acyl-CoA:cholesterol Acyltransferase Research Articles

25-hydroxycholesterol inhibits classical swine fever virus entry into porcine alveolar macrophages by depleting plasma membrane cholesterol

Classical swine fever virus (CSFV) is an enveloped positive-sense RNA virus belonging to the Flaviviridae family. The virus utilizes cellular lipids and manipulates host lipid metabolism to ensure its replication, especially during virus invasion and replication steps. Therefore, identification of the molecular lipid metabolism pathways that are suitable targets is critical for the development of anti-CSFV therapeutics. In this study, we screened the anti-CSFV activity of 12 compounds targeting synthesis of cholesterol and fatty acids, cholesterol esters, and cholesterol transport. We found that 25-hydroxycholesterol (25HC), a regulator of cholesterol metabolism and transport, has potent anti-CSFV activity. Mechanistically, we showed that 25HC inhibited CSFV proliferation by blocking the entry of virions into porcine alveolar macrophages (3D4/21) by decreasing cholesterol abundance in the plasma membrane through activation of acyl-CoA:cholesterol acyltransferase (ACAT). Finally, we revealed that cholesterol 25-hydroxylase (CH25H), a redox enzyme that mediates 25HC production, also restricted CSFV infection via both enzyme activity-dependent and -independent mechanisms. Collectively, our results shed light on the mechanisms by which 25HC inhibits CSFV entry into cells and suggests a potential new therapeutic method against CSFV infection.

Morphological predictors of the efficacy of mitotane therapy in adrenocortical cancer

Adrenocortical cancer (ACC) is an orphan malignant tumor of the adrenal cortex with a predominantly poor prognosis and an aggressive clinical course. Nowadays, mitotane is a non-alternative drug in the treatment of ACC. The search for prognostic parameters that determine the sensitivity of ACC to ongoing treatment is currently an urgent task. Expression levels of the large subunit of ribonucleotide reductase M1 (RRM1), cytochrome P450 2W1 (CYP2W1), and sterol- O-acyltransferase-1 (SOAT1) are considered as potential predictors of response to mitotane therapy. To assess the immunohistochemical expression of RRM1, CYP2W1 and SOAT1 in ACC as markers of clinical outcomes and response to the therapy with mitotane. The study included 62 patients older than 17 years of age with a diagnosis of ACC confirmed histologically and immunohistochemically. Mitotane therapy was initiated in 29 patients in the postoperative period, 33 patients were under dynamic observation without concomitant drug treatment. Antibodies to RRM1, CYP2W1, SOAT1 were used diluted in accordance with recommendations of firms-manufacturers for immunohistochemical detection. In the group of patients with low and moderate RRM1, CYP2W1 and SOAT1 immunoreactivity in the tumor and no antitumor therapy, a better DFS was noted (p=0.037, p=0.020 and p=0.001, respectively) compared to the group of patients receiving mitotane therapy at this level of marker expression. With high immunoreactivity of the markers, no statistically significant differences in DFS were found. Consistent with the findings in our study, low expression of RRM1, CYP2W1 and SOAT1 was associated with worse DFS with antitumor therapy. The results of the work indicate the need to assess the levels of immunoreactivity of these markers in patients with ACC before starting treatment with mitotane in order to predict the efficiency of therapy.

A pan-cancer analysis identifies SOAT1 as an immunological and prognostic biomarker.

Sterol o-acyltransferase1 (SOAT1) is an enzyme that regulates lipid metabolism. Nevertheless, the predictive value of SOAT1 regarding immune responses in cancer is not fully understood. Herein, we aimed to expound the predictive value and the potential biological functions of SOAT1 in pan-cancer. Raw data related to SOAT1 expression in 33 different types of cancer were acquired from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. SOAT1 expression was significantly increased in most cancers and showed a distinct correlation with prognosis. This enhanced expression of the SOAT1 gene was confirmed by evaluating SOAT1 protein expression using tissue microarrays. In addition, we found significant positive associations between SOAT1 expression levels and infiltrating immune cells, including T cells, neutrophils, and macrophages. Moreover, the co-expression analysis between SOAT1 and immune genes showed that many immune-related genes were increased with enhanced SOAT1 expression. A gene set enrichment analysis (GSEA) revealed that the expression of SOAT1 correlated with the tumor microenvironment, adaptive immune response, interferon signaling, and cytokine signaling. These findings indicate that SOAT1 is a potential candidate marker for predicting prognosis and a promising target for tumor immunotherapy in cancers.

