The overall goal of this project is to unravel how long-term hematopoietic stem cells (HSCLT) overproduce specific lineages of mature blood cells in disease conditions. In particular, we are interested in identifying the mechanisms responsible for the aberrant production of myeloid cells from transformed HSCLT to uncover novel molecular targets for the treatment of myeloid malignancies such as myeloproliferative neoplasms (MPN). This proposal is based on a novel model of early blood lineage specification we are currently developing in our laboratory in which specific HSCLT differentiation pathways facilitate the production of myeloid cells independently of the lymphoid lineage. We recently discovered two new populations of myeloid-biased multipotent progenitors (MPPs) that normally serve as transient compartments of myeloid amplification but are aberrantly expanded during MPN development. We propose that the hijacking of this myeloid-specific HSCLT differentiation pathway fuels the overproduction of myeloid cells in MPNs, and predict that blockade of its pathological activation may correct aberrant myeloid cell production in disease conditions. We will test these hypotheses using an inducible Scl-tTA:TRE-BCR/ABL (tTA-BA) mouse model of human chronic myelogenous leukemia (CML) that we have extensively characterized in our laboratory (Reynaud et al., 2011). Based on our preliminary data and already published results, we will investigate how cell intrinsic deregulations in the mechanisms controlling HSCLT fate decisions, such as impaired Notch pathway activity, cooperate with changes in the bone marrow (BM) environment, such as increased levels of pro-inflammatory cytokines, to drive MPN development.
In Specific Aim 1, we will address how aberrant activation of HSCLT differentiation pathways leads to myeloid expansion, and will dissect the role of Notch signaling in this process.
In Specific Aim 2, we will investigate how pro-inflammatory signals control HSCLT differentiation pathways in both normal and disease conditions, and will probe for potential crosstalk with Notch signaling.
In Specific Aim 3, we will test whether manipulating HSCLT differentiation pathways by blocking the mechanisms responsible for their aberrant activation could rep- resent a valid approach to treat MPNs. We will perform proof-of-principle experiments in mice and validate key findings using normal human cells and MPN patient samples. Taken together, these approaches will uncover how changes in early blood lineage specification contribute to MPN development, and provide rationales for the clinical use of HSC-based anti-differentiation therapies to treat myeloid malignancies.

Public Health Relevance

A major barrier to developing effective therapeutic interventions for blood disorders is our lack of understanding of what causes long-term hematopoietic stem cells (HSCLT) to overproduce specific types of mature blood cells in disease conditions. Our research project seeks to remove this critical roadblock by investigating how aberrant activation of myeloid-specific differentiation pathways in transformed HSCLT contributes to the development of myeloproliferative neoplasms (MPN) such as chronic myelogenous leukemia (CML). Our experiments address the exciting possibility that manipulating HSCLT differentiation pathways could represents a powerful approach to treat myeloid malignancies.

National Institute of Health (NIH)
Research Project (R01)
Project #
Application #
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Thomas, John
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California San Francisco
Internal Medicine/Medicine
Schools of Medicine
San Francisco
United States
Zip Code
Kohli, Latika; Passegué, Emmanuelle (2014) Surviving change: the metabolic journey of hematopoietic stem cells. Trends Cell Biol 24:479-87
Flach, Johanna; Bakker, Sietske T; Mohrin, Mary et al. (2014) Replication stress is a potent driver of functional decline in ageing haematopoietic stem cells. Nature 512:198-202
Pietras, Eric M; Lakshminarasimhan, Ranjani; Techner, Jose-Marc et al. (2014) Re-entry into quiescence protects hematopoietic stem cells from the killing effect of chronic exposure to type I interferons. J Exp Med 211:245-62
Schepers, Koen; Pietras, Eric M; Reynaud, Damien et al. (2013) Myeloproliferative neoplasia remodels the endosteal bone marrow niche into a self-reinforcing leukemic niche. Cell Stem Cell 13:285-99
Bakker, Sietske T; Passegue, Emmanuelle (2013) Resilient and resourceful: genome maintenance strategies in hematopoietic stem cells. Exp Hematol 41:915-23
Warr, Matthew R; Binnewies, Mikhail; Flach, Johanna et al. (2013) FOXO3A directs a protective autophagy program in haematopoietic stem cells. Nature 494:323-7
Reynaud, Damien; Pietras, Eric; Barry-Holson, Keegan et al. (2011) IL-6 controls leukemic multipotent progenitor cell fate and contributes to chronic myelogenous leukemia development. Cancer Cell 20:661-73
Forsberg, E Camilla; Passegue, Emmanuelle; Prohaska, Susan S et al. (2010) Molecular signatures of quiescent, mobilized and leukemia-initiating hematopoietic stem cells. PLoS One 5:e8785
Santaguida, Marianne; Schepers, Koen; King, Bryan et al. (2009) JunB protects against myeloid malignancies by limiting hematopoietic stem cell proliferation and differentiation without affecting self-renewal. Cancer Cell 15:341-52