Cytokine-STATs Signalings Upregulate C/EBPβ In BCR-ABL+ Leukemic Cells Independently From BCR-ABL/JAK-STAT Pathway

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1468-1468
Author(s):  
Asumi Yokota ◽  
Hideyo Hirai ◽  
Yoshihiro Hayashi ◽  
Akihiro Tamura ◽  
Atsushi Sato ◽  
...  

Abstract Since residual chronic myelogenous leukemia (CML) stem cells may be a cause of relapse after Imatinib (IM) cessation, targeting these IM-resistant stem cells is mandatory for complete cure of this disease. CCAAT/enhancer binding protein β (C/EBPβ), a leucine zipper transcription factor, promotes both cell cycle progression and differentiation toward granulocytes in hematopoietic stem/progenitor cells under stress conditions such as infection. We have recently reported that C/EBPβ was upregulated in leukemic stem/progenitor cells derived from patients in chronic phase of CML (CP-CML) through STAT5, a major downstream target of BCR-ABL. In CML mouse model, C/EBPβ enhanced exhaustion of CML stem cells through promoting their differentiation (Hayashi Y et al, Leukemia 2013). In spite of the upregulation of C/EBPβ by BCR-ABL, CML stem cells will not be exhausted spontaneously in patients with CP-CMP. Therefore, we hypothesized that quiescent CML stem cells maintain their immature status in the bone marrow niche by suppressing C/EBPβ expression or function induced by BCR-ABL and that induction of C/EBPβ expression in CML stem cells through BCR-ABL-independent pathways may be a novel therapeutic strategy targeting CML stem cells. The aim of this study is to propose a novel therapeutic strategy that can stimulate quiescent CML stem cells with cytokine-STATs signalings and induce their exhaustion through C/EBPβ-mediated differentiation. STATs are family members of molecules which convey signals from various kinds of cytokine receptors to nucleus. In order to investigate whether STAT molecules can induce C/EBPβ expression, we first examined the effects of constitutive active (CA) form of STAT1, STAT3 and STAT5 on C/EBPβ expression in a murine hematopoietic stem cell line, EML cells. Retroviral transduction of CA-STAT5 significantly upregulated C/EBPβ mRNA and protein in EML cells. EML cells begun to differentiate toward CD11b+ myeloid lineage upon introduction of CA-STAT5. CA-STAT1 and CA-STAT3 also upregulated C/EBPβ mRNA when they were retrovirally transduced into EML cells (Figure 1). These results suggest that signaling mediated by various kinds of STATs can upregulate C/EBPβ. Consensus binding sites for STATs were not found in the proximal (∼ 4 kb) promoter region of C/EBPβ and we are currently identifying the cis-regulatory elements responsible for the STATs-dependent activation of C/EBPβ.Figure 1Figure 1. Interferon-α (IFNα) exerts STATs-mediated signaling in hematopoietic stem cells and has been used for therapy of CML. Therefore we investigated the possible involvement of C/EBPβ in efficacy of IFNα in CML treatments. Stimulation of EML cells with 500 U/ml IFNα upregulated C/EBPβ mRNA (Figure 2). Higher levels of phosphorylation of STAT1 than those of STAT3 or STAT5 were observed after stimulation with IFNα, suggesting that STAT1 mediated activation of C/EBPβ was induced by IFNα. As previously reported, C/EBPβ was upregulated in EML cells transduced with BCR-ABL (EMLBCR-ABL). Treatment of EMLBCR-ABL cells with IFNα augmented this effect significantly. IM effectively inhibited phosphorylation of STAT5 and blunted the upregulation of C/EBPβ in EMLBCR-ABL cells. Simultaneous treatment of EMLBCR-ABL cells with IFNα and IM resulted in maintained upregulation of C/EBPβ with increased phosphorylation of STAT1 and decreased phosphorylation of STAT5. These data suggested that IFNα treatment can upregulate C/EBPβ independently of signals mediated by BCR-ABL.Figure 2Figure 2. In conclusion, cytokine-STATs signalings can induce C/EBPβ expression in BCR-ABL+ leukemic cells independently from BCR-ABL/JAK-STAT pathway. Stimulations of dormant CML stem cells with cytokines might be a novel treatment strategy to eliminate these populations, leading to complete cure of CML. We are currently evaluating the in vivo effects of IFNα treatment on CML stem cells in mice models. Disclosures: No relevant conflicts of interest to declare.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 743-743
Author(s):  
Daniela S. Krause ◽  
Katherine Lazarides ◽  
Ulrich H. von Andrian ◽  
Richard A. Van Etten

