POTENT INHIBITION OF CELL DENSITY-DEPENDENT APOPTOSIS AND ENHANCEMENTOF SURVIVAL BY DIMETHYL-SULFOXIDE IN HUMAN MYELOBLASTIC HL-60 CELLS

Human myeloblastic cell line HL-60 cells undergo apoptosis during in v itro culture in a cell density-dependent manner, and this cell density -dependent apoptosis was observed when the concentration of cultured c ells exceeded 8-10 x 10(5) cells/ml. Dimethyl sulfoxide (DMSO), a diff erentiation inducer of HL-60 cells, did not amplify, but rather potent ly inhibited, this apoptosis. In a low density culture condition, DMSO attenuated proliferation of HL-60 cells in spite of its inhibition of apoptosis. In contrast, DMSO did support cell survival under high cel l density conditions, and DMSO-treated HL-60 cells reached an extremel y high concentration of 2-3 x 10(6) cells/ml, a condition which could never be possible in a usual culture environment. Thus, DMSO exerted d ual effects on cell proliferation, i.e., growth inhibition and apoptos is inhibition, and the sum of these effects resulted in an apparently distinct phenomenon according to the culture conditions including cell density. (C) 1998 Wiley-Liss, Inc.