New synthetic inhibitors of fatty acid synthase with anticancer activity

Inhibition of Cancer Stem-like Cells by Curcumin and Other Polyphenol Derivatives in MDA-MB-231 TNBC Cells

Triple-negative breast cancer (TNBC) accounts for 15% of all breast cancers and is highly aggressive. Despite an initial positive response to chemotherapy, most patients experience rapid disease progression leading to relapse and metastasis. This is attributed to the presence of breast cancer stem cells (BCSCs) within the tumor, which are characterized by self-renewal, pluripotency, and resistance mechanisms. Targeting BCSCs has become critical as conventional therapies fail to eradicate them due to a lack of specific targets. Curcumin, a polyphenol derived from turmeric (Curcuma longa), exhibits anticancer effects against breast cancer cells and BCSCs. The use of curcumin derivatives has been suggested as an approach to overcome the bioavailability and solubility problems of curcumin in humans, thereby increasing its anticancer effects. The aim of this study was to evaluate the cellular and molecular effects of six synthetic compounds derived from the natural polyphenol epigallocatechin gallate (EGCG) (TL1, TL2) and curcumin derivatives (TL3, TL4, TL5, and TL6) on a TNBC mesenchymal stem-like cell line. The activity of the compounds against BCSCs was also determined by a mammosphere inhibition assay and studying different BCSC markers by Western blotting. Finally, a drug combination assay was performed with the most promising compounds to evaluate their potential synergistic effects with the chemotherapeutic agents doxorubicin, cisplatin, and paclitaxel. The results showed that compounds exhibited specific cytotoxicity against the TNBC cell line and BCSCs. Interestingly, the combination of the curcumin derivative TL3 with doxorubicin and cisplatin displayed a synergistic effect in TNBC cells.

Fatty acid synthase (FASN) signalome: A molecular guide for precision oncology

The initial excitement generated more than two decades ago by the discovery of drugs targeting fatty acid synthase (FASN)-catalyzed de novo lipogenesis for cancer therapy was short-lived. However, the advent of the first clinical-grade FASN inhibitor (TVB-2640; denifanstat), which is currently being studied in various phase II trials, and the exciting advances in understanding the FASN signalome are fueling a renewed interest in FASN-targeted strategies for the treatment and prevention of cancer. Here, we provide a detailed overview of how FASN can drive phenotypic plasticity and cell fate decisions, mitochondrial regulation of cell death, immune escape and organ-specific metastatic potential. We then present a variety of FASN-targeted therapeutic approaches that address the major challenges facing FASN therapy. These include limitations of current FASN inhibitors and the lack of precision tools to maximize the therapeutic potential of FASN inhibitors in the clinic. Rethinking the role of FASN as a signal transducer in cancer pathogenesis may provide molecularly driven strategies to optimize FASN as a long-awaited target for cancer therapeutics.

Tea-break with epigallocatechin gallate derivatives - Powerful polyphenols of great potential for medicine

Epigallocatechin gallate (EGCG) is a polyphenol present in green tea (Camellia sinensis), which has revealed anti-cancer effects toward a variety of cancer cells in vitro and protective potential against neurodegenerative diseases such as Alzheimer's and Parkinson's. Unfortunately, EGCG presents disappointing bioavailability after oral administration, primarily due to its chemical instability and poor absorption. Due to these limitations, EGCG is currently not used in medication, but only as a dietary supplement in the form of green tea extract. Therefore, it needs further modifications before being considered suitable for extensive medical applications. In this article, we review the scientific literature about EGCG derivatives focusing on their biological properties and potential medical applications. The most common chemical modifications of epigallocatechin gallate rely on introducing fatty acid chains or sugar molecules to its chemical structure to modify solubility. Another frequently employed procedure is based on blocking EGCG's hydroxyl groups with various substituents. Novel derivatives reveal interesting properties, of which, antioxidant, anti-inflammatory, antitumor and antimicrobial, are especially important. It is worth noting that the most promising EGCG derivatives present higher stability and activity than base EGCG.

Progress of potential drugs targeted in lipid metabolism research

Lipids are a class of complex hydrophobic molecules derived from fatty acids that not only form the structural basis of biological membranes but also regulate metabolism and maintain energy balance. The role of lipids in obesity and other metabolic diseases has recently received much attention, making lipid metabolism one of the attractive research areas. Several metabolic diseases are linked to lipid metabolism, including diabetes, obesity, and atherosclerosis. Additionally, lipid metabolism contributes to the rapid growth of cancer cells as abnormal lipid synthesis or uptake enhances the growth of cancer cells. This review introduces the potential drug targets in lipid metabolism and summarizes the important potential drug targets with recent research progress on the corresponding small molecule inhibitor drugs. The significance of this review is to provide a reference for the clinical treatment of metabolic diseases related to lipid metabolism and the treatment of tumors, hoping to deepen the understanding of lipid metabolism and health.

Epigallocatechin gallate triggers apoptosis by suppressing de novo lipogenesis in colorectal carcinoma cells

The de novo lipogenesis (DNL) pathway has been identified as a regulator of cancer progression and aggressiveness. Downregulation of key lipogenesis enzymes has been shown to activate apoptosis in cancerous cells. Epigallocatechin gallate (EGCG) inhibits cancer cell proliferation without causing cytotoxicity in healthy cells. The aim of the present study is to investigate the effects of EGCG on the promotion of apoptosis associated with the DNL pathway inhibition in cancer cells, both in vitro and in vivo. We observed that two colorectal cancer (CRC) cell lines (HCT116 and HT-29) had a higher cytotoxic response to EGCG treatment than hepatocellular carcinoma cells, including HepG2 and HuH-7. EGCG treatment decreased cell viability and increased mitochondrial damage-triggered apoptosis in both HCT116 and HT-29 cancer cells. Additionally, we treated mice transplanted with HCT116 cells with 30 or 50 mg/kg EGCG for 7 days to evaluate the apoptotic effects of EGCN treatment in a xenograft mouse model of cancer. We observed a decrease in intracellular fatty acid levels, which suggested that EGCG-induced apoptosis was associated with a decrease in fatty acid levels in cancer. Suppression of adenosine triphosphate synthesis by EGCG indicated that cell death induction in cancer cells could be mediated by shared components of the DNL and energy metabolism pathways. In addition, EGCG-induced apoptosis suppressed the expression of the phosphorylation protein kinase B and extracellular signal-regulated kinase 1/2 signaling proteins in tumors from xenografted mice. Cytotoxic effects in unaffected organs and tissues of the mouse xenograft model were absent upon EGCG treatment.

