stearoyl-CoA Desaturase Inhibitors Research Articles

Hypoxia-responsive micelles deprive cofactor of stearoyl-CoA desaturase-1 and sensitize ferroptotic ovarian cancer therapy

Ferroptosis has been recognized as a promising therapeutic strategy for cancer due to its unique mechanism of action. However, the upregulation of stearoyl-CoA desaturase 1 (SCD1) in ovarian cancer leads to resistance to ferroptotic therapy. Zinc ion (Zn2+) serves as the cofactor of SCD1. It was hypothesized that selective deprivation of Zn2+ from SCD1 could sensitize ferroptotic ovarian cancer therapy. Here, we report a hypoxia-responsive polymer micelle for enhanced ferroptosis of ovarian cancer cells. A SCD1 inhibitor, PluriSIn 1 (Plu), and a ferroptosis inducer, Auranofin (Aur), were co-encapsulated in nitroimidazole-bearing micelles. Under the hypoxic tumor microenvironment, the conversion of nitroimidazole to aminoimidazole triggered the cargo release and induced the depletion of antioxidant molecules (e.g., glutathione, thioredoxin, and NADPH). Meanwhile, because of the strong coordination between aminoimidazole and Zn2+ compared to that of histidine and Zn2+, such conversion can deprive the metal cofactor of SCD1, hence sensitizing the action of Plu and Aur. The proof-of-concept was demonstrated in cell and animal models with minimal systemic toxicity. The current work integrates ferroptosis induction with SCD1 inhibition in a hypoxia-responsive vehicle, offering a promising strategy for addressing the ferroptosis resistance and opening novel avenues for managing the difficult-to-treat ovarian cancer.

P-596 Impaired fatty acid desaturation in COV434 human granulosa cells leads to increased omega-6 phospholipid abundance

Abstract Study question How does fatty acid desaturation in COV434 granulosa cells influence their lipogenic pathway? Summary answer Suppressing fatty acid desaturation in human granulosa cells leads to a depletion of polyunsaturated phospholipids and an increase in omega-6 fatty acid-containing lipids. What is known already Maintaining the balance between saturated and unsaturated lipids in oocyte-surrounding granulosa cells is crucial to supporting oocyte maturation. We have shown the link between the de novo production of oleic acid through fatty acid desaturation and the main functional parameters of granulosa cells, such as cell proliferation and steroid production. A potential contributor to the observed pathophysiological outcomes lies in the dysregulation of cellular lipids as a consequence of insufficient intracellular oleic acid availability. This lipidomic study investigates the adaptive lipogenic response of granulosa cells to deficient fatty acid desaturation. Study design, size, duration We tested the influence of a chemical inhibitor against stearoyl-CoA desaturase 1 (SCD1), a major fatty acid desaturase enzyme, on cell membrane lipid packing, lipidome, and lipogenic-related genes in immortalized granulosa cells, COV434. We applied free oleic acid to conduct a rescue experiment. Three independent technical replicates were performed for each experimental condition, and mean values were compared among test conditions using one-way ANOVA analysis. Participants/materials, setting, methods The level of membrane fluidity was estimated using the membrane polarity-sensitive dye Laurdan. We used liquid chromatography–mass spectrometry to investigate the lipidome profiles. Data were obtained by calculating the peak areas of intact lipid species. We used quantitative PCR with TaqMan primers to assess the expression of mechanistic target of rapamycin (mTOR), diacylglycerol acyltransferase 1 (DGAT1), and fatty acid synthase (FASN), with 18S ribosomal RNA as the internal control. Main results and the role of chance Reduced oleic acid availability increased cholesterol content 1.2-fold (p = 0.007) and membrane packing, representing intended modifications in de novo desaturation. We used data comprising 459 lipid species. SCD1 inhibition caused a significant increase in dipalmitoyl phosphatidic acid 32:0 (7.4-fold increase vs. untreated controls, p < 0.001) and a substantial decrease in dioleoyl phosphatidic acid 36:2 (-38% reduction, p < 0.001). SCD1 inhibition also led to an elevation of omega-6 phospholipids (e.g., 38:4, 40:4), but conversely, a depletion of polyunsaturated lipids (e.g., 34:2, 36:2). In contrast, oleic acid supplementation resulted in an enrichment of oleic acid-containing lipids (e.g. 34:1, 36:1) but also caused a significant depletion of all polyunsaturated lipids, including omega-6 species (e.g., 20:3, 20:4). These findings indicate that the de novo generation of oleic acid intricately modulates polyunsaturated phospholipid metabolism, especially that of omega-6 phospholipids.Although the reductions in the expression levels of lipogenic-related genes due to SCDinhib treatment were not statistically significant, the addition of oleic acid significantly enhanced the suppression of FASN by 67% (p = 0.022). This suggests the presence of an interaction effect that potentiates the downregulation of the de novo fatty acid synthesis and diverts metabolic pathways away from omega-6 fatty acid production. Limitations, reasons for caution Examining lipidomic profile in isolated primary ovarian cells is crucial for a better understanding of their biological significance. Wider implications of the findings We identified that the role of de novo oleic acid generation in polyunsaturated phospholipid metabolism has significance for cellular physiology in oocyte-surrounding granulosa cells. Potential future applications include targeted metabolic interventions for reproductive disorders impacting oogenesis. Trial registration number not

