Comparison of the Transcriptomic Signatures in Pediatric and Adult CML.

Children with chronic myeloid leukemia (CML) tend to present with higher white blood counts and larger spleens than adults with CML, suggesting that the biology of pediatric and adult CML may differ. To investigate whether pediatric and adult CML have unique molecular characteristics, we studied the transcriptomic signature of pediatric and adult CML CD34+ cells and healthy pediatric and adult CD34+ control cells. Using high-throughput RNA sequencing, we found 567 genes (207 up- and 360 downregulated) differentially expressed in pediatric CML CD34+ cells compared to pediatric healthy CD34+ cells. Directly comparing pediatric and adult CML CD34+ cells, 398 genes (258 up- and 140 downregulated), including many in the Rho pathway, were differentially expressed in pediatric CML CD34+ cells. Using RT-qPCR to verify differentially expressed genes, VAV2 and ARHGAP27 were significantly upregulated in adult CML CD34+ cells compared to pediatric CML CD34+ cells. NCF1, CYBB, and S100A8 were upregulated in adult CML CD34+ cells but not in pediatric CML CD34+ cells, compared to healthy controls. In contrast, DLC1 was significantly upregulated in pediatric CML CD34+ cells but not in adult CML CD34+ cells, compared to healthy controls. These results demonstrate unique molecular characteristics of pediatric CML, such as dysregulation of the Rho pathway, which may contribute to clinical differences between pediatric and adult patients.

Arsenic Trioxide Consolidation Allows Anthracycline Dose Reduction for Pediatric Patients With Acute Promyelocytic Leukemia: Report From the Children's Oncology Group Phase III Historically Controlled Trial AAML0631.

Purpose The Children's Oncology Group AAML0631 trial for newly diagnosed pediatric acute promyelocytic leukemia (APL) was a phase III historically controlled trial to determine the survival of patients receiving arsenic trioxide (ATO) consolidation and reduced doses of anthracyclines. Patients and Methods Patients age 2 to 21 years with de novo APL confirmed by PML-RARα polymerase chain reaction were stratified as standard risk (SR) or high risk (HR) on the basis of diagnostic WBC count. All patients received all-trans retinoic acid (ATRA) during induction, each consolidation course, and maintenance. All patients received two cycles of ATO therapy during consolidation 1, an additional two (SR) or three (HR) consolidation courses that included high-dose cytarabine and anthracycline, and maintenance therapy comprising ATRA, oral methotrexate, and mercaptopurine. Results One hundred one patients (66 SR and 35 HR) were evaluable for outcome. The 3-year overall survival was 94%, and event-free survival (EFS) was 91%. For SR and HR patients with APL, the overall survival was 98% versus 86% ( P = .003), and EFS was 95% versus 83% ( P = .03), respectively. The EFS for SR patients in AAML0631 was noninferior to that of patients in the AIDA 0493 historical control, which used a significantly higher anthracycline dose and did not include ATO consolidation. Relapse risk for patients in AAML0631 from end consolidation 1 (after ATO treatment) was only 4% at 3 years and did not differ significantly between SR and HR patients. Conclusion ATO consolidation cycles were well tolerated in pediatric patients with APL and allowed significant reduction in cumulative anthracycline doses while maintaining excellent survival and a low relapse risk for both SR and HR patients with APL.

Bortezomib, Dexamethasone, Mitoxantrone, and Vinorelbine (BDMV): An Active Reinduction Regimen for Children With Relapsed Acute Lymphoblastic Leukemia and Asparaginase Intolerance.

