Dietary γ-mangostin triggers immunogenic cell death and activates cGAS signaling in acute myeloid leukemia.

Immunogenic cell death (ICD), one of cell-death types through release of damage-associated molecular patterns from dying tumor cells, activates tumor-specific immune response and elicits anti-tumor immunity by traditional radiotherapy and chemotherapy. However, whether natural products could induce ICD in leukemia is not elucidated. Here, we report dietary γ-mangostin eradicates murine primary leukemic cells and prolongs the survival of leukemic mice. As well, it restrains primary leukemic cells and CD34+ leukemic progenitor cells from leukemia patients. Strikingly, γ-mangostin attenuates leukemic cells by inducing ICD as characterized by expression of HSP90B1, ANXA1 and IL1B. Additionally, γ-mangostin accelerates cytoplasmic chromatin fragments generation, promoting DNA damage response, and enhances cGAS activation, leading to up-regulation of chemokines. Meanwhile, it induces HDAC4 degradation and acetylated histone H3 accumulation, which promotes chemokines transcription. Ultimately, CD8+ T cell is activated and recruited by γ-mangostin-induced chemokines in the microenvironment. Our study identifies γ-mangostin triggers ICD and activates cGAS signaling through DNA damage response and epigenetic modification. Therefore, dietary γ-mangostin would act as a potential agent to provoke anti-tumor immunity in the prevention and treatment of leukemia.

STAT5 promotes PD-L1 expression by facilitating histone lactylation to drive immunosuppression in acute myeloid leukemia.

Immunotherapy is a revolutionized therapeutic strategy for tumor treatment attributing to the rapid development of genomics and immunology, and immune checkpoint inhibitors have successfully achieved responses in numbers of tumor types, including hematopoietic malignancy. However, acute myeloid leukemia (AML) is a heterogeneous disease and there is still a lack of systematic demonstration to apply immunotherapy in AML based on PD-1/PD-L1 blockage. Thus, the identification of molecules that drive tumor immunosuppression and stratify patients according to the benefit from immune checkpoint inhibitors is urgently needed. Here, we reported that STAT5 was highly expressed in the AML cohort and activated the promoter of glycolytic genes to promote glycolysis in AML cells. As a result, the increased-lactate accumulation promoted E3BP nuclear translocation and facilitated histone lactylation, ultimately inducing PD-L1 transcription. Immune checkpoint inhibitor could block the interaction of PD-1/PD-L1 and reactive CD8+ T cells in the microenvironment when co-culture with STAT5 constitutively activated AML cells. Clinically, lactate accumulation in bone marrow was positively correlated with STAT5 as well as PD-L1 expression in newly diagnosed AML patients. Therefore, we have illustrated a STAT5-lactate-PD-L1 network in AML progression, which demonstrates that AML patients with STAT5 induced-exuberant glycolysis and lactate accumulation may be benefited from PD-1/PD-L-1-based immunotherapy.

SOX1 acts as a tumor hypnotist rendering nasopharyngeal carcinoma cells refractory to chemotherapy.

SOX1, a well-known tumor suppressor, delays malignant progression in most cancer types. However, high expression of SOX1 in late-stage head and neck squamous cell carcinoma leads to poor prognosis. In this study, we show that SOX1 induces nasopharyngeal carcinoma (NPC) cells to enter a quiescent state. Using a model that mimics therapeutic resistance and tumor recurrence, a subpopulation of SOX1-induced NPC cells is refractory to paclitaxel, a cell cycle-specific chemotherapy drug. These cells maintain a quiescent state with decreased translational activity and down-regulated cell growth potential. However, once SOX1 expression is decreased, the NPC cells recover and enter a proliferative state. The chemotherapy resistance induced by SOX1 can not pass to next generation, as the cells that undergo re-proliferation become sensitive to paclitaxel again. Moreover, SOX1 directly binds to the promoter region of the MYC gene, leading to transcriptional suppression. When switching to a paclitaxel-free culture environment, the cells with decreased levels of SOX1 re-express MYC, resulting in increased abundance of proliferative cancer cells. Our study presents an evolutionary trade-off between tumor growth and chemoresistance orchestrated by SOX1-MYC in NPC. Basing on the dynamic role of SOX1 in different stages of cancer development, SOX1 would be regarded as a "tumor hypnotist".

