Overexpression of fatty acid synthase in oesophageal squamous cell dysplasia and carcinoma

Variation in Fatty Acid Synthase, Ki67 and p53 Esophageal Mucosa Expressions in Barrett's Esophagus Patients Treated for One Year with Two Esomeprazole Different Regimens

Barrett's esophagus (BE) is an acquired pre-malignant condition that results from chronic gastroesophageal reflux. The malignant transformation occurred in 0.5% of patients/year and was independent of medical and endoscopic conservative treatments. Fatty acid synthase (FAS) is a multifunctional enzyme that catalyzes the synthesis of long-chain fatty acids from acetyl-coenzyme A, malonyl-coenzyme A, a reduced form of nicotinamide adenine dinucleotide phosphate (NADPH), and adenosine triphosphate. Activation of FAS is closely linked to malignant transformation. The aim of the present study was to evaluate the variation of FAS, p53, and Ki67 expressions in two groups of 21 BE patients each, after one year of continuous (group A) or discontinuous (group B) treatment with esomeprazole 40 mg/day in comparison to the initial expression. In both the two groups of BE patients, biopsies were taken from pathologic sites of the mucosa for histological and immuno-histochemical detection of FAS, Ki67, and p53 at entry and after one year of Esomeprazole 40 mg treatment. FAS expression was positive when a strong granular cytoplasmic staining was observed in esophageal cells. Ki67 and p53 were defined as positive when nuclear staining was clearly detected at ×10 magnification. FAS expression was reduced in 43% of patients treated with Esomeprazole continuously in comparison to the 10% of patients treated with Esomeprazole on demand (p = 0.002). Ki67 expression was reduced in 28% of continuously treated patients in comparison to 5% of patients treated on demand (p = 0.001). The p53 expression decreased in 19% of continuously treated patients in comparison to an increase in 2 patients (9%) treated on demand (p = 0.05). Continuously Esomeprazole treatment could help in the diminution of metabolic and proliferative activities in the esophageal columnar epithelium and in part it can help prevent the oxidative damage against cellular DNA, resulting in a diminution in p53 expression.

Fatty acid synthase as a potential new therapeutic target for cervical cancer

Fatty acid synthase (FASN) is the rate-limiting enzyme for the de novo synthesis of fatty acids in the cytoplasm of tumour cells. Many tumour cells express high levels of FASN, and its expression is associated with a poorer prognosis. Cervical cancer is a major public health problem, representing the fourth most common cancer affecting women worldwide. To date, only a few in silico studies have correlated FASN expression with cervical cancer. This study aimed to investigate in vitro FASN expression in premalignant lesions and cervical cancer samples and the effects of a FASN inhibitor on cervical cancer cells. FASN expression was observed in all cervical cancer samples with increased expression at more advanced cervical cancer stages. The FASN inhibitor (orlistat) reduced the in vitro cell viability of cervical cancer cells (C-33A, ME-180, HeLa and SiHa) in a time-dependent manner and triggered apoptosis. FASN inhibitor also led to cell cycle arrest and autophagy. FASN may be a potential therapeutic target for cervical cancer, and medicinal chemists, pharmaceutical researchers and formulators should consider this finding in the development of new treatment approaches for this cancer type.

Immunohistochemical Expression of Fatty Acid Synthase (FASN) is Correlated to Tumor Aggressiveness and Cellular Differentiation in Salivary Gland Carcinomas

Fatty acid synthase (FASN) expression is closely related to cancer progression, in particular, tumor aggressiveness and poor prognosis. This study aimed to analyse the expression of FASN in carcinomas of the salivary glands and correlate it with Ki-67 expression. We analysed by immunohistochemistry the expression of FASN and Ki-67 on tissue sections from 7 cases of adenocarcinoma, not otherwise specified (AdNOS), 6 cases of polymorphous adenocarcinoma (PAC), 16 cases of acinic cell carcinoma (AcCC), 19 cases of adenoid cystic carcinoma (AdCC), 15 cases of epithelial-myoepithelial carcinoma (EMC); 10 cases of secretory carcinoma (SC), 13 cases of mucoepidermoid carcinoma (MEC), 10 cases of salivary duct carcinoma (SDC) and 7 cases of myoepithelial carcinoma (MC). These carcinomas were classified into aggressive and indolent regarding their biological behaviour. Additionally, MEC and AdCC were also classified according to the histological grade. High expression of FASN was found in SDC (100%), SC (100%), AcCC (68.7%) and AdNOS (57.2%). No association was found between FASN and Ki-67 expression. Aggressive carcinomas showed a higher rate of Ki-67 proliferation (p < 0.001) and greater expression of FASN when compared to indolent carcinomas (p < 0.05). With regards to carcinomas categorized as indolent, FASN expression was much higher in the lesions that presented cell differentiation (SC and AcCC). Also, FASN expression was significantly higher in high-grade AdCC and MEC when compared to low-grade tumors (p < 0.05). We concluded that FASN expression was correlated to tumor aggressiveness and cellular differentiation in salivary gland carcinomas.

