Diverse effects of G-protein-coupled free fatty acid receptors on the regulation of cellular functions in lung cancer cells.

Free fatty acids (FFAs) are dietary nutrients which mediate a variety of biological effects through binding to G-protein-coupled FFA receptors (FFARs). G-protein-coupled receptor 120 (GPR120) and GPR40 are identified as FFARs for long- and medium-chain fatty acids. Here we investigated whether GPR120 and GPR40 are involved in the acquisition of malignant properties in lung cancer cells. Three lung cancer RLCNR, LL/2 and A549 cells used in this study expressed GPR120 and GPR40 genes. The cell motile activities of all cells were significantly suppressed by a GPR40 antagonist GW1100. In addition, GPR40 knockdown inhibited the cell motile activity of A549 cells. In gelatin zymography, matrix metalloproteinase-2 (MMP-2) activity in GPR40 knockdown was significantly lower than that in control cells. Next, to evaluate effects of GPR120 and GPR40 on cellular functions induced by anti-cancer drug, the long-term cisplatin (CDDP) treated (A549-CDDP) cells were generated. The expression levels of GPR120 and GPR40 were significantly decreased in A549-CDDP cells. While A549-CDDP cells showed the high cell motile activity, GW1100 suppressed the cell motile activity of A549-CDDP cells. These results demonstrate that GPR120 negatively and GPR40 positively regulate cellular functions during tumor progression in lung cancer cells.

Different induction of LPA receptors by chemical liver carcinogens regulates cellular functions of liver epithelial WB-F344 cells.

Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6 ) mediates a variety of cellular functions, including cell motility. In the present study, we investigated the effects of LPA receptors on cell motile activity during multi-stage hepatocarcinogenesis in rat liver epithelial WB-F344 cells treated with chemical liver carcinogens. Cells were treated with a initiator (N-nitrosodiethylamine (DEN)) and three promoters (phenobarbital (PB), okadaic acid (OA) and clofibrate) every 24 h for 2 days. Cell motile activity was elevated by DEN, correlating with Lpar3 expression. PB, OA, and clofibrate elevated Lpar1 expression and inhibited cell motile activity. To evaluate the effects of long-term treatment on cell motility, cells were treated with DEN and/or PB for at least 6 months. Lpar3 expression and cell motile activity were significantly elevated by the long-term DEN treatment with or without further PB treatment. In contrast, long-term PB treatment with or without further DEN elevated Lpar1 expression and inhibited cell motility. When the synthesis of extracellular LPA was blocked by a potent ATX inhibitor S32826 before cell motility assay, the cell motility induced by DEN and PB was markedly suppressed. These results suggest that activation of the different LPA receptors may regulate the biological functions of cells treated with chemical carcinogens. © 2015 Wiley Periodicals, Inc.

Negative effects of G-protein-coupled free fatty acid receptor GPR40 on cell migration and invasion in fibrosarcoma HT1080 cells.

G-protein-coupled receptor 40 (GPR40) and GPR120 mediate a variety of biological functions by the binding of long and medium chain free fatty acids. In the present study, we investigated a role of GPR40 in the pathogenesis of fibrosarcoma HT1080 cells. The GPR40 gene expression was detected in HT1080 cells, but not the GPR120 gene. The cell motile and invasive activities were markedly enhanced by GPR40 knockdown, compared with control cells. To evaluate whether GPR40 is involved in the cellular functions of HT1080 cells during anticancer drug treatment, HT1080 cells were maintained in condition medium containing cisplatin (CDDP) (0.01-1.0 µM) for 6 mo. The expression levels of the GPR40 gene was elevated by the long-term CDDP treatment in HT1080 cells, while the GPR120 gene expression remained unchanged. The cell motile and invasive activities of HT1080 cells treated with CDDP were significantly lower than those of untreated cells. In gelatin zymography, the activities of matrix metalloproteinase-2 (MMP-2) and MMP-9 of HT1080 cells were enhanced by the long-term CDDP treatment. In addition, GW9508 which is an agonist of GPR40 and GPR120 suppressed the cell motile and invasive activities of HT1080 cells treated with CDDP as well as the MMP activation. These results suggest that GPR40 negatively regulates the tumor progression of fibrosarcoma cells. © 2015 Wiley Periodicals, Inc.

Different roles of GPR120 and GPR40 in the acquisition of malignant properties in pancreatic cancer cells.

