αPD-1 Therapy Research Articles

Trem2 deficiency attenuates breast cancer tumor growth in lean, but not obese or weight loss, mice and is associated with alterations of clonal T cell populations.

Obesity is an established risk factor for breast cancer development and worsened prognosis; however, the mechanisms for this association - and the potential benefits of weight loss - have not been fully explored. The adipose environment surrounding breast tumors, which is inflamed in obesity, has been implicated in tumor progression. An emerging therapeutic target for cancer is TREM2, a transmembrane receptor of the immunoglobulin superfamily that is expressed on macrophages in adipose tissue and tumors. We utilized genetic loss of function (Trem2 +,+ and Trem2 -/-) models and dietary (lean, obese, and weight loss) intervention approaches to examine impacts on postmenopausal breast cancer. Remarkably, Trem2 deficiency ameliorated tumor growth in lean, but not obese or weight loss mice. Single-cell RNA sequencing, in conjunction with VDJ sequencing of tumor and tumor-adjacent mammary adipose tissue (mATTum-adj) immune cells, revealed that tumors of lean Trem2 -/- mice exhibited a shift in clonal CD8+ T cells from an exhausted to an effector memory state, accompanied with increased clonality of CD4+ Th1 cells, that was not observed in any other diet-genotype group. Notably, identical T cell clonotypes were identified in the tumor and mATTum-adj of the same mouse. Finally, an immune checkpoint study demonstrated that αPD-1 therapy restricted tumor growth in lean and weight loss, but not obese mice. We conclude that weight history is relevant when considering potential efficacy of TREM2 inhibition in postmenopausal breast cancer. This work reveals immunological interactions between tumors and surrounding adipose tissue, highlighting significant differences under obese and weight loss conditions.

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...

ITGB6 as an inhibitor of T-cell killing via modulation of paracrine TGFβ signaling in pancreatic ductal adenocarcinoma.

e16334 Background: Immunotherapy has experienced limited success in PDAC, with αPD-1 therapy being approved only in a subset that makes up < 2% of all PDAC cancers. TGFβ is a contributor to T-cell suppression in the PDAC tumor microenvironment. However, the success of blocking TGFβ in preclinical models has failed to translate into the clinic due to the off-target effects of systemic TGFβ blockade. Integrin ITGB6 is an activator of the inert latent TGFβ into the active, immunosuppressive form. Consequently, inhibition of ITGB6 is a potent and targeted therapeutic approach for disrupting TGFβ to overcome T-cell suppression in PDAC. Methods: Analysis of TCGA molecular and survival data was performed to determine the specificity and prognostic value of ITGB6 in PDAC. Subsequently, candidate cell lines were screened for ITGB6 expression using flow cytometry to facilitate an in vitro model. Using a lentiviral system, PDAC cells were transduced with a doxycycline-inducible short hairpin RNA (shRNA) knockdown (KD) of ITGB6. Both KD and control shRNA cell lines were induced with doxycycline and subsequently co-cultured with TALL-104 T-cells. Furthermore, conditioned media was analyzed for secreted active TGFβ levels using a luciferase-based TGFβ reporter cell line. Finally, a clonogenic assay was performed to determine the autocrine effects of TGFβ activation in PDAC. Results: ITGB6 is highly specific to PDAC and also shows upregulation in comparison to normal pancreatic tissue (FC 3.38, p < 0.0001). Capan-2 cells were chosen as a model for high integrin PDAC (Capan-2 99.73% cells ITGB6+, negative control: HCT116WT 0.96% cells ITGB6+). Fluorescent microscopy of the co-culture revealed that the KD of ITGB6 increased T-cell killing over 24 hours (Capan-2 CTRL shRNA 7.71%±3.63 dead vs. Capan-2 ITGB6 shRNA 21.68%±4.57 dead, p < 0.05). Media from ITGB6 KD cells contained significantly decreased TGFβ (+TGFβ: 673000 RLU vs. CTRL: 175500 RLU, p = 0.015). A clonogenic assay of Capan-2 cells treated with active-TGFβ demonstrates that PDAC cells resist the autocrine growth inhibitory effects of TGFβ through loss of SMAD4. TCGA survival data revealed ITGB6 as prognosis marker in PDAC (high ITGB6 median survival 16.79 mos, vs. low ITGB6 21.88 mos, HR = 2.730, p < 0.004). Conclusions: Survival data that clearly demonstrates the poor prognosis of ITGB6 expression, as well as the presently proposed mechanism of immunosuppression, provide ample justification for deploying anti-ITGB6 combination therapies to in vivo studies that facilitate translation of our findings into therapeutic clinical trials.