Sevoflurane attenuates proliferative and migratory activity of lung cancer cells via mediating the microRNA-100-3p/sterol O-Acyltransferase 1 axis.

Recently, evidence has shown that microRNA-100-3p (miR-100-3p) has been revealed as a tumor suppressor in diverse human diseases, while its capability in lung cancer warrants further validation. In this work, we aimed to discuss the impact of sevoflurane on biological functions of lung cancer cells by modulating the miR-100-3p/sterol O-acyltransferase 1 (SOAT1) axis. Lung cancer cell lines (A549 and H460) were treated with various concentrations of sevoflurane. Cell viability, proliferation, migration, and invasion were evaluated using MTT, colony formation, wound healing, and transwell assays. Moreover, miR-100-3p and SOAT1 expressions were evaluated by reverse transcription-quantitative polymerase chain reaction in lung cancer cells. The target interaction between miR-100-3p and SOAT1 was predicted by bioinformatics analysis and verified by the dual-luciferase reporter gene assay. The findings of our work demonstrated that sevoflurane impeded the abilities on viability, proliferation, migration, and invasion of A549 and H460 cells. The expression of miR-100-3p was reduced, and SOAT1 expression was elevated in lung cancer cells. miR-100-3p targeted SOAT1. Besides, sevoflurane could lead to expressed improvement of miR-100-3p or limitation of SOAT1. Downregulation of miR-100-3p or upregulation of SOAT1 restored the suppression of sevoflurane on abilities of viability, proliferation, migration, and invasion in A549 and H460 cells. In the rescue experiment, downregulation of SOAT1 reversed the impacts of downregulation of miR-100-3p on sevoflurane on lung cancer cells. Collectively, our study provides evidence that sevoflurane restrained the proliferation and invasion in lung cancer cells by modulating the miR-100-3p/SOAT1 axis. This article provides a new idea for further study of the pathogenesis of lung cancer.

Sterol O-Acyltransferase Inhibition Ameliorates High-Fat Diet-Induced Renal Fibrosis and Tertiary Lymphoid Tissue Maturation after Ischemic Reperfusion Injury

Metabolic syndrome is associated with the development of chronic kidney disease (CKD). We previously demonstrated that aged kidneys are prone to developing tertiary lymphoid tissues (TLTs) and sustain inflammation after injury, leading to CKD progression; however, the relationship between renal TLT and metabolic syndrome is unknown. In this study, we demonstrated that a high-fat diet (HFD) promoted renal TLT formation and inflammation via sterol O-acyltransferase (SOAT) 1-dependent mechanism. Mice fed a HFD prior to ischemic reperfusion injury (IRI) exhibited pronounced renal TLT formation and sustained inflammation compared to the controls. Untargeted lipidomics revealed the increased levels of cholesteryl esters (CEs) in aged kidneys with TLT formation after IRI, and, consistently, the Soat1 gene expression increased. Treatment with avasimibe, a SOAT inhibitor, attenuated TLT maturation and renal inflammation in HFD-fed mice subjected to IRI. Our findings suggest the importance of SOAT1-dependent CE accumulation in the pathophysiology of CKDs associated with TLT.

Targeting Sterol O-Acyltransferase/Acyl-CoA:Cholesterol Acyltransferase (ACAT): A Perspective on Small-Molecule Inhibitors and Their Therapeutic Potential.

Sterol O-acyltransferase (SOAT) is a membrane-bound enzyme that aids the esterification of cholesterol and fatty acids to cholesterol esters. SOAT has been studied extensively as a potential drug target, since its inhibition can serve as an alternative to statin therapy. Two SOAT isozymes that have discrete functions in the human body, namely, SOAT1 and SOAT2, have been characterized. Over three decades of research has focused on candidate SOAT1 inhibitors with unsatisfactory results in clinical trials. Recent research has focused on targeting SOAT2 selectively. In this perspective, we summarize the literature covering various SOAT inhibitory agents and discuss the design, structural requirements, and mode of action of SOAT inhibitors.

