scholarly journals Mdm2 Maintains Cholesterol Biosynthesis in Hematopoietic Stem/Progenitor Cells Independent of p53

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1152-1152
Author(s):  
Rasoul Pourebrahim ◽  
Rafael Heinz Montoya ◽  
Edward Ayoub ◽  
Joseph D. Khoury ◽  
Michael Andreeff
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Progenitor Cells ◽  
Myeloid Leukemia ◽  
Research Funding ◽  
Cholesterol Biosynthesis ◽  
Heterozygous Deletion ◽  
Mdm2 Snp309 ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract Background: The Mdm2 protein is an E3 ubiquitin ligase that directly interacts with p53 protein leading to its degradation. The expression of MDM2 is controlled by p53 activity through an autoregulatory feedback loop. In addition, a single nucleotide polymorphism (SNP) in the MDM2 promoter modulates its expression and is associated with the risk of cancer. Emerging evidence emphasizes the metabolic activities of MDM2 to be essential for the maintenance of cellular homeostasis. We hypothesized that MDM2 maintains the metabolic homeostasis of hematopoietic stem cells (HSCs) and its downregulation in TP53-mutant leukemias leads to metabolic vulnerabilities independent of p53. Investigation of the metabolic role of MDM2 in hematopoietic stem cells can provide valuable insight into the pathology of TP53 mutant leukemias. Methods: To understand the function of Mdm2 in HSCs, we generated a conditional mouse model driven by Vav-Cre to genetically label and trace the fate of HSCs after heterozygous deletion of Mdm2 in early development and adult bone marrow. We utilized fluorescence microscopy, flow cytometry, apoptosis assays and RNA-seq to functionally characterize the fate of HSCs after heterozygous deletion of Mdm2. Using Trp53 floxed allele and a new Trp53 mutant allele that switches from wildtype to Trp53R172H mutant, we deleted and/or mutated Trp53 gene concomitantly in Mdm2 haplo-insufficient HSCs. Additionally, MDM2 copy number as well as MDM2 SNP309 status were determined in 95 samples from p53 mutant AML patients and 24 controls. Results: Heterozygous deletion of Mdm2 in hematopoietic stem cells (Vav-Cre;mTmG;Mdm2 fl/+) resulted in massive apoptosis of emerging hematopoietic progenitor cells in the aorta-gonad-mesonephros (AGM) region at E11.5. Strikingly, hematopoietic cells residing in fetal liver displayed minimal apoptosis evident by a few TUNEL positive cells. Colony forming assays revealed a myeloid biased hematopoiesis in Mdm2 haplo-insufficient HSCs. Vav-Cre;Mdm2 fl/+ mice displayed a marked reduction in Lin -/CD150 +/c-Kit +/Sca-1 + HSCs cells and significant decrease in peripheral blood counts. Deletion of Trp53 in these mice (Vav-Cre;Trp53 fl/fl;Mdm2 fl/+) resulted in marked decrease in CD19+ B lymphocytes cells whereas the population of CD11b+ myeloid cells did not change. The population of Lin neg-c-Kit + hematopoietic