De novo synthesis of monounsaturated fatty acids modulates exosome-mediated lipid export from human granulosa cells

BackgroundOvarian somatic cells support the maturation and fertility of oocytes. Metabolic desaturation of fatty acids in these cells has a positive paracrine impact on the maturation of oocytes. We hypothesized that the enzyme stearoyl-CoA desaturase 1 (SCD1) in granulosa cells regulates the lipid cargo of exosomes secreted from these cells by maintaining the balance between saturated and unsaturated lipids. We investigated the effect of SCD1 on exosome lipid content in a cumulus-granulosa cell model under physiologically relevant in vitro conditions. MethodsNon-luteinized human COV434 granulosa cells were subjected to treatment with an inhibitor of SCD1 (SCDinhib) alone, in combination with oleic acid, or under control conditions. Subsequently, the exosomes were isolated and characterized via nanoparticle tracking analysis, transmission electron microscopy, and Western blotting. We used liquid chromatography mass spectrometry to investigate the lipidomic profiles. We used quantitative PCR with TaqMan primers to assess the expression of genes involved in lipogenesis and control of cell cycle progression. ResultsA trend toward exosome production was observed with a shift toward smaller exosome sizes in cells treated with SCD1inhib. This trend reached statistical significance when SCDinhib was combined with oleic acid supplementation. SCD1 inhibition led to the accumulation of saturated omega-6 lipids in exosomes. The latter effect was reversed by oleic acid supplementation, which also improved exosome production and suppressed the expression of fatty acid synthase and Cyclin D2. ConclusionThese findings underscore the critical role of de novo fatty acid desaturation in the regulation of the export of specific lipids through exosomes, with potential implications for controlling intercellular communication within the ovary.

A Multimodal Drug-Diet-Immunotherapy Combination Restrains Melanoma Progression and Metastasis.

The genetic landscape of cancer cells can lead to specific metabolic dependencies for tumor growth. Dietary interventions represent an attractive strategy to restrict the availability of key nutrients to tumors. In this study, we identified that growth of a subset of melanoma was severely restricted by a rationally designed combination therapy of a stearoyl-CoA desaturase (SCD) inhibitor with an isocaloric low-oleic acid diet. Despite its importance in oncogenesis, SCD underwent monoallelic codeletion along with PTEN on chromosome 10q in approximately 47.5% of melanoma, and the other SCD allele was methylated, resulting in very low-SCD expression. Although this SCD-deficient subset was refractory to SCD inhibitors, the subset of PTEN wild-type melanoma that retained SCD was sensitive. As dietary oleic acid could potentially blunt the effect of SCD inhibitors, a low oleic acid custom diet was combined with an SCD inhibitor. The combination reduced monounsaturated fatty acids and increased saturated fatty acids, inducing robust apoptosis and growth suppression and inhibiting lung metastasis with minimal toxicity in preclinical mouse models of PTEN wild-type melanoma. When combined with anti-PD1 immunotherapy, the SCD inhibitor improved T-cell functionality and further constrained melanoma growth in mice. Collectively, these results suggest that optimizing SCD inhibitors with diets low in oleic acid may offer a viable and efficacious therapeutic approach for improving melanoma treatment. Significance: Blockade of endogenous production of fatty acids essential for melanoma combined with restriction of dietary intake blocks tumor growth and enhances response to immunotherapy, providing a rational drug-diet treatment regimen for melanoma.

FADS2 confers SCD1 inhibition resistance to cancer cells by modulating the ER stress response

