovascular diseases.

Cardiotoxicity and cardioprotection in childhood cancer

Children diagnosed with cancer are now living longer as a result of advances in treatment. However, some commonly used anticancer drugs, although effective in curing cancer, can also cause adverse late effects. The cardiotoxic effects of anthracycline chemotherapy, such as doxorubicin, and radiation can cause persistent and progressive cardiovascular damage, emphasizing a need for effective prevention and treatment to reduce or avoid cardiotoxicity. Examples of risk factors for cardiotoxicity in children include higher anthracycline cumulative dose, higher dose of radiation, younger age at diagnosis, female sex, trisomy 21 and black race. However, not all who are exposed to toxic treatments experience cardiotoxicity, suggesting the possibility of a genetic predisposition. Cardioprotective strategies under investigation include the use of dexrazoxane, which provides short- and long-term cardioprotection in children treated with doxorubicin without interfering with oncological efficacy, the use of less toxic anthracycline derivatives and nutritional supplements. Evidence-based monitoring and screening are needed to identify early signs of cardiotoxicity that have been validated as surrogates of subsequent clinically significant cardiovascular disease before the occurrence of cardiac damage, in patients who may be at higher risk.

Prevention of diabetes-induced cardiovascular complications upon treatment with antioxidants

Oxidative stress is considered to play an important role in the pathogenesis of diabetes-induced cardiovascular disease (CVD), which is invariably associated with abnormal blood lipid profile, insulin resistance and metabolic syndrome. Stress, smoking, high saturated fat intake as well as low fruit and vegetable intakes have been shown to increase oxidative stress and hyperlipidemia, which increase the predisposition of diabetic subjects to atherosclerosis, stroke and coronary heart disease. The oxidation of low-density lipoprotein by oxidative stress is essential for the development of atherosclerosis, and the reduction in oxidative stress as well as blood glucose and cholesterol is considered critical for the prevention of diabetes-induced CVD. Although epidemiological studies have demonstrated that vitamin C and vitamin E decrease the incidence of coronary heart disease, different clinical trials have failed to support the beneficial effect of these antioxidants. Nonetheless, it has been suggested that natural forms of these vitamins may be more efficacious than synthetic vitamins, and this may explain the inconsistencies in results. Antioxidants, N-acetyl-L-cysteine and resveratrol, have also been shown to attenuate the diabetes-induced cardiovascular complications. It has been indicated that the antioxidant therapy may be effective in a prevention strategy rather than as a treatment for CVD. The evidence presented here supports the view that cardiovascular complications in diabetes may be induced by oxidative stress and appropriate antioxidant therapy may be promising for attenuating the progression of diabetes-induced CVD.

Evaluation and management of patients with heart disease and cancer: cardio-oncology

The care for patients with cancer has advanced greatly over the past decades. A combination of earlier cancer diagnosis and greater use of traditional and new systemic treatments has decreased cancer-related mortality. Effective cancer therapies, however, can result in short- and long-term comorbidities that can decrease the net clinical gain by affecting quality of life and survival. In particular, cardiovascular complications of cancer treatments can have a profound effect on the health of patients with cancer and are more common among those with recognized or unrecognized underlying cardiovascular diseases. A new discipline termed cardio-oncology has thus evolved to address the cardiovascular needs of patients with cancer and optimize their care in a multidisciplinary approach. This review provides a brief introduction and background on this emerging field and then focuses on its practical aspects including cardiovascular risk assessment and prevention before cancer treatment, cardiovascular surveillance and therapy during cancer treatment, and cardiovascular monitoring and management after cancer therapy. The content of this review is based on a literature search of PubMed between January 1, 1960, and February 1, 2014, using the search terms cancer, cardiomyopathy, cardiotoxicity, cardio-oncology, chemotherapy, heart failure, and radiation.