Isoprenylcysteine Carboxylmethyltransferase-Based Therapy for Hutchinson-Gilford Progeria Syndrome

Hutchinson-Gilford progeria syndrome (HGPS, progeria) is a rare genetic disease characterized by premature aging and death in childhood for which there were no approved drugs for its treatment until last November, when lonafarnib obtained long-sought FDA approval. However, the benefits of lonafarnib in patients are limited, highlighting the need for new therapeutic strategies. Here, we validate the enzyme isoprenylcysteine carboxylmethyltransferase (ICMT) as a new therapeutic target for progeria with the development of a new series of potent inhibitors of this enzyme that exhibit an excellent antiprogeroid profile. Among them, compound UCM-13207 significantly improved the main hallmarks of progeria. Specifically, treatment of fibroblasts from progeroid mice with UCM-13207 delocalized progerin from the nuclear membrane, diminished its total protein levels, resulting in decreased DNA damage, and increased cellular viability. Importantly, these effects were also observed in patient-derived cells. Using the Lmna ^G609G/G609G progeroid mouse model, UCM-13207 showed an excellent in vivo efficacy by increasing body weight, enhancing grip strength, extending lifespan by 20%, and decreasing tissue senescence in multiple organs. Furthermore, UCM-13207 treatment led to an improvement of key cardiovascular hallmarks such as reduced progerin levels in aortic and endocardial tissue and increased number of vascular smooth muscle cells (VSMCs). The beneficial effects go well beyond the effects induced by other therapeutic strategies previously reported in the field, thus supporting the use of UCM-13207 as a new treatment for progeria.

The Pharmacological or Genetic Blockade of Endogenous De Novo Fatty Acid Synthesis Does Not Increase the Uptake of Exogenous Lipids in Ovarian Cancer Cells

Ovarian cancer(OC) is a serious threat to women worldwide. Peritoneal dissemination, ascites and omental metastasis are typical features for disease progression, which occurs in a micro-environment that is rich in high-energy lipids. OC cells require high amounts of lipids for survival and growth. Not only do they import lipids from the host, they also produce lipids de novo. Inhibitors of fatty acid(FA) synthase(FASN) – the rate-limiting enzyme of endogenous FA synthesis that is overexpressed in OC – induce growth-arrest and apoptosis, rendering them promising candidates for cancer drug development. However, cancer researchers have long hypothesized that the lipid deficiency caused by FASN inhibition can be circumvented by increasing the uptake of exogenous lipids from the host, which would confer resistance to FASN inhibitors. In contrast to a very recent report in colorectal cancer, we demonstrate in OC cells (A2780, OVCAR3, SKOV3) that neither FASN inhibitors (G28UCM, Fasnall) nor FASN-specific siRNAs can stimulate a relief pathway leading to enhanced uptake of extrinsic FAs or low density lipoproteins (LDLs). Instead, we observed that the growth-arrest due to FASN inhibition or FASN knock-down was associated with significant dose- and time-dependent reduction in the uptake of fluorescently labeled FAs and LDLs. Western blotting showed that the expression of the FA receptor CD36, the LDL receptor(LDLR) and the lipid transport proteins fatty acid binding proteins 1–9 (FABP1–9) was not affected by the treatment. Next, we compared experimental blockade of endogenous lipid production with physiologic depletion of exogenous lipids. Lipid-free media, similar to FASN inhibitors, caused growth-arrest. Although lipid-depleted cells have diminished amounts of CD36, LDLR and FABPs, they can still activate a restorative pathway that causes enhanced import of fluorophore-labeled FAs and LDLs. Overall, our data show that OC cells are strictly lipid-depend and exquisitely sensitive to FASN inhibitors, providing a strong rationale for developing anti-FASN strategies for clinical use against OC.

Membrane disruption, but not metabolic rewiring, is the key mechanism of anticancer-action of FASN-inhibitors: a multi-omics analysis in ovarian cancer

Fatty-acid(FA)-synthase(FASN) is a druggable lipogenic oncoprotein whose blockade causes metabolic disruption. Whether drug-induced metabolic perturbation is essential for anticancer drug-action, or is just a secondary—maybe even a defence response—is still unclear. To address this, SKOV3 and OVCAR3 ovarian cancer(OC) cell lines with clear cell and serous histology, two main OC subtypes, were exposed to FASN-inhibitor G28UCM. Growth-inhibition was compared with treatment-induced cell-metabolomes, lipidomes, proteomes and kinomes. SKOV3 and OVCAR3 were equally sensitive to low-dose G28UCM, but SKOV3 was more resistant than OVCAR3 to higher concentrations. Metabolite levels generally decreased upon treatment, but individual acylcarnitines, glycerophospholipids, sphingolipids, amino-acids, biogenic amines, and monosaccharides reacted differently. Drug-induced effects on central-carbon-metabolism and oxidative-phosphorylation (OXPHOS) were essentially different in the two cell lines, since drug-naïve SKOV3 are known to prefer glycolysis, while OVCAR3 favour OXPHOS. Moreover, drug-dependent increase of desaturases and polyunsaturated-fatty-acids (PUFAs) were more pronounced in SKOV3 and appear to correlate with G28UCM-tolerance. In contrast, expression and phosphorylation of proteins that control apoptosis, FA synthesis and membrane-related processes (beta-oxidation, membrane-maintenance, transport, translation, signalling and stress-response) were concordantly affected. Overall, membrane-disruption and second-messenger-silencing were crucial for anticancer drug-action, while metabolic-rewiring was only secondary and may support high-dose-FASN-inhibitor-tolerance. These findings may guide future anti-metabolic cancer intervention.

Lipids and cancer: Emerging roles in pathogenesis, diagnosis and therapeutic intervention

With the advent of effective tools to study lipids, including mass spectrometry-based lipidomics, lipids are emerging as central players in cancer biology. Lipids function as essential building blocks for membranes, serve as fuel to drive energy-demanding processes and play a key role as signaling molecules and as regulators of numerous cellular functions. Not unexpectedly, cancer cells, as well as other cell types in the tumor microenvironment, exploit various ways to acquire lipids and extensively rewire their metabolism as part of a plastic and context-dependent metabolic reprogramming that is driven by both oncogenic and environmental cues. The resulting changes in the fate and composition of lipids help cancer cells to thrive in a changing microenvironment by supporting key oncogenic functions and cancer hallmarks, including cellular energetics, promoting feedforward oncogenic signaling, resisting oxidative and other stresses, regulating intercellular communication and immune responses. Supported by the close connection between altered lipid metabolism and the pathogenic process, specific lipid profiles are emerging as unique disease biomarkers, with diagnostic, prognostic and predictive potential. Multiple preclinical studies illustrate the translational promise of exploiting lipid metabolism in cancer, and critically, have shown context dependent actionable vulnerabilities that can be rationally targeted, particularly in combinatorial approaches. Moreover, lipids themselves can be used as membrane disrupting agents or as key components of nanocarriers of various therapeutics. With a number of preclinical compounds and strategies that are approaching clinical trials, we are at the doorstep of exploiting a hitherto underappreciated hallmark of cancer and promising target in the oncologist's strategy to combat cancer.