Phytosterol of lotus seed core powder alleviates hypercholesterolemia by regulating gut microbiota in high-cholesterol diet-induced C57BL/6J mice

The present study aimed to investigate the regulatory mechanisms of lotus seed core powder phytosterol extract (LSP-PE) on hypercholesterolemia and intestinal microbiota in high-cholesterol diet (HCD)-induced C57BL/6 J mice. Gavage with LSP-PE reduced levels of serum total cholesterol (TC), ratio of low-density lipoprotein cholesterol (LDL-C) to high-density lipoprotein cholesterol (HDL-C), hepatic TC, hepatic triglyceride (TG), hepatic LDL-C, hepatic very low-density lipoprotein (VLDL), fecal TC and fecal total bile acid (TBA), while augmented hepatic HDL-C content. In contrast with HCD group, high-dose LSP triggered significant diminutions of serum ALT, serum AST, hepatic ALT and hepatic AST levels in HCD-fed mice, which were 16.49, 28.94, 43.42, and 44.47%, respectively, thus remarkably ameliorating the pathological changes of liver and small intestine. In-depth genetic research found that LSP was effective in down-regulating the expression of cholesterol metabolism related genes including Niemannpick C1-like protein 1 (NPC1L1), acyl-coA cholesterol acyl-transferase 2 (ACAT2), microsomal triglyceride transporter (MTP) and ATP binding cassette subfamily G member 5 (ABCG5). Moreover, LSP-PE could restore the disorder of intestinal flora via augmenting the Actinobacteria abundance as well as decreasing the Firmicutes/Bacteroidetes ratio and abundances of Proteobacteria and Verrucomicrobia to regulate cholesterol metabolism-related genes. In summary, LSP-PE possessed excellent cholesterol-lowering activity by positively regulating the gut microbiota and the expression levels of genes related to cholesterol absorption and metabolism. Therefore, this work suggested LSP phytosterol as a potential supplement to alleviate the symptoms of hypercholesterolemia.

TMET-31. CHOLESTEROL ESTERIFICATION IN A PATIENT WITH DIFFUSE ASTROCYTOMA PROGRESSING TO GLIOBLASTOMA

Abstract Metabolic profiles of diffuse astrocytoma and recurrent tumor tissues were compared in a patient with diffuse astrocytoma who showed tumor recurrence and progressed to glioblastoma (GBM). The patient presented with a diffuse infiltrating tumor and was operated in April 2018. The pathology report showed that the tumor was a diffusely infiltrating astrocytoma with Ki-67 of 5% (WHO Grade II). In addition, the molecular testing results indicated that the tumor was IDH1wt with TERTp mutation and showed an indeterminate MGMT promoter status. Given diffuse brain involvement and IDH1wt status, an aggressive behavior was suggested for this tumor. After ~3.5 years (January 2022), the MRI examination showed tumor recurrence and the patient underwent craniotomy for the resection of the recurrent tumor. The pathology report showed a high-grade glial neoplasm composed of ovoid tumor cells with nuclear pleomorphism (GBM, WHO Grade IV). We collected the tumor specimens from both surgeries and compared the metabolic profiles using 1H NMR spectroscopy. The tumor specimens were extracted using methanol-chloroform (2:1 ratio) extraction-method. The methanol-layer of the recurrent tumor showed decreased levels of N-acetylaspartate (NAA) and myo-inositol, and the elevated levels of phosphocholine (PC) and glycine, compared to the diffuse astrocytoma. Decreased NAA and elevated PC and glycine are metabolic features of high-grade gliomas, suggesting progression of the low-grade astrocytoma to GBM. The chloroform-layers of both tumors showed the presence of cholesterol; however, cholesteryl ester (CE) was detected only in the recurrent tumor (GBM). The ratio of CE to cholesterol was 0.44, suggesting that 44% of cholesterol pool was esterified in GBM. Cholesterol esterification is dysregulated in GBM and targeting this metabolic pathway using AcylCoA:cholesterol acyltransferase (ACAT) inhibitors would be promising in the treatment of GBM and astrocytomas with TERTp mutation which transform to GBM.

Chromosomally Unstable Gastric Cancers Overexpressing Claudin-6 Disclose Cross-Talk between HNF1A and HNF4A, and Upregulated Cholesterol Metabolism.

