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Tyrosine kinase inhibitors (TKI) are very effective in treating chronic myelogenous leukemia (CML), but primitive, quiescent leukemia stem cells persist as a barrier to cure. We performed a comprehensive evaluation of metabolic adaptation to TKI treatment and its role in CML hematopoietic stem and progenitor cell persistence. Using a CML mouse model, we found that glycolysis, glutaminolysis, TCA cycle and oxidative phosphorylation (OXPHOS) were initially inhibited by TKI treatment in CML committed progenitors but were restored with continued treatment, reflecting both selection and metabolic reprogramming of specific subpopulations. TKI treatment selectively enriched primitive CML stem cells with reduced metabolic gene expression. Persistent CML stem cells also showed metabolic adaptation to TKI treatment through altered substrate utilization and maintenance of mitochondrial respiration. Evaluation of transcription factors underlying these changes identified increased HIF-1 protein levels and activity in TKI-treated stem cells. Treatment with a HIF-1 inhibitor depleted murine and human CML stem cells in combination with TKI treatment. HIF-1 inhibition increased mitochondrial activity and ROS levels, and reduced quiescence, increased cycling, and reduced self-renewal and regenerating potential of dormant CML stem cells. We therefore identify HIF-1-mediated inhibition of OXPHOS and ROS and maintenance of CML stem cell dormancy and repopulating potential as a key mechanism of CML stem cell adaptation to TKI treatment. Our results identify a key metabolic dependency in CML stem cells persisting after TKI treatment that can be targeted to enhance their elimination.

Figure S6. Cumulative incidence of death in complete remission between two consolidation cohort

Supplementary Tables S1-S5

Chromosome translocations in the 5q31-33 region are associated with a range of hematologic malignancies, some of which involve the platelet derived growth factor receptor beta (PDGFRB) gene. We report a case of acute myeloid leukemia (AML) with a mutation in the NPM1 gene (NPM1-mut AML) and a subclonal gene rearrangement involving the PDGFRB gene. We identified a novel fusion gene, STRN3::PDGFRB, resulting from t(5;14) (q32;q12) chromosomal rearrangement. Sequential FISH confirmed that approximately 15% of leukemic cells carried the PDGFRB gene rearrangement, which suggests that STRN3::PDGFRB is a previously unreported fusion gene in a subclone. Reverse transcription PCR (RT-PCR) and Sanger sequencing confirmed that the fusion gene consisted of STRN3 exon 7 fused to PDGFRB exon 11, resulting in a chimeric protein containing the coiled-coil domain of striatin-3 and the transmembrane and intracellular tyrosine kinase domains of the PDGFRB. The new protein exhibited distinct cytoplasmic localization and had leukemogenic effects, as demonstrated by its ability to transform Ba/F3 cells to growth factor independence and cause a fatal myelodysplastic/myeloproliferative neoplasms (MDS/MPN)-like disease in mice, which then transformant to T-cell lymphoblastic lymphoma in secondary recipients. Ba/F3 cells expressing STRN3::PDGFRB or ETV6::PDGFRB were sensitive to tyrosine kinase inhibitors (TKIs) and selinexor, but in virto experiments showed that the combination of imatinib and selinexor had a marked synergistic effect, although only the imatinib alone group could prolong the survival of T-cell blast transformation recipient mice. Our findings demonstrate the leukemogenic effects of the novel fusion gene and provide insights into the clone evolution of AML, which can be influenced by therapy selection. Furthermore, our results provide insight into the potential therapeutic options for patients with this type of mutation, as well as the need for careful consideration of treatment selection to prevent undesirable side effects.

