Role Of PD-1 Research Articles

Cancer and immune response: The role of PD-1/PD-L1 checkpoint in laryngeal carcinoma. Preliminary results

PurposeThe overall survival of laryngeal squamous cell carcinoma (LSCC) hasn’t changed significantly in the last decades, leading to a negative prognosis in advanced stages. So, the immunotherapy takes space with the inhibition of PD-1/PD-L1 checkpoint, involved in suppression of immune response.MethodsA prospective study was conducted on LSCC patients, selected according to strict criteria. The study was approved by the ethics committee of our Hospital. Parameters were: sex, age, smoking and alcohol habits, C-reactive protein (CRP) level in the serum, laryngeal subsite involved, differentiation-based histopathologic grading of tumor, neck node involvement, tumor stage, expression levels of PD-L1 (as Combined Positive Score – CPS). P-value < 0.05 was statistically significant.Results58 patients were included: 31.03% were females, mean age 63.55±10.09. A statistically significant correlation between CPS and smoking habits and N stage was found. CRP resulted increased in 44.83% of patients with a statistically significant correlation with CPS. The most cases were glottic cancers (46.55%). 75.86% of tumors were moderately-differentiated, without correlation with CPS.ConclusionPD-L1 expression levels are variables independent of sex, age, alcohol consumption, differentiation degree of LSCC. A statistically significant correlation between PD-L1 expression levels and smoking habits, neck node status and CRP was found. This last finding demonstrates the involvement of PD-1/PD-L1 checkpoint in immune response in case of cancer. However, these results need further studies to detect the best patients tailored for treatment with anti-PD-1/PD-L1 blocking antibodies.

Abstract IA016: The evolving role of immune-based treatment strategies in metastatic urothelial cancer

Abstract Immune checkpoint blockade has changed the treatment landscape for metastatic urothelial cancer. However, the role of PD-1/PD-L1 blockade in the treatment of metastatic diseaes continues to rapidly evolve since the initialy regulatory approval of these therapies in 2016. Defining biomarkers with sufficient predictive ability to establish clinical utility for selection of patients who can receive single agent PD-1/PD-L1 blockade has been challenging. However, combination regimens with either cisplatin-based chemotherapy or enfortumab vedotin has for the first time in decades improved survival compared with platinum-based chemotherapy alone. Refining the use of such combination regimens requires a better understanding of the potential immunomodulatory effects of cytotoxic therapies. Citation Format: Matthew D. Galsky. The evolving role of immune-based treatment strategies in metastatic urothelial cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr IA016.

PD-1/PD-L1 axis is involved in the interaction between microglial polarization and glioma

The tumor microenvironment plays a vital role in glioblastoma growth and invasion. PD-1 and PD-L1 modulate the immunity in the brain tumor microenvironment. However, the underlying mechanisms remain unclear. In the present study, in vivo and in vitro experiments were conducted to reveal the effects of PD-1/PD-L1 on the crosstalk between microglia and glioma. Results showed that glioma cells secreted PD-L1 to the peritumoral areas, particularly microglia containing highly expressed PD-1. In the early stages of glioma, microglia mainly polarized into the pro-inflammatory subtype (M1). Subsequently, the secreted PD-L1 accumulated and bound to PD-1 on microglia, facilitating their polarization toward the microglial anti-inflammatory (M2) subtype primarily via the STAT3 signaling pathway. The role of PD-1/PD-L1 in M2 polarization of microglia was partially due to PD-1/PD-L1 depletion or application of BMS-1166, a novel inhibitor of PD-1/PD-L1. Consistently, co-culturing with microglia promoted glioma cell growth and invasion, and blocking PD-1/PD-L1 significantly suppressed these processes. Our findings reveal that the PD-1/PD-L1 axis engages in the microglial M2 polarization in the glioma microenvironment and promotes tumor growth and invasion.

Abstract 74: Exploring the expression of cancer-intrinsic PD1 in osteosarcoma cells: A comprehensive proteomic analysis of its functional landscape

