Antitumor T-cell Responses Research Articles

Neudesin regulates dendritic cell function and antitumor CD8+ T cell immunity

Dendritic cells (DCs) are essential for antitumor T-cell responses to immune checkpoint inhibitor therapies. We have previously reported that the secreted protein neudesin suppresses DC function. In contrast, neudesin has been found to be abundantly expressed in human cancers. In this study, we evaluated the role of neudesin in cancer immunity. Cancer-related database analysis revealed that patients with melanoma with low neudesin expression exhibited increased infiltration of DCs and CD8+ T cells and improved outcomes of checkpoint inhibitor therapy. In mouse tumor models, neudesin deficiency delayed tumor growth and increased the proportions of Type 1 conventional DCs (cDC1s) and tumor antigen-specific CD8+ T cells in tumors and tumor-infiltrating lymph nodes. Neudesin-deficient antitumor cDC1 vaccine enhanced the systemic immunity more effectively than the wild-type cDC1 vaccine. Overall, our findings highlight the importance of neudesin in cancer immunity, providing a novel target for immunotherapy.

A dual-pathway pyroptosis inducer based on Au–Cu2-xSe@ZIF-8 enhances tumor immunotherapy by disrupting the zinc ion homeostasis

The regulation of intracellular ionic homeostasis to trigger antigen-specific immune responses has attracted extensive interest in tumor therapy. In this study, we developed a dual-pathway nanoreactor, Au-Cu2-xSe@ZIF-8@P18 NPs (ACS-Z-P NPs), which targets danger-associated molecular patterns (DAMPs) and releases Zn2+ and reactive oxygen species (ROS) within the tumor microenvironment (TME). Zn2+ released from the metal–organic frameworks (MOFs) was deposited in the cytoplasm, leading to aberrant transcription levels of intracellular zinc-regulated proteins and DNA damage, thereby inducing pyroptosis and immunogenic cell death (ICD) dependent on caspase1/gasdermin D (GSDMD) pathway. Furthermore, upon laser irradiation, ACS-Z-P NPs could break through the limitations of inherent defects of immunosuppression in TME, enhance ROS generation through a Fenton-like reaction cascade, which subsequently triggered the activation of inflammatory vesicles and the release of damage-associated molecular patterns (DAMPs). This cascade effect led to the amplification of pyroptosis and immunogenic cell death (ICD), thereby remodeling the immunosuppressed TME. Consequently, this process improved dendritic cell (DC) antigen presentation and augmented anti-tumor T-cell responses, effectively initiating antigen-specific immune responses and further enhancing pyroptosis and ICD. This study explores the therapeutic properties of these mechanisms in detail. Statement of significanceThe synthesized Au-Cu2-xSe@ZIF-8@P18 nanoparticles (ACS-Z-Ps) can effectively enhance the bodyʼs immune response by regulating zinc ion levels within cells. This regulation leads to abnormal levels of zinc-regulated protein transcription and DNA damage, which induces cellular pyroptosis. As a result, antigen presentation to dendritic cells (DCs) is improved, and anti-tumor T-cell responses are enhanced.The ACS-Z-P NPs overcome the limitations of ROS deficiency and immunosuppression in the tumor microenvironment by using H2O2 in the tumor microenvironment through a Fenton-like reaction. This leads to an increased production of ROS and O2, remodeling of the immunosuppressed tumor microenvironment, and enhanced induction of cell pyroptosis and immunogenic cell death.ACS-Z-P NPs targeted B16 cells using the photosensitizer P18 in combination with PDT treatment. This approach significantly inhibited the proliferation of B16 cells and effectively inhibited tumor growth.

Anti-4-1BB×PDL1 Bispecific Antibody Reinvigorates Tumor-Specific Exhausted CD8+ T Cells and Enhances the Efficacy of Anti-PD1 Blockade.

