regulators of the cancer.pdf

Hindawi Publishing CorporationInternational Journal of Cell BiologyVolume 2013 Article ID 639401 16 pageshttpdxdoiorg1011552013639401

Review ArticleNatural Compounds as Regulators of the CancerCell Metabolism

Claudia Cerella1 Flavia Radogna1 Mario Dicato1 and Marc Diederich2

1 Laboratoire de Biologie Moleculaire et Cellulaire du Cancer Hopital Kirchberg 9 Rue Edward Steichen2540 Luxembourg Luxembourg

2Department of Pharmacy College of Pharmacy Seoul National University Seoul 151-742 Republic of Korea

Correspondence should be addressed to Marc Diederich marcdiederichsnuackr

Received 20 December 2012 Accepted 22 April 2013

Academic Editor Young-Joon Surh

Copyright copy 2013 Claudia Cerella et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Even though alteredmetabolism is an ldquooldrdquo physiologicalmechanism only recently its targeting became a therapeutically interestingstrategy and by now it is considered an emerging hallmark of cancer Nevertheless a very poor number of compounds areunder investigation as potential modulators of cell metabolism Candidate agents should display selectivity of action towardscancer cells without side effects This ideal favorable profile would perfectly overlap the requisites of new anticancer therapies andchemopreventive strategies as well Nature represents a still largely unexplored source of bioactive molecules with a therapeuticpotential Many of these compounds have already been characterized for their multiple anticancer activities Many of them areabsorbed with the diet and therefore possess a known profile in terms of tolerability and bioavailability compared to newlysynthetized chemical compounds The discovery of important cross-talks between mediators of the most therapeutically targetedaberrancies in cancer (ie cell proliferation survival and migration) and the metabolic machinery allows to predict the possibilitythat many anticancer activities ascribed to a number of natural compounds may be due in part to their ability of modulatingmetabolic pathways In this review we attempt an overview of what is currently known about the potential of natural compoundsas modulators of cancer cell metabolism

1 (Re-)Evaluating the Targeting of MetabolicAlterations in Cancer

Deregulated metabolism is one of the oldest mechanismsassociated with cancer physiology The actual meaning andthe selective advantages induced by this deregulation remainnowadays still a matter of debate despite the pioneering workofWarburg about the impact of the alteration of the energeticmetabolism in cancer cells Certainly several reasons havesignificantly contributed to delay the advancement in thisarea of investigation For many years the search for newanticancer therapeutic agents has been extremely focusedon fighting the two most intuitive altered features of cancercells namely their sustained and uncontrolled proliferationand their ability of evading death Accordingly we haveassisted over the years in the development of different classesof therapeutic agents reducing cancer cell proliferation orinducing cancer cell death The main target of these studies

was the differential susceptibility of cancer versus normalcells to these treatments Over the time however we havealso learned about the limits of this approach consideringthe high incidence of therapeutic failure and the frequentdevelopment of systemic toxicity

Recently the high level of complexity and heterogeneityof cancer allowed considering this disease as a dynamicmulticellular system with complex forms of interactions andcellular communications with the own environment It hasbecome evident that consolidated cancer hallmarks includingsustained anduncontrolled cell proliferation and resistance tocell death need to be reconsidered in a much more complexmodulatory context if we want to therapeutically succeedwith cancer

At the light of this new vision the ability of cancercells to reprogram their cellular energetic metabolism ispassing through a renaissance of interest in cancer biology forthese chapters of fundamental biochemistry The discovery

2 International Journal of Cell Biology

of unexpected cross-talks between well-known metabolicfactors and mediators of unrelated processes is fuellingthis renewed interest On one side noncanonical regulatoryfunctions of specific metabolic enzymes or substrates areemerging on the other side oncogenes tumour suppressorsas well as modulators controlling events typically alteredat the very early stages of cancer progression includingimmune response cell proliferation or cell death appear inthe dual role of controlledcontrollers of metabolic processesDecoding the roles of metabolic changes occurring duringcarcinogenesis and identifying the key nodes that differen-tiate pathological and healthy behavior have two importantimplications novel predictive biomarkers and new drug dis-covery strategies Consequently additional knowledge mayoffer new tools to troubleshoot frequent chemotherapeuticfailures additionally compounds targeting metabolic pro-cesses may also be potentially used for chemopreventivepurposes This research is only emerging transforming theidentification of metabolically active agents into an oppor-tune challenge

Nature provides a considerable source of biologicallyactive compounds with a diversified pharmacological poten-tial Remarkably almost 80 of all anticancer compounds areisolated from plants fungi and microorganisms Both natu-ral and chemically modified molecules (in order to improvestability specificity andor activity) are able to counteracteach of the cancer hallmarks [1 2] recently reclassified byHanahan and Weinberg [3] Accumulating evidence alsoconcerns cancer metabolism [2] Remarkably many of thesecompounds are food constituents or have been used since along time in traditionalmedicineThus they show a favorableprofile in terms of their absorptionmetabolism in the bodywith low toxicity

2 Advantages of Altered Metabolism in Cancerversus Normal Cells

21 Metabolic Switch from Mitochondrial Respiration to Gly-colysis The preferential switch from oxidative phosphory-lation to aerobic glycolysis represents the most discussedand investigated altered metabolic feature of cancer cellsand was first described by Otto Warburg in the 1920sHe already hypothesized mitochondrial dysfunctions as thecausative event Defects in the enzymatic respiratory chainexist in cancer cells [4] however there is no clear correlationbetween the incidence ofmitochondrial dysfunctions and themetabolic switch to glycolysis the latter being commonlyreported in cancer cells In a number of instances insteadcancer tissuescells even consistently rely on mitochondrialrespiration to produce ATP [5] Furthermore under specificcircumstances cancer cells may also be forced to reactivatemitochondrial energy production [6] These observationsclearly show that mitochondria are generally functional incancer cells and support the hypothesis that the propensityof cancer cells to exacerbate the glycolytic pathway whiledecreasing oxidative phosphorylation must be an activeoption conferring important advantages despite the evident

energetic inefficiency of glycolysis Nevertheless identifica-tion of these selective advantages is not an obvious task beingindeed matter of debate

Theoreticallymetabolic alterations during carcinogenesiscould provide multiple benefits as cancer cells need tosatisfy a continuous demand in macromolecule precursorsto maintain their high proliferation rate As a matter offact the reduction of mitochondrial respiration prevents acomplete degradation of glucose to carbon dioxide (CO

2)

and water and leads to accumulation of precursors usedby the major cellular synthesis pathways leading to aminoacids nucleotides and lipids Consequently this metabolicalteration inevitably fuels these anabolic pathways Secondcancer cells experience moderate to severely reduced oxygentension and the fact to preferentially exploit glycolysis toproduce energy in this situation represents an interestingadaptation Accordingly overexpression or stabilization ofthe hypoxia-inducible factor (HIF) in response to low-oxygenconditions promotes the glycolytic metabolism by inducingtranscription of glucose transporters and numerous keyglycolytic enzymes [7]

An increased glycolytic flux means also very frequentlyoverexpression andor increased activity of specific isoformsof several glycolysis-related enzymes Glucose transportersor key enzymes as hexokinase II (HKII) glyceraldehyde-3-phosphate dehydrogenase (GAPDH) lactate dehydrogenase(LDH) and the isoform M2 of pyruvate kinase (PKM2)are upregulated in cancer cells and accordingly suggestedas potential therapeutic targets [8 9] Interestingly nong-lycolytic functions are also emerging for several of theseenzymes and the novel activities ascribed do further promotecancer aggressiveness For example GAPDH LDH or PKM2may additionally activate gene expression by working asdirect transcriptional factors or by interacting with andtherebymodulating the activity of other nuclear proteins [10ndash12] (including HIF-1 and the Signal Transducer and Activatorof Transcription 3 (STAT3) [13 14]) required in the tran-scription of genes especially implicated in cell proliferation(eg histones H2A and H2B MEK5 c-Myc cyclin D1 andandrogen receptor [10 13ndash15])

The hyperproduction of lactate plays a dual role On oneside it activates the glycolytic pathway ensuring the regen-eration of nicotinamide adenosine diphosphate (NAD+) aspart of a feedback regulatory mechanism on the other side itis secreted outside the cells where it promotes angiogenesisand spreading of cancer cells from their primary site Amutual control exists between events controlling lactate pro-duction and synthesis of proangiogenic factors For examplethe extracellular acidification due to the transport of lactatecoupled to H+ extrusion promotes upregulation of HIF-1[16 17] HIF-1 in turn transactivates the LDH-A promoter[16] Besides acidic conditions destabilizes the behavior ofthe immune system which further contributes to cancerinvasion Lactate secretion indeed impairs the function ofspecific immune cells (including cytotoxic T lymphocytes)and cytokine production [18] Furthermore it promotes cellmotility by controlling the expression level of constituents ofthe matrix [19 20]

International Journal of Cell Biology 3

Identifying further advantages of the Warburg effectother intriguing explanations involve mitochondria Reduc-ing the mitochondrial metabolism may inevitably decreaseaccumulation of reactive oxygen species (ROS) Suppressionof ROS formation has been suggested as an importantadvantage for rapidly proliferating cell systems these cellsmay be better protected against the risk of DNA damageduring DNA synthesis [21] This model seems to be encour-aged by the observation that healthy highly proliferatingsystems temporarily switch to glycolysis before entering in S-phase [22] Moreover c-Myc which activates transcription ofthe glycolytic enzymes HKII enolase-1 (ENO-1) and LDH(subunit A) further promotes this switch in concomitancewith the entry in S-phase [22ndash24]

More recently unconventional roles were ascribed topyruvate the end product of glycolysis which is massivelyconverted into lactate in cancer cells instead of beingtransported into mitochondria to initiate mitochondrialmetabolismThe plasma membrane transporter SLC5A8 wasreported to be downregulated in different human cancercells [25 26] Its silencing occurs at very early stages ofcarcinogenesis moreover the restoration of its expressiontriggers cell death [27] Accordingly it has been hypothesizedthat SLC5A8may act as a tumour suppressorThis transportercouples Na+ extrusion to the intake of extracellular mono-carboxylates including pyruvate into the cell The group ofGanapathy has proposed an interesting model to explain thetumour suppressor activity of SLC5A8 specifically centeredon the role of pyruvate [28] According to their findingspyruvate acts as a specific inhibitor of histone deacetylase-(HDAC-)1 and -3 isoforms an event that in turn promotescell death [28] Therefore keeping low levels of pyruvatemay stabilize specific epigenetic aberrations established incancer cells and promote cancer cell survival Remarkablypyruvate is maintained at very low levels in cancer cells [27]Accordingly several mechanismsmay participate in bufferingthe intracellular pyruvate levels together with upregulatedLDH-A in cancer cells They include also transporters asSLC5A8 and conceivably other monocarboxylate-specifictransporters whose expression is modulated in cancer cells[29] This model has fascinating implications It assignsto pyruvate itself the role of a tumour suppressor [27]Therefore the control of intracellular pyruvate levels couldplay an active and central role in the altered metabolicprofile of cancer cells Moreover it prompts us to consideradditional roles for typical altered metabolic conditions incancer cells that deal directly or indirectly with pyruvateaccumulationThe preferential expression of the less efficientdimeric form of PKM2 (slowly accumulating pyruvate) orthe relevance of the exacerbated conversion of pyruvateinto lactate would be two interesting conditions to furtherinvestigate In addition these considerations remind us howmuch each metabolic alteration in cancer may play multiplefunctions well exploited by cancer cells to succeed andultimately survive and proliferate

22 Relevance of Other Altered Metabolic Pathways in CancerPreferential exploitation of aerobic glycolysis by cancer cells

is a key issue of reprogrammed metabolism It is becomingclear that other metabolic pathways or mediators may play afundamental role in cancerThe availability of recent sophisti-cated experimental approaches to study the metabolic profileof cancer cells has allowed identification of an impressivenumber of alterations They essentially concern levels ofexpressionaccumulation or status of enzymes or inter-mediate substrates involved in several anabolic pathwaysDespite the evident advantage of these modifications withinthe anabolic process in which they are mainly involvedadditional noncanonical functions have emerged includingcontrol of redox homeostasis or specific signalling eventsenabling the high cellular proliferation rate In this sectionwewill briefly discuss two key pathways suitable for therapeutictargeting

