Unrelated donor vs HLA-haploidentical a/b T-cell- and B-cell-depleted HSCT in children with acute leukemia

Traditionally, hematopoietic stem cell transplantation (HSCT) from both HLA-matched related and unrelated donors (UD) has been used for treating children with acute leukemia (AL) in need of an allograft. Recently, HLA-haploidentical HSCT after ab T-cell/B-cell depletion (abhaplo-HSCT) was shown to be effective in single-center studies. Here, we report the first multicenter retrospective analysis of 127 matched UD (MUD), 118 mismatched UD (MMUD), and 98 abhaplo-HSCT recipients, transplanted between 2010 and 2015, in 13 Italian centers. All these AL children were transplanted in morphological remission after a myeloablative conditioning regimen. Graft failure occurred in 2% each of UD-HSCT and abhaplo-HSCT groups. In MUD vs MMUD-HSCT recipients, the cumulative incidence of grade II to IV and grade III to IV acute graft-versus-host disease (GVHD) was 35% vs 44% and 6% vs 18%, respectively, compared with 16% and 0% in abhaplo-HSCT recipients (P < .001). Children treated with abhaplo-HSCT also had a significantly lower incidence of overall and extensive chronic GVHD (P < .01). Eight (6%) MUD, 32 (28%) MMUD, and 9 (9%) abhaplo-HSCT patients died of transplant-related complications. With a median follow-up of 3.3 years, the 5-year probability of leukemia-free survival in the 3 groups was 67%, 55%, and 62%, respectively. In the 3 groups, chronic GVHD-free/relapse-free (GRFS) probability of survival was 61%, 34%, and 58%, respectively (P < .001). When compared with patients given MMUD-HSCT, abhaplo-HSCT recipients had a lower cumulative incidence of nonrelapse mortality and a better GRFS (P < .001). These data indicate that abhaplo-HSCT is a suitable therapeutic option for children with AL in need of transplantation, especially when an allele-matched UD is not available

CRLF2 over-expression is a poor prognostic marker in children with high risk T-cell acute lymphoblastic leukemia

Pediatric T-ALL patients have a worse outcome compared to BCP-ALL patients and they could benefit from new prognostic marker identification. Alteration of CRLF2 gene, a hallmark correlated with poor outcome in BCP-ALL, has not been reported in T-ALL. We analyzed CRLF2 expression in 212 T-ALL pediatric patients enrolled in AIEOP-BFM ALL2000 study in Italian and German centers. Seventeen out of 120 (14.2%) Italian patients presented CRLF2 mRNA expression 5 times higher than the median (CRLF2-high); they had a significantly inferior event-free survival (41.2%±11.9 vs. 68.9%±4.6, p=0.006) and overall survival (47.1%±12.1 vs. 73.8%±4.3, p=0.009) and an increased cumulative incidence of relapse/resistance (52.9%±12.1 vs. 26.2%±4.3, p=0.007) compared to CRLF2-low patients. The prognostic value of CRLF2 over-expression was validated in the German cohort. Of note, CRLF2 over-expression was associated with poor prognosis in the high risk (HR) subgroup where CRLF2-high patients were more frequently allocated. Interestingly, although in T-ALL CRLF2 protein was localized mainly in the cytoplasm, in CRLF2-high blasts we found a trend towards a stronger TSLP-induced pSTAT5 response, sensitive to the JAK inhibitor Ruxolitinib. In conclusion, CRLF2 over-expression is a poor prognostic marker identifying a subset of HR T-ALL patients that could benefit from alternative therapy, potentially targeting the CRLF2 pathway

Molecular characterisation and clinical outcome of B-cell precursor acute lymphoblastic leukaemia with IG-MYC rearrangement

Rarely, immunophenotypically immature B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) carries an immunoglobulin-MYC rearrangement (IG-MYC-r). This can result in diagnostic confusion with Burkitt lymphoma/leukaemia and use of unproven individualised treatment schedules. Here we contrast the molecular characteristics of these conditions and investigate historic clinical outcome data. We identified 90 cases registered on a national BCP-ALL clinical trial/registry. Where present, diagnostic material underwent cytogenetic, exome, methylome and transcriptome analysis. Outcome was analysed to define 3-year event free survival (EFS) and overall survival (OS). IG-MYC-r was identified in diverse cytogenetic backgrounds, co-existing with either: established BCP-ALL specific abnormalities (high hyperdiploidy n=3, KMT2A-rearrangement n=6, iAMP21 n=1, BCR-ABL n=1); BCL2/BCL6-rearrangements (n=15); or, most commonly, as the only defining feature (n=64). Within this final group, precursor-like V(D)J breakpoints predominated (8/9) and KRAS mutations were common (5/11). DNA methylation identified a cluster of V(D)J rearranged cases, clearly distinct from Burkitt leukaemia/lymphoma. Children with IG-MYC-r within that subgroup had 3-year EFS of 47% and OS of 60%, representing a high-risk BCP-ALL. To develop effective management strategies this patient group must be allowed access to contemporary, minimal residual disease adapted, prospective clinical trial protocols

DNA variants in DHFR gene and response to treatment in children with childhood B ALL: revisited in AIEOP-BFM protocol.