The prognostic factors to stratify acute myeloid leukaemia (AML) with double-mutated CCAAT/enhancer-binding protein alpha (CEBPAdm) into different risk groups remains to be determined. In this retrospective study, we evaluated 171 consecutive patients with newly diagnosed AML with CEBPAdm by a Cox proportional hazards regression model. In univariate analyses, colony stimulating factor 3 receptor (CSF3R) and Wilms tumour 1 (WT1) mutations were associated with poor relapse-free survival (RFS). The induction regimens including homoharringtonine (omacetaxine mepesuccinate) or intermediate-dose cytarabine was associated with favourable RFS and overall survival (OS). The induction regimen including both homoharringtonine and intermediate-dose cytarabine was associated with the most favourable RFS (3-year RFS 84.7%) and OS (3-year OS 92.8%) compared to the conventional cytarabine and daunorubicin regimen (3-year RFS 27.7%, hazard ratio [HR] 0.126, 95% confidence interval [CI] 0.051-0.313, Wald p 0.001; and 3-year OS 56.4%, HR 0.179, 95% CI 0.055-0.586, Wald p = 0.005). In multivariate analyses, the induction regimen including intermediate-dose cytarabine (HR 0.364, 95% CI 0.205-0.646, Wald p 0.001) and CSF3R mutations (HR 2.667, 95% CI 1.276-5.572, Wald p = 0.009) were independently associated with RFS. Taken together, we found that induction regimen and CSF3R mutations were independent prognostic factors for AML with CEBPAdm.

Key Points MEF2D is highly expressed in MLL-rearranged AML and required for leukemia development in vitro and in vivo.MEF2D suppresses CEBPE-mediated myeloid differentiation in AML., Visual Abstract, Acute myeloid leukemia (AML) with MLL-rearrangement (MLL-r) comprises ∼10% of all AML cases and portends poor outcomes. Much remains uncovered on how MLL-r AML drives leukemia development while preventing cells from normal myeloid differentiation. Here, we identified that transcription factor MEF2D is a super-enhancer-associated, highly expressed gene in MLL-r AML. Knockout of MEF2D profoundly impaired leukemia growth, induced myeloid differentiation, and delayed oncogenic progression in vivo. Mechanistically, MEF2D loss led to robust activation of a CEBPE-centered myeloid differentiation program in AML cells. Chromatin profiling revealed that MEF2D binds to and suppresses the chromatin accessibility of CEBPE cis-regulatory regions. In human acute leukemia samples, MEF2D expression showed a strong negative correlation with the expression of CEBPE. Depletion of CEBPE partially rescued the cell growth defect and myeloid cell differentiation induced by the loss of MEF2D. Lastly, we show that MEF2D is positively regulated by HOXA9, and downregulation of MEF2D is an important mechanism for DOT1L inhibitor-induced antileukemia effects. Collectively, our findings suggest that MEF2D plays a critical role in human MLL-r AML and uncover the MEF2D-CEBPE axis as a crucial transcriptional mechanism regulating leukemia cell self-renewal and differentiation block.

Despite the efficacy of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML), malignant long-term hematopoietic stem cells (LT-HSC) persist as a source of relapse. However, LT-HSC are heterogenous and the most primitive, drug-resistant LT-HSC subpopulations are not well characterized. In normal hematopoiesis, self-renewal and long-term reconstitution capacity is enriched within LT-HSCs with low c-Kit expression (c-KitLow). Here, using a transgenic CML mouse model, we found that long-term engraftment and leukemogenic capacity were restricted to c-KitLow CML LT-HSC. CML LT-HSC demonstrated enhanced differentiation with expansion of mature progeny following exposure to the c-Kit ligand, stem cell factor (SCF). Conversely, SCF deletion led to depletion of normal LT-HSC but increase in c-KitLow and total CML LT-HSC with reduced generation of mature myeloid cells. CML c-KitLow LT-HSC showed reduced cell cycling, and expressed enhanced quiescence and inflammatory gene signatures. SCF administration led to enhanced depletion of CML primitive progenitors but not LT-HSC after TKI treatment. Human CML LT-HSC with low or absent c-Kit expression were markedly enriched after TKI treatment. We conclude that CML LT-HSC expressing low c-Kit levels are enriched for primitive, quiescent, drug-resistant leukemia initiating cells and represent a critical target for eliminating disease persistence.

