Control of cell growth and survival by enzymes of the fatty acid synthesis pathway in HCT-116 colon cancer cells

Targeting dysregulated lipid metabolism in the tumor microenvironment

The reprogramming of lipid metabolism and its association with oncogenic signaling pathways within the tumor microenvironment (TME) have emerged as significant hallmarks of cancer. Lipid metabolism is defined as a complex set of molecular processes including lipid uptake, synthesis, transport, and degradation. The dysregulation of lipid metabolism is affected by enzymes and signaling molecules directly or indirectly involved in the lipid metabolic process. Regulation of lipid metabolizing enzymes has been shown to modulate cancer development and to avoid resistance to anticancer drugs in tumors and the TME. Because of this, understanding the metabolic reprogramming associated with oncogenic progression is important to develop strategies for cancer treatment. Recent advances provide insight into fundamental mechanisms and the connections between altered lipid metabolism and tumorigenesis. In this review, we explore alterations to lipid metabolism and the pivotal factors driving lipid metabolic reprogramming, which exacerbate cancer progression. We also shed light on the latest insights and current therapeutic approaches based on small molecular inhibitors and phytochemicals targeting lipid metabolism for cancer treatment. Further investigations are worthwhile to fully understand the underlying mechanisms and the correlation between altered lipid metabolism and carcinogenesis.

Downregulation of ACC expression suppresses cell viability and migration in the malignant progression of breast cancer

Exploring new diagnostic biomarkers and molecular targets is of great importance in breast cancer treatment. The present study investigated the effects of acetyl-CoA carboxylase (ACC) expression interference on the malignant progression of breast cancer cells. ACC expression was knocked down using a lentiviral vector and this was verified by quantitative polymerase chain reaction and western blotting. MCF-7 and MDA-MB-231 breast cancer cells were randomly allocated into the following groups: Normal breast cancer cells (control), breast cancer cells transduced with a negative control lentiviral vector and breast cancer cells transduced with an ACC knockdown lentiviral vector. Screening for stable transgenic strains was successful. Cell viability, apoptosis and migration were determined using Cell Counting Kit-8, flow cytometry and scratch test, respectively. The protein expression levels of N-cadherin, Vimentin and Bax were detected by western blotting. In addition, a nude mouse model of subcutaneous metastatic tumor was established using MCF-7 breast cancer cells, and tumor volume was assessed. Furthermore, pathological condition and apoptosis were detected using hematoxylin and eosin, and TUNEL staining, respectively. The protein expression levels of N-cadherin, Vimentin and Bax were detected by western blotting. The in vitro experiments showed that knockdown of ACC expression significantly decreased the viability and migration, and increased the apoptosis of MCF-7 and MDA-MB-231 breast cancer cells. In vivo experiments revealed that ACC knockdown effectively reduced the tumor volume in nude mice, and promoted tumor cell apoptosis. Both in vitro and in vivo experiments showed that ACC knockdown can reduce the protein expression levels of N-cadherin and Vimentin, and increase Bax expression. These findings suggested that downregulation of ACC expression may significantly reduce the malignant progression of breast cancer, and could be considered a potential therapeutic target.

Body fatness associations with cancer: evidence from recent epidemiological studies and future directions

This narrative review highlights current evidence linking greater body fatness to risk of various cancers, with focus on evidence from recent large cohort studies and pooled analyses of cohort studies as well as Mendelian randomization studies (which utilized genetic variants associated with body mass index to debrief the causal effect of higher body fatness on cancer risk). This review also provides insights into the biological mechanisms underpinning the associations. Data from both observational and Mendelian randomization studies support the associations of higher body mass index with increased risk of many cancers with the strongest evidence for digestive system cancers, including esophageal, stomach, colorectal, liver, gallbladder, and pancreatic cancer, as well as kidney, endometrial, and ovarian (weak association) cancer. Evidence from observational studies suggests that greater body fatness has contrasting effects on breast cancer risk depending on menopausal status and on prostate cancer risk depending on disease stage. Experimental and Mendelian randomization studies indicate that adiponectin, insulin, and sex hormone pathways play an important role in mediating the link between body fatness and cancer risk. The possible role of specific factors and pathways, such as other adipocytokines and hormones and the gut microbiome in mediating the associations between greater body fatness and cancer risk is yet uncertain and needs investigation in future studies. With rising prevalence of overweight and obesity worldwide, the proportion of cancer caused by excess body fatness is expected to increase. There is thus an urgent need to identify efficient ways at the individual and societal level to improve diet and physical activity patterns to reduce the burden of obesity and accompanying comorbidities, including cancer.

circCAPRIN1 interacts with STAT2 to promote tumor progression and lipid synthesis via upregulating ACC1 expression in colorectal cancer

BACKGROUND

Circular RNAs (circRNAs) generated by back-splicing of precursor mRNAs (pre-mRNAs) are often aberrantly expressed in cancer cells. Accumulating evidence has revealed that circRNAs play a critical role in the progression of several cancers, including colorectal cancer (CRC). However, the current understandings of the emerging functions of circRNAs in CRC lipid metabolism and the underlying molecular mechanisms are still limited. Here, we aimed to explore the role of circCAPRIN1 in regulating CRC lipid metabolism and tumorigenesis.

METHODS

circRNA microarray was performed with three pairs of tumor and non-tumor tissues from CRC patients. The expression of circRNAs were determined by quantitative PCR (qPCR) and in situ hybridization (ISH). The endogenous levels of circRNAs in CRC cells were manipulated by transfection with lentiviruses overexpressing or silencing circRNAs. The regulatory roles of circRNAs in the occurrence of CRC were investigated both in vitro and in vivo using gene expression array, RNA pull-down/mass spectrometry, RNA immunoprecipitation assay, luciferase reporter assay, chromatin immunoprecipitation analysis, and fluorescence in situ hybridization (FISH).

RESULTS

Among circRNAs, circCAPRIN1 was most significantly upregulated in CRC tissue specimens. circCAPRIN1 expression was positively correlated with the clinical stage and unfavorable prognosis of CRC patients. Downregulation of circCAPRIN1 suppressed proliferation, migration, and epithelial-mesenchymal transition of CRC cells, while circCAPRIN1 overexpression had opposite effects. RNA sequencing and gene ontology analysis indicated that circCAPRIN1 upregulated the expressions of genes involved in CRC lipid metabolism. Moreover, circCAPRIN1 promoted lipid synthesis by enhancing Acetyl-CoA carboxylase 1 (ACC1) expression. Further mechanistic assays demonstrated that circCAPRIN1 directly bound signal transducer and activator of transcription 2 (STAT2) to activate ACC1 transcription, thus regulating lipid metabolism and facilitating CRC tumorigenesis.

CONCLUSIONS

These findings revealed the oncogenic role and mechanism of circCAPRIN1 in CRC. circCAPRIN1 interacted with STAT2 to promote CRC tumor progression and lipid synthesis by enhancing the expression of ACC1. circCAPRIN1 may be considered as a novel potential diagnostic and therapeutic target for CRC patients.

Identification of fatty acid metabolism-related lncRNAs in the prognosis and immune microenvironment of colon adenocarcinoma

BACKGROUND

Cancer metabolism is largely altered compared to normal cells. This study aims to explore critical metabolism pathways in colon adenocarcinoma (COAD), and reveal the possible mechanism of their role in cancer progression.

METHODS

Expression data and sequencing data of COAD samples were obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases. The expression profiles between tumor and normal samples were compared to identify differential metabolism pathways through single sample gene set enrichment analysis.

RESULTS

Fatty acid synthesis was identified as a key metabolism pathway in COAD. Based on fatty acid-related lncRNAs, two molecular subtypes (C1 and C2) were defined. C2 subtype with worse prognosis had higher immune infiltration and higher expression of immune checkpoints. Five transcription factors (TFs) including FOS, JUN, HIF1A, STAT3 and STAT2 were highly expressed in C2 subtype. Five fatty acid-related lncRNAs were identified to be biomarkers for predicting COAD prognosis. Finally, further experients showed that knockdown of lncRNA PAXIP1-AS1 decreased the triglyceride content and the fatty acid synthase and acetyl-CoA carboxylase 1 expressions, which suggested that lncRNA PAXIP1-AS1 plays an important role in fatty acid metabolism of COAD.