Abstract In chronic myeloid leukemia (CML) patients treated by autologous hematopoietic stem cell (HSC) transplantation, malignant progenitors in the graft can contribute to relapse of leukemia (Deisseroth et al., Blood1994; 83:3068), but the mechanisms of homing and engraftment of leukemic CML stem cells are unknown. Although the frequency of autografting in CML has decreased following the introduction of imatinib, most imatinib-responsive patients harbor residual BCR-ABL-expressing stem cells (Graham et al., Blood2002; 99:319) and some will develop progressive leukemia. Autografting with cells harvested at the time of minimal residual disease could be an important salvage therapy, but methods to selectively block the engraftment of leukemic stem cells are needed. In this study, we show that CD44 expression is increased on murine BCR-ABL-expressing stem/progenitor cells and contributes to the ability of these cells to bind to Selectins. In a retroviral transduction/transplantation model of CML, BCR-ABL-transduced progenitors from CD44-deficient donors were defective in homing to recipient marrow, resulting in defective engraftment and impaired induction of CML-like myeloproliferative disease. By contrast, CD44-deficient stem cells transduced with empty retrovirus engrafted as efficiently as wild-type HSC. In addition, CD44 was not required for induction of acute B-lymphoblastic leukemia (B-ALL) by BCR-ABL, indicating that the engraftment requirement for CD44 is specific to leukemic cells initiating CML, not B-ALL. The requirement for donor CD44 was bypassed by direct intrafemoral injection of BCR-ABL-transduced CD44-deficient stem cells, or by co-expression of human CD44 with BCR-ABL. Treatment of BCR-ABL-transduced stem/progenitor cells from wild-type donors with antibody to CD44 attenuated the induction of CML-like leukemia in recipients. These results demonstrate a major role for CD44 in homing and engraftment of BCR-ABL-expressing leukemic stem cells, possibly through adhesive interactions with Selectins and/or hyaluronan in the recipient bone marrow niche. They further argue that BCR-ABL-transduced stem/progenitor cells depend to a greater extent on CD44 for engraftment than do normal HSC, and suggest that CD44 blockade may be beneficial in autologous transplantation in CML.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 964-964
Author(s):  
Tomohiko Sato ◽  
Susumu Goyama ◽  
Keisuke Kataoka ◽  
Takako Tsuruta ◽  
Masahiro Nakagawa ◽  
...  

