Deletion of the inhibitory co-receptor CTLA-4 enhances and invigorates chimeric antigen receptor T cells.

Chimeric antigen receptor (CAR) T cell therapy targeting CD19 has achieved tremendous success treating B cell malignancies; however, some patients fail to respond due to poor autologous T cell fitness. To improve response rates, we investigated whether disruption of the co-inhibitory receptors CTLA4 or PD-1 could restore CART function. CRISPR-Cas9-mediated deletion of CTLA4 in preclinical models of leukemia and myeloma improved CAR T cell proliferation and anti-tumor efficacy. Importantly, this effect was specific to CTLA4 and not seen upon deletion of CTLA4 and/or PDCD1 in CAR T cells. Mechanistically, CTLA4 deficiency permitted unopposed CD28 signaling and maintenance of CAR expression on the T cell surface under conditions of high antigen load. In clinical studies, deletion of CTLA4 rescued the function of T cells from patients with leukemia that previously failed CAR T cell treatment. Thus, selective deletion of CTLA4 reinvigorates dysfunctional chronic lymphocytic leukemia (CLL) patient T cells, providing a strategy for increasing patient responses to CAR T cell therapy.

An NK-like CAR T cell transition in CAR T cell dysfunction.

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable success in hematological malignancies but remains ineffective in solid tumors, due in part to CAR T cell exhaustion in the solid tumor microenvironment. To study dysfunction of mesothelin-redirected CAR T cells in pancreatic cancer, we establish a robust model of continuous antigen exposure that recapitulates hallmark features of T cell exhaustion and discover, both in vitro and in CAR T cell patients, that CAR dysregulation is associated with a CD8+ T-to-NK-like T cell transition. Furthermore, we identify a gene signature defining CAR and TCR dysregulation and transcription factors, including SOX4 and ID3 as key regulators of CAR T cell exhaustion. Our findings shed light on the plasticity of human CAR T cells and demonstrate that genetic downmodulation of ID3 and SOX4 expression can improve the efficacy of CAR T cell therapy in solid tumors by preventing or delaying CAR T cell dysfunction.

Intratumoral nanoplexed poly I:C BO-112 in combination with systemic anti-PD-1 for patients with anti-PD-1-refractory tumors.

Intratumoral therapies, especially Toll-like receptor agonists, can trigger both the innate and adaptive immune systems. BO-112 is a nanoplexed form of polyinosinic:polycytidylic acid (poly I:C) that induces local and systemic immunotherapeutic effects in mouse models. In a multicenter phase 1 clinical trial, repeated intratumoral administrations of BO-112 induced an increase in tumor cell necrosis and apoptosis, as well as augmented immune reactivity according to gene expression profiling. The first three cohorts receiving BO-112 as a monotherapy resulted in a recommended dose of 1 mg that could be safely repeated. Two grade 3 to 4 adverse reactions in the form of reversible thrombocytopenia were reported. In a fourth cohort of 28 patients with tumors that had primary resistance to anti-programmed cell death protein-1 (PD-1), the combination of intratumoral BO-112 with nivolumab or pembrolizumab was also well tolerated, and 3 patients (2 with melanoma and 1 with renal cell carcinoma) achieved partial responses, with 10 more patients having stable disease at 8 to 12 weeks. Thus, local BO-112 combined with a systemic anti-PD-1 agent might be a strategy to revert anti-PD-1 resistance.

Intratumor Adoptive Transfer of IL-12 mRNA Transiently Engineered Antitumor CD8+ T Cells.

Retroviral gene transfer of interleukin-12 (IL-12) into T cells markedly enhances antitumor efficacy upon adoptive transfer but has clinically shown unacceptable severe side effects. To overcome the toxicity, we engineered tumor-specific CD8+ T cells to transiently express IL-12. Engineered T cells injected intratumorally, but not intravenously, led to complete rejections not only of the injected lesion but also of distant concomitant tumors. Efficacy was further enhanced by co-injection with agonist anti-CD137 mAb or by transient co-expression of CD137 ligand. This treatment induced epitope spreading of the endogenous CD8+ T cell immune response in a manner dependent on cDC1 dendritic cells. Mouse and human tumor-infiltrating T lymphocyte cultures can be transiently IL-12 engineered to attain marked immunotherapeutic effects.

Immunotherapeutic effects of intratumoral nanoplexed poly I:C.