Abstract Cancer treatment was revolutionized by immune checkpoint inhibitors (ICIs) targeting the PD1/PDL1 axis - a brake to the immune system. Despite remarkable success, some patients do not respond to therapy or rapidly deteriorate due to an unclear mechanism. As reported for several types of tumors, PD1 receptor is not solely expressed on immune cells but also on cancer cells. Depending on the tumor type, it may act either as a suppressor or a tumor promoter. The limited response to ICIs was also reported in osteosarcoma (OSA), the most common type of bone cancer, mostly affecting children and young adults. With no significant improvement in therapy over the past 30 years, there is an urgent need for therapeutic advancement. This study aimed to determine if PD1 protein is expressed in OSA and whether it has a functional role, potentially affecting the response to ICIs. Strikingly, our results revealed both surface and intracellular PD1 expression in U2OS osteosarcoma cells, confirmed by Western Blot, flow cytometry and immunofluorescence analyses. siRNA-mediated PDCD1 gene silencing significantly increased cell migration and viability in scratch and viability assays. LC-MS-based global proteomics showed that PDCD1 knockdown markedly affects U2OS cells’ proteomic landscape compared to the control. To dissect PD1 receptor downstream signaling effects, we subjected the identified proteins to GO and GSEA large-scale data interpretation tools. The results strongly suggested that PDCD1 silencing leads to the enrichment of proteins involved in cell growth, migration and motility, corresponding to the cellular effects we initially observed. Importantly, the analysis clearly indicated positive regulation of MAPK cascade in cells with perturbed PD1 expression, aligning with PD1 mediated MAPK regulation in T cells. To reveal the mechanism underlying PD1 signaling, we focused on proteins with significantly changed expression in response to the knockdown. Using the STRING database, we created their interacting network, revealing that numerous proteins are closely related, and the majority of them are phosphoproteins, indicating significance in cellular signaling. Remarkably, many of the STRING-analyzed proteins belong to intersecting pathways, such as AKT1S1 and LAMTOR proteins, the critical components for mTORC1 signaling, or selected members of the Src family kinases along with their negative regulator CSK. In summary, we report previously undiscovered functional expression of PD1 in OSA cells, providing insights into the landscape of PD1 downstream signaling. Our studies indicate the role of PD1 in regulating cell growth, proliferation, and motility, suggesting osteosarcoma-expressed PD1 as a tumor suppressor. Further studies are urgently needed to investigate its therapeutic significance and explore if we could make ICIs more effective to treat osteosarcoma. Citation Format: Katarzyna Joanna Dziubek, Jakub Faktor, Ted Hupp, Maciej Parys, Sachin Kote. Exploring the expression of cancer-intrinsic PD1 in osteosarcoma cells: A comprehensive proteomic analysis of its functional landscape [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 74.

Role of PD-1 and immune cells in HSV infection and latency.

A large proportion of the world's population is infected with HSV-1. Antiviral CD8+ T cells and CD8α+ dendritic cells are closely related to HSV-1 infection and latency. Latency-associated transcript of HSV-1 and PD-1are involved in the regulation of latency and reactivation of HSV-1. Here, the role of latency-associated transcript, PD-1, CD8+ T cellsand CD8α+ dendritic cells in HSV-1 infection, the inter-relationships betweenthemand how these interactions leadto latency are discussed, possibly providing new ideas for the treatment of HSV-1 infection.

DOP81 Rosnilimab, a novel PD-1 agonist monoclonal antibody, reduces T cell proliferation, inflammatory cytokine secretion, and PD-1high expressing CD4 and CD8 T cells: Results from a Phase 1 healthy volunteer clinical trial

Abstract Background Programmed cell death protein 1 (PD-1) is expressed on activated T cells and is a key co-inhibitory node in immune regulation. By targeting regulatory mechanisms to modulate immune cells driving disease, there is an opportunity to restore immune balance. Rosnilimab is a PD-1 agonist antibody designed to reduce T cell proliferation and inflammatory cytokine secretion and deplete PD-1high T follicular helper, T peripheral helper, and T effector cells. It is being studied for ulcerative colitis (UC), where PD-1+ T cells are prevalent in inflamed lamina propria (&amp;gt;40%) and the periphery. The primary objective of this healthy volunteer Phase 1 study was to assess the safety and tolerability of single ascending doses (SAD) and multiple ascending doses (MAD) of rosnilimab. Findings from pharmacokinetic (PK) and pharmacodynamic (PD) assessments are summarized. Methods This single-centre study included 14 cohorts in SAD and 3 cohorts in MAD. Each cohort had 8 participants (6 active, 2 placebo [PBO]). Cohorts were enrolled sequentially in each phase. Intravenous (IV) and subcutaneous (SC) administration were assessed in SAD; SC route was assessed in MAD. Results A total of 144 participants were enrolled; 90 to active SAD cohorts, 18 to active MAD cohorts, and 30 and 6 to SAD and MAD PBO cohorts, respectively. Rosnilimab was well tolerated with no dose-limiting toxicities or deaths. Two serious adverse events were reported in SAD (deemed unrelated to treatment) and 0 in MAD. PD-1 expressing cells were reduced by ~50% in both CD4+ and CD8+ subsets, in a dose-dependent manner and in correlation with full receptor occupancy (RO) through Day 30 in SAD. PD activity was rapid with sustained reduction in PD-1+ T cells, and ex-vivo stimulation resulted in reduced T cell functional activity. This reduction was maximized on PD-1high expressing T cells: ~90% reduction vs baseline. There was no significant impact on the overall total T cell or regulatory T (Treg) cell numbers, resulting in restoration of T cell composition to a less activated state and a positive shift in the Treg:Teff ratio. An antigen-specific functional T cell assay measuring ex vivo interferon-gamma release in response to antigen challenge was inhibited up to ~90% vs baseline and the response lasted for more than 30 days following a single dose. Rosnilimab had a favourable PK profile consistent with full RO, a 2-week half-life, and dose-proportional exposure in IV and SC dosing. Conclusion Rosnilimab demonstrated favourable safety, PK, and PD activity. The role of PD-1 in UC pathophysiology coupled with these results and translational data, demonstrate proof of mechanism and support progression into a Phase 2 study of rosnilimab in UC. (NCT06127043)