Fatty acid synthase (FASN) as a therapeutic target in breast cancer

INTRODUCTION

Ten years ago, we put forward the metabolo-oncogenic nature of fatty acid synthase (FASN) in breast cancer. Since the conception of this hypothesis, which provided a model to explain how FASN is intertwined with various signaling networks to cell-autonomously regulate breast cancer initiation and progression, FASN has received considerable attention as a therapeutic target. However, despite the ever-growing evidence demonstrating the involvement of FASN as part of the cancer-associated metabolic reprogramming, translation of the basic science-discovery aspects of FASN blockade to the clinical arena remains a challenge. Areas covered: Ten years later, we herein review the preclinical lessons learned from the pharmaceutical liabilities of the first generation of FASN inhibitors. We provide an updated view of the current development and clinical testing of next generation FASN-targeted drugs. We also discuss new clinico-molecular approaches that should help us to convert roadblocks into roadways that will propel forward our therapeutic understanding of FASN. Expert opinion: With the recent demonstration of target engagement and early signs of clinical activity with the first orally available, selective, potent and reversible FASN inhibitor, we can expect Big pharma to revitalize their interest in lipogenic enzymes as well-credentialed targets for oncology drug development in breast cancer.

Molecular profiles in foregut oncology

Oncology is and will continue to evolve resulting from a better understanding of the biology and intrinsic genetic profile of each cancer. Tumor biomarkers and targeted therapies are the new face of precision medicine, so it is essential for all physicians caring for cancer patients to understand and assist patients in understanding the role and importance of such markers and strategies to target them. This review was initiated in an attempt to identify, characterize, and discuss literature supporting clinically relevant molecular markers and interventions. The efficacy of targeting specific markers will be examined with data from clinical trials focusing on treatments for esophageal, gastric, liver, gallbladder, biliary tract, and pancreatic cancers.

Prolyl hydroxylase mediated inhibition of fatty acid synthase to combat tumor growth in mammary gland carcinoma

Cancer is a group of cells which grow in an uncontrolled manner and invades to the adjacent organs to form malignant tumors. Tumor hypoxia results due to contrast between the cellular oxygen expenditure and oxygen supply to the cells. Hypoxia inducible factor (HIF) is a heterodimeric transcription factor encompass of oxygen sensitive α subunit and constitutively expressed β subunit both of which are basic helix-loop-helix protein. The stability of HIF is primarily regulated by post translational prolyl hydroxylation, catalyzed by prolyl hydroxylase 2 (Phd-2). Phd-2 is a group of enzymes that acts as an oxygen sensor. Cancer cells have altered metabolism as they fulfil their energy needs through glycolysis and lipid biogenesis. HIF-1α is known to upregulate glycolysis by activating the transcription of enzymes on the glycolytic pathway and through lipogenesis. Cancer cells have over expressed fatty acid synthase owing to altered glycolytic pathway. Considering the above, it is hypothesized that chemical activation of Phd-2 can curtail down HIF-1α and subsequently fatty acid synthase expression.

Orlistat and antisense-miRNA-loaded PLGA-PEG nanoparticles for enhanced triple negative breast cancer therapy

BACKGROUND

This study explores the use of hydrophilic poly(ethylene glycol)-conjugated poly(lactic-co-glycolic acid) nanoparticles (PLGA-PEG-NPs) as delivery system to improve the antitumor effect of antiobesity drug orlistat for triple-negative breast cancer (TNBC) therapy by improving its bioavailability.

MATERIALS & METHODS

PLGA-PEG-NPs were synthesized by emulsion-diffusion-evaporation method, and the experiments were conducted in vitro in MDA-MB-231 and SKBr3 TNBC and normal breast fibroblast cells.

RESULTS

Delivery of orlistat via PLGA-PEG-NPs reduced its IC50 compared with free orlistat. Combined treatment of orlistat-loaded NPs and doxorubicin or antisense-miR-21-loaded NPs significantly enhanced apoptotic effect compared with independent doxorubicin, anti-miR-21-loaded NPs, orlistat-loaded NPs or free orlistat treatments.

CONCLUSION

We demonstrate that orlistat in combination with antisense-miR-21 or current chemotherapy holds great promise as a novel and versatile treatment agent for TNBC.

