Kiyama Satoshi, Morrison Kevin, Zellweger Tobias, Akbari Majid, Cox Michael, Yu Duan, Miyake Hideaki, Gleave Martin E
The Prostate Centre, Vancouver General Hospital, and Division of Urology, University of British Columbia, Canada.
Cancer Res. 2003 Jul 1;63(13):3575-84.
Activation of alternative growth factor pathways after androgen withdrawal is one mechanism mediating androgen-independent (AI) progression in advanced prostate cancer. Insulin-like growth factor (IGF) I activation is modulated by a family of IGF binding proteins (IGFBPs). Although IGFBP-2 is one of the most commonly overexpressed genes in hormone refractory prostate cancer, the functional significance of changes in IGF-I signaling during AI progression remains poorly defined. In this article, we characterize changes in IGFBP-2 in the LNCaP tumor model after androgen withdrawal and evaluate its functional significance in AI progression using gain-of-function and loss-of-function analyses. IGFBP-2 mRNA and protein levels increase 2-3-fold after androgen withdrawal in LNCaP cells in vitro in LNCaP tumors during AI progression in vivo. Increased IGFBP-2 levels after castration were also identified using a human prostate tissue microarray of untreated and posthormone therapy-treated prostatectomy specimens. LNCaP cell transfectants that stably overexpressed IGFBP-2 progressed more rapidly after castration than control tumors. Antisense oligonucleotides (ASOs) targeting the translation initiation site of IGFBP-2 reduced IGFBP-2 mRNA and protein expression by >70% in a dose-dependent and sequence-specific manner. ASO-induced decreases in IGFBP-2-reduced LNCaP cell growth rates and increased apoptosis 3-fold. LNCaP tumor growth and serum prostate-specific antigen levels in mice treated with castration plus adjuvant IGFBP-2 ASOs were significantly reduced compared with mismatch control oligonucleotides. Increased IGFBP-2 levels after androgen ablation may represent an adaptive response that helps potentiate IGF-I-mediated survival and mitogenesis and promote androgen-independent tumor growth. Inhibiting IGFBP-2 expression using ASO technology may offer a treatment strategy to delay AI progression.
雄激素撤除后替代生长因子途径的激活是介导晚期前列腺癌雄激素非依赖（AI）进展的一种机制。胰岛素样生长因子（IGF）-I的激活受IGF结合蛋白（IGFBP）家族调控。尽管IGFBP-2是激素难治性前列腺癌中最常过度表达的基因之一，但在AI进展过程中IGF-I信号变化的功能意义仍不清楚。在本文中，我们描述了雄激素撤除后LNCaP肿瘤模型中IGFBP-2的变化，并通过功能获得和功能丧失分析评估其在AI进展中的功能意义。在体外LNCaP细胞中雄激素撤除后以及在体内AI进展期间的LNCaP肿瘤中，IGFBP-2 mRNA和蛋白水平增加2至3倍。使用未治疗和激素治疗后前列腺切除标本的人前列腺组织微阵列也确定了去势后IGFBP-2水平升高。稳定过度表达IGFBP-2的LNCaP细胞转染子在去势后比对照肿瘤进展更快。靶向IGFBP-2翻译起始位点的反义寡核苷酸（ASO）以剂量依赖性和序列特异性方式将IGFBP-2 mRNA和蛋白表达降低>70%。ASO诱导的IGFBP-2降低使LNCaP细胞生长速率降低，凋亡增加3倍。与错配对照寡核苷酸相比，去势加辅助IGFBP-2 ASO治疗的小鼠中LNCaP肿瘤生长和血清前列腺特异性抗原水平显著降低。雄激素消融后IGFBP-2水平升高可能代表一种适应性反应，有助于增强IGF-I介导的存活和有丝分裂，并促进雄激素非依赖性肿瘤生长。使用ASO技术抑制IGFBP-2表达可能提供一种延缓AI进展的治疗策略。
