Cerebrospinal fluid distribution and pharmacokinetics of ponatinib in Ph1+ acute lymphoblastic leukemia.

ABSTRACT: Tyrosine kinase inhibitors efficacy in central nervous system (CNS) disease remains uncertain. Ponatinib was studied for CNS distribution in 16 patients with Philadelphia-positive acute lymphoblastic leukemia. Cerebrospinal fluid concentrations fell below the 40 nM threshold, suggesting suboptimal CNS exposure.

Nilotinib with or without cytarabine for Philadelphia-positive acute lymphoblastic leukemia.

ABSTRACT: We previously demonstrated that a reduced-intensity chemotherapy schedule can safely replace hyper-CVAD (cyclophosphamide-vincristine-doxorubicin [Adriamycin]-dexamethasone) cycle 1 when combined with imatinib in adults with Philadelphia-positive acute lymphoblastic leukemia. In the present randomized GRAAPH-2014 trial, we used nilotinib and addressed the omission of cytarabine (Ara-C) in consolidation. The primary objective was the major molecular response (MMR) rate measured by BCR::ABL1 quantification after cycle 4 (end of consolidation). All patients were eligible for allogeneic stem cell transplant (SCT), whereas those in MMR could receive autologous SCT, followed by 2-year imatinib maintenance in both cases. After the enrollment of 156 of 265 planed patients, the data and safety monitoring board decided to hold the randomization because of an excess of relapse in the investigational arm. Among the 155 evaluable patients, 76 received Ara-C during consolidation (arm A) and 79 did not (arm B). Overall, 133 patients (85%) underwent SCT, 93 allogeneic and 40 autologous. The noninferiority end point regarding MMR was reached with 71.1% (arm A) and 77.2% (arm B) of patients reaching MMR. However, the 4-year cumulative incidence of relapse was higher in arm B compared with arm A (31.3% [95% confidence interval {CI}, 21.1%-41.9%] vs 13.2% [95% CI, 6.7%-21.9%]; P = .017), which translated to a lower relapse-free survival. With a median follow-up of 3.8 years, 4-year overall survival was 79.0% (95% CI, 70.6%-89.3%) in arm A vs 73.4% (95% CI, 63.9%-84.4%) in arm B (P = .35). Despite a noninferior rate of MMR, more relapses were observed when ARA-C was omitted without impact on survival. ClinicalTrials.gov ID, NCT02611492.

Genetic alterations and MRD refine risk assessment for KMT2A-rearranged B-cell precursor ALL in adults: a GRAALL study.

KMT2A-rearranged (KMT2A-r) B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is widely recognized as a high-risk leukemia in both children and adults. However, there is a paucity of data on adults treated in recent protocols, and the optimal treatment strategy for these patients is still a matter of debate. In this study, we set out to refine the prognosis of adult KMT2A-r BCP-ALL treated with modern chemotherapy regimen and investigate the prognostic impact of comutations and minimal residual disease (MRD). Of 1091 adult patients with Philadelphia-negative BCP-ALL enrolled in 3 consecutive trials from the Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL), 141 (12.9%) had KMT2A-r, with 5-year cumulative incidence of relapse (CIR) and overall survival (OS) rates of 40.7% and 53.3%, respectively. Molecular profiling highlighted a low mutational burden in this subtype, reminiscent of infant BCP-ALL. However, the presence of TP53 and/or IKZF1 alterations defined a subset of patients with significantly poorer CIR (69.3% vs 36.2%; P = .001) and OS (28.1% vs 60.7%; P = .006) rates. Next, we analyzed the prognostic implication of MRD measured after induction and first consolidation, using both immunoglobulin (IG) or T-cell receptor (TR) gene rearrangements and KMT2A genomic fusion as markers. In approximately one-third of patients, IG/TR rearrangements were absent or displayed clonal evolution during the disease course, compromising MRD monitoring. In contrast, KMT2A-based MRD was highly reliable and strongly associated with outcome, with early good responders having an excellent outcome (3-year CIR, 7.1%; OS, 92.9%). Altogether, our study reveals striking heterogeneity in outcomes within adults with KMT2A-r BCP-ALL and provides new biomarkers to guide risk-based therapeutic stratification.