Free fatty acids (FFAs) act as extracellular signaling molecules through binding to G-protein-coupled FFA receptors (FFARs). GPR120 and GPR40 are identified as FFARs for medium- and long-chain fatty acids. In the present study, we investigated roles of GPR120 and GPR40 in cellular functions of pancreatic cancer PANC-1 cells, using GPR120 and GPR40 knockdown cells (PANC-sh120 and PANC-sh40 cells respectively). In cell motility assay, PANC-sh120 cells showed the low cell motility, compared with control cells. In contrast, the cell motility of PANC-sh40 cells was significantly higher than that of control cells. Activity levels of matrix metalloproteinases (MMPs) were measured by gelatin zymography. While PANC-sh120 cells indicated the reduced MMP-2 activity, MMP-2 activity in PANC-sh40 cells was significantly higher than that in control cells. On the other hand, no activation of MMP-9 was detected in all cells. In colony assay, the large sized colonies were markedly formed in PANC-sh40 cells. No colony formation was observed in PANC-sh120 cells as well as control cells. These results suggest that distinct effects of GPR120 and GPR40 are involved in the acquisition of malignant property in pancreatic cancer cells.

LPA signaling through LPA receptors regulates cellular functions of endothelial cells treated with anticancer drugs.

Lysophosphatidic acid (LPA) signaling via LPA receptors provides a variety of cellular functions, including angiogenesis. In this study, to assess an involvement of LPA receptors in cell motile activities of endothelial cells during chemotherapy, F-2 cells were treated with cisplatin (CDDP) and doxorubicin (DOX) at a concentration of 0.01 µM every 24 h for at least 1 month. The treatment of CDDP and DOX inhibited the expression levels of the LPA receptor-1 (Lpar1), Lpar2, and Lpar3 genes in F-2 cells. The cell motile activities of CDDP and DOX treated cells were relatively lower than those of untreated cells. Next, we investigated whether cancer cells could stimulate the cell motile activities of F-2 cells treated with CDDP and DOX. For cell motility assay, CDDP- and DOX-treated cells were co-cultured with pancreatic cancer PANC-1 cells. The cell motile activities of CDDP- and DOX-treated cells were significantly enhanced by the existence of PANC-1 cells, correlating with the LPA receptor expressions. In addition, the elevated cell motile activities were suppressed by the pretreatment of an autotaxin inhibitor S32826. These results suggest that LPA signaling via LPA receptors may regulate the cell motile activities of F-2 cells treated with anticancer drugs.

Diverse effects of LPA4, LPA5 and LPA6 on the activation of tumor progression in pancreatic cancer cells.

Lysophosphatidic acid (LPA) is an extracellular biological lipid which interacts with G protein-coupled LPA receptors (LPA1 to LPA6). LPA signaling via LPA receptors mediates several cellular responses. In the present study, to assess the roles of LPA4, LPA5 and LPA6 in cellular functions of pancreatic cancer cells, we generated LPA receptor knockdown cells from PANC-1 cells (PANC-sh4, PANC-sh5 and PANC-sh6 cells, respectively). In cell motility assay, PANC-sh4 and PANC-sh5 cells enhanced the cell motile activities, compared with control cells. In contrast, the cell motile activity of PANC-sh6 cells was suppressed. The invasive activities of PANC-sh4 and PANC-sh5 cells were markedly stimulated, while PANC-sh6 cells showed the low invasive activity. In colony assay, PANC-sh4 and PANC-sh5 cells formed the large sized colonies, but not PANC-sh6 cells. When endothelial cells were incubated with supernatants from PANC-sh4 and PANC-sh5 cells, the cell motility and tube formation of endothelial cells were significantly induced, but not PANC-sh6 cells. These results suggest that the diverse roles of LPA4, LPA5 and LPA6 are involved in the activation of tumor progression in pancreatic cancer cells.

Opposite effects of GPR120 and GPR40 on cell motile activity induced by ethionine in liver epithelial cells.

Free fatty acids (FFAs) are dietary nutrients which act as ligands for FFAs receptors. G-protein-coupled receptor 120 (GPR120) and GPR40 are activated by long and medium chain FFAs. In the present study, we investigated the role of the GPR120 and GPR40 in cell motile activity stimulated by ethionine in rat liver epithelial WB-F344 cells. Cells were treated with ethionine at a concentration of 10µM every 24h for 2days. The expression levels of the Gpr120 and Gpr40 genes in WB-F344 cells treated ethionine were significantly higher than those in untreated cells. In cell motility assay, the cell motile activity of WB-F344 cells was markedly elevated by ethionine, compared with untreated cells. To evaluate the effects of GPR120 on the cell motile activity by ethionine, we established GPR120 knockdown cells from WB-F344 cells. The cell motile activity stimulated by ethionine was significantly suppressed by GPR120 knockdown. In addition, a potent GPR40 antagonist GW1100 enhanced the cell motile activity by ethionine. These results suggest that opposite effects of GPR120 and GPR40 may be involved in the cell motile activity stimulated by ethionine in WB-F344 cells.

