ALBERT

Description: Key Points Infant acute lymphoblastic leukemia is sensitive to therapeutic targeting by apoptosis, necoptosis, and autophagy activation whether MLL is rearranged or germline. The disease-specific form of triple death mode killing by obatoclax overcomes the intrinsic resistance of MLL-rearranged infant acute lymphoblastic to cell death.

Description: Introduction Pediatric chronic myeloid leukemia (CML) accounts for 10 to 15% of children with myeloid leukemia and 2 to 9% of all pediatric leukemias. Prior to the discovery of tyrosine kinase inhibitors (TKI) such as imatinib, stem cell transplantation was the only curative treatment for both adults and children with CML. However, due to the small numbers of patients, standardized treatment approaches for pediatric CML have not been established. There are several unique characteristics of CML diagnosed in children and adolescents, and young adults (AYA; 16-29 years), compared to adults. Children and AYA with CML present with a higher white blood count and have larger spleens, higher peripheral blast counts, and lower hemoglobin levels, suggesting that the biology of pediatric CML is different than adult CML. In addition, potential side effects of TKIs unique to pediatric CML patients include impaired bone growth, fertility and immune function, however none have been extensively studied. We hypothesize that the differences in clinical presentation of pediatric CML patients are due to unique molecular characteristics that are absent in adult CML patients. To test this hypothesis, we studied the transcriptomic signature of pediatric CD34+ CML cells compared to adult CML and normal age-matched bone marrow CD34+ cells. Methods CD34+ cells were isolated from pediatric CML (n=7), adult CML (n=8), pediatric normal (n=2) and adult normal (n=3) bone marrow samples. Total RNA was isolated from cells, and then cDNA libraries were generated. Prepared libraries were sequenced on the Illumina HiSeq 4000 instrument. We aligned reads using the HISAT2 alignment software, and mapped to genes with HT-Seq. We removed genes that had zero reads across all the samples, resulting in a set of 4,696 genes that were detected in one or more samples. In case of technical replicates, we used mean of replicates. We performed three differential expression comparisons with edgeR: (1) Pediatric CML vs Adult CML, (2) Adult CML vs Adult Normal, and (3) Pediatric CML vs Pediatric Normal. We used a False Discovery Rate (FDR) of £ 20% and absolute log2 fold-change ³ 1 for selecting differentially expressed genes in each comparison. We used Fisher's exact test to identify significant KEGG pathways for the differentially expressed genes in each comparison. Results Pediatric CML vs Adult CML We found 24 differentially expressed genes (15 over- and 9 under-expressed). Though no pathway was found to be significant at the false discovery rate (FDR) £ 20%, we identified a number of sub-pathways that are relevant. For example, the Chemokine Signaling pathway shows at the top of the list (ordered by raw p-value) because of two genes, XCR1 and HCK, associated with VEGF and MAPK pathways involved in cell proliferation, angiogenesis, DNA repair, and cancer pathogenesis. Adult CML vs Adult Normal We found 60 genes (30 over- and 30 under-expressed) differentially expressed when comparing adult CML patients to normal adults. Ten genes overlapped with 24 genes we identified when comparing pediatric and adult CML patients. We found 11 pathways as significant at FDR £ 10%. Multiple pathways, including Cell adhesion, allograft rejection, Graft versus Host Disease, and Type I diabetes pathways, showed downregulation of MHC, with subsequent downstream reduction in expression of apoptosis-related genes. The IL-17 pathway makes sense, as MAPK, well-known to be associated with various cancers, is down-regulated. Lastly, in the NK pathway the gene DAP12 is up-regulated. This gene is known as a tyrosine kinase binding protein, and although tyrosine kinase inhibitors are the standard treatment for CML, the role of DAP12 in relation to leukemia has not yet been described. Pediatric CML vs Pediatric Normal We found 509 genes (350 over- and 159 under-expressed) differentially expressed in pediatric CML patients compared to normal. Interestingly, transcriptional regulators are differentially enriched in the hematopoietic stem cell differentiation function group including GATA1, GATA2, KLF1 and KLF2. RFC is down-regulated. RFC is a mismatch repair gene known to be involved in colorectal cancer. Many of the significant pathways are involved in glucose and fatty acid metabolism. Our pilot study identified novel molecular features of pediatric CML bone marrow stem cells, providing new insights into the novel biomarkers and pathogenesis of pediatric CML. Disclosures Gotlib: Blueprint Medicines: Consultancy, Honoraria, Research Funding; Promedior: Research Funding; Deciphera: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding; Kartos: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding.

