| 1. |
- Dudenhöffer-Pfeifer, Monika, et al.
(författare)
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Immunoediting is not a primary transformation event in a murine model of MLL-ENL AML
- 2018
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Ingår i: Life Science Alliance. - : Life Science Alliance, LLC. - 2575-1077. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Although it is firmly established that endogenous immunity can prevent cancer outgrowth, with a range of immunomodulatory strategies reaching clinical use, most studies on the topic have been restricted to solid cancers. This applies in particular to cancer initiation, where model constraints have precluded investigations of immunosurveillance and immunoediting during the multistep progression into acute myeloid leukemia (AML). Here, we used a mouse model where the chimeric transcription factor MLL-ENL can be conditionally activated in vivo as a leukemic “first-hit,” which is followed by spontaneous transformation into AML. We observed similar disease kinetics regardless of whether AML developed in WT or immunocompromised hosts, despite more permissive preleukemic environments in the latter. When assessing transformed AML cells from either primary immunocompetent or immunocompromised hosts, AML cells from all sources could be targets of endogenous immunity. Our data argue against immunoediting in response to selective pressure from endogenous immunity as a universal primary transformation event in AML.
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| 2. |
- Eldeeb, Mohamed, et al.
(författare)
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A fetal tumor suppressor axis abrogates MLL-fusion-driven acute myeloid leukemia
- 2023
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 42:2
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Tidskriftsartikel (refereegranskat)abstract
- MLL-rearrangements (MLL-r) are recurrent genetic events in acute myeloid leukemia (AML) and frequently associate with poor prognosis. In infants, MLL-r can be sufficient to drive transformation. However, despite the prenatal origin of MLL-r in these patients, congenital leukemia is very rare with transformation usually occurring postnatally. The influence of prenatal signals on leukemogenesis, such as those mediated by the fetal-specific protein LIN28B, remains controversial. Here, using a dual-transgenic mouse model that co-expresses MLL-ENL and LIN28B, we investigate the impact of LIN28B on AML. LIN28B impedes the progression of MLL-r AML through compromised leukemia-initiating cell activity and suppression of MYB signaling. Mechanistically, LIN28B directly binds to MYBBP1A mRNA, resulting in elevated protein levels of this MYB co-repressor. Functionally, overexpression of MYBBP1A phenocopies the tumor-suppressor effects of LIN28B, while its perturbation omits it. Thereby, we propose that developmentally restricted expression of LIN28B provides a layer of protection against MYB-dependent AML.
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| 3. |
- Säwen, Petter, et al.
(författare)
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Murine HSCs contribute actively to native hematopoiesis but with reduced differentiation capacity upon aging
- 2018
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Ingår i: Elife. - 2050-084X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- A hallmark of adult hematopoiesis is the continuous replacement of blood cells with limited lifespans. While active hematopoietic stem cell (HSC) contribution to multilineage hematopoiesis is the foundation of clinical HSC transplantation, recent reports have questioned the physiological contribution of HSCs to normal/steady-state adult hematopoiesis. Here, we use inducible lineage tracing from genetically marked adult HSCs and reveal robust HSC-derived multilineage hematopoiesis. This commences via defined progenitor cells, but varies substantially in between different hematopoietic lineages. By contrast, adult HSC contribution to hematopoietic cells with proposed fetal origins is neglible. Finally, we establish that the HSC contribution to multilineage hematopoiesis declines with increasing age. Therefore, while HSCs are active contributors to native adult hematopoiesis, it appears that the numerical increase of HSCs is a physiologically relevant compensatory mechanism to account for their reduced differentiation capacity with age.
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| 4. |
- Velasco-Hernandez, Talia, et al.
(författare)
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Hif-1 alpha Deletion May Lead to Adverse Treatment Effect in a Mouse Model of MLL-AF9-Driven AML
- 2019
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 12:1, s. 112-121
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Tidskriftsartikel (refereegranskat)abstract
- Relapse of acute myeloid leukemia (AML) remains a significant clinical challenge due to limited therapeutic options and poor prognosis. Leukemic stem cells (LSCs) are the cellular units responsible for relapse in AML, and strategies that target LSCs are thus critical. One proposed potential strategy to this end is to break the quiescent state of LSCs, thereby sensitizing LSCs to conventional cytostatics. The hypoxia-inducible factor (HIF) pathway is a main driver of cellular quiescence and a potential therapeutic target, with precedence from both solid cancers and leukemias. Here, we used a conditional knockout Hif-1 alpha mouse model together with a standard chemotherapy regimen to evaluate LSC targeting in AML. Contrary to expectation, our studies revealed that Hif-1 alpha-deleted-leukemias displayed a faster disease progression after chemotherapy. Our studies thereby challenge the general notion of cancer stem cell sensitization by inhibition of the HIF pathway, and warrant caution when applying HIF inhibition in combination with chemotherapy in AML.
