Tumor Antigen Presentation Research Articles

Abstract C051: Epigenetic reprogramming of brain-infiltrating myeloid cells deters brain metastasis outgrowth

Abstract The unique brain immune microenvironment (BrIME) co-evolves with brain metastasis (BrM) and is marked by immune suppression, posing a significant therapeutic challenge. BrIME is dominated by myeloid cells, with monocyte-derived macrophages (MDMs) comprising nearly half of the tumor-infiltrating leukocytes. Targeting MDMs remains challenging due to their inherent heterogeneity and high plasticity, which are regulated by epigenetic modifiers, including histone deacetylases (HDACs). Yet, the impact of HDAC inhibition in BrIME and its implications for BrM immunotherapy remains unclear. Here, we establish BrM syngenetic model by intracarotid artery (ICA) injection. Immune profiling by mass cytometry (CyTOF) analysis shows that selective class I HDAC inhibitor (HDACi) Entinostat (ENT) significantly enriches inflammatory MDMs in E0771 murine mammary tumor BrM model. Additionally, functional assay with bone marrow-derived macrophages (BMDMs) shows that ENT significantly enhances tumor cell phagocytosis and antigen presentation, increasing the proliferation of antigen-specific T cells in vitro. To test whether HDAC inhibition enhances antitumoral response in the BrIME, we designed a novel sequential treatment: with (1) ENT pre-conditioning the BrIME, (2) low- dose whole brain radiotherapy (LD-WBRT) to release tumor antigen followed by (3) anti-PD1 immune checkpoint therapy (ICT) to reinvigorate tumor-infiltrating. Our result shows that sequential triple treatment demonstrates significant BrM deterrence and induce a specific interferon-responsive MDM subset with robust type I interferon response in single-cell RNA sequencing, correlating with improved ICT clinical outcomes. Our data show that selective HDACi treatment reprograms the suppressive BrIME by steering the BrM-infiltrating MDMs toward immuno-stimulatory status. Sequential triple combinatorial therapy impedes BrM by activating innate and adaptive immunity simultaneously and is well tolerated in the animal model. Our findings highlight the potential of HDACi-mediated epigenetic reprogramming of the BrIME to enhance therapeutic efficacy in treating BrM. Citation Format: Shao-Ping Yang, Yimin Duan, Xiangliang Yuan, Lin Zhang, Wendao Liu, Jun Yao, Patrick Zhang, Jason T Huse, Zhongming Zhao, Dihua Yu. Epigenetic reprogramming of brain-infiltrating myeloid cells deters brain metastasis outgrowth [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C051.

Abstract C011: The impact of reproductive factors on breast tumor and normal-adjacent tissue immune profile from menarche to menopause

Abstract Background: Reproductive factors and sex hormones are tightly linked to systemic immunity. However, no studies have examined whether reproductive factors and exogenous hormone use modulate the immune microenvironment of breast tissue. Methods: We prospectively evaluated the associations of reproductive factors (age at menarche, parity, age at first birth, age at menopause, and menopausal status) and exogenous hormone use (oral contraceptives, and menopausal hormone therapy (MHT)) with breast tumor and normal-adjacent tissue immune cell markers among 935 breast cancer cases in the Nurses’ Health Studies. We deconvoluted immune cell abundance using CIBERSORTx and derived gene expression signatures of markers for immune checkpoint (PD1, PDL1, and CTLA4), co-regulatory signal and antigen presentation (MHC class I/ II and T cell receptor) and mammary cytokine signaling (IFN gamma, IL2, IL4, IL12, IL13, TGF beta). Linear regression was used with adjustment for potential confounders. Results: Majority of participants had estrogen receptor (ER)-positive breast cancer (81%) and were post-menopausal at diagnosis (72%). Compared to tumors from pre-menopausal women, tumors from post-menopausal women had higher signature scores for tumor pro-inflammatory cytokine signaling (IFN gamma, IL2, IL4, IL12, IL13, TGF beta) and antigen presentation (FDR≤0.05). Several of the inflammatory cytokine signatures showed modest inverse relations with signatures of immune checkpoint markers (ρ=-0.3 to -0.4). Women who reported current use of estrogen only MHT had higher expression of CTLA4 in ER-positive breast tumors. For normal-adjacent tissues of ER-positive tumors, parity was associated with higher CD8+ T cell abundance, higher PDL1 expression and lower cytokine signaling in normal-adjacent tissues at p≤0.05; while breastfeeding was associated with lower abundance of CD8+ T cell and higher expression of cytokine signaling in normal-adjacent tissues of ER-negative tumors (p≤0.05). None of the associations in normal-adjacent tissues met FDR significance. The associations between other reproductive factors and immune cell profiles were in general weak. Conclusions: Our study suggests pre-diagnostic reproductive factors may influence breast tumor immune profiles. Future studies are needed to validate these results. Citation Format: Cheng Peng, Yuxi Liu, Yujing Heng, Clara Bodelon, Daniel Stover, Wendy Y. Chen, Michelle D. Holmes, A. Heather Eliassen, Peter Kraft, Rulla M. Tamimi. The impact of reproductive factors on breast tumor and normal-adjacent tissue immune profile from menarche to menopause [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C011.

