title: Alpha-tocopheryl succinate, an agent with in vivo anti-tumour activity, induces apoptosis by causing lysosomal instability.
abstract: Certain vitamin E analogues, such as alpha-tocopheryl succinate (alpha-TOS), exhibit in vivo anti-tumour activity and, in vitro, induce apoptosis of cultured tumour cells. In the present study we report that these effects may be explained, at least in part, by destabilization of lysosomal membranes. alpha-TOS, but not alpha-tocopheryl acetate or alpha-tocopherol (alpha-TOH), induced early lysosomal destabilization followed by apoptosis. Similar effects were observed with beta-TOS, whereas beta-TOH was inactive. Cathepsin D-deficient cells were more resistant to alpha-TOS than their normal counterparts, and featured delayed caspase activation. Possible detergent and lysosomotropic effects of alpha- and beta-TOS were suggested by their haemolytic activity in an in vitro test and their release of beta-galactosidase from isolated lysosomes, whereas the non-succinylated analogues were inactive. The pro-apoptotic activity of alpha-TOS was pH-dependent, being greater at lower pH, typical of the interstitium of solid tumours. These findings indicate that lysosomal destabilization may partially or fully explain the induction of apoptosis in cultured cells by alpha-TOS and the mechanism whereby this agent exerts in vivo anti-tumour effects.
authors.affiliation: Department of Pathology II, University Hospital, Linköping 581 85, Sweden. jneuzil@hotmail.com
authors.forename: Jiri
authors.initials: J
authors.lastname: Neuzil
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.forename: Georg
authors.initials: G
authors.lastname: Ostermann
authors.forename: Martin
authors.initials: M
authors.lastname: Sticha
authors.forename: Nina
authors.initials: N
authors.lastname: Gellert
authors.forename: Christian
authors.initials: C
authors.lastname: Weber
authors.forename: John W
authors.initials: JW
authors.lastname: Eaton
authors.forename: Ulf T
authors.initials: UT
authors.lastname: Brunk
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000187:drug effects / Q000648:ultrastructure; D019169:Jurkat Cells; D007700:Kinetics; D008247:Lysosomes / Q000187:drug effects / Q000648:ultrastructure*; D024505:Tocopherols; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D014810:Vitamin E; D020169:Caspases; D024505:Tocopherols