221 Glutamine Metabolism Beside glucose cancer cellsfrequently rely on glutamine metabolism This amino acidis uptaken through specific transporters and directed tothe mitochondria where it is converted first in glutamate(by a mitochondrial glutaminase) Glutamate then fuels thetricarboxylic acid cycle (TCA) upon further conversionto 120572-ketoglutarate in a reaction catalyzed by glutamatedehydrogenase (GDH) Exceeding substrates from the TCAcycle can be again available in the cytosol where theybecome the precursors of several anabolic pathways leadingto biosynthesis of lipids other aminoacids and nucleotidesBeside its relevant role in anabolic pathways glutaminemetabolism may also promote further accumulation of lac-tate (via malate formation) and therefore exacerbate gly-colysis and nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) generation (glutaminolysis) the latter fur-ther buffering potential oxidative stress into the cells Studieshighlight that specific forms of cancer including glioblastomadevelop an impressively high rate of glutamine metabolismwhich goes beyond the real nitrogen demand thus suggestingthat glutamine consumption in cancer cells may representa fast and preferential carbon source to replenish severalbiosynthetic pathways [30]This preferential use of glutaminemay be further promoted by other factors whose expressionlevel is altered in cancer cells for example the NFE2-relatedfactor (NRF2) [31] Altogether these observations imply thatcancer cells may become addicted to glutamine metabolismto maintain their high rate of proliferationTherefore target-ing their ability to degrade glutamine may be of therapeuticrelevance especially in glutamine-dependent types of cancer

222 Lipid Metabolism A growing body of evidence depictsa determinant role of altered lipid homeostasis in enabling thecancer cell phenotype The pattern of alterations describedsuggests that lipid metabolism plays a multitasking role incancer Beyond the relevance of metabolic modifications thatpromote lipogenesis and therefore specific anabolic activitieslipid-related factors appear essential in controlling redoxhomeostasis and accumulation of specific lipid messengersincluding lysophosphatidic acid and prostaglandins Accord-ingly several enzymes and transcription factors controlling


lipogenesis and lipid homeostasis are overexpressed in can-cer as we will detail later These alterations were initiallyidentified in hormone-dependent malignancies such as thoseaffecting breast [32] and prostate [33] thus confirming therelevance of steroid hormone-dependent pathways in theobserved altered lipid metabolism More recently compara-ble patterns of alterations were identified in other cancer celllines derived from melanoma [34] osteosarcoma [35] col-orectal [36 37] and lung cancer [38] as well as in hematopoi-etic cancer cells [39 40]These cellular environments allowedto identify additionalmodulatory upstream pathways includ-ing mitogen-activated protein kinase-(MAPK-) dependent[41] phosphatidylinositol-3-kinase (PI3K)Akt pathway [4142] H-ras [41] and AMP-activated protein kinase AMPK[43] In addition a lipid-related transcription factor the sterolregulatory element-binding protein (SREBP) whose targetgenes promote cancer aggressiveness [44] is upregulated incancer

It is well-known that fatty acid neosynthesis is triggeredby excess glucose leading to increased mitochondrial cit-rate concentrations Citrate is then converted in the cyto-plasm into palmitoyl-CoA the precursor of triglyceridesand phospholipids synthesis Accumulation of triglyceridesmay be reverted after starvation when a decrease of thelipogenic intermediate malonyl-CoA reactivates carnitinepalmitoyltransferase-1 (CPT-1) thus leading to mitochon-drial fatty acid oxidation [45]

In cancer cells de novo fatty acid synthesis is sustainedand several lipogenic enzymes are typically upregulated Theconsequent burst in lipidogenesis confers the advantage tofurther exacerbate additional biosynthetic anabolic activitiesenabling cell growth The enzymes ATP-citrate lyase (ACL)acetyl-CoA carboxylase (ACC) and the fatty acid synthase(FAS) are frequently overexpressed in cancer cells [46]Especially FAS was described as a potential cancer biomarker[47 48] for therapeutic purposes [49] This dual clinicalpotential is supported by the observation that FAS inhibitorssuppress carcinogenesis in in vivo procarcinogenic modelsof breast [50] and lung [38] tissues moreover they triggercell death in a number of cancer cell lines [34 47 51ndash53]without affecting normal lipogenic tissues [54] AdditionallyFAS expression correlates with metastasis formation [35]and its targeting alleviates chemoresistance when combinedwith chemotherapeutic agents [55]Thesemultiple anticanceractivities together with the observation that FAS are overex-pressed in premalignant lesions [56 57] strongly point at avery early role of FAS overexpression in carcinogenesis andled to the speculation that this enzyme may effectively beconsidered an oncogene [58ndash60]

Besides cancer cells show a preferential synthesis ofphospholipids (ie lysophosphatidic acid) instead of triglyc-eride [49] This biosynthetic diversion of lipid precursorsleads to the accumulation of lipid messengers regulating anumber of signalling events promoting cancer cell growthsurvival andmigration to other tissues [61] An accumulationof prostaglandins (ie prostaglandin E) strengthens theprocarcinogenic roles played by proinflammatory signallingevents during carcinogenesis [62] Remarkably a tight cross-talk exists between lipid metabolism and modulation of the

expression of the main proinflammatory mediator cyclo-oxygenase 2 (COX-2) which is constitutively overexpressedin cancer [62 63] In line with these observations is also thefact that lipolytic enzymes like the monoacylglycerol lipase(MAGL) [64] are overexpressed in cancer and may directlycontrol the prostaglandin levels [65]

Taking into account recent publications about the rolesof lipid metabolism in cancer we are convinced that furtherdiscoveries will further strengthen the importance of thesepathways in cancer treatment and prevention

23 Role of Altered Metabolism in Promoting Specific CancerHallmarks Cell death resistance and angiogenesis are twoimportant pathways involved in tumour progression andsurvival [66ndash68] These independent processes are closelylinked to cancer cell metabolism [67 69] Recent publicationshighlight mitochondria as modulators of these two criticalpathways and promoters of metabolic homeostasis in cancercells [70] The mitochondrion is the most important coordi-nator of both energy production and accumulation of biosyn-thetic precursors for cellular maintenance and survival

Altered mitochondrial bioenergetics and functions playan important role in tumorigenesis by affecting cancer cellmetabolism decreasing mitochondria-dependent apoptosisand contributing to angiogenesis [66 70ndash72] Cancer cellspresent frequently a mitochondrial metabolic shift fromglucose oxidation (GO) to glycolysis thus assimilating alarger amount of glucose compared to normal cells [73] Bythis way cancer cells refuel themselves with phosphorylatedintermediates required for growth and proliferation throughregulation of the metabolic key enzymes that govern thebalance between GO to glycolysis and by reducing the entryof pyruvate into mitochondria thus reducing the rate ofTCA cycle [17 73 74] The accumulated pyruvate is in partconverted to lactate during aerobic glycolysis and secretedto keep glycolysis active The extracellular secreted lactateinfluences the extracellular matrix lowering the pH of thetumour environment allowing a remodelling of the matrixand inducing blood vessel invasion in response to tumour-induced angiogenic factors [17]Therefore the reducedmito-chondrial efficiency may induce the activation of HIF-1120572resulting in angiogenesis activation cell migration increasedcell survival and energy metabolism [75 76] Converselyrestoration of themitochondrial activity inhibits HIF-1120572 [77ndash79] It has been demonstrated that dichloroacetate (DCA)which inhibits pyruvate dehydrogenase kinase (PDK) acti-vates GO in mitochondria thus leading to decreased tumourgrowth in many cancer cell lines this event is accompaniedby the inhibition of HIF-1120572 [69]

Alterations in mitochondrial function not only influencethe cellular metabolic status but also contribute to the controlof the redox status of cancer cells The large amounts ofglucose available in the cells are metabolized through thepentose phosphate pathway (PPP) producing nucleosides andgenerating NADPH [70 73]

NADPH is essentially involved in redox control protect-ing cells against ROSHigh levels of ROS as generated in can-cer cells can promote oxidative damage-induced cell death


Therefore cancer cells maximize their ability to produceNADPH to reduce ROS activity [73] The difference in theredox status between normal and cancer cells may be a targetto selectively kill cancer cells by ROS-generating drugsThusthe elicitation of ROS can be exploited to induce cancer cellsto undergo oxidative damage-induced cell death

Another important modulator of the redox status incancer cells is B-cell lymphoma-2 (Bcl-2) protein that isoverexpressed in a variety of cancer cells [80] The potentialtumorigenic activity of Bcl-2 is due to its antiapoptoticproperties maintaining the integrity of the outer mitochon-drial membrane and preventing its permeabilisation throughsequestration of the proapoptotic protein B-Cell lymphoma-associated X (BAX) and Bcl-2 homologous antagonist killer(BAK) However regulation of ROS levels by Bc-2 was alsodemonstrated [81 82] as Bcl-2 may affect the intracellularredox status in order to maintain the ROS potential at themost favorable level for cancer cell survival

Autophagy is another alternative pathway that sustainstumour cell survival Moreover autophagy is a major pro-cess fueling cell metabolism [67] It supplies intracellularnutrients when the external ones are not available Unlikenormal cells cancer cells are placed in an environmentdeprived of nutrients and oxygen due to an insufficientvascularization Autophagy may support tumour growthensuring the availability of endogenous metabolic substratesnecessary to feed glycolysis ATP production and pyruvatefor the mitochondrial metabolism [67] Autophagy recyclesintracellular organelles and the resulting breakdownproductscontribute to produce energy and build up new proteinsand membranes Indeed autophagy provides an internalsource of sugar nucleosides amino acids and fatty acids bythe degradation of protein lipids carbohydrate and nucleicacids [83] Thus autophagy sustains cell metabolism andsubsequently favors cancer cell survival in nutrient lackingtumours besides preventing that cancer cellsmay accumulatedysfunctions in their mitochondria [84]

Impaired mitochondrial functions oxidative stress andautophagy are tightly correlated Emerging evidence under-lines how much autophagy may affect mitochondrial func-tions and accumulation of ROS [85] Number and the healthstatus of mitochondria are controlled by an autophagic pro-cess called mitophagy Mitophagy is a mitochondrial qualitycontrol by means of which excessively damaged mitochon-dria become a substrate for autophagic degradation Hypoxiaand hypoxia-inducible factors (HIFs) can induce mitophagy[86] Dysfunctional mitochondria are linked to ROS gener-ation induction of DNA damage and cell death [87] Thusdegradation of these defective organelles by mitophagy mayprotect cells from carcinogenesis However both activationand inhibition of the autophagic pathways may play a rolein cancer therapy It has been demonstrated that inhibitorsof autophagy may target autophagy-dependent cancer cellsbecause this modulation inevitably impairs cancer cell sur-vival [88] On the other side an excessive autophagic fluxcan induce cell death Therefore cytotoxic cancer therapiesexacerbating autophagy may provoke increased oxidativestress or severe cell damage thus sensitizing cancer cellsto cell death (ie apoptosis) [89] Interestingly autophagy

and apoptosis are both regulated by Bcl-2 Bcl-2 regulatesautophagy by binding to the proautophagy protein Beclin-1and the proapoptotic protein Bax [72] Therefore the cross-talk between autophagy and the mitochondrial metabolismis an important issue to be considered for cancer therapyMoreover redox alterations associated with mitochondrialdysfunctions may be pivotal in preventing cancer formationgrowth and establishment at very early steps of carcinogene-sis

3 Potentially Targetable Metabolic Actors byNatural Compounds

The logical consequence of the elucidation of the multi-ple roles played by altered metabolism in cancer is theexploitation of this knowledge for preventive and therapeuticpurposes The existence of specific patterns of modulationsidentifies also potential molecular targets for future novelclasses of anticancer compounds In this section we suggestan overview of natural compounds regulating the mostinteresting metabolic pathway intermediates