Molecular Imaging and In Situ Quantitative Profiling of Fatty Acid Synthase with a Chemical Probe

Cancer cells rely on fatty acid synthase (FASN), a key enzyme for de novo biosynthesis of long chain fatty acids, to sustain their proliferative potential and drive invasion. Unfortunately, conventional FASN assays are technically inadequate for discerning otherwise elusive FASN activity in complex biological milieux, which has hindered progress in the functional study of FASN and development of its inhibitors. Here, we describe a chemical probe with unprecedented selectivity and sensitivity for the labeling of active FASN in living cells, thus demonstrating a new analytical modality for visualizing endogenous FASN activity and exploring opportunities for drug discovery.

4-1BBL Regulates the Polarization of Macrophages, and Inhibition of 4-1BBL Signaling Alleviates Imiquimod-Induced Psoriasis

4-1BBL, a member of the TNF superfamily, regulates the sustained production of inflammatory cytokines in macrophages triggered by TLR signaling. In this study, we have investigated the role of 4-1BBL in macrophage metabolism and polarization and in skin inflammation using a model of imiquimod-induced psoriasis in mice. Genetic ablation or blocking of 4-1BBL signaling by Ab or 4-1BB-Fc alleviated the pathology of psoriasis by regulating the expression of inflammatory cytokines associated with macrophage activation and regulated the polarization of macrophages in vitro. We further linked this result with macrophage by finding that 4-1BBL expression during the immediate TLR response was dependent on glycolysis, mitochondrial oxidative phosphorylation, and fatty acid metabolism, whereas the late-phase 4-1BBL-mediated sustained inflammatory response was dependent on glycolysis and fatty acid synthesis. Correlating with this, administration of a fatty acid synthase inhibitor, cerulenin, also alleviated the pathology of psoriasis. We further found that 4-1BBL-mediated psoriasis development is independent of its receptor 4-1BB, as a deficiency of 4-1BB augmented the severity of psoriasis linked to a reduced regulatory T cell population and increased IL-17A expression in γδ T cells. Additionally, coblocking of 4-1BBL signaling and IL-17A activity additively ameliorated psoriasis. Taken together, 4-1BBL signaling regulates macrophage polarization and contributes to imiquimod-induced psoriasis by sustaining inflammation, providing a possible avenue for psoriasis treatment in patients.

The Race to Bash NASH: Emerging Targets and Drug Development in a Complex Liver Disease

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD) characterized by liver steatosis, inflammation, and hepatocellular damage. NASH is a serious condition that can progress to cirrhosis, liver failure, and hepatocellular carcinoma. The association of NASH with obesity, type 2 diabetes mellitus, and dyslipidemia has led to an emerging picture of NASH as the liver manifestation of metabolic syndrome. Although diet and exercise can dramatically improve NASH outcomes, significant lifestyle changes can be challenging to sustain. Pharmaceutical therapies could be an important addition to care, but currently none are approved for NASH. Here, we review the most promising targets for NASH treatment, along with the most advanced therapeutics in development. These include targets involved in metabolism (e.g., sugar, lipid, and cholesterol metabolism), inflammation, and fibrosis. Ultimately, combination therapies addressing multiple aspects of NASH pathogenesis are expected to provide benefit for patients.

Essentiality of fatty acid synthase in the 2D to anchorage-independent growth transition in transforming cells

Upregulation of fatty acid synthase (FASN) is a common event in cancer, although its mechanistic and potential therapeutic roles are not completely understood. In this study, we establish a key role of FASN during transformation. FASN is required for eliciting the anaplerotic shift of the Krebs cycle observed in cancer cells. However, its main role is to consume acetyl-CoA, which unlocks isocitrate dehydrogenase (IDH)-dependent reductive carboxylation, producing the reductive power necessary to quench reactive oxygen species (ROS) originated during the switch from two-dimensional (2D) to three-dimensional (3D) growth (a necessary hallmark of cancer). Upregulation of FASN elicits the 2D-to-3D switch; however, FASN's synthetic product palmitate is dispensable for this process since cells satisfy their fatty acid requirements from the media. In vivo, genetic deletion or pharmacologic inhibition of FASN before oncogenic activation prevents tumor development and invasive growth. These results render FASN as a potential target for cancer prevention studies.

A Potent Isoprenylcysteine Carboxylmethyltransferase (ICMT) Inhibitor Improves Survival in Ras-Driven Acute Myeloid Leukemia

Blockade of Ras activity by inhibiting its post-translational methylation catalyzed by isoprenylcysteine carboxylmethyltransferase (ICMT) has been suggested as a promising antitumor strategy. However, the paucity of inhibitors has precluded the clinical validation of this approach. In this work we report a potent ICMT inhibitor, compound 3 [UCM-1336, IC₅₀ = 2 μM], which is selective against the other enzymes involved in the post-translational modifications of Ras. Compound 3 significantly impairs the membrane association of the four Ras isoforms, leading to a decrease of Ras activity and to inhibition of Ras downstream signaling pathways. In addition, it induces cell death in a variety of Ras-mutated tumor cell lines and increases survival in an in vivo model of acute myeloid leukemia. Because ICMT inhibition impairs the activity of the four Ras isoforms regardless of its activating mutation, compound 3 surmounts many of the common limitations of available Ras inhibitors described so far. In addition, these results validate ICMT as a valuable target for the treatment of Ras-driven tumors.

EGCG-Derivative G28 Shows High Efficacy Inhibiting the Mammosphere-Forming Capacity of Sensitive and Resistant TNBC Models

Recent studies showed that Fatty Acid Synthase (FASN), a lipogenic enzyme overexpressed in several carcinomas, plays an important role in drug resistance. Furthermore, the enrichment of Breast Cancer Stem Cell (BCSC) features has been found in breast tumors that progressed after chemotherapy. Hence, we used the triple negative breast cancer (TNBC) cell line MDA-MB-231 (231) to evaluate the FASN and BCSC population role in resistance acquisition to chemotherapy. For this reason, parental cell line (231) and its derivatives resistant to doxorubicin (231DXR) and paclitaxel (231PTR) were used. The Mammosphere-Forming Assay and aldehyde dehydrogenase (ALDH) enzyme activity assay showed an increase in BCSCs in the doxorubicin-resistant model. Moreover, the expression of some transcription factors involved in epithelial-mesenchymal transition (EMT), a process that confers BCSC characteristics, was upregulated after chemotherapy treatment. FASN inhibitors C75, (−)-Epigallocatechin 3-gallate (EGCG), and its synthetic derivatives G28, G56 and G37 were used to evaluate the effect of FASN inhibition on the BCSC-enriched population in our cell lines. G28 showed a noticeable antiproliferative effect in adherent conditions and, interestingly, a high mammosphere-forming inhibition capacity in all cell models. Our preliminary results highlight the importance of studying FASN inhibitors for the treatment of TNBC patients, especially those who progress after chemotherapy.

