αvβ6 Integrin Upregulates Matrix Metalloproteinase 9 and Promotes Migration of Normal Oral Keratinocytes

Abstract

The integrin alpha v beta 6 is a fibronectin receptor that is undetectable on normal keratinocytes in situ, but is increased significantly in wound healing and in culture-established keratinocytes, suggesting that it may promote changes associated with cell motility. Using normal human oral keratinocytes we have shown that cultured cells express relatively high levels of alpha v beta 6 and this integrin has a functional role in both cell adhesion and migration towards fibronectin. We provide experimental evidence that the increased expression of alpha v beta 6 by normal human oral keratinocytes results in coordinate changes, which promote a more migratory phenotype. Thus increased expression of alpha v beta 6 results in a fibronectin-dependent increase in pro-matrix metalloproteinase 9, matrix metalloproteinase 9 activity increases normal human oral keratinocyte migration, and this may be further dependent on plasmin activation. The results suggest a key role for alpha v beta 6 in these processes and indicate a coordinated link between alpha v beta 6 expression and upregulation of matrix metalloproteinase 9. It appears that alpha v beta 6 may function in normal human oral keratinocyte migration through matrix-metalloproteinase-9-dependent and -independent mechanisms.

Upregulation of Eps8 in oral squamous cell carcinoma promotes cell migration and invasion through integrin-dependent Rac1 activation

“…Sequence 3 gave the most efficient knockdown and was used in subsequent experiments. VB6, BICR56 and CA1 express high levels of endogenous Eps8 and we have shown previously that these cells migrate well in vitro (Thomas et al, 2001;Ramsay et al, 2007). Although inhibition of Eps8 expression had no effect on cell growth in any of the cell lines (data not shown), migration of VB6, BICR56 and CA1 cells towards fibronectin was significantly suppressed (VB6, Po0.02; BICR56 Po0.02; CA1 Po0.0003; Figure 3b).…”

“…We have shown previously that around 80-90% of OSCC express high levels of avb6, and that it promotes tumor cell migration and invasion (Thomas et al, 2001;Nystrom et al, 2006). Furthermore, we have shown recently that avb6-dependent invasion of VB6 Figure 5 Eps8 modulates integrin-dependent Rac1 activation and migration.…”

“…We have shown previously that VB6 cells adhere to, and migrate towards, the latency-associated peptide (LAP) of TGF-b1 solely through avb6 (Thomas et al, 2002). Similarly, H357 cells adhere to, and migrate towards, fibronectin solely through a5b1 (Thomas et al, 2001). Transfection of VB6 cells with siRNAs against Eps8 or Rac1, or treatment of cells with an avb6-blocking antibody resulted in a significant inhibition of migration (Eps8 Po0.005; Rac1 Po0.01; anti-avb6 Po0.004; Figure 5ci).…”

“…Cell migration assays Cells were transfected with siRNAs and after 48 h haptotactic migration assays were carried out using fibronectin-coated (10 mg/ ml) or TGF-b1 latency-associated peptide (LAP)-coated (0.5 mg/ ml) polycarbonate filters (8 mm pore size, Transwell, Costar, Corning, Schiphol-Rijk, The Netherlands), which were performed as described (Thomas et al, 2001). Cells were plated into the upper chamber and allowed to migrate for 24 h. Cells migrating to the lower chamber were trypsinized and counted on a Casy 1 counter (Scha¨rfe System GmbH, Reutlingen, Germany).…”

Binding of TGF-β1 latency-associated peptide (LAP) to αvβ6 integrin modulates behaviour of squamous carcinoma cells

“…The avb6 heterodimer has been shown to modulate several processes in keratinocytes, including migration on fibronectin and vitronectin, and also fibronectin-dependent upregulation of matrix metalloproteinase-9 (MMP-9) (Huang et al, 1998;Thomas et al, 2001a). In addition to promoting cell migration and MMP-9 upregulation, we have demonstrated that increased expression of avb6 in squamous cell carcinoma cell lines produces a more invasive phenotype; such increased aggressive behaviour is avb6-dependent and is modulated through altered protease expression (Thomas et al, 2001b,c).…”