Retinoic Acid Receptor Responder Research Articles

TMET-33. INVESTIGATING THE ROLE OF CHEMERIN SIGNALING IN GLIOBLASTOMA

Abstract Glioblastoma multiforme (GBM) is one of the most common and lethal primary brain tumors in adults. Despite clinical efforts, patient prognosis remains poor with a median survival of approximately 14 months. Thus, identification of novel treatment avenues is needed. Metabolic rewiring is a hallmark of cancer and lipid homeostasis has an increasingly appreciated role in cancer cell survival. It has been shown that the disruption of lipid metabolic balance can lead to lipotoxicity, creating a new avenue in GBM treatment. Therefore, identifying methods to disrupt said lipid metabolic balance in GBM could provide a needed foothold. Previous studies from the lab have identified chemerin, a multifunctional adipokine encoded by the retinoic acid receptor responder 2 (RARRES2) gene, as an important and targetable lipid metabolism modulator in Clear cell renal cell carcinoma (ccRCC). Chemerin has also been implicated in the mesenchymal-phenotype promoting network between GBM cells and tumor-associated macrophages. Given similarities in GBM and ccRCC lipid metabolism and the existing role of chemerin in the tumor immune microenvironment in GBM, we hypothesize that chemerin drives GBM development by regulating lipid metabolism in addition to immune cell trafficking. This study aims to investigate the role and therapeutic opportunities of altered lipid metabolism in GBM by examining chemerin and its receptors (CMKLR1 and GPR1). Immunocompetent GBM mouse models generated through CRISPR-in utero electroporation (IUE) show that mice bearing RARRES2, CMKLR1, and GPR1 knockout tumors have prolonged survival. In addition, in vitro molecular inhibition of CMKLR1 in both human and murine GBM cell lines results in cell death. Ongoing studies involving in vitro CRISPR knockouts of RARRES2, CMKLR1, and GPR1 aim to elucidate the mechanisms by which in vivo inhibition of chemerin signaling results in slower tumor progression.

Plasma proteome and incident myocardial infarction: sex-specific differences.

Few population-based cohort studies, including both men and women, have explored circulating proteins associated with incident myocardial infarction (MI). This study investigated the relationships between circulating cardiometabolic-related proteins and MI risk using cohort-based and Mendelian randomization (MR) analyses and explored potential sex-specific differences. The discovery cohort included 11 751 Swedish adults (55-93 years). Data on 259 proteins assessed with Olink proximity extension assays, biochemical, and questionnaire-based information were used. Participants were followed up for incident MI and death over 8 years through linkage to Swedish registers. Replication analyses were conducted on the UK Biobank sample (n = 51 613). In MR analyses, index cis-genetic variants strongly related to the proteins were used as instrumental variables. Genetic association summary statistic data for MI were obtained from the CARDIoGRAMplusC4D consortium and FinnGen. Forty-five proteins were associated with incident MI in discovery and replication samples following adjustment for potential confounders and multiple testing. In the secondary analysis, 13 of the protein associations were sex-specific, with most associations identified among women. In MR analysis, genetically predicted higher levels of renin, follistatin, and retinoic acid receptor responder protein 2 were linked to an increased risk of MI. Tissue factor pathway inhibitor, tumor necrosis factor receptors 1 and 2, placenta growth factor had an inverse association with MI. This study identified both new and confirmed previously established associations between circulating proteins and incident MI and, for the first time, suggested sex-specific patterns in multiple protein-MI associations.

Preventing MMP23-mediated cleavage of podocyte RARRES1: a novel strategy to halt chronic kidney disease progression?

Glomerular issues and affected podocytes are at the origin of 80% of chronic kidney disease cases. Thus, acquiring a deeper understanding in this domain is necessary to halt progressive kidney damage. In this study, the authors investigated the harmful impact of podocyte-cleaved soluble retinoic acid receptor responder protein-1 on podocytes and proximal tubular cells and identified matrix metalloprotease 23 as the enzyme responsible for cleaving retinoic acid receptor responder protein-1. These findings provide new insights into chronic kidney disease progression, suggesting innovative treatment avenues.

