Assessing the impact of COVID-19 on acute leukemia patients: a comparative analysis of hematological and biochemical parameters.

BACKGROUND: The impact of COVID-19 infection on the blood system remains to be investigated, especially with those encountering hematological malignancies. It was found that a high proportion of cancer patients are at an elevated risk of encountering COVID-19 infection. Leukemic patients are often suppressed and immunocompromised, which would impact the pathology following COVID-19 infection. Therefore, this research aims to bring valuable insight into the mechanism by which COVID-19 infection influences the hematological and biochemical parameters of patients with acute leukemia. METHODS: This retrospective investigation uses repeated measures to examine changes in hematological and biochemical parameters among patients with acute leukemia before and after COVID-19 infection at a major Saudi tertiary center. The investigation was conducted at the Ministry of National Guard-Health Affairs in Riyadh, Saudi Arabia, on 24 acute leukemia patients with COVID-19 between April 2020 and July 2023. The impact of COVID-19 on clinical parameters, comorbidities, and laboratory values was evaluated using data obtained from the electronic health records at four designated time intervals. The relative importance of comorbidities, testing preferences, and significant predictors of survival was ascertained. RESULTS: The majority of leukemic COVID-19-infected patients, primarily detected through PCR tests, were diagnosed with acute lymphoblastic leukemia (70.8%). The hematological and biochemical parameters exhibited stability, except for a brief increase in ALT and a sustained rise in AST. These changes were not statistically significant, and parameters remained normal at all time points. Additionally, an increase in monocyte count was shown at time point-3, as well as platelet counts at time point 2. CONCLUSION: While this study did not detect statistically significant effects of COVID-19 on biochemical and hematological parameters in acute leukemia patients, further investigation is needed to fully understand the potential adverse reactions and modifications following COVID-19 infection.

Long non-coding RNA as potential diagnostic markers for acute myeloid leukemia: A systematic review and meta-analysis.

BACKGROUND: Acute myeloid leukemia (AML) is aggressive type of hematological malignancy. Its poses challenges in early diagnosis, necessitating the identification of an effective biomarker. This study aims to assess the diagnostic accuracy of long noncoding RNAs (lncRNA) in the diagnosis of AML through a meta-analysis. The study is registered on the PROSPERO website with the number 493518. METHOD: A literature search was conducted in the PubMed, Embase, Hinari, and the Scopus databases to identify relevant studies. We pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the summary receiver operating characteristics (ROC) using Stata 14.1 software. Heterogeneity between studies was determined through the I2 statistic and Cochran-Q test. A random effect model was chosen due to significant heterogeneity among included studies. Meta-regression and subgroup analysis were performed to assess the potential source of heterogeneity. Furthermore, potential publication bias was estimated using Deek's funnel plot asymmetry test. RESULTS: A total of 14 articles covering 19 studies were included in this meta-analysis comprising 1588 AML patients and 529 healthy participants. The overall pooled sensitivity, specificity, PLR, NLR, DOR, and the area under the summary ROC curve were 0.85 (95% CI = 0.78-0.91), 0.82 (95% CI = 0.72-0.89), 4.7 (95% CI = 2.9-7.4), 0.18 (95% CI = 0.12-0.28), 26 (95% CI = 12-53), and 0.90 (95% CI = 0.87-0.93), respectively. Moreover, lncRNAs from non-bone marrow mononuclear cells (BMMC) had superior diagnostic value with pooled sensitivity, specificity, and AUC were 0.93, 0.82, and 0.95, respectively. CONCLUSION: This meta-analysis demonstrated that circulating lncRNAs can serve as potential diagnostic markers for AML. High accuracy of diagnosis was observed in non-BMMC lncRNAs, given cutoff value, and the GADPH internal reference gene used. However, further studies with large sample size are required to confirm our results.

Modification of the Antibiotic, Colistin, with Dextrin Causes Enhanced Cytotoxicity and Triggers Apoptosis in Myeloid Leukemia.

