Autotaxin expression and its connection with the TNF-alpha-NF-kappaB axis in human hepatocellular carcinoma

Exogenous interleukin-1 beta stimulation regulates equine tenocyte function and gene expression in three-dimensional culture which can be rescued by pharmacological inhibition of interleukin 1 receptor, but not nuclear factor kappa B, signaling

We investigated how Interleukin 1 beta (IL-1β) impacts equine tenocyte function and global gene expression in vitro and determined if these effects could be rescued by pharmacologically inhibiting nuclear factor-κB (NF-KB) or interleukin 1 signalling. Equine superficial digital flexor tenocytes were cultured in three-dimensional (3D) collagen gels and stimulated with IL-1β for two-weeks, with gel contraction and interleukin 6 (IL6) measured throughout and transcriptomic analysis performed at day 14. The impact of three NF-KB inhibitors on gel contraction and IL6 secretion were measured in 3D culture, with NF-KB-P65 nuclear translocation by immunofluorescence and gene expression by qPCR measured in two-dimensional (2D) monolayer culture. In addition, daily 3D gel contraction and transcriptomic analysis was performed on interleukin 1 receptor antagonist-treated 3D gels at day 14. IL-1β increased NF-KB-P65 nuclear translocation in 2D culture and IL6 secretion in 3D culture, but reduced daily tenocyte 3D gel contraction and impacted > 2500 genes at day 14, with enrichment for NF-KB signaling. Administering direct pharmacological inhibitors of NF-KB did reduce NF-KB-P65 nuclear translocation, but had no effect on 3D gel contraction or IL6 secretion in the presence of IL-1β. However, IL1Ra restored 3D gel contraction and partially rescued global gene expression. Tenocyte 3D gel contraction and gene expression is adversely impacted by IL-1β which can only be rescued by blockade of interleukin 1 receptor, but not NF-KB, signalling.

First insight about the ability of specific glycerophospholipids to discriminate non-small cell lung cancer subtypes

Introduction: Discrimination between adenocarcinoma (ADC) and squamous cell carcinoma (SCC) subtypes in non-small cell lung cancer (NSCLC) patients is a significant challenge in oncology. Lipidomics analysis provides a promising approach for this differentiation. Methods: In an accompanying paper, we explored oxPCs levels in a cohort of 200 NSCLC patients. In this research, we utilized liquid chromatography coupled with mass spectrometry (LC-MS) to analyze the lipidomics profile of matching tissue and plasma samples from 25 NSCLC patients, comprising 11 ADC and 14 SCC cases. This study builds upon our previous findings, which highlighted the elevation of oxidised phosphatidylcholines (oxPCs) in NSCLC patients. Results: We identified eight lipid biomarkers that effectively differentiate between ADC and SCC subtypes using an untargeted approach. Notably, we observed a significant increase in plasma LPA 20:4, LPA 18:1, and LPA 18:2 levels in the ADC group compared to the SCC group. Conversely, tumour PC 16:0/18:2, PC 16:0/4:0; CHO, and plasma PC 16:0/18:2; OH, PC 18:0/20:4; OH, PC 16:0/20:4; OOH levels were significantly higher in the ADC group. Discussion: Our study is the first to report that plasma LPA levels can distinguish between ADC and SCC patients in NSCLC, suggesting a potential role for LPAs in NSCLC subtyping. This finding warrants further investigation into the mechanisms underlying these differences and their clinical implications.

Bioactive signalling lipids as drivers of chronic liver diseases

Lipids are important in multiple cellular functions, with most having structural or energy storage roles. However, a small fraction of lipids exert bioactive roles through binding to G protein-coupled receptors and induce a plethora of processes including cell proliferation, differentiation, growth, migration, apoptosis, senescence and survival. Bioactive signalling lipids are potent modulators of metabolism and energy homeostasis, inflammation, tissue repair and malignant transformation. All these events are involved in the initiation and progression of chronic liver diseases. In this review, we focus specifically on the roles of bioactive lipids derived from phospholipids (lyso-phospholipids) and poly-unsaturated fatty acids (eicosanoids, pro-resolving lipid mediators and endocannabinoids) in prevalent chronic liver diseases (alcohol-associated liver disease, non-alcoholic fatty liver disease, viral hepatitis and hepatocellular carcinoma). We discuss the balance between pathogenic and beneficial bioactive lipids as well as potential therapeutic targets related to the agonism or antagonism of their receptors.

Infliximab, a Monoclonal Antibody against TNF-α, Inhibits NF-κB Activation, Autotaxin Expression and Breast Cancer Metastasis to Lungs

An inflammatory milieu in the tumor microenvironment leads to immune evasion, resistance to cell death, metastasis and poor prognosis in breast cancer patients. TNF-α is a proinflammatory cytokine that regulates multiple aspects of tumor biology from initiation to progression. TNF-α-induced NF-κB activation initiates inflammatory pathways, which determine cell survival, death and tumor progression. One candidate pathway involves the increased secretion of autotaxin, which produces lysophosphatidate that signals through six G-protein-coupled receptors. Significantly, autotaxin is one of the 40-50 most upregulated genes in metastatic tumors. In this study, we investigated the effects of TNF-α by blocking its action with a monoclonal antibody, Infliximab, and studied the effects on autotaxin secretion and tumor progression. Infliximab had little effect on tumor growth, but it decreased lung metastasis by 60% in a syngeneic BALB/c mouse model using 4T1 breast cancer cells. Infliximab-treated mice also showed a decrease in proliferation and metastatic markers like Ki-67 and vimentin in tumors. This was accompanied by decreases in NF-κB activation, autotaxin expression and the concentrations of plasma and tumor cytokines/chemokines which are involved in metastasis. We also demonstrated a positive correlation of TNF-α -NF-κB and ATX expression in breast cancer patients using cancer databases. Studies in vitro showed that TNF-α-induced NF-κB activation increases autotaxin expression and the clone forming ability of 4T1 breast cancer cells. This report highlights the potential role of Infliximab as an additional approach to attenuate signaling through the autotaxin-lysophosphatidate-inflammatory cycle and decrease mortality from metastatic cancer.

Autotaxin suppresses cytotoxic T cells via LPAR5 to promote anti-PD-1 resistance in non-small cell lung cancer

Non-small cell lung cancers that harbor concurrent KRAS and TP53 (KP) mutations are immunologically warm tumors with partial responsiveness to anti-PD-(L)1 blockade; however, most patients observe little or no durable clinical benefit. To identify novel tumor-driven resistance mechanisms, we developed a panel of KP murine lung cancer models with intrinsic resistance to anti-PD-1 and queried differential gene expression between these tumors and anti-PD-1-sensitive tumors. We found that the enzyme autotaxin (ATX), and the metabolite it produces, lysophosphatidic acid (LPA), were significantly upregulated in resistant tumors and that ATX directly modulated antitumor immunity, with its expression negatively correlating with total and effector tumor-infiltrating CD8+ T cells. Pharmacological inhibition of ATX, or the downstream receptor LPAR5, in combination with anti-PD-1 was sufficient to restore the antitumor immune response and efficaciously control lung tumor growth in multiple KP tumor models. Additionally, ATX was significantly correlated with inflammatory gene signatures, including a CD8+ cytolytic score in multiple lung adenocarcinoma patient data sets, suggesting that an activated tumor-immune microenvironment upregulates ATX and thus provides an opportunity for cotargeting to prevent acquired resistance to anti-PD-1 treatment. These data reveal the ATX/LPA axis as an immunosuppressive pathway that diminishes the immune checkpoint blockade response in lung cancer.

Combined inhibition of EZH2 and the autotaxin-LPA-LPA2 axis exerts synergistic antitumor effects on colon cancer cells

Autotaxin (ATX), also known as ENPP2, is the key enzyme in lysophosphatidic acid (LPA) production. LPA acts on its receptors on the cell membrane to promote cell proliferation and migration, and thus, the ATX-LPA axis plays a critical role in tumorigenesis. Clinical data analysis indicated that in colon cancer, there is a strong negative correlation between the expression of ATX and EZH2, the enzymatic catalytic subunit of polycomb repressive complex 2 (PRC2). Here, we demonstrated that ATX expression was epigenetically silenced by PRC2, which was recruited by MTF2 and catalyzed H3K27me3 modification in the ATX promoter region. EZH2 inhibition is a promising strategy for cancer treatment, and ATX expression is induced in colon cancer cells by EZH2 inhibitors. With both EZH2 and ATX as targets, their combined inhibition exerted synergistic antitumor effects on colon cancer cells. In addition, LPA receptor 2 (LPA2) deficiency significantly enhanced the sensitivity to EZH2 inhibitors in colon cancer cells. In summary, our study identified ATX as a novel PRC2 target gene and found that cotargeting EZH2 and the ATX-LPA-LPA2 axis may be a potential combination therapy strategy for colon cancer.

