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  • Title: Heat shock protein 27 increases after androgen ablation and plays a cytoprotective role in hormone-refractory prostate cancer.
    Author: Rocchi P, So A, Kojima S, Signaevsky M, Beraldi E, Fazli L, Hurtado-Coll A, Yamanaka K, Gleave M.
    Journal: Cancer Res; 2004 Sep 15; 64(18):6595-602. PubMed ID: 15374973.
    Abstract:
    Heat shock protein 27 (Hsp27) is a chaperone implicated as an independent predictor of clinical outcome in prostate cancer. Our aim was to characterize changes in Hsp27 after androgen withdrawal and during androgen-independent progression in prostate xenografts and human prostate cancer to assess the functional significance of these changes using antisense inhibition of Hsp27. A tissue microarray was used to measure changes in Hsp27 protein expression in 232 specimens from hormone naive and posthormone-treated cancers. Hsp27 expression was low or absent in untreated human prostate cancers but increased beginning 4 weeks after androgen-ablation to become uniformly highly expressed in androgen-independent tumors. Androgen-independent human prostate cancer PC-3 cells express higher levels of Hsp27 mRNA in vitro and in vivo, compared with androgen-sensitive LNCaP cells. Phosphorothioate Hsp27 antisense oligonucleotides (ASOs) and small interference RNA potently inhibit Hsp27 expression, with increased caspase-3 cleavage and PC3 cell apoptosis and 87% decreased PC3 cell growth. Hsp27 ASO and small interference RNA also enhanced paclitaxel chemosensitivity in vitro, whereas in vivo, systemic administration of Hsp27 ASO in athymic mice decreased PC-3 tumor progression and also significantly enhanced paclitaxel chemosensitivity. These findings suggest that increased levels of Hsp27 after androgen withdrawal provide a cytoprotective role during development of androgen independence and that ASO-induced silencing can enhance apoptosis and delay tumor progression.
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