Viability Of Acute Myeloid Leukemia Cells Research Articles

High STAT4 expression correlates with poor prognosis in acute myeloid leukemia and facilitates disease progression by upregulating VEGFA expression.

The aim of our study is to explore the mechanism of transcription-4 (STAT4) in acute myeloid leukemia (AML). STAT4 level in AML bone marrow samples/cells was analyzed using bioinformatics and quantitative real-time PCR. The correlation between high STAT4 expression and the prognosis of AML patients was analyzed. The viability, apoptosis, and angiogenesis of AML cells were detected. The levels of STAT4, vascular endothelial growth factor A (VEGFA), and apoptosis-related proteins (Bcl-2 and Bax) in transfected AML cells were examined. STAT4 level was upregulated in AML. STAT4 silencing decreased the viability and angiogenesis, yet increased the apoptosis of AML cells, while overexpressed STAT4 did conversely. VEGFA silencing counteracted the impacts of overexpressed STAT4 upon promoting viability and angiogenesis as well as repressing the apoptosis of AML cells. High STAT4 expression was correlated with poor prognosis of AML patients and facilitated disease progression via upregulating VEGFA expression.

Sirtuin 5 regulates acute myeloid leukemia cell viability and apoptosis by succinylation modification of glycine decarboxylase.

Acute myeloid leukemia (AML) is a blood system malignancy where sirtuin 5 (SIRT5) is abnormally expressed in AML cell lines. This study aimed to investigate the SIRT5 effects on the viability and apoptosis of AML cell lines. The mRNA and protein expression levels of succinylation regulatory enzyme in clinical samples and AML cell lines were detected by real-time quantitative polymerase chain reaction and western blotting while cell viability was measured using cell counting kit-8 assay. The apoptosis rate was assessed with flow cytometry. The interaction between SIRT5 and glycine decarboxylase (GLDC) was determined by co-immunoprecipitation and immunofluorescence staining techniques. Results indicated higher mRNA and protein expression levels of SIRT5 in clinical AML samples of AML than in normal subjects. Similarly, cell viability was inhibited, and apoptosis was promoted by downregulating SIRT5, in addition to inhibition of SIRT5-mediated GLDC succinylation. Moreover, rescue experiment results showed that GLDC reversed the effects of SIRT5 knockdown on cell viability and apoptosis. These results, in combination with SIRT5 and GLDC interactions, suggested that SIRT5 was involved in mediating AML development through GLDC succinylation. SIRT5 inhibits GLDC succinylation to promote viability and inhibit apoptosis of AML cells, suggesting that SIRT5 encourages the development of AML.

Oncogenic lncRNA FAM215A promotes the malignant cell phenotypes of acute myeloid leukemia (AML) cell lines.

Acute myeloid leukemia (AML) is a form of blood cancer that arise as a result of clonal proliferation of malignant myeloid precursors acquiring genetic abnormalities. Primary resistance to initial treatment and disease recurrence continues to be huge challenge in treating AML. Herein, GSE114868 was analyzed for differentially-expressed lncRNAs between AML patients' mononucleated cells and healthy normal control mononucleated cells and 191 lncRNAs were significantly deregulated in AML patients' mononucleated cells. The correlation between candidate lncRNAs and AML patients' overall survival was analyzed and 6 lncRNAs, including MIR181A1HG, TRAF3IP2-AS1, STARD4-AS1, E2F3-IT1, FAM215A, and HHIP-AS1 were dramatically linked to AML patients' OS. Using a Cox proportional-hazards model, we identified risk factors and found FAM215A as a risk factor for AML patients' prognosis. The expression level of FAM215A showed to be upregulated within blood samples and cells. Genes correlated with FAM215A were correlated to cell division, modulation of cell apoptosis, and modulation of programmed cell death. FAM215A knockdown inhibited AML cell viability, elicited G0/G1-phase arrest of cell cycle, enhanced cell apoptosis, increased proapoptotic Bax and cleaved-caspase3 levels, and decreased antiapoptotic Bcl2. FAM215A overexpression exerted opposite effects on AML cells. Conclusively, FAM215A serves as an oncogenic lncRNA in AML, promoting cell viability, relieving cell cycle arrest, and suppressing cell apoptosis. FAM215A might be un underlying biological prognostic marker and therapeutic target for AML.

MiR-26b-5p Affects the Progression of Acute Myeloid Leukemia by Regulating the USP48-Mediated Wnt/β-Catenin Pathway.

Acute myeloid leukemia (AML) is a highly heterogeneous disease. Exploring the pathogenesis of AML is still an important topic in the treatment of AML. The expression levels of miR-26b-5p and USP48 were measured by qRT-PCR. The expression levels of related proteins were detected by Western blot. Cell proliferation and apoptosis were detected by CCK-8 and flow cytometry, respectively. Coimmunoprecipitation was used to examine the interaction between USP48 and Wnt5a. Bioinformatics analysis showed that high levels of miR-26b-5p and low levels of USP48 were associated with poor prognosis in AML. miR-26b-5p can negatively regulate the expression of USP48. Downregulation of miR-26b-5p inhibited EMT, cell viability and proliferation of AML cells and accelerated apoptosis. Furthermore, the influence of miR-26b-5p inhibition and USP48 knockdown on AML progression could be reversed by a Wnt/β-catenin signaling pathway inhibitor. This study revealed that miR-26b-5p regulates AML progression, possibly by targeting the USP48-mediated Wnt/β-catenin molecular axis to affect AML cell biological behavior.

Targeting S100A9 protein affects mTOR-ER stress signaling and increases venetoclax sensitivity in Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is a heterogeneous disease with limited treatment options and a high demand for novel targeted therapies. Since myeloid-related protein S100A9 is abundantly expressed in AML, we aimed to unravel the therapeutic impact and underlying mechanisms of targeting both intracellular and extracellular S100A9 protein in AML cell lines and primary patient samples. S100A9 silencing in AML cell lines resulted in increased apoptosis and reduced AML cell viability and proliferation. These therapeutic effects were associated with a decrease in mTOR and endoplasmic reticulum stress signaling. Comparable results on AML cell proliferation and mTOR signaling could be observed using the clinically available S100A9 inhibitor tasquinimod. Interestingly, while siRNA-mediated targeting of S100A9 affected both extracellular acidification and mitochondrial metabolism, tasquinimod only affected the mitochondrial function of AML cells. Finally, we found that S100A9-targeting approaches could significantly increase venetoclax sensitivity in AML cells, which was associated with a downregulation of BCL-2 and c-MYC in the combination group compared to single agent therapy. This study identifies S100A9 as a novel molecular target to treat AML and supports the therapeutic evaluation of tasquinimod in venetoclax-based regimens for AML patients.