Stearoyl-CoA desaturase 1 (SCD1) is an attractive target for cancer therapy. However, the clinical efficacy of SCD1 inhibitor monotherapy is limited. There is thus a need to elucidate the mechanisms of resistance to SCD1 inhibition and develop new therapeutic strategies for combination therapy. In this study, we investigated the molecular mechanisms by which cancer cells acquire resistance to endoplasmic reticulum (ER) stress-dependent cancer cell death induced by SCD1 inhibition. SCD1 inhibitor-sensitive and -resistant cancer cells were treated with SCD1 inhibitors in vitro, and SCD1 inhibitor-sensitive cancer cells accumulated palmitic acid and underwent ER stress response-induced cell death. Conversely, SCD1-resistant cancer cells did not undergo ER stress response-induced cell death because fatty acid desaturase 2 (FADS2) eliminated the accumulation of palmitic acid. Furthermore, genetic depletion using siRNA showed that FADS2 is a key determinant of sensitivity/resistance of cancer cells to SCD1 inhibitor. A549 cells, an SCD1 inhibitor-resistant cancer cell line, underwent ER stress-dependent cancer cell death upon dual inhibition of SCD1 and FADS2. Thus, combination therapy with SCD1 inhibition and FADS2 inhibition is potentially a new cancer therapeutic strategy targeting fatty acid metabolism.

A patient-based iPSC-derived hepatocyte model of alcohol-associated cirrhosis reveals bioenergetic insights into disease pathogenesis.

Only ~20% of heavy drinkers develop alcohol cirrhosis (AC). While differences in metabolism, inflammation, signaling, microbiome signatures and genetic variations have been tied to the pathogenesis of AC, the key underlying mechanisms for this interindividual variability, remain to be fully elucidated. Induced pluripotent stem cell-derived hepatocytes (iHLCs) from patients with AC and healthy controls differ transcriptomically, bioenergetically and histologically. They include a greater number of lipid droplets (LDs) and LD-associated mitochondria compared to control cells. These pre-pathologic indicators are effectively reversed by Aramchol, an inhibitor of stearoyl-CoA desaturase. Bioenergetically, AC iHLCs have lower spare capacity, slower ATP production and their mitochondrial fuel flexibility towards fatty acids and glutamate is weakened. MARC1 and PNPLA3, genes implicated by GWAS in alcohol cirrhosis, show to correlate with lipid droplet-associated and mitochondria-mediated oxidative damage in AC iHLCs. Knockdown of PNPLA3 expression exacerbates mitochondrial deficits and leads to lipid droplets alterations. These findings suggest that differences in mitochondrial bioenergetics and lipid droplet formation are intrinsic to AC hepatocytes and can play a role in its pathogenesis.

Stearoyl-CoA desaturase 1 inhibition induces ER stress-mediated apoptosis in ovarian cancer cells

Ovarian cancer is a leading cause of death among gynecologic tumors, often detected at advanced stages. Metabolic reprogramming and increased lipid biosynthesis are key factors driving cancer cell growth. Stearoyl-CoA desaturase 1 (SCD1) is a crucial enzyme involved in de novo lipid synthesis, producing mono-unsaturated fatty acids (MUFAs). Here, we aimed to investigate the expression and significance of SCD1 in epithelial ovarian cancer (EOC). Comparative analysis of normal ovarian surface epithelial (NOSE) tissues and cell lines revealed elevated SCD1 expression in EOC tissues and cells. Inhibition of SCD1 significantly reduced the proliferation of EOC cells and patient-derived organoids and induced apoptotic cell death. Interestingly, SCD1 inhibition did not affect the viability of non-cancer cells, indicating selective cytotoxicity against EOC cells. SCD1 inhibition on EOC cells induced endoplasmic reticulum (ER) stress by activating the unfolded protein response (UPR) sensors and resulted in apoptosis. The addition of exogenous oleic acid, a product of SCD1, rescued EOC cells from ER stress-mediated apoptosis induced by SCD1 inhibition, underscoring the importance of lipid desaturation for cancer cell survival. Taken together, our findings suggest that the inhibition of SCD1 is a promising biomarker as well as a novel therapeutic target for ovarian cancer by regulating ER stress and inducing cancer cell apoptosis.

Central inhibition of stearoyl-CoA desaturase has minimal effects on the peripheral metabolic symptoms of the 3xTg Alzheimer’s disease mouse model

Evidence from genetic and epidemiological studies point to lipid metabolism defects in both the brain and periphery being at the core of Alzheimer’s disease (AD) pathogenesis. Previously, we reported that central inhibition of the rate-limiting enzyme in monounsaturated fatty acid synthesis, stearoyl-CoA desaturase (SCD), improves brain structure and function in the 3xTg mouse model of AD (3xTg-AD). Here, we tested whether these beneficial central effects involve recovery of peripheral metabolic defects, such as fat accumulation and glucose and insulin handling. As early as 3 months of age, 3xTg-AD mice exhibited peripheral phenotypes including increased body weight and visceral and subcutaneous white adipose tissue as well as diabetic-like peripheral gluco-regulatory abnormalities. We found that intracerebral infusion of an SCD inhibitor that normalizes brain fatty acid desaturation, synapse loss and learning and memory deficits in middle-aged memory-impaired 3xTg-AD mice did not affect these peripheral phenotypes. This suggests that the beneficial effects of central SCD inhibition on cognitive function are not mediated by recovery of peripheral metabolic abnormalities. Given the widespread side-effects of systemically administered SCD inhibitors, these data suggest that selective inhibition of SCD in the brain may represent a clinically safer and more effective strategy for AD.