N-acetylcysteine reduces oxidative stress, nuclear factor‑κB activity and cardiomyocyte apoptosis in heart failure

The roles of oxidative stress on nuclear factor (NF)‑κB activity and cardiomyocyte apoptosis during heart failure were examined using the antioxidant N‑acetylcysteine (NAC). Heart failure was established in Japanese white rabbits with intravenous injections of doxorubicin, with ten rabbits serving as a control group. Of the rabbits with heart failure, 12 were not treated (HF group) and 13 received NAC (NAC group). Cardiac function was assessed using echocardiography and hemodynamic analysis. Myocardial cell apoptosis, apoptosis‑related protein expression, NF‑κBp65 expression and activity, total anti‑oxidative capacity (tAOC), 8‑iso‑prostaglandin F2α (8‑iso‑PGF2α) expression and glutathione (GSH) expression levels were determined. In the HF group, reduced tAOC, GSH levels and Bcl‑2/Bax ratios as well as increased 8‑iso‑PGF2α levels and apoptosis were observed (all P<0.05), which were effects that were attenuated by the treatment with NAC. NF‑κBp65 and iNOS levels were significantly higher and the P‑IκB‑α levels were significantly lower in the HF group; expression of all three proteins returned to pre‑HF levels following treatment with NAC. Myocardial cell apoptosis was positively correlated with left ventricular end-diastolic pressure (LVEDP), NF‑κBp65 expression and 8‑iso‑PGF2α levels, but negatively correlated with the maximal and minimal rates of increase in left ventricular pressure (+dp/dtmax and ‑dp/dtmin, respectively) and the Bcl‑2/Bax ratio (all P<0.001). The 8‑iso‑PGF2α levels were positively correlated with LVEDP and negatively correlated with +dp/dtmax and ‑dp/dtmin (all P<0.001). The present study demonstrated that NAC increased the antioxidant capacity, decreased the NF‑κB activation and reduced myocardial cell apoptosis in an in vivo heart failure model.

Cardiac effects of anticancer therapy in the elderly

Cancer incidence increases with age, and as life expectancy increases, the number of elderly patients with cancer is increasing. Cancer treatments, including chemotherapy and radiotherapy, have significant short- and long-term effects on cardiovascular function. These cardiotoxic effects can be acute, such as changes in electrocardiogram (ECG), arrhythmias, ischemia, and pericarditis and/or myocarditis-like syndromes, or they can be chronic, such as ventricular dysfunction. Anticancer therapies can also have indirect effects, such as alterations in blood pressure, or can cause metabolic abnormalities that subsequently increase risk for cardiac events. In this review, we explore both observational and clinical trial evidence of cardiac risk in the elderly. In both observational and clinical trial data, risk of cardiotoxicity with anthracycline-based chemotherapy increases with age. However, it is less clear whether the association between age and cardiotoxicity exists for newer treatments. The association may not be well demonstrated as a result of under-representation of elderly patients in clinical trials and avoidance of these therapies in this population. In addition, we discuss strategies for surveillance and prevention of cardiotoxicity in the elderly. In the elderly, it is important to be aware of the potential for cardiotoxicity during long-term follow-up and to consider both prevention and surveillance of these late effects.

Redox proteomic identification of HNE-bound mitochondrial proteins in cardiac tissues reveals a systemic effect on energy metabolism after doxorubicin treatment

Doxorubicin (DOX), one of the most effective anticancer drugs, is known to generate progressive cardiac damage, which is due, in part, to DOX-induced reactive oxygen species (ROS). The elevated ROS often induce oxidative protein modifications that result in alteration of protein functions. This study demonstrates that the level of proteins adducted by 4-hydroxy-2-nonenal (HNE), a lipid peroxidation product, is significantly increased in mouse heart mitochondria after DOX treatment. A redox proteomics method involving two-dimensional electrophoresis followed by mass spectrometry and investigation of protein databases identified several HNE-modified mitochondrial proteins, which were verified by HNE-specific immunoprecipitation in cardiac mitochondria from the DOX-treated mice. The majority of the identified proteins are related to mitochondrial energy metabolism. These include proteins in the citric acid cycle and electron transport chain. The enzymatic activities of the HNE-adducted proteins were significantly reduced in DOX-treated mice. Consistent with the decline in the function of the HNE-adducted proteins, the respiratory function of cardiac mitochondria as determined by oxygen consumption rate was also significantly reduced after DOX treatment. Treatment with Mn(III) meso-tetrakis(N-n-butoxyethylpyridinium-2-yl)porphyrin, an SOD mimic, averted the doxorubicin-induced mitochondrial dysfunctions as well as the HNE-protein adductions. Together, the results demonstrate that free radical-mediated alteration of energy metabolism is an important mechanism mediating DOX-induced cardiac injury, suggesting that metabolic intervention may represent a novel approach to preventing cardiac injury after chemotherapy.

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.

Cardiotoxicity and oncological treatments

BACKGROUND

Cardiotoxic and other side effects limit the usefulness of treatments for cancer.

