Javier G. Blanco

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.

Genetic polymorphisms in the carbonyl reductase 3 gene CBR3 and the NAD(P)H: quinone oxidoreductase 1 gene NQ01 in patients who developed anthracycline-related congestive heart failure after childhood cancer

Exposure to anthracyclines as part of cancer therapy has been associated with the development of congestive heart failure (CHF). The potential role of genetic risk factors in anthracycline‐related CHF remains to be defined. Thus, in this study, the authors examined whether common polymorphisms in candidate genes involved in the pharmacodynamics of anthracyclines (in particular, the nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1 gene NQO1 and the carbonyl reductase 3 gene CBR3) had an impact on the risk of anthracycline‐related CHF.

Genetic polymorphisms in CYP3A5, CYP3A4 and NQO1 in children who developed therapy-related myeloid malignancies

Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-ML) are serious complications that affect some patients after acute lymphoblastic leukemia (ALL) treatment. Genetic polymorphisms in the promoter of CYP3A4 (CYP3A4*1B) and in NAD(P)H:quinone oxidoreductase (NQO1609C-->T substitution) have been associated with the risk of t-ML. A polymorphism in CYP3A5 (CYP3A5*3) affects CYP3A activity and the wild-type allele (CYP3A5*1) is in partial linkage with the CYP3A4*1B allele. We compared the genotype frequencies for the CYP3A5*3, the CYP3A4*1B and the NQO1609C-->T substitution in 224 children with ALL who did not develop t-ML (controls) and in 53 children with ALL who did develop the complication. The allele frequencies differed significantly among whites, blacks and Hispanics (P < 0.001 for CYP3A5*3, P < 0.001 for CYP3A4*1B and P = 0.004 for NQO1609), thus we performed the comparisons between ALL controls and t-ML patients after accounting for race. We found no differences in the CYP3A4*1B allele distribution between ALL controls and t-ML patients in whites (P = 0.339, 6.6% vs. 9.8%), blacks (P = 0.498, 93.8% vs. 87.5%) or Hispanics (P = 0.523, 39.1% vs. 25.0%). The frequencies for the NQO1609C-->T allele did not differ between control and t-ML groups in whites (P = 0.191, 35.0% vs. 44.9%), blacks (P = 0.664, 37.5% vs. 37.5%) or Hispanics (P = 0.447, 65.2% vs. 50.0%). We found no differences between the control and t-ML group in the incidence of homozygous CYP3A5*3 genotypes: 82.0% vs. 85.4% in whites (P = 0.403), 6.5% vs. 12.5% in blacks (P = 0.508), and 69.6% vs. 75.0% in Hispanics (P= 0.663). Our data do not support an association between common CYP3A4, NQO1 or CYP3A5 polymorphisms and the risk of t-ML in children treated for ALL.

Hyaluronan Synthase 3 Variant and Anthracycline-Related Cardiomyopathy: A Report From the Children's Oncology Group

PURPOSE The strong dose-dependent association between anthracyclines and cardiomyopathy is further exacerbated by the co-occurrence of cardiovascular risk factors (diabetes and hypertension). The high morbidity associated with cardiomyopathy necessitates an understanding of the underlying pathogenesis so that targeted interventions can be developed. PATIENTS AND METHODS By using a two-stage design, we investigated host susceptibility to anthracycline-related cardiomyopathy by using the ITMAT/Broad CARe cardiovascular single nucleotide polymorphism (SNP) array to profile common SNPs in 2,100 genes considered relevant to de novo cardiovascular disease. RESULTS By using a matched case-control design (93 cases, 194 controls), we identified a common SNP, rs2232228, in the hyaluronan synthase 3 (HAS3) gene that exerts a modifying effect on anthracycline dose-dependent cardiomyopathy risk (P = 5.3 × 10(-7)). Among individuals with rs2232228 GG genotype, cardiomyopathy was infrequent and not dose related. However, in individuals exposed to high-dose (> 250 mg/m(2)) anthracyclines, the rs2232228 AA genotype conferred an 8.9-fold (95% CI, 2.1- to 37.5-fold; P = .003) increased cardiomyopathy risk compared with the GG genotype. This gene-environment interaction was successfully replicated in an independent set of 76 patients with anthracycline-related cardiomyopathy. Relative HAS3 mRNA levels measured in healthy hearts tended to be lower among individuals with AA compared with GA genotypes (P = .09). CONCLUSION Hyaluronan (HA) produced by HAS3 is a ubiquitous component of the extracellular matrix and plays an active role in tissue remodeling. In addition, HA is known to reduce reactive oxygen species (ROS) -induced cardiac injury. The high cardiomyopathy risk associated with AA genotype could be due to inadequate remodeling and/or inadequate protection of the heart from ROS-mediated injury on high anthracycline exposure.