PD-1 Expression in Lymphoma Cells Mediates Cellular Proliferation By Engaging Phosphatase SHP-1/SHP-2

Introduction: Despite the improved clinical outcomes with novel therapies in patients with chronic lymphocytic leukemia (CLL), Richter transformation (RT) of CLL remains a major clinical challenge. Our group showed a selective response (~40%) with the PD-1 blocking antibody pembrolizumab in patients with RT, particularly after prior exposure to ibrutinib (Ding et al, Blood, 2017). It has been established that PD-1 inhibits cytotoxic T-cell functions via the interaction with its ligands, PD-L1 and PD-L2. However, the role of PD-1 in tumor B-cells is understudied. Here we show the expression and functional implications of the PD-1 signaling axis in B-cell pathobiology. Methods: CLL-involved lymph node (LN) (n=26) and RT (with diffuse large B-cell lymphoma [DLBCL] histology) -involved LN (n=20) samples were tested for PD-1 expression by immunohistochemistry (IHC) (mouse clone NAT105, Abcam). Then, PD-1 expression was examined in 10 lymphoma cell lines and 1 CLL-like cell line (MEC-1) by both flow cytometry (FC) and Western blot (WB) analysis. PD-1 overexpression using pLEX-lentiviral packaging system (Thermo Scientific) was evaluated for its impact on in vitro cell cycle regulation and in vivo tumor growth. CRISPR/CAS9 mediated PD-1 knockdown evaluated on cell growth in MEC-1 and Mino cells. Role of PD-1 was further examined on the regulation of cell signaling pathways using human phospho kinase array kit (R&amp;D) and WB analysis. Additionally, gene expression signatures were evaluated by RNA-seq using pLEX-lentiviral-PD-1 transfected DLBCL cell lines OCI-LY7 and OCI-LY19. Results: PD-1 expression was significantly increased in RT-LN compared to CLL-LN (mean ± SEM in RT vs. CLL, 30.6% ± 4.7% vs. 11.5% ± 2.8%, p&amp;lt;0.001) as determined by IHC. PD-1 expression was highest in patients with RT where the last prior CLL therapy was ibrutinib. To test the role of PD-1 in tumor B-cells, its expression was assessed in lymphoma and CLL cell lines. The expression of PD-1 was found to be variable by both FC and WB analysis, but at very low-levels in DLBCL cell lines OCI-LY7 and OCI-LY19. Constitutive lentiviral (pLEX-PD-1)-mediated overexpression of PD-1 in OCI-LY7 and OCI-LY19 cells led to increased cell growth (1.4 and 1.9 fold, respectively, compared to original lines after 4 days of culturing of equal number of cells), which was further confirmed by cell cycle analysis which showed an increase in S phase by 20.4% (p&amp;lt;0.05) and 24.5% (p&amp;lt;0.05) in OCI-LY7 and OCI-LY19 cells, respectively. When the luciferase+ PD-1 overexpressing OCI-LY7 cells (1X10 6) were injected intravenously into NSG mice, increased tumor growth (p&amp;lt;0.01) was observed by bioluminescence imaging after 22 days of follow-up. PD-1 knockdown in MEC-1 and Mino cells (high basal PD-1 expression) led to significant inhibition of cell growth (85% and 79.5%, respectively, p&amp;lt;0.05). Using phospho-kinase array, an overall decrease of phosphorylation was detected on multiple sites of p53 (S392, S15, S46) and Chk-2 (T68) in PD-1 overexpressing OCI-LY7 and OCI-LY19 cell lines. This finding was further confirmed by WB analyses. In addition, decreased total p53 and increased phosphorylation on both SHP-1 and SHP-2 were found in PD-1 overexpressing OCI-LY7 and OCI-LY19 cell lines. SHP-1 (TPI-1) and SHP-1+SHP-2 (TPI-1+TNO155) inhibitor treatment promoted OCI-LY19 cell death and led to recovery of phosphorylation on ATM, Chk-2 and p53 in these cells. RNA sequencing data in PD-1 overexpressing OCI-LY7 and OCI-LY19 cells revealed increased expression of genes that promote cell cycle progression and DNA replication. Conclusion: Our data showed robust PD-1 expression in patients with Richter transformation from CLL to DLBCL. PD-1 overexpression in DLBCL lymphoma cell lines enhanced cell proliferation in vitro and in vivo. Further investigation identified that PD-1 modified the phosphorylation/function of SHP phosphatases and thereby regulated p53 pathways ( Figure 1). These findings indicate that RT with DLBCL cells have the ability to “hijack” the PD-1 pathway which results in downregulation of p53 mediated DNA repair. This novel finding provides for new strategies to further evaluate the interaction of PD-1 signals with DNA repair pathways and suggest potential novel targets for RT.