Abstract Abstract 964 Chronic myelogenous leukemia (CML) is a hematopoietic stem cell (HSC) disease caused by BCR-ABL oncogene, and now newly targeted therapies are warrented for CML due to the minimal effect of BCR-ABL-targeted tyrosine kinase inhibitors toward CML stem cells. As CML stem cells are known to show some similarity with HSC, utilizing HSC-specific factors as a guide for analyzing CML stem cells is of great significance. Since Evi1 is a transcription factor which is highly expressed within normal HSC compartment and it is frequently activated in myeloid malignancies including a blastic phase (blast crisis) of CML (CML-BC), it is supposed that CML stem cells could have a close relation with Evi1. Here in this study, with Evi1-GFP knock-in mice, which we have recently generated, we developed murine models of CML in a chronic phase (CML-CP) and CML-BC for uncovering new properties of CML stem cells. In Evi1-GFP knock-in CML-CP model, we found that Evi1 positive CML cells account for about 0.1–0.5% of total bone marrow (BM) cells and that almost all of them showed no lineage markers. Furthermore, Evi1 is predominantly expressed in the CML stem cell fraction (Lin- Sca-1+ c-kit+ (LSK)), but its expression is sharply downregulated even in myeloid progenitor (Lin- Sca1- c-kit+ (MP)) cells and in more differentiated cells. Even within CML LSK cells, Evi1 expression widely varies and Evi1-high LSK cells show an enhanced colony-forming capacity compared with Evi1-low LSK cells. As for cell cycle status, Evi1-high CML LSK cells are mostly in G0/G1 phase although Evi1-low CML LSK cells or CML myeloid progenitor are more in S/G2/M phase. When CML LSK cells are cocultured with OP-9 stromal cells, only Evi1-high LSK cells could made cobblestone areas. Comparison of Evi1-high cells with Evi1-low cells in normal and CML LSK compartments by gene expression profiles showed that a more quiescent feature and a less differentiated feature in Evi-high CML LSK cells than in Evi1-low CML LSK cells. Moreover, Evi1-high CML LSK cells have a close correlation with TGF-beta signaling and calcium signaling. In addition, Evi1-high normal LSK cells had the most quiescent and the least differentiated profiles, which suggested that Evi1-high CML LSK cells could keep self-renewal capacity with high proliferation capacity. In concert with our data of Evi1-trafficking CML mouse, in CML patients, we have also recently found that CD34+ 38- CML stem cells showed higher EVI1 expression than CD34+ 38+ CML progenitor cells or total CML cells, which implies that EVI1 could mark CML stem cells as well as normal HSCs. These data indicate that in our Evi1 trafficking CML model high Evi1 expression could enrich CML stem cells and that Evi1 could have a crucial role in CML pathogenesis. In Evi1-GFP knock-in CML-BC model, which more differentiated myeloid progenitors are likely to have a high leukemia initiating potential, a sizable fraction of MP leukemic cells show distinct Evi1 expression. Remarkably, in vivo transplantation assay revealed CML-BC stem cells that can recapitulate the disease are exclusively enriched in Evi1-high MP fraction. Evi1-high MP cells showed a replating capacity in colony assay while Evi1-low MP cells could not. Moreover, Evi1-high MP cells are more actively cycling than Evi1-low MP cells. Our data revealed a limited fraction with high Evi1 expression within stem/progenitor cells possesses enhanced proliferative and leukemia-initiating capacities in CML. As opposed to these CML models noted above, in Evi1-GFP knock-in AML model by MLL-ENL, Evi1-high leukemic cells showed no advantage in leukemia initiating potential. Additionally, other Evi1-GFP knock-in AML models by MOZ-TIF2 and TEL-PDGFRb/AML1-ETO never showed Evi1-high fraction both in BM and spleen, which might suggest the high affinity of Evi1 with stem cell disease as CML. The current study provides us with a new tool for dissecting pathogenesis and exploiting novel targeted therapies to eradicate CML stem cells. An establishment of Evi1-related therapy for CML stem cells, which could be applied to EVI1-high malignancies, is currently being explored. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2005 ◽  
Vol 105 (7) ◽  
pp. 2733-2740 ◽  
Author(s):  
Baijun Fang ◽  
Chunmei Zheng ◽  
Lianming Liao ◽  
Qin Han ◽  
Zhao Sun ◽  
...  

AbstractOverwhelming evidence from leukemia research has shown that the clonal population of neoplastic cells exhibits marked heterogeneity with respect to proliferation and differentiation. There are rare stem cells within the leukemic population that possess extensive proliferation and self-renewal capacity not found in the majority of the leukemic cells. These leukemic stem cells are necessary and sufficient to maintain the leukemia. Interestingly, the BCR/ABL fusion gene, which is present in chronic myelogenous leukemia (CML), was also detected in the endothelial cells of patients with CML, suggesting that CML might originate from hemangioblastic progenitor cells that can give rise to both blood cells and endothelial cells. Here we isolated fetal liver kinase-1–positive (Flk1+) cells carrying the BCR/ABL fusion gene from the bone marrow of 17 Philadelphia chromosome–positive (Ph+) patients with CML and found that these cells could differentiate into malignant blood cells and phenotypically defined endothelial cells at the single-cell level. These findings provide direct evidence for the first time that rearrangement of the BCR/ABL gene might happen at or even before the level of hemangioblastic progenitor cells, thus resulting in detection of the BCR/ABL fusion gene in both blood and endothelial cells.


2019 ◽  
Vol 3 (3) ◽  
pp. 419-431 ◽  
Author(s):  
Fang Dong ◽  
Haitao Bai ◽  
Xiaofang Wang ◽  
Shanshan Zhang ◽  
Zhao Wang ◽  
...  

