Expression of AC133 and CD117 on candidate normal stem cell populations inchildhood B-cell precursor acute lymphoblastic leukaemia

To identify residual candidate normal progenitor/ stem cell populations in childhood B-cell precursor acute lymphoblastic leukaemia (ALL), expression of AC133 and CD117 was analysed on the leukaemic cell clone and on immature B-lineage-negative CD34(+)CD19(-) bone marrow cells. 10/25 patients (40%) had no detectable expression of AC133 within the leukaemic cell clone. 24/2 6 patients (92%) lacked expression of CD117 on the leukaemic blast cell pop ulation. In contrast, a distinct AC133-positive cell population was found i n 8/8 children with AC133-negative ALL and a CD117-positive cell population could be identified in 12/12 children with CD117-negative ALL, within the CD34(+)CD19(-) progenitor/stem cell compartment. These observations provide further evidence that in B-cell precursor ALL, unlike in acute myelogenous leukaemia, it may be possible to distinguish residual normal progenitor/st em cells from the leukaemic cell clone.