31 Glycolysis-Related Factors

311 Glucose Transporters It is essential for a cancer cell toactivate the glycolytic pathway to satisfy the anabolic demandin consistent amounts of intracellular glucose Glucose iscarried into cells via specific plasma membrane transportersthat lead to glucose internalization by facilitation or activecoupling to ion fluxes like the extrusion of Na+ [90]

Frequently specific isoforms of glucose transporters areoverexpressed in cancer cells The facilitative glucose trans-porters (GLUTs) belonging to the solute carrier (SLC2) genefamily are frequently overexpressed Consistent data waspublished about isoforms 1 3 4 and 12 Therefore targetingabnormal expression or activity of those carriers representsone promising strategy Several natural compounds havebeen described as potential modulators of glucose trans-porters (Figure 1) A critical reading of the literature indi-cates that these compounds most likely affect expression ofglucose transporters indirectly rather controlling upstreammodulatory mechanisms This is also true for natural com-pounds Annonaceous acetogenins are long chained fattyacid derivatives extracted from different tropical plants suchas the tree Annona muricata also known as Graviola Ithas been recently shown that Graviola extracts exert mul-tiple anticancer activities on pancreatic cancer cell models[91] The extract reduces cell proliferation and viability byinducing necrosis besides it counteracts cell motility Thepotential anticancer properties have been confirmed withmouse xenograft models where Graviola extract reducesboth tumour growth and formation ofmetastasis An analysiscentered on metabolic parameters underlines the ability ofthis compound to inhibit glucose uptake besides it stronglyreduces the expression levels of several metabolic actorsincluding GLUT1 and GLUT4 HKII and LDH-A Thispattern of modulation is the consequence of the modulationof multiple factors and pathways including the reduction of


120572KG 120572KG

Succinate

Fumarate

Oxaloacetate

Glutamine

IsocitrateMalate

Glutamate

GDH

GS

Amino acids

GLUT1

Glucose

G6P

3PG

FBP

6PGluconate

PPP

F6P

NADPH G3P

Citrate Citrate

IDH1

Lactate

HK2

GAPDH

PyruvatePEPPKM2

Saframycin

ThiazolidinedionesNaphtoquinones

SulfonamidesPyridazones

MCT4

Methyl jasmonate

AcetylCoA

ACL

AcetogeninsGlucopiericidin A

Flavonoids

EGCGGCG

MalonylCoAPalmitate

FAS

TCA

AcetylCoA

Palmitoyl-CoA

EGCGLuteolin

QuercetinLignans

SecoiridoidsOleuropein

Hydroxytyrosol

ManassantinsAlpinumisoflavones

BaccharinDrupanin

Oxaloacetate

HIF-1

LDH

minus

minus

minus

minus

minus

+

Resveratrol

(Arylsulfonyl)indolines

Figure 1 Targetable metabolic actors by natural compounds A summary of the most relevant compounds affecting metabolic pathwaysof cancer cells Many of these molecules correspond to natural compounds alternatively they are chemical structures found as activethat may act as a template for the identification of promising natural compounds with similar activity Molecules indicated in blue affectenzymatic activity (+ or minus stands for activators or inhibitors resp) the ones in green affect the expression level of the targeted enzymethe ones in brown affect nonmetabolic activities Abbreviations ATP citrate lyase ACL gallocatechin gallate GCG epigallocatechingallate (EGCG) fatty acid synthase FAS fructose-6-phosphate F6P fructose-16-biphosphate FBP hypoxia-inducible factor 1 HIF-1glucose-6-phosphate G6P glutamine synthetase GS hexokinase II HK2 glyceraldehyde-3-phosphate G3P glyceraldehyde-3-phosphatedehydrogenase GAPDH glucose transporter GLUT glutamate dehydrogenase GDH 120572-ketoglutarate (120572KG) isocitrate dehydrogenase1 IDH1 lactate dehydrogenase LDH nicotinamide adenine dinucleotide phosphate-oxidase NADPH pentose phosphate pathway 3-phosphoglycerate 3PG phosphoenolpyruvate PEP pyruvate kinase isoform M2 PKM2


HIF-1 and nuclear factor 120581B (NF-120581B) expression levels andthe inhibition of ERK (extracellular-regulated kinase) andAkt activation

Due to the difficulties of specifically targeting glucosetransporter expression without affecting many other intra-cellular pathways an interesting alternative is to identifymolecules that modulate the activity of glucose transportersIn this context several natural compounds deserve attention

Following a natural product screening assay based oncrude extracts of microbial origin aimed at identifyingnew inhibitors of filopodia protrusion (special membranestructures involved in promoting metastasis) Kitagawa andcolleagues have isolated and characterized in the broth ofLechevalieria sp bacterial strain glucopiericidin A (GPA)as a novel inhibitor of glycolysis [92] The authors showedthat GPA specifically impairs glucose uptake into the cellsAccordingly the compound impairs the accumulation of thenonmetabolizable tritiated glucose analog 2-deoxyglucose(DG) without affecting the key glycolytic enzyme HK Theirfindings suggest that GPA may act by mimicking a GLUT1substrate

From plants polyphenols are interesting bioactive anti-cancer molecules as several of them have been repeatedlyreported to control glucose transporter activity in differentcancer cell models fisetin myricetin quercetin apigeningenistein cyaniding daidzein hesperetin naringenin andcatechin are well-known inhibitors of glucose uptake [93]Investigations designated hexose and dehydroascorbic acidtransporters including GLUT1 and GLUT4 [94 95] as theirtargets Comparative studies indicate that these compoundsdo not exhibit the same mode of action as they bind differentdomains of GLUT1 Genistein binds the transporter on theexternal face whereas quercetin interacts with the internalface [95] The ability of these compounds to act as protein-tyrosine kinase inhibitors is currently considered as the mainmechanism responsible for the modulation of the glucoseuptake

312 Glycolytic Enzymes Hexokinase (HK) is the enzymecontrolling the first enzymatic step of glycolysis allowingintracellular transformation of glucose via phosphorylation(Figure 1) In cancer cells HKII is the main isoform and isinvolved in the Warburg effect and in enhanced cell prolifer-ation [96] HK associates with the outer mitochondrial mem-brane in proximity of ATPmolecules required for HKrsquos enzy-matic activity The destabilization of this physical interactionnegatively affects the overall cancer cell energetics moreoverit dramatically perturbs mitochondria triggering the releaseof cytochrome c and subsequently inducing apoptosis [97]Some natural compounds have been described as promotingthe detachment of HK frommitochondriaMethyl jasmonateis a plant stress hormone produced by many plants includingrosemary (Rosmarinus officinalis L) olive (Olea europea L)or ginger (Zingiber officinalis) it binds to HK and perturbsits association with the voltage-dependent anion channel(VDAC) in cancer cells [98] This event leads to overallenergetic impairment moreover it promotes the releaseof cytochrome c from mitochondria triggering apoptosis

Its use in combination with the antiglycolytic agent 2-deoxyglucose or chemotherapeutic agents is currently underinvestigation [98]

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)is a key glycolytic enzyme catalyzing the conversion ofglyceraldehyde-3-phosphate to glycerate 13-biphosphateaccompanied by the generation of NADH There is evidencethat GAPDH may play multiple noncanonical functionsimplicated in cell growth and survival The bis-quinone alka-loid saframycin a bacterial product of fermentation exhibitsantiproliferative properties in both adherent and nonadher-ent cancer cell models This compound possesses activitiescomparable to alkylating agents The group of Myers hasshown that saframycin may form a nuclear ternary complexwith GAPDH and DNA [99] involved in the antiproliferativeeffect ascribed to this compound [99]

Recently the embryonic isoformM2 (PKM2) is attractinginterest for diagnostic and therapeutic purposes in cancer[5] Enzymes of the pyruvate kinase family catalyze the finalrate-limiting step of glycolysis leading to the accumulationof pyruvate from phosphoenolpyruvate in an ATP-producingreaction Cancer cells exclusively express the embryonicisoform M2 instead of adult M1 This switch is requiredfor the maintenance of aerobic glycolysis [8] Also rapidlyproliferating cells selectively express PKM2 ImportantlyPKM2 exists as a dimeric or a tetrameric form the latter oneefficiently catalyzes pyruvate formation whereas the dimericform is nearly inactive In cancer cells the dimeric form is thepreponderant one This paradoxical behavior is believed tofurther promote glycolysis and several anabolic activities

Currently two main PKM2 targeting strategies are underevaluation The first attempt consists in identifying com-pounds inhibiting PKM2 High-throughput screenings basedon an enzymatic LDH assay to explore a compound libraryincluding molecules approved from the Food and Drugadministration (FDA) and purified natural products have ledto the identification of three potential chemical structuresassociated with a potential inhibitory activities on PKM2[100] Active compounds include thiazolidinediones andnatural compounds belonging to the group of naphtho-quinones shikonin alkannin and their derivatives (extractedfrom different plants including Arnebia sp and Alkannatinctoria) have been recently shown as the most potent andspecific inhibitors of PKM2 [101]These compounds reducinglactate production and glucose consumption in cancer cellsare also known to induce necroptosis [102] However theinhibitory effect on PKM2 is independent of their effecton cell viability rather suggesting an impairment of theglycolytic metabolism Even though PKM2 is crucial forcancer cell survival [101] there is a potential risk to affectalso healthy PKM2-expressing cells Subsequently a secondline of research currently aims at promoting the reactiva-tion of PKM2 in cancer cells The increase of tetramericversus dimeric PKM2 isoform ratio abrogates the Warburgeffect and may reactivate oxidative phosphorylation [103]So far a few promising studies have been published iden-tifying some chemical scaffolds as potential PKM2 activa-tors They include sulfonamides thieno[32-b]pyrrole[32-d]pyridazinones and 1-(sulphonyl)-5-(arylsulfonyl)indolines


that act as small-molecule allosteric modulators binding to asurface pocket of the enzyme thus facilitating the associationof different PKM2 subunits

Although PKM2 targeting appears a promising area fordrug discovery research remains preliminary Identificationof first chemical scaffolds may be the basis for the discoveryof structurally related natural compounds

32 Hypoxia-Inducible Factor-1 The Hypoxic Rheostat Thereis no doubt that HIF-1 is a central molecule in the controlof the expression of glucose transporters and key glycolyticenzymes as well (Figure 1) Accordingly an important strat-egy is the identification of small molecule inhibitors of HIF-1 Several attempts rely on cell-based assays with reportergene constructs under the control of a HIF-1 responseelementThe group of Zhou has discovered and characterizednovel HIF-1 inhibitors in (i) manassantins (manassantin Band 4-o-demethylmanassantin) extracted from the aquaticplant Saururus cernuus [104] and (ii) alpinumisoflavones(alpinumisoflavone and 41015840-O-methyl alpinumisoflavone) iso-lated from the tropical legomaceous plant Lonchocarpusglabrescens [105] These compounds inhibit hypoxia-inducedHIF-1 activation besides they may affect the expression ofHIF-1 andHIF-1 target genes including GLUT1 andor VEGFSimilarly the group of Nagasawa has identified the cinnamicacid derivatives baccharin and drupanin extracted from theBrazilian green propolis as inhibitors of HIF-1-dependentluciferase activity [106] They inhibit the expression of HIF-1and its target genes (GLUT1 HKII and VEGF) besides theyexhibit antiangiogenic effects

33 Modulation of Mitochondrial Metabolism and FunctionsSeveral natural compounds have been shown to be ableto target mitochondrial metabolism and functions besidesaffecting cell death and angiogenesis both important path-ways involved in cancer progression

Curcumin is a natural compound extracted from Cur-cuma longa widely used as a spice Its anticarcinogenic andchemopreventive effects target mitochondrial metabolismand function inducing cell death and angiogenesis in a varietyof cancer models [107] In human colorectal carcinomacells curcumin induces mitochondrial membrane potentialinduces procaspase-3 and -9 cleavage and apoptosis in a dose-and time-dependent manner accompanied by changes andrelease of lactate dehydrogenase It leads to cell cycle arrestin S phase accompanied by the release of cytochrome ca significant increase of Bax and p53 levels and a markedreduction of Bcl-2 and survivin in LoVo cells [108]

