Inhibition of Fatty Acid Synthase Induces Endoplasmic Reticulum Stress in Tumor Cells

A Novel Lipid Metabolism and Endoplasmic Reticulum Stress-Related Risk Model for Predicting Immune Infiltration and Prognosis in Colorectal Cancer

Lipid metabolism and endoplasmic reticulum stress exhibit crosstalk in various cancer types, which are closely associated with the progression of colorectal cancer (CRC). This study constructs a prognostic signature based on lipid metabolism and endoplasmic reticulum stress-related genes (LERGs) for CRC patients, aiming to predict the prognosis and immune response. RNA sequencing and clinical data from the TCGA and GEO databases were analyzed to identify differentially expressed LERGs with prognostic relevance using univariate Cox regression. Subsequently, a risk model was developed using the LASSO regression. CRC patients were stratified into low-risk and high-risk groups based on risk scores, with the high-risk cohort demonstrating a poorer clinical prognosis in multiple databases. The risk model showed robust correlations with clinical features, gene mutations, and treatment sensitivity. Significant differences in immune cell infiltration and the expression of immune-related factors were also detected between risk groups, and elevated scores of cytokines and failure factors were detected in single-cell RNA sequencing analysis. This research indicates that lipid metabolism and endoplasmic reticulum stress in CRC are correlated with tumor progression, an immunosuppressive landscape, and alterations of drug sensitivity. The developed risk model can serve as a powerful prognostic tool, offering critical insights for refining clinical management and optimizing treatment in CRC patients.

Anticancer Activity of Nano-formulated Orlistat-Dopamine Conjugates Through Self-Assembly

Orlistat, an FDA-approved fatty acid inhibitor for obesity treatment, demonstrates certain low and greatly varied anticancer abilities. In a previous study, we revealed a synergistic effect between orlistat and dopamine in cancer treatment. Here, orlistat-dopamine conjugates (ODCs) with defined chemical structures were synthesized. The ODC by design underwent polymerization and self-assembly in the presence of oxygen to form nano-sized particles (Nano-ODCs) spontaneously. The resulted Nano-ODCs of partial crystalline structures demonstrated good water dispersion to form stable Nano-ODC suspensions. Because of the bioadhesive property of the catechol moieties, once administered, Nano-ODCs were quickly accumulated on cell surfaces and efficiently uptaken by cancer cells. In the cytoplasm, Nano-ODC experienced biphasic dissolution followed by spontaneous hydrolysis to release intact orlistat and dopamine. Besides elevated levels of intracellular reactive oxygen species (ROS), the co-localized dopamine also induced mitochondrial dysfunctions through monoamine oxidases (MAOs)-catalyzed dopamine oxidation. The strong synergistic effects between orlistat and dopamine determined a good cytotoxicity activity and a unique cell lysis mechanism, explaining the distinguished activity of Nano-ODC to drug-sensitive and -resistant cancer cells. This new technology-enabled orlistat repurposing will contribute to overcoming drug resistance and the improvement of cancer chemotherapy.

Hypomethylated gene RAC3 induces cell proliferation and invasion by increasing FASN expression in endometrial cancer

BACKGROUND

Endometrial cancer (EC) is one of the most prevalent gynecological cancers with a 5-year survival rate of 20-60%. Feasible prognostic molecular biomarkers of EC are necessary for accurate prediction of EC prognosis.

METHODS

RAC3 is a member of the Rho GTPases. Public databases including Gene Expression Profiling Interactive Analysis (GEPIA2), Tumor Immune Estimation Resource (TIMER), LinkedOmics, Search Tool for the Retrieval of Interacting Genes/Proteins (STRING), TISIDB and cBioPortal were employed to analyze the differential expression, clinicopathologic characteristics, functional networks, immune cell infiltrates and genetic alteration of RAC3 in EC patients.

RESULTS

RAC3 expression was elevated in EC patients analyzed by TIMER and GEPIA. Overexpression of RAC3 was obviously correlated with clinical stage, histological type, histological grade and DNA hypomethylation. Patients with high RAC3 expression displayed poor overall survival. Functional enrichment analysis showed that RAC3 was involved in translational initiation, DNA replication and mRNA processing. RAC3 expression was negatively associated with infiltrating levels of B cells, CD8+ T cells, macrophages and dendritic cells in EC. Experiments in vitro showed that RAC3 was upregulated in EC tissues and cell lines, and RAC3 induced cell proliferation and invasion by increasing fatty acid synthase (FASN) expression.

CONCLUSION

High expression of RAC3iscorrelated with poor prognosis and low infiltration of immune cells in EC. RAC3 promotes cell proliferation and invasion via FASN. These results demonstrate thatRAC3 functions as an EC oncogene and reveal its underlying mechanism in EC progression, suggesting that RAC3 may serve as a potential therapeutic target in EC.

How cancer cells remodel lipid metabolism: strategies targeting transcription factors

Reprogramming of lipid metabolism has received increasing recognition as a hallmark of cancer cells because lipid dysregulation and the alteration of related enzyme profiles are closely correlated with oncogenic signals and malignant phenotypes, such as metastasis and therapeutic resistance. In this review, we describe recent findings that support the importance of lipids, as well as the transcription factors involved in cancer lipid metabolism. With recent advances in transcription factor analysis, including computer-modeling techniques, transcription factors are emerging as central players in cancer biology. Considering the limited number and the crucial role of transcription factors associated with lipid rewiring in cancers, transcription factor targeting is a promising potential strategy for cancer therapy.

Fatty Acid Metabolism Reprogramming in Advanced Prostate Cancer

Prostate cancer (PCa) is a carcinoma in which fatty acids are abundant. Fatty acid metabolism is rewired during PCa development. Although PCa can be treated with hormone therapy, after prolonged treatment, castration-resistant prostate cancer can develop and can lead to increased mortality. Changes to fatty acid metabolism occur systemically and locally in prostate cancer patients, and understanding these changes may lead to individualized treatments, especially in advanced, castration-resistant prostate cancers. The fatty acid metabolic changes are not merely reflective of oncogenic activity, but in many cases, these represent a critical factor in cancer initiation and development. In this review, we analyzed the literature regarding systemic changes to fatty acid metabolism in PCa patients and how these changes relate to obesity, diet, circulating metabolites, and peri-prostatic adipose tissue. We also analyzed cellular fatty acid metabolism in prostate cancer, including fatty acid uptake, de novo lipogenesis, fatty acid elongation, and oxidation. This review broadens our view of fatty acid switches in PCa and presents potential candidates for PCa treatment and diagnosis.

Prostate Cancer Progression: as a Matter of Fats

Advanced prostate cancer (PCa) represents the fifth cause of cancer death worldwide. Although survival has improved with second-generation androgen signaling and Parp inhibitors, the benefits are not long-lasting, and new therapeutic approaches are sorely needed. Lipids and their metabolism have recently reached the spotlight with accumulating evidence for their role as promoters of PCa development, progression, and metastasis. As a result, interest in targeting enzymes/transporters involved in lipid metabolism is rapidly growing. Moreover, the use of lipogenic signatures to predict prognosis and resistance to therapy has been recently explored with promising results. Despite the well-known association between obesity with PCa lethality, the underlying mechanistic role of diet/obesity-derived metabolites has only lately been unveiled. Furthermore, the role of lipids as energy source, building blocks, and signaling molecules in cancer cells has now been revisited and expanded in the context of the tumor microenvironment (TME), which is heavily influenced by the external environment and nutrient availability. Here, we describe how lipids, their enzymes, transporters, and modulators can promote PCa development and progression, and we emphasize the role of lipids in shaping TME. In a therapeutic perspective, we describe the ongoing efforts in targeting lipogenic hubs. Finally, we highlight studies supporting dietary modulation in the adjuvant setting with the purpose of achieving greater efficacy of the standard of care and of synthetic lethality. PCa progression is "a matter of fats", and the more we understand about the role of lipids as key players in this process, the better we can develop approaches to counteract their tumor promoter activity while preserving their beneficial properties.

