[Show abstract][Hide abstract] ABSTRACT: Lysophosphatidic acid (LPA) is a bioactive lipid promoting cancer metastasis. LPA activates a series of six G protein-coupled receptors (LPA1-6). While blockage of LPA1
in vivo inhibits breast carcinoma metastasis, down-stream genes mediating LPA-induced metastasis have not been yet identified. Herein we showed by analyzing publicly available expression data from 1488 human primary breast tumors that the gene encoding the transcription factor ZEB1 was the most correlated with LPAR1 encoding LPA1. This correlation was most prominent in basal primary breast carcinomas and restricted to cell lines of basal subtypes. Functional experiments in three different basal cell lines revealed that LPA-induced ZEB1 expression was regulated by the LPA1/Phosphatidylinositol-3-Kinase (Pi3K) axis. DNA microarray and real-time PCR analyses further demonstrated that LPA up-regulated the oncomiR miR-21 through an LPA1/Pi3K/ZEB1-dependent mechanism. Strikingly, treatment with a mirVana miR-21 inhibitor, or silencing LPA1 or ZEB1 completely blocked LPA-induced cell migration in vitro, invasion and tumor cell bone colonization in vivo, which can be restored with a mirVana miR-21 mimic. Finally, high LPAR1 expression in basal breast tumors predicted worse lung-metastasis-free survival. Collectively, our results elucidate a new molecular pathway driving LPA-induced metastasis, thus underscoring the therapeutic potential of targeting LPA1 in patients with basal breast carcinomas.
[Show abstract][Hide abstract] ABSTRACT: Autotaxin (ATX) through its lysophospholipase D activity controls physiological levels of lysophosphatidic acid (LPA) in blood. ATX is overexpressed in multiple types of cancers and together with LPA generated during platelet activation promotes skeletal metastasis of breast cancer. However, the pathophysiological sequelae of regulated interactions between circulating LPA, ATX, and platelets remain undefined in cancer. Here we show that ATX is stored in α-granules of resting human platelets and released upon tumor cell-induced platelet aggregation, leading to the production of LPA. Our in vitro and in vivo experiments using human breast cancer cells that do not express ATX (MDA-MB-231, MDA-B02) demonstrate that non-tumoral ATX controls the early stage of bone colonization by tumor cells. Moreover, expression of a dominant negative integrin αVβ3-Δ744 or treatment with the anti human αVβ3 monoclonal antibody LM609 completely abolished binding of ATX to tumor cells, demonstrating the requirement of a fully active integrin αVβ3 in this process. The present results establish a new mechanism for platelet contribution to LPA-dependent metastasis of breast cancer cells and demonstrate the therapeutic potential of disrupting the binding of non-tumor-derived ATX with the tumor cells for the prevention of metastasis.
[Show abstract][Hide abstract] ABSTRACT: Lysophosphatidic acid (LPA) is a natural bioactive lipid with growth factor-like functions due to activation of a series of six G protein-coupled receptors (LPA1-6). LPA receptor type 1 (LPA1) signaling influences the pathophysiology of many diseases including cancer, obesity, rheumatoid arthritis, as well as lung, liver and kidney fibrosis. Therefore, LPA1 is an attractive therapeutic target. However, most mammalian cells co-express multiple LPA receptors whose co-activation impairs the validation of target inhibition in patients because of missing LPA receptor-specific biomarkers. LPA1 is known to induce IL-6 and IL-8 secretion, as also do LPA2 and LPA3. In this work, we first determined the LPA induced early-gene expression profile in three unrelated human cancer cell lines expressing different patterns of LPA receptors (PC3: LPA1,2,3,6; MDA-MB-231: LPA1,2; MCF-7: LPA2,6). Among the set of genes upregulated by LPA only in LPA1-expressing cells, we validated by QPCR and ELISA that upregulation of heparin-binding EGF-like growth factor (HB-EGF) was inhibited by LPA1-3 antagonists (Ki16425, Debio0719). Upregulation and downregulation of HB-EGF mRNA was confirmed in vitro in human MDA-B02 breast cancer cells stably overexpressing LPA1 (MDA-B02/LPA1) and downregulated for LPA1 (MDA-B02/shLPA1), respectively. At a clinical level, we quantified the expression of LPA1 and HB-EGF by QPCR in primary tumors of a cohort of 234 breast cancer patients and found a significantly higher expression of HB-EGF in breast tumors expressing high levels of LPA1. We also generated human xenograph prostate tumors in mice injected with PC3 cells and found that a five-day treatment with Ki16425 significantly decreased both HB-EGF mRNA expression at the primary tumor site and circulating human HB-EGF concentrations in serum. All together our results demonstrate that HB-EGF is a new and relevant biomarker with potentially high value in quantifying LPA1 activation state in patients receiving anti-LPA1 therapies.