Blockade of histamine receptor H1 augments immune checkpoint therapy by enhancing MHC-I expression in pancreatic cancer cells

BackgroundAlthough immune checkpoint blockade (ICB) therapy has proven to be extremely effective at managing certain cancers, its efficacy in treating pancreatic ductal adenocarcinoma (PDAC) has been limited. Therefore, enhancing the effect of ICB could improve the prognosis of PDAC. In this study, we focused on the histamine receptor H1 (HRH1) and investigated its impact on ICB therapy for PDAC.MethodsWe assessed HRH1 expression in pancreatic cancer cell (PCC) specimens from PDAC patients through public data analysis and immunohistochemical (IHC) staining. The impact of HRH1 in PCCs was evaluated using HRH1 antagonists and small hairpin RNA (shRNA). Techniques including Western blot, flow cytometry, quantitative reverse transcription polymerase chain reaction (RT-PCR), and microarray analyses were performed to identify the relationships between HRH1 and major histocompatibility complex class I (MHC-I) expression in cancer cells. We combined HRH1 antagonism or knockdown with anti-programmed death receptor 1 (αPD-1) therapy in orthotopic models, employing IHC, immunofluorescence, and hematoxylin and eosin staining for assessment.ResultsHRH1 expression in cancer cells was negatively correlated with HLA-ABC expression, CD8+ T cells, and cytotoxic CD8+ T cells. Our findings indicate that HRH1 blockade upregulates MHC-I expression in PCCs via cholesterol biosynthesis signaling. In the orthotopic model, the combined inhibition of HRH1 and αPD-1 blockade enhanced cytotoxic CD8+ T cell penetration and efficacy, overcoming resistance to ICB therapy.ConclusionsHRH1 plays an immunosuppressive role in cancer cells. Consequently, HRH1 intervention may be a promising method to amplify the responsiveness of PDAC to immunotherapy.

Acod1 expression in cancer cells promotes immune evasion through the generation of inhibitory peptides

Targeting programmed cell death protein 1 (PD-1) is an important component of many immune checkpoint blockade (ICB) therapeutic approaches. However, ICB is not an efficacious strategy in a variety of cancer types, in part due to immunosuppressive metabolites in the tumor microenvironment. Here, we find that αPD-1-resistant cancer cells produce abundant itaconate (ITA) due to enhanced levels of aconitate decarboxylase (Acod1). Acod1 has an important role in the resistance to αPD-1, as decreasing Acod1 levels in αPD-1-resistant cancer cells can sensitize tumors to αPD-1 therapy. Mechanistically, cancer cells with high Acod1 inhibit the proliferation of naive CD8+ Tcells through the secretion of inhibitory factors. Surprisingly, inhibition of CD8+ Tcell proliferation is not dependent on the secretion of ITA but is instead a consequence of the release of small inhibitory peptides. Our study suggests that strategies to counter the activity of Acod1 in cancer cells may sensitize tumors to ICB therapy.

Abstract 6528: Integrin ɑvβ6 upregulation as a mechanism of T-cell evasion in head and neck squamous cell carcinoma

