PTEN Loss Confers BRAF Inhibitor Resistance to Melanoma Cells through the Suppression of BIM Expression
PTEN Loss Confers BRAF Inhibitor Resistance to Melanoma Cells through the Suppression of BIM Expression
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DOI：
10.1158/0008-5472.can-10-2954
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发表时间：
2011-04-01
期刊：
影响因子：
11.2
通讯作者：
Smalley, Keiran S. M.
中科院分区：
文献类型：
--
作者：
Paraiso, Kim H. T.;Xiang, Yun;Smalley, Keiran S. M.
本研究探讨了PTEN缺失在BRAF抑制剂PLX4720内在抗性中的作用。覆盖黑素细胞瘤所有阶段（n = 192）的组织阵列免疫组化染色显示，在所有黑素瘤病例中，有10%的患者PTEN表达缺失。虽然PTEN表达状态不能预测PLX4720对生长抑制作用的敏感性，但它可以预测细胞凋亡，在缺乏PTEN表达的黑色素瘤中只观察到有限的细胞死亡（PTEN-）。从机制上讲，PLX4720可以刺激PTEN-而不是PTEN+细胞系的AKT信号传导。采用液相色谱-多反应监测质谱法（LC-MRM）鉴定两种细胞系组间凋亡信号的差异。与PTEN-细胞系（4倍）相比，PLX4720处理显著增加了PTEN+细胞系（>）中BIM的表达（14倍）。PTEN在plx4720介导的BIM表达调控中的作用通过PTEN的siRNA敲低和将PTEN重新引入PTEN-细胞中得到证实。进一步研究表明，siRNA敲低BIM可显著减弱PTEN+黑色素瘤细胞的凋亡反应。PLX4720和PI3K抑制剂双重处理PTEN-细胞，在mRNA和蛋白水平上增强了BIM的表达，并通过AKT3和FOXO3a激活的机制增加了凋亡水平。总之，我们首次证明PTEN的缺失通过抑制bim介导的细胞凋亡促进了BRAF抑制剂的内在抗性。癌症Res;71 (7);2750 - 60。AACR (C) 2011。
This study addresses the role of PTEN loss in intrinsic resistance to the BRAF inhibitor PLX4720. Immunohistochemical staining of a tissue array covering all stages of melanocytic neoplasia (n = 192) revealed PTEN expression to be lost in > 10% of all melanoma cases. Although PTEN expression status did not predict for sensitivity to the growth inhibitory effects of PLX4720, it was predictive for apoptosis, with only limited cell death observed in melanomas lacking PTEN expression (PTEN-). Mechanistically, PLX4720 was found to stimulate AKT signaling in the PTEN- but not the PTEN+ cell lines. Liquid chromatography multiple reaction monitoring mass spectrometry (LC-MRM) was performed to identify differences in apoptosis signaling between the two cell line groups. PLX4720 treatment significantly increased BIM expression in the PTEN+ (> 14-fold) compared with the PTEN- cell lines (four-fold). A role for PTEN in the regulation of PLX4720-mediated BIM expression was confirmed by siRNA knockdown of PTEN and through reintroduction of PTEN into cells that were PTEN-. Further studies showed that siRNA knockdown of BIM significantly blunted the apoptotic response in PTEN+ melanoma cells. Dual treatment of PTEN- cells with PLX4720 and a PI3K inhibitor enhanced BIM expression at both the mRNA and protein level and increased the level of apoptosis through a mechanism involving AKT3 and the activation of FOXO3a. In conclusion, we have shown for the first time that loss of PTEN contributes to intrinsic BRAF inhibitor resistance via the suppression of BIM-mediated apoptosis. Cancer Res; 71(7); 2750-60. (C)2011 AACR.