Polyoxyethylene-modified superoxide dismutase reduces side effects of adriamycin and mitomycin C

Recommendations for genetic testing to reduce the incidence of anthracycline-induced cardiotoxicity

AIMS

Anthracycline-induced cardiotoxicity (ACT) occurs in 57% of treated patients and remains an important limitation of anthracycline-based chemotherapy. In various genetic association studies, potential genetic risk markers for ACT have been identified. Therefore, we developed evidence-based clinical practice recommendations for pharmacogenomic testing to further individualize therapy based on ACT risk.

METHODS

We followed a standard guideline development process, including a systematic literature search, evidence synthesis and critical appraisal, and the development of clinical practice recommendations with an international expert group.

RESULTS

RARG rs2229774, SLC28A3 rs7853758 and UGT1A6 rs17863783 variants currently have the strongest and the most consistent evidence for association with ACT. Genetic variants in ABCC1, ABCC2, ABCC5, ABCB1, ABCB4, CBR3, RAC2, NCF4, CYBA, GSTP1, CAT, SULT2B1, POR, HAS3, SLC22A7, SCL22A17, HFE and NOS3 have also been associated with ACT, but require additional validation. We recommend pharmacogenomic testing for the RARG rs2229774 (S427L), SLC28A3 rs7853758 (L461L) and UGT1A6*4 rs17863783 (V209V) variants in childhood cancer patients with an indication for doxorubicin or daunorubicin therapy (Level B - moderate). Based on an overall risk stratification, taking into account genetic and clinical risk factors, we recommend a number of management options including increased frequency of echocardiogram monitoring, follow-up, as well as therapeutic options within the current standard of clinical practice.

CONCLUSIONS

Existing evidence demonstrates that genetic factors have the potential to improve the discrimination between individuals at higher and lower risk of ACT. Genetic testing may therefore support both patient care decisions and evidence development for an improved prevention of ACT.

Cardiomyopathies: Evolution of pathogenesis concepts and potential for new therapies

Cardiomyopathies are defined as diseases of the myocardium with associated structural and functional abnormalities. Knowledge of these pathologies for a long period was not clear in clinical practice due to uncertainties regarding definition, classification and clinical diagnosis. In recent decades, major advances have been made in the understanding of the molecular and genetic issues, pathophysiology, and clinical and radiological assessment of the diseases. Progress has been made also in management of several types of cardiomyopathy. Advances in the understanding of these diseases show that cardiomyopathies represent complex entities. Here, special attention is given to evolution of classification of cardiomyopathies, with the aim of assisting clinicians to look beyond schematic diagnostic labels in order to achieve more specific diagnosis. Knowledge of the genotype of cardiomyopathies has changed the pathophysiological understanding of their etiology and clinical course, and has become more important in clinical practice for diagnosis and prevention of cardiomyopathies. New approaches for clinical and prognostic assessment are provided based on contemporary molecular mechanisms of contribution in the pathogenesis of cardiomyopathies. The genotype-phenotype complex approach for assessment improves the clinical evaluation and management strategies of these pathologies. The review covers also the important role of imaging methods, particularly echocardiography, and cardiac magnetic resonance imaging in the evaluation of different types of cardiomyopathies. In summary, this review provides complex presentation of current state of cardiomyopathies from genetics to management aspects for cardiovascular specialists.

Cardioprotective interventions for cancer patients receiving anthracyclines

BACKGROUND

Anthracyclines are among the most effective chemotherapeutic agents in the treatment of numerous malignancies. Unfortunately, their use is limited by a dose-dependent cardiotoxicity. In an effort to prevent this cardiotoxicity, different cardioprotective agents have been studied.

OBJECTIVES

The objective of this review was to assess the efficacy of different cardioprotective agents in preventing heart damage in cancer patients treated with anthracyclines.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 10), MEDLINE (1966 to November 2010) and EMBASE (1980 to November 2010) databases. In addition, we handsearched reference lists, conference proceedings of the International Society of Paediatric Oncology (SIOP) and American Society of Clinical Oncology (ASCO) meetings (1998 to 2010) and ongoing trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in which any cardioprotective agent was compared to no additional therapy or placebo in cancer patients (children and adults) receiving anthracyclines.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection, risk of bias assessment and data extraction including adverse effects.

