Cytogenetic evidence of clonal proliferation of leukemic progenitor cells from patients with acute promyelocytic leukemia (APL).

We have studied in-vitro growth of leukemic progenitor cells (L-CFU) in ten patients with acute promyelocytic leukemia (APL). All patients showed consistently an extraordinarily high incidence of cluster formation under the stimulation of human placental conditioned medium (HPCM) and/or phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM). Cytogenetic analyses of clusters or colonies disclosed the presence of a 15;17 translocation. These findings may represent the close relationship between specific chromosomal aberration, t(15;17), and the growth pattern of L-CFU of APL in vitro.