METHOD

This article is based on pertinent articles that were retrieved by a selective search in PubMed and other databases, and on the guidelines of the European Society of Cardiology, the Association of Scientific Medical Societies in Germany, and the European Society of Medical Oncology.

RESULTS

Prospective studies have shown that some treatments for cancer are cardiotoxic. The heart damage that they cause can manifest itself as arrhythmia, arterial hypertension, thromboembolism, angina pectoris, myocardial infarction, or heart failure. It has been observed that potentially lethal complications can arise as late as 40 years after treatment of the original cancer. The anthracycline drug doxorubicin, given in a dose of 500 mg/m2 of body surface area, has been found to cause cardiac complications in 4-36% of the patients treated with it. Trastuzumab and epirubicin cause dose-limiting cardiac events in 1.7-5% of patients, depending on the dosage. Paclitaxel causes bradycardia, intracardiac conduction block, or arrhythmia in 0.5% of patients. 18% of patients treated with sunitimib or sorafenib have clinical manifestations relating to the heart (angina pectoris, dyspnea). 5-fluorouracil can cause angina pectoris at the beginning of treatment and rarely causes myocardial infarction. Cardiac radiation therapy, a form of treatment practiced in earlier decades, can cause cardiac complications 20 years after the event. The opportunity to prevent cardiac complications of anthracycline drugs with dexrazoxane is decidedly limited, but initial studies have shown that treatment with beta-blockers and ACE inhibitors lessens the likelihood of cardiotoxic side effects. When cardiac complications arise, the generally applicable rules for the treatment of each type of cardiac problem should be followed. The oncological treatment protocol should be adjusted or switched to one that is less damaging to the heart.

CONCLUSION

Treating physicians need to be thoroughly acquainted with the cardiotoxic effects of anti-cancer drugs so that they can diagnose them early on and avoid jeopardizing the overall success of treatment.

ROCK1 deficiency enhances protective effects of antioxidants against apoptosis and cell detachment

We have recently reported that the homologous Rho kinases, ROCK1 and ROCK2, play different roles in regulating stress-induced stress fiber disassembly and cell detachment, and the ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has remarkable anti-apoptotic, anti-detachment and pro-survival effects against doxorubicin, a chemotherapeutic drug. This study investigated the roles of ROCK isoforms in doxorubicin-induced reactive oxygen species (ROS) generation which is believed to be the major mechanism underlying its cytotoxicity to normal cells, and especially to cardiomyocytes. Different antioxidants have been shown to provide a protective role reported in numerous experimental studies, but clinical trials of antioxidant therapy showed insufficient benefit against the cardiac side effect. We found that both ROCK1-/- and ROCK2-/- MEFs exhibited reduced ROS production in response to doxorubicin treatment. Interestingly, only ROCK1 deficiency, but not ROCK2 deficiency, significantly enhanced the protective effects of antioxidants against doxorubicin-induced cytotoxicity. First, ROCK1 deficiency and N-acetylcysteine (an anti-oxidant) treatment synergistically reduced ROS levels, caspase activation and cell detachment. In addition, the reduction of ROS generation in ROCK1-/- MEFs in response to doxorubicin treatment was in part through inhibiting NADPH oxidase activity. Furthermore, ROCK1 deficiency enhanced the inhibitory effects of diphenyleneiodonium (an inhibitor of NADPH oxidase) on ROS generation and caspase 3 activation induced by doxorubicin. Finally, ROCK1 deficiency had greater protective effects than antioxidant treatment, especially on reducing actin cytoskeleton remodeling. ROCK1 deficiency not only reduced actomyosin contraction but also preserved central stress fiber stability, whereas antioxidant treatment only reduced actomyosin contraction without preserving central stress fibers. These results reveal a novel strategy to enhance the protective effect of antioxidant therapy by targeting the ROCK1 pathway to stabilize the actin cytoskeleton and boost the inhibitory effects on ROS production, apoptosis and cell detachment.