Abstract The cell of origin, defined as the normal cell in which the transformation event first occurs, is poorly identified in leukemia, despite its importance in understanding of leukemogenesis and improving leukemia therapy. Although hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) were used for leukemia models, whether their self-renewal and differentiation potentials influence the initiation and development of leukemia is largely unknown. In this study, the self-renewal and differentiation potentials in 2 distinct types of HSCs (HSC1 [CD150+CD41−CD34−Lineage−Sca-1+c-Kit+ cells] and HSC2 [CD150−CD41−CD34−Lineage−Sca-1+c-Kit+ cells]) and 3 distinct types of HPCs (HPC1 [CD150+CD41+CD34−Lineage−Sca-1+c-Kit+ cells], HPC2 [CD150+CD41+CD34+Lineage−Sca-1+c-Kit+ cells], and HPC3 [CD150−CD41−CD34+Lineage−Sca-1+c-Kit+ cells]) were isolated from adult mouse bone marrow, and examined by competitive repopulation assay. Then, cells from each population were retrovirally transduced to initiate MLL-AF9 acute myelogenous leukemia (AML) and the intracellular domain of NOTCH-1 T-cell acute lymphoblastic leukemia (T-ALL). AML and T-ALL similarly developed from all HSC and HPC populations, suggesting multiple cellular origins of leukemia. New leukemic stem cells (LSCs) were also identified in these AML and T-ALL models. Notably, switching between immunophenotypical immature and mature LSCs was observed, suggesting that heterogeneous LSCs play a role in the expansion and maintenance of leukemia. Based on this mouse model study, we propose that acute leukemia arises from multiple cells of origin independent of the self-renewal and differentiation potentials in hematopoietic stem and progenitor cells and is amplified by LSC switchover.


Blood ◽  
2002 ◽  
Vol 99 (1) ◽  
pp. 15-23 ◽  
Author(s):  
James C. Mulloy ◽  
Jörg Cammenga ◽  
Karen L. MacKenzie ◽  
Francisco J. Berguido ◽  
Malcolm A. S. Moore ◽  
...  

The acute myelogenous leukemia–1 (AML1)–ETO fusion protein is generated by the t(8;21), which is found in 40% of AMLs of the French-American-British M2 subtype. AML1-ETO interferes with the function of the AML1 (RUNX1, CBFA2) transcription factor in a dominant-negative fashion and represses transcription by binding its consensus DNA–binding site and via protein-protein interactions with other transcription factors. AML1 activity is critical for the development of definitive hematopoiesis, and haploinsufficiency of AML1 has been linked to a propensity to develop AML. Murine experiments suggest that AML1-ETO expression may not be sufficient for leukemogenesis; however, like the BCR-ABL isoforms, the cellular background in which these fusion proteins are expressed may be critical to the phenotype observed. Retroviral gene transfer was used to examine the effect of AML1-ETO on the in vitro behavior of human hematopoietic stem and progenitor cells. Following transduction of CD34+ cells, stem and progenitor cells were quantified in clonogenic assays, cytokine-driven expansion cultures, and long-term stromal cocultures. Expression of AML1-ETO inhibited colony formation by committed progenitors, but enhanced the growth of stem cells (cobblestone area-forming cells), resulting in a profound survival advantage of transduced over nontransduced cells. AML1-ETO–expressing cells retained progenitor activity and continued to express CD34 throughout the 5-week long-term culture. Thus, AML1-ETO enhances the self-renewal of pluripotent stem cells, the physiological target of many acute myeloid leukemias.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3088-3088
Author(s):  
Eishi Ashihara ◽  
Yoko Nakagawa ◽  
Hisayuki Yao ◽  
Asumi Yokota ◽  
Yasuo Miura ◽  
...  

