简介：Objective:ActivatingKRASmutationsarethemostcommondriversinthedevelopmentofnon-smallcelllungcancer(NSCLC).However,unsuccessoftreatmentbydirectinhibitionofKRAShasbeenproven.DeregulationofPI3KsignalingplaysanimportantroleintumorigenesisanddrugresistanceinNSCLC.TheactivityofPI3Kα-selectiveinhibitionagainstKRAS-mutatedNSCLCremainslargelyunknown.Methods:CellproliferationwasdetectedbysulforhodamineBassay.Cellcycledistributionandapoptosisweremeasuredbyflowcytometry.CellsignalingwasassessedbyWesternblotandimmunohistochemistry.RNAinterferencewasusedtodown-regulatetheexpressionofcyclinD1.HumanNSCLCxenograftswereemployedtodetecttherapeuticefficacyinvivo.Results:CYH33possessedvariableactivityagainstapanelofKRAS-mutatedNSCLCcelllines.AlthoughCYH33blockedAKTphosphorylationinalltestedcells,RbphosphorylationdecreasedinCYH33-sensitive,butnotinCYH33-resistantcells,whichwasconsistentwithG1phasearrestinsensitivecells.CombinedtreatmentwiththeCDK4/6inhibitor,PD0332991,andCYH33displayedsynergisticactivityagainsttheproliferationofbothCYH33-sensitiveandCYH33-resistantcells,whichwasaccompaniedbyenhancedG1-phasearrest.Moreover,down-regulationofcyclinD1sensitizedNSCLCcellstoCYH33.Reciprocally,CYH33abrogatedthePD0332991-inducedup-regulationofcyclinD1andphosphorylationofAKTinA549cells.Co-treatmentwiththesetwodrugsdemonstratedsynergisticactivityagainstA549andH23xenografts,withenhancedinhibitionofRbphosphorylation.Conclusions:SimultaneousinhibitionofPI3KαandCDK4/6displayedsynergisticactivityagainstKRAS-mutatedNSCLC.ThesedataprovideamechanisticrationaleforthecombinationofaPI3KαinhibitorandaCDK4/6inhibitorforthetreatmentofKRASmutatedNSCLC.