DIMETHYL SULFOXIDE-INDUCED APOPTOSIS IN HUMAN LEUKEMIC U937 CELLS

Dimethyl sulfoxide (DMSO), which induces differentiation of myeloid ce lls, was found to cause apoptosis in human leukemic U937 cells. Apopto sis was assessed by DNA electrophoresis and flow cytometry. The time n eeded to induce apoptosis varied from a few hours to 2-3 days, dependi ng on the concentration of DMSO used. The plasma membrane remained int act long after DNA fragmentation had occurred. DMSO-induced apoptosis was inhibited by zinc ions and, to a lesser extent, by the protein kin ase C activator: phorbol 12-myristate 13-acetate (PMA), Cycloheximide and actinomycin D did not prevent DMSO-induced apoptosis, showing that U937 cells do not require protein or RNA synthesis to undergo apoptos is. DMSO induced apoptosis despite the expression of the anti-apoptoti c Bcl-2 protein in U937 cells, The amount of Bcl-2 remained unchanged during DMSO-induced apoptosis.