Programmed Cell Death-1 Expression Research Articles

Tumor cells inhibit the activation of ILC2s through up-regulating PD-1 expression

Objective Up-regulating programmed cell death ligand-1(PD-L1) expressed on tumor cells and tumor-infiltrating myeloid cells interacting with up-regulated programmed cell death-1 (PD-1) expressed on tumor-infiltrating lymphoid cells greatly hinder their tumor-inhibiting effect. It is necessary to explore the deep mechanism of this negative effect, so as to find the potential methods to improve the immunotherapy efficiency. Methods and Results In this study, we found that the PD-1 expression in lung cancer-infiltrating type II innate lymphoid cells (ILC2s) was highly up-regulated, which greatly restrained the activation and function of ILC2s. Furthermore, anti-PD-1 could restore the inhibition and effective cytokine secretion of ILC2s when co-cultured with tumor cells. In vivo studies proved that anti-PD-1 treatment promoted the activation of tumor-infiltrating ILC2s and inhibited the tumor growth of LLC-bearing nude mice. Discussion Our studies demonstrate a new PD-1/PD-L1 axis regulating mechanism on innate immune cells, which provide a useful direction to ILC2s-based immunotherapy to cancer diseases.

Abstract LB445: USP24 suppresses T cell anti-tumor activity by enhancing the stability of the PD-1 protein

Abstract Persistent programmed cell death-1 (PD-1)/PD-L1 inhibitory signaling disrupts T cell cytotoxic function, leading to T cell exhaustion—a phenomenon strongly associated with advanced cancer progression and immunotherapy failure. Deciphering the mechanisms behind dysregulated PD-1 expression and reactivating tumor-infiltrating lymphocytes (TILs) in the tumor microenvironment (TME) is crucial. Our previous research established that tumor-associated macrophage-derived IL-6 promotes STAT3-dependent PD-1 transcriptional activity and immunotherapy resistance. The current study further explores whether IL-6 abundance in the TME contributes to PD-1 protein stability. Results indicate that IL-6 extended PD-1 protein half-life in T cells, suggesting its role in modulating PD-1 protein stability. Furthermore, analysis of the GEO database showed a positive correlation between the expression of ubiquitin-specific-processing protease (USP) family enzymes and PD-1 in non-responding patients receiving anti-PD-1 therapy. Knockdown experiments revealed that USP24 strongly downregulated PD-1 protein expression and stability. USP24 depletion reversed IL-6-induced PD-1 expression and stability, with USP24 colocalizing with PD-1 at the plasma membrane upon IL-6 stimulation. Immunoprecipitation-Western blot assays confirmed that USP24 directly interacted with PD-1 and countered E3 ligase c-Cbl-mediated ubiquitination. Depleting USP24 suppressed PD-1-mediated immunosuppression both in vitro and in vivo. In lung-specific EGFRL858R/USP24C1698A functional knockout mice, tumor progression was slower, and exhausted tumor-infiltrating PD-1+ TIM-3+ CD8+ T cells reduced compared to EGFRL858R mice. Inhibiting PD-1 stability with an IL-6 neutralizing antibody or the novel inhibitor USP24-i-101 decreased tumor volume and increased activated cytotoxic T cell infiltration in vivo. Moreover, USP24-i-101 enhanced therapeutic effects in combination with anti-CTLA4 immunotherapy. Clinically, our in-house cohort revealed elevated USP24 expression in tumor-infiltrating lymphocytes or peripheral T cells, correlating with worse clinical outcomes and unfavorable responses to immunotherapy in lung cancer patients. This study uncovers USP24 as a novel PD-1 regulator, deubiquitinating PD-1 to enhance protein stability and suppress T cell function. In conclusion, USP24 emerges as a potential target for enhancing anti-tumor immunity and as a biomarker predicting clinical responses to immunotherapy in lung cancer. Citation Format: Hung-Chia Hsieh, Jan-Jong Hung, Yi-Ching Wang. USP24 suppresses T cell anti-tumor activity by enhancing the stability of the PD-1 protein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB445.

Transcriptional, growth factors, components of the AKT/mTOR signaling pathway, receptors and ligands of programmed cell death expression in melanoma