Background TBLR1-RARα (TR) is a novel oncogene to induce acute promyelocytic leukemia (APL) identified in our previous studies, which elicited differed response and worse prognosis in contrast to the canonical PML-RARα (PR) fusion gene. Despite the textbook rationale of all-trans retinoid acid (ATRA) and arsenic trioxide (ATO) has turned most PR-driven APL from highly fatal to highly curable, TR-driven APL did not yield long-term remission, highlighting the necessity to decipher drug unresponsiveness and explore novel therapies. Methods In this study, doxycycline-inducible cell models were established to initiate the expression of TR and PR in U937 cells, respectively. Then RNA-seq was performed to identify differential genes and pathways directly induced by TR and PR oncogene. Based on transcriptomic analyses, different drugs were administered to compare therapy responses and biological phenotypes between TR and PR-induced leukemia through in vitro studies. The efficacy of IFNs and its upstream regulator STING agonist were further validated in TR murine models with survival analysis. Results Transcriptome sequencing analyses showed interferon (IFN) pathway were significantly suppressed in TR- rather than PR-induced APL. IFNs as well as the traditional regimen of ATRA and ATO elicit differed responses in biological phenotypes between TR- and PR-induced APL. Specifically, in TR-induced APL, firstly, ATO failed to elicit oncoprotein degradation, apoptosis and loss of self-renewal. Secondly, increasing doses of ATRA further promoted oncoprotein degradation with impaired colony formation capacity, and ultimately conferred survival benefits. Thirdly, type I IFNs is promising, which induced apoptosis, cooperated with ATRA to boost differentiation, and exhibited potential to reduce self-renewal. Finally, type I IFNs combining with ATRA and STING agonist significantly endowed TR mice with extended survival. Conclusions For TR-driven APL, the canonical regimen of ATO and lower doses of ATRA are unresponsive and inadequate to elicit oncoprotein degradation, apoptosis and loss of self-renewal, while type I IFNs and STING agonist are promising to endow TR mice with extended survival. Our study aims to gain further understanding of TR-driven APL and integrate insights into leukemogenesis mediated by rare RARα fusion genes, which may benefit a therapy-resistant population and enable APL to be bona fide curable leukemia.

The FLT3-ITD mutation is associated with poor prognosis in acute myeloid leukemia (AML). FLT3 tyrosine kinase inhibitors (TKIs) demonstrate clinical efficacy but fail to target leukemia stem cells (LSC) and do not generate sustained responses. Autophagy is an important cellular stress response contributing to hematopoietic stem cells (HSC) maintenance and promoting leukemia development. Here we investigated the role of autophagy in regulating FLT3-ITD AML stem cell function and response to TKI treatment. We show that autophagy inhibition reduced quiescence and depleted repopulating potential of FLT3-ITD AML LSC, associated with mitochondrial accumulation and increased oxidative phosphorylation. However, TKI treatment reduced mitochondrial respiration and unexpectedly antagonized the effects of autophagy inhibition on LSC attrition. We further show that TKI-mediated targeting of AML LSC and committed progenitors was p53-dependent, and that autophagy inhibition enhanced p53 activity and increased TKI mediated targeting of AML progenitors, but decreased p53 activity in LSC and reduced TKI-mediated LSC inhibition. These results provide new insights into the role of autophagy in differentially regulating AML stem and progenitor cells, reveal unexpected antagonistic effects of combined oncogenic tyrosine kinase inhibition and autophagy inhibition in AML LSC, and suggest an alternative approach to target AML LSC quiescence and regenerative potential.

Acute leukemias of ambiguous lineage, not otherwise specified (ALAL-NOS) is a rare type of acute leukemia. Management of relapse/refractory (R/R) patients is still challenging.traditional chemotherapy treatment is not effective. In this paper, we reported 6 R/R patients diagnosed as ALAL-NOS in our hospital, who were treated with venetoclax based treatment (venetoclax combining with azacitidine or chemotherapy). All 6 patients achieved CR. Five of the six patients received allo-HSCT, four patients were still alive in CR until the follow-up day. Our data provide preliminary evidence and show that venetoclax based regimens are effective and safety in patients with R/R ALAL-NOS. Supplementary Information The online version contains supplementary material available at 10.1186/s40164-021-00239-w.

