The added value of IKZF1 gene deletion (IKZF1(del)) as a stratifying criterion in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is still debated. We performed a comprehensive analysis of ...the impact of IKZF1(del) in a large cohort of children (n=1223) with BCR-ABL1-negative BCP-ALL treated in the EORTC-CLG trial 58951. Patients with IKZF1(del) had a lower 8-year event-free survival (EFS, 67.7% versus 86.5%; hazard ratio (HR)=2.41; 95% confidence interval (CI)=1.75-3.32; P<0.001). Importantly, despite association with high-risk features such as high minimal residual disease, IKZF1(del) remained significantly predictive in multivariate analyses. Analysis by genetic subtype showed that IKZF1(del) increased risk only in the high hyperdiploid ALLs (HR=2.57; 95% CI=1.19-5.55; P=0.013) and in 'B-other' ALLs, that is, lacking classifying genetic lesions (HR=2.22; 95% CI=1.45-3.39; P<0.001), the latter having then a dramatically low 8-year EFS (56.4; 95% CI=44.6-66.7). Among IKZF1(del)-positive patients randomized for vincristine-steroid pulses during maintenance, those receiving pulses had a significantly higher 8-year EFS (93.3; 95% CI=61.3-99.0 versus 42.1; 95% CI=20.4-62.5). Thus, IKZF1(del) retains independent prognostic significance in the context of current risk-adapted protocols, and is associated with a dismal outcome in 'B-other' ALL. Addition of vincristine-steroid pulses during maintenance may specifically benefit to IKZF1(del) patients in preventing relapses.
Oncogenic subtypes in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) are used for risk stratification. However, a significant number of BCP-ALL patients are still genetically ...unassigned. Using array-comparative genomic hybridization in a selected BCP-ALL cohort, we characterized a recurrent V(D)J-mediated intragenic deletion of the ERG gene (ERG(del)). A breakpoint-specific PCR assay was designed and used to screen an independent non-selected cohort of 897 children aged 1-17 years treated for BCP-ALL in the EORTC-CLG 58951 trial. ERG(del) was found in 29/897 patients (3.2%) and was mutually exclusive of known classifying genetic lesions, suggesting that it characterized a distinct leukemia entity. ERG(del) was associated with higher age (median 7.0 vs. 4.0 years, P=0.004), aberrant CD2 expression (43.5% vs. 3.7%, P<0.001) and frequent IKZF1 Δ4-7 deletions (37.9% vs. 5.3%, P<0.001). However, ERG(del) patients had a very good outcome, with an 8-year event-free survival (8-y EFS) and an 8-year overall survival of 86.4% and 95.6%, respectively, suggesting that the IKZF1 deletion had no impact on prognosis in this genetic subtype. Accordingly, within patients with an IKZF1 Δ4-7 deletion, those with ERG(del) had a better outcome (8-y EFS: 85.7% vs. 51.3%; hazard ratio: 0.16; 95% confidence interval: 0.02-1.20; P=0.04). These findings have implications for further stratification including IKZF1 status.
Deletion of the Ikaros (IKZF1) gene is an oncogenic lesion frequently associated with BCR-ABL1-positive acute lymphoblastic leukemias. It is also found in a fraction of BCR-ABL1-negative B-cell ...precursor acute lymphoblastic leukemias, and early studies showed it was associated with a higher risk of relapse. Therefore, screening tools are needed for evaluation in treatment protocols and possible inclusion in risk stratification. Besides monosomy 7 and large 7p abnormalities encompassing IKZF1, most IKZF1 alterations are short, intragenic deletions. Based on cohorts of patients, we mapped the microdeletion breakpoints and developed a breakpoint-specific fluorescent multiplex polymerase chain reaction that allows detection of recurrent intragenic deletions. This sensitive test could also detect IKZF1 subclonal deletions, whose prognostic significance should be evaluated. Moreover, we show that consensus breakpoint sequences can be used as clonal markers to monitor minimal residual disease. This paper could be useful for translational studies and in clinical management of BCP-ALL.
Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and ...minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.
Risk-adjusted treatment stratification in T-cell acute lymphoblastic leukemias (T-ALLs) is currently based only on early response to chemotherapy. We investigated the prognostic implication of ...hyperactivation of NOTCH pathway resulting from mutations of NOTCH1 or FBXW7 in children with T-ALL enrolled in EORTC-CLG trials. Overall, 80 out of 134 (60%) patients were NOTCH+ (NOTCH1 and/or FBXW7 mutated). Although clinical presentations were not significantly associated with NOTCH status, NOTCH+ patients showed a better early response to chemotherapy as compared with NOTCH- patients, according to the rate of poor pre-phase 'responders' (25% versus 44%; P=0.02) and the incidence of high minimal residual disease (MRD) levels (11% (7/62) versus 32% (10/31); P=0.01) at completion of induction. However, the outcome of NOTCH+ patients was similar to that of NOTCH- patients, with a 5-year event-free survival (EFS) of 73% and 70% (P=0.82), and 5-year overall survival of 82% and 79% (P=0.62), respectively. In patients with high MRD levels, the 5-year EFS rate was 0% (NOTCH+) versus 42% (NOTCH-), whereas in those with low MRD levels, the outcome was similar: 76% (NOTCH+) versus 78% (NOTCH-). The incidence of isolated central nervous system (CNS) relapses was relatively high in NOTCH1+ patients (8.3%), which could be related to a higher propensity of NOTCH+ leukemic blasts to target the CNS.
