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Endocrinology Vol. 147, No. 9 4056-4066
Copyright © 2006 by The Endocrine Society

Targeting Fatty Acid Synthase in Breast and Endometrial Cancer: An Alternative to Selective Estrogen Receptor Modulators?

Ruth Lupu and Javier A. Menendez

Department of Medicine (R.L.), Evanston Northwestern Healthcare Research Institute, Evanston, Illinois 60201; Department of Medicine (R.L.), Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60211; Robert H. Lurie Comprehensive Cancer Center of Northwestern University (R.L.), Chicago, Illinois 60611; Fundació d’ Investigació Biomèdica de Girona Dr. Josep Trueta (J.A.M.), 17007 Girona, Catalonia, Spain; Institut Catalá d’ Oncología de Girona-Hospital Universitari de Girona Dr. Josep Trueta, Girona (J.A.M.), 170010 Catalonia, Spain

Address all correspondence and requests for reprints to: Ruth Lupu, Ph.D., Evanston Northwestern Healthcare Research Institute, 1001 University Place, Evanston, Illinois 60201. E-mail: r-lupu{at}northwestern.edu.


   Abstract
Top
 Abstract
Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
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 p21WAF1/CIP1 and p27Kip1, 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.


   Introduction
Top
 Abstract
 Introduction
Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
THERE IS A QUEST FOR a selective estrogen receptor modulator (SERM) with an ideal profile. The ultimate goal of breast cancer therapeutics (i.e. to identify and block a critical promoter of carcinogenesis, prevention, and to identify and block critical survival pathways, treatment) has successfully been achieved by exploiting knowledge of the estrogen (E2)/estrogen receptor (ER) signal transduction system (1).

On the prevention hand, the proper application of long-term anti-E2 therapy such as tamoxifen (TAM) decreases the incidence of breast cancer in high-risk women (2, 3). Certainly, the major effect of TAM and other SERMs is to reduce the incidence of ER-positive breast tumors by inhibiting the progression of subclinical ER-positive cancers to clinically evident cancers (4, 5, 6). Indeed, nearly all premalignant breast lesions are strongly ER positive and would be expected to be sensitive to the antiproliferative effects of SERMs, thus explaining the prominent reduction in breast cancer incidence (both ER positive and ER negative) in the TAM trial in women with a prior breast biopsy showing atypical hyperplasia (4, 5, 6). However, some ER-negative breast cancers may not evolve through an ER-positive, premalignant stage and thus might not be influenced at all by SERM-based therapies. Moreover, TAM is not an antiestrogen in all E2 target tissues in the body, and the most serious adverse effect of TAM is a consequence of its estrogenic activity in the endometrium, which results in endometrial hyperplasia and low-grade endometrial cancers (7, 8).

On the treatment hand, endocrine therapy is the primary treatment approach for patients with ER- and/or progesterone receptor (PR)-positive tumor who do not have immediately life-threatening disease, and TAM therapy continues to be valuable for the treatment of ER-positive breast cancer in postmenopausal women (1, 2, 3, 4, 5, 6). Unfortunately, only 40–50% of those patients respond to TAM treatment, whereas all patients with metastatic breast cancer ultimately develop resistance to treatment (9, 10, 11). Mechanisms for this resistance have not been fully explained but are probably multifactorial (9, 10, 11, 12, 13). Furthermore, disease progresses during TAM therapy in some patients because the drug begins to stimulate tumor growth (14, 15). Noteworthy, the quest for a SERM with an ideal profile (i.e. a desirable constellation of antibreast, -endometrium, and -estrogenic effects) has been paralleled by the development of novel antiestrogenic agents, namely aromatase inhibitors (AIs), that do no depend on achieving selectivity of interaction with ER. These drugs inhibit activity of aromatase (E2 synthase), a product of the CYP19 gene and the rate-limiting enzyme in E2 synthesis (16, 17, 18, 19, 20). Based on the clinical results so far, AIs are believed to play a key role in future adjuvant therapy of postmenopausal breast cancer patients and potentially also for breast cancer prevention (16, 17, 18, 19, 20). Although it has been shown the superiority that AIs have over TAM in the metastatic, adjuvant, and neoadjuvant settings, little is known about specific molecular markers to assist in selecting patients for AI therapies.

Therefore, three results have been reached: 1) there is an urgent need to identify and develop a new generation of therapeutic agents and systemic therapies targeting the E2/ER signaling to avoid the treatment of unresponsive breast carcinomas (21); 2) further benefits of clinical trials for SERMs and/or AIs should include the study of predictive biomarkers of disease to provide insights into SERM- and AI-based therapy resistance and sensitivity; and 3) 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 and reduce side effects or both.


   Fatty Acid Synthase (FASN)-Catalyzed Endogenous Fatty Acid Biogenesis and Tumor-Associated FASN (Oncogenic Antigen-519)
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
FASN is a multifunctional enzymatic complex that synthesizes palmitate from acetyl-coenzyme A and malonyl-coenzyme A. FASN functions normally in the liver to make lipids for export to metabolically active tissues or storage in adipose tissue (22, 23). On the contrary, FASN is minimally expressed in most other normal human tissues because they appear to use preferentially circulating fatty acids for the synthesis of new structural lipids (24, 25). Interestingly, after numerous clinical and basic research studies, it now appears that a biologically aggressive subset of carcinomas constitutively express high levels of FASN and undergo significant endogenous fatty acid biosynthesis independently of the regulatory signals that down-regulate fatty acid synthesis in normal cells (26, 27, 28, 29). Moreover, up-regulation of FASN gene expression is an early event in cancer development (30, 31, 32, 33, 34), it is more pronounced in more advanced tumors, and it often correlates with a poor prognosis (27, 28, 35, 36, 37). Importantly, pharmacological inhibition of FASN activity as well as RNA interference (RNAi) of FASN gene expression result in apoptosis of cancer cells and prolong survival of cancer xenograft hosts (26, 38, 39, 40, 41), thus suggesting that tumor-associated FASN (also called oncogenic antigen-519) plays a central role in the maintenance of the malignant phenotype by enhancing cancer cell survival and proliferation. Remarkably, the differential expression of FASN between cancer and normal cells provides a useful drug target for development of novel therapeutic antimetabolites (26). Not surprisingly, pharmacological inhibition of tumor-associated FASN hyperactivity is currently under investigation as a chemotherapeutic target. These findings, altogether, strongly suggest that FASN, the major enzyme required for the anabolic conversion of dietary carbohydrate to fatty acids and largely considered of minor importance in human, may be ultimately be used for diagnosis, prognosis, early intervention, and treatment of human breast cancer.


   Hormonal Regulation of FASN in Hormone-Sensitive Carcinomas
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
Under normal conditions, FASN is highly expressed in hormone-sensitive cells (42). During the menstrual cycle, the expression of FASN in the human endometrium is closely linked to the expression of the proliferation antigen Ki-67, ER, and PR, suggesting a connection between FASN and the E2/ER-dependent signaling in endometrial cell proliferation. Thus, FASN expression increases in endometrial glands and stromal cells from the proliferative to the early secretory phase, and after cessation of cell proliferation in the mid- to the late-secretory phase, the endometrial tissue becomes FASN negative (43, 44). In normal mammary glands, the stimulation of FASN at lactation is considered to be due to stimulatory effects of cortisol, prolactin, and insulin, facilitated by decreased production of progesterone. Progestins appear to decrease FASN as well as FASN activity in normal alveolar mammary explants (45, 46). Strikingly, overexpression and hyperactivity of FASN is a common molecular feature in subsets of sex steroid-related tumors including breast and endometrium carcinomas (35, 36, 37, 47).