MAP3K1 mutations confer tumor immune heterogeneity in hormone receptor-positive HER2-negative breast cancer.

Hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer, the most common type of breast cancer, is facing challenges such as endocrine therapy resistance and distant relapse. Immunotherapy has shown progress in treating triple-negative breast cancer, but immunological research on HR+/HER2- breast cancer is still in its early stages. Here, we performed a multi-omics analysis of a large cohort of HR+/HER2- breast cancer patients (n = 351) and revealed that HR+/HER2- breast cancer possessed a highly heterogeneous tumor immune microenvironment. Notably, the immunological heterogeneity of HR+/HER2- breast cancer was related to MAP3K1 mutation and we validated experimentally that MAP3K1 mutation could attenuate CD8+ T cell-mediated antitumor immunity. Mechanistically, MAP3K1 mutation suppressed MHC-I-mediated tumor antigen presentation through promoting the degradation of antigen peptide transporter 1/2 (TAP1/2) mRNAs, thereby driving tumor immune escape. In preclinical models, the postbiotics tyramine could reverse the MAP3K1 mutation-induced MHC-I reduction, thereby augmenting the efficacy of immunotherapy. Collectively, our study identified the vital biomarker driving the immunological heterogeneity of HR+/HER2- breast cancer and elucidated the underlying molecular mechanisms, which provided the promise of tyramine as a novel therapeutic strategy to enhance the efficacy of immunotherapy.

Multi-omics reveal immune microenvironment alterations in multiple myeloma and its precursor stages

Tumor immune microenvironmental alterations occur early in multiple myeloma (MM) development. In this study, we aim to systematically characterize the tumor immune microenvironment (TME) and the tumor-immune interactions from precursor stages, i.e., monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM), to newly diagnosed MM, comparing these to healthy donors. Using CIBERSORT, mass cytometry (CyTOF), and single-cell RNA sequencing (scRNA-Seq), we examined innate and adaptive immune changes across these stages. We found a decrease in granulocytes in the TME predicts MM outcomes. HLA-DR is reduced in CD16+ monocytes and plasmacytoid dendritic cells, while myeloid dendritic cells show decreased expression of stress and immune-response genes. NK cells and CD8+ T cells shift from a GZMK+ to a GZMB+ cytotoxic phenotype in the TME, with increased inhibitory markers TIM3 and TIGIT. In paired samples, the proportion and gene expression pattern in patient-specific GZMB+CD8+ T cells remain largely unchanged despite MM progression. Our findings provide a comprehensive immune landscape of MM and its precursors, offering insights into therapeutic strategies. Enhancing neutrophil and NK cell cytotoxicity, tumor antigen presentation, and CD8+ T cell versatility in precursor stages may prevent MM progression.

Dendritic cell maturation is induced by p53-armed oncolytic adenovirus via tumor-derived exosomes enhancing systemic antitumor immunity.

Dendritic cells (DCs) are crucial in cancer immunity, because they activate cytotoxic T cells by presenting tumor antigens. Recently, oncolytic virus therapy has been recognized as a systemic immune stimulator. We previously developed a telomerase-specific oncolytic adenovirus (OBP-301) and a p53-armed OBP-301 (OBP-702), demonstrating that these viruses strongly activate systemic antitumor immunity. However, their effects on DCs remained unclear. In the present study, the aim was to elucidate the mechanisms of DC activation by OBP-702, focusing particularly on tumor-derived exosomes. Exosomes (Exo53, Exo301, or Exo702) were isolated from conditioned media of human or murine pancreatic cancer cell lines (Panc-1, MiaPaCa-2, and PAN02) after treatment with Ad-p53, OBP-301, or OBP-702. Exo702 derived from Panc-1 and MiaPaCa-2 cells significantly upregulated CD86, CD80, CD83 (markers of DC maturation), and IFN-γ in DCs in vitro. Similarly, Exo702 derived from PAN02 cells upregulated CD86 and IFN-γ in bone marrow-derived DCs in a bilateral PAN02 subcutaneous tumor model. This DC maturation was inhibited by GW4869, an inhibitor of exosome release, and anti-CD63, an antibody targeting the exosome marker. Intratumoral injection of OBP-702 into PAN02 subcutaneous tumors significantly increased the presence of mature DCs and CD8-positive T cells in draining lymph nodes, leading to long-lasting antitumor effects through the durable activation of systemic antitumor immunity. In conclusion, tumor-derived exosomes play a significant role in DC maturation following OBP-702 treatment and are critical for the systemic activation of antitumor immunity, leading to the abscopal effect.