#972 A Novel Single Compound from Chinese Herbs as a Potential Candidate for Reducing obesity induced diabetic nephropathy via ATF3-RARRES1 axis pathway

Abstract Background and Aims Billions of people have obesity induced diabetic nephropathy. Promoting the browning of white adipose tissue has been suggested as a potential strategy for, but a drug still needs to be identified. Method First, WT and ATF3 knockout mice fed a high-fat diet were treated with STZ to determine that ATF3 plays an important role in obesity-induced diabetic nephropathy. Second, DBA mice fed a high-fat diet were infused with STZ, and db/db KO mice were fed a high-fat diet, and the two mouse models were injected intraperitoneally with or without the ATF3 inducer ST32da (the structure is a single drug designed based on the traditional Chinese medicine Salvia miltiorrhiza). After about one and a half months, all related kidneys function values were measured. Results After analysis the relationship between ATF3 and diabetic nephropathy in human GEO DataSet Browser indicated that the gene expression of ATF3 was lower in patients groups. Genetic deletion of activating transcription factor 3 (ATF3−/−) in mice under a high-fat diet (HFD) and STZ treatment resulted in more aggravated nephropathy phenomenon syndrome including higher urine albumin, lower creatinine clearance and high risk in death. ST32da, a synthetic ATF3 inducer isolated from Salvia miltiorrhiza, promoted ATF3 expression to downregulate inflammatory genes and ameliorated foot process effacement resulting in reduced diabetic nephropathy by suppressing the podocyte apoptosis via interleukin (IL)-6 and retinoic acid receptor responder protein 1 (RARRES1) axis. Conclusion Our study identified the ATF3 inducer ST32da and Salvia miltiorrhiza extraction, may as a promising therapeutic drug for treating diet-induced obesity induced diabetic nephropathy.

Podocyte-derived soluble RARRES1 drives kidney disease progression through direct podocyte and proximal tubular injury

Retinoic acid receptor responder protein-1 (RARRES1) is a podocyte-enriched transmembrane protein whose increased expression correlates with human glomerular disease progression. RARRES1 promotes podocytopenia and glomerulosclerosis via p53-mediated podocyte apoptosis. Importantly, the cytopathic actions of RARRES1 are entirely dependent on its proteolytic cleavage into a soluble protein (sRARRES1) and subsequent podocyte uptake by endocytosis, as a cleavage mutant RARRES1 exerted no effects invitro or invivo. As RARRES1 expression is upregulated in human glomerular diseases, here we investigated the functional consequence of podocyte-specific overexpression of RARRES1 in mice in the experimental focal segmental glomerulosclerosis and diabetic kidney disease. We also examined the effects of long-term RARRES1 overexpression on slowly developing aging-induced kidney injury. As anticipated, the induction of podocyte overexpression of RARRES1 (Pod-RARRES1WT) significantly worsened glomerular injuries and worsened kidney function in all three models, while overexpression of RARRES1 cleavage mutant (Pod-RARRES1MT) did not. Remarkably, direct uptake of sRARRES1 was also seen in proximal tubules of injured Pod-RARRES1WT mice and associated with exacerbated tubular injuries, vacuolation, and lipid accumulation. Single-cell RNA sequence analysis of mouse kidneys demonstrated RARRES1 led to a marked deregulation of lipid metabolism in proximal tubule subsets. We further identified matrix metalloproteinase 23 (MMP23) as a highly podocyte-specific metalloproteinase and responsible for RARRES1 cleavage in disease settings, as adeno-associated virus 9-mediated knockdown of MMP23 abrogated sRARRES1 uptake in tubular cells invivo. Thus, our study delineates a previously unrecognized mechanism by which a podocyte-derived protein directly facilitates podocyte and tubular injury in glomerular diseases and suggests that podocyte-specific functions of RARRES1 and MMP23 may be targeted to ameliorate glomerular disease progression invivo.

Genes involved in metastasis in oral squamous cell carcinoma: A systematic review.