Abstract The prognosis of patients with multiple myeloma (MM) has been improved by the emergence of new molecular targeting agents including proteasome inhibitors and immunomodurating agents. Nevertheless, MM remains incurable at present because it is likely that MM stem cells are resistant to these targeting agents. Thus, it is important to further investigate the biology of MM stem cells to cure the MM patients. We have demonstrated that b-catenin is a novel and attractive target against MM (Ashihara et al. Clin Cancer Res, 2009; Yao et al. Blood Cancer J, 2011). We next investigate novel targets focused on the hypoxic bone marrow (BM) environment. BM is known to have low levels of oxygen, particularly at the epiphysis, which is distant form the BM arterial blood supply. Normal hematopoietic stem cells (HSCs) reside in this hypoxic epiphyseal region “niche”, and HSCs are protected from DNA damage induced by reactive oxygen species. We have previously found that chronic myelogenous leukemia (CML) cells engrafted in the BM survived and proliferated in the severely hypoxic environment and that these hypoxia-adapted (HA) leukemic cells acquired stem cell-like characters (Takeuchi et al. Cell Death Differ, 2010). In this study, we investigated the characteristics of hypoxia-adapted MM (HA-MM) cells. We first confirmed oxygen status in the BM of the MM cell-engrafted mice. Irradiated NOD/SCID mice were inoculated with 2 x 106 AMO-1 cells. After 2 or 4 weeks transplantation, we sacrificed mice and confirmed engraftment. The inoculated MM cells engrafted in the epiphysis in recipient mice after 2 weeks transplantation, and populated endosteum of epiphysis after 4 weeks. These MM cells were positive for pimonidazole, which specifically accumulated in hypoxic cells (< 1.3% O2 concentration). These observations suggested that MM cells resided in the BM are hypoxic. We then established AMO-1, OPM-2, and IM-9 HA-MM cells cultured under hypoxic conditions (O2 1%). These HA cells can continue to proliferate in hypoxic conditions for more than six months. In flow cytometric analysis, the G0 fraction cells as well as side population fraction cells significantly increased in HA-MM cells compared with those in the parental MM cells. We next transplanted parental or HA-MM AMO-1 cells with same cell numbers into irradiated NOD/SCID mice. The survival durations of mice transplanted with HA-AMO-1 cells were significantly shorter than that of mice transplanted with parental cells. Moreover, in serial transplantation experiments, all 5 HA-MM cell-transplanted mice died of MM whereas 1 out of 5 parental MM cell-transplanted mice (Figure 1). Quantitative RT-PCR analysis demonstrated that Sox2, Oct3, and Nanog mRNA transcripts increased in the HA-MM AMO-1 cells (Figure 2). We next investigated the signaling pathway activated in HA-MM cells. Interestingly, phosphorylated Smad2 expression was increased in HA-AMO-1 cells. These findings suggest that HA-MM cells possess stem cell-like character, and these cells may provide a useful model to investigate the mechanism of MM stem cells (myeloma-initiating cells) resistant to molecular target agents. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4627-4627
Author(s):  
Hiroto Horiguchi ◽  
Masayoshi Kobune ◽  
Shohei Kikuchi ◽  
Wataru Jomen ◽  
Kazuyuki Murase ◽  
...  

Abstract The failure of normal hematopoiesis in myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) could be induced by a variety of mechanism such as the alteration of property of hematopoietic stem cells and stem cell niche. However, it has not yet been clarified precise mechanism how MDS stem/progenitor cells could replace normal hematopoietic stem/progenitor cells especially regarding involvement of mesenchymal stromal cells (MSCs). To gain insight into the mechanism of stromal dysfunction, comparative analyses of transcriptomes were conducted between normal and MDS/AML-derived MSCs. Further, we attempted to identify certain effectors originated from MDS/AML cells could alter the function of bone marrow (BM) MSCs. The MSCs derived from healthy volunteer (HV)-derived (normal) and MDS/AML-derived stromal cells were established and analyzed mRNA expression by quantitive PCR (qPCR) array. Additionally, the supporting activity of MSCs for BM CD34+ progenitor/stem cells was examined using serum free coculture system. The interaction between MDS/AML cells and MSCs were evaluated by using Boyden Chamber and the changes of mRNA expression were analyzed. The results of qPCR array revealed that the expression of hematopoietic factors was drastically altered in MDS/AML-derived MSCs as compared with normal MSCs. Among these factors, the expression of SCF and JAG1 mRNA were significantly and consistently reduced in all MDS/AML patients examined. Functional assay of these MSCs demonstrated that the number of colony-forming units (CFU) mixed cells (MIXs) and cobblestone area-forming cells (CAFCs) derived from CD34+ cells was significantly reduced after coculture with MDS/AML-derived MSCs as compared with normal MSCs. Even non-contact culture using Boyden Chamber between leukemic cells and MSCs induced the reduction of SCF and JAG1 mRNA, indicating that certain inducers could be soluble factors. Interestingly, this effect of transcriptomes alteration was negated by nSMase2 inhibitor (GW4869). Exosome transfer assay using Boyden Chamber revealed that GFP and PKH26 in leukemic cells transmit onto MSCs in non-contact coculture system and this transfer of exosome was significantly inhibited by GW4869 or nSMase siRNA. The multiple type of microRNA in exosome derived from MDS/AML cells was transferred into MSCs, suggesting that exosome could contribute to the alteration of mRNA expression in stromal cells. Collectively, these results indicated that exosome derived from MDS/AML cells could be involved in the reduction of SCF/JAG mRNA and the stromal supporting activity of normal hematopoietic stem/progenitor cells. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2856-2856
Author(s):  
Ulrike Höckendorf ◽  
Yabal Monica ◽  
Christian Peschel ◽  
Philipp J. Jost

