THE ROLE OF SUBCELLULAR-LOCALIZATION IN INITIATION OF APOPTOSIS BY PHOTODYNAMIC THERAPY

Rapid initiation of apoptosis can be induced by photodynamic therapy, depending on the cell line and sensitizer employed, In this study, we evaluated the photodynamic responses to two structurally related photo sensitizing agents, using the P388 murine leukemia cell line in cultur e, Photodamage mediated by tin etiopurpurin involved lysosomes and mit ochondria and yielded a rapid apoptotic response; apoptotic nuclei wer e observed within 60 min after PDT, A drug analog, tin octaethylpurpur in amidine, targeted lysosomes, mitochondria and cell membranes; apopt otic nuclei were not observed until 24 h after PDT, These results, tog ether with other recent reports, are consistent with the hypothesis th at membrane photodamage can delay or prevent an apoptotic response to PDT.