Early T-cell Precursor Research Articles

Advances in the Genetics and Therapy of Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) remains an important cause of morbidity in children and adults. In this article, we highlight advances in the genetics and therapy of three key subtypes of ALL: T-cell ALL, BCR-ABL1 (Philadelphia [Ph] chromosone-positive), and Ph-like ALL. T-ALL is an aggressive disease that accounts for about 15% and 25% of ALL among pediatric and adult cohorts, respectively, and exhibits a multistep nature of cancer initiation and progression. The integration of cytogenetics, molecular biology, and immunophenotype analyses has led to the identification of defined T-ALL subgroups, such as early T-cell precursor ALL and novel lesions with a prognostic role, for which specific inhibitors are being developed. Ph-positive ALL was historically regarded as a subtype of ALL with a poor prognosis, and allogeneic stem cell transplant was recommended for all patients who could undergo this procedure. The deep complete responses seen with combination tyrosine kinase inhibitors (TKIs) and chemotherapy in Ph-positive ALL, and the reports of long-term survival among some patients not undergoing allogeneic stem cell transplant, has raised the question of whether there is a subset of patients who could be cured without this intervention. Ph-like ALL is a subtype of B-progenitor ALL common among older children and adults and associated with a diverse range of genetic alterations that activate kinase signaling. Ph-like ALL is also associated with poor outcome, for which precision medicine trials identifying kinase alterations and testing TKI therapy are being developed.

How We Treat Patients with Acute Lymphoblastic Leukemia

How We Treat Patients with Acute Lymphoblastic Leukemia

Co-Expression of NUP98-HOXD13 and Mutant IDH2 Triggers an Early T-Cell Precursor-like Leukemia in Mice

Background and hypothesis: Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy, comprising of B lineage ALL and T-cell lineage ALL (about 85% and 15%, respectively). In most cases, treatment regimens for ALL patients have proved efficient and prognosis is usually encouraging. However, a recently described subgroup of T-cell ALL patients have been found to have a poor prognosis when treated with conventional therapy. These higher risk T-cell leukemias have a cell of origin thought to resemble an early T-cell precursor (ETP), which retains the capability to differentiate into both myeloid or T-lineage cells, and are therefore termed ETP ALL. ETP ALL is characterized by lack of or low expression of typical T-cell surface markers, aberrant expression of myeloid and hematopoietic stem cell (HSC) surface markers and a gene expression signature resembling that of murine ETP cells. Recently, ETP ALL patients were found to have a unique mutational landscape that includes acquired mutations in genes typically associated with myeloid differentiation. The ambiguous lineage attributes of ETP ALL may explain the ineffectiveness of current therapies, stressing the need for establishing pre-clinical animal models. Here we show that co-expression of Nup98-Hoxd13 (NHD13) fusion gene and a mutant IDH2 gene (IDH2 R140Q) triggers an ETP-like leukemia in mice. Expression of NHD13 has been reported in MDS and AML patients, and NHD13 mice have been previously shown to develop MDS, AML, and T-cell ALL. Mutations in IDH1/2 genes occur in several cancers, including AML; the most common IDH mutation in AML patients is the IDH2 R140Q. However, expression of mutant IDH1/2 in mice has been reported to induce an expansion of the HSC compartment but was not sufficient for establishment of leukemia. Targeted sequencing of NHD13 mice has identified recurrent mutations in IDH1, suggesting that these two aberrations may collaborate to cause leukemia.Study Design and Methods: IDH2 R140Q mice were crossed with NHD13 mice and the progeny were monitored for survival. Classification of leukemic samples was done using flow cytometry and PCR analysis of TCRβ gene rearrangements. Global expression and mutational patterns of IDH2/NHD13 leukemias were analyzed using gene chip arrays and whole exome sequencing (WES).Results and conclusions: Transgenic IDH2/NHD13 mice showed decreased survival compared to all control groups. Detailed analysis of surface marker expression revealed that most double Tg cases (10/11 tested) developed leukemias resembling ETP (cKit+CD44+CD25-) or double negative (DN) 2 cells (cKit+CD44+CD25+). PCR analysis of the TCRβ locus revealed that unlike NHD13 T-cell leukemias, IDH2/NHD13 leukemias do not have clonal VDJ rearrangements. However, most of IDH2/NHD13 leukemias have clonal or oligoclonal DJ rearrangements of the TCRβ locus, suggesting that these leukemias emerged during an early stage in T cell development. Expression analysis revealed that the IDH2/NHD13 leukemia expression signature is enriched in genes that are upregulated in ETP or DN2 cells. In addition, we found that the IDH2/NHD13 leukemia expression signature is also enriched in genes uniquely expressed in ETP ALL patients. Finally, WES showed correspondence between genes mutated in the mouse ETP-like leukemia and genes recurrently mutated in ETP ALL patients. These results indicate that IDH2/NHD13 leukemias resemble ETP ALL in terms of gene expression, immunophenotype, and cooperative mutations.Relevance and importance: The poor prognosis of ETP ALL may be related to incomplete effectiveness of treatment strategies, emphasizing the need for novel therapies. IDH2/NHD13 mice can serve as an excellent pre-clinical model to study ETP ALL and to test potential treatments. DisclosuresAplan:NIH Office of Technology Transfer: Patents & Royalties.

Multi-Institution Review of Adult Early T-Cell Precursor Acute Lymphoblastic Leukemia/Lymphoma (ETP-ALL)

