Cross-presentation Of Tumor Antigens Research Articles

Ultrasound-Activatable In Situ Vaccine for Enhanced Antigen Self- and Cross-Presentation to Overcome Cancer Immunotherapy Resistance.

Insufficient antigen self-presentation of tumor cells and ineffective antigen cross-presentation by dendritic cells (DCs) contribute to diminished immune recognition and activation, which cause resistance to immunotherapies. Herein, we present an ultrasound-activatable in situ vaccine by utilizing a hybrid nanovesicle composed of a thylakoid (TK)/platelet (PLT) membrane and a liposome encapsulating DNA methyltransferase inhibitor zebularine (Zeb) and sonosensitizer hematoporphyrin monomethyl ether (HMME). Upon local exposure to ultrasound, reactive oxygen species (ROS) are generated and induce the sequential release of the payloads. Zeb can efficiently inhibit tumor DNA hypermethylation, promoting major histocompatibility complex class I (MHC-I) molecules-mediated antigen self-presentation to improve immune recognition. Meanwhile, the catalase on the TK membrane can decompose the tumoral overexpressed H2O2 into O2, which boosts the generation of ROS and the destruction of tumor cells, resulting in the in situ antigen release and cross-presentation of tumor antigens by DCs. This in situ vaccine simultaneously promotes antigen self-presentation and cross-presentation, resulting in heightened antitumor immunity to overcome resistance.

Hydrogel activation of Mincle receptors for tumor cell processing: A novel approach in cancer immunotherapy

An obstacle in current tumor immunotherapies lies in the challenge of achieving sustained and tumor-targeting T cell immunity, impeded by the limited antigen processing and cross-presentation of tumor antigens. Here, we propose a hydrogel-based multicellular immune factory within the body that autonomously converts tumor cells into an antitumor vaccine. Within the body, the scaffold, formed by a calcium-containing chitosan hydrogel complex (ChitoCa) entraps tumor cells and attracts immune cells to establish a durable and multicellular microenvironment. Within this context, tumor cells are completely eliminated by antigen-presenting cells (APCs) and processed for cross-antigen presentation. The regulatory mechanism relies on the Mincle receptor, a cell-phagocytosis-inducing C-type lectin receptor specifically activated on ChitoCa-recruited APCs, which serves as a recognition synapse, facilitating a tenfold increase in tumor cell engulfment and subsequent elimination. The ChitoCa-induced tumor cell processing further promotes the cross-presentation of tumor antigens to prime protective CD8+ T cell responses. Therefore, the ChitoCa treatment establishes an immune niche within the tumor microenvironment, resulting in effective tumor regression either used alone or in combination with other immunotherapies. This hydrogel-induced immune factory establishes a functional organ-like multicellular colony for tumor-specific immunotherapy, paving the way for innovative strategies in cancer treatment.

Effect of BCL9/BCL9L inhibition–derived Th1 cells on dendritic cells–mediated antigen presentation in hepatocellular carcinoma and on the efficacy of CAR-T immunotherapy.

e16180 Background: Hepatocellular carcinoma (HCC) is an aggressive malignancy with limited treatment options. The emerging field of tumor immunotherapy, primarily focusing on CD8+ T cells and the tumor microenvironment (TME), has garnered substantial attention. CD4+ T cells, on the other hand, play a crucial role in maintaining immune equilibrium and orchestrating immune responses through interactions with various cell types. As crucial participants and coordinators in innate and adaptive immune responses, the role of CD4+ T cells in tumor development remain further exploration. Conventional dendritic cells (cDCs) are thought to perform antigen presentation to prime CD4+ T cells or CD8+ T cells. However, the reverse regulatory impact of CD4+ T cells on cDCs remains poorly understood. Methods: Initially, we examined the role of CD4+ T cell subsets in HCC development using TCGA database. Subsequently, we established Cd4-Cre Bcl9fl/fl Bcl9lfl/fl mice to explore the impact of T cell-specific Bcl9/Bcl9l deficiency on HCC development. We further investigate the impact of Bcl9/Bcl9l deficiency in CD4+ T cells on the therapeutic efficacy of mouse CAR-T treatment. Moreover, using single-cell RNA sequencing (scRNA-seq) databases from Bcl9/Bcl9l KO tumor-bearing mice and HCC patients, we investigated the regulatory role of CD4+ T cells on the function of cDCs. Finally, we validated the mechanism by which CD4+ T cells regulate cDCs function in a mouse HCC model and explored their influence on tumor-specific CD8+ T cells response. Results: We found elevated Th1 cell infiltration in various cancers including liver hepatocellular carcinoma (LIHC). High Th1 infiltration is associated with a favorable prognosis in LIHC, but there is a significant negative correlation between the expression of B-cell lymphoma 9/B-cell lymphoma 9-like (BCL9/BCL9L) and the infiltration of Th1 cells. We found that blocking T cell-intrinsic BCL9/BCL9L increased frequencies of Th1 cells, thereby suppressing HCC tumor growth. The enrichment of Th1 cells inversely regulates innate immune response to augment cDCs activation. BCL9/BCL9L inhibition amplifies CD4+ T cell and cDCs crosstalk and promotes cDCs antigen presentation. The reinforced cross-presentation of tumor antigens by cDCs promotes activation and proliferation of CD8+ T cells. Moreover, genetic editing of BCL9/BCL9L in CD4+ T cells can enhance the anti-tumor immunity by promoting CAR-T cell toxicity. Conclusions: Thus, BCL9/BCL9L inhibition orchestrate an adaptive immune to innate immune circuit wherein Th1 cells triggers cDCs antigen presentation in turn activate tumor-specific CD8+ T cells response to promote cancer immunity.

