Definition of a small core transcriptional circuit regulated by AML1-ETO.

Transcription factors regulate gene networks controlling normal hematopoiesis and are frequently deregulated in acute myeloid leukemia (AML). Critical to our understanding of the mechanism of cellular transformation by oncogenic transcription factors is the ability to define their direct gene targets. However, gene network cascades can change within minutes to hours, making it difficult to distinguish direct from secondary or compensatory transcriptional changes by traditional methodologies. To overcome this limitation, we devised cell models in which the AML1-ETO protein could be quickly degraded upon addition of a small molecule. The rapid kinetics of AML1-ETO removal, when combined with analysis of transcriptional output by nascent transcript analysis and genome-wide AML1-ETO binding by CUT&RUN, enabled the identification of direct gene targets that constitute a core AML1-ETO regulatory network. Moreover, derepression of this gene network was associated with RUNX1 DNA binding and triggered a transcription cascade ultimately resulting in myeloid differentiation.

LYL1 facilitates AETFC assembly and gene activation by recruiting CARM1 in t(8;21) AML.

Transcription factors (TFs) play critical roles in hematopoiesis, and their aberrant expression can lead to various types of leukemia. The t(8;21) leukemogenic fusion protein AML1-ETO (AE) is the most common fusion protein in acute myeloid leukemia and can enhance hematopoietic stem cell renewal while blocking differentiation. A key question in understanding AE-mediated leukemia is what determines the choice of AE to activate self-renewal genes or repress differentiation genes. Toward the resolution of this problem, we earlier showed that AE resides in the stable AETFC complex and that its components colocalize on up- or down-regulated target genes and are essential for leukemogenesis. In the current study, using biochemical and genomic approaches, we show that AE-containing complexes are heterogeneous, and that assembly of the larger AETFC (containing AE, CBFß, HEB, E2A, LYL1, LMO2, and LDB1) requires LYL1. Furthermore, we provide strong evidence that the LYL1-containing AETFC preferentially binds to active enhancers and promotes AE-dependent gene activation. Moreover, we show that coactivator CARM1 interacts with AETFC and facilitates gene activation by AETFC. Collectively, this study describes a role of oncoprotein LYL1 in AETFC assembly and gene activation by recruiting CARM1 to chromatin for AML cell survival.

Reinforced erythroid differentiation inhibits leukemogenic potential of t(8;21) leukemia.

Oncoprotein AML1-ETO (AE) derived from t(8;21)(q22;q22) translocation is typically present in a portion of French-American-British-M2 subtype of acute myeloid leukemia (AML). Although these patients have relatively favorable prognoses, substantial numbers of them would relapse after conventional therapy. Here, we explored whether reinforcing the endogenous differentiation potential of t(8;21) AML cells would diminish the associated malignancy. In doing so, we noticed an expansion of immature erythroid blasts featured in both AML1-ETO9a (AE9a) and AE plus c-KIT (N822K) (AK) murine leukemic models. Interestingly, in the AE9a murine model, a spontaneous step-wise erythroid differentiation path, as characterized by the differential expression of CD43/c-Kit and the upregulation of several key erythroid transcription factors (TFs), accompanied the decline or loss of leukemia-initiating potential. Notably, overexpression of one of the key erythroid TFs, Ldb1, potently disrupted the repopulation of AE9a leukemic cells in vivo, suggesting a new promising intervention strategy of t(8;21) AML through enforcing their erythroid differentiation.

JMJD1C is required for the survival of acute myeloid leukemia by functioning as a coactivator for key transcription factors.

RUNX1-RUNX1T1 (formerly AML1-ETO), a transcription factor generated by the t(8;21) translocation in acute myeloid leukemia (AML), dictates a leukemic program by increasing self-renewal and inhibiting differentiation. Here we demonstrate that the histone demethylase JMJD1C functions as a coactivator for RUNX1-RUNX1T1 and is required for its transcriptional program. JMJD1C is directly recruited by RUNX1-RUNX1T1 to its target genes and regulates their expression by maintaining low H3K9 dimethyl (H3K9me2) levels. Analyses in JMJD1C knockout mice also establish a JMJD1C requirement for RUNX1-RUNX1T1's ability to increase proliferation. We also show a critical role for JMJD1C in the survival of multiple human AML cell lines, suggesting that it is required for leukemic programs in different AML cell types through its association with key transcription factors.

Nanomicelles co-loading CXCR4 antagonist and doxorubicin combat the refractory acute myeloid leukemia.