Oral squamous cell carcinoma is the most prevalent malignancy in the oral cavity, with a significant mortality rate. In oral squamous cell carcinoma patients, the survival rate could decrease because of delayed diagnosis. Thus, prevention, early diagnosis, and appropriate treatment can effectively increase the survival rate in patients. In this systematic review, we discussed the role of different genes in oral squamous cell carcinoma metastasis. Herein, we aimed to summarize clinical results, regarding the potential genes that promote oral squamous cell carcinoma metastasis. This systematic review was carried out under the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. An electronic search for all relevant articles published in English between January 2018 and April 2022 was performed using Scopus, PubMed, and Google Scholar search engines. All original studies published in English were included, and we excluded studies that were in a non-English language. A total of 4682 articles were found, of which 14 were relevant and detected significant genes in oral squamous cell carcinoma progression. These findings investigated the overexpression of interferon-induced proteins with tetratricopeptide repeats 1 and 3 (IFIT1, IFT3), high-mobility group A2 (HMGA2), transformed growth factor-beta-induced, lectin galactoside-binding soluble 3 binding protein (LGALS3BP), bromodomain containing 4, COP9 signaling complex 6, heterogeneous nuclear ribonucleoproteins A2B1 (HNRNPA2B1), 5'-3' exoribonuclease 2 (XRN2), cystatin-A (CSTA), fibroblast growth factors 8 (FGF8), forkhead box P3, cadherin-3, also known as P-cadherin and Wnt family member 5A, ubiquitin-specific-processing protease 7, and retinoic acid receptor responder protein 2 genes lead to promote metastasis in oral squamous cell carcinoma. Overexpression of some genes (IFIT1, 3, LGALS3BP, HMGA2, HNRNPA2B1, XRN2, CSTA, and FGF8) was proven to be correlated with poor survival rates in oral squamous cell carcinoma patients. Studies suggest that metastatic genes indicate a poor prognosis for oral squamous cell carcinoma patients. Detecting these metastatic genes in oral squamous cell carcinoma patients may be of predictive value and can also facilitate assessing oral squamous cell carcinoma development and its response to treatment.

Proteomic associations with forced expiratory volume: a Mendelian randomisation study

BackgroundA decline in forced expiratory volume (FEV1) is a hallmark of respiratory diseases that are an important cause of morbidity among the elderly. While some data exist on biomarkers that are related to FEV1, we sought to do a systematic analysis of causal relations of biomarkers with FEV1.MethodsData from the population-based AGES-Reykjavik study were used. Serum proteomic measurements were done using 4782 DNA aptamers (SOMAmers). Data from 1479 participants with spirometric data were used to assess the association of SOMAmer measurements with FEV1 using linear regression. Bi-directional two-sample Mendelian randomisation (MR) analyses were done to assess causal relations of observationally associated SOMAmers with FEV1, using genotype and SOMAmer data from 5368 AGES-Reykjavik participants and genetic associations with FEV1 from a publicly available GWAS (n = 400,102).ResultsIn observational analyses, 530 SOMAmers were associated with FEV1 after multiple testing adjustment (FDR < 0.05). The most significant were Retinoic Acid Receptor Responder 2 (RARRES2), R-Spondin 4 (RSPO4) and Alkaline Phosphatase, Placental Like 2 (ALPPL2). Of the 257 SOMAmers with genetic instruments available, eight were associated with FEV1 in MR analyses. Three were directionally consistent with the observational estimate, Thrombospondin 2 (THBS2), Endoplasmic Reticulum Oxidoreductase 1 Beta (ERO1B) and Apolipoprotein M (APOM). THBS2 was further supported by a colocalization analysis. Analyses in the reverse direction, testing whether changes in SOMAmer levels were caused by changes in FEV1, were performed but no significant associations were found after multiple testing adjustments.ConclusionsIn summary, this large scale proteogenomic analyses of FEV1 reveals circulating protein markers of FEV1, as well as several proteins with potential causality to lung function.

Chronic noise exposure induces Alzheimer's disease-like neuropathology and cognitive impairment via ferroptosis in rat hippocampus.

Chronic noise exposure poses a remarkable public health concern, drawing attention to its impacts on the brain. Ferroptosis is involved in several brain-related diseases. However, the role of ferroptosis in the effects of chronic noise on the brain remains elusive. This study aimed to investigate the effects of chronic noise exposure on the brain and elucidate the underlying mechanisms. A chronic noise-induced cognitive impairment model in rats was constructed and validated. The pathological state and ferroptosis level of the rat hippocampus were determined using Western blotting and immunohistochemistry. Bioinformatics was employed to investigate the interrelationship between chronic noise exposure and genes. Genetic relationships were analyzed using Mendelian randomization (MR) analysis. Cytoscape was employed for the prediction of upstream molecular and drug targets. In vivo experiments revealed that chronic noise exposure could induce Alzheimer's disease (AD)-like neuropathological changes in rat hippocampus and cognitive impairment. Moreover, protein markers indicative of ferroptosis and levels of lipid peroxidation were quantified to elucidate underlying mechanisms. Thereafter, oxidative stress- and ferroptosis-related differentially expressed genes (DEGs) underwent functional enrichment and PPI network analyses. Additionally, 8 genes with diagnostic significance were identified. In MR analysis, retinoic acid receptor responder 2 (Rarres2) gene exhibited a negative genetic relationship with AD. Chronic noise exposure could induce AD-like neuropathological changes and cognitive impairment via ferroptosis. The results of MR analysis indicated that Rarres2 gene may act as a protective factor in AD. This gene may be upstream of ferroptosis and serve as a target for the prevention and treatment of chronic noise-induced cognitive impairment.