Combined Radiotherapy and Hyperthermia: A Systematic Review of Immunological Synergies for Amplifying Radiation-Induced Abscopal Effects.

The abscopal effect is a systemic immune response characterized by metastases regression at sites distant from the irradiated lesion. This systematic review aims to explore the immunological mechanisms of action underlying the abscopal effect and to investigate how hyperthermia (HT) can increase the chances of radiotherapy (RT) triggering systemic anti-tumor immune responses. This review is created in accordance with the PRISMA guidelines. HT and RT have both complementary and synergistic immunological effects. Both methods trigger danger signal release, promoting cytokine and chemokine secretion, which increases T-cell infiltration and facilitates cell death. Both treatments upregulate extracellular tumor HSP70, which could amplify DAMP recognition by macrophages and DCs, leading to stronger tumor antigen presentation and CTL-mediated immune responses. Additionally, the combined increase in cell adhesion molecules (VCAM-1, ICAM-1, E-selectin, L-selectin) could enhance leukocyte adhesion to tumors, improving lymphocyte trafficking and boosting systemic anti-tumor effects. Lastly, HT causes vasodilation and improves blood flow, which might exacerbate those distant effects. We suggest the combination of local radiotherapy with fever-range whole-body hyperthermia to optimally enhance the chances of triggering the abscopal effect mediated by the immune system.

AML-VAC-XS15-01: protocol of a first-in-human clinical trial to evaluate the safety, tolerability and preliminary efficacy of a multi-peptide vaccine based on leukemia stem cell antigens in acute myeloid leukemia patients.

Acute myeloid leukemia (AML) has a dismal prognosis, mostly due to minimal residual disease-driven relapse, making an elimination of persisting therapy-resistant leukemia progenitor/stem cells (LPCs) the main goal for novel therapies. Peptide-based immunotherapy offers a low-side-effect approach aiming to induce T cell responses directed against human leukocyte antigen (HLA) presented tumor antigens on malignant cells by therapeutic vaccination. Mass spectrometry-based analysis of the naturally presented immunopeptidome of primary enriched LPC and AML samples enabled the selection of antigens exclusively expressed on LPC/AML cells, which showed de novo induction and spontaneous memory T cell responses in AML patients, and whose presentation and memory T cell recognition was associated with improved disease outcome. Based on these data the therapeutic vaccine AML-VAC-XS15 was designed, comprising two mutated HLA class I-restricted peptides from the common AML-specific mutation in NPM1 and seven HLA class II-restricted peptides (six non-mutated high-frequent AML/LPC-associated antigens and one mutated peptide from the AML-specific mutation R140Q in IDH2), adjuvanted with the toll like receptor 1/2 ligand XS15 and emulsified in Montanide ISA 51 VG. A phase I open label clinical trial investigating AML-VAC-XS15 was designed, recruiting AML patients in complete cytological remission (CR) or CR with incomplete blood count recovery. Patients are vaccinated twice with a six-week interval, with an optional booster vaccination four months after 2nd vaccination, and are then followed up for two years. The trial's primary objectives are the assessment of the vaccine's immunogenicity, safety and toxicity, secondary objectives include characterization of vaccine-induced T cell responses and assessment of preliminary clinical efficacy. The AML-VAC-XS15-01 study was approved by the Ethics Committee of the Bavarian State medical association and the Paul-Ehrlich Institut (P01392). Clinical trial results will be published in peer-reviewed journals.

TET2 promotes tumor antigen presentation and T cell IFN-γ which is enhanced by vitamin C.

Immune evasion by tumors is promoted by low T cell infiltration, ineffective T cell activity directed against the tumor and reduced tumor antigen presentation. The TET2 DNA dioxygenase gene is frequently mutated in hematopoietic malignancies and loss of TET enzymatic activity is found in a variety of solid tumors. We showed previously that vitamin C (VC), a co-factor of TET2, enhances tumor-associated T cell recruitment and checkpoint inhibitor therapy responses in a TET2-dependent manner. Using single-cell RNA sequencing (scRNA-seq) analysis performed on B16-OVA melanoma tumors, we have shown here that an additional function for TET2 in tumors is to promote expression of certain antigen presentation machinery genes, which is potently enhanced by VC. Consistently, VC promoted antigen presentation in cell-based and tumor assays in a TET2-dependent manner. Quantifying intercellular signaling from the scRNA-seq dataset showed that T cell-derived IFNγ-induced signaling within the tumor and tumor microenvironment requires tumor-associated TET2 expression which is enhanced by VC treatment. Analysis of patient tumor samples indicated that TET activity directly correlates with antigen-presentation gene expression and with patient outcomes. Our results demonstrate the importance of tumor-associated TET2 activity as a critical mediator of tumor immunity which is augmented by high-dose VC therapy.

