Characterization and functional analysis of a murine model for chronic myeloid leukemia stem cells.

摘要

Chronic myeloid leukemia (CML) can be viewed as newly formed, abnormal hematopoietic tissue, initiated by a few leukemic stem cells (LCSs) that originate from hematopoietic stem cells. These LSCs undergo aberrant and poorly generated organogenesis by clonal expansion. The disease is characterized by the presence of the Philadelphia (Ph) chromosome and the BCR/ABL oncogene. Despite the LSC's proven importance in leukemia, studies using human LSCs are limited due to the lack of in vivo experimental systems. Thus, we have employed a murine model of leukemogenesis to allow detailed in vivo analysis of the LSC.; The purpose of this study is to characterize the phenotype, analyze the functional characteristics of murine CML-stem cells (CML-SCs) and to search for a specific and an efficient treatment modality in leukemia. Therefore the current experiments were designed using a retrovirus transduction model of p210/BCR/ABL encoding green fluorescent protein (GFP) for detection in cells. Transplantation studies of BCR/ABL infected cells into recipient mice demonstrated an aggressive myeloproliferative disease within ∼3 weeks. Phenotypic analysis of bone marrow from the GFP+ cells of BCR/ABL mice indicates positive staining with multiple lineage (Lin) markers, suggesting a primitive stem/progenitor cell gives rise to the disease. Subsequent analysis of primary cells that arise in vivo showed the leukemia-initiating activity resides in cells that are Sca-1+/c-kit+/Lin-. Cell cycle analyses (as detected by BrdU incorporation) of the Lin-/c-kit+/Sca-1+ compartment of BCR/ABL mice demonstrate an enhanced cycle rate (∼2-fold) in the leukemic population, signifying a possible increase in the self-renewal or proliferative properties of this primitive compartment that could lead to development/progression of the disease. Also, preferential over expression of CD24 was shown in the primitive leukemic cells, revealing a possible BCR/ABL induced activation of the antigen that facilitates the reacquisition of stem cell function. Furthermore, analysis of in vitro and in vivo effect of the proteasome inhibitor (PS-341) and radiation, both of which are known to be associated with the NF-kB pathway which is an important component of myeloid leukemia biology revealed that combined treatment reduces tumor burden in vivo. Further studies are necessary to determine the role of NF-kB or other pathways in induction of CML-SCs death.