non-APL Acute Myeloid Leukemia Research Articles

Inhibition of NRF2 signaling overcomes acquired resistance to arsenic trioxide in FLT3-mutated Acute Myeloid Leukemia.

De novo acute myeloid leukemia (AML) patients with FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) have worse treatment outcomes. Arsenic trioxide (ATO) used in the treatment of acute promyelocytic leukemia (APL) has been reported to be effective in degrading the FLT3 protein in AML cell lines and sensitizing non-APL AML patient samples in-vitro. We have previously reported that primary cells from FLT3-ITD mutated AML patients were sensitive to ATO in-vitro compared to other non-M3 AML and molecular/pharmacological inhibition of NF-E2 related factor 2 (NRF2), a master regulator of antioxidant response improved the chemosensitivity to ATO and daunorubicin even in non FLT3-ITD mutated cell lines and primary samples.We examined the effects of molecular/pharmacological suppression of NRF2 on acquired ATO resistance in the FLT3-ITD mutant AML cell line (MV4-11-ATO-R). ATO-R cells showed increased NRF2expression, nuclear localization, and upregulation of bonafideNRF2 targets. Molecular inhibition of NRF2 in this resistant cell line improved ATO sensitivity in vitro. Digoxin treatment lowered p-AKT expression, abrogating nuclear NRF2 localization and sensitizing cells to ATO. However, digoxin and ATO did not sensitize non-ITD AML cell line THP1 with high NRF2 expression. Digoxin decreased leukemic burden and prolonged survival in MV4-11 ATO-R xenograft mice. We establish that altering NRF2 expression may reverse acquired ATO resistance in FLT3-ITD AML.

Biomarkers of bleeding and venous thromboembolism in patients with acute leukemia

BackgroundCoagulopathy and associated bleeding and deep vein thrombosis (DVT) are major causes of morbidity and mortality in patients with acute leukemia. The underlying mechanisms of these complications have not been fully elucidated. ObjectivesTo evaluate the associations between biomarker levels and bleeding and DVT in acute leukemia patients. MethodsWe examined plasma levels of activators, inhibitors, and biomarkers of the coagulation and fibrinolytic pathways in patients aged ≥18 years with newly diagnosed acute leukemia compared with those of normal controls. Multivariable regression models were used to examine the association of biomarkers with bleeding and DVT in acute leukemia patients. The study included 358 patients with acute leukemia (29 with acute promyelocytic leukemia [APL], 253 with non-APL acute myeloid leukemia, and 76 with acute lymphoblastic leukemia) and 30 normal controls. ResultsPatients with acute leukemia had higher levels of extracellular vesicle tissue factor (EVTF) activity, phosphatidylserine-positive extracellular vesicles, plasminogen activator inhibitor-1, plasmin-antiplasmin complexes, and cell-free DNA and lower levels of citrullinated histone H3-DNA complexes compared with normal controls. APL patients had the highest levels of EVTF activity and the lowest levels of tissue plasminogen activator among acute leukemia patients. There were 41 bleeding and 24 DVT events in acute leukemia patients. High EVTF activity was associated with increased risk of bleeding (sHR, 2.30; 95% CI, 0.99-5.31), whereas high plasminogen activator inhibitor-1 was associated with increased risk of DVT (sHR, 3.00; 95% CI, 0.95-9.47) in these patients. ConclusionOur study shows alterations in several biomarkers in acute leukemia and identifies biomarkers associated with risk of bleeding and DVT.

Epigenetic Modulation Enhances the Therapeutic Potential of All-Trans Retinoic Acid in Acute Myeloid Leukemia

Epigenetic dysregulation has been strongly associated with the development and progression of acute myeloid leukemia (AML). While all-trans retinoic acid (ATRA), a derivative of vitamin A, has demonstrated significant anti-cancer effects in acute promyelocytic leukemia (APL-AML), its clinical efficacy in non-APL AMLs has been limited. This limited response can be attributed, in part, to the epigenetic silencing of genes targeted by or involved in the ATRA pathway, rendering them unresponsive to the drug. Consequently, our research aims to overcome the epigenetic barriers in AML by combining ATRA with small molecules that possess epigenetic modulating properties. To investigate the activation of the retinoic acid pathway in response to ATRA and a library of over 650 small molecules with epigenetic activity, we transduced HEK-293 cells with the p-GreenFire-RARE-Tk-Luc reporter construct. Through the screening process, we have identified 11 compounds that show promise as potential candidates for combination therapy with ATRA in non-APL AML. Notably, when combined with ATRA, two specific compounds, a dual PI3K HDAC inhibitor, and a pan-PKC inhibitor, demonstrated a significant 4-5 fold increase in RARE activity, indicating a synergistic effect. To determine the impact of selected compounds on the functional level, we evaluated the viability, differentiation, and phosphorylation status of ERK1/2, AKT1, MAPK9, p38, and MAPK9 in various cell lines, including HL-60, KG1a, BMNC, and primary MSC and AML cells. The dual PI3K HDAC inhibitor and a pan-PKC inhibitor were noncytotoxic to HL60, BMNC, and primary MSC. Interestingly, dual PI3K HDAC inhibitor with and without ATRA reduced the viability of KG1α by more than 95%. Moreover, dual PI3K HDAC inhibitor and a pan-PKC inhibitor, when combined with ATRA, lead to a 2-3 fold increase in the differentiation of HL60 cells and a 2-4 fold increase in the differentiation of AML cells ex vivo compared to ATRA in combination with the LSD1 inhibitor TCP (treatment control protocol) and untreated cells from AML subtypes M1, M2, and M4. PI3K HDAC inhibitor combined with ATRA significantly reduced p-MAPK and p-p38 levels while increasing the phosphorylation of p53 in HL-60 cells. Furthermore, RNA sequencing and chromatin profiling by Cleavage Under Targets and Tagmentation (CUT&Tag) were performed to gain additional insights into the molecular mechanisms involved. Based on obtained results, the combination of ATRA with specific dual PI3K HDAC and pan-PKC inhibitors holds promise as a potential therapeutic approach for AML. Nevertheless, further investigations, including studies utilizing patient-derived xenograft models, are warranted to validate the efficacy and feasibility of this proposed treatment strategy.