To overcome the limited efficacy of immune checkpoint blockade, there is a need to find novel cancer immunotherapeutic strategies for the optimal treatment of cancer. The novel anti-4-1BB×PDL1 bispecific antibody-ABL503 (also known as TJ-L14B)-was designed to simultaneously target PDL1 and 4-1BB and demonstrated strong antitumor T-cell responses without considerable toxicity. In this study, we investigated the mechanisms by which the combination of ABL503 and anti-PD1 blockade affected the reinvigoration of exhausted tumor-infiltrating CD8+ T cells (CD8+ TIL) and antitumor efficacy. Single-cell suspensions of hepatocellular carcinoma and ovarian cancer tissues from treatment-naïve patients were used for immunophenotyping of CD8+ TILs and in vitro functional assays. Humanized hPD1/hPDL1/h4-1BB triple-knock-in mice were used to evaluate the effects of ABL503 and anti-PD1 blockade in vivo. We observed that ABL503 successfully restored the functions of 4-1BB+ exhausted CD8+ TILs, which were enriched for tumor-specific T cells but unresponsive to anti-PD1 blockade. Importantly, compared with anti-PD1 blockade alone, the combination of ABL503 and anti-PD1 blockade further enhanced the functional restoration of human CD8+ TILs in vitro. Consistently, the combination of ABL503 with anti-PD1 in vivo significantly alleviated tumor growth and induced enhanced infiltration and activation of CD8+ TILs. ABL503, a PDL1 and 4-1BB dual-targeting bispecific antibody, elicits pronounced additive tumor growth inhibition, with increased infiltration and functionality of exhausted CD8+ T cells, which in turn enhances the anticancer effects of anti-PD1 blockade. These promising findings suggest that ABL503 (TJ-L14B) in combination with PD1 inhibitors will likely further enhance therapeutic benefit in clinical trials. See related commentary by Molero-Glez et al., p. 3971.

S100A9 and HMGB1 orchestrate MDSC-mediated immunosuppression in melanoma through TLR4 signaling

BackgroundImmunotherapies for malignant melanoma are challenged by the resistance developed in a significant proportion of patients. Myeloid-derived suppressor cells (MDSC), with their ability to inhibit antitumor T-cell responses, are a...

Malic enzyme 2 maintains metabolic state and anti-tumor immunity of CD8+ T cells

The functional integrity of CD8+ Tcells is closely linked to metabolic reprogramming; therefore, understanding the metabolic basis of CD8+ Tcell activation and antitumor immunity could provide insights into tumor immunotherapy. Here, we report that ME2 is critical for mouse CD8+ Tcell activation and immune response against malignancy. ME2 deficiency suppresses CD8+ Tcell activation and anti-tumor immune response invitro and invivo. Mechanistically, ME2 depletion blocks the TCA cycle flux, leading to the accumulation of fumarate. Fumarate directly binds to DAPK1 and inhibits its activity by competing with ATP for binding. Notably, pharmacological inhibition of DAPK1 abolishes the anti-tumor function conferred by ME2 to CD8+ Tcells. Collectively, these findings demonstrate a role for ME2 in the regulation of CD8+ Tcell metabolism and effector functions as well as an unexpected function for fumarate as a metabolic signal in the inhibition of DAPK1.

Crucial role of dendritic cells in the generation of anti-tumor T-cell responses and immunogenic tumor microenvironment to suppress tumor development.

Dendritic cells (DCs) are known as unique professional antigen (Ag)-presenting cells (APCs) to prime naïve T cells for the initiation of adaptive immunity. While DCs are believed to play a pivotal role in generating anti-tumor T-cell responses, the importance of DCs in the protection from the progression of tumors remains elusive. Here, we show how the constitutive deficiency of CD11chi DCs influences the progression of tumors with the use of binary transgenic mice with constitutive loss of CD11chi DCs. Constitutive loss of CD11chi DCs not only enhances the progression of tumors but also reduces the responses of Ag-specific T cells. Furthermore, the congenital deficiency of CD11chi DCs generates the immunosuppressive tumor microenvironment (TME) that correlates with the marked accumulation of myeloid-derived suppressor cells (MDSCs) and the prominent productions of immunosuppressive mediators. Thus, our findings suggest that CD11chi DCs are crucial for generating anti-tumor T-cell responses and immunogenic TME to suppress the development of tumors.