CONCLUSIONS

This study demonstrated that fatty acid synthesis was greatly altered in COAD. Fatty acid-related lncRNAs were speculated to be involved in cancer progression through associating with TFs. The five screened TFs may serve as new drug targets for treating COAD.

Acetyl-CoA-Carboxylase 1-mediated de novo fatty acid synthesis sustains Lgr5+ intestinal stem cell function

Basic processes of the fatty acid metabolism have an important impact on the function of intestinal epithelial cells (IEC). However, while the role of cellular fatty acid oxidation is well appreciated, it is not clear how de novo fatty acid synthesis (FAS) influences the biology of IECs. We report here that interfering with de novo FAS by deletion of the enzyme Acetyl-CoA-Carboxylase (ACC)1 in IECs results in the loss of epithelial crypt structures and a specific decline in Lgr5⁺ intestinal epithelial stem cells (ISC). Mechanistically, ACC1-mediated de novo FAS supports the formation of intestinal organoids and the differentiation of complex crypt structures by sustaining the nuclear accumulation of PPARδ/β-catenin in ISCs. The dependency of ISCs on cellular de novo FAS is tuned by the availability of environmental lipids, as an excess delivery of external fatty acids is sufficient to rescue the defect in crypt formation. Finally, inhibition of ACC1 reduces the formation of tumors in colitis-associated colon cancer, together highlighting the importance of cellular lipogenesis for sustaining ISC function and providing a potential perspective to colon cancer therapy.

Here the authors report that inhibition of de novo fatty acid synthesis by deleting the enzyme Acetyl-CoA-Carboxylase 1 in the intestinal epithelium results in the loss of crypt structures and a specific decline in Lgr5+ intestinal epithelial stem cells.

Emerging Roles of the Tumor Suppressor p53 in Metabolism

Metabolism plays critical roles in maintaining the homeostasis of cells. Metabolic abnormalities are often considered as one of the main driving forces for cancer progression, providing energy and substrates of biosynthesis to support neoplastic proliferation effectively. The tumor suppressor p53 is well known for its roles in inducing cell cycle arrest, apoptosis, senescence and ferroptosis. Recently, emerging evidence has shown that p53 is also actively involved in the reprogramming of cellular metabolism. In this review, we focus on recent advances in our understanding of the interplay between p53 and metabolism of glucose, fatty acid as well as amino acid, and discuss how the deregulation of p53 in these processes could lead to cancer.

Discovery of metabolomic biomarkers for discriminating platinum-sensitive and platinum-resistant ovarian cancer by using GC-MS

This study aims to determine ovarian cancer (OC) patients with platinum resistance for alternative treatment protocols by using metabolomic methodologies. Urine and serum samples of platinum-resistant and platinum-sensitive OC were analyzed using GC-MS. After data processing of GC-MS raw data, multivariate analyses were performed to interpret complex data for biologically meaningful information and to identify the biomarkers that cause differences between two groups. The biomarkers were verified after univariate, multivariate, and ROC analysis. Finally, metabolomic pathways related to group separations were specified. The results of biomarker analysis showed that 3,4-dihydroxyphenylacetic acid, 4-hydroxybutyric acid, L-threonine, D- mannose, and sorbitol metabolites were potential biomarkers in urine samples. In serum samples, L-arginine, linoleic acid, L-glutamine, and hypoxanthine were identified as important biomarkers. R2Y, Q2, AUC, sensitivity and specificity values of platinum-resistant and sensitive OC patients' urine and serum samples were 0.85, 0.545, 0.844, 91.30%, 81.08 and 0.570, 0.206, 0.743, 77.78%, 74.28%, respectively. In metabolic pathway analysis of urine samples, tyrosine metabolism and fructose and mannose metabolism were found to be statistically significant (p < 0.05) for the discrimination of the two groups. While 3,4-dihydroxyphenylacetic acid, L-tyrosine, and fumaric acid metabolites were effective in tyrosine metabolism. D-sorbitol and D-mannose metabolites were significantly important in fructose and mannose metabolism. However, seven metabolomic pathways were significant (p < 0.05) in serum samples. In terms of p-value, L-glutamine in the nitrogen metabolic pathway from the first three pathways; L-glutamine and pyroglutamic acid metabolites in D-glutamine and D-glutamate metabolism. In the arginine and proline metabolic pathway, L-arginine, L-proline, and L-ornithine metabolites differed significantly between the two groups.

Interplay between Epigenetics and Cellular Metabolism in Colorectal Cancer

Cellular metabolism alterations have been recognized as one of the most predominant hallmarks of colorectal cancers (CRCs). It is precisely regulated by many oncogenic signaling pathways in all kinds of regulatory levels, including transcriptional, post-transcriptional, translational and post-translational levels. Among these regulatory factors, epigenetics play an essential role in the modulation of cellular metabolism. On the one hand, epigenetics can regulate cellular metabolism via directly controlling the transcription of genes encoding metabolic enzymes of transporters. On the other hand, epigenetics can regulate major transcriptional factors and signaling pathways that control the transcription of genes encoding metabolic enzymes or transporters, or affecting the translation, activation, stabilization, or translocation of metabolic enzymes or transporters. Interestingly, epigenetics can also be controlled by cellular metabolism. Metabolites not only directly influence epigenetic processes, but also affect the activity of epigenetic enzymes. Actually, both cellular metabolism pathways and epigenetic processes are controlled by enzymes. They are highly intertwined and are essential for oncogenesis and tumor development of CRCs. Therefore, they are potential therapeutic targets for the treatment of CRCs. In recent years, both epigenetic and metabolism inhibitors are studied for clinical use to treat CRCs. In this review, we depict the interplay between epigenetics and cellular metabolism in CRCs and summarize the underlying molecular mechanisms and their potential applications for clinical therapy.

Fine-Tuning Lipid Metabolism by Targeting Mitochondria-Associated Acetyl-CoA-Carboxylase 2 in BRAFV600E Papillary Thyroid Carcinoma

Background: BRAF^V600E acts as an ATP-dependent cytosolic kinase. BRAF^V600E inhibitors are widely available, but resistance to them is widely reported in the clinic. Lipid metabolism (fatty acids) is fundamental for energy and to control cell stress. Whether and how BRAF^V600E impacts lipid metabolism regulation in papillary thyroid carcinoma (PTC) is still unknown. Acetyl-CoA carboxylase (ACC) is a rate-limiting enzyme for de novo lipid synthesis and inhibition of fatty acid oxidation (FAO). ACC1 and ACC2 genes encode distinct isoforms of ACC. The aim of our study was to determine the relationship between BRAF^V600E and ACC in PTC. Methods: We performed RNA-seq and DNA copy number analyses in PTC and normal thyroid (NT) in The Cancer Genome Atlas samples. Validations were performed by using assays on PTC-derived cell lines of differing BRAF status and a xenograft mouse model derived from a heterozygous BRAF^WT/V600E PTC-derived cell line with knockdown (sh) of ACC1 or ACC2. Results:ACC2 mRNA expression was significantly downregulated in BRAF^V600E-PTC vs. BRAF^WT-PTC or NT clinical samples. ACC2 protein levels were downregulated in BRAF^V600E-PTC cell lines vs. the BRAF^WT/WT PTC cell line. Vemurafenib increased ACC2 (and to a lesser extent ACC1) mRNA levels in PTC-derived cell lines in a BRAF^V600E allelic dose-dependent manner. BRAF^V600E inhibition increased de novo lipid synthesis rates, and decreased FAO due to oxygen consumption rate (OCR), and extracellular acidification rate (ECAR), after addition of palmitate. Only shACC2 significantly increased OCR rates due to FAO, while it decreased ECAR in BRAF^V600E PTC-derived cells vs. controls. BRAF^V600E inhibition synergized with shACC2 to increase intracellular reactive oxygen species production, leading to increased cell proliferation and, ultimately, vemurafenib resistance. Mice implanted with a BRAF^WT/V600E PTC-derived cell line with shACC2 showed significantly increased tumor growth after vemurafenib treatment, while vehicle-treated controls, or shGFP control cells treated with vemurafenib showed stable tumor growth. Conclusions: These findings suggest a potential link between BRAF^V600E and lipid metabolism regulation in PTC. BRAF^V600E downregulates ACC2 levels, which deregulates de novo lipid synthesis, FAO due to OCR, and ECAR rates. ShACC2 may contribute to vemurafenib resistance and increased tumor growth. ACC2 rescue may represent a novel molecular strategy for overcoming resistance to BRAF^V600E inhibitors in refractory PTC.

