Discovery of potent LPA2 (EDG4) antagonists as potential anticancer agents

Functional modulation of lysophosphatidic acid type 2 G-protein coupled receptor facilitates alveolar bone formation

Lipid biosynthesis is recently studied its functions in a range of cellular physiology including differentiation and regeneration. However, it still remains to be elucidated in its precise function. To reveal this, we evaluated the roles of lysophosphatidic acid (LPA) signaling in alveolar bone formation using the LPA type 2 receptor (LPAR2) antagonist AMG-35 (Amgen Compound 35) using tooth loss without periodontal disease model which would be caused by trauma and usually requires a dental implant to restore masticatory function. In this study, in vitro cell culture experiments in osteoblasts and periodontal ligament fibroblasts revealed cell type-specific responses, with AMG-35 modulating osteogenic differentiation in osteoblasts in vitro. To confirm the in vivo results, we employed a mouse model of tooth loss without periodontal disease. Five to 10 days after tooth extraction, AMG-35 facilitated bone formation in the tooth root socket as measured by immunohistochemistry for differentiation markers KI67, Osteocalcin, Periostin, RUNX2, transforming growth factor beta 1 (TGF-β1) and SMAD2/3. The increased expression and the localization of these proteins suggest that AMG-35 elicits osteoblast differentiation through TGF-β1 and SMAD2/3 signaling. These results indicate that LPAR2/TGF-β1/SMAD2/3 represents a new signaling pathway in alveolar bone formation and that local application of AMG-35 in traumatic tooth loss can be used to facilitate bone regeneration and healing for further clinical treatment.

Emerging opportunities to treat idiopathic pulmonary fibrosis: Design, discovery, and optimizations of small-molecule drugs targeting fibrogenic pathways

Idiopathic pulmonary fibrosis (IPF) is the most common fibrotic form of idiopathic diffuse lung disease. Due to limited treatment options, IPF patients suffer from poor survival. About ten years ago, Pirfenidone (Shionogi, 2008; InterMune, 2011) and Nintedanib (Boehringer Ingelheim, 2014) were approved, greatly changing the direction of IPF drug design. However, limited efficacy and side effects indicate that neither can reverse the process of IPF. With insights into the occurrence of IPF, novel targets and agents have been proposed, which have fundamentally changed the treatment of IPF. With the next-generation agents, targeting pro-fibrotic pathways in the epithelial-injury model offers a promising approach. Besides, several next-generation IPF drugs have entered phase II/III clinical trials with encouraging results. Due to the rising IPF treatment requirements, there is an urgent need to completely summarize the mechanisms, targets, problems, and drug design strategies over the past ten years. In this review, we summarize known mechanisms, target types, drug design, and novel technologies of IPF drug discovery, aiming to provide insights into the future development and clinical application of next-generation IPF drugs.

In vitro pharmacological characterization of standard and new lysophosphatidic acid receptor antagonists using dynamic mass redistribution assay

Lysophosphatidic acid (LPA) is a bioactive phospholipid that acts as an agonist of six G protein-coupled receptors named LPA receptors (LPA1-6). LPA elicits diverse intracellular events and modulates several biological functions, including cell proliferation, migration, and invasion. Overactivation of the LPA-LPA receptor system is reported to be involved in several pathologies, including cancer, neuropathic pain, fibrotic diseases, atherosclerosis, and type 2 diabetes. Thus, LPA receptor modulators may be clinically relevant in numerous diseases, making the identification and pharmacodynamic characterization of new LPA receptor ligands of strong interest. In the present work, label-free dynamic mass redistribution (DMR) assay has been used to evaluate the pharmacological activity of some LPA1 and LPA2 standard antagonists at the recombinant human LPA1 and LPA2 receptors. These results are compared to those obtained in parallel experiments with the calcium mobilization assay. Additionally, the same experimental protocol has been used for the pharmacological characterization of the new compound CHI. KI 16425, RO 6842262, and BMS-986020 behaved as LPA1 inverse agonists in DMR experiments and as LPA1 antagonists in calcium mobilization assays. Amgen compound 35 behaved as an LPA2 antagonist, while Merck compound 20 from WO2012028243 was detected as an LPA2 inverse agonist using the DMR test. Of note, for all the compounds, similar potency values were estimated by DMR and calcium assay. The new compound CHI was found to be an LPA1 inverse agonist, but with potency lower than that of the standard compounds. In conclusion, we have demonstrated that DMR assay can be successfully used to characterize LPA1 and LPA2 ligands. Compared to the classical calcium mobilization assay, DMR offers some advantages, in particular allowing the identification of inverse agonists. Finally, in the frame of this study, a new LPA1 inverse agonist has been identified.