The role of antioxidants in the era of cardio‑oncology

Although most chemotherapeutic drugs have the potential to exert cardiotoxicity, these drugs have been chosen for use in cancer treatment because survival and curability benefits outweigh the risk of these complications. Anthracyclines, for example, are a powerful class of chemotherapeutic agents; however, their use is restricted by dose-related cardiotoxicity. Experimental evidence strongly supports the role of reactive oxygen species in this process, suggesting that antioxidants may be effective in protecting the heart from toxicity. Clinical use of antioxidants to protect the heart during anthracycline chemotherapy has been controversial due to the potential for reduced cytotoxic efficacy toward cancer cells. Results from randomized clinical trials addressing whether antioxidants either reduce the incidence of clinical heart failure among patients undergoing anthracycline-based chemotherapy or reduce the response rates to anthracycline-based chemotherapy have been unclear. While anthracyclines are by far the most well-studied antitumor agents with cardiotoxic properties, evidence now shows that reactive oxygen species may play roles in cardiotoxicity induced by other chemotherapeutic agents such as cyclophosphamide, cisplatin, 5-fluorouracil, and trastuzumab. Thus, in the new era of combination therapy and long-term survival of cancer patients, the use of antioxidants to support cancer therapy should be revisited.

Co-enzyme Q10 supplementation for the primary prevention of cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) remains the number one cause of death and disability worldwide and public health interventions focus on modifiable risk factors, such as diet. Coenzyme Q10 (CoQ10) is an antioxidant that is naturally synthesised by the body and can also be taken as a dietary supplement. Studies have shown that a CoQ10 deficiency is associated with cardiovascular disease.

OBJECTIVES

To determine the effects of coenzyme Q10 supplementation as a single ingredient for the primary prevention of CVD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2013, Issue 11); MEDLINE (Ovid, 1946 to November week 3 2013); EMBASE (Ovid, 1947 to 27 November 2013) and other relevant resources on 2 December 2013. We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) lasting at least three months involving healthy adults or those at high risk of CVD but without a diagnosis of CVD. Trials investigated the supplementation of CoQ10 alone as a single supplement. The comparison group was no intervention or placebo. The outcomes of interest were CVD clinical events and major CVD risk factors, adverse effects and costs. We excluded any trials involving multifactorial lifestyle interventions to avoid confounding.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials for inclusion, abstracted data and assessed the risk of bias.We contacted authors for additional information where necessary.

MAIN RESULTS

We identified six RCTs with a total of 218 participants randomised, one trial awaiting classification and five ongoing trials. All trials were conducted in participants at high risk of CVD, two trials examined CoQ10 supplementation alone and four examined CoQ10 supplementation in patients on statin therapy; we analysed these separately. All six trials were small-scale, recruiting between 20 and 52 participants; one trial was at high risk of bias for incomplete outcome data and one for selective reporting; all studies were unclear in the method of allocation and therefore for selection bias. The dose of CoQ10 varied between 100 mg/day and 200 mg/day and the duration of the interventions was similar at around three months.No studies reported mortality or non-fatal cardiovascular events. None of the included studies provided data on adverse events.Two trials examined the effect of CoQ10 on blood pressure. For systolic blood pressure we did not perform a meta-analysis due to significant heterogeneity. In one trial CoQ10 supplementation had no effect on systolic blood pressure (mean difference (MD) -1.90 mmHg, 95% confidence interval (CI) -13.17 to 9.37, 51 patients randomised). In the other trial there was a statistically significant reduction in systolic blood pressure (MD -15.00 mmHg, 95% CI -19.06 to -10.94, 20 patients randomised). For diastolic blood pressure we performed a random-effects meta-analysis, which showed no evidence of effect of CoQ10 supplementation when these two small trials were pooled (MD -1.62 mmHg, 95% CI -5.2 to 1.96).One trial (51 patients randomised) looked at the effect of CoQ10 on lipid levels. The trial showed no evidence of effect of CoQ10 supplementation on total cholesterol (MD 0.30 mmol/L, 95% CI -0.10 to 0.70), high-density lipoprotein (HDL)-cholesterol (MD 0.02 mmol/L, 95% CI -0.13 to 0.17) or triglycerides (MD 0.05 mmol/L, 95% CI -0.42 to 0.52).Of the four trials that investigated CoQ10 supplementation in patients on statin therapy, three of them showed that simultaneous administration of CoQ10 did not significantly influence lipid levels or systolic blood pressure levels between the two groups. The fourth trial showed a significant increase in the change in total and low-density lipoprotein (LDL)-cholesterol at three months across the four arms of the trial (α-tocopherol, CoQ10, CoQ10 + α-tocopherol and placebo), however the way in which the data were presented meant that we were unable to determine if there was any significant difference between the CoQ10 only and placebo arms. In contrast, there was no significant difference in the change in HDL-cholesterol and triglycerides after three months between the four arms of the trial.

