Faculty Bibliography

Recent genomic profiling of childhood acute lymphoblastic leukemia (ALL) identified a high-risk subtype with an expression signature resembling that of Philadelphia chromosome-positive ALL and poor prognosis (Ph-like ALL). However, the role of inherited genetic variation in Ph-like ALL pathogenesis remains unknown. In a genome-wide association study (GWAS) of 511 ALL cases and 6,661 non-ALL controls, we identified a susceptibility locus for Ph-like ALL (GATA3, rs3824662; P = 2.17 x 10(-14), odds ratio (OR) = 3.85 for Ph-like ALL versus non-ALL; P = 1.05 x 10(-8), OR = 3.25 for Ph-like ALL versus non-Ph-like ALL), with independent validation. The rs3824662 risk allele was associated with somatic lesions underlying Ph-like ALL (CRLF2 rearrangement, JAK gene mutation and IKZF1 deletion) and with variation in GATA3 expression. Finally, genotype at the GATA3 SNP was also associated with early treatment response and risk of ALL relapse. Our results provide insights into interactions between inherited and somatic variants and their role in ALL pathogenesis and prognosis.

PURPOSE: Five-year overall survival (OS) for children with B-cell precursor acute lymphoblastic leukemia (B-ALL) exceeds 90% with risk-adapted therapy. Age, initial WBC count, genetic aberrations, and minimal residual disease (MRD) are used for risk stratification. Intrachromosomal amplification of a region of chromosome 21 (iAMP21; three or more extra copies of RUNX1 on an abnormal chromosome 21) is a recently identified recurrent genomic lesion associated with inferior outcome in some studies. We investigated the impact of iAMP21 in a large cohort treated in contemporary Children's Oncology Group (COG) ALL trials. PATIENTS AND METHODS: Fluorescent in situ hybridization for specific genetic aberrations was required at diagnosis. MRD was measured by flow cytometry at end induction. Outcome was measured as event-free survival (EFS) and OS. RESULTS: iAMP21 was found in 158 (2%) of 7,793 patients with B-ALL age >/= 1 year; 74 (1.5%) of 5,057 standard-risk (SR) patients, and 84 (3.1%) of 2,736 high-risk (HR) patients. iAMP21 was associated with age >/= 10 years, WBC less than 50,000/muL, female sex, and detectable MRD at day 29. Four-year EFS and OS were significantly worse for patients with iAMP21 and SR B-ALL, but iAMP21 was not a statistically significant prognostic factor in HR patients. There was no interaction between MRD and iAMP21. Among SR patients, day 29 MRD >/= 0.01% and iAMP21 were associated with the poorest EFS and OS; absence of both was associated with the best outcome. CONCLUSION: iAMP21 is associated with inferior outcome in pediatric B-ALL, particularly SR patients who require more intensive therapy and are now treated on HR COG ALL protocols.

Children's Oncology Group AALL07P2 tested whether substitution of Erwinia asparaginase 25,000-IU/m2 for 6 doses intramuscularly (IM) given Monday/Wednesday/Friday to children and young adults with acute lymphoblastic leukemia (ALL) and clinical allergy to pegaspargase would provide a 48-hour nadir serum asparaginase activity (NSAA) >/=0.10-IU/mL in at least 70% of patients. AALL07P2 enrolled 55 eligible/evaluable patients. NSAA >/=0.1-IU/mL was achieved in 38/41 patients (92.7%) with samples meeting acceptability criteria 48-hours after dosing and in 38/43 patients (88.4%) 72-hours after dosing during course 1. Among acceptable samples obtained during all therapy courses, 95.8% (252/263) of 48-hour samples and 84.5% (125/148) of 72-hour samples had NSAA >/=0.10-IU/mL. Pharmacokinetic parameters were estimated by fitting the serum asparaginase activity-time course for all 6 doses given during course 1 to a one compartment open model with first order absorption. Erwinia asparaginase administered with this schedule achieved therapeutic NSAA at both 48- and 72-hours and was well tolerated with no reports of hemorrhage, thrombosis, or death, and few cases of grade 2-3 allergic reaction (n=6), grade 1-3 hyperglycemia (n=6), and grade 1 pancreatitis (n=1). Following allergy to pegaspargase, Erwinia asparaginase 25,000-IU/m2 x 6 doses IM Monday/Wednesday/Friday for 2 weeks can be substituted for a single dose of pegaspargase.

