Expression of the anthracycline-metabolizing enzyme carbonyl reductase 1 in hearts from donors with Down syndrome

Down syndrome-associated leukaemias: current evidence and challenges

Children with Down syndrome (DS) are at increased risk of developing haematological malignancies, in particular acute megakaryoblastic leukaemia and acute lymphoblastic leukaemia. The microenvironment established by abnormal haematopoiesis driven by trisomy 21 is compounded by additional genetic and epigenetic changes that can drive leukaemogenesis in patients with DS. GATA-binding protein 1 (GATA1) somatic mutations are implicated in the development of transient abnormal myelopoiesis and the progression to myeloid leukaemia of DS (ML-DS) and provide a model of the multi-step process of leukaemogenesis in DS. This review summarises key genetic drivers for the development of leukaemia in patients with DS, the biology and treatment of ML-DS and DS-associated acute lymphoblastic leukaemia, late effects of treatments for DS-leukaemias and the focus for future targeted therapy.

Down syndrome and leukemia: An insight into the disease biology and current treatment options

Children with Down syndrome (DS) have a 10- to 20-fold greater predisposition to develop acute leukemia compared to the general population, with a skew towards myeloid leukemia (ML-DS). While ML-DS is known to be a subtype with good outcome, patients who relapse face a dismal prognosis. Acute lymphocytic leukemia in DS (DS-ALL) is considered to have poor prognosis. The relapse rate is high in DS-ALL compared to their non-DS counterparts. We have a better understanding about the mutational spectrum of DS leukemia. Studies using animal, embryonic stem cell- and induced pluripotent stem cell-based models have shed light on the mechanism by which these mutations contribute to disease initiation and progression. In this review, we list the currently available treatment strategies for DS-leukemias along with their outcome with emphasis on challenges with chemotherapy-related toxicities in children with DS. We focus on the mechanisms of initiation and progression of leukemia in children with DS and highlight the novel molecular targets with greater success in preclinical trials that have the potential to progress to the clinic.

State-of-the-art therapy for Down syndrome

In the last decade, an important effort was made in the field of Down syndrome to find new interventions that improve cognition. These therapies have added to the traditional symptomatic treatments and to the drugs for treating Alzheimer disease in the general population repurposed for Down syndrome. Defining next-generation therapeutics will involve biomarker-based therapeutic decision-making, and preventive and multimodal interventions. However, translation of specific findings into effective therapeutic strategies has been disappointingly slow and has failed in many cases at the clinical level, leading to reduced credibility of mouse studies. This is aggravated by a tendency to favour large-magnitude effects and highly significant findings, leading to high expectations but also to a biased view of the complex pathophysiology of Down syndrome. Here, we review some of the most recent and promising strategies for ameliorating the cognitive state of individuals with Down syndrome. We studied the landscape of preclinical and clinical studies and conducted a thorough literature search on PubMed and ClinicalTrials.gov for articles published between June 2012 and August 2022 on therapies for ameliorating cognitive function in individuals with Down syndrome. We critically assess current therapeutic approaches, why therapies fail in clinical trials in Down syndrome, and what could be the path forward. We discuss some intrinsic difficulties for translational research, and the need for a framework that improves the detection of drug efficacy to avoid discarding compounds too early from the companies' pipelines.

Pharmacogenomics in drug-induced cardiotoxicity: Current status and the future

Drug-induced cardiotoxicity (DICT) is an important concern of drug safety in both drug development and clinical application. The clinical manifestations of DICT include cardiomyopathy, arrhythmia, myocardial ischemia, heart failure, and a series of cardiac structural and functional changes. The occurrence of DICT has negative impacts on the life quality of the patients, brings additional social and economic burden. It is important to identify the potential factors and explore the mechanisms of DICT. Traditional cardiovascular risk factors can only partially explain the risk of DICT. Pharmacogenomic studies show accumulated evidence of genetics in DICT and suggest the potential to guide precision therapy to reduce risk of cardiotoxicity. The comprehensive application of technologies such as third-generation sequencing, human induced pluripotent stem (iPS) cells and genome editing has promoted the in-depth understanding of the functional role of susceptible genes in DICT. This paper reviewed drugs that cause DICT, the clinical manifestations and laboratory tests, as well as the related content of genetic variations associated with the risk of DICT, and further discussed the implication of new technologies in pharmacogenomics of DICT.