The Structures and Bioactivities of Fatty Acid Synthase Inhibitors

Background:

Fatty Acid Synthase (FAS or FASN) is a vital enzyme which catalyzes the de novo synthesis of long chain fatty acids. A number of studies have recently been reported that FAS was combined targets for the discovery of anti-obesity and anti-cancer drugs. Great interest has been developed in finding novel FAS inhibitors, and result in more than 200 inhibitors being reported.

Methods:

The reported research literature about the FAS inhibitors was collected and analyzedsised through major databases including Web of Science, and PubMed. Then the chemical stractures, FAS inhibitory activities, and Structure-Activity Relationships (SAR) were summarized focused on all these reported FAS inhibitors.

Results:

The 248 FAS inhibitors, which were reported during the past 20 years, could be divided into thiolactone, butyrolactone and butyrolactam, polyphenols, alkaloids, terpenoids, and other structures, in view of their structure characteristics. And the SAR of high inhibitory structures of each type was proposed in this paper.

Conclusion:

A series of synthetic quinolinone derivatives show strongest inhibitory activity in the reported FAS inhibitors. Natural polyphenols, existing in food and herbs, show more adaptive in medicine exploration because of their safety and efficiency. Moreover, screening the FAS inhibitors from microorganism and marine natural products could be the hot research directions in the future.

(-)-Epigallocatechin 3-Gallate Synthetic Analogues Inhibit Fatty Acid Synthase and Show Anticancer Activity in Triple Negative Breast Cancer

(−)-Epigallocatechin 3-gallate (EGCG) is a natural polyphenol from green tea with reported anticancer activity and capacity to inhibit the lipogenic enzyme fatty acid synthase (FASN), which is overexpressed in several human carcinomas. To improve the pharmacological profile of EGCG, we previously developed a family of EGCG derivatives and the lead compounds G28, G37 and G56 were characterized in HER2-positive breast cancer cells overexpressing FASN. Here, diesters G28, G37 and G56 and two G28 derivatives, monoesters M1 and M2, were synthesized and assessed in vitro for their cytotoxic, FASN inhibition and apoptotic activities in MDA-MB-231 triple-negative breast cancer (TNBC) cells. All compounds displayed moderate to high cytotoxicity and significantly blocked FASN activity, monoesters M1 and M2 being more potent inhibitors than diesters. Interestingly, G28, M1, and M2 also diminished FASN protein expression levels, but only monoesters M1 and M2 induced apoptosis. Our results indicate that FASN inhibition by such polyphenolic compounds could be a new strategy in TNBC treatment, and highlight the potential anticancer activities of monoesters. Thus, G28, G37, G56, and most importantly M1 and M2, are anticancer candidates (alone or in combination) to be further characterized in vitro and in vivo.

Orlistat as a FASN inhibitor and multitargeted agent for cancer therapy

INTRODUCTION

Cancer cells have increased glycolysis and glutaminolysis. Their third feature is increased de novo lipogenesis. As such, fatty acid (FA) synthesis enzymes are over-expressed in cancer and their depletion causes antitumor effects. As fatty acid synthase (FASN) plays a pivotal role in this process, it is an attractive target for cancer therapy.

AREAS COVERED

This is a review of the lipogenic phenotype of cancer and how this phenomenon can be exploited for cancer therapy using inhibitors of FASN, with particular emphasis on orlistat as a repurposing drug.

EXPERT OPINION

Disease stabilization only has been observed with a highly selective FASN inhibitor used as a single agent in clinical trials. It is too early to say whether the absence of tumor responses other than stabilization results because even full inhibition of FASN is not enough to elicit antitumor responses. The FASN inhibitor orlistat is a 'dirty' drug with target-off actions upon at least seven targets with a proven role in tumor biology. The development of orlistat formulations suited for its intravenous administration is a step ahead to shed light on the concept that drug promiscuity can or not be a virtue.

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.

Multi-level suppression of receptor-PI3K-mTORC1 by fatty acid synthase inhibitors is crucial for their efficacy against ovarian cancer cells

Receptor-PI3K-mTORC1 signaling and fatty acid synthase (FASN)-regulated lipid biosynthesis harbor numerous drug targets and are molecularly connected. We hypothesize that unraveling the mechanisms of pathway cross-talk will be useful for designing novel co-targeting strategies for ovarian cancer (OC). The impact of receptor-PI3K-mTORC1 onto FASN is already well-characterized. However, reverse actions–from FASN towards receptor-PI3K-mTORC1–are still elusive. We show that FASN-blockade impairs receptor-PI3K-mTORC1 signaling at multiple levels. Thin-layer chromatography and MALDI-MS/MS reveals that FASN-inhibitors (C75, G28UCM) augment polyunsaturated fatty acids and diminish signaling lipids diacylglycerol (DAG) and phosphatidylinositol 3,4,5-trisphosphate (PIP3) in OC cells (SKOV3, OVCAR-3, A2780, HOC-7). Western blotting and micropatterning demonstrate that FASN-blockers impair phosphorylation/expression of EGF-receptor/ERBB/HER and decrease GRB2–EGF-receptor recruitment leading to PI3K-AKT suppression. FASN-inhibitors activate stress response-genes HIF-1α-REDD1 (RTP801/DIG2/DDIT4) and AMPKα causing mTORC1- and S6-repression. We conclude that FASN-inhibitor-mediated blockade of receptor-PI3K-mTORC1 occurs due to a number of distinct but cooperating processes. Moreover, decrease of PI3K-mTORC1 abolishes cross-repression of MEK-ERK causing ERK activation. Consequently, the MEK-inhibitor selumetinib/AZD6244, in contrast to the PI3K/mTOR-inhibitor dactolisib/NVP-BEZ235, increases growth inhibition when given together with a FASN-blocker. We are the first to provide deep insight on how FASN-inhibition blocks ERBB-PI3K-mTORC1 activity at multiple molecular levels. Moreover, our data encourage therapeutic approaches using FASN-antagonists together with MEK-ERK-inhibitors.

