stearoyl-CoA Desaturase Inhibitors Research Articles

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.

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.

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.

Radiosynthesis and Preliminary Evaluation of [11C]SSI-4 for the Positron Emission Tomography Imaging of Stearoyl CoA Desaturase 1.

Stearoyl CoA desaturase 1 (SCD1) is the rate-limiting enzyme for converting saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs) and plays a key role in endogenous (de novo) fatty acid metabolism. Given that this pathway is broadly upregulated across many tumor types with an aggressive phenotype, SCD1 has emerged as a compelling target for cancer imaging and therapy. The ligand 2-(4-(2-chlorophenoxy)piperidine-1-carboxamido)-N-methylisonicotinamide (SSI-4) was identified as a potent and highly specific SCD1 inhibitor with a strong binding affinity for SCD1 at our laboratory. We herein report the radiosynthesis of [11C]SSI-4 and the preliminary biological evaluation including in vivo PET imaging of SCD1 in a human tumor xenograft model. Radiotracer [11C]SSI-4 was labeled at the carbamide position via the direct [11C]CO2 fixation on the Synthra MeIplus module in high molar activity and good radiochemical yield. In vitro cell uptake assays were performed with three hepatocellular carcinoma (HCC) cell lines and three renal cell carcinoma (RCC) cell lines. Additionally, in vivo small animal PET/CT imaging with [11C]SSI-4 and the biodistribution were carried out in a mouse model bearing HCC xenografts. Radiotracer [11C]SSI-4 afforded a 4.14 ± 0.44% (decay uncorrected, n = 10) radiochemical yield based on starting [11]CO2 radioactivity. The [11C]SSI-4 radiosynthesis time including HPLC purification and SPE formulation was 25 min from the end of bombardment to the end of synthesis (EOS). The radiochemical purity of [11C]SSI-4 was 98.45 ± 1.43% (n = 10) with a molar activity of 225.82 ± 33.54 GBq/μmol (6.10 ± 0.91 Ci/μmol) at the EOS. In vitro cell uptake study indicated all SSI-4 responsive HCC and RCC cell line uptakes demonstrate specific uptake and are blocked by standard compound SSI-4. Preliminary small animal PET/CT imaging study showed high specific uptake and block of [11C]SSI-4 uptake with co-injection of cold SSI-4 in high SCD1-expressing organs including lacrimal gland, brown fat, liver, and tumor. In summary, novel radiotracer [11C]SSI-4 was rapidly and automatedly radiosynthesized by direct [11C]CO2 fixation. Our preliminary biological evaluation results suggest [11C]SSI-4 could be a promising radiotracer for PET imaging of SCD1 overexpressing tumor tissues.

Abstract A031: A fat lot of good: A novel monounsaturated fatty acid promotes prostate cancer growth and survival

Abstract Advanced prostate cancer (PCa) is currently incurable, and development of novel treatments requires a greater understanding of key pathways that are altered during PCa progression. We have focussed on fatty acid metabolism, as the major source of energy for PCa cells, and have implicated a monounsaturated fatty acid (MUFA), cis-vaccenic acid (cVA), as a critical regulator of PCa cell homeostasis. Production of cVA requires stearoyl-CoA desaturase 1 (SCD1), the enzyme attributed to general MUFA production, and whose activity is important in a range of cancer types. Nonetheless, the specific role of cVA has not previously been studied, in PCa nor cancer more generally. To elucidate the role of cVA in PCa more precisely, we used SCD1 inhibition to study PCa responses to broad MUFA depletion and specific MUFA supplementation, comparing the responses of cVA with its more common structural isomer oleate. To accomplish these aims, we utilised cell line models of PCa (LNCaP, MR49F and V16D) and a benign prostate cell line (PNT1A) to perform cell viability, lipidomic and flow cytometric assays. In addition, responses in clinically-relevant patient-derived tumor explants were measured by proliferative (Ki67) and cell death (CC3) marker staining. Pharmacological SCD1 inhibition (SCDi; A939572) decreased cell viability and increased cell death in PCa cell lines and patient-derived tumor explants, while only minimally affecting the benign prostate cell line PNT1A. Phenotypically, analysis of mitochondrial function and lipidomic changes under SCDi suggested a role for MUFAs in regulating mitochondrial membrane composition via cardiolipins, and oxidative stress levels. This in turn has the potential to regulate cell death, control tumor burden, and influence overall PCa patient survival. Supplementation of cVA or oleate under SCDi demonstrated that only cVA was successful at rescuing cell viability, and cVA, but not oleate, could rescue changes observed in mitochondrial-related lipids, suggesting that cVA regulation of mitochondrial function was a major determinant of its effect on cell viability. Additionally, cVA alone dose-dependently increased PCa cell viability, implicating cVA as an important oncogenic factor. Together, these data identify cVA as a novel substrate required for PCa cell viability, likely via regulation of mitochondrial homeostasis and associated cell death pathways. In summary, this research has revealed more precise insights into the oncogenic effects of an overlooked MUFA, cVA, in PCa, and may uncover new druggable targets that are more selective, to improve treatment options for advanced PCa. Citation Format: Julia S. Scott, Reuben Young, Swati Irani, Jonas Dehairs, Stephen Blanksby, Johannes V. Swinnen, Zeyad D. Nassar, Lisa M. Butler. A fat lot of good: A novel monounsaturated fatty acid promotes prostate cancer growth and survival [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A031.

