Targeting fatty acid synthase: potential for therapeutic intervention in her-2/neu-overexpressing breast cancer

Lipid metabolism in malignant tumor brain metastasis: reprogramming and therapeutic potential

INTRODUCTION

Brain metastasis is a highly traumatic event in the progression of malignant tumors, often symbolizing higher mortality. Metabolic alterations are hallmarks of cancer, and the mask of lipid metabolic program rearrangement in cancer progression is gradually being unraveled.

AREAS COVERED

In this work, we reviewed clinical and fundamental studies related to lipid expression and activity changes in brain metastases originating from lung, breast, and cutaneous melanomas, respectively. Novel roles of lipid metabolic reprogramming in the development of brain metastasis from malignant tumors were identified and its potential as a therapeutic target was evaluated. Published literature and clinical studies in databases consisting of PubMed, Embase, Scopus and www.ClinicalTrials.gov from 1990 to 2022 were searched.

EXPERT OPINION

Lipid metabolic reprogramming in brain metastasis is involved in de novo lipid synthesis within low lipid availability environments, regulation of lipid uptake and storage, metabolic interactions between brain tumors and the brain microenvironment, and membrane lipid remodeling, in addition to being a second messenger for signal transduction. Although some lipid metabolism modulators work efficiently in preclinical models, there is still a long way to go from laboratory to clinic. This area of research holds assurance for the organ-targeted treatment of brain metastases through drug-regulated metabolic targets and dietary interventions.

Fatty acid synthase: A druggable driver of breast cancer brain metastasis

INTRODUCTION

Brain metastasis (BrM) is a key contributor to morbidity and mortality in breast cancer patients, especially among high-risk epidermal growth factor receptor 2-positive (HER2+) and triple-negative/basal-like molecular subtypes. Optimal management of BrM is focused on characterizing a "BrM dependency map" to prioritize targetable therapeutic vulnerabilities.

AREAS COVERED

We review recent studies addressing the targeting of BrM in the lipid-deprived brain environment, which selects for brain-tropic breast cancer cells capable of cell-autonomously generating fatty acids by upregulating de novo lipogenesis via fatty acid synthase (FASN). Disruption of FASN activity impairs breast cancer growth in the brain, but not extracranially, and mapping of the molecular causes of organ-specific patterns of metastasis has uncovered an enrichment of lipid metabolism signatures in brain metastasizing cells. Targeting SREBP1-the master regulator of lipogenic gene transcription-curtails the ability of breast cancer cells to survive in the brain microenvironment.

EXPERT OPINION

Targeting FASN represents a new therapeutic opportunity for patients with breast cancer and BrM. Delivery of brain-permeable FASN inhibitors and identifying strategies to target metabolic plasticity that might compensate for impaired brain FASN activity are two potential roadblocks that may hinder FASN-centered strategies against BrM.

Too complex to fail? Targeting fatty acid metabolism for cancer therapy

Given the central role of fatty acids in cancer pathophysiology, the exploitation of fatty acid metabolism as a potential antineoplastic therapy has gained much attention. Several natural and synthetic compounds targeting fatty acid metabolism were hitherto identified, and their effectiveness against cancer cell proliferation and survival was determined. This review will discuss the most clinically viable inhibitors or drugs targeting various proteins or enzymes mapped on nine interconnected fatty acid metabolism-related processes. We will discuss the general significance of each of these processes and the effects of their inhibition on cancer cell progression. Moreover, their mechanisms of action, limitations, and future perspectives will be assessed.

Multi-Omic Approaches to Breast Cancer Metabolic Phenotyping: Applications in Diagnosis, Prognosis, and the Development of Novel Treatments

Breast cancer (BC) is characterized by high disease heterogeneity and represents the most frequently diagnosed cancer among women worldwide. Complex and subtype-specific gene expression alterations participate in disease development and progression, with BC cells known to rewire their cellular metabolism to survive, proliferate, and invade. Hence, as an emerging cancer hallmark, metabolic reprogramming holds great promise for cancer diagnosis, prognosis, and treatment. Multi-omics approaches (the combined analysis of various types of omics data) offer opportunities to advance our understanding of the molecular changes underlying metabolic rewiring in complex diseases such as BC. Recent studies focusing on the combined analysis of genomics, epigenomics, transcriptomics, proteomics, and/or metabolomics in different BC subtypes have provided novel insights into the specificities of metabolic rewiring and the vulnerabilities that may guide therapeutic development and improve patient outcomes. This review summarizes the findings of multi-omics studies focused on the characterization of the specific metabolic phenotypes of BC and discusses how they may improve clinical BC diagnosis, subtyping, and treatment.

Non-Coding and Regulatory RNAs as Epigenetic Remodelers of Fatty Acid Homeostasis in Cancer

Cancer cells commonly display metabolic fluctuations. Together with the Warburg effect and the increased glutaminolysis, alterations in lipid metabolism homeostasis have been recognized as a hallmark of cancer. Highly proliferative cancer cells upregulate de novo synthesis of fatty acids (FAs) which are required to support tumor progression by exerting multiple roles including structural cell membrane composition, regulators of the intracellular redox homeostasis, ATP synthesis, intracellular cell signaling molecules, and extracellular mediators of the tumor microenvironment. Epigenetic modifications have been shown to play a crucial role in human development, but also in the initiation and progression of complex diseases. The study of epigenetic processes could help to design new integral strategies for the prevention and treatment of metabolic disorders including cancer. Herein, we first describe the main altered intracellular fatty acid processes to support cancer initiation and progression. Next, we focus on the most important regulatory and non-coding RNAs (small noncoding RNA-sncRNAs-long non-coding RNAs-lncRNAs-and other regulatory RNAs) which may target the altered fatty acids pathway in cancer.

The effect of FASN inhibition on the growth and metabolism of a cisplatin-resistant ovarian carcinoma model

Overexpression of fatty acid synthase (FASN), a key regulator of the de novo synthesis of fatty acids, has been demonstrated in a variety of cancers and is associated with poor prognosis and increased multidrug resistance. Inhibition of FASN with the anti-obesity drug orlistat has been shown to have significant anti-tumourigenic effects in many cancers, notably breast and prostate. In our study, we investigated whether FASN inhibition using orlistat is an effective adjunctive treatment for ovarian cancers that have become platinum resistant using a cisplatin-resistant ovarian tumour xenograft model in mice. Mice were treated with orlistat or cisplatin or a combination and metabolite analysis and histopathology were performed on the tumours ex vivo. Orlistat decreased tumour fatty acid metabolism by inhibiting FASN, cisplatin reduced fatty acid β-oxidation, and combination treatment delayed tumour growth and induced apoptotic and necrotic cell death in cisplatin-resistant ovarian cancer cells over and above that with either treatment alone. Combination treatment also decreased glutamine metabolism, nucleotide and glutathione biosynthesis and fatty acid β-oxidation. Our data suggest that orlistat chemosensitised platinum-resistant ovarian cancer to treatment with platinum and resulted in enhanced efficacy.

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.

Circulating Phospholipids as Biomarkers of Breast Cancer: A Review

Breast cancer is the most common cancer in women and the second leading cause of cancer deaths in women. The key to surviving breast cancer is early detection and treatment. Current technologies rely heavily on imaging of the breast, and although considered the gold standard, they have their limitations. There is a need for a more accurate screening test for women of all ages, which can detect the cancer at a cellular level and before metastasis. There have been extensive studies into markers for breast cancer including protein and nucleic acid biomarkers, but to date, these have been unsuccessful. A growing field of interest is the association between breast cancer (tissue and cells) and lipids, which is documented in the literature, and may be considered as a leading candidate in the breast cancer detection space.