Fatty acid synthase inhibitors induce apoptosis in non-tumorigenic melan-a cells associated with inhibition of mitochondrial respiration

The metabolic enzyme fatty acid synthase (FASN) is responsible for the endogenous synthesis of palmitate, a saturated long-chain fatty acid. In contrast to most normal tissues, a variety of human cancers overexpress FASN. One such cancer is cutaneous melanoma, in which the level of FASN expression is associated with tumor invasion and poor prognosis. We previously reported that two FASN inhibitors, cerulenin and orlistat, induce apoptosis in B16-F10 mouse melanoma cells via the intrinsic apoptosis pathway. Here, we investigated the effects of these inhibitors on non-tumorigenic melan-a cells. Cerulenin and orlistat treatments were found to induce apoptosis and decrease cell proliferation, in addition to inducing the release of mitochondrial cytochrome c and activating caspases-9 and -3. Transfection with FASN siRNA did not result in apoptosis. Mass spectrometry analysis demonstrated that treatment with the FASN inhibitors did not alter either the mitochondrial free fatty acid content or composition. This result suggests that cerulenin- and orlistat-induced apoptosis events are independent of FASN inhibition. Analysis of the energy-linked functions of melan-a mitochondria demonstrated the inhibition of respiration, followed by a significant decrease in mitochondrial membrane potential (ΔΨm) and the stimulation of superoxide anion generation. The inhibition of NADH-linked substrate oxidation was approximately 40% and 61% for cerulenin and orlistat treatments, respectively, and the inhibition of succinate oxidation was approximately 46% and 52%, respectively. In contrast, no significant inhibition occurred when respiration was supported by the complex IV substrate N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). The protection conferred by the free radical scavenger N-acetyl-cysteine indicates that the FASN inhibitors induced apoptosis through an oxidative stress-associated mechanism. In combination, the present results demonstrate that cerulenin and orlistat induce apoptosis in non-tumorigenic cells via mitochondrial dysfunction, independent of FASN inhibition.

Orlistat, a novel potent antitumor agent for ovarian cancer: proteomic analysis of ovarian cancer cells treated with Orlistat

Orlistat is an orally administered anti-obesity drug that has shown significant antitumor activity in a variety of tumor cells. To identify the proteins involved in its antitumor activity, we employed a proteomic approach to reveal protein expression changes in the human ovarian cancer cell line SKOV3, following Orlistat treatment. Protein expression profiles were analyzed by 2-dimensional polyacrylamide gel electrophoresis (2-DE) and protein identification was performed on a MALDI-Q-TOF MS/MS instrument. More than 110 differentially expressed proteins were visualized by 2-DE and Coomassie brilliant blue staining. Furthermore, 71 proteins differentially expressed proteins were positively identified via mass spectrometry (MS)/MS analysis. In particular, PKM1/2, a key enzyme involved in tumorigenesis, was found to be significantly downregulated in SKOV3 cells following treatment with Orlistat. Moreover, PKM1/2 was proved to be downregulated in SKOV3 cells by western blot analysis after treatment with Orlistat. Taken together, using proteomic tools, we identified several differentially expressed proteins that underwent Orlistat-induced apoptosis, particularly PKM2. These changes confirmed our hypothesis that Orlistat is a potential inhibitor of ovarian cancer and can be used as a novel adjuvant antitumor agent.

Fatty acid synthase expression and esophageal cancer

Fatty acid synthase (FASN) overexpression has also been associated with a variety of human malignancies including tumor progression, aggressiveness, and metastasis. To investigate the role of FASN expression in esophageal cancer, we evaluated 60 cases of squamous cell carcinoma, 20 cases of adenocarcinoma, and 10 cases of normal esophageal tissues. We found that FASN was detected in 95 % human squamous cell carcinoma, and in 90 % human adenocarcinoma samples. However, all cases of normal esophageal epithelium did not express the protein of FASN. Further, to investigate the role of FASN in tumorigenesis and development, we analyze the growth and migration by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation and wound healing assay. We found that inhibition of FASN expression in TE13 cells by RNAi suppressed the growth of cells. Decreased FASN expression mitigated the migration of TE13 cells. These studies demonstrated the functional importance of FASN in esophageal tumorigenesis, and suggested that inhibiting FASN might be applied to treat esophageal cancer.

Overexpression of fatty acid synthase in human urinary bladder cancer and combined expression of the synthase and Ki-67 as a predictor of prognosis of cancer patients

To investigate the status of fatty acid synthase (FAS) in bladder tumors and evaluate its prognostic significance, we immunohistochemically examined the expression of FAS in normal urothelium, carcinoma in situ (CIS), and urothelial carcinoma (UC) in cystectomized bladder. In normal urothelium, only the surface layer expressed FAS, whereas the protein was detected in the basal layer or whole layer of CIS and UC in every specimen. Of the clinicopathological factors in UC, pathological tumor (pT) stage and histological grade were significantly correlated to FAS expression (P = 0.002, P < 0.0001, respectively). Univariate analysis for disease-specific survival indicated that the combination scores of FAS and Ki-67 expression, which were not associated with each other, was a more predictive variable than the individual score of each protein expression. Kaplan-Meier analysis showed that high combination scores of both proteins were significantly associated with poor prognosis (P = 0.04). In conclusion, FAS expression can be a biomarker for tumor aggressiveness and loss of differentiation of bladder cancer, and the evaluation of its expression level in combination with Ki-67 labeling index may be a precise predictor for poor prognosis of cancer patients.

