Epithelial cells usually trigger their “migratory machinery” upon loss of adhesion to their neighbors. This default is important for both physiological (e.g., wound healing) and pathological (e.g., tumor metastasis) processes. However, the underlying mechanism for such a default remains unclear. In this study, we used the human head and neck squamous cell carcinoma (HNSCC) SAS cells as a model and found that loss of cell–cell adhesion induced reactive oxygen species (ROS) generation and vimentin expression, both of which were required for SAS cell migration upon loss of cell–cell adhesion. We demonstrated that Tiam1-mediated Rac1 activation was responsible for the ROS generation through NADPH-dependent oxidases. Moreover, the ROS–Src–STAT3 signaling pathway that led to vimentin expression was important for SAS cell migration. The activation of ROS, Src, and STAT3 was also detected in tumor biopsies from HNSCC patients. Notably, activated STAT3 was more abundant at the tumor invasive front and correlated with metastatic progression of HNSCC. Together, our results unveil a mechanism of how cells trigger their migration upon loss of cell–cell adhesion and highlight an important role of the ROS–Src–STAT3 signaling pathway in the progression of HNSCC.
Epidermal growth factor receptor (EGFR) activation is a major cause of metastasis in many cancers, such as head and neck squamous cell carcinoma (HNSCC). However, whether the induction of pyruvate dehydrogenase kinase 1 (PDK1) mediates EGF-enhanced HNSCC metastasis remains unclear. Interestingly, we found that EGF induced PDK1 expression in HNSCC. The tumor cell transformation induced by EGF was repressed by the depletion of PDK1. The down-regulation of PDK1 expression or inhibition of its activity significantly blocked EGF-enhanced cell migration and invasion. In addition, depletion of PDK1 impeded EGF-enhanced binding of HNSCC cells to endothelial cells and tumor cells metastastic seeding of the lungs. Knockdown of PDK1 also inhibited EGF-induced matrix metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-9, and fibronectin expression and Rac1/cdc42 activation. These results demonstrate that EGF-induced PDK1 expression enhances HNSCC metastasis via activation of the fibronectin signaling pathway. The inhibition of PDK1 may be a potential strategy for the treatment of EGFR-mediated HNSCC metastasis. Citation Format: Ben-Kuen Chen, Jinn-Yuan Hsu, Wen-Chang Chang. Epidermal growth factor-induced pyruvate dehydrogenase kinase 1 enhances head and neck squamous cell carcinoma metastasis through fibronectin up-regulation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 710.
Epidermal growth factor receptor (EGFR) activation is a major cause of cell metastasis in many cancers, such as head and neck squamous cell carcinoma (HNSCC). However, whether the induction of cyclooxygenase-2 (COX-2) correlates with EGF-enhanced HNSCC metastasis remains unclear. Interestingly, we found that EGF induced COX-2 expression mainly in HNSCC. The tumor cell transformation induced by EGF was repressed with COX-2 knockdown, and this repression was reversed by simultaneously treating the cells with EGF and prostaglandin E2 (PGE2). The down-regulation of COX-2 expression or inhibition of COX-2 activity significantly blocked EGF-enhanced cell migration and invasion, but the addition of PGE2 compensated for this blockage in COX-2-knockdown cells. Interestingly, COX-2 depletion inhibited EGF-induced matrix metalloproteinase-1 (MMP-1), MMP3 and fibronectin expression and Rac1/cdc42 activation; this reduction in MMPs and the fibronectin/Rac1/cdc42 axis by the depletion of COX-2 was also rescued when the cells were treated with PGE2. Furthermore, the depletion of fibronectin impeded the COX-2-enhanced binding of HNSCC cells to endothelial cells and tumor cells metastatic seeding of the lungs. These results provide new insight that EGF-induced COX-2 enhances HNSCC metastasis via activation of the fibronectin signaling pathway. The inhibition of COX-2 expression and activation suggests a potential strategy for the treatment of EGFR-mediated HNSCC metastasis. Citation Format: Jinn-Yuan Hsu, Kwang-Yu Chang, Shang-Hung Chen, Chung-Ta Lee, Sheng-Tsung Chang, Hung-Chi Cheng, Wen-Chang Chang, Ben-Kuen Chen. Epidermal growth factor-induced cyclooxygenase-2 enhances head and neck squamous cell carcinoma metastasis through fibronectin up-regulation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4149. doi:10.1158/1538-7445.AM2015-4149
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