Acute myeloid leukemia (AML) is featured with poor prognosis and high mortality, because chemo-resistance, nonspecific distribution and dose-limiting toxicity lead to a high rate of relapse and a very low 5-year survival percentage of less than 25%. CXCR4 is a highly expressed chemokine receptor in multiple types of AML cells and closely associated with the drug resistance and relapse. In this work, we integrate a chemically synthesized CXCR4 antagonistic peptide and doxorubicin using DSPE-mPEG2000 micelles (referred to as M-E5-Dox) that is applied to a very challenging refractory AML mouse model as well as human AML cell lines. Results showed that M-E5-Dox can effectively bind to the CXCR4-expressing AML cells, downregulating the signaling proteins mediated by CXCR4/CXCL12 axis and increasing the cellular uptake of Dox. Importantly, M-E5-Dox remarkably decreases the leukemic cells in the peripheral blood and bone marrow, as well as their infiltration in the spleen and liver of the AML mice, which in turn prolongs the survival significantly. Meanwhile, M-E5-Dox did not increase the cardiotoxicity of Dox. In conclusion, M-E5-Dox harnesses the functions of CXCR4 specific binding and CXCR4 antagonism of the peptide and the tumor cell killing capacity of Dox, which displays significant therapeutic effects and promising translational potentials for the treatment of refractory AML.

Different roles of E proteins in t(8;21) leukemia: E2-2 compromises the function of AETFC and negatively regulates leukemogenesis.

The AML1-ETO fusion protein, generated by the t(8;21) chromosomal translocation, is causally involved in nearly 20% of acute myeloid leukemia (AML) cases. In leukemic cells, AML1-ETO resides in and functions through a stable protein complex, AML1-ETO-containing transcription factor complex (AETFC), that contains multiple transcription (co)factors. Among these AETFC components, HEB and E2A, two members of the ubiquitously expressed E proteins, directly interact with AML1-ETO, confer new DNA-binding capacity to AETFC, and are essential for leukemogenesis. However, the third E protein, E2-2, is specifically silenced in AML1-ETO-expressing leukemic cells, suggesting E2-2 as a negative factor of leukemogenesis. Indeed, ectopic expression of E2-2 selectively inhibits the growth of AML1-ETO-expressing leukemic cells, and this inhibition requires the bHLH DNA-binding domain. RNA-seq and ChIP-seq analyses reveal that, despite some overlap, the three E proteins differentially regulate many target genes. In particular, studies show that E2-2 both redistributes AETFC to, and activates, some genes associated with dendritic cell differentiation and represses MYC target genes. In AML patients, the expression of E2-2 is relatively lower in the t(8;21) subtype, and an E2-2 target gene, THPO, is identified as a potential predictor of relapse. In a mouse model of human t(8;21) leukemia, E2-2 suppression accelerates leukemogenesis. Taken together, these results reveal that, in contrast to HEB and E2A, which facilitate AML1-ETO-mediated leukemogenesis, E2-2 compromises the function of AETFC and negatively regulates leukemogenesis. The three E proteins thus define a heterogeneity of AETFC, which improves our understanding of the precise mechanism of leukemogenesis and assists development of diagnostic/therapeutic strategies.

AML1-ETO-Related Fusion Circular RNAs Contribute to the Proliferation of Leukemia Cells.

The AML1-ETO (RUNX1-RUNX1T1) fusion gene created by the chromosome translocation t(8;21) (q21;q22) is one of the essential contributors to leukemogenesis. Only a few studies in the literature have focused on fusion gene-derived circular RNAs (f-circRNAs). Here, we report several AML1-ETO-related fusion circular RNAs (F-CircAEs) in AML1-ETO-positive cell lines and primary patient blasts. Functional studies demonstrate that the over-expression of F-CircAE in NIH3T3 cells promotes cell proliferation in vitro and in vivo. F-CircAE expression enhances the colony formation ability of c-Kit+ hematopoietic stem and progenitor cells (HSPCs). Meanwhile, the knockdown of endogenous F-CircAEs can inhibit the proliferation and colony formation ability of AML1-ETO-positive Kasumi-1 cells. Intriguingly, bioinformatic analysis revealed that the glycolysis pathway is down-regulated in F-CircAE-knockdown Kasumi-1 cells and up-regulated in F-CircAE over-expressed NIH3T3 cells. Further studies show that F-CircAE binds to the glycolytic protein ENO-1, up-regulates the expression level of glycolytic enzymes, and enhances lactate production. In summary, our study demonstrates that F-CircAE may exert biological activities on the growth of AML1-ETO leukemia cells by regulating the glycolysis pathway. Determining the role of F-CircAEs in AML1-ETO leukemia can lead to great strides in understanding its pathogenesis, thus providing new diagnostic markers and therapeutic targets.