Combination Treatment with Orlistat-Containing Nanoparticles and Taxanes Is Synergistic and Enhances Microtubule Stability in Taxane-Resistant Prostate Cancer Cells

Taxane-based therapy provides a survival benefit in patients with metastatic prostate cancer, yet the median survival is less than 20 months in this setting due in part to taxane-associated resistance. Innovative strategies are required to overcome chemoresistance for improved patient survival. Here, NanoOrl, a new experimental nanoparticle formulation of the FDA-approved drug, orlistat, was investigated for its cytotoxicity in taxane-resistant prostate cancer utilizing two established taxane-resistant (TxR) cell lines. Orlistat is a weight loss drug that inhibits gastric lipases, but is also a potent inhibitor of fatty acid synthase (FASN), which is overexpressed in many types of cancer. NanoOrl was also investigated for its potential to synergize with taxanes in TxR cell lines. Both orlistat and NanoOrl synergistically inhibited cell viability when combined with paclitaxel, docetaxel, and cabazitaxel in PC3-TxR and DU145-TxR cells, yet these combinations were also additive in parental lines. We observed synergistic levels of apoptosis in TxR cells treated with NanoOrl and docetaxel in combination. Mechanistically, the synergy between orlistat and taxanes was independent of effects on the P-glycoprotein multidrug resistance protein, as determined by an efflux activity assay. On the other hand, immunoblot and immunofluorescence staining with an anti-detyrosinated tubulin antibody demonstrated that enhanced microtubule stability was induced by combined NanoOrl and docetaxel treatment in TxR cells. Furthermore, TxR cells exhibited higher lipid synthesis, as demonstrated by ¹⁴C-choline incorporation that was abrogated by NanoOrl. These results provide a strong rationale to assess the translational potential of NanoOrl to overcome taxane resistance. Mol Cancer Ther; 16(9); 1819-30. ©2017 AACR.

A strategy for dual inhibition of the proteasome and fatty acid synthase with belactosin C-orlistat hybrids

The proteasome, a validated cellular target for cancer, is central for maintaining cellular homeostasis, while fatty acid synthase (FAS), a novel target for numerous cancers, is responsible for palmitic acid biosynthesis. Perturbation of either enzymatic machine results in decreased proliferation and ultimately cellular apoptosis. Based on structural similarities, we hypothesized that hybrid molecules of belactosin C, a known proteasome inhibitor, and orlistat, a known inhibitor of the thioesterase domain of FAS, could inhibit both enzymes. Herein, we describe proof-of-principle studies leading to the design, synthesis and enzymatic activity of several novel, β-lactone-based, dual inhibitors of these two enzymes. Validation of dual enzyme targeting through activity-based proteome profiling with an alkyne probe modeled after the most potent inhibitor, and preliminary serum stability studies of selected derivatives are also described. These results provide proof of concept for dual targeting of the proteasome and fatty acid synthase-thioesterase (FAS-TE) enabling a new approach for the development of drug-candidates with potential to overcome resistance.

Synthesis of Functionalized Biaryls and Poly(hetero)aryl Containing Medium-Sized Lactones with Cyclic Diaryliodonium Salts

A novel one-pot procedure is described for the transition-metal catalyzed sequential difunctionalization of diaryliodonium reagents. Reaction of commercially available anthranilic acid derivatives with readily available cyclic diaryliodonium salts followed by a Sonogashira coupling afforded various alkyne substituted biaryls in good to excellent yields. The functionalized biaryls were then utilized for the rapid and efficient one-pot synthesis of novel poly(hetero)aryl containing 10-membered lactones which are potential G-quadruplex binders and telomerase inhibitors.

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

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

Development of a Nucleotide Exchange Inhibitor That Impairs Ras Oncogenic Signaling

Despite more than three decades of intense effort, no anti-Ras therapies have reached clinical application. Contributing to this failure has been an underestimation of Ras complexity and a dearth of structural information. In this regard, recent studies have revealed the highly dynamic character of the Ras surface and the existence of transient pockets suitable for small-molecule binding, opening up new possibilities for the development of Ras modulators. Herein, a novel Ras inhibitor (compound 12) is described that selectively impairs mutated Ras activity in a reversible manner without significantly affecting wild-type Ras, reduces the Ras-guanosine triphosphate (GTP) levels, inhibits the activation of the mitogen-activated protein kinase (MAPK) pathway, and exhibits remarkable cytotoxic activity in Ras-driven cellular models. The use of molecular dynamics simulations and NMR spectroscopy experiments has enabled the molecular bases responsible for the interactions between compound 12 and Ras protein to be explored. The new Ras inhibitor binds partially to the GTP-binding region and extends into the adjacent hydrophobic pocket delimited by switch II. Hence, Ras inhibitor 12 could represent a new compound for the development of more efficacious drugs to target Ras-driven cancers; a currently unmet clinical need.

Recent advances in targeting the fatty acid biosynthetic pathway using fatty acid synthase inhibitors

INTRODUCTION

Elevated lipogenesis has been associated with a variety of diseases including obesity, cancer and nonalcoholic fatty liver disease (NAFLD). Fatty acid synthase (FASN) plays a pivotal role in de novo lipogenesis, making this multi-catalytic protein an attractive target for therapeutic intervention. Recently, the first FASN inhibitor successfully advanced through the drug development process and entered clinical evaluation in oncology. Areas covered: This review discusses the biological roles of FASN in three prominent disease areas: cancer, obesity-related disorders and NAFLD. Recent advances in drug discovery strategies and design of newer FASN inhibitors are also highlighted. Expert opinion: Despite the abundance of evidence linking the lipogenic pathway to cancer, progression of FASN-targeted molecules has been rather slow and challenging and no compounds have moved past the preclinical phase. The landscape has recently changed with the recent advancement of the first FASN inhibitor into clinical evaluation for solid tumors. Needless to say, the successful translation into the clinical setting will open opportunities for expanding the therapeutic utility of FASN inhibitors not just in oncology but in other diseases associated with elevated lipogenesis such as obesity, type 2 diabetes, and NAFLD.

Metabolic Regulation of Apoptosis in Cancer

Apoptosis is a cellular suicide program that plays a critical role in development and human diseases, including cancer. Cancer cells evade apoptosis, thereby enabling excessive proliferation, survival under hypoxic conditions, and acquired resistance to therapeutic agents. Among various mechanisms that contribute to the evasion of apoptosis in cancer, metabolism is emerging as one of the key factors. Cellular metabolites can regulate functions of pro- and antiapoptotic proteins. In turn, p53, a regulator of apoptosis, also controls metabolism by limiting glycolysis and facilitating mitochondrial respiration. Consequently, with dysregulated metabolism and p53 inactivation, cancer cells are well-equipped to disable the apoptotic machinery. In this article, we review how cellular apoptosis is regulated and how metabolism can influence the signaling pathways leading to apoptosis, especially focusing on how glucose and lipid metabolism are altered in cancer cells and how these alterations can impact the apoptotic pathways.