Podoplanin Expression Measured By Flow Cytometry Accurately Identifies Patients with Acute Promyelocytic Leukemia at Diagnosis

Acute promyelocytic leukemia (APL) is a hematological emergency associated with high early mortality rates, thus requiring prompt diagnosis and treatment initiation. Currently, diagnostic suspicion relies on morphological criteria, which can be further corroborated by immunophenotypic analyses, until results based on molecular techniques confirm the diagnosis. However, while both cytology and immunophenotypic analyses are very important in this setting, their accuracy can be influenced by inherent morphological variation of blasts, as well as by gating and other technical issues related to flow cytometry. In this context, novel parameters that could contribute to the segregation of APL from other forms of acute myeloid leukemia (AML) would be desirable. Recently, Lavallée et al demonstrated that the aberrant expression of podoplanin (PDPN), a protein that mediates platelet activation in inflammatory contexts, by leukemic cells is as a relevant mediator of the coagulopathy of APL, as well potential biomarker of this condition based on the analysis of primary cells from patients with AML. The aim of this study was to prospectively and independently validate whether the surface expression of PDPN by leukemic promyelocytes measured by flow cytometry can contribute to the differential diagnosis between APL and other forms of AML. We also explored the association of PDPN expression with clinical and laboratory characteristics of these patients. The study population consisted of all consecutive patients diagnosed with APL by cytological, immunophenotypical and molecular techniques in our adult academic hematology hospital from 2020 to 2023. Exclusion criteria included the presence of hemodynamic instability or refusal to participate. The expression of PDPN was measured by flow cytometry using BD FACSCanto II™ cytometer. Analysis was performed in accordance with EuroFlow protocols, with a panel that includes CD45, CD33, CD34, MPO, CD117, CD13, HLA-DR, as well as an antibody against PDPN (PE anti-human Podoplanin Antibody - Catalog# 337004 - BioLegend). Lymphocytes were used as internal negative control for PDPN expression. Data were analyzed with Infinicyt™ software and reported both as the % of PDPN + cells or according to mean fluorescence intensity (MFI). Patients with other forms of AML diagnosed during the same period and matched for age, gender and peripheral blast count were used to compare the diagnostic accuracy of PDPN measurement. Clinical and laboratory data were obtained from the medical records. The study was approved by the Institutional Review Board and all participants provided written informed consent. In total, 19 consecutive patients with confirmed diagnosis of APL were compared with 18 patients with non-APL AML. Clinical and laboratory data from the study population are shown in table 1. The expression of PDPN in leukemic blasts was significantly higher in APL compared to non-APL AML, considering either the percentage of PDPN + cells or the MFI (table 1; figure 1a-b). When considered as a categorical variable, the expression of PDPN was strongly associated with the diagnosis of APL (Chi-square test= 19.169; P<0.001). PDPN expression was inversely correlated with platelet count (R S= -0.47; P=0.003) and fibrinogen (R S= -0.51; P=0.001), but not with other laboratory parameters such as PT and aPTT. No association of PDPN expression with the available clinical variables was observed, although it should be noted that our study is underpowered to confirm these findings. We next estimated the diagnostic accuracy of PDPN expression by flow cytometry by ROC analysis. As shown in figures 1c-d, the area under the ROC curve was higher than 0.9 for both analytical strategies. In conclusion, our prospective study demonstrated that measurement of the expression of PDPN by flow cytometry at diagnosis is capable to accurately segregate APL from other forms of AML. Additional studies are warranted to explore the clinical association of PDPN expression in larger and independent cohorts.

Genomic Characterization of Newly Diagnosed Acute Myeloid Leukemia in Patients Age 60 Years and Older; A Report from the Beat AML Master Trial

Background. Acute myeloid leukemia (AML) is a heterogenous disease that occurs primarily in older adults with a median age of 69 years at diagnosis. Most studies that characterize the genomic landscape of AML include younger adults with the majority of patients being younger than 60 years of age. We aimed to study the mutational landscape of newly diagnosed AML patients aged 60 years or older. Methods.Samples were collected from the multi-center Beat AML Master Trial (Burd, Nat Med 2020). Patients were enrolled between 2016 and 2023. Informed consent was obtained according to the Declaration of Helsinki. Patients diagnosed with non-APL AML and who were aged ≥ 60 years old were included. Patients underwent bone marrow aspiration and biopsy, cytogenetic analysis, FLT3-ITD ratio assessment (LeukoStrat CDx FLT3 Mutation Assay, Invivoscribe) and next generation sequencing (NGS) using FoundationOne®Heme(Foundation Medicine) to interrogate the entire coding region of 406 genes and select introns of 31 genes involved in rearrangements, as well as RNA sequencing to interrogate 265 genes known to be somatically altered in human hematological malignancies. The presence of multiple hotspot mutations within one gene in an individual patient was counted as one gene mutation. Patterns of co-occurrence between gene mutations were calculated using the Phi correlation coefficient. Statistical analyses were performed using R statistical software. P<0.01 was considered statistically significant. Results. A total of 1088 newly diagnosed AML patients were identified, of whom 1032 were 60 years or older. Patients had a median age of 72 years at time of diagnosis (range 60-92 years). Forty-two percent of the patients were female, most patients were non-Hispanic and 79% were Caucasian. NGS data were available for 1024 patients and mutations were identified in 461 different genes. Patients had a median number of 11.0 mutations (range 3.0 to 28.0). The most frequently mutated genes were DNMT3A (n=257; 25.1%), TP53(n=255; 24.9%), TET2 (n=243; 23.7%), RUNX1 (n=225; 22.0%), SRSF2 (n=221; 21.6%), ASXL1 (n=216; 21.1%), NPM1 (n=206; 20.1%), FLT3 (n=205; 20.0%), IDH2 (n=190; 18.6%), NRAS (n=208; 16.9%), PTPN11(n=104; 10.2%), STAG2 (n=101, 9.9% and IDH1 (n=99; 9.7%) (Figure 1A). FLT3-ITD was present in 98 (12.1%) of the 810 patients who were tested. Strongest significant co-occurrence was found between FLT3and NPM1 (n=103), STAG2 and ASXL1 (n=63), ASXL1 and RUNX1 (n=92), ASXL1 and SRSF2 (n=88), RUNX1 and SRSF2 (n=94), STAG2 and SRSF2 (n=51) and DNMT3A and NPM1 (n=92) (p<0.01). Pairwise negative correlations were observed between TP53 and NPM1 (n=6), TP53 and SRSF2 (n=17), and between NPM1 and RUNX1 (n=6) (p<0.01) (Figure 1B). The cytogenetic profiles and the full genomic landscape will be presented during the ASH meeting. Discussion. This is the largest study investigating the mutational profile in older adults with AML aged 60 years and older. Due to the 7-day screening period of the Beat AML study, patient selection was biased towards less-rapidly proliferative AML. We showed that the pattern of gene mutations was markedly different from other studies in AML that mainly included younger AML patients (Papaemmanuil, NEJM 2016; TCGA, NEJM 2013 ). The frequency of mutated TP53 was substantially higher in older AML patients, as was the occurrence of myelodysplasia-related gene mutations (e.g., SRSF2, RUNX1, ASXL1, STAG2, U2AF1, and SF3B1) and gene mutations in IDH1, IDH2 and TET2. In contrast, NPM1 mutation was less frequently mutated in older AML patients. Furthermore, we demonstrated that a large proportion (46%) of the AML patients older than 60 years of age do have a mutation that is potentially targetable for treatment ( FLT3 IDH1 IDH2 and NPM1). The high incidence of mutated TP53 and MDS-related gene mutations underscores the increased incidence of high-risk AML and the need for innovative personalized therapies in this older age group. Figure 1. A. Co-occurrence of the 15 most frequently mutated genes, and B. co-correlation between the 15 most frequently mutated genes. Blue indicates positive correlation, red indicated negative correlation. Only significant correlations (p<0.01) are shown.