PD-1/PD-L1 axis in organ fibrosis.

Fibrosis is a pathological tissue repair activity in which many myofibroblasts are activated and extracellular matrix are excessively accumulated, leading to the formation of permanent scars and finally organ failure. A variety of organs, including the lung, liver, kidney, heart, and skin, can undergo fibrosis under the stimulation of various exogenous or endogenous pathogenic factors. At present, the pathogenesis of fibrosis is still not fully elucidated, but it is known that the immune system plays a key role in the initiation and progression of fibrosis. Immune checkpoint molecules are key regulators to maintain immune tolerance and homeostasis, among which the programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) axis has attracted much attention. The exciting achievements of tumor immunotherapy targeting PD-1/PD-L1 provide new insights into its use as a therapeutic target for other diseases. In recent years, the role of PD-1/PD-L1 axis in fibrosis has been preliminarily explored, further confirming the close relationship among PD-1/PD-L1 signaling, immune regulation, and fibrosis. This review discusses the structure, expression, function, and regulatory mechanism of PD-1 and PD-L1, and summarizes the research progress of PD-1/PD-L1 signaling in fibrotic diseases.

Ablation of PD-1 Reduces the Stability and Lipid Metabolism of Regulatory T Cells in the Tumor Microenvironment

Abstract Regulatory T cells (T regcells) are responsible for immune homeostasis and highly express PD-1 in the tumor microenvironment (TME). However, the role of PD-1 in tumor-infiltrating (TI) T regcells remains controversial. Indeed, PD-1 expression in T regcells was even higher than in CD8 +T cells and conventional CD4 +T cells. Here, we identified that conditional deletion of PD-1 in T regcells delayed tumor growth by reducing TI T regcell pool and amplifying the functionality of TI CD8 +and CD4 +T cells. In Pdcd1 fl/flFoxp3 eGFP-Cre-ERT2(+/−)mice, in which both PD-1 WTand PD-1 KOT regcells coexisted, TI PD-1 KOT regcells exhibited the impaired proliferative and suppressive capacity compared to TI PD-1 WTT regcells. Additionally, exT regcells, which lost their Foxp3 expression, were more abundant in PD-1 KOT regcells than PD-1 WTT regcells. In TC-1 lung cancer, PD-1 antibody therapy was effective in reducing TI T regcell pool. Single-cell analysis identified that PD-1 signaling promoted various pathways related to lipid metabolism, proliferation, and suppression in TI T regcells. Single-cell TCR sequencing revealed that the clonal expansion of TI T regcells was enriched in PD-1 WTT regcells compared to PD-1 KOT regcells. We also showed that conditional deletion of PD-1 in T regcells reduced lipid uptake and mitochondrial mass of T regcells in TME. These results suggest that PD-1 ablation or blockade can enhance antitumor immunity by exacerbating T regcell stability and metabolic fitness in the TME. This study was supported by National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIT) (2017R1A5A1014560, 2019M3A9B6065221 to S-.J.H.; 2018R1A5A2025079, 2019M3A9B6065192 to I.L.). This study was also supported by the Korean Health Technology R&amp;D Project (HV20C0144, HN21C1410 to S-.J.H.) through the Korean Health Industry Development Institute (KHIDI) funded by the Ministry of Health &amp; Welfare. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

PD-1 protects expanding human T cells from premature restimulation-induced cell death.