Background:The Early T-cell precursor (ETP) variant of acute lymphoblastic lymphoma/leukemia (ALL) is a recognized high risk variant, recognized by the absence of CD1a, with aberrant myeloid antigen expression (CD13, CD33, CD117, and CD34), and frequent absence of CD4 or CD8. Treatment intensification may improve outcome in this subset. We undertook a multi-center retrospective analysis to explore clinical features, treatment exposure, and outcomes in ETP ALL as compared to non-ETP variants.MethodsAdult T-ALL/T-LBL cases were compiled from 3 high volume cancer centers between the years 2003-2015. Data collected included patient demographics, tumor characteristics (white count at diagnosis, flow cytometry, FISH, cytogenetics, bone marrow involvement), treatment regimens and patient outcomes. ETP cases were defined as definite (CD1a-/CD8-/myeloid+) or probable (CD1a unk/CD8-/myeloid+, or CD1a-/myeloid+ with CD4+ and/or CD8+). All other cases were defined as non-ETP. Demographic data were compared using independent t-test assuming non-equal variance. OS and PFS were calculated from diagnosis and compared by Kaplan Meier and log-rank testing.ResultsAmong 95 cases, 33 met criteria for definite/probable ETP (35%). OS and PFS data were indistinguishable between these groups (p=0.24, p=0.34), and were subsequently analyzed as a single group.Within the ETP group, no factors were associated with OS, including histology (CD1a+ vs unk, CD3cyt vs CD3sur, CD5dim vs CD5+, CD1a+/13+ vs CD1a+/13-, or CD13, CD33, CD117, CD34, & TdT status), marrow blast burden, peripheral blast burden, white blood cell count (wbc), hemoglobin (hgb), platelet count (plt), cytogenetics/FISH status, chemotherapy choice, or allogeneic transplant (in CR1 or at any time). With regards to PFS, only the inclusion of asparaginase with induction was associated with outcome (p=0.009), while all other covariates failed to show any significance.The ETP group was compared with the non-ETP subset (table 1). ETP were more likely to abuse marijuana, possibly reflecting unrecognized pesticide exposure, and were more likely to abnormalities of chrom 5 & 7. ETP trended towards lower response and higher rate of relapse, with lower PFS. Comparison of OS was not significant, likely related to small numbers (5y OS 37% vs 22%, figure 1). Non-ETP failed to show PFS benefit with frontline asparaginase, otherwise no treatment differences were apparent.ConclusionsIn this muti-center cohort we were able to identify and characterize ETP cases, confirming poor outcomes. Improvement in PFS among ETP patients treated with frontline asparaginase warrants attention and prospective confirmation. Unfortunately, OS remains poor independent of treatment or receipt of allogeneic transplant, suggesting a critical need remains for development and study novel therapies.Table 1ETPNon-ETPp-valueMedian Age37.4534.740.42Male82%66%0.89FamilyHx of Lymph/Leuk21%8%0.112FamilyHx of Ca42%25%0.09THC24%5%0.021P blasts40%28%0.158>25% M blasts30%55%0.0571WBC78.4576.550.948wbc>10024%24%0.995Hgb10.7211.780.148hgb<1267%47%0.097plt151.59138.660.644Chrom 5/740%7%0.005Remission61%79%0.096Relapse76%58%0.073OS27.0022.000.595PFS13.0017.000.048PFS AspETP (asp no vs yes)12590.009non-ETP (asp no vs yes)17150.777 [Display omitted] DisclosuresShah:Acetylon: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; PLexus Communications: Honoraria; Pharmacyclics: Speakers Bureau; Rosetta Genomics: Research Funding; Seattle Genetics: Research Funding. Kota:Pfizer: Membership on an entity's Board of Directors or advisory committees; Leukemia Lymphoma Society: Research Funding. Hathaway:OnQ Health: Research Funding.

The Genomic Landscape of Childhood T-Lineage Acute Lymphoblastic Leukemia

Comprehensive studies examining the genomic landscape of T-lineage ALL are lacking, but are important to identify all oncogenic drivers. Here we report sequencing of 264 T-ALL consecutive cases treated on the Children's Oncology Group AALL0434 clinical trial. Whole exome sequencing, copy number analysis using exome and single nucleotide polymorphism array analysis of tumor and remission DNA, and RNA-sequencing of tumor RNA were performed. Cases with immunophenotypic data (N=189) included 19 early T-cell precursor (ETP) cases, 24 near-ETP (with normal CD5 expression) and 146 Non-ETP cases. Median exomic coverage was 89% (72%-96%) of exons with at least 20-fold coverage.We identified 4657 non-synonymous clonal and subclonal somatic mutations (3926 single nucleotide variants (SNV) and 731 insertion-deletion mutations; indels) in 3030 genes, with a mean of 17.6 per case (range 1-50). 176 potential driver genes were identified statistical analysis or by known pathogenic role in cancer. These included NOTCH1 (n=194, 73%), FBXW7 (n=64, 24%), PHF6 (n=50, 19%), PTEN (n=37, 14%), USP7 (n=32, 12%), DNM2 (n=29, 11%) and BCL11B (n=27, 10%). New mutations in T-ALL included CCND3 (n=15, 6%), MYB (n=13, 5%), CTCF (n=13, 5%), MED12 (n=7, 3%), USP9X (n=7, 3%), SMARCA4 (n=7, 3%) and CREBBP (n=6, 2%). In addition to MYB amplification, we identified missense mutations and in-frame protein insertions at the N-terminus of MYB, with a hotspot at codon 14 in a region of six acidic residues in an otherwise hydrophilic N-terminal tail. These mutations resulted in a disordered region that is predicted to affect nuclear localization. The MYB mutations detected were enriched in non-ETP cases (n=13; 8 non-ETP, 1 near-ETP, 4 unknown). Other genes enriched in non-ETP cases included RPL10, CNOT3, MYCN and DDX3X. MED12 mutations were more common in ETP ALL.Sub-clonal mutations (mutant allele fraction of less than 30%) were identified in 111 of 176 driver genes in 198 (75%) cases including NOTCH1 (n=94), FBXW7 (n=29) and PTEN (n=17) indicating that sub-clonal evolution is a hallmark of T-ALL. In addition, multiple mutations in individual genes were commonly observed in single cases. For example, up to 3 different somatic NOTCH1 mutations were detected in each of 9 patients, with 2 different NOTCH1 mutations in 49 cases.Integration of sequence mutations with copy number aberration data showed the following pathways to be most frequently mutated: cell cycle/tumor suppression (N=225; CDKN2A/B (n=206), CDKN1B (n=35), RB1 (n=28)); NOTCH1/FBXW7 (n=212), PI3K-AKT (n=130), JAK-STAT (n=99) and Ras (n=51). Mutations in the PI3K-AKT, JAK-STAT and Ras signaling pathways were mutually exclusive. We identified a high frequency of mutations in transcriptional regulators in 222 cases, including 108 cases with mutations in a core regulatory complex comprising TAL1 (n=51), MYB (n=45) RUNX1 (n=18) and GATA3 (n=13). In 90 of these 108 cases (83%), only a single mutation was present in any of the four genes, consistent with a central role of this complex in leukemogenesis. Epigenetic alterations were identified in 178 cases, including PHF6 (n=63), SMARCA4 (n=23), KDM6A (n=22) and EZH2 (n=18), and new deletions and mutations in KMT2A (MLL; n=11).Interim analysis of transcriptome sequencing data of 126 T-ALL cases detected fusions in 61 (48%) samples, which could be separated into two categories. One weres in-frame fusions resulting in a chimeric protein. The most frequent included MLLT10 fusions (PICALM-MLLT10 (n=3), DDX3X-MLLT10 (n=2) and NAP1L1-MLLT10 (n=1)), KMT2A fusions (KMT2A-MLLT1 (n=4), MLLT6-KMT2A (n=1) and MKT2A-MLLT4 (n=1)), as well as internal tandem duplication mutations involving FLT3 (n=6; 3 ETP, 1 near-ETP, 1 non-ETP, 1 unknown) and NOTCH1 (n=2). We also identified novel fusions including ETV6-CTNNB1 and STMN1-SPI1 (n=1 each). The other category contains rearrangement-driven aberrant expression, including rearrangements in TLX1 (n=11), TLX3 (n=4), TAL1 (n=2), and TAL2 (n=3). Moreover, we found a novel TAL2 transcript in all the 3 cases with TAL2 rearrangement, hijacking a new exon 6kb upstream of the canonical TAL2 transcription start site and extending approximate 3.5kb downstream.These findings provide the first comprehensive landscape of genomic alterations in T-ALL and have provided new insights into the genes and pathways mutated in this disease, their interaction, and the nature of clonal heterogeneity in T-ALL. DisclosuresHunger:Spectrum Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy; Sigma Tau: Consultancy; Merck: Equity Ownership. Mullighan:Cancer Science Institute: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria; Loxo Oncology: Research Funding.