Novel Antagonist of the Type 2 Lysophosphatidic Acid Receptor (LPA2), UCM-14216, Ameliorates Spinal Cord Injury in Mice

Spinal cord injuries (SCIs) irreversibly disrupt spinal connectivity, leading to permanent neurological disabilities. Current medical treatments for reducing the secondary damage that follows the initial injury are limited to surgical decompression and anti-inflammatory drugs, so there is a pressing need for new therapeutic strategies. Inhibition of the type 2 lysophosphatidic acid receptor (LPA₂) has recently emerged as a new potential pharmacological approach to decrease SCI-associated damage. Toward validating this receptor as a target in SCI, we have developed a new series of LPA₂ antagonists, among which compound 54 (UCM-14216) stands out as a potent and selective LPA₂ receptor antagonist (E_max = 90%, IC₅₀ = 1.9 μM, K_D = 1.3 nM; inactive at LPA_1,3–6 receptors). This compound shows efficacy in an in vivo mouse model of SCI in an LPA₂-dependent manner, confirming the potential of LPA₂ inhibition for providing a new alternative for treating SCI.

A Direct Method for Synthesis of Fluorinated Quinazolinones and Quinoxalines Using Fluorinated Acids without Metals or Additives

The trifluoromethyl group only exists in synthetic compounds. Owing to the unique bioactivities of this group, the trifluoromethylation of alkanes, arenes, unsaturated compounds like olefins, aldehydes­, and ketones, and heterocycles has been studied constantly in recent decades. Herein, a direct method using trifluoroacetic acid as a CF3 source for the synthesis of 2-(trifluoromethyl)quinazolin-4-ones and 4-(trifluoromethyl)pyrrolo/indolo[1,2-a]quinoxalines without any catalysts or additives is reported; a wide range of fluorinated compounds were obtained in 52%–94% yield.

The LPA-CDK5-tau pathway mediates neuronal injury in an in vitro model of ischemia-reperfusion insult

Lysophosphatidic acid (LPA) is a common glycerol phospholipid and an important extracellular signaling molecule. LPA binds to its receptors and mediates a variety of biological effects, including the pathophysiological process underlying ischemic brain damage and traumatic brain injury. However, the molecular mechanisms mediating the pathological role of LPA are not clear. Here, we found that LPA activates cyclin-dependent kinase 5 (CDK5). CDK5 phosphorylates tau, which leads to neuronal cell death. Inhibition of LPA production or blocking its receptors reduced the abnormal activation of CDK5 and phosphorylation of tau, thus reversing the death of neurons. Our data indicate that the LPA-CDK5-Tau pathway plays an important role in the pathophysiological process after ischemic stroke. Inhibiting the LPA pathway may be a potential therapeutic target for treating ischemic brain injury.

