stearoyl-CoA Desaturase Inhibitors Research Articles

From pathogenesis of acne vulgaris to anti-acne agents.

Acne vulgaris is a cutaneous chronic inflammatory disorder with complex pathogenesis. Four factors play vital roles in acne pathophysiology: hyperseborrhea and dysseborrhea, altered keratinization of the pilosebaceous duct, Cutibacterium acnes (C. acnes) and inflammation. The main hormones responsible for the development of acne vulgaris include androgens, insulin and insulin-like growth factor-1. Other factors involved in this process are corticotropin-releasing hormone, α-melanocyte-stimulating hormone and substance P. Wnt/β-catenin signaling pathway, phosphoinositide 3-kinase (PI3K)/Akt pathway, mitogen-activated protein kinase pathway, adenosine 5'-monophosphate-activated protein kinase pathway and nuclear factor kappa B pathway participate in the modulation of sebocyte, keratinocyte and inflammatory cell (e.g. lymphocytes, monocytes, macrophages, neutrophils) activity. Among all the triggers and pathways mentioned above, IGF-1-induced PI3K/Akt/Forkhead box protein O1/mammalian target of rapamycin (mTOR) C1 pathway is the most important signaling responsible for acne pathogenesis. Commonly used anti-acne agents include retinoids, benzoyl peroxide, antibiotics and hormonal agents (e.g. spironolactone, combination oral contraceptive and flutamide). New approaches including peroxisome proliferator-activated receptor γ modifier, melanocortin receptor antagonists, epigallocatechin-3-gallate, metformin, olumacostat glasaretil, stearoyl-CoA desaturase inhibitor omiganan pentahydrochloride, KDPT, afamelanotide, apremilast and biologics have been developed as promising treatments for acne vulgaris. Although these anti-acne agents have various pharmacological effects against the diverse pathogenesis of acne, all of them have a synergistic mode of action, the attenuation of Akt/mTORC1 signaling and enhancement of p53 signal transduction. In addition to drug therapy, diet with no hyperglycemic carbohydrates, no milk and dairy products is also beneficial for treatment of acne.

Stearoyl-CoA desaturase-1 is required for flavivirus RNA replication

Dengue virus (DENV) is the most prevalent human arthropod-borne virus and causes severe problems worldwide, mainly in tropical and sub-tropical regions. However, there is no specific antiviral drug against DENV infection. We and others recently reported that stearoyl-CoA desaturase-1 (SCD1) inhibitor showed potent suppression of hepatitis C virus replication. In this study, we examined the impact of SCD1 on DENV replication. We found that SCD1 inhibitors (MK8245 and #1716) dramatically suppressed DENV replication in a dose-dependent manner without cytotoxicity. This anti-DENV efficacy was observed against all four DENV serotypes and other flaviviruses, including Zika virus and Japanese encephalitis virus. A subgenomic replicon system of DENV was used to confirm that SCD1 inhibitor suppressed viral RNA replication. Interestingly, exogenous supplementation of unsaturated fatty acids resulted in recovery of the DENV titer even in the presence of SCD1 inhibitor, suggesting that fatty acid biosynthesis contributes to DENV genome replication. These findings indicate that SCD1 is a novel host factor required for DENV replication, and SCD1 inhibitor is a potential candidate for treating dengue fever.

Angiotensin II promotes ovarian cancer spheroid formation and metastasis by upregulation of lipid desaturation and suppression of endoplasmic reticulum stress