Role of GPR120 in cell motile activity induced by 12-O-tetradecanoylphorbol-13-acetate in liver epithelial WB-F344 cells.

G-protein-coupled receptor 120 (GPR120) is identified as a G-protein-coupled receptor for unsaturated long-chain free fatty acids that mediates insulin signaling and anti-inflammatory effects. Recently, it has been reported that GPR120 promotes the cell motile activity and angiogenesis in cancer cells. In this study, we assessed the role of GPR120 in the cell motile activity induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in rat liver epithelial WB-F344 cells. Cells were treated with TPA at a concentration of 5 nM for 72 h. The expression level of the Gpr120 gene was measured by quantitative real-time RT-PCR analysis. Cells treated with TPA showed the elevated Gpr120 expression, in comparison with untreated cells. In cell motility assays, the cell motile activity of cells treated with TPA was significantly higher than that of untreated cells. To confirm whether GPR120 is involved in the cell motile activity mediated by TPA, we generated GPR120 knockdown cells from WB-F344 cells. The cell motile activity induced by TPA was significantly suppressed by GPR120 knockdown. These results suggest that GPR120 plays an important role in the cell motile activity induced by TPA in WB-F344 cells.

Inhibitory effects of lysophosphatidic acid receptor-5 on cellular functions of sarcoma cells.

Lysophosphatidic acid (LPA) is a bioactive lipid that interacts with G protein-coupled LPA receptors (LPA receptor-1 (LPA1) to LPA6). Here, we investigated the effects of LPA signaling via LPA5 on cellular functions of sarcoma cells by generating Lpar5 overexpressing and Lpar5 knockdown cells from rat osteosarcoma and malignant fibrous histiocytoma cells, respectively. The cell motility activity of Lpar5 overexpressing cells was significantly lower, while Lpar5 knockdown cells showed high cell motility, compared with respective controls. Gelatin zymography showed that LPA5 suppressed the activation of matrix metalloproteinase-2. LPA5 also inhibited the cell motility activity of endothelial cells, correlating with the expression levels of vascular endothelial growth factor genes. These results suggest that LPA signaling via LPA5 negatively regulates the cellular functions of rat sarcoma cells.

Lysophosphatidic acid receptor-5 negatively regulates cellular responses in mouse fibroblast 3T3 cells.

Lysophosphatidic acid (LPA) signaling via G protein-coupled LPA receptors (LPA1-LPA6) mediates a variety of biological functions, including cell migration. Recently, we have reported that LPA1 inhibited the cell motile activities of mouse fibroblast 3T3 cells. In the present study, to evaluate a role of LPA5 in cellular responses, Lpar5 knockdown (3T3-L5) cells were generated from 3T3 cells. In cell proliferation assays, LPA markedly stimulated the cell proliferation activities of 3T3-L5 cells, compared with control cells. In cell motility assays with Cell Culture Inserts, the cell motile activities of 3T3-L5 cells were significantly higher than those of control cells. The activity levels of matrix metalloproteinases (MMPs) were measured by gelatin zymography. 3T3-L5 cells stimulated the activation of Mmp-2, correlating with the expression levels of Mmp-2 gene. Moreover, to assess the co-effects of LPA1 and LPA5 on cell motile activities, Lpar5 knockdown (3T3a1-L5) cells were also established from Lpar1 over-expressing (3T3a1) cells. 3T3a1-L5 cells increased the cell motile activities of 3T3a1 cells, while the cell motile activities of 3T3a1 cells were significantly lower than those of control cells. These results suggest that LPA5 may act as a negative regulator of cellular responses in mouse fibroblast 3T3 cells, similar to the case for LPA1.

Lysophosphatidic acid receptor-5 negatively regulates cell motile and invasive activities of human sarcoma cell lines.

LPA signaling via LPA receptors [LPA receptor-1 (LPA1)-LPA6] mediates the several cellular responses in cancer cells, including cell motility and invasion. In the present study, to investigate a role of LPA5 in the cell motile and invasive activities of sarcoma cells, LPAR5 knockdown (HOSL5 and HT1080L5) cells were generated from human osteosarcoma HOS and fibrosarcoma HT1080 cells, respectively. In cell motility assays with cell culture inserts, HOSL5 and HT1080L5 cells indicated the high cell motile activities, compared with control cells. The cell invasive activities of HOSL5 and HT1080L5 cells were significantly higher than those of control cells. Moreover, the activities of matrix metalloproteinase (MMP)-2 and MMP-9 were measured by gelatin zymography. MMP-2 was significantly activated in HOSL5 cells, but not MMP-9. The elevated activities of MMP-2 and MMP-9 were found in HT1080L5 cells, in comparison with control cells. These results suggest that LPA signaling via LPA5 negatively regulates the cell motile and invasive activities of human sarcoma cells.

