Epidermal growth factor (EGF) is important for cancer cell proliferation, angiogenesis and metastasis in many types of cancer. However, the mechanisms involved in EGF-induced head and neck squamous cell carcinoma (HNSCC) metastasis remain largely unknown. In this study, we reveal that angiopoietin-like 4 (ANGPTL4) plays an important role in the regulation of EGF-induced cancer metastasis. We showed that EGF-induced ANGPTL4 expression promoted anoikis resistance and cancer cell migration and invasion in HNSCC. In addition, depletion of ANGPTL4 inhibited EGF-induced cancer cell invasion. Autocrine production of EGF-induced ANGPTL4 regulated the expression of matrix metalloproteinases (MMPs). The induction of MMP-1 gene expression by ANGPTL4-activated integrin β1 signalling occurred through the AP-1 binding site in the MMP-1 gene promoter. Furthermore, down-regulation of MMP-1 impeded EGF- and recombinant ANGPTL4-enhanced HNSCC cell migration and invasion. Depletion of ANGPTL4 significantly blocked EGF-primed extravasation and metastatic seeding of tumour cells and MMP-1 expression in lungs. However, no effect of ANGPTL4 on tumour growth was observed. These results suggest that EGF-induced expression and autocrine production of ANGPTL4 enhances HNSCC metastasis via the up-regulation of MMP-1 expression. Inhibition of ANGPTL4 expression may be a potential strategy for the treatment of EGFR-mediated HNSCC metastasis.

Epidermal growth factor receptor (EGFR) expression and activation are the major causes of metastasis in cancers such as head and neck squamous cell carcinoma (HNSCC). However, the reciprocal effect of EGF‐induced COX‐2 and angiopoietin‐like 4 (ANGPTL4) on HNSCC metastasis remains unclear. In this study, we revealed that the expression of ANGPTL4 is essential for COX‐2‐derived prostaglandin E2 (PGE2)‐induced tumor cell metastasis. We showed that EGF‐induced ANGPTL4 expression was dramatically inhibited with the depletion and inactivation of COX‐2 by knockdown of COX‐2 and celecoxib treatment, respectively. Prostaglandin E2 induced ANGPTL4 expression in a time‐ and dose‐dependent manners in various HNSCC cell lines through the ERK pathway. In addition, the depletion of ANGPTL4 and MMP1 significantly impeded the PGE2‐induced transendothelial invasion ability of HNSCC cells and the binding of tumor cells to endothelial cells. The induction of molecules involved in the regulation of epithelial‐mesenchymal transition was also dependent on ANGPTL4 expression in PGE2‐treated cells. The depletion of ANGPTL4 further blocked PGE2‐primed tumor cell metastatic seeding of lungs. These results indicate that the EGF‐activated PGE2/ANGPTL4 axis enhanced HNSCC metastasis. The concurrent expression of COX‐2 and ANGPTL4 in HNSCC tumor specimens provides insight into potential therapeutic targets for the treatment of EGFR‐associated HNSCC metastasis.