Dimethoxycurcumin (Dimc) a synthetic analogue ofcurcumin induces cell cycle arrest in S phase and apop-tosis in human breast carcinoma MCF-7 cells by affectingmitochondrial dysfunction by oxidative stress Accordinglyit was observed that DNA damage and apoptosis followed aninduction of ROS generation and a reduction of glutathionelevels [109] Mitochondrial dysfunction was also witnessedby a reduction of the mitochondrial membrane potentialand a decrease of the cellular energy status (ATPADP) bythe inhibition of ATP synthase Therefore the mitochondrial

dysfunctions correlated with changes in the expression ofapoptotic markers like Bax and Bcl-2 [109] Several stud-ies indicated redox alterations as a causative mechanismimplicated in mitochondrial dysfunction in cancer Chenet al published a novel pathway for curcumin regulationof the ROS-lysosomal-mitochondrial pathway (LMP) andidentified cathepsin B (cath B) and cathepsin D (cath D) askey mediators of this pathway in apoptosis In lung A549cancer cells curcumin induces apoptosis via lysosomalmem-brane permeabilisation depending on ROS increase whichprecedes the occurrence of mitochondrial alterations [110]Further studies demonstrated that curcumin-induced ROSgeneration decreases the mitochondrial membrane potentialfollowed by downregulation of Bcl-2 expression Bax activa-tion and release of cytochrome c into the cytosol paralleledby the activation of caspase-9 and -3 in small cell lungcancer (SCLC) and NPC-TW 076 human nasopharyngealcarcinoma cells [111 112]

Curcumin-induced apoptosis in the colon cancer cellline HCT116 is significantly enhanced by the suppressionof mitochondrial NADP(+)-dependent isocitrate dehydro-genase activity which plays an essential role in the celldefense against oxidative stress by supplying NADPH for theantioxidant systems [113]

Amaryllidaceae alkaloid pancratistatin isolated from thebulb ofHymenocallis littoralis exhibits potent apoptotic activ-ity against a broad panel of cancer cells lines with modesteffects on noncancerous cell lines [114] Pancratistatin led toROS generation andmitochondrial depolarization leading tocaspase-independent cell death in breast carcinoma cells Incolorectal carcinoma cell lines but not in noncancerous colonfibroblast cells pancratistatin decreasedmitochondrialmem-brane potential and induced apoptotic nuclear morphologyindependently on Bax and caspase activation [114] In coloncancer cells resveratrol a natural stilbene from grapes blue-berries or cranberries induces apoptosis by nitric oxide pro-duction and caspase activation [115] Conversely in multiplemyeloma cells resveratrol increased apoptosis by blockingthe activation of NF-120581B and subsequently downregulation oftarget genes including interleukin-2 and Bcl-2 leading to cellcycle arrest [116]

The cross-talk between mitochondria and the autophagicmachinery could be used as a therapeutic strategy Resver-atrol has several beneficial effects such as neuroprotectionand cytotoxicity in glioblastoma cell lines It has beendemonstrated that resveratrol induced a crosstalk amongautophagy and apoptosis to reduce glioma growth [117]Indeed resveratrol has an impact on the formation ofautophagosomes in three human GBM cell lines accompa-nied by an upregulation of autophagic proteins Atg5 beclin-1and LC3-II [117] However the inhibition of resveratrol-induced autophagy triggered apoptosis with an increase inBax expression and cleavage of caspase-3 Only the inhibi-tion of both cell death pathways abrogated the toxicity ofresveratrol Thus resveratrol activates autophagy by inflict-ing oxidative stress or cell damage in order to sensitizeglioblastoma cancer cells to apoptosis [117] Also curcumintreatment of human liver-derived HepG2 cells induces thereduction of mitochondrial membrane potential and the


activation of autophagy Moreover it has been demonstratedthat curcumin activates mitophagy This finding underlinesthe importance of mitophagy in the process of cell death ofnasopharyngeal carcinoma cells [118]

As mentioned earlier another important pathway inmitochondrial dysfunction involved in tumour progressionis HIF-1120572 It has been published that curcumin plays apivotal role in tumour suppression via the inhibition ofHIF-1120572-mediated angiogenesis in MCF-7 breast cancer cellsand in HepG2 hepatocellular carcinoma cells [119 120]Anticancer activity of curcumin is attributable to HIF-1 inactivation by Aryl hydrocarbon nuclear translocator(ARNT) degradation Another natural compound with apotent antiangiogenic activity is the flavonoid bavachininBavachinin inhibited increased HIF-1120572 activity in human KBcarcinoma derived from HeLa cells [121] In human HOSosteosarcoma cells under hypoxia bavachinin decreasedtranscription of genes associated with angiogenesis andenergy metabolism that are regulated by HIF-1 such as vas-cular endothelial growth factors (VEGFs) GLUT1 and HKII[121] Bavachininmay be used as a therapeutic agent to inhibittumour angiogenesis Indeed in vivo studies showed thatinjecting bavachinin significantly reduced tumour volume innude mice with KB xenografts [121]

Figure 2 summarizes the major mechanisms of actiondescribed for natural compounds as mitochondrial modula-tors

34 Targeting Other Altered MetabolicPathways in Cancer Cells

341 Glutamine Metabolism Glutamine and glucose arethe main carbon sources used by cancer cells to satisfytheir anabolic demand Published data indicate a role forglutamine metabolism within the malignant cell phenotypeAccordingly several cancer cell lines present a high rate ofglutamine consumption and strategies are investigated totarget enzymes implicated in this pathway Inhibiting theactivity of glutamate dehydrogenase (GDH) is an effectiveanticancer strategy as documented in glioblastoma cellswith combinatorial treatments with agents depleting cells ofglucose or inhibiting specific kinase-(ie AKT-) dependentpathways [122] Polyphenols extracted from green tea includ-ing epigallocatechin gallate (EGCG) and catechin gallate(CG) inhibit GDH by recognizing and binding to the site ofthe allosteric regulator ADP [123 124] These findings allowto speculate about the potential use of these polyphenolsand of their derivatives with improved bioavailability in thetreatment of glutamine-dependent forms of cancer

342 Lipid Metabolism FAS sustains the altered lipid meta-bolism in cancer cells As discussed in Section 222 severalreports support the relevance of this enzyme as a target incancer cells This enzyme is a complex system with seven dif-ferent functional domains [125] This property amplifies thepossibility of impairing its enzymatic activity with differentspecific compounds

Four major specific FAS inhibitors are known [126] Theantibiotic cerulenin (extracted from the fungus Cephalospo-rium caerulens) acts as noncompetitive inhibitor of the 120573-ketoacyl synthase domain [127] Tetrahydrolipstatin alsoknown as Orlistat (a derivative of the natural compoundlipstatin) targets the thioesterase domain of FAS [128]Triclosan affects the enoyl-reductase activity of the enzyme[129] Finally the synthetic chemical derivative of ceruleninC75 is the most potent compound in vitro able to affect all thethree domainsmentioned earlier in a competitive irreversibleway [129] Orlistat was approved by the Food and DrugAdministration (FDA) for its ability to reduce body weightBesides all these molecules display anticancer activities byblocking cancer cell proliferation and triggering cancer celldeath [126] Nevertheless their actual application for cancertreatment is hindered by several side effects which includetheir ability to modulate other enzymes (ie the increase ofCPT-1 activity and fatty acid oxidation by cerulenin and C75leading to weight loss [130 131]) their reduced bioavailability(ie Orlistat [126]) or stability in vivo (ie C75 inactivationby intracellular glutathione and other small thiols [132])Current research efforts focus on the design of new syntheticderivatives of this first group ofmolecules on one side and onthe identification of new compounds of natural origin on theother side both potentially showing improved characteristicsof specificity and bioavailabilitystability in vivo

In this context the potential identification of new FASinhibitor from natural compounds is a particularly inter-esting strategy especially by investigating compounds ofvegetal origin showing the double favorable profile of beingregularly consumed in the diet and displaying at the sametime hypolipidemic and anticancer activities Several classesof polyphenols appear as very good candidates Extractsfrom green and black tea have been repeatedly provedas lipidogenic inhibitors [133] Further investigations haveidentified catechin gallate derivatives (including EGCGepicatechin gallate (ECG) and catechin gallate (CG)) asspecific FAS inhibitors as demonstrated by in vitro assaysof FAS enzymatic activity [134 135] The galloyl moiety ofthe catechins is essential for the inhibitory activity of thesemolecules it directly interacts and modulates the functionof the 120573-ketoacyl reductase domain of FAS [134 135] TheFAS inhibitory activity is common to other polyphenoliccompounds The group of Tian has first described severalflavones including luteolin quercetin kaempferol myricetinfisetin and baicalein as inhibitors of the 120573-ketoacyl reductasedomain [136]Theflavone luteolin and the flavonols quercetinand kaempferol (and with a lower extent the flavone apigeninand the flavanone taxifolin) have been shown to act as potentinhibitors of lipogenesis in a comparative studywith EGCG inprostate cancer [137] An in vitro FAS enzymatic activity assayconfirmed their ability to inhibit FAS however less potentlycompared to ECGC [137] Tian and colleagues suggestedthat all polyphenolic FAS inhibitors share a biphenyl corepotentially responsible for their described inhibitory activity[138] Possible differences may account for a structure-dependent mechanism of action where flavones as quercetinand kaempferol containing hydroxyl groups at specific posi-tions [137] display a reversible fast binding inhibitory activity


Resveratrol

Curcumin

Curcumin

ResveratrolCurcumin

ROS

LMP pathwayactivation

Mitochondrial enzymes activity

modulationCell cycle

arrest

Pancratistatin

Autophagy(mitophagy)

ROSNOS

Metabolic enzymes

modulation

Bavachinin

MMPalterations

BavachininCurcumin

BavachininCurcumin

MMPdecrease

ATP synthaseinhibition

HIF-1120572inhibition

Bcl-2 proteinsmodulation

NF-120581Binhibition

Figure 2 Mitochondrial dysfunctions as pharmacological targets Examples of natural compounds with a potential efficacy in cancertreatment The figure schematizes their mechanism of action linked to mitochondrial dysfunctions The compounds discussed herein havedifferent mitochondrial targets such as mitochondrial membrane potential (MMP) Bcl-2 family proteins (Bcl-2) reactive oxygen species(ROS) HIF-1120572 mitochondrial metabolism (MM) and autophagy

whereas EGCG and ECG exhibit an irreversible slow bindingactivity [134] It has been taken into account however thatfurther variability may be associated with differential uptakemetabolization and intrinsic stability of the compoundsFinally the effects on lipid metabolism may be the resultof multiple intracellular signalling events modulated bypolyphenolic compounds and eventually converging towardsthe control of the lipid metabolism Curcumin has beenshown to affect lipid accumulation and FAS activity [139]This ability may be partially linked to the known antagonisticactivity of this compound towards theNF-120581B-mediated path-way [140] Besides curcumin and its derivatives have recentlybeen shown to modulate the AMPK-SREBP pathway [141142] Green tea extracts prevent EGF-induced upregulationof FAS in MCF-7 via modulation of a PI3 KAKT-dependentpathway [143] Other polyphenolic compounds have beenidentified as inhibitors of lipidogenesis by targeting FASandor the transcription factor SREBP expression throughthe modulation of specific pathways These findings maytherefore suggest further relevant pathways involved in thecontrol of the lipid metabolism in cancer cells For exampleresveratrol a stilbene contained in grapes produces hypolipi-demic effects by activating the NAD-dependent deacetylasesirtuin 1 (SIRT-1) which positively modulates AMPK [144]AMPK activation in turn prevents lipid accumulation bycontrolling several events including FAS downregulation[144] The activation of AMPK by resveratrol has been alsoconfirmed in other studies [145] Moreover it is a commonproperty shared with compounds from other plants showinghypolipidemic properties as observed with extracts fromHibiscus sabdariffa [146] Promising interesting therapeuticimplications may derive also from phenolic compounds con-tained in the extra-virgin olive oil which was described as avery active inhibitor of FAS expression and controller of lipid

biosynthesis in breast cancer cell models [147] Compoundsbelonging to lignans (1-[+]-pinoresinol and 1-[+]-acetoxy-pinoresinol) flavonoids (apigenin and luteolin) and secoiri-doids (deacetoxyoleuropein aglycone ligstroside aglyconeoleuropein glycoside and oleuropein aglycone) appear as themost active compounds by activating AMPK and reducingSREBP-1 expression [147] Similarly polyphenols oleuropeinand hydroxytyrosol from extra-virgin olive oil were able toinhibit FAS activity in colorectal cancer SW260 cells and thiseffect correlated with their antiproliferative potential [148]However this effect could not be confirmed in another colonmodel (HT-29) suggesting cell-type specific effect and furtherunrelated mechanisms [148] Targeting lipid metabolismand especially FAS activity remains a promising perspectiveto target cancer cell survival Brusselmans and colleaguesshowed that palmitate added to the culture medium ofprostate cancer cells allowed to bypass the downstreameffects of FAS inhibition by luteolin on lipid metabolismand prevented the cytotoxic effect of this compound [137]moreover the silencing of FAS expression with FAS siRNAproduced similar cellular alterations as luteolin [137] Thesefindings allow predicting a causative role of FAS inhibitionin the antiproliferative and cytotoxic effect of polyphenolsand prompt to explore the relevance of the control of thelipid metabolism by polyphenols in the anticancer activitiesascribed to many of these compounds