Introduction. Melanoma is the most dangerous neoplasm of the skin, characterized by a malignant and aggressive course. Transcriptional and growth factors, components of the AKT/mTOR signaling pathway, receptors and ligands of programmed cell death are involved in significant processes of oncogenesis.Aim. To study the expression of components of the AKT/mTOR (mTOR – mammalian target of rapamycin) signaling pathway, transcription and growth factors, expression of AMPK, LC3B, programmed cell death 1 (PD-1), programmed death-ligand 1 PD-L1 and programmed death-ligand 2 (PD-L2) in skin and mucosal tumor tissues.Materials and methods. The study included 21 patients with a verified diagnosis of melanoma of the skin of various localizations and mucous membranes of the nasal cavity T1a–4bN0M0 (I–IV stages) and 18 patients with basal cell carcinoma of the skin of various localizations T1–4N0M0 (I–VIA stages), aged 45 to 72 years old, who were treated in the department of head and neck tumors of the Cancer Research Institute, Tomsk National Research Medical Center. The presence of tumor ulceration was determined by microscopy and registration of the true absence of the epidermis over the tumor or due to traumatization of the epidermis. Expression of components of the AKT/mTOR signaling pathway, transcription and growth factors, expression of AMPK, LC3B, PD-1, PD-L1 and PD-L2 in the tumor tissue was determined by real-time polymerase chain reaction.Results. An increase in the expression of 70 S6 kinase and VHL was found in melanoma tissues compared to basal cell carcinoma. At the same time, the presence of signs of ulceration was associated with a low level of c-RAF, nuclear factor kappa B (NF-kB) p50 and hypoxia-inducible factor 1 (HIF-1) matrix RNA (mRNA) against the background of an increase in the expression of the hypoxia-inducible factor 2 (HIF-2) transcription factor. The study of the molecular features of neoplasms in relation to the tumor thickness according to Breslow revealed the contribution of transcription and growth factors, the intensity of intracellular signaling processes, modification of the microenvironment, autophagy and neoangiogenesis.Conclusion. The molecular and biological features of melanomas associated with invasive tumor growth have been identified. An increase in the expression of 70 S6 kinase and VHL are characteristic of a malignant skin tumor. The presence of signs of ulceration and tumor invasion were associated with a change in the transcriptional characteristics of factors with the induction of key markers, oncogenesis, which contributes to the formation of the invasive potential of the tumor.

Antibody-Mediated Depletion of Autoreactive T Lymphocytes through PD-1 Improves Disease Outcomes and Visualizes T Cell Activation in Experimental Autoimmune Encephalomyelitis.

Long-term therapeutic outcomes of multiple sclerosis (MS) remain hindered by the chronic nature of immune cell stimulation toward self-antigens. Development of novel methods to target and deplete autoreactive T lymphocytes remains an attractive target for therapeutics for MS. We developed a programmed cell death 1 (PD-1)-targeted radiolabeled mAb and assessed its ability to deplete activated PD-1+ T lymphocytes invitro and its ability to reduce disease burden of the myelin oligodendrocyte glycoprotein 35-55 experimental autoimmune encephalomyelitis (EAE) model in C57BL/6 mice. We also investigated the upregulation of PD-1 on infiltrating lymphocytes in an animal model of MS. Finally, we demonstrate the (to our knowledge) first reported positron-emission tomography/computed tomography imaging of activated PD-1+ cells in the EAE animal model of MS. We found that the 177Lu radioisotope-labeled anti-PD-1 mAb demonstrated significant invitro cytotoxicity toward activated CD4+PD-1+ T lymphocytes and led to significant reduction in overall disease progression in the EAE animal model. Our results show high expression of PD-1 on infiltrating lymphocytes in the spinal cords of EAE diseased animals. Positron-emission tomography/computed tomography imaging of the anti-PD-1 mAb demonstrated significant uptake in the cervical draining lymph nodes highlighting accumulation of activated lymphocytes. Targeted depletion of T lymphocytes using T cell activation markers such as PD-1 may present a novel method to reduce autoimmune attack and inflammation in autoimmune diseases such as MS. Development of multimodal nuclear theranostic agents may present the opportunity to monitor T cell activation via imaging radioisotopes and simultaneously treat MS using therapeutic radioisotopes.

Expression and prognostic significance of the PD-1/PD-L1 pathway in AIDS-related non-Hodgkin lymphoma.

Immune tolerance and evasion play a critical role in virus-driven malignancies. However, the phenotype and clinical significance of programmed cell death 1 (PD-1) and its ligands, PD-L1 and PD-L2, in aggressive acquired immunodeficiency syndrome (AIDS)-related non-Hodgkin lymphoma (AR-NHL) remain poorly understood, particularly in the Epstein-Barr virus (EBV)-positive subset. We used insitu hybridization with EBV-encoded RNA (EBER) to assess the EBV status. We performed immunohistochemistry and flow cytometry analysis to evaluate components of the PD-1/PD-L1/L2 pathway in a multi-institutional cohort of 58 patients with AR-NHL and compared EBV-positive and EBV-negative cases. The prevalence of EBV+ in AR-NHL was 56.9% and was associated with a marked increase in the expression of PD-1/PD-L1/PD-L2 in malignant cells. Patients with AR-NHLs who tested positive for both EBER and PD-1 exhibited lower survival rates compared to those negative for these markers (47.4% vs. 93.8%, p = 0.004). Similarly, patients positive for both EBER and PD-L1 also demonstrated poorer survival (56.5% vs. 93.8%, p = 0.043). Importantly, PD-1 tissue-expression demonstrated independent prognostic significance for overall survival in multivariate analysis and was correlated to elevated levels of LDH (r = 0.313, p = 0.031), increased PD-1+ Tregs (p = 0.006), and robust expression of EBER (r = 0.541, p < 0.001) and PD-L1 (r = 0.354, p = 0.014) expression. These data emphasize the importance of PD-1-mediated immune evasion in the complex landscape of immune oncology in AR-NHL co-infected with EBV, and contribute to the diagnostic classification and possible definition of immunotherapeutic strategies for this unique subgroup.