The Combination of Lanraplenib, a Selective SYK Inhibitor, and Gilteritinib, a FLT3 Inhibitor, Targets Aberrant Proliferation and Differentiation Blockade in Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) is an aggressive disease characterized by uncontrolled clonal proliferation of poorly differentiated myeloid progenitor cells in the bone marrow and blood. Deregulated spleen tyrosine kinase (SYK) impairs myeloid differentiation and has been implicated in the pathogenesis of AML driven by FMS-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) mutation (FLT3-ITD). While SYK is rarely mutated, it is highly activated in FLT3-ITD-mutated AML and directly phosphorylates FLT3-ITD, resulting in aberrant expression of multiple oncogenic pathways. Lanraplenib (LANRA) is a selective, next-generation, SYK inhibitor that has shown favorable PK, PD, and safety in healthy volunteers and patients with autoimmune diseases. LANRA is currently being evaluated in combination with gilteritinib, a FLT3 inhibitor, in patients with relapsed or refractory (R/R) FLT3-mutated AML (NCT05028751). By jointly inhibiting the leukemogenic network created by SYK and mutant FLT3, LANRA and gilteritinib potentially provide a new treatment regimen in a patient population with few treatment options. Method: AML cell viability in response to LANRA, gilteritinib or their combination was assessed by CellTiter Glo (CTG) at 5 days. Apoptosis was evaluated by measuring Annexin V and propidium iodide staining by flow cytometry. Myeloid differentiation was assessed by flow cytometry using CD11b and CD14 cell surface markers and/or immunohistochemistry. In addition, RNA-seq was performed to evaluate differential changes in gene expression in response to LANRA. Gene set enrichment analysis (GSEA) was performed to evaluate perturbation in leukemogenic signaling pathways. In vivo studies were conducted using the MV4;11 cell line-derived xenograft model. LANRA was administered twice daily at a dose of 75 mg/kg via subcutaneous injections, either alone or in combination with gilteritinib at a dose of 2 mg/kg dosed once daily by oral gavage, for 28 days. Results: Treatment of FLT3-ITD mutated AML cells with LANRA results in dose- and time-dependent increase in myeloid differentiation and reductions in leukemic cell viability. RNA-seq analysis of MV4;11 cells revealed that LANRA abrogates multiple downstream FLT3-ITD leukemogenic signaling pathways including JAK/STAT3/5, MAPK, mTOR and OXPHOS. Combined pharmacologic inhibition of SYK with LANRA and FLT3-ITD with gilteritinib results in robust antileukemic effects in preclinical models of FLT3 ITD-driven AML. Additionally, the combination of LANRA and gilteritinib demonstrated increased differentiation and apoptosis induction in vitro. LANRA in combination with gilteritinib showed significant tumor growth inhibition compared to either single agent in a subcutaneous FLT3-ITD AML cell line-derived xenograft mouse model. In line with these observations, a retrospective analysis of bone marrow-engrafted AML cells from a disseminated FLT3-ITD AML patient-derived xenograft mouse model showed evidence of increased myeloid differentiation and inhibition of cell proliferation. Conclusion: In preclinical models, LANRA demonstrates compelling anti-leukemic activity in combination with gilteritinib. By jointly targeting hyperproliferation and differentiation blockade, LANRA and gilteritinib may provide a new therapeutic approach that can be exploited in AML. Additionally, LANRA disrupts downstream signaling of key pathways often associated with resistance to gilteritinib, providing additional mechanistic support for continued testing of LANRA in combination with gilteritinib in FLT3-ITD-mutated AML patients. These studies helped motivate the ongoing clinical combination with gilteritinib in patients with (R/R) FLT3-mutated AML (NCT05028751).

Synthetic Lethal Interactions with IRAK4 Inhibition in Myeloid Malignancies

Overexpression of immune-related genes is widely reported in acute myeloid leukemia (AML). Research from our lab and others has demonstrated that AML leukemic stem and progenitor cells (LSPC) rely on innate immune signaling through IRAK4 (reviewed in Bennett et al., Blood 2023). Moreover, AML LSPCs express a hypermorphic isoform of IRAK4 (IRAK4-L), due to U2AF1- and SF3B1-dependent mis-splicing. Building on this preclinical evidence, several IRAK4 inhibitors are now undergoing clinical trials in AML patients. In Phase-1 findings with a selective IRAK4 inhibitor (CA-4948; Curis Therapeutics), it was found that MDS and AML patients with splicing factor mutations responded best to monotherapy IRAK4 inhibition, although the overall response rate with monotherapy was modest. These findings suggest that IRAK4 is a relevant target in myeloid malignancies, but the identification of synthetic lethal dependencies may be crucial in revealing effective combination therapies. In this study, we sought to identify synthetic lethal interactions upon IRAK4 inhibition in AML. For this, we first generated isogenic AML cells that are proficient (WT THP1) or deficient for IRAK4 (IRAK4 KO THP1) using site-directed mutagenesis with CRISPR-Cas9. Deletion of IRAK4 resulted in a modest (~50%) reduction in leukemic colony formation and negligible differences in growth potential. We used the isogenic WT and IRAK4 KO AML cells to screen for synthetic lethal interactions by performing a 2400+ drug in vitro screen. Hits were prioritized for potency in IRAK4 KO cells vs WT AML cells, degree of fitness, and overall effect. Among these hits, the Cereblon E3 ligase modulator (CELMoD) CC-885 emerged as the top target. Independent validation confirmed that CC-885 significantly decreased proliferation and viability of isogenic IRAK4 KO MDS (MDSL) and AML (THP1) cells by approximately 3-4-fold compared to WT MDS or AML cells. Colony formation in methylcellulose after treatment with CC-885 was also significantly reduced in IRAK4 KO compared to WT MDS and AML cells. Based on Caspase-3 activation and AnnexinV staining, CC-885 induced significantly more apoptosis of IRAK4 KO cells as compared to WT AML cells. We extended our synthetic lethal analysis to a clinical-stage IRAK4 inhibitor (CA-4948). MDS and AML cells were treated with CA-4948 concurrently with CC-885 or pretreated for 7 days prior to treatment with CC-885. Unexpectedly, we found that only prior exposure of the AML cells to the IRAK4 inhibitors resulted in sensitivity to CC-885. These findings indicate that IRAK4 inhibition reprograms AML cells so that they acquire a synthetic lethal interaction with CC-885. CC-885 is known to target multiple substrates for degradation by the ubiquitin proteasome, including IKZF1, IKZF3, CK1a, and GSPT1. We compared the effect of CC-885 to CC-90009, a CELMoD with GSPT1 specific activity in the isogenic IRAK4 KO and WT AML cell lines. CC-90009 did not result in complete cell death up to concentrations of 10mM in both WT and IRAK4 KO, suggesting that the selective sensitivity of IRAK4 KO AML cells to CC-885 is not due to inhibition of GSPT1. In support of these interpretations, IRAK4 deficient AML cells exhibit increased protein expression of IKZF2 and IKZF3, but not GSPT1 or CK1a. Given the unique responses of IRAK4 KO cells to CELMoDs, we posited that IRAK4 inhibition alters the neosubstrate profile of CELMoDs in AML cells. Total proteome characterization of CC-885 treated WT and IRAK4 KO THP1 cells by mass spectrometry identified a significant decrease in 90 protein substrates in IRAK4 KO cells treated with CC-885 as compared to WT cells treated with CC-885. These findings suggest that IRAK4 inhibition alters the pool of neosubstrates in AML cells for certain CELMoDs. Overall, our study demonstrates that IRAK4 is a therapeutic target in AML, but that combination therapies, such as with certain CELMoDs, will be necessary to achieve better clinical responses.