Increased fatty acid synthase activity in non-small cell lung cancer tissue is a weaker predictor of shorter patient survival than increased lipoprotein lipase activity

BACKGROUND AND AIMS

Cumulative evidence suggests the involvement of fatty acid synthase (FAS) in tumor growth. We tested the hypothesis that increased FAS activity and gene expression in non-small cell lung cancer (NSCLC) tissue have a prognostic significance that is independent of that of increased lipoprotein lipase (LPL) activity in the same tissue.

METHODS

Forty two consecutive patients with resected NSCLC were enrolled in the study. Paired samples of lung cancer tissue and adjacent non-cancer lung tissue were collected from resected specimens for estimation of FAS activity and expression of its gene. LPL activity had previously been measured in the same tissues. During a 4-year follow-up, 21 patients died due to tumor progression. One patient died due to a non-cancer reason and was not included in the analysis.

RESULTS

High FAS activity in cancerous tissue relative to that in the adjacent non-cancer lung tissue was associated with weight loss in the 3 months immediately before tumor excision and patient death during the follow-up. Higher FAS activity in the cancer tissue was associated with higher LPL activity in the same tissue, which also predicted shorter patient survival, but LPL was the stronger predictor. FAS gene expression was higher in the adjacent non-cancer tissue than in the cancer tissue but had no predictive value.

CONCLUSION

Our study further underlines the involvement of cancer tissue FAS activity in tumor growth but also indicates its weaker importance compared to LPL activity.

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.

Increased expression of fatty acid synthase in human aberrant crypt foci: possible target for colorectal cancer prevention

Aberrant crypt foci (ACF), the earliest identified monoclonal lesions in the colon, provide insights into changes that promote and/or accompany the transformation of normal colonic epithelial cells to colorectal cancer. Fatty acid synthase (FAS), the primary enzyme involved in de novo lipogenesis from carbohydrates, is expressed at low levels in most normal human tissues but is elevated in several human neoplasms including colorectal adenomas and carcinomas. To determine if this pathway is altered even earlier in colorectal tumorigenesis, 35 human ACF from 21 patients were evaluated for the immunohistochemical expression of FAS. Sections of colon cancer served as positive controls, and normal colonic mucosa distant from cancer or ACF served as negative controls. FAS expression was increased in 30 (86%) ACF compared with that in adjacent normal colonic mucosa. The expression of FAS in ACF was not related to the degree of dysplasia or to the number of crypts in the ACF. The over expression of FAS in a high proportion of ACF suggests that this enzyme plays an important role very early in colorectal tumorigenesis and may be a target for chemoprevention.

Evaluation of fatty acid synthase expression in oesophageal mucosa of patients with oesophagitis, Barrett's oesophagus and adenocarcinoma

BACKGROUND AND AIM

To evaluate the expression of fatty acid synthase (FAS) in the oesophagitis-Barrett's oesophagus-oesophageal adenocarcinoma sequence compared with p53 and Ki67 expressions, retained for a long time reliable markers of oesophageal cells biological behaviour.

METHODS

In Barrett's oesophagus, oesophagitis and oesophageal adenocarcinoma patients, biopsies were taken from pathologic sites of the mucosa for histological and immuno-histochemical detection of FAS, p53 and Ki67. FAS expression was positive, when a strong granular cytoplasmic staining was observed in oesophageal cells. Ki67 and p53 was defined positive, when nuclear staining was clearly detected at 10x magnification.

RESULTS

A mild expression of FAS was found in 39% of patients with oesophagitis. The amount of FAS expression increased up to 70% in Barrett's oesophagus while this was present in all patients with oesophageal adenocarcinoma (p = 0.0001). In Barrett's oesophagus, p53 was mildly or intensely expressed in 77% and in 15% of cases, respectively, and mildly or intensely expressed in 33% and 67% of patients with oesophageal adenocarcinoma, respectively, (p = 0.0001). Ki67 was mildly expressed in 17% of oesophagitis cases and was absent in the majority of cases. In Barrett's oesophagus, a mild Ki67 expression was present in 46% of cases, and in oesophageal adenocarcinoma it was present prevalently in intense form (67%; p = 0.0001).

CONCLUSIONS

The over-expression of p53, Ki67 and FAS in otherwise similar morphological groups may be useful to stratify patients into selected prognostic subgroups in order to achieve better clinical approaches.