E2F7 drives autotaxin/Enpp2 transcription via chromosome looping: Repression by p53 in murine but not in human carcinomas

Dysregulation of the autotaxin (ATX, Enpp2)-lysophosphatidic acid (LPA) signaling in cancerous cells contributes to tumorigenesis and therapy resistance. We previously found that ATX activity was elevated in p53-KO mice compared to wild-type (WT) mice. Here, we report that ATX expression was upregulated in mouse embryonic fibroblasts from p53-KO and p53R172H mutant mice. ATX promoter analysis combined with yeast one-hybrid testing revealed that WT p53 directly inhibits ATX expression via E2F7. Knockdown of E2F7 reduced ATX expression and chromosome immunoprecipitation showed that E2F7 promotes Enpp2 transcription through cooperative binding to two E2F7 sites (promoter region -1393 bp and second intron 996 bp). Using chromosome conformation capture, we found that chromosome looping brings together the two E2F7 binding sites. We discovered a p53 binding site in the first intron of murine Enpp2, but not in human ENPP2. Binding of p53 disrupted the E2F7-mediated chromosomal looping and repressed Enpp2 transcription in murine cells. In contrast, we found no disruption of E2F7-mediated ENPP2 transcription via direct p53 binding in human carcinoma cells. In summary, E2F7 is a common transcription factor that upregulates ATX in human and mouse cells but is subject to steric interference by direct intronic p53 binding only in mice.

Autotaxin promotes the degradation of the mucus layer by inhibiting autophagy in mouse colitis

Autotaxin (ATX or ENPP2) is an autocrine enzyme associated with the metabolism of various phospholipids. ATX has recently been identified as a regulatory factor in immune-related and inflammation-associated diseases, such as inflammatory bowel disease, but the exact mechanism is unclear. Here, we treated mice with recombinant ATX protein or an ATX inhibitor to investigate the effect of ATX on colitis in mice and the underlying mechanism. In a mouse model of colitis, ATX expression was increased, autophagy was impaired, and the mucus barrier was disrupted. Recombinant ATX protein promoted intestinal inflammation, inhibited autophagy, and disrupted the mucus barrier, while an ATX inhibitor had the opposite effect. Next, we treated mice that received ATX with an autophagy activator and an adenosine 5'-monophosphate-activated protein kinase (AMPK) agonist. We observed that autophagy activator and AMPK agonist could repair the mucus barrier and alleviate intestinal inflammation in ATX-treated mice. In vitro, we obtained consistent results. Thus, we concluded that ATX could inhibit autophagy through the AMPK pathway, which consequently disordered the mucus barrier and aggravated intestinal inflammation.

Emerging roles of lysophosphatidic acid receptor subtype 5 (LPAR5) in inflammatory diseases and cancer

Lysophosphatidic acid (LPA) is a bioactive lipid mediator that regulates a variety of cellular functions such as cell proliferation, migration, survival, calcium mobilization, cytoskeletal rearrangements, and neurite retraction. The biological actions of LPA are mediated by at least six G protein-coupled receptors known as LPAR1-6. Given that LPAR1-3 were among the first LPARs identified, the majority of research efforts have focused on understanding their biology. This review provides an in-depth discussion of LPAR5, which has recently emerged as a key player in regulating normal intestinal homeostasis and modulating pathological conditions such as pain, itch, inflammatory diseases, and cancer. We also present a chronological overview of the efforts made to develop compounds that target LPAR5 for use as tool compounds to probe or validate LPAR5 biology and therapeutic agents for the treatment of inflammatory diseases and cancer.

Circulating autotaxin levels in healthy teenagers: Data from the Vitados cohort

Autotaxin (ATX) is a secreted enzyme with a lysophospholipase D activity, mainly secreted by adipocytes and widely expressed. Its major function is to convert lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA), an essential bioactive lipid involved in multiple cell processes. The ATX-LPA axis is increasingly studied because of its involvement in numerous pathological conditions, more specifically in inflammatory or neoplastic diseases, and in obesity. Circulating ATX levels gradually increase with the stage of some pathologies, such as liver fibrosis, thus making them a potentially interesting non-invasive marker for fibrosis estimation. Normal circulating levels of ATX have been established in healthy adults, but no data exist at the pediatric age. The aim of our study is to describe the physiological concentrations of circulating ATX levels in healthy teenagers through a secondary analysis of the VITADOS cohort. Our study included 38 teenagers of Caucasian origin (12 males, 26 females). Their median age was 13 years for males and 14 years for females, ranging from Tanner 1 to 5. BMI was at the 25th percentile for males and 54th percentile for females, and median blood pressure was normal. ATX median levels were 1,049 (450-2201) ng/ml. There was no difference in ATX levels between sexes in teenagers, which was in contrast to the male and female differences described in the adult population. ATX levels significantly decreased with age and pubertal status, reaching adult levels at the end of puberty. Our study also suggested positive correlations between ATX levels and blood pressure (BP), lipid metabolism, and bone biomarkers. However, except for LDL cholesterol, these factors were also significantly correlated with age, which might be a confounding factor. Still, a correlation between ATX and diastolic BP was described in obese adult patients. No correlation was found between ATX levels and inflammatory marker C-reactive protein (CRP), Body Mass Index (BMI), and biomarkers of phosphate/calcium metabolism. In conclusion, our study is the first to describe the decline in ATX levels with puberty and the physiological concentrations of ATX levels in healthy teenagers. It will be of utmost importance when performing clinical studies in children with chronic diseases to keep these kinetics in mind, as circulating ATX might become a non-invasive prognostic biomarker in pediatric chronic diseases.

Autotaxin and Lysophosphatidic Acid Signalling: the Pleiotropic Regulatory Network in Cancer

Autotaxin, also known as ecto-nucleotide pyrophosphatase/phosphodiesterase family member 2, is a secreted glycoprotein that plays multiple roles in human physiology and cancer pathology. This protein, by converting lysophosphatidylcholine into lysophosphatidic acid, initiates a complex signalling cascade with significant biological implications. The article outlines the autotaxin gene and protein structure, expression regulation and physiological functions, but focuses mainly on the role of autotaxin in cancer development and progression. Autotaxin and lysophosphatidic acid signalling influence several aspects of cancer, including cell proliferation, migration, metastasis, therapy resistance, and interactions with the immune system. The potential of autotaxin as a diagnostic biomarker and promising drug target is also examined.

Autotaxin in Breast Cancer: Role, Epigenetic Regulation and Clinical Implications

Autotaxin (ATX), the protein product of Ectonucleotide Pyrophosphatase Phosphodiesterase 2 (ENPP2), is a secreted lysophospholipase D (lysoPLD) responsible for the extracellular production of lysophosphatidic acid (LPA). ATX-LPA pathway signaling participates in several normal biological functions, but it has also been connected to cancer progression, metastasis and inflammatory processes. Significant research has established a role in breast cancer and it has been suggested as a therapeutic target and/or a clinically relevant biomarker. Recently, ENPP2 methylation was described, revealing a potential for clinical exploitation in liquid biopsy. The current review aims to gather the latest findings about aberrant signaling through ATX-LPA in breast cancer and discusses the role of ENPP2 expression and epigenetic modification, giving insights with translational value.

KAI1/CD82 gene and autotaxin-lysophosphatidic acid axis in gastrointestinal cancers

The KAI1/CD82 gene inhibits the metastasis of most tumors and is remarkably correlated with tumor invasion and prognosis. Cell metabolism dysregulation is an important cause of tumor occurrence, development, and metastasis. As one of the important characteristics of tumors, cell metabolism dysregulation is attracting increasing research attention. Phospholipids are an indispensable substance in the metabolism in various tumor cells. Phospholipid metabolites have become important cell signaling molecules. The pathological role of lysophosphatidic acid (LPA) in tumors was identified in the early 1990s. Currently, LPA inhibitors have entered clinical trials but are not yet used in clinical treatment. Autotaxin (ATX) has lysophospholipase D (lysoPLD) activity and can regulate LPA levels in vivo. The LPA receptor family and ATX/lysoPLD are abnormally expressed in various gastrointestinal tumors. According to our recent pre-experimental results, KAI1/CD82 might inhibit the migration and metastasis of cancer cells by regulating the ATX-LPA axis. However, no relevant research has been reported. Clarifying the mechanism of ATX-LPA in the inhibition of cancer metastasis by KAI1/CD82 will provide an important theoretical basis for targeted cancer therapy. In this paper, the molecular compositions of the KAI1/CD82 gene and the ATX-LPA axis, their physiological functions in tumors, and their roles in gastrointestinal cancers and target therapy are reviewed.