Down Syndrome: A Review of Key Perioperative Implications

Down syndrome (DS) is the most common chromosomal abnormality in humans that is compatible with life. This syndrome occurs when there is an extra copy of the 21st chromosome. Down syndrome is associated with numerous comorbidities that can pose challenges for the perioperative nurse caring for a patient with DS undergoing surgery. These challenges can affect the patient assessment, communication with the patient, and patient safety (eg, preventing complications). As the life expectancy of people with DS has increased, so too have the chances that perioperative nurses will care for a patient with this disorder. This article reviews the pathophysiology of DS, discusses common comorbidities that may directly affect perioperative care, and reviews an exemplar case study that demonstrates how personnel with knowledge of DS can positively influence surgical team decision making for these patients in the perioperative setting.

Improved outcomes for myeloid leukemia of Down syndrome: a report from the Children's Oncology Group AAML0431 trial

Patients with myeloid leukemia of Down syndrome (ML-DS) have favorable event-free survival (EFS), but experience significant treatment-related morbidity and mortality. ML-DS blast cells ex vivo have increased sensitivity to cytarabine (araC) and daunorubicin, suggesting that optimizing drug dosing may improve outcomes while reducing toxicity. The Children's Oncology Group (COG) AAML0431 trial consisted of 4 cycles of induction and 2 cycles of intensification therapy based on the treatment schema of the previous COG A2971 trial with several modifications. High-dose araC (HD-araC) was used in the second induction cycle instead of the intensification cycle, and 1 of 4 daunorubicin-containing induction cycles was eliminated. For 204 eligible patients, 5-year EFS was 89.9% and overall survival (OS) was 93.0%. The 5-year OS for 17 patients with refractory/relapsed leukemia was 34.3%. We determined the clinical significance of minimal residual disease (MRD) levels as measured by flow cytometry on day 28 of induction I. MRD measurements, available for 146 of the 204 patients, were highly predictive of treatment outcome; 5-year disease-free survival for MRD-negative patients (n = 125) was 92.7% vs 76.2% for MRD-positive patients (n = 21) (log-rank P = .011). Our results indicated that earlier use of HD-araC led to better EFS and OS in AAML0431 than in past COG studies. A 25% reduction in the cumulative daunorubicin dose did not impact outcome. MRD, identified as a new prognostic factor for ML-DS patients, can be used for risk stratification in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00369317.

Primary Prevention Strategies for Anthracycline Cardiotoxicity: A Brief Overview

The clinical use of doxorubicin and other antitumor anthracyclines is limited by a dose-related risk of cardiomyopathy and heart failure which may occur “on treatment” or any time, from months to years, after completing chemotherapy. Dose reductions diminish the incidence of cardiac events attributable to anthracyclines, but heart failure still occurs in some patients exposed to low or moderate anthracycline doses. Because anthracyclines improve the life expectancy of patients with, for example, breast cancer or lymphomas, preventing or diminishing the risk of early or delayed cardiotoxicity is of obvious clinical importance. Here, we briefly review some potential strategies of primary prevention that are based on what we know about the molecular mechanisms of cardiotoxicity, and what can be done, or might be done, to interfere with the pharmacokinetic, pharmacodynamic, and genetic determinants of cardiotoxicity.

Pharmacotherapeutic Considerations for Individuals with Down Syndrome

Down syndrome (DS; trisomy 21) is the most common survivable disorder due to aneuploidy. Individuals with DS may experience multiple comorbid health problems including congenital heart defects, endocrine abnormalities, skin and dental problems, seizure disorders, leukemia, dementia, and obesity. These associated conditions may necessitate pharmacotherapeutic management with various drugs. The complex pathobiology of DS may alter drug disposition and drug response in some individuals. For example, reports have documented increased rates of adverse drug reactions in patients with DS treated for leukemia and dementia. Intellectual disability resulting from DS may impact adherence to medication regimens. In this review, we highlight literature focused on pharmacotherapy for individuals with DS. We discuss reports of altered drug disposition or response in patients with DS and explore social factors that may impact medication adherence in the DS setting. Enhanced monitoring during drug therapy in individuals with DS is justified based on reports of altered drug disposition, drug response, and other characteristics present in this population.