Abstract 6686: The mechanism of gut microbiome-mediated immune activation on the clinical efficacy of PD-1 blocking treatment in solid tumors

Abstract Gut microbiota is associated with antitumor efficacy of immune checkpoint blockade therapies, yet the mechanism is not largely understood. Here, we show that a novel bacterial strain of Ruminococcaceae isolated from the feces of patients who respond to PD-1 (programmed cell death 1) blockade efficiently primes/activates tumor-specific CD8+ T cells through effective stimulation/maturation of CD103+ dendritic cells (DCs) during migration from the gut to the tumor microenvironment (TME). The administration of this bacteria strain with PD-1 blockade significantly inhibited tumor growth, even when adding them to fecal transplantation of non-responder patients in animal models. Mechanistically, the bacterial strain promoted the IRF8-driven differentiation of CD103+ DCs by stimulating multiple Toll-like receptors and the accumulation of these DCs in tumors and tumor-draining lymph nodes. These CD103+ DCs prolonged engagement with cognate antigen-specific CD8+ T cells, which induced the activation of CD8+ T cells specific for a wide variety of tumor antigens and fostered their PD-1 expression through enhanced T-cell activation signals with NFATc1 nuclear translocation, thereby leading to abundant PD-1+CD8+ T cells, a key effector cell population in PD-1 blockade, with a broader T-cell receptor repertoire in the TME. Our findings with novel single bacterium isolated from feces of responder patients demonstrate the mode of action by gut microbiota to augment antitumor immunity. Citation Format: Nina Yi-Tzu Lin, Shota Fukuoka, Daisuke Motooka, Yuko Shigeno, Takuma Irie, Dieter M. Tourlousse, Kazutoshi Murotomi, Yuji Sekiguchi, Hideyuki Tamaki, Mariko Shindo, Takahiro Tsuji, Hiroaki Wake, Koichi Goto, Toshihiko Doi, Kohei Shitara, Keisuke Watanabe, Yuka Maeda, Shota Nakamura, Yoshimi Benno, Hiroyoshi Nishikawa, Shohei Koyama. The mechanism of gut microbiome-mediated immune activation on the clinical efficacy of PD-1 blocking treatment in solid tumors [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 6686.

PD-1 regulates ILC3-driven intestinal immunity and homeostasis

Interleukin-(IL) 22 production by intestinal group 3 innate lymphoid cells (ILC3) is critical to maintain gut homeostasis. However, IL-22 needs to be tightly controlled; reduced IL-22 expression is associated with intestinal epithelial barrier defect while its overexpression promotes tumor development. Here, using a single cell RNAseq approach, we identified a core set of genes associated with increased IL-22 production by ILC3. Among these genes, Programmed cell death 1 (PD-1), extensively studied in the context of cancer and chronic infection, was constitutively expressed on a subset of ILC3. These cells, found in the crypt of the small intestine and colon, displayed superior capacity to produce IL-22. PD-1 expression on ILC3 was dependent on the microbiota and was induced during inflammation in response to IL-23 but, conversely, was reduced in the presence of Notch ligand. PD-1+ ILC3 exhibited distinct metabolic activity with increased glycolytic, lipid and polyamine synthesis associated with augmented proliferation compared with their PD-1- counterparts. Further, PD-1+ ILC3 showed increased expression of mitochondrial antioxidant proteins which enable the cells to maintain their levels of reactive oxygen species (ROS). Loss of PD-1 signaling in ILC3 led to reduced IL-22 production in a cell intrinsic manner. During inflammation, PD-1 expression was increased on NCR- ILC3 while deficiency in PD-1 expression resulted in increased susceptibility to experimental colitis and failure to maintain gut barrier integrity. Collectively, our findings uncover a new function of the PD-1 and highlight the role of PD-1 signaling in the maintenance of gut homeostasis mediated by ILC3 in mice.

"Expression and prognostic relevance of PD-1, PD-L1 and CTLA-4 immune checkpoints in adrenocortical carcinoma".

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with poor prognosis in advanced stages. While therapies targeting the checkpoint molecules programmed cell death 1 (PD-1), its ligand PD-L1 and the cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have revolutionized treatment in many cancers, the results in ACC were heterogeneous. Their expression in ACC has not been systematically studied and might explain the variable response to checkpoint inhibitors. The expression of PD-1, PD-L1 and CTLA-4 was examined in 162 tumor samples from 122 ACC patients by immunohistochemistry (threshold of >1%) and correlated with tumoral T lymphocyte infiltration and clinical endpoints. Finally, uni- and multivariate analyses of progression-free and overall survival were performed. PD-1 and PD-L1 were expressed in 26.5% and 24.7% of samples, respectively, with low expression in most tumor samples (median positive cells: 2.1% and 21.7%. In contrast, CTLA-4 expression was observed in 52.5% of ACC with a median of 38.4% positive cells. Positive PD-1 expression was associated with longer progression-free survival (HR: 0.50, 95% CI 0.25-0.98, p=0.04) even after considering prognostic factors. In contrast, PD-L1 and CTLA-4 did not correlate with clinical outcome. Additionally, PD-1 and PD-L1 expression correlated significantly with the amount of CD3+, CD4+, FoxP3+ and CD8+ T cells. The heterogeneous expression of PD1, PD-L1, and CTLA-4 in this large series of well-annotated ACC samples might explain the heterogeneous results of the immunotherapies in advanced ACC. In addition, PD-1 expression is a strong prognostic biomarker that can easily be applied in routine clinical care and histopathological assessment.

Prognostic effect of programmed cell death ligand 1/programmed cell death 1 expression in cancer stem cells of human oral squamous cell carcinoma.

