Enhancement of migration and invasion of hepatoma cells via a Rho GTPase signaling pathway

Intrahepatic extension is the main cause of liver failure and death in hepatocellular carcinoma patients. The small GTPase Rho and one of its effector molecules ROCK regulate cytoskeleton and actomyosin contractility, and play a crucial role in cell adhesion and motility. We investigated the role of small GTPase Rho in biological behaviors of hepatocellular carcinoma to demonstrate the importance of Rho in cancer invasion and metastasis.Using Western blotting, we quantitated Rho protein expression in SMMC-7721 cells induced by Lysophosphatidic acid (LPA). Furthermore, we examined the role of Rho signaling in regulating the motile and invasive properties of tumor cells.Rho protein expression was stimulated by LPA. Using the Rhotekin binding assay to assess Rho activation, we observed that the level of GTP-bound Rho was elevated transiently after the addition of LPA, and Y-27632 decreased the level of active Rho. LPA enhanced the motility of tumor cells and facilitated their invasion. Rho played an essential role in the migratory process, as evidenced by the inhibition of migration and motility of cancer cells by a specific inhibitor of ROCK, Y-27632.The finding that invasiveness of hepatocellular carcinoma is facilitated by the Rho/Rho-kinase pathway is likely to be relevant to tumor progression and Y-27632 may be a new potential effective agent for the prevention of intrahepatic extension of human liver cancer.