Fatty Acid Metabolism-Related lncRNAs Are Potential Biomarkers for Predicting the Overall Survival of Patients With Colorectal Cancer

Abnormal metabolism, including abnormal fatty acid metabolism, is an emerging hallmark of cancer. The current study sought to investigate the potential prognostic value of fatty acid metabolism-related long noncoding RNAs (lncRNAs) in colorectal cancer (CRC). To this end, we obtained the gene expression data and clinical data of patients with CRC from The Cancer Genome Atlas (TCGA) database. Through gene set variation analysis (GSVA), we found that the fatty acid metabolism pathway was related to the clinical stage and prognosis of patients with CRC. After screening differentially expressed RNAs, we constructed a fatty acid metabolism-related competing endogenous RNA (ceRNA) network based on the miRTarBase, miRDB, TargetScan, and StarBase databases. Next, eight fatty acid metabolism-related lncRNAs included in the ceRNA network were identified to build a prognostic signature with Cox and least absolute shrinkage and selection operator (LASSO) regression analyses, and a nomogram was established based on the lncRNA signature and clinical variables. The signature and nomogram were further validated by Kaplan–Meier survival analysis, Cox regression analysis, calibration plots, receiver operating characteristic (ROC) curves, decision curve analysis (DCA). Besides, the TCGA internal and the quantitative real-time polymerase chain reaction (qRT-PCR) external cohorts were applied to successfully validate the robustness of the signature and nomogram. Finally, in vitro assays showed that knockdown of prognostic lncRNA TSPEAR-AS2 decreased the triglyceride (TG) content and the expressions of fatty acid synthase (FASN) and acetyl-CoA carboxylase 1 (ACC1) in CRC cells, which indicated the important role of lncRNA TSPEAR-AS2 in modulating fatty acid metabolism of CRC. The result of Oil Red O staining showed that the lipid content in lncRNA TSPEAR-AS2 high expression group was higher than that in lncRNA TSPEAR-AS2 low expression group. Our study may provide helpful information for fatty acid metabolism targeting therapies in CRC.

Anticancer properties of the fatty acid synthase inhibitor TVB-3166 on oral squamous cell carcinoma cell lines

OBJECTIVE

Fatty acid synthase (FASN) is overexpressed in several human cancers, including oral squamous cell carcinoma (OSCC). TVB-3166 is a recently described FASN inhibitor with antitumor effects and potential clinical relevance. The objective of this study was to evaluate the effects of TVB-3166 on OSCC cell lines.

MATERIALS AND METHODS

The OSCC cell line SCC-9 modified to express ZsGreen (ZsG) (SCC-9 ZsG) and its in vivo selected metastatic derivative LN-1A were used to evaluate anticancer properties of TVB-3166. Cell viability was determined using MTT assays and proliferation determined by cell counting in a Neubauer chamber. Cell death and cell cycle progression were analyzed by Annexin V-PE/7-ADD-PerCP labeling and PI staining, respectively. Cell migration was assayed by scratch assays and cell adhesion using myogel. Production of FASN, p-AKT, CPT1-α, and epithelial-mesenchymal transition (EMT) markers were examined by Western blotting.

RESULTS

TVB-3166 significantly reduced cell viability and proliferation, promoted cell cycle arrest and apoptosis, and increased adhesion to myogel in both OSCC cell lines. Finally, the drug reduced SCC-9 ZsG migration.

CONCLUSION

Our results demonstrated that TVB-3166 has anticancer effects on both SCC-9 ZsG and its metastatic version LN-1A, which are worthy of investigation in preclinical models for OSCC.

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.

Metformin Inhibits Tumor Metastasis through Suppressing Hsp90α Secretion in an AMPKα1-PKCγ Dependent Manner

Metformin has been documented in epidemiological studies to mitigate tumor progression. Previous reports show that metformin inhibits tumor migration in several cell lines, such as MCF-7 and H1299, but the mechanisms whereby metformin exerts its inhibitory effects on tumor metastasis remain largely unknown. The secreted proteins in cancer cell-derived secretome have been reported to play important roles in tumor metastasis, but whether metformin has an effect on tumor secretome remains unclear. Here we show that metformin inhibits tumor metastasis by suppressing Hsp90α (heat shock protein 90α) secretion. Mass spectrometry (MS) analysis and functional validation identify that eHsp90α (extracellular Hsp90α) is one of the most important secreted proteins for metformin to inhibit tumor cells migration, invasion and metastasis both in vitro and in vivo. Moreover, we find that metformin inhibits Hsp90α secretion in an AMPKα1 dependent manner. Our data elucidate that AMPKα1 (AMP-activated protein kinase α1) decreases the phosphorylation level of Hsp90α by inhibiting the kinase activity of PKCγ (protein kinase Cγ), which suppresses the membrane translocation and secretion of Hsp90α. Collectively, our results illuminate that metformin inhibits tumor metastasis by suppressing Hsp90α secretion in an AMPKα1 dependent manner.

The identification and pharmacological evaluation of potent, selective and orally available ACC1 inhibitor

In our effort to explore the potential of ACC1-selective inhibitor as in vivo probe molecule, a series of 1,3-benzoxazole derivatives was synthesized. Previously, we reported a series of novel bicyclic and monocyclic ACC1-selective inhibitors. Among them, compound 1a exhibited highly potent cellular activity (acetate uptake IC₅₀ = 0.76 nM) as well as promising in vivo PD efficacy. However, compound 1a caused severe body weight reduction in repeated dose administration in the mouse model. Since 1a showed potent inhibitory activity against mouse ACC1 as well as strong inhibition of mouse ACC2, we further examined a series of 1a analogues in order to reduce undesirable body weight change. The replacement of acetamide moiety with ureido moiety dramatically improved selectivity of mouse ACC1 against ACC2. In addition, analogue 1b displayed favorable bioavailability in mouse cassette dosing PK study, hence in vivo PD studies were also carried out. Oral administration of 1b significantly reduced the concentration of malonyl-CoA in HCT-116 xenograft tumors at doses of more than 30 mg/kg. Furthermore, compound 1b showed significant antitumor efficacy in 786-O xenograft mice at an oral dose of 30 mg/kg (T/C = 0.5%). Accordingly, our novel potent ACC1-selective inhibitor represents a set of useful orally-available research tools, as well as potential therapeutic agents particularly in terms of new cancer therapies.

Acetyl-CoA carboxylase (ACC) as a therapeutic target for metabolic syndrome and recent developments in ACC1/2 inhibitors

Introduction: Acetyl-CoA Carboxylase (ACC) is an essential rate-limiting enzyme in fatty acid metabolism. For many years, ACC inhibitors have gained great attention for developing therapeutics for various human diseases including microbial infections, metabolic syndrome, obesity, diabetes, and cancer. Areas covered: We present a comprehensive review and update of ACC inhibitors. We look at the current advance of ACC inhibitors in clinical studies and the implications in drug discovery. We searched ScienceDirect ( https://www.sciencedirect.com/ ), ACS ( https://pubs.acs.org/ ), Wiley ( https://onlinelibrary.wiley.com/ ), NCBI ( https://www.ncbi.nlm.nih.gov/ ) and World Health Organization ( https://www.who.int/ ). The keywords used were Acetyl-CoA Carboxylase, lipid, inhibitors and metabolic syndrome. All documents were published before June 2019. Expert opinion: The key regulatory role of ACC in fatty acid synthesis and oxidation pathways makes it an attractive target for various metabolic diseases. In particular, the combination of ACC inhibitors with other drugs is a new strategy for the treatment of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Expanding the clinical indications for ACC inhibitors will be one of the hot directions in the future. It is also worth looking forward to exploring safe and efficient inhibitors that act on the BC domain of ACC.

