Contributions
Abstract: S876
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 16:00 - 16:15
Location: Room A7
Background
Hemizygous, interstitial deletion of chromosome 5q is the most common cytogenetic abnormality in myelodysplastic syndrome (MDS) and has been the focus of functional analysis. Some patients with this molecular lesion have the 5q− syndrome, a disorder with a highly consistent clinical phenotype, characterized by a distinct clinical phenotype including severe macrocytic anemia, a high or elevated platelet count with hypolobulated megakaryocytes in the bone marrow and a low rate of progression to acute myelogenous leukemia. The full clinical phenotype is likely caused by the integration of effects from allelic insufficiency for multiple genes. RPS14, CSNK1A1 and mir-145 are universally co-deleted in 5q-syndrome but mouse models of each gene deficiency recapitulate only a subset of the composite clinical features of del(5q) MDS.
Aims
We aimed to dissect the combinatorial effect of haploinsufficiency for Rps14, Csnk1a1 and miRNA-145 on the hematopoietic stem cell function in a novel murine model for del (5q) MDS We hypothesized that compound loss of Rps14, Csnk1a1 and miRNA145/146a has additive effects leading to recapitulation of the del(5q) MDS phenotype and an aggravated inflammatory response resulting in a more severe erythroid phenotype.
Methods
For in vivo studies, hematopoietic stem and progenitor cells (HSPCs) from compound haploinsufficient Rps14, Csnk1a1 mice were retrovirally transduced and miR-145/146a were stably knocked down, followed by transplantation of the cells into lethally irradiated recipient mice. In order to further dissect the mechanisms, we generated granulocyte-macrophage colony-stimulating factor (GM-CSF) estrogen-receptor (ER)-Hoxb8 cells and Fms-related tyrosine kinase 3 ligand (FL) ER-Hoxb8 cells from the del (5q) murine models.
Results
We demonstrate that compound deficiency has high fidelity to human MDS and recapitulates the del(5q) MDS phenotype including 1) anemia, 2) thrombocytosis, 3) hypolobulated megakaryocytes and 4) clonal dominance. Macrophages, regulatory cells of erythropoiesis and the innate immune response, were significantly increased in Rps14/Csnk1a1/miR-145/146a deficient mice as well as in del(5q) MDS patient bone marrows and showed activation of the innate immune response, reflected by increased expression of S100A8, and decreased phagocytic function.
The bone marrow microenvironment is abnormal in MDS, but whether this is a direct consequence of changes in hematopoietic cells or instead independent of the disease has not been determined. Using 1) our new mouse model, 2) co-culture models with a defined mesenchymal stromal cell population, 3) immunohistochemistry and RNA-sequencing in del(5q) MDS patient samples, we demonstrate that increased expression of S100A8 in MDS-derived macrophages induces S100A8 expression in neighboring mesenchymal stromal cells. We show that S100A8-expression in stromal cells leads to loss-of their hematopoiesis-supporting capacity.
Conclusion
In conclusion, our data support the hypothesis that the combined haploinsufficiency of multiple genes on 5q has additive effects in the del(5q) phenotype and in the activation of the innate immune system. Our data indicate that intrinsic defects of the del(5q) MDS hematopoietic stem cell directly alter the surrounding microenvironment, which in turn negatively affects hematopoiesis as an extrinsic mechanism.
Session topic: 9. Myelodysplastic syndromes – Biology & Translational Research
Keyword(s): Macrophage, MDS, Microenvironment
Abstract: S876
Type: Oral Presentation
Presentation during EHA23: On Saturday, June 16, 2018 from 16:00 - 16:15
Location: Room A7
Background
Hemizygous, interstitial deletion of chromosome 5q is the most common cytogenetic abnormality in myelodysplastic syndrome (MDS) and has been the focus of functional analysis. Some patients with this molecular lesion have the 5q− syndrome, a disorder with a highly consistent clinical phenotype, characterized by a distinct clinical phenotype including severe macrocytic anemia, a high or elevated platelet count with hypolobulated megakaryocytes in the bone marrow and a low rate of progression to acute myelogenous leukemia. The full clinical phenotype is likely caused by the integration of effects from allelic insufficiency for multiple genes. RPS14, CSNK1A1 and mir-145 are universally co-deleted in 5q-syndrome but mouse models of each gene deficiency recapitulate only a subset of the composite clinical features of del(5q) MDS.
Aims
We aimed to dissect the combinatorial effect of haploinsufficiency for Rps14, Csnk1a1 and miRNA-145 on the hematopoietic stem cell function in a novel murine model for del (5q) MDS We hypothesized that compound loss of Rps14, Csnk1a1 and miRNA145/146a has additive effects leading to recapitulation of the del(5q) MDS phenotype and an aggravated inflammatory response resulting in a more severe erythroid phenotype.
Methods
For in vivo studies, hematopoietic stem and progenitor cells (HSPCs) from compound haploinsufficient Rps14, Csnk1a1 mice were retrovirally transduced and miR-145/146a were stably knocked down, followed by transplantation of the cells into lethally irradiated recipient mice. In order to further dissect the mechanisms, we generated granulocyte-macrophage colony-stimulating factor (GM-CSF) estrogen-receptor (ER)-Hoxb8 cells and Fms-related tyrosine kinase 3 ligand (FL) ER-Hoxb8 cells from the del (5q) murine models.
Results
We demonstrate that compound deficiency has high fidelity to human MDS and recapitulates the del(5q) MDS phenotype including 1) anemia, 2) thrombocytosis, 3) hypolobulated megakaryocytes and 4) clonal dominance. Macrophages, regulatory cells of erythropoiesis and the innate immune response, were significantly increased in Rps14/Csnk1a1/miR-145/146a deficient mice as well as in del(5q) MDS patient bone marrows and showed activation of the innate immune response, reflected by increased expression of S100A8, and decreased phagocytic function.
The bone marrow microenvironment is abnormal in MDS, but whether this is a direct consequence of changes in hematopoietic cells or instead independent of the disease has not been determined. Using 1) our new mouse model, 2) co-culture models with a defined mesenchymal stromal cell population, 3) immunohistochemistry and RNA-sequencing in del(5q) MDS patient samples, we demonstrate that increased expression of S100A8 in MDS-derived macrophages induces S100A8 expression in neighboring mesenchymal stromal cells. We show that S100A8-expression in stromal cells leads to loss-of their hematopoiesis-supporting capacity.
Conclusion
In conclusion, our data support the hypothesis that the combined haploinsufficiency of multiple genes on 5q has additive effects in the del(5q) phenotype and in the activation of the innate immune system. Our data indicate that intrinsic defects of the del(5q) MDS hematopoietic stem cell directly alter the surrounding microenvironment, which in turn negatively affects hematopoiesis as an extrinsic mechanism.
Session topic: 9. Myelodysplastic syndromes – Biology & Translational Research
Keyword(s): Macrophage, MDS, Microenvironment