stem/progenitor cells isolated from the bone marrow of Vav-Cre;Mdm2 fl/+ mice displayed marked downregulation of cholesterol biosynthesis and mevalonate pathway (-log2 pvalue=20). Strikingly, 85% of genes involved in cholesterol biosynthesis (29 genes) were downregulated in Vav-Cre;Mdm2 fl/+ mice. Homozygous deletion of Trp53 in Vav-Cre;Mdm2 fl/+ mice did not rescue the metabolic alterations driven by Mdm2 haplo-insufficiency. In addition, the gene signature of oxidative phosphorylation(oxphos), was remarkably upregulated in Vav-Cre;Mdm2 fl/+ mice independent of p53. We further demonstrate that Cre-mediated induction of a Trp53R172 mutation in Mdm2 haplo-insufficient mice resulted in malignant transformation of HSCs leading to acute myeloid leukemia (AML). Of note, mice with homozygote Trp53 mutation and/or deletion without Mdm2- haplo-insufficiency developed lymphoma and not leukemia. In human, MDM2 loss of heterozygosity (MDM2 LOH) in AML was always concomitant with TP53 missense mutations (log2 odds ratio>3, p<.001), and not TP53 deletions or truncations whereas in lymphomas, MDM2 LOH and TP53 mutations were mutually exclusive. Conclusion: Using a genetic model, we have shown that Mdm2 haplo-insufficiency in HSCs leads to apoptosis and clonal selection towards myeloid biased hematopoiesis. Mechanistically, Mdm2 haplo-insufficiency resulted in a metabolic switch from cholesterol biosynthesis to oxphos in HSCs. Notably, this metabolic reprograming is not rescued by deletion of Trp53. However, mutation of Trp53 in Mdm2 haplo-insufficient hematopoietic stem cells resulted in leukemic transformation of HSCs leading to acute myeloid leukemia. Lastly, we demonstrate that MDM2 SNP309 is associated with TP53 mutation in AML and provide clinical evidence that MDM2 loss of heterozygosity is concomitant with TP53 mutations in AML with lower survival compared to TP53 mutant patients with diploid MDM2. Our findings demonstrate a p53-independent role for Mdm2 in metabolic maintenance of hematopoietic stem/progenitor cells. Figure 1 Figure 1. Disclosures Khoury: Kiromic: Research Funding; Angle: Research Funding; Stemline Therapeutics: Research Funding. Andreeff: Glycomimetics: Consultancy; Medicxi: Consultancy; Karyopharm: Research Funding; ONO Pharmaceuticals: Research Funding; Senti-Bio: Consultancy; Reata, Aptose, Eutropics, SentiBio; Chimerix, Oncolyze: Current holder of individual stocks in a privately-held company; Syndax: Consultancy; Amgen: Research Funding; Daiichi-Sankyo: Consultancy, Research Funding; Breast Cancer Research Foundation: Research Funding; Novartis, Cancer UK; Leukemia & Lymphoma Society (LLS), German Research Council; NCI-RDCRN (Rare Disease Clin Network), CLL Foundation; Novartis: Membership on an entity's Board of Directors or advisory committees; Oxford Biomedica UK: Research Funding; AstraZeneca: Research Funding; Aptose: Consultancy.

