BackgroundInformation | I.TESTPRINCIPLE TheUPSTATE®colorimetricSTAR(SignalTransductionAssayReaction)ELISAkitisasolidphasesandwichenzymelinkedimmunosorbentassaythatprovidesafast,sensitivemethodtodetectspecificlevelsofsignalingtargetsinwholecellextracts.TheEGFRplateiscoatedwithaspecificmousemonoclonalanti-EGFRcaptureantibody.SamplelysateorthestandardincludedinthekitareincubatedinthemicrowellsallowingEGFRantigentobecapturedintheplatewells.Theplateisthenwashedtoremoveanyun-boundnon-nspecificmaterial.Aspecificrabbitanti-EGFRantibodyisaddedtodetectthecapturedfulllengthEGFRontheplatewell.TheunbounddetectionantibodyiswashedawayfollowedbyincubationwithanHRP-conjugatedanti-rabbitantibody.AftertheadditionofTMBsubstrateandstopsolutiontheabsorbanceismeasuredat450nmusingaplatereader.Thisallowsforasensitiveenzymaticdetectionofthesample. Theentireassaytakeslessthan5hourstocompletewithminimalhands-ontime.Manyofthereagentsaresuppliedinready-touseformulationsforeaseofuse.ThekitalsoincludesastandardthatisrunasbothapositivecontrolandtotogenerateastandardcurveforEGFRmeasurement.
II.EGFRBACKGROUND Epidermalgrowthfactorreceptor(EGFR)isareceptortyrosinekinasethatplaysakeyroleintheregulationofessentialnormalcellularprocessesandinthepathophysiologyofhyperproliferativediseasessuchascancer.Epidermalgrowthfactorreceptor(EGFR)isareceptortyrosinekinaseknowntobeessentialformediationofbothproliferativeandsurvivalsignalstocells.ActivationoftheEGFRsignalingpathwayhasbeenlinkedwithincreasedcellproliferation,angiogenesis,metastasisanddecreasedapoptosis.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. |