Prognostic impact of <i>CEBPA </i>mutational subgroups in adult AML

Despite recent refinements in the diagnostic and prognostic assessment of CEBPA mutations in AML, several questions remain open, i.e. implications of different types of basic region leucin zipper (bZIP) mutations, the role of co-mutations and the allelic state. Using pooled primary data analysis on 1010 CEBPA-mutant adult AML patients, a comparison was performed taking into account the type of mutation (bZIP: either typical in-frame insertion/deletion (InDel) mutations (bZIP InDel), frameshift InDel or nonsense mutations inducing translational stop (bZIP STOP) or single base-pair missense alterations (bZIP ms), and transcription activation domain (TAD) mutations) and the allelic state (single (smCEBPA) vs. double mutant (dmCEBPA)). Only bZIP InDel patients had significantly higher rates of complete remission and longer relapse free and overall survival (OS) compared with all other CEBPA-mutant subgroups. Moreover, co-mutations in bZIP InDel patients (e.g. GATA2, FLT3, WT1 as well as ELN2022 adverse risk aberrations) had no independent impact on OS, whereas in non-bZIP InDel patients, grouping according to ELN2022 recommendations added significant prognostic information. In conclusion, these results demonstrate bZIP InDel mutations to be the major independent determinant of outcome in CEBPA-mutant AML, thereby refining current classifications according to WHO (including all dmCEBPA and smCEBPA bZIP) as well as ELN2022 and ICC recommendations (including CEBPA bZIP ms). (Figure presented.)</p

Prognostic impact of CEBPA mutational subgroups in adult AML

Despite recent refinements in the diagnostic and prognostic assessment of CEBPA mutations in AML, several questions remain open, i.e. implications of different types of basic region leucin zipper (bZIP) mutations, the role of co-mutations and the allelic state. Using pooled primary data analysis on 1010 CEBPA-mutant adult AML patients, a comparison was performed taking into account the type of mutation (bZIP: either typical in-frame insertion/deletion (InDel) mutations (bZIPInDel), frameshift InDel or nonsense mutations inducing translational stop (bZIPSTOP) or single base-pair missense alterations (bZIPms), and transcription activation domain (TAD) mutations) and the allelic state (single (smCEBPA) vs. double mutant (dmCEBPA)). Only bZIPInDel patients had significantly higher rates of complete remission and longer relapse free and overall survival (OS) compared with all other CEBPA-mutant subgroups. Moreover, co-mutations in bZIPInDel patients (e.g. GATA2, FLT3, WT1 as well as ELN2022 adverse risk aberrations) had no independent impact on OS, whereas in non-bZIPInDel patients, grouping according to ELN2022 recommendations added significant prognostic information. In conclusion, these results demonstrate bZIPInDel mutations to be the major independent determinant of outcome in CEBPA-mutant AML, thereby refining current classifications according to WHO (including all dmCEBPA and smCEBPA bZIP) as well as ELN2022 and ICC recommendations (including CEBPA bZIPms)

Activating FLT3 mutants show distinct gain-of-function phenotypes in vitro and a characteristic signaling pathway profile associated with prognosis in acute myeloid leukemia.

About 30% of patients with acute myeloid leukemia (AML) harbour mutations of the receptor tyrosine kinase FLT3, mostly internal tandem duplications (ITD) and point mutations of the second tyrosine kinase domain (TKD). It was the aim of this study to comprehensively analyze clinical and functional properties of various FLT3 mutants. In 672 normal karyotype AML patients FLT3-ITD, but not FLT3-TKD mutations were associated with a worse relapse free and overall survival in multivariate analysis. In paired diagnosis-relapse samples FLT3-ITD showed higher stability (70%) compared to FLT3-TKD (30%). In vitro, FLT3-ITD induced a strong activating phenotype in Ba/F3 cells. In contrast, FLT3-TKD mutations and other point mutations--including two novel mutations--showed a weaker but clear gain-of-function phenotype with gradual increase in proliferation and protection from apoptosis. The pro-proliferative capacity of the investigated FLT3 mutants was associated with cell surface expression and tyrosine 591 phosphorylation of the FLT3 receptor. Western blot experiments revealed STAT5 activation only in FLT3-ITD positive cell lines, in contrast to FLT3-non-ITD mutants, which displayed an enhanced signal of AKT and MAPK activation. Gene expression analysis revealed distinct difference between FLT3-ITD and FLT3-TKD for STAT5 target gene expression as well as deregulation of SOCS2, ENPP2, PRUNE2 and ART3. FLT3-ITD and FLT3 point mutations show a gain-of-function phenotype with distinct signalling properties in vitro. Although poor prognosis in AML is only associated with FLT3-ITD, all activating FLT3 mutations can contribute to leukemogenesis and are thus potential targets for therapeutic interventions