Targeting ROS-sensing Nrf2 potentiates anti-tumor immunity of intratumoral CD8+ T and CAR-T cells

Cytotoxic T lymphocytes (CTLs) play a crucial role in cancer rejection. However, CTLs encounter dysfunction and exhaustion in the immunosuppressive tumor microenvironment (TME). Although the reactive oxygen species (ROS)-rich TME attenuates CTL function, the underlying molecular mechanism remains poorly understood. The nuclear factor erythroid 2-related 2 (Nrf2) is the ROS-responsible factor implicated in increasing susceptibility to cancer progression. Therefore, we examined how Nrf2 is involved in anti-tumor responses of CD8+ T and chimeric antigen receptor (CAR) Tcells in the ROS-rich TME. Here, we demonstrated that tumor growth in Nrf2-/- mice was significantly controlled and was reversed by Tcell depletion and further confirmed that Nrf2 deficiency in Tcells promotes anti-tumor responses using an adoptive transfer model of antigen-specific CD8+ Tcells. Nrf2-deficient CTLs are resistant to ROS, and their effector functions are sustained in the TME. Furthermore, Nrf2 knockdown in human CAR-Tcells enhanced the survival and function of intratumoral CAR-Tcells in a solid tumor xenograft model and effectively controlled tumor growth. ROS-sensing Nrf2 inhibits the anti-tumor Tcell responses, indicating that Nrf2 may be a potential target for Tcell immunotherapy strategies against solid tumors.

Pan-lysyl oxidase inhibition disrupts fibroinflammatory tumor stroma, rendering cholangiocarcinoma susceptible to chemotherapy.

Cholangiocarcinoma (CCA) features highly desmoplastic stroma that promotes structural and functional resistance to therapy. Lysyl oxidases (LOX, LOXL1-4) catalyze collagen cross-linking, thereby increasing stromal rigidity and facilitating therapeutic resistance. Here, we evaluate the role of lysyl oxidases in stromal desmoplasia and the effects of pan-lysyl oxidase (pan-LOX) inhibition in CCA. Resected CCA and normal liver specimens were analyzed from archival tissues. Spontaneous and orthotopic murine models of intrahepatic CCA (iCCA) were used to assess the impact of the pan-LOX inhibitor PXS-5505 in treatment and correlative studies. The functional role of pan-LOX inhibition was interrogated through in vivo and ex vivo assays. All 5 lysyl oxidases are upregulated in CCA and reduced lysyl oxidase expression is correlated with an improved prognosis in resected patients with CCA. Spontaneous and orthotopic murine models of intrahepatic cholangiocarcinoma upregulate all 5 lysyl oxidase isoforms. Pan-LOX inhibition reversed mechanical compression of tumor vasculature, resulting in improved chemotherapeutic penetrance and cytotoxic efficacy. The combination of chemotherapy with pan-LOX inhibition increased damage-associated molecular pattern release, which was associated with improved antitumor T-cell responses. Pan-LOX inhibition downregulated macrophage invasive signatures in vitro, rendering tumor-associated macrophages more susceptible to chemotherapy. Mice bearing orthotopic and spontaneously occurring intrahepatic cholangiocarcinoma tumors exhibited delayed tumor growth and improved survival following a combination of pan-LOX inhibition with chemotherapy. CCA upregulates all 5 lysyl oxidase isoforms, and pan-LOX inhibition reverses tumor-induced mechanical forces associated with chemotherapy resistance to improve chemotherapeutic efficacy and reprogram antitumor immune responses. Thus, combination therapy with pan-LOX inhibition represents an innovative therapeutic strategy in CCA.

Combination of oncolytic Maraba virus with immune checkpoint blockade overcomes therapy resistance in an immunologically cold model of advanced melanoma with dysfunctional T-cell receptor signalling

BackgroundOver the past decade, cancer immunotherapies have revolutionized the treatment of melanoma; however, responses vary across patient populations. Recently, baseline tumor size has been identified as an independent prognostic factor...

