title: Silencing of survivin gene by small interfering RNAs produces supra-additive growth suppression in combination with 17-allylamino-17-demethoxygeldanamycin in human prostate cancer cells.
abstract: Survivin is an antiapoptotic gene, which is overexpressed in most human tumors and involved in mitotic checkpoint control. Recent evidence points to an essential role for heat shock protein 90 (Hsp90) in survivin function regulation. Although the survivin-Hsp90 association may promote tumor cell proliferation, it may also suggest new opportunities for the design of novel anticancer approaches. We evaluated the effect of small interfering RNA (siRNA)-mediated inhibition of survivin on the proliferative potential of prostate cancer cells and their sensitivity to the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). Human androgen-independent prostate cancer cell lines (DU145 and PC-3) were transfected with four 21-mer double-stranded siRNAs (100 nmol/L) directed against different portions of survivin mRNA. After transfection, cells were collected and analyzed for survivin mRNA and protein expression, cell proliferation rate, ability to undergo apoptosis, and sensitivity to 17-AAG. Transfection of prostate cancer cells with siRNAs induced a variable extent of inhibition of survivin mRNA expression (39-60% compared with controls), which was paralleled by a 38% to 75% reduction in survivin protein abundance. The three siRNAs able to induce the greatest inhibition of survivin expression also significantly reduced cell proliferation and enhanced the rate of apoptosis, with a concomitant increase in caspase-9 activity. Sequential treatment with siRNA and 17-AAG induced supra-additive antiproliferative effects in all cell lines, with an enhanced caspase-9-dependent apoptotic response. These findings suggest that combined strategies aimed at interfering with the survivin-Hsp90 connection may provide novel approaches for treatment of androgen-independent prostate cancer.
authors.affiliation: Department of Experimental Oncology, Istituto Nazionale per lo Studio e la Cura dei Tumori, Unit 10, Via Venezian 1, 20133 Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paduano
authors.forename: Raffaella
authors.initials: R
authors.lastname: Villa
authors.forename: Marzia
authors.initials: M
authors.lastname: Pennati
authors.forename: Marco
authors.initials: M
authors.lastname: Folini
authors.forename: Mara
authors.initials: M
authors.lastname: Binda
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Daidone
authors.forename: Nadia
authors.initials: N
authors.lastname: Zaffaroni
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D016227:Benzoquinones; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D047029:Lactams, Macrocyclic; D008297:Male; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000235:genetics*; D009363:Neoplasm Proteins / Q000187:drug effects / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077022:Survivin; D014162:Transfection
chemical_list: C107489:BIRC5 protein, human; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D051034:Inhibitor of Apoptosis Proteins; D047029:Lactams, Macrocyclic; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D000077022:Survivin; D017828:Rifabutin; C112765:tanespimycin