Targeting lipid metabolism is an emerging strategy to enhance the efficacy of anti-HER2 therapies in HER2-positive breast cancer

De novo or acquired resistance of cancer cells to currently available Human Epidermal Growth Factor Receptor 2 (HER2) inhibitors represents a clinical challenge. Several resistance mechanisms have been identified in recent years, with lipid metabolism reprogramming, a well-established hallmark of cancer, representing the last frontier of preclinical and clinical research in this field. Fatty Acid Synthase (FASN), the key enzyme required for fatty acids (FAs) biosynthesis, is frequently overexpressed/activated in HER2-positive (HER2+) breast cancer (BC), and it crucially sustains HER2+ BC cell growth, proliferation and survival. After the synthesis of new, selective and well tolerated FASN inhibitors, clinical trials have been initiated to test if these compounds are able to re-sensitize cancer cells with acquired resistance to HER2 inhibition. More recently, the upregulation of FA uptake by cancer cells has emerged as a potentially new and targetable mechanism of resistance to anti-HER2 therapies in HER2+ BC, thus opening a new era in the field of targeting metabolic reprogramming in clinical setting. Here, we review the available preclinical and clinical evidence supporting the inhibition of FA biosynthesis and uptake in combination with anti-HER2 therapies in patients with HER2+ BC, and we discuss ongoing clinical trials that are investigating these combination approaches.

FASN inhibition as a potential treatment for endocrine-resistant breast cancer

PURPOSE

The majority of breast cancers are estrogen receptor (ERα) positive making endocrine therapy a mainstay for these patients. Unfortunately, resistance to endocrine therapy is a common occurrence. Fatty acid synthase (FASN) is a key enzyme in lipid biosynthesis and its expression is commensurate with tumor grade and resistance to numerous therapies.

METHODS

The effect of the FASN inhibitor TVB-3166 on ERα expression and cell growth was characterized in tamoxifen-resistant cell lines, xenografts, and patient explants. Subcellular localization of ERα was assessed using subcellular fractionations. Palmitoylation and ubiquitination of ERα were assessed by immunoprecipitation. ERα and p-eIF2α protein levels were analyzed by Western blotting after treatment with TVB-3166 with or without the addition of palmitate or BAPTA.

RESULTS

TVB-3166 treatment leads to a marked inhibition of proliferation in tamoxifen-resistant cells compared to the parental cells. Additionally, TVB-3166 significantly inhibited tamoxifen-resistant breast tumor growth in mice and decreased proliferation of primary tumor explants compared to untreated controls. FASN inhibition significantly reduced ERα levels most prominently in endocrine-resistant cells and altered its subcellular localization. Furthermore, we showed that the reduction of ERα expression upon TVB-3166 treatment is mediated through the induction of endoplasmic reticulum stress.

CONCLUSION

Our preclinical data provide evidence that FASN inhibition by TVB-3166 presents a promising therapeutic strategy for the treatment of endocrine-resistant breast cancer. Further clinical development of FASN inhibitors for endocrine-resistant breast cancer should be considered.

Post-Translational Modifications That Drive Prostate Cancer Progression

While a protein primary structure is determined by genetic code, its specific functional form is mostly achieved in a dynamic interplay that includes actions of many enzymes involved in post-translational modifications. This versatile repertoire is widely used by cells to direct their response to external stimuli, regulate transcription and protein localization and to keep proteostasis. Herein, post-translational modifications with evident potency to drive prostate cancer are explored. A comprehensive list of proteome-wide and single protein post-translational modifications and their involvement in phenotypic outcomes is presented. Specifically, the data on phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and lipidation in prostate cancer and the enzymes involved are collected. This type of knowledge is especially valuable in cases when cancer cells do not differ in the expression or mutational status of a protein, but its differential activity is regulated on the level of post-translational modifications. Since their driving roles in prostate cancer, post-translational modifications are widely studied in attempts to advance prostate cancer treatment. Current strategies that exploit the potential of post-translational modifications in prostate cancer therapy are presented.

Fatty Acid Synthase: An Emerging Target in Cancer

In recent years, lipid metabolism has garnered significant attention as it provides the necessary building blocks required to sustain tumor growth and serves as an alternative fuel source for ATP generation. Fatty acid synthase (FASN) functions as a central regulator of lipid metabolism and plays a critical role in the growth and survival of tumors with lipogenic phenotypes. Accumulating evidence has shown that it is capable of rewiring tumor cells for greater energy flexibility to attain their high energy requirements. This multi-enzyme protein is capable of modulating the function of subcellular organelles for optimal function under different conditions. Apart from lipid metabolism, FASN has functional roles in other cellular processes such as glycolysis and amino acid metabolism. These pivotal roles of FASN in lipid metabolism make it an attractive target in the clinic with several new inhibitors currently being tested in early clinical trials. This article aims to present the current evidence on the emergence of FASN as a target in human malignancies.

Synergistic apoptosis following endoplasmic reticulum stress aggravation in mucinous colon cancer

Background

Mucinous colon cancers (MCC) are characterized by abundant production of mucin 2 (MUC2) protein and are less sensitive to standard systemic chemotherapy. We postulated that severe/persistent endoplasmic reticulum stress (ERS) aggravation in MCC would overwhelm compensatory cytoprotective pathways and induce apoptosis.

Results

Basal levels of ERS markers were higher in MCC and dnTCF-LS174T cells than non-mucinous tumors and these levels were significantly increased by combinatorial treatment with ERS aggravators celecoxib + orlistat. Combination treatment inhibited cell viability and synergistically induced apoptosis. Treatment-induced cell death was ERS-dependent, apoptotic pathways were not activated following knockdown of ERS protein CHOP. Dual drug treatment significantly reduced mucinous tumor growth in vivo and induced ERS and apoptosis, consistent with in vitro experiments.

Conclusions

Novel therapies are needed since MCC are more resistant to standard systemic chemotherapy. This study suggests ERS aggravation is a viable therapeutic strategy to reduce tumor growth in MCC.

Identification of lipid biomarkers of metastatic potential and gene expression (HER2/p53) in human breast cancer cell cultures using ambient mass spectrometry

In breast cancer, overexpression of human epidermal growth factor receptor 2 (HER2) correlates with overactivation of lipogenesis, mutation of tumor suppressor p53, and increased metastatic potential. The mechanisms through which lipids mediate p53, HER2, and metastatic potential are largely unknown. We have developed a desorption electrospray ionization mass spectrometry (DESI-MS) method to identify lipid biomarkers of HER2/p53 expression, metastatic potential, and disease state (viz. cancer vs. non-cancerous) in monolayer and suspension breast cancer cell cultures (metastatic potential: MCF-7, T-47D, MDA-MB-231; HER2/p53: HCC2218 (HER2+++/p53+), HCC1599 (HER2-/p53-), HCC202 (HER2++/p53-), HCC1419 (HER2+++/p53-) HCC70 (HER2-/p53+++); non-cancerous: MCF-10A). Unsupervised principal component analysis (PCA) of DESI-MS spectra enabled identification of twelve lipid biomarkers of metastatic potential and disease state, as well as ten lipids that distinguish cell lines based on HER2/p53 expression levels (> 200 lipids were identified per cell line). In addition, we developed a DESI-MS imaging (DESI-MSI) method for mapping the spatial distribution of lipids in metastatic spheroids (MDA-MB-231). Of the twelve lipids that correlate with changes in the metastatic potential of monolayer cell cultures, three were localized to the necrotic core of spheroids, indicating a potential role in promoting cancer cell survival in nutrient-deficient environments. One lipid species, which was not detected in monolayer MDA-MB-231 cultures, was spatially localized to the periphery of the spheroid, suggesting a potential role in invasion and/or proliferation. These results demonstrate that combining DESI-MS/PCA of monolayer and suspension cell cultures with DESI-MSI of spheroids is a promising approach for identifying lipid biomarkers of specific genotypes and phenotypes, as well as elucidating the potential function of these biomarkers in breast cancer. Graphical Absract.