Glucagon-like Peptide-1 Secretion Is Inhibited by Lysophosphatidic Acid

Glucagon-like peptide-1 (GLP-1) potentiates glucose-stimulated insulin secretion (GSIS). While dozens of compounds stimulate GLP-1 secretion, few inhibit. Reduced GLP-1 secretion and impaired GSIS occur in chronic inflammation. Lysophosphatidic acids (LPAs) are bioactive phospholipids elevated in inflammation. The aim of this study was to test whether LPA inhibits GLP-1 secretion in vitro and in vivo. GLUTag L-cells were treated with various LPA species, with or without LPA receptor (LPAR) antagonists, and media GLP-1 levels, cellular cyclic AMP and calcium ion concentrations, and DPP4 activity levels were analyzed. Mice were injected with LPA, with or without LPAR antagonists, and serum GLP-1 and DPP4 activity were measured. GLUTag GLP-1 secretion was decreased ~70–90% by various LPAs. GLUTag expression of Lpar1, 2, and 3 was orders of magnitude higher than Lpar4, 5, and 6, implicating the former group in this effect. In agreement, inhibition of GLP-1 secretion was reversed by the LPAR1/3 antagonist Ki16425, the LPAR1 antagonists AM095 and AM966, or the LPAR2 antagonist LPA2-antagonist 1. We hypothesized involvement of Gαi-mediated LPAR activity, and found that intracellular cyclic AMP and calcium ion concentrations were decreased by LPA, but restored by Ki16425. Mouse LPA injection caused an ~50% fall in circulating GLP-1, although only LPAR1 or LPAR1/3 antagonists, but not LPAR2 antagonism, prevented this. GLUTag L-cell and mouse serum DPP4 activity was unchanged by LPA or LPAR antagonists. LPA therefore impairs GLP-1 secretion in vitro and in vivo through Gαi-coupled LPAR1/3 signaling, providing a new mechanism linking inflammation with impaired GSIS.

Transaminase Catalysis for Enantiopure Saturated Heterocycles as Potential Drug Scaffolds

As efforts in rational drug design are driving the pharmaceutical industry towards more complex molecules, the synthesis and production of these new drugs can benefit from new reaction routes. In addition to the introduction of new centers of asymmetry, complexity can be also increased by ring saturation, which also provides improved developability measures. Therefore, in this report, our aim was to develop transaminase (TA)-catalyzed asymmetric synthesis of a new group of potential chiral drug scaffolds comprising a saturated amine heterocycle backbone and an asymmetric primary amine sidechain (55a–g). We screened the Codex® Amine Transaminase Kit of 24 transaminases with the morpholine containing ketone 57a, resulting in one (R)-selective TA and three (S)-selective TAs operating at 100 mM substrate concentration and 25 v/v% isopropylamine (IPA) content. The optimized reaction conditions were than applied for asymmetric transamination of further six ketones (57b–g) containing various amine heterocycles, in which a strong effect of the substitution pattern of the γ-position relative to the substituted N-atom could be observed. Mediated by the most enantiotope selective (S)-TAs in scaled-up process, the (S)-amines [(S)-55a–g] were isolated with moderate-to-excellent yields (47–94%) in enantiopure form (>99% ee).

The development of modulators for lysophosphatidic acid receptors: A comprehensive review

Lysophosphatidic acids (LPAs) are bioactive phospholipids implicated in a wide range of cellular activities that regulate a diverse array of biological functions. They recognize two types of G protein-coupled receptors (LPARs): LPA_1-3 receptors and LPA_4-6 receptors that belong to the endothelial gene (EDG) family and non-endothelial gene family, respectively. In recent years, the LPA signaling pathway has captured an increasing amount of attention because of its involvement in various diseases, such as idiopathic pulmonary fibrosis, cancers, cardiovascular diseases and neuropathic pain, making it a promising target for drug development. While no drugs targeting LPARs have been approved by the FDA thus far, at least three antagonists have entered phase Ⅱ clinical trials for idiopathic pulmonary fibrosis (BMS-986020 and BMS-986278) and systemic sclerosis (SAR100842), and one radioligand (BMT-136088/¹⁸F-BMS-986327) has entered phase Ⅰ clinical trials for positron emission tomography (PET) imaging of idiopathic pulmonary fibrosis. This article provides an extensive review on the current status of ligand development targeting LPA receptors to modulate LPA signaling and their therapeutic potential in various diseases.

Synthesized 2-Trifluoromethylquinazolines and Quinazolinones Protect BV2 and N2a Cells against LPS- and H2O2-induced Cytotoxicity

BACKGROUND

Microglia are associated with neuroinflammation, which play a key role in the pathogenesis of neurodegenerative diseases. It has been reported that some quinazolines and quinazolinones possess anti-inflammatory properties. However, the pharmacological properties of certain quinazoline derivatives are still unknown.