Exposure toxicity of venetoclax in acute myeloid leukemia patients in the real-life setting: impact of high exposure on delayed neutropenia.

Not available.

Hypomethylating agent monotherapy in core binding factor acute myeloid leukemia: a French multicentric retrospective study.

Very few data are available about hypomethylating agent (HMA) efficiency in core binding factor acute myeloid leukemias (CBF-AML). Our main objective was to evaluate the efficacy and safety of HMA in the specific subset of CBF-AML. Here, we report the results of a multicenter retrospective French study about efficacy of HMA monotherapy, used frontline or for R/R CBF-AML. Forty-nine patients were included, and received a median of 5 courses of azacitidine (n = 46) or decitabine (n = 3). ORR was 49% for the whole cohort with a median time to response of 112 days. After a median follow-up of 72.3 months, median OS for the total cohort was 10.6 months. In multivariate analysis, hematological relapse of CBF-AML at HMA initiation was significantly associated with a poorer OS (HR: 2.13; 95%CI: 1.04-4.36; p = 0.038). Responders had a significantly improved OS (1-year OS: 75%) compared to non-responders (1-year OS: 15.3%; p < 0.0001). Hematological improvement occurred for respectively 28%, 33% and 48% for patients who were red blood cell or platelet transfusion-dependent, or who experienced grade 3/4 neutropenia at HMA initiation. Adverse events were consistent with the known safety profile of HMA. Our study highlights that HMA is a well-tolerated therapeutic option with moderate clinical activity for R/R CBF-AML and for patients who cannot handle intensive chemotherapy.

Comparative clinical and molecular landscape of primary and secondary myelofibrosis: Superior performance of MIPSS70+ v2.0 over MYSEC-PM.

Comparative clinical characteristics, molecular landscape and prognosis scoring for primary (PMF) and secondary myelofibrosis (SMF).

Prognostic significance of concurrent gene mutations in intensively treated patients with IDH-mutated AML: an ALFA study.

In patients with isocitrate dehydrogenase (IDH)-mutated acute myeloid leukemia (AML) treated by intensive chemotherapy (IC), prognostic significance of co-occurring genetic alterations and allogeneic hematopoietic stem cell transplantation (HSCT) are of particular interest with the advent of IDH1/2 mutant inhibitors. We retrospectively analyzed 319 patients with newly diagnosed AML (127 with IDH1, 135 with IDH2R140, and 57 with IDH2R172 mutations) treated with IC in 3 Acute Leukemia French Association prospective trials. In each IDH subgroup, we analyzed the prognostic impact of clinical and genetic covariates, and the role of HSCT. In patients with IDH1 mutations, the presence of NPM1 mutations was the only variable predicting improved overall survival (OS) in multivariate analysis (P < .0001). In IDH2R140-mutated AML, normal karyotype (P = .008) and NPM1 mutations (P = .01) predicted better OS. NPM1 mutations were associated with better disease-free survival (DFS; P = .0009), whereas the presence of DNMT3A mutations was associated with shorter DFS (P = .0006). In IDH2R172-mutated AML, platelet count was the only variable retained in the multivariate model for OS (P = .002). Among nonfavorable European LeukemiaNet 2010-eligible patients, 71 (36%) underwent HSCT in first complete remission (CR1) and had longer OS (P = .03) and DFS (P = .02) than nontransplanted patients. Future clinical trials testing frontline IDH inhibitors combined with IC may consider stratification on NPM1 mutational status, the primary prognostic factor in IDH1- or IDH2R140-mutated AML. HSCT improve OS of nonfavorable IDH1/2-mutated AML and should be fully integrated into the treatment strategy.