Mdm2 Haplo-Insufficiency in Hematopoietic and Mesenchymal Progenitor Cells Results in Cell Death

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 10-10
Author(s):  
Rasoul Pourebrahim ◽  
Rafael Heinz Montoya ◽  
Zoe Alaniz ◽  
Lauren B Ostermann ◽  
Edward Ayoub ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Progenitor Cells ◽  
Research Funding ◽  
Hematopoietic Cells ◽  
Mesenchymal Progenitor Cells ◽  
Heterozygous Deletion ◽  
Hematopoietic Stem ◽  
Osteoprogenitor Cells

The murine double minute 2 (Mdm2) protein is an important negative regulator of the p53 tumor suppressor, required for normal embryonic development and homeostasis. In humans, a single nucleotide polymorphism in the MDM2 promoter is associated with increased risk of cancer suggesting the importance of MDM2 levels in tumorigenesis (Bond et al., 2004). Mice with Mdm2 haploinsufficiency were previously reported as phenotypically normal with increased p53-dependent response to ionizing radiation (IR) resulting in lethal bone marrow failure (Terzian et al., 2007). However, the mechanism of radiosensitivity in these mice is unknown. To better characterize the phenotype of Mdm2 haploinsufficient mice and explore the mechanism of IR sensitivity, we developed a lineage tracing system to genetically label and trace the fate of cells after heterozygous deletion of Mdm2 in hematopoietic as well as mesenchymal progenitor cells. We utilized mTmG allele as a traceable reporter in which green fluorescence (GFP) replaces red fluorescence (TdTomato) after Cre-mediated recombination. Using Vav-Cre or Mx1-Cre, we first targeted Mdm2 in hematopoietic cells and marked them by TdTomato (Mdm2-WT) and GFP (Mdm2+/-). Heterozygous deletion of Mdm2 in hematopoietic stem cells using Vav-Cre resulted in massive apoptosis of emerging hematopoietic progenitor cells in the aorta-gonad-mesonephros (AGM) region at E10.5. Marker segregation analysis by fluorescence microscopy and flow cytometry revealed a population of hematopoietic stem cells having both TdTomato and GFP markers that escaped from apoptosis and reconstituted the hematopoietic cells in the fetal liver. Deletion of p53 in these mice did not rescue the apoptotic phenotype of hematopoietic cells with Mdm2 haploinsufficiency suggesting that a non-p53 dependent function of Mdm2 is necessary for proper development of hematopoietic stem cells in early development. In adult mice, Mdm2 haploinsufficiency in hematopoietic cells resulted in significant reduction in bone marrow hematopoietic stem cells in the absence of IR induced cellular stress. In Mx1-Cre;mTmG;Mdm2fl/+ mice, induction of Cre activity by pIpC injection resulted in hematopoietic failure evident by pancytopenia in peripheral blood. To test whether the same apoptotic response to Mdm2 haploinsufficiency can occur in other lineages, we generated a traceable conditional model of Mdm2 haploinsufficiency in mesenchymal progenitor cells using Osx-Cre and Prx1-Cre. Mice with heterozygous deletion of Mdm2 (Osx-Cre;mTmG;Mdm2fl/+) showed apoptosis of emerging osteoprogenitor cells at E16.5. Analysis of bone at 4 weeks revealed significant apoptosis of emerging osteoprogenitor cells further supporting our findings in the hematopoietic lineage. Together, our data highlights the importance of Mdm2 levels in hematopoietic and mesenchymal stem cell hemostasis and identifies depletion of hematopoietic stem cells in the bone marrow as the mechanism of radiosensitivity in Mdm2 haploinsufficient mice. Disclosures Andreeff: Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding.

scholarly journals Evidence for malignant transformation in acute myeloid leukemia at the level of early hematopoietic stem cells by cytogenetic analysis of CD34+ subpopulations

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 2906-2912 ◽  
Author(s):  
D Haase ◽  
M Feuring-Buske ◽  
S Konemann ◽  
C Fonatsch ◽  
C Troff ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Malignant Transformation ◽  
Cell Sorting ◽  
Myeloid Leukemia ◽  
De Novo ◽  
Leukemic Cells ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Acute myeloid leukemia (AML) is a heterogenous disease according to morphology, immunophenotype, and genetics. The retained capacity of differentiation is the basis for the phenotypic classification of the bulk population of leukemic blasts and the identification of distinct subpopulations. Within the hierarchy of hematopoietic development and differentiation it is still unknown at which stage the malignant transformation occurs. It was our aim to analyze the potential involvement of cells with the immunophenotype of pluripotent stem cells in the leukemic process by the use of cytogenetic and cell sorting techniques. Cytogenetic analyses of bone marrow aspirates were performed in 13 patients with AML (11 de novo and 2 secondary) and showed karyotype abnormalities in 10 cases [2q+, +4, 6p, t(6:9), 7, +8 in 1 patient each and inv(16) in 4 patients each]. Aliquots of the samples were fractionated by fluorescence-activated cell sorting of CD34+ cells. Two subpopulations, CD34+/CD38-(early hematopoietic stem cells) and CD34+/CD38+ (more mature progenitor cells), were screened for karyotype aberations as a marker for leukemic cells. Clonal abnormalities and evaluable metaphases were found in 8 highly purified CD34+/CD38-populations and in 9 of the CD34+/CD38-specimens, respectively. In the majority of cases (CD34+/CD38-, 6 of 8 informative samples; CD34+/CD38+, 5 of 9 informative samples), the highly purified CD34+ specimens also contained cytogenetically normal cells. Secondary, progression-associated chromosomal changes (+8, 12) were identified in the CD34+/CD38-cells of 2 patients. We conclude that clonal karyotypic abnormalities are frequently found in the stem cell-like (CD34+/CD38-) and more mature (CD34+/CD38+) populations of patients with AML, irrespective of the phenotype of the bulk population of leukemic blasts and of the primary or secondary character of the leukemia. Our data suggest that, in AML, malignant transformation as well as disease progression may occur at the level of CD34+/CD38-cells with multilineage potential.