The complement system as a target in cancer immunotherapy.

Malignant cells are part of a complex network within the tumor microenvironment, where their interaction with host cells and soluble mediators, including complement components, is pivotal. The complement system, known for its role in immune defense and homeostasis, exhibits a dual effect on cancer progression. This dichotomy arises from its antitumoral opsonophagocytosis and cytotoxicity versus its protumoral chronic inflammation mediated by the C5a/C5aR1 axis, influencing antitumor T-cell responses. Recent studies have revealed distinct co-expression patterns of complement genes in various cancer types, correlating with prognosis. Notably, some cancers exhibit co-regulated overexpression of complement genes associated with poor prognosis, while others show favorable outcomes. However, significant intra-patient heterogeneity further complicates this classification. Moreover, the involvement of locally produced and intracellular complement proteins adds complexity to the tumor microenvironment dynamics. This review highlights the unique interplay of complement components within different cancers and patient cohorts, showing that "one size does not fit all", for complement in cancer. It summarizes the clinical trials for complement targeting in cancer, emphasizing the need for tailored therapeutic approaches. By elucidating the mechanistic basis of complement's context-dependent role, this review aims to facilitate the development of personalized cancer therapies, ultimately improving patient care and outcomes.

Blockade of IL1β and PD1 with Combination Chemotherapy Reduces Systemic Myeloid Suppression in Metastatic Pancreatic Cancer with Heterogeneous Effects in the Tumor.

Innate inflammation promotes tumor development, although the role of innate inflammatory cytokines in established human tumors is unclear. Herein, we report clinical and translational results from a phase Ib trial testing whether IL1β blockade in human pancreatic cancer would alleviate myeloid immunosuppression and reveal antitumor T-cell responses to PD1 blockade. Patients with treatment-naïve advanced pancreatic ductal adenocarcinoma (n = 10) were treated with canakinumab, a high-affinity monoclonal human antiinterleukin-1β (IL1β), the PD1 blocking antibody spartalizumab, and gemcitabine/n(ab)paclitaxel. Analysis of paired peripheral blood from patients in the trial versus patients receiving multiagent chemotherapy showed a modest increase in HLA-DR+CD38+ activated CD8+ T cells and a decrease in circulating monocytic myeloid-derived suppressor cells (MDSC) by flow cytometry for patients in the trial but not in controls. Similarly, we used patient serum to differentiate monocytic MDSCs in vitro and showed that functional inhibition of T-cell proliferation was reduced when using on-treatment serum samples from patients in the trial but not when using serum from patients treated with chemotherapy alone. Within the tumor, we observed few changes in suppressive myeloid-cell populations or activated T cells as assessed by single-cell transcriptional profiling or multiplex immunofluorescence, although increases in CD8+ T cells suggest that improvements in the tumor immune microenvironment might be revealed by a larger study. Overall, the data indicate that exposure to PD1 and IL1β blockade induced a modest reactivation of peripheral CD8+ T cells and decreased circulating monocytic MDSCs; however, these changes did not lead to similarly uniform alterations in the tumor microenvironment.

Nivolumab Reaches Brain Lesions in Patients with Recurrent Glioblastoma and Induces T-cell Activity and Upregulation of Checkpoint Pathways.

Glioblastoma (GBM) is an aggressive brain tumor with poor prognosis. Although immunotherapy is being explored as a potential treatment option for patients with GBM, it is unclear whether systemic immunotherapy can reach and modify the tumor microenvironment in the brain. We evaluated immune characteristics in patients receiving the anti-PD-1 immune checkpoint inhibitor nivolumab 1 week prior to surgery, compared with control patients receiving salvage resection without prior nivolumab treatment. We observed saturating levels of nivolumab bound to intratumorally and tissue-resident T cells in the brain, implicating saturating levels of nivolumab reaching brain tumors. Following nivolumab treatment, significant changes in T-cell activation and proliferation were observed in the tumor-resident T-cell population, and peripheral T cells upregulated chemokine receptors related to brain homing. A strong nivolumab-driven upregulation in compensatory checkpoint inhibition molecules, i.e., TIGIT, LAG-3, TIM-3, and CTLA-4, was observed, potentially counteracting the treatment effect. Finally, tumor-reactive tumor-infiltrating lymphocytes (TIL) were found in a subset of nivolumab-treated patients with prolonged survival, and neoantigen-reactive T cells were identified in both TILs and blood. This indicates a systemic response toward GBM in a subset of patients, which was further boosted by nivolumab, with T-cell responses toward tumor-derived neoantigens. Our study demonstrates that nivolumab does reach the GBM tumor lesion and enhances antitumor T-cell responses both intratumorally and systemically. However, various anti-inflammatory mechanisms mitigate the clinical efficacy of the anti-PD-1 treatment.

