The SKM-1 leukemic cell line established from a patient with progression to myelomonocytic leukemia in myelodysplastic syndrome (MDS)-contribution to better understanding of MDS

RSL3 enhances ROS-mediated cell apoptosis of myelodysplastic syndrome cells through MYB/Bcl-2 signaling pathway

Myelodysplastic syndromes (MDS) are clonal hematopoietic malignancies and seriously threaten people's health. Current therapies include bone marrow transplantation and several hypomethylating agents. However, many elderly patients cannot benefit from bone marrow transplantation and many patients develop drug resistance to hypomethylating agents, making it urgent to explore novel therapy. RSL3 can effectively induce ferroptosis in various tumors and combination of RSL3 and hypomethylating agents is promising to treat many tumors. However, its effect in MDS was unknown. In this study, we found that RSL3 inhibited MDS cell proliferation through inducing ROS-dependent apoptosis. RSL3 inhibited Bcl-2 expression and increased caspase 3 and PARP cleavage. RNA-seq analysis revealed that MYB may be a potential target of RSL3. Rescue experiments showed that overexpression of MYB can rescue MDS cell proliferation inhibition caused by RSL3. Cellular thermal shift assay showed that RSL3 binds to MYB to exert its function. Furthermore, RSL3 inhibited tumor growth and decreased MYB and Bcl-2 expression in vivo. More importantly, RSL3 decreased the viability of bone marrow mononuclear cells (BMMCs) isolated from MDS patients, and RSL3 had a synergistic effect with DAC in MDS cells. Our studies have uncovered RSL3 as a promising compound and MYB/Bcl-2 signaling pathway as a potential target for MDS treatment.

DNA methyltransferases-associated long non-coding RNA PRKCQ-AS1 regulate DNA methylation in myelodysplastic syndrome

INTRODUCTION

Myelodysplastic syndrome (MDS) is a group of clonal hematopoietic stem cell disorders. DNA hypermethylation is considered to be the key mechanism of pathogenesis for MDS. Studies have demonstrated that DNA methylation can be regulated by the co-effect between long non-coding RNAs (lncRNAs) and DNA methyltransferases (DNMTs). The aim of this study was to identify DNMTs-associated differentially expressed (DE) lncRNAs, which may be a novel diagnostic and therapeutic target for MDS.

METHODS

Two gene expression profile datasets (GSE4619 and GSE19429) were downloaded from the Gene Expression Omnibus (GEO) database. Systematic bioinformatics analysis was conducted. Then we verified the expression of PRKCQ-AS1 in MDS patients and features in SKM-1 cells.

RESULTS

Bioinformatics analysis revealed that the DNMT-associated DE-lncRNA PRKCQ-AS1 was functionally related to DNA methylation. The target genes of PRKCQ-AS1 associated with DNA methylation are mainly methionine synthetase (MTR) and ten-eleven-translocation 1 (TET1). Moreover, the high expression of PRKCQ-AS1 was verified in real MDS cases. Further cellular analysis in SKM-1 cells revealed that overexpressed PRKCQ-AS1 promoted methylation levels of long interspersed nuclear element 1 (LINE-1) and cell proliferation, and apparently elevated both mRNA and protein levels of MTR and TET1, while knockdown of PRKCQ-AS1 showed opposite trend in SKM-1 cells.

CONCLUSION

DNMT-associated DE-lncRNA PRKCQ-AS1 may affects DNA methylation levels by regulating MTR and TET1.

Glutathione promotes the synergistic effects of venetoclax and azacytidine against myelodysplastic syndrome‑refractory anemia by regulating the cell cycle

Azacitidine is a DNA methyltransferase inhibitor that has been used as a singular agent for the treatment of myelodysplastic syndrome-refractory anemia with excess blast-1 and -2 (MDS-RAEB I/II). However, recurrence and overall response rates following this treatment remain unsatisfactory. The combination of azacitidine and venetoclax has been used for the clinical treatment of a variety of hematological diseases due to the synergistic killing effect of the two drugs. Venetoclax is a BCL-2 inhibitor that can inhibit mitochondrial metabolism. In addition, azacitidine has been shown to reduce the levels of myeloid cell leukemia 1 (MCL-1) in acute myeloid leukemia cells. MCL-1 is an anti-apoptotic protein and a potential source of resistance to venetoclax. However, the mechanism underlying the effects of combined venetoclax and azacitidine treatment remains to be fully elucidated. In the present study, the molecular mechanism underlying the impact of venetoclax on the efficacy of azacitidine was investigated by examining its effects on cell cycle progression. SKM-1 cell lines were treated in vitro with 0-2 µM venetoclax and 0-4 µM azacytidine. After 24, 48 and 72 h of treatment, the impact of the drugs on the cell cycle was assessed by flow cytometry. Following drug treatment, changes in cellular glutamine metabolism pathways was analyzed using western blotting (ATF4, CHOP, ASCT2, IDH2 and RB), quantitative PCR (ASCT2 and IDH2), liquid chromatography-mass spectrometry (α-KG, succinate and glutathione) and ELISA (glutamine and glutaminase). Venetoclax was found to inhibit mitochondrial activity though the alanine-serine-cysteine transporter 2 (ASCT2) pathway, which decreased glutamine uptake. Furthermore, venetoclax partially antagonized the action of azacitidine through this ASCT2 pathway, which was reversed by glutathione (GSH) treatment. These results suggest that GSH treatment can potentiate the synergistic therapeutic effects of venetoclax and azacitidine combined treatment on a myelodysplastic syndrome-refractory anemia cell line at lower concentrations.