Mixed Lineage Leukemia Rearrangements (MLL-R) Are Determinants of High Risk Disease in Homeobox A (HOXA)-deregulated T-Lineage Acute Lymphoblastic Leukemia: A Children's Oncology Group Study

Acute leukemias are the most commonly occurring cancers among children, adolescents and young adults. Approximately 15% of newly-diagnosed patients present with T-lineage acute lymphoblastic leukemia (T-ALL). In contrast to B-precursor ALL, molecular lesions that deregulate homeobox (HOX) genes appear to be widely prevalent in T-ALL, but their impact on outcome is unclear. We hypothesized that the molecular lesions associated with HOXA -deregulated T-ALL might identify patients with high-risk disease. We performed gene expression profiling (GEP) on a cohort of 213 T-ALL diagnostic samples obtained from children and young adults enrolled on Children's Oncology Group (COG) treatment studies 9404 (n=50) and AALL0434 (n=163). We identified a cluster of 54 cases (25%) characterized by increased expression of HOXA3, 5, 7, 9, and 10 (FDR ≤ 0.05; fold change cut off 3). We screened our database for the presence of MLL-R, AF10-R (MLLT10) and other HOXA deregulating lesions using an analysis of cytogenetics, FISH, LDI-PCR and RNA sequencing. We identified 15 cases with MLL-R, including MLL-AF6 (n = 5), del3'MLL (n = 3), MLL-ENL (n = 5), MLL-AF17 (n = 1), and PICALM-MLL (n = 1). Five cases were confirmed to have PICALM-AF10 fusions and two cases showed DDX3X-AF10 lesions. Two cases harbored NUP98 fusions, two cases had inv(7)(p15q34), and one case each was identified for HOXA10-(3'UTR)TRBC, STAG2-LMO2, LOC338817-CCDC91. We could not identify fusion transcripts in 3 cases, but MLL -R and AF10-Rwere confidently excluded with RNA sequencing. Almost 90% of cases identified to have MLL-R or AF10-R had ≥ 8-fold over-expression of HOXA9/10. Because HOXA-deregulated T-ALL is characterized by a high degree of molecular heterogeneity, we hypothesized that subset analyses might identify lesions that were more likely to be associated with an inferior outcome. We found that chromosomal abnormalities involving the MLL gene, but not AF10, were associated with induction failure (IF) in T-ALL (P = 0.02, OR = 5.34). Since MLL- and AF10 -R leukemias also demonstrate features of undifferentiated leukemias, we discriminated early T-cell precursor (ETP) from non-ETP cases using a GEP developed by Coustan-Smith et al. (Lancet Oncol, 2009). Among the 26 cases that showed ETP features, eleven (42%) also co-expressed HOXA9/10 (≥ 8-fold increase over the median). We found an association between ETP-ALL and early treatment failure (P = 0.01, OR = 4.37), and next assessed whether ETP cases are enriched with translocations harboring MLL or AF10 genes. We found overlap between MLL-R and the ETP cases (P = 0.03, OR = 4.14). We confirmed that ETP-ALL and MLL-R are risk features for IF (P = 0.026, OR = 4.37), and that cases with MLL-R (n = 11) had an inferior EFS compared to those that did not (N = 89) (P = 0.0158). We extended these observations to assess the impact of ETP/MLL-R (n = 6 vs. non-MLL/non-ETP, n = 69) on EFS, and found a significant association with treatment failure (P = 0.0007). For T-ALL, MRD has emerged as a prognostic indicator of high-risk disease. While MLL-ENL (n = 5)cases did not fail therapy regardless of Day 29 MRD levels, all patients with Day 29 MRD > 0.1 and MLL-AF6 (n = 5) or FISH-identified del3'MLL (n = 3) either failed induction or relapsed. Patients with AF10 -R (N = 7) have been reported to have inferior EFS, but we observed that only patients with Day 29 MRD ≥10% failed treatment. Our findings show a heterogeneity of outcomes related to MLL-R, but those with MLL-AF6 and del3'MLL should be considered high-risk. We propose that cytogenetic testing including specific FISH should be performed on all T-ALL patients at diagnosis and relapse. The current development of epigenetic modifying therapies targeted against HOXA-deregulating lesions warrants further study in T-ALL. DisclosuresAplan:NIH Office of Technology Transfer: Patents & Royalties. Mullighan:Amgen: Honoraria, Speakers Bureau; Cancer Science Institute: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Honoraria; Loxo Oncology: Research Funding. Hunger:Merck: Equity Ownership; Sigma Tau: Consultancy; Jazz Pharmaceuticals: Consultancy; Spectrum Pharmaceuticals: Consultancy.

