Different effects of G-protein-coupled receptor 120 (GPR120) and GPR40 on cell motile activity of highly migratory osteosarcoma cells.

G-protein-coupled receptor 120 (GPR120) and GPR40 are members of free fatty acid (FFA) receptors and mediate a variety of biological responses through binding of medium- and long-chain FFAs. Recently, it has been reported that GPR120 and GPR40 regulated cellular functions of cancer cells. In the present study, to assess whether GPR120 and GPR40 are involved in the enhancement of cell motile activity of osteosarcoma cells, we established highly migratory (MG63-R7) cells from osteosarcoma MG-63 cells. The expression level of GPR120 gene was significantly higher in MG63-R7 cells than in MG-63 cells, while no change of GPR40 expression was observed. In cell motility assay, the cell motile activity of MG63-R7 cells was approximately 200 times higher than that of MG-63 cells. The cell motile activity of MG63-R7 cells was stimulated by GW9508, which is an agonist of GPR120 and GPR40. Moreover, a GPR40 antagonist GW1100 elevated the cell motile activity of MG63-R7 cells in the presence of GW9508. To confirm the effects of GPR120 and GPR40 on the cell motile activity of MG63-R7 cells, GPR120 knockdown cells were generated from MG63-R7 cells. The cell motile activity of MG63-R7 cells was markedly suppressed by GPR120 knockdown. These results indicated that GPR120 enhanced and GPR40 inhibited the cell motile activity of highly migratory osteosarcoma cells.

Lysophosphatidic acid (LPA) signaling via LPA4 and LPA6 negatively regulates cell motile activities of colon cancer cells.

Lysophosphatidic acid (LPA) is an extracellular biological lipid and interacts with six subtypes of G protein-coupled LPA receptors (LPA1 to LPA6). LPA receptors exhibit a variety of cellular functions, depending on types of cancer cells. In this study, to assess the roles of LPA4 and LPA6 in cell growth and motile activities of colon cancer cells, LPA4 and LPA6 knockdown cells were established from DLD1 and HCT116 cells. LPA treatment increased the cell growth activities of LPA4 and LPA6 knockdown cells, compared with control cells. The cell motile activities of LPA4 and LPA6 knockdown cells were significantly higher than those of control cells. To evaluate the effects of LPA4 and LPA6 on cell motile activity induced by anticancer drug, long-term fluorouracil (5-FU) treated (DLD-5FU) cells were generated. The expression levels of LPAR1, LPAR4 and LPAR6 genes were significantly increased in DLD-5FU cells. DLD-5FU cells showed the high cell motile activity, compared with DLD1 cells. The increased cell motile activity was markedly stimulated by LPA4 and LPA6 knockdown. In contrast, the cell motile activity enhanced by 5-FU treatment was suppressed by LPA1 knockdown. These results suggest that LPA signaling via LPA4 and LPA6 negatively regulates the cell motile activities of DLD1 and HCT116 cells as well as long-term 5-FU treated cells.