Preparation, Characterization, and Biological Evaluation of Poly(Glutamic Acid)-b-Polyphenylalanine Polymersomes

Different types of amphiphilic macromolecular structures have been developed within recent decades to prepare the polymer particles considered as drug delivery systems. In the present research the series of amphiphilic block-copolymers containing poly(glutamatic acid) as hydrophilic, and polyphenylalanine as hydrophobic blocks was synthesized and characterized. Molecular weights for homo- and copolymers were determined by gel-permeation chromatography (GPC) and amino acid analysis, respectively. The copolymers obtained were applied for preparation of polymer particles. The specific morphology of prepared polymerosomes was proved using transmission electron microscopy (TEM). The influence on particle size of polymer concentration and pH used for self-assembly, as well as on the length of hydrophobic and hydrophilic blocks of applied copolymers, was studied by dynamic light scattering (DLS). Depending on different experimental conditions, the formation of nanoparticles with sizes from 60 to 350 nm was observed. The surface of polymersomes was modified with model protein (enzyme). No loss in biocatalytic activity was detected. Additionally, the process of encapsulation of model dyes was developed and the possibility of intracellular delivery of the dye-loaded nanoparticles was proved. Thus, the nanoparticles discussed can be considered for the creation of modern drug delivery systems.

Fasnall, a Selective FASN Inhibitor, Shows Potent Anti-tumor Activity in the MMTV-Neu Model of HER2(+) Breast Cancer

Many tumors are dependent on de novo fatty acid synthesis to maintain cell growth. Fatty acid synthase (FASN) catalyzes the final synthetic step of this pathway, and its upregulation is correlated with tumor aggressiveness. The consequences and adaptive responses of acute or chronic inhibition of essential enzymes such as FASN are not fully understood. Herein we identify Fasnall, a thiophenopyrimidine selectively targeting FASN through its co-factor binding sites. Global lipidomics studies with Fasnall showed profound changes in cellular lipid profiles, sharply increasing ceramides, diacylglycerols, and unsaturated fatty acids as well as increasing exogenous palmitate uptake that is deviated more into neutral lipid formation rather than phospholipids. We also showed that the increase in ceramide levels contributes to some extent in the mediation of apoptosis. Consistent with this mechanism of action, Fasnall showed potent anti-tumor activity in the MMTV-Neu model of HER2(+) breast cancer, particularly when combined with carboplatin.

Fatty Acids and Breast Cancer: Make Them on Site or Have Them Delivered

Brisk fatty acid (FA) production by cancer cells is accommodated by the Warburg effect. Most breast and other cancer cell types are addicted to fatty acids (FA), which they require for membrane phospholipid synthesis, signaling purposes, and energy production. Expression of the enzymes required for FA synthesis is closely linked to each of the major classes of signaling molecules that stimulate BC cell proliferation. This review focuses on the regulation of FA synthesis in BC cells, and the impact of FA, or the lack thereof, on the tumor cell phenotype. Given growing awareness of the impact of dietary fat and obesity on BC biology, we will also examine the less-frequently considered notion that, in addition to de novo FA synthesis, the lipolytic uptake of preformed FA may also be an important mechanism of lipid acquisition. Indeed, it appears that cancer cells may exist at different points along a "lipogenic-lipolytic axis," and FA uptake could thwart attempts to exploit the strict requirement for FA focused solely on inhibition of de novo FA synthesis. Strategies for clinically targeting FA metabolism will be discussed, and the current status of the medicinal chemistry in this area will be assessed. J. Cell. Physiol. 231: 2128-2141, 2016. © 2016 Wiley Periodicals, Inc.

Role of cystathionine beta synthase in lipid metabolism in ovarian cancer

Elevated lipid metabolism is implicated in poor survival in ovarian cancer (OC) and other cancers; however, current lipogenesis-targeting strategies lack cancer cell specificity. Here, we identify a novel role of cystathionine beta-synthase (CBS), a sulphur amino acid metabolizing enzyme highly expressed in several ovarian cancer cell lines, in driving deregulated lipid metabolism in OC. We examined the role of CBS in regulation of triglycerides, cholesterol and lipogenic enzymes via the lipogenic transcription factors SREBP1 and SREBP2. CBS silencing attenuated the expression of number of key enzymes involved in lipid synthesis (FASN and ACC1). Additionally CBS abrogates lipid uptake in OC cells. Gene silencing of CBS or SREBPs abrogated cellular migration and invasion in OC, while ectopic expression of SREBPs can rescue phenotypic effects of CBS silencing by restoring cell migration and invasion. Mechanistically, CBS represses SREBP1 and SREBP2 at the transcription levels by modulating the transcription factor Sp1. We further established the roles of both CBS and SREBPs in regulating ovarian tumor growth in vivo. In orthotopic tumor models, CBS or SREBP silencing resulted in reduced tumor cells proliferation, blood vessels formation and lipid content. Hence, cancer-selective disruption of the lipid metabolism pathway is possible by targeting CBS and, at least for OC, promises a profound benefit.

Dual fatty acid synthase and HER2 signaling blockade shows marked antitumor activity against breast cancer models resistant to anti-HER2 drugs

Blocking the enzyme Fatty Acid Synthase (FASN) leads to apoptosis of HER2-positive breast carcinoma cells. The hypothesis is that blocking FASN, in combination with anti-HER2 signaling agents, would be an effective antitumor strategy in preclinical HER2+ breast cancer models of trastuzumab and lapatinib resistance. We developed and molecularly characterized in vitro HER2+ models of resistance to trastuzumab (SKTR), lapatinib (SKLR) and both (SKLTR). The cellular interactions of combining anti-FASN polyphenolic compounds (EGCG and the synthetic G28UCM) with anti-HER2 signaling drugs (trastuzumab plus pertuzumab and temsirolimus) were analyzed. Tumor growth inhibition after treatment with EGCG, pertuzumab, temsirolimus or the combination was evaluated in two in vivo orthoxenopatients: one derived from a HER2+ patient and another from a patient who relapsed on trastuzumab and lapatinib-based therapy. SKTR, SKLR and SKLTR showed hyperactivation of EGFR and p-ERK1/2 and PI3KCA mutations. Dual-resistant cells (SKLTR) also showed hyperactivation of HER4 and recovered levels of p-AKT compared with mono-resistant cells. mTOR, p-mTOR and FASN expression remained stable in SKTR, SKLR and SKLTR. In vitro, anti-FASN compounds plus pertuzumab showed synergistic interactions in lapatinib- and dual- resistant cells and improved the results of pertuzumab plus trastuzumab co-treatment. FASN inhibitors combined with temsirolimus displayed the strongest synergistic interactions in resistant cells. In vivo, both orthoxenopatients showed strong response to the antitumor activity of the combination of EGCG with pertuzumab or temsirolimus, without signs of toxicity. We showed that the simultaneous blockade of FASN and HER2 pathways is effective in cells and in breast cancer models refractory to anti-HER2 therapies.