Fatty acid synthase and adenosine monophosphate-activated protein kinase regulate cell survival and drug sensitivity in diffuse large B-cell lymphoma

Fatty acid synthesis is crucial in supporting the survival and proliferation of multiple forms of cancer. The high metabolic demands of fatty acid synthesis are regulated by the AMP-activated kinase and activity of the fatty acid synthase enzyme. In this study, the roles of these enzymes in diffuse large B-cell lymphoma (DLBCL) were investigated by genetic knock-down and pharmacological activation of AMP-activated kinase by metformin, and selective inhibition of fatty acid synthase using the novel drug Fasnall. We observed distinct heterogeneity and adaptive plasticity of lipid metabolism in a panel of DLBCL cell lines and demonstrate the therapeutic potential of inhibiting fatty acid synthesis in a subset of DLBCL cells. The translational relevance of these in vitro data is supported by the strong correlation between AMP-activated protein kinase expression in primary DLBCL samples and disease relapse. Inhibition of fatty acid synthase with Fasnall may represent a therapeutic option for DLBCL that preferentially subverts to de novo fatty acid synthesis.

Immunohistochemical Expression of Fatty Acid Synthase and Vascular Endothelial Growth Factor in Primary Colorectal Cancer: a Clinicopathological Study

BACKGROUND

Fatty acid synthase (FAS) is a valuable lipid enzyme involved in lipid biosynthesis and suggested to contribute in tumor carcinogenesis. Vascular endothelial growth factor (VEGF) is considered a serious angiogenic growth factor in the angiogenic pathway which is a very important in tumor growth and metastasis. Thus, inhibition of lipid biosynthesis and tumor angiogenesis can be new goals for colorectal cancer (CRC) treatment.

AIM OF THE WORK

The assessment of the expression of FAS and VEGF protein and the relationship between them in CRC with the clinicopathological parameters.

METHODS

The present retrospective study included 63 paraffin blocks previously diagnosed as primary cases of CRC. The slides were subjected to FAS and VEGF immunohistochemical staining using a streptavidin-biotin-peroxidase. The relationships among FAS and VEGF expression and clinicopathological parameters were statistically analyzed.

RESULTS

The expression rate of FAS was 81% and VEGF was 84.1% in the studied cases. FAS expression was significantly associated with histopathological type (p = 0.02) and grade (p = 0.04), and highly associated with lymph node metastasis and stage (p < 0.001).VEGF was significantly associated with histopathological type (p = 0.01) and tumor depth (p = 0.02); highly associated with grade, lymph node metastasis, and stage (p < 0.001). There was a positive association between FAS and VEGF expression in CRC (p < 0.001).

CONCLUSION

FAS and VEGF showed a highly significant expression in the studied primary CRC cases. A significant association was observed between their expressions, suggesting the involvement of FAS in tumor angiogenesis. So they constitute potential targets in cancer prevention and treatment and make FAS an attractive antiangiogenic target.

Atovaquone is active against AML by upregulating the integrated stress pathway and suppressing oxidative phosphorylation

Atovaquone, a US Food and Drug Administration-approved antiparasitic drug previously shown to reduce interleukin-6/STAT3 signaling in myeloma cells, is well tolerated, and plasma concentrations of 40 to 80 µM have been achieved with pediatric and adult dosing. We conducted preclinical testing of atovaquone with acute myeloid leukemia (AML) cell lines and pediatric patient samples. Atovaquone induced apoptosis with an EC50 <30 µM for most AML lines and primary pediatric AML specimens. In NSG mice xenografted with luciferase-expressing THP-1 cells and in those receiving a patient-derived xenograft, atovaquone-treated mice demonstrated decreased disease burden and prolonged survival. To gain a better understanding of the mechanism of atovaquone, we performed an integrated analysis of gene expression changes occurring in cancer cell lines after atovaquone exposure. Atovaquone promoted phosphorylation of eIF2α, a key component of the integrated stress response and master regulator of protein translation. Increased levels of phosphorylated eIF2α led to greater abundance of the transcription factor ATF4 and its target genes, including proapoptotic CHOP and CHAC1. Furthermore, atovaquone upregulated REDD1, an ATF4 target gene and negative regulator of the mechanistic target of rapamycin (mTOR), and caused REDD1-mediated inhibition of mTOR activity with similar efficacy as rapamycin. Additionally, atovaquone suppressed the oxygen consumption rate of AML cells, which has specific implications for chemotherapy-resistant AML blasts that rely on oxidative phosphorylation for survival. Our results provide insight into the complex biological effects of atovaquone, highlighting its potential as an anticancer therapy with novel and diverse mechanisms of action, and support further clinical evaluation of atovaquone for pediatric and adult AML.

A Metabolomic Approach for the In Vivo Study of Gold Nanospheres and Nanostars after a Single-Dose Intravenous Administration to Wistar Rats

Gold nanoparticles (AuNPs) are promising nanoplatforms for drug therapy, diagnostic and imaging. However, biological comparison studies for different types of AuNPs fail in consistency due to the lack of sensitive methods to detect subtle differences in the expression of toxicity. Therefore, innovative and sensitive approaches such as metabolomics are much needed to discriminate toxicity, specially at low doses. The current work aims to compare the in vivo toxicological effects of gold nanospheres versus gold nanostars (of similar ~40 nm diameter and coated with 11-mercaptoundecanoic acid) 24 h after an intravenous administration of a single dose (1.33 × 10¹¹ AuNPs/kg) to Wistar rats. The biodistribution of both types of AuNPs was determined by graphite furnace atomic absorption spectroscopy. The metabolic effects of the AuNPs on their main target organ, the liver, were analyzed using a GC-MS-based metabolomic approach. Conventional toxicological endpoints, including the levels of ATP and reduced and oxidized glutathione, were also investigated. The results show that AuNPs preferentially accumulate in the liver and, to a lesser extent, in the spleen and lungs. In other organs (kidney, heart, brain), Au content was below the limit of quantification. Reduced glutathione levels increased for both nanospheres and nanostars in the liver, but ATP levels were unaltered. Multivariate analysis showed a good discrimination between the two types of AuNPs (sphere- versus star-shaped nanoparticles) and compared to control group. The metabolic pathways involved in the discrimination were associated with the metabolism of fatty acids, pyrimidine and purine, arachidonic acid, biotin, glycine and synthesis of amino acids. In conclusion, the biodistribution, toxicological, and metabolic profiles of gold nanospheres and gold nanostars were described. Metabolomics proved to be a very useful tool for the comparative study of different types of AuNPs and raised awareness about the pathways associated to their distinct biological effects.

CPT1A Supports Castration-Resistant Prostate Cancer in Androgen-Deprived Conditions

Prostate cancer (PCa) is the most common cancer in men, and the global burden of the disease is rising. The majority of PCa deaths are due to metastasis that are highly resistant to current hormonal treatments; this state is called castration-resistant prostate cancer (CRPC). In this study, we focused on the role of the lipid catabolism enzyme CPT1A in supporting CRPC growth in an androgen-dependent manner. We found that androgen withdrawal promoted the growth of CPT1A over-expressing (OE) tumors while it decreased the growth of CPT1A under-expressing (KD) tumors, increasing their sensitivity to enzalutamide. Mechanistically, we found that CPT1A-OE cells burned more lipid and showed increased histone acetylation changes that were partially reversed with a p300 specific inhibitor. Conversely, CPT1A-KD cells showed less histone acetylation when grown in androgen-deprived conditions. Our results suggest that CPT1A supports CRPC by supplying acetyl groups for histone acetylation, promoting growth and antiandrogen resistance.