Introduction The current framework for risk stratification is still insufficient for highly heterogeneous intermediate-risk acute myeloid leukemia (IRC-AML), which lacks specific genomic abnormalities. Methods In order to incorporate novel biomarkers to refine current risk stratification strategies for patients with this subtype, we investigated pretreatment telomere length (TL), which is essential for maintaining genomic stability, in 204 adults with de novo AML (non-acute promyelocytic leukemia). Results We found that TL measured at diagnosis did not decrease with advancing age in 204 patients with AML (R2 = 0.001, P = .695). A multivariate analysis demonstrated that short TL was independently associated with an inferior relapse-free survival (hazard ratio [HR] 3.08, 95% confidence interval [CI] 1.48-6.41, P = .003); event-free survival (HR 2.14, 95% CI 1.12-4.08, P = .021); and overall survival (HR 2.26, 95% CI 1.09-4.67, P = .028) in IRC-AML patients. In addition, IRC-AML patients with short TL also exhibited an increased cumulative incidence of hematologic relapse (HR 2.32, 95% CI 1.08-5.26, P = .032). Conclusion Short TL is an independent prognostic factor for poor prognosis in patients with IRC-AML and may represent a novel mechanism that links genomic stability and disease progression.

Alternative splicing (AS) is a critical regulatory process of gene expression. In bone marrow microenvironment, AS plays a critical role in mesenchymal stem cells fate determination by forming distinct isoforms of important regulators. As a spliceosome factor, U2AF1 is essential for the catalysis of pre-mRNA splicing, and its mutation can cause differential AS events. In the present study, by forced expression of mutant U2AF1 (U2AF1S34F) in the mouse bone marrow stroma OP9 cells, we determine AS changes in U2AF1S34F transduced OP9 cells and investigate their role in stroma cell biological functions. We find that abundant differential RNA splicing events are induced by U2AF1S34F in OP9 cells. U2AF1S34F causes increased generation of hydrogen peroxide, promotes production of cytokines and chemokines. U2AF1S34F transduced OP9 cells also exhibit dysfunction of mitochondria. RNA-seq data, gene ontology (GO), and gene set enrichment analysis reveal that differentially expressed genes downregulated in response to U2AF1S34F are enriched in peroxisome component and function. U2AF1S34F can also cause release of hydrogen peroxide from OP9 cells. Furthermore, we investigate the influence of U2AF1S34F-induced oxidative stress in stromal cells on hematopoietic cells. When co-culturing mouse bone marrow mononuclear cells with OP9 cells, the U2AF1S34F expressing OP9 cells induce phosphorylation of histone H2AX in hematopoietic cells. Collectively, our results reveal that mutant U2AF1-induced differential AS events cause oxidative stress in bone marrow stromal cells and can further lead to DNA damage and genomic instability in hematopoietic cells.

Chronic myeloid leukemia (CML) results from hematopoietic stem cell transformation by the BCR-ABL kinase. Despite the success of BCR-ABL tyrosine kinase inhibitors (TKIs) in treating CML patients, leukemia stem cells (LSCs) resist elimination and persist as a major barrier to cure. Previous studies suggest that overexpression of the sirtuin 1 (SIRT1) deacetylase may contribute to LSC maintenance in CML. Here, by genetically deleting SIRT1 in transgenic CML mice, we definitively demonstrated an important role for SIRT1 in leukemia development. We identified a previously unrecognized role for SIRT1 in mediating increased mitochondrial oxidative phosphorylation in CML LSCs. We showed that mitochondrial alterations were kinase independent and that TKI treatment enhanced inhibition of CML hematopoiesis in SIRT1-deleted mice. We further showed that the SIRT1 substrate PGC-1α contributed to increased oxidative phosphorylation and TKI resistance in CML LSCs. These results reveal an important role for SIRT1 and downstream signaling mechanisms in altered mitochondrial respiration in CML LSCs.

