Leukemia stem cells in 2010: current understanding and future directions.

Myeloid leukemias are clonal disorders originating in a primitive multipotential hematopoietic cell and characterized by aberrant proliferation, differentiation and maturation of leukemic progenitors and precursor cells. These diseases are the result of multiple genetic and epigenetic events, although the nature and number of events vary widely among patients. For over four decades, studies have identified sub-populations of leukemic cells possessing different functional capabilities. Investigators have struggled to understand the origin and significance of this heterogeneity. The stem cell model for myeloid malignancies has offered one potential explanation. Since 1994, experimental data supporting the presence of leukemia stem cells has been reported and validated in numerous studies. We will review the history of the model, data from the past decade supporting the stem cell model for myeloid malignancies, more recent data regarding patient specific variability in leukemic stem cell surface antigen phenotype and the impact the stem cell model has on the care of patients with myeloid malignancies.