Clonal MDS/AML cells with enhanced TWIST1 expression reprogram the differentiation of bone marrow MSCs

Bone marrow-derived mesenchymal stem cells (BMMSCs) derived from myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) patients often show a shift in the balance between osteoblastogenesis and adipogenesis. It was suggested that BMMSCs can potentially undergo reprogramming or educational processes. However, the results of reprogrammed differentiation have been inconclusive. In this study, clinical samples, co-culture models and mouse models were employed to explore the association of MDS/AML clonal cells and BMMSCs differentiation. We found that clonal MDS/AML cells promoted adipogenic differentiation and inhibited osteogenic differentiation of BMMSCs, which in turn promoted MDS expansion. Mass spectrometry and cytokine array were used to identify the molecules to drive the BMMSCs differentiation in MDS/AML. Mechanistically, highly expressed transcription factor TWIST1 in clonal MDS/AML cells induces MDS/AML cells to secrete more IFN-γ, which can induce oxidative stress through STAT1-dependent manner, ultimately causing enhanced adipogenic differentiation and inhibited osteogenic differentiation in BMMSCs. Overall, our findings suggest that targeting the driving oncogenes in malignant clonal cells, such as TWIST1, may offer new therapeutic strategies by remodeling the surrounding bone marrow microenvironment in the treatment of MDS/AML and other hematopoietic malignancies.

WEE1 and PARP-1 play critical roles in myelodysplastic syndrome and acute myeloid leukemia treatment

BACKGROUND

Myelodysplastic syndrome (MDS) is a clonal bone marrow disorder defined by cytopenia and is associated with an increased risk of transformation to acute myeloid leukemia (AML). The outcome of MDS is poor, so alternative therapeutic approaches are needed to improve survival. The inhibition of the DNA damage response pathway, including poly (ADP-ribose) polymerase-1 (PARP-1), has been approved to treat several cancers. In addition, WEE1, a nuclear kinase, is overexpressed in many cancers. Therefore, a WEE1 inhibitor combined with a PARP-1 inhibitor could inhibit the proliferation of MDS and AML.

METHODS

We analyzed whether WEE1 was regulated in the progression of MDS and AML. We also evaluated the efficacy of MK-1775 (WEE1 inhibitor) and talazoparib (PARP-1 inhibitor).

RESULTS

PARP-1 expression was higher in the AML cells than in the MDS cells. However, WEE1 expression remained unchanged. MK-1775 or talazoparib alone inhibited MDS and AML cells after 72 h, and cellular cytotoxicity and caspase 3/7 activity were increased. The combined use of MK-1775 and talazoparib produced superior efficacy than either drug alone and SKM-1 colony formation was reduced. Significant cell populations in the sub-G1 phase were found in the cell-cycle analyses. Additionally, γ-H2AX expression and caspase 3 activity were increased. The combined treatment also changed the mitochondrial membrane potential.

CONCLUSIONS

The combination of a WEE1 inhibitor and PARP-1 inhibitor had enhanced efficacy and is proposed as a new therapeutic option for patients with MDS or AML. Our findings have clinical implications for a potential novel therapeutic strategy for MDS and AML patients.

DHX9-mediated pathway contributes to the malignant phenotype of myelodysplastic syndromes

DHX9 is a member of the DEAH (Asp-Glu-Ala-His) helicase family and regulates DNA replication and RNA processing. DHX9 dysfunction promotes tumorigenesis in several solid cancers. However, the role of DHX9 in MDS is still unknown. Here, we analyzed the expression of DHX9 and its clinical significance in 120 MDS patients and 42 non-MDS controls. Lentivirus-mediated DHX9-knockdown experiments were performed to investigate its biological function. We also performed cell functional assays, gene microarray, and pharmacological intervention to investigate the mechanistic involvement of DHX9. We found that overexpression of DHX9 is frequent in MDS and associated with poor survival and high risk of acute myeloid leukemia (AML) transformation. DHX9 is essential for the maintenance of malignant proliferation of leukemia cells, and DHX9 suppression increases cell apoptosis and causes hypersensitivity to chemotherapeutic agents. Besides, knockdown of DHX9 inactivates the PI3K-AKT and ATR-Chk1 signaling, promotes R-loop accumulation, and R-loop-mediated DNA damage.

MDM2 antagonist improves therapeutic activity of azacitidine in myelodysplastic syndromes and chronic myelomonocytic leukemia

Failure of hypomethylation agent (HMA) treatments is an important issue in myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML). Recent studies indicated that function of wildtype TP53 positively impacts outcome of HMA treatments. We investigated the combination of the HMA azacitidine (AZA) with DS-3032b and DS-5272, novel antagonists of the TP53 negative regulator MDM2, in cellular and animal models of MDS and CMML. In TP53 wildtype myeloid cell line, combinational effects of DS-3032b or DS-5272 with AZA were observed. In Tet2-knockout mouse model of MDS and CMML, DS-5272 and AZA combination ameliorated disease-like phenotype. RNA-Seq analysis in mouse bone marrow hematopoietic stem and progenitors indicated that DS-5272 and AZA combination caused down-regulation of leukemia stem cell marker genes and activation of pathways of TP53 function and stability. These findings demonstrate that combining an MDM2 antagonist with AZA has potential to improve AZA treatment in TP53 wildtype MDS and CMML.