12312 A Comparative Genomic Analysis Between Parathyroid Adenomas And Carcinomas With Heterozygous Germline Cdc73 Mutations

Abstract Disclosure: Y. Li: None. W.F. Simonds: None. H. Chen: None. Introduction: Parathyroid cancer is responsible for ∼1% of primary hyperparathyroidism. The hereditary form of this malignancy has been linked to germline mutations of the CDC73 gene. We previously reported that only the germline CDC73 mutations causing a significant impact on the function/expression of its encoded protein are associated with parathyroid carcinomas. On the other hand, these germline mutations may lead to only parathyroid adenomas or no parathyroid disease, suggesting incomplete penetrance. This observation raises the question of what additional genomic events are required for parathyroid tumorigenesis in carriers with germline CDC73 mutations. Methods: Twelve patients harboring heterozygous germline CDC73 mutations were included in this study. Whole exome sequencing was performed in all 12 parathyroid tumors (6 adenomas and 6 carcinomas) and the paired normal tissues. RNA sequencing was successfully performed in three of each parathyroid carcinomas, adenomas, and normal glands. The sequencing raw data were processed using the CCBR-Pipeliner. EnrichR, Gene Set Enrichment Analysis, and CIBERSORT were used for the downstream analyses. Results: All parathyroid carcinomas and adenomas had gained one somatic event predicted to cause a complete inactivation of the second CDC73 allele. Several distinctive genomic features were identified in parathyroid carcinomas compared to adenomas, including more single nucleotide variants bearing the signature of APOBEC deamination, frequent mutations among the genes involved in the PI-3K/mTOR signaling, and substantially more copy number variations and differentially expressed genes. Parathyroid carcinomas also share some genomic features with adenomas. For instance, both tumors have frequent somatic mutations and copy number loss that impact the genes related to T-cell receptor signaling and tumor antigen presentation, suggesting a shared strategy to evade immune surveillance. Consistent with these findings, an in silico estimation of immune cell composition in tumors found an absence of CD8+ T-cells in parathyroid adenomas and carcinomas. Conclusion: Our study provides evidence that biallelic inactivation of CDC73 is essential for parathyroid tumorigenesis in carriers with germline mutations of this gene. Despite sharing some genomic features with adenomas, parathyroid carcinomas have more distinctive alterations in the genome, some of which may be critical for cancer formation. Presentation: 6/2/2024

12312 A Comparative Genomic Analysis Between Parathyroid Adenomas And Carcinomas With Heterozygous Germline Cdc73 Mutations

Abstract Disclosure: Y. Li: None. W.F. Simonds: None. H. Chen: None. Introduction: Parathyroid cancer is responsible for ∼1% of primary hyperparathyroidism. The hereditary form of this malignancy has been linked to germline mutations of the CDC73 gene. We previously reported that only the germline CDC73 mutations causing a significant impact on the function/expression of its encoded protein are associated with parathyroid carcinomas. On the other hand, these germline mutations may lead to only parathyroid adenomas or no parathyroid disease, suggesting incomplete penetrance. This observation raises the question of what additional genomic events are required for parathyroid tumorigenesis in carriers with germline CDC73 mutations. Methods: Twelve patients harboring heterozygous germline CDC73 mutations were included in this study. Whole exome sequencing was performed in all 12 parathyroid tumors (6 adenomas and 6 carcinomas) and the paired normal tissues. RNA sequencing was successfully performed in three of each parathyroid carcinomas, adenomas, and normal glands. The sequencing raw data were processed using the CCBR-Pipeliner. EnrichR, Gene Set Enrichment Analysis, and CIBERSORT were used for the downstream analyses. Results: All parathyroid carcinomas and adenomas had gained one somatic event predicted to cause a complete inactivation of the second CDC73 allele. Several distinctive genomic features were identified in parathyroid carcinomas compared to adenomas, including more single nucleotide variants bearing the signature of APOBEC deamination, frequent mutations among the genes involved in the PI-3K/mTOR signaling, and substantially more copy number variations and differentially expressed genes. Parathyroid carcinomas also share some genomic features with adenomas. For instance, both tumors have frequent somatic mutations and copy number loss that impact the genes related to T-cell receptor signaling and tumor antigen presentation, suggesting a shared strategy to evade immune surveillance. Consistent with these findings, an in silico estimation of immune cell composition in tumors found an absence of CD8+ T-cells in parathyroid adenomas and carcinomas. Conclusion: Our study provides evidence that biallelic inactivation of CDC73 is essential for parathyroid tumorigenesis in carriers with germline mutations of this gene. Despite sharing some genomic features with adenomas, parathyroid carcinomas have more distinctive alterations in the genome, some of which may be critical for cancer formation. Presentation: 6/2/2024

Synergizing autophagic cell death and oxaliplatin-induced immunogenic death by a self-delivery micelle for enhanced tumor immunotherapy