Dual-Mechanism-Driven Strategy for High-Coverage Detection of Serum Lipids on a Novel SALDI-MS Target

Serum lipid metabolites have been emerging as ideal biomarkers for disease diagnosis and prediction. In the current stage, nontargeted or targeted lipidomic research mainly relies on a liquid chromatography-mass spectrometry (LC-MS) platform, but future clinical applications need more robust and high-speed platforms. Surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) has shown excellent advantages in the high-speed analysis of lipid metabolites. However, the platform in the positive ion mode is more inclined to target a certain class of lipids, leading to the low coverage of lipid detection and limiting its practical translation to clinical applications. Herein, we proposed a dual-mechanism-driven strategy for high-coverage detection of serum lipids on a novel SALDI-MS target, which is a composite nanostructure comprising vertical silicon nanowires (VSiNWs) decorated with AuNPs and polydopamine (VSiNW-Au-PDA). The performance of laser desorption and ionization on the target can be enhanced by charge-driven desorption coupled with thermal-driven desorption. Simultaneous detection of 236 serum lipids (S/N ≥ 5) including neutral and polar lipids can be achieved in the positive ion mode. Among these, 107 lipid peaks were successfully identified. When combined with VSiNW-Au-PDA and VSiNW chips, 479 lipid peaks can be detected in serum samples in positive and negative ion modes, respectively. Based on the platform, serum samples from 57 hepatocellular carcinoma (HCC) patients and 76 healthy controls were analyzed. After data mining, 14 lipids containing different lipid types (TAG, CE, PC) were selected as potential lipidomic biomarkers. With the assistance of an artificial neural network, a diagnostic model with a sensitivity of 92.7% and a specificity of 96% was constructed for HCC diagnosis.

ENPP2 (Endothelial Ectonucleotide Pyrophosphatase/Phosphodiesterase 2) Increases Atherosclerosis in Female and Male Mice

BACKGROUND

Maladapted endothelial cells (ECs) secrete ENPP2 (ectonucleotide pyrophosphatase/phosphodiesterase 2; autotaxin)-a lysophospholipase D that generates lysophosphatidic acids (LPAs). ENPP2 derived from the arterial wall promotes atherogenic monocyte adhesion induced by generating LPAs, such as arachidonoyl-LPA (LPA20:4), from oxidized lipoproteins. Here, we aimed to determine the role of endothelial ENPP2 in the production of LPAs and atherosclerosis.

METHODS

We quantified atherosclerosis in mice harboring loxP-flanked Enpp2 alleles crossed with Apoe^-/- mice expressing tamoxifen-inducible Cre recombinase under the control of the EC-specific bone marrow X kinase promoter after 12 weeks of high-fat diet feeding.

RESULTS

A tamoxifen-induced EC-specific Enpp2 knockout decreased atherosclerosis, accumulation of lesional macrophages, monocyte adhesion, and expression of endothelial CXCL (C-X-C motif chemokine ligand) 1 in male and female Apoe^-/- mice. In vitro, ENPP2 mediated the mildly oxidized LDL (low-density lipoprotein)-induced expression of CXCL1 in aortic ECs by generating LPA20:4, palmitoyl-LPA (LPA16:0), and oleoyl-LPA (LPA18:1). ENPP2 and its activity were detected on the endothelial surface by confocal imaging. The expression of endothelial Enpp2 established a strong correlation between the plasma levels of LPA16:0, stearoyl-LPA (LPA18:0), and LPA18:1 and plaque size and a strong negative correlation between the LPA levels and ENPP2 activity in the plasma. Moreover, endothelial Enpp2 knockout increased the weight of high-fat diet-fed male Apoe^-/- mice.

CONCLUSIONS

We demonstrated that the expression of ENPP2 in ECs promotes atherosclerosis and endothelial inflammation in a sex-independent manner. This might be due to the generation of LPA20:4, LPA16:0, and LPA18:1 from mildly oxidized lipoproteins on the endothelial surface.

Role of SLC39A6 in the development and progression of liver cancer

Liver cancer is one of the most common malignant solid tumor types worldwide. The solute carrier (SLC)39A family is a main member of the SLC group of membrane transport proteins, which transfer zinc to the cytoplasm when cells are depleted of zinc; thus, it may provide a novel therapeutic target for human cancer. However, the prognostic value of SLC39A genes in patients with liver cancer has remained elusive. Therefore, the present study aimed to explore whether SLC39A family genes are associated with the survival rate of patients with liver cancer and to investigate the role of key genes of the SLC39A family in liver cancer. The mRNA expression of the SLC39A family in liver cancer was obtained from the UALCAN database. Survival curve analysis was performed to investigate the prognostic value of SLC39A family genes in the overall survival of patients with liver cancer. In addition to the bioinformatics analysis, SLC39A6 was knocked down in HepG2 and Hep3B cells to examine the effect on the proliferation, migration and invasion of liver cancer cells. The results suggested that SLC39A6 was significantly upregulated in liver cancer tissues compared with normal liver tissues. High expression of SLC39A6 was significantly associated with poor overall survival of patients with liver cancer. Furthermore, knockdown of SLC39A6 inhibited the proliferation, migration and invasion of liver cancer cells in vitro and in vivo. Collectively, the results of the present study suggested that SLC39A6 may be a promising prognostic biomarker for liver cancer and is associated with the proliferation, migration and invasion of liver cancer.

Roles of Autotaxin/Autotaxin-Lysophosphatidic Acid Axis in the Initiation and Progression of Liver Cancer

Autotaxin (ATX) is a secreted glycoprotein and catalyzes the hydrolysis of lysophosphatidylcholine to lysophosphatidic acid (LPA), a growth factor-like signaling phospholipid. ATX has been abundantly detected in the culture medium of various cancer cells, tumor tissues, and serum or plasma of cancer patients. Biological actions of ATX are mediated by LPA. The ATX-LPA axis mediates a plethora of activities, such as cell proliferation, survival, migration, angiogenesis, and inflammation, and participates in the regulation of various physiological and pathological processes. In this review, we have summarized the physiological function of ATX and the ATX-LPA axis in liver cancer, analyzed the role of the ATX-LPA axis in tumorigenesis and metastasis, and discussed the therapeutic strategies targeting the ATX-LPA axis, paving the way for new therapeutic developments.

ENPP2 Methylation in Health and Cancer

Autotaxin (ATX) encoded by Ectonucleotide Pyrophosphatase/Phosphodiesterase 2 (ENPP2) is a key enzyme in Lysophosphatidic Acid (LPA) synthesis implicated in cancer. Although its aberrant expression has been reported, ENPP2 methylation profiles in health and malignancy are not described. We examined in silico the methylation of ENPP2 analyzing publicly available methylome datasets, to identify Differentially Methylated CpGs (DMCs) which were then correlated with expression at gene and isoform levels. Significance indication was set to be FDR corrected p-value < 0.05. Healthy tissues presented methylation in all gene body CGs and lower levels in Promoter Associated (PA) regions, whereas in the majority of the tumors examined (HCC, melanoma, CRC, LC and PC) the methylation pattern was reversed. DMCs identified in the promoter were located in sites recognized by multiple transcription factors, suggesting involvement in gene expression. Alterations in methylation were correlated to an aggressive phenotype in cancer cell lines. In prostate and lung adenocarcinomas, increased methylation of PA CGs was correlated to decreased ENPP2 mRNA expression and to poor prognosis parameters. Collectively, our results corroborate that methylation is an active level of ATX expression regulation in cancer. Our study provides an extended description of the methylation status of ENPP2 in health and cancer and points out specific DMCs of value as prognostic biomarkers.