A facile approach to preparing personalized cancer vaccines using iron-based metal organic framework.

Considering the diversity of tumors, it is of great significance to develop a simple, effective, and low-cost method to prepare personalized cancer vaccines. In this study, a facile one-pot synthetic route was developed to prepare cancer vaccines using model antigen or autologous tumor antigens based on the coordination interaction between Fe3+ ions and endogenous fumarate ligands. Herein, Fe-based metal organic framework can effectively encapsulate tumor antigens with high loading efficiency more than 80%, and act as both delivery system and adjuvants for tumor antigens. By adjusting the synthesis parameters, the obtained cancer vaccines are easily tailored from microscale rod-like morphology with lengths of about 0.8 μm (OVA-ML) to nanoscale morphology with sizes of about 50~80 nm (OVA-MS). When cocultured with antigen-presenting cells, nanoscale cancer vaccines more effectively enhance antigen uptake and Th1 cytokine secretion than microscale ones. Nanoscale cancer vaccines (OVA-MS, dLLC-MS) more effectively enhance lymph node targeting and cross-presentation of tumor antigens, mount antitumor immunity, and inhibit the growth of established tumor in tumor-bearing mice, compared with microscale cancer vaccines (OVA-ML, dLLC-ML) and free tumor antigens. Our work paves the ways for a facile, rapid, and low-cost preparation approach for personalized cancer vaccines.

Hypofractionated radiotherapy combined with lenalidomide improves systemic antitumor activity in mouse solid tumor models.

Background: Hypofractionated radiotherapy (hRT) can induce a T cell-mediated abscopal effect on non-irradiated tumor lesions, especially in combination with immune checkpoint blockade (ICB). However, clinically, this effect is still rare, and ICB-mediated adverse events are common. Lenalidomide (lena) is an anti-angiogenic and immunomodulatory drug used in the treatment of hematologic malignancies. We here investigated in solid tumor models whether lena can enhance the abscopal effect in double combination with hRT. Methods: In two syngeneic bilateral tumor models (B16-CD133 melanoma and MC38 colon carcinoma), the primary tumor was treated with hRT. Lena was given daily for 3 weeks. Besides tumor size and survival, the dependence of the antitumor effects on CD8+ cells, type-I IFN signaling, and T cell costimulation was determined with depleting or blocking antibodies. Tumor-specific CD8+ T cells were quantified, and their differentiation and effector status were characterized by multicolor flow cytometry using MHC-I tetramers and various antibodies. In addition, dendritic cell (DC)-mediated tumor antigen cross-presentation in vitro and directly ex vivo and the composition of tumor-associated vascular endothelial cells were investigated. Results: In both tumor models, the hRT/lena double combination induced a significant abscopal effect. Control of the non-irradiated secondary tumor and survival were considerably better than with the respective monotherapies. The abscopal effect was strongly dependent on CD8+ cells and associated with an increase in tumor-specific CD8+ T cells in the non-irradiated tumor and its draining lymph nodes. Additionally, we found more tumor-specific T cells with a stem-like (TCF1+ TIM3- PD1+) and a transitory (TCF1- TIM3+ CD101- PD1+) exhausted phenotype and more expressing effector molecules such as GzmB, IFNγ, and TNFα. Moreover, in the non-irradiated tumor, hRT/lena treatment also increased DCs cross-presenting a tumor model antigen. Blocking type-I IFN signaling, which is essential for cross-presentation, completely abrogated the abscopal effect. A gene expression analysis of bone marrow-derived DCs revealed that lena augmented the expression of IFN response genes and genes associated with differentiation, maturation (including CD70, CD83, and CD86), migration to lymph nodes, and T cell activation. Flow cytometry confirmed an increase in CD70+ CD83+ CD86+ DCs in both irradiated and abscopal tumors. Moreover, the hRT/lena-induced abscopal effect was diminished when these costimulatory molecules were blocked simultaneously using antibodies. In line with the enhanced infiltration by DCs and tumor-specific CD8+ T cells, including more stem-like cells, hRT/lena also increased tumor-associated high endothelial cells (TA-HECs) in the non-irradiated tumor. Conclusions: We demonstrate that lena can augment the hRT-induced abscopal effect in mouse solid tumor models in a CD8 T cell- and IFN-I-dependent manner, correlating with enhanced anti-tumor CD8 T cell immunity, DC cross-presentation, and TA-HEC numbers. Our findings may be helpful for the planning of clinical trials in (oligo)metastatic patients.

