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Annals
of
Hepatology
j o ur na l h o me p a g e : w w w . e l s e v i e r . e s / a n n a l s o f h e p a t o l o g y
Original
article
Differential
capacity
of
CD90+
cells
in
autophagy
activation
following
chemotherapy
in
hepatocellular
carcinoma
Huy
Q
Do
a,b,1,
An
B
Luong
a,c,1,
Deborah
Bonazza
d,
Cristina
Bottin
e,
Thao
PT
Doan
f,
Long
DC
Tran
g,
Nhung
H
Truong
b,
Gianluca
Tell
h,
Hoa
LT
Pham
g,
Claudio
Tiribelli
a,
Caecilia
HC
Sukowati
a,h,∗aFondazioneItalianaFegato-ONLUS,AREASciencePark,Basovizza,Trieste,Italy
bLaboratoryofStemCellResearchandApplication,VNUHCM-UniversityofScience,HoChiMinh,Vietnam cCenterforMolecularBiomedicine,UniversityofMedicineandPharmacyatHoChiMinh,Vietnam
dSurgicalPathologyUnit,CattinaraHospital,AziendaSanitariaUniversitariaGiulianaIsontina(ASUGI),Trieste,Italy eDepartmentofMedical,SurgicalandHealthSciences,UniversityofTrieste,Trieste,Italy
fDepartmentofPathology,UniversityofMedicineandPharmacyatHoChiMinh,Vietnam gUniversityMedicalCenter,UniversityofMedicineandPharmacyatHoChiMinh,Vietnam
hLaboratoryofMolecularBiologyandDNArepair,DepartmentofMedicine(DAME),UniversityofUdine,Udine,Italy
a
r
t
i
c
l
e
i
n
f
o
Articlehistory: Received26June2020 Accepted11July2020 Availableonlinexxx Keywords: hepatocellularcarcinoma autophagycancerstemcells CD90
chemoresistance
a
b
s
t
r
a
c
t
IntroductionandObjectives.Analysisofcancerbiomarkersisanimportanttoolindeveloping targeted-therapyandinmodulatingchemoresistance.Here,weanalyzetherelevanceofCD90,amarkerofcancer stemcells(CSC)inhepatocellularcarcinoma(HCC)anditscorrelationwithautophagy.Materialsand Methods.Forinvivostudy,86specimenswerecollectedfrom43patientsundergoingliverresections.In eachpatient,HCCnodule(HCC)andsurroundingnon-tumor(SNT)werecollected.Forinvitrostudy,HCC cellsJHH6subpopulationsexpressingCD90+andCD90-wereisolatedusingmagnetic-sorterand con-firmedbyflow-cytometry.Upondoxorubicintreatment,autophagyturn-overwasanalyzedbyRTqPCR formRNAexpression,Westernblotforproteinexpression,andautophagosomestainingfor autophagy-flux.CytotoxicitytestwasperformedbyMTTassay.Geneandproteinanalysiswereperformedinclinical samplestogetherwithimmunohistostaining.Results.CD90mRNAexpressionwashigherinHCCthan inSNTfor8-fold(p<0.001).LC3-IIproteinwasup-regulatedintheHCCincomparisonwiththeSNT (p<0.05).InvitromodelshowedthatCD90+andCD90-cellshaddiverseexpressionsof autophagy-relatedgenes.Upondoxorubicintreatment,autophagywasactivatedinbothcellsbyincreasingLC3-II proteinexpression,autophagicvacuoles,anddysregulationofautophagy-relatedmRNAs.Adifferential autophagiccapacitywasnoticedbetweentwosubpopulationsanditwascorrelatedwithcellular toxic-ityassay.Conclusions.WedemonstratedtherelevanceofdifferentialautophagycapacityofCD90+cells inHCC.Autophagywasinvolvedincancer-defensemechanismagainstdoxorubicin.Cancerpromoting functionofautophagyinCD90+cellswasalsorelatedtocancerenvironment.
©2020Fundaci ´onCl´ınicaM ´edicaSur,A.C.PublishedbyElsevierEspa ˜na,S.L.U.Thisisanopenaccess articleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Abbreviations: CSC,cancerstemcells;HCC,hepatocellularcarcinoma;SNT, surroundingnon-tumor;RTqPCR,reversetranscriptionquantitativepolymerase chain reaction; MTT, (4,5-dimethyl thiazolyl-2)-2,5 diphenyltetrazolium; IHC, immunohistochemistry;WB,Westernblot;ESgrade,EdmonsonSteinergrade; HBV,HepatitisBvirus;HCV,HepatitisCVirus;CTP,Child-Turcotte-Pugh;ALT, alanine transaminase; AST, aspartate transaminase; AFP, alpha fetoprotein; ATG8/GABARAPL1,GABAtypeAreceptorassociatedproteinlike1.