Characterization of sabatolimab, a novel immunotherapy with immuno-myeloid activity directed against TIM-3 receptor

Objectives

Sabatolimab is a humanized monoclonal antibody (hIgG4, S228P) directed against human T-cell immunoglobulin domain and mucin domain-3 (TIM-3). Herein, we describe the development and characterization of sabatolimab.

Methods

Sabatolimab was tested for binding to its target TIM-3 and blocking properties. The functional effects of sabatolimab were tested in T-cell killing and myeloid cell cytokine assays. Antibody-mediated cell phagocytosis (ADCP) by sabatolimab was also assessed.

Results

Sabatolimab was shown to (i) enhance T-cell killing and inflammatory cytokine production by dendritic cells (DCs); (ii) facilitate the phagocytic uptake of TIM-3-expressing target cells; and (iii) block the interaction between TIM-3 and its ligands PtdSer/galectin-9.

Conclusion

Taken together, our results support both direct anti-leukemic effects and immune-mediated modulation by sabatolimab, reinforcing the notion that sabatolimab represents a novel immunotherapy with immuno-myeloid activity, holding promise for the treatment of myeloid cell neoplasms.

Deferasirox combination with eltrombopag shows anti-myelodysplastic syndrome effects by enhancing iron deprivation-related apoptosis

Iron overload (IO) affected the survival of patients with myelodysplastic syndrome (MDS). Deferasirox (DFX) is widely used in patients with MDS for iron chelation therapy, but is not suitable for MDS patients with severe thrombocytopenia. Eltrombopag (ELT) is a type of thrombopoietin receptor (TPOR) analog used in the treatment of thrombocytopenia. Therefore, we sought to explore the synergistic effects and possible mechanisms of DFX combination with ELT in MDS cells. In our study, the combination of DFX with ELT synergistically inhibited proliferation, induced apoptosis and arrested cell cycle of MDS cells. Through the RNA-sequence and gene set enrichment analysis (GSEA), iron metabolism-related pathway played important roles in apoptosis of SKM-1 cells treated with DFX plus ELT. Transferrin receptor (TFRC) was significantly highly expressed in combination group than that in single agent groups, without affecting TPOR. Furthermore, the apoptosis of the combination group MDS cells could be partially reversed by ferric ammonium citrate (FAC), accompanied with decreased expression of TFRC. These results suggested that the combination of DFX and ELT synergistically induced apoptosis of MDS cells by enhancing iron deprivation-related pathway.

Targeting acute myeloid leukemia cells by CD33 receptor-specific MoS2-based nanoconjugates

Acute myeloid leukemia (AML) is a highly aggressive type of cancer caused by the uncontrolled proliferation of undifferentiated myeloblasts, affecting the bone marrow and blood. Systemic chemotherapy is considered the primary treatment strategy; unfortunately, healthy cells are also affected to a large extent, leading to severe side effects of this treatment. Targeted drug therapies are becoming increasingly popular in modern medicine, as they bypass normal tissues and cells. Two-dimensional MoS₂-based nanomaterials have attracted attention in the biomedical field as promising agents for cancer diagnosis and therapy. Cancer cells typically (over)express distinctive cytoplasmic membrane-anchored or -spanning protein-based structures (e.g., receptors, enzymes) that distinguish them from healthy, non-cancerous cells. Targeting cancer cells via tumor-specific markers using MoS₂-based nanocarriers loaded with labels or drugs can significantly improve specificity and reduce side effects of such treatment. SKM-1 is an established AML cell line that has been employed in various bio-research applications. However, to date, it has not been used as the subject of studies on selective cancer targeting by inorganic nanomaterials. Here, we demonstrate an efficient targeting of AML cells using MoS₂nanoflakes prepared by a facile exfoliation route and functionalized with anti-CD33 antibody that binds to CD33 receptors expressed by SKM-1 cells. Microscopic analyses by confocal laser scanning microscopy supplemented by label-free confocal Raman microscopy proved that (anti-CD33)-MoS₂conjugates were present on the cell surface and within SKM-1 cells, presumably having been internalized via CD33-mediated endocytosis. Furthermore, the cellular uptake of SKM-1 specific (anti-CD33)-MoS₂conjugates assessed by flow cytometry analysis was significantly higher compared with the cellular uptake of SKM-1 nonspecific (anti-GPC3)-MoS₂conjugates. Our results indicate the importance of appropriate functionalization of MoS₂nanomaterials by tumor-recognizing elements that significantly increase their specificity and hence suggest the utilization of MoS₂-based nanomaterials in the diagnosis and therapy of AML.

SPAG6-silencing enhances decitabine-induced apoptosis and demethylation of PTEN in SKM-1 cells and in a xenograft mouse model

Myelodysplastic syndromes (MDS) are a group of malignant diseases that are characterized by disordered hematopoiesis with a high risk of transforming into leukemia. In the present study, SPAG6-knockdown and decitabine (DAC) treatment resulted in a decreased DNA methyltransferases and methyl-CpG-binding domain protein expression. In addition, DAC and LBH589 were shown to promote apoptosis in SKM-1 cells, and SPAG6-knockdown to enhance the pro-apoptotic effect of DAC. DAC could reduce PTEN methylation and increase PTEN expression in SKM-1 cells. SPAG6-knockdown and LBH589 treatment could increase DAC-mediated demethylation of PTEN promoter. Finally, a mouse model was constructed, and an enhanced efficacy of DAC following SPAG6-knockdown was confirmed in vivo. In conclusion, DAC-mediated apoptosis and PTEN promoter demethylation may be synergistically enhanced by SPAG6-silencing. Therefore, in the present study it was indicated that SPAG6 may be a potential target for demethylation therapy in MDS.