Minimal residual disease (MRD) quantification is widely used for therapeutic stratification in pediatric acute lymphoblastic leukemia (ALL). A robust, reproducible, sensitivity of at least 0.01% has ...been achieved for IG/TCR clonal rearrangements using allele-specific quantitative PCR (IG/TCR-QPCR) within the EuroMRD consortium. Whether multiparameter flow cytometry (MFC) can reach such inter-center performance in ALL MRD monitoring remains unclear. In a multicenter study, MRD was measured prospectively on 598 follow-up bone marrow samples from 102 high-risk children and 136 adult ALL patients, using IG/TCR-QPCR and 4/5 color MFC. At diagnosis, all 238 patients (100%) had at least one suitable MRD marker with 0.01% sensitivity, including 205/238 samples (86%) by using IG/TCR-QPCR and 223/238 samples (94%) by using MFC. QPCR and MFC were evaluable in 495/598 (83%) samples. Qualitative results (<0.01% or ≥0.01%) concurred in 96% of samples and overall positivity (including <0.01% and nonquantifiable positivity) was concurrent in 84%. MRD values ≥0.01% correlated highly (r(2)=0.87) and 69% clustered within half-a-log(10). QPCR and MFC can therefore be comparable if properly standardized, and are highly complementary. MFC strategies will benefit from a concerted approach, as does molecular MRD monitoring, and will contribute significantly to the achievement of 100% MRD informativity in adult and pediatric ALL.
Isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) mutations in Myeloid Neoplams (MNs) exhibit DNA hypermethylation via 2-hydroxyglutarate (2HG) over-production. Clinical impact of azacitidine (AZA) ...remains inconsistent in IDH1/2-mutated MNs and the potential of serum 2HG as a suitable marker of response to AZA is unknown. To address these questions, we retrospectively analyzed 93 MNs patients (78 AML, 11 MDS, 4 CMML) with IDH1/2 mutations treated with AZA. After a median of 5 cycles of AZA, overall response rate was 28% (including 15% complete remission) and median OS was 12.3 months (significantly shorter in AML compared to MDS/CMML patients). In multivariate analysis of AML patients, DNMT3A mutation was associated with shorter OS while IDH1/2 mutation subtypes had no independent impact. No difference was observed in serum 2HG levels upon AZA treatment between responding and refractory patients suggesting that serum 2HG cannot be used as a surrogate marker of AZA response.
Leukemia-initiating/repopulating cells (LICs), also named leukemic stem cells, are responsible for propagating human acute leukemia. Although they have been characterized in various leukemias, their ...role in T-cell acute lymphoblastic leukemia (T-ALL) is unclear. To identify and characterize LICs in T-ALL (T-LIC), we fractionated peripheral blood cell populations from patient samples by flow cytometry into three cell fractions by using two markers: CD34 (a marker of immature cells and LICs) and CD7 (a marker of early T-cell differentiation). We tested these populations in both in vitro culture assays and in vivo for growth and leukemia development in immune-deficient mice. We found LIC activity in CD7(+) cells only as CD34(+)CD7(-) cells contained normal human progenitors and hematopoietic stem cells that differentiated into T, B lymphoid and myeloid cells. In contrast, CD34(+)CD7(+) cells were enriched in LICs, when compared with CD34(-)CD7(+) cells. These CD34(+)CD7(+) cells also proliferated more upon NOTCH activation than CD34(-)CD7(+) cells and were sensitive to dexamethasone and NOTCH inhibitors. These data show that CD34 and CD7 expression in human T-ALL samples help in discriminating heterogeneous cell populations endowed with different LIC activity, proliferation capacity and responses to drugs.
In childhood B-cell precursor acute lymphoblastic leukaemias (BCP-ALL), the presence of an ETV6-RUNX1 fusion transcript defines one of the most prevalent genetic subgroups, together with the high ...hyperdiploidy (HeH) ALL. Although ETV6-RUNX1pos ALLs are associated with favourable outcome, their proper treatment strategies remain debatable, some groups suggesting crucial impact of upfront intensive treatment while others favour low-intensity antimetabolite-based therapy.
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