Pharmacokinetics of Chemotherapeutic Drugs in Pediatric Patients With Down Syndrome and Leukemia

Children with Down syndrome (DS) have a 10- to 30-fold increased risk of developing acute myeloid leukemia or acute lymphoblastic leukemia. Patients with DS and leukemia are treated with the same chemotherapeutic agents as patients without DS. Treatment regimens for pediatric leukemia comprise multiple cytotoxic drugs including methotrexate, doxorubicin, vincristine, cytarabine, and etoposide. There have been reports of increased toxicity, as well as altered therapeutic outcomes in pediatric patients with DS and leukemia. This review is focused on the pharmacokinetics of cytotoxic drugs in pediatric patients with leukemia and DS. The available literature suggests that methotrexate and thioguanine display altered pharmacokinetic parameters in pediatric patients with DS. It has been hypothesized that the variable pharmacokinetics of these drugs may contribute to the increased incidence of treatment-related toxicities seen in DS. Data from a small number of studies suggest that the pharmacokinetics of vincristine, etoposide, doxorubicin, and busulfan are similar between patients with and without DS. Definitive conclusions regarding the pharmacokinetics of cytotoxic drugs in pediatric patients with leukemia and DS are difficult to reach due to limitations in the available studies.

Development of a CART Model to Predict the Synthesis of Cardiotoxic Daunorubicinol in Heart Tissue Samples From Donors With and Without Down Syndrome

Daunorubicin (DAUN) and doxorubicin (DOX) are used to treat a variety of cancers. The use of DAUN and DOX is hampered by the development of cardiotoxicity. Clinical evidence suggests that patients with leukemia and Down syndrome are at increased risk for anthracycline-related cardiotoxicity. Carbonyl reductases and aldo-keto reductases (AKRs) catalyze the reduction of DAUN and DOX into cardiotoxic C-13 alcohol metabolites. Anthracyclines also exert cardiotoxicity by triggering mitochondrial dysfunction. In recent studies, a collection of heart samples from donors with and without Down syndrome was used to investigate determinants for anthracycline-related cardiotoxicity including cardiac daunorubicin reductase activity (DA), carbonyl reductase/AKRs protein expression, mitochondrial DNA content (mtDNA), and AKR7A2 DNA methylation status. In this study, the available demographic, biochemical, genetic, and epigenetic data were integrated through classification and regression trees analysis with the aim of pinpointing the most relevant variables for the synthesis of cardiotoxic daunorubicinol (i.e., DA). Seventeen variables were considered as potential predictors. Leave-one-out-cross-validation was performed for model selection and to estimate the generalization error. The classification and regression trees analysis model and variable importance measures suggest that cardiac mtDNA content, mtDNA(4977) deletion frequency, and AKR7A2 protein content are the most important variables in determining DA.

Heart Transplantation in the Short Term After Chemotherapy

Anthracycline antibiotics are an effective therapy for a variety of neoplastic diseases. Dilated cardiomyopathy is a known risk of their use. Because of the risk of new or recurrent neoplasm with immunosuppression transplantation is often delayed. Our patient developed early cardiomyopathy with congestive heart failure 3 months after completion of chemotherapy. Given the severity of her cardiac symptoms the decision was made to proceed with heart transplantation in the short term after completion of her chemotherapy. We report the success to 1 year of this decision and discuss the implications of her genetic and oncologic diagnoses in this clinical scenario.

Role of DNA Methylation on the Expression of the Anthracycline Metabolizing Enzyme AKR7A2 in Human Heart

The intracardiac synthesis of anthracycline alcohol metabolites by aldo-keto reductases (AKRs) contributes to the pathogenesis of anthracycline-related cardiotoxicity. AKR7A2 is the most abundant anthracycline reductase in hearts from donors with and without Down syndrome (DS), and its expression varies between individuals (≈tenfold). We investigated whether DNA methylation impacts AKR7A2 expression in hearts from donors with (n = 11) and without DS (n = 30). Linear models were used to test for associations between methylation status and cardiac AKR7A2 expression. In hearts from donors without DS, DNA methylation status at CpG site -865 correlated with AKR7A2 mRNA (Pearson's regression coefficient, r = -0.4051, P = 0.0264) and AKR7A2 protein expression (r = -0.5818, P = 0.0071). In heart tissue from donors with DS, DNA methylation status at CpG site -232 correlated with AKR7A2 protein expression (r = 0.8659, P = 0.0025). Multiple linear regression modeling revealed that methylation at several CpG sites is associated with the synthesis of cardiotoxic daunorubicinol. AKR7A2 methylation status in lymphoblastoid cell lines from donors with and without DS was examined to explore potential parallelisms between cardiac tissue and lymphoid cells. These results suggest that DNA methylation impacts AKR7A2 expression and the synthesis of cardiotoxic daunorubicinol.