Azacitidine Plus Venetoclax Maintenance in Acute Myeloid Leukemia Produces Sustained Remissions with Low Toxicity: Results of a Phase 2 Study

Background: Most patients diagnosed with acute myeloid leukemia (AML) achieve remission following induction therapy. However, disease relapse remains a major clinical concern. The QUAZAR AML-001 study demonstrated improved overall and relapse-free survival with oral azacitidine (CC-486) maintenance. We designed a phase 2 study (NCT04062266) to evaluate low doses of azacitidine plus venetoclax as maintenance therapy following both intensive and low-intensity induction in AML. We present updated results of this study with close to 2 years of median follow-up. Methods: Patients ≥ 18 years of age with non-APL AML in first complete remission (CR) or CR with incomplete count recovery (CRi) not immediately eligible for allogeneic stem cell transplantation (SCT) were eligible. Cohort 1 enrolled patients who had received at least 2 cycles of intensive therapy (defined as containing intermediate to high-dose cytarabine). Cohort 2 enrolled patients who had received at least 3 cycles of low-intensity therapy (defined as hypomethylating agent or low-dose cytarabine-based). Patients with positive measurable residual disease (MRD) by flow cytometry were eligible in CR1 or beyond. Other inclusion requirements were ECOG ≤ 3, adequate hepatic/renal function, and adequate bone marrow reserve (defined as absolute neutrophil count > 0.5 x 10 9/L and platelets > 30 x 10 9/L). Treatment consisted of azacitidine 50 mg/m 2 SQ/IV on D1-5 and venetoclax 400 mg PO (adjusted for concomitant CYP3A inhibitors) on D1-14 in 28-day cycles, up to 24 cycles. Venetoclax duration could be reduced to D1-7 per physician discretion to mitigate myelosuppression and dose modifications during subsequent cycles were allowed. Antibacterial, antifungal, and antiviral prophylaxis were recommended in all patients. The primary objective was relapse-free survival (RFS, defined as time from enrollment to progression or death). Secondary objectives included overall survival (OS), safety/toxicity, and MRD clearance. Patients subsequently becoming eligible for SCT were taken off study and censored for analyses at the time of SCT. Results: 35 patients have been enrolled (25 in cohort 1 and 10 in cohort 2). The median age was 47 years in cohort 1 and 71 years in cohort 2. The baseline characteristics are shown in table 1. The median number of cycles given was 9 (range 1-24). 22/35 (63%) patients had 7 days of venetoclax during cycle 1. Median follow-up is currently 20.9 months (m). For the full cohort, the median RFS was not reached (NR; 2-year 60%) and the median OS was NR (2-year 75%). In cohort 1, the median RFS and OS were NR (2-year 71%) and NR (2-year 77%), respectively. In cohort 2, the median RFS and OS were 23.5 m (2-year 34%) and NR (2-year 67%), respectively. When stratified by ELN 2017, patients who were favorable (n=16), intermediate (n=11), and adverse (n=8) had a median RFS of NR (2-year 85%), NR (2-year 64%), and 4.0 m (2-year 0%), respectively. Corresponding median OS were NR (2-year 91%), NR (2-year 76%), and 14.9 m (2-year 27%), respectively. 4/8 (50%) of the ELN adverse patients had complex cytogenetics and/or TP53 mutations. Patients who were MRD-positive at enrollment (n=7, 3 with prior venetoclax exposure) had significantly shorter RFS compared to those who were MRD-negative (median 4.0 m versus NR, p<0.01). Only 2/7 (29%) MRD-positive patients converted to MRD-negative while on maintenance. As mutations in NPM1, IDH1, or IDH2 may sensitize AML to venetoclax, we analyzed RFS based on the presence or absence of these mutations (figure 1). Patients with sensitizing mutations had a trend towards longer RFS (median RFS NR versus 23.5 m, 2-year RFS 79% vs 36%, p=0.08). The most common grade 3/4 adverse events were infections (26%), neutropenia (17%), thrombocytopenia (17%), hypotension (6%), and neutropenic fever (6%). 4 (11%) patients required cycle 2 venetoclax dose reductions. 8 (23%) of patients went off protocol to receive SCT. All observed deaths (n=8) occurred following AML relapse (n=7) or SCT-related complications (n=1). Conclusions: Lower dose azacitidine plus venetoclax is a feasible and safe maintenance strategy in AML. This approach yields encouraging results in MRD-negative patients with non-adverse ELN risk (favorable or intermediate risk). A genetic-guided strategy may help select patients who benefit the most from this combination (i.e. those with NPM1, IDH1, or IDH2 mutations).

Venetoclax in Combination with Intermediate Doses of Cytarabine in Consolidation Phase for Acute Myeloid Leukemia Patients in First Complete Remission; Results of the Part 1 of the Phase 1/2 Multicentric Covenidac Study