Molecular emergence of acute myeloid leukemia during treatment for acute lymphoblastic leukemia

Therapy-related acute myeloid leukemias (t-AML) with translocations of the MLL gene are associated with the use of topoisomerase II inhibitors. We established the emergence of the malignant clone in a child who developed t-AML with a t(11;19) (q23;p13.3) during treatment for acute lymphoblastic leukemia (ALL). The MLL-ENL and the reciprocal ENL-MLL genomic fusions and their chimeric transcripts were characterized from samples collected at the time of t-AML diagnosis. We used PCR with patient-specific genomic primers to establish the emergence of the MLL-ENL fusion in serially obtained DNA samples. The MLL-ENL fusion was not detectable in bone marrow at the time of ALL diagnosis or after 2 months of chemotherapy (frequency <8.3 × 10−7 cells−1). The genomic fusion was first detected in bone marrow after 6 months of treatment at a frequency of one in 4,000 mononuclear bone marrow cells; the frequency was one in 70 cells after 20 months of therapy. At the first detection of MLL-ENL, the only topoisomerase II inhibitors the patient had received were one dose of daunorubicin and two doses of etoposide. The MLL-ENL fusion was not detectable in blood at the time of ALL diagnosis or after 0.7, 2, 8, 10, and 12 months of therapy but was detectable in blood at 16 months (one in 2.3 × 104 cells). Recombinogenic Alu sequences bracketed the breakpoints in both fusions. These data indicate that the malignant clone was not present before therapy, arose early during chemotherapy, and was able to proliferate even during exposure to antileukemic therapy.

A Functional Genetic Polymorphism on Human Carbonyl Reductase 1 (CBR1 V88I) Impacts on Catalytic Activity and NADPH Binding Affinity

Human carbonyl reductase 1 (CBR1) metabolizes endogenous and xenobiotic substrates such as the fever mediator, prostaglandin E2 (PGE2), and the anticancer anthracycline drug, daunorubicin. We screened 33 CBR1 full-length cDNA samples from white and black liver donors and performed database analyses to identify genetic determinants of CBR1 activity. We pinpointed a single nucleotide polymorphism on CBR1 (CBR1 V88I) that encodes for a valine-to-isoleucine substitution for further characterization. We detected the CBR1 V88I polymorphism in DNA samples from individuals with African ancestry (p = 0.986, q = 0.014). Kinetic studies revealed that the CBR1 V88 and CBR1 I88 isoforms have different maximal velocities for daunorubicin (Vmax CBR1 V88, 181 ± 13 versus Vmax CBR1 I88, 121 ± 12 nmol/min · mg, p < 0.05) and PGE2 (Vmax CBR1 V88, 53 ± 7 versus Vmax CBR1 I88, 35 ± 4 nmol/min · mg, p < 0.01). Concomitantly, CBR1 V88 produced higher levels of the cardiotoxic metabolite daunorubicinol compared with CBR1 I88 (1.7-fold, p < 0.0001). Inhibition studies demonstrated that CBR1 V88 and CBR1 I88 are distinctively inhibited by the flavonoid, rutin (IC50 CBR1 V88, 54.0 ± 0.4 μM versus IC50 CBR1 I88, 15.0 ± 0.1 μM, p < 0.001). Furthermore, isothermal titration calorimetry analyses together with molecular modeling studies showed that CBR1 V88I results in CBR1 isoforms with different binding affinities for the cofactor NADPH (Kd CBR1 V88, 6.3 ± 0.6 μM versus Kd CBR1 I88, 3.8 ± 0.5 μM). These studies characterize the first functional genetic determinant of CBR1 activity toward relevant physiological and pharmacological substrates.

