Depletion of conventional type-1 dendritic cells in established tumors suppresses immunotherapy efficacy.

The ability of conventional type-1 dendritic cells (cDC1) to cross-present tumor antigens to CD8+ T cells is critical for the induction of antitumor cytotoxic T lymphocytes. Mice that are constitutively deficient in cDC1 cells have been reported to fail to respond to immunotherapy strategies based on checkpoint inhibitors. However, further work is needed to clarify the precise time during immunotherapy treatment that cDC1 cells are required for the beneficial effect of treatment. Here, we used a refined XCR1-DTR-Venus transgenic mouse model to acutely deplete cDC1 cells and trace their behavior using intravital microscopy. Diphtheria toxin-mediated cDC1 depletion prior to immunotherapy treatment with anti-PD-1 and/or anti-CD137 immunostimulatory monoclonal antibodies (mAbs) completely ablated anti-tumor efficacy. The efficacy of adoptive T-cell therapy was also hampered by prior cDC1 depletion. After the onset of immunotherapy treatment, depletion of cDC1s only moderately reduced the therapeutic efficacy of anti-PD-1 and anti-CD137 mAbs. Intravital microscopy of liver-engrafted tumors revealed changes in the intratumoral behavior of cDC1 cells in mice receiving immunotherapy, and treatment with diphtheria toxin to deplete cDC1s impaired tumor T-cell infiltration and function. These results reveal that the functional integrity of the cDC1 compartment is required at the onset of various immunotherapies to successfully treat established tumors.This work was supported by Spanish Ministry of Economy and Competitiveness and Spanish Ministry of Research (MINECO SAF2014-52361-R and SAF 2017-83267-C2-1R and PID2020-112892RB-100, PID2020-113174-RA-100 [AEI/FEDER,UE], financed by MCIN/AEI/10.13039/501100011033), Cancer Research Institute under the CRI-CLIP, Asociación Española Contra el Cancer (AECC) Foundation under Grant GCB15152947MELE, Joint Translational Call for Proposals 2015 (JTC 2015) TRANSCAN-2 (code: TRS-2016-00000371), projects PI14/01686, PI13/00207, PI16/00668, PI19/01128, funded by Instituto de Salud Carlos III and co-funded by European Union (ERDF, “A way to make Europe”), European Commission within the Horizon 2020 Programme (PROCROP - 635122), Gobierno de Navarra Proyecto LINTERNA Ref: 0011–1411, Mark Foundation, Fundación BBVA and Fundación Olga Torres. AT is supported by the Ramon y Cajal program from the Spanish Ministry of Science (RYC2019-026406-I financiada por MCIN/AEI /10.13039/501100011033 y por El FSE invierte en tu futuro).S

CD137 (4-1BB) requires physically associated cIAPs for signal transduction and antitumor effects

CD137 (4-1BB) is a member of the TNFR family that mediates potent T cell costimulatory signals upon ligation by CD137L or agonist monoclonal antibodies (mAbs). CD137 agonists attain immunotherapeutic antitumor effects in cancer mouse models, and multiple agents of this kind are undergoing clinical trials. We show that cIAP1 and cIAP2 are physically associated with the CD137 signaling complex. Moreover, cIAPs are required for CD137 signaling toward the NF-κB and MAPK pathways and for costimulation of human and mouse T lymphocytes. Functional evidence was substantiated with SMAC mimetics that trigger cIAP degradation and by transfecting cIAP dominant-negative variants. Antitumor effects of agonist anti-CD137 mAbs are critically dependent on the integrity of cIAPs in cancer mouse models, and cIAPs are also required for signaling from CARs encompassing CD137’s cytoplasmic tail.I.M. has been granted with PID2020-112892RB funded by MICIN/AEI/10.13039/501100011033 and SAF2017-83267-C2-1-R funded by MICIN/AEI/10.13039/501100011033/ and by FEDER “Una manera de hacer Europa,” (HR21-00083) the Fundación La Caixa, “MINCITH. Metabolic requirements for immune INfiltration in effective Cancer ImmunoTHerapy” “AYUDAS FUNDACIÓN BBVA A EQUIPOS DE INVESTIGACIÓN CIENTÍFICA 2019” Fundación BBVA, the Instituto de Salud Carlos III (PI20/00002 and PI19/01128), cofinanced by the Fondos FEDER “A way to make Europe” and Joint Translational Call for Proposals 2015 (JTC 2015), TRANSCAN456 2 (code TRS-2016-00000371), and the Gobierno de Navarra Proyecto LINTERNA (reference 0011-1411-2020-000075). Funding was also received from B. J. Baselga (Fundación FERO) and the T2-EVOLVE project from the EU. I.M. and M.A. receive grant funding from Pharmamar and Highlight Therapeutics. M.A. is supported by AECC (INVES1904ALVA). J.M.Z. has been granted with PID2019-110405RB-I00 funded by MICIN/AEI/10.13039/501100011033 and with P2022/BMD-7225 funded by Consortium in Biomedicine of Comunidad de Madrid.Peer reviewe