Abstract Acute myeloid leukemia (AML) is a heterogeneous group of hematopoietic neoplasms driven partly by the loss of differentiation and theblockade of cell death. AML is sustained by leukemia-initiating cells (LICs) that arise from pre-leukemic hematopoietic stem and progenitor cells (HSPCs) that carry genetic alterations being selected for during leukemogenesis. The resistance of LICs to standard chemotherapies presents a major clinical challenge as they eventually cause disease relapse and death. Understanding the mechanisms of LIC resistance to undergoing cell death is therefore critical for a curative therapy of AML. While the regulatory factors that maintain HSPC proliferation and differentiation under normal conditions are well understood, significantly less is known about how LIC fate is regulated. As many hematopoietic disorders are characterized by the overproduction of pro-inflammatory cytokines, we hypothesized that necroptosis controlled cytokine secretion and inflammatory cell death might influence AML development. We therefore addressed the role of MLKL and XIAP in AML and tested whether deletion of Mlkl or Xiap would affect disease progression. Here we show that MLKL limits oncogene-mediated leukemogenesis by promoting the inflammatory cell death of common myeloid progenitors (CMPs) and short-term hematopoietic stem cells (HSCs) in experimental mice. Upon oncogenic stress MLKL-dependent necroptosis and subsequent inflammasome activation were triggered, promoting the production of IL-1β, a potent stimulator of HSPC differentiation and maturation, thus, suppressing the emergence of LICs and limiting leukemogenesis. In a murine bone marrow transplantation model of AML the absence of MLKL accelerated AML development significantly. The enhanced disease was due to the expansion of common myeloid progenitors (CMPs) and short-term hematopoietic stem cells (ST-HSCs), being the cellular compartments to contain LICs. The survival advantage of Mlkl-/- HSPCs became apparent in colony-forming assays and liquid cultures specifically within the CMP and ST-HSC compartments. Sorted ST-HSCs from Mlkl-/- produced more GEMM colonies than WT, the colony type harboring the multipotential myeloid progenitor cells, and both ST-HSCs and CMPs retained significantly more lineage-negative cells in liquid culture. In addition, Mlkl-/- colonies showed a reduction in propidium iodide (PI)-positive dead cells compared with WT colonies. Importantly, WT cells showed caspase activation and produced substantial amounts of the inflammatory cytokine IL-1β which was severely blunted by Mlkl deficiency. We also observed reduced expression of MLKL in leukemic cells on both mRNA and protein level, implying that suppression of cell death was beneficial for the survival of LICs. In contrast, deletion of Xiap did not alter survival or differentiation of leukemic cells when compared with WT cells. Furthermore, XIAP was not differentially expressed on mRNA or protein level compared with WT, indicating that XIAP does not play a critical role in leukemogenesis. In agreement with the murine data, gene expression analysis from primary leukemia cells from two large patient cohorts newly diagnosed with AML showed significantly lower expression of MLKL, but not XIAP, in a variety of AML subtypes compared to healthy controls. Overall, our data demonstrate a key role for MLKL-mediated cell death and activation of the inflammasome in AML and represents a novel tumor-suppressive mechanism. Disclosures Peschel: MophoSys: Honoraria.


Blood ◽  
2021 ◽  
Author(s):  
Shuo Yang ◽  
Xiao-na Zhu ◽  
Hui-Lin Zhang ◽  
Qian Yang ◽  
Yu-Sheng Wei ◽  
...  