∗ Correspondingauthor.
E-mailaddress:caecilia.sukowati@fegato.it(C.H.Sukowati). 1 Theauthorsequallycontributedtothestudy.
1. Introduction
RecentepidemiologydataGlobocan2018predictedthatliver cancer,mainlydominatedbyhepatocellularcarcinoma(HCC),tobe thesixthmostcommonlydiagnosedcancerandthefourthleading causeofcancer-relatedmortalityworldwide.Inthemale popula-tion,itsincidenceandmortalityare2to3timeshighercompared to female,thus it ranks fifthin terms of globalcases and sec-ondintermsofdeaths[1].PoorclinicaloutcomeofHCCpatients isattributedtothelatediagnosis,theresistanceofHCCcells to currentlyavailabletherapies,andtumorrecurrenceaftercurative therapies[2].
https://doi.org/10.1016/j.aohep.2020.07.007
1665-2681/©2020Fundaci ´onCl´ınicaM ´edicaSur,A.C. Publishedby ElsevierEspa ˜na,S.L.U.Thisis anopenaccessarticleundertheCCBY-NC-NDlicense(http://
Hepaticcancerstemcells(CSC)arewidelyacceptedasamajor originofHCC[3,4].These cellspopulationsareknownfortheir resistancetoradio-andchemotherapies,leadingtotherapyfailure andmetastasis[5,6].Variousproteinmarkershadbeenproposed forthedetectionandtheclassificationofhepaticCSC[7].TheCD90 (Thy-1)isoneofthemostcommonhepaticCSCusedinmultiple invitroand invivostudies[8–10].It is a 25-37kDa glycophos-phatidylinositol(GPI)-anchoredproteinexpressedinvariouscells. BesidesTcellactivation,CD90hasnumerous non-immunologic biologicalprocesses,asanimportantregulatorofthecelltocelland celltomatrixinteraction,apoptosis,adhesion,migration,cancer, andfibrosis[11,12].Basedonageneontologyanalysis,the over-expressedgenesin CD90+cells fromHCCwereassociatedwith inflammation,drugresistance,andlipidmetabolismcomparedto CD90+fromnontumoralliver[13].
Autophagy,aself-digestionmechanismfortheeliminationof cytoplasmicmaterials,cellularcomponents(lipid,proteins),and organelles,isoneofthekeyfactorsforcellhomeostasisinnormal physiology.Itinvolvestheformationof double-membrane vesi-cles(autophagosomes)engulfingthecargostothelysosomes.The outermembraneoftheautophagosomethenfuseswiththe lyso-somalmembrane,andtheinnervesicle,togetherwithitscargo,is degraded[14].
Incancer,autophagyisacknowledgedasadouble-edgedsword asitfunctionsbothascancer-suppressorandcancerpromoter[15]. Cancersuppressivefunctionofautophagyiswidelycharacterized tobeinvolvedinpreventionofcellsinflammation[16],whilethe cancer-promotingfactorsarerelatedtohypoxia[17–20]and exten-sivereactiveoxygenspecies[21–25].However,inHCC,thisdual roleofautophagyisevenmorecomplicated,beingattributedby thecomplexity ofcellularheterogeneity,variousetiologies, and multiplefactors(lifestyle,treatmentchoice,gender,etc.)during long-termdiseasedevelopment.
Asrecently reviewed, dysregulation of autophagy is known in CSC populations of several cancers [15]. As for HCC, how-ever, information on autophagy preference to hepatic CSC is still unclear and is mainly limited to the CD133+ phenotype. AutophagywasinvolvedinthemaintenanceofCD133+CSCunder theoxygen-andnutrient-deprivedconditionsthataretypicalofthe HCCmicroenvironment[26,27].Autophagywasalsoactivatedin CD133+cellsuponaninsufficientradiofrequencyablation[28]and immunotherapyusinginterferon-gamma[29].Recently,an inter-estinglineage-tracingstudyintransgenicratlivercirrhosisshowed thathepaticCSCAxin2/EGFP+CD90+cellsweregenerated exclu-sivelyincirrhoticliverswithaberrantautophagyandpromoted hepatocarcinogenesis[30].