Programmed Death Ligand 1 (PD-L1) Expression in Lymphomas: State of the Art.

The interaction of programmed death-1 (PD-1) on T lymphocytes with its ligands Programmed Death Ligand 1 (PD-L1) and Programmed Death Ligand 2 (PD-L2) on tumor cells and/or tumor-associated macrophages results in inhibitory signals to the T-cell receptor pathway, consequently causing tumor immune escape. PD-L1/PD-L2 are currently used as predictive tissue biomarkers in clinical practice. Virtually PD-L1 levels expressed by tumor cells are associated with a good response to immune checkpoint blockade therapies targeting the PD-1/PD-L1 axis. These therapies restore T-cell antitumor immune response by releasing T-lymphocytes from the inhibitory effects of tumor cells. Immune checkpoint therapies have completely changed the management of patients with solid cancers. This therapeutic strategy is less used in hematological malignancies, although good results have been achieved in some settings, such as refractory/relapsed classic Hodgkin lymphoma and primary mediastinal large B-cell lymphoma. Variable results have been obtained in diffuse large B-cell lymphoma and T-cell lymphomas. Immunohistochemistry represents the main technique for assessing PD-L1 expression on tumor cells. This review aims to describe the current knowledge of PD-L1 expression in various types of lymphomas, focusing on the principal mechanisms underlying PD-L1 overexpression, its prognostic significance and practical issues concerning the evaluation of PD-L1 immunohistochemical results in lymphomas.

Individualized neoantigen therapy mRNA-4157 (V940) plus pembrolizumab in resected melanoma: 3-year update from the mRNA-4157-P201 (KEYNOTE-942) trial.

LBA9512 Background: mRNA-4157 is a novel, mRNA-based individualized neoantigen therapy designed to increase endogenous antitumor T-cell responses by targeting unique patient (pt) tumor mutations. In the primary analysis of the Ph 2 mRNA-4157-P201 (KEYNOTE-942) trial (median planned follow-up, 23 mo), pts with completely resected high-risk stage IIIB–IV cutaneous melanoma receiving mRNA-4157 + pembrolizumab (pembro; combo) had prolonged recurrence-free survival (RFS) and distant metastasis-free survival (DMFS) vs pembro alone (Weber JS, et al. Lancet. 2024). Methods: Pts were assigned 2:1 to mRNA-4157 (1 mg IM, max 9 doses) + pembro (200 mg IV, max 18 cycles) or pembro alone. The primary endpoint was investigator-assessed RFS; secondary endpoints were DMFS and safety. This planned supportive analysis was triggered when the last randomized pt had ≥2 y follow-up. Translational subgroup analyses were also reported. HLA genotypes were analyzed by exome sequencing of DNA from PBMC. RFS and DMFS were not formally tested; nominal 2-sided p-values are descriptive. Results: With an additional year follow-up (data cutoff, 03 Nov 2023; median [range], 34.9 [25.1–51.0] mo) after primary analysis, minimal new events occurred. RFS benefit in the combo vs pembro arm was maintained with 49% risk reduction in recurrence and/or death (HR [95% CI], 0.510 [0.288–0.906]; 2-sided nominal p-value 0.019). The 2.5-yr RFS rate of combo treatment (tx) vs pembro alone was 74.8% vs 55.6%. Combo tx also produced clinically meaningful, sustained improvement in DMFS vs pembro alone (HR [95% CI], 0.384 [0.172–0.858], 2-sided nominal p-value 0.0154). OS favored combo vs pembro alone; 2.5-y OS rate was 96.0% vs 90.2% (HR [95% CI], 0.425 [0.114–1.584]). RFS benefit of combo vs pembro was maintained in TMB high (HR [95% CI], 0.564 [0.253–1.258]), TMB non-high (0.571 [0.245–1.331]), PD-L1 positive (0.471 [0.226–0.979]), PD-L1 negative (0.147 [0.034–0.630]), and ctDNA negative (0.207 [0.091–0.470]) subgroups; ctDNA positive HR was not estimable. No significant associations between individual HLA alleles and RFS were observed in either tx arm. Maximal heterozygosity at HLA class I genotype loci (A, B, C) improved RFS vs homozygosity for ≥1 locus in the pembro arm (HR [95% CI], 0.425 [0.179–1.01]) but not combo arm (1.252 [0.498–3.146]). mRNA-4157 was well tolerated and combo tx had a safety profile consistent with previous analysis with no potentiation of immune-related AEs. Conclusions: The current analysis with ∼3 y median follow-up showed durable and meaningful long-term RFS and DMFS benefit with mRNA-4157 + pembro vs pembro alone. A trend for improved OS with combo tx was also observed. HLA and translational subgroup results suggest mRNA-4157 + pembro may benefit a broader pt population vs pembro alone. Clinical trial information: NCT03897881 .