For authors: Please: L Gastaud and P Peterlin: co-primary, H dombret et C Recher: co-last Background: The French ALFA-FILO AML intergroup launched the BIG-1 trial (EudraCT No.: 2014-000699-24) in 2015 to evaluate different intensive chemotherapy (ICT) strategies aiming at improving the survival of younger adults with acute myeloid leukemia (AML). All patients (pts) with previously untreated non-APL and non-CBF AML aged 18-60 years were eligible for this trial. The trial design included several randomization types. Results of the R1 and R2 randomizations, namely idarubicin vs daunorubicin for induction and IDAC vs HDAC for consolidation, will be reported at this meeting. In patients who achieved first complete remission (CR), randomizations R4 consisted of nested randomized Phase 2 or 1/2 studies evaluating the addition of new drugs to the IDAC/HDAC consolidation cycles. The protocol was designed to allow several sequential multicenter R4 evaluations of various new agents over the trial period. Venetoclax (VEN) has proved its efficacy when combined to azacitidine or low dose cytarabine in unfit AML pts (DiNardo et al. 2020; Wei et al. Blood 2020). Its role in fit patients treated with ICT is still under investigation. The COVENIDAC Phase 1/2 R4 sub-study is evaluating the safety and efficacy of VEN added to IDAC during the consolidation cycles of CR pts. We report herein the result of the Phase 1 part. Methods: The primary objective of this Phase 1 study was to determine the maximum tolerated dose (MTD) of VEN in combination with IDAC during the consolidation cycles, which will be the recommended dose for the Phase 2 (RP2D). Dose limiting toxicities (DLTs) were assessed during the first cycle of consolidation (C1) according to a 3+3 design. A maximum of 3 consolidation cycles was planned depending on the AML risk group. Hematological DLT was defined as no peripheral blood count recovery within 56 days from day 1 of the cycle. Non-hematological DLTs were defined as Grade ≥4 toxicities or Grade ≤3 toxicities which have not recovery by day 56 and deemed related to VEN per investigator opinion. VEN was started at dose level (DL) 1: 100 mg/d from day 1 to 8. In the absence of DLTs at DL1, 3 others DL were planned: 200 mg/d from day 1 to 8 (DL2); 400 mg/d from day 1 to 8 (DL3), and 400 mg/d from day 1 to 14 (DL4). IDAC was administrated at 1.5 gr/m² twice daily on day 1/3/5 for DL1, DL2 and DL3 pts, then on day 1/2/3 for DL4 pts after a protocol amendment. Main inclusion criteria were: pts in first CR following 1 or 2 courses of induction chemotherapy fit for further ICT; favorable and intermediate risk AML as defined by the protocol; ECOG PS ≤2; written informed consent. Measurable residual disease (MRD) was assessed by multiparametric flow cytometry (MFC) in all pts as well as NPM1-qPCR in NPM1-mutated pts. Results: Between 06/2021 and 04/2022, 15 pts from 9 centers were screened and enrolled. Pt characteristics were as follows: median age, 42 years (IQR, 30-49); 2 males/7 females; ECOG-PS, 0 in 10 pts and 1 in 5 pts; favorable/intermediate/adverse ELN-2017 risk, 9/2/4. Neutropenia and thrombocytopenia durations are shown in Table 1. Only 1 hematological DLT was observed at DL3 (platelet count of 96 giga/L at day 56 in a patient who was infected by Covid-19). Overall, there were very few non hematological AEs ( Table 2, no grade 4) and only 4 SAEs (1 related to IDAC/VEN during C1, 3 non-related). No non-hematological DLT was observed. No patient died during the DLT observation period, 1 experienced a septic shock (C2, DL2). One pt received only C1 (due to DLT), 7 received 2 cycles, and 7 received 3 cycles. Median time between initiation of subsequent consolidation cycles was 37.5 days (IQR, 35-41) for C1/C2 and 40 days (IQR, 35-43) for C2/C3. One pt had to stop VEN during C3. Six pts received an allogeneic HSCT (5 in CR1, 1 after salvage). With a median follow-up of 13.5 months, 3 pts relapsed and 2 died. MRD results will be presented. Conclusion: VEN/IDAC combination appears to be feasible and safe as consolidation therapy, with expected thrombocytopenia and neutropenia durations. These durations appeared even shorter at DL4, when IDAC was given on 3 consecutive days. VEN at 400 mg/d from day 1 to 14 combined with IDAC on day 1/2/3 was thus retained as RP2D for the randomized Phase 2 with RFS as primary endpoint. This phase 2 has already recruited 29 of the 200 pts planned.

Arsenic Trioxide Combine with G-CSF Triggers Distinct TP53 Mutations Acute Myeloid Leukemia Cells Ferroptosis through TP53-SLC7A11-GPX4 Pathway

Abstract ： Background ： Acute myeloid leukemia (AML) is a complex disease with diverse molecular subtypes. Approximately 8% of AML patients carry the TP53 mutation, which is associated with an aggressive disease course and dismal survival rates. Arsenic trioxide (ATO) has been remarkably effective in treating acute promyelocytic leukemia (APL), but its clinical activity in other AML subtypes remains limited. Recent evidence indicates that ATO demonstrates potential in rescuing multiple TP53 mutations effectively, offering promise as an individualized therapeutic strategy targeting mutant TP53 in leukemic cells. Our previous study showed that the upregulation of AQP9 by G-CSF enhanced the effect of ATO in non-APL AML cells. This demonstrates that ATO holds therapeutic promise in AML cases harboring distinct TP53 mutations. Methods ： We conducted a comprehensive analysis of TP53 mutations in the Analysis of Whole Genomes cohort, encompassing patients from the TCGA and OHSU databases. The frequency and distribution of TP53 mutations were determined. Median overall survival (OS) was calculated using the Kaplan-Meier method. To functionally assess the effect of TP53 mutation on AML phenotype, various cell lines harboring distinct TP53 mutation types were used for this study, including KASUMI-1 TP53 R248Q THP-1 TP53frameshift_delHL-60 TP53 deletionMOLM13 TP53 wild-type. The cellular lipid oxidation levels were measured by a C11 BODIPY flow cytometry assay and it was also observed by fluorescence microscopy. Additionally, the RNA and protein expressions of GPX4 and SLC7A11 were analyzed by real-time quantitative Polymerase Chain Reaction (QRT-PCR) and Western Blot. Results ： In the OHSU cohort and TCGALAML database, including 1005 newly diagnosed patients with 120 TP53 mutations, we found that missense mutations are the most common TP53 mutations and R248Q has the highest mutation frequency. Furthermore, TP53 mutationwas significantly associated with lower survival ( P <0.001). ATO potently induced cell death in each cell line. The KASUMI-1 R248Q cell line was the most sensitive to ATO (IC50=0.3607) and showed the most pronounced change in the IC50 of ATO with the addition of ferrostatin-1(Fer-1, ferroptosis inhibitor). ATO induced cell death was prevented by the addition of lipophilic antioxidant ferrostatin-1, supporting the hypothesis that ATO induced cell death occurred by ferroptosis. In KASUMI-1 R248Q cell line, ATO increases the lipid oxidation levels (observed by C11 BODIPY flow cytometry assay and fluorescence microscopy), MDA levels and decreases the expression of GPX4 and SLC7A11 (including RNA level and protein level). Whereas, in MOLM13 TP53 wildtype cell line, ATO increases the lipid oxidation levels but cannot prevented by Fer-1. THP-1 TP53 frameshift_del and HL-60 TP53 deletion only decrease the RNA expression of GPX4 and SLC7A11, nothing else changed in ferroptosis. These suggest that ATO has a more pronounced effect on missense mutations such as TP53 R248Q. In KASUMI-1 R248Q cell line, associated with G-CSF can further promote lipid oxidation levels (observed by C11 BODIPY flow cytometry assay and fluorescence microscopy) and further reduce the expression of GPX4 and SLC7A11. These results suggest that G-CSF promotes ATO-induced ferroptosis in KASUMI-1 R248Q cell line. Conclusion: We have demonstrated that ATO induces AML with distinct TP53 mutation cell death by ferroptosis resulting from depletion of GPX4 and SLC7A11. ATO associated with G-CSF may be able to be a new therapeutic strategy for the treatment of AML with distinct TP53 mutation.