Abstract Head and neck squamous cell carcinoma (HNSCC) encompasses malignancies of the mucosal epithelium in the oral cavity, pharynx, and larynx. The lack of effective screening strategies and the typically late stage of detection are contributors to a considerable annual death toll of HNSCC. Additionally, the anatomical proximity of the malignancy to delicate structures of the head and neck leads to tremendous treatment-related morbidity. Therefore, there is great interest in developing life-saving therapies and strategies for treatment de-escalation. The immune checkpoint inhibitor pembrolizumab (αPD-1) has been approved for recurrent or metastatic HNSCC and as a frontline therapy for unresectable disease. However, only about a quarter of patients respond to αPD-1 therapy. The immunosuppressive effect of TGFβ has been widely described as relevant to the HNSCC tumor microenvironment. However, attempts to blockade TGFβ have failed mainly due to the widespread side effects of disrupting a highly promiscuous cytokine. Integrin αvβ6 is a major activator of the inert latent TGFβ into the active, immunosuppressive form. With its high relative specificity to HNSCC tissue, inhibition of αvβ6 could offer a safer approach for disrupting TGFβ to overcome resistance to immune checkpoint blockade. After screening ɑvβ6 expression levels of HNSCC cell lines via flow cytometry, cell lines FaDu and CAL27 were selected for further investigation due to high endogenous ITGB6 expression (FaDu 35.57% cells ITGB6+, CAL27 95.69% cells ITGB6+). The cell lines were transduced with a doxycycline-inducible short hairpin RNA (shRNA) knockdown of αvβ6 using a lentiviral system. Both knockdown and control shRNA cell lines were pretreated with 1 μg/mL of doxycycline for five days to induce the shRNA and subsequently co-cultured with TALL-104 T-cells. Quantitative fluorescence microscopy of the co-culture revealed that the knockdown of αvβ6 substantially increased T-cell killing over 24hrs (FaDu CTRL shRNA 6.72%±2.49 dead vs. FaDu ITGB6 shRNA 12.80%±3.16 dead, p<0.001). However, treatment of FaDu and CAL27 cell lines with active-TGFβ showed no change in PD-L1 expression via flow cytometric analysis. To determine whether the T cell evasive effect of αvβ6 is driven by other immune checkpoints on the cancer cells or by the direct effect that TGFβ has on immune cells, we show the generation of relevant mouse αvβ6 shRNA knockdown cells. These syngeneic in vivo studies will facilitate cytokine profiling to uncover the dynamics of tumor-immune cell interactions in response to αvβ6 inhibition. Citation Format: William J. MacDonald, Praveen R. Srinivasan, Maximilian Pinho-Schwermann, Shengliang Zhang, Vida Tajiknia, Connor Purcell, Jillian Strandberg, Nolan Stubbs, Wafik S. El-Deiry. Integrin ɑvβ6 upregulation as a mechanism of T-cell evasion in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6528.

Spiky metal-organic framework nanosystem for enhanced cuproptosis-mediated cancer immunotherapy

Immunotherapy, particularly αPD-1 therapy, has been hailed as a significant breakthrough in cancer treatment. However, the limited response rates and unknown mechanisms hinder the clinical application of αPD-1 blockade boosting with hybrid nanoparticles. Herein, we introduce a strategy to enhance cancer immunotherapy by leveraging cuproptosis, initiated by the spiky copper-based metal-organic framework (S@Cu-MOF) loaded with polyphyllin I (PPI) and synergized with αPD-1 therapy. Interestingly, the unique spiky structure of S@Cu-MOF not only significantly enhances tumor cell uptake but also leads to pronounced DNA damage. The application of S@Cu-MOF/PPI with αPD-1 therapy led to obvious tumor regression and prolonged survival due to cuproptosis, which involved substantial mitochondrial damage. This process amplifies the cGAS/STING immune pathway, enhancing the immune response against cancer. Additionally, this strategy promoted immunogenic cell death (ICD), recruitment of mature dendritic cells (DCs), T cell-mediated immunity, and effective memory CD8+ T cells, resulting in significant abscopal tumor suppression and lung metastasis reduction. Our study highlights the potential of S@Cu-MOF/PPI as a sensitizer for αPD-1 with the mechanism of cuproptosis and the cGAS/STING pathway, offering a promising strategy for the next generation of immunotherapy.

Radionuclide-Labeled Antisilencing Function 1a Inhibitory Peptides for Tumor Identification and Individualized Therapy.

Immune checkpoint blockade (ICB) therapy is promising to revolutionize cancer regimens, but the low response rate and the lack of a suitable patient stratification method have impeded universal profit to cancer patients. Noninvasive positron emission tomography (PET) imaging in the whole body, upon coupling with specific biomarkers closely related to the immune response, could provide spatiotemporal information to prescribe cancer therapy. Herein, we demonstrate that antisilencing function 1a (ASF1a) could serve as a biomarker target to delineate tumor immune microenvironments by immune PET (iPET). The iPET radiotracer (68Ga-AP1) is designed to target ASF1a in tumors and predict immune response, and the signal intensity predicts anti-PD-1 (αPD-1) therapy response in a negative correlation manner. The ICB-resistant tumors with a high level of ASF1a as revealed by iPET (ASF1aHigh-iPET) are prescribed to be treated by either the combined 177Lu-labeled AP1 and αPD-1 or the standalone α particle-emitting 225Ac-labeled AP1, both achieving enhanced therapeutic efficacy and prolonged survival time. Our study not only replenishes the iPET arsenal for immune-related response evaluation by designing a reliable biomarker and a facile radiotracer but also provides optional therapeutic strategies for ICB-resistant tumors with versatile radionuclide-labeled AP1 peptides, which is promising for real-time clinical diagnosis and individualized therapy planning simultaneously.