Structural and PK-guided identification of indole-based non-acidic autotaxin (ATX) inhibitors exhibiting high in vivo anti-fibrosis efficacy in rodent model

In recent decades, pharmacological targeting of the autotaxin (ATX)/lysophosphatidic acid (LPA) axis accounted for excellent disease management benefits. Herein, to extend the scope of structure-activity relationships (SARs), fifteen indole-based carbamate derivatives (1-15) were prepared to evaluate the ATX inhibitory potency. Among them, compound 4 bearing morpholine moiety was identified as the optimal ATX inhibitor (0.41 nM), superior to the positive control GLPG1690 (2.90 nM). To resolve the intractable issue of poor pharmacokinetic (PK) property, urea moiety was introduced as a surrogate of carbamate which furnished compounds 16-30. The dedicated modification identified the diethanolamine entity 30 with satisfactory water solubility and PK profiles with a minimum sacrifice of ATX inhibition (2.17 nM). The most promising candidate 30 was evaluated for anti-fibrosis effect in a bleomycin challenged mice lung fibrosis model. Upon treatment with 30, the in vivo ATX activity in both lung homogenate and broncheoalveolar fluid (BALF) sample was significantly down-regulated. Furthermore, the gene expression of pro-fibrotic cytokines transforming growth factor-β (TGF-β), interleukin- 6 (IL-6) and tumor necrosis factor-α (TNF-α) in lung tissue was reduced to normal level. Collectively, the promising biological effects may advocate potential application of 30 in fibrosis relevant diseases.

Development of a KRAS-Associated Metabolic Risk Model for Prognostic Prediction in Pancreatic Cancer

Background

KRAS was reported to affect some metabolic genes and promote metabolic reprogramming in solid tumors. However, there was no comprehensive analysis to explore KRAS-associated metabolic signature or risk model for pancreatic cancer (PC).

Methods

In the current study, multiple bioinformatics analyses were used to identify differentially expressed metabolic genes based on KRAS mutation status in PC. Then, we developed and validated a prognostic risk model based on the selected KRAS-associated metabolic genes. Besides, we explored the association between the risk model and the metabolic characteristics as well as gemcitabine-associated chemoresistance in PC.

Results

6 KRAS-associated metabolic genes (i.e., CYP2S1, GPX3, FTCD, ENPP2, UGT1A10, and XDH) were selected and enrolled to establish a prognostic risk model. The prognostic model had a high C-index of 0.733 for overall survival (OS) in TCGA pancreatic cancer database. The area under the curve (AUC) values of 1- and 3-year survival were both greater than 0.70. Then, the risk model was validated in two GEO datasets and also presented a satisfactory discrimination and calibration performance. Further, we found that the expression of some KRAS-driven glycolysis-associated genes (PKM, GLUT1, HK2, and LDHA) and gemcitabine-associated chemoresistance genes (i.e., CDA and RMM2) was significantly upregulated in high-risk PC patients evaluated by the risk model.

Conclusions

We constructed a risk model based on 6 KRAS-associated metabolic genes, which predicted patients' survival with high accuracy and reflected tumor metabolic characteristics and gemcitabine-associated chemoresistance in PC.

Inhibition of autotaxin by bile salts and bile salt-like molecules increases its expression by feedback regulation

BACKGROUND

Autotaxin is an enzyme that converts lysophospholipid into lysophosphatidic acid (LPA), a highly potent signaling molecule through a range of LPA receptors. It is therefore important to investigate which factors play a role in regulating ATX expression. Since we have reported that ATX levels increase dramatically in patients with various forms of cholestasis, we embarked on a study to reveal factors that influence the enzyme activity ATX as well as its expression level in vitro and in vivo.

METHODS

Bile from cholestatic patients was fractionated by HPLC and analyzed for modulation of ATX activity. ATX expression was measured in fibroblasts upon stimulation or inhibition of LPA signaling.

RESULTS

Surprisingly, ATX activity was stimulated by most forms of its product LPA, but it was inhibited by bile salts and bile salt-like molecules, particularly by 3-OH sulfated bile salts and sulfated progesterone metabolites that are known to accumulate during chronic cholestasis and cholestasis of pregnancy, respectively. Activation of fibroblasts by LPA decreased ATX expression by 72%. Conversely, inhibition of LPA signaling increased ATX expression 3-fold, indicating strong feedback regulation by LPA signaling. In fibroblasts, we could verify that inhibition of ATX activity by bile salts induces its expression. Furthermore, induction of cholestasis in mice causes increased plasma ATX activity.

CONCLUSIONS

Multiple biliary compounds that accumulate in the systemic circulation during cholestasis inhibit ATX activity and thereby increase ATX expression through feedback regulation. This mechanism may contribute to increased serum ATX activity in patients with cholestasis.

Long-Term Decrease of Intraocular Pressure in Rats by Viral Delivery of miR-146a

Purpose

To evaluate the effects of miR-146a in trabecular meshwork (TM) cells and on intraocular pressure (IOP) in vivo via viral delivery of miR-146a to the anterior chamber of rat eyes.

Methods

Human TM cells were transfected with miR-146 mimic or inhibitor. Some cells from each group were then subjected to cyclic mechanical stress (CMS). Other cells from each group had no force applied. Gene expression was then analyzed by quantitative polymerase chain reaction (qPCR). Replication-deficient adenovirus and lentivirus expressing miR-146a were inoculated into the anterior segment of Brown Norway rat eyes. IOP was monitored by rebound tonometry, visual acuity was evaluated by optokinetic tracking (OKT), and inflammation markers in the anterior segment were examined by slit-lamp, qPCR, and semi-thin sections.

Results

miR-146 affected the expression of genes potentially involved in outflow homeostasis at basal levels and under CMS. Both lentiviral and adenoviral vectors expressing miR-146a resulted in sustained decreases in IOP ranging from 2.6 to 4.4 mmHg. Long term follow-up of rats injected with lentiviral vectors showed a sustained effect on IOP of 4.4 ± 2.9 mmHg that lasted until rats were sacrificed more than 8 months later. Eyes showed no signs of inflammation, loss of visual acuity, or other visible abnormalities.

Conclusions

Intracameral delivery of miR-146a can provide a long-term decrease of IOP in rats without signs of inflammation or other visible adverse effects.

Transitional Relevance

The IOP-lowering effects of miR-146 observed in rats provides a necessary step toward the development of an effective gene therapy for glaucoma in humans.

Lysophosphatidic Acid: Promoter of Cancer Progression and of Tumor Microenvironment Development. A Promising Target for Anticancer Therapies?

Increased expression of the enzyme autotaxin (ATX) and the consequently increased levels of its product, lysophosphatidic acid (LPA), have been reported in several primary tumors. The role of LPA as a direct modulator of tumor cell functions—motility, invasion and migration capabilities as well as resistance to apoptotic death—has been recognized by numerous studies over the last two decades. Notably, evidence has recently been accumulating that shows that LPA also contributes to the development of the tumor microenvironment (TME). Indeed, LPA plays a crucial role in inducing angiogenesis and lymphangiogenesis, triggering cellular glycolytic shift and stimulating intratumoral fibrosis. In addition, LPA helps tumoral cells to escape immune surveillance. Treatments that counter the TME components, in order to deprive cancer cells of their crucial support, have been emerging among the promising new anticancer therapies. This review aims to summarize the latest knowledge on how LPA influences both tumor cell functions and the TME by regulating the activity of its different elements, highlighting why and how LPA is worth considering as a molecular target for new anticancer therapies.

Therapeutic Strategies for Targeting Ovarian Cancer Stem Cells

Ovarian cancer is a fatal gynecological malignancy. Although first-line chemotherapy and surgical operation are effective treatments for ovarian cancer, its clinical management remains a challenge owing to intrinsic or acquired drug resistance and relapse at local or distal lesions. Cancer stem cells (CSCs) are a small subpopulation of cells inside tumor tissues, and they can self-renew and differentiate. CSCs are responsible for the cancer malignancy involved in relapses as well as resistance to chemotherapy and radiation. These malignant properties of CSCs are regulated by cell surface receptors and intracellular pluripotency-associated factors triggered by internal or external stimuli from the tumor microenvironment. The malignancy of CSCs can be attenuated by individual or combined restraining of cell surface receptors and intracellular pluripotency-associated factors. Therefore, targeted therapy against CSCs is a feasible therapeutic tool against ovarian cancer. In this paper, we review the prominent roles of cell surface receptors and intracellular pluripotency-associated factors in mediating the stemness and malignancy of ovarian CSCs.