Influence on therapeutic outcome of platelet count at diagnosis in patients with de novo non-APL acute myeloid leukemia

BackgroundPlatelet (PLT) count at diagnosis plays an important role in cancer development and progression in solid tumors. However, it remains controversial whether PLT count at diagnosis influences therapeutic outcome in patients with non-acute promyelocytic leukemia (APL) acute myeloid leukemia (AML).MethodsThis study analyzed the relationship between PLT count at diagnosis and genetic mutations in a cohort of 330 newly diagnosed non-APL AML patients. The impact of PLT count on complete remission, minimal residual disease status and relapse-free survival (RFS) were evaluated after chemotherapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT).ResultsOur studies showed that patients with DNMT3A mutations have a higher PLT count at diagnosis, while patients with CEBPA biallelic mutations or t(8;21)(q22; q22) translocation had lower PLT count at diagnosis. Furthermore, non-APL AML patients with high platelet count (> 65 × 109/L) at diagnosis had worse response to induction chemotherapy and RFS than those with low PLT count. In addition, allo-HSCT could not absolutely attenuated the negative impact of high PLT count on the survival of non-APL AML patients.ConclusionPLT count at diagnosis has a predictive value for therapeutic outcome for non-APL AML patients.

The transcription factor HIF2α partakes in the differentiation block of acute myeloid leukemia.

One of the defining features of acute myeloid leukemia (AML) is an arrest of myeloid differentiation whose molecular determinants are still poorly defined. Pharmacological removal of the differentiation block contributes to the cure of acute promyelocytic leukemia (APL) in the absence of cytotoxic chemotherapy, but this approach has not yet been translated to non-APL AMLs. Here, by investigating the function of hypoxia-inducible transcription factors HIF1α and HIF2α, we found that both genes exert oncogenic functions in AML and that HIF2α is a novel regulator of the AML differentiation block. Mechanistically, we found that HIF2α promotes the expression of transcriptional repressors that have been implicated in suppressing AML myeloid differentiation programs. Importantly, we positioned HIF2α under direct transcriptional control by the prodifferentiation agent all-trans retinoic acid (ATRA) and demonstrated that HIF2α blockade cooperates with ATRA to trigger AML cell differentiation. In conclusion, we propose that HIF2α inhibition may open new therapeutic avenues for AML treatment by licensing blasts maturation and leukemia debulking.

The Promise of Retinoids in the Treatment of Cancer: Neither Burnt Out Nor Fading Away.

Since the introduction of all-trans retinoic acid (ATRA), acute promyelocytic leukemia (APL) has become a highly curable malignancy, especially in combination with arsenic trioxide (ATO). ATRA's success has deepened our understanding of the role of the RARα pathway in normal hematopoiesis and leukemogenesis, and it has influenced a generation of cancer drug development. Retinoids have also demonstrated some efficacy in a handful of other disease entities, including as a maintenance therapy for neuroblastoma and in the treatment of cutaneous T-cell lymphomas; nevertheless, the promise of retinoids as a differentiating therapy in acute myeloid leukemia (AML) more broadly, and as a cancer preventative, have largely gone unfulfilled. Recent research into the mechanisms of ATRA resistance and the biomarkers of RARα pathway dysregulation in AML have reinvigorated efforts to successfully deploy retinoid therapy in a broader subset of myeloid malignancies. Recent studies have demonstrated that the bone marrow environment is highly protected from exogenous ATRA via local homeostasis controlled by stromal cells expressing CYP26, a key enzyme responsible for ATRA inactivation. Synthetic CYP26-resistant retinoids such as tamibarotene bypass this stromal protection and have shown superior anti-leukemic effects. Furthermore, recent super-enhancer (SE) analysis has identified a novel AML subgroup characterized by high expression of RARα through strong SE levels in the gene locus and increased sensitivity to tamibarotene. Combined with a hypomethylating agent, synthetic retinoids have shown synergistic anti-leukemic effects in non-APL AML preclinical models and are now being studied in phase II and III clinical trials.

Association of CDSS score and 60-day mortality in Chinese patients with non-APL acute myeloid leukemia: a retrospective cohort study.

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy, and is one of the triggers of DIC, the latter is an essential factor in the early death of patients with AML. However, the timely identification of DIC remains a challenge. The Chinese DIC Scoring System (CDSS) is a common consensus widely used in China; but, there are few reports on its application in patients with AML. We undertake this retrospective cohort study to investigate the association between CDSS score and 60-day mortality. CDSS scores were evaluated after admission. The outcome was all-cause 60-day mortality. Multivariate Cox regression analyses were performed to calculate the adjusted hazard ratio (HR) and the corresponding 95% confidence interval (CI). Survival curves were plotted by Kaplan-Meier and log-rank analyses. Subgroup analyses were stratified by relevant effect covariates. A total of 570 consecutive patients with primary AML were included. We found an association between a 39% increase in 60-day mortality and a 1 point increase in CDSS score (HR = 1.39, 95% CI 1.25-1.54), which was associated with a 189% increase in 60-day mortality in CDSS scores ≥ 6 compared with that in the CDSS scores < 6 (HR = 2.89, 95% CI 1.91-4.38). After adjusting for all potential con-founders, a 27% and a 198% increase were observed (HR = 1.27, 95% CI 1.01-1.61; HR = 2.98, 95% CI 1.24-7.19), respectively. There is association between 60-day mortality and CDSS score in patients with AML. These findings may help hematologists in making informed treatment decisions.

