ALKYLPHOSPHOCHOLINES INDUCE APOPTOSIS IN HL-60 AND U-937 LEUKEMIC-CELLS

Alkylphosphocholines (APC) represent a new group of ether-lipid-relate d compounds with remarkable activity against transformed cells in vitr o and good tolerability in vivo. Their mechanism of action remains unk nown. The aim of the present study was to investigate the effects of a series of APC on three human leukemic cell lines: K-562. HL-60, and U -937. The tetrazolium dye-reduction (MTT) assay and cell counting were used to determine the cytotoxicity of the APC used. DNA gel electroph oresis and enzyme-linked immunosorbent assay (ELISA) detection of olig onucleosomes were performed to identify and quantify DNA fragmentation . Electron and phase-contrast microscopy were used to detect morpholog ic changes specific for programmed cell death. HL-60 and U-937 cells w ere found to be sensitive, but K-562 cells were relatively resistant t o APC exposure. APC with long alkyl chains exerted stronger cytotoxici ty than did those with short alkyl chains. DNA fragmentation was found after treatment with APC in HL-60 and U-937 cells but not in K-562 ce lls. In HL-60 cells the increase in mono-and oligonucleosome formation as measured by ELISA was correlated with the length of the alkyl chai ns at 14 h of exposure to APC but plateaued at 20 h. The morphologic a lterations in HL-60 and U-937 cell lines, such as cell shrinkage, chro matin condensation, and formation of apoptotic bodies, confirmed the i nduction of apoptosis after APC exposure. It is concluded that program med cell death plays an important role in the cytotoxicity of APC agai nst certain human leukemic cell lines. The antineoplastic profiles of APC with long alkyl chains render them attractive for further therapeu tic application.