The hematopoietic stem cell compartment of JAK2V617F-positive myeloproliferative disorders is a reflection of disease heterogeneity by Chloe James, Frederic Mazurier, Sabrina Dupont, Ronan Chaligne, Isabelle Lamrissi-Garcia, Micheline Tulliez, Eric Lippert, François-Xavier Mahon, Jean-Max Pasquet, Gabriel Etienne, François Delhommeau, Stephane Giraudier, William Vainchenker, and Hubert de Verneuil Blood Volume 112(6):2429-2438 September 15, 2008 ©2008 by American Society of Hematology

The JAK2V617F mutation is present in LT-SRCs. The JAK2V617F mutation is present in LT-SRCs. CD34+CD45+ cells present in the mouse BM were sorted and grown in LTC-IC medium. The LTC-IC frequencies were determined (y-axis), and LTC-IC-derived erythroid and granulocytic colonies were genotyped. Each histogram represents a mouse reconstituted with PV or PMF sample. On each histogram is indicated the proportion and the number of wild-type (▭), JAK2V617F heterozygous (), and homozygous () colonies. Chloe James et al. Blood 2008;112:2429-2438 ©2008 by American Society of Hematology

The SRCs from patients with PV and JAK2V617F-positive myelofibrosis have a different differentiation program. The SRCs from patients with PV and JAK2V617F-positive myelofibrosis have a different differentiation program. (A) The percentages of myeloid (▭) and B-lymphoid () cells within the human graft of PV (n = 8), PMF (n = 4), and PPV-MF3 reconstituted mice. (B) Flow cytometric analysis of the BM of 3 representative mice, receiving a transplant of PV, PMF, or PPV-MF CD34+ cells. (Top panel) SSC versus CD45 analysis showing human cells (CD45+). (Bottom panel) CD45+ cells analyzed for CD33 and CD19 expression, showing human myeloid (CD45+CD33+) and B-lymphoid (CD45+CD19+) cells. Chloe James et al. Blood 2008;112:2429-2438 ©2008 by American Society of Hematology

JAK2V617F SRCs are capable to give rise to multilineage differentiated cells. JAK2V617F SRCs are capable to give rise to multilineage differentiated cells. (A) Human B-lymphoid (CD45+CD19+) and myeloid (CD45+CD33+) cells engrafted in 10 NOD/SCID mice 15 weeks after transplantation were sorted and genotyped for JAK2V617F. The percentage of JAK2V617F over total JAK2 is reported. (B) Single CD34+CD38− cells from 2 PV, 3 PMF, and one post-PV MF were cultured in B/NK/myeloid differentiation conditions. Clones with lympho-myeloid potentialities (MNK and BMNK) were genotyped. The histograms represent the numbers of lympho-myeloid clones from each patient. ▭ represents wild-type JAK2; bars, heterozygous JAK2V617F; , homozygous JAK2V617F. Chloe James et al. Blood 2008;112:2429-2438 ©2008 by American Society of Hematology

Kinetics of engraftment suggests that leukemic SRCs have not acquired proliferative advantage, except for a subset of patients. Kinetics of engraftment suggests that leukemic SRCs have not acquired proliferative advantage, except for a subset of patients. Analysis of the kinetics of human cell engraftment by sequential BM aspiration of the right femur (RF) 6, 12, and 15 weeks after transplantation. Chloe James et al. Blood 2008;112:2429-2438 ©2008 by American Society of Hematology

Putative model of evolution from PV toward post-PV myelofibrosis, through modification of the HSC compartment. Putative model of evolution from PV toward post-PV myelofibrosis, through modification of the HSC compartment. The left diagram shows a model of hematopoiesis from the HSCs to mature cells in PV. JAK2V617F cells are in gray, and JAK2WT cells in white. The properties of JAK2V617F HSCs are not modified, compared with JAK2 WT HSC, either in term of self-renewal or proliferation. However, a major amplification of terminal myeloid differentiation is observed, from the stage of differentiation when progenitors express homodimeric type I cytokine receptors. We hypothesize that JAK2V617F cells would produce TGF-β1, responsible for the progressive development of myelofibrosis, and another cytokine or chemokine (X-factor) responsible for the progressive destruction of normal hematopoiesis, that could also be TGF-β1. As JAK2WT HSCs would express the receptors of X-factor, they would be sensitive to X-factor–negative regulatory signals and therefore progressively destructed. On the contrary, JAK2V617F HSCs would have a decreased expression of X-factor receptor or signaling and would express antiapoptotic proteins, such as bcl-xl, being therefore insensitive to apoptosis. The right panel shows the stage of post-PV myelofibrosis, when the increasing and persistent production of TGF-β1 would induce myelofibrosis and when JAK2WT HSCs have been destructed following X-factor stimulation. The only remaining HSCs are thus JAK2V617F, without any increase in self-renewing properties. Chloe James et al. Blood 2008;112:2429-2438 ©2008 by American Society of Hematology