Genetic identification of patients with AML older than 60 years achieving long-term survival with intensive chemotherapy.

To design a simple and reproducible classifier predicting the overall survival (OS) of patients with acute myeloid leukemia (AML) ≥60 years of age treated with 7 + 3, we sequenced 37 genes in 471 patients from the ALFA1200 (Acute Leukemia French Association) study (median age, 68 years). Mutation patterns and OS differed between the 84 patients with poor-risk cytogenetics and the 387 patients with good (n = 13), intermediate (n = 339), or unmeasured (n = 35) cytogenetic risk. TP53 (hazards ratio [HR], 2.49; P = .0003) and KRAS (HR, 3.60; P = .001) mutations independently worsened the OS of patients with poor-risk cytogenetics. In those without poor-risk cytogenetics, NPM1 (HR, 0.57; P = .0004), FLT3 internal tandem duplications with low (HR, 1.85; P = .0005) or high (HR, 3.51; P < 10-4) allelic ratio, DNMT3A (HR, 1.86; P < 10-4), NRAS (HR, 1.54; P = .019), and ASXL1 (HR, 1.89; P = .0003) mutations independently predicted OS. Combining cytogenetic risk and mutations in these 7 genes, 39.1% of patients could be assigned to a "go-go" tier with a 2-year OS of 66.1%, 7.6% to the "no-go" group (2-year OS 2.8%), and 3.3% of to the "slow-go" group (2-year OS of 39.1%; P < 10-5). Across 3 independent validation cohorts, 31.2% to 37.7% and 11.2% to 13.5% of patients were assigned to the go-go and the no-go tiers, respectively, with significant differences in OS between tiers in all 3 trial cohorts (HDF [Hauts-de-France], n = 141, P = .003; and SAL [Study Alliance Leukemia], n = 46; AMLSG [AML Study Group], n = 223, both P < 10-5). The ALFA decision tool is a simple, robust, and discriminant prognostic model for AML patients ≥60 years of age treated with intensive chemotherapy. This model can instruct the design of trials comparing the 7 + 3 standard of care with less intensive regimens.

A personalized approach to guide allogeneic stem cell transplantation in younger adults with acute myeloid leukemia.

A multistage model instructed by a large dataset (knowledge bank [KB] algorithm) has recently been developed to improve outcome predictions and tailor therapeutic decisions, including hematopoietic stem cell transplantation (HSCT) in acute myeloid leukemia (AML). We assessed the performance of the KB in guiding HSCT decisions in first complete remission (CR1) in 656 AML patients younger than 60 years from the ALFA-0702 trial (NCT00932412). KB predictions of overall survival (OS) were superior to those of European LeukemiaNet (ELN) 2017 risk stratification (C-index, 68.9 vs 63.0). Among patients reaching CR1, HSCT in CR1, as a time-dependent covariate, was detrimental in those with favorable ELN 2017 risk and those with negative NPM1 minimal residual disease (MRD; interaction tests, P = .01 and P = .02, respectively). Using KB simulations of survival at 5 years in a scenario without HSCT in CR1 (KB score), we identified, in a similar time-dependent analysis, a significant interaction between KB score and HSCT, with HSCT in CR1 being detrimental only in patients with a good prognosis based on KB simulations (KB score ≥40; interaction test, P = .01). We could finally integrate ELN 2017, NPM1 MRD, and KB scores to sort 545 CR1 patients into 278 (51.0%) HSCT candidates and 267 (49.0%) chemotherapy-only candidates. In both time-dependent and 6-month landmark analyses, HSCT significantly improved OS in HSCT candidates, whereas it significantly shortened OS in chemotherapy-only candidates. Integrating KB predictions with ELN 2017 and MRD may thus represent a promising approach to optimize HSCT timing in younger AML patients.

Allogeneic transplantation in acute myelogenous leukemia: a comprehensive single institution's experience.