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| 5. |
- Yang, W., et al.
(författare)
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Enhancing Hematopoiesis from Murine Embryonic Stem Cells through MLL1-Induced Activation of a Rac/Rho/Integrin Signaling Axis
- 2020
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Ingår i: Stem Cell Reports. - : Elsevier BV. - 2213-6711. ; 14:2, s. 285-299
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Tidskriftsartikel (refereegranskat)abstract
- The Mixed Lineage Leukemia (MLL1, KMT2A) gene is critical for development and maintenance of hematopoietic stem cells (HSCs), however, whether this protein is limiting for HSC development is unknown due to lack of physiologic model systems. Here, we develop an MLL1-inducible embryonic stem cell (ESC) system and show that induction of wild-type MLL1 during ESC differentiation selectively increases hematopoietic potential from a transitional c-Kit(+)/Cd41(+) population in the embryoid body and also at sites of hematopoiesis in embryos. Single-cell sequencing analysis illustrates inherent heterogeneity of the c-Kit(+)/Cd41(+) population and demonstrates that MLL1 induction shifts its composition toward multilineage hematopoietic identities. Surprisingly, this does not occur through increasing Hox or other canonical MLL1 targets but through an enhanced Rac/Rho/integrin signaling state, which increases responsiveness to Vla4 ligands and enhances hematopoietic commitment. Together, our data implicate a Rac/Rho/integrin signaling axis in the endothelial to hematopoietic transition and demonstrate that MLL1 actives this axis.
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| 6. |
- Yuan, Ouyang, et al.
(författare)
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A somatic mutation in moesin drives progression into acute myeloid leukemia
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:16
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Tidskriftsartikel (refereegranskat)abstract
- Acute myeloid leukemia (AML) arises when leukemia-initiating cells, defined by a primary genetic lesion, acquire subsequent molecular changes whose cumulative effects bypass tumor suppression. The changes that underlie AML pathogenesis not only provide insights into the biology of transformation but also reveal novel therapeutic opportunities. However, backtracking these events in transformed human AML samples is challenging, if at all possible. Here, we approached this question using a murine in vivo model with an MLL-ENL fusion protein as a primary molecular event. Upon clonal transformation, we identified and extensively verified a recurrent codon-changing mutation (Arg(295)Cys) in the ERM protein moesin that markedly accelerated leukemogenesis. Human cancer-associated moesin mutations at the conserved arginine-295 residue similarly enhanced MLL-ENL-driven leukemogenesis. Mechanistically, the mutation interrupted the stability of moesin and conferred a neomorphic activity to the protein, which converged on enhanced extracellular signal-regulated kinase activity. Thereby, our studies demonstrate a critical role of ERM proteins in AML, with implications also for human cancer.
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| 7. |
- Bhattacharya, Deepta, et al.
(författare)
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Niche recycling through division-independent egress of hematopoietic stem cells
- 2009
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 114:22, s. 37-37
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic stem cells (HSCs) are thought to reside in discrete niches through stable adhesion, yet previous studies have suggested that host HSCs can be replaced by transplanted donor HSCs, even in the absence of cytoreductive conditioning. To explain this apparent paradox, we calculated, through cell surface phenotyping and transplantation of unfractionated blood, that similar to 1-5% of the total pool of HSCs enters into the circulation each day. Bromodeoxyuridine (BrdU) feeding experiments demonstrated that HSCs in the peripheral blood incorporate BrdU at the same rate as do HSCs in the bone marrow, suggesting that egress from the bone marrow to the blood can occur without cell division and can leave behind vacant HSC niches. Consistent with this, repetitive daily transplantations of small numbers of HSCs administered as new niches became available over the course of 7 d led to significantly higher levels of engraftment than did large, single-bolus transplantations of the same total number of HSCs. These data provide insight as to how HSC replacement can occur despite the residence of endogenous HSCs in niches, and suggest therapeutic interventions that capitalize upon physiological HSC egress.