Lipid Metabolism and Endocrine Resistance in Prostate Cancer, and New Opportunities for Therapy

Prostate cancer (PCa) is the most common cancer in men, and more than 10% of men will be diagnosed with PCa during their lifetime. Patients that are not cured with surgery or radiation are largely treated with endocrine therapies that target androgens or the androgen receptor (AR), a major driver of PCa. In response to androgen deprivation, most PCas progress to castrate resistant PCa, which is treated with anti-androgens like enzalutamide, but tumors still progress and become incurable. Thus, there is a critical need to identify cellular pathways that allow tumors to escape anti-androgen therapies. Epidemiological studies suggest that high-fat diets play important roles in PCa progression. Lipid metabolism rewires the PCa metabolome to support growth and resistance to endocrine therapies, although the exact mechanisms remain obscure. Therapeutic effects have been observed inhibiting several aspects of PCa lipid metabolism: Synthesis, uptake, and oxidation. Since AR remains a driver of PCa in advanced disease, strategies targeting both lipid metabolism and AR are starting to emerge, providing new opportunities to re-sensitize tumors to endocrine therapies with lipid metabolic approaches.

Oleic acid ameliorates palmitic acid-induced ER stress and inflammation markers in naive and cerulein-treated exocrine pancreas cells

Dietary fat overload (typical to obesity) increases the risk of pancreatic pathologies through mechanisms yet to be defined. We previously showed that saturated dietary fat induces pancreatic acinar lipotoxicity and cellular stress. The endoplasmic reticulum (ER) of exocrine pancreas cells is highly developed and thus predisposed to stress. We studied the combination of saturated and unsaturated FAs in metabolic and pancreatitis like cerulein (CER)-induced stress states on cellular ER stress.

Exocrine pancreas AR42J and rat primary exocrine acinar cells underwent acute (24 h) challenge with different FAs (saturated, monounsaturated) at different concentrations (250 and 500 µM) and in combination with acute CER-induced stress, and were analyzed for fat accumulation, ER stress unfolded protein response (UPR) and immune and enzyme markers. Acute exposure of AR42J and pancreatic acinar cells to different FAs and their combinations increased triglyceride accumulation. Palmitic acid significantly dose-dependently enhanced the UPR, immune factors and pancreatic lipase (PL) levels, as demonstrated by XBP1 splicing and elevation in UPR transcripts and protein levels (Xbp1,Atf6, Atf4, Chop, Tnfα, Tgfβ and Il-6). Exposure to high palmitic levels in a CER-induced stress state synergistically increased ER stress and inflammation marker levels. Exposure to oleic acid did not induce ER stress and PL levels and significantly decreased immune factors in an acute CER-induced stress state. Combination of oleic and palmitic acids significantly reduced the palmitic-induced ER stress, but did not affect the immune factor response. We show that combination of monounsaturated and saturated FAs protects from exocrine pancreatic cellular ER stress in both metabolic and CER-induced stress.

The peculiarities of cancer cell metabolism: A route to metastasization and a target for therapy

The last decade has witnessed the peculiarities of metabolic reprogramming in tumour onset and progression, and their relevance in cancer therapy. Also, it has been indicated that the metastatic process may depend on the metabolic rewiring and adaptation of cancer cells to the pressure of tumour microenvironment and limiting nutrient availability. The present review gatherers the existent knowledge on the influence of tumour microenvironment and metabolic routes driving metastasis. A focus will be given to glycolysis, fatty acid metabolism, glutaminolysis, and amino acid handling. In addition, the role of metabolic waste driving metastasization will be explored. Finally, we discuss the status of cancer treatment approaches targeting metabolism. This knowledge revision will highlight the critical metabolic targets in metastasis and the chemicals already used in preclinical studies and clinical trials, providing clues that would be further exploited in medicinal chemistry research.

Fenofibrate induces human hepatoma Hep3B cells apoptosis and necroptosis through inhibition of thioesterase domain of fatty acid synthase

This study demonstrated that fenofibrate, a lipid-lowering drug, induced a significant time-dependent cytotoxicity of hepatoma Hep3B cells. Hep3B cells are significantly more sensitive to cell killing by fenofibrate than hepatoma HepG2, lung cancer CH27 and oral cancer HSC-3 cells. From the result of docking simulation, fenofibrate can bind excellently to the thioesterase domain of fatty acid synthase (FASN) binding site as orlistat, a FASN inhibitor, acts. The fenofibrate-induced cell cytotoxicity was protected by addition of palmitate, indicating that the cytotoxic effect of fenofibrate is due to starvation of Hep3B cells by inhibiting the formation of end product in the FASN reaction. Inhibition of lipid metabolism-related proteins expression, such as proteins containing thioesterase domain and fatty acid transport proteins, was involved in the fenofibrate-induced Hep3B cell death. Fenofibrate caused S and G2/M cell cycle arrest by inducing cyclin A/Cdk2 and reducing cyclin D1 and E protein levels in Hep3B cells. The anti-tumor roles of fenofibrate on Hep3B cells by inducing apoptosis and necroptosis were dependent on the expression of Bcl-2/caspase family members and RIP1/RIP3 proteins, respectively. These results suggest that fenofibrate has an anti-cancer effect in Hep3B cells and inhibition of lipid metabolism may be involved in fenofibrate-induced Hep3B cells apoptosis and necroptosis.

Strategies for targeting energy metabolism in Kirsten rat sarcoma viral oncogene homolog -mutant colorectal cancer

Alterations in cellular energy metabolism play critical roles in colorectal cancer (CRC). These alterations, which correlate to KRAS mutations, have been identified as energy metabolism signatures. This review summarizes the relationship between colorectal tumors associated with mutated KRAS and energy metabolism, especially for the deregulated energy metabolism that affects tumor cell proliferation, invasion, and migration. Furthermore, this review will concentrate on the role of metabolic genes, factors and signaling pathways, which are coupled with the primary energy source connected with the KRAS mutation that induces metabolic alterations. Strategies for targeting energy metabolism in mutated KRAS CRC are also introduced. In conclusion, deregulated energy metabolism has a close relationship with KRAS mutations in colorectal tumors. Therefore, selective inhibitors, agents against metabolic targets or KRAS signaling, may be clinically useful for colorectal tumor treatment through a patient-personalized approach.

Inhibition of endoplasmic reticulum stress in high-fat-diet-induced obese C57BL/6 mice: Efficacy of a novel extract from mulberry (Morus alba) leaves fermented with Cordyceps militaris

A few clues about correlation between endoplasmic reticulum (ER) stress and mulberry (Morus alba) leaves were investigated in only the experimental autoimmune myocarditis and streptozotocin-induced diabetes. To investigate whether a novel extract of mulberry leaves fermented with Cordyceps militaris (EMfC) could suppress ER in fatty liver, alterations in the key parameters for ER stress response were measured in high fat diet (HFD)-induced obese C57L/6 mice treated with EMfC for 12 weeks. The area of adipocytes in the liver section were significantly decreased in the HFD+EMfC treated group as compared to the HFD+Vehicle treated group, while their level was higher in HFD+Vehicle treated group than No treated group. The level of the eukaryotic initiation factor 2 alpha (eIF2α) and inositol-requiring enzyme 1 beta (IRE1α) phosphorylation and CCAAT-enhancer-binding protein homologous protein (CHOP) expression were remarkably enhanced in the HFD+Vehicle treated group. However, their levels were restored in the HFD+EMfC treated group, although some differences were detected in the decrease rate. Similar recovery was observed on the ER stress-induced apoptosis. The level of Caspase-3, Bcl-2 and Bax were decreased in the HFD+EMfC and HFD+orlistat (OT) treated group compared to the HFD+Vehicle treated group. The results of the present study therefore provide first evidence that EMfC with the anti-obesity effects can be suppressed ER stress and ER stress-induced apoptosis in the hepatic steatosis of HFD-induced obesity model.