Abstract LB014: Targeting Stearoyl-coA desaturase (SCD) as a therapeutic strategy in STK11/KEAP1 co-mutant non-small cell lung cancer

Abstract Introduction: Non-small cell lung cancer (NSCLC) is a highly prevalent subtype of lung cancer. Recent findings in the field have improved the clinical outcomes for only a subset of patients who are responsive to immunotherapy or have targetable oncogenic drivers. We have previously showed that concomitant loss of Serine/Threonine Kinase 11 (STK11) and Kelch-like ECH Associated Protein1 (KEAP1) detected in up to 10% NSCLC cases, dramatically enhances cell proliferation and invasion in vitro and in vivo. Bulk RNA sequencing identified upregulation of genes involved in ferroptosis, which is an iron dependent form of programmed cell death, in STK11/KEAP1 double mutant models, nominating ferroptosis as a potential vulnerability in these tumors. However, the mechanism of ferroptosis evasion in this subset in not well understood. Methods: We performed an in vitro CRISPR screen in STK11/KEAP1 co-mutant, single mutant and wild type cell lines. To further characterize the role of ferroptosis regulators in STK11/KEAP1 co-mutant setting, we performed phospho-kinase arrays and RNA sequencing in STK11/KEAP1 cell lines followed by validation through western blotting. Additionally, we performed gene expression analysis in patient derived xenografts (PDX) models treated with the SCD inhibitor to further characterize the mechanisms by which SCD inhibition has synthetic lethal effects in STK11/KEAP1 co-mutant background. Results: CRISPR/Cas9 based genetic screening identified stearoyl-CoA desaturase (SCD), a gene involved in ferroptosis protection, as a potential therapeutic target in the STK11/KEAP1 double mutant tumors. We further demonstrate that SCD overexpression protects STK11/KEAP1 co-mutant NSCLCs from undergoing ferroptosis. Pharmacological inhibition of SCD significantly reduced viability of STK11/KEAP1 co-mutant NSCLCs and made the co-mutant cells sensitive to ferroptosis induction. Phospho-kinase array showed downregulation of JAK-STAT and AKT signaling, in STK11/KEAP1 co-mutant NSCLCs as compared to both STK11 and KEAP1 single mutant isogenic conditions. The downregulation of these pathways was confirmed by gene expression profiling. To further understand the role of SCD in regulating ferroptosis we are studying the effect of concurrent loss of STK11 and KEAP1 on SCD on lipid oxidizing capacity and ferroptosis in a comprehensive panel of NSCLC cell lines and testing whether ferroptosis protection due to SCD overexpression leads to enhanced tumorigenesis in this co-mutant subtype of NSCLC in vivo and in vitro. Conclusions: Our study demonstrates the biological differences between STK11/KEAP1 co-mutant NSCLC as compared to the single mutants or wildtype counterparts in a KRAS mutation agnostic manner. In this study, we further establish SCD as a potential therapeutic strategy in STK11/KEAP1 co-mutant NSCLCs. We also show that SCD-mediated ferroptosis evasion is linked to multiple oncogenic signaling pathways which could be associated with ferroptosis. In summary we define a new therapeutic approach to STK11/KEAP1 co-mutant NSCLC to improve survival outcomes for patients diagnosed with this devastating disease. Citation Format: Utsav Sen, Triparna Sen. Targeting Stearoyl-coA desaturase (SCD) as a therapeutic strategy in STK11/KEAP1 co-mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB014.