Novel epigallocatechin-3-gallate (EGCG) derivative as a new therapeutic strategy for reducing neuropathic pain after chronic constriction nerve injury in mice

Neuropathic pain is common in peripheral nerve injury and often fails to respond to ordinary medication. Here, we investigated whether the two novel epigallocatechin-3-gallate (EGCG) polyphenolic derivatives, compound 23 and 30, reduce the neuropathic pain in mice chronic constriction nerve injury (CCI). First, we performed a dose-response study to evaluate nociceptive sensation after administration of EGCG and its derivatives 23 and 30, using the Hargreaves test at 7 and 21 days after injury (dpi). We daily administered EGCG, 23 and 30 (10 to 100 mg/Kg; i.p.) during the first week post-CCI. None of the doses of compound 23 caused significant pain diminution, whereas 50mg/kg was optimal for both EGCG and 30 to delay the latency of paw withdrawal. With 50 mg/Kg, we showed that EGCC prevented the thermal hyperalgesia from 7 to 21 dpi and compound 30 from 14 to 56 dpi. To evaluate the molecular mechanisms underpinning why EGCG and compound 30 differentially prevented the thermal hyperalgesia, we studied several biochemical parameters in the dorsal horn of the spinal cord at 14 and 56 dpi. We showed that the effect observed with EGCG and compound 30 was related to the inhibition of fatty acid synthase (FASN), a known target of these polyphenolic compounds. Additionally, we observed that EGCG and compound 30 reduced the expression of CCI-mediated inflammatory proteins and the nuclear localization of nuclear factor-kappa B at 14 dpi, but not at 56 dpi. We also strongly detected a decrease of synaptic plasma membrane levels of N-methyl-D-asparte receptor 2B in CCI-mice treated with compound 30 at 56 dpi. Altogether, compound 30 reduced the chronic thermal hyperalgesia induced by CCI better than the natural compound EGCG. Thus, our findings provide a rationale for the preclinical development of compound 30 as an agent to treat neuropathic pain.

Modulation of tumor fatty acids, through overexpression or loss of thyroid hormone responsive protein spot 14 is associated with altered growth and metastasis

Introduction

Spot14 (S14), encoded by the THRSP gene, regulates de novo fatty acid synthesis in the liver, adipose, and lactating mammary gland. We recently showed that S14 stimulated fatty acid synthase (FASN) activity in vitro, and increased the synthesis of fatty acids in mammary epithelial cells in vivo. Elevated de novo fatty acid synthesis is a distinguishing feature of many solid tumors compared with adjacent normal tissue. This characteristic is thought to be acquired during tumor progression, as rapidly proliferating cells have a heightened requirement for membrane phospholipids. Further, overexpression of FASN is sufficient to stimulate cell proliferation. While many studies have focused on the FASN enzyme in cancer biology, few studies have addressed the roles of proteins that modify FASN activity, such as S14.

Methods

Tumor fatty acids were modulated using two mouse models, mouse mammary tumor virus (MMTV)-neu mice overexpressing S14 and MMTV-polyomavirus middle T antigen (PyMT) mice lacking S14, and associations between elevated or impaired fatty acid synthesis on tumor latency, growth, metastasis, and signaling pathways were investigated. We evaluated S14-dependent gene expression profiles in mouse tumors by microarray and used publicly available microarray datasets of human breast tumors.

Results

S14 overexpression in the MMTV-Neu transgenic model is associated with elevated medium-chain fatty acids, increased proliferation and a shorter tumor latency, but reduced tumor metastasis compared to controls. Loss of S14 in the MMTV-PyMT model decreased FASN activity and the synthesis of medium-chain fatty acids but did not alter tumor latency. Impaired fatty acid synthesis was associated with reduced solid tumor cell proliferation, the formation of cystic lesions in some animals, and decreased phosphorylation of Src and protein kinase B (Akt). Analysis of gene expression in these mouse and human tumors revealed a relationship between S14 status and the expression of genes associated with luminal epithelial differentiation.

Conclusions

This study demonstrates a potential role for S14 in regulating mammary tumor growth and fatty acid synthesis in vivo. Furthermore, these results suggest that modulating the amount of medium chain fatty acids, by changing the levels of S14, has the potential to impact malignant mammary tumor phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0481-z) contains supplementary material, which is available to authorized users.

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.

Adipocyte-derived players in hematologic tumors: useful novel targets?

INTRODUCTION

Adipocytes and their products play essential roles in tumor establishment and progression. As the main cellular component of the bone marrow, adipocytes may contribute to the development of hematologic tumors.

AREAS COVERED

This review summarizes experimental data on adipocytes and their interaction with various cancer cells. Special focus is set on the interactions of bone marrow adipocytes and normal and transformed cells of the hematopoietic system such as myeloma and leukemia cells. Current in vitro and in vivo data are summarized and the potential of novel therapeutic targets is critically discussed.

EXPERT OPINION

Targeting lipid metabolism of cancer cells and adipocytes in combination with standard therapeutics might open novel therapeutic avenues in these cancer entities. Adipocyte-derived products such as free fatty acids and specific adipokines such as adiponectin may be vital anti-cancer targets in hematologic malignancies. However, available data on lipid metabolism is currently mostly referring to peripheral fat cell/cancer cell interactions and results need to be evaluated specifically for the bone marrow niche.

Crystal structure of the human fatty acid synthase enoyl-acyl carrier protein-reductase domain complexed with triclosan reveals allosteric protein-protein interface inhibition

Human fatty acid synthase (FAS) is a large, multidomain protein that synthesizes long chain fatty acids. Because these fatty acids are primarily provided by diet, FAS is normally expressed at low levels; however, it is highly up-regulated in many cancers. Human enoyl-acyl carrier protein-reductase (hER) is one of the FAS catalytic domains, and its inhibition by drugs like triclosan (TCL) can increase cytotoxicity and decrease drug resistance in cancer cells. We have determined the structure of hER in the presence and absence of TCL. TCL was not bound in the active site, as predicted, but rather at the protein-protein interface (PPI). TCL binding induces a dimer orientation change that causes downstream structural rearrangement in critical active site residues. Kinetics studies indicate that TCL is capable of inhibiting the isolated hER domain with an IC50 of ∼ 55 μM. Given the hER-TCL structure and the inhibition observed in the hER domain, it seems likely that TCL is observed in the physiologically relevant binding site and that it acts as an allosteric PPI inhibitor. TCL may be a viable scaffold for the development of anti-cancer PPI FAS inhibitors.