Inhibition of de novo lipogenesis targets androgen receptor signaling in castration-resistant prostate cancer

Standard of care for metastatic castration-resistant prostate cancer (mCRPC) mainly relies on suppression of androgen receptor (AR) signaling. This approach has no lasting benefit due to the emergence of resistance mechanisms, such as ligand-independent splicing variant AR-V7. A metabolic feature of mCRPC is the upregulation of de novo lipogenesis to provide substrates and fuel for metastatic spread. Whether increased levels of fats affect AR signaling to promote an aggressive disease remains to be determined. Using a selective and potent inhibitor of fatty acid synthase we demonstrate that suppression of this key enzyme inhibits AR, most importantly AR-V7, and reduces mCRPC growth. Our findings offer a therapeutic opportunity for mCRPC and a potential mechanism to overcome resistance to AR inhibitors.

A hallmark of prostate cancer progression is dysregulation of lipid metabolism via overexpression of fatty acid synthase (FASN), a key enzyme in de novo fatty acid synthesis. Metastatic castration-resistant prostate cancer (mCRPC) develops resistance to inhibitors of androgen receptor (AR) signaling through a variety of mechanisms, including the emergence of the constitutively active AR variant V7 (AR-V7). Here, we developed an FASN inhibitor (IPI-9119) and demonstrated that selective FASN inhibition antagonizes CRPC growth through metabolic reprogramming and results in reduced protein expression and transcriptional activity of both full-length AR (AR-FL) and AR-V7. Activation of the reticulum endoplasmic stress response resulting in reduced protein synthesis was involved in IPI-9119–mediated inhibition of the AR pathway. In vivo, IPI-9119 reduced growth of AR-V7–driven CRPC xenografts and human mCRPC-derived organoids and enhanced the efficacy of enzalutamide in CRPC cells. In human mCRPC, both FASN and AR-FL were detected in 87% of metastases. AR-V7 was found in 39% of bone metastases and consistently coexpressed with FASN. In patients treated with enzalutamide and/or abiraterone FASN/AR-V7 double-positive metastases were found in 77% of cases. These findings provide a compelling rationale for the use of FASN inhibitors in mCRPCs, including those overexpressing AR-V7.

Ginseng metabolite protopanaxadiol interferes with lipid metabolism and induces endoplasmic reticulum stress and p53 activation to promote cancer cell death

Protopanaxadiol (PPD), a ginseng metabolite generated by the gut bacteria, was shown to induce colorectal cancer cell death and enhance the anticancer effect of chemotherapeutic agent 5-FU. However, the mechanism by which PPD promotes cancer cell death is not clear. In this manuscript, we showed that PPD activated p53 and endoplasmic reticulum (ER) stress and induced expression of BH3-only proteins Puma and Noxa to promote cell death. Induction of Puma by PPD was p53-dependent, whereas induction of Noxa was p53-independent. On the other hand, PPD also induced prosurvival mechanisms including autophagy and expression of Bcl2 family apoptosis regulator Mcl-1. Inhibition of autophagy or knockdown of Mcl-1 significantly enhanced PPD-induced cell death. Interestingly, PPD inhibited expression of genes involved in fatty acid and cholesterol biosynthesis and induced synergistic cancer cell death with fatty acid synthase inhibitor cerulenin. As PPD-induced ER stress was not significantly affected by inhibition of new protein synthesis, we suggest PPD may induce ER stress directly through causing lipid disequilibrium.

Lipid Metabolic Reprogramming in Hepatocellular Carcinoma

Metabolic reprogramming for adaptation to the local environment has been recognized as a hallmark of cancer. Although alterations in fatty acid (FA) metabolism in cancer cells have received less attention compared to other metabolic alterations such as glucose or glutamine metabolism, recent studies have uncovered the importance of lipid metabolic reprogramming in carcinogenesis. Obesity and nonalcoholic steatohepatitis (NASH) are well-known risk factors of hepatocellular carcinoma (HCC), and individuals with these conditions exhibit an increased intake of dietary FAs accompanied by enhanced lipolysis of visceral adipose tissue due to insulin resistance, resulting in enormous exogenous FA supplies to hepatocytes via the portal vein and lymph vessels. This “lipid-rich condition” is highly characteristic of obesity- and NASH-driven HCC. Although the way in which HCC cells adapt to such a condition and exploit it to aid their progression is not understood, we recently obtained new insights into this mechanism through lipid metabolic reprogramming. In addition, accumulating evidence supports the importance of lipid metabolic reprogramming in various situations of hepatocarcinogenesis. Thus, in this review, we discuss the latest findings regarding the role of FA metabolism pathways in hepatocarcinogenesis, focusing on obesity- and NASH-driven lipid metabolic reprogramming.

Strategies to target energy metabolism in consensus molecular subtype 3 along with Kirsten rat sarcoma viral oncogene homolog mutations for colorectal cancer therapy

Alterations in cellular energy metabolism play a critical role in colorectal cancer (CRC), which has been identified as the definition of consensus molecular subtypes (CMSs), and CMS3 tumors exhibit energy metabolism signatures along with Kirsten rat sarcoma viral oncogene homolog (KRAS)-activating mutations. This review summarizes the relationship between CMS3 tumors associated with mutated KRAS and energy metabolism in CRC, especially for the dysregulated energy metabolism that affects tumor cell proliferation, invasion, and migration. Furthermore, this review concentrates on the role of metabolic genes and factors and signaling pathways, which coupled with a primary energy source connected with the CMS3 associated with mutated KRAS, induce metabolic alterations. The strategies to target energy metabolism for the metabolic alterations in mutated KRAS CRC are also introduced. In conclusion, dysregulated energy metabolism has a close relationship with mutated KRAS in CMS3 tumors. Therefore, selective inhibitors or agents against metabolic targets or KRAS signaling may be clinically useful for CMS3 tumor treatment through a personalized approach for patients with cancer.

Placental insufficiency contributes to fatty acid metabolism alterations in aged female mouse offspring

Intrauterine growth restriction (IUGR) is an accepted risk factor for metabolic disorders in later life, including obesity and type 2 diabetes. The level of metabolic dysregulation can vary between subjects and is dependent on the severity and the type of IUGR insult. Classical IUGR animal models involve nutritional deprivation of the mother or uterine artery ligation. The latter aims to mimic a placental insufficiency, which is the most frequent cause of IUGR. In this study, we investigated whether IUGR attributable to placental insufficiency impacts the glucose and lipid homeostasis at advanced age. Placental insufficiency was achieved by deletion of the transcription factor AP-2y ( Tfap2c), which serves as one of the major trophoblast differentiation regulators. TdelT-IUGR mice were obtained by crossing mice with a floxed Tfap2c allele and mice with Cre recombinase under the control of the Tpbpa promoter. In advanced adulthood (9-12 mo), female and male IUGR mice are respectively 20% and 12% leaner compared with controls. At this age, IUGR mice have unaffected glucose clearance and lipid parameters (cholesterol, triglycerides, and phospholipids) in the liver. However, female IUGR mice have increased plasma free fatty acids (+87%) compared with controls. This is accompanied by increased mRNA levels of fatty acid synthase and endoplasmic reticulum stress markers in white adipose tissue. Taken together, our results suggest that IUGR by placental insufficiency may lead to higher lipogenesis in female mice in advanced adulthood, at least indicated by greater Fasn expression. This effect was sex specific for the aged IUGR females.