MAIN RESULTS

We identified RCTs for the eight cardioprotective agents N-acetylcysteine, phenethylamines, coenzyme Q10, a combination of vitamins E and C and N-acetylcysteine, L-carnitine, carvedilol, amifostine and dexrazoxane (mostly for adults with advanced breast cancer). All studies had methodological limitations and for the first seven agents there were too few studies to allow pooling of results. None of the individual studies showed a cardioprotective effect. The 10 included studies on dexrazoxane enrolled 1619 patients. The meta-analysis for dexrazoxane showed a statistically significant benefit in favour of dexrazoxane for the occurrence of heart failure (risk ratio (RR) 0.29, 95% CI 0.20 to 0.41). No evidence was found for a difference in response rate or survival between the dexrazoxane and control groups. The results for adverse effects were ambiguous. No significant difference in the occurrence of secondary malignancies was identified.

AUTHORS' CONCLUSIONS

No definitive conclusions can be made about the efficacy of cardioprotective agents for which pooling of results was impossible. Dexrazoxane prevents heart damage and no evidence for a difference in response rate or survival between the dexrazoxane and control groups was identified. The evidence available did not allow us to reach any definite conclusions about adverse effects. We conclude that if the risk of cardiac damage is expected to be high, it might be justified to use dexrazoxane in patients with cancer treated with anthracyclines. However, clinicians should weigh the cardioprotective effect of dexrazoxane against the possible risk of adverse effects for each individual patient.

Glutathione peroxidase 1-deficient mice are more susceptible to doxorubicin-induced cardiotoxicity

Doxorubicin (DOX)-induced cardiotoxicity is thought to be mediated by the generation of superoxide anion radicals (superoxide) from redox cycling of DOX in cardiomyocyte mitochondria. Reduction of superoxide generates H(2)O(2), which diffuses throughout the cell and potentially contributes to oxidant-mediated cardiac injury. The mitochondrial and cytosolic glutathione peroxidase 1 (Gpx1) primarily functions to eradicate H(2)O(2). In this study, we hypothesize that Gpx1 plays a pivotal role in the clearance of H(2)O(2) generated by DOX. To test this hypothesis, we compared DOX-induced cardiac dysfunction, mitochondrial injury, protein nitration, and apoptosis in Gpx1-deficient and wild type mouse hearts. The Gpx1-deficient hearts showed increased susceptibility to DOX-induced acute functional derangements than wild type hearts, including impaired contractility and diastolic properties, decreased coronary flow rate, and reduced heart rate. In addition, DOX treatment impaired the mitochondrial function of Gpx1-deficient hearts. Specifically, Gpx1-deficient hearts treated with DOX demonstrated an increased rate of NAD-linked state 4 respiration and a decline in the P/O ratio relative to wild type hearts, suggesting that DOX uncouples the electron transfer chain and oxidative phosphorylation in Gpx1-deficient hearts. Finally, apoptosis and protein nitration were significantly increased in Gpx1-deficient mouse hearts compared to wild type hearts. These studies suggest that Gpx1 plays significant roles in protecting DOX-induced mitochondrial impairment and cardiac dysfunction in the acute phase.

Cardioprotective interventions for cancer patients receiving anthracyclines

BACKGROUND

Anthracyclines are among the most effective chemotherapeutic agents in the treatment of numerous malignancies. Unfortunately, their use is limited by a dose-dependent cardiotoxicity. In an effort to prevent this cardiotoxicity, different cardioprotective agents have been studied.

OBJECTIVES

The objective of this review was to assess the efficacy of different cardioprotective agents in preventing heart damage in cancer patients treated with anthracyclines.

SEARCH STRATEGY

We searched the databases of the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 2, 2007), MEDLINE (1966 to April 2007) and EMBASE (1980 to April 2007). In addition, we handsearched reference lists and conference proceedings of the SIOP and ASCO meetings (1998 to 2006).

SELECTION CRITERIA

Randomised controlled trials (RCTs) in which any cardioprotective agent was compared to no additional or placebo therapy in cancer patients (children and adults) receiving anthracyclines.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection, quality assessment and data-extraction including adverse effects.

