IL-12 expression reduces significantly the tumorigenicity of AML cells. SJL mice (8 to 10 mice/group) were injected IV with increasing numbers of live IL12-AML cells or control pac-AML cells. Mice injected with 10⁵ (▴) or 2 × 10⁶ (•) IL12-AML cells do not develop leukemia. Control mice injected with 10⁵ pac-AML cells (□) develop lethal leukemia. This graph is representative of 3 independent experiments.