New strategies for targeting glucose metabolism-mediated acidosis for colorectal cancer therapy

Colorectal cancer (CRC) is a heterogeneous group of diseases that are the result of abnormal glucose metabolism alterations with high lactate production by pyruvate to lactate conversion, which remodels acidosis and offers an evolutional advantage for tumor cells, even enhancing their aggressive phenotype. This review summarizes recent findings that involve multiple genes, molecules, and downstream signaling in the dysregulated glycolytic pathway, which can allow a tumor to initiate acid byproducts and to progress, thereby resulting in acidosis commonly found in the tumor microenvironment of CRC. Moreover, the relationship between CRC cells and the tumor acidic microenvironment, especially for regulating lactate production and lactate dehydrogenase A levels, is also discussed, as well as comprehensively defining different aspects of glycolytic pathways that affect cancer cell proliferation, invasion, and migration. Furthermore, this review concentrates on glucose metabolism-mediated transduction factors in CRC, which include acid-sensing ion channels, triosephosphate isomerase and key glycolysis-related enzymes that regulate glycolytic metabolites, coupled with the effect on tumor cell glycolysis as well as signaling pathways. In conclusion, glucose metabolism mediated by glycolytic pathways that are integral to tumor acidosis in CRC is demonstrated. Therefore, selective metabolic inhibitors or agents against these targets in glucose metabolism through glycolytic pathways may be clinically useful to regulate the tumor's acidic microenvironment for CRC treatment and to identify specific targets that regulate tumor acidosis through a cancer patient-personalized approach. Furthermore, strategies for modifying the metabolic processes that effectively inhibit cancer cell growth and tumor progression and activate potent anticancer effects may provide more effective antitumor prospects for CRC therapy.

Global metabolite profiling analysis of lipotoxicity in HER2/neu-positive breast cancer cells

Recent work has shown that HER2/neu-positive breast cancer cells rely on a unique Warburg-like metabolism for survival and aggressive behavior. These cells are dependent on fatty acid (FA) synthesis, show markedly increased levels of stored fats and disruption of the synthetic process results in apoptosis. In this study, we used global metabolite profiling and a multi-omics network analysis approach to model the metabolic changes in this physiology under palmitate-supplemented growth conditions to gain insights into the molecular mechanism and its relevance to disease prevention and treatment. Computational analyses were used to define pathway enrichment based on the dataset of significantly altered metabolites and to integrate metabolomics and transcriptomics data in a multi-omics network analysis. Network-predicted changes and functional relationships were tested with cell assays in vitro. Palmitate-supplemented growth conditions induce distinct metabolic alterations. Growth of HER2-normal MCF7 cells is unaffected under these conditions whereas HER2/neu-positive cells display unchanged neutral lipid content, AMPK activation, inhibition of fatty acid synthesis and significantly altered glutamine, glucose and serine/glycine metabolism. The predominant upregulated lipid species is the novel bioactive lipid N-palmitoylglycine, which is non-toxic to these cells. Limiting the availability of glutamine significantly ameliorates the lipotoxic effects of palmitate, reduces CHOP and XBP1(s) induction and restores the expression levels of HER2 and HER3. The study shows that HER2/neu-positive breast cancer cells change their metabolic phenotype in the presence of palmitate. Palmitate induces AMPK activation and inhibition of fatty acid synthesis that feeds back into glycolysis as well as anaplerotic glutamine metabolism.

Orlistat as a FASN inhibitor and multitargeted agent for cancer therapy

INTRODUCTION

Cancer cells have increased glycolysis and glutaminolysis. Their third feature is increased de novo lipogenesis. As such, fatty acid (FA) synthesis enzymes are over-expressed in cancer and their depletion causes antitumor effects. As fatty acid synthase (FASN) plays a pivotal role in this process, it is an attractive target for cancer therapy.

AREAS COVERED

This is a review of the lipogenic phenotype of cancer and how this phenomenon can be exploited for cancer therapy using inhibitors of FASN, with particular emphasis on orlistat as a repurposing drug.

EXPERT OPINION

Disease stabilization only has been observed with a highly selective FASN inhibitor used as a single agent in clinical trials. It is too early to say whether the absence of tumor responses other than stabilization results because even full inhibition of FASN is not enough to elicit antitumor responses. The FASN inhibitor orlistat is a 'dirty' drug with target-off actions upon at least seven targets with a proven role in tumor biology. The development of orlistat formulations suited for its intravenous administration is a step ahead to shed light on the concept that drug promiscuity can or not be a virtue.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

NADPH accumulation is responsible for apoptosis in breast cancer cells induced by fatty acid synthase inhibition

Fatty acid synthase (FAS), as a key enzyme involved in de novo lipogenesis, is highly expressed in many cancers. FAS inhibition induces cell death in vivo and in vitro, rendering FAS as an attractive target for cancer therapy, but the defined mechanism is still not well understood. Herein, we confirmed that FAS was highly expressed in breast cancers and FAS inhibition by its inhibitors or knockdown induced apoptosis in breast cancer cells. Our results showed that a significantly high level of reactive oxygen species was induced but not responsible for apoptosis in breast cancer cells by FAS inhibition. Instead, NADPH accumulation resulting from FAS inhibition was found to stimulate NADPH oxidase to generate reactive oxygen species and highly associated with apoptosis induction. Suppression of NADPH oxidase almost totally blocked reactive oxygen species generation while significantly potentiated the in vitro and in vivo killing of breast cancers by FAS inhibition. Taken together, these data suggest that FAS plays a critical role in maintaining cellular redox homeostasis and its inhibition leads to NADPH accumulation-mediated apoptosis. Our finding may provide new insights into cancer metabolism and aid in designing effective anticancer treatments.

Stereochemical Structure Activity Relationship Studies (S-SAR) of Tetrahydrolipstatin

Tetrahydrolipstatin (THL), its enantiomer, and an additional six diastereomers were evaluated as inhibitors of the hydrolysis of p-nitrophenyl butyrate by porcine pancreatic lipase. IC₅₀s were found for all eight stereoisomers ranging from a low of 4.0 nM for THL to a high of 930 nM for the diastereomer with the inverted stereocenters at the 2,3,2'-positions. While the enantiomer of THL was also significantly less active (77 nM) the remaining five stereoisomers retained significant inhibitory activities (IC₅₀s = 8.0 to 20 nM). All eight compounds were also evaluated against three human cancer cell lines (human breast cancers MCF-7 and MDA-MB-231, human large-cell lung carcinoma H460). No appreciable cytotoxicity was observed for THL and its seven diastereomers, as their IC₅₀s in a MTT cytotoxicity assay were all greater than 3 orders of magnitude of camptothecin.

Pancreatic adenocarcinoma, chronic pancreatitis, and MODY-8 diabetes: is bile salt-dependent lipase (or carboxyl ester lipase) at the crossroads of pancreatic pathologies?

Pancreatic adenocarcinomas and diabetes mellitus are responsible for the deaths of around two million people each year worldwide. Patients with chronic pancreatitis do not die directly of this disease, except where the pathology is hereditary. Much current literature supports the involvement of bile salt-dependent lipase (BSDL), also known as carboxyl ester lipase (CEL), in the pathophysiology of these pancreatic diseases. The purpose of this review is to shed light on connections between chronic pancreatitis, diabetes, and pancreatic adenocarcinomas by gaining an insight into BSDL and its variants. This enzyme is normally secreted by the exocrine pancreas, and is diverted within the intestinal lumen to participate in the hydrolysis of dietary lipids. However, BSDL is also expressed by other cells and tissues, where it participates in lipid homeostasis. Variants of BSDL resulting from germline and/or somatic mutations (nucleotide insertion/deletion or nonallelic homologous recombination) are expressed in the pancreas of patients with pancreatic pathologies such as chronic pancreatitis, MODY-8, and pancreatic adenocarcinomas. We discuss the possible link between the expression of BSDL variants and these dramatic pancreatic pathologies, putting forward the suggestion that BSDL and its variants are implicated in the cell lipid metabolism/reprogramming that leads to the dyslipidemia observed in chronic pancreatitis, MODY-8, and pancreatic adenocarcinomas. We also propose potential strategies for translation to therapeutic applications.