Introduction Major resources of our current knowledge on acute leukemia epidemiology and prognosis are based on data from clinical trials. Due to the selective bias of clinical trials, data might differ from the general leukemia population in real-life setting. National Clinical Research Center for Blood Disease established a comprehensive database through the electronic health records (EHR) to facilitate research of the hematologic cancers i.e. acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and acute promyelocytic leukemia (APL). The aim of the database is to gain insight into the epidemiology of these cancers, to evaluate treatment responses, to compare results between geographical regions of China. Furthermore, with the privilege of national research center, the database expects to identify prognostic and predictive factors for outcome to improve the quality of treatment and patients care. Methods The database development was initiated in 2001. Standard data elements were established to capture the key clinical variables. For individual patients, data from EHRs were extracted, integrated and quality checked. The implement of database facilitated the clinical professions to identify eligible patients, establish research projects, conduct retrospective analysis and follow-up patient outcomes. Continued efforts were made for improving the construction and quality of the database over two decades. We performed a 10-year real-world data review in the database to evaluate the quality of the recorded data and, moreover to describe the clinical, cytogenetic characteristics and survival of acute leukemia patients. The completeness for collected variables was acceptable for statistical analysis. In total, 3,404 patients (1,895 males and 1,509 females) who were diagnosed and treated between Jan. 1, 2010 and Dec. 31, 2020 were enrolled. A substantial proportion (>60%) of patients were residents of the northern and northeast region of China. Demographic and baseline characteristics also included age, age class, baseline blood test, transplantation and research participation. Molecular mutations such as nucleophosmin-1 (NPM1), FMS-related tyrosine kinase 3 (FLT3), and CCAAT/enhancer-binding protein alpha (CEBPA) et al were included in the screening panels. We explored the treatment remission rate and prognosis of different chromosomal karyotype groups among AML patients. Results The patient numbers of the AML, ALL and APL subgroups were 2,345, 769 and 290 respectively. Blood routine results well demonstrated the clinical characteristics of each subgroup (Tbl. 1). In AML group, the frequencies of NPM1, FLT3-ITD, KIT and CEBPA double mutations were 17.9%, 13.2%, 8.7% and 10.1%, respectively (Tbl. 2). In term of ALL, 640 cases (83.2%) were B-ALL and 129 (16.8%) were T-ALL. Among B-ALL, 256 cases (33.3%) were Ph positive. 10-year analysis for overall survival shown that AML patients had better outcomes as compared with ALL group (Fig. 1). In this database, 1,780 AML cases (excluding APL) were enrolled in cytogenetic analysis. The survival rates of different cytogenetic risk groups from our real-world data were separated by the ELN2017 and MRC risk stratification respectively (Fig. 2A-B). Remarkably, we found two rare but recurrent abnormalities, 16 cases with t(7;11) (p15;p15) and 12 cases with t(16;21)(p11;q22/q24;q22). Cases showed high relapse and mortality rate. Compared with the normal karyotype group, the survival of both subentities was worse and transplantation might be recommended in CR1 phase (Fig. 2C), therefore, we recommend that these two subtypes might be regarded as the worse risk group, although neither is mentioned in the current guidelines. The incidence of t(8;21) in our database was 17.9% (Fig. 3). To explore the impact of additional chromosomal abnormalities on the prognosis of t(8;21), we found that the overall survival of patients with additional trisomy 4 was worse than those without trisomy 4 (Fig. 2D), which was rarely mentioned in previous reports. Conclusion The real-world database is of great importance for defining the comprehensive features of AML, APL and ALL in clinical setting. The results offered a remarkable contribution to our knowledge on acute leukemia and identified the prognosis of rare chromosomal karyotype in AML. Figure 1 Figure 1. Disclosures Wang: AbbVie: Consultancy; Astellas Pharma, Inc.: Research Funding.

Acute myeloid leukemia (AML) is an aggressive disease with uncontrolled proliferation of myeloid progenitor cells and a failure of proper cell differentiation. Chromosomal translocations of the KMT2A (MLL) gene are found in about 10% AMLs affecting both children and adults. Patients harboring MLL rearrangement (MLL-r) have a high relapse rate and poor overall survival, emphasizing an unmet need to understand MLL-r AML pathogenesis and develop new therapeutic means. Through a comparative analysis of super-enhancers in AML cell lines and primary samples, we discovered that MLL-r leukemia cells preferentially gain super-enhancer signals at the MEF2D gene. MEF2D is aberrantly activated in MLL-r AML patient samples and predicts poor disease outcomes, implying a potential oncogenic role of MEF2D. Indeed, depletion of MEF2D inhibits human MLL-r leukemia growth and induces profound differentiation. Mechanistically, MEF2D directly represses CEBPE, a master regulator of myeloid differentiation. CEBPE depletion could rescue the growth defect and cell differentiation induced by MEF2D loss. We also demonstrated that MEF2D is positively regulated by HOXA9, and downregulation of MEF2D is an important mechanism for DOT1L inhibitor-induced anti-leukemia effects. Interestingly, MEF2C, a target of MLL fusion oncoproteins, is by far the most studied MEF2 family member with essential roles in MLL-r AML. Our genetic, biochemical, and integrative genomic data shows that MEF2D and MEF2C, both upregulated in MLL-r AML, interact with each other, colocalize genome-widely, and co-regulate target gene expression. We are currently investigating the molecular mechanisms underlying the interdependent function between MEF2 paralogs in MLL-r AML. Collectively, our findings suggest that MEF2D is a novel transcriptional dependency in MLL-r AML and uncover the MEF2-CEBPE axis as a crucial transcriptional mechanism regulating leukemia cell self-renewal and differentiation block. Disclosures No relevant conflicts of interest to declare.