BACKGROUND: Children with relapsed acute lymphoblastic leukemia (ALL) typically receive vincristine-prednisone-L-asparaginase-doxorubicin reinduction chemotherapy similar to contemporary induction regimens. However, up to 20% of patients are unable to receive vincristine-prednisone-L-asparaginase-doxorubicin secondary to asparaginase intolerance. We report our experience with a promising reinduction regimen for children with relapsed ALL who are unable to receive asparaginase. PATIENTS AND METHODS: This is a single institution, retrospective review of the safety and activity of bortezomib, dexamethasone, mitoxantrone, and vinorelbine (BDMV) in patients with relapsed ALL. Complete remission and adverse events after reinduction were study endpoints. Patients treated with BDMV between 2012 and 2015 were identified. Response and adverse events (AEs) were assessed by review of medical records. Standard response criteria were used and AEs were graded based on NCI CTCAEv4.0. RESULTS: Seven of 10 patients achieved complete remission after 1 cycle of BDMV, with 4 achieving minimal residual disease negativity. The most common ≥grade 3 nonhematological toxicities were infection (91%), gastrointestinal (45%), metabolic (45%), and cardiovascular (9%). CONCLUSIONS: BDMV is an active reinduction regimen for children with relapsed ALL who cannot receive asparaginase. The toxicity profile is as expected for this patient population. Further prospective clinical trials are warranted to evaluate the safety and efficacy of BDMV.

A Heritable Missense Polymorphism in CDKN2A Confers Strong Risk of Childhood Acute Lymphoblastic Leukemia and Is Preferentially Selected during Clonal Evolution.

Genome-wide association studies (GWAS) have identified SNPs in six genes that are associated with childhood acute lymphoblastic leukemia (ALL). A lead SNP was found to occur on chromosome 9p21.3, a region that is deleted in 30% of childhood ALLs, suggesting the presence of causal polymorphisms linked to ALL risk. We used SNP genotyping and imputation-based fine-mapping of a multiethnic ALL case-control population (Ncases = 1,464, Ncontrols = 3,279) to identify variants of large effect within 9p21.3. We identified a CDKN2A missense variant (rs3731249) with 2% allele frequency in controls that confers three-fold increased risk of ALL in children of European ancestry (OR, 2.99; P = 1.51 × 10(-9)) and Hispanic children (OR, 2.77; P = 3.78 × 10(-4)). Moreover, of 17 patients whose tumors displayed allelic imbalance at CDKN2A, 14 preferentially retained the risk allele and lost the protective allele (PBinomial = 0.006), suggesting that the risk allele provides a selective advantage during tumor growth. Notably, the CDKN2A variant was not significantly associated with melanoma, glioblastoma, or pancreatic cancer risk, implying that this polymorphism specifically confers ALL risk but not general cancer risk. Taken together, our findings demonstrate that coding polymorphisms of large effect can underlie GWAS "hits" and that inherited polymorphisms may undergo directional selection during clonal expansion of tumors.

Obesity is associated with residual leukemia following induction therapy for childhood B-precursor acute lymphoblastic leukemia.

Obesity is associated with poorer event-free survival (EFS) in pediatric acute lymphoblastic leukemia (ALL). Persistent minimal residual disease (MRD) in the bone marrow as measured by multidimensional flow cytometry (MDF) is a key early prognostic indicator and is strongly associated with EFS. We therefore hypothesized that obesity during induction would be associated with positive end-of-induction MRD (≥0.01%). We analyzed MDF of end-induction bone marrow samples from a historical cohort of 198 children newly diagnosed with B-precursor ALL (BP-ALL) and treated with Children's Oncology Group induction regimens. We assessed the influence of body mass index on risk for positive end-induction MRD in the bone marrow. In our cohort of BP-ALL, 30 children (15.2%) were overweight and 41 (20.7%) were obese at diagnosis. Independent of established predictors of treatment response, obesity during induction was associated with significantly greater risk for persistent MRD (odds ratio, 2.57; 95% confidence interval, 1.19 to 5.54; P = .016). Obesity and overweight were associated with poorer EFS irrespective of end-induction MRD (P = .012). Obese children with newly diagnosed BP-ALL are at increased risk for positive end-induction MRD and poorer EFS.