Defective Necroptosis Mediates Chemotherapy Resistance in AML

Acute myeloid leukemia (AML) is a hematopoietic malignancy that can affect individuals of any age and, if left untreated, is always fatal. Standard induction chemotherapy, known as “7+3,” using drugs like cytarabine (Ara-C) and an anthracycline (daunorubicin or idarubicin), is typically given to young and fit older patients. While this treatment regimen has shown positive outcomes in patients who respond to it, relapse and refractory disease remain the primary causes of death. Prognostic classification, which combines cytogenetic and mutational status, can estimate overall and event-free survival but is not effective in predicting induction failure. Despite decades of research and treatment with 7+3 chemotherapy, the reasons behind variable treatment responses in AML patients remain unclear, especially for those who experience induction failure. Understanding these mechanisms could aid in risk-adapted treatment decisions and the identification of new therapeutic targets. Recent research has investigated gene expression and signaling patterns in leukemic cells at the time of diagnosis to categorize patients according to their response to chemotherapy. Notably, increased NF-kB signaling at diagnosis has been linked to chemotherapy resistance. NF-kB is a family of transcription factors involved in regulating genes linked to cancer cell survival, proliferation, and therapy resistance. However, the exact mechanism by which NF-kB activation contributes to chemotherapy failure and resistance in AML is yet to be determined. Using publicly available datasets, we found that AML patients undergoing induction failure exhibited elevated expression of TNFAIP3/A20, which is driven by NF-kB signaling and leads to a worse prognosis for patients undergoing 7+3 chemotherapy. In experiments with primary AML samples, it was observed that A20-High AML are resistant to Doxorubicin treatment, whereas A20-Low AML samples are sensitive to Doxorubicin. Knockdown of A20 in A20-High AML samples resulted in increased cell sensitivity to Doxorubicin, suggesting that elevated A20 expression reduces AML cells' response to the Doxorubicin both in vitro and in vivo. To understand why A20 is overexpressed in AML, we investigated its requirement on AML cell function in various models, including human AML cell lines, patient-derived samples, and mouse models of AML. Deletion or knockdown of A20 led to reduced leukemic progenitor function, cell viability, and AML development in vitro and in vivo. A20 is a dual ubiquitin-editing protein that regulates signaling pathways by acting either as a deubiquitinase to modulate NF-kB signaling or as an E3 ligase to control necroptosis. Further analyses revealed that A20 prevents necroptosis by targeting the necroptosis effector, RIPK1, for degradation through the proteasome in AML. Preventing necroptosis, either pharmacologically or genetically, restored the viability and clonogenicity of A20-deficient AML cells in vitro and in vivo. Notably, Doxorubicin, but not AraC, induced necroptosis in AML cells, which is suppressed in leukemic clones expressing A20. Examination of single-cell RNA-sequencing data from AML patients before and after Doxorubicin treatment confirmed the persistence of A20-expressing clones during treatment. These findings demonstrate that NF-kB-driven overexpression of A20 contributes to failed induction chemotherapy in AML, highlighting the therapeutic potential of targeting an alternative cell death pathway in AML.

Polyamines Are Required for AML LSC Function through Their Role in Regulating eIF5A Dependent Protein Synthesis