Clinical and therapeutic relevance of the metabolic oncogene fatty acid synthase in HER2+ breast cancer

Fatty acid synthase (FASN) is a key lipogenic enzyme for de novo fatty acid biosynthesis and a druggable metabolic oncoprotein that is activated in most human cancers. We evaluated whether the HER2-driven lipogenic phenotype might represent a biomarker for sensitivity to pharmacological FASN blockade. A majority of clinically HER2-positive tumors were scored as FASN overexpressors in a series of almost 200 patients with invasive breast carcinoma. Re-classification of HER2-positive breast tumors based on FASN gene expression predicted a significantly inferior relapse-free and distant metastasis-free survival in HER2+/FASN+ patients. Notably, non-tumorigenic MCF10A breast epithelial cells engineered to overexpress HER2 upregulated FASN gene expression, and the FASN inhibitor C75 abolished HER2-induced anchorage-independent growth and survival. Furthermore, in the presence of high concentrations of C75, HER2-negative MCF-7 breast cancer cells overexpressing HER2 (MCF-7/HER2) had significantly higher levels of apoptosis than HER2-negative cells. Finally, C75 at non-cytotoxic concentrations significantly reduced the capacity of MCF-7/HER2 cells to form mammospheres, an in vitro indicator of cancer stem-like cells. Collectively, our findings strongly suggest that the HER2-FASN lipogenic axis delineates a group of breast cancer patients that might benefit from treatment with therapeutic regimens containing FASN inhibitors.

N-phenylmaleimides affect adipogenesis and present antitumor activity through reduction of FASN expression

In light of the evidence that in contrast to most healthy tissues, several neoplasms overexpress fatty acid synthase (FASN) upon their dependence on increased lipogenesis; targeting of this protein is being considered as a valuable strategy in anticancer drug development. This can be particularly relevant for aggressive tumors such as melanoma in which FASN overexpression has been associated with increased depth of invasion and worse prognosis. We have previously shown that a sub-class of cyclic imides, the N-phenylmaleimides, presented antitumor activity against L1210 leukemia and B16F10 melanoma with evidences of interference in the energetic metabolism. Here, we aimed to investigate if some selected N-phenylmaleimides (M1 and M5) interfere with fatty acids metabolism and its relation with cancer. For that, a model of pre-adipocytes differentiation (3T3-L1 cells) and also human melanoma cells (SK-Mel-147) were used. As results, when 3T3-L1 cells were exposed to non-cytotoxic concentrations of M1 and M5 in the presence of an adipogenic cocktail, intracellular lipid content decreased by 26-36%, marking the inhibition of adipocyte differentiation. High selectivity indexes were obtained for both compounds for tumoral cells. Cell cycle phases analysis revealed a remarkable proportion of cells with DNA fragmentation after their exposure to M1 and M5. This was correlated to both apoptosis and necrosis, showed by Annexin-V/PI assay. Furthermore, M1 and M5 reduced FASN expression by 19-39%, respectively. In conclusion, M1 and M5 presented antiadipogenic and antitumoral activities. The antitumoral activity that was associated to apoptosis and necrosis is a possible consequence of the FASN reduction, which in turn, might result in a fuel decrease to cell proliferation. As it happens with antiangiogenic activity, reduction of fatty acid synthesis might be a potential target for cancer treatment in a strategy of hunger-strike, which valorizes these N-phenylmaleimides as candidates for drug development.

Targeting SREBP-1-driven lipid metabolism to treat cancer

Metabolic reprogramming is a hallmark of cancer. Oncogenic growth signaling regulates glucose, glutamine and lipid metabolism to meet the bioenergetics and biosynthetic demands of rapidly proliferating tumor cells. Emerging evidence indicates that sterol regulatory element-binding protein 1 (SREBP-1), a master transcription factor that controls lipid metabolism, is a critical link between oncogenic signaling and tumor metabolism. We recently demonstrated that SREBP-1 is required for the survival of mutant EGFR-containing glioblastoma, and that this pro-survival metabolic pathway is mediated, in part, by SREBP-1-dependent upregulation of the fatty acid synthesis and low density lipoprotein (LDL) receptor (LDLR). These results have identified EGFR/PI3K/Akt/SREBP-1 signaling pathway that promotes growth and survival in glioblastoma, and potentially other cancer types. Here, we summarize recent insights in the understanding of cancer lipid metabolism, and discuss the evidence linking SREBP-1 with PI3K/Akt signaling-controlled glycolysis and with Myc-regulated glutaminolysis to lipid metabolism. We also discuss the development of potential drugs targeting the SREBP-1- driven lipid metabolism as anti-cancer agents.

Resveratrol suppresses the proliferation of breast cancer cells by inhibiting fatty acid synthase signaling pathway

In breast cancer cells, overexpression of human epidermal growth factor receptor 2 (HER2) increases the translation of fatty acid synthase (FASN) by altering the activity of PI3K/Akt signaling pathways. Cancer chemotherapy causes major side effects and is not effective enough in slowing down the progression of the disease. Earlier studies showed a role for resveratrol in the inhibition of FASN, but the molecular mechanisms of resveratrol-induced inhibition are not known. In the present study, we examined the novel mechanism of resveratrol on Her2-overexpressed breast cancer cells. The effect of resveratrol on the growth of breast cancer cells was assessed as percent cell viability by cytotoxicity-based MTT assay and the induction of apoptosis was determined by cell-death detection ELISA and flow cytometric analysis of Annexin-V-PI binding. Western immunobloting was used to detect signaling events in human breast cancer (SKBR-3) cells. Data showed that resveratrol-mediated down-regulation of FASN and HER2 genes synergistically induced apoptotic death in SKBR-3 cells. This concurrently caused a prominent up-regulation of PEA3, leads to down-regulation of HER2 genes. Resveratrol also alleviated the PI3K/Akt/mTOR signaling by down-regulation of Akt phosphorylation and up-regulation of PTEN expression. These findings suggest that resveratrol alters the cell cycle progression and induce cell death via FASN inhibition in HER2 positive breast cancer.

Effects of anti-proliferative lichen metabolite, protolichesterinic acid on fatty acid synthase, cell signalling and drug response in breast cancer cells

BACKGROUND

The lichen compound (+)-protolichesterinic acid (+)-PA, isolated from Iceland moss, has anti-proliferative effects on several cancer cell lines. The chemical structure of (+)-PA is similar to a known fatty acid synthase (FASN) inhibitor C75.

AIMS

To test whether the anti-proliferative activity of (+)-PA is associated with effects on FASN and HER2 (human epidermal growth factor receptor 2) and major signalling pathways. Synergism between (+)-PA and lapatinib, a HER2 active drug, was also evaluated.

MATERIALS AND METHODS

Pure compound was isolated by preparative high-performance liquid chromatography (HPLC) and purity of (+)-PA analyzed by analytical HPLC. Cell viability was assessed using Crystal violet staining. FASN and HER2 expression was estimated by immunofluorescence. The Meso Scale Discovery (MSD)(®) assay was used to measure activation of ERK1/2 and AKT. Synergism was estimated by the CalcuSyn software.

RESULTS

Treatment with (+)-PA increased FASN expression in SK-BR-3 cells, which overexpress FASN and HER2, implying a compensatory response to inhibition of FASN activity. HER2 expression was decreased suggesting secondary downregulation. ERK1/2 and AKT signalling pathways were inhibited, probably due to reduced levels of HER2. No effects were observed in T-47D cells. Synergism between (+)-PA and lapatinib was observed in the SK-BR-3 cells.

CONCLUSION

Results suggest that the primary effect of (+)-PA is inhibition of FASN activity. Synergistic effects with lapatinib were seen only in SK-BR-3 cells, and not T-47D cells, further supporting the notion that (+)-PA acts by inhibiting FASN with secondary effects on HER2 expression and signalling. (+)-PA could therefore be a suitable agent for further testing, alone or in combination treatment against HER2-overexpressing breast cancer.

