Growth characteristics in vitro of myeloid leukaemic cells with t(6;9)

We report an analysis of in vitro growth characteristics of leukaemic cells from five patients with t(6;9)(p23;q34). Consistent with other reports of this abnormality, our patients were comparatively young (median age at diagnosis, 29 years), and responded poorly to conventional treatment (median survival from diagnosis, 10 months). During active disease the CFU-GM growth patterns were characterized by an abundance of granulocytic aggregates (mostly 20-100 cells in size) whose leukaemic origin was confirmed by cytogenetic analysis. During remission induction, colonies derived from regenerating normal progenitor cell colonies could be distinguished from those derived from persisting leukaemic cells on the basis of differences in size, morphology, in situ staining characteristics, and karyotype. Remission growth patterns were those of a normal bone marrow. Our findings add to a growing recognition that the t(6;9) identifies a subset of leukaemic patients with distinctive clinical, haematologic, molecular, and in vitro growth characteristics for whom conventional treatment offers little hope of cure or long survival.