cyclin-d1 and lysophosphatidic-acid

Lysophosphatidic acid (LPA) is a bioactive lipid component of ovarian cancer activating factor, which is present at a high concentration in the ascitic fluid and plasma of patients with ovarian cancer. A group of six lysophosphatidic acid receptors (LPARs), LPAR1 through LPAR6, which belong to the G protein-coupled receptor superfamily (GPCR), mediate cellular activities of LPA and activates a series of downstream molecules and cellular responses, including biological and pathological effects. LPARs are widely expressed in normal ovary, benign tumor, and ovarian cancer tissues and cancer cell lines with a broad range of levels. The LPA/LPAR axis is involved in tumorigenesis and development of ovarian cancer through mediating the cellular responses to LPA and influencing the expression and function of oncogenic molecules. In the present review, the roles of LPARs in ovarian cancer, including the expression, function, and downstream molecules, are summarized, and we discuss the implications for ovarian cancer treatment that targets LPARs.

Topics: AMP-Activated Protein Kinases; Cell Transformation, Neoplastic; Chemokine CXCL1; Cyclin D1; Cyclooxygenase 2; Cytoskeletal Proteins; Disease Progression; Female; Gene Expression Regulation, Neoplastic; Humans; Interleukins; Lysophospholipids; Ovarian Neoplasms; Peptide Fragments; Receptors, Lysophosphatidic Acid; Signal Transduction; Urokinase-Type Plasminogen Activator; Vascular Endothelial Growth Factor A

Lysophosphatidic acid (LPA) is a lipid growth factor that induces proliferation of fibroblasts by activating the cAMP response element binding protein (CREB). Here, we further investigated whether LPA induces proliferation of P19 cells, a line of pluripotent embryonic carcinoma cells. 5'-Bromo-2-deoxyuridine incorporation and cell viability assays showed that LPA stimulated proliferation of P19 cells. Immunoblot experiments with P19 cells revealed that the mitogen activated protein kinases, including p-ERK, p38, pAKT, glycogen synthase kinase 3β, and CREB were phosphorylated by treatment with 10 μM LPA. LPA-induced phosphorylation of CREB was efficiently blocked by U0126 and H89, inhibitors of the MAP kinases ERK1/2 and mitogen- and stress-activated protein kinase 1, respectively. Involvement of cyclin D1 in LPA-induced P19 cell proliferation was verified by immunoblot analysis in combination with pharmacological inhibitor treatment. Furthermore, LPA up-regulated CRE-harboring cyclin D1 promoter activity, suggesting that CREB and cyclin D1 play significant roles in LPA-induced proliferation of P19 embryonic carcinoma cells.

Topics: Animals; Carcinoma, Embryonal; Cell Line, Tumor; Cell Proliferation; Cyclic AMP Response Element-Binding Protein; Cyclin D1; Lysophospholipids; MAP Kinase Signaling System; Mice; Mice, Inbred C3H; p38 Mitogen-Activated Protein Kinases; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 90-kDa; Up-Regulation

The endogenous phospholipid lysophosphatidic acid (LPA) regulates fundamental cellular processes such as proliferation, survival, motility, and invasion implicated in homeostatic and pathological conditions. Hence, delineation of the full range of molecular mechanisms by which LPA exerts its broad effects is essential. We report avid binding of LPA to the receptor for advanced glycation end products (RAGE), a member of the immunoglobulin superfamily, and mapping of the LPA binding site on this receptor. In vitro, RAGE was required for LPA-mediated signal transduction in vascular smooth muscle cells and C6 glioma cells, as well as proliferation and migration. In vivo, the administration of soluble RAGE or genetic deletion of RAGE mitigated LPA-stimulated vascular Akt signaling, autotaxin/LPA-driven phosphorylation of Akt and cyclin D1 in the mammary tissue of transgenic mice vulnerable to carcinogenesis, and ovarian tumor implantation and development. These findings identify novel roles for RAGE as a conduit for LPA signaling and suggest targeting LPA-RAGE interaction as a therapeutic strategy to modify the pathological actions of LPA.

Topics: Animals; Cell Line, Tumor; Cyclin D1; Female; Humans; Lysophospholipids; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Muscle, Smooth, Vascular; Neoplasms; Proto-Oncogene Proteins c-akt; Rats; Receptor for Advanced Glycation End Products; Receptors, Immunologic; Recombinant Proteins; Signal Transduction

Lysophospholipids regulate a wide array of biological processes including cell survival and proliferation. In our previous studies, we found that in addition to SRE, CRE is required for maximal c-fos promoter activation triggered by lysophosphatidic acid (LPA). c-fos is an early indicator of various cells into the cell cycle after mitogenic stimulation. However, role of CREB activation in LPA-stimulated proliferation has not been elucidated yet. Here, we investigate how LPA induces proliferation in Rat-2 fibroblast cell via CREB activation. We found that total cell number and BrdU-positive cells were increased by LPA. Moreover, levels of c-fos mRNA and cyclin D1 protein were increased via LPA-induced CREB phosphorylation. Furthermore, LPA-induced Rat-2 cell proliferation was decreased markedly by ERK inhibitor (U0126) and partially by MSK inhibitor (H89). Taken together, these results suggest that CREB activation could partially up-regulate accumulation of cyclin D1 protein level and proliferation of LPA-stimulated Rat-2 fibroblast cells.

