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

Pharmacogenomics in Children

Historically genetics has not been considered when prescribing drugs for children. However, it is clear that genetics are not only an important determinant of disease in children but also of drug response for many important drugs that are core agents used in the therapy of common problems in children. Advances in therapy and in the ethical construct of children's research have made pharmacogenomic assessment for children much easier to pursue. It is likely that pharmacogenomics will become part of the therapeutic decision-making process for children, notably in areas such as childhood cancer where weighing benefits and risks of therapy is crucial.

Long-term and quality of survival in patients treated for acute lymphoblastic leukemia during the pediatric age

Long-term survival for acute lymphoblastic leukemia (ALL) in children improved over the last three decades up to 80-90% of affected patients. Consequently, the quality of life of survivors has become increasingly important. This study analyses the clinical features and outcome of 119 children with ALL, focusing on the quality of long-term survival in a subset of 22 patients over 18 years of age. Among this group, the 10-year event-free survival and overall survival were 83.1% (C.I. 74.0-89.2) and 88.4% (C.I. 80.9-93.1), respectively. Treatment related long-term medical complications were reported only in 2 patients (9.1%). Secondary school was completed successfully in 20 of 22 patients (89.9%). The remaining 2 patients were still attending at the time of the analysis. In conclusion, current treatment for ALL is well tolerated and does not compromise significantly the quality of life of survivors.

Brain Development and Heart Function after Systemic Single-Agent Chemotherapy in a Mouse Model of Childhood Leukemia Treatment

PURPOSE

Chemotherapy for childhood acute lymphoblastic leukemia (ALL) can cause late-appearing side effects in survivors that affect multiple organs, including the heart and brain. However, the complex ALL treatment regimen makes it difficult to isolate the causes of these side effects and impossible to separate the contributions of individual chemotherapy agents by clinical observation. Using a mouse model, we therefore assessed each of eight representative, systemically-administered ALL chemotherapy agents for their impact on postnatal brain development and heart function.

EXPERIMENTAL DESIGN

Mice were treated systemically with a single chemotherapy agent at an infant equivalent age, then allowed to age to early adulthood (9 weeks). Cardiac structure and function were assessed using in vivo high-frequency ultrasound, and brain anatomy was assessed using high-resolution volumetric ex vivo MRI. In addition, longitudinal in vivo MRI was used to determine the time course of developmental change after vincristine treatment.

RESULTS

Vincristine, doxorubicin, and methotrexate were observed to produce the greatest deficiencies in brain development as determined by volumes measured on MRI, whereas doxorubicin, methotrexate, and l-asparaginase altered heart structure or function. Longitudinal studies of vincristine revealed widespread volume loss immediately following treatment and impaired growth over time in several brain regions.

CONCLUSIONS

Multiple ALL chemotherapy agents can affect postnatal brain development or heart function. This study provides a ranking of agents based on potential toxicity, and thus highlights a subset likely to cause side effects in early adulthood for further study.

Assessment of Fundamental Movement Skills in Childhood Cancer Patients

BACKGROUND

The improved treatment protocols and subsequent improved survival rates among childhood cancer patients have shifted the focus toward the long-term consequences arising from cancer treatment. Children who have completed cancer treatment are at a greater risk of delayed development, diminished functioning, disability, compromised fundamental movement skill (FMS) attainment, and long-term chronic health conditions. The aim of the study was to compare FMS of childhood cancer patients with an aged matched healthy reference group.

METHODS

Pediatric cancer patients aged 5-8 years (n = 26; median age 6.91 years), who completed cancer treatment (<5 years) at the Sydney Children's Hospital, were assessed performing seven key FMS: sprint, side gallop, vertical jump, catch, over-arm throw, kick, and leap. Results were compared to the reference group (n = 430; 6.56 years).

RESULTS

Childhood cancer patients scored significantly lower on three out of seven FMS tests when compared to the reference group. These results equated to a significantly lower overall score for FMS.

