Aim:To investigate whether a similar process mediates cytotoxicity of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH_3,edelfosine) inboth yeasts and human tumor cells.Methods:A modified version of a previouslydescribed assay for the intracellular conversion of nitro blue tetrazolium to formazanby superoxide anion was used to measure the generation of reactive oxygen spe-cies (ROS).Apoptotic yeast cells were detected using terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay.DNA fragmenta-tion and the generation of ROS were measured by cytofluorimetric analysis inJurkat cells.Results:Edelfosine induced apoptosis in Saccharomyces cerevisiae,as assessed by TUNEL assay.Meanwhile,edelfosine induced a time-and con-centration-dependent generation of ROS in yeasts.Rotenone,an inhibitor of themitochondrial electron transport chain,prevented ROS generation and apoptosisin response to edelfosine in S cerevisiae.α-Tocopherol abrogated the edelfosine-induced generation of intracellular ROS and apoptosis.Edelfosine also inducedan increase of ROS in human leukemic cells that preceded apoptosis.Theoverexpression of Bcl-2 by gene transfer abrogated both ROS generation andapoptosis induced by edelfosine in leukemic cells.Changes in the relative mito-chondrial membrane potential were detected in both yeasts and Jurkat cells.Conclusion:These results indicate that edelfosine induces apoptosis in yeasts inaddition to human tumor cells,and this apoptotic process involves mitochondria,likely through mitochondrial-derived ROS.These data also suggest that yeastscan be used as a suitable cell model in elucidating the antitumor mechanism ofaction of edelfosine. Aim: To investigate whether a similar process mediates cytotoxicity of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH 3, edelfosine) inboth yeasts and human tumor cells. Methods: A modified version of a previouslydescribed assay for the intracellular conversion of nitro blue tetrazolium to formazanby superoxide anion was used to measure the generation of reactive oxygen spe cies (ROS). Apoptotic yeast cells were detected using terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay. DNA fragmenta- tion and the generation of ROS were measured by cytofluorimetric analysis in Jurkat cells. Results: Edelfosine induced apoptosis in Saccharomyces cerevisiae, as as by TUNEL assay. Meanwhile, edelfosine induced a time-and con-centration-dependent generation of ROS in yeast. Rotenone, an inhibitor of the mitochondrial electron transport chain, prevented ROS generation and apoptosis in response to edelfosine in S cerevisiae. [alpha] -Tocopherol abrogated the edelfosine -induced generation of intracellular ROS and apoptosis. Edelfosine also induced an increase of ROS in human leukemic cells that preceded apoptosis. Overexpression of Bcl-2 by gene transfer abrogated both ROS generation andapoptosis induced by edelfosine in leukemic cells. Changes in the relative mito-chondrial membrane potential were detected in both yeasts and Jurkat cells. Confc: These results indicate that edelfosine induces apoptosis in yeasts in addition to human tumor cells, and this apoptotic process involves mitochondria, likely through mitochondrial-derived ROS. The data also suggests that yeastscan be used as a suitable cell model in elucidating the antitumor mechanism ofaction of edelfosine.