Although the ultimate mechanism of cancer-associated FASN overexpression is not completely understood, it has been shown that E2 and progestins have a role in FASN regulation in hormonally responsive tumors. Thus, FASN expression is part of the E2-driven cellular response that leads to proliferation in hormone-dependent endometrial carcinoma cells and associated with higher endometrial tumor grades (48). Recent evidence from our and other research teams likewise indicates that steroid hormones (SHs) can stimulate lipogenic gene expression in hormone-dependent prostate, breast, and endometrial cancer cells. Thus, in the human prostate cancer cell line LNCaP, androgens coordinately stimulate the expression of several genes belonging to two major lipogenic pathways: FASN-dependent fatty acid synthesis and cholesterol synthesis (48, 49). In the breast cancer cell line MCF-7, FASN expression has been shown to be affected by progestins and E2 and that this effect, similarly to androgen-regulated FASN in prostate cancer cells, seems also to be mediated by the sterol receptor element binding protein (SREBP) pathway (50). Thus, SHs up-regulate the proteolytical activation of the key lipogenic transcription factor SREBP-1c and enhance the expression of one of its primary lipogenic target enzymes (i.e. FASN) by stimulating the transcriptional activity of the FASN promoter harboring a complex SREBP-binding site (49).

The use of various inhibitors of different signal transduction pathways has further revealed that the regulatory effects of SH on FASN gene expression, downstream of androgen receptor (AR), PR, and ER, are complex and involve activation of and/or cross talk between multiple signal transduction pathways. First, the up-regulatory effects of SHs on FASN expression are completely inhibited in the presence of anti-SH agents [e.g. the antiandrogen casodex bicalutamide, the antiprogestin mifepristone (RU486), or the antiestrogens TAM and faslodex (ICI 182,780)], suggesting that SH receptors (i.e. AR, PR, and ER) are actively involved (51, 52, 53). Second, pharmacological and genetic modulation of MAPK and extracellular signal-regulated kinase (MEK)-1/MEK2 and phosphoinositide 3-kinase (PI-3'K) activities significantly affects the ability of SHs to regulate FASN gene expression (29, 54, 55, 56, 57). These findings suggest that SH bound SH receptors trigger a transduction mechanism that, up-stream of FASN gene promoter, functionally link MEK1/MEK2 -> ERK1/ERK2 MAPK and PI-3'K -> AKT signaling cascades to SREBP-1c. Finally, the fact that SHs including E2 can stimulate FASN gene expression via an indirect pathway involving SREBP-1c strongly suggests that steroid receptor-dependent activation of the SREBP pathway appears to be a key molecular event regulating FASN expression in hormone-sensitive carcinomas (Fig. 1Go).


Figure 1
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  		FIG. 1. Hormonal regulation of FASN gene expression in cancer cells. FASN gene regulation in hormone-sensitive neoplastic cells seems to occur through modulation of the transcription factor SREBP-1c, a critical intermediate in the pro- and antilipogenic actions of several hormones and nutrients that binds to sterol regulatory elements (SREBP-BS) in the promoter region of the target gene FASN. SREBP-1c up-regulation and nuclear maturation appears to be driven by the activation of MEK1/MEK2 -> ERK1/2 MAPK, and PI-3'K -> AKT signaling cascades that occurs in response to the specific binding of SHs such as androgens (A), progestins (P), and E2 to their receptors (AR, PR and ER, respectively).

 
Indeed, overexpression of lipogenic enzymes has been found to correlate with SREBP expression and the expression of SH receptors (58, 59, 60, 61). Moreover, well-characterized cancer-related growth factors and oncogenes also activate the SREBP pathway and lead to increased FASN gene expression (62, 63). An interesting question that remains to be elucidated is whether activation of the SREBP pathway by SHs, growth factors, and/or oncogenic stimuli is restricted to cancer cells or represents a more general physiological regulation in noncancerous tissues as well. Of note, it has recently been concluded that SREBP expression levels do not coincide with the expected changes in adipose lipogenic gene expression including FASN (64).


   FASN Regulation of ER Signaling in Cancer Cells
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
We recently demonstrated that pharmacological and RNAi-mediated inhibition of FASN dramatically reduces the expression of Her-2/neu (erbB-2) oncogene in cancer cells (65, 66). Considering that Her-2/neu overexpression stimulates the activity of FASN gene promoter and ultimately mediates increased endogenous fatty acid biosynthesis (67, 68, 69), these findings revealed that a bidirectional nature of the molecular connection between FASN and Her-2/neu exists in cancer cells and suggested that: 1) cancer-associated FASN not only is necessary to integrate a number of signaling pathways that regulate metabolism, proliferation, and survival in cancer cells but also plays further an active role in cancer evolution by regulating the activity and/or expression of proteins and/or genes closely related to malignant transformation and 2) unraveling the functional organization of the molecular interplay between well-characterized cancer-related networks and the regulatory actions emanating from FASN-dependent neoplastic lipogenesis is a major challenge that the field is only beginning to take on.

Our most recent findings illustrate that inhibition of FASN activity can regulate the genomic and nongenomic activities of ER in breast and endometrial cancer cells (70, 71, 72, 73, 74) (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication; and Menendez, J. A., B. P. Oza, R. Colomer, and R. Lupu, submitted for publication).

First, pharmacological FASN blockade synergistically enhanced E2-stimulated ER transcriptional activity in ER-positive MCF-7 breast cancer cells and in MDA-MB-231 cells stably transfected with ER (S30 cells) but not in ER-negative MDA-MB-231 parental cells, as assessed by estrogen-responsive element (ERE) reporter assays. Accordingly, treatment with either the mycotoxin cerulenin (a covalent FASN inactivator; Fig. 2Go) or the novel small compound C75 (a slow-binding FASN inhibitor; Fig. 2Go) specifically modulated endogenous E2-responsive genes as it synergistically augmented the stimulatory effects of E2 on PR expression and the inhibitory effects of E2 on Her-2/neu oncogene expression and significantly enhanced E2-mediated down-regulation of ER protein and mRNA expression (Fig. 3Go). These results pointed out the ability of FASN blockers to specifically enhance ligand (i.e. E2)-dependent ER signaling in breast cancer cells. Our results also demonstrated that specific depletion of FASN expression by RNAi dramatically decreases E2 requirements for optimal activation of ER-dependent transcriptional activity, further confirming the specificity of chemical FASN inhibitors for its FASN target to modulate the state of sensitivity of breast cancer cells to E2. Interestingly, a completely different picture emerged when we examined the effects of FASN blockade on E2 and TAM-regulated ER-transcriptional activity in Ishikawa cells, an in vitro model of well-differentiated human endometrial carcinoma (71). Thus, antiestrogenic effects of the chemical FASN blockers were observed by dose-dependent inhibition of E2- and TAM-stimulated ER-dependent transcription, whereas FASN inhibition slightly increased the levels of ER transcriptional activity in the absence of E2 or TAM. The reliability of transient transfection assays was confirmed when the effects of FASN inhibition on E2-inducible gene products were evaluated in endometrial carcinoma cells. Thus, FASN blockade induced a dose-dependent decrease in E2-inducible alkaline phosphatase activity, whereas E2-stimulated accumulation of PR and Her-2/neu was abolished on FASN inhibition (Fig. 3Go).


