Endothelin receptor emerges as a potential target of Hoxa9-mediated leukemogenesis.
View details for PubMedID 30401485
Bone marrow histomorphologic criteria can accurately diagnose hemophagocytic lymphohistiocytosis.
Hemophagocytic lymphohistiocytosis is a rare multi-system inflammatory disorder with diagnostic criteria based on the HLH-2004 trial. Hemophagocytosis is the only histomorphologic criterion, but in isolation is neither specific nor sensitive for the diagnosis of hemophagocytic lymphohistiocytosis. While objective thresholds for clinical and laboratory criteria have been established, specific criteria for histomorphologic evidence of hemophagocytosis in hemophagocytic lymphohistiocytosis have not been rigorously evaluated or established. We sought to determine if numerical and objective criteria for morphologic hemophagocytosis could be identified, and if such criteria would aid in the diagnosis of hemophagocytic lymphohistiocytosis. We analyzed the morphologic features of hemophagocytosis in 78 patients presenting with clinical features suspicious for hemophagocytic lymphohistiocytosis: 40 patients with hemophagocytic lymphohistiocytosis and 38 patients without hemophagocytic lymphohistiocytosis. We demonstrate that non-nucleated erythrophagocytosis alone is a non-specific finding, while hemophagocytosis of granulocytes (1 per 1000 cells, area under the curve: 0.92, 95% confidence interval: 0.86, 0.99), nucleated erythrocytes (4 per 1000 cells, area under the curve: 0.92, 95% confidence interval: 0.87, 0.98), and at least one hemophagocyte containing multiple nucleated cells (area under the curve: 0.91, 95% confidence interval: 0.85, 0.95) are strongly associated with hemophagocytic lymphohistiocytosis. Joint modeling of hemophagocytes containing engulfed granulocytes, nucleated erythrocytes, and lymphocytes effectively distinguished between hemophagocytic lymphohistiocytosis and non-hemophagocytic lymphohistiocytosis (cross-validated area under curve: 0.90, 95% confidence interval: 0.83, 0.97).
View details for PubMedID 29903767
A replicable CD271+ mesenchymal stromal cell density score: bringing the dysfunctional myelodysplastic syndrome niche to the diagnostic laboratory.
Leukemia & lymphoma
View details for PubMedID 27808583
Endothelial cell derived angiocrine support of acute myeloid leukemia targeted by receptor tyrosine kinase inhibition.
2015; 39 (9): 984–89
In acute myeloid leukemia (AML), refractory disease is a major challenge and the leukemia microenvironment may harbor refractory disease. Human AML cell lines KG-1 and HL-60 expressed receptors also found on endothelial cells (ECs) such as VEGFRs, PDGFRs, and cKit. When human AML cells were co-cultured with human umbilical vein endothelial cells (HUVECs) and primary bone marrow endothelial cell (BMECs), the AML cells were more resistant to cytarabine chemotherapy, even in transwell co-culture suggesting angiocrine regulation. Primary BMECs secreted significantly increased levels of VEGF-A and PDGF-AB after exposure to cytarabine. Pazopanib, a receptor tyrosine kinase inhibitor (RTKI) of VEGFRs, PDGFRs, and cKit, removed EC protection of AML cells and enhanced AML cell sensitivity to cytarabine. Xenograft modeling showed significant regression of AML cells and abrogation of BM hypervascularity in RTKI treated cohorts. Together, these results show direct cytotoxicity of RTKIs on AML cells and reversal of EC protection. Combining RTKIs with chemotherapy may serve as promising therapeutic strategy for patients with AML.
View details for DOI 10.1016/j.leukres.2015.05.015
View details for PubMedID 26189107
Activation of the vascular niche supports leukemic progression and resistance to chemotherapy.