Tumor-derived autophagosome vaccines combined with immune adjuvants mediate antitumor immune responses via the neoantigen pathway.

Vaccines composed of autophagosomes derived from tumor cells called DRibbles (DRiPs-containing blebs) are involved in the cross-presentation of tumor antigens, thus inducing cross-reactive T-cell responses against the tumor. Compared with traditional tumor lysate vaccines, autophagosome vaccines were found to be better sources of multiple tumor-associated antigens (TAAs) that activate antigen-specific T-cells. However, the involvement of tumor neoantigens in the immune responses of autophagosome vaccines remains unclear. The present study showed that exogenous autophagosome vaccines (DRibbles) combined with immune adjuvants (anti-OX40 antibody and ATP) can effectively activate functional T cells in vitro. Importantly, the combination of exogenous tumor-derived autophagosome vaccines and immune adjuvants was found to induce tumor regression in B16F10 and 4T1 tumor-bearing mice. The combination of autophagosome-enriched DRibbles with anti-OX40 antibody and ATP also exhibited optimal immune stimulation and antitumor efficiency in vivo. The effectiveness of exogenous DRibble vaccines was mainly due to their enhancement of tumor immunogenicity by increasing the presentation and release of tumor neoantigens. These findings suggest that this immunotherapeutic method may be effective in the treatment of cancer.

Liposomal Delivery of an Immunostimulatory CpG Induces Robust Antitumor Immunity and Long-Term Immune Memory by Reprogramming Tumor-Associated Macrophages.

Tumor-associated macrophages (TAMs)-representative immune-suppressive cells in the tumor microenvironment (TME)-are known to promote tumor progression and metastasis, and thus are considered an attractive target for cancer therapy. However, current TAM-targeting strategies are insufficient to result in robust antitumor efficacy. Here, a small lipid nanoparticle encapsulating immunostimulatory CpG oligodeoxynucleotides (SLNP@CpG) is reported as a new immunotherapeutic modality that can reprogram TAMs and further bridge innate-to-adaptive immunity. It is found that SLNP@CpG treatment enhances macrophage-mediated phagocytosis of cancer cells and tumor antigen cross-presentation, and skews the polarization state of macrophages invitro. Intratumoral injection of SLNP@CpG into an established murine E.G7-OVA tumor model significantly suppresses tumor growth and considerably prolongs survival, completely eradicating tumors in 83.3% of mice. Furthermore, tumor-free mice resist rechallenge with E.G7-OVA cancer cells through induction of immunological memory and long-term antitumor immunity. SLNP@CpG even exerts antitumor efficacy in an aggressive B16-F10 melanoma model by remodeling TME toward immune stimulation and tumor elimination. These findings suggest that, by modulating the function of TAMs and reshaping an immunosuppressive TME, the SLNP@CpG nanomedicine developed here may become a promising immunotherapeutic option applicable to a variety of tumors.

Cytotoxicity as a form of immunogenic cell death leading to efficient tumor antigen cross-priming.