Photoacoustic imaging as a tool to probe the tumour microenvironment

The tumour microenvironment (TME) is a complex cellular ecosystem subjected to chemical and physical signals that play a role in shaping tumour heterogeneity, invasion and metastasis. Studying the roles of the TME in cancer progression would strongly benefit from non-invasive visualisation of the tumour as a whole organ in vivo, both preclinically in mouse models of the disease, as well as in patient tumours. Although imaging techniques exist that can probe different facets of the TME, they face several limitations, including limited spatial resolution, extended scan times and poor specificity from confounding signals. Photoacoustic imaging (PAI) is an emerging modality, currently in clinical trials, that has the potential to overcome these limitations. Here, we review the biological properties of the TME and potential of existing imaging methods that have been developed to analyse these properties non-invasively. We then introduce PAI and explore the preclinical and clinical evidence that support its use in probing multiple features of the TME simultaneously, including blood vessel architecture, blood oxygenation, acidity, extracellular matrix deposition, lipid concentration and immune cell infiltration. Finally, we highlight the future prospects and outstanding challenges in the application of PAI as a tool in cancer research and as part of a clinical oncologist's arsenal.

Summary: This Review details the potential of photoacoustic imaging to visualise features of the tumour microenvironment such as blood vessels, hypoxia, fibrosis and immune infiltrate to provide unprecedented insight into tumour biology.

Design and synthesis of a novel 1H-pyrrolo[3,2-b]pyridine-3-carboxamide derivative as an orally available ACC1 inhibitor

We initiated our structure-activity relationship (SAR) studies for novel ACC1 inhibitors from 1a as a lead compound. Our initial SAR studies of 1H-Pyrrolo[3,2-b]pyridine-3-carboxamide scaffold revealed the participation of HBD and HBA for ACC1 inhibitory potency and identified 1-methyl-1H-pyrrolo[3,2-b]pyridine-3-carboxamide derivative 1c as a potent ACC1 inhibitor. Although compound 1c had physicochemical and pharmacokinetic (PK) issues, we investigated the 1H-pyrrolo[3,2-b]pyridine core scaffold to address these issues. Accordingly, this led us to discover a novel 1-isopropyl-1H-pyrrolo[3,2-b]pyridine-3-carboxamide derivative 1k as a promising ACC1 inhibitor, which showed potent ACC1 inhibition as well as sufficient cellular potency. Since compound 1k displayed favorable bioavailability in mouse cassette dosing PK study, we conducted in vivo Pharmacodynamics (PD) studies of this compound. Oral administration of 1k significantly reduced the concentration of malonyl-CoA in HCT-116 xenograft tumors at a dose of 100 mg/kg. Accordingly, our novel series of potent ACC1 inhibitors represent useful orally-available research tools, as well as potential therapeutic agents for cancer and fatty acid related diseases.

ACC1 is overexpressed in liver cancers and contributes to the proliferation of human hepatoma Hep G2 cells and the rat liver cell line BRL 3A

Acetyl-coenzyme A carboxylase 1 (ACC1) serves a major role in fatty acid synthesis. Previous reports have indicated that ACC1 is a promising drug target for treating human diseases, particularly cancers and metabolic diseases; however, the role of ACC1 in liver cancer and normal liver function remains unknown. In the present study, bioinformatics analysis indicated that ACC1 is overexpressed in liver cancer. Kaplan-Meier survival analysis revealed that the expression levels of ACC1 are highly associated with the prognosis of patients with liver cancer. To determine the role of ACC1 in cancer and normal liver cells, ACC1 expression was downregulated in human hepatoma Hep G2 cells and the rat liver cell line BRL 3A using RNA interference technology, which demonstrated that silencing of ACC1 significantly suppressed the cell viability in the two cell lines. Additionally, ACC1 knockdown decreased the mRNA and protein expression levels of the cell proliferation-associated genes MYCN, JUN, cyclin D1 (CCND1) and cyclin A2 (CCNA2) in BRL 3A. Furthermore, the number of cells in division phase (G2/M) was significantly reduced in the interference group, as detected by flow cytometry. Thus, ACC1 may bind and activate CCNA2, CCND1, MYCN and JUN to promote BRL 3A proliferation. In summary, the results of present study indicated that overexpression of ACC1 is significantly associated with the survival time of patients with liver cancer, and may provide insight into the association between ACC1 and cell proliferation in BRL 3A cells.

Aging, Metabolism, and Cancer Development: from Peto's Paradox to the Warburg Effect

Medical advances made over the last century have increased our lifespan, but age-related diseases are a fundamental health burden worldwide. Aging is therefore a major risk factor for cardiovascular disease, cancer, diabetes, obesity, and neurodegenerative diseases, all increasing in prevalence. However, huge inter-individual variations in aging and disease risk exist, which cannot be explained by chronological age, but rather physiological age decline initiated even at young age due to lifestyle. At the heart of this lies the metabolic system and how this is regulated in each individual. Metabolic turnover of food to energy leads to accumulation of co-factors, byproducts, and certain proteins, which all influence gene expression through epigenetic regulation. How these epigenetic markers accumulate over time is now being investigated as the possible link between aging and many diseases, such as cancer. The relationship between metabolism and cancer was described as early as the late 1950s by Dr. Otto Warburg, before the identification of DNA and much earlier than our knowledge of epigenetics. However, when the stepwise gene mutation theory of cancer was presented, Warburg's theories garnered little attention. Only in the last decade, with epigenetic discoveries, have Warburg's data on the metabolic shift in cancers been brought back to life. The stepwise gene mutation theory fails to explain why large animals with more cells, do not have a greater cancer incidence than humans, known as Peto's paradox. The resurgence of research into the Warburg effect has given us insight to what may explain Peto's paradox. In this review, we discuss these connections and how age-related changes in metabolism are tightly linked to cancer development, which is further affected by lifestyle choices modulating the risk of aging and cancer through epigenetic control.

(-)-UB006: A new fatty acid synthase inhibitor and cytotoxic agent without anorexic side effects

C75 is a synthetic anticancer drug that inhibits fatty acid synthase (FAS) and shows a potent anorexigenic side effect. In order to find new cytotoxic compounds that do not impact food intake, we synthesized a new family of C75 derivatives. The most promising anticancer compound among them was UB006 ((4SR,5SR)-4-(hydroxymethyl)-3-methylene-5-octyldihydrofuran-2(3H)-one). The effects of this compound on cytotoxicity, food intake and body weight were studied in UB006 racemic mixture and in both its enantiomers separately. The results showed that both enantiomers inhibit FAS activity and have potent cytotoxic effects in several tumour cell lines, such as the ovarian cell cancer line OVCAR-3. The (-)-UB006 enantiomer's cytotoxic effect on OVCAR-3 was 40-fold higher than that of racemic C75, and 2- and 38-fold higher than that of the racemic mixture and its opposite enantiomer, respectively. This cytotoxic effect on the OVCAR-3 cell line involves mechanisms that reduce mitochondrial respiratory capacity and ATP production, DDIT4/REDD1 upregulation, mTOR activity inhibition, and caspase-3 activation, resulting in apoptosis. In addition, central and peripheral administration of (+)-UB006 or (-)-UB006 into rats and mice did not affect food intake or body weight. Altogether, our data support the discovery of a new potential anticancer compound (-)-UB006 that has no anorexigenic side effects.

Inhibitory effect of emodin on fatty acid synthase, colon cancer proliferation and apoptosis

Fatty acid synthase (FASN) is a key anabolic enzyme for de novo fatty acid synthesis, which is important in the development of colon carcinoma. The high expression of FASN is considered a promising molecular target for colon cancer therapy. Emodin, a naturally occurring anthraquinone, exhibits an anticancer effect in various types of human cancer, including colon cancer; however, the molecular mechanisms remain to be fully elucidated. Cell viability was evaluated using a Cell Counting Kit‑8 assay. The apoptosis rate of cells was quantified via flow cytometry following Annexin V/propidium iodide staining. FASN activity was measured by monitoring oxidation of nicotinamide adenine dinucleotide phosphate at a wavelength of 340 nm, and intracellular free fatty acid levels were detected using a Free Fatty Acid Quantification kit. Western blot analysis and reverse transcription‑polymerase chain reaction were used to detect target gene and protein expression. The present study was performed to investigate whether the gene expression of FASN and its enzymatic activity are regulated by emodin in a human colon cancer cell line. Emodin markedly inhibited the proliferation of HCT116 cells and a higher protein level of FASN was expressed, compared with that in SW480, SNU-C2A or SNU‑C5 cells. Emodin significantly downregulated the protein expression of FASN in HCT116 cells, which was caused by protein degradation due to elevated protein ubiquitination. Emodin also inhibited intracellular FASN enzymatic activity and reduced the levels of intracellular free fatty acids. Emodin enhanced antiproliferation and apoptosis in a dose‑ and time‑dependent manner. The combined treatment of emodin and cerulenin, a commercial FASN inhibitor, had an additive effect on these activities. Palmitate, the final product of the FASN reaction, rescued emodin‑induced viability and apoptosis. In addition, emodin altered FASN‑involved signaling pathways, including phosphatidylinositol 3-kinase/Akt and mitogen‑activated protein kinases/extracellular signal-regulated kinases 1/2. These results suggested that emodin-regulated cell growth and apoptosis were mediated by inhibiting FASN and provide a molecular basis for colon cancer therapy.