Poly I:C is a powerful immune adjuvant as a result of its agonist activities on TLR-3, MDA5 and RIG-I. BO-112 is a nanoplexed formulation of Poly I:C complexed with polyethylenimine that causes tumor cell apoptosis showing immunogenic cell death features and which upon intratumoral release results in more prominent tumor infiltration by T lymphocytes. Intratumoral treatment with BO-112 of subcutaneous tumors derived from MC38, 4 T1 and B16-F10 leads to remarkable local disease control dependent on type-1 interferon and gamma-interferon. Some degree of control of non-injected tumor lesions following BO-112 intratumoral treatment was found in mice bearing bilateral B16-OVA melanomas, an activity which was enhanced with co-treatment with systemic anti-CD137 and anti-PD-L1 mAbs. More abundant CD8+ T lymphocytes were found in B16-OVA tumor-draining lymph nodes and in the tumor microenvironment following intratumoral BO-112 treatment, with enhanced numbers of tumor antigen-specific cytotoxic T lymphocytes. Genome-wide transcriptome analyses of injected tumor lesions were consistent with a marked upregulation of the type-I interferon pathway. Inspired by these data, intratumorally delivered BO-112 is being tested in cancer patients (NCT02828098).

A tumor-targeted trimeric 4-1BB-agonistic antibody induces potent anti-tumor immunity without systemic toxicity.

The costimulation of immune cells using first-generation anti-4-1BB monoclonal antibodies (mAbs) has demonstrated anti-tumor activity in human trials. Further clinical development, however, is restricted by significant off-tumor toxicities associated with FcγR interactions. Here, we have designed an Fc-free tumor-targeted 4-1BB-agonistic trimerbody, 1D8N/CEGa1, consisting of three anti-4-1BB single-chain variable fragments and three anti-EGFR single-domain antibodies positioned in an extended hexagonal conformation around the collagen XVIII homotrimerization domain. The1D8N/CEGa1 trimerbody demonstrated high-avidity binding to 4-1BB and EGFR and a potent in vitro costimulatory capacity in the presence of EGFR. The trimerbody rapidly accumulates in EGFR-positive tumors and exhibits anti-tumor activity similar to IgG-based 4-1BB-agonistic mAbs. Importantly, treatment with 1D8N/CEGa1 does not induce systemic inflammatory cytokine production or hepatotoxicity associated with IgG-based 4-1BB agonists. These results implicate FcγR interactions in the 4-1BB-agonist-associated immune abnormalities, and promote the use of the non-canonical antibody presented in this work for safe and effective costimulatory strategies in cancer immunotherapy.

CD137 (4-1BB) Costimulation Modifies DNA Methylation in CD8+ T Cell-Relevant Genes.

CD137 (4-1BB) costimulation imprints long-term changes that instruct the ultimate behavior of T cells that have previously experienced CD137 ligation. Epigenetic changes could provide a suitable mechanism for these long-term consequences. Genome-wide DNA methylation arrays were carried out on human peripheral blood CD8+ T lymphocytes stimulated with agonist monoclonal antibody to CD137, including urelumab, which is in phase I/II clinical trials for cancer immunotherapy. Several genes showed consistent methylation patterns in response to CD137 costimulation, which were confirmed by pyrosequencing in a series of healthy donors. CD96, HHLA2, CCR5, CXCR5, and CCL5 were among the immune-related genes regulated by differential DNA methylation, leading to changes in mRNA and protein expression. These genes are also differentially methylated in naïve versus antigen-experienced CD8+ T cells. The transcription factor TCF1 and the microRNA miR-21 were regulated by DNA methylation upon CD137 costimulation. Such gene-expression regulatory factors can, in turn, broaden the effects of DNA methylation by controlling expression of their target genes. Overall, chromatin remodeling is postulated to leave CD137-costimulated T lymphocytes poised to differentially respond upon subsequent antigen recognition. Accordingly, CD137 connects costimulation during priming to genome-wide DNA methylation and chromatin reprogramming. Cancer Immunol Res; 6(1); 69-78. ©2017 AACR.

CD69 is a direct HIF-1α target gene in hypoxia as a mechanism enhancing expression on tumor-infiltrating T lymphocytes.