Alterations in lipid mediated signaling and Wnt/ β -catenin signaling in DMH induced colon cancer on supplementation of fish oil

Ceramide mediates inhibition of cyclooxygenase-2 (COX-2) which catalyzes formation of prostaglandin further activating peroxisome proliferator-activated receptorγ (PPARγ) and Wnt/β-catenin pathway; and hence plays a critical role in cancer. Therefore, in current study, ceramide, COX-2, 15-deoxy prostaglandin J₂(15-deoxy PGJ₂), PPARγ, and β-catenin were estimated to evaluate the effect of fish oil on lipid mediated and Wnt/β-catenin signaling in colon carcinoma. Male Wistar rats in Group I received purified diet while Groups II and III received modified diet supplemented with FO : CO(1 : 1) and FO : CO(2.5 : 1), respectively. These were further subdivided into controls receiving ethylenediaminetetraacetic acid and treated groups receiving dimethylhydrazine dihydrochloride (DMH)/week for 4 weeks. Animals sacrificed 48 hours after last injection constituted initiation phase and those sacrificed after 16 weeks constituted postinitiation phase. Decreased ceramide and increased PPARγ were observed in postinitiation phase only. On receiving FO+CO(1 : 1)+DMH and FO+CO(2.5 : 1)+DMH in both phases, ceramide was augmented whereas COX-2, 15-deoxy PGJ₂, and nuclear translocation of β-catenin were reduced with respect to cancerous animals. Decrease was more significant in postinitiation phase with FO+CO(2.5 : 1)+DMH. Treatment with oils increased PPARγ in initiation phase but decreased it in postinitiation phase. Hence, fish oil altered lipid mediated signalling in a dose and time dependent manner so as to inhibit progression of colon cancer.

Alpha-mangostin inhibits intracellular fatty acid synthase and induces apoptosis in breast cancer cells

Background

Fatty acid synthase (FAS) has been proven over-expressed in human breast cancer cells and consequently, has been recognized as a target for breast cancer treatment. Alpha-mangostin, a natural xanthone found in mangosteen pericarp, has a variety of biological activities, including anti-cancer effect. In our previous study, alpha-mangostin had been found both fast-binding and slow-binding inhibitions to FAS in vitro. This study was designed to investigate the activity of alpha-mangostin on intracellular FAS activity in FAS over-expressed human breast cancer cells, and to testify whether the anti-cancer activity of alpha-mangostin may be related to its inhibitory effect on FAS.

Methods

We evaluated the cytotoxicity of alpha-mangostin in human breast cancer MCF-7 and MDA-MB-231 cells. Intracellular FAS activity was measured by a spectrophotometer at 340 nm of NADPH absorption. Cell Counting Kit assay was used to test the cell viability. Immunoblot analysis was performed to detect FAS expression level, intracellular fatty acid accumulation and cell signaling (FAK, ERK1/2 and AKT). Apoptotic effects were detected by flow cytometry and immunoblot analysis of PARP, Bax and Bcl-2. Small interfering RNA was used to down-regulate FAS expression and/or activity.

Results

Alpha-mangostin could effectively suppress FAS expression and inhibit intracellular FAS activity, and result in decrease of intracellular fatty acid accumulation. It could also reduce cell viability, induce apoptosis in human breast cancer cells, increase in the levels of the PARP cleavage product, and attenuate the balance between anti-apoptotic and pro-apoptotic proteins of the Bcl-2 family. Moreover, alpha-mangostin inhibited the phosphorylation of FAK. However, the active forms of AKT, and ERK1/2 proteins were not involved in the changes of FAS expression induced by alpha-mangostin.

Conclusions

Alpha-mangostin induced breast cancer cell apoptosis by inhibiting FAS, which provide a basis for the development of xanthone as an agent for breast cancer therapy.

Fatty acid synthase overexpression in adult testicular germ cell tumors: potential role in the progression of non-seminomatous germ cell tumors

Overexpression of fatty acid synthase (FASN), which is a key enzyme responsible for the endogenous synthesis of fatty acids, and its association with multistep progression have been demonstrated in various human malignant tumors. We aimed to clarify the potential role of FASN overexpression in the development and progression of adult testicular germ cell tumors (TGCTs). From the primary sites of a cohort of 113 TGCT cases, we obtained 221 histological components: 53 intratubular germ cell neoplasias, unclassified (IGCNUs), 84 seminomas, 32 embryonal carcinomas, seven choriocarcinomas, 21 yolk sac tumors, and 24 teratomas. Samples were analyzed for overexpression of FASN by immunohistochemistry. Intensities of immunoreactivity and the fraction of positive cells were classified into each four categories (intensity, 0 to 3; fraction, 0-10 % = 1, 11-50 % = 2, 51-80 % = 3, and >80 % = 4). The overall score was determined by multiplication of both scores and overall scores greater than 6 were considered FASN overexpression. On a component basis, FASN overexpression was detected in 8 % of seminomas but not in IGCNUs (0 %) and was detected frequently in non-seminomatous germ cell tumors (NSGCTs) (88 % of embryonal carcinomas, all choriocarcinomas, 81 % of yolk sac tumors, and 54 % of teratomas). There were no cases of a mixed tumor (i.e., a tumor with multiple histological components) that overexpressed FASN in seminoma components but not in co-existing NSGCT components, suggesting sequential progression. Our immunohistochemical data suggest that FASN overexpression occurs as a late event during the progression from IGCNUs/seminomas to NSGCTs.

Loss of fatty acid synthase inhibits the "HER2-PI3K/Akt axis" activity and malignant phenotype of Caco-2 cells

Background

Fatty acid synthase (FASN) is frequently activated and overexpressed in human cancers, and plays a crucial role in the carcinogenesis of various cancers. In this study, our aims were to explore the role of FASN in regulating the “HER2-PI3K/Akt axis” activity and malignant phenotype of colorectal cancer.

Methods

Caco-2 cells with a high expression of both HER2 and FASN were selected for functional characterization. Caco-2 cells were transfected with either the FASN specific RNAi plasmid or the negative control RNAi plasmid, followed by the RT-qPCR and western blot to examine the expression of FASN, HER2, PI3K and Akt. The MTT and colony formation assays were used to assess the proliferation potential. The migration was investigated by the transwell, and the apoptosis and cell cycle were assayed by the flow cytometry.

Results

Notably, the expression of FASN, HER2, PI3K and Akt were downregulated upon a silence of FASN. The proliferation was decreased after a downregulation of FASN, which was consistent with an increased apoptosis rate. The migration was also impaired in FASN-silenced cells.

Conclusion

A downregulation of FASN effectively inhibits the activity of “HER2-PI3K/Akt axis” and alters the malignant phenotype in colorectal cancer cells.

The mitochondrial H(+)-ATP synthase and the lipogenic switch: new core components of metabolic reprogramming in induced pluripotent stem (iPS) cells

Induced pluripotent stem (iPS) cells share some basic properties, such as self-renewal and pluripotency, with cancer cells, and they also appear to share several metabolic alterations that are commonly observed in human tumors. The cancer cells' glycolytic phenotype, first reported by Otto Warburg, is necessary for the optimal routing of somatic cells to pluripotency. However, how iPS cells establish a Warburg-like metabolic phenotype and whether the metabolic pathways that support the bioenergetics of iPS cells are produced by the same mechanisms that are selected during the tumorigenic process remain largely unexplored. We recently investigated whether the reprogramming-competent metabotype of iPS cells involves changes in the activation/expression status of the H(+)-ATPase, which is a core component of mitochondrial oxidative phosphorylation that is repressed at both the activity and protein levels in human carcinomas, and of the lipogenic switch, which refers to a marked overexpression and hyperactivity of the acetyl-CoA carboxylase (ACACA) and fatty acid synthase (FASN) lipogenic enzymes that has been observed in nearly all examined cancer types. A comparison of a starting population of mouse embryonic fibroblasts and their iPS cell progeny revealed that somatic cell reprogramming involves a significant increase in the expression of ATPase inhibitor factor 1 (IF1), accompanied by extremely low expression levels of the catalytic β-F1-ATPase subunit. The pharmacological inhibition of ACACA and FASN activities markedly decreases reprogramming efficiency, and ACACA and FASN expression are notably upregulated in iPS cells. Importantly, iPS cells exhibited a significant intracellular accumulation of neutral lipid bodies; however, these bodies may be a reflection of intense lysosomal/autophagocytic activity rather than bona fide lipid droplet formation in iPS cells, as they were largely unresponsive to pharmacological modulation of PPARgamma and FASN activities. The AMPK agonist metformin, which endows somatic cells with a bioenergetic infrastructure that is protected against reprogramming, was found to drastically elongate fibroblast mitochondria, fully reverse the high IF1/β-F1-ATPase ratio and downregulate the ACACA/FASN lipogenic enzymes in iPS cells. The mitochondrial H(+)-ATP synthase and the ACACA/FASN-driven lipogenic switch are newly characterized as instrumental metabolic events that, by coupling the Warburg effect to anabolic metabolism, enable de-differentiation during the reprogramming of somatic cells to iPS cells.