Prognostic value of combined WT1 and multiparameter flow cytometry assessment for measurable residual disease after induction in non-APL acute myeloid leukemia

The objective of this study was to investigate the expression pattern of Wilms tumor 1 (WT1) gene at diagnosis, complete remission (CR) and relapse status in non-acute promyelocytic leukemia (non-APL) acute myeloid leukemia (AML) patients, and further explore the prognostic value of measurable residual disease (MRD) assessment by WT1 gene and multiparameter flow cytometry (MFC). Our results showed that the average expression level of WT1 was 4026 ± 616.1 copies/104 ABL at diagnosis, 155.3 ± 36.03 copies/104 ABL at CR, and 1766 ± 238.8 copies/104 ABL at relapse, with statistically significant differences (p = .000). ROC analysis showed that WT1 expression levels were 118.1 copies/104 ABL and MFC-MRD was 0.155%, which had good predictive efficacy for relapse of patients during consolidation therapy. Both WT1-MRD and MFC-MRD had a significant impact on relapse-free survival (RFS) and overall survival (OS). Patients with WT1-MRD positive or MFC-MRD positive were associated with worse RFS (HR 3.840, 95% CI 1.582–9.320, p = .003), (HR 4.464, 95% CI 1.841–10.984, p = .001) and worse OS (HR 2.963, 95% CI 1.058–8.295, p = .039), (HR 3.590, 95% CI 1.254–10.280, p = .017). Besides, compared with patients who were negative for both WT1-MRD and MFC-MRD, patients who were positive both WT1-MRD and MFC-MRD were associated with worse RFS (HR 6.200, 95% CI 2.206–17.430, p = .001) and worse OS (HR 4.886, 95% CI 1.388–17.197, p = .013). This study demonstrates that combined assessment of MRD by WT1 and MFC improves relapse and prognosis prediction in non-APL AML patients, and may help guide interventions for disease relapse.

A convolutional neural network-based, quantitative complete blood count scattergram-mapping framework promptly screens acute promyelocytic leukemia with high sensitivity.

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML) characterized by its rapidly progressive and fatal clinical course if untreated, although it is curable if treated in a timely manner. Promptly screening patients who have results that are suspicious for APL is vital to overcome early death. The authors developed an innovative framework consisting of ResNet-18, a convolutional neural network architecture, with the objective of quantitatively mapping a complete blood count (CBC) scattergram to quickly and robustly indicate a probable susceptibility to APL. Three hundred and twenty scattergrams of the white blood cell differential channel from 51 patients with APL, 510 scattergrams from 105 patients who had non-APL AML, and 320 scattergrams from 320 healthy controls were randomly stratified at a ratio of 4:1 and split into training and testing data sets to accomplish five-fold cross-validation. Both the area under the curve and the average precision of >0.99 were achieved in each fold. Three hundred four of the 320 APL scattergrams (95%) were correctly flagged by the model, which outcompeted the CBC review rules recommended by the International Society of Laboratory Hematology (all p<.001). External validation based on an independent testing data set that included 56 scattergrams from 31 patients with APL, 56 scattergrams from 55 patients with non-APL AML, and 64 scattergrams from 64 healthy controls also confirmed the sensitivity and specificity of the framework. To the authors' knowledge, their convolutional neural network-based framework is the first to use scattergram output from routine CBC analysis to map suspicious APL early with outstanding sensitivity, specificity, and precision. The authors also describe a new CBC workflow incorporating this framework upstream of the morphologic review, which would provide the earliest flag for APL. The authors propose an innovative way to visualize complete blood counts (CBCs) by mapping the difference in white blood cell counts using automated CBC analysis to identify potential acute promyelocytic leukemia (APL) using a convolutional neural network (CNN), which can eliminate the potential pitfalls of manual observation. Analyses of an unprecedented, realistic data set validated that the quantitative relationship between the CBC scattergram and an APL abnormality is highly consistent. This is the first study to date focusing on screening for APL using scattergrams of the difference in white blood cell counts from routine CBC tests and has significant clinical relevance. The authors recommend using this method even before analyzing cell images, which could provide the earliest way to screen for APL in a sensitive and accurateway.

Combined Application of Salinomycin and ATRA Induces Apoptosis and Differentiation of Acute Myeloid Leukemia Cells by Inhibiting WNT/β-Catenin Pathway.

All-trans retinoic acid (ATRA) is only effective in acute promyelocytic leukemia (APL), but not in other subtype of acute myeloid leukemia (AML). Salinomycin targets tumor cells rather than non-tumorigenic cells, and WNT/β-catenin pathway inhibition is one of the mechanisms of its anti-tumor activity. There is a crosstalk between RA and WNT/β-catenin pathway. Here, we investigate the effect of the combination of salinomycin and ATRA (S+RA) in non-APL AML cells. Apoptosis was evaluated by cell viability and Annexin-V assay. Cell differentiation was analyzed by CD11c expression and morphology. To explore the underlying mechanisms, Western blot analysis and mitochondrial transmembrane potentials (ΔΨm) were used. S+RA induced differentiation and apoptosis in AML cell lines and AML primary cells. S+RA inhibited the β-catenin signal pathway as determined by the decreased protein levels of β-catenin, the low-density lipoprotein receptor-related proteins 6 (LRP6), and its downstream proteins such as survivin, c-Myc, caspase-3/7, cdc25A and cyclinD1 and reduced phosphorylation level of GSK3β S9. S+RA also increased the protein levels of CCAAT/enhancer-binding proteins (C/EBPs) and PU.1 and collapsed Δψm. The above molecular and cellular changes induced by S+RA were inhibited by β-catenin specific activator and promoted by β-catenin specific inhibitor. S+RA induced differentiation by β-catenin-inhibition-mediated up-regulation of C/EBPs and PU.1 and suppression of c-Myc. S+RA triggered apoptosis through β-catenin-inhibition-regulated ΔΨm collapse and caspase-3/7 activation. Taken together, our findings may provide novel therapeutic strategies for AML patients by targeting the WNT/β-catenin pathway.

Dual inhibition of EZH2 and G9A/GLP histone methyltransferases by HKMTI-1-005 promotes differentiation of acute myeloid leukemia cells.