BackgroundAngiotensin II (ANGII) and its receptor (AGTR1) have been proposed as significant contributors to metastasis in multiple cancers. Further, high AGTR1 levels are associated with poor epithelial ovarian cancer (EOC) outcomes. However, the mechanistic basis for these effects is unknown. Recent studies have suggested that ovarian cancer metastasis is highly dependent on the formation of multicellular spheroids (MCS). To understand the associations between the ANGII/AGTR1 pathway and cancer outcomes, we evaluated the effects of ANGII on MCS formation by ovarian cancer cells and used a proteomic approach to analyze the mechanistic basis.MethodsWe used the data from the GENT database and immunohistochemistry staining to assess the AGTR1 expression in epithelial ovarian cancer (EOC) patients and to assess its role in cancer progression. Colony formation assay, 3D culture assay, and transwell assays were used to analyze the effect of ANGII on the MCS formation and cell migration. The signaling pathways of AGTR1 and transactivation of epidermal growth factor receptor (EGFR) transactivation were investigated by the western blotting analysis. Xenograft models were used to determine the role of AGTR1 in ovarian cancer metastasis. ANGII release from ovarian cancer cells and ANGII levels in the EOC ascites fluid were measured by immunoassay. A shotgun proteomic approach was used to explore the detail molecular mechanism. Modulation of lipid desaturation and endoplasmic reticulum stress were verified by the in vitro and in vivo functional assays.ResultsAGTR1 expression was negatively correlated with EOC prognosis. AGTR1activation significantly enhanced the MCS formation and cell migration. ANGII triggered both of the classical AGTR1 pathway and the EGFR transactivation. ANGII administration increased peritoneal metastasis. In addition, ovarian cancer cells secreted ANGII and enhanced cancer metastasis in a positive feedback manner. Based on the proteomic data, lipid desaturation was activated by induction of stearoyl-CoA desaturase-1 (SCD1), which suggests that inhibition of SCD1 may significantly reduce MCS formation by increasing endoplasmic reticulum stress.ConclusionsANGII promotes MCS formation and peritoneal metastasis of EOC cells. AGTR1 activation increases the lipid desaturation via SCD1 upregulation, which ultimately reduces endoplasmic reticulum stress in MCS. This mechanism explained the association between high levels of AGTR1 and poor clinical outcomes in EOC patients.

Inhibition of Stearoyl-CoA Desaturase-1 Activity Suppressed SREBP Signaling in Colon Cancer Cells and Their Spheroid Growth

Unsaturated fatty acids are critical in promoting colon tumorigenesis and its stemness. Stearoyl-CoA desaturase-1 (SCD1) is a rate-limiting lipid desaturase associated with colon cancer cell proliferation and metastasis control. This study aims to evaluate the effects of SCD1 inhibition on colon cancer spheroid growth in a three-dimensional cell culture system. An analysis of clinical data showed that increased SCD1 gene expression in colon tumors was negatively correlated with the prognosis. A chemical inhibitor of SCD1, CAY10566, inhibited the growth of colon cancer cells in both monolayer and sphere cultures. In addition, oleic acid administration—a monounsaturated fatty acid generated by the action of SCD1—prevented the suppression of sphere formation by CAY10566. RNA-sequencing data from 382 colon tumor patient samples obtained from the Cancer Genome Atlas database showed that 806 genes were SCD1-associated genes in human colon cancer. Correlation analysis identified the master regulator of lipid homeostasis sterol regulatory element-binding protein 2 (SREBP2) as a prominent transcription factor, whose expression was positively correlated with SCD1 in human colon cancer. SCD1 knockdown using siRNA in colon cancer samples, suppressed SREBP2 gene expression, providing direct evidence that SREBP signaling is under the control of SCD1 in these cells. Pathway analysis in the Ingenuity Pathways Analysis platform showed that SCD1 expression positively correlated with genes involved in multiple pathways, including lipid synthesis and incorporation, cell proliferation, and tissue tumorigenesis. Further network analysis revealed a central role for Myc in the network hierarchy of the SCD1-correlated genes. These findings suggested that SCD1 inhibition would be an effective strategy for suppressing colon cancer spheroid growth, partly through downregulating SREBP-mediated lipid and cholesterol metabolism and Myc signaling.

Inhibition of stearoyl CoA desaturase-1 activity suppresses tumour progression and improves prognosis in human bladder cancer.

Urinary bladder neoplasm is one of the most common cancers worldwide. Cancer stem cells (CSCs) have been proven to be an important cause of cancer progression and poor prognosis. In the present study, we established bladder CSCs and identified the crucial differentially expressed genes (DEGs) between these cells and parental bladder cancer cells. Analyses of bioinformatics data and clinical samples from local hospitals showed that stearoyl CoA desaturase‐1 (SCD) was the key factor among the DEGs. A significant correlation between SCD gene expression and poor prognosis among patients with bladder cancer was observed in our data. Loss‐of‐function experiments further revealed that the SCD inhibitor A939572 and SCD gene interference reduced cell proliferation and invasion. The above data suggest that SCD may serve as a novel marker for the prediction of tumour progression and poor prognosis in patients with bladder cancer.