The relationship between cancer stem cells (CSCs) in oral squamous cell carcinoma (OSCC) and programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) remains unclear. Therefore, the present study aimed to clarify the association between the CD44v3high/CD24low immunophenotype of CSCs in OSCC and PD-L1/PD-1 co-expression, and to assess the prognostic effect of CSCs in terms of immune checkpoint molecules. Formalin-fixed, paraffin-embedded tissue samples and clinicopathological data from 168 patients with OSCC were retrospectively retrieved. Immunohistochemical staining and reverse transcription quantitative polymerase chain reaction were applied to a tissue microarray of the invasive front of each case. Semi-automated cell counting was used to assess CD44v3, CD24, PD-L1 and PD-1 expression by immunohistochemistry (IHC) using a digital image analysis program. Associations between immunological markers and clinicopathological variables were estimated. Patients with the CSC immunophenotype CD44v3high/CD24low, and patients with a high PD-L1/PD-1-positive cell density in the tumor parenchyma and stroma had significantly lower survival rates. Furthermore, patients with the CSC immunophenotype (CD44v3high/CD24low) and high PD-L1/PD-1 co-expression had even lower survival rates (P<0.01, log-rank test). Notably, there was a positive correlation between CD44v3 and PD-L1 expression (τ=0.1096, P=0.0366, Kendall rank correlation coefficient) and a negative correlation between CD24 and PD-1 expression (τ=-0.1387, P=0.0089, Kendall rank correlation coefficient). Additionally, the high CD44v3 expression group, as determined by IHC, exhibited significantly decreased expression of U2 small nuclear RNA auxiliary factor 1 (U2AF1) at the mRNA level compared with that in the low CD44v3 expression group (P<0.001, Mann-Whitney U test), and U2AF1 and PD-L1 mRNA expression exhibited a significant negative correlation (τ=-0.3948, P<0.001, Kendall rank correlation coefficient). In conclusion, CSCs in OSCC may evade host immune mechanisms and maintain CSC stemness via PD-L1/PD-1 co-expression, resulting in unfavorable clinical outcomes.

Comparative analysis of immune infiltrates in head and neck cancers across anatomical sites

BackgroundThe response rate to immune checkpoint inhibitors targeting programmed cell death 1 (PD-1) receptor is 13%–18% for patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). Detailed...

PD-1 and LAG-3 as early prognostic markers in the treatment of patients with chronic lymphocytic leukemia

Background. Recently, studies have been conducted all over the world to study the role of immune checkpoints in the pathogenesis of chronic lymphocytic leukemia (CLL) and the possibility of their use as prognostic markers. Of greatest interest are PD-1 (programmed cell death-1) and LAG-3 protein (lymphocyte-activation gene 3).Aim. To study the features of PD-1 (CD279) and LAG-3 (CD223) expression on blood B-cells of CLL patients and the possibility of their use as early markers for predicting the hematological response to therapy.Materials and methods. The blood of 30 patients with CLL in stage C according to Binet and 20 healthy individuals was studied by 10-color flow cytometry.Results. In patients with CLL, there were significant differences in the initial lymphocytes level, PD-1 and LAG-3 expression on B-lymphocytes, both with persons in the control group and among themselves with different hematological responses to therapy with rituximab according to the results of minimal residual disease monitoring.Conclusion. PD-1 and LAG-3 can be used as early markers for predicting the response of CLL patients to therapy. The combined use of initial lymphocytes level and PD-1 and LAG-3 expression on CD19+ blood cells has a greater prognostic value. New data obtained from the study of immune checkpoints PD-1 and LAG-3 may be useful in the development of targeted therapeutic agents.

Vactosertib, a Novel TGFb Type I Receptor Kinase Inhibitor, Improves T-Cell Fitness:a Single-Arm, Phase 1b Trial in Relapsed/Refractory Multiple Myeloma