Introduction: Acute myeloid leukemia (AML) remains difficult to treat due to its heterogeneity in molecular landscape, epigenetics and cell signaling alterations. Precision medicine is a major goal in AML therapy towards developing agents that can be used to treat patients with different 'subtypes' in combination with current chemotherapies. We have previously developed dextrin-colistin conjugates to combat the rise in multi-drug resistant bacterial infections and overcome dose-limiting nephrotoxicity. Recent evidence of colistin's anticancer activity, mediated through inhibition of intracellular lysine-specific histone demethylase 1 (LSD1/KDM1A), suggests that dextrin-colistin conjugates could be used to treat cancer cells, including AML. This study aimed to evaluate whether dextrin conjugation (which reduces in vivo toxicity and prolongs plasma half-life) could enhance colistin's cytotoxic effects in myeloid leukemia cell lines and compare the intracellular uptake and localization of the free and conjugated antibiotic. Results: Our results identified a conjugate (containing 8000 g/mol dextrin with 1 mol% succinoylation) that caused significantly increased toxicity in myeloid leukemia cells, compared to free colistin. Dextrin conjugation altered the mechanism of cell death by colistin, from necrosis to caspase 3/7-dependent apoptosis. In contrast, conjugation via a reversible ester linker, instead of an amide, had no effect on the mechanism of the colistin-induced cell death. Live cell confocal microscopy of fluorescently labelled compounds showed both free and dextrin-conjugated colistins were endocytosed and co-localized in lysosomes, and increasing the degree of modification by succinoylation of dextrin significantly reduced colistin internalization. Discussion: Whilst clinical translation of dextrin-colistin conjugates for the treatment of AML is unlikely due to the potential to promote antimicrobial resistance (AMR) and the relatively high colistin concentrations required for anticancer activity, the ability to potentiate the effectiveness of an anticancer drug by polymer conjugation, while reducing side effects and improving biodistribution of the drug, is very attractive, and this approach warrants further investigation.

Single-cell transcriptomic analysis of the immune microenvironment in pediatric acute leukemia.

Relapse and treatment resistance pose significant challenges in the management of pediatric B cell acute lymphoblastic leukemia (B-ALL) and acute myeloid leukemia (AML). The efficacy of immunotherapy in leukemia remains limited due to factors such as the immunosuppressive tumor microenvironment (TME) and lack of suitable immunotherapeutic targets. Thus, an in-depth characterization of the TME in pediatric leukemia is warranted to improve the efficacy of immunotherapy. Here, we used single-cell RNA sequencing (scRNA-seq) to characterize the TME of pediatric B-ALL and AML, focusing specifically on bone-marrow-derived T cells. Moreover, we investigated the transcriptome changes during the initiation, remission, and relapse stages of pediatric AML. Our findings revealed that specific functional expression programs correlated with fluctuations in various T cell subsets, which may be associated with AML progression and relapse. Furthermore, our analysis of cellular communication networks led to the identification of VISTA, CD244, and TIM3 as potential immunotherapeutic targets in pediatric AML. Finally, we detected elevated proportions of γδ T cells and associated functional genes in samples from pediatric patients diagnosed with B-ALL and AML, which could inform the development of novel therapeutic approaches, potentially focusing on γδ T cells.

[Successful induction therapy for acute myeloid leukemia under management with extracorporeal membrane oxygenation].

A 53-year-old woman presented with shortness of breath and hyperleukocytosis and was admitted to our hospital. Shortly after, she went into cardiopulmonary arrest and was resuscitated. Her white blood cell count was 566,000/µl, with 94.5% cup-like blasts positive for MPO staining and FLT3-ITD positive, so she was diagnosed with acute myeloid leukemia (AML) M1. She also had disseminated intravascular coagulation and tumor lysis syndrome. Extracorporeal membrane oxygenation (ECMO) was started to manage bilateral pulmonary thromboembolism that had developed due to deep vein thrombosis, and induction therapy was performed under ECMO. On the third day of illness, the patient developed cerebral hemorrhage. Hematological remission was confirmed on the 39th day of illness. After consolidation therapy with chemotherapy and an FLT3 inhibitor, she underwent allogeneic hematopoietic stem cell transplantation, and remains alive. Case reports suggest strong evidence of mortality benefit from ECMO in patients with hematologic malignancies, particularly when ECMO served as a bridge through chemotherapy. Our patient suffered from cardiopulmonary arrest due to hyperleukocytosis and pulmonary thromboembolism, but was saved by induction of remission under ECMO. Improvements in supportive care should lead to reduction in early deaths during induction therapy.

[Expectations and challenges for clinical application of cancer genome panels in acute myeloid leukemia].