Abstract 5489: Synergistic activity of SCD1 blockade in combination with tyrosine kinase inhibitors lenvatinib and cabozantinib in hepatocellular carcinoma (HCC)

Abstract Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer. Tyrosine kinase inhibitors (TKIs) are approved as a first-line treatment for unresectable HCC. Lenvatinib and cabozantinib are two of the most used TKIs, but the therapeutic duration is limited due to the development of drug resistance. Therefore, understanding the mechanisms of resistance and combining TKIs with other drugs antagonizing resistance should lead to antitumor synergy, eliminating drug resistance. It turns out that the simultaneous use of TKIs together with an inhibitor of stearoyl-CoA desaturase 1 (SCD1) prevents the development of drug resistance, leading to a durable response. SCD1 is the enzyme responsible for de novo fatty acid (FAs) synthesis, converting saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs). MUFAs are an alternative energy source to glucose, integral to cellular membranes, and prevent endoplasmic reticulum (ER) stress and other signaling pathways. In our laboratory, we developed a novel, highly specific SCD1 inhibitor - SSI-4. We have tested the biological activity of SSI-4 against different HCC cell lines and patient-derived xenografts (PDX) mouse models. Of the twelve tested HCC cell lines, four were highly sensitive to SSI-4 (IC50 1-50 nM). Other cell lines showed moderate or no sensitivity to SSI-4. We tested the concomitant use of SSI-4 with lenvatinib and cabozantinib, tyrosine kinase inhibitors (TKIs) FDA-approved for HCC, in HCC cell lines in vitro and using HCC PDX in vivo mouse models. Our studies showed that the combination of the SCD1 inhibitor with both lenvatinib and cabozantinib showed a highly synergistic effect and no development of drug resistance i.e. durable response versus single TKI therapy. Ongoing mechanistic studies are examining whether known molecular targets of tested TKI’s such as VEGFR1, 2, and 3, PDGFRα, FGFR, KIT, and RET dominate in HCC drug resistance to lenvatinib and cabozantinib, and how the use of SSI-4 overcomes the phenomenon of resistance. Citation Format: Justyna J. Gleba, Aylin Alasonyalilar-Demirer, Matthew L. Pawlush, Ahmet Bilgili, Peyton G. Hickman, Kabir Mody, Lewis R. Roberts, Steven R. Alberts, Mark J. Truty, Tushar C. Patel, Han W. Tun, John A. Copland. Synergistic activity of SCD1 blockade in combination with tyrosine kinase inhibitors lenvatinib and cabozantinib in hepatocellular carcinoma (HCC). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5489.

Icaritin Derivative IC2 Induces Cytoprotective Autophagy of Breast Cancer Cells via SCD1 Inhibition.

Breast cancer is one of the most prevalent malignancies and the leading cause of cancer-associated mortality in China. Icaritin (ICT), a prenyl flavonoid derived from the Epimedium Genus, has been proven to inhibit the proliferation and stemness of breast cancer cells. Our previous study demonstrated that IC2, a derivative of ICT, could induce breast cancer cell apoptosis by Stearoyl-CoA desaturase 1 (SCD1) inhibition. The present study further investigated the mechanism of the inhibitory effects of IC2 on breast cancer cells in vitro and in vivo. Our results proved that IC2 could stimulate autophagy in breast cancer cells with the activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling and mitogen-activated protein kinase (MAPK) signaling. Combination treatment of the AMPK inhibitor decreased IC2-induced autophagy while it markedly enhanced IC2-induced apoptosis. In common with IC2-induced apoptosis, SCD1 overexpression or the addition of exogenous oleic acid (OA) could also alleviate IC2-induced autophagy. In vivo assays additionally demonstrated that IC2 treatment markedly inhibited tumor growth in a mouse breast cancer xenograft model. Overall, our study was the first to demonstrate that IC2 induced cytoprotective autophagy by SCD1 inhibition in breast cancer cells and that the autophagy inhibitor markedly enhanced the anticancer activity of IC2. Therefore, IC2 was a potential candidate compound in combination therapy for breast cancer.

