Fan Yibo, Qu Xiujuan, Ma Yanju, Liu Yunpeng, Hu Xuejun
Department of Medical Oncology, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China.
Department of Respiratory Medicine, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China.
Oncol Lett. 2016 Aug;12(2):1113-1118. doi: 10.3892/ol.2016.4730. Epub 2016 Jun 15.
Cancer cell detachment from the primary tumor site represents the first stage of metastasis. Previous studies have identified that cell detachment is triggered by cytoskeletal disruption, which may induce a wide variety of cellular changes. Focal adhesion kinase (FAK) exhibits crucial cellular functions, including regulation of the cytoskeleton. These observations have provided exciting insights into the effect of FAK in cell detachment; however, the involvement of FAK in cell detachment remains controversial. The aim of the present study was to evaluate the effect of FAK and its function in the process of cell detachment. The results revealed that FAK expression was downregulated following trypsin treatment in human gastric, lung, colon and breast cancer cell lines, as well as a human gastric epithelial cell line. Knockdown of FAK enhanced cell detachment in gastric cancer MGC803 cells, indicating that FAK inhibits cell detachment. Further investigation revealed that trypsin induced monoubiquitination of FAK. In addition, the lysosome inhibitor, NHCl, decreased trypsin-induced degradation of FAK. Casitas B-lineage lymphoma-b (Cbl-b), an E3 ubiquitin ligase, was involved in this process, which interacted with FAK, as demonstrated by co-precipitation experiments, and promoted trypsin-induced ubiquitin-lysosome degradation of FAK. These results indicate that Cbl-b promotes cell detachment via ubiquitination of FAK. These findings provide novel insights regarding the effect of FAK and Cbl-b in the process of cancer cell detachment.
癌细胞从原发性肿瘤部位脱离是转移的第一阶段。先前的研究已经确定细胞脱离是由细胞骨架破坏引发的，这可能会诱导多种细胞变化。粘着斑激酶（FAK）具有关键的细胞功能，包括对细胞骨架的调节。这些观察结果为FAK在细胞脱离中的作用提供了令人兴奋的见解；然而，FAK在细胞脱离中的参与仍存在争议。本研究的目的是评估FAK在细胞脱离过程中的作用及其功能。结果显示，在人胃癌、肺癌、结肠癌细胞系以及人胃上皮细胞系中，胰蛋白酶处理后FAK表达下调。在胃癌MGC803细胞中敲低FAK可增强细胞脱离，表明FAK抑制细胞脱离。进一步研究发现，胰蛋白酶诱导FAK发生单泛素化。此外，溶酶体抑制剂NHCl可减少胰蛋白酶诱导的FAK降解。共沉淀实验表明，E3泛素连接酶Casitas B系淋巴瘤-b（Cbl-b）参与了这一过程，它与FAK相互作用，并促进胰蛋白酶诱导的FAK泛素-溶酶体降解。这些结果表明，Cbl-b通过FAK的泛素化促进细胞脱离。这些发现为FAK和Cbl-b在癌细胞脱离过程中的作用提供了新的见解。