The blood cancer field has played a pioneering role in advancing precision medicine, with milestones such as development of ABL1 inhibitors for chronic myeloid leukemia. The significance of gene mutation information in AML treatment has increased, evident in classifications and guidelines from organizations such as WHO and ELN. This article examines the anticipated roles of cancer genome panels (CGPs) in AML treatment from three perspectives: diagnosis, risk stratification, and treatment selection. Use of CGPs enables more accurate diagnosis and risk stratification. In treatment selection, CGPs not only complements but also substitutes existing companion diagnostics, and is expected to be a crucial information source for future drug adoption and investigation of tumor-agnostic therapies. However, various challenges remain to be addressed, including the purpose and timing of CGPs, the time required for the tests, and how to utilize expert panels.

Venetoclax therapy and emerging resistance mechanisms in acute myeloid leukaemia.

Acute myeloid leukaemia (AML) is a highly aggressive and devastating malignancy of the bone marrow and blood. For decades, intensive chemotherapy has been the frontline treatment for AML but has yielded only poor patient outcomes as exemplified by a 5-year survival rate of < 30%, even in younger adults. As knowledge of the molecular underpinnings of AML has advanced, so too has the development new strategies with potential to improve the treatment of AML patients. To date the most promising of these targeted agents is the BH3-mimetic venetoclax which in combination with standard of care therapies, has manageable non-haematological toxicity and exhibits impressive efficacy. However, approximately 30% of AML patients fail to respond to venetoclax-based regimens and almost all treatment responders eventually relapse. Here, we review the emerging mechanisms of intrinsic and acquired venetoclax resistance in AML and highlight recent efforts to identify novel strategies to overcome resistance to venetoclax.

CoHIT: a one-pot ultrasensitive ERA-CRISPR system for detecting multiple same-site indels.

Genetic testing is crucial for precision cancer medicine. However, detecting multiple same-site insertions or deletions (indels) is challenging. Here, we introduce CoHIT (Cas12a-based One-for-all High-speed Isothermal Test), a one-pot CRISPR-based assay for indel detection. Leveraging an engineered AsCas12a protein variant with high mismatch tolerance and broad PAM scope, CoHIT can use a single crRNA to detect multiple NPM1 gene c.863_864 4-bp insertions in acute myeloid leukemia (AML). After optimizing multiple parameters, CoHIT achieves a detection limit of 0.01% and rapid results within 30 minutes, without wild-type cross-reactivity. It successfully identifies NPM1 mutations in 30 out of 108 AML patients and demonstrates potential in monitoring minimal residual disease (MRD) through continuous sample analysis from three patients. The CoHIT method is also competent for detecting indels of KIT, BRAF, and EGFR genes. Integration with lateral flow test strips and microfluidic chips highlights CoHIT's adaptability and multiplexing capability, promising significant advancements in clinical cancer diagnostics.

A CD36-dependent non-canonical lipid metabolism program promotes immune escape and resistance to hypomethylating agent therapy in AML.

Environmental lipids are essential for fueling tumor energetics, but whether these exogenous lipids transported into cancer cells facilitate immune escape remains unclear. Here, we find that CD36, a transporter for exogenous lipids, promotes acute myeloid leukemia (AML) immune evasion. We show that, separately from its established role in lipid oxidation, CD36 on AML cells senses oxidized low-density lipoprotein (OxLDL) to prime the TLR4-LYN-MYD88-nuclear factor κB (NF-κB) pathway, and exogenous palmitate transfer via CD36 further potentiates this innate immune pathway by supporting ZDHHC6-mediated MYD88 palmitoylation. Subsequently, NF-κB drives the expression of immunosuppressive genes that inhibit anti-tumor T cell responses. Notably, high-fat-diet or hypomethylating agent decitabine treatment boosts the immunosuppressive potential of AML cells by hijacking CD36-dependent innate immune signaling, leading to a dampened therapeutic effect. This work is of translational interest because lipid restriction by US Food and Drug Administration (FDA)-approved lipid-lowering statin drugs improves the efficacy of decitabine therapy by weakening leukemic CD36-mediated immunosuppression.

IL-33-dependent NF-κB activation inhibits apoptosis and drives chemoresistance in acute myeloid leukemia.