CD69 is an early activation marker on the surface of T lymphocytes undergoing activation by cognate antigen. We observed intense expression of CD69 on tumor-infiltrating T-lymphocytes that reside in the hypoxic tumor microenvironment and hypothesized that CD69 could be, at least partially, under the control of the transcriptional hypoxia response. In line with this, human and mouse CD3-stimulated lymphocytes cultured under hypoxia (1% O2) showed increased expression of CD69 at the protein and mRNA level. Consistent with these findings, mouse T lymphocytes that had recently undergone hypoxia in vivo, as denoted by pimonidazole staining, were more frequently CD69+ in the tumor and bone marrow hypoxic tissue compartments. We found evidence for HIF-1α involvement both when using T-lymphocytes from inducible HIF-1α-/- mice and when observing tumor-infiltrating T-lymphocytes in mice whose T cells are HIF-1α-/-. Direct pro-transcriptional activity of HIF-1α on a newly identified hypoxia response element (HRE) found in the human CD69 locus was demonstrated by ChIP experiments. These results uncover a connection between the HIF-1α oxygen-sensing pathway and CD69 immunobiology.

Intratumoral Delivery of Immunotherapy-Act Locally, Think Globally.

Immune mechanisms have evolved to cope with local entry of microbes acting in a confined fashion but eventually inducing systemic immune memory. Indeed, in situ delivery of a number of agents into tumors can mimic in the malignant tissue the phenomena that control intracellular infection leading to the killing of infected cells. Vascular endothelium activation and lymphocyte attraction, together with dendritic cell-mediated cross-priming, are the key elements. Intratumoral therapy with pathogen-associated molecular patterns or recombinant viruses is being tested in the clinic. Cell therapies can be also delivered intratumorally, including infusion of autologous dendritic cells and even tumor-reactive T lymphocytes. Intralesional virotherapy with an HSV vector expressing GM-CSF has been recently approved by the Food and Drug Administration for the treatment of unresectable melanoma. Immunomodulatory monoclonal Abs have also been successfully applied intratumorally in animal models. Local delivery means less systemic toxicity while focusing the immune response on the malignancy and the affected draining lymph nodes.

Abscopal Effects of Radiotherapy Are Enhanced by Combined Immunostimulatory mAbs and Are Dependent on CD8 T Cells and Crosspriming.

Preclinical and clinical evidence indicate that the proimmune effects of radiotherapy can be synergistically augmented with immunostimulatory mAbs to act both on irradiated tumor lesions and on distant, nonirradiated tumor sites. The combination of radiotherapy with immunostimulatory anti-PD1 and anti-CD137 mAbs was conducive to favorable effects on distant nonirradiated tumor lesions as observed in transplanted MC38 (colorectal cancer), B16OVA (melanoma), and 4T1 (breast cancer) models. The therapeutic activity was crucially performed by CD8 T cells, as found in selective depletion experiments. Moreover, the integrities of BATF-3-dependent dendritic cells specialized in crosspresentation/crosspriming of antigens to CD8+ T cells and of the type I IFN system were absolute requirements for the antitumor effects to occur. The irradiation regimen induced immune infiltrate changes in the irradiated and nonirradiated lesions featured by reductions in the total content of effector T cells, Tregs, and myeloid-derived suppressor cells, while effector T cells expressed more intracellular IFNγ in both the irradiated and contralateral tumors. Importantly, 48 hours after irradiation, CD8+ TILs showed brighter expression of CD137 and PD1, thereby displaying more target molecules for the corresponding mAbs. Likewise, PD1 and CD137 were induced on tumor-infiltrating lymphocytes from surgically excised human carcinomas that were irradiated ex vivo These mechanisms involving crosspriming and CD8 T cells advocate clinical development of immunotherapy combinations with anti-PD1 plus anti-CD137 mAbs that can be synergistically accompanied by radiotherapy strategies, even if the disease is left outside the field of irradiation. Cancer Res; 76(20); 5994-6005. ©2016 AACR.

Hypoxia-induced soluble CD137 in malignant cells blocks CD137L-costimulation as an immune escape mechanism.