(1) Abnormally increased expression of claudin-6 in gastric cancer is considered a prognostic marker of the chromosomal unstable molecular subtype. However, a detailed molecular profile analysis of differentially expressed genes and affected pathways associated with claudin-6 increased (Cldn6high) expression has not been assessed. (2) The TCGA Stomach Adenocarcinoma Pan-Cancer Atlas Data was evaluated using Cytoscape's Gene Mania, MCODE, and Cytohubba bioinformatic software. (3) 96.88% of Cldn6high gastric cancer tumors belonging to the chromosomal unstable molecular subtype are associated with a worse prognosis. Cldn6expression coincided with higher mutations in TP53, MIEN1, STARD3, PGAP3, and CCNE1 genes compared to Cldn6low expression. In Cldn6high cancers, 1316 genes were highly expressed. Cholesterol metabolism was the most affected pathway as APOA1, APOA2, APOH, APOC2, APOC3, APOB-100, LDL receptor-related protein 1/2, Sterol O-acyltransferase, STARD3, MAGEA-2, -3, -4, -6, -9B, and -12 genes were overexpressed in Cldn6high gastric cancers; interestingly, APOA2 and MAGEA9b were identified as top hub genes. Functional enrichment of DEGs linked HNF-4α and HNF-1α genes as highly expressed in Cldn6high gastric cancer. (4) Our results suggest that APOA2 and MAGEA9b could be considered as prognostic markers for Cldn6high gastric cancers.

YM750, an ACAT Inhibitor, Acts on Adrenocortical Cells to Inhibit Aldosterone Secretion Due to Depolarization.

Primary aldosteronism (PA) is considered the most common form of secondary hypertension, which is associated with excessive aldosterone secretion in the adrenal cortex. The cause of excessive aldosterone secretion is the induction of aldosterone synthase gene (CYP11B2) expression by depolarization of adrenocortical cells. In this study, we found that YM750, an Acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor, acts on adrenocortical cells to suppress CYP11B2 gene expression and aldosterone secretion. YM750 inhibited the induction of CYP11B2 gene expression by KCl stimulation, but not by angiotensin II and forskolin stimulation. Interestingly, YM750 did not inhibit KCl-stimulated depolarization via an increase in intracellular calcium ion concentration. Moreover, ACAT1 expression was relatively abundant in the zona glomerulosa (ZG) including these CYP11B2-positive cells. Thus, YM750 suppresses CYP11B2 gene expression by suppressing intracellular signaling activated by depolarization. In addition, ACAT1 was suggested to play an important role in steroidogenesis in the ZG. YM750 suppresses CYP11B2 gene expression and aldosterone secretion in the adrenal cortex, suggesting that it may be a potential therapeutic agent for PA.

PACS-2 deficiency in tubular cells aggravates lipid-related kidney injury in diabetic kidney disease

BackgroundLipid accumulation in tubular cells plays a key role in diabetic kidney disease (DKD). Targeting lipid metabolism disorders has clinical value in delaying the progression of DKD, but the precise mechanism by which molecules mediate lipid-related kidney injury remains unclear. Phosphofurin acidic cluster sorting protein 2 (PACS-2) is a multifunctional sorting protein that plays a role in lipid metabolism. This study determined the role of PACS-2 in lipid-related kidney injury in DKD.MethodsDiabetes was induced by a high-fat diet combined with intraperitoneal injections of streptozotocin (HFD/STZ) in proximal tubule-specific knockout of Pacs-2 mice (PT-Pacs-2−/− mice) and the control mice (Pacs-2fl/fl mice). Transcriptomic analysis was performed between Pacs-2fl/fl mice and PT-Pacs-2−/− mice.ResultsDiabetic PT-Pacs-2−/− mice developed more severe tubule injury and proteinuria compared to diabetic Pacs-2fl/fl mice, which accompanied with increasing lipid synthesis, uptake and decreasing cholesterol efflux as well as lipid accumulation in tubules of the kidney. Furthermore, transcriptome analysis showed that the mRNA level of sterol O-acyltransferase 1 (Soat1) was up-regulated in the kidney of control PT-Pacs-2−/− mice. Transfection of HK2 cells with PACS-2 siRNA under high glucose plus palmitic acid (HGPA) condition aggravated lipid deposition and increased the expression of SOAT1 and sterol regulatory element-binding proteins (SREBPs), while the effect was blocked partially in that of co-transfection of SOAT1 siRNA.ConclusionsPACS-2 has a protective role against lipid-related kidney injury in DKD through SOAT1/SREBPs signaling.

Role of sortilin 1 (SORT1) on fatty acid-mediated cholesterol metabolism in primary calf hepatocytes.