Description: Mutations in the all-trans retinoic acid (ATRA)–targeted ligand binding domain of PML-RARα (PRα/LBD+) have been implicated in the passive selection of ATRA-resistant acute promyelocytic leukemia clones leading to disease relapse. Among 45 relapse patients from the ATRA/chemotherapy arm of intergroup protocol C9710, 18 patients harbored PRα/LBD+ (40%), 7 of whom (39%) relapsed Off-ATRA selection pressure, suggesting a possible active role of PRα/LBD+. Of 41 relapse patients coanalyzed, 15 (37%) had FMS-related tyrosine kinase 3 internal tandem duplication mutations (FLT3-ITD+), which were differentially associated with PRα/LBD+ depending on ATRA treatment status at relapse: positively, On-ATRA; negatively, Off-ATRA. Thirteen of 21 patients (62%) had additional chromosome abnormalities (ACAs); all coanalyzed PRα/LBD mutant patients who relapsed off-ATRA (n = 5) had associated ACA. After relapse Off-ATRA, ACA and FLT3-ITD+ were negatively associated and were oppositely associated with presenting white blood count and PML-RARα type: ACA, low, L-isoform; FLT3-ITD+, high, S-isoform. These exploratory results suggest that differing PRα/LBD+ activities may interact with FLT3-ITD+ or ACA, that FLT3-ITD+ and ACA are associated with different intrinsic disease progression pathways manifest at relapse Off-ATRA, and that these different pathways may be short-circuited by ATRA-selectable defects at relapse On-ATRA. ACA and certain PRα/LBD+ were also associated with reduced postrelapse survival.

Description: Introduction Infant acute lymphoblastic leukemia (ALL) is an orphan disease with unmet need for safe effective therapies. This is an urgent problem because conventional chemotherapies are ineffective and have life-threatening toxicities in infants. Although the MLL rearrangements occurring in 75% of cases are associated with poor outcome, survival is inferior whether MLL is rearranged or not. We recently reported that infant ALL proved sensitive to obatoclax mesylate (GeminX Pharmaceuticals; now an indirect, wholly owned subsidiary of Teva Pharmaceutical Industries Ltd.) in vitro regardless of poor prognostic features including MLL gene rearrangement. Moreover, we showed that the leukemia cell killing by obatoclax involved apoptosis, necroptosis and autophagy (Urtishak et al., Blood 2013). Therefore, the recent pharmaceutical abandonment of obatoclax led us to search for similarly acting drugs, the Results of which identified the well-known antipsychotic thioridazine as a candidate for potential repurposing. Methods Correlative analyses were performed between basal gene expression profiles at leukemia diagnosis and single agent obatoclax EC50 values from MTT assays in 47 cases of infant ALL from the Children's Oncology Group P9407 trial (25 MLL-AF4; 8 MLL-ENL; 7 other MLL-rearranged; 7 MLL-germline) in order to find a priori determinants of obatoclax sensitivity; significant genes were further studied by Ingenuity Pathway Analysis (IPA). A search for similarly acting compounds was conducted by Connectivity Map analysis of gene expression profiles of MLL-AF4 ALL cell lines after obatoclax treatment. MTT assays without and with cell death pathway inhibition, Western blot and flow cytometric cell death assays, and phosphoflow cytometric signaling analyses were utilized to investigate activity and target modulation by potential candidates. Results IPA identified significant correlations between basal gene expression of the mTOR and downstream intersecting eIF4/p70S6K signaling programs and obatoclax EC50 in all 47 primary cases of infant ALL, as well as in the subset of the 25 cases with MLL-AF4 rearrangements. Consistent with the relevance of this pathway in leukemia cell killing that was suggested by the basal gene expression profiles in the primary cases, the Connectivity Map analysis of obatoclax-treated cell lines for compound matching returned a number of highly ranked PI3K/AKT/mTOR signal transduction inhibitors as potential obatoclax substitutes. Three of the compounds (LY294002, wortmannin, thioridazine) were not only cytotoxic in MLL-AF4 ALL cell lines, but also they abrogated PI3K/AKT/mTOR signaling as indicated by robust inhibition of phosphorylated S6. Of these compounds, the phenothiazine derivative thioridazine, which has been used clinically for decades as a neuroleptic, was of high interest because of potential advantages of drug repurposing for more rapid drug advancement. Moreover, detailed flow cytometric and Western blot analyses, and MTT assays of thioridazine in the presence of cell death pathway inhibitors validated activation of all three cell death mechanisms in the MLL-AF4 ALL cell lines similarly to