Disruption of mitochondrial oxidative phosphorylation by chidamide eradicates leukemic cells in AML.

PURPOSE: Nowadays, the oxidative phosphorylation (OXPHOS) correlated with leukemogenesis and treatment response is extensive. Thus, exploration of novel approaches in disrupting OXPHOS in AML is urgently needed. MATERIALS AND METHODS: Bioinformatical analysis of TCGA AML dataset was performed to identify the molecular signaling of OXPHOS. The OXPHOS level was measured through a Seahorse XFe96 cell metabolic analyzer. Flow cytometry was applied to measure mitochondrial status. Real-time qPCR and western blot were used to analyze the expression of mitochondrial or inflammatory factors. MLL-AF9-induced leukemic mice were conducted to measure the anti-leukemia effect of chidamide. RESULTS: Here, we reported that AML patients with high OXPHOS level were in a poor prognosis, which was associated with high expression of HDAC1/3 (TCGA). Inhibition of HDAC1/3 by chidamide inhibited cell proliferation and induced apoptotic cell death in AML cells. Intriguingly, chidamide could disrupt mitochondrial OXPHOS as assessed by inducing mitochondrial superoxide and reducing oxygen consumption rate, as well as decreasing mitochondrial ATP production. We also observed that chidamide augmented HK1 expression, while glycolysis inhibitor 2-DG could reduce the elevation of HK1 and improve the sensitivity of AML cells exposed to chidamide. Furthermore, HDAC3 was correlated with hyperinflammatory status, while chidamide could downregulate the inflammatory signaling in AML. Notably, chidamide eradicated leukemic cells in vivo and prolonged the survival time of MLL-AF9-induced AML mice. CONCLUSION: Chidamide disrupted mitochondrial OXPHOS, promoted cell apoptosis and reduced inflammation in AML cells. These findings exhibited a novel mechanism that targeting OXPHOS would be a novel strategy for AML treatment.

Mutant C/EBPα p30 alleviates immunosuppression of CD8+ T cells by inhibiting autophagy-associated secretion of IL-1ß in AML.

OBJECTIVES: Mutant C/EBPα p30 (mp30), the product of C/EBPα double mutations (DM), lacks transactivation domain 1 and has C-terminal loss-of-function mutation. Acute myeloid leukaemia (AML) patients harbouring C/EBPα DM could be classified as a distinct subgroup with favourable prognosis. However, the underlying mechanism remains elusive. MATERIALS AND METHODS: Autophagy regulated by mp30 was detected by western blot and immunofluorescence. Immune infiltration analysis and GSEA were performed to investigate autophagic and inflammatory status of AML patients from the GSE14468 cohort. Flow cytometry was applied to analyse T cell activation. RESULTS: Mp30 inhibited autophagy by suppressing nucleus translocation of NF-κB. Autophagy-associated secretion of IL-1ß was decreased in mp30-overexpressed AML cells. Bioinformatic analysis revealed that inflammatory status was attenuated, while CD8+ T cell infiltration was upregulated in C/EBPα DM AML patients. Consistently, the proportion of CD8+ CD69+ T cells in peripheral blood mononuclear cells (PBMCs) was upregulated after co-culture with mp30 AML cell conditional culture medium. Knock-out of IL-1ß in AML cells also enhanced CD8+ T cell activation. Accordingly, IL-1ß expression was significantly reduced in the bone marrow (BM) cells of C/EBPα DM AML patients compared to the wildtype, while the CD8+ CD69+ T cell proportion was specifically elevated. CONCLUSIONS: C/EBPα DM alleviates immunosuppression of CD8+ T cells by inhibiting the autophagy-associated secretion of IL-1ß, which elucidated that repression of autophagy-related inflammatory response in AML patients might achieve a favourable clinical benefit.

cGAS/STING cross-talks with cell cycle and potentiates cancer immunotherapy.