4 Concluding Remarks

The targeting of altered cell metabolism in cancer cell is apromising still unexplored area in anticancer strategies Inthis review we have highlighted that many of these modifi-cations take place at very early steps of carcinogenesis thus


at preneoplastic stages Therefore their targeting may be apowerful weapon for chemopreventive purposes Besides theliterature clearly shows the crucial addiction of cancer cellsto several metabolic aberrations to proliferate and survivefurther underlining the importance of the targeting of somemetabolic-related factors in future anticancer therapies

Identification of specific aberrantly regulated metabolickeynodes in terms of the expression andor activity of thesefactors delineates the nature of potential pursuable molec-ular targets Despite all these considerations the effectivenumber of agents under investigations for antimetabolicpurposes is still very poor and at a very preliminary stageGood candidates should present a favorable profile ensuringexcellent differential toxicity against cancer versus healthycells a reduced risk of systemic toxicity combined toa favorable profile in specific pharmacological propertiesincluding bioavailability half-life and stability Many nat-ural compounds have so far been identified as anticanceragents by affecting almost each cancer hallmark [2] Takinginto account recently identified cross-talks between alteredmetabolic mediators and altered proliferation survival ormigration properties we may suspect that many of theanticancer properties so far ascribed to natural compoundsare mainly due to a their potential in modulating cellu-lar metabolism Remarkably we have reported here manyexamples of dietary polyphenolic compounds from fruits andvegetables which display specific antimetabolic functions(Figure 1) Although there is consistent evidence of multiplebeneficial biological properties on health there are yet someobstacles which hinder promising natural compounds frombeing already used for chemopreventive and therapeuticpurposes including bioavailability and adsorptionMoreoverinformation concerning the stability and the clearance ofnatural occurring compounds frequently remains to be yetdetermined additional efforts will be required towards theelucidation of this important properties in the next future

Nature represents an impressively huge ldquodatabaserdquo ofdifferent and diversified molecular scaffolds Rapid advance-ment in new screening systems allowing the analysis oflarge libraries of isolated naturally occurring compoundsoffers new important and fast tools for the selection ofpromising antimetabolic compounds especially from dietaryorigins with reduced side effects Relatively low costs fortheir extractionproduction in large amounts make theminteresting for commercial objectives and represent a goodbasis for chemical modifications that may further improvetheir anticancer activities and facilitate their pharmacologicaluse and efficiency

Abbreviations

AMPK AMP-activated protein kinaseAtg5 Autophagy protein 5ARNT Aryl hydrocarbon nuclear translocatorBcl-2 B Cell Lymphoma-2BAX B Cell Lymphoma-Associated XBAK Bcl-2 homologous antagonist killerCO2 Carbon dioxide

CG Catechin gallate

COX-2 Cyclo-oxygenase-2DCA DichloroacetateENO-1 Enolase-1ERK Extracellular-regulated kinaseFAS Fatty acid synthaseHIF Hypoxia-inducible factorEGCG Epigallocatechin gallateGCG Gallocatechin gallateHKII Hexokinase IIHDACs Histone deacetylasesGAPDH Glyceraldehyde-3-phosphate

dehydrogenaseGO Glucose oxidationGLUT Glucose transporterGDH Glutamate dehydrogenaseLDH Lactate dehydrogenaseLMP Lysosomal-mitochondrial pathwayMAPK Mitogen-activated protein kinaseMMP Mitochondrial membrane potentialNAD Nicotinamide adenosine diphosphateNF-120581B Nuclear factor 120581BNADPH Nicotinamide adenine dinucleotide phos-

phate-oxidasePPP Pentose phosphate pathwayPI3K Phosphatidylinositol-3-kinasePDK Pyruvate dehydrogenase kinasePKM2 Pyruvate kinase isoformM2ROS Reactive oxygen speciesSTAT3 Signal Transducer and Activator of Tran-

scription 3SREBP Sterol regulatory element-binding proteinsTCA Tricarboxylic acid cycleVEGF Vascular endothelial growth factors

Acknowledgments

C Cerella is supported by a ldquoWaxweiler grant for cancerprevention researchrdquo from the Action LIONS ldquoVaincre leCancerrdquo F Radonga is recipient of a postdoctoral Televiegrant Research at the Laboratoire de Biologie Moleculaire etCellulaire duCancer (LBMCC) is financially supported by theldquoRecherche Cancer et Sangrdquo foundation by the ldquoRecherchesScientifiques Luxembourgrdquo association by ldquoEen Haerz firkriibskrank Kannerrdquo association by the Action Lions ldquoVain-cre le Cancerrdquo association and by Televie Luxembourg MDiederich is supported by the National Research Foundation(NRF) by the MEST of Korea for Tumor MicroenvironmentGlobal Core Research Center (GCRC) Grant [no 2012-0001184] by the Seoul National University Research grantand by the Research Settlement Fund for the new faculty ofSNU

References

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[2] B Orlikova and M Diederich ldquoPower from the garden plantcompounds as inhibitors of the hallmarks of cancerrdquo CurrentMedicinal Chemistry vol 19 no 14 pp 2061ndash2087 2012

[3] D Hanahan and R AWeinberg ldquoHallmarks of cancer the nextgenerationrdquo Cell vol 144 no 5 pp 646ndash674 2011

[4] F Chiaradonna R M Moresco C Airoldi et al ldquoFrom cancermetabolism to new biomarkers and drug targetsrdquo BiotechnologyAdvances vol 30 no 1 pp 30ndash51 2012

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[6] V R Fantin J St-Pierre and P Leder ldquoAttenuation of LDH-Aexpression uncovers a link between glycolysis mitochondrialphysiology and tumor maintenancerdquo Cancer Cell vol 9 no 6pp 425ndash434 2006

[7] G L Semenza ldquoRegulation of metabolism by hypoxia-indu-cible factor 1rdquo Cold Spring Harbor Symposia on QuantitativeBiology vol 76 pp 347ndash353 2011

[8] H R Christofk M G Vander Heiden M H Harris et al ldquoTheM2 splice isoform of pyruvate kinase is important for cancermetabolism and tumour growthrdquoNature vol 452 no 7184 pp230ndash233 2008

[9] R Diaz-Ruiz M Rigoulet and A Devin ldquoThe Warburg andCrabtree effects on the origin of cancer cell energy metabolismand of yeast glucose repressionrdquo Biochimica et Biophysica Actavol 1807 no 6 pp 568ndash576 2011

[10] L Zheng R G Roeder and Y Luo ldquoS phase activation of thehistone H2B promoter by OCA-S a coactivator complex thatcontains GAPDH as a key componentrdquo Cell vol 114 no 2 pp255ndash266 2003

[11] TMitani R Yamaji YHigashimuraNHarada YNakano andH Inui ldquoHypoxia enhances transcriptional activity of androgenreceptor through hypoxia-inducible factor-1120572 in a low androgenenvironmentrdquo Journal of Steroid Biochemistry and MolecularBiology vol 123 no 1-2 pp 58ndash64 2011

[12] C Tristan N Shahani T W Sedlak and A Sawa ldquoThediverse functions of GAPDH views from different subcellularcompartmentsrdquo Cellular Signalling vol 23 no 2 pp 317ndash3232011

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[21] K A Brand and U Hermfisse ldquoAerobic glycolysis by proliferat-ing cells a protective strategy against reactive oxygen speciesrdquoThe FASEB Journal vol 11 no 5 pp 388ndash395 1997

[22] K Brand ldquoAerobic glycolysis by proliferating cells protectionagainst oxidative stress at the expense of energy yieldrdquo Journalof Bioenergetics and Biomembranes vol 29 no 4 pp 355ndash3641997

[23] H Shim C Dolde B C Lewis et al ldquoc-Myc transactivationof LDH-A implications for tumor metabolism and growthrdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 94 no 13 pp 6658ndash6663 1997

[24] C V Dang and G L Semenza ldquoOncogenic alterations ofmetabolismrdquo Trends in Biochemical Sciences vol 24 no 2 pp68ndash72 1999

[25] J Y Park W Zheng D Kim et al ldquoCandidate tumor suppres-sor gene SLC5A8 is frequently down-regulated by promoterhypermethylation in prostate tumorrdquo Cancer Detection andPrevention vol 31 no 5 pp 359ndash365 2007

[26] J Helm D Coppola V Ganapathy et al ldquoSLC5A8 nucleartranslocation and loss of expression are associated with pooroutcome in pancreatic ductal adenocarcinomardquo Pancreas vol41 no 6 pp 904ndash909 2012

[27] M Thangaraju E Gopal P M Martin et al ldquoSLC5A8 triggerstumor cell apoptosis through pyruvate-dependent inhibitionof histone deacetylasesrdquo Cancer Research vol 66 no 24 pp11560ndash11564 2006

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[29] V Paroder S R Spencer M Paroder et al ldquoNa+mono-carboxylate transport (SMCT) protein expression correlateswith survival in colon cancer molecular characterization ofSMCTrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 103 no 19 pp 7270ndash7275 2006

[30] R J DeBerardinis A Mancuso E Daikhin et al ldquoBeyondaerobic glycolysis transformed cells can engage in glutaminemetabolism that exceeds the requirement for protein andnucleotide synthesisrdquo Proceedings of the National Academy ofSciences of the United States of America vol 104 no 49 pp19345ndash19350 2007

[31] Y Mitsuishi K Taguchi Y Kawatani et al ldquoNrf2 redirectsglucose and glutamine into anabolic pathways in metabolicreprogrammingrdquo Cancer Cell vol 22 no 1 pp 66ndash79 2012

[32] D Chalbos M Chambon G Ailhaud and H Rochefort ldquoFattyacid synthetase and its mRNA are induced by progestins inbreast cancer cellsrdquoThe Journal of Biological Chemistry vol 262no 21 pp 9923ndash9926 1987

[33] J V Swinnen M Esquenet K Goossens W Heyns and GVerhoeven ldquoAndrogens stimulate fatty acid synthase in thehuman prostate cancer cell line LNCaPrdquo Cancer Research vol57 no 6 pp 1086ndash1090 1997

[34] T S Ho Y P Ho W Y Wong L Chi-Ming Chiu Y SWong and V Eng-Choon Ooi ldquoFatty acid synthase inhibitors


cerulenin andC75 retard growth and induce caspase-dependentapoptosis in human melanoma A-375 cellsrdquo Biomedicine ampPharmacotherapy vol 61 no 9 pp 578ndash587 2007

[35] Z L Liu G Wang A F Peng et al ldquoFatty acid synthaseexpression in osteosarcoma and its correlation with pulmonarymetastasisrdquo Oncology Letters vol 4 no 5 pp 878ndash882 2012

[36] J N Li M A Mahmoud W F Han M Ripple and E SPizer ldquoSterol regulatory element-binding protein-1 participatesin the regulation of fatty acid synthase expression in colorectalneoplasiardquo Experimental Cell Research vol 261 no 1 pp 159ndash165 2000