20(S)-Protopanaxatriol Promotes Fatty Acid-Induced ER Stress and Apoptosis in Multiple Myeloma By Down-Regulating SCD1 Expression

Multiple myeloma (MM), is a hematological malignancy characterized by the accumulation of clonal malignant plasma cells. Nowadays more and more studies concern that alert metabolism including glycolysis, glutaminolysis and lipid metabolism has potent in vivo anticancer activity in multiple myeloma. While glycolysis and glutaminolysis was well established, lipid metabolism of MM is poorly understood and there is a need for a new low-toxic therapy that selectively target MM.Lipid metabolism studies such as on the use of inhibitors of fatty acid synthesis and their effects on MM cell survival have been reported. Our study showed the increase of the expression of stearoyl CoA desaturase 1 (SCD1) and the elevated fatty acid biosynthesis in MM cells (Fig.1A, p<0.001). We found that SCD1 is overexpression in MM patients' samples and associated with clinical stage of myeloma (Fig 1B, p<0.05). Then we examined the level of lipid droplets(LDs) in MM cells, and the high level of LDs detected in MM cells demonstrated the lipid accumulation in MM (Fig.1C). Stable depletion of SCD1 inhibited fatty acid biosynthesis and decreased LDs levels and this reduction of LDs remained at low levels in MM cells (Fig.1D, E). These results suggest that MM cell growth party relies on SCD1-mediated fatty acid metabolism.The finding that 20(S)-protopanaxatriol(PPT) has significant effect on inhibiting the transcription of lipogenic genes have reported. Western blotting analysis shows that PPT decreased SCD1 protein levels in RPMI-8226, ARH-77 cell lines. In addition, PPT treatment decreased fatty acid biosynthesis and blocked lipid storage in lipid droplets(LDs) (Fig.1F). The proportion of saturated and monounsaturated was also decreased after treatment (Fig. 1G). Given that 20(S)-protopanaxatriol(PPT) has lipid-lowering effect in MM, we hypothesized that PPT exerts anti-myeloma effects by disrupting lipogenesis. In vitro experiments demonstrate the significant effect of PPT on decreasing proliferation and inducing apoptosis in multiple myeloma (Fig.1H). Supplementation with the SCD1 enzymatic product, oleic acid, rescued MM cells from PPT cell killing and SCD1 silencing, decreasing levels of SCD1 inhibition induced apoptosis and proliferation inhibition (Fig.1I). The results of Western Blot Analysis show a positive correlation between SCD1 inhibition and endoplasmic reticulum stress (ER stress) (Fig.1J). In addition, PPT can obviously induce ER stress after inhibiting SCD1, while ER-stress inhibitor TUDCA can significantly reverse the induced apoptosis of PPT treatment in MM cells (Fig.1K, p<0.05). These results suggest that excessive endoplasmic reticulum stress is the main cause of PPT induced apoptosis.In summary, our studies reveal that regulation of fatty acid metabolism in MM cells is an essential target. We show that the redeployed drug PPT killed MM cells by decreasing SCD1 protein levels and promoting fatty acid-induced ER stress. This study is relevant to the wider context of multiple myeloma therapeutics that developing therapeutics which can disrupt fatty acid biosynthesis. To our knowledge, this is the first study to describe the aglycone of ginsenosides 20(S)-protopanaxatriol with demonstrable anti-myeloma activity that target fatty acid biosynthesis [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Discovery of potent liver-selective stearoyl-CoA desaturase-1 (SCD1) inhibitors, thiazole-4-acetic acid derivatives, for the treatment of diabetes, hepatic steatosis, and obesity

SCD1 is a rate-limiting enzyme in the conversion of saturated fatty acids to monounsaturated fatty acids. SCD1 inhibitors have potential effects on obesity, diabetes, acne, and cancer, but the adverse effects associated with SCD1 inhibition in the skin and eyelids are impediments to clinical development. To avoid mechanism-based adverse effects, we explored the compounds that selectively inhibit SCD1 in the liver in an ex vivo assay. Starting from a systemically active lead compound, we focused on the physicochemical properties tPSA and cLogP to minimize exposure in the off-target tissues. This effort led to the discovery of thiazole-4-acetic acid analog 48 as a potent and liver-selective SCD1 inhibitor. Compound 48 exhibited significant effects in rodent models of diabetes, hepatic steatosis, and obesity, with sufficient safety margins in a rat toxicology study with repeated dosing.