The correct duplication and transfer of genetic material to daughter cells is the major event of cell division. Dysfunction of DNA replication or chromosome segregation presents challenges in cancer initiation and development as well as opportunities for cancer treatment. Cyclic GMP-AMP synthase (cGAS) of the innate immune system detects cytoplasmic DNA and mediates downstream immune responses through the molecule stimulator of interferon genes (STING). However, how cytosolic DNA sensor cGAS participates in guaranteeing accurate cell division and preventing tumorigenesis is still unclear. Recent evidence indicates malfunction of cGAS/STING pathway in cancer progression. Cell cycle-targeted therapy synergizes with immunotherapy via cGAS/STING activation, leading to promising therapeutic benefit. Here, we review the interactions between cell cycle regulation and cGAS/STING signaling, thus enabling us to understand the role of cGAS/STING in cancer initiation, development, and treatment.

Microbial community and functional prediction during the processing of salt production in a 1000-year-old marine solar saltern of South China.

In Hainan Island, South China, a 1000-year-old marine saltern has been identified as an intangible cultural heritage due to its historical complicated salt-making techniques, whereas the knowledge about this saltern is extremely limited. Herein, DNA sequencing and biochemical technologies were applied to determine bacterial and fungal communities of this saltern and their possible functions during four stages of salt-making, i.e. seawater storage, mud solarization, brine concentrating, and solar crystallization. The results showed that both of bacterial and fungal communities were suffered from significant changes during processing of salt-making in Danzhou Ancient Saltern, whereas the richness and diversity of bacterial community dominated by Proteobacteria, Bacteroidota and Cyanobacteria was considerably greater than that of fungal community dominated by Ascomycota, Basidiomycota and Mortierellomycota. Additionally, the succession of bacterial community was closely associated with both of salt physicochemical properties (Na+, Cl-, total phosphorus, total nitrogen, Ca2+ and Mg2+) and bacteria themselves, whereas fungal community was more closely associated with physicochemical properties than fungi themselves. Importantly, Cyanobium_PCC-6307, Synechococcus_CC9902, Marinobacter, Prevotella and Halomonas as dominant bacterial genera respectively related to the metabolisms of amino acid, carbohydrate, terpenoids/polyketides, lipid and nucleotide were correlated with salt flavors. Saprophytic and saprotroph-symbiotroph fungi dominated by Aspergillus, Mortierella, Amanita, Neocucurbitaria and Tausonia also played core roles in the formation of salt flavors including umami and sweet smells. These findings revealed the highly specified microbiome community in this 1000-year-old saltern that mainly selected by brine solarization on basalt platforms, which is helpful to explore the underlying mechanisms of traditional salt-making techniques and to explore the useful microbes for nowadays food, medicine and chemical industries.

A Novel Aurora Kinase Inhibitor Attenuates Leukemic Cell Proliferation Induced by Mesenchymal Stem Cells.

