αvβ6 integrin down-regulates the MMP-13 expression in oral squamous cell carcinoma cells

The integrin αvβ6, a receptor for fibronectin, vitronectin, tenascin and TGF-β latency-associated peptide (LAP), is not detectable on normal oral epithelium but is neo-expressed in oral squamous cell carcinomas (OSCC) and epithelial dysplasia. Previously it has been shown that αvβ6 integrin can up-regulate MMP-3 and -9 expression in OSCC cells. Using β6-transfected and control OSCC cells we demonstrate that αvβ6 integrin down-regulates MMP-13 expression at both mRNA and protein level. Although expressing less MMP-13, β6-transfected cells were found to have similar collagenolytic activity as control cells and invade at similar levels through type I collagen. Growth of the tumour cells in organotypic culture and confocal microscopy confirmed low levels of MMP-13 in cells with high αvβ6 expression. Furthermore, human squamous cell carcinomas of the tongue with high expression of αvβ6 showed lower MMP-13 levels than carcinomas with low levels of αvβ6. Our results suggest that αvβ6 down-regulates MMP-13 expression in OSCC cells and that MMP-13 is not essential for the degradation of type I collagen by OSCC cells.