[37] Y Zhan N Ginanni M R Tota et al ldquoControl of cell growthand survival by enzymes of the fatty acid synthesis pathway inHCT-116 colon cancer cellsrdquo Clinical Cancer Research vol 14no 18 pp 5735ndash5742 2008

[38] H Orita J Coulter E Tully F P Kuhajda and E GabrielsonldquoInhibiting fatty acid synthase for chemoprevention of chemi-cally induced lung tumorsrdquoClinical Cancer Research vol 14 no8 pp 2458ndash2464 2008

[39] E S Pizer F D Wood G R Pasternack and F P KuhajdaldquoFatty acid synthase (FAS) a target for cytotoxic antimetabolitesinHL60 promyelocytic leukemia cellsrdquoCancer Research vol 56no 4 pp 745ndash751 1996

[40] A P Bhatt S R Jacobs A J Freemerman et al ldquoDysregu-lation of fatty acid synthesis and glycolysis in non-Hodgkinlymphomardquo Proceedings of the National Academy of Sciences ofthe United States of America vol 109 no 29 pp 11818ndash11823

[41] Y A Yang W F Han P J Morin F J Chrest and E SPizer ldquoActivation of fatty acid synthesis during neoplastictransformation role of mitogen-activated protein kinase andphosphatidylinositol 3-kinaserdquo Experimental Cell Research vol279 no 1 pp 80ndash90 2002

[42] N Li X Bu X Tian et al ldquoFatty acid synthase regulatesproliferation andmigration of colorectal cancer cells via HER2-PI3KAkt signaling pathwayrdquo Nutrition and Cancer vol 64 no6 pp 864ndash870 2012

[43] Z Luo M Zang and W Guo ldquoAMPK as a metabolic tumorsuppressor control of metabolism and cell growthrdquo FutureOncology vol 6 no 3 pp 457ndash470 2010

[44] W Shao and P J Espenshade ldquoExpanding roles for SREBP inmetabolismrdquo Cell Metabolism vol 16 no 4 pp 414ndash419 2012

[45] J R Cantor and D M Sabatini ldquoCancer cell metabolism onehallmark many facesrdquo Cancer Discovery vol 2 no 10 pp 881ndash898 2012

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[47] S Bandyopadhyay S K Pai M Watabe et al ldquoFAS expressioninversely correlates with PTEN level in prostate cancer anda PI 3-kinase inhibitor synergizes with FAS siRNA to induceapoptosisrdquo Oncogene vol 24 no 34 pp 5389ndash5395 2005

[48] K Walter S M Hong S Nyhan et al ldquoSerum fatty acid syn-thase as a marker of pancreatic neoplasiardquo Cancer EpidemiologyBiomarkers and Prevention vol 18 no 9 pp 2380ndash2385 2009

[49] F P Kuhajda ldquoFatty acid synthase and cancer new applicationof an old pathwayrdquo Cancer Research vol 66 no 12 pp 5977ndash5980 2006

[50] S Lu and M C Archer ldquoFatty acid synthase is a potentialmolecular target for the chemoprevention of breast cancerrdquoCarcinogenesis vol 26 no 1 pp 153ndash157 2005

[51] S Bandyopadhyay R Zhan Y Wang et al ldquoMechanism ofapoptosis induced by the inhibition of fatty acid synthase inbreast cancer cellsrdquo Cancer Research vol 66 no 11 pp 5934ndash5940 2006

[52] J L Little F B Wheeler D R Fels C Koumenis and S JKridel ldquoInhibition of fatty acid synthase induces endoplasmicreticulum stress in tumor cellsrdquo Cancer Research vol 67 no 3pp 1262ndash1269 2007

[53] I Samudio R Harmancey M Fiegl et al ldquoPharmacologicinhibition of fatty acid oxidation sensitizes human leukemiacells to apoptosis inductionrdquo Journal of Clinical Investigationvol 120 no 1 pp 142ndash156 2010

[54] TM LoftusD E Jaworsky C L Frehywot et al ldquoReduced foodintake and body weight in mice treated with fatty acid synthaseinhibitorsrdquo Science vol 288 no 5475 pp 2379ndash2381 2000

[55] J A Menendez L Vellon and R Lupu ldquoTargeting fattyacid synthase-driven lipid rafts a novel strategy to overcometrastuzumab resistance in breast cancer cellsrdquoMedical Hypothe-ses vol 64 no 5 pp 997ndash1001 2005

[56] C J Piyathilake A R Frost U Manne et al ldquoThe expression offatty acid synthase (FASE) is an early event in the developmentand progression of squamous cell carcinoma of the lungrdquoHuman Pathology vol 31 no 9 pp 1068ndash1073 2000

[57] J V Swinnen T Roskams S Joniau et al ldquoOverexpressionof fatty acid synthase is an early and common event inthe development of prostate cancerrdquo International Journal ofCancer vol 98 no 1 pp 19ndash22 2002

[58] A Baron T Migita D Tang andM Loda ldquoFatty acid synthasea metabolic oncogene in prostate cancerrdquo Journal of CellularBiochemistry vol 91 no 1 pp 47ndash53 2004

[59] J A Menendez J P Decker and R Lupu ldquoIn support of FattyAcid Synthase (FAS) as a metabolic oncogene extracellularacidosis acts in an epigenetic fashion activating FAS geneexpression in cancer cellsrdquo Journal of Cellular Biochemistry vol94 no 1 pp 1ndash4 2005

[60] T Migita S Ruiz A Fornari et al ldquoFatty acid synthase ametabolic enzyme and candidate oncogene in prostate cancerrdquoJournal of the National Cancer Institute vol 101 no 7 pp 519ndash532 2009

[61] G B Mills and W H Moolenaar ldquoThe emerging role oflysophosphatidic acid in cancerrdquo Nature Reviews Cancer vol 3no 8 pp 582ndash591 2003

[62] C Sobolewski C Cerella M Dicato L Ghibelli and MDiederich ldquoThe role of cyclooxygenase-2 in cell proliferationand cell death in human malignanciesrdquo International Journal ofCell Biology vol 2010 Article ID 215158 21 pages 2010

[63] C Cerella C Sobolewski M Dicato and M Diederich ldquoTar-geting COX-2 expression by natural compounds a promisingalternative strategy to synthetic COX-2 inhibitors for cancerchemoprevention and therapyrdquo Biochemical Pharmacology vol80 no 12 pp 1801ndash1815 2010

[64] D K Nomura J Z Long S Niessen H S Hoover S W Ngand B F Cravatt ldquoMonoacylglycerol lipase regulates a fatty acidnetwork that promotes cancer pathogenesisrdquo Cell vol 140 no1 pp 49ndash61 2010

[65] A Vila A Rosengarth D Piomelli B Cravatt and LJ Marnett ldquoHydrolysis of prostaglandin glycerol esters bythe endocannabinoid-hydrolyzing enzymes monoacylglycerollipase and fatty acid amide hydrolaserdquo Biochemistry vol 46 no33 pp 9578ndash9585 2007

[66] P Carmeliet and R K Jain ldquoAngiogenesis in cancer and otherdiseasesrdquo Nature vol 407 no 6801 pp 249ndash257 2000


[67] J D Rabinowitz and E White ldquoAutophagy and metabolismrdquoScience vol 330 no 6009 pp 1344ndash1348 2010

[68] L T Jia S Y Chen and A G Yang ldquoCancer gene therapy tar-geting cellular apoptosismachineryrdquoCancer Treatment Reviewsvol 38 no 7 pp 868ndash876 2012

[69] G Sutendra P Dromparis A Kinnaird et al ldquoMitochondrialactivation by inhibition of PDKII suppresses HIF1a signalingand angiogenesis in cancerrdquo Oncogene vol 32 no 13 pp 1638ndash1650 2012

[70] D C Wallace ldquoMitochondria and cancerrdquo Nature ReviewsCancer vol 12 no 10 pp 685ndash698 2012

[71] T N Milovanova V M Bhopale E M Sorokina et al ldquoLactatestimulates vasculogenic stem cells via the thioredoxin systemand engages an autocrine activation loop involving hypoxia-inducible factor 1rdquo Molecular and Cellular Biology vol 28 no20 pp 6248ndash6261 2008

[72] R T Marquez and L Xu ldquoBcl-2Beclin 1 complex multiplemechanisms regulating autophagyapoptosis toggle switchrdquoAmerican Journal of Cancer Research vol 2 no 2 pp 214ndash2212012

[73] A J Levine and A M Puzio-Kuter ldquoThe control of themetabolic switch in cancers by oncogenes and tumor suppressorgenesrdquo Science vol 330 no 6009 pp 1340ndash1344 2010

[74] D C Wallace ldquoMitochondria and cancer Warburg addressedrdquoCold Spring Harbor Symposia on Quantitative Biology vol 70pp 363ndash374 2005

[75] N C Denko ldquoHypoxia HIF1 and glucose metabolism in thesolid tumourrdquoNature Reviews Cancer vol 8 no 9 pp 705ndash7132008

[76] G L Semenza ldquoHypoxia-inducible factors in physiology andmedicinerdquo Cell vol 148 no 3 pp 399ndash408 2012

[77] G L Wang B H Jiang and G L Semenza ldquoEffect ofaltered redox states on expression and DNA-binding activityof hypoxia-inducible factor 1rdquo Biochemical and BiophysicalResearch Communications vol 212 no 2 pp 550ndash556 1995

[78] L E Huang Z Arany D M Livingston and H Franklin BunnldquoActivation of hypoxia-inducible transcription factor dependsprimarily upon redox-sensitive stabilization of its 120572 subunitrdquoThe Journal of Biological Chemistry vol 271 no 50 pp 32253ndash32259 1996

[79] S Salceda and J Caro ldquoHypoxia-inducible factor 1120572 (HIF-1120572) protein is rapidly degraded by the ubiquitin-proteasomesystem under normoxic conditions Its stabilization by hypoxiadepends on redox-induced changesrdquo The Journal of BiologicalChemistry vol 272 no 36 pp 22642ndash22647 1997

[80] S Krishna I C C Low and S Pervaiz ldquoRegulation ofmitochondrial metabolism yet another facet in the biology ofthe oncoprotein Bcl-2rdquo Biochemical Journal vol 435 no 3 pp545ndash551 2011

[81] S Cristofanon S Nuccitelli M DrsquoAlessio M Dicato MDiederich and L Ghibelli ldquoOxidation-dependent maturationand survival of explanted blood monocytes via Bcl-2 up-regulationrdquo Biochemical Pharmacology vol 76 no 11 pp 1533ndash1543 2008

[82] B R You andWH Park ldquoTrichostatin A induces apoptotic celldeath of HeLa cells in a Bcl-2 and oxidative stress-dependentmannerrdquo International Journal of Oncology vol 42 no 1 pp359ndash366 2013

[83] B J Altman and J C Rathmell ldquoAutophagy not good or badbut good and badrdquo Autophagy vol 5 no 4 pp 569ndash570 2009

[84] J Y Guo H Y Chen R Mathew et al ldquoActivated Ras requiresautophagy to maintain oxidative metabolism and tumorigene-sisrdquo Genes and Development vol 25 no 5 pp 460ndash470 2011

[85] J Lee S Giordano and J Zhang ldquoAutophagy mitochondriaand oxidative stress cross-talk and redox signallingrdquo TheBiochemical Journal vol 441 no 2 pp 523ndash540 2012

[86] L Liu D Feng G Chen et al ldquoMitochondrial outer-membraneprotein FUNDC1 mediates hypoxia-induced mitophagy inmammalian cellsrdquoNature Cell Biology vol 14 no 2 pp 177ndash1852012

[87] A Y Andreyev Y E Kushnareva andAA Starkov ldquoMitochon-drial metabolism of reactive oxygen speciesrdquo Biochemistry vol70 no 2 pp 200ndash214 2005

[88] A Apel I Herr H Schwarz H P Rodemann and A MayerldquoBlocked autophagy sensitizes resistant carcinoma cells toradiation therapyrdquoCancer Research vol 68 no 5 pp 1485ndash14942008