Low-dose radiation as a preconditioning regimen for dendritic cell vaccines.

e14519 Background: Dendritic cells are potent antigen-presenting cells that induce the adaptive immune system to protect against cancer. While anti-tumor immunity can be improved with dendritic cell vaccines, it is not fully known what approved preconditioning agents, if any, improve dendritic cell vaccine-induced antitumor T-cell response and tumor elimination. We explored the effect of low-dose radiation (LDR), cyclophosphamide, and paclitaxel as preconditioning regiments for a dendritic cell vaccine. Methods: KP tumors were engineered with ovalbumin and orthotopically injected subcutaneously (SQ) into the flank of wild type B6 mice. Preconditioning regiments of a control, LDR (2 Gy), cyclophosphamide (20mg/kg), LDR (2 Gy) + cyclophosphamide (20mg/kg), and paclitaxel (20mg/kg) were given on day 4. Bone marrow dendritic cells (DCs) were electroporated with ovalbumin peptide SIINFEKL and then one million cells were injected i.v. on day 5 and 8. Blood collection was done and ovalbumin-specific T-cell populations were examined by tetramer staining for SIINFEKL-specific TCR over time. Tumor size was measured over time and survival data was analyzed accordingly. Results: LDR effectively produced a significant increase in CD8+ SIINFEKL tetramer+ T-cell count per uL of blood compared to the non-preconditioned group. In addition, this LDR preconditioning regiment produced a significantly improved tumor response over time. The overall survival rate of subjects receiving LDR was significantly improved compared to all other groups. Conclusions: Here, we find that LDR is most effective as a preconditioning regimen prior to dendritic cell vaccination for inducing an antitumor T-cell response and achieving tumor control over time. LDR provides a promising method to supplement dendritic cell vaccination and potentially improve patient outcomes. Further study is needed to confirm its efficacy.

A CD36-dependent non-canonical lipid metabolism program promotes immune escape and resistance to hypomethylating agent therapy in AML