The prognosis for Multiple Myeloma (MM) patients (pts) has improved substantially over the past two decades with the success of immunomodulatory drugs (IMiDs), monoclonal antibodies, chimeric antigen receptor (CAR) T-cells and bispecific T-cell engagers (BiTEs) that broke the circulus vitiosus of tumor-induced immunosuppression to reengage the immune system. Functional blockade of the transforming growth factor-beta (TGF) signaling pathway improves the efficacy of cytotoxic and immune therapies, therefore we investigator the impact of TGF-inhibition in an steroid free regimn. Methods: We conducted a phase 1b study to determine the safety, efficacy, and maximal tolerated dose (200 mg po bid) of the potent, orally-available TGF type I receptor kinase inhibitor vactosertib in relapsed and/or refractory multiple myeloma (RRMM) pts who had received -2 lines of chemoimmunotherapy in combination with standard dosage of Pomalidomide without any corticosteroids. Results: Twenty one pts were enrolled in the phase 1b dose escalation cohort and received vactosertib plus pomalidomide as indicated (Fig. 1A). Pts' characteristics are described in Table 1The summary of grade 1-4 adverse events is shown (Table 2). A single grade 4 elevated bilirubin (5%) and a single grade 4 elevated lipase (5%) were observed as well as four grade 4 events of decreased neutrophils (19%). Four pts demonstrated a PR, two had a MR, nine had SD and four had disease progression (Fig. 1B). The median time to response for all pts and the responders eight weeks and median duration of response was ~12 weeks. The best overall response for individual pts to treatment is shown (Fig. 1C). Clinical activity was observed across all four dose levels (Table 3). To probe the tumor intrinsic anti-myeloma activity of vactosertib, we first determined the relative effect of vactosertib compared to the IMiDs pomalidomide and lenalidomide (Fig. 2A, B). The effect of vactosertib was greater than that observed with either lenalidomide or pomalidomide. MMCLs and patient CD138 + cells were then treated with vactosertib in combination with pomalidomide, and importantly, vactosertib with pomalidomide synergistically reduced myeloma viability (Fig. 3A). We next probed the systemic, tumor extrinsic effects of vactosertib by analyzing cytokines immune and tumor cells present within patient BM samples. (Fig. 4A). (Fig. 4B). Therefore, we explored the immunophenotype of CD8 + T-cells isolated from patient BM prior to and at the EOT. The relative percentage of T-cells that expressed the immunosuppressive markers programmed cell death-1 (PD-1), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3), B and T lymphocyte attenuator (BTLA), and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) was reduced following treatment relative to their expression prior to treatment (Fig. 4C). Results indicated that vactosertib and pomalidomide treatment in vivo reduced PD-1, TIM3, BTLA and CTLA-4 expression on patient CD8 + T-cells. Next, CD8 + T-cells were isolated from patient peripheral blood and cultured in the presence of TGF-1, vactosertib, pomalidomide, or vactosertib plus pomalidomide (Fig. 5B). Treatment of patient CD8 + T-cells with vactosertib decreased PD-1 expression up to 40% and decreased TIM3 expression up to 65%. Pomalidomide alone did not significantly reduce PD-1, TIM3, BTLA, or LAG-3 on patient CD8 + T-cells. Vactosertib and pomalidomide also reduced TIM3 levels on CD8 + T-cells from most pts. (Fig. 5C, D). (Fig. 5 G, H). Results indicated that vactosertib or pomalidomide did not increase CD138 + cell death (Fig. 5I). Conclusion: Vactosertib combined with pomalidomide was well-tolerated at all doses, had a manageable adverse event profile and induced durable responses with 80% progression-free survival (PFS-6) at 6 months, Vactosertib reduced TGF- in patient bone marrow and suppressed PD-1 expression on CD8 + T-cells and lead to reduction of PD-L1/PD-L2 expression on CD138 + cells and enhanced autologous T-cell cytotoxicity. Taken together, our results support the safety and efficacy of vactosertib to treat RRMM and revealed that vactosertib modulates the T-cell immunophenotype and reinvigorates T-cell fitness.

PD-1 Expression By Dendritic Cells Is a Key Regulator of T-Cell Immunity in Cancer

Programmed cell death 1 (PD-1) is an inhibitory receptor expressed on a variety of immune cells and a therapeutic target of checkpoint immunotherapy for cancer patients. PD-1 engagement by PD-L1 or PD-L2 can inhibit activation and expansion of tumor antigen-specific T cells. PD-1 expression in tumor-associated macrophages (TAM) correlates with impaired phagocytosis and antigen presenting function and enhanced immunosuppression. PD-1 is also expressed in dendritic cells (DC) and has been shown to correlate negatively with the outcome of DC-based cancer vaccines. On DC, PD-1 can interact with PD-L1 in cis when both of these receptors are expressed on the same cell surface. DCs are the major antigen presenting cells for cross-presenting tumor antigens to T cells, and PD-L1 upregulation protects them from killing by cytotoxic T lymphocytes, yet dampens the antitumor responses. Very little is known about the specific role of PD-1 on DCs function. In the present study, we sought to understand the role of PD-1 on DCs in the context of cancer. We generated mice with conditional targeting of the Pdcd1 gene (encoding for PD-1) and crossed them with CD11cCre ( Pdcd1 f/fCD11cCre) or Clec9Cre ( Pdcd1 f/fClec9Cre) resulting in specific deletion of PD-1 in DC cells. We used the MC17 fibrosarcoma syngeneic mouse model to investigate the tentative implications of DC-specific PD-1 ablation on anti-tumor responses. We found larger tumor sizes and weights in tumor-bearing Pdcd1 f/fCD11cCre mice compared to their Pdcd1 wt/wtCD11cCre control counterparts. Pdcd1 f/fCD11cCre tumor-bearing mice had significantly higher fractions of DCs in spleens and tumor-draining lymph nodes (tdLNs) but only minimal differences in their activation state and checkpoint marker expression. Similarly, CD4 + and CD8 + T cells from spleens and tdLNs were comparable in percentages and activation states. However, characterization of the immune cells at the tumor site, indicated that Pdcd1 f/fCD11cCre tumor-bearing mice had a more immunosuppressive tumor microenvironment with increased fractions of CD11b +Ly6C hiLy6G -monocytic myeloid derived suppressor cells (M-MDSCs) compared to control tumor-bearing mice. Moreover, flow cytometric analysis revealed that intratumoral M-MDSC in Pdcd1 f/fCD11cCre mice displayed enhanced expression of PD-L1 and CD38, consistent with a more activated and more immunosuppressive phenotype. Characterization of tumor infiltrating CD4 + and CD8 + T cells also revealed vast differences in composition and activation states. Specifically, Pdcd1 f/fCD11cCre mice had larger populations of intratumoral CD3 + T cells, with a greater CD4/CD8 T cell ratio, and higher percentages of CD4 + T regulatory cells. Conversely, intratumoral CD8 + T cells were reduced, and were characterized by diminished expansion of CD8 + T effector cells, and a less activated phenotype as determined by lower expression of CD25, CD69, and GITR. In syngeneic tumor experiments with B16 melanoma expressing ovalbumin (B16-Ova), Pdcd1 f/fCD11cCre mice and Pdcd1 f/fClec9Cre mice similarly had greater tumor sizes and weights compared to their control counterparts. These results indicate that selective ablation of PD-1 in DCs cells confers a more immunosuppressive tumor microenvironment by promoting T regulatory cell expansion and diminishing CD8 + T effector cell activation compromising anti-tumor responses.