Proper regulation of p53 signaling is critical for the maintenance of hematopoietic stem cells (HSCs) and leukemic stem cells (LSCs). The hematopoietic cell-specific mechanisms regulating p53 activity remain largely unknown. Here, we demonstrate that conditional deletion of acidic leucine-rich nuclear phosphoprotein 32B (ANP32B) in hematopoietic cells impairs repopulation capacity and post-injury regeneration of HSCs. Mechanistically, ANP32B forms a repressive complex with and thus inhibits the transcriptional activity of p53 in hematopoietic cells, and p53 deletion rescues the functional defect in Anp32b-deficient HSCs. Of great interest, ANP32B is highly expressed in leukemic cells from chronic myelogenous leukemia (CML) patients. Anp32b deletion enhances p53 transcriptional activity to impair LSCs function in a murine CML model, and exhibits synergistic therapeutic effects with tyrosine kinase inhibitors in inhibiting CML propagation. In summary, our findings provide a novel strategy to enhance p53 activity in LSCs by inhibiting ANP32B, and identify ANP32B as a potential therapeutic target in treating CML.


Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4034-4034
Author(s):  
Kenji Takahashi ◽  
Satoru Monzen ◽  
Ikuo Kashiwakura

Abstract Tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 2 (Tie-2) and its ligand, angiopoietin-1 (Ang-1) play an important role in the remodeling and maturation the vessels. However, Tie-2 expressed in hematopoietic stem cells has been reported to interact with Ang-1 on stromal osteoblasts in the bone marrow niche. This interaction leads to tight adhesion of hematopoietic stem cells to stromal cells, resulting in the maintenance of long-term repopulating activity of hematopoietic stem cells. Although the high radio-sensitivity of hematopoietic stem/progenitor cells is a serious cause of radiation damage in accidentally irradiated victims, the relationship of Tie-2/Ang-1-signals relate to radio-sensitivity is unclear. In addition, a diagnosis of specific radio-sensitivity in patients with malignant diseases allows radio- and/or chemo-therapy to be performed more effectively. Therefore, the radio-protection activity and the possible association of to radio-sensitivity in hematopoietic stem/progenitor of Tie-2/Ang-1 signaling was evaluated. This study was approved by the Committee of Medical Ethics of Hirosaki University School of Medicine. CD34+ hematopoietic stem/progenitor cells were isolated using a magnet sorting kit from human placental and umbilical cord blood units (n = 33) at the end of full-term deliveries after obtaining informed consent from the mothers. Each purified CD34+ fraction individually (81.3 ± 13.7%) was analyzed for the expression of Tie-2 using a flow cytometer. The range of Tie-2-expression was 1.6 ∼ 12.4% (mean = 5.13%). Based on the Tie-2-positive rate, all 33 fractions were classified into CD34+/Tie-2low fraction (Tie-2 positive rate; < 5%, n = 17) or CD34+/Tie-2high fraction (Tie-2 positive rate; ≥ 5%, n = 16). The CD34+ cells were exposed to X-rays at 2 Gy by an X-rays generator (150 kVp, 20 mA, 0.8 ∼ 0.95 Gy/min). The radio-sensitivity of the hematopoietic stem/progenitor cells of each specimen was measured using clonogenic assays. Specifically, the BFU-E, CFU-GM and CFU-GEMM of each sample were assessed in triplicate using a 14-day culture assay in a methylcellulose medium with 5 growth factors (EPO; 4 U/ml, SCF and IL-3; 100 ng/ml, G-CSF and GM-CSF; 10 ng/ml). In addition, CFU-Meg was assessed in triplicate using a 14-day plasma clot technique with 2 growth factors (TPO; 50 ng/ml, SCF; 100 ng/ml). Unexpectedly, the total CFC number decreased with the expression of Tie-2 in CD34+ cells and the total CFC number in CD34+/Tie-2high fractions was lower than that of CD34+/Tie-2low fractions. Moreover, the survival of total CFC at 2 Gy and Tie-2-expression were positively correlated in the CD34+ cells and the total CFC number in CD34+/Tie-2high fractions was more resistant to X-rays than that of CD34+/Tie-2low fractions. Furthermore, to clarify the interaction radio-sensitivity and Tie-2-expression, the effect of Ang-1 on the radio-protective activity in X-irradiated CD34+ cells was examined. However, no protective effect was observed. Although previous reports have showed that CD34+/Tie-2+ cells were more primitive than CD34+/Tie-2− cells, these results suggested that Tie-2-expression appeared to enhance the radio-resistant ability of CD34+ cells and that it was a marker for a radio-sensitivity. Since the direct activation by Ang-1 was not associated with the survival of X-irradiated CD34+ cells, another signaling mechanism may thus be involved in the radio-resistance activity of Tie-2.


Sign in / Sign up

Export Citation Format

Share Document