4-methylene-2-octyl-5-oxofuran-3-carboxylic-acid and Ovarian-Neoplasms

Fatty acid synthase (FASN), the enzyme responsible for de novo synthesis of fatty acids, has been shown to be deregulated in several cancers, including epithelial ovarian carcinoma (EOC). In this study, we investigated the function of the FASN signaling pathway in a large series of Middle Eastern EOC patient samples, a panel of cell lines and nude mouse model. Using immunohistochemistry, we detected overexpression of FASN in 75.5% (114/151) of the tumor samples. Overexpression of FASN was associated significantly with tumor proliferative marker Ki-67 (P = 0.0009), activated AKT (P = 0.0117) and XIAP (P = 0.0046). Treatment of EOC cell lines with C-75, a selective inhibitor of FASN, caused inhibition of EOC cell viability via induction of apoptosis. Inhibition of FASN by C-75 led apoptosis via the mitochondrial pathway. FASN inhibition caused downregulation of activated AKT and its downstream targets. In addition, inhibition by FASN siRNA caused downregulation of FASN and activation of caspases, suggesting the role of FASN in C-75 mediated apoptosis. Furthermore, treatment of EOC cells with subtoxic doses of C-75 augmented the effect of cisplatin-mediated induction of apoptosis. Finally, treatment of EOC cell line xenografts with a combination of C-75 and cisplatin resulted in growth inhibition of tumors in nude mice through downregulation of FASN and activation of caspases. Altogether, our results show overexpression of FASN in Middle Eastern EOC, suggesting that FASN may be a potential therapeutic target in a subset of EOC, alone or in combination with other conventional chemotherapeutic agents.

Topics: 4-Butyrolactone; Adult; Aged; Aged, 80 and over; Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Carcinoma, Ovarian Epithelial; Cisplatin; Drug Synergism; Fatty Acid Synthases; Female; Humans; Immunohistochemistry; Mice; Mice, Nude; Middle Aged; Middle East; Neoplasms, Glandular and Epithelial; Ovarian Neoplasms; Proto-Oncogene Proteins c-akt; RNA Interference; Tissue Array Analysis; Xenograft Model Antitumor Assays; Young Adult

Aberrations within the phosphoinositide-3-kinase (PI3K) pathway occur in greater than 45% of ovarian carcinomas. The PI3K cascade transmits signals from ErbB receptors downstream to S6 and 4EBP1, which are involved in protein biosynthesis. Many ovarian carcinomas reveal hyperactivation of ErbB1 (epidermal growth factor receptor) or ErbB2 (HER2/neu). Unfortunately, the benefit of anti-ErbB drugs is yet rather limited in ovarian carcinomas. Thus, novel targeting strategies are needed for ovarian carcinomas. The lipogenic enzyme fatty acid synthase (FASN) is overexpressed in approximately 80% of ovarian carcinomas. It stimulates cell growth and signifies poor prognosis. FASN inhibition impedes (ErbB) membrane receptor signaling and sensitizes cells against anti-ErbB drugs. Here, we show that the FASN inhibitor C75 and FASN-targeting siRNAs abrogate growth, induce apoptosis, and downregulate phosphorylation/expression of the PI3K effectors AKT, mTOR, p70S6K, S6, and 4EBP1. In contrast, FASN inhibition impairs expression but only weakly affects phosphorylation of ERK1/2 mitogen-activated protein kinases in ovarian carcinoma cells. Cycloheximide-mediated blockade of protein translation reveals that C75- or FASN siRNA-induced shutdown of FASN accelerates decomposition of signaling proteins. This effect is caused by C75- or FASN siRNA-dependent stimulation of ubiquitination followed by lysosomal-autophagosomal proteolysis. In contrast, PI3K inhibitor LY294002 blocks phosphorylation but does not reduce expression/stability of PI3K effectors. Forced expression of hyperactive (HA) AKT1, unlike HA-MEK1, impairs the growth-inhibitory action of C75. We provide first evidence that the anticancer action of FASN inhibitors is at least partially mediated by drug-dependent proteolysis of PI3K effectors. FASN is a promising cancer target, whose inhibition not only abrogates lipogenesis, which is indispensable for cancer growth, but also downregulates oncogenic PI3K signaling.

Topics: 4-Butyrolactone; Adaptor Proteins, Signal Transducing; Apoptosis; Cell Cycle Proteins; Cell Proliferation; Chromones; ErbB Receptors; Fatty Acid Synthases; Female; Gene Expression Regulation, Neoplastic; Humans; Lipogenesis; Morpholines; Ovarian Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoproteins; Phosphorylation; Proteolysis; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Small Interfering; Signal Transduction; TOR Serine-Threonine Kinases; Ubiquitination

Fatty acid synthase (FASN) represents a metabolic oncogene. It produces phospholipids for membrane microdomains that accommodate receptor tyrosine kinases including Epidermal Growth Factor-Receptor (EGFR, ErbB1) and ErbB2 (HER2/neu). FASN and ErbBs are overexpressed in ovarian cancer. We examined the effect of FASN and ErbB inhibition on A2780 and SKOV3 ovarian cancer cells. Growth assays reveal that FASN inhibitor C75 sensitizes tumor cells against anti-ErbB drugs (pelitinib [EKB-569], canertinib [CI-1033], erlotinib, cetuximab, matuzumab, trastuzumab) suggesting FASN/ErbB cooperation. qRT-PCR and Western blotting revealed that C75 represses FASN, EGFR, ErbB2, and AKT suggesting that FASN-induced membrane microdomains accommodate/stabilize ErbBs and facilitate AKT recruitment/activation. Our data indicate that AKT is crucial for ErbB/FASN interaction, AKT cross-inhibits ERK and feeds loops that boost FASN and EGFR transcription, and EGFR and ErbB2 must be co-silenced for maximal FASN downregulation. Taken together, interference with FASN and ErbB abrogates their oncogenicity and should be exploited for ovarian cancer treatment.