All-trans-retinoic acid (ATRA)-based differentiation therapy of acute promyelocytic leukemia (APL) represents one of the most clinically effective examples of precision medicine and the first example of targeted oncoprotein degradation. The success of ATRA in APL, however, remains to be translated to non-APL acute myeloid leukemia (AML). We previously showed that aberrant histone modifications, including histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) methylation, were associated with this lack of response and that epigenetic therapy with small molecule inhibitors of the H3K4 demethylase LSD1/KDM1A could reprogram AML cells to respond to ATRA. Serving as the enzymatic component of Polycomb Repressive Complex 2, EZH2/KMT6A methyltransferase plays a critical role in normal hematopoiesis by affecting the balance between self-renewal and differentiation. The canonical function of EZH2 is methylation of H3K27, although important non-canonical roles have recently been described. EZH2 mutation or deregulated expression has been conclusively demonstrated in the pathogenesis of AML and response to treatment, thus making it an attractive therapeutic target. In this study, we therefore investigated whether inhibition of EZH2 might also improve the response of non-APL AML cells to ATRA-based therapy. We focused on GSK-343, a pyridone-containing S-adenosyl-L-methionine cofactor-competitive EZH2 inhibitor that is representative of its class, and HKMTI-1-005, a substrate-competitive dual inhibitor targeting EZH2 and the closely related G9A/GLP H3K9 methyltransferases. We found that treatment with HKMTI-1-005 phenocopied EZH2 knockdown and was more effective in inducing differentiation than GSK-343, despite the efficacy of GSK-343 in terms of abolishing H3K27 trimethylation. Furthermore, transcriptomic analysis revealed that in contrast to treatment with GSK-343, HKMTI-1-005 upregulated the expression of differentiation pathway genes with and without ATRA, while downregulating genes associated with a hematopoietic stem cell phenotype. These results pointed to a non-canonical role for EZH2, which was supported by the finding that EZH2 associates with the master regulator of myeloid differentiation, RARα, in an ATRA-dependent manner that was enhanced by HKMTI-1-005, possibly playing a role in co-regulator complex exchange during transcriptional activation. In summary, our results strongly suggest that addition of HKMTI-1-005 to ATRA is a new therapeutic approach against AML that warrants further investigation.

At What Point Are Long-Term (>5 Years) Survivors of APL Safe? A Study from the SEER Database.

Acute promyelocytic leukemia (APL) is a highly curable cancer, but it is not clear whether it is also necessary to monitor long-term toxicity in "cured" patients who survive for more than five years, which is critical to ensuring maximum survival in APL patients. A total of 1952 APL 5-year survivors and 5973 non-APL acute myeloid leukemia (AML) 5-year survivors were included from the Surveillance, Epidemiology, and End Results (SEER) database. The standardized mortality ratio (SMR) was calculated to measure the risk of death. Cumulative mortality is calculated as the incidence of specific causes of death under competing risk events. The SMR of all causes of death in >5-year survivors of APL was higher than that of the general population only at 60-119 months (SMR, 1.41). This was mainly because a significant increase in mortality from AML (SMR, 87.67) and second malignant neoplasms (SMNs) (SMR, 1.56) was found only at 60-119 months. However, there was no higher risk of death from non-cancer-related disease in >5-year survivors of APL than that of the general population (SMR, 0.89). The SMR of all-cause deaths in >5-year survivors of non-APL AML decreased year by year and was no higher than that of the general population until after 216 months. The cumulative incidence of AML-related death, SMN-related death, and non-cancer-related death was significantly lower in APL patients than in non-APL AML patients throughout the follow-up period. Compared with the general population, the risk of death of patients with APL was higher within 5 to 10 years but not higher over 10 years. Therefore, we believe that long-term survivors of APL are safe after 10 years.

CD34 negative HLA-DR negative acute myeloid leukaemia: A higher association with NPM1 and FLT3-ITD mutations.

CD34 and HLA-DR negativity is often used as a characteristic immunophenotypic feature of acute promyelocytic leukaemia (APL) that differentiates APL from other subtypes of acute myeloid leukaemia (AML). However, other subtypes of AML, without expression of CD34 and HLA-DR antigens, have also been reported. We analysed the HLA-DR negative de novo non-APL AML cases by dividing HLA-DR negative non-APL group into 2 sub-groups based on CD34 expression and compared the characteristics of CD34 negative HLA-DR negative with CD34 positive HLA-DR negative non-APL AML cases with respect to morphologic, immunophenotypic, molecular and clinical parameters. There were 70 cases (8.54%) which were CD34 negative HLA-DR negative and 52 cases (6.34%) were CD34 positive HLA-DR negative. The median age at diagnosis was higher in CD34 negative HLA-DR negative AML than in CD34 positive HLA-DR negative AML group (38 years vs. 12 years, p < 0.001). DIC rate was higher in CD34 negative HLA-DR negative group than the other group (p < 0.001). Median total leucocyte count was higher with higher blast count in peripheral blood and bone marrow in CD34 negative HLA-DR negative AML cases than the other group (p < 0.05). CD34 negative HLA-DR negative AML was more associated with normal karyotype (96.2% vs. 38.5%; p < 0.001), NPM1 mutation (67.8% vs. 8.3%; p < 0.001) and FLT-ITD mutation (37.3% vs. 13.9%; p < 0.05). In CD34 negative HLA-DR negative group, 16 cases had co-occurrence of NPM1 and FLT3-ITD mutations, whereas no case of CD34 positive HLA-DR negative group had such dual mutation positivity. There was poor median overall survival [3.8months (95%CI: 2.3-7.8months) vs. 20.4months (95% CI: 12.8-25.7months); p=0.0148] in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases. We found that the CD34 negative HLADR negative non APL AML is highly associated with NPM1 and FLT3-ITD mutation, older age at diagnosis, DIC, higher total leucocyte count, higher blast counts and normal karyotype in comparison to CD34 positive HLA-DR negative AML group. Co-occurrence of NPM1 and FLT3-ITD mutation was also exclusively seen in CD34 negative HLA-DR negative group. There was poor overall survival in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases.

Outcomes of Acute Myeloid Leukemia (AML) in Adolescents and Young Adults (AYAs) Compared to Adults in a Referral Center from Lower Myanmar