OBJECTIVE

The antioxidant, cytotoxic, and protective effects of a series of synthesized 2- trifluoromethylquinazolines (2, 4, and 5) and quinazolinones (6-8) in lipopolysaccharide (LPS)- murine microglia (BV2) and hydrogen peroxide (H₂O₂)-mouse neuroblastoma-2a (N2a) cells were investigated.

METHOD

The antioxidant activity of synthesized compounds was evaluated with ABTS and DPPH assays. The cytotoxic activities were determined by MTS assay in BV2 and N2a cells. The production of nitric oxide (NO) in LPS-induced BV2 microglia cells was quantified.

RESULTS

The highest ABTS and DPPH scavenging activities were observed for compound 8 with 87.7% of ABTS scavenge percentage and 54.2% DPPH inhibition. All compounds were noncytotoxic in BV2 and N2a cells at 5 and 50 μg/mL. The compounds which showed the highest protective effects in LPS-induced BV2 and H₂O₂-induced N2a cells were 5 and 7. All tested compounds, except 4, also reduced NO production at concentrations of 50 μg/mL. The quinazolinone series 6-8 exhibited the highest percentage of NO reduction, ranging from 38 to 60%. Compounds 5 and 8 possess balanced antioxidant and protective properties against LPS- and H₂O₂-induced cell death, thus showing great potential to be developed into anti-inflammatory and neuroprotective agents.

CONCLUSION

Compounds 5 and 7 were able to protect the BV2 and N2a cells against LPS and H₂O₂ toxicity, respectively, at a low concentration (5 μg/mL). Compounds 6-8 showed potent reduction of NO production in BV2 cells.

Lysophosphatidic Acid Signaling in Cancer Cells: What Makes LPA So Special?

Lysophosphatidic acid (LPA) refers to a family of simple phospholipids that act as ligands for G protein-coupled receptors. While LPA exerts effects throughout the body in normal physiological circumstances, its pathological role in cancer is of great interest from a therapeutic viewpoint. The numerous LPA receptors (LPARs) are coupled to a variety of G proteins, and more than one LPAR is typically expressed on any given cell. While the individual receptors signal through conventional GPCR pathways, LPA is particularly efficacious in stimulating cancer cell proliferation and migration. This review addresses the mechanistic aspects underlying these pro-tumorigenic effects. We provide examples of LPA signaling responses in various types of cancers, with an emphasis on those where roles have been identified for specific LPARs. While providing an overview of LPAR signaling, these examples also reveal gaps in our knowledge regarding the mechanisms of LPA action at the receptor level. The current understanding of the LPAR structure and the roles of LPAR interactions with other receptors are discussed. Overall, LPARs provide insight into the potential molecular mechanisms that underlie the ability of individual GPCRs (or combinations of GPCRs) to elicit a unique spectrum of responses from their agonist ligands. Further knowledge of these mechanisms will inform drug discovery, since GPCRs are promising therapeutic targets for cancer.

Electrophilically Activated Nitroalkanes in Synthesis of 3,4-Dihydroquinozalines

Nitroalkanes activated with polyphosphoric acid serve as efficient electrophiles in reactions with various nucleophilic amines. Strategically placed second functionality allows for the design of annulation reactions enabling preparation of various heterocycles. This strategy was employed to develop an innovative synthetic approach towards 3,4-dihydroquinazolines from readily available 2-(aminomethyl)anilines.

Lysophosphatidic acid (LPA) receptor modulators: Structural features and recent development

Lysophosphatidic acid (LPA) activates six LPA receptors (LPAR_1-6) and regulates various cellular activities such as cell proliferation, cytoprotection, and wound healing. Many studies elucidated the pathological outcomes of LPA are due to the alteration in signaling pathways, which include migration and invasion of cancer cells, fibrosis, atherosclerosis, and inflammation. Current pathophysiological research on LPA and its receptors provides a means that LPA receptors are new therapeutic targets for disorders associated with LPA. Various chemical modulators are developed and are under investigation to treat a wide range of pathological complications. This review summarizes the physiological and pathological roles of LPA signaling, development of various LPA modulators, their structural features, patents, and their clinical outcomes.

