BackgroundInformation | I.TESTPRINCIPLE TheUPSTATE®colorimetricSTAR(SignalTransductionAssayReaction)ELISAkitisasolidphasesandwichenzymelinkedimmunosorbentassaythatprovidesafast,sensitivemethodtodetectspecificlevelsofsignalingtargetsinwholecellextracts.TheEGFRplateiscoatedwithaspecificmousemonoclonalEGFRcaptureantibody.SamplelysateorthestandardincludedinthekitareincubatedinthemicrowellsallowingEGFRantigentobecaptured.Theplateisthenwashedtoremoveanyunboundnon-specificmaterial.Aspecificrabbitanti-phospho-EGFRantibodyisaddedtodetectthecapturedphosphorylaterEGFR(Tyr1068)ontheplatewell.TheunbounddetectionantibodyiswashedawayfollowedbyincubationwithanHRP-conjugatedanti-rabbitantibody.AftertheadditionofTMBsubstrateandstopsolutiontheabsorbanceismeasuredat450nmusingaplatereader.Thisallowsforasensitiveenzymaticdetectionofthesample. Theentireassaytakeslessthan5hourstocompletewithminimalhands-ontime.Manyofthereagentsaresuppliedinready-touseformulationsforeaseofuse.ThekitalsoincludesastandardthatisrunasbothapositivecontrolandtogenerateastandardcurveforphosphorylatedEGFR(Tyr1068)measurement.
II.EGFRBACKGROUND
Epidermalgrowthfactorreceptor(EGFR)isareceptortyrosinekinasethatplaysakeyroleintheregulationofessentialnormalcellularprocessesandinthepathophysiologyofhyperproliferativediseasessuchascancer.EGFRisareceptortyrosinekinaseknowntobeessentialformediationofbothproliferativeandsurvivalsignalstocells.ActivationoftheEGFRsignalingpathwayhasbeenlinkedwithincreasedcellproliferation,angiogenesis,metastasis,anddecreasedapoptosis.EGFRisfoundinmostsolidtumorsanditsautophosphorylationactivatestheintrinsickinaseactivitytowardheterologoussubstrates,aswellascreatingdockingsitesforadapterproteinsformultipleadapterproteinstobindandnucleatesignalingcomplexesthatactivatetheRas,PI3Kinase,andPLCpathways.ManyoftheEGFRmutationsaredirectlyrelatedtovariousdiseasesandarethetargetofnumerousdrugs.Forinstance,theaminoacidsubstitutionL858RisoneofseveralheterozygousmutationsthathavebeenidentifiedinNon-Small-CellLungCancer(NSCLC)patientswhohaveclinicalresponsestotheEGFRinhibitorIressa®.ThereissomeevidencethatthesemutationsresultinelevatedactivityandenhancedsensitivitytoIressa®.InpatientswithtumorsbearingIressa®-sensitivemutations,resistantsubclonescontaininganadditionalEGFRmutation,T790M,emergeinthepresenceofthedrug.IthasbeenshownexperimentallythattheT790Mmutationleadstohigh-levelfunctionalresistancetoIressa®.InpatientswithtumorsbearingIressa®-sensitivemutations(eg.L858R,L861Q),resistantsubclonescontainingtheT790Mmutationemergeinthepresenceofthedrug. |