Figure 2
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  		FIG. 2. Chemical structures of E2, cerulenin, and C75. Cerulenin, a natural mycotoxin, is an antagonist of the ß-ketoacyl synthase domain (the condensing enzyme) of FASN and functions by covalently modifying the active site cysteine, thus resulting in FASN activity dead-end inhibition. C75, a synthetic analog of cerulenin, also blocks FASN by targeting its condensing activity.

 

Figure 3
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  		FIG. 3. Differential effects of FASN inhibition on the E2/ER-driven signaling in breast and endometrial cancer cells. Diagrammatic representation of the effects of FASN blockade on several cellular targets closely related to E2 action in breast and endometrial cancer cells. Changes in the expression, activity and cellular localization of E2-targeted proteins including ER, PR, Her-2/neu, p21WAF1/CIP1, p27Kip1, MAPK, and AKT were evaluated prior and after pharmacological or small interfering RNA-induced inhibition of FASN activity. Similarly to SERMs, FASN inhibition appears to exert E2 agonist actions in some target tissues (i.e. breast) and act as E2 antagonist in others (i.e. endometrium).

 
Second, FASN inhibition synergistically enhanced E2-induced down-regulation of ER protein and mRNA expression in breast cancer cells. In endometrial cancer cells, FASN blockade synergistically enhanced E2-stimulated ER expression. In both cases, E2-promoted nuclear accumulation was noticeably impaired in the presence of FASN blockers (70, 71, 72, 73, 74) (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication; and Menendez, J. A., B. P. Oza, R. Colomer, and R. Lupu, submitted for publication).

Third, the opposite nature of the interaction between FASN inhibition and ER transcriptional activity in breast (synergistic) and endometrial (antagonistic) cancer cells (Fig. 4Go, A and B) strongly suggests that FASN activity modulates ER-dependent transcriptional activity by regulating additional signaling pathways that converge on ER actions. ER cross talks with a number of mitogenic signaling pathways such as MAPK and AKT, and these molecular interactions may support ligand-independent and -dependent ER transcription (75). A working model designed to explain FASN-regulated ER signaling is summarized in Fig. 5Go. We postulate that FASN inhibition might trigger activation of a nongenomic, E2-regulated, ER/MAPK cross talk that molecularly explains the appearance of an exacerbated transcriptional response of ER to E2 in breast cancer cells and blocks E2- and TAM-stimulated ER transcriptional activation in endometrial cancer cells: 1) MAPK activity is dramatically enhanced in E2-stimulated breast cancer cells upon FASN blockade. Conversely, FASN inhibition enhances E2-independent MAPK hyperactivation in endometrial carcinomas cells (Fig. 4Go, A and B); 2) the synergistic effect of FASN blockade on E2-stimulated ER transcriptional activity returns back to the baseline response obtained with E2 in the presence of the MAPK inhibitor U0126, thus signifying that MAPK activation does participate mechanistically in the hypersensitivity process (Fig. 4Go, A and B); 3) although an important component, MAPK does not appear to be solely responsible because the blockade of this enzyme does not completely abrogate ER transcriptional hyperactivity (Fig. 4Go, A and B); and 4) cotreatment with the pure antiestrogen ICI 182,780 reverses FASN inhibition-enhanced E2-dependent ER transcriptional activity to the basal level seen in E2-depleted (not stimulated) breast cancer cells. Similarly, ICI 182,780 coexposure impedes FASN inhibition-promoted E2-independent ER transcriptional activation in endometrial cancer cells (Fig. 4Go, A and B). These observations support the notion that the regulatory effects on the genomic activity of ER on FASN blockade depend on the upstream involvement of an ER-regulated MAPK signaling cascade (76, 77). Because FASN inhibition-induced activation of MAPK may reflect a constitutive increase in the secretion of endogenous growth factors (GFs), a constitutive activation of GF receptors, or other mechanisms, this observation rules out GF/GF receptor-related effects after FASN inhibition. Moreover, considering that MAPK hyperactivity has been shown to induce loss of ER expression (78) and that FASN inhibition concomitantly stimulates MAPK activation and enhancing E2-induced down-regulation of ER protein and mRNA, a hypothetical model is supported by our data, which indicate that, on FASN blockade, activation of the Ras/Raf/MEK/MAPK signaling pathway can down-regulate ER expression without promoting ligand (E2)-independent activation of ER transcriptional activity in breast cancer cells.


Figure 4
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  		FIG. 4. FASN inhibition differentially regulates, in a MAPK-related manner, E2-independent and E2-dependent ER-driven transcriptional activity in breast and endometrial carcinoma cells. MCF-7 breast cancer cells (A) and Ishikawa endometrial adenocarcinomas cells (B) were transiently cotransfected with an ERE-containing reporter plasmid (ERE-Luciferase) and pRL/CMV (an internal reporter plasmid to control for transfection efficiency). The transfected cells were incubated for 24 h in the presence of vehicles (control), E2, the pure antiestrogen ICI 182,780, the chemical FASN blocker C75, or the MEK1/2 inhibitor U0126 individually or in combination as specified, and cell extracts were analyzed for luciferase activity. The data shown here represent means (columns) ± SD (bars) (n = 3).

 

Figure 5
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  		FIG. 5. FASN-ER cross talk in hormone-sensitive cancer cells: a working model. Diagrammatic representation of the two main pathways involved in E2 action and their modulation by FASN. The genomic pathway involves the entry of E2 into the cell and migration to the nucleus, in which E2 induces genomic-nuclear ER activity that results in increased gene transcription and E2-induced mitogenesis. Pure nonsteroidal antiestrogens, e.g. ICI 182,780, antagonize the proliferative activity of E2 through ER degradation and also by promoting the up-regulation of CDKis p21WAF1/CIP1 and p27Kip1 expression and their nuclear recruitment into cyclin E-Cdk2 complexes, which ultimately promotes growth arrest. FASN inhibition may prevent E2-stimulated ER genomic activity and cell growth by interfering with E2-induced ER nuclear accumulation and/or up-regulating the expression and nuclear accumulation of CDKis p21WAF1/CIP1 and p27Kip1. Via the nongenomic pathways, E2 binds to an ER near or in the cell membrane, which, in turn, can activate tyrosine kinase receptors and cellular kinase cascades. Subsequent phosphorylation of ER by these kinases (e.g. ERK/MAPK and AKT) then potentiates the genomic-nuclear activity ER activity. FASN blockade seems to enhance ER genomic activity through the activation of a nongenomic ER/MAPK cross-talk, which results in the exacerbation of ER transcriptional activity. The ability of FASN blockade to inactivate the prosurvival nongenomic ER/AKT cross talk, in conjunction with its inhibitory actions in the ER genomic pathway may determine why FASN inhibition-induced ER transcriptional activity does not enhance E2-dependent breast cell growth-promoting actions. ERE, Promoters containing diverse ER-responsive genes, e.g. PR and HER-2/neu.