Outcomes for patients with acute myeloid leukemia (AML) remain poor due to the inability of current therapies to fully eradicate disease initiating leukemia stem cells (LSCs) (Shlush et al., 2017). Many studies have demonstrated that LSCs have unique metabolic properties compared to AML blasts and normal hematopoietic stem and progenitor cells (HSPCs) (Jones et al., 2021). In this study we sought to quantify metabolite levels in LSCs compared to HSPCs using an unbiased metabolites screen. To examine metabolite levels in enriched LSCs and HSPCs we used mass spectrometry-based metabolomics analysis on enriched LSCs from 18 AML patients and HSPCs from 5 normal bone marrow (BM) specimens. Pathway analysis showed that arginine metabolism and biosynthesis were the most significantly enriched pathways in LSCs compared to HSPCs. Clinical studies have shown limited efficacy of targeting arginine levels using arginine degrading enzymes; therefore, we sought to target pathways downstream of arginine. To identify the pathways that arginine metabolism supports in LSCs, we used stable isotope labeled tracing analysis which showed arginine was metabolized through the urea cycle into polyamines in LSCs. Interestingly, the polyamine spermidine was the most significantly enriched metabolite in LSCs compared to HSPCs in our metabolomics analysis. Moreover, expression of SAT1, the enzyme catalyzing the export of polyamines from the cells, was decreased in AML compared to normal BM. Based on these observations, we sought to determine if the polyamine pathway represents a metabolic vulnerability that can be exploited to target LSCs. Polyamines are cationic compounds which have been previously shown to be important for the growth of various cancers but their role in AML LSCs has yet to be determined. To investigate if polyamines are essential for LSC survival and function, we treated LSCs and HSPCs with N 1, N 11-diethylnorspermine (DENSpm), a polyamine analog causing polyamine depletion through increased SAT1 expression and subsequent cellular export. DENSpm treatment decreased the viability of LSCs in 10 out of 12 of patients tested but had no impact on HSPCs viability. Further, treatment with DENSpm resulted in decreased engraftment potential of 5 AML specimens but did not alter the engraftment of HSPCs from 3 normal BM specimens, suggesting that targeting polyamines represents a promising approach to kill LSCs while sparing HSPCs. We then investigated the mechanisms by which polyamines are essential in LSCs. Using RNA-sequencing analysis on enriched LSCs from 5 AML patients and HSPCs from 3 normal BM specimens we observed an enrichment in myeloid differentiation signatures in DENSpm-treated LSCs but not in DENSpm-treated HSPCs. In line with this, expression of myeloid markers CD11b and CD15 were increased in patient-derived xenograft models engrafted with DENSpm-treated LSCs. As we did not observe such dysregulation in mice engrafted with DENSpm-treated HSPCs, these data suggest polyamine depletion promotes differentiation of LSCs but not HSPCs. Our transcriptomic analysis also unveiled decreased expression of genes involved in protein synthesis in DENSpm-treated LSCs but not in normal HSPCs. Protein synthesis and its regulation are critical for AML survival (Chen et al., 2019; Messling et al., 2022) but the role of polyamines in protein synthesis in LSCs has not been explored. Polyamines stimulate translation notably by serving as precursors for the hypusination of eukaryotic translation initiation factor 5A (eIF5A) (Park et al., 2010). Accordingly, DENSpm led to decreased hypusination of eIF5A in AML cells. This was associated with reduced protein synthesis level in AML cell lines and LSCs but not in normal HSPCs. Strikingly, eIF5A hypusination, protein synthesis and viability were rescued upon co-treatment with spermidine. Moreover, knockdown of eIF5A using siRNA resulted in impaired colony forming potential of AML and altered engraftment in patient-derived xenograft models. Altogether, these results suggest that DENSpm alters AML cell and LSC viability and function at least in part through decreased eIF5A-mediated protein translation. Altogether, our data demonstrates that depletion of polyamines decreased LSC function while sparing normal HSPCs. Mechanistically, our data suggest that LSC targeting is accomplished through decreased eIF5A-mediated synthesis of proteins crucial for LSCs.

Cephalochromin-Induced Mitochondrial Damage Overcomes Venetoclax-Resistance in Acute Myeloid Leukemia Models

The combination of the BCL2 inhibitor venetoclax (VEN) with hypomethylating agents (e.g. azacytidine, AZA) significantly increased complete remission (CR) rates and prolonged overall survival of adults with Acute Myeloid Leukemia (AML) who were ineligible to intensive chemotherapy. However, VEN+AZA is not a curative treatment and resistance to VEN and/or relapses are common. Therefore, the search for new agents able to improve the depth and duration of CR or to overcome VEN resistance are needed. Cephalochromin (CPC), a natural compound easily obtained from Comospora vilior, emerges as a potential candidate. Here, we initially accessed the effects of CPC and VEN monotherapies regarding the cell survival of a large panel of AML cell lines (n=12), covering the main different molecular profiles observed in AML patients. Each cell model exhibited a degree of sensitivity to each drug, with no correlation between the sensitivity for both compounds across the cell models. IC 50 values for CPC ranged from 0.45 to >20 µM, while VEN IC 50 values ranged from <0.001 to 17.5 µM upon 72 h of treatment. To evaluate the cytotoxic effects of CPC in healthy cells, we treated human peripheral blood mononuclear cells from 4 healthy donors, which revealed IC50 values ranging from 3.7 to 8.8 µM at 72 h, suggesting a potential feasible therapeutic window. To evaluate the potential combination effects of CPC + VEN in AML, we performed combination experiments in AML models, chosen based on their VEN sensitivity (Kasumi-1 and U937 cells as partially resistant and OCI-AML3 displaying higher VEN resistance). Combination effects in all AML models revealed an significant improvement on the performance of VEN when combined to CPC, even in low doses of both compounds. We next evaluated the molecular mechanisms associated with the effects of CPC on cell proliferation and survival. Clonogenic assays revealed that CPC treatment was associated with decreased stemness capacity, in a concentration-dependent manner. Cell cycle analysis on CPC-treated cells revealed a progressive increase in sub-G1 cells population, suggesting apoptosis induction in a dose-dependent manner, which was further corroborated by increased Annexin-V levels on treated cells. The effects of CPC regarding the apoptosis induction were more evident in Kasumi-1 cells when compared with U937 and OCI-AML3 cells. In OCI-AML3 cells (which display the highest MCL1 expression across the different AML models), combination of low concentrations of VEN (1 µM) and CPC (1.8 µM) showed an apoptosis induction in 95% of the cells. Similarly, the combination CPC + VEN resulted in higher levels of apoptosis induction in U937 (monocytic leukemia; VEN 2.5 + CPC 2.5 µM) and Kasumi-1 ( TP53 R248Q mutant; VEN 0.6 + CPC 2.5 µM) cells. Metabolic analysis of CPC treated cells revealed extensive mitochondrial damage associated with reduction in the mitochondria mass. Proteomic analysis showed increase PARP1 cleavage (apoptosis) and γH2AX (DNA damage) levels upon CPC treatment in all evaluated models, whereas MCL1 was reduced in Kasumi-1 cells. Moreover, SQSTM1/p62 levels were reduced in U937 and Kasumi-1 cells, suggesting induction of autophagy as a mechanism of response to CPC in these cells. Finally, these findings were confirmed in a cohort of ex vivo treated AML samples (n=10) treated with CPC and VEN alone or in combination, where the combination of VEN 0.1 + CPC 2.5 µM displayed strong synergistic effect when compared to the monotherapies. Treatment with CPC reduced the mitochondrial membrane potential, suggesting the disturbance on the mitochondrial metabolism as one of the key phenomena associated with the efficiency of the CPC+VEN combination therapy. In summary, by using multiple cellular models, we demonstrated that CPC treatment was able to decrease cell viability and survival of AML cells, while it spares healthy counterparts. We uncovered the potential combination effects of CPC with VEN in leukemic models of resistance to VEN. Mechanistically, CPC treatment induced impaired mitochondrial metabolism, DNA damage and decreased the expression of proteins related with VEN-resistance in AML, possibly explaining the synergic effects observed between VEN and CPC.

