title: Claudin-4 expression decreases invasiveness and metastatic potential of pancreatic cancer.
abstract: Claudin-4 has been identified as an integral constituent of tight junctions and has been found to be highly expressed in pancreatic cancer. The aim of the present study was to elucidate the effect of claudin-4 on growth and metastatic potential in pancreatic cancer cells, as well as the regulation of claudin-4 by oncogenic pathways. Claudin-4 was stably overexpressed in SUIT-2 pancreatic cancer cells, and its effect on invasion and growth in vitro was examined by using two-chamber invasion assays, soft agar assays, and fluorescence-activated cell sorter analysis. Claudin-4 localization was characterized by light and electron microscopy, and pulmonary colonization was analyzed in vivo after injection of claudin-4 overexpressing cells into the tail vein of nude mice. Overexpression of claudin-4 was associated with significantly reduced invasive potential in vitro and inhibited colony formation in soft agar assays. In vivo, tail vein-injected claudin-4 overexpressing cells formed significantly less pulmonary metastases in comparison with mock-transfected cells. These effects were not caused by changes in proliferation, cell cycle progression, or matrix metalloproteinase gelatinolytic activity, but were paralleled by increased cell contact formation. Moreover, proinvasive transforming growth factor beta was able to down-regulate claudin-4 in PANC-1 cells. Inhibition of Ras signaling by using dominant-negative Ras and specific inhibitors of both downstream effectors mitogen-activated protein/extracellular signal-regulated kinase kinase and phosphatidylinositol 3'-kinase also decreased claudin-4 expression. Our findings identify claudin-4 as a potent inhibitor of the invasiveness and metastatic phenotype of pancreatic cancer cells, and as a target of the transforming growth factor beta and Ras/Raf/extracellular signal-regulated kinase pathways.
authors.affiliation: Department of Internal Medicine I, University Hospital, University of Ulm, Robert-Koch-Strasse 8, 89081 Ulm, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Michl
authors.forename: Claudia
authors.initials: C
authors.lastname: Barth
authors.forename: Malte
authors.initials: M
authors.lastname: Buchholz
authors.forename: Markus M
authors.initials: MM
authors.lastname: Lerch
authors.forename: Monika
authors.initials: M
authors.lastname: Rolke
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Holzmann
authors.forename: Andre
authors.initials: A
authors.lastname: Menke
authors.forename: Heiko
authors.initials: H
authors.lastname: Fensterer
authors.forename: Klaudia
authors.initials: K
authors.lastname: Giehl
authors.forename: Matthias
authors.initials: M
authors.lastname: Löhr
authors.forename: Gerhard
authors.initials: G
authors.lastname: Leder
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwamura
authors.forename: Guido
authors.initials: G
authors.lastname: Adler
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gress
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002448:Cell Adhesion / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D062506:Claudin-4; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000378:metabolism / Q000556:secondary; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D008565:Membrane Proteins; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: C568157:CLDN4 protein, human; D062506:Claudin-4; C568158:Cldn4 protein, mouse; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D016212:Transforming Growth Factor beta; C105422:Clostridium perfringens enterotoxin receptor; D020778:Matrix Metalloproteinase 2; D018631:ras Proteins