BACKGROUND: Despite recent advances in therapeutic regimens, the prognosis of acute myeloid leukemia (AML) remains poor. Following our previous finding that interleukin-33 (IL-33) promotes cell survival along with activated NF-κB in AML, we further investigated the role of NF-κB during leukemia development. METHODS: Flow cytometry was performed to value the apoptosis and proliferation. qRT-PCR and western blot were performed to detect the expression of IL-6, active caspase 3, BIRC2, Bcl-2, and Bax, as well as activated NF-κB p65 and AKT. Finally, xenograft mouse models and AML patient samples were used to verify the findings observed in AML cell lines. RESULTS: IL-33-mediated NF-κB activation in AML cell lines contributes to a reduction in apoptosis, an increase in proliferation rate as well as a decrease in drug sensitivity, which were reversed by NF-κB inhibitor, Bay-117085. Moreover, IL-33 decreased the expression of active caspase-3 while increasing the levels of BIRC2, Bcl-2, and Bax, and these effects were blocked by Bay-117085. Additionally, NF-κB activation induced by IL-33 increases the production of IL-6 and autocrine activation of AKT. Co-culture of bone marrow stroma with AML cells resulted in increased IL-33 expression by leukemia cells, along with decreased apoptosis level and reduced drug sensitivity. Finally, we confirmed the in vivo pro-tumor effect mediated by IL-33/ NF-κB axis using a xenograft model of AML. CONCLUSION: Our data indicate that IL-33/IL1RL1-dependent signaling contributes to AML cell activation of NF-κB, which in turn causes autocrine IL-6-induced activation of pAKT, supporting IL-33/NF-κB/pAKT as a potential target for AML therapy.

Multi-target measurable residual disease assessed by error-corrected sequencing in patients with acute myeloid leukemia: An ALFA study.

The evaluation of measurable residual disease (MRD) in acute myeloid leukemia (AML) using comprehensive mutation analysis by next-generation sequencing (NGS) has been investigated in several studies. However controversial results exist regarding the detection of persisting mutations in DNMT3A, TET2, and ASXL1 (DTA). Benchmarking of NGS-MRD taking into account other molecular MRD strategies has to be done. Here, we performed error-corrected-NGS-MRD in 189 patients homogeneously treated in the ALFA-0702 study (NCT00932412). Persistence of non-DTA mutations (HR = 2.23 for RFS and 2.26 for OS), and DTA mutations (HR = 2.16 for OS) were associated with poorer prognosis in multivariate analysis. Persistence of at least two mutations in complete remission (CR) was associated with a higher cumulative incidence of relapse (CIR) (HR = 3.71, p < 0.0001), lower RFS (HR = 3.36, p < 0.0001) and OS (HR = 3.81, p = 0.00023) whereas persistence of only one mutation was not. In 100 analyzable patients, WT1-MRD, but not NGS-MRD, was an independent factor for RFS and OS. In the subset of 67 NPM1 mutated patients, both NPM1 mutation detection (p = 0.0059) and NGS-MRD (p = 0.035) status were associated with CIR. We conclude that detectable NGS-MRD including DTA mutations correlates with unfavorable prognosis in AML. Its integration with alternative MRD strategies in AML management warrants further investigations.

FLT3-TKD Measurable Residual Disease Detection Using Droplet Digital PCR and Clinical Applications in Acute Myeloid Leukemia.

The tyrosine kinase domain of the FMS-Like tyrosine kinase 3 (FLT3-TKD) is recurrently mutated in acute myeloid leukemia (AML). Common molecular techniques used in its detection include PCR and capillary electrophoresis, Sanger sequencing and next-generation sequencing with recognized sensitivity limitations. This study aims to validate the use of droplet digital PCR (ddPCR) in the detection of measurable residual disease (MRD) involving the common FLT3-TKD mutations (D835Y, D835H, D835V, D835E). Twenty-two diagnostic samples, six donor controls, and a commercial D835Y positive control were tested using a commercial Bio-rad® ddPCR assay. All known variants were identified, and no false positives were detected in the wild-type control (100% specificity and sensitivity). The assays achieved a limit of detection suitable for MRD testing at 0.01% variant allelic fraction. Serial samples from seven intensively-treated patients with FLT3-TKD variants at diagnosis were tested. Five patients demonstrated clearance of FLT3-TKD clones, but two patients had FLT3-TKD persistence in the context of primary refractory disease. In conclusion, ddPCR is suitable for the detection and quantification of FLT3-TKD mutations in the MRD setting; however, the clinical significance and optimal management of MRD positivity require further exploration.

Distinct Responses to Menin Inhibition and Synergy with DOT1L Inhibition in KMT2A-Rearranged Acute Lymphoblastic and Myeloid Leukemia.