Abstract Programmed cell death-1 (PD-1) is a co-inhibitory protein that dampens TCR/CD28 signaling in part by recruiting the phosphatase SHP2 to the immunological synapse. Chronic antigenic restimulation of T cells can induce apoptosis or elicit PD-1-mediated exhaustion, rendering them hyporesponsive and ineffectual. While the checkpoint function of PD-1 has profound implications for cancer immunotherapy, the role of PD-1 in conventional effector T cell responses remains unclear. Restimulation-induced cell death (RICD) is a critical propriocidal apoptosis program triggered in activated T cells upon robust TCR re-engagement, constraining effector T cell expansion and longevity to prevent collateral tissue damage. We hypothesized that PD-1 attenuates RICD sensitivity in human effector T cells by modulating TCR signal strength. Here we show that transient upregulation of PD-1 helps to protect newly activated human CD4+ and CD8+ T cells from premature RICD during clonal expansion, with lesser effects noted in terminally differentiated T cells. Both antibody-mediated blockade of PD-1-PD-L1 and SHP2 inhibition increased RICD sensitivity to a similar extent. Conversely, concomitant addition of recombinant PD-L1 with TCR restimulation significantly reduced RICD in a dose-dependent manner, with more pronounced protection noted uopn CD28 coligation. Our ongoing work aims to define the role of recently discovered downstream PD-1 signaling nodes (e.g. PAG, VRK2) and specific pro/anti-apoptotic proteins in this process. These findings present significant implications for understanding how PD-1 blockade may influence apoptosis sensitivity in both normal and exhausted T cells to alter adaptive immune responses. Supported by grants from NIH (R35GM139619)

PD-1 limits differentiation and plasticity of Tc17 cells.

Blockade of surface co-inhibitory receptor programmed cell death-1 (PD-1; CD279) has been established as an important immunotherapeutic approach to treat malignancies. On a cellular level, PD-1 is demonstrated to be of particular importance in inhibiting differentiation and effector function of cytotoxic Tc1 cells (CTLs). Nevertheless, the role of PD-1 in modulating interleukin (IL)-17-producing CD8+ T-cells (Tc17 cells), which generally display suppressed cytotoxic nature, is not well understood. To evaluate the impact of PD-1 in Tc17 responses, we examined its functioning using different in vitro and in vivo models. Upon activation of CD8+ T-cells in Tc17 environment, we found that PD-1 was rapidly expressed on the surface of CD8+ T-cells and triggered a T-cell-internal mechanism that inhibited the expression of IL-17 and Tc17-supporting transcription factors pSTAT3 and RORγt. Expression of type17-polarising cytokine IL-21 and the receptor for IL-23 were also suppressed. Intriguingly, adoptively transferred, PD-1-/- Tc17 cells were highly efficient in rejection of established B16 melanoma in vivo and displayed Tc1 like characteristics ex vivo. When using IL-17A-eGFP reporter mice for in vitro fate tracking, IL-17A-eGFP expressing cells lacking PD-1 signaling upon re-stimulation with IL-12 quickly acquired Tc1 characteristics such as IFN-γ, and granzyme B expression, implicating lineage independent upregulation of CTL-characteristics that are needed for tumor control. In line with plasticity characteristics, absence of PD-1 signaling in Tc17 cells increased the expression of the stemness and persistence-associated molecules TCF1 and BCL6. Thus, PD-1 plays a central role in the specific suppression of Tc17 differentiation and its plasticity in relation to CTL-driven tumor rejection, which provides further explanation as to why the blockade of PD-1 is such an efficient therapeutic target for inducing tumor rejection.

Regulation of the PD-1/PD-L1 axis in relapsing-remitting Multiple Sclerosis (P2-3.001)