Debates on the role and timing of allogeneic hemtopoietic stem cell transplantation (HSCT) in acute myelogenous leukemia (AML) have persisted for decades. Time to transplant introduces an immortal time and current treatment algorithm mainly relies on the European LeukemiaNet disease risk classification. Previous studies are also limited to age groups, remission status and other ill-defined parameters. We studied all patients at diagnosis irrespective of age and comorbidities to estimate the cumulative incidence and potential benefit or disadvantage of HSCT in a single center. As a time-dependent covariate, HSCT improved overall survival in intermediate- and poor-risk patients (hazard ratio =0.51; P=0.004). In goodrisk patients only eight were transplanted in first complete remission. Overall, the 4-year cumulative incidence of HSCT was only 21.9% but was higher (52.1%) for patients in the first age quartile (16-57 years old) and 26.4% in older patients (57-70 years old) (P<0.001). It was negligible in patients older than 70 years reflecting our own transplant policy but also barriers to transplantation (comorbidities and remission status). However, HSCT patients need to survive, be considered eligible both by the referring and the HSCT physicians and have a suitable donor to get transplantation. We, thus, comprehensively analyzed the complete decision-making and outcome of all our AML patients from diagnosis to last followup to decipher how patient allocation and therapy inform the value of HSCT. The role of HSCT in AML is shifting with broad access to different donors including haploidentical ones. Thus, it may (or may not) lead to increased numbers of allogeneic HSCT in AML in adults.

Benefits of dexamethasone on early outcomes in patients with acute myeloid leukemia with hyperleukocytosis: a propensity score matched analysis.

Hyperleukocytosis is associated with a significant early mortality rate in patients with acute myeloid leukemia (AML). To date, no controlled trial has ever evaluated a strategy to reduce this risk, and the initial management of these patients remains heterogeneous worldwide. The aim of the present study was to evaluate the influence of a short course of intravenous dexamethasone on the early outcomes of patients with hyperleukocytic AML with white blood cell (WBC) count above 50 × 109/L. Clinical and biological data of all consecutive patients (1997-2017) eligible for intensive chemotherapy from a single center were retrospectively collected. A total of 251 patients with a median age of 51 years and a median WBC count of 120 × 109/L were included, 95 of whom received dexamethasone. Patients treated with dexamethasone had higher WBC count and a more severe disease compared with those who did not, and they presented more often with leukostasis and hypoxemia, resulting in a more frequent need for life-sustaining therapies (p < 0.001). To account for these imbalances, patients were compared after adjusting for a propensity score, which included all variables with a prognostic influence in the overall cohort. In the matched cohort, dexamethasone was associated with lower early death (OR = 0.34, p = 0.0026) and induction failure rate (OR = 0.44, p = 0.02) and better overall survival (HR = 0.60, p = 0.011), with no impact on relapse risk (cHR = 0.73, p = 0.39). The overall survival benefit was confirmed among all tested subgroups. This study suggests that dexamethasone administration is safe and associated with a lower risk of induction mortality in patients with hyperleukocytic AML and deserves prospective evaluation.

Mutational profile and benefit of gemtuzumab ozogamicin in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a highly heterogeneous disease both in terms of genetic background and response to chemotherapy. Although molecular aberrations are routinely used to stratify AML patients into prognostic subgroups when receiving standard chemotherapy, the predictive value of the genetic background and co-occurring mutations remains to be assessed when using newly approved antileukemic drugs. In the present study, we retrospectively addressed the question of the predictive value of molecular events on the benefit of the addition of gemtuzumab ozogamicin (GO) to standard front-line chemotherapy. Using the more recent European LeukemiaNet (ELN) 2017 risk classification, we confirmed that the benefit of GO was restricted to the favorable (hazard ratio [HR], 0.54, 95% confidence interval [CI], 0.30-0.98) and intermediate (HR, 0.57; 95% CI, 0.33-1.00) risk categories, whereas it did not influence the outcome of patients within the adverse risk subgroup (HR, 0.93; 95% CI, 0.61-1.43). Interestingly, the benefit of GO was significant for patients with activating signaling mutations (HR, 0.43; 95% CI, 0.28-0.65), which correlated with higher CD33 expression levels. These results suggest that molecular aberrations could be critical for future differentially tailored treatments based on integrated genetic profiles that are able to predict the benefit of GO on outcome.