Specific PD-1 Deletion on Regulatory T Cells Leads to Enhanced Anti-Tumor Responses

Programmed cell death 1 (PD-1) is a T cell inhibitory receptor and the most extensively exploited therapeutic target of checkpoint immunotherapy in cancer. Ligation of PD-1 by its ligands PD-L1 or PD-L2 leads to inhibition of CD4 + and CD8 + T cell responses. However, very little is known about the specific role of PD-1 in regulatory T (Treg) cells. Previous studies have shown that PD-1 engagement during induction of Treg polarization by TCR/CD28 signaling in the presence of IL-2 and TGF-β promoted the generation and expansion of Treg cells with potent suppressive function. It has also been shown that patients with high numbers of PD-1 + Treg cells have unfavorable responses to PD-1 checkpoint immunotherapy. Moreover, patients who developed hyperprogressive disease after PD-1 blocking immunotherapy exhibited enhanced Treg cell proliferative ability compared to patients with non-hyperprogressive disease. In the present study, we sought to understand the role of PD-1 on Treg cells in the context of cancer. We generated mice with conditional targeting of the Pdcd1 gene (encoding for PD-1) and crossed them with FoxP3Cre-YFP ( Pdcd1 f/fFoxP3Cre) resulting in specific deletion of PD-1 in Treg cells. Under steady-state conditions, the percentage of Treg cells in the spleen and lymph nodes remained comparable between Pdcd1 f/fFoxP3Cre and Pdcd1 wt/wtFoxP3Cre control mice. However, PD-1-deficient Treg cells had a more activated phenotype compared to their counterparts in control mice, with higher expression of CD69, ICOS, and PD-L1. Furthermore, Treg cells in Pdcd1 f/fFoxp3Cre mice expressed increased levels of GITR, CTLA-4, ICOS, and PD-L1 compared to endogenous CD4 + T conventional cells (CD4 +Foxp3 -, Tconv) and CD8 + T cells. To investigate the implications of these immunological changes in anti-tumor responses, we used the MC38 colon adenocarcinoma syngeneic mouse model. We found a smaller tumor size in Pdcd1 f/fFoxP3Cre mice compared to their control counterparts. Treg cells from spleens and tumor-draining lymph nodes (tdLNs) showed minimal differences in their activation state, expression of checkpoint markers, and proliferation levels, as determined by direct ex vivo assessment. Similarly, CD4 + Tconv and CD8 + T cells from spleens and tdLNs showed a very low level of activation that was comparable between the two experimental groups. In the tumor site, however, Pdcd1 f/fFoxp3Cre tumor-bearing mice had a significant reduction in the fractions of CD4 + Tconv and Treg cells and a significant increase in the fraction of CD8 + T cells compared to control tumor-bearing mice. Detailed analysis revealed that in tumor-bearing Pdcd1 f/fFoxp3Cre mice intratumoral naive and central memory CD4 + T cells were reduced whereas CD4 + T effector cells were increased. Similarly, in Pdcd1 f/fFoxp3Cre tumor-bearing mice we noticed a reduction in naïve and central memory CD8 + T cells but a significant expansion in the effector CD8 + T cells . No significant differences were detected in the expression of activation markers in tumor infiltrating Treg cells between the two groups. In contrast, in Pdcd1 f/fFoxp3Cre tumor-bearing mice, tumor infiltrating CD4 + Tconv cells displayed an activated phenotype with upregulation of PD-L1, ICOS, TIM3, CD69, and CTLA-4, downregulated PD-1, and increased IFN-γ production. Tumor infiltrating CD8 + T cells also displayed an activated phenotype with upregulation of activation markers such as CD69, ICOS, PD-L1, TIM3, and LAG3 but reduced PD-1 expression. Notably, both CD4 + Tconv and CD8 + T cells proliferated more robustly in the Pdcd1 f/fFoxp3Cre tumor-bearing mice as determined by the high expression of the proliferation marker Ki67. These results indicate that selective ablation of PD-1 in Treg cells confers a less suppressive immunological environment and allows for expansion and activation of CD4 + and CD8 + T cells, leading to anti-tumor responses from CD4 + and CD8 + T effector cells.

