Interaction of Integrin alphavbeta8 With Type I Collagen Promotes Squamous Cell Carcinoma Cell Motility via RAC1 Activation.

BACKGROUND/AIM: The interaction of integrin alphavbeta8 with type I collagen was shown to promote oral squamous cell carcinoma (SCC) cell proliferation via the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. However, the role of integrin alphavbeta8 in SCC progression remains poorly understood. In this study, the role of integrin alphavbeta8 in oral SCC progression was therefore investigated. MATERIALS AND METHODS: Integrin alphav and beta8 protein expression in oral SCC cells was examined by western blotting. Oral SCC cell motility was investigated using modified Boyden chamber assays. Behavior of oral SCC cells was examined in three-dimensional culture using type I collagen gel. Ras homolog family member A (RHOA), Ras-related C3 botulinum toxin substrate 1 (RAC1), and cell division control protein 42 homolog (CDC42) activity of oral SCC cells was analyzed by pull-down assays. RESULTS: SCC cells with high integrin alphavbeta8 expression levels had a high ability to migrate on type I collagen and exhibited enhanced invasion into type I collagen gel. In SCC cells with high integrin alphavbeta8 expression level, cultivation on type I collagen induced RAC1 activation. Treatment with RAC1 inhibitor reduced type I collagen-induced motility of SCC cells. Down-regulation of integrin beta8 by specific antisense oligonucleotide reduced type I collagen-induced RAC1 activation and suppressed cell motility and invasion into type I collagen gel. CONCLUSION: The interaction of integrin alphavbeta8 with type I collagen facilitates SCC cell motility and invasion via RAC1 activation. Therefore, integrin alphavbeta8 and RAC1 may represent new targets for inhibiting metastasis and invasion in patients with oral SCC.