[89] Y Yu SM Fan J K Song et al ldquoHydroxyl radical (sdotOH) playeda pivotal Role in oridonin-induced apoptosis and autophagyin human epidermoid carcinoma A431 cellsrdquo Biological ampPharmaceutical Bulletin vol 35 no 12 pp 2148ndash2159 2012

[90] V Ganapathy M Thangaraju and P D Prasad ldquoNutrienttransporters in cancer relevance to Warburg hypothesis andbeyondrdquo Pharmacology andTherapeutics vol 121 no 1 pp 29ndash40 2009

[91] M P Torres S Rachagani V Purohit et al ldquoGraviola a novelpromising natural-derived drug that inhibits tumorigenicityand metastasis of pancreatic cancer cells in vitro and in vivothrough altering cell metabolismrdquo Cancer Letters vol 323 no1 pp 29ndash40 2012

[92] M Kitagawa S Ikeda E Tashiro T Soga and M ImotoldquoMetabolomic identification of the target of the filopodiaprotrusion inhibitor glucopiericidin Ardquo Chemistry amp Biologyvol 17 no 9 pp 989ndash998 2010

[93] J B Park ldquoFlavonoids are potential inhibitors of glucoseuptake in U937 cellsrdquo Biochemical and Biophysical ResearchCommunications vol 260 no 2 pp 568ndash574 1999

[94] P Strobel C Allard T Perez-Acle R Calderon R Aldunateand F Leighton ldquoMyricetin quercetin and catechin-gallateinhibit glucose uptake in isolated rat adipocytesrdquo BiochemicalJournal vol 386 no 3 pp 471ndash478 2005

[95] A Perez P Ojeda L Ojeda et al ldquoHexose transporter GLUT1harbors several distinct regulatory binding sites for flavones andtyrphostinsrdquo Biochemistry vol 50 no 41 pp 8834ndash8845 2011

[96] A Wolf S Agnihotri J Micallef et al ldquoHexokinase 2 is a keymediator of aerobic glycolysis and promotes tumor growth inhuman glioblastoma multiformerdquo The Journal of ExperimentalMedicine vol 208 no 2 pp 313ndash326 2011

[97] N Shulga R Wilson-Smith and J G Pastorino ldquoHexokinaseII detachment from the mitochondria potentiates cisplatininduced cytotoxicity through a caspase-2 dependent mecha-nismrdquo Cell Cycle vol 8 no 20 pp 3355ndash3364 2009

[98] S Cohen and E Flescher ldquoMethyl jasmonate a plant stresshormone as an anti-cancer drugrdquo Phytochemistry vol 70 no13-14 pp 1600ndash1609 2009

[99] C Xing J R LaPorte J K Barbay and A G Myers ldquoIden-tification of GAPDH as a protein target of the saframycinantiproliferative agentsrdquo Proceedings of the National Academyof Sciences of the United States of America vol 101 no 16 pp5862ndash5866 2004


[100] M G Vander Heiden H R Christofk E Schuman et alldquoIdentification of small molecule inhibitors of pyruvate kinaseM2rdquo Biochemical Pharmacology vol 79 no 8 pp 1118ndash11242010

[101] J Chen J Xie Z Jiang et al ldquoShikonin and its analogs inhibitcancer cell glycolysis by targeting tumor pyruvate kinase-M2rdquoOncogene vol 30 no 42 pp 4297ndash4306 2011

[102] W Han L Li S Qiu et al ldquoShikonin circumvents cancerdrug resistance by induction of a necroptotic deathrdquoMolecularCancer Therapeutics vol 6 no 5 pp 1641ndash1649 2007

[103] D Anastasiou Y Yu W J Israelsen et al ldquoPyruvate kinase M2activators promote tetramer formation and suppress tumorige-nesisrdquo Nature Chemical Biology vol 8 no 12 p 1008 2012

[104] T W Hodges C F Hossain Y P Kim Y D Zhouand D G Nagle ldquoMolecular-targeted antitumor agents theSaururus cernuus dineolignans manassantin B and 4-O-demethylmanassantin B are potent inhibitors of hypoxia-activated HIF-1rdquo Journal of Natural Products vol 67 no 5 pp767ndash771 2004

[105] Y Liu C K Venna J B Morgan et al ldquoMethylalpinu-misoflavone inhibits hypoxia-inducible factor-1 (HIF-1) acti-vation by simultaneously targeting multiple pathwaysrdquo TheJournal of Biological Chemistry vol 284 no 9 pp 5859ndash58682009

[106] H Hattori K Okuda T Murase et al ldquoIsolation identificationand biological evaluation of HIF-1-modulating compoundsfrom Brazilian green propolisrdquo Bioorganic amp Medicinal Chem-istry vol 19 no 18 pp 5392ndash5401 2011

[107] MH Teiten S EifesMDicato andMDiederich ldquoCurcumin-the paradigm of a multi-target natural compound with applica-tions in cancer prevention and treatmentrdquo Toxins vol 2 no 1pp 128ndash162 2010

[108] L D Guo X J Chen Y H Hu et al ldquoCurcumin inhibitsproliferation and induces apoptosis of human colorectal cancercells by activating the mitochondria apoptotic pathwayrdquo Phy-totherapy Research vol 27 no 3 pp 422ndash430 2012

[109] AKunwar S JayakumarAK Srivastava andK I PriyadarsinildquoDimethoxycurcumin-induced cell death in human breast car-cinoma MCF7 cells evidence for pro-oxidant activity mito-chondrial dysfunction and apoptosisrdquo Archives of Toxicologyvol 86 no 4 pp 603ndash614 2012

[110] Q Y Chen J G Shi Q H Yao et al ldquoLysosomal membranepermeabilization is involved in curcumin-induced apoptosis ofA549 lung carcinoma cellsrdquo Molecular and Cellular Biochem-istry vol 359 no 1-2 pp 389ndash398 2012

[111] C L Kuo S YWu SW Ip et al ldquoApoptotic death in curcumin-treated NPC-TW 076 human nasopharyngeal carcinoma cellsis mediated through the ROS mitochondrial depolarizationand caspase-3-dependent signaling responsesrdquo InternationalJournal of Oncology vol 39 no 2 pp 319ndash328 2011

[112] C L Yang Y G Ma Y X Xue et al ldquoCurcumin inducessmall cell lung cancer NCI-H446 cell apoptosis via the reactiveoxygen species-mediated mitochondrial pathway and not thecell death receptor pathwayrdquo DNA and Cell Biology vol 31 no2 pp 139ndash150 2012

[113] K H Jung and J W Park ldquoSuppression of mitochondrialNADP+-dependent isocitrate dehydrogenase activity enhancescurcumin-induced apoptosis in HCT116 cellsrdquo Free RadicalResearch vol 45 no 4 pp 431ndash438 2011

[114] A McLachlan N Kekre J McNulty and S Pandey ldquoPancratis-tatin a natural anti-cancer compound that targets mitochon-dria specifically in cancer cells to induce apoptosisrdquo Apoptosisvol 10 no 3 pp 619ndash630 2005

[115] M Y Kim L J Trudel and G N Wogan ldquoApoptosis inducedby capsaicin and resveratrol in colon carcinoma cells requiresnitric oxide production and caspase activationrdquo AnticancerResearch vol 29 no 10 pp 3733ndash3740 2009

[116] J Z Boyer J Jandova J Janda et al ldquoResveratrol-sensitizedUVA induced apoptosis in human keratinocytes through mito-chondrial oxidative stress and pore openingrdquo Journal of Photo-chemistry and Photobiology B vol 113 pp 42ndash50 2012

[117] E C Filippi-Chiela E S Villodre L L Zamin and G LenzldquoAutophagy interplay with apoptosis and cell cycle regulation inthe growth inhibiting effect of resveratrol in glioma cellsrdquo PLoSONE vol 6 no 6 Article ID e20849 2011

[118] X Wang A W Leung J Luo and C Xu ldquoTEM observation ofultrasound-induced mitophagy in nasopharyngeal carcinomacells in the presence of curcuminrdquo Experimental andTherapeu-tic Medicine vol 3 no 1 pp 146ndash148 2012

[119] H Qian Y Yang and X Wang ldquoCurcumin enhancedadriamycin-induced human liver-derived Hepatoma G2 celldeath through activation of mitochondria-mediated apoptosisand autophagyrdquo European Journal of Pharmaceutical Sciencesvol 43 no 3 pp 125ndash131 2011

[120] M Strofer W Jelkmann and R Depping ldquoCurcumin decreasessurvival of Hep3B liver and MCF-7 breast cancer cells the roleof HIFrdquo Strahlentherapie und Onkologie vol 187 no 7 pp 393ndash400 2011

[121] MNepal H J Choi B Y Choi et al ldquoAnti-angiogenic and anti-tumor activity of Bavachinin by targeting hypoxia-induciblefactor-1alphardquo European Journal of Pharmacology vol 691 no1ndash3 pp 28ndash37 2012

[122] C Yang J Sudderth T Dang R M Bachoo J G McDonaldand R J DeBerardinis ldquoGlioblastoma cells require glutamatedehydrogenase to survive impairments of glucose metabolismor Akt signalingrdquo Cancer Research vol 69 no 20 pp 7986ndash7993 2009

[123] C Li A Allen J Kwagh et al ldquoGreen tea polyphenols modulateinsulin secretion by inhibiting glutamate dehydrogenaserdquo TheJournal of Biological Chemistry vol 281 no 15 pp 10214ndash102212006

[124] C Li M Li P Chen et al ldquoGreen tea polyphenols controldysregulated glutamate dehydrogenase in transgenic mice byhijacking the ADP activation siterdquo The Journal of BiologicalChemistry vol 286 no 39 pp 34164ndash34174 2011

[125] S Smith ldquoThe animal fatty acid synthase one gene onepolypeptide seven enzymesrdquoThe FASEB Journal vol 8 no 15pp 1248ndash1259 1994

[126] H Liu J Y Liu X Wu and J T Zhang ldquoBiochemistrymolecular biology and pharmacology of fatty acid synthase anemerging therapeutic target and diagnosisprognosis markerrdquoInternational Journal of Biochemistry andMolecular Biology vol1 no 1 pp 69ndash89 2010

[127] D Vance I Goldberg O Mitsuhashi and K Bloch ldquoInhibitionof fatty acid synthetases by the antibiotic ceruleninrdquo Biochemi-cal and Biophysical Research Communications vol 48 no 3 pp649ndash656 1972

[128] S J Kridel F Axelrod N Rozenkrantz and J W Smith ldquoOrli-stat is a novel inhibitor of fatty acid synthase with antitumoractivityrdquo Cancer Research vol 64 no 6 pp 2070ndash2075 2004


[129] B Liu Y Wang K L Fillgrove and V E Anderson ldquoTriclosaninhibits enoyl-reductase of type I fatty acid synthase in vitro andis cytotoxic to MCF-7 and SKBr-3 breast cancer cellsrdquo CancerChemotherapy and Pharmacology vol 49 no 3 pp 187ndash1932002

[130] Y J Jin S Z Li Z S Zhao et al ldquoCarnitine palmitoyl-transferase-1 (CPT-1) activity stimulation by cerulenin viasympathetic nervous system activation overrides ceruleninrsquosperipheral effectrdquo Endocrinology vol 145 no 7 pp 3197ndash32042004

[131] S H Cha Z Hu S Chohnan and M D Lane ldquoInhibitionof hypothalamic fatty acid synthase triggers rapid activationof fatty acid oxidation in skeletal musclerdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 102 no 41 pp 14557ndash14562 2005

[132] A R Rendina and D Cheng ldquoCharacterization of the inacti-vation of rat fatty acid synthase by C75 inhibition of partialreactions and protection by substratesrdquo Biochemical Journalvol 388 no 3 pp 895ndash903 2005

[133] W X Tian ldquoInhibition of fatty acid synthase by polyphenolsrdquoCurrent Medicinal Chemistry vol 13 no 8 pp 967ndash977 2006

[134] X Wang K S Song Q X Guo and W X Tian ldquoThe galloylmoiety of green tea catechins is the critical structural feature toinhibit fatty-acid synthaserdquo Biochemical Pharmacology vol 66no 10 pp 2039ndash2047 2003