Ezh2 Loss Promotes the Transformation of Early T Cell Precursor Leukemia Via Suppressing Critical Genes for T-Cell Differentiation

Early T cell precursor (ETP) acute lymphoblastic leukemia (ALL) has been identified as a new pathologic entity with poor outcome in patients with T-ALL. In contrast to cortical T-ALL, ETP-ALL has been characterized by the activating mutations in genes regulating cytokine signaling and the inactivating mutations in the polycomb repressor complex 2 (PRC2) component genes including EZH2. EZH2 catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3) that mediates silencing of critical genes for cell proliferation and differentiation. Given that loss-of-function mutations in EZH2 are often found in ETP-ALL, EZH2 may play a tumor suppressor role in the pathogenesis of ETP-ALL. To determine how EZH2 dysfunction promotes the development of ETP-ALL in vivo, we generated a novel mouse model of ETP-ALL by utilizing Ezh2 and p53 conditional knockout mice. We harvested bone marrow cells from Cre-ERT (WT), Cre-ERT;Ezh2flox/flox (Ezh2 KO), Cre-ERT;Trp53flox/flox (p53 KO) and Cre-ERT;Trp53flox/flox;Ezh2flox/flox (DKO) mice, and transplanted them into lethally-irradiated Ly5.1+ recipient mice. We deleted p53 and Ezh2 via administration of tamoxifen 4 weeks post-transplantation. We observed that p53 KO mice died dominantly due to CD3+ CD8+ cortical T-ALL (median survival; 137 days), as previously reported. While 2 out of 8 DKO mice developed CD8+ cortical T-ALL, we found that 6 out of 8 DKO mice developed CD4- CD8- (DN) T-ALL with a longer latency (median survival; 189 days). At the time of sacrifice, DKO mice showed significantly enlarged thymus due to the expansion of c-Kit+ CD44+ CD25- DN1 and c-Kit+ CD44+ CD25+ DN2 cells, which were markedly compromised in differentiation into DN3 and further down to CD4+ CD8+ (DP) cells. Histological analysis demonstrated the expansion of cytoplasmic CD3+ (cyCD3) tumor cells in the thymus of DKO mice with DN T-ALL. Thus, DKO mice faithfully recapitulated the phenotypic features of human ETP-ALL, indicating that the loss of Ezh2 is prerequisite to the development of c-Kit+ CD44+ CD25+ cyCD3+ DN ALL in mice lacking p53.To understand the underlying molecular mechanism in the pathogenesis of Ezh2 loss-induced ETP-ALL, we performed gene expression analysis in DN1, DN2 and DN3 cells isolated from WT and DKO mice at pre-disease and ETP-ALL stages. Since NOTCH1 activating mutations are not frequently found in patients with ETP-ALL, we observed no significant difference in activation of Notch1-target genes between WT and DKO ETP-ALL cells. In contrast, Ras-target genes were significantly activated in DKO ETP-ALL DN2 cells relative to WT DN2 cells. Thus, our ETP-ALL mouse model shows active Ras signaling but lacks Notch1 activation, consistent with the molecular features of human ETP-ALL. Furthermore, we found that the genes critical for T-cell commitment, including Tcf7 or Bcl11b, were transcriptionally repressed in DKO ETP-ALL DN2 cells compared to WT DN2 cells, while the signature genes of both HSCs and myeloid cells were retained in DKO ETP-ALL DN2 cells. Taken together, Ezh2 and p53 deletions cooperate to activate the function of HSCs and impede the transcriptional program of T-cell differentiation at the DN2 stage with sustaining myeloid potential. To determine how H3K27me3 modification contributed to induce ETP-ALL in the absence of Ezh2, we performed H3K27me3-chromatin immunoprecipitation (ChIP) sequencing in WT and DKO ETP-ALL DN1/2 cells. We found that H3K27me3 marks were lost or kept at low levels at the promoter regions of T-cell differentiation regulators in ETP-ALL cells. Thus, we sought to determine whether altered DNA hypermethylation contributed to silencing the expression of T-cell differentiation regulators. The transduction of either Tcf7 or Bcl11b expression alone was not sufficient to induce differentiation of DKO DN1/2 cells in vitro, however, we found that treatment of decitabine, a demethylating agent, clearly induced the differentiation of DKO DN1/2 cells beyond the DN3 stage in vitro, implying that Ezh2 loss and p53 loss cooperatively induced aberrant DNA hypermethylation, thereby impeding the differentiation of DN1/2 cells. In conclusion, we demonstrated that combined deletion of Ezh2 and p53 altered the epigenetic regulation to an extent not seen in either deletion alone, and induced highly penetrant ETP-ALL characterized by the molecular profile similar to that in patients with ETP-ALL harboring mutations in the PRC2 components. DisclosuresNo relevant conflicts of interest to declare.

Early T-Cell Precursor Acute Lymphoblastic Leukemia (ETP-ALL) Is a High-Risk Subtype in Adults