Association of RARRES2 rs17173608 gene polymorphism and serum Chemerin with acute myocardial infarction and its risk factors: A case-control study in an Iranian population

ObjectiveThe adipokine Chemerin and the retinoic acid receptor responder 2 (RARRES2) gene have been associated with an increased incidence of obesity, insulin resistance, endothelial dysfunction, type 2 diabetes mellitus, and coronary artery disease. The impact of RARRES2 rs17173608 gene polymorphism on acute myocardial infarction and Chemerin levels has not yet been entirely elucidated. This study aimed to assess the association of RARRES2 rs17173608 gene polymorphism and serum Chemerin with acute myocardial infarction (AMI) and its risk factors in an Iranian population. MethodsIn this case-control study, 134 AMI patients and 100 healthy controls were recruited from tertiary referral hospitals in Zanjan, Iran. Whole blood samples were collected for DNA extraction and Chemerin level determination. An enzyme-linked immunosorbent assay was used to quantify plasma levels of Chemerin. Tetra‐primer amplification refractory mutation system‐polymerase chain reaction and agarose gel electrophoresis techniques were used to detect gene polymorphism of Chemerin rs17173608 from DNA samples. ResultsSerum Chemerin levels were higher in the control group than in the AMI group. However, after adjusting for age, sex, and other risk factors, there was no significant association between serum Chemerin level and AMI occurrence. In the genotype analysis, 21.6% of patients had the TT genotype, and 78.4% had the TG genotype. The GG genotype was not detected in any patient. The genotype distribution of the healthy control group was 19.0% TT genotype, 80.0% TG genotype, and 1.0% GG genotype. Serum Chemerin levels in participants with TG genotype were statistically different between case and control groups. ConclusionSerum Chemerin levels and RARRES2 rs17173608 gene polymorphism were not correlated with AMI occurrence after adjusting for AMI risk factors in Iranian patients. More research with a larger sample size and diverse ethnicities is needed to corroborate our findings.

Using proteomics and metabolomics to identify therapeutic targets for senescence mediated cancer: genetic complementarity method.

Senescence have emerged as potential factors of lung cancer risk based on findings from many studies. However, the underlying pathogenesis of lung cancer caused by senescence is not clear. In this study, we try to explain the potential pathogenesis between senescence and lung cancer through proteomics and metabonomics. And try to find new potential therapeutic targets in lung cancer patients through network mendelian randomization (MR). The genome-wide association data of this study was mainly obtained from a meta-analysis and the Transdisciplinary Research in Cancer of the Lung Consortium (TRICL), respectively.And in this study, we mainly used genetic complementarity methods to explore the susceptibility of aging to lung cancer. Additionally, a mediation analysis was performed to explore the potential mediating role of proteomics and metabonomics, using a network MR design. GNOVA analysis revealed a shared genetic structure between HannumAge and lung cancer with a significant genetic correlation estimated at 0.141 and 0.135, respectively. MR analysis showed a relationship between HannumAge and lung cancer, regardless of smoking status. Furthermore, genetically predicted HannumAge was consistently associated with the proteins C-type lectin domain family 4 member D (CLEC4D) and Retinoic acid receptor responder protein 1 (RARR-1), indicating their potential role as mediators in the causal pathway. HannumAge acceleration may increase the risk of lung cancer, some of which may be mediated by CLEC4D and RARR-1, suggestion that CLEC4D and RARR-1 may serve as potential drug targets for the treatment of lung cancer.