Fatty acid synthase activity in tumor cells

While normal tissues are tightly regulated by nutrition and a carefully balanced system of glycolysis and fatty acid synthesis, tumor cells are under significant evolutionary pressure to bypass many of the checks and balances afforded normally. Cancer cells have high energy expenditure from heightened proliferation and metabolism and often show increased lipogenesis. Fatty acid synthase (FASN), the enzyme responsible for catalyzing the ultimate steps of fatty acid synthesis in cells, is expressed at high levels in tumor cells and is mostly absent in corresponding normal cells. Because of the unique expression profile of FASN, there is considerable interest not only in understanding its contribution to tumor cell growth and proliferation, but also in developing inhibitors that target FASN specifically as an anti-tumor modality. Pharmacological blockade of FASN activity has identified a pleiotropic role for FASN in mediating aspects of proliferation, growth and survival. As a result, a clearer understanding of the role of FASN in tumor cells has been developed.

Expression of liver-type fatty-acid-binding protein, fatty acid synthase and vascular endothelial growth factor in human lung carcinoma

OBJECTIVE

A key enzyme of fatty acid synthesis, fatty acid synthase (FAS), is expressed in human cancers, including squamous-cell carcinoma of the lung, and long-chain fatty acids are intracellularly transported and/or taken up from blood by fatty-acid-binding proteins (FABPs). Since the liver-type (L-) FABP, a member of the FABPs, is detected in a subset of gastric adenocarcinomas, the expression of FAS, L-FABP and vascular endothelial growth factor (VEGF) was investigated in human lung carcinomas to elucidate the mechanisms of production and transportation of fatty acid(s) in cancer.

METHODS

Expression of L-FABP, FAS and VEGF in 199 surgically resected lung carcinomas was examined immunohistochemically. Possible associations of the expression of each protein with major clinicopathological factors were analyzed.

RESULTS

L-FABP was detected in 60% (120 of 199) of the lung carcinoma cases; detection was increased in large-cell carcinoma (80%) and adenosquamous carcinoma (83%), but low in squamous-cell carcinoma (47%) and in small-cell carcinoma (57%). Overall expression of FAS was 67.3% (134 of 199 cases) and that of VEGF was 86.8% (158 of 199 cases), respectively. Expression of L-FABP was not correlated with the FAS status, but there was a tendency to co-expression of L-FABP and VEGF. There was no association between L-FABP, FAS or VEGF expression and clinicopathological data.

CONCLUSIONS

L-FABP, FAS and VEGF are highly expressed in human lung cancer, and expression of L-FABP is associated with that of VEGF but not that of FAS, suggesting that L-FABP might be involved in the uptake of fatty acid(s) from the bloodstream.

Fatty acid synthase expression in Paget's disease of the vulva

We explored the immunohistochemical expression of fatty acid synthase (FAS) in Paget's disease of the vulva (PDV) and its association with clinico-pathological features. FAS is a recently discovered molecule involved in energy supply of normal cells. FAS is also overexpressed in neoplastic tissues because of their increased necessity of energy. Specimens from 20 patients with PDV were immunohistochemically evaluated; increased FAS expression was observed in 7 of 8 patients with invasive PDV (87%), in 3 of 4 patients with microinvasive PDV (75%), and in 1 of 8 patients with noninvasive PDV (12%). Statistical analysis revealed that increased FAS expression was associated with invasive PDV (p = 0.04). To our knowledge, this association of FAS in PDV is the first to be reported in literature. These observations reveal that FAS is a reliable marker of aggressiveness in PDV. The knowledge of FAS statistical association in invasive PDV is an important finding that may stratify these patients in different prognostic groups and determine therapeutic approaches for patient care.

KGF induces lipogenic genes through a PI3K and JNK/SREBP-1 pathway in H292 cells

Lipid synthesis is required for cell growth and is subject to pharmacologic regulation. Keratinocyte growth factor (KGF) stimulates proliferation and lipogenesis in H292 cells, a pulmonary epithelial cancer cell line, but the signaling pathways are not known. KGF stimulated the expression of the transcription factors sterol-regulatory element binding protein-1 (SREBP-1), CCAAT/enhancer binding protein alpha (C/EBPalpha), and C/EBPdelta and two key enzymes involved in lipogenesis, FAS and stearoyl coenzyme A desaturase-1 (SCD-1). We found that KGF induced rapid activation of Akt, p70 S6K, JNK, and extracellular signal-regulated (ERK). Induction of SREBP-1, SCD-1, and FAS by KGF was inhibited by the JNK inhibitor SP600125 and the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 but not by the ERK inhibitor PD98059. Using FAS and SCD-1-luciferase promoter constructs, we observed that KGF stimulated the transcription of these promoters and that exogenous cholesterol inhibited the induction. Mutation of the SREBP-1 binding site in the SCD-1 promoter abolished the effect of KGF on SCD-1 transcription. In addition, overexpression of active SREBP-1 directly stimulated SCD-1 and FAS. Conversely, adenovirus-mediated overexpression of a dominant negative form of SREBP-1 inhibited the KGF effect on FAS and SCD-1 expression. In summary, we conclude that KGF requires both PI3K and JNK signaling pathways to induce SREBP-1, which in turn induces SCD-1 and FAS expression in H292 cells.

