Sánchez-Paulete, Alfonso RCueto, Francisco J.Martínez-López, MaríaLabiano, SaraMorales-Kastresana, AizeaRodríguez-Ruiz, María EJure-Kunkel, MariaAzpilikueta, ArantzaAznar, M AngelaQuetglas, José ISancho, DavidMelero, Ignacio2020-04-232020-04-232016-01Cancer Discov. 2016; 6(1):71-92159-8274http://hdl.handle.net/20.500.12105/9721UNLABELLED: Weak and ineffective antitumor cytotoxic T lymphocyte (CTL) responses can be rescued by immunomodulatory mAbs targeting PD-1 or CD137. Using Batf3(-/-) mice, which are defective for cross-presentation of cell-associated antigens, we show that BATF3-dependent dendritic cells (DC) are essential for the response to therapy with anti-CD137 or anti-PD-1 mAbs. Batf3(-/-) mice failed to prime an endogenous CTL-mediated immune response toward tumor-associated antigens, including neoantigens. As a result, the immunomodulatory mAbs could not amplify any therapeutically functional immune response in these mice. Moreover, administration of systemic sFLT3L and local poly-ICLC enhanced DC-mediated cross-priming and synergized with anti-CD137- and anti-PD-1-mediated immunostimulation in tumor therapy against B16-ovalbumin-derived melanomas, whereas this function was lost in Batf3(-/-) mice. These experiments show that cross-priming of tumor antigens by FLT3L- and BATF3-dependent DCs is crucial to the efficacy of immunostimulatory mAbs and represents a very attractive point of intervention to enhance their clinical antitumor effects. SIGNIFICANCE: Immunotherapy with immunostimulatory mAbs is currently achieving durable clinical responses in different types of cancer. We show that cross-priming of tumor antigens by BATF3-dependent DCs is a key limiting factor that can be exploited to enhance the antitumor efficacy of anti-PD-1 and anti-CD137 immunostimulatory mAbs.engAMhttp://creativecommons.org/licenses/by-nc-nd/4.0/AnimalsAntibodies, MonoclonalBasic-Leucine Zipper Transcription FactorsCell Line, TumorDendritic CellsHumansImmunotherapyLymphocyte ActivationMelanoma, ExperimentalMiceMice, TransgenicProgrammed Cell Death 1 ReceptorRepressor ProteinsTumor Necrosis Factor Receptor Superfamily, Member 9Attribution-NonCommercial-NoDerivatives 4.0 Internacional264939616171-910.1158/2159-8290.CD-15-05102159-8290Cancer discoveryopen access