Faculty Bibliography

Minimal residual disease (MRD) is highly prognostic in pediatric B-precursor acute lymphoblastic leukemia (ALL). In COG High Risk B-ALL study AALL0232 we investigated MRD in subjects randomized in a 2X2 factorial design to receive either High-Dose (HD-MTX) or Capizzi Methotrexate (C-MTX) during interim maintenance (IM), or Prednisone or Dexamethasone during induction. Subjects with end induction MRD>=0.1% or those with morphologic slow early response were non-randomly assigned to receive a second IM and delayed intensification phase. MRD was measured by 6-color flow cytometry in one of two reference labs, with excellent agreement between the two. Subjects with end induction MRD<.01% had a 5y EFS of 87+/-1% vs 74+/-4% for those with MRD 0.01%-0.1%; increasing MRD amounts was associated with progressively worse outcome. Subjects converting from MRD positive to negative by end consolidation had a relatively favorable 79+/-5% 5 y DFS vs 39+/-7% for those with MRD>=0.01%. Although HD-MTX was superior to C-MTX, MRD retained prognostic significance in both groups (86+/-2% vs 58+/-4% for MRD negative vs positive C-MTX subjects; 88+/-2% vs 68+/-4% for HD-MTX subjects). Intensified therapy given to subjects with MRD>0.1% did not improve either 5y EFS or OS. However, these subjects showed an early relapse rate similar to that seen in MRD negative ones, with EFS/OS curves for patients with 0.1%-1% MRD crossing those with 0.01%-0.1% MRD at 3 and 4 years, thus suggesting that the intensified therapy altered the disease course of MRD positive subjects. Additional interventions targeted at the MRD positive group may further improve outcome. NCT00075725 at www.clinicaltrials.gov.

Asparaginase is used to treat acute lymphoblastic leukemia (ALL); however, hypersensitivity reactions can lead to suboptimal asparaginase exposure. Our objective was to use a genome-wide approach to identify loci associated with asparaginase hypersensitivity in children with ALL enrolled on St. Jude Children's Research Hospital (SJCRH) protocols Total XIIIA (n = 154), Total XV (n = 498) and Total XVI (n = 271) or Children's Oncology Group protocols POG 9906 (n = 222) and AALL0232 (n = 2,163). Germline DNA was genotyped using the Affymetrix 500K, Affymetrix 6.0, or the Illumina Exome Beadchip array. In multivariate logistic regression, the intronic rs6021191 variant in NFATC2 had the strongest association with hypersensitivity (P = 4.1x10-8, OR = 3.11). RNA-seq data available from 65 SJCRH ALL tumor samples and 52 Yoruban HapMap samples showed that samples carrying the rs6021191 variant had higher NFATC2 expression compared to non-carriers (P = 1.1x10-3 and 0.03, respectively). The top ranked non-synonymous polymorphism was rs17885382 in HLA-DRB1 (P = 3.2x10-6, OR = 1.63), which is in near complete linkage disequilibrium with the HLA-DRB1*07:01 allele we previously observed in a candidate gene study. The strongest risk factors for asparaginase allergy are variants within genes regulating the immune response.

BACKGROUND: Given the success of immunotherapeutic approaches in hematologic malignancies, the COG designed a phase I/II study to determine whether the addition of epratuzumab (anti-CD22) to an established chemotherapy platform improves rates of second remission (CR2) in pediatric patients with B-lymphoblastic leukemia (B-ALL) and early bone marrow relapse. PROCEDURE: Therapy consisted of three established blocks of re-induction chemotherapy. Epratuzumab (360 mg/m2 /dose) was combined with chemotherapy on weekly x 4 (B1) and twice weekly x 4 [eight doses] (B2) schedules during the first re-induction block. Remission rates and minimal residual disease (MRD) status were compared to historical rates observed with the identical chemotherapy platform alone. RESULTS: CR2 was achieved in 65 and 66%, of the evaluable B1 (n = 54) and B2 patients (n = 60), respectively; unchanged from that observed historically without epratuzumab. Rates of MRD negativity (<0.01%) were 31% in B1 (P = 0.4128) and 39% in B2 patients (P = 0.1731), compared to 25% in historical controls. The addition of epratuzumab was well tolerated, with a similar toxicity profile to that observed with the re-induction chemotherapy platform regimen alone. CONCLUSIONS: Epratuzumab was well tolerated in combination with re-induction chemotherapy. While CR2 rates were not improved compared to historical controls treated with chemotherapy alone, there was a non-significant trend towards improvement in MRD response with the addition of epratuzumab (twice weekly for eight doses) to re-induction chemotherapy. Pediatr Blood Cancer (c) 2015 Wiley Periodicals, Inc.

