Faculty Bibliography

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.

There is incomplete understanding of genetic heterogeneity and clonal evolution during cancer progression. Here we use deep whole-exome sequencing to describe the clonal architecture and evolution of 20 pediatric B-acute lymphoblastic leukaemias from diagnosis to relapse. We show that clonal diversity is comparable at diagnosis and relapse and clonal survival from diagnosis to relapse is not associated with mutation burden. Six pathways were frequently mutated, with NT5C2, CREBBP, WHSC1, TP53, USH2A, NRAS and IKZF1 mutations enriched at relapse. Half of the leukaemias had multiple subclonal mutations in a pathway or gene at diagnosis, but mostly with only one, usually minor clone, surviving therapy to acquire additional mutations and become the relapse founder clone. Relapse-specific mutations in NT5C2 were found in nine cases, with mutations in four cases being in descendants of the relapse founder clone. These results provide important insights into the genetic basis of treatment failure in ALL and have implications for the early detection of mutations driving relapse.