Chromosome 21-derived hsa-miR-155-5p regulates mitochondrial biogenesis by targeting Mitochondrial Transcription Factor A (TFAM)

The regulation of mitochondrial biogenesis is under the control of nuclear genes including the master Mitochondrial Transcription Factor A (TFAM). Recent evidence suggests that the expression of TFAM is regulated by microRNAs (miRNAs) in various cellular contexts. Here, we show that hsa-miR-155-5p, a prominent miRNA encoded in chromosome 21, controls the expression of TFAM at the post-transcriptional level. In human fibroblasts derived from a diploid donor, downregulation of TFAM by hsa-miR-155-5p decreased mitochondrial DNA (mtDNA) content. In contrast, downregulation of TFAM by hsa-miR-155-5p did not decrease mtDNA content in fibroblasts derived from a donor with Down syndrome (DS, trisomy 21). In line, downregulation of mitochondrial TFAM levels through hsa-miR-155-5p decreased mitochondrial mass in diploid fibroblasts but not in trisomic cells. Due to the prevalence of mitochondrial dysfunction and cardiac abnormalities in subjects with DS, we examined the presence of potential associations between hsa-miR-155-5p and TFAM expression in heart samples from donors with and without DS. There were significant negative associations between hsa-miR-155-5p and TFAM expression in heart samples from donors with and without DS. These results suggest that regulation of TFAM by hsa-miR-155-5p impacts mitochondrial biogenesis in the diploid setting but not in the DS setting.

Analysis of mtDNA, miR-155 and BACH1 expression in hearts from donors with and without Down syndrome

Cancer patients with Down syndrome (DS) are at increased risk for anthracycline-related cardiotoxicity. Mitochondrial DNA (mtDNA) alterations in hearts with-DS may contribute to anthracycline-related cardiotoxicity. Cardiac mtDNA and the mtDNA(4977) deletion were quantitated in samples with- (n = 11) and without-DS (n = 31). Samples with-DS showed 30% lower mtDNA (DS(MT-ND1/18Sratio): 1.48 ± 0.72 versus non-DS(MT-ND1/18Sratio): 2.10 ± 1.59; p = 0.647) and 30% higher frequency of the mtDNA(4977) deletion (DS(% frequency mtDNA(4977)) deletion: 0.0086 ± 0.0166 versus non-DS(% frequency mtDNA(4977)) deletion: 0.0066 ± 0.0124, p = 0.514) than samples without-DS. The BACH1 and microRNA-155 (miR-155) genes are located in chromosome 21, and their products have demonstrated roles during oxidative stress. BACH1 and miR-155 expression did not differ in hearts with- and without-DS. An association between BACH1 and miR-155 expression was detected in hearts without-DS, suggesting alterations between BACH1-miR-155 interactions in the DS settings.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

MicroRNAs differentially regulate carbonyl reductase 1 (CBR1) gene expression dependent on the allele status of the common polymorphic variant rs9024

MicroRNAs (miRNAs) are small RNAs responsible for the post-transcriptional regulation of a variety of human genes. To date, their involvement in the regulation of CBR1 is unknown. This study reports for the first time the identification of microRNA-574-5p (hsa-miR-574-5p) and microRNA-921 (hsa-miR-921) as two miRNAs capable of interacting with the 3'-untranslated region (3'-UTR) of the CBR1 gene and downregulating CBR1 expression. Furthermore, we demonstrate that a common single-nucleotide polymorphism (SNP) in the CBR1 3'-UTR (rs9024, CBR1 1096G>A) differentially impacts the regulation of CBR1 by hsa-miR-574-5p and hsa-miR-921 dependent on genotype. First, four candidate miRNAs were selected based on bioinformatic analyses, and were tested in Chinese hamster ovary (CHO) cells transfected with CBR1 3'-UTR constructs harboring either the G or A allele for rs9024. We found that hsa-miR-574-5p and hsa-miR-921 significantly decreased luciferase activity in CHO cells transfected with the CBR1 3'-UTR construct carrying the major rs9024 G allele by 35% and 46%, respectively. The influence of these miRNAs was different in cells transfected with a CBR1 3'-UTR construct containing the minor rs9024 A allele in that only hsa-miR-574-5p had a demonstrable effect (i.e., 52% decrease in lucifersase activity). To further determine the functional effects of miRNA-mediated regulation of polymorphic CBR1, we assessed CBR1 protein expression and CBR1 enzymatic activity for the prototypical substrate menadione in human lymphoblastoid cell lines with distinct rs9024 genotypes. We found that hsa-miR-574-5p and hsa-miR-921 significantly decreased CBR1 protein (48% and 40%, respectively) and CBR1 menadione activity (54% and 18%, respectively) in lymphoblastoid cells homozygous for the major rs9024 G allele. In contrast, only hsa-miR-574-5p decreased CBR1 protein and CBR1 activity in cells homozygous for the minor rs9024 A allele, and did so by 49% and 56%, respectively. These results suggest that regulation of human CBR1 expression by hsa-miR-574-5p and hsa-miR-921 depends upon rs9024 genotype status.