Research progress of stearoyl-CoA desaturase-1 on obesity and non-alcoholic fatty liver disease Abstract

Stearoyl-CoA desaturase-1 (SCD-1) is the key rate-limiting enzyme to catalyze the conversion of saturated fatty acids to monounsaturated fatty acids. The monounsaturated fatty acids in the catalytic products are important substrates for the formation of triglycerides, cholesteryl esters and phospholipids. Therefore, SCD-1 plays an important regulatory role in the metabolic process of fat. Currently, obesity and non-alcoholic fatty liver disease are widely prevalent worldwide. SCD-1 has gradually become a potential drug target for the treatment of such diseases due to its important regulatory role in fat metabolism. We summarize the recent research progress of SCD-1 in obesity and non-alcoholic fatty liver disease and the developmental status of SCD-1 inhibitors in order to provide new ideas and references related to disease and target drugs.

Abstract 5480: Colorectal cancer cell lines harboring mutation in Wnt/β-catenin pathway shows enhanced sensitivity to the stearoyl-CoA desaturase (SCD) inhibitor, DSP-0692

Abstract Colorectal cancer (CRC) is one of the most frequent malignant diseases worldwide. Recent studies suggest that a small subpopulation of cells known as cancer stem cells (CSCs) may promote the high metastasis and relapse associated with CRC. It has been reported that Wnt/β-catenin signaling is aberrantly activated in a variety of cancer including colorectal cancer, and plays a critical role in CSC maintenance. Here it is shown that a novel SCD inhibitor, DSP-0692, may inhibited Wnt/β-catenin signaling pathway through two different mechanisms in CRC. The effect of SCD inhibition on Wnt3A secretion, in which process post-translational fatty acylation (with palmitoleic acid) is required, was investigated. DSP-0692 led to reduced Wnt3A protein levels secreted in the media in Wnt3A-overexpressing cell line. This result was further confirmed by the TCF/LEF reporter assay in HCT116 incubated with conditional media from L-Wnt3A cells, with or without DSP-0692. DSP-0692 also inhibited exogenous Wnt3A-induced reporter activity. This indicates DSP-0692 may inhibit the β-catenin/Tcf transactivation by additional mechanism in addition to inhibiting Wnt secretion. To clarify this additional mechanism, the effect of DSP-0692 on nuclear translocation of β-catenin was investigated. SCD inhibition led to a decrease of β-catenin amounts within the nucleus. Currently, how SCD inhibition affects nuclear translocation of β-catenin is being investigated. It was confirmed that DSP-0692 exhibited lower IC50 value to sphere cells carrying mutations related to Wnt/β-catenin signaling pathway than those without these mutations. Next, the effect of SCD inhibition on Wnt/β-catenin signaling pathway in vivo was investigated. Treatment with DSP-0692 in a SW620 colorectal cancer xenograft model suppressed mRNA expression of the Wnt/β-catenin target genes, as well as CSC marker gene. Taken together, these results suggest fatty acid desaturation in tumor cells may have an impact on Wnt/β-catenin signaling pathway and involve in CSC maintenance. The approaches targeting SCD could be a new therapeutic strategy for anti-CSC therapy in CRC. Citation Format: Yudai Furuta, Yuichi Fukunaga, Satoshi Ikeda, Erina Koga, Hiroki Umehara, Tsuguteru Otsubo, Manabu Watanabe, Futoshi Hasegawa, Hitoshi Ban, Eiji Sugaru. Colorectal cancer cell lines harboring mutation in Wnt/β-catenin pathway shows enhanced sensitivity to the stearoyl-CoA desaturase (SCD) inhibitor, DSP-0692 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5480.

Discovery of Cytochrome P450 4F11 Activated Inhibitors of Stearoyl Coenzyme A Desaturase.

Stearoyl-CoA desaturase (SCD) catalyzes the first step in the conversion of saturated fatty acids to unsaturated fatty acids. Unsaturated fatty acids are required for membrane integrity and for cell proliferation. For these reasons, inhibitors of SCD represent potential treatments for cancer. However, systemically active SCD inhibitors result in skin toxicity, which presents an obstacle to their development. We recently described a series of oxalic acid diamides that are converted into active SCD inhibitors within a subset of cancers by CYP4F11-mediated metabolism. Herein, we describe the optimization of the oxalic acid diamides and related N-acyl ureas and an analysis of the structure-activity relationships related to metabolic activation and SCD inhibition.

