Impact of CD133 (AC133) and CD90 expression analysis for acute leukemia immunophenotyping

Background and Objectives. AC133 is a novel monoclonal antibody (Moab) reacting with a population of immature/primitive or guanulo-monocytic committed CD34(+ve) cells. Up to now, only few studies with small numbers of cas es have examined AC133 (recently designated CD133) expression in acute leukemia. To determine the value of this Moab for acute leukemia immunophenotyping, we investigated a large series of leukemic cell samples for their reactivity with Moab AC133, Design and Methods. A total of 298 cell samples from patients with de novo acute myeloid leukemia (AML) (n=142),acute lymphoblastic leukemia (ALL) (n=119), CD34(+ve) biphenotypic acute leukemia (n=13), and CD34(+ve) CML blast crisis (PBC; 21 myeloid BC/3 lymphoid BC) were investigated by flow cytometry for Moab AC133 reactivity. CD133 expression was compared with CD90(Thy-1) expression, another CD34-associated antigen. Results. Fifteen (5%) samples expressed CD90, whereas 114 (38%) samples were positive for Moab AC133 (20% cut-off level), No significant differences in CD133 and CD90 expression levels between AML and ALL were observed. in AML, but not AU, CD133 was more often expressed in; CD34(+ve) cases than in CD34(-ve) ones (p<0.00001). However er, CD133 expression was not restricted to CD34(+ve) leukemic cells in individual cell samples. All 8 pro-B-ALL cell samples with 11q23-anomalies and MU (mixed lineage leukemia) gene translocations were positive far CD133, whereas only 2 of 9 pro-B-ALL without MLL gene translocations expressed CD133 (p<0.002). In contrast, none of the 5 AML cell sam: plea with a t(9;11) and MLL gene translocation reacted with Moab AC133. CD34(+ve) CML cells in myeloid BC were less often positive for CD133 than CD34(+ve) de novo AML cells (p <0.0001), Interpretation and Conclusions. CD133 and CD90 expression analysis is not helpful for lineage determination in acute leukemia immunophenotyping, However, Moab AC133 may be an informative marker for the detection and further char: acterization of immature AML cells, as well as pro-B-AIL cells with MLL gene translocations, by flow cytometry. (C) 2001, Ferrata Storti Foundation.