Normal blast colony formation: an in vitro tool for monitoring human bone marrow 'purging'

A major problem in autologous bone marrow transplantation is that it is impossible to evaluate in vitro the effect of drug treatment on haematopoiesis. However, Gordon and colleagues have recently established a colony forming assay which detects very immature blast progenitor cells. This method can be used to measure the myelotoxicity of drugs used for removing malignant cells from bone marrow ('purging') before autografting and we have analysed the action of mafosfamide on normal blast colony formation. Treatment in vitro with mafosfamide did not impair the formation of blast colonies containing very primitive cells (type I) but suppressed the formation of the colonies of more mature cells (types II and III) which grow under the same culture conditions. The surviving type I blast colony-forming cells were capable of self-renewal and differentiation. In contrast granulocyte-macrophage colony-forming units (GM-CFU) were totally destroyed by treatment with mafosfamide.