Pediatric acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) exhibit favorable survival rates. However, for AML and ALL patients carrying KMT2A gene translocations clinical outcome remains unsatisfactory. Key players in KMT2A-fusion-driven leukemogenesis include menin and DOT1L. Recently, menin inhibitors like revumenib have garnered attention for their potential therapeutic efficacy in treating KMT2A-rearranged acute leukemias. However, resistance to menin inhibition poses challenges, and identifying which patients would benefit from revumenib treatment is crucial. Here, we investigated the in vitro response to revumenib in KMT2A-rearranged ALL and AML. While ALL samples show rapid, dose-dependent induction of leukemic cell death, AML responses are much slower and promote myeloid differentiation. Furthermore, we reveal that acquired resistance to revumenib in KMT2A-rearranged ALL cells can occur either through the acquisition of MEN1 mutations or independently of mutations in MEN1. Finally, we demonstrate significant synergy between revumenib and the DOT1L inhibitor pinometostat in KMT2A-rearranged ALL, suggesting that such drug combinations represent a potent therapeutic strategy for these patients. Collectively, our findings underscore the complexity of resistance mechanisms and advocate for precise patient stratification to optimize the use of menin inhibitors in KMT2A-rearranged acute leukemia.

Immunotherapeutic targeting of surfaceome heterogeneity in AML.

Immunotherapy remains underexploited in acute myeloid leukemia (AML) compared to other hematological malignancies. Currently, gemtuzumab ozogamicin is the only therapeutic antibody approved for this disease. Here, to identify potential targets for immunotherapeutic intervention, we analyze the surface proteome of 100 genetically diverse primary human AML specimens for the identification of cell surface proteins and conduct single-cell transcriptome analyses on a subset of these specimens to assess antigen expression at the sub-population level. Through this comprehensive effort, we successfully identify numerous antigens and markers preferentially expressed by primitive AML cells. Many identified antigens are targeted by therapeutic antibodies currently under clinical evaluation for various cancer types, highlighting the potential therapeutic value of the approach. Importantly, this initiative uncovers AML heterogeneity at the surfaceome level, identifies several antigens and potential primitive cell markers characterizing AML subgroups, and positions immunotherapy as a promising approach to target AML subgroup specificities.

[Effects of PIM1 Gene on Proliferation, Apoptosis and JAK2/STAT3 Signaling Pathway of Acute Myeloid Leukemia U937 Cells].

OBJECTIVE: To investigate the effects of the serine/threonine kinase family member 1 (PIM1) gene on the proliferation and apoptosis of acute myeloid leukemia (AML) U937 cells, and the regulation effect on Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway. METHODS: Bone marrow mononuclear cells from newly diagnosed adult AML patients and patients with iron deficiency anemia were collected and PIM1 mRNA expression was detected by RT-qPCR. AML cell line U937 cells were divided into U937 group (U937 cells were cultured normally), Si-PIM1 group (U937 cells were transfected with low expression adenovirus vector containing PIM1 mRNA), Si-NC group (U937 cells were transfected with low expression adenovirus vector without PIM1 mRNA), coumermycin A1 (CoA1) group (JAK2 activator CoA1 was added to U937 cells at a concentration of 20 µmol/L), and Si-PIM1+CoA1 group (U937 cells were transfected with adenoviral vector containing low expression of PIM1 mRNA and added with CoA1 at a concentration of 20 µmol/L). After culture for 24 h, the expressions of PIM1 mRNA and protein, JAK2/STAT3 pathway, cell cycle and apoptosis-related proteins in U937 cells were detected by RT-qPCR and Western blot, the cell proliferation activity was detected by MTT assay, and flow cytometry was used to detect cell cycle changes and apoptosis rate. RESULTS: The PIM1 mRNA expression level in bone marrow mononuclear cells in AML patients was higher than that in patients with iron deficiency anemia (P < 0.05). Compared with U937 group, PIM1 mRNA and protein, phosphorylated JAK2 (p-JAK2)/JAK2, phosphorylated STAT3 (p-STAT3)/STAT3, Cyclin D1, cyclin-dependent kinase 2 (CDK2) protein, cell proliferation activity, S phase and G 2/M phase proportions were decreased in Si-PIM1 group (all P < 0.05), while p27, Caspase-3 protein, G0/G1 phase proportion and apoptosis rate were increased (all P < 0.05). However, the changes of above indicators in CoA1 group were just opposite to those in Si-PIM1 group, indicating that CoA1 could reverse the effect of Si-PIM1 on U937 cells. There were no significant differences in above indexes of U937 cells between U937 group, Si-PIM1+CoA1 group and Si-NC group (P >0.05). CONCLUSION: Knockdown of PIM1 gene expression can inhibit U937 cell proliferation and promote apoptosis, in order to alleviate ALM process, which may be related to the inhibition of JAK2/STAT3 pathway activation.