Ketosis is a common metabolic disorder in peripartal dairy cows that is caused by excessive mobilization of fat and incomplete hepatic metabolism of fatty acids (FFA). Recent data in nonruminant models revealed that sortilin 1 (SORT1) is involved in a variety of lipid metabolism-related diseases. It plays important roles in the regulation of triglyceride (TAG) and total cholesterol (TC) levels. In this study, we first used liver biopsies from healthy cows (serum β-hydroxybutyrate concentration <0.6 mM) and cows diagnosed with clinical ketosis (serum β-hydroxybutyrate concentration >3.0 mM) to assess alterations in cholesterol synthesis, transport, and excretion. Then, to assess mechanistic links between SORT1 and fatty acid-mediated cholesterol metabolism, hepatocytes isolated from 4 healthy female calves (1 d old, 35-45 kg) were challenged with or without a mixture of free fatty acids (FFA; 1.2 mM) to induce metabolic stress. Hepatocytes were then treated with empty adenovirus vectors (with green fluorescent protein; Ad-GFP) or with SORT1-overexpressing adenovirus (Ad-SORT1) for 6 h or with SORT1 inhibitor (SORT1i) for 2 h, followed by a challenge with (Ad-GFP+FFA, Ad-SORT1+FFA, or SORT1i+FFA) or without (Ad-GFP, Ad-SORT1, or SORT1i) 1.2 mM FFA mixture for 12 h. Data analysis of calf hepatocyte treatment comparisons were assessed by 2-way ANOVA, and multiplicity for each experiment was adjusted using the Bonferroni procedure. Expression levels of factors related to cholesterol synthesis, transport, and excretion in liver tissue of cows with ketosis was lower. Hepatocytes challenged with FFA had lower concentrations of TC and mRNA and protein abundances of sterol regulatory element-binding protein 2 (SREBF2), acetyl acyl coenzyme A-cholesterol acyltransferase 2 (ACAT2), ATP-binding cassette transporter A1 (ABCA1), ABC subfamily G member 5 (ABCG5), and ABC subfamily G member 8 (ABCG8). Compared with FFA challenge alone, SORT1i + FFA led to greater protein abundance of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGCR), ACAT2, and ABCG5, and greater mRNA abundance of ABCG5. Compared with FFA challenge alone, SORT1 overexpression led to lower protein abundance of SREBF2. In contrast, protein abundance of ABCA1 was greater. Overall, our data suggested that exogenous FFA induced abnormal cholesterol metabolism in hepatocytes, whereas a high abundance of SORT1 affected cholesterol esterification and potentially influx into bile. Thus, downregulation of hepatic SORT1 might be a cholesterol-regulated protective mechanism in the presence of a marked increase in FFA.

Lipid Metabolism in Glioblastoma: From De Novo Synthesis to Storage.

Glioblastoma (GBM) is the most lethal primary brain tumor. With limited therapeutic options, novel therapies are desperately needed. Recent studies have shown that GBM acquires large amounts of lipids for rapid growth through activation of sterol regulatory element-binding protein 1 (SREBP-1), a master transcription factor that regulates fatty acid and cholesterol synthesis, and cholesterol uptake. Interestingly, GBM cells divert substantial quantities of lipids into lipid droplets (LDs), a specific storage organelle for neutral lipids, to prevent lipotoxicity by increasing the expression of diacylglycerol acyltransferase 1 (DGAT1) and sterol-O-acyltransferase 1 (SOAT1), which convert excess fatty acids and cholesterol to triacylglycerol and cholesteryl esters, respectively. In this review, we will summarize recent progress on our understanding of lipid metabolism regulation in GBM to promote tumor growth and discuss novel strategies to specifically induce lipotoxicity to tumor cells through disrupting lipid storage, a promising new avenue for treating GBM.

Genetic diversity of DGAT1 gene linked to milk production in cattle populations of Ethiopia

