Expression and distribution of VLA receptors in the pancreas: an immunohistochemical study

Very late activation (VLA) receptors mediate cell adhesion to extracellular matrix, mainly by acting as adhesion receptors to fibronectin, collagen, and laminin as well as to other cells. These interactions not only regulate normal cell-extracellular matrix contact, but also are thought to be involved in metastasis and invasive tumor growth. Using immunohistochemistry [the alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique] we compared the expression and distribution of VLA receptors in normal pancreatic tissue, chronic pancreatitis, and ductal pancreatic adenocarcinoma. Immunohistochemically, VLA alpha 2 and VLA alpha 6 were moderately to strongly expressed on the basal surface of ductal and acinar cells in normal pancreatic tissue, whereas centroacinar cells predominantly expressed VLA alpha 3 and VLA alpha 5. Similarly, pancreatic carcinoma showed an intensive staining for VLA alpha 2 and VLA alpha 6 with a diffuse distribution on the cell surface. Expression of VLA alpha 3 and VLA alpha 5 in pancreatic carcinoma was heterogeneous, ranging from moderate to weak and lost in about 50% of the cells. As our results suggest, cell-basement membrane interaction in ductal and acinar pancreatic cells is primarily mediated through VLA alpha 2 and VLA alpha 6, whereas VLA alpha 3 and VLA alpha 5 are the major VLA receptors on centroacinar cells. In pancreatic carcinoma a loss (VLA alpha 5) or redistribution (VLA alpha 2, VLA alpha 6) of VLAs was observed. This redistribution of VLA alpha 2 and VLA alpha 6 may reflect a loss of spatial arrangement of tumor cells and their ability to randomly interact with extracellular matrix structures during invasion and metastasis.