Microinjection of macromolecules into leukemic cells by cell fusion technique: search for intracellular growth-suppressive factors.

To investigate the intracellular molecular events during leukemic cell proliferation, we have examined the method of ghost-mediated microinjection of macromolecules into leukemic cell line cells (HL-60). Samples were packed into red cell ghosts. Microinjection was performed by the fusion of ghosts and HL-60 cells using the hemagglutinating virus of Japan (HVJ). Fusion rate was about 80-90%, when determined by the injection of FITC-labeled globulins (IgG) or diphtheria toxin fragment A into HL-60 cells. When the nuclear protein extract from normal granulocytes was injected into HL-60 cells, their growth was significantly suppressed. The injection of the nuclear protein extract from HL-60 itself into HL-60 cells did not inhibit their growth. This finding suggests that leukemic cells may be deficient in intracellular regulatory factors which have suppressive activity on cell growth.