Antileukemic effect of recombinant tumor necrosis factor alpha in vitro and its modulation by alpha and gamma interferons

Abstract

The effect of recombinant human tumor necrosis factor alpha (rTNF-alpha) on human myelogenous leukemia clonogenic cells growing either in semisolid media or in suspension cultures was studied and compared with the effect on normal granulocyte-macrophage progenitors (GM-CFC). Exposure of cells to a range of rTNF-alpha doses including pharmacologically achievable plasma concentrations revealed a large heterogeneity in the response of leukemic clonogenic growth to rTNF-alpha. Only one of 13 specimens was highly resistant to rTNF-alpha. Eight of ten leukemic samples were significantly more sensitive than were normal GM-CFC, particularly within the in vivo achievable dose range (1 x 10(0) to 1 x 10(2) ng/mL). No significantly increased inhibition of either normal or leukemic clonogenic growth could be achieved by increasing the rTNF-alpha concentration above 250 ng/mL. Proliferation of leukemic clonogenic cells (L-CFC) was studied in suspension cultures. In five cases the clonogenic cells were significantly inhibited by rTNF-alpha while in one case no inhibition was observed. The inhibition of L-CFC growth by rTNF-alpha was dose dependent between 1 x 10(0) and 1 x 10(2) ng/mL. In suspension cultures, the TNF effect on L-CFC was a function of time of exposure, particularly with low concentrations of TNF. A remarkably higher inhibition of L-CFC as compared with the total leukemic population was observed in suspension cultures. Stimulation of L-CFC growth by rTNF-alpha was not observed. Normal GM-CFC were inhibited by alpha and gamma interferons (INF-alpha, -gamma) in a dose-related manner, with higher sensitivity of colonies than clusters. The response of GM-CFC to combination of recombinant IFNs and TNF was influenced by the size of clones scored and the source of colony-stimulating activity. The response of L-CFC to recombinant IFN-alpha and/or -gamma was highly variable, and sensitivity to one of the lymphokines did not predict for sensitivity to another. The response of L-CFC to combinations of rTNF-alpha and either IFN-alpha or IFN-gamma was complex, varying from synergistic to additive and indifferent. In three of six specimens, IFN-gamma acted antagonistically with rTNF-alpha, a phenomenon not observed with IFN-alpha. These observations suggest that the action of rTNF-alpha in acute myelogenous leukemia could be exploited therapeutically and the dose-time-response relationship should be considered in designing treatment schedules.(ABSTRACT TRUNCATED AT 400 WORDS)