Leukemia - Associated Changes Identified by Quantitative Flow Cytometry . IV . CD 34 Overexpression in Acute Myelogenous Leukemia

During the immunodiagnosis of 517 cases of acute myelogenous leukemia (AML) entered into the Medical Research Council (MRC) AMLIO trials, we have observed the CD34 precursor cell antigen more frequently in AML of M2 morphology, especially in the 84% of cases with the t(8;21) chromosomal translocation, than in any other French-AmericanBritish classification group. CD34 expression was then quantified (using QlFl and Quantum Simply Cellular beads [Flow Cytometry Standards, Research Triangle Park, NCI and CD34+ standard cells). When CD34 antibody-binding capacity (ABC) of normal bone marrow (BM) precursors and leukemic blasts was compared, it was shown that AML M2 cases with t(8;21) not only had the highest percentages of CD34+ blasts, but in >80% of CD34+ cases the individual blasts expressed higher than normal levels of CD34 antigen (>60 x I O 3 ABC per cell). In addition, in 73% of this group CD34 antigen was overexpressed in an asynchronous combination with cytoplasmic myeloperoxidase (MPO). Other signs of asynchrony included high CD34 expression with CD15 andl