RARRES2 regulates lipid metabolic reprogramming to mediate the development of brain metastasis in triple negative breast cancer

BackgroundTriple negative breast cancer (TNBC), the most aggressive subtype of breast cancer, is characterized by a high incidence of brain metastasis (BrM) and a poor prognosis. As the most lethal form of breast cancer, BrM remains a major clinical challenge due to its rising incidence and lack of effective treatment strategies. Recent evidence suggested a potential role of lipid metabolic reprogramming in breast cancer brain metastasis (BCBrM), but the underlying mechanisms are far from being fully elucidated.MethodsThrough analysis of BCBrM transcriptome data from mice and patients, and immunohistochemical validation on patient tissues, we identified and verified the specific down-regulation of retinoic acid receptor responder 2 (RARRES2), a multifunctional adipokine and chemokine, in BrM of TNBC. We investigated the effect of aberrant RARRES2 expression of BrM in both in vitro and in vivo studies. Key signaling pathway components were evaluated using multi-omics approaches. Lipidomics were performed to elucidate the regulation of lipid metabolic reprogramming of RARRES2.ResultsWe found that down-regulation of RARRES2 is specifically associated with BCBrM, and that RARRES2 deficiency promoted BCBrM through lipid metabolic reprogramming. Mechanistically, reduced expression of RARRES2 in brain metastatic potential TNBC cells resulted in increased levels of glycerophospholipid and decreased levels of triacylglycerols by regulating phosphatase and tensin homologue (PTEN)-mammalian target of rapamycin (mTOR)-sterol regulatory element-binding protein 1 (SREBP1) signaling pathway to facilitate the survival of breast cancer cells in the unique brain microenvironment.ConclusionsOur work uncovers an essential role of RARRES2 in linking lipid metabolic reprogramming and the development of BrM. RARRES2-dependent metabolic functions may serve as potential biomarkers or therapeutic targets for BCBrM.

Chemerin is resident to vascular tunicas and contributes to vascular tone.

The adipokine chemerin may support blood pressure, evidenced by a fall in mean arterial pressure after whole body antisense oligonucleotide (ASO)-mediated knockdown of chemerin protein in rat models of normal and elevated blood pressure. Although the liver is the greatest contributor of circulating chemerin, liver-specific ASOs that abolished hepatic-derived chemerin did not change blood pressure. Thus, other sites must produce the chemerin that supports blood pressure. We hypothesize that the vasculature is a source of chemerin independent of the liver that supports arterial tone. RNAScope, PCR, Western blot analyses, ASOs, isometric contractility, and radiotelemetry were used in the Dahl salt-sensitive (SS) rat (male and female) on a normal diet. Retinoic acid receptor responder 2 (Rarres2) mRNA was detected in the smooth muscle, adventitia, and perivascular adipose tissue of the thoracic aorta. Chemerin protein was detected immunohistochemically in the endothelium, smooth muscle cells, adventitia, and perivascular adipose tissue. Chemerin colocalized with the vascular smooth muscle marker α-actin and the adipocyte marker perilipin. Importantly, chemerin protein in the thoracic aorta was not reduced when liver-derived chemerin was abolished by a liver-specific ASO against chemerin. Chemerin protein was similarly absent in arteries from a newly created global chemerin knockout in Dahl SS rats. Inhibition of the receptor Chemerin1 by the receptor antagonist CCX832 resulted in the loss of vascular tone that supports potential contributions of chemerin by both perivascular adipose tissue and the media. These data suggest that vessel-derived chemerin may support vascular tone locally through constitutive activation of Chemerin1. This posits chemerin as a potential therapeutic target in blood pressure regulation.NEW & NOTEWORTHY Vascular tunicas synthesizing chemerin is a new finding. Vascular chemerin is independent of hepatic-derived chemerin. Vasculature from both males and females have resident chemerin. Chemerin1 receptor activity supports vascular tone.

RARRES2 is Downregulated in Isocitrate Dehydrogenase 1 Mutant Glioma Patients and Served as an Unfavorable Prognostic Factor of Glioma