Effects of bisphenol A and 4-nonylphenol on cellular responses through the different induction of LPA receptors in liver epithelial WB-F344 cells.

Lysophosphatidic acid (LPA) signaling via G protein-coupled transmembrane LPA receptors (LPA1 to LPA6) mediates a variety of cellular functions, including cell proliferation, migration, morphogenesis, and differentiation. Recently, we demonstrated that the different induction of LPA receptors by estrogens regulates cell motile activity of rat liver epithelial WB-F344 cells. In the present study, to assess whether endocrine disruptors (EDs) are involved in cellular functions through LPA signaling, we measured cell motile activity and LPA receptor expressions in WB-F344 cells treated with bisphenol A (BPA) and 4-nonylphenol (4-NP). Using quantitative real time RT-PCR analysis, the Lpar1 expression was elevated in BPA-treated cells, whereas the Lpar3 expression was decreased. In contrast, 4-NP increased the Lpar3 expression, but not the Lpar1 and Lpar2. For cell motility assay with a Cell Culture Insert, cell motile activity of BPA-treated cells was significantly lower than that of untreated cells. In contrast, 4-NP markedly enhanced cell motile activity. The effects of BPA and 4-NP on cell motility were inhibited by the Lpar1 or Lpar3 knockdown. These results suggest that BPA and 4-NP may regulate cell motile activity through the different induction of LPA receptors in WB-F344 cells.

Diverse effects of LPA receptors on cell motile activities of cancer cells.

Lysophosphatidic acid (LPA) is a bioactive lipid that interacts with G protein-coupled transmembrane LPA receptors (LPA1 to LPA6). LPA mediates a variety of cellular responses in normal cells, including cell growth, motility, differentiation, morphogenesis, and prevention from apoptosis. Furthermore, LPA signaling via LPA receptors is involved in the pathogenesis of several diseases, including cancer. Cell motility is one of the important properties during the progression of cancer cells. In recent studies, it has been demonstrated that LPA receptors have the diverse effects in the cell motile activities of cancer cells, depending on the cell types involved. In this review, we provide the current knowledge for the biological roles of LPA receptors in the cell motile activities of cancer cells.

Lysophosphatidic acid receptors in cancer pathobiology.

Lysophosphatidic acid (LPA) receptors (LPA1 to LPA6) are G protein-coupled transmembrane and mediate a variety of biological responses through the binding of LPA, such as cell proliferation, migration, morphogenesis and differentiation. Previously, high secretion levels of LPA were found in blood and ascites from patients with aggressive ovarian cancer. So far, numerical studies have demonstrated that LPA signaling via LPA receptors contributes to the acquisition of malignant potency by several cancer cells. Moreover, genetic and epigenetic alterations of LPA receptor genes have been detected in cancer cells. Therefore, it is suggested that LPA signaling may be a target molecule for the establishment of chemoprevention agents in clinical cancer approaches. Here, we review the current knowledge for the biological roles of LPA signaling via LPA receptors in the pathogenesis of cancer cells.

Inhibitory effects of LPA1 on cell motile activities stimulated by hydrogen peroxide and 2,3-dimethoxy-1,4-naphthoquinone in fibroblast 3T3 cells.

Reactive oxygen species (ROS) are known to mediate a variety of biological responses, including cell motility. Recently, we indicated that lysophosphatidic acid (LPA) receptor-3 (LPA3) increased cell motile activity stimulated by hydrogen peroxide. In the present study, we assessed the role of LPA1 in the cell motile activity mediated by ROS in mouse fibroblast 3T3 cells. 3T3 cells were treated with hydrogen peroxide and 2,3-dimethoxy-1,4-naphthoquinone (DMNQ) at concentrations of 0.1 and 1 µM for 48 h. In cell motility assays with Cell Culture Inserts, the cell motile activities of 3T3 cells treated with hydrogen peroxide and DMNQ were significantly higher than those of untreated cells. 3T3 cells treated with hydrogen peroxide and DMNQ showed elevated expression levels of the Lpar3 gene, but not the Lpar1 and Lpar2 genes. To investigate the effects of LPA1 on the cell motile activity induced by hydrogen peroxide and DMNQ, Lpar1-overexpressing (3T3-a1) cells were generated from 3T3 cells and treated with hydrogen peroxide and DMNQ. The cell motile activities stimulated by hydrogen peroxide and DMNQ were markedly suppressed in 3T3-a1 cells. These results suggest that LPA signaling via LPA1 inhibits the cell motile activities stimulated by hydrogen peroxide and DMNQ in 3T3 cells.