BackgroundDiacylglycerol acyl-CoA acyltransferase 1 (DGAT1) has become a promising candidate gene for milk production traits because of its important role as a key enzyme in catalyzing the final step of triglyceride synthesis. Thus use of bovine DGAT1 gene as milk production markers in cattle is well established. However, there is no report on polymorphism of the DGAT1 gene in Ethiopian cattle breeds. The present study is the first comprehensive report on diversity, evolution, neutrality evaluation and genetic differentiation of DGAT1 gene in Ethiopian cattle population. The aim of this study was to characterize the genetic variability of exon 8 region of DGAT1 gene in Ethiopian cattle breeds.ResultsAnalysis of the level of genetic variability at the population and sequence levels with genetic distance in the breeds considered revealed that studied breeds had 11, 0.615 and 0.010 haplotypes, haplotype diversity and nucleotide diversity respectively. Boran-Holstein showed low minor allele frequency and heterozygosity, while Horro showed low nucleotide and haplotype diversities. The studied cattle DGAT1 genes were under purifying selection. The neutrality test statistics in most populations were negative and statistically non-significant (p > 0.10) and consistent with a populations in genetic equilibrium or in expansion. Analysis for heterozygosity, polymorphic information content and inbreeding coefficient revealed sufficient genetic variation in DGAT1 gene. The pairwise FST values indicated significant differentiation among all the breeds (FST = 0.13; p ≤ 0.05), besides the rooting from the evolutionary or domestication history of the cattle inferred from the phylogenetic tree based on the neighbourhood joining method. There was four separated cluster among the studied cattle breeds, and they shared a common node from the constructed tree.ConclusionThe cattle populations studied were polymorphic for DGAT1 locus. The DGAT1 gene locus is extremely crucial and may provide baseline information for in-depth understanding, exploitation of milk gene variation and could be used as a marker in selection programmes to enhance the production potential and to accelerate the rate of genetic gain in Ethiopian cattle populations exposed to different agro ecology condition.

High-affinity SOAT1 ligands remodeled cholesterol metabolism program to inhibit tumor growth

BackgroundAlthough cholesterol metabolism is a common pathway for the development of antitumor drugs, there are no specific targets and drugs for clinical use. Here, based on our previous study of sterol O-acyltransferase 1 (SOAT1) in hepatocelluar carcinoma, we sought to screen an effective targeted drug for precise treatment of hepatocelluar carcinoma and, from the perspective of cholesterol metabolism, clarify the relationship between cholesterol regulation and tumorigenesis and development.MethodsIn this study, we developed a virtual screening integrated affinity screening technology for target protein drug screening. A series of in vitro and in vivo experiments were used for drug activity verification. Multi-omics analysis and flow cytometry analysis were used to explore antitumor mechanisms. Comparative analysis of proteome and transcriptome combined with survival follow-up information of patients reveals the clinical therapeutic potential of screened drugs.ResultsWe screened three compounds, nilotinib, ABT-737, and evacetrapib, that exhibited optimal binding with SOAT1. In particular, nilotinib displayed a high affinity for SOAT1 protein and significantly inhibited tumor activity both in vitro and in vivo. Multi-omics analysis and flow cytometry analysis indicated that SOAT1-targeting compounds reprogrammed the cholesterol metabolism in tumors and enhanced CD8+ T cells and neutrophils to suppress tumor growth.ConclusionsTaken together, we reported several high-affinity SOAT1 ligands and demonstrated their clinical potential in the precision therapy of liver cancer, and also reveal the potential antitumor mechanism of SOAT1-targeting compounds.Graphical

Targeting of the Lipid Metabolism Impairs Resistance to BRAF Kinase Inhibitor in Melanoma.

Drug resistance limits the achievement of persistent cures for the treatment of melanoma, in spite of the efficacy of the available drugs. The aim of the present study was to explore the involvement of lipid metabolism in melanoma resistance and assess the effects of its targeting in cellular models of melanoma with acquired resistance to the BRAF-inhibitor PLX4032/Vemurafenib. Since transcriptional profiles pointed to decreased cholesterol and fatty acids synthesis in resistant cells as compared to their parental counterparts, we examined lipid composition profiles of resistant cells, studied cell growth dependence on extracellular lipids, assessed the modulation of enzymes controlling the main nodes in lipid biosynthesis, and evaluated the effects of targeting Acetyl-CoA Acetyltransferase 2 (ACAT2), the first enzyme in the cholesterol synthesis pathway, and Acyl-CoA Cholesterol Acyl Transferase (ACAT/SOAT), which catalyzes the intracellular esterification of cholesterol and the formation of cholesteryl esters. We found a different lipid composition in the resistant cells, which displayed reduced saturated fatty acids (SFA), increased monounsaturated (MUFA) and polyunsaturated (PUFA), and reduced cholesteryl esters (CE) and triglycerides (TG), along with modulated expression of enzymes regulating biosynthetic nodes of the lipid metabolism. The effect of tackling lipid metabolism pathways in resistant cells was evidenced by lipid starvation, which reduced cell growth, increased sensitivity to the BRAF-inhibitor PLX4032, and induced the expression of enzymes involved in fatty acid and cholesterol metabolism. Molecular targeting of ACAT2 or pharmacological inhibition of SOAT by avasimibe showed antiproliferative effects in melanoma cell lines and a synergistic drug interaction with PLX4032, an effect associated to increased ferroptosis. Overall, our findings reveal that lipid metabolism affects melanoma sensitivity to BRAF inhibitors and that extracellular lipid availability may influence tumor cell response to treatment, a relevant finding in the frame of personalized therapy. In addition, our results indicate new candidate targets for drug combination treatments.