Inhibition of Acetyl-CoA Carboxylase 1 (ACC1) and 2 (ACC2) Reduces Proliferation and De Novo Lipogenesis of EGFRvIII Human Glioblastoma Cells

Tumor cell proliferation and migration processes are regulated by multiple metabolic pathways including glycolysis and de novo lipogenesis. Since acetyl-CoA carboxylase (ACC) is at the junction of lipids synthesis and oxidative metabolic pathways, we investigated whether use of a dual ACC inhibitor would provide a potential therapy against certain lipogenic cancers. The impact of dual ACC1/ACC2 inhibition was investigated using a dual ACC1/ACC2 inhibitor as well as dual siRNA knock down on the cellular viability and metabolism of two glioblastoma multiform cancer cell lines, U87 and a more aggressive form, U87 EGFRvIII. We first demonstrated that while ACCi inhibited DNL in both cell lines, ACCi preferentially blunted the U87 EGFRvIII cellular proliferation capacity. Metabolically, chronic treatment with ACCi significantly upregulated U87 EGFRvIII cellular respiration and extracellular acidification rate, a marker of glycolytic activity, but impaired mitochondrial health by reducing maximal respiration and decreasing mitochondrial ATP production efficiency. Moreover, ACCi treatment altered the cellular lipids content and increased apoptotic caspase activity in U87 EGFRvIII cells. Collectively these data indicate that ACC inhibition, by reducing DNL and increasing cellular metabolic rate, may have therapeutic utility for the suppression of lipogenic tumor growth and warrants further investigation.

Pregnane X Receptor and Cancer: Context-Specificity is Key

Pregnane X receptor (PXR) is an adopted orphan nuclear receptor that is activated by a wide-range of endobiotics and xenobiotics, including chemotherapy drugs. PXR plays a major role in the metabolism and clearance of xenobiotics and endobiotics in liver and intestine via induction of drug-metabolizing enzymes and drug-transporting proteins. However, PXR is expressed in several cancer tissues and the accumulating evidence strongly points to the differential role of PXR in cancer growth and progression as well as in chemotherapy outcome. In cancer cells, besides regulating the gene expression of enzymes and proteins involved in drug metabolism and transport, PXR also regulates other genes involved in proliferation, metastasis, apoptosis, anti-apoptosis, inflammation, and oxidative stress. In this review, we focus on the differential role of PXR in a variety of cancers, including prostate, breast, ovarian, endometrial, and colon. We also discuss the future directions to further understand the differential role of PXR in cancer, and conclude with the need to identify novel selective PXR modulators to target PXR in PXR-expressing cancers.

MicroRNAs and oncogenic transcriptional regulatory networks controlling metabolic reprogramming in cancers

Altered cellular metabolism is a fundamental adaptation of cancer during rapid proliferation as a result of growth factor overstimulation. We review different pathways involving metabolic alterations in cancers including aerobic glycolysis, pentose phosphate pathway, de novo fatty acid synthesis, and serine and glycine metabolism. Although oncoproteins, c-MYC, HIF1α and p53 are the major drivers of this metabolic reprogramming, post-transcriptional regulation by microRNAs (miR) also plays an important role in finely adjusting the requirement of the key metabolic enzymes underlying this metabolic reprogramming. We also combine the literature data on the miRNAs that potentially regulate 40 metabolic enzymes responsible for metabolic reprogramming in cancers, with additional miRs from computational prediction. Our analyses show that: (1) a metabolic enzyme is frequently regulated by multiple miRs, (2) confidence scores from prediction algorithms might be useful to help narrow down functional miR-mRNA interaction, which might be worth further experimental validation. By combining known and predicted interactions of oncogenic transcription factors (TFs) (c-MYC, HIF1α and p53), sterol regulatory element binding protein 1 (SREBP1), 40 metabolic enzymes, and regulatory miRs we have established one of the first reference maps for miRs and oncogenic TFs that regulate metabolic reprogramming in cancers. The combined network shows that glycolytic enzymes are linked to miRs via p53, c-MYC, HIF1α, whereas the genes in serine, glycine and one carbon metabolism are regulated via the c-MYC, as well as other regulatory organization that cannot be observed by investigating individual miRs, TFs, and target genes.

Adiponectin and colorectal cancer

Colorectal cancer is an obesity-related malignancy. Adiponectin is an adipokine produced exclusively by adipose tissue, and its concentration in the serum is reduced in obesity. A low serum level of adiponectin is associated with an increased risk of various types of malignancies including colorectal cancer. These facts suggest that the epidemiological link between obesity and cancer may have a significant association with adiponectin. Although numerous studies of colorectal cancer have been reported, the results are conflicting about the anti-cancer effect of adiponectin, and how adiponectin affects carcinogenesis or cancer development remains controversial. Because adiponectin has multiple systemic effects and exists as a high serum concentration protein, the main role of adiponectin should be regulation of homeostasis, and it would not likely act as an anti-cancerous hormone. However, as epidemiological evidence shows, a low adiponectin level may be a basic risk factor for colorectal cancer. We speculate that when the colonic epithelium is stimulated or damaged by another carcinogen under the condition of a low adiponectin level, carcinogenesis is promoted and cancer development is facilitated. In this report, we summarize recent findings of the correlation between adiponectin and colorectal cancer and investigate the effect of adiponectin on colorectal cancer.

ACLY and ACC1 Regulate Hypoxia-Induced Apoptosis by Modulating ETV4 via α-ketoglutarate

In order to propagate a solid tumor, cancer cells must adapt to and survive under various tumor microenvironment (TME) stresses, such as hypoxia or lactic acidosis. To systematically identify genes that modulate cancer cell survival under stresses, we performed genome-wide shRNA screens under hypoxia or lactic acidosis. We discovered that genetic depletion of acetyl-CoA carboxylase (ACACA or ACC1) or ATP citrate lyase (ACLY) protected cancer cells from hypoxia-induced apoptosis. Additionally, the loss of ACLY or ACC1 reduced levels and activities of the oncogenic transcription factor ETV4. Silencing ETV4 also protected cells from hypoxia-induced apoptosis and led to remarkably similar transcriptional responses as with silenced ACLY or ACC1, including an anti-apoptotic program. Metabolomic analysis found that while α-ketoglutarate levels decrease under hypoxia in control cells, α-ketoglutarate is paradoxically increased under hypoxia when ACC1 or ACLY are depleted. Supplementation with α-ketoglutarate rescued the hypoxia-induced apoptosis and recapitulated the decreased expression and activity of ETV4, likely via an epigenetic mechanism. Therefore, ACC1 and ACLY regulate the levels of ETV4 under hypoxia via increased α-ketoglutarate. These results reveal that the ACC1/ACLY-α-ketoglutarate-ETV4 axis is a novel means by which metabolic states regulate transcriptional output for life vs. death decisions under hypoxia. Since many lipogenic inhibitors are under investigation as cancer therapeutics, our findings suggest that the use of these inhibitors will need to be carefully considered with respect to oncogenic drivers, tumor hypoxia, progression and dormancy. More broadly, our screen provides a framework for studying additional tumor cell stress-adaption mechanisms in the future.