PD-1 deficiency aggravates spinal cord injury by regulating the reprogramming of NG2 glia and activating the NgR/RhoA/ROCK signaling pathway

Spinal cord injury (SCI) is a devastating disorder and a leading cause of disability in adults worldwide. Multiple studies have reported the upregulation of programmed cell death 1 (PD-1) following SCI. However, the underlying mechanism of PD-1 deficiency in SCI is not well established. Therefore, we aimed to investigate the role and potential mechanism of PD-1 in SCI pathogenesis. PD-1 Knockout (KO) SCI mouse model was established, and PD-1 expression was evaluated in tissue samples by western blot assay. We then used a series of function gain-and-loss assays to determine the role of PD-1 in SCI pathogenesis. Moreover, mechanistic assays were performed to explore the association between PD-1, neuron-glia antigen-2 (NG2) glia cells, and miR-23b-5p and then investigated the involved signaling pathway. Results illustrated that PD-1 deficiency enhanced the inflammatory response, neuron loss, and functional impairment induced by SCI. We found that NG2 glia depletion aggravated inflammation, reduced neural survival, and suppressed locomotor recovery in murine SCI model. Further analysis indicated that NG2+ cells were increased in the spinal cord of SCI mice, and PD-1 deficiency increased the number of NG2+ cells by activating the Nogo receptor/ras homolog family member A/Rho kinase (NgR/RhoA/ROCK) signaling. Mechanistically, miR-23b-5p was identified as the negative regulator of PD-1 in NG2 glia. MiR-23b-5p deficiency reduced the expression of inflammatory cytokines, enhanced neural survival, and promoted locomotor recovery in SCI mice, which was counteracted by PD-1 deficiency. In conclusion, PD-1 deficiency exacerbates SCI in vivo by regulating reprogramming of NG2 glia and activating the NgR/RhoA/ROCK signaling.

Expression of the immune checkpoint molecules PD‑L1 and PD‑1 in EBV‑associated lymphoproliferative disorders: A meta‑analysis.

Epstein-Barr virus (EBV) has been implicated in the development of a wide range of lymphoproliferative disorders. In this process, the role of programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) has remained to be clarified. A meta-analysis of 20 studies was performed and risk ratios (RRs) with 95% confidence intervals (CIs) were used to evaluate the association between PD-L1/PD-1 expression and the status of EBV infection. The results showed that the expression level of PD-L1 in tumor cells was significantly higher in EBV+ cases with a pooled RR of 2.26 (95% CI, 1.63-3.14; P<0.01), particularly in subtypes of diffuse large B-cell lymphoma (DLBCL) and classical Hodgkin lymphoma. Similarly, EBV infection increased the expression of PD-L1 in immune cells with a pooled RR of 2.20 (95% CI, 1.55-3.12; P<0.01). In subtypes of DLBCL and post-transplant lymphoproliferative disorder, the expression of PD-L1 in immune cells is increased in EBV+ cases. Regarding the expression level of PD-1 in tumor-infiltrating lymphocytes (TILs), no significance was found between EBV infection and PD-1 expression, with a pooled RR of 1.10 (95% CI, 0.81-1.48; P>0.05). The present meta-analysis demonstrated that in EBV-associated lymphoproliferative disorders, EBV infection was associated with the expression level of PD-L1 in tumor cells and immune cells but was not associated with the expression of PD-1 in TILs.

Relationships between intravoxel incoherent motion parameters and expressions of programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1) in patients with cervical cancer

To determine the associations of intravoxel incoherent motion (IVIM) parameters with expression of programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1), and evaluate the performance of the combined model established based on IVIM and clinicopathological parameters in predicting PD-L1and PD-1 status of cervical cancer (CC) patients. Seventy-eight consecutive CC patients were enrolled prospectively and underwent magnetic resonance imaging (MRI) including IVIM. IVIM quantitative parameters were measured, compared, and correlated with PD-L1 and PD-1 expression. Independent factors related to PD-L1 and PD-1 positivity were identified and were used to establish the combined model. The combined model's diagnostic performance was evaluated using the receiver operating characteristic (ROC) analysis. The Shapley additive explanation (SHAP) algorithm was used to explain the contribution of each parameter in the combined model. The real diffusion coefficient (D) value was significantly lower in the PD-L1-positive group than in the PD-L1-negative group (0.64±0.12 versus 0.72±0.11, p=0.021). The PD-1-positive and PD-1-negative groups showed similar trends (0.63±0.13 versus 0.73±0.09, p=0.003). Parametrial invasion, lymph node status, pathological grade, FIGO (International Federation of Gynecology and Obstetrics) staging, and D values were independently associated with PD-L1 and PD-1expression. A combined model incorporating these parameters showed good discrimination with the sensitivity, specificity of 90.9%, 82.6% for PD-L1, and 93.5%, 72% for PD-1. According to the SHAP value, FIGO staging and pathological grade were the most influential features of the prediction model. IVIM parameters were found to correlate with PD-L1 and PD-1 expression. The combined model, incorporating parametrial invasion, lymph node status, pathological grade, FIGO staging, and D values, showed good discrimination in predicting PD-L1 and PD-1 status, providing the basis for CC immunotherapy.

T Cell Invigoration is Associated with the Clinical Response to Anti-PD-1-Based Immunotherapy in Non-Small Cell Lung Cancer.