Three-dimensional colon cancer organoids model the response to CEA-CD3 T-cell engagers

Rationale: The CEA-CD3 T cell bispecific antibody cibisatamab (CEA-TCB) is currently undergoing clinical trials. Here we study its performance against three-dimensional tumor organoids in cocultures with T cells as compared to a higher affinity CEACAM5-CD3 (CEACAM5-TCB) bispecific antibody using time-lapse confocal microscopy. Methods: Pre-labelled spheroids derived from colon cancer cell lines and primary organoids derived from four colorectal cancer surgical specimens, which expressed different graded levels of CEA, were exposed in cocultures to T lymphocytes. Cocultures were treated with CEA-CD3 T-cell engagers and were followed by live confocal microscopy. Caspase 3 activation detected in real-time was used as an indicator of tumor cell death. Co-cultures were also set up with autologous tumor-associated fibroblasts to test the co-stimulatory effect of a fibroblast activated protein (FAP)- targeted 4-1BBL bispecific antibody fusion protein currently undergoing clinical trials. Results: Tumor-cell killing of 3D colon carcinoma cultures was dependent on the levels of surface CEA expression, in such a way that the lower affinity agent (CEA-TCB) did not mediate killing by human preactivated T cells below a certain CEA expression threshold, while the high affinity construct (CEACAM5-TCB) remained active on the low CEA expressing organoids. Modelling heterogeneity in the levels of CEA expression by coculturing CEA high and low organoids showed measurable but weak bystander killing. Cocultures of tumor organoids, autologous fibroblasts and T cells allowed to observe a costimulatory effect of anti-FAP-4-1BBL both to release IFNγ and to attain more efficacious tumor cell killing. Conclusion: Three-dimensional tumor cocultures with T cells using live confocal microscopy provide suitable models to test the requirements for colon-cancer redirected killing as elicited by CEA-targeted T-cell engagers undergoing clinical trials and treatment allow combinations to be tested in a relevant preclinical system

Intratumoral co‐injection of NK cells and NKG2A‐neutralizing monoclonal antibodies

Abstract NK‐cell reactivity against cancer is conceivably suppressed in the tumor microenvironment by the interaction of the inhibitory receptor NKG2A with the non‐classical MHC‐I molecules HLA‐E in humans or Qa‐1b in mice. We found that intratumoral delivery of NK cells attains significant therapeutic effects only if co‐injected with anti‐NKG2A and anti‐Qa‐1b blocking monoclonal antibodies against solid mouse tumor models. Such therapeutic activity was contingent on endogenous CD8 T cells and type‐1 conventional dendritic cells (cDC1). Moreover, the anti‐tumor effects were enhanced upon combination with systemic anti‐PD‐1 mAb treatment and achieved partial abscopal efficacy against distant non‐injected tumors. In xenografted mice bearing HLA‐E‐expressing human cancer cells, intratumoral co‐injection of activated allogeneic human NK cells and clinical‐grade anti‐NKG2A mAb (monalizumab) synergistically achieved therapeutic effects. In conclusion, these studies provide evidence for the clinical potential of intratumoral NK cell‐based immunotherapies that exert their anti‐tumor efficacy as a result of eliciting endogenous T‐cell responses