Abstract 641: SCD1 upregulation due to STK11/KEAP1 loss upregulates SLC7A11 and causes deregulation of fatty acid metabolism leading to ferroptosis evasion

Abstract Introduction: Non-small cell lung cancer (NSCLC) with co-occurring loss-of-function (LOF) mutations in serine/threonine kinase 11 (STK11) and Kelch-like ECH-associated protein1 (KEAP1) (SK) are notably aggressive and unresponsive to chemo and immunotherapy, in current care standards. Novel therapeutic strategies are in demand to improve the outcomes for SK co-mutant NSCLC patients. We reported earlier that SK LOF mutations enhance cell proliferation and tumor growth in xenograft lung cancer models. We also found the ferroptosis evasion genes are enriched, and targeting ferroptosis regulators is a therapeutic opportunity in SK co-mutant NSCLC. Methods: We used CRISPR/Cas9 gene editing to create stable knockouts of STK11 (SKO), KEAP1 (KKO) or both (DKO), non-targeting control (NTC) in two NSCLC lines. We performed an in vitro druggable genome library CRISPR screening in the same NSCLC lines. We performed kinase profiling and RNA-seq in the cell lines to depict the transcriptomic and proteomic landscape, followed by western blotting and qRT-PCR validation. We also performed BODIPY/C11 assay and lipidomics to explore the ferroptosis and metabolic landscape of SK co-mutant NSCLC models. Results: Stearoyl CoA desaturase-1 (SCD1) was the top CRISPR screen hit, a critical modulator of fatty acid metabolism and ferroptosis evasion. SCD1 expression is significantly higher in NSCLC tissue than adjacent normal tissue (p<0.0001), and high SCD1 expression correlates with poorer prognosis in patients with NSCLC (p=0.027). GSEA from the bulk RNA sequencing in SK co-mutant cells pre-and post-SCD1 inhibitor treatment showed SCD1 inhibition leads to upregulation of the glutathione and glutamic acid pathways compared to NTC cells. Moreover, SK co-mutant cells have a significantly higher expression of SLC7A11, enabling cystine uptake and subsequent conversion to cysteine, essential for maintaining redox balance and cell survival. Hence, SK co-mutant cells are more resistant to cysteine depletion than NTC cells. SCD1 inhibition causes a decrease in SLC7A11 expression exclusively in DKO cells. Eventually, SCD1 inhibition leads to global metabolomic changes in SK co-mutant cells, including key pathways involved in lipid and glucose metabolism. Finally, genetic and pharmacological inhibition of SCD1 prevents tumor growth and sensitizes DKO cells to ferroptosis inducers like erastin. Conclusions: Our findings highlight the importance of the SCD1-SLC7A11 axis in regulating ferroptosis in SK co-mutant models. Current data impact our understanding of ferroptosis in NSCLC and its ability to target SCD1 or ferroptosis in cancer treatment. Compounds such as inhibitors of SLC7A11 (Erastin/IKE) are safe to use with acceptable toxicity and established doses. Hence, our study will facilitate the translation of ferroptosis inducers or SCD1 inhibitors in clinical trials. Citation Format: Utsav Sen, Charles Coleman, Dan Hasson, Triparna Sen. SCD1 upregulation due to STK11/KEAP1 loss upregulates SLC7A11 and causes deregulation of fatty acid metabolism leading to ferroptosis evasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 641.

Targeting Stearoyl-CoA Desaturase: A novel approach for diabetes therapy

Diabetes mellitus is an epidemic with serious health and financial consequences. While glycemic control is the primary focus of current diabetic care, new evidence points to the crucial role that lipid metabolism plays in the emergence of insulin resistance, particularly in type 2 diabetes. The enzyme stearoyl-CoA desaturase (SCD), which transforms saturated fatty acids into monounsaturated fatty acids, has drawn interest as a possible therapeutic target for the treatment of diabetes. The complicated connection between SCD, lipid metabolism, and insulin resistance is examined in this research, underlining the therapeutic potential of SCD inhibitors in the management of diabetes.

An insight into advances and challenges in the development of potential stearoyl Co-A desaturase 1 inhibitors.