Background: Early T-cell precursor (ETP) acute lymphoblastic leukemia/lymphoma (ALL) is a recently recognized high-risk T-ALL subgroup. The optimal therapeutic approaches to adult patients with ETP-ALL are poorly characterized. In this study, we compared the outcomes of adults with ETP-ALL who received treatment on frontline regimens to those of patients with other T-ALL immunophenotypic subtypes.Methods: Patients with newly-diagnosed T-ALL who received frontline chemotherapy between the years 2000 and 2014 at The University of Texas MD Anderson Cancer Center (MDACC) were identified and immunophenotypically categorized into early, thymic, and mature per the European Group for the Immunologic Classification of Leukemia (EGIL)/WHO classification. Patients with ETP-ALL were identified on the basis of the following immunophenotype: CD1a(-), CD8(-), CD5(-/dim), and positivity for one or more stem cell or myeloid antigens. Patients received frontline treatment with the following chemotherapy regimens: hyper-CVAD alone (n=43), hyper-CVAD + nelarabine (n=44) or augmented BFM regimen (n=24).Results: A total of 111 patients with T-ALL with adequate immunophenotype data were identified. There was no difference in the outcomes of patients based on the EGIL/WHO subtypes (Fig 1). A total of 19 patients (17%) had ETP-ALL. The complete remission rate (CR)/CR with incomplete platelet recovery (CRp) rate in patients with ETP-ALL was significantly lower than that of non-ETP-ALL patients (73% vs. 91%; p=0.03). The median overall survival for patients with ETP-ALL was 20 months vs. not reached for the non-ETP-ALL patients (p = 0.008) (Fig 2). ETP-ALL remained a high-risk subgroup within the WHO 'Early' group (Fig 3). A subset of patients with early T-ALL had an immunophenotype that resembled that of ETP-ALL except for having ≥75% CD5 expression (ETP+CD5). The OS of patients with ETP+CD5 (n=19) was similar to that of non-ETP-ALL patients and differed from that of ETP-ALL patients (p=0.059).By univariate analysis, the following variables were significant for survival: age, WBC count (<50 vs. ≥50 x109 /L), platelet count (<100 vs. ≥100 x109 /L), LDH (<600 vs. ≥600 IU/L) and ETP-ALL (Table 1). By multivariate analysis, only age (HR: 2.862; 95%CI: 1.140-7.183; p=0.025) and ETP-ALL (HR: 2.275; 95%CI: 1.117-4.631; p=0.023) were significant.Conclusions: ETP-ALL represents a high-risk disease subtype of adult ALL. Allogeneic stem cell transplant in CR1 should be considered. Novel treatment strategies are needed to improve treatment outcomes in this T-ALL subset.Table 1Univariate and multivariate analysis for survivalParameterSurvivalUVAMVAPPHR95%CIAge ≥600.0130.0252.8621.140-7.183Gender0.24---Diagnosis (ALL vs. LBL)0.13---WBC < 50.0 (x 109 /L)0.009---Hemoglobin <10 (g/dL)0.36---Platelet <100 (x 109 /L)0.036---LDH <600 (IU/L)0.045---CNS involvement at Dx0.18---WHO classification (early, thymic, mature)0.101---ETP-ALL0.0080.0232.2751.117-4.631Treatment received0.43--- [Display omitted] [Display omitted] [Display omitted] DisclosuresKonopleva:Novartis: Research Funding; AbbVie: Research Funding; Stemline: Research Funding; Calithera: Research Funding; Threshold: Research Funding. Cortes:Astellas: Consultancy, Research Funding; BerGenBio AS: Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Teva: Research Funding; Ambit: Consultancy, Research Funding; Arog: Research Funding; Celator: Research Funding; Jenssen: Consultancy.

Epigenetics Directing Therapy in Acute Lymphocytic Leukemia: Emerging Roles and New Therapies

In the last 15 years, our understanding of the contribution of epigenetic mechanisms to ALL leukemogenesis has increased exponentially. Epigenetic alterations are particularly interesting from a therapeutic standpoint, as they are potentially reversible and amenable to pharmacologic modulation. Indeed, inhibitors of DNA methylation, histone deactylation and histone methylation all have entered clinical trials, and early results for several of these agents are encouraging. Incorporating epigenetic modulation into ALL therapy may therefore hold great promise in improving tolerability and outcomes. Specifically, this session will address: - Patterns of aberrant DNA methylation and clinical trials combining "demethylating" agents with standard chemotherapy for relapsed ALL.DNA methylation patterns have been shown to correlate with outcome. Basic studies failed to conclusively link the regulation of specific genes or pathways to aberrant DNA methylation, and upfront methylation patterns poorly predict response to demethylating agents. Nevertheless, several clinical trials combining demethylating agents and chemotherapy in relapsed ALL are ongoing, with encouraging early results. These included responses of patients treated with decitabine and HyperCVAD who had previously failed to respond HyperCVAD alone. - Patterns of aberrant histone acetylation, the biology of histone acetyl transferases (HATs) and histone deacetylases (HDACS) in ALL, and clinical trials modulating histone acetylation. Histone acetylation patterns and a high frequency of deletions of the HAT CBP at relapse suggest that aberrant histone acetylation contributes to relapse and resistance. HDAC inhibitors show efficacy on ALL cells in preclinical studies, and clinical trials are ongoing. - The role of the histone acetylation "reader" protein Brd4 in ALL. In addition to "writers" (HAT) and "erasers" (HDACs), readers of histone acetylation may play a role in leukemia. Inhibition of Brd4 showed activity in several lymphoblastic leukemia models, and two Brd4 inhibitors are currently in clinical trials for relapsed/refractory hematologic malignancies including ALL. - Patterns of aberrant histone methylation, biology and therapeutic possibilities. Aberrant histone methylation is also emerging as a contributor to leukemogenesis, and may offer opportunities for therapeutic intervention. Loss of function mutations of the H3K27 histone methyltransferase EZH2 or other members of its complex (SUZ12, EED) are often found in early T-cell precursor ALL (ETP), and loss of EED or EZH2 contributes to aberrant T-cell development and leukemic transformation in mouse models. Gain of function of the H3K36 histone methyltransferase NSD2 have recently been described in pre-B ALL, raising the obvious question whether these leukemias depend on H3K36 hypermethylation, and NSD2 inhibition would have a therapeutic effect. Finally, aberrant recruitment of the histone methyltransferase DOT1L is observed in MLL-rearranged ALL, and an inhibitor of DOT1L is in clinical trials for MLL-rearranged malignancies, including ALL. Basic and translational studies support a critical role for epigenetic mechanisms in ALL leukemogenesis, drug resistance and relapse. Early results from clinical trials demonstrate that pharmacologic modulation of epigenetic modifiers can produce clinically meaningful responses. The next few years will likely see an increased number of compounds that modulate epigenetics enter clinical trials. Current assignment of patients to studies/compounds is crude, based on tumor type and status (i.e. "relapsed hematologic malignancy") or cytogenetics (i.e. MLL-rearrangement), rather than epigenetic profiling or an understanding of the biology that drives an individual patient's leukemia. As our diagnostic and therapeutic tools improve, epigenetic modulation may become an important component of ALL therapy. Disclosures Off Label Use: This presentation will include discussion of the use of decitabine, azacitidine, vorinostat, rhomidepsin and EPZ-5676 for ALL..