Tunable PhenoCycler imaging of the murine pre-clinical tumour microenvironments

BackgroundThe tumour microenvironment (TME) consists of tumour-supportive immune cells, endothelial cells, and fibroblasts. PhenoCycler, a high-plex single cell spatial biology imaging platform, is used to characterize the complexity of the TME. Researchers worldwide harvest and bank tissues from mouse models which are employed to model a plethora of human disease. With the explosion of interest in spatial biology, these panoplies of archival tissues provide a valuable resource to answer new questions. Here, we describe our protocols for developing tunable PhenoCycler multiplexed imaging panels and describe our open-source data analysis pipeline. Using these protocols, we used PhenoCycler to spatially resolve the TME of 8 routinely employed pre-clinical models of lymphoma, breast cancer, and melanoma preserved as FFPE.ResultsOur data reveal distinct TMEs in the different cancer models that were imaged and show that cell-cell contacts differ depending on the tumour type examined. For instance, we found that the immune infiltration in a murine model of melanoma is altered in cellular organization in melanomas that become resistant to αPD-1 therapy, with depletions in a number of cell-cell interactions.ConclusionsThis work presents a valuable resource study seamlessly adaptable to any field of research involving murine models. The methodology described allows researchers to address newly formed hypotheses using archival materials, bypassing the new to perform new mouse studies.

Abstract PR05: CheMo4METPANC: Combination Chemotherapy (gemcitabine and nab-paclitaxel), chemokine (C-X-C) Motif receptor 4 inhibitor (motixafortide), and immune checkpoint blockade (cemiplimab) in METastatic treatment-naïve PANCreatic adenocarcinoma

Abstract Background: Metastatic pancreatic ductal adenocarcinoma (mPDAC) is a uniformly fatal disease. Immune checkpoint inhibitors have thus far failed to improve outcomes due to an immunosuppressive tumor microenvironment (TME). In preclinical mouse models, signaling through the C-X-C motif chemokine receptor 4 (CXCR4)/C-X-C motif chemokine ligand 12 (CXCL12) axis results in exclusion of anti-tumor immune cells. Using the KPC mouse PDAC model, we have demonstrated that treatment with the combination of a CXCR4 inhibitor (CXCR4i), αPD-1, and gemcitabine improves survival when compared to mice treated with either gemcitabine alone or the combination of CXCR4i and αPD-1 therapy. The goal of this first-in-human study was to test preliminary safety and radiologic response rate of motixafortide (CXCR4i), cemiplimab (αPD1), gemcitabine, and nab-paclitaxel (MCGN) in treatment-naïve mPDAC. Methods: This was an open label, multicenter, investigator-initiated, single arm pilot study evaluating MCGN in mPDAC. This signal seeking study incorporated a six-patient safety run-in cohort with enrollment of four additional patients (N=10). The primary aim of this trial was to study the safety of MCGN. If ≥3 of the initial 10 patients within the pilot stage experienced a partial response (PR) by RECIST criteria within 16 weeks, the combination would be considered promising and an expansion cohort of an additional 30 patients would be enrolled. Clinical trial information: NCT04543071. Results: A total of 11 patients (1 over-enrolled) with mPDAC participated in the study at Columbia University and Brown University (11/9/2020-3/3/2023). The median age was 58y. Two (18%) patients were female and 3 (27%) were black. As of 05/05/23, 6 (55%) patients experienced a partial response (PR) of which 4 (36%) were confirmed PRs with 1 patient experiencing resolution of the hepatic metastatic lesion. Three (27%) patients experienced stable disease. At a median follow-up of 9.5m, 5 remain on study (duration on treatment [DOT]: 11.6, 6.7, 3.7, 2.7, and 2 months), 4 are off treatment due to disease progression (DOT: 13.4, 9.7, 3.7, and 1.5 months), 1 withdrew consent, and 1 was removed per physician discretion. Five patients have died. As of 03/31/23, 9 patients experienced grade 3-4 treatment-related adverse events, including urticaria (18%), and allergic reaction, bone pain, hypertension, hypotension, pain, rash (each 9%). Analyses interrogating the TME, including single-cell profiling, will be presented on paired tumor biopsies obtained on all patients. Conclusions: Preliminary results from this pilot study of MCGN in mPDAC were promising, with a durable PR rate of 55% and disease control rate (DCR) of 82%, compared to historic PRs and DCRs of 23% and 48% reported with gemcitabine and nab-paclitaxel (GN), respectively. Based on these results, the study was amended to transition to a randomized phase 2 trial testing MCGN compared to GN (N=112). The primary endpoint is progression free survival (PFS). Citation Format: Gulam A. Manji, Michael May, Morteza Hajkarim Chalabi, Ilenia Pellicciotta, Sarah I. Sta Ana, Naomi Sender, Samuel S. Pan, Isabelle V. Ross, Kenneth P. Olive, Shikun Wang, Benjamin Izar, Ruth A. White, Susan E. Bates, Alexander G. Raufi. CheMo4METPANC: Combination Chemotherapy (gemcitabine and nab-paclitaxel), chemokine (C-X-C) Motif receptor 4 inhibitor (motixafortide), and immune checkpoint blockade (cemiplimab) in METastatic treatment-naïve PANCreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR05.