Decitabine Induces Change of Biological Traits in Myelodysplastic Syndromes via FOXO1 Activation

Decitabine (DAC) is considered to be a profound global DNA demethylation, which can induce the re-expression of silenced tumor suppressor genes. Little is known about the function of tumor suppressor gene FOXO1 in myelodysplastic syndromes (MDS). To address this issue, the study firstly investigated differentially expressed genes (DEGs) for DAC treatment in MDS cell lines, then explored the role of FOXO1 through silencing its expression before DAC treatment in MDS. The results showed that FOXO1 exists in a hyperphosphorylated, inactive form in MDS-L cells. DAC treatment both induces FOXO1 expression and reactivates the protein in its low phosphorylation level. Additionally, the results also demonstrated that this FOXO1 activation is responsible for the DAC-induced apoptosis, cell cycle arrest, antigen differentiation, and immunoregulation in MDS-L cells. We also demonstrated DAC-induced FOXO1 activation upregulates anti-tumor immune response in higher-risk MDS specimens. Collectively, these results suggest that DAC induces FOXO1 activation, which plays an important role in anti-MDS tumors.

Genome-wide methylation sequencing identifies progression-related epigenetic drivers in myelodysplastic syndromes

The potential mechanism of myelodysplastic syndromes (MDS) progressing to acute myeloid leukemia (AML) remains poorly elucidated. It has been proved that epigenetic alterations play crucial roles in the pathogenesis of cancer progression including MDS. However, fewer studies explored the whole-genome methylation alterations during MDS progression. Reduced representation bisulfite sequencing was conducted in four paired MDS/secondary AML (MDS/sAML) patients and intended to explore the underlying methylation-associated epigenetic drivers in MDS progression. In four paired MDS/sAML patients, cases at sAML stage exhibited significantly increased methylation level as compared with the matched MDS stage. A total of 1090 differentially methylated fragments (DMFs) (441 hypermethylated and 649 hypomethylated) were identified involving in MDS pathogenesis, whereas 103 DMFs (96 hypermethylated and 7 hypomethylated) were involved in MDS progression. Targeted bisulfite sequencing further identified that aberrant GFRA1, IRX1, NPY, and ZNF300 methylation were frequent events in an additional group of de novo MDS and AML patients, of which only ZNF300 methylation was associated with ZNF300 expression. Subsequently, ZNF300 hypermethylation in larger cohorts of de novo MDS and AML patients was confirmed by real-time quantitative methylation-specific PCR. It was illustrated that ZNF300 methylation could act as a potential biomarker for the diagnosis and prognosis in MDS and AML patients. Functional experiments demonstrated the anti-proliferative and pro-apoptotic role of ZNF300 overexpression in MDS-derived AML cell-line SKM-1. Collectively, genome-wide DNA hypermethylation were frequent events during MDS progression. Among these changes, ZNF300 methylation, a regulator of ZNF300 expression, acted as an epigenetic driver in MDS progression. These findings provided a theoretical basis for the usage of demethylation drugs in MDS patients against disease progression.

Identification and validation of prognosis-related DLX5 methylation as an epigenetic driver in myeloid neoplasms

The deregulated DLX gene family members DLX1/2/3/4/5/6 (DLXs) caused by DNA methylation has been demonstrated in various cancers with therapeutic target value. However, the potential role of DLXs methylation in myeloid neoplasms such as acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) remains to be elucidated. Clinical significance of DLXs methylation/expression was analyzed in patient with AML and MDS. The functional roles of DLXs were determined in vitro. In the identification stage, we found that lower DLX5 expression was correlated with prognosis in AML among all DLXs analyzed by The Cancer Genome Atlas datasets. In the validation stage, we revealed that reduced DLX5 expression was frequently occurred, and was also correlated with promoter hypermethylation in AML evaluated by targeted bisulfite sequencing. Epigenetic studies also showed that DLX5 promoter DNA methylation was associated with its expression. By quantitative polymerase chain reaction, we also validated that DLX5 hypermethylation was frequent event in both AML and MDS, and also correlated with MDS transformation to leukemia. Moreover, DLX5 hypermethylation was associated with lower rate of complete remission and shorter time of leukemia‐free/overall survival, and was also confirmed by Logistic/Cox regression analysis. Functional studies revealed the antiproliferative and pro‐apoptotic effects of DLX5 in MDS‐derived AML cell‐line SKM‐1. Finally, bioinformatics analysis demonstrated that DLX5 functioned in leukemogenesis may be through the association with PI3K/Akt signaling pathway. Collectively, our findings demonstrated that DLX5 methylation, negatively correlated DLX5 expression, was a potential prognostic and predictive indicator in patients with AML and MDS, which could also act as an epigenetic driver in myeloid neoplasms.

Arsenic Disulfide Promoted Hypomethylation by Increasing DNA Methyltransferases Expression in Myelodysplastic Syndrome

Background

Previous studies have shown that DNA methylation plays a significant role in myelodysplastic syndrome (MDS). In addition to hypermethylation, aberrant hypomethylation can result in the transcriptional activation of oncogenes in cancer, including MDS. Therefore, drugs targeting DNA hypomethylation are needed for the treatment of MDS. This study aimed to investigate whether As₂S₂ promoted hypomethylation by increasing DNA methyltransferases (DNMTs) expression in MDS.