Regulation of Tumor Immunity by Lysophosphatidic Acid

The tumor microenvironment (TME) may be best conceptualized as an ecosystem comprised of cancer cells interacting with a multitude of stromal components such as the extracellular matrix (ECM), blood and lymphatic networks, fibroblasts, adipocytes, and cells of the immune system. At the center of this crosstalk between cancer cells and their TME is the bioactive lipid lysophosphatidic acid (LPA). High levels of LPA and the enzyme generating it, termed autotaxin (ATX), are present in many cancers. It is also well documented that LPA drives tumor progression by promoting angiogenesis, proliferation, survival, invasion and metastasis. One of the hallmarks of cancer is the ability to modulate and escape immune detection and eradication. Despite the profound role of LPA in regulating immune functions and inflammation, its role in the context of tumor immunity has not received much attention until recently where emerging studies highlight that this signaling axis may be a means that cancer cells adopt to evade immune detection and eradication. The present review aims to look at the immunomodulatory actions of LPA in baseline immunity to provide a broad understanding of the subject with a special emphasis on LPA and cancer immunity, highlighting the latest progress in this area of research.

DABCO-catalyzed one-pot three component synthesis of dihydropyrano[3,2-c]chromene substituted quinazolines and their evaluation towards anticancer activity

A facile DABCO promoted one-pot three component synthesis of a new series of C-C linked bis-heterocycle containing dihydropyrano[c]chromene as highly fused oxa-heteryl group at C-2 position of quinazoline was developed. Quinazoline-2-carbaldehyde, substituted 4-hydroxycoumarin and ethyl cyanoacetate were used as key components in the Knoevenagel-Michael addition reaction to get the titled compounds. These compounds were screened for anti-cancer activity against the breast cancer cell lines of MDA-MB 231, and MDA-MB 453.

Modulation of Hexadecyl-LPA-Mediated Activation of Mast Cells and Microglia by a Chemical Probe for LPA5

Mast cells and microglia play a critical role in innate immunity and inflammation and can be activated by a wide range of endogenous and exogenous stimuli. Lysophosphatidic acid (LPA) has recently been reported to activate mast cells and microglia. Using the human mast cell line HMC-1 and the mouse microglia cell line BV-2, we show that LPA-mediated activation can be prevented by blockade of the LPA receptor 5 (LPA5) in both cell lines. The identification of new LPA5-specific antagonists as tool compounds to probe and modulate the LPA5/LPA axis in relevant in vitro and in vivo assays should contribute to better understanding of the underlying role of LPAs in the development and progression of (neuro-) inflammatory diseases.

The autotaxin-LPA2 GPCR axis is modulated by γ-irradiation and facilitates DNA damage repair

In this study we characterized the effects of radiation injury on the expression and function of the autotaxin (ATX)-LPA2 GPCR axis. In IEC-6 crypt cells and jejunum enteroids quantitative RT-PCR showed a time- and dose-dependent upregulation of lpa2 in response to γ-irradiation that was abolished by mutation of the NF-κB site in the lpa2 promoter or by inhibition of ATM/ATR kinases with CGK-733, suggesting that lpa2 is a DNA damage response gene upregulated by ATM via NF-κB. The resolution kinetics of the DNA damage marker γ-H2AX in LPA-treated IEC-6 cells exposed to γ-irradiation was accelerated compared to vehicle, whereas pharmacological inhibition of LPA2 delayed the resolution of γ-H2AX. In LPA2-reconstituted MEF cells lacking LPA1&3 the levels of γ-H2AX decreased rapidly, whereas in Vector MEF were high and remained sustained. Inhibition of ERK1&2 or PI3K/AKT signaling axis by pertussis toxin or the C311A/C314A/L351A mutation in the C-terminus of LPA2 abrogated the effect of LPA on DNA repair. LPA2 transcripts in Lin(-)Sca-1(+)c-Kit(+) enriched for bone marrow stem cells were 27- and 5-fold higher than in common myeloid or lymphoid progenitors, respectively. Furthermore, after irradiation higher residual γ-H2AX levels were detected in the bone marrow or jejunum of irradiated LPA2-KO mice compared to WT mice. We found that γ-irradiation increases plasma ATX activity and LPA level that is in part due to the previously established radiation-induced upregulation of TNFα. These findings identify ATX and LPA2 as radiation-regulated genes that appear to play a physiological role in DNA repair.