 
Because all these effects were recapitulated when FASN gene expression was specifically silenced by RNAi, it is reasonable to consider FASN activity as a novel molecular sensor regulating the state of sensitivity of breast and endometrial carcinoma cells to E2-regulated ER transcriptional activity.

Fourth, our studies establish that FASN inhibition does not promote either ligand-independent ER transcriptional activity or E2-dependent growth-promoting actions. Indeed, a dose-dependent decrease in cell proliferation and cell viability via stimulated apoptosis is observed after FASN blockade in breast and endometrial carcinoma cells (70, 71, 72, 73, 74) (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication; and Menendez, J. A., B. P. Oza, R. Colomer, and R. Lupu, submitted for publication). Moreover, it is reasonable to suggest that a divergent regulation of MAPK and AKT may explain the striking ability of FASN inhibition to enhance E2-induced ER transcriptional activity without promoting E2-stimulated breast cancer cell growth. E2, bound to membrane ER, may interact with a heterodimer of the erbB family of receptor-containing erbB-2, inducing its activation (10, 11, 12, 79). The heterodimer may activate PI-3'K, which in turn can activate AKT. AKT may phosphorylate nuclear ER, leading to the modulation of its expression and activity. Interestingly, we have shown that FASN blockade significantly blocks AKT activity and completely prevents E2-stimulated anchorage-independent growth of MCF-7 breast cancer cells in soft agar, which is mediated by a nongenomic cross talk between ER and the erbB-2/PI-3'K/AKT transduction cascade (10, 11, 12, 79) (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication). Although it remains to be elucidated how FASN blockade positively and negatively regulates MAPK and AKT activities, respectively, interruption of the prosurvival AKT cascade appears to be dominant over activation of the proliferative MAPK signaling.

Fifth, FASN blockade may also inhibit E2-stimulated breast and endometrial cancer cell growth through modulation of key cell cycle regulators such as the cyclin-dependent kinase inhibitors (CDKis) p21WAF1/CIP1 and p27Kip1. p21WAF1/CIP1 and p27Kip1 are essential mediators of SERM-induced cell growth arrest through their binding to the cyclin E-Cdk2 complex, thus operating as suppressors of E2-promoted cell cycle (81, 82, 83, 84). FASN blockade up-regulates p21WAF1/CIP1/p27Kip1 expression and dramatically increases the ratio of nuclear to cytoplasmic p21WAF1/CIP1/p27Kip1 (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication). Although the ultimate determinants of a molecular connection between FASN activity and the CDKis p21WAF1/CIP1 and p27Kip1 obviously require further investigation, it is likely that, on E2 stimulation, FASN blockade is inducing the amount of p21WAF1/CIP1 and p27Kip1 available for binding to and inhibiting CDK2 activity, thus leading to prolonged cell cycle arrest and apoptosis in breast and endometrial cancer cells.


   Molecular and Clinical Perspectives
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 
From a molecular perspective, we here propose that cancer-associated FASN modulates E2-stimulated ER genomic and nongenomic activities in hormone-sensitive breast and endometrial cancer cells (Fig. 5Go). Whereas the hyperactivation of a nongenomic ER/MAPK cross talk seems to be responsible for the exacerbated E2-stimulated ER transcriptional activation occurring on FASN blockade, the concomitant inactivation of the prosurvival nongenomic ER/AKT cross talk in conjunction with inhibitory actions on the ER genomic pathway (i.e. interference with E2-induced nuclear accumulation of ER and/or up-regulation of the expression and nuclear accumulation of the CDKis p21WAF1/CIP1 and p27Kip1) seems to determine that FASN blockade does not ultimately enhance E2-dependent cell growth promoting actions in breast cancer cells.

Although the ultimate molecular mechanism responsible for the molecular connection between cancer-associated FASN hyperactivity and ER signaling certainly merits further investigation, the proposed mechanism of action for chemical FASN blockers links high levels of intracellular malonyl-coenzyme A, a substrate of FASN, to potential downstream effects (40, 85, 86). How malonyl-coenzyme A, a key metabolite in the regulation of energy homeostasis, can modulate ER signaling remains to be elucidated. In this regard, a very recent study by Lelliott et al. (87) revealed that TAM-treated livers have increased saturated fatty acid content despite changes in gene expression, indicating decreasing de novo lipogenesis and increased fatty acid oxidation (87). Indeed, their results established that TAM predominantly down-regulates FASN expression and activity as indicated by the accumulation of the FASN substrate malonyl-coenzyme A, a known inhibitor of mitochondrial ß-oxidation. They concluded that, in the face of a continued supply of exogenous free fatty acids, the blockade of fatty acid oxidation produced by elevated malonyl-coenzyme A is likely to be the major factor leading to TAM-induced hepatic steatosis (87). These findings, altogether, support the notion that a functional interaction involving FASN and E2- and TAM-regulated ER is complex and seems to occur at multiple molecular levels and in a tissue-dependent manner.

Considering that vastly higher levels of FASN are expressed in premalignant, invasive, and metastatic lesions of the breast than in normal tissues, in which FASN is down-regulated and compensated by exogenously derived (dietary) fatty acids, this difference provides an attractive approach to cancer therapy having the potential for a large therapeutic index (27, 28). From a clinical perspective, our current approach strongly suggests that chemical FASN inhibitors might be novel members of the SERM family because, by definition, SERMs exert E2 agonist actions in some target tissues and act as E2 antagonists in others. Further studies are required to assess the physiological significance of FASN inhibition on E2/ER signaling, and a more complete understanding of the hypersensitivity to E2-stimulated ER transcriptional activation occurring on FASN blockade is needed to clarify the circumstances under which FASN blockers can be used. Nonetheless, the characterization of FASN (oncogenic antigen-519) as a novel ER-related factor conferring a selective cancer growth advantage should allow an invaluable adjunct to gene expression profiling or proteomics in the characterization of a biologically aggressive subset of hormone-related human carcinomas. On the other hand, the results derived from our studies should ultimately offer a molecular rationale for a novel preventive and therapeutic approach based on the specific targeting of FASN activity or expression.


   Targeting Cancer-Associated FASN: From the Bench to the Clinic?
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
Tumor Fatty Acid Metabolism:...
 References
 
Drug resistance hampers successful endocrine therapies, and its prevention and/or reversal are still awaiting new sensitizing strategies or pharmaceuticals. Our current findings not only support the therapeutic relevance of targeting FASN-dependent neoplastic lipogenesis in endocrine-related carcinomas lipogenesis but also further suggest that the predictive value of measuring FASN expression could help in the selection of better responders to currently used endocrine therapies. In this regard, an immunohistochemical study evaluating FASN expression in Japanese breast cancer patients showed that FASN associates with ER and PR status (88). The low FASN group showed better disease-free survival and overall survival in all but ER-negative/PR-negative cases, thus suggesting that the use of FASN expression may increase the diagnostic utility of ER and PR and may be able to predict in premenopausal breast cancer patients (88). Moreover, a very recent immunohistochemical analysis using tissue microarrays composed of breast tumors of different pathological stages demonstrated that FASN overexpression occurred in 38.9% of ductal carcinoma in situ, 51.0% of primary invasive tumors, and 50.0% of metastatic-distant and lymph node-breast carcinomas (32). Importantly, FASN expression was significantly higher in ER- or Her-2/neu (erbB-2)-positive high-grade tumors (32, 89).

