Cell transformation, by kk

INTRODUCTION

ROLE IN CELL LINE CHARACTERIZATION

CAUSES OF TRANSFORMATION

METHODS OF TRANSFECTION
CHARACTERISTICS OF TRAANSFORMED CELLS
GENETIC INSTABILITY
IMMORTALIZATION
ABRERANT GROWTH CONTROL
TUMORIGENECITY
CHROMOSOMAL ABERATION

APPLICATION
CONCLUSION
REFERENCE

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CELL TRANSFORMATION 01 01
CELL TRANSFORMATION
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

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SYNOPSIS
CELL TRANSFORMATION 02
INTRODUCTION
ROLEINCELLLINECHARACTERIZATION
CAUSESOFTRANSFORMATION
METHODSOFTRANSFECTION

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CELL TRANSFORMATION 02
CHARACTERISTICSOFTRAANSFORMEDCELLS
GENETICINSTABILITY
IMMORTALIZATION
ABRERANTGROWTHCONTROL
TUMORIGENECITY
CHROMOSOMALABERATION
APPLICATION
CONCLUSION
REFERENCE

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CELL TRANSFORMATION 04 04
INTRODUCTION
Transformationofculturedcellsimpliesaspontaneousorinduced
permanentphenotypicchangeresultingfromaheritablechangein
DNAandgeneexpression.

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Transformationisassociatedwithgeneticinstabilityandthree
majorclassesofphenotypicchange:
immortalization,theacquisitionofaninfinitelifespan.
Malignancy
aberrantgrowthcontrol,thelossofcontactinhibitionofcell
motility,densitylimitationofcellproliferation,andanchorage
dependence,

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Itisimportantthattransformationcharacteristicsbeincluded
whenacelllineisvalidatedtodeterminewhetheritoriginatesfrom
neoplasticcellsorhasundergonetransformationinculture.
Thetransformationstatusmustbeknownwhenculturingcells
fromtumours,inordertoconfirmthatthecellsarederivedfromthe
neoplasticcomponentofthetumour,ratherthanfromnormal
equivalentcells,infiltratingfibroblasts,bloodvesselcells,or
inflammatorycells.
ROLEINCELLLINECHARACTERIZATION

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CAUSESOFTRANSFORMATION
Spontaneous
Infection with transforming virus
From gene transfection
Exposure to ionizing radiations.

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METHODSOFTRANSFECTION

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CHARACTERISTICS OF TRANSFORMED CELLS

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GENETIC INSTABILITY
Thecharacteristicsofacelllinedonotalwaysremainstable.In
additiontothephenotypicalterations,celllinesarepronetogenetic
instability.
Normalhumanfinitecelllinesareusuallygeneticallystable,but
celllinesfromotherspecies,particularlythemouse,aregenetically
unstableandtransformquitereadily.

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CHROMOSOMAL ABERRATION
Evidenceofgeneticrearrangementcanbeseeninchromosome
countsandkaryotypeanalysis.
Althoughthemousekaryotypeismadeupexclusivelyofsmall
telocentricchromosomes,severalmetacentricsariseinmany
continuousmurinecelllinesduetoRobertsonianfusionofthe
telomeres.

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IMMORTALIZATION
Theacquisitionofaninfinitelifespanbyacellisreferredtoas
immortalization.
Mostnormalcellshaveafinitelifespanof20to100generations,
butsomecells,notablythosefromrodentsandfrommosttumours,
haveindefinitelifespan,astheygoonproducingcontinuouscellline.

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CONTROL OF SENECENCE
Thefinitelifespanofculturedcellisregulatedbyabout10
senescencegenes.Thesedominantlyactinggenessynthesizeproduct
whichinhibitthecellcycleprogression.
Itisstronglybelievedthatimmortalizationoccursdueto
inactivationofthesomeofthecellcycleregulatorygeneseg.Rb,p53
genes.

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IMMORTALIZATION WITH VIRAL GENE
Anumberofviralgeneshavebeenusedtoimmortalizecells.It
hasbeenrecognizedforsometimethatSV40canbeusedto
immortalizecells,andthegeneresponsibleforthisappearstobethe
largeT(LT)gene.
Otherviralgenesthathavebeenusedtoimmortalizecellsare
adenovirusE1a,humanpapillomavirus(HPV)E6andE7etc.

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TELOMERASE INDUCED IMMORTALIZATION
Themostimportantcausesoffinitelifespanofcells(i.e.
Senescence)isduetotelomericshortening,followedbycell
death(apoptosis).
Ifthecellsaretransfectedwithtelomerasegenehtrt,the
lifespanofcellscanbeextended.Andasmallpopulationof
thesecellbecomeimmortal.

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ANCHORAGE INDEPENDENCE
Thereoccurseveralchangesonthecellsurfacesoftransformedcells.
Theseincludealterationinthecellsurfaceglycoproteinandintegrins,
andlossoffibronectin.Someofthetransformedcellmaytotallylack
celladhesionmolecules(CAMs)surfaceoftransformed.
Themodificationonthesurfaceoftransformedcellsleadsto
decreaseincell-cellandcellsubstrateadhesion.Thenetresultisthat
thereisareducedrequirementforattachmentandspreadingofthe
cellstoproliferate.

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CONTACT INHIBITION
Thetransformedcellsarecharacterizedbylossofcontact
inhibition.Thiscanbeobservedbythemorphologicalchanges
inthedisorientadanddisorganizedmonolayercells.
Thisresultinareduceddensitylimitationofgrowth,
consequentlyleadingtohighersaturationdensitycomparedto
normalcell.

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SERUM DEPENDENCE
Transformedcellshavealowerserumdependencethantheir
normalcounterpartsdueto,inpart,tothesecretionofgrowth
factorsbytumorcells.Thesefactorshavebeencollectively
describedasautocrinegrowthfactors.

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ONCOGENES
Autonomousgrowthcontrolisalsoachievedin
transformedcellsbyoncogenes.
AndthemodifiedGprotein,suchasmutantras,orbythe
overexpressionofgenesregulatingstagesinsignal
transduction(e.g.,srckinase).

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TUMORIGENICITY
Celltransformationisacomplexprocessthatoftenresultin
theformationofneoplasticcells.Thecelllineobtainedfrom
malignanttumorarealreadytransformed.Suchcellsmay
undergofurthertransformationinvitroculturedueto
Increasedgrowthrate
Immortalization
Reducedanchoreddependence

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APPLICATION
Celllinepreservation:
Animalcellcultureandmaintenancerequireexpertiseandexperience.These
celllinescannotbemaintainedforalongtime,insomecasesfreshbatchofcell
cultureshavetobeinitiatedandsomehastobetransferredtofreshmediafor
someperiodoftime.Someofthecelllinesaregeneticallytransformed.One
hastouseallhisingenuitytokeepthemintactandfunctional.
StudyofGenotypeandPhenotype:
Thestudyoftransformationhasimplicationsforcelllinecharacterization,
helpstoidentifygenotypicandphenotypicchangesrelatingtocancer,and
providestechnologywhichcanbeusedtoimmortalizecelllines

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Thetransformationofanimalcellswithforeigngeneticmaterial
offersanimportantmechanismforadvancingknowledgeabout
thestructureandfunctionofanimalgenomes,aswellasforthe
generationofanimalswithnewtraits.

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References
1.CULTURE OF ANIMAL CELLS 5
TH
EDITION : BY R. IAN
FRESHNEY
2. BIOTECHNOLOGY BY U. STAYANARAYAN.