We have previously reported an association of dihydrofolate reductase promoter polymorphisms with reduced event-free survival in childhood acute lymphoblastic leukemia (ALL) patients treated with Dana Farber Cancer Institute protocol. Here, we assessed whether these associations are applicable to other protocol, based on different methotrexate doses. Genotypes for six tag polymorphisms and resulting haplotypes were analyzed for an association with ALL outcome. The association was found with the polymorphisms A-680C, A-317G and C-35T in high-risk group patients. Carriers of haplotype *1 had a remarkably higher risk of events compared with noncarriers and a lower probability of event-free survival (21.4 vs 81.3%). The role of DHFR variants in predicting the outcome of childhood ALL extends beyond single-treatment protocol and can be useful biomarker in personalizing treatment

Phosphoproteomic analysis reveals hyperactivation of mTOR/STAT3 and LCK/Calcineurin axes in pediatric early T-cell precursor ALL

Early T-cell Precursor ALL (ETP-ALL) is a subgroup of acute T leukemias with a peculiar immunophenotypic profile. Patients display a poor early response to conventional induction treatment, but an outcome after intensified therapy not worse than the other T-ALL. ETP-ALL was extensively characterized from a genetic point of view in the paper published by Zhang et al in 2012, but information about proteomic aberrancies is still lacking. In this study we profiled, by Reverse Phase Protein Arrays, the activation and expression of a considerable number of proteins in a significative cohort of 16 pediatric patients affected by ETP-ALL at diagnosis. We compared protein activation in these patients versus a group of 62 other T-ALL pediatric patients. Phosphoprotemic data were also related to mutational status of ETP-ALL patients. Our most interesting findings concern the hyperactivation of the LCK/Calcineurin and mTOR/STAT3 signaling pathways in ETP-ALL patients. LCK, despite of a lower expression, resulted strikingly boosted in these patients with a concomitant overexpression of the downstream target Calcineurin. The LCK/Calcineurin axis, followed by the activation of the NFAT family of transcription factors, was already demonstrated to be critical for T cell leukemogenesis. We also observed a possible feedback loop which could sustain mTOR activation through p70 S6Kinase hyperphosphorylation. mTOR, in turn, phosphorylates and activates STAT3, counteracting cell differentiation. The mTOR/STAT3 axis activity thus could sustain cell proliferation and survival while maintaining the markedly undifferentiated phenotype typical of ETP-ALL. Interestingly, the activation of the mTOR/STAT3 pathways is not influenced by the presence of FLT3 or PTEN mutations. Our paper also reports in ETP-ALL patients the hyperactivation of the RAS/MAPK and the JAK/STAT signaling pathways, that is not dependant from BRAF, NRAS, IL7R, JAK1 or JAK3 somatic mutations. In conclusion, our study is the first one investigating the activation of a such number of proteins in a wide cohort of pediatric ETP-ALL patients. We identified the specific activation of signaling pathways, such as the LCK/Calcineurin and the mTOR/STAT3 ones, important for T cell leukemogenesis and for the support of cancer cell viability and block of differentiation. Our results will help to explain the mechanism responsible of the poor response to conventional treatment of these patients, and might also suggest new druggable targets for personalized and less toxic therapies

Minimal residual disease monitored after induction therapy by RQ-PCR can contribute to tailor treatment of patients with t(8;21) RUNX1-RUNX1T1 rearrangement.

Multiparametric flow cytometry is an alternative approach to the polymerase chain reaction method for evaluating minimal residual disease in treatment protocols for primary acute lymphoblastic leukemia. Given considerable differences between primary and relapsed acute lymphoblastic leukemia treatment regimens, flow cytometric assessment of minimal residual disease in relapsed leukemia requires an independent comprehensive investigation. In the present study we addressed evaluation of minimal residual disease by flow cytometry in the clinical trial for childhood relapsed acute lymphoblastic leukemia using eight-color flow cytometry. The major challenge of the study was to reliably identify low amounts of residual leukemic cells against the complex background of regeneration, characteristic of follow-up samples during relapse treatment. In a prospective study of 263 follow-up bone marrow samples from 122 patients with B-cell precursor acute lymphoblastic leukemia, we tested various B-cell markers, adapted the antibody panel to the treatment protocol, and evaluated its performance by a blinded parallel comparison with the polymerase chain reaction data. The resulting eight-color single-tube panel showed a consistently high overall concordance (P<0.001) and, under optimal conditions, sensitivity similar to that of the reference polymerase chain reaction method. Overall, evaluation of minimal residual disease by flow cytometry can be successfully integrated into the clinical management of relapsed childhood acute lymphoblastic leukemia either as complementary to the polymerase chain reaction or as an independent risk stratification tool. ALL-REZ BFM 2002 clinical trial information: NCT0011434