During the development of most solid tumors, there are characteristic physiological differences in the tumor that result from tumor cells outgrowing their local blood supply. Two of these physiological differences, or “stresses,” that occur in the tumor are low oxygen levels (hypoxia) and an accumulation of lactic acidic (lactic acidosis). Cancer cells experiencing hypoxia and lactic acidosis tend to be more resistant to chemo- and radio-therapy and metastasize more readily. Therefore, it is important to understand how tumor cells adapt to and survive these stresses. We used a large scale screening experiment in order to find which genes and proteins are involved in tumor cell adaptation and survival under hypoxia or lactic acidosis. We found that inhibiting either of two genes involved in lipid synthesis allowed tumor cells to survive hypoxia. This occurred because silencing these genes led to an increase in the metabolite α-ketoglutarate, which repressed a transcription factor that contributed to cell death under hypoxia. This research specifically advances our understanding of how tumor cells survive hypoxia and lactic acidosis and more broadly enhances our understanding of the cellular biology of solid tumors.

A Cellular Assay for Inhibitors of the Fatty Acid Biosynthetic Pathway Using Scintillating Microplates

A simplified method for monitoring the incorporation of radiolabeled acetate into lipids in a cellular system is described. The assay eliminates the commonly employed labor-intensive organic extraction step by plating the cells in 96-well tissue culture-treated ScintiPlates(®) that enable direct measurement of radiolabeled cell membrane-embedded lipids. Since the scintillant is entrenched in the plates, radioactivity in close proximity to the scintillant is measured without the need for liquid scintillation cocktail. The utility of this method for evaluating inhibitors of the de novo fatty acid synthetic pathway is demonstrated here with fatty acid synthase (FASN). Due to the upregulation of FASN activity in many tumor types, development of inhibitors to block the FASN activity in cells shows promise as an attractive and tractable approach for therapeutic intervention.

Loss of fatty acid synthase suppresses the malignant phenotype of colorectal cancer cells by down-regulating energy metabolism and mTOR signaling pathway

PURPOSE

Altered cellular metabolism has received increased attention as an important hallmark of cancer. Activation of FASN has been found to be involved in many human tumors. Despite extensive research in FASN function on cancer, the underlying mechanism is not entirely understood yet.

METHODS

Cerulenin was used to suppress the FASN expression in human colorectal cancer cell lines (HT29 and LoVo). Expression of PI3K, Akt, p-Akt, mTOR, p-mTOR, FASN, and AZGP1 was measured using western blotting and qPCR. ATP and lactic acid were assessed to investigate the activation of energy metabolism. Cell cytotoxicity assay was studied by cell counting kit-8 assay. The capacity of cell proliferation and migration was investigated by clonogenic and invasion assay. Analysis of apoptosis and the cell cycle was detected by flow cytometry.

RESULTS

We found that the expression of FASN was down-regulated, while the expression of PI3K, p-Akt, p-mTOR, and AZGP1 was down-regulated in HT29 and LoVo cells treated with FASN inhibitor. Proliferation was reduced in FASN inhibitor-treated cells, which is consistent with an increased apoptosis rate. Furthermore, the migration of FASN inhibitor-treated cells was decreased and the content of ATP and lactic acid was also dropped.

CONCLUSION

These findings suggest that inhibited FASN suppresses the malignant phenotype of colorectal cancer cells by down-regulating energy metabolism and mTOR signaling pathway. The results have paved the way to understand the relations of FASN, mTOR signaling pathway, and energy metabolism in colorectal cancer cells.

Remodeling of phospholipid composition in colon cancer cells by 1α,25(OH)2D3 and its analogs

Alterations in cellular phospholipid composition are emerging as important traits in the development and progression of cancer. In this study we investigated the effects of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] and two of its more antiproliferative analogs on the cellular phospholipid composition of various human colon cancer cell lines. Treatment of Caco-2, SW1417 and SW480-ADH cells with 3×10(-8)M 1,25(OH)2D3, CD578 or WU515 evoked significant changes in phospholipid composition, with the analogs being more potent than the natural compound. Observed effects included changes in acyl chain elongation and acyl chain saturation, and were substantially different in the various cell lines. Consistent with the alterations in phospholipid profiles, 1,25(OH)2D3 and its analogs provoked changes in several lipogenic enzymes such as fatty acid synthase (FASN), acetyl-CoA carboxylase (ACACA) and fatty acid elongases (ELOVLs). These effects were also cell line dependent. Taken together these findings indicate that 1,25(OH)2D3 and its analogs have divergent effects on the phospholipid composition of different colon cancer cell lines and warrant further investigation of the effect of 1,25(OH)2D3 and its analogs on lipid metabolism in various subtypes of primary human colon cancers.

Acetyl-CoA synthetase 2 promotes acetate utilization and maintains cancer cell growth under metabolic stress

A functional genomics study revealed that the activity of acetyl-CoA synthetase 2 (ACSS2) contributes to cancer cell growth under low-oxygen and lipid-depleted conditions. Comparative metabolomics and lipidomics demonstrated that acetate is used as a nutritional source by cancer cells in an ACSS2-dependent manner, and supplied a significant fraction of the carbon within the fatty acid and phospholipid pools. ACSS2 expression is upregulated under metabolically stressed conditions and ACSS2 silencing reduced the growth of tumor xenografts. ACSS2 exhibits copy-number gain in human breast tumors, and ACSS2 expression correlates with disease progression. These results signify a critical role for acetate consumption in the production of lipid biomass within the harsh tumor microenvironment.

Hooked on fat: the role of lipid synthesis in cancer metabolism and tumour development

An increased rate of lipid synthesis in cancerous tissues has long been recognised as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids to cellular transformation, tumour development and tumour progression, as well as their potential role in facilitating the spread of cancerous cells to secondary sites, are not yet fully understood. In this article, we review the recent findings that support the importance of lipid synthesis and metabolism in tumorigenesis. Specifically, we explore the role of aberrant lipid biosynthesis in cancer cell migration and invasion, and in the induction of tumour angiogenesis. These processes are crucial for the dissemination of tumour cells and formation of metastases, which constitute the main cause of cancer mortality.

Lipogenesis in cancer progression (review)

In normal tissues, energy-providing lipids come principally from circulating lipids. However, in growing tumors, energy supply is mainly provided by lipids coming from de novo synthesis. It is not surprising to see elevated expression of several lipogenic genes in tumors from different origins. The role of lipogenic genes in the establishment of the primary tumor has been clearly established. A large number of studies demonstrate a role of fatty acid synthase in the activation of cell cycle and inhibition of apoptosis in tumor cells. Other lipogenic genes such as the acetyl CoA carboxylase (ACC) and the stearoyl CoA desaturase 1 (SCD1) are highly expressed in primary tumors and also appear to play a role in their development. However, the role of lipogenesis in the metastatic process is less clear. In the present review, we aim to present the most recent evidences for the key role of lipogenic enzymes in the metastatic process and in epithelial to mesenchymal transition.

Cancer cell-associated fatty acid synthase activates endothelial cells and promotes angiogenesis in colorectal cancer

Upregulation of fatty acid synthase (FASN), a key enzyme of de novo lipogenesis, is associated with metastasis in colorectal cancer (CRC). However, the mechanisms of regulation are unknown. Since angiogenesis is crucial for metastasis, we investigated the role of FASN in the neovascularization of CRC. The effect of FASN on tumor vasculature was studied in orthotopic CRCs, the chick embryo chorioallantoic membrane (CAM) and Matrigel plug models using immunohistochemistry, immunofluorescent staining and confocal microscopy. Cell secretion was evaluated by ELISA and antibody arrays. Proliferation, migration and tubulogenesis of endothelial cells (ECs) were assessed in CRC-EC coculture models. In this study, we found that stable knockdown of FASN decreased microvessel density in HT29 and HCT116 orthotopic CRCs and resulted in 'normalization' of tumor vasculature in both orthotopic and CAM models. Furthermore, FASN regulated secretion of pro- and antiangiogenic factors, including vascular endothelial growth factor-A (VEGF-A). Mechanisms associated with the antiangiogenic activity noted with knockdown of FASN included: downregulation of VEGF(189), upregulation of antiangiogenic isoform VEGF(165b) and a decrease in expression and activity of matrix metalloproteinase-9. Furthermore, conditioned medium from FASN knockdown CRC cells inhibited activation of vascular endothelial growth factor receptor-2 and its downstream signaling and decreased proliferation, migration and tubulogenesis of ECs as compared with control medium. Together, these results suggest that cancer cell-associated FASN regulates tumor vasculature through alteration of the profile of secreted angiogenic factors and regulation of their bioavailability. Inhibition of FASN upstream of VEGF-A and other angiogenic pathways can be a novel therapeutic strategy to prevent or inhibit metastasis in CRC.