[Show abstract][Hide abstract] ABSTRACT: Lysophosphatidic acid (LPA) is a natural bioactive lipid that acts through six different G protein-coupled receptors (LPA1–6) with pleiotropic activities on multiple cell types. We have previously demonstrated that LPA is necessary for successful
in vitro osteoclastogenesis of bone marrow cells. Bone cells controlling bone remodeling (i.e. osteoblasts, osteoclasts, and osteocytes) express LPA1, but delineating the role of this receptor in bone remodeling is still pending. Despite Lpar1−/− mice displaying a low bone mass phenotype, we demonstrated that bone marrow cell-induced osteoclastogenesis was reduced in
Lpar1−/− mice but not in Lpar2−/− and Lpar3−/− animals. Expression of LPA1 was up-regulated during osteoclastogenesis, and LPA1 antagonists (Ki16425, Debio0719, and VPC12249) inhibited osteoclast differentiation. Blocking LPA1 activity with Ki16425 inhibited expression of nuclear factor of activated T-cell cytoplasmic 1 (NFATc1) and dendritic cell-specific
transmembrane protein and interfered with the fusion but not the proliferation of osteoclast precursors. Similar to wild type
osteoclasts treated with Ki16425, mature Lpar1−/− osteoclasts had reduced podosome belt and sealing zone resulting in reduced mineralized matrix resorption. Additionally,
LPA1 expression markedly increased in the bone of ovariectomized mice, which was blocked by bisphosphonate treatment. Conversely,
systemic treatment with Debio0719 prevented ovariectomy-induced cancellous bone loss. Moreover, intravital multiphoton microscopy
revealed that Debio0719 reduced the retention of CX3CR1-EGFP+ osteoclast precursors in bone by increasing their mobility in the bone marrow cavity. Overall, our results demonstrate that
LPA1 is essential for in vitro and in vivo osteoclast activities. Therefore, LPA1 emerges as a new target for the treatment of diseases associated with excess bone loss.
Full-text · Article · Jan 2014 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: This chapter contains sections titled: Introduction LPA Signaling in Osteolytic Bone Metastases Role of LPA on Bone Resorbing Cells (Osteoclasts) LPA Signaling in Osteoblastic Bone Metastases Role of LPA on Bone-Forming Cells (Osteoblasts) Origin of LPA at the Bone Metastatic Site Conclusion Methods Acknowledgments References
[Show abstract][Hide abstract] ABSTRACT: Bone is a common metastatic site for solid cancers. Bone homeostasis is tightly regulated by intimate cross-talks between osteoblast (bone forming cells) and osteoclasts (bone resorbing cells). Once in the bone microenvironment, metastatic cells do not alter bone directly but instead perturb the physiological balance of the bone remodeling process controlled by bone cells. Tumor cells produce growth factors and cytokines stimulating either osteoclast activity leading to osteolytic lesions or osteoblast function resulting in osteoblastic metastases. Growth factors, released from the resorbed bone matrix or throughout osteoblastic bone formation, sustain tumor growth. Therefore, bone metastases are the sites of vicious cycles wherein tumor growth and bone metabolism sustain each other. Lysophosphatidic acid (LPA) promotes the growth of primary tumors and metastatic dissemination of cancer cells. We have shown that by acting on cancer cells via the contribution of blood platelets and the LPA-producing enzyme Autotaxin (ATX), LPA promotes the progression of osteolytic bone metastases in animal models. In the light of recent reports it would appear that the role of LPA in the context of bone metastases is complex involving multiple sources of lipid combined with direct and indirect effects on target cells. This review will present our current knowledge on the LPA/ATX axis involvement in osteolytic and osteoblastic skeletal metastases and will discuss the potential activity of LPA upstream and downstream metastasis seeding of cancer cells to bone as well as its implication in cancer induced bone pain. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.