Allogeneic Transplantation Versus Chemotherapy as Postremission Therapy for Acute Myeloid Leukemia: A Prospective Matched Pairs Analysis

Purpose The majority of patients with acute myeloid leukemia (AML) who achieve complete remission (CR) relapse with conventional postremission chemotherapy. Allogeneic stem-cell transplantation (alloSCT) might improve survival at the expense of increased toxicity. It remains unknown for which patients alloSCT is preferable. Patients and Methods We compared the outcome of 185 matched pairs of a large multicenter clinical trial (AMLCG99). Patients younger than 60 years who underwent alloSCT in first remission (CR1) were matched to patients who received conventional postremission therapy. The main matching criteria were AML type, cytogenetic risk group, patient age, and time in first CR. Results In the overall pairwise compared AML population, the projected 7-year overall survival (OS) rate was 58% for the alloSCT and 46% for the conventional postremission treatment group (P = .037; log-rank test). Relapse-free survival (RFS) was 52% in the alloSCT group compared with 33% in the control group (P < .001). OS was significantly better for alloSCT in patient subgroups with nonfavorable chromosomal aberrations, patients older than 45 years, and patients with secondary AML or high-risk myelodysplastic syndrome. For the entire patient cohort, postremission therapy was an independent factor for OS (hazard ratio, 0.66; 95% CI, 0.49 to 0.89 for alloSCT v conventional chemotherapy), among age, cytogenetics, and bone marrow blasts after the first induction cycle. Conclusion AlloSCT is the most potent postremission therapy for AML and is particularly active for patients 45 to 59 years of age and/or those with high-risk cytogenetics

Multivariable analysis of prognostic factors for OS, RFS and CR.

<p>To evaluate the independent prognostic impact of FLT3-ITD and FLT3-TKD on OS, RFS and CR, all candidate prognostic factors were included in the Cox regression model without selection of variables. The analyses were performed using 535 complete datasets of patients with regard to OS for the candidate prognostic factors. HR: Hazard Ratio; CI: confidence interval; CL: confidence limit.</p

FLT3 mutants display a wide range of activating phenotypes in Ba/F3 cells.

<p>Ba/F3 cells stably transduced with indicated constructs were seeded at a density of 4×10⁴ cells/ml and cultured in presence and absence of 10 ng/ml IL-3. (A) Viable cells were counted after 72 h using trypan blue exclusion. Control indicates viable Ba/F3 MIY cells treated with 10 ng/ml IL-3. Values are expressed as mean +/− S.D. of nine independent experiments. (*) indicates significant higher growth compared to FLT3-WT expressing cells. (B) After incubation for 48 hours cells were stained with Annexin-V and 7-AAD. The percentage of apoptotic cells was determined using flow cytometry. Values are expressed as mean +/− S.D. of at least three independent experiments. (*) indicates significant higher apoptosis compared to FLT3-WT expressing cells. (C) Ba/F3 cells expressing FLT3 mutations were cultured without IL-3 for 24 hours. Cells were treated with 100 ng FLT3-ligand for 10 minutes prior to lysis to analyze phosphorylation of FLT3 receptor at Tyr591 in a chemiluminescent ELISA assay. The differences of FLT3-ligand stimulated to untreated results are shown. Values are expressed as mean +/− S.D. of three independent experiments. For further statistical analyses FLT3 mutants were divided into groups of FLT3-WT-like (FLT3-I867S/-V592A), FLT3-TKD (FLT3-D839G/-D835V/-D835Y) and FLT3-ITD (FLT3-ITD1/-ITD2/-ITD3) cell lines. In grouped analysis FLT3-WT expressing cells were significantly different compared to the FLT3-TKD (p = 0.019) but not to FLT3-WT-like cell lines. Groups of FLT3-WT-like, FLT3-TKD and FLT3-ITD cell lines were significant among each other (p≤0.030). (*) indicates significance of grouped analyses and individually compared to FLT3-WT expressing cells. RLU: Relative light units.</p