Liu Xin-Li, Zhang Xu-Tao, Meng Jin, Zhang Hong-Fei, Zhao Yong, Li Chen, Sun Yang, Mei Qi-Bing, Zhang Feng, Zhang Tao
Key Laboratory of Gastrointestinal Pharmacology of Chinese Materia Medica of the State Administration of Traditional Chinese Medicine, Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi'an, China.
Department of Thoracic Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.
Oncotarget. 2017 Apr 21;8(33):54265-54276. doi: 10.18632/oncotarget.17346. eCollection 2017 Aug 15.
ING5 belongs to the Inhibitor of Growth (ING) candidate tumor suppressor family, whose functions have been involved in the regulation of chromatin remodeling, cell cycle progression, proliferation and apoptosis. Our previous study has shown that ING5 overexpression inhibits lung cancer aggressiveness via suppressing epithelial to mesenchymal transition (EMT). However, the mechanisms remain largely unknown. In the current study, by Phospho-Kinase array and western blot, we have defined significantly upregulated EGFR/PI3K/Akt and IL-6/STAT3 oncogenic signaling pathways in ING5 knockdown A549 cells, which could be downregulated by ING5 overexpression. PI3K inhibitor ZSTK474 or STAT3 inhibitor Niclosamide not only abolished ING5 knockdown-promoted proliferation, colony formation, migration and invasion of lung cancer A549 cells, but also impaired ING5 knockdown-stimulated metastasis of cancer cells in mouse xenograft models with tail vein injection of A549 cells. Furthermore, treatment with ZSTK474 or Niclosamide decreased protein level of EGFR, p-Akt, IL-6 and p-STAT3, and reversed ING5 knockdown-promoted EMT, as indicated by downregulated expression of EMT marker E-cadherin, an epithelial marker, increased expression of N-cadherin, a mesenchymal marker, and EMT-related transcription factors including Snail, Slug, Smad3 and Twist. Taken together, these results demonstrate that loss of ING5 enhances aggressiveness of lung cancer cells by promoting EMT via activation of EGFR/PI3K/Akt and IL-6/STAT3 signaling pathways.
ING5属于生长抑制（ING）候选肿瘤抑制因子家族，其功能涉及染色质重塑、细胞周期进程、增殖和凋亡的调节。我们之前的研究表明，ING5过表达通过抑制上皮-间质转化（EMT）来抑制肺癌的侵袭性。然而，其机制仍 largely未知。在本研究中，通过磷酸化激酶阵列和蛋白质印迹法，我们确定了在ING5敲低的A549细胞中，EGFR/PI3K/Akt和IL-6/STAT3致癌信号通路显著上调，而ING5过表达可使其下调。PI3K抑制剂ZSTK474或STAT3抑制剂氯硝柳胺不仅消除了ING5敲低促进的肺癌A549细胞的增殖、集落形成、迁移和侵袭，还削弱了ING5敲低刺激的癌细胞在尾静脉注射A549细胞的小鼠异种移植模型中的转移。此外，用ZSTK474或氯硝柳胺处理可降低EGFR、p-Akt、IL-6和p-STAT3的蛋白水平，并逆转ING5敲低促进的EMT，这表现为上皮标志物E-钙黏蛋白表达下调、间质标志物N-钙黏蛋白表达增加以及包括Snail、Slug、Smad3和Twist在内的EMT相关转录因子表达增加。综上所述，这些结果表明，ING5的缺失通过激活EGFR/PI3K/Akt和IL-6/STAT3信号通路促进EMT，从而增强肺癌细胞的侵袭性。