However,untilnow,thereislimitedinformationonthe rele-vanceofautophagyinCD90HCCcellularsubpopulations.Here,we providenewevidenceofautophagypreferenceinCD90+cells,both ininvitroand clinicalHCCtissues,includingitsactivationafter chemotherapy.Thisfindingrevealsnewprospectsonthe develop-mentoffuturestrategiestomanageHCC.
2. MaterialsandMethods 2.1. Samples
2.1.1. Humantissuesamples
Eighty-six specimens were collected from 43 selected HCC patientsundergoingliverresectionsintheUniversityMedical Cen-ter Ho Chi Minh City, Vietnam between2014 and 2017. From each patient,HCC nodule(HCC) and the mostdistant tissue of theresectedHCC(surroundingnon-tumoral;SNT)werecollected. FreshtissueswerekeptinRNAlaterStabilizationSolution (Invit-rogen,ThermoFisherScientific,Waltham, MA,USA)and stored
in−80◦Cbeforefurtherprocessing.Thediagnosisofpatientswas establishedoninternationalcriteriatogetherwithitsEdmondson Steiner(ES)HCCgrading,tumorparameters,laboratoryresults,and otherclinicalfindings.Informedconsenttoparticipateinthestudy wasobtainedfromeachpatientorbyalegalrepresentativeandthe protocolwasapprovedbytheethicalcommitteeoftheUMPHoChi MinhCityno.240/DHYD-HDDD.
2.1.2. Cellline
HumanHCCcelllineJHH6wasusedasinvitromodel. JHH6 subpopulations expressing CSCmarker CD90+ and its negative counterpartCD90-wereisolatedbyusingMACSmagneticcell sort-ing(MiltenyiBiotecGmbH,BergischGladbach,Germany)according tomanufacturer’sinstruction.Thepurity andthepercentage of CD90+cellswerevalidatedbyflowcytometry(FACSCalibur,BD Bio-sciences,NJ,USA).Detailsoncellseparationandsubpopulations’ characteristicswerereportedpreviously[31]. Cellsweregrown inWilliams’Emediumsupplementedwith10%(v/v)FBS,1% L-glutamineand1%antibiotics.Theyweremaintainedat37◦Cina humidified5%CO2incubatorandwereroutinelyexpandedby0.05% trypsindetachment.
2.2. Histologicalanalysis
Immediatelyaftersurgery,livertissueswerefixedinformalin andincludedinaparaffinblock.Thefixedslicesweresubjected tohematoxylin &eosin andimmunostaining.Twoindependent pathologists(UMCHCM Cityand ASUGI)performedhistological analysisandfinaldiagnosis.
2.3. Immunostaining
Immunohistochemistry(IHC)analysiswasperformed onthe paraffinatedtissuessectionusedforhistologicalanalysis.Paired HCCandSNTtissuesweresubjectedtoimmunostainingforLC3 protein.Briefly, hepaticslices werede-paraffinizedwithxylene andrehydratedwitha gradualconcentrationofethanol.Tissues wereincubatedwithantibodyagainstLC3(PA1-16930, Thermo Scientific,Rockford,IL,USA)followedbyincubationwithprimary universalantibodyenhancerandHRPpolymer(ThermoFisher Sci-entific,Cheshire,UK).ThecomplexwasvisualizedwiththeDBA peroxidasesubstratekit(VectorLaboratories,UK)andthenucleus was stained withhematoxylin. IHC imageswere generated by microscopicalsystemsLeicaDM2000(Leica,Wetzlar,Germany). 2.4. Treatmentinvitro
E64D(SC201280,SantaCruzBiotechnology,Dallas,Texas,USA), aninhibitoroflysosomalproteases,wasdissolvedinDMSO.JHH6 CD90+andCD90-cellswereplatedwithconcentrationof30,000 cells/cm2for24hours.Cellsthenwereexposedfor24hoursto5M doxorubicin(Pfizer)withandwithoutthepresenceof50ME64D. DMSOconcentrationwascalculatedtobe0.3%ineachtreatment. Cellviabilitywasdeterminedby3(4,5-dimethylthiazolyl-2)-2,5 diphenyltetrazolium(MTT,SigmaAldrich,StLouis,MO,USA)assay. TotalproteinandRNAextractswerecollectedforproteinandgene analysis,respectively.Inparallel,MTTassaywasalsoperformedfor autophagyinducerrapamycinandautophagyinhibitorchloroquine (EnzoLifeSciences,Farmingdale,NY,USA)
2.5. Assessmentofautophagyflux
Table1
ClinicalandpathologicalcharacteristicsoftheHCCpatients.