Multifaceted roles of adiponectin in cancer

Obesity is linked to increased cancer risk. Pathological expansion of adipose tissue impacts adipocyte function and secretion of hormonal factors regulating tissue homeostasis and metabolism. Adiponectin is an adipocyte-secreted, circulating hormone with pleiotropic functions in lipid and glucose metabolism, and beneficial roles in cardiovascular functions and inflammation. In obesity, decreased Adiponectin plasma levels correlate with tumor development and progression. The association of Adiponectin with potential tumor-limiting functions has raised significant interest in exploring this adipokine as a target for cancer-diagnostic and therapeutic applications. Recent studies, however, also implicate Adiponectin in supporting malignancy. This review highlights the evidence that links Adiponectin signaling to either cancer-protective or cancer-supporting functions. In this context, we discuss Adiponectin interactions with its receptors and associated signaling pathways. Despite significant advances in understanding Adiponectin functions and signaling mechanisms, its role in cancer remains multifaceted and subject to controversy.

Liver fatty acid-binding protein (L-Fabp) modifies intestinal fatty acid composition and adenoma formation in ApcMin/+ mice

Evidence suggests a relationship between dietary fat intake, obesity, and colorectal cancer, implying a role for fatty acid metabolism in intestinal tumorigenesis that is incompletely understood. Liver fatty acid-binding protein (L-Fabp), a dominant intestinal fatty acid-binding protein, regulates intestinal fatty acid trafficking and metabolism, and L-Fabp deletion attenuates diet-induced obesity. Here, we examined whether changes in intestinal fatty acid metabolism following L-Fabp deletion modify adenoma development in Apc(Min)(/+) mice. Compound L-Fabp(-/-)Apc(Min)(/+) mice were generated and fed a 10% fat diet balanced equally between saturated, monounsaturated, and polyunsaturated fat. L-Fabp(-/-)Apc(Min)(/+) mice displayed significant reductions in adenoma number and total polyp area compared with Apc(Min)(/+)controls, reflecting a significant shift in distribution toward smaller polyps. Adenomas from L-Fabp(-/-)Apc(Min)(/+) mice exhibited reductions in cellular proliferation, high-grade dysplasia, and nuclear β-catenin translocation. Intestinal fatty acid content was increased in L-Fabp(-/-)Apc(Min)(/+) mice, and lipidomic profiling of intestinal mucosa revealed significant shifts to polyunsaturated fatty acid species with reduced saturated fatty acid species. L-Fabp(-/-)Apc(Min)(/+) mice also showed corresponding changes in mRNA expression of enzymes involved in fatty acid elongation and desaturation. Furthermore, adenomas from L-Fabp(-/-)Apc(Min)(/+) mice displayed significant reductions in mRNA abundance of nuclear hormone receptors involved in cellular proliferation and in enzymes involved in lipogenesis. These findings collectively implicate L-Fabp as an important genetic modifier of intestinal tumorigenesis, and identify fatty acid trafficking and metabolic compartmentalization as an important pathway linking dietary fat intake, obesity, and intestinal tumor formation.

Targeting the latest hallmark of cancer: another attempt at 'magic bullet' drugs targeting cancers' metabolic phenotype

The metabolism of tumors is remarkably different from the metabolism of corresponding normal cells and tissues. Metabolic alterations are initiated by oncogenes and are required for malignant transformation, allowing cancer cells to resist some cell death signals while producing energy and fulfilling their biosynthetic needs with limiting resources. The distinct metabolic phenotype of cancers provides an interesting avenue for treatment, potentially with minimal side effects. As many cancers show similar metabolic characteristics, drugs targeting the cancer metabolic phenotype are, perhaps optimistically, expected to be 'magic bullet' treatments. Over the last few years there have been a number of potential drugs developed to specifically target cancer metabolism. Several of these drugs are currently in clinical and preclinical trials. This review outlines examples of drugs developed for different targets of significance to cancer metabolism, with a focus on small molecule leads, chemical biology and clinical results for these drugs.

Natural compounds as regulators of the cancer cell metabolism

Even though altered metabolism is an "old" physiological mechanism, only recently its targeting became a therapeutically interesting strategy and by now it is considered an emerging hallmark of cancer. Nevertheless, a very poor number of compounds are under investigation as potential modulators of cell metabolism. Candidate agents should display selectivity of action towards cancer cells without side effects. This ideal favorable profile would perfectly overlap the requisites of new anticancer therapies and chemopreventive strategies as well. Nature represents a still largely unexplored source of bioactive molecules with a therapeutic potential. Many of these compounds have already been characterized for their multiple anticancer activities. Many of them are absorbed with the diet and therefore possess a known profile in terms of tolerability and bioavailability compared to newly synthetized chemical compounds. The discovery of important cross-talks between mediators of the most therapeutically targeted aberrancies in cancer (i.e., cell proliferation, survival, and migration) and the metabolic machinery allows to predict the possibility that many anticancer activities ascribed to a number of natural compounds may be due, in part, to their ability of modulating metabolic pathways. In this review, we attempt an overview of what is currently known about the potential of natural compounds as modulators of cancer cell metabolism.

The anticancer effect of oridonin is mediated by fatty acid synthase suppression in human colorectal cancer cells

BACKGROUND

Fatty acid synthase (FAS) inhibitors could be a therapeutic target in cancer treatment. However, only a few FAS inhibitors showing clinical potential have been reported. Oridonin is a diterpenoid isolated from Rabdosia rubescens. Although it has antiproliferative activity in cancers, little was known about its anticancer effect on colorectal cancer. In this regard, we aimed to investigate if oridonin could be a novel FAS inhibitor and its anticancer mechanism in human colorectal cancer cells.

METHODS

Two human colorectal cancer cell lines SW480 and SW620 were used as models for this study.

RESULTS

We demonstrated that oridonin reduced viability and induced apoptosis in colorectal cancer cells. Knockdown of the expression of FAS in colorectal cancer cells by siRNA induced apoptosis. This led us to examine whether oridonin-induced apoptosis was mediated by FAS suppression in these cells. We found that oridonin effectively inhibited FAS and SREBP1 mRNA and protein expression in human colorectal cancer cells. In a transient reporter assay, oridonin also reduced transcriptional activity of the FAS promoter region containing the SREBP1 binding site. The FAS inhibition was paralleled by reduction in cellular palmitate and stearic acid. Upregulation of SREBP1 and FAS expression by insulin rescued these cells from oridonin-induced apoptosis.

CONCLUSION

These results not only provide a novel molecular mechanism for the anticancer effect of oridonin in colorectal cancer, but also suggest oridonin could be a novel FAS inhibitor in cancer treatment. These results strengthen the scientific basis for the therapeutic use of oridonin in colorectal cancer.

G protein-coupled estrogen receptor mediates the up-regulation of fatty acid synthase induced by 17β-estradiol in cancer cells and cancer-associated fibroblasts

Activation of lipid metabolism is an early event in carcinogenesis and a central hallmark of many tumors. Fatty acid synthase (FASN) is a key lipogenic enzyme catalyzing the terminal steps in the de novo biogenesis of fatty acids. In cancer cells, FASN may act as a metabolic oncogene, given that it confers growth and survival advantages to these cells, whereas its inhibition effectively and selectively kills tumor cells. Hormones such as estrogens and growth factors contribute to the transcriptional regulation of FASN expression also through the activation of downstream signaling and a cross-talk among diverse transduction pathways. In this study, we demonstrate for the first time that 17β-estradiol (E2) and the selective GPER ligand G-1 regulate FASN expression and activity through the GPER-mediated signaling, which involved the EGF receptor/ERK/c-Fos/AP1 transduction pathway, as ascertained by using specific pharmacological inhibitors, performing gene-silencing experiments and ChIP assays in breast SkBr3, colorectal LoVo, hepatocarcinoma HepG2 cancer cells, and breast cancer-associated fibroblasts. In addition, the proliferative effects induced by E2 and G-1 in these cells involved FASN as the inhibitor of its activity, named cerulenin, abolished the growth response to both ligands. Our data suggest that GPER may be included among the transduction mediators involved by estrogens in regulating FASN expression and activity in cancer cells and cancer-associated fibroblasts that strongly contribute to cancer progression.

