Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
Oncogene. 2011 Apr 7;30(14):1643-52. doi: 10.1038/onc.2010.555. Epub 2010 Dec 6.
Mesothelioma is an asbestos-associated and notoriously chemotherapy-resistant neoplasm. Activation of the receptor tyrosine kinases (RTKs), epidermal growth factor receptor and MET, has been described in subsets of mesothelioma, suggesting that TKs might represent therapeutic targets in this highly lethal disease. We employed proteomic screening by phosphotyrosine immunoaffinity purification and tandem mass spectrometry to characterize RTK activation in mesothelioma cell lines. These assays demonstrated expression and activation of the AXL protein, which is an RTK with known oncogenic properties in non-mesothelial cancer types. AXL was expressed and activated strongly in 8 of 9 mesothelioma cell lines and 6 of 12 mesothelioma biopsies, including each of 12 mesotheliomas with spindle-cell histology. Somatic AXL mutations were not found, but all mesotheliomas expressed an alternatively spliced AXL transcript with in-frame deletion of exon 10, and six of seven mesothelioma cell lines expressed the AXL ligand, growth arrest-specific 6 (GAS6). GAS6 expression appeared to be functionally relevant, as indicated by modulation of AXL tyrosine phosphorylation by knockdown of endogeneous GAS6, and by administration of exogenous GAS6. AXL silencing by lentivirus-mediated short hairpin RNA suppressed mesothelioma migration and cellular proliferation due to G1 arrest. The AXL inhibitor DP-3975 inhibited cell migration and proliferation in mesotheliomas with strong AXL activation. DP-3975 response in these tumors was characterized by inhibition of PI3-K/AKT/mTOR and RAF/MAPK signaling. AXL inhibition suppressed mesothelioma anchorage-independent growth, with reduction in colony numbers and size. These studies suggest that AXL inhibitors warrant clinical evaluation in mesothelioma.
间皮瘤是一种与石棉相关且以化疗耐药而著称的肿瘤。在一些间皮瘤亚群中已经描述了受体酪氨酸激酶（RTKs），表皮生长因子受体和 MET 的激活，这表明 TK 可能是这种高度致命疾病的治疗靶点。我们通过磷酸酪氨酸免疫亲和纯化和串联质谱法进行蛋白质组学筛选，以表征间皮瘤细胞系中的 RTK 激活。这些测定法表明，AXL 蛋白的表达和激活，AXL 是一种在非间皮癌类型中具有已知致癌特性的 RTK。AXL 在 9 种间皮瘤细胞系中的 8 种和 12 种间皮瘤活检中的 6 种中表达和强烈激活，包括 12 种具有纺锤形细胞组织学的间皮瘤中的每一种。未发现体细胞 AXL 突变，但所有间皮瘤均表达具有外显子 10 框内缺失的选择性剪接 AXL 转录本，并且 7 种间皮瘤细胞系中的 6 种表达 AXL 配体生长停滞特异性 6（GAS6）。GAS6 的表达似乎具有功能相关性，因为内源性 GAS6 的敲低调节了 AXL 酪氨酸磷酸化，并且外源性 GAS6 的给药也调节了 AXL 酪氨酸磷酸化。慢病毒介导的短发夹 RNA 沉默 AXL 抑制了由于 G1 期阻滞导致的间皮瘤迁移和细胞增殖。AXL 抑制剂 DP-3975 抑制了具有强烈 AXL 激活的间皮瘤的细胞迁移和增殖。这些肿瘤中的 DP-3975 反应的特征在于抑制 PI3-K/AKT/mTOR 和 RAF/MAPK 信号转导。AXL 抑制抑制了间皮瘤的锚定非依赖性生长，减少了菌落数量和大小。这些研究表明，AXL 抑制剂值得在间皮瘤中进行临床评估。