Mutations in isocitrate dehydrogenase 1 (IDH1) induce extensive transcriptional alterations to promote glioma development. However, IDH1 mutation contributes the better clinical outcomes of glioma. Further understanding the transcriptional and DNA methylation changes mediated by IDH1 mutation will provide new therapeutic targets for glioma. Public glioma cohorts were collected and processed using R software. The transcriptional changes mediated by IDH1 mutation were determined and presented using heatmap. The differentially expressed genes in IDH1 mutant glioma were overlapped using TBtools. The prognostic effects of IDH1 regulated genes were determined by Kaplan-Meier survival analysis. Retinoic acid receptor responder 2 (RARRES2) was upregulated in IDH1 wild type lower-grade glioma (LGG) patients, and higher expression levels of RARRES2 were associated with worse clinical outcomes of LGG. Moreover, IDH1 wild type LGG patients with higher expression levels of RARRES2 had even worse overall survival. Compared with LGG, RARRES2 was upregulated in grade IV glioma (glioblastoma multiforme, GBM). Also, RARRES2 represented an unfavorable prognostic factor of glioma. In GBM, RARRES2 was also associated with IDH1 mutation. In both LGG and GBM, IDH1 mutation induced extensive DNA hypermethylation, and more than half genes that were downregulated in IDH1 mutant glioma were contributed by DNA hypermethylation. RARRES2 was also hypermethylated in IDH1 mutant LGG or GBM patients. Furthermore, RARRES2 hypomethylation was an unfavorable prognostic factor in patients with LGG. RARRES2 was downregulated by IDH1 mutation and served as an unfavorable prognostic factor in glioma.

Abstract 5139: Chemerin suppresses prostate tumor growth by modulating the recruitment of NK and CD8+ T-cells to tumor microenvironment

Abstract Infiltration of immune cells into the tumor microenvironment (TME) can regulate growth and survival of malignant cells, thereby affecting tumorigenesis and tumor progression. While immune checkpoint inhibitors and agonism of costimulatory molecules can act to stimulate leukocytes, the lack of adequate recruitment of effector cells into TME often results in suboptimal immune responses. Chemerin (retinoic acid receptor responder 2, RARRES2) is an endogenous chemoattractant that is widely expressed by many tissues and recruits innate leukocytes through its receptor, CMKLR1 which is expressed on NK cells, some dendritic cells, and macrophages. Previous studies show that RARRES2 is downregulated across multiple tumor types including prostate cancer. Here, using a syngeneic transgenic adenocarcinoma mouse prostate (TRAMP-C1) model, we show that forced overexpression of RARRES2 by tumor cells results in significant tumor suppression and recruitment of NK and CD8+ T-cells within the TME. Male C57/BL/6 mice were inoculated with either RARRES2-overexpressing, vector control (VC) or mixed (50:50; VC: RARRES2) TRAMP-C1 cells. Chemerin overexpression in TRAMP-C1 cells did not alter their phenotypic behavior in vitro, but significantly suppressed tumor growth in vivo in mice. Furthermore, we observed a significantly higher influx of NK (CD3-CD19-NK1.1+) and CD8+ T-cells (CD3+CD8+) in tumor-infiltrating leukocytes (TILs) from mice with mixed tumors compared with VC tumors. Depletion of NK cells, CD4+, or CD8+ T cells showed that NK cells and CD8+ T-cells, but not CD4+ T-cells, were required for chemerin-dependent suppression of TRAMP-C1 tumor growth. We found significant increases in splenic NK and CD8 T cells, and a concomitant significant decrease in splenic G-MDSC in mice with chemerin-expressing tumors compared to controls, suggesting chemerin expression within the TME has an effect on systemic immune responses. Treatment of control tumors with anti-PD1 checkpoint inhibition did not result in significant tumor suppression, while anti-PD1 treatment of chemerin-expressing tumors significantly reduced tumor growth, doubling the complete response rate in these unresponsive tumors. Thus, for the first time we have demonstrated that increasing chemerin expression within the prostate TME can suppress growth by augmenting recruitment of NK and CD8+ T-cells and has the potential to be combined with checkpoint inhibitors in order to improve response rates in non-responsive tumors. Overall, these data suggest that a tumor-targeted chemerin therapeutic may have potential to treat human prostate cancers. Citation Format: Muhammad A. Saeed, Kevin Kim, Russell K. Pachynski. Chemerin suppresses prostate tumor growth by modulating the recruitment of NK and CD8+ T-cells to tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5139.

Phospholipase A and acyltransferase 4/retinoic acid receptor responder 3 at the intersection of tumor suppression and pathogen restriction.

Phospholipase A and acyltransferase (PLAAT) 4 is a class II tumor suppressor with phospholipid metabolizing abilities. It was characterized in late 2000s, and has since been referred to as 'tazarotene-induced gene 3' (TIG3) or 'retinoic acid receptor responder 3' (RARRES3) as a key downstream effector of retinoic acid signaling. Two decades of research have revealed the complexity of its function and regulatory roles in suppressing tumorigenesis. However, more recent findings have also identified PLAAT4 as a key anti-microbial effector enzyme acting downstream of interferon regulatory factor 1 (IRF1) and interferons (IFNs), favoring protection from virus and parasite infections. Unveiling the molecular mechanisms underlying its action may thus open new therapeutic avenues for the treatment of both cancer and infectious diseases. Herein, we aim to summarize a brief history of PLAAT4 discovery, its transcriptional regulation, and the potential mechanisms in tumor prevention and anti-pathogen defense, and discuss potential future directions of PLAAT4 research toward the development of therapeutic approaches targeting this enzyme with pleiotropic functions.