Synergistic Activity of Adefovir Dipivoxil and Venetoclax to Target the Bioenergetic Metabolism of Acute Myeloid Leukemia

Adefovir dipivoxil (ADV) is an oral prodrug of the nucleotide analogue adefovir that inhibits viral DNA polymerase and is an FDA-approved drug for the treatment of hepatitis B virus. Preliminary evidence of the antileukemic activity of ADV was recently reported in a patient with acute promyelocytic leukemia (APL; Gong, X., et al. Exp Hematol Oncol, 2022). Herein we report on the antileukemic activity of ADV, alone and in combination with venetoclax (VEN), an oral FDA-approved BCL-2 inhibitor for the treatment of acute myeloid leukemia (AML). Firstly, a significant dose-dependent reduction of cell growth and increase in apoptosis were observed in FLT3-ITD+ MV4-11 (IC50: 97nΜ) and Molm-13 (IC50: 0.816μM) cells, and in primary CD34+ blasts from refractory/relapsed (R/R) AML patients (n=5; IC50: 1.285-3.703μM), exposed to serial concentrations of ADV for 48 hours (hrs). In contrast, no significant changes were observed in ADV-treated CD34+ cells from healthy donors (n=5). Combination of ADV and VEN were synergistic (combination index < 1.0) in reducing cell viability of AML cells (i.e., MV-4-11, U937, KG1 and THP-1) and CD34+ blasts from R/R AML patients (n=3). To gain insights into the molecular mechanisms underlying the antileukemic activity of ADV alone and in combination with VEN, we performed RNA-Seq on AML CD34+ blasts from R/R AML patients (n=6) treated with vehicle, ADV (5 μΜ), VEN (100 nΜ), or ADV+VEN for 24 hrs. Gene set enrichment analysis (GSEA) highlighted upregulation of p53 pathway and apoptosis signaling, and downregulation of oxidative phosphorylation (OXPHOS), glycolysis, and MYC target hallmark gene sets in ADV- and ADV+VEN-treated cells compared with vehicle-treated controls. These results were confirmed by western blot analysis showing a dose-dependent reduction in c-MYC, anti-apoptotic proteins (i.e., BCL-2 and MCL-1), and carnitine palmitoyltransferase-1a [CPT1A, a key enzyme for fatty acid oxidation (FAO), a process that feeds into OXPHOS], and an increase in pro-apoptotic proteins (i.e., BAX and BAK) in ADV- and ADV+VEN-treated MV4-11 and primary AML CD34+ cells, compared with vehicle-treated control cells. Seahorse analysis confirmed a significant reduction of OXPHOS [measured by oxygen consumption rate (OCR)], associated with decreased mitochondrial numbers and sizes evaluated by electron microscopy imaging of AML CD34+ blasts treated with ADV or ADV+VEN compared with vehicle-treated controls. To test in vivo the antileukemic activity of ADV+VEN, we treated a cohort of CD45.1 recipient mice transplanted with BM cells from congenic CD45.2 Mll PTD/WT/Flt3 ITD/ITD AML mice with vehicle, ADV (100mg/kg, oral gavage), VEN (100mg/kg, oral gavage), or ADV+VEN (n=10 per group) for 4 weeks. ADV+VEN-treated mice lived longer (median survival: 60 days after treatment completion) than ADV (20 days, p=0.0001), VEN (20 days, p=0.0001), or vehicle (14 days, p=0.0002) -treated controls (Figure 1). We then performed secondary transplants by engrafting 10 6 BM cells from treated donors into CD45.1 recipient mice (n=10 per group). Recipients of BM from ADV+VEN-treated donors survived longer (median survival: 83 days) than recipients of BM from ADV (60.5 days, p<0.01), VEN (45.5 days, p<0.0001), and vehicle (42.5 days, p<0.0001) -treated donors (Figure 2), confirming a decrease in leukemic stem cell (LSC) burden by ADV+VEN. Next, we examined the antileukemic activity of ADV+VEN in human AML models. We first treated a cohort of NSG mice (n=10 per group) transplanted with luciferase-expressing Molm-13 cells. ADV+VEN-treated mice survived longer (median survival: 59.5 days) than ADV (52 days, p=0.04), VEN (40 days, p<0.0001), and vehicle (40.5 days, p<0.0001) -treated mice. We then treated a cohort of NSG mice (n=8 per group) transplanted with FLT3-ITD+ blasts from a patient with R/R AML. ADV+VEN-treated mice survived longer (median: 38.5 days) than ADV (34.5 days, p=0.035), VEN (25 days, p<0.0001), and vehicle (18.5 days, p<0.0001) -treated mice. In summary, ADV has in vivo anti-leukemic activity in AML likely by interfering with the bioenergetic metabolism of leukemic cells and decreasing their apoptotic threshold. The combination of ADV and VEN is seemingly synergistic and prolonged survival of murine and human AML models, providing a rationale of translating this “all oral” regimen to the clinic for treatment of AML patients, especially those requiring low intensity therapy.

Pinostrobin modulates FOXO3 expression, nuclear localization, and exerts antileukemic effects in AML cells and zebrafish xenografts

Acute myeloid leukemia (AML) is a disease characterized by abnormal cell proliferation in the bone marrow and is the most common quickly progressive leukemia in adults. Pinostrobin, a flavonoid phytochemical, has been reported to exhibit antioxidant, anti-inflammatory, and anticancer properties. In this study, we aimed to investigate the antileukemic effects of pinostrobin and its molecular mechanisms in human AML cells. Our study found that pinostrobin (0–80 μM) significantly reduced the viability of human AML cells, with the pronounced cytotoxic effects observed in MV4-11 > MOLM-13 > HL-60 > U-937 > THP-1 cells. Pinostrobin was found to suppress leukemia cell proliferation, modulate cell cycle progression, promote cell apoptosis, and induce monocytic differentiation in MV4-11 cells. In animal studies, pinostrobin significantly suppressed the growth of leukemia cells in a zebrafish xenograft model. Microarray-based transcriptome analysis showed that the differentially expressed genes (DEGs) in pinostrobin-treated cells were strongly associated with enriched Gene Ontology (GO) terms related to apoptotic process, cell death, cell differentiation, cell cycle progression, and cell division. Combining DisGeNET and STRING database analysis revealed that pinostrobin upregulates forkhead box 3 (FOXO3), a tumor suppressor in cancer development, and plays an essential role in controlling AML cell viability. Our study demonstrated that pinostrobin increases FOXO3 gene expression and promotes its nuclear translocation, leading to the inhibition of cell growth. Finally, the study found that pinostrobin, when combined with cytarabine, synergistically reduces the viability of AML cells. Our current findings shed light on pinostrobin's mechanisms in inhibiting leukemia cell growth, highlighting its potential as a chemotherapeutic agent or nutraceutical supplement for AML prevention or treatment.