<h3>Objective:</h3> The PD-1/PD-L1 (programmed cell death protein 1/programmed cell death ligand 1) axis plays an important role in the adaptive immune system and has influence on neoplastic and inflammatory diseases. The role of the PD-1/PD-L1 axis in multiple sclerosis (MS) has not yet been investigated in detail. We aimed to delineate distinct expression patterns in peripheral blood mononuclear cell (PBMC) subsets and to evaluate the role of soluble PD-1/PD-L1 in the context of MS. <h3>Background:</h3> PD-L1/PD-1 also exist in soluble forms (sPD-L1/sPD-1) shedded from cellular surfaces. In systemic autoimmune diseases, sPD-1/sPD-L1 serum levels and membrane-bound PD-1/PD-L1 on T and antigen-presenting cells are linked to disease activity and treatment response. In MS, the PD-1/PD-L1 axis and in particular the role of soluble PD-1/PD-L1 is poorly understood but may offer relevance as disease marker and potential target for therapeutic intervention. <h3>Design/Methods:</h3> In depth immunophenotyping by flow cytometry was performed on PBMCs of 49 patients with relapsing-remitting MS (RRMS) and 27 controls. sPD-1/sPD-L1 serum levels were analyzed in a cohort of 84 patients with RRMS and 36 controls. To evaluate the therapeutic potential of soluble PD-L1, 600 μg/kg recombinant protein was systemically administered in Experimental Autoimmune Encephalomyelitis (EAE), an animal model of MS. <h3>Results:</h3> Patients with RRMS displayed distinct cellular PD-1/PD-L1 expression patterns in PBMCs and an association of sPD-L1 with MS subtype and disease severity. Systemic administration of recombinant PD-L1 in EAE resulted in ameliorated disease severity and reduced infiltration of peripheral immune cells into the CNS. <h3>Conclusions:</h3> The marked expression of PD-1/PD-L1 in immune cell subsets of patients with RRMS, and the correlation of sPD-L1 with disease-severity offers promising potential for the use as a serum marker in the context of MS. Furthermore, enhancement of coregulatory PD-1/PD-L1 signaling by exogenous supplementation of sPD-L1 may serve as a novel therapeutic strategy for severe stages of acute neuroinflammation. <b>Disclosure:</b> Dr. Tsaktanis has nothing to disclose. Mr. Linnerbauer has nothing to disclose. Mrs. Loesslein has nothing to disclose. Prof. Hemmer has received personal compensation in the range of $0-$499 for serving as a Consultant for Vaccitech. Prof. Hemmer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Prof. Hemmer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Polpharma. Prof. Hemmer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for TG Therapeutics. Prof. Hemmer has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for Allergy Care. The institution of Prof. Hemmer has received research support from Regeneron. The institution of Prof. Hemmer has received research support from German Research Foundation. The institution of Prof. Hemmer has received research support from German Ministry for Education and Research. The institution of Prof. Hemmer has received research support from European Commission. Prof. Hemmer has received intellectual property interests from a discovery or technology relating to health care. Prof. Hemmer has received intellectual property interests from a discovery or technology relating to health care. Mark Mühlau has nothing to disclose. Dr. Quintana has nothing to disclose. Prof. Rothhammer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Novartis. Prof. Rothhammer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Merck. The institution of Prof. Rothhammer has received research support from German Research Foundation. The institution of Prof. Rothhammer has received research support from European Research Council.

The Role of BCL-2 and PD-1/PD-L1 Pathway in Pathogenesis of Myelodysplastic Syndromes.

Myelodysplastic syndromes (MDSs) belong to a group of clonal bone marrow malignancies. In light of the emergence of new molecules, a significant contribution to the understanding of the pathogenesis of the disease is the study of the B-cell CLL/lymphoma 2 (BCL-2) and the programmed cell death receptor 1 (PD-1) protein and its ligands. BCL-2-family proteins are involved in the regulation of the intrinsic apoptosis pathway. Disruptions in their interactions promote the progression and resistance of MDSs. They have become an important target for specific drugs. Bone marrow cytoarchitecture may prove to be a predictor of response to its use. The challenge is the observed resistance to venetoclax, for which the MCL-1 protein may be largely responsible. Molecules with the potential to break the associated resistance include S63845, S64315, chidamide and arsenic trioxide (ATO). Despite promising in vitro studies, the role of PD-1/PD-L1 pathway inhibitors has not yet been established. Knockdown of the PD-L1 gene in preclinical studies was associated with increased levels of BCL-2 and MCL-1 in lymphocytes T, which could increase their survival and promote tumor apoptosis. A trial (NCT03969446) is currently underway to combine inhibitors from both groups.

