Determinants of rapamycin sensitivity in breast cancer cells
Determinants of rapamycin sensitivity in breast cancer cells
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DOI：
10.1158/1078-0432.ccr-03-0043
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发表时间：
2004-02-01
影响因子：
11.5
通讯作者：
Meric-Bernstam, F
中科院分区：
文献类型：
--
作者：
Noh, WC;Mondesire, WH;Meric-Bernstam, F
目的：雷帕霉素抑制丝氨酸-苏氨酸激酶哺乳动物雷帕霉素靶蛋白（mTOR），阻断p70 S6激酶（S6K1）和4e结合蛋白1 （4E-BP1）的磷酸化，抑制蛋白翻译和细胞周期进程。雷帕霉素及其类似物目前正在临床试验中作为新型靶向抗癌药物进行测试。尽管雷帕霉素类似物在临床试验中显示出活性，但只有部分接受治疗的患者有反应。本研究的目的是确定雷帕霉素敏感性的决定因素，这可能有助于选择合适的患者进行治疗。实验设计：在mTOR信号通路中表现出一系列畸变的乳腺癌细胞系进行了雷帕霉素敏感性测试。在雷帕霉素存在和不存在的情况下，通过Western blot检测该通路多个组分的表达和磷酸化状态。结果：在15个乳腺癌细胞系中，雷帕霉素显著抑制了12个细胞系的细胞增殖。4E- bp1总蛋白水平与其结合伙伴真核起始因子4E的比值并不能预测雷帕霉素的敏感性。相比之下，S6K1的过表达以及独立于磷酸酶和10号染色体上缺失的紧张素同源物的磷酸化Akt与雷帕霉素敏感性相关。分别用小干扰RNA和显性阴性构建体靶向S6K1和Akt，降低了雷帕霉素的敏感性。雷帕霉素抑制了雷帕霉素耐药和敏感细胞中S6K1、核糖体S6蛋白和4E-BP1的磷酸化，表明其抑制mTOR途径的能力不足以赋予雷帕霉素敏感性。相比之下，雷帕霉素治疗与雷帕霉素敏感细胞中cyclin D1水平的降低有关，但与雷帕霉素耐药细胞无关。结论：S6K1的过表达和磷酸化Akt的表达可作为乳腺癌患者雷帕霉素敏感性的预测指标。此外，细胞周期蛋白D1水平的变化提供了对雷帕霉素反应的潜在药效学标志物。
Purpose: Rapamycin inhibits the serine-threonine kinase mammalian target of rapamycin (mTOR), blocking phosphorylation of p70 S6 kinase (S6K1) and 4E-binding protein 1 (4E-BP1) and inhibiting protein translation and cell cycle progression. Rapamycin and its analogues are currently being tested in clinical trials as novel-targeted anticancer agents. Although rapamycin analogues show activity in clinical trials, only some of the treated patients respond. The purpose of this study is to identify determinants of rapamycin sensitivity that may assist the selection of appropriate patients for therapy.Experimental Design: Breast cancer cell lines representing a spectrum of aberrations in the mTOR signaling pathway were tested for rapamycin sensitivity. The expression and phosphorylation state of multiple components of the pathway were tested by Western blot analysis, in the presence and absence of rapamycin.Results: Cell proliferation was significantly inhibited in response to rapamycin in 12 of 15 breast cancer cell lines. The ratio of total protein levels of 4E-BP1 to its binding partner eukaryotic initiation factor 4E did not predict rapamycin sensitivity. In contrast, overexpression of S6K1, and phosphorylated Akt independent of phosphatase and tensin homologue deleted from chromosome 10 status, were associated with rapamycin sensitivity. Targeting S6K1 and Akt with small interfering RNA and dominant-negative constructs, respectively, decreased rapamycin sensitivity. Rapamycin inhibited the phosphorylation of S6K1, ribosomal S6 protein, and 4E-BP1 in rapamycin-resistant as well as -sensitive cells, indicating that its ability to inhibit the mTOR pathway is not sufficient to confer sensitivity to rapamycin. In contrast, rapamycin treatment was associated with decreased cyclin D1 levels in the rapamycin-sensitive cells but not in rapamycin-resistant cells.Conclusions: Overexpression of S6K1 and expression of phosphorylated Akt should be evaluated as predictors of rapamycin sensitivity in breast cancer patients. Furthermore, changes in cyclin D1 levels provide a potential pharmacodynamic marker of response to rapamycin.