Stearoyl-CoA desaturase 1 (SCD1) is one of the key enzymes involved in lipid metabolism, plays a vital role in the synthesis of monounsaturated fatty acids (MUFAs) from saturated fatty acids (SFAs). Due to its promising therapeutic potential in treating metabolic disorders, cancers, and skin diseases there is an increasing interest in the development of novel inhibitors against SCD1. This review comprehensively explores the evolution of potential SCD1 inhibitors, focusing on systemic and liver-targeted inhibitors and discusses their structure-activity relationship (SAR) pattern. Among the various small molecules reported, natural products like sterculic acid have emerged as significant SCD1 inhibitors, highlighting the potential of naturally derived compounds in therapeutic development. This review also addresses the challenges in optimizing pharmacokinetic properties and reducing adverse effects, providing insights into the future directions for the development of potential novel SCD1 inhibitors with maximum therapeutic effect and minimum side effects.

Oncogenic Fatty Acid Metabolism Rewires Energy Supply Chain in Gastric Carcinogenesis

Background & AimsGastric carcinogenesis develops within a sequential carcinogenic cascade from pre-cancerous metaplasia to dysplasia and adenocarcinoma, and oncogenic gene activation can drive the process. Metabolic reprogramming is considered a key mechanism for cancer cell growth and proliferation. However, it remains unclear how metabolic changes contribute to the progression of metaplasia to dysplasia. We have examined metabolic dynamics during gastric carcinogenesis using a novel mouse model that induces Kras activation in zymogen-secreting chief cells. MethodsWe generated a Gif-rtTA;TetO-Cre;KrasG12D (GCK) mouse model which continuously induces active Kras expression in chief cells following doxycycline treatment. Histological examination and imaging mass spectrometry were performed in the GCK mouse stomachs at 2 to 14 weeks after doxycycline treatment. Mouse and human gastric organoids were used for metabolic enzyme inhibitor treatment. The GCK mice were treated with a stearoyl-CoA desaturase (SCD) inhibitor to inhibit the fatty acid desaturation. Tissue microarrays were used to assess the SCD expression in human gastrointestinal cancers. ResultsThe GCK mice developed metaplasia and high-grade dysplasia within 4 months. Metabolic reprogramming from glycolysis to fatty acid metabolism occurred during metaplasia progression to dysplasia. Altered fatty acid desaturation through SCD produces a novel Eicosenoic acid, which fuels dysplastic cell hyperproliferation and survival. The SCD inhibitor killed both mouse and human dysplastic organoids and selectively targeted dysplastic cells in vivo. SCD was upregulated during carcinogenesis in human gastrointestinal cancers. ConclusionsActive Kras expression only in gastric chief cells drives the full spectrum of gastric carcinogenesis. Also, oncogenic metabolic rewiring is an essential adaptation for high energy demand in dysplastic cells.

Lipogenic stearoyl-CoA desaturase-1 (SCD1) targeted virtual screening for chemical inhibitors: molecular docking / dynamics simulation and in vitro assessment of anti-NAFLD efficacy.

Amidst rising global prevalence of metabolic syndrome, the associated risk of non-alcoholic fatty liver disease (NAFLD) is also rapidly increasing. The pathogenesis of NAFLD starts with fat accumulation and progresses through inflammation and fibrotic sequel, often involving complex molecular mechanisms involving de novo lipogenesis. Stearoyl-CoA desaturase 1 (SCD1) enzyme, expressed in liver and adipose tissue, converts saturated fatty acids to monounsaturated fatty acids (MUFAs), contributing to triglyceride and cholesterol ester formation. In this study, potential SCD1 inhibitors were screened using the ZINC database of curated medically-approved drugs by virtual screening, molecular docking, and molecular dynamics simulations. The top-scoring five ligands with strong binding affinity against SCD1 were ZINC000003831151 > ZINC000001540998 > ZINC000003830713 > ZINC000000897251 > ZINC000002005305, which showed stable protein-ligand complexation and favorable pharmacokinetic attributes. The top ligand, Montelukast, was experimentally validated for its pharmacological efficacy in an in vitro cell culture model of steatosis (NAFLD). Montelukast showed a dose-dependent decrease in hepatic fat accumulation, reduced levels of free radicals, and lowered oxidative stress (P < 0.05). These outcomes suggest Montelukast to be a potential SCD1 inhibitor, with anti-NAFLD efficacy. These findings open new avenues for therapeutic development of the top 5 ligands in metabolic disorders involving SCD1.