Cytosolic malic enzyme 1 (ME1) mediates high fat diet-induced adiposity, endocrine profile, and gastrointestinal tract proliferation-associated biomarkers in male mice

BACKGROUND

Obesity and associated hormonal disturbances are risk factors for colon cancer. Cytosolic Malic Enzyme (ME1) generates NADPH used for lipogenesis in gastrointestinal (GI), liver and adipose tissues. We have reported that inclusion of soy protein isolate (SPI) in the diet lowered body fat content and colon tumor incidence of rats fed AIN-93G diet, while others have demonstrated SPI inhibition of rat hepatic ME1 expression. The present study examined the individual and combined effects of dietary SPI and absence of ME1 on: 1) serum concentrations of hormones implicated in colon cancer development, 2) expression of lipogenic and proliferation-associated genes in the mouse colon and small intestine, and 3) liver and adipose expression of lipogenic and adipocytokine genes that may contribute to colon cancer predisposition.

METHODS

Weanling wild type (WT) and ME1 null (MOD-1) male mice were fed high-fat (HF), iso-caloric diets containing either casein (CAS) or SPI as sole protein source for 5 wks. Somatic growth, serum hormone and glucose levels, liver and adipose tissue weights, GI tissue parameters, and gene expression were evaluated.

RESULTS

The MOD-1 genotype and SPI-HF diet resulted in decreases in: body and retroperitoneal fat weights, serum insulin, serum leptin, leptin/adiponectin ratio, adipocyte size, colon mTOR and cyclin D1 mRNA abundance, and jejunum FASN mRNA abundance, when compared to WT mice fed CAS-HF. Regardless of diet, MOD-1 mice had reductions in liver weight, liver steatosis, and colon crypt depth, and increases in adipose tissue expression of IRS1 and IRS2, compared to WT mice. SPI-HF diet reduced ME1 gene expression only in retroperitoneal fat.

CONCLUSIONS

Data suggest that the pharmacological targeting of ME1 or the inclusion of soy protein in the diet may provide avenues to reduce obesity and its associated pro-tumorigenic endocrine environment and improve insulin sensitivity, potentially disrupting the obesity-colon cancer connection.

Pregnane xenobiotic receptor in cancer pathogenesis and therapeutic response

Pregnane xenobiotic receptor (PXR) is an orphan nuclear receptor that regulates the metabolism of endobiotics and xenobiotics. PXR is promiscuous and unique in that it is activated by a diverse group of xenochemicals, including therapeutic anticancer drugs and naturally-occurring endocrine disruptors. PXR has been predominantly studied to understand its regulatory role in xenobiotic clearance in liver and intestine via induction of drug metabolizing enzymes and drug transporters. PXR, however, is widely expressed and has functional implications in other normal and malignant tissues, including breast, prostate, ovary, endometrium and bone. The differential expression of PXR and its target genes in cancer tissues has been suggested to determine the prognosis of chemotherapeutic outcome. In addition, the emerging evidence points to the implications of PXR in regulating apoptotic and antiapoptotic as well as growth factor signaling that promote tumor proliferation and metastasis. In this review, we highlight the recent progress made in understanding the role of PXR in cancer, discuss the future directions to further understand the mechanistic role of PXR in cancer, and conclude with the need to identify novel selective PXR modulators.

The music of lipids: how lipid composition orchestrates cellular behaviour

BACKGROUND

Lipids are best known for their fundamental role in forming biological membranes and as intracellular signalling molecules. Interactions between proteins and lipids are central to nearly every cellular process yet these crucial relationships often go overlooked. Changes or switches in the lipid profile of a cell drastically affects cellular metabolism and signal transduction. In relationship to cancer, upregulation of lipid metabolism is often observed during the early stages of neoplasia and is a recognised hallmark of many types of cancer.

METHODS

We performed a comprehensive review of the literature using PubMed regarding lipid metabolism in cancer and the importance of protein-lipid interactions in the function of mitochondria.

RESULTS

An increase in the basal rate of de novo lipogenesis generates a substantial rise in the saturated fatty acid content of cellular membranes. The ensuing alteration in the acyl chain profile of phospholipids has severe consequences on the function of organelles and membrane-bound proteins, and result in a host of pathologies including the cardiac disorder Barth Syndrome.

CONCLUSIONS

Although increased lipogenesis is specifically selected for during cellular transformation it remains unclear if it confers an advantage for survival or is a byproduct of more global changes in cellular metabolism. We discuss the current data regarding the potential of targeting the lipogenic switch as a cancer therapy. In addition, we describe the importance of mitochondrial phospholipid composition during a number mitochondria-driven events observed to have roles in cancer. We specifically highlight the function of cardiolipin in maintaining mitochondrial structure, regulating mitochondrial dynamics and bioenergetics as well as its contributions to mitophagy/autophagy and apoptosis.

Targeting cancer metabolism--aiming at a tumour's sweet-spot

Targeting cancer metabolism has emerged as a hot topic for drug discovery. Most cancers have a high demand for metabolic inputs (i.e. glucose/glutamine), which aid proliferation and survival. Interest in targeting cancer metabolism has been renewed in recent years with the discovery that many cancer-related (e.g. oncogenic and tumour suppressor) pathways have a profound effect on metabolism and that many tumours become dependent on specific metabolic processes. Considering the recent increase in our understanding of cancer metabolism and the increasing knowledge of the enzymes and pathways involved, the question arises: could metabolism be cancer's Achilles heel? During recent years, interest into the possible therapeutic benefit of targeting metabolic pathways in cancer has increased dramatically with academic and pharmaceutical groups actively pursuing this aspect of tumour physiology. Therefore, what has fuelled this revived interest in targeting cancer metabolism and what are the major advances and potential challenges faced in the race to develop new therapeutics in this area? This review will attempt to answer these questions by summarising recent developments in this field. We aim to illustrate why we, and others, believe that targeting metabolism in cancer presents such a promising therapeutic rationale.

Effects of olive oil polyphenols on fatty acid synthase gene expression and activity in human colorectal cancer cells

Oleuropein (OL) and hydroxytyrosol (HT), the main olive oil polyphenols, possess anti-proliferative effects in vitro. Fatty acid synthase, a key anabolic enzyme of biosynthesis of fatty acids, plays an important role in colon carcinoma development. Our aim was to investigate whether gene expression of FAS, as well as its enzymatic activity, is regulated by HT and OL in two human colon cancer cell lines, as HT-29 and SW620. In addition, we investigated the effects of these polyphenols on growth and apoptosis in these cells. FAS gene expression and activity in treated HT-29 and SW620 cells were evaluated by real-time PCR and radiochemical assay, respectively. Cell growth and apoptosis, after polyphenols treatment, were measured by MTT test and flow cytometry, respectively. The inhibition of proliferation, detected after HT treatment, was mediated by an inhibition of FAS expression and its enzymatic activity in SW620 cells, while the anti-proliferative effect in HT-29 cells seems to be independent from FAS. OL exerted an anti-proliferative effect only on SW620 cells with a mechanism which excluded FAS. Olive oil polyphenols used were able to induce apoptosis in both cell lines studied. The increase of apoptosis in these cells was accompanied by the block of cell cycle in the S phase. This study demonstrates that HT and OL may induce anti-proliferative and pro-apoptotic effects only in certain human colorectal cancer cell types. These effects are FAS mediated only in SW620 cells after treatment with HT.

The LKB1-AMPK pathway: metabolism and growth control in tumour suppression

In the past decade, studies of the human tumour suppressor LKB1 have uncovered a novel signalling pathway that links cell metabolism to growth control and cell polarity. LKB1 encodes a serine-threonine kinase that directly phosphorylates and activates AMPK, a central metabolic sensor. AMPK regulates lipid, cholesterol and glucose metabolism in specialized metabolic tissues, such as liver, muscle and adipose tissue. This function has made AMPK a key therapeutic target in patients with diabetes. The connection of AMPK with several tumour suppressors suggests that therapeutic manipulation of this pathway using established diabetes drugs warrants further investigation in patients with cancer.