Responses of MAC-T Cells to Inhibited Stearoyl-CoA Desaturase 1 during cis-9, trans-11 Conjugated Linoleic Acid Synthesis.

Cis-9-conjugated, trans-11-conjugated linoleic acid (CLA) is known for its positive activities on human health. The synthesis of cis-9, trans-11 CLA in mammary glands is generally thought to be catalyzed by stearoyl-CoA desaturase 1 (SCD1), but this has not been rigorously established. In this study, we hypothesized that the inhibition of SCD1 (by CAY10566) would block the synthesis of cis-9, trans-11 CLA in bovine mammary alveolar cells (MAC-T) cells. Results showed that MAC-T cells incubated with 10 nM CAY10566 for 12 h (CAY) produced less cis-9, trans-11 CLA (p < 0.01), lower 14:1/(14:1 + 14:0)% (p < 0.01), more trans-11 18:1 (TVA) accumulation (p < 0.01), and reduced SCD1 mRNA levels (p < 0.01) compared with the control group (CON). Moreover, the mRNA abundances of sterol regulatory element-binding protein 1 [SREBPF1], acyl-CoA synthetase short-chain family member 2 [ACSS2], and lipin 1 [LPIN1] were significantly elevated when SCD1 was inhibited in the CAY group (p < 0.05). Taken together, CAY10566 inhibition of SCD1 resulted in lower cis-9, trans-11 CLA synthesis ability, and SREBF1, ACSSS2, and LPIN1 were negatively associated with SCD1. These findings not only provide the direct evidence that cis-9, trans-11 CLA synthesis is catalyzed by SCD1, but also help us understand the responses of MAC-T cells to SCD1 inhibition.

Dietary polyunsaturated fatty acids mediate the inverse association of stearoyl-CoA desaturase activity with the risk of fatty liver in dyslipidaemic individuals.

The activity of stearoyl-CoA desaturase-1 (SCD1) is increased in non-alcoholic fatty liver disease (NAFLD). Polyunsaturated fatty acids (PUFA) inhibit SCD1, but clinical studies on whether all dietary PUFA species are equal in SCD1 inhibition are scarce. Serum phospholipids are an objective proxy of dietary intake of plant-derived PUFA (C18:2n-6, C18:3n-3) and marine-derived PUFA (C20:5n-3, C22:6n-3). In 355 participants with primary dyslipidemia, we cross-sectionally investigated whether the presumed association between surrogate markers of NAFLD and SCD1 activity is mediated by intake of PUFA, and, if it is, what PUFA species are relevant in this regard. We determined the fatty acid profile of serum phospholipids by gas chromatography, and used the ratio C16:1n-7/C16:0 as a marker of SCD1 activity. NAFLD was diagnosed by values ≥ 60 in the fatty liver index (FLI), a surrogate recently validated against ultrasonography. FLI ≥ 60 was detected in 37.5% (n = 133) of study participants. In a multivariate model, SCD1 activity showed an expected significant association with the risk of NAFLD, with odds ratio (OR) (95% confidence interval) of 1.44 (1.04-2.01) for each 0.01 increase. In a model further allowing the stepwise inclusion of plant-derived PUFA, marine-derived PUFA, and total PUFA (vegetable + marine), total PUFA replaced SCD1 activity as a significant (inverse) association of NAFLD, with OR 0.89 (0.81-0.99). Total PUFA, regardless of their origin, mediates the relationship between SCD1 activity and NAFLD. This provides a new insight in the protective effects of PUFA against NAFLD, heretofore mostly focussed on PUFA species from marine origin.

IRE1α RNase-dependent lipid homeostasis promotes survival in Myc-transformed cancers.

Myc activation is a primary oncogenic event in many human cancers; however, these transcription factors are difficult to inhibit pharmacologically, suggesting that Myc-dependent downstream effectors may be more tractable therapeutic targets. Here, we show that Myc overexpression induces endoplasmic reticulum (ER) stress and engages the inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 (XBP1) pathway through multiple molecular mechanisms in a variety of c-Myc- and N-Myc-dependent cancers. In particular, Myc-overexpressing cells require IRE1α/XBP1 signaling for sustained growth and survival in vitro and in vivo, dependent on elevated stearoyl-CoA-desaturase 1 (SCD1) activity. Pharmacological and genetic XBP1 inhibition induces Myc-dependent apoptosis, which is alleviated by exogenous unsaturated fatty acids. Of note, SCD1 inhibition phenocopies IRE1α RNase activity suppression in vivo. Furthermore, IRE1α inhibition enhances the cytotoxic effects of standard chemotherapy drugs used to treat c-Myc-overexpressing Burkitt's lymphoma, suggesting that inhibiting the IRE1α/XBP1 pathway is a useful general strategy for treatment of Myc-driven cancers.