Antigen cross-priming of CD8+ T cells is a critical process necessary for the effective expansion and activation of CD8+ T cells endowed with the ability to recognize and destroy tumor cells. The cross-presentation of tumor antigens to cross-prime CD8+ T cells is mainly mediated, if not only, by a subset of professional antigen-presenting cells termed type-1 conventional dendritic cells (cDC1). The demise of malignant cells can be immunogenic if it occurs in the context of premortem stress. These ways of dying are termed immunogenic cell death (ICD) and are associated with biochemical features favoring cDC1 for the efficient cross-priming of tumor antigens. Immunosurveillance and the success of immunotherapies heavily rely on the ability of cytotoxic immune cells, primarily CD8+ T cells and NK cells, to detect and eliminate tumor cells through mechanisms collectively known as cytotoxicity. Recent studies have revealed the significance of NK- and CTL-mediated cytotoxicity as a prominent form of immunogenic cell death, resulting in mechanisms that promote and sustain antigen-specific immune responses. This review focuses on the mechanisms underlying the cross-presentation of antigens released during tumor cell killing by cytotoxic immune cells, with an emphasis on the role of cDC1 cells. Indeed, cDC1s are instrumental in the effectiveness of most immunotherapies, underscoring the significance of tumor antigen cross-priming in contexts of immunogenic cell death. The notion of the potent immunogenicity of cell death resulting from NK or cytotoxic T lymphocyte (CTL)-mediated cytotoxicity has far-reaching implications for cancer immunotherapy.

The self-adjuvant heterocyclic lipid nanoparticles encapsulated with vaccine and STAT3 siRNA boost cancer immunotherapy through DLN-targeted and STING pathway

A great potential of tumor vaccine-based immunotherapy has been emerged; however, the low cross-presentation of tumor antigens, intrinsic immunosuppressive signaling of dendritic cells (DCs) and the immunosuppression in tumor microenvironment (TME) hindered the progress of tumor vaccine. In this article, approaches employed heterocyclic lipid nanoparticles (LNP) as a tumor vaccine and signal transduction and activator of transcription 3 (STAT3) siRNA carrier as well as a “self-adjuvant” by targeting draining lymph node (DLN) and stimulating stimulator of interferon genes (STING)-mediated type I interferon (IFN) innate immune response were proposed. Model antigens ovalbumin peptide 257–264 (OVA) were cross-presented to activate T cells; STAT3 siRNA acted synergistically with OVA to improve DCs maturation, enhance antigen presentation and abrogate immunosuppressive TME; heterocyclic lipids induced the production of type I IFN via activating the STING pathway. Compared to DLin-MC3-DMA LNP, heterocyclic LNPs, especially A18-LNP, targeted DLN, delivered much OVA and STAT3 siRNA into cytoplasm of antigen-presenting cells (APCs, mainly DCs), activated STING pathway, promoted DCs maturation and antigen presentation, abrogated immunosuppression in TME, therefore, leading to robust anti-cancer response. Thus, heterocyclic LNPs efficiently delivered tumor vaccine and STAT3 siRNA and simultaneously activated the immune system through DLN-targeted and STING pathway, provided better antitumor effects, suggesting a promising strategy for cancer immunotherapy.

A distinct stimulatory cDC1 subpopulation amplifies CD8+ Tcell responses in tumors for protective anti-cancer immunity.

Type 1 conventional dendritic cells (cDC1) can support Tcell responses within tumors but whether this determines protective versus ineffective anti-cancer immunity is poorly understood. Here, we use imaging-based deep learning to identify intratumoral cDC1-CD8+ Tcell clustering as a unique feature of protective anti-cancer immunity. These clusters form selectively in stromal tumor regions and constitute niches in which cDC1 activate TCF1+ stem-like CD8+ Tcells. We identify a distinct population of immunostimulatory CCR7neg cDC1 that produce CXCL9 to promote cluster formation and cross-present tumor antigens within these niches, which is required for intratumoral CD8+ Tcell differentiation and expansion and promotes cancer immune control. Similarly, in human cancers, CCR7neg cDC1 interact with CD8+ Tcells in clusters and are associated with patient survival. Our findings reveal an intratumoral phase of the anti-cancer Tcell response orchestrated by tumor-residing cDC1 that determines protective versus ineffective immunity and could be exploited for cancer therapy.

Cracking cancer with engineered skin commensals

The use of bacterial colonists as therapy carriers is gaining interest for treating cancer. In a recent publication in Science, the work by Chen etal. proposes the engineering of a commensal bacterium of the human skin microbiota to cross-present tumor antigens to Tcells and counteract tumor progression.

