Upregulation and redistribution of integrin α6β4 expression occurs at an early stage in pancreatic adenocarcinoma progression

Pancreatic adenocarcinomas are highly invasive cancers for reasons that are currently unclear. Here we sought to determine if the proinvasive integrin α6β4 may be related to pancreatic adenocarcinoma tumor progression. Expression of integrin α6β4 was analyzed via immunohistochemistry for the β4 subunit in normal pancreas, pancreatic intraepithelial neoplasia (PanIN) lesions, pancreatic adenocarcinomas and chronic pancreatitis. In normal pancreatic ducts, integrin α6β4 was noted only at the cell's basal interface with the basement membrane. In pancreatic adenocarcinomas, 92% (104/113) demonstrated overexpression of integrin α6β4 and altered localization to the cytoplasm and membranous regions. This pattern of expression was observed in all PanIN lesions as early as PanIN-1A, and was evident in lesions that were juxtapositioned to normal epithelium. In contrast, 93% (13/14) of chronic pancreatitis samples resembled the staining pattern of normal pancreas. When cancer was present in areas of chronic pancreatitis, this altered expression of α6β4 integrin identified the cancer. We conclude that integrin α6β4 is expressed only on the basal surface of ductal cells in normal pancreas and chronic pancreatitis. During pancreatic adenocarcinoma progression, the α6β4 integrin is dramatically overexpressed and displays altered localization at the earliest stages of PanIN, thus representing an early event in pancreatic adenocarcinoma progression.