Inhibition of topoisomerase II by the marine alkaloid ascididemin and induction of apoptosis in leukemia cells.

摘要: Ascididemin (ASC) is a pentacyclic DNA-intercalating agent isolated from the Mediterranean ascidian Cystodytes dellechiajei. This marine alkaloid exhibits marked cytotoxic activities against range of tumor cells, but its mechanism action remains poorly understood. We investigated effects ASC on DNA cleavage by human topoisomerases I and II. Relaxation assays using supercoiled showed that stimulated double-stranded topoisomerase II, exerted only very weak effect I. conventional II poison significantly promoted cleavage, essentially at sites having C 3′ side cleaved bond (−1 position), as observed with etoposide. The stimulation in presence was considerably weaker than camptothecin. Cytotoxicity measurements even less toxic to P388 leukemia cells P388CPT5 resistant In addition, found be equally HL-60 sensitive or mitoxantrone. It therefore unlikely are main cellular targets for ASC. strongly induce apoptosis cells. Cell cycle analysis treatment associated loss G1 phase accompanied large increase sub-G1 region. Cleavage experiments poly(ADP-ribose) polymerase (PARP) revealed caspase-3 mediator apoptotic pathway induced ASC-treated severely fragmented. Collectively, these findings indicate potent inducer