Met gene amplification has been found in a subset of malignant carcinomas, including diffuse-type gastric carcinoma (DGC), which has a poor prognosis owing to rapid infiltrative invasion and frequent peritoneal dissemination. Met is considered a promising therapeutic target for DGC. However, DGC cells with Met gene amplification eventually acquire resistance to Met inhibitors. Therefore, identification of alternate targets that mediate Met signaling and confer malignant phenotypes is critical. In this study, we conducted a phosphoproteomic analysis of DGC cells possessing Met gene amplification and identified Pleckstrin Homology Domain Containing A5 (PLEKHA5) as a protein that is tyrosine-phosphorylated downstream of Met. Knockdown of PLEKHA5 selectively suppressed the growth of DGC cells with Met gene amplification by inducing apoptosis, even though they had acquired resistance to Met inhibitors. Moreover, PLEKHA5 silencing abrogated the malignant phenotypes of Met-addicted DGC cells, including peritoneal dissemination in vivo. Mechanistically, PLEKHA5 knockdown dysregulates glycolytic metabolism, leading to activation of the JNK pathway that promotes apoptosis. These results indicate that PLEKHA5 is a novel downstream effector of amplified Met and is required for the malignant progression of Met-addicted DGC.

在包括扩散型胃癌（DGC）在内的一系列恶性肿瘤中发现了Met基因扩增，由于快速浸润性浸润和频繁的腹膜扩散，预后较差。Met被认为是DGC的有希望的治疗靶标。但是，具有Met基因扩增的DGC细胞最终获得了对Met抑制剂的抗性。因此，鉴定介导Met信号传导并赋予恶性表型的替代靶标至关重要。在这项研究中，我们对具有Met基因扩增的DGC细胞进行了磷酸化蛋白质组学分析，并鉴定了含A5的Pleckstrin同源结构域（PLEKHA5）是在Met下游被酪氨酸磷酸化的蛋白质。敲低PLEKHA5可以通过诱导细胞凋亡，通过Met基因扩增选择性抑制DGC细胞的生长，即使他们已经获得了对Met抑制剂的抵抗力。此外，PLEKHA5沉默消除了Met上瘾的DGC细胞的恶性表型，包括体内腹膜扩散。从机制上讲，PLEKHA5组合物失调调节糖酵解代谢，导致激活JNK通路，从而促进细胞凋亡。这些结果表明，PLEKHA5是扩增的Met的新型下游效应子，是Met上瘾的DGC恶性进展所必需的。