Patients and Methods

Ten bone marrow samples from MDS patients and 3 healthy donors were obtained for the examination of the DNA methylation with a Human Methylation 850K BeadChip. The mRNA expressions for the DNMTs in the ten MDS patients and 3 controls were compared by Q-PCR. Then, the MDS cell line SKM-1 was treated with As₂S₂. After 2 days of treatment, Human Methylation 850K BeadChip was applied to analyze the changes of gene methylation status in the cells. Q-PCR and Western blot were taken to test the changes of mRNA and protein expressions for DNMTs in SKM-1 cells after treatment.

Results

Five hundred ninety-two abnormally hypomethylated genes were found in MDS patients compared to those in controls by Human Methylation 850K. The mRNA expressions of DNMTs (DNMT1, DNMT3a and DNMT3b) in MDS patients were significantly lower than those in healthy individuals. The IC50 value of As₂S₂ for SKM-1 cells was 4.97 μmol/L.Treatment with As₂S₂ at 2 μmoL/L resulted in significant alterations in the methylation levels at 1718 sites in SKM-1 cells compared to those in the controls. Hypermethylation was observed in 1625 sites (94.58%), corresponding to 975 genes, compared to those in the controls. Finally, the expression levels of DNMTs (DNMT1, DNMT3a, and DNMT3b) significantly increased in SKM-1 cells treated with As₂S₂ at 2 μmoL/L and 4 μmoL/L.

Conclusion

These data show a potential clinical application of As₂S₂ as an innovative hypermethylation agent in MDS.

Decitabine shows synergistic effects with arsenic trioxide against myelodysplastic syndrome cells via endoplasmic reticulum stress-related apoptosis

Most of the International Prognostic Scoring System (IPSS) high-risk patients with myelodysplastic syndrome partly responded to hypomethylating therapy even with transient remission, while arsenic trioxide (ATO) had partial effect in patients with MDS. Therefore, we sought to investigate the effects and possible mechanisms of the combination of ATO and decitabine (DAC) in MDS cells. In our study, the MUTZ-1 and SKM-1 cells were treated with ATO, DAC or both. Cell viability, cell apoptosis, levels of reactive oxygen species (ROS) and expressions of the endoplasmicreticulum (ER) stress-associated genes and proteins were examined. Results showed the combination of ATO and DAC synergistically inhibited the proliferation and induced apoptosis of MDS cells. Through the RNA-sequence and GSEA gene function analysis, ER stress-related pathway played an important role in apoptosis of MDS cells induced by the combination of ATO and DAC. ER stress-related genes DNA damage inducible transcript 3, GRP78, and activating transcription factor-6 were significantly highly expressed in combination group than those in single agent groups; proteins were confirmed by western blot. The levels of ROS significantly increased in the combination group. Furthermore, the apoptosis of (ATO+DAC) group MDS cells could be partially reversed by antioxidant agent N-acetylcysteine, accompanied by decreased expression of intracellular ROS and ER stress-related genes. These results suggested that the combination of ATO and DAC synergistically induced the apoptosis of MDS cells by increased ROS-related ER stress in MDS cells.

Synergistic inhibitory effects of deferasirox in combination with decitabine on leukemia cell lines SKM-1, THP-1, and K-562

A multi-center study from the French Myelodysplastic Syndrome (MDS) Group confirmed that iron chelation therapy is an independent prognostic factor that can increase the survival rate of patients who are suffering from transfusion-dependent low-risk MDS. In this study, we aimed to explore this clinical phenomena in vitro, by exploring the synergistic effect of the iron chelator Deferasirox (DFX) and the DNA methyl transferase inhibitor Decitabine (DAC) in the leukemia cell lines SKM-1, THP-1, and K-562. Treatment with both DFX or DAC promoted apoptosis, induced cell cycle arrest, and inhibited proliferation in all three of these cell lines. The combination of DFX and DAC was much greater than the effect of using either drug alone. DFX showed a synergistic effect with DAC on cell apoptosis in all three cell lines and on cell cycle arrest at the G0/G1 phase in K-562 cells. DFX decreased the ROS levels to varying degrees. In contrast, DAC increased ROS levels and an increase in ROS was also noted when the two drugs were used in combination. Treatment of cells with DAC induced re-expression of ABAT, APAF-1, FADD, HJV, and SMPD3, presumably through demethylation. However the combination of DAC and DFX just had strong synergistic effect on the re-expression of HJV.

Ribosomal protein L23 negatively regulates cellular apoptosis via the RPL23/Miz-1/c-Myc circuit in higher-risk myelodysplastic syndrome

Ribosomal protein (RP) L23 is a negative regulator of cellular apoptosis, and RPL23 overexpression is associated with abnormal apoptotic resistance in CD34+ cells derived from patients with higher-risk myelodysplastic syndrome (MDS). However, the mechanism underlying RPL23-induced apoptotic resistance in higher-risk MDS patients is poorly understood. In this study, we showed that reduced RPL23 expression led to suppressed cellular viability, increased apoptosis and G1-S cell cycle arrest. Gene microarray analysis comparing RPL23-knockdown and control cells identified an array of differentially expressed genes, of which, Miz-1, was upregulated with transactivation of the cell cycle inhibitors p15^Ink4b and p21^Cip1, and Miz-1’s functional repressor, c-Myc, was downregulated. Cells derived from higher-risk MDS patients demonstrated consistently increased expression of RPL23 and c-Myc and decreased Miz-1 expression compared with cells from lower-risk patients. In conclusion, Miz-1-dependent induction of p15^Ink4b and p21^Cip1 was depressed with decreased Miz-1 and increased c-Myc expression under conditions of elevated RPL23 expression, leading to apoptotic resistance in higher-risk MDS patients. Because RPL23 is encoded by a target gene of c-Myc, the RPL23/Miz-1/c-Myc regulatory circuit provides a feedback loop that links efficient RPL23 expression with c-Myc’s function to suppress Miz-1-induced Cdk inhibitors and thereby leads to apoptotic resistance in higher-risk MDS patients.