Age and space irradiation modulate tumor progression: implications for carcinogenesis risk

Age plays a major role in tumor incidence and is an important consideration when modeling the carcinogenesis process or estimating cancer risks. Epidemiological data show that from adolescence through middle age, cancer incidence increases with age. This effect is commonly attributed to a lifetime accumulation of cellular, particularly DNA, damage. However, during middle age the incidence begins to decelerate and, for many tumor sites, it actually decreases at sufficiently advanced ages. We investigated if the observed deceleration and potential decrease in incidence could be attributed to a decreased capacity of older hosts to support tumor progression, and whether HZE [high atomic number (Z), high energy (E)] radiation differentially modulates tumor progression in young vs. middle-age hosts, issues that are relevant to estimating carcinogenesis risk for astronauts. Lewis lung carcinoma (LLC) cells were injected into syngeneic mice (143 and 551 days old), which were then subject to whole-body (56)Fe irradiation (1 GeV/amu). Three findings emerged: (1) among unirradiated animals, substantial inhibition of tumor progression and significantly decreased tumor growth rates were seen for middle-aged mice compared to young mice, (2) whole-body (56)Fe irradiation inhibited tumor progression in both young and middle-aged mice (with greater suppression seen in case of young animals), with little effect on tumor growth rates, and (3) (56)Fe irradiation suppressed tumor progression in young mice to a degree that was not significantly different than transiting from young to middle-aged. Thus, (56)Fe irradiation acted similar to aging with respect to tumor progression. We further investigated the molecular underpinnings driving the radiation modulation of tumor dynamics in young and middle-aged mice. Through global gene expression analysis, the key players, FASN, AKT1 and the CXCL12/CXCR4 complex, were determined to be contributory. In sum, these findings demonstrated a reduced capacity of middle-aged hosts to support the progression phase of carcinogenesis and identify molecular factors that contribute to HZE radiation modulation of tumor progression as a function of age.

Different fatty acid metabolism effects of (-)-epigallocatechin-3-gallate and C75 in adenocarcinoma lung cancer

Background

Fatty acid synthase (FASN) is overexpressed and hyperactivated in several human carcinomas, including lung cancer. We characterize and compare the anti-cancer effects of the FASN inhibitors C75 and (−)-epigallocatechin-3-gallate (EGCG) in a lung cancer model.

Methods

We evaluated in vitro the effects of C75 and EGCG on fatty acid metabolism (FASN and CPT enzymes), cellular proliferation, apoptosis and cell signaling (EGFR, ERK1/2, AKT and mTOR) in human A549 lung carcinoma cells. In vivo, we evaluated their anti-tumour activity and their effect on body weight in a mice model of human adenocarcinoma xenograft.

Results

C75 and EGCG had comparable effects in blocking FASN activity (96,9% and 89,3% of inhibition, respectively). In contrast, EGCG had either no significant effect in CPT activity, the rate-limiting enzyme of fatty acid β-oxidation, while C75 stimulated CPT up to 130%. Treating lung cancer cells with EGCG or C75 induced apoptosis and affected EGFR-signaling. While EGCG abolished p-EGFR, p-AKT, p-ERK1/2 and p-mTOR, C75 was less active in decreasing the levels of EGFR and p-AKT. In vivo, EGCG and C75 blocked the growth of lung cancer xenografts but C75 treatment, not EGCG, caused a marked animal weight loss.

Conclusions

In lung cancer, inhibition of FASN using EGCG can be achieved without parallel stimulation of fatty acid oxidation and this effect is related mainly to EGFR signaling pathway. EGCG reduce the growth of adenocarcinoma human lung cancer xenografts without inducing body weight loss. Taken together, EGCG may be a candidate for future pre-clinical development.

A novel inhibitor of fatty acid synthase shows activity against HER2+ breast cancer xenografts and is active in anti-HER2 drug-resistant cell lines

Introduction

Inhibiting the enzyme Fatty Acid Synthase (FASN) leads to apoptosis of breast carcinoma cells, and this is linked to human epidermal growth factor receptor 2 (HER2) signaling pathways in models of simultaneous expression of FASN and HER2.

Methods

In a xenograft model of breast carcinoma cells that are FASN+ and HER2+, we have characterised the anticancer activity and the toxicity profile of G28UCM, the lead compound of a novel family of synthetic FASN inhibitors. In vitro, we analysed the cellular and molecular interactions of combining G28UCM with anti-HER drugs. Finally, we tested the cytotoxic ability of G28UCM on breast cancer cells resistant to trastuzumab or lapatinib, that we developed in our laboratory.

Results

In vivo, G28UCM reduced the size of 5 out of 14 established xenografts. In the responding tumours, we observed inhibition of FASN activity, cleavage of poly-ADPribose polymerase (PARP) and a decrease of p-HER2, p- protein kinase B (AKT) and p-ERK1/2, which were not observed in the nonresponding tumours. In the G28UCM-treated animals, no significant toxicities occurred, and weight loss was not observed. In vitro, G28UCM showed marked synergistic interactions with trastuzumab, lapatinib, erlotinib or gefitinib (but not with cetuximab), which correlated with increases in apoptosis and with decreases in the activation of HER2, extracellular signal-regulated kinase (ERK)1/2 and AKT. In trastuzumab-resistant and in lapatinib-resistant breast cancer cells, in which trastuzumab and lapatinib were not effective, G28UCM retained the anticancer activity observed in the parental cells.

Conclusions

G28UCM inhibits fatty acid synthase (FASN) activity and the growth of breast carcinoma xenografts in vivo, and is active in cells with acquired resistance to anti-HER2 drugs, which make it a candidate for further pre-clinical development.

CDDO-methyl ester delays breast cancer development in BRCA1-mutated mice

The breast cancer-associated gene 1 (BRCA1) is the most frequently mutated tumor suppressor gene in familial breast cancers. Mutations in BRCA1 also predispose to other types of cancers, pointing to a fundamental role of this pathway in tumor suppression and emphasizing the need for effective chemoprevention in these high-risk patients. Because the methyl ester of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me) is a potent chemopreventive agent, we tested its efficacy in a highly relevant mouse model of BRCA1-mutated breast cancer. Beginning at 12 weeks of age, Brca1(Co/Co); MMTV-Cre;p53(+/-) mice were fed powdered control diet or diet containing CDDO-Me (50 mg/kg diet). CDDO-Me significantly (P < 0.05) delayed tumor development in the Brca1-mutated mice by an average of 5.2 weeks. We also observed that levels of ErbB2, p-ErbB2, and cyclin D1 increased in a time-dependent manner in the mammary glands in Brca1-deficient mice, and CDDO-Me inhibited the constitutive phosphorylation of ErbB2 in tumor tissues from these mice. In BRCA1-deficient cell lines, the triterpenoids directly interacted with ErbB2, decreased constitutive phosphorylation of ErbB2, inhibited proliferation, and induced G(0)-G(1) arrest. These results suggest that CDDO-Me has the potential to prevent BRCA1-mutated breast cancer.

Anticancer Properties of PPARalpha-Effects on Cellular Metabolism and Inflammation

Peroxisome proliferator-activated receptors (PPARs) have lately attracted much attention as therapeutic targets. Previously, PPAR ligands were associated with the treatment of diabetes, hyperlipidemia and cardiovascular diseases, as they modulate the expression of genes regulating glucose and lipid metabolism. Recently, PPAR ligands have been also considered as potential anticancer agents, with relatively low systemic toxicity. The emerging evidence for antiproliferative, proapoptotic, antiinflammatory and potential antimetastatic properties of PPARα ligands prompted us to discuss possible roles of PPARα in tumor suppression. PPARα activation can target cancer cells energy balance by blocking fatty acid synthesis and by promoting fatty acid β-oxidation. In the state of limited nutrient availability, frequently presents in the tumor microenvironment, PPARα cooperates with AMP-dependent protein kinase in: (i) repressing oncogenic Akt activity, (ii) inhibiting cell proliferation, and (iii) forcing glycolysis-dependent cancer cells into “metabolic catastrophe.” Other potential anticancer effects of PPARα include suppression of inflammation, and upregulation of uncoupling proteins (UCPs), which attenuates mitochondrial reactive oxygen species production and cell proliferation. In conclusion, there are strong premises that the low-toxic and well-tolerated PPAR ligands should be considered as new therapeutic agents to fight disseminating cancer, which represents the major challenge for modern medicine and basic research.