[135] R Zhang W Xiao X Wang X Wu and W Tian ldquoNovelinhibitors of fatty-acid synthase from green tea (Camelliasinensis Xihu Longjing) with high activity and a new reactingsiterdquo Biotechnology and Applied Biochemistry vol 43 no 1 pp1ndash7 2006

[136] B H Li and W X Tian ldquoInhibitory effects of flavonoids onanimal fatty acid synthaserdquo Journal of Biochemistry vol 135 no1 pp 85ndash91 2004

[137] K Brusselmans R Vrolix G Verhoeven and J V SwinnenldquoInduction of cancer cell apoptosis by flavonoids is associatedwith their ability to inhibit fatty acid synthase activityrdquo TheJournal of Biological Chemistry vol 280 no 7 pp 5636ndash56452005

[138] B H Li X F Ma Y Wang and W X Tian ldquoStructure-activityrelationship of polyphenols that inhibit fatty acid synthaserdquoJournal of Biochemistry vol 138 no 6 pp 679ndash685 2005

[139] J Zhao X B Sun F Ye and W X Tian ldquoSuppression offatty acid synthase differentiation and lipid accumulation inadipocytes by curcuminrdquo Molecular and Cellular Biochemistryvol 351 no 1-2 pp 19ndash28 2011

[140] A A Nanji K Jokelainen G L Tipoe A Rahemtulla PThomas and A J Dannenberg ldquoCurcumin prevents alcohol-induced liver disease in rats by inhibiting the expression of NF-120581B-dependent genesrdquo American Journal of Physiology vol 284no 2 pp G321ndashG327 2003

[141] C M Hung Y H Su H Y Lin et al ldquoDemethoxycur-cuminModulates ProstateCancerCell Proliferation viaAMPK-Induced Down-regulation of HSP70 and EGFRrdquo Journal ofAgricultural and Food Chemistry vol 60 no 34 pp 8427ndash84342012

[142] V Soetikno F R Sari V Sukumaran et al ldquoCurcumin decreasesrenal triglyceride accumulation through AMPK-SREBP signal-ing pathway in streptozotocin-induced type 1 diabetic ratsrdquoTheJournal of Nutritional Biochemistry vol 24 no 5 pp 796ndash8022012

[143] C W Yeh W J Chen C T Chiang S Y Lin-Shiau and J KLin ldquoSuppression of fatty acid synthase in MCF-7 breast cancer

cells by tea and tea polyphenols a possible mechanism for theirhypolipidemic effectsrdquo The Pharmacogenomics Journal vol 3no 5 pp 267ndash276 2003

[144] X Hou S Xu K A Maitland-Toolan et al ldquoSIRT1 regulateshepatocyte lipid metabolism through activating AMP-activatedprotein kinaserdquoThe Journal of Biological Chemistry vol 283 no29 pp 20015ndash20026 2008

[145] S M Shin I J Cho and S G Kim ldquoResveratrol protects mito-chondria against oxidative stress through AMP-activated pro-tein kinase-mediated glycogen synthase kinase-3120573 inhibitiondownstream of poly(ADP-ribose) polymerase-LKB1 pathwayrdquoMolecular Pharmacology vol 76 no 4 pp 884ndash895 2009

[146] M Y Yang C H Peng K C Chan Y I S Yang C N HuangandC JWang ldquoThe hypolipidemic effect ofHibiscus sabdariffapolyphenols via inhibiting lipogenesis and promoting hepaticlipid clearancerdquo Journal of Agricultural and Food Chemistry vol58 no 2 pp 850ndash859 2010

[147] J A Menendez A Vazquez-Martin C Oliveras-Ferraros et alldquoAnalyzing effects of extra-virgin olive polyphenols on breastcancer-associated fatty acid synthase protein expression usingreverse-phase protein microarraysrdquo International Journal ofMolecular Medicine vol 22 no 4 pp 433ndash439 2008

[148] M Notarnicola S Pisanti V Tutino et al ldquoEffects of olive oilpolyphenols on fatty acid synthase gene expression and activityin human colorectal cancer cellsrdquo Genes and Nutrition vol 6no 1 pp 63ndash69 2011


of unexpected cross-talks between well-known metabolicfactors and mediators of unrelated processes is fuellingthis renewed interest On one side noncanonical regulatoryfunctions of specific metabolic enzymes or substrates areemerging on the other side oncogenes tumour suppressorsas well as modulators controlling events typically alteredat the very early stages of cancer progression includingimmune response cell proliferation or cell death appear inthe dual role of controlledcontrollers of metabolic processesDecoding the roles of metabolic changes occurring duringcarcinogenesis and identifying the key nodes that differen-tiate pathological and healthy behavior have two importantimplications novel predictive biomarkers and new drug dis-covery strategies Consequently additional knowledge mayoffer new tools to troubleshoot frequent chemotherapeuticfailures additionally compounds targeting metabolic pro-cesses may also be potentially used for chemopreventivepurposes This research is only emerging transforming theidentification of metabolically active agents into an oppor-tune challenge

Nature provides a considerable source of biologicallyactive compounds with a diversified pharmacological poten-tial Remarkably almost 80 of all anticancer compounds areisolated from plants fungi and microorganisms Both natu-ral and chemically modified molecules (in order to improvestability specificity andor activity) are able to counteracteach of the cancer hallmarks [1 2] recently reclassified byHanahan and Weinberg [3] Accumulating evidence alsoconcerns cancer metabolism [2] Remarkably many of thesecompounds are food constituents or have been used since along time in traditionalmedicineThus they show a favorableprofile in terms of their absorptionmetabolism in the bodywith low toxicity

2 Advantages of Altered Metabolism in Cancerversus Normal Cells

21 Metabolic Switch from Mitochondrial Respiration to Gly-colysis The preferential switch from oxidative phosphory-lation to aerobic glycolysis represents the most discussedand investigated altered metabolic feature of cancer cellsand was first described by Otto Warburg in the 1920sHe already hypothesized mitochondrial dysfunctions as thecausative event Defects in the enzymatic respiratory chainexist in cancer cells [4] however there is no clear correlationbetween the incidence ofmitochondrial dysfunctions and themetabolic switch to glycolysis the latter being commonlyreported in cancer cells In a number of instances insteadcancer tissuescells even consistently rely on mitochondrialrespiration to produce ATP [5] Furthermore under specificcircumstances cancer cells may also be forced to reactivatemitochondrial energy production [6] These observationsclearly show that mitochondria are generally functional incancer cells and support the hypothesis that the propensityof cancer cells to exacerbate the glycolytic pathway whiledecreasing oxidative phosphorylation must be an activeoption conferring important advantages despite the evident

energetic inefficiency of glycolysis Nevertheless identifica-tion of these selective advantages is not an obvious task beingindeed matter of debate

Theoreticallymetabolic alterations during carcinogenesiscould provide multiple benefits as cancer cells need tosatisfy a continuous demand in macromolecule precursorsto maintain their high proliferation rate As a matter offact the reduction of mitochondrial respiration prevents acomplete degradation of glucose to carbon dioxide (CO

2)

and water and leads to accumulation of precursors usedby the major cellular synthesis pathways leading to aminoacids nucleotides and lipids Consequently this metabolicalteration inevitably fuels these anabolic pathways Secondcancer cells experience moderate to severely reduced oxygentension and the fact to preferentially exploit glycolysis toproduce energy in this situation represents an interestingadaptation Accordingly overexpression or stabilization ofthe hypoxia-inducible factor (HIF) in response to low-oxygenconditions promotes the glycolytic metabolism by inducingtranscription of glucose transporters and numerous keyglycolytic enzymes [7]

An increased glycolytic flux means also very frequentlyoverexpression andor increased activity of specific isoformsof several glycolysis-related enzymes Glucose transportersor key enzymes as hexokinase II (HKII) glyceraldehyde-3-phosphate dehydrogenase (GAPDH) lactate dehydrogenase(LDH) and the isoform M2 of pyruvate kinase (PKM2)are upregulated in cancer cells and accordingly suggestedas potential therapeutic targets [8 9] Interestingly nong-lycolytic functions are also emerging for several of theseenzymes and the novel activities ascribed do further promotecancer aggressiveness For example GAPDH LDH or PKM2may additionally activate gene expression by working asdirect transcriptional factors or by interacting with andtherebymodulating the activity of other nuclear proteins [10ndash12] (including HIF-1 and the Signal Transducer and Activatorof Transcription 3 (STAT3) [13 14]) required in the tran-scription of genes especially implicated in cell proliferation(eg histones H2A and H2B MEK5 c-Myc cyclin D1 andandrogen receptor [10 13ndash15])

The hyperproduction of lactate plays a dual role On oneside it activates the glycolytic pathway ensuring the regen-eration of nicotinamide adenosine diphosphate (NAD+) aspart of a feedback regulatory mechanism on the other side itis secreted outside the cells where it promotes angiogenesisand spreading of cancer cells from their primary site Amutual control exists between events controlling lactate pro-duction and synthesis of proangiogenic factors For examplethe extracellular acidification due to the transport of lactatecoupled to H+ extrusion promotes upregulation of HIF-1[16 17] HIF-1 in turn transactivates the LDH-A promoter[16] Besides acidic conditions destabilizes the behavior ofthe immune system which further contributes to cancerinvasion Lactate secretion indeed impairs the function ofspecific immune cells (including cytotoxic T lymphocytes)and cytokine production [18] Furthermore it promotes cellmotility by controlling the expression level of constituents ofthe matrix [19 20]































120572KG 120572KG

Succinate

Fumarate

Oxaloacetate

Glutamine

IsocitrateMalate

Glutamate

GDH

GS

Amino acids

GLUT1

Glucose

G6P

3PG

FBP

6PGluconate

PPP

F6P

NADPH G3P

Citrate Citrate

IDH1

Lactate

HK2

GAPDH

PyruvatePEPPKM2

Saframycin



MCT4

Methyl jasmonate

AcetylCoA

ACL


Flavonoids

EGCGGCG

MalonylCoAPalmitate

FAS

TCA

AcetylCoA

Palmitoyl-CoA

EGCGLuteolin

QuercetinLignans


Hydroxytyrosol


BaccharinDrupanin

Oxaloacetate

HIF-1

LDH

minus

minus

minus

minus

minus

+

Resveratrol


































Resveratrol

Curcumin

Curcumin

ResveratrolCurcumin

ROS




arrest

Pancratistatin


ROSNOS

Metabolic enzymes

modulation

Bavachinin

MMPalterations

BavachininCurcumin

BavachininCurcumin

MMPdecrease














Abbreviations


CG Catechin gallate





Acknowledgments


References


























































































































































































120572KG 120572KG

Succinate

Fumarate

Oxaloacetate

Glutamine

IsocitrateMalate

Glutamate

GDH

GS

Amino acids

GLUT1

Glucose

G6P

3PG

FBP

6PGluconate

PPP

F6P

NADPH G3P

Citrate Citrate

IDH1

Lactate

HK2

GAPDH

PyruvatePEPPKM2

Saframycin



MCT4

Methyl jasmonate

AcetylCoA

ACL


Flavonoids

EGCGGCG

MalonylCoAPalmitate

FAS

TCA

AcetylCoA

Palmitoyl-CoA

EGCGLuteolin

QuercetinLignans


Hydroxytyrosol


BaccharinDrupanin

Oxaloacetate

HIF-1

LDH

minus

minus

minus

minus

minus

+

Resveratrol


































Resveratrol

Curcumin

Curcumin

ResveratrolCurcumin

ROS




arrest

Pancratistatin


ROSNOS

Metabolic enzymes

modulation

Bavachinin

MMPalterations

BavachininCurcumin

BavachininCurcumin

MMPdecrease














Abbreviations


CG Catechin gallate





Acknowledgments


References



























































































































































































Resveratrol

Curcumin

Curcumin

ResveratrolCurcumin

ROS




arrest

Pancratistatin


ROSNOS

Metabolic enzymes

modulation

Bavachinin

MMPalterations

BavachininCurcumin

BavachininCurcumin

MMPdecrease














Abbreviations


CG Catechin gallate





Acknowledgments


References
































































































































































Abbreviations


CG Catechin gallate





Acknowledgments


References




























































































































































regulators of the cancer.pdf

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