Lmo2's Oncogenic Function in T-Cell Leukemia Requires Ldb1

LIM domain Only-2 (LMO2) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL). LMO2 encodes a small protein with 2 LIM domains that is part of a large multiprotein complex in hematopoietic stem and progenitor cells, where it is required for HSC specification and maintenance. Many of LMO2's protein partners in HSPCs are expressed in T-ALL implying that protein complexes similar to those nucleated by LMO2 in HSPCs also play a role in leukemia. In this study, we analyzed a critical component of the LMO2 associated complex, LIM domain binding1 (LDB1). LDB1 appears to be an obligate partner of LMO2 in HSPCs but it is not required for T-cell development from committed progenitors. LDB1 is concordantly expressed with LMO2 in human T-ALL although its expression is more widespread than LMO2. To further define Ldb1's role in leukemia, we induced its conditional knockout in CD2-Lmo2 transgenic mice. CD2-Lmo2 transgenic mice develop T-ALL with high penetrance and closely model the human disease. We discovered that Lmo2-induced T-ALL was markedly attenuated in penetrance and latency by Ldb1 deletion. Since Lmo2 induces a distinct differentiation arrest in T-cell progenitors prior to leukemic transformation, we analyzed the differentiation of T-cell progenitors in CD2-Lmo2 transgenic/floxed-Ldb1/Lck-Cre mice and in non-Lmo2 transgenics: floxed-Ldb1/Lck-Cre mice. Ldb1 deletion by Lck-Cre was efficient in double negative and double positive T-cell progenitors. In striking contrast, Ldb1 deletion could not be induced in CD2-Lmo2 transgenic T-cell progenitors. Consistent with this finding, T-ALLs that developed in CD2-Lmo2/floxed-Ldb1/Lck-Cre mice had incomplete deletion of Ldb1. These results imply that Ldb1 is a required factor for Lmo2 to induce T-ALL. Lastly, gene expression analysis of Lmo2-induced T-ALLs and ChIP-exonuclease analysis of Ldb1 occupancy in T-ALL suggested that the Lmo2/Ldb1 complex enforced a gene signature similar to that seen in HSPCs and in Early T-cell Precursor ALL. In conclusion, Ldb1 is a required partner for Lmo2 to induce T-ALL. Additionally, the HSPC function of Lmo2/Ldb1 complexes may be recapitulated in T-cell progenitors prior to T-ALL. DisclosuresNo relevant conflicts of interest to declare.

Acute Lymphoblastic Leukemia, Version 2.2015.

Treatment of acute lymphoblastic leukemia (ALL) continues to advance, as evidenced by the improved risk stratification of patients and development of newer treatment options. Identification of ALL subtypes based on immunophenotyping and cytogenetic and molecular markers has resulted in the inclusion of Philadelphia-like ALL and early T-cell precursor ALL as subtypes that affect prognosis. Identification of Ikaros mutations has also emerged as a prognostic factor. In addition to improved prognostication, treatment options for patients with ALL have expanded, particularly with regard to relapsed/refractory ALL. Continued development of second-generation tyrosine kinase inhibitors and the emergence of immunotherapy, including blinatumomab and chimeric antigen receptor T-cell therapy, have improved survival. Furthermore, incorporation of minimal residual disease (MRD) monitoring has shown insight into patient outcomes and may lead to treatment modification or alternative treatment strategies in select populations. This excerpt focuses on the sections of the ALL guidelines specific to clinical presentation and diagnosis, treatment of relapsed/refractory ALL, and incorporation of MRD monitoring. To view the most recent complete version of these guidelines, visit NCCN.org.

Early T-cell Precursor Acute Lymphoblastic Leukemia (ETP-ALL) in Adults: A High-Risk Subtype

Background: Early T-cell precursor (ETP) acute lymphoblastic leukemia/lymphoma (ALL) is a recently recognized high-risk T-ALL subgroup. The optimal therapeutic approaches to adult patients with ETP-ALL are poorly characterized. In this study, we compared the outcomes of adults with ETP-ALL who received treatment on frontline regimens to those of patients with other T-ALL immunophenotypic subtypes. Methods: Patients with newly-diagnosed T-ALL who received frontline chemotherapy between the years 2000 and 2014 at The University of Texas MD Anderson Cancer Center (MDACC) were identified and immunophenotypically categorized into early, thymic, and mature per the EGIL/WHO classification. Patients with ETP-ALL were identified on the basis of the following immunophenotype: CD1a(-), CD8(-), CD5(-/dim), and positivity for one or more stem cell or myeloid antigens. Results: A total of 111 patients with T-ALL with adequate immunophenotype data were identified. There was no difference in the outcomes of patients based on the EGIL/WHO subtypes. A total of 19patients (17%)hadETP-ALL.The completeremission rate(CR)/ CR with incomplete platelet recovery (CRp) rate in patients with ETP-ALL wassignificantly lowerthanthatofnon-ETP-ALL patients (73% vs. 91%; p¼0.03). The median overall survival for ETP-ALL patientswas20monthsvs.notreachedforthenon-ETP-ALLpatients (p ¼ 0.008). Conclusions: ETP-ALL represents a high-risk disease subtype of adult ALL. Allogeneic stem cell transplant in CR1 should be considered. Novel treatment strategies are needed to improve treatment outcomes in this T-ALL subset. Keywords: Acute leukemia, Lymphoblastic Leukemia, T-cell, Immunophenotype, Hyper-CVAD Chemotherapy, Flow Cytometry.

T-lymphoblastic leukemia/lymphoma.

To review important concepts from the 2013 Society for Hematopathology/European Association for Haematopathology Workshop session on T-acute lymphoblastic leukemia/T-lymphoblastic lymphoma (T-ALL/T-LBL). Twenty-one submitted cases are reviewed and summarized, with emphasis on key diagnostic or biologic points, and supplemented with relevant literature citations. Early T-cell precursor (ETP)-ALL represented about one-third of all cases submitted. It is important to recognize ETP-ALL, because these patients have a poor prognosis if treated with standard therapy. A consensus immunophenotype has been developed to aid in the recognition of these cases. Other cases submitted illustrated rare entities, including two cases of Philadelphia chromosome-positive T-ALL, two cases of T-ALL associated with MYC translocations, and single cases illustrating various diseases. A subset of cases submitted illustrated issues related to differential diagnosis of T-ALL/T-LBL. In view of the growing importance of molecular genetic analysis in the diagnosis and prognosis of T-ALL/T-LBL, it is important for pathologists to keep abreast of these developments. Currently, routine histopathology, immunophenotyping, conventional cytogenetic analysis, fluorescence in situ hybridization, and clonality testing are usually adequate to establish the diagnosis. However, as therapies become more targeted, assessment for relevant genetic abnormalities, either through candidate gene or broad-scale unbiased approaches, may become necessary.

Abstract B26: Role of ribosomal protein, Rpl22 in regulating leukemic transformation.