MAIN RESULTS

We identified RCTs for seven cardioprotective agents: N-acetylcysteine, phenetylamines, coenzyme Q10, combination of vitamins E and C and N-acetylcysteine, L-carnitine, carvedilol and dexrazoxane (mostly adults with advanced breast cancer). All studies had methodological limitations. For the first six agents, there were too few studies to allow pooling of results. None of the individual studies showed a cardioprotective effect. The nine included studies of dexrazoxane enrolled 1403 patients. The meta-analysis of dexrazoxane showed a statistically significant benefit in favour of dexrazoxane for the occurrence of heart failure (Relative Risk (RR) 0.29, 95% CI 0.20 to 0.41). No evidence was found for a difference in response rate or survival between the dexrazoxane and control group. Only for one adverse effect (abnormal white blood cell count at nadir) a difference in favour of the control group was identified.

AUTHORS' CONCLUSIONS

For cardioprotective agents for which pooling was impossible, no definitive conclusions can be made about their efficacy. Dexrazoxane prevents heart damage and no evidence for a difference in response rate or survival between the dexrazoxane and control group was identified. Only for an abnormal white blood cell count at nadir a clearly significant difference in favour of the control group was identified. We conclude that if the risk of cardiac damage is expected to be high, it might be justified to use dexrazoxane in patients with cancer treated with anthracyclines. However, for each individual patient clinicians should weigh the cardioprotective effect of dexrazoxane against the possible risk of adverse effects.

Attenuation of doxorubicin-induced contractile and mitochondrial dysfunction in mouse heart by cellular glutathione peroxidase

The cardiac toxicity of doxorubicin (DOX), a potent anticancer anthracycline antibiotic, is believed to be mediated through the generation of reactive oxygen species (ROS) in cardiomyocytes. This study aims to determine the function of cellular glutathione peroxidase (Gpx1), which is located in both mitochondria and cytosol, in defense against DOX-induced cardiomyopathy using a line of transgenic mice with cardiac overexpression of Gpx1. The Gpx1-overexpressing hearts were markedly more resistant than nontransgenic hearts to DOX-induced acute functional derangements, including impaired contractility and diastolic properties, decreased coronary flow rate, and reduced heart rate. In addition, DOX treatment impairs mitochondrial function of nontransgenic hearts as evident in a decreased rate of NAD-linked State 3 respiration, presumably a result of inactivation of complex I activity. This is associated with increases in the rates of NAD- and FAD-linked State 4 respiration and declines in P/O ratio, suggesting that the electron transfer and oxidative phosphorylation are uncoupled in these mitochondrial samples. These functional deficits of mitochondria could be largely prevented by Gpx1 overexpression. Taken together, these studies provide new evidence to further support the role of ROS, particularly H(2)O(2) and/or fatty acid hydroperoxides, in causing contractile and mitochondrial dysfunction in mouse hearts acutely exposed to DOX.

Cardioprotective interventions for cancer patients receiving anthracyclines

BACKGROUND

Anthracyclines are among the most effective chemotherapeutic agents in the treatment of numerous malignancies. Unfortunately, their use is limited by a dose-dependent cardiotoxicity. In an effort to prevent this cardiotoxicity, different cardioprotective agents have been studied.

OBJECTIVES

The objective of this review was to assess the efficacy of different cardioprotective agents in preventing heart damage in cancer patients treated with anthracyclines.

SEARCH STRATEGY

We searched the databases of CENTRAL (The Cochrane Library, Issue 3, 2002), MEDLINE (1966 to August 2002) and EMBASE (1980 to August 2002). In addition, we handsearched reference lists and conference proceedings of the International Society for Paediatric Oncology (SIOP) and the American Society of Clinical Oncology (ASCO) (1998 to 2002).

SELECTION CRITERIA

Randomised controlled trials (RCTs) in which any cardioprotective agent was compared to no additional or placebo therapy in cancer patients (children and adults) receiving anthracyclines.

DATA COLLECTION AND ANALYSIS

Two reviewers independently performed the study selection, quality assessment and data-extraction including adverse effects.