Phase 1 study to evaluate Crenigacestat (LY3039478) in combination with dexamethasone in patients with T-cell acute lymphoblastic leukemia and lymphoma.

BACKGROUND: Deregulated Notch signaling is implicated in T-cell acute lymphoblastic leukemia (T-ALL)/T-cell lymphoblastic lymphoma (T-LBL). Crenigacestat (LY3039478) prevents cleavage of Notch proteins and may benefit patients with relapsed/refractory T-ALL/T-LBL. METHODS: JJCB was a multicenter, nonrandomized, open-label, dose-escalation, phase 1 study in adult patients with relapsed/refractory T-ALL/T-LBL. Eligible patients received Crenigacestat orally 3 times per week plus dexamethasone at 24 mg twice daily on days 1 to 5 every other week in a 28-day cycle. The starting level of Crenigacestat was 50 mg, and dose escalation was performed with a modified 3+3 scheme for the estimation of dose-limiting toxicity (DLT) at the recommended dose level. RESULTS: In total, 36 patients with T-ALL (n = 31 [86.1%]) or T-LBL (n = 5 [13.9%]) were treated with Crenigacestat and dexamethasone. Six patients (16.7%) experienced DLTs: 2 of 12 (16.7%) in the 75-mg cohort (grade 4 gastrointestinal hemorrhage and grade 3 nausea, vomiting, and diarrhea), 1 of 15 (6.7%) in the 100-mg cohort (grade 3 diarrhea), and 3 of 3 (100%) in the 125-mg cohort (grade 3 diarrhea, nausea, and vomiting). The maximum tolerated dosewas 75 mg plus 24 mg of dexamethasone daily on days 1 to 5. Twenty-eight patients (77.8%) experienced 1 or more treatment-emergent adverse events related to the study treatment. The best overall response was a confirmed response, with 1 patient (2.8%) having a duration of response of 10.51 months. Six patients (16.7%) achieved stable disease, and 12 patients (33.3%) experienced progressive disease. The remaining 17 patients (47.2%) were not evaluable. The median event-free survival was 1.18 months (95% confidence interval, 0.76-2.14 months) among all groups. A pharmacodynamic analysis showed decreased plasma amyloid ß levels. CONCLUSIONS: Crenigacestat demonstrated limited clinical activity at the recommended dose in adult patients with relapsed/refractory T-ALL/T-LBL.

Altered NFE2 activity predisposes to leukemic transformation and myelosarcoma with AML-specific aberrations.

In acute myeloid leukemia (AML), acquired genetic aberrations carry prognostic implications and guide therapeutic decisions. Clinical algorithms have been improved by the incorporation of novel aberrations. Here, we report the presence and functional characterization of mutations in the transcription factor NFE2 in patients with AML and in a patient with myelosarcoma. We previously described NFE2 mutations in patients with myeloproliferative neoplasms and demonstrated that expression of mutant NFE2 in mice causes a myeloproliferative phenotype. Now, we show that, during follow-up, 34% of these mice transform to leukemia presenting with or without concomitant myelosarcomas, or develop isolated myelosarcomas. These myelosarcomas and leukemias acquired AML-specific alterations, including the murine equivalent of trisomy 8, loss of the AML commonly deleted region on chromosome 5q, and mutations in the tumor suppressor Trp53 Our data show that mutations in NFE2 predispose to the acquisition of secondary changes promoting the development of myelosarcoma and/or AML.