Antitumor effect of orlistat, a fatty acid synthase inhibitor, is via activation of caspase-3 on human colorectal carcinoma-bearing animal

We established a HT-29/tk-luc human colorectal carcinoma-bearing animal model for the study of the inhibition effect and mechanism of orlistat, a fatty acid synthase (FASN) inhibitor. The results showed that orlistat caused cell cycle arrest at G1 phase, and triggered apoptosis through caspase-3 activation. The tumor inhibition effect of orlistat may also due to the inhibition of fatty acid synthesis without altering FASN activity. The tumor size of orlistat-treated mice in vivo was significantly smaller than that of the controls with 55% inhibition. The therapeutic efficacy was further confirmed with the bioluminescent imaging and nuclear molecular imaging with ¹³¹I-FIAU/gamma scintigraphy and ¹¹C-acetate/microPET. We suggest that FASN is a potential target for the treatment of human colorectal carcinoma.

ErbB receptors and fatty acid synthase expression in aggressive head and neck squamous cell carcinomas

SUMMARY

Overexpression of ErbB receptors is frequent in head and neck squamous cell carcinomas (HNSCC) and seems to be correlated with tumor progression and metastasis. Fatty acid synthase (FASN), the key lipogenic enzyme responsible for the endogenous synthesis of fatty acids, is regulated by ErbB2 and overexpressed in several human malignancies.

METHODS

This study was performed to examine the immunohistochemical expression patterns of ErbB1, ErbB2, ErbB3, ErbB4, and FASN in a tissue microarray, containing 33 representative areas from aggressive primary HNSCC (whose patients had distant metastasis), and 21 matched lung metastasis.

RESULTS

Strong correlation among the expression of ErbB family receptors was found (ErbB1-ErbB2 P = 0.008, ErbB1-ErbB4 P = 0.018, EbB2-ErbB3 P = 0.001, ErbB2-ErbB4 P = 0.006, ErbB3-ErbB4 P=0.012) in the HNSCC. FASN expression was significantly associated with ErbB2 (P = 0.024). Lymphatic permeation was correlated with ErbB3 (P = 0.033) and histological grade with ErbB4 staining (P = 0.050). ErbB1 and ErbB2 were found mainly in patients with smoking habit (P = 0.011 and P = 0.027), and ErbB2 was associated with alcohol consumption and clinical stage (P = 0.014 and P = 0.031). Finally, FASN was overexpressed in lung metastasis, in comparison with matched HNSCC samples (P = 0.006).

CONCLUSIONS

  The results showed that high FASN immunohistochemical expression is a feature of HNSCC lung metastasis, and ErbB1-ErbB2, ErbB1-ErbB4, ErbB2-ErbB3, ErbB2-ErbB4, and ErbB3-ErbB4 expression levels are correlated in the respective primary tumors, being ErbB2 the preferred coexpression partner of all the other ErbB receptors.

Metabolic alterations and targeted therapies in prostate cancer

Cancer cells synthesize de novo large amounts of fatty acids and cholesterol, irrespective of the circulating lipid levels and benefit from this increased lipid synthesis in terms of growth advantage, self-survival and drug resistance. Key lipogenic alterations that commonly occur in prostate cancer include over-expression of the enzyme fatty acid synthase (FASN) and deregulation of the 5-AMP-activated protein kinase (AMPK). FASN is a key metabolic enzyme that catalyses the synthesis of palmitate from the condensation of malonyl-CoA and acetyl-CoA de novo and plays a central role in energy homeostasis, by converting excess carbon intake into fatty acids for storage. AMPK functions as a central metabolic switch that governs glucose and lipid metabolism. Recent interest has focused on the potential of targeting metabolic pathways that may be altered during prostate tumorigenesis and progression. Several small molecule inhibitors of FASN have now been described or in development for therapeutic use; in addition, drugs that directly or indirectly induce AMPK activation have potential benefit in prostate cancer prevention and treatment.

Fatty acid synthase phosphorylation: a novel therapeutic target in HER2-overexpressing breast cancer cells

Introduction

The human epidermal growth factor receptor 2 (HER2) is a validated therapeutic target in breast cancer. Heterodimerization of HER2 with other HER family members results in enhanced tyrosine phosphorylation and activation of signal transduction pathways. HER2 overexpression increases the translation of fatty acid synthase (FASN), and FASN overexpression markedly increases HER2 signaling, which results in enhanced cell growth. However, the molecular mechanism and regulation of HER2 and FASN interaction are not well defined. Lapatinib is a small-molecule tyrosine kinase inhibitor that blocks phosphorylation of the epidermal growth factor receptor and HER2 in breast cancer cells, resulting in apoptosis. We hypothesized that FASN is directly phosphorylated by HER2, resulting in enhanced signaling and tumor progression in breast cancer cells.

Methods

Using mass spectrometry, we identified FASN as one of the proteins that is dephosphorylated by lapatinib in SKBR3 breast cancer cells. Immunofluorescence, immunoprecipitation, Western blotting, a kinase assay, a FASN enzymatic activity assay, an invasion assay, a cell viability assay and zymography were used to determine the role of FASN phosphorylation in invasion of SKBR3 and BT474 cells. The FASN inhibitor C75 and small interfering RNA were used to downregulate FASN expression and/or activity.

Results

Our data demonstrated that FASN is phosphorylated when it is in complex with HER2. FASN phosphorylation was induced by heregulin in HER2-overexpressing SKBR3 and BT474 breast cancer cells. Heregulin-induced FASN phosphorylation resulted in increased FASN enzymatic activity, which was inhibited by lapatinib. The FASN inhibitor C75 suppressed FASN activity by directly inhibiting HER2 and FASN phosphorylation. Blocking FASN phosphorylation and activity by lapatinib or C75 suppressed the activity of matrix metallopeptidase 9 and inhibited invasion of SKBR3 and BT474 cells.

Conclusions

FASN phosphorylation by HER2 plays an important role in breast cancer progression and may be a novel therapeutic target in HER2-overexpressing breast cancer cells.

Fatty acid synthase as a potential therapeutic target in cancer

Fatty acid synthase (FASN) is a key enzyme involved in neoplastic lipogenesis. Overexpression of FASN is common in many cancers, and accumulating evidence suggests that it is a metabolic oncogene with an important role in tumor growth and survival, making it an attractive target for cancer therapy. Early small-molecule FASN inhibitors such as cerulenin, C75 and orlistat have been shown to induce apoptosis in several cancer cell lines and to induce tumor growth delay in several cancer xenograft models but their mechanism is still not well understood. These molecules suffer from pharmacological limitations and weight loss as a side effect that prevent their development as systemic drugs. Several potent inhibitors have recently been reported that may help to unravel and exploit the full potential of FASN as a target for cancer therapy in the near future. Furthermore, novel sources of FASN inhibitors, such as green tea and dietary soy, make both dietary manipulation and chemoprevention potential alternative modes of therapy in the future.