Shikonin improves the effectiveness of PD-1 blockade in colorectal cancer by enhancing immunogenicity via Hsp70 upregulation

BackgroundPD-1 blockade has shown impressive clinical outcomes in colorectal cancers patients with high microsatellite instability (MSI-H). However, the majority of patients with colorectal cancer who present low microsatellite instability (MSI-L) or stable microsatellites (MSS) show little response to PD-1 blockade therapy. Here, we have demonstrated that Shikonin (SK) could induce cell death of CT26 cells via classically programmed and immunogenic pathways.Methods and resultsSK promoted the membrane exposure of calreticulin and upregulated the expression of heat shock protein 70 (Hsp70). The upregulation of Hsp70 was dependent on ROS induced by SK and silencing of PKM2 in CT26 cells reverts ROS upregulation. Besides, SK synergizes with PD-1 blockade in CT26 tumor mice model, with the increase of intramural DC cells and CD8+ T cells. The expression of Hsp70 in tumor tissue was also increased in combinational SK plus αPD-1 therapy group.ConclusionsOur study elucidated the potential role of ‘Shikonin-PKM2-ROS-Hsp70’ axis in the promotion of efficacy of PD-1 blockade in CRC treatments, providing a potential strategy and targets for improving the efficacy of PD-1 blockade in colorectal cancer.

EXTH-77. EXTENDED HALF-LIFE IL-2 SYNERGIZES WITH Α-PD-1 FOR TREATMENT OF PRECLINICAL MURINE GLIOBLASTOMA MODELS

Abstract α-PD-1 checkpoint blockade is a promising immunotherapeutic approach for many solid tumors; however, this strategy is minimally effective for GBM patients as a monotherapy. One potential reason why α-PD-1 checkpoint blockade is ineffective is the tumor microenvironment and systemic derangements of the immune system which are prevalent in GBM patients. We have successfully modeled peripheral immune derangements in experimental murine GBM models. These include low peripheral blood CD4 T cell counts, reduced MHC class II expression on monocytes, and atrophy of primary immune organs in animals harboring gliomas. We therefore hypothesized that extended half-life IL-2, a potent cytokine which promotes the proliferation, differentiation, and killing activity of T cells, could overcome immune derangements and could potentially synergize with α-PD-1 checkpoint blockade therapy. In cohorts of C57Bl/6 mice, we supplemented α-PD-1 checkpoint blockade with multiple bio-engineered extended half-life IL-2 molecules to treat GL261 and CT2A orthotopic glioma models which are normally resistant to monotherapy. We observe a statistically significant increase in survival in GL261-bearing animals receiving the combination of extended half-life IL-2 reagents and αPD-1 therapy relative to control-treated mice. Some animals receiving this combination therapy had a reduction in tumor burden to levels below detection. These long-term survivors underwent a rechallenge experiment with a second inoculation of GL261-Luc and effectively cleared tumor without further therapeutic intervention. This intervention causes a significant shift in the immune profile, including the formation of mature T cell responses, as well as restoring the diminished peripheral immune cell counts in GL261-bearing animals. Finally, combining extended half-life IL-2 with α-PD-1 checkpoint blockade is effective independently of the CD8 T cell response. Together, these data suggest that combination immunotherapies employing extended half-life IL-2 fusion proteins are translational to the clinic and do not require the identification of tumor specific antigens for efficacy

DGKα/ζ inhibitors combine with PD-1 checkpoint therapy to promote T cell-mediated antitumor immunity.