Germline DDX41 mutations define a significant entity within adult MDS/AML patients.

Germline DDX41 mutations are involved in familial myelodysplastic syndromes (MDSs) and acute myeloid leukemias (AMLs). We analyzed the prevalence and characteristics of DDX41-related myeloid malignancies in an unselected cohort of 1385 patients with MDS or AML. Using targeted next-generation sequencing, we identified 28 different germline DDX41 variants in 43 unrelated patients, which we classified as causal (n = 21) or unknown significance (n = 7) variants. We focused on the 33 patients having causal variants, representing 2.4% of our cohort. The median age was 69 years; most patients were men (79%). Only 9 patients (27%) had a family history of hematological malignancy, and 15 (46%) had a personal history of cytopenia years before MDS/AML diagnosis. Most patients had a normal karyotype (85%), and the most frequent somatic alteration was a second DDX41 mutation (79%). High-risk DDX41 MDS/AML patients treated with intensive chemotherapy (n = 9) or azacitidine (n = 11) had an overall response rate of 100% or 73%, respectively, with a median overall survival of 5.2 years. Our study highlights that germline DDX41 mutations are relatively common in adult MDS/AML, often without known family history, arguing for systematic screening. Salient features of DDX41-related myeloid malignancies include male preponderance, frequent preexisting cytopenia, additional somatic DDX41 mutation, and relatively good outcome.

Minimal residual disease monitoring in acute myeloid leukemia with non-A/B/D-NPM1 mutations by digital polymerase chain reaction: feasibility and clinical use.

Not available.

Characteristics and outcome of patients with low-/intermediate-risk acute promyelocytic leukemia treated with arsenic trioxide: an international collaborative study.

The aim of this study was to characterize a large series of 154 patients with acute promyelocytic leukemia (median age, 53 years; range, 18-90 years) and evaluate real-life outcome after up-front treatment with arsenic trioxide and all-trans retinoic acid. All patients were included in the prospective NAPOLEON registry (NCT02192619) between 2013 and 2019. The acute promyelocytic leukemia was de novo in 91% (n=140) and therapy-related in 9% (n=14); 13% (n=20) of the patients were older than 70 years. At diagnosis bleeding/hemorrhage was present in 38% and thrombosis in 3%. Complete remission was achieved in 152 patients (99%), whereas two patients (1%) experienced induction death within 18 days after starting therapy. With a median follow-up of 1.99 years (95% confidence interval: 1.61-2.30 years) 1-year and 2-year overall survival rates were 97% (95% confidence interval: 94-100%) and 95% (95% confidence interval: 91-99%), respectively. Age above 70 years was associated with a significantly shorter overall survival (P<0.001) compared to that of younger patients. So far no relapses have been observed. Six patients (4%) died in complete remission at a median of 0.95 years after diagnosis (range, 0.18-2.38 years). Our data confirm the efficiency and durability of arsenic trioxide and all-trans retinoic acid therapy in the primary management of adults with low-/intermediate-risk acute promyelocytic leukemia in the real-life setting, irrespective of age.

Should Transplantation Still Be Considered for Ph1-Negative Myeloproliferative Neoplasms in Transformation?

BCR-ABL-negative myeloproliferative neoplasms (MPNs) in transformation have a dismal prognosis, and allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered the sole curative therapeutic option. We retrospectively analyzed 53 molecularly annotated patients treated at Saint Louis Hospital, Paris, diagnosed with MPN in transformation between 2008 and 2018. The median patient age was 65 years, and the median interval between MPN diagnosis and MPN transformation was 46 months. The median overall survival (OS) of the entire cohort after transformation was 7.1 months. OS was better for patients treated with hypomethylating agents (HMAs) or with chemotherapy compared than for those treated by best supportive care or single-agent targeted therapy (median, 9.1 months versus 1.5 months; P < .001). Patients treated with chemotherapy more often achieved complete remission compared with those treated with HMAs (68% versus 29%; P = .02), and were more often candidates for transplantation (59% versus 14%; P = .02), but the median OS was similar in the 2 groups. We then compared the outcomes in transplant recipients and nonrecipients using the Mantel-Byar methodology and found that allo-HSCT did not improve survival. In multivariate analysis, independent factors in prognosis were performance status at transformation (P < .01), initial treatment with HMAs or chemotherapy (P = .02), and the ability to achieve complete remission during follow-up (P < .01). Our data demonstrate that the indication for allo-HSCT for high-risk MPN should be discussed before transformation, because transplantation rescues few patients after transformation.

