Wnt-signalling pathway

Wnt-signalling pathway

BritishJournalofCancer(2003)89,1298–1304

&2003CancerResearchUKAllrightsreserved0007–0920/03$25.00

doc.guandang.net

Wnt-signallingpathwayinovarianepithelialtumours:increasedexpressionofb-cateninandGSK3b

¨nnstro¨m2,PCarlsson3,PHellberg2,P-OJanson2,LHedin4andKSundfeldt*,1,2KRask1,ANilsson1,MBra

1

DepartmentofPhysiology,Go¨teborgUniversity,Go¨teborg,Sweden;2DepartmentofObstetricsandGynaecology,Go¨teborgUniversity,Go¨teborg,Sweden;

34DepartmentofMolecularBiology,Go¨teborgUniversity,Go¨teborg,Sweden;DepartmentofAnatomyandCellBiology,UniversityofBergen,Bergen,Norway

Beta-cateninisinvolvedinbothcell–celladhesionandintranscriptionalregulationbytheWingless/Wntsignallingpathway.Alterationsofcomponentsofthispathwayhavebeensuggestedtoplayacentralroleintumorigenesis.Thepresentstudyinvestigated,byimmunohistochemistryandimmunoblotting,theproteinexpressionandlocalisationofb-catenin,adenomatouspolyposiscoli(APC),glycogensynthasekinase3b(GSK3b)andlymphocyteenhancerfactor-1(Lef-1)innormalhumanovariesandinepithelialovariantumoursinvivoandinvitro.Immortalisedhumanovariansurfaceepitheliumandovariancancercellcells(OVCAR-3)expressedb-catenin,APC,GSK3bandLef-1.Nuclearstainingofb-cateninandLef-1weredemonstratedonlyinOVCAR-3cells.Thereweresignificantincreasesofb-cateninandGSK3b,whileAPCwasreducedinovariancancercomparedtothenormalovary.Beta-cateninandLef-1werecoimmunoprecipitatedinovariantumours,butnotinthenormalovary.Nuclearlocalisationofb-cateninorLef-1couldnotbedemonstratedinthenormalovaryorintheovariantumours.Theabsenceofnuclearlocalisationofb-catenincouldbeduetoanincreasedbindingtothecadherin–a-catenincelladhesioncomplex.Infact,wehaveearlierreportedanincreasedexpressionofE-cadherininovarianadenocarcinomas.Insummary,thisstudydemonstratesanincreaseintheexpressionofcomponentsoftheWingless/Wntpathwayinmalignantovariantumours.Theincreasesuggestsaroleforthissignallingpathwayincelltransformationandintumourprogression.However,itremainstobedemonstratedwhetheritisanincreasedparticipationofb-cateninintranscriptionalregulation,orinthestabilisationofcellularintegrity,orboth,thatisthecrucialeventinovariantumorigenesis.

BritishJournalofCancer(2003)89,1298–1304.doi:10.1038/sj.bjc.6601265doc.guandang.net

Keywords:Wnt-signalling;normalovary;ovariancancer;b-catenin;GSK3b;Tcf/Lef;APC

MolecularandCellularPathology

Thecytoplasmicproteinb-catenin,initiallydiscoveredasacomponentofcell–celladhesivejunctions,hasalsobeendemon-stratedtobeacriticaldownstreammediatorofWnt-signalling

´etal,1998).Beta-cateninisphosphorylatedbyglycogen(Giarre

synthasekinase3b(GSK3b),inconnectionwiththetumour-suppressorgeneproductadenomatouspolyposiscoli(APC)andAxin.TheformationofthiscomplexdependsontheGSK3bphosphorylationstatus.Inthenormalcell,degradationofb-cateninthroughtheubiquitinpathwayisfacilitatedbyphosphorylation(BenZeevandGeiger,1998).Mutationalchangestothecomplexwillleadtoanincreasedfreepoolofb-catenininthecytoplasm.Apartfrombeingimportantforcell–celladhesion,b-cateninalsobindstothetranscriptionfactorT-cellfactor/lymphocyteenhancerfactor(Tcf/Lef)eitherinthecytoplasmorinthenucleus.Thisisfollowedbytranscriptionalactivationoftargetgenes,thatis,c-myc,E-cadherinandcyclinD1(reviewedbyRooseandClevers,1999).Inadherensjunctions,b-cateninbindsdirectlytothecytoplasmictailofcadherinsandwilltherebystabilisecell–*Correspondence:DrKSundfeldt,DepartmentofPhysiology,UniversityofGo¨teborg,Box434,S-40530Go¨teborg,Sweden;E-mail:

karin.sundfeldt@fysiologi.gu.se

Revised15May2003;accepted8July2003celladhesion.Theregulationofthisdualfunctionofb-cateninis

´etal,1998).notclear(Giarre

Themajorityofovariantumoursareepithelial-derivedadeno-masoradenocarcinomas.Theyarebelievedtoarisefrominclusioncystssituatedintheovarianstromaandwilltypicallygrowincysticformationsorsolidformations(Scully,1995).Theadenocarcinomasinvadethenearbypelvicsurroundingsandlatertheabdomenbydirectgrowthorviaascitesfluid.Haematogenousspreadwithperipheralmetastases,forexample,totheliverandlung,arerare.

Cell–celladhesionhasbeenimplicatedtobeofgreatimportancefortheinvasivecapacityofmosttumourtypes.Thedownregulationofcadherinsordysfunctionofthecadherin–catenincomplexhasbeennotedindifferenttypesoftumours.Inthehumanovary,neuronal(N)cadherin,butnotepithelial(E)cadherin,isexpressedinthenormalovariansurfaceepithelium(OSE)(Sundfeldtetal,1997;Auerspergetal,2001).However,E-cadherinisupregulatedininclusioncystsofthenormalovaryandinovariantumourswithinvasivecapacity(Sundfeldtetal,1997;Auerspergetal,2001).Attheproteinlevel,botha-andb-cateninareexpressedinnormalOSEandinvasiveovariantumours(Auerspergetal,2001).Mutationsoftheb-cateningeneatthebindingsiteforGSK3bwasdemonstratedin16–30%oftheendometrioidtypeofovarianadenocarcinomas,butnotinother