Metformin-induced killing of triple-negative breast cancer cells is mediated by reduction in fatty acid synthase via miRNA-193b

The anti-diabetic drug metformin (1,1-dimethylbiguanide hydrochloride) reduces both the incidence and mortality of several types of cancer. Metformin has been shown to selectively kill cancer stem cells, and triple-negative breast cancer (TNBC) cell lines are more sensitive to the effects of metformin as compared to luminal breast cancer. However, the mechanism underlying the enhanced susceptibility of TNBC to metformin has not been elucidated. Expression profiling of metformin-treated TNBC lines revealed fatty acid synthase (FASN) as one of the genes most significantly downregulated following 24 h of treatment, and a decrease in FASN protein was also observed. Since FASN is critical for de novo fatty acid synthesis and is important for the survival of TNBC, we hypothesized that FASN downregulation facilitates metformin-induced apoptosis. Profiling studies also exposed a rapid metformin-induced increase in miR-193 family members, and miR-193b directly targets the FASN 3'UTR. Addition of exogenous miR-193b mimic to untreated TNBC cells decreased FASN protein expression and increased apoptosis of TNBC cells, while spontaneously immortalized, non-transformed breast epithelial cells remained unaffected. Conversely, antagonizing miR-193 activity impaired the ability of metformin to decrease FASN and cause cell death. Further, the metformin-stimulated increase in miR-193 resulted in reduced mammosphere formation by TNBC lines. These studies provide mechanistic insight into metformin-induced killing of TNBC.

Alpha-2-glycoprotein 1(AZGP1) regulates biological behaviors of LoVo cells by down-regulating mTOR signaling pathway and endogenous fatty acid synthesis

AZGP1 is a multifaceted protein associated with lipid mobilization, a process that is regulated by FASN and other metabolic pathways such as mTOR signaling. The active mTOR signaling pathway has been found to be involved in a variety of tumors. However, it remains unclear whether it is involved in the regulation of AZGP1 and FASN. An AZGP1-expressing plasmid was transfected into a human colorectal cancer cell line (LoVo) with a low expression of AZGP1. The expression of AZGP1, FASN, eIF4E, p-mTOR, p-S6,and S6K1 were measured by Western blot analysis, and target genes were detected by RT-PCR. Cell proliferation was studied using the MTT and colony formation assays. The analysis of apoptosis and the cell cycle phase were assessed by flow cytometry. The capacity of cell migration was investigated using the transwell migration assay. We found that the expression of AZGP1 was up-regulated while the expression of FASN, eIF4E, p-mTOR, p-S6, and S6K1 were down-regulated in LoVo cells after AZGP1 was expressed. The proliferation of malignant cells was reduced in AZGP1-overexpression cells, which is consistent with an increased in the G2-arrest and apoptosis rate. Furthermore, the migration of AZGP1-overexpression cells was decreased. The overexpression of AZGP1 suppressed the activation of the mTOR pathway and endogenous FASN-regulated fatty acid synthesis, mitigating the malignant phenotype of LoVo cells. Herein, we provide evidence that AZGP1 may constitute a novel tumor suppressor for LoVo colorectal cancer cells.

Identification of a new scaffold for hsp90 C-terminal inhibition

Inhibition of Hsp90 C-terminal function is an advantageous therapeutic paradigm for the treatment of cancer. Currently, the majority of Hsp90 C-terminal inhibitors are derived from novobiocin, a natural product traditionally used as an antibiotic. Assisted by molecular docking studies, a scaffold containing a biphenyl moiety in lieu of the coumarin ring system found in novobiocin was identified for development of new Hsp90 C-terminal inhibitors. Initial structure-activity studies led to derivatives that manifest good antiproliferative activity against two breast cancer cell lines through Hsp90 inhibition. This platform serves as a scaffold upon which new Hsp90 C-terminal inhibitors can be readily assembled for further investigation.

HOXB1 restored expression promotes apoptosis and differentiation in the HL60 leukemic cell line

BACKGROUND

Homeobox (HOX) genes deregulation has been largely implicated in the development of human leukemia. Among the HOXB cluster, HOXB1 was silent in a number of analyzed acute myeloid leukemia (AML) primary cells and cell lines, whereas it was expressed in normal terminally differentiated peripheral blood cells.

METHODS

We evaluated the biological effects and the transcriptome changes determined by the retroviral transduction of HOXB1 in the human promyelocytic cell line HL60.

RESULTS

Our results suggest that the enforced expression of HOXB1 reduces cell growth proliferation, inducing apoptosis and cell differentiation along the monocytic and granulocytic lineages. Accordingly, gene expression analysis showed the HOXB1-dependent down-regulation of some tumor promoting genes, paralleled by the up-regulation of apoptosis- and differentiation-related genes, thus supporting a tumor suppressor role for HOXB1 in AML. Finally, we indicated HOXB1 promoter hypermethylation as a mechanism responsible for HOXB1 silencing.

CONCLUSIONS

We propose HOXB1 as an additional member of the HOX family with tumour suppressor properties suggesting a HOXB1/ATRA combination as a possible future therapeutic strategy in AML.

Synthetic inhibitors of bacterial cell division targeting the GTP-binding site of FtsZ

Cell division protein FtsZ is the organizer of the cytokinetic Z-ring in most bacteria and a target for new antibiotics. FtsZ assembles with GTP into filaments that hydrolyze the nucleotide at the association interface between monomers and then disassemble. We have replaced FtsZ's GTP with non-nucleotide synthetic inhibitors of bacterial division. We searched for these small molecules among compounds from the literature, from virtual screening (VS), and from our in-house synthetic library (UCM), employing a fluorescence anisotropy primary assay. From these screens we have identified the polyhydroxy aromatic compound UCM05 and its simplified analogue UCM44 that specifically bind to Bacillus subtilis FtsZ monomers with micromolar affinities and perturb normal assembly, as examined with light scattering, polymer sedimentation, and negative stain electron microscopy. On the other hand, these ligands induce the cooperative assembly of nucleotide-devoid archaeal FtsZ into distinct well-ordered polymers, different from GTP-induced filaments. These FtsZ inhibitors impair localization of FtsZ into the Z-ring and inhibit bacterial cell division. The chlorinated analogue UCM53 inhibits the growth of clinical isolates of antibiotic-resistant Staphylococcus aureus and Enterococcus faecalis. We suggest that these interfacial inhibitors recapitulate binding and some assembly-inducing effects of GTP but impair the correct structural dynamics of FtsZ filaments and thus inhibit bacterial division, possibly by binding to a small fraction of the FtsZ molecules in a bacterial cell, which opens a new approach to FtsZ-based antibacterial drug discovery.