Abstract Inactivation of ribosomal proteins (RP) is known to cause diseases called ribosomopathies, which are often associated with abnormal hematopoiesis and an increased risk for development of leukemia. Our laboratory has recently reported an important link between inactivation of one such ribosomal protein, Rpl22, and poor survival in T cell acute lymphoblastic leukemia (T-ALL) patients. Preliminary bioinformatic analysis shows that RPL22 is lost in ~10% of pediatric T-ALL patients, who exhibit a more aggressive disease course. Deletion of the RPL22 locus is also enriched in the early T-cell precursor (ETP-ALL) subset of T-ALL patients, which exhibit a more aggressive disease course. Thus, RPL22 loss appears to be a marker for poor outcome in pediatric T-ALL patients. While RP inactivation has previously been linked to increased cancer risk, the mechanistic basis for this linkage remained unclear. We have recently demonstrated that inactivation of Rpl22 promotes leukemic transformation by activating NF-kB and inducing the stem cell gene, LIN28B. Nevertheless, the molecular link between Rpl22 inactivation and the induction of NF-kB activity remained unclear. We have now determined that inactivation of Rpl22 activates NF-kB signaling by exacerbating ER stress responses. Indeed, Rpl22 loss results in hyperactivation of the PERK-EIF2α-ATF4 stress pathway, which is known to activate NF-kB. We have demonstrated that knockdown of PERK using shRNA abrogates the activation of NF-kB in Rpl22 mutant cells and returns Lin28B expression levels to baseline. This reduction in Lin28B eliminates the predisposition to transformation exhibited by Rpl22 mutant cells, as evidenced by decreased formation of colonies in soft agar. Taken together, these data suggest that RPL22 inactivation may serve as a negative prognostic indicator in T-ALL and that pharmacologic targeting of ER stress pathways may represent a novel therapeutic alternative in this molecularly-defined subclass of T-ALL. Citation Format: Nehal Solanki Patel, Noa Greenberg, Suraj Peri, Shuyun Rao, Michele Rhodes, David Wiest. Role of ribosomal protein, Rpl22 in regulating leukemic transformation. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr B26.

Abstract 1269: Role of ribosomal protein, Rpl22 in regulating leukemic transformation

Abstract Inactivation of ribosomal proteins (RP) is known to cause diseases called ribosomopathies, which are often associated with abnormal hematopoiesis and an increased risk for development of leukemia. Our laboratory has recently reported an important link between inactivation of one such ribosomal protein, Rpl22, and poor survival in T cell acute lymphoblastic leukemia (T-ALL) patients. Preliminary bioinformatic analysis shows that RPL22 is lost in ∼10% of pediatric T-ALL patients, who exhibit a more aggressive disease course. Deletion of the RPL22 locus is also enriched in the early T-cell precursor (ETP-ALL) subset of T-ALL patients, which exhibit a more aggressive disease course. Thus, RPL22 loss appears to be a marker for poor outcome in pediatric T-ALL patients. While RP inactivation has previously been linked to increased cancer risk, the mechanistic basis for this linkage remained unclear. We have recently demonstrated that inactivation of Rpl22 promotes leukemic transformation by activating NF-κB and inducing the stem cell gene, LIN28B. Nevertheless, the molecular link between Rpl22 inactivation and the induction of NF-κB activity remained unclear. We have now determined that inactivation of Rpl22 activates NF-κB signaling by exacerbating ER stress responses. Indeed, Rpl22 loss results in hyperactivation of the PERK-EIF2a-ATF4 stress pathway, which is known to activate NF-κB. We have demonstrated that knockdown of PERK using shRNA abrogates the activation of NF-κB in Rpl22 mutant cells and returns Lin28B expression levels to baseline. This reduction in Lin28B eliminates the predisposition to transformation exhibited by Rpl22 mutant cells, as evidenced by decreased formation of colonies in soft agar. Taken together, these data suggest that RPL22 inactivation may serve as a negative prognostic indicator in T-ALL and that pharmacologic targeting of ER stress pathways may represent a novel therapeutic alternative in this molecularly-defined subclass of T-ALL. Citation Format: Nehal Solanki Patel, Noa Greenberg Kushnir, Shuyun Rao, Suraj Peri, Michele Rhodes, Panduka Nagahawatte, Charles Mullighan, David L. Wiest. Role of ribosomal protein, Rpl22 in regulating leukemic transformation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1269. doi:10.1158/1538-7445.AM2015-1269

Abstract 3276: Evaluation of the Bcl-2 inhibitor ABT-199 in xenograft models of acute lymphoblastic leukemia by the pediatric preclinical testing program

Abstract Targeting the apoptosis pathway with BH3 mimetics such as ABT-263 (navitoclax) and ABT-199 is an appealing strategy for cancer therapy. While the Bcl-2/Bcl-w/Bcl-xL inhibitor navitoclax has shown promising activity in adults with lymphoid malignancies and in preclinical models of pediatric acute lymphoblastic leukemia (ALL), its application in pediatric patients has been limited by Bcl-xL-mediated thrombocytopenia. The specific Bcl-2 inhibitor ABT-199 has shown remarkable efficacy against adult chronic lymphocytic leukemia in recent clinical trials, although its activity against pediatric ALL is yet to be tested. The aim of this study was to evaluate the in vivo efficacy of ABT-199 against a large panel of pediatric ALL patient-derived xenografts (PDXs), and to identify biomarkers predictive of ABT-199 response. Immune-deficient (NOD/SCID or NSG) mice inoculated with PDXs derived from patients with infant ALL harboring rearrangement of the Mixed Lineage Leukemia (MLL) oncogene (infant MLL-ALL, n = 4), B-cell precursor ALL (BCP-ALL, n = 6), BCP-ALL categorized as Ph-like (n = 4), T-cell ALL (T-ALL, n = 4) or early T-cell precursor ALL (ETP-ALL, n = 2) were treated with ABT-199 (100 mg/kg x 21 days, p.o.) or vehicle control. Responses were assessed by time to event measurements or stringent objective response criteria modeled after the clinical setting. ABT-199 significantly delayed the progression of 12/20 PDXs by between 0.4 and 28 days, and elicited objective responses in 6/20 (30%) of PDXs (4 complete responses and 2 partial responses). No objective responses were observed in the T-ALL or ETP-ALL PDXs. By comparison, navitoclax administered on the same dose and schedule as ABT-199 elicited objective responses in 19/31 (61%) of PDXs derived from the same pediatric ALL subtypes. Analysis of basal gene and protein expression revealed that high Bcl-xL and low Bcl-2 expression were significantly associated with in vivo ABT-199 resistance. Moreover, the Bcl-2/Bcl-xL gene (P = 0.03) and protein (P = 0.002) expression ratios were significantly elevated in PDXs that responded to ABT-199 in vivo compared with non-responders. Notably, Mcl-1 expression at the gene or protein level showed no significant correlation with in vivo ABT-199 sensitivity. In conclusion, the inferior objective response rate observed for ABT-199 (30%) compared with navitoclax (61%) indicates that pediatric ALL PDXs are less dependent on Bcl-2 for cell survival compared with adult chronic lymphocytic leukemia. Moreover, Bcl-xL appears to be a more significant ABT-199 resistance factor than Mcl-1 in pediatric ALL. While ABT-199 has the potential to exert significant efficacy in the treatment of aggressive and chemoresistant pediatric ALL, the prospective identification of patients who might benefit from such treatment is of paramount importance. Supported by NCI NO1CM42216. Citation Format: Santi Suryani, Kathryn Evans, Jennifer Richmond, Alissa Robbins, Lauryn Bracken, Raushan Kurmasheva, Peter J. Houghton, Malcolm A. Smith, Richard B. Lock. Evaluation of the Bcl-2 inhibitor ABT-199 in xenograft models of acute lymphoblastic leukemia by the pediatric preclinical testing program. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3276. doi:10.1158/1538-7445.AM2015-3276