Programmed cell death protein 1 (PD-1) immune checkpoint blockade therapy has revolutionized cancer treatment. Although PD-1 blockade is effective in a subset of patients with cancer, many fail to respond because of either primary or acquired resistance. Thus, next-generation strategies are needed to expand the depth and breadth of clinical responses. Toward this end, we designed a human primary T cell phenotypic high-throughput screening strategy to identify small molecules with distinct and complementary mechanisms of action to PD-1 checkpoint blockade. Through these efforts, we selected and optimized a chemical series that showed robust potentiation of T cell activation and combinatorial activity with αPD-1 blockade. Target identification was facilitated by chemical proteomic profiling with a lipid-based photoaffinity probe, which displayed enhanced binding to diacylglycerol kinase α (DGKα) in the presence of the active compound, a phenomenon that correlated with the translocation of DGKα to the plasma membrane. We further found that optimized leads within this chemical series were potent and selective inhibitors of both DGKα and DGKζ, lipid kinases that constitute an intracellular T cell checkpoint that blunts T cell signaling through diacylglycerol metabolism. We show that dual DGKα/ζ inhibition amplified suboptimal T cell receptor signaling mediated by low-affinity antigen presentation and low major histocompatibility complex class I expression on tumor cells, both hallmarks of resistance to PD-1 blockade. In addition, DGKα/ζ inhibitors combined with αPD-1 therapy to elicit robust tumor regression in syngeneic mouse tumor models. Together, these findings support targeting DGKα/ζ as a next-generation T cell immune checkpoint strategy.

Para-toluenesulfonamide, a novel potent carbonic anhydrase inhibitor, improves hypoxia-induced metastatic breast cancer cell viability and prevents resistance to αPD-1 therapy in triple-negative breast cancer

Overexpression of the hypoxia-induced transmembrane enzyme carbonic anhydrase IX (CA9) has been associated with poor prognosis and chemoresistance in aggressive breast cancer. This study aimed to investigate the involvement of CA9 in the anti-tumor activity of para-toluenesulfonamide (PTS) and elucidate its mechanism of action against breast cancer both in vitro and in vivo. MCF-7 and MDA-MB-231 breast cancer cells were treated with PTS or subjected to hypoxic conditions using cobalt chloride (CoCl2), with acetazolamide serving as a positive control. Additionally, 4T1 breast cancer cell allograft mice were co-treated with PTS and α-programmed cell death 1 (αPD-1) monoclonal antibody for one month. The results demonstrated that PTS effectively reduced cell viability and reversed migration ability in MCF-7 and MDA-MB-231 cells under CoCl2-induced hypoxia. Furthermore, PTS upregulated the expression of apoptosis-related proteins and downregulated CA9, hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF) proteins, possibly through modulation of p38 MAPK and ERK1/2 phosphorylated proteins. In the animal model, PTS100 inhibited tumor growth and lung metastasis in mammary tumor allograft mice, exhibiting synergistic effects when combined with αPD-1 therapy. Collectively, our findings suggest that PTS inhibits breast cancer growth and metastasis through the p38 MAPK/ERK1/2 pathway. Moreover, PTS may have the potential to prevent the development of resistance to αPD-1 therapy in breast cancer.

RNA Sequencing Reveals Unique Transcriptomic Signatures of the Thyroid in a Murine Lung Cancer Model Treated with PD-1 and PD-L1 Antibodies.

Immune checkpoint inhibitors (ICI) are commonly associated with thyroid immune-related adverse events, yet the mechanism has not been fully elucidated. We aimed to further explore the mechanism of ICI-induced thyroid dysfunction by assessing changes induced in the thyroid transcriptome by ICI treatment (αPD-1/αPD-L1) in a lung cancer murine model. RNA-sequencing of thyroid tissues revealed 952 differentially expressed genes (DEGs) with αPD-1 treatment (|fold-change| ≥1.8, FDR < 0.05). Only 35 DEG were identified with αPD-L1, and we therefore focused on the αPD-1 group alone. Ingenuity Pathway Analysis revealed that of 952 DEGs with αPD-1 treatment, 362 were associated with functions of cell death and survival, with predicated activation of pathways for apoptosis and necrosis (Z = 2.89 and Z = 3.21, respectively) and negative activation of pathways for cell viability and cell survival (Z = -6.22 and Z = -6.45, respectively). Compared to previously published datasets of interleukin-1β and interferon γ-treated human thyroid cells, apoptosis pathways were similarly activated. However, unique changes related to organ inflammation and upstream regulation by cytokines were observed. Our data suggest that there are unique changes in gene expression in the thyroid associated with αPD-1 therapy. ICI-induced thyroid dysfunction may be mediated by increased tissue apoptosis resulting in destructive thyroiditis.

