The Ordway Research Institute, Albany, New York, USA.
Mol Cancer. 2010 Apr 26;9:89. doi: 10.1186/1476-4598-9-89.
Castration resistant prostate cancer (CRPC) develops as a consequence of hormone therapies used to deplete androgens in advanced prostate cancer patients. CRPC cells are able to grow in a low androgen environment and this is associated with anomalous activity of their endogenous androgen receptor (AR) despite the low systemic androgen levels in the patients. Therefore, the reactivated tumor cell androgen signaling pathway is thought to provide a target for control of CRPC. Previously, we reported that Hedgehog (Hh) signaling was conditionally activated by androgen deprivation in androgen sensitive prostate cancer cells and here we studied the potential for cross-talk between Hh and androgen signaling activities in androgen deprived and androgen independent (AI) prostate cancer cells.
Treatment of a variety of androgen-deprived or AI prostate cancer cells with the Hh inhibitor, cyclopamine, resulted in dose-dependent modulation of the expression of genes that are regulated by androgen. The effect of cyclopamine on endogenous androgen-regulated gene expression in androgen deprived and AI prostate cancer cells was consistent with the suppressive effects of cyclopamine on the expression of a reporter gene (luciferase) from two different androgen-dependent promoters. Similarly, reduction of smoothened (Smo) expression with siRNA co-suppressed expression of androgen-inducible KLK2 and KLK3 in androgen deprived cells without affecting the expression of androgen receptor (AR) mRNA or protein. Cyclopamine also prevented the outgrowth of AI cells from androgen growth-dependent parental LNCaP cells and suppressed the growth of an overt AI-LNCaP variant whereas supplemental androgen (R1881) restored growth to the AI cells in the presence of cyclopamine. Conversely, overexpression of Gli1 or Gli2 in LNCaP cells enhanced AR-specific gene expression in the absence of androgen. Overexpressed Gli1/Gli2 also enabled parental LNCaP cells to grow in androgen depleted medium. AR protein co-immunoprecipitates with Gli2 protein from transfected 293T cell lysates.
Collectively, our results indicate that Hh/Gli signaling supports androgen signaling and AI growth in prostate cancer cells in a low androgen environment. The finding that Gli2 co-immunoprecipitates with AR protein suggests that an interaction between these proteins might be the basis for Hedgehog/Gli support of androgen signaling under this condition.
去势抵抗性前列腺癌（CRPC）是由于晚期前列腺癌患者使用激素疗法耗尽雄激素而发展而来的。CRPC 细胞能够在低雄激素环境中生长，尽管患者体内的系统性雄激素水平较低，但这与它们内源性雄激素受体（AR）的异常活性有关。因此，重新激活的肿瘤细胞雄激素信号通路被认为是控制 CRPC 的一个靶点。之前，我们报道雄激素剥夺可条件激活 Hedgehog（Hh）信号通路在雄激素敏感的前列腺癌细胞中，在这里我们研究了 Hh 和雄激素信号活性在雄激素剥夺和雄激素非依赖性（AI）前列腺癌细胞中的交叉对话的潜力。
用 Hh 抑制剂环巴胺处理各种雄激素剥夺或 AI 前列腺癌细胞，导致受雄激素调节的基因表达的剂量依赖性调节。环巴胺对雄激素剥夺和 AI 前列腺癌细胞内源性雄激素调节基因表达的影响与环巴胺对两种不同雄激素依赖性启动子的报告基因（荧光素酶）表达的抑制作用一致。同样，用 siRNA 降低 smoothened（Smo）的表达也会抑制雄激素剥夺细胞中雄激素诱导的 KLK2 和 KLK3 的表达，而不影响雄激素受体（AR）mRNA 或蛋白的表达。环巴胺还阻止了 AI 细胞从依赖雄激素生长的亲本 LNCaP 细胞中生长，并抑制了明显的 AI-LNCaP 变体的生长，而补充雄激素（R1881）在环巴胺存在的情况下恢复了 AI 细胞的生长。相反，Gli1 或 Gli2 在 LNCaP 细胞中的过表达在没有雄激素的情况下增强了 AR 特异性基因表达。过表达 Gli1/Gli2 也使亲本 LNCaP 细胞能够在雄激素耗尽的培养基中生长。AR 蛋白与转染 293T 细胞裂解物中的 Gli2 蛋白共免疫沉淀。
总的来说，我们的结果表明，在低雄激素环境中，Hh/Gli 信号通路支持前列腺癌细胞中的雄激素信号通路和 AI 生长。Gli2 与 AR 蛋白共免疫沉淀的发现表明，在这种情况下，这些蛋白质之间的相互作用可能是 Hedgehog/Gli 支持雄激素信号的基础。