Chemotherapy has become an emerging strategy to activate cytotoxic T cell responses by inducing immunogenic cell death (ICD), but the level of antitumor immunity induced by chemotherapeutic agents, such as oxaliplatin (OXA), is limited due to inadequate tumor antigen presentation and T cell activation. Inducing autophagic cell death (ACD) promotes the release of tumor antigen and the recruitment of dendritic cells, therefore strengthening antitumor immune responses. Here we simultaneously activate ICD and ACD with tumor targeting micelle to achieve enhanced antitumor chemo-immunotherapy. A self-delivery micelle is formulated by conjugating OXA prodrug with tocopherol succinate (TOS) as a hydrophobic segment and further encapsulates autophagy activator SMER28 to afford TOPR/SMER28, which specifically targets αvβ3 on tumor cells with c(RGDfK). Upon cellular internalization, OXA is released from the prodrug in response to the high concentration of reduced glutathione (GSH) in tumor cells, triggering ICD and releasing associated molecular patterns (DAMPs) signaling molecules to stimulate immunity. Meanwhile, SMER28 over-activates autophagy to induce autophagic cell death, which further leads to the maturation of dendritic cells and ultimately activates anti-tumor immune response. In the 4T1 tumor-bearing mice, the combination of OXA and SMER28 effectively inhibits tumor growth and activates antitumor immune responses. The tumor targeted micelle releases OXA and SMER28 in an on-demand profile and strengthens tumor chemo-immunotherapy by synergizing ICD and ACD, providing an alternative for antitumor immunotherapy. Statement of significanceChemotherapy induces immunogenic cell death (ICD) to activate anti-tumor immunity. However, the efficacy is limited by low levels of antigen presentation and T cell activation. To strengthen the antitumor immune responses induced by ICD, we first combine autophagic cell death (ACD) with ICD by formulating a glutathione-responsive oxaliplatin prodrug micelle co-encapsulating the autophagy activator SMER28. The activated autophagic level by SMER28 enhances the release of antigen and the recruitment of APCs, and ultimately bolsters T cell-mediated antitumor immune responses. We provide a potential strategy to amplify antitumor immune effects by combining autophagy activation with chemotherapy.

Single-cell transcriptome analysis reveals evolving tumour microenvironment induced by immunochemotherapy in nasopharyngeal carcinoma.

Combinatory therapeutic strategy containing immunochemotherapy as part of induction therapy components is one of the current trends in the treatment of high-risk metastatic locally advanced nasopharyngeal carcinoma (NPC). However, the mechanism underlying the heterogeneity of response at the single-cell level has not been underexplored. 18 bulks and 11 single-cell RNA sequencing from paired before-treatment and on-treatment samples in patients with treatment-naive high-risk metastatic locally advanced NPCs were obtained. Following quality control, a total of 87191 cells were included in the subsequence bioinformatics analysis. Immunochemotherapy was associated with on-treatment tumour microenvironment (TME) remodelling, including upregulation of anti-TMEs signatures, downregulation of pro-TMEs signatures, reversing CD8+ T exhaustion, and repolarizing proinflammatory TAMs. For the patients achieving a complete response, the cytotoxic activity of CD8+ T cells was stimulated and more interferon-gamma was provided, which would be the key for TAMs proinflammatory repolarization and eventually promote the CD8+ T cells maturation in turn. Among patients who did not reach complete response, differentiation and hypoxia signatures for endothelial cells were elevated after therapy. These patients exhibited higher levels of immune checkpoint genes in malignant cells at the baseline (before treatment), and decreased tumour antigen presentation activity, which may underlie the resistance mechanism to therapy. This study pictures a map of TME modulation following immunochemotherapy-based combination induction therapy and provides potential future approaches. Immunochemotherapy remodeled T cell phenotypes. For the patients achieving complete response, more interferon gamma was provided by CD8+ T cells after therapy, which would be the key for TAMs pro-inflammatory repolarization and eventually promote the CD8+ T cells maturation in turns. Among patients who did not reach complete response, malignant cells exhibited higher level of immune checkpoint genes before therapy, and decreased tumor antigen presentation activity, which may underlie the resistance mechanism to therapy.