[Efficacy of Decitabine Combined with Preexcitation Regimen in Treatment of Newly Diagnosed AML Patients Who Did not Respond to Initial Standard Induction Chemotherapy].

OBJECTIVE: To investigate the efficacy of decitabine combined with preexcitation regimen in the treatment of newly diagnosed acute myeloid leukemia (AML) patients who have not been relieved by the first standard induction chemotherapy and its influence on the relative content of regulatory T lymphocytes (Tregs). METHODS: The clinical data of 102 newly diagnosed AML patients (except acute promyelocytic leukemia) who did not relieve after initial standard induction chemotherapy in Shaanxi Provincial People's Hospital from March 2013 to March 2019 were retrospectively analyzed. Fifty-one patients who accepted pre-excitation regimen were divided into regular group, while another 51 patients treated with decitabine combined with pre-excitation regimen were divided into combination group. The efficacy, incidence of toxic and side effects, Core Scale of Quality of Life (QLQ-C30) score before and after treatment, T lymphocyte subsets (CD3+, CD4+, CD4+/CD8+, Tregs) and 3-year overall survival (OS) rate were compared between the two groups. RESULTS: The total effective rate of combination group was 80.39%, which was significantly higher than 62.75% of regular group (P < 0.05). After treatment, the QLQ-C30 score of combination group was 60.27±6.96, which was significantly lower than 65.73±7.96 of regular group (P < 0.001). There was no statistical difference in the incidence of toxic and side effects between the two groups (P >0.05). After treatment, the levels of CD3+, CD4+, CD4+/CD8+ in the combination group were higher than those in the regular group (all P < 0.001), while Treg was lower (P < 0.001). The 3-year OS rate in the combination group was 72.55%, which was significantly higher than 52.94% in the regular group (P < 0.001). CONCLUSION: Decitabine combined with preexcitation regimen has a significant effect on AML patients who have not been alleviated by standard induction chemotherapy in the first course of treatment. It can reduce anti-tumor immune suppression and improve immune function by regulating the relative content of Tregs, thus prolongs survival time and improves life quality of patients without increasing adverse reactions.

[Effect of TLK2 Expression Regulated by MiR-21 on Proliferation and Apoptosis of Acute Myeloid Leukemia Cells].

OBJECTIVE: To investigate the effect of TLK2 expression regulated by miR-21 on proliferation and apoptosis of acute myeloid leukemia cells. METHODS: Seventy patients with AML admitted to our hospital from January 2019 to July 2022 were selected, while 30 patients with iron deficiency anemia were selected as the control group. Bone marrow mononuclear cells (BMMNCs) of the patients were obtained using Ficoll density gradient centrifugation. RT-qPCR was used to determine the expression levels of miR-21 and TLK2 mRNA in BMMNCs. Mimics-miR-21, mimics-NC, inhibitor-miR-21, inhibitor-NC and NC were transfected into HL-60 cells using liposome-mediated transfection technology. CCK-8 method was used to determine the activity of transfected HL-60 cells after treatment with cytarabine. The apoptosis rate of HL-60 transfected cells was determined by TUNEL method. The expression of TLK2 mRNA in HL-60 cells transfected with inhibitor-miR-21 was determined by RT-qPCR. RESULTS: The relative expression levels of miR-21 and TLK2 mRNA in BMMNCs of AML patients were significantly higher than those of controls (both P < 0.05). After HL-60 cells were treated with cytarabine, both the cell activity of inhibitor-miR-21 group and mimics-miR-21 group decreased significantly with the increase of cytarabine concentration (both P < 0.05). However, at each concentration point of cytarabine, the cell activity of inhibitor-miR-21 group was lower than that of control group (P < 0.05), while mimics-miR-21 group was higher than control group (P < 0.05). After HL-60 cells were treated with cytarabine, the apoptosis rate of inhibitor-miR-21 group was significantly increased (P < 0.05), while that of mimics-miR-21 group was significantly decreased (P < 0.05). After HL-60 cells were treated with inhibitor-miR-21, the relative expression of TLK2 mRNA decreased significantly (P < 0.05). CONCLUSION: miR-21 is highly expressed in AML patients, which may promote the apoptosis of AML cells by inhibiting the expression of TLK2.