Topics: Animals; Cell Proliferation; Cells, Cultured; Cyclic AMP Response Element-Binding Protein; Cyclin D1; Fibroblasts; Lysophospholipids; Mitogen-Activated Protein Kinase Kinases; Phosphorylation; Proto-Oncogene Proteins c-fos; Rats; Up-Regulation

This study was designed to elucidate the molecular mechanism underlying lysophosphatidic acid (LPA) and adenylyl cyclase inhibitor SQ22536 (ACI)-induced senescent human diploid fibroblast (HDF) proliferation. Because adenosine monophosphate (AMP)-activated protein kinase (AMPK) is known to inhibit cell proliferation, we examined the phosphorylation status of AMPK and p53 and the expression level of p21(waf1/cip1) after treating HDFs with LPA and ACI. Phosphorylation of AMPKalpha on threonine-172 (p-Thr172-AMPKalpha) increases its catalytic activity but phosphorylation on serine-485/491 (p-Ser485/491-AMPKalpha) reduces the accessibility of the Thr172 phosphorylation site thereby inhibiting its catalytic activity. LPA increased p-Ser485/491-AMPKalpha, presumably by activating cAMP-dependent protein kinase (PKA). However, ACI reduced p-Thr172-AMPKalpha by inhibiting the LKB signaling. Our data demonstrated that both LPA and ACI inhibit the catalytic activity of AMPKalpha and p53 by differentially regulating phosphorylation of AMPKalpha, causing increased senescent cell proliferation. These findings suggest that the proliferation potential of senescent HDFs can be modulated through the regulation of the AMPK signaling pathway.

Topics: Adenine; Adenylyl Cyclase Inhibitors; AMP-Activated Protein Kinases; Cell Proliferation; Cells, Cultured; Cellular Senescence; Cyclic AMP-Dependent Protein Kinases; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Diploidy; Enzyme Inhibitors; Fibroblasts; Humans; Lysophospholipids; Models, Biological; Multienzyme Complexes; Phosphorylation; Protein Serine-Threonine Kinases; S Phase; Signal Transduction

Sphingosine 1-phosphate (Sph-1-P), a product of sphingomyelin metabolism, can act via a family of cognate G protein-coupled receptors or as an intracellular second messenger for agonists acting through their membrane receptors. In view of the general growth promoting and developmental effects of Sph-1-P on target cells, we hypothesized that it plays a role in adaptation of the uterus to pregnancy. We analyzed its potential role and that of the related lysophospholipid lysophosphatidic acid in the pregnant rat uterus by examining changes in mRNA levels of cognate receptors and enzymes involved in their turnover. Of these, only sphingosine kinase-1 (SphK1) was markedly changed ( approximately 30-fold increase), being localized in the glandular epithelium, vasculature, and the myometrium. Uterine SphK1 mRNA and protein levels paralleled those of serum progesterone, and treatment with progesterone or an antagonist elevated or reduced SphK1 mRNA expression, respectively. Progesterone also increased SphK1 mRNA steady-state levels in a rat myometrial/leiomyoma cell line (ELT3). Overexpressing human SphK1 in these cells resulted in increased levels of the cell cycle regulator cyclin D1 and increased myosin light-chain phosphorylation. Ectopic expression of SphK1 also resulted in increased proliferation rates, possibly in conjunction with increased cyclin D1 expression. These studies suggest that the uterine expression of SphK1 mediates processes involved in growth and differentiation of uterine tissues during pregnancy.

Topics: Animals; bcl-X Protein; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Enzymes; Female; Genes, Dominant; Humans; Immunologic Techniques; Leiomyoma; Lysophospholipids; Mutation; Myometrium; Myosin Light Chains; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Pregnancy; Pregnancy, Animal; Progesterone; Progestins; Rats; Rats, Sprague-Dawley; Receptors, Lysophospholipid; RNA, Messenger; Signal Transduction; Sphingosine; Uterus

Macrophage migration inhibitory factor (MIF) plays an important role not only in the immune system, but also in tumorigenesis. Lysophosphatidic acid (LPA), a unique lipid mediator, shares several biological functions with MIF, including promotion of tumor cell growth and associated angiogenesis. In this study, we investigated the signaling cross-talk between these two molecules during tumorigenesis and angiogenesis. We first examined the expression of MIF mRNA on a murine colon cancer cell line, colon 26, by LPA. We found that LPA enhanced the expression of MIF mRNA in a dose-dependent manner in vitro. In parallel, LPA stimulated cell growth and up-regulated the vascular endothelial growth factor (VEGF). These effects were dramatically blocked by 21 base double strand (ds) RNA specific for mouse MIF mRNA (RNAi). In vivo, colon 26 cells treated with MIF dsRNA were injected into the backs of mice. The size of tumor volumes became significantly smaller than that of controls. Angiogenesis examined by a Millipore chamber method was also suppressed by the MIF dsRNA. Next, we evaluated the signal transduction pathway relevant to the mitogen-activated protein kinase (MAPK) and Akt/PI3K pathways in response to LPA by RNAi. Ras activation and phosphorylation of Akt and ERK1/2 were strongly suppressed by the dsRNA. On the other hand, tyrosine phosphorylation was minimally changed by the treatment. Taken together, these results suggest that MIF could promote both tumor cell growth and angiogenesis induced by LPA via both the Ras-MAPK and Ras-Akt/PI3K signaling pathways.

Topics: Animals; Cell Division; Cell Line, Tumor; Cyclin D1; DNA; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Female; Immunoblotting; Lysophospholipids; Macrophage Migration-Inhibitory Factors; Mice; Mice, Inbred BALB C; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Neovascularization, Pathologic; Phosphorylation; ras Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; RNA, Double-Stranded; RNA, Messenger; Signal Transduction; Time Factors; Transfection; Tyrosine; Up-Regulation; Vascular Endothelial Growth Factor A