One of the most common mutations in adult AML is a constitutively activating internal tandem duplication in the juxtamembrane domain of the Flt3 receptor (Flt3-ITD), which portends poor prognosis due to high recurrence rates and defines a distinct subtype of disease with unique features and biology. Although several FLT3 TKIs have been developed for clinical use, responses to these drugs, especially as single agents, are limited and are not sustained. The objective of our study was to determine the contribution of bone marrow stromal populations to LSC resistance to Flt3-targeted TKI in Flt3-ITD AML. We utilized a newly generated Flt3-ITD TET2flox/flox Mx1-cre mouse model of AML, as well as primary Flt3-ITD TET2 mutant AML patient samples, to identify phenotypic populations with leukemia initiating capacity (LIC) in Flt3-ITD AML. In the animal model, administration of pIpC leads to deletion of TET2 and development of AML characterized by leukocytosis, accumulation of blasts, splenomegaly, anemia, thrombocytopenia, and lethality. Limiting dilution transplantation of FACS-sorted ST-HSC, MPP and GMP populations revealed that LIC were absent from GMPs and almost exclusively limited to the phenotypic ST-HSC population (calculated stem cell frequencies: We characterized bone marrow stromal cells in Flt3-ITD AML mice by flow cytometry on collagenase digested bone fragments. We also transplanted murine AML cells into CXCL12-GFP mice to assess alterations in CXCL12-expressing stromal populations in AML bone marrow. We found expansion of several stromal populations in AML vs. WT mice, including a 3.5-fold increase in mesenchymal stem cells (CD45-Ter119-CD31-VECadherin-Sca1+CD51+) and a 1.5-fold increase in osteoprogenitors (CD45-Ter119-CD31-VECadherin-Sca1-CD51+). CXCL12 expression, however, was greater than 2-fold higher in osteoprogenitors and 2-fold lower in mesenchymal stem cells in AML vs. WT mice. We also showed that Flt3-ITD AML HSPCs have nearly 2-fold higher CXCR4 expression than WT HSPCs. These data taken together supported further exploration of the role of a CXCL12-expressing niche in supporting Flt3-ITD AML LSC. To assess the effect of CXCL12 deletion from the marrow microenvironment on AML TKI response, we transplanted murine AML cells into CXCL12flox/flox UBC-cre mice and control Cre-ve mice. We found that AML developing in Cre-ve control mice was resistant to single agent Flt3 TKI (AC220, Quizartinib) treatment, but that CXCL12 deletion modestly improved response to TKI. We next tested a combination of standard-of-care "7+3" chemotherapy (cytarabine + doxorubicin) and AC220, and found that this approach resulted in more effective and selective, but only partial, reduction of leukemia cells in this model. We found that control AML mice showed an initial response to combination chemo + TKI, but developed disease recurrence by 3 weeks of treatment. In contrast, CXCL12-deleted AML mice maintained peripheral blood response for up to 3 weeks, and showed enhanced suppression of LIC-containing populations compared to control mice. We are now performing secondary transplants using BM cells harvested from these treated mice to assess long-term effects on leukemia stem cell capacity. We are also testing the effect of the combination of chemotherapy and TKI following osteoblast-specific deletion of CXCL12, using CXCL12flox/flox BGLAP-cre mice, to assess whether osteoblastic cells are the source of CXCL12 responsible for this effect. In conclusion, our results suggest that LSC in Flt3-ITD AML are found within a primitive phenotypic ST-HSC population as opposed to GMP populations as seen in some other types of AML. Furthermore, CXCL12-expressing bone marrow microenvironmental cells contribute to drug resistance in AML LSC and global knockout of CXCL12 enhances drug response in these populations. Our studies support a potential role for a CXCL12-expressing osteoprogenitor niche in supporting Flt3-ITD AML LSC growth and drug resistance, targeting of which could improve responses and outcomes in Flt3-ITD AML. Disclosures No relevant conflicts of interest to declare.