Nitric Oxide Synthase Variants and Disease-Free Survival among Treated and Untreated Breast Cancer Patients in a Southwest Oncology Group Clinical Trial

Purpose: Numerous chemotherapeutic agents are cytotoxic through generation of reactive species, and variability in genes related to oxidative stress may influence disease-free survival (DFS). We examined relationships between DFS and variants in NOS3, as well as NQO1, NQO2, and CBR3, among treated and untreated breast cancer patients in a Southwest Oncology Group clinical trial (S8897). Experimental Design: In the parent trial, women were assigned according to prognostic features; the high-risk group was randomized to cyclophosphamide, i.v. methotrexate, and 5-fluorouracil or to cyclophosphamide, i.v. doxorubicin, and 5-fluorouracil ± tamoxifen, and the low-risk group did not receive adjuvant therapy. We extracted DNA from normal lymph node tissue and examined functional polymorphisms in NOS3, NQO1, NQO2, and CBR3, in relation to DFS, using Cox proportional hazard model. Results: There were significant interactions between DFS, adjuvant therapy, and NOS3 Glu298Asp and −786 polymorphisms, alone and in combination (P for interaction = 0.008). When NOS3 genotypes were combined, women with genotypes encoding for lower nitric oxide who received chemotherapy had a >2-fold increase in hazard of progression (hazard ratio, 2.32; 95% confidence interval, 1.26-4.25), whereas there was reduced risk for those who did not receive adjuvant therapy (hazard ratio, 0.42; 95% confidence interval, 0.19-0.95). There were no associations between the other genotypes and DFS in either group. Conclusion: Variants encoding lower activity of NOS3 may affect outcomes in breast cancer patients, with the direction of risk differing depending on chemotherapy status. These results may mirror the known dual functions of nitric oxide and nitric oxide synthase, depending on oxidative environment. (Clin Cancer Res 2009;15(16):5258–66) (Clin Cancer Res 2009;15(16):5258–)

Functional characterization of the promoter of human carbonyl reductase 1 (CBR1). Role of XRE elements in mediating the induction of CBR1 by ligands of the aryl hydrocarbon receptor.

Human carbonyl reductase 1 (CBR1) metabolizes a variety of substrates, including the anticancer doxorubicin and the antipsychotic haloperidol. The transcriptional regulation of CBR1 has been largely unexplored. Therefore, we first investigated the promoter activities of progressive gene-reporter constructs encompassing up to 2.4 kilobases upstream of the translation start site of CBR1. Next, we investigated whether CBR1 mRNA levels were altered in cells incubated with prototypical receptor activators (e.g., dexamethasone and rifampicin). CBR1 mRNA levels were significantly induced (5-fold) by the ligand of the aryl hydrocarbon receptor (AHR) β-naphthoflavone. DNA sequence analysis revealed two xenobiotic response elements (–122XRE and –5783XRE) with potential regulatory functions. CBR1 promoter constructs lacking the –122XRE showed diminished (9-fold) promoter activity in AHR-proficient cells incubated with β-naphthoflavone. Fusion of –5783XRE to the –2485CBR1 reporter construct enhanced its promoter activity after incubations with β-naphthoflavone by 5-fold. Furthermore, we tested whether the potent AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced Cbr1 expression in Ahr+/– and Ahr–/– mice. TCDD induced hepatic Cbr1 mRNA (TCDD, 2-fold) and Cbr1 protein levels (TCDD, 2-fold) in Ahr+/– mice compared with vehicle-injected controls. In contrast, no significant Cbr1 mRNA and Cbr1 protein induction was detected in livers from Ahr–/– mice treated with TCDD. These studies provide the first insights on the functional characteristics of the human CBR1 gene promoter. Our data indicate that the AHR pathway contributes to the transcriptional regulation of CBR1.