Novel Inhibitors of Fatty Acid Synthase with Anticancer Activity

PURPOSE: Fatty acid synthase (FASN) is overexpressed in human breast carcinoma. The natural polyphenol (-)-epigallocatechin-3-gallate blocks in vitro FASN activity and leads to apoptosis in breast cancer cells without any effects on carnitine palmitoyltransferase-1 (CPT-1) activity, and in vivo, does not decrease body weight. We synthesized a panel of new polyphenolic compounds and tested their effects on breast cancer models. EXPERIMENTAL DESIGN: We evaluated the in vitro effects of the compounds on breast cancer cell growth (SK-Br3, MCF-7, and MDA-MB-231), apoptosis [as assessed by cleavage of poly(ADP-ribose) polymerase], cell signaling (HER2, ERK1/2, and AKT), and fatty acid metabolism enzymes (FASN and CPT-1). In vivo, we have evaluated their antitumor activity and their effect on body weight in a mice model of BT474 breast cancer cells. RESULTS: Two compounds potently inhibited FASN activity and showed high cytotoxicity. Moreover, the compounds induced apoptosis and caused a marked decrease in the active forms of HER2, AKT, and ERK1/2 proteins. Interestingly, the compounds did not stimulate CPT-1 activity in vitro. We show evidence that one of the FASN inhibitors blocked the growth of BT474 breast cancer xenografts and did not induce weight loss in vivo. CONCLUSIONS: The synthesized polyphenolic compounds represent a novel class of FASN inhibitors, with in vitro and in vivo anticancer activity, that do not exhibit cross-activation of beta-oxidation and do not induce weight loss in animals. One of the compounds blocked the growth of breast cancer xenografts. These FASN inhibitors may represent new agents for breast cancer treatment. (Clin Cancer Res 2009;15(24):7608-15).

Fine-tuning the lipogenic/lipolytic balance to optimize the metabolic requirements of cancer cell growth: molecular mechanisms and therapeutic perspectives

Evolving evidence suggest that metabolic requirements for cell proliferation are identical in all normal and cancer cells. HER2 oncogene-overexpressors, a highly aggressive subtype of human cancer cells, constitute one of the best examples of how malignant cells maximize their ability to acquire and metabolize nutrients in a manner conductive to proliferation rather than efficient ATP production. HER2-overexpressors optimize their requirements of rapid cancer cell growth by fine-tuning a double [lipogenic/lipolytic]-edged metabolic sword. On the one edge, HER2 oncogene overexpression triggers redundant signaling cascades to ensure that all the major enzymes involved in de novo fatty acid (FA) synthesis will facilitate aerobic glycolysis instead of oxidative phosphorylation for energy production (Warburg effect). HER2 also establishes a positive bidirectional relationship with the key lipogenic enzyme Fatty Acid Synthase (FASN) that rapidly senses and respond to any disturbance in the flux of lipogenic substrates (e.g. NADPH and acetyl-CoA) and lipogenesis end-products (i.e. palmitate). On the other edge, HER2 overexpression arranges detoxifying mechanisms by upregulating PPARgamma, a well established positive regulator role of adipogenesis and lipid storage in cell types with active lipid metabolism. PPARgamma establishes a lipogenesis/lipolysis joining-point that enables HER2-positive cancer cells to avoid endogenous palmitate toxicity while securing palmitate into fat stores to avoid palmitate feedback on FASN functioning. The ability of HER2 to supercharge lipogenesis (by activating regulatory circuits that activate and fuel the lipogenic enzyme FASN) while averting lipotoxicity (by promoting conversion and storage of excess FAs to triglycerides in a PPARgamma-dependent manner) supports the notion that best adapted cancer phenotypes are addicted to oncogenic lipid metabolism for cell proliferation and survival. It is conceptually attractive to assume that we can crash HER2-driven rapid cell proliferation by inhibiting "motor refueling" (upon blockade of lipogenic enzymes), by losing the "lipolytic brake" (upon blockade of PPARgamma) and/or by sticking the "lipogenic gas pedal" (upon supplementation with dietary FAs).

Biomolecular markers in cancer of the tongue

The incidence of tongue cancer is increasing worldwide, and its aggressiveness remains high regardless of treatment. Genetic changes and the expression of abnormal proteins have been frequently reported in the case of head and neck cancers, but the little information that has been published concerning tongue tumours is often contradictory. This review will concentrate on the immunohistochemical expression of biomolecular markers and their relationships with clinical behaviour and prognosis. Most of these proteins are associated with nodal stage, tumour progression and metastases, but there is still controversy concerning their impact on disease-free and overall survival, and treatment response. More extensive clinical studies are needed to identify the patterns of molecular alterations and the most reliable predictors in order to develop tailored anti-tumour strategies based on the targeting of hypoxia markers, vascular and lymphangiogenic factors, epidermal growth factor receptors, intracytoplasmatic signalling and apoptosis.

[Fatty acid synthase: a new anti-tumor target]

Fatty acid synthase (FASN), an enzyme capable of de novo fatty acid synthesis, is highly expressed and activated in most human carcinomas. FASN is associated with poor prognosis in prostate and breast cancer and its inhibition is selectively cytotoxic to human cancer cells. Thus, FASN and fatty acid metabolism have become an important focus for the diagnostic and treatment of cancer. In this sense, there is an increasing interest in identifying and developing new antitumor compounds that inhibit FASN.

The tyrosine kinase receptor HER2 (erbB-2): from oncogenesis to adipogenesis

Recent experimental evidences begin to support the notion that the proto-oncogene HER2 (erbB-2) might unexpectedly function to modulate the adipogenic conversion of preadipocytes. Two opposing scenarios have been proposed, however, to explain the influence of HER2 on adipocyte differentiation. In one hand, down-modulation of HER2 expression and pharmacological reduction of HER2 activity have been related to enhanced adipocyte differentiation. On the contrary, an increased abundance in HER2 has been described in differentiated adipocytes compared with preadipocytes. Considering that expression and activity of the lipogenic enzyme Fatty Acid Synthase (FASN) become up-regulated during adipogenic conversion, we recently hypothesized that a "HER2 --> FASN axis" -a "lipogenic benefit" that has been shown to enhance cancer cell proliferation, survival, chemoresistance and metastasis in biologically aggressive subgroups of breast carcinomas-might also naturally work during the differentiation of preadipocytes. To definitely clarify if the discrepancy between the opposing theories for a role of HER2 during adipocyte differentiation related to the experimental approach utilized to compare the abundance of HER2 in undifferentiated and differentiated adipocytes (i.e., cell lysates containing equivalent protein content versus cell lysates generated from similar cell numbers), we here took advantage of a high content microscopy approach. Using an automated confocal imaging platform, we monitored the expression status of the adipogenic marker FASN and its timing relationship with HER2 not only in individual 3T3-L1 cells but further in whole cultures of 3T3-L1 preadipocytes undergoing adipogenic conversion. Our findings not only confirm a non-oncogenic role for HER2 in the process of adipose differentiation but further suggest that HER2 might represent a previously unrecognized target to manage obesity via the lipogenic enzyme FASN.

Altered detoxification status and increased resistance to oxidative stress by K-ras transformation

Mutated K-ras is frequently found in human malignancies and plays a key role in many signal transduction processes resulting in an altered gene and/or protein expression pattern. Proteins controlled by a constitutive activated mitogen-activated protein kinase pathway are primarily related to alterations in the mitochondrial and nuclear compartments. Therefore, different K-Ras mutants and respective control cells were subjected to two-dimensional gel electrophoresis using basic pH gradients. This approach led to the identification of differentially expressed proteins, such as members of the heterogeneous ribonucleoprotein family, and enzymes involved in cellular detoxification as well as in oxidative stress. Increased expression of these enzymes was paralleled by an elevated tolerance of K-ras mutants against the cytotoxic potential of hydrogen peroxide and formaldehyde as well as an altered redox status based on enhanced intracellular glutathione (GSH) levels indicating an improved detoxification potential of defined K-ras transfectants, whereas down-regulation by RNA interference of candidate proteins reversed the tolerance against these compounds. This hypothesis is supported by an up-regulated expression of a key enzyme of the pentose phosphate pathway resulting in an increased production of NADPH required for anabolic processes as well as the rebuilding of oxidized GSH. Both the enhanced resistance against xenobiotic compounds as well as an altered oxidative pathway might confer growth advantages for tumor cells carrying dominant-positive K-ras mutations such as in lung or pancreatic adenocarcinoma.