Targeting stearoyl-CoA desaturase 1 to repress endometrial cancer progression.

Stearoyl-CoA desaturase 1 (SCD1) is an established molecular target in many primary tumors including breast, lung, pancreatic, colon and hepatocellular carcinomas. However, its potential role in supporting endometrial cancer growth and progression has not yet been determined. In this study, we evaluated the value of SCD1 as a candidate therapeutic target in human endometrial cancer. Compared with secretory and post-menopausal endometrium, SCD1 was highly expressed in normal endometrium of proliferative phase, endometrial hyperplasia and endometrial carcinoma, while was absent or low expression in non-malignant control stromal cells and adjacent normal endometrium. Knockdown of SCD1 significantly repressed endometrial cancer cell growth and induced cell apoptosis. Both short hairpin RNA targeted knockdown and chemical inhibitor of SCD1 suppressed the foci formation of AN3CA, a metastatic endometrial cell line. Xenograft model further demonstrated that reduced SCD1 expression impaired endometrial cancer growth in vivo. Taken together, these findings indicate that SCD1 is a potentially therapeutic target in human endometrial cancer. Inhibiting lipid metabolism in cancer cells would be a promising strategy for anti-cancer therapy.

Blockade of Stearoyl-CoA-desaturase 1 activity reverts resistance to cisplatin in lung cancer stem cells

Poor prognosis in lung cancer has been attributed to the presence of lung cancer stem cells (CSCs) which resist chemotherapy and cause disease recurrence. Hence, the strong need to identify mechanisms of chemoresistance and to develop new combination therapies. We have previously shown that Stearoyl-CoA-desaturase 1 (SCD1), the enzyme responsible for the conversion of saturated to monounsaturated fatty acids is upregulated in 3D lung cancer spheroids and is an upstream activator of key proliferation pathways β-catenin and YAP/TAZ. Here we first show that SCD1 expression, either alone or in combination with a variety of CSCs markers, correlates with poor prognosis in adenocarcinoma (ADC) of the lung. Treatment of lung ADC cell cultures with cisplatin enhances the formation of larger 3D tumor spheroids and upregulates CSCs markers. In contrast, co-treatment with cisplatin and the SCD1 inhibitor MF-438 reverts upregulation of CSCs markers, strongly synergizes in the inhibition of 3D spheroids formation and induces CSCs apoptosis. Mechanistically, SCD1 inhibition activates endoplasmic reticulum stress response and enhances autophagy. These data all together support the use of combination therapy with SCD1 inhibitors to achieve better control of lung cancer.

Feedback activation of AMPK-mediated autophagy acceleration is a key resistance mechanism against SCD1 inhibitor-induced cell growth inhibition.

Elucidating the bioactive compound modes of action is crucial for increasing success rates in drug development. For anticancer drugs, defining effective drug combinations that overcome resistance improves therapeutic efficacy. Herein, by using a biologically annotated compound library, we performed a large-scale combination screening with Stearoyl-CoA desaturase-1 (SCD1) inhibitor, T-3764518, which partially inhibits colorectal cancer cell proliferation. T-3764518 induced phosphorylation and activation of AMPK in HCT-116 cells, which led to blockade of downstream fatty acid synthesis and acceleration of autophagy. Attenuation of fatty acid synthesis by small molecules suppressed the growth inhibitory effect of T-3764518. In contrast, combination of T-3764518 with autophagy flux inhibitors synergistically inhibited cellular proliferation. Experiments using SCD1 knock-out cells validated the results obtained with T-3764518. The results of our study indicated that activation of autophagy serves as a survival signal when SCD1 is inhibited in HCT-116 cells. Furthermore, these findings suggest that combining SCD1 inhibitor with autophagy inhibitors is a promising anticancer therapy.