Histone deacetylase 3 preferentially binds and collaborates with the transcription factor RUNX1 to repress AML1-ETO-dependent transcription in t(8;21) AML.

In up to 15% of acute myeloid leukemias (AMLs), a recurring chromosomal translocation, termed t(8;21), generates the AML1-eight-twenty-one (ETO) leukemia fusion protein, which contains the DNA-binding domain of Runt-related transcription factor 1 (RUNX1) and almost all of ETO. RUNX1 and the AML1-ETO fusion protein are coexpressed in t(8;21) AML cells and antagonize each other's gene-regulatory functions. AML1-ETO represses transcription of RUNX1 target genes by competitively displacing RUNX1 and recruiting corepressors such as histone deacetylase 3 (HDAC3). Recent studies have shown that AML1-ETO and RUNX1 co-occupy the binding sites of AML1-ETO-activated genes. How this joined binding allows RUNX1 to antagonize AML1-ETO-mediated transcriptional activation is unclear. Here we show that RUNX1 functions as a bona fide repressor of transcription activated by AML1-ETO. Mechanistically, we show that RUNX1 is a component of the HDAC3 corepressor complex and that HDAC3 preferentially binds to RUNX1 rather than to AML1-ETO in t(8;21) AML cells. Studying the regulation of interleukin-8 (IL8), a newly identified AML1-ETO-activated gene, we demonstrate that RUNX1 and HDAC3 collaboratively repress AML1-ETO-dependent transcription, a finding further supported by results of genome-wide analyses of AML1-ETO-activated genes. These and other results from the genome-wide studies also have important implications for the mechanistic understanding of gene-specific coactivator and corepressor functions across the AML1-ETO/RUNX1 cistrome.

Combined use of interferon alpha-1b, interleukin-2, and thalidomide to reverse the AML1-ETO fusion gene in acute myeloid leukemia.

This study aims to explore the effect of the ITI (interferon alpha-1b, thalidomide, and interleukin-2) regimen on the AML1-ETO fusion gene in patients with t(8;21) acute myeloid leukemia (AML) who were in hematologic remission but positive for the AML1-ETO fusion gene. From September 2014 to November 2020; 20 patients with AML (15 from The Affiliated Cancer Hospital of Zhengzhou University, 4 from The First Affiliated Hospital; and College of Clinical Medicine of Henan University of Science and Technology, and 1 from Anyang District Hospital) with hematological remission but AML1-ETO fusion gene positivity were treated with different doses of the ITI regimen to monitor changes in AML1-ETO fusion gene levels. Twenty patients were treated with a routine dose of the ITI regimen, including 13 males and 7 females. The median patient age was 38 (14-70 years). The fusion gene was negative in 10 patients after 1 (0.5 ~ 8.6) month, significantly decreased in 4 patients after 2.8 (1 ~ 6) months, increased in 4 patients, and unchanged in 2 patients. The 4 patients with elevated levels of the fusion gene were treated with an increased dose of the ITI regimen, and all four patients became negative, for a total effective rate of 90%. The ITI regimen reduces AML1-ETO fusion gene levels in patients with AML who are in hematologic remission but are fusion gene-positive. Improvement was observed in patients' response to a higher dose administration, and patients tolerated the treatment well.

Transcription Factor RBPJ as a Molecular Switch in Regulating the Notch Response.

The Notch signal transduction cascade requires cell-to-cell contact and results in the proteolytic processing of the Notch receptor and subsequent assembly of a transcriptional coactivator complex containing the Notch intracellular domain (NICD) and transcription factor RBPJ. In the absence of a Notch signal, RBPJ remains at Notch target genes and dampens transcriptional output. Like in other signaling pathways, RBPJ is able to switch from activation to repression by associating with corepressor complexes containing several chromatin-modifying enzymes. Here, we focus on the recent advances concerning RBPJ-corepressor functions, especially in regard to chromatin regulation. We put this into the context of one of the best-studied model systems for Notch, blood cell development. Alterations in the RBPJ-corepressor functions can contribute to the development of leukemia, especially in the case of acute myeloid leukemia (AML). The versatile role of transcription factor RBPJ in regulating pivotal target genes like c-MYC and HES1 may contribute to the better understanding of the development of leukemia.

