Expression Of stearoyl-CoA Desaturase Research Articles

Abstract PO1-13-08: Comparative analysis of stearoyl-CoA desaturase 1 expression and activity index in model cell lines of breast cancer subclasses

Abstract Introduction Due to the unique conditions of the tumor microenvironment, such as hypoxia, poor angiogenesis, and mitochondrial dysfunction, cancer cells face challenges in obtaining nutrients and energy supply. However, monounsaturated fatty acids have been identified as preferred substrates for energy generation and maintenance of cellular structures in cancer cells. These fatty acids can be obtained through de novo fatty acid synthesis. Stearoyl-CoA desaturase 1 (SCD1) is the primary enzyme involved in the biosynthesis of monounsaturated fatty acids from saturated fatty acids and is known to be upregulated in various malignancies, including breast cancer. This study aimed to assess the expression and activity index of SCD1 in well-characterized MCF-7, SK-BR3, and MDA-MB231 breast cancer cell lines, representing luminal A/B, HER2-enriched, and triple-negative subtypes, respectively. Methods The breast cancer cell lines were cultured in RPMI-1640 medium with 10% fetal bovine serum at 37°C, 5% CO2, and 95% humidity for 72 hours. After harvesting the cells, SCD1 expression was analyzed using real-time quantitative PCR, and the activity index was determined by measuring the ratio of monounsaturated fatty acids to saturated fatty acids using capillary gas-liquid chromatography. Results MCF-7 cell line showed a significantly higher SCD1 expression compared to MDA-MB231 (250-fold, p< 0.0001) and SK-BR3 (83-fold, p< 0.0001) cell lines. The activity index of SCD1 was significantly higher in both MCF-7 and MDA-MB231 cell lines with fold changes of 2.6 and 2.5, respectively, compared to SK-BR3 cell line (p=0.004 for both). Conclusion Cell model assays demonstrated that the luminal A/B and triple-negative subtypes showed a higher capacity to convert saturated fatty acids to monounsaturated fatty acids through SCD1 enzyme activity, indicating a different lipid metabolism profile in the HER2-enriched subtype. These new findings reveal differences in SCD1 expression and activity among breast cancer subclasses. They highlight vulnerabilities in metabolism and identify potential therapeutic targets with clinical implications for managing breast cancer. Citation Format: Hamid-Reza Feizi, Amir Mehdizadeh, Zohreh Sanaat, Khadijeh Abbasi, Frank Gieseler, Masoud Darabi. Comparative analysis of stearoyl-CoA desaturase 1 expression and activity index in model cell lines of breast cancer subclasses [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-13-08.

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.

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.

Scd1 and monounsaturated lipids are required for autophagy and survival of adipocytes

ObjectiveExposure of adipocytes to ‘cool’ temperatures often found in the periphery of the body induces expression of Stearoyl-CoA Desaturase-1 (Scd1), an enzyme that converts saturated fatty acids to monounsaturated fatty acids. The goal of this study is to further investigate the roles of Scd in adipocytes. MethodIn this study, we employed Scd1 knockout cells and mouse models, along with pharmacological Scd1 inhibition to dissect the enzyme's function in adipocyte physiology. ResultsOur study reveals that production of monounsaturated lipids by Scd1 is necessary for fusion of autophagosomes to lysosomes and that with a Scd1-deficiency, autophagosomes accumulate. In addition, Scd1-deficiency impairs lysosomal and autolysosomal acidification resulting in vacuole accumulation and eventual cell death. Blocking autophagosome formation or supplementation with monounsaturated fatty acids maintains vitality of Scd1-deficient adipocytes. ConclusionThis study demonstrates the indispensable role of Scd1 in adipocyte survival, with its inhibition in vivo triggering autophagy-dependent cell death and its depletion in vivo leading to the loss of bone marrow adipocytes.