Abstract 192: Targeting stearoyl CoA desaturase 1 (SCD1) in hepatobilliary carcinoma

Abstract Background: The paucity of effective therapeutic agents for hepatocellular cancer (HCC) underscores the critical need for more effective therapeutic strategies. Recent studies indicate lipid biosynthesis and desaturation is required for HCC survival. Targeting these may prove beneficial because such changes contribute to therapeutic resistance. Stearoyl CoA desaturase (SCD1), a key mediator of fatty acid (FA) biosynthesis and rate-limiting in conversion of saturated fatty acids (SFAs) to mono-unsaturated fatty acids (MUFAs), is upregulated in HCC and many other cancers. As such, we therapeutically targeted a novel lipogenic tumor survival mechanism mediated by SCD1 as a means to combat the chemoresistance associated with HCC. In so doing, we evaluated a novel lead SCD1 inhibitor in HCC. Methods: Paraffin embedded patient HCC tissues were examined for SCD1 expression. Using combined computational and synthetic chemistry approaches, we synthesized four novel specific SCD1 inhibitors with SSI-4 being the lead SCD1 inhibitor. HCC cell lines were examined using proliferation assays for response to SSI-4. IC50 concentrations for blocking SCD1 enzyme activity was determined. Blood half-life and bioavailability of single dose SSI-4 was determined. Mechanisms of action of SCD1 were examined that included Endoplasmic reticulum (ER) stress. In vivo, antitumor activity was determined using HCC patient derived xenograft (PDX) mouse models. Results: We identified elevated SCD1 mRNA and protein in HCCs tissues. SSI-4 dose-dependently inhibits cell proliferation in HCC cell lines with specificity demonstrated by oleic acid (MUFA) co-culture. Single dose oral gavage SSI-4 demonstrated a half-life of ~4 hours and excellent oral bioavailability. SSI-4 was well tolerated with long-term daily dosing. SSI-4 treatment of HCC cells and tumors led to endoplasmic reticulum (ER) stress followed by apoptotic cell death. Single agent SSI-4 demonstrated antitumor activity in HCC PDX mouse models with suppression of ER stress regulated proteins. Conclusions: Targeting a novel lipid metabolic pathway in HCC may provide effective therapy for aggressive HCC. Citation Format: John Alton Copland, Laura A. Marlow, Ilah Bok, James L. Miller, Matsuda Akiko, Yan W. Asmann, Vivekananda Sarangi, Steven R. Alberts, Kabir Mody, Lewis R. Roberts, Mark J. Truty, Tushar C. Patel. Targeting stearoyl CoA desaturase 1 (SCD1) in hepatobilliary carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 192. doi:10.1158/1538-7445.AM2017-192

Abstract 4772: Stearoyl-CoA Desaturase (SCD1) regulates liver tumor initiating cells through modulating ER stress

Abstract Sorafenib is the FDA approved drug for patients with advanced hepatocellular carcinoma (HCC), but the survival benefit is only modest, partly due to drug resistance. Increasing evidence shows that tumor-initiating cells (T-ICs) are intrinsically resistant to conventional treatments, and targeting signaling pathways in T-ICs provides potential therapeutic targets for HCC. In our established enriched T-IC population, we identified the activation of a lipogenesis pathway in which expression of stearoyl-CoA desaturase-1 (SCD1), an enzyme involved in the conversion of saturated into monounsaturated fatty acids, was most significant. SCD1 overexpression is frequently found in HCC samples and is significantly associated with poorer patient survival. Using overexpression and knockdown approaches, SCD1 was found to regulate the traits of T-ICs, including tumorigenicity, self-renewal, differentiation, drug resistance and the expression of liver T-IC markers. Interestingly, SCD1 was markedly upregulated in our established sorafenib-resistant cell lines as well as patient-derived xenografts (PDTXs), and its overexpression predicts the clinical response of HCC patients to sorafenib treatment. Consistently, pharmacological inhibition of SCD1 suppressed T-IC phenotypes and enhanced sensitivity to sorafenib treatment. Using a patient-derived xenograft model, we found that a novel SCD1 inhibitor (SSI-4) in combination with sorafenib demonstrated a maximal tumor suppressive effect. Induction of endoplasmic reticulum (ER) stress-mediated T-IC differentiation can account for the enhanced sensitivity towards sorafenib treatment upon SCD1 suppression. In conclusion, SCD1-induced ER stress may specifically increase the sensitivity of liver T-ICs to the effects of sorafenib treatment. Targeting SCD1 in combination with sorafenib therapy may be a novel therapeutic regimen against HCC. Citation Format: Kin Fai Ma, Eunice Yuen Ting Lau, Irene Oi Lin Ng, Kin Wah Lee. Stearoyl-CoA Desaturase (SCD1) regulates liver tumor initiating cells through modulating ER stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4772. doi:10.1158/1538-7445.AM2017-4772