The effects of αPD-1 and αPD-L1 therapy on macrophage remodeling within the solid tumor microenvironment

Abstract PD-1- and PD-L1-targeted immune checkpoint blockade therapy has shown great clinical potential. Unfortunately, this therapy has been ineffective in a majority of patients bearing solid tumors due to the highly immunosuppressive nature of the tumor microenvironment. As macrophages compose the most abundant myeloid cell subset within the tumor, current macrophage-targeted treatments aim to deplete macrophages within the tumor to reduce immune suppression. However, our goal is to determine whether αPD-1 and αPD-L1 therapy can harness macrophage potential by shifting tumor associated macrophages (TAMs) from a suppressive M2 to a pro-inflammatory M1 phenotype. Our preliminary data has shown that αPD-1/αPD-L1 treatment of mice bearing B16 murine melanoma leads to controlled tumor growth and this was accompanied by a higher M1:M2 ratio and CD8 T-cell abundance. Therefore, we hypothesized that αPD-1/αPD-L1 therapy may drive TAMs towards a pro-inflammatory phenotype and to become better activators of CD8 T-cells. By analyzing antigen presentation machinery on TAMs, we show that in the presence of tumor cells, αPD-L1 blockade upregulates expression of MHC1 and MHC2 on TAMs. Unexpectedly, direct αPD-L1 blockade on TAMs leads to reduced CD80 surface due to mechanisms still to be elucidated. Further, we analyzed co-cultures of αPD-L-treated TAMs loaded with ovalbumin and naïve OT1 cells, which led to greater proliferation of naïve CD8 T-cells compared to their isotype control counterparts. Our observations thus far support the ability of αPD-1/αPD-L1 therapy to induce an M1-phenotype shift among macrophages and also αPD-L1 blockade alone can drive TAMs to become better CD8 T-cell activators. Mayo Clinic David and Margaret Grohne Cancer Immunotherapy and Mayo Clinic Immune Monitoring Core Pilot Awards

Abstract 5833: Crosstalk between cancer-associated fibroblasts and CD8 T cells leads to improved T cell activation in head and neck cancer

Abstract Cancer-associated fibroblasts (CAFs) have been shown to modulate immune responses in the tumor microenvironment (TME), however, the extensive heterogeneity of these cells has precluded rigorous understanding of their immunoregulatory role in the head and neck TME. To gain a better understanding of the relationship between CAFs and the immune environment in head and neck cancer, we leveraged protein activity inference tools to analyze single-cell RNA sequencing of advanced-stage head and neck squamous cell carcinoma (HNSCC) patients pre- and post-treatment with the αPD-1 therapy, nivolumab. From this analysis, we identified a novel CAF population predictive of patient response to αPD-1 therapy. Utilizing in vitro co-culture assays with primary human CD8 T cells, we discovered that this novel CAF population was able to elicit features associated with enhanced CD8 T cell function, namely the reduction of PD-1+TIM-3+ exhaustive phenotypes and induction of CD103+NKG2A+ tissue-resident memory phenotypes and cytotoxicity. Due to their unique ability to stimulate T cells in this manner, we termed this novel CAF population T cell-stimulating CAFs (tsCAFs). In efforts to elucidate the mechanism behind this pro-inflammatory function, we determined that tsCAFs secrete a heat-sensitive small molecule/s in order to alter CD8 T cell behavior. However, tsCAFs will only secrete this factor in the presence of activated T cells demonstrating crosstalk between T cells and CAFs in the head and neck TME. This pro-inflammatory crosstalk between CAFs and T cells represents a novel finding that further contributes to the idea of immunoregulatory pleiotropy among CAFs. Accordingly, our findings highlight the functional importance of distinct CAF subsets in modulating the immunoregulatory milieu of human HNSCC and warrant more extensive characterization of CAF-T cell interactions in human squamous cell carcinoma. Citation Format: Diana Graves, Aleksandar Obradovic, Henry Schares, Michael Korrer, Brian Bachmann, Young Kim, Ben Park, Paula Hurley. Crosstalk between cancer-associated fibroblasts and CD8 T cells leads to improved T cell activation in head and neck cancer [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 5833.