Preleukemic fusion genes typical for acute myeloid leukemia.

Acute myeloid leukemia (AML) is a highly heterogeneous subtype of leukemia, accounting for 25 % of childhood leukemias. By the presence of genetic mutations in hematopoietic/ progenitor stem cells, the bone marrow produces a large number of abnormal undifferentiated leukocytes (blasts), which significantly impairs the proper differentiation of cells. AML is induced by two interventions. Chromosomal translocation during hematopoiesis of intrauterine development is the first intervention. This creates preleukemic fusion genes (PFG), which can later be transformed by a second intervention (point genetic mutation - deletion, insertion ) into a functional malignant clone. Characteristic AML fusion genes include AML1-ETO, PML-RARA or MLL-AF9, which in turn produce hybrid proteins with altered function. Several studies suggest that these PFGs are considered an important prognostic tool in disease assessment. While the incidence of PFG characteristic of acute lymphoblastic leukemia (ALL) has been relatively well studied by several research groups and has been estimated at 1 to 5% in the umbilical cord blood of healthy neonates, PFG relevant to AML are still not sufficiently clarified.

Epigenetic silencing of miR564 contributes to the leukemogenesis of t(8;21) acute myeloid leukemia.

The AML1-ETO oncoprotein, which results from t(8;21) translocation, is considered an initial event of t(8;21) acute myeloid leukemia (AML). However, the precise mechanisms of the oncogenic activity of AML1-ETO is yet to be fully determined. The present study demonstrates that AML1-ETO triggers the heterochromatic silencing of microRNA-564 (miR564) by binding at the AML1 binding site along the miR564 promoter region and recruiting chromatin-remodeling enzymes. Suppression of miR564 enhances the oncogenic activity of the AML1-ETO oncoprotein by directly inhibiting the expression of CCND1 and the DNMT3A genes. Ectopic expression of miR564 can induce retardation of G1/S transition, reperform differentiation, promote apoptosis, as well as inhibit the proliferation and colony formation of AML1-ETO+ leukemia cells in vitro. Enhanced miR564 levels can significantly inhibit the tumor proliferation of t(8;21)AML in vivo. We first identify an unexpected and important epigenetic circuitry of AML1-ETO/miR564/CCND1/DNMT3A that contributes to the leukemogenesis in vitro/vivo of AML1-ETO+ leukemia, indicating that miR564 enhancement could provide a potential therapeutic method for AML1-ETO+ leukemia.

Targeting miR-193a-AML1-ETO-ß-catenin axis by melatonin suppresses the self-renewal of leukaemia stem cells in leukaemia with t (8;21) translocation.

AML1-ETO, the most common fusion oncoprotein by t (8;21) in acute myeloid leukaemia (AML), enhances hematopoietic self-renewal and leukemogenesis. However, currently no specific therapies have been reported for t (8;21) AML patients as AML1-ETO is still intractable as a pharmacological target. For this purpose, leukaemia cells and AML1-ETO-induced murine leukaemia model were used to investigate the degradation of AML1-ETO by melatonin (MLT), synthesized and secreted by the pineal gland. MLT remarkedly decreased AML1-ETO protein in leukemic cells. Meanwhile, MLT induced apoptosis, decreased proliferation and reduced colony formation. Furthermore, MLT reduced the expansion of human leukemic cells and extended the overall survival in U937T-AML1-ETO-xenografted NSG mice. Most importantly, MLT reduced the infiltration of leukaemia blasts, decreased the frequency of leukaemia stem cells (LSCs) and prolonged the overall survival in AML1-ETO-induced murine leukaemia. Mechanistically, MLT increased the expression of miR-193a, which inhibited AML1-ETO expression via targeting its putative binding sites. Furthermore, MLT decreased the expression of ß-catenin, which is required for the self-renewal of LSC and is the downstream of AML1-ETO. Thus, MLT presents anti-self-renewal of LSC through miR-193a-AML1-ETO-ß-catenin axis. In conclusion, MLT might be a potential treatment for t (8;21) leukaemia by targeting AML1-ETO oncoprotein.

RUNX1-ETO: Attacking the Epigenome for Genomic Instable Leukemia.