Because overexpression of the human EGF receptor Her-2/neu is well known to promote more aggressive breast cancer that is nonresponsive to E2 and TAM (12, 90), we recently evaluated whether FASN-dependent signaling, in a Her-2/neu-related manner, actively participates in the acquisition of an E2-independent breast cancer phenotype. As described above, E2 stimulation specifically up-regulated FASN gene promoter activity in ER-positive breast cancer cells, whereas FASN inhibition was as efficient as TAM at blocking E2-promoted anchorage-dependent and -independent growth of breast cancer cells (73) (Menendez, J. A., B. P. Oza, and R. Lupu, submitted for publication). Interestingly, ER-positive breast cancer cells overexpressing the Her-2/neu oncogene (MCF-7/Her2–18 and BT-474 cells) exhibited a constitutive up-regulation of FASN gene expression unresponsive to E2 and/or TAM. Moreover, FASN inhibition in E2-independent MCF-7/Her2–18 and BT-474 breast cancer cells did overcome their endocrine resistance to the SERMs TAM and faslodex. These findings suggested that, in hormone-dependent in vitro breast cancer models, FASN expression and activity is part of the E2-driven response that leads to breast cancer cell proliferation and survival, whereas its linkage to proliferation is such that FASN overexpression and hyperactivity is maintained in metastatic breast cancer cells acquiring Her-2/neu-related hormone independence (73). If a new generation of chemically stable anti-FASN metabolites or cell-selective systems able to deliver RNAi targeting FASN gene demonstrate anticancer effects in vivo, additional preclinical and clinical studies definitely characterizing their tumoricidal actions in hormone-related breast carcinomas should be of great interest because the specific blockade of FASN may also provide a protective means against endometrial carcinoma associated with TAM-based breast cancer therapy.


   Tumor Fatty Acid Metabolism: More than FASN?
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
References
 
Most attention in the past few years on the role of the endogenous fatty acid metabolism in tumor biology has been directed on the molecular and cellular consequences of FASN expression and activity. However, we cannot forget other two key lipogenic protagonists closely related to cancer etiology and progression, acetyl-coenzyme A carboxylase-{alpha} (ACC{alpha}) and Spot 14 (S14). ACC{alpha} is the rate-limiting enzyme in the endogenous fatty acid metabolism that catalyzes the condensation of the FASN substrate malonyl-coenzyme A using acetyl-coenzyme A and CO2 as precursors (30, 33). ACC{alpha} is highly expressed in human breast carcinomas (30), and a potential association between the presence of certain ACC{alpha} sequence changes and breast cancer development has been described (91). In this regard, the inhibition of ACC{alpha} activity by RNAi has recently been demonstrated to induce a marked decrease of endogenous lipogenesis in prostate and breast cancer cells, leading to specific induction of apoptosis in tumor cells (92, 93). Interestingly, ACC{alpha} has been identified as a novel partner of breast cancer susceptibility gene 1 (BRCA1), the first susceptibility gene linked to breast and ovarian cancer (94, 95, 96). Indeed, BRCA1 appears to affect tumoral lipogenesis by preventing P-ACC{alpha} dephosphorylation, thus providing not only a new mechanism by which BRCA1 may exert a tumor suppressor function but also supporting a model in which control of lipid synthesis in cancer cells would be mediated via the BRCA1-ACC{alpha} interaction (95).

S14 may also act as a master regulator of tumoral lipogenesis (97, 98, 99, 100, 101). Similar to FASN, S14 gene transcription is controlled by dietary substrates, such as glucose and polyunsaturated fatty acids, and fuel-related hormones including insulin and glucagon. Also, a differential expression of S14 exists between breast cancer and normal cells because S14 mRNA has been found to be expressed in most breast cancer-derived cell lines but not in normal nonlactating mammary glands. Moreover, S14 gene is amplified in approximately 15% of breast cancers and high-level expression of S14 protein can identify a subset of high-risk breast cancer, whereas providing a molecular correlate to histological features that predict disease free survival in invasive breast cancer (100). A single genetic abnormality involving genes coding for FASN, ACC{alpha}, and S14 lipogenic enzymes cannot explain the enhanced tumoral lipogenesis because their genes reside at different chromosomal locations. However, when considering that S14 regulates expression of several lipogenic enzymes including ACC{alpha} and FASN (97), an increase in its expression via SREBP-1c may provide a unitary explanation for the increased endogenous fatty acid metabolism in tumor cells, particularly in hormone-sensitive tumors (101).

As auspiciously suggested by Brusselmans et al. (92), the ability to selectively inhibit different steps in the lipogenic pathway should contribute to a better understanding of the ultimate mechanisms by which increased lipogenesis and inhibition of this increased lipogenesis specifically alters tumor cell behavior. We lately found that small interfering RNA-induced specific depletion of FASN protein strongly antagonizes the ability of exogenous (dietary) unsaturated fatty acids to block the expression of the Her-2/neu, a key oncogene determining breast cancer resistance to endocrine therapies (80). In view of that metabolic pathways (including FASN) are highly expressed in Her-2/neu-positive breast carcinomas (103), it will be of interest to evaluate whether ACC{alpha} and/or S14 functionally interacts with the energy sensor Her-2/neu, thus illuminating an oncogenic role of endogenous lipogenesis in the development, maintenance, and aggressive progression of endocrine-related human cancers.


   Footnotes
 
This work was supported by Grant R01CA116623 from the Nacional Institute of Health (to R.L.) and Grant CP05-00090 from the Instituto de Salud Carlos III (to J.A.M.), Ministerio de Sanidad y Consumo, Fondo de Investigación Sanitaria, Spain.

First Published Online June 29, 2006

Abbreviations: ACC{alpha}, Acetyl-coenzyme A carboxylase-{alpha}; AI, aromatase inhibitor; AR, androgen receptor; BRCA1, breast cancer susceptibility gene 1; CDKi, cyclin-dependent kinase inhibitor; E2, estrogen; ER, E2 receptor; ERE, estrogen-responsive element; FASN, fatty acid synthase; GF, growth factor; MEK, MAPK and extracellular signal-regulated kinase; PI-3'K, phosphoinositide 3-kinase; PR, progesterone receptor; RNAi, RNA interference; S14, Spot 14; SERM, selective estrogen receptor modulator; SH, steroid hormone; SREBP, sterol receptor element binding protein; TAM, tamoxifen.

Received April 13, 2006.

Accepted for publication June 19, 2006.