Hhex is Required at Multiple Stages of Adult Hematopoietic Stem and Progenitor Cell Differentiation.

Hhex encodes a homeodomain transcription factor that is widely expressed in hematopoietic stem and progenitor cell populations. Its enforced expression induces T-cell leukemia and we have implicated it as an important oncogene in early T-cell precursor leukemias where it is immediately downstream of an LMO2-associated protein complex. Conventional Hhex knockouts cause embryonic lethality precluding analysis of adult hematopoiesis. Thus, we induced highly efficient conditional knockout (cKO) using vav-Cre transgenic mice. Hhex cKO mice were viable and born at normal litter sizes. At steady state, we observed a defect in B-cell development that we localized to the earliest B-cell precursor, the pro-B-cell stage. Most remarkably, bone marrow transplantation using Hhex cKO donor cells revealed a more profound defect in all hematopoietic lineages. In contrast, sublethal irradiation resulted in normal myeloid cell repopulation of the bone marrow but markedly impaired repopulation of T- and B-cell compartments. We noted that Hhex cKO stem and progenitor cell populations were skewed in their distribution and showed enhanced proliferation compared to WT cells. Our results implicate Hhex in the maintenance of LT-HSCs and in lineage allocation from multipotent progenitors especially in stress hematopoiesis.

Efficacy of JAK/STAT pathway inhibition in murine xenograft models of early T-cell precursor (ETP) acute lymphoblastic leukemia

AbstractEarly T-cell precursor (ETP) acute lymphoblastic leukemia (ALL) is a recently described subtype of T-ALL characterized by a unique immunophenotype and genomic profile, as well as a high rate of induction failure. Frequent mutations in cytokine receptor and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways led us to hypothesize that ETP-ALL is dependent on JAK/STAT signaling. Here we demonstrate aberrant activation of the JAK/STAT pathway in ETP-ALL blasts relative to non-ETP T-ALL. Moreover, ETP-ALL showed hyperactivation of STAT5 in response to interleukin-7, an effect that was abrogated by the JAK1/2 inhibitor ruxolitinib. In vivo, ruxolitinib displayed activity in 6 of 6 patient-derived murine xenograft models of ETP-ALL, with profound single-agent efficacy in 5 models. Ruxolitinib treatment decreased peripheral blast counts relative to pretreatment levels and compared with control (P < .01) in 5 of 6 ETP-ALL xenografts, with marked reduction in mean splenic blast counts (P < .01) in 6 of 6 samples. Surprisingly, both JAK/STAT pathway activation and ruxolitinib efficacy were independent of the presence of JAK/STAT pathway mutations, raising the possibility that the therapeutic potential of ruxolitinib in ETP-ALL extends beyond those cases with JAK mutations. These findings establish the preclinical in vivo efficacy of ruxolitinib in ETP-ALL, a biologically distinct subtype for which novel therapies are needed.

ZEB2 drives immature T-cell lymphoblastic leukaemia development via enhanced tumour-initiating potential and IL-7 receptor signalling.

Early T-cell precursor leukaemia (ETP-ALL) is a high-risk subtype of human leukaemia that is poorly understood at the molecular level. Here we report translocations targeting the zinc finger E-box-binding transcription factor ZEB2 as a recurrent genetic lesion in immature/ETP-ALL. Using a conditional gain-of-function mouse model, we demonstrate that sustained Zeb2 expression initiates T-cell leukaemia. Moreover, Zeb2-driven mouse leukaemia exhibit some features of the human immature/ETP-ALL gene expression signature, as well as an enhanced leukaemia-initiation potential and activated Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signalling through transcriptional activation of IL7R. This study reveals ZEB2 as an oncogene in the biology of immature/ETP-ALL and paves the way towards pre-clinical studies of novel compounds for the treatment of this aggressive subtype of human T-ALL using our Zeb2-driven mouse model.

Genomic and pharmacogenetic studies of childhood acute lymphoblastic leukemia.

With the cure rate of childhood acute lymphoblastic leukemia (ALL) approaching 90%, further improvement in the treatment outcome and quality of life of patients will require better understanding of the mechanisms of drug resistance, identifying new leukemic cell genetic lesions that are amendable to available target therapy, and optimizing treatment based on host pharmacodynamics and pharmacogenomics. Deeper characterization of leukemic cell genetic abnormalities has discovered new subtypes of leukemia such as early T-cell precursor ALL and Philadelphia chromosome-like ALL, and identified many genomic alterations that have diagnostic, prognostic, or therapeutic implications. In this regard, several novel fusion transcripts are responsive to ABL tyrosine kinase inhibitors and potentially to JAK inhibitors. Genome-wide analyses have also unraveled the role of inherited cancer predisposing genes and small nucleotide polymorphisms of several genes in the development of childhood ALL. These advances promise to lead to more sophisticated personalized treatment strategies in the near future.