Tobacco smoke exposure and the risk of childhood acute lymphoblastic and myeloid leukemias by cytogenetic subtype.

BACKGROUND: Tobacco smoke contains carcinogens known to damage somatic and germ cells. We investigated the effect of tobacco smoke on the risk of childhood acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML), especially subtypes of prenatal origin such as ALL with translocation t(12;21) or high-hyperdiploidy (51-67 chromosomes). METHODS: We collected information on exposures to tobacco smoking before conception, during pregnancy, and after birth in 767 ALL cases, 135 AML cases, and 1,139 controls (1996-2008). Among cases, chromosome translocations, deletions, or aneuploidy were identified by conventional karyotype and fluorescence in situ hybridization. RESULTS: Multivariable regression analyses for ALL and AML overall showed no definite evidence of associations with self-reported (yes/no) parental prenatal active smoking and child's passive smoking. However, children with history of paternal prenatal smoking combined with postnatal passive smoking had a 1.5-fold increased risk of ALL [95% confidence interval (CI), 1.01-2.23], compared to those without smoking history (ORs for pre- or postnatal smoking only were close to one). This joint effect was seen for B-cell precursor ALL with t(12;21) (OR = 2.08; 95% CI, 1.04-4.16), but not high hyperdiploid B-cell ALL. Similarly, child's passive smoking was associated with an elevated risk of AML with chromosome structural changes (OR = 2.76; 95% CI, 1.01-7.58), but not aneuploidy. CONCLUSIONS: Our data suggest that exposure to tobacco smoking was associated with increased risks of childhood ALL and AML; and risks varied by timing of exposure (before and/or after birth) and cytogenetic subtype, based on imprecise estimates. IMPACT: Parents should limit exposures to tobacco smoke before and after the child's birth.

Inverse association between brown adipose tissue activation and white adipose tissue accumulation in successfully treated pediatric malignancy.

BACKGROUND: Although the accumulation of white adipose tissue (WAT) is a risk factor for disease, brown adipose tissue (BAT) has been suggested to have a protective role against obesity. OBJECTIVE: We studied whether changes in BAT were related to changes in the amounts of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) in children treated for malignancy. DESIGN: We examined the effect of BAT activity on weight, SAT, and VAT in 32 pediatric patients with cancer whose positron emission tomography-computed tomography (PET-CT) scans at diagnosis showed no BAT activity. Changes in weight, SAT, and VAT from diagnosis to remission for children with metabolically active BAT at disease-free follow-up (BAT+) were compared with those in children without visualized BAT when free of disease (BAT-). RESULTS: Follow-up PET-CT studies (4.7 ± 2.4 mo later) after successful treatment of the cancer showed BAT+ in 19 patients but no active BAT (BAT-) in 13 patients. BAT+ patients, in comparison with BAT- patients, gained significantly less weight (3.3 ± 6.6% compared with 11.0 ± 11.6%; P = 0.02) and had significantly less SAT (18.2 ± 26.5% compared with 67.4 ± 71.7%; P = 0.01) and VAT (22.6 ± 33.5% compared with 131.6 ± 171.8%; P = 0.01) during treatment. Multiple regression analysis indicated that the inverse relations between BAT activation and measures of weight, SAT, and VAT persisted even after age, glucocorticoid treatment, and the season when the PET-CT scans were obtained were accounted for. CONCLUSION: The activation of BAT in pediatric patients undergoing treatment of malignancy is associated with significantly less adipose accumulation. This trial was registered at clinicaltrials.gov as NCT01517581.

Higher dose imatinib for children with de novo chronic phase chronic myelogenous leukemia: a report from the Children's Oncology Group.