obatoclax. Conclusions Thioridazine is a well-known antipsychotic drug that also has recently recognized properties as a PI3K/AKT/mTOR signaling inhibitor and as an inhibitor of other pathways relevant to cancer. In MLL-AF4 ALL cell lines characterized by the most common chromosomal translocation in infant ALL, single-agent thioridazine is highly cytotoxic, robustly inhibits PI3K/AKT/mTOR signaling and, moreover, like obatoclax, demonstrates activity as a multi-cell-death pathway agonist. Further preclinical studies now are warranted to determine the extent to which thioridazine inhibits PI3K/AKT/mTOR signaling and causes leukemia cell killing in primary infant ALL cells in vitro and in vivo. The repurposing strategy that this drug may allow could have promise to streamline drug development in infant ALL where the need for new therapies is so urgent. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2752 Introduction: We recently identified a poor prognostic subgroup of pediatric BCR-ABL1 negative ALL patients characterized by deletion of IKZF1 (encoding the lymphoid transcription factor IKAROS) and a gene expression signature similar to BCR-ABL1 positive ALL, raising the possibility of activated tyrosine kinase signaling within this leukemia subtype. Targeted sequencing revealed activating sequence mutations in the Janus tyrosine kinases (JAK1 (N=3), JAK2 (N=17) and JAK3 (N=1)) in 21 of 187 (11.2%) BCR-ABL1 negative, high-risk pediatric ALL cases. All 21 cases with JAK mutations had the BCR-ABL1-like expression profile, accounting for about 50% of the cases with this phenotype, suggesting that mutations in JAK kinases account for some, but not all, cases with this distinctive profile. To determine whether mutations in other kinases might also be associated with this distinctive gene expression profile, we sequenced 126 genes encoding tyrosine kinases and mediators of kinase signaling in an additional 46 high-risk ALL cases with a BCR-ABL1-like expression profile. The genes sequenced included the entire tyrosine kinome. Methods: The 46 leukemia specimens studied were from patients enrolled on COG clinical trials for high risk ALL (P9906, n=23 and AALL0232, n=23), with risk defined primarily by elevated WBC and/or age 〉 10 years. All 46 cases had a BCR-ABL1 like expression profile. The 23 P9906 cases all lacked JAK mutations, while 3 of the 23 AALL0232 cases were found to have activating JAK mutations (JAK1 (N=1), JAK2 (N=2)). The entire coding region and UTRs of each gene was amplified by PCR of whole genome amplified genomic DNA, and subjected to Sanger sequencing. A CEPH sample (NA19085) was also included as a normal control DNA. Results: A total of 1,149,117 bases were sequenced bi-directionally for each sample; 96% of the targeted bases were covered with high-quality sequencing data. We identified a total of 2,302 variations predicted to change protein sequences, 173 of which are novel, putative variations after removing germline variations found in dbSNP, The Cancer Genome Atlas Project (TCGA) and the normal CEPH sample NA19085 in this study. For each novel variation, the tumor DNA was resequenced and matching normal DNA was sequenced to validate the original observation and to distinguish somatic from inherited variants. The results show that 105 variations are germline, 20 are false positives while the remaining markers failed in validation assay. Aside from 1 FLT3 mutation (23aainsN609), there are no confirmed somatic mutations in any other tyrosine kinase genes. Conclusion: Aside from JAK mutations, somatically acquired sequence mutations in tyrosine kinase genes are rare in children with high risk ALL and BCR-ABL1 like gene expression profiles. We are pursuing the identification of alternative mechanisms for kinase activation that might explain the distinctive expression profile observed in these cases. Disclosures: Relling: St. Jude Children's Research Hospital: Employment, Patents & Royalties; Enzon Pharmaceuticals: Research Funding. Hunger:bristol myers squibb: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; eisai: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Description: Background:Ph-like acute lymphoblastic leukemia (ALL) is a high-risk subtype of ALL in children. There are limited and conflicted data on the incidence and prognosis of Ph-like ALL in adults. Methods:Patients with newly-diagnosed B-ALL who received frontline chemotherapy at MD Anderson Cancer Center underwent gene expression profiling of leukemic cells to identify Ph-like ALL. Gene expression profiling was performed on 148 RNA samples using either U133 Plus 2.0 microarrays, or a customized Taqman low density array (LDA) card to identify