BACKGROUND: Nelarabine has shown impressive single agent clinical activity in T-cell acute lymphoblastic leukemia (T-ALL), but has been associated with significant neurotoxicities in heavily pre-treated patients. We showed previously that it was safe to add nelarabine to a BFM-86 chemotherapy backbone (AALL00P2). Children's Oncology Group (COG) AALL0434 is a Phase III study designed to test the safety and efficacy of nelarabine when incorporated into a COG augmented BFM-based regimen, which increases exposure to agents with potential neurotoxicity compared to the historical AALL00P2 regimen. PROCEDURE: AALL0434 included a safety phase to assess nelarabine toxicity. Patients with high-risk (HR) T-ALL were randomized to receive Capizzi-style escalating methotrexate (MTX) plus pegaspargase or high dose (HD) MTX with/without six five-days courses of nelarabine. We report results from 94 patients who participated in the initial safety phase of the study. RESULTS: There were no differences in the incidence of peripheral motor neuropathies, sensory neuropathies or central neurotoxicities among those randomized to the nelarabine (n = 47) and non-nelarabine arms (n = 47). CONCLUSIONS: The addition of nelarabine to COG-augmented BFM chemotherapy regimen is safe and feasible. The ongoing AALL0434 Efficacy Phase will determine whether the addition of nelarabine treatment improves outcome for patients with T-ALL. Pediatr Blood Cancer (c) 2015 Wiley Periodicals, Inc.

Abnormal gene expression in cancer represents an under-explored source of cancer markers and therapeutic targets. In order to identify gene expression signatures associated with survival in acute lymphoblastic leukemia (ALL), a strategy was designed to search for aberrant gene activity, which consists of applying several filters to transcriptomic datasets from two pediatric ALL studies. Six genes whose expression in leukemic blasts was associated with prognosis were identified:three genes predicting poor prognosis (AK022211, FASTKD1 and STARD4) and three genes associated with a favorable outcome (CAMSAP1, PCGF6 and SH3RF3). Combining the expression of these 6 genes could successfully predict prognosis not only in the two discovery pediatric ALL studies, but also in two independent validation cohorts of adult patients, one from a publicly available study and one consisting of 62 newly recruited Chinese patients. Moreover, our data demonstrate that our six gene based test is particularly efficient in stratifying MLL or BCR.ABL negative patients. Finally, common biological traits characterizing aggressive forms of ALL in both children and adults were found, including features of dormant hematopoietic stem cells, suggesting new therapeutic strategies.

There is increasing evidence from genome-wide association studies for a strong inherited genetic basis of susceptibility to acute lymphoblastic leukaemia (ALL) in children, yet the effects of protein-coding variants on ALL risk have not been systematically evaluated. Here we show a missense variant in CDKN2A associated with the development of ALL at genome-wide significance (rs3731249, P=9.4 × 10(-23), odds ratio=2.23). Functional studies indicate that this hypomorphic variant results in reduced tumour suppressor function of p16(INK4A), increases the susceptibility to leukaemic transformation of haematopoietic progenitor cells, and is preferentially retained in ALL tumour cells. Resequencing the CDKN2A-CDKN2B locus in 2,407 childhood ALL cases reveals 19 additional putative functional germline variants. These results provide direct functional evidence for the influence of inherited genetic variation on ALL risk, highlighting the important and complex roles of CDKN2A-CDKN2B tumour suppressors in leukaemogenesis.

Glucocorticoids are universally used in the treatment of acute lymphoblastic leukemia (ALL), and resistance to glucocorticoids in leukemia cells confers poor prognosis. To elucidate mechanisms of glucocorticoid resistance, we determined the prednisolone sensitivity of primary leukemia cells from 444 patients newly diagnosed with ALL and found significantly higher expression of CASP1 (encoding caspase 1) and its activator NLRP3 in glucocorticoid-resistant leukemia cells, resulting from significantly lower somatic methylation of the CASP1 and NLRP3 promoters. Overexpression of CASP1 resulted in cleavage of the glucocorticoid receptor, diminished the glucocorticoid-induced transcriptional response and increased glucocorticoid resistance. Knockdown or inhibition of CASP1 significantly increased glucocorticoid receptor levels and mitigated glucocorticoid resistance in CASP1-overexpressing ALL. Our findings establish a new mechanism by which the NLRP3-CASP1 inflammasome modulates cellular levels of the glucocorticoid receptor and diminishes cell sensitivity to glucocorticoids. The broad impact on the glucocorticoid transcriptional response suggests that this mechanism could also modify glucocorticoid effects in other diseases.