Environmental lipids are essential for fueling tumor energetics, but whether these exogenous lipids transported into cancer cells facilitate immune escape remains unclear. Here, we find that CD36, a transporter for exogenous lipids, promotes acute myeloid leukemia (AML) immune evasion. We show that, separately from its established role in lipid oxidation, CD36 on AML cells senses oxidized low-density lipoprotein (OxLDL) to prime the TLR4-LYN-MYD88-nuclear factor κB (NF-κB) pathway, and exogenous palmitate transfer via CD36 further potentiates this innate immune pathway by supporting ZDHHC6-mediated MYD88 palmitoylation. Subsequently, NF-κB drives the expression of immunosuppressive genes that inhibit anti-tumor Tcell responses. Notably, high-fat-diet or hypomethylating agent decitabine treatment boosts the immunosuppressive potential of AML cells by hijacking CD36-dependent innate immune signaling, leading to a dampened therapeutic effect. This work is of translational interest because lipid restriction by US Food and Drug Administration (FDA)-approved lipid-lowering statin drugs improves the efficacy of decitabine therapy by weakening leukemic CD36-mediated immunosuppression.

Apoptosis, a Metabolic "Head-to-Head" between Tumor and T Cells: Implications for Immunotherapy.

Induction of apoptosis represents a promising therapeutic approach to drive tumor cells to death. However, this poses challenges due to the intricate nature of cancer biology and the mechanisms employed by cancer cells to survive and escape immune surveillance. Furthermore, molecules released from apoptotic cells and phagocytes in the tumor microenvironment (TME) can facilitate cancer progression and immune evasion. Apoptosis is also a pivotal mechanism in modulating the strength and duration of anti-tumor T-cell responses. Combined strategies including molecular targeting of apoptosis, promoting immunogenic cell death, modulating immunosuppressive cells, and affecting energy pathways can potentially overcome resistance and enhance therapeutic outcomes. Thus, an effective approach for targeting apoptosis within the TME should delicately balance the selective induction of apoptosis in tumor cells, while safeguarding survival, metabolic changes, and functionality of T cells targeting crucial molecular pathways involved in T-cell apoptosis regulation. Enhancing the persistence and effectiveness of T cells may bolster a more resilient and enduring anti-tumor immune response, ultimately advancing therapeutic outcomes in cancer treatment. This review delves into the pivotal topics of this multifaceted issue and suggests drugs and druggable targets for possible combined therapies.

PVRIG is Expressed on Stem-Like T Cells in Dendritic Cell-Rich Niches in Tumors and Its Blockade May Induce Immune Infiltration in Non-Inflamed Tumors.

Cancers that are poorly immune infiltrated pose a substantial challenge, with current immunotherapies yielding limited clinical success. Stem-like memory T cells (TSCM) have been identified as a subgroup of T cells that possess strong proliferative capacity and that can expand and differentiate following interactions with dendritic cells (DCs). In this study, we explored the pattern of expression of a recently discovered inhibitory receptor poliovirus receptor-related immunoglobulin domain protein (PVRIG) and its ligand, poliovirus receptor-related ligand 2 (PVRL2), in the human tumor microenvironment. Using spatial and single-cell RNA transcriptomics data across diverse cancer indications, we found that among the T-cell checkpoints, PVRIG is uniquely expressed on TSCM and PVRL2 is expressed on DCs in immune aggregate niches in tumors. PVRIG blockade could therefore enhance TSCM-DC interactions and efficiently drive T-cell infiltration to tumors. Consistent with these data, following PVRIG blockade in patients with poorly infiltrated tumors, we observed immune modulation including increased tumor T-cell infiltration, T-cell receptor (TCR) clonality, and intratumoral T-cell expansion, all of which were associated with clinical benefit. These data suggest PVRIG blockade as a promising strategy to induce potent antitumor T-cell responses, providing a novel approach to overcome resistance to immunotherapy in immune-excluded tumors.

In Situ Sprayed Exosome-Cross-Linked Gel as Artificial Lymph Nodes for Postoperative Glioblastoma Immunotherapy.