MAIN RESULTS

We identified RCTs for 5 cardioprotective agents: N-acetylcysteine (1 study; 54 patients), phenetylamines (2 studies; 100 patients), coenzyme Q10 (1 study; 20 patients), combination of vitamin E, vitamin C and N-acetylcysteine (1 study; 14 patients) and dexrazoxane (6 studies; 1013 patients). All studies had methodological limitations. Due to the insufficient number of studies, for the first four mentioned cardioprotective agents pooling of the results was impossible. None of the individual studies showed a cardioprotective effect. The meta-analysis of the dexrazoxane-studies showed a statistically significant benefit in favour of dexrazoxane for the occurrence of heart failure (Relative Risk (RR) = 0.28, 95% Confidence Interval (CI) 0.18 to 0.42, P < 0.00001). No statistically significant difference in response rate between the dexrazoxane and control group was found (RR = 0.88, 95% CI 0.77 to 1.01, P = 0.06), but there was some suggestion that patients treated with dexrazoxane might have a lower anti-tumour response rate. Our meta-analysis of survival showed no significant difference between the dexrazoxane and control group. For adverse effects pooling was impossible. However, no important differences in the occurrence of side effects were found. The majority of the patients included in this meta-analysis were adults with advanced breast cancer.

AUTHORS' CONCLUSIONS

For cardioprotective agents for which pooling was impossible no high quality evidence was available and therefore, no definitive conclusions can be made about their efficacy. Dexrazoxane prevents heart damage, however there was some suggestion that patients treated with dexrazoxane might have a lower anti-tumour response rate. There was no significant difference in survival between the dexrazoxane and control group. We conclude that if the risk of cardiac damage is expected to be high, it might be justified to use dexrazoxane in patients with cancer treated with anthracyclines. However, for each individual patient clinicians should weigh the cardioprotective effect of dexrazoxane against the possible risk of a lower response rate.

Manganese superoxide dismutase protects mitochondrial complex I against adriamycin-induced cardiomyopathy in transgenic mice

Adriamycin (ADR) is a potent anticancer drug that causes severe cardiomyopathy. We have previously demonstrated that ADR-induced ultrastructural mitochondrial injury in the heart was attenuated in manganese superoxide dismutase (MnSOD) transgenic mice. To further investigate the biochemical mechanisms by which MnSOD protected mitochondria against ADR-induced damage, cardiac mitochondrial function and activities were evaluated. The results showed that ADR caused significant decrease in state 3 respiration and respiratory control ratio using both complex I and II substrates in nontransgenic mice. In transgenic mice, state 3 respiration for complex I substrates remained unaffected by ADR, but was reduced for complex II substrate. Complex I activity was significantly decreased in nontransgenic, but not in transgenic mice after ADR treatment, suggesting that mitochondrial complex I is sensitive to inactivation by superoxide radicals. The activities of complex II and mitochondrial creatine kinase were decreased by ADR in both nontransgenic and transgenic mice. These results support our previous observations on the protective role of MnSOD on the ultrastructural damage of the heart after ADR treatment and extend the understanding of its mechanisms in mitochondria.

The protective role of manganese superoxide dismutase against adriamycin-induced acute cardiac toxicity in transgenic mice

Adriamycin (ADR) is a potent anticancer drug known to cause severe cardiac toxicity. Although ADR generates free radicals, the role of free radicals in the development of cardiac toxicity and the intracellular target for ADR-induced cardiac toxicity are still not well understood. We produced three transgenic mice lines expressing increased levels of human manganese superoxide dismutase (MnSOD), a mitochondrial enzyme, as an animal model to investigate the role of ADR-mediated free radical generation in mitochondria. The human MnSOD was expressed, functionally active, and properly transported into mitochondria in the heart of transgenic mice. The levels of copper-zinc SOD, catalase, and glutathione peroxidase did not change in the transgenic mice. Electron microscopy revealed dose-dependent ultrastructural alterations with marked mitochondrial damage in nontransgenic mice treated with ADR, but not in the transgenic littermates. Biochemical analysis indicated that the levels of serum creatine kinase and lactate dehydrogenase in ADR-treated mice were significantly greater in nontransgenic than their transgenic littermates expressing a high level of human MnSOD after ADR treatment. These results support a major role for free radical generation in ADR toxicity as well as suggesting mitochondria as the critical site of cardiac injury.