P53 deficiency affects cholesterol esterification to exacerbate hepatocarcinogenesis.

Cholesterol ester (CE) biosynthesis and homeostasis play critical roles in many cancers, including HCC, but their exact mechanistic contributions to HCC disease development require further study. Here, we report on a proposed role of tumor suppressor P53 in its repressing ubiquitin-specific peptidase 19 (USP19) and sterol O-acyltransferase (SOAT) 1, which maintains CE homeostasis. USP19 enhances cholesterol esterification and contributes to hepatocarcinogenesis (HCG) by deubiquitinating and stabilizing SOAT1. Loss of either SOAT1 or USP19 dramatically attenuates cholesterol esterification and HCG in P53-deficient mice fed with either a normal chow diet or a high-cholesterol, high-fat diet (HCHFD). SOAT1 inhibitor avasimibe has more inhibitory effect on HCC progression in HCHFD-maintained P53-deficient mice when compared to the inhibitors of de novo cholesterol synthesis. Consistent with our findings in the mouse model, the P53-USP19-SOAT1 signaling axis is also dysregulated in human HCCs. Collectively, our findings demonstrate that SOAT1 participates in HCG by increasing cholesterol esterification, thus indicating that SOAT1 is a potential biomarker and therapeutic target in P53-deficient HCC.

Abstract 5468: A pharmacological inhibition of sterol O-acyltransferase 1improves response to enzalutamide in prostate cancer

Abstract Prostate cancer (PCa) growth is mediated by androgens via activation of androgen receptor (AR). Accordingly, androgen deprivation therapy (ADT) is the gold standard for the treatment of advanced PCa, but progression to castration-resistant PCa (CRPC) follows. Enzalutamide (ENZ) is an AR antagonist used for the management of CRPC. However, patients acquire resistance to the drug in a short period. Meanwhile, cholesterol is a precursor to androgen and its metabolism is dysregulated in PCa. In addition, cholesteryl ester (CE) accumulation aggravates tumor growth but its association with ENZ treatment has not been studied. Thus, we hypothesized that inhibition of CE formation by blockage of sterol-O-acyltransferase 1 (SOAT1) could enhance the response to ENZ. We found that SOAT1 mRNA is upregulated in clinical prostate tumors compared to normal/benign tissues in TCGA dataset. SOAT1 mRNA level was also highly correlated with AR expression in SU2CF/PCF cohorts and TCGA dataset, suggesting critical role of the cholesterol metabolism in prostate tumor progression and potential association to AR signaling pathway. We treated 22RV1 prostate cancer cells with ENZ in the presence or absence of SOAT1 inhibitor, avasimibe, and found the combination treatment effectively reduced the level of CEs compared to control, which accompanied inhibition of colony formation and cell proliferation. Combination index value was calculated and the relationship between the two drugs showed synergism. Furthermore, genetic knockdown of SOAT1 sensitized cells to ENZ treatment and also reduced the number of colonies formed. In TCGA dataset, patients who had previously undergone ADT were analyzed, and their Kaplan-Meier survival curve showed low SOAT1 expressing patients had a significantly longer progression-free survival rate than their counterpart, indicating that SOAT1 could act as a prognostic biomarker predicting PCa treatment outcome. Gene set enrichment analysis of patients with ADT history showed androgen response gen sets were enriched in high SOAT1 expressing PCa patient group. Inhibition of SOAT1 and the combination treatment did not change AR and ARV7 protein level, but downstream genes such as PSA were down regulated upon the combination treatment. In summary, our in vitro results showed blockage of SOAT1 enzyme sensitized PCa cells to ENZ treatment and analysis of PCa patient data suggested that SOAT1 gene expression has potential as a prognostic marker. Citation Format: Sora Q. Kim, Sagar Utturkar, Nadia M. Atallah, Kee-Hong Kim. A pharmacological inhibition of sterol O-acyltransferase 1improves response to enzalutamide in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5468.