Acute myeloid leukemia (AML) mesenchymal stem cells (MSCs) play an essential role in protecting leukemic cells from chemotherapeutic agents through activating a wide range of adhesion molecules and cytokines. Thus, more attention should be paid to attenuate the protection of leukemic cells by MSCs. By examining the gene expression files of MSCs from healthy donors and AML patients through high-throughput microarrays, we found that interleukin (IL)-6 was an important cytokine secreted by AML MSCs to protect leukemic cells, contributing to disease progression. Strikingly, Aurora A (AURKA) was activated by IL-6, offering a new target to interfere with leukemia. Importantly, a novel AURKA inhibitor, PW21, showed excellent AURKA kinase inhibitory activities and attenuated the interaction of leukemic cells and the microenvironment. PW21 inhibited MSC-induced cell proliferation, colony formation, and migration, and it induced cell apoptosis. Mechanically, PW21 could inhibit IL-6 secreted by MSCs. Moreover, we found that PW21 displayed a strong anti-leukemia effect on non-obese diabetic (NOD)-severe combined immunodeficiency (SCID) and murine MLL-AF9 leukemic models. PW21 significantly prolonged the survival of leukemic mice and eliminated the leukemic progenitor cells. AURKA inhibitor PW21 could provide a new approach for treatment of leukemia through blocking the protection by the leukemic microenvironment in clinical application.

SOX1 promotes differentiation of nasopharyngeal carcinoma cells by activating retinoid metabolic pathway.

Undifferentiation is a key feature of nasopharyngeal carcinoma (NPC), which presents as a unique opportunity for intervention by differentiation therapy. In this study, we found that SOX1 inhibited proliferation, promoted differentiation, and induced senescence of NPC cells, which depended on its transcriptional function. RNA-Seq-profiling analysis showed that multiple undifferentiated markers of keratin family, including KRT5, KRT13, and KRT19, were reduced in SOX1 overexpressed NPC cells. Interestingly, gene ontology (GO) analysis revealed genes in SOX1 overexpressed cells were enriched in extracellular functions. The data of LC/MS untargeted metabolomics showed that the content of retinoids in SOX1 overexpressed cells and culture medium was both higher than that in the control group. Subsequently, we screened mRNA level of genes in retinoic acid (RA) signaling or metabolic pathway and found that the expression of UDP-glucuronosyltransferases was significantly decreased. Furtherly, UGT2B7 could rescue the differentiation induced by SOX1 overexpression. Inhibition of UGTs by demethylzeylasteral (T-96) could mimic SOX1 to promote the differentiation of NPC cells. Thus, we described a mechanism by which SOX1 regulated the differentiation of NPC cells by activating retinoid metabolic pathway, providing a potential target for differentiation therapy of NPC.

Aurora kinase inhibitor restrains STAT5-activated leukemic cell proliferation by inducing mitochondrial impairment.

Current chemotherapy regimens on acute myeloid leukemia (AML) still have some drawbacks, such as intolerance and drug resistance, which calls need for the development of targeted therapy. Signal transducer and activator of transcription 5 (STAT5) is often overexpressed or abnormally activated in leukemia and involved in cell self-renewal, proliferation, and stress adaptation. Overexpressed Aurora A (AURKA) is associated with poor prognosis in tumors, and inhibitors against AURKA are already in clinical trials. However, it has rarely been reported whether AURKA inhibitors restrain STAT5-activated leukemia cells. In this study, we constructed STAT5 constitutively activated (cS5) cells and found that STAT5 promoted cell proliferation and colony formation. Moreover, cS5 cells showed elevated reactive oxygen species (ROS) and adenosine triphosphate (ATP) levels, which indicated higher mitochondrial metabolism in cS5 cells. A novel AURKA inhibitor AKI604 was synthesized and showed significant inhibitory effects to the proliferation and colony formation in both STAT5 constitutively activated and nonactivated AML cells. AKI604 induced mitochondrial impairment, leading to the disruption of mitochondrial membrane potential and the elevation of ROS as well as cellular calcium (Ca2+ ) levels. AKI604 could also decline basal oxygen consumption rate and ATP biosynthesis, indicating the damage of oxidative phosphorylation. Furthermore, AKI604 exhibited significant antitumor effect in the HL-60 cS5 xenograft model of the BALB/c nude mice without an obvious influence on mice body weight and other healthy indicators. This study suggested that AKI604 was a potential strategy to overcome STAT5-induced leukemic proliferation in AML treatment by inducing mitochondrial impairment.