patients with the Ph-like ALL gene signature (Roberts et al. NEJM 2014). An additional 7 previously untreated patients were found to have CRLF2 overexpression by multicolor flow-cytometry (MFC), and received induction chemotherapy at MDACC were included in the outcome analysis (but not for subtype frequency calculation). We performed targeted sequencing of 303 recurrently mutated genes (L300 panel, MDACC) in 40 patients with CRFL2 rearrangements (15 with matched germline control). Minimal residual disease (MRD) was assessed by MFC, with a sensitivity of 0.01%. Results:Of 148 patients, 49 (33.1%) were Ph-like, 46 patients (31.1%) were Ph+, and 53 patients (35.8%) were of other B-ALL subtypes (B-other). The median age of Ph-like cohort was 33.5 years (range, 15-71), Ph+ cohort was 49 years (range, 22-84), and B-other was 38 years (range, 15-79). Within the Ph-like ALL cohort, 61% had overexpression of CRLF2. Patients received hyper-CVAD (80%) or an augmented-BFM regimen (20%). The rate of CR/CRp was similar in the 3 disease subgroups (Ph-like ALL 89%, Ph+ ALL 93%, B-other 94%, p = 0.57). However, patients with Ph-like ALL were significantly less likely to achieve MRD-negative remission (30% vs. 56% for Ph+ ALL vs. 87% for B-other, p

Description: INTRODUCTION. Most studies of AML biomarkers have examined cryopreserved mononuclear cells (MNCs) obtained from repositories. These MNCs typically include non-leukemic cells (e.g., lymphocytes) and heterogeneous populations of viable and nonviable AML blasts at various stages of differentiation. We hypothesize that these variables negatively impact the prognostic power of current biomarkers. In an attempt to improve the prognostic power of such biomarkers, we examined enriched populations of viable AML blasts from 190 randomly selected AML patients on SWOG trials. To our knowledge, this study represents the largest examination of the quality of cryopreserved AML blasts and the potential prognostic benefit of enriching for viable leukemic blasts. METHODS. Cryopreserved bone marrow (BM, N=124) and peripheral blood (PB, N=116) samples from 190 AML patients on SWOG trials (SWOG-9031, SWOG-9333, S0106, and S0112) were randomly selected. The samples were thawed and sorted for viable AML blasts using a combination of fluorochrome-conjugated antibodies and DAPI. DNA and RNA were extracted and evaluated from both the unsorted AML samples (A-MNCs) and viable AML blasts (A-Blasts). FLT3-ITD allelic ratio (AR) was quantified by fragment analyses. Expression of 13 potentially prognostic transcripts was quantified via quantitative RT/PCR: BAALC, CCNA1, CEBPA, ERG1, EVI1, FLT3, GATA2, IL3RA, JAG1, KIT, MN1, RUNX1, and WT1. Fold expression differences were computed by the comparative CT method. Associations between quantitative biomarkers (FLT3-ITD AR and transcript expression) and survival (overall, OS and relapse-free, RFS) were analyzed using Cox proportional hazards regression, with interaction terms for biomarker by cell population (A-MNCs vs. A-Blasts) or CD34 expression (separately for A-MNCs and A-Blasts). A predetermined FLT3-ITD AR cutoff of 0.5 was utilized based on results by Schneider et al. (Blood, 2012) and others. For paired samples, BM was used. RESULTS. Lymphocyte percentage varied (median 7.1%, range 0.4 - 70.1%) and was correlated with patients' pre-treatment blast percentages (rs = -0.29, P = 0.0002). Viability by DAPI varied widely (median 66.5%, range 5.2 - 95.6%), and AML blasts displayed inter- and intra-sample immunophenotypic heterogeneity, with the slight majority expressing CD34 (54%) using a predetermined immunofluorescence cut-off 〉 104. For OS, there was no significant difference (P=0.67) in the effect of FLT3-ITD AR between A-Blasts (HR=0.91, P=0.78) and A-MNCs (HR=1.05, P=0.88). However, for RFS, the effect of FLT3/ITD AR differed significantly (P=0.025) between A-Blasts (HR=1.93, P=0.14) and A-MNCs (HR=0.87, P=0.73). Kaplan-Meier curves of RFS by FLT3-ITD AR for A-MNCs (Figure 1A) and A-Blasts (Figure 1B) also suggest this trend. A similar, but nonsignificant, trend towards higher HRs in A-Blasts was displayed in analyses restricted to NPM1 mutated patients (Table 1). Similar analyses did not show such a striking interaction between cell population and transcript biomarkers, but we found that most transcripts displayed significant associations with immunophenotype (data not shown). Therefore, we examined if CD34 expression might impact the prognostic value of transcripts, separately by cell population. The expression of two genes (CCNA1 and GATA2) displayed significant interactions with CD34 expression in relation to clinical outcomes (Table 1). Moreover, the interaction