A new mechanism of drug resistance in breast cancer cells: fatty acid synthase overexpression-mediated palmitate overproduction

Multidrug resistance is a major problem in successful cancer chemotherapy. Various mechanisms of resistance, such as ABC transporter-mediated drug efflux, have been discovered using established model cancer cell lines. While characterizing a drug-resistant breast cancer cell line, MCF7/AdVp3000, we found that fatty acid synthase (FASN) is overexpressed. In this study, we showed that ectopic overexpression of FASN indeed causes drug resistance and that reducing the FASN expression increased the drug sensitivity in breast cancer cell lines MCF7 and MDA-MB-468 but not in the normal mammary epithelial cell line MCF10A1. Use of FASN inhibitor, Orlistat, at low concentrations also sensitized cells with FASN overexpression to anticancer drugs. The FASN-mediated drug resistance appears to be due to a decrease in drug-induced apoptosis from an overproduction of palmitic acid by FASN. Together with previous findings of FASN as a poor prognosis marker for breast cancer patients, our results suggest that FASN overexpression is a new mechanism of drug resistance and may be an ideal target for chemosensitization in breast cancer chemotherapy.

ErbB2 and fatty acid synthase (FAS) expression in 102 squamous cell carcinomas of the tongue: Correlation with clinical outcomes

The oncoprotein ErbB2 (HER-2/neu) is a tyrosine kinase cell surface receptor overexpressed in several human malignancies, including oral squamous cell carcinoma (OSCC). ErbB2 was recently shown to regulate the expression of fatty acid synthase (FAS), a multifunctional enzyme complex responsible for the de novo biosynthesis of saturated fatty acids. Here we evaluated the relationship between the immunohistochemical expression of ErbB2, FAS, and Ki-67 with the clinicopathologic characteristics of tongue squamous cell carcinoma (SCC). One hundred and two patients with tongue SCC treated from 1990 to 1995 were studied. Clinical and treatment data were obtained from the medical records and histopathological features revised. Paraffin-embedded tissues were submitted to standard immunohistochemical reactions for ErbB2, FAS and Ki-67. A strong positive correlation between ErbB2 labeling at the cell membrane and FAS expression was found in the tongue SCC samples (p<0.0001). The intracytoplasmatic expression of ErbB2 as well as Ki-67 nuclear staining were significantly associated with a high risk of recurrence by predicting both disease free survival (log-rank test, p=0.0096 and p=0.0047, respectively) and overall survival (log-rank test, p=0.0029 and p=0.0001, respectively). Taken together, our results suggest that the immunolocalization of ErbB2 at the cell surface of malignant oral keratinocytes is linked to FAS expression whereas the intracytoplasmatic ErbB2 or Ki-67 staining predict high risk of recurrence of tongue SCC.

An easy, rapid and objective mathematical method to identify fatty acid synthase (oncogenic antigen-519) modulators with potential anticancer value

Fatty acid synthase (FASN) is a novel druggable target for metabolically treating and preventing human malignancies. We envisioned that if loss of sensitivity to C75 (a slow-binding FASN inhibitor) occurs in parallel with loss of FASN expression and/or activity, a mathematical assessment of the nature of the interaction between investigational FASN modulators and C75 may predict the ability of experimental compounds to regulate FASN. We statistically compared the arithmetical sums of the anti-proliferative effects obtained when FASN modulators and C75 were used as single agents to those observed experimentally when agents were actually combined in a sequential schedule (i.e., FASN modulator-->C75). A reduced sensitivity to C75 (antagonism) occurred when compounds down-regulated FASN activity/expression, while an enhanced C75 efficacy (synergism) was found following exposure to FASN up-regulators. This "C75-sensitivity test" might offer an easy, rapid and objective method to identify FASN inhibitors with potential anticancer value in human cancer.

Dietary soy protein inhibits DNA damage and cell survival of colon epithelial cells through attenuated expression of fatty acid synthase

Dietary intake of soy protein decreases tumor incidence in rat models of chemically induced colon cancer. We hypothesized that decreased expression of fatty acid synthase (FASN) underlies, in part, the tumor-preventive effects of soy protein, since FASN overexpression characterizes early tumorigenesis. Here, we show that colonic FASN levels are reduced with dietary intake of soy protein isolate (SPI), compared with a control casein diet, in male Sprague-Dawley rats administered the colon carcinogen azoxymethane. SPI consumption resulted in decreased serum insulin levels and decreased azoxymethane-induced tumor suppressor p53 phosphorylation in colon crypt epithelium. To evaluate potential links between insulin and FASN leading to DNA damage, C2(BBe)1 colon epithelial cells, treated with insulin and/or the carcinogen N-nitroso-N-methylurea (NMU), were evaluated for DNA damage and apoptosis after transfection with control or FASN small interfering RNAs (siRNAs). While the numbers of DNA apurinic/apyrimidinic sites (biomarker of DNA damage) induced by NMU were unaffected by transfection of FASN siRNA, insulin induction of these sites was decreased with FASN knockdown. By contrast, NMU-induced apoptosis of C2(BBe)1, as well as intestinal epithelial cell (IEC)-6, was enhanced by transfected FASN siRNA. Increased FASN expression in IEC-6 cells by addition of liver X receptor agonist T0901317 did not affect apurinic/apyrimidinic site number, but enhanced cell killing by cerulenin, a FASN inhibitor. Moreover, insulin rescued NMU-treated cells from apoptosis in an FASN-dependent manner. Results suggest that dietary SPI, by decreasing circulating insulin levels and colon FASN expression, attenuates insulin-induced DNA damage and FASN-mediated anti-apoptosis during carcinogenesis, resulting in an overall reduced tumorigenic state.

Overexpression of fatty acid synthase gene activates HER1/HER2 tyrosine kinase receptors in human breast epithelial cells

OBJECTIVES

More than 50 years ago, we learned that breast cancer cells (and those of many other types of tumour) endogenously synthesize 95% of fatty acids (FAs) de novo, despite having adequate nutritional lipid supply. Today, we know that breast cancer cells benefit from this phenomenon in terms of enhanced cell proliferation, survival, chemoresistance and metastasis. However, the exact role of the major lipogenic enzyme fatty acid synthase (FASN) as cause, correlate or facilitator of breast cancer remains unidentified.

MATERIALS AND METHODS

To evaluate a causal effect of FASN-catalysed endogenous FA biosynthesis in the natural history of breast cancer disease, HBL100 cells (an SV40-transformed in vitro model for near-normal gene expression in the breast epithelium), and MCF10A cells (a non-transformed, near diploid, spontaneously immortalized human mammary epithelial cell line) were acutely forced to overexpress the human FASN gene.

RESULTS

Following transient transfection with plasmid pCMV6-XL4 carrying full-length human FASN cDNA (gi: NM 004104), HBL100 cells enhanced their endogenous lipid synthesis while acquiring canonical oncogenic properties such as increased size and number of colonies in semisolid (i.e. soft-agar) anchorage-independent cultures. Anchorage-dependent cell proliferation assays in low serum (0.1% foetal bovine serum), MTT-based assessment of cell metabolic status and cell death ELISA-based detection of apoptosis-induced DNA-histone fragmentation, together revealed that sole activation of endogenous FA biosynthesis was sufficient to significantly enhance breast epithelial cell proliferation and survival. When analysing molecular mechanisms by which acute activation of de novo FA biosynthesis triggered a transformed phenotype, HBL100 cells, transiently transfected with pCMV6-XL4/FASN, were found to exhibit a dramatic increase in the number of phosphor-tyrosine (Tyr)-containing proteins, as detected by 4G10 antiphosphor-Tyr monoclonal antibody. Phosphor-Tyr-specific antibodies recognizing the phosphorylation status of either the 1173 Tyr residue of epidermal growth factor receptor (HER1) or the 1248 Tyr residue of HER2, further revealed that FASN-induced Tyr-phosphorylation at approximately 180 kDa region mainly represented that of these key members of the HER (erbB) network, which remained switched-off in mock-transfected HBL100 cells. ELISA and immunoblotting procedures demonstrated that FASN overactivation significantly increased (> 200%) expression levels of epidermal growth factor receptor and HER2 proteins in HBL100 cells. Proteome Profilertrade mark antibody arrays capable of simultaneously detecting relative levels of phosphorylation of 42 phospho-receptor Tyr-kinases (RTKs) confirmed that acute activation of endogenous FA biosynthesis specifically promoted hyper-Tyr-phosphorylation of HER1 and HER2 in MCF10A cells. This FASN-triggered HER1/HER2-breast cancer-like phenotype was specifically inhibitable either by FASN inhibitor C75 or by Tyr-kinase inhibitors (TKIs) gefitinib (Iressa) and lapatinib (Tykerb) but not by chemotherapeutic agents such as cisplatin. Transient overexpression of FASN dramatically increased HBL100 breast epithelial cells' sensitivity to cytotoxic effects of C75, gefitinib and lapatinib (approximately 8, 10 and > 15 times, respectively), while significantly decreasing (approximately 3 times) cisplatin efficacy.