Prediction of competing endogenous RNA coexpression network as prognostic markers in AML.

Recently, competing endogenous RNAs (ceRNAs) hypothesis has gained a great interest in the study of molecular biological mechanisms of cancer occurrence and progression. However, studies on leukemia are limited, and there is still a lack of comprehensive analysis of lncRNA-miRNA-mRNA ceRNA regulatory network of AML based on high-throughput sequencing and large-scale sample size. We obtained RNA-Seq data and compared the expression profiles between 407 normal whole blood (GTEx) and 151 bone marrows of AML (TCGA). The similarity between two sets of genes with trait in the network was analyzed by weighted correlation network analysis (WGCNA). MiRcode, starBase, miRTarBase, miRDB and TargetScan was used to predict interactions between lncRNAs, miRNAs and target mRNAs. At last, we identified 108 lncRNAs, 10 miRNAs and 8 mRNAs to construct a lncRNA-miRNA-mRNA ceRNA network, which might act as prognostic biomarkers of AML. Among the network, a survival model with 8 target mRNAs (HOXA9+INSR+KRIT1+MYB+SPRY2+UBE2V1+WEE1+ZNF711) was set up by univariate and multivariate cox proportional hazard regression analysis, of which the AUC was 0.831, indicating its sensitivity and specificity in AML prognostic prediction. CeRNA networks could provide further insight into the study on gene regulation and AML prognosis.

UHRF1 suppression promotes cell differentiation and reduces inflammatory reaction in anaplastic thyroid cancer.

Anaplastic thyroid cancer (ATC), an undifferentiated subtype of thyroid cancer, is one of the most malignant endocrine cancer with low survival rate, and resistant to chemotherapy and radiation therapy. Here we found that UHRF1 was highly expressed in human ATC compared with normal tissue and papillary thyroid cancer (PTC). Knockdown of UHRF1 inhibited proliferation of ATC in vitro and in vivo. Consistently, overexpression of UHRF1 promoted the proliferation of thyroid cancer cells. Moreover, UHRF1 suppression induced differentiation of three-dimensional (3D) cultured ATC cells and down-regulated the expression of dedifferentiation marker (CD97). The stem cell markers (Sox2, Oct4 and Nanog) were suppressed simultaneously. In addition, UHRF1 knockdown reduced the transcription of cytokines (IL-8, TGF-α and TNF-α), which might relieve the inflammatory reaction in ATC patients. This study demonstrated a role of UHRF1 in ATC proliferation, dedifferentiation and inflammatory reaction, presenting UHRF1 as a potential target in ATC therapy.

Synthesis and biological evaluation of aurora kinases inhibitors based on N-trisubstituted pyrimidine scaffold.

The inhibition of the members of aurora kinase family using ATP-competitive small molecules is an effective method for anticancer therapeutics. Based on our previous work, we synthesized 12 new N-trisubstituted pyrimidine derivatives and evaluated their biological activities and stabilities. Among them, compound 11j showed the best inhibition against aurora A kinase (IC50 = 7.1 nM), human leukemia cell line U937 (IC50 = 12.2 nM) and the growth of U937 xenograft tumors in vivo. By the flow cytometry and immunofluorescence analysis of U937, we found that compound 11j can induced polyploidy formation including (4N, 8N and 16N) and induce defects in both chromosome alignment and spindle formation. Furthermore, compound 11j exhibited good chemical, physical, and thermal stabilities. All these results suggested that 11j is a promising lead compound for further development of anticancer drugs.

The neuroleptic drug pimozide inhibits stem-like cell maintenance and tumorigenicity in hepatocellular carcinoma.