Abstract LB344: Complement-mediated signaling during cross-presentation of tumor antigen augments T cell responses

Abstract Production of complement C3a and C5a locally at the immune synapse by activated dendritic cells (DCs) enhances T cell responses in multiple experimental models. Complement signaling through cognate C3a receptor (C3aR) and C5a receptor (C5aR) modulate effector T cell stability, proliferation and differentiation. We have previously shown that complement C3 plays a mechanistic role in driving synergistic anti-tumor effects of blocking indoleamine 2,3-dioxygenase (IDO) during radiation and chemotherapy in a murine brain tumor model that expresses the gp10025-33 peptide antigen. We hypothesize that, when anti-tumor responses are allowed to happen, complement C3 production by local DCs acts as a costimulation factor, operating through C3aR and C5aR on the T cell surface to allow optimal T cell activation and proliferation. To study the role of complement C3 as a costimulation factor during T cell responses against a nominal tumor antigen (gp10025-33 peptide, expressed by B16F10 melanoma), we used T cells from syngeneic pmel-1 mice (TCR transgenic with CD8 T cells that recognize the cross-presented gp10025-33 peptide) co-cultured with gp10025-33 peptide and dendritic cells from either wild-type (WT) or C3-defiecient (C3-KO) mice. In addition, we used in vitro culture conditions where gp10025-33 tumor peptide was in stringent limited supply to model homeostatic conditions of the tumor microenvironment. We found that, when stimulated by DCs from C3-KO mice, pmel-1 CD8 T cells had decreased activation marker expression, proliferation, and cytokine effector function relative to stimulation by DCs from WT mice. Next, we bred pmel-1 mice onto a syngeneic background deficient in receptors for both C3a and C5a complement factors (C3aR-KO/C5aR-KO double knock-out mice). We used CD8 T cells from the resulting mouse strain (pmel-1/C3aR-KO/C5aR-KO) co-cultured with WT DCs to study the role of complement signaling in T cells during responses to tumor antigen. Using the same stringent antigen conditions, CD8 T cells from the pmel-1/C3aR-KO/C5aR-KO mice had decreased activation marker expression and proliferation, and differences in cytokine function compared to CD8 T cells from the pmel-1 mice. These findings suggest that lack of local complement production by the DCs in the tumor microenvironment may inhibit anti-tumor immune responses, and that complement signaling through C3aR and C5aR on T cells may play an important role during such anti-tumor responses. Citation Format: Caryn L. Bird, Gabriela A. Pacholczyk, Theodore S. Johnson. Complement-mediated signaling during cross-presentation of tumor antigen augments T cell responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB344.

Abstract 6365: TRIM21 is a novel endogenous partner of the inhibitory myeloid checkpoint CLEC-1 involved in tumor antigen cross-presentation

Abstract Myeloid cells represent the most abundant immune component of the tumor microenvironment, where they often assume immunosuppressive roles. Therefore, understanding the mechanisms regulating the immunosuppressive activity of myeloid cells is of major interest in oncology. We have identified CLEC-1, a member of the C-type lectin receptor (CLR) family, as a myeloid cell-driven brake for anti-tumor T cell response in different murine models, including mesothelioma, hepatocellular and colorectal carcinomas. However, the molecular mechanism underlying the immunomodulatory role of CLEC-1 remained to be fully elucidated. Here, using both murine and human cells, we identified and characterized a novel endogenous ligand for CLEC-1, shedding new light on CLEC-1 driven inhibitory myeloid checkpoint activity. First, using single cell RNA sequencing, we confirmed that CLEC-1 is expressed by human myeloid cells, especially by conventional type-one dendritic cells and by tumor-associated macrophages. Using an Fc-fusion human CLEC-1 protein (huCLEC-1) as a bait for potential endogenous ligands, we observed both in human and murine cells that huCLEC-1 binds specifically to stressed or dying cells following programmed necrosis, for instance after X-ray or chemotherapy treatments. CLEC-1 interaction with its ligand expressed by necrotic cells was able to activate the NFAT promoter in a CLEC-1-CD3zeta NFAT reporter cell line in vitro; furthermore, CLEC-1 ligand targeting via Fc-CLEC-1 treatment in vivo extended the overall survival of chemotherapy-treated mc38-colorectal cancer bearing mice, altogether demonstrating the functional relevance of CLEC-1 interaction with its ligand. Immunoprecipitation of proteins bound to huCLEC-1 subsequently enabled the identification of TRIM21, an intra-cellular Fc receptor and E3 ubiquitin ligase as a novel interaction partner for CLEC-1. Direct interaction between recombinant TRIM21 and CLEC-1 human proteins was subsequently confirmed by ELISA and Biacore affinity analysis. TRIM21 was indeed detected at the cell surface of necrotic cells following genotoxic treatments in vitro in several human cancer cell lines and, interestingly, high TRIM21 expression was predictive of worse overall survival in patients with hepatocellular carcinoma, pancreatic cancer, or glioma. Mechanistically, we demonstrated that CLEC-1 genetic deletion in mice enhances the capacity of dendritic cells to cross-present tumor antigens, a process known to be regulated by TRIM21 through its E3 ubiquitin ligase activity. Antagonist anti-CLEC-1 or anti-TRIM21 antibodies are therefore being evaluated to further confirm the involvement of the newly identified CLEC-1 interaction with TRIM21 in the regulation of CLEC-1’s function as an inhibitory myeloid checkpoint. Altogether our data highlight the CLEC-1/TRIM21 axis as a new target for cancer immunotherapy. Citation Format: Irene Baccelli, Vanessa Gauttier, Marion Drouin, Caroline Mary, Isabelle Girault, Emmanuelle Wilhelm, Sabrina Pengam, Géraldine Teppaz, Julien Taurelle, Ariane Desselle, Virginie Thepenier, Nicolas Poirier, Elise Chiffoleau. TRIM21 is a novel endogenous partner of the inhibitory myeloid checkpoint CLEC-1 involved in tumor antigen cross-presentation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6365.