Iron overload promotes erythroid apoptosis through regulating HIF-1a/ROS signaling pathway in patients with myelodysplastic syndrome

Erythroid apoptosis increases significantly in myelodysplastic syndrome (MDS) patients with iron overload, but the underlying mechanism is not fully clear. In this study, we aim to explore the effect of HIF-1a/ROS on erythroid apoptosis in MDS patients with iron overload. We found that iron overload injured cellular functions through up-regulating ROS levels in MDS/AML cells, including inhibited cell viability, increased cell apoptosis and blocked cell cycle at G0/G1 phase. Interestingly, overexpression of hypoxia inducible factor-1a (HIF-1a), which was under-expressed in iron overload models, reduced ROS levels and attenuated cell damage caused by iron overload in MDS/AML cells. And gene knockdown of HIF-1a got the similar results as iron overload in MDS/AML cells. Furthermore, iron overload caused high erythroid apoptosis was closely related with ROS in MDS patients. Importantly, the HIF-1a protein levels of erythrocytes elevated obviously after incubation with desferrioxamine (DFO) from MDS patients with iron overload, accompanied by ROS levels inhibited and erythroid apoptosis reduced. Taken together, our findings determine that the HIF-1a/ROS signaling pathway plays a key role in promoting erythroid apoptosis in MDS patients with iron overload.

Total coumarins of Hedyotis diffusa induces apoptosis of myelodysplastic syndrome SKM-1 cells by activation of caspases and inhibition of PI3K/Akt pathway proteins

ETHNOPHARMACOLOGICAL RELEVANCE

Hedyotis diffusa is an ethno-medicine used for anti-cancer treatment in the clinic of traditional Chinese medicine (TCM). The total coumarins of Hedyotis diffusa (TCHD) was a selected extract with observed antiproliferative activity, which has not been tested in treatment of myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML).

AIM OF THE STUDY

This study aimed to evaluate the apoptosis-inducing effect of TCHD on human MDS cell line (SKM-1) and explore its action mechanism in association with caspase family and PI3K/Akt signaling pathway.

MATERIALS AND METHODS

The chemical constituents and total coumarins content of TCHD were determined by High Performance Liquid Chromatography-tandem mass spectrometry (HPLC-MS/MS) and UV-vis spectrophotometry, respectively. MTT assay, Hoechst 33258 staining, and Annexin V-FITC/PI double labeling were applied to evaluate TCHD's efficacy on SKM-1 cells. Western blot analysis was also used to clarify the action mechanism of TCHD on protein expression level.

RESULTS

Two compounds, p-coumaric acid and E-6-O-p-coumaroyl scandoside methyl ester, were identified in TCHD, and its total coumarins content reached 87.4%. By MTT assay, apoptosis-inducing effect of TCHD on SKM-1 cells was found in a dose-dependent manner after 24-48h treatment, with IC₅₀ values of 104.48μg/ml and 100.66μg/ml, respectively. Morphological and flow cytometry observation also confirmed such effect of TCHD. Western blot analysis clarified its action mechanism associating with the activation of caspases and inhibition of PI3K/Akt pathway proteins.

CONCLUSIONS

This is the first report regarding the apoptosis-inducing efficacy and mechanism of TCHD on SKM-1 cells, providing a promising candidate of TCM for MDS and AML therapy with fewer side effects.

Identification of microRNA-regulated pathways using an integration of microRNA-mRNA microarray and bioinformatics analysis in CD34+ cells of myelodysplastic syndromes

The effect of microRNA (miRNA) and targeted mRNA on signal transduction is not fully understood in myelodysplastic syndromes (MDS). Here, we tried to identify the miRNAs-regulated pathways through a combination of miRNA and mRNA microarray in CD34+ cells from MDS patients. We identified 34 differentially expressed miRNAs and 1783 mRNAs in MDS. 25 dysregulated miRNAs and 394 targeted mRNAs were screened by a combination of Pearson’s correlation analysis and software prediction. Pathway analysis showed that several pathways such as Notch, PI3K/Akt might be regulated by those miRNA-mRNAs pairs. Through a combination of Pathway and miRNA-Gene or GO-Network analysis, miRNAs-regulated pathways, such as miR-195-5p/DLL1/Notch signaling pathway, were identified. Further qRT-PCR showed that miR-195-5p was up-regulated while DLL1 was down-regulated in patients with low-grade MDS compared with normal controls. Luciferase assay showed that DLL1 was a direct target of miR-195-5p. Overexpression of miR-195-5p led to increased cell apoptosis and reduced cell growth through inhibition of Notch signaling pathway. In conclusion, alteration expression of miRNAs and targeted mRNAs might have an important impact on cancer-related cellular pathways in MDS. Inhibition of Notch signaling pathway by miR-195-5p-DLL1 axis contributes to the excess apoptosis in low-grade MDS.