Drug repurposing is currently an important approach for accelerating drug discovery and development for clinical use. Hepatocellular carcinoma (HCC) presents drug resistance to chemotherapy, and the prognosis is poor due to the existence of liver cancer stem-like cells. In this study, we investigated the effect of the neuroleptic agent pimozide to inhibit stem-like cell maintenance and tumorigenicity in HCC. Our results showed that pimozide functioned as an anti-cancer drug in HCC cells or stem-like cells. Pimozide inhibited cell proliferation and sphere formation capacities in HCC cells by inducing G0/G1 phase cell cycle arrest, as well as inhibited HCC cell migration. Surprisingly, pimozide inhibited the maintenance and tumorigenicity of HCC stem-like cells, particularly the side population (SP) or CD133-positive cells, as evaluated by colony formation, sphere formation and transwell migration assays. Furthermore, pimozide was found to suppress STAT3 activity in HCC cells by attenuating STAT3-dependent luciferase activity and down-regulating the transcription levels of downstream genes of STAT3 signaling. Moreover, pimozide reversed the stem-like cell tumorigenic phenotypes induced by IL-6 treatment in HCC cells. Further, the antitumor effect of pimozide was also proved in the nude mice HCC xenograft model. In short, the anti-psychotic agent pimozide may act as a novel potential anti-tumor agent in treating advanced HCC.

Aurora A Kinase Inhibitor AKI603 Induces Cellular Senescence in Chronic Myeloid Leukemia Cells Harboring T315I Mutation.

The emergence of resistance to imatinib mediated by mutations in the BCR-ABL has become a major challenge in the treatment of chronic myeloid leukemia (CML). Alternative therapeutic strategies to override imatinib-resistant CML are urgently needed. In this study, we investigated the effect of AKI603, a novel small molecule inhibitor of Aurora kinase A (AurA) to overcome resistance mediated by BCR-ABL-T315I mutation. Our results showed that AKI603 exhibited strong anti-proliferative activity in leukemic cells. AKI603 inhibited cell proliferation and colony formation capacities in imatinib-resistant CML cells by inducing cell cycle arrest with polyploidy accumulation. Surprisingly, inhibition of AurA by AKI603 induced leukemia cell senescence in both BCR-ABL wild type and T315I mutation cells. Furthermore, the induction of senescence was associated with enhancing reactive oxygen species (ROS) level. Moreover, the anti-tumor effect of AKI603 was proved in the BALB/c nude mice KBM5-T315I xenograft model. Taken together, our data demonstrate that the small molecule AurA inhibitor AKI603 may be used to overcome drug resistance induced by BCR-ABL-T315I mutation in CML.

Celecoxib suppresses autophagy and enhances cytotoxicity of imatinib in imatinib-resistant chronic myeloid leukemia cells.

BACKGROUND: Chronic myelogenous leukemia (CML) is a hematological stem cell disorder. Tyrosine kinase inhibitors (TKIs) are the standard treatments for CML, but a number of patients fail to respond effectively due to gene mutations. Celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, has been shown to have anti-tumor effect on solid tumor whereas the anti-CML effect and its underlying mechanism have not been completely elucidated. METHODS: The cytotoxic effects of celecoxib and/or imatinib were evaluated by MTT assay. Cell cycle distribution was examined by propidium iodide (PI) assay. Apoptosis or necrosis was analyzed by Annexin-V/PI, Hoechst 33342 staining and Western blot assays. Autophagy suppression effect of celecoxib was examined by Western blot and LysoTracker probe labelling. Lysosensor probe labelling was used to detect the effect of celecoxib on the lysosomal function. RESULTS: In this study, we found that celecoxib had therapy efficacy in KBM5 and imatinib-resistant KBM5-T315I CML cell lines. Celecoxib caused significant cytotoxic effect in both cell lines, especially in KBM5-T315I cells exposed to celecoxib for 72 h. Moreover, celecoxib induced necrosis and apoptosis while inhibited autophagy in CML cell lines and patient samples. Furthermore, this study demonstrated that celecoxib prevented the autophagic flux by inhibiting lysosome function. Celecoxib was tested in combination with imatinib, demonstrating that celecoxib could strengthen the cytotoxicity of imatinib in imatinib-resistant CML cells. CONCLUSIONS: These findings showed that celecoxib had therapy efficacy on CML cells. And it is first time to demonstrate that celecoxib is an autophagy suppresser and a combination of celecoxib and imatinib might be a promising new therapeutic strategy for imatinib-resistant CML cells.