Effects of dietary Clostridium butyricum and rumen protected fat on meat quality, oxidative stability, and chemical composition of finishing goats

BackgroundClostridium butyricum (CB) is a probiotic that can regulate intestinal microbial composition and improve meat quality. Rumen protected fat (RPF) has been shown to increase the dietary energy density and provide essential fatty acids. However, it is still unknown whether dietary supplementation with CB and RPF exerts beneficial effects on growth performance and nutritional value of goat meat. This study aimed to investigate the effects of dietary CB and RPF supplementation on growth performance, meat quality, oxidative stability, and meat nutritional value of finishing goats. Thirty-two goats (initial body weight, 20.5 ± 0.82 kg) were used in a completely randomized block design with a 2 RPF supplementation (0 vs. 30 g/d) × 2 CB supplementation (0 vs. 1.0 g/d) factorial treatment arrangement. The experiment included a 14-d adaptation and 70-d data and sample collection period. The goats were fed a diet consisted of 400 g/kg peanut seedling and 600 g/kg corn-based concentrate (dry matter basis).ResultInteraction between CB and RPF was rarely observed on the variables measured, except that shear force was reduced (P < 0.05) by adding CB or RPF alone or their combination; the increased intramuscular fat (IMF) content with adding RPF was more pronounced (P < 0.05) with CB than without CB addition. The pH24h (P = 0.009), a* values (P = 0.007), total antioxidant capacity (P = 0.050), glutathione peroxidase activities (P = 0.006), concentrations of 18:3 (P < 0.001), 20:5 (P = 0.003) and total polyunsaturated fatty acids (P = 0.048) were increased, whereas the L* values (P < 0.001), shear force (P = 0.050) and malondialdehyde content (P = 0.044) were decreased by adding CB. Furthermore, CB supplementation increased essential amino acid (P = 0.027), flavor amino acid (P = 0.010) and total amino acid contents (P = 0.024) as well as upregulated the expression of lipoprotein lipase (P = 0.034) and peroxisome proliferator-activated receptor γ (PPARγ) (P = 0.012), and downregulated the expression of stearoyl-CoA desaturase (SCD) (P = 0.034). The RPF supplementation increased dry matter intake (P = 0.005), averaged daily gain (trend, P = 0.058), hot carcass weight (P = 0.046), backfat thickness (P = 0.006), concentrations of 16:0 (P < 0.001) and c9-18:1 (P = 0.002), and decreased the shear force (P < 0.001), isoleucine (P = 0.049) and lysine content (P = 0.003) of meat. In addition, the expressions of acetyl-CoA carboxylase (P = 0.003), fatty acid synthase (P = 0.038), SCD (P < 0.001) and PPARγ (P = 0.022) were upregulated due to RPF supplementation, resulting in higher (P < 0.001) content of IMF.ConclusionsCB and RPF could be fed to goats for improving the growth performance, carcass traits and meat quality, and promote fat deposition by upregulating the expression of lipogenic genes of Longissimus thoracis muscle.

Allele-specific effect of various dietary fatty acids and ETS1 transcription factor on SCD1 expression

Overnutrition and genetic predisposition are major risk factors for various metabolic disorders. Stearoyl-CoA desaturase-1 (SCD1) plays a key role in these conditions by synthesizing unsaturated fatty acids (FAs), thereby promoting fat storage and alleviating lipotoxicity. Expression of SCD1 is influenced by various saturated and cis-unsaturated FAs, but the possible role of dietary trans FAs (TFAs) and SCD1 promoter polymorphisms in its regulations has not been addressed. Therefore, we aimed to investigate the impact of the two main TFAs, vaccenate and elaidate, and four common promoter polymorphisms (rs1054411, rs670213, rs2275657, rs2275656) on SCD1 expression in HEK293T and HepG2 cell cultures using luciferase reporter assay, qPCR and immunoblotting. We found that SCD1 protein and mRNA levels as well as SCD1 promoter activity are markedly elevated by elaidate, but not altered by vaccenate. The promoter polymorphisms did not affect the basal transcriptional activity of SCD1. However, the minor allele of rs1054411 increased SCD1 expression in the presence of various FAs. Moreover, this variant was predicted in silico and verified in vitro to reduce the binding of ETS1 transcription factor to SCD1 promoter. Although we could not confirm an association with type 2 diabetes mellitus, the FA-dependent and ETS1-mediated effect of rs1054411 polymorphism deserves further investigation as it may modulate the development of lipid metabolism-related conditions.

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.