Abstract B035: Nanoparticle delivery of innate immune agonists combines with senescence- inducing agents to mediate T cell control of pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma has quickly risen to become the 3rd leading cause of cancer- related death. This is in part due to its fibrotic tumor microenvironment (TME) that contributes to poor vascularization and immune infiltration and subsequent chemo- and immunotherapy failure. Here we investigated an innovative immunotherapy approach combining delivery of STING and TLR4 innate immune agonists via lipid-based nanoparticles (NPs) co-encapsulation with senescence-inducing RAS-targeted therapies that can remodel the immune suppressive PDAC TME through the senescence-associated secretory phenotype. Treatment of transplanted and autochthonous PDAC mouse models with these regimens led to enhanced uptake of NPs by multiple cell types in the PDAC TME, induction of type I interferon and other pro-inflammatory signaling, increased antigen presentation by tumor cells and antigen presenting cells, and subsequent activation of both innate and adaptive immune responses. This two-pronged approach produced potent T cell-driven and Type I interferon-mediated tumor regressions and long-term survival in preclinical PDAC models dependent on both tumor and host STING activation. STING and TLR4-mediated Type I interferon signaling were also associated with enhanced NK and CD8+ T cell immunity in human PDAC. Thus, combining localized immune agonist delivery with systemic tumor-targeted therapy can synergize to orchestrate a coordinated Type I interferon-driven innate and adaptive immune assault to overcome immune suppression and activate durable anti-tumor T cell responses against PDAC. Citation Format: Kelly D DeMarco, Loretah Chibaya, Christina F Lusi, Griffin I Kane, Meghan L Brassil, Chaitanya N Parikh, Katherine C Murphy, Shreya R Chowdury, Junhui Li, Boyang Ma, Tiana E Taylor, Julia Cerrutti, Haruka Mori, Miranda Diaz-Infante, Jessica Peura, Jason R Pitarresi, Lihua Julie Zhu, Katherine A Fitzgerald, Prabhani U Atukorale, Marcus Ruscetti. Nanoparticle delivery of innate immune agonists combines with senescence- inducing agents to mediate T cell control of pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B035.

Abstract B063: Elucidating treatment induced tumor antigen presentation in pancreatic cancer

Abstract Introduction Pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, is projected to become the second leading cause of cancer-related deaths by 2030. The 5-year survival rate remains stubbornly low at just 13%. These discouraging statistics primarily stem from the lack of effective treatments till date. Despite the success of immunotherapy for several malignancies, immunotherapy for PDAC has yielded disappointing results alone or in combination with other therapies. Successful immunotherapy will require a deeper understanding of PDAC immunobiology and immune recognition of cancer during its progression, and treatment regimens. Immunosurveillance of cancer requires the presentation of peptide antigens on Major Histocompatibility complex class I (MHC-I). Understanding the repertoire of MHC-I associated peptides (pMHC-I), collectively termed as the “immunopeptidome”, is essential for anti-tumor immunity and successful immunotherapies. Using a collection of preclinical tools and human cell lines, we aim to uncover treatment induced antigens in PDAC that can be used for targeted immunotherapy approaches. Methods To understand the biogenesis of the immunopeptidome, our group has developed a novel genetically engineered mouse model (GEMM), which integrates inducible affinity tags on MHC-I (KbStrep) and ribosomes (RiboTag) into the Kras LSL-G12D/+ ; P53 fl/fl (KP) mouse model (KP/RiboMHC). This approach enabled us to precisely measure protein synthesis and antigen presentation in malignant PDAC cells in vivo with paired ribosome profiling and mass spectrometry based immunopeptidomics. In parallel we have employed a collection of human PDAC cell lines for immunopeptidomics analysis. About 93% of PDACs have KRAS mutation, with G12D mutation being the most common. In addition, PDAC is subjected to a deregulated metabolic milieu, with a strong dependence on glutamine utilization. Therefore, to examine treatment induced changes in PDAC antigen presentation, we examined the impact of KRAS inhibition (MRTX1133) and glutamine antagonism (6-diazo-5-oxo-L-norleucine, DON) on the biogenesis of the immunopeptidome in vitro and in vivo. Results Using our GEMM model, we have started to uncover MRTX1133 and DON induced alterations in protein synthesis and in pMHC-I repertoire in vivo using the KP/RiboMHC model and in vitro in mouse and human cell lines. We have identified unique antigen peptides that are induced by MRTX1133 and DON, including those derived from non-canonical translation events that were defined by ribosome profiling. Conclusions Our data demonstrates that KRAS inhibition with MRTX1133 or glutamine antagonism with DON reshapes the antigen landscape of PDAC. We are actively exploring which of the induced peptides harbor potential to mount an anti-tumor CD8+ T cell response. Collectively, these results could pave the way forward for rationally designed treatment regimens that pair targeted therapies with antigen specific immunotherapy in PDAC. Citation Format: Emma Adhikari, Andrew Weeden, Emily Brennan, Christopher Polera, Victoria lzumi, Bin Fang, John Koomen, Paul Stewart, Alex Jaeger. Elucidating treatment induced tumor antigen presentation in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B063.

Engineered Nanoparticles for Enhanced Antitumoral Synergy Between Macrophages and T Cells in the Tumor Microenvironment.