Interacting Cancer Machineries: Cell Signaling, Lipid Metabolism, and Epigenetics

Cancer-specific perturbations of signaling, metabolism, and epigenetics can be a cause and/or consequence of malignant transformation. Evidence indicates that these regulatory systems interact with each other to form highly flexible and robust cybernetic networks that promote malignant growth and confer treatment resistance. Deciphering these plexuses using holistic approaches known from systems biology can be instructive for the future design of novel anticancer strategies. In this review, I discuss novel findings elucidating the multiple molecular interdependence among cancer-specific signaling, cell metabolism, and epigenetics to provide an insightful understanding of how major cancer machineries interact with each other during cancer development and progression, and how this knowledge may be used for future co-targeting strategies.

Fatty acid synthase reprograms the epigenome in uterine leiomyosarcomas

SK-UT-1 uterine leiomyosarcomas (Ut-LMS) cells were transduced with a fatty acid synthase (FASN)-containing retroviral vector to recapitulate the "lipogenic phenotype of cancer." Consistent with this model, forced expression of FASN enhanced SK-UT-1 proliferation, migration, and cellular motion. Further investigation showed FASN promotes trimethylation of H3K9 (H3K9me3) and acetylation of H3K27 (H3K27ac) in SK-UT-1 cells. In contrast, siRNA targeting of FASN in high endogenous FASN expressing SK-LMS-1 Ut-LMS cells inhibits trimethylation of H3K9 and acetylation of H3K27. Palmitate, the predominant fatty acid product of FASN, increased H3K9me3, H3K27ac and H3K27me3 detection in SK-UT-1 cells. FASN promoted histone 3 methylation and acetylation through alteration of histone 3-modifying enzymatic activities (HDAC, HDM, HMT and HAT). ChIP-seq in SK-UT-1-FASN cells with anti-H3K9me3 antibody identified regions of enriched binding compared to vector-only cells. One differentially-enriched gene, CRISP1, was investigated further by ChIP-PCR. The transcriptionally repressive function of H3K9me3 was confirmed in CRISP1. Our results provide mechanistic insight into the pathobiology of the "lipogenic phenotype of cancer." Here, FASN reprograms the Ut-LMS epigenome through chromatin remodeling to promote the "malignant phenotype."

Oroxylin A suppresses the development and growth of colorectal cancer through reprogram of HIF1α-modulated fatty acid metabolism

The occurrence and progress of colon cancer are closely associated with obesity. Therefore, the lipid metabolism, especially fatty acid metabolism, is a significant section of energy homeostasis in colon cancer cells, and it affects many important cellular processes. Oroxylin A is one of the main bioactive flavonoids of Scutellariae radix, which has a strong anticancer effect but low toxicity to normal tissue. In previous studies, we have proved that oroxylin A reprogrammes metabolism of cancer cells by inhibiting glycolysis. Here, we further investigated the metabolism-modulating effects of oroxylin A on the fatty acid metabolism in colon cancer cells under hypoxia. We found that HIF1α upregulated adipophilin, fatty acid synthase and sterol regulatory element-binding protein 1, and downregulated carnitine palmitoyltransferase 1 (CPT1), resulting in the promoted lipid uptake and transport, increased de novo fatty acid synthesis and suppressed fatty acid oxidation. Oroxylin A inactivated HIF1α and reprogrammed fatty acid metabolism of HCT116 cells, decreasing intracellular fatty acid level and enhancing fatty acid oxidation. Furthermore, the rapid decrease of fatty acid level caused by oroxylin A inhibited the nuclear translocation of β-cantenin and inactivated the Wnt pathway, arousing cell cycle arrest in G2/M phase. In vivo studies demonstrated that high-fat diet increased the incidence of colon cancer and accelerated tumor development. Importantly, besides the growth inhibitory effects on colon cancer xenograft, oroxylin A prevented carcinogenesis and delayed progress of primary colon cancer as well. Our studies enriched the metabolic regulatory mechanism of oroxylin A, and suggested that oroxylin A was a potent candidate for the treatment and prevention of colorectal cancer.

Clove extract functions as a natural fatty acid synthesis inhibitor and prevents obesity in a mouse model

Numerous medicinal plants have been reported to prevent various chronic diseases.

Inhibition of acetyl-CoA carboxylase suppresses fatty acid synthesis and tumor growth of non-small-cell lung cancer in preclinical models

Continuous de novo fatty acid synthesis is a common feature of cancer required to meet the biosynthetic demands of a growing tumor. This process is controlled by the rate-limiting enzyme acetyl-CoA carboxylase (ACC), an attractive but traditionally intractable drug target. Here, we provide genetic and pharmacological evidence that in preclinical models ACC is required to maintain de novo fatty acid synthesis needed for growth and viability of non-small cell lung cancer (NSCLC). We describe the ability of ND-646—an allosteric inhibitor of the ACC enzymes ACC1 and ACC2 that prevents ACC subunit dimerization—to suppress fatty acid synthesis in vitro and in vivo. Chronic ND-646 treatment of xenograft and genetically engineered mouse models of NSCLC inhibited tumor growth. When administered as a single agent or in combination with the standard-of-care drug carboplatin, ND-646 markedly suppressed lung tumor growth in the Kras;Trp53^−/− (also known as KRAS p53) and Kras;Stk11^−/− (also known as KRAS Lkb1) mouse models of NSCLC. These findings demonstrate that ACC mediates a metabolic liability of NSCLC and that ACC inhibition by ND-646 is detrimental to NSCLC growth, supporting further examination of the use of ACC inhibitors in oncology.

Palmitate-induced ER stress increases trastuzumab sensitivity in HER2/neu-positive breast cancer cells

BACKGROUND

HER2/neu-positive breast cancer cells have recently been shown to use a unique Warburg-like metabolism for survival and aggressive behavior. These cells exhibit increased fatty acid synthesis and storage compared to normal breast cells or other tumor cells. Disruption of this synthetic process results in apoptosis. Since the addition of physiological doses of exogenous palmitate induces cell death in HER2/neu-positive breast cancer cells, the pathway is likely operating at its limits in these cells. We have studied the response of HER2/neu-positive breast cancer cells to physiological concentrations of exogenous palmitate to identify lipotoxicity-associated consequences of this physiology. Since epidemiological data show that a diet rich in saturated fatty acids is negatively associated with the development of HER2/neu-positive cancer, this cellular physiology may be relevant to the etiology and treatment of the disease. We sought to identify signaling pathways that are regulated by physiological concentrations of exogenous palmitate specifically in HER2/neu-positive breast cancer cells and gain insights into the molecular mechanism and its relevance to disease prevention and treatment.

METHODS

Transcriptional profiling was performed to assess programs that are regulated in HER2-normal MCF7 and HER2/neu-positive SKBR3 breast cancer cells in response to exogenous palmitate. Computational analyses were used to define and predict functional relationships and identify networks that are differentially regulated in the two cell lines. These predictions were tested using reporter assays, fluorescence-based high content microscopy, flow cytometry and immunoblotting. Physiological effects were confirmed in HER2/neu-positive BT474 and HCC1569 breast cancer cell lines.