Topics: 4-Butyrolactone; Cell Line, Tumor; Enzyme Inhibitors; ErbB Receptors; Fatty Acid Synthase, Type I; Female; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Ovarian Neoplasms; Phosphorylation; Proto-Oncogene Proteins c-akt; Receptor, ErbB-2

Activation of AKT and overexpression of fatty acid synthase (FAS) are frequently observed in human ovarian cancer. To explore a possible connection between AKT and FAS, immunohistochemical analyses were conducted on an ovarian cancer tissue microarray, which revealed a significant correlation between phosphorylated AKT (phospho-AKT) and expression of FAS. To investigate the relationship between phospho-AKT and FAS in vitro, a variety of experiments employing a specific phosphatidylinositol 3-OH kinase (PI3K) inhibitor (LY294002), inducible PTEN expression in PTEN-null cells, or AKT1 siRNA demonstrated that phosphatidylinositol-3 kinase (PI3K)/AKT signaling modulates FAS expression. In contrast, inhibition of FAS activity by the drug C75 resulted in downregulation of phospho-AKT and increased cell death. To explore the functional relationship between phospho-AKT and FAS, we used SKOV3, C200, and OVCAR10 ovarian carcinoma cells, which have constitutively active AKT, and OVCAR5 cells, which have very low basal phospho-AKT levels. Treatment with LY294002 abolished AKT activity and potentiated apoptosis induced by FAS inhibitors cerulenin or C75 only in cells with constitutively active AKT, suggesting that constitutive activation of AKT protects against FAS inhibitor-induced cell death. Furthermore, inhibition of FAS activity by cerulenin or C75 resulted in downregulation of phospho-AKT, which preceded the induction of apoptosis. To investigate the relationship between phospho-AKT and FAS in vivo, severe combined immunodeficient mice injected intraperitoneally with SKOV3 cells were treated with C75. Growth of SKOV3 xenografts was markedly inhibited by C75. Analysis of the levels of phospho-AKT and FAS in C75-treated tumors revealed concordant downregulation of phospho-AKT and FAS. Collectively, our findings are consistent with a working model in which AKT activation regulates FAS expression, at least in part, whereas FAS activity modulates AKT activation.

Topics: 4-Butyrolactone; Animals; Apoptosis; Blotting, Western; Cell Line, Tumor; Enzyme Activation; Enzyme Inhibitors; Fatty Acid Synthases; Feedback, Physiological; Female; Humans; Immunohistochemistry; Mice; Ovarian Neoplasms; Phosphatidylinositol 3-Kinases; Phosphoric Monoester Hydrolases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; RNA, Small Interfering; Tumor Suppressor Proteins

Fatty acid synthase (FAS) activity is a potential therapeutic target to treat cancer and obesity. Here, we have identified a molecular link between FAS and HER2 (erbB-2) oncogene, a marker for poor prognosis that is overexpressed in 30% of breast and ovarian cancers. Pharmacological FAS inhibitors cerulenin and C75 were found to suppress p185(HER2) oncoprotein expression and tyrosine-kinase activity in breast and ovarian HER2 overexpressors. Similarly, p185(HER2) expression was dramatically down-regulated when FAS gene expression was silenced by using the highly sequence-specific mechanism of RNA interference (RNAi). Pharmacological and RNAi-mediated silencing of FAS specifically down-regulated HER2 mRNA and, concomitantly, caused a prominent up-regulation of PEA3, a transcriptional repressor of HER2. A cytoplasmic redistribution of p185(HER2) was associated with marked morphological changes of FAS RNAi-transfected cells, whereas chemical inhibitors of FAS promoted a striking nuclear accumulation of p185(HER2). The simultaneous targeting of FAS and HER2 by chemical FAS inhibitors and the humanized antibody directed against p185(HER2) trastuzumab, respectively, was synergistically cytotoxic toward HER2 overexpressors. Similarly, concurrent RNAi-mediated silencing of FAS and HER2 genes synergistically stimulated apoptotic cell death in HER2 overexpressors. p185(HER2) was synergistically down-regulated after simultaneous inhibition of FAS and HER2 by either pharmacological inhibitors or small interfering RNA. These findings provide evidence of an active role of FAS in cancer evolution by specifically regulating oncogenic proteins closely related to malignant transformation, strongly suggesting that HER2 oncogene may act as the key molecular sensor of energy imbalance after the perturbation of tumor-associated FAS hyperactivity in cancer cells.

Topics: 4-Butyrolactone; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antifungal Agents; Antineoplastic Agents; Apoptosis; Biomarkers, Tumor; Breast Neoplasms; Cell Line; Cell Size; Cell Survival; Cerulenin; Fatty Acid Synthases; Female; Gene Expression Regulation, Neoplastic; Genes, erbB-2; Humans; Ovarian Neoplasms; Receptor, ErbB-2; RNA, Small Interfering; Signal Transduction; Transcription Factors; Trastuzumab