Lipid Handling Induces Ferroptosis and Conveys Sensitivity to Anti-BCMA Immunotherapy in Multiple Myeloma

Lipid metabolic changes in cancer are attracting increased attention. BAFF/APRIL axis is a multifaceted immune regulator of adipose tissue function and an emerging target for anti-BCMA therapy in multiple myeloma (MM). However, lipid analyses are scarce in MM onset and response to treatment. First, we measured metabolites and proteins in sera obtained from matched bone marrow and peripheral blood of 17 newly diagnosed and 9 relapsed/refractory MM patients, by LC-MS/MS. String analysis identified crucial pathways including fibrinogen regulation, inflammatory response, structural integrity of lipoproteins and lipid transport, with a significant increase of apoliproteins APO-A1 (key component of HDL particle and cofactor for lecithin-cholesterol acyltransferase (LCAT) which is responsible for the formation of most plasma cholesteryl esters), A2,C2 (which hydrolyzes triglycerides to provide free fatty acids for cells), C3, components of HDL and LDL, confirming a deranged lipid handling in RR-MM patients. Second, we studied the lipid metabolic changes upon anti-BCMA exposure with Elranatamab (EL), an investigational, off-the-shelf, humanized BCMA-CD3-directed bispecific antibody engineered to elicit potent T-cell-mediated anti-MM activity. Combining in vitro assays, FACS, qRT-PCR, immunofluorescence, Western Blot and RNA-seq we evaluated the response to EL treatment in 3 human myeloma cell lines U266, NCI-H929 and OPM2 (3 cell lines chosen for their different basal bioenergetics profile). MM cells were co-incubated with various concentrations of EL in presence of CD3+T cells isolated from healthy donors in 96- well U-bottom plates for 4 h and 24 h at an E:T ratio of 1:5 and 1:10, then stained with anti-CD138-PE antibody . CD138 + cells were detected by flow cytometry and counted as surviving MM cells. BODIPY™ 581/591 C11 (Lipid Peroxidation Sensor) and BODIPY 493/503 for Neutral Lipid Droplets Staining for FACS and immunofluorescence were used to quantify lipid peroxidation and cytoplasmatic LDs on surviving CD138 + cells. Despite the BCMA target was equally expressed on U266, NCI-H929 and OPM2, the sensitivity to EL was different, inducing cell cycle arrest in the G2/M phase in U266 and NCI-H929 cell lines but not in OPM2, in E:T ratio independent-manner. The expression of the activation markers CD69 and CD25 on T cells and the release of cytokines by T cells were target-dependent and occurred only in the presence of BCMA-positive cells. Oil-Red-O staining revealed an increased lipid content after EL exposure in all tested MM cell lines, with OPM2 the richest in basal lipids content. To dissect the contribution of lipophagy versus lipolysis we performed an autophagy flux analysis by western blot and RNA-seq essay, showing that lipolysis was the emerging response to EL treatment. In EL-sensitive U266 we found an increase of lipid peroxides, hallmark of ferroptosis, a form of cell death due to missed control of membrane lipid peroxidation, a phenomenon negligible in EL-resistant OPM2. Lipidomics demonstrated higher levels of monounsaturated fatty acids (MUFA) than polyunsaturated fatty acids (PUFA) in OPM2, associated to an increased expression of Stearoyl CoA desaturase 1 (SCD1), the enzyme that catalyzes the rate-limiting step in the production of MUFA. While the PUFA oxidation is pro-ferroptotic, MUFA activation promotes a ferroptosis-resistant cell state. Indeed, a ferroptosis-primed resistant phenotype in EL-sensitive U266 was associated to downregulation of lipid peroxides scavengers GPX4 and SLC7A11 and up-regulation of pro-ferroptotic acyl-CoA synthetase long-chain family member 4 (ACSL4). Exogenous MUFA (via supplementation with palmitic acid 125 µM conjugated to BSA 1:6) alleviated ferroptosis induction in U266 making them resistant to EL, a phenotype associated to overexpression of CD36, the main free fatty acids (FFA) transporter. Conversely, in OPM2, inducing iron-dependent lipid peroxidation through RSL3 (3 µM) treatment rescued EL resistance, resulting in a time-dependent increase in cytosolic lipid peroxidation beginning at 6 hours, and overt cell death via ferroptosis at 18 hours. Taken together, our findings suggest that MUFA/PUFA ratio drives ferroptosis and mediates EL sensitivity, addressing lipid handling as a novel means to tailor immunotherapy in RRMM.

Improving Shelf Life and Content of Unsaturated Fatty Acids in Meat of Lambs Fed a Diet Supplemented with Grape Dregs.