One key challenge in postoperative glioblastoma immunotherapy is to guarantee a potent and durable T-cell response, which is restricted by the immunosuppressive microenvironment within the lymph nodes (LNs). Here, we develop an in situ sprayed exosome-cross-linked gel that acts as an artificial LN structure to directly activate the tumor-infiltrating T cells for prevention of glioma recurrence. Briefly, this gel is generated by a bio-orthogonal reaction between azide-modified chimeric exosomes and alkyne-modified alginate polymers. Particularly, these chimeric exosomes are generated from dendritic cell (DC)-tumor hybrid cells, allowing for direct and robust T-cell activation. The gel structure with chimeric exosomes as cross-linking points avoids the quick clearance by the immune system and thus prolongs the durability of antitumor T-cell immunity. Importantly, this exosome-containing immunotherapeutic gel provides chances for ameliorating functions of antigen-presenting cells (APCs) through accommodating different intracellular-acting adjuvants, such as stimulator of interferon genes (STING) agonists. This further enhances the antitumor T-cell response, resulting in the almost complete elimination of residual lesions after surgery. Our findings provide a promising strategy for postsurgical glioma immunotherapy that warrants further exploration in the clinical arena.

Abstract PO3-22-01: Characterization of peripheral T-cell dynamics in the patients with bone metastasis from breast cancer following stereotactic body radiotherapy

Abstract Purpose: Preclinical studies suggest that radiotherapy (RT) elicits various effects on antitumor T-cell responses. However, systemic T-cell responses upon RT in real-world cancer patients, including those with metastatic breast cancer, are poorly characterized. This study aims to investigate the detailed dynamics of peripheral T cells upon stereotactic body radiotherapy (SBRT) in metastatic breast cancer patients. Methods: Peripheral blood samples of 32 prospectively recruited patients who received SBRT to bone metastasis of breast cancer, which were acquired at pre-SBRT (W0), 1 week after SBRT (W1), and 4 weeks after SBRT (W4), were analyzed using multi-color flow cytometry and cytometric bead array. Most patients (n = 30) received SBRT of 1 fraction (n = 16) or 3 fractions (n = 14). We also performed a subgroup analysis of 22 patients who did not start a new systemic therapy within 1 month before SBRT (new systemic Tx >1mo) to exclude the effects of systemic therapies. Results: Peripheral PD-1+ CD8+ T cells, which are enriched for tumor-specific clonotypes, were activated with increased expression of Ki-67 at W1 compared to W0. Expression of Ki-67 on PD-1+ CD8+ T cells remained higher at W4 than W0, although it was not statistically significant. Moreover, expressions of Ki-67 and CTLA-4 on circulating regulatory T (TREG) cells were increased at W1 compared to W0. The suppressive (Foxp3hiCD45RA–) TREG cells also exhibited enhanced expressions of Ki-67 and CTLA-4 at W1. We defined immunologic responders (ImmRs) as patients with Ki-67 expression on PD-1+ CD8+ T cells at W1 greater than 1.5-times of W0, and otherwise immunologic non-responders (ImmNRs). Notably, fold changes in expressions of Ki-67 and CTLA-4 on TREG cells and proportion of suppressive TREG cells among total TREG cells at W1 over W0 were higher in ImmRs than ImmNRs. Similar phenotypical changes of T cells were observed in the subgroup analysis of the patients with new systemic Tx >1mo. The peripheral T-cell changes were not significantly different between the dose-fractionation schedules (1 fraction vs. 3 fractions) nor molecular subtypes of cancer. In patients with new systemic Tx >1mo, plasma level changes of TGF-β1, sCTLA-4, and s4-1BB at W1 compared to W0 were significantly higher in ImmRs compared to ImmNRs, while only change of s4-1BB was associated with the immunologic response. Conclusions: Our results suggest that circulating PD-1+ CD8+ T cells are activated upon SBRT. However, SBRT also results in the activation of circulating TREG cells, which was more prominent in patients with a significant activation of circulating PD-1+ CD8+ T cells. Alterations in plasma levels of TGF-β1, sCTLA-4, and s4-1BB are associated with the peripheral T-cell responses. Dose-fractionation schedule is not associated with the peripheral T-cell responses. Work supported by grants from the National Research Foundation of Korea (NRF-2023R1A2C3003782) Citation Format: Seung Hyuck Jeon, Eui-Cheol Shin, In Ah Kim. Characterization of peripheral T-cell dynamics in the patients with bone metastasis from breast cancer following stereotactic body radiotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-22-01.