Background : Flow cytometric measurement of DNA can reveal G0/G1, S, G2/M phases of cell cycle, and BrdU labeling can determine the percentage of cells in active DNA synthesis. A monoclonal antibody (MoAb), Ki-67, recognizes a protein that is present only in the nucleus of cycling cells but absent in resting cells. We analyzed whether the resting and the proliferating fraction could be differentiated by double staining with Ki-67 MoAb and propidium iodide (PI), and observed the effects of
GM-CSF on cell cycle in acute myelogenous leukemia (AML) cells by Ki-67 MoAb.
Method: Blast cells were prepared from 9 AML patients. The cells were incubated for 48 hours wit or without GM-CSF. Cells were stained with BrdU/PI and Ki-67/Pl. Cell cycle was analyzed by flow cytometry.
Results : The average fraction of G0/G1, S, and G2/M phases was 84.6%, 10.9%, and 4.5% byBrdU/PI and 87.8%, 8.6%, and 3.7% by Ki-67/Pl, respectively. Ki-67/Pl staning discriminated between G0 and G1 phases and the average was 71.5% and 16.3%, respectively. In cells incubated with GM-CSF,BrdU/PI method showed that the average S phase fraction (SPF) significantly increased from 10.9 to 16.2%(P=0.01) and the fraction of G0/G1 phase decreased from 84.6% to 78.4%(P=.02). Ki-67/Pl method showed that the median SPF significantly increased from 8.6% to 13.7% (P=0.05) and G0 fraction decreased from 71.5% to 58.1% (P=0.02) but G1 fraction increased from 16.3 to 22.3% (P=0.01).
Conclusion : Cell cycle analysis by Ki-67 MoAb and Pl in AML is rapid and simple. It is especially useful to determine the growth fraction and G0 fraction compared to BrdU/Pl staining.

Keywords: Acute myelogenous leukemia, Cell cycle, Ki-67 antigen, G0 phase, Granulocyte-macrophage colony-stimulating factor,