Clonal heterogeneity and chromosomal instability at disease presentation in high hyperdiploid acute

Clonalheterogeneityandchromosomalinstabilityatdiseasepresentation

inhighhyperdiploidacutelymphoblasticleukemia

AnnaTalamoa,YvesChalandonb,AlfioMarazzic,MartineJotterandd,*

CancerCytogeneticsUnit,MedicalGeneticsService,UniversityHospitalandUniversityofLausanne(CHUV-UNIL),Lausanne,Switzerland

bHematologyDivision,InternalMedicineDepartment,UniversityHospitalofGeneva(HUG),Geneva,Switzerland

cInstituteofSocialandPreventiveMedicine,UniversityofLausanne,Lausanne,Switzerland

dMedicalGeneticsService,UniversityHospitalandUniversityofLausanne(CHUV-UNIL),Av.PierreDecker2,CH1011,Lausanne,Switzerland

Received21June2010;receivedinrevisedform27August2010;accepted1September2010

aAbstract

Althoughaneuploidyhasmanypossiblecauses,itoftenresultsfromunderlyingchromosomalinsta-bility(CIN)leadingtoanunstablekaryotypewithcell-to-cellvariationandmultiplesubclones.TotestforthepresenceofCINinhighhyperdiploidacutelymphoblasticleukemia(HeHALL)atdiagnosis,weinvestigated20patients(10HeHALLand10non-HeHALL),usingautomatedfour-colorinterphasefluorescenceinsituhybridization(I-FISH)withcentromericprobesforchromosomes4,6,10,and17.InHeHALL,theproportionofabnormalcellsrangedfrom36.3%to92.4%,andavarietyofaneuploidpopulationswereidentified.Comparedwithconven-tionalcytogenetics,I-FISHrevealednumerousadditionalclones,someofthemverysmall.Toinvestigatethenatureandoriginofthisclonalheterogeneity,wedeterminedaveragenumericalCINvaluesforallfourchromosomestogetherandforeachchromosomeandpatientgroup.TheCINvaluesinHeHALLwererelativelyhigh(range,22.2e44.7%),comparedwiththoseinnon-HeHALL(3.2e6.4%),thusaccountingforthepresenceofnumericalCINinHeHALLatdiag-nosis.WeconcludethatnumericalCINmaybeattheoriginofthehighlevelofclonalheteroge-neityrevealedbyI-FISHinHeHALLatpresentation,whichwouldcorroboratethepotentialroleofCINintumorpathogenesis.Ó2010ElsevierInc.Allrightsreserved.

1.Introduction

Althoughaneuploidyisaremarkablycommoncytoge-neticfeatureinhumancancers,whetheritisacauseoraconsequenceofmalignanttransformationremainsamatterofdebate[1].Sometumorsrevealastableaneuploidy,duetoachromosomemissegregationoccurringatsomepointduringtumordevelopmentandleadingtoastablypropa-gatingabnormalkaryotype.Moreoften,however,aneu-ploidyresultsfromchromosomalinstability(CIN),whichischaracterizedbyanincreaseintherateoflossorgainofwholechromosomesduringmitosis,leadingtounstablekaryotypeswithcell-to-cellvariationandmultiplerelatedandunrelatedsubclones[2,3].Althoughthetwoaresometimesequatedwithoneanother,aneuploidyandCINarenotsynonymous.Aneuploidydescribesthestateofan

*Correspondingauthor.Tel.:þ41-21-314.94.83;fax:þ41-21-314.33.92.

E-mailaddress:Martine.Jotterand@chuv.ch(M.Jotterand).0165-4608/$-seefrontmatterÓ2010ElsevierInc.Allrightsreserved.doi:10.1016/j.cancergencyto.2010.09.005

abnormalchromosomenumber,whereasCINreferstotherateofchangeinchromosomenumber.

Chromosomalinstabilitydefinedasthepercentageofcellswithanonmodalchromosomenumberwasfirststudiedincolorectalcancers[4].Ithassincebeenfurtherinvestigatedinothertypesofsolidtumors[1,4e7],andrecentlyalsoinmyeloidmalignanthemopathies[8],butithasnotpreviouslybeenstudiedinacutelymphoblasticleukemia(ALL).

Highhyperdiploidy(HeH)with51e67chromosomesoccursinnearly25%ofpediatricB-cellprecursorALLcases[9];itislessfrequentinadultcases,andisrarelyfoundinT-cellormatureB-cellALL.InHeHALL,thepatternofchro-mosomegainsisclearlynonrandom,withextracopiesofchromosomesX,4,6,10,14,17,18,and21occurringmuchmorefrequentlythanextracopiesofotherchromosomes[10].TheoriginofaneuploidyinHeHALL,alongwiththequestionofwhetherHeHALLiskaryotypicallystable,hasbeenamatterofconjecture[9].Basedonconventionalcytogenetics(CC),15e20%ofchildhoodHeHALLcasespresentsubclonesdifferingfromthestemlinebyadditional

210A.Talamoetal./CancerGeneticsandCytogenetics203(2010)209e214

Table1

Demographicandcytogeneticfindingsatdiseasepresentationfor10studypatientsand10negativecontrolsubjectswithacutelymphoblasticleukemiaCase2385/95683/99a694/99a,b387/00a454/00a192/01a131/05241/0588/06363/09199/07c446/07c,d619/07c1085/07c1159/07c,e600/08c990/08c,e1198/08c1538/08c284/09c,fAge,yr/Sex26/M4/M18/M5/M2/M3/M21/F51/M18/M66/F60/F55/F42/F44/F21/F39/F46/M34/M32/F27/M

G-bandingkaryotype

Studypatients:abnormalI-FISHfindings

52~57,XY,þX,þ5,þ6,add(7)(p13~15),þ9,þ10,þ11,À13,þ18,þ21,þ21,þ22,þ22,þder(?)t(1;?)(q12~21;?)[cp6]/46,XY[10]

,XY,þX,dup(1)(q21q32),þ2,þ4,þ5,þ6,þ7,þ?8,þ?10,?der(11)(p?),þ11,þ12,þ14,þ14,þ17,þ18,þ21,þ21,þ21,þ22[3]/46,XY[14]

55,XY,þX,þ4,þ6,þ9,þ14,þ17,þ18,þ21,þ21[2]/55,idem,add(19)(p13)[5]/46,XY[1]56,XY,þX,þ6,þ10,þ10,þ14,þ18,þ18,þ21,þ21,þmar[7]/46,XY[4]54~55,XY,þX,þ6,inc[10]/46,XY[12]

55,XY,þX,þ4,þ6,þ10,þ14,þ17,þ18,þ21,þmar[14]/46,XY[22]

52,XX,þX,þ4,þ10,þ11,þ14,?der(16)t(1;16)(p22;q22),del(17)(p11.2),À21,þmar1,þmar2[4]/46,XX[36]54,XY,þX,þ2,þ4,þ4,þ6,inv(9)(p11q13)c,t(9;22)(q34;q11.2),þ21,þ21,þder(22)t(9;22)[3]/55,idem,?del(2)(q3?2q3?5),add(2)(q35~37),þ18[4]/46,XY,inv(9)c[12]

55,XY,þX,dup(1)(q25q32),þ4,þ6,9p?,þ10,?10,þ14,þ17,þ18,þ21,þ21[25]/46,XY[5]55,XX,þX,þ6,þ10,þ14,þ17,þ18,þ18,þ21,þ21[7]/46,XX[3]Negativecontrolsubjects:normalI-FISHfindings

46,XX,der(9)idic(9)(p?13)t(9;22)(q34;q11.2),der(22)t(9;22)[15]/46,XX[3]47~48,XX,þX,inv(9)(p11q13),þ21[cp4]/46,XX,inv(9)(p11q13)[16]47,XX,t(4;11)(q21;q23),þ21[20]

46,XX,t(4;11)(q21;q23)[10]/46,XX[5]46,XX[8]

46,XX,der(19)t(1;19)(q23;p13.3)[8]/46,idem,dup(1)(q21q32)[2]/46,XX[2]46,XY[7]

44,XY,þX,À3,À7,À9,À16,þ22[4]/46,XY[6]46,XX,t(4;11)(q21;q23)[10]

46,XY,t(11;19)(q23;p13.3)[1]/46,XY[15]

Abbreviations:I-FISH,interphasefluorescenceinsituhybridization.

Studypatientshadhighhyperdiploidacutelymphoblasticleukemiawithtrisomyforatleastoneofchromosomes4,6,10,and17accordingtoconven-tionalcytogeneticanalysis.Thenegativecontrolsubjectshadacutelymphoblasticleukemiawithpseudodiploidy,lowhyperdiploidy.orafewnormalmeta-phaseswithoutevidenceofextracopiesofchromosomes4,6,10,and17byconventionalcytogenetics.

aPatientsreportedinpartbyBlandinetal.,2008[11].bPatientincludedintheLALA-94study[13].cPatientsincludedintheGRAALL2005study(NCT00327678athttp://www.clinicaltrials.gov).dTheinv(9)(p11q13)mostprobablyisconstitutional,giventhatitispresentinaneuploidaswellasinnonaneuploidcells.Howevera‘‘c’’wasnotaddedtothedescription,becausetheconstitutionalkaryotypeofperipheralbloodTlymphocyteswasnotstudiedinthisrespect.

eWouldbeconsideredafailureaccordingtoGRAALL2005cytogeneticguidelines.fOnlyoneabnormalmetaphasewasobserved;however,theresultwasconsideredmeaningfulbecauseofanMLLrearrangementdetectedbyFISH.

chromosomesorstructuraldefects.Giventhepresenceofasinglesubcloneinmostcases,PaulssonandJohansson[9]suggestedthatclonalevolutionmaybemorefrequentthanCINinthesecases.Incontrastwithpreviouslypub-lisheddatasuggestingacell-to-cellvariationinHeHALLatdiagnosis[11,12],however,theirowninterphasefluorescenceinsituhybridization(I-FISH)resultsdidnotrevealsignificantvariationinthecasesstudieddevidenceoftheneedforfurtherstudies.Herewereportonrecentdataobtainedbyfour-colorI-FISHthatbringfurtherevidenceofahighlevelofinstabilityofchromosomes4,6,10,and17inHeHALLpatientsatinitialpresentation.2.Materialsandmethods2.1.Patients

TenpatientswithHeHALLestablishedbyCCandwithtrisomyforatleastoneofchromosomes4,6,10,and17wereincludedinthestudygroup.Fivecaseswerereportedinpartinapreviousmethodologicalarticle[11].TenALLpatientswithpseudodiploidy,lowhyperdiploidy,orafewnormalmetaphaseswithoutevidenceofextracopiesofchromosomes4,6,10,or17byCCservedasnegativecontrols.CytogeneticfindingsaregiveninTable1.Becauseofthesmallnumberofpatientsinthisstudy,nodistinctionwasmadeforALLsubtypeorforpediatricversusadultcases(4childrenand16adults).

Patientswerereferredbetween1995and2009toourlaboratoryfromthehematologydepartmentsoftheUniversityHospitalsofLausanne,Basel,Bern,Geneva,andZurichandofthecantonalandregionalhospitalsofSt.Gallen,Lucerne,Aarau,Sion,andBellinzona.Allpatientsreceivedinductionandconsolidationchemotherapyandsomealsoreceivedeventualstemcelltransplantation.OnepatientwasenrolledintheLALA-94study[13],and10patients(servingasnegativecontrols)wereenrolledintheGRAALL2005study(NCT00327678athttp://www.clinicaltrials.gov).TheGroupforResearchonAdultAcuteLymphoblasticLeukemia(GRAALL)includestheformerFranceeBelgiumGroupfor

A.Talamoetal./CancerGeneticsandCytogenetics203(2010)209e214211

Fig.1.Interphasenucleiwerehybridizedwithlabeledcentromericprobesspecificforchromosomes4(green),6(red),10(magenta),and17(turquoise):pretreatmentbonemarrowfromnegativecontrol(A)andhighhyperdiploidacutelymphoblasticleukemia(B,C)patients.

LymphoblasticAcuteLeukemiainAdults(LALA),theFrenchWesterneEasternGroupforLymphoblasticAcuteLeukemia(GOELAM),andtheSwissGroupforClinicalCancerResearch(SAKK).

Ethicalapprovalforthisprojectwasobtainedinaccor-dancewiththeguidelinesofthelocalEthicalReviewBoard.

2.2.Conventionalcytogeneticsandfour-colorI-FISHConventionalcytogenetics(G-banding)andI-FISHanalysesusingcentromericprobesspecificforchromosome4(p-4n1/4;kindlyprovidedbyProf.MarianoRocchi,UniversityofBari,Italy)andforchromosomes6,10,and17(D6Z1,D10Z1,andD17Z1,respectively;AmericanTypeCultureCollectioneATCC,Manassas,VA)wereperformedonpretreatmentbonemarrowsamples(Fig.1).Probesweredirectlylabeledbynicktranslationwithfourdifferentfluorochromes(FITC,Cy3,Cy3.5,andDEAC)thathaveemissionwavelengthssufficientlydistinctfromeachother.TheconventionalandFISHmethodswereusedaspreviouslydescribed[11].2.3.Automatedanalysis

Automatedfour-colorI-FISHanalysiswasperformedwiththescanningsystemMetafer4/MetaCyte(MetaSys-tems,Altlussheim,Germany)accordingtoamodificationofourpreviouslyreportedmethodthatincludesuseofamotorizedepifluorescencemicroscope(AxioImagerZ1;Zeiss,Feldbach,Germany)equippedwitha40Âobjective(Zeiss)[11,14e16].Optimalvaluesoftheparametersfor

nucleusselectionandfluorescentsignaldetectionwereadaptedinthisrespect(Tables2and3).2.4.Chromosomalinstability

Wedeterminedthemodalchromosomenumberforeachchromosometestedandcalculatedthepercentageofcellswhosenumberdiffersfromthemodalvalue(CIN),accordingtoLengaueretal.[4].AverageCINwasfirstdeterminedforallfourchromosomestogetherandthenforeachselectedchromosome,accordingtoLingleetal.[6]andMiyoshietal.[7].2.5.Statisticalanalysis

Ineachsample,aminimumof500nucleiwasscored.SignificantaneuploidiesweredeterminedbasedoncutoffvaluesestablishedaccordingtothePoissondistribution,aspreviouslydefined[11].Forallpatients,combinationsofaneuploidieswereconsideredrelevantwhenatleastoneaneuploidywasdeterminedtobesignificant.

Table2

ParametersfornucleusselectionParameter

RelativeDAPIintensitythresholdforsegmentingnuclei,%Minimumobjectarea,mm2Maximumobjectarea,mm2MaximumconcavitydepthMaximumaspectratioNumberoffocalplanes

Value10376000.11.81

Abbreviation:DAPI,4’,6-diamidino-2-phenylindole(blue,counterstain).

212

Table3

ParametersforFISHsignaldetectionParameter

Spotmeasurementarea,mm2Minimumspotdistance,mmMinimumrelativespotintensity,%

Maximumspotarea,mm2Minimumspotcontrast,&Numberoffocalplanes

A.Talamoetal./CancerGeneticsandCytogenetics203(2010)209e214

FITC461540

Cy3463239

Cy3.5433037

DEAC1019472010

505046101010

5(ataspacingof0.2mm)

Abbreviations:Cy3,cyaninedye3(redsignal);Cy3.5,cyaninedye3.5(magentasignal);DEAC,diethylaminocoumarin(C27H33N4O16P3)(turquoisesignal);FITC,fluoresceinisothiocyanate(greensignal).

3.Results

Forseveralofourpatients(andasisgenerallythecaseinALL),thenumberofabnormalmetaphasesavailableforCCanalysiswasrelativelysmall,becauseofthelowprolif-erationrateofabnormalcellsinvitro,poorchromosomequality,orbothfactors.Allabnormalmetaphasesavailablewerekaryotyped,butsometimesonlypartially,inwhichcasecompositeorincompletekaryotypesarereported.Despitethelimitednumberofabnormalmetaphasesanalyzedinsomecases,allabnormalclonesreportedherefulfillISCN2009clonalitycriteria[17]andshouldbeconsideredsignificant.Nonetheless,abnormalclones

observedinthesecasesmayaccountforonlyasmallfrac-tionofthetumorkaryotypediversity.

Inthenegativecontrolgroupofpatients,nosignificantaneuploidyforchromosomes4,6,10,and17wasdetectedbyI-FISH,whichconfirmsresultsobtainedbyCC.

Inthestudypatients,thenumberofabnormalcellskaryo-typedrangedbetween3and25,andI-FISHrevealedapropor-tionoftotalabnormalcellsrangingfrom36.3%to92.4%ofscorednuclei.Variouscombinationsofaneuploidieswereidentified(Table4).AllclonesdetectedbyCCwerealsoobservedbyI-FISH,butI-FISHrevealednumerousaddi-tionalclonesinallpatients,indicativeofahighlevelofheterogeneityatdiseasepresentationinHeHALLpatients.Thesizeofabnormalclonesvariedbetween!1%and33.4%.Verysmallabnormalclones(!1%)represented2.2e8.6%ofthetotal(reportedasOthersinTable4).

Overall,thelargestclonesobservedharboredbothtriso-mies4and6(33.4%)andbothtrisomies6and10(31.2%).Theproportionofcellswitharelevanttetrasomygenerallywasverysmall(!1e3.0%),exceptthatinthecaseofthePhiladelphia-positivepatient(case241/05)theclonewithtetrasomy4andtrisomy6amountedto13.6%.

AverageCINvaluesdeterminedforallfourchromo-somestogetherrangedfrom22.2%to44.7%instudypatientsandfrom3.2%to6.4%inthenegativecontrolgroup(Table5).

Table4

Clonesinvolvingchromosomes4,6,10,and17inpatientswithhighhyperdiploidacutelymphoblasticleukemia

Clonesatdiseasepresentation,%2385/95

Normalþ4þ6þ10þ17þ6,þ17þ6,þ10þ4,þ17þ4,þ6þ4,þ10þ10,þ17þ4,þ10,þ17þ4,þ6,þ10þ6,þ10,þ17þ4,þ6,þ17

þ4,þ6,þ10,þ17þ4,þ4þ4,þ4,þ6

þ4,þ4,þ6,þ10þ6,þ6

þ6,þ6,þ10þ6,þ10,þ10

þ6,þ10,þ17,þ17þ4,þ10,þ17,þ17þ6,þ17,þ17Othersa24.201.2017.2015.00dd31.20dddddd1.00ddddd1.403.00dddd5.80

683/9963.733.533.933.072.53d2.271.332.071.87d1.005.07d1.004.13ddddddddd4.47

694/997.607.8010.60d1.135.07d4.6033.40ddd2.13d23.071.07ddddddddd3.53

387/0017.472.8030.872.672.273.2715.07d6.47ddd3.532.20ddddd2.201.271.33ddd8.60

454/0020.552.4027.022.135.3414.085.34d3.80d1.33dd3.402.741.07ddd1.20dddd1.208.40

192/0153.077.407.131.807.331.53d2.874.53ddd1.67d3.202.00ddddddddd7.47

131/0518.408.60d15.805.40dd4.80d16.809.2014.00ddddddddddd1.20d5.80

241/0553.809.004.00ddddd8.80ddddddd8.6013.60ddddddd2.20

88/0651.003.802.602.202.60d4.001.202.603.601.202.405.201.801.607.001.20d1.40dddddd4.60

363/099.80d6.208.607.607.4020.20ddd10.80dd23.20d1.00dddddd1.20dd4.00

The10studypatientsarefurtherdetailedinTable1.

Clonesdetectedbybothinterphasefluorescenceinsituhybridizationandconventionalcytogenetics(Table1)arehighlightedinbolditalictype.aCumulativepercentageformultipleverysmallclones(!1%each).

A.Talamoetal./CancerGeneticsandCytogenetics203(2010)209e214213

Table5

Chromosomalinstabilityatdiseasepresentationin10studypatientswithhighhyperdiploidacutelymphoblasticleukemiaandin10negativecontrolsubjects

Modalnumber(cellsdifferingfrommodalnumber,%)

Case2385/95683/99694/99387/00454/00192/01131/05241/0588/06363/09199/07446/07619/071085/071159/07600/090/081198/081538/08284/09

Chr4

Chr6

Chr1032222232232222222222(47.60)(22.80)(6.60)(32.33)(19.61)(12.00)(41.40)(NA)(35.00)(33.40)(4.80)(4.80)(2.50)(3.80)(4.80)(4.20)(3.40)(4.40)(1.40)(3.20)

Chr1722222222232222222222(9.20)(18.33)(39.67)(15.80)(38.29)(24.27)(41.80)(NA)(25.60)(49.00)(7.00)(9.60)(7.10)(7.00)(9.60)(7.60)(9.00)(6.40)(5.60)(5.20)

Average2.522.52.252.2522.5222.752222222222(27.65)(22.23)(23.84)(25.88)(28.27)(22.90)(44.73)(36.90)(32.40)(40.40)(5.55)(6.35)(4.18)(4.53)(5.90)(4.95)(6.10)(5.35)(3.20)(4.65)

Studypatients2(5.80)3(48.00)2(24.87)2(22.93)3(26.47)3(22.60)2(21.27)3(34.13)2(16.88)3(38.29)2(29.33)2(26.00)3(51.00)2(NA)2(44.00)2(29.80)2(35.20)2(33.80)2(NA)3(38.80)Negativecontrolsubjects2(6.20)2(4.20)2(6.00)2(5.00)2(4.90)2(2.20)2(5.50)2(1.80)2(5.40)2(3.80)2(3.80)2(4.20)2(6.80)2(5.20)2(5.60)2(5.00)2(3.40)2(2.40)2(5.80)2(4.40)

Abbreviations:NA,notaneuploid.

StudypatientsandcontrolsubjectsarefurtherdetailedinTable1.

ThedistributionofCINvaluesbychromosomeandpatientgroupispresentedinFigure2.Basedondataob-tained,samplesweresubdividedintotwodistinctsubgroups,onebeingtheHeHALLpatientswithrelativelyhighCINvalues(range,27.9e32.7%)andtheotherthenegativecontrolsubjectswithmuchlowervalues(range,3.7e7.4%).4.Discussion

MostFISHstudiesindicatethatusingtwodifferentprobesissufficienttodistinguishdiploidfromaneuploidclones.Nonetheless,usingmorethantwoprobeshastheadvantageofallowingrecognitionofadditionalclonalpopulationsandidentificationofhighclonalheterogeneity[6,18].Inthisrespect,thetwonotablequalitiesofautomatedfour-colorI-FISHarethatalargenumberofnucleicanbeobservedandavarietyofclonalaneuploidcombinationsidentified,evenifpresentinasmallnumberofcells.AlongwiththelargerclonesidentifiedbothbyCCandI-FISH,theI-FISHobservationsrevealedanumberofadditionalclonesofvarioussize,someofthembeingverysmall.Thepresentfindingscorroborateourpreviousresultsandthewidelyre-porteddiscrepanciesbetweenCCandI-FISH,mainlyduetothedifferencesinthesensitivityofbothapproaches[11],andalsodemonstrateahighlevelofclonalchromosomeheterogeneityinHeHALLatinitialpresentation.

Becausehighclonalheterogeneityislikelyduetoananeuploidyresultingfromachromosomalinstability,wecalculatedtheCINvaluesforbothgroupsofpatients.Initiallycalculatedtotesttherateofchangeinchromosomenumberofdifferentcolorectalcelllinesthroughanumberofgenerations,CINvalueshavesincebeenusedtotestforchro-mosomalinstabilityincelllines,solidtumors,andmyelodys-plasticsyndromesatfirstpresentation[6e8,19].OurdatarevealedgenuinedifferencesintheratesofchromosomegainorlossinpatientswithHeHALL,comparedwithnegativecontrols.Instudypatients,CINvaluesweremuchhigherthanthoseinthenegativecontrolgroup.ThecontrolgrouppercentageswerecomparabletothebackgroundnumbersobservedbyLengaueretal.[4]innear-diploidcelllinesandinnormallymphocytes,aswellastothenumericalCINlevelsdetectedbyHeiligetal.[8]intheircontrolpatients(Table5).ItthusappearsthatHeHALLhasnumer-icalCINatdiseasepresentation.OurpresentfindingsareconsistentwithkaryotypicandFISHobservations,suggest-ingthatHeHALLmaybegeneticallyunstable[12].

ThischromosomalinstabilityisprobablyresponsibleforthekaryotypicheterogeneitydetectedbyI-FISHandforthesimultaneouspresenceofnumerousrelatedandunrelatedclones,someofthemundetectedinCCinvestiga-tionbecauseoftheirsmallsizeorlowproliferationrate.In7ofthe10studypatients,cloneswithtwoorthreeconcom-itantaneuploidiesweremorefrequentthanthosewithasingletrisomy,illustratingapossibleproliferativeadvan-tageofcellswithtwoormoreaneuploidies,relativetothosewithasingleaneuploidy(Table4).Consideringthenonrandompatternofadditionalchromosomes,certainchromosomecombinationsmayconferaproliferativeadvantagetoleukemiccellsandthusleadtoanincreasedcapacityofclonalexpansionandclonalevolution.

214

A.Talamoetal./CancerGeneticsandCytogenetics203(2010)209e214

0504)0%3( NIC02010461017Chromosome

Fig.2.Distributionofchromosomalinstability(CIN)valuesforchromo-somes4,6,10,and17inhighhyperdiploidacutelymphoblasticleukemiapatients(solidsymbols)andinnegativecontrolpatients(opensymbols)atdiseasepresentation.

FurtherstudiesareneededtodeterminewhetherCINisageneralfeatureofHeHALL,howitbehavesduringdiseaseevolution,andtowhatextentitmayaffectoutcomeandsoconstituteadditionalusefulinformationforprog-nosticassessmentandtherapydecisionmaking.

Acknowledgments

WeareindebtedtoDr.MayaBeckPopovic,Dr.CorneliaDessing,ProfessorsMichelDuchosalandOlivierSpertini(UniversityHospital,Lausanne),Dr.UrsHess(CantonalHospital,St.Gallen),Dr.ThomasPabst(UniversityHospital,Bern),Dr.UrsSchanz(UniversityHospital,Zurich),ProfessorAndr󰀁eTichelli(UniversityHospital,Basel),Dr.Val󰀁erieFrossard(ValaisHospital,Sion),Dr.MichaelGregor(CantonalHospital,Lucerne),andDr.OliviaPagani(RegionalHospital,Mendrisio)forreferringpatientsamples.WethankthecollaboratorsoftheCancerCytogeneticsUnit(MedicalGeneticsService,UniversityHospitalandUniversityofLausanne,Lausanne).WeareindebtedtoAnneDevaudforhertechnicalassistance.WearegratefultoProfessorJacquesS.Beckmann(MedicalGeneticsService,DepartmentofMedicalGenetics,UniversityHospitalandUniversityofLausanne,Lausanne)andtoDr.GuyvanMelle(InstituteofSocialandPreventiveMedicine,UniversityofLausanne,Lausanne).WethanktheGRAALLandSAKKcooperativegroupsforallowingustoanalyzethesamplesfromthepatientswhowereincludedintheGRAALL2005studyandofonepatientincludedintheLALA-94study.WeareindebtedalsototheMacheGaensslenStiftung(Schweiz)forawardtoProfessorMartineJotterand.

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