Targeting de novo lipid synthesis induces lipotoxicity and impairs DNA damage repair in glioblastoma mouse models.

Deregulated de novo lipid synthesis (DNLS) is a potential druggable vulnerability in glioblastoma (GBM), a highly lethal and incurable cancer. Yet the molecular mechanisms that determine susceptibility to DNLS-targeted therapies remain unknown, and the lack of brain-penetrant inhibitors of DNLS has prevented their clinical evaluation as GBM therapeutics. Here, we report that YTX-7739, a clinical-stage inhibitor of stearoyl CoA desaturase (SCD), triggers lipotoxicity in patient-derived GBM stem-like cells (GSCs) and inhibits fatty acid desaturation in GSCs orthotopically implanted in mice. When administered as a single agent, or in combination with temozolomide (TMZ), YTX-7739 showed therapeutic efficacy in orthotopic GSC mouse models owing to its lipotoxicity and ability to impair DNA damage repair. Leveraging genetic, pharmacological, and physiological manipulation of key signaling nodes in gliomagenesis complemented with shotgun lipidomics, we show that aberrant MEK/ERK signaling and its repression of the energy sensor AMP-activated protein kinase (AMPK) primarily drive therapeutic vulnerability to SCD and other DNLS inhibitors. Conversely, AMPK activation mitigates lipotoxicity and renders GSCs resistant to the loss of DNLS, both in culture and in vivo, by decreasing the saturation state of phospholipids and diverting toxic lipids into lipid droplets. Together, our findings reveal mechanisms of metabolic plasticity in GSCs and provide a framework for the rational integration of DNLS-targeted GBM therapies.

TGF-β1 promotes SCD1 expression via the PI3K-Akt-mTOR-SREBP1 signaling pathway in lung fibroblasts

BackgroundLung fibroblast activation is associated with airway remodeling during asthma progression. Stearoyl-CoA desaturase 1 (SCD1) plays an important role in the response of fibroblasts to growth factors. This study aimed to explore the effects of SCD1 on fibroblast activation induced by transforming growth factor-β1 (TGF-β1) and the role of the phosphatidylinositol-3-kinase-AKT serine-threonine protein kinase-mechanistic target of rapamycin (PI3K-Akt-mTOR) pathway on the regulation of SCD1 expression in airway remodeling.MethodsFemale C57BL/6 mice were sensitized and challenged with house dust mites to generate a chronic asthma model. The inhibitor of SCD1 was injected i.g. before each challenge. The airway hyper-responsiveness to methacholine was evaluated, and airway remodeling and airway inflammation were assessed by histology. The effects of SCD1 on fibroblast activation were evaluated in vitro using an SCD1 inhibitor and oleic acid and via the knockdown of SCD1. The involvement of the PI3K-Akt-mTOR-sterol regulatory element-binding protein 1 (SREBP1) pathway in lung fibroblasts was investigated using relevant inhibitors.ResultsThe expression of SCD1 was increased in fibroblasts exposed to TGF-β1. The inhibition of SCD1 markedly ameliorated airway remodeling and lung fibroblast activation in peripheral airways. The knockdown or inhibition of SCD1 resulted in significantly reduced extracellular matrix production in TGF-β1-treated fibroblasts, but this effect was reversed by the addition of exogenous oleic acid. The PI3K-Akt-mTOR-SREBP1 pathway was found to be involved in the regulation of SCD1 expression and lung fibroblast activation.ConclusionsThe data obtained in this study indicate that SCD1 expression contributes to fibroblast activation and airway remodeling and that the inhibition of SCD1 may be a therapeutic strategy for airway remodeling in asthma.