CONCLUSIONS

Although we cannot definitely establish FASN as a novel oncogene in breast cancer, this study reveals for the first time that exacerbated endogenous FA biosynthesis in non-cancerous epithelial cells is sufficient to induce a cancer-like phenotype functionally dependent on the HER1/HER2 duo. These findings may perhaps radically amend our current perspective of endogenously synthesized fat, as on its own, it appears to actively increase signal-to-noise ratio in the HER1/HER2-driven progression of human breast epithelial cells towards malignancy.

Fatty acid synthase and the lipogenic phenotype in cancer pathogenesis

There is a renewed interest in the ultimate role of fatty acid synthase (FASN)--a key lipogenic enzyme catalysing the terminal steps in the de novo biogenesis of fatty acids--in cancer pathogenesis. Tumour-associated FASN, by conferring growth and survival advantages rather than functioning as an anabolic energy-storage pathway, appears to necessarily accompany the natural history of most human cancers. A recent identification of cross-talk between FASN and well-established cancer-controlling networks begins to delineate the oncogenic nature of FASN-driven lipogenesis. FASN, a nearly-universal druggable target in many human carcinomas and their precursor lesions, offers new therapeutic opportunities for metabolically treating and preventing cancer.

Fatty acid synthase inhibitors cerulenin and C75 retard growth and induce caspase-dependent apoptosis in human melanoma A-375 cells

Fatty acid synthase (FAS) has been shown previously to be highly expressed in breast and prostate carcinomas, but has low expression level in normal tissues. We also found in this study that FAS was expressed in a number of cancer cell lines of different histotypes. The growth-inhibitory effects of FAS inhibitors cerulenin and C75 were then investigated on these cancer cell lines, particularly the human melanoma A-375. MTT assay revealed that the cancer cell proliferation and viability was reduced dose- and time-dependently by 20.8%-87.1% of the control levels after 24 and 48 h of treatment with 20-160 microM of the inhibitor. Immunoblotting studies showed that both cerulenin and C75 induced poly(ADP-ribose) polymerase (PARP) cleavage in the melanoma cells dose-dependently. Procaspase-3 was also found to be processed into the active and smaller 17 and 19 kDa subunits, and administration of pan-caspase inhibitor Z-VAD-FMK completely rescued the cells from PARP cleavage. This indicated that the cerulenin- and C75-induced apoptosis involved caspase activation. The proapoptotic effects of the FAS inhibitors were further confirmed using confocal microscopy with annexin-V FITC and propidium iodide staining. DNA flow cytometric studies demonstrated that the FAS inhibitors accumulated G2/M cells preceding the elevation of sub G1 or apoptotic cells with fragmented DNA. The induced cell cycle arrest and apoptosis were associated with elevation of p21 and depletion of Bcl-xL and Mcl-1, respectively. Results from this study suggest that FAS inhibitors retard growth of melanoma A-375 cells, involving activation of caspase-dependent apoptosis.

Novel antagonists of the thioesterase domain of human fatty acid synthase

Fatty acid synthase (FAS) is up-regulated in a wide range of cancers and has been recently identified as a potential therapeutic target. Indeed, previous research has shown that inhibition of FAS with active site-modifying agents can block tumor cell proliferation, elicit tumor cell death, and prevent tumor growth in animal models. Here, we use a high-throughput fluorogenic screen and identify a novel pharmacophore, 5-(furan-2-ylmethylene) pyrimidine-2,4,6-trione, which inhibits the thioesterase domain of FAS. The novel antagonists are competitive inhibitors of the thioesterase domain, inhibit de novo fatty acid synthesis, and elicit FAS-dependent tumor cell death. This set of novel FAS antagonists provides an important pharmacologic lead for further development of anticancer therapeutics.

Targeting fatty acid synthase in breast and endometrial cancer: An alternative to selective estrogen receptor modulators?

There is an urgent need to identify and develop a new generation of therapeutic agents and systemic therapies targeting the estradiol (E2)/estrogen receptor (ER) signaling in breast cancer. In this regard, new information on the mechanisms of E2/ER function and/or cross talk with other prosurvival cascades should provide the basis for the development of other ideal anti-E2 therapies with the intent to enhance clinical efficacy, reduce side effects or both. Our very recent assessment of the mechanisms by which cancer-associated increased lipogenesis and its inhibition alters the E2/ER signaling discovered that fatty acid synthase (FASN), the enzyme catalyzing the terminal steps in the de novo biosynthesis of long-chain fatty acids, differentially modulates the state of sensitivity of breast and endometrial cancer cells to E2-stimulated ER transcriptional activation and E2-dependent cell growth and survival: 1) pharmacological inhibition of FASN activity induced a dramatic augmentation of E2-stimulated ER-driven gene transcription, whereas interference (RNAi)-mediated silencing of FAS gene expression drastically lowered E2 requirements for optimal activation of ER transcriptional activation in breast cancer cells; conversely, pharmacological and RNAi-induced inhibition of FASN worked as an antagonist of E2- and tamoxifen-dependent ER transcriptional activity in endometrial adenocarcinoma cells; 2) pharmacological and RNAi-induced inhibition of FASN synergistically enhanced E2-mediated down-regulation of ER protein and mRNA expression in breast cancer cells, whereas specific FASN blockade resulted in a marked down-regulation of E2-stimulated ER expression in endometrial cancer cells; and 3) FASN inhibition decreased cell proliferation and cell viability by promoting apoptosis in hormone-dependent breast and endometrial cancer cells. In this review we propose that, through a complex mechanism involving the regulation of MAPK/ER cross talk as well as critical E2-related proteins including the Her-2/neu (erbB-2) oncogene and the cyclin-dependent kinase inhibitors p21(WAF1/CIP1) and p27(Kip1), a previously unrevealed connection exists between FASN and the genomic and nongenomic ER activities in breast and endometrial cancer cells. From a clinical perspective, we suggest that if chemically stable FASN inhibitors or cell-selective systems able to deliver RNAi targeting FASN gene demonstrate systemic anticancer effects of FASN inhibition in vivo, additional preclinical studies to characterize their anti-breast cancer actions should be of great interest as the specific blockade of FASN activity may also provide a protective means against endometrial carcinoma associated with tamoxifen-based breast cancer therapy.

Oncogenic properties of the endogenous fatty acid metabolism: molecular pathology of fatty acid synthase in cancer cells

PURPOSE OF REVIEW

This review documents our rapidly changing perspectives on the function of fatty acid synthase-catalyzed endogenous fatty acid biogenesis in cancer biology.

RECENT FINDINGS

Up-regulation of fatty acid synthase gene expression and fatty acid synthase biosynthetic activity are molecular events accompanying the pathogenesis and natural history of cancer disease. First, the increased fatty acid synthase gene expression in precursor, preinvasive and invasive cancer lesions appears to represent an indirect, early epiphenomenon, occurring in response to a microenvironment containing regions of poor oxygenation and high acidity due to, for example, lack of an adequate angiogenesis and/or nutritional supply. Second, aberrant transduction cascades driven by cancer-associated oncogenic changes subvert the downregulatory effects of circulating fatty acids. Third, fatty acid synthase-dependent endogenous fatty acid metabolism actively contributes to cancer evolution by specifically regulating the expression, activity and/or cellular localization of proteins closely related to malignant transformation and/or cancer progression.

SUMMARY

Fatty acid synthase-catalyzed endogenous fatty acid metabolism appears to be an obligatory acquisition selecting a biologically aggressive sub-group of cancer cells capable of growth and survival upon stresses such as hypoxia, low pH and/or nutritional deprivation. Considering that an ever-growing body of evidence demonstrates that fatty acid synthase-driven signalling actively regulates key cancer-controlling networks, we may hereafter redefine fatty acid synthase as a metabolic oncogene in human cancer cells.