MicroRNA-29a Is An Oncogene in Acute Myeloid Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 683-683
Author(s):  
Christopher Y. Park ◽  
Yoon-Chi Han ◽  
Govind Bhagat ◽  
Jian-Bing Fan ◽  
Irving L Weissman ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Mirna Expression ◽  
Myeloid Leukemia ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract microRNAs (miRNAs) are short, non-protein encoding RNAs that bind to the 3′UTR’s of target mRNAs and negatively regulate gene expression by facilitating mRNA degradation or translational inhibition. Aberrant miRNA expression is well-documented in both solid and hematopoietic malignancies, and a number of recent miRNA profiling studies have identified miRNAs associated with specific human acute myeloid leukemia (AML) cytogenetic groups as well as miRNAs that may prognosticate clinical outcomes in AML patients. Unfortunately, these studies do not directly address the functional role of miRNAs in AML. In fact, there is no direct functional evidence that miRNAs are required for AML development or maintenance. Herein, we report on our recent efforts to elucidate the role of miRNAs in AML stem cells. miRNA expression profiling of AML stem cells and their normal counterparts, hematopoietic stem cells (HSC) and committed progenitors, reveals that miR-29a is highly expressed in human hematopoietic stem cells (HSC) and human AML relative to normal committed progenitors. Ectopic expression of miR-29a in mouse HSC/progenitors is sufficient to induce a myeloproliferative disorder (MPD) that progresses to AML. During the MPD phase of the disease, miR-29a alters the composition of committed myeloid progenitors, significantly expedites cell cycle progression, and promotes proliferation of hematopoietic progenitors at the level of the multipotent progenitor (MPP). These changes are manifested pathologically by marked granulocytic and megakaryocytic hyperplasia with hepatosplenomegaly. Mice with miR-29a-induced MPD uniformly progress to an AML that contains a leukemia stem cell (LSC) population that can serially transplant disease with as few as 20 purified LSC. Gene expression analysis reveals multiple tumor suppressors and cell cycle regulators downregulated in miR-29a expressing cells compared to wild type. We have demonstrated that one of these genes, Hbp1, is a bona fide miR-29a target, but knockdown of Hbp1 in vivo does not recapitulate the miR-29a phenotype. These data indicate that additional genes are required for miR-29a’s leukemogenic activity. In summary, our data demonstrate that miR-29a regulates early events in normal hematopoiesis and promotes myeloid differentiation and expansion. Moreover, they establish that misexpression of a single miRNA is sufficient to drive leukemogenesis, suggesting that therapeutic targeting of miRNAs may be an effective means of treating myeloid leukemias.

CD52 Expression In Leukemic Stem/Progenitor Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2743-2743 ◽  
Author(s):  
Vivian G. Oehler ◽  
Roland B. Walter ◽  
Carrie Cummings ◽  
Olga Sala-Torra ◽  
Derek L. Stirewalt ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Progenitor Cells ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Research Funding ◽  
Lymphoblastic Leukemia ◽  
Cell Populations ◽  
Cell Surface Glycoprotein ◽  
Hematopoietic Stem