The Effect of SCD-1 Inhibition on Human Hematopoietic Stem Cell Mitochondrial Metabolism, Cell Proliferation, and Differentiation Potential

Hematopoietic stem cells (HSC) give rise to all blood lineages and sustain the production of blood cells throughout life. Due to their inherently high regenerative potential, HSC are used in a variety of clinical settings, including bone marrow transplantation (BMT) directly to cure a variety of hematologic and oncologic disorders often with gene therapy. During regeneration, HSC are activated into cycle. For this, HSC undergo drastic mitochondrial and metabolic remodeling to meet the bioenergetic and biosynthetic needs of activated HSC. A growing body of evidence indicates that HSC sustain injury during activation. This remodeling is important for optimal HSC function but is permanently changed after HSC activating stress. It is thus important to identify the metabolic needs of activated HSC to improve HSC functions for therapeutic purposes. In both murine and human HSC, numerous metabolic enzymes get upregulated during activation, including those involved in de novo lipid synthesis. This metabolism is poorly understood in human HSC. Our overarching question is to understand the metabolic needs of HSC within the human system. Stearoyl-co-A-desaturase 1 (SCD-1), an enzyme responsible for conversion of stearic to oleic acid within the de novo lipid synthesis pathway, is suspected to play a role in metabolic reprogramming after stress. Using CD34+ mobilized human peripheral blood, we analyzed the effect of SCD-1 inhibition on HSC and progenitor proliferation, mitochondrial metabolism, and lineage differentiation potential. Cells were cultured either in vehicle control conditions or with SCD-1 inhibitor (SCDi). Subsequently, cells were counted and analyzed by flow cytometry on Days 4-5 and 10-15. More primitive or stem cell markers were utilized on Days 0 and 5 whereas differentiation markers were utilized on Day 10-15. Both tetramethylrhodamine-ethyl ester dye (TMRE) and MitoSOX reagents were used to assess mitochondrial membrane potential and mitochondrial ROS, respectively. Our results demonstrate that the size of the HSC population generated by SCDi-treated CD34+ cells within 5 days of culture was similar to vehicle treated cells and was composed of similar proportion of CD34+CD38+, CD34+CD38-, and CD38+CD34- cells, indicating that SCD-1 inhibition does not alter HSC expansion under these culture conditions. However, TMRE levels were lower in all HSC populations whereas mitoSOX levels were unchanged by SCD-1 inhibition compared to vehicle. In differentiation conditions, SCDi cultures were composed of a larger proportion of myeloid progenitors and a smaller proportion of erythroid cells after 10-15 days, compared to vehicle-treated cultures. These findings suggest that de novo lipid synthesis is necessary for HSC differentiation but dispensable for proliferation/expansion in vitro. We then used a xenotransplant model to assess the effect of SCDi on HSC regenerative potential in vivo. CD34+ mobilized human peripheral blood cells were cultured for 3 days under conditions that maintain HSC functions in vitro and transplanted into immunodeficient, sublethally irradiated NSG mice. Peripheral blood of xenotransplanted mice was analyzed monthly for human cell chimerism and mature blood lineage potential from 1 to 6 months post-transplant. Bone marrow analysis was performed at the 6 month time point as well, assessing for both HSC markers and lineage markers. Mice that received SCDi-treated cells exhibited human cell chimerism at a level similar to mice that were transplanted with vehicle treated cells, at about 3 to 30%. However, SCDi-treated cells gave rise to a lymphoid-biased graft, in particular T cells, both in the peripheral blood and in the bone marrow of xenotransplanted mice, compared to a more balanced myeloid-lymphoid graft from vehicle treated cells. In conclusion, these findings suggest that de novo lipid synthesis is critically important for HSC lineage fate and balanced differentiation in vitro and in vivo. This is especially clinically relevant as this work may implicate a possible therapeutic target as improving de novo lipid synthesis may aid in patients who suffer from persistent cytopenias after BMT and graft failure.

Overexpression of ZNF488 supports pancreatic cancer cell proliferation and tumorigenesis through inhibition of ferroptosis via regulating SCD1-mediated unsaturated fatty acid metabolism