PURPOSE: To determine the efficacy of imatinib in children with newly diagnosed chronic phase (CP) chronic myelogenous leukemia (CML). METHODS: This was an open label, multi-center phase II clinical trial. Courses were defined as consecutive 28-day intervals. Oral imatinib was administered daily at 340 mg/m² without interruption in the absence of toxicity. RESULTS: Fifty-one children received 978 28-day courses of imatinib. The most common toxicities encountered were hematologic. Forty-one patients (80%) achieved a complete hematologic response by the end of course 2. Nineteen children (38%) obtained a complete cytogenetic response (CCyR) at the end of course 3. Overall, 72% achieved CCyR at a median time of 5.6 months. The rate of complete molecular response (>3 log reduction) was 27%. Progression-free and overall survival at 3 years were 72% ± 6.4% and 92% ± 3.9%, respectively. CONCLUSIONS: Daily oral imatinib at a dose of 340 mg/m² is well tolerated in children. In addition, imatinib therapy is effective in inducing a high percent of hematologic, cytogenetic and molecular responses, comparable to adults with CML. (This study was registered at ClinicalTrials.gov under identifier NCT00030394.).

Graft-versus-leukemia effect on infant lymphoblastic leukemia relapsed after sibling hematopoietic stem cell transplantation.

INTRODUCTION: Infant acute lymphoblastic leukemia (ALL) is considered a high-risk entity. Patients diagnosed in the first 3 months of life have especially high mortality. By morphology, infant ALL is classified as a lymphoid lineage leukemia; however, its physiologic behavior has brought many to consider it a pathologic hybrid between lymphoid leukemia and myeloid leukemias. As such, standard of care currently employs the use of chemotherapeutic agents used commonly in ALL protocols and agents typically reserved for the treatment of myelogenous lineage leukemias. The role of hematopoietic stem cell transplantation and graft-versus-leukemia effect in these patients has not been well studied. CASE PRESENTATION: An earlier healthy 9-week-old Hispanic male diagnosed with precursor B-cell lymphoblastic leukemia was treated with protocol P9407 and matched sibling hematopoietic stem cell transplantation. Relapse was noted on posttransplant day +114 with blasts on peripheral blood smear. The sole antigraft-versus-host disease (GVHD) agent, cyclosporine, was discontinued. Blast clearance from the peripheral blood was obtained by posttransplant day +128 with the appearance of skin and liver GVHD at posttransplant day +181. Bone marrow examination on posttransplant day +205 revealed normal marrow with no evidence of leukemic cells. He remains disease free more than 2 years posttransplant. CONCLUSION: Traditionally, graft-versus-leukemia effect was thought to contribute therapeutically little to the treatment of ALL by hematopoietic stem cell transplantation (HSCT). The effects of graft-versus-leukemia immunologic phenomenon in our patient with infant acute lymphoblastic leukemia underscore the potential that infant ALL may not be entirely the same biologic entity as standard pediatric ALL and may be more responsive than understood earlier. Therapeutic response and appearance of GVHD after the withdrawal of immunosuppression in this patient provides evidence that graft-versus-leukemia effect may play a role in disease control in infant ALL after HSCT. Patients who relapse after the HSCT may be salvaged with the withdrawal of immunosuppression. This suggests that other immunotherapeutic interventions in the context of relapse may offer potential clinical benefit in this disease.

PEG-asparaginase.

L-asparaginases have been established components in the treatment of acute leukemias for nearly 40 years. Their antitumor effect results from the depletion of asparagine, an amino acid essential to leukemic cells, and subsequent inhibition of protein synthesis leading to considerable cytotoxicity. The efficacy of L-asparaginases has been limited by a high rate of hypersensitivity reactions and development of anti-asparaginase antibodies, which neutralize their activity. PEG-asparaginase, a form of Escherichia coli L-asparaginase covalently linked to polyethylene glycol, was rationally synthesized to decrease immunogenicity of the enzyme and prolong its half-life. In recent years, clinical trials have established the importance of intramuscular PEG-asparaginase in frontline pediatric and adult acute lymphoblastic leukemia therapy. Present studies are evaluating the feasibility of intravenous PEG-asparaginase administration.