Abstract 5164: Liposomal Delivery of an Immunostimulatory CpG Induces Robust Antitumor Immunity and Long-Term Immune Memory by Reprogramming Tumor-Associated Macrophages

Abstract Background: The efficacy of current T cell-based immunotherapy is known to be limited by various factors that induce immune suppression in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are representative TME-comprising immune suppressive cells and influence tumor growth and progression. TAMs are considered as an attractive target for cancer immunotherapy. However, current TAMs-targeting strategies are not sufficient to induce continuous antitumor responses. Here, we suggest a new strategy that can reprogram TAMs and further bridge innate-to-adaptive immunity by utilizing immunostimulatory CpG oligodeoxynucleotides (ODNs). In this study, we investigated the new role of TLR9 agonist CpG ODN as an immunotherapeutic agent and tested whether liposomal delivery of CpG could modulate the function of TAMs and lead to remodeling of the TME. Methods: A liposome-based nanomaterial encapsulating CpG ODN was constructed. A small lipid nanoparticle (SLNP) used as the CpG delivery platform in this study was made of a cationic cholesterol derivative and two biocompatible phospholipids. The CpG-encapsulating SLNP (SLNP@CpG) was prepared by a thin-film formation and rehydration method. In vitro studies were conducted to assess whether SLNP@CpG could reprogram macrophages. To assess antitumor therapeutic efficacy of the SLNP@CpG, two subcutaneous tumor models were established in mice and tumor growth and survival rates of mice were monitored. For tumor rechallenge experiment, mice showing complete tumor regression were rechallenged with same cancer cells and their splenocytes were analyzed to confirm the development of immune memory. To elucidate the immunological mechanism of SLNP@CpG-mediated antitumor efficacy, changes of immune cell subpopulations in treated tumors were analyzed by flow cytometry. Results: SLNP@CpG enhanced macrophage-mediated phagocytosis of cancer cells and tumor antigen cross-presentation, and skewed the polarization state of macrophages in vitro. Intratumorally injected SLNP@CpG exerted its therapeutic efficacy in an established E.G7-OVA tumor via uptake by TAMs. SLNP@CpG treatment significantly suppressed the E.G7 tumor growth and also considerably prolonged the survival of mice, with 83.3% of mice becoming tumor-free. Local administration of SLNP@CpG resisted E.G7 tumor rechallenge by inducing immunological memory and long-term antitumor immunity. Local administration of SLNP@CpG even exerted its antitumor efficacy in an aggressive B16-F10 melanoma by remodeling TME towards immune stimulation and tumor elimination. Conclusion: Liposomal delivery of CpG via local treatment reprogrammed TAMs by enhancing phagocytic activity and repolarizing M2 to M1 phenotype and also reshaped immunosuppressive TME, leading to antitumor immunity and long-term memory responses. Citation Format: Yujin Kim, Sangyong Jon. Liposomal Delivery of an Immunostimulatory CpG Induces Robust Antitumor Immunity and Long-Term Immune Memory by Reprogramming Tumor-Associated Macrophages. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5164.

Inhibitor of Apoptosis Proteins Antagonist Induces T-cell Proliferation after Cross-Presentation by Dendritic Cells.