Abstract 4989: 3D spheroid screen yields SCD1 pathway inhibitors for the treatment of cancer

Abstract With three-dimensional growth conditions, multicellular tumor spheroids reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients, characteristic of poorly vascularized tumor regions. 3D high content screening (HCS) identified compounds that selectively kill tumor cells in the inner core of tumor cell spheroids by targeting the Stearoyl CoA Desaturase 1 (SCD1) pathway. SCD1 catalyzes the rate-limiting step in the production of mono-unsaturated fatty acids (MUFAs). Cancer cells are dependent on higher levels of MUFAs compared to normal cells and SCD1 is highly expressed in multiple tumor types. Changes in the MUFA / SFA (saturated fatty acid) ratio alters lipid biosynthesis and thus triggers cellular (ER) stress and induces the Unfolded Protein Response. Although the lead compound was very effective in vitro, it had unfavorable PK and physical chemistry properties, including low permeability and solubility and very high lipophilicity. This led to insufficient oral bioavailability, which could be overcome by optimization of PK and physical chemistry properties. Here, we report on the in vitro/in vivo effects of our 3D HCS compounds which showed high potency in the 3D spheroid inner core death assay with T47D breast cancer cells. In this in vitro model compound-induced inner core cell death is enhanced by SCD1 substrates palmitic or stearic acid and rescued by the SCD1 products palmitoleic or oleic acid. Furthermore, the effects can be reproduced in 2D cultures, which become increasingly sensitive to inhibition by our 3D HCS compounds with decreasing FBS concentration in the culture medium and this effect can also be rescued by addition of MUFAs but not of palmitic acid. Mode of action analysis showed that our compounds reduced palmitoleoyl- or oleoyl-CoA levels and simultaneously increased saturated fatty acyl-CoAs of palmitate or stearate in several cell lines as well as in vivo. In the sensitive T47D cells, the compounds induced expression of stress response genes and genes related to lipid metabolism. While these results support the SCD1 pathway as target for our 3D HCS compounds, we also observed striking differences to published SCD1 inhibitors suggesting a new cancer target beyond SCD1. Thus, further validation of our inhibitors in vitro and in vivo will be required, but these results suggest that 3D spheroid cultures may be a valuable tool for elucidation of new drug targets for cancer therapy. Citation Format: Sylvia Gruenewald, Carolyn Sperl, Patrick Steigemann, Alexander Walter, Sylvia Zacharias, Uwe Eberspaecher, Roland Neuhaus, Ludwig Zorn, Wolfgang Schwede, Kai Thede, Sven Christian. 3D spheroid screen yields SCD1 pathway inhibitors for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4989. doi:10.1158/1538-7445.AM2017-4989

Abstract LB-189: Blockade of stearoyl CoA desaturase 1 promotes immunogenic clearance of tumors

Abstract Metabolic reprogramming plays a critical role in carcinogenesis, in part due its ability to promote immune suppressive properties within tumors. Agents that specifically target crucial metabolic enzymes utilized by cancer are been actively investigated. However, it is unclear whether inhibition of fatty acid metabolism in tumors affects their immunogenicity. Here, we show for the first time that inhibition of stearoyl-CoA desaturase 1 (SCD1), a key enzyme involved in fatty-acid synthesis and a potential prognostic marker for human cancers, increases the immunogenicity of poorly immunogenic tumors. The enhanced immune activation is accompanied by upregulated endoplasmic reticulum (ER) stress and is dependent on the translocation of ER protein calreticulin to the tumor cell surface. Inhibition of SCD1 increased both recruitment and activation of immune cells in vivo, which when combined with PD-1 blockade resulted in potent and durable anti-tumor T cell responses. Together, our results indicate that inhibition of tumorigenic de novo lipogenesis represents a novel approach to enhance T cell based cancer immunotherapy. Citation Format: Christina Anna Elizabeth Von Roemeling, Thomas Caulfield, Yaqing Qie, Derek C. Radisky, Xiujie Liu, Yuanxin Chen, Joshua Knight, John Copland, Betty Kim. Blockade of stearoyl CoA desaturase 1 promotes immunogenic clearance of tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-189. doi:10.1158/1538-7445.AM2017-LB-189