This study was conducted to evaluate the potential effects of dietary grape residue levels on the slaughter indicators, meat quality, meat shelf-life, unsaturated fatty acid content, and expression of fatty acid deposition genes in the muscle of lambs. Sixty 30-month-old male Dorper and Small-Tailed Han F1 hybrid lambs were assigned to a single factor complete randomized trial design and fed with four different diets including 0%, 8%, 16%, and 24% grape dregs, respectively. The findings regarding meat production efficacy in the lambs revealed substantial differences. The control group showed notably lower dressing percentage, carcass weight, net meat weight, meat percentage concerning carcass, meat-to-bone ratio, relative visceral and kidney fat mass, and rib eye area compared to the other groups (p < 0.05). Additionally, the meat shearing force of lambs fed a diet with 16% grape pomace (GP) was significantly higher than that of the 24% GP group (p < 0.05), while the 24 h meat color parameter a* value of the control group was notably higher than that of the 8% GP group (p < 0.05). In addition, compared to the control group, lambs fed with a diet containing 16% GP had higher levels of oleic acid (C18:1n-9c), linoleic acid (C18:2n-6c), behenic acid (C22:0), tricosanoic acid (C23:0), lignoceric acid (C24:0), and conjugated linoleic acid (CLA), at a ratio of ∑CLA/TFA, ∑n-6, ∑MUFA, and ∑PUFA in the longissimus dorsi muscle (p < 0.05), but the reverse case was applicable for Total Volatile Basic Nitrogen (TVB-N) content (p < 0.05). GP supplementation did not substantially affect the expression of stearoyl-CoA desaturase (SCD), peroxisome proliferator activated receptor alpha (PPARα), and peroxisome proliferator-activated receptor gamma (PPARγ) genes (p > 0.05). The findings indicated that incorporating grape dregs in the diets of fattening lambs leads to notable enhancements in meat production and the antioxidant capacity of lamb meat, and effectively extends the shelf life of the meat.

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.

Genetic Variants in WNT16 and PKD2L1 Locus Affect Heel Ultrasound Bone Stiffness: Analyses from the General Population and Patients Evaluated for Osteoporosis.

Osteoporosis, a complex chronic disease with increasing prevalence, is characterised by reduced bone mineral density (BMD) and increased fracture risk. The high heritability of BMD suggests substantial impact of the individual genetic disposition on bone phenotypes and the development of osteoporosis. In the past years, genome-wide association studies (GWAS) identified hundreds of genetic variants associated with BMD or osteoporosis. Here, we analysed 1103 single nucleotide polymorphisms (SNPs), previously identified as associated with estimated BMD (eBMD) in the UK Biobank. We assessed whether these SNPs are related to heel stiffness index obtained by quantitative ultrasound in 5665 adult participants of the Study of Health in Pomerania (SHIP). We confirmed 45 significant associations after correction for multiple testing. Next, we analysed six selected SNPs in 631 patients evaluated for osteoporosis [rs2707518 (CPED1/WNT16), rs3779381 (WNT16), rs115242848 (LOC101927709/EN1), rs10239787 (JAZF1), rs603424 (PKD2L1) and rs6968704 (JAZF1)]. Differences in minor allele frequencies (MAF) of rs2707518 and rs3779381 between SHIP participants (higher MAF) and patients evaluated for osteoporosis (lower MAF) indicated a protective effect of the minor allele on bone integrity. In contrast, differences in MAF of rs603424 indicated a harmful effect. Co-localisation analyses indicated that the rs603424 effect may be mediated via stearoyl-CoA desaturase (SCD) expression, an enzyme highly expressed in adipose tissue with a crucial role in lipogenesis. Taken together, our results support the role of the WNT16 pathway in the regulation of bone properties and indicate a novel causal role of SCD expression in adipose tissue on bone integrity.

Stearoyl-CoA desaturase 1 inhibition impairs triacylglycerol accumulation and lipid droplet formation in colorectal cancer cells.