BackgroundPancreatic cancer is a malignancy with high mortality. Once diagnosed, effective treatment strategies are limited and the five-year survival is extremely poor. Recent studies have shown that zinc finger proteins play important roles in tumorigenesis, including pancreatic cancer. However, it remains unknown on the clinical significance, function and underlying mechanisms of zinc finger protein 488 (ZNF488) during the development of pancreatic cancer.MethodsThe clinical relevance of ZNF488 and stearoyl-CoA desaturase 1 (SCD1) was examined by analyzing the data from The Cancer Genome Atlas (TCGA) and immunohistochemical staining of the tissue microarray. Gain-of-function and loss-of-function experiments were performed by transfecting the cells with overexpressing lentivirus and siRNAs or shRNA lentivirus, respectively. The function of ZNF488 in pancreatic cancer was assessed by CCK8, colony formation, EdU staining, PI/Annexin V staining and xenografted tumorigenesis. Chip-qPCR assay was conducted to examine the interaction between ZNF488 and the promoter sequence of SCD1. Transcription activity was measured by dual luciferase reporter assay. mRNA and protein expression was detected by qRT-PCR and immunoblotting experiment, respectively. Fatty acid was quantified by gas chromatography mass spectrometry.ResultsZNF488 was overexpressed in pancreatic cancer samples compared with normal tissues. High expression of ZNF488 predicted the poor prognosis of the patients. In vitro, ZNF488 upregulation contributed to the EuU cooperation, proliferation and colony formation of MIAPaCa-2 and PANC-1 cells. Based on PI/Annexin V and trypan blue staining results, we showed that ZNF488 suppressed the ferroptosis and apoptosis of pancreatic cancer cells. Mechanistically, ZNF488 directly interacted with the promoter sequence of SCD1 gene and promoted its transcription activity, which resulted in enhanced palmitoleic and oleic acid production, as well as the peroxidation of fatty acid. In vivo, ZNF488 overexpression promoted the xenograted tumorigenesis of PANC-1, which was reversed by SCD1 knockdown. Importantly, combination of erastin and SCD1 inhibitors A939572 completely blunted the growth of ZNF488 overexpressed MIAPaCa-2 and PANC-1 cells. Usage of A939572 or erastin recovered the sensitivity of pancreatic cancer cells to the treatment of gemcitabine. Lastly, we found a positive correlation between ZNF488 and SCD1 in pancreatic cancer patients based on TCGA and immunohistochemical staining results.ConclusionOverexpression of ZNF488 suppresses the ferroptosis and apoptosis to support the growth and tumorigenesis of pancreatic cancer through augmentation of SCD1-mediated unsaturated fatty acid metabolism. Combination of SCD1 inhibitors, ferroptosis inducers or gemcitabine could be applied for the treatment of pancreatic cancer with overexpression of ZNF488.

SCD1 inhibition enhances the effector functions of CD8+ T cells via ACAT1-dependent reduction of esterified cholesterol.

We previously reported that the inhibition of stearoyl-CoA desaturase 1 (SCD1) enhances the antitumor function of CD8+ T cells indirectly via restoring production of DC recruiting chemokines by cancer cells and subsequent induction of antitumor CD8+ T cells. In this study, we investigated the molecular mechanism of direct enhancing effects of SCD1 inhibitors on CD8+ T cells. In vitro treatment of CD8+ T cells with SCD1 inhibitors enhanced IFN-γ production and cytotoxic activity of T cells along with decreased oleic acid and esterified cholesterol, which is generated by cholesterol esterase, acetyl-CoA acetyltransferase 1 (ACAT1), in CD8+ T cells. The addition of oleic acid or cholesteryl oleate reversed the enhanced functions of CD8+ T cells treated with SCD1 inhibitors. Systemic administration of SCD1 inhibitor to MCA205 tumor-bearing mice enhanced IFN-γ production of tumor-infiltrating CD8+ T cells, in which oleic acid and esterified cholesterol, but not cholesterol, were decreased. These results indicated that SCD1 suppressed effector functions of CD8+ T cells through the increased esterified cholesterol in an ACAT1-dependent manner, and SCD1 inhibition enhanced T cell activity directly through decreased esterified cholesterol. Finally, SCD1 inhibitors or ACAT1 inhibitors synergistically enhanced the antitumor effects of anti-PD-1 antibody therapy or CAR-T cell therapy in mouse tumor models. Therefore, the SCD1-ACAT1 axis is regulating effector functions of CD8+ T cells, and SCD1 inhibitors, and ACAT1 inhibitors are attractive drugs for cancer immunotherapy.

SCD1-related epigenetic modifications affect hormone-sensitive lipase (Lipe) gene expression in cardiomyocytes

Stearoyl-CoA desaturase 1 (SCD1) is an enzyme that is involved in the regulation of lipolysis in the heart. SCD1 also affects epigenetic mechanisms, such as DNA and histone modifications, in various tissues. Both epigenetic modifications and changes in lipid metabolism are involved in the heart's response to hypoxia. The present study tested the hypothesis that SCD1 and epigenetic modifications interact to control lipolysis in cardiomyocytes under normoxic and hypoxic conditions. We found that the inhibition of SCD1 activity and loss of SCD1 expression reduced global DNA methylation levels, DNA methyltransferase (DNMT) activity, and DNMT1 expression in HL-1 cardiomyocytes and the mouse heart. We also found that the inhibition of adipose triglyceride lipase is involved in the control of global DNA methylation levels in cardiomyocytes in an SCD1-independent manner. Additionally, SCD1 inhibition reduced expression of the hormone-sensitive lipase (Lipe) gene through an increase in methylation of the Lipe gene promoter. Under hypoxic conditions, SCD1 inhibition abolished hypoxia-inducible transcription factor 1α, likely through decreases in histone deacetylase, protein kinase A, and abhydrolase domain containing 5 protein levels, leading to the attenuation of DNA hypomethylation by DNMT1. Hypoxia led to demethylation of the Lipe promoter in cardiomyocytes with SCD1 inhibition, which increased Lipe expression. These results indicate that SCD1 is involved in the control of epigenetic mechanisms in the heart and may affect Lipe expression through changes in methylation in its promoter region. Therefore, SCD1 may be considered a key player in the epigenetic response to normoxia and hypoxia in cardiomyocytes.