Immune checkpoint inhibitors (ICIs) have been developed for clinical application and proven effective for non-small cell lung cancer (NSCLC). Blockade of the programmed cell death 1 (PD-1) protein can partially reinvigorate circulating exhausted-phenotype CD8+ T cells (Tex cells) in preclinical models, however the clinical implication in anti-PD-1-based immunotherapy in NSCLC is unknown. Serum specimens were obtained before and during treatment from 145 patients with NSCLC patients who received anti-PD-1 treatment and their prognoses were followed-up. Indicators such as cellsubpopulations, T cell invigoration were detected by clinical laboratory testing. Survival curves were estimated by the Kaplan-Meier method, Cox regression analysis was used to identify factors associated with prognoses of NSCLC patients. The expressions of Ki-67 in PD-1+/CD8+ T cells in most NSCLC patients (97 of 145 cases) increased after treatment. The responding Ki-67+/CD8+ T cell population was mainly CD45RAlo CD27hi, containing cells with high expression of CTLA-4, PD-1, and 2B4 and low expression of NKG2-D (P < 0.0001). The maximum fold change of Ki-67+/PD-1+/CD8+T cells in treatment cycles and the tumor burden determined by imaging may be associated with survival. Patients with higher Ki-67 expression on PD-1+CD8+ T-cells (pretreatment) had statistically significant increased progression-free survival (PFS). A Ki-67 expression to tumor burden ratio greater than 0.6 at the 1st cycle of anti-PD-1 immunotherapy was associated with improvement of PFS and overall survival (P < 0.05). Activation of circulating Tex cells before or during therapy related to tumor burden may be associated with clinical efficacy of anti-PD-1 immune therapy in NSCLC.

Blockade of PD-1 and LAG-3 expression on CD8+ T cells promotes the tumoricidal effects of CD8+ T cells.

The diffuse large B-cell lymphoma (DLBCL) has the highest incidence of all lymphomas worldwide. To investigate the functions of lymphocyte activation gene 3 (LAG-3) and programmed cell death 1 (PD-1) in tissues and peripheral blood of patients with DLBCL, the expression of LAG-3 and PD-1 genes in DLBCL-TCGA were analyzed. LAG-3 and PD-1 mRNA levels in DLBCL were analyzed using data from The Cancer Genome Atlas (TCGA) database. Utilize the Genotype-Tissue Expression (GTEx) database for assessing the variance in the expression of LAG-3, PD-1, and other associated factors between the tissues of DLBCL patients and healthy individuals. Immunohistochemistry was applied to detect the expression of LAG-3 and PD-1 levels in 137 cases of DLBCL tissues and 20 cases of reactive lymphoid hyperplasia. The prognostic value of LAG-3 and PD-1 were assessed using the Kaplan-Meier curve. The Estimation of Stromal and Immune cells in Malignant Tumor tissues using Expression data (ESTIMATE) and ssGSEA algorithm were used to explore the immune microenvironment of DLBCL. Additionally, the expression and co-expression of LAG-3 and PD-1 were detected on CD4 and CD8 T cells in peripheral blood samples from 100 cases of DLBCL tissues and 30 cases of healthy individuals using flow cytometry. According to TCGA database, LAG-3 and PD-1 gene expression levels were significantly up-regulated in DLBCL tissues. LAG-3 and PD-1 levels were also strongly positively correlated with those of most infiltrating immune cells. Overall survival of patients with high LAG-3 and PD-1 co-expression was significantly shorter than that of patients with low co-expression. In DLBCL patients, LAG-3 and PD-1 were highly expressed in peripheral blood CD8+ T cells. In addition, LAG-3 was highly expressed in CD4+ T cells, while the expression of PD-1 in CD4+ T cells of DLBCL patients showed no significant difference compared to healthy individuals. Additionally, CD8+ T cells and SU-DHL6/OCI-LY3 from patients with DLBCL were co-cultured in vitro; after addition of LAG-3 and/or PD-1 inhibitors alone, an increased perforin and granzyme B secretion levels by CD8+ T cells were detected, as well as an increase in the overall proportion of tumor cells undergoing apoptosis. High LAG-3 and PD-1 levels significantly inhibit CD8+ T cell function, resulting in weakened ability to kill tumor cells. Combined LAG-3 and PD-1 blockade can restore CD8+ T cell function and provides a potential avenue for development of personalized cellular immunotherapy for DLBCL.

Microbial metabolite butyrate promotes anti-PD-1 antitumor efficacy by modulating T cell receptor signaling of cytotoxic CD8 T cell

ABSTRACT Recent studies have demonstrated that the antitumor immunity of immune cells can be modulated by gut microbiota and their metabolites. However, the underlying mechanisms remain unclear. Here, we showed that the serum butyric acid level is positively correlated with the expression of programmed cell death-1 (PD-1) on circulating CD8+ and Vγ9 Vδ2 (Vδ2+) T cells in patients with non-small cell lung cancer (NSCLC). Responder NSCLC patients exhibited higher levels of serum acetic acid, propionic acid, and butyric acid than non-responders. Depletion of the gut microbiota reduces butyrate levels in both feces and serum in tumor-bearing mice. Mechanistically, butyrate increased histone 3 lysine 27 acetylation (H3K27ac) at the promoter region of Pdcd1 and Cd28 in human CD8+ T cells, thereby promoting the expression of PD-1/CD28 and enhancing the efficacy of anti-PD-1 therapy. Butyrate supplementation promotes the expression of antitumor cytokines in cytotoxic CD8+ T cells by modulating the T-cell receptor (TCR) signaling pathway. Collectively, our findings reveal that the metabolite butyrate of the gut microbiota facilitates the efficacy of anti-PD-1 immunotherapy by modulating TCR signaling of cytotoxic CD8 T cells, and is a highly promising therapeutic biomarker for enhancing antitumor immunity.