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| 8. |
- Bryder, David
(författare)
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Hematopoiesis at single-cell resolution
- 2016
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 128:8, s. 1025-1026
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Bryder, David, et al.
(författare)
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Interleukin-3 supports expansion of long-term multilineage repopulating activity after multiple stem cell divisions in vitro
- 2000
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Ingår i: Blood. - 1528-0020. ; 96:5, s. 1748-1755
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Tidskriftsartikel (refereegranskat)abstract
- Although long-term repopulating hematopoietic stem cells (HSC) can self-renew and expand extensively in vivo, most efforts at expanding HSC in vitro have proved unsuccessful and have frequently resulted in compromised rather than improved HSC grafts. This has triggered the search for the optimal combination of cytokines for HSC expansion. Through such studies, c-kit ligand (KL), flt3 ligand (FL), thrombopoietin, and IL-11 have emerged as likely positive regulators of HSC self-renewal. In contrast, numerous studies have implicated a unique and potent negative regulatory role of IL-3, suggesting perhaps distinct regulation of HSC fate by different cytokines. However, the interpretations of these findings are complicated by the fact that different cytokines might target distinct subpopulations within the HSC compartment and by the lack of evidence for HSC undergoing self-renewal. Here, in the presence of KL+FL+megakaryocyte growth and development factor (MGDF), which recruits virtually all Lin(-)Sca-1(+)kit(+) bone marrow cells into proliferation and promotes their self-renewal under serum-free conditions, IL-3 and IL-11 revealed an indistinguishable ability to further enhance proliferation. Surprisingly, and similar to IL-11, IL-3 supported KL+FL+MGDF-induced expansion of multilineage, long-term reconstituting activity in primary and secondary recipients. Furthermore, high-resolution cell division tracking demonstrated that all HSC underwent a minimum of 5 cell divisions, suggesting that long-term repopulating HSC are not compromised by IL-3 stimulation after multiple cell divisions. In striking contrast, the ex vivo expansion of murine HSC in fetal calf serum-containing medium resulted in extensive loss of reconstituting activity, an effect further facilitated by the presence of IL-3. (Blood. 2000;96:1748-1755)
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| 10. |
- Dybedal, Ingunn, et al.
(författare)
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Tumor necrosis factor (TNF)-mediated activation of the p55 TNF receptor negatively regulates maintenance of cycling reconstituting human hematopoietic stem cells
- 2001
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Ingår i: Blood. - 1528-0020. ; 98:6, s. 1782-1791
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic stem cell (HSC) fate decisions between self-renewal and commitment toward differentiation are tightly regulated in vivo. Recent developments in HSC culture and improvements of human HSC assays have facilitated studies of these processes in vitro. Through such studies stimulatory cytokines critically involved in HSC maintenance in vivo have been demonstrated to also promote HSC self-renewing divisions in vitro. Evidence for negative regulators of HSC self-renewal is, however, lacking. Tumor necrosis factor (TNF), if overexpressed, has been implicated to mediate bone marrow suppression. However, whether and how TNF might affect the function of HSC with a combined myeloid and lymphoid reconstitution potential has not been investigated. In the present studies in vitro conditions recently demonstrated to promote HSC self-renewing divisions in vitro were used to study the effect of TNF on human HSCs capable of reconstituting myelopoiesis and lymphopoiesis in nonobese diabetic-severe combined immunodeficient (NOD-SCID) mice. Although all cord blood and adult bone marrow CD34(+)CD38(-) cells were capable of undergoing cell divisions in the presence of TNF, cycling HSCs exposed to TNF in vitro and in vivo were severely compromised in their ability to reconstitute NOD-SCID mice and long-term cultures. The negative effect of TNF was not dependent on the Fas pathway, and a similar effect could be observed using a mutant TNF exclusively targeting the p55 TNF receptor. TNF did not appear to enhance apoptosis or affect cell-cycle distribution of cultured progenitors, but rather promoted myeloid differentiation. Thus, TNF might regulate HSC fate by promoting their differentiation rather than self-renewal.
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