Intratumoral neoadjuvant immunotherapy based on the BO-112 viral RNA mimetic

ABSTRACTBO-112 is a poly I:C-based viral mimetic that exerts anti-tumor efficacy when intratumorally delivered in mouse models. Intratumoral BO-112 synergizes in mice with systemic anti-PD-1 mAbs and this combination has attained efficacy in PD1-refractory melanoma patients. We sought to evaluate the anti-tumor efficacy of BO-112 pre-surgically applied in neoadjuvant settings to mouse models. We have observed that repeated intratumoral injections of BO-112 prior to surgical excision of the primary tumor significantly reduced tumor metastasis from orthotopically implanted 4T1-derived tumors and subcutaneous MC38-derived tumors in mice. Such effects were enhanced when combined with systemic anti-PD-1 mAb. The anti-tumor efficacy of this neoadjuvant immunotherapy approach depended on the presence of antigen-specific effector CD8 T cells and cDC1 antigen-presenting cells. Since BO-112 has been successful in phase-two clinical trials for metastatic melanoma, these results provide a strong rationale for translating this pre-surgical strategy into clinical settings, especially in combination with standard-of-care checkpoint inhibitors

Soluble CD137 as a dynamic biomarker to monitor agonist CD137 immunotherapies

Background On the basis of efficacy in mouse tumor models, multiple CD137 (4-1BB) agonist agents are being preclinically and clinically developed. The costimulatory molecule CD137 is inducibly expressed as a transmembrane or as a soluble protein (sCD137). Moreover, the CD137 cytoplasmic signaling domain is a key part in approved chimeric antigen receptors (CARs). Reliable pharmacodynamic biomarkers for CD137 ligation and costimulation of T cells will facilitate clinical development of CD137 agonists in the clinic.Methods We used human and mouse CD8 T cells undergoing activation to measure CD137 transcription and protein expression levels determining both the membrane-bound and soluble forms. In tumor-bearing mice plasma sCD137 concentrations were monitored on treatment with agonist anti-CD137 monoclonal antibodies (mAbs). Human CD137 knock-in mice were treated with clinical-grade agonist anti-human CD137 mAb (Urelumab). Sequential plasma samples were collected from the first patients intratumorally treated with Urelumab in the INTRUST clinical trial. Anti-mesothelin CD137-encompassing CAR-transduced T cells were stimulated with mesothelin coated microbeads. sCD137 was measured by sandwich ELISA and Luminex. Flow cytometry was used to monitor CD137 surface expression.Results CD137 costimulation upregulates transcription and protein expression of CD137 itself including sCD137 in human and mouse CD8 T cells. Immunotherapy with anti-CD137 agonist mAb resulted in increased plasma sCD137 in mice bearing syngeneic tumors. sCD137 induction is also observed in human CD137 knock-in mice treated with Urelumab and in mice transiently humanized with T cells undergoing CD137 costimulation inside subcutaneously implanted Matrigel plugs. The CD137 signaling domain-containing CAR T cells readily released sCD137 and acquired CD137 surface expression on antigen recognition. Patients treated intratumorally with low dose Urelumab showed increased plasma concentrations of sCD137.Conclusion sCD137 in plasma and CD137 surface expression can be used as quantitative parameters dynamically reflecting therapeutic costimulatory activity elicited by agonist CD137-targeted agents

mRNAs encoding IL-12 and a decoy-resistant variant of IL-18 synergize to engineer T cells for efficacious intratumoral adoptive immunotherapy

Interleukin-12 (IL-12) gene transfer enhances the therapeutic potency of adoptive T cell therapies. We previ-ously reported that transient engineering of tumor-specific CD8 T cells with IL-12 mRNA enhanced their sys-temic therapeutic efficacy when delivered intratumorally. Here, we mix T cells engineered with mRNAs to ex-press either single-chain IL-12 (scIL-12) or an IL-18 decoy-resistant variant (DRIL18) that is not functionally hampered by IL-18 binding protein (IL-18BP). These mRNA-engineered T cell mixtures are repeatedly in-jected into mouse tumors. Pmel-1 T cell receptor (TCR)-transgenic T cells electroporated with scIL-12 or DRIL18 mRNAs exert powerful therapeutic effects in local and distant melanoma lesions. These effects are associated with T cell metabolic fitness, enhanced miR-155 control on immunosuppressive target genes, enhanced expression of various cytokines, and changes in the glycosylation profile of surface proteins, enabling adhesiveness to E-selectin. Efficacy of this intratumoral immunotherapeutic strategy is recapitu-lated in cultures of tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor (CAR) T cells on IL -12 and DRIL18 mRNA electroporation