between biomarker and CD34 expressions differed depending on which cell population was examined, such that the interaction was significant in the A-Blasts but not A-MNCs. CONCLUSION. Cryopreserved samples vary widely in percentages of non-leukemic, dying cells and differentiation stage of leukemic blasts. These factors impact the measurement of quantitative biomarkers and may also impact the significance and prognostic value of these biomarkers. Future studies must consider the effects that sample viability, composition, and differentiation stage may have on quantitative biomarkers. In addition, we are examining the potential impact that mutations in other genes (e.g., ASXL1, DNMT3A, RUNX1, etc.) may have on our results. ACKNOWLEDGEMENT. The authors wish to gratefully acknowledge the important contributions of the late Dr. Stephen H. Petersdorf to SWOG and to study S0106. SUPPORT. NIH/NCI grants CA160872,CA180819, CA180828, and CA180888. Disclosures Wood: Seattle Genetics: Honoraria, Other: Laboratory Services Agreement; Amgen: Honoraria, Other: Laboratory Services Agreement; Pfizer: Honoraria, Other: Laboratory Services Agreement; Juno: Other: Laboratory Services Agreement. Erba:Jannsen: Consultancy, Research Funding; Sunesis: Consultancy; Gylcomimetics: Other: DSMB; Agios: Research Funding; Celgene: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Incyte: Consultancy, DSMB, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy; Astellas: Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding; Pfizer: Consultancy; Daiichi Sankyo: Consultancy; Celator: Research Funding; Juno: Research Funding. Othus:Celgene: Consultancy; Glycomimetics: Consultancy. Radich:Incyte: Consultancy; Novartis: Consultancy, Research Funding; Ariad: Consultancy; Gilliad: Consultancy.

Description: The genetic basis underlying inferior outcome of adolescent and young adult acute lymphoblastic leukemia (AYA ALL) as compared to childhood cases is largely unknown. To comprehensively characterize the genetic landscape of AYA ALL we studied 423 adolescent (16-21 yrs; median 17.7±1.3 yrs) and 250 young adult (21-39 yrs; median 28.3±7.0 yrs) samples from the Children's Oncology Group high-risk trial AALL0232, St Jude Children's Research Hospital Total XV and XVI, Eastern Cooperative Oncology Group E2993, MD Anderson Cancer Center and the Alliance - CALGB trials. Single nucleotide polymorphism (SNP) microarray analysis and gene expression profiling were performed to identify copy number alterations and distinct genetic subgroups. Samples were also sub classified using hierarchical clustering, ROSE outlier and PAM analysis of gene expression profiling data. Sequence mutation analysis was performed on candidate genes known to be mutated in pediatric ALL (including IKZF1, PAX5, JAK1/2, NRAS, KRAS, FLT3, IL7R, SH2B3, TP53 and CREBBP), and mRNA-seq was performed on selected BCR-ABL1-like cases (n=41). The genetic subgroups were divided into ETV6-RUNX1, TCF3-PBX1, hyperdiploid (〉50 chromosomes), MLL rearrangements, BCR-ABL1, BCR-ABL1-like, ERG and other (cases with no known lesions). As expected, ETV6-RUNX1 and hyperdiploid ALL were less frequent in adolescents (4% and 11%, respectively) and adults (2% for both) than in childhood ALL (

Description: Improved outcomes for children with acute lympboblastic leukemia (ALL) have been achieved, in part, from adaptation of risk-stratified therapy. The Children’s Oncology Group (COG) has implemented a real-time risk classification system (AALL03B1) using a combination of NCI-Rome risk criteria, blast cell genetic features, and early treatment response to determine the intensity of post-induction therapy. Between December 29, 2003 and June 1, 2007, more than 4,000 children over 1 year of age with B-precursor ALL were enrolled on AALL03B1, including 2293 (62%) with NCI Standard Risk (SR) and 1406 (38%) with NCI High Risk (HR) features who were subsequently enrolled on companion clinical trials. The most favorable genetic features used in AALL03B1 were identified in legacy COG studies and included TEL/AML1(TEL) or triple trisomies of chromosomes 4, 10, and 17 (TT). Unfavorable genetic features included the presence of BCR/ABL, MLL rearrangements, or extreme hypodiploidy (DNA index 1% received extended induction (EI) for two weeks followed by an additional evaluation of BM morphology and MRD at day 43 of induction. One hundred and nineteen patients received EI, with 40% having NCI SR features at diagnosis. Of the patients who received EI, 63% achieved an M1 marrow with MRD 〈 1% by day 43 and were eligible to continue on protocol therapy. This was more likely to occur in NCI SR patients (77% vs. 55%, p 220 COG institutions.