Regulation of Cell Signaling Pathways and miRNAs by Resveratrol in Different Cancers

14 Pages·2017·2.05 MB·English

International Journal o f
Molecular Sciences
Review
Regulation of Cell Signaling Pathways and miRNAs
by Resveratrol in Different Cancers
AmmadAhmadFarooqi1,SumbulKhalid2andAamirAhmad3,* ID
1 InstituteofBiomedicalandGeneticEngineering(IBGE),Islamabad44000,Pakistan;
[email protected]
2 DepartmentofBioinformaticsandBiotechnology,InternationalIslamicUniversity,
Islamabad44000,Pakistan;[email protected]
3 DepartmentofOncologicSciences,MitchellCancerInstitute,UniversityofSouthAlabama,
Mobile,AL36604,USA
* Correspondence:[email protected];Tel.:[phone]
Received:28January2018;Accepted:25February2018;Published:26February2018
Abstract: Genomic and proteomic studies have helped improve our understanding of the
underlying mechanism(s) of cancer development and progression. Mutations, overexpressed
oncogenes, inactivated/downregulated tumor suppressors, loss of apoptosis, and dysregulated
signal transduction cascades are some of the well-studied areas of research. Resveratrol has
gained considerable attention in the last two decades because of its pleiotropic anticancer
activities. Inthisreview,wehavesummarizedtheregulationofWNT,SHH(sonichedgehog)/GLI
(glioma-associatedoncogenehomolog),TGFβ1(transforminggrowthfactorbeta1)/SMAD,NOTCH,
TRAIL (tumornecrosis factor-related apoptosis-inducing ligand), STAT (signal transducer and
activator of transcription), and microRNAs by resveratrol in different cancers. The importance
ofthesesignalingpathwaysincancerprogression,alongwiththeirmodulationbyresveratrol,is
discussed. Further, we also evaluate the mechanisms and implications of the downregulation of
oncogenicmiRNAsandtheupregulationoftumorsuppressormiRNAsbyresveratrol,bothofwhich
alsodefineitsabilitytoinhibittumorgrowthandmetastasis. Itisenvisionedthatdesigningeffective
clinicaltrialswillbehelpfulfortheidentificationofresveratrolrespondersandnon-respondersand
the elucidation of how this phytochemical can be combined with current therapeutic options to
improvetheirclinicalefficacyandreduceoff-targeteffects.
Keywords: resveratrol;cellsignaling;miRNAs
1. Introduction
Using high-throughput technologies, it has been shown that the bulk tumor includes a
diversifiedcollectionofcellsthatharborcharacteristicallyuniquemolecularfeatureswithvariable
levels of sensitivity to therapeutic options [1,2]. This heterogeneity results in an uneven
distribution of genetically distinct subpopulations of tumor cells across and within disease sites
(spatialheterogeneity) [3,4]. In addition, tumors are marked by temporal heterogeneity, wherein
cells temporally change their molecular makeup [3,4]. Combining high-throughput genotyping
platformsandnext-generationsequencingtechnologieshasbroughtusonestepcloserinthepursuit
forgeneticvariants,fromSNPs(singlenucleotidepolymorphisms)tolarge-scalecopynumbervariants.
Translationalandfunctionalstudieshavedemystifiedtheunderlyingmechanismsandbio-molecular
signaturesofdifficult-to-treatcancers. Naturalproductchemistryandthediscoveryofdrugsfrom
plants (phytochemicals) has enjoyed a renaissance in the past decade [5,6]. Based on the insights
gleanedfromdecadesofresearch,itseemsclearthatoff-targeteffectsofmodernmedicinesandrapidly
developingresistanceagainstdifferenttherapeuticsaresomeofthechallengesthatmustbeovercome.
Int.J.Mol.Sci. 2018,19,652;doi:10.3390/ijms19030652 www.mdpi.com/journal/ijms
Int.J.Mol.Sci. 2018,19,652 2of14
Muchattentioniscurrentlybeinggiventotheidentificationofnaturalproductsthatcanmodulate
multipletargets,aresignificantlyeffective,andminimizeoff-targeteffects[6,7].Inaccordancewiththis
approach,thereisarapidlygrowinglistofnaturalproductswithconsiderablemedicinalimportance
andsubIsntta. Jn. Mtioal.l Spci.h 2a01r8m, 19a, cxo logicalproperties[8]. 2 of 14
Resveratrol,apolyphenolicphytoalexin,isanextensivelystudiedphytochemicalwithremarkable
challenges that must be overcome. Much attention is currently being given to the identification of
pharmacologicalpropertiesandauniqueabilitytomodulatemultipletargetsindifferentcancers[9].
natural products that can modulate multiple targets, are significantly effective, and minimize
Itregulaotfef-staorxgiedt aetfifvecetss t[r6e,7s]s. ,Iwn ahciccohrdisanacne iwnittehr ethstisin agpparsopaeccht, othfeirtes ias nat ircaapnidcleyr garcotwiviintgy l[i1st0 o,1f 1n]a.tRureaslv eratrol
has a mporoledcuuctlsa wr iwthe ciognhsitdeorfab2l2e 8m.2e4d7icinga/l mimoploratnandcea antdo psuoblsotganictiaall pphoalramracsoulorfgaiccael parroepaertoiefs 6[80]..7 A2 [12].
BecauseoftRheesvrearpaitrdolly, aa ccpuomlypuhleantionligc wpheyatlotahleoxfini,n fiso ramn ateixotnenasibvoeluyt rsteusdvieedra tprhoyl,tomchaenmyicrael vwieiwth papers
remarkable pharmacological properties and a unique ability to modulate multiple targets in
have summarized important biological mechanisms targeted by resveratrol for the treatment of
different cancers [9]. It regulates oxidative stress, which is an interesting aspect of its anticancer
different cancers [13–16]. Most recently published reviews have provided a summary of the role
activity [10,11]. Resveratrol has a molecular weight of 228.247 g/mol and a topological polar surface
of resvearraetar oofl 6in0.7d Aif2f e[1r2e]n. tBeccaanuscee rosf; thheo rwapeivdelyr ,aicncurmeucleantitngy ewaerasl,thn oofn inefoorfmtahtieonr eavboieuwt rseshvaervaetroplr, ovided
anin-dempatnhya rnevdiecwo mpappreersh heanvsei vsuemomvearrivzeiedw imopfotrhtaentc beilollosiggicnaal lminegchpanaitshmws atayrgsettaedrg beyt eredsvbeyrartreoslv feorr atrolin
differentthcea ntrceeartsm[e1n7t –o1f9 ]d.iWffeerehnat vceanecxecrlsu s[1iv3–e1ly6].f oMcuosset dreocnenvtlayr ipouubslissihgenda lretvraienwssd uhcatvieo npcroavsicdaedde sa andthe
summary of the role of resveratrol in different cancers; however, in recent years, none of the reviews
miRNAsthataremodulatedbyresveratrolindifferentcancers. Inparticular,inthisreview,wehave
have provided an in-depth and comprehensive overview of the cell signaling pathways targeted by
summarizedtheregulationofTGFβ1/SMAD,WNT,SHH/GLI,NOTCH,TRAIL,STATpathways,
resveratrol in different cancers [17–19]. We have exclusively focused on various signal transduction
andtheoncogenicaswellastumorsuppressormiRNAs,byresveratrol.
cascades and the miRNAs that are modulated by resveratrol in different cancers. In particular, in this
review, we have summarized the regulation of TGFβ1/SMAD, WNT, SHH/GLI, NOTCH, TRAIL,
2. RegulationoftheTGFβ1/SMADPathway
STAT pathways, and the oncogenic as well as tumor suppressor miRNAs, by resveratrol.
TGFβ1/SMADpathwayiswellknowntocontributetocancerdevelopmentandprogression
2. Regulation of the TGFβ1/SMAD Pathway
(Figure 1). Signalosome formed by phosphorylated receptor-mediated SMADs triggers the
TGFβ1/SMAD pathway is well known to contribute to cancer development and progression
accumulationofactiveSMADcomplexesinthenucleus,whichtranscriptionallyupregulatetarget
(Figure 1). Signalosome formed by phosphorylated receptor-mediated SMADs triggers the
genes in conjunction with transcriptional factors, histone modifiers, and chromatin-remodeling
accumulation of active SMAD complexes in the nucleus, which transcriptionally upregulate target
machinegreyne[s2 0in]. cIonnjtuhnicstisoenc twioitnh, wtraenswcriilpltpiornoavl ifdaectoarns, ohvisetrovniee wmoodfiftiheres,m anodd echorfoamcattiionn-reomfordeeslvinegr atrolto
inhibitSmMacAhiDne-rmy e[2d0i]a. tIend thiins tsreacctieolnlu, wlaer wsiilgl nparolivnidge. aRne osvveerrvaietwro olfe tfhfee cmtiovdeel yof ianchtiiobni tosf SreMsvAerDatrpolr otot einsby
eitherafinfehcibtiint gSMpAoDst--mtreadniastleadt iionntraalcemlluoldari fisicgantailoinngs. bRyesvdeirfafetrroeln etffeecntzivyemly einshtiobittsa rSgMeAtDSM prAotDeinpsr boyte insfor
either affecting post-translational modifications by different enzymes to target SMAD proteins for
degradationorbyinhibitingthephosphorylationandactivationofSMADs.
degradation or by inhibiting the phosphorylation and activation of SMADs.

Figure 1. TGF/TGFR signaling axis. SMAD proteins play a central role in transducing the signals
Figure1. TGF/TGFRsignalingaxis. SMADproteinsplayacentralroleintransducingthesignals
intracellularly. SIRT7 modulates SMAD4 degradation via β-transducin repeat-containing protein
intracell(uβ-lTarrClyP.1)S. ISRMTA7Dm4,o dβ-uTlraCtPe1s, SaMndA SDIR4Td7 ecgormadplaetxi ofnormviaatioβn- trreasnusltds uicni nshruetpdeowatn-c oofn ttahien iTnGgF protein
(β-TrCPp1a)t.hwSaMy. ASMDA4D, :β S-mTraC MPo1t,hearns dAgSaIinRsTt 7Deccoampepntlaepxlefgoicr;m β-aTtriConP: rβe-tsruanltssduicnins rheupetdato-cwonntaionfintgh e TGF
pathwayp.roSteMinA; CDX:CSLm8:a cMhemotohkeinrse ACXgCa inmsottiDf, elcigaapnedn 8ta; pTlGeFg:i ct;raβns-TforrCmPin:gβ g-trroawntshd fuacctionr; reApNeGaPt-TcLo4n: taining
protein;anCgXioCpLoi8et:inc-lhikeem 4.o kine CXC motif, ligand 8; TGF: transforming growth factor; ANGPTL4:
angiopoietin-like4.
Int.J.Mol.Sci. 2018,19,652 3of14
InastudydemonstratingregulationoftheTGFβ1/SMADpathwaybyresveratrol,lungmetastases
were developed in Balb/c mice by intravenous injection of highly metastatic murine 4T1 cells [21].
Further, intravenous injection of the SIRT7-inhibited development of these metastatic nodules and
SIRT7-knockdowninducedactivationoftheTGF-βpathwayin4T1andMDA-MB-231cells,whileSIRT7
overexpressionexertedinhibitoryeffectsontheTGF-βpathway. SIRT7physicallyinteractedwithand
de-acetylatedSMAD4[21]. SignificantlyincreasedlevelsofacetylatedlysineresiduesofSMAD4were
notedinSIRT7-silencedcancercells. ThebindingaffinityofSMAD4forSMAD2markedlydecreased
in cells that ectopically expressed SIRT7. When protein synthesis was inhibited by cycloheximide,
ectopicallyexpressedSIRT7promotedSMAD4degradation,andSIRT7inhibitionprotectedSMAD4
from degradation machinery [21]. Furthermore, K428R, which mimicked a hypo-acetylated form
ofSMAD4, accelerateditsdegradation, whereasK428Q,whichresembledahyper-acetylatedform
of SMAD4, inhibited its degradation. SIRT7 deletion by CRISPR/Cas9 inhibited HA-SMAD4
ubiquitination, whereas SIRT7 overexpression increased ubiquitination. SIRT7 modulated SMAD4
degradation by β-transducin repeat-containing protein (β-TrCP1). Protein studies have provided
evidenceoftheinteractionofSMAD4,β-TrCP1,andSIRT7[21](Figure1). β-TrCP1inhibitionabolished
the increased ubiquitination and accelerated SMAD4 degradation caused by ectopically expressed
SIRT7. Resveratroldose-dependentlyenhanceddeacetylationofHA-SMAD4. Italsoexertedrepressive
effectsonTGF-β1-inducedmesenchymalmorphology,downregulatedSMAD4,andsuppressedcellular
migration. TGF-βresponsivegenesANGPTL4andCXCL8,requiredforbreastcancerlungmetastases
andthedevelopmentofresistanceagainstdrugs,wereconsiderablyrepressedbyresveratrol[21].
Resveratrolhasbeenreportedtoreducephosphorylated-SMAD2/3incolorectalcancerLoVo
cells [22]. Resveratrol (150 mg/Kg) reduced metastatic lesions in the lungs and liver of mice
orthotopicallytransplantedwithLoVocells. InalveolarrhabdomyosarcomaPLA-802cells,resveratrol
(40µmol/L)downregulatedSMAD4[23]. Upontreatmentwithresveratrol(20µmol/L),nosignificant
changes in expression of TGF-β1 and SMAD4 were noticed; however, at a dose of 40 µmol/L,
resveratrolsignificantlydecreasedtheexpressionofSMAD4andTGF-β1[23]. Resveratroldecreased
expressionofTGFβ-2inSCCsandskinofp53+/−/SKH-1micechronicallyirradiatedwithUVB[24].
Therewasa2–3-foldincreaseintheinvasivecapacityofcellsthatexpressedconstitutivelyactiveAkt.
OverexpressionofactiveAktinducedTGF-β2intheabsenceofresveratrol,whichsuggestedaclear
associationbetweenTGFβ2andAkt. ActiveAktsignificantlyimpairedresveratrol-inducedinhibitory
effectsonTGF-β2. Resveratroldose-dependentlyreducedphospho-SMAD2/3levelsandcompletely
abolishedthephosphorylationofSMAD2/3atadoseof100µM[24].
ThesefindingsindicatethatresveratrolaffectstheTGFβ1/SMADpathwayviapost-translational
modifications,eitherbydegradingSMADsorinhibitingtheiractivitybyblockingthephosphorylation
ofSMADs.
3. RegulationoftheWNTPathway
A WNT ligand is a secreted glycoprotein that binds to Frizzled receptors and results in the
formation of a larger cell surface complex with low-density lipoprotein-receptor-related protein
(LRP5/6) [25] (Figure 2). In the absence of any signal, β-catenin is post-translationally modified
bytheAPC/AXIN/GSK-3β-complexleadingtoitsubiquitinationanddegradationbyproteasomal
machinery. WhentheWNTpathwayisactive, β-cateningetssequesteredawayfromdegradation
machineryandmovesintothenucleustotriggertheexpressionoftargetgenes. Therehasbeenafocus
onstrategiestoinhibitthetransportationofβ-cateninintothenucleus[25,26].
ResveratrolcandownregulateWNT2andupregulateAXIN2inColo16cells[27].Furthermore,there
wasanearlierinductionofapoptosisinresveratrol-treatedβ-catenin-silencedColo16cells[27].Resveratrol
dose-dependentlydecreasedexogenouslyoverexpressedMyc-taggedTCF4proteinincolorectalcancer
cells [28] and increased TCF4 phosphorylation through ERK- and p38-MAPK-modulated pathways.
KnockdownofTCF4reducedTCF/β-catenin-regulatedtranscriptionalactivitiesandsensitizedcancer
cellstoresveratrol-mediatedapoptosis[28].
Int.J.Mol.Sci. 2018,19,652 4of14
Int. J. Mol. Sci. 2018, 19, x 4 of 14

FigFuirgeu2r.e (2A. )(AW) NWTN/Tβ/β-c-acatetenninins sigignnaalliinngg aaxxiiss.. RReessvveerraattrrooll eeffffeecctitviveelyly ininhihbiibtsit tshteh neunculecaler aarccauccmuumlautiloanti on
ofβo-fc βa-tceanteinn.inβ. -βc-acatetenninin wwoorrkkss ssyynncchhrroonnoouusslyly wwitiht hvavraioruiosu psroptreointesi ntos mtoodmuoladtue ltahtee ttrhaenstcrrainpsticornip otfi on
of ddiiffffeerreenntt ggeenneess;; ((BB)) SSRRSSFF11 iinnhhiibbitists YYAAPP aanndd rreepprreessssees sththee ββ-c-caatetnenini-nm-medeidatieadte dupurpegreuglautiloanti oonf of
MAMLAALTA1;T(1C; )(Cβ)- cβa-cteanteinninw worokrkssw witihth MMAALLAATT11 aanndd iinnccrreeaasseess tthhee eexxpprersessisoino nofo Mf MMMP7P a7nadn Cd-MC-yMc. yc.
APC: adenomatous polyposis coli; CK: casein kinase; GSK-3β: glycogen synthase kinase 3 beta; LRP:
APC:adenomatouspolyposiscoli;CK:caseinkinase;GSK-3β:glycogensynthasekinase3beta;LRP:
low-density lipoprotein-receptor-related protein; MALAT1: metastasis-associated lung
low-densitylipoprotein-receptor-relatedprotein;MALAT1:metastasis-associatedlungadenocarcinoma
adenocarcinoma transcript 1; MMP&: matrix metalloproteinase-7; SRSF1: serine and arginine rich
transcript1;MMP&:matrixmetalloproteinase-7;SRSF1:serineandargininerichsplicingfactor1;TCF:
splicing factor 1; TCF: T-cell factor; YAP: YES-associated protein; 65-KD.
T-cellfactor;YAP:YES-associatedprotein;65-KD.
Response to resveratrol was noted to be highly heterogeneous among glioma stem cells.
ReRsevsepraotnrosle intohibrietsevde crealtl rporlolwifearsatnioont,e idnctroeasbeed hceigllh mlyorhtaeltiteyr,o agnedn estoruonsgalym roendugcegdli othme amosttielmity ocef lls.
Restvheer acetrlolsl [i2n9h]i.b Iinte GdBcMell2p, Gro1l6if6e,r GatBioMn7,,i nacnrde aGse1d79c ecellllm lionretsa,l ibtoy,tha nWdNstTro1 nagnldy MredYuCc ewderthe eumproetgiuliltayteodf,t he
cellws[h2i9le] .iInn GG1B4M4 c2e,lGls1 t6h6e,sGe BtwMo7 ,gaenndesG w1e7r9ec delolwlinnreesg,ubolatthedW bNyT r1esavnedraMtroYlC. FwZeDr4e uanpdre TgCulFa7t ecdh,awngheilde in
G14o4nlcye lilns 3th oeuset otwf 7o GgSeCne lsinwese raeftdero wrensvreegrautlraotle tdrebaytmreesnvt e[r2a9t]r. oRl.esFvZeDra4traonl dsigTnCifFi7cacnhtalyn greedduocnedly ciyncl3ino ut
of7DG1S Canldin eβs-caaftteenrirne sivne rxaetnroolgtrraefat tmbreenatst[ 2t9u]m.Roerss v[e3r0a]t.r oβl-sciagtennifiinc aonvtleyrerxepdruecsesdiocny cmlianrkDe1dalyn dreβd-ucacetedn in
inxreensvoegrraatrfotlb-mreeadsitattuedm ocyrsto[t3o0x]i.c βe-fcfeactetsn, inwhoivcehr eixnpdriceastseido nthmaat rrkeesdvleyrarterdolu cinehdibreitsevde rbarteraoslt- mcaendcieart ed
stem-like cells and induced autophagy, at least partially, by suppression of the Wnt/β-catenin
cytotoxiceffects,whichindicatedthatresveratrolinhibitedbreastcancerstem-likecellsandinduced
cascade [30]. In HCT116 cells, resveratrol reduced β-catenin [31]. Resveratrol did not appear to
autophagy, at least partially, by suppression of the Wnt/β-catenin cascade [30]. In HCT116 cells,
influence the total levels of GSK-3β but did decrease GSK-3β phosphorylation. A β-catenin/Tcf4
resveratrolreducedβ-catenin[31]. ResveratroldidnotappeartoinfluencethetotallevelsofGSK-3β
reporter assay provided evidence that resveratrol, concentration-dependently, inhibited reporter
butdiddecreaseGSK-3βphosphorylation. Aβ-catenin/Tcf4reporterassayprovidedevidencethat
activity [31].
resveratrol,concentration-dependently,inhibitedreporteractivity[31].
β-catenin has been shown to interact with different non-coding RNAs and transcriptionally
β-catenin has been shown to interact with different non-coding RNAs and transcriptionally
upregulate their expression, thereby stimulating the expression of a target gene network.
upregulatetheirexpression,therebystimulatingtheexpressionofatargetgenenetwork. Resveratrol
Resveratrol increases the cytosolic levels of β-catenin with a concomitant inhibition of its nuclear
increasesthecytosoliclevelsofβ-cateninwithaconcomitantinhibitionofitsnuclearaccumulation
accumulation (Figure 2), with little effects on the total cellular β-catenin [32]. Resveratrol exerted
(Figiunhreib2i)t,owryi tehffleitcttlse oefnf etchtes oWnntth/eβ-tcoattaelncienl lpualathrwβa-cya ttehnroinug[3h2 ]t.hRe ersevgeurlaattrioolne oxfe rMteAdLinAhTib1.i tTohrye euffseec tosf on
thelWithniut/mβ -cchaltoernidine pinahthibwitaedy tGhSroKu3gβh frtohme rbeignudliantgio tno oβf-McatAenLiAnT a1n.dT threigugseereodf lWithnitu/βm-cacthelnoirnid peaitnhhwibayit ed
GSKac3tβivaftrioomn. bRiensdvienrgatrtool βd-ocasete-dneinpeannddenttrliyg gdeorwednrWegnutla/tβed-c alotenngi nnpona-tchowdainyg aRctNivAa-tMioAn.LARTe1sv [e3r2a]t.r ol
dosKe-ndoecpkdenowdenn otlfy MdAowLAnrTe1g uimlaptaeidreldo nthgen nounc-lceoadr iancgcuRmNuAla-tMioAn LoAf Tβ-1ca[3te2n]i.nK, wnohcickhd orewsunltoefdM inA tLhAe T1
imptraainresdcritphteionnuacl lereaprraecscsuiomn uolfa tMioMnoPf7 βa-ncdat ecn-Miny,cw, hwichhiler esMuAltLedATin1 tohveetrreaxnpsrcersispiotino nparlormepotreeds sitohne of
MMtrPa7nsacnrdipcti-oMnyacl ,uwprheigleuMlatAioLnA oTf 1MoMvePr7e xapnrde scs-Mionycp (rFoimguortee d2)t. hTehter adnastac rcilpetairolnya sluugpgreesgt uthlaatti oMnAoLfAMTM1 P7
andanc-dM βy-cca(tFeingiunr eco2-)e.xTishteedd ainta tchlee anrulyclseuugs,g aenstdt hthaet MtaArgLeAteTd1 inanhidbiβti-ocna toenf iMnAcoL-AexTi1s teisd ninectehsesanryu ctloe us,
inhibit synchronous activity of MALAT1 and β-catenin for the transcriptional repression of target
and the targeted inhibition of MALAT1 is necessary to inhibit synchronous activity of MALAT1
andgeβn-ecsa ten[3i2n].f orYtEhSe-atrsasoncsicartiepdt ionparoltreeipn res(sYiAonP)o ftuaprrgeegtuglaetneeds [3M2]A.LYAETS1- asstroacniascteridptpiornoatel ina(nYdA P)
Int.J.Mol.Sci. 2018,19,652 5of14
upregulatedMALAT1transcriptionalandpost-transcriptionallevels,whereasserine/arginine-rich
splicingfactor1(SRSF1)resistedYAP-mediatedeffects[33]. SRSF1exertedinhibitoryeffectsonYAP
activityandpreventeditsco-existencewithTCF/β-cateninonthepromoterregionofMALAT1[33]
(Figure2). Thesetworeportstogetherarehelpfulinputtingdifferentpiecesofanincompletejigsaw
puzzle together. It seems clear that β-catenin co-operates with different proteins to trigger the
expression of MALAT1 and works synchronously with MALAT1 to drive the expression of WNT
signalingtargetgenes.
Despite these studies on the regulation of the WNT pathway by resveratrol, there remain a
fewoutstandingquestionsthatneedtobeadequatelyaddressedtounderstandmechanisticdetails.
Forexample,themodulationofLRP5/6andSFRPsbyresveratrolhasnotbeensufficientlystudied.
Futurestudiesneedtocomprehensivelyfocusonthedetailedmechanism(s)ofregulationofWNT
signalingbyresveratrolsothattheinformationcanbeutilizedforthetargetingofWNTsignalingby
resveratrolinclinicalsettings.
4. RegulationoftheSHH/GLIPathway
Inappropriate activation of the Sonic hedgehog–GLI signaling cascade has been extensively
studiedindifferentcancers[34–36]. BCR-ABLisanoncoproteinthatre-wiresintracellularsignaling
cascadesinchronicmyeloidleukemiaandPhiladelphiachromosome-positiveacutelymphoblastic
leukemia[37]. Invitroandpreclinicalstudieshaveshownthatimatinibexertedpreferentialinhibitory
effectsontheviabilityandexpressionofBCR-ABLinimatinib-sensitiveK562cells,butimatinibwas
noteffectiveagainstK562RcellsthatoverexpressedBCR-ABL.BothK562R(imatinib-resistant)and
parentalK562cellsexpressedmRNAsofmoleculesinvolvedintheSHHpathway,includingSHH,
Smoothened(SMO),Patched(PTCH),andGLI-1. TherewasasignificantreductioninBCR-ABLin
GLI-1-silencedK562RandK562cells. TheuseofSHHpeptidenotonlyenhancedGLI-1andSHHbut
alsoupregulatedBCR-ABLintestedcelllines.ResveratroleffectivelyinhibitedSMOandBCR-ABLand
exertedinhibitoryeffectsonthenuclearaccumulationofGLIproteinstotranscriptionallyupregulate
the expression of cancer promoting genes [37]. PTCH, SMO, and GLI-1 were also inhibited in
resveratrol-treatedcolorectalcancerHCT116cells[38]. Resveratrolinhibitedthenuclearaccumulation
ofGLI-1ininterleukin-6(IL-6)-stimulatedHL-60cells[39].
Resveratrolandcyclopaminehavebeenreportedtosynergisticallyinhibitmetastasesandreduce
theinvasivepotentialofgastricSGC-7901cancercells[40]. ResveratrolwasnotedtoinhibitGLI-1
activityanddownregulateSnailandN-cadherininSGC-7901cells.Previously,ithasbeenreportedthat
SnailrepressedtheexpressionofE-cadherin,butresveratrolupregulatedE-cadherinandmarkedly
reduced the metastasizing potential of SGC-7901 cells [40]. Based on the reports discussed above,
resveratrolseemstosignificantlyaffectstheSHH-Glipathway.
It is now well established that CpG islands are heavily hypomethylated in cancer cells [41].
Resveratrol enhances the methylation levels of CpG sites within enhancers of MAML2 and
GLI2. Interestingly, active enhancers are enriched with H3K27ac. Data obtained through the
chromatin-immunoprecipitationtechniqueprovidedinformationaboutthepresenceofhistonemarks
at MAML2 in cancer cells but its occupancy reduced considerably in resveratrol-treated cancer
cells[41]. Occupancyofactivatinghistonemarks(H3K9acetylation)andrepressivehistonemarks
(H3K27tri-methylation)wasbiochemicallyanalyzed. Datasuggesteda30%decreaseinH3K9acanda
2-foldincreaseinH3K27me3occupancywithintheMAML2enhancer,whereasresveratrolinduced
anincreaseinDNAmethylationlevels. OCT1,atranscriptionfactor,transcriptionallyupregulated
MAML2;however,resveratrolinhibitedthebindingofOCT1totheMAML2enhancer. Resveratrol
withaconcentrationof15µMpromotedtheaccumulationofDNMT3BintheMAML2enhancerin
MCF10CA1acells,resultinginepigeneticinactivation[41].
Int.J.Mol.Sci. 2018,19,652 6of14
5. RegulationoftheNOTCHPathway: ADouble-EdgedSword
TheNOTCHpathwayisinvolvedintheregulationofdifferentstagesofcancer[42,43]. Although
somereportsdocumentefficientinhibitionofdifferentproteinsoftheNOTCHpathwaybyresveratrol
to inhibit cancer, there are conflicting reports that resveratrol can activate the NOTCH pathway,
leadingtoitsanticanceractivity. Resveratrolhasbeennotedtoinducedifferentiation-associatedgenes
in anaplastic thyroid carcinoma mainly through Notch1 activation [44]. Resveratrol was a strong
inducerofTTF1, whichincreased4-foldat25µmol/Land6-foldat50µmol/Lintestedcelllines.
SignificantlyelevatedTTF2wasobservedat50µmol/Linthyroidcancercells. Moreover,therewas
anincrease(5-fold)inPax8inHTh7cellsata50µmol/Ldoseofresveratrol. Theupregulationof
Pax8,TTF1,andTTF2wasobservedinresveratrol-treatedNOTCH1-competent8505Ccells. However,
nodetectablerisehasbeenfoundinthelevelsofPax8orTTF1inresveratrol-treated,NOTCH1-silenced
ATCcells. Tumorvolumedecreasedconsiderably(~69%)afterfiveinjectionsofresveratrolinmice
xenograftedwitheitherHTh7or8505Ccells[44].
Resveratrol(50µM)increasedbothactivep53andNOTCH-1inglioblastomacells[45]. Western
blot data suggest that expression of the Notch-1 intracellular domain (NICD) was 3.2-fold and
2.9-foldhigherintheA172andT98Gcells,respectively,afterresveratroltreatment. Similarpatterns
were observed and p53 was also found to be upregulated as evidenced by 1.2-fold and 1.1-fold
higherexpressionsinA172andT98Gcells,respectively,aftertreatmentwithresveratrol[45]. Taken
together,theeffectofresveratrolonNOTCHsignalingseemstobecontext-dependent. WhenNOTCH
signaling is oncogenic, it is effectively inhibited by resveratrol; however, when it leans towards a
tumor-suppressiveaction,itispotentiatedbyresveratrol.
6. RegulationofTRAILSignaling
The discovery of TRAIL revolutionized the field of molecular oncology because of its ability
to differentially target cancer cells while leaving normal cells intact [46]. However, circumstantial
evidencehasalsoindicatedthedevelopmentofresistanceagainstTRAIL-basedtherapeutics. TRAIL
resistanceemergedasamajorsetbackinthestandardizationoftherapy,andattemptshavebeenmade
tosensitizeresistantcancercellstoTRAIL.Analysesofdifferentcancershaveshownanimbalancein
stoichiometricratiosofpro-andanti-apoptoticproteins. However,overthepast10years,therehas
beenaworldwideresurgenceofstudiesemphasizingdifferentstrategiesforrestoringTRAIL-induced
apoptosisinresistantcancercells. ResveratrolhasshownpotentialasaTRAILsensitizer.
Resveratrolhasbeenfoundtoincreasethecell-surfaceexpressionofNKG2DligandsandDR4
alongwiththedownregulationofdecoyreceptor1(DcR1)inKG-1acells[47].Asuppressorofcytokine
signaling (SOCS3) was found to considerably impair TRAIL-driven apoptosis in cancer cells [48].
SOCS3 overexpression reduced apoptosis in DU145 cells co-treated with resveratrol and TRAIL.
Moreover,SOCS3inhibitionincreasedapoptosisinTRAIL-treatedLNCaPandPC-3cells[48]. Survivin
isafrequentlyoverexpressedproteininTRAIL-resistantcancercells. Resveratroldose-dependently
downregulated survivin in HepG2 cells. Moreover, 10ng/mL TRAIL and 50µmol/L resveratrol
worked with effective synergy and increased the apoptotic rate up to 49.6% in HepG2 cells [49].
Inxenograftedtumors, resveratrolupregulatedDR4, DR5, Bax, andp27(/KIP1)andinhibitedthe
expressionofcyclinD1andBcl-2[50].
7. RegulationofSTATSignaling
Prostatecancerassociatedtranscript29(PCAT29),atumorsuppressor,isfrequentlyoverexpressed
inprostatecanceranddownregulatedbyinterleukin(IL-6)inDU145andLNCaPcells[51].Significantly
enhancedphopsphorylated-STAT3hasbeenobservedfollowingtreatmentwithIL-6(10ng/mL)in
DU145andLNCaPcells[51]. STAT3knockdowninducedanincreaseinPCAT29expressioninboth
DU145 and LNCaP cells. Mechanistically, it was shown that STAT3 triggered the upregulation of
miR-21,whichconsequentlynegativelyregulatedPCAT29inPCacells. ResveratrolrepressedSTAT
Int.J.Mol.Sci. 2018,19,652 7of14
signaling and stimulated expression of PCAT29 via repression of miR-21 [51] (Figure 3). Further,
proteininhibitorofactivatedSTAT3(PIAS3)hasbeenfoundtobedownregulatedinmedulloblastomas,
andresveratrolshowntosignificantlyupregulatePIAS3inUW228-2,UW228-3,andDAOYcellswith
therepressionofp-STAT3levels[52].
Int. J. Mol. Sci. 2018, 19, x 7 of 14

Figure 3. An overview of resveratrol-mediated targeting of multiple signaling pathways. (A)
Figure3.Anoverviewofresveratrol-mediatedtargetingofmultiplesignalingpathways.(A)TGF/SMAD
TGF/SMAD signaling pathway regulation by resveratrol; (B) WNT/Catenin pathway regulation by
signaling pathway regulation by resveratrol; (B) WNT/Catenin pathway regulation by resveratrol;
resveratrol; (C) Resveratrol increases negative regulators of STAT signaling (SHP-2, PIAS, and PTP)
(C)ResveratrolincreasesnegativeregulatorsofSTATsignaling(SHP-2, PIAS,andPTP)andinhibits
and inhibits JAK-mediated STAT phosphorylation. STAT3 transcriptionally upregulates miR-21, and
JAK-mediatedSTATphosphorylation.STAT3transcriptionallyupregulatesmiR-21,andtargetsthetumor
targets the tumor suppressor gene PCAT29.
suppressorgenePCAT29.
Resveratrol exerts inhibitory effects on the constitutive activation of STAT3 and STAT5. It
inhRiebsivtse rtahter oslheuxtetlritnsgi nohf ibSiTtAorTy3e fafnedct sSTonATth5e icnoton stthiteu tnivuecleauctsi vaantdio nsigonfiSfiTcAanTt3lya nreddSuTceAsT t5h.eI tDinNhAib its
thebsihnudtintlgin agffoinfiStTy AoTf 3SaTnAdTS TpAroTte5inins toint h7e86n-uOc laenuds aCnadkis-i1g nciefillcsa n[5t3ly]. rRedesuvceersattrhoel DwNasA ablsion dfionugndaf fiton ity
of SmTaArkTedplryo treeidnuscein th7e8 6co-OnstaitnudtivCea akcit-i1vacteiollns o[5f 3J]a.nuRse ksvinearsaetsr o(JlAwKa1s aanldso JAfoKu2n) dint o78m6-Oar kanedd lCyarkeid-1u ce
thececlolsn. stPitruottievine atcytrivosaitnioe npohfoJsapnhuastaskeisn as(PesTP(J AaKnd1 aSnHdPJ-A2)K 2w)eirne 78co6n-OsidaenradblCy akuip-1recgeulllast.edP rointe in
resveratrol-treated 786-O and Caki-1 cells (Figure 3). Targeted inhibition of either PTP or SHP-2
tyrosinephosphatases(PTPandSHP-2)wereconsiderablyupregulatedinresveratrol-treated786-O
substantially impaired the resveratrol-mediated decrease in the level of phosphorylated-STAT [53].
and Caki-1 cells (Figure 3). Targeted inhibition of either PTP or SHP-2 substantially impaired the
Resveratrol has also been shown to prevent the activation of JAK, resulting in the inhibition of the
resveratrol-mediateddecreaseinthelevelofphosphorylated-STAT[53]. Resveratrolhasalsobeen
JAK-mediated phosphorylation of STAT1 [54].
showntopreventtheactivationofJAK,resultingintheinhibitionoftheJAK-mediatedphosphorylation
ofSTAT1[54].
8. Regulation of Other Signaling Pathways
8. RegulationofOtherSignalingPathways
8.1. AKT and MAPK
8.1. AKTReasnidstaMnAceP Kagainst different chemotherapeutic drugs is a frequently noted mechanism [55].
Docetaxel increased HER-2 in SK-BR-3 cells and induced Akt (Ser 473) phosphorylation within a
Resistance against different chemotherapeutic drugs is a frequently noted mechanism [55].
time period as short as 30 min. Docetaxel induced extracellular signal-regulated kinase (ERK), c-Jun
Docetaxel increased HER-2 in SK-BR-3 cells and induced Akt (Ser 473) phosphorylation within
N-terminal kinase (JNK), and P38 phosphorylation, which was significantly inhibited by resveratrol
a time period as short as 30min. Docetaxel induced extracellular signal-regulated kinase (ERK),
[55]. It has also been noted that a high glucose-driven increase in the levels of phosphorylated-ERK
c-Jun N-terminal kinase (JNK), and P38 phosphorylation, which was significantly inhibited by
and phosphorylated-p38 were inhibited by resveratrol in Panc-1 cells [56].
resveratrol [55]. It has also been noted that a high glucose-driven increase in the levels of
pho8s.2p.h Tohrey AlaTtMed/-pE5R3 KPaathnwdapy hosphorylated-p38wereinhibitedbyresveratrolinPanc-1cells[56].
ATM (ataxia telangiectasia mutated) is an important sensor of DNA damage and transduces
8.2. TheATM/p53Pathway
the signals to downstream effectors, particularly p53 [57]. In glioblastoma-initiating cells treated
wiAthT Ma (caotmaxbiiantaetlioann goief cttaesmiaozmoulotmatiedde) iasnadn riemsvpeorrattarnolt, sepnhsoosrphoofrDyNlatAedd-AamTMag ewaansd ftoruanndsd tuoc ebset he
signmaoldsetroatdeolyw unpsrteregaumlateedff,e wcthoirlse, pp5a3r taicnudl aprhlyospp5h3or[y5l7a]t.edIn-pg5l3i owbelarest ofomuna-di ntiot isaitginnigficcaenlltslyt rienactreedaswe. ith
Resveratrol has also been found to be more effective against HCT-116 p53 wild-type colon
carcinoma cells, as compared to HCT-116 p53−/− cells [58]. Resveratrol induced DNA damage, as
evidenced by the presence of multiple γ-H2AX foci after treatment with 25 μM resveratrol.
Int.J.Mol.Sci. 2018,19,652 8of14
acombinationoftemozolomideandresveratrol,phosphorylated-ATMwasfoundtobemoderately
upregulated,whilep53andphosphorylated-p53werefoundtosignificantlyincrease. Resveratrolhas
alsobeenfoundtobemoreeffectiveagainstHCT-116p53wild-typecoloncarcinomacells,ascompared
toHCT-116p53−/− cells[58]. ResveratrolinducedDNAdamage,asevidencedbythepresenceof
multipleγ-H2AXfociaftertreatmentwith25µMresveratrol. DNA-damage-associatedsignalingwas
Int. J. Mol. Sci. 2018, 19, x 8 of 14
initiatedthroughtheactivationofATMkinase. p53wasfoundtobephosphorylatedonserine15by
ATMDNinAr-edsapmoangsee-atossroecsiavteerda tsriogln[a5l8in].g was initiated through the activation of ATM kinase. p53 was
found to be phosphorylated on serine 15 by ATM in response to resveratrol [58].
8.3. MultipleSignalingPathways
8.3. Multiple Signaling Pathways
Beingapleiotropicagent,resveratrolhasbeenreportedtotargetmultipleproteinsinovarian
cancer, Bmeainrkg ead plylerioetdruopciinc gagNenOt,T rCesHv2eraatnrdol HhaEsS b1eienn OreVpoCrAteRd -t3o atnardgeCt AmOuVlti-p3lec eplrlsot[e5in9]s. inIn ovCaAriOanV -3
cellcsa,nrceesrv, emraatrrkoelddlyo wrendruecginugla NteOdTWCHN2T a2nadn HdErSe1d uinc eOdVtChAeRn-u3 calenadr CaAccOuVm-3u lcaetlilosn [5o9f]. βIn-c aCtAenOinV-[35 9].
cells, resveratrol downregulated WNT2 and reduced the nuclear accumulation of β-catenin [59].
Moreover,theaccumulationofSTAT3wasevidentinthenucleiofnaïveOVCAR-3cells,andresveratrol
Moreover, the accumulation of STAT3 was evident in the nuclei of naïve OVCAR-3 cells, and
significantly reduced this nuclear accumulation. Although there is general agreement about the
resveratrol significantly reduced this nuclear accumulation. Although there is general agreement
multi-protein targeting of resveratrol, there are still important mechanistic details related to the
about the multi-protein targeting of resveratrol, there are still important mechanistic details related
interwovennetworkofsignaltransductionpathwaysthatremaintobeelucidated.
to the interwoven network of signal transduction pathways that remain to be elucidated.
9. RegulationofMicroRNAsbyResveratrol
9. Regulation of MicroRNAs by Resveratrol
Injustovertwodecades,sincethediscoveryofthefirstmicroRNA(miRNA),therehasbeenan
In just over two decades, since the discovery of the first microRNA (miRNA), there has been an
exponentialriseinthenumberofreportsthatprovidein-depthanalysisofregulationofsignaling
exponential rise in the number of reports that provide in-depth analysis of regulation of signaling
pathways by miRNAs in different cancers [60]. Categorically, miRNAs are classified into tumor
pathways by miRNAs in different cancers [60]. Categorically, miRNAs are classified into tumor
supspurpepsrseosrsoarn adnodn ocnocgoegneincicm miRiRNNAAs.s. DDiiffffeerreenntt ssttrraatteeggiieess aarree ccuurrrernentltyl ybebienign gusuesde dto toincinrecarseea stehet he
experxepsrseiossnioonf otfu tmumorors usupppprreessssoorr mmiiRRNNAAss aanndd ddowownrnergeugluatlea toencoongceongice nmiciRmNiARsN. IAn st.hiIsn setchtiisons,e wcteio n,
wewwiillll ffooccuuss oonn ththe erergeguulaltaiotino nofo ofnocnocgoegneicn aicnadn tdumtuomr sourpspurpepssroers smoriRmNiARsN bAys rebsyvreersavtreorla (tFrioglu(rFei g4u).r e4).

FigFuirgeu4r.e R4e. sRveesravterroaltrporlo pforuofnodulnydalyff eacftfsectthse tmhei RmNiRANmAa cmhaincehriny.erIyt.i nIht iibnihtsiboitnsc oognecongicenaiscw aes llwaesllt uams or
suptpurmeossro rsumppiRreNssAosr tmoiaRffNeActst htoe caeflfleuclta rthoen ccoeglleunlaicr monaccohgineneircy ,mreascuhlitninergy,i nrreesudluticnegd ienx prreedsuscioend of
expression of oncogenes and increased expression of tumor suppressor genes.
oncogenesandincreasedexpressionoftumorsuppressorgenes.
9.1. Regulation of Oncogenic miRNAs
9.1. RegulationofOncogenicmiRNAs
Insulin-like growth factor binding protein-3 (IGFBP3) has been noted to be frequently
Insulin-like growth factor binding protein-3 (IGFBP3) has been noted to be frequently
downregulated in acute lymphocytic leukemia (ALL) cells [61]. Detailed mechanistic insights
downregulatedinacutelymphocyticleukemia(ALL)cells[61]. Detailedmechanisticinsightsrevealed
revealed that miR-1290 and miR-196b quantitatively controlled IGFBP3 in the ALL cell line. More
thatmiR-1290andmiR-196bquantitativelycontrolledIGFBP3intheALLcellline. Moreimportantly,
importantly, resveratrol considerably reduced the expression of miRNA-196b/miRNA-1290 in
TALL-104/SUP-B15 cell lines. The research findings were suggestive of a resveratrol-induced
upregulation of IGFBP3 (mRNA, protein) in SUP-B15 as well as TALL-104 cells. Resveratrol arrested
TALL-104 cells at the G1 phase and arrested SUP-B15 cells at the S phase. Resveratrol strongly
induced apoptosis in the SUP-B15 and TALL-104 cells [61].
Int.J.Mol.Sci. 2018,19,652 9of14
resveratrolconsiderablyreducedtheexpressionofmiRNA-196b/miRNA-1290inTALL-104/SUP-B15
cell lines. The research findings were suggestive of a resveratrol-induced upregulation of IGFBP3
(mRNA,protein)inSUP-B15aswellasTALL-104cells. ResveratrolarrestedTALL-104cellsatthe
G1phaseandarrestedSUP-B15cellsattheSphase. Resveratrolstronglyinducedapoptosisinthe
SUP-B15andTALL-104cells[61].
Activationofnaturalkillercellsisawell-coordinatedmechanism,triggeredbysignalsderived
from activating receptor ligation [62]. Natural killer group-2 member-D (NKG2D) or killer cell
lectin-likereceptor,subfamily-K,member-1(KLRK1)isanextensivelystudiedactivatingreceptorof
naturalkiller(NK)cells. Inhumans,theNKG2Dligand(NKG2DLs)familyhaseightglycoproteins
presentonthecellsurface,includingthemajorhistocompatibilitycomplexclassIchain-relatedproteins
AandB(MICA/B)[62]. Resveratrolwasfoundtodose-dependentlyenhanceMICAandMICBon
the surface of breast cancer cells. Resveratrol-mediated increases in MICA and MICB were more
pronouncedintheMDA-MB-231andBCap37celllines. TransfectionofBCap37cellswithmiRNA-17
inhibitorsresultedintheupregulationofMICAandMICB,whiletransfectionofBCap37cellswith
miRNA-17 mimics resulted in the downregulation of MICA and MICB. c-Myc binding sites had
previouslybeenidentifiedintranscriptionalinitiationsitesinmiR-17-92clusters,andc-Myctriggered
anincreaseintheexpressionofthisgenecluster[62]. Resveratroldose-dependentlyrepressedc-Myc
(mRNA,protein)intreatedbreastcancercells,whichconsequentlyresultedinareductionofmiR-17.
c-Mycknockdownresultedinareductionofpri-miR-17-92andmiR-17,whereasc-Myc-overexpression
markedlyenhancedpri-miR-17-92andmiR-17[62].
A chromatin immunoprecipitation assay revealed that resveratrol decreases the association
of NF-κB with FOXC2 promoter [63]. Specific Akt inhibition resulted in the suppression of
phosphorylated-Akt, FOXC2, and mobility of A549 cells. Resveratrol-mediated inhibitory effects
onNF-κBactivitywereimpairedincancercellswithconstitutivelyactiveAkt[63]. PP2A/C,acatalytic
subunit of serine/threonine phosphatase PP2A, inhibited Akt activity by Akt dephosphorylation.
Resveratrol,dose-andtime-dependently,increasedtheexpressionandactivityofPP2A/Cproteinin
cancercells. ResveratrolenhancedthelevelsofPP2A/CviatheinhibitionofmiR-520h. Intriguingly,
theresveratrol-mediatedincreaseinPP2A/CwasdramaticallyabolishedafterrestorationofmiR-520h
expression [63]. For a deeper understanding of the crosstalk among these proteins, molecular
analysiswasconductedincervicalcancercells,andtheresultssuggestedthatthePP2A/C-driven
dephosphorylationoftheinhibitorofkappa-Bkinase(IKK)resultedinitsinactivation[64].Inactivation
ofIKKprotectedIκBfromphosphorylationbyIKK;consequently,activationofNF-κBwasinhibited.
Inactivation of NF-κB resulted in transcriptional repression of its target gene, CXCR4 [64]. These
findingsprovideinsightintothemechanismsbywhichmiR-520hquantitativelyreducesPP2A/C
to facilitate the tumor-promoting activities of NF-κB via the transcriptional upregulation of its
targetgenes.
9.2. TheRegulationofTumorSuppressormiRNAs
Pyruvate kinase M2 (PKM2) has been found to be overexpressed in different cancers [65].
Resveratrol,dose-dependently,increasedthemRNAandproteinexpressionlevelsofGRP78,CHOP,
and caspase-12 in both HeLa and DLD1 cells. A reversal of these changes was observed in
PKM2-overexpressingcancercells. Mechanistically,itwasshownthatresveratrolrepressedPKM2by
increasingtheexpressionofmiR-326. Interestingly,resveratrol-mediatedrepressiveeffectsonPKM2
wereimpairedinmiR-326inhibitor-transfectedcancercells[65].
Stemcellfactor(SCF,KITLG)isfrequentlyoverexpressedincolorectalcancercells[66]. KITLG
isquantitativelycontrolledbymiR-34c. Studieshaveshownthatp53transcriptionallyupregulated
miR-34cincolorectalcancertissuesandcelllines.Resveratrolwasnotedtoincreasep53inp53-positive
HT-29cells,andmiR-34cupregulationwasmorepronouncedinp53-positiveHT-29cells,ascompared
top53-negativeHCT-116cells[66]. OverexpressionofIsoformA2ofeukaryotictranslationelongation
factor(eEF1A2)playedacontributoryroleinbreastcancerprogression[67]. miR-663andmiR-744
Int.J.Mol.Sci. 2018,19,652 10of14
have been found to negatively regulate eEF1A2 in breast cancer. Resveratrol induced a 4.5-fold
upregulationofmiR-663andatwo-foldincreaseinmiR-744. ItalsoreducedEEF1A2inbreastcancer
cells. Aresveratrol-induceddecreaseinEEF1A2levelswasnotfoundinMCF7cellstransfectedwith
inhibitors of miR-663 and miR-744 [67]. Resveratrol was noted to reduce MMP2 via upregulation
ofmiR-328inosteosarcomacells[68]. Theresveratrol-mediatedsuppressiveeffectsonMMP2were
impairedinHOScellstransfectedwithmiR-328inhibitors,whereastransientorstableoverexpression
ofmiR-328markedlyreducedtheinvasivepotentialofHOScells[68].
10. ResveratrolinClinicalTrials
MPX, powdered muscadine grape skin that contains ellagic acid, resveratrol, and quercetin,
wastestedforefficacyinbiochemicallyrecurrentprostatecancerpatients[69]. 6outof14patients
dropped out of the ongoing trial because the disease progressed post-treatment for a median of
15months. Sevenpatientsremainedinstudy. Moreimportantly,thelackofdose-limitingtoxicities
wasencouragingevenatahighdoseof4000mg/day[69].
Randomizeddoubleblindplacebocontroltrialshavegainedappreciationasthe“goldstandard”
of epidemiological studies. Recently, a trial was conducted in which 22 biochemically recurrent
prostatecancerpatientswereenrolled[70]. Thesepatientshadamoderateriserate. Doublingtimeof
prostatespecificantigen(PSA)was4–15monthswithnoevidenceofmetastasis. Anon-significant
riseinthelog-slopeofPSAwasexperiencedbythetreatmentgroup. Pre-treatmentdoublingtime
was 10.2months, whereas post-treatment doubling time was 5.5 months. However, no change in
the log-slope of PSA was experienced by the placebo group. Doubling time before treatment was
10.8months,whilethedoublingtimeaftertreatmentwas10.9months[70].
A Phase I clinical trial was conducted where colon cancer patients were enrolled in a study
designed to evaluate the effects of low doses of resveratrol-containing freeze-dried grape powder
(GP) and a plant-derived resveratrol formulation on the Wnt signal transduction cascade in the
colon [71]. Patients treated with resveratrol/GP did not show any change in the Wnt target gene
expression[71]. Inanotherstudy,SRT501,micronizedresveratrol,wasgiven5.0gdailyfor2weeks
tocolorectalcancerpatients. SRT501wasalsogiventopatientswithlivermetastasesscheduledto
undergohepatectomy[72]. ThemeanplasmalevelofresveratrolaftersingleadministrationsofSRT501
was1942±1422ng/mL.ResveratrolwasdetectedinhepatictissuesaftertheadministrationofSRT501
(upto2287ng/g)[72]. Thepromisingpre-clinicaldatahasledtotheinterestinclinicalevaluationof
resveratrol. Moreelaboratetrialsneedtobeconductedtofurtherestablishtheclinicalrelevanceof
resveratrol’santicancerproperties.
11. ConcludingRemarks
Deregulation of spatio-temporally controlled cell signaling pathways contributes to cancer
initiation, progression, and its metastatic spread. Therefore, the identification of novel anticancer
therapeutics, such as natural products with significant anticancer activity and an ability to target
multiple proteins of oncogenic pathways, is required. Resveratrol has been shown to modulate
keyregulatorsofoncogenicsignalingpathways. ItstronglyinhibitstheTGF/SMADpathwayand
reducesphosphorylatedSMADs,resultingintheinhibitionofcancercellproliferationandmetastasis.
ResveratrolhasshownexperimentallyverifiedactivityagainstWNTsignalingandcaninhibitthe
translocationofβ-cateninintothenucleus. Resveratrol,context-dependently,regulatestheNOTCH
pathwayincancercells,allofwhichunderlinesitsflexibleandpotentanticanceractivity. Reduced
apoptosisisahallmarkofaggressivecancercells,andresveratrolre-balancespro-andanti-apoptotic
proteinstoimprovetheefficacyofTRAIL-basedtherapeutics. Itseemsexcitingtonotethatresveratrol
mayprovetobeaclinicallyeffectiveagent;however,lowerbioavailabilityisamajorshortcoming
thatneedstobeovercome. Inaccordancewiththisidea,nanotechnologicalstrategiesarecurrently
beingtestedtoenhancethebioavailabilityofresveratrol. Resveratrolhasbeenshowntoefficiently
upregulate various tumor suppressor miRNAs in different cancers, and its suppressive effects on