Increases in fatty acid (FA) biosynthesis meet the higher lipid demand by intensely proliferating cancer cells and promoting their progression. Stearoyl-CoA desaturase 1 (SCD1) is the key enzyme in FA biosynthesis, converting saturated FA (SFA) into monounsaturated FA (MUFA). Increases in the MUFA/SFA ratio and SCD1 expression have been observed in cancers of various origins and correlate with their aggressiveness. However, much is still unknown about the SCD1-dependent molecular mechanisms that promote specific changes in metabolic pathways of cancer cells. The present study investigated the involvement of SCD1 in shaping glucose and lipid metabolism in colorectal cancer (CRC) cells. Excess FAs that derive from de novo lipogenesis are stored in organelles, called lipid droplets (LDs), mainly in the form of triacylglycerol (TAG) and cholesteryl esters. LD accumulation is associated with key features of cancer development and progression. Consistent with our findings, the pharmacological inhibition of SCD1 activity affects CRC cell viability and impairs TAG accumulation and LD formation in these cells through the activation of lipolytic and lipophagic pathways. We showed that SCD1 suppression affects crucial lipogenic processes that promote lipid accumulation in CRC cells but in a sterol regulatory element-binding protein 1-independent manner. We propose that adenosine monophosphate-activated protein kinase contributes to these changes through the activation of lipolysis and inhibition of TAG synthesis. We also provide evidence of the involvement of SCD1 in the regulation of glucose uptake and utilization in CRC cells. These findings underscore the importance of SCD1 in regulating cellular processes that promote cancer development and progression.

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

Serum Free Fatty Acid Changes Caused by High Expression of Stearoyl-CoA Desaturase 1 in Tumor Tissues Are Early Diagnostic Markers for Ovarian Cancer.

Measurement of serum FFA levels by changes in the expression of fatty acid metabolizing enzymes in tumor tissue would allow early detection of ovarian cancer. In particular, the SCD1-associated FFAs, oleic and arachidic acid, would be powerful new screening tools for early-stage ovarian cancer.

Pirfenidone ameliorates liver steatosis by targeting the STAT3-SCD1 axis.

Previous studies reported that pirfenidone (PFD) is associated with liver disease. However, the effects of pirfenidone on energy metabolism and hepatic lipid accumulation are still poorly understood. In this study, C57BL/6J mice were randomly divided into two groups, and fed a normal chow diet (NCD) or a high-fat diet (HFD) for 16weeks. At the end of the eighth week, half of the mice fed on both diets were treated with PFD. Biochemical and lipid metabolism-related indices were analyzed. Furthermore, Hepa 1-6 cells and mouse primary hepatocytes (MPHs) were incubated with PFD with or without free fatty acid (FFA) treatment. Then, stattic (a p-STAT3 inhibitor) or Ad-shSTAT3 was used to further elucidate the effects of Signal Transducer and Activator of Transcription 3 (STAT3) signaling on PFD regulation of hepatic steatosis. PFD ameliorated obesity and hepatic lipid deposition in HFD mice by decreasing stearoyl-CoA desaturase 1 (SCD1) expression and upregulating p-STAT3 in the liver. In Hepa 1-6 cells and MPHs, PFD also down-regulated the expression of SCD1. STAT3 inhibition treatment eliminated the benefits of PFD on both SCD1 and hepatic steatosis. In summary, our data reveal that PFD may play an important role in mitigating hepatic steatosis in a STAT3-SCD1-dependent manner.

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.

Stearoyl-CoA Desaturase 1 as a Therapeutic Biomarker: Focusing on Cancer Stem Cells.

The dysregulation of lipid metabolism and alterations in the ratio of monounsaturated fatty acids (MUFAs) to saturated fatty acids (SFAs) have been implicated in cancer progression and stemness. Stearoyl-CoA desaturase 1 (SCD1), an enzyme involved in lipid desaturation, is crucial in regulating this ratio and has been identified as an important regulator of cancer cell survival and progression. SCD1 converts SFAs into MUFAs and is important for maintaining membrane fluidity, cellular signaling, and gene expression. Many malignancies, including cancer stem cells, have been reported to exhibit high expression of SCD1. Therefore, targeting SCD1 may provide a novel therapeutic strategy for cancer treatment. In addition, the involvement of SCD1 in cancer stem cells has been observed in various types of cancer. Some natural products have the potential to inhibit SCD1 expression/activity, thereby suppressing cancer cell survival and self-renewal activity.

