Opposite roles of LPA₁ and LPA₃ on cell motile and invasive activities of pancreatic cancer cells

Lysophosphatidic acid (LPA) interacts with at least six G protein-coupled transmembrane LPA receptors. Recently, it has been demonstrated that each LPA receptor acts as a positive or negative regulator of cellular function. In the present study, to assess a biological role of LPA receptors on cell migration of pancreatic cancer cells, we generated LPA receptor-1 (LPA₁) and LPA₃ knockdown cells from hamster pancreatic cancer cells by transfection with short hairpin RNA plasmids and measured their cell motile and invasive abilities. In cell motility and invasion assay, a Cell Culture Insert, coated with or without a Matrigel, was used. While the cell motility and invasion of Lpar1 knockdown cells were markedly enhanced than those of control cells, Lpar3 knockdown cells showed significantly lower cell motility and invasion. Moreover, to investigate an involvement of LPA₁ and LPA₃ in the development of pancreatic cancers, we also measured the expression levels of Lpar1 and Lpar3 genes in hamster pancreatic duct adenocarcinomas (PDAs) induced by a nitroso compound. The expressions of Lpar1 gene in PDAs were significantly lower than those in normal pancreatic tissues. By contrast, the elevated expressions of Lpar3 gene were detected in PDAs. We thus demonstrate that LPA₁ and LPA₃ play the different roles on cell migration ability of pancreatic cancer cells, suggesting the opposite effects via LPA₁ and LPA₃ may contribute to the pathogenesis of pancreatic cancers in hamsters.