Purpose: Cytarabine, 100–200 mg/mE+2/day, is commonly used in induction therapy of acute myelogenous leukemia (AML). Whether a higher dose of cytarabine would be more effective is unknown. Also, there is controversy whether high-dose cytarabine is better than an intermediate-dose combined with other drugs for post-remission therapy. In this open-label, randomized controlled, parallel group study, roles of intermediate-dose cytarabine were investigated. Patients and Methods: Subjects with AML age 15–55 years were randomized to receive daunorubicin, omacetaxine mepesuccinate, and conventional- or intermediate-dose cytarabine. Subjects achieving complete remission were randomized to receive 3 courses of high-dose cytarabine or 2 courses of intermediate-dose cytarabine with daunorubicin in the 1st and mitoxantrone in the 2nd course. The primary endpoint was disease-free survival (DFS). Results: 591 subjects were randomized to intermediate- (N = 295) or conventional-dose (N = 296) cytarabine group. Three-year DFSs were 67% [95% confidence interval (CI), 61–73] in the intermediate-dose cohort compared with 54% (95% CI, 48–61) in the conventional-dose cohort [Hazard Ratio (HR), 0.67; 95%CI, 0.51–0.89; P = 0.005). Three-year survivals were 68% (95%CI, 63–74) and 59% (95%CI, 53–65; HR, 0.720; 95%CI, 0.56–0.94; P = 0.014). Two courses of intermediate-dose cytarabine with daunorubicin or mitoxantrone resulted in similar DFS and survival as three courses of high-dose cytarabine when used for post-remission therapy. Conclusions: Induction therapy with intermediate-dose cytarabine with daunorubicin and omacetaxine mepesuccinate increases DFS and survival in persons with AML ages 15–55 years compared with conventional-dose cytarabine. See related commentary by Watts and Bradley, p. 3073

The study of candidemia in Chinese leukemia patients has been limited. This retrospective study aims to investigate the characteristics and prognostic factors of candidemia among leukemia patients. From 2009 to 2015, 30 isolates of candidemia were detected in 19 patients with acute leukemia after chemotherapy. The overall incidence of candidemia was 2.12 episodes per 1000 admissions. Candida tropicalis was the most common Candida species (n = 17; 89.5%). The vast majority of candidal infections are endogeneous. The overall 30-day crude mortality rate was 31.6%. Neutrophil recovery (P = 0.000) and initiation of empiric antifugal treatment before first positive blood culture (P = 0.041) were associated with a significant improvement in overall survival. Early diagnosis, followed by rapid antifungal treatment remains the cornerstone of successful management. The widespread use of newer antifungal agents as prophylaxis among patients with acute leukemia may result in a decreased candidemia incidence.

Minimal residual disease (MRD) levels monitored by polymerase chain reaction are associated with outcomes in acute myeloid leukemia with RUNX1–RUNX1T1. The objectives of our study were to quantitatively compare the predictive value of MRD reduction and absolute copies and assess the influence of other prognostic factors on MRD. A total of 224 consecutive patients with RUNX1–RUNX1T1 aged ≤55 years were included in the MRD study. Patients received different induction regimens including conventional- or intermediate-dose cytarabine plus low-dose daunorubicin and omacetaxine mepesuccinate or daunorubicin at 60 mg/m2/day on days 1–3. As continuous variables, both MRD reduction and absolute MRD level were significantly associated with cumulative incidence of relapse (CIR; hazard ratio [HR] = 1.610, 95% confidence interval [CI]: 1.370–1.890, p