T cells and macrophages have the potential to collaborate to eliminate tumor cells efficiently. Macrophages can eliminate tumor cells through phagocytosis and subsequently activate T cells by presenting tumor antigens. The activated T cells, in turn, can kill tumor cells and redirect tumor-associated macrophages toward an antitumoral M1 phenotype. However, checkpoint molecules expressed on tumor cells impede the collaborative action of these immune cells. Meanwhile, monotherapy with a single immune checkpoint inhibitor (ICI) for either macrophages or T cells yields suboptimal efficacy in cancer patients. To address this challenge, here a nanoparticle capable of efficiently delivering dual ICIs to tumors for both macrophages and T cells is developed. These programmed cell death protein 1 (PD-1)-transfected macrophage membrane-derived nanoparticles (PMMNPs) can target tumors and provide signal-regulatory protein alpha and PD-1 to block CD47 and programmed cell death-ligand 1 (PD-L1), respectively, on tumor cells. PMMNPs enhance macrophage-mediated cancer cell phagocytosis and antigen presentation, promote T cell activation, and induce the reprogramming of macrophages toward an antitumoral phenotype. In syngeneic tumor-bearing mice, PMMNPs demonstrate superior therapeutic efficacy compared to nanoparticles delivering single ICIs and non-targeted delivery of anti-CD47 and anti-PD-L1 antibodies. PMMNPs capable of augmenting the antitumoral interplay between macrophages and T cells may offer a promising avenue for cancer immunotherapy.

Preparation of a Plasma‐Induced Dendritic Cell Vaccine and its Anti‐Tumor Immunity in a Murine Model of Melanoma

AbstractDendritic cell (DC) vaccines play an important role in anti‐tumor immunotherapy. Tumor‐associated cells or cytokines in the tumor microenvironment (TME) can inhibit the antigen‐presenting function of DC. Immunogenic cell death (ICD) can enhance the uptake and presentation of tumor antigens by DC. This study investigates the maturation mechanism of DC induced by low‐temperature plasma (LTP), as well as the therapeutic and protective effects of LTP‐induced DC vaccine in a tumor model. DC2.4 that is co‐cultured with LTP‐treated B16F10 (LTP‐B16) or with these supernatants exhibited decreased phagocytic activity, increased production of cytokines (IL‐12, IL‐6, TNF‐α, and IL‐1β), and increased expression of cell surface activation markers (CD80, CD86, and MHC II). The expression of CD80+/CD86+ is decreased after pre‐treatment with TLR4 and NF‐κB (p65) inhibitors, respectively. In vivo, trials indicated that the LTP‐induced DC vaccine‐induced anti‐tumor immunity and, when combined with cisplatin, synergistically reduced tumor growth.

The Role of Caspases in Melanoma Pathogenesis.

Melanoma (malignant melanoma, MM) is an aggressive malignant skin cancer with an increasing incidence rate. The complete pathogenesis of MM in not clear. Due to DNA damage, mutations, dysregulation of growth factors, inactivation of tumor suppressor genes, and activation of oncogenes, excessive uncontrolled growth of abnormal melanocytes occurs in melanomas. Caspases are a group of proteolytic enzymes that participate in several processes important in regulating mechanisms at the cellular level. They play a role in cell homeostasis and programmed cell death (apoptosis) and in the regulation of non-apoptotic cell death processes. Dysregulation of caspase activation plays a role in the etiology of cancers, including melanoma. Caspases can initiate and execute apoptosis and are involved in regulating cell death and controlling tumor growth. These enzymes also inhibit tumor growth by cleaving and inactivating proteins that are involved in cell proliferation and angiogenesis. Moreover, caspases are involved in the activation of immune processes through the processing and presentation of tumor antigens, which facilitates recognition of the tumor by the immune system. The role of caspases in melanoma is complex, and they may inhibit melanoma growth and progression. This work aims to review the current knowledge of the role of individual caspases in melanoma pathogenesis.

Effect of heterozygosity loss of HLA-I on immune evasion and promotion of non-small cell lung cancer brain metastasis and immunotherapy resistance.

209 Background: HLA-I play a crucial role in T cell recognition and killing of tumor cells as well as in PD-1/PD-L1 immunotherapy. Loss of heterozygosity (LOH) of HLA-I alleles has been found to be common in lung cancer patients and influences immune escape during tumor evolution. This study aims to explore the incidence of HLA-I LOH in intracranial metastases of advanced non-small cell lung cancer patients with brain metastasis and its impact on the efficacy of immunotherapy. Methods: A total of 29 patients with non-small cell lung cancer brain metastasis were included in this study. All enrolled patients underwent either percutaneous biopsy or surgical resection of intracranial metastases and had tissue specimens from the primary lung lesions. Whole-exome sequencing was performed on all primary/metastatic lesions to determine HLA-I typing/LOH and calculate tumor mutation burden (TMB). Additionally, we assessed the expression levels of CD8 T cells in the tumor immune microenvironment. Among the enrolled patients, 20 received PD-1/PD-L1 treatment. Results: Among the enrolled patients, 82.8% (24/29) had heterozygous HLA-I typing, with HLA-I LOH present in 25% (6/24) of patients' primary lesions and 58.3% (14/24) in brain metastatic lesions. Analysis of TMB in different lesions revealed a median TMB of 7.8 mut/Mb in lesions with intact HLA-I and 11.4 mut/Mb in lesions with HLA-I LOH. Notably, the median TMB in brain metastatic lesions with HLA-I LOH was 13.2 mut/Mb, higher than that in HLA-I LOH primary lung lesions (10.1 mut/Mb). Immunohistochemistry demonstrated that CD8 T cell expression levels were lowest in brain metastatic lesions with HLA-I LOH and highest in intact HLA-I primary lung lesions. Among patients who received immunotherapy, four cases exhibited inconsistent lesion responses, with stable or regressing primary lesions but progressive intracranial metastases. Survival analysis revealed that patients with HLA-I LOH in brain metastases had significantly lower PFS compared to those without (4.1 months vs. 6.9 months, P < 0.05), with no significant difference in OS. Conclusions: This study indicates that the incidence of HLA-I LOH in brain metastases of lung cancer is higher than that in primary lung lesions, accompanied by higher TMB, possibly due to the ineffective presentation of tumor antigens resulting in the accumulation of mutations in lost HLA-I. Moreover, tumors with HLA-I LOH have reduced levels of CD8 T cell infiltration, suggesting impaired tumor antigen presentation impedes immune cytotoxicity. These phenomena contribute to the poorer efficacy of immunotherapy in such patients. In conclusion, HLA-I LOH may be one of the important mechanisms of immune escape in lung cancer brain metastases.