Abstract Abstract 2743 CD52 is a cell surface glycoprotein of unknown function that is expressed in B and T lymphocytes, macrophages, and monocytes, but is not expressed in normal hematopoietic stem/progenitor cells. CD52 is also expressed in chronic lymphocytic leukemia (CLL), B-cell acute lymphoblastic leukemia (ALL), and some cases of T-ALL. Alemtuzumab, a recombinant humanized monoclonal antibody, targets CD52 and is used to treat CLL. In contrast to normal hematopoietic stem/progenitor cells, CD52 expression has been described in acute myeloid leukemia (AML) and in blast crisis (BC) chronic myeloid leukemia (CML). Based on these observations we were curious whether CD52 expression distinguished normal from malignant or more mature from immature stem/progenitors cells, and whether these cells were sensitive to alemtuzumab. CD52 expression was examined in three blast cell populations (CD34+/CD38-, CD34+/CD38+, and CD34-) in patients with myeloid (44) and lymphoid (18) neoplasms, and normal patients (6). In normal hematopoietic cells, stems cells are enriched in the first population; more mature cells are characterized by increasing CD38 expression and loss of CD34 expression. In AML and CML leukemia stem cells may arise within either CD34+ population and possibly in the CD34- population. Relative to normal lymphocytes average CD52 expression could be characterized as low to moderate. Using an expression cutoff of > 20%, in contrast to normal patients, CD52 was detected in at least one of three blast populations in almost all patients. Using a more stringent cutoff of > 50%, CD52 was expressed in CD34+/CD38- cells in 7/11 B-ALL and 6/7 T-ALL cases and was concordantly expressed in the other two populations. Using the same criteria in myeloid malignancies (Table 1), expression occurred more frequently in AML, AML arising from myelodysplastic syndrome (MDS), and BC CML. In AML and AML arising from MDS, CD52 was expressed in the 34+/38- population in 7/15 cases (47%) and 4/7 cases (57%), respectively; it was expressed in both BC CML patients. In AML and BC CML patients, CD52 was expressed at similar levels in the CD34+/CD38+ fraction. No clear association between CD52 expression and cytogenetic abnormalities was found. We then examined whether CD52 expression differentiated normal from malignant blasts (CD34+/CD38- and CD34+/CD38+) in two CML myeloid BC patients. FISH and quantitative PCR demonstrated that BCR-ABL was expressed in all 4 populations, which were also morphologically distinct. Colony forming unit (CFU) assays demonstrated a significantly decreased ability to form CFU (on average 5–20 fold decrease) in CD52+/CD34+/CD38- CML cells suggesting CD52 cells may be more mature. Lastly and not previously described, we found that several BC CML cell lines express CD52, and complement-mediated cell cytotoxicity was similar in the highest expressing cell lines to that seen in EHEB (B-CLL) cells known to be targeted by alemtuzumab. Thus, alemtuzumab may have clinical efficacy in BC CML. In conclusion, CD52 is expressed on blast populations enriched for leukemic stem cells. Whether the absence or presence of CD52 more precisely segregates a leukemia stem cell containing population currently remains unknown and requires functional testing in a murine model. Our preliminary experiments in CML suggest CD52 may not differentiate between normal and malignant stem/progenitor cells. However, CD52 expression may distinguish normal and malignant stem cell populations in cases where CD52 and CD38 are more highly expressed. The observation that CD52 expression is increased in acute vs. chronic leukemias raises the intriguing possibility that CD52, if not directly involved, may be a marker for genes or pathways contributing to the block in differentiation seen with progression to acute leukemia. Furthermore, given that CD52 expression is heterogeneous in chronic disorders, it is possible that CD52 expression within these populations may correlate with poor prognosis or impending leukemic conversion. Table 1. The proportion of patients (44) expressing CD52 at levels > 50% in 3 blast populations. Three populations were present in most, but not all patients. Gray shading indicates chronic myeloid diseases. MPN is myeloproliferative neoplasm; NOS is not otherwise specified; ET is essential thrombocythemia; CMML is chronic myelomonocytic leukemia; and an arrow represents progressed to. Disclosure: Oehler: Pfizer: Research Funding. Radich:Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

Targeting Acute Myeloid Leukemia Stem Cells by MUC1-C Subunit Inhibition

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 848-848 ◽  
Author(s):  
Dina Stroopinsky ◽  
Jacalyn Rosenblatt ◽  
Keisuke Ito ◽  
Li Yin ◽  
Hasan Rajabi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Colony Formation ◽  
Myeloid Leukemia ◽  
Muc1 Expression ◽  
Hematopoietic Stem ◽  
Flow Cytometric ◽  
Control Peptide ◽  
Cd34 Cells ◽  
Acute Myeloid