Role of Diacylglycerol Kinases in Acute Myeloid Leukemia.

Diacylglycerol kinases (DGKs) play dual roles in cell transformation and immunosurveillance. According to cancer expression databases, acute myeloid leukemia (AML) exhibits significant overexpression of multiple DGK isoforms, including DGKA, DGKD and DGKG, without a precise correlation with specific AML subtypes. In the TGCA database, high DGKA expression negatively correlates with survival, while high DGKG expression is associated with a more favorable prognosis. DGKA and DGKG also feature different patterns of co-expressed genes. Conversely, the BeatAML and TARGET databases show that high DGKH expression is correlated with shorter survival. To assess the suitability of DGKs as therapeutic targets, we treated HL-60 and HEL cells with DGK inhibitors and compared cell growth and survival with those of untransformed lymphocytes. We observed a specific sensitivity to R59022 and R59949, two poorly selective inhibitors, which promoted cytotoxicity and cell accumulation in the S phase in both cell lines. Conversely, the DGKA-specific inhibitors CU-3 and AMB639752 showed poor efficacy. These findings underscore the pivotal and isoform-specific involvement of DGKs in AML, offering a promising pathway for the identification of potential therapeutic targets. Notably, the DGKA and DGKH isoforms emerge as relevant players in AML pathogenesis, albeit DGKA inhibition alone seems insufficient to impair AML cell viability.

Vitamin D Receptor Antagonist MeTC7 Inhibits PD-L1.

Small-molecule inhibitors of PD-L1 are postulated to control immune evasion in tumors similar to antibodies that target the PD-L1/PD-1 immune checkpoint axis. However, the identity of targetable PD-L1 inducers is required to develop small-molecule PD-L1 inhibitors. In this study, using chromatin immunoprecipitation (ChIP) assay and siRNA, we demonstrate that vitamin D/VDR regulates PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells. We have examined whether a VDR antagonist, MeTC7, can inhibit PD-L1. To ensure that MeTC7 inhibits VDR/PD-L1 without off-target effects, we examined competitive inhibition of VDR by MeTC7, utilizing ligand-dependent dimerization of VDR-RXR, RXR-RXR, and VDR-coactivators in a mammalian 2-hybrid (M2H) assay. MeTC7 inhibits VDR selectively, suppresses PD-L1 expression sparing PD-L2, and inhibits the cell viability, clonogenicity, and xenograft growth of AML cells. MeTC7 blocks AML/mesenchymal stem cells (MSCs) adhesion and increases the efferocytotic efficiency of THP-1 AML cells. Additionally, utilizing a syngeneic colorectal cancer model in which VDR/PD-L1 co-upregulation occurs in vivo under radiation therapy (RT), MeTC7 inhibits PD-L1 and enhances intra-tumoral CD8+T cells expressing lymphoid activation antigen-CD69. Taken together, MeTC7 is a promising small-molecule inhibitor of PD-L1 with clinical potential.

Dexamethasone enhances venetoclax-induced apoptosis in acute myeloid leukemia cells.

Acute myeloid leukemia (AML) therapies have been significantly improved by the development of medicines that can target BCL-2. On the other hand, non-recurrent alterations in oncogenic pathways and gene expression patterns have already been linked to therapeutic resistance to venetoclax therapy. Bone marrow mesenchymal stromal cells (BM-MSCs) support leukemic cells in preventing chemotherapy-induced apoptosis by mitochondrial transfer in leukemic microenvironment. In this study, we investigated the enhancement of the antitumor effect of BCL-2 inhibitor venetoclax by dexamethasone. In particular, dexamethasone had no significant effect on the viability of AML cells, but dexamethasone combined with venetoclax could significantly increase the apoptosis of AML cells induced by venetoclax. When AML cells were co-cultured with BM-MSCs, dexamethasone combined with venetoclax showed additional anti-tumor effect compared to venetoclax alone. Venetoclax increased reactive oxygen species level in co-cultured AML cells, contributed to transfer more mitochondria from BM-MSCs to AML cells and protect AML cells from apoptosis. Dexamethasone combined with venetoclax induced more apoptosis, but dexamethasone reduced the venetoclax-induced reactive oxygen species level in AML cells and reduced the transfer of mitochondria from BM-MSCs to AML cells. This may lead to a diminished protective effect of BM-MSCs on AML cells. Together, our findings indicated that venetoclax in combination with dexamethasone could be a promising therapy in AML.

Lycorine induces apoptosis of acute myeloid leukemia cells and inhibits triglyceride production via binding and targeting FABP5.

Acute myeloid leukemia (AML) is the most common hematopoietic malignancy with abnormal lipid metabolism. However, currently available information on the involvement of the alterations in lipid metabolism in AML development is limited. In this study, we demonstrate that FABP5 expression facilitates AML cell viability, protects AML cells from apoptosis, and maintains triglyceride production. Our bioinformatics analysis revealed that FABP5 expression was upregulated and correlated with unfavorable overall survival of AML patients. FABP5 expression may be used to distinguish normal and AML with high accuracy. FABP5-based risk score was an independent risk factor for AML patients. AML patients with highly expressed FABP5 predicted resistance to drugs. In vitro study showed that FABP5 expression was remarkably elevated in primary AML blasts and an AML cell line. Silencing FABP5 expression attenuated AML cell viability, reduced triglyceride production and lipid droplet accumulation, and induced apoptosis. We utilized AutoDock online tool to identify lycorine as an FABP5 inhibitor by binding FABP5 at amino acid residues Ile54, Thr56, Thr63, and Arg109. Lycorine treatment downregulated the expression levels of FABP5 and its target PPARγ, impaired AML cell viability, triggered apoptosis, and reduced triglyceride production in AML cells. These results demonstrate that FABP5 is critical for AML cell survival and highlight a novel metabolic vulnerability for AML.