The Expression Regulation and Biological Function of Autotaxin

Autotaxin (ATX) is a secreted glycoprotein and functions as a key enzyme to produce extracellular lysophosphatidic acid (LPA). LPA interacts with at least six G protein-coupled receptors, LPAR1-6, on the cell membrane to activate various signal transduction pathways through distinct G proteins, such as Gi/0, G12/13, Gq/11, and Gs. The ATX-LPA axis plays an important role in physiological and pathological processes, including embryogenesis, obesity, and inflammation. ATX is one of the top 40 most unregulated genes in metastatic cancer, and the ATX-LPA axis is involved in the development of different types of cancers, such as colorectal cancer, ovarian cancer, breast cancer, and glioblastoma. ATX expression is under multifaceted controls at the transcription, post-transcription, and secretion levels. ATX and LPA in the tumor microenvironment not only promote cell proliferation, migration, and survival, but also increase the expression of inflammation-related circuits, which results in poor outcomes for patients with cancer. Currently, ATX is regarded as a potential cancer therapeutic target, and an increasing number of ATX inhibitors have been developed. In this review, we focus on the mechanism of ATX expression regulation and the functions of ATX in cancer development.

Lysophosphatidic acid mediated PI3K/Akt activation contributed to esophageal squamous cell cancer progression

Lysophosphatidic acid (LPA) and its G-protein-coupled receptors (Lpar1-Lpar6) mediate a plethora of activities associated with cancer growth and progression. However, there is no systematic study about whether and how LPA promotes esophageal squamous cell carcinoma (ESCC). Here, we show that autotaxin (ATX), a primary LPA-producing enzyme, is highly expressed in ESCC, and overexpressed ATX is associated with the poor outcome of ESCC patients. Meanwhile, the expression of Lpar1 was much higher in ESCC cells compared with Het-1a (human esophagus normal epithelial cells). Functional experiments showed that LPA remarkably increased the proliferation and migration of ESCC cells. Furthermore, Lpar1 knockdown abolished the effect of LPA on ESCC cell proliferation and migration. Mechanistic studies revealed that LPA promoted ESCC cell lines proliferation and migration through PI3K/Akt pathway. Treatment of KYSE30 cell xenografts with Lpar1 inhibitor BMS-986020 significantly repressed tumor growth. Our results shed light on the important role of LPA in ESCC, and Lpar1 might be a potential treatment target for ESCC.

NSun2 promotes cell migration through methylating autotaxin mRNA

NSun2 is an RNA methyltransferase introducing 5-methylcytosine into tRNAs, mRNAs, and noncoding RNAs, thereby influencing the levels or function of these RNAs. Autotaxin (ATX) is a secreted glycoprotein and is recognized as a key factor in converting lysophosphatidylcholine into lysophosphatidic acid (LPA). The ATX-LPA axis exerts multiple biological effects in cell survival, migration, proliferation, and differentiation. Here, we show that NSun2 is involved in the regulation of cell migration through methylating ATX mRNA. In the human glioma cell line U87, knockdown of NSun2 decreased ATX protein levels, whereas overexpression of NSun2 elevated ATX protein levels. However, neither overexpression nor knockdown of NSun2 altered ATX mRNA levels. Further studies revealed that NSun2 methylated the 3'-UTR of ATX mRNA at cytosine 2756 in vitro and in vivo Methylation by NSun2 enhanced ATX mRNA translation. In addition, NSun2-mediated 5-methylcytosine methylation promoted the export of ATX mRNA from nucleus to cytoplasm in an ALYREF-dependent manner. Knockdown of NSun2 suppressed the migration of U87 cells, which was rescued by the addition of LPA. In summary, we identify NSun2-mediated methylation of ATX mRNA as a novel mechanism in the regulation of ATX.

The impact of achieving a sustained virological response with direct-acting antivirals on serum autotaxin levels in chronic hepatitis C patients

Background

Autotaxin (ATX) is an emerging biomarker for liver fibrosis. Achievement of sustained virological response (SVR) by direct-acting antivirals (DAAs) results in hepatic fibrosis regression in chronic hepatitis C (CHC) patients. In this context, the clinical implications of ATX have not yet been well-defined. In this study, we aimed to assess the impact of achieving SVR with DAA therapy on serum ATX levels and whether these levels can reflect the regression of hepatic fibrosis in CHC patients. We evaluated serum ATX levels at baseline and 12 weeks post-DAA therapy in 48 CHC patients. We compared ATX with FIB4 score and AST-to-Platelet Ratio Index (APRI) as regards the detection of grade F3–4 fibrosis.

Results

Serum ATX levels were significantly declined in 47 patients after the achievement of SVR12 (p < 0.001). The diagnostic ability of ATX for the detection of grade F3–4 fibrosis was inferior to FIB4 and APRI scores at baseline and SVR12.

Conclusion

Achievement of SVR with DAA therapy causes a significant decline in serum autotaxin concentrations, suggesting early regression of hepatic fibrosis in CHC patients. However, its diagnostic capability for routine patient monitoring and follow-up is still under debate.

Autotaxin loss accelerates intestinal inflammation by suppressing TLR4-mediated immune responses

Autotaxin (ATX) converts lysophosphatidylcholine and sphingosyl-phosphorylcholine into lysophosphatidic acid and sphingosine 1-phosphate, respectively. Despite the pivotal function of ATX in lipid metabolism, mechanisms by which ATX regulates immune and inflammatory disorders remain elusive. Here, using myeloid cell lineage-restricted Atx knockout mice, we show that Atx deficiency disrupts membrane microdomains and lipid rafts, resulting in the inhibition of Toll-like receptor 4 (TLR4) complex formation and the suppression of adaptor recruitment, thereby inhibiting TLR4-mediated responses in macrophages. Accordingly, TLR4-induced innate immune functions, including phagocytosis and iNOS expression, are attenuated in Atx-deficient macrophages. Consequently, Atx^-/- mice exhibit a higher bacterial prevalence in the intestinal mucosa compared to controls. When combined with global Il10^-/- mice, which show spontaneous colitis due to the translocation of luminal commensal microbes into the mucosa, myeloid cell lineage-restricted Atx knockout accelerates colitis development compared to control littermates. Collectively, our data reveal that Atx deficiency compromises innate immune responses, thereby promoting microbe-associated gut inflammation.

Plasma metabolomic profiles in liver cancer patients following stereotactic body radiotherapy

Background

Stereotactic body radiotherapy (SBRT) is an effective treatment for hepatocellular carcinoma (HCC). This study sought to identify differentially expressed plasma metabolites in HCC patients at baseline and early during SBRT, and to explore if changes in these metabolites early during SBRT may serve as biomarkers for radiation-induced liver injury and/or tumour response.

Methods

Forty-seven HCC patients were treated with SBRT on previously published prospective trials. Plasma samples were collected at baseline and after one to two fractions of SBRT, and analysed by GC/MS and LC/MS for untargeted and targeted metabolomics profiling, respectively.

Findings

Sixty-nine metabolites at baseline and 62 metabolites after one to two fractions of SBRT were differentially expressed, and strongly separated the Child Pugh (CP) B from the CP A HCC patients. These metabolites are associated with oxidative stress and alterations in hepatic cellular metabolism. Differential upregulation of serine, alanine, taurine, and lipid metabolites early during SBRT from baseline was noted in the HCC patients who demonstrated the greatest increase in CP scores at three months post SBRT, suggesting that high protein and lipid turnover early during SBRT may portend increased clinical liver toxicity. Twenty annotated metabolites including fatty acids, glycerophospholipids, and acylcarnitines were differentially upregulated early during SBRT from baseline and separated patients with complete/partial response from those with stable disease at three months post SBRT.

Interpretation

Dysregulation of amino acid and lipid metabolism detected early during SBRT are associated with subsequent clinical liver injury and tumour response in HCC.

Lipid Phosphate Phosphatases and Cancer

Lipid phosphate phosphatases (LPPs) are a group of three enzymes (LPP1–3) that belong to a phospholipid phosphatase (PLPP) family. The LPPs dephosphorylate a wide spectrum of bioactive lipid phosphates, among which lysophosphatidate (LPA) and sphingosine 1-phosphate (S1P) are two important extracellular signaling molecules. The LPPs are integral membrane proteins, which are localized on plasma membranes and intracellular membranes, including the endoplasmic reticulum and Golgi network. LPPs regulate signaling transduction in cancer cells and demonstrate different effects in cancer progression through the breakdown of extracellular LPA and S1P and other intracellular substrates. This review is intended to summarize an up-to-date understanding about the functions of LPPs in cancers.

Plasma metabolomic fingerprint of advanced cirrhosis stages among HIV/HCV-coinfected and HCV-monoinfected patients

BACKGROUND & AIMS

Hepatitis C virus (HCV), human immunodeficiency virus (HIV) and cirrhosis induce metabolic disorders. Here, we aimed to evaluate the association of plasma metabolites with Child-Turcotte-Pugh (CTP) score and hepatic decompensation in HIV/HCV-coinfected and HCV-monoinfected patients with advanced cirrhosis.

