CD19 Expression in t(8;21)-Negative Acute Myeloid Leukemia Is Not Restricted to Cytogenetically Aberrant Populations.

Abstract 4128

Aberrant expression of the B lymphoid marker, CD19, in acute myeloid leukemia (AML) has frequently been associated with t(8;21)(q22;q22). However, AML cases lacking this translocation may occasionally express CD19. We identified eight such cases at Roswell Park Cancer Institute. Three of these cases had noticeable CD19-positive leukemic subsets with the following karyotypic abnormalities. The first case had monosomy X in 6 cells and normal karyotype in 14, the second case had trisomy 22 in 19 cells and normal karyotype in one, and the third case had monosomy 7 in 18 cells and trisomy 18 in two. We therefore asked if CD19 expression is restricted to the karyotypically abnormal leukemic cells. Bone marrow cells were sorted according to the specific immunophenotype. First, a generous mononuclear sorting region was drawn in the bivariate display of forward versus side scatter to exclude debris and aggregates. Next, the CD45-negative to CD45-dim, CD19-positive and CD34-positive leukemic cells were sorted. Fluorescent in situ hybridization (FISH) studies were carried out on the sorted samples using the following commercially available probes: the Centromere enumeration probe CEP X (SpectrumGreen) in the first case; the locus specific BCR (22q11) (SpectrumGreen)/ABL1 (9q34) (SpectrumOrange) dual color, dual fusion, translocation probe in the second, and the locus specific D7S486 (7q31) SpectrumOrange/CEP 7 SpectrumGreen probe in the third. A total of 200 nuclei were assessed in each case. The results are displayed in the Table below. There were no significant differences in the signal pattern between the CD19-positive and CD19-negative leukemic populations. These results indicate that aberrant CD19 expression in t(8;21)-negative AML is not restricted to leukemic cells that harbor specific karyotypic abnormalities.