RIPK3 Deficiency Caused By DNA Hypermethylation Blocks R-2-Hydroxyglutarate Induced Necroptosis in AML with IDH Mutation

Background Mutations in isocitrate dehydrogenases (IDH) are frequently identified in 10% - 20% of acute myeloid leukemia (AML) cases. IDH mutations induce a neomorphic enzymatic function that catalyzes the conversion of α-ketoglutarate (α-KG) to the R enantiomer of 2-hydroxyglutarate (R-2HG). α-KG is also a co-substrate, together with oxygen and the co-factor iron, for α-KG-dependent dioxygenases. R-2HG is structurally close to α-KG and competitively inhibits the activity of α-KG-dependent dioxygenases. It has been reported that R-2HG inhibits the growth of IDH-wild-type AML cells by inhibiting the activity of fat mass and obesity-associated protein (FTO) and then reducing MYC and CEBPA expression. Recently, R-2HG was found to suppress aerobic glycolysis and proliferation in myeloid leukemia cells. However, why AML cells carrying IDH mutations tolerated high levels of R-2HG is not clear. Results In line with the previous study, we found that R-2HG markedly inhibited the viability of AML cells in a dose- and time-dependent manner. Interestingly, Necrostatin-1(Nec-1), a necroptosis inhibitor, could significantly prevent cell death induced by R-2HG in AML cell lines, but not Ferrostatin-1 (a ferroptosis inhibitor), Z-VAD (an apoptosis inhibitor), 3-MA (an autophagy inhibitor) and VX-765 (a pyroptosis inhibitor), suggesting that necroptosis contributed to the anti-leukemia activity of R-2HG. We evaluated the expression of genes involved in the necroptosis pathway and found the level of RIPK1 was significantly increased in R-2HG treated SKM-1 and THP-1 cells, while the expressions of RIPK3 and MLKL did not change. The knockdown of RIPK1 reduced the necroptosis caused by R-2HG in SKM-1 and THP-1 cells. Besides, a significant decrease in proliferation was observed when RIPK1 was overexpressed in AML cells which was significantly rescued by Nec-1. Among α-KG-dependent dioxygenases, the expression of lysine demethylase 2B (KDM2B) was negatively correlated with that of RIPK1. Moreover, KDM2B deficiency significantly increased RIPK1 expression and triggered necroptosis. ChIP followed by qPCR (ChIP-qPCR) showed that the RIPK1 promoter region was significantly enriched by H3K4me3, a main target of KDM2B. R-2HG treatment or knockdown of KDM2B activated H3K4me3 and increased RIPK1 expression. By comparing the expression of necroptosis-related genes between R-2HG-resistant and sensitive cell lines (GSE87187), we found that RIPK3, another key player of necroptosis, was under-expressed in R-2HG-resistant cell lines. Consistently, RIPK3 was lowly expressed in IDH-mutant primary AML cells compared to that of IDH wild-type primary AML cells. We found that enhanced RIPK3 levels increased the toxicity of R-2HG in R-2HG-resistant cell lines. Methylation-specific PCR (MS-PCR) revealed that methylation occurred in this region of genomic DNA near the TSS of RIPK3 in R-2HG-resistant cell lines. Primary cells from IDH-mutant AML patients were more sensitive to decitabine than those from IDH wild-type AML patients. Conclusion Herein, we reported that R-2HG triggered necroptosis in AML cell lines and IDH wild-type primary AML cells via KDM2B/RIPK1 signal pathway. The loss of RIPK3 expression resulting from RIPK3 promoter hypermethylation contributed to R-2HG tolerance in IDH mutated primary AML cells and R-2HG-resistant AML cell lines. IDH-mutant AML cells were more sensitive to DNMT inhibitor. These results implicate that restoring RIPK3 activity is a promising way to reverse R-2HG-resistant in AML cells with IDH mutation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Hexamethylene Amiloride Sensitizes AML to Venetoclax through Inducing Lysosomal Membrane Permeabilization

Chemotherapy remains the standard therapeutic approach for acute myeloid leukemia (AML). Although several new drugs have received approval for clinical usage, including the selective BCL2 inhibitor venetoclax, refractory disease or resistance continues to be a recurring theme, and exploring more effective therapies for AML treatment remains necessary. Intracellular pH dynamics are vital determinants for cancer progression and chemoresistance. Tumors maintain a more alkaline intracellular pH (pHi) dependent on proton exporters, including sodium-hydrogen exchangers (NHEs). Elevated NHE1 expression has emerged as a biomarker for the tumorigenesis and prognosis of solid tumors. However, whether targeting NHE1 with inhibitors could inhibit AML cell growth and the underlying mechanisms remain unknown. We found that NHE1 was highly expressed in AML and predicted a worse prognosis based on data analysis of public database. Moreover, NHE1 knockdown inhibited the growth of AML cells. In addition, NHE1 inhibitor Hexamethylene amiloride (HA) significantly inhibited proliferation and promoted apoptosis in a concentration-dependent manner in both AML cell lines and primary AML cells. Next, we combined HA with several first-line or novel drugs and found that HA combined with venetoclax significantly inhibited viability of AML cells. AML patients with higher NHE1 expression were less sensitive to BCL-2 inhibitors. This suggested that HA and venetoclax might be an effective combination to treat AML. As expected, HA synergized with venetoclax to inhibit proliferation and promote apoptosis. In vivo potential of HA combined with venetoclax was evaluated in a MV4-11-derived xenograft mouse model (Fig.1). The combinational regimen prolonged survival and alleviated leukemia burden in bone marrow, spleen and peripheral blood. We further validated the effect of HA with venetoclax with primary AML cells. Consistent with results in cell lines, HA combined with venetoclax also exerted synergistic effect in inhibiting viability and promoting apoptosis. RNA-Seq analysis revealed that lysosome pathway was significantly enriched in the combination group. We further verified the increased quantity of lysosome, and the swelling and rupture of lysosome with TEM (Fig.2). Moreover, HA combined with venetoclax induced obvious LGALS3 puncta formation in this cell line, which represented the occurrence of lysosomal membrane permeabilization (LMP), leading to the release of proteases which eventually results in cell death. In conclusion, our results for the first time provide evidence that the NHE1 inhibitor HA or its combination with venetoclax efficiently inhibits the growth of AML in vitro and in vivo. This study might shed light on the clinical treatment of AML involving proton exporter inhibitors with venetoclax as combinatory regime. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Selected Articles from This Issue