Aggressive B-cell lymphomas in patients with myelofibrosis receiving JAK1/2 inhibitor therapy.

Inhibition of Janus-kinase 1/2 (JAK1/2) is a mainstay to treat myeloproliferative neoplasms (MPN). Sporadic observations reported the co-incidence of B-cell non-Hodgkin lymphomas during treatment of MPN with JAK1/2 inhibitors. We assessed 626 patients with MPN, including 69 with myelofibrosis receiving JAK1/2 inhibitors for lymphoma development. B-cell lymphomas evolved in 4 (5.8%) of 69 patients receiving JAK1/2 inhibition compared with 2 (0.36%) of 557 with conventional treatment (16-fold increased risk). A similar 15-fold increase was observed in an independent cohort of 929 patients with MPN. Considering primary myelofibrosis only (N = 216), 3 lymphomas were observed in 31 inhibitor-treated patients (9.7%) vs 1 (0.54%) of 185 control patients. Lymphomas were of aggressive B-cell type, extranodal, or leukemic with high MYC expression in the absence of JAK2 V617F or other MPN-associated mutations. Median time from initiation of inhibitor therapy to lymphoma diagnosis was 25 months. Clonal immunoglobulin gene rearrangements were already detected in the bone marrow during myelofibrosis in 16.3% of patients. Lymphomas occurring during JAK1/2 inhibitor treatment were preceded by a preexisting B-cell clone in all 3 patients tested. Sequencing verified clonal identity in 2 patients. The effects of JAK1/2 inhibition were mirrored in Stat1-/- mice: 16 of 24 mice developed a spontaneous myeloid hyperplasia with the concomitant presence of aberrant B cells. Transplantations of bone marrow from diseased mice unmasked the outgrowth of a malignant B-cell clone evolving into aggressive B-cell leukemia-lymphoma. We conclude that JAK/STAT1 pathway inhibition in myelofibrosis is associated with an elevated frequency of aggressive B-cell lymphomas. Detection of a preexisting B-cell clone may identify individuals at risk.

Mesenchymal stromal cells confer chemoresistance to myeloid leukemia blasts through Side Population functionality and ABC transporter activation.

Targeting chemoresistant malignant cells is one of the current major challenges in oncology. Therefore, it is mandatory to refine the characteristics of these cells to monitor their survival and develop adapted therapies. This is of particular interest in acute myeloid leukemia (AML), for which the 5-year survival rate only reaches 30%, regardless of the prognosis. The role of the microenvironment is increasingly reported to be a key regulator for blast survival. In this context, we demonstrate that contact with mesenchymal stromal cells promotes a better survival of blasts in culture in the presence of anthracycline through the activation of ABC transporters. Stroma-dependent ABC transporter activation leads to the induction of a Side Population (SP) phenotype in a subpopulation of primary leukemia blasts through alpha (α)4 engagement. The stroma-promoting effect is reversible and is observed with stromal cells isolated from either healthy donors or leukemia patients. Blasts expressing an SP phenotype are mostly quiescent and are chemoresistant in vitro and in vivo in patient-derived xenograft mouse models. At the transcriptomic level, blasts from the SP are specifically enriched in the drug metabolism program. This detoxification signature engaged in contact with mesenchymal stromal cells represents promising ways to target stroma-induced chemoresistance of AML cells.