PD-1/PD-L1 Immunotherapy: Combating Drug Resistance in Breast Cancer

In recent years, immune-checkpoint blocking therapy targeting the PD-1/PD-L1 axis has advanced tumor immunotherapy to a new level, with positive outcomes in a variety of malignant tumors. Tumors can avoid an antigen-specific T cell immune response by means of PD-1/PD-L1 signaling, which adversely controls T cell-mediated immune response. In clinical practice, it was shown that while some patients did have long-term success with immunotherapy, the majority eventually had resistance to drugs and recurrence. Hence, one of the main challenges that severely restricts the long-lasting benefits and widespread use of PD-1/PD-L1 blocking treatment is both primary and acquired resistance. Therefore, it is high time to understand the mechanisms of resistance for improving anti-PD-1/PD-L1 efficacy. In this review, we describe major signaling pathways that regulate PD-1/PD-L1 axis in cancers as well as the role of PD-1/PD-L1 in breast cancer development and progression. In addition, we further discuss the involvement of PD-1/PD-L1 axis in multi-drug resistance in cancers, which affected breast cancer and other solid tumor response rates and durability to treatment strategies.

Immunotherapy Use Prior to Liver Transplant in Patients with Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide, and its incidence has increased rapidly in the United States over the past two decades. Liver transplant is considered curative, but is not always possible, and pre-transplant immunotherapy is of great interest as a modality for downstaging the tumor burden. We present a review of the literature on pre-liver transplant immunotherapy use in patients with HCC. Our literature search queried publications in Ovid MEDLINE, Ovid Embase, and Web of Science, and ultimately identified 24 original research publications to be included for analysis. We found that the role of PD-1 and PD-L1 in risk stratification for rejection is of special interest to researchers, and ongoing randomized clinical trials PLENTY and Dulect 2020-1 will provide insight into the role of PD-1 and PD-L1 in liver transplant management in the future. This literature search and the resulting review represents the most thorough collection, analysis, and presentation of the literature on the subject to date.

PD-1 expression on mouse intratumoral NK cells and its effects on NK cell phenotype

SummaryAlthough PD-1 was shown to be a hallmark of T cells exhaustion, controversial studies have been reported on the role of PD-1 on NK cells. Here, we found by flow cytometry and single cell RNA sequencing analysis that PD-1 can be expressed on MHC class I-deficient tumor-infiltrating NK cells in vivo. We also demonstrate distinct alterations in the phenotype of PD-1-deficient NK cells and a more mature phenotype which might reduce their capacity to migrate and kill in vivo. Tumor-infiltrating NK cells that express PD-1 were highly associated with the expression of CXCR6. Furthermore, our results demonstrate that PD-L1 molecules in membranes of PD-1-deficient NK cells migrate faster than in NK cells from wild-type mice, suggesting that PD-1 and PD-L1 form cis interactions with each other on NK cells. These data demonstrate that there may be a role for the PD-1/PD-L1 axis in tumor-infiltrating NK cells in vivo.

The role of PD-1/PD-L1 and application of immune-checkpoint inhibitors in human cancers.

Programmed cell death protein-1 (PD-1) is a checkpoint receptor expressed on the surface of various immune cells. PD-L1, the natural receptor for PD-1, is mainly expressed in tumor cells. Studies have indicated that PD-1 and PD-L1 are closely associated with the progression of human cancers and are promising biomarkers for cancer therapy. Moreover, the interaction of PD-1 and PD-L1 is one of the important mechanism by which human tumors generate immune escape. This article provides a review on the role of PD-L1/PD-1, mechanisms of immune response and resistance, as well as immune-related adverse events in the treatment of anti-PD-1/PD-L1 immunotherapy in human cancers. Moreover, we summarized a large number of clinical trials to successfully reveal that PD-1/PD-L1 Immune-checkpoint inhibitors have manifested promising therapeutic effects, which have been evaluated from different perspectives, including overall survival, objective effective rate and medium progression-free survival. Finally, we pointed out the current problems faced by PD-1/PD-L1 Immune-checkpoint inhibitors and its future prospects. Although PD-1/PD-L1 immune checkpoint inhibitors have been widely used in the treatment of human cancers, tough challenges still remain. Combination therapy and predictive models based on integrated biomarker determination theory may be the future directions for the application of PD-1/PD-L1 Immune-checkpoint inhibitors in treating human cancers.

Expression of PD-1 on Memory T Lymphocytes Predicts 28-Day Mortality of Patients with Sepsis: A Prospective Observational Study.

