The Effect Of Lysophosphatidic Acid On The Migration Of Hepatocellular Carcinoma Cells And The Underlying Mechanisms

Liver cancer is one of the most common cancers worldwide, and ranks as the 2nd most common cause of cancer deaths. Recently, the incidence of liver cancer is increasing constantly and leading to about 700000 death each year. Generally, there are several interventions to treat liver cancer. For instance: surgery, radiation therapy and chemical therapy. However, these methods are unefficient to impede the recurrence and metastasis of liver cancer. It is still a challenge to prevent and treat cancer liver clinically.Lysophosphatidic acid(LPA) is a small bioactive lipid mediator and has significant effects on cell physiologic and pathological process. It has been reported that the LPA may accelerate tumor development, which exists in malignant tissues with higher concentration than normal tissues. The cell migration capacity acts an vital role in the metastasis of cancer cell. Increasing ecidences revealed that LPA regulates the migration capacity of vatious cancer cells, inculding liver cancer cell. However, the mechanisms of LPA on liver cancer cells are still unclear. Hence, our study investigated the effect of LPA on migration capacity of hapatocelluar carcinoma cells and explored the underlying mechanisms. The main methods and resultes of this paper have been listed as follows:(1) The effect of LPA on cell migration of MHCC97 H and HepG2.We utilized transwell to investigate the impact of LPA on cell migration of MHCC97 H and HepG2, and we found the LPA significantly promoted the migration of MHCC97 H, and present a dose-dependent in 0μM-10μM. But the results showed that there was no significant effect of LPA on migration capacity of HepG2.(2) The role of LPA receptor(LPAR) in the process of cell migration induced by LPAIn order to evaluate the cause of the different response of cancer cells to LPA, we utilized RT-PCR to investigate the LPAR expression in MHCC97 H and HepG2. The result of RT-PCR shown that MHCC97 H expressed LPAR1, LPAR2, LPAR5 and LPAR6, while HepG2 expressed LPAR2, LPAR3, LPAR4, LPAR5 and LPAR6. It seems that the distinction in LPAR pattern attributes the different responses of MHCC97 H and HepG2. Furthermore, we found that the Ki16425(an inhibitor of LPAR1/3) obviously blocked the increased migration of MHCC97 H induced by LPA. These results suggested that the LPA promotes the migration of MHCC97 H mainly through LPAR1.(3) The mechanisms in the process of cell migration induced by LPAIn order to evaluate the role of ROCK in the process of cell migration induced by LPA, we used the Y-27632(an inhibitor of ROCK) and found that Y-27632 dramatically attenuated the increased migration of MHCC97 H induced by LPA.Cell migration is a dynamic and highly regulated process, which depends on the actin system. The remodeling of actin cytoskeleton provides a driving force to push the membrane forward at the leading edge and a traction force to move the cell body. In order to elucidate the role of F-actin in the process of cell migration of MHCC97 H induced by LPA. We evaluated the reorganization of F-actin. The phalloidin staining and western bloting results demostrated that LPA promoted the polymerization of F-actin, while Ki16425 and Y27632 both dramatically abrogated this effect. Furthermore, We treated MHCC97 H with Cytochalasin B(Cyt B) and found that CytB obviously impeded the cell increased migration of MHCC97 H induced by LPA. Our results suggested that LPA stimulates the MHCC97 H migration mainly through LPAR1-ROCK-F-actin signaling pathway. Finally, we utilized atomic force microscopy to measure the effect of LPA on biomechanical profile of MHCC97 H. The data showed that LPA decreased the cell stiffness of MHCC97 H. Thus, the change in the deformability of MHCC97 H caused by LPA may also contribute to the increased cell migration.In summary, our study demonstrated that LPA accelerates MHCC97 H migration, while LPA has no significant effect on cell migration of HepG2. We propose that LPA promote MHCC97 H migration mainly through LPAR1-ROCK-F-actin pathway. And the data also shown that LPA can significantly decrease the cell stiffness to induce cell migration. Our findings shed light on the understanding of the impact of LPA on cancer cell migration and the underlying mechanisms, which have important implications in the prevention and intervention of tumor metastasis.