Angiopoietin‐like 4 is upregulated by amphiregulin and activates cell proliferation and migration through p38 kinase in head and neck squamous cell carcinoma.

Background: Angiopoietin‐like 4 is a molecular hallmark that correlates with the growth and metastasis of head and neck squamous cell carcinoma, one of the most prevalent cancers worldwide. However, the molecular mechanisms by which angiopoietin‐like 4 promotes head and neck squamous cell carcinoma tumorigenesis are unclear. Methods: Using well‐characterized cell lines of head and neck squamous cell carcinoma development, including human normal oral keratinocytes, dysplastic oral keratinocytes, oral leukoplakia‐derived oral keratinocytes, and head and neck squamous cell carcinoma cell lines, HN13, HN6, HN4, HN12, and CAL27, we investigated the signaling pathways upstream and downstream of angiopoietin‐like 4‐induced head and neck squamous cell carcinoma tumorigenesis. Results: We found that both epidermal growth factor receptor ligands, epithelial growth factor, and amphiregulin led to angiopoietin‐like 4 upregulation in normal oral keratinocytes and dysplastic oral keratinocytes and cooperated with the activation of hypoxia‐inducible factor‐1 in this effect. Interestingly, amphiregulin and angiopoietin‐like 4 were increased in dysplastic oral keratinocytes and head and neck squamous cell carcinoma cell lines, and amphiregulin‐induced activation of cell proliferation was dependent on angiopoietin‐like 4. Although both p38 mitogen‐activated protein kinases (p38 MAPK) and protein kinase B (AKT) were activated by angiopoietin‐like 4, only pharmacological inhibition of p38 MAPK was sufficient to prevent head and neck squamous cell carcinoma cell proliferation and migration. We further observed that angiopoietin‐like 4 promoted the secretion of interleukin 11 (IL‐11), interleukin 12 (IL‐12), interleukin‐1 alpha (IL‐1α), vascular endothelial growth factor, platelet‐derived growth factor (PDGF), and tumour necrosis factor alpha (TNF‐α), cytokines and chemokines previously implicated in head and neck squamous cell carcinoma pathogenesis. Conclusion: Our results demonstrate that angiopoietin‐like 4 is a downstream effector of amphiregulin and promotes head and neck squamous cell carcinoma development both through direct activation of p38 kinase as well as paracrine mechanisms. [ABSTRACT FROM AUTHOR]