Introduction Acute myeloid leukemia (AML) is the second most common form of haematological malignancies with high prevalence among all age groups in Myanmar. However, there are very limited data particularly related to AML in adolescents and young adults (AYAs). To fill the gap in AML data from resource-constraint countries and to compare the treatment outcomes of AYAs (15-39 years) with adults (40 years and above), a hospital-based, prospective study was conducted between January 2019 to October 2021, on the cases of AML treated at the North Okkalapa General and Teaching Hospital, one of three referral centers of Myanmar. Methods All cases of AML other than acute promyelocytic leukemia (APL) received two courses of induction containing daunorubicin and cytarabine followed by three courses of consolidation with high dose cytarabine. Treatment of APL included differentiation agents (all-trans-retinoeic acid and arsenic trioxide) based induction with addition of daunorubicin and cytarabine in high-risk cases until remission followed by chemotherapy free consolidation and maintenance up to two years. Patients were followed up for a minimum of one year and overall survival (OS) was calculated using the Kaplan-Meier method. Results A total of 140 including 81 (57.9%) AYAs and 59 (42.1%) adults with newly diagnosed de-novo AML were treated during 34-months period. Median age of AYA AML was 22 years (range-13-39 years) whereas that of adult AML was 54 years (range-40-76 years). There was no gender difference (49.2% versus 50.7%, for male and female). Among AML subtypes, M4 was the commonest subtype (28.5%) and APL, M3 (22.8%) was the second most prevalent AML followed by M2 (18.5%) and M5 (10.7%) subtypes. Cytogenetic data was available in 37 of 108 (34.2 %) non-APL cases with 16.2 %, 67.6% and 16.2 % respectively had good, intermediate, and high-risk cytogenetics. Of 108 non-APL including 61 (56.5%) AYAs and 47 (43.5%) adults, 46 (42.6%) died within one week or during induction and remaining 62 (57.4%) achieved remission at the end of induction. Among 32 APL (20 AYAs and 12 adults), mortality rate was 21.9% due to early death (12.5%) and induction death (9.4%) with only 78% achieved remission after induction. There was no statistically significant difference between the remission rates of AYAs and adults, in both APL (75.0% versus 83.3%, respectively, p=0.68) and non-APL groups (60.65% versus 53.2% respectively, p=0.43). During follow-up, 29 (20.7 %) were lost to follow-up while 6 non-APL AML (5 AYAs and 1 adult, 5.6%) relapsed within one year with 18 of 32 APL (56.3%) and 32 of 108 non-APL AML (29.6%) remained alive at one year. Two-year cumulative survival for AYAs compared to adults was 47% vs 42% respectively for non-APL AML (p=0.42) and 74% vs 83% for APL (p=0.608) with no statistically significant difference between two age groups. Conclusion In this resource limited setting, although having higher proportion of younger population and better prognostic types like APL, remission rate and survival was still low due to higher number of early and induction deaths which could be improved by early diagnosis and better supportive care.

Homoharringtonine-Based Induction Regimens Combined with ATRA-Based Maintenance in Chinese Pediatric AML: A Report from the Cclg-AML 2015 Protocol Study

Introduction Acute myeloid leukemia (AML) is a heterogeneous group of hematological malignancy. Classical induction therapy of DAE composed of etoposide (VP-16), cytarabine arabinoside (Ara-C) and anthracycline (DNR) is commonly applied in childhood AML, but etoposide has been reported to increase the risk of secondary cancer, especially for AML with MLL rearrangement. Although homoharringtonine (HHT) is commonly used for the treatment of Chinese adult AML, the efficacy and safety of HHT-based induction therapy have not been confirmed for childhood AML. And whether survival of pediatric AML will benefit from maintenance therapy without increasing toxicity is a matter of debate. All-trans retinoic acid (ATRA)-based therapy has been less reported and verified among non-APL AML patients. Here, we seek to evaluate the efficacy and safety of HHT-based induction regimens combined ATRA-based maintenance therapy for Chinese childhood AML (Chinese Clinical Trial Registry: ChiCTR-IPR-15006816). Methods The 2015 open-label, multicenter, randomized Chinese Children's Leukemia Group (CCLG) study was performed across 35 centers in China between July 2015 and October 2019. Newly diagnosed 0- to 18-year-old children with AML were first randomly assigned to receive HHT-based (H arm) or etoposide-based (E arm) induction regimens [HHT (3 mg/m2 per day from days 1 to 5) or VP-16 (100 mg/m2 per day from days 1 to 5) combined with DA regimen (D: 40 mg/m2 per day on days 1, 3 and 5; A: 100 mg/m2 every 12 hours from day 1 to 7)] and then randomly allocated to receive cytarabine-based (AC arm) or ATRA-based (AT arm) maintenance therapy. The primary endpoint is the complete remission (CR) rate after two courses of induction therapy between H arm and E arm. The secondary endpoints include the 3-year overall survival (OS) and 3-year event-free survival (EFS) of patients in the intent-to-treat population among four arms (H+AT arm, H+AC arm, E+AT arm and E+AC arm). What we should explained is that the study was initially designed as a multicenter randomized controlled trial, however, due to a shortage of HHT, which lasted for half a year in some local hospitals, we had to give priority to ensuring patient benefit and assign these patients to the E arm until HHT became available, and then patients in the H arm were supplemented in those hospitals. So patients were unevenly distributed among the four arms. Results We enrolled 1253 intent-to-treat de novo AML patients, of whom 895 were included in the induction therapy analysis, and 554 received maintenance therapy (Figure 1). The median age was 75.0 months (IQR 36.0-118.0), and 57% of the patients were male. The median follow-up time was 29.4 months (IQR 8.4-47.4). 185 of 1253 patients (14.8%) were lost to follow-up, of whom 70.0% patients have been followed for over 12 months. The CR rates were 88.3% in the H arm versus 83.3% in the E arm (p=0.03). The CR rate of patients with t(8;21)/AML1-ETO was higher in the H arm than in the E arm (94.7% vs. 87.5%, p=0.018). According to the intention-to-treat analysis, the 3-year OS and EFS were significantly higher in the H arm than in the E arm [3-year OS: 69.2% vs. 62.8%, p=0.025 (Figure 2); 3-year EFS 61.1% vs. 53.4%, p=0.022]. Among patients who were enrolled in maintenance therapy (per-protocol population), the 3-year EFS (H+AT arm: 70.7%, 95% CI 61.1-78.3; H+AC arm: 74.8%, 95% CI 67.0-81.0, p=0.933; E+AC arm: 72.9%, 95% CI 65.1-79.2, p=0.789; E+AT arm: 66.2%, 95% CI 56.8-74.0, p=0.336) did not differ significantly across the four arms. In subgroup analysis, patients with AML1-ETO positivity in the H+AT arm had significantly better OS (82.4% vs. 66.4%, p=0.043) and EFS (73.6% vs. 52.8%, p=0.013) than those in the E+AC arm. Conclusions Our study demonstrated, in childhood AML, HHT-based induction regimens (DAH) could significantly obtain higher complete remission rate compared with patients who received etoposide-based regimens, especially for those with AML1-ETO positive. And The HTT-based regimen resulted in a significantly improved 3-year OS and EFS compared with VP-16-based regimen. More patients with AML1-ETO positive who took DAH achieved complete remission, and these patients had longer overall survival and event-free survival, than those who took DAE. And ATRA-based maintenance has comparable effects to cytarabine-based maintenance in terms of OS and EFS. ATRA may be an alternative option for pediatric AML. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal