Chronic Inflammation Links Cancer and Parkinson’s Disease
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MINIREVIEWpublished:03June2016doi:10.3389/fnagi.2016.00126
Editedby:YingXu,TheStateUniversityofNewYorkatBuffalo,USA
Reviewedby:ValentinaEcheverriaMoran,BayPinesVAHealthcareSystem,USARalfJ.Braun,UniversitätBayreuth,Germany
*Correspondence:Chi-MengTzengcmtzeng@xmu.edu.cn
Received:15February2016Accepted:13May2016Published:03June2016
Citation:LiZ,ZhengZ,RuanJ,LiZandTzengC-M(2016)ChronicInflammationLinksCancerandParkinson’sDisease.Front.AgingNeurosci.8:126.doi:10.3389/fnagi.2016.00126
ChronicInflammationLinksCancerandParkinson’sDisease
ZhimingLi1,2,ZaozaoZheng1,2,JunRuan1,2,ZhiLi1,2andChi-MengTzeng1,2,3,4*
1TranslationalMedicineResearchCenter,SchoolofPharmaceuticalSciences,XiamenUniversity,Xiamen,China,2KeyLaboratoryforCancerT-CellTheranosticsandClinicalTranslation,Xiamen,China,3INNOVACellTheranostic,Yangzhou,China,4TRANSLAHealthGroup,Xiamen,China
AnincreasingnumberofgeneticstudiessuggestthatthepathogenesisofParkinson’sdisease(PD)andcancersharecommongenes,pathways,andmechanisms.Despiteadisruptioninawiderangeofsimilarbiologicalprocesses,theendresultisverydifferent:uncontrolledproliferationandearlyneurodegeneration.Thus,thelinksbetweenthemolecularmechanismsthatcausePDandcancerremaintobeelucidated.WeproposethatchronicinflammationinneuronsandtumorscontributestoamicroenvironmentthatfavorstheaccumulationofDNAmutationsandfacilitatesdiseaseformation.Thisarticleappraisesthekeyroleofmicroglia,establishesthegeneticroleofCOX2andCARD15inPDandcancer,anddiscussespreventionandtreatmentwiththisnewperspectiveinmind.WeexaminetheevidencethatchronicinflammationisanimportantlinkbetweencancerandPD.
Keywords:PD,cancer,chronicinflammation,microglia,COX2,CARD15
INTRODUCTIONThethreeearly,typicalsymptomsofParkinson’sdisease(PD)arestatictremors,musclerigidity,andbradykinesia,whichresultfromthedegenerationofdopaminergicneuronsinthemidbrain.Incontrast,cancerisadiseasecausedbytheclonalproliferationofselectivelyadvantageouscells.Althoughthetwomayappeardistinct,epidemiologicalstudieshaverevealedsomeparallels.Doshay(1954)foundadecreasedfrequencyofcancerincidenceinpatientswithPD,butthereasonforthiswasunknown.Case-controlledandlargeprospectivestudiesreportedalowerrateofsmoking-relatedandnon-smoking-relatedcancersinPDpatients.Melanoma,thyroid,andbreastcancerwererevealedtohaveanincreasedincidenceinPDpatients(D’Amelioetal.,2009;Liuetal.,2011).Thereareanumberofpotentialexplanationsfortheinverseassociation.OneoftheoriesbetweenPDandskincancermaybeassociatedwiththemodeoftherapy,suchasLevodopa,ratherthanwiththediseaseitself(Paisan-RuizandHoulden,2010).However,someobservationsdonotagreewiththeviewthatthismaybearesultofdrugtreatment(Fialaetal.,2003;Zanettietal.,2006).Moreover,itwassuggestedthatPDpatientswithalowincidenceofcancermaybeassociatedwiththenegativecorrelationbetweenPDandsmoking(Hernanetal.,2002).Althoughthereducedriskofsmoking-relatedcancerscanbeexplainedinPDpatients,itcannotdeciphertheriskofnon-smoking-relatedcancers.Thus,moredataareneededtoconfirmtheepidemiologicalrelationshipbetweenPDandcancer.Recently,theunusualepidemiologicalinformationbetweenPDandcancerisincreasinglybecomingofinteresttomanyinvestigators.Geneticstudiesprovideadditionalunderstanding,sincemanyfamilialPDgeneshavebeenassociatedwithcancer,suchasparkin(PARK2),PINK1(PARK6),DJ-1(PARK7),andLRRK2(PARK8;Table1).However,thesamegene’svariantsmay
FrontiersinAgingNeuroscience|www.frontiersin.org1June2016|Volume8|Article126Lietal.Inflammation,Cancer,Parkinson’sDiseaseTABLE1|Parkinson’sdisease(PD)involvedgenesidentifiedincancer.GenePDlocusChromosomelocationInheritanceinPDExpressionincancerProliferationincancerbCancer
α-SynucleinPARK1/PARK44q21–q23ADOverexpressed(notexpressinnormaltissue)+Braintumors(Kawashimaetal.,2000),Melanoma(MatsuoandKamitani,2010),andOvarycancer(Brueningetal.,2000)
ParkinPARK26q25.2–q27ARDecreaseda−Glioblastoma,Coloncancer,andLungcancer(Veeriahetal.,2010)
UCHL1PARK54p14ADSilenced(viaCpGmethylation)−Nasopharyngealcarcinoma(Lietal.,2010),Colorectalcancer(Okochi-Takadaetal.,2006)
PINK1PARK61p35–p36ARDecreaseda−Breastcancer(Berthieretal.,2011)DJ-1PARK71p36AROverexpressed+Non-small-celllungcancer(MacKeiganetal.,2003)LRRK2PARK812p11.2–q13.1ADOverexpressed+PapillaryrenalcellcarcinomaandThyroidcancer(Looyengaetal.,2011)
AD,autosomaldominant;AR,autosomalrecessive.aThetelomericendofchromosome1pissubjecttofrequentdeletionandrearrangementinmanycancers.b±denotesproliferationandanti-proliferation.
leadtodistincteffectsduetothedifferentcellbackgroundsassociatedwithdopaminergicneuronsandcancercells.PD-relatedgenesparticipateinawidevarietyofcellularprocesses,includingthemisfoldinganddegradationofproteins,mitochondrialdamage,responsetooxidativestress,cellcyclecontrol,andDNArepair(Figure1).TheseprocessesallhaveanimportantinfluenceontheoccurrenceanddevelopmentofPDandcancer.ThePI3K/AKT/mTORpathwayalsoplaysimportantrolesinbothcellgrowthanddeath.Somecommoncellularpathwaysandgeneshavebeenexplainedinourwork(Zhimingetal.,2014).Notably,neuroinflammationisincreasinglyconsideredadouble-edgedsword(Wyss-CorayandMucke,2002).Acuteinflammationcanrepairdamageandpromotehealing,butlong-termchronicinflammationcanseverelydamagethebody.Chronicinflammationisconsideredadrivingforcebehindmanychronicdiseases,certainlyincludingcancerandneurodegenerativedisease.Inthisarticle,wefurtherdiscusstherelationshipbetweenPDandcancerfromtheperspectiveofchronicinflammation.Thiswillprovideanincreasedunderstandingandimprovedtreatmentapproachesforbothdiseases.MICROGLIA:AKEYPLAYERInflammationandPDhaveanestablishedlinkviamicroglia,whicharetheresidentimmunecellsofthecentralnervoussystem(CNS).Underphysiologicalconditions,microgliaareinactive,haveasmallcellbody,andexhibithighlyramifiedmorphology.Inresponsetoinjuryortoxicfactors,microgliatransformintoactivatedmicroglia,migratetothelesionarea,andphagocytosecellulardebrisordamagedneurons.ItisnowwelldocumentedthatactivatedmicroglialsurroundthelostdopaminergicneuronsinpatientswithPDandPDanimalmodels,whichprovidesforthespeculationthatmicrogliaactivationresultsininitiationanddevelopmentofPD(TanseyandGoldberg,2010).Arecentinvestigationrevealedthatneuronscouldreleaseα-synucleinoligomers,themaincomponentofLewybodies(LBs)inthesubstantianigraparscompacta(SNc)ofthemidbrain,whichcanbindtotoll-likereceptors(TLRs)toactivatemicroglia,mediatingthenuclearfactorkappaB(NF-κB)pathwayandcausingthesecretionofinflammatorymediators,suchascytokines,eicosanoids,andchemokines,alteringimmunologicalfunctions(BeraudandMaguire-Zeiss,2012).Theseimmunefactorsnotonlydirectlyactondopaminergicneuronstocauseneuronaldeathbutalsoaggravatetheinflammatoryreactionandcontinuetoactivatemicroglia.Activatedmicrogliaalsogenerateandreleaseawiderangeofreactive-freeradicalsandincreasingevidencehasshownthattheoxidativestressresponseplaysacrucialroleinPD.Thesustainedproductionoffreeradicalsandnoxiouscompounds,likesuperoxideorperoxynitrite,caninteractwithbiologicalmacromolecules,leadingtodisruptiontotheredoxbalanceofneurons.Additionally,levelsofpro-inflammatorymediators,includingtumornecrosisfactor(TNF)-α,interleukin(IL)-1β,IL-6,andeicosanoidsareenhancedinperipheralbloodmononuclearcells(PBMCs)ofPDpatients(Bessleretal.,1999).Recentstudieshaveshownthatinhibitingthemicrogliacascadereactionscouldpreventthedegradationofneurons(Burguillosetal.,2011).TheimmunohistochemicaldemonstrationofreactivemicrogliasuggeststhatchronicinflammationoccursinaffectedbrainregionsinPD.Thebrainisacommonmetastaticsiteforvarioustypesofcancers,especiallylungcancer,whichsuggestsfailureoftheimmunedefenseinthebrainenvironment.MicrogliaarebelievedtobethemostimportantimmunecellsintheCNS.Interestingly,significantmicroglialactivationhasbeenobservedinthevicinityofgliomatumorcells(Roggendorfetal.,1996).IncontrasttoCNSinflammation,microgliaassociatedwithbraintumorsdonotseemtobeactiveininducinganeffectiveantitumorresponse.Theexactmechanismofthismicroglialinactivationremainsunclear.Thereisevidencethatsomecytokines,suchasIL-10releasedfromactivatedmicroglia,playimportantrolesinlocalimmunosuppressionandprogressionofglioma,particularlypromotingproliferationoftumorcellsandtheirinfiltrationintosurroundingnormalbraintissue(Wagneretal.,1999).Microgliaalsoplayanimportantroleinphagocytosingtumorcells.Duringthepastdecades,moreattentionhasbeenpaidtothesecretorypropertyandchemotaxisofmicroglia,butmicroglialphagocytosisisnotwell-studied.