Whole-exome and targeted sequencing identify ROBO1 and ROBO2 mutations as progression-related drivers in myelodysplastic syndromes

The progressive mechanism underlying myelodysplastic syndrome remains unknown. Here we identify ROBO1 and ROBO2 as novel progression-related somatic mutations using whole-exome and targeted sequencing in 6 of 16 (37.5%) paired MDS patients with disease progression. Further deep sequencing detects 20 (10.4%) patients with ROBO mutations in a cohort of 193 MDS patients. In addition, copy number loss and loss of heterogeneity (LOH) of ROBO1 and ROBO2 are frequently observed in patients with progression or carrying ROBO mutations. In in vitro experiments, overexpression of ROBO1 or ROBO2 produces anti-proliferative and pro-apoptotic effects in leukaemia cells. However, this effect was lost in ROBO mutants and ROBO-SLIT2 signalling is impaired. Multivariate analysis shows that ROBO mutations are independent factors for predicting poor survival. These findings demonstrate a novel contribution of ROBO mutations to the pathogenesis of MDS and highlight a key role for ROBO-SLIT2 signalling in MDS disease progression.

Gene expression profiling in myelodysplastic syndrome after SPARC overexpression associated with Ara-C

Secreted protein acidic and rich in cysteine (SPARC) is involved in many biological processes, including erythropoiesis and cell proliferation. However, the role of SPARC in myelodysplastic syndrome (MDS) remains to be elucidated. Pyrimidine analogue cytosine arabinoside (Ara-C) is among the most effective agents used in the treatment of acute leukemia. The aim of the present study was to determine whether the chemotherapeutic activity of Ara-C was enhanced by the overexpression of SPARC. DNA microarray technology and RNA sequencing were employed to examine differential gene expression in the apoptosis signaling pathway after gene change occurred in cells following drug treatment. The results showed that upregulation of the expression of SPARC induced SKM-1 cell death and inhibited proliferation. Additionally, the apoptotic rate of SPARC overexpression combined with Ara-C increased significantly. Transcription factors CPBP and ZNF333 regulated the 69 genes and long non-coding RNA (lncRNA). Moreover, the mRNA and protein expression of apoptosis-related genes in the DNA microarray results were increased. These results suggest that SPARC expression changes with Ara-C, revealing a possible application in the treatment of MDS.

[Functional study of hENT1 on SKM-1 cell resistance to decitabine]

OBJECTIVE

To investigate the effect of human equilibrative nucleoside transporters 1 (hENT1) silencing on proliferation, apoptosis and demethylation of human myelodysplastic syndrome (MDS) derived cell line SKM-1 treated with 5-aza-2'-deoxycytidine (decitabine, DAC).

METHODS

hENT1 was silenced in SKM-1 cells mediated by lentivirus transfection. The infection efficiency was detected by flow cytometry, and the mRNA expression level of hENT1 was confirmed by qRT-PCR. The proliferation ratio of SKM-1 cells treated with different concentrations (0.5, 1, 5 mmol/L) of DAC for 24, 48 and 72 h was detected by CCK-8 method after hENT1 silencing. The apoptosis of SKM-1 cells was detected by Western blot for cleaved level of caspase-3 and evaluated by flow cytometry after staining with anti-Annexin V-PE and 7-AAD. The p15(INK4B) DNA methylation status was measured by methylation specific PCR using EZ DNA Methylation-Gold™ Kit.

RESULTS

The expression level of hENT1 silenced group (0.253±0.030) was statistically decreased compared with that in control group (1.000±0.091) (P<0.01). Compared with control, the proliferation inhibition rate of hENT1 silenced group was significantly decreased by different concentrations of DAC (0.5, 1, 5 μmol/L) treatment for 24, 48, 72 h (P<0.05), which was (49.41±4.02)% and (33.03±2.47)%, respectively (P=0.007) at 5 μmol/L DAC treatment for 72 h in hENT1 silenced group and the control group. Western blot showed that cleaved caspase3 of hENT1 silenced group was also significantly inhibited. The percentage of Annexin Ⅴ⁺ cells and demethylation status of p15(INK4B) were significantly decreased.

CONCLUSION

Apoptosis of hENT1 silenced SKM-1 cells induced by DAC was decreased, and the susceptibility of these cells to demethylation treatment was also decreased.

Rigosertib as a selective anti-tumor agent can ameliorate multiple dysregulated signaling transduction pathways in high-grade myelodysplastic syndrome

Rigosertib has demonstrated therapeutic activity for patients with high-risk myelodysplastic syndrome (MDS) in clinical trials. However, the role of rigosertib in MDS has not been thoroughly characterized. In this study, we found out that rigosertib induced apoptosis, blocked the cell cycle at the G2/M phase and subsequently inhibited the proliferation of CD34+ cells from MDS, while it minimally affected the normal CD34+ cells. Further studies showed that rigosertib acted via the activation of the P53 signaling pathway. Bioinformatics analysis based on gene expression profile and flow cytometry analysis revealed the abnormal activation of the Akt-PI3K, Jak-STAT and Wnt pathways in high-grade MDS, while the p38 MAPK, SAPK/JNK and P53 pathways were abnormally activated in low-grade MDS. Rigosertib could markedly inhibit the activation of the Akt-PI3K and Wnt pathways, whereas it activated the SAPK/JNK and P53 pathways in high-grade MDS. A receptor tyrosine kinase phosphorylation array demonstrated that rigosertib could increase the activation of RET and PDGFR-β while reducing the activation of Tie2 and VEGFR2 in MDS cells. Taken together, these data indicate that rigosertib is a selective and promising anti-tumor agent that could ameliorate multiple dysregulated signaling transduction pathways in high-grade MDS.