Induction of carbonyl reductase 1 (CBR1) expression in human lung tissues and lung cancer cells by the cigarette smoke constituent benzo[a]pyrene

Carbonyl reductase 1 (CBR1) reduces various xenobiotic carbonyl substrates to corresponding alcohol metabolites. Here we demonstrated that benzo[a]pyrene (B[a]P), a potent pro-carcinogen and predominant polycyclic aromatic hydrocarbon (PAH) compound in cigarette smoke and air pollutants, upregulates CBR1 gene expression in vitro and in vivo, and that a proximal xenobiotic response element (XRE) motif (₋₁₂₂XRE) mediates the induction effect of B[a]P. First, we observed 46% and 50% increases in CBR1 mRNA and CBR1 protein levels, respectively, in human lung tissue samples from smokers compared to never-smokers. Second, we detected 3.0-fold (p<0.0001) induction of CBR1 mRNA and 1.5-fold (p<0.01) induction of CBR1 protein levels in cells of the human lung cancer cell line A549 incubated with 2.5 μM B[a]P for 24h. Third, results from experiments with CBR1 promoter constructs indicated that a proximal XRE motif ₋₁₂₂XRE) mediates induction of reporter activity in response to B[a]P. Furthermore, we detected enhanced nuclear translocation of aryl hydrocarbon receptor (AhR) following B[a]P exposure in A549 cells. Finally, we demonstrated increased binding of specific protein complexes to ₋₁₂₂XRE in nuclear extracts from B[a]P-treated cells and the presence of the AhR/Arnt complex in the specific nuclear protein ₋₁₂₂XRE complexes.

Anthracycline-related cardiomyopathy after childhood cancer: role of polymorphisms in carbonyl reductase genes--a report from the Children's Oncology Group

PURPOSE

Carbonyl reductases (CBRs) catalyze reduction of anthracyclines to cardiotoxic alcohol metabolites. Polymorphisms in CBR1 and CBR3 influence synthesis of these metabolites. We examined whether single nucleotide polymorphisms in CBR1 (CBR1 1096G>A) and/or CBR3 (CBR3 V244M) modified the dose-dependent risk of anthracycline-related cardiomyopathy in childhood cancer survivors.

PATIENTS AND METHODS

One hundred seventy survivors with cardiomyopathy (patient cases) were compared with 317 survivors with no cardiomyopathy (controls; matched on cancer diagnosis, year of diagnosis, length of follow-up, and race/ethnicity) using conditional logistic regression techniques.

RESULTS

A dose-dependent association was observed between cumulative anthracycline exposure and cardiomyopathy risk (0 mg/m(2): reference; 1 to 100 mg/m(2): odds ratio [OR], 1.65; 101 to 150 mg/m(2): OR, 3.85; 151 to 200 mg/m(2): OR, 3.69; 201 to 250 mg/m(2): OR, 7.23; 251 to 300 mg/m(2): OR, 23.47; > 300 mg/m(2): OR, 27.59; P(trend) < .001). Among individuals carrying the variant A allele (CBR1:GA/AA and/or CBR3:GA/AA), exposure to low- to moderate-dose anthracyclines (1 to 250 mg/m(2)) did not increase the risk of cardiomyopathy. Among individuals with CBR3 V244M homozygous G genotypes (CBR3:GG), exposure to low- to moderate-dose anthracyclines increased cardiomyopathy risk when compared with individuals with CBR3:GA/AA genotypes unexposed to anthracyclines (OR, 5.48; P = .003), as well as exposed to low- to moderate-dose anthracyclines (OR, 3.30; P = .006). High-dose anthracyclines (> 250 mg/m(2)) were associated with increased cardiomyopathy risk, irrespective of CBR genotype status.

CONCLUSION

This study demonstrates increased anthracycline-related cardiomyopathy risk at doses as low as 101 to 150 mg/m(2). Homozygosis for G allele in CBR3 contributes to increased cardiomyopathy risk associated with low- to moderate-dose anthracyclines, such that there seems to be no safe dose for patients homozygous for the CBR3 V244M G allele. These results suggest a need for targeted intervention for those at increased risk of cardiomyopathy.