Cross-presentation of tumor antigens by dendritic cells (DC) is crucial to prime, stimulate and restimulate CD8+ T cells. This process is important in initiating and maintaining an antitumor response. Here, we show that the presence of conventional type 1 DCs (cDC1), a DC subtype that excels in cross-presentation, in the tumor correlated with response to neoadjuvant immune checkpoint blockade (ICB) in melanoma. This led us to hypothesize that patients failing to respond to ICB could benefit from enhanced cross-presentation of tumor antigens. We therefore established a cross-presentation assay to screen over 5,500 compounds for enhancers of DC cross-presentation using induced T-cell proliferation as the readout. We identified 145 enhancers, including AZD5582, an antagonist of inhibitor of apoptosis proteins (IAP) cIAP1, cIAP2, and XIAP. AZD5582 treatment led to DC activation of the noncanonical NF-kB pathway, enhanced antigen import from endolysosomes into the cytosol, and increased expression of genes involved in cross-presentation. Furthermore, it upregulated expression of CD80, CD86, MHC class II, CD70 and secretion of TNF by DCs. This enhanced DC activation and maturation program was observed also in tumor-bearing mice upon AZD5582 treatment, culminating in an increased frequency of systemic tumor antigen-specific CD8+ T cells. Our results merit further exploration of AZD5582 to increase antigen cross-presentation for improving the clinical benefit of ICB in patients who are unlikely to respond to ICB.

Canvassing Prospects of Glyco-Nanovaccines for Developing Cross-Presentation Mediated Anti-Tumor Immunotherapy.

In view of the severe downsides of conventional cancer therapies, the quest of developing alternative strategies still remains of critical importance. In this regard, antigen cross-presentation, usually employed by dendritic cells (DCs), has been recognized as a potential solution to overcome the present impasse in anti-cancer therapeutic strategies. It has been established that an elevated cytotoxic T lymphocyte (CTL) response against cancer cells can be achieved by targeting receptors expressed on DCs with specific ligands. Glycans are known to serve as ligands for C-type lectin receptors (CLRs) expressed on DCs, and are also known to act as a tumor-associated antigen (TAA), and, thus, can be harnessed as a potential immunotherapeutic target. In this scenario, integrating the knowledge of cross-presentation and glycan-conjugated nanovaccines can help us to develop so called 'glyco-nanovaccines' (GNVs) for targeting DCs. Here, we briefly review and analyze the potential of GNVs as the next-generation anti-tumor immunotherapy. We have compared different antigen-presenting cells (APCs) for their ability to cross-present antigens and described the potential nanocarriers for tumor antigen cross-presentation. Further, we discuss the role of glycans in targeting of DCs, the immune response due to pathogens, and imitative approaches, along with parameters, strategies, and challenges involved in cross-presentation-based GNVs for cancer immunotherapy. It is known that the effectiveness of GNVs in eradicating tumors by inducing strong CTL response in the tumor microenvironment (TME) has been largely hindered by tumor glycosylation and the expression of different lectin receptors (such as galectins) by cancer cells. Tumor glycan signatures can be sensed by a variety of lectins expressed on immune cells and mediate the immune suppression which, in turn, facilitates immune evasion. Therefore, a sound understanding of the glycan language of cancer cells, and glycan-lectin interaction between the cancer cells and immune cells, would help in strategically designing the next-generation GNVs for anti-tumor immunotherapy.

Expanding cross-presenting dendritic cells enhances oncolytic virotherapy and is critical for long-term anti-tumor immunity

Immunotherapies directly enhancing anti-tumor CD8+ T cell responses have yielded measurable but limited success, highlighting the need for alternatives. Anti-tumor T cell responses critically depend on antigen presenting dendritic cells (DC), and enhancing mobilization, antigen loading and activation of these cells represent an attractive possibility to potentiate T cell based therapies. Here we show that expansion of DCs by Flt3L administration impacts in situ vaccination with oncolytic Newcastle Disease Virus (NDV). Mechanistically, NDV activates DCs and sensitizes them to dying tumor cells through upregulation of dead-cell receptors and synergizes with Flt3L to promote anti-tumor CD8+ T cell cross-priming. In vivo, Flt3L-NDV in situ vaccination induces parallel amplification of virus- and tumor-specific T cells, including CD8+ T cells reactive to newly-described neoepitopes, promoting long-term tumor control. Cross-presenting conventional Type 1 DCs are indispensable for the anti-tumor, but not anti-viral, T cell response, and type I IFN-dependent CD4+ Th1 effector cells contribute to optimal anti-tumor immunity. These data demonstrate that mobilizing DCs to increase tumor antigen cross-presentation improves oncolytic virotherapy and that neoepitope-specific T cells can be induced without individualized, ex vivo manufactured vaccines.

Fast peptide exchange on major histocompatibility complex class I molecules by acidic stabilization of a peptide-empty intermediate.

The cell biology and biochemistry of peptide exchange on major histocompatibility complex class I (MHC-I) proteins are of great interest in the study of immunodominance, which requires iterative optimization of peptide affinity, and cross-presentation of pathogen and tumor antigens, in which endogenous peptides are exchanged for exogenous ones. Even though several methods exist to catalyze peptide exchange on recombinant MHC-I proteins, the cellular conditions and mechanisms allowing for peptide exchange in vivo remain unclear. Here, we demonstrate that low pH, as present in endosomes, indeed triggers peptide exchange, and we dissect the individual steps of the exchange reaction. We find that low pH stabilizes the peptide-empty forms of MHC-I that occur as intermediates of the exchange reaction, and that is synergizes with dipeptides and with disulfide-mediated stabilization of MHC-I.