Design, Synthesis, and Biological Evaluation of Substituted Pyrimidines as Potential Phosphatidylinositol 3-Kinase (PI3K) Inhibitors.

Three series of substituted pyrimidines were designed and synthesized. All target compounds were screened for kinase inhibitory activities against PI3Kα, and most IC50 values were found within the nanomolar range. Compounds 5d and 5p displayed comparable activities relative to the positive control 5a. 5p also showed a significant isozyme selectivity (PI3Kß/α). Furthermore, the cytotoxicities of these pyrimidines against human cancer cell lines were evaluated and the in vivo anticancer effect of 5d was also tested.

The Philadelphia chromosome in leukemogenesis.

The truncated chromosome 22 that results from the reciprocal translocation t(9;22)(q34;q11) is known as the Philadelphia chromosome (Ph) and is a hallmark of chronic myeloid leukemia (CML). In leukemia cells, Ph not only impairs the physiological signaling pathways but also disrupts genomic stability. This aberrant fusion gene encodes the breakpoint cluster region-proto-oncogene tyrosine-protein kinase (BCR-ABL1) oncogenic protein with persistently enhanced tyrosine kinase activity. The kinase activity is responsible for maintaining proliferation, inhibiting differentiation, and conferring resistance to cell death. During the progression of CML from the chronic phase to the accelerated phase and then to the blast phase, the expression patterns of different BCR-ABL1 transcripts vary. Each BCR-ABL1 transcript is present in a distinct leukemia phenotype, which predicts both response to therapy and clinical outcome. Besides CML, the Ph is found in acute lymphoblastic leukemia, acute myeloid leukemia, and mixed-phenotype acute leukemia. Here, we provide an overview of the clinical presentation and cellular biology of different phenotypes of Ph-positive leukemia and highlight key findings regarding leukemogenesis.

Targeting GLI1 Suppresses Cell Growth and Enhances Chemosensitivity in CD34+ Enriched Acute Myeloid Leukemia Progenitor Cells.

BACKGROUND/AIMS: Resistance of leukemia stem cells (LSCs) to chemotherapy in patients with acute myeloid leukemia (AML) causes relapse of disease. Hedgehog (Hh) signaling plays a critical role in the maintenance and differentiation of cancer stem cells. Yet its role in AML remains controversial. The purpose of the present study is to investigate the role of GLI1, the transcriptional activator of Hh signaling, in AML progenitor cells and to explore the anti-AML effects of GLI small-molecule inhibitor GANT61. METHODS: The expression of GLI1 mRNA and protein were examined in AML progenitor cells and normal cells. The proliferation, colony formation, apoptosis and differentiation of AML progenitor cells were also analyzed in the presence of GANT61. RESULTS: Kasumi-1 and KG1a cells, containing more CD34+ cells, expressed higher level of GLI1 compared to U937 and NB4 cells with fewer CD34+ cells. Consistently, a positive correlation between the protein levels of GLI1 and CD34 was validated in the bone marrow mononuclear cells (BMMC) of AML patients tested. GANT61 inhibited the proliferation and colony formation in AML cell lines. Importantly, GANT61 induced apoptosis in CD34+ enriched Kasumi-1 and KG1a cells, whereas it induced differentiation in U937 and NB4 cells. Furthermore, GANT61 enhanced the cytotoxicity of cytarabine (Ara-c) in primary CD34+ AML cells, indicating that inhibition of GLI1 could be a promising strategy to enhance chemosensitivity. CONCLUSIONS: The present findings suggested that Hh signaling was activated in AML progenitor cells. GLI1 acted as a potential target for AML therapy.