Derivation and Characterization of Myeloproliferative Disorder Stem Cells From Human ES Cells
Cancer is the leading cause of death for people younger than 85. High cancer mortality rates underscore the need for more sensitive diagnostic techniques as well as therapies that selectively target cells responsible for cancer propagation. Compelling studies suggest that human cancer stem cells (CSC) arise from aberrantly self-renewing tissue specific stem or progenitor cells and are responsible for cancer propagation and resistance to therapy. Although the majority of cancer therapies eradicate rapidly dividing cells within the tumor, the rare CSC population may be quiescent and then reactivate resulting in disease progression and relapse. We recently demonstrated that CSC are generated in chronic myeloid leukemia by activation of catenin, a gene that allows cells to reproduce themselves extensively. However, relatively little is known about the sequence of events responsible for the 36-fold increased risk of leukemic transformation in more common myeloproliferative disorders (MPDs) that express an activating mutation in the JAK2 gene. Because human embryonic stem cells (hESC) have robust self-renewal capacity and can provide a potentially limitless source of tissue specific stem and progenitor cells in vitro, they represent an ideal model system for generating and characterizing human JAK2+ MPD stem cells. Thus, hESC cell research harbors tremendous potential for developing life-saving therapy for patients with cancer by providing a platform to rapidly and rationally test new therapies that specifically target CSC. To provide a robust model system for screening novel anti-CSC therapies, we propose to generate and characterize JAK2+ MPD stem cells from hESC. We will investigate the role of genes that are essential for initiation of these MPDS such as JAK2 V617F and additional mutations such as b-catenin implicated in CSC propagation. The efficacy of a selective JAK2 inhibitor, TG101348, at inhibiting JAK2+ human ES cell self-renewal, survival and proliferation alone and in combination with potent and specific Wnt/b-catenin antagonists will be assessed in robust in vitro and in vivo assays with the ultimate aim of developing highly active anti-JAK2+ MPD stem cell therapy that may halt MPD progression and obviate therapeutic resistance.
Use of both federally approved and non-approved human embryonic stem cells (hESC) to engineer an inexhaustible supply of cancer stem cells (CSC) involved in leukemic transformation of myeloproliferative disorders (MPD) would establish California as a leader in cancer stem cell biology. Relatively little is known about the molecular pathogenesis of Philadelphia chromosome negative (Ph-) MPDs that confer a 1.4 fold increased rate of fatal thrombotic events as well as a striking 36-fold increased risk of death from transformation to acute leukemia compared with the general population. Recently, a point mutation, JAK2 V617F (JAK2+), resulting in constitutive activation of the JAK2 cytokine signaling pathway, was discovered in a large proportion of MPD patients. We found that JAK2 V617F is expressed at the hematopoietic stem cell level in these MPDs and that JAK2 skewed differentiation is normalized with a selective JAK2 inhibitor, TG101348, produced by TargeGen, a San Diego company. However, a detailed characterization of leukemic transforming events has been hampered by the paucity of stem and progenitor cells in JAK2 V617F+ MPD blood and marrow samples. Because hESC have robust self-renewal capacity and can provide a potentially limitless source of tissue specific stem and progenitor cells in vitro, they represent an ideal model system for generating human JAK2+ MPD stem cells. Thus, California hESC research harbors tremendous potential for understanding the MPD initiating events that skew differentiation versus events that produce self-renewing CSC. Moreover, a more comprehensive understanding of primitive stem cell fate decisions may yield key insights into methods to expand blood cell production that may have major implications for blood banking.
Generation of JAK2+ MPD stem cells from hESC would provide an experimentally amenable and relevant platform to expedite the development of sensitive diagnostic techniques to predict disease progression and to develop potentially curative therapies based on a small molecule JAK2 inhibitor, TG101348, developed by a California company, TargeGen for early phase disease and likely a combination of TG101348 and a self-renewal antagonist, such as dBHD, a -catenin inhibitor developed at UCSD.
The translational research performed in the context of this grant will help to train California’s future R&D workforce in addition to developing leaders in translational medicine. This grant will provide the personnel working on the project with a clear view of the importance of their research to cancer therapy and a better perspective on future career opportunities in California as well as direct revenue generated by innovative clinical trials aimed at eradicating JAK2+ MPDs that may be more broadly applicable to CSC in other malignancies.