Abstract PR008: Overcoming PDAC T cell therapy barriers with CD47-targeted costimulatory fusion proteins

Abstract T cell therapy is a promising immunotherapy treatment option that uses genetically modified immune cells (T cells) to eliminate tumors. This approach uses the patients’ own immune cells to generate a “living drug” and can avoid the toxic side effects of other common therapies, such as radiation or chemotherapies. However, the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME) can establish several obstacles to protect the tumor from T cells, including delivery of inhibitory and death signals that shut down T cells, usurping metabolic nutrients, and recruiting and/or converting immune cells to inhibitory phenotypes that block the T cell response. CD47 is upregulated in PDAC tumors, and patients with CD47hi tumors exhibit worse survival. CD47 serves as a “don’t eat me” signal by binding to the SIRPα receptor on macrophages to block phagocytosis. CD47 expression also inhibits T cell-mediated tumor rejection by blocking cross-presentation of tumor antigens by SIRPα+ dendritic cells. Reagents that interfere with SIRPα-CD47 signaling, such as monoclonal antibodies, are currently in clinical trials and have been shown to synergize with chemotherapy in PDA models, but native CD47 expression can produce erythrocyte and platelet depletion. Costimulatory signals delivered by surface-bound receptors can initiate gene expression programs that address multiple issues in the PDAC TME by mechanisms such as lowering the threshold of activation, altering metabolic programming, and reducing exhaustion. We develop engineering strategies to deliver costimulatory signals to engineered T cells. Immunomodulatory fusion proteins (IFPs) combine the ectodomain of an inhibitory T cell receptor with an intracellular costimulatory signaling domain and we have shown in proof-of-concept studies that this effectively “replaces a brake with an accelerator” in CD8 T cells. We have found that generating IFPs is not as simple as indiscriminately fusing any two proteins together and we have developed critical design concepts that inform the selection of the fusion site, ectodomain and costimulatory signaling domain pairing, and immunological synapse localization to enhance signaling. To develop a CD47-targeted IFP, we combined the SIRPa ectodomain with the CD28 signaling endodomain and tested this technology with our mesothelin-targeted TCR-T cell platform. In in vitrostudies, SIRPa-CD28 T cells exhibited enhanced proliferation, accumulation, and tumor cytotoxicity. SIRPa IFP-T cells exhibited increased intratumoral accumulation and therapeutic efficacy in the KrasLSL-G12D/+; Trp53LSL-R172H/+;p48Cre/+ (KPC) model, without toxicity or erythrocyte depletion. Here we describe how a thoughtfully engineered fusion protein can “armor” T cells against multiple obstacles and significantly improve therapeutic efficacy against PDAC. Citation Format: Shannon Oda, Leah Schmidt, Ashley Thelen, Cody Jenkins, Edison Chiu, Aitong Ruan, Philip Greenberg. Overcoming PDAC T cell therapy barriers with CD47-targeted costimulatory fusion proteins [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR008.

Tumor factors stimulate lysosomal degradation of tumor antigens and undermine their cross-presentation in lung cancer

Activities of dendritic cells (DCs) that present tumor antigens are often suppressed in tumors. Here we report that this suppression is induced by tumor microenvironment-derived factors, which activate the activating transcription factor-3 (ATF3) transcription factor and downregulate cholesterol 25-hydroxylase (CH25H). Loss of CH25H in antigen presenting cells isolated from human lung tumors is associated with tumor growth and lung cancer progression. Accordingly, mice lacking CH25H in DCs exhibit an accelerated tumor growth, decreased infiltration and impaired activation of intratumoral CD8+ T cells. These mice do not establish measurable long-term immunity against malignant cells that undergo chemotherapy-induced immunogenic cell death. Mechanistically, downregulation of CH25H stimulates membrane fusion between endo-phagosomes and lysosomes, accelerates lysosomal degradation and restricts cross-presentation of tumor antigens in the intratumoral DCs. Administration of STING agonist MSA-2 reduces the lysosomal activity in DCs, restores antigen cross presentation, and increases therapeutic efficacy of PD-1 blockade against tumour challenge in a CH25H-dependent manner. These studies highlight the importance of downregulation of CH25H in DCs for tumor immune evasion and resistance to therapy.