METHODS

A cross-sectional study was carried out in 62 HIV/HCV-coinfected and 28 HCV-monoinfected patients. Metabolomics analysis was performed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The statistical association analysis was performed by partial least squares discriminant analysis (PLS-DA) and generalized linear model (GLM) with binomial distribution (to analyse HIV coinfection, high alcohol intake, treatment with statins, previous HCV therapy failure and decompensation) and ordinal logistic regression (OLR) models to analyse different stages of cirrhosis (CTP score).

RESULTS

The statistical analysis identified plasma metabolites associated with HIV coinfection, high alcohol intake, CTP score and hepatic decompensation. Overall, fatty acids, bile acids, aromatic and sulphur amino acids, butyrate derivatives, oxidized phospholipids, energy-related metabolites and bacterial fermentation-related metabolites were increased in more advanced cirrhosis stages; while lysophosphatidylcholines and lysophosphatidylethanolamines, branched-chain amino acids (BCAA) and metabolites of tricarboxylic acid cycle, among others, were decreased in more advanced cirrhosis. Most of the significant metabolites displayed a similar trend after stratifying for HIV/HCV- and HCV-infected patients. Glycolic acid, LPC (16:0) and taurocholic acid had high accuracy for discriminating patients according to decompensated cirrhosis (CTP ≥ 7).

CONCLUSION

Altered plasma metabolomic profile was associated with advanced stages of cirrhosis in HIV/HCV-coinfected and HCV-monoinfected patients.

Plasma Lipid Profiling of Three Types of Drug-Induced Liver Injury in Japanese Patients: A Preliminary Study

Drug-induced liver injury (DILI) is a major adverse event caused by drug treatment, which can be categorized into three types: hepatocellular, mixed, and cholestatic. Although nearly every class of drugs can cause DILI, an overall understanding of lipid profiles in DILI patients is lacking. We used lipidomics to analyze the plasma lipid profiles of patients to understand their hepatic pathophysiology and identify DILI biomarkers. We identified 463 lipids and compared their levels between the acute and recovery phases of the three types of DILI patients. Mixed and cholestatic types demonstrated specific plasma lipid alterations between the phases, but the hepatocellular type did not. Moreover, as specific indicators of mixed-type DILI, levels of several ceramides increased in the acute phase, while those of arachidonic acid-containing ether-linked phosphoglycerolipids decreased. In contrast, as specific indicators of cholestatic-type DILI, levels of palmitic acid-containing saturated or monounsaturated phosphatidylcholines increased in the acute phase, while those of arachidonic acid- or docosahexaenoic acid-containing ether-linked phosphoglycerolipids and phosphatidylinositols decreased. We also identified lipids with a relatively high capacity to discriminate the acute phase from the recovery phase and healthy subjects. These findings may help with understanding the pathophysiology of different DILI types and identify candidate biomarkers.

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.

MAPK signaling determines lysophosphatidic acid (LPA)-induced inflammation in microglia

Background

In the extracellular environment, lysophosphatidic acid (LPA) species are generated via autotaxin (ATX)-mediated hydrolysis of lysophospholipid precursors. Members of the LPA family are potent lipid mediators transmitting signals via six different G protein-coupled LPA receptors (LPAR1-6). The LPA signaling axis is indispensable for brain development and function of the nervous system; however, during damage of the central nervous system, LPA levels can increase and aberrant signaling events counteract brain function. Here, we investigated regulation of the ATX/LPA/LPAR axis in response to lipopolysaccharide-induced systemic inflammation in mice and potential neurotoxic polarization programs in LPA-activated primary murine microglia.

Methods

In vivo, LPAR1-6 expression was established by qPCR in whole murine brain homogenates and in FACS-sorted microglia. ELISAs were used to quantitate LPA concentrations in the brain and cyto-/chemokine secretion from primary microglia in vitro. Transcription factor phosphorylation was analyzed by immunoblotting, and plasma membrane markers were analyzed by flow cytometry. We used MAPK inhibitors to study signal integration by the JNK, p38, and ERK1/2 branches in response to LPA-mediated activation of primary microglia.

Results

Under acute and chronic inflammatory conditions, we observed a significant increase in LPA concentrations and differential regulation of LPAR, ATX (encoded by ENPP2), and cytosolic phospholipase A2 (encoded by PLA2G4A) gene expression in the brain and FACS-sorted microglia. During pathway analyses in vitro, the use of specific MAPK antagonists (SP600125, SB203580, and PD98059) revealed that JNK and p38 inhibition most efficiently attenuated LPA-induced phosphorylation of proinflammatory transcription factors (STAT1 and -3, p65, and c-Jun) and secretion of IL-6 and TNFα. All three inhibitors decreased LPA-mediated secretion of IL-1β, CXCL10, CXCL2, and CCL5. The plasma membrane marker CD40 was solely inhibited by SP600125 while all three inhibitors affected expression of CD86 and CD206. All MAPK antagonists reduced intracellular COX-2 and Arg1 as well as ROS and NO formation, and neurotoxicity of microglia-conditioned media.

Conclusion

In the present study, we show that systemic inflammation induces aberrant ATX/LPA/LPAR homeostasis in the murine brain. LPA-mediated polarization of primary microglia via MAPK-dependent pathways induces features reminiscent of a neurotoxic phenotype.

Role of the autotaxin-lysophosphatidate axis in the development of resistance to cancer therapy

Autotaxin (ATX) is a secreted enzyme that hydrolyzes lysophosphatidylcholine to produce lysophosphatidate (LPA), which signals through six G-protein coupled receptors (GPCRs). Signaling through LPA is terminated by its degradation by a family of three lipid phosphate phosphatases (LPPs). LPP1 also attenuates signaling downstream of the activation of LPA receptors and some other GPCRs. The ATX-LPA axis mediates a plethora of activities such as cell proliferation, survival, migration, angiogenesis and inflammation, which perform an important role in facilitating wound healing. This wound healing response is hijacked by cancers where there is decreased expression of LPP1 and LPP3 and increased expression of ATX. This maladaptive regulation of LPA signaling also causes chronic inflammation, which has been recognized as one of the hallmarks in cancer. The increased LPA signaling promotes cell survival and migration and attenuates apoptosis, which stimulates tumor growth and metastasis. The wound healing functions of increased LPA signaling also protect cancer cells from effects of chemotherapy and radiotherapy. In this review, we will summarize knowledge of the ATX-LPA axis and its role in the development of resistance to chemotherapy and radiotherapy. We will also offer insights for developing strategies of targeting ATX-LPA axis as a novel part of cancer treatment. This article is part of a Special Issue entitled Lysophospholipids and their receptors: New data and new insights into their function edited by Susan Smyth, Viswanathan Natarajan and Colleen McMullen.

Role of lipids in pathophysiology, diagnosis and therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an aggressive and widespread cancer. Patients with liver cirrhosis of different aetiologies are at a risk to develop HCC. It is important to know that in approximately 20% of cases primary liver tumors arise in a non-cirrhotic liver. Lipid metabolism is variable in patients with chronic liver diseases, and lipid metabolites involved therein do play a role in the development of HCC. Of note, lipid composition of carcinogenic tissues differs from non-affected liver tissues. High cholesterol and low ceramide levels in the tumors protect the cells from oxidative stress and apoptosis, and do also promote cell proliferation. So far, detailed characterization of the mechanisms by which lipids enable the development of HCC has received little attention. Evaluation of the complex roles of lipids in HCC is needed to better understand the pathophysiology of HCC, the later being of paramount importance for the development of urgently needed therapeutic interventions. Disturbed hepatic lipid homeostasis has systemic consequences and lipid species may emerge as promising biomarkers for early diagnosis of HCC. The challenge is to distinguish lipids specifically related to HCC from changes simply related to the underlying liver disease. This review article discusses aberrant lipid metabolism in patients with HCC.

Autotaxin Implication in Cancer Metastasis and Autoimunne Disorders: Functional Implication of Binding Autotaxin to the Cell Surface

Autotaxin (ATX) is an exoenzyme which, due to its unique lysophospholipase D activity, is responsible for the synthesis of lysophosphatidic acid (LPA). ATX activity is responsible for the concentration of LPA in the blood. ATX expression is increased in various types of cancers, including breast cancer, where it promotes metastasis. The expression of ATX is also remarkably increased under inflammatory conditions, particularly in the osteoarticular compartment, where it controls bone erosion. Biological actions of ATX are mediated by LPA. However, the phosphate head group of LPA is highly sensitive to degradation by the action of lipid phosphate phosphatases, resulting in LPA inactivation. This suggests that for efficient action, LPA requires protection, which is potentially achieved through docking to a carrier protein. Interestingly, recent reports suggest that ATX might act as a docking molecule for LPA and also support the concept that binding of ATX to the cell surface through its interaction with adhesive molecules (integrins, heparan sulfate proteoglycans) could facilitate a rapid route of delivering active LPA to its cell surface receptors. This new mechanism offers a new vision of how ATX/LPA works in cancer metastasis and inflammatory bone diseases, paving the way for new therapeutic developments.