Sequential combination of decitabine and idarubicin synergistically enhances anti-leukemia effect followed by demethylating Wnt pathway inhibitor promoters and downregulating Wnt pathway nuclear target

Background

The methylation inhibitor 5-Aza-2′-deoxycytidine (decitabine, DAC) has a great therapeutic value for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). But decitabine monotherapy was associated with a relatively low rate of complete remission in AML and MDS. We aimed to investigate the effect of several anti-leukemia drugs in combination with decitabine on the proliferation of myeloid leukemia cells, to select the most efficient combination group and explore the associated mechanisms of these combination therapies.

Methods

Cell proliferation was tested by MTT assay and CFU-GM assay. Cell apoptosis was evaluated by Annexin V and PI staining in cell culture, TUNEL assay and transmission electron microscopy in animal study. MicroPET was used to imaging the tumor in mouse model. Molecular studies were conducted using microarray expression analysis, which was used to explore associated pathways, and real-time quantitative reverse transcription-PCR, western blot and immunohistochemistry, used to assess regulation of Wnt/β-catenin pathway. Statistical significance among groups was determined by one-way ANOVA analysis followed by post hoc Bonferroni’s multiple comparison test.

Results

Among five anti-leukemia agents in combining with decitabine, the sequential combination of decitabine and idarubicin induced synergistic cell death in U937 cells, and this effect was verified in HEL, SKM-1 cells and AML cells isolated from AML patients. Importantly, tumor growth inhibition in this sequential combination was found to be higher than in single agent or controls in vivo. Moreover, sequential combination of the two agents induced apoptosis and depression of the Wnt/β-catenin pathway in both AML cell culture and animal studies.

Conclusions

The findings demonstrated that sequentially combination of decitabine and idarubicin had synergistic anti-leukemia effects. These effects were mainly attributed to demethylation of Wnt/β-catenin pathway inhibitors and downregulation of Wnt/β-catenin pathway nuclear targets.

SPARC silencing inhibits the growth of acute myeloid leukemia transformed from myelodysplastic syndrome via induction of cell cycle arrest and apoptosis

Secreted protein acidic and rich in cysteine (SPARC) plays key roles in erythropoiesis; haploinsufficiency of SPARC is implicated in the progression of the 5q- syndrome. However, the role of SPARC in other subtypes of myelodysplastic syndrome (MDS) is not fully understood, particularly in the del(5q) type with a complex karyotype, which has a high risk to transform into acute myeloid leukemia (AML). In the present study, we investigated the role of SPARC in the proliferation and apoptosis of SKM-1 cells, an acute myeloid leukemia cell line transformed from an MDS cell line. SKM-1 cells were infected with SPARC-RNAi-LV or NC-GFP-LV lentivirus. Apoptosis and cell cycle profiling were assessed by flow cytometry, and cell proliferation was evaluated by MTS assay. The mRNA and protein expression levels of SPARC, p53, caspase-3, caspase-9 and Fas were detected by RT-PCR, real-time PCR and western blot assay. The SPARC shRNA constructed by us led to a significant reduction in SPARC expression in SKM-1 cells. SPARC knockdown inhibited the proliferation of SKM-1 cells by inducing cell cycle arrest at the G1/G0 phase and apoptosis. SPARC knockdown elevated the expression of p53, caspase-9, caspase-3 and Fas at both the mRNA and protein levels. SPARC silencing inhibited the growth of AML transformed from MDS by activating p53-induced apoptosis and cell cycle arrest. These data indicate that SPARC acts as an oncogene in transformed MDS/AML and is a potential therapeutic target in MDS/AML.

In Vivo RNAi screening identifies a leukemia-specific dependence on integrin beta 3 signaling

We used an in vivo small hairpin RNA (shRNA) screening approach to identify genes that are essential for MLL-AF9 acute myeloid leukemia (AML). We found that Integrin Beta 3 (Itgb3) is essential for murine leukemia cells in vivo and for human leukemia cells in xenotransplantation studies. In leukemia cells, Itgb3 knockdown impaired homing, downregulated LSC transcriptional programs, and induced differentiation via the intracellular kinase Syk. In contrast, loss of Itgb3 in normal hematopoietic stem and progenitor cells did not affect engraftment, reconstitution, or differentiation. Finally, using an Itgb3 knockout mouse model, we confirmed that Itgb3 is dispensable for normal hematopoiesis but is required for leukemogenesis. Our results establish the significance of the Itgb3 signaling pathway as a potential therapeutic target in AML.

Inactivating mutations of the histone methyltransferase gene EZH2 in myeloid disorders

Abnormalities of chromosome 7q are common in myeloid malignancies, but no specific target genes have yet been identified. Here, we describe the finding of homozygous EZH2 mutations in 9 of 12 individuals with 7q acquired uniparental disomy. Screening of a total of 614 individuals with myeloid disorders revealed 49 monoallelic or biallelic EZH2 mutations in 42 individuals; the mutations were found most commonly in those with myelodysplastic/myeloproliferative neoplasms (27 out of 219 individuals, or 12%) and in those with myelofibrosis (4 out of 30 individuals, or 13%). EZH2 encodes the catalytic subunit of the polycomb repressive complex 2 (PRC2), a highly conserved histone H3 lysine 27 (H3K27) methyltransferase that influences stem cell renewal by epigenetic repression of genes involved in cell fate decisions. EZH2 has oncogenic activity, and its overexpression has previously been causally linked to differentiation blocks in epithelial tumors. Notably, the mutations we identified resulted in premature chain termination or direct abrogation of histone methyltransferase activity, suggesting that EZH2 acts as a tumor suppressor for myeloid malignancies.