Generation of Devil Facial Tumour Cells Co-Expressing MHC With CD80, CD86 or 41BBL to Enhance Tumour Immunogenicity.

The major histocompatibility complex (MHC) molecules play an integral role in the adaptive immune response to transmissible cancers through tumour antigen presentation and recognition of allogeneic MHC molecules. The transmissible devil facial tumours 1 and 2 (DFT1 and DFT2) modulate MHC-I antigen presentation to evade host immune responses and facilitate transmission of tumours cells to new Tasmanian devil (Sarcophilus harrisii) hosts. To enhance T-cell-driven tumour immunogenicity for vaccination and immunotherapy, DFT1 and DFT2 cells were co-transfected with (i) NLRC5 for MHC-I expression or CIITA for MHC-I and MHC-II expression, and (ii) a co-stimulatory molecule, either CD80, CD86 or 41BBL. The co-transfected DFT cells presented enhanced expression of MHC-I and/or MHC-II. As few devil-specific monoclonal antibodies exist, we used recombinant CTLA4 and 41BB fused to a fluorescent protein to confirm expression of cell surface CD80, CD86 and 41BBL. The capacity for these cells to induce T-cell responses including PD1 and IFNG expression was evaluated in in vitro co-culture assays with captive devil peripheral blood mononuclear cells (PBMCs). Although PBMC viability had increased, there was no evidence of enhanced T-cell activation. This system can be used to identify additional factors required to promote activation of naïve devil T-cells in vitro.

TDERS, an exosome RNA-derived signature predicts prognosis and immunotherapeutic response in clear cell renal cell cancer: A multicohort study

BackgroundTumor-derived exosomes are involved in tumor progression and immune invasion and might function as promising noninvasive approaches for clinical management. However, there are few reports on exosomal-based markers for predicting the progression and adjuvant therapy response rate among patients with clear cell renal cell carcinoma (ccRCC). MethodsThe signatures differentially expressed in exosomes from tumor and normal tissues from ccRCC patients were correspondingly deregulated in ccRCC tissues. We adopted a two-step strategy, including Lasso and bootstrapping, to construct a novel risk stratification system termed the TDERS (Tumor-Derived Exosome-Related Risk Score). During the testing and validation phase, we leveraged multiple external datasets containing over 2000 RCC cases from eight cohorts and one inhouse cohorts to evaluate the accuracy of the TDERS. In addition, enrichment analysis, immune infiltration signatures, mutation landscape and therapy sensitivity between the high and low TDERS groups were compared. Finally, the impact of TDERS on the tumor microenvironment (TME) was also analysed in our single-cell datasets. ResultsTDERS consisted of 12 mRNAs deregulated in both exosomes and tissues from patients with ccRCC. TDERS achieved satisfactory performance in both prognosis and immune checkpoint inhibitor (ICI) response across all ccRCC cohorts and other pathological types, since the average area under curve (AUC) to predict 5-year overall survival (OS) was larger than 0.8 across the four cohorts. Patients divided into the TDERS high group were resistant to ICIs, while mercaptopurine might function as a promising agent for those patients. Patients with a high TDERS were characterized by coagulation and hypoxia, which induced hampered tumor antigen presentation and relative resistance to ICIs. In addition, single cells from 12 advanced samples validated this phenomenon since the interaction between dendritic cells and macrophages was limited. Finally, PLOD2, which is highly expressed in fibro- and epi‑tissue, could be a potential therapeutic target for ccRCC patients since inhibiting PLOD2 altered the malignant phenotype of ccRCC in vitro. ConclusionAs a novel, non-invasive and repeatable monitoring tool, the TDERS could work as a robust risk stratification system for patients with renal cancer and precisely inform treatment decisions about ICI therapy.