No preview · Article · Jun 2012 · Biochimica et Biophysica Acta
[Show abstract][Hide abstract] ABSTRACT: Metastasis is the main cause of death for cancer patients. Targeting factors that control metastasis formation is a major challenge for clinicians. Lysophosphatidic acid (LPA) is a bioactive phospholipid involved in cancer. LPA activates at least six independent G protein-coupled receptors (LPA1-6). Tumor cells frequently co-express multiple LPA receptors, puzzling the contribution of each one to cancer progression. All three receptors, LPA1, LPA2 and LPA3, act as oncogenes and prometastatic factors in the mouse mammary gland. The competitive inhibitor of LPA1 and LPA3 receptors, Ki16425, inhibits efficiently breast cancer bone metastases in animal models. We showed here that Debio 0719, which corresponds to the R-stereoisomer of Ki16425 exhibited highest antagonist activities at LPA1 (IC50=60 nM) and LPA3 (IC50=660 nM) than Ki16425 [IC50=130 nM (LPA1); IC50=2.3 µM (LPA3)]. In vitro, Debio 0719, inhibited LPA-dependent invasion of the 4T1 mouse mammary cancer cells. In vivo, early but not late administration of Debio 0719 (50 mg/kg p.o. twice daily) to BALB/c mice during the course of orthotopic 4T1 primary tumor growth reduced the number of spontaneously disseminated tumor cells to bone and lungs without affecting the growth of primary tumors and tumor-induced angiogenesis. We found that increased LPA1 mRNA expression in primary tumors of breast cancer patients correlated significantly with their positive lymph node status (p<0.001). Altogether, our results suggest that LPA1 controls early events of metastasis independently of cell proliferation and angiogenesis. Therefore, targeting this receptor with Debio 0719 has a high therapeutic potential against metastasis formation for breast cancer patients.
Preview · Article · Dec 2011 · International Journal of Oncology
[Show abstract][Hide abstract] ABSTRACT: Sphingosine 1-phosphate (S1P) is a phospholipid that binds to a set of G protein-coupled receptors (S1P(1)-S1P(5)) to initiate an array of signaling cascades that affect cell survival, differentiation, proliferation, and migration. On a larger physiological scale, the effects of S1P on immune cell trafficking, vascular barrier integrity, angiogenesis, and heart rate have also been observed. An impetus for the characterization of S1P-initiated signaling effects came with the discovery that FTY720 [fingolimod; 2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol] modulates the immune system by acting as an agonist at S1P(1). In the course of structure-activity relationship studies to better understand the functional chemical space around FTY720, we discovered conformationally constrained FTY720 analogs that behave as S1P receptor type-selective antagonists. Here, we present a pharmacological profile of a lead S1P(1/3) antagonist prodrug, 1-(hydroxymethyl)-3-(3-octylphenyl)cyclobutane (VPC03090). VPC03090 is phosphorylated by sphingosine kinase 2 to form the competitive antagonist species 3-(3-octylphenyl)-1-(phosphonooxymethyl)cyclobutane (VPC03090-P) as observed in guanosine 5'-O-(3-[(35)S]thio)triphosphate binding assays, with effects on downstream S1P receptor signaling confirmed by Western blot and calcium mobilization assays. Oral dosing of VPC03090 results in an approximate 1:1 phosphorylated/alcohol species ratio with a half-life of 30 h in mice. Because aberrant S1P signaling has been implicated in carcinogenesis, we applied VPC03090 in an immunocompetent mouse mammary cancer model to assess its antineoplastic potential. Treatment with VPC03090 significantly inhibited the growth of 4T1 primary tumors in mice. This result calls to attention the value of S1P receptor antagonists as not only research tools but also potential therapeutic agents.
Preview · Article · Jun 2011 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Bone metastases are highly frequent complications of breast cancers. Current bone metastasis treatments using powerful anti-resorbtive agents are only palliative indicating that factors independent of bone resorption control bone metastasis progression. Autotaxin (ATX/NPP2) is a secreted protein with both oncogenic and pro-metastatic properties. Through its lysosphospholipase D (lysoPLD) activity, ATX controls the level of lysophosphatidic acid (LPA) in the blood. Platelet-derived LPA promotes the progression of osteolytic bone metastases of breast cancer cells. We asked whether ATX was involved in the bone metastasis process. We characterized the role of ATX in osteolytic bone metastasis formation by using genetically modified breast cancer cells exploited on different osteolytic bone metastasis mouse models.
[Show abstract][Hide abstract] ABSTRACT: Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are naturally arising bioactive lipids. The roles of LPA and S1P in angiogenesis, tumor growth and metastasis have recently emerged. Blood platelets are an important source of LPA and S1P in the organism. However, other types of cells including cancer cells expressing autotaxin and sphingosine kinases have the capacity to produce LPA and S1P, respectively. During the past decade, studies revealed that LPA and S1P interact with a large series of G-protein-coupled receptors, at least seven for LPA (LPA1-5, GPR-87, P2Y5) and five for S1P (S1P1-5). This may account for the wide variety of cell types reacting to LPA and S1P stimulation and for the wide range of cellular functions controlled by these lysophospholipids such as proliferation, survival and motility. Genetic and pharmacological approaches were developed to block the activities of LPA or S1P in the context of cancer progression. This article presents recent findings based on extensive cell culture experiments and preliminary in vivo studies which demonstrate that targeting the lysophospholipid tracks would be extremely beneficial for patients suffering from cancer.
No preview · Article · Jun 2009 · Anti-cancer agents in medicinal chemistry