A POSSIBLE CORRELATION BETWEEN GROWTH-FACTOR SENSITIVITY AND RESPONSETO MITOXANTRONE TREATMENT IN A MURINE MYELOID-LEUKEMIA (SA7HD) CELL-LINE

SA7 murine myeloid leukaemia cells usually respond to stimulation in v itro by WEHI-conditioned medium by displaying increased dose;dependent proliferation. However, at recurrence following in vivo treatment of the leukaemia with mitoxantrone, the leukaemia cells developed signifi cant insensitivity (p = 0.04) to stimulation by WEHI-conditioned mediu m. This altered growth-factor sensitivity was detected when two differ ent assays were used. The recurrent leukaemic cells were morphological ly indistinguishable from untreated leukaemic cells, but in normal mic e they regained sensitivity to growth factors after a single transplan t. The recurrent leukaemic cells were significantly resistant to some concentrations of mitoxantrone in vitro (p = 0.012). The magnitude of this resistance was mainly a function of the dose of mitoxantrone used in the initial treatment of the leukaemia. These data suggest an asso ciation between growth-factor sensitivity and response to mitoxantrone treatment including the development of resistance in the SA7HD murine myeloid leukaemia cell line.