Astragalus polysaccharide alleviates angiotensin II-induced glomerular podocyte dysfunction by inhibiting the expression of RARRES1 and LCN2.

Podocyte loss is a predictor of kidney disease development, including diabetic nephropathy. Astragalus polysaccharide (APS) was considered a renoprotective drug, whereas the mechanisms operated by APS on podocyte dysfunction are rarely mentioned. This study aims at the mechanistic underlying of APS on angiotensin II (Ang II)-induced podocyte dysfunction. Mouse glomerular podocytes MPC5 were induced with Ang II, the morphologic changes were observed and nephrin, desmin and Wilms' tumour protein-1 (WT-1) levels were determined. The MPC5 cells were treated with APS (50, 100 and 200 μg/mL) and transduced with retinoic acid receptor responder protein 1 (RARRES1) overexpression vectors. The expression of RARRES1, lipocalin-2 (LCN2), nephrin and desmin was tested, MPC5 cell viability and apoptosis were evaluated, and the levels of an endocytotic receptor megalin, Bcl-2, Bax, interleukin (IL)-6, IL-1β and tumour necrosis factor (TNF)-α were assessed. The binding of RARRES1 to LCN2 was predicted and verified. Mice were infused with Ang II to evaluate histopathological alterations and 24-h urinary albumin content. Ang II induction suppressed MPC5 cell viability, reduced the expression of nephrin, WT-1, megalin and Bcl-2, and augmented the expression of desmin, Bax, IL-6, IL-1β and TNF-α, which were significantly nullified by APS treatment. RARRES1 interacted with LCN2, and APS treatment inhibited RARRES1 and LCN2 expression in a dose-dependent manner, thereby alleviating Ang II-induced podocyte dysfunction. Ang II infusion in mice facilitated pathological alterations in renal tissues and increased urinary albumin content, which were attenuated after APS treatment. Overall, APS treatment alleviated Ang II-induced podocyte dysfunction by inhibiting RARRES1/LCN2 expression and blocked kidney injury development in vivo.

Alternative splicing is not a key source of chemerin isoforms diversity

BackgroundChemerin is a chemoattractant protein with adipokine and antimicrobial properties encoded by the retinoic acid receptor responder 2 (RARRES2) gene. Chemerin bioactivity largely depends on carboxyl-terminal proteolytic processing that generates chemerin isoforms with different chemotactic, regulatory, and antimicrobial potentials. While these mechanisms are relatively well known, the role of alternative splicing in generating isoform diversity remains obscure.Methods and resultsUsing rapid amplification of cDNA ends (RACE) PCR, we determined RARRES2 transcript variants present in mouse and human tissues and identified novel transcript variant 4 of mouse Rarres2 encoding mChem153K. Moreover, analyses of real-time quantitative PCR (RT-qPCR) and publicly-available next-generation RNA sequencing (RNA-seq) datasets showed that different alternatively spliced variants of mouse Rarres2 are present in mouse tissues and their expression patterns were unaffected by inflammatory and infectious stimuli except brown adipose tissue. However, only one transcript variant of human RARRES2 was present in liver and adipose tissue.ConclusionOur findings indicate a limited role for alternative splicing in generating chemerin isoform diversity under all tested conditions.

Methyltransferase 3A-mediated promoter methylation represses retinoic acid receptor responder 3 expression in basal-like breast cancer