Parameter n Parameter n
n 43
Age(mean,95%CI) 58(55-61) Serummarkers
Sex(M/F) 35/8 ALT(U/ml)[mean(95%CI)] 58(32-84)
Etiology AST(U/ml)[mean(95%CI)] 74(46-102)
HBV 28 GGT(U/ml)[mean(95%CI)] 95(53-137)
HCV 6 Alphafetoprotein
Metabolic/Alcohol 9 <20ng/mL 14
Diseasescores 20-400ng/mL 14
CTPA/B/C 36/2/nd >400ng/mL 9
Tumorparameters
Number(single/multiple) 27/8 Biggestlesionsize
Diameter<2cm 5
Diameter>2and<5cm 16
Large 17
Vascularinvasion(yes/no) 6/37 ESgrade(ES1/ES2/ES3-4) 15/11/11
detectionkit(EnzoLifeSciences,Farmingdale,NY,USA)wasused todetectacidautophagicvacuoles.Briefly,JHH6CD90+and CD90-cellswereseeded ina 96-welldarkfluorescenceplatefor24h. Cellsthenwereexposed for24hto5Mdoxorubicinwithand without the presence of 50M E64D. 100M chloroquine, an autophagyfluxinhibitor,wasusedasa positive controlforthe detectionofautophagicvacuoles,basedonthemanufacturer’s sug-gestion.DMSOconcentrationwascalculated tobe0.3%in each treatment.Aftertreatment,cellswerestainedwithCyto-IDGreen and Hoechst 33342 nuclearstain dyes for 30minutes at 37◦C, followedbywashing.Thefluorescentsignalwasmeasuredbya fluorescentmicroplatereader(PerkinElmer,EnSpireMultimode Plate Reader,Hamburg, Germany). Simultaneous detectionwas performedfor theCyto-IDGreen and Hoechst33342 ona FITC filter(Excitation∼480nm,Emission∼530nm)andblueDAPI fil-ter(Excitation∼340nm,Emission∼480nm).Thegreenautophagy signalwasthennormalizedwiththebluesignalandtheresults expressedasrelativetocontrolcells.
2.6. Proteinisolationandquantification
24hoursaftertreatment,totalproteinsfromcellswerecollected usingcelllysisbuffer(CellSignalingTechnology,Danvers,MA,USA) andhomogenizedbyscrappingandvortexing.Theextractwas cen-trifugatedfor10minutesat14,000xginarefrigeratedmicrofuge. Attheend,supernatantswererecoveredandproteinconcentration wasdeterminedbythebicinchonicacidproteinassay.
2.7. WesternBlotanalysis
LC3proteinanalysiswasperformedbyusingWesternblot(WB) ontotalproteinextractobtainedfromhumanlivertissuesandJHH6 CD90+andCD90-fractions.Proteins(20g)weresize-separated bySDS–PAGEon12%polyacrylamidegel.Electro-transferredgel onPVDFmembranewasimmunoblottedwiththeLC3antibody whileactin(A2066,Sigma)wasusedashousekeepingprotein.The peroxidasereactionwasobtainedbyexposureofmembraneinthe ECL-PlusWBdetectionsystemsolutions(ECLPlusWesternBlotting DetectionReagents,GE Healthcare,Italy).Proteinquantification wasperformedafterthedensitometricanalysisofbandsvs.actin ineachsample(ImageStudioTM,LI-COR,Lincoln,Nebraska,USA). 2.8. ReverseTranscription–quantitativeReal-TimePCR(RT– qPCR)
Reverse Transcription (RT) was performed to obtain cDNA from1gofpurifiedRNAwiththeHighCapacitycDNAReverse
TranscriptionKits(AppliedBiosystem,USA)accordingtothe man-ufacture’sprotocol.Real-timePCRwasperformedaccordingtothe SYBRGreenSupermixprotocol(Bio-RadLaboratories,Hercules,CA, USA).PCRamplificationwascarriedoutin15Lreactionvolume containing25ngcDNA,1xSYBRGreenSupermix–composedby 100nMKCl,40nMTris-HCl,pH8.4,0.4mMeachdNTP,40U/mL iTaqDNApolymerase,6mMMgCl2,SYBRGreenI,20mM fluores-cein,andstabilizers(Bio-Rad),and250nMofgene-specificforward andreverseprimers.ThereactionwasruninCFX9600real-time PCRsystem(Bio-Rad).Theprimersequencesarelistedin Supple-mentaryDataTableS1.
2.9. Statisticalanalysis
Student’s t-test was performed for statistical comparison between groups using software GraphPad Prism version 8.0 (GraphPad Software, Inc., La Jolla, CA, USA). For human tissue samples,continuousvariables ofmRNAdistributionbyRT-qPCR werecalculatedusingt-testfollowingnormalitytestandvalues wererepresentedasmean(95%CI).Datainvitrowereobtained fromatleastthreeindependentexperimentsandareexpressedas mean±SD. Statisticalsignificance wassettop-value<0.05and reportedasindicatedhere:*p<0.05,**p<0.01,and***p<0.001. 3. Results
3.1. BaselinecharacteristicsofHCCclinicalsamples
Thedemographic features ofthe HCCpatientsareshown in Table1.Theparticipantswerepredominantlymale(35malevs8 female)withameanageof58±10yearold.Theaetiologyofchronic liverdiseasewas63%HepatitisBvirus(HBV),14%HepatitisCVirus (HCV),and21%othercauses(metabolic/alcohol).
0 50 100 150 0 2 1 3 4 relative mRNA e xpression relative mRNA e xpression LC3-II pr otein / Actin LC3 e x pression
CD90/THY-1
SNT
HCC
SNT
HCC
A
C
E
B
D
ATG8/GABARAPL1
Paired LC3-II protein
LC3 protein HCC 1 SNT HCC SNT HCC SNT HCC SNT HCC SNT HCC SNT HCC HCC 2 HCC 3 HCC 4 0 0 2 4 6 8 1 2 3 4 5 6 7 8 9 10 11 4 8 12 16 MW 21 17 42 LC3-I LC3-II LC3-I LC3-II Actin
Fig.1.RelevanceofautophagyinHCCtissues.
A.mRNAexpressionofCSCmarkerCD90/THY-1.B.mRNAexpressionofautophagymarkerATG8/GABARAPL1C.RepresentativeofLC3blottingofpairedHCCandits correspondingsurroundingnon-tumoraltissue(SNT)showedthepresenceofLC3-I(21kDa)andLC3-II(17kDa).Actinwasusedashousekeepingprotein.D.RelativeLC3-II expressionofelevenpairedHCCandSNT.DensitometricanalysiswasperformedbynormalizingLC3-IIsignaltoactin.E.MeanvalueofLC3-IandLC3-IIproteinexpression. TargetgenewasnormalizedtotworeferencegenesACTBand18sRNA.Theexpressionofanormalsamplewasconsideredas1.0.Student’st-test:*p<0.05,***p<0.001
3.2. HighLC3proteinexpressioninHCCtissues
Ourpreviousstudyshowedahighup-regulationofCSCmarker CD90/THY-1 in HCC tissues in European cohort [31]. Here we checkeditsexpressioninthisVietnamesecohortbyquantitative RT-PCR.WeanalyzedmRNAexpressionfromatotalof86tissue samplespecimensbyRT-qPCRandexpressedinarbitraryunit(au) withasampleconsideredas1.0au.AsignificantincreaseofCD90 wasobservedin HCC compared toitspaired surrounding non-tumoraltissue(SNT),withthemeanvalueexpressed(95%CI)of 23.2(14.2-32.4)and 2.7(1.0-4.5)forHCC andSNT,respectively (p<0.001)(Fig.1A).
UsingthesamesetofsamplesasforCD90,autophagymarkersof theATGfamily,theGABAtypeAreceptorassociatedproteinlike1
Table2
CorrelationbetweenATG8mRNAandclinicalparameters.
Parameter n ATG8mRNAexpression(mean+/-SD)
HCC p SNT p Age <=58 21 0.66±0.73 ns 0.51±0.48 ns >58 22 0.83±1.00 0.71±0.74 Sex M 35 0.79±0.97 ns 0.54±0.61 ns F 8 0.51±0.40 0.98±0.61 Etiology HBV 28 1.15±1.42 <0.05 0.72±0.71 <0.05 HCV 6 0.59±0.75 0.48±0.53 Metabolic 9 0.96±0.91 1.08±0.80 HCCsize <5cm 21 0.61±0.61 ns 0.51±0.49 ns >5cm 17 0.82±1.10 0.59±0.72 ESgrade ES1 15 0.48±0.58 ns 0.44±0.56 ns ES2 11 0.84±1.24 0.75±0.51 ES3-4 11 1.01±1.05 0.58±0.81 ALT <59(U/mL) 31 0.57±0.69 <0.05 0.43±0.44 <0.01 >59(U/mL) 12 1.32±1.20 1.09±0.82 AST <75(U/mL) 33 0.72±0.88 ns 0.53±0.52 ns >75(U/mL) 10 0.87±0.98 0.82±0.81 AFP <20ng/mL 14 0.87±0.86 ns 0.54±0.60 ns 20-400ng/mL 14 0.67±0.89 0.38±0.24 >400ng/mL 9 0.34±0.44 0.40±0.38
TherelativeexpressionofLC3proteininpairedHCCandSNT tissueswasthendeterminedbyWesternblot(Fig.1C).Asshownin Fig.1E,bothLC3bands,theLC3-I(21kDa),andtheLC3-II(17kDa) werehighlyexpressedinHCCtissues(p<0.05).Densitometric anal-ysisinarepresentativeelevenpairedHCCanditscorresponding SNTshowedthatLC3-II,theautophagyturnovermarker,was sig-nificantlyup-regulatedinHCCforaround5-fold(Fig.1D). 3.3. Differentialexpressionofautophagymarkersinisolated CD90+cells
SincetheCD90isamarkerfordifferentcelltypes,weexplored thefunctionofCD90+cellsinHCCbyusinganinvitromodelusinga HCCcellline.CD90+cellsfromJHH6wereisolatedbymagneticflow sortingandconfirmedbyflowcytometryaspreviouslydescribed [31].ThepurityofCD90+subpopulationsusedintheanalysiswas chosenhigherthan70%ofpositivity(upto5thpassageaftersorting) (Fig.2A).Asexpected,atbasallevel,theCD90mRNAwasaround 60-foldhigherinisolatedCD90+subpopulationsthanits CD90-counterpart(p<0.001)(Fig.2A-B).Wecheckedalsoseveral mark-erssuchashepatocytegrowthfactor(HGF)andAXIN2whichwere previouslyreportedtoberelatedtoautophagyinCD90,showing up-regulationinthiscellsubpopulation(Fig.2B).
TheexpressionsofautophagygenesandbasalLC3proteinin JHH6 CD90+and CD90- cells were then determined by mRNA expression(RTq-PCR)andWesternblot,respectively. Autophagy-relatedgenes ATG8(p<0.05)and ATG18werelower expressed inCD90+comparedtoitsCD90-counterpartforaround50%and 80%,respectively,whileREDD1expressionwascomparable.The mRNAexpressionresultwasthen confirmedbyprotein expres-sionusingLC3blotting.Atbasallevel(ctrlandDMSO),bothcells expressedLC3-II(17kDa)band.However,bothLC3-IIband(17kDa) andLC3-I(21kDa)werehigher intheCD90-cells comparedto CD90+(p<0.05)inlinewiththeATG8andATG18mRNAexpression data(Fig.2C-D).
InordertocheckLC3-IIturnoveruponautophagystimulation, bothcellsweretreatedwithE64D,aninhibitoroflysosomal pro-teases,atconcentrationsrangingfrom5to200Mfor24hours. DMSOconcentrationwascalculatedbeing0.3%ineachtreatment. MTTtestperformedtocheckcellviabilityupontreatmentdidnot showanytoxicityforthechosenconcentrationof50M(Fig.2E). UpontreatmentwithE64DandvehicleDMSO,theextentof LC3-IIaccumulationwasmorenoticeableinCD90+cells(about6-fold and2-fold,forE64DandDMSO,respectively)comparedto
CD90-cells (about3-foldforE64D)(Fig.2D-E).Thisdatamaysuggest thatCD90cellsresultmoresensitivetoautophagystimulationeven thoughthissensitivitywasnotreflectedbycellviability.Cell via-bilitytestsforrapamycin,anm-TORinhibitor,andchloroquine,a lysosomeproteasomalinhibitor,bothinvolvedinautophagy path-way,werealsoperformed,showinghigherviabilitiesfortheCD90+ cells(Fig.2E).
3.4. EffectofdoxorubicinonautophagyinCD90+cells
Autophagyisassociatedwithacelldefensemechanismagainst chemotherapy.HerewetreatedbothCD90+andCD90-cellswith doxorubicin,ananti-neoplasticdrugcommonlyusedtotreatHCC intheearly-intermediatestage.Concentrationof5Mwaschosen basedonourpreviousdataontheLC50ofdoxorubicininseveral HCCcelllines,includingintheJHH6[32].
Upondoxorubicintreatmentfor24hours,bothLC3bandswere increasedinCD90+andCD90-subpopulations.TheincreaseofLC3-I levelwasalsoapparent,alsoincomparisonwithE64D,indicatedan activationofautophagy-translatedgenesafterdoxorubicin expo-sure.Afterthetreatment,theextentofLC3-IIup-regulationwas higherinCD90+comparedtoCD90-cells(p<0.05)(Fig.3A).The patternofgenemodulationsbetweenthetwocellpopulationswas alsodissimilar.TheincreaseofATG8wasnoticedonlyinCD90+ cells(Fig.3B).
Thepresenceofautophagicvacuoleswasdetectedby fluores-cencereading.Greenautophagysignalwasthennormalizedwith thebluenucleussignalandthedatawerepresentedasrelativeto controlofeachsubpopulation.Thepresenceofautophagicvacuoles afterE64DwasslightlynoticedforCD90+comparedtoCD90-cells (Fig.3C).Tocomparedatadoxorubicintreatmentinvitroin clini-calsample,wecheckedalsotwoHCCsampleswhosepatienthad receivedapreviouslocoregionaltherapybydoxorubicin,showing positivityofLC3onthetissues(Fig.3D).
4. Discussion
Fig.2.DifferentialbasalautophagyactivitybetweenCD90+andCD90-subpopulationofJHH6.
A
B
C
D
CD90-CD90+ CELLS
CD90+ CELLS
CD90+ H&E staining LC3 SNT HCC ctrl DMSO E64d E64d + Doxo DoxoE64d + Doxo + ChloroQ ChloroQ CD90-300 200 100 0 fluorescence signal (%) 2.5 2.0 1.5 1.0 0.5 0.0 2.0 1.5 1.0 0.5 0.0 REDD1 ATG18 ATG8 REDD1 ctrl 0.3% dmso 5μM doxo ATG18 ATG8
*
***
*
*
*
*
* *
fold mRNA expression fold mRNA expression LC3-I LC3-II LC3-II Actin MW 17 21 42CD90+
CD90-CTRL DMSO E64D DOX
4 3 2 1 0 CD90+ ctrl 0.3% dmso 50 u M E64 D 5 uM Do xo 5 uM Doxo E6 4D + Doxo ctrl 0.3 % dmso 50 uM E6 4D 5 u M Doxo 5 uM Do xo E64 D + Do xo
Fig.3. AutophagyactivationafterdoxorubicininCD90+andCD90-subpopulationofJHH6.
A.LC-3blottingofdoxorubicin-treatedcellstogetherwithitsrelativeLC3-IIproteinexpression.DensitometricanalysiswasperformedbynormalizingLC3-IIsignalto actin.CD90-DMSOwasindicatedas1.0.Redboxshowedcellstreatedwithdoxorubicin.B.mRNAexpressionofautophagymarkerATG8/GABARAPL1,ATG18/WIPI1,and REDD1/DDIT4.TargetgenewasnormalizedtotworeferencegenesACTBand18sRNA.Theexpressionofnon-treatedinCD90-cellswasconsideredas1.0.C.Determination ofautophagicvacuolesalsointhepresenceoflysosomalproteosomalinhibitorchloroquine.Untreatedcontrolcellsforeachcellsubpopulationswastakenas100%.Student’s t-test*p<0.05vsCTRLofeachsubpopulation.D.Upperpanel:ArepresentativeofHEandLC3staininginaHCCnodulewithanadministrationofdoxorubicin(arrow).Lower panel:LC3expressioninpairedSNTandHCCtissue.
Currently,chemotherapybytransarterialchemoembolization isaninternationally-approvedtreatmentoptionforHCCpatients [33].Doxorubicinisoneofthemostcommonchemotherapyagents usedtotreatHCC;however,HCCresistancetodoxorubicinisa com-monfeatureoftherapeuticregimens,thusreducingtheefficacyof thetreatment.Furthermore,responsetodoxorubicinmightvary notonlyamongpatientsbutalsoinanindividualHCCcases. Dis-paratesensitivitiesmayberelatedtoHCCheterogeneity,including inthepresenceofvariouscellularpopulations.
dif-ferentiation,inflammation,ABCtransporters,drugresistance,and lipidmetabolismcomparedtoCD90-cellsorCD90+cellsfrom non-tumoralliver[9,10,34].
Invitrostudieshadshownthatdoxorubicininducedcytotoxicity and alteration of cellularorganelles together withthe upregu-lationofLC3-IIproteinand theinvolvementof autophagy[35]. InthisstudyweshowedthatinJHH6,apoor-differentiatedHCC cellline, autophagyactivation extentby doxorubicin were dis-tinctbetweenCD90+andCD90-subpopulations,withthehigher capacityobservedinthepositivesubpopulation.FrombothmRNA (ATG8/LC3/GABARAPL1) and LC3 immunoblotting data, it was noticedthateventhoughtheCD90+subpopulationshadalower basalexpression,theyweremoresensitivetoautophagic induc-tionshownbythehigherup-regulationascomparedtoCD90-cells. ThisincreasewasnotonlyobservedindoxorubicinandE64D treat-ments,butasubstantialeffectwasalsonoticedupon0.3%DMSO asavehicle.
In HCC tissues, ATG8 mRNA distributions were compara-ble between HCC nodules (high CD90) and SNT (low CD90), whileinJHH6cellline,ATG8expressionwassignificantlylower in CD90+ cells. This data was in line with a previous report showing that a low level of ATG8 in HCC tissues was related to the bad prognosis of the patient [36], similarly to what observed for the high level of CD90. From clinical data, we observed that ATG8 expression is significantly high in HBV-relatedHCCsandpatientswithhighALTlevels.Furthermore,ATG8 expressioninHCCnodulesprogressivelyincreasedmovingfrom well-differentiated(ES1),moderate-differentiated(ES2)to poor-differentiatedHCC(ES3/ES4).Aninversecorrelationwasfoundfor AFPlevel,alsoobserved forhighCD90+expression inprevious studies[8,31].
ToconfirmmRNAdata,weperformedLC3proteinexpression inlivertissues.Ourdatawasinlinewithpreviousstudies[37–39] showingahighLC3expressioninHCCcomparedtoSNTtissues. Fromimmunoblotting data ofpaired HCCtissues, we observed highvariabilityof LC3expression,withthemajoritybeinghigh intheHCCnodulecomparedtoitsSNT(72%).Itshouldbenoted thattheassociationbetweenautophagygenesandproteininHCC nodulesandtheclinicalvariablescouldbecontrasting.We con-sider that a direct quantification ofLC3 or autophagygenes in differentHCCspecimensmightberathercomplicatedsince nor-malcells have a basal autophagic flux that mayvary between individualsina physiologicmanner.Widecancerheterogeneity and cancer microenvironmentfurther complicate the data.For this reason,in-depth analysisof HCC subpopulations as shown inthis studywould beuseful tobetterunderstandthe mecha-nism.
Inconclusion,weconfirmthatHCCCD90+andCD90-cellshave differentautophagyactivation.Autophagyisinvolvedin cancer-defense mechanism against doxorubicin. Cancer promotingthe functionofautophagyinCD90+cellswasrelatedtoHCC environ-ment.
Conflictofinterest
Authorsdeclarenoconflictofinterest.
Financialsupport
ThisworkwasfundedbyagrantofInternationalCooperation withVietnamfromtheRegioneofFriuliVeneziaGiuliatothe Fon-dazioneItalianaFegato.CHCSwassupportedbythegrantfrom AssociazioneItalianaperlaRicercasulCancro(AIRC)(IG19862)to GT.
Acknowledgments
The authors thank Dr. C Bellarosa for the reagents on the autophagyinvitroexperimentsattheFondazioneItalianaFegato. TheauthorsalsothanktheVietnamNationalFoundationforScience and Technology Development (NAFOSTED; grant no. 108.05-2017.30)forreagentsontheautophagyexperimentinVietnam. AppendixA. Supplementarydata
Supplementarymaterialrelatedtothisarticlecanbefound,in theonlineversion,atdoi:https://doi.org/10.1016/j.aohep.2020.07. 007.
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