Uncovering unique roles of LPA receptors in the tumor microenvironment

The role of the lysophospholipase D autotaxin (ATX) and lysophosphatidic acid (LPA) in cancer is emerging and represents two key players in regulating cancer progression. In this brief review, we will discuss some of our recent findings, which highlight a central role that LPA and its receptor plays in orchestrating melanoma-stroma interactions in the establishment of lung metastases. In particular, we evaluated not only the function of LPA receptors on tumor cells but also their role on host tissues and how they can influence melanoma growth and metastasis. Using the syngeneic B16F10 murine melanoma model, we made three key observations. First, our in vitro findings demonstrate that LPA receptors, specifically LPA₂ and LPA₅ expressed in B16F10 cells appear to have opposing roles in cell invasion; the former seems to be responsible for the high basal invasion rate of B16F10 cells while the latter is anti-invasive upon exogenous LPA stimulation. Second, we observed a profound reduction in the incidence of pulmonary melanoma metastasis in LPA₁- and LPA₅-knockout (KO) mice, respectively, when compared to wild-type (WT) mice. Third, no differences in terms of subcutaneous tumor growth between LPA₁KO, LPA₅KO and WT mice were observed. These findings suggest that LPA receptors exert different functions in melanoma cells versus host tissues in terms of invasion and metastasis.

Promising pharmacological directions in the world of lysophosphatidic Acid signaling

Lysophosphatidic acid (LPA) is a signaling lipid that binds to six known lysophosphatidic acid receptors (LPARs), named LPA₁-LPA₆. These receptors initiate signaling cascades relevant to development, maintenance, and healing processes throughout the body. The diversity and specificity of LPA signaling, especially in relation to cancer and autoimmune disorders, makes LPA receptor modulation an attractive target for drug development. Several LPAR-specific analogues and small molecules have been synthesized and are efficacious in attenuating pathology in disease models. To date, at least three compounds have passed phase I and phase II clinical trials for idiopathic pulmonary fibrosis and systemic sclerosis. This review focuses on the promising therapeutic directions emerging in LPA signaling toward ameliorating several diseases, including cancer, fibrosis, arthritis, hydrocephalus, and traumatic injury.

Autotaxin and LPA1 and LPA5 receptors exert disparate functions in tumor cells versus the host tissue microenvironment in melanoma invasion and metastasis

Autotaxin (ENPP2/ATX) and lysophosphatidic acid (LPA) receptors represent two key players in regulating cancer progression. The present study sought to understand the mechanistic role of LPA G protein-coupled receptors (GPCR), not only in the tumor cells but also in stromal cells of the tumor microenvironment. B16F10 melanoma cells predominantly express LPA5 and LPA2 receptors but lack LPA1. LPA dose dependently inhibited invasion of cells across a Matrigel layer. RNAi-mediated knockdown of LPA5 relieved the inhibitory effect of LPA on invasion without affecting basal invasion. This suggests that LPA5 exerts an anti-invasive action in melanoma cells in response to LPA. In addition, both siRNA-mediated knockdown and pharmacologic inhibition of LPA2 reduced the basal rate invasion. Unexpectedly, when probing the role of this GPCR in host tissues, it was found that the incidence of melanoma-derived lung metastasis was greatly reduced in LPA5 knockout (KO) mice compared with wild-type (WT) mice. LPA1-KO but not LPA2-KO mice also showed diminished melanoma-derived lung metastasis, suggesting that host LPA1 and LPA5 receptors play critical roles in the seeding of metastasis. The decrease in tumor cell residence in the lungs of LPA1-KO and LPA5-KO animals was apparent 24 hours after injection. However, KO of LPA1, LPA2, or LPA5 did not affect the subcutaneous growth of melanoma tumors.