Differential proteomics analysis of JEG-3 and JAR placental cell models and the effect of androgen treatment

The placenta is a vital fetal organ that plays an important role in maintaining fetal sex hormone homeostasis. Xenobiotics can alter placental sex-steroidogenic enzymes and transporters, including enzymes such as aromatase (CYP19A1) and the hydroxysteroid dehydrogenases (HSDs) but studying how compounds disrupt in vivo placental metabolism is complex. Utilizing high-throughput in vitro models is critical to predict the disruption of placental sex-steroidogenic enzymes and transporters, particularly by drug candidates in the early stages of drug discovery. JAR and JEG-3 cells are the most common, simple, and cost-effective placental cell models that are capable of high-throughput screening, but how well they express the sex-steroidogenic enzymes and transporters is not well known. Here, we compared the proteomes of JAR and JEG-3 cells in the presence and absence of physiologically relevant concentrations of dehydroepiandrosterone (DHEA, 8 µM) and testosterone (15 nM) to aid the characterization of sex-steroidogenic enzymes and transporters in these cell models. Global proteomics analysis detected 2931 and 3449 proteins in JAR cells and JEG-3 cells, respectively. However, dramatic differences in sex-steroidogenic enzymes and transporters were observed between these cells. In particular, the basal expression of steroid sulfatase (STS), HSD17B1, and HSD17B7 were unique to JEG-3 cells. JEG-3 cells also showed significantly higher protein levels of aldo-keto reductase (AKR) 1A1 and AKR1B1, while JAR cells showed significantly higher levels of HSD17B4 and HSDB12. Aldehyde dehydrogenase (ALDH) 3A2 and HSD17B11 enzymes as well as the transporters sterol O-acyltransferase (SOAT) 1 and ATP binding cassette subfamily G2 (ABCG2) were comparable between the cell lines, whereas sulfotransferases (SULTs) were uniquely present within JAR cells. Androgen treatments significantly lowered HSD17B11, HSD17B4, HSD17B12, and ALDH3A2 levels in JAR cells. DHEA treatment significantly raised the level of HSD17B1 by 51 % in JEG-3 cells, whereas CYP19A1 was increased to significant levels in both JAR and JEG-3 cells after androgen treatments. The proteomics data were supported by a complementary targeted metabolomics analysis of culture media in the DHEA (8 µM) and testosterone (15 nM) treated groups. This study has indicated that untreated JEG-3 cells express more sex-steroidogenic enzymes and transporters. Nevertheless, JEG-3 and JAR cells are unique and their respective proteomics data can be used to select the best model depending on the hypothesis.

Plasma FA composition in familial LCAT deficiency indicates SOAT2-derived cholesteryl ester formation in humans

AbstractMutations in the LCAT gene cause familial LCAT deficiency (Online Mendelian Inheritance in Man ID: #245900), a very rare metabolic disorder. LCAT is the only enzyme able to esterify cholesterol in plasma, whereas sterol O-acyltransferases 1 and 2 are the enzymes esterifying cellular cholesterol in cells. Despite the complete lack of LCAT activity, patients with familial LCAT deficiency exhibit circulating cholesteryl esters (CEs) in apoB-containing lipoproteins. To analyze the origin of these CEs, we investigated 24 carriers of LCAT deficiency in this observational study. We found that CE plasma levels were significantly reduced and highly variable among carriers of two mutant LCAT alleles (22.5 [4.0–37.8] mg/dl) and slightly reduced in heterozygotes (218 [153–234] mg/dl). FA distribution in CE (CEFA) was evaluated in whole plasma and VLDL in a subgroup of the enrolled subjects. We found enrichment of C16:0, C18:0, and C18:1 species and a depletion in C18:2 and C20:4 species in the plasma of carriers of two mutant LCAT alleles. No changes were observed in heterozygotes. Furthermore, plasma triglyceride-FA distribution was remarkably similar between carriers of LCAT deficiency and controls. CEFA distribution in VLDL essentially recapitulated that of plasma, being mainly enriched in C16:0 and C18:1, while depleted in C18:2 and C20:4. Finally, after fat loading, chylomicrons of carriers of two mutant LCAT alleles showed CEs containing mainly saturated FAs. This study of CEFA composition in a large cohort of carriers of LCAT deficiency shows that in the absence of LCAT-derived CEs, CEs present in apoB-containing lipoproteins are derived from hepatic and intestinal sterol O-acyltransferase 2.