[Activity of various hematopoietic growth factors on acute myeloblastic leukemia blasts]

Acute myeloblastic leukaemia (AML) cells respond to some extent to the action of haemopoietic growth factors (HGF). This work is aimed to analyse the effect of IL-3, GM-CSF and G-CSF on the proliferative and self-replication capabilities of AML cells and to correlate such response with the morphological and immunological characteristics of the blast cells.

Mononucleated cells from the peripheral blood of 26 AML patients were incubated in liquid medium without serum in presence of IL-3 and GM-CSF alone and in combination with G-CSF. Cell proliferation was evaluated by determination of the increase in the number of cells harvested after incubation with the HGF. The proliferative response was studied in 8 cases by flow cytometry analysis of the cell cycle (number of cells in S-phase). The capability of IL-3 and GM-CSF to induce self-replication of the leukaemic clonogenic cell (CFU-L) was analysed in 9 cases by techniques of replanting on semi-solid medium.

Cell proliferation was induced with IL-3 in more cases than with GM-CSF (50% vs 28%); furthermore, the stimulus induced by IL-3 was also more evident, as the number of cells harvested was greater than that corresponding to GM-CSF (2.1 +/- 1.1 x 10(6) cell/mL vs 1.4 +/- 1.4 x 10(6) cells/mL, p = 0.10). Although no clear correlation was seen between the proliferative response to HGF and the immunologic or morphologic subtype of the blast cells, no response to GM-CSF was detected in those cases classified as M2 nor in the CD15-positive leukaemias. A synergistic effect of G-CSF and IL-3 or GM-CSF was found in only 20% of the cases. Both IL-3 and GM-CSF augmented the number of cells in S phase in all the cases analysed; this increase was higher in M1 and M2 with respect to the leukaemias with monocytic component.

IL-3 and GM-CSF induced self-replication of CFU-L in a half of the cases. This effect was not dependent upon the kind of stimulating agent used (IL-3 or GM-CSF), and appeared unrelated to the morphologic or immunologic characteristics of the leukaemia.