RESULTS

Exogenous palmitate induces functionally distinct transcriptional programs in HER2/neu-positive breast cancer cells. In the lipogenic HER2/neu-positive SKBR3 cell line, palmitate induces a G2 phase cell cycle delay and CHOP-dependent apoptosis as well as a partial activation of the ER stress response network via XBP1 and ATF6. This response appears to be a general feature of HER2/neu-positive breast cancer cells but not cells that overexpress only HER2/neu. Exogenous palmitate reduces HER2 and HER3 protein levels without changes in phosphorylation and sensitizes HER2/neu-positive breast cancer cells to treatment with the HER2-targeted therapy trastuzumab.

CONCLUSIONS

Several studies have shown that HER2, FASN and fatty acid synthesis are functionally linked. Exogenous palmitate exerts its toxic effects in part through inducing ER stress, reducing HER2 expression and thereby sensitizing cells to trastuzumab. These data provide further evidence that HER2 signaling and fatty acid metabolism are highly integrated processes that may be important for disease development and progression.

Targeting ACLY sensitizes castration-resistant prostate cancer cells to AR antagonism by impinging on an ACLY-AMPK-AR feedback mechanism

The androgen receptor (AR) plays a central role in prostate tumor growth. Inappropriate reactivation of the AR after androgen deprivation therapy promotes development of incurable castration-resistant prostate cancer (CRPC). In this study, we provide evidence that metabolic features of prostate cancer cells can be exploited to sensitize CRPC cells to AR antagonism. We identify a feedback loop between ATP-citrate lyase (ACLY)-dependent fatty acid synthesis, AMPK, and the AR in prostate cancer cells that could contribute to therapeutic resistance by maintaining AR levels. When combined with an AR antagonist, ACLY inhibition in CRPC cells promotes energetic stress and AMPK activation, resulting in further suppression of AR levels and target gene expression, inhibition of proliferation, and apoptosis. Supplying exogenous fatty acids can restore energetic homeostasis; however, this rescue does not occur through increased β-oxidation to support mitochondrial ATP production. Instead, concurrent inhibition of ACLY and AR may drive excess ATP consumption as cells attempt to cope with endoplasmic reticulum (ER) stress, which is prevented by fatty acid supplementation. Thus, fatty acid metabolism plays a key role in coordinating ER and energetic homeostasis in CRPC cells, thereby sustaining AR action and promoting proliferation. Consistent with a role for fatty acid metabolism in sustaining AR levels in prostate cancer in vivo, AR mRNA levels in human prostate tumors correlate positively with expression of ACLY and other fatty acid synthesis genes. The ACLY-AMPK-AR network can be exploited to sensitize CRPC cells to AR antagonism, suggesting novel therapeutic opportunities for prostate cancer.

MicroRNA-26a/b and their host genes synergistically regulate triacylglycerol synthesis by targeting the INSIG1 gene

The microRNA-26 (miR-26) family is known to control adipogenesis in non-ruminants. The genomic loci of miR-26a and miR-26b have been localized in the introns of genes encoding for the proteins of the C-terminal domain RNA polymerase II polypeptide A small phosphatase (CTDSP) family. Insulin-induced gene 1 (INSIG1) encodes a protein with a key role in the regulation of lipogenesis in rodent liver. In the present study, we investigated the synergistic function of the miR-26 family and their host genes in goat mammary epithelial cells (GMEC). Downregulation of miR-26a/b and their host genes in GMEC decreased the expression of genes relate to fatty acid synthesis (PPARG, LXRA, SREBF1, FASN, ACACA, GPAM, LPIN1, DGAT1 and SCD1), triacylglycerol accumulation and unsaturated fatty acid synthesis. Luciferase reporter assays confirmed INSIG1 as a direct target of miR-26a/b. Furthermore, inhibition of the CTDSP family also downregulated the expression of INSIG1. Taken together, our findings highlight a functional association of miR-26a/b, their host genes and INSIG1, and provide new insights into the regulatory network controlling milk fat synthesis in GMEC. The data indicate that targeting this network via nutrition might be important for regulating milk fat synthesis in ruminants.

Development of a Self-Assembled Nanoparticle Formulation of Orlistat, Nano-ORL, with Increased Cytotoxicity against Human Tumor Cell Lines

Fatty acid synthase (FASN), the enzyme that catalyzes de novo synthesis of fatty acids, is expressed in many cancer types. Its potential as a therapeutic target is well recognized, but inhibitors of FASN have not yet been approved for cancer therapy. Orlistat (ORL), an FDA-approved lipase inhibitor, is also an effective inhibitor of FASN. However, ORL is extremely hydrophobic and has low systemic uptake after oral administration. Thus, new strategies are required to formulate ORL for cancer treatment as a FASN inhibitor. Here, we report the development of a nanoparticle (NP) formulation of ORL using amphiphilic bioconjugates that are derived from hyaluronic acid (HA), termed Nano-ORL. The NPs were loaded with up to 20 wt % weight of ORL at greater than 95% efficiency. The direct inhibition of the human recombinant thioesterase domain of FASN by ORL extracted from Nano-ORL was similar to that of stock ORL. Nano-ORL demonstrated a similar ability to inhibit cellular FASN activity when compared to free ORL, as demonstrated by analysis of (14)C-acetate incorporation into lipids. Nano-ORL treatment also disrupted mitochondrial function similarly to ORL by reducing adenosine triphosphate turnover in MDA-MB-231 and LNCaP cells. Nano-ORL demonstrated increased potency compared to ORL toward prostate and breast cancer cells. Nano-ORL decreased viability of human prostate and breast cancer cell lines to 55 and 57%, respectively, while free ORL decreased viability to 71 and 79% in the same cell lines. Moreover, Nano-ORL retained cytotoxic activity after a 24 h preincubation in aqueous conditions. Preincubation of ORL dramatically reduced the efficacy of ORL as indicated by high cell viability (>85%) in both breast and prostate cell lines. These data demonstrate that NP formulation of ORL using HA-derived polymers retains similar levels of FASN, lipid synthesis, and ATP turnover inhibition while significantly improving the cytotoxic activity against cancer cell lines.

Lipid metabolic reprogramming in cancer cells

Many human diseases, including metabolic, immune and central nervous system disorders, as well as cancer, are the consequence of an alteration in lipid metabolic enzymes and their pathways. This illustrates the fundamental role played by lipids in maintaining membrane homeostasis and normal function in healthy cells. We reviewed the major lipid dysfunctions occurring during tumor development, as determined using systems biology approaches. In it, we provide detailed insight into the essential roles exerted by specific lipids in mediating intracellular oncogenic signaling, endoplasmic reticulum stress and bidirectional crosstalk between cells of the tumor microenvironment and cancer cells. Finally, we summarize the advances in ongoing research aimed at exploiting the dependency of cancer cells on lipids to abolish tumor progression.

The unfolded protein response in glioblastomas: targetable or trouble?

Glioblastomas are devastating central nervous system tumors with abysmal prognoses. These tumors are often difficult to resect surgically, are highly invasive and proliferative, and are resistant to virtually all therapeutic attempts, making them universally lethal diseases. One key enabling feature of their tumor biology is the engagement of the unfolded protein response (UPR), a stress response originating in the endoplasmic reticulum (ER) designed to handle the pathologies of aggregating malfolded proteins in that organelle. Glioblastomas and other tumors have co-opted this stress response to allow their continued uncontrolled growth by enhanced protein production (maintained by chaperone-assisted protein folding) and lipid biosynthesis driven downstream of the UPR. These features can account for the extensive extracellular remodeling/invasiveness/angiogenesis and proliferative capacity, and ultimately result in tumor phenotypes of chemo- and radio-resistance. The UPR in general, and its chaperoning capacity in particular, are thus putative high-value targets for treatment intervention. Such therapeutic strategies, and potential problems with them, will be discussed and analyzed.