URI alleviates tyrosine kinase inhibitors-induced ferroptosis by reprogramming lipid metabolism in p53 wild-type liver cancers

The clinical benefit of tyrosine kinase inhibitors (TKIs)-based systemic therapy for advanced hepatocellular carcinoma (HCC) is limited due to drug resistance. Here, we uncover that lipid metabolism reprogramming mediated by unconventional prefoldin RPB5 interactor (URI) endows HCC with resistance to TKIs-induced ferroptosis. Mechanistically, URI directly interacts with TRIM28 and promotes p53 ubiquitination and degradation in a TRIM28-MDM2 dependent manner. Importantly, p53 binds to the promoter of stearoyl-CoA desaturase 1 (SCD1) and represses its transcription. High expression of URI is correlated with high level of SCD1 and their synergetic expression predicts poor prognosis and TKIs resistance in HCC. The combination of SCD1 inhibitor aramchol and deuterated sorafenib derivative donafenib displays promising anti-tumor effects in p53-wild type HCC patient-derived organoids and xenografted tumors. This combination therapy has potential clinical benefits for the patients with advanced HCC who have wild-type p53 and high levels of URI/SCD1.

SAT265 Stearoyl CoA Desaturase Knockdown Increases Saturated And Monounsaturated Fatty Acid Concentrations In SDHB KD Cells But Not In hPheo1 Wild-type Progenitor Cells

Abstract Disclosure: H.K. Ghayee: Other; Self; Royalties form the University of Texas Southwestern Medical Center. N. Bala: None. Y. Xu: None. S.G. Tevosian: None. M. Kozuch: None. N.D. Denslow: None. A.A. Alli: None. Introduction: Pheochromocytoma and paraganglioma (PPGL) patients with mutations in the succinate dehydrogenase B subunit (SDHB) frequently develop metastatic lesions and have a poor prognosis. The stearoyl-CoA desaturase 1 (SCD1) protein plays an important role in lipid metabolism. SCD1 inhibitors have shown great potential as new treatments for various diseases including cancer. Hypothesis: siRNA mediated knockdown of SCD1 compared to non-targeting siRNA would result in differences in the concentrations of saturated fatty acids and monounsaturated fatty acids in SDHB KD cells compared to hPheo1 wild-type (WT) progenitor cells. Methods: Fatty acid concentrations were assessed by fatty acid methyl ester (FAME) analysis. SCD1 expression was assessed by quantitative polymerase chain reaction (qPCR) and Western blotting analysis. Results: Analyses showed a significant decrease in SCD1 in SDHB KD cells compared to hPheo1 WT cells. Fatty acid methyl ester analysis showed the concentrations of the saturated fatty acids myristic acid, palmitic acid, and stearic acid, and the monounsaturated fatty acids palmitoleic acid and oleic acid are increased at least 2-fold in SDHB KD cells transfected with SCD1 siRNA compared to non-targeting siRNA. Conclusions: Fatty acid changes noted in hPheo1 SDHB KD cells were not seen in hPheo1 WT cells after siRNA mediated knockdown of SCD1. This suggests that SDHB deficiency and loss of FADH2 production interacts specifically with lipid desaturation pathways. Presentation: Saturday, June 17, 2023

Advances in regulation and function of stearoyl-CoA desaturase 1 in cancer, from bench to bed.

Stearoyl-CoA desaturase 1 (SCD1) converts saturated fatty acids to monounsaturated fatty acids. The expression of SCD1 is increased in many cancers, and the altered expression contributes to the proliferation, invasion, sternness and chemoresistance of cancer cells. Recently, more evidence has been reported to further support the important role of SCD1 in cancer, and the regulation mechanism of SCD1 has also been focused. Multiple factors are involved in the regulation of SCD1, including metabolism, diet, tumor microenvironment, transcription factors, non-coding RNAs, and epigenetics modification. Moreover, SCD1 is found to be involved in regulating ferroptosis resistance. Based on these findings, SCD1 has been considered as a potential target for cancer treatment. However, the resistance of SCD1 inhibition may occur in certain tumors due to tumor heterogeneity and metabolic plasticity. This review summarizes recent advances in the regulation and function of SCD1 in tumors and discusses the potential clinical application of targeting SCD1 for cancer treatment.