Hypoxia is a common feature in solid tumors that has been implicated in immune evasion. Previous studies from our group have shown that hypoxia upregulates the co-stimulatory receptor CD137 on activated T lymphocytes and on vascular endothelial cells. In this study, we show that exposure of mouse and human tumor cell lines to hypoxic conditions (1% O2) promotes CD137 transcription. However, the resulting mRNA is predominantly an alternatively spliced form that encodes for a soluble variant, lacking the transmembrane domain. Accordingly, soluble CD137 (sCD137) is detectable by ELISA in the supernatant of hypoxia-exposed cell lines and in the serum of tumor-bearing mice. sCD137, as secreted by tumor cells, is able to bind to CD137-Ligand (CD137L). Our studies on primed T lymphocytes in co-culture with stable transfectants for CD137L demonstrate that tumor-secreted sCD137 prevents co-stimulation of T lymphocytes. Such an effect results from preventing the interaction of CD137L with the transmembrane forms of CD137 expressed on T lymphocytes undergoing activation. Indeed, silencing CD137 with shRNA renders more immunogenic tumor-cell variants upon inoculation to immunocompetent mice but which readily grafted on immunodeficient or CD8+ T-cell-depleted mice. These mechanisms are interpreted as a molecular strategy deployed by tumors to repress lymphocyte co-stimulation via CD137/CD137L.

Successful Immunotherapy against a Transplantable Mouse Squamous Lung Carcinoma with Anti-PD-1 and Anti-CD137 Monoclonal Antibodies.

INTRODUCTION: Anti-programmed cell death 1 (anti-PD-1) and anti-programmed cell death ligand 1 (PD-L1) antagonist monoclonal antibodies (mAbs) against metastatic non-small cell lung cancer with special efficacy in patients with squamous cell lung cancer are being developed in the clinic. However, robust and reliable experimental models to test immunotherapeutic combinations in squamous lung tumors are still lacking. METHODS: We generated a transplantable squamous cell carcinoma cell line (UN-SCC680AJ) from a lung tumor induced by chronic N-nitroso-tris-chloroethylurea mutagenesis in A/J mice. Tumor cells expressed cytokeratins, overexpressed p40, and lacked thyroid transcription factor 1, confirming the squamous lineage reported by histological analysis. More than 200 mutations found in its exome suggested potential for antigenicity. Immunocompetent mice subcutaneously implanted with this syngeneic cell line were treated with anti-CD137 and/or anti-PD-1 mAbs and monitored for tumor growth/progression or assessed for intratumoral leukocyte infiltration using immunohistochemical analysis and flow cytometry. RESULTS: In syngeneic mice, large 12-day-established tumors derived from the transplantable cell line variant UN-SCC680AJ were amenable to curative treatment with anti-PD-1, anti-PD-L1, or anti-CD137 immunostimulatory mAbs. Single-agent therapies lost curative efficacy when treatment was started beyond day +17, whereas a combination of anti-PD-1 plus anti-CD137 achieved complete rejections. Tumor cells expressed weak baseline PD-L1 on the plasma membrane, but this could be readily induced by interferon-γ. Combined treatment efficacy required CD8 T cells and induced a leukocyte infiltrate in which T lymphocytes co-expressing CD137 and PD-1 were prominent. CONCLUSIONS: These promising results advocate the use of combined anti-PD-1/PD-L1 plus anti-CD137 mAb immunotherapy for the treatment of squamous non-small cell lung cancer in the clinical setting.

Deciphering CD137 (4-1BB) signaling in T-cell costimulation for translation into successful cancer immunotherapy.

CD137 (4-1BB, TNF-receptor superfamily 9) is a surface glycoprotein of the TNFR family which can be induced on a variety of leukocyte subsets. On T and NK cells, CD137 is expressed following activation and, if ligated by its natural ligand (CD137L), conveys polyubiquitination-mediated signals via TNF receptor associated factor 2 that inhibit apoptosis, while enhancing proliferation and effector functions. CD137 thus behaves as a bona fide inducible costimulatory molecule. These functional properties of CD137 can be exploited in cancer immunotherapy by systemic administration of agonist monoclonal antibodies, which increase anticancer CTLs and enhance NK-cell-mediated antibody-dependent cell-mediated cytotoxicity. Reportedly, anti-CD137 mAb and adoptive T-cell therapy strongly synergize, since (i) CD137 expression can be used to select the T cells endowed with the best activities against the tumor, (ii) costimulation of the lymphocyte cultures to be used in adoptive T-cell therapy can be done with CD137 agonist antibodies or CD137L, and (iii) synergistic effects upon coadministration of T cells and antibodies are readily observed in mouse models. Furthermore, the signaling cytoplasmic tail of CD137 is a key component of anti-CD19 chimeric antigen receptors that are used to redirect T cells against leukemia and lymphoma in the clinic. Ongoing phase II clinical trials with agonist antibodies and the presence of CD137 sequence in these successful chimeric antigen receptors highlight the importance of CD137 in oncoimmunology.