Substrate recognition by the human fatty-acid synthase

The human fatty-acid synthase (HFAS) is a potential target for anti-tumor drug discovery. As a prelude to the design of compounds that target the enoyl reductase (ER) component of HFAS, the recognition of NADPH and exogenous substrates by the ER active site has been investigated. Previous studies demonstrate that modification of Lys-1699 by pyridoxal 5'-phosphate results in a specific decrease in ER activity. For the overall HFAS reaction, the K1699A and K1699Q mutations reduced kcat and kcat/KNADPH by 8- and 600-fold, respectively (where KNADPH indicates the Km value for NADPH). Thus, Lys-1699 contributes 4 kcal/mol to stabilization of the rate-limiting transition state following NADPH binding, while also stabilizing the most stable ground state after NADPH binding by 3 kcal/mol. A similar effect of the mutations on the ER partial reaction was observed, in agreement with the proposal that Lys-1699 is located in the ER NADPH-binding site. Most unexpectedly, however, both kcat and kcat/KNADPH for the beta-ketoacyl reductase (BKR) reaction were also impacted by the Lys-1699 mutations, raising the possibility that the ER and BKR activities share a single active site. However, based on previous data indicating that the two reductase activities utilize distinct cofactor binding sites, mutagenesis of Lys-1699 is hypothesized to modulate BKR activity via allosteric effects between the ER and BKR NADPH sites.

Increased ratio of saturated to unsaturated C18 fatty acids in colonic adenocarcinoma: implications for cryotherapy and lipid raft function

Mammalian fatty acid synthase (FASE) overexpression has been shown in a number of human malignancies including colonic adenocarcinoma. Since FASE synthesizes only saturated fatty acids, we hypothesized that cancer cells have a greater proportion of long-chain saturated fatty acids. We studied and found an unequivocal increase in saturated C18 fatty acid (stearic acid) in colonic adenocarcinoma compared to adjacent normal colonic mucosa. The increase is even more striking when measured as a ratio of stearic acid to the unsaturated C18 fatty acids (oleic acid and linoleic acid). This change in fatty acid composition of the cancer cells should significantly alter their physical and biological properties. The increase in relative proportion of saturated fatty acids should make the cancer cells more susceptible to cryodamage and measurement of fatty acid composition of cancer cells may help individualize the temperature for cryotherapy. Also, the lipid alterations may affect the structure and functions of lipid rafts, which may enable the cancer cells to affect signaling mechanisms such as those involved in cell growth and apoptosis. Dietary or therapeutic interventions targeting lipid rafts may thus be an option for cancer treatment.

Fatty acid synthase expression in cutaneous melanocytic neoplasms

Mammalian fatty acid synthase is a multifunctional enzyme complex involved in de novo synthesis of saturated fatty acids, and inhibitors of fatty acid synthase are being evaluated as potential therapeutic agents. Increased fatty acid synthase expression has been demonstrated in subsets of malignancies, including colon, breast, endometrium, prostate and ovarian carcinomas, and recently malignant melanomas. We evaluated the immunohistochemical expression of fatty acid synthase in 155 cutaneous melanocytic lesions. They included 30 congenital nevi, 19 compound nevi, 40 Spitz nevi, 48 primary melanomas, and 18 metastatic melanomas. Fatty acid synthase expression was stronger in malignant melanomas in comparison to conventional nevi and Spitz nevi, and was the highest for metastatic melanoma. Of the primary malignant melanomas, mean fatty acid synthase scores were significantly greater for Clark levels IV and V compared to Clark levels I and II (P<0.001). In addition, melanomas with Breslow thickness 0.75-1.50 mm and >1.50 mm showed significantly higher mean fatty acid synthase scores compared with those with Breslow thickness <0.75 mm (P=0.013 and <0.001, respectively). Of interest, congenital melanocytic nevi also showed strong fatty acid synthase expression, similar to that seen in metastatic melanoma. This may represent persistence of or regression to a fetal phenotype since normal fetal tissues are known to express high levels of fatty acid synthase.

Why does tumor-associated fatty acid synthase (oncogenic antigen-519) ignore dietary fatty acids?