BackgroundPD-1 is an important immune checkpoint expressed on T lymphocytes and is associated with T-cell function in sepsis. However, the role of PD-1 in naive and memory T-cell responses in sepsis is not well understood. We aimed to determine the expression of PD-1 induced on naive and memory T lymphocytes in patients with sepsis and its association with clinical outcome.MethodsA prospective observational study was conducted at a general intensive care unit (ICU). Whole blood samples were collected from patients within 48 h after sepsis diagnosis. PD-1 expression on naive and memory T cells was measured by flow cytometry. The levels of IFN-γ, IL-2 and TNF-α released by memory T cells were also determined. All patients were followed up to 28 days, and 28-day mortality was recorded.ResultsPD-1 expression showed no difference in naive CD4+ T cells (P=0.617) or naive CD8+ T cells (P=0.079) between survivors (n = 21) and nonsurvivors (n = 9). Increased PD-1 expression on memory CD4+ T cells was found in nonsurvivors (P=0.030) and memory CD8+ T cells (P=0.006) in comparison with survivors. According to the cutoff value of the percentage of PD-1 on memory CD8+ T cells in predicting 28-day mortality of patients with sepsis, patients were divided into two groups. The 28-day mortality rates between the two groups were significantly different (P=0.009). A Kaplan Meier curve was constructed to derive a hazard ratio of 9.33 (95% CI: 2.52–34.60) for the percentage of PD-1 on memory CD8+ T cells regarding 28-day mortality. In addition, the IFN-γ secretion of memory CD4+ T cells (P=0.046) and IL-2 secretion of memory CD8+ T cells (P=0.014) were significantly greater in survivors than nonsurvivors.ConclusionFlow cytometric assessment of PD-1 expression on memory CD8+ T cells identifies patients with poor outcomes during sepsis.

Antibody-mediated depletion of programmed death 1-positive (PD-1+) cells.

PD-1 immune checkpoint has been intensively investigated in pathogenesis and treatments for cancer and autoimmune diseases. Cells that express PD-1 (PD-1+ cells) draw ever-increasing attention in cancer and autoimmune disease research although the role of PD-1+ cells in the progression and treatments of these diseases remains largely ambiguous. One definite approach to elucidate their roles is to deplete these cells in disease settings and examine how the depletion impacts disease progression and treatments. To execute the depletion, we designed and generated the first depleting antibody (D-αPD-1) that specifically ablates PD-1+ cells. D-αPD-1 has the same variable domains as an anti-mouse PD-1 blocking antibody (RMP1-14). The constant domains of D-αPD-1 were derived from mouse IgG2a heavy and κ-light chain, respectively. D-αPD-1 was verified to bind with mouse PD-1 as well as mouse FcγRIV, an immuno-activating Fc receptor. The cell depletion effect of D-αPD-1 was confirmed in vivo using a PD-1+ cell transferring model. Since transferred PD-1+ cells, EL4 cells, are tumorigenic and EL4 tumors are lethal to host mice, the depleting effect of D-αPD-1 was also manifested by an absolute survival among the antibody-treated mice while groups receiving control treatments had median survival time of merely approximately 30days. Furthermore, we found that D-αPD-1 leads to elimination of PD-1+ cells through antibody-dependent cell-mediate phagocytosis (ADCP) and complement-dependent cytotoxicity (CDC) mechanisms. These results, altogether, confirmed the specificity and effectiveness of D-αPD-1. The results also highlighted that D-αPD-1 is a robust tool to study PD-1+ cells in cancer and autoimmune diseases and a potential therapeutic for these diseases.

Lack of Functional P110δ Affects Expression of Activation Marker CD80 but Does Not Influence Functions of Neutrophils.

Neutrophils are specialized immune cells that are essential constituents of the innate immune response. They defend the organism against pathogens through various mechanisms. It was reported that phosphatidylinositols are key players in neutrophil functions, especially in the activity of class-I phosphoinositide 3-kinases (PI3Ks). P110δ, one of the PI3K subunits, is mostly expressed in immune cells, and its activity plays an important role in inflammatory responses. The aim of this study was to investigate the role of p110δ in neutrophil antimicrobial functions, activation status and cytokine production. To this end, we used bone marrow and splenic neutrophils isolated from a murine model expressing catalytically inactive p110δD910A/D910A. The level of phagocytosis and degranulation, the expressions of activation markers and cytokine production were determined by flow cytometry. ROS generation and NET release were assessed by fluorometry and fluorescent microscopy. We observed a significantly higher percentage of CD80-positive cells among the splenic granulocytes and found granulocytes subpopulations of differing phenotypes between WT and p110δD910A/D910A mice by multiparametric tSNE analysis. Moreover, we detected some differences in the expressions of activation markers, intracellular production of cytokines and bacterial killing. However, we did not observe any alterations in the selected neutrophil functions in p110δ mutant mice. Altogether, our data suggest that the catalytic p110 subunit(s), other than p110δ, is a key player in most neutrophil functions in mice. A follow-up study to correlate these in vitro results with in vivo observations is highly recommended.