Enhancer-mediated enrichment of interacting JMJD3-DDX21 to ENPP2 locus prevents R-loop formation and promotes transcription

ENPP2, which encodes for the enzyme autotaxin (ATX), is overexpressed during chronic inflammatory diseases and various cancers. However, the molecular mechanism involved in the ENPP2 transcription remains elusive. Here, in HEK 293T cells, we demonstrated that lipopolysaccharide (LPS) increased the transcription process at ENPP2 locus through a NF-кB pathway and a reduction of H3K27me3 level, a histone repressive mark, by the demethylase UTX. Simultaneously, the H3K27me3 demethylase JMJD3/KDM6B was recruited to the transcription start site (TSS), within the gene body and controlled the expression of ENPP2 in a non-enzymatic manner. Mass spectrometry data revealed a novel interaction for JMJD3 with DDX21, a RNA helicase that unwinds R-loops created by nascent transcript and DNA template. Upon LPS treatment, JMJD3 is necessary for DDX21 recruitment at ENPP2 locus allowing the resolution of aberrant R-loops. CRISPR-Cas9-mediated deletion of a distant-acting enhancer decreased the expression of ENPP2 and lowered the recruitment of JMJD3–DDX21 complex at TSS and its progression through the gene body. Taken together, these findings revealed that enhancer-mediated enrichment of novel JMJD3–DDX21 interaction at ENPP2 locus is necessary for nascent transcript synthesis via the resolution of aberrant R-loops formation in response to inflammatory stimulus.

Elevated Autotaxin and LPA Levels During Chronic Viral Hepatitis and Hepatocellular Carcinoma Associate with Systemic Immune Activation

Circulating autotaxin (ATX) is elevated in persons with liver disease, particularly in the setting of chronic hepatitis C virus (HCV) and HCV/HIV infection. It is thought that plasma ATX levels are, in part, attributable to impaired liver clearance that is secondary to fibrotic liver disease. In a discovery data set, we identified plasma ATX to be associated with parameters of systemic immune activation during chronic HCV and HCV/HIV infection. We and others have observed a partial normalization of ATX levels within months of starting interferon-free direct-acting antiviral (DAA) HCV therapy, consistent with a non-fibrotic liver disease contribution to elevated ATX levels, or HCV-mediated hepatocyte activation. Relationships between ATX, lysophosphatidic acid (LPA) and parameters of systemic immune activation will be discussed in the context of HCV infection, age, immune health, liver health, and hepatocellular carcinoma (HCC).

Deregulated Lysophosphatidic Acid Metabolism and Signaling in Liver Cancer

Liver cancer is one of the leading causes of death worldwide due to late diagnosis and scarcity of treatment options. The major risk factor for liver cancer is cirrhosis with the underlying causes of cirrhosis being viral infection (hepatitis B or C), metabolic deregulation (Non-alcoholic fatty liver disease (NAFLD) in the presence of obesity and diabetes), alcohol or cholestatic disorders. Lysophosphatidic acid (LPA) is a bioactive phospholipid with numerous effects, most of them compatible with the hallmarks of cancer (proliferation, migration, invasion, survival, evasion of apoptosis, deregulated metabolism, neoangiogenesis, etc.). Autotaxin (ATX) is the enzyme responsible for the bulk of extracellular LPA production, and together with LPA signaling is involved in chronic inflammatory diseases, fibrosis and cancer. This review discusses the most important findings and the mechanisms related to ATX/LPA/LPAR involvement on metabolic, viral and cholestatic liver disorders and their progression to liver cancer in the context of human patients and mouse models. It focuses on the role of ATX/LPA in NAFLD development and its progression to liver cancer as NAFLD has an increasing incidence which is associated with the increasing incidence of liver cancer. Bearing in mind that adipose tissue accounts for the largest amount of LPA production, many studies have implicated LPA in adipose tissue metabolism and inflammation, liver steatosis, insulin resistance, glucose intolerance and lipogenesis. At the same time, LPA and ATX play crucial roles in fibrotic diseases. Given that hepatocellular carcinoma (HCC) is usually developed on the background of liver fibrosis, therapies that both delay the progression of fibrosis and prevent its development to malignancy would be very promising. Therefore, ATX/LPA signaling appears as an attractive therapeutic target as evidenced by the fact that it is involved in both liver fibrosis progression and liver cancer development.

Osteoclast-Derived Autotaxin, a Distinguishing Factor for Inflammatory Bone Loss

OBJECTIVE

The severity of rheumatoid arthritis (RA) correlates directly with bone erosions arising from osteoclast (OC) hyperactivity. Despite the fact that inflammation may be controlled in patients with RA, those in a state of sustained clinical remission or low disease activity may continue to accrue erosions, which supports the need for treatments that would be suitable for long-lasting inhibition of OC activity without altering the physiologic function of OCs in bone remodeling. Autotaxin (ATX) contributes to inflammation, but its role in bone erosion is unknown.

METHODS

ATX was targeted by inhibitory treatment with pharmacologic drugs and also by conditional inactivation of the ATX gene Ennp2 in murine OCs (ΔATX^{C tsk} ). Arthritic and erosive diseases were studied in human tumor necrosis factor-transgenic (hTNF^+/- ) mice and mice with K/BxN serum transfer-induced arthritis. Systemic bone loss was also analyzed in mice with lipopolysaccharide (LPS)-induced inflammation and estrogen deprivation. Joint inflammation and bone erosion were assessed by histology and micro-computed tomography. The role of ATX in RA was also examined in OC differentiation and activity assays.

RESULTS

OCs present at sites of inflammation overexpressed ATX. Pharmacologic inhibition of ATX in hTNF^+/- mice, as compared to vehicle-treated controls, significantly mitigated focal bone erosion (36% decrease; P < 0.05) and systemic bone loss (43% decrease; P < 0.05), without affecting synovial inflammation. OC-derived ATX was revealed to be instrumental in OC bone resorptive activity and was up-regulated by the inflammation elicited in the presence of TNF or LPS. Specific loss of ATX in OCs from mice subjected to ovariectomy significantly protected against the systemic bone loss and erosion that had been induced with LPS and K/BxN serum treatments (30% reversal of systemic bone loss [P < 0.01]; 55% reversal of erosion [P < 0.001]), without conferring bone-protective properties.

CONCLUSION

Our results identify ATX as a novel OC factor that specifically controls inflammation-induced bone erosions and systemic bone loss. Therefore, ATX inhibition offers a novel therapeutic approach for potentially preventing bone erosion in patients with RA.

CPAP promotes angiogenesis and metastasis by enhancing STAT3 activity

Centrosomal P4.1-associated protein (CPAP) is overexpressed in hepatocellular carcinoma (HCC) and positively correlated with recurrence and vascular invasion. Here, we found that CPAP plays an important role in HCC malignancies. Functional characterization indicated that CPAP overexpression increases tumor growth, angiogenesis, and metastasis ex vivo and in vivo. In addition, overexpressed CPAP contributes to sorafenib resistance. Mechanical investigation showed that the expression level of CPAP is positively correlated with activated STAT3 in HCC. CPAP acts as a transcriptional coactivator of STAT3 by directly binding with STAT3. Interrupting the interaction between CPAP and STAT3 attenuates STAT3-mediated tumor growth and angiogenesis. Overexpression of CPAP upregulates several STAT3 target genes such as IL-8 and CD44 that are involved in angiogenesis, and CPAP mRNA expression is positively correlated with the levels of both mRNAs in HCC. Knocked-down expression of CPAP impairs IL-6-mediated STAT3 activation, target gene expression, cell migration, and invasion abilities. IL-6/STAT3-mediated angiogenesis is significantly increased by CPAP overexpression and can be blocked by decreased expression of IL-8. Our findings not only shed light on the importance of CPAP in HCC malignancies, but also provide potential therapeutic strategies for inhibiting the angiogenesis pathway and treating metastatic HCC.