Oncogenic fusion protein RUNX1-ETO is the product of the t(8;21) translocation, responsible for the most common cytogenetic subtype of acute myeloid leukemia. RUNX1, a critical transcription factor in hematopoietic development, is fused with almost the entire ETO sequence with the ability to recruit a wide range of repressors. Past efforts in providing a comprehensive picture of the genome-wide localization and the target genes of RUNX1-ETO have been inconclusive in understanding the underlying mechanism by which it deregulates native RUNX1. In this review; we dissect the current data on the epigenetic impact of RUNX1 and RUNX1-ETO. Both share similarities however, in recent years, research focused on epigenetic factors to explain their differences. RUNX1-ETO impairs DNA repair mechanisms which compromises genomic stability and favors a mutator phenotype. Among an increasing pool of mutated factors, regulators of DNA methylation are frequently found in t(8;21) AML. Together with the alteration of both, histone markers and distal enhancer regulation, RUNX1-ETO might specifically disrupt normal chromatin structure. Epigenetic studies on the fusion protein uncovered new mechanisms contributing to leukemogenesis and hopefully will translate into clinical applications.

[Galectin-3 Expression and Its Clinical Significance in Acute Myeloid Leukemia with Positive AML1/ETO Fusion Gene].

OBJECTIVE: To investigate the mRNA expression of galectin-3 and its clinical significance in acute myeloid leukemia (AML) patients carrying AML1/ETOfusion gene. METHODS: RQ-PCR method was used to detect the expression of galectin-3 mRNA in bone marrow mononuclear cells of 53 AML patients with AML1/ETO+, ELISA was used to detect the expression of galectin-3 protein in peripheral blood, and the correlations of galectin-3 expression with clinical and laboratory features and outcomes were analyzed. RESULTS: The mRNA and protein levels of galectin-3 were significantly higher in newly diagnosed AML1/ETO+ AML patients compared with the control ( P<0.001). Galectin-3 mRNA and protein expressions were positively correlated (r=0.732, P<0.001). Galectin-3 protein was significantly decreased during the period of complete remission (CR)( P<0.001). The mRNA expression of galectin-3 was negatively correlated with the count of white blood cells ( P=0.014), and positively correlated with CD34 expression and additional cytogenetic aberrations (ACA) ( P=0.001, P=0.026). There was no significant difference in CR, partial remission (PR), induction death (early mortality) between galectin-3 high-expression group and low-expression group ( P>0.05), but there was significant difference in recurrence rate between the two groups ( P=0.029). The median overall survival (OS) rate and disease-free survival (DFS) rate were shortened in the high-expression group ( P=0.007, P=0.015) and the cumulative incidence of relapse was increased ( P=0.045), but there was no significant difference in the cumulative incidence of CM(155mm]mortality ( P>0.05). Cox regression analysis suggested galectin-3 mRNA level an independent indicator of OS and DFS in AML1/ETO+ AML patients. CONCLUSION: Bone marrow galectin-3 mRNA level may be an important reference index for evaluating the prognosis and guiding the treatment of AML1/ETO+ AML patients.

Polyphyllin I Inhibits Proliferation and Induces Apoptosis by Downregulating AML1-ETO and Suppressing C-KIT/Akt Signaling in t(8;21) Acute Myeloid Leukemia.

Polyphyllin I (PPI), a bioactive constituent extracted from traditional medicinal herbs, is cytotoxic to several cancer types. However, whether PPI can be used to treat t(8;21) acute myeloid leukemia (AML) cells requires further investigation. Here, we determined the inhibitory effects of PPI on t(8;21) AML cells by Cell Counting Kit-8 (CCK-8) and the trypan blue dye exclusion assay. DAPI staining and Wright-Giemsa staining were performed to check for apoptosis. Detection of apoptotic protein and AML1-ETO signaling protein expression were conducted by Western blot analysis. Our results suggested that PPI decreased growth and induced apoptosis in a dosage-dependent manner in the t(8;21) AML cell line Kasumi-1. PPI significantly downregulated AML1-ETO expression in a dosage- and time-dependent manner. PPI also upregulated P21 and downregulated survivin expression by reducing AML1-ETO. Mechanistically, PPI significantly reduced the expression of C-KIT, another therapeutic target for AML with t(8;21), followed by inhibition of Akt signaling. These results suggest that PPI can suppress growth and induce apoptosis of t(8;21) AML by suppressing the AML1-ETO and C-KIT/Akt signaling pathways. Therefore, PPI may be an anticancer therapeutic to treat t(8;21) AML.

Chaperonin TRiC/CCT Modulates the Folding and Activity of Leukemogenic Fusion Oncoprotein AML1-ETO.

