Hepatoma cell migration through a mesothelial cell monolayer is inhibited by cyclic AMP-elevating agents via a Rho-dependent pathway

1-Oleoyl lysophosphatidic acid (LPA) induces transmonolayer migration (in vitro invasion) of rat ascites hepatoma MM1 cells and their morphological changes leading to the migration. We have previously shown that an LPA analog, palmitoyl cyclic phosphatidic acid (Pal-cPA), suppresses transmonolayer migration of MM1 cells by rapidly increasing the intracellular cyclic AMP (cAMP) concentration. We report here that various cAMP-elevating agents, including dibutyryl cAMP, forskolin, cholera toxin and 3-isobutyl-1-methylxanthine, consistently inhibited LPA-induced transmonolayer migration of MM1 cells. Moreover, pull-down assays for GTP-bound, active RhoA demonstrated that the blockage by cAMP-elevating agents of morphological changes leading to the migration was probably mediated through inhibiting RhoA activation.