The hyperactivation of fatty acid synthase (FAS)-catalyzed de novo biosynthesis of fatty acids is a molecular marker linked to tumor virulence in population studies of human malignancies. This activation appears to be linked to neoplastic transformation, since high levels of FAS have also been identified in pre-malignant lesions. This dependence of cancer upon accelerated lipogenesis differs from normal human tissues, in which FAS is suppressed by the presence of small amounts of fatty acids in the diet. The molecular mechanisms by which cancer cells constitutively exhibit FAS overexpression and hyperactivity have begun to emerge. The active involvement of the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (MAPK ERK1/2) and phosphatidylinositol-3'-kinase (PI-3'K)/protein kinase B (AKT) transduction cascades in the overexpression of FAS has been recently demonstrated in several cancer cell models. Strikingly, insulin-regulated stimulation of FAS expression in adipose cells is also mediated by the PI-3'K pathway with AKT being involved as a downstream effector. Moreover, FAS overexpression in tumor cells has been demonstrated to occur through a modification of the transcription factor sterol regulatory element-binding protein-1c (SREBP-1c), the major regulatory factor of FAS in liver and adipose tissues, which, in turn, is known to be regulated by MAPK ERK1/2 and PI-3'K/AKT pathways. Therefore, the signal transduction pathways regulating FAS expression in normal and cancer cells seem to share several downstream elements. However, the upstream mechanisms controlling FAS expression in cancer cells must be different from those in normal tissues, since tumor-associated FAS expression seems to be insensitive to nutritional signals. In pre-neoplastic lesions, we hypothesize that the early activation of FAS in pre-malignant cells represents a survival strategy which occurs to compensate for an insufficiency of both oxygen and dietary fatty acids due to, e.g., lack of angiogenesis. Thus, FAS activation reflects an epigenetic dysregulation of the lipogenic pathway in response to the microenvironment of tumors containing regions of poor oxygenation. Upon this unusual metabolic situation, FAS up-regulation also represent a metabolic strategy to maintain high proliferation rates of surviving cells in the absence of exogenous dietary fatty acids. Concomitantly, a variety of oncogenic changes (H-ras, erb B-2, etc.) may result in the constitutive activation of MAPK and PI-3'K/AKT signaling cascades, which, in turn, can activate SREBP-1c and, subsequently, tumor-associated FAS-catalyzed endogenous lipogenesis. Thereafter, high levels of FAS are maintained in coordination with increased demand for fatty acid metabolism and/or membrane synthesis in response to cancer-related overexpression of growth factors (e.g., EGF, heregulin) and/or growth factor receptors (e.g., EGFR, Her-2/neu). The aberrant MAPK and PI-3'K/AKT cascades driven by these oncogenic changes subvert the downregulatory effects of physiological concentrations of dietary fatty acids, resulting in a cancer-associated FAS insensitivity to nutritional signals. This model does not exclude that fundamental differences in the ability of FAS gene to respond to normal fatty acid's downregulatory actions may also synergistically interact with oncogenic signals to constitutively maintain an elevated FAS-dependent de novo endogenous fatty acid biogenesis in cancer cells in spite of high levels of circulating dietary fatty acids.

Expression of heart-type fatty acid-binding protein in human gastric carcinoma and its association with tumor aggressiveness, metastasis and poor prognosis

OBJECTIVE

Fatty acid-binding proteins (FABPs) are involved in lipid metabolism by intracellular transport of long-chain fatty acids. Heart-type (H-) FABP has been reported to inhibit cell growth and induce cell differentiation, but to our knowledge the significance of H-FABP expression in human gastric carcinoma has not been elucidated. The aim of the current study was to examine the expression of H-FABP and its relation to clinicopathologic parameters and fatty acid synthase (FAS) status of gastric carcinoma, since gastric cancer shows increased expression of FAS.

METHODS

Immunohistochemistry with anti-H-FABP antibody was performed in 669 gastric carcinomas and 60 tubular adenomas of the stomach. H-FABP-positive and H-FABP-negative carcinomas were analyzed for their clinicopathologic characteristics and FAS status.

RESULTS

None of the adenomas expressed H-FABP, whereas 127 of 669 carcinomas (19.0%) were positive for the protein. H-FABP positivity was associated with the depth of invasion (p <0.0001), vascular invasion (p <0.0001), lymph node metastasis (p <0.0001), hepatic metastasis (p=0.0011), stage of the carcinoma (p <0.0001) and FAS status of the carcinoma (p=0.0476). A higher survival rate was noted in H-FABP-negative cases compared with H-FABP-positive cases (p=0.0004).

CONCLUSIONS

A subset of human gastric carcinoma expresses H-FABP and its expression is associated with FAS status, disease progression, tumor aggressiveness and poor patient survival.

Fatty acid synthase inhibitors are chemopreventive for mammary cancer in neu-N transgenic mice

High levels of fatty acid synthase (FAS) have been found in cancer precursor lesions of the colon, stomach, esophagus, oral cavity, prostate, and breast. Inhibition of FAS with C75 has led to a significant antitumor effect in both human breast and prostate cancer xenografts. Recently, HER2/neu, which has also been identified in preneoplastic breast lesions, has been shown to regulate FAS expression through the PI3K/Akt signal transduction pathway rendering them susceptible to FAS inhibition. Utilizing the neu-N transgenic mouse model of mammary cancer, weekly treatment of the neu-N mice with C75 (30 mg/kg) for 10 weeks significantly delayed tumor progression. Only 20% of the C75-treated transgenic mice developed mammary carcinoma by 220 days, compared to 50% in the vehicle control animals. Two C75-treated animals never developed mammary cancer. Analysis of mammary tissue following 10 weeks of C75 treatment revealed a significant delay in mammary maturation as manifested by a reduction of the number and caliber of mammary ducts and budding epithelial structures. Apoptotic changes were increased, DNA synthesis was decreased, and the expressions of FAS, neu, Akt, phospho-Akt, and p21(waf1) were all decreased when compared to vehicle controls and FVB/N mice. Importantly, these effects were restricted to the breast epithelial cells that overexpressed neu, not involving other normal duct structures in the skin, liver, or kidney. C247, an FAS inhibitor chemically distinct from C75, significantly delayed mammary maturation similar to C75. Thus, pharmacological inhibition of FAS affects the expression of key oncogenes involved in both cancer development and maintenance of the malignant phenotype. Moreover, these data identify FAS as a potential novel drug target for breast cancer chemoprevention.

