Detection of cytogenetic aberrations both in CD90 (Thy-1)-positive and (Thy-1)-negative stem cell (CD34) subfractions of patients with acute and chronic myeloid leukemias

Acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) are thought to arise from malignant hematopoietic progenitor cells representing early and undifferentiated stem cell clones. In CML there is evidence for a proge nitor cell subset free of leukemic clones, depending on the course of the d isease. Additionally, it has been suggested that in AML, the early stem cel l compartment (CD34(+)/90(+)) does not harbor the malignant clone. We analy zed white blood cells from leukemia patients for the presence of aberrant c ells in stem cell subfractions, Sixteen patients with CML, six patients wit h AML, two patients with acute lymphatic leukemia (ALL) and one with chroni c myelomonocytic leukemia (CMMOL), all with known cytogenetic abnormalities , were evaluated according to their CD90 (Thy-1)-positive or -negative phen otype. Subsets were sorted on to slides and further characterized by FISH a nd/or standard cytogenetic testing. The bcr-abl translocation or gross chro mosomal abnormalities could be detected in equally high amounts of 92.2% an d 89.2% in both stem cell subsets. We conclude, that in progressed AML and CML cells characterized by specific genetic aberrations implicated in the m alignant state can be found in the CD34(+)/CD90(+) and CD90(+) population, thus making CD90 an inappropriate marker to distinguish benign from maligna nt cells in these leukemias.