IMPLICATIONS

These findings suggest that tumor and stromal LPA receptors, in particular LPA1 and LPA5, play different roles in invasion and the seeding of metastasis.

LPA receptor signaling: pharmacology, physiology, and pathophysiology

Lysophosphatidic acid (LPA) is a small ubiquitous lipid found in vertebrate and nonvertebrate organisms that mediates diverse biological actions and demonstrates medicinal relevance. LPA's functional roles are driven by extracellular signaling through at least six 7-transmembrane G protein-coupled receptors. These receptors are named LPA1-6 and signal through numerous effector pathways activated by heterotrimeric G proteins, including Gi/o, G12/13, Gq, and Gs LPA receptor-mediated effects have been described in numerous cell types and model systems, both in vitro and in vivo, through gain- and loss-of-function studies. These studies have revealed physiological and pathophysiological influences on virtually every organ system and developmental stage of an organism. These include the nervous, cardiovascular, reproductive, and pulmonary systems. Disturbances in normal LPA signaling may contribute to a range of diseases, including neurodevelopmental and neuropsychiatric disorders, pain, cardiovascular disease, bone disorders, fibrosis, cancer, infertility, and obesity. These studies underscore the potential of LPA receptor subtypes and related signaling mechanisms to provide novel therapeutic targets.

Development of lysophosphatidic acid pathway modulators as therapies for fibrosis

Lysophosphatidic acid (LPA) is a class of bioactive phospholipid that displays a wide range of cellular effects via LPA receptors, of which six have been identified (LPAR1–6). In serum and plasma, LPA production occurs mainly by the hydrolysis of lysophosphatidylcholine by the phospholipase D activity of autotaxin (ATX). The involvement of the LPA pathway in driving chronic wound-healing conditions, such as idiopathic pulmonary fibrosis, has suggested targets in this pathway could provide potential therapeutic approaches. Mice with LPAR1 knockout or tissue-specific ATX deletion have demonstrated reduced lung fibrosis following bleomycin challenge. Therefore, strategies aimed at antagonizing LPA receptors or inhibiting ATX have gained considerable attention. This Review will summarize the current status of identifying small-molecule modulators of the LPA pathway. The therapeutic utility of LPA modulators for the treatment of fibrotic diseases will soon be revealed as clinical trials are already in progress in this area.

Comparing the differential effects of LPA on the barrier function of human pulmonary endothelial cells

Lysophosphatidic acid (LPA) is a class of bioactive lyso-phospholipid that mediates most of its biological effects through a family of G protein-coupled receptors of which six have been identified. The role of the LPA pathway in driving chronic lung diseases such as idiopathic pulmonary fibrosis (IPF) has gained considerable academic and industry attention. Modulation of the pulmonary artery endothelial barrier function by the LPA1 receptor has been shown to drive pulmonary fibrosis in murine models of disease. The purpose of this study was (i) to assess the effect of LPA on the barrier function of human pulmonary arterial (HPAEC) and microvascular (HMVEC) endothelial cells and (ii) to identify the LPA receptor subtype(s) responsible for changes in human pulmonary endothelial cell permeability using LPA receptor antagonists and siRNA technology. Analysis of the LPA receptor subtype expression demonstrated predominant expression of LPA2 and LPA6 receptor subtypes in both HPAECs and HMVECs. HPAECs also exhibit low expression of LPA1, LPA3, and LPA4 receptor subtypes. Treatment of cells with increasing concentrations of LPA caused loss of barrier function in HPAECs but not HMVECs, despite both cell types exhibiting very similar LPA receptor expression profiles. The LPA-mediated loss of barrier function in HPAECs appears to be independent of the LPA1 receptor and likely to be mediated via the LPA6 receptor although we cannot exclude an additional role for the LPA2 and LPA4 receptors in mediating these effects. These results suggest cell-specific mechanisms exist in human pulmonary endothelial cells to permit regulation of barrier function downstream of LPA receptors. More importantly, our data indicate that selective LPA1 receptor antagonism may be insufficient for therapeutic use in pulmonary diseases where impaired endothelial barrier function is related to disease initiation and progression.