Mesenchymal stem cells elicits Anti-PD1 immunotherapy by targeted delivery of CX3CL1.

Anti-PD1/PDL1 monotherapy has failed to acquire sufficiently ideal results in most solid tumors. Mesenchymal stem cells (MSCs) have been reported to exert therapeutic effects on some tumors, but the functions of MSCs in colorectal cancer (CRC) need further research. In this study, we aimed to investigate the therapeutic effect and the improvement of sensitivity of MSCs to anti-PD1 antibodies (αPD1) in CRC and to evaluate the possible mechanism. The relative distribution of immune cells in tumor microenvironment was examined after the mice were treated with MSC and/or αPD1. Our study revealed that MSC recruits CX3CR1high macrophages and promotes M1 polarization to inhibit tumor growth via highly secretion of CX3CL1.The combination of MSC and αPD1 was superior to monotherapy against CRC. MSC inhibits PD1 expression on CD8+ T cells by facilitating M1 macrophage polarization, which promotes the proliferation of CD8+ T cells, thus improving the sensitivity to αPD1 therapy in CRC. Additionally, the above therapeutic effect disappeared after inhibiting the secretion of CX3CL1 in MSC. Our MSC-based immunotherapeutic strategy simultaneously recruited and activated immune effector cells at the tumor site, suggesting that the combination of MSC and αPD1 could be a potential therapy for CRC.

Diselenide-Based Dual-Responsive Prodrug as Pyroptosis Inducer Potentiates Cancer Immunotherapy.

Pyroptosis is demonstrated to trigger antitumor immunity and represents a promising new strategy to potentiate cancer immunotherapy. The number of potent pyroptosis inducers, however, is limited and without tumor-targeting capability, which inevitably causes damage in normal tissues. Herein, a small molecular prodrug of paclitaxel-oxaliplatin is rationally synthesized, which can be covalently self-assembled with diselenide-containing cross-linking (Dse11), producing a diselenide nanoprodrug (DSe@POC) to induce pyroptosis for the first time. The diselenide bonds within DSe@POC can be split by high glutathione in the tumor microenvironment (TME) and reactive oxygen species induced by photodynamic therapy, thus possessing excellent TME on-target effects. Additionally, DSe@POC is able to elicit intense pyroptosis to remodel the immunostimulated TME and trigger a robust immune response. Furthermore, combined αPD-1 therapy effectively inhibits the growth of remote tumors through the abscopal effect, amplifies a long-term immune memory response to reject rechallenged tumors, and prolongs survival. Collectively, DSe@POC, as the first TME dual-responsive diselenide-based pyroptosis inducer, will open up an attractive approach for cancer immunotherapy.

PA-MSHA induces inflamed tumor microenvironment and sensitizes tumor to anti-PD-1 therapy

A low response rate to immune checkpoint inhibitor (ICI) therapy has impeded its clinical use. As reported previously, an inflamed tumor microenvironment (TME) was directly correlated with patients’ response to immune checkpoint blockade (ICB). Thus, restoring the cytotoxic effect of immune cells in the TME is a promising way to improve the efficacy of ICB and overcome primary resistance to immunotherapy. The effect of Pseudomonas aeruginosa mannose-sensitive-hemagglutinin (PA-MSHA) in facilitating T cell activation was determined in vitro and in vivo. Subsets of immune cells were analyzed by flow cytometry. Proteomics was carried out to comprehensively analyze the discriminated cellular kinases and transcription factors. The combinational efficacy of PA-MSHA and αPD-1 therapy was studied in vivo. In this study we demonstrated that PA-MSHA, which is a clinically used immune adjuvant, effectively induced the anti-tumor immune response and suppressed the growth of non-small cell lung cancer (NSCLC) cells. PA-MSHA showed great potential to sensitize refractory “cold” tumors to immunotherapy. It effectively enhanced macrophage M1 polarization and induced T cell activation. In vivo, in combination with αPD-1, PA-MSHA suppressed tumor growth and prolonged the survival time of allograft model mice. These results indicate that PA-MSHA is a potent agent to stimulate immune cells infiltration into the TME and consequently induces inflammation in tumors. The combination of PA-MSHA with αPD-1 is a potential strategy to enhance the clinical response rate to ICI therapy.