AUTHORS' CONCLUSIONS

There are very few studies to date examining CoQ10 for the primary prevention of CVD. The results from the ongoing studies will add to the evidence base. Due to the small number of underpowered trials contributing to the analyses, the results presented should be treated with caution and further high quality trials with longer-term follow-up are needed to determine the effects on cardiovascular events.

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.

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.

Isorhamnetin protects against doxorubicin-induced cardiotoxicity in vivo and in vitro

Doxorubicin (Dox) is an anthracycline antibiotic for cancer therapy with limited usage due to cardiotoxicity. Isorhamnetin is a nature antioxidant with obvious cardiac protective effect. The aim of this study is going to investigate the possible protective effect of isorhamnetin against Dox-induced cardiotoxicity and its underlying mechanisms. In an in vivo investigation, rats were intraperitoneally (i.p.) administered with Dox to duplicate the model of Dox-induced chronic cardiotoxicity. Daily pretreatment with isorhamnetin (5 mg/kg, i.p.) for 7 days was found to reduce Dox-induced myocardial damage significantly, including the decline of cardiac index, decrease in the release of serum cardiac enzymes and amelioration of heart vacuolation. In vitro studies on H9c2 cardiomyocytes, isorhamnetin was effective to reduce Dox-induced cell toxicity. A further mechanism study indicated that isorhamnetin pretreatment can counteract Dox-induced oxidative stress and suppress the activation of mitochondrion apoptotic pathway and mitogen-activated protein kinase pathway. Isorhamnetin also potentiated the anti-cancer activity of Dox in MCF-7, HepG2 and Hep2 cells. These findings indicated that isorhamnetin can be used as an adjuvant therapy for the long-term clinical use of Dox.

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.

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.

Using germline genomics to individualize pediatric cancer treatments

The amazing successes in cure rates for children with cancer over the last century have come in large part from identifying clinical, genetic, and molecular variables associated with response to therapy in large cooperative clinical trials and stratifying therapies according to the predicted risk of relapse. There is an expanding interest in identifying germline genomic variants, as opposed to genetic variants within the tumor, that are associated with susceptibility to toxicity and for risk of relapse. This review highlights the most important germline pharmacogenetic and pharmacogenomic studies in pediatric oncology. Incorporating germline genomics into risk-adapted therapies will likely lead to safer and more effective treatments for children with cancer.

Lack of effect of coenzyme q10 on doxorubicin cytotoxicity in breast cancer cell cultures

BACKGROUND/HYPOTHESES: Doxorubicin is a standard adjuvant therapy for early-stage breast cancer, and it significantly improves disease-free and overall survival. However, 3% to 20% of breast cancer patients develop chronic cardiomyopathic changes and congestive heart failure because of doxorubicin therapy. Doxorubicin-induced cardiotoxicity is thought to be due to the increased generation of reactive oxygen species within cardiac myocyte mitochondria. Coenzyme Q10 (CoQ10) is a lipid-soluble antioxidant that may protect against mitochondrial reactive oxygen species and thus prevent doxorubicin-induced cardiotoxicity. Despite the potential benefits of CoQ10 in preventing cardiotoxicity, it is not known if CoQ10 diminishes the antineoplastic effects of doxorubicin therapy.

STUDY DESIGN

In vitro cell culture experiments.

METHODS

Breast cancer cell lines (MDA-MB-468 and BT549) were tested for their ability to uptake exogenous CoQ10 using high-performance liquid chromatography. Breast cancer cell lines were then treated with doxorubicin and a range of CoQ10 concentrations to determine the effect of CoQ10 on doxorubicin's cytotoxicity.

RESULTS

This study demonstrated that intracellular and mitochondrial CoQ10 concentrations increased substantially as higher exogenous concentrations were administered to breast cancer cells. CoQ10 had no effect on the ability of doxorubicin to induce apoptosis or inhibit growth or colony formation in both the cell lines tested when applied over a wide dose range, which encompassed typical basal plasma levels and plasma levels above those typically achieved by supplemented patients.

CONCLUSION

The clinical testing of CoQ10 as a supplement to prevent doxorubicin-induced cardiotoxicity requires confidence that it does not decrease the efficacy of chemotherapy. These results support the hypothesis that CoQ10 does not alter the antineoplastic properties of doxorubicin. Further in vivo studies, as well as combination chemotherapy studies, would be reassuring before a large-scale clinical testing of CoQ10 as a cardioprotective drug.