Laboratoire de Validation et Identification de Nouvelles Cibles en Oncologie (VINCO), INSERM U916, Institut Bergonié, Université Victor Segalen Bordeaux 2, Bordeaux, France.
CNRS - CIRID, Bordeaux Cedex, France.
Oncogene. 2016 Jun 16;35(24):3190-200. doi: 10.1038/onc.2015.379. Epub 2015 Nov 2.
Often described as a mediator of cell cycle arrest or as a pro-apoptotic factor in stressful conditions, the MAP3K ZAK (Sterile alpha motif and leucine zipper-containing kinase) has also been proven to positively regulate epidermal growth factor receptor (EGFR) and WNT signaling pathways, cancer cell proliferation and cellular neoplastic transformation. Here, we show that both isoforms of ZAK, ZAK-α and ZAK-β are key factors in cancer cell migration. While ZAK depletion reduced cell motility of HeLa and HCT116 cells, its overexpression triggered the activation of all three mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK) and p38, as well as an increase in cell motion. On the contrary, the kinase-dead mutants, ZAK-α K45M and ZAK-β K45M, were not able to provoke such events, and instead exerted a dominant-negative effect on MAPK activation and cell migration. Pharmacological inhibition of ZAK by nilotinib, preventing ZAK-autophosphorylation and thereby auto-activation, led to the same results. Activated by epidermal growth factor (EGF), we further showed that ZAK constitutes an essential element of the EGF/ERK-dependent cell migration pathway. Using public transcriptomic databases and tissue microarrays, we finally established that, as strong factors of the EGFR signaling pathway, ZAK-α and/or ZAK-β transcripts and protein(s) are frequently upregulated in colorectal adenoma and carcinoma patients. Notably, gene set enrichment analysis disclosed a significant correlation between ZAK+ colorectal premalignant lesions and gene sets belonging to the MAPK/ERK and motility-related signaling pathways of the reactome database, strongly suggesting that ZAK induces such pro-tumoral reaction cascades in human cancers.
ZAK（含 sterile alpha 基序和亮氨酸拉链的丝裂原激活蛋白激酶）通常被描述为细胞周期阻滞的介质或应激条件下的促凋亡因子，也已被证明可正向调节表皮生长因子受体 (EGFR) 和 WNT 信号通路、癌细胞增殖和细胞恶性转化。在这里，我们表明 ZAK 的两种同工型，ZAK-α 和 ZAK-β 都是癌细胞迁移的关键因素。虽然 ZAK 耗竭降低了 HeLa 和 HCT116 细胞的运动能力，但它的过表达触发了所有三种丝裂原激活蛋白激酶 (MAPK)、细胞外信号调节激酶 (ERK)、c-JUN N 末端激酶 (JNK) 和 p38 的激活，以及细胞运动的增加。相反，激酶失活突变体 ZAK-α K45M 和 ZAK-β K45M 不能引起这种情况，反而对 MAPK 激活和细胞迁移产生显性负效应。通过 nilotinib 抑制 ZAK 的激酶活性，阻止 ZAK 自磷酸化从而自动激活，也会导致相同的结果。通过表皮生长因子 (EGF) 的激活，我们进一步表明 ZAK 是 EGF/ERK 依赖性细胞迁移途径的一个重要组成部分。使用公共转录组数据库和组织微阵列，我们最终确定，作为 EGFR 信号通路的强因子，ZAK-α 和/或 ZAK-β 转录本和蛋白在结直肠腺瘤和癌患者中经常上调。值得注意的是，基因集富集分析揭示了 ZAK+结直肠前病变与 reactome 数据库中 MAPK/ERK 和与运动相关的信号通路的基因集之间存在显著相关性，这强烈表明 ZAK 在人类癌症中诱导这种促肿瘤反应级联。