Retinoic acid receptor responder 3 (RARRES3) has been characterized as a tumor suppressor in multiple types of cancer. This study aimed to examine the expression profile of RARRES3 across the PAM50 subtypes of breast cancer. The DNA methylation status of RARRES3 was checked in the basal-like subtype, and the underlying mechanisms of its dysregulation were explored. RNA-sequencing (seq) and methylation data from The Cancer Genome Atlas were used for in-silico analysis. Basal-like representative SUM149 and MDA-MB-468 cell lines were used for in vitro and in vivo studies. Compared to tumor-adjacent normal tissues, only the basal-like tumor tissues had significantly downregulated RARRES3 expression. The methylation level of four CpG sites in the promoter region showed a strong negative correlation with RARRES3 expression. The gene coding for DNA methyltransferase 3A (DNMT3A) had consistent positive correlations with the methylation of the CpG sites. Chromatin Immunoprecipitation-quantitative polymerase chain-reaction and bisulfite sequencing PCR showed that DNMT3A could bind to the promoter region of RARRES3 and promote methylation of the CpG sites within the region. DNMT3A knockdown significantly restored RARRES3 expression at the mRNA and protein level in the two cell lines. CCK-8, colony formation, and flow cytometric analysis showed that RARRES3 overexpression attenuated the growth-promoting effects of DNMT3A overexpression and also weakened the DNMT3A overexpression-induced activation of ERK1/2 and PI3K/AKT signaling. In summary, this study revealed that DNMT3A enhances promoter methylation of the RARRES3 gene and suppresses its transcription in basal-like breast cancer. The DNMT3A-RARRES3 signaling pathway might be a potential target for the treatment of this tumor subtype.

Retinoic acid receptor responder protein 2 and intelectin-1 in visceral adipose tissue from pregnant women with gestational diabetes mellitus

Introduction: The adipose tissue secretes chemerin and omentin related to metabolic diseases. It has been reported that both proteins encoded by retinoic acid receptor responder protein 2 (RARRES2) and intelectin-1 (ITLN1) genes, respectively, are abnormally expressed in gestational diabetes mellitus (GDM). Aim: To evaluate the expression of these genes in visceral adipose tissue in pregnant women with GDM. Methods: Descriptive cross-sectional study, with two groups, (A) GDM and (B) control group (pregnant women without GDM). Body mass index (BMI), blood pressure, lipids, and glucose were measured. RARRES2 and ITLN1 mRNA expression were evaluated using quantitative real-time Reverse transcription-polymerase chain reaction using TaqMan probes. Statistical analysis was performed using Kolmogórov–Smirnov, Pearson-Spearman correlation, Kruskal–Wallis tests, and R language with Shapiro–Wilk, SPSS V21.0. Results: Sixty-six women were included. Women with normal weight were more frequent in the control group (33.3%) than GDM (15.2%); overweight was similar in both groups (45.5%), and obesity was less common in the control group (21.2%) than GDM (39.3%). No differential expression of RARRES2 and ITLN1 genes among cases and controls were found, but RARRES2 expression differed (P = 0.016) between normal-weight and overweight women in the control group, and ITLN1 expression significantly differed (P = 0.002) between overweight and obese women in the GDM group. Conclusions: ITLN1 could have a role in the GDM severity based on the BMI of the patients.

Interferon-α2b-Induced RARRES3 Upregulation Inhibits Hypertrophic Scar Fibroblasts' Proliferation and Migration Through Wnt/β-Catenin Pathway Suppression

Hypertrophic scar (HS) is a severe skin fibrotic disorder with unclear pathogenesis. Interferon-α2b (IFN-α2b) exerts inhibitory effects on HS in vivo and in vitro; however, the exact mechanism remains unclear. In this study, we aimed to evaluate the inhibitory effects of IFN-α2b on hypertrophic scar fibroblasts' (HSFs) proliferation and migration, and to further investigate the associated molecular mechanism. Cell Counting Kit-8 and CyQUANT assays were used to assess HSFs' proliferation; wound healing and Transwell assays were used to assess HSFs' migration; real-time quantitative polymerase chain reaction and Western blotting were used to detect messenger RNA and protein levels, respectively, of related genes; bioinformatics analysis was performed to predict the downstream target of IFN-α2b. Our findings are as follows: (1) IFN-α2b inhibited HSFs' proliferation and migration in a dose-dependent manner. (2) IFN-α2b inhibited HSFs' proliferation and migration by suppressing the Wnt/β-catenin pathway. (3) Retinoic-acid receptor responder 3 (RARRES3) was predicted as a functional downstream molecule of IFN-α2b, which was low in HSFs. (4) IFN-α2b inhibited HSF phenotypes and the Wnt/β-catenin pathway by upregulating RARRES3 expression. (5) RARRES3 restrained HSFs' proliferation and migration by repressing the Wnt/β-catenin pathway. In conclusion, IFN-α2b-induced RARRES3 upregulation inhibited HSFs' proliferation and migration through Wnt/β-catenin pathway suppression.