   References
Top
 Abstract
 Introduction
 Fatty Acid Synthase (FASN)...
 Hormonal Regulation of FASN...
 FASN Regulation of ER...
 Molecular and Clinical...
 Targeting Cancer-Associated...
 Tumor Fatty Acid Metabolism:...
 References
 

  1. Jensen EV, Jordan VC 2003 The estrogen receptor: a model for molecular medicine. Clin Cancer Res 9:1980–1989[Abstract/Free Full Text]
  2. Jordan VC 2003 Tamoxifen: a most unlikely pioneering medicine. Nat Rev Drug Discov 2:205–213[CrossRef][Medline]
  3. Fisher B, Costantino JP, Wickerham DL, Redmond CK, Kavanah M, Cronin WM, Vogel V, Robidoux A, Dimitrov N, Atkins J, Daly M, Wieand S, Tan-Chiu E, Ford L, Wolmark N 1998 Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst 90:1371–1388[Abstract/Free Full Text]
  4. Dunn BK, Wickerham DL, Ford LG 2005 Prevention of hormone-related cancers: breast cancer. J Clin Oncol 23:357–367[Abstract/Free Full Text]
  5. Osborne CK, Zhao H, Fuqua SA 2000 Selective estrogen receptor modulators: structure, function, and clinical use. J Clin Oncol 18:3172–3186[Abstract/Free Full Text]
  6. Gradishar WJ, Jordan VC 2003 Advances in endocrine therapy for the treatment and prevention of breast cancer. Cancer Chemother Biol Response Modif 21:211–222[Medline]
  7. Fornander T, Rutqvist LE, Cedermark B, Glas U, Mattsson A, Silfversward C, Skoog L, Somell A, Theve T, Wilking N, et al 1989 Adjuvant tamoxifen in early breast cancer: occurrence of new primary cancers. Lancet 1:117–120[Medline]
  8. Fisher B, Costantino JP, Redmond CK, Fisher ER, Wickerham DL, Cronin WM 1994 Endometrial cancer in tamoxifen-treated breast cancer patients: findings from the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-14. J Natl Cancer Inst 86:527–537[Abstract/Free Full Text]
  9. Osipo C, Liu H, Meeke K, Jordan VC 2004 The consequences of exhaustive antiestrogen therapy in breast cancer: estrogen-induced tumor cell death. Exp Biol Med (Maywood) 229:722–731[Abstract/Free Full Text]
  10. Kurokawa H, Arteaga CL 2003 ErbB (HER) receptors can abrogate antiestrogen action in human breast cancer by multiple signaling mechanisms. Clin Cancer Res 9(1 Pt 2):511S–515S
  11. Kurokawa H, Arteaga CL 2001 Inhibition of erbB receptor (HER) tyrosine kinases as a strategy to abrogate antiestrogen resistance in human breast cancer. Clin Cancer Res 7(12 Suppl):4436s–4442s
  12. Shou J, Massarweh S, Osborne CK, Wakeling AE, Ali S, Weiss H, Schiff R 2004 Mechanisms of tamoxifen resistance: increased estrogen receptor-HER2/neu cross-talk in ER/HER2-positive breast cancer. J Natl Cancer Inst 96:926–935[Abstract/Free Full Text]
  13. Osborne CK, Shou J, Massarweh S, Schiff R 2005 Crosstalk between estrogen receptor and growth factor receptor pathways as a cause for endocrine therapy resistance in breast cancer. Clin Cancer Res 11(2 Pt 2):865s–870s
  14. Yao K, Lee ES, Bentrem DJ, England G, Schafer JI, O’Regan RM, Jordan VC 2000 Antitumor action of physiological estradiol on tamoxifen-stimulated breast tumors grown in athymic mice. Clin Cancer Res 6:2028–2036[Abstract/Free Full Text]
  15. Osipo C, Gajdos C, Liu H, Chen B, Jordan VC 2003 Paradoxical action of fulvestrant in estradiol-induced regression of tamoxifen-stimulated breast cancer. J Natl Cancer Inst 95:1597–1608[Abstract/Free Full Text]
  16. Smith IE, Dowsett M 2003 Aromatase inhibitors in breast cancer. N Engl J Med 348:2431–2442[Free Full Text]
  17. Simpson ER, Dowsett M 2002 Aromatase and its inhibitors: significance for breast cancer therapy. Recent Prog Horm Res 57:317–338[Abstract/Free Full Text]
  18. Santen RJ, Harvey HA 1999 Use of aromatase inhibitors in breast carcinoma. Endocr Relat Cancer 6:75–92[Abstract]
  19. Goss PE, Strasser K 2001 Aromatase inhibitors in the treatment and prevention of breast cancer. J Clin Oncol 19:881–894[Abstract/Free Full Text]
  20. Goss PE, Strasser K 2002 Tamoxifen resistant and refractory breast cancer: the value of aromatase inhibitors. Drugs 62:957–966[CrossRef][Medline]
  21. Lewis JS, Cheng D, Jordan VC 2004 Targeting oestrogen to kill the cancer but not the patient. Br J Cancer 90:944–949[CrossRef][Medline]
  22. Wakil S 1989 Fatty acid synthase, a proficient multifunctional enzyme. Biochemistry 28:4523–4530[CrossRef][Medline]
  23. Weiss L, Hoffmann GE, Schreiber R, Andres H, Fuchs E, Korber E, Kolb HJ 1986 Fatty-acid biosynthesis in man, a pathway of minor importance. Purification, optimal assay conditions, and organ distribution of fatty-acid synthase. Biol Chem Hoppe Seyler 367:905–912[Medline]
  24. Clarke SD 1993 Regulation of fatty acid synthase gene expression: an approach for reducing fat accumulation. J Anim Sci 71:1957–1965[Abstract]
  25. Katsurada A, Iritani N, Fukuda H, Matsumara Y, Nishimoto N, Noguchi T, Tanaka T 1990 Effects of nutrients and hormones on transcriptional and post-transcriptional regulation of fatty acid synthase in rat liver. Eur J Biochem 190:427–433[Medline]
  26. Kuhajda FP, Jenner K, Wood FD, Hennigar RA, Jacobs LB, Dick JD, Pasternack GR 1994 Fatty acid synthesis: a potential selective target for antineoplastic therapy. Proc Natl Acad Sci USA 91:6379–6383[Abstract/Free Full Text]
  27. Kuhajda FP 2000 Fatty-acid synthase and human cancer: new perspectives on its role in tumor biology. Nutrition 16:202–208[CrossRef][Medline]
  28. Menendez JA, Lupu R 2004 Fatty acid synthase-catalyzed de novo fatty acid biosynthesis: from anabolic-energy-storage pathway in normal tissues to jack-of-all-trades in cancer cells. Arch Immunol Ther Exp (Warsz) 52:414–426[Medline]
  29. Menendez JA, Ropero S, Mehmi I, Atlas E, Colomer R, Lupu R 2004 Overexpression and hyperactivity of breast cancer-associated fatty acid synthase (oncogenic antigen-519) is insensitive to normal arachidonic fatty acid-induced suppression in lipogenic tissues but it is selectively inhibited by tumoricidal {alpha}-linolenic and {gamma}-linolenic fatty acids: a novel mechanism by which dietary fat can alter mammary tumorigenesis. Int J Oncol 24:1369–1383[Medline]
  30. Milgraum LZ, Witters LA, Pasternack GR, Kuhajda FP 1997 Enzymes of the fatty acid synthesis pathway are highly expressed in in situ breast carcinoma. Clin Cancer Res 3:2115–2120[Abstract]