Etoposide induces chimeric Mll gene fusions

MLL gene fusions are the hallmark of more than 70% of therapy‐related leukemias (t‐ML) associated with topoisomerase II inhibitors (e.g., etoposide) and cause leukemia in murine transgenic models. To determine whether Mll genomic fusions can occur after exposure to topoisomerase II inhibitors, we developed a long‐distance inverse PCR DNA‐based assay for chimeric Mll fusions in mouse embryonic stem cells. We detected Mll fusions at a higher frequency following 100 µM etoposide for 8 h (16×10‒6 cell−1) than in no‐drug controls (1.0×10‒6 cell−1, P=0.0002) or after treatment with a comparably cytotoxic exposure to the antimicrotubule drug vincristine (1.0×10‒6 cell‐1, P=0.0047). The fusion points in Mll chimeric products induced by etoposide were localized to a 1.5 kb region between exons 9 and 11, analogous to the MLL breakpoint cluster region in human leukemia. All 49 Mll fusion partners analyzed matched known genomic murine sequences, with 40 (82%) matching annotated genes covering eighteen murine autosomes. One partner was Runxl, the murine homologue of the transcription factor AML‐l, a target of human translocations in therapy‐related leukemia. These findings indicate that etoposide triggers the formation of Mll gene fusions, a critical step for the development of treatment‐induced leukemic transformation.

A Rapid, Reproducible, On-the-Fly Orthogonal Array Optimization Method for Targeted Protein Quantification by LC/MS and Its Application for Accurate and Sensitive Quantification of Carbonyl Reductases in Human Liver

Liquid chromatography (LC)/mass spectrometry (MS) in selected-reactions-monitoring (SRM) mode provides a powerful tool for targeted protein quantification. However, efficient, high-throughput strategies for proper selection of signature peptides (SP) for protein quantification and accurate optimization of their SRM conditions remain elusive. Here we describe an on-the-fly, orthogonal array optimization (OAO) approach that enables rapid, comprehensive, and reproducible SRM optimization of a large number of candidate peptides in a single nanoflow-LC/MS run. With the optimized conditions, many peptide candidates can be evaluated in biological matrixes for selection of the final SP. The OAO strategy employs a systematic experimental design that strategically varies product ions, declustering energy, and collision energy in a cycle of 25 consecutive SRM trials, which accurately reveals the effects of these factors on the signal-to-noise ratio of a candidate peptide and optimizes each. As proof of concept, we developed a highly sensitive, accurate, and reproducible method for the quantification of carbonyl reductases CBR1 and CBR3 in human liver. Candidate peptides were identified by nano-LC/LTQ/Orbitrap, filtered using a stringent set of criteria, and subjected to OAO. After evaluating both sensitivity and stability of the candidates, two SP were selected for quantification of each protein. As a result of the accurate OAO of assay conditions, sensitivities of 80 and 110 amol were achieved for CBR1 and CBR3, respectively. The method was validated and used to quantify the CBRs in 33 human liver samples. The mean level of CBR1 was 93.4 +/- 49.7 (range: 26.2-241) ppm of total protein, and of CBR3 was 7.69 +/- 4.38 (range: 1.26-17.9) ppm. Key observations of this study: (i) evaluation of peptide stability in the target matrix is essential for final selection of the SP; (ii) utilization of two unique SP contributes to high reliability of target protein quantification; (iii) it is beneficial to construct calibration curves using standard proteins of verified concentrations to avoid severe biases that may result if synthesized peptides alone are used. Overall, the OAO method is versatile and adaptable to high-throughput quantification of validated biomarkers identified by proteomic discovery experiments.