Special Agents Hunting Down Women Silent Killer: The Emerging Role of the p38α Kinase

Ovarian cancer is sensitive to chemotherapy with platinum compounds; however, the therapy success rate is significantly lowered by a high incidence of recurrence and by the acquisition of drug resistance. These negative outcomes mainly depend on altered apoptotic and drug resistance pathways, determining the need for the design of new therapeutic strategies to improve patient survival. This challenge has become even more critical because it has been recognized that hindering uncontrolled cell growth is not sufficient as the only curative approach. In fact, while current therapies are mostly conceived to impair survival of highly proliferating cells, several lines of research are now focusing on cancer-specific features to specifically target malignant cells with the aim of avoiding drug resistance and reducing adverse effects. Recently, great interest has been generated by the identification of metabolic reprogramming mechanisms occurring in cancer cells, such as the increase in glycolysis levels. In this light, pharmacologic manipulation of relevant pathways involved in cancer-specific metabolism and drug resistance could prove an effective approach to treat ovarian cancer patients.

Optimizing molecular-targeted therapies in ovarian cancer: the renewed surge of interest in ovarian cancer biomarkers and cell signaling pathways

The hallmarks of ovarian cancer encompass the development of resistance, disease recurrence and poor prognosis. Ovarian cancer cells express gene signatures which pose significant challenges for cancer drug development, therapeutics, prevention and management. Despite enhancements in contemporary tumor debulking surgery, tentative combination regimens and abdominal radiation which can achieve beneficial response rates, the majority of ovarian cancer patients not only experience adverse effects, but also eventually relapse. Therefore, additional therapeutic possibilities need to be explored to minimize adverse events and prolong progression-free and overall response rates in ovarian cancer patients. Currently, a revival in cancer drug discovery is devoted to identifying diagnostic and prognostic ovarian cancer biomarkers. However, the sensitivity and reliability of such biomarkers may be complicated by mutations in the BRCA1 or BRCA2 genes, diverse genetic risk factors, unidentified initiation and progression elements, molecular tumor heterogeneity and disease staging. There is thus a dire need to expand existing ovarian cancer therapies with broad-spectrum and individualized molecular targeted approaches. The aim of this review is to profile recent developments in our understanding of the interrelationships among selected ovarian tumor biomarkers, heterogeneous expression signatures and related molecular signal transduction pathways, and their translation into more efficacious targeted treatment rationales.

Aiming drug discovery at lysophosphatidic acid targets

Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is the prototype member of a family of lipid mediators and second messengers. LPA and its naturally occurring analogues interact with G protein-coupled receptors on the cell surface and a nuclear hormone receptor within the cell. In addition, there are several enzymes that utilize LPA as a substrate or generate it as a product and are under its regulatory control. LPA is present in biological fluids, and attempts have been made to link changes in its concentration and molecular composition to specific disease conditions. Through their many targets, members of the LPA family regulate cell survival, apoptosis, motility, shape, differentiation, gene transcription, malignant transformation and more. The present review depicts arbitrary aspects of the physiological and pathophysiological actions of LPA and attempts to link them with select targets. Many of us are now convinced that therapies targeting LPA biosynthesis and signalling are feasible for the treatment of devastating human diseases such as cancer, fibrosis and degenerative conditions. However, successful targeting of the pathways associated with this pleiotropic lipid will depend on the future development of as yet undeveloped pharmacons.

The biology of ovarian cancer: new opportunities for translation

Over the past two decades, the 5-year survival for ovarian cancer patients has substantially improved owing to more effective surgery and treatment with empirically optimized combinations of cytotoxic drugs, but the overall cure rate remains approximately 30%. Many investigators think that further empirical trials using combinations of conventional agents are likely to produce only modest incremental improvements in outcome. Given the heterogeneity of this disease, increases in long-term survival might be achieved by translating recent insights at the molecular and cellular levels to personalize individual strategies for treatment and to optimize early detection.