Separation of lymphoid and myeloid blasts in the mixed blast crisis of
chronic myelogenous leukemia: no evidence for Ig gene rearrangement in
CALLA-positive blasts
K Ha, MH Freedman, A Hrincu, D Petsche, A Poon and EW Gelfand
Recent studies suggest that lymphoid blast crisis cells of chronic
myelogenous leukemia (CML) expressing the common acute lymphoblastic
leukemia antigen (CALLA) are B precursor cells, based on the demonstration
of immunoglobulin (Ig) gene rearrangement similar to common acute
lymphocytic leukemia. There is little evidence to suggest whether the cells
with similar lymphoid characteristics in the mixed blast crisis of CML are
also committed to B cell lineage. A patient in "mixed" blast crisis of CML
was studied. On the basis of morphology, cytochemistry, and immunological
studies, the blasts were classified as having either lymphoid or myeloid
characteristics. A proportion of the leukemic blasts expressed CALLA,
whereas others expressed My7 antigen. In order to characterize both
populations of cell further, CALLA+ blasts and My7+ (myeloid) blasts were
isolated by fluorescence- activated cell sorting. The My7+ cells were
highly proliferative in cell culture blast colony assays, retained the Ph1
chromosome, and were indistinguishable from acute myelogenous leukemia
blasts. The CALLA+ cells were also Ph1-chromosome positive, but in
contrast, were poorly proliferative in vitro. Of particular note was their
retention of germline configuration of Ig genes, thus distinguishing them
from blasts in the lymphoid crisis of CML. We conclude that the lymphoid
component in mixed blast crisis may represent a stage of differentiation
prior to commitment to B lineage.
Volume 66,
Issue 6,
pp. 1404-1408,
12/01/1985
Copyright © 1985 by The American Society of Hematology