AML1-ETO is the most common fusion oncoprotein causing acute myeloid leukemia (AML), a disease with a 5-year survival rate of only 24%. AML1-ETO functions as a rogue transcription factor, altering the expression of genes critical for myeloid cell development and differentiation. Currently, there are no specific therapies for AML1-ETO-positive AML. While known for decades to be the translational product of a chimeric gene created by the stable chromosome translocation t(8;21)(q22;q22), it is not known how AML1-ETO achieves its native and functional conformation or whether this process can be targeted for therapeutic benefit. Here, we show that the biosynthesis and folding of the AML1-ETO protein is facilitated by interaction with the essential eukaryotic chaperonin TRiC (or CCT). We demonstrate that a folding intermediate of AML1-ETO binds to TRiC directly, mainly through its ß-strand rich, DNA-binding domain (AML-(1-175)), with the assistance of HSP70. Our results suggest that TRiC contributes to AML1-ETO proteostasis through specific interactions between the oncoprotein's DNA-binding domain, which may be targeted for therapeutic benefit.

RUNX1-ETO Leukemia.

AML1-ETO leukemia is the most common cytogenetic subtype of acute myeloid leukemia, defined by the presence of t(8;21). Remarkable progress has been achieved in understanding the molecular pathogenesis of AML1-ETO leukemia. Proteomic surveies have shown that AML-ETO forms a stable complex with several transcription factors, including E proteins. Genome-wide transcriptome and ChIP-seq analyses have revealed the genes directly regulated by AML1-ETO, such as CEBPA. Several lines of evidence suggest that AML1-ETO suppresses endogenous DNA repair in cells to promote mutagenesis, which facilitates acquisition of cooperating secondary events. Furthermore, it has become increasingly apparent that a delicate balance of AML1-ETO and native AML1 is important to sustain the malignant cell phenotype. Translation of these findings into the clinical setting is just beginning.

[Correlations Between AML1-ETO Fusion Gene and Clinical Features of Acute Myeloid Leukemia in Sichuan.]

OBJECTIVES: To determine the correlations between AML1-ETO fusion gene and clinical characteristics of patients with AML,and its association with the prognosis of AML-M2. METHODS: Medical records of 94 AML-M2 cases with positive AML1-ETO fusion gene and 51 AML-M2 cases with negative AML1-ETO gene were retrospective reviewed.Their clinical characteristics,treatment responses and prognostic outcomes were compared. RESULTS: No significant differences in the clinical symptoms,predominantly anemia,fever and hemorrhage,were found between the AML1-ETO fusion gene positive and negative AML-M2 (P>0.05).However,lower levels of red blood cell (RBC) and platelet (PLT),and higher levels of ratio of grain to red,percentage of bone marrow granulocyte (NC),CD34,human leukocyte antigen DR (HLA-DR),CD56 and CD19 were found in those with positive AML1-ETO fusion gene (P<0.05).The efficacy of treatments and survival curves showed no significant differences between the two groups (P>0.05).CD56 and original percentage of bone marrow granulocyte were predictors of poor long-term survival.Complete remission was the only predictor of better long-term survival. CONCLUSIONS: AML1-ETO fusion gene is neither associated with clinical symptoms,nor with survival and long term prognosis in Sichuan.As many factors affect the efficacy of treatments and prognosis of AML-M2,stratified analysis is needed to determine the role of AML1-ETO.

Increased expression of amyloid precursor protein promotes proliferation and migration of AML1/ETO-positive leukemia cells and be inhibited by panobinostat.

Amyloid precursor protein (APP) is a highly conserved integral membrane protein extensively expressed in various types of cells. Previously we found that overexpression of APP in patients with AML1/ETO-positive acute myeloid leukemia (AML) associated with a higher incidence of extramedullary infiltrationin and indicate a poor prognosis. In this study, we attempted to define the roles of APP in AML1/ETO-positive leukemia cells. Western blotting and qRT-PCR analysis showed that protein levels of APP are significantly higher in Kasumi-1, a t(8;21)/ AML1/ETO-positive M2-type AML cell line. Stable knockdown of APP by lentivirus-based RNA interference (RNAi) dramatically impaired colony-formation and migration ability of Kasumi-1 cells, whereas APP knockdown had very little effect on cell viability, apoptosis, cell cycle and differentiation. We further explored whether the pan-histone deacetylase inhibitor panobinostat could deplete the protein levels of APP in Kasumi-1 cells. Treatment with panobinostat caused depletion of APP in Kasumi-1 cells. These findings indicate that overexpression of APP is involved in promoting proliferation and migration of AML1/ETO-positive leukemia cells and can be inhibited by panobinostat, which provide an attractive prospect for treatment of AML1/ETO-positive AML.