Heterogeneity in acute myeloblastic leukemia.

Morphological-identified blast populations are the hallmark of the malignant clones that dominate hemopoiesis in acute myeloblastic leukemia (AML). Marked heterogenity is characteristic of AML blasts. Patient-to-patient variation is seen in their biological properties but is particularly evident in the response to treatment. Intraclonal variation is generated during clonal expansion, particularly as blast stem cells either undergo self-renewal or enter into a series of terminal divisions. These two alternative activities can be monitored in cell culture using a clonogenic assay and a suspension assay. The balance between renewal and differentiation can be altered by exposing blast populations to various growth factors in culture. Further, certain drugs, particularly ara-C, appear to be more toxic for self-renewing divisions than cell-cycle events generally. We suggest that both drugs and growth factors should be assessed for their effects on self-renewal as part of preclinical testing.