METHYLATION OF ThE ANDROGEN RECEPTOR CPG ISLAND

Survivinis a memberofthe inhibitor ofapoptosis protein (IAP)family. WeInvestigated the antiapoptotic mechanism ofSurvivin, as well as its expressionIn 60 human tumor cell lines used for the National Cancer lontitute's anticancer drag screening program, In cotransfection experhnents, cell deathInduced by Bax or Faa (CD 95) was partially inhibited (mean ±SD,65%±8%)bySurvivin,whereasXIAP,anotherlAPfamilymember,almostcompletely blocked cell death (93% ±4%) under the same conditions.Survh'In and XIAP also protected 293 cells from apoptosis induced byoverexpreulon of procaspase-3 and -7 and inhibited the processing of thesezymogeta Into active caspases. In vitm binding experiments indicated that, like other lAP-family proteins, Survivin binds specifically to the terminalmeator cell death proteases, caspase-3 and -7, but not to the proximalinitiator pretense caspase-8. Using a cell-free system in which cytosolic extracts were derived from controlor Survivin-transfected cells and wherecaspases were activated either by addition of cytochrome c and dATP or byadding recombinant active caspase.8, Survivin was able to substantiallyredlM@ecaspase activity, as measured by deavage of a tetrapeptide substrate,AspGIuValAsp-amlnofluorocoumarin. Similar results were obtained in intactedis when Survivin was overexpressed by gene transfection and caspaseactivation wes induced by the anticancer drug etoposlde@Survivin was expremed In all 60 cancer cell lines analyzed, with highest leveLsin breast andlung cancam and lowest levels in renal cancers. These findings indicate thatSurvivin, which is commonly expressed In human tumor cell lines, can bindthe affecter cdl death proteases caspase-3 and -7 in vibv and inhibits caspaseactivity and cell death in cells exposed to diverse apoptotic stinsulLAlthoughquantitative differences may exist, these observations suggest commonality inthe mechanisms used by lAP-family proteins to suppress apoptosis.