Mutant NRASG12V drives acute myeloid leukemia (AML) cell proliferation and self-renewal in a mutually exclusive manner. Previous studies demonstrated that AML cell proliferation and self-renewal are associated with differential NRASG12V transcript levels, but whether different NRASG12V protein levels dictate proliferative versus self-renewal phenotypes is not known. To address that knowledge gap, Kurata and colleagues engineered AML cell lines in which tetracycline-inducible NRASG12V expression levels are tunable using various doxycycline doses. The authors found that moderate NRASG12V protein expression promotes AML cell proliferation, whereas higher NRASG12V protein expression facilitates AML cell senescence and self-renewal. Using mass cytometry, the authors showed that abundances of several downstream NRASG12V effectors, including known stemness mediators such as β-catenin, increase in a dose-dependent fashion, whereas others, such as phosphorylated STAT1, are not dose-dependent. Overall, this study demonstrates that differential NRASG12V protein levels disparately drive AML cell proliferation and self-renewal and illuminates the downstream signaling dynamics underlying each phenotype.Tumor cell heterogeneity is a major impedance in eliminating cancer, as it promotes therapy-resistant clone selection in response to treatment. Identifying biomarkers indicative of tumor heterogeneity may help quantify it and uncover therapeutic vulnerabilities, but such biomarkers remain elusive. In their study, So and colleagues discovered that DNA methyltransferase 3B (DNMT3B) protein expression displays marked heterogeneity in primary tumors from triple-negative breast cancer (TNBC) patients and TNBC mouse models. By selecting DNMT3B-high and -low clones from 4T1 cells, labeling them with different fluorescent dyes, and quantifying them in circulation and lung metastases after orthotopic injection, the authors found that DNMT3B-high cells are more metastatic than DNMT3B-low cells. Mechanistically, prostaglandin E2 (PGE2) induces DNMT3B expression, and DNMT3B regulates expression of epithelial–mesenchymal transition effectors including vimentin, Twist2, and Snai1. Perioperative treatment with celecoxib, which lowers PGE2 expression, alongside DNMT inhibitor 5-azacytidine and other chemotherapeutic drugs decreases tumor recurrence and metastasis after primary tumor removal. Taken together, this study presents DNMT3B as a therapeutically targetable marker and effector of tumor heterogeneity.Therapeutic challenges and poor outcomes in pancreatic cancer make further elucidating its underlying molecular mechanisms and therapeutic vulnerabilities critical. While long non-coding RNA (lncRNA) α-2-macroglobulin-antisense 1 (A2M-AS1) expression positively correlates with overall survival in pancreatic cancer as well as ferroptosis-related genes, how A2M-AS1 might regulate ferroptosis and whether it does so in pancreatic cancer has not been solved. In their study, Qiu and colleagues found that pharmacologically inducing ferroptosis in pancreatic cell lines augments A2M-AS1 expression, and that modulating A2M-AS1 abundance using shRNA and overexpression inhibits and enhances ferroptosis, respectively. Accordingly, A2M-AS1 overexpression limits pancreatic cancer cell growth both in vitro and in vivo. An RNA pull-down and mass spectrometry revealed that A2M-AS1 interacts with PCBP3. Additional experiments demonstrated that the interaction between A2M-AS1 and PCBP3 abrogates mTOR and AKT activation, while increasing p38 activation and ferroptosis. In sum, this study unveils a novel molecular mechanism by which ferroptosis evasion occurs in pancreatic cancer.Acute myeloid leukemia (AML) cells are dependent on oxidative metabolism. However, electron transport chain complex II (CII) targeting agents and their potential effects on AML cell metabolism and viability have not been assessed. To evaluate CII therapeutic targeting in AML, Roma and colleagues abrogated expression of CII chaperone protein succinate dehydrogenase assembly factor 1 (SDHAF1) using shRNA in AML cell lines. Using an in silico screen and HPLC analysis, the authors also identified shikonin as a CII small molecule inhibitor. Both SDHAF1 ablation and shikonin promote AML cell death in vitro and in vivo, and stable isotope tracing demonstrated concurrent tricarboxylic acid (TCA) cycle truncation. The authors also showed that SDHAF1 ablation and shikonin increase glutamine flux into the TCA cycle via deamination to α-ketoglutarate as well as reductive flux to aspartate. Accordingly, supplementing α-ketoglutarate undermines shikonin effectiveness, and pharmacologically inhibiting glutaminase augments it. Altogether, this study reveals a novel therapeutic target and accompanying therapeutic agent in AML and identifies anaplerotic glutamine metabolism as a compensatory mechanism and therapeutic vulnerability in CII inhibition.

Hsa_circ_0044907 promotes acute myeloid leukemia progression through upregulating oncogene KIT via sequestering miR-186-5p

ABSTRACT Background: It has been reported that circular RNA hsa_circ_0044907 (circ_0044907) expression is overtly elevated in acute myeloid leukemia (AML) patient-derived BMMCs. However, the effect of circ_0044907 on AML progression remains un-clarified. Methods: Expression of circ_0044907 in BM and AML cells were detected with real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Cell viability, proliferation, apoptosis, and cycle progression were determined by 3-(4,5-Dimethylthiazol-2-yl)−2,5-Diphenyltetrazolium Bromide (MTT), 5-ethynyl-2’-deoxyuridine (EDU), and flow cytometry assays. The regulatory mechanism of circ_0044907 was predicted by bioinformatics analysis and validated by dual-luciferase reporter, RNA pull-down, and RNA immunoprecipitation (RIP) assays. In vivo experiments were carried out to verify the function of circ_0044907. Results: Circ_0044907 was overexpressed in AML patient-derived BM and AML cells. Furthermore, circ_0044907 could distinguish AML patients from healthy controls, and high circ_0044907 expression in BM had a poor prognosis for AML patients, implying that circ_0044907 served as a diagnostic and prognostic indicator for AML. Functionally, circ_0044907 silencing reduced cell viability, restrained cell proliferation, arrested cell cycle progression, and induced cell apoptosis in AML cells in vitro. Furthermore, circ_0044907 knockdown decreased AML cell growth in xenograft mouse models. Mechanically, circ_0044907 sponged miR-186-5p to block the inhibiting effect of miR-186-5p on KIT. Silenced miR-186-5p expression weakened circ_0044907 knockdown mediated suppression on AML cell viability, proliferation, and cycle progression. Also, forced KIT expression weakened miR-186-5p upregulation mediated inhibition on AML cell viability, proliferation, and cycle progression. Conclusion: Circ_0044907 absorbed miR-186-5p to block the inhibiting impact of miR-186-5p on KIT, thus promoting AML progression.