Autotaxin and chronic inflammatory diseases

Autotaxin (ATX) is a secreted glycoprotein, widely present in biological fluids including blood. ATX catalyzes the hydrolysis of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), a growth factor-like, signaling phospholipid. LPA exerts pleiotropic effects mediated by its G-protein-coupled receptors that are widely expressed and exhibit overlapping specificities. Although ATX also possesses matricellular properties, the majority of ATX reported functions in adulthood are thought to be mediated through the extracellular production of LPA. ATX-mediated LPA synthesis is likely localized at the cell surface through the possible interaction of ATX with integrins or other molecules, while LPA levels are further controlled by a group of membrane-associated lipid-phosphate phosphatases. ATX expression was shown to be necessary for embryonic development, and ATX deficient embryos exhibit defective vascular homeostasis and aberrant neuronal system development. In adult life, ATX is highly expressed in the adipose tissue and has been implicated in diet-induced obesity and glucose homeostasis with multiple implications in metabolic disorders. Additionally, LPA has been shown to affect multiple cell types, including stromal and immune cells in various ways. Therefore, LPA participates in many processes that are intricately involved in the pathogenesis of different chronic inflammatory diseases such as vascular homeostasis, skeletal and stromal remodeling, lymphocyte trafficking and immune regulation. Accordingly, increased ATX and LPA levels have been detected, locally and/or systemically, in patients with chronic inflammatory diseases, most notably idiopathic pulmonary fibrosis (IPF), chronic liver diseases, and rheumatoid arthritis. Genetic and pharmacological studies in mice have confirmed a pathogenetic role for ATX expression and LPA signaling in chronic inflammatory diseases, and provided the proof of principle for therapeutic interventions, as exemplified by the ongoing clinical trials for IPF.

Pleotropic Roles of Autotaxin in the Nervous System Present Opportunities for the Development of Novel Therapeutics for Neurological Diseases

Autotaxin (ATX) is a soluble extracellular enzyme that is abundant in mammalian plasma and cerebrospinal fluid (CSF). It has two known enzymatic activities, acting as both a phosphodiesterase and a phospholipase. The majority of its biological effects have been associated with its ability to liberate lysophosphatidic acid (LPA) from its substrate, lysophosphatidylcholine (LPC). LPA has diverse pleiotropic effects in the central nervous system (CNS) and other tissues via the activation of a family of six cognate G protein-coupled receptors. These LPA receptors (LPARs) are expressed in some combination in all known cell types in the CNS where they mediate such fundamental cellular processes as proliferation, differentiation, migration, chronic inflammation, and cytoskeletal organization. As a result, dysregulation of LPA content may contribute to many CNS and PNS disorders such as chronic inflammatory or neuropathic pain, glioblastoma multiforme (GBM), hemorrhagic hydrocephalus, schizophrenia, multiple sclerosis, Alzheimer's disease, metabolic syndrome-induced brain damage, traumatic brain injury, hepatic encephalopathy-induced cerebral edema, macular edema, major depressive disorder, stress-induced psychiatric disorder, alcohol-induced brain damage, HIV-induced brain injury, pruritus, and peripheral nerve injury. ATX activity is now known to be the primary biological source of this bioactive signaling lipid, and as such, represents a potentially high-value drug target. There is currently one ATX inhibitor entering phase III clinical trials, with several additional preclinical compounds under investigation. This review discusses the physiological and pathological significance of the ATX-LPA-LPA receptor signaling axis and summarizes the evidence for targeting this pathway for the treatment of CNS diseases.

Autotaxin is a novel target of microRNA-101-3p

Autotaxin (ATX), a vital enzyme that generates lysophosphatidic acid (LPA), affects many biological processes, including tumorigenesis, via the ATX–LPA axis. In this study, we demonstrate that microRNA‐101‐3p (miR‐101‐3p), a well‐known tumor suppressor, downregulates ATX expression at the posttranscriptional level. We found that miR‐101‐3p inhibits ATX regulation by directly targeting a conserved sequence in the ATX mRNA 3′UTR. Moreover, we observed an inverse correlation between ATX and miR‐101‐3p levels in various types of cancer cells. ATX is highly expressed in several human cancers. Here, we verified that ATX expression is significantly inhibited by miR‐101‐3p in U87 and HCT116 cells. ATX downregulation contributed to the suppression of migration, invasion, and proliferation mediated by miR‐101‐3p; furthermore, the tumor‐suppressing activity of miR‐101‐3p was partially reduced by the addition of LPA in U87 cells. Our data suggest that ATX is a novel target of miR‐101‐3p.

Cancer-related gene expression is associated with disease severity and modifiable lifestyle factors in non-alcoholic fatty liver disease

OBJECTIVE

The aim of this study was to determine whether hepatic gene expression related to hepatocellular carcinoma (HCC) is associated with disease severity and modifiable lifestyle factors in non-alcoholic fatty liver disease (NAFLD).

METHODS

In a cross-sectional study, the associations between hepatic gene expression and liver histology, insulin resistance, anthropometrics, diet, and physical activity were assessed in patients with non-alcoholic steatohepatitis (NASH; n = 19) or simple steatosis (SS; n = 20). In a group of patients with NASH, we then conducted a 1-y, single-arm, pilot study using ω-3 polyunsaturated fatty acid (PUFA) supplementation to determine whether changes in hepatic PUFA content would have a modulating effect on hepatic gene expression and would affect liver histology.

RESULTS

In the cross-sectional study, histological features of disease severity correlated with AKR1B10, ANXA2, PEG10, SPP1, STMN2, MT1A, and MT1B in NASH and with EEF1A2, PEG10, and SPP1 in SS. In addition, PEG10, SPP1, ANXA2, and STMN2 expression correlated positively with insulin resistance in NASH. SPP1 and UBD correlated strongly with body mass index in SS. Associations between ENPP2, AKR1B10, SPP1, UBD, and waist circumference depended on sex and diagnosis. Several genes correlated with protein, fat, or carbohydrate intake. PEG10 correlated positively with physical activity in NASH and inversely with plasma vitamin C in both groups. Despite increased erythrocyte and hepatic ω-3 PUFA, supplementation did not alter hepatic gene expression and liver histology.

CONCLUSIONS

HCC-related gene expression was associated with liver histology, body mass index, waist circumference, diet, and physical activity but was not affected by ω-3 PUFA supplementation.

Inhibition of autotaxin alleviates inflammation and increases the expression of sodium-dependent glucose cotransporter 1 and Na+/H+ exchanger 3 in SAMP1/Fc mice

Crohn's disease (CD) is a chronic, relapsing, inflammatory disease that is often associated with malnutrition because of inflammation in the small intestine. Autotaxin (ATX) is a secreted enzyme that produces extracellular lysophosphatidic acid. Increasing evidence suggests that ATX is upregulated during inflammation, and inhibition of ATX has been effective in attenuating chronic inflammatory conditions, such as arthritis and pulmonary fibrosis. This study aims to determine whether inhibition of ATX alleviates CD-associated inflammation and malnutrition by using SAMP1/Fc mice, a model of CD-like ileitis. SAMP1/Fc mice were treated the ATX inhibitor PF-8380 for 4 wk. Inhibition of ATX led to increased weight gain in SAMP1/Fc mice, decreased T helper 2 cytokine expression, including IL-4, IL-5, and IL-13, and attenuated immune cell migration. SAMP1/Fc mice have low expression of Na⁺-dependent glucose transporter 1 (SGLT1), suggesting impaired nutrient absorption associated with ileitis. PF-8380 treatment significantly enhanced SGLT1 expression in SAMP1/Fc mice, which could reflect the increased weight changes. However, IL-4 or IL-13 did not alter SGLT1 expression in Caco-2 cells, ruling out their direct effects on SGLT1 expression. Immunofluorescence analysis showed that the expression of sucrase-isomaltase, a marker for intestinal epithelial cell (IEC) differentiation, was decreased in inflamed regions of SAMP1/Fc mice, which was partially restored by PF-8380. Moreover, expression of Na⁺/H⁺ exchanger 3 was also improved by PF-8380, suggesting that suppression of inflammation by PF-8380 enhanced IEC differentiation. Our study therefore suggests that ATX is a potential target for treating intestinal inflammation and restoration of the absorptive function of the intestine. NEW & NOTEWORTHY This study is the first, to our knowledge, to determine whether autotoxin (ATX) inhibition improves inflammation and body weights in SAMP1/Fc mice, a mouse model of ileitis. ATX inhibition increased body weights of SAMP1/Fc mice and increased Na⁺-dependent glucose transporter 1 (SGLT1) expression. Increased SGLT1 expression in the inflamed regions was not a direct effect of cytokines but an indirect effect of increased epithelial cell differentiation upon ATX inhibition.