Division of General Medical Sciences-Oncology, Case Comprehensive Cancer Center Research Laboratories, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
Mol Cancer Res. 2012 Jun;10(6):821-33. doi: 10.1158/1541-7786.MCR-11-0615. Epub 2012 Mar 27.
Although hyperactivated mTOR is well recognized as being pivotal to prostate cancer growth and progression, the underlying mechanisms by which it promotes such responses remain incompletely understood. Here, we show that rapamycin activates Smads 1 and 5 in human prostate cancer cells and tissues through blocking mTORC1 kinase. Small hairpin RNA-based gene silencing and gene overexpression approaches reveal that Smads 1 and 5 mediate, whereas Smad8 represses, rapamycin-induced cell death and expression of the bone morphogenetic protein (BMP) transcriptional target Id1 in human prostate cancer cell lines. Moreover, such phospho-Smad1/5-mediated rapamycin responses were blocked by LDN-193189 (a BMPRI kinase inhibitor) or Noggin (a BMP antagonist) in LNCaP prostate cancer cells. Likewise, the mTOR kinase inhibitors Ku-0063794 and WYE-354 each enhanced phosphorylation of Smad1/5. Intriguingly, silencing raptor alone enhanced, whereas silencing rictor repressed, the phosphorylation of Smad1/5, indicating that mTORC1 represses, whereas mTORC2 activates, BMP signaling. Immunohistochemical analysis showed increased levels of phospho-Smad1/5 concomitant with suppression of phospho-S6 and survivin levels in PC3 human prostate cancer xenografts in athymic mice administered rapamycin (intraperitoneally, 5 mg/kg/d, 2-6 days). Moreover, we show that compared with prostate tumor tissue from untreated patients, levels of phospho-Smad1/5 were significantly elevated in the prostate tumor tissue of patients with high-risk prostate cancer who received 8 weeks of the rapalog everolimus as part of a neoadjuvant clinical trial before undergoing local definitive therapy by radical prostatectomy. Taken together, our data implicate Smads 1, 5 and 8 as potential prognostic markers and therapeutic targets for mTOR inhibition therapy of prostate cancer.
尽管过度激活的 mTOR 被认为是前列腺癌生长和进展的关键，但它促进这些反应的潜在机制仍不完全清楚。在这里，我们表明雷帕霉素通过阻断 mTORC1 激酶在人类前列腺癌细胞和组织中激活 Smads 1 和 5。基于小发夹 RNA 的基因沉默和基因过表达方法表明，Smads 1 和 5 介导，而 Smad8 抑制，雷帕霉素诱导的细胞死亡和人前列腺癌细胞系中骨形态发生蛋白 (BMP) 转录靶标 Id1 的表达。此外，在 LNCaP 前列腺癌细胞中，这种磷酸化 Smad1/5 介导的雷帕霉素反应被 LDN-193189（BMPRI 激酶抑制剂）或 Noggin（BMP 拮抗剂）阻断。同样，mTOR 激酶抑制剂 Ku-0063794 和 WYE-354 均增强 Smad1/5 的磷酸化。有趣的是，单独沉默 raptor 增强，而沉默 rictor 抑制 Smad1/5 的磷酸化，表明 mTORC1 抑制，而 mTORC2 激活 BMP 信号。免疫组织化学分析显示，在接受雷帕霉素（腹腔内，5mg/kg/d，2-6 天）治疗的裸鼠 PC3 人前列腺癌异种移植瘤中，磷酸化 Smad1/5 的水平升高，同时磷酸化 S6 和 survivin 水平降低。此外，我们表明，与未经治疗的患者的前列腺肿瘤组织相比，接受 8 周雷帕莫司（作为新辅助临床试验的一部分）的高危前列腺癌患者的前列腺肿瘤组织中磷酸化 Smad1/5 的水平显着升高，然后接受根治性前列腺切除术的局部确定性治疗。总之，我们的数据表明 Smads 1、5 和 8 可作为 mTOR 抑制治疗前列腺癌的潜在预后标志物和治疗靶点。