Pharmacological inhibition of fatty acid synthase (FAS): a novel therapeutic approach for breast cancer chemoprevention through its ability to suppress Her-2/neu (erbB-2) oncogene-induced malignant transformation

We designed our experiments to evaluate whether fatty acid synthase (FAS), a lipogenic enzyme linked to tumor virulence in population studies of human cancer, is necessary for the malignant transformation induced by Her-2/neu (erbB-2) oncogene, which is overexpressed not only in invasive breast cancer but also in premalignant atypical duct proliferations and in ductal carcinoma in situ of the breast. To avoid the genetic complexities associated with established breast cancer cell lines, we employed NIH-3T3 mouse fibroblasts engineered to overexpress human Her-2/neu coding sequence. NIH-3T3/Her-2 cells demonstrated a significant upregulation of FAS protein expression, which was dependent on the upstream activation of mitogen-activated protein kinase and phosphatidylinositol 3'-kinase/AKT pathways. Remarkably, pharmacological FAS blockade using the mycotoxin cerulenin or the novel small compound C75 completely suppressed the state of Her-2/neu-induced malignant transformation by inhibiting the ability of NIH-3T3/Her-2 cells to grow under either anchorage-independent (i.e., to form colonies in soft agar) or low-serum monolayer conditions. Moreover, NIH-3T3/Her-2 fibroblasts were up to three times more sensitive to chemical FAS inhibitors relative to untransformed controls as determined by MTT-based cell viability assays. In addition, pharmacological FAS blockade preferentially induced apoptotic cell death of NIH-3T3/Her-2 fibroblasts, as determined by an ELISA for histone-associated DNA fragments and by the terminal deoxynucleotidyltransferase (TdT)-mediated nick end labeling assay (TUNEL). Interestingly, the degree of Her-2/neu oncogene expression in a panel of breast cancer cell lines was predictive of sensitivity to chemical FAS inhibitors-induced cytotoxicity, while low-FAS expressing and chemical FAS inhibitors-resistant MDA-MB-231 breast cancer cells became hypersensitive to FAS blockade when they were engineered to overexpress Her-2/neu. Our observations strongly suggest that inhibition of FAS activity may provide a new molecular avenue for chemotherapeutic prevention and/or treatment of Her-2/neu-related breast carcinomas.

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Fatty acid synthase expression is induced by the Epstein-Barr virus immediate-early protein BRLF1 and is required for lytic viral gene expression

The Epstein-Barr virus (EBV) immediate-early (IE) protein BRLF1 (R) is a transcription factor that induces the lytic form of EBV infection. R activates certain early viral promoters through a direct binding mechanism but induces transcription of the other EBV IE gene, BZLF1 (Z), indirectly through cellular factors binding to a CRE motif in the Z promoter (Zp). Here we demonstrate that R activates expression of the fatty acid synthase (FAS) cellular gene through a p38 stress mitogen-activated protein kinase-dependent mechanism. B-cell receptor engagement of Akata cells also increases FAS expression. The FAS gene product is required for de novo synthesis of the palmitate fatty acid, and high-level FAS expression is normally limited to liver, brain, lung, and adipose tissue. We show that human epithelial tongue cells lytically infected with EBV (from oral hairy leukoplakia lesions) express much more FAS than uninfected cells. Two specific FAS inhibitors, cerulenin and C75, prevent R activation of IE (Z) and early (BMRF1) lytic EBV proteins in Jijoye cells. In addition, cerulenin and C75 dramatically attenuate IE and early lytic gene expression after B-cell receptor engagement in Akata cells and constitutive lytic viral gene expression in EBV-positive AGS cells. However, FAS inhibitors do not reduce lytic viral gene expression induced by a vector in which the Z gene product is driven by a strong heterologous promoter. In addition, FAS inhibitors do not reduce R activation of a naked DNA reporter gene construct driven by the Z promoter (Zp). These results suggest that cellular FAS activity is important for induction of Z transcription from the intact latent EBV genome, perhaps reflecting the involvement of lipid-derived signaling pathways or palmitoylated proteins. Furthermore, using FAS inhibitors may be a completely novel approach for blocking the lytic form of EBV replication.