Abstract Abstract 848 Introduction: Acute myeloid leukemia (AML) arises from a malignant stem cell population that is resistant to cytotoxic therapy and represents a critical reservoir of conferring disease recurrence. A major focus of investigation is the identification of unique markers on leukemia stem cells (LSCs) that differentiate them from normal hematopoietic stem cells and thereby serve as potential therapeutic targets. MUC1 is a high molecular weight transmembrane glycoprotein that is aberrantly expressed in many epithelial tumors and confers cell growth and survival. We have developed an inhibitor of the MUC1-C receptor subunit that blocks oligomer formation and nuclear localization. In the present study, we have examined expression of MUC1 on LSCs as compared to normal hematopoietic stem cells and studied the effect of MUC1-C inhibition on the functional properties of LSCs. Methods and Results: Using multichannel flow cytometric analysis, we isolated the LSC compartment as defined by CD34+/CD38-/lineage- cells from bone marrow specimens obtained from patients with active AML. The majority of LSCs strongly expressed MUC1 with a mean percentage of 77% (n=6). These findings were confirmed by immunocytochemical staining of LSCs isolated by flow cytometric sorting. MUC1 expression was not detectable on the CD34- fraction of AML cells, but was present on the granulocyte-macrophage progenitor (GMP) fraction (CD34+/CD38+ cells) (mean=83%; n=6). In contrast, MUC1 expression was not observed on CD34+ progenitors isolated from normal donors (18%, n=6). In concert with these findings, RT-PCR analysis for MUC1 RNA demonstrated expression in CD34+ cells isolated from AML patients, but not normal volunteers. Notably, we also found that MUC1 expression selectively identifies malignant hematopoietic progenitors in a patient with chimerism between normal and leukemia derived stem cells. The presence of MUC1+CD34+ cells was detected in a patient with AML who achieved a morphologic complete remission following sex mismatched allogeneic transplantation. Using Bioview technology, we found that MUC1 is expressed only in the recipient (XX) CD34+ cells, representing residual malignant cells, whereas the donor (XY) derived CD34+ cells, representing the majority of the progenitors, lacked MUC1 expression. We subsequently examined the effects of MUC1-C inhibition on the capacity of leukemic progenitors to proliferate and support colony formation. MUC1-C inhibition with the GO-203 cell-penetrating peptide resulted in downregulation of the β-catenin pathway, an important modulator of cell division and survival, which is known to support the LSC phenotype. No significant change was detected with a control peptide, or with MUC1-C inhibition of progenitors isolated from a normal control. Furthermore, MUC1-C inhibition resulted in apoptosis, as demonstrated by flow cytometric staining for AnnexinV in AML CD34+ cells, but not in CD34+ progenitors isolated from normal volunteers (mean Annexin positive cells 53% and 5%, respectively, n=4). Consistent with these findings, the MUC1-C inhibitor, but not the control, peptide resulted in cell death of CD34+ cells isolated from AML patients, but not normal controls. Most significantly, exposure of CD34+ AML cells to the MUC1-C inhibitor resulted in loss of their capacity for colony formation in vitro with mean colonies of 4 and 40 for those cells exposed to the MUC1 inhibitor and a control peptide (n=2). In contrast, colony formation by normal hematopoietic stem cells was unaffected. Conclusions: MUC1 is selectively expressed by leukemic progenitors and may be used to differentiate malignant from normal hematopoietic stem cell populations. MUC1-C receptor subunit inhibition results in (i) downregulation of b-catenin signaling, (ii) induction of apoptosis and cell death, and (iii) disruption of the capacity to induce leukemia colony formation. Disclosures: Stone: genzyme: Consultancy; celgene: Consultancy; novartis: Research Funding. Kufe:Genus Oncology: Consultancy, Equity Ownership.

