PANCREATIC CARCINOMAS DEPOSIT LAMININ-5, PREFERABLY ADHERE TO LAMININ-5, AND MIGRATE ON THE NEWLY DEPOSITED BASEMENT-MEMBRANE

We studied the adhesion mechanism of pancreatic carcinoma using in vit ro adhesion and migration assays of stable cell lines and tumors grown from these cell lines in nude mice. We also compared the results with the expression profiles of laminins and their receptors in pancreatic carcinomas to evaluate the relevance of these mechanisms in vivo. All of the cell Lines preferably adhered to laminin-5, irrespective of th eir capability to synthesize laminin-5. Cell migration was studied in the presence of hepatocyte growth factor, as it increased the speed of migration manyfold. Herbimycin A treatment and antibodies against the beta(1) and alpha(3) integrin subunits and laminin alpha(3) chain alm ost entirely blocked cell migration of the BxPC-3 cell line, whereas m igration was nearly unaffected by RGD peptide and only moderately inhi bited by antibody against the alpha(6) integrin subunit. Indirect immu nofluorescence microscopy of wounded BxPC-3 cells suggested a rapid en docytosis of alpha(3) integrin subunit in the cells at the margin of t he wound and a rapid, polarized rearrangement of the alpha(6) beta(4) integrin. Especially HGF-treated cultures showed a prominent cytoplasm ic reaction for laminin-5 at the margin of the wound. Xenografted cell s formed tumors that produced and deposited the same laminin chains as the in vitro cultures. Frozen sections of human pancreatic carcinomas showed reactivity for laminin chains suggestive for expression of lam inin-1 and laminin-5. Both xenografted tumors and human pancreatic car cinomas also showed stromal reactivity for laminin-5. Electron microsc opy of the human tumors suggested that this was due toan abundant redu plication the basement-membrane-like material around the nests of mali gnant cells. Our results suggest that pancreatic carcinomas synthesize and deposit laminin-5 in the basement membrane in an abnormal manner. Invading cells adhere to this newly produced basement membrane and mi grate on it by using the alpha(3) beta(1) integrin receptor recognizin g laminin-5.