BACKGROUND: The discovery of effective re-induction regimens for children with more than one relapse of acute lymphoblastic leukemia (ALL) remains elusive. The novel nucleoside analog clofarabine exhibits modest single agent efficacy in relapsed ALL, though optimal combinations of this agent with other active chemotherapy drugs have not yet been defined. Herein we report the response rates of relapsed ALL patients treated on Children's Oncology Group study AAML0523, a Phase I/II study of the combination of clofarabine and cytarabine. PROCEDURE: AAML0523 enrolled 21 children with ALL in second or third relapse, or those refractory to re-induction therapy. The study consisted of two phases: a dose finding phase and an efficacy phase. The dose finding portion consisted of a single dose escalation/de-escalation of clofarabine for 5 days in combination with a fixed dose of cytarabine (1 g/m(2) /day for 5 days). Eight patients received clofarabine at 40 mg/m(2) /day and 13 patients at 52 mg/m(2) /day. RESULTS: Toxicities observed at all doses of clofarabine were typical of intensive chemotherapy regimens for leukemia, with infection being the most common. We did not observe significant hepatotoxicity as reported in other clofarabine combination regimens. The recommended pediatric Phase II dose of clofarabine in combination with cytarabine for the efficacy portion of AAML0523 was 52 mg/m(2) . Of 21 patients with ALL, 3 (14%) achieved a complete response (CR). Based on the two-stage design definition of first-stage inactivity, the therapy was deemed ineffective. CONCLUSION: The combination of clofarabine and cytarabine in relapsed/refractory childhood ALL does not warrant further clinical investigation. Pediatr Blood Cancer (c) 2013 Wiley Periodicals, Inc.

Approximately 90% of the 2,000 children, adolescents, and young adults enrolled each year in Children's Oncology Group acute lymphoblastic leukemia (ALL) trials will be cured. However, high-risk subsets with significantly inferior survival remain, including infants, newly diagnosed patients with age >/=10 years, white blood count >/=50,000/microl, poor early response or T-cell ALL, and relapsed ALL patients. Effective strategies to improve survival include better risk stratification, optimizing standard chemotherapy and combining targeted therapies with cytotoxic chemotherapy, the latter of which is dependent upon identification of key driver mutations present in ALL. Pediatr Blood Cancer (c) 2012 Wiley Periodicals, Inc.

A 6-year-old male presented with a testicular mass, hepatosplenomegaly, and a pleural effusion while undergoing maintenance chemotherapy for treatment of T-cell acute lymphoblastic leukemia (T-ALL). He was subsequently diagnosed with a lymphoproliferative disorder that resembled hepatosplenic lymphoma (HSL). While the extranodal presentation and the protracted yet aggressive clinical course are consistent with HSL, the findings of monosomy 8 and polymorphic cell populations are unique and have not been previously described in this type of lymphoma. Pediatr Blood Cancer (c) 2013 Wiley Periodicals, Inc.

Background: The poor prognosis of relapsed ALL warrants the need for new insights into drug resistance mechanisms. We have previously shown that relapsed blasts can be re-sensitized to chemotherapy by the reversal of their gene expression signature using epigenetic agents.[1] Objectives: We hypothesize that aberrant epigenetic mechanisms may play a role in chemoresistance. To assess the degree to which the histone code evolves from diagnosis to relapse, we have used an unbiased, whole genome approach to examine changes in the epigenomic landscape by mapping the genome-wide location of key histone marks in diagnosis/relapse patient pairs with ALL enrolled on Children's Oncology Group protocols. Design/Method: We have performed Chromatin-immunoprecipitation sequencing (ChIP-seq) on two cryopreserved matched diagnosis/relapse pairs using active (H3K4me3, H3K9ac) and repressive (H3K9me3, H3K27me3) histone "mark" antibodies, with non-immunoprecipitated DNA (input) as control. Libraries for each patient pair were multiplexed in a single lane and sequenced in duplicate. 51-cycle single-end sequencing was performed using the Illumina HiSeq2000 Analyzer. Reads were aligned to reference genome using BWA and filtered using Samtools to remove multiple mapping reads. Peaks were called using MACS (v2.0.9) with default settings for histone marks. Results: 94.2% of the sequence reads passed filter (PF) and 96.4% of PF reads had quality score of more than 30. Using a p-value<0.00001, we identified 83,380 and 74,453 peaks (enriched regions) for activating and, 37,483 and 46,143 peaks for repressive histone marks at diagnosis and relapse respectively; suggesting that relapsed blasts are enriched with repressive marks and depleted of activating marks compared to those at diagnosis. Sixty-six genes had shared peaks for various histone marks between the two patients. Upon analyzing the top most differentially expressed transcripts at relapse from our previous cohort[2],64% genes showed concordant histone modificatio!

BUBR1 is a mitotic phosphoprotein essential for the maintenance of chromosome stability by promoting chromosome congression and proper kinetochore-microtubule (K-fiber) attachment, but the underlying mechanism(s) has remained elusive. Here we identify BUBR1 as a binding partner of the B56 family of Protein Phosphatase 2A regulatory subunits. The interaction between BUBR1 and the B56 family is required for chromosome congression, since point mutations in BUBR1 that block B56 binding abolish chromosome congression. The BUBR1:B56-PP2A complex opposes Aurora B kinase activity, since loss of the complex can be reverted by inhibiting Aurora B. Importantly, we show that the failure of BUBR1 to recruit B56-PP2A also contributes to the chromosome congression defects found in cells derived from patients with the Mosaic Variegated Aneuploidy (MVA) syndrome. Together, we propose that B56-PP2A is a key mediator of BUBR1's role in chromosome congression and functions by antagonizing Aurora B activity at the kinetochore for establishing stable kinetochore-microtubule attachment at the metaphase plate.