Important stem-cell functions are shared by HSCs and LSCs. Both normal HSCs and neoplastic LSCs have the ability to self-renew and initially differentiate into less pluripotent daughter cells. However, HSCs produce short-lived progenitors, such as common myeloid progenitors (CMPs) and granulocyte monocyte progenitors (GMPs), which terminally differentiate into mature monocytes and granulocytes. In contrast, LSCs give rise to leukemic blasts, which harbor a block in their terminal differentiation. Recent experiments using murine transplantation models suggest that both HSCs and committed myeloid progenitors can transform into an LSC.^5-7