TIM-3 Is a Promising Target to Eradicate Acute Myeloid Leukemia Stem Cells Sparing Normal Hematopoietic Stem Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 559-559
Author(s):  
Toshihiro Miyamoto ◽  
Yoshikane Kikushige ◽  
Takahiro Shima ◽  
Koichi Akashi
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Leukemia Cell ◽  
Cytotoxic Activities ◽  
Antibody Treatment ◽  
Hematopoietic Stem ◽  
Acute Myeloid

Abstract Abstract 559 Acute myeloid leukemia (AML) originates from self-renewing leukemic stem cells (LSCs), an ultimate therapeutic target for permanent cure. To selectively kill AML LSCs sparing normal hematopoietic stem cells (HSCs), one of the most practical approaches is to target the AML LSCs-specific surface or functionally indispensable molecules. Based on differential transcriptome analysis of prospectively-purified CD34+CD38− LSCs from AML patient samples and normal HSCs, we found that T-cell immunoglobulin mucin-3 (TIM-3) was highly expressed in AML LSCs but not in normal HSCs (Kikushige et al., Cell Stem Cell, 2010). In normal hematopoiesis, TIM-3 is mainly expressed in mature monocytes and a fraction of NK cells, but not in granulocytes, T cells or B cells. In the bone marrow, TIM-3 is expressed only in a fraction of granulocyte/macrophage progenitors (GMPs) at a low level, but not in HSCs, common myeloid progenitors, or megakaryocyte/erythrocyte progenitors. In contrast, in human AML, TIM-3 was expressed on cell surface of the vast majority of CD34+CD38− LSCs and CD34+CD38+ leukemic progenitors in AML of most FAB types, except for acute promyelocytic leukemia (M3). FACS-sorted TIM-3+ but not TIM-3− AML cells reconstituted human AML in the immunodeficient mice, indicating that the TIM-3+ population contains most of functional LSCs. To selectively eradicate TIM-3-expressing AML LSCs, we established an anti-human TIM-3 mouse IgG2a antibody, ATIK2a, possessing antibody-dependent cellular cytotoxic and complement-dependent cytotoxic activities in leukemia cell lines transfected with TIM-3. We first tested the effect of ATIK2a treatment on reconstitution of normal HSCs in a xenograft model. ATIK2a was intraperitoneally injected to the mice once a week after 12 hours of transplantation of human CD34+ cells. Injection of ATIK2a did not affect reconstitution of normal human hematopoiesis except removing TIM-3-expressing mature monocytes. In contrast, injection of TIM-3 to the mice transplanted with human AML samples markedly reduced leukemic repopulation. In some mice transplanted with AML bone marrow, only normal hematopoiesis was reconstituted after anti-TIM-3 antibody treatment, suggesting that the antibody selectively killed AML cells, sparing residual normal HSCs. To further test the inhibitory effect of ATIK2a on established human AML, eight weeks after transplantation of human AML cells, engraftment of human AML cells was confirmed by blood sampling and thereafter ATIK2a was injected to these mice. In all cases tested, ATIK2a treatment significantly reduced human TIM-3+ AML fraction as well as the CD34+CD38− LSCs fraction. In addition, to verify the anti-AML LSCs effect of ATIK2a treatment, human CD45+AML cells from the primary recipients were re-transplanted into secondary recipients. All mice transplanted from primary recipients treated with control IgG developed AML, whereas none of mice transplanted with cells from ATIK2a-treated primary recipients developed AML, suggesting that functional LSCs were effectively eliminated by ATIK2a treatment in primary recipients. Thus, TIM-3 is a promising surface molecule to target AML LSCs. Our experiments strongly suggest that targeting this molecule by monoclonal antibody treatment is a practical approach to eradicate human AML. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Clonal Evolution of Preleukemic Hematopoietic Stem Cells Precedes Human Acute Myeloid Leukemia

2012 ◽  
Vol 4 (149) ◽  
pp. 149ra118-149ra118 ◽  
Author(s):  
M. Jan ◽  
T. M. Snyder ◽  
M. R. Corces-Zimmerman ◽  
P. Vyas ◽  
I. L. Weissman ◽  
...  
Keyword(s):  
Stem Cells ◽  
Acute Myeloid Leukemia ◽  
Hematopoietic Stem Cells ◽  
Myeloid Leukemia ◽  
Clonal Evolution ◽  
Hematopoietic Stem ◽  
Human Acute Myeloid Leukemia ◽  
Acute Myeloid
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