CONCLUSIONS

This study highlighted the significant deficits in FMS within pediatric patients having completed cancer treatment. In order to reduce the occurrence of significant FMS deficits in this population, FMS interventions may be warranted to assist in recovery from childhood cancer, prevent late effects, and improve the quality of life in survivors of childhood cancer.

Identifying cancer patients at risk for cardiotoxicity

Improvements in therapies have significantly changed survival of cancer patients. However, the clinical history and oncologic treatment put cancer patients at higher risk for developing cardiovascular problems. Anthracyclines, but also the targeted therapy and angiogenesis inhibitors, are all treatments associated with cardiotoxicity. The most common adverse event is a reduction in left ventricular ejection fraction that may progress to overt heart failure. Recognition of a cardiac impairment during or after a potential cardiotoxic treatment requires a stringent assessment of clinical symptoms and signs of heart failure associated with an evaluation of the left ventricular ejection fraction, which, however, detects the damage already installed. Circulating cardiac biomarkers are promising in detecting cardiotoxicity and will likely change the approach for identifying patients at risk.

Bone marrow stroma-derived PGE2 protects BCP-ALL cells from DNA damage-induced p53 accumulation and cell death

Background

B cell precursor acute lymphoblastic leukaemia (BCP-ALL) is the most common paediatric cancer. BCP-ALL blasts typically retain wild type p53, and are therefore assumed to rely on indirect measures to suppress transformation-induced p53 activity. We have recently demonstrated that the second messenger cyclic adenosine monophosphate (cAMP) through activation of protein kinase A (PKA) has the ability to inhibit DNA damage-induced p53 accumulation and thereby promote survival of the leukaemic blasts.

Development of BCP-ALL in the bone marrow (BM) is supported by resident BM-derived mesenchymal stromal cells (MSCs). MSCs are known to produce prostaglandin E₂ (PGE₂) which upon binding to its receptors is able to elicit a cAMP response in target cells. We hypothesized that PGE₂ produced by stromal cells in the BM microenvironment could stimulate cAMP production and PKA activation in BCP-ALL cells, thereby suppressing p53 accumulation and promoting survival of the malignant cells.

Methods

Primary BCP-ALL cells isolated from BM aspirates at diagnosis were cocultivated with BM-derived MSCs, and effects on DNA damage-induced p53 accumulation and cell death were monitored by SDS-PAGE/immunoblotting and flow cytometry-based methods, respectively. Effects of intervention of signalling along the PGE₂-cAMP-PKA axis were assessed by inhibition of PGE₂ production or PKA activity. Statistical significance was tested by Wilcoxon signed-rank test or paired samples t test.

Results

We demonstrate that BM-derived MSCs produce PGE₂ and protect primary BCP-ALL cells from p53 accumulation and apoptotic cell death. The MSC-mediated protection of DNA damage-mediated cell death is reversible upon inhibition of PGE₂ synthesis or PKA activity. Furthermore our results indicate differences in the sensitivity to variations in p53 levels between common cytogenetic subgroups of BCP-ALL.

Conclusions

Our findings support our hypothesis that BM-derived PGE₂, through activation of cAMP-PKA signalling in BCP-ALL blasts, can inhibit the tumour suppressive activity of wild type p53, thereby promoting leukaemogenesis and protecting against therapy-induced leukaemic cell death. These novel findings identify the PGE₂-cAMP-PKA signalling pathway as a possible target for pharmacological intervention with potential relevance for treatment of BCP-ALL.

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).