Krüppel-like factor 4 (KLF4) facilitates lipid production in immortalized human sebocytes via regulating the expression of SREBP1

BackgroundAcne is associated with the excessive production of sebum, a complex mixture of lipids, in the sebaceous glands. The transcription factor Krüppel-like factor 4 (KLF4) plays an important role in skin morphogenesis, but its role in sebum production by sebocytes is not well known. PurposeIn this study, we investigated the possible action mechanism of KLF4 during calcium-induced lipogenesis in immortalized human sebocytes. MethodsSebocytes were treated with calcium, and lipid production was confirmed by thin-layer chromatography (TLC) and Oil Red O staining. To investigate the effect of KLF4, sebocytes were transduced with the KLF4-overexpressing adenovirus, and then lipid production was evaluated. ResultsCalcium treatment resulted in increased sebum production in terms of squalene synthesis in sebocytes. In addition, calcium increased the expression of lipogenic regulators such as sterol-regulatory element binding protein 1 (SREBP1), sterol-regulatory element binding protein 2 (SREBP2), and stearoyl-CoA desaturase (SCD). Similarly, the expression of KLF4 was increased by calcium in sebocytes. To investigate the effect of KLF4, we overexpressed KLF4 in sebocytes using recombinant adenovirus. As a result, KLF4 overexpression increased the expression of SREBP1, SREBP2, and SCD. Parallel to this result, lipid production was also increased by KLF4 overexpression. Chromatin immunoprecipitation revealed the binding of KLF4 to the SREBP1 promoter, indicating that KLF4 may directly regulate the expression of lipogenic regulators. ConclusionThese results suggest that KLF4 is a novel regulator of lipid production in sebocytes.

SLC25A22 as a key mitochondrial transporter against ferroptosis by producing GSH and MUFAs.

Ferroptosis, a type of oxidative cell death driven by unlimited lipid peroxidation, is emerging as a target for cancer therapy. Although mitochondrial dysfunction may lead to ferroptosis, the underlying molecular mechanisms and metabolic pathways for ferroptosis are incompletely understood. Here, we identify solute carrier family 25 member 22 (SLC25A22), a mitochondrial glutamate transporter, as a driver of ferroptosis resistance in pancreatic ductal adenocarcinoma (PDAC) cells. The downregulation of SLC25A22 expression was associated with increased sensitivity to ferroptosis, but not to apoptosis. Mechanistically, on the one hand, SLC25A22-dependent NAPDH synthesis blocks ferroptotic cell death in PDAC cells through mediating the product of glutathione, the most important hydrophilic antioxidant. On the other hand, SLC25A22 promotes the expression of stearoyl-CoA desaturase (SCD) in PDAC cells in an AMP-activated protein kinase (AMPK)-dependent manner, resulting in the production of anti-ferroptotic monounsaturated fatty acids (MUFAs). The animal study further confirms that SLC25A22 inhibits ferroptosis-mediated tumor suppression. SLC25A22 is a novel metabolic repressor of ferroptosis by producing GSH and MUFAs. These findings establish a previously unrecognized metabolic defense pathway to limit ferroptotic cell death in vitro and in vivo.

Lithium Chloride Promotes Endogenous Synthesis of CLA in Bovine Mammary Epithelial Cells.

Although conjugated linoleic acid (CLA) can promote human health, its content in milk is insufficient to have a significant impact. The majority of the CLA in milk is produced endogenously by the mammary gland. However, research on improving its content through nutrient-induced endogenous synthesis is relatively scarce. Previous research found that the key enzyme, stearoyl-CoA desaturase (SCD) for the synthesis of CLA, can be expressed more actively in bovine mammary epithelial cells (MAC-T) when lithium chloride (LiCl) is present. This study investigated whether LiCl can encourage CLA synthesis in MAC-T cells. The results showed that LiCl effectively increased SCD and proteasome α5 subunit (PSMA5) protein expression in MAC-T cells as well as the content of CLA and its endogenous synthesis index. LiCl enhanced the expression of proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein 1 (SREBP1), and its downstream enzymes acetyl CoA carboxylase (ACC), fatty acid synthase (FASN), lipoprotein lipase (LPL), and Perilipin 2 (PLIN2). The addition of LiCl significantly enhanced p-GSK-3β, β-catenin, p-β-catenin protein expression, hypoxia-inducible factor-1α (HIF-1α), and downregulation factor genes for mRNA expression (P < 0.05). These findings highlight that LiCl can increase the expression of SCD and PSMA5 by activating the transcription of HIF-1α, Wnt/β-catenin, and the SREBP1 signaling pathways to promote the conversion of trans-vaccenic acid (TVA) to the endogenous synthesis of CLA. This data suggests that the exogenous addition of nutrients can increase CLA content in milk through pertinent signaling pathways.