2014; 42 (11): 976–86.e3
Understanding the intricate cellular components of the bone marrow microenvironment can lead to the discovery of novel extrinsic factors that are responsible for the initiation and progression of leukemic disease. We have shown that endothelial cells (ECs) provide a fertile niche that allows for the propagation of primitive and aggressive leukemic clones. Activation of the ECs by vascular endothelial growth factor (VEGF)-A provides cues that enable leukemic cells to proliferate at higher rates and also increases the adhesion of leukemia to ECs. Vascular endothelial growth factor A-activated ECs decrease the efficacy of chemotherapeutic agents to target leukemic cells. Inhibiting VEGF-dependent activation of ECs by blocking their signaling through VEGF receptor 2 increases the susceptibility of leukemic cells to chemotherapy. Therefore, the development of drugs that target the activation state of the vascular niche could prove to be an effective adjuvant therapy in combination with chemotherapeutic agents.
View details for DOI 10.1016/j.exphem.2014.08.003
View details for PubMedID 25179751
View details for PubMedCentralID PMC4254082
Human ESC-derived hemogenic endothelial cells undergo distinct waves of endothelial to hematopoietic transition.
2013; 121 (5): 770–80
Several studies have demonstrated that hematopoietic cells originate from endotheliumin early development; however, the phenotypic progression of progenitor cells during human embryonic hemogenesis is not well described. Here, we define the developmental hierarchy among intermediate populations of hematopoietic progenitor cells (HPCs) derived from human embryonic stem cells (hESCs). We genetically modified hESCs to specifically demarcate acquisition of vascular (VE-cadherin) and hematopoietic (CD41a) cell fate and used this dual-reporting transgenic hESC line to observe endothelial to hematopoietic transition by real-time confocal microscopy. Live imaging and clonal analyses revealed a temporal bias in commitment of HPCs that recapitulates discrete waves of lineage differentiation noted during mammalian hemogenesis. Specifically, HPCs isolated at later time points showed reduced capacity to form erythroid/ megakaryocytic cells and exhibited a tendency toward myeloid fate that was enabled by expression of the Notch ligand Dll4 on hESC-derived vascular feeder cells. These data provide a framework for defining HPC lineage potential, elucidate a molecular contribution from the vascular niche in promoting hematopoietic lineage progression, and distinguish unique subpopulations of hemogenic endothelium during hESC differentiation.Live imaging of endothelial to hematopoietic conversion identifies distinct subpopulations of hESC-derived hemogenic endothelium. Expression of the Notch ligand DII4 on vascular ECs drives induction of myeloid fate from hESC-derived hematopoietic progenitors.
View details for DOI 10.1182/blood-2012-07-444208
View details for PubMedID 23169780
Development of a vascular niche platform for expansion of repopulating human cord blood stem and progenitor cells.
2012; 120 (6): 1344–47
Transplantation of ex vivo expanded human umbilical cord blood cells (hCB) only partially enhances the hematopoietic recovery after myelosuppressive therapy. Incubation of hCB with optimal combinations of cytokines and niche cells, such as endothelial cells (ECs), could augment the efficiency of hCB expansion. We have devised an approach to cultivate primary human ECs (hECs) in serum-free culture conditions. We demonstrate that coculture of CD34(+) hCB in direct cellular contact with hECs and minimal concentrations of thrombopoietin/Kit-ligand/Flt3-ligand resulted in a 400-fold expansion of total hematopoietic cells, 150-fold expansion of CD45(+)CD34(+) progenitor cells, and 23-fold expansion of CD45(+) Lin(-)CD34(hi+)CD45RA(-)CD49f(+) stem and progenitor cells over a 12-day period. Compared with cytokines alone, coculture of hCB with hECs permitted greater expansion of cells capable of multilineage engraftment and serial transplantation, hallmarks of long-term repopulating hematopoietic stem cells. Therefore, hECs establish a cellular platform for expansion of hematopoietic stem and progenitor cells and treatment of hematologic disorders.
View details for DOI 10.1182/blood-2011-12-398115
View details for PubMedID 22709690
View details for PubMedCentralID PMC3418723