Downregulation of activation factors of endothelia and fibroblasts via lysophosphatidic acid signaling in a mouse lung cancer LL/2 cell line.

Angiogenesis stimulates the invasive and metastatic process of cancer cells. It is also known that activated fibroblasts promote cancer cell growth and enhance invasive and metastatic potential. Lysophosphatidic acid (LPA) is a biological mediator and interacts with G protein-coupled transmembrane LPA receptors (LPA1 to LPA6). In this study, to assess an involvement of LPA3 on angiogenesis and fibroblast activation, the Lpar3-expressing cells were generated from mouse lung cancer LL/2 cells, which unexpressed LPA3. The Lpar3-expressing cells were maintained in serum-free Dulbecco's modified Eagle's medium for 48 h, and cell motility assay was performed with a cell culture Insert. When endothelial F-2 cells and 3T3 fibroblasts were cultured with conditioned medium from the Lpar3-expressing cells, their cell motile activities were significantly lower than the Lpar3-unexpressing (control) cells. Expression levels of vascular endothelial growth factor (Vegf) and fibroblast growth factor (Fgf) genes in the Lpar3-expressing cells were measured by quantitative real time reverse transcription polymerase chain reaction analysis. The expressions of Vegf-A. Fgfa and Fgfb genes in the Lpar3-expressing cells were significantly lower than those in control cells, correlating with the effects on cell motile activities of F-2 and 3T3 cells. These results suggest that LPA signaling through LPA3 may inhibit angiogenesis and fibroblast activation in mouse lung cancer cells.

Ethionine regulates cell motile activity through LPA receptor-3 in liver epithelial WB-F344 cells.

Lysophosphatidic acid (LPA) receptors (LPA1 to LPA6) indicate a variety of cellular responses, such as cell proliferation, migration, differentiation, and morphogenesis. However, the role of each LPA receptor is not functionally equivalent. Ethionine, an ethyl analog of methionine, is well known to be one of the potent liver carcinogens in rats. In this study, to assess whether ethionine may regulate cell motile activity through LPA receptors, rat liver epithelial (WB-F344) cells were treated with ethionine for 48 h. In cell motility assay with a cell culture insert, the treatment of ethionine at 1.0 and 10 µM enhanced significantly high cell motile activity, compared with untreated cells. The expression levels of LPA receptor genes in cells treated with ethionine were measured by quantitative real time RT-PCR analysis. The expression of the Lpar3 gene in ethionine-treated cells was significantly higher than that in untreated cells. Furthermore, to confirm an involvement of LPA3 on cell motility increased by ethionine, the Lpar3 knockdown cells were also used. The cell motile activity by ethionine was completely suppressed in the Lpar3 knockdown cells. These results suggest that LPA signaling through LPA3 may be involved in cell motile activity stimulated by ethionine in WB-F344 cells.

Hydrogen peroxide stimulates cell motile activity through LPA receptor-3 in liver epithelial WB-F344 cells.

Hydrogen peroxide which is one of reactive oxygen species (ROS) mediates a variety of biological responses, including cell proliferation and migration. In the present study, we investigated whether lysophosphatidic acid (LPA) signaling is involved in cell motile activity stimulated by hydrogen peroxide. The rat liver epithelial WB-F344 cells were treated with hydrogen peroxide at 0.1 or 1 µM for 48 h. In cell motility assays, hydrogen peroxide treated cells showed significantly high cell motile activity, compared with untreated cells. To measure the expression levels of LPA receptor genes, quantitative real time RT-PCR analysis was performed. The expressions of LPA receptor-3 (Lpar3) in hydrogen peroxide treated cells were significantly higher than those in control cells, but not Lpar1 and Lpar2 genes. Next, to assess the effect of LPA3 on cell motile activity, the Lpar3 knockdown cells from WB-F344 cells were also treated with hydrogen peroxide. The cell motile activity of the knockdown cells was not stimulated by hydrogen peroxide. Moreover, in liver cancer cells, hydrogen peroxide significantly activated cell motility of Lpar3-expressing cells, but not Lpar3-unexpressing cells. These results suggest that LPA signaling via LPA3 may be mainly involved in cell motile activity of WB-F344 cells stimulated by hydrogen peroxide.