The tell-tale heart: molecular and cellular responses to childhood anthracycline exposure

Since the modern era of cancer chemotherapy that began in the mid-1940s, survival rates for children afflicted with cancer have steadily improved from 10% to current rates that approach 80% (60). Unfortunately, many long-term survivors of pediatric cancer develop chemotherapy-related health effects; 25% are afflicted with a severe or life-threatening medical condition, with cardiovascular disease being a primary risk (96). Childhood cancer survivors have markedly elevated incidences of stroke, congestive heart failure (CHF), coronary artery disease, and valvular disease (96). Their cardiac mortality is 8.2 times higher than expected (93). Anthracyclines are a key component of most curative chemotherapeutic regimens used in pediatric cancer, and approximately half of all childhood cancer patients are exposed to them (78). Numerous epidemiologic and observational studies have linked childhood anthracycline exposure to an increased risk of developing cardiomyopathy and CHF, often decades after treatment. The acute toxic effects of anthracyclines on cardiomyocytes are well described; however, myocardial tissue is comprised of additional resident cell types, and events occurring in the cardiomyocyte do not fully explain the pathological processes leading to late cardiomyopathy and CHF. This review will summarize the current literature regarding the cellular and molecular responses to anthracyclines, with an important emphasis on nonmyocyte cardiac cell types as well as those that mediate the myocardial injury response.

Targeted therapy with MXD3 siRNA, anti-CD22 antibody and nanoparticles for precursor B-cell acute lymphoblastic leukaemia

Conventional chemotherapy for precursor B-cell (preB) acute lymphoblastic leukaemia (ALL) has limitations that could be overcome by targeted therapy. Previously, we discovered a potential therapeutic molecular target, MDX3 (MAX dimerization protein 3), in preB ALL. In this study, we hypothesize that an effective siRNA therapy for preB ALL can be developed using antiCD22 antibody (αCD22 Ab) and nanoparticles. We composed nanocomplexes with super paramagnetic iron oxide nanoparticles (SPIO NPs), αCD22 Abs and MXD3 siRNA molecules based on physical interactions between the molecules. We demonstrated that the MXD3 siRNA-αCD22 Ab-SPIO NP complexes entered leukaemia cells and knocked down MXD3, leading the cells to undergo apoptosis and resulting in decreased live cell counts in the cell line Reh and in primary preB ALL samples in vitro. Furthermore, the cytotoxic effects of the MXD3 siRNA-αCD22 Ab-SPIO NP complexes were significantly enhanced by addition of the chemotherapy drugs vincristine or doxorubicin. We also ruled out potential cytotoxic effects of the MXD3 siRNA-αCD22 Ab-SPIO NP complexes on normal primary haematopoietic cells. Normal B cells were affected while CD34-positive haematopoietic stem cells and non-B cells were not. These data suggest that MXD3 siRNA-αCD22 Ab-SPIO NP complexes have the potential to be a new targeted therapy for preB ALL.

Anthracycline-related cardiotoxicity in childhood cancer survivors

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Pharmacogenomics and adverse drug reactions in children

Adverse drug reactions are a common and important complication of drug therapy in children. Over the past decade it has become increasingly apparent that genetically controlled variations in drug disposition and response are important determinants of adverse events for many important adverse events associated with drug therapy in children. While this research has been difficult to conduct over the past decade technical and ethical evolution has greatly facilitated the ability of investigators to conduct pharmacogenomic studies in children. Some of this research has already resulted in changes in public policy and clinical practice, for example in the case of codeine use by mothers and children. It is likely that the use of pharmacogenomics to enhance drug safety will first be realized among selected groups of children with high rates of drug use such as children with cancer, but it also likely that this research will be extended to other groups of children who have high rates of drug utilization and as well as providing insights into the mechanisms and pathophysiology of adverse drug reactions in children.

Pharmacogenomics in children

Historically genetics has not been considered when prescribing drugs for children. However, it is clear that genetics are not only an important determinant of disease in children but also of drug response for many important drugs that are core agents used in the therapy of common problems in children. Advances in therapy and in the ethical construct of children's research have made pharmacogenomic assessment for children much easier to pursue. It is likely that pharmacogenomics will become part of the therapeutic decision making process for children, notably in areas such as childhood cancer where the benefits and risks of therapy are considerable.

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.