Cancer Immunotherapy with Immunomodulatory Anti-CD137 and Anti-PD-1 Monoclonal Antibodies Requires BATF3-Dependent Dendritic Cells.

UNLABELLED: 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.

Evolving synergistic combinations of targeted immunotherapies to combat cancer.

Immunotherapy has now been clinically validated as an effective treatment for many cancers. There is tremendous potential for synergistic combinations of immunotherapy agents and for combining immunotherapy agents with conventional cancer treatments. Clinical trials combining blockade of cytotoxic T lymphocyte-associated antigen 4 (CTLA4) and programmed cell death protein 1 (PD1) may serve as a paradigm to guide future approaches to immuno-oncology combination therapy. In this Review, we discuss progress in the synergistic design of immune-targeting combination therapies and highlight the challenges involved in tailoring such strategies to provide maximal benefit to patients.

Virotherapy with a Semliki Forest Virus-Based Vector Encoding IL12 Synergizes with PD-1/PD-L1 Blockade.

Virotherapy and checkpoint inhibitors can be combined for the treatment of cancer with complementarity and potential for synergistic effects. We have developed a cytolytic but nonreplicative viral vector system based on Semliki Forest virus that encodes IL12 (SFV-IL12). Following direct intratumoral injection, infected cells release transgenic IL12, die, and elicit an inflammatory response triggered by both abundantly copied viral RNA and IL12. In difficult-to-treat mouse cancer models, such as those derived from MC38 and bilateral B16-OVA, SFV-IL12 synergized with an anti-PD-1 monoclonal antibody (mAb) to induce tumor regression and prolong survival. Similar synergistic effects were attained upon PD-L1 blockade. Combined SFV-IL12 + anti-PD-1 mAb treatment only marginally increased the elicited cytotoxic T-lymphocyte response over SFV-IL12 as a single agent, at least when measured by in vivo killing assays. In contrast, we observed that SFV-IL12 treatment induced expression of PD-L1 on tumor cells in an IFNγ-dependent fashion. PD-L1-mediated adaptive resistance thereby provides a mechanistic explanation of the observed synergistic effects achieved by the SFV-IL12 + anti-PD-1 mAb combination.

Routing cancer immunology and immunotherapy from the lab to the clinic 4-5 th March 2014, Center for Applied Medical Research and University Clinic, Pamplona, Spain.

New approaches to generate effective anticancer responses by either inducing immune responses or inhibiting immunosuppression are under development to improve efficacy in patients. On March 4-5th, 2014, a symposium was held in Pamplona, Spain, to report the new strategies showing preclinical and clinical results regarding translational research efforts on the topic. Participants interacted through oral presentations of 15 speakers and further discussions on topics that included novel therapeutic agents for cancer immunotherapy, viral vectors and interferon-based approaches, experimental tumor imaging and immunostimulatory monoclonal antibodies. Promising agents to target cancer cells and therapeutic approaches that are under translation from bench to patients were presented.

Expression of MALT1 oncogene in hematopoietic stem/progenitor cells recapitulates the pathogenesis of human lymphoma in mice.

Chromosomal translocations involving the MALT1 gene are hallmarks of mucosa-associated lymphoid tissue (MALT) lymphoma. To date, targeting these translocations to mouse B cells has failed to reproduce human disease. Here, we induced MALT1 expression in mouse Sca1(+)Lin(-) hematopoietic stem/progenitor cells, which showed NF-κB activation and early lymphoid priming, being selectively skewed toward B-cell differentiation. These cells accumulated in extranodal tissues and gave rise to clonal tumors recapitulating the principal clinical, biological, and molecular genetic features of MALT lymphoma. Deletion of p53 gene accelerated tumor onset and induced transformation of MALT lymphoma to activated B-cell diffuse large-cell lymphoma (ABC-DLBCL). Treatment of MALT1-induced lymphomas with a specific inhibitor of MALT1 proteolytic activity decreased cell viability, indicating that endogenous Malt1 signaling was required for tumor cell survival. Our study shows that human-like lymphomas can be modeled in mice by targeting MALT1 expression to hematopoietic stem/progenitor cells, demonstrating the oncogenic role of MALT1 in lymphomagenesis. Furthermore, this work establishes a molecular link between MALT lymphoma and ABC-DLBCL, and provides mouse models to test MALT1 inhibitors. Finally, our results suggest that hematopoietic stem/progenitor cells may be involved in the pathogenesis of human mature B-cell lymphomas.