  31. Alo PL, Visca P, Botti C, Galati GM, Sebastiani V, Andreano T, Di Tondo U, Pizer ES 2001 Immunohistochemical expression of human erythrocyte glucose transporter and fatty acid synthase in infiltrating breast carcinomas and adjacent typical/atypical hyperplastic or normal breast tissue. Am J Clin Pathol 116:129–134[CrossRef][Medline]
  32. Porter D, Lahti-Domenici J, Keshaviah A, Bae YK, Argani P, Marks J, Richardson A, Cooper A, Strausberg R, Riggins GJ, Schnitt S, Gabrielson E, Gelman R, Polyak K 2003 Molecular markers in ductal carcinoma in situ of the breast. Mol Cancer Res 1:362–375[Abstract/Free Full Text]
  33. Swinnen JV, Vanderhoydonc F, Elgamal AA, Eelen M, Vercaeren I, Joniau S, Van Poppel H, Baert L, Goossens K, Heyns W, Verhoeven G 2000 Selective activation of the fatty acid synthesis pathway in human prostate cancer. Int J Cancer 88:176–179[CrossRef][Medline]
  34. Bull JH, Ellison G, Patel A, Muir G, Walker M, Underwood M, Khan F, Paskins L 2001 Identification of potential diagnostic markers of prostate cancer and prostatic intraepithelial neoplasia using cDNA microarray. Br J Cancer 84:1512–1519[CrossRef][Medline]
  35. Alo PL, Visca P, Marci A, Mangoni A, Botti C, Di Tondo U 1996 Expression of fatty acid synthase (FAS) as a predictor of recurrence in stage I breast carcinoma patients. Cancer 77:474–482[CrossRef][Medline]
  36. Alo PL, Visca P, Trombetta G, Mangoni A, Lenti L, Monaco S, Botti C, Serpieri DE, Di Tondo U 1999 Fatty acid synthase (FAS) predictive strength in poorly differentiated early breast carcinomas. Tumori 85:35–40[CrossRef][Medline]
  37. Jensen V, Ladekarl M, Holm-Nielsen P, Melsen F, Soerensen FB 1995 The prognostic value of oncogenic antigen 519 (OA-519) expression and proliferative activity detected by antibody MIB-1 in node-negative breast cancer. J Pathol 176:343–352[CrossRef][Medline]
  38. Pizer ES, Jackisch C, Wood FD, Pasternack GR, Davidson NE, Kuhajda FP 1996 Inhibition of fatty acid synthesis induces programmed cell death in human breast cancer cells. Cancer Res 56:2745–2747[Abstract/Free Full Text]
  39. Pizer ES, Wood FD, Heine HS, Romantsev FE, Pasternack GR, Kuhajda FP 1996 Inhibition of fatty acid synthesis delays disease progression in a xenograft model of ovarian cancer. Cancer Res 56:1189–1193[Abstract/Free Full Text]
  40. Pizer ES, Thupari J, Han WF, Pinn ML, Chrest FJ, Frehywot GL, Townsend CA, Kuhajda FP 2000 Malonyl-coenzyme-A is a potential mediator of cytotoxicity induced by fatty-acid synthase inhibition in human breast cancer cells and xenografts. Cancer Res 60:213–218[Abstract/Free Full Text]
  41. De Schrijver E, Brusselmans K, Heyns W, Verhoeven G, Swinnen JV 2003 RNA interference-mediated silencing of the fatty acid synthase gene attenuates growth and induces morphological changes and apoptosis of LNCaP prostate cancer cells. Cancer Res 63:3799–3804[Abstract/Free Full Text]
  42. Kusakabe T, Maeda M, Hoshi N, Sugino T, Watanabe K, Fukuda T, Suzuki T 2000 Fatty acid synthase is expressed mainly in adult hormone-sensitive cells or cells with high lipid metabolism and in proliferating fetal cells. J Histochem Cytochem 48:613–622[Abstract/Free Full Text]
  43. Escot C, Joyeux C, Mathieu M, Maudelonde T, Pages A, Rochefort H, Chalbos D 1990 Regulation of fatty acid synthetase ribonucleic acid in the human endometrium during the menstrual cycle. J Clin Endocrinol Metab 70:1319–1324[Abstract]
  44. Pizer ES, Kurman RJ, Pasternack GR, Kuhajda FP 1997 Expression of fatty acid synthase is closely linked to proliferation and stromal decidualization in cycling endometrium. Int J Gynecol Pathol 16:45–51[Medline]
  45. Chalbos D, Joyeux C, Galtier F, Escot C, Chambon M, Maudelonde T, Rochefort H 1990 Regulation of fatty acid synthetase by progesterone in normal and tumoral human mammary glands. Rev Esp Fisiol 46:43–46[Medline]
  46. Chalbos D, Chambon M, Ailhaud G, Rochefort H 1987 Fatty acid synthetase and its mRNA are induced by progestins in breast cancer cells. J Biol Chem 262:9923–9926[Abstract/Free Full Text]
  47. Pizer ES, Lax SF, Kuhajda FP, Pasternack GR, Kurman RJ 1998 Fatty acid synthase expression in endometrial carcinoma: correlation with cell proliferation and hormone receptors. Cancer 83:528–537[CrossRef][Medline]
  48. Swinnen JV, Ulrix W, Heyns W, Verhoeven G 1997 Coordinate regulation of lipogenic gene expression by androgens: evidence for a cascade mechanism involving sterol regulatory element binding proteins. Proc Natl Acad Sci USA 94:12975–12980[Abstract/Free Full Text]
  49. Heemers H, Maes B, Foufelle F, Heyns W, Verhoeven G, Swinnen JV 2001 Androgens stimulate lipogenic gene expression in prostate cancer cells by activation of the sterol regulatory element-binding protein cleavage activating protein/sterol regulatory element-binding protein pathway. Mol Endocrinol 15:1817–1828[Abstract/Free Full Text]
  50. Lacasa D, Le Liepvre X, Ferre P, Dugail I 2001 Progesterone stimulates adipocyte determination and differentiation 1/sterol regulatory element-binding protein 1c gene expression: potential mechanism for the lipogenic effect of progesterone in adipose tissue. J Biol Chem 276:11512–11516[Abstract/Free Full Text]
  51. Swinnen JV, Esquenet M, Goossens K, Heyns W, Verhoeven G 1997 Androgens stimulate fatty acid synthase in the human prostate cancer cell line LNCaP. Cancer Res 57:1086–1090[Abstract/Free Full Text]
  52. Joyeux C, Rochefort H, Chalbos D 1989 Progestin increases gene transcription and messenger ribonucleic acid stability of fatty acid synthetase in breast cancer cells. Mol Endocrinol 3:681–686[Abstract]
  53. Menendez JA, Oza BP, Colomer R, Lupu R 2005 The estrogenic activity of synthetic progestins used in oral contraceptives enhances fatty acid synthase-dependent breast cancer cell proliferation and survival. Int J Oncol 26:1507–1515[Medline]
  54. Van de Sande T, De Schrijver E, Heyns W, Verhoeven G, Swinnen JV 2002 Role of the phosphatidylinositol 3'-kinase/PTEN/Akt kinase pathway in the overexpression of fatty acid synthase in LNCaP prostate cancer cells. Cancer Res 62:642–646[Abstract/Free Full Text]
  55. Menendez JA, Colomer R, Lupu R 2005 Why does tumor-associated fatty acid synthase (oncogenic antigen-519) ignore dietary fatty acids? Med Hypotheses 64:342–349[CrossRef][Medline]
  56. Kotzka J, Muller-Wieland D, Koponen A, Njamen D, Kremer L, Roth G, Munck M, Knebel B, Krone W 1998 ADD1/SREBP-1c mediates insulin-induced gene expression linked to the MAP kinase pathway. Biochem Biophys Res Commun 249:375–379[CrossRef][Medline]
  57. Fleischmann M, Iynedjian PB 2000 Regulation of sterol regulatory-element binding protein 1 gene expression in liver: role of insulin and protein kinase B/cAkt. Biochem J 349:13–17[CrossRef][Medline]
  58. Rossi S, Graner E, Febbo P, Weinstein L, Bhattacharya N, Onody T, Bubley G, Balk S, Loda M 2003 Fatty acid synthase expression defines distinct molecular signatures in prostate cancer. Mol Cancer Res 1:707–715[Abstract/Free Full Text]
  59. Yang YA, Morin PJ, Han WF, Chen, T, Bornman DM, Gabrielson EW, Pizer ES 2003 Regulation of fatty acid synthase expression in breast cancer by sterol regulatory element binding protein-1c. Exp Cell Res 282:132–137[CrossRef][Medline]
  60. Ettinger SL, Sobel R, Whitmore TG, Akbari M, Bradley DR, Gleave ME, Nelson CC 2004 Dysregulation of sterol response element-binding proteins and downstream effectors in prostate cancer during progression to androgen independence. Cancer Res 64:2212–2221[Abstract/Free Full Text]
  61. Li JN, Mahmoud MA, Han WF, Ripple M, Pizer ES 2000 Sterol regulatory element-binding protein-1 participates in the regulation of fatty acid synthase expression in colorectal neoplasia. Exp Cell Res 261:159–165[CrossRef][Medline]
  62. Yang YA, Han WF, Morin PJ, Chrest FJ, Pizer ES 2002 Activation of fatty acid synthesis during neoplastic transformation: role of mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Exp Cell Res 279:80–90[CrossRef][Medline]
  63. Yang YA, Morin PJ, Han WF, Chen T, Bornman DM, Gabrielson EW, Pizer ES 2003 Regulation of fatty acid synthase expression in breast cancer by sterol regulatory element binding protein-1c. Exp Cell Res 282:132–137[CrossRef][Medline]
  64. Bertile F, Raclot T 2004 mRNA levels of SREBP-1c do not coincide with the changes in adipose lipogenic gene expression. Biochem Biophys Res Commun 325:827–834[CrossRef][Medline]
  65. Menendez JA, Vellon L, Mehmi I, Oza BP, Ropero S, Colomer R, Lupu R 2004 Inhibition of fatty acid synthase (FAS) suppresses HER2/neu (erbB-2) oncogene overexpression in cancer cells. Proc Natl Acad Sci USA 101:10715–10720[Abstract/Free Full Text]
  66. Menendez JA, Vellon L, Colomer R, Lupu R 2005 Targeting fatty acid synthase: potential for therapeutic intervention in her-2/neu-overexpressing breast cancer. Drug News Perspect 18:375–385[CrossRef][Medline]
  67. Kumar-Sinha C, Ignatoski KW, Lippman ME, Ethier SP, Chinnaiyan AM 2003 Transcriptome analysis of HER2 reveals a molecular connection to fatty acid synthesis. Cancer Res 63:132–139[Abstract/Free Full Text]
  68. Menendez JA, Mehmi I, Verma VA, Teng PK, Lupu R 2004 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. Mol Carcinog 41:164–178[CrossRef][Medline]
  69. Menendez JA, Decker JP, Lupu R 2005 In support of fatty acid synthase (FAS) as a metabolic oncogene: extracellular acidosis acts in an epigenetic fashion activating FAS gene expression in cancer cells. J Cell Biochem 94:1–4[CrossRef][Medline]
  70. Menendez JA, Oza BP, Atlas E, Mehmi I, Lupu R, Fatty acid synthase (FAS) inhibitor C75 induces hyperactivation of ERK1/2 MAPK-estrogen receptor {alpha} (ER-{alpha}) cross-talk, loss of ER-{alpha} expression, inhibition of cell growth, and apoptotic cell death in hormone-dependent breast cancer cells. Proc 15th Annual AACR-NCI-EORTC Symposium, San Francisco, CA, 2003 (Abstract A157)
  71. Menendez JA, Oza BP, Atlas E, Verma VA, Mehmi I, Lupu R 2004 Inhibition of tumor-associated fatty acid synthase activity antagonizes estradiol- and tamoxifen-induced agonist transactivation of estrogen receptor (ER) in human endometrial adenocarcinoma cells. Oncogene 23:4945–4958[CrossRef][Medline]
  72. Menendez JA, Oza BP, Atlas E, Vazquez-Martin A, Colomer R, Lupu R, The anorectic fatty acid synthase (FAS) inhibitor C75 regulates genomic and nongenomic estrogen receptor-{alpha} activities in breast cancer cells. Proc 95th Annual AACR, Orlando, FL, 2004, Late-Breaking Abstract LB268
  73. Menendez JA, Rubinstein W, Lupu R, Inhibition of fatty acid synthase (FAS) activity reverses tamoxifen resistance in Her-2/neu-overexpressing breast cancer cells. Proc 96th Annual AACR, Anaheim, CA, 2005 (Abstract 5072)
  74. Menendez JA, Lupu R, Heregulin induces transcriptional activation of breast cancer-associated fatty acid synthase (FAS) gene expression by an autocrine mechanism that requires activation of Her-2/neu, MAPK and PI-3'K. Proc 96th Annual AARC, Anaheim, CA, 2005 (Abstract 3670)
  75. Castoria G, Migliaccio A, Bilancio A, Di Domenico M, de Falco A, Lombardi M, Fiorentino R, Varricchio L, Barone MV, Auricchio F 2001 PI3-kinase in concert with Src promotes the S-phase entry of oestradiol-stimulated MCF-7 cells. EMBO J 20:6050–6059[CrossRef][Medline]
  76. Migliaccio A, Castoria G, Di Domenico M, De Falco A, Bilancio A, Auricchio F 2002 Src is an initial target of sex steroid hormone action. Ann NY Acad Sci 963:185–190[Abstract/Free Full Text]
  77. Migliaccio A, Di Domenico M, Castoria G, de Falco A, Bontempo P, Nola E, Auricchio F 1996 Tyrosine kinase/p21ras/MAP-kinase pathway activation by estradiol-receptor complex in MCF-7 cells. EMBO J 15:1292–1300[Medline]
  78. Oh AS, Lorant LA, Holloway JN, Miller DL, Kern FG, El-Ashry D 2001 Hyperactivation of MAPK induces loss of ER{alpha} expression in breast cancer cells. Mol Endocrinol 15:1344–1359[Abstract/Free Full Text]
  79. Stoica GE, Franke TF, Moroni M, Mueller S, Morgan E, Iann MC, Winder AD, Reiter R, Wellstein A, Martin MB, Stoica A 2003 Effect of estradiol on estrogen receptor-{alpha} gene expression and activity can be modulated by the ErbB2/PI 3-K/Akt pat