
Human CD47 (IAP, Integrin Associated Protein) is a broadly expressed Ig superfamily glycoprotein of about 50kD with a long extracellular Ig like domain, 5 transmembrane domains and an alternatively spliced intracellular c-terminal domain. It interacts with it ligand SIRP alpha (CD172a, Signal Regulatory Protein) expressed mainly on myeloid cells serving as a negative immune regulator, inhibiting phagocytosis. The CD47-SIRPa axis is being investigated as possible anti-tumor immune intervention point. Blockade of this interaction has shown promise in models of HNSCC(2), Glioma(3) and Breast Cancer(4)
Isotype: Mouse IgG1k
Immunogen: Recombinant human CD47 (extracellular Ig domain)
Specificity: Clone ANC2F6 binds to an epitope within the extracellular Ig-like domain of human CD47.
References:
1) Xiaojuan Liu, Yang-xin Fu, et al. (2017) J Hematol Oncol 10:12. doi:10.1186/s13045-016-0381-z PMID: 28077173.
2) Wu L, Sun ZJ, et al. (2018) Oncoimmunology 7(4): e1397248. Doi: 10.1080/2162402X.2017.1397248.
3)Lif F, Jiang X, et al. (2017) Oncoimmunology 7(2): e1391973. doi: 10.1080/2162402X.2017.1391973.
4) Norman MZ, Janji B, et al. (2018) Oncoimmunology. 7(4):e1345415. doi: 10.1080/2162402X.2017.1345415.
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QianWang,JessamyTiffen,CharlesG.Bailey,MelanieL.Lehman,WilliamRitchie,LadanFazli,CynthiaMetierre,Yue(Julie)Feng,EstelleLi,MartinGleave,GrantBuchanan,ColleenC.Nelson,JohnE.J.Rasko,JeffHolst
Correspondenceto:JeffHolst,PhD,OriginsofCancerLaboratory,LockedBag6,Newtown,NSW2042Australia.(e-mail:j.holst@centenary.org.au).
BackgroundL-typeaminoacidtransporters(LATs)uptakeneutralaminoacidsincludingL-leucineintocells,stimulatingmammaliantargetofrapamycincomplex1signalingandproteinsynthesis.LAT1andLAT3areoverexpressedatdifferentstagesofprostatecancer,andtheyareresponsIBLeforincreasingnutrientsandstimulatingcellgrowth.
MethodsWeexaminedLAT3proteinexpressioninhumanprostatecancertissuemicroarrays.LATfunctionwasinhibitedusingaleucineanalog(BCH)inandrogen-dependentand-independentenvironments,withgeneexpressionanalyzedbymicroarray.APC-3xenograftmousemodelwasusedtostudytheeffectsofinhibitingLAT1andLAT3expression.ResultswereanalyzedwiththeMann-WhitneyUorFisherexacttests.Allstatisticaltestsweretwo-sided.
ResultsLAT3proteinwasexpressedatallstagesofprostatecancer,withastatisticallysignificantdecreaseinexpressionafter4–7monthsofneoadjuvanthormonetherapy(4–7monthmean=1.571;95%confidenceinterval=1.155to1.987vs0month=2.098;95%confidenceinterval=1.962to2.235;P=.0187).InhibitionofLATfunctionledtoactivatingtranscriptionfactor4–mediatedupregulationofaminoacidtransportersincludingASCT1,ASCT2,and4F2hc,allofwhichwerealsoregulatedviatheandrogenreceptor.LATinhibitionsuppressedM-phasecellcyclegenesregulatedbyE2Ffamilytranscriptionfactorsincludingcriticalcastration-resistantprostatecancerregulatorygenesUBE2C,CDC20,andCDK1.InsilicoanalysisofBCH-downregulatedgenesshowedthat90.9%arestatisticallysignificantlyupregulatedinmetastaticcastration-resistantprostatecancer.Finally,LAT1orLAT3knockdowninxenograftsinhibitedtumorgrowth,cellcycleprogression,andspontaneousmetastasisinvivo.
ConclusionInhibitionofLATtransportersmayprovideanoveltherapeutictargetinmetastaticcastration-resistantprostatecancer,viasuppressionofmammaliantargetofrapamycincomplex1activityandM-phasecellcyclegenes.
L-typeaminoacidtransporters(LATs)supplycellswithlargeneutralaminoacids,whicharenotonlyrequiredforproteinsynthesisbutalsocontributetovarioussignalingpathways.Intracellularleucinelevelsaresensedbytheleucyl-transferRNAsynthetase,previouslyknowntocatalyzetheadenosinetriphosphate–dependentligationofL-leucinetotransferRNAduringproteinsynthesis(1,2).Leucyl-transferRNAsynthetaseactivatestheRagguanosinetriphosphatasecomplexandbindstoRaptortoactivatemammaliantargetofrapamycincomplex1(mTORC1)signalingonthesurfaceoflysosomes(1–3).Inthiswayleucineisnotonlyanessentialaminoacidbutactsasarate-limitingsignalingmoleculeinthemTORC1pathway.
Incellsdeprivedofaminoacids,thereisanaccumulationofunchargedtransferRNA,whichbindstoandactivatesthegeneralcontrolnonrepressed2(GCN2)kinase.Inturn,GCN2phosphorylatesthetranslationinitiationfactor2α(eIF2α)onserine51,triggeringtranslationalupregulationofactivatingtranscriptionfactor(ATF)4(4).ATF4itselfupregulatestheexpressionofaminoacidtransportersasameansofrestoringintracellularaminoacidlevels(5).Therefore,understandinghowaminoacidtransportersregulateintracellularleucinelevels,andgeneratingnovelinhibitorsofthesetransporters,mayleadtopotentsuppressorsofmTORC1signaling.
ThetwodistinctfamiliesofLATsare1)solutecarrier7(SLC7)members(LAT1/SLC7A5andLAT2/SLC7A8),whichmediateNa+-independentneutralaminoacidexchangeasheterodimerswiththe4F2cell-surfaceantigenheavychain(4F2hc/SLC3A2/CD98)glycoprotein(6,7);and2)SLC43proteins(LAT3/SLC43A1andLAT4/SLC43A2)thatmediateNa+-independentuniportofneutralaminoacids(8,9).AlthoughtheexpressionofeachLATmembervariesdramaticallyindifferenttissues,thesetransportersarecommonlyupregulatedincancer.IncreasedLAT1expressionhasbeendetectedinlungcancer,coloncancer,breastcancer,headandneckcancer,genitalcancers,andsofttissuesarcomas(10–12).WeandothershaveshownthatLAT1andLAT3areoverexpressedinprostatecancer(11–14),withLAT1expressionincreasedinmetastasiscomparedwithprimarycancer(10,12).
WehypothesizedthatinhibitionofLAT1andLAT3mayofferaneffectivetherapeuticapproachforprostatecancer.
转运体是介导分子或离子转运跨过生物膜的物质。通常是蛋白质或酶。说得简单一点就是“运输工具”
受体是能与细胞外专一信号分子(配体)结合引起细胞反应的